On an industrial scale, carbon dioxide can be obtained in the following ways:
- from limestone, which contains up to 40% CO 2, coke or anthracite up to 18% CO 2 by firing them in special furnaces;
- in installations operating using the sulfuric acid method due to reactions of interaction of sulfuric acid with chalk emulsion;
- from gases formed during the fermentation of alcohol, beer, and the breakdown of fats;
- from the flue gases of industrial boilers burning coal, natural gas and other fuels. Flue gas contains 12-20% CO 2;
- from waste gases of chemical production, primarily synthetic ammonia and methanol. The exhaust gases contain approximately 90% CO 2 .
For now The most common way to obtain carbon dioxide is from gases during fermentation. The waste gas in these cases is almost pure carbon dioxide and is a cheap by-product of production.
In hydrolysis plants, during the fermentation of yeast with sawdust, gases containing 99% CO 2 are released.
1 - fermentation tank; 2 - gas tank; 3 - washing tower; 4 - pre-compressor; 5 - tubular refrigerator; 6 - oil separator; 7 - tower; 8 - tower; 9 - two-stage compressor; 10 - refrigerator; 11 - oil separator; 12 - tank.
Scheme for producing carbon dioxide at hydrolysis plants
Gas from fermentation tank 1 is supplied by pumps, and if there is sufficient pressure, it enters gas tank 2 on its own, where solid particles are separated from it. Then the gas enters the washing tower 3, filled with coke or ceramic rings, where it is washed by a counter flow of water and is finally freed from solid particles and water-soluble impurities. After washing, the gas enters the pre-compressor 4, where it is compressed to a pressure of 400-550 kPa.
Since during compression the temperature of carbon dioxide rises to 90-100°C, after the compressor the gas enters the tubular refrigerator 5, where it is cooled to 15°C. Then the carbon dioxide is sent to the oil separator 6, where the oil that got into the gas during compression is separated. After this, carbon dioxide is purified with aqueous solutions of oxidizing agents (KMnO 4, K 2 Cr 2 P 7, hypochromite) in tower 7, and then dried with activated carbon or silica gel in tower 8.
After cleaning and drying, carbon dioxide enters a two-stage compressor 9. At stage I, it is compressed to 1-1.2 MPa. Then carbon dioxide enters refrigerator 10, where it is cooled from 100 to 15°C, passes through oil separator 11 and enters the second stage of the compressor, where it is compressed to 6-7 MPa, converted into liquid carbon dioxide and collected in tank 12, from which refueling is carried out standard cylinders or other containers (tanks).
The most common processes for the formation of this compound are the rotting of animal and plant remains, the combustion of various types of fuel, and the respiration of animals and plants. For example, one person emits about a kilogram of carbon dioxide into the atmosphere per day. Carbon monoxide and dioxide can also be formed in inanimate nature. Carbon dioxide is released during volcanic activity and can also be produced from mineral water sources. Carbon dioxide is found in small quantities in the Earth's atmosphere.
The peculiarities of the chemical structure of this compound allow it to participate in many chemical reactions, the basis for which is carbon dioxide.
Formula
In the compound of this substance, the tetravalent carbon atom forms a linear bond with two oxygen molecules. The appearance of such a molecule can be represented as follows:
The hybridization theory explains the structure of the carbon dioxide molecule as follows: the two existing sigma bonds are formed between the sp orbitals of carbon atoms and the two 2p orbitals of oxygen; The p-orbitals of carbon, which do not take part in hybridization, are bonded in conjunction with similar orbitals of oxygen. In chemical reactions, carbon dioxide is written as: CO 2.
Physical properties
Under normal conditions, carbon dioxide is a colorless, odorless gas. It is heavier than air, which is why carbon dioxide can behave like a liquid. For example, it can be poured from one container to another. This substance is slightly soluble in water - about 0.88 liters of CO 2 dissolve in one liter of water at 20 ⁰C. A slight decrease in temperature radically changes the situation - 1.7 liters of CO 2 can dissolve in the same liter of water at 17⁰C. With strong cooling, this substance precipitates in the form of snow flakes - the so-called “dry ice” is formed. This name comes from the fact that at normal pressure the substance, bypassing the liquid phase, immediately turns into a gas. Liquid carbon dioxide is formed at a pressure just above 0.6 MPa and at room temperature.
Chemical properties
When interacting with strong oxidizing agents, 4-carbon dioxide exhibits oxidizing properties. The typical reaction of this interaction is:
C + CO 2 = 2CO.
Thus, with the help of coal, carbon dioxide is reduced to its divalent modification - carbon monoxide.
Under normal conditions, carbon dioxide is inert. But some active metals can burn in it, removing oxygen from the compound and releasing carbon gas. A typical reaction is the combustion of magnesium:
2Mg + CO 2 = 2MgO + C.
During the reaction, magnesium oxide and free carbon are formed.
In chemical compounds, CO 2 often exhibits the properties of a typical acid oxide. For example, it reacts with bases and basic oxides. The result of the reaction is carbonic acid salts.
For example, the reaction of a compound of sodium oxide with carbon dioxide can be represented as follows:
Na 2 O + CO 2 = Na 2 CO 3;
2NaOH + CO 2 = Na 2 CO 3 + H 2 O;
NaOH + CO 2 = NaHCO 3.
Carbonic acid and CO 2 solution
Carbon dioxide in water forms a solution with a small degree of dissociation. This solution of carbon dioxide is called carbonic acid. It is colorless, weakly expressed and has a sour taste.
Recording a chemical reaction:
CO 2 + H 2 O ↔ H 2 CO 3.
The equilibrium is shifted quite strongly to the left - only about 1% of the initial carbon dioxide is converted into carbonic acid. The higher the temperature, the fewer carbonic acid molecules in the solution. When the compound boils, it disappears completely, and the solution disintegrates into carbon dioxide and water. The structural formula of carbonic acid is presented below.
Properties of carbonic acid
Carbonic acid is very weak. In solutions, it breaks down into hydrogen ions H + and compounds HCO 3 -. CO 3 - ions are formed in very small quantities.
Carbonic acid is dibasic, so the salts formed by it can be medium and acidic. In the Russian chemical tradition, medium salts are called carbonates, and strong salts are called bicarbonates.
Qualitative reaction
One possible way to detect carbon dioxide gas is to change the clarity of the lime mortar.
Ca(OH) 2 + CO 2 = CaCO 3 ↓ + H 2 O.
This experience is known from a school chemistry course. At the beginning of the reaction, a small amount of white precipitate is formed, which subsequently disappears when carbon dioxide is passed through water. The change in transparency occurs because during the interaction process, an insoluble compound - calcium carbonate - is converted into a soluble substance - calcium bicarbonate. The reaction proceeds along this path:
CaCO 3 + H 2 O + CO 2 = Ca(HCO 3) 2.
Production of carbon dioxide
If you need to get a small amount of CO2, you can start the reaction of hydrochloric acid with calcium carbonate (marble). The chemical notation for this interaction looks like this:
CaCO 3 + HCl = CaCl 2 + H 2 O + CO 2.
Also for this purpose, combustion reactions of carbon-containing substances, for example acetylene, are used:
CH 4 + 2O 2 → 2H 2 O + CO 2 -.
A Kipp apparatus is used to collect and store the resulting gaseous substance.
For the needs of industry and agriculture, the scale of carbon dioxide production must be large. A popular method for this large-scale reaction is to burn limestone, which produces carbon dioxide. The reaction formula is given below:
CaCO 3 = CaO + CO 2.
Applications of carbon dioxide
The food industry, after large-scale production of “dry ice,” switched to a fundamentally new method of storing food. It is indispensable in the production of carbonated drinks and mineral water. The CO 2 content in drinks gives them freshness and significantly increases their shelf life. And carbidization of mineral waters allows you to avoid mustiness and unpleasant taste.
In cooking, the method of extinguishing citric acid with vinegar is often used. The carbon dioxide released during this process imparts fluffiness and lightness to confectionery products.
This compound is often used as a food additive to increase the shelf life of food products. According to international standards for the classification of chemical additives contained in products, it is coded E 290,
Powdered carbon dioxide is one of the most popular substances included in fire extinguishing mixtures. This substance is also found in fire extinguisher foam.
It is best to transport and store carbon dioxide in metal cylinders. At temperatures above 31⁰C, the pressure in the cylinder can reach critical and liquid CO 2 will go into a supercritical state with a sharp rise in operating pressure to 7.35 MPa. The metal cylinder can withstand internal pressure up to 22 MPa, so the pressure range at temperatures above thirty degrees is considered safe.
CO - carbon monoxide and CO2 - carbon dioxide are often confused. The names sound similar, they are both colorless and odorless gases, and in high concentrations both can be fatal. The difference is that CO2 is a common natural gas needed by all plant and animal life. CO is not common. Most often it is a by-product of oxygen-starved fuel combustion.
The media often adds to the confusion. We used to hear stories about committing suicide by inserting a garden hose into the exhaust pipe and car window, then running the engine until the CO (carbon monoxide) blew out the car's occupant. Today we are told that our car tailpipe is the main source of the "deadly" greenhouse gas CO2. It is easy to understand why they are confused.
It's helpful to understand the similarities and differences between CO and CO2:
About carbon monoxide
- CO is formed naturally in trace amounts in partial methane oxidation atmosphere, volcanoes and forest fires
- CO is formed at dangerous levels by combustion with oxygen in improperly vented fuel burning appliances such as oil and gas furnaces, gas water heaters, gas furnaces, gas or kerosene heaters, fireplaces and wood stoves
- CO is produced at dangerous levels internal combustion engine that DO NOT use a catalytic converter
- This is the most common type of fatal poisoning in the world.
- 0.1 ppm - current average CO level on the planet
- OSHA limits long-term workplace exposure levels to 50 ppm (parts per million)
- Symptoms of mild CO poisoning include headaches and dizziness at concentrations less than 100 ppm
- Concentrations up to 700 ppm can be life-threatening
About carbon dioxide
- CO2 is a common gas in the atmosphere and is required for plant life
- CO2 is a natural byproduct of human and animal respiration, fermentation, chemical reactions, and the burning of fossil fuels and wood
- CO2 is non-flammable
- CO2 is generated by internal combustion engines that DO use a catalytic converter
- CO2 poisoning is rare; however scuba divers should watch out for this (bends)
- Leaking pressurized CO2 tanks in enclosed spaces can be hazardous to occupants - both from high levels of CO2 and from relatively lower levels of oxygen (displacement)
- 400 ppm is the current average CO2 level on the planet
- ASHRAE recommends a 1,000 ppm limit for office buildings and classrooms
- OSHA limits long-term workplace exposure levels to 5,000 ppm
- Drowsiness may occur at 10,000 ppm - common in closed cars or auditoriums
- Symptoms of mild CO2 poisoning include headaches and dizziness at concentrations less than 30,000 ppm (3%)
- At 80,000 ppm (8%) CO2 can be life-threatening
What are the similarities between CO and CO2?
- Carbon and oxygen combine to form both gases
- Both are colorless, tasteless and odorless
- Both are found in the air around the world (albeit in different concentrations)
- Both are released during combustion or fire
Understanding PPM - parts per million
Parts per million (ppm or ppmv) is how scientists measure small amounts of gas molecules in the air, since the number of gas molecules in a volume is significantly less than 1%. Instead of saying "1% gas by volume", scientists will say "10,000 ppmv" (10,000 / 1,000,000 = 1%) or shorten it to "10,000 ppm".
For example, it is easier to write that the CO2 level in a room increased from 400 ppm to 859 ppm than to write that the CO2 level increased from 0.04% to 0.0859%. However, both of them are true.
How monoxide and dioxide got their names
You can thank the ancient Greeks for giving us their names for numbers:
Mono = 1
di = 2
tri = 3
tetra = 4
penta = 5
hexa = 6
hepta = 7
octa = 8
ennea = 9
deca = 10
This is how we get English words like three corner (3 sides), US Penta gon (one-sided 5) or soundboard thlon (10 competitions). So first half mono xide means oxygen atom 1 and the first half di oxide means oxygen atoms 2.
For the second half of the word we have oxide An oxide is the name for a simple compound of oxygen with another element or group. For example, add oxygen to the element hydrogen and you get hydrogen di oxide(H20) or water. Other oxides you may have heard of are nitrous oxide (NO2 - laughing gas) or zinc oxide (ZnO - the active ingredient in sunscreen).
The content of the article
CARBON DIOXIDE(carbon(IV) monoxide, carbonic anhydride, carbon dioxide) CO 2 , a well-known bubbly ingredient in carbonated soft drinks. Man has known about the healing properties of “fizzy water” from natural sources since time immemorial, but only in the 19th century. I learned to get it myself. At the same time, the substance that makes water effervescent was identified - carbon dioxide. For the first time for carbonization purposes, this gas was obtained in 1887 during the reaction between crushed marble and sulfuric acid; it was also isolated from natural sources. Later, CO 2 began to be produced on an industrial scale by burning coke, calcining limestone and fermenting alcohol. For more than a quarter of a century, carbon dioxide was stored in pressurized steel cylinders and used almost exclusively to carbonate drinks. In 1923, solid CO 2 (dry ice) began to be produced as a commercial product, and around 1940, liquid CO 2 was produced, which was poured into special sealed tanks under high pressure.
Physical properties.
At normal temperatures and pressures, carbon dioxide is a colorless gas with a slightly sour taste and odor. It is 50% heavier than air, so it can be poured from one container to another. CO 2 is a product of most combustion processes and, in sufficiently large quantities, can extinguish flames by displacing oxygen from the air. When the concentration of CO 2 increases in a poorly ventilated room, the oxygen content in the air decreases so much that a person can suffocate. CO 2 dissolves in many liquids; solubility depends on the properties of the liquid, temperature and CO 2 vapor pressure. The ability of carbon dioxide to dissolve in water determines its widespread use in the production of soft drinks. CO 2 is highly soluble in organic solvents, such as alcohol, acetone and benzene.
With increasing pressure and cooling, carbon dioxide easily liquefies and is in a liquid state at temperatures from +31 to –57 ° C (depending on pressure). Below –57°C it turns into a solid state (dry ice). The pressure required for liquefaction depends on the temperature: at +21° C it is 60 atm, and at –18° C it is only 20 atm. Liquid CO 2 is stored in sealed containers under appropriate pressure. When it passes into the atmosphere, part of it turns into gas, and some into “carbon snow,” while its temperature drops to –84 ° C.
Absorbing heat from the environment, dry ice passes into a gaseous state, bypassing the liquid phase - sublimates. To reduce sublimation losses, it is stored and transported in sealed containers that are strong enough to withstand the increase in pressure as the temperature rises.
Chemical properties.
CO 2 is a low-active compound. When dissolved in water, it forms weak carbonic acid, which turns litmus paper red. Carbonic acid improves the taste of carbonated drinks and prevents the growth of bacteria. Reacting with alkali and alkaline earth metals, as well as with ammonia, CO 2 forms carbonates and bicarbonates.
Prevalence in nature and production.
CO 2 is formed during the combustion of carbon-containing substances, alcoholic fermentation, and the rotting of plant and animal residues; it is released when animals breathe, and it is released by plants in the dark. In the light, on the contrary, plants absorb CO 2 and release oxygen, which maintains the natural balance of oxygen and carbon dioxide in the air we breathe. The CO 2 content in it does not exceed 0.03% (by volume).
There are five main ways to produce CO 2: combustion of carbon-containing substances (coke, natural gas, liquid fuel); formation as a by-product during ammonia synthesis; calcination of limestone; fermentation; pumping from wells. In the last two cases, almost pure carbon dioxide is obtained, and when burning carbon-containing substances or calcining limestone, a mixture of CO 2 with nitrogen and traces of other gases is formed. This mixture is passed through a solution that absorbs only CO 2 . Then the solution is heated and almost pure CO 2 is obtained, which is separated from the remaining impurities. Water vapor is removed by freezing and chemical drying.
The purified CO 2 is liquefied by cooling it at high pressure and stored in large containers. To produce dry ice, liquid CO 2 is fed into a closed chamber of a hydraulic press, where the pressure is reduced to atmospheric pressure. With a sharp decrease in pressure, loose snow and very cold gas are formed from CO 2. The snow is compressed and dry ice is obtained. CO 2 gas is pumped out, liquefied and returned to the storage tank.
APPLICATION
Receiving low temperatures.
In liquid and solid form, CO 2 is used mainly as a refrigerant. Dry ice is a compact material, easy to handle and allows you to create different temperature conditions. With the same mass, it is more than twice as cold as ordinary ice, occupying half the volume. Dry ice is used in food storage. It is used to cool champagne, soft drinks and ice cream. It is widely used in the “cold grinding” of heat-sensitive materials (meat products, resins, polymers, dyes, insecticides, paints, seasonings); when tumbling (cleaning from burrs) stamped rubber and plastic products; during low-temperature testing of aircraft and electronic devices in special chambers; for “cold mixing” of semi-finished muffins and cakes so that they remain homogeneous during baking; for rapid cooling of containers with transported products by blowing them with a stream of crushed dry ice; when hardening alloy and stainless steels, aluminum, etc. in order to improve their physical properties; for tight fit of machine parts during their assembly; for cooling cutters when processing high-strength steel workpieces.
Carbonization.
The main application of CO 2 gas is the carbonation of water and soft drinks. First, water and syrup are mixed in the required proportions, and then the mixture is saturated with CO 2 gas under pressure. Carbonation in beers and wines usually occurs as a result of chemical reactions occurring in them.
Applications based on inertia.
CO 2 is used as an antioxidant during long-term storage of many food products: cheese, meat, milk powder, nuts, instant tea, coffee, cocoa, etc. As a combustion suppressant, CO 2 is used in the storage and transportation of flammable materials, such as rocket fuel, oils, gasoline, paints, varnishes, and solvents. It is used as a protective medium in electric welding of carbon steels in order to obtain a uniform, strong weld, while welding work is cheaper than when using inert gases.
CO 2 is one of the most effective means of extinguishing fires that occur when flammable liquids ignite and electrical breakdowns. Various carbon dioxide fire extinguishers are produced: from portable ones with a capacity of no more than 2 kg to stationary automatic supply units with a total cylinder capacity of up to 45 kg or low-pressure gas tanks with a capacity of up to 60 tons of CO 2. Liquid CO 2, which is under pressure in such fire extinguishers, when released, forms a mixture of snow and cold gas; the latter has a higher density than air and displaces it from the combustion zone. The effect is also enhanced by the cooling effect of snow, which, evaporating, turns into gaseous CO 2.
Chemical aspects.
Carbon dioxide is used in the production of aspirin, white lead, urea, perborates, and chemically pure carbonates. Carbonic acid, formed when CO 2 is dissolved in water, is an inexpensive reagent for neutralizing alkalis. In foundries, carbon dioxide is used to cure sand molds by reacting CO 2 with sodium silicate mixed with sand. This allows you to obtain higher quality castings. Refractory bricks used to line furnaces for smelting steel, glass and aluminum become more durable after treatment with carbon dioxide. CO 2 is also used in urban water softening systems using soda lime.
Creation of increased pressure.
CO 2 is used for pressure testing and leak testing of various containers, as well as for calibrating pressure gauges, valves, and spark plugs. It is used to fill portable containers for inflating life belts and inflatable boats. A mixture of carbon dioxide and nitrous oxide has long been used to pressurize aerosol cans. CO 2 is injected under pressure into sealed containers with ether (in devices for quick engine starting), solvents, paints, insecticides for subsequent spraying of these substances.
Application in medicine.
CO 2 is added in small quantities to oxygen (to stimulate breathing) and during anesthesia. In high concentrations it is used for the humane killing of animals.
(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.
