Gasification, coal methane formation

At the temperatures used in coal gasification 870°C), methane formation also occurs by hydrogenation of carbon ... 

As in any gasification of coal the exothermic reaction of carbon with oxygen to CO (60) and C02 (Eq. 78) and the endothermic reaction with water (Eq. 61) run in parallel in different extent it seems to be often a mere semantic question whether to classify- a process as a partial oxidation or to use just the more general expression of coal gasification. Bouduard equilibrium (Eq. 46), water gas shift equilibrium (Eq. 37) and methane formation equilibrium (Eq. 71) are additional determinants... 

After the devolatilization and rapid-rate methane formation stages are completed, char gasification occurs at a relatively slow rate various models to describe the gasification kinetics of this material for various limited ranges of conditions have been proposed. The differential rates of reaction of devolatilized coal chars are a function of temperature, pressure, gas composition, carbon conversion, and prior history. 

Non-conventional gas is natural gas found in unusual underground conditions, such as very impermeable reservoirs which require massive stimulation in order to be recovered, or in underground occurrences of gas hydrates, or dissolved in formation water, or coal-bed methane, or gas from in-situ gasification of coal. 

The distinguishing characteristic of non-plasma and plasma methods of gasification is that the products are different the non-plasma conventional carbonization process yields gas and tar plasma processes yield gas and soot. Based on the representative data collated for hvab coal in Table 17 it is inferred that the gas from carbonization is richer in methane, the chief component of natural gas and the preferred product the gas from plasma is richer in acetylene. In most of the plasma methods collated in Table 17 the gas temperatures were 1300 K or more and any methane formed would readily decompose to yield acetylene. Clearly, in-so-far as the plasma formation of methane is concerned the temperature region of 700—1000 K needs to be investigated. Her 60 Hz discharges, with or without electrodes, in reactors heated to the desired temperature may be advantageous. 

Wang, J., Jiang, M., Yao, Y., Zhang, Y., Cao, J. (2009). Steam gasification of coal char catalyzed hy K2CO3 for enhanced production of hydrogen without formation of methane. Fuel, 88, 1572-1579. 

The non-catalytic partial oxidation [486] (POX, Texaco, Shell) needs high temperature to ensure complete conversion of methane and to reduce soot formation. Some soot is normally formed and is removed in a separate soot scrubber system downstream of the partial oxidation reactor. The thermal processes typically result in a product gas with H2/C0=1.7—1.8. Gasification of heavy oil fractions, petcoke, coal and biomass may play an increasing role as these fiaetions are becoming more available and natural gas (NG) less available. 

Other reactions that would permit the selective formation of a given alcohol from synthesis gas are the focus of much current research, because synthesis gas is readily available by the gasification of coal or other biomass in the presence of water, or by the partial oxidation of methane. 

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