Carbochemistry

About: Carbochemistry is a research topic. Over the lifetime, 1010 publications have been published within this topic receiving 16626 citations.

Chemistry of Fossil Fuels and Biofuels: Carbonization and coking of coal

Abstract: Thermal decomposition of coals Often the terms carbonization and pyrolysis are used almost interchangeably. Pyrolysis has the broader meaning: breaking apart of molecules by application of heat or thermal energy. As discussed in Chapters 19 and 22, pyrolysis processes could be run to make gases or liquids rather than solids as the primary product. Carbonization, more narrowly defined, refers to conversion of a starting material into carbon, or a carbon-rich solid. It is entirely possible, and indeed often done, to pyrolyze a hydrocarbon feedstock for the purpose of carbonization, but carbonization is not simply pyrolysis by another name. Carbonization can be effected without using heat as the primary driving force, a good example being carbonization of sucrose (ordinary table sugar) by pouring concentrated sulfuric acid on it; carbonization occurs very promptly and very effectively. Carbonization driven by thermal energy usually requires temperatures >500 °C. A carbonaceous solid that appears to have passed through an intermediate fluid state when being produced is called a coke . Carbonaceous solids that do not pass through such a fluid state during formation are chars . These definitions apply to carbonization processes using any feedstock, including biomass, petroleum, and polymers. All coals, regardless of whether they are caking or coking coals, leave a solid carbonaceous residue at the end of the carbonization process. Chars, if heat-treated to extreme temperatures, e.g. ≥2500 °C, do not form graphite, while cokes do. That is, chars are non-graphitizable, while cokes are graphitizable [A].

Review of supporting research at Oak Ridge National Laboratory for underground coal conversion

Abstract: Chemical and physical properties of lignite, subbituminous coal, bituminous coal, and overburden have been measured in research that began in 1974 at Oak Ridge National Laboratory. Generally, large, monolithic blocks of sample have been dried and pyrolyzed. Thermal data and product yields can be correlated to provide an extrapolation from powder pyrolysis to the pyrolysis steps in underground coal gasification. Significant results of the past year include correlation of block pyrolysis data for low-rank coals, interpretation of mechanisms, and comparison between low-rank and bituminous coals; heating tests of overburden cores from the Hoe Creek field gasification site; and measurement of physical properties, particularly thermal diffusivity and thermal conductivity of low-rank coals. Correlations, mechanisms, and property measurements are reviewed, and applications to underground coal gasification are discussed.

Coal flash pyrolysis in a free-jet reactor

Abstract: Coal pyrolysis was examined in a novel free-jet reactor capable of achieving heating rates greater than 10/sup 4//sup 0/C/s and reaction time on the order of 10 ms. Liquid yields equivalent to the volatile matter in the coals were obtained at temperatures between 900 and 1000/sup 0/C. Below this temperature range, it was found that all coal particles were not reacting. Above this temperature range, secondary cracking of the primary coal liquid produced lighter liquids and gas. Oxygen in the coal associates with the volatile material, concentrating in the liquids below 900/sup 0/c, and then in the gas product as vapor-phase cracking becomes important.

Methane formation and water-gas shift reactions over potassium carbonate loaded on coal char at elevated pressure in H2-CO-H2O system

Abstract: The rate of methane formation over potassium carbonate catalyst loaded on coal char was measured at elevated pressure in the range 1.5-2.0 MPa in the H2-CO-H2O system. The rate of simultaneous progress of the water-gas shift reaction was also measured. The effect of gaseous components on these reactions was investigated to obtain the respective rate equations. The existence of H2O in the reactant gas decreased the rate of methane formation through CO hydrogenation and enhanced that through carbon hydrogenation. In the H2-CO-H2O system, the rate of carbon hydrogenation is comparable to that of the CO hydrogenation as reaction temperature becomes high and suitable for steam gasification. The fixed-bed gasification was carried out at 2 MPa and 1023 K, and the exit gas compositions were simulated on the basis of these kinetic data. The calculated results agreed fairly well with the experimental ones.