Gasification by oxygen

The oxidation of carbon in practice is, perhaps, better described in terms of the influence of mass and heat transfer on the kinetics of the chemical reaction, and these aspects of gasification by oxygen have been reviewed by Mulcahy, ... 

The thermodynamics of the gasification reactions has been considered in detail in reference 177. Gasification by oxygen and hydrogen is exothermic, but reaction with steam or carbon dioxide is endothermic. The reaction between carbon and hydrogen may be restricted by equilibrium at normal working temperatures and pressures, but the other reactions are not. 

Marsh H, Taylor DA, Lander JR. Kinetic study of gasification by oxygen and carbon dioxide of pure and doped graphitizable carbons of increasing heat treatment temperature. Carbon 1981 19(3) 375-381. 

Synthesis Gas Generation Routes. Any hydrocarbon that can be converted into a synthesis gas by either reforming with steam (eq. 4) or gasification with oxygen (eq. 5) is a potential feedstock for methanol. 

Regeneration of coked catalysts may be accomplished by gasification with oxygen, steam, hydrogen, or carbon dioxide ... 

Mechanisms A and B both state that carbon monoxide retards the gasification of carbon by carbon dioxide by decreasing the fraction of the surface which is covered by oxygen atoms under steady state conditions. In mechanism A, fli is decreased by the chemisorption of carbon monoxide by a fraction of the active sites. In mechanism B, 61 is decreased by the reaction of a portion of the chemisorbed oxygen with gaseous carbon monoxide to produce gaseous carbon dioxide. Reif (57) shows that only one of these reactions can control retardation at one time. 

The gas feed stream is split, recycle CO2 is added to each stream and the combined streams are fed to each of the two gasification trains. Oxygen from the Air Separation Unit (ASU) is preheated by steam, split and fed to the two gasification trains. Partial oxidation and reforming reactions take place in the Gasifiers. 

Drying followed by low-temperature pyrolysis (500-550°C) in a rotary kiln for about 1 h. Gasification of produced gas at 1000°C to obtain CO/H2-rich gas char fines are separately gasified by oxygen at 1500°C... 

A combination of controlled atmosphere electron microscopy and flow reactor techniques have been used to investigate the influence of hydrogen sulfide on the catalytic activity of cobalt. Changes in the behavior of cobalt were monitored by the use of probe reactions which are sensitive to the chemical nature of the catalyst surface. These included graphite gasification in oxygen and hydrogen, and carbon deposition from decomposition of hydrocarbons. 

Of these reactions, gasification with oxygen (or combustion) is undoubtedly the most important process and has received by far the most attention. Both chemical and chemical engineering aspects of the problem have been recently reviewedand only a brief review will be presented here. 

The Reaction of Carbon with Oxygen. - The gasification of carbon by oxygen is of great importance, particularly in connection with coal conversion. The subject has received much attention and two recent reviews have given excellent accounts of the chemical and chemical engineering aspects of the problem. 

It should be emphasized that the brevity of this Section does not reflect the lack of interest in gasification of carbons by oxygen but, rather, the existence of excellent reviews that describe most of the recent studies and place them in context one with another.The interested reader is referred to these papers. 

The process can be stimulated by vibrationally excited H2 molecules through their surface dissociation and diffusion of H atoms into the crystal structure. The process can be considered to be gasification of oxygen from the crystal structure by vibrationally excited hydrogen (Legasov et al., 1978c). Metal reduction starts from the surface. The front of metal formation propagates from the surface into the solid body. The depth of the reduction layer is limited by the recombination of H atoms ... 

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