How to separate carbon dioxide and hydrogen sulfide

I guess you need to desulfurize first, and then extract carbon dioxide

C02 separation technologies: The main techniques for separating C02 from combustion exhaust gases include solvent absorption, pressure swing adsorption gas separation, cryogenic distillation, membrane separation, and combined separation methods. When selecting a process for recovering CO2 from power plant exhaust gases, factors such as technology, economics, and the commercial operational experience of the recovery techniques must also be taken into consideration. 1.1 Absorption methods: The solvent absorption method can be divided into physical absorption and chemical absorption. Physical absorption involves using organic solvents with high solubility for CO2 as absorbents; carbon dioxide is compressed to dissolve it in the solvent, and then decompressed to release the CO2, thereby capturing and separating it through this alternating process. The physical absorption method has advantages such as high absorption capacity, low amount of absorbent required, and low energy consumption. However, this method is only suitable under conditions of high carbon dioxide partial pressure. Chemical absorption is a method that uses an absorbing solution capable of reacting with CO2 and possessing absorption properties to absorb and separate it. The liquid after absorption is heated to around 100°C; after releasing high-concentration CO2, it is reused. This method belongs to the wet absorption type and is highly practical. The absorption method is suitable for handling gases with low CCh contents, offering good separation performance and enabling the recovery of CO2 at concentrations as high as 99.99%. The American company DO W Chemicals developed the MEA process suitable for recovering CO2 from power plant exhaust gases in the early 1980s. Currently, this process is applicable in multiple **regions. The ShadyPoint power plant in Oklahoma uses the MEA method to recover 200 tons of CO2 per day, which can be used in the beverage industry. However, the disadvantage of the MEA separation method is its high operating cost. 1.2 Physical adsorption methods: Adsorption methods can be divided into pressure swing adsorption (PSA) and temperature swing adsorption (TSA). The PSA method relies on the principle that solid adsorbents have a selective adsorption capacity for CO2; the amount of adsorption is high under high pressure, and CO2 is desorbed when the pressure is reduced. The TSA method adsorbs and desorbs CO2 by changing the temperature of the adsorbent. The pressure swing adsorption method is more commonly used in industry. The adsorption method is suitable for gases with a CO2 content of less than 50%. This method features simple processes, low equipment investment, low energy consumption, and strong adaptability, and has already been applied in China. Currently, new technologies are being developed to recover CO2 from flue gas using the PSA method. 1.3 Low-temperature distillation method (cryogenic separation method): The low-temperature distillation method takes advantage of the difference in boiling points between CO2 and other gas components; it involves liquefying the gases at low temperatures and then separating CO2 from the other gases through distillation. This method is costly and is primarily used to improve the recovery rate of crude oil; its application for recovering CO2 from flue gas is still at the theoretical research stage. 1.4 Membrane separation method: The membrane separation method makes use of gas membrane separation technology, which has developed rapidly over the past two decades. It is a technique that relies on the difference in the rates at which CO2 and other components in a mixed gas pass through the membrane material to achieve separation. This method features low investment, easy operation, and low energy consumption; it is an energy-saving gas separation technology that is developing very rapidly. The biggest drawback of membrane separation is the difficulty in obtaining high-purity CO2. The main materials of separation membranes used in industry include acetate fiber, ethyl cellulose, polyphenylene oxide, and polysulfone, among others【111】. Currently, most research focuses on the development of efficient and low-cost membrane materials. Among the various membrane materials suitable for CO2 separation, polyimide membranes exhibit excellent chemical stability, high-temperature resistance, and mechanical properties, making them suitable for flue gas recovery. It is believed that with the continuous development of polymer materials and the ongoing improvement of film-forming technologies, membrane separation methods will surely play a significant role. The UK’s IEA Greenhouse Gas Research and Development organization used simulation calculations to conduct a comprehensive evaluation of carbon dioxide recovery technologies for power plants. Membrane separation is the most efficient recovery technique among those methods for power plants, while the combination of membrane separation and MEA methods results in the lowest operating costs for CO2 recovery; the adsorption method, on the other hand, has the highest operating costs.