Application of carbonic acid (carbon dioxide)
Currently, carbon dioxide in all its states is widely used in all sectors of industry and the agro-industrial complex.
In gaseous state (carbon dioxide)
In the food industry
1. To create an inert bacteriostatic and fungistatic atmosphere (at concentrations above 20%):
· when processing plant and animal products;
· when packaging food products and medicines to significantly increase their shelf life;
· when dispensing beer, wine and juices as a displacing gas.
2. In the production of soft drinks and mineral waters (saturation).
3. In brewing and production of champagne and sparkling wines (carbonation).
4. Preparation of carbonated water and drinks using siphons and saturators, for personnel in hot shops and in the summer.
5. Use in vending machines for the sale of bottled gas and water and for the manual sale of beer and kvass, carbonated water and drinks.
6. In the production of carbonated milk drinks and carbonated fruit and berry juices (“sparkling products”).
7. In the production of sugar (defecation - saturation).
8. For long-term preservation of fruit and vegetable juices while preserving the smell and taste of a freshly squeezed product by saturating with CO2 and storing under high pressure.
9. To intensify the processes of precipitation and removal of tartaric acid salts from wines and juices (detartation).
10. For the preparation of drinking desalinated water using the filtration method. To saturate salt-free drinking water with calcium and magnesium ions.
In the production, storage and processing of agricultural products
11. To increase the shelf life of food products, vegetables and fruits in a controlled atmosphere (2-5 times).
12. Storing cut flowers for 20 days or more in a carbon dioxide atmosphere.
13. Storing cereals, pasta, grains, dried fruits and other food products in a carbon dioxide atmosphere to protect them from damage by insects and rodents.
14. For treating fruits and berries before storing, which prevents the development of fungal and bacterial rot.
15. For high-pressure saturation of cut or whole vegetables, which enhances flavor notes (“sparkling products”) and improves their shelf life.
16. To improve growth and increase productivity of plants in protected soil.
Today, in vegetable and flower growing farms in Russia, the issue of fertilizing plants in protected soil with carbon dioxide is an urgent issue. CO2 deficiency is a more serious problem than deficiency of mineral nutrients. On average, a plant synthesizes 94% of its dry matter mass from water and carbon dioxide; the plant receives the remaining 6% from mineral fertilizers! Low carbon dioxide content is now a factor limiting yield (primarily in small-volume crops). The air in a 1-hectare greenhouse contains about 20 kg of CO2. At maximum lighting levels in the spring and summer months, CO2 consumption by cucumber plants during photosynthesis can approach 50 kg h/ha (i.e., up to 700 kg/ha CO2 per daylight hours). The resulting deficit is only partially covered by the influx of atmospheric air through the transoms and the leakage of the enclosing structures, as well as by the night respiration of plants. In ground greenhouses, an additional source of carbon dioxide is soil filled with manure, peat, straw or sawdust. The effect of enriching greenhouse air with carbon dioxide depends on the amount and type of these organic substances that undergo microbiological decomposition. For example, when adding sawdust moistened with mineral fertilizers, the level of carbon dioxide at first can reach high values at night, and during the day when the transoms are closed. However, in general, this effect is not great enough and satisfies only part of the plants’ needs. The main disadvantage of biological sources is the short duration of increasing the concentration of carbon dioxide to the desired level, as well as the impossibility of regulating the feeding process. Often in ground greenhouses on sunny days with insufficient air exchange, the CO2 content as a result of intensive absorption by plants can fall below 0.01% and photosynthesis practically stops! Lack of CO2 becomes the main factor limiting the assimilation of carbohydrates and, accordingly, the growth and development of plants. It is possible to completely cover the deficit only through the use of technical sources of carbon dioxide.
17. Production of microalgae for livestock. When water is saturated with carbon dioxide in installations for autonomous algae cultivation, the algae growth rate increases significantly (4-6 times).
18. To improve the quality of silage. When ensiling succulent feed, the artificial introduction of CO2 into the plant mass prevents the penetration of oxygen from the air, which contributes to the formation of a high-quality product with a favorable ratio of organic acids, a high content of carotene and digestible protein.
19. For safe disinfestation of food and non-food products. An atmosphere containing more than 60% carbon dioxide within 1-10 days (depending on temperature) destroys not only adult insects, but their larvae and eggs. This technology is applicable to products with bound water content up to 20%, such as grain, rice, mushrooms, dried fruits, nuts and cocoa, animal feed and much more.
20. For the total destruction of mouse-like rodents by briefly filling burrows, storage facilities, and chambers with gas (a sufficient concentration of 30% carbon dioxide).
21. For anaerobic pasteurization of animal feed, mixed with water vapor at a temperature not exceeding 83 degrees C - as a replacement for granulation and extrusion, which does not require large energy costs.
22. For euthanizing poultry and small animals (pigs, calves, sheep) before slaughter. For anesthesia of fish during transportation.
23. For anesthesia of queen bees and bumblebees in order to accelerate the onset of oviposition.
24. To saturate drinking water for chickens, which significantly reduces the negative impact of elevated summer temperatures on poultry, helps thicken egg shells and strengthen the bones.
25. To saturate working solutions of fungicides and herbicides for better action of the preparations. This method allows you to reduce solution consumption by 20-30%.
In medicine
26. a) mixed with oxygen as a respiratory stimulant (at a concentration of 5%);
b) for dry carbonated baths (at a concentration of 15-30%) in order to lower blood pressure and improve blood flow.
27. Cryotherapy in dermatology, dry and water carbon dioxide baths in balneotherapy, breathing mixtures in surgery.
In the chemical and paper industries
28. For the production of soda, ammonium carbon salts (used as fertilizers in crop production, additives in ruminant animal feed, instead of yeast in baked goods and flour confectionery), white lead, urea, hydroxycarboxylic acids. For the catalytic synthesis of methanol and formaldehyde.
29. For neutralization of alkaline wastewater. Due to the self-buffering effect of the solution, precise pH regulation avoids corrosion of equipment and waste pipes, and there is no formation of toxic by-products.
30. In the production of paper for processing pulp after alkaline bleaching (increases the efficiency of the process by 15%).
31. To increase the yield and improve the physical and mechanical properties and bleachability of cellulose during oxygen-soda cooking of wood.
32. To clean heat exchangers from scale and prevent its formation (a combination of hydrodynamic and chemical methods).
In construction and other industries
33. For rapid chemical hardening of molds for steel and cast iron castings. The supply of carbon dioxide to casting molds accelerates their hardening 20-25 times compared to thermal drying.
34. As a foaming gas in the production of porous plastics.
35. For strengthening refractory bricks.
36. For semi-automatic welding machines for repairing bodies of passenger and passenger cars, repairing cabins of trucks and tractors and for electric welding of thin-sheet steel products.
37. In the manufacture of welded structures with automatic and semi-automatic electric welding in an environment of carbon dioxide as a protective gas. Compared to welding with a stick electrode, the convenience of work increases, productivity increases by 2-4 times, the cost of 1 kg of deposited metal in a CO2 environment is more than two times lower compared to manual arc welding.
38. As a protective medium in mixtures with inert and noble gases during automated welding and metal cutting, thanks to which very high quality seams are obtained.
39. Charging and recharging of fire extinguishers, for fire-fighting equipment. In fire extinguishing systems, for filling fire extinguishers.
40. Charging cans for gas weapons and siphons.
41. As a nebulizer gas in aerosol cans.
42. For filling sports equipment (balls, balls, etc.).
43. As an active medium in medical and industrial lasers.
44. For precise calibration of instruments.
In the mining industry
45. For softening of the coal rock mass during the mining of hard coal in rock-prone formations.
46. For carrying out blasting operations without creating a flame.
47. Increasing the efficiency of oil production by adding carbon dioxide to oil reservoirs.
In liquid state (low temperature carbon dioxide)
In the food industry
1. For quick freezing, to a temperature of -18 degrees C and below, of food products in contact freezers. Along with liquid nitrogen, liquid carbon dioxide is most suitable for direct contact freezing of various types of products. As a contact refrigerant, it is attractive due to its low cost, chemical passivity and thermal stability, does not corrode metal components, is not flammable, and is not dangerous to personnel. Liquid carbon dioxide is supplied to the product moving on the conveyor belt from the nozzles in certain portions, which at atmospheric pressure instantly turns into a mixture of dry snow and cold carbon dioxide, while fans constantly mix the gas mixture inside the apparatus, which, in principle, is capable of cooling the product from +20 degrees. C to -78.5 degrees C in a few minutes. The use of contact quick freezers has a number of fundamental advantages compared to traditional freezing technology:
Freezing time is reduced to 5-30 minutes; enzymatic activity in the product quickly ceases;
· the structure of tissues and cells of the product is well preserved, since ice crystals are formed of much smaller sizes and almost simultaneously in the cells and in the intercellular space of tissues;
· with slow freezing, traces of bacterial activity appear in the product, while with shock freezing they simply do not have time to develop;
· product weight loss as a result of shrinkage is only 0.3-1% (versus 3-6%);
· Easily volatile valuable aromatic substances will be preserved in much larger quantities. Compared to freezing with liquid nitrogen, freezing with carbon dioxide:
· cracking of the product is not observed due to too large a temperature difference between the surface and the core of the frozen product
· during the freezing process, CO2 penetrates into the product and during defrosting it protects it from oxidation and the development of microorganisms. Fruits and vegetables subjected to quick freezing and packaging on site most fully retain their taste and nutritional value, all vitamins and biologically active substances, which makes it possible to widely use them for the production of products for children's and dietary nutrition. It is important that non-standard fruit and vegetable products can be successfully used to prepare expensive frozen mixtures. Quick-freezers using liquid carbon dioxide are compact, simple in design and inexpensive to operate (if there is a nearby source of cheap liquid carbon dioxide). The devices exist in mobile and stationary versions, spiral, tunnel and cabinet types, which are of interest to agricultural producers and product processors. They are especially convenient when production requires freezing of various food products and raw materials at different temperature conditions (-10...-70 degrees C). Quick-frozen foods can be dried under high vacuum conditions - freeze drying. Products dried using this method are of high quality: they retain all nutrients, have increased restorative capacity, have minimal shrinkage and porous structure, and retain their natural color. Freeze-dried products are 10 times lighter than the original ones due to the removal of water from them, they are stored for a very long time in sealed bags (especially when the bags are filled with carbon dioxide) and can be cheaply delivered to the most remote areas.
2. For rapid cooling of fresh food products, packaged and unpackaged, to +2…+6 degrees C. Using installations whose operation is similar to the operation of quick-freezers: when liquid carbon dioxide is injected, tiny dry snow is formed, with which the product is processed for a certain time. Dry snow is an effective means of quickly reducing temperature, which does not lead to drying out of the product, like air cooling, and does not increase its moisture content, as happens when cooling with water ice. Dry snow cooling provides the required temperature reduction in just a few minutes, rather than the hours required with conventional cooling. The natural color of the product is preserved and even improved due to the slight diffusion of CO2 inside. At the same time, the shelf life of products increases significantly, since CO2 suppresses the development of both aerobic and anaerobic bacteria and mold fungi. It is convenient and profitable to refrigerate poultry meat (cut or in carcasses), portioned meat, sausages and semi-finished products. The units are also used where the technology requires rapid cooling of the product during or before molding, pressing, extruding, grinding or slicing. Devices of this type are also very convenient for use in poultry farms for in-line ultra-fast cooling from 42.7 degrees C to 4.4-7.2 degrees C of freshly laid chicken eggs.
3. To remove the skin from berries using the freezing method.
4. For cryopreservation of sperm and embryos of cattle and pigs.
In the refrigeration industry
5. For use as an alternative refrigerant in refrigeration systems. Carbon dioxide can serve as an effective refrigerant because it has a low critical temperature (31.1 degrees C), a relatively high triple point temperature (-56 degrees C), a high triple point pressure (0.5 mPa) and a high critical pressure ( 7.39 mPa). As a refrigerant it has the following advantages:
· very low price compared to other refrigerants;
· non-toxic, non-flammable and non-explosive;
· compatible with all electrical insulating and structural materials;
· does not destroy the ozone layer;
· makes a moderate contribution to the increase in the greenhouse effect compared to modern halogenated refrigerants. A high critical pressure has the positive aspect of a low compression ratio, resulting in significant compressor efficiency, allowing for compact and low-cost refrigeration designs. At the same time, additional cooling of the condenser electric motor is required, and the metal consumption of the refrigeration unit increases due to the increase in the thickness of the pipes and walls. It is promising to use CO2 in low-temperature two-stage installations for industrial and semi-industrial applications, and especially in air conditioning systems for cars and trains.
6. For high-performance frozen grinding of soft, thermoplastic and elastic products and substances. In cryogenic mills, those products and substances that cannot be ground in their usual form, for example gelatin, rubber, any polymers, tires, are ground quickly and with low energy consumption in frozen form. Cold grinding in a dry, inert atmosphere is necessary for all herbs and spices, cocoa beans and coffee beans.
7. For testing technical systems at low temperatures.
In metallurgy
8. For cooling difficult-to-cut alloys when processed on lathes.
9. To form a protective environment for smoke suppression in copper, nickel, zinc and lead smelting or bottling processes.
10. When annealing solid copper wire for cable products.
In the mining industry
11. As a low-blasting explosive in coal mining, which does not lead to the ignition of methane and coal dust during an explosion, and does not produce toxic gases.
12. Prevention of fires and explosions by displacing air from containers and mines containing explosive vapors and gases with carbon dioxide.
Supercritical
In extraction processes
1. Capturing aromatic substances from fruit and berry juices, obtaining plant extracts and medicinal herbs using liquid carbon dioxide. In traditional methods of extraction of plant and animal raw materials, various types of organic solvents are used, which are highly specific and rarely ensure the extraction of the full complex of biologically active compounds from raw materials. Moreover, the problem of separating solvent residues from the extract always arises, and the technological parameters of this process can lead to partial or even complete destruction of some components of the extract, which causes a change not only in the composition, but also in the properties of the isolated extract. Compared to traditional methods, extraction processes (as well as fractionation and impregnation) using supercritical carbon dioxide have a number of advantages:
· energy-saving nature of the process;
· high mass transfer characteristics of the process due to low viscosity and high penetrating ability of the solvent;
· high degree of extraction of relevant components and high quality of the resulting product;
· virtual absence of CO2 in finished products;
· an inert dissolving medium is used at a temperature that does not threaten thermal degradation of materials;
· the process does not produce waste water and waste solvents; after decompression, CO2 can be collected and reused;
· the unique microbiological purity of the resulting products is ensured;
· lack of complex equipment and multi-stage process;
· A cheap, non-toxic and non-flammable solvent is used. The selective and extraction properties of carbon dioxide can vary widely with changes in temperature and pressure, which makes it possible to extract most of the spectrum of currently known biologically active compounds from plant materials at low temperatures.
2. To obtain valuable natural products - CO2 extracts of spices, essential oils and biologically active substances. The extract practically copies the original plant material; as for the concentration of its constituent substances, we can state that there are no analogues among classical extracts. Chromatographic analysis data show that the content of valuable substances exceeds classical extracts tens of times. Production on an industrial scale has been mastered:
· extracts from spices and medicinal herbs;
· fruit aromas;
· extracts and acids from hops;
· antioxidants, carotenoids and lycopenes (including from tomato raw materials);
· natural coloring substances (from red pepper fruits and others);
lanolin from wool;
· natural plant waxes;
· sea buckthorn oils.
3. For the extraction of highly purified essential oils, in particular from citrus fruits. When extracting essential oils with supercritical CO2, highly volatile fractions are also successfully extracted, which give these oils fixing properties, as well as a more complete aroma.
4. To remove caffeine from tea and coffee, nicotine from tobacco.
5. To remove cholesterol from food (meat, dairy products and eggs).
6. For the production of low-fat potato chips and soy products;
7. For the production of high-quality tobacco with specified technological properties.
8. For dry cleaning of clothes.
9. To remove uranium compounds and transuranium elements from radioactively contaminated soils and from the surfaces of metal bodies. At the same time, the volume of water waste is reduced hundreds of times, and there is no need to use aggressive organic solvents.
10. For environmentally friendly PCB etching technology for microelectronics, without generating toxic liquid waste.
In fractionation processes
The separation of a liquid substance from a solution, or the separation of a mixture of liquid substances is called fractionation. These processes are continuous and therefore much more efficient than the separation of substances from solid substrates.
11. For refining and deodorizing oils and fats. To obtain commercial oil, it is necessary to carry out a whole range of measures, such as removing lecithin, mucus, acid, bleaching, deodorization and others. When extracting with supercritical CO2, these processes are carried out during one technological cycle, and the quality of the oil obtained in this case is much better, since the process takes place at relatively low temperatures.
12. To reduce the alcohol content in drinks. The production of non-alcoholic traditional drinks (wine, beer, cider) is in increasing demand for ethical, religious or dietary reasons. Even if these low-alcohol drinks are often of lower quality, their market is significant and growing rapidly, so improving such technology is a very attractive issue.
13. For energy-saving production of high-purity glycerin.
14. For energy-saving production of lecithin from soybean oil (with a phosphatidyl choline content of about 95%).
15. For flow-through purification of industrial wastewater from hydrocarbon pollutants.
In impregnation processes
The process of impregnation - the introduction of new substances, is essentially the reverse process of extraction. The required substance is dissolved in supercritical CO2, then the solution penetrates into the solid substrate, when the pressure is released, the carbon dioxide instantly evaporates, and the substance remains in the substrate.
16. For environmentally friendly dyeing technology for fibers, fabrics and textile accessories. Painting is a special case of impregnation. Dyes are usually dissolved in a toxic organic solvent, so dyed materials must be thoroughly washed, causing the solvent to either evaporate into the atmosphere or end up in wastewater. In supercritical dyeing, water and solvents are not used; the dye is dissolved in supercritical CO2. This method provides an interesting opportunity to dye different types of synthetic materials at the same time, such as plastic teeth and the fabric lining of a zipper.
17. For environmentally friendly technology, paint application. The dry dye dissolves in a stream of supercritical CO2, and along with it flies out of the nozzle of a special gun. Carbon dioxide immediately evaporates, and the paint settles on the surface. This technology is especially promising for painting cars and large equipment.
18. For homogenized impregnation of polymer structures with drugs, thereby ensuring a constant and prolonged release of the drug in the body. This technology is based on the ability of supercritical CO2 to easily penetrate many polymers, saturate them, causing micropores to open and swell.
In technological processes
19. Replacing high-temperature water vapor with supercritical CO2 in extrusion processes, when processing grain-like raw materials, allows the use of relatively low temperatures, the introduction of dairy ingredients and any heat-sensitive additives into the recipe. Supercritical fluid extrusion allows the creation of new products with an ultra-porous internal structure and a smooth, dense surface.
20. For the production of polymer and fat powders. A stream of supercritical CO2 with some polymers or fats dissolved in it is injected into a chamber with lower pressure, where they are “condensed” in the form of a completely homogeneous finely dispersed powder, the finest fibers or films.
21. To prepare for drying greens and fruits by removing the cuticular wax layer with a jet of supercritical CO2.
In chemical reaction processes
22. A promising area of application of supercritical CO2 is its use as an inert medium during chemical reactions of polymerization and synthesis. In a supercritical environment, synthesis can occur a thousand times faster than the synthesis of the same substances in traditional reactors. It is very important for industry that such a significant acceleration of the reaction rate, due to high concentrations of reagents in a supercritical medium with its low viscosity and high diffusivity, makes it possible to correspondingly reduce the contact time of the reagents. In technological terms, this makes it possible to replace static closed reactors with flow reactors that are fundamentally smaller, cheaper and safer.
In thermal processes
23. As a working fluid for modern power plants.
24. As a working fluid of gas heat pumps producing high-temperature heat for hot water supply systems.
In solid state (dry ice and snow)
In the food industry
1. For contact freezing of meat and fish.
2. For contact quick freezing of berries (red and black currants, gooseberries, raspberries, chokeberries and others).
3. Sales of ice cream and soft drinks in places remote from the power grid, cooled with dry ice.
4. When storing, transporting and selling frozen and chilled food products. The production of briquetted and granulated dry ice for buyers and sellers of perishable products is being developed. Dry ice is very convenient for transportation and for selling meat, fish, and ice cream in hot weather - the products remain frozen for a very long time. Since dry ice only evaporates (sublimates), there is no melted liquid, and transport containers always remain clean. Autorefrigerators can be equipped with a small-sized dry-ice cooling system, which is characterized by extreme simplicity of the device and high operational reliability; its cost is many times lower than the cost of any classical refrigeration unit. When transporting over short distances, such a cooling system is the most economical.
5. To pre-cool containers before loading products. Blowing dry snow in cold carbon dioxide is one of the most effective ways to pre-cool any containers.
6. For air transportation as a primary refrigerant in isothermal containers with an autonomous two-stage refrigeration system (granulated dry ice - freon).
During surface cleaning work
8. Cleaning of parts and components, engines from contaminants using treatment plants using dry ice granules in a gas flow. To clean the surfaces of components and parts from operational contaminants. Recently, there has been a great demand for non-abrasive express cleaning of materials, dry and wet surfaces with a jet of finely granulated dry ice (blasting). Without disassembling the units, you can successfully carry out:
· cleaning of welding lines;
· removal of old paint;
· cleaning of foundry molds;
· cleaning of printing machine units;
· cleaning of equipment for the food industry;
· cleaning of molds for the production of polyurethane foam products.
· cleaning of molds for the production of car tires and other rubber products;
· cleaning of molds for the production of plastic products, including cleaning of molds for the production of PET bottles; When dry ice pellets hit a surface, they instantly evaporate, creating a micro-explosion that removes contaminants from the surface. When removing brittle material such as paint, the process creates a pressure wave between the coating and the substrate. This wave is strong enough to remove the coating, lifting it from the inside. When removing sticky or sticky materials such as oil or dirt, the cleaning process is similar to a strong jet of water.
7. For cleaning stamped rubber and plastic products from burrs (tumbling).
During construction work
9. In the process of manufacturing porous building materials with the same size of carbon dioxide bubbles, evenly distributed throughout the entire volume of the material.
10. For freezing soils during construction.
11. Installation of ice plugs in pipes with water (by freezing them from the outside with dry ice), during repair work on pipelines without draining the water.
12. For cleaning artesian wells.
13. When removing asphalt surfaces in hot weather.
In other industries
14. Receiving low temperatures down to minus 100 degrees (when mixing dry ice with ether) for testing product quality, for laboratory work.
15. For cold fitting of parts in mechanical engineering.
16. In the production of ductile grades of alloy and stainless steels, annealed aluminum alloys.
17. When crushing, grinding and preserving calcium carbide.
18. To create artificial rain and obtain additional precipitation.
19. Artificial dispersal of clouds and fog, combating hail.
20. To generate harmless smoke during performances and concerts. Obtaining a smoke effect on pop stages during artist performances using dry ice.
In medicine
21. For the treatment of certain skin diseases (cryotherapy).
We all know from school that carbon dioxide is emitted into the atmosphere as a product of human and animal life, that is, it is what we exhale. In fairly small quantities, it is absorbed by plants and converted into oxygen. One of the causes of global warming is carbon dioxide, or in other words carbon dioxide.
But not everything is as bad as it seems at first glance, because humanity has learned to use it in a wide area of its activity for good purposes. For example, carbon dioxide is used in carbonated waters, or in the food industry it can be found on the label under code E290 as a preservative. Quite often, carbon dioxide acts as a leavening agent in flour products, where it enters during the preparation of dough. Most often, carbon dioxide is stored in a liquid state in special cylinders, which are used repeatedly and can be refilled. You can find out more about this on the website https://wice24.ru/product/uglekislota-co2. It can be found both in a gaseous state and in the form of dry ice, but storage in a liquefied state is much more profitable.
Biochemists have proven that fertilizing the air with carbon gas is a very good means of obtaining large yields from various crops. This theory has long found its practical application. Thus, in Holland, flower growers effectively use carbon dioxide to fertilize various flowers (gerberas, tulips, roses) in greenhouse conditions. And if previously the necessary climate was created by burning natural gas (this technology was considered ineffective and harmful to the environment), today carbon gas reaches the plants through special tubes with holes and is used in the required quantity, mainly in winter.
Carbon dioxide is also widely used in the fire industry as a fire extinguisher refill. Carbon dioxide in cans has found its way into air guns, and in aircraft modeling it serves as a source of energy for engines.
In its solid state, CO2 has, as already mentioned, the name dry ice, and is used in the food industry for food storage. It is worth noting that compared to ordinary ice, dry ice has a number of advantages, including high cooling capacity (2 times higher than usual), and when it evaporates, no by-products remain.
And these are not all the areas where carbon dioxide is used effectively and efficiently.
Keywords: Where is carbon dioxide used, Use of carbon dioxide, industry, in everyday life, refilling cylinders, carbon dioxide storage, E290
In industry, the main methods of producing carbon dioxide CO2 are its production as a by-product of the reaction of converting methane CH4 into hydrogen H2, combustion reactions (oxidation) of hydrocarbons, the reaction of decomposition of limestone CaCO3 into lime CaO and water H20.
CO2 as a by-product of steam reforming of CH4 and other hydrocarbons into hydrogen H2
Hydrogen H2 is required by industry, primarily for its use in the process of producing ammonia NH3 (Haber process, catalytic reaction of hydrogen and nitrogen); Ammonia is needed for the production of mineral fertilizers and nitric acid. Hydrogen can be produced in different ways, including the electrolysis of water, which is beloved by ecologists - however, unfortunately, at this time, all methods of producing hydrogen, except for reforming hydrocarbons, are absolutely economically unjustified on the scale of large-scale production - unless there is an excess of “free” materials in production. electricity. Therefore, the main method of producing hydrogen, during which carbon dioxide is also released, is steam reforming of methane: at a temperature of about 700...1100°C and a pressure of 3...25 bar, in the presence of a catalyst, water vapor H2O reacts with methane CH4 with the release of synthesis gas (the process is endothermic, that is, it occurs with the absorption of heat):
CH4 + H2O (+ heat) → CO + 3H2
Propane can be steam reformed in a similar way:
С3H8 + 3H2O (+ heat) → 2CO + 7H2
And also ethanol (ethyl alcohol):
C2H5OH + H2O (+ heat) → 2CO + 4H2
Even gasoline can be steam reformed. Gasoline contains more than 100 different chemical compounds, the steam reforming reactions of isooctane and toluene are shown below:
C8H18 + 8H2O (+ heat) → 8CO + 17H2
C7H8 + 7H2O (+ heat) → 7CO + 11H2
So, in the process of steam reforming of one or another hydrocarbon fuel, hydrogen and carbon monoxide CO (carbon monoxide) are obtained. In the next step of the hydrogen production process, carbon monoxide, in the presence of a catalyst, undergoes the reaction of moving an oxygen atom O from water to gas = CO is oxidized to CO2, and hydrogen H2 is released in free form. The reaction is exothermic, releasing about 40.4 kJ/mol of heat:
CO + H2O → CO2 + H2 (+ heat)
In industrial settings, carbon dioxide CO2 released during steam reforming of hydrocarbons can be easily isolated and collected. However, CO2 in this case is an undesirable by-product, simply releasing it freely into the atmosphere, although now the prevailing way of getting rid of CO2, is undesirable from an environmental point of view, and some enterprises practice more “advanced” methods, such as, for example, pumping CO2 into declining oil fields or injected into the ocean.
Production of CO2 from complete combustion of hydrocarbon fuels
When burned, that is, oxidized with a sufficient amount of oxygen, hydrocarbons such as methane, propane, gasoline, kerosene, diesel fuel, etc., carbon dioxide and, usually, water are formed. For example, the combustion reaction of CH4 methane looks like this:
CH 4 + 2O 2 → CO 2 + 2H 2 O
CO2 as a by-product of H2 production by partial oxidation of fuel
About 95% of the world's industrially produced hydrogen is produced by the above-described method of steam reforming of hydrocarbon fuels, primarily CH4 methane contained in natural gas. In addition to steam reforming, hydrogen can be produced from hydrocarbon fuel with fairly high efficiency by the method of partial oxidation, when methane and other hydrocarbons react with an amount of oxygen insufficient for complete combustion of the fuel (remember that in the process of complete combustion of fuel, briefly described just above, carbon dioxide is obtained CO2 gas and H20 water). When a smaller than stoichiometric amount of oxygen is supplied, the reaction products are predominantly hydrogen H2 and carbon monoxide, also known as carbon monoxide CO; carbon dioxide CO2 and some other substances are produced in small quantities. Since usually, in practice, this process is carried out not with purified oxygen, but with air, there is nitrogen at both the input and output of the process, which does not participate in the reaction.
Partial oxidation is an exothermic process, meaning the reaction produces heat. Partial oxidation typically proceeds much faster than steam reforming and requires a smaller reactor volume. As can be seen from the reactions below, partial oxidation initially produces less hydrogen per unit of fuel than is produced by the steam reforming process.
Reaction of partial oxidation of methane CH4:
CH 4 + ½O 2 → CO + H 2 (+ heat)
Propane C3H8:
C 3 H 8 + 1½O 2 → 3CO + 4H 2 (+ heat)
Ethyl alcohol C2H5OH:
C 2 H 5 OH + ½O 2 → 2CO + 3H 2 (+ heat)
Partial oxidation of gasoline using the example of isooctane and toluene, from more than a hundred chemical compounds present in gasoline:
C 8 H 18 + 4O 2 → 8CO + 9H 2 (+ heat)
C 7 H 18 + 3½O 2 → 7CO + 4H 2 (+ heat)
To convert CO into carbon dioxide and produce additional hydrogen, the oxygen shift reaction water→gas, already mentioned in the description of the steam reforming process, is used:
CO + H 2 O → CO 2 + H 2 (+ small amount of heat)
CO2 from sugar fermentation
In the production of alcoholic beverages and baked goods from yeast dough, the process of fermentation of sugars is used - glucose, fructose, sucrose, etc., with the formation of ethyl alcohol C2H5OH and carbon dioxide CO2. For example, the fermentation reaction of glucose C6H12O6 is:
C 6 H 12 O 6 → 2C 2 H 5 OH + 2CO 2
And the fermentation of fructose C12H22O11 looks like this:
C 12 H 22 O 11 + H 2 O → 4C 2 H 5 OH + 4CO 2
Equipment for the production of CO2 manufactured by Wittemann
In the production of alcoholic beverages, the resulting alcohol is a desirable and even, one might say, necessary product of the fermentation reaction. Carbon dioxide is sometimes released into the atmosphere, and sometimes left in the drink to carbonate it. In bread baking, the opposite happens: CO2 is needed to form bubbles that cause the dough to rise, and ethyl alcohol evaporates almost completely during baking.
Many enterprises, primarily distilleries, for which CO 2 is a completely unnecessary by-product, have established its collection and sale. Gas from the fermentation tanks is supplied through alcohol traps to the carbon dioxide shop, where the CO2 is purified, liquefied and bottled. Actually, it is distilleries that are the main suppliers of carbon dioxide in many regions - and for many of them, the sale of carbon dioxide is by no means the last source of income.
There is a whole industry in the production of equipment for the separation of pure carbon dioxide in breweries and alcohol factories (Huppmann/GEA Brewery, Wittemann, etc.), as well as its direct production from hydrocarbon fuels. Gas suppliers such as Air Products and Air Liquide also install stations to separate CO2 and then purify it and liquefy it before filling it into cylinders.
CO2 in the production of quicklime CaO from CaCO3
The process for producing the widely used quicklime, CaO, also has carbon dioxide as a by-product of the reaction. The decomposition reaction of limestone CaCO3 is endothermic, requires a temperature of about +850°C and looks like this:
CaCO3 → CaO + CO2
If limestone (or another metal carbonate) reacts with an acid, carbon dioxide H2CO3 is released as one of the reaction products. For example, hydrochloric acid HCl reacts with limestone (calcium carbonate) CaCO3 as follows:
2HCl + CaCO 3 → CaCl 2 + H 2 CO 3
Carbonic acid is very unstable, and under atmospheric conditions it quickly decomposes into CO2 and water H2O.
(IV), carbon dioxide or carbon dioxide. It is also called carbonic anhydride. It is a completely colorless, odorless gas with a sour taste. Carbon dioxide is heavier than air and is poorly soluble in water. At temperatures below - 78 degrees Celsius, it crystallizes and becomes like snow.
This substance goes from a gaseous state to a solid, since it cannot exist in a liquid state under atmospheric pressure. The density of carbon dioxide under normal conditions is 1.97 kg/m3 - 1.5 times higher. Carbon dioxide in solid form is called “dry ice”. It becomes a liquid state in which it can be stored for a long time when the pressure increases. Let's take a closer look at this substance and its chemical structure.
Carbon dioxide, whose formula is CO2, consists of carbon and oxygen, and it is obtained as a result of the combustion or decay of organic substances. Carbon monoxide is found in the air and underground mineral springs. Humans and animals also emit carbon dioxide when they exhale. Plants without light release it and intensively absorb it during photosynthesis. Thanks to the metabolic process of the cells of all living beings, carbon monoxide is one of the main components of the surrounding nature.
This gas is not toxic, but if it accumulates in high concentrations, suffocation (hypercapnia) can begin, and with its deficiency, the opposite condition develops - hypocapnia. Carbon dioxide transmits and reflects infrared. It is which directly affects global warming. This is due to the fact that the level of its content in the atmosphere is constantly increasing, which leads to the greenhouse effect.
Carbon dioxide is produced industrially from smoke or furnace gases, or by the decomposition of dolomite and limestone carbonates. The mixture of these gases is thoroughly washed with a special solution consisting of potassium carbonate. Next, it turns into bicarbonate and decomposes when heated, resulting in the release of carbon dioxide. Carbon dioxide (H2CO3) is formed from carbon dioxide dissolved in water, but in modern conditions it is also obtained by other, more advanced methods. After the carbon dioxide is purified, it is compressed, cooled and pumped into cylinders.
In industry, this substance is widely and universally used. Food producers use it as a leavening agent (for example, for making dough) or as a preservative (E290). With the help of carbon dioxide, various tonic drinks and sodas are produced, which are so loved not only by children, but also by adults. Carbon dioxide is used in the production of baking soda, beer, sugar, and sparkling wines.
Carbon dioxide is also used in the production of effective fire extinguishers. With the help of carbon dioxide, an active medium is created, which is necessary at high temperatures of the welding arc, carbon dioxide breaks down into oxygen and carbon monoxide. Oxygen interacts with liquid metal and oxidizes it. Carbon dioxide in cans is used in air guns and pistols.
Aircraft modelers use this substance as fuel for their models. With the help of carbon dioxide, you can significantly increase the yield of crops grown in a greenhouse. It is also widely used in industry in which food products are preserved much better. It is used as a refrigerant in refrigerators, freezers, electric generators and other thermal power plants.
Carbon dioxide, carbon monoxide, carbon dioxide - all these are names for one substance known to us as carbon dioxide. So what properties does this gas have, and what are its areas of application?
Carbon dioxide and its physical properties
Carbon dioxide consists of carbon and oxygen. The formula for carbon dioxide looks like this – CO₂. In nature, it is formed during the combustion or decay of organic substances. The gas content in the air and mineral springs is also quite high. In addition, humans and animals also emit carbon dioxide when they exhale.
Rice. 1. Carbon dioxide molecule.
Carbon dioxide is a completely colorless gas and cannot be seen. It also has no smell. However, with high concentrations, a person may develop hypercapnia, that is, suffocation. Lack of carbon dioxide can also cause health problems. As a result of a lack of this gas, the opposite condition to suffocation can develop - hypocapnia.
If you place carbon dioxide in low temperature conditions, then at -72 degrees it crystallizes and becomes like snow. Therefore, carbon dioxide in a solid state is called “dry snow.”
Rice. 2. Dry snow – carbon dioxide.
Carbon dioxide is 1.5 times denser than air. Its density is 1.98 kg/m³. The chemical bond in the carbon dioxide molecule is polar covalent. It is polar due to the fact that oxygen has a higher electronegativity value.
An important concept in the study of substances is molecular and molar mass. The molar mass of carbon dioxide is 44. This number is formed from the sum of the relative atomic masses of the atoms that make up the molecule. The values of relative atomic masses are taken from the table of D.I. Mendeleev and are rounded to whole numbers. Accordingly, the molar mass of CO₂ = 12+2*16.
To calculate the mass fractions of elements in carbon dioxide, it is necessary to follow the formula for calculating the mass fractions of each chemical element in a substance.
n– number of atoms or molecules.
A r– relative atomic mass of a chemical element.
Mr– relative molecular mass of the substance.
Let's calculate the relative molecular mass of carbon dioxide.
Mr(CO₂) = 14 + 16 * 2 = 44 w(C) = 1 * 12 / 44 = 0.27 or 27% Since the formula of carbon dioxide includes two oxygen atoms, then n = 2 w(O) = 2 * 16 / 44 = 0.73 or 73%
Answer: w(C) = 0.27 or 27%; w(O) = 0.73 or 73%
Chemical and biological properties of carbon dioxide
Carbon dioxide has acidic properties because it is an acidic oxide, and when dissolved in water it forms carbonic acid:
CO₂+H₂O=H₂CO₃
Reacts with alkalis, resulting in the formation of carbonates and bicarbonates. This gas does not burn. Only certain active metals, such as magnesium, burn in it.
When heated, carbon dioxide breaks down into carbon monoxide and oxygen:
2CO₃=2CO+O₃.
Like other acidic oxides, this gas easily reacts with other oxides:
СaO+Co₃=CaCO₃.
Carbon dioxide is part of all organic substances. The circulation of this gas in nature is carried out with the help of producers, consumers and decomposers. In the process of life, a person produces approximately 1 kg of carbon dioxide per day. When we inhale, we receive oxygen, but at this moment carbon dioxide is formed in the alveoli. At this moment, an exchange occurs: oxygen enters the blood, and carbon dioxide comes out.
Carbon dioxide is produced during the production of alcohol. This gas is also a by-product in the production of nitrogen, oxygen and argon. The use of carbon dioxide is necessary in the food industry, where carbon dioxide acts as a preservative, and carbon dioxide in liquid form is found in fire extinguishers.