What is calcium carbide and what gas does it produce?

What does carbide look like?

To determine where to find carbide on the street, you need to know its physical properties. Physically, the substance is solid, its color can be dark, having a grayish or brown tint. The color depends on the amount of carbon. There is also a specific odor that characterizes this substance.

It is solid in consistency, but crumbles easily, turning into powder. If you bring a match, combustion will begin, releasing carbon and decomposing calcium. True, this can be achieved at high temperatures, for example with a hunting match.

Appearance and characteristics of technical calcium carbide

Calcium carbide is produced by fusing coke and quicklime in electric furnaces. Molten calcium carbide is released from the furnace into special forms - molds, in which it hardens. The solidified calcium carbide is crushed and sorted into pieces of certain sizes.

Technical calcium carbide is a solid crystalline substance. In appearance, calcium carbide is a dark gray or brown solid. It produces a gray crystalline fracture with varying shades depending on purity. Calcium carbide greedily absorbs water. When interacting with water, even in the cold, calcium carbide decomposes with the rapid release of acetylene and a large amount of heat. The decomposition of calcium carbide also occurs under the influence of atmospheric moisture.

According to GOST 1460-56, the following dimensions (granulation) of calcium carbide pieces are established: 2×8; 8x15; 15×25; 25x80. Technical calcium carbide contains up to 80% of chemically pure calcium carbide, the rest is made up of impurities - quicklime, carbon, silicic acid and more.

What is carbide?

Homemade bombs. This is what comes to mind first when we hear the word carbide. And no, the production of these dangerous toys was not carried out by defense industry enterprises, but, as a rule, by boys, about ten years old.

Twenty years ago it was a favorite pastime among teenagers. Now everyone sits at their tablets, but back then the world was ruled by the inquisitive mind of a child who strove to try everything in practice.

In order to feel like Rimbaud, you needed to get one miracle stone. Children most often found them at construction sites. And then everything was simple: a plastic vessel, a stone, water, a tightly screwed cap. All this was zealously shaken, and at best, thrown away. And in the worst case, the “shell” exploded right in the hands, then injuries could not be avoided.

Calcium carbide

There were also safer ways to use the find, for example, simply throwing it into a puddle, then you could observe something similar to the effect of modern bath bombs. So what kind of popular “toy” is this? Most of us believed that nature produced carbide as we know it. But actually it is not. And today you will see this.

So, this substance is always very hard, plus, in order to melt it, you need to make a remarkable effort. They look like dark, light, greenish stones, or powder, it all depends on the composition. Its shelf life is short, usually six months. It will not be possible to place containers in a general warehouse; such potentially dangerous substances must have their own compartment.

As you already know, carbide constantly strives to explode. Moreover, some connections do not even need special conditions. It is enough just to pour the powder from container to container, and it can suddenly explode.

Properties and composition

To obtain this stone, you need at least two elements. First is carbon. Its presence is mandatory. And then there is a choice: metal or non-metal. The main thing is that the rule is followed: the electronegativity (the force with which the atoms of an element attract foreign electrons) of the required component is higher than that of its “partner”. Otherwise you will get completely different connections.

Calcium Carbide Formula

This connection was first discussed in England back in the 19th century. However, the fame of the discoverer went to the Frenchman, thanks to whose experiments the substance was officially recognized; this happened only towards the end of the century. And now about what qualities are inherent in this compound:

• The material is unusually hard. According to this indicator, it almost caught up with diamond. Among the record holders is tungsten carbide (9 out of 10 possible points). This opens up hundreds of ways to use it.
• It will take a lot of effort to melt the stone. After all, for this it is necessary to heat it to 2, or even 3 thousand degrees Celsius. This figure will be higher than the values ​​​​necessary to change the state of metallic substances before they were included in the carbide.
• This is a very “non-contact” connection. Thus, the reaction of carbide to many substances will be zero. This requires special conditions. Therefore, they are not afraid of acids and other substances that promote corrosion.
• But the previous point does not apply to water. As you already understood from the story above, carbide and water often go hand in hand. In the case, for example, when calcium carbide is involved, absolutely any moisture is suitable for this, no conventions are needed. If the work is silicon carbide, then there is no way without heating - you need hot steam (1800 degrees).

Kinds

Science knows three types of such compounds:

• Covalent

What sets them apart is the very strong bonds between atoms. When this type is mentioned, we are talking about only two elements adjacent to carbon: the first is bromine, the second is silicon. All of the above properties in these compounds are “set” to the maximum. This is both unprecedented hardness and durability. If you want to dissolve it, it won’t be possible without the participation of caustic acids of enormous concentration. The same applies to interaction with oxygen. It just won’t work, you need heating, and not too bad – up to 1000 degrees.

• Salt-like or ionic

Here, either aluminum or metal comes into contact with carbon, but not just any metal, but only from 1-2 chemical groups. tables. It is still not very easy to give such a compound a liquid form; extreme heating is required. But the acid will not go unnoticed; as a result of such a “meeting,” the carbide will disintegrate.

• Metal-like

They are obtained from metals belonging to groups 4-8, this also includes cobalt, as well as nickel, and, of course, iron. If we consider their chemical structure, we will see that the carbon atoms are literally scattered, there are no bonds between them, they are like inclusions in the gaps formed in the metal. Because they are very refractory, one might even say they are champions in this matter. This allows them to be used in the manufacture of drills (pobedite drills).

Application

As already mentioned, this substance can most often be found at construction sites. And there they find dozens of ways to use it. It is difficult to do without this material in grinding; special materials are produced from it. disks. But it is good not only as an abrasive, but also in the form of sharp cutting wheels, knives and the like.

Acitylene generator for gas welding, inside of which calcium carbide is poured

Mechanical engineering is another opportunity to use this connection. Not only various car parts are made from carbide, but also spare parts. parts for radio devices. And thanks to its thermal conductivity, it will also cope well with heating tasks. Even in the nuclear industry it is impossible without such a component. All this requires special strength, so here we are most often talking about covalent types.

Those compositions that contain iron carbide make it possible to obtain steel, and the well-known cast iron. Silicon compounds are also valued by jewelers and manufacturers of lighting elements. Artificial rubber and resins, and even acetic acid - such is the wide range of applications of carbides.

But the matter does not stop there. This artificial mineral is also important for gardeners. After all, with its help a special type of fertilizer is obtained. They are able to regulate the growth rate of various crops.

But perhaps the most popular of all is calcium carbide. After all, it is precisely this that welders actively use in their work. It would seem, how can this dark pebble with a garlic aroma be involved in such a process?

It’s very simple, because gas welding, which is logical, requires flammable gas. In our case it gives acetylene carbide. As soon as it “meets” oxygen, we get a very intense flame; its temperature exceeds three thousand degrees.

If you take ready-made volatile gas, then special packaging is used for it. containers in which the substance is delivered to the site of action. There should be no shaking or shock during such a trip - it is deadly.

This raw material can flare up, even without extra “help”, so attention should always be at the limit. If the fire could not be avoided, do not use any moisture when extinguishing it. Only powder extinguishing methods should be used.

There is a second way - to produce this “fuel” right at the work site. To do this, you need to know what hydrolysis of carbides is. Simply put, it is the reaction of a compound upon contact with water. Moreover, even one drop can cause this very reaction.

Therefore, if you are planning to carry out welding work, very carefully open the sealed container with carbide. It is especially important that there are no signs of fire in the neighborhood, otherwise an emergency is guaranteed. You should completely forget about cigarettes.

Also, make sure that even the smallest crumbs do not end up on your skin, especially on the mucous membranes, otherwise, at best, there will be irritation, at worst, burns and swollen parts of the body. So arm yourself with special equipment. uniform: everything needs to be protected, from head to toe, including the respiratory tract. First aid, if contact cannot be avoided: pour plenty of water on the affected area, cover it with thick cream. If necessary, call a doctor.

If we talk about consumption, if the mass of carbide is one kilogram, then this makes it possible to produce up to three hundred cubic decimeters of gas. These are quite good indicators. Also, this amount of raw material will require approximately 20 liters of water, although manufacturers say that half a liter will be enough. How long this all takes depends on the size of the compound fractions and their purity.

After the work is finished, the remaining waste, and this is lime slag, is not left anywhere, but is disposed of. For such work you will need a specialist. generator. They come in impressive sizes and are installed in one place, for example, when large-scale work is planned. But there is also a mini version, portable.

First, fill the compartment in which the gas should form with water, then add carbide there. The reaction takes place, and the resulting acetylene flows through a soft tube directly to the gas burner. This path must be long enough; the hose must be chosen no shorter than ten meters.

Boron carbide

Boron carbide is also used. Items based on it provide reliable protection against fire. And not only from fire, by the way, because such products are actively used by manufacturers of body armor. Firstly, it “catches” bullets, and secondly, it will not allow radiation to pass through. As for such a union as aluminum carbide, the sparkling sparks during fireworks are its merit. But in appearance it is an unremarkable yellow powder.

How is carbide obtained?

First about calcium carbide. Its production is in demand. And although such factories require large expenses, especially when it comes to electricity, enterprises do not abandon the usual manufacturing method. Because the demand for such products is in no hurry to fall. After all, it is hardly possible to imagine at least a single construction site without acetylene. To save on electricity, such enterprises are opened in countries with a large number of hydroelectric power stations, in Canada, for example.

Why not switch to working with methane, since such a volatile gas can also be obtained from it? Yes, because calcium carbide produces an almost pure product, it is not difficult to bring it to 98 percent gas. And it is much easier to transport than the one obtained with the participation of methane.

The main object in such industries are electric furnaces. They are loaded with hard coal, which is also called coke, and calcium oxide (lime, any kind of lime will not work, it needs to be purified and homogeneous). All this heats up to 2 thousand degrees. And voila, the reaction started.

The result is a liquid substance, which will then become a familiar compound to us. But first it needs to cool in the molds. After the degree is reduced, these layers are crushed into pieces that are more convenient to use.

Now about the silicon version. We got it absolutely by accident, as usually happens. An American scientist tried to create an artificial diamond. As a result of the experiments, silicon carbides were obtained (by the way, they are in second place in hardness after uncut diamonds).

He patented it and opened the first plant for the production of the material. It’s impossible to say that technology has changed a lot since then. Unless sand and salt were excluded from it, what remained was carbon and silica, which are still heated to maximum temperatures in furnaces.

Method for producing calcium carbide

The invention is intended for the chemical industry and can be used in the production of acetylene and steel smelting. Coke-ash residue from thermal processing of oxidized brown coals, composition, wt.%: CaO - 47.5, C - 35.4, Fe2O3 - 6.6, SiO2 - 5.0, Mg - 3.3, Al2O3 - 1.6, S - 0.1, the rest - 0.5 is mixed with 12.9 - 28.3% by weight of the mixture of calcium carbonate in the form of limestone, subjected to high-temperature smelting at 2000-2100oC, cooled, CaC2 and ferrosilicon are separated. The method does not require expensive products, the volume of CaC2 is 275-285 l/kg, the ferrosilicon content is 0.1-0.2 wt.%. 1 salary.

The invention relates to chemical technology, in particular to the production of calcium carbide.

There is a known method for producing calcium carbide /Kuznetsov L.A. Production of calcium carbide. M., 1954, p. 32, 33/, including the melting of a charge consisting of lime and carbon, while up to 30% of thermally processed production waste is added to fresh lime - sludge from “dry” acetylene generators, which is a source of calcium oxide, silicon and iron, which reduces the cost of calcium carbide and improves the environmental situation, since part of the hazardous waste going to landfills is recycled. The disadvantage of this known method is the use of expensive products /metallurgical coke, anthracite, burnt lime/ as part of the main charge /70%/, as well as the costs of anthracite, electricity, steam during thermal processing of sludge. There is a known method for producing calcium carbide / USSR author's certificate N 664476, C 01 B 31/32, class. C 01 B, 1976/, by electrothermal melting of lime and a carbonaceous reducing agent with periodic supply of correction material, which is used as a coke-ash residue from the thermal processing of carbonate-containing oil shale in an amount of up to 10% of the weight of the charge, while the coke-ash residue is a source of calcium oxides /24 .0 - 31.0%/, silicon /14 - 20%/, iron /2.3 - 3.5%/ and carbon reducing agent /16 - 18%/. This reduces the cost of calcium carbide and increases the content of the main substance in the product and allows the use of production waste /coke ash residue/. The disadvantage of this known method is the consumption of expensive products /electrode graphite, burnt lime/ in the main part of the charge /90 - 99%/. There is a known method for producing calcium carbide / USSR author's certificate N 1168508, class. C 01 B 31/32, 1983/, including melting a charge consisting of lime and carbon, cooling the melt and separating the reaction products - calcium carbide and ferrosilicon, while the melting of the charge is carried out in the presence of limestone or shale ash coke in an amount of 12.9 - 28.3% by weight of the charge. To adjust the ratio of silicon to iron in the charge, the missing amount of iron is introduced in the form of chips, ensuring a weight ratio of silicon to iron of 1: 2, thereby obtaining calcium carbide with a quality mark /liter of acetylene - up to 300 l/kg of carbide/. The disadvantage of the known method is the use of expensive products in the main composition of the charge (lime and carbonaceous material). The invention is based on the task of obtaining calcium carbide using waste from the coal mining industry in the main composition of the charge, which reduces the cost of calcium carbide and improves the environmental situation by processing waste dumps. The problem is solved by the fact that in the method of producing calcium carbide, including melting a charge from a material containing oxides of calcium, silicon, iron and carbon, cooling the melt and separating the reaction products - calcium carbide and ferrosilicon, while melting the charge is carried out in the presence of limestone in an amount 12.9 - 28.3% by weight of the charge, according to the invention, coal mining waste is used as the specified material, in particular the coke ash residue from the thermal processing of oxidized brown coals, composition, wt.%: calcium oxide 47.5; carbon 35.4; iron oxide 6.6; silicon oxide 5.0; magnesium oxide 3.3; aluminum oxide 1.6; sulfur 0.1; phosphorus - traces, the rest 0.5. The use of coal mining waste - coke-ash residue from the thermal processing of oxidized brown coal with the average composition given above, allows you to reduce the cost of calcium carbide, since this waste is transported to dumps, while occupying arable land. Currently, there are 6,000 hectares of arable land under dumps in the Kansk-Achinsk coal basin alone, previously producing a grain harvest of 25 centners per hectare / Gavrilin K.V., A.Yu. Ozersky. Kansk-Achinsk coal basin. M.: Nedra, 1996, p. 93, 152, 154/, while the raw material base for the Berezovsky Kabassa open-pit mine alone is 1 billion tons of off-balance coal with a high content of calcium oxide in the coke ash residue /up to 50%/. Obtaining calcium carbide from coal mining waste reduces its cost by 30%, since the raw material component of the cost is up to 1/3 of the cost of calcium carbide (Production of calcium carbide in the USSR and abroad. Series “Production of phosphorus and calcium carbide.” - M.: NIITEKHIM, 1973). Moreover, thermal processing of waste does not require expensive products /anthracite, steam, electricity/, since the coke-ash residue from the thermal processing of oxidized brown coals is a product of their incomplete combustion using the thermal energy of this process. Example 1. A charge is prepared from the coke-ash residue from the thermal processing of oxidized brown coals with the composition, wt.%: calcium oxide 47.5; carbon 35.4; iron oxide 6.6; silicon oxide 5.0; magnesium oxide 3.3; aluminum oxide 1.6; sulfur 0.1; the rest 0.5; /phosphorus - traces/. The weight ratio of silicon to iron in the charge is 1:2. The average particle size of the charge is 2 - 3 mm. The resulting mixture is subjected to high-temperature smelting in a graphite crucible at 2000 - 2100oC for 15 minutes, then the melt is cooled to room temperature. The resulting melt consists of 96.5 parts by weight. calcium carbide /containing 75% CaC2/ and 3.5 parts by weight. ferrosilicon in the form of independent immiscible phases. The volume of calcium carbide is 275 l/kg. The ferrosilicon content in calcium carbide is 3.4%. Example 2. A charge is prepared from the coke-ash residue from the thermal processing of oxidized brown coals /of the same composition as in example 1/ and calcium carbonate is introduced in the form of limestone /containing 96 - 98% CaCO3/ into amount of 12.9% by weight of the charge. The particle size of the mixed components is 2 - 3 mm. The resulting mixture is subjected to high-temperature smelting at 2000 - 2100oC for 15 minutes, then the melt is cooled to room temperature and the smelting products are separated. After phase separation, 93.3 parts by weight are formed. calcium carbide and 6.7 wt. including ferrosilicon. The volume of the resulting carbide is 284 l/kg, with a ferrosilicon content of 0.2%. Example 3. A mixture is prepared from the coke ash residue of the thermal processing of oxidized brown coals / of the same composition as in example 1 / and calcium carbonate is added in the form of limestone / containing CaCO3 96 - 98%/ in an amount of 28.3% by weight of the charge. The particle size of the mixed components is 2 - 3 mm. The resulting mixture is subjected to high-temperature smelting at 2000 - 2100oC for 15 minutes, then the melt is cooled to room temperature and the smelting products are separated. After phase separation, 93.2 parts by weight are formed. calcium carbide and 6.8 wt. including ferrosilicon. The volume of the resulting carbide is 285 l/kg, with a ferrosilicon content of 0.1%. The use of the proposed method makes it possible to obtain high-quality carbide from coal mining waste going to the dump. Ferrosilicon is also used for deoxidation of steels in the ferrous metallurgy. The presence of small amounts of sulfur and traces of phosphorus allows the use of industrial furnaces to produce carbide in this way, and the unlimited raw material base /17% of all brown coal mined in the open pit/ suggests the possibility of large-scale production, which eliminates the growth of dumps, since coal mining waste can be processed into valuable a product that currently costs $500 per ton and is in short supply.

Formula of the invention
1. A method for producing calcium carbide, including melting a charge from a material containing oxides of calcium, silicon, iron and carbon, cooling the melt and separating the reaction products - calcium carbide and ferrosilicon, while the melting is carried out in the presence of calcium carbonate in the form of limestone in an amount 12.9 - 28.3% by weight of the charge, characterized in that the specified material is the coke ash residue from the thermal processing of oxidized brown coals.2. The method according to claim 1, characterized in that the coke ash residue from the thermal processing of oxidized brown coals has the following composition, wt.%: Calcium oxide - 47.5 Carbon - 35.4 Iron oxide - 6.6 Silicon oxide - 5.0 Magnesium oxide — 3.3 Aluminum oxide — 1.6 Sulfur — 0.1 The rest — 0.5

Properties

Physical properties

• Colorless tetragonal crystals.
• Density: 228 (+20 °C, g/cm3).
• Specific heat capacity at constant pressure (in J/g·K): 0.92 (+20–325 °C).
• Standard enthalpy of formation ΔfH (298 K, kJ/mol): −62.8 (t).
• Standard Gibbs energy of formation ΔfG (298 K, kJ/mol): −67.8 (t).
• Standard entropy of formation S (298 K, J/mol·K): 70.3 (t).
• Standard molar heat capacity Cp (298 K, J/mol·K): 62.34 (t).
• Melting enthalpy ΔHmelt (kJ/mol): 32.2.
• Calcium carbide has a strong garlicky odor.

Chemical properties

When interacting with water, calcium carbide hydrolyzes to form acetylene and calcium hydroxide (slaked lime):

CaC2 + 2H2O → Ca(OH)2 + C2H2↑

The above reaction is exothermic.

Melting temperature

2160 ºC

Boiling point

CC2 boils at 2300ºC with decomposition. The boiling point must be measured in an inert atmosphere, that is, without oxygen and moisture.

Density

2.22 g/cm3

Molecular weight

64.0992 g/mol

Physiological action

• Among all inorganic calcium derivatives, CaC2 is very toxic.
• In terms of the degree of impact on the human body, calcium carbide belongs to the 1st hazard class according to GOST 12.1.007.
• Getting calcium carbide into the body is also dangerous.
• Calcium carbide dust has an irritating effect on the skin and mucous membranes of the respiratory system.
• Calcium carbide CaC2 is extremely dangerous for the environment.

In reducing CO2 emissions

The residues obtained from the production of acetylene from CaC2 (also called "calcium carbide residue" or "calcium carbide residues") are used to produce clinker or concrete.

Calcium carbide mud has a high content of calcium hydroxide (Ca(OH)2) (about 90%), some calcium carbonate (CaCO3) and has a pH greater than 12.

For these reasons, it can react with SiO.2 or Al2OR3 to form a product similar to that obtained during cement hydration.

One of the human activities that produces the most CO2 emissions is the construction industry. Cooperation2 it is formed in the east to separate from calcium carbonate during the reaction to form concrete.

Using calcium carbide sludge to replace calcium carbonate (CaCO3) has been found to reduce CO2 emissions by 39%.

Welding, cutting and soldering of metals

when interacting with water. Other methods for producing acetylene, for example from oil by treating it with arc discharges (engineer Tatarinov, USSR), have not yet left the stage of laboratory research.

Technical calcium carbide is a solid crystalline substance, very refractory, dark gray in color with a specific gravity of 2.2 and a characteristic pungent garlic odor caused by the interaction of the carbide with water vapor in the atmospheric air. Calcium carbide reacts violently with water, as well as with water vapor, releasing acetylene and leaving calcium oxide hydrate according to the equation

In air, calcium carbide decomposes, interacting with water vapor, which is always present in the air, releasing acetylene and emitting a garlicky odor. Therefore, long-term storage of calcium carbide is possible only in hermetically sealed sheet iron drums. Calcium carbide is obtained by fusing lime with coal at high temperature in special carbide electric furnaces according to the equation

Calcium carbide is obtained in molten form and is periodically released from the furnace into molds, where, upon solidification, it forms ingots - blocks. Electricity consumption per 1 ton of calcium carbide ranges from 3000 to 4000 kWh for powerful industrial furnaces. Calcium carbide is produced in large quantities in large carbide plants for metal welding and cutting, chemical production and other purposes. After cooling, the carbide blocks are crushed and sorted by size of the pieces. Commercial carbide is produced in seven granulations from 2-4 to 80-100 mm. Carbide dust resulting from crushing is waste and is unsuitable for normal acetylene generators due to too vigorous decomposition by water, overheating and the danger of explosion. Granular carbide is packed into drums made of thin sheet iron, hermetically sealed; the drum holds 100-120 kg of carbide. Technical carbide contains 10-15% impurities, mainly unreacted coal and lime.

gives about 340 liters of acetylene (15°

and 760 mm Hg). According to the current standard, technical carbide should yield in laboratory tests, depending on the grade and granulation, from 230 to 300 liters of acetylene. The reaction for producing acetylene from calcium carbide is exothermic (about 400 kcal is released per 1 kg of technical carbide), therefore it is necessary to take measures to vigorously cool the reaction zone, otherwise severe overheating, polymerization and explosion of acetylene are possible.

Discontinued use

TsK2 it was used in so-called carbide lamps. They work by dripping water onto calcium carbide to form acetylene, which ignites and thus produces light.

These lamps were used in coal mines, but their use was discontinued due to the presence of CH4 methane in those mines. This gas is highly flammable and the flame of a carbide lamp may ignite or explode.

They were widely used in slate, copper and tin mines, and in early cars, motorcycles and bicycles as headlights or headlights.

Currently, they are being replaced by electric lamps or even LED lamps. However, they are still used in countries such as Bolivia, in the Potosi silver mines.

Transportation and storage

Due to the fact that moisture instantly decomposes carbide with the release of a large amount of heat and the formation of explosive acetylene gas, the substance must be stored in hermetically sealed drums or cans. It should be remembered that acetylene is lighter than air and can accumulate in the upper areas of the room. This gas, in addition to its narcotic effect, has the ability to spontaneously ignite. Therefore, calcium carbide must be used with great care. Special attention is paid to packaging in production. The finished substance is placed in special drums (containers resembling tin cans). This packaging requires careful opening. In this case, a tool that does not lead to the formation of sparks (a hammer or a special knife) should be used. If carbide gets on the skin or mucous membranes, immediately rinse the affected area with water and treat the area with Vaseline or greasy cream. Transportation of the connection is carried out using only covered modes of transport. Air delivery of carbide is prohibited. The premises where CaC2 is stored must be well ventilated. It is also not allowed to store carbide together with other chemicals. This can lead to unwanted, and possibly dangerous, reactions. The shelf life of carbide is six months.

Application area

Calcium carbide (Calcium carbide) is used to produce calcium cyanamide (by reaction with nitrogen), from which cyanide compounds and fertilizers are synthesized, for the production of carbide-urea plant growth regulators and carbide powder reagent.

Autogenous work and lighting, the production of acetylene black and other materials: synthetic rubber, alkonitrile, styrene, vinyl chloride, acetic acid, acetylene chloride derivatives, artificial resins, ethylene, acetone, etc., cannot be done without this substance. It is also used in the gas welding process, production of carbide lamps.

From a special fraction of calcium carbide (processed using waste and substandard raw materials) by reaction with water, acetylene gas and a by-product - slaked lime - are obtained. This procedure is accompanied by the release of a significant amount of heat. The volume of gas produced depends on the purity of calcium carbide (the purer the material, the more acetylene will be released) and varies between 235-285 liters from 1 kg of carbide.

Theoretically, 0.56 liters of water are required to decompose 1 kg of calcium carbide, but in practice, 5 to 26 liters of liquid are used to better cool the acetylene and ensure the safety of the process. The rate of decomposition will depend on the granulation and purity of the starting material, as well as on the temperature and purity of the water (the purer and smaller the size, the higher the temperature, the faster the reaction rate).

Preparation of calcium carbide

Technical calcium carbide is obtained by reacting calcined lime (CaO) with coke (3C) or anthracite in electric furnaces at a temperature of 1900-2300°C. A charge consisting of a mixture of coke or anthracite and lime in a certain proportion is loaded into an electric furnace, the charge is melted, and an endothermic chemical reaction occurs (with heat absorption) according to the formula:

CaO+3C = CaC2+CO -108 kcal/mol

Thus, to obtain 1 ton of calcium carbide it is required:

• 4000 kg lime
• 600 kg coke
• 1965 kWh of electricity

However, due to significant energy losses in carbide furnaces, practically to produce 1 ton of technical calcium carbide, from 2800 to 3700 kWh are consumed, depending on the power of the furnace. If the furnace power is less than 1000 kW, then the electricity consumption can reach 4000 kWh/t or more.

Molten calcium carbide is poured from the furnace into special molds, in which it cools and hardens. After hardening, it is crushed in jaw crushers and sorted in lattice drums into pieces of various sizes from 2 to 80 mm.

The yield of pieces of various sizes during crushing is given below:

Commercial calcium carbide is considered to have a granulation size of 2 to 100 mm. The carbide dust produced by crushing is unsuitable for normal acetylene generators due to its too vigorous reaction with water, overheating and risk of explosion.

The dependence of the specific gravity of technical calcium carbide on the CaC2 content in it is shown in the table below:

Technical calcium carbide produced in electric furnaces contains a number of impurities that enter it from the raw materials used in its production. Average chemical composition used for welding:

As can be seen from the given composition, the main impurity is lime.

Impurities contained in the starting materials used for production deteriorate its quality. Particularly harmful impurities are phosphorus and sulfur, which pass into calcium carbide in the form of calcium phosphorous and sulfur compounds, and during the decomposition of the carbide they enter acetylene in the form of hydrogen phosphorous and hydrogen sulfide.

Calcium carbide

Details Category:

CALCIUM CARBIDE

, CaC2, crystalline solid, specific gravity from 2.2 to 2.28; The melting point has not been precisely established and is indicated in the range of 1850-2300°. The fracture of technical calcium carbide, depending on the production conditions, varies from earthy to clearly crystalline; its color also varies, varying from gray to shiny black, often opalescent; the chemically pure product is colorless.

Chemical properties. The structure of the calcium carbide molecule is expressed by the formula

in the absence of moisture at ordinary temperatures, metals and air oxygen have no effect on it; under the same conditions, strong acids have little effect on it. At high temperatures, the chemical activity of calcium carbide increases, and at a temperature of about 1000° it enters into a chemical interaction even with nitrogen according to the equation:

C aC2 +
N2 = C aCN2 + C
When interacting with water, calcium carbide, even in the cold, decomposes with the rapid release of acetylene, C2H2; the reaction is accompanied by the release of a large amount of heat and is expressed by the equation:

CaC2 + 2H2O = C2H2 + Ca(OH)2 +414.6 Cal.

This reaction occurs even under the influence of atmospheric moisture, and pieces of calcium carbide are covered with a layer of slaked lime, which gives them a light gray color; Therefore, calcium carbide should only be stored in sealed containers. 1 kg of chemically pure calcium carbide gives 406.25 grams of acetylene, which at 0° and 760 mm Hg occupies a volume of 348.7 liters.

Calcium carbide was first obtained by Heru in 1840 during experiments with an electric furnace; Wöhler, who obtained a larger amount of calcium carbide in 1862 by alloying calcium with coal, had the opportunity to study its properties. In 1890, Moissan obtained calcium carbide by melting quicklime in an electric furnace, which gave the mentioned product by reacting with the carbon of the furnace electrodes. In 1894, Moissan's collaborator, Bullier, filed the first patent in France for an industrial method for producing calcium carbide, which is basically the same to this day. In the same year, the first electric carbide furnace was built, marking the beginning of the production of calcium carbide, which is currently expressed in millions of tons.

Modern industrial production of calcium carbide is based on the reduction of calcium oxide at high temperatures with carbon and the interaction of reduced calcium with coal. This process corresponds to the following equation:

2CaO + 3C2 = 2CaC2 + 2CO –210700 Cal.

This reaction is highly endothermic, and therefore can only occur in the presence of an intense heat source, such as the voltaic arc of an electric furnace. The reaction is a reversible process. The system is monovariant: each at equilibrium corresponds to a certain elasticity of CO. What is the minimum temperature at which the formation of calcium carbide begins has not been established with accuracy; most researchers believe that it lies between 1800 and 1900°. At a temperature of about 2500° lime melts; in the molten state, the latter serves as a solvent for the carbide, which greatly facilitates the further course of the reaction. Calcium carbide itself, under the conditions of its formation in a furnace, has a dough-like consistency and only with a further increase in temperature does it become liquid. With very strong overheating, the resulting calcium carbide decomposes according to the equation:

C aC2 = C a + 2C.

A feature of the production of calcium carbide is the absence of by-products, since impurities contained in the starting materials (if their quantity does not exceed a certain limit) dissolve in the resulting carbide without harming its technical qualities and only slightly reducing the percentage of CaC2, and as a result and acetylene yield.

Theoretically, calcium carbonate can also be used to produce calcium carbide, but in practice it is not used due to the excessive consumption of electrodes and energy caused by the following endothermic reactions:

CaCO3 = CaO + CO2 and CO2 + C = 2CO.

For the production of calcium carbide, only quicklime is used, which in most cases is obtained right there at carbide factories that develop nearby limestone deposits. Limestone being fired, b. relatively pure and contain, in any case, no less than 97% CaCO3 so that the burnt lime obtained from it contains no more than 4-5% impurities in the form of SiO2, Al2O3 and Fe2O3. The most unpleasant is the MgO impurity, the presence of which in an amount of 3-4% can significantly reduce the productivity of furnaces and even cause them to stop, since magnesia does not form carbide with carbonaceous materials and makes it difficult to dissolve calcium carbide in lime; The MgO content in limestone should not exceed 0.5%. Phosphates and sulfates may only be present in trace form; the maximum allowable is: 0.01% for phosphates and 0.3% for sulfates. These limestone impurities are completely transferred into the carbide in the form of calcium phosphorous and calcium sulphide - impurities that are extremely undesirable when using calcium carbide. Burnt lime going into production, b. in the form of fairly dense, not easily weathered pieces; It is best to use it immediately after leaving the furnace, crushing it into pieces 50-60 mm in size with as little dust as possible.

The carbon material for carbide production must also be very clean, which helps the furnace run properly and improves efficiency. Either low-ash anthracite or gas coke with a minimum ash content is used. Before the war of 1914-18. the maximum standard for ash content was considered to be 9%; Currently, some excess of this norm is allowed, but if possible it should be. minimal.

Coke, arriving from gas plants very raw, is first thoroughly dried until its moisture content is below 1%; In large plants, coke is dried in rotary dryers. Gas coke is highly electrically conductive and porous, allowing it to react easily with lime. Charcoal, especially hardwood, is also an excellent raw material for carbide production, since it is porous and contains little ash and harmful impurities; it increases the efficiency of the carbide furnace and produces a high-quality product, but for economic reasons its use is limited. Anthracite is very dense, difficult to react and is only suitable for working on powerful furnaces. With a low ash content (sometimes about 5%) it has an advantage over coke.

Phosphorus and sulfur in carbonaceous material are less harmful than in lime, since a significant part of them volatilizes during the process; Therefore, in carbonaceous material, phosphorus content up to 0.01-0.02%, and sulfur content up to 1.25% is permissible. The purer the lime, the more impurities can be tolerated in the carbonaceous material.

Carbide furnaces. To avoid electrolysis phenomena, alternating current is used in carbide furnaces. Depending on the type of installation, furnaces are powered with either single-phase or three-phase current. According to the operating principle, carbide furnaces are divided into: a) batch furnaces, from which calcium carbide is extracted in a solid state after cooling, b) continuous furnaces, from which the product is released in molten form through a special outlet. Periodically working with the formation of a solidified block of calcium carbide in a furnace is characteristic of the initial period of the carbide industry and is now almost never used. The first carbide furnaces were built with a power of 100–300 kW and had the form of small quadrangular iron crucibles mounted on trolleys. A fairly frequently used type of furnace is shown in Fig. 1.

The bottom of the furnace has a coal lining A and is one of the electrodes, the second electrode B enters from above; B - channel for CO removal. The method of operation in such furnaces is based on the electrical conductivity of heated carbide. Several furnaces are connected in a circuit in series, each with a voltage of 35-40 V. When the upper electrode is lowered, a voltaic arc is formed between it and the bottom of the furnace, and then the prepared charge is poured in: after melting a significant part of the charge, the arc is poured again. To maintain a constant current, the upper electrode is made movable. Work in batch furnaces continues until the carbide fills the crucible to its full height. Due to the fact that the heat capacity and latent heat of fusion of carbide are insignificant, it hardens quite quickly, after which the furnace is turned off, taken away and replaced with a new one. The carbide is easily separated from the furnace hearth; the block is removed using a tap and left for 12-24 hours to cool completely, after which they begin to separate the unreacted charge and crush the carbide.

Significant progress was the introduction of furnaces of higher power, up to 450-500 kW, without lower contact, but with two separate suspended electrodes with independent adjustment of each. The structure of such a furnace is shown in Fig. 2; two arcs connected in series are formed in it.

The advantage of such a furnace design is the high voltage in the network and low voltage at the furnace floor; The carbide here, as it forms, leaves the sphere of action of the current, which passes only through the upper layer. At the beginning of the work, two separate blocks are formed, which then merge into one large one, weighing up to 1 ton. These furnaces operate much more economically than small ones and in their design represent a transition to modern large multi-hearth furnaces.

The method of periodic operation is technically imperfect and uneconomical. Here, significant losses of the charge are inevitable, since the finished block of usable calcium carbide sometimes contains only about 50% by weight; In addition, periodic operation is associated with uneconomical use of energy and electrodes, and maintaining the furnace, cleaning it, crushing and sorting blocks requires a significant number of workers. The elimination of these inconveniences was associated with solving the problem of a continuous process, with the periodic release of the finished product from the furnace in molten form.

The main difficulty along this path was the rapid solidification of calcium carbide in the furnace: the high electrical conductivity of the molten carbide forces the upper electrode to be raised, i.e., to remove the voltaic arc from the hearth, as a result of which the lower part of the block hardens; opening the outlet (glass) becomes extremely difficult, and with a frozen layer of 15-20 cm - completely impossible. Therefore, in order to avoid blocking the glass, the carbide is not allowed to harden in the channel, for which purpose the thickened carbide is pushed inside the furnace with the thickened end of the crowbar, so that the channel itself remains free. In addition, in high-power furnaces (600 kW and above), they resort to periodic melting of the crust using a voltaic arc, for which an iron scrap (sometimes a carbon rod) connected to the upper electrode is inserted into the outlet hole and produces a voltaic arc, which melts the solidified carbide . The problem of producing calcium carbide by a continuous process was finally solved in 1904-07. construction of very high power furnaces, measured in thousands of kW. The designs of such furnaces are extremely varied: sometimes the lower part of the furnace serves as one of the electrodes; the other electrode is suspended movably in the upper part of the furnace

(Fig. 3, where A is the top electrode, B is the refractory lining); sometimes both electrodes A are placed horizontally (Fig. 4, Swedish three-phase oven).

Recently, three-phase furnaces have become widespread, having three electrodes located in the upper part; current passes from one electrode to another through a hot mixture, which forms a resistance. In fig. Figure 5 shows such a three-phase furnace with three vertical electrodes A and flexible bare copper bars C.

Modern furnaces for calcium carbide almost always operate with resistance, that is, they are designed so that during operation of the furnace the mixture of starting materials forms a source of resistance; molten calcium carbide flows down onto the furnace floor, and the newly poured charge replaces the reacted one and gradually enters the reaction zone. The end of the electrode is immersed in the mixture tens of centimeters; All the work of the maintenance personnel, in addition to filling the charge, is to prevent the white fire of the voltaic arc from breaking out, which is achieved by crowding the charge around the upper electrode and by punching the resulting arches from the sintered charge. This penetration prevents the formation of crusts, which can form during the cooling process of the furnace along the entire perimeter of the furnace shaft and reduce efficiency due to the occurrence of partial current short circuits.

Furnaces with an open voltaic arc have not been used for the production of calcium carbide over the past 15-20 years, since their operation is accompanied by the formation of local overheating, leading to the dissociation of the carbide produced, which in turn causes excessive loss of energy and materials, irregular operation, increased release of dust and hot gases, which make it difficult for maintenance personnel, and significant consumption of electrodes with reduced furnace output.

The power of furnaces, which at the beginning of the development of carbide production did not exceed 350-500 kW, currently reaches 1500, 3000, 6000 and even 12000 kW (the latter exclusively for three-phase furnaces). Round furnaces for 1000 kW have a diameter of 2.25–2.5 m, square furnaces of the same power have a cross-section from 2.25×2.25 to 2.75×2.75 m. A modern three-phase furnace for 4000–4500 kW has the following approximate dimensions: length 9 m, width 3 m and height 2.5 m. With units of higher power, work, due to the high temperature and fumes from the furnace, is extremely difficult. For every ton of calcium carbide produced, about 0.44 tons of carbon monoxide, CO, is released from the furnace, which in open-shaft furnaces, upon exiting the charge layer, burns into carbon dioxide, CO2.

To improve working conditions and use of CO, which can return about 30% of the energy usefully spent on carbide production, modern technical thought is working on the design of a closed furnace. An example of such a furnace is the one shown in Fig. 6 oven proposed by A. Gelfenstein.

The practical implementation of closed furnaces encounters great difficulties due to the fact that CO and air form an explosive mixture. Since it is very difficult to achieve complete tightness and avoid air leaks at the high temperatures prevailing in the furnace, working with such furnaces becomes dangerous and, as a result, explosions often occur. In view of this, none of the existing designs of closed carbide furnaces are widely used in technology, and the development of such furnaces is still experimental.

To obtain a temperature in the furnace of about 3000 °, required for a continuous process, it is necessary to establish the proper current density at the electrodes. The lower limit of current density is considered to be 2 A/cm2, the upper limit depends on the properties of the electrode material; at a load of 8-9 A/cm2, the carbon electrodes become red-hot along their entire length to the terminals. For mixed heating (voltage arc and resistance), used in modern Helfenstein furnaces, the following rule has been established: the higher the operating voltage, the greater the d.b. current density is taken. At the currently most common operating voltages of 50–90 V, the current density should be in the range of 3–6 A/cm2, depending on the nature of the electrodes. In carbide furnaces, ch. arr. solid baked electrodes made from a mixture of low-ash anthracite, retort coal and petroleum coke with coal tar and pitch. Good electrodes must have a homogeneous structure, high mechanical strength and high electrical conductivity. In practice, electrodes in the form of cylinders or bars of rectangular cross-section are used. The largest sizes of electrodes in American industry reach 5 meters in length with a square cross-section of up to 95 x 95 cm; in Western Europe, electrodes are prepared up to 3 meters long with a cross-section of up to 60 x 60 cm. However, smaller electrodes are more often used (25 x 25 x 200 cm; 40 x 40 x 250 cm; etc.). At high ampere loads of modern furnaces, such electrodes are collected in packages. A very important role in the design of the furnace is played by the electrode clamps, which connect the copper conductor that supplies current to the furnace with the electrode. Depending on the size of the furnace, the shape of the electrodes, and whether or not water cooling is used, the types of clamps vary greatly. In all kinds of clamps, the parts used to supply current are made of copper or bronze; the same parts that are directly adjacent to the surface of the electrodes are made of iron, steel or cast steel. The current density for water-cooled clamps is allowed at 7-8 A per cm2 of contact surface; in the absence of cooling, it should not exceed 3-4 A per cm2 of the contact surface. Recently, the so-called. Zederberg's "continuous soft electrodes"; they reach several meters in height, due to which the upper part of the electrode is located at a considerable distance from the hot part of the furnace in a specially designed cabin A (Fig. 7).

The electrode has a jacket made of thin boiler iron with holes on the side surface for the exit of gases; Inside the shirt there are several iron ribs that give it some rigidity. The inner cavity of the jacket is filled with a special highly sintered coal mass. The work of stuffing and compacting the mass is carried out in the mentioned cabin, which makes it possible to build up the electrode from above without interrupting the operation of the furnace. Zederberg electrodes are much cheaper than solid carbon electrodes, although, on the other hand, their consumption per 1 ton of calcium carbide is approximately twice as much as conventional solid ones, and they must be large in size, since their ampere load should not exceed 3-4 A /cm2.

The most expensive part of high-power furnaces are the copper busbars connecting the electrodes to the transformers. These tires should be used for some distance. must be flexible, so that as the electrodes are used up, the latter can be lowered; At the same time, the tires must allow the electrodes to move to the sides. They consist of a series of small-diameter copper cables adjacent to the rigid part of the electrode holders, consisting of copper plates. Normal current density in busbars is up to 1.5 A/mm2.

The ampere load of the furnace is regulated by moving the movable electrodes using winches. On small furnaces, such winches are manually driven, and on large furnaces with electrode packages they are powered by motors. In the newest installations, automatic Thury regulators, manufactured by N. Guenod near Geneva, or Siemens-Schuckert regulators are often used.

Progress of production. To obtain 1 ton of calcium carbide, according to theoretical calculations, 900 kg of quicklime, CaO, and 560 kg of carbon are required. The practical consumption of materials, depending on the design of the furnace, its power and operating conditions, is shown in table. 1.

The dosage of starting materials is carried out by weighing each of the products, and the amount of lime may be. slightly modified depending on the quality of the product desired. A certain excess of lime favors the reaction. The burnout of carbon in the charge in open furnaces, which occurs from contact with air, is compensated by the carbon of the electrodes.

Factories that operate several furnaces at the same time usually install them in one line in spacious rooms with good ventilation. Carbonaceous material and lime, previously crushed and mixed in devices equipped with automatic scales, are transported to the top of the furnace by a conveyor equipped with special buckets for filling. In large factories, materials are transported in railway cars directly to factory warehouses with a strongly sloping floor, along which they are sent by gravity to Black crushers. After crushing, these materials are lifted by mechanical elevators into special bins, from where they flow into two automatic scales. From the scales, materials are simultaneously transferred to conveyors, which dump them into one common drain. Thus, the prepared mixture is supplied using trolleys to electric furnaces into loading buckets. With such mechanization, one person can prepare 20 tons of mixture within 8 hours.

In furnaces operating on the principle of a continuous process, up to 3 releases per hour can be obtained. Both the amount of loaded charge and the loss of lime from evaporation during overheating significantly depend on the depth of immersion of the upper electrode into the mixture. When the furnace operates correctly, the charge, gradually warming up, descends along the electrode to the reaction zone. The melting zone, measured by the distance from the center of the electrode to the outer boundary of the liquid carbide, depends on the amount of heat emitted per unit surface of the electrode. To ensure proper operation of the furnace, it is necessary to accurately establish the most favorable current density corresponding to the melting of a given charge and the formation of liquid carbide; if the current density is insufficient, complete reduction of lime is not achieved, and if the current density is too high, the resulting carbide dissociates and partially evaporates.

Modern carbide furnaces produce about 6 kg of calcium carbide per kW-day; studies show that greater efficiency may be. obtained only in furnaces with a power of at least 3000 kW. Some foreign factories have installed three-phase carbide furnaces with 4000, 8000 and even 15000 kW, which work quite satisfactorily. On the other hand, attempts are being made to use the energy of carbon monoxide generated during the carbide production reaction to preheat the charge. The practical importance of CO utilization can be seen from the following approximate calculation: 1 kg of CaO and 0.7 kg of C yield 0.8 kg of pure CaC2 or 1 kg of commercial calcium carbide. Assuming the reaction temperature to be 3000° and taking the heat capacity of CaO equal to 0.2, and the heat capacity of the carbonaceous material to be 0.45, we obtain the amount of heat q required to heat the primary materials to 3000°:

q = (0.2 1 3000) + (0.45 0.7 3000) = 1545 Cal.

According to Vorkrand, the amount of heat required to form 0.8 kg of CaC2 from CaO and C is q' = 1316 Cal; therefore, the amount of heat Q required to produce 1 kg of commercial calcium carbide (0.8 kg of pure CaC2):

Q = q+q' = 1545 + 1316 = 2861 Cal;

1 kW-day = 20650 Cal, therefore, the output of the furnace is theoretically b. 20650:2861 = 7.21 kg of carbide per kW-day. If you use the heat of combustion of carbon monoxide in this process, then with the same energy consumption, the efficiency of the furnace will increase significantly. Indeed, upon production of 0.8 kg of CaC2 (1 kg of commercial calcium carbide), 350 grams of CO are released, yielding 850 Cal upon combustion. Therefore, the amount of heat required to form 1 kg of commercial calcium carbide will be 2861 - 850 = 2011 Cal, and the theoretical furnace output will increase to 20650: 2011 = 10.5 kg calcium carbide per kW-day. As stated above, the practical output in modern furnaces is expressed as 6 kg per kW-day, therefore, the efficiency reaches 85% without using the caloric power of CO; if we consider this use as possible, then the efficiency of a modern furnace is expressed only 57% of the theoretically calculated output. From this calculation it is clear that heat losses when carbon monoxide is not used are very large, and the successful resolution of the issue of at least partial elimination of these losses is of great practical importance.

From furnaces operating on the principle of a continuous process, calcium carbide is released from 1 to 3 times per hour in a fiery liquid state into cast iron molds of appropriate capacity, in which it quickly turns into a solid state. The hardened carbide, while still hot, in the form of ingots reaching a weight of 250 kg, is transported using mechanical conveyor devices to special dry rooms for cooling. After 10-12 hours, the cooled carbide is crushed using Black-type mechanical crushers. Crushed calcium carbide, depending on market requirements, is supplied to packaging either in unsorted pieces (uniformly sized) or sorted into pieces of certain sizes. Carbide sizes have pieces ranging from 15 to 100 mm with an average size of 125-40 mm; in such a product, pieces less than 15 mm are allowed in an amount of up to 5% of the total weight. Sorted calcium carbide is divided into 3 or 4 grades with the following piece sizes in mm:

In addition, calcium carbide is marketed in smaller pieces, sizes 1-2 mm, 2-4 mm, 4-8 mm and 8-15 mm. This carbide is often marketed as “granular.” Sorting of crushed calcium carbide by piece size is carried out in rotating mesh steel drums or on shaking flat sieves. The average ratio between the weight and volume of commercial calcium carbide, depending on the size of the pieces, can be seen from table. 2.

Since calcium carbide decomposes when it comes into contact with moisture, its storage requires a strong, sealed container, for which cylindrical drums made of 4-4.5 kg iron roofing are used. For greater tightness, the longitudinal seams are made into a double fold or welded using an autogenous method or electric welding, and to add rigidity, the side surface of large drums is corrugated. The loading holes of the drums are closed with a tin lid, soldered to the bottom with tin, or the edges of the lid are hermetically rolled onto the bent edges of the bottom hole. During transportation and storage of calcium carbide, it is necessary to carefully monitor the tightness of the container. It should be borne in mind that the penetration of moisture into the drum, even through small holes, ultimately leads to damage to the integrity of the drum, since the lime formed from decomposition occupies a larger volume than the carbide from which it was obtained. If the container is in good working order, calcium carbide can be stored without change for an indefinitely long time, and therefore only the number of drums required for work during the day is opened. Opening the drums should be done carefully, using pliers and trying to separate the loading hole cover along the soldering line; it is necessary to avoid the use of impact tools such as chisels, hammers, etc., since the impact may produce sparks and, if there is an explosive mixture of acetylene with air inside the drum, lead to an explosion. For the same reason, when opening drums, you should not use soldering torches or lamps. Calcium carbide is usually produced in drums weighing 100, 50, 30, 20, 10, 5 and 1 kg.

When shipped by railways and ships, according to the rules of the People's Commissariat of Railways, iron drums with calcium carbide must be packed in wooden cases to protect them from puncture; an exception is made only for large wagonload shipments. Instructions regarding the arrangement of warehouses and the procedure for storing calcium carbide are available in the mandatory decree of the People's Commissariat of Labor of the USSR dated January 14, 1926 (published in Izvestia NKTrud dated February 8, 1926, No. 4-5).

Technical analysis of calcium carbide. In view of the fact that the value of calcium carbide is determined mainly by the yield of acetylene from its weight unit, technical control of carbide production and determination of the quality of the product during acceptance are usually limited to determining the yield of crude (unrefined) acetylene from 1 kg of carbide. The volume of released acetylene is reduced to a temperature of 15° and a pressure of 760 mmHg. Since technical calcium carbide is a heterogeneous substance, the selection of average samples must be done especially carefully. There are usually precise rules for sample collection, set out in the description of the standard norms adopted in a particular state. A generally accepted device for the technical analysis of calcium carbide is the O.S.A. device. Its device is shown in Fig. 8.

It consists of a movable iron bell with a scale, an iron tank and an acetylene generator with accessories. The generator is connected to the bell by a rubber tube. The tank of the apparatus is filled with acetylene-saturated water. The bell is equipped with an equalizing counterweight, which plays an important role in all analysis operations.

As stated above, 1 kg of chemically pure CaC2 gives 348.7 liters of acetylene (at 0° and 760 mm Hg). Technical calcium carbide is considered benign if 1 kg of it produces from 280 to 300 liters of C2H2. Calcium carbide with an acetylene yield of more than 300 liters per kg is usually prepared only on special orders; This is explained by the fact that as the quality of the carbide approaches the theoretical one, it becomes less fusible, as a result of which electricity consumption increases disproportionately. In practice, the quantity and quality of impurities in calcium carbide are much more important than the high yield of acetylene from it. Constant impurities of calcium carbide are unreacted lime and coal. In addition, ferrosilicon is always present in the technical product, resulting in ch. arr. from ash elements of carbonaceous material; the amount of ferrosilicon in individual batches sometimes reaches 3% of the carbide weight.

Calcium carbide always also contains calcium sulphide and calcium phosphorous. Reducing the amount of the last three impurities can only be achieved by improving the quality of the starting materials.

Application. Calcium carbide serves as ch. arr. for the production of acetylene; In addition, significant quantities of calcium carbide are consumed in the production of calcium cyanamide by the Frank and Caro process.

Source: Martens. Technical encyclopedia. Volume 9 - 1929

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Application of the substance

Calcium carbide is actively used in industry. It is a catalyst in the synthesis of organic compounds. With its help, it became possible to synthesize rubber at a lower price. However, to do this, you first need to carry out the necessary chemical reactions to synthesize your own carbide, and only then rubber. More and more chemists are wondering where to find carbide in nature to make their work easier.

Carbide has found its application in gardening. Based on it, farmers obtain a fertilizer called calcium cyanide. Used to improve the growth of the root system of seedlings and adult plants.

How much does carbide cost?

Calcium carbide in RUSSIA from 50 rub./unit. Widely used in various industries, but mainly for mining. up to 130 rub./pcs.

Interesting materials:

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Safety precautions and storage

Calcium carbide belongs to hazard class 1 based on the degree of impact on the body. Its dust irritates the skin, mucous membranes and respiratory tract. The reagent is very dangerous if inhaled (symptoms: intermittent breathing, cough, runny nose, feeling of suffocation, pulmonary edema), contact with the skin (burns, ulcers) and in the eyes (soreness, lacrimation, swelling of the eyelids).

When using the material, it is necessary to use special protective clothing, a gas mask, gloves and special shoes. Work only in well-ventilated areas. In case of contact with skin, rinse the affected area with plenty of water, lubricate with a rich cream and call a doctor.

Store in sealed containers in a vertical position (no more than 3 rows) in fireproof, well-ventilated warehouses or in open areas under a canopy, protecting from moisture. Shared storage with other substances is not allowed. Shelf life – 6 months from the date of production.

Is it possible to extinguish calcium carbide with water?

Calcium carbide is a non-flammable product, but the acetylene released during its decomposition is explosive and fire hazardous. It ignites easily even with short-term contact with air and has the ability to spontaneously ignite even in its pure form. It also readily reacts with copper, silver and mercury salts to form unstable explosive acetelides. It has a narcotic effect due to hydrogen phosphide in its composition.

Under no circumstances should the reagent be extinguished with water! Explosions may occur if liquid gets into containers containing the substance. For extinguishing, dry powder fire extinguishers, dry sand, carbon dioxide, and asbestos sheet should be used.

Acetylene is lighter than air, so it can accumulate in the highest points of poorly ventilated rooms.

Sources

• https://pressadv.ru/metally-svarka/gde-vzyat-karbid.html
• https://stpoyka.ru/chto-takoe-karbid-opisanie-osobennosti-primenenie-i-cena-karbida/
• https://charchem.org/ru/subst-ref/?id=2004
• https://chem.ru/karbid-kalcija.html
• https://ru.warbletoncouncil.org/carburo-de-calcio-9133
• https://www.syl.ru/article/150446/mod_karbid-kaltsiya-svoystva-i-primenenie-poluchenie-atsetilena
• https://weldering.com/karbid-kalciya-acetilen-druzya-razley-voda
• https://him-kazan.ru/stati/karbid-kalcziya