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Annexure - Checklists & Tips

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ANNEXURE CHECKLISTS & TIPS FOR ENERGY EFFICIENCY IN THERMAL UTILITIES Boilers Preheat combustion air with waste heat. (22 0C reduction in flue gas temperature increases boiler efficiency by 1%) Use variable speed drives on large boiler combustion air fans with variable flows. Burn wastes if permitted. Insulate exposed heated oil tanks. Clean burners, nozzles, strainers, etc. Inspect oil heaters for proper oil temperature. Close burner air and/or stack dampers when the burner is off to minimize heat loss up the stack. Improve oxygen trim control (e.g. -- limit excess air to less than 10% on clean fuels). (5% reduction in excess air increases boiler efficiency by 1% or: 1% reduction of residual oxygen in stack gas increases boiler efficiency by 1%) Automate/optimize boiler blowdown. Recover boiler blowdown heat. Use boiler blowdown to help warm the back-up boiler. Optimize deaerator venting. Inspect door gaskets. Inspect for scale and sediment on the water side. (A 1 mm thick scale (deposit) on the water side could increase fuel consumption by 5 to 8%.) Inspect for soot, flyash, and slag on the fire side. (A 3 mm thick soot deposition on the heat transfer surface can cause an increase in fuel consumption to the tune of 2.5%) Optimize boiler water treatment. Add an economizer to preheat boiler feedwater using exhaust heat. Recycle steam condensate. Study part-load characteristics and cycling costs to determine the most-efficient mode for operating multiple boilers. Consider multiple or modular boiler units instead of one or two large boilers. Establish a boiler efficiency-maintenance program. Start with an energy audit and follow-up, then make a boiler efficiency-maintenance program a part of your continuous energy management program. Steam System Fix steam leaks and condensate leaks. (A 3 mm diameter hole on a pipe line carrying 7 Kg/cm2 steam would waste 33 Kilo litres of fuel oil per year) Bureau of Energy Efficiency 186 Checklists & Tips for Energy Efficiecy in Thermal Utilities Accumulate work orders for repair of steam leaks that can't be fixed during the heating season due to system shutdown requirements. Tag each such leak with a durable tag with a good description. Use back pressure steam turbines to produce lower steam pressures. Use more-efficient steam desuperheating methods. Ensure process temperatures are correctly controlled. Maintain lowest acceptable process steam pressures. Reduce hot water wastage to drain. Remove or blank off all redundant steam piping. Ensure condensate is returned or re-used in the process. (60C raise in feed water temperature by economiser/condensate recovery corresponds to a 1% saving in fuel consumption, in boiler) Preheat boiler feed-water. Recover boiler blowdown. Check operation of steam traps. Remove air from indirect steam using equipment (0.25 mm thick air film offers the same resistance to heat transfer as a 330 mm thick copper wall) Inspect steam traps regularly and repair malfunctioning traps promptly. Consider recovery of vent steam (e.g. -- on large flash tanks). Use waste steam for water heating. Use an absorption chiller to condense exhaust steam before returning the condensate to the boiler. Use electric pumps instead of steam ejectors when cost benefits permit Establish a steam efficiency-maintenance program. Start with an energy audit and followup, then make a steam efficiency-maintenance program a part of your continuous energy management program. Furnaces Check against infiltration of air: Use doors or air curtains Monitor O2 /CO2/CO and control excess air to the optimum level Improve burner design, combustion control and instrumentation. Ensure that the furnace combustion chamber is under slight positive pressure Use ceramic fibres in the case of batch operations Match the load to the furnace capacity Retrofit with heat recovery device Investigate cycle times and reduce Provide temperature controllers Ensure that flame does not touch the stock Bureau of Energy Efficiency 187 Checklists & Tips for Energy Efficiecy in Thermal Utilities Insulation Repair damaged insulation. (A bare steam pipe of 150 mm diameter and 100 m length, carrying saturated steam at 8 kg/cm2 would waste 25,000 litres furnace oil in a year) Insulate any hot or cold metal or insulation. Replace wet insulation. Use an infrared gun to check for cold wall areas during cold weather or hot wall areas during hot weather. Ensure that all insulated surfaces are cladded with aluminum Insulate all flanges, valves and couplings Insulate open tanks (70% heat losses can be reduced by floating a layer of 45 mm diameter polypropylene (plastic) balls on the surface of 900C hot liquid/condensate) Waste heat recovery Recover heat from flue gas, engine cooling water, engine exhaust, low pressure waste steam, drying oven exhaust, boiler blowdown, etc. Recover heat from incinerator off-gas. Use waste heat for fuel oil heating, boiler feedwater heating, outside air heating, etc. Use chiller waste heat to preheat hot water. Use heat pumps. Use absorption refrigeration. Use thermal wheels, run-around systems, heat pipe systems, and air-to-air exchangers. Bureau of Energy Efficiency 188

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