压缩机和压缩空气系统

1、1 Presentation from the “Energy Efficiency Guide for Industry in Asia”Electrical Equipment/Compressors2 Electrical Equipment/CompressorsIntroductionTypes of compressorsAssessment of compressors and compressed air systemsEnergy efficiency opportunities3 Compressors: 5 to 5

2、0,000 hp70 90% of compressed air is lostSignificant InefficienciesElectrical Equipment/Compressors(McKane and Medaris, 2003)4 (eCompressedAir)Electricity savings: 20 50%Maintenance reduced, downtime decreased, production increased and product quality improvedBenefits of managed systemElectrical Equi

3、pment/Compressors5 Intake air filters Inter-stage coolers After coolers Air dryers Moisture drain traps ReceiversMain Components in Compressed Air SystemsElectrical Equipment/Compressors6 Electrical Equipment/CompressorsIntroductionTypes of compressorsAssessment of compressors and compressed air sys

4、temsEnergy efficiency opportunities7 Two Basic Compressor TypesElectrical Equipment/CompressorsType ofcompressorPositivedisplacementDynamic ReciprocatingRotaryCentrifugalAxial8 (King, Julie)Used for air and refrigerant compressionWorks like a bicycle pump: cylinder volume reduces while pressure incr

5、eases, with pulsating outputMany configurations availableSingle acting when using one side of the piston, and double acting when using both sidesReciprocating CompressorElectrical Equipment/Compressors9 Screw compressorRotors instead of pistons: continuous dischargeBenefits: low cost, compact, low w

6、eight, easy to maintainSizes between 30 200 hpTypes Lobe compressor Screw compressor Rotary vane / Slide vane Rotary CompressorElectrical Equipment/Compressors10 (King, Julie)Rotating impeller transfers energy to move airContinuous dutyCentrifugal CompressorElectrical Equipment/CompressorsDesigned o

7、il freeHigh volume applications 12,000 cfm11 Efficiency at full, partial and no loadNoise levelSizeOil carry-overVibrationMaintenanceCapacityPressureComparison of CompressorsElectrical Equipment/Compressors12 Electrical Equipment/CompressorsIntroductionTypes of compressorsAssessment of compressors a

8、nd compressed air systemsEnergy efficiency opportunities13 Capacity: full rated volume of flow of compressed gasActual flow rate: free air delivery (FAD)FAD reduced by ageing, poor maintenance, fouled heat exchanger and altitudeEnergy loss: percentage deviation of FAD capacityCapacity of a Compresso

9、rElectrical Equipment/Compressors14 Isolate compressor and receiver and close receiver outlet Empty the receiver and the pipeline from water Start the compressor and activate the stopwatch Note time taken to attain the normal operational pressure P2 (in the receiver) from initial pressure P1 Calcula

10、te the capacity FAD: Simple Capacity Assessment MethodElectrical Equipment/CompressorsP2 = Final pressure after filling (kg/cm2a)P1 = Initial pressure (kg/cm2a) after bleeding)P0 = Atmospheric pressure (kg/cm2a)V = Storage volume in m3 which includes receiver, after cooler and delivery pipingT = Tim

11、e take to build up pressure to P2 in minutes15 Compressor EfficiencyElectrical Equipment/CompressorsMost practical: specific power consumption (kW / volume flow rate)Other methods Isothermal Volumetric Adiabatic Mechanical16 Isothermal efficiencyP1 = Absolute intake pressure kg / cm2Q1 = Free air de

12、livered m3 / hrr = Pressure ratio P2/P1Compressor EfficiencyElectrical Equipment/CompressorsIsothermal efficiency = Actual measured input power / Isothermal powerIsothermal power (kW) = P1 x Q1 x loger / 36.717 Volumetric efficiencyD = Cylinder bore, meter L = Cylinder stroke, meter S = Compressor s

13、peed rpm = 1 for single acting and 2 for double acting cylinders n = No. of cylinders Compressor EfficiencyElectrical Equipment/CompressorsVolumetric efficiency= Free air delivered m3/min / Compressor displacementCompressor displacement = x D2/4 x L x S x x n 18 Consequences Energy waste: 20 30% of

14、output Drop in system pressure Shorter equipment lifeCommon leakage areas Couplings, hoses, tubes, fittings Pressure regulators Open condensate traps, shut-off valves Pipe joints, disconnects, thread sealantsLeaksElectrical Equipment/Compressors19 Total leakage calculation:T = on-load time (minutes)

15、t = off-load time (minutes)Well maintained system: less than 10% leakages Leak Quantification MethodElectrical Equipment/CompressorsLeakage (%) = (T x 100) / (T + t)20 Shut off compressed air operated equipments Run compressor to charge the system to set pressure of operation Note the time taken for

16、 “Load” and “Unload” cyclesCalculate quantity of leakage (previous slide)If Q is actual free air supplied during trial (m3/min), then:Quantifying leaks on the shop floorElectrical Equipment/CompressorsSystem leakage (m3/minute) = Q T / (T + t) 21 Compressor capacity (m3/minute) = 35 Cut in pressure,

17、 kg/cm2 = 6.8 Cut out pressure, kg/cm2 = 7.5 Load kW drawn = 188 kW Unload kW drawn = 54 kW Average Load time =1.5 min Average Unload time = 10.5 min ExampleElectrical Equipment/CompressorsLeakage = (1.5)/(1.5+10.5) x 35 = 4.375 m3/minute 22 Electrical Equipment/CompressorsIntroductionTypes of compr

18、essorsAssessment of compressors and compressed air systemsEnergy efficiency opportunities23 Significant influence on energy useElectrical Equipment/Compressors1. Location2. Elevation Higher altitude = lower volumetric efficiency24 3. Air IntakeElectrical Equipment/Compressors Keep intake air free fr

19、om contaminants, dust or moist Keep intake air temperature lowEvery 4 oC rise in inlet air temperature = 1% higher energy consumption Keep ambient temperature low when an intake air filter is located at the compressor25 4. Pressure Drops in Air FilterElectrical Equipment/Compressors Install filter i

20、n cool location or draw air from cool location Keep pressure drop across intake air filter to a minimumEvery 250 mm WC pressure drop = 2% higher energy consumption26 5. Use Inter and After CoolersElectrical Equipment/Compressors Inlet air temperature rises at each stage of multi-stage machine Inter

21、coolers: heat exchangers that remove heat between stages After coolers: reduce air temperature after final stage Use water at lower temperature: reduce power27 Electrical Equipment/Compressors Higher pressure More power by compressors Lower volumetric efficiency Operating above operating pressures W

22、aste of energy Excessive wear6. Pressure Settings28 Electrical Equipment/Compressorsa. Reducing delivery pressureOperating a compressor at 120 PSIG instead of 100 PSIG: 10% less energy and reduced leakage rate6. Pressure Settingsb. Compressor modulation by optimum pressure settingsApplicable when di

23、fferent compressors connectedc. Segregating high/low pressure requirementsPressure reducing valves no longer needed29 Electrical Equipment/Compressorsd. Design for minimum pressure drop in the distribution linePressure drop: reduction in air pressure from the compressor discharge to the point of use

24、Pressure drop 10%Pressure drops caused by corrosion inadequate sized piping, couplings hoses choked filter elements6. Pressure Settings30 Electrical Equipment/Compressorsd. Design for minimum pressure drop in the distribution line6. Pressure SettingsTypical pressure drop in compressed air line for d

25、ifferent pipe size (Confederation of Indian Industries)31 7. Minimizing LeakageElectrical Equipment/CompressorsUse ultrasonic acoustic detectorTighten joints and connectionsReplace faulty equipment8. Condensate RemovalCondensate formed as after-cooler reduces discharge air temperatureInstall condens

26、ate separator trap to remove condensate32 9. Controlled usageElectrical Equipment/Compressors Do not use for low-pressure applications: agitation, combustion air, pneumatic conveying Use blowers instead10. Compressor controls Automatically turns off compressor when not needed33 9. Maintenance PracticesElectrical Equipment/Compressors Lubrication: Checked regularly Air filters: Replaced regularly Condensate