Methane production during coal

Although porosity dictates the rate at which methane can diffuse out of the coal (in the seam) and there may also be some influence during preparation operations in terms of mineral matter removal, the major influence of the porous nature of coal is seen during the utilization of coal. For example, during conversion, chemical reactions occur between gas (and/or liquid) products and surface features, much of which exists within the pore systems. 

Coal formations offer another opportunity to store CO2 because it adsorbs strongly on the coal surfaces. Contacting coal surfaces with CO2 via flue gas injection may have application at coal-fired power plants near coal mines and in other areas where suitable coals are accessible. Since CO2 adsorbs more strongly than methane on coal surfaces, there is the potential for increasing methane production from coal bed methane operations. The effectiveness of adsorption processes will depend heavily on the type and permeahility of the coal formations. BP operates an ECBM project in northwestern New Mexico and southwestern Colorado. We are adding a commercial-scale demonstration of C02-nitrogen injection during 2001-2002. 

Synthetic Natural Gas. Another potentially very large appHcation of coal gasification is the production of synthetic natural gas (SNG). The syngas produced from coal gasification is shifted to produce a H2-to-CO ratio of approximately 3 to 1. The carbon dioxide produced during shifting is removed, and CO and H2 react to produce methane (CH, or SNG, and water in a methanation reactor. 

Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. More information on methane. 

During the past several decades, coal made hydrogen is mainly used in areas for the production of chemicals such as ammonia, methanol, methane, and Fischer-Tropsch products (Figure 3.2). 

The carbonization of coal illustrates the formation of organic compounds by the disruption of large molecules to form smaller ones. Coal is a mixture of complex organic compounds whose nature is mostly unknown. Heating causes disruption of the molecules. Some of the fragments, such as methane, CH4, carbon dioxide, COi, appear in the products others combine to form such compounds as benzene, CoHe, toluene, CtHs, naphthalene, CioHs, which are isolated from the viscous tar. The coke which remains in the retort consists of carbon produced during the decomposition,... 

In contrast to stream water, groundwater in the Warrior coalfield may have elevated arsenic concentrations. Waters produced during methane recovery from coal (n=28) were found to have a mean arsenic content of 25 ppb with a maximum of 475 ppb (O Neil et al., 1993). These production waters are typically saline and not potable. However, the presence of elevated arsenic in the deep groundwater samples indicates that arsenic may be mobilized from the coal into solution. Shallow drinking-water wells in the Warrior coalfield are lower in arsenic than the production waters, having a mean of 2 ppb and a maximum of 44 ppb (n=35)(0 Neil et al., 1993). The highest of these arsenic contents exceed the present drinking water standard and indicate the potential for at least isolated arsenic contamination. 

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