The widely used biogas purification technologies include pressure swing adsorption, water washing, physical absorption of organic solvents, chemical absorption of organic solvents, high pressure membrane separation and low temperature purification. In Sweden, pressurized water washing is the most widely used method; in Germany, pressure swing adsorption is more widely used; in the Netherlands, pressurized water washing, pressure swing adsorption and membrane separation technology are more common.
The cost of biogas purification is related to the methane content of raw gas and the methane content of finished products. The original biogas with high methane content has lower purification cost. This is mainly due to the increase of energy output, and the total cost is related to high energy levels. The actual energy consumption can be reduced by increasing efficiency (reducing energy consumption per unit output) and using high calorific value of raw biogas, thus reducing the cost.
The economic benefits of biogas purification stations are also related to other factors, such as operability and rated load. The rated operating load of biogas purification station depends not only on the high stability of the purification station itself, but also on the reliability of the original biogas flow rate and subsequent units, such as charging station and gas station.
Short shutdown time, good operation of equipment, normal and continuous operation of equipment under rated load and sufficient raw gas conditions, is an efficient and available standard for biogas purification station. Quick response time is necessary, so it is essential for technology providers to provide good network services. In addition, remote monitoring can also be used. When the operation is interrupted, technicians can find the fault directly, and take necessary remedial measures immediately according to the type of fault, which avoids time delay and does not require service technicians to travel long distances to the scene to solve the problem.
These methods of carbon dioxide/methane separation have been used in other industries for decades, and are the most advanced methods of biogas purification. In recent years, the development trend is to reduce energy consumption, increase recovery and reduce methane emission. The main measures are as follows: reducing the pressure of finished gas to reduce power consumption, reducing the temperature level of desorption process (amine washing), developing carbon dioxide/methane membrane with high selectivity, promoting liquefied biomethane technology and combined treatment technology (such as membrane and low temperature separation).
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