Calcium carbide manufacture

Occurrence. Carbon monoxide is a product of incomplete combustion and is not likely to result where a flame bums in an abundant air supply, yet may result when a flame touches a cooler surface than the ignition temperature of the gas. Gas or coal heaters in the home and gas space heaters in industry have been frequent sources of carbon monoxide poisoning when not provided with effective vents. Gas heaters, though properly adjusted when installed, may become hazardous sources of carbon monoxide if maintained improperly. Automobile exhaust gas is perhaps the most familiar source of carbon monoxide exposure. The manufacture and use of synthesis gas, calcium carbide manufacture, distillation of coal or wood, combustion operations, heat treatment of metals, fire fighting, mining, and cigarette smoking represent additional sources of carbon monoxide exposure (105—107). 

Coke is employed for a number of purposes, but the major use is in the manufacture of carbon electrodes for aluminum refining that requires a high-purity carbon— low in ash and sulfur free. In addition, petroleum coke is employed in the manufacture of carbon brushes, silicon carbide abrasives, and structural carbon (pipes, Rashig rings, and so on), as well as calcium carbide manufacture from which acetylene is produced. 

Essentially all the energy is consumed in calcium carbide manufacture. In the electrothermal process, the reaction is carried out at temperatures in excess of 1850°C. If we ignore the lime (recovered), and convert other consumption/by-product figures to energy values, we obtain (per mol acetylene equivalent) ... 

The original method for the manufacture of ethyne, the action of water on calcium carbide, is still of very great importance, but newer methods include the pyrolysis of the lower paraffins in the presence of steam, the partial oxidation of natural gas (methane) and the cracking of hydrocarbons in an electric arc. 

Historically, the use of acetylene as raw material for chemical synthesis has depended strongly upon the avadabihty of alternative raw materials. The United States, which until recendy appeared to have limitless stocks of hydrocarbon feeds, has never depended upon acetylene to the same extent as Germany, which had more limited access to hydrocarbons (1). During Wodd War 1 the first manufacture of a synthetic mbber was undertaken ia Germany to replace imported natural mbber, which was no longer accessible. Acetylene derived from calcium carbide was used for preparation of... 

The first process for manufacture of calcium carbide [75-20-7] and acetylene [74-86-2] involved the reaction of coke and lime. The carbide process operates at a temperature of about 2000°C according to the following reaction ... 

Properties and handling, Manufacture from calcium carbide, Bibliography,... 

Chemical Uses. In Europe, products such as ethylene, acetaldehyde, acetic acid, acetone, butadiene, and isoprene have been manufactured from acetylene at one time. Wartime shortages or raw material restrictions were the basis for the choice of process. Coking coal was readily available in Europe and acetylene was easily accessible via calcium carbide. 

A number of high temperature processes for the production of titanium carbide from ores have been reported (28,29). The aim is to manufacture a titanium carbide that can subsequently be chlorinated to yield titanium tetrachloride. In one process, a titanium-bearing ore is mixed with an alkah-metal chloride and carbonaceous material and heated to 2000°C to yield, ultimately, a highly pure TiC (28). Production of titanium carbide from ores, eg, ilmenite [12168-52-4], EeTiO, and perovskite [12194-71 -7], CaTiO, has been described (30). A mixture of perovskite and carbon was heated in an arc furnace at ca 2100°C, ground, and then leached with water to decompose the calcium carbide to acetjdene. The TiC was then separated from the aqueous slurry by elutriation. Approximately 72% of the titanium was recovered as the purified product. In the case of ilmenite, it was necessary to reduce the ilmenite carbothermaHy in the presence of lime at ca 1260°C. Molten iron was separated and the remaining CaTiO was then processed as perovskite. 

Boron Triiodide. Boron ttiiodide is not manufactured on a large scale. Small-scale production of BI from boron and iodine is possible in the temperature range 700—900°C (70—72). Excess I2 can be removed as Snl by reaction with Sn, followed by distillation (71). The reaction of metal tetrahydroborates and I2 is convenient for laboratory preparation of BI (73,74). BI can also by synthesized from B2H and HI in a furnace at 250°C (75), or by the reaction of B with excess Agl or Cul between 450—700°C, under vacuum (76). High purity BI has been prepared by the reaction of I2 with mixtures of boron carbide and calcium carbide at elevated temperatures. 

Calcium Carbide and its Derivatives. Although hydrocarbon-based acetylene production has become mote important, eady manufacture of acetylene was based on manufacture of the iatermediate, calcium carbide [73-20-7J, CaC2. This ionic acetyUde is produced by reaction of lime and carbon ia electric-arc furnaces (16). 

With the exception of carbon use in the manufacture of aluminum, the largest use of carbon and graphite is as electrodes in electric-arc furnaces. In general, the use of graphite electrodes is restricted to open-arc furnaces of the type used in steel production whereas, carbon electrodes are employed in submerged-arc furnaces used in phosphoms, ferroalloy, and calcium carbide. 

For the manufacture of calcium cyanamide, cmde calcium carbide (ca 3.36 x 1.68 mm or 6 x 12 mesh) can be used, whereas for cyanamide and dicyandiamide, a 74 p.m (200 mesh) anhydrous carbide is used. 

The filtered cake produced from the manufacture of dicyandiamide contains about 86% calcium carbonate. American Cyanamid Co. blends the dried waste for the manufacture of calcium carbide-based desulfurized reagents as a gas releasiag agent. 

Source of Heat Industrial furnaces are either fuel-fired or electric, and the first decision that a prospective furnace user must make is between these two. Although elecdric furnaces are uniquely suited to a few apphcations in the chemical industiy (manufacture of sihcon carbide, calcium carbide, and graphite, for example), their principal use is in the metallurgical and metal-treatment industries. In most cases the choice between elecdric and fuel-fired is economic or custom-dictated, because most tasks that can be done in one can be done equally well in the other. Except for an occasional passing reference, electric furnaces will not be considered further here. The interested reader will find useful reviews of them in Kirk-Othmer Encyclopedia of Chemical Technology (4th ed., vol. 12, articles by Cotchen, Sommer, and Walton, pp. 228-265, Wiley, New York, 1994) and in Marks Standard Handbook for Mechanical Engineers (9th ed., article by Lewis, pp. 7.59-7.68, McGraw-Hill, New York, 1987). 

Although the current source of acetylene is petroleum, it can be manufactured from calcium carbide, a product of the reachon of limestone and coke (carbon). During World War II, Germany, having a shortage of petroleum, used the latter technology to develop a chemical industry based on acetylene. 

Acetylene is manufactured by the controlled reaction between water and calcium carbide ... 

Although a great variety of chlorinated hydrocarbons of the lower carbon numbers had been well known and produced in small quantities for many years, the large scale manufacture and use of such compounds other than chloroform and carbon tetrachloride is a fairly recent development. And although synthesis, particularly of the two-carbon derivatives, has in great measure depended on acetylene from calcium carbide, more and more reliance has been placed on petroleum raw materials in this field in the last few years. 

Acetylene is usually thought of as a coke-derived product via calcium carbide. But acetylene, used for vinyl resins manufacture, has been made by partial oxidation of natural gas methane for over a year now in a major installation in Texas, which is now being expanded (6). Moreover, another Gulf Coast plant now under construction will also produce acetylene from natural gas, utilizing this product for acrylonitrile as well as vinyl chloride production (28). These moves represent a momentous advance, pointing to the future entry of natural gas to an even greater degree into aliphatic syntheses. 

The Union of Two Elementary Substances.— The most obvious way in which to prepare a binary compound is by the union of the two constituent elements, though in many cases this is not the most practicable way. Sometimes, the elements are first prepared in pure form and are then combined in other cases, the preparation of the elements and their union is effected in one operation, as in the manufacture of calcium carbide and carborundum. In general, the more dissimilar the two elements the more likely they are to combine readily, but elements of the same general kind sometimes combine with ease, as is the case with chlorine and iodine, sulfur and phosphorus, or sodium and lead. 

Calcium carbide is an important chemical in the manufacture of acetylene... 

Acetylene is still manufactured by the action of calcium carbide, a product of the electric furnace. 

In the early days of the chemical industry, acetylene was a key starting material for many important products. Initially it was obtained for chemical purposes by reaction of calcium carbide with water but that practice has given way to acetylene recovery from hydrocarbon cracking, so that now 86 percent of acetylene used in chemical manufacturing is made in this way. Owing to difficulty in its safe collection and transport, it is almost always used where it is prepared. 

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