Preparation of acetylene Interaction of calcium carbide with water

Chemical compound
Calcium carbide

Calcium carbide

, also known as
calcium acetylide
, is a chemical compound with the chemical formula of C2. Its main industrial use is the production of acetylene and calcium cyanamide.[3]

The pure material is colorless, but pieces of technical calcium carbide are gray or brown in color and consist of approximately 80–85% CaC2 (the rest is CaO (calcium oxide), Ca3n2 (calcium phosphide), CaS (calcium sulfide), Ca3N2 (calcium nitride), SiC (Silicon Carbide), etc.). In the presence of traces of moisture, commercial calcium carbide emits an unpleasant odor reminiscent of garlic.[4]

Applications of calcium carbide include the production of acetylene gas, and also for the production of acetylene in carbide lamps; production of chemicals for fertilizers; and in steelmaking.

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.

Production

Calcium carbide is industrially produced in an electric arc furnace from a mixture of lime and coke at approximately 2200 °C (3990 °F).[5] This endothermic reaction requires 110 kilocalories (460 kJ) per mole[6] and high temperatures to remove carbon monoxide. This method has not changed since its invention in 1892:

CaO + 3 C → CaC2 + CO

The high temperature required for this reaction is practically unattainable with traditional combustion, so the reaction is carried out in an electric arc furnace with graphite electrodes. The resulting carbide product typically contains about 80% calcium carbide by weight. The carbide is crushed, forming small lumps ranging in size from a few to 50 mm. Impurities are concentrated in smaller fractions. CK2 Product content is determined by measuring the amount of acetylene formed during hydrolysis. For example, British and German standards for larger fractions are 295 L/kg and 300 L/kg respectively (at 101 kPa pressure and 20 °C (68 °F)). Impurities present in carbide include phosphide, which produces phosphine upon hydrolysis.[7]

This reaction was an important part of the Industrial Revolution in chemistry, and it was made possible in the United States as a result of the huge amount of low-cost hydroelectric power produced at Niagara Falls before the turn of the 20th century.[8]

The electric arc furnace production method was discovered in 1892 by T. L. Wilson and independently by H. Moissan in the same year.[9][10][11] In Bosnia and Herzegovina, the city of Jajce, the Austrian industrialist, Dr. Josef Kranz and his “Bosnische-Elektrizitäts AG”

the company, which was later succeeded by
Elektro-Bosna
, opened the largest chemical plant in Europe for the production of calcium carbide in 1899. Hydroelectric power station on Pliva to supply the plant with electricity was built along the river with an installed capacity of 8 MW. It was the first power station of its kind in South-Eastern Europe and was commissioned on 24 March 1899.[12]

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.

Carbide - fun for children of the 90s

In the 90s there were no computer gadgets or the Internet yet, the kids had fun as best they could. Some shot birds with slingshots, others made smoke bombs. But the most dangerous thing was playing with carbide. There were many options: they threw it into a fire, it burns well when wet, they threw it into water and watched it bubble, they made bombs from plastic bottles.

Carbide was easy to obtain; gas welders threw it away right at the welding site. The boys, seizing the moment, picked up as much as they could carry and ran away from this place. The most interesting activity was exploding plastic bottles with carbide. They put carbide in a bottle, filled it with water, shook it and moved away. They occupied an observation position and waited for the explosion. The carbide fumes inflated the plastic until the bottle burst. It always happened suddenly, which added to the fun. There was such a case: the guys were sitting, as usual, exploding plastic bottles, and one they came across was very strong and did not want to explode. She was swollen and that's it. Tired of waiting for an explosion, we decided to do something else, for example, throw carbide into the fire. They were sitting, watching the burning of the reagent, and suddenly it occurred to someone to throw that same bottle that never exploded into the fire. They took her with them and carried her almost all day. Here comes the realization that the explosion will not be weak, but with fire. They only managed to run a couple of steps when a deafening explosion followed, the guys felt a blow to the back from the blast wave, and fell to the ground. All the residents of the yard ran out into the street to see what had exploded. By that time, the guys had rushed away from the scene at breakneck speed. They had never run so fast before. In addition to the bomb, they made a cannon from a beer can. They took an empty jar, cut off the top, and made a small hole in the side, closer to the bottom. A piece of carbide was placed inside and slightly wetted. They plugged the holes and shook them a little. Then they opened the top, and brought a burning match to the small hole, which produced a loud shot of accumulated gases. The fun was very dangerous, and there were quite a few casualties. They received severe burns to their hands and face. The scars remained for life. It’s still good if he escaped with scars, because he could have burned out his eyes and remained blind for life. There were such cases too. This is how the kids of the dashing 90s had fun. Today's youth are far from such fun. On the one hand, it’s good that they don’t risk their health.

You may also be interested: “Rubik’s Snake” - a puzzle from the 90s

Transportation and storage

Calcium carbide powder decomposes almost instantly when exposed to moisture. This produces acetylene, which in high concentrations is flammable and explosive. That is why it is necessary to pay quite a lot of attention to the storage of calcium carbide, for which cans and special drums are often used. Other storage features include the following:

1. The released acetylene is lighter than air, so it accumulates at the top. It is worth considering that it has narcotic effects and can spontaneously ignite.
2. When producing large volumes of a substance, special attention is paid to safety precautions. Special packaging is used for packaging.
3. To open the package, use tools that do not cause sparks.
4. If the substance gets on the skin or mucous membrane, it must be removed immediately. In this case, the affected surface is treated with a special cream or other protective and healing substance.
5. According to established rules, transportation can only be carried out using a covered vehicle. However, delivery by air is prohibited.

Transport container

Regulations also prohibit storing calcium carbide with other chemicals and heat sources. This is because the resulting gases can react chemically with other chemicals and ignite.

Application

The structural formula of acetylene shows us a fairly strong bond between carbon atoms. When it ruptures, for example during combustion, a lot of energy is released. For this reason, the acetylene flame has a record high temperature - about 4000 °C. It is used in torches for welding and cutting metal, as well as in rocket engines.

The acetylene combustion flame also has a very high brightness, so it is often used in lighting devices. It is also used in explosives. True, it is not acetylene itself that is used, but its salts.

As can be seen from its varied chemical properties, acetylene can be used as a raw material for the synthesis of other important substances: solvents, varnishes, polymers, synthetic fibers, plastics, organic glass, explosives and acetic acid.

Explosion hazard of acetylene and safety when handling it:

Acetylene has explosive properties.

Therefore, handling acetylene requires strict adherence to safety regulations.

Acetylene burns and explodes even in the absence of oxygen and other oxidizing agents.

Mixtures of acetylene with air are explosive over a very wide range of concentrations.

A stream of acetylene released into the open air can ignite from the slightest spark, including from a discharge of static electricity from a finger.

The explosiveness of acetylene depends on many factors: pressure, temperature, purity of acetylene, moisture content in it, the presence of catalysts and other substances, and a number of other reasons.

The auto-ignition temperature of acetylene at normal - atmospheric pressure ranges from 500-600 °C. As the pressure increases, the auto-ignition temperature of acetylene decreases significantly. Thus, at a pressure of 2 kgf/cm2 (0.2 MPa, 1.935682 atm.), the auto-ignition temperature of acetylene is 630 °C. And at a pressure of 22 kgf/cm2 (2.2 MPa, 21.292502 atm.), the auto-ignition temperature of acetylene is 350 °C.

Application[edit | edit code]

Calcium carbide is used in autogenous work and lighting, as well as in the production of acetylene black and organic synthesis products, of which synthetic rubber is the main one.

Calcium carbide is used in the production of calcium cyanamide, from which fertilizers and cyanide compounds are obtained.

Calcium carbide is used to obtain carbide-urea plant growth regulator and to produce powdered carbide reagent.

From 1 kg of technical carbide, 235 to 285 liters of acetylene are obtained, depending on its grade and granulation: the purer and larger the calcium carbide, the greater the amount of acetylene it produces during decomposition.

The decomposition of 1 kg of calcium carbide theoretically requires 0.56 liters of water. In practice, take from 5 to 20 liters of water to better cool the acetylene and ensure safety during operation. The rate of decomposition of calcium carbide by water depends on its purity, granulation, temperature and water purity. The purer the calcium carbide, the smaller the size of its pieces, the higher the temperature and the purer the water, the greater the speed[3].

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%.

Recommendations

1. Massalimov, I. A.; Kireeva, M. S.; Sangalov, Yu. A. (2002). "Structure and properties of mechanically activated barium peroxide". Inorganic materials
   .
   38
   (4): 363. doi:10.1023/A: 1015105922260. S2CID 91881752.
2. NFPA Hazard Rating Information for Common Chemicals. Northeastern University
3. Patnaik, Pradyat (2003). Handbook of Inorganic Chemical Compounds
   . McGraw-Hill. ISBN 0-07-049439-8.
4. Vincoli, Geoffrey Wayne (25 November 1996). Risk Management for Hazardous Chemicals
   . CRC Press. p. 429. ISBN 978-1-56670-200-3.
5. ^ a b c d
   Greenwood, Norman N.;
   Earnshaw, Alan (1997). Chemistry of elements
   (2nd ed.). Butterworth-Heinemann. p. 298. ISBN 978-0-08-037941-8.
6. Calculated from data in the CRC Handbook of Chemistry and Physics
   .
7. ^ a b
   Calcium Carbide, Bernhard Langhammer, Ullmann's Encyclopedia of Industrial Chemistry, Wiley Interscience. (Subscription required)
8. Freeman, Horace (1919). "Production of cyanamide." Chemical News and Journal of Physical Sciences
   .
   117
   :232.
9. Morehead, J. T. & de Chalmotte, G. (1896). "Production of calcium carbide." Journal of the American Chemical Society
   .
   18
   (4): 311–331. Doi:10.1021/ja02090a001.CS1 maint: several names: list of authors (link)
10. Moissan, H. (1892). "Chimie Minérale - Description d'un nouveau four électrique." Comptes rendus hebdomadaires des séances de l'Académie des Sciences
    .
    115
    :1031.
11. Renouf, Edward (1899). "Use of Acetylene". Monthly Popular Science Magazine
    : 335–347.
12. “Zgrada Prve hidrocentrale na Balkanu - Komisija za očuvanje nacionalnih spomenika.” old.kons.gov.ba
    (in Serbo-Croatian). CONS. Retrieved March 15, 2022.
13. ^ a b
    Greenwood, Norman N.;
    Earnshaw, Alan (1997). Chemistry of elements
    (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
14. Dong, I (01/23/2006). "Troubles in the PVC industry." Hong Kong Trade Development Council. Archived December 28, 2007.CS1 maint: BOT: Source URL status unknown (link)
15. “The government is taking action to curb the development of calcium carbide.” China Daily via BusyTrade.com. 2007-05-16. Archived February 11, 2007.CS1 maint: BOT: Source URL status unknown (link)
16. Lacson, Jamie; Schlag, Stefan; Toki, Goro (December 2004). "Calcium carbide". Research Institute Consulting.
17. "Speleological Equipment and Culture (from Te Ara New Zealand Encyclopedia)".
18. Clemmer, Gregg (1987). American Miners' Carbide Lamps: A Collectors' Guide to American Carbide Mine Lighting
    . Westernlore Publications.
19. Abeles, F. B., & Gahagan, H. E. III (1968). "Uptake: the role of ethylene, ethylene analogues, carbon dioxide and oxygen". Plant Physiol. 43
    (8):1255–1258. Doi:10.1104 / p.43.8.1255. PMC 1087003. PMID 16656908.CS1 maint: several names: list of authors (contact)
20. “Bet on it. Your mango is ripened using carbide.” DNA
    . 2013-05-18. Received 2018-08-25.
21. “Eating artificially ripened fruits is harmful.”
22. "Carbidschieten wordt feest" (in Dutch). Algemin Dagblad. 2016-12-24.
23. Singh, Randhir. "Determination of water content in soil - calcium carbide method." Civil Engineering Portal
    . Retrieved September 7, 2022.
24. ASTM International. "ASTM D4944-18, Standard Test Method for Determining Water (Moisture) Content of Soil Under Field Conditions Using a Calcium Carbide Gas Pressure Meter." ASTM International. Retrieved September 7, 2022.