The Research On Equipment And Process Of Biogas Upgrading With Water Scrubbing In High Pressure

In the dual background of energy crisis and environmental pollution, all countries in the world realized that the development of renewable energy is an inevitable choice. In renewable energy, biogas is an important kind of biomass energy, when the concentration of methane in biogas is more than 90%, we can get biological gas which can take place of natural gas. At present, the main biogas purification methods include PSA, water scrubbing, chemical scrubbing, organic physical scrubbing and membrane separation, and they are commercial. Through comparing of several methods, there are obvious advantages of water scrubbing. The paper mainly researched the mechanism of biogas water scrubbing. There are three main influence factors of biogas purification with water scrubbing, including temperature, gas water ratio and pressure. By experiments of biogas atomization upgrading with water scrubbing at atmospheric pressure, we get the effect of gas water ratio and temperature. In order to get influence of pressure, the biogas purification system at atmosphere is reformed, intermittent biogas water scrubbing system in high pressure is put forward, and the water scrubbing control system is designed.The principle of biogas purification with water scrubbing mainly includes two aspects, first, the difference of solubility of CH4 and CO2 in water. Under the same condition, the solubility of CO2 in water is 30 times than CH4 in water; second, the transfer of CO2 in water. Through analysis, the temperature and pressure have effects by the solubility of CO2 and CH4, gas water ratio have influence by gas-liquid mass transfer. The paper also analyzes some other factors, such as the vibration of the water, water level and PH value. In order to get the influence of temperature and gas water ratio, the paper carried out a series of experiments. Through the contrast test, the influence of temperature is obviously. When the water temperature is 3.5℃, elevated CH4 concentration value is 8%. When the water temperature is 22℃, elevated CH4 concentration values is only about 4%. When temperature remains constant, there is an optimal value of the gas water ratio, when the gas water ratio increases more than the best value, effect is reduced. According to the test, the paper gets the best gas water ratio, maximum concentration CH4 of in biogas after upgrading, CO2 removal rate, and energy consumption for processing a cubic biogas.Due to the effect of biogas purification with water scrubbing at atmospheric pressure is limited by pressure, and for getting the influence of the pressure, so the biogas purification system is reformed. The paper proposed scheme of intermittent biogas water scrubbing system in high pressure, constructed the system of biogas purification, determined process of system and parameters of the main equipment, designed the pressure piping, improved gas atomizer, and designed water atomizer. According to technological process of biogas purification, the paper forward two kinds of control schemes, and made a comparison and selection. Control scheme by single chip microcomputer is identified. Then the paper draw hardware principle diagram, and wrote the control program. And the paper performed a small test which showed the control system is feasibility. Finally, the paper put forward the testing program. The parameters of testing program are clear, and test steps are detailed.In summary, the paper has made a detailed study about biogas purification with water scrubbing, the solubility of CO2 and CH4 in the water was obtained under the different temperature and pressure. The paper get the effect of temperature, gas water ratio and the technological parameters of the system of biogas purification at atmosphere, the handling capacity of system is 5 to 16 m3/h, can be directly used in the actual production. Aiming at the shortcomings of biogas upgrading with at atmospheric pressure, the paper puts forward intermittent biogas water scrubbing system in high pressure, compared with continuous washing purification system, the requirement of equipment is lower. The design pressure of system is 0.7 Mpa and the design capacity is 100m3/h. In this paper, the two technology methods can provide sample and new ideas for biogas purification and provide the reference for researcher.