Producing carbon dioxide in the laboratory. Receipt and production of industrial gases Carbon dioxide production in the laboratory
You already know that when you exhale, carbon dioxide comes out of your lungs. But what do you know about this substance? Probably a little. Today I will answer all your questions regarding carbon dioxide.
Definition
This substance under normal conditions is a colorless gas. In many sources it can be called differently: carbon monoxide (IV), and carbon anhydride, and carbon dioxide, and carbon dioxide.
Properties
Carbon dioxide (formula CO 2) is a colorless gas, has an acidic odor and taste, and is soluble in water. If it is cooled properly, it forms a snow-like mass called dry ice (photo below), which sublimates at a temperature of -78 o C.
It is one of the products of decay or combustion of any organic matter. It dissolves in water only at a temperature of 15 o C and only if the water:carbon dioxide ratio is 1:1. The density of carbon dioxide may vary, but under standard conditions it is equal to 1.976 kg/m3. This is if it is in gaseous form, and in other states (liquid/gaseous) the density values will also be different. This substance is an acidic oxide; adding it to water produces carbonic acid. If you combine carbon dioxide with any alkali, the subsequent reaction results in the formation of carbonates and bicarbonates. This oxide cannot support combustion, with some exceptions. These are reactive metals, and in this type of reaction they take oxygen away from it.
Receipt
Carbon dioxide and some other gases are released in large quantities when alcohol is produced or natural carbonates decompose. The resulting gases are then washed with dissolved potassium carbonate. This is followed by their absorption of carbon dioxide, the product of this reaction is bicarbonate, upon heating the solution of which the desired oxide is obtained.
But now it is successfully replaced by ethanolamine dissolved in water, which absorbs carbon monoxide contained in the flue gas and releases it when heated. This gas is also a byproduct of those reactions that produce pure nitrogen, oxygen and argon. In the laboratory, some carbon dioxide is produced when carbonates and bicarbonates react with acids. It is also formed when baking soda and lemon juice or the same sodium bicarbonate and vinegar react (photo).
Application
The food industry cannot do without the use of carbon dioxide, where it is known as a preservative and leavening agent, code E290. Any fire extinguisher contains it in liquid form.
Also, tetravalent carbon oxide, which is released during the fermentation process, serves as a good feed for aquarium plants. It is also found in the well-known soda, which many people often buy at the grocery store. Wire welding occurs in a carbon dioxide environment, but if the temperature of this process is very high, then it is accompanied by the dissociation of carbon dioxide, which releases oxygen, which oxidizes the metal. Then welding cannot be done without deoxidizing agents (manganese or silicon). Carbon dioxide is used to inflate bicycle wheels; it is also present in the cans of air guns (this type is called a gas cylinder). Also, this oxide in a solid state, called dry ice, is needed as a refrigerant in trade, scientific research and when repairing some equipment.
This is how beneficial carbon dioxide is for humans. And not only in industry, it also plays an important biological role: without it, gas exchange, regulation of vascular tone, photosynthesis and many other natural processes cannot occur. But its excess or shortage in the air for some time can negatively affect the physical condition of all living organisms.
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).
Description of methods for obtaining and producing industrial gases (nitrogen, argon, hydrogen, helium, oxygen, propane, carbon dioxide).
Receipt and production of industrial gases.
Currently, the main way to obtain atmospheric industrial gases - oxygen, nitrogen, argon is air separation. There are three methods of air separation: cryogenic, adsorption and membrane.
Cryogenic air separation
Atmospheric dry air is a mixture containing oxygen 21% and nitrogen 78% by volume, argon 0.9% and other inert gases, carbon dioxide, water vapor, etc. To obtain technically pure atmospheric gases, the air is subjected to deep cooling and liquefied (temperature boiling of liquid air at atmospheric pressure -194.5° C.)
The process looks like this: the air sucked in by a multi-stage compressor first passes through an air filter, where it is cleaned of dust, passes through a moisture separator, where the water that condenses during air compression is separated, and a water cooler, which cools the air and removes the heat generated during compression. To absorb carbon dioxide from the air, a decarbonizer is turned on, filled with an aqueous solution of caustic soda. Complete removal of moisture and carbon dioxide from the air is essential, since water and carbon dioxide freezing at low temperatures clog pipelines and the installation has to be stopped for thawing and purging.
After passing through the drying battery, the compressed air enters the so-called expander, where a sharp expansion occurs and, accordingly, it is cooled and liquefied. The resulting liquid air is subjected to fractional distillation or rectification in distillation columns. With the gradual evaporation of liquid air, mainly nitrogen is evaporated first, and the remaining liquid is increasingly enriched with oxygen. By repeating a similar process many times on the distillation trays of air separation columns, liquid oxygen, nitrogen and argon of the required purity are obtained. The possibility of successful rectification is based on a fairly significant difference (about 13°) in the boiling temperatures of liquid nitrogen (-196° C) and oxygen (-183° C). It is somewhat more difficult to separate argon from oxygen (-185 ° C). Next, the separated gases are removed for accumulation in special cryogenic containers, from which they are supplied for their own use or for sale.
The cryogenic method of air separation allows you to obtain gases of the highest quality - oxygen up to 99.9%, argon and nitrogen up to 99.9995%. Productivity can be up to 70,000 cubic meters per hour.
Pressure cycle adsorption (SCA) method.
Cryogenic air separation, with all its quality parameters, is a rather expensive method for producing industrial gases. The adsorption method of air separation, based on the selective absorption of a particular gas by adsorbents, is a non-cryogenic method, and is widely used due to the following advantages:
- high separation capacity for adsorbed components depending on the choice of adsorbent;
- quick start and stop compared to cryogenic plants;
- Greater installation flexibility, i.e. the ability to quickly change the operating mode, productivity and cleanliness depending on the need;
- automatic mode regulation;
- possibility of remote control;
- low energy costs compared to cryogenic blocks;
- simple hardware design;
- low maintenance costs;
- low cost of installations compared to cryogenic technologies;
The adsorption method is used to produce nitrogen and oxygen, as it provides excellent quality parameters at low cost.
Receipt principle nitrogen using PCA is simple but effective. Air is supplied to the adsorber - carbon molecular sieves at elevated pressure and ambient temperature. During the process, oxygen (O 2) is absorbed by the adsorbent, while nitrogen (N 2) passes through the apparatus. The adsorbent absorbs gas to a state of equilibrium between adsorption and desorption, after which the adsorbent must be regenerated, i.e. remove absorbed components from the surface of the adsorbent. This can be done either by increasing the temperature or by releasing the pressure. Typically, pressure-release regeneration is used in pressure-swing adsorption. The short duration of the adsorption and regeneration cycles, usually within a few minutes, gave the actual name to the process - “short-cycle adsorption”. The purity of nitrogen using this technology is 99.999%.
In production plants oxygen uses the known fact that nitrogen is adsorbed aluminosilicate molecular sieves significantly faster than oxygen. To separate nitrogen from oxygen, air is first compressed and then passed through an adsorber, resulting in relatively pure oxygen. The purity of oxygen as a product obtained using this technology is up to 95%. Its main contaminant is argon. Regeneration of the adsorbent is carried out at atmospheric pressure or vacuum.
Pressure swing adsorption units are usually completely assembled and tested at the manufacturing plant, i.e. are delivered to the consumer in a state of complete factory readiness, which ensures quick installation, and have a performance range from 10 to 6000 nm 3/h.
Membrane technology
The industrial use of membrane gas separation technology began in the 70s and revolutionized the gas separation industry. Until today, this technology is actively developing and becoming increasingly widespread due to its high economic efficiency. In cases where very pure gas, mainly nitrogen, is not required, with relatively large volumes of consumption, this technology has almost completely replaced alternative methods of producing gases - cryogenic and adsorption. When producing nitrogen with a purity of up to 99.9% and a productivity of up to 5000 nm³/h, membrane plants are significantly more profitable than others. The design of modern membrane gas separation and air separation plants is extremely reliable. First of all, this is ensured by the fact that there are no moving elements in them, so mechanical breakdowns are almost excluded. A modern gas separation membrane, the main element of the installation, is no longer a flat membrane or film, but a hollow fiber. A hollow fiber membrane consists of a porous polymer fiber with a gas separation layer applied to its outer surface. The essence of the operation of a membrane installation is the selective permeability of the membrane material by various gas components. Air separation using selective membranes is based on the fact that the molecules of air components have different permeability through polymer membranes. The air is filtered, compressed to the desired pressure, dried and then passed through the membrane module. Faster oxygen and argon molecules pass through the membrane and are removed outside. The more air passes through the modules, the greater the concentration of nitrogen N2 becomes. It is most cost-effective to obtain nitrogen with a basic substance content of 93-99.5%.
Below are graphs for choosing the use of certain types of production of industrial gases, depending on the volume of consumption and the required purity.
Helium production
Helium is a transparent gas, tasteless and odorless, and the element with the next largest atomic weight after hydrogen. It is absolutely inert, that is, it does not enter into any reactions. Of all substances, helium has the lowest boiling point -269°C. Liquid helium is the coldest liquid. Helium “freezes” at -272° C. This temperature is only one degree above the temperature of absolute zero. On an industrial scale, helium can be obtained in two ways - either from the bowels of the earth or by air separation. This gas is rare on Earth: 1 m 3 of air contains only 5.2 cm 3 of helium, i.e. only 0.00052%., and every kilogram of earthly material is 0.003 mg of helium. In terms of abundance in the Universe, helium ranks second after hydrogen: helium accounts for about 23% of cosmic mass.
On Earth, helium is constantly formed from the decay of uranium, thorium and other radioactive elements. Helium accumulates in free gas accumulations in the subsurface and in oil; Such deposits reach industrial scale. Maximum concentrations of helium (10-13%) were found in free gas accumulations and gases of uranium mines and (20-25%) in gases spontaneously released from groundwater. The older the age of gas-bearing sedimentary rocks and the higher the content of radioactive elements in them, the more helium in the composition of natural gases.
Helium is produced on an industrial scale from natural and petroleum gases of both hydrocarbon and nitrogen composition. Based on the quality of raw materials, helium deposits are divided into: rich (He content > 0.5% by volume); ordinary (0.10-0.50) and poor (<0,10). Месторождения таких газов имеются в России, США, Канаде, Китае, Алжире, Польше и Катаре.
To separate it from other gases, the exceptional volatility of helium, associated with its low liquefaction temperature, is used. After all other components of the natural gas have condensed during deep cooling, the helium gas is pumped out. It is then cleaned of impurities. The purity of factory helium reaches 99.995%. The largest producer of helium in Europe is the Orenburg Helium Plant (10 million liters of liquid helium per year).
When obtaining helium by air separation large air separation plants (1000 - 3000 tons of oxygen per day) are equipped with special concentrators and column-type devices that separate and accumulate mixtures of krypton and xenon in oxygen, neon and helium in nitrogen. The crude mixtures are then processed to produce a pure product. Helium purity can reach up to 99.9999%. One of the largest producers of helium from air is the Iceblick company.
Producing carbon dioxide
The following industrial methods for producing carbon dioxide are distinguished:
— by carbon dioxide recovery from fermentation gases at distilleries and breweries;
— by carbon dioxide recovery from waste gases various production processes;
— by extraction from underground natural sources;
from flue gases and combustion products;
- by producing carbon dioxide direct combustion method gaseous or liquid fuel.
Accordingly, depending on the concentration of carbon dioxide, its sources can be divided into three groups.
First The group consists of raw material sources from which pure carbon dioxide can be produced without special equipment to increase its concentration. This group includes:
a) gases from chemical and petrochemical industries (production of ammonia, hydrogen and other products) containing 98-99% CO 2; b) gases of alcoholic fermentation at breweries, alcohol and hydrolysis plants with 98-99% CO 2; c) gases from natural sources with 92-99% CO 2.
Second The group is formed by sources of raw materials, the use of which ensures the production of pure carbon dioxide by the method of fractional condensation.
This group includes gases from some chemical industries containing 80-95% CO 2.
Settings recovery CO 2 are designed to extract carbon dioxide from gases of the first and second groups. The gases produced during fermentation processes in the production of alcohol or beer are practically pure carbon dioxide containing water vapor and traces of organic compounds (sulfur dioxide, hydrogen sulfide, fusel oils and aldehydes), easily washed off with water. The carbon dioxide content in the so-called. expansion gases depends on the type of technological processes in chemical production and can be up to 99.9%. The rest of the volume is occupied by water vapor and low-boiling impurities, mainly hydrogen. To bring carbon dioxide to food grade (99.995% CO 2 and 0.0005% O 2), these installations are equipped with a rectification (distillation) purification system.
IN third The group includes sources of raw materials, the use of which makes it possible to produce pure carbon dioxide only with the help of special equipment. This group includes sources:
a) consisting mainly of nitrogen and carbon dioxide (combustion products of carbon-containing substances, for example, natural gas, liquid fuel, coke in boiler houses, gas piston and gas turbine units containing 8-20% CO 2; from-
exhaust gases from lime and cement factories with 30-40% CO 2; top gases of blast furnaces with 21-23% CO 2);
b) consisting mainly of methane and carbon dioxide and containing significant admixtures of other gases (biogas and landfill gas from bioreactors with 30-45% CO2; associated gases during the extraction of natural gas and oil containing 20-40% CO2).
When using raw material sources of the third group, carbon dioxide absorption-desorption stations with liquid chemical absorbents are most often used. This is one of the main industrial methods for producing pure CO 2. The most common feedstock for carbon dioxide production is flue gases, with natural gas considered the optimal feedstock source. When natural gas is burned, there are no sulfur compounds or mechanical impurities in the smoke.
A typical scheme for producing CO 2 looks like this: CO 2 enriched steam enters scrubbers, where mechanical impurities and heavy hydrocarbons are separated. The gas is compressed and forced through a purifier, which removes moisture and unwanted gases.
The produced carbon dioxide can be accumulated in long-term storage tanks, supplied to a charging station for cylinders and fire extinguishers, transport tanks, installations for the production of dry ice, and directly to production carbonation lines.
Hydrogen production
There are two main schemes for producing hydrogen.
Electrolysis plants. For small hydrogen consumers, electrolyzers with a capacity from 0.5 to 1000 m3/hour are offered. Purity of 99.9% and higher can meet the requirements of enterprises in the food, chemical, and electronics industries. Production of technical hydrogen by electrolysis includes the following main sequentially implemented stages: electrolytic decomposition of water into hydrogen and oxygen 2H2O→2H2+O2; catalytic purification of the resulting hydrogen from oxygen; its compression in piston compressors; adsorption drying; filling into cylinders or containers.
Steam reforming. Using a source of hydrocarbons and a reforming process, it is possible to produce hydrogen in small, medium, large volumes and the quality that the consumer needs. Typically, units are offered from 100 to 5000 m3/hour; oil refineries use units with a capacity of more than 20,000 m3/hour. The process looks like this:at hydrocarbons (methanol, propane, natural gas, oil) used as fuel are mixed in process steam, heated to 480 degrees C and separated in a reactor using a nickel-based catalyst according to the simple formula CH 4 + H 2 O + 230 kJ=CO+3H 2
The hydrogen adsorption unit is integrated into the existing control system and is fully automated.
Acetylene production
Acetylene was first obtained in 1836 by Edmond Davy by treating potassium carbide K2C2 with water and was so named by the chemist Berthelot in 1860.
The industrial production of acetylene began with the mass production of calcium carbide. In turn, calcium carbide is obtained by sintering limestone and coke (coal) CaO + 3C = CaC 2 + CO. There is no significant production of calcium carbide in Ukraine.
When calcium carbide is treated with water, acetylene is formed:
CaC 2 +2H 2 O=C 2 H 2 +Ca(OH) 2
Most of the acetylene produced in Ukraine is obtained from calcium carbide. For this purpose, special industrial generators are used, in which acetylene is purified from impurities of sulfur, ammonia and phosphorus, and moisture, and then pumped into cylinders by compressors.
Small portable generators are used for domestic use, but the acetylene produced in them is usually wet and contains impurities. In addition, it is impossible to stop the acetylene formation process, which can be inconvenient for small jobs. In cold weather, the use of small generators is also problematic due to the danger of water freezing.
The second method for producing acetylene is oxidative pyrolysis of methane and other hydrocarbons according to the formula 2CH 4 →C 2 H 2 +3H 2, carried out at an elevated temperature of 1200-1500 degrees. followed by rapid cooling. Acetylene here is an intermediate product in the further production of organic synthesis products. The pyrolysis method is economically unprofitable only for the production of acetylene, therefore it is used in factories that further process it into synthetic rubber, vinyl acetate, vinyl chloride, ethylene, butadiene, styrene and other products. In Ukraine it is Severodonetsk Azot.
Getting propane.
Propane is usually understood as a liquefied mixture of hydrocarbons, which includes the following gases:
Ethane - C 2 H 6- a gas with a density close to air. Included in liquefied gases in small quantities. The most important reason for limiting its content is that at a temperature of 45°C ethane cannot be in a liquefied state. At 30 °C, the elasticity of its vapor reaches 4.8 MPa, while the operating pressure of above-ground liquefied gas supply systems is 1.6 MPa, and underground – 1.0 MPa. At the same time, a small amount of ethane in the propane-butane mixture increases the total saturated vapor pressure of the gas mixture, which provides the excess pressure necessary for normal gas supply in winter.
Propane – C 3 H 8— heavy gas (density in air 1.52). Technical propane is the main component of liquefied gases; its percentage in the winter mixture must be at least 75%. Boiling point – 42.1°C.
Butane – C 4 H 10— heavy gas (density in air 2.06). Boiling point –0.5°C.
Pentane – C 5 H 12— heavy gas (density in air 2.49). Boiling point +36°C. The content in the mixture is 1-2% by volume.
Liquefied gas is usually produced in two ways - by processing natural gas at gas processing plants at gas processing plants and at oil refineries at oil refineries, which determines the affordable price for the consumer.
The technological chain for the production of liquefied gases begins with the production of “crude” oil or “wet” natural gas and ends with the storage of liquid propane and butane, completely free of light gases, heavy oil and purified from traces of sulfur compounds and water.
On gas fields The production of methane-rich natural gas is often accompanied by the release of small quantities of a mixture of heavy hydrocarbons: from ethane and the main components of liquefied gas to compounds of distillate components (“natural gasoline”). If they are present in significant quantities, then liquefied gases and distillates are removed from natural gas to avoid technological complications from condensate when compressing the gas before feeding it into the pipeline, as well as to obtain the necessary chemicals or additional fuel. The resulting mixture of liquefied gases and distillate is of low quality, but nevertheless is in demand due to its low price.
At oil production Directly at the site of production, “crude” oil is stabilized in order to prepare it for further transportation through pipelines or in tankers to the place of consumption. The degree of stabilization, the effectiveness of which depends on the conditions at the well head (temperature and pressure), in turn determines the amount of light gases removed. These gases are sometimes flared, but are now increasingly used as an additional product, and are called "associated natural gas". The amount of liquefied gases remaining in crude oil depends on the degree of stabilization at the site of its production. Some types of oil can sometimes be specially supplemented with liquefied gas before transportation. The liquefied gases contained in the oil entering the refinery are captured during the distillation process. Their yield ranges from 2 to 3% of the volume of processed oil. The liquefied gases obtained through fractional distillation are subject to subsequent conversion, which is carried out primarily to increase the yield and improve the quality of gasoline, but it also separates impurities from the liquefied gas itself.
Thus, it is preferable to use liquefied gas obtained during oil refining, since it has a more stable composition, it does not contain moisture, nitrogen impurities, carbon dioxide, which are usually present in liquefied gas obtained from gas fields.
Carbon dioxide, having universal properties, is used in industry, medicine, and agriculture. Today, CO2 is an agricultural fertilizer, a medical tool, a temperature regulator, and a source of new energy.
The production of carbon dioxide in industry is methodologically diverse. It is found in smoke waste released into the atmosphere by thermal power plants and power plants; it is obtained during the fermentation of alcohol and acts as a reaction product with natural carbonates.
The carbon dioxide production industry is broad. Gas can be absorbed in several ways from a single source. In all cases, this is a step-by-step process of removing impurities (to achieve GOST requirements) and achieving the desired consistency and state of aggregation.
Production of carbon dioxide gas
CO2 gas is recovered from industrial (petroleum) fumes by adsorption of monoethanolamine (commercially viable) and potassium carbonate (rare). The principle of collecting carbon particles is the same for both substances. They are sent through a pipeline to the waste and collect carbon dioxide. After collection, carbon dioxide-saturated gases are sent for purification.
In special containers, the reaction occurs at elevated temperatures or low pressure. The process releases pure carbon dioxide and decomposition products (ammonia and others).
Carbon dioxide extraction plant
Schematically the process looks like this:
- The exhaust smoke is mixed with adsorbents (gaseous potassium carbonate or monoethanolamine);
- The gases that have accumulated carbon dioxide enter a special gas holder for purification;
- In a reaction with high temperature or low pressure, carbon dioxide is separated from the adsorbent.
Chemical industry:
- Participates in the synthesis of artificial chemicals;
- Regulates temperature in reactions;
- Neutralizes alkalis;
- Cleans animal and plant tissues;
- Can be reduced to methane.
Metallurgy:
- Exhaust smoke deposition;
- Regulates the direction of water flow when draining mines;
- Some lasers use CO2 as their energy source (neon).
Paper production:
- Regulates the pH value in wood pulp or cellulose;
- Increases the power of production machines.
Dry ice plays a special role in industrial and related industries. It is applied as:
- Source of cooling in freezers during transportation;
- Cooling during solidification of alloys;
- Cleaning equipment with dry ice (cryoblasting).
Fish frozen with dry ice.
Application in other fields of activity
People also use carbon dioxide in other areas of activity and in everyday life. The availability of dioxide makes it widespread, and its properties make it in demand even among ordinary people.
Where else is carbon dioxide used:
- When welding. Protects the metal from heating and oxidation by flowing around the electric arc.
- In agriculture. Carbon dioxide combined with sunlight is an ideal way to fertilize any crop. Spraying gas in a greenhouse or greenhouse increases productivity by 2-3 times;
- In medicine, it is used to create an atmosphere close to the real one when performing artificial operations on organs. It is used as a stimulant to restore the patient’s breathing and when inducing anesthesia;
- Pharmaceuticals. Creates an ideal environment for chemical synthesis and low-temperature water transportation;
- Instruments and equipment. Cools equipment and units without disassembling them into modules, acts as an abrasive cleaning element;
- Environment protection. Regulates the hydrogen level in waste water;
- Food industry. Used as a preservative and leavening agent for dough. Added to drinks, making them carbonated;
- To create pressure in air guns.
The use of carbon dioxide is especially in demand in fire extinguishing systems. It is filled into carbon dioxide gas fire extinguishers and, in the event of a fire, allows the fire to be isolated from the source of oxygen. Combustion cannot continue for long without air supply, and gasification with carbon dioxide will not allow it to penetrate the fire.
Obtained in small quantities from alcoholic fermentation, it is used as a way to carbonate drinks. It also protects flour, dried fruits, and peanuts from insects without affecting the quality and speed of their spoilage.
Carbon dioxide is a first-class medium for growing flowers, feeding vegetables and underwater plants. It accelerates photosynthesis and improves metabolic processes in plant cells. The main thing is that it has an affordable price even for ordinary people.
Carbon dioxide can also be used in cryodestruction, as a freezing agent. It burns the surface of warts and moles with cold, causing them to fall off, but not leaving scars from a scalpel and stitches.
Conclusion
Carbon dioxide is a simple and widespread substance throughout the planet that plays a practical function in key industries. Industry, medicine, the food industry and even simple human life cannot do without it.
Recently, CO2 has been used as a basis for the production of a fuel source (methanol). The use of geothermal as a renewable energy source is gaining popularity and can increase electricity production and.
Goals:
- Expand your understanding of the history of discovery, properties and practical applications of carbon dioxide.
- Introduce students to laboratory methods for producing carbon dioxide.
- Continue building students' experimental skills.
Techniques used:“true and false statements”, “zigzag-1”, clusters.
Laboratory equipment: laboratory stand, device for obtaining gases, 50 ml beaker, pieces of marble, hydrochloric acid (1:2), lime water, Mohr clamp.
I. Calling stage
At the challenge stage, the “true and false statements” technique is used.
Statements |
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II. Conception stage
1. Organization of activities in working groups, the participants of which receive texts on the five main topics of the “zigzag”:
- History of the discovery of carbon dioxide
- Carbon dioxide in nature
- Producing carbon dioxide
- Properties of carbon dioxide
- Practical applications of carbon dioxide
There is an initial acquaintance with the text, initial reading.
2. Work in expert groups.
Expert groups bring together “experts” on specific issues. Their task is to carefully read the text, highlight key phrases and new concepts, or use clusters and various schemes to graphically depict the content of the text (the work is carried out individually).
3. Selection of material, its structuring and addition (group work)
4. Preparation for broadcasting text in working groups
- 1st group experts compile a reference summary “The History of the Discovery of Carbon Dioxide”
- 2nd group experts draw up a diagram of the distribution of carbon dioxide in nature
- 3rd group experts draw up a scheme for producing carbon dioxide and a drawing of the installation for its production
- 4th group experts compile a classification of the properties of carbon dioxide
- 5th group experts draw up a scheme for the practical use of carbon dioxide
5. Preparing for the presentation (poster)
III. Reflection stage
Return to workgroups
- Broadcast in a group of topics 1–5 sequentially.
- Assembling a plant for producing carbon dioxide.
- Obtaining carbon dioxide and studying its properties.
- Discussion of the experimental results.
Presentation of individual topics.
Statements |
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| Return to “true and false statements.” Testing your initial assumptions. Arrangement of new icons. | ||
| It might look like this: | ||
| 1. Carbon dioxide is a “wild gas”. | ||
| 2. The seas and oceans contain 60 times more carbon dioxide than the earth's atmosphere. | ||
| 3. Natural sources of carbon dioxide are called mofets. | ||
| 4. In the vicinity of Naples there is a “Dog Cave” in which dogs are not allowed. | ||
| 5. In laboratories, carbon dioxide is produced by the action of sulfuric acid on pieces of marble. | ||
| 6. Carbon dioxide is a colorless and odorless gas, lighter than air, highly soluble in water. |
7. Solid carbon dioxide is called “dry ice”.
8. Lime water is a solution of calcium hydroxide in water.
Texts on the five main topics of “zigzag”
1. History of the discovery of carbon dioxide
Carbon dioxide was the first among all other gases to be opposed to air under the name “wild gas” by the alchemist of the 16th century. Van't Helmont.
The discovery of CO 2 marked the beginning of a new branch of chemistry - pneumatochemistry (chemistry of gases).
The Scottish chemist Joseph Black (1728 - 1799) in 1754 established that the calcareous mineral marble (calcium carbonate) decomposes when heated, releasing gas and forming quicklime (calcium oxide):
The released gas could be recombined with calcium oxide to form calcium carbonate again:
CaO + CO 2 CaCO 3
calcium oxide carbon dioxide calcium carbonate
This gas was identical to the “wild gas” discovered by Van Helmont, but Black gave it a new name - “bound air” - since this gas could be bound and again become a solid substance, and it also had the ability to be attracted to lime water (calcium hydroxide) and cause it to become cloudy:
carbon dioxide calcium hydroxide calcium carbonate water
A few years later, Cavendish discovered two more characteristic physical properties of carbon dioxide - its high density and significant solubility in water.
2. Carbon dioxide in nature
The carbon dioxide content in the atmosphere is relatively small, only 0.04–0.03% (by volume). CO 2 concentrated in the atmosphere has a mass of 2200 billion tons.
60 times more carbon dioxide is found dissolved in the seas and oceans.
During each year, approximately 1/50 of the total CO 2 contained in it is removed from the atmosphere by the plant cover of the globe through the process of photosynthesis, which converts mineral substances into organic matter.
The bulk of carbon dioxide in nature is formed as a result of various processes of decomposition of organic substances. Carbon dioxide is released during the respiration of plants, animals, and microorganisms. The amount of carbon dioxide released by various industries is constantly increasing. Carbon dioxide is contained in volcanic gases, and it is also released from the ground in volcanic areas. The “Dog Cave” has been operating as a permanent CO 2 generator for several centuries near the city of Naples in Italy. It is famous for the fact that dogs cannot be in it, but a person can remain there in normal condition. The fact is that in this cave carbon dioxide is released from the ground, and since it is 1.5 times heavier than air, it is located below, approximately at the height of a dog (0.5 m). In such air, where carbon dioxide is 14%, dogs (and other animals, of course) cannot breathe, but an adult standing on his feet does not feel the excess carbon dioxide in this cave. The same caves exist in Yellowstone National Park (USA).
Natural sources of carbon dioxide are called mofets. Mofets are characteristic of the last, late stage of volcanic attenuation, in which, in particular, the famous Elbrus volcano is located. Therefore, there are numerous outlets of hot springs saturated with carbon dioxide breaking through the snow and ice.
Outside the globe, carbon monoxide (IV) is found in the atmospheres of Mars and Venus, “terrestrial” planets.
3. Producing carbon dioxide
In industry, carbon dioxide is obtained mainly as a by-product of burning limestone, alcoholic fermentation, etc.
In chemical laboratories, they either use ready-made cylinders with liquid carbon dioxide, or obtain CO 2 in Kipp apparatus or a device for producing gases by the action of hydrochloric acid on pieces of marble:
CaCO 3 + 2HCl CaCl 2 + CO 2 + H 2 O
calcium carbonate hydrochloric acid calcium chloride carbon dioxide water
It is impossible to use sulfuric acid instead of hydrochloric acid, because then instead of calcium chloride, which is soluble in water, you would get gypsum - calcium sulfate (CaSO 4) - a salt that is slightly soluble in water. When deposited on pieces of marble, gypsum makes it extremely difficult for acid to reach them and thereby greatly slows down the reaction.
To produce carbon dioxide:
- Attach a device for obtaining gases to the leg of a laboratory stand
- Remove the stopper with a funnel from the test tube with the appendage
- Place 2-3 pieces of marble in the nozzle, the size of ? peas
- Insert the funnel stopper into the test tube again.
- Open the clamp
- Pour hydrochloric acid (1:2) into the funnel (carefully!) so that the acid lightly covers the marble
Fill the beaker with carbon(IV) monoxide and close the clamp.
4. Properties of carbon dioxide
CO 2 is a colorless gas, odorless, 1.5 times heavier than air, difficult to mix with it (in the words of D.I. Mendeleev, “sinks” in the air), which can be proven by the following experiment: above a glass, in in which a burning candle is fixed, overturn a glass filled with carbon dioxide. The candle goes out instantly.
Carbon monoxide (IV) is acidic and when this gas dissolves in water, carbonic acid is formed. When CO 2 is passed through litmus-tinted water, you can observe a change in the color of the indicator from purple to red.
A qualitative reaction to the carbon dioxide content in the air is to pass the gas through a dilute solution of calcium hydroxide (limewater). Carbon dioxide causes the formation of insoluble calcium carbonate in this solution, causing the solution to become cloudy:
CO 2 + Ca(OH) 2 CaCO 3 + H 2 O
carbon dioxide calcium hydroxide calcium carbonate water
When excess CO2 is added, the cloudy solution becomes clear again due to the conversion of insoluble carbonate to soluble calcium bicarbonate:
CaCO 3 + H 2 O + CO 2 Ca(HCO 3) 2
calcium carbonate water carbon dioxide calcium bicarbonate
5. Practical applications of carbon dioxide
The pressed solid carbon dioxide is called “dry ice.”
Solid CO 2 is more like compressed dense snow, with a hardness reminiscent of chalk. The temperature of “dry ice” is –78 o C. Dry ice, unlike water ice, is dense. He sinks in the water, cooling it sharply. Burning gasoline can be quickly extinguished by throwing a few pieces of dry ice into the flame.
The main use of dry ice is the storage and transportation of food: fish, meat, ice cream, etc. The value of dry ice lies not only in its cooling effect, but also in the fact that food in carbon dioxide does not mold or rot.
Dry ice is used in laboratories to test parts, instruments, and mechanisms that will serve at low temperatures. Dry ice is used to test the frost resistance of rubber car tires.
Carbon dioxide is used to carbonate fruit and mineral waters, and in medicine – for carbon dioxide baths.
Liquid carbon dioxide is used in carbon dioxide fire extinguishers, fire extinguishing systems in aircraft and ships, and in carbon dioxide fire engines. It is especially effective in cases where water is unsuitable, for example, when extinguishing fires of flammable liquids or when there is electrical wiring or unique equipment in the room that may be damaged by water.
In many cases, CO 2 is not used in finished form, but is obtained during the use of, for example, baking powders containing a mixture of sodium bicarbonate and potassium tartrate. When such powders are mixed with dough, the salts dissolve and a reaction occurs, releasing CO 2 . As a result, the dough rises, filling with bubbles of carbon dioxide, and the product baked from it turns out soft and tasty.
Literature
- Change // International journal on the development of thinking through reading and writing. – 2000. – No. 1, 2.
- Modern student in the field of information and communication: Educational and methodological manual. – St. Petersburg: PETROC, 2000.
- Zagashev I.O., Zair-Bek S.I. Critical thinking: development technology. – St. Petersburg: Alliance Delta Publishing House, 2003.