Pyrolysis, coal

Pyrolysis gasoline Pyrolysis-gc Pyrolysis of coal Pyrolysis processes Pyrolysis yields... 

Although small amounts of hquids are produced during coal pyrolysis, significant amounts of coal-derived hquids did not become available until after the... 

Coal pyrolysis has been studied at both reduced and elevated pressures (136), and in the presence of a variety of agents and atmospheres (137). Although important to the study of coal stmcture and reactions, coal pyrolysis, as a means to generate Hquids, has proved to have limited commercial value. 

Because of the importance of the petroleum-based processes discussed previously, only about 1% of the U.S. supply of BTX currentiy comes from coal pyrolysis (21). 

Outside the United States, coal pyrolysis is more important as a source of BTX. The proportions are about 70 20 10, but can vary greatiy depending on the coal and on the pyrolysis process used. Product quaUty is not as good as petroleum-derived BTX. This source could become more important again if petroleum costs escalate. Much higher yields of BTX from coal can be obtained by first hydrogenating the coal (22). 

Other large-scale coal pyrolysis process developments were carried out by the Tosco Corp., with its TOSCO AT, process (36). Essentially a direct copy of Tosco s rotating kiln technology that was developed for pyrolysis of oil shale, this slow heating scheme achieved tar yields at maximum temperatures of 482—521°C that were essentially identical to those obtained by a Eischer assay. 

Tai yields of approximately 0.32 m /1 were quoted. Because the scheme used hydrogen, the pyrolysis Hquids generally exhibited lower heteroatom contents than conventional tars derived from coal pyrolysis ia an iaert atmosphere. Process development proceeded through a 270 t/d semiworks plant which was operated successfully on noncaking coals. OperabiUty for caking coals was difficult, however. 

Liquid fuels for use in internal-combustion engines are extracted and refined from crude oil, with diesel fuels being part of the middle distillate or kerosene fraction. Kerosene was initially derived from coal pyrolysis. The initial main use of this type of distillate was for the kerosene lamp, which had replaced lamps based on whale oil. 

Van Krevelen et al. [529,530] in rising temperature studies of coal pyrolysis, used the rate equation... 

Conversion of coal to benzene or hexane soluble form has been shown to consist of a series of very fast reactions followed by slower reactions (2 3). The fast initial reactions have been proposed to involve only the thermal disruption of the coal structure to produce free radical fragments. Solvents which are present interact with these fragments to stabilize them through hydrogen donation. In fact, Wiser showed that there exists a strong similarity between coal pyrolysis and liquefaction (5). Recent studies by Petrakis have shown that suspensions of coals in various solvents when heated to 450°C produce large quantities of free radicals (. 1 molar solutions ) even when subsequently measured at room temperature. The radical concentration was significantly lower in H-donor solvents (Tetralin) then in non-donor solvents (naphthalene) (6). 

Conversion from coal to natural gas. Sasol 1 was designed as a coal-to-liquids facility. A natural gas pipeline was constructed and commissioned in 2004. This allowed the Sasol 1 facility to be converted to a gas-to-liquids plant. Although it implied that the associated coal tar refinery would become redundant, the decision was made by Sasol to keep the coal-to-chemicals units at Sasol 1 in operation by supplying coal pyrolysis products from its larger CTL facility in Secunda. 

E.M. Coal pyrolysis experiments, kinetic rates and mechanisms, Prog. Energy Combust. Sci., 18, 133-220, (1992). 

Pyrolysis In pyrolysis, coal is heated in the absence of oxygen to drive off volatile components, leaving behind a solid residue enriched in carbon and known as char or coke. Most coal pyrolysis operations are for the purpose of producing metallurgical coke, with the liquids... 

The reduction in thermoplasticity of the metaplast is possibly the result of the promotion of aromadsation/char condensation reaaions at die expense of production of stable volatile species during coal pyrolysis. In this way, the generation of specific char types at 1273 K in the EFR can be related to the proportion of elemental oxygen within the original coal stmcture of the oxidised or weathered coal particle below an atomic 0/C ratio of =0.15 the predominant char is that of the cenosphere variety due to the maintenance of nunaplast fluidity during pyrolysis. 

However, the question whether the combustion of oxidised or weathered pulverised coal would maintain a self-sustaining flame in a full-size industrial boiler at maximum load cannot be addressed within the present study. The inhibition of volatile matter release, due to the promotion of char condensation reactions during coal pyrolysis, suggests that this may not be the case, a point pertaining especially to the more severely oxidised coals (i.e. 373 K for 112 days). Clearly there is need for ture work within this area of pulverised coal combustion. 

The volatile components from coal pyrolysis are primarily small hydrocarbons and oxygen-containing molecules. By adding H2O and limited O2 and while heating coal, these products incorporate considerable 0 atoms into the volatile products to form alcohols, aldehydes, ketones, and acids. However, these products consist of many molecules that... 

Milton Denekas. The implication of the relation of crude oil composition to a Fischer-Tropsch product is that oil has been produced by a synthetic process (building-up) rather than by a degradative process. Can you assume that the products from coal pyrolysis are also produced by a synthetic building-up) process rather than by degradation ... 

CNDO/2 MO, 2, 120 Cneorin NMR, 4, 573 Cneorin-C structure, 4, 533 Coal pyrolysis... 

The use of gas chromatography to determine oxygen in coal is considerably faster than the methods just described. The oxygen produced from coal pyrolysis in a vacuum was converted to carbon monoxide catalytically, and the total quantity of gas was measured. Gas chromatography was then used to measure the concentration of carbon monoxide in the gas. 

Further developments of the work include a more accurate study of the mechanisms of desulfurization processes using instrumental improvements. This will enable an easy quantitation of gas yield and a thermochemical approach of elemental processes. We also have been using model polymers to better study the interactions of pyrite and sulfur with the organic matrix during coal pyrolysis, oxidation and combustion (34 and to examine more accurately the specific role of organic sulfur in thermal degradation processes. 

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