Carbon/coke

It is not possible, however, to calculate accurately actual gas composition by using the relationships of reactions (27-14) to (27-19) in Table 27-12. Since the gasification of coal always takes place at elevated temperatures, thermal decomposition (pyrolysis) takes place as coal enters the gasification reactor. Reaction (27-15) treats coal as a compound of carbon and hydrogen and postulates its thermal disintegration to produce carbon (coke) ana methane. Reaction (27-21) assumes the stoichiometiy of hydrogasifying part of the carbon to produce methane and carbon. 

Figure 12-8A. Piston rings. The piston rod is manufactured from heat-treated stainless steel and is coated with wear-resistant overlays, such as ceramic, chromium oxide, and tungsten carbide applied by plasma techniques. Piston rod cross-head attachment has mechanical preloading system for the threads. Rider rings and seal rings are manufactured from PTFE filled resins fillers are matched to the gas, piston speed, and liner specifications. Typical fillers are glass, carbon, coke, or ceramic. (Used by permission Bui. BCNA-3P100. Howden Process Compressors Incorporated. All rights reserved.)...

Phosphorus is prepared by heating a mixture of Ca2(P04)2, sand, and carbon (coke). White phosphorus, P4, distills out and can be cooled and collected under water. 

Carbon (coke) consumption, as a fuel and as a producer of the gaseous reductant, carbon monoxide, takes place in the blast furnace. An alternative source of such carbon, along with... 

Figure 7.7b shows the essential features of a refinery catalytic cracker. Large molar mass hydrocarbon molecules are made to crack into smaller hydrocarbon molecules in the presence of a solid catalyst. The liquid hydrocarbon feed is atomized as it enters the catalytic cracking reactor and is mixed with the catalyst particles being carried by a flow of steam or light hydrocarbon gas. The mixture is carried up the riser and the reaction is essentially complete at the top of the riser. However, the reaction is accompanied by the deposition of carbon (coke) on the surface of the catalyst. The catalyst is separated from the gaseous products at the top of the reactor. The gaseous products leave the reactor... 

The reaction between CaO and carbon (coke) at very high temperature produces CaC2... 

Hojanas Also called Siurin. An iron extraction process. Magnetite, mixed with carbon-coke breeze and limestone, is heated in a ceramic retort by passage through a tunnel kiln at 1,200°C. Used commercially in Sweden since 1911. See also DR. 

Elemental silicon is produced commercially by heating silica with carbon (coke) in an electric furnace using carbon electrodes ... 

Silicon carbide is prepared by heating fine sdica with carbon (coke) and a little salt and sawdust in an electric furnace. 

The charge-discharge profile of amorphous carbon (coke) electrodes is... 

The traditional synthesis route involves the direct reaction of silicon with nitrogen at temperatures above 1,300 °C, or by heating silica with carbon (coke) in a stream of nitrogen and hydrogen at 1,500 °C.41 However, as in the case of silicon carbide, the high processing and fabrication temperatures focused attention on the need for alternative access routes based on preceramic polymers. 

Catalyst plugging the deposition of carbon (coke) or metal contaminants that decreases flow through the catalyst bed. 

The elements can be obtained by reduction of oxides or halides. Highly divide carbon black is used as a catalyst and black pigment, and impure carbon (coke) for reducing some metal oxides (e.g., in the manufacture of iron). Pure silicon prepared by reduction of SiCl4 with Mg is used in electronics (silicon chips) although much larger quantities of impure Si are used in steels. 

Possible pollution sources in the area include dust, ash, scum, slag, carbon coke residues, minerals, heavy oils, hydrocarbons, and combustion residues. The minerals used to produce cast iron and steel were imported mainly from Africa (Liberia and Mauritania), Canada, India, the former USSR, and from the American Continent (L Industria Mineraria, 1979a). 

In the case of carbon (coke), the variation of concentration over the catalyst bed gives an indication of the origin of the deposit. A decreasing profile implies that some compound in the feed is responsible. If the main reactant brings about coke formation, one has a so-called parallel coking . An increasing profile indicates that coke is formed from a reaction product ( consecutive coking ). 

Although all the side reactions affect the selectivity, from the point of view of the catalyst, the production of carbon (coke) is the biggest problem as it remains in situ and acts as a poison. The use of superheated steam plays a vital role here, as it helps to clean the catalyst by gasification of carbon at the working temperature (Equation 10). 

In this method, lime (calcium oxide) is reduced by carbon (coke or anthracite) CaO -i- 3C - CaCj + CO = 465 kJ/mol... 

However there are several major hurdles. The most common catalysts are based on acid catalysis with Bronsted or Lewis acid sites these sites promote the formation of propylene rather than ethylene as is witnessed by conventional FCC operations. Ethylene is promoted by free radical processes. Catalysis of free radical reactions is rare, but not unknown . One route is to take a conventional acid catalysis and to neutraUse the acid sites with alkaline metals (magnesium, calcium) or phosphorus or a mixture of such. This can generate a further problem, in that the catalyst promotes the formation of carbon (coke) and hydrogen which are thermodynamically favoured at the reaction temperatures. 

Conradson carbon coke deposits shortly after feed introduction. If high conradson carbon feed is processed in a MST unit, coke will deposit shortly after feed introduction. As the MST reactor consists of a fixed bed reactor, the feed will still meet clean catalyst after passing the first zone, where CCR coke deposits. Consequently the mechanism is different compared to commercial units. It can also be shown that material boiling above the MST reactor temperature does not leave the reactor, resulting in a low mass balance (9, 10). Therefore it is recommended to test high CCR feeds (CCR> 4-5%) in a fluidized bed system or in a riser unit. 

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