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Calcium carbide

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Calcium carbide Basic information
As an important kind of chemical raw materials Physical properties Reaction with water Hazardous characteristics Chemical Properties Uses Production method Category Hazardous characteristics of explosive Flammability and hazard characteristics Storage characteristics Extinguishing agent
Product Name:Calcium carbide
Synonyms:Acetylenestones;calciumacetylide(ca(c2));calciumcarbide(cac2);calciumdicarbide;carburedecalcium;carburedecalcium(french);carburocalcico;ethyne,calciumderiv
CAS:75-20-7
MF:C2Ca
MW:64.1
EINECS:200-848-3
Product Categories:Inorganics;Carbides;Ceramics;Metal and Ceramic Science;Non metallic mineral;inorganic chemical raw material
Mol File:75-20-7.mol
Calcium carbide Structure
Calcium carbide Chemical Properties
mp 447°C
bp 2300°C
density 2.22 g/mL at 25 °C(lit.)
storage temp. water-free area
form pieces
Water Solubility hydrolyses
Sensitive Moisture Sensitive
Merck 14,1656
Stability:Stability Reacts violently with water liberating highly flammable gas (acetylene). Do not use water if this material is involved in a fire. Incompatible with moisture, water, strong oxidizing agents, alcohols, hydrogen chloride, magnesium.
EPA Substance Registry SystemCalcium carbide (Ca(C2))(75-20-7)
Safety Information
Hazard Codes F
Risk Statements 15-41-37/38
Safety Statements 8-43-43A-39-26
RIDADR UN 1402 4.3/PG 2
WGK Germany 1
10-21
HazardClass 4.3
PackingGroup II
Hazardous Substances Data75-20-7(Hazardous Substances Data)
MSDS Information
ProviderLanguage
SigmaAldrich English
Calcium carbide Usage And Synthesis
As an important kind of chemical raw materialsCalcium carbide (molecule formula: CaC2), is a kind of important chemical raw materials produced from the chemical processing of limestone. In 1892, H. Maysan (French) and H. Wilson (United state) simultaneously developed a calcium carbide production approach based on furnace Reduction. The United State had successfully achieved industrial production in 1895. The property of calcium carbide is related to its purity. Its industrial product is mostly the mixture of calcium carbide and calcium oxide, and also contains trace amounts of sulfur, phosphorus, nitrogen and other impurities. With the increasing content of impurities, it color exhibits gray, brown to black. The melting point and electrical conductivity both decrease with the decrease of the purity. The purity of its industrial product is usually 80% with m.p. being 1800 ~ 2000 °C. At room temperature, it does not react with air, but it can have oxidation reaction at above 350 ℃, and have reaction with nitrogen at 600 ~ 700 ℃ to generate calcium cyanamide. Calcium carbide, when coming across with water or steam, generates acetylene and release a large amount of heating. CaC2 + 2H2O─ → C2H2 + Ca (OH) 2 + 125185.32J, 1kg of pure calcium carbide can produce 366 L of acetylene 366l (15 ℃, 0.1MPa). Thereby, for its storage: calcium carbide should be strictly kept away from water. It is usually packed in a sealed iron container, and sometimes stored in a dry warehouse being filled with nitrogen if necessary.
Electric furnace reduction method is the only method for industrial production of calcium carbide at present. Put calcium oxide and coke for reduction reaction at 2000 ~ 2200 ℃: CaO + 3C─ → CaC2 + CO-480644.64J, the resulting molten calcium carbide flow into the receiver tank from the bottom of the reactor, and we obtain the final product after cooling. Calcium carbide production belongs to high temperature operation with relative large amount dust being produced and consuming a large amount of electrical energy. In 1980s, the production of per ton of calcium carbide consumes industrial power of about 10 ~ 11GJ. In order to reduce the power consumption, people mostly apply large-scale and closed calcium carbide furnace to reduce heat loss and also do good to the recycling of carbon monoxide.
Calcium carbide is mainly used as the raw material for the production of acetylene. Acetylene is an important and basic organic chemical raw material. But with the rise of the petrochemical industry, organic chemicals supplied acetylene has gradually provided by petrochemicals. The acetylene generator of metal cutting and welding applies calcium carbide. In places without electricity power, people usually apply calcium carbide lamp as the light source. Industrially, people apply calcium carbide for being heated in ammonia to produce calcium cyanamide, which is a kind of nitrogen fertilizer, plant defoliants and herbicides. With the development of acetylene chemical industry, the China's production of calcium carbide increases from the 3000 tons in 1949 to 1.808 million tons in 1983, ranking first in the world. But the production technology is still relatively lagged behind. The majority are small open furnace with high energy consumption rate and serious pollution. In order to reduce the energy consumption, modern production of calcium carbide mostly applied closed large-scale furnace to reduce heat loss and facilitate the recycling of carbon monoxide.
The above information is edited by the chemicalbook of Dai Xiongfeng.
Physical propertiesChemically pure calcium carbide is almost colorless and transparent crystals. Very pure calcium carbide crystals are large sky-blue crystal with its color being same as quenched steel. Industrial calcium carbide is divided according to their purity: gray, brown or black. Its crystallization section is gray while high purity version exhibits purple color. The new section of calcium carbide exhibits shiny surface with losing its luster and becoming gray-white due to absorption of air moisture upon exposure to the air. Calcium carbide is actually an impure calcium carbide containing lime and a small amount of impurities such as silica, alumina, calcium sulfide, and calcium phosphate. The chemical composition of electrical stone containing 85% of CaC2 is as following: CaC2 85.17%, CaO 10.60%, SiO2 2. 34%, (Fe2O3 + Al2O3) 2.55%, and MgO: 0.15%. Its density will decreases with increasing content of CaC2. Its melting point varies upon varying on CaC2 content. The melting point of pure CaC2 is around 2300 ℃; industrial calcium carbide generally contain CaC2: 80% with a melting point being about 2000 ℃; the lowest melting point is observed for calcium carbide containing 69%of CaC2, 1750 ℃; when CaC2 content further reduces, melting point begins increases again and then further reduce to 1800 ℃ later (equivalent containing CaC235.6%). There is a maximal melting temperature point between 1750 ℃ ​​and 1800 ℃: 1980 ℃ (equivalent to containing CaC2 52.5%); When the content of CaC2 is lower than 35.6, the melting point increased again.
Reaction with waterCalcium carbide will immediately have reaction upon coming across with water, generating acetylene and calcium hydroxide, which is the approach of industrial preparation of acetylene (carbide method), the reaction equation is:
CaC2 + 2H2O = C2H2 + Ca (OH) 2.
Since the impurity of calcium carbide, the generated acetylene gas is usually mixed with a small amount of hydrogen sulfide, phosphine gas and other contaminants, so there is a bad smell. Calcium carbide is produced from the lime and coke in an electric furnace at a high temperature of 3000 ℃:
3C + CaO = CaC2 + CO.
Upon the laboratory preparation of acetylene, owing to the reaction between calcium carbide and water is very fierce, we can apply saturated brine to substitute water so that a pure and smooth airflow of acetylene can be obtained. Calcium carbide won’t have reaction with sodium chloride.
Hazardous characteristicsCalcium carbide can absorb moisture in the air. It can be conductive with higher purity yielding higher conductivity. Its meeting with water or water vapor can generate explosive acetylene gas (commonly known as electronic gas stone). This gas can be ignited in case of fire, and can also be ignited by the heat released from the reaction. Acetylene gas can generate advanced explosive mixture upon being mixed with some heavy metal salts. Calcium carbide often contains impurities such as phosphorus and sulfur with its reaction with water also releasing toxic gases such as phosphine and hydrogen sulfide. When the content of phosphine exceeds 0.08% and the hydrogen sulfide content exceeds 0.15%, it is prone to result in spontaneous combustion explosion. The powder has irritation effects on the eyes and respiratory organs and can also cause skin burn injury. Calcium carbide is one of the basic raw materials in organic synthesis industry. It can not only generate acetylene gas for being applied to welding and cutting metals, but also can be the raw materials for manufacturing of PVC materials. Dust can cause irritation symptoms of the skin with the resulted impurities, in particular hydrogen sulfide and phosphine impurities being able to make people be poisoned. Also because it can easily generate flammable and explosive acetylene upon coming across water, thus being classified as dangerous goods. It should be stored in a cool, ventilated, dry place with the premises being not allowed for leaking of water. Therefore, make sure to be gentle when loading and unloading and also make sure its transportation equipment equipped with facilitator for preventing water and rain. Moreover, it should be kept away from steel and copper alloys and salts. During the transportation, make sure that: first load and then unload. It should be prohibited to mount it on the deck in order to avoid sunshine exposure. Upon fire extinguishing, it is prohibited to apply water and foam, instead you can apply dry powder and dry sand. However, carbon dioxide is not valid. After poisoning, the human should be immediately moved to place with fresh air. You should further help facilitate his/her breathing by applying oxygen containing 5% carbon dioxide. This product is produced from the co-heating of coke or anthracite in an electric furnace to a high temperature. United nation number (UN. No): 1402/4335 / 4.3-03 / 705. Domestic commodity number: 43025.
Chemical PropertiesIts industrial products are gray, brown or black solid with the product containing higher calcium carbide content exhibiting purple color.
Uses1. It can be used for the production of acetylene gas, PVC, lime nitrogen, dicyandiamide, iron and steel desulfurization agent.
2. It can be used for the electronics industry.
3. It can be used for teaching reagents.
4. Calcium carbide used in chemical production accounts for about 60% with the remaining 40% being applied for metal welding and cutting. It can produce a series of chemical product using calcium carbide, such as PVC resin, polyvinyl alcohol, vinyl acetate, chloroprene rubber, butanol, octanol, tri-cyanoethylene, tetracyanoethylene, acetaldehyde, acetylene coke, lime nitrogen, and so on. The largest amount is for PVC resin production, accounting for 60% of the chemical calcium carbide consumption. Calcium carbide powder is irritating which can do harm to the skin and respiratory system.
Production methodElectric furnace reduction method is the only method for the production of calcium carbide in the industry at present. This approach has achieved industrial production in early 1895 (US). The production process demands high-temperature operation with yielding a large amount of dusts and large power consumption. The technology improvements can improve the operating conditions, reduce the heat loss and improve the recovery efficiency of carbon monoxide. People mostly apply closed and large of calcium carbide furnace. Crash the coke and lime, mixed evenly according to the proportion and add into closed calcium carbide furnace, give electricity for heating and perform reduced reaction at 2000-2200 ℃, generating molten calcium carbide, and flowing into the electric furnace from inside furnace, cool, crush and pack. Kg / ton of coke (84% of fixed carbon) 550 limestone (92% of CaO) 840 electric electrode paste, 3200 (kWh / ton).
CategoryCombustible goods upon water combustible goods.
Hazardous characteristics of explosivegenerate acetylene when mixed with water and is explosive upon mixing with an oxidizing agent.
Flammability and hazard characteristicscontact with water releases flammable acetylene gas; water emit a small amount of toxic hydrogen sulfide, phosphine gas.
Storage characteristicsTreasury: ventilation, low-temperature and drying; should be stored separately from oxidants and strong acids.
Extinguishing agentDry powder, dry sand, dry powder.
Chemical Propertiesgrey or black solid with a garlic-like odour
Usageused as desulfurizer and dehydrant of steel and for cutting and welding metals.?in organic synthesis industry, Acetylene obtanied from calcium carbide is raw material to make ethylene, chloroprene rubber, calcium cyanamide, acetic acd, acetaldehydr, ethylacetate, cyanide acetate, dicyandiamide, acetone, octanol, trichloride ethylene etc
General DescriptionGrayish-black irregular lump solid. Used to make acetylene and in steel manufacture.
Air & Water ReactionsReacts rapidly with water to generate the flammable gas acetylene and the base calcium hydroxide. Enough heat may be generated to ignite the gas [Jones, G.W. BM Report Invest. 3755 1944].
Reactivity ProfileCalcium carbide is a reducing agent. May react vigorously with oxidizing materials. The powdered mixture of the acetylide and iron oxide and iron chloride burns violently upon ignition, producing molten iron. Calcium carbide incandesces with chlorine, bromine, or iodine at 245, 350, or 305°C., respectively, [Mellor, 1946, Vol. 5, 862]. The carbide burns incandescently when mixed and heated with lead difluoride, magnesium, hydrogen chloride, and tin (II) chloride, [Mellor, 1946, 1940, 1946, and 1941], respectively. Interaction of Calcium carbide with methanol to give calcium methoxide is vigorous , but subject to an induction period of variable length. Once reaction starts, evolution of acetylene gas is very rapid, unpublished observations [Bretherick 1995]. Mixing Calcium carbide with silver nitrate solutions forms silver acetylide, a highly sensitive explosive. Copper salt solutions would behave similarly, [Photogr. Sci. Eng., 1966, 10, 334]. The mixture of Calcium carbide and sodium peroxide is explosive, as is Calcium carbide and perchloryl fluoride as gases at 100-300°C.
Health HazardEye and skin irritation
Fire HazardBehavior in Fire: If wet by water, highly flammable acetylene gas is formed.
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