The main purpose of biogas purification is to remove carbon dioxide and get high purity methane. Biogas purification technology mainly comes from decarbonization technology of natural gas and synthetic ammonia conversion gas. Since the consumption of biogas is far less than that of natural gas or ammonia conversion gas, we should pay attention to miniaturization and energy saving when choosing decarbonization technology. At present, biogas purification technology can be roughly divided into adsorption, adsorption, membrane separation and low-temperature purification.
The widely used biogas purification technologies include pressure swing adsorption, water washing, organic solvent physical adsorption, organic solvent chemical adsorption, high-pressure membrane separation, low-temperature purification, etc. The following table shows the key parameters of six biogas purification technologies.
In Sweden, pressure cleaning is the most common; in Germany, PSA is more common. In the Netherlands, pressure cleaning, PSA and membrane separation have been widely used. The following table shows the economic comparison of five biogas purification technologies.
注:电力消耗成本(12 ~ 18欧元美分/千瓦时),热耗成本(3 ~ 5欧分/千瓦时),水的成本是5欧元/ m?(包括污水处理费用)。没有考虑进一步的处理费用(如分离硅氧烷或氨)。所有值都基于满负荷运行。
Note: the cost of electricity consumption (12-18 euro cents / kWh), heat consumption (3-5 euro cents / kWh), and water is 5 euro / M 3 (including the cost of sewage treatment). No further treatment costs (such as separation of siloxane or ammonia) were considered. All values are based on full load operation.
The cost of biogas purification is related to the methane content of feed gas and finished product. Untreated biogas has high methane content and low purification cost. This is mainly due to the increase in energy production, with total costs associated with higher energy levels. The cost can be reduced by improving efficiency (reducing energy consumption per unit output) and using high calorific value biogas to reduce the actual energy consumption.
The economy of biogas purification station is also related to other factors, such as operability and rated load. The rated operation load of the biogas purification station not only depends on the high stability of the purification station itself, but also depends on the reliability of the original biogas flow and subsequent devices (such as charging station and gas filling station).
Short shutdown time, good operation of the equipment, normal and continuous operation of the equipment under rated load and sufficient feed gas conditions, is the standard of high efficiency and availability of biogas purification station. Fast response time is very important, so it is very important for technology providers to provide good network services. In addition, remote monitoring can also be used. When the operation is interrupted, the technical personnel can find the fault directly. According to the fault type, necessary remedial measures can be taken immediately to avoid time delay. The service technical personnel who do not need long-distance travel can go to the site to solve the problem.
These CO2 / methane separation methods have been used in other industries for decades and are the most advanced methane purification methods. In recent years, the development trend is to reduce the energy consumption, improve the recovery rate and reduce the emission of methane, mainly including the following measures: reduce the pressure of finished gas, reduce the power consumption, reduce the temperature level (amine) of desorption process, develop high selectivity of carbon dioxide / methane, and promote the liquefaction technology and comprehensive treatment technology of biomethane (such as membrane and low-temperature separation).