Advanced. FOR B.E / B.Tech MECHANICAL ENGINEERING STUDENTS

Transcription

1 Advanced ENERGY ENGINEERING FOR BE / BTech MECHANICAL ENGINEERING STUDENTS As Per Revised Syllabus of Leading Universities in India Including Dr APJ Abdul Kalam Technological University, Kerala Dr S Ramachandran, ME, PhD, Prof R Devaraj, ME, (PhD) Professors - Mech Sathyabama Institute of Science and Technology Chennai (Near All India Radio) 80, Karneeshwarar Koil Street, Mylapore, Chennai Ph: , aishram2000@gmailcom, airwalk800@gmailcom wwwairwalkbookscom, wwwsrbooksorg

2 First Edition : ISBN : / wwwairwalkbookscom Cell: , wwwsrbooksorg

3 ME403 ADVANCED ENERGY ENGINEERING Course Plan Module Contents Hours I II III Introduction to the course Global and Indian energy resources Energy Demand and supply Components, layout and working principles of steam, hydro, nuclear, gas turbine and diesel power plants Solar Energy- passive and active solar thermal energy, solar collectors, solar thermal electric systems, solar photovoltaic systems Economics of solar power Sustainability attributes FIRST INTERNAL EXAM Wind Energy-Principle of wind energy conversion system, wind data and energy estimation, wind turbines, aerodynamics of wind turbines, wind power economics Introduction to solar-wind hybrid energy systems IV Biomass Energy Biomass as a fuel, thermo-chemical, bio-chemical and agro-chemical conversion of biomass- pyrolysis, gasification, combustion and fermentation, transesterification, economics of biomass power generation, future prospects V VI SECOND INTERNAL EXAM Other Renewable Energy sources Brief account of Geothermal, Tidal, Wave, MHD power generation, Small, mini and micro hydro power plants Fuel cells general description, types, applications Hydrogen energy conversion systems, hybrid systems- Economics and technical feasibility Environmental impact of energy conversion ozone layer depletion, global warming, greenhouse effect, loss of biodiversity, eutrophication, acid rain, air and water pollution, land degradation, thermal pollution, Sustainable energy, promising technologies, development pathways END SEMESTER EXAM Sem Exam Marks 7 15% 7 15% 7 15% 6 15% 8 20% 7 20%

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5 Contents C1 Table of Contents Module - I INTRODUCTION TO ADVANCED ENERGY ENGINEERING 11 Introduction To The Course Global Energy Resources Indian Energy Resources Energy Demand and Supply Steam Power Plant Layout of Steam Power Plant Working principle of Steam Power Plant Layout of Steam Power Plant Coal and ash Circuit: Air and Flue gas circuit Feed water and steam flow circuit: Cooling Water Circuit Selection of Site for a Steam Power Plant Sub System of Thermal Power Plant Boiler Accessories Diesel Engine Power Plant Introduction Applications Site selection Advantages Disadvantages Types of Diesel Power Plants Layout of Diesel Power Plant Diesel Engine Used for Diesel Power Plants Selection of Engine Type Hydel Power Plants Essential Elements of Hydel Power Plant Reservoir Dam 141

6 C2 Advanced Energy Engineering - wwwairwalkbookscom 1143 Trash rack Surge tank Fore bay Penstock Spillway Power house Draft tube Site Selection For Hydel Power Plant Working of Hydro Electric Power Plant Major Hydroelectric Power Plants in India Nuclear Power Plant Nuclear Fission and Chain Reaction Layout of Nuclear Power Plant Site Selection for a Nuclear Power Plant Nuclear Reactor Gas Turbine Power Plant Classification of Gas Turbine Power Plants Layout of Open Cycle Gas Turbine Power Plant Working of Gas Turbine Power Plant Fuels for Gas Turbines Gas Turbine Materials Open and Closed Cycles 174 Module - II SOLAR ENERGY 21 Solar Energy - Introduction Solar Geometry Solar Radiation Measurements of Solar Radiation Passive and Active Solar thermal Energy Solar Collectors Types of Solar Collectors 27

7 Contents C3 222 Solar Direct Thermal Applications Solar Photovoltaic System Functioning of the photovoltaic cells Types of photovoltaic system Solar PV application Types of Solar Power Plant Solar Central Receiver System The Economics of Solar Energy Sustainability Attributes 224 Module - III WIND ENERGY 31 Wind Principle of Wind Energy Conversion System Application of Wind Power: Wind Characteristics Wind Availability and Measurement Human observation and log book Mechanical cup - counter anemometer Data Logger Continuous record of velocity and direction Source/origin of Wind Local winds Planetary winds Advantages and Disadvantages of Wind Energy Wind Power Terms and Definitions in Wind Power Wind Turbines Horizontal axis machines Vertical axis machine Performance of Wind Mills Aerodynamics of Wind Turbines 313

8 C4 Advanced Energy Engineering - wwwairwalkbookscom 3121 Drag and lift force in wind turbine Force acting on the blade Site selection for wind power plant Power Density Wind Power Economics Problems in Operating Large Wind Power Generators Introduction to Solar - Wind Hybrid Energy Systems Wind/PV Hybrid System 323 Module - IV BIOMASS ENERGY 41 Biomass Energy Sources of Biomass Biogas problems Biomass as Fuel Biomass Conversion Processes Thermo-chemical conversion Biochemical conversion Direct Combustion Transesterification Biogas Plant Economics of Biomass Power Generation Future Prospects of Biomass Energy in India 416 Module - V OTHER RENEWABLE ENERGY SOURCES AND ECONOMICS 51 Small, Mini and Micro Hydro Power Plants Components of Micro hydro power plant Power from a micro hydro plant Suitable conditions for micro-hydro power Turbines for micro hydro power Turgo Turbine Load factor 56

9 Contents C5 517 Load control governors Electrical power from micro hydro plant Economics of micro hydro power plant Low cost grid connection Tidel Power Plant Introduction Tidal power plants Components of Tidal power plants Geo Thermal Power Plant Geothermal sources Hydrothermal convective system Advantages of Geothermal Energy: Disadvantages: Ocean Thermal Energy Conversion (OTEC) Plant The Basic principle Types of OTEC Closed-cycle OTEC System Open-Cycle OTEC system Hybrid OTEC System Important points about OTEC Fuel Cell Hydro Energy Conversion System Hydrogen-oxygen fuel cell Advantages of fuel cells Disadvantage of fuel cell Application of fuel cell MHD Power Plant MHD Power Cycle Principles Types of MHD generators: Economics in Plant Selection Important Terms and Definitions: Economics of Power Generation 540

10 C6 Advanced Energy Engineering - wwwairwalkbookscom 591 Land, building and equipment cost and installation cost Depreciation cost Insurance Management cost Operating cost Total cost Cost of power generation Power Tariffs Aim of tariffs Selection of tariffs Types of tariffs Choice of Power Plant and its Site An Electric Load (or) Power Distribution System Load Duration Curves Important terms and definition: 559 Module - VI ENVIRONTMENTAL IMPACT OF ENERGY CONVERSION 60 Promising Technologies for Pollution Control Air Pollution Major Sources of Air Pollution (Causes of Air Pollution) Effects of Air Pollution Green House Effect (or) Global Warming Ozone Layer Depletion Acid Rain Photochemical Smog Water Pollution Control Measures of Water Pollution Thermal Pollution Causes of Thermal Pollution Harmful effects of thermal pollution 617

11 Contents C Control of Thermal Pollution: Land Degradation Causes of land degradation Control of Land Degradation Biodiversity Characteristic features of biodiversity Threats to biodiversity Habitat loss Loss of Biodiversity Control of Atmospheric Pollution by Thermal Power Plants Control devices for particulate contaminants 625 (i) Gravitational separators 625 (ii) Cyclone Separators (Cyclone dust collector): 626 (iii) Bag house dust collector 626 (iv) Electro Static Precipitator (ESP) 627 (v) Wet Collectors (Scrubbers) Water Pollution By Thermal Power Plant And Its Control Instrument used to monitor pollution: 6144 Automatic controls for feed water Indian Boiler Act Boiler Inspection Boiler Performance Boiler safety regulations as per Indian Boiler Act Nuclear Waste Disposal and Safety Radioactive waste Types of Radio active waste Collection, storage and disposal of nuclear materials Waste disposal process from nuclear reactor Approaches to radio-active waste disposal Control of Nuclear Radiation Sustainable Energy Development Pathways 658

12 Module - I INTRODUCTION TO ADVANCED ENERGY ENGINEERING Introduction to the course Global and Indian energy resources Energy Demand and supply Components, layout and working principles of steam, hydro, nuclear, gas turbine and diesel power plants 11 INTRODUCTION TO THE COURSE In this course, the various types of energy resources and their production methods will be studied in detail Electricity is the important form of energy It can be easily transmitted from one place to another It is easy to produce and use this energy Electricity can be produced using power plants such as (i) Thermal power plant (ii) Nuclear power plant (iii) Hydraulic power plant (iv) Geo-thermal power plant (v) Gas turbine The working fluid used is steam in thermal,nuclear and geo thermal power plants Gas turbines differ from these power plants Hydraulic power plants are very difficult to build and expensive Thermal power plants produces more than 80% of total electricity in the world Fossil fuels,coal and natural gas are the main energy source Steam is used as the working fluid The location (of the power plant) is the important parameter for constructing the plant In recent days, renewable energy resources are used for safeguarding the world from global warming and climate change Various environmental impacts such as ozone depletion, acid rain and pollution (CO 2 emission) are reducing the usage of non-renewable energy resources in certain countries All the countries in the world are making efforts to create green environment for future generation

13 12 Advanced Energy Engineering - wwwairwalkbookscom Some renewable energy resources are solar, wind, tidal and biomass energy Solar energy is easily obtained from the sun Similarly, all the other energy sources can be utilized easily Sustainable energy is an important aspect in future Hence,renewable energy resources can be used in wide range to meet the electricity demands in future 12 GLOBAL ENERGY RESOURCES Non renewable energy resources are coal, petroleum, natural gas and nuclear Renewable energy resources are solar, bioenergy, wind and geothermal The global primary energy consumption is shown in Fig 11 From this graph, the global energy consumption [terawatt-hours (TWH)] is identified for various years In 1800, only biomass was used After that, coal was used (only 2%) Global Primary Energy Consumption, Global Primary Energy Consumption, Measurement in terawatt-hours (Twh) p er Year Here other Renewable are Renewable Technologies not Including Solar, Wind, Hydropower and Traditional Biofuels (Te ra = 1 012) 140,000 TWh 120,000 TWh 12 [Tera = 10 ] other Renewable Solar Wind Nuclear Hydropower Natural Gas 100,000 TWh 80,000 TWh Crude Oil 60,000 TWh 40,000 TWh Coal 20,000 TWh 0 TWh Traditional Biofuels Fig 11

14 Introduction to Advanced Energy Engineering 13 But, expansion of oil did not begin until 1870 Coal consumption had increased significantly by 1900 Then, the oil usage increased in the mid of 20 th century The world has moved into nuclear electricity production by 1960 In 1990, the renewable energy resources (solar, wind, tidal) were not used After that, the resources are being used in larger quantity Other energy resources such as geothermal and marine technologies are not used because of small amount of production In 2015, the world consumed 146,000 terawatt-hours (TWh) of primary energy It is 25 times more than in 1800 The production of renewable energy resources has improved These energy resources are used for pollution free environment Electricity access to people Number of People in the World with and without Electricity Access Absolute Number of the Global Population with and without Access to Electricity in a given Year 7 Billion 6 Billion 5 Billion 4 Billion 3 Billion Number of People with Access to Electricity 2 Billion Number of 1 Billion People without Access to E lectricity Fig 12

15 14 Advanced Energy Engineering - wwwairwalkbookscom The graph (shown in Fig 12) indicates the number of people in the world with and without electricity access The number of people without electricity access is decreasing in recent years In 1990, 141 billion people lived without electricity access In 2014, 107 billion people lived without electricity access Reduction in value indicates the development in the electricity facilities for the people In 2014, the number of people with electricity access is increased by 23 billion 13 INDIAN ENERGY RESOURCES The energy sources in India are classified as Renewable energy (solar, wind, geothermal, tidal) Non-renewable energy (coal, petroleum and nuclear power) India is the fourth largest energy consumer in the world Installed Capacity (GW ) Renewable, 2946 other,15979 Coal,13821 Hydro, 3989 nuclear,478 Gas,2038 Diesel,12 Thermal-67% Renewable-13% Nuclear-2% Hydro-17% Fig 13 Energy Resources in India

16 Introduction to Advanced Energy Engineering 15 Energy consumption in India is relatively increasing due to population growth But, in India, it is possible to give to electricity to all in future The energy sources and their percentage are given (shown in Fig 13) Thermal - 67% Nuclear - 2% Renewable energy - 13% Hydro - 17% Renewable Energy Potential Resources Estimated Potential (MW) 1 Solar Power (30-50 MW/sq km) 100,000 2 Wind power (At 80 m height) 100,000 3 Small Hydro Power (upto 25 MW) 20,000 4 (i) Bio-Power (Agro-Residues) 17,000 4 (ii) Bio-Power (Cogeneration-Bagasse) 5,000 4 (iii) Waste to Energy (Municipal Solid Waste to Energy) 4 (iv) Waste to Energy (Industrial Waste to Energy) 2,600 1,280 Total 2,45,880 Wind Energy The use of wind power is rapidly increasing in India India had installed the total capacity of 19,933 MW The wind energy in India (68%) is used largely than other energies

17 16 Advanced Energy Engineering - wwwairwalkbookscom Geothermal Energy Geothermal energy is obtained from earth s crust It can be divided into four types; Hydrothermal field, Geo pressured geothermal resource, Hot dry rock deposit and Magma resource In 1992, geothermal binary cycle plant (capacity 5 MW) was installed in Himachal Pradesh Biomass energy Biomass is a renewable energy resource obtained from waste material In India, bioenergy is installed with capacity of MW Solar Energy Solar energy can be easily used The sun gives 1000 times more power than the required amount we need According to ministry of new and renewable energy, solar in India has crossed 2 GW land mark In 2013, total capacity of 2219 MW was installed Tidal Energy Tide is periodic rise and fall of water level of the sea It gives no harmful greenhouse emissions Tidal energy in India - Started in Gulf of kutch, in Gujarat It is still not completed Ocean Thermal Energy Conversion Ocean thermal energy conversion is an energy technology that converts solar radiation to electric power In India, 1 MW floating OTFC plant near Tamilnadu was constructed Conclusion There is an energy deficits (67%) in our country In India, largest solar park was installed in Karnataka state It gives an output of 2,000 MW More number of renewable energy sources are used to meet the required demand

18 Introduction to Advanced Energy Engineering ENERGY DEMAND AND SUPPLY Global energy demand will increase by around 30% in 2035 with an average growth of 13% per year, driven by increasing prosperity in developing countries, partially offset by rapid gains in energy efficiency Non-fossil fuels are expected to account for half of the growth in energy supplies over the next 20 years Oil demand grows at an average of 07% per year Transport sector continues to consume most of the world s oil with its share of global demand remaining close to 60% in 2035 Gas grows more quickly than either oil or coal over the outlook, with demand growing an average of 16% per year By 2035, imported gas comprises nearly 40% of total consumption India s energy demand was increased by 37% in 2016, but imports increased by 57% for CNG, LPG and gasoline In India - the unbalanced consumption and demand equation clearly reflect the shortages in supply India lags behind China in overall energy production, as China is among the top 5 energy producers in the world India is not expected to hit any major increase in its production capacities of any of the primary sources of energy, but an increase is expected in the natural gas production rates in the next 5 years 15 STEAM POWER PLANT Steam power plant is also called as Thermal power plant A steam power plant uses steam as a working fluid It uses coal as a fuel and water for producing steam The heat energy available in steam is converted into mechanical energy which is used for driving steam turbines The steam turbine is coupled to generator from which power is produced 151 Layout of Steam Power Plant 1 Primary Air Fan It sucks air named primary air from the atmosphere and discharges the air through air heater to the Mill The function of the mill is to produce pulverized coal The primary air carries pulverized coal for combustion to the burner

19 18 Advanced Energy Engineering - wwwairwalkbookscom Raw coal bunker Super heated steam Turbine G Super heater Generator Air from atmosphere Air from atmosphere Primary Air Cold Primary Air fan Forced Draft fan Air heater Secondary Air Cold Feeder Hot Air Flue gas to ESP Air heater coal Mill Flue gas Hot Air Boiler Hot Flue gas Flue gas Exhaust steam Economiser Hot flue gas Chimney Induced Draft fan Hot gas ESP Electro-Static Precipitator Feed water Feed pump Feed water Fig 14 Layout of a Steam Power Plants Heater Condenser

20 Introduction to Advanced Energy Engineering 19 2 Forced Draft Fan Forced Draft Fan also sucks air named secondary air from the atmosphere and discharges it to the boiler through the air heater Secondary air is heated in air heater and sent to boiler for complete combustion 3 Induced Draft Fan The function of the Induced Draft Fan is to discharge flue gas into the atmosphere through chimney by sucking force The flue gas coming out from the boiler is allowed to flow through air heater before sucked by the Induced Draft Fan 4 Air heater The function of air heater is to heat the primary and secondary air sucked from the atmosphere Flue gas coming out from the boiler heats the atmospheric air inside the air heater 5 Electrostatic precipitator The function of electrostatic precipitator is to remove the ash coming along with the flue gas The hot flue gas coming out from the boiler carries ash with it Thus, ash from the flue gas is removed by electrostatic precipitator before discharging it through chimney 6 Feed pump The function of the feed pump is to supply the condensed water to the boiler through the economiser 7 Boiler Boiler is a major component in a steam power plant It is a closed vessel in which water is flowing inside a number of water tubes Coal placed in the grate of boiler is heated along with the supply of atmospheric air due to which hot flue gas is produced Water inside water tubes are converted into steam by absorbing heat from flue gas 8 Generator The function of a generator is to generate electricity Generator is coupled to the steam turbine Steam from the boiler drives the turbine, which inturn drives the generator

21 110 Advanced Energy Engineering - wwwairwalkbookscom 9 Feed water heaters The function of feed water heater is to heat water from the condenser Hot water from feed water heater is sucked by the feed pump 10 Economiser Economiser is used for preheating the feed water, such that water entering the boiler will be already hot Economiser reduces the requirement of heat energy inside the boiler to some extent 11 Raw coal bunker The function of Raw coal bunker is to supply the stored raw coal to the mill through the Raw coal feeder 12 Super heater The function of super heater is to heat the saturated steam coming out from the boiler The super heated steam is supplied to the turbine 152 Working principle of Steam Power Plant In the steam power plant, coal from the storage is initially taken to boiler with the help of bucket elevators, belt conveyers etc, Then the coal is burnt in the boiler at 1500C to 2000C by the supply of atmospheric air through Forced Draft Fan and Primary Air Fan Boiler contains number of water tubes, which gets heated by burning coal Water inside the tube gets converted into super heated steam The super heated steam is allowed to flow through the turbine for rotating turbine blades Shaft of turbine is coupled with shaft of the generator Due to the rotation of the turbine, electricity is generated The steam coming out from the turbine is condensed by the condenser and the condensed water is recirculated into the boiler water tubes by the Feed pump The flue gas out from the boiler is allowed to flow through air heater Primary and secondary atmospheric air in the air heater absorbs heat from the flue gas Finally flue gas is forced out to the atmosphere through chimney

22 Introduction to Advanced Energy Engineering LAYOUT OF MODERN COAL POWER PLANT (OR) LAYOUT OF STEAM POWER PLANT In steam power plant, the water is converted into steam and the steam expanded in a turbine to produce kinetic energy which is converted into mechanical energy The steam power plant has four major circuits by which the layout can be studied in detail These are 1 Coal and ash circuit 2 Air and flue gas circuit 3 Feed water and steam circuit 4 Cooling water circuit Ash Storage Hot Ash or Slag Handling Air from atmosphere FD Fan To Atmosphere Chimney Coal handling Coal Preparation Coal Storage Fuel Superheater Boiler Feed Pump Fig 15 Steam Preheated air Control High Pressure Heater Air Preheater Valve Economiser Pump Deaerator IDFan Dust Collector Turbine Low Pressure Heater Power Plant or Thermal Power Plant Generator Turbine Exhaust Hot Water Cooling Water In Cooling Tower

23 112 Advanced Energy Engineering - wwwairwalkbookscom 161 Coal and ash Circuit: This circuit consists of coal delivery, preparation of coal, handling of coal to the boiler furnace,ash handling and ash storage The coal which is received from the mines are stored in coal storage This raw coal is sized by crushers and then this prepared coal is transferred to the boilers In the boiler, the coal is burnt and converted into ash This ash is usually quenched to reduce the temperature, corrosion and dust content Then it is stored at ash storage 162 Air and Flue gas circuit This circuit consists of Forced Draught Fan, Air-preheater, Boiler furnace, Super heater, Economiser, Dust collector, Induced Draught (ID) Fan and Chimney Superheater Control Valve Economiser Pump Turbine Generator Turbine Exhaust Hot Water Boiler Feed Pump High Pressure Heater Deaerator Low Pressure Heater Fig 1 6 Feed Water And Steam Flow Circuit The air from the atmosphere is forced into the circuit by a forced draught fan This air is preheated in the air preheater by flue gases This pre heated air is supplied to the furnace where this air is converted into flue gases This flue gases pass over the boiler tubes by which the water is converted into steam Then this flue gas is passed to the super heater, where the steam is converted into super heated steam Then it is passed to the economiser to heat the feed water and to the air preheater The dust in the flue gases are collected by the dust collector and then left to atmosphere through chimney

24 Introduction to Advanced Energy Engineering Feed water and steam flow circuit: Air from Atmosphere To Atmosphere FD F an Chimney Super Heater Preheated Air Air Preheater IDFan Dust Collector Economizer Fig17 Air and Flue Gas Circuit This circuit consists of feed pump, economiser, boiler drum super heater, turbine and condenser From the hot well, the feed water is pumped to the economiser where the water is preheated by the flue gases This preheated water is supplied to the boiler drum In the boiler drum, the pre heated water is converted into steam by burning of coal The steam raised in boiler is passed through the super heater where the steam is converted into super heated steam The super heated steam is expanded in turbine which is coupled with generator The expanded steam is then passed through the condenser in which the steam is converted into water and this water is recirculated 164 Cooling Water Circuit This circuit consists of a pump, condenser and cooling tower In the condenser, cold water is circulated to condense the steam into waterthe steam is condensed by loosing its latent heat to the circulating cold water By this, the circulating water is heated This hot water is cooled at the cooling tower, where the water is sprayed in the form Turbine Exhaust Steam Hot Water Cooling Water in Cooling Tower water Fig 18 Cooling Water Circuit

25 114 Advanced Energy Engineering - wwwairwalkbookscom of droplet through nozzles The cold air enters the cooling tower from the bottom which cools the sprayed hot water The cooled water is collected in the cooling pond and the same is re circulated again and again To compensate the water lost due to vapourisation, the make up water is added to the pond by means of a pump 17 SELECTION OF SITE FOR A STEAM POWER PLANT The following consideration should be taken while selecting the site for a steam power plant 1 Availability of raw materials Huge quantity of coal as fuel are required to run a steam (thermal) power plant Therefore, it is important to locate the plant as near as possible to the coal fields to reduce the transportation cost If it is not possible to locate the plant near the coal field, then it should be located near the railway station or near to a port 2 Ash disposal facilities As a huge quantity of coal is burnt, this results in a huge quantity of ash too The ash handling problem is more serious as compared to handling of coal because it comes out very hot and is very corrosive If not disposed properly, it will result in environmental pollution and other hazards Therefore there must be sufficient space to dispose this large quantity of ash 3 Nature of land The land should have good bearing capacity about 1 MN/m 2 as it has to withstand the dead load of plant and force transmitted to the foundation due to working of heavy machinery 4 Cost of land Large area is required to build a thermal power plant, therefore the land price should be affordable (cheap) For eg: Large plant in the heart of city will be very costly

26 Introduction to Advanced Energy Engineering Availability of water Water is the working fluid in a steam power plant, and a large quantity of water is converted to steam in order to run the turbine It is important to locate the plant near the water source to fulfill its water demand through out the year 6 Size of the plant The capacity of the plant decides the size of the plant, large plant requires large area and the smaller plant requires considerably smaller area Therefore, the size of the plant and its capacity play an important role in selection of site 7 Availability of workforce During construction of plant, enough labour is required The labour should be available at the proposed site at cheap rate 8 Transportation facilities Availability of proper transportation is another important consideration for the selection of site as a huge quantity of raw materials (coal & fuel) through out the year and heavy machinery are to be brought to the site during the installation 9 Load centre The plant must be near to the load centre to which it is supplying power in order to decrease transmission loss and minimize transmission line cost 10 Public problems The plant should be away from the town or city in order to avoid nuisance from smoke, ash, heat and noise from the plant 11 Future extension A choice for future extension of the plant should be made in order to meet the power demand in future

27 116 Advanced Energy Engineering - wwwairwalkbookscom 18 SUB SYSTEM OF THERMAL POWER PLANT The sub systems of thermal power plant are the auxiliary plants required for the plant for its proper operation and for the increase of their efficiency Some of the sub systems are discussed as follows: 181 Boiler Accessories The appliances used to increase the efficiency of the boiler are known as boiler accessories The important boiler accessories are: 1 Feed pump, 2 Economiser, 3 Air preheater, 4 Superheater, 5 Steam separator, 6 Injector 1 Feed pumps Feed pumps are used to deliver water to the boiler It is essential to use a feed pump because the quantity of water supplied should meet amount of water evaporated and supplied to the engine Steam Suction Valves Delivery Valves Air Cock Steam Cylinder Stuffing Drain Box Cock Piston Rod Cross Head Water Cylinder Drain Plug Fig19 Feed Pump

28 Introduction to Advanced Energy Engineering 117 Basically two types of pump are in use 1 Reciprocating feed pump 2 Rotary feed pump Reciprocating feed pump consists of a cylinder and a piston The piston displaces water as it reciprocates inside the cylinder The reciprocating pump may be of two types (i) Single acting pump and (ii) Double acting pump They are continuously run by steam from the same boiler to which water is to be fed Rotary feed pumps are of centrifugal types and are commonly run either by a small steam turbine or by electric motor The duplex feed pump is a double acting reciprocating feed pump In this pump, there are two simple engine cylinders placed side by side The pressure of steam acts directly on the piston to pump the water Each pump has one steam cylinder and water cylinder 2 Economiser It is a device in which the waste heat of the flue gases is utilized for heating feed water The uses of a economiser has many advantages 1 The temperature range between various parts of the boiler is reduced which results in reduction of stress on the inner wall of boiler drum due to uneven thermal expansion 2 Evaporate capacity of the boiler is increased 3 Less fuel is required to turn the feed water into steam 4 Overall efficiency of the plant is increased

29 118 Advanced Energy Engineering - wwwairwalkbookscom W orm W heel Pulley H ot Water Safety valve Scrape Soot Chamber Feed Water Fig110 Green s Vertical Tube Economiser Greens vertical tube economiser is shown in Fig110 Economiser is used to preheat the feed water using furnace flue gases It consists of a large number of cast iron vertical tubes These tubes are connected at the top and bottom by two horizontal pipes and are placed in the main flue between the boiler and the chimney The water is pumped to the lower horizontal pipe and then flows through the vertical tubesthe water becomes heated by absorbing heat from the flue gas which passes over the tubes The hot water enters the upper horizontal pipe and is fed to the boiler To remove the deposits of soot from the surface of the tubes, scrapers are provided These scrapers move up and down slowly by means of a chain passing over the pulleys to remove the soots

30 Introduction to Advanced Energy Engineering Air preheater: Air preheater is an auxiliary system that increase the temperature of air before it enters the furnance It is generally placed after the economiser - ie in between economiser and chimney Preheated air accelerates the combustion and facilitates the burning of coal There are two types of Air preheaters (a) Recuperative and (b) Regenerative Air inlet Flue Gas Inlet Flue Gas Outlet Soot Hopper Air Outlet To Chimney In a recuperative air preheater, Soot Fig111 Air Preheater the heat from the flue gases is transferred to air through a metallic medium In a regenerative air preheater, air and flue gases are made to pass alternatively through the matrix When the hot gases pass through the matrix it transfers heat to the cold air The preheating of air helps the burning of low grade fuel, thus permitting a reduction in excess air and thereby increasing the efficiency The overall efficiency of the plant may be increased by 10% by its one 4 Super heater The function of the super heater is to increase the temperature of the steam above its saturation point Super heater steam has the following advantages 1 Steam consumption by the turbine is reduced 2 Loss due to condensation is reduced 3 Erosion of turbine blade is eliminated 4 Efficiency of the plant is increased A superheater is located in the path of the hot furnace gases Fig112 shows a Sudgen s superheater

31 120 Advanced Energy Engineering - wwwairwalkbookscom Main Steam Pipe A B Stop Valve Water Level C Boiler H 2 H 1 Heaters Boiler Handle Steel Tubes Bottom Flue Damper Fig112 Sudgen s Super Heater Down Take When the superheater is in operation, the valve A is closed The wet steam from the boiler enters the right heater through the valve C The steam flows through the number of U tubes where it receives heat from the hot flue gases and becomes superheated The superheated steam then passes to the discharge header and then to the main steam pipe connected to one end of the discharge header through the valve B The overheating of the superheater tubes is prevented by using a damper which is controlled by the Handle It controls the flow of flue gases to the superheater chamber When the damper is horizontal, the hot flue gases pass over the U tubes (superheated tubes) But when the damper is vertical, the hot flue gases directly pass to the bottom flue without superheating Thus degree of superheating is controlled by changing the position of damper 5 Steam separator The steam generated may be either wet steam (or) dry steam (or) superheated steam The wet steam must be seperated from the dry steam

32 Introduction to Advanced Energy Engineering 121 before letting it enter the main steam line This separation is done by steam separator It prevents the wet steam from entering the main steam line, thus prevents the turbine blades from corrosion 6 Injector An injector is used to feed water into vertical and locomotive boilers using steam from the same boiler It consists of three jets - steam jet, suction jet, combining and delivery jet The steam expands in the steam nozzle where its pressure drops but its velocity increases As the steam passes across space between steam and suction nozzles, a vacuum is developed in the suction chamber The water is drawn into the suction chamber from the feed tank The high speed steam jet takes the water along with the steam into the combining and delivery jet Here, the steam is condensed and mixed with the water The delivery jet is so designed that a considerable amount of kinetic energy of the jet changes into pressure energy which is sufficient to force the water in the boiler There will be no overflow when the steam and water are in proper ratio For the injector to act properly, there is a definite relation between the quantity of steam and water entering into the injector

33 122 Advanced Energy Engineering - wwwairwalkbookscom 7 Wagon tippler It is the machine used to tip the coal from the wagon The coal tipped is directly fed to conveyor belt which takes the coal to the coal mills 8 Coal mills Coal feeds in the coal mill are converted into pulverised form and they are fed to the boiler furnance 9 Boiler furnance It is the chamber in which fuel burns and fire blows 10 Boiler Drum It contains feed water for boiling 11 Electro Static Precipitator (ESP) ESP is located between the boiler and the chimney It extracts the fly ash from the flue gases and thus prevents the fly ash from entering the atmosphere Electrodes are used to attract the fly ash when the flue gas coming out of the boiler is passed through the ESP Working Principle: Here, the dust particles are separated from flue gases by electrostatic attraction It has two steps of operation One is charging of dust particles and other is to collect dust particles In charging section, the flue gas is ionized and in collecting section, dust particles are collected on the collector electrodes Construction The Fig 114(a) shows the general layout of an electro-static precipitator In a single stage electro-static precipitator, a pair of electrodes serve both the particle charging and collecting function and in two stage electro static precipitator, two pair of electrodes are used - one for charging and other for collecting The discharge electrode is connected to the high tension power supply The collector electrode is earthed An electro-static field is setup in between two electrodes A weight is kept to align the electrode along the cylinder axis

34 Introduction to Advanced Energy Engineering 123 Grounded Cylinders Dust Collecting Plates Dust Laden Gas in + Clean Gas Out Charged Wires Grounded Charging Section 400V AC Rectifier Transformer Fig 114(a) Layout of Different Components of Electrostatic Precipitator Electro- Static Precipitaor Control Panel E arth High Tension Transform er Earth High Tension Rectifier Dust Laden Gas in Discharge Electrodes Receiving E lectrodes In Fig114(b), the flue gas is passing through the bottom of the precipitator When gas moves upward, the dust particles and the flue gases are ionized by the high voltage (30,000 to 60,000 Volts) applied between the conductors The electro-static field exerts a force on the dust particles and they are driven towards the grounded plates The dust particles are deposited on the collector electrodes and they are removed by rapping (Shaking motion given to electrode) by means of cams The dust particles are collected in hopper and removed periodically { Earth Dust Fig 114(b) General Arrangement of an Electrostatic Precipitator Fig 114 Electro - Static Precipitator Clean Gas out

35 124 Advanced Energy Engineering - wwwairwalkbookscom Advantages: 1 Best suitable for high dust laded gases 2 Very small particles, mist and fly ashes enter the atmosphere 3 The dust is collected in dry form and can be removed in dry or wet form 4 Maintenance cost is less compared to other types 5 It has efficiency of 995% Disadvantages: 1 Power requirement is high for charging the dust particles and fly ash 2 Space requirement is more than wet system 3 Efficiency varies inversely with the gas velocity 4 The dust carried with the gases increases with an increase of gas velocity Electrical equipments are needed for conversion of low voltage to high voltage This increases the capital cost Even though its cost is more, it is frequently used with pulverised coal firing system because of its effectiveness 12 Chimney It is used to release flue gas into the atmosphere The chimney is constructed 25 to 3 times of height of the power plant The main purpose of this is to emit the flue gas at a considerable height to avoid nuisance to the surrounding people There are two types of loads acting on the chimney namely 1 Its own weight which is considered to act as a single vertical force acting through the centroid 2 Wind pressure, which is considered to act as a horizontal force acting on the centroid of vertical projected area It is found, from the experiments, that the wind pressure acting on a cylinder is 2/3 times of vertical plane surface of same projected area and shape For design considerations, the wind pressure on the chimney, is taken as 15 kn/m 2

36 Introduction to Advanced Energy Engineering 125 Three different types of chimney and their design considerations are given below 1 Steel Chimney This type of chimney is preferred for short exhaust stacks, where the draft is created by fan To increase the life of the chimney, these are lined with bricks The erection period of this type of chimney is less compared to that of other types This type of chimney is constructed by welded section and erected by horizontal welding joints (or) by riveting Because of low capital cost of the chimney, the number of steel chimney constructed were increased considerably But the sulphur content in the flue gas creates severe problems such as acid condensation and severe attack inside surface of brick, concrete and steel chimneys This has been rectified by the insulation of the steel chimneys by aluminium cladding Cold air inversion is being faced by the system when several number of boilers are attached to a single chimney In order to avoid this nowadays, One boiler - One chimney pattern is used The chimneys in the gas turbine power plants often face the thermal shock brought by an increase in temperature of about C during a period of full load The steel chimneys are capable of handling this because of thin wall and high coefficient of expansion of steel 2 Site constructed chimneys Site constructed chimneys of brick (or) concrete are used where very tall chimneys are necessary for power stations (or) where the life requirement is more than 30 years Nowadays perforated radial bricks are used, instead of common bricks, as they give better results The perforations aid the structural stability The crushing strength of perforated radial brick is more than that of the design value required in the actual practice Another common material that is used for building chimneys is pre-casted reinforced concrete Due to structural difficulties, it is limited to chimneys of height around 80m There are two methods 1 Jump forming where the shuttering is moved up the stack in steps (or) 2 Slip forming

37 126 Advanced Energy Engineering - wwwairwalkbookscom where the shuttering is gradually moved up with continuous concrete pouring The second method is the fastest method of construction Concrete is not suitable for chimneys due to its high thermal inertia which leads to cracking The steel chimneys are preferred where the cost factor is important and concrete chimney is preferred where the life of the chimney is most important 3 Plastic chimneys These chimneys are made of glass fiber reinforced plastic They cannot be operated at high temperature Because at high temperature, the flue gas catches fire and leads to disintegration of chimney This kind of chimney plays a vital role where a low stress, low temperature chimney is required for highly corrosive effluents 19 DIESEL ENGINE POWER PLANT 191 Introduction Diesel engine power plants (prime mover is a diesel engine) are installed where supply of coal and water is not available in sufficient quantity These plants produce power in the range of 2 to 50 MW The diesel power plants are more efficient than any other heat engines of comparable size It is cheap in cost It can be started quickly and brought into the service The diesel engine will provide the most economic means of generating electricity on small scale, particularly where there is no convenient site for micro hydro power plants, cheap fuels are not available and load factors are considerably large 192 Applications Suitable for small or medium capacity range of 2 to 50 MW Used in industries where power requirement is up to 500 kw Used as standby plants to hydro and steam power plant Used as mobile power generation system such as automobile, ship, aeroplane, railways and road transport Used as peak load plants in combination with thermal or hydro-plants to meet the power demands during peak hours

38 Introduction to Advanced Energy Engineering Site selection Site selection for the diesel power plant should be nearer to the load centre; this is to reduce the cost of transmission of power and also reduce the power loss The site for the diesel power plant should be nearer to the source of fuel supply, to decrease the transportation charges The site for the diesel power plant should be far away from the town, so that smoke and flue gases released from the plant will not affect human life Sufficient quantity of water should be available at the site selected The selection of the site for the plant should be in such a way that, it has road and rail transportation facilities 194 Advantages Diesel power plant can be located at any place The quantity of the water required for these plants for cooling is less Diesel power plant is simple in design and diesel fuel is easy to handle Less fuel storage space It can be started quickly Longer life than steam power plant High thermal efficiency than steam power plant Requires no operating staff 195 Disadvantages Diesel fuel is costly Cost of lubrication is very high Maintenance charges are generally high Limited capacity about 50 MW of power Not suitable for overload condition In a diesel power plant noise is a serious problem

39 128 Advanced Energy Engineering - wwwairwalkbookscom 110 TYPES OF DIESEL POWER PLANTS Diesel power plants are mainly classified as stationary diesel power plants and mobile diesel power plants Stationary units use two-stroke (or) four-stroke diesel engines coupled with synchronous generators These units are considered average in their power rating if the rating does not exceed 750 kw Large diesel plants have power ratings of 2,200 kw or more These plants are mainly used in areas remote from transmission lines and where the construction of steam (or) hydro-electric power plant is not feasible Mobile diesel power plants can be used as main auxiliary or stand by power source They are widely used in agriculture, transportation, forestry and by expeditions involving geological exploration The diesel electric power-plants are classified based on their applications as follows: 1 Peak load plant When there is high demand for electricity, diesel power plants are used in combination with thermal or hydro-plants as peak load plants Peak loads can occur in the evening after work hours when household appliances are heavily used or during summer months when the airconditioning load is high Diesel power plant is particularly preferable as peak load plant as it can be started quickly and it has no standby losses as in the case of thermal plants, where boilers always must be kept hot 2 Mobile plants Mobile diesel plants can be used for temporary or emergency purposes such as for supplying power to large civil engineering works for supplementing electricity supply systems that are temporarily short of power They are mounted on skids or trailers and transported to the required site

40 Introduction to Advanced Energy Engineering Stand-by Units Diesel plants can be used as standby units to supply part load when required For example, a diesel plant can be used with a hydro-plant as a stand-by unit, if the water available is not sufficient due to reduced rainfall Here, the diesel unit supplies power in parallel with the hydro-power plant The diesel unit is used temporarily till sufficient water is available to take the full load 4 Emergency plant The plants are normally idle but are used for emergency purposes, where power interruption would mean financial loss or danger such as in key industrial processes, tunnel lighting and operating rooms of hospitals Under emergency conditions, these plants are also used for telecommunication and water supply 5 Nursery station When a temporary power plant is required to supply the power to a small town until the main grid is available, it is known as Nursery Station A Nursery station can be moved to another area which needs power on a small scale A diesel power plant is suitable for this purpose 6 Starting stations Small diesel units can be used for starting purposes of large steam plants These units run the auxiliaries initially for starting, after which they are disconnected 7 Central stations In places where the capacity required is small (5 to 10 MW), Diesel units can be used as central stations, such as for commercial purposes and public utilities eg, cinema hall, hospital and municipalities The capacity limits of the plant generally decided by the cost of the plant and local conditions regarding the availability of fuel and water, space requirements and non-availability of the grid

41 130 Advanced Energy Engineering - wwwairwalkbookscom 111 LAYOUT OF DIESEL POWER PLANT The essential components of a Diesel power plant are: (i) Diesel engine It is a compression ignition engine They are generally two stroke or four stroke cycle engines Air is admitted into the cylinder of the engine and is compressed At the end of compression stroke, fuel (Diesel) is injected The burnt gases, expand and do work on piston The engine is directly coupled to the generator These gases from the cylinder are then exhausted to the atmosphere Day Ta nk Starting Air tank Air filter Diesel Engine Fuel Injection Filter Pump Silencer Generator Jacket water pump Air compressor Pump Filter Lubricating oil tank Oil pump Coolant Oil cooler Heat exchanger Cooling torner Fuel storage tank Fig 115 Layout of Diesel Engine Power Plant Raw water pump (ii) Engine starting system This system contains an air compressor and a starting air tank This system starts the Diesel engine of a Diesel power plant under cold condition (iii) Fuel system The fuel is delivered to the plant gate by trucks, rail barge (or) and by tankers and stored in the fuel storage tank The piping equipment with the necessary heaters, by passes, drain lines, relief valves, strainers and filters, flowmeter and temperature indicator are arranged in a proper manner to make the main flow workable and practical The tank should contain a