Conversion of Furnace Oil Fired Boiler to Briquette Fired ...

Online International Interdisciplinary Research Journal, {Bi-Monthly}, ISSN 2249-9598, Volume-07, June 2017 Special Issue (02)

w w w . o i i r j . o r g I S S N 2 2 4 9- 9 5 9 8 Page 463

Conversion of Furnace Oil Fired Boiler to Briquette Fired External Furnace Boiler

aM.Nirish, bBayya SrinivasS, cA.Srihar

aAssistant professor ,Department of Mechanical Engineering, Nishitha College of Engineering and Technology, Lemoor(Village),Kandukur(Mandal), R.R Dist-501359. Telangana, India. b,cAssistant professor, Department of Mechanical Engineering, Bomma institute of technology and science, Allipuram(Village),Khammam dist-507318. Telangana, India.

In the present area of neck-to-neck competition, the cost of production plays vital role. As the price of liquid fuels, especially Furnace oil are growing at steeper rate than solid fuel price, substitution of Furnace oil to solid briquette is one of the alternative available. Furnace oil used in Boiler or Thermic oil heater can be totally substituted by Briquette with an equivalent ratio of 2.2:1 Kg/lit on the basis of calorific value. This usually results in saving of more than 50% in operating cost and will have attractive payback period of 3-4 months. India has a large agriculture base but still there has been very little work done in the field of agro residue usage as fuel. Coal, another fossil fuel, is primarily used in the power generation sector. The agro waste can be converted by an easy mechanical process to briquettes that can be used as fuel in the industry. This conversion is not only beneficial as fuel substitution but is a potential link between urban and rural economy. The Objective of the article is to undertake a CONVERSION OF FURNACE OIL FIRED BOILER TO BRIQUETTE FIRED EXTERNAL FURNACE BOILER, techno economical study of project & commissioning. The details of technical and commercial aspects of this unique opportunity. Wealth from Waste.

I. Introduction

Background

At present we are having 3Mt/hr Furnace Oil-fired boiler, we are using this boiler as stand by to Unit-I boiler i.e. whenever there is a breakdown or short supply of steam from Unit-I boiler, we will be firing this boiler to overcome the short supply of steam. (Even some times we supply steam to Unit-I in case of any emergency requirement.)

Since few months the steam requirement of Unit-I has increased & we are falling short of steam supply, hence on an average we are running this boiler for 10 to 12 hrs/day. As with Furnace oil as fuel the steam generation cost is too high, so we are proposing to convert Furnace oil fired boiler to Briquette fired boiler.

Gases from the boiler will move towards the water pre heater, where the temperature of flue gases will be reduced to 140 to 1500C.

II. Steam Generators

II.I. Steam

Abstract



Steam is a vaporized form of water. It is obtained by boiling or evaporating the water in a boiler. Steam is widely used as, a working fluid in thermal power plant to produce power. It is also used for processing in chemical industries and sugar factories, for bleaching in cotton and paper mills and to drive Locomotives and ships.

As a working fluid in power plants, the steam has the following advantages:

• high heat capacity • can easily be condensed and evaporated • Work of compression is very small

II.II Steam Boiler

Boiler is a closed vessel in which given fluid is heated and evaporated or in which steam is generated from the water by combustion of fuel. It is also called steam generator, large size steam boilers are also called steam generating plants.

Basic elements of boiler are shell, Furnace, heating source, heating surface, steam space, mountings and accessories. Shell of very small boilers such as domestic, experimental, clinical etc. is made of copper or stainless steel. Big boilers are made of cast iron or steel.

Furnace is the fire bore of boiler. Fuel is burnt in the furnace which provides combustion chamber. The part of the boiler which is exposed to hot gases is called heating surface.

II.III. Steam Generating Unit

Combination of apparatus for producing the heat and transferring the Available heat to water is called steam generating unit.

The basic elements of steam generating unit are boiler drum, super heater, economizer and air pre-heater.

II.IV. Requirements Of Good Boiler

The primary requirements of a boiler or steam generating unit are:

• It should be capable of producing maximum amount of steam • It should be occupy less space and should be capable of quick starting • It should be safe in working i.e., the water must be contained • Safely and steam must be safely delivered in desired condition. • All parts should be easily accessible for inspection and repairs.

II.V. Selection of Boiler

The following factors are to be considered while selecting the boiler for a particular use.

- Operating pressure

- Steam generating rate



- Quality of steam required

- Availability of floor spare

- Fuel to be used

- Nature of the load on the boiler

- Initial cost.

The two important factors which dictate the selection of boilers are operating pressure and steam rate. Fire tube boilers can be used only up to 25 bar and 10 tons/hr capacity. Above this range water tube boilers have to be used.

II.VI. Classification Of Boilers

II.VI.I. Boilers may be classified as:

1. According to the content in the tubes:

• Fire tube boilers

• Water tube boilers.

In fire tube boiler, the hot gases pass through the tubes surrounded by the water from which the steam is generated.

Examples: Simple vertical boiler, locomotive boiler, Cochran boiler, Cornish boiler.

In water tube boiler, water is made to pass through a large number of tubes over which the hot gases flow. Most modern boilers are built as water tube boilers.

Examples: Babcock and Wilcox boiler, sterling boiler, yarrow boiler.

Boilers may be further classified as given below:

2. Location of furnace

(a) Internally fired boilers –

Furnace is located inside the boilers

(b) Externally fired boilers –

Furnace is located outside the boilers.

3. Axis of the shell

(a) Vertical boiler

(b) Horizontal boiler

4. Circulation of water

(a) Natural circulation –

No pump is required circulation of water is due to difference in densities.

(b) Forced circulation

Uses pump to force water

5. Service to which they are employed

(a) Stationary boilers

Boilers installed in power plants and industrial

units.



(b) Mobile boilers

- Marine boilers and locomotive boilers

II.VI.II. Fire Tube Boiler

In fire tube boiler the hot flue gases are led through the tubes around which the water circulates. Fig shows the essential features of a simple fire-tube boiler having a single large tube. The boiler shell contains water and steam under pressure. The fire tube contains the grate. The water level is at B, the space above being filled with steam. Air for combustion of fuel flowing beneath the grate moves up wards through the fire bars. Burnt flue gases pass along the fire tube to the exit. The water surrounding the tube evaporates with the heat of flue gases. Super heater tubes are generally placed in the path of the flue gases at the exit side.

Examples: Cochran boiler, Lancashire boiler, Locomotive, Simple vertical boiler

Figure1.Fire tube boiler

II.VI.III. Water Tube Boiler

In water tube boiler the hot gases pass over the surface of small tube and water flows inside the tubes. Fig shows the essential features of water tube boiler.

It consists of a large number of parallel tubes containing water and connected to boiler drum through the headers. Feed water is supplied to the drum. From the drum water flows into the tubes via down-take header. Evaporation takes place in the tubes due to heat of flue gases. The steam formed is returned to the drum through up take header, and steam leaves the drum through a stop-valve.

Examples: Babcock and Wilcox boiler, Yarrow boiler, Benson, Lamont Boiler.

Figure2.Water tube boiler.

II.VII. Boiler Mountings and Accessories

II.VII.I. Boiler Mountings



The devices or components fitted to the boiler for safety and proper operation of the boiler are called boiler mountings. These are essential components for operation of the boiler.

The important boiler mountings are,

1. Pressure gauge

2. Water level indicator

3. Safety valve

4. Fusible plug

5. Feed check valve

6. Blow off cock

7. Stop valve

II.VII.II. Boiler Accessories

The auxiliary devices installed with the boiler for proper operation and to increase the efficiency of the plant are known as boiler accessories.

The following accessories are more commonly employed in steam power plant.

1. Feed pump

2. Economiser

3. Super heater

4. Air-preheater

5. Steam trap.

6. Steam separator

7. Steam injector

The relative positions of important accessories indicating their functions.

Figure3.Boiler Accessories

A. Economiser

Exhaust gases leaving the boiler furnaces possess consider able quantity of heat. If they are imply allowed to escape into atmosphere through the chimney, we will be wasting a lot of heat content. This leads to lesser thermal efficiency of the boiler hence attempt made to recover heat from these flue gases by installing economizer , air preheater, super heater etc. in the way of these hot gases.



Economizer is located between boiler furnace and air preheater. Water that is fed to the boiler is passed through the tubes of economizer .at the same time , hot flue gases are allowed to flow over these tubes. Heat transfer takes place between exhaust (flue) gases and cold feed water. Temperature of feed water, thereby, increases. Feed water, which is thus relatively at higher temperature needs less heat for its evaporation into steam.

Obviously this leads to saving in fuel consumption and time of evaporation.

B. Air Preheater

Air preheater (or) simple air heater is a waste heat recovery device It is located between the economizer and chimney. Heat of exhaust gases increases the temperature of air which is on its way to furnace.

Air preheater show in fig. is a tubular type recuperative air heater. the flue gases from economises enters at one end and air required for combustion enter from other end. Air is made to pass in a Zig-Zag manner as shown by arrows so that max, heat transfer takes place between

Air and flue gases. Hot air leaves out to furnace of the boiler.

Figure4.Air Preheater

C. Super Heater

Super heater is an important boiler accessory. It is used to recover the part of heat being wasted in flue gases. Super heater is placed in the path of hot gases on their way to chimney.

III. Fuels For Steam Generator

Definition Fuel is any material that is capable of releasing energy when its chemical or physical

structure is altered. The various types of fuels like liquid, solid and gaseous fuels are available for firing in boilers, furnaces and other combustion equipments.

Agricultural output from India has seen phenomenal growth. Factors, which contributed to the development, were research in seeds, access to water and power, effective pesticides, communication and improvement in storage facility. With the growth in production of agricultural output agro-waste production is also increased. However local thermal energy needs of rural sector were mainly managed through cow dung, wood, kerosene and lately LPG. Agro mass had few takers. In fact storage of



agro-mass posed problems such as security risk due to fire hazard, growth of pests, blockage of covered space etc. Simplest solution, which is

Briquetting was therefore the right answer. Fiscal and economical incentives were announced and that led to installation of various briquetting plants. Early birds however, did not have the beginner’s advantage. On the contrary arm-twisting techniques of urban buyers, poor credit facility, enforced most of the entrepreneurs to shut the shop. Today however, due to movement called clean development mechanism, renewed vigour is felt in this area.

Coal and its nuisances are known to industry. New fuels like briquette having calorific value equivalent to coal in GCV are available in the market. These are made from dry bagasse, groundnut shale, sawdust etc. Usually no binding material is added. Landed rates in western Maharashtra are same as coal, it is renewable fuel.

III.I. Furnace Oil

III.I.I Definition A dark viscous residual fuel obtained by blending mainly heavier components from

crude distillation unit, short residue and clarified oil from fluidized catalytic cracker unit.

III.I.II. Nomenclature Bunker fuel, Furnace oil, Fuel oil are other names for the same product. Though Fuel

oil is a general term applied to any oil used for generation of power or heat, Fuel oil can included distillates and blends of distillates and residue such as Light Diesel Oil.

III.I.III. Specification

Furnace oil in the current marketing range meets Bureau of Indian Standards specification IS: 1593 - 1982 for fuel oils, grade MV2.

III.I.IV. Viscosity Viscosity is the most important characteristic in the Furnace oil specification. It

influences the degree of pre-heat required for handling, storage and satisfactory atomization. If the oil is too viscous it may become difficult to pump, burner may be hard to light and operation may be erratic. Poor atomization may result in the carbon deposits on the burner tips or on the walls. The upper viscosity limit for Furnace oil is such that it can be handled without heating in the storage tank is excepting under server cold conditions. Pre-heating is necessary for proper atomization.

III.I.V. Flash Point As per the Controller of Explosives classification, Furnace oil falls in the class "C"

category with minimum flash point standard of 66 deg. C. Since Pens key Martens Closed Cup method is used, it is apparent that a small quantity of low boiling point hydrocarbons is sufficient to lower the flash point drastically.

III.I.VI. Pour Point



It is a very rough indication of the lowest temperature at which Furnace oil is readily pump able. In the specification the pour point of Furnace oil is not stipulated. However, for Furnace oil manufactured indigenously and for imported parcels, the pour point is such that current supplies normally can be handled without heating the fuel oil handling installation.

III.I.VII. Water Water may be present in free or emulsified form and can on combustion cause damage

to the inside furnace surfaces especially if it contains dissolved salts. It can also cause sputtering of the flame at the burner tip. Water content of Furnace oil when supplied is normally very low as the product at refinery site is handled hot and maximum limit of 1% is specified in the standard.

III.I.VIII. Sediment Furnace oil being a blend of residues contains some quantity of sediments. These have

adverse effect on the burners and cause blockage of filters etc. However, the typical values are normally much lower than the stipulated value of maximum 0.25 percent, by mass.

III.I.IX. Ash

Ash is incombustible component of the Furnace oil and is expressed as a percentage mass of the Furnace oil sample. Ash consists of extraneous solids, residues of organ metallic compounds in solution and salts dissolved in water present in the fuel. These salts may be compounds of sodium, vanadium, calcium magnesium, silicon, iron etc.Ash has erosive effect on the burner tips, causes damage to the refractoriness at high temperatures and gives rise to high temperature corrosion and fouling of equipments.

III.I.X. Sulphur

Sulphur determination includes burning of known quantity of oil, treating the sulphur oxidation products formed during combustion and weighing of sulphur in the form of sulphate.

The sulphur dioxide may come in direct contact with the product during the combustion process and may create adverse quality effects in the product.

III.I.XI. Calorific Value

Calorific value of a fuel is the quantity of heat generated in kilocalories by complete burning of one kilogram weight of fuel. Gross calorific value is higher than net calorific value to the extent of heat required to change water formed by combustion into water vapors.

III.II. Bio Mass Briquette Process

Briquettes can be defined as a compressed wood product .It is a project to convert agro forestry waste to Bio coal .Shortly this project for Best from waste. In brief it can describe, it is machinery which is capable of binding any agro-forestry waste in to finished Briquettes / Bio-coal / White coal. For this project any type of Agro-forestry Waste / Bio-mass can be converted in to Finished Briquettes. i.e. Saw Dust, Ground-nut



Shell , Custer Shell , Sugar-cane Bag gas, Cotton Stalk , Bamboo Dust , Wheat Husk , Sarsav Husk etc.

The Shape of the finished Briquettes is cylindrical shape with 90 mm diameter and length is approx. 1 ft. Briquettes have high specific density (1200 Kg/m3) and bulk density (800 Kg/m3) compared to 60 to 180 Kg/m3 of loose biomass. Very low ash content as low as 2 to 5% compared to 20% to 40% in coal.

Super60 : 600–750kg/hr*

Jumbo-90 : 1500kg/hr*

III.II.I. Agro-waste Briquettes – Manufacturing Pro cess Briquetting is process of converting loose, high volume, density mass into

compact, high density, low volume lumps by mechanical compression.

Figure5.Manufacturing process

• No oil or additive used as binder.

• Only possible contamination in the process – loose soil from agricultural Operation.

IV. Boiler Conversion Methods IV.I. Types of Conversion Various ways by which existing oil fired boiler can be converted depends on steam load pattern, relative cost, manpower cost, labor laws etc.

IV.I.II. Internal Grate with ID FAN Lightly loaded boilers say up to 40% & with uniform load pattern can be converted to internal firing. Modification of boiler involves removal of burner, blower & providing supports for cast iron grate bars on the inside of combustion chamber (first pass). At the firing end ash door & one feeding door is provided.

IV.I.II. External Grate Firing In this type of modification external furnace is erected with sufficient grate area. Hot combustion chamber of external furnace, multi window for air supply enables a firing and cleaning to be carried out simultaneously. Therefore steam generation capacity is constant. Two third of oil fired boiler capacity is achievable easily and up to 80% with disciplines on operating side.

IV.I.IV. IBR Act and Pollution

As there are no changes made in pressure parts, usually IBR has no relevance in prating Furnace oil. Boiler on briquette. Exhaust gases coming out of chimney are made free from dust and impurities as a result of clean combustion technology. Sufficient bends and turns provided in the path of flue gas help elimination of particles in exhaust.



IV.I.V. Modification In Existing Boiler and Attachm ents Needed

The boiler operating at 30% of its capacity requires removal of F.O. burner-blower setup, and addition of internal grate in present combustion chamber. However, for operating boiler at higher capacity external fired furnace is recommended .To get the sufficient draft induced draft (ID) fan is required instead of FD fan. The above additions are fully reversible and boiler can be run on Furnace oil back again if price of latter drops in future.

V. Environmental Benefits Introduction

As from the ash analysis it is cleared that ash contain 0% Sulphur, so briquette ash can be used as fertilizer.

V.I. Carbon Credit Facility Bagasse is considered as an ecofriendly renewable fuel. Its use in India can fetch

carbon credits if the unit has such requirement abroad or in developed countries.

V.II. Ash Analysis By: ITA LABS. (Industrial and analytical laborites)

Address: Maher house-18, cawed ji Patel Street, Mumbai-400001.

s.no Particular Percentage

1 Potassium (as K2O)

0.73

2 Phosphorus (as P) (P2O3)

0.18

3 Calcium (as Ca) 1.93

4 Magnesium (as Mg)

Nil

5 Sulphur (as S) Nil 6 Iron (as Fe) 0.90 7 Zinc (as Zn) 0.16

8 Electrical conductivity

1611

Table-2 (Results of analysis) briquette.

V.III. Stack Analysis As from the stack analysis it is cleared that all air pollution emission parameters are

under permissible limit as per pollution control board.

By : ENVIRO Labs.

Attached to: Boiler (Nestler, MR-9965)

Specification: round, Diameter of chimney: 0.90 m, Height of chimney: 23.60 m,



Temperature of stack: 1150C, Material of construction: mild steel, Velocity of flue gases: 5.38 m/sec, Volume flow rate of flue gases: 9465.30 Nm3/hr., Type of fuel: bagasse bricks

S.No Parameter Result Unit

1 TPM 86.13 Mg/Nm3

2 SO2 0.12 Kg/hr

3 NOX 0.52 Mg/Nm3

4 CO NIL PPM

5 CO2 8.5 PPM

Table-4 (Result of analysis) briquette.

VI. Standard Operating Procedures For Briquette Fired Boiler Introduction The Standard procedures adopted for operating briquette fired boiler may be summarized as below

• Keep the steam delivery valve of the boiler shut & open air vent valve.

• Make sure that boiler feed water tank level is filled up to high level with soft water. The soft water hardness should be below 5 ppm.

• Ensure the water level in the boiler gauge glass within the operational limit.

• Add water treatment chemicals like oxygen scavenger, PH booster and anticipant in the feed water tank

• Check the I.D. Fan belt alignment and its direction of rotation. • Open the I.D. fan inlet damper. • Blow on the air for 20 seconds for initial startup. • Ensure that the blow down valve is closed properly.

• Ensure pressure switch isolation valve is opened. • Briquette feeding & Startup procedure for External Furnace in cold condition • Ensure sufficient stock of briquette near the working area.

• Feed 50 kgs of Briquette on the grate area behind each fire door and light up the mass • Briquette will start burning under natural draft condition. • Keep the feeding rate of Briquette 50 kg/hr for first 24 hours. • Close the air vent valve after reaching the steam pressure in the boiler 1 kg/cm².

• Increase the firing rate 75 kg/hr for next 12 hours. • Increase the firing rate between 75-100 kg/hr for next 12 hours. Ensure the Boiler

steam pressure in the range of 6-8 kg/cm². • After 48 hours of feeding start I.D. fan, adjust the inlet damper as per the smoke

colour.

• When smoke is black then air requirement is more. Smoke should be colorless.



• tart the feeding of the briquette on the grate bars till the Boiler pressure raises to 10 kg/cm².Open the steam delivery valve of boiler slowly.

• Adjust the feeding rate of the briquette in the external furnace as per the steam requirement.

VII. Boiler Maintenance Introduction

Maintenance of a boiler is an important part throughout the life span of a boiler and it is to be systematically followed. The summary of them is explained in this chapter

VII.I. Preventive Maintenance

• Tighten the pump stuffing box.

• Check oil level in dust collector.

• Check 10 fan bolts and V-groove pulley.

• Check condition of refractory.

• Tighten all foundation bolts of pump. 1.0. & F.O. fans.

• Grease the dust collector chain.

• Clean the boiler tubes.

• Lubricate the bearing of water pump. 10 fan. FD fans.

• Tighten the terminals of the motor and glands.

• Grease all the motor bearings

• Check hardness of water.

• Check all starter connection controls.

VII.II. Boiler Tests The following tests are to be conducted at the frequency noted and logged on the

check sheet found at the end of this chapter. All tests are to be conducted in accordance with the applicable legislations and codes.

VII.III. Blow downs Boilers should be blown down (surface and bottom) daily. Surface blow downs are

conducted to remove surface film, oil etc., Bottom blow downs are conducted to lower Total Dissolved Solids (TDS), limit sludge buildup and adjust boiler chemistry. When conducting blow downs, the operator must ensure that all persons are clear of the blow down piping escape point. Simultaneous blow down of two or more boilers is not to be performed if they are serviced by the same discharge piping system.

VII.IV. Water Chemistry Boiler chemicals are caustic and are to be handled by trained personnel only. Proper

PPE, as indicated on the MSDS, is to be used at all times. Spills of boiler chemicals are to be cleaned up as they occur. Operating Parameters Operation of the boiler in the proper ranges will help ensure the mechanical integrity and expected lifetime of the boiler.



VIII. Boiler Inspection VIII.I. Regular inspection of boiler

• Feed water hardness to be checked for every 8 hours of boiler operation.

• Required chemical to be add for every 8 hours of boiler operation.

• Motor, blower and pumps should be checked. They should run smoothly and without any vibrations.

• Check all pipe lines and manhole joints, It should not leak.

• Steady steam pressure is to be maintained.

• Blow down the Moberly level, gauge glasses regularly.

• Check the smoke color of boiler it should be hazy brown at chimney top.

VIII.II. Hazards

Boiler operation hazards include steam/ hot water burns, burns from hot equipment, steam explosions, fuel fires and chemical exposure.

VIII. III. Hazard Control VIII. III.I. Engineering Controls

Engineered boiler safety controls include insulation of hot areas such as piping and boiler components, automatic shutdown devices, automatic fire and fuel controls, relief valves and water level controls.

VIII. III. II. External Inspections

External inspections should normally be conducted annually. The inspection should be performed by a certified boiler inspector.

VIII.III.III. External Inspection Areas

Leaks cause an excessive make-up rate to the boiler which will cause increased introduction of oxygen and a reduction in oxygen control chemicals. This action will result in higher corrosion rates inside the boiler ad an increase in scale and sludge buildup. This effect will, in turn, reduce boiler efficiency requiring higher uel consumption. Additionally, the life of the boiler will be significantly reduced.

VIII.III.IV. Internal Inspections

Internal inspections should normally be conducted annually. The inspection should be performed by a certified boiler inspector.

VIII.III.V. Internal Inspection Areas

• Fire Side inspection points

• Door gaskets

• Fire side insulation

• Tube sheet

• Tubes



• Blower

• Stack

VIII.III.VI. Water Side inspection points

• Tube bundle

• Scale buildup

• Condensate feed water tanks

• Chemistry control systems and Level floats

IX. Pictures of Briquette Fired Boiler



Bibliography

1. Industrial Biolers By David Gunn / Robert Horton.

2. Engineering Thermodynamics By P.K. Nag.

3. Thermal Engineering By P.L. Baliany.

4. Themal Engineering By R.K. Rajput.

5. Yajna Fuel Services

6. Thermal Engineering By Pakirappa.

Conversion of Furnace Oil Fired Boiler to Briquette Fired ...

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