Castner Process

The Castner process operates without intermediate resistive materials. The heat is thus exclusively produced in the carbon articles themselves, which are directly spanned between two electrodes at lea.st one of which is movable to allow for changes in dimensions. 

Castner furnaces are smaller than Acheson furnaces. Heating up and cooling down phases are significantly shorter than in the Acheson process. Also here there is a switch to continuous operation. 

The Castner process is characterized by more efficient energy utilization and by more uniform graphitization compared with the Acheson process. Disadvantageous is the more complex furnace construction and restrictions concerning the dimensions of the carbon articles. 

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Cast-link belt furnaces Cast molding Castner cell Castner process... 

In early times hydrogen cyanide was manufactured from beet sugar residues and recovered from coke oven gas. These methods were replaced by the Castner process in which coke and ammonia were combined with Hquid sodium to form sodium cyanide. If hydrogen cyanide was desired, the sodium cyanide was contacted with an acid, usually sulfuric acid, to Hberate hydrogen cyanide gas, which was condensed for use. This process has since been supplanted by large-scale plants, using catalytic synthesis from ammonia and hydrocarbons. 

The Beilby process started in 1891 and by 1899 accounted for half of the total European production of cyanide. In this process, a fused mixture of sodium and potassium carbonates reacts with ammonia ia the presence of carbon. In 1900, the Castner process, in which molten sodium, ammonia, and charcoal react to give a high (98%) grade sodium cyanide, superseded the Beilby process. Sodium cyanide became an article of commerce and soon replaced potassium cyanide in all except special uses. 

The historic Castner process that was developed in the 1800s and operated throughout the world until the late 1960s is now obsolete. 

Until the 1960s, when HCN became widely available, NaCN was made by the Castner process via sodamide and sodium cyanamide ... 

Acheson (2) A process for converting carbon articles into graphite, invented by E. G. Acheson in 1895 and commercialized in 1897. This process uses transverse graphitization, unlike the Castner process, which uses lengthwise graphitization. 

The fused product is poured into molds. The process was invented by G. T. Beilby in Scotland and first used in 1891 in 1900 it was replaced by the Castner process. 

A preparative method similar to the Castner process for the production of sodium cyanide involves adding red-hot charcoal slowly to molten potassium in a steel vessel. The mixture is heated to about 750°C and then ammonia is introduced gradually. The fused product is pumped to a filter furnace at high tempeature where the molten potassium cyanide is filtered in a nitrogen atmosphere. The overall reaction for the process is ... 

Because water is reacting with sodium produced at the cathode, the yield of sodium is reduced almost hy 50%. Lesser yield is the major disadvantage of the Castner process. At present, this process is not used commercially. 

Castner process -for cyanides [CYANIDES] (Vol 7) -for hydrogen cyanide [CYANIDES] (Vol 7)... 

The salts of hydrazoic acid, M+Ns, have already been discussed in Section 3.2.4, but a variety of other alkali pseudohalides exist. The most important of these are the cyanides M+CN , preparable by neutralization of HCN with the appropriate alkali base. NaCN and KCN reached such industrial importance that alternative bulk syntheses have been developed (e.g. equation 10). This Castner process fed the gold extraction industry and continued to feed the electroplating and nylon synthesis markets until cheaper routes directly to HCN were found. In cases where the alkali cyanides are still required, the simple neutralization route is now most economic. 

Graphitization processes are carried out at 2600 to 3000°C in inert atmospheres in direct or indirect processes. In direct processes (e.g. Acheson and Castner processes) the carbon articles between the electrodes are heated, either directly or indirectly with resistive materials in between, and the required temperature for graphite formation attained by resistive heating. In indirect processes there is no physical contact between the energy source and the carbon article. 

The Castner Process (see English Patents, 12,219 of 1894 21,732 of 1894. See also the German Patents, 117,623, 124,977 (1900) 126,241 (1900) 148,045 (1901).—One of the most important syntheses of cyanide from ammonia was successfully worked on the large scale by the Frankfurter Scheideanstalt in 1900, the process having been worked out by H. Y. Castner some years... 

Castner process. A method of producing sodium metal from fused sodium hydroxide by means of an electrolytic cell with heavy iron anodes surrounding the cathode in the bath. Sodium is collected on an iron gauze diaphragm midway between the electrodes. Hydrogen and oxygen are also collected during the process. 

Graphitization of the baked and impregnated carbon products occurs at temperatures from 2,500 to 3,000 °C, using the Acheson process (transverse graphitization) or the Castner process (lengthwise graphitization). 

By 1899, half the cyanide manufactured in Europe was produced by the Beilby process. From 1900 to 1961, another process, called the Castner process, was used to make sodium cyanide. The Castner process is shown helow ... 

In 1888, the Castner process was industrialized for the production of sodium by electrolysis in molten NaOH at 330 °C [1]. The Downs cell for the electrolytic production of sodium was patented in 1922 [2], and soon after, it replaced the Castner process for Na production, and a modified Downs cell is still being used industrially. The original Downs cell is shown in Fig. 1. A modified version of the Downs cell is shown in Fig. 2. The modified Downs cell is equipped with four anodes and four cathodes. The steel gauze diaphragm prevents direct contact between the products chlorine bubbles evolved on graphite anodes and liquid sodium deposited on steel cathodes. 

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