Co2 in solid state. Carbon dioxide (carbon dioxide)

Carbon dioxide CO 2(carbon dioxide, carbon dioxide, carbon dioxide, carbonic anhydride) depending on pressure and temperature can be in a gaseous, liquid or solid state.

In its gaseous state, carbon dioxide is a colorless gas with a slightly sour taste and odor. The Earth's atmosphere contains about 0.04% carbon dioxide. Under normal conditions, its density is 1.98 g/l - approximately 1.5 times the density of air.

Diagram. Phase equilibrium of carbon dioxide

Liquid carbon dioxide (carbon dioxide) is a colorless, odorless liquid. At room temperature it exists only at pressures above 5850 kPa. The density of liquid carbon dioxide is highly dependent on temperature. For example, at temperatures below +11°C, liquid carbon dioxide is heavier than water; at temperatures above +11°C, it is lighter. As a result of the evaporation of 1 kg of liquid carbon dioxide under normal conditions, approximately 509 liters of gas are formed.

At a temperature of about -56.6 ° C and a pressure of about 519 kPa, liquid carbon dioxide turns into a solid - "dry ice".

In industry, there are 3 most common ways to produce carbon dioxide:

from waste gases of chemical production, primarily synthetic ammonia and methanol; the exhaust gas contains approximately 90% carbon dioxide;
from flue gases of industrial boiler houses burning natural gas, coal and other fuels; flue gas contains 12-20% carbon dioxide;
from waste gases formed during fermentation in the process of producing beer, alcohol, and during the breakdown of fats; the exhaust gas is almost pure carbon dioxide.

According to GOST 8050-85, gaseous and liquid carbon dioxide is supplied in three types: premium, first and second grade. For welding, it is recommended to use carbon dioxide of the highest and first grade. The use of second grade carbon dioxide for welding is allowed, but the presence of gas dryers is desirable. The permissible content of carbon dioxide and some impurities in various brands of carbon dioxide is given in the table below.

Table. Characteristics of carbon dioxide brands

Safety precautions when working with carbon dioxide:

Carbon dioxide is not toxic and not explosive, however, when its concentration in the air exceeds 5% (92 g/m3), the proportion of oxygen decreases, which can lead to oxygen deficiency and suffocation. Therefore, you should be wary of its accumulation in poorly ventilated areas. To record the concentration of carbon dioxide in the air of industrial premises, gas analyzers are used - stationary automatic or portable.
When the pressure decreases to atmospheric pressure, liquid carbon dioxide turns into gas and snow with a temperature of -78.5°C and can lead to damage to the mucous membrane of the eyes and frostbite of the skin. Therefore, when taking samples of liquid carbon dioxide, it is necessary to use protective glasses and gloves.
Inspection of the internal container of a previously used tank for storing and transporting liquid carbon dioxide must be carried out using a hose gas mask. The tank must be warmed to ambient temperature, and the internal container must be purged with air or ventilated. The gas mask may not be used until the volume fraction of carbon dioxide inside the equipment drops below 0.5%.

Use of carbon dioxide in welding

Carbon dioxide is used as an active shielding gas for arc welding(usually in semi-automatic welding) with a consumable electrode (wire), including as part of a gas mixture (with oxygen, argon).

Welding stations can be supplied with carbon dioxide in the following ways:

directly from an autonomous carbon dioxide production station;
from a stationary storage vessel - with significant volumes of carbon dioxide consumption and the enterprise does not have its own autonomous station;
from the transport carbon dioxide tank - with smaller volumes of carbon dioxide consumption;
from cylinders - when the volume of carbon dioxide used is insignificant or it is impossible to lay pipelines to the welding station.

An autonomous station for the production of carbon dioxide is a separate specialized workshop of an enterprise that produces carbon dioxide for its own needs and for supply to other organizations. Carbon dioxide is supplied to welding stations through gas pipelines laid in welding shops.

In case of large volumes of carbon dioxide consumption and the enterprise does not have an autonomous station, carbon dioxide is stored in stationary storage vessels into which it comes from transport tanks (see figure below).

Drawing. Scheme of supplying welding stations with carbon dioxide from a stationary storage vessel

For smaller consumption volumes, carbon dioxide can be supplied through pipelines directly from the transport tank. The characteristics of some stationary and transport containers are shown in the table below.

Table. Characteristics of containers for storing and transporting carbon dioxide (carbon dioxide)

Brand	Mass of carbon dioxide, kg	Purpose	Carbon dioxide storage time, days	Gasifier brand
TsZHU-3.0-2.0	2 950	Transport automobile ZIL-130	6-20	EGU-100
NZHU-4-1.6	4 050	Stationary storage	6-20	EGU-100
TsZHU-9.0-1.8	9 000	Transport automobile MAZ 5245	6-20	GU-400
NZHU-12.5-1.6	12 800	Stationary storage	6-20	GU-400
UDH-12.5	12 300	Stationary storage		UGM-200M
TsZHU-40-2	39 350	Transport railway	40	GU-400
RDH-25-2	25 500	Stationary storage	Unlimited, equipped with refrigeration unit	GU-400
NZHU-50D	50 000	Stationary storage	Unlimited, equipped with refrigeration unit	GU-400

When the volume of carbon dioxide consumption is small or it is impossible to lay pipelines to the welding stations, cylinders are used to supply carbon dioxide. A standard black cylinder with a capacity of 40 liters is filled with 25 kg of liquid carbon dioxide, which is usually stored at a pressure of 5-6 MPa. As a result of the evaporation of 25 kg of liquid carbon dioxide, approximately 12,600 liters of gas are formed. The diagram for storing carbon dioxide in a cylinder is shown in the figure below.

Drawing. Scheme of storing carbon dioxide (carbon dioxide) in a cylinder

To extract gas from a cylinder, it must be equipped with a reducer, a gas heater and a gas dryer. When carbon dioxide leaves the cylinder as a result of its expansion, adiabatic cooling of the gas occurs. At high gas flow rates (more than 18 l/min), this can lead to freezing of the water vapor contained in the gas and blockage of the reducer. In this regard, it is advisable to place a gas heater between the reducer and the cylinder valve. As gas passes through the coil, it is heated by an electric heating element connected to a 24 or 36 V network.

A gas dryer is used to extract moisture from carbon dioxide. It is a housing filled with a material (usually silica gel, copper sulfate or aluminum gel) that absorbs moisture well. Dryers come in high pressure, installed before the reducer, and low pressure, installed after the reducer.

Soda, volcano, Venus, refrigerator - what do they have in common? Carbon dioxide. We have collected for you the most interesting information about one of the most important chemical compounds on Earth.

What is carbon dioxide

Carbon dioxide is known mainly in its gaseous state, i.e. as carbon dioxide with the simple chemical formula CO2. In this form, it exists under normal conditions - at atmospheric pressure and “ordinary” temperatures. But at increased pressure, above 5,850 kPa (such as, for example, the pressure at a sea depth of about 600 m), this gas turns into liquid. And when strongly cooled (minus 78.5°C), it crystallizes and becomes so-called dry ice, which is widely used in trade for storing frozen foods in refrigerators.

Liquid carbon dioxide and dry ice are produced and used in human activities, but these forms are unstable and easily disintegrate.

But carbon dioxide gas is ubiquitous: it is released during the respiration of animals and plants and is an important part of the chemical composition of the atmosphere and ocean.

Properties of carbon dioxide

Carbon dioxide CO2 is colorless and odorless. Under normal conditions it has no taste. However, if you inhale high concentrations of carbon dioxide, you may experience a sour taste in your mouth, caused by the carbon dioxide dissolving on mucous membranes and in saliva, forming a weak solution of carbonic acid.

By the way, it is the ability of carbon dioxide to dissolve in water that is used to make carbonated water. Lemonade bubbles are the same carbon dioxide. The first apparatus for saturating water with CO2 was invented back in 1770, and already in 1783, the enterprising Swiss Jacob Schweppes began industrial production of soda (the Schweppes brand still exists).

Carbon dioxide is 1.5 times heavier than air, so it tends to “settle” in its lower layers if the room is poorly ventilated. The “dog cave” effect is known, where CO2 is released directly from the ground and accumulates at a height of about half a meter. An adult, entering such a cave, at the height of his growth does not feel the excess of carbon dioxide, but dogs find themselves directly in a thick layer of carbon dioxide and are poisoned.

CO2 does not support combustion, which is why it is used in fire extinguishers and fire suppression systems. The trick of extinguishing a burning candle with the contents of a supposedly empty glass (but in fact carbon dioxide) is based precisely on this property of carbon dioxide.

Carbon dioxide in nature: natural sources

Carbon dioxide is formed in nature from various sources:

Respiration of animals and plants.
Every schoolchild knows that plants absorb carbon dioxide CO2 from the air and use it in the processes of photosynthesis. Some housewives try to make up for shortcomings with an abundance of indoor plants. However, plants not only absorb, but also release carbon dioxide in the absence of light - this is part of the respiration process. Therefore, a jungle in a poorly ventilated bedroom is not a good idea: CO2 levels will rise even more at night.
Volcanic activity.
Carbon dioxide is part of volcanic gases. In areas with high volcanic activity, CO2 can be released directly from the ground - from cracks and fissures called mofets. The concentration of carbon dioxide in valleys with mofets is so high that many small animals die when they get there.
Decomposition of organic matter.
Carbon dioxide is formed during the combustion and decay of organic matter. Large natural emissions of carbon dioxide accompany forest fires.

Carbon dioxide is “stored” in nature in the form of carbon compounds in minerals: coal, oil, peat, limestone. Huge reserves of CO2 are found in dissolved form in the world's oceans.

The release of carbon dioxide from an open reservoir can lead to a limnological disaster, as happened, for example, in 1984 and 1986. in lakes Manoun and Nyos in Cameroon. Both lakes were formed on the site of volcanic craters - now they are extinct, but in the depths the volcanic magma still releases carbon dioxide, which rises to the waters of the lakes and dissolves in them. As a result of a number of climatic and geological processes, the concentration of carbon dioxide in waters exceeded a critical value. A huge amount of carbon dioxide was released into the atmosphere, which went down the mountain slopes like an avalanche. About 1,800 people became victims of limnological disasters on Cameroonian lakes.

Artificial sources of carbon dioxide

The main anthropogenic sources of carbon dioxide are:

industrial emissions associated with combustion processes;
road transport.

Despite the fact that the share of environmentally friendly transport in the world is growing, the vast majority of the world's population will not soon have the opportunity (or desire) to switch to new cars.

Active deforestation for industrial purposes also leads to an increase in the concentration of carbon dioxide CO2 in the air.

CO2 is one of the end products of metabolism (the breakdown of glucose and fats). It is secreted in the tissues and transported by hemoglobin to the lungs, through which it is exhaled. The air exhaled by humans contains about 4.5% carbon dioxide (45,000 ppm) - 60-110 times more than in the air inhaled.

Carbon dioxide plays a large role in regulating blood flow and respiration. An increase in CO2 levels in the blood causes the capillaries to dilate, allowing more blood to pass through, which delivers oxygen to the tissues and removes carbon dioxide.

The respiratory system is also stimulated by an increase in carbon dioxide, and not by a lack of oxygen, as it might seem. In reality, the lack of oxygen is not felt by the body for a long time and it is quite possible that in rarefied air a person will lose consciousness before he feels the lack of air. The stimulating property of CO2 is used in artificial respiration devices: where carbon dioxide is mixed with oxygen to “start” the respiratory system.

Carbon dioxide and us: why CO2 is dangerous

Carbon dioxide is necessary for the human body just like oxygen. But just like with oxygen, an excess of carbon dioxide harms our well-being.

A high concentration of CO2 in the air leads to intoxication of the body and causes a state of hypercapnia. With hypercapnia, a person experiences difficulty breathing, nausea, headache, and may even lose consciousness. If the carbon dioxide content does not decrease, then oxygen starvation occurs. The fact is that both carbon dioxide and oxygen move throughout the body on the same “transport” - hemoglobin. Normally, they “travel” together, attaching to different places on the hemoglobin molecule. However, increased concentrations of carbon dioxide in the blood reduce the ability of oxygen to bind to hemoglobin. The amount of oxygen in the blood decreases and hypoxia occurs.

Such unhealthy consequences for the body occur when inhaling air with a CO2 content of more than 5,000 ppm (this can be the air in mines, for example). To be fair, in ordinary life we practically never encounter such air. However, a much lower concentration of carbon dioxide does not have the best effect on health.

According to some findings, even 1,000 ppm CO2 causes fatigue and headaches in half of the subjects. Many people begin to feel stuffiness and discomfort even earlier. With a further increase in carbon dioxide concentration to 1,500 – 2,500 ppm critically, the brain is “lazy” to take the initiative, process information and make decisions.

And if a level of 5,000 ppm is almost impossible in everyday life, then 1,000 and even 2,500 ppm can easily be part of the reality of modern man. Ours showed that in rarely ventilated school classrooms, CO2 levels remain above 1,500 ppm much of the time, and sometimes jump above 2,000 ppm. There is every reason to believe that the situation is similar in many offices and even apartments.

Physiologists consider 800 ppm to be a safe level of carbon dioxide for human well-being.

Another study found a link between CO2 levels and oxidative stress: the higher the carbon dioxide level, the more we suffer from oxidative stress, which damages our body's cells.

Carbon dioxide in the Earth's atmosphere

There is only about 0.04% CO2 in the atmosphere of our planet (this is approximately 400 ppm), and more recently it was even less: carbon dioxide crossed the 400 ppm mark only in the fall of 2016. Scientists attribute the rise in CO2 levels in the atmosphere to industrialization: in the mid-18th century, on the eve of the Industrial Revolution, it was only about 270 ppm.

, carbon dioxide, properties of carbon dioxide, production of carbon dioxide

It is not suitable for supporting life. However, it is this that plants “feed” on, turning it into organic substances. In addition, it is a kind of “blanket” for the Earth. If this gas suddenly disappeared from the atmosphere, the Earth would become much cooler and rain would virtually disappear.

"Blanket of the Earth"

(carbon dioxide, carbon dioxide, CO 2) is formed when two elements combine: carbon and oxygen. It is formed during the combustion of coal or hydrocarbon compounds, during the fermentation of liquids, and also as a product of the respiration of people and animals. It is also found in small quantities in the atmosphere, from where it is assimilated by plants, which, in turn, produce oxygen.

Carbon dioxide is colorless and heavier than air. Freezes at −78.5°C to form snow consisting of carbon dioxide. In aqueous solution it forms carbonic acid, but it is not stable enough to be easily isolated.

Carbon dioxide is the Earth's blanket. It easily transmits ultraviolet rays that heat our planet and reflects infrared rays emitted from its surface into outer space. And if carbon dioxide suddenly disappears from the atmosphere, this will primarily affect the climate. It will become much cooler on Earth, and rain will fall very rarely. It’s not hard to guess where this will ultimately lead.

True, such a catastrophe does not yet threaten us. Quite the contrary. The combustion of organic substances: oil, coal, natural gas, wood - gradually increases the carbon dioxide content in the atmosphere. This means that over time we must expect significant warming and humidification of the earth’s climate. By the way, old-timers believe that it is already noticeably warmer than it was in the days of their youth...

Carbon dioxide is released liquid low temperature, high pressure liquid And gaseous. It is obtained from waste gases from ammonia and alcohol production, as well as from special fuel combustion and other industries. Gaseous carbon dioxide is a colorless and odorless gas at a temperature of 20 ° C and a pressure of 101.3 kPa (760 mm Hg), density - 1.839 kg / m 3. Liquid carbon dioxide is simply a colorless, odorless liquid.

Non-toxic and non-explosive. At concentrations of more than 5% (92 g/m3), carbon dioxide has a harmful effect on human health - it is heavier than air and can accumulate in poorly ventilated areas near the floor. This reduces the volume fraction of oxygen in the air, which can cause oxygen deficiency and suffocation.

Producing carbon dioxide

In industry, carbon dioxide is obtained from furnace gases, from decomposition products of natural carbonates(limestone, dolomite). The mixture of gases is washed with a solution of potassium carbonate, which absorbs carbon dioxide, turning into bicarbonate. When heated, the bicarbonate solution decomposes, releasing carbon dioxide. During industrial production, gas is pumped into cylinders.

In laboratory conditions small amounts are obtained interaction of carbonates and bicarbonates with acids, for example, marble with hydrochloric acid.

"Dry ice" and other beneficial properties of carbon dioxide

Carbon dioxide is used quite widely in everyday practice. For example, sparkling water with the addition of aromatic essences - a wonderful refreshing drink. IN food industry carbon dioxide is also used as a preservative - it is indicated on the packaging under the code E290, and also as a dough leavening agent.

Carbon dioxide fire extinguishers used in fires. Biochemists have found that fertilization... of the air with carbon dioxide a very effective means for increasing the yield of various crops. Perhaps this fertilizer has a single, but significant drawback: it can only be used in greenhouses. At plants that produce carbon dioxide, liquefied gas is packaged in steel cylinders and sent to consumers. If you open the valve, snow comes out with a hiss. What kind of miracle?

Everything is explained simply. The work expended on compressing the gas is significantly less than that required to expand it. And in order to somehow compensate for the resulting deficit, carbon dioxide cools sharply, turning into "dry ice". It is widely used to preserve food and has significant advantages over ordinary ice: firstly, its “cooling capacity” is twice as high per unit weight; secondly, it evaporates without a trace.

Carbon dioxide is used as an active medium in wire welding, since at arc temperature, carbon dioxide decomposes into carbon monoxide CO and oxygen, which, in turn, interacts with the liquid metal, oxidizing it.

Carbon dioxide in cans is used in air guns and as energy source for engines in aircraft modeling.

The article describes the food additive (gas for saturation of drinks, gas environment for packaging and storage) carbon dioxide (E290, carbon dioxide), its use, effect on the body, harm and benefits, composition, consumer reviews
Other names for the additive: carbon dioxide, carbonic acid anhydride, carbon dioxide, carbon dioxide, E290, E-290, E-290

Functions performed

gas for saturation of drinks, gas environment for packaging and storage

Legality of use

Ukraine EU Russia

Carbon dioxide, E290 – what is it?

Carbon dioxide E290 is used in the production of carbonated soft drinks

Carbon dioxide, also called carbon dioxide, is known to be used in food production as the additive E290. The chemical formula of the additive E290 is CO 2 . Carbon dioxide under normal conditions is an odorless, colorless gas. Carbon dioxide is easily soluble in water (1 liter of CO 2 in one liter of water at a temperature of 15 ° C) and forms a weak acid.

Carbon dioxide is formed as a result of combustion and biological decomposition (rotting) of various organic substances, during the vital activity of living organisms (during the rotting and decomposition of soil humus, during forest fires, as a result of burning oil products, gas and coal, during the respiration of plants, animals and The human body, in which carbon dioxide plays a vital role, releases it in an amount of approximately 2.3 kg per day.

Carbon dioxide is a substance that is very common in nature. Carbon dioxide is present in colossal quantities in the atmosphere and in mineral springs; a significant amount of it is dissolved in the water of the seas and oceans. In the atmosphere of our planet, the concentration of carbon dioxide is approximately 0.04%. The density of carbon dioxide is one and a half times the density of air. This substance is one of the so-called greenhouse gases, and its accumulation in the atmosphere is one of the reasons for the acceleration of global warming. Carbon dioxide is also part of the atmosphere of several planets in our solar system: for example, Mars and Venus, and makes up a significant part of it.

In industrial quantities, carbon dioxide is obtained from flue gases or during the decomposition of mineral carbonates (dolomite and limestone), and also as a by-product of alcoholic fermentation. The resulting mixture of gases is separated, purified, and the final product is pure carbon dioxide. There is also a method for producing E290 by producing pure oxygen, argon and nitrogen in air separation plants.

Carbon dioxide, E290 – effects on the body, harm or benefit?

Carbon dioxide is non-toxic and not hazardous to health. It must be remembered that carbon dioxide accelerates the absorption of various substances into the gastric mucosa, and can cause rapid intoxication when drinking alcoholic beverages containing it. Drinks carbonated with carbon dioxide are actually a diluted solution of weak carbonic acid, so active consumption of drinks containing the E290 additive is contraindicated for people with medical problems with the stomach and gastrointestinal tract (gastritis, ulcers, etc.).

Food additive E290, carbon dioxide – use in food products

In food production, the E290 additive is used as a gas for saturating drinks, a preservative, an antioxidant, an acidity regulator and a protective gas. Carbon dioxide is widely used in the production of soft and alcoholic carbonated drinks. Carbonic acid, which is formed when CO 2 is dissolved in water, exhibits antimicrobial and disinfecting properties.

In the confectionery and bakery industry, the E290 additive is used as a leavening agent, adding volume to confectionery and bakery products. Carbon dioxide is also widely used in winemaking, where it functions as a fermentation regulator. Carbon dioxide is used as a protective gas in the storage of various food products.

Other names: carbon dioxide, carbon dioxide, carbon monoxide (IV), carbonic anhydride.

Carbon dioxide is an inorganic compound with the chemical formula CO 2 ; colorless and odorless gas.

Physical properties

Chemical properties and methods of preparation

Cleaning

Purification of CO 2 stored in steel cylinders. Commercial CO 2 in steel cylinders may contain the following impurities: water vapor, O 2, N 2, less often traces of H 2 S and SO 2. In most cases, commercial CO 2 is of sufficient purity to allow chemical reactions to occur. Only under higher requirements (for example, during physical research) does commercial CO 2 need to be subjected to additional purification. To do this, the gas is passed through a saturated CuSO 4 solution, then through a KHCO 3 solution and finally through a fractionator, which is part of an industrial plant for the production of pure H 2 S. CO 2 fractionation uses four vertical washers, eight U-tubes for deep cooling and two freeze traps. Before the last freezer there is also a branch to a mercury manometer. CO 2 passes through the first four U-shaped tubes for deep cooling (maintained at the specified temperature) and is frozen into 8. When 8 is filled, open tap 9, seal it off at point 10 and create a high vacuum in this part of the equipment. After this, cool the remaining four 11-shaped tubes to -78 °C (dry ice + 4-acetone), remove liquid air cooling from 5, pump out the first gas stream, and then immerse it in a vessel for condensation 11 into liquid air. The middle fraction is collected in 11, and the remainder in 8. The fraction of 11 is sublimated twice more and the purity of the gas is monitored by determining the vapor pressure at different temperatures. The gas is stored in 25-liter glass flasks, which are degassed by heating for many hours in a high vacuum at 350 °C.

Fig.1. Installation for producing hydrogen sulfide.

Dry ice

“Dry ice” is solid carbon dioxide, which under normal conditions (atmospheric pressure and room temperature) transforms into a vapor state, bypassing the liquid phase. In appearance it resembles ice (hence the name).

The sublimation temperature at normal pressure is -78.5˚ C. Technical “dry ice” has a density of about 1560 kg/m 3, and during sublimation it absorbs about 590 kJ/kg (140 kcal/kg) of heat. Produced in carbon dioxide plants.

List of used literature

Volkov, A.I., Zharsky, I.M. Big chemical reference book / A.I. Volkov, I.M. Zharsky. - Mn.: Modern School, 2005. - 608 with ISBN 985-6751-04-7.
Hoffman W., Rüdorf W., Haas A., Schenk P. W., Huber F., Schmeisser M., Baudler M., Becher H.-J., Dönges E., Schmidbaur H., Ehrlich P., Seifert H. I. . Guide to inorganic synthesis: In 6 volumes. T.3. Per. With. German/Ed. G. Brouwer. - M.: Mir, 1985. - 392 p., ill. [With. 682]