Essay: IMPROVE THE BOILER EFFICIENCY TO OPTIMIZE THE COMBUSTION OF COAL FIRED IN BOILER

Chapter 1
Introduction
1.1 Company information
Thermal Power Plant is a very huge area having a no. of different sectors including Mechanical, Electrical, Instruments and Control and many more. The main aim of the Wanakbori thermal Power station is to produce electricity at minimum cost. The thermal power plant works on Rankin’s Cycle. There are number of power generating companies in Gujarat like GSECL, Adani, and Reliance etc. Wanakbori Thermal Power Station is Gujarat’s Biggest Thermal power station. Wanakbori Thermal Power Station has total 7 units having 210 MW capacity of each unit and 1470 MW capacity of whole power station. There is one boiler per unit. The boilers in Wanakbori thermal power station are regenerative reheat water tube boiler. The circulation in boiler is natural circulation. The pulverized coal is supplied to the furnace. The tangential firing system is used which is mostly common in pulverized coal fired boiler. The draught of the system is maintained through balanced draught arrangement.
Electricity is produced in power plants. There different types of plant like: (a) Thermal, (b) Hydraulic, (c) Gas Turbine, (d) Nuclear, (e) Geothermal. Thermal power plants play an important role in the total power generation in the country. Fossil fuel, coal and natural gas are the energy supply, and steam is the working fluid. A steam power plant continuously converts the energy Stored in fossil fuels (coal, natural gas) into shaft Work and finally into electrical energy. The working fluid is water which is Sometimes in the liquid phase and sometimes in the vapors phase during its cycle of Operations. Energy released by the burning of fuel is transferred to water in the boiler (B) to generate steam, which then go to the Turbine (T) to produced shaft work. The mechanical work (shaft work) convert in to electricity by the generator (G). The steam exit from the turbine is Condenser (C) where cooling water from a river or circulates moving away the Heat released through reduction. The water (condensate) is then feedback to boiler by the Boiler feed pump (BFP), and the cycle go on repeat itself.
1.1GENERAL LAYOUT OF PLANT:
The general layout of steam power plant is shown in fig. 1.1. It consists mainly four circuits
Coal and ash circuit
Air and gas circuit
Feed water and steam circuit
Cooling water circuit
Coal and ash circuit: Coal is received at the coal yard and supplied to boiler furnace after applying necessary coal handling process through fuel feeding devices. After combustion of coal, some percentage of ash is collected though ESP and some percentage is transfer to the ash pond through ash handling equipment.
Air and gas circuit: Air is take from the atmosphere by the forced draught fan and induced draught fan. The air is passed on to the boiler furnace after it is heated by the air preheater by the use of flue gases before these are discharged through the chimney. High temperature flue gases formed in the combustion chamber are used for transferring heat to feed water in boiler tubes and to steam in the super heater tube. These gases are then passes over the reheater, then passed over economiser and air preheater. Then the flue gases carrying ash are passed through electro electrostatic precipitator in order to remove ash.
Feed water and steam circuit: Steam generated in boiler and superheated in super heater is feed to H.P, I.P, and L.P turbine to develop mechanical power. After expansion of steam in H.P turbine, a part of the steam is passed to reheater for reheating the steam. This steam in now passes in I.P turbine and then L.P turbine. The mechanical power develop by turbine is supplied to generator where the mechanical energy is converted into electrical energy
Cooling water circuit: The quantity of cooling water is required to be circulated in the condenser for condensing the steam exit from the turbine. The water is usually taken from the various sources such as river, lake, sea etc. If the sufficient quantity of water is not available, the heated water coming out of the condenser is cooled in cooling tower and it is recirculate through the condenser
1.2 BOILER:
As per the Indian Boiler Act & Regulations (IBR), a boiler may be defined as”A Boiler is a closed vessel, in which steam is produced by evaporation of water, at a nominated pressure and temperature, on application of heat is generated by firing fuel. It is important to say that in a boiler by firing fuel, chemical energy gets converted into heat energy, and the heat generated is transferred to water, under storage or circulation in a system, by way of convection, conduction or radiation process. The fuel fired may be either in solid, liquid or gaseous form.
1.2.1 Classification of boiler:-
The essential qualities of a good boiler:-
It should be capable of quick start-up,
Should meet large load fluctuations,
Occupy less floor space,
Should afford easy maintenance and inspection,
Should essentially posses the capacity of producing maximum steam with minimum fuel consumption,
Should be light and simple in construction,
Various joints should be accessible for inspection and should be away from direct flame impact,
Tubes should be sufficiently strong to resist wear and corrosion,
Mud and other deposits should not collect on heated plates and
The velocity of water and that of flue gas should be a minimum.
1.2.1 Boiler Mountings: For the safety of the boiler and for better control over the steam generation process, various fitting are provided on the boiler, which are called boiler mountings. A boiler cannot function safely without mountings.
They are mainly,
(1) Safety valves
(2) Water level indicator or gauge
(3) High Steam Low-Water Alarm or High Steam Pressure Alarm
(4) Fusible Plug
(5) Steam Pressure Gauge
(6) Steam stop valve
(7) Feed check valve
(8) Blow-off cock or blow-down valve etc.
1.2.2Boiler Accessories: These are the items that form an integral part of the boiler but are not mounted on the boiler. They are mainly for increasing the plant load and overall boiler efficiency and they help in smooth running of the plant under desired operating conditions.
They are mainly,
(1) Superheater
(2) Economizer
(3) Air Pre-heater
(4) Feed water pumps or Injectors
(5) Feed water heaters etc.
1.2.3Basically following pressure parts are used
Economiser
Boiler drum
Water wall system
Super heater
Reheated
Economise:economiser is used to Preheat the boiler feed water and this heat is gained from the flue gases.Economise is located rear gas pass below the rear horizontal SH. It is in staggered arrangement and continuous finned tube. Basically tube size is 44.5 mm× 4.5 mm (thick)
Advamtages of economiser is as below
as the econimise recover the heat in flue gases that leaves the boiler and transfer to working fuid will be saveings in fuel consumption
as the feed water is preheated in the economiser and enter the boiler tubes at an elevated temperature, the heat transfer area required for the evaporation surface required will be reduced considerably.
Drum:in a sub-critical re-circulation boiler, thedrum plays an important functional role. The function of the drum are
To separete steam and water from the mixture generated from water wall.
Mixing feed water from economiser and water separated from steam-water mixture, and re-circulate through the evaporating tubes
Carrying out blow down for reduction of water salt concentration
Water wall system:the water walls are the tubes panels through which the water for steam generation will be circulated
Super heater:super heater are provided in the boiler to rise the steam temperature above the saturation temperature by absorbing heat from flue gas
Reheater:The steam is first enter at h.p turbine so its temperture and pressure reduce before entering I.p turbine so a reheater is used to reheat the cooled steam.
the amount of heat absorb as a percent of total heat absorbed by feed water and steam in boiler at different pressure is illustrated in table
Component
% of heat absorption at cycle pressure
140 Kg/cm2 185 Kg/cm2 255 Kg/cm2
with single R.H 255 Kg/cm2
with double R.H
economise 14 17 15 10
Water wall 44 32 37 37
Super heater 28 35 28 25
Re heater 14 16 20 28
1.2.3EMISSION CONTROL SYSTEM: – As the boiler emissions have many ill effects on the environment as a whole, there is need to control emissions to a level admissible to environment. In a boiler if specifically applies to the removal of fly ash from the flue gas. For this ESP is used
ELECTROSTATIC PRECIPITATORS:-
WORKING PRINCIPLE: – Electrostatic precipitation is a method collection of dust that uses electrostatic forces, and consists of discharge wires and collecting plates. A high voltage D.C is applied to the discharge wires to form an electrical field between the wires and the collecting plates, and also ionizes the gas around the discharge wires to supply ions. When gas that contains an aerosol (dust, mist) flows between the collecting plates and the discharge wires, the aerosol particles in the gas are charged by the ions. The Coulomb force caused by the electric field causes the charged particles to be collected on the collecting plates, and the gas is purified. This is the principle of electrostatic precipitation, and Electrostatic precipitator apply this principle on an industrial scale. The particles collected on the collecting plates are removed by methods such as
Dislodging by rapping the collecting plates.
Scraping off with a brush.
Washing off with water, and removing from a hopper.
1.2.4. DM water:-The overall objective of good water management both in quality and quantity in power plant are: –
D.M. Water generation and quality of DM water.
Prevention of corrosion in the Boiler water cycle and feed/steam system.
Prevention of scale and deposits on all heating surface/heat exchangers/coolers.
Maintenance of a high level of steam purity.
All water treatment programs should also ensure that chemicals employed one environmentally acceptable and cause no pollution problems.
1.3 Turbine:-
STEAM TURBINE IS A ROTATING MACHINE WHICH CONVERTS HEAT ENERGY OF STEAM TO MECHANICAL ENERGY
1.3.1 Principle of turbine:-
When steam is allowed to expand through a narrow orifice, is assumes energy at the expense of its enthalpy. This kinetic energy of steam is changed to mechanical (rotational) energy through the impact or reaction of steam against the blades.
It should be realized that the blade of the turbine obtains no motive force from the static pressure of the steam or from any impact of the steam jet. The blade are design such a way, that steam will glide on and off the blade without any tendency to strike it.
As the steam moves over the blade, its continuously changing and centrifugal pressure exerted as the result is normal to the blade surface points. The total motive force acting on the blade is thus the results of all the centrifugal plus the change of momentum. This causes the rotational motion of the blade.
1.3.2. TURBINE TYPES
Basically there are two broad classification of steam turbine
Impulse: In impulse turbine the steam is expanded infixed nozzles. The high velocity steam issuing from the nozzles does work on the moving blades which causes the shaft to rotate. The essential feature of an impulse turbine is that all the pressure drops occur in the nozzles only, and there is no pressure drop over the moving blades.
Reaction turbine: in this type of turbine, pressure is reduced in both fixed and moving blades. Both fixed and moving blades act like nozzle and are of some shape. Work is done by the impulse affect due to the reversal of direction of the high velocity steam plus a reaction effect due to the expansion of steam through the moving blades. This turbine is commonly called a reaction turbine
Impulse – Reaction turbine: In this turbine drop in pressure of steam takes place in fixed blade as well as moving blade. It may be noted that energy transformation occur in both fixed blade & moving blade. The rotor blade cause energy transfer & energy transformation
1.3.4. DESCRIPTION OF 210 MW STEAM TURBINE:
Fig. shows the schematic of a 210MW steam turbine
Superheated steam at 130Kg/cm2, 535c from the boiler enters into through two emergency stop valves and four control valves. In The high pressure turbine there are 12 stage, the first stage is governing stage. The steam flow in HPT being in reverse direction, the blades in HPT are designed for anticlockwise rotation, when viewed in the direction of steam flow. After passing through HPT, steam at 27Kg/cm2, 327c flows to the boiler for reheating. Re heated steam at 24.5 Kg/cm2, 535c comes to intermediate pressure turbine through two interceptor valve and four control valve. After flowing to IPT, steam at enters the low pressure turbine through two crossover pipes. After leaving the LPT the exhaust steam condenses on condenser.
1.3.5 TURBINE COMPONENTS:
Casing
Rotors
Blades
Turning gear
Couplings
1. CASING: – A casing is essentially a pressure vessel which must be capable of withstand the maximum working pressure and temperature that can be produced within it. The cylinder is supported at each end. The cylinder has to be extremely stiff in a longitudinal direction in order to prevent bending and to allow accurate clearances to be maintained between the fixed and the moving parts of the turbine
Following three types of casing design.
Single shell casing
Double shell casing
Barrel type casing
1) Double shell casing: –
3. BLADES: – these are the most important part of the turbine as these are responsible for the function of turbine, i.e. converting heat energy to mechanical energy. A blade has three main parts:
AEROFOIL – it is the working part of the blade
ROOT – it is the portion of the blade which is fixed with the rotor or casing
SHROUD – it can be riveted to the main blade or can integrally machine with the blade
4. TURNING GEAR: – Turning gear is provided to rotate turbine shaft slowly during the pre-run up operation and after shut down to prevent uneven heating and cooling of the shaft. The uneven heating or cooling would lead to bending and misalignment of the shaft with possible fouling of stationary and moving part. Use of turning gear during starting eliminate the necessity of admitting suddenly a large flow of steam to rotate the turbine from the rest.
5. COUPLINGS:- the need of coupling arises from the limiting length of shaft which is possible to forge in one piece and from the frequent need to use different material for the various rotors, in view of the various conditions of temperature and stress. Coupling are important device for transmitting torque, but may also have to allow relative angular misalignment, transmit axial thrust and ensure axial location or allow relative axial movement. They may classified as rigid flexible or semi-flexible.
1.4 Condensate System: – A condensate system consists:
Condenser( with hot-well)
Condensate pump
Air extraction system
Gland coolers and L.P. heater
Deaerator
1.4.1. CONDESNSE:
The function of condenser are:
To convert exhaust steam from L.P.T to water for reuse.
To provide lowest economical heat rejection temperature
Deaeration of make-up water introduce in condenser
Form a convenient point for introducing make up water
TYPE OF CONDENSER:-
1) Direct contact type: – in this type steam is condense by directly mixing of exhaust steam and cooling water
2) Surface condenser: – condensation of steam take place on the outer surface of tube which are cooled by water flowing in the tube
DESCRIPTION OF CONDENSER FOR 210MW TURBINE: -The condenser group consists of two condensers, each connected with exhaust part of low pressure casing.These two condensers have been interconnected by a by-pass branch pipe. The condenser has been designed to create vacuum at the exhaust of steam turbine and to provide pure condensate for re-using as feed water for the boilers. The tube layout of condenser has been arranged to ensure efficient heat transfer from steam to cooling water passing through the tubes, and at the same time the resistance to flow of steam has been reduced to the barest minimum
1) CONDESATE PUMP: – condensate pump are normally vertical, multistage, centrifugal pump. They are basically required to operate on minimum net positive suction heat. They are provide for pumping the condensate to deaerator. In 210MW there are three pump with 50% capacity.
2) AIR EXTRACTION SYSTEM: – air extraction system is required to extract air and non-condensable gases from the condenser for maintain vacuum.Amount of air to be extracted from condenser during start up is large and the extraction should be done as rapidly as possible so as to allow the turbine to be started.Under normal operating conditions quantity of air to be extracted is lower. It consists of air leakage into the condenser via flanges and glands and also of very little non condensable gases present in steam. To guard against excessive water vapour extraction along with air, the space beneath the air extraction baffles has been provided with its own cooling tubes in order to condense as much water vapour as possible and thus preventing its removal from condenser.
3) L.P heater:-It is used for pre-heating the water before water enter into boiler.A low pressure surface heater consist of a cylindrical body fabricated from mild steel and sealed at its upper end by a cast steel water box, which houses a nest of solid brass U-tubes. The ends of the tubes are expanded into a tube plate trapped between a flange on the body and a corresponding flange on the water box. Baffles are provided to secure that the steam is directed across the tubes. The upper section of the quadrant of the tube nest, which carries the condensate in its last pass through the heater, is. Totally enclosed by vertical baffles, so forming a flashed-steam drain cooler section of the heater.
4)GLAND COOLER:-Gland cooler has been designed to condensate the leak-off steam from intermediate chambers of end sealings of HP & IP turbines.The main condensate flows through the tubes in four paths before leaving the cooler. The leak off steam enters the shell through a pipe and flow over the tube nest. The participation walls installed in the tube system lead to zig-zag flow of steam over the tube nest. Condensate of leak off steam referred as drain trickles down the tubes and is taken out from the lower portion of the shell by automatic level control valve, installed on the drain line.
5) DEAERATOR: -The pressure of certain gases like O2, CO2 and NH3 dissolved in water is harmful because of their corrosive attack on metals, particularly at elevated, temperatures. Thus in modern high pressure boiler, to prevent internal corrosion, the feed water should be free, as far as practicable, of all dissolved gases, especially oxygen. This is achieved by embodying into the freed system a deaerating unit.
A deaerator also serves the following functions:-
Heating incoming feed water.
To act as a reservoir to provide a sudden or instantaneous demand.
Principle of Deaeration:-
The solublity of any gas dissolved in a liquid is directly proportional to the partial pressure of the gas. This holds within close limits for any gas which does not react chemically with the solvent.
Solubility of gases decrease with increase in solution temperature and or decrease in pressure.
1.4 Boiler Feed Pump: – Boiler feed pump is a multi-stage pump provided for pumping feed water to economiser.
Description of feed Pump:-
Feed pump consists of following major parts
Pump barrel
Rotor
Stator
Mechanical seal
Balancing device
Need of boiler feed pump:-As the water is fed to the steam generator it has to be at the temperature & Pressure that of the steam generator.
Process of water flow:-Boiler feed pump extract water from de-aerator and feed it to the boiler drum via H.P heaters and economizer
General configuration of Boiler feed pump:-
Generally 2 Turbine driven boiler feed pumps (1 Working & 1 Standby) & 1 Motor driven boiler feed pump is used for 1 unit.
Turbine driven boiler feed pump: It works with the steam extraction from Intermediate Pressure (I.P.) turbine exhaust.
Motor driven boiler feed pump: It works with a motor as the name specifies.
1.5 GENERATOR: – A DC generator operates on the principle of dynamically induced e.m.f. in conductor
PRINCIPLE: – FARADY’S LAW OF ELECTRO MAGNETIC INDUCTION
“Whenever conductor cuts the magnetic field an e.m.f. is induced.” E= (dØ/dt)
=rate of change of flux
1.5.1 CONSTRUCTION OF DC GENERATOR:-
1.5.1 MAIN PARTS OF GENERATOR:-
Yoke:-yoke is called frame. It provides protection to the rotating and other parts of the machine from moisture, dust ect.
field winding:- the coils wound around the pole cores are called field coils
Poles:- a pole of a generator is an electromagnet. The field winding is wound over the poles
armature:-it is a cylindrical drum mounted on the shaft which provide a low reluctance path to the flux produced by the field winding
commutator:-it convert the alternating emf generated internally in d.c voltage
brushes:-current is conducted from the armature to the external load by the carbon brushes which are held against the surface of commutator
Chapter 2
Liturature reviwe
“Energy Efficiency Improvement in Thermal Power Plants” Genesis Murehwa, Davison Zimwara, Wellington Tumbudzuku, Samson Mhlanga et al. describe improvement efficiency of Zimbabwe’s thermal power plant by identifying major energy loss area in power plant and develop a plan to reduce them by using energy and exergy analysis as the tools. The energy supply to demand is reducing day by day around the world due to the growing demand and sometimes due to ageing of machinery. Most of power plants are designed by the energetic performance criteria based not only on the 1st law of thermodynamic, but the real useful energy loss can’t be averred by the 1st law of thermodynamic, because it doesn’t differentiate between the quality and quantity of energy.
This paper describe the method of improve efficiency of 2100 MW thermal power plants
Performance Improvement of Pulverized Coal Fired Thermal Power Plant: A Retrofitting Option R.Paul, L.Pattanayak et al.describe the possibilities of renovation and modernization options in an existing 210 MW pulverized coal fired thermal power plant.Three different options along with its cost implications have been discussed based on the performance and levelised cost of generation. The performance of the unit for all the three options is examined under the consideration of increasing the availability of the unit and continuous capabilities to generate power maintaining normal operating parameters over an extended life of at least 15 years. The results revels that with the renovation and modernization approach the unit availability can be increase to more than 85%, with a capacity enhancement of 215 MW and the heat rate of the unit will be approximately 2544 kcal/kWh.
This paper describe description of plant and methodology of 210 MW unit
Improvement Power Plant Efficiency with Condenser Pressure, Amir vosough, Alirezafalahat, Sadeghvosough, Hasan nasresfehani, Azambehjat, Roya naseri rad et al. describe the energy analysis and exergy analysis of an ideal Rankin cycle with reheat is presented. The objects of paper are to analyze the system component independently and exergy losses in cycle. The effect of varying the condenser pressure on this analysis will also be presented.The performance of the plant was determined by a component-wise modeling and a detailed break-up of energy and exergy losses for the considered plant has been presented. Energy losses mainlyoccurred in the condenser where 2126KW is lost to the environment while nothing was lost from the boiler system because it assumed adiabatic The boiler is the major source of irreversibility. For improvement the power plant efficiency the effect condenser pressure has been studied.
This paper also describe condenser and its type.
Improvement of Boiler Efficiency in Thermal Power Plants, A. Ashokkumar et al.The world over energy resources are getting scant and more and more exorbitant with time. In India there is big gap between energy demand and supply by increasing supply is an expensive option. The share of energy costs in total production costs can, therefore improve profit levels in all the industries. This reduction can be gained by improving the efficiency of industrial operations and equipments. Energy audit plays an important role in identifying energy conservationopportunities in the industrial sector, while they do not provide the final answer to the problem; they do help to identify potential for energy conservation and induces the companies to concentrate their efforts in this area in a focused manner
This paper describe the boiler description and improvement boiler efficiency
PERFORMANCE BASED COMPARATIVE ANALYSIS OF THERMAL POWER PLANT, Man Mohan Kakkar, Raj Kumar &Mukesh Gupta et al.Coal based thermal power stations are the major source of electricity generation in India. In this paper, the author attempts to investigate the gap between demand & supply and cost reduction to make the existing power plants more efficient. Efficient power generation is expected to make more power available at a lower cost for economic and other activities, which in turn shall make the country more competitive. The target of the study is on the coal fired thermal power plants in the country. The performance calculation and rectification measures are essential for performance calculation and efficiency improvement.
This paper describe about method to analysis performance of thermal power plant
CHAPTER 3
METHODOLOGY
3.1Introduction
Efficiency of any plant or equipment is the ratio of output to its input, expressed as percentage. Output and input are expressed in same physical units. The output is the electrical energy sent out to the grid and input is the heat energy of the fuels fired in boiler. This is normally termed as overall station efficiency or overall plant efficiency. Thus:
Overall station efficiency= (out put of station)/(input of station)×100
=(Energy sent out (KW))/(Fuel nurnt(Kg)×calorific value of fuel(KCal/Kg))
3.2Power plant cycle: – The Rankine cycle is a reversible cycle. It is used in the steam power plants. The fluid used in this cycle is steam. The complete condensation of vapour in condenser & the water is pumped isentropically to the boiler at boiler pressure in the Rankine cycle for solve the problem occurs in the other cycles of pumping vapour & liquids mixture. It is consists of the four main components can be given as, 1) Boiler, 2) Turbine, 3) Condenser, 4) Feed Pump.
[Diagram of rankine cycle]
The energy liberated in the fuel is converted into the shaft power through this steam turbine power plant. The T-S diagram & Block diagram is shown in the figures 1 & 2 respectively.
Process 1-2:-The steam (Wet, Dry saturated or Superheated) at high pressure & high temperature is isentropically expands into the turbine. Due to expansion of steam the turbine produce mechanical work, Wt.
Process 2-3:-The steam exhausted from the turbine is started to condense in the condenser at constant pressure. The heat of the steam is transferred to the cooling water which is which is circulating in the tubes. The steam is converted into saturated water. The heat rejected through exhaust steam is given as Qr.
Process 3-4:-The water coming from condenser is pumped to boiler at boiler pressure through feed pump. To do that, feed pump requiresExternal work, Wp.
Process 4-1:-The boiler converts feed water into the steam at constant pressure. The heat supplied in this process is Qs.
Net output of the power plant (Shaft Power) = Turbine Work — Pump Work
.∙. Ws = Wt – Wp
Efficiency of Rankine Cycle:
So, efficiency of the rankine cycle is È R = Ws/Qs
Overall plant efficiency=
Boiler efficiency ×Turbine efficiency× cycle efficiency ×generator efficiency
= ȠB×ȠT×ȠC×ȠG
1. DIRECT METHOD:-
Heat rate is usual way of find efficiency
Ƞos=860/HR×100
Or
Ƞos=(Electrical output sent out(Kwhr))/(heat supply to steam(KCal))×100
2. INDIRECT METHOD:-
Overall plant efficiency
= Boiler efficiency ×Turbine efficiency× cycle efficiency ×generator efficiency
= ȠB×ȠT×ȠC×ȠG
2.1Boiler efficiency:-Thermal efficiency of boiler is defined as the percentage of heat input that is effectively utilized to generate steam. There are two methods of assessing boiler efficiency.
(1)The Direct Method: – this method is straight forward and consist of measuring the heat supplyto the boiler in given time
Efficiency =((enthalpy of Stm.-enthalpy of feed water)×Stm.flow)/((qty.of coal ×C.V))
=WS ([Cp(t-to)+L+(To-t)])/(Mf×C.V)
Ws = Steam flow rate
Cp = specific heat of steam
T = S.H steam temperature
To = saturation temperature of steam
L = latent heat of conversion
T = Feed water inlet temperature
Mf = fuel burring rate
C.V = calorific value of fuel
(2) The Indirect Method: – if losses are known, the efficiency can be derive easily. An important advantages of this method is that the errors in measurement o not make significant change in efficiency
Boiler losses:-
Loss of heat due to dry flue gas(L1)
Loss of heat due to combustion of hydrogen(L2)
Loss of heat due to moisture in fuel(L3)
Loss of heat due to moisture in air(L4)
Loss of heat due to CO formation(L5)
Loss of heat due to unburnt in fly ash(L6)
Loss of heat due to unburnt in bottom ash(L7)
Loss of heat due to radiation(L8)
Boiler Efficiency = 100 — (various heat loss)
È B = 100 — (L1+L2+L3+L4+L5+L6+L7+L8)
% Heat loss in dry flue gas(L1) = (mCp(tf-ta))/(CV of fuel)×100
% losses due to H2 in fuel(L2) = (9H2{584+Cp(tf-ta})/(CV of fuel)×100
% losses due to moisture in fuel(L3)=(M{584+Cp(tf-ta})/(CV of fuel)×100
% losses due to moisture in air(L4)=(AAS×Humidity factor {Cp(tf-ta)})/(CV of fuel)×100
% losses due to CO-generation(L5)= (5744{% of CO}×C)/((% of CO+% of CO2}CV of fuel)×100
% losses due to surface radiation and convection(L6)= 0.548[(Ts/55.55 )4-(Ta/55.55)4]+[1.957(Ts-Ta)1.25√((196.85Vw+68.9)/68.9)
% losses due to unburnt in fly ash(L7)=(Total ash collect per kg fuel burnt×CV of fly ash)/(CV of fuel)×100
% losses due to unburnt in bottom ash (L8)=(Totalash colect per Kg of fuel burnt×CV of bottom ash)/(CV of fuel)×100
Air Preheater Efficiency = FG Temperature at APH I/L – FG Temperature at APH O/L
FG Temperature at APH I/L- Design Ambient Temp.
Effectiveness of Economiser =((Mean F.G temp at Eco-Mean F.G temp at Eco O/l))/((Mean F.G temp at Eco i/l-F.W temp at Eco i/l))
3.4 Turbine efficiency:
Heat rate = (Steam flow (TPH)×(enthalpy of main stream at Turbine I/l- enthalpy of main feed water at HPH O/l))/(Units(MWH) generated per Hour)
Turbine efficiency ȠT=3600/HR×100
Heater Performance:-
Feed Water temperature rise=Feed water temp at Heater O/l – Feed water temp at Heater I/l
Terminal temp. Difference = Saturation temp of extraction-Feed water temp at Heater O/l
Initial tem. Difference=Drain temperature-Feed water temp at Heater I/l
Log mean temp. Difference=(Initial temp Diff —Terminal temp Diff )/(Ln ((Initial temp Diff)/(Terminal temp Diff)) )
3.6 Electrostatic Precipitator Performance:- the basic formula for efficiency of ESP is y=100(1-e^k)
3.5Cycle efficiency:
ȠC = (Energy available for conversion in work(KCal))/(Energy given as heat in boiler(KCal))×100
=(S(hB-hA))/(S(hB-hA))×100
3.6Generator efficiency:
ȠG = (Electric energy send out (K Whr×860))/(Mechanical work)×100