1. solvent absorption method. When CO2 is absorbed and desorbed by solvent, the concentration of CO2 can reach above 98%. This method is only suitable for recovering CO2 from low-concentration CO2 waste gas, with complicated process and high operating cost.
2. Pressure swing adsorption method. CO2 in mixed gas can be absorbed by solid adsorbent, and the concentration can reach above 60%. This method is only suitable for removing CO2 from shift gas in chemical fertilizer plant, and the CO2 concentration is too low to be used as a product.
3. Organic membrane separation method. Using hollow fiber membrane to separate CO2 under high pressure is only suitable for the occasions where the gas source is clean and the CO2 concentration is not higher than 90%. At present, this technology is in the development stage in China.
4. Catalytic combustion method. Combustible impurities in CO2 are converted into CO2 and water by using catalyst and pure oxygen. This method can only remove combustible impurities, which has high energy consumption and cost and has been eliminated.
The CO2 produced by the above method is gaseous, and it needs to be further purified, rectified and liquefied by adsorption distillation before it can be stored and transported in liquid state. Adsorption distillation technology is a general technology that must be used in the connection process of the above methods.
According to the research of American Electric Power Research Institute (EPRI), ammonia washing in power plant can reduce CO2 10%, while the old MEA (amine washing) method can reduce CO2 by 29%.
The development of new carbon dioxide recovery and capture technologies in the world is accelerating.
1. BASF, a new solvent for carbon dioxide removal, and JGC of Japan jointly developed a new technology, which can reduce the carbon dioxide removal and storage cost contained in natural gas by 20%. The project was supported by the Ministry of Economy, Trade and Industry of Japan. CO2 can be captured from the flue gas generated in the combustion process by an absorbent such as monoethanolamine (MEA). However, regeneration of absorbent requires extra energy, and for MEA, it takes about 900 kcal/kg CO2 to recover CO2 from flue gas, which is usually uneconomical. Japan's Mitsubishi Heavy Industries (MHI) and Kansai Electric Power Company (KEPCO) have jointly developed a new process, which can bring new changes to the way of CO2 recovery. The new carbon dioxide absorbents discovered by MHI are hindered amines named KS- 1 and KS-2, and the energy required to recover them is about 20% less than that of MEA. Because KS- 1 and KS-2 are more stable to heat and less corrosive than MEA, the total loss of amine during operation is about 1/20 of that of conventional absorbent. In areas where energy costs are not expensive, new processes are adopted for large-scale plants, and the cost of recovering CO2 (including compression cost) is about $20/ton CO2, which is about 30% lower than that of conventional methods based on MEA. MHI has verified this technology in a urea plant in Malaysia, which can recover 200 tons of carbon dioxide from flue gas every day.
2. New Process Based on Ammonia: A CO2 capture process has been developed by American Powerspan Company, which can capture CO2 from power plant flue gas (FG) with ammonia (AA) solution. This is the result of joint research with the National Energy Technology Laboratory (NETL) of the US Department of Energy. BP Alternative Energy Company and Powerspan Company are developing and verifying the aminoCO2 capture technology called ECO2 by Powerspan Company, and will apply it to coal-fired power plants for commercialization. This post-combustion CO2 capture process is suitable for reforming existing coal-fired generating units and building new coal-fired power plants. The ECO2 capture process is combined with the electrocatalytic oxidation technology of Powerspan Company, and ammonia water is used to absorb a large amount of SO2, nitrogen oxides and mercury. The CO2 treatment step is arranged downstream of the SO2, nitrogen oxides and mercury removal step of e CO. According to the research on CO2 absorption by ammonia water in National Energy Technology Laboratory (NETL), the traditional MEA process for CO2 removal has the disadvantages of low CO2 loading (CO2 absorption per kilogram of absorbent), high corrosion rate of equipment, amine degradation by other flue gas components and high energy consumption during the regeneration of absorbent. Comparatively speaking, ammonia water has high loading capacity, no corrosion problem, does not degrade in flue gas environment, can minimize the amount of absorbent replenishment, requires less energy for regeneration, and the cost is much lower than that of MEA. Especially, compared with conventional amines, the ammonia process developed by Powerspan Company adopted by NETL has the following advantages: the steam load is small (500Btu/ pound of CO2)； captured); Generating a relatively concentrated CO2 carrier; Reduce the cost of chemicals; Produce by-products that can be sold and realize multi-pollutant control.
3.CO2 adsorption technology In recent years, the standard requirements of industrial and food-grade CO2 are getting higher and higher, but the recovered CO2 products, such as solvent absorption method, pressure swing adsorption method, organic membrane separation method and catalytic combustion method, can not meet the food-grade standard requirements, and their application in industrial fields is also limited. A super sponge-like substance newly developed in the United States can absorb a large amount of carbon dioxide emitted by power plants or automobile exhaust. As a new method to purify greenhouse gases, this super spongy substance is more effective and cheaper than the existing methods (including aqueous solution treatment). Researchers at the University of Michigan in the United States made this sponge-like substance through chemical synthesis. This kind of material is called metal-organic framework (MOF) mixture, and it is a stable crystalline porous substance, which is composed of organic linking groups and metal clusters. It is reported that this MOF can capture CO2 well. One of its compounds, MOF? 177 can capture 140w%(33.5 mmol/g) of CO2 at normal temperature and moderate pressure (about 3.0 MPa), which far exceeds the CO2 storage capacity of any other porous material. The super sponge MOF- 177 is composed of octahedral Zn4 carboxylate clusters connected with organic groups. This material has a very high surface area, reaching 4500 square meters/gram, which is equivalent to the area of about 4 football fields per gram. After carbon dioxide is captured, it can easily release gas with a little heating, and then it can be used as a reagent for various reactions, including the polymerization process of making polycarbonate building materials and the carbonation of soft drinks.
4. Use LSCF tube to make carbon dioxide easy to capture. A recent scientific research achievement shows that by controlling the combustion process, microtubes made of advanced ceramic materials are expected to reduce the greenhouse gas emissions of power stations to near zero. This material, called LSCF, has the remarkable characteristic of filtering oxygen in the air. In this way, by burning the fuel in pure oxygen, an air flow close to pure CO2 can be generated, and the pure CO2 has potential commercial use of being reprocessed into useful chemicals. LSCF is a relatively new material, originally developed for fuel cell technology, and has been studied in many countries for decades, mainly used as the cathode of fuel cells.
5. Membrane technology for separating carbon dioxide. The improved plastic materials developed by engineers at the University of Texas in the United States can greatly improve the ability to separate carbon dioxide from natural gas. This new polymer film can naturally imitate the holes that can only be found in battery films. According to their shapes, their unique hourglass shape can effectively separate molecules. The evaluation of the Scientific Industry Research Organization in June 2007 (5438+ 10) shows that it can separate CO2 from methane. Like a sponge, it only absorbs certain chemicals. New plastics allow carbon dioxide or other small molecules to pass through hourglass-shaped pores, while natural gas (methane) does not migrate through these pores. Thermal rearrangement (TR) plastics are superior to conventional membranes in separating CO2 through pores. Professor BennyFreeman's laboratory research also shows that the separation speed of thermal rearrangement plastic film is also faster, which is hundreds of times faster than that of conventional film to remove CO2.
6. Technology of directly capturing carbon dioxide from the atmosphere Scientists from Columbia University in the United States announced from June 5 to mid-October 2007 that they were accelerating the development of industrial technology for directly capturing carbon dioxide from the atmosphere. According to the analysis, even if carbon capture and storage (CCS) technology is not fully adopted, 50% of global greenhouse gas CO2 can be captured from scattered and mobile emission sources. According to statistics, large stationary emission sources produce more than 0. 1 megaton of CO2 every year. Based on KlausLackner's previous work at Columbia University, the technology proposed by FrankZeman has established the thermodynamic feasibility of this specific air capture process. In 1999, KlausLackner first proposed to remove CO2 from the air for the purpose of carbon capture and storage. This new research result has been published in the June 2007 edition of American Environmental Science and Technology.
7. Develop underground gasification of chinchilla coal (UCG) by removing CO2 from algae bioreactor. At the end of 2007 10, Linc Energy Company of Australia announced that it would set up a joint venture with BioCleanCoal Company, with 60% and 40% shares respectively, to develop a seaweed bioreactor to convert CO2 in the process into oxygen and biomass. The joint venture company will develop a bioreactor to convert carbon dioxide into oxygen and solid biomass through photosynthesis, thus permanently and safely removing carbon dioxide from the atmosphere. Linc Energy Company will invest A $654.38 million in the next year to develop a prototype device running in chinchilla. BioCleanCoal is a biotechnology company, which specializes in converting CO2 into oxygen and biomass through algae.