How much do you know about the operation of air compression system

How much do you know about the operation of air compression system

According to the "Limited Values ​​and Energy Efficiency Grades of Positive Displacement Air Compressors" standard GB19153-2009, the input specific power values ​​of each energy efficiency level of screw air compressors can be found (the input specific power represents the specific exhaust pressure and flow rate range The electric power required to produce each cubic of compressed air). This is the most important parameter for professionals or insiders to evaluate the energy consumption level of screw air compressors. However, screw air compressor users are accustomed to using the actual power consumption value, namely KWH (kilowatt hour), to more intuitively measure the energy-saving level of screw air compressors of different brands. The following takes a 45KW screw air compressor as an example to introduce how to convert the specific power KW/m?/min into an electrical value KWH, and compare the actual annual power consumption of screw air compressors of different energy efficiency levels.

　　 1. Actual power consumption under full load operation

　　 Convert the specific power KW/m³/min into the power consumption per unit displacement (per cubic compressed air produced):

　　 The specific power numerator KW×60 (minutes)=KWh;

　　 Set the specific power denominator m³/min×60 (minutes)=60 m³/h;

　　 After the numerator and denominator of the specific power are multiplied by 60 (minutes), it means the electricity consumed to produce 60 m³ compressed air. This number of electricity is divided by 60, that is, the number of electricity consumed to produce a cube of compressed air.

　　 1. The unit input specific power value of each energy efficiency class of the screw air compressor with a motor rated output power of 45KW specified in GB19153-2009.

　　2. When the energy efficiency rating of the air-cooled screw air compressor with an exhaust pressure of 0.7MPa is 3, the number of electricity consumed per cubic meter of compressed air:

　　7.9÷60=0.1317 (KWh);

　　3. When the energy efficiency level of the air-cooled screw air compressor with the discharge pressure of the screw air compressor is 0.7MPa, the power consumption per cubic meter of compressed air is 6.9÷60=0.115 (KWh);

　　4. The number of electricity consumed for the third-level energy efficiency of producing a cubic compressed air than the second-level energy efficiency:

　　0.1317-0.115=0.0167(KWh)

5. When the rated input power of the driving motor is 55KW, the rated output power of the motor is about 45KW (here is just an approximate algorithm), which is equivalent to a screw air compressor with a rated displacement of 7m³/min, which runs 8000 hours a year. Compared with the three-level energy efficiency, the energy-saving machine can save electricity in one year: 0.0167×7 (pressure)×60 (minutes)×8000=56112 (KWh)

　　 It saves 56112 degrees of electricity a year. It can be seen that the operating costs of screw air compressors with different energy efficiency levels are very different.

　　 2. A second-class energy efficiency machine saves electricity compared to a third-class energy efficiency machine under partial load conditions

In most cases, the gas production of screw air compressors is different from the gas consumption. Screw air compressors adjust the gas production through loading and unloading. It is assumed that the compressor runs for 10 hours a day, and the cumulative unloading is 2 hours a day. The unloading power is 30% of the rated. 360 working days a year.

　　 (0.0167×7×60×8+55×2×0.3)×360=32080.32 (KWh).

　　 means: saving 32080.32 degrees a year, which shows that even under partial load conditions, the operating costs of screw air compressors with different energy efficiency levels are very different.

In summary, when choosing a screw air compressor, users must understand the energy efficiency level (specific power value) of the screw air compressor they purchased, because the purchase cost only accounts for 10% to 10% of the total cost of the machine. Twenty percent, and the remaining 70% comes from the cost of power consumption of the screw air compressor, and the last 15% is the maintenance cost of the screw air compressor.

　　 Air compression system operation common sense, how much do you know?

　　 Three, common sense that air compressor system operation management must know:

　　A. When the process requirements are met, try to reduce the output pressure of the system

　　 Relevant test data show that for every increase of 1 bar in the air compressor set pressure, the electricity bill needs to be increased by 5% to 7%, and the exhaust volume reduced by 8%.

b. Reduce the temperature and humidity of the air compressor room as much as possible. When the air inlet temperature and humidity increase, the air compressor exhaust volume will decrease and the electricity bill will increase (for every 10℃ increase in the air compressor intake temperature, the actual exhaust volume decreases by 2%~4% ; When the ambient temperature drops by 20°F, the water content in the compressed air drops by 50%).

　　C. The refrigerated and adsorption dryers are reasonably selected, and the pressure dew point needs to be monitored (for each increase of 10°C in the air inlet temperature of the dryer, a 25% increase in energy consumption is required to maintain the same pressure dew point).

　　D. Air compressor (6-10bar rated pressure level) discharge per minute Nm³/min*6 times approximately equal to the total power of the air compressor;

　　 4. System energy saving measures

　　 (1) Turn off idle equipment to reduce leakage.

　　 (2) Confirm peak and off-peak demand, plan to replace single machine with multiple machines, with variable frequency unit to reduce the number and hours of empty vehicles and capacity adjustment (minimize the unloading operation time). It can also reduce the standby rate (for example, when a 100HP single machine is originally planned, one 100HP machine must be prepared for a total of 200HP; if the plan is for 50HP+50HP chain operation, the standby machine only needs one 50HP for a total of 150HP).

　　 (3) Reduce the use of BLOW-OFFS, try to use Fan or Blower instead of air compressor.

　　 (4) High pressure (above 3.5bar) and low pressure requirements are treated separately, avoiding the use of high pressure compressed air with a pressure regulating valve to reduce it to low pressure. This is the same as trying to take the elevator to 5F, but first to 7F and then to 5F, wasting electric energy.

　　 (5) In any case, trying to reduce the exhaust pressure of the air compressor, and the system is configured according to the highest pressure required by the process, is actually a great waste.

　　 (6) Choose an air compressor with a better energy consumption ratio (> 3.5 CFM/HP) instead of an imported air compressor with a larger FAD. Eliminate air compressors with poor energy consumption ratio (< 2.5 CFM/HP) instead of air compressors that are older or have been used for a long time.

　　 (7) Increase the gas storage barrel at the gas end to cope with the instantaneous peak demand. Instead of increasing the horsepower of the air compressor as suggested by general air compressor equipment manufacturers (when the process department submits parameters, the peak flow rate is often submitted. Purchasing equipment according to this demand will result in high or even greater system redundancy. Outrageous);

　　(8) Oil-free air compressor and adsorption dryer are used for reduction.

　　(9) Install air-cooled air compressor waste heat recovery devices, such as process heating, winter air conditioning preheating; 94% of the air compressor waste heat can be recovered.

　　(10) Carefully determine the quality of compressed air (pressure dew point, oil content, and particulate content) to meet the process requirements. You must not blindly pursue high quality and cause unnecessary costs.