Steam Power Plant and Boiler power plant.pptx

Steam Power Plant and Boiler power plant.pptx

• 1.
  COAL BASED THERMAL POWER PLANT
• 2.
  Major Components ofa Thermal Power Plant  Coal Handling Plant  Pulverizing Plant  Draft or Draught fan  Boiler  Ash Handling Plant  Turbine and Generator  Condenser  Cooling Tower And Ponds  Feed Water Heater  Economiser  Evaporator  Super heater and Reheater  Air pre heater  Alternator with Exciter  Protection and control equipment  Instrumentation
• 5.
  COAL BASED THERMALPOWER PLANT
• 7.
  Main circuits inthermal Power Plant  Coal and Ash Circuit Coal from the storage is fed into the boiler through coal handling equipment for the generation of steam. Ash produced due to the combustion of coal is removed to ash storage through ash handling system.  Air and Gas Circuit Air is supplied to the combustion chamber through FD fan or ID fan. The dust from the air is removed before supplying to the combustion chamber. The exhaust gases carrying sufficient quantity of heat and ash are passed through the dust collectors where most of the dust is removed before exhausting the gases to the atm. through chimney.
• 8.
   Feed waterand steam flow Circuit The steam generated in the boiler is fed to the steam prime mover to develop the power. The steam coming out of the prime mover is condensed in the condenser and then fed to the boiler with the help of the pump.  Cooling water circuit The quantity of cooling water required to condense the steam is considerably large and it is taken either from lake, river or sea. if adequate cooling water is available throughout the year then we can use the river- open system if not, we can use cooling pond or cooling tower – closed system. Due to the evaporative loss 2-5% of cooling water lost in the system. For that we need to use make up water.
• 9.
  SITE SELECTION FORTHERMAL POWER STATIONS  Availability of coal-400MW coal 5000-6000tons/day  Ash disposal facilities -1500-2000tons/day(20-40% ash in coal)  Space requirements  Nature of land – bearing capacity of the land should be 10 bar  Availability of water-60MW plant (20-30 thousand tons/hr) (for cooling towers make up water 500-600tons/hr.) (for 1000MW – 3.78million litres of fresh water/day)  Transport facilities  Availability of labour  Public problem  Size of the plant
• 10.
  COAL HANDLING
• 11.
  Preparation of coal
• 12.
  Ash handling system
• 13.
  Ash handling systemdesign
• 14.
   The modernash handling system usually used in large steam power plants are ……. Belt conveyor system(Mechanical) Pneumatic system Hydraulic system Steam jet system For bottom ash disposal
• 15.
  Mechanical sys
• 16.
  Hydraulic system Low velocityHigh velocity 50 tons/hr. 120 tons/hr 500 m 1000 m 3-5m/s above 5 m/s
• 18.
  Pneumatic system
• 19.
  Removal of ashfrom Hot flue gas There are two methods adopted for removing the ash. Cyclone separator Electrostatic Precipitator
• 20.
  Crushing Process There arefour basic process to reduce the size  Impact  attrition  Shear  compression
• 21.
  CRUSHING PLANT
• 22.
  IMPACT CRUSHER
• 23.
  Screening Process: There arethree basic type of screening process  Scalping  Fine removals  Grading
• 24.
  Draught System  Thedraught is to supply required quantity of air for combustion and remove the burnt products from the system.  Difference of pressure required to maintain the constant flow of air and to discharge the gases through the chimney to atmosphere is known as draught. A draught may be  1. Natural Draught  2. Mechanical Draught
• 25.
  Natural Draught A NATURALDRAUGHT IS PROVIDED BY THE CHIMNEY OR STACK. NATURAL DRAUGHT HAS ITS LIMITATION . MODERN PLANTS HAS HIGH RATE OF HEAT TRANSFER AND DRAUGHT LOSSES ARE VERY HIGH. IN VIEW OF THIS NATURAL DRAUGHT IS USED ONLY FOR SMALL BOILERS.
• 26.
  MECHANICAL DRAUGHT MODERN LARGESIZE PLANTS USE VERY LARGE SIZE OF BOILERS OF CAPACITY ABOVE 1000,000 KG PER HOUR. SUCH BOILER NEEDS TREMENDOUS VOLUME OF AIR (AROUND 200000 M3) PER MINUTE. A CHIMNEY PROVIDE THIS. THEREFORE MECHANICAL DRAUGHT IS USED. FORCED DRAUGHT IN FORCED DRAUGHT SYSTEM THE FAN IS INSTALLED NEAR THE BOILER .THE FAN FORCE THE AIR THROUGH THE FURNACE , ECONOMIZER, AIR PREHEATER AND CHIMNEY. THE PRESSURE OF AIR, THROUGHOUT THE SYSTEM, IS ABOVE ATMOSPHERIC AND AIR IS FORCED TO FLOW THROUGH THE SYSTEM.
• 27.
   Induced draught Inan induced draught system , the fan is installed near the base of the chimney . The burnt gases are sucked out from the boiler , thus reducing the pressure inside the boiler to less than atmosphere. This induces fresh air to enter the furnace.
• 28.
  Balanced Draught system
• 29.
  Cooling Towers andSpray Ponds Condensers need huge quantity of water to condense the steam. Water is led into the plants by means of circulating water pumps and after passing through the condenser is discharged back into the river. If such a source is not available closed cooling water circuit is used where the warm water coming out of the condenser is cooled and reused. Types Wet type Dry type
• 30.
  Wet type Types Natural draughtcooling tower Mechanical draught cooling tower Natural draught cooling tower Natural draft spray filled tower Natural draft packed type tower Hyperbolic cooling tower
• 31.
   Natural draftspray filled tower  Hyperbolic cooling tower
• 32.
   Forced draught Induced draught MECHANICAL DRAUGHT SYSTEM:
• 33.
  Dry type coolingtower  Direct type  Indirect type with surface condenser
• 34.
   Indirect withspray condenser  Indirect with ammonia
• 35.
  Condensers The function ofthe condenser is to condense the steam exiting the turbine. The condenser helps maintain low pressure at the exhaust.  Two types of condensers are used.
• 36.
  Surface condenser(non contact)
• 37.
  Low level jetcondenser (contact type)
• 39.
  Feed water treatment River water contains dissolved minerals Cl-, SO4 2-, HCO3 - of Na+, Mg2+, Ca2+ and Fe2+  These are the materials in the water. These unwanted materials can be removed by the following processes, Mechanical method Thermal method chemical method Purpose of feed water treatment is to remove the unwanted materials Undissolved and suspended solid materials dissolved salts and minerals dissolved gases other materials (as oil, acid) either in mixed or unmixed forms
• 40.
  Undissolved and suspendedsolid materials  Turbidity and sediment  Sodium and potassium salts  Chlorides  Iron  Manganese  Silica  Microbiological growths  colour
• 41.
  Undissolved and suspendedsolid materials Usually the turbidity in muddy and turbulent river will be 60,000 ppm. The turbidity of feed water should not exceed 5 ppm. These materials can be removed by settling, coagulation and filtration. Heating and evaporation produces hard stony scale deposits Standard measurement – CaCO3 in water (ppm)
• 42.
  Dissolved salts andminerals  It contains Calcium and Magnesium salts. Its in the form of carbonates, bicarbonatees, sulphates and chlorides.  It recognised by hardness of the water  Temporary hardness  caused by bicarbonates of calcium and magnesium that can be removed by boiling  Permanent hardness  caused by chlorides, sulphates and nitrates of calcium and magnesium.  removed by boiling. Because they form a hard scale on heating surfaces.
• 43.
  Steam Rate andHeat Rate  Steam Rate  It is defined as the rate of steam flow required to produce unit shaft output.  Steam Rate=1/Wnet kg/kWs  Heat Rate  It is defined as the rate of heat input required to produce unit shaft output.  Heat Rate = Q1/(Wt- Wp)=kJ/kWs
• 44.
  SUPERCRITICAL BOILERS  Pressurefrom 125 bar, T = 510 ̊C to 300 bar & 660 ̊C  The power plant which is operated above the critical pressure and temperature condition is called supercritical power plant.  Sub critical Boiler Super critical Boiler Economiser Economiser Evaporator Superheater Superheater  The super critical boilers are above 300 MW capacity units available.  Water reaches to this state at a critical pressure above 22.1 MPa and 374 oC  Heat transfer coefficient for sub critical boiler is 165000 kJ/m2 hr. C  For super critical boilers – 2,20,000 kJ/m2 hr. C  Higher thermal efficiency 40-42%  Presently 246 bar and 538 ͦC are used for unit sizes above 500 MW.
• 45.
  Supercritical boiler
• 47.
  Types of supercritical boilers
• 48.
  Cont..
• 49.
  A LA-MONT BOILERIS A TYPE OF FORCED CIRCULATION WATER-TUBE 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 IN ORDER TO HAVE AN ADEQUATE AND POSITIVE CIRCULATION IN STEAM AND HOT WATER BOILERS. A CENTRIFUGAL PUMP WHICH FORMS THE HEART OF THIS BOILER IS RESPONSIBLE TO CIRCULATE WATER WITHIN THE BOILER SYSTEM. IT RECEIVES WATER FROM THE DRUM AND DELIVERS THIS WATER TO A DISTRIBUTION HEADER AS SHOWN IN THE DIAGRAM HERE. THE NUMBER OF HEADERS MAY DIFFER IN NUMBERS AND DEPENDS ON THE SIZE AND BOILER DESIGN OF EACH BOILER. THE BOILER HEATING SURFACES INCLUDES A NUMBER OF TUBES ARRANGED IN A PARALLEL FORM AND THE INLET ENDS ARE WELDED TO THE DISTRIBUTORS OR THE HEADERS. A CIRCULATION PRESSURE IS TO BE PROVIDED DURING THE INSTALLATION OF THE PUMP AS PER THE BOILER DESIGN AND IT SHOULD BE SUFFICIENT TO OVERCOME THE RESISTANCE OFFERED BY THE TUBES. AN EVEN
• 50.
  Benson Boiler A Bensonboiler is a type of Once-Through Boiler patented by Marc Benson in Germany in 1923. Feed water enters the bottom of the furnace at high sub-critical or supercritical pressure and is evaporated to high quality in the spiral section. A balancing header is commonly provided near the top of the furnace to alleviate any differences in steam quality resulting from variations in heat absorption in different parallel spiral circuits before the steam/water mixture is introduced to the open boiler pass. Here, it is superheated in the upper parts of the furnace envelope and subsequently in pendant tube banks. The balancing header also serves as a means of separating excess liquid when, at low loads, the furnace flow rate exceeds the steam demand from the boiler as a whole. As in other forms of Fossil Fuel-Fired Boilers, the flue gasses are used for reheat, economizer and air-heating duties.
• 51.
  LOEFFLER BOILER The Loefflerboiler is an addition of the Lamont boiler. In LaMont boiler, a major problem was experienced which is the salt and sediment deposition in the inner surface of the water tube through which water the flows. This deposition of salt and sediment decreases the heat transfer in the inner surface area of the water tube. LaMont boilers also have overheating problems due to the salt deposits. For these problems of La Mont boilers have been solved with the Loeffler boiler by preventing the flow of water in the tubes. The Loeffler boiler is an internally fired furnace with forced circulation, high pressure and water tube boiler. In Loeffler boiler, 75% of superheated steam is used to evaporate the water within the evaporator drum and the remaining 25% of the steam from the superheater is utilised by the turbine. Steam circulating pump is employed to circulate steam inside the boiler.
• 52.
   Velox boileris based on the principle that heat transfer rate increases when velocity of flue gas is more than speed of sound. This increases steam generation rate. Flue gases are used to turn a turbine which is connected to the compressor. It increases the flow of hot air to or above the speed of sound. This increases the rate of heat transfer to the water coming from the economizer into the boiler tubes causing more steam to generate which then goes into a superheater via a steam separator. Steam from superheater is at high temperature and pressure. This is used to operate turbines. Velox boiler
• 53.
  Fluidized Bed Reactor A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase chemical reactions.  Simple> Conversion of Solid Fuel (usually coal) into Liquid
• 54.
  Fluidized Bed Combustion Fluidized bed combustion is a combustion technology used to burn solid fuels.  In its most basic form, fuel particles are suspended in a hot, bubbling fluidity bed of ash and other particulate materials through which jets of air are blown to provide the oxygen required for combustion or gasification. Ground limestone is used in some coal-fired power generation facilities to control the release of sulfur gases (SOx) though the flue. This is known as the dry scrubbing process as opposed to the wet scrubbing process, where a slurry of ground limestone or calcium hydroxide is used for stack gas purification.