Principle:
During the pressurization process, CO2 is adsorbed on the surface of a certain material and separated from biogas. When the pressure is reduced, CO2 is naturally released, and the adsorbent can be reused. This technology is called pressure swing adsorption, and commonly used adsorbents include activated carbon and zeolite.

Process:
The raw gas after desulfurization enters the biogas compression system and is pressurized to the design pressure. After compression, the biogas enters the PSA adsorption unit after passing through a tank for impurities removal (optional) and a cold dryer for cooling and dehydration. The PSA consists of adsorption towers, buffer tanks, vacuum pumps (optional), and a control system. Under the control of the system, the raw gas alternately enters each adsorption tower, and impurities such as carbon dioxide and water are adsorbed by the adsorbent. The unabsorbed methane gas is sent to the subsequent product system in the form of product gas from the top of the tower. The impurities adsorbed in the adsorbent are desorbed by reducing pressure and extracting with a vacuum pump, and then the adsorption work is carried out again after equalizing the pressure with other adsorption towers to reach the operating pressure.
Products Quality:
Meet different natural gas standards, the main standard indicators are listed as follows:
Main equipment: biogas compressor, impurity removal tank (optional), cold drying and dehydration equipment, filtering equipment, PSA tower group, program-controlled valve group (optional rotary valve), vacuum pump, instruments.
Characters:
Low energy consumption
High level of automation
High methane purity but lower yield compared to other processes
If rotary valve technology is used, CH4 yield can reach 97%.

Application:
Large gas volume with stable flow rate
Low investment
Reference Project:
Project: Chancheng Biogas Purification Project
Location: Foshan City, Guangdong Province
Capacity: 840 Nm3/h
Technology: BD-II & PSA
Operation: Since 2021