ENERGY AUDITING OF THERMAL POWER PLANT: A Case Study

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1 ENERGY AUDITING OF THERMAL POWER PLANT: A Case Study M. S. NARWAL 1, VINIT 2 1 Associate Professor In Dcrust,Me Deptt. Murthal M.Tech Student In Dcrust, Me Deptt. Murthal Abstract In the present, studied Energy Auditing of Thermal Power Plant: A Case Study The Energy aspects tell us how we can increase the efficiency of a thermal power plant. In this work, I have studied various parameters like boiler, turbine, thermal insulation, cost benefit analysis etc. It is an engineering technique which can be used for accounting of energy used by a particular system or sub-system. By applying this technique of energy audit, we can know whether energy is being used efficiently or not. The Results of the energy audit studies also tell us about the problem areas of a process or equipment which are under study and define the energy losses. These days Energy Conservation has become a top most priority in order to achieve a sustainable growth, productivity, enhancement & Environmental Protection. The Govt. of India enacted the Energy Conservation Act 2001 by considering the huge potential of energy savings and benefits of energy efficiency as per the report prepared by National Development Council (NDC) Committee on power. For development of policies and strategies with a thrust on self regulation and market principles, with the primary objective of reducing the energy intensity of the Indian Economy, the Govt. of India has set up the Bureau of Energy Efficiency (BEE) under the provision of the Energy Conservation Act 2001 Keywords- Energy Audit, Boiler, Turbine, Economizer, Air Pre-heater, Heat Rate Improvement, Efficiency, Heat Correction Factor, Cost Benefit Analysis I. INTRODUCTION Energy Audit is that the key to a scientific approach for decision-making within the area of energy management. It tries to balance the total energy inputs with its use and serves to spot all the energy streams in a facility. As per the Energy Conservation Act, 2001, Energy Audit is outlined as "the verification, observance and analysis of energy as well as submission of technical report containing recommendations for improving energy potency with cost benefit analysis and an action plan to reduce energy consumption". Energy audit is mainly carried out in 3 phase: 1. The Pre-audit Phase. 2. The Audit Phase. 3. The Post-audit Phase. Table 1: Methodology Step for Energy Auditing [1] Phase I Pre Audit Phase Plan and organize. Walk through audit. Informal interview with energy manager, plant or production manager. Resource planning, Establish/organize a energy audit team. Organize instrument & time frame. Macro data collection. Familiarization of process/plant activities. DOI : /IJRTER NTHZU 208

2 2. Conduct of brief meeting / awareness program with all divisional heads and person connected. Phase II Audit Phase 3. Primary data gathering, process International Journal of Recent Trends in Engineering & Research (IJRTER) Building up cooperation. Issue questionnaire for each department. Orientation awareness creation. Historic data analysis. Prepare process flow chart. Design, operating data and schedule of operation. flow diagram & energy utility diagram. 4. Conduct surveys and meeting. Measurements: Motor survey, insulation and lighting survey with portable instruments for collection of more and accurate data. Conform and compare operating data with design data. 5. Conduct detail trials. 6. Analysis of energy use. 7. Identification & development of energy conservation opportunities. 24 hour power monitoring. Load variation trend in pump, fan & compressor. Boilers / efficiency trials. Energy and material balance. Conceive, develop and refine ideas. Review the previous idea suggested by unit personnel. Use brain-storming technique. Contact vendor for new efficient technology. 8. Cost benefit analysis Select the most promising project. Priorities by long, medium and short term measures. 9. Reporting and presentation to top Documentation and report presenting to top management management Phase III Post Audit Phase 10. Implementation and follow up Assist and implement the plan and monitor the performance. Follow up and periodic review. II. LITERATURE VIEW Vikrant Bhardwaj, Rohit Garg, Mandeep Chahal (October 2012) presented the Energy Audit work on sub-unit like Boiler,Turbine and Generator,Condenser, Pre-heater of Panipat Thermal Power Station and the result was Overall Plant efficiency at lower loads decreases so we should run the Plant at higher load. [2] Paljinder singh, Parag Nijhawan, Suman Bhuller (2013) presented the performance of Boiler, Air-preheater, Furnace of Guru Hargovind Thermal Power Station Barnala (Bathinda). And the result was radiation loss in furnace is more than 6% and this loss can be reduced by improving the insulation of furnace. [3] Vikas Duhan, Jitendar Singh (March 2014) presented a study of dynamic responses of power plants through mathematical modeling, identification, and simulation of Rajiv Gandhi thermal power plant Hisar (600MW).From the analysis part of this work, it is concluded that the overall plant efficiency varies with the variation or small change in the output loads. [4] Sourabh Das, Mainak Mukherjee, Surajit Mondal (2015) presented the Energy Audit work on waste heat recovery boiler (WHRB) ID fan, WHRB FD fan, Cooling Tower of Jindal Steel and Power limited (JSPL) at Raigarh, Chhattisgarh. And the result was modifying WHRB FD fan suction duct and then install variable frequency drive (VFD) to reduce the head loss and to reduce the pressure drop across the condensate line, which in turn increase the efficiency of the plant. [5] III. PROBLEM FORMULATION 1. Heat Rate improvement by improving operating parameter like the main steam pressure and temperature, condenser back pressure and reheat steam All Rights Reserved 209

3 2. Cost benefit analysis of the above i.e. how the improvement in above parameter can reduce the cost 3. Identification of equipment and process having possibility of improving the energy efficiency. IV. UNIT OVERVIEW V. PERFORMANCE EVALUATION OF BOILER Table 2: calculation of boiler efficiency by Indirect Method [6] SI. No Design Value Actual Value at 18/05/16, 11.00AM Gross Generator Output 250 MW 250 MW 1 Oxygen Content in Coal 5.91 % 5.45 % 2 Carbon Content in Coal % % 3 Hydrogen Content in Coal 2.81 % 2.41 % 4 Sulphur Content in Coal 0.35 % 0.38 % 5 Nitrogen Content in Coal 0.71 % 1.67 % 6 Flue Gas Temperature at APH outlet (FGT) 140 C C 7 Dry Bulb Temperature (DBT) 46 C 39 C 8 % Excess Air supplied in flue gas(ea) % % 9 Theoretical Air Required for Complete combustion (TA) (calculated) 5.51 kg/kg of coal 5.56 kg/kg of coal 10 Actual mass of air supplies (AAS) (calculated) 6.25 kg/kg of 6.38 kg/kg of coal coal 11 Actual mass of dry flue gas (calculated) 6.50 kg/kg of 6.68 kg/kg of coal coal 12 Loss due to dry flue gases (L 1 )=Dry flue gas 3.89 % 4.00 % quantity Cp (FGT-DBT) 100/GCV 13 Hydrogen(H) Content in Fuel 2.81 % 2.41 % 14 Loss due to Formation of Water from H 2 in Fuel 4.19 % 3.59 % (L 2 )=9 Hydrogen Content(abs.) {(584+Cp(FGT- DBT)} 100/GCV 15 Total moisture Content in Fuel % % 16 Loss due to moisture in Fuel (L 3 ) = M ( ( % 2.31 All Rights Reserved 210

4 (FGT - DBT)+584) 100/GCV 17 Humidity % % 18 Loss due to moisture in Air (L 4 ) = % % AAS Humidity 2.09 (FGT-DBT) 100/ GCV 19 CO in Flue Gas(%CO) 0.48 % 0.48 % 20 Carbon Content in Coal(C) % % 21 Carbon dioxide content at outlet(%co2) % % 22 Loss due to Partial Conversion of CO to CO2 (L 5 )= 2.05 % 1.86 % {(%CO C(abs.) / (%CO + %CO2)} ( /GCV of Fuel) 23 GCV of Carbon(Cv) kj/kg kj/kg 24 Ash Content in Coal(Ac) kg kg 25 Amount of Bottom Ash in 1 Kg of Coal(BA) kg kg 26 Amount of Fly Ash in 1 Kg of Coal(FA) % % 27 Un-burnt Carbon in Fly Ash(UCFA) 1.0 % 1.86 % 28 Un-burnt Carbon in Bottom Ash(UCBA) 4.00 % % 29 Loss due to Unburnt Carbon in Fly Ash (L 6 ) = 0.65 % 1.14 % Cv FA UCFA/GCV of Coal 30 Loss due to Unburnt Carbon in Bottom Ash (L 7 ) 0.29 % 0.75 % =Cv BA UCBA/GCV of Coal 31 Radiation and Convection Loss (L 8 ) 1.2 % 3.2 % 32 Total Loss(L) = L 1 +L 2 +L 3 +L 4 +L 5 +L 6 +L 7 +L % % 33 Boiler Efficiency=100-L % % Figure 1 : Various types of losses from Boiler VI. PERFORMANCE EVALUATION OF TURBINE Table 3 : Performance Analysis of Turbine Parameter Actual Value at 19/05/16, AM Main Steam Flow (M ms ) kg/h Main Steam Pressure N/m 2 Main Steam Temperature 535 C Main Steam Enthalpy (h ms ) corresponding to above P & T kj/kg [7] Feed Water Temperature C Feed Water Pressure N/m All Rights Reserved 211

5 Feed Water Enthalpy (h f ) corresponding to above P & T [7] kj/kg Reheat Steam Flow (M rhs ) kg/h Hot Reheat Temperature 536 C Hot Reheat Pressure N/m 2 Hot Reheat Enthalpy (h hrh ) corresponding to above P & T kj/kg [7] Cold Reheat Temperature C Cold Reheat Pressure N/m 2 Cold Reheat Enthalpy (h crh ) corresponding to above P & T kj/kg [7] RH Spray(M ir ) kg/h Gross Generator Output(P gen ) 250 MW Turbine H eat Rate= [M ms (h ms -h f )+ M rhs (h hrh -h crh ) kj/kwh +M ir (h hrh - h f )] / P gen [8] Boiler Efficiency(ή) Unit Heat Rate=Turbine Heat Rate / ή kj/kwh Turbine Cycle Efficiency=3600/Turbine Heat Rate 100 [8] % Figure 2 : Various Losses of Thermal Power Plant Here the total outlet energy at the exit of the turbine is found to be %, as shown in fig. Now, Total Coal Flow = 162 TPH = = 45 kg/sec GCV of coal = kj/kg Coal Flow Rate GCV of coal Total Energy input = 100 = / 1000 = MW Total Energy Output = 250 MW Efficiency = Output / Input = 250 / = (35.12%) Increase in Efficiency Due to Regeneration, Super heater, Economizer & Air Pre-heater = All Rights Reserved 212

6 = 1.28 % Now, as we know that a huge part of the thermal energy is lost in the form of Dry Flue Gas, so superheater, economizer and air pre-heater are used in the thermal power plant to increase the efficiency of the plant by utilizing the heat of the flue gas. Total thermal energy input = MW Losses due to dry flue gas = 4% of total energy = 4% of MW = MW To utilizing the heat of the flue gas, firstly, it passes through Super-heater, then, it passes through the Air Pre-heater, then, it passes through the Economizer and at last it passes through chimney to atmosphere as shown in fig. below. Figure 3 : Flue Gas Flow VII. PERFORMANCE EVALUATION OF AIR PREHEATER Table 4 : Performance Analysis of Air Pre-Heater Particulars Design Value Actual Value at 20/05/16, AM Air Quantity at APH outlet (Primary) TPH TPH Air Quantity at APH outlet (Secondary) TPH TPH Total Combustion air TPH TPH Air I/L Temperature of APH (Primary) C C Air O/L Temperature of APH (Primary) (Topa) C C Air I/L Temperature of APH (secondary) C 39.5 C Air O/L Temperature of APH (secondary) C C Oxygen Content in Flue Gas before APH(Oin) 3.56 % 2.86 % Oxygen Content in flue gas after APH(Oout) 4.00 % 4.62 % Flue gas APH inlet temperature(tifg) C C Flue gas APH outlet temperature(tofg) C C APH effectiveness= (Topa-Ambient temperature) / (Tifg-Ambient % % Temperature) [8] Heat Pick-up in APH= (Ma Specific heat of Flue Gas (Topa kj/h kj/h Ambient Temperature) [8] Gross Generator Output 250 MW 250 MW VII. PERFORMANCE EVALUATION OF ECONOMIZER Particulars Table 5 : Performance Analysis of Economizer Design Value Actual Value of at All Rights Reserved 213

7 1.00 PM Feed water Pressure at Economizer Inlet N/m 2 N/m 2 Feed water flow (M w ) TPH 740 TPH Feed water temperature at the inlet (T FWi ) 246 C C Feed water temperature at the outlet (T FWo ) 286 C 290 C Flue Gas Economizer Inlet Temperature (T FGi ) 485 C 411 C Flue Gas Economizer outlet Temperature 347 C 337 C (T FGo ) Effectiveness of Economizer= (T FWo T FWi )/(T FGi T FGo ) [8] Heat Pick-up in Economizer = M w Cp (T FWo T FWi ) [8] kj/h kj/h Figure 4 : Various Losses of Thermal Power Plant VIII. COST BENEFIT ANALYSIS FOR MAIN STEAM TEMPERATURE Table 6 : Cost Benefit Analysis for MS Temperature Correction Particulars Actual Value of at 21/05/16, AM MS Temperature ( Measured) 535 C MS Temperature ( Guaranteed) 540 C Deviation from Guaranteed value -5 C Heat Rate Correction Factor [8] Calculator Turbine Heat rate (From Table NO. 3) kj/kwh Actual Turbine Heat Rate considering Correction Factor kj/kwh Heat Rate will be decreased By improving MS Temperature kj/kwh Output Power 250 MW Annual Kcal Saved By Improving the MS Temperature Parameter = (Improved Kj heat rate output power ) GCV of oil (GCV) per liter kj/l Annual Total Tonn of Oil in liters Equivalent (TOE) Saved = {Annual kcal energy saved TOE / (GCV 1000)} Total Financial per TOE Rs. 1,02,29,322 Investment Required NIL Payback Period All Rights Reserved 214

8 IX. COST BENEFIT ANALYSIS FOR HOT REHEAT STEAM TEMPERATURE Table 7 : Cost Benefit Analysis for HRH Outlet Temperature Correction Particulars Actual Value of at 21/05/16, 1.00 PM HRH Temperature ( Measured) 536 C HRH Temperature ( Guaranteed) 540 C Deviation from Guaranteed value -4 C Heat Rate Correction Factor [8] Calculator Turbine Heat rate (From Table NO. 3) kj/kwh Actual Turbine Heat Rate considering Correction Factor kj/kwh Heat Rate will be decreased By improving HRH Temperature kj/kwh Output Power 250 MW Annual Kcal Saved By Improving the HRH Temperature Parameter Kj (Improved heat rate output power ) GCV of oil (GCV) per liter kj/l Annual Total Tonnes of Oil Equivalent (TOE) Saved TOE Total Financial Saving Rs. 1,70,38,114 Investment Required NIL Payback Period Immediate The hot re-heat steam temperature was near design value (536 C as compared to guaranteed value 540 C). There is a heat rate loss of kj/kwh. X. COST BENEFIT ANALYSIS FOR CONDENSER BACK PRESSURE Condenser Backpressure is the difference between the Atmospheric Pressure and the Vacuum Reading of the Condenser, that is: Backpressure = Atm. Pressure - Condenser Vacuum Pressure Reading. The condenser back pressure was measured as N/m 2 against the guaranteed value of N/m 2. The increase in heat rate due to poor condenser vacuum is kj/kwh. Table 8 : Cost Benefit Analysis for Condenser Back Pressure Correction Parameter Actual Value of at 22/05/16, AM Condenser Back Pressure ( Measured) N/m 2 Condenser Back Pressure ( Guaranteed) N/m 2 Deviation from Guaranteed value N/m 2 Heat Rate Correction Factor [8] Calculator Turbine Heat rate (From Table NO. 3) kj/kwh Actual Turbine Heat Rate considering Correction Factor kj/kwh Heat Rate will be decreased By improving MS Pressure kj/kwh Output Power 250 MW Annual kcal Saved By Improving the MS Pressure Parameter= All Rights Reserved 215

9 (Improved heat rate output power ) GCV of oil (GCV) per liter kj/l Annual Total Tonnes of Oil Equivalent (TOE) Saved = {Annual Kcal TOE energy saved / (GCV 1000)} Total Financial per TOE Rs. 1,35,53,045 Investment Required NIL Payback Period Immediate XI. THERMAL INSULATION The thermal insulation is one of the most important parameter to reduce the heat loss from various parts. It is characterized by the critical radius of insulation which is defined as the radius up to which heat loss decreases and after which heat loss increases. Name of the Non- Insulated Area Table 9 : Details of Heat Loss through Damaged Insulated Area Length of Surface Temp. Non Surface Damaged Area in C Insulated Heat Loss (m) Area (m 2 ) kj/h.m 2 Total Heat Loss kj/h HRH at 56 M EX-15 at De-aerator Floor Boiler Drum HRH(R) at Turbine Floor HRH(L) at Turbine Floor MS(L) at 34M CRH(L) at 34M XII. COST BENEFIT ANALYSIS FOR THERMAL INSULATION OF DAMAGED AREA Table 10 : Cost Benefit Analysis for Thermal Insulation of Damaged Area Particulars Actual Value of at 22/05/16,1.00 PM Total Heat Loss (THL) kj/h Annual Heat Loss (AHL) 365 Days of Running hour = (THL ) Kj GCV of Oil kj/l Boiler Efficiency(η) % Annual total tonnes of Equivalent Oil Loss (TOE) = {(AHL)/(GCV η 1000)} TOE Financial Saving per TOE Rs. 20,09,547 Investment Required (IR) Rs. 10,00,000 Payback Period {(FS/IR) 12} 5.97 Months XIII. ENERGY CONSERVATION OPTION FOR UNIT-7 OF PANIPAT THERMAL POWER PLANT Table 11 : Energy Conservation option for Unit-7 of Panipat Thermal Power Plant Energy Conservation option for Unit-7 of Panipat Thermal Power Plant S.I No. Improve Efficiency Energy Saving Financial Saving Investment in Rs. A Turbine per Rate TOE in Rs. Turbine cycle Heat Rate Energy Saving in kj / Year Annual TOE saving in Pay Back Period in All Rights Reserved 216

10 Improvement in kj/kwh TOE /Year 1 Improving ,02,29,322 Nil Immediate Main Steam Temperature 2 Improving ,70,38,114 Nil Immediate HRH Steam Temp. 3 Improving ,35,53,045 Nil Immediate condenser MS pressure B Thermal Insulation 5 Thermal NA ,09, Insulation of Damaged Area Total ,28,30,028 10,00, XIV. CONCLUSION AND RECOMMENDATION 1. Main Steam Temperature of boiler - The average main steam temperature was slightly lower than design value (535 C compared to guaranteed value of 540 C). The heat rate loss due to lower main steam temperature is kj/kwh by virtue of which a total of Rs.1,02,29,322 loss per annum to the plant. In current we use the cascade PID control to control the MS Temperature. Neural Network control is one of most popular alternative to control the MS Temperature exactly to the design point. It is recommended to improve the heat rate by improving MS Temperature by improving the control system. 2. Hot Re-Heat steam temperature of turbine- The hot re-heat steam temperature was 536 as compared to guaranteed value 540 C. There is a loss of kj/kwh by virtue of which a total of Rs. 1,70,38,114 loss per annum to the plant. It is recommended to improve the Heat Rate by improving HRH Temperature by improving the control system. 3. Condenser Back Pressure - The condenser back pressure was measured as N/m 2 against the guaranteed value of N/m 2. The increase in heat rate due to poor condenser vacuum is kj/kwh. It is recommended for improve heat rate by improving the condenser vacuum by: Improving the performance of vacuum ejector system. Flange joints shall be tightened properly to avoid any ingress of air. Exhaust side of the turbine shall be properly sealed to avoid any ingress of air. 4. Thermal insulation The thermal insulation at various places of Boiler, Turbine and steam pipe lines is damaged and same is furnished in the detail report. It is recommended for improving heat rate, by applying new insulation to damaged insulated area. 5. The calculate boiler efficiency is at Turbine Maximum Continuous Rating (TMCR) % against the design value of 86.52%.The shortfall is substantial considering the aging factor of the plant. This can be partial recovered by implementing short term measures and implementation of better O & M practices. The main reason for falling in efficiency is high unburnt carbon in bottom ash (10.96%) and poor combustion. This can be reduced by combustion optimization such secondary air damper control, synchronization of burner tilt. 6. The flue gas temperature at APH found to be C against the design value of 140 C.This requires the detailed inspection of APH All Rights Reserved 217

11 XV. SCOPE OF FUTURE WORK In spite of my best efforts, there still remains sufficient scope to extend this work further by introducing various kinds of complexities about the domain area. These are below: 1. Energy Auditing For Draft system 2. Energy Auditing for Coal Mills 3. Energy Audit can also be made for other units 4. Ash handling or disposal system can also be Audit. 5. Energy Auditing for electro static precipitator Energy Auditing for Heating, Ventilation, and Air Conditioning System can also be done REFERENCES 1. Guide to Energy Management, 7 th Edition- kindle Edition by William Kennedy (author), Barney Cape Hart, Wayne Turner. 2. Vikrant Bhardwaj, Rohit Garg, Mandeep Chahal, Energy Audit of 250 MW Thermal Power Stations PTPS, Panipat, Proceedings of the National Conference on Trends and Advances in Mechanical Engineering, YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, Paljinder singh, Parag Nijhawan, Suman Bhuller, A Thiesis Report on Energy Auditing of Thermal Power Plant, Department of Electrical and Instrumentation Engineering Thapar University, Vikas Duhan, Jitendar Singh, Energy Audit of Rajiv Gandhi Thermal Power Plant Hisar, JRPS International Journal for Research Publication & Seminar Vol 05 Issue 02 March -July Sourabh Das, Mainak Mukherjee, Surajit Mondal, Thermal Audit of Power Plant WSN 21 (2015) 68-82, EISSN Steam Boiler Operation by James J. Jackson, Prentice-Hall Book Company, U.S, All Rights Reserved 218