Energy Audit of 250 MW Thermal Power Stations PTPS, Panipat

Transcription

1 Energy Audit of 250 MW Thermal Power Stations PTPS, Panipat Vikrant Bhardwaj 1, Rohit Garg 2, Mandeep Chahal 3, Baljeet Singh 4 1 Asstt. Professor in Deptt. Of Mechanical Engineering, IIET, (Kinana) Jind (Haryana), India vikrantwish@gmail.com 2 Professor in Deptt. Of Mechanical Engineering, IIET, (Kinana) Jind (Haryana), India rohit_garg123@yahoo.com 3 Asstt. Professor in Deptt. Of Mechanical Engineering, HCTM, Kaithal (Haryana), India mandeepchahal17@yahoo.in 4 Asstt. Professor in Deptt. Of Mechanical Engineering, HCTM, Kaithal (Haryana), India baljeetchahal86@gmail.com Abstract Energy conservation means, the need is to use energy efficiently and effectively.energy Audit is a technical survey of a plant in which the machine/section wise/ department wise pattern of energy consumption studied and attempts to balance the total energy input correlating with production. As a result of the study the areas where the energy is wastefully used and the improvements are felt, are identified and corrective measures are recommended so that the overall plant efficiency could be improved.fundamental understanding of the process is essential if we are to improve the overall efficiency of the system. In this work an energy audit of 250MW Power Plant (Coal based) is presented at different loads. In thermal power station approximately 90% of the fuel i.e. Coal alone. In my work the overall plant efficiency observed 33.67% (210MW), 35.89% (232MW) and 36.74% (250MW). The component efficiencies found 85.23% (Boiler), 41.19% (Turbo-Gen.) and 53.33% (condenser) at full load. 1. Introduction Energy Audit: An energy audit is a technique for identifying energy losses, quantifying them, estimating conservation potential, evolving technological options for conservation and evaluating techno economics for the measures suggested e.g. Assist industries in reducing their energy consumption, To promote energy-efficient technologies among industry sectors, Disseminate information on energy efficiency through training programs and workshops, To promote transfer of energy-efficient and environmental-sound technologies to the industrial sectors in the context of climate change. Energy Audit Technique: The energy audit evaluates the efficiency of all process equipment/systems that require energy. The energy auditor begins at the utility meters, locating all energy sources coming into a facility. The auditor then identifies energy streams for each fuel, quantifies those energy streams into discrete functions, evaluates the efficiency of each of those functions, and identifies energy and cost savings opportunities. Total System Audit: This approach analysis the total system by detailed analysis as the total energy data is entered in a master database file. This contains design data and also the observed data. This approach gives the energy performance of the total system and identifies areas of improvements on energy cost or energy quantity basis. This method requires rigorous data entry and analysis. Problem Formulation In PTPS, Panipat 250 MW units is consideration for energy Audit for Energy Audit and Efficiencies of main sub-units as like Boiler, Turbine and generator, Condenser & Heater are calculated and compared are different loads which highlights in PTPS 250 MW units energy efficiency has to be improved to survive in Global Market. 2. Working Cycle of Typical Coal Fired Power Station Layout shows a Coal Fired Power Station. Its main raw material is Coal, air and Water. The Coal brought to the station by trains or by the other means & this travels from Coal handling plant by conveyor belt to the coalbunkers, from where it is fed to the Pulverizing Mills, which grind it as fine as face as face powder. The finely powdered coal mixed with pre-heated air, is then blown into the Boiler by a fan called Primary Air Fan where it burns, more like a gas than as a solid in the conventional domestic or industrial grate, with additional amount of air called secondary air supplied by a Forced Draft Fan.As the coal has been ground, finely the resultant ash is also a fine powder. Some of it binds together to from lumps, which fall into the ash pits at the bottom of furnace. The water-quenched ash from the bottom of furnace is conveyed to pits subsequent disposal or sale. Most of ash, still in fine particles form is carried out of the boiler to the Precipitators as dust, The dust is then conveyed by water to disposal areas or to Bunkers for sale while the cleaned flue gases pass on through Induced Draft Fan to be discharged up the Chimney. 120

2 Figure 1 Table 1. DATA OF 250 MW THERMAL POWER PLANT AT LOAD 250 MW Description Press Tem Flow Enthalpy Entropy S.I HPT S.O. HPT& I Re-heater S.O. Re-heat & I. IPT S. O. IPT & I. LPT th Extraction HPT & I. HPH Data Analysis Data Analysis of plant at 250 MW Boiler Section Inlet in Boiler (i) At (40) Coal = 120T/hr = 120 x 1000/3600 =33.33 Kg. /Sec. Calorific Value = (C.V) of Coal = 4860 K Cal/Kg Energy = 4860 x x 4.2/

3 = MW (ii) At (2) Energy = MW (iii) At (24) Energy = MW Outlet from Boiler (iv) At (1) Energy = MW (v) At (3) Energy = MW (vi) Flue Gases Total Inlet Total Outlet Loss in Boiler Proceedings of the National Conference on = (i) + (ii) + (iii) = = MW = (iv) + (v) + (vi) = = MW = Inlet Outlet = = MW Efficiency of Boiler = x 100/ = % Section Turbine & Gen. (i) HPT Inlet (1) = MW Outlet (2) + (5) = = MW Net Energy at HPT= = MW (ii) IPT Inlet (3) = MW Outlet (4) + (7) = = MW Net Energy at IPT= = MW (iii) LPT Inlet (4) = MW =Outlet (9) + (11) + (13) = = 42.3 MW Net Energy at LPT= = MW Net Input at Turbine (HPT, IPT & LPT) = = 607 MW Efficiency of Turbo Generator= 250 x 100/ 607 = % Section Condenser: Condenser Efficiency= Actual Cooling Water Temp rise Max Possible Temp. Rise Overall station efficiency = Output of Station x 100 = (T42 T41) x100 T 15 T41 = (38 30) x = % 122

4 Input of Station = Energy sent out (KW). Fuel burnt (Kg) x Calorific value of fuel (K Cal/kg) Proceedings of the National Conference on Fuel burnt (Coal) = 120 T/ Hr = Kg/Sec C.V = 4860 K Cal/kg = 4860 x 4.2 = KW Heat Input =20412 x 33.33/10 = MW Overall Efficiency of Plant= 250 x 100/ = % Data Analysis for Table No.-1 (250 MW) Sr. No. 01 Pressure =150 Kg/cm² Temperature =540 ºC = 813 K Flow =782 T/Hr. =782 x 1000/3600 = Kg/sec Enthalpy (CpxT) =4.2 x 813 = KJ/Kg Energy = x /1000 = MW 4. MAIN RESULTS The efficiencies / effectiveness of typical 250 MW Plant at different loads are compared as follows:- Description Table MW 232 MW 220 MW Boiler Efficiency 85.23% 85.20% 84.66% Turbine & Generator Efficiency 41.19% 31.51% 29.88% Condenser Efficiency 53.33% 46.67% 43% Heater LPH1 Effectiveness Heater LPH2 Effectiveness Heater LPH3 Effectiveness Heater HPH5 Effectiveness Heater HPH6 Effectiveness Overall Plant Efficiency 36.74% 35.89% 33.67% Coal Consumption 120 T/Hr 114 T/Hr 110 T/Hr 123

5 Graph 1 250MW 232MW 210 MW 100% 90% 85.23% 85.20% 84.66% 80% 70% 60% 50% 40% 30% 41.19% 31.51% 29.88% 53.33% 46.67% 43% 20% 10% 0% Boiler Efficiency Turbine & Gen. Efficiency Condensor Efficiency 250MW 232MW 210 MW 50% 40% 36.74% 35.89% 33.67% 30% 20% 10% 0% Overall Plant Efficiency Graph 2 5. CONCLUSIONS (1) Overall Plant efficiency at lower loads decreases so we should run the Plant at higher load. (2) Boiler has scaling problem which aggravates localized corrosion and affects the boiler life. Scale formation in the boiler is caused due to water hardness. A layer of scale on a boiler tube acts as an insulator and results in inefficient heat transfer and overheating of metal walls. It is estimated that about 2% coal consumption can be reduced or saved by eliminating scale accumulation in the boiler. (3) The decrease in the amount of steam flowing through the low pressure end of the turbine and the amount of steam to be condensed. (4) The boiler efficiency found % to %; this can be increased up to 90 % to 95 % by adopting following recommendation.the effect of supplying only the theoretical amount of air for combustion with coal. Some coal remains into chemical combustion with the constituents of the fuel, which results great loss of available heat as the gases are only partially brunt. In the case being considered 10% of the heat may be lost as unburant carbon in ash, and possibly a further 15 % app. Lost up chimney as unburant gas. Thus about 75 % of the heat is liberated in the furnace. Admitting more air will reduce the losses considerable, as the chance of the carbon and hydrogen atoms meeting the necessary oxygen atoms has increased greatly. 124

6 Figure 2 (5) Boiler efficiency is mainly attributed to dry flue gas, wet gas & sensible heat loss, which may reduced quite significantly by reducing the flue gas exhaust temperature. Reduction in flue gas temperature less than that of the dew point temperature may cause loss of boiler life even more than that saving money on flue cost because of higher efficiency. (6) To increase the heat available compared to the heat rejected is to increase the superheated steam temperature. Unfortunately this is only possible to a very small degree because metallurgical limitations. Thus there is very little scope in this direction. (7) For improving condenser efficiency main factors is the improvement in quality of cooling water and close cycle. At present in plant using open cycle. (8) Overall efficiency of plant can be increased by using wash-coal which helps to eliminate the ash contents from the coal. By doing so, we can save the energy waste with ash. References 1. Bergander, Mark J. Porter, R.W. (2003) Most troublesome component of electric power generation plant, Energy conservation in coal fired boilers, Vol. 32, 2003, Page No Hatt, Roderick, M. & Lewis, W (2003) Coal ash deposits in coal fired boilers Energy conservation of coal fired boilers, Vol. 14, 2003, Page No