On the mitigating environmental aspects of a vertical well in underground coal gasification method

Shahbazi, Mohammadreza; Najafi, Mohammad; Marji, Mohammad Fatehi

doi:10.1007/s11027-018-9816-x

Cited by 12 publications

(5 citation statements)

References 23 publications

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“…With the consumption of coal resources, its mining depth and difficulty are increasing, accompanied by higher ground temperature. At the same time, new technologies are becoming increasingly mature, such as underground coal gasification and coalbed methane heat injection exploitation proposed for mining the residual coal, reducing transportation costs and efficiently recovering energy 1 , 2 . In the mining process of coal resources under a different high-temperature environment, the main difficulty was the uneven heating of coal seam, which will lead to the difficulty in predicting the germination, expansion, and penetration of internal cracks, and ultimately result in the difficulty in predicting the subsidence law of overburden rock, the displacement direction of the coal seam, and even the stability of surrounding rock of mining shaft.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties and acoustic emission characteristics of deep hard coal after segmented high-temperature treatment

Chun

Cheng

et al. 2023

Sci Rep

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Based on engineering background that local heating of coal seam is uneven due to underground coal gasification, coal-bed gas exploitation via heat injection, spontaneous combustion of coal seam, etc., segmented heating coal sample was used to simulate coal seam under uneven heating condition, and experimental study on mechanical behaviors of coal sample after segmented heat treatment at high temperatures was conducted. Test results show that temperature at 100 °C ~ 400 °C did not reach ignition temperature of deep hard coal for the experiment and was not enough to change main ingredients of coal sample, which less affected compression strength, elastic modulus, acoustic emission behavior of coal sample. Although compaction stage-elastic stage-plastic stage-broken stage appeared in compression stress–strain curve of coal sample, height increase led to decrease of compression strength, elastic modulus of coal sample, cumulative amplitude and ringing count for acoustic emission in the form of power function. Meanwhile, it is found that final failure modes of coal sample after segmented heat were mainly shear failure and separation failure and friction mixed failure was secondary. In addition, influence of heating temperature at 100 °C ~ 400 °C on failure modes of coal sample was small. However, height increase in the heating section of coal sample made shear failure surface gradually move to the heating section and separation failure surface moved with the change of contact surface position between heating section and non-heating section. Furthermore, the integral failure degree of coal sample was more serious. Finally, based on variation behaviors of acoustic emission parameter for coal sample after segmented heating, inversion formula on acoustic emission parameter for strength of coal sample was discussed and verified via experimental result of coal sample with different segmented heat height after heating treatment at 200 °C.

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Section: Introductionmentioning

confidence: 99%

Mechanical properties and acoustic emission characteristics of deep hard coal after segmented high-temperature treatment

Chun

Cheng

et al. 2023

Sci Rep

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“…Different from coal surface gasification, UCG technology ignites coal at the coal seam to form a gasifier. In the process of coal gasification, the temperature of combustible gas in the cavity will exceed 1000℃ [6][7][8] . This kind of ultra-high temperature will change the physical and chemical properties of coal seam and surrounding rock, and affect the stability of UCG process [9] .…”

Section: Introductionmentioning

confidence: 99%

Study on Stress Field of Underground Coal Gasification Shaft Based on Thermo-Mechanical Coupling

Yuan

Zhang

Che

et al. 2022

Proceedings of the 2022 International Conference on Smart Manufacturing and Material Processing (SMMP2022)

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According to the characteristics of high bottom hole temperature and large temperature difference between the inner and outer walls of reservoir casing in the process of underground coal gasification (underground coal gasification), the temperature field and stress field model of wellbore in gas production wells is established based on thermo-mechanical coupling, and the stress distribution of different steel grades of casing under limit working conditions is studied. The results show that: (1) under the condition of daily gas production rate of 30×104m3/d and gasifier temperature of 1000°C, P110 steel grade casing always meets the strength requirement; N80/L80 steel casing yielded at 188°C, and the critical gas temperature of J55 steel casing was 990°C after cooling by spraying device. (2) J55 steel grade casing can be selected when the temperature of gasifier is lower than 600C, N80/L80 steel grade casing can be selected when the temperature is in the range of 600°C–900°C, and P110 steel grade casing can be selected when the temperature exceeds 900°C.

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“…Currently, there is sufficient number of studies analyzing the features of design and technological solutions in terms of expediency of underground gas generator tightness [58][59][60][61], methods of supply and directionality of blow flows with the provided adaptivity and intensification of the processes of coal seam gasification [62][63][64][65] including controlled retracting injection point (CRIP) system [66,67], influence of mining and geological conditions of coal seam occurrence on the underground gasification process [68][69][70][71][72], and influences of underground coal gasification on the environment [46,58,[73][74][75][76].…”

Section: Introductionmentioning

confidence: 99%

Experimental Studies of the Effect of Design and Technological Solutions on the Intensification of an Underground Coal Gasification Process

et al. 2021

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This paper represents the results of experimental studies of physical modeling of the underground coal gasification process in terms of implementation of design and technological solutions aimed at intensification of a gasification process of thin coal seams. A series of experimental studies were performed in terms of a stand unit with the provided criteria of similarity to field conditions as well as kinetics of thermochemical processes occurring within a gas generator. Hard coal (high volatile bituminous coal) was selected as the raw material to be gasified, as that coal grade prevails in Ukrainian energy balance since it is represented by rather great reserves. Five blow types were tested during the research (air, air–steam, oxygen–steam, oxygen–enriched, and carbon dioxide and oxygen). As a result, the effect of tightness of a gas generator on the quantitative and qualitative parameters of coal gasification while varying the blow by reagents and changing the pressure in a reaction channel has been identified. Special attention was paid to the design solutions involving blow supply immediately into the combustion face of a gas generator. The experimental results demonstrate maximum efficiency of the applied gas generator design involving flexible pipelines and activator in the reaction channel and a blow direction onto the reaction channel face combined with blow stream reversing which will make it possible to improve caloricity of the generator gas up to 18% (i.e., from 8.4 to 12.8 MJ/m3 depending upon a blow type). Consideration of the obtained results of physical modelling can be used with sufficient accuracy to establish modern enterprises based on the underground coal seam gasification; this will help develop more efficiently the substandard coal reserves to generate heat energy as well as power-producing and chemical raw material. The research conclusions can provide technical reference for developing a new generation of underground coal gasification technology.

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On the mitigating environmental aspects of a vertical well in underground coal gasification method

Cited by 12 publications

References 23 publications

Mechanical properties and acoustic emission characteristics of deep hard coal after segmented high-temperature treatment

Mechanical properties and acoustic emission characteristics of deep hard coal after segmented high-temperature treatment

Study on Stress Field of Underground Coal Gasification Shaft Based on Thermo-Mechanical Coupling

Experimental Studies of the Effect of Design and Technological Solutions on the Intensification of an Underground Coal Gasification Process

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