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Steam generator part 1

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Try to explain about the steam generator (boiler), it has three parts. Part 1 cover the types, part 2 about its parts & auxiliaries & accessories and part 3 about performance.

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Steam generator part 1

  1. 1. BOILER Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor Saba Power Plant
  2. 2. Steam Generator (Boiler) Hello, I am trying to explain about Steam Generator (Boiler) in this session, due to length of said presentation, I am deciding to divide it in three parts. Part 1 cover the “Introduction & Types of Steam Generator” Part 2 cover about the “Parts of Steam Generator and Its Accessories & Auxiliaries” and Part 3 cover the “Efficiency & Performance” Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor Saba Power Plant
  3. 3. BOILER Part 1 Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor Saba Power Plant
  4. 4. Steam Fundamentals  Steam is uniquely adapted, by its availability and advantageous properties, for use in industrial and heating processes and in power cycles. The fundamentals of the steam generating process and the core technologies upon which performance and equipment design are based are described in this section Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  5. 5. What is Steam? Steam is an invisible gas that's generated by heating water to a temperature that brings it to the boiling point. When this happens, water changes its physical state and vaporizes, turning from a liquid into a gas. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  6. 6. How the Energy of Steam Is Used The uses for steam are many and varied. Like : 1. Power Generation 2. Industrial Process 3. Heating From the plastic and vinyl components of our automobiles to the paints and stains we use on our homes to the preparation and presentation of the food we eat, steam is used in a variety of ways to make our lives more comfortable and convenient. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  7. 7. What is a Boiler?  A boiler is an enclosed vessel that provides a means for combustion heat to be transferred to water until it becomes heated water or steam. OR  Steam generators, or boilers, use heat to convert water into steam for a variety of applications. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  8. 8. What is a Boiler Capacity  Boiler loads, or the capacity of steam boilers, are often rated in boiler horse powers (BHP), lbs of steam delivered per hour, or BTU.  Large boiler capacities are often given in lbs of steam evaporated per hour under specified steam conditions. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  9. 9. Boiler Capacity Boiler Horsepower - BHP The Boiler Horsepower (BHP) is the amount of energy required to produce 34.5 pounds of steam per hour at a pressure and temperature of 0 Psig and 212 oF, with feed water at 0 Psig and 212 oF. A BHP is equivalent to 33,475 BTU/hr or 8430 Kcal/hr and it should be noted that a boiler horsepower is 13.1547 times a normal horsepower. 1 horsepower (boiler) = 33445.6 Btu (mean)/hr = 140671.6 calorie/min (thermo) = 140469.4 calorie (mean)/min = 140742.3 calorie (20oC)/min 9.8095x1010 erg/sec = 434107 foot-pound-force/min = 13.1548 horsepower (mech) = 13.1495 horsepower (electric) = 13.3372 horsepower (metric) = 13.1487 horsepower (water) = 9809.5 joule/sec = 9.8095 kilowatt Horsepower (hp) can be converted into lbs of steam by multiplying hp with 34.5. or some time called 1 BHP = 33479 Btu/hr Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  10. 10. INTRODUCTION STEAM TO POWER GENERATION, INDUSTRIAL PROCESS & HEATING EXHAUST GAS STACK VENT DEAERATOR BFW PUMPS ECONOMIZER VENT BOILER BURNER BLOW DOWN SEPARATOR WATER SOURCE FUEL BRINE CHEMICAL FEED SOFTENERS Figure: Schematic overview of a boiler room Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  11. 11. Classification Steam Generator Boiler Fuel Fossil, Waste, Nuclear Tube Contain Fire Tube, Water Tube Furnace Natural, Pressurized, Induced, Balance Pressure Method Water of Firing Circulation of Steam Externally, Internally, HRSG Natural, Forced Low, Medium, High Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  12. 12. Classification Fossil Fuel Fuel Waste Heat Nuclear Fuel Waste Fuel Biomass Oil Natural Gas Coal Gas Turbine Exhaust Diesel or Gas Engine Exhaust Uranium Bagasse Fission Rise Husk Wood Pallets Forestry Residues Mill Residues Agricultural Residues Chemical Recovery Fuels Animal Wastes Dry Animal Manure Wet Animal Manure (Dairy Manure Slurry) Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  13. 13. Types of Boilers 1. Fire Tube Boiler 2. Water Tube Boiler 3. Packaged Boiler 4. Fluidized Bed (FBC) Boiler 5. Stoker Fired Boiler 6. Pulverized Fuel Boiler 7. Waste Heat Boiler (HRSG) 8. Nuclear Steam Generating Systems Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  14. 14. CLASSIFICATION BASED ON PRESSURE  Low pressure boiler under 20 kg/cm2.  Medium pressure boiler 20 – 75 kg/cm2.  High pressure boiler over 75 kg/cm2. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  15. 15. Fire Tubes Vs Water Tubes Boilers  Fire tubes boilers has a large volume of water, therefore      more flexible and can meet the sudden demand of steam without much drop of pressure. Fire tubes boiler is rigid and of simple mechanical construction, so greater reliability and low in first cost. Fire tube boilers can be made in smallest sizes therefore simple to fabricate and transport, occupies less floor space but more height. Due to mostly externally fired water tubes boiler so furnace can be altered considerably to meet the fuel requirements. Water tubes boilers are more readily accessible for cleaning, inspection and repairs, compared to the fire tube boilers. Modern trend is in the favors of water tube boiler due to continuous increase in capacities and steam pressures. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  16. 16. FIRE TUBE BOILER Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  17. 17. FIRE TUBE BOILER  Relatively small steam capacities (12,000 kg/hour), 3,500 to 35,000 lbs/hr (120 Bhp – 1,200 Bhp)  Low to medium steam pressures (18 kg/cm2), 350 psig  Operates with oil, gas or solid fuels  Scotch Marine – most popular  Two, three, and four pass designs  Constant pressure with wide load fluctuations Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  18. 18. FIRE TUBE BOILER  Simple Vertical Boiler  Cochran Boiler  Locomotive Boiler  Lancashire Boiler  Cornish Boiler Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  19. 19. FIRE TUBE BOILER Simple Vertical Boiler: The image shows the simplest form of an internally fired vertical fire-tube boiler. It does not require heavy foundation and requires very small floor area. Parts • Cylinder Shell • Cross Tubes • Furnace or Fire Box • Grate • Fire Door • Chimney or Stack • Manhole • Hand Hole • Ash Pit Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  20. 20. FIRE TUBE BOILER Cochran Boiler It is a multi-tubular vertical fire tube boiler having a number of horizontal fire tubes. T is the modification of a simple vertical boiler where the heating surface has been increased by means of a number of fire tubes. Parts • Shell • Crate • Fire box • Flue pipe • Fire tubes • Combustion chamber • Chimney • Man-hole Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  21. 21. FIRE TUBE BOILER Locomotive Boiler Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  22. 22. FIRE TUBE BOILER Locomotive Boiler Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  23. 23. FIRE TUBE BOILER Lancashire Boiler It is a stationary, fire tube, internally fired boiler. The size is approximately from 7-9 meters in length and 2-3 meters in diameter. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  24. 24. FIRE TUBE BOILER Cornish Boiler  It is a similar type of Lancashire boiler in all respects, except there is only one flue tube in Cornish boiler instead of two in Lancashire boiler.  The diameter of Cornish boiler is generally 1m to 2m and its length various from 5m to 7.5m.  The diameter of flue tube may be 0.6 times that of shell. as compared to Lancashire boiler. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  25. 25. WATER TUBE BOILER • La-Mont boiler • Loeffler boiler • Benson boiler • Babcock and Wilcox boiler Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  26. 26. WATER TUBE BOILER  Fuel burned within combustion         chamber Combustion gas surrounds water tubes within vessel Low water content allows rapid steam production Capable of high pressure and superheated steam Preferred ranges are below 3,500 lbs/hr (120 Bhp) and above 35,000 lbs/hr (1,200 Bhp) Capacity range of 4,500 – 120,000 kg/hour Used for high steam demand and pressure requirements Combustion efficiency enhanced by induced draft provisions Lower tolerance for water quality and needs water treatment plant Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  27. 27. WATER TUBE BOILER Water tube boilers are designed to circulate hot combustion gases around the outside of a large number of water filled tubes. The tubes extend between an upper header, called a steam drum, and one or more lower headers or drums. Almost any solid, liquid or gaseous fuel can be burnt in a water tube boiler. Coal-fired water tube boilers are classified into three major categories: stoker fired units, PC fired units and FBC boilers. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  28. 28. WATER TUBE BOILER  Modular Boilers  Array of smaller boilers meet load more effectively without cycling  Improved combustion efficiency  Reduced jacket losses  Fin tube design less durable  Piping and controls important  Mostly for commercial markets Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  29. 29. WATER TUBE BOILER La-Mont boiler A La-Mont boiler is a type of forced circulation watertube boiler in which the boiler water is circulated through an external pump through long closely spaced tubes of small diameter. The mechanical pump is employed to in order to have an adequate and positive circulation in steam and hot water boilers. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  30. 30. WATER TUBE BOILER Loeffler Boiler This is also a modern high pressure water tube boiler using the forced circulation principle and named after Prof. Loeffler. Salient features of Loeffler Boiler The novel feature of the Loeffler Boiler is to evaporate water solely by means of superheated steam. The furnace heat is supplied only to economizer and super heater. In other words, steam is used as a heat absorbing medium. Capacity of the Loeffler boiler is about 100 tones/hr of superheated steam generated at a pressure of 140 kg/sq.cm and at a temperature of 500’C. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  31. 31. WATER TUBE BOILER Benson boiler A Benson boiler is a type of Once-Through Boiler patented by Marc Benson in Germany in 1923.  A high pressure, drum less, water tube steam boiler works on forced circulation.  Feed water enters at one end and discharge superheated steam at the other end.  Feed pump increase pressure of water to supercritical pressure.  Water directly transforms into steam without boiling. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  32. 32. WATER TUBE BOILER Babcock and Wilcox boiler. It is a water tube boiler used in steam power plants. In this, water is circulated inside the tubes and hot gases flow over the tubes. The Babcock & Wilcox boiler is built in two general classes, the longitudinal drum type and the cross drum type. Either of these designs may be constructed with vertical or inclined headers. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  33. 33. WATER TUBE BOILER Babcock and Wilcox boiler. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  34. 34. Packaged Boiler • Comes in complete package • Features • High heat transfer • Faster evaporation • Good convective heat transfer • Good combustion efficiency • High thermal efficiency To Chimney Oil Burner • Classified based on number of passes Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  35. 35. Packaged Boiler All have steam drums for the separation of the steam from the water, and one or more mud drums for the removal of sludge . “A Type”. This design is more susceptible to tube starvation if bottom blows are not performed properly because “A” type boilers have two mud drums symmetrically below the steam drum. Drums are each smaller than the single mud drums of the “D” or “O” type boilers. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  36. 36. Packaged Boiler “D” type boilers have the most flexible design. They have a single steam drum and a single mud drum, vertically aligned. The boiler tubes extend to one side of each drum. “D” type boilers generally have more tube surface exposed to the radiant heat than do other designs. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  37. 37. Packaged Boiler “O” design boilers have a single steam drum and a single mud drum. The drums are directly aligned vertically with each other, and have a roughly symmetrical arrangement of riser tubes. Circulation is more easily controlled, and the larger mud drum design renders the boilers less prone to starvation due to flow blockage, although burner alignment and other factors can impact circulation. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  38. 38. Fluidized Bed Combustion (FBC) Boiler • Particles (e.g. sand) are suspended in high velocity air stream: bubbling fluidized bed • Combustion at 840 – 950 C • Capacity range 0,5 T/hr to 100 T/hr • Fuels: coal, washery rejects, rice husk, bagasse and agricultural wastes • Benefits: compactness, fuel flexibility, higher combustion efficiency, reduced SOx & NOx Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  39. 39. Fluidized Bed Combustion (FBC) Boiler Fluidized bed combustion (FBC) is a combustion technology used in power plants. Fluidized beds suspend solid fuels in upward-blowing jets of air during the combustion process. The result is a turbulent mixing of gas and solids. The tumbling action, much like a bubbling fluid, provides more effective chemical reactions and heat transfer. Since limestone is used as particle bed, control of sulfur dioxide and nitrogen oxide emissions in the combustion chamber is achieved without any additional control equipment. This is one of the major advantages over conventional boilers. Combustion process requires the three “T”s that is Time, Temperature and Turbulence. In FBC, turbulence is promoted by fluidisation. Improved mixing generates evenly distributed heat at lower temperature. Residence time is many times greater than conventional grate firing. Thus an FBC system releases heat more efficiently at lower temperatures. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  40. 40. Fluidized Bed Combustion (FBC) Boiler principle of fluidisation Fixing, bubbling and fast fluidized beds As the velocity of a gas flowing through a bed of particles increases, a value is reaches when the bed fluidises and bubbles form as in a boiling liquid. At higher velocities the bubbles disappear; and the solids are rapidly blown out of the bed and must be recycled to maintain a stable system. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  41. 41. Fluidized Bed Combustion (FBC) Boiler FBC systems fit into essentially two major groups, atmospheric systems (FBC) and pressurized systems (PFBC), and two minor subgroups, circulating fluidized bed (CFB) & bubbling fluidized bed (BFB). Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  42. 42. Advantages of Fluidised Bed Combustion Boilers 1. High Efficiency FBC boilers can burn fuel with a combustion efficiency of over 95% irrespective of ash content. FBC boilers can operate with overall efficiency of 84% (plus or minus 2%). 2. Reduction in Boiler Size High heat transfer rate over a small heat transfer area immersed in the bed result in overall size reduction of the boiler. 3. Fuel Flexibility FBC boilers can be operated efficiently with a variety of fuels. Even fuels like flotation slimes, washer rejects, agro waste can be burnt efficiently. These can be fed either independently or in combination with coal into the same furnace. 4. Ability to Burn Low Grade Fuel FBC boilers would give the rated output even with inferior quality fuel. The boilers can fire coals with ash content as high as 62% and having calorific value as low as 2,500 kcal/kg. Even carbon content of only 1% by weight can sustain the fluidised bed combustion. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  43. 43. 5. Ability to Burn Fines Coal containing fines below 6 mm can be burnt efficiently in FBC boiler, which is very difficult to achieve in conventional firing system. 6. Pollution Control SO2 formation can be greatly minimised by addition of limestone or dolomite for high sulphur coals. 3% limestone is required for every 1% sulphur in the coal feed. Low combustion temperature eliminates NOx formation. 7. Low Corrosion and Erosion The corrosion and erosion effects are less due to lower combustion temperature, softness of ash and low particle velocity (of the order of 1 m/sec). 8. Easier Ash Removal – No Clinker Formation Since the temperature of the furnace is in the range of 750 – 900o C in FBC boilers, even coal of low ash fusion temperature can be burnt without clinker formation. Ash removal is easier as the ash flows like liquid from the combustion chamber. Hence less manpower is required for ash handling. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  44. 44. 9. Less Excess Air – Higher CO2 in Flue Gas The CO2 in the flue gases will be of the order of 14 – 15% at full load. Hence, the FBC boiler can operate at low excess air - only 20 – 25%. 10. Simple Operation, Quick Start-Up High turbulence of the bed facilitates quick start up and shut down. Full automation of start up and operation using reliable equipment is possible. 11. Fast Response to Load Fluctuations Inherent high thermal storage characteristics can easily absorb fluctuation in fuel feed rates. Response to changing load is comparable to that of oil fired boilers. 12. No Slagging in the Furnace-No Soot Blowing In FBC boilers, volatilisation of alkali components in ash does not take place and the ash is non sticky. This means that there is no slagging or soot blowing. 13 Provisions of Automatic Coal and Ash Handling System Automatic systems for coal and ash handling can be incorporated, making the plant easy to operate comparable to oil or gas fired installation. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  45. 45. 14 Provision of Automatic Ignition System Control systems using micro-processors and automatic ignition equipment give excellent control with minimum manual supervision. 15 High Reliability The absence of moving parts in the combustion zone results in a high degree of reliability and low maintenance costs. 16 Reduced Maintenance Routine overhauls are infrequent and high efficiency is maintained for long periods. 17 Quick Responses to Changing Demand A fluidized bed combustor can respond to changing heat demands more easily than stoker fired systems. This makes it very suitable for applications such as thermal fluid heaters, which require rapid responses. 18 High Efficiency of Power Generation By operating the fluidized bed at elevated pressure, it can be used to generate hot pressurized gases to power a gas turbine. This can be combined with a conventional steam turbine to improve the efficiency of electricity generation and give a potential fuel savings of at least 4%. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  46. 46. Fluidized Bed Combustion (FBC) Boiler a. Atmospheric Fluidized Bed Combustion (AFBC) Boiler Atmospheric fluidized beds use limestone or dolomite to capture sulfur released by the combustion of coal. Jets of air suspend the mixture of sorbent and burning coal during combustion, converting the mixture into a suspension of red-hot particles that flow like a fluid. These boilers operate at atmospheric pressure. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  47. 47. Fluidized Bed Combustion (FBC) Boiler b. Pressurized Fluidized Bed Combustion (PFBC) Boiler • Compressor supplies the forced draft and combustor is a pressure vessel • Used for cogeneration or combined cycle power generation. • The first-generation PFBC system also uses a sorbent and jets of air to suspend the mixture of sorbent and burning coal during combustion. However, these systems operate at elevated pressures and produce a high-pressure gas stream at temperatures that can drive a Gas Turbine. Steam generated from the heat in the fluidized bed is sent to a Steam Turbine, creating a highly efficient Combined Cycle system. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  48. 48. PFBC Boiler for Cogeneration Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  49. 49. Fluidized Bed Combustion (FBC) Boiler Atmospheric Circulating Fluidized Bed Combustion (CFBC) Boiler • Solids lifted from bed, rise, return to bed • Steam generation in convection section • Benefits: more economical, better space utilization and efficient combustion Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  50. 50. Fluidized Bed Combustion (FBC) Boiler This CFBC technology utilizes the fluidized bed principle in which crushed (6 –12 mm size) fuel and limestone are injected into the furnace or combustor. The particles are suspended in a stream of upwardly flowing air (60-70% of the total air), which enters the bottom of the furnace through air distribution nozzles. The fluidising velocity in circulating beds ranges from 3.7 to 9 m/sec. The balance of combustion air is admitted above the bottom of the furnace as secondary air. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  51. 51. Bubbling Bed Boilers In the bubbling bed type boiler, a layer of solid particles (mostly limestone, sand, ash and calcium sulfate) is contained on a grid near the bottom of the boiler. This layer is maintained in a turbulent state as low velocity air is forced into the bed from a plenum chamber beneath the grid. Fuel is added to this bed and combustion takes place. Normally, raw fuel in the bed does not exceed 2% of the total bed inventory. Velocity of the combustion air is kept at a minimum, yet high enough to maintain turbulence in the bed. Velocity is not high enough to carry significant quantities of solid particles out of the furnace. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  52. 52. Bubbling Bed Boilers Features of bubbling bed boiler Fluidised bed boiler can operate at near atmospheric or elevated pressure and have these essential features: • Distribution plate through which air is blown for fluidizing. • Immersed steam-raising or water heating tubes which extract heat directly from the bed. • Tubes above the bed which extract heat from hot combustion gas before it enters the flue duct. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  53. 53. Bubbling Bed Boiler
  54. 54. Stoke Fired Boilers Stokers are classified according to the method of feeding fuel to the furnace and by the type of grate. The main classifications are spreader stoker and chain-gate or traveling-gate stoker. a) Spreader stokers • Coal is first burnt in suspension then in coal bed • Flexibility to meet load fluctuations • Favored in many industrial applications Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  55. 55. Stoke Fired Boilers b) Chain-grate or traveling-grate stoker • Coal is burnt on moving steel grate • Coal gate controls coal feeding rate • Uniform coal size for complete combustion Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  56. 56. Pulverized Fuel Boiler • Coal is pulverized to a fine powder, so that less than 2% is +300 microns, and 70-75% is below 75 microns. • Pulverized coal powder blown with combustion air into boiler through burner nozzles • Combustion temperature 1300 -1700 °C • Benefits: varying coal quality coal, quick response to load changes and high pre-heat air temperatures at Tangential firing Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  57. 57. Pulverized Fuel Boiler Advantages  Its ability to burn all ranks of coal from anthracitic to lignitic, and it permits combination firing (i.e., can use coal, oil and gas in same burner). Because of these advantages, there is widespread use of pulverized coal furnaces. Disadvantages  High power demand for pulverizing  Requires more maintenance, fly ash erosion and pollution complicate unit operation Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  58. 58. Waste Heat Boiler • Used when waste heat available at medium/high temp • Auxiliary fuel burners used if steam demand is more than the waste heat can generate • Used in heat recovery from exhaust gases from gas turbines and diesel engines Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  59. 59. Waste Heat Boiler (HRSG) • A waste heat boiler can be economically installed wherever waste heat can be available at medium or high temperatures. • Wherever the steam demand is more than the steam generated during waste heat, auxiliary fuel burners are also used. If there is no direct use of steam, the steam may be let down in a steam turbine-generator set and power produced from it. It is widely used in the heat recovery from exhaust gases from gas turbines and diesel engines. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  60. 60. Waste Heat Boiler (HRSG) Heat recovery steam generator (HRSG), located at the exhaust end of gas turbine or Engine. During plant operation, the gas turbine engine discharges a high volume of exhaust flue gas containing a considerable amount of thermal energy. The HRSG reclaims the exhausted thermal energy for the purpose of generating superheated steam for use in the steam turbine generator. Efficient reclamation of the gas turbine exhaust prevents wasted energy, resulting in a significant increase of overall plant efficiency. The installation of the HRSG gives the plant its ’combined cycle’ status, in that it represents a major component of the Rankine cycle portion of the power plant. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  61. 61. Waste Heat Boiler (HRSG) Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  62. 62. Waste Heat Boiler (HRSG) Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  63. 63. Nuclear Steam Generating Systems Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  64. 64. Nuclear Steam Generating Systems Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors (PWR) between the primary and secondary coolant loops. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  65. 65. Nuclear Steam Generating Systems Nuclear steam generating systems include a series of highly specialized heat exchangers, pressure vessels, pumps and components which use the heat generated by nuclear fission reactions to efficiently and safely generate steam. The system is based upon the energy released when atoms within certain materials, such as uranium, break apart or fission. Fission occurs when a fissionable atom nucleus captures a free subatomic particle – a neutron. This upsets the internal forces which hold the atom nucleus together. The nucleus splits apart producing new atoms as well as an average of two to three neutrons, gamma radiation and energy. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  66. 66. Nuclear Steam Generating Systems In commercial power plants steam generators can measure up to 70 feet (~21m) in height and weigh as much as 800 tons. Each steam generator can contain anywhere from 3,000 to 16,000 tubes, each about three-quarters of an inch (~19mm) in diameter. The coolant (treated water), which is maintained at high pressure to prevent boiling, is pumped through the nuclear reactor core. Heat transfer takes place between the reactor core and the circulating water and the coolant is then pumped through the primary tube side of the steam generator by coolant pumps before returning to the reactor core. This is referred to as the primary loop. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  67. 67. Nuclear Steam Generating Systems Types Westinghouse and Combustion Engineering designs have vertical U-tubes with inverted tubes for the primary water. Canadian, Japanese, French, and German PWR suppliers use the vertical configuration as well. Russian VVER reactor designs use horizontal steam generators, which have the tubes mounted horizontally. Babcock and Wilcox plants have smaller steam generators that force water through the top of the OTSGs (once-through steam generators; counterflow to the feedwater) and out the bottom to be recirculated by the reactor coolant pumps. The horizontal design has proven to be less susceptible to degradation than the vertical U-tube design. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor
  68. 68. Prepared by: Mohammad Shoeb Siddiqui Sr. Shift Supervisor Saba Power Plant shoeb.siddiqui@sabapower.com shoeb_siddiqui@hotmail.com www.youtube.com/shoebsiddiqui

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