CNG Frequency Conversion Substation Compressor Unit

Technical Structural Characteristics

1. The compressor structure is a symmetrical balanced type (P-type), with inertial forces completely balanced, and the inertial moment also fully balanced through counterweights, resulting in very smooth operation.  

2. The compressor always starts air intake from Level I, completely abandoning the existing mode of starting from Level II and forcing a switch to the upper level intake when the pressure in the tank truck drops to (7-8) MPa. This is beneficial for the stable operation of the compressor and can greatly increase the gas supply capacity of the compressor. (The compressors at the current import substation have also begun to adopt this type of air intake method.)  

3. It uses variable frequency starting, with a small starting current (1.5 times), causing no impact on the power grid; during operation, the PLC performs logical calculations and adjustments to provide real-time signals (4-20) mA to the inverter based on changes in intake pressure, which then outputs the real-time speed of the motor: during the variable speed operation of the compressor, the actual operating power remains at 99% of the motor's rated power, achieving high power utilization and power factor, thus reaching the goal of energy saving.  

4. To achieve the same gas volume, the variable frequency substation compressor unit only needs to be equipped with 1/2 to 2/3 of the electric power of a conventional compressor unit, reducing the station's power distribution requirements (smaller transformer capacity), which can save about 50,000 yuan in equipment procurement costs for building the station; at the same time, it can also save about 30,000 yuan annually in reactive power electricity costs (this only requires the transformer to be connected to the grid, regardless of whether the compressor is running).  

5. After unloading a tank truck of gas, the variable frequency substation compressor has an unloading efficiency that is about 67% higher compared to conventional compressors, with energy consumption reduced by about 18.4%; all of this translates into economic benefits, potentially generating an additional income of about 1.2 million yuan annually.  

6. The variable frequency substation compressor unit with the same power can increase the gas supply volume per unit time by about 67% compared to the conventional substation compressor unit, allowing for a reduction in the number of compressors needed under the same gas volume configuration, thus achieving less land use and lower equipment procurement costs for building the station.  

7. With a smaller main motor power, the power distribution for the accompanying cooling system is also smaller, saving about 10,000 yuan annually in auxiliary electricity costs.  

8. The crankcase and middle body are cast as one, greatly increasing rigidity. Coupled with high-precision machining centers, the front and rear bearing holes and left and right slideway holes are processed as a whole, significantly improving the concentricity of the shaft holes, the verticality of the slideways, and the precision of dimensional tolerances, reducing the leakage rate of conventional compressors from 3% to 1%. Thus, a 1500 Nm3/h compressor will leak 16,800 Nm3 less per year, which helps reduce the operating costs of gas stations and decreases environmental pollution.  

9. The cylinders and packing use oil-free lubrication, ensuring that the compressed gas is not contaminated, saving about 40,000 yuan annually in operating oil costs.  

10. The cylinders have a single-row, reverse differential structure, making assembly and maintenance convenient, with fewer specifications and quantities of easily worn parts. With two-stage compression, both the piston rings and guide rings have only one specification, and their quantity is halved compared to conventional compressors, saving about 20,000 yuan annually in operating costs.  

11. The Level I gas valve uses a combination valve with a small dead space volume, achieving a gas extraction rate of 90% for tank trucks.  

12. The PLC provides full automatic control, with fault detection, alarm, and shutdown functions during unit operation.

KEY CURVE COMPARISON OF INVERTER AND CONVENTIONAL BUS STATION COMPRESSOR

Chart annotations

1. The average gas supply of the variable frequency 55KW substation unit is basically consistent with that of the conventional 90KW unit;  

2. The average gas supply of the variable frequency 90KW substation unit is far greater than that of the conventional 90KW unit;  

3. The power utilization rate of the variable frequency 55KW substation unit is higher than that of the conventional 90KW unit for a considerable period of time.

Technical Parameters