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Natural Gas, Crude Oil, Heavy Crude Oil, Extra-Heavy Crude Oil, and Tar Sand Bitumen
Published in James G. Speight, Refinery Feedstocks, 2020
Coalbed methane is a gas formed as part of the geological process of coal generation and is contained in varying quantities within all coal. Coalbed methane is exceptionally pure compared to conventional natural gas, containing only very small proportions of higher-molecular-weight hydrocarbon derivatives such as ethane and butane and other gases (such as hydrogen sulfide and carbon dioxide). Coalbed gas is over 90% methane and, subject to gas composition, may be suitable for introduction into a commercial pipeline with little or no treatment (Rice, 1993; Levine, 1993; Mokhatab et al., 2006; Speight, 2013a). Methane within coalbeds is not structurally trapped by overlying geologic strata, as in the geologic environments typical of conventional gas deposits (Speight, 2013a, 2014a). Only a small amount (on the order of 5% v/v–10% v/v) of the coalbed methane is present as free gas within the joints and cleats of coalbeds. Most of the coalbed methane is contained within the coal itself (adsorbed to the sides of the small pores in the coal).
The Reuse and Recycling of Coal Mining Waste with Zero-Waste Approach by Technological Development and Integrated Management for Sustainable Growth and Benefits
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Hossain Md Anawar, Vladimir Strezov, Tanveer M. Adyel
Coal mining liberates methane gas trapped in the coal seams. Waste coal mine gas is a safety hazard and impediment in underground coal mines. It must be extracted by mine ventilation and coal seam drainage. The extracted methane can be used as a power generation fuel. Due to the uneconomical extraction of coal bed methane, it has previously been extracted by ventilation and released directly into the air without treatment, which resulted in wasting the resources, contributing to the greenhouse effect and pneumoconiosis (Tang et al., 2007; Islam and Hayashi, 2008; Hemza et al., 2009; Myers, 2009). Thus, it is necessary to develop sustainable and economic resource recovery techniques that can prevent and reduce mine disasters (Xueyu, 2004) on the one hand and provide economic benefits on the other hand. At present, China has established the largest scale of CBM extraction wells (e.g., 1000 m digger in module type), CBM compression and liquefaction capacity in Asia. Coal bed methane is released from the mine by three different processes such as extraction, hole extraction and wind emission. The CBM has been widely used in many industries, such as civil usage, industrial production (pre-concentration of low concentration gas), power generating, car fuel, and so forth. In addition, the CBM is also a high-quality raw chemical material for synthetic methanol, synthetic ammonia and acetylene. It can produce the carbon black applied to the tire rubber industry, plastics production, printing ink, batteries, alloys, smelting, and so on.
Feedstock Preparation
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Briefly, and because it is sometimes combined with petroleum-based natural gas for processing purposes, coalbed methane is the generic term given to methane gas held in coal and released or produced when the water pressure within the buried coal is reduced by pumping from either vertical or inclined to horizontal surface holes. Thermogenic coalbed methane is predominantly formed during the coalification process whereby organic matter is slowly transformed into coal by increasing temperature and pressure as the organic matter is buried deeper and deeper by additional deposits of organic and inorganic matter over long periods of geological time. On the other hand, late-stage biogenic coalbed methane is formed by relatively recent bacterial processes (involving naturally occurring bacteria associated with meteoric water recharge at outcrop or sub-crop) can dominate the generation of coalbed methane. The amount of methane stored in coal is closely related to the rank and depth of the coal, the higher the coal rank and the deeper the coal seam is presently buried (causing pressure on coal) the greater its capacity to produce and retain methane gas. Gas derived from coal is generally pure and requires little or no processing because it is solely methane and not mixed with heavier hydrocarbon derivatives, such as ethane, which is often present in conventional natural gas.
A comprehensive gas extraction system coupling high-level suction roadway and boreholes for gas disaster prevention in closely-spaced multiple coal seams
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Feng Yang, Zhaolong Ge, Jiufu Chen, Liang Cheng, Hongbo Lei, Lishuang Zou
The traditional emission methods for coal mine gasses are return airways and tail drainage. Gas with low methane concentrations (less than 2%) cannot be used for power generation so this low-CH4 gas is discharged into the atmosphere, contributing to air pollution and the atmosphere’s greenhouse gasses. In 2015, 13.6 billion cubic meters of coalbed methane was extracted from coal in underground coal mines in China, but the gas utilization rate was only 35.3%. After the initiation of the high-level gas extraction system in the Datong mine, 4.4 million cubic meters of coalbed methane were extracted in 9 months and with methane concentrations greater than 30%. That gas could be used for power generation. This gas extraction system promotes both coal mine development and coalbed methane utilization and achieves clear economic and social benefits.
Study on the influence of mining conditions on the occurrence law of CO in coal seams with low metamorphic grade
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Hongqing Zhu, Haoran Wang, Hongyi Wei, Hongru Zhao
At present, many scholars have found that carbon is continuously enriched in the process of coal formation, accompanied by the removal reaction of elements such as hydrogen and oxygen, which is the source of gas from coal seams. It generally believed that hydrocarbons dominated the gas in the coal seam (Moore 2012), and the CO was a non-hydrocarbon gas product inevitably produced in the coal forming process (Jiang et al. 2010). Melton (Melton and Giardini 1976) performs fracture and dissolution analysis of coal samples under high vacuum conditions, he found that the CO is present under both crushing and dissolving conditions, and the volume fraction could be as high as 21%. Solomon (Solomon et al. 1990), Mae (Mae, Maki, and Miura 2002), WANG (Wang et al. 2008) and others simulate the coal-forming process, which proves that the non-hydrocarbon coalbed methane is the product of the cross-linking reaction of oxygen-containing functional groups in the coal-forming process. Under certain special geological conditions, a large amount of coalbed methane will be present in the coal seam. The source of coalbed methane can divide into organic gas and inorganic gas, and organic gas can subdivide into biogenetic gas and thermogenic gas. Plant body decomposed by bacteria under the condition of isolation of air, leading to the biogenetic gas. The interaction between the decomposition products led to the presence of a large number of reactive groups, and the interaction of the reactive groups further produced CO. The specific content is related to the complexity of the coal-forming environment(Gao et al. 2013; Tao et al. 2007).The biogenetic gas production process was shown in equations (1)-(6).