005 energy saving tips

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PGDC of NPTI Nagpur


<ul><li> 1. Anil Palamwar anilpalamwar@yahoo.com Energy Saving methods with typical examples and exercises for power stations 1 </li></ul><p> 2. General Undertake regular Energy Audits. Plug all Oil Leakages. Leakage of one drop of oil per second amounts to a loss of over 2000 liters/year. Filter Fuel oil in stages. Impurities in Fuel oil affect combustion. Pre-heat the oil. (Reduces viscocity) For proper combustion, oil should be at right viscosity at the burner tip.Better atomisation. 2 3. General Provide adequate Pre-heat capacity for fuel oil. Incomplete combustion leads to wastage of fuel. Observe the colour of smoke emitted from chimney. Black smoke indicates improper combustion and fuel wastage. White smoke indicates excess air &amp; hence loss of heat. Hazy brown smoke indicates proper combustion. Use of Low air pressure film burners helps save oil up-to 15% in furnaces. 3 4. Furnace Recover &amp; utilize waste heat from furnace flue gas for preheating of combustion air. (Air-pre-heater) Every 21C rise in combustion air temperature results in 1% fuel oil savings. Control excess air in furnaces. A 10% drop in excess air amounts to 1% saving of fuel in furnaces. For an annual consumption of 3000 kl. of furnace oil. This means a saving of Rs 3 Lacs. (Cost of furnace oil- Rs. 10 per litre). 4 5. Furnace Reduce heat losses through furnace openings. Observations show that a furnace operating at a temperature of 1000C having an open door (1500mm*750mm) results in a fuel loss of 10 lit/hr. For a 4000 hrs. furnace operation this translates into a loss of approx. Rs. 4 Lacs per year. Improve insulation if the surface temperature exceeds 20C above ambient. Studies have revealed that heat loss form a furnace wall 115mm thick at 650C amounting to 2650 Kcal/m2/hr can be cut down to 850 kcal/m2/he by using 65 mm thick insulation on the 115 mm wall. 5 6. Boiler Remove soot deposits when flue gas temperature rises 40C above the normal. A coating of 3mm thick soot on the heat transfer surface can cause an increase in fuel consumption of as much as 2.5%. Recover heat from steam condense. For every 6C rise in boiler feed water temperature through condensate return, there is 1% saving in fuel. 6 7. Improve boiler efficiency. Boilers should be monitored for flue gas losses, radiation losses, incomplete combustion, blow down losses, excess air etc. Proper control can decrease the consumption up- to 20%. Use only treated water in boilers. A scale formation of 1mm thickness on the waterside would increase fuel consumption by 5-8%. Stop steam leakage. Steam leakage from a 3 mm-diameter hole on a pipeline carrying steam at 7kg/cm2 would waste 32 kl of fuel oil per year amounting to a loss of Rs. 3 Lacs. 7 8. Maintain steam pipe insulation. It has been estimated that a bare steam pipe, 150 mm in diameter and 100m in length, carrying saturated steam at 8kg/cm2 would waste 25 kl of furnace oil in a year amounting to an annual loss of Rs. 2.5 Lacs. Frequently, insulation is not restored after maintenance work. 8 9. D.G. Sets Maintain diesel engines regularly. A poorly maintained injection pump increases fuel consumption by 4Gms/KWH. A faulty nozzle increases fuel consumption by 2Gms/KWH. Blocked filters increase fuel consumption by 2Gms/KWH. A continuously running DG set can generate 0.5 Ton/Hr of steam at 10 to 12 bars from the residual heat of the engine exhaust per MW of the generator capacity. Measure fuel consumption per KWH of electricity generated regularly. Take corrective action in case this shows a rising trend. 9 10. Electrical Energy Conservation Improve power factor by installing capacitors to reduce KVA demand charges and also line losses. Improvement of power factor from 0.85 to 0.96 will give 11.5% reduction of peak KVA. And 21.6% reduction in peak losses. This corresponds to 14.5% reduction in average losses for a load factor of 0.8. 10 11. 11 12. Avoid repeated rewinding of motors. Observations show that rewound motors practically have an efficiency loss of up-to 5%. This is mainly due to increase in no load losses. Hence use such rewound motors on low duty cycle applications only. Use variable frequency drives, and fluid couplings for variable speed applications such as fans, pumps etc. This helps in minimizing consumption. 12 13. Illumination Electronic ballast in place of conventional choke saves energy up-to 20%. CFL lamp in place of GLS lamp can save energy up-to 70%. Clean the lamps &amp; fixtures regularly. Illumination levels fall by 20-30% due to collection of dust. Use of 36W tube-light instead of 40 W tube-light saves electricity by 8 to 10%. Use of sodium vapour lamps for area lighting in place of Mercury vapour lamps saves electricity up-to 40%. 13 14. Compressed Air Compressed air is very energy intensive. Only 5% of electrical energy are converted to useful energy. Use of compressed air for cleaning is rarely justified. Ensure low temperature of inlet air. Increase in inlet air temperature by 3C increases power consumption by 1%. It should be examined whether air at lower pressure can be used in the process. Reduction in discharge pressure by 10% saves energy consumption up-to 5%. 14 15. A leakage from a diameter hole from a compressed air line working at a pressure of 7kg/cm2 can drain almost Rs. 2500 per day. Air output of compressors per unit of electricity input must be measured at regular intervals. Efficiency of compressors tends to deteriorate with time. 15 16. Refrigeration &amp; Air Conditioning Double doors, automatic door closers, air curtains, double glazed windows, polyester sun films etc. reduce heat ingress and air- conditioning load of buildings. Maintain condensers for proper heat exchange. A 5C decrease in evaporator temperature increases the specific power consumption by 15%. Utilisation of air-conditioned/refrigerated space should be examined and efforts made to reduce cooling load as far as possible. 16 17. Utillise waste heat of excess steam or flue gases to change over from gas compression systems to absorption chilling systems and save energy costs in the range of 50-70%. Specific power consumption of compressors should be measured at regular intervals. The most efficient compressors to be used for continuous duty and others on standby. 17 18. Cooling Towers Replacement of inefficient aluminium or fabricated steel fans by moulded FRP fans with aerofoil designs results in electricity savings in the range of 15%. A study on a typical 20ft. diameter fan revealed that replacing wooden blade drift eliminators with newly developed cellular PVC drift eliminators reduces the drift losses from 0.01-0.02% with a fan power energy saving of 10%. Install automatic ON-OFF switching of cooling tower fans and save up-to 40% on electricity costs. Use of PVC fills in place of wooden bars results in a saving in pumping power of up-to 20%. 18 19. Pumps Improper selection of pumps can lead to large wastage of energy. A pump with 85% efficiency at rated flow may have only 65% efficiency at half the flow. Use of throttling valves instead of variable speed drives to change flow of fluids is a wasteful practice. Throttling can cause wastage of power to the tune of 50 to 60%. It is advisable to use a number of pumps in series and parallel to cope with variations in operating conditions by switching on or off pumps rather than running one large pump with partial load. 19 20. Drive transmission between pumps &amp; motors is very . important. Loose belts can cause energy loss up-to 1-20%. Modern synthetic flat belts in place of conventional V-belts can save 5% to 10% of energy. Properly organized maintenance is very important. Efficiency of worn out pumps can drop by 10-15% unless maintained properly. 20 21. HEAT RATE AND AUXILIARY POWER CONSUMPTION IMPROVEMENT REDUCTION OF APC 21 22. Gross TG Heat Rate = {(Main Steam Flow X MS Enthalpy) - (FW Enthalpy at Eco I/L X Feedwater flow at I/L) + CRH Steam Flow X (HRH Enthalpy - CRH Enthalpy) + RH Spray X (HRH St Enthalpy - FW Enthalpy at Eco I/L)} Gross Generation xxxxxxxxxxxxxxxxxxx Gross Unit Heat Rate = Gross TG Heat Rate / Boiler Efficiency 22 23. Heat Rate in Short Therefore the heat rate in K.Cal / KWh = Net heat used by the System in K.Cal/ Electrical output in KWh. 23 24. 24 HEAT INPUT TO TURBINE AND HEAT RETURN HOT R/H LIVE STEAM COLD R/H TO ECONOMISER HPT IPT HPH RH LPHDEA LPTLPT C Maximum effort is made to return as much heat as possible to the Boiler, But latent heat is lost in the Condenser. 25. THERMAL POWER PROCESS INPUT &amp; OUTPUT 25 C.W.OUTLET C.W.INLET 253.03 MW FEEDWATER CONDENSATE HEAT INPUT BY FUEL FIRING= 585.28 MW (2397K.Cal/KWH) BOILER EFFICIENCY = 86.17 % STEAM OUTPUT FROM BOILER &amp; INPUT TO TURBINE =504.34 MW 2065 K.Cal / KWH EFFICIENCY=92.41 % GENERATOR EFFICIENCY =98.58% LP &amp; HP HEATERS 26. Heat Energy To Electrical Energy Conversion Factor :- 860 Kcal = 1 Kwh TG Heat Rate = 2065 Kcal / Kwh At 33 deg. C.W. Inlet Gross TG Efficiency (860/2065) = 41.65 % Boiler Efficiency = 86.17 % Gross Unit Heat Rate (2065 / 0.8617) = 2397 Kcal / Kwh Gross Unit Efficiency (860 / 2397 ) = 35.88 % 26 27. WHY A.P.C.Reduction ???? A TPS is like any other factory. A TPS has to handle the INPUTS and discharge the OUTPUTS of its process of power generation. COAL AIR WATER are the inputs . FLUE GASES ASH are the outputs. Fans Pumps Crushers Conveyors Feeders etc. are needed to handle these. These auxiliaries use a motor as the prime mover. The motors consume part of the electricity produced. The export of power is reduced by Auxy. Consmn. 27 28. Boiler Auxiliaries - Schematic 28 29. FD Fan-A FD Fan-B W I ND B OX FD Fan / Secondary Air Circuit Scanner Air Fan Igniter Fan APH-B APH-A SCAPH-A SCAPH-B FLUE GAS FLUE GAS PRDS PRDS 29 30. PA Fan-A PA Fan-B Filter Filter SA Fan-B SA Fan-A HotAirToMills ColdAirToMills COLDPAHEADER Primary Air Circuit To Mills A/H A A/H B SCAPH SCAPH HotPAHeader 30 31. Flue gas PA SA Flue gas SAPA A I R S I D E G A S S I D E Regenerative Air Heater 31 32. 32 33. Air Circuit Cold Secondary Air Hot Secondary Air to Wind Box Cold Primary Air Hot Primary Air to Bowl Mills TemperingAir Bowl Mill Pulverized Coal &amp; Air Mixture to Burners Atmos Air Atmos Air Seal Air Fan Scanner Air Fan To scanners To Mills PA Sector SA Sector F/Gas Sector Tri-sector Air Pre-Heater 33 34. Wind box Secondary Air Dampers-Coal &amp; Oil Burners Igniters. 34 35. Secondary Air Dampers (S.A.D.) 35 36. Louvres &amp; Drift Eliminators 36 37. Efficiency Loading of the Plant If the auxiliaries do not work efficiently, they will consume more power. This will reduce the export and the Efficiency of the plant as a whole. Proper maintenance of the auxiliaries will reduce APC. Every auxiliary has a no-load power consumption. When it runs at less capacity than design, then % consumption will be high. Hence the need to run the PLANT at OPTIMUM capacity. 37 38. Reasons for inefficiency Auxiliary not running as designed. Due to wear and tear in operation.(Neck Rings) Worn Grinding elements, fan blades. Dampers not functioning properly Inadequate Loading on the TG Set. Deposition of soot / ash on heat transfer surfaces. Water side deposition on tubes of Boiler / Condensor. Poor D.M. water chemistry. Poor Cooling water chemistry and Poor C.W. system. Poor vacuum condition. 38 39. Boiler Efficiency by Loss Method Boiler Losses Design Value % 1. Un-burnt Carbon (In B/A &amp; F/A) 0.331 2. Dry Gas Loss 4.918 3. Moisture in Fuel 1.243 4. Hydrogen In Fuel 5.217 5. Moisture in Air 0.074 6. Radiation Losses (Fixed) 0.200 7. Sensible Heat in Bottom Ash 0.071 8. Sensible Heat in Fly Ash 0.102 9. Unmeasured Losses[1.5+(7)+(8)] 1.673 10. TOTAL 13.83 11. Design Blr.Effi. (100-13.83) = 86.17 39 40. Turbine Losses Internal Losses A] Friction Losses Nozzle Friction Blade Friction Disc Friction B] Diaphragm Gland &amp; Blade Tip Friction C] Partial Admission (Throttling) D] Wetness E] Exhaust (Leaving Loss) 40 41. External Losses A] Shaft Gland Leakage B] Journal &amp; Thrust Bearing. C] Governor &amp; Oil Pump 41 42. Turbine Cycle Heat Rate Deviations Due to 1]] Main Steam Pressure 2]] Main Steam Temp.. 3]] HRH Steam Temp.. 4]] Pressure Drop Across Re-Heater 5]] Condenser Vacuum 6]] F.W..Temp at Economiser Inlet 42 43. Loading of HPT IPT -LPT Design Turbine Cylinder Efficiency &amp; Load Sharing of 210 MW LMZ M//C Load -%- Load MW Cylender HPT : 24.76 % 52 MW 88.11% IPT : 45.24 % 95 MW 89.93% LPT : 30.00 % 63 MW 85% TOTAL: 100 % 210 MW 43 44. # 45. Generator Losses 45 Losses MW % % of Total Losses Iron Loss (Core Loss) 0.436 0.208 14.63 Windage &amp; Friction Loss (Core Loss) 0.720 0.343 24.16 Stator Copper Loss 1.010 0.481 33.89 Rotor Copper Loss 0.814 0.388 27.32 Total Losses 2.980 1.420 100.00 46. 46 0.000 0.200 0.400 0.600 0.800 1.000 1.200 Iron Loss (Core Loss) Windage &amp; Friction Loss (Core Loss) Stator Copper Loss Rotor Copper Loss GENERATOR LOSSES - MW MW 47. WHY ENERGY EFFICIENCY IS IMPORTANT ? Depleting fossil fuel-Resources are scarce Optimum plant utilization-Competitiveness Global warming-Carbon Credit Designated consumer-E.A. made it Mandatory. Generate more energy with same fuel 47 48. PERIOD STEAM PRESSURE&amp; TEMPERATURE UNIT SIZE (MW) TURBINE Heat Rate (Kcal/kWh) Unit Heat Rate (Kcal/kWh)/ Efficiency 1951-60 60 kg/cm2, 482oC 30 57.5 2470 1961-75 70 kg/cm2, 496oC to 90 ata 538oC 60 100 2370 1961-75 130 ata 535/535oC 110 120 2170 2060 2552-2423 1977-82 130 ata 535/535oC 210 (Russian) 2060 2423/ 35.4% 1983+ 150 ata 535/535oC 210 (Siemens) 2024 2335 36.8% 1984+ 170 ata 535/535oC 500 1950 (TDBFP) 2294 37.4% 1990+ 150 ata 535/535oC 170 ata 538/538 oC 210/ 250 250/ 500 1950 (MDBFP) 1950 (TDBFP) 2294 2294 *Above are best design values (design rates of individual unit varies based on reference ambient, coal quality, design and supply dates) 48 49. EFFICIENCY IMPROVEMENT CAN GIVE YOU For an average increase of 1 % in the Efficiency would result in:- Coal savings of approx. 11 million tons per annum worth Rs.13,000 Million CO2 reduction about 13.5 million tons per annum Lower generation cost per kWh- as more efficient the unit works, the more economical it is 1% increase in efficiency for 210 Mw unit with heat rate 2335 kcal/kwh means heat rate improvement to 2275 kcal/kwh 49 50. MAJOR CAUSE OF INEFFICENCY IN POWER PLANT High Flue gas exit Temp Excessive amount of excess air(O2) Poor Mill/Burners performance causing high unburnt carbon in fly and bottom ash Poor insulation Poor house Keeping Poor instrumentation and automation 50 51. MAJOR CAUSE OF INEFFICENCY IN POWER PLANT (Cont) Not running the units on design parameter Heaters not in service or poor performance of regenerative system Poor condenser vacuum Excessive DM water consum...</p>