Internship Report on Cogeneration

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ContentsACKNOWLEDGEMENTS..............................................................................................3

CONCEPT OF COGENERATION.........................................................................4

COGENERATION PRINCIPLES............................................................................7

COGENERATION TECHNOLOGY.......................................................................7

GAS TURBINE.........................................................................................................8

Reciprocating engine based cogeneration system................................................13

COMBINED STEAM/GAS TURBINE BASED COGENERATION SYSTEM...................15

Other Classifications of Cogeneration Systems......................................................15

ELECTRIC POWER GENERATORS....................................................................18

Synchronous machines............................................................................................20

HEAT RECOVERY BOILERS......................................................................................23

COGENERATION WITH STEAM TURBINE CYCLE.....................................26

Transmission & Distribution:..................................................................................29

INDUSTRIAL CASESTUDIES AT USW...........................................................31

EQUIPMENTS....................................................................................................31

NORMAL OPERATING PHILOSOPHY.......................................................................33

POWER PLANT PERFORMANCE ANALYSIS............................................................34

CONTROLLING AND MONITORING SYSTEM...............................................37

CONCLUSION.......................................................................................................39

RESOURCES..........................................................................................................40

2 INTERNSHIP REPORT| Ugar Sugar Works Ltd

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ACKNOWLEDGEMENTS

At the outset We profusely thank the management of Ugar Sugar Works Ltd Ugar-Khurdh for introducing internship in Ugar-Khurdh with all urban amenities. We thank the management of Ugar Sugar Works Ltd, Ugar-Khurdh for giving us opportunity to undertake this internship and enlightened with a practical working of cogeneration structure. We extend our gratitude to Shri S.S.Sardesai- DGM(Cogeneration Electrical),Shri S.N.Gurav-Deputy Manager(personnel and welfare),Shri B.N.Naik(Assistant Engineer Cogeneration) & B.K.Komalinge(Junior Engineer Cogeneration) who are constant source of inspiration throughout our study for one month.

We extend our heartfelt thanks to Shri N.M.Patil-Training Officer USWL for his noble guidance and co-operation.

We extend our special thanks to R.D.Hanje ,L.V.Kokane, Gopi Kulkarni M.V.Handigund and cogeneration staff who have continuously played an important role in enabling us to transform our dream come true.

We thank all who helped us directly or indirectly during internship course.We also thankful to our college Gogte Institute of Technology,Belgavi for their support. Last but not least, We express our special thanks to our parents who are the main source for the present position and future prospects.

Thanks once again.


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CONCEPT OF COGENERATION Combined heat and power (CHP) systems (also known as cogeneration) generate 2 energy sources from a single fuel in a single integrated system

1) Generation of electric energy.2) Production of heat(exhaust steam)

Thus Cogeneration is on-site generation and utilisation of energy in different forms simultaneously by utilising fuel energy at optimum efficiency in a cost-effective and environmentally responsible way. Cogeneration systems are of several types and almost all types primarily generate electricity along with making the best practical use of the heat,which is an inevitable by-product.

CHP systems consist of a number of individual components – prime mover (heat engine), generator, heat recovery, and electrical interconnection – configured into an integrated whole. The type of equipment that drives the overall system (i.e. the prime mover) typically identifies the CHP system. Prime movers for CHP systems include reciprocating engines, combustion or gas turbines, steam turbines, micro-turbines, and fuel cells. These prime movers are capable of burning a variety of fuels, including natural gas, coal, oil, and alternative fuels to produce shaft power or mechanical energy. Although mechanical energy from the prime mover is most often used to drive a generator to produce electricity, it can also be used to drive rotating equipment such as compressors,pumps,andfans. Thermal energy from the system can be used in direct process applications or indirectly to produce steam, hot water, hot air for drying, or chilled water for process cooling.


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Fig1 Schematic diagram for Cogeneration power plant

Advantages of Cogeneration High efficiency compared to conventional generation. Lower emissions to the environment, in particular of CO2 Increases the cost-effectiveness and reduces the need for waste

disposal Large cost savings, providing additional competitiveness for

industrial and commercial users while offering affordable heat for domestic users

Using existing industrial and commercial sites for incremental power generation rather than building new power plant capacity at greenfield sites

Providing on-site electricity generation that is resilient in the face of grid outages thus providing power for critical services in emergencies and avoiding economic losses

An opportunity to move towards more decentralized forms of electricity generation,where plants are designed to meet the needs of local consumers, providing high efficiency, avoiding transmission losses and increasing flexibility in system use. This will particularly be the case if natural gas is the energy carrier


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An opportunity to increase the diversity of generation plant, and provide competition in generation. Cogeneration provides one of the most important vehicles for promoting liberalization in energy markets.

Consider the following scenario. A plant require 24 units of electrical energy and 34 units of steam for its processes. If the electricity requirement is to be met from a centralised power plant (grid power) and steam from a fuel fired steam boiler,the total fuel input needed is 100 units. Refer figure-2 (top)

Figure 2: Cogeneration (Bottom) compared with conventional generation (top)

If the same end use of 24 units of electricity and 34 units of heat, by opting for the cogeneration route , as in fig 2( bottom), fuel input requirement would be only 68 units compared to 100 units with conventional generation.


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COGENERATION PRINCIPLES

The fallowing basic options of COGENERATION PRINCIPLES are basically distinguished

Cogeneration with Steam turbine: They are operated by hard coal, brown coal, oil,wood,waste,peat or nuclear fuel Steam is medium by which thermal energy is converted into mechanical energy.

Cogeneration with Gas turbine: Oil and Gas are the only suitable fuels. The working medium is the exhaust gas of combustion chamber.

Cogeneration with Combined cycle: The high heat and oxygen content of gas turbine exhaust gases is used in a second process with steam turbine.

Cogeneration with Reciprocating Engine: The chemical bounded energy of natural gas or diesel for example is directly transformed by combustion into mechanical energy.

COGENERATION TECHNOLOGY A proper selection of a cogeneration system configuration, from a few basic system configurations described below, makes it feasible to produce first either electrical energy or thermal energy.

1 Steam turbine based cogeneration system 2 Gas turbine based cogeneration system 3 Combined steam/gas turbine based cogeneration system 4 Reciprocating engine based cogeneration system

All combinations of cogeneration systems are based on the First and Second Laws of Thermodynamics. Basic concepts of possible different configurations of cogeneration systems, consisting of a primary energy source, a prime mover driven electric power generator and arrangement to use the waste heat energy rejected from the prime mover

GAS TURBINE Gas turbine systems operate on the thermodynamic cycle known as the Brayton cycle. In a Brayton cycle, atmospheric air is compressed, heated, and then


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expanded, with the excess of power produced by the turbine or expander over that consumed by the compressor used for power generation. Gas turbine cogeneration systems can produce all or a part of the energy requirement of the site, and the energy released at high temperature in the exhaust stack can be recovered for various heating and cooling applications (see Fig). Though natural gas is most commonly used, other fuels such as light fuel oil or diesel can also be employed. The typical range of gas turbines varies from a fraction of a MW to around 100 MW.They are of 2 types1) Opened Cycle 2) Closed Cycle

Fig 3 Gas Turbine or Engine with Heat Recovery Unit

Open-cycle gas turbine cogeneration systems

The air is delivered through a diffuser to a constant-pressure combustion chamber, where fuel is injected and burned. The diffuser reduces the air velocity to values acceptable in the combustor. There is a pressure drop across the combustor in the range of 1.2%. Combustion takes place with high excess air. The exhaust gases exit the combustor at high temperature and with oxygen concentrations of up to 15-16%. The highest temperature of the cycle appears at this point; the higher this temperature is, the higher the cycle efficiency is. The upper limit is placed by the temperature the materials of the gas turbine can withstand, as well as by the efficiency of the cooling blades. With current technology this is about 1300°C.The high pressure and temperature exhaust gases enter the gas turbine producing mechanical work to drive the compressor and the load (e.g. electric generator). The


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exhaust gases leave the turbine at a considerable temperature (450-600°C), which makes high-temperature heat recovery ideal. This is affected by a heat recovery boiler of single-pressure order double pressure, for more efficient recovery of heat. The steam produced can have high pressure and temperature, which makes it appropriate not only for thermal processes but also for driving a steam turbine thus producing additional power.

Air Fig 4 Open Cycle Gas Turbine Cogeneration

Closed-cycle gas turbine cogeneration systems


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Fig 5 Closed Cycle Gas Turbine Cogeneration Systems

In the closed-cycle system, the working fluid (usually helium or air) circulates in a closed circuit. It is heated in a heat exchanger before entering the turbine, and it is cooled down after the exit of the turbine releasing useful heat. Thus, the working fluid remains clean and it does not cause corrosion or erosion. Source of heat can be the external combustion of any fuel. Also, nuclear energy or solar energy can be used .

STEAM TURBINE The thermodynamic cycle for the steam turbine is the Rankine cycle. Steam turbines systems can use a variety of fuels, including natural gas, solid waste, coal, wood, wood waste, and agricultural by-products. Steam turbines are highly reliable and can meet multiple heat grade requirements. Steam turbines typically have capacities between 50 kW and 250 MW and work by combusting fuel in a boiler to heat water and create high-pressure steam, which turns a turbine to generate electricity. The low-pressure steam that subsequently exits the steam turbine can then be used to provide useful thermal energy. Ideal applications of steam turbine-based cogeneration systems include medium- and large-scale industrial or institutional facilities with high thermal loads and where solid or waste fuels are readily available for boiler use.


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Depends on the quantities of power and heat, quality of heat, and economic factors they are classified into

1. Back Pressure Steam Turbine2. Extraction Condensing Steam Turbine

BACK PRESSURE STEAM TURBINE A back pressure steam turbine is the simplest configuration. Steam exits the turbine at a pressure higher or at least equal to the atmospheric pressure, which depends on the needs of the thermal load. This is why the term back- pressure is used. It is also possible to extract steam from intermediate stages of the steam turbine, at a pressure and temperature appropriate for the thermal load. After the exit from the turbine, the steam is fed to the load,where it releases heat and is condensed. The condensate returns to the system with a flow rate which can be lower than the steam flow rate, if steam mass is used in the process or if there are losses along the piping. Make- up water retains the mass balance.

Fig4 Back pressure steam turbine

Advantages: Simple configuration with few components. The costs of expensive low-pressure stages of the turbine are avoided. Low capital cost.


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Reduced or even no need of cooling water. High total efficiency, because there is no heat rejection to the environment

through condenserDisadvantages:

The steam turbine is larger for the same power output, because it operates under a lower enthalpy difference of steam

Little flexibility in design and operation More impact on environment in case of use of low quality fuel Higher civil construction cost due to complicated foundations

EXTRACTION CONDENSING STEAM TURBINE In such a system, steam for the thermal load is obtained by extraction from one or more intermediate stages at the appropriate pressure and temperature. The remaining steam is exhausted to the pressure of the condenser, which can be as low as 0.05 bar with a corresponding condensing temperature of about 33°C. It is rather improbable that such low temperature heat finds useful applications. Consequently, it is rejected to the environment. In comparison to the back - pressure system, the condensing type turbine has a higher capital cost and, in general, a lower total efficiency. However, to a certain extent, it can control the electrical power independent of the thermal load by proper regulation of the steam flow rate through the turbine.


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Extraction Condensing Steam Turbine

Advantages: High flexibility in design and operation Well suited to all types of fuels, highquality or low quality Good part load efficiency More suitable for varying steam demand

Disadvantages: More specific capital cost Low fuel efficiency rating, in case of more condensing More impact on environment in case of use of low quality fuel Higher civil construction cost due to complicated foundations High cooling water demand for condensing steam turbine

Reciprocating engine based cogeneration system In this system, the reciprocating engine is fired with fuel to drive the generator to produce electrical power. The process steam is then generated by recovery of waste heat available in engine exhaust in WHRB. The engine jacket cooling water heat exchanger and lube-oil cooler are other sources of waste heat recovery to produce hot water or hot air. The reciprocating engines are available with low, medium or high-speed versions with efficiencies in the range of 35 - 42 %.


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Fig Reciprocating engine based cogeneration system with unfired WHRB

When diesel engines are operated alone for power generation, a large portion of fuel energy is rejected via exhaust flue gases. In cogeneration cycle, practically all the heat energy in engine jacket cooling water and lube-oil cooler, and substantial portion of heat in exhaust gases is recovered to produce steam or hot water. With this, the overall system efficiency of around 65-75% is achieved.

Advantages: Low civil construction cost due to block type foundations and least

nos. of auxiliaries High Reliability Reciprocating engines start quickly, follow load well High electrical power efficiency Better suitability as emergency standby plant Least specific capital cost Low cooling water demand

Disadvantages: Suitability for low quality fuels with high cleaning cost


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Low overall plant efficiency in cogeneration mode High maintenance cost More impact on environment with low quality fuel Least potential for waste heat recovery

COMBINED STEAM/GAS TURBINE BASED COGENERATION SYSTEM It is clear from the title of system itself that it works on the basis of combination of both Rankine and Bryton cycles, and hence it is called combined steam/gas turbine based cogeneration system. In this system, fuel energy is first utilised in operating the gas turbine as described in Gas turbine based cogeneration system. Waste heat of high temperature exhaust flue gases from the gas turbine is recovered in WHRB to generate a high pressure steam. This high-pressure steam is expanded through a back-pressure steam turbine, or an extraction-cum-back pressure steam turbine, or an extraction-cum condensing steam turbine to generate some additional electric power. The low-pressure steam available either from the exhaust of back-pressure steam turbine or from extraction is supplied to the process consumer.

Advantages: Such combination of two cycles gives a definite thermodynamic advantage

with very high fuel utilisation factor under various operating conditions. The process in which the demand of electricity remains very high even

when the demand of steam is very low, then extraction-cum-condensing steam turbine can be used instead of back pressure steam turbine.

Other Classifications of Cogeneration Systems

Cogeneration systems are normally classified according to the sequence of energy use and the operating schemes adopted. On this basis cogeneration systems can be classified as either a topping or a bottoming cycle.

Topping cycleIn a topping cycle, the fuel supplied is used to first produce power and then thermal energy,which is the by-product of the cycle and is used to satisfy process heat or other thermal requirements. Topping cycle cogeneration is widely used and is the most popular method of cogeneration.


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Combined-cycle toppingsystemA gas turbine or diesel engineproducing electrical ormechanical power followed bya heat recovery boiler to createsteam to drive a secondarysteam turbine.

Steam-turbine topping systemThe second type of systemburns fuel (any type) to producehigh-pressure steam that thenpasses through a steam turbineto produce power with theexhaust provides low-pressureprocess steam

Heat recovery topping systemThis type employs heat


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recovery from an engineexhaust and/or jacket coolingsystem flowing to a heatrecovery boiler, where it isconverted to process steam / hotwater for further use.

Gas turbine topping systemA natural gas turbine drives agenerator. The exhaust gas goesto a heat recovery boiler thatmakes process steam andprocess heat.

Bottoming CycleIn a bottoming cycle, the primary fuel produces high temperature thermal energy and the heat rejected from the process is used to generate power through a recovery boiler and a turbine generator. Bottoming cycles are suitable for manufacturing processes that require heat at high temperature in furnaces and kilns, and reject heat at significantly high temperatures. Typical areas of application include cement, steel, ceramic, gas and petrochemical industries.

Bottoming cycle plants are much less common than topping cycle plants. Figure 9 illustrates the bottoming cycle where fuel is burnt in a furnace to produce synthetic rutile. The waste gases coming out of the furnace is utilized in a boiler to generate steam, which drives the turbine to produce electricity.


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Bottoming Cycle cogeneration system

ELECTRIC POWER GENERATORS All cogeneration systems,with the exception of fuel cells that produce electricity directly, require an electric generator driven by the prime mover .Reciprocating engines operate at speeds that are compatible with generator speeds,so a direct drive with no reduction gear is recquired.But single –shaft turbines usually operate at high speeds, and a reduction gear is therefore needed.

Multistage stem turbines or multistage gas turbines can operate the shaft connected to the generator at lower speeds, which are compatible with the speeds of the generators.Generator efficiency typically lies in the range of 95-98%,although small asynchronous generators or generators operating at partial load may have efficiencies which are as low as 85%,since the efficiency decreases nonlinearly with the load.

PRINCIPLES OF ELECTRIC MACHINES


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Rotating electric machines are electromagnetic transducers converting electrical energy into mechanical(motors) or, the reverse , mechanical energy is converted into electrical energy(generators). The essential link in the chain of conversion is the energy of electromechanical field developed in the machine`s “airgap” by the currents flowing in the “windings”.

Pictures showing electric motor and generator

The stator and rotor windings are usually formed in such a way that the electromagnetic flux in the air gap is,approximately ,sinusoidally distributed.In this case ,the developed electromagnetic torque , due to the interaction of the stator and rotor fields, is proportional to the magnetic of each field(i.e to the value of the stator and rotor currents ,is&ir)and the sinus of the angle of θ of the vectors representing the fluxes in the air gap:T=Kisir sinθ

Thus ,the development of a mean electromagnetic torque in the steady-state of operation of the machine requires a constant (time-varient) angle θ between the stator and rotor fields.The essential requirement is met in a different way for each of the three main types of electric machines that are - Synchronous machines- Asynchronous (Induction)machines- Direct Current machines


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Synchronous machines

Definition of Alternator The definition of alternator is hidden in the name of this machine itself. An alternator is such a machine which produces alternation electricity. It is a kind of generators which converts mechanical energy into alternating electrical energy. It is also known as synchronous generator.

Principle of operation Faraday’s law of electromagnetic induction which says the current is induced in the conductor inside a magnetic field when there is a relative motion between that conductor and the magnetic field. During discussion of basic working of alternator, we have considered that the magnetic field is stationary and conductors (armature) is rotating. But generally in practical construction of alternator, armature conductors are stationary and field magnets rotate between them. The rotor of an alternator or a synchronous generator is mechanically coupled to the shaft or the turbine blades, which on being made to rotate at synchronous speed Ns under some mechanical force results in magnetic flux cutting of the stationary armature conductors housed on the stator. As a direct consequence of this flux cutting an induced emf and current starts to flow through the armature conductors which first flow in one direction for the first half cycle and then in the other direction for the second half cycle for each winding with a definite time lag of 120° due to the space displaced arrangement of 120° between them as shown in the figure below. This particular phenomena results in 3φ power flow out of the alternator which is then transmitted to the distribution stations for domestic and industrial uses.3 Phase Generated Voltage

Construction of Alternator


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Construction wise, an alternator generally consists of field poles placed on the rotating fixture of the machine i.e. rotor as shown in the figure above. Once the rotor or the field poles are made to rotate in the presence of armature conductors housed on the stator, an alternating 3 φ voltage represented by aa’ bb’ cc’ is induced in the armature conductors thus resulting in the generation of 3φ electrical power.

Types of AlternatorAlternators or synchronous generators can be classified in may ways depending upon their application and design. According to application these machines are classified as- a)Automotive type – used in modern automobile. b)Diesel electric locomotive type – used in diesel electric multiple unit. c)Marine type – used in marine. d)Brush less type – used in electrical power generation plant as main source of power. e)Radio alternators – used for low brand radio frequency transmission. But synchronous generators are mainly classiffied in two types1)Salient pole type It is used as low and medium speed alternator. It has a large number of projecting poles having their cores bolted or dovetailed onto a heavy magnetic wheel of cast iron or steel of good magnetic quality. Such generators are characterized by their large diameters and short axial lengths. These generator are look like big wheel. These are mainly used for low speed turbine such as in hydral power plant.


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2) Smooth cylindrical type It is used for steam turbine driven alternator. The rotor of this generator rotates in very high speed. The rotor consists of a smooth solid forged steel cylinder having a number of slots milled out at intervals along the outer periphery for accommodation of field coils. These rotors are designed mostly for 2 pole or 4 pole turbo generator running at 36000 rpm or 1800 rpm respectively.

Use of Alternator*The power for electrical system of modern vehicles produces from alternator. The dc dynamos are replaced by more robust and light weight alternator. This special type of generator which is used in vehicle is known as automotive alternator.*This machine is also used in marine similar to diesel electric locomotive. *Another use of alternator is in diesel electric locomotive. These dc traction motors drive the wheel of the locomotive.

HEAT RECOVERY BOILERS Bagasse is the matted cellulose fiber residue from sugar cane that has been processed in a sugar mill. Previously, bagasse was burned as a means of solid waste disposal. However, as the cost of fuel oil, natural gas, and electricity has increased, bagasse has come to be regarded as a fuel rather than refuse. Bagasse is a fuel of varying composition, consistency, and heating value. These characteristics depend on the climate, type of soil upon which the cane is grown, variety of cane,harvesting method, amount of cane washing, and the efficiency of the milling plant

Definition of Boiler22 INTERNSHIP REPORT| Ugar Sugar Works Ltd

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Steam boiler or simply a boiler is basically a closed vessel into which water is heated until the water is converted into steam at required pressure. Working Principle of Boiler

The basic working principle of boiler is very simple.The boiler is essentially a closed vessel inside which water is stored. Fuel (generally coal) is bunt in a furnace and hot gasses are produced. These hot gasses come in contact with water vessel where the heat of these hot gases transfer to the water and consequently steam is produced in the boiler. Then this steam is piped to the turbine of thermal power plant. There are many different types of boiler utilized for different purposes like running a production unit, sanitizing some area, sterilizing equipment, to warm up the surroundings etc.

In sugarmill bagasse is used and its outlook

Boiler Plant Outlook


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Types of Boiler

There are mainly two types of boiler – water tube boiler and fire tube boiler.

In fire tube boiler, there are numbers of tubes through which hot gases are passed and water surrounds these tubes.

Water tube boiler is reverse of the fire tube boiler. In water tube boiler the water is heated inside tubes and hot gasses surround these tubes.

Water Tube Boiler


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The above fig. shows water tube boiler with schematic diagram.

In Ugar Sugar Works, Water tube boiler is used for steam generating in cogeneration unit.

Functions of each parts1) RBC (return bagasse conveyor chain)-which weighs bagasse into the furnace.2) Secondary Air Fan-which blows bagasse to fall at far distance.3) FD (forced draft) fan-which supplies the required air into the furnace for combustion of fuel. It handles air at normal temperature. 4) ID (induced draft) fan-It pulls out flue gas from the furnace of boiler. It is located between dust precipitators(ESPs) and Chimney. Obviously it handles hotAir or dust. note-The capacity power rating of ID fan will be more than that of FD fan 5) Clarifier- This is a vessel, in which clarification of ash is done.6) Ash Bed-which stores ash.7) Furnace- This is a big thick vessel .In which bagasse is fed and heated at high temp to produce high pressure steam. 8) Super heaters-a component of a boiler unit that superheats steam, heats steam above its saturation temperature. A superheater consists of parallel-mounted steel tubes .There are used as following type of coilsa) PSH(primary super heater)coils-


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b) SSH(sec super heater) coils-9) Super heater Safety valve-10) Stop valve- Used for emergency stop of steam flow.11) NRV (non return valve)-12) Steam drum-where steam is stored. 13)Economizer- An economizer is a heat exchanger in which feed water is heated by flue gases before the water is supplied to the boiler.An economizer increases the efficiency of a boiler unit.14) Wet scrubber-A device designed to clean a gas steam by bringing it into contact with a liquid.15) RCC Chimney- Used as out lets for waste gas.

COGENERATION WITH STEAM TURBINE CYCLE Introduction

The steam turbine based cogeneration is the oldest and most prevalent in our country.The factors considered for choosing of steam turbine for different applications are reliability, variable speed operation and possibility of energy savings. Besides power generation, the steam turbines are used as prime-mover for many process equipment such as pumps, fans, blowers and compressors. It is generally preferred to keep steam turbine driven equipment for running critical services, where power tripping may causeserious problems. The electrical efficiency of industrial duty steam turbine generators varies over a wide range depending on whether the steam turbine is extraction-cumcondensing type or back-pressure type The steam turbine based cogeneration plant consists of a steam turbine generator of back-pressure, extraction-cum-back pressure or extraction-cum-condensing type in accordance with requirement of steam for the process plant and a steam generator or boiler fired with conventional fuels such as coal, lignite, fuel oil, natural gas, etc. or nonconventional fuels such as bagasse, rice husk, etc. Single stage steam turbines are used where the power requirement is low and multi-stage steam turbines are used for meeting high power requirements

Performance of Steam turbines


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Performance of steam turbines is expressed in terms of Theoretical Steam Rate (TSR) and Actual Steam Rate (ASR), which is the quantity of heat in kJ required to generate one kWh of electric power.

Back-pressure steam turbines are providing better thermal efficiency in the range of 70 –85%.

Extraction-cum-condensing/back-pressure steam turbines are commonly installed for totalgeneration schemes due to their excellent flexibility to meet power requirement coupledwith the steam requirement at different levels. Such systems achieve thermal efficiency inthe range of 50 – 75%.

Condensing steam turbines works at low thermal efficiency between 15 – 35% due to wastage of substantial useful heat in condensing of the steam.

Plant operating stage

i. Best operational mode Power or heat operated - Depending on the total power load of the industry, number of steam turbines are arranged on one line so that one or more steam turbines can be operated according to demand of power. With such philosophy of operation, it is possible to run the turbines close to the optimal operating range. ii. Steam conditionsDecentralised cogeneration power plants of low and medium output in the range of 1to 10 MW can be considered. Input steam conditions may be fixed between 30 – 70 bar and live steam temperature may be fixed between 400 – 500 0C to obtaindesired steam turbine performance.iii. Steam quality Maintaining of steam quality injected into a steam turbine as per specifiedparameters is one of the vital factors for performance of equipment. Steam qualitydepends on the quality of water and boiler feed water sent to the boiler. On-line monitoring of steam conductivity is must as a part of instrumentation, which provides the data whether any impurity is going to the turbine.iv. Control for steam turbinesSpeed of steam turbine should be mantained(controlled) constant at irrespective of varying load.And this is achieved by some methods of governing

• Throttle governing• Nozzle governing• By pass governing• Combination governing• Emergency governing


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Steam Turbine

Monitoring for steam turbinesContinuous or on-line monitoring of following parameters would be vital to avoid fall in the steam turbine performance.

Monitoring of conductivity of steam to ensure silica content in steam, as silica would deposit on the blades to adversely affect the output.

Monitoring of axial differential expansion, vibrations, etc. must be carried out using suitable microprocessor based instrumentation.

Monitoring of lube-oil circulation in bearings along with continuous cleaning of lube-oil through centrifuge is very important.

Checking of safety devices, such as operation of over speed trips


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Transmission & Distribution:

Above diagram shows transmission & distribution of powerThere are four steps

i. Primary transmission- This is also called as high voltage transmission. By using step up transformer voltage is raised from 11kV to 220V.Here voltage is generated at generating station

ii. Secondary transmission- Voltage is received by a receiving station .And voltage is step down from 220kV to 33kV and then transmitted through feeders.

iii. Primary distribution- Here voltage is received at substation. And it is again step down from 33kV to 6.6kV.It is then transmitted to


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distribution substation or directly to some large bulky loads like factories, industries etc

iv. Secondary distribution- This is the last stage of distribution voltage is step down from 6.6kV to 400V or 230V.It is then send to distibutors,consumers through service mains.


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FIG TRANSMISSION AND DISTRIBUTION SHOWING FROM GENERATING STATION TO HOME LOAD

INDUSTRIAL CASESTUDIES AT USW

B ACK PRESSURE STEAM TURBINE AND BAGASSE FIRED BOILER SUGARMILL Generally, in Ugar Sugar Works factory, the cogeneration system having configuration of steam turbine generator (back-pressure type) and fired boiler is found working, providing the best performance results. Moreover, this type of cogeneration system fires non-conventional fuel bagasse (sugar cane waste) in the boiler and then also works at optimum efficiency. Thus steam power cycle involving direct combustion of bagasse in a boiler to raise steam, which is then expanded through a turbo alternator to generate electricity. Some of the steam generated(Exhaust Steam) will be used in the sugar plant processes and equipment, while the power generated will be used internally by the company and the excess (25 MW) will be exported to the national grid.

EQUIPMENTS EXISTING BOILERS AT USWSteamCapacity(t/hr)

Pressure SteamTemperature

Number ofUnits

75 TPH 62 480 2 80 TPH 62 480 2 55 TPH 32 480 1

EXISTING TURBOGENERATORS AT USW31 INTERNSHIP REPORT| Ugar Sugar Works Ltd

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NAME InstalledCapacity(MW)

RATING Number ofUnits

SNM 1 21.8 MW 28500 KVA 1SIEMENS 32 MW 37500 KVA 1SNM2 22.8MW 28500 KVA 1TRIVENI 12.5MW 15000 KVA 1

STEAM TURBINE GENERATOR DATA

STEAM TURBINE DATA

Type Nos.Installed Rating(Mw)

Speed Of Turbine(rpm)

Back pressure Single Stage(SN1)

1 22.8 5615

Extraction-cum-back-pressure type

1 18 3000

Back pressure Single Stage(SN2)

1 22.8 5615

Back pressure Single Stage(TRI)

1 12.5 7018

REDUCTION GEARBOX DATA TYPE SPEED RATIOOil Filled SNM1 5615/1500Oil Filled SNM2 5615/1500Triveni Oil Filled 7018/1500

STEAM PARAMETERS

Inlet SteamPressure(kg/cm2)

Inlet SteamTemperature(0C)

Exhaust steamPressure(kg/cm2)

Exhaust steamTemperature(0C)

Specific steamConsumption(Kg/kWhr)

58(SNM1) 490 1.5 141


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62(SIEMENS) 490 - 7558(SNM2) 490 1.5 14132(TRIVENI) 490 1.5 191

GENERATOR DATARating for apparent power(KVA)

28500 37500 28500 15000

Power output at rated pf (KW)

22800 18000 22800 12500

Full load current(A)

1496 1885 1496 787

Full Load voltage(V)

11000 11500 11000 11000

Excitation voltage(V)

248 213 248 144

Excitation current(A)

430 343 430 620

Rated Power Factor

0.8 0.8 0.8 0.8

Frequency(Hz) 50 50 50 50Generator Shaft Speed(RPM)

1500 1500 1500 1500

Type SNM1 SIEMENS SNM2 TRIVENI

NORMAL OPERATING PHILOSOPHY

The sugar manufacturing plant works on seasonal basis, i.e. generally for a period of 5-6 months from November to April every year, when the sugarcane crop would be available for crushing. In remaining 5 months, rigorous preventive maintenance of all the equipment is carried out so that the plant works without any problem during ensuing season.

Generally in USW, 2 x 22.8 MW ( SNM1 & SNM2) and 1 x18MW Siemens steam turbine generator with 2 x 60 TPH& 2 x 80 TPH boilers, and 1 x 12.5 MW (NEW) Triveni steam turbine generator with 50 TPH boilers in required numbers are operated at full load. As 2 x 22.8MW and 1 x18MW steam turbine generators and 2 x 60 TPH& 80 TPH boilers are matching with each other so far steam parameters is concerned, i.e. it becomes one island. Second island is formed by remaining steam turbine


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generators i.e Triveni and 50TPH boiler due to matching of steam parameters.

Thus the steam from 4 boilers is brought to a Header which is operating at High Pressure and is fed to SNM1 & SNM2 steam turbogenerators and for the Triveni turbogenerator, steam is provided with separate 50TPH boiler operating at Lower Pressure..As for Siemens TG steam supply is cut as its not in working mode.

Remaining equipment(STG) is operated either in the event of breakdown or shutdown of any of the above units, or according to the power and steam load requirements by the production. The USW meets the total electric power and steam requirements of the manufacturing plant as soon as the production is commenced consequent to availability of sugarcane for crushing. The plant is working conforming to the concept of total co-generation power plant technology, which is encouraged all around the world in a big way due to conformance to very vital concept of energy conservation..

The electric power generated in USW is totally utilised to operate the process equipment, utilities and plant/office/area illumination. During normal plant operations, the power generation is maintained at more than 90% of machine rating and around 0.85 power factor so as to get optimum efficiency.

POWER PLANT PERFORMANCE ANALYSIS WORKSHEET CHART

NO PARAMETERS UNITS VALUES 1 Power Generation (P) KW

2 Steam Generation (M) TPH3 Stream Pressure kg/cm2 (g)4 Steam Temperature 0C5 Steam Enthalpy (hs) kCal/kg6 Feed Water Temperature7 Feed Water Enthalpy (h4) kCal/kg8 Number of Extractions9 1st Extraction Conditions


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Pressure kg/cm2 (g)Temperature 0CActual Enthalpy (h1) kCal/kgTheoretical Enthalpy (H1) kCal/kg

10 2nd Extraction ConditionsPressure kg/cm2 (g)Temperature 0CActual Enthalpy (h1) kCal/kgTheoretical Enthalpy (H1) kCal/kg

11 Condensing ConditionPressure kg/cm2 (g)Temperature 0CActual Enthalpy (h1) kCal/kgTheoretical Enthalpy (H1) kCal/kg

12 Efficiency of 1st Stage {(h1 – h2) / (h1 – H1)}

%

13 Efficiency of 2st Stage {(h2 – h3) / (H1 – H2)}

%

14 Efficiency of Condensing Stage{(h3 – h4) / (H2 – H3)}

%

15 Plant Heat Rate [ M x (hs – h4) ] / (P x 1000)

kCal/kWh

The power load on new steam turbine generator is maintained almost constant due to their better performance, the steam load is also maintained on the connected boiler, and as such the plant load factor and efficiency are observed better in this system. The power load variations are generally taken care off by the system consisting of older steam turbines and boilers.

The average age of the steam turbines and boilers is around 8 years. The specific steam consumption derived based on the enthalpy difference method is found only marginally offset from the data provided by the manufacturer, which could also be due to some disparity between required and actual inlet steam parameters.


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There is no provision for measurement of actual quantity of Bagasse being fired in the boilers. Based on derivation of specific steam consumption, noted steam parameters such as pressure and temperature, power load maintained and analysis of Bagasse, the fuel consumption can be derived, which would provide reasonably accurate data. The calibrated energy meters are provided for measurement of electricity.

The bagasse and steam balance is monitored and recorded

Bagasse Balance at USW


TOTAL BAGASSE

Bagasse used in Boiler(60T,60T,70T,80T)

Own BagasseExcess Bagasse

Bagasse used in 50T boiler

Purchased bagasse

Bagasse recquired for 50T boiler

Bagasse recquired in 4Boiler (60T,60T,70T,80T)

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STEAM BALANCE AT USW

CONTROLLING AND MONITORING SYSTEM All the basic sub-systems that constitute the cogeneration system must operate efficiently as an integral system with optimized performance to produce the greatest benefit.In this respect, prime movers must be regulated to respond to changing load conditions,generators must hold frequency and voltage within close limits,while the heat recovery equipment must deliver energy to the required demand.Additionally overrides and safeguards must be built-in to ensure safety and plant protection.

The main components of a CHP installation each have their own dedicated control system with panels that may be local to the equipment or in control room. Primary mover controls usually incorporate condition-monitoring equipment, which provides warnings and automotive shutdown in the event of component malfunction, and which also assists of long term mgmt and operation of plant.


Exhaust steam

Steam Generated from4(60T,60T,70T,80T) Boilers

Total steam Available

Steam Generated from 50T Boiler Total Steam

Available

Steam Used For Power Generation in SNM1&SNM2 TG

Steam Used For Power Generation in Triveni TG

Sugarcane Processing Unit

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Control systems are usually based on high integrity programmable logic controllers (PLC) and include all the monitoring , control and protection systems required for the safe start up, operation and normal shutdown of the equipment.

LONG TERM PERFORMANCE MONITORING

Monitoring of a wide range of parameters can be used in order to

Detect faults, malfunctions, under performance etc. at the earliest possible stage so that they can be promptly rectified.

Enable fine tuning and optimization of the equipment Facilitate modifications in order to respond to alterations in site energy loads

, new or amended electricity supply tariffs,fuel price/availability fluctuations etc

Audit the return on Investment

For a turbine and geardrive the variables are

the variation and phase angles at each bearing, shell, rotor and differential expansion , total control valve position, speed, rotor eccentricity, Inspecting auxillaries Lubricating oil pumps Coolers and oil strainers Lubrication of bearings steam temperatures, shell and bearing metal temperatures, exhaust pressure

etc.

Optical sensors can measure many system parameters , including temperatures, pressure, strain, voltage, current, electric field and chemical concentrations.

Thus Overall system control techniques need to flexible enough to ensure optimum performance of the whole installation.

Operating features normally incorporated in the control systems may include

Start up and shut down procedures


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Normal operating parameters, with alarams and automatic shutdown facilities

Protection of individual motors and components Input and output of condition signals Modulation in response to control inputs Synchronisation with the local electricity supply system Monitoring of vibration

A plant monitoring system will collect current and historical data for a wide range of plant parameters while it can store and process data to provide information for evaluation and plant diagnosis purposes. Typical parameters would include

Heat and power outputs Fuel consumptions Water consumption Ambient air conditions Steam pressure and temperature Exhaust and cooling system conditions Exhaust steam constituents Electricity import and export metering

CONCLUSION

This REPORT presents an overview of the key issues, details, introduction concerning the cogeneration power plant in USW Sugar Mill. A detailed discussion has been introduced of the various cogeneration technologies ,transmission and distribution, monitoring and controlling system and also brief description about the turbogenerator set of CHP has been presented. Cogeneration in USW study provides that plant can generate 44MW during season and it can export 375 lakh units of electricity in the season. And during off-season it can generate 16MW and nearly it can export ... units of electricity.


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RESOURCES

California Energy Commission. Cogeneration Handbook. 1982

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