Unit2 diesel engine power plant

1. DIESEL ENGINE POWER PLANT APPLICATIONS OF DG SETS PEAK LOAD PLANT MOBILE PLANT STAND BY UNIT EMERGENCY PLANT NURSERY STATION STARTING STATION CENTRAL STATION S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

2. ADVANTAGES OF DIESEL ENGINE POWER PLANT • EASY TO DESIGN & INSTALL • EASILY AVAILABLE IN STANDARD CAPACITIES • RESPOND TO LOAD VARIATION SMOOTHLY • LESS STANDBY LOSSES • OCCUPY LESS SPACE • STARTED & STOPPED QUICKLY • REQUIRE LESS COOLING WATER • LESS CAPITAL COST • LESS OPERATING & SUPERVISING STAFF • EFFICIENCY IN PART LOADS HIGHER • NO ASH HANDLING PROBLEM • EASIER LUBRICATION SYSTEM • LESS CIVIL ENGG. WORKS S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

3. DISADVANTAGES OF DIESEL ENGINE POWER PLANT • HIGH OPERATING COST • HIGH MTCE & LUBRICATION COST • CAPACITY IS RESTRICTED • NOISE PROBLEM • CANNOT SUPPLY OVERLOAD • UNHYGENIC EMISSION S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

4. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

7. DIESEL POWERPLANT LAYOUT S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

8. DIESEL ENGINE POWER PLANT • ENGINE • AIR INTAKE SYSTEM • EXHAUST SYSTEM • FUEL SYSTEM • COOLING SYSTEM • LUBRICATING SYSTEM • STARTING OF ENGINE S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

9. Fuel Injection System` Functions 1.Filter the fuel 2.Meter the correct quantity of injected fuel 3.Time the injection process injected 4.Regulate the fuel supply 5.Secure fine atomization of fuel 6.Distribute the atomized fuel in Combustion chamber S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

10. Oil atomization • Air blast fuel atomization ;l Compressed air at 70 bar used to atomize & inject fuel. For this Compressor and storage tank required which is expensive. • Solid Injection : Fuel oil is forced to flow thro spray nozzles at a pressure of above 100 bar. a) Common rail injection system b) Individual pump injection system c) Distributor system. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

11. Common Rail Injection system • A single pump supplies fuel under pressure to fuel header or common rail. • High pressure in the header forces the fuel to each of the nozzles located in the cylinder • At the proper time, a mechanically operated valve allows fuel to enter cylinder thro nozzle • The amount of fuel entering cylinder is regulated by varying the length of the push rod stroke. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

13. Fuel oil injection system (contd.) • Individual pump injection system • Distributor system S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

15. Cooling & Lubricating System • THERMO SIPHON COOLING • THERMOSTAT COOLING • Splash lubricating system • Bypass type wet sample lubrication S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

22. Comparisons of various Power plants S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

23. Classification of gas turbines : • Gas turbines are classified according to three factors , These are : 1. Combustion process 2. Path of working substance 3. Action of combustion gases in turbine S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

24. Classification of Gas turbine Combustion process Path of Gases Action of Gases Const. volume Const. pressure Impulse Turbine Impulse-Reaction Turbine Open Cycle GT Closed Cycle GT Semi Closed Cycle GT S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

25. 25 Brayton Cycle: Ideal Cycle for Gas-Turbine Engines Gas turbines usually operate on an open cycle (Fig. 9–29). Air at ambient conditions is drawn into the compressor, where its temperature and pressure are raised. The high pressure air proceeds into the combustion chamber, where the fuel is burned at constant pressure. The high-temperature gases then enter the turbine where they expand to atmospheric pressure while producing power output. Some of the output power is used to drive the compressor. The exhaust gases leaving the turbine are thrown out (not re- circulated), causing the cycle to be classified as an open cycle. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

26. 26 The open gas-turbine cycle can be modelled as a closed cycle, using the air-standard assumptions (Fig. 9–30). The compression and expansion processes remain the same, but the combustion process is replaced by a constant-pressure heat addition process from an external source. The exhaust process is replaced by a constant-pressure heat rejection process to the ambient air. Closed Cycle Model S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

27. 27 The ideal cycle that the working fluid undergoes in the closed loop is the Brayton cycle. It is made up of four internally reversible processes: 1-2 Isentropic compression; 2-3 Constant-pressure heat addition; 3-4 Isentropic expansion; 4-1 Constant-pressure heat rejection. The T-s and P-v diagrams of an ideal Brayton cycle are shown in Fig. 9–31. Note: All four processes of the Brayton cycle are executed in steady-flow devices thus, they should be analyzed as steady-flow processes. The Brayton Cycle S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

28. 28 Thermal Efficiency The energy balance for a steady-flow process can be expressed, on a unit–mass basis, as The heat transfers to and from the working fluid are: The thermal efficiency of the ideal Brayton cycle, is the pressure ratio.where Constant specific heats S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

29. 29 The thermal efficiency of an ideal Brayton cycle depends on the pressure ratio, rp of the gas turbine and the specific heat ratio, k of the working fluid. The thermal efficiency increases with both of these parameters, which is also the case for actual gas turbines. A plot of thermal efficiency versus the pressure ratio is shown in Fig. 9–32, for the case of k =1.4. Parameters Affecting Thermal Efficiency S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

30. 30 The early gas turbines (1940s to 1959s) found only limited use despite their versatility and their ability to burn a variety of fuels, because its thermal efficiency was only about 17%. Efforts to improve the cycle efficiency are concentrated in three areas: 1. Increasing the turbine inlet (or firing) temperatures. The turbine inlet temperatures have increased steadily from about 540°C (1000°F) in the 1940s to 1425°C (2600°F) and even higher today. 2. Increasing the efficiencies of turbo-machinery components (turbines, compressors). The advent of computers and advanced techniques for computer-aided design made it possible to design these components aerodynamically with minimal losses. 3. Adding modifications to the basic cycle (intercooling, regeneration or recuperation, and reheating). The simple-cycle efficiencies of early gas turbines were practically doubled by incorporating intercooling, regeneration (or recuperation), and reheating. Improvements of Gas Turbine’s Performance S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

31. 31 Actual Gas-Turbine Cycles Some pressure drop occurs during the heat-addition and heat rejection processes. The actual work input to the compressor is more, and the actual work output from the turbine is less, because of irreversibilities. Deviation of actual compressor and turbine behavior from the idealized isentropic behavior can be accounted for by utilizing isentropic efficiencies of the turbine and compressor. Turbine: Compressor: S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

32. 32 Brayton Cycle With Regeneration Temperature of the exhaust gas leaving the turbine is higher than the temperature of the air leaving the compressor. The air leaving the compressor can be heated by the hot exhaust gases in a counter-flow heat exchanger (a regenerator or recuperator) – a process called regeneration (Fig. 9-38 & Fig. 9-39). The thermal efficiency of the Brayton cycle increases due to regeneration since less fuel is used for the same work output. Note: The use of a regenerator is recommended only when the turbine exhaust temperature is higher than the compressor exit temperature. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

33. 33 Effectiveness of the regenerator, Effectiveness under cold-air standard assumptions, Thermal efficiency under cold-air standard assumptions, Effectiveness of the Regenerator Assuming the regenerator is well insulated and changes in kinetic and potential energies are negligible, the actual and maximum heat transfers from the exhaust gases to the air can be expressed as S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

34. 34 Thermal efficiency of Brayton cycle with regeneration depends on: a) ratio of the minimum to maximum temperatures, and b) the pressure ratio. Regeneration is most effective at lower pressure ratios and small minimum-to-maximum temperature ratios. Factors Affecting Thermal Efficiency S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

35. 35 Brayton Cycle With Intercooling, Reheating, & Regeneration The net work output of a gas-turbine cycle can be increased by either: a) decreasing the compressor work, or b) increasing the turbine work, or c) both. The compressor work input can be decreased by carrying out the compression process in stages and cooling the gas in between (Fig. 9-42), using multistage compression with intercooling. The work output of a turbine can be increased by expanding the gas in stages and reheating it in between, utilizing a multistage expansion with reheating. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

36. 36 Physical arrangement of an ideal two-stage gas- turbine cycle with intercooling, reheating, and regeneration is shown in Fig. 9-43. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

37. 37 The work input to a two-stage compressor is minimized when equal pressure ratios are maintained across each stage. This procedure also maximizes the turbine work output. Thus, for best performance we have, Conditions for Best Performance Intercooling and reheating always decreases thermal efficiency unless are accompanied by regeneration. Therefore, in gas turbine power plants, intercooling and reheating are always used in conjunction with regeneration. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

38. 38 Compare Open cycle and Closed cycle Gas turbines Open cycle: 1.Warm-up time. Once the turbine is brought up to the rated speed by the starting motor and the fuel is ignited, the gas turbine will be accelerated from cold start to full load without warm-up time. 2. Low weight and size. The weight in kg per kW developed is less. 3. Open cycle plants occupy comparatively little space. 4. Open-cycle gas turbine power plant, except those having an intercooler, does not require cooling water. 5. The part load efficiency of the open cycle plant decreases rapidly as the considerable percentage of power developed by the turbine is used to drive the compressor. 6. The open-cycle gas turbine plant has high air rate compared to the other cycles, therefore, it results in increased loss of heat in the exhaust gases. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

39. 39 Compare Open cycle and Closed cycle Gas turbines Contd… Closed cycle: 1. The machine can be smaller and cheaper than the machine used to develop the same power using open cycle plant. 2. The closed cycle avoids erosion of the turbine blades due to the contaminated gases and fouling of compressor blades due to dust. Therefore, it is practically free from deterioration of efficiency in service. 3. The need for filtration of the incoming air which is a severe problem in open cycle plant is completely eliminated. 4. The maintenance cost is low and reliability is high due to longer useful life. 5. The system is dependent on external means as considerable quantity of cooling water is required in the pre-cooler. 6. The response to the load variations is poor compared to the open-cycle plant S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

40. Gas Turbines • Gas turbines also called combustion turbines, a type of IC engine in which burning of an air-fuel mixture produces hot gases that spin a turbine to produce power. • It is the production of hot gas during fuel combustion, not the fuel itself that the gives gas turbines the name. • Combustion occurs continuously in gas turbines, as opposed to reciprocating IC engines, in which combustion occurs intermittently. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

41. Working They Work On Brayton Cycle.  Air is compressed(squeezed) to high pressure by a compressor.  Then fuel and compressed air are mixed in a combustion chamber and ignited.  Hot gases are given off, which spin the turbine wheels S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

42. General View of a Gas Turbine S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

43. Components Of Gas Turbine Gas turbines have three main parts: i)Air compressor ii) Combustion chamber iii) Turbine

44. Air compressor: The air compressor and turbine are mounted at either end on a common shaft, with the combustion chamber between them. Gas turbines are not self starting. A starting motor is used. The air compressor sucks in air and compresses it, thereby increasing its pressure. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

45. Combustion chamber: In the combustion chamber, the compressed air combines with fuel and the resulting mixture is burnt. The greater the pressure of air, the better the fuel air mixture burns. Modern gas turbines usually use liquid fuel, but they may also use gaseous fuel, natural gas or gas produced artificially by gasification of a solid fuel. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

46. Turbine: Hot gases move through a multistage gas turbine. Like in steam turbine, the gas turbine also has stationary and moving blades. The stationary blades guide the moving gases to the rotor blades adjust its velocity. The shaft of the turbine is coupled to a generator. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

47. APPLICATIONS drive pumps, compressors and high speed cars. aircraft and ships.  Power generation (used for peak load and as stand-by unit). S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

48. Combined Cycle Power Plants The maximum steam temp. in a power cycle does not exceed 600 deg.C, although the temp. in a dry bottom pulversied coal furnace is about 1300 deg. C. There fore , there is great thermal irreversibility and a decrease of availability because of heat transfer from combustion gases to steam through a such large temp. differences. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

49. • By superposing a high temp. power plant as a topping unit to the steam power plant, a higher energy conversion efficiency from fuel to electricity could be achieved, • since the combined plant operates through a higher temp. range. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

50. • Combined cycle plants may be of the following types Gas Turbine- Steam Turbine plant MHD- Steam Plant Thermionic – Steam plant Thermoelectric – Steam plant. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

51. • The air standard cycle for a gas turbine power plant is the Brayton Cycle, which like Rankine cycle also consists of two reversibile adiabatics and two reversible isobars, • but in Brayton cycle working fluid does not undergo phase change where as in Rankine cycle, the working fluid is water gets phase change as steam. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

52. • To overcome GT plant’s low cycle efficiency, a Gas Turbine may be used in conjunction with a steam turbine plant in an utility base load station to offer the utilities the gas turbine advantages of quick starting and stopping and permit flexible operation of the combined plant over a wide range of loads. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

53. Combined Cycle Power Plant S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

54. Combined Cycle Power Plant S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

55. Coal based combined cycle plants Coal is low grade fuel compared to oil and natural gas, but reserves of coal are very large, much effort has been devoted to developing clean coal technologies to reduce harmful emissions of SOx & Nox. Successful usage of coals for combined cycle power generation necessitated the development of firing systems whose products of combustion have 1.Sufficiently low concentration of particulates to reduce erosion and ensure a satisfactory life of GT. 2.Sufficiently low concentrations of pollutant gases and particulates in the exhaust to satisfy environmental regulation relating to discharges from power plants. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

56. • To reduce the concentration of particulates in products of combustion before entering the gas turbine, hot clean-up systems like multi- cyclones, ceramic filters etc. developed. • To control emission of oxides of sulphur and nitrogen, different techniques like low NOx burners, staged combustion, flue gas scrubbing etc. are being put into use. • Following are two dominant coal based technologies. 1.Pressurised fluidized bed combustion (PFBC) system, which may be either bubbling fluidized or circulating fluidized bed. 2. Integrated Gasified Combined cycle (IGCC) S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

57. PFBC based combined cycle • This system supplies hot gas at elevated pressure to gas turbine via hot gas cleanup system. • Coal and lime stone are supplied to the pressurized combustor. Limestone is used as the bed material to absorb sulphur. • Cooling tubes immersed in the fluidized bed are used to generate steam which is supplied to steam turbine. • The combustion products leaving the combustor are passed through a clean-up system before being expanded in the gas turbine. • Exhaust gases are then passed through a heat exchanger which heats the feed water before being discharged. • Temp. in PFBC is limited to about 850 deg. C because this is the most favorable temp of sulphur retention and is below the ash fusion temp. of coal S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

58. Integrated gasification Combined Cycle (IGCC) • Coal is gasified, either partially or fully and the gas produced after clean-up is burnt in the combustion chamber of GT. It is called an integrated gasification combined cycle (IGCC) • Coal and limestone are fed to a pressure vessel, the coal being gasified by oxygen and steam. The ash and limestone form a slag which is discharged and the gas is cooled. • The use of air instead of oxygen produces a gas of lower calorific value. • Exhaust gases from GT raise steam in the HRSG. • The thermo dynamic performance of an IGCC power plant shows that there is an optimum pressure ratio for the gas cycle at a given temp. ratio (T3/T0) for max. cycle efficiency. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

59. IGCC • An integrated gasification combined cycle (IGCC) is a technology that uses a high pressure gasifier to turn coal and other carbon based fuels into pressurized gas—synthesis gas . Impurities removed from the syngas prior to the power generation cycle. • Some of these pollutants, such as sulfur, can be turned into re-usable byproducts through the Claus Process. This results in lower emissions of Sulfur dioxide, mercury and in some cases Carbon dioxide. • With additional process equipment, a water gas reaction can increase gasification efficiency and reduce carbon monoxide emissions by converting it to carbon dioxide. The resulting carbon dioxide from the shift reaction can be separated, compressed, and stored through sequestration. • Excess heat from the primary combustion and syngas fired generation is then passed to a steam cycle, similar to a combined cycle gas turbine. • This process results in improved thermodynamic efficiency compared to conventional pulverized coal combustion. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

60. Block diagram of IGCC Plant S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

61. • The plant is called integrated because • the syngas produced in the gasification section is used as fuel for the gas turbine in the combined cycle and • the steam produced by the syngas coolers in the gasification section is used by the steam turbine in the combined cycle. • In this example the syngas produced is used as fuel in a gas turbine which produces electrical power. In a normal combined cycle, so-called "waste heat" from the gas turbine exhaust is used in a Heat Recovery Steam Generator (HRSG) to make steam for the steam turbine cycle. • An IGCC plant improves the overall process efficiency by adding the higher-temperature steam produced by the gasification process to the steam turbine cycle. This steam is then used in steam turbines to produce additional electrical power. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

62. Advantages & Disadvantages of IGCC • IGCC plants are advantageous in comparison to conventional coal power plants due to their high thermal efficiency, low non-carbon greenhouse gas emissions, and capability to process low grade coal. • The disadvantages include higher capital and maintenance costs, and the amount of CO2 released without pre-combustion capture. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

63. Process of IGCC • The solid coal is gasified to produce syngas, or synthetic gas. • Syngas is synthesized by gasifying coal in a closed pressurized reactor with a shortage of oxygen. • The shortage of oxygen ensures that coal is broken down by the heat and pressure as opposed to burning completely. • The chemical reaction between coal and oxygen produces a product that is a mixture of carbon and hydrogen, or syngas. CxHy + (x/2)O2 → (x)CO2 + (y/2)H2 S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

64. • The heat from the production of syngas is used to produce steam from cooling water which is then used for steam turbine electricity production. • The syngas must go through a pre- combustion separation process to remove CO2 and other impurities to produce a more purified fuel. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

65. • Three steps are necessary for the separation of impurities :  Water gas shift reaction : The reaction that occurs in a water-gas-shift reactor is CO + H2O CO⇌ 2 + H2. This produces a syngas with a higher composition of hydrogen fuel which is more efficient for burning later in combustion.  Physical separation process: This can be done through various mechanisms such as absorption, adsorption or membrane separation.  Drying, compression and storage/shipping. • The resulting syngas fuels a combustion turbine that produces electricity. At this stage the syngas is fairly pure H2. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

66. Thermodynamics of Brayton – Rankine combined cycle plant • Improvising of Brayton Cycle plant by combining with Steam turbine with Rankine cycle are possible in the following methods : • 1.1Two cyclic power plants coupled in series : The topping plant (GT) operating on Brayton cycle and the bottom one (ST) operating on Rankine cycle. • Over all efficiency of the combined plant is given by =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 • WhereȠ1 = Thermal efficiency of Brayton Cycle (GT) and Ƞ2 = thermal Efficiency of Rankine • In the above all the heat rejected by the topping plant (GT) is absorbed by the bottom plant (ST)S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

67. • 1.2 Heat losses between two plants in series : There is always some heat loss and the heat absorbed is less than the heat rejected. • Let QLbe the heat loss between two plants, then the overall efficiency is =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - Ƞ2XL • XL= fraction of heat lost (Q1/QL) • Two cyclic plants operating in parallel : let us consider two plants operating in parallel , one in Brayton cycle and other one from Rankine Cycle. • The total heat supplied Q1 is divided beteen two plants as Q2 and Q4, so that X1= Q2/Q1 = Q2/(Q2+Q4) • The overall efficiency of the combined plant = Ƞ2 + X1(Ƞ1 - Ƞ2 ) ………. AS.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

68. • If X2 = Q4/Q1 = Q4/(Q2+Q4) • The overall efficiency of the combined plant = Ƞ1 - x2(Ƞ1 - Ƞ2 ) ………. B • If Ƞ1 > Ƞ2, then >Ƞ Ƞ2 as per A • <Ƞ Ƞ1 as per B • Hence lies betweenȠ Ƞ1 and Ƞ2 • Thus no advantage to parallel system. • If the Cyclic plant 1 operating on Brayton cycle could absorb more heat say equal to Q1 + Q4, then it would be advantangeous to use that plant alone. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

69. Series parallel plants with two cyclic plants in series having supplementary firing • Let the fraction of the total heat supplied is used for supplementary heating be X2= Q4/Q1 • overall efficiency is =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - Ƞ1X2(1- Ƞ2 ) • Therefore the overall efficiency of a series – parallel plant is less than that of two coupled cycles in series since the last term is positive. • In the absence of supplementary heating ie. When x2 =0, the overall efficiency is that of ideal series plant.S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

70. • Series parallel plants with two cyclic plants in series having supplementary firing and heat loss in between the two plants: • Let the fraction of the total heat supplied is used for supplementary heating be x2= Q4/Q1 and XL fraction of heat loss to heat supply XL = QL /Q1 , where QL = heat loss to surrounding • Overall efficiency is =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - XLȠ2- Ƞ1X2(1- Ƞ2 ) : • If X2 = 0 =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - XLȠ2 S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

71. • Combined Cycle Plants with limited supplementary firing : Supplementary firing raises the temp. of the exhaust gas to 800 to 900 deg. C. relatively high flue gas temp. raises the condition of steam ( 84 bar, 525 deg.C) there by improving the efficiency of the steam cycle. • Combined Cycle Plants with maximum supplementary firing : Maximum supplementary firing refers to the maximum fuel that can be fired with the oxygen available in the Gas turbine exhaust. The use of large supplementary firing in Combined cycle plants with GT inlet temp. causes the efficiency to drop. • For this reason Combined cycle plants with maximum supplementary firing are only of minimal importance in comparison to simple Combined Cycle plants. S.PALANIVEL ASSOCIATE PROF./MECH ENGG KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

Unit2 diesel engine power plant

Unit2 diesel engine power plant

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