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Why does vacuum in steam condenser reduce or drop??

  1-High exhaust temperature: Vacuum drops or maintains at lower side due to high exhaust steam temperature flow into steam condenser. This high exhaust temperature is mainly due to 1-Operation of Turbine at lower loads 2-More clearance in labyrinth seals 3-Not operating exhaust hood sprays 4-More load on condenser 5-Breaking of ejector U loop 2-Low circulating cooling water flow Vacuum in condenser reduces due to inadequate cooling water flow through steam condenser. This is mainly due to; 1-Problems associated with pumps 2-Air pockets in pipe line 3-Leakages in cooling water line 4-Stuck of discharge valve of pump 3-High cooling water temperature at condenser inlet Higher cooling water temperature at condenser inlet results into reduction of vacuum due to poor heat transfer from steam to water 4-Poor heat transfer in condenser Very less or poor heat transfer in steam condenser reduces vacuum to very low level resulting into high exhaust temperature &am

Opportunities for energy conservation in power plants





   
Energy conservation in Boilers:
  • Control excess air in combustion which can lead to huge dry flue gas loss. Install online O2 analyzer for better controlling of excess air.
  • Control Air pre-heater (APH) out let flue gas temperature, it is said that on every 22 °C rise in boiler outlet flue gas temperature leads to decrease in boiler efficiency by 1%.
  • Optimize fuel moisture, which can lead to loss due to moisture.
  • Installation of fuel (bagasse) driers for recovering potential heat from chimney inlet flue gas.
  • Control unburnt in bed ash and fly ash, which can lead heat and fuel loss.
  • Maintain maximum possible feed water inlet temperature at economizer inlet. On 6–7 °C rise in temperature of feed water at economizer inlet leads to 1% fuel saving. And 15 °C rise can lead to increase in overall thermal efficiency by 3%.
  • Utilize unburnt from Economiser, bank zones by incorporating Cinder reinjection (CR) system
  • Optimize boiler continuous blow down to reduce heat loss with hot water
  • Create the ideas for utilizing blow down water for heating of combustion air, or feed water and even boiler blow down water can be used for cooling tower make up by reducing its temperature
  • Utilize blow down flash steam for heating feed water in deaerator. Continuous blow down (CBD) from steam drum operating at 115 kg/cm2 releases 42–45% flash steam.
  • Reduce boiler pressure if permissible, for process, boiler pressure can be maintained as per process requirement. This is the most effective way of fuel saving.
  • Incorporate VFD to all boiler auxiliaries like fans and fuel feeding systems.
  • Instead of throttling discharge air dampers ,provide inlet guide vanes to fans to control the air flow.
  • Arrest all boiler steam, flue gas and water leakages.
  • Operate boiler on optimum loads, boilers give more efficiency at 65–85% of full load.
  • Inspect air distribution nozzles, dampers regularly.
  • Try to get maximum temperature of combustion air by incorporating Steam coil air preheaters (SCAPH).It is said that on every 20 °C rise in combustion air temperature leads to increase in boiler efficiency by 1%.
  • 10–12% of hot air recirculation into FD fan suction can maintain rated APH inlet air temperature, which can lead to elimination of SCPAH thereby reducing LP steam consumption.
  • Utilize DG exhaust flue gas temperatures for heating systems like combustion air, feed water etc.
  • Operate the soot blowers regularly to remove soot formed on heating surfaces. It is estimated that 2.5% of fuel consumption will increase on deposition of 3 mm soot on heating surfaces of pressure parts.
  • Operate boiler feed pumps at rated or maximum possible suction pressure to reduce auxiliary power consumption.
  • Incorporate VFD to boiler feed pumps and reduce speed whenever possible
  • Operate feed water control valve at maximum opening i.e. control valves should open 70–80% for normal operation. It will reduce the pressure drop in control valves and hence load on boiler feed pumps.
  • Attend the the leakage of Boiler feed pumps ARC valves.
  • Use Neutra pit water or ETP treated water for ash quenching and other services.
  • Use Neutra pit water or ETP treated water for ash quenching and other services.
  • Operate the pneumatic ash handling system in probe mode instead of timer mode to save the compressor power.If run in timer mode optimise ash conveying time & cycle time.
  • Use high temperature coatings for valves, lines etc. o reduce heat loss.
  • Optimize deaerator steam vent line and orifice size to avoid excess steam vent or utlise this vent out steam for heating combustion air.Deaerator steam vent loss is around 0.1 % of Boiler steam generation.
  • Remove air from indirect steam using equipments, as 0.25 mm thick air offers the same resistance to heat transfer as a 330 mm thick copper wall.
  • Maintain water quality to avoid boiler scaling. A 1 mm thick scale deposit in the water side could increase fuel consumption by 5–8%.
  • Insulate all hot water storage tanks.
Energy conservation in Fuel handling & storage system:
  • Always store fuel in fuel shed to avoid wetting and excess drying of fuel in rainy and summer seasons respectively.
  • Store fuel on PCC (Plain cement concrete) bed to avoid carpet loss of fuel.
  • Cover fuel yard and storage shed by trees (bamboo) to reduce handling and feeding loss of fuels during high wind speed.
  • Conveyors should have seal proof hood covers to avoid flying/escaping of fuel during high wind speed.
Energy conservation in Turbine and its auxiliary system:
  • Maintain maximum rated pressure at Turbine inlet to achieve less SSC.
  • Maintain maximum possible vacuum to reduce SSC.
  • Maintain optimum cooling water inlet and outlet temperatures for all heat exchangers like steam condensers, oil coolers and Generator air coolers
  • Optimize cooling tower blade angles, more the angle more the power consumption.
  • Reduce the clearance between CT fan blade and concrete hood or fiber hood; generally it should be up to 25–30 mm.
  • Provide VFDs to cooling tower fans and Main cooling water pumps to control speed as per requirement.
  • Replace all aluminum blades by energy efficient FRP blades.
  • Clean cooling tower water spray nozzles regularly.
  • Arrange drift eliminators and fills properly for uniform spreading of air and water.
  • Clean condenser and ejector tubes yearly to achieve proper heat transfer
  • Keep cooling tower surrounding free from structures, building, trees to enable free air movement.
  • Ensure cooling water pump top casing crub level is below the normal operating level of cooling tower toavoid carrying of air in water or it may lead to cavitation.
  • Make a provision for online backwash systems for surface condenser and oil coolers to improve heat transfer.
  • Clean oil pumps filters regularly.
  • Incorporate VFD to Condensate extraction pumps (CEPs).
  • Install condensate recovery system from all process line drains and traps.
  • Use CEP discharge water instead of BFP discharge water for desuperheating of low pressure process steam.
  • Select optimum head condensate extraction pumps. If Deaerator working pressure is 2.75 kg/cm2A CEP of 80 meter discharge head considering all losses is sufficient.
  • Try to get maximum percentage of condensate from processes.
Energy conservation in other balance of plant (BOP) areas:
  • Replace all globe valves by ball valves of instrument pressurized air.
  • Clean suction air filters of compressors regularly as 250 mmwc pressure drop in suction filter will lead to the reduction of compressor efficiency by 2%.
  • Opening of air filters should be sufficient to suck enough air.
  • Locate compressors at lower level as at higher elevation compressors consume more power.
  • Install compressors in well ventilated areas.
  • Ensure cool water and air for compressors air cooling system. At every 4 °C rise in inlet cooling water temperature will increase power consumption by 1%.
  • Clean after and inter coolers regularly to get better heat transfer.
  • Install auto moisture drains for air lines.
  • Avoid unnecessary use of compressed air for applications like cleaning, washing, pneumatic tools etc.
  • Optimize discharge air pressure of compressor, on reduction of 1 kg/cm2 discharge air pressure leads to input power saving by 6–10% And on reduction of discharge air pressure by 1 kg/cm2 will reduce air leakage by 10%.
  • Carryout periodic air leakages test.
  • Prefer two stage reciprocating air compressors over single stage for same FAD and pressure as single stage compressors consume much power than multi stage.
  • In centrifugal fans (ID, FD and SA fans) Maintain optimum cone clearance and overlap gap to reduce power consumption.
  • Provide optimum height  silencers for high speed centrifugal fans and take care the silencer is free from all obstacles.
  • Modify ducting system by removing all obstacles to avoid pressure drop.
  • Incorporate VFDs to ventilation blowers to control speed during low temperature season (Winter and rainy seasons).
  • Provide VFDs to all possible pumps.
  • Replace all loose V belts as loose and damaged V belts conribute in more power consumption
  • Timely checking of equipment vibrations and alignment to avoid unnecessary power consumption and machine failure.
  • Avoid over greasing of bearings to reduce churning effect and energy consumption.
  • Replace higher rated capacity pumps with rated to avoid running of higher capacity pumps under load.
  • Replace all worn out wear rings of impellers and casing, as more clearance between wear ring and pump suction will contribute in more power consumption to maintain required flow.
  • Instead of controlling discharge valve, impeller trimming is the best way to control flow and power consumption.
  • Use booster pumps for small loads requiring higher pressure.
  • Provide all measuring instruments like flow, pressures for pumps to monitor their performance regularly.
  • Avoid bends and U seal pattern for suction line of pumps.
  • Use mechanical seals over gland packings.
  • Avoid connecting small size pump discharge line to higher size header, the ratio of header and discharge line should be in the range of 1.3 to 1.6 only. For higher size ratio power consumption will be more.
  • Replace all conventional gear boxes like worm-worm wheel and helical by more efficient planetary gear box.
  • Replace DOL starter motors of heavy equipments like chain conveyors with soft starters.
  • Modify the chain conveyor system to reduce unwanted dead loads like slat weights, link size etc.
  • Incorporate timers of street and plant lighting system.
  • Replace all the plant lighting bulbs by high efficient LED bulbs.
  • Maintain higher power factor at all the load ends by installing capacitor banks to reduce excess reactive power.
  • Provide forced cooling system for higher capacity power transformers to reduce losses.
  • Provide proper ventilation to the motors. For every 10 °C increase in motor operating 
  • temperatures over recommended peak, the motor life is estimated to be halved.
  • Synchronous motors are more suitable to improve power factor.
  • Balance the three phase power supply, an unbalanced voltage can increase motor input power by 3–5%.
  • Ensure the motor proper rewinding, an improper rewinding could lead to efficiency reduction.
  • Ensure proper alignment between motor and load ends (fans, pump, gear box, blower etc.) to avoid more power consumption and failures.
  • Optimize the quantity of lubricants in bearings and gearboxes to reduce unwanted load due to excessive lubricants.
  • Provide an alternate arrangement for connecting river water directly into clarifier; it will save power consumption for lifting water from reservoir to clarifier.
  • Prefer gravity make up system for condenser hot well make up, it will save pump power for hot well



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