Report on Boiler Modification for 100% Over bed Firing

30 December, 2012

REPORT ON BOILER DESIGN & PERFORMANCE IMPROVEMENT STUDY AND FOR TROUBLE FREE OPERATION WITH FIBROUS AGRO FUELS

By Venus Energy Audit System

About the boiler

The boiler parameters are 15 TPH, 64kg/cm2 g, 485 deg C with feed water temperature at 105 deg C. Design fuel is 100% rice husk. The boiler is provided underbed feeding system of rice husk. The boiler is bottom supported at water drum level. The bed coils are bottom supported. There are two compartments. Totally six 150 nb husk feed lines are used. Boiler is with radiant SH ( primary) and secondary SH, boiler bank, economiser and airpreheater. Husk is fed by rotary feeder. Boiler was originally designed for under bed firing system and over bed fuel. Over bed feeding system was commissioned in the month of November 2004.

Modification carried out

The boiler was later modified for multi fuel agro fuel firing. The fuels currently fired are rice husk, Channa gram straw, Ground nut shell, Soya straw.

a) Rice Husk and Rice based fuel 5-7%

b) Ground nut shell 15-20%

c) Soya straw, mustard straw, Gram straw etc. 73-80%

The boiler capacity is derated as per OEM to 80%, that is 12 TPH.

Agenda for the study- as expressed by plant personnel

The following are the problems reported and the requirements by the plant.

1. There is variance in Superheated Steam temperature between 4550-5400C whereas the desired range is 485 ± 50C. This is to be reduced.

2. There is frequent variation in steam pressure whereas the requirement is a constant pressure of 75.0 kg/Cm2.

3. Fuel consumption per KWH is very high 1.70 whereas the desired Fuel consumption per KWH is 1.25.

4. Auxiliary power consumption of the plant is 20% and this is high. 5. There is no control on the sizing and percentage fines, moisture content and calorific value of the

fuel being used for the boiler. But whatever is the situation, optimum output from power plant is desired against existing reduced output of a level 80-82%. Up to Sept. 2006, a maximum of 40% Soya straw, Gram straw & Mustard straw were used. The steam parameters were under control and turbine capacity utilisation was at 90-95%. But after increasing the fibrous fuels to 100%, overheating of super heater tubes took place. Once melting of super heater tubes took

place. In the month of Sept 2009, complete set of super heater tubes replaced with new one. 6. Turbine’s nozzle chest body cracking was experienced in the month of Nov 2011. Steam

temperature excursions need to be under control to avoid this problem. 7. An optimized fuel feeding arrangement of a combination of agro based fuels having less calorific

value compared to rice husk is required. The SPM from the boiler stack while using such fuels. 8. The suitability of existing super heater tube arrangements in the boiler needs to be reviewed for

the fuels being used currently. 9. We want some type of automation with regard to controlling the temperature of the super heater

tubes within the OEM recommended range and it’s interlocking with boiler feeding system. 10. The rated MCR of the boiler is desired using a mixture Soya straw, Gram straw, Mustered straw

and other local fuels. 11. The Superheated Steam temperature has to be under control in the desired range of 485 ± 50C. 12. The steam pressure variance has to be avoided. 13. The boiler efficiency needs to be improved and power consumption needs to be reduced. Combustor design review of the boiler for 100% rice husk

The rice husk fuel GCV is reported as 3150 Kcal/kg and with a moisture of 8.68%. This matches with the standard analysis adopted for boiler design.

The furnace design calculations are made and enclosed in annexure 5. The calculations are made for 15 TPH output. For underbed firing 20% excess air has been considered. The findings are as below. The furnace layout is made and the furnace volume is calculated from drawing. The present furnace volume above the bed is working out to be 52.456 m3. The present bed cross section is 2.95 m x 2.95 m. The area is 8.7 m2. The fluidisation velocity works out to be 2.74 m/s as against a requirement of 2.6 m/s and less. The DP nozzle pressure drop with 10% secondary air works out to be 162 mmWC. This is in order. The bed coil length immersed in the bed works out to be 237 m as against requirement of 226 m. The gas residence time in the furnace works out to be 2.2 sec.

Inadequacy of furnace volume for overbed feeding of any fuel Agro fuels are low density fuels and bulk density ranges from 90 kg/m3 to 120 kg/m3. They also have high volatile matter with a minimum of 50%. We may see the fuel analysis report given by the plant personnel in annexure 4. Due to this fact any overbed feeding of agro fuels need more furnace volume. As the moisture content increases, even as much as 3-4 seconds of furnace residence time is provided. After the site visit and drawing study, it is found possible to increase the furnace volume by lowering the DP plate. As such the underbed feeding system is troublesome due to fibre content in fuel and the stones. It is seen that the dechoking is being done regularly resulting in drop in steam pressure and temperature during such time. Due to above problem, it is proposed to adopt open hopper design with sparger air nozzles to drain off the stones and to go for 100% overbed feeding of all fuels. With this concept we can go for a 1.5 m pit below the open hopper.

Thermax themselves have supplied boiler for agro waste with such arrangement. See the arrangement in annexure 6. Open hopper combustor design is offered by many boiler makers for sponge iron plants where the fuel ash contains have iron particles. Combustor design of the boiler for 100% rice husk by over bed feeding – new The agro fuels moisture content varies and GCV also varies depending upon the decay during storage. Currently the fuel mix GCV reported at plant is 3320 kcal/kg for underbed fuel mix (moisture 7.78%) and 3640 kcal/kg (moisture 9.1%) for overbed fed soya straw. The ash for underbed fuel mix is reported to be 5.98% and 2.88% for overbed. For design check, 100% overbed firing of rice husk is considered, as this is the worst fuel and a consistent analysis is available from many plants.

A layout is made with the proposed modification of the boiler. See views of the drawings in annexure 7. The modification suggested is extension of waterwall below the present operating floor. With this the effective furnace volume (above bed) is seen to increase from 52.456 m3 to 85.4 m3.

The furnace design calculations are made and enclosed in annexure 7. The calculations are made for 15 TPH output. The excess air will be in the range of 35% for overbed combustion of fuels. The findings are as below. The furnace layout is made for the case of new combustor and the furnace volume is calculated from drawing. See the figure in annexure 7.

The revised bed cross section is 3.145 m x 3.145 m. The bed cross sectional area is 9.89 m2. This is due to removal of refractory wall and due to extension of waterwall itself to form furnace walls. The furnace wall tube OD is 63.5 and stud length is 16 mm. The studs will be lined with high alumina phosphate bonded refractory. The fluidisation velocity works out to be 2.44 m/s for 15 TPH generation. Due to overbed combustion, actual velocity at bed will be less by a factor of 0.9.

The residence time for 35% Excess air condition is seen to be 3.19 sec above the bed. The height gain by this modification will be 2.7 metres. Due to this the waterwall projected

heating surface will increase by 4*3.24*2.7 = 36.72 m2. This will help in bringing down the gas inlet temperature at APH outlet. But the temperature can vary as per the fines and dryness. It is not possible to increase the furnace height any further. Furnaces with 4 seconds residence time can handle the fuels more efficiently.

There will be no PA fan or SA fan requirement. Since the wind box pressure will be around 450 mmWC and the furnace depth is 1.6 m (one side), the FD air itself will suffice for turbulence. That is SA tapping will be from APH outlet itself. There will be power saving in this respect.

Since the combustion takes place overbed, the bed coil HTA comes down. The bed coil is formed from the side waterwall tubes. The bed coils are studded with 5 x 4 pattern of SS studs. The front wall and rearwall tubes now participate for heat transfer. The free board heat release will be as high as 30%. Any adjustment required to achieve better bed temperature is possible by covering the bed tube with refractory coating.

The new air nozzles are to be made of SS tip. The DP drop is designed for 176 mmWC. About

25% of the air will be used for SA & fuel spreading. The FD fan capacity and ID fan capacity are found to be inadequate. The fan flow and head data

are taken from the torque speed curve provided to us. See the details in the annexure 7. For 15 TPH steam generation, this will change. However looking at the present load of 12 TPH & the high exit temperature, margin may be available to some extent. The fan KW may not change.

Some details about the modifications that are required are as below Waterwall

The waterwall is extended to create additional furnace volume. In addition the openings are made for overbed feeding of the both rice husk and mustard stalk. The overbed ports are lowered appropriately. New seal boxes are added at all fuel feed points.

Waterwall support

At present the waterwall is supported at the extended header portion of front & rear bottom headers. Now the waterwall is to be supported at the panel but at the same elevation. Support is taken from the fins. The support is known as girth support.

Downcomer

The downcomer routing is changed. The waterwall bottom headers are now connected by the four downcomers.

Bed coils

At present two rows of bed coils are provided. For overbed feeding and for agro fuels, the heat transfer area of bed coils required is less and the extended waterwall area come in to heat transfer. For this the two side waterwall tubes are bent to form the bed coils. The bed coils are studded for erosion protection. Seal boxes are added at the bed coil zone. The bottom side of the front waterwall and rear waterwall (about 1 m above air nozzle) are also studded and plastered with heat conducting refractory. The refractory lining is for erosion protection of vertical tubes, as they generally get polished in six years time.

Bottom drains

The bottom headers are now shifted below the concrete floor. There are four drains provided in the header ends. The drain piping are to be rerouted at site suiting the present layout.

Open hopper FBC furnace

Stones ingress in rice husk and other agro fuels lead to defluidisation and accelerated bed coil erosion. Open hopper FBC furnace is the ideal choice for removal of stones without boiler stoppage. The combustion air is now supplied through five no sparger header fitted with SS tipped air nozzles. The hopper is suspended from the waterwall bottom headers. There are four outlets to this hopper. Each outlet is provided with roller gates for draining the bed material / bed ash as the bottom thermocouples become dead due to settled stones. The sparger headers get air supply from the hot FD air ducts. Each sparger header is provided with drain pipes for removing

the seeped bed material. These headers are provided with dampers for turning down the load and for start up purpose.

There are six direct ash drain pipes provided directly below the over bed fuel feed points for direct draining oversize stones.

The open hopper is sealed with waterwall bottom header with provisions for taking care of differential thermal expansion.

In order to operate the hopper drain gates and ash drain gates, the present ground floor is to be excavated by 1.5 m. The approach to the pit is to be made from right side of the furnace.

Instrumentation for the fluidised bed

The bed thermocouples are inserted in guide pipes from the bottom. There are eight thermocouples envisaged. The guide pipes are welded to the open hopper walls. The air box pressure tappings are to be located at each of the sparger header.

Fuel feeding system- rice husk

Overbed feeding system is proposed due to reasons explained below.

One is that the furnace has to be lowered to have additional furnace volume for burning of fuel fed from overbed. For this total underbed feed system has to be lowered. Then the pit area will have to be including the underbed and for the fuel cross drains. At present stone ingress is there with rice husk. The mixing nozzles and cross dechoking requirement is quite frequent. Hence the objection was about the free access for operation. When the bed is present with ash accumulations falling from superheater, the bed fluidisation gets disturbed. Hence overbed feeding system was chosen.

Rotary feeder system is now removed. To take of horizontal transportation to overbed feed points, screw feeders are proposed. Screw feeders drop the fuel in to the over bed feed chutes provided at the left side waterwall.

The air for pushing the fuel and for sealing is taken from main FD air duct itself. A 100 nb line with a damper is provided at each of the four feed chutes.

Part of the overbed feed chute will be of SS material. Screw feeders are to be provided with VFD. Each screw feeder is provided with slide gate for

isolation purpose.

Fuel feeding system – Fibrous fuels

At present there is single feed point at the furnace. This is made as two numbers for better use of furnace volume.

At present there is no control of over feeding of the fuel. In case of excess feeding the superheater temperature will shoot and there is risk of header failures. To control this, a drum feeder is added below the present hopper. This drum feeder is same as the one used in bagasse fired boiler at sugar mills. This drum feeder is also to be provided with VFD.

The drum feeder discharge is bifurcated in to two and connected to over feed chutes. The furnace side of chute is made of SS. Air for pushing and sealing is taken from FD header. Two no 100 nb pipes with dampers are considered for this.

Secondary air system

The secondary air (SA) system is now modified as explained here. The existing SA headers are used. New SS tube tips are welded to waterwall. These tips are inclined to promote turbulence for volatile matter combustion and increased residence time for particles.

The air tapping for SA system is taken directly from the APH outlet. The SA headers are provided with draft tappings to indicate SA header pressure. Two number draft gauges are to be provided. The SA tappings are provided only at front and rear walls.

Refractory in seal boxes, waterwall and open hopper

Refractory castables are to be poured in all over bed chute seal boxes.

In the front and rear waterwall tubes at bed zone, refractory lining is done. This refractory is high alumina plastic refractory. This is done only up to stud tips. Same is applicable for two vertical tubes in side walls.

The bottom headers are refractory lined to protect direct heating of the headers. This is done by high alumina castable to a thickness of 75 mm.

The open hopper is provided with 40 thick refractory tiles of IS 8 grade

Insulation

The extended portion of the waterwall is to be insulated with 100 mm thick light resin bonded mattress. The seal boxes are to be insulated with 40 mm thick mattress. Open hopper is not to be insulated. The air ducts are to be insulated with 50 mm thick Light resin bonded mattress.

For further details, the detailed drawings would have to be referred.

OBSERVATIONS AT PLANT The boiler was inspected during the shut down. Further the boiler was seen in operation as well. The following are the observations at the plant. Some recommendations are given as well. See annexure 1- ash fouling and combustion at superheater section The fuel feed point at present is with horizontal spreading air. The height of the SH coil bottom

from the fuel feed point is 2.3 m. This is too less. Hence the combustion takes place around superheater area resulting in temperature swings. This has resulted in burning of the superheater alignment bands. When the modification is taken up the alignment bands have to be reinstated.

Mustard straw, GN shell and soya straw contain alkali (Sodium, Potassium) ash and this can form ash deposits. The deposit effect is reduced by the silica ash from rice husk. Deposits are seen at superheater sections. However it is seen, it is not to extent of blocking the passage.

APH tube plugging & failure occurs due to condensation of fuel moisture & fuel hydrogen. The presence of rice husk ash may reduce the plugging to some extent. The cold end tubes of APH need replacement every two years.

See annexure 2- Fuel handling / feeding system The mix of fuels for underbed contains fibres and long pieces. Generally this poses bridging

problem above feeder and above venturi. The stones present in this fuel mix can block the venturi. The stones settle at fuel cross and

demand frequent dechoking. The fuel consumption goes high due to this. Whenever fuel feeding is disturbed in the furnace, the steam pressure & steam temperature would swing.

By overbed feeding both the problems are eliminated. At present, only 25% of the total fuel is being handled by underbed. Open hopper design will eliminate the problem of PA line choking. However hopper drains have to be operated as required to lower the settled stones.

The overbed feeding system needs an improvement. A rotating leveller is required at the main conveyor to ensure a fairly constant feeding is available. The present capacity of the conveyor seems inadequate. Spillage is seen. The conveyor may be provided with skirt board to complete length or the increasing of belt speed may be reviewed with manufacturer.

See annexure 3- Flame test and air ingress report The boiler is not leak proof on gas side. There are air ingress points. They can be seen in the

photographs in annexure 3. The air ingress from outside loads the ID fan. This increases the power consumption.

There is considerable air ingress in the roof panel. This matters a lot with respect to secondary combustion in superheater area.

Such leakages are encountered at many plants. The causes are design defects, incomplete seal box work during boiler installation / maintenance. It is advised to seal the roof from leakages by using plaster of paris. A typical photograph at another plant and the application procedure are presented in annexure 3.

See annexure 4- Observations in boiler operation Stones are present in the fuel fed in to the boiler. This affects the fluidisation and leads to

overbed burning. The bed coil erosion also would take place due to haphazard gas flow in the bed.

The dechoking process in underbed is a nuisance for boiler operation personnel. There is no way the stone ingress can be avoided. Also the separation by any mechanical screen system is not possible.

Due to inadequate furnace volume & heating surface, the boiler exit gas temperature goes up to 211 deg C, even for a load of 12 TPH. There is a need to increase furnace heat transfer area to reduce the exit gas temperature.

Due to bed defluidization, the bed temperatures are seen to be haphazard. This makes the bed coils inefficient to heat trasfer. Thus freeboard temperatures rise further.

It is seen that the Trema cyclone outlet draft is as high as -350 mmWC, whereas the fan design itself is – 370 mmWC.

It is seen that fuel moistures are under control. This is seen to be less than 10%. As the

percentage goes higher, the boiler efficiency comes down and the flue gas quantity increases. Boiler capacity will be derated mainly due to this factor.

Ash fouling is related to ash chemical analysis. Presence of sodium and potassium in straw leads to fouling and calls for periodical cleaning. This is unavoidable. Usage of sand as bed material and the mix of rice husk can bring down the fouling to some extent.

Conclusions

1. Combustor volume can be increased to the extent possible to take care of residence time requirement. Thus problems related to high exit temperature & high steam temperature can be controlled.

2. Elimination of PA fan results in power savings. 3. For emission control Electrostatic precipitator is advised. This will result in power savings as

well. The fan head requirement will come down to 150 mmWC as against the present 370 mmWC. The power required by ESP is much lesser.

4. Overbed fuel feed control is the key point on swings of steam temperature. A leveller would help. Further the rotary feeder, below the fuel surge hopper will avoid the excess feeding even if there is more feeding from conveyor.

5. Boiler efficiency is dependent on excess air, boiler exit temperature and fuel moisture. The combustion efficiency will be 80% theoretically. Actual efficiency would by lower by 2% due to blow down, fuel GCV variance and fuel moisture variance and fuel mix consistency. Online O2 meter / CO meter is recommended so that the incomplete combustion can be known immediately by the operator.

It is feasible to increase the furnace volume in the present boiler layout. The feasibility of lowering the combustor was studied at plant by our engineer and discussions were held. Based on the problems faced in underbed feed system, it was proposed to switch over to open hopper system. Accordingly the detailed layout drawings, production drawings and specifications would be furnished.

ANNEXURE 1– OBSERVATIONS INSIDE THE BOILER

Photo 01: Generally the boiler designed for Biomass fuel should have large furnace volume in order to make effective combustion. This boiler is originally designed for Underbed and later overbed provisions were made. The free board height is physically measured to be 2300mm only. So once the fuel enters the boiler it will fly away to superheater zone allowing the combustion to occur in Superheater area. The least residential time of 3 Secs will not be able to achieved here.

Photo 02: The above picture shows the boiler design data. The boiler is originally designed for rice husk fuel and the fuel firing is only through underbed system. Hence furnace volume was designed optimally.

Photo 03: The above photo is showing the condition of Secondary superheater support clamps. The clamps were seen to have failed long time ago. This is due to high gas temperature.

Photo 04: In one of the RSH coils, the binding clamp is burnt off. The furnace temperature sometimes touches even 1000 Deg C. Due to this some clamps have got melted.

Photo 05: Along the CSH zone most of the support clamps have failed and the coils have come out of position. This will restrict the flue gas path and thus leading the way to ash choking along the CSH flue path.

Photo 06: The Supports given for coil expansion for CSH coils have failed.

Photo 07: The Ash deposition is also seen in Economiser coil but its deposition rate is low as compared to Superheater coils and Bank tubes. Sonic soot blower is installed in economiser zone.

Photo 08: It is seen that around 15 APH tubes are dummied because of leakage. APH tubes are subject to corrosion in agro waste. The flue gas moisture condenses inside the tube.

ANNEXURE 2 – FUEL HANDLING / FEEDING DETAILS

Fuel Mixing Ratio:

Rice Husk - 16 Scoops per Shift

Ground nut Shell + Gram staw - 35 Scoops per Shift (Grounut Shell 90%, Gram Straw 10% if available)

Soya Straw - 20 Trolley per Shift.

1 Scoop of rice husk / Gn shell = 180 Kg.

1 Trolley = 1200 Kg.

So,

Rice Husk = 2880 Kg (8.7%)

Ground nut Shell + G. Straw = 6300 Kg (19.0%)

Soya Straw = 24000 Kg (72.3%)

Note: Soya straw alone is fed into the bunker through Overbed. Other fuels are fed through Underbed.

Photo 01: The above photo shows the grinding of Ground nut shell and Channa straw together. Channa straw will be fed into the bunker only if it is available.

Photo 02: The above photo shows the mixture of ground nut shell and gram straw. The size of Channa straw is varying and sometimes it causes choking above the rotary feeder. As the fiber content increases rotary feeder will not be able to handle this.

Photo 03: A tractor brings the rice husk from nearby place and mixes it with Ground nut shell and Channa straw. The mixing is done by tractor.

Photo 04: The above photo shows the fuel mix done by tractor. At some place the volume of Ground nut shell seems to be more and in some place the volume of rice husk is more.

Photo 05: This is the closer view of Ground nut shell, Rice husk & Gram straw mixed together. The size of gram straw alone not uniform as this may sometime leads to choking in rotary feder, mixing nozzle throat.

Photo 06: There is an vibratory feeder in the fuel yard into which Soya straw is fed manually by worker. There is no controlling for the size, foreign particle of the fuel.

Photo 07: Since the fuel is fed manually, there is no regularity in fuel flow in the overbed Conveyor. This irregular fuel flow highly impacts the main steam parameters as there is no Rotary or Screw feeder on the overbed bunker.

Photo 08: Irregular fuel flow through Overbed belt conveyor. Skirt board system is advised to avoid spillage. In addition a rotary leveller can be added to achieve somewhat uniform feeding. The belt speed may have to be increased to avoid spillage.

Photo 10: Recently VFD is installed at Overbed conveyor motor to control the conveyor RPM and there by controlling Steam parameters. This will work better with uniformity in fuel flow to the conveyor.

Photo 11: Irregular fuel flow through Overbed belt conveyor.

Photo 12: Recently they had gone for VFD to Overbed conveyor motor to control the conveyor RPM and there by controlling Steam parameters. This will not work unless there is uniformity in fuel flow in the conveyor.

Photo 13: This panel photo shows the interlock made between main steam pressure and overbed conveyor motor. The steam pressure set point is 62 Kg/cm2.

Photo 14: The closer picture showing the physical appearance of Soya straw. This fuel can be fed in over bed only.

Photo 15: Stones present in fuel.

Photo 16: Bulk density of different fuels. The bulk densities are fairly same. However flowability can vary due to size distribution.

ANNEXURE 3 – FLAME TEST AND AIR INGRESS REPORT

Photo 01: It is found that there is some leakage in Eco/APH hopper. Due to this additional atmospheric air gets into the boiler leading to ID fan loading.

Photo 02: Some Air ingress has been observed in the seal box where the Soot blower line is located. All seal box should be fully welded to avoid air ingress.

Photo 03: Air ingress along the boiler rear side panel.

Photo 04: Air ingress along the Radiant SH O/L header. It is seen that the sealing is not proper at roof.

Photo 05: The condition of roof panel is very poor as there is considerable amount of ash seen above the roof. Entire roof panel needs insulation rework as this leads to poor efficiency and secondary combustion at SH area.

Photo 06: It is seen that the sparks are coming out of the roof panel. This is because the sealing is not good.

Photo 07: The above photo shows the application of Plaster of paris for better sealing of roof. This avoids the air ingress from the roof. This insulation is so hard finished; the persons can walk over the roof.

Photo 08: General drawing of plaster of paris / Cement + Mineral wool + Sand mastic finishes on insulation which helps on sealing. This shall be done at roof tube area.

Photo 09: This is a typical sealing arrangement in the roof zone where the superheater coils enters. 150 thk mineral wool should be applied over the seal box. Above that 12 thk plaster of paris has to be applied. Finally it shall be covered with Hessian cloth with two coats of black bitumen paint.

ANNEXURE 4 – OBSERVATIONS IN BOILER OPERATION

Photo 1: Stones present in bed ash.

Photo 2: Fuel lines being dechoked due stones ingress. Due to stones, there is fuel loss and there is operational disturbance.

Photo 3: The economiser outlet gas temperature will have to be around 260 deg C and APH outlet gas temperature has to be around 160 deg C. The APH outlet gas temperature is 211 deg C. There is considerable heat loss roughly the loss can be around 4.5%. The bed temperatures are haphazard indicating settling of bed with stones. The low temperatures can be due to over bed firing. The higher amount of bed coil also causes this low temperature. This is with a less load of 11.5 TPH.

Photo 4: Trema cyclone outlet draft is -350 mmWC. This is too high. Across dust collector nearly 290 mmWC drop is seen. The hot air temperature is quite high. Normally it is designed for 150 deg C.

Photo 5: The as fired moisture in fuel is well within control. GCV of fuel mix is also good.

Photo 6: The above is the data collected from plant on fuel ultimate and proximate analysis. The ash analysis was not available. The fuel ash from mustard straw / soya straw / gram straw can contain alkalis which can deposit over the superheater tubes.

ANNEXURE 5- COMBUSTOR DESIGN CALCULATIONS FOR 100% RICE HUSK FIRING BY UNDERBED

EWS 604

PROJECT : INPUTS FOR COMBUSTION CALCULATIONSAIR & GAS CALCULATIONS

Ta Ambient temperature 40 Deg CP1 Relative humidity 60 %Ma Moisture in dry air ( from tables) 0.02851 kg/kgE Excess air 20 %Te Boiler outlet gas temperature 160 Deg CEl Site elevation 300 MetresP Flue gas pressure 5 mmwc

Constituents of fuelFUEL Std husk

C Carbon 35.51 % by wt 38.5H Hydrogen 5.08 % by wt 3.7O Oxygen 34.55 % by wt 36.31S Sulphur 0.01 % by wt 0N Nitrogen 0.12 % by wt 0.46M Moisture 8.68 % by wt 8A Ash 16.06 % by wt 20

100.00GCV Gross GCV of fuel 3150.00 Kcal /kg 3200

INPUTS FOR EFFICIENCY CALCULATIONS

HLS1 Carbon loss ( calculated ) 1.36 %HLS6 Radiation loss ( assumed ) 1 %HLS7 Manufacturer margin (assumed ) 0.5 %

LocationsA1 % Ash collection at location 1 Bed 5 %A2 % Ash collection at location 2 Bank 5 %A3 % Ash collection at location 3 Economiser 5 %A4 % Ash collection at location 4 Airheater 5 %A5 % Ash collection at location 5 MDC 60 %A6 % Ash collection at location 6 Trema 20 %

100T1 Temperature of ash at location1 900 Deg CT2 Temperature of ash at location2 300 Deg CT3 Temperature of ash at location3 250 Deg CT4 Temperature of ash at location4 140 Deg CT5 Temperature of ash at location5 140 Deg CT6 Temperature of ash at location6 140 Deg C

INPUTS FOR BOILER DUTY CALCULATIONS

Steam generation rate Nett 15000 Kg/hMain steam pressure 64 kg/cm2 gMain steam temperature 490 Deg CFeed water inlet temperature 105 Deg CSuperheater Pressure drop 3 kg/cm2 gSaturated steam flow from drum 0 kg/h

Deepak spinners - 100% rice husk- as per lab report- underbed

Rice husk

EWS 604

Boiler efficiency Calculated 80.86Boiler efficiency 80.00 %

INPUTS FOR AIR,GAS DUCT,CHIMNEY SIZING CALCULATIONS

Flue gas ducting Gas tempBoiler bank outlet 350 Deg CEconomiser outlet 235 Deg CAirheater outlet 160 Deg CAir ducting Air tempAirheater outlet 150 Deg CDesign velocitiesDesign velocity in gas duct 14 m/sChimney design gas velocity 15 m/sDesign velocity in air duct 12 m/s

INPUTS FOR FAN SIZING CALCULATIONS

Design air velocity in fuel piping 16 m/s

No off compartments 2Total no of fuel feed points 7Fan sizing FD fan capacity (% MCR ) 100 %FD fan efficency 75 %ID fan capacity (% MCR) 100 %ID fan efficency 75 %PA fan capacity (% MCR ) 100 %PA fan efficiency 70 %

FD fan design head 750 mmwcPA fan design head 700 mmwcID fan design head 370 mmwc Margin on FD fan flow 20 %Margin on PA fan flow 20 %Margin on ID fan flow 20 %

INPUTS FOR FLUIDISED BED SIZING CALCULATIONS

Design bed temperature = 850 Deg CFluidisation velocity = 2.6 m/s

INPUTS FOR DUST EMISSION CALCULATIONS

Percentage ash entering dust collector = 50 %Efficency of Dust collector = 99.5 %

EWS 604

COMBUSTION CALCULATIONS FOR FUEL PER KG BASIS Date & time: 12/30/12 7:50 AMPROJECT :

INPUTS FOR AIR & GAS CALCULATIONS Rice husk

Ta, Ambient temperature = 40 deg C P1, Relative humidity = 60 % Ma, Moisture in dry air = 0.02851 kg / kg

E, Excess air = 20 % Constituents of fuel ( % by weight )

C, Carbon = 35.505 % Carbon lost in ash = 0.53 %

carbon burnt = 34.975 % H, Hydrogen = 5.077 %

O, Oxygen = 34.546 % S, Sulphur = 0.009 %

N, Nitrogen = 0.119 % M, Moisture = 8.68 %

A, Ash = 16.063 %

Air requirement calculations

O2 reqd, kg/kg of Carbon in fuel = 2.644 kg/kg O2 reqd, kg/kg of Hydrogen in fuel = 7.937 kg/kg

O2 reqd, kg/kg of Sulphur in fuel = 0.998 kg/kg Solid crbon unburnt from Efficiency calc, = 0.0053 kg/kg

O2 reqd, for the Carbon in fuel =( 0.35505 - 0.0053)x2.644 /100) kg/kg = 0.925 kg/kg

O2 reqd, for the Hydrogen in fuel =( 7.937x5.077 /100) kg/kg = 0.403 kg/kg

O2 reqd, for the Sulphur in fuel =( 0.998x0.009 /100) kg/kg = 0.000 kg/kg

Stochiometric O2 reqd / kg of fuel = O2 reqd for C,H,S in fuel - O2 in fuel) kg/kg Stochiometric O2 reqd / kg of fuel = ( 0.925+0.403+0.000) -(34.546 / 100) kg/kg

= 0.98254 kg /kg of fuel Excess O2 required / kg of fuel = ( 0.98254x / 100 ) kg /kg of fuel

= ( 0.98254x 20 / 100 ) kg /kg of fuel = 0.196508 kg/kg

Total O2 required / kg of fuel = ( 0.98254+ 0.196508) kg/kg = 1.179048 kg/kg

Weight fraction of O2 in atmospheric air = 0.23 kg/kg Dry air required for Combustion, kg/kg of fuel =( 1.179048/ 0.23) kg/kg

= 5.126 kg/kg Due to relative Humidity, wet air reqd, kg/kg of fuel =( 1 + 0.02851) x 5.126) kg/kg

Wet air required, kg /kg of fuel fired = 5.272 kg/kg

Dry air required, kg /kg of fuel fired = 5.126 kg/kg


EWS 604

Gas weight constituents calculations

CO2 produced, kg/kg of Carbon in fuel = 3.644 kg/kg H2O produced, kg/kg of Hydrogen in fuel = 8.937 kg/kg

SO2 produced, kg/kg of Sulphur in fuel = 1.998 kg/kg

CO2 produced, for the Carbon in fuel =( 3.644x34.975 /100) kg/kg = 1.274 kg/kg

H2O produced, for the Hydrogen in fuel =( 8.937x5.077 /100) kg/kg = 0.454 kg/kg

H2O in combustion air = 0.02851x5.126 kg/kg = 0.146 kg/kg

H2O due to moisture in fuel = 8.68/100 kg/kg = 0.0868 kg/kg

H2O due to air & H2 combustion& fuel moisture =( 0.146+0.454+0.0868) kg/kg = 0.6868 kg/kg

SO2 produced, for the Sulphur in fuel =( 1.998x0.009 /100) kg/kg = 0.000 kg/kg

O2 in flue gas ( Excess O2 added ) = 0.196508 kg/kg

N21,Nitrogen due to fuel = N kg/kg = 0.00119 kg/kg

Weight fraction of Nitrogen in Dry Air = 0.77 kg/kg N22 due to Air, kg per kg of fuel = 0.77 x 5.126 kg/kg

= 3.947 kg/kg Total N2 in flue gas , kg/kg of fuel fired = N21+N22 kg/kg

= ( 0.00119+3.947) kg/kg = 3.94819 kg/kg of fuel

Qfgw, Total wet flue gas produced per kg of fuel fired = 1.274+0.6868+0.000+0.196508+3.94819 = 6.105498 kg/kg

Wet flue gas produced, kg /kg of fuel fired = 6.105 kg/kg

Qfgd, Total dry flue gas produced per kg of fuel fired = 1.274+0.000+0.196508+3.94819 = 5.419 kg/kg

Dry flue gas produced, kg /kg of fuel fired = 5.419 kg/kg

wet gas kg / kg of

fuel

Mol. weight

CO2 1.274 44.04H2O 0.687 18.02SO2 0.000 64.06O2 0.19651 32.00N2 3.94819 28.01

Total 6.1055 Total moles = 0.029+0.038+0.000+0.006+0.141=0.214

Mole.wt of flue gas = ((13.55x 44.01)+(17.76x 18.02)+(0.00x64.06)+(2.80x32)+(65.89x28.01)) / 100Mole.wt of flue gas = 28.52

100x1.274/6.105498=20.866 1.274/44.04 = 0.029 100x0.029/0.214=13.55100x0.038/0.214=17.76

Flue gas ( wet ) composition by % wt

Flue gas ( wet ) composition by % vol

No of moles / kg of fuel

Composition of Flue gas

100x0.6868/6.105498=11.249100x0.000/6.105498=0.000100x0.196508/6.105498=3.21

0.6868/18.02 = 0.038

100x3.94819/6.105498=64.66

100x0.000/0.214=0.00100x0.006/0.214=2.80100x0.141/0.214=65.89

0.000/64.06 = 0.0000.196508/32 = 0.0063.94819/28.01 = 0.141

EWS 604

Results Summary



Dry Flue gas produced, kg /kg of fuel fired = 5.419 kg/kg

Flue gas produced, kg /kg of fuel fired = 6.105 kg/kg

Flue gas composition summary

Wet by vol % Dry by vol%

Carbon di oxide = 13.55 % = 16.48 %

Water vapour = 17.76 % = 0 %

Sulfur di oxide = 0.00 % = 0.00 %

Oxygen = 2.80 % = 3.40 %

Nitrogen = 65.89 % = 80.12 %

EWS 604

DESIGN EFFICIENCY CALCULATIONS Date & time : 12/30/12 7:50 AM

PROJECT :


HLS1, assumed unburnt carbon loss = 1.36 %HLS6, Assumed radiation loss = 1 %

HLS7, Manufacturer margin = 0.5 % Ta, Ambient temperature = 40 deg C

Rh, Relative humidity = 60 % Ma, Moisture in dry air = 0.02851 kg / kg

E, Excess air = 20 % Te, Boiler outlet gas temperature = 160 Deg C

A1, % Ash collection at location 1 = 5 % BedA2, % Ash collection at location 2 = 5 % BankA3, % Ash collection at location 3 = 5 % EconomiserA4, % Ash collection at location 4 = 5 % AirheaterA5, % Ash collection at location 5 = 60 % MDCA6, % Ash collection at location 6 = 20 % Trema

T1, Temperature of ash at location1 = 900 deg C T2, Temperature of ash at location2 = 300 deg C T3, Temperature of ash at location3 = 250 deg C T4, Temperature of ash at location4 = 140 deg C T5, Temperature of ash at location5 = 140 deg C T6, Temperature of ash at location6 = 140 deg C

Constituents of fuel H, Hydrgen = 5.077 % M, Moisture = 8.68 %

A, Ash = 16.063 % GCV, Gross calorific value of fuel = 3150 kcal /kg

DESIGN EFFICENCY CALCULATIONS

Assumed heat loss through unburnt carbon in ash

Heat loss through unburnt carbon in furnace ashA, Ash content in fuel = 0.16063 kg/kg

M1, % ash collection in furnace hopper = 5 % 5

LOI in ash = 1 % Calorific value of carbon = 8050 kcal/kg

Fuel GCV = 3150 kcal/kgCarbon Loss =M1x A x LOI x 8050 / ((100-LOI) x 3150) %

=5 x 0.16063 x 1 x 8050 /( (100-1 ) x 3150) % HLS1-1, Unburnt carbon loss in furnace ash = 0.0207 %




EWS 604

LOI in ash = 3.5 % Calorific value of carbon = 8050 kcal/kg


=90 x 0.16063 x 3.5 x 8050 /( (100-3.5 ) x 3150) % HLS1-1, Unburnt carbon loss in furnace ash = 1.3400 %

HLS1, Total unburnt carbon loss = 1.36 % Solid carbon loss = 1.36x3150 / 8050 %

= 0.53 %

HLS1, Unburnt carbon loss = 1.36 % Calculations for Heat loss though ash

A, Ash content in fuel = 0.16063 kg/kg C, Specific heat of ash = 0.22 kcal/kg Deg C

HLn, % Heat lost through ash at n'th location = A x (An /100 ) x C x (Tn-Ta) x 100 / GCV

HL1, % Heat lost through ash at a location 1 = 0.16063x (5 / 100 ) x0.22x (900-40) x 100 / 3150 % HL1, % Heat lost through ash at a location 1 = 0.05 %






HLS2, Total Heat loss through the ash = HL1+HL2+HL3+HL4+HL5+HL6

= ( 0.05+0.01+0.01+ 0.01+0.07+0.02 )%

HLS2, Total Heat loss through the ash = 0.17 %

Calculations for Heat loss through moisture in air

Ww, wieght of water in air = 0.02851 kg/kg Wd, Dry air required per kg of fuel = 5.126 kg/kg from combustion calc

Cp1, specific heat of water vapor at boiler exit temp = 0.4872 kcal/kg CCp2, specific heat of water vapor at ambient temp = 1 kcal/kg C

Ta, Ambient temperature = 40 deg C Te, Boiler exit temperature = 160 deg C

EWS 604

HLS3, % Heat lost through moisture in air = Ww x Wd x{(Cp1x Te)-(Cp2 x Ta)}x100/(GCV) = 0.02851x5.126x[(0.4872x160)-(1x40]x100 /(3150)

HLS3, % Heat lost through moisture in air = 0.18 %

Calculations for Heat loss through moisture & hydrogen in fuel

H, hydrogen in fuel = 0.05077 kg/kg M, moisture in fuel = 0.0868 kg/kg

Cp1, Specific heat of water vapor at boiler exit temp = 0.4872 kcal/kg L, latent heat of water = 595.4 kcal/kg


HLS4, % Heat lost through moisture & H2 in fuel ={M+(8.94 x H)} x [595.4+(Cp1 x Te) -Ta] x 100 / (GCV)HLS4, % Heat lost through moisture & H2 in fuel

HLS4, % Heat lost through moisture & H2 in fuel = 10.87 %

Calculations for Heat loss through dry flue gas

Qfgd, Dry flue gas produced per kg of fuel = 5.419 kg/kg Cp3, specfic heat of flue gas at boiler exit temp = 0.243 kcal/kg deg C

Cp4, specfic heat of flue gas at ambient temp = 0.236 kcal/kg deg C Ta, Ambient temperature = 40 deg C

Te, Boiler exit temperature = 160 deg C HLS5, % Heat lost through dry flue gas =Qfgd x{ (Cp3 x Te) - (Cp4 x Ta)} x100/(GCV)

HLS5, % Heat lost through dry flue gas = 5.06 %

Assumed heat loss through radiation

HLS6, Radiation loss = 1 %

Manufacturer margin

HLS7, Manufacturer margin = 0.5 %

Total efficiency break up

HLS1, Unburnt carbon loss = 1.36 %


HLS3, Heat lost through moisture in air = 0.18 %

HLS4, Heat lost through moisture & H2 in fuel = 10.87 %

HLS5, Heat lost through dry flue gas = 5.06 %



Total losses = 1.36+0.17+0.18+10.87+5.06+1+0.5

= 19.14 %

Therefore, Boiler efficiency, = 100 - 19.14 %

Boiler Efficiency = 80.86 %

={ 0.0868+ (8.94 x 0.05077)}x [ 595.4+(0.4872x 160) -40]x100/(3150) %

=5.419x { ( 0.243 x 160) - (0.236x40)} x 100/(3150) %

EWS 604

BOILER HEAT DUTY CALCULATIONS Date & time: 12/30/12 7:50 AMPROJECT :


Steam generation rate Nett = 15000 Kg/hMain steam pressure = 64 kg/cm2 g

Main steam temperature = 490 Deg CFeed water inlet temperature = 105 Deg C

Superheater Pressure drop = 3 kg/cm2 gSaturated steam flow from drum = 0 kg/h

Selected boiler efficiency = 80 %

BOILER HEAT DUTY CALCULATIONS

Msup, Steam generation rate = 15000 kg / h P1, Main steam pressure = 64 kg/cm2 g

Ts, Main steam temperature = 490 deg C Tw, Feed water inlet temperature = 105 deg C

Hw, Feed water inlet enthalphy = 105 kcal / kg Hs, Main steam enthalpy = 810.47 kcal / kg

H, Heat added per kg of water = ( Hs - Hw ) = ( 810.47 - 105) kcal / kg

H, Heat added per kg of water = 705.47 kcal / kg Heat output of the boiler ( SH steam) = ( Msup x H) kcal / hr

= ( 15000 x 705.47) kcal / hr Qo Heat output of the boiler ( SH steam) = 10582050 kcal / h

Msat Saturated steam flow from drum = 0 kg / h Saturated steam enthalpy = 663.44 kcal/kg Heat output thorugh the sat. steam = 0x( 663.44-105) kcal/kg

Qs heat output of the boiler ( saturated steam) = 0 kcal/hr

Qt Total heat output of the boiler = Qo+Qs kcal/hr = ( 10582050 + 0 )kcal/hr

Qt Total heat output of the boiler = 10582050 kcal/hr

Calculated Boiler efficiency = 80.86 %Selected Boiler Efficiency = 80 %

Fuel GCV = 3150 kcal /kgFuel firing rate = Qt x 100 / ( Eff x GCV )

= 10582050 x 100 / ( 80 x 3150 ) % = 4,199 kg / hr

Results

Total heat output of the boiler = 10582050 kcal / hr

Calculated boiler efficiency = 80.86 %

Selected boiler efficency = 80%

Fuel firing rate = 4,199 kg / hr

Steam fuel ratio = 3.57 kg / kg


EWS 604

FAN SIZING CALCULATION Date & time:PROJECT :


Site elevation = 300 metresGas temp at Airheater outlet = 160 deg C

Air temp at Airheater air inlet = 40 deg CAirheater outlet = 150 deg C

Design air velocity in fuel piping = 16 m/s

Fan details No off compartments = 2No of PA lines per compartment = 7

FD fan capacity (% MCR ) = 100 %FD fan efficiency = 75 %

ID fan capacity (% MCR) = 100 %ID fan efficiency = 75 %

PA fan capacity (% MCR ) = 100 %PA fan efficiency = 70 %

FD fan design head = 750 mmwcPA fan design head = 700 mmwcID fan design head = 370 mmwc

Flue gas generated per kg of fuel = 6.105 kg/kgMolecular wt of flue gas = 28.52

Actual Fuel burnt rate = 4,199 kg/hWet air required per kg of fuel = 5.272 kg/kg

Margin on FD fan flow = 20 %Margin on PA fan flow = 20 %Margin on ID fan flow = 20 %

FAN SIZING CALCULATIONS

Calculations of volumetric gas flow rate

Wet flue gas produced per kg of fuel = 6.105 kg/kgFuel firing rate = 4,199 kg/h

Wet flue gas flow rate = 6.105 x 4,199 kg/h = 25634.895 kg/h

Molecular wt of flue gas = 28.52 from air & gas calcK, altitude correction factor = 0.965

Flue Gas volume flow rate at 0 deg C = 25634.895 x 22.4 / ( 28.52 x 0.965 ) = 20,864.25 Nm3 /hr

Flue Gas volume flow rate at 0 deg C = 5.80 Nm3 / sec

12/30/12 7:50 AMDeepak spinners - 100% rice husk- as per lab report- underbed

EWS 604

Boiler exit temperature, deg C = 160 Deg CGas flow at boiler exit temperature = ( 5.80x ( 273 + 160 ) / 273 )m3 /sec

= 9.20 m3 /sec

Calculations of volumetric Air flow rate

Wet air required per kg of fuel = 5.272 kg/kgFuel firing rate = 4,199 kg/h

Wet air flow rate = 5.272 x 4,199 kg/h = 22137.13 kg/h

Molecular wt of wet air = 28.50K, Altidue correction factor = 0.965

Wet air volume flow rate at 0 deg C = 22137.13 x 22.4 / ( 28.50 x 0.965) = 18,030.06 Nm3 /hr

Wet air volume flow rate at 0 deg C = 5.01 Nm3 / sec

Air temp at Airheater air inlet = 40 Deg C Hence, Volumetric Air flow rate = ( 5.80x ( 273 + 40 ) / 273 )m3 /sec

Volumetric air flow rate = 5.74 m3 /sec

Estimation of Fuel transport air flow

No of compartments = 2No fof fuel lines = 7

Fuel flow per line = ( 4,199 / 7) = 600Selected fuel line size, mm Nb, 100 / 125 / 150 = 150

Design air velocity in fuel piping = 16 m/sTotal Fuel air flow rate = 7 x 3.1416 x (150/2000)^2 x 16 m3/sTotal Fuel air flow rate = 1.979 m3/s


FD fan sizing

FD fan capacity (% MCR ) = 100 %MCR airflow required for combustion = 5.74 m3/s

MCR airflow of FD fan = ( 5.74x 100 / 100 ) m3/sMCR airflow of FD fan = 5.74 m3/sMargin on FD fan flow = 20 %

Design Flow for FD fan = 5.74 x ( 100 +20 ) / 100 m3/s = 6.89 m3/s

FD fan Design head = 750 mmwcAssumed FD fan efficiency = 75 %

FD fan operating power required = 100 x 6.89 x 750/ ( 101 x 75 ) kw = 68.2 kw

FD fan operating power BKW required = 100 x 5.74 x 750/ ( 101 x 75 ) kw = 56.8 kw

Minimum motor power required = 1.15 x 68.2 kwMinimum motor power required for FD fan = 78.4 kw

EWS 604

PA fan sizing

PA fan capacity (% MCR ) = 100 %MCR fuel transport airflow required = 1.979 m3/s

MCR airflow of PA fan = ( 1.979x 100 / 100 ) m3/sMCR airflow of PA fan = 1.979 m3/sMargin on PA fan flow = 20 %

Design Flow for PA fan = 1.979 x ( 100 +20 ) / 100 m3/s = 2.37 m3/s

PA fan Design head = 700 mmwcAssumed PA fan efficiency = 70 %

PA fan operating power required = 100 x 2.37 x 700/ ( 101 x 70 ) kw = 23.5 kw

PA fan operating power BKW required = 100 x 1.979 x 700/ ( 101 x 70 ) kw = 19.6 kw

Minimum motor power required = 1.15 x 23.5 kwMinimum motor power required for PA fan = 27.0 kw

ID fan sizing

ID fan capacity (% MCR ) = 100 %MCR gas flow produced = 9.20 m3/s MCR gas flow of ID fan = ( 9.20x 100 / 100 ) m3/sMCR gas flow of ID fan = 9.2 m3/s

Margin on ID fan flow = 20 %Design Flow for ID fan = 9.2 x ( 100 +20 ) / 100 m3/s

= 11.04 m3/sID fan Design head = 370 mmwc

Assumed ID fan efficiency = 75 %ID fan operating power required = 100 x 11.04 x 370/ ( 101 x 75 ) kw

= 53.9 kwID fan operating power BKW required = 100 x 20 x 370/ ( 101 x 75 ) kw

= 44.9 kwMinimum motor power required = 1.15 x 53.9 kw

Minimum motor power required for ID fan = 62.0 kw

Results summary

FD fan PA fan ID fan supply

m3/s 6.89 6.83 2.37 2.17 11.0 10.5

mmwc 750 750 700 700 370 370

Deg C 40 150 160

% 75 70 75

kw 68.2 23.5 53.9

kw 78.4 27.0 62.0

kw 90 90 30 30 75 75

Design flowDesign head

Design temperature

Selected motor Kw

Operating powerMin motor power

Assumed effciency

EWS 604

UNDER FED FLUIDISED BED SIZING Date & time : 12/30/12 7:55 AM

PROJECT :

INPUTS FOR FLUIDISED BED SIZING

Vf, Fluidisation velocity = 2.6 m/s Tb, Design bed temperature = 850 Deg C

Steam generated nett = 15000 kg/hMain steam temperature = 490 Deg C

Main steam pressure = 64 kg/cm2 aFuel burnt rate = 4,199 kg/h

Wet air required, kg /kg of fuel fired = 5.272 kg/kg Flue gas produced, kg /kg of fuel fired = 6.105 kg/kg

Flue gas molecular weight = 28.52Te, Boiler exit temperature = 160 Deg C

Tca, Combustion air temperature = 150 Deg C Ta, Ambient temperature = 40 Deg C

Assumed carbon loss = 1.36 % Ts, Saturation temperature = 283.9 deg C

Constituents of fuel H, Hydrgen = 2.484 % M, Moisture = 8 %

A, Ash = 46.65 % GCV, Gross calorific value of fuel = 3515.42 kcal /kg

UNDERBED FLUIDISED BED SIZING

Calculations for bed cross sectional area




Flue Gas volume flow rate at 0 deg C = 25634.895 x 22.4 / 28.52 x 0.965= 20,864.25 Nm3 /hr


Design bed temperature = 850 Deg CGas flow at bed temperature = ( 5.80x ( 273 + 850 ) / 273 )m3 /sec

= 23.86 m3 /sec

Factor for over bed combustion = 1

Vf, Fluidisation velocity = 2.6 m/s Therefore, bed cross sectional area = 23.86 x 1 / 2.6

Bed cross sectional area required = 9.18 m2


EWS 604

bed length = 2950 m

bed width = 2950 m

Bed cross sectional area available = 8.7 m2

Therefore, corrected fluidisation velocity = 2.6x9.18 / 8.7 = 2.74 m/s

Calculations for bed heat transfer area

Unburnt carbon loss

HL1, % design Unburnt carbon loss = 3.5 %

Calculations for Heat loss though ash


Ta, Ambient temperature = 40 deg C Tb, Design bed temperature = 850 deg C

HL2, % Heat lost through ash = A x C x (Tb-Ta) x 100 / GCV = 0.4665x 0.22x (850-40) x 100 / 3515.42 %

HL2, % Heat lost through ash = 2.36 %


Ww, weight of water in air = 0.02851 kg/kg Wd, Dry air required per kg of fuel = 5.126 kg/kg from combustion calc

Cp1, specific heat of water vapor at bed temp = 0.5685 kcal/kg CCp2, specific heat of water vapor at ambient temp = 0.3592 kcal/kg C

Tca, Combustion air temperature = 150 deg C Tb, Design bed temperature = 850 deg C

HL3, % Heat lost through moisture in air = Ww x Wd x {(Cp1 x Tb) -(Cp2 x Tca)}x 100 / GCV = 0.02851x5.126x[(0.5685x850)-(0.3592x150]x100 /351

HL3, % Heat lost through moisture in air = 1.78 %



Cpb, Specific heat of water vapor at bed temp = 0.5685 kcal/kg L, latent heat of water = 595.4 kcal/kg


HL4, % Heat lost through moisture & H2 in fuel ={M+(8.94 x H)} x [595.4+(Cpb x Tb) -Ta] x 100 / GCVHL4, % Heat lost through moisture & H2 in fuel

HL4, % Heat lost through moisture & H2 in fuel = 8.92 %


Qfgd, Dry flue gas produced per kg of fuel = 5.419 kg/kg

={ 0.08+ (8.94 x 0.02484)}x [ 595.4+(0.5685x 850) -40]x100/3515.42 %

EWS 604

Cpb, specific heat of flue gas at bed temp = 0.285478044013218 kcal/kg deg C Cpa, specific heat of flue gas at Tca = 0.242431854976819 kcal/kg deg C

Tb, Design bed temperature = 850 deg C Tca, Combustion air temperature = 150 deg C

HL5, % Heat lost through dry flue gas =Qfgd x{ (Cp1 x Tb) - (Cp2 x Tca)} x 100 / GCV

HL5, % Heat lost through dry flue gas = 31.80 %

Calculation for Heat loss through radiation to waterwall

Ab, Bed cross sectional area = 8.7 m2e, Emissivity of waterwall surface = 0.9

S, Steafan boltzmann constant = 4.9 x 10 ^ -8 Tb, bed temperature = 850 Deg C

Ts, saturation temperature = 283.921318253176 Deg C

Radiation heat loss to waterwall =Ab x e x S x {( Tb + 273 )^4 - ( Ts + 273 )^4}= 8.7x0.9x4.9 x 10^-8x{( 850+273)^4-(283.9213182531 = 573,297 kcal/h

Fuel heat input in the bed = 4,199x 3515.42= 14761248.58 kcal/hHL6, % Radiation loss to waterwall = 100x 573,297/ 14761248.58HL6, % Radiation loss to waterwall = 3.88 %

Bed heat balance & HTA required

HL1, Unburnt carbon loss = 3.5 % HL2, Total Heat loss through the ash = 2.36 % HL3, Heat lost through moisture in air = 1.78 %

HL4, Heat lost through moisture & H2 in fuel = 8.92 % HL5, Heat lost through dry flue gas = 31.80 % HL6, % Radiation loss to waterwall = 3.88 %

Total losses = 3.5+2.36+1.78+8.92+31.80+3.88 = 52.24 %

Therefore, % heat to be transferred to Bed coil = 100 - 52.24 % % Heat transferred to Bed coil = 47.76 %

Fuel heat input in the bed = 14761248.58 kcal/hActual heat to be transferred to Bed coil = 47.76 x 14761248.58/ 100

= 7,049,972 kcal/hTb, bed temperature = 850 Deg C

Ts, Saturation temperature = 283.9 Deg CTemperature difference = (850 - 283.9)= 566.1 deg C

Heat transfer coeff = 220 kcal / kg m2 Deg CBed coil area required = 7,049,972/ ( 220 x 566.1)

Bed Coil HT area required, if plain = 56.61 m2free board combustion = 20 %

Then, Bed Coil HT area with free board combn = 45.288 m2

=5.419x { ( 0.285478044013218 x 850) -

EWS 604

Bed Coil length required = 45.288/ ( 3.1416 x 0. 051) = 282.6592 m

Bed coil required after considering stud effect = 226.12736 mChecking the available bed area

Bed coil length per coil- type 1 = 2633 mmNo off bed coils- type 1 = 36 No

Bed coil length per coil- type 2 = 2068 mmNo off bed coils-type 2 = 36 No

Total eff length of bed coil = 169.236 mTotal length of bed coil with studs = 236.9304 m

Furnace residence time

Furnace volume as existing = 52.456 m3Flue gas quantity at furnace temperature = 23.86 m/s

Furnace residence time = 52.456 / 23.86 = 2.2 sec

Summary of results



Bed Coil length required = 226.12736 m

Bed Coil length available = 236.9304 m

Fluidisation velocity = 2.74 m/s

Furnace residence time = 2.2 sec

EWS 604

PROJECT :

INPUTS FOR DP NOZZLE SIZING CALCULATIONS

Air temp at Airheater air inlet = 40 deg CAirheater air outlet = 150 deg C

No off compartments = 2No of PA lines per compartment = 7

Bed cross sectional area available = 8.7 m2Volumetric air flow rate = 5.01 Nm3/s

Fuel transport air flow = 1.979 m3/s

Air nozzle hole size 5 mmNo of hole per nozzle 9

fuel Line size 150 nbEquiv no of nozzles per fuel feed point 0

No of air nozzles selected 641Selected distributor plate length 2950 mmSelected distributor plate width 2950 mm

Calculations of volumetric Air flow rate and air densities

Total airflow at 0 deg C = 5.01 Nm3 / sTa, ambient temperature = 40 deg C

V 40, Total airflow at ambient temperature = 5.01x ( 273 +40 ) / 273 V 40, Total airflow at ambient temperature = 5.744 m3/s

Air temp at Airheater air outlet = 150 Deg C

V 150, Total airflow after airheating = 5.01x ( 273 +150 ) / 273 V 150, Total airflow at after airheating = 7.763 m3/s

Air nozzle hole diameter = 5No of holes per air nozzle = 9

Flow area per nozzle = 9 x 3.1416 x (5/ 2000 )^2 = 0.00018 m2

D0, Density of air at 0 deg C with elevation corr. = 1.233D1, Density of air at 40 deg C = 273 x 1.233/ (273 +40)

= 1.075 kg/m3 D2, Density of air at 150 deg C = 273 x 1.233/ (273 +150)

= 0.796 kg/m3Pressure drop in distributor plate during MCR flow condition

V 150, Total airflow at after airheating = 7.763 m3/sSa + spreader % = 10 %

= 0.7763 m3/sPA flow = 1.979 m3/s

MCR air flow through DP at hot condn = 7.763 - 0.7763 - 1.979


Design by:Name:

Sign:

Approved by:Name:

Sign:

EWS 604

= 5.0077 m3/sCd, Coefficient of discharge = 0.7

Actual No of air nozzles = 641Air velocity through a nozzle hole = 5.0077/ (641x0.00018)

= 44.21 m/sPressure drop at MCR condition = 0.796 x 44.21^2 / ( 2 x 9.81 x 0.7^ 2)Pressure drop at MCR condition = 162 mmwc

Pressure drop during MFC ( minimum fluidisation condition )

Selected distributor plate length = 2950Selected distributor plate width = 2950 mm

Actual Distributor plate area provided = 2950 x 2950/ 1000000 = 8.7025 m2

Minimum fluidisation velocity at cold condition = 0.7 m/sMinimum fluidisation airflow = 0.7 x 8.7025

= 6.09175 m3/sDensity of air at ambient condition = 1.075 kg/m3

No off nozzles provided = 641Flow area per nozzle = 0.00018

Velocity through air nozzle hole = 6.09175 / ( 641x0.00018) = 54 m/s

Pressure drop at Min fluidisation condition = 1.075 x 54^2 / ( 2 x 9.81 x0.77^2) = 326 mmwc

Results summary

No off nozzles provided = 641

Selected distributor plate width = 2950 mm

Selected distributor plate length = 2950 mm

Pressure drop at MCR condition = 162 mmwc

Pressure drop at Min fluidisation condition = 326 mmwc

Design by:Name:

Sign:

Approved by:Name:

Sign:

ANNEXURE 6 – OPEN HOPPER DESIGN FOR AGRO FUELS

Photo 1: Open hopper design supplied by Thermax for high ah coal.

Photo 2: Typical FBC boiler with sparger nozzle system.

OPEN HOPPER FBC COMBUSTOR INSTALLATION BY THERMAX AT JOCIL, GUNTUR

JOCIL is a subsidiary of Andhra Sugars, thatmanufactures fatty acids, glycerin and toiletsoap. They sell their product to HLL, Godrej andmany other OEMs. Their process requires steam.By 1999, they already had a retrofit FBC boilerby Thermax and one 10 TPH FBC boiler.However to cut down the power bill they wereputting up a 6 MW power plant. The new boilerbeing bought was to be used for the process aswell as power generation.An Engineering InnovationAlso, JOCIL was looking for a strategic solutionfor its supply problems - the quality of coalavailable was poor and the other time-testedbiomass fuels like bagasse and rice husk were

available only for 6 to 8 months in a year. At thisjuncture, TBW suggested the use of Julia Flora (awild weed available near the plant in abundancethroughout the year) as a fuel and innovated asolution comprising of boilers that use newbiomass fuels such as Julia Flora, chilli stalks,cotton stalks apart from rice husk and coal.In 1999, TBW were awarded the order for theDesign, Manufacturing, Packing & Forwarding,Inspection, supervision of erection, commissioning& Testing of 1 X 30 TPH/ 66ata/ 4850C BiomassFired Boiler & accessories. In effect, JOCILbecame the first Cogen power plant in India, thatused multiple biomass as fuel.

Hopper Bottom FluidizedBed Biomass Boiler

Jocil, Guntur

Installation

The boiler is a balanced draft, bi-drum, bottom supported, withrefractory enclosure for the lower combuster and water wallpanel for the upper combuster. The unit operates on the naturalcirculation principle. The bed temperature is control by extractingheat by the inbed evaporator tubes. The inbed tubes areprovided with pin studding, to improve the life of tubes.The entire super heater is located in the convection pass in thefree board. The super heater is arranged in two stages with aninterstage direct contact spray attemperator. The water is tappedoff from the boiler feed line. In the last stage of the heat recovery,plain tube economiser and vertical tubular air preheater areprovided to get a back end temperature of 140 -1500 C.The combuster, called Hopper Bottom design, and Bed design isspecial and unique in that the stone that come along with the

Thermax Babcock & Wilcox LimitedD - 1 Block, Plot No. - 7/2, M. I. D. C.Chinchwad, Pune - 411019.Tel: 91-20-4126464http://www.tbwindia.com

Technical DataBoiler output : 30 TPHSteam pressure : 66 ataSteam temperature : 485 + 5 oCSteam temperature : 60-100% MCRcontrol rangeFeed water temperature : 105 oCFuelsMain : Rice Husk, Cotton Stalk,Chilly StalkAuxiliary : Coal,De-oiled BranSupport fuel : CoalStart-up fuel : Charcoal

Firing equipment : Bubbling fluid-bed with overBed feed and Hopper Bottomdesign.Type of feedersBio mass � screw feeder with pneumatic distributorsCoal � drag chain with mechanical spreaderParticulate emission control equipment � ElectroStaticPrecipitatorPerformance guaranteesThermal efficiency : 82 + 2 % on rice husk83.8 + 1.5 % on coalParticulate emission: 115 mg/Nm3 max.

Rice Husk and agglomerates formed due to the combustion ofhigh alkali fuels are removed effectively with the least amount ofeffort and wastage of bed material. The conventional bubblingbed has the bed plate and air nozzles mounted on that, whereasthe Hopper Bottom design has air nozzles mounted on air pipeslocated inside the hopper. This arrangement helps in removal ofsettled solids and agglomerates effectively and without the needto stop the boiler to clean the bed from time to time. Thesecondary air ports are located at two levels and has theflexibility to vary the quantity depending upon the type of fuelfired.The running of the unit has shown that the boiler has met andexceeded the original expectations of the customer and hasdemonstrated the capability to burn high alkali fuels andhandle stones and agglomerates.

LITERATURE ON OPEN HOPPER FBC COMBUSTOR

Bubbling Fluidized Bed BoilersBubbling Fluidized Bed Boilers

Experience and ResearchFor more than 130 years, industries worldwide have benefitedfrom Babcock & Wilcox’s (B&W) engineering, manufacturingtechnology and operating experience as a major supplier ofsteam generating equipment.

B&W’s involvement in fluid beds dates back to the 1950s andthe first combustor at its Alliance, Ohio, U.S.A. research center.A technical cooperation agreement gives B&W combined globalexperience of 34 units with more than 200 cumulative yearsoperating data. B&W’s fluid bed combustion facilities are helpingthe world realize the promise of clean energy from a widevariety of fuels.

B&W continues as a leader in the power generation industrywith its bubbling fluidized bed (BFB) boiler.

100 Percent Open Bottom Bed Drain SystemFluidized beds must have a system to remove oversized or foreign bed materialwhile the boiler is in operation. B&W uses the original open bottom design.Fluidizing air bubble caps and pipes are mounted on widely spaced air distributionducts. Ample pipe spacing allows total draining from the entire bed area. Thisdesign effectively removes rocks and debris that enter the furnace with the fuelwhich would otherwise hinder good combustion.

The open bottom design minimizes the bed drain rate required for a given fuel.The bed material is removed in small quantities and can take days to reach thehopper outlet. This gives the material sufficient time to cool and eliminates theneed for water-cooled screw conveyors, saving capital and maintenance costs.The material is cool enough that the hoppers are not insulated. Significant savingsare also realized as the small amount of material removed from the bed minimizeslandfilling or disposal costs.

As the supplier of the original open bottom design, B&W has drawn from fourdecades of fluid bed experience.

DomeValve

MaintenanceSlide Gate

Header

Air Duct

Fuel Feed

Bubble Caps

Table

B&W’s Bubbling Fluidized Bed (BFB) Technology

B&W’s open bottom bed provides a clear pathfor effective removal of oversized or foreignbed material.

Batchingvalves regulatematerial flowat the hopperdischarge.

Fluidizing air inlet bubble caps are mounted onair distribution ducts arranged to allow totaldraining capability from the entire bed area.

B&W was the first inNorth America to offerthe open bottom BFBdesign. Our 100 percentopen bottom designresults in completedebris removal withlower capital costs andmaintenance expenses.

14

12

10

8

6

4

2

01980 1981 - 1984 1985 - 1988 1989 - 1992 1993 - 1998

Through a technical cooperation agreement, B&W has steadilyincreased its global experience base.

Fluidized Bed Boiler Installed Units

Num

ber o

f Uni

ts

Top or Bottom Boiler Support SystemsB&W can supply either top supported or bottom supported BFB units,depending on the desired size. Regardless of boiler supportarrangement, the hopper system is always bottom supported, reducingcapital.

B&W’s bottom supported hopper design isolates the bubbling bedfoundation and steel from the boiler steel. For top supported units,this feature isolates the additional load of the bubbling bed and sandfrom the boiler and eliminates modifications to boiler support steel.

Bottom supporting the bubbling bed also reduces potential mechanicalstresses between water cooled and non-cooled components, providinglong term reliability and reduced maintenance costs.

Other Design BenefitsB&W’s BFB furnace walls are constructed entirely of water cooled, gas tight, membranedtubes. This eliminates the maintenance problems associated with the use of thick refractory.

For top supported boilers, a flexible expansion joint is providedbetween the boiler and bottom supported bed hoppers.

The fuel feeding system consists of windswept spouts with no movingparts coming in contact with the fuel. This simple design eliminatesthe potential damage caused by debris, and is considered a distinctadvantage compared to a mechanical feeder. Fuel is introduced tothe furnace by natural downward forces. A blanket of high pressureair sweeps the bottom of the spout and spreads the fuel evenly onthe bubbling bed surface. The spout is equipped with a rotating airdamper to vary air flow (and thus fuel trajectory) over a timed cycle.This feature, along with an angled, adjustable spout bottom plate,enhances fuel distribution.

B&W’s underbed ash removal system consistsof bottom supported hoppers which isolatesthe bubbling bed foundation and steel fromthe boiler steel. This design is considered anadvantage, particularly when retrofitting anexisting top supported unit to a BFB.

At this mill, B&W replaced two stoker-fired boilers with a BFB unitdirectly into the existing boiler bay, minimizing structural modifications.

Windswept spoutsare considered adesign advantagecompared to amechanical fuelfeeder because oftheir simpledesign.

Features Benefits and Operating ResultsFeatures Benefits and Operating Results

Controlled BedTemperature

• Staged air and low combustion temperatures limit NOx emissions• Prevents bed overheating

Simple Construction • Low maintenance due to a lack of moving parts

High Bed Turbulence • High combustion efficiency via prolonged solids-to-gas contact• Excellent fuel and air mixing for low unburned carbon losses without ash reinjection

Combustion Air System • Completes combustion in a staged manner• Low CO emissions• Low NOx emissions• Low VOC emissions

Expansion Joint • Allows for differential expansion of bed hoppers and boiler

100 Percent Open Bottom • Clear vertical path eliminates debris without creating dead zones in the fluid bed• Even air distribution and bubble cap reliability• Low sand removal

Fuel Flexibility • Bark and woodwastes• Paper mill and sewage sludges• Most high moisture fuels

• tire derived fuel• oil or natural gas• coal

Leading the way in bubbling fluidized bedtechnology, B&W combines experience, provendesigns and technical expertise to provide costeffective solutions for your steam generation needs.

Babcock & Wilcox

Reduce Your Capital and Operating Costs

• Are you considering a new process recovery boiler? Convert your old recovery boiler to a BFB power boiler at a significantly lower

cost than a new boiler. The large furnace and plan area of a recovery boiler are idealfor BFB technology and can provide a significant increase in steam production.

• Is your existing stoker-fired power boiler limited by the amount ofsludge it can burn?

Convert it to a BFB boiler at a lower cost than a new boiler. The BFB requiresabout the same plan area as the existing stoker.

• Do you want to burn less expensive waste fuels? A BFB is a reliable means to do so.

• Are your sludge disposal costs too high? A B&W open bottom BFB will minimize landfill needs.

Fuel FlexibilityB&W’s BFB boiler is uniquely suited for paper mill operations inboth new and retrofit applications. The strength of the BFB is itsability to efficiently burn a wide range of fuels such as wood wastesand sludges, in combination or alone. These fuels typically burncooler, and allow the required bed temperature to be maintainedwithout the use of an in-bed cooling surface. If desired, oil andnatural gas can be fired, as well as other fuels such as coal and tirederived fuel. Where waste fuels are being consumed to generatesteam, they often replace more expensive fuels, thus reducingoperating costs.

Environmental BenefitsSignificant environmental benefits are also achieved with BFBtechnology. The BFB produces relatively low levels of nitrogenoxides and carbon monoxide. With the addition of limestone, itcan remove high levels of sulfur dioxide without the expense of aflue gas scrubber. Also, landfill operations are greatly reduced inthose cases where mill byproducts can be consumed as fuel.

Process:Inert material, typically sand, and fuel form a bed in the bottom of the furnace which is suspended by a stream of upwardlyflowing fluidizing air. Fuel introduced to the bed is quickly volatilized. A significant amount of volatiles escape the bed andare burned in the freeboard area above the bed. The remaining volatiles and fixed carbon burn in the bed. To achieve efficientcombustion and low emissions, the bed temperature is controlled in the range of 1400 F to 1600 F (760 C to 871 C).

Design features:• top or bottom supported• one or two drum designs• proven effective in retrofit applications• provides an option to reduce SO2 and

NOx emissions• reduces sludge volume while

producing steam• superior to other technologies for

burning wet wood based fuels—between approximately 2800 and3500 Btu/lb HHV (6513 and 8141 kJ/kg)without support fuels

Steam pressure:to 2400 psig (165 bar gauge) throttle pressure

Superheater outlet temperatures:as required, up to 950 F (510 C)

Fuels:able to burn a wide range of conventionalfuels and waste fuels with high moisture,including:• wood wastes and bark• paper mill sludges• recycled paper facility sludges• sewage sludge• tire derived fuel• oil and natural gas• coal

Specifications

B&W’s BFB boiler for this customer significantly reduced the amountof mill sludge which needed to be landfilled. The boiler producesadditional steam to feed the plant’s existing system while meetingstringent emissions requirements.

Limestone, Sludgeand Wood

Fuel Mixing Screw

Superheater

MeteringBin

Rotary Airlocks

Overfire AirSystem

Burners

Fuel Spouts

Fluidized Bed

AshConveyors

Economizer

GeneratingBank

TubularAir Heater

ForcedDraft Fan

Gas

Air

Steam CoilAirheater

Silencer

Attemperator

AirGasWater

SteamFuelBed Material

Whether a new BFB boiler, or a conversion of your recovery or stoker-fired powerboiler, fluidized bed combustion offers significant operational advantages:

• fuel flexibility• high efficiency• low environmental emissions• reduced capital costs and operating expenses

Why B&W’s fluidized bed technology?• the original completely open bottom design has proven advantages• extensive research and development of fluid bed combustion• operating experience with a wide range of unit sizes and high moisture fuels

B&W offers quality and commitment to service• innovative design and technical expertise to increase production,

optimize equipment, and lower costs• capability, experience and track record to ensure your project

will progress on schedule and reach performance targets• a tradition of excellence since 1867

From engineering anddesign through constructionand start-up, B&W providestotal support for yourcomplete BFB project.

E101-3161 5MR9B

While others may use the Babcock name, we are the original Babcock & Wilcox with more than 130 years of experience inengineering, constructing and servicing steam generating systems. Insist on us by name.

For more information, or a complete listing of our sales and service offices worldwide, call 1-800-BABCOCK (222-2625)in North America. Outside North America, call (330) 753-4511 or fax (330) 860-1886 (Barberton, Ohio, USA). Or access ourWeb site at http://www.babcock.com.

Canada:Cambridge, OntarioEdmonton, AlbertaMontreal, QuebecSaint John, New BrunswickVancouver (Richmond), British Columbia

Egypt: CairoIndia: PuneIndonesia: JakartaMexico: Mexico CityPeople’s Republic of China: BeijingSingapore: SingaporeTaiwan: TaipeiTurkey: Ankara

United States of America:Atlanta, GeorgiaBarberton, OhioCharlotte, North CarolinaChicago (Downers Grove), IllinoisCincinnati, OhioDallas, TexasDenver (Sheridan), ColoradoFairfield, New JerseyHouston, TexasKansas City, MissouriMt. Holly, New JerseySan Francisco (Napa), CaliforniaSt. Petersburg, Florida

Powering the World Through Teamwork and InnovationSM

© 1999 The Babcock & Wilcox Company. All rights reserved.

The information contained herein is provided for general information purposes only and is not intended orto be construed as a warranty, an offer, or any representation of contractual or other legal responsibility.

Powering the World Through Teamwork and Innovation is a service mark of The Babcock & Wilcox Company.

ANNEXURE 7- COMBUSTOR DESIGN CALCULATIONS FOR 100% RICE HUSK FIRING BY OVERBED

EWS 604

PROJECT : INPUTS FOR COMBUSTION CALCULATIONSAIR & GAS CALCULATIONS

Ta Ambient temperature 40 Deg CP1 Relative humidity 60 %Ma Moisture in dry air ( from tables) 0.02851 kg/kgE Excess air 35 %Te Boiler outlet gas temperature 165 Deg CEl Site elevation 300 MetresP Flue gas pressure 5 mmwc

Constituents of fuelFUEL Std husk

C Carbon 35.51 % by wt 38.5H Hydrogen 5.08 % by wt 3.7O Oxygen 34.55 % by wt 36.31S Sulphur 0.01 % by wt 0N Nitrogen 0.12 % by wt 0.46M Moisture 8.68 % by wt 8A Ash 16.06 % by wt 20

100.00GCV Gross GCV of fuel 3150.00 Kcal /kg 3200


HLS1 Carbon loss ( calculated ) 1.36 %HLS6 Radiation loss ( assumed ) 1 %HLS7 Manufacturer margin (assumed ) 0.5 %

LocationsA1 % Ash collection at location 1 Bed 5 %A2 % Ash collection at location 2 Bank 5 %A3 % Ash collection at location 3 Economiser 5 %A4 % Ash collection at location 4 Airheater 5 %A5 % Ash collection at location 5 MDC 60 %A6 % Ash collection at location 6 Trema 20 %

100T1 Temperature of ash at location1 900 Deg CT2 Temperature of ash at location2 300 Deg CT3 Temperature of ash at location3 250 Deg CT4 Temperature of ash at location4 140 Deg CT5 Temperature of ash at location5 140 Deg CT6 Temperature of ash at location6 140 Deg C


Steam generation rate Nett 15000 Kg/hMain steam pressure 64 kg/cm2 gMain steam temperature 490 Deg CFeed water inlet temperature 105 Deg CSuperheater Pressure drop 3 kg/cm2 gSaturated steam flow from drum 0 kg/h

Deepak spinners - 100% rice husk- as per lab report- OVERBED

Rice husk

EWS 604

Boiler efficiency Calculated 79.95Boiler efficiency 79.00 %

INPUTS FOR AIR,GAS DUCT,CHIMNEY SIZING CALCULATIONS

Flue gas ducting Gas tempBoiler bank outlet 350 Deg CEconomiser outlet 235 Deg CAirheater outlet 160 Deg CAir ducting Air tempAirheater outlet 150 Deg CDesign velocitiesDesign velocity in gas duct 14 m/sChimney design gas velocity 15 m/sDesign velocity in air duct 12 m/s


Design air velocity in fuel piping 16 m/s

No off compartments 2Total no of fuel feed points 0Fan sizing FD fan capacity (% MCR ) 100 %FD fan efficency 75 %ID fan capacity (% MCR) 100 %ID fan efficency 75 %

FD fan design head 750 mmwcID fan design head 370 mmwc Margin on FD fan flow 20 %Margin on PA fan flow 20 %Margin on ID fan flow 20 %

INPUTS FOR FLUIDISED BED SIZING CALCULATIONS

Design bed temperature = 850 Deg CFluidisation velocity = 2.6 m/s

INPUTS FOR DUST EMISSION CALCULATIONS

Percentage ash entering dust collector = 50 %Efficency of Dust collector = 99.5 %

EWS 604

COMBUSTION CALCULATIONS FOR FUEL PER KG BASIS Date & time: 12/30/12 8:20 AMPROJECT :

INPUTS FOR AIR & GAS CALCULATIONS Rice husk

Ta, Ambient temperature = 40 deg C P1, Relative humidity = 60 % Ma, Moisture in dry air = 0.02851 kg / kg

E, Excess air = 35 % Constituents of fuel ( % by weight )

C, Carbon = 35.505 % Carbon lost in ash = 0.53 %

carbon burnt = 34.975 % H, Hydrogen = 5.077 %

O, Oxygen = 34.546 % S, Sulphur = 0.009 %

N, Nitrogen = 0.119 % M, Moisture = 8.68 %

A, Ash = 16.063 %

Air requirement calculations

O2 reqd, kg/kg of Carbon in fuel = 2.644 kg/kg O2 reqd, kg/kg of Hydrogen in fuel = 7.937 kg/kg

O2 reqd, kg/kg of Sulphur in fuel = 0.998 kg/kg Solid crbon unburnt from Efficiency calc, = 0.0053 kg/kg

O2 reqd, for the Carbon in fuel =( 0.35505 - 0.0053)x2.644 /100) kg/kg = 0.925 kg/kg

O2 reqd, for the Hydrogen in fuel =( 7.937x5.077 /100) kg/kg = 0.403 kg/kg

O2 reqd, for the Sulphur in fuel =( 0.998x0.009 /100) kg/kg = 0.000 kg/kg

Stochiometric O2 reqd / kg of fuel = O2 reqd for C,H,S in fuel - O2 in fuel) kg/kg Stochiometric O2 reqd / kg of fuel = ( 0.925+0.403+0.000) -(34.546 / 100) kg/kg

= 0.98254 kg /kg of fuel Excess O2 required / kg of fuel = ( 0.98254x / 100 ) kg /kg of fuel

= ( 0.98254x 35 / 100 ) kg /kg of fuel = 0.343889 kg/kg

Total O2 required / kg of fuel = ( 0.98254+ 0.343889) kg/kg = 1.326429 kg/kg

Weight fraction of O2 in atmospheric air = 0.23 kg/kg Dry air required for Combustion, kg/kg of fuel =( 1.326429/ 0.23) kg/kg

= 5.767 kg/kg Due to relative Humidity, wet air reqd, kg/kg of fuel =( 1 + 0.02851) x 5.767) kg/kg




EWS 604

Gas weight constituents calculations

CO2 produced, kg/kg of Carbon in fuel = 3.644 kg/kg H2O produced, kg/kg of Hydrogen in fuel = 8.937 kg/kg

SO2 produced, kg/kg of Sulphur in fuel = 1.998 kg/kg

CO2 produced, for the Carbon in fuel =( 3.644x34.975 /100) kg/kg = 1.274 kg/kg

H2O produced, for the Hydrogen in fuel =( 8.937x5.077 /100) kg/kg = 0.454 kg/kg

H2O in combustion air = 0.02851x5.767 kg/kg = 0.164 kg/kg

H2O due to moisture in fuel = 8.68/100 kg/kg = 0.0868 kg/kg

H2O due to air & H2 combustion& fuel moisture =( 0.164+0.454+0.0868) kg/kg = 0.7048 kg/kg

SO2 produced, for the Sulphur in fuel =( 1.998x0.009 /100) kg/kg = 0.000 kg/kg

O2 in flue gas ( Excess O2 added ) = 0.343889 kg/kg

N21,Nitrogen due to fuel = N kg/kg = 0.00119 kg/kg

Weight fraction of Nitrogen in Dry Air = 0.77 kg/kg N22 due to Air, kg per kg of fuel = 0.77 x 5.767 kg/kg

= 4.441 kg/kg Total N2 in flue gas , kg/kg of fuel fired = N21+N22 kg/kg

= ( 0.00119+4.441) kg/kg = 4.44219 kg/kg of fuel

Qfgw, Total wet flue gas produced per kg of fuel fired = 1.274+0.7048+0.000+0.343889+4.44219 = 6.764879 kg/kg

Wet flue gas produced, kg /kg of fuel fired = 6.765 kg/kg

Qfgd, Total dry flue gas produced per kg of fuel fired = 1.274+0.000+0.343889+4.44219 = 6.060 kg/kg

Dry flue gas produced, kg /kg of fuel fired = 6.060 kg/kg

wet gas kg / kg of

fuel

Mol. weight

CO2 1.274 44.04H2O 0.705 18.02SO2 0.000 64.06O2 0.34389 32.00N2 4.44219 28.01

Total 6.76488 Total moles = 0.029+0.039+0.000+0.011+0.159=0.238

Mole.wt of flue gas = ((12.18x 44.01)+(16.39x 18.02)+(0.00x64.06)+(4.62x32)+(66.81x28.01)) / 100Mole.wt of flue gas = 28.51

100x0.000/6.764879=0.000100x0.343889/6.764879=5.08

0.7048/18.02 = 0.039

100x4.44219/6.764879=65.66

100x0.000/0.238=0.00100x0.011/0.238=4.62100x0.159/0.238=66.81

0.000/64.06 = 0.0000.343889/32 = 0.0114.44219/28.01 = 0.159

100x1.274/6.764879=18.833 1.274/44.04 = 0.029 100x0.029/0.238=12.18100x0.039/0.238=16.39

Flue gas ( wet ) composition by % wt

Flue gas ( wet ) composition by % vol

No of moles / kg of fuel

Composition of Flue gas

100x0.7048/6.764879=10.419

EWS 604

Results Summary



Dry Flue gas produced, kg /kg of fuel fired = 6.060 kg/kg

Flue gas produced, kg /kg of fuel fired = 6.765 kg/kg

Flue gas composition summary

Wet by vol % Dry by vol%

Carbon di oxide = 12.18 % = 14.57 %

Water vapour = 16.39 % = 0 %

Sulfur di oxide = 0.00 % = 0.00 %

Oxygen = 4.62 % = 5.53 %

Nitrogen = 66.81 % = 79.91 %

EWS 604

DESIGN EFFICIENCY CALCULATIONS Date & time : 12/30/12 8:20 AM

PROJECT :


HLS1, assumed unburnt carbon loss = 1.36 %HLS6, Assumed radiation loss = 1 %

HLS7, Manufacturer margin = 0.5 % Ta, Ambient temperature = 40 deg C

Rh, Relative humidity = 60 % Ma, Moisture in dry air = 0.02851 kg / kg

E, Excess air = 35 % Te, Boiler outlet gas temperature = 165 Deg C

A1, % Ash collection at location 1 = 5 % BedA2, % Ash collection at location 2 = 5 % BankA3, % Ash collection at location 3 = 5 % EconomiserA4, % Ash collection at location 4 = 5 % AirheaterA5, % Ash collection at location 5 = 60 % MDCA6, % Ash collection at location 6 = 20 % Trema

T1, Temperature of ash at location1 = 900 deg C T2, Temperature of ash at location2 = 300 deg C T3, Temperature of ash at location3 = 250 deg C T4, Temperature of ash at location4 = 140 deg C T5, Temperature of ash at location5 = 140 deg C T6, Temperature of ash at location6 = 140 deg C

Constituents of fuel H, Hydrgen = 5.077 % M, Moisture = 8.68 %

A, Ash = 16.063 % GCV, Gross calorific value of fuel = 3150 kcal /kg

DESIGN EFFICENCY CALCULATIONS

Assumed heat loss through unburnt carbon in ash



LOI in ash = 1 % Calorific value of carbon = 8050 kcal/kg


=5 x 0.16063 x 1 x 8050 /( (100-1 ) x 3150) % HLS1-1, Unburnt carbon loss in furnace ash = 0.0207 %




EWS 604

LOI in ash = 3.5 % Calorific value of carbon = 8050 kcal/kg


=90 x 0.16063 x 3.5 x 8050 /( (100-3.5 ) x 3150) % HLS1-1, Unburnt carbon loss in furnace ash = 1.3400 %

HLS1, Total unburnt carbon loss = 1.36 % Solid carbon loss = 1.36x3150 / 8050 %

= 0.53 %

HLS1, Unburnt carbon loss = 1.36 % Calculations for Heat loss though ash


HLn, % Heat lost through ash at n'th location = A x (An /100 ) x C x (Tn-Ta) x 100 / GCV







HLS2, Total Heat loss through the ash = HL1+HL2+HL3+HL4+HL5+HL6

= ( 0.05+0.01+0.01+ 0.01+0.07+0.02 )%



Ww, wieght of water in air = 0.02851 kg/kg Wd, Dry air required per kg of fuel = 5.767 kg/kg from combustion calc

Cp1, specific heat of water vapor at boiler exit temp = 0.4853 kcal/kg CCp2, specific heat of water vapor at ambient temp = 1 kcal/kg C


EWS 604

HLS3, % Heat lost through moisture in air = Ww x Wd x{(Cp1x Te)-(Cp2 x Ta)}x100/(GCV) = 0.02851x5.767x[(0.4853x165)-(1x40]x100 /(3150)

HLS3, % Heat lost through moisture in air = 0.21 %



Cp1, Specific heat of water vapor at boiler exit temp = 0.4853 kcal/kg L, latent heat of water = 595.4 kcal/kg


HLS4, % Heat lost through moisture & H2 in fuel ={M+(8.94 x H)} x [595.4+(Cp1 x Te) -Ta] x 100 / (GCV)HLS4, % Heat lost through moisture & H2 in fuel

HLS4, % Heat lost through moisture & H2 in fuel = 10.91 %


Qfgd, Dry flue gas produced per kg of fuel = 6.060 kg/kg Cp3, specfic heat of flue gas at boiler exit temp = 0.243 kcal/kg deg C

Cp4, specfic heat of flue gas at ambient temp = 0.236 kcal/kg deg C Ta, Ambient temperature = 40 deg C

Te, Boiler exit temperature = 165 deg C HLS5, % Heat lost through dry flue gas =Qfgd x{ (Cp3 x Te) - (Cp4 x Ta)} x100/(GCV)

HLS5, % Heat lost through dry flue gas = 5.90 %

Assumed heat loss through radiation


Manufacturer margin


Total efficiency break up

HLS1, Unburnt carbon loss = 1.36 %


HLS3, Heat lost through moisture in air = 0.21 %

HLS4, Heat lost through moisture & H2 in fuel = 10.91 %

HLS5, Heat lost through dry flue gas = 5.90 %



Total losses = 1.36+0.17+0.21+10.91+5.90+1+0.5

= 20.05 %

Therefore, Boiler efficiency, = 100 - 20.05 %

Boiler Efficiency = 79.95 %

={ 0.0868+ (8.94 x 0.05077)}x [ 595.4+(0.4853x 165) -40]x100/(3150) %

=6.060x { ( 0.243 x 165) - (0.236x40)} x 100/(3150) %

EWS 604

BOILER HEAT DUTY CALCULATIONS Date & time: 12/30/12 8:20 AMPROJECT :


Steam generation rate Nett = 15000 Kg/hMain steam pressure = 64 kg/cm2 g

Main steam temperature = 490 Deg CFeed water inlet temperature = 105 Deg C

Superheater Pressure drop = 3 kg/cm2 gSaturated steam flow from drum = 0 kg/h

Selected boiler efficiency = 79 %

BOILER HEAT DUTY CALCULATIONS

Msup, Steam generation rate = 15000 kg / h P1, Main steam pressure = 64 kg/cm2 g

Ts, Main steam temperature = 490 deg C Tw, Feed water inlet temperature = 105 deg C

Hw, Feed water inlet enthalphy = 105 kcal / kg Hs, Main steam enthalpy = 810.47 kcal / kg

H, Heat added per kg of water = ( Hs - Hw ) = ( 810.47 - 105) kcal / kg

H, Heat added per kg of water = 705.47 kcal / kg Heat output of the boiler ( SH steam) = ( Msup x H) kcal / hr

= ( 15000 x 705.47) kcal / hr Qo Heat output of the boiler ( SH steam) = 10582050 kcal / h

Msat Saturated steam flow from drum = 0 kg / h Saturated steam enthalpy = 663.44 kcal/kg Heat output thorugh the sat. steam = 0x( 663.44-105) kcal/kg

Qs heat output of the boiler ( saturated steam) = 0 kcal/hr

Qt Total heat output of the boiler = Qo+Qs kcal/hr = ( 10582050 + 0 )kcal/hr

Qt Total heat output of the boiler = 10582050 kcal/hr

Calculated Boiler efficiency = 79.95 %Selected Boiler Efficiency = 79 %

Fuel GCV = 3150 kcal /kgFuel firing rate = Qt x 100 / ( Eff x GCV )

= 10582050 x 100 / ( 79 x 3150 ) % = 4,252 kg / hr

Results

Total heat output of the boiler = 10582050 kcal / hr

Calculated boiler efficiency = 79.95 %

Selected boiler efficency = 79%

Fuel firing rate = 4,252 kg / hr

Steam fuel ratio = 3.53 kg / kg


EWS 604

FAN SIZING CALCULATION Date & time:PROJECT :


Site elevation = 300 metresGas temp at Airheater outlet = 165 deg C

Air temp at Airheater air inlet = 40 deg CAirheater outlet = 150 deg C

Design air velocity in fuel piping = 16 m/s

Fan details No off compartments = 2No of PA lines per compartment = 0

FD fan capacity (% MCR ) = 100 %FD fan efficiency = 75 %

ID fan capacity (% MCR) = 100 %ID fan efficiency = 75 %

FD fan design head = 750 mmwcID fan design head = 370 mmwc

Flue gas generated per kg of fuel = 6.765 kg/kgMolecular wt of flue gas = 28.51

Actual Fuel burnt rate = 4,252 kg/hWet air required per kg of fuel = 5.931 kg/kg

Margin on FD fan flow = 20 %Margin on ID fan flow = 20 %


Calculations of volumetric gas flow rate




Flue Gas volume flow rate at 0 deg C = 28764.78 x 22.4 / ( 28.51 x 0.965 ) = 23,419.87 Nm3 /hr


Boiler exit temperature, deg C = 165 Deg CGas flow at boiler exit temperature = ( 6.51x ( 273 + 165 ) / 273 )m3 /sec

= 10.44 m3 /sec

12/30/12 8:20 AMDeepak spinners - 100% rice husk- as per lab report- OVERBED

EWS 604

Calculations of volumetric Air flow rate

Wet air required per kg of fuel = 5.931 kg/kgFuel firing rate = 4,252 kg/h

Wet air flow rate = 5.931 x 4,252 kg/h = 25218.61 kg/h

Molecular wt of wet air = 28.50K, Altidue correction factor = 0.965

Wet air volume flow rate at 0 deg C = 25218.61 x 22.4 / ( 28.50 x 0.965) = 20,539.84 Nm3 /hr

Wet air volume flow rate at 0 deg C = 5.71 Nm3 / sec

Air temp at Airheater air inlet = 40 Deg C Hence, Volumetric Air flow rate = ( 6.51x ( 273 + 40 ) / 273 )m3 /sec

Volumetric air flow rate = 6.55 m3 /sec


FD fan sizing

FD fan capacity (% MCR ) = 100 %MCR airflow required for combustion = 6.55 m3/s

MCR airflow of FD fan = ( 6.55x 100 / 100 ) m3/sMCR airflow of FD fan = 6.55 m3/sMargin on FD fan flow = 20 %

Design Flow for FD fan = 6.55 x ( 100 +20 ) / 100 m3/s = 7.86 m3/s

FD fan Design head = 750 mmwcAssumed FD fan efficiency = 75 %

FD fan operating power required = 100 x 7.86 x 750/ ( 101 x 75 ) kw = 77.8 kw

FD fan operating power BKW required = 100 x 6.55 x 750/ ( 101 x 75 ) kw = 64.9 kw

Minimum motor power required = 1.15 x 77.8 kwMinimum motor power required for FD fan = 89.5 kw

ID fan sizing

ID fan capacity (% MCR ) = 100 %MCR gas flow produced = 10.44 m3/s MCR gas flow of ID fan = ( 10.44x 100 / 100 ) m3/sMCR gas flow of ID fan = 10.44 m3/s

Margin on ID fan flow = 20 %Design Flow for ID fan = 10.44 x ( 100 +20 ) / 100 m3/s

= 12.528 m3/sID fan Design head = 370 mmwc

Assumed ID fan efficiency = 75 %ID fan operating power required = 100 x 12.528 x 370/ ( 101 x 75 ) kw

= 61.2 kw

EWS 604

ID fan operating power BKW required = 100 x 20 x 370/ ( 101 x 75 ) kw = 51.0 kw

Minimum motor power required = 1.15 x 61.2 kwMinimum motor power required for ID fan = 70.4 kw

Results summary

FD fan Supply ID fan supply

m3/s 7.86 6.83 12.5 10.5

mmwc 750 750 370 370

Deg C 40 165

% 75 75

kw 77.8 61.2

kw 89.5 70.4

kw 90 90 75 75

Design flowDesign head

Design temperature

Selected motor Kw

Operating powerMin motor power

Assumed effciency

EWS 604

UNDER FED FLUIDISED BED SIZING Date & time : 12/30/12 8:20 AM

PROJECT :

INPUTS FOR FLUIDISED BED SIZING

Vf, Fluidisation velocity = 2.6 m/s Tb, Design bed temperature = 850 Deg C

Steam generated nett = 15000 kg/hMain steam temperature = 490 Deg C

Main steam pressure = 64 kg/cm2 aFuel burnt rate = 4,252 kg/h

Wet air required, kg /kg of fuel fired = 5.931 kg/kg Flue gas produced, kg /kg of fuel fired = 6.765 kg/kg

Flue gas molecular weight = 28.51Te, Boiler exit temperature = 165 Deg C

Tca, Combustion air temperature = 150 Deg C Ta, Ambient temperature = 40 Deg C

Assumed carbon loss = 1.36 % Ts, Saturation temperature = 283.9 deg C

Constituents of fuel H, Hydrgen = 2.484 % M, Moisture = 8 %

A, Ash = 46.65 % GCV, Gross calorific value of fuel = 3515.42 kcal /kg

UNDERBED FLUIDISED BED SIZING

Calculations for bed cross sectional area




Flue Gas volume flow rate at 0 deg C = 28764.78 x 22.4 / 28.51 x 0.965= 23,419.87 Nm3 /hr


Design bed temperature = 850 Deg CGas flow at bed temperature = ( 6.51x ( 273 + 850 ) / 273 )m3 /sec

= 26.78 m3 /sec

Factor for over bed combustion = 0.9

Vf, Fluidisation velocity = 2.6 m/s Therefore, bed cross sectional area = 26.78 x 0.9 / 2.6



EWS 604

bed length = 3144.5 m

bed width = 3144.5 m


Therefore, corrected fluidisation velocity = 2.6x9.27 / 9.89 = 2.44 m/s

Calculations for bed heat transfer area

Unburnt carbon loss

HL1, % design Unburnt carbon loss = 3.5 %

Calculations for Heat loss though ash



HL2, % Heat lost through ash = A x C x (Tb-Ta) x 100 / GCV = 0.4665x 0.22x (850-40) x 100 / 3515.42 %

HL2, % Heat lost through ash = 2.36 %


Ww, weight of water in air = 0.02851 kg/kg Wd, Dry air required per kg of fuel = 5.767 kg/kg from combustion calc

Cp1, specific heat of water vapor at bed temp = 0.5685 kcal/kg CCp2, specific heat of water vapor at ambient temp = 0.3592 kcal/kg C

Tca, Combustion air temperature = 150 deg C Tb, Design bed temperature = 850 deg C

HL3, % Heat lost through moisture in air = Ww x Wd x {(Cp1 x Tb) -(Cp2 x Tca)}x 100 / GCV = 0.02851x5.767x[(0.5685x850)-(0.3592x150]x100 /351

HL3, % Heat lost through moisture in air = 2.01 %



Cpb, Specific heat of water vapor at bed temp = 0.5685 kcal/kg L, latent heat of water = 595.4 kcal/kg


HL4, % Heat lost through moisture & H2 in fuel ={M+(8.94 x H)} x [595.4+(Cpb x Tb) -Ta] x 100 / GCVHL4, % Heat lost through moisture & H2 in fuel

HL4, % Heat lost through moisture & H2 in fuel = 8.92 %


Qfgd, Dry flue gas produced per kg of fuel = 6.060 kg/kg

={ 0.08+ (8.94 x 0.02484)}x [ 595.4+(0.5685x 850) -40]x100/3515.42 %

EWS 604

Cpb, specific heat of flue gas at bed temp = 0.284594539902954 kcal/kg deg C Cpa, specific heat of flue gas at Tca = 0.242476289357631 kcal/kg deg C

Tb, Design bed temperature = 850 deg C Tca, Combustion air temperature = 150 deg C

HL5, % Heat lost through dry flue gas =Qfgd x{ (Cp1 x Tb) - (Cp2 x Tca)} x 100 / GCV

HL5, % Heat lost through dry flue gas = 35.43 %

Calculation for Heat loss through radiation to waterwall

Ab, Bed cross sectional area = 9.89 m2e, Emissivity of waterwall surface = 0.9

S, Steafan boltzmann constant = 4.9 x 10 ^ -8 Tb, bed temperature = 850 Deg C

Ts, saturation temperature = 283.921318253176 Deg C

Radiation heat loss to waterwall =Ab x e x S x {( Tb + 273 )^4 - ( Ts + 273 )^4}= 9.89x0.9x4.9 x 10^-8x{( 850+273)^4-(283.921318253 = 651,714 kcal/h

Fuel heat input in the bed = 4,252x 3515.42= 14947565.84 kcal/hHL6, % Radiation loss to waterwall = 100x 651,714/ 14947565.84HL6, % Radiation loss to waterwall = 4.36 %

Bed heat balance & HTA required

HL1, Unburnt carbon loss = 3.5 % HL2, Total Heat loss through the ash = 2.36 % HL3, Heat lost through moisture in air = 2.01 %

HL4, Heat lost through moisture & H2 in fuel = 8.92 % HL5, Heat lost through dry flue gas = 35.43 % HL6, % Radiation loss to waterwall = 4.36 %

Total losses = 3.5+2.36+2.01+8.92+35.43+4.36 = 56.58 %

Therefore, % heat to be transferred to Bed coil = 100 - 56.58 % % Heat transferred to Bed coil = 43.42 %

Fuel heat input in the bed = 14947565.84 kcal/hActual heat to be transferred to Bed coil = 43.42 x 14947565.84/ 100

= 6,490,233 kcal/hTb, bed temperature = 850 Deg C

Ts, Saturation temperature = 283.9 Deg CTemperature difference = (850 - 283.9)= 566.1 deg C

Heat transfer coeff = 220 kcal / kg m2 Deg CBed coil area required = 6,490,233/ ( 220 x 566.1)

Bed Coil HT area required, if plain = 52.11 m2free board combustion = 30 %

Then, Bed Coil HT area with free board combn = 36.477 m2

=6.060x { ( 0.284594539902954 x 850) -

EWS 604

Bed Coil length required = 36.477/ ( 3.1416 x 0. 0635) = 182.8502 m

Checking the available bed area

Bed coil length per coil- type 1 = 2673 mmNo off bed coils- type 1 = 22 No

Bed coil length per coil- type 2 = 1923 mmNo off bed coils-type 2 = 22 No

Total length of bed coil = 101.112 mTotal length of bed coil with studs = 101.112 x 1.4 m ( 1.4 effectiveness)

= 141.5568 mrearwall & front wall tube area with studs = 2 x 26 x .85 x 1.4 m ht

= 61.88 mTotal length tubes for heat transfer = 203.4368 m

Furnace residence time

Furnace volume as modified = 85.4 m3Flue gas quantity at furnace temperature = 26.78 m/s

Furnace residence time = 85.4 / 26.78 = 3.19 sec

Summary of results



Bed Coil length required = 182.8502 m

Bed Coil length available = 203.4368 m

Fluidisation velocity = 2.44 m/s

Furnace residence time = 3.19 sec

EWS 604

PROJECT :

INPUTS FOR DP NOZZLE SIZING CALCULATIONS

Air temp at Airheater air inlet = 40 deg CAirheater air outlet = 150 deg C

Bed cross sectional area available = 9.89 m2Volumetric air flow rate = 5.71 Nm3/s

Fuel transport air flow = 0.000 m3/s

Air nozzle hole size 3.4 mmNo of hole per nozzle 30

No of air nozzles selected 529Selected distributor plate length 3144.5 mmSelected distributor plate width 3144.5 mm

Calculations of volumetric Air flow rate and air densities

Total airflow at 0 deg C = 5.71 Nm3 / sTa, ambient temperature = 40 deg C

V 40, Total airflow at ambient temperature = 5.71x ( 273 +40 ) / 273 V 40, Total airflow at ambient temperature = 6.547 m3/s

Air temp at Airheater air outlet = 150 Deg C

V 150, Total airflow after airheating = 5.71x ( 273 +150 ) / 273 V 150, Total airflow at after airheating = 8.847 m3/s

Air nozzle hole diameter = 3.4No of holes per air nozzle = 30

Flow area per nozzle = 30 x 3.1416 x (3.4/ 2000 )^2 = 0.00027 m2

D0, Density of air at 0 deg C with elevation corr. = 1.233D1, Density of air at 40 deg C = 273 x 1.233/ (273 +40)

= 1.075 kg/m3 D2, Density of air at 150 deg C = 273 x 1.233/ (273 +150)

= 0.796 kg/m3Pressure drop in distributor plate during MCR flow condition

V 150, Total airflow at after airheating = 8.847 m3/sSa + spreader % = 25 %

= 2.21175 m3/sPA flow = 0 m3/s

MCR air flow through DP at hot condn = 8.847 - 2.21175 - 0 = 6.63525 m3/s

Cd, Coefficient of discharge = 0.7Actual No of air nozzles = 529

Air velocity through a nozzle hole = 6.63525/ (529x0.00027)


Design by:Name:

Sign:

Approved by:Name:

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EWS 604

= 46.05 m/sPressure drop at MCR condition = 0.796 x 46.05^2 / ( 2 x 9.81 x 0.7^ 2)Pressure drop at MCR condition = 176 mmwc

Pressure drop during MFC ( minimum fluidisation condition )

Selected distributor plate length = 3144.5Selected distributor plate width = 3144.5 mm

Actual Distributor plate area provided = 3144.5 x 3144.5/ 1000000 = 9.88788025 m2

Minimum fluidisation velocity at cold condition = 0.7 m/sMinimum fluidisation airflow = 0.7 x 9.88788025

= 6.921516175 m3/sDensity of air at ambient condition = 1.075 kg/m3

No off nozzles provided = 529Flow area per nozzle = 0.00027

Velocity through air nozzle hole = 6.921516175 / ( 529x0.00027) = 48 m/s

Pressure drop at Min fluidisation condition = 1.075 x 48^2 / ( 2 x 9.81 x0.77^2) = 258 mmwc

Results summary

No off nozzles provided = 529

Selected distributor plate width = 3144.5 mm

Selected distributor plate length = 3144.5 mm

Pressure drop at MCR condition = 176 mmwc

Pressure drop at Min fluidisation condition = 258 mmwc

Design by:Name:

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Approved by:Name:

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FAN DATA FROM PLANT

VIEWS OF BOILER WITH PROPOSED OPEN HOPPER COMBUSTOR MODIFICATIONS

Report on Boiler Modification for 100% Over bed Firing

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