Comparison of pressure swing adsorption and membrane separation technology
(1) Requirements for inlet temperature and pressure of Biogas
The pressure swing adsorption and membrane separation technology have the same requirements for biogas inlet temperature and pressure, which are normal temperature and 0.60-0.80mpa.
(2) Requirements for imported impurities of Biogas
The pressure swing adsorption technology requires that the particle size of imported biogas dust should be less than 1.0 μ m. The maximum mass concentration of dust is less than or equal to 5.0mg/m3. The technology of membrane separation requires that the particle size of imported biogas dust should be less than 0.1 μ m. The mass concentration of residual oil is less than 0.1mg/m3.
(3) Service life of separation materials
The service life of PSA adsorbent is usually not less than 15 years, while the service life of membrane used in membrane separation technology is usually not more than 8 years due to dust or residual oil pollution.
(4) As PSA requires 5-7 steps to complete an adsorption process, the top solenoid valve of the adsorption tower is frequently opened and closed, so the solenoid valve needs to be replaced frequently. Membrane separation technology is a continuous operation, in terms of maintenance and pressure swing adsorption is relatively simple, small workload.
(5) CH4 content in export natural gas
Using pressure swing adsorption technology, the CH4 volume fraction of natural gas after adsorption separation can reach 96%, or even higher, and the CH4 yield after biogas purification is not less than 92%. Using membrane separation technology, the volume fraction of CH4 can reach about 95%, but the yield of CH4 after biogas purification is generally not higher than 92%.
(6) Equipment cost and operation cost
Due to the high cost of membrane separation equipment, the total cost of membrane separation technology is higher than that of PSA technology. For the treatment of Biogas of the same scale, the total cost of membrane separation technology is generally 1.2-1.3 times that of pressure swing adsorption technology, and the operation cost of membrane separation technology is generally 1.2-1.3 times that of pressure swing adsorption technology.
Pressure swing adsorption (PSA) technology has the advantages of low impurity requirements for imported biogas separation equipment, long service life of adsorbent and relatively high CH4 yield. At present, the application of PSA technology in biogas decarbonization and purification is more than that of membrane separation technology. No matter which process, there are two aspects of advantages and disadvantages. Especially for the membrane separation technology, if the polysiloxane membrane material is further optimized and improved to improve its service life and price.
