Seeking methods for large-scale CO2 treatment?

CO2 is used in many places. It can be used in oil extraction, welding, beer and beverage production, and the preservation of fruits and vegetables.

　 Development and utilization of carbon dioxide: The domestic market for CO2 consumption holds great potential, with regular usage set to increase further, and new areas of application continuing to emerge. The beverage industry is the largest market for CO2 consumption within this sector, accounting for around 30%; however, the per capita consumption of beverages in China is currently less than 5 kilograms per year. While in the United States it is 150 kilograms per person per year. As China’s **living standards continue to improve, the beverage industry’s consumption of CO2 is set to increase significantly. CO2 gas shielded welding has always been one of the key technologies promoted in China; it currently accounts for around 20% of CO2 consumption, making it the second-largest market for CO2. China currently has over 10,000 gas shielded welding machines, and this number will continue to increase; the demand for CO2 will keep rising as well, with an average growth rate of around 11% over the next five years. CO2 consumption in the food processing industry accounts for about 15% of the domestic CO2 market. It is primarily used for food freezing, refrigeration, sterilization, mold prevention, and preservation. To meet the demands of the international food market competition as well as the needs for preserving high-quality foods domestically, this represents a huge potential market for liquid and solid CO2. CO2 and Freon are two commonly used tobacco swelling agents, but the latter has been listed as a substance to be phased out; its use is being gradually reduced until it is completely banned. This provides a rare and valuable opportunity for CO2 in the development of the tobacco industry. Liquid CO2 is used for the swelling treatment of tobacco shreds, allowing each box of cigarettes to save 5%~6% (about 2.5~3 kilograms) of tobacco shreds, while also improving the quality of the tobacco shreds. Bulking the tobacco for each box of cigarettes (approximately 50 kilograms of tobacco) consumes 30 kilograms of CO2. China produces around 20 million boxes of cigarettes per year; if 10% of them are processed using CO2, then about 60,000 tons of CO2 will be required. If all cigarettes were processed using CO2, then 600,000 tons of CO2 would be needed. Therefore, CO2 has very promising prospects for application and promotion in the tobacco industry. The CO2 consumption market holds great potential, with many fields only just beginning to see the introduction of such applications or are still in the process of developing them. Examples include: (1) use as a gaseous fertilizer for plants – using CO2 as a gaseous fertilizer can promote plant growth, increase yields, and improve plant varieties. By applying CO2 via pipes (at a concentration of 2%–5%) inside plastic greenhouses for 6–38 days, vegetable yields can be increased by 5 times, and the maturity period can be shortened by 2–5 days ； In soybean sprouts and mung bean sprouts, the hypocotyls grow longer and thicker; the sprouts become shiny, transparent, and plump, allowing the growth time to be reduced by 3–4 days, while yield and quality are significantly improved ； Applied before rice flowering at a concentration of 0.9%, it can increase yield by over 170 kilograms per mu. In recent years, the Shandong Academy of Agricultural Sciences and Dalian Chemical Industry Company have successively developed CO2 gas fertilizers, which have been widely applied in provinces such as Shandong, Hebei, Henan, Liaoning, Jilin, and Heilongjiang, yielding excellent economic benefits. It is reported that to build a CO2 gas fertilizer plant with a production capacity of 3,000–5,000 tons per year, the equipment investment is only in the tens of thousands of yuan, while the annual profit can reach millions of yuan. This makes it suitable for small and medium-sized ammonia synthesis plants to utilize excess CO2 resources for diversified business activities. (2) CO2 as a preservative for fruits and vegetables: Natural oxygen reduction and modified atmosphere preservation – relatively modern methods that are widely used in practice. CO2 gas modification for preservation involves injecting high concentrations of CO2 to reduce oxygen levels, thereby suppressing the biological respiration of fruits and vegetables and preventing the growth of pathogens. CO2 is widely used abroad for pest control and preservation. CO2 has great potential in food preservation; the main shortage is technical personnel for its promotion and application. (3) Used as an oilfield production aid: In oilfields, for wells that have undergone primary recovery (natural flow) and secondary recovery (water injection to assist production), CO2 can be injected to carry out third-party recovery of the oil remaining underground. Under high pressure, CO2 can penetrate into the dead corners and edges of the formation, increasing the fluidity of the remaining crude oil and driving it toward the oil wells to emerge to the surface, thereby enhancing oil recovery. In the United States, CO2 used for oil extraction accounts for about 11% of its total consumption, amounting to roughly 530,000 to 550,000 tons per year. Our country has conducted research on CO2 in oil fields such as Xinjiang, Daqing, and Shengli, accumulating certain data and practical experience; however, there are few mineral-related tests, and the work remains largely at the experimental stage. (4) Used for supercritical extraction. Supercritical extraction is a new separation technique that has been developed in recent years. It utilizes the high solvating capacity and low viscosity of fluids in their critical state to extract and separate certain substances. This method features high separation efficiency, the ability to operate at lower temperatures, and suitability for separating heat-sensitive and easily oxidizable substances. CO2 is widely used in the extraction of essential oils from aromatic plants, the extraction of fats from oilseeds, the extraction of caffeine from coffee beans, and the extraction of nicotine from tobacco leaves, owing to its safety, low cost, wide availability, low supercritical temperature and pressure, as well as high extraction efficiency and selectivity. In recent years, it has been used in various fields such as food, pharmaceuticals, and the environment for the separation, purification, and monitoring analysis of many substances, with extensive research being conducted abroad. For example, supercritical CO2 can extract organic chlorides from polluted water in a very short time, and it can also separate various toxic substances accumulated in fish tissue. Many environmental monitoring and oversight agencies abroad use this method to determine the extent of environmental pollution. Germany has built industrial facilities for extracting caffeine from tea using CO2 ； The UK and Australia have built extraction facilities for edible oils and spices. In China, several institutions and research organizations, such as Beijing University of Technology, Beijing Research Institute of Chemical Technology, and the Shanxi Institute of Coal Chemistry under the Chinese Academy of Sciences, have used supercritical CO2 as an extractant to study extraction and separation techniques for fragrances, wheat germ oil, rapeseed oil, etc. Some of these processes have already been put into industrial use. (5) Use as a blowing agent instead of chlorofluorocarbons. CO2 has the following advantages as a blowing agent for foam plastics: ① It causes less environmental pollution compared to the use of pentane, butane, or chlorofluorocarbons as blowing agents ； ②Low usage, only 1/2 of that of HCFC blowing agents ； ③The foam plastic produced is easy to recycle. PS foam plastics produced using CO2 as a blowing agent can be used to manufacture fast-food containers, boxes, plates, and bowls for the food industry, as well as containers in supermarkets for storing fish, meat, eggs, and similar items. After years of research, DOW Chemical has successfully developed CO2 as a substitute for the blowing agents used in existing PS foam boards, and has licensed this new technology worldwide. Using this technology, foam PS boards with a thickness of 6.35 mm can be produced entirely using CO2 as a foaming agent, offering advantages such as minimal environmental pollution and reduced usage of foaming agents. (6) Used in wastewater treatment: CO2 dissolves in water and is weakly acidic; it can be used to treat alkaline pollution and control the pH value. Factories that discharge alkaline wastewater include textile dyeing and printing plants, metal processing plants, oil refineries, ethylene production plants, and paper mills. Treating pulp black liquor with flue gas containing CO2 not only neutralizes the black liquor but also enables the recovery of 200 kilograms to 300 kilograms of sulfated lignin per ton of black liquor, with an extraction rate of over 80%. China’s first industrial plant to utilize the CARIX process was built at the Second Fertilizer Plant of Qilu Petrochemical Company, where it is used to treat the make-up water for the circulating cooling water system. Practice has shown that the CARIX process is not complex; by adding a set of equipment for preparing CO2 regeneration liquid to the existing ion exchange unit, a conventional acid-base regeneration ion exchange unit can be converted into a CO2 regeneration ion exchange unit. Ammonia synthesis plants have an abundant supply of CO2, require large amounts of circulating water, and have high demands regarding water quality, making them the most promising application area for the CARIX process. (7) Used in the production of inorganic chemical products. Inorganic chemical products manufactured from CO2 as a raw material include lightweight MgCO3, Na2CO3, NaHCO3, CaCO3, K2CO3, BaCO3, PbCO3, Li2CO3, MgO, silica, borax, etc. These are mostly basic chemical raw materials that are widely used in industries such as metallurgy, chemicals, building materials, light industry, electronics, pharmaceuticals, and machinery. ①Silica gel can be produced by reacting sodium silicate with purified CO2 gas. It is used as a rubber reinforcement, plastic filler, lubricant, and insulating material, among other things. ②Borax can be produced by mixing pretreated boromagnesite powder with a carbonate solution and heating it; after introducing CO2 to increase the pressure, borax is obtained. It is mainly used in the glass and enamel industries. ] ③ Light magnesium oxide: Light magnesium oxide is obtained by calcining and nitrating dolomite, followed by a series of treatments such as CO2 carbonization and pyrolysis. It is mainly used as a filler in ceramics, enamel, refractory materials, polishing agents, paints, and paper. ④Crystalline calcium carbonate is obtained by reacting calcium hydroxide with hydrochloric acid to produce calcium chloride; subsequent carbonation with CO2 yields calcium carbonate, which is then refined through crystallization, separation, washing, dehydration, drying, and screening to yield the final product in the form of crystalline calcium carbonate. It is mainly used in toothpaste, pharmaceuticals, insulation materials, etc. ⑤Barium carbonate is produced by carbonizing barite and coal powder after reduction roasting, using CO2. It is widely used in the manufacture of optical glass, as well as in the production of fireworks, cosmetics, tiles, pottery, enamel, and more. (8) Application in organic chemical industry: The use of CO2 in organic synthesis chemistry has become one of the most important topics in modern chemistry, and CO2 could become an important carbon source in the future. Research on CO2 in our country started late and has not been utilized effectively to date. Given the current shortage of energy and basic chemical raw materials, there are broad prospects for utilizing CO2 resources to develop chemical raw materials and synthesize chemical products. ①Ethanol: Mitsubishi in Japan and Tokyo Electric Power have jointly developed a technology to convert CO2 into fuel ethanol using green algae, but progress has been delayed due to the great complexity and difficulty of the process for synthesizing ethanol from CO2. ②Catalytic hydrogenation of methanol with CO2 to produce methanol is an important way to make use of CO2, and extensive research has been conducted on this topic abroad. Topsoe has achieved industrial production of methanol synthesized directly from CO2 and H2. Tokyo Gas in Japan has developed a technology for synthesizing methanol from CO2. The key to this new process is the use of a novel catalyst made of alumina along with copper and zinc, which enables the reaction of CO2 and H2 to produce methanol gas; after cooling, the product is obtained, with a yield of around 25%. The remaining 75% is gas, consisting of unreacted CO2 and CO, which can be converted back into raw materials for reuse, enabling a methanol yield of 98%. German companies Lurgi and Sudchemie have developed a new process for producing methanol from CO2, introducing new reactors and catalyst systems. Compared to traditional processes, the equipment size in the synthetic loop system is smaller, and the investment cost for the circulation rate is also lower. ③Products are manufactured using CO2 as a carbonylating agent. The main products include salicylic acid, p-carboxybenzoic acid, 2,4-dihydroxybenzoic acid (resorcinol), 2,5-dihydroxybenzoic acid (2,3-acid), and o-methylsalicylic acid. The manufacturing processes and equipment for these products are complex. For example, salicylic acid is primarily produced by reacting phenol with NaOH solution at 130°C, followed by the introduction of CO2 and subsequent processing; it is used in pharmaceuticals, dyes, fragrances, food preservatives, rubber additives, UV absorbers, and more. 2,4-Dihydroxybenzoic acid is produced by the hydroxylation of resorcinol with CO2, and it serves as a raw material for organic synthesis. O-methyl salicylic acid is produced by reacting o-cresol with NaOH followed by the introduction of CO2; it is an important intermediate for dyes, and is also used in disinfectants, plant growth regulators, herbicides, etc. This product has long relied on imports. ④Dimethyl carbonate: Japan’s NIMCR has developed a technology for producing dimethyl carbonate from polyoxymethylene and supercritical CO2, replacing the traditional phosgene or CO-based methods and improving environmental protection and safety. ⑤Styrene can be produced from CO2, with energy consumption reduced by 90%. Replacing high-temperature water vapor with CO2 to react benzene and ethylene in order to produce styrene also helps protect the Earth’s environment. ⑥Dicyandiamide is produced through processes such as the hydrolysis of calcium cyanamide, vacuum filtration, calcium removal using CO2, alkaline polymerization, and crystallization drying. It is used in dyes, coatings, adhesives, synthetic detergents, and other products. ⑦Propylene carbonate is synthesized from CO2 and propylene oxide under certain temperature and pressure conditions. It is widely used in industries such as printing and dyeing, light textiles, fertilizers, and organic synthesis. ⑧Formic acid and its derivatives: Formic acid is efficiently synthesized from CO2 and H2 using supercritical CO2 as both solvent and reactant, in the presence of trimethylphosphine-based catalysts. Formic acid is not only a raw material for acetic acid as well as fragrances and pharmaceuticals, but it can also be decomposed into CO2 and H2 when heated. This method can also be used to transport and store H2 in the form of formic acid, which is extremely convenient and safe. ⑨CO2 methanation: Canadian scientists have achieved the CO2 methanation reaction under mild conditions in the laboratory, with yields of 60%–70%, which is still a long way from industrial application ； Tokyo Electric Power and Hitachi have jointly developed a new catalyst for converting CO2 into methane; at normal pressure and 300°C, with a ratio of CO2 to H2 of 1:4, the conversion rate of CO2 reaches 90% ； The Japanese company NEC improved the catalyst by replacing manganese with palladium; at normal pressure and 300°C, the CO2 conversion rate reached 96% with no by-products. The Department of Industry at Gunma University in Japan employs a biochemical electrolysis combined process, in which a membrane of methane-producing bacteria is attached to the cathode of the electrolysis device. CO2 is introduced into the water within the device and the pressure is increased; hydrogen generated through electrolysis is then used to convert CO2 into methane, with a conversion rate of up to 90%. ⑩Harbin Normal University has developed a method for converting natural gas and CO2 into syngas composed of CO and H2, thereby replacing syngas produced from petroleum as a raw material and opening up a new production pathway separate from those used in the petrochemical and coal chemical industries. ⑾CO2 to ethylene: The University of Tokyo in Japan has used two reactors connected in series to rapidly convert CO2 into ethylene. (9) CO2 dyeing method: German researchers have recently invented a new process that uses CO2 as a dyeing medium, allowing textiles to be colored without the need for traditional water treatment. Nylon and other polymeric fiber fabrics treated with the CO2 dyeing method achieve the same coloring results as those treated with water, and even very fine fabrics can be subjected to this treatment without any problems. Additionally, the greatest advantage is that textile companies no longer have to pay high costs for dyed wastewater, and the textiles do not need to be dried anymore. (10) Synthesis of organic polymers: Since research reports on the use of CO2 as a raw material for synthesizing polymers appeared in 1969, development in this field has progressed rapidly, with many types of polymers being synthesized, several of which have already reached the practical application stage. ①Polycarbonate can be obtained with high molecular weight by copolymerizing CO2 with ethylene oxide, propylene oxide, and other substances. Products such as polycarbonate can be processed into transparent and flexible films that are heat-resistant, non-toxic, and have better breathability than PE and PP films; they can also release CO2, which makes them suitable for food packaging and preservation, offering broad prospects for further development and application. ②Polyurea can be produced through the condensation reaction of CO2 and aromatic diamines. It is an excellent engineering plastic with special biodegradability, and can be used as a medical polymer material. ③Polyether carbonate is a new type of non-ionic surfactant synthesized from CO2. It can be widely used in applications such as washing, emulsification, dispersion, and solubilization. Its notable advantage is its good biodegradability; it can be hydrolyzed into environmentally harmless diethylene glycol simply by adding soap water, which helps to prevent pollution from industrial wastewater, making it highly valuable for further development. There are also other high-molecular compounds such as liquid crystal polymers, polythions, and polyethers, which can be synthesized by reacting CO2 with other organic substances as raw materials. (11) Development of dry ice applications: At present, dry ice in China is mainly used for the preservation of seafood and fruits and vegetables, as well as for food freezing and preservation. There are still many areas that need to be explored and developed, such as wood preservatives. In enclosed warehouses, fumigating wood with dry ice vapor containing 0.1%–10% allyl isothiocyanate can extend its shelf life ； Concrete additives: Powdered dry ice is mixed into concrete during mixing, which helps to control the thermal decomposition of concrete ； Nuclear reactor purifiers, which utilize dry ice generation devices in nuclear reactions, can remove radioactive substances from them ； Dust covering hot metals can reduce dust emission by about 87%, which is beneficial for environmental protection ； Explosive formers are also used in fields such as healthcare, drug preparation, and fire fighting. It is not widely used in China at present, mainly due to its high price; if costs can be further reduced, consumption volume could increase even more. Common uses of dry ice: ◎ Dry ice refrigeration is widely used for storing airline food. ◎By adding dry ice when making ice cream, it does not melt easily. Dry ice is particularly suitable for cooling takeaway ice cream. ◎Seafood specialty dishes prepared in star-rated hotels and restaurants can have dry ice added to them at the time of serving, creating a white smoke effect that enhances the elegance of the banquet; this is especially true for dishes such as lobster sashimi. ◎Freezing and refrigeration of seafood such as lobsters, crabs, and shark fins. Dry ice does not turn into water, and it provides a cleaner cooling effect than regular ice, which is why it is widely used in countries such as Europe, the United States, and Japan. ◎Living cell specimens from biological laboratories are transported under refrigeration using dry ice, which is easier to handle, safer, and more convenient than transporting them using liquid nitrogen tanks. It has been adopted by a considerable number of universities worldwide (mainly in the life sciences) as well as research institutes. ◎During the preparation of nanopowders, dry ice is used to be added to ethane in order to create a cooling fluid at temperatures below -70°C, thereby providing the low-temperature environment necessary for the production of nanomaterials. ◎In the cold assembly process of mechanical parts, dry ice is often used as a cooling source. Moreover, it is more operational than using liquid nitrogen as a cooling source. ◎When growing flowers and vegetables in greenhouses, carbon dioxide fertilizers are used, and dry ice can be employed to apply them at regular intervals and in controlled amounts. ◎Dry ice is used to create mist effects on stages and in films and television, and is widely adopted by the entertainment industry. ◎Dry ice is used in industrial cleaning to effectively remove deposits from industrial equipment such as molds. It is one of the most important uses of dry ice at present and in the future. ◎ Edible dry ice – adding dry ice cubes to wine, cocktails, or beverages creates a cool and pleasant taste, along with mist in the glass, which is very enjoyable. (12) Others: Supercritical CO2 cleaning. Compared with conventional cleaning methods using water or other solvents, this method can reduce cleaning costs by 1/2; the cleaned components do not require drying, the cleaning time is significantly reduced (only a few minutes), and it does not pollute the environment. It is now being promoted for widespread use. Extraction of beta-carotene using supercritical CO2 in a spiral. In Shouguang County, Shandong Province, CO2 gas fertilizer technology has been vigorously promoted as one of the new technologies for vegetable production in greenhouses. Zhongbo Aolifu Farm has introduced a complete set of greenhouse production facilities from the Netherlands, along with original CO2 enrichment systems that prove to be highly effective. It is reported that there are currently hundreds of millions of mu of greenhouses across the country. Assuming that 0.3 to 0.4 tons of CO2 fertilizer are applied per mu of greenhouse vegetables, if 10% of the greenhouses use CO2 fertilizer, then 3 to 4 million tons would be required. This shows that there is huge market potential for CO2 fertilizer, given its low cost, convenience, and safety. The demand for CO2 as a gas fertilizer is highest during the months of January, February, March, April, November, and December each year, whereas the demand for food-grade CO2 is highest from April to October. These two products are complementary in terms of their applications. Joint production allows for the maximum utilization of resources and plant capacity, thereby achieving better economic benefits. According to predictions by experts, by 2100, conventional oil worldwide will be almost exhausted; therefore, the production of unconventional oil has been put on the agenda. Scientists first thought that the exhaust gases produced by burning oil and other fuels contain large amounts of CO2, which could be utilized to produce oil by reversing this process. In 1988, the Golden Colorado Solar Research Institute in the United States was the first to discover that algae and CO2 could be used to produce oil, and successful experiments were conducted ； In 1989, a Japanese company discovered that a single-celled algal plant, a green alga, could absorb large amounts of CO2 and use it to produce oil. Thus, in October 1989, Japan’s Idemitsu Kosan Company began experiments on using the photosynthesis of green algae to convert CO2 into oil, by collecting the CO2 gas emitted from combustion and pumping it into tanks where the green algae were cultivated, thereby causing the algae to absorb all of this CO2. Recent years have seen new progress in research on producing oil using seaweed and CO2. Paul Jenkins and his colleagues at the University of West England in the UK began researching a new type of seaweed material. They focused on a common type of Chlorella; the CO2 emissions from engines were pumped into the tanks where Chlorella is grown, thereby promoting its growth. Experiments have shown that by introducing CO2 gas into a pond, the amount of algae in it can increase by a factor of a thousand within a single day; such a rate of growth is several times higher than that in equatorial tropical rainforests. Dry ice: used in penicillin production, for preserving fish, cream, cheese, ice cream, etc., in low-temperature transportation, as a fire extinguishing agent, and as a coolant. Liquid carbon dioxide: coolant, welding and foundry industries, soft drinks, fire extinguishants, production of carbonates, insecticides, oxidation inhibitors, plant growth promoters, fermentation industry, pharmaceuticals (local anesthetics), manufacturing industry, production of adhesives and animal glues, etc. Carbon dioxide gas: used for oxidation, diffusion, and chemical vapor deposition in semiconductor manufacturing; for preserving vegetables; as an inert medium in certain reactions; as a heat carrier in graphite reactors; as a pushing gas for transporting flammable liquids; as a standard gas, a calibration gas, a standard gas for online instruments, and as special mixed gases.

1. There are many factors to consider for large-scale application, such as the scale and where the main sales markets will be in the future Storage, transportation, and so on? 2. There are many methods available at present, but in my opinion we are still in a phase where of mixed quality; those that are more mature for large-scale use seem to be fertilizers, methanol, and gaseous fertilizers. However, the specific method to be used depends on where your market is located and on the overall costs involved.

In the future, transactions will be carried out to sell emission allowances, but it seems that this has not started yet.

By \"large-scale\" as mentioned by the original poster, I understand it to refer to an annual release volume of over 1 million tons. Such a large amount is difficult to utilize aside from in coalbed methane extraction and tertiary oil recovery. The reuse of carbon dioxide is a topic of widespread concern within the international community. As mentioned earlier, although there are many uses for carbon dioxide, they account for only a very small fraction of the annual release volume. Moreover, consumption of carbon dioxide is regionalized – developed areas have high consumption levels; for example, not enough carbon dioxide is recovered in the East China region, and 600,000 tons of liquid carbon dioxide are still extracted each year from the Huangqiao gas field in Jiangsu. In less developed regions such as the west, consumption is much lower. Many chemical plants recycle carbon dioxide to produce food-grade liquid carbon dioxide, but the delivery range of this product is limited, not exceeding 500 kilometers at most.