Mechanical performance evolution and size determination of strip coal pillars with an account of thermo-mechanical coupling in underground coal gasification

AbstractA flow injection analysis method for spectrophotometric determination of ammonium in waters produced during underground coal gasification (UCG) of lignite and hard coal was described. The analysis of UCG water samples is very difficult because of their very complicated matrix and colour. Due to a huge content of organic and inorganic substances and intensive colour of samples (sometimes yellow, quite often dark brown or even black), most analytical methods are not suitable for practical application. Flow injection analysis (FIA) is based on diffusion of ammonia through a hydrophobic gas permeable membrane from an alkaline solution stream into an acid-base indicator solution stream. Diffused ammonia causes a colour change of indicator solution, and ammonia is subsequently quantified spectrophotometrically at 590 nm wavelength. The reliability of the results provided by applied method was evaluated by checking validation parameters like accuracy and precision. Accuracy was evaluated by recovery studies using multiple standard addition method. Precision as repeatability was expressed as a coefficient of variation (CV).

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Determination of the Technological Parameters of Borehole Underground Coal Gasification for Thin Coal Seams

Journal of Sustainable Mining ◽

10.46873/2300-3960.1296 ◽

2021 ◽

Vol 12 (3) ◽

Author(s):

Volodymyr S. Falshtynskyi ◽

Roman O. Dychkovskyi ◽

Vasyl G. Lozynskyi ◽

Pavlo B. Saik

Keyword(s):

Coal Gasification ◽

Underground Coal Gasification ◽

Technological Parameters ◽

Coal Seams

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Preliminary modeling for module estimation on the underground coal gasification project

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/882/1/012041 ◽

2021 ◽

Vol 882 (1) ◽

pp. 012041

Author(s):

Zulfahmi ◽

M Huda ◽

B Sirait ◽

A Maulana ◽

A Lubis

Keyword(s):

Feasibility Study ◽

Coal Gasification ◽

Soil Surface ◽

Reduction Factor ◽

Underground Coal Gasification ◽

The Finite Element Method ◽

Strength Reduction Factor ◽

Maximum Deformation ◽

2D And 3D

Abstract Designing the module is one of the initial works of the underground coal gasification (UCG) feasibility study, consisting of the coal area to be gasified as panels and the coal to be left as pillars. Three models have been designed with each panel dimension 380 m in length, 150 m in width and 18 m thick. The finite element method is used in the study and the 2D and 3D geotechnical simulations have been carried out with variations of the pillars. As a result of 2D modeling, the critical strength reduction factor (SRF) is 0.25 with the highest deformation on the surface is 0.04 m (SMA-C) and 0.03 (SM-D) if the pillar is 50 m width. If SRF is increased to 0.37, the deformation on the surface is 0.36 (SMA-C) and is 13.5 (SM-D), respectively. From the 3D modeling results, if it is assumed that the velocity of the UCG reactor hole rate is 0.24 m/day until it reaches the final target length of the reactor hole 380 m, the maximum deformation of the soil surface at the SMA-C and SM-D locations is 0.074 m and 0.096 m, respectively. Determination of the module is important in the feasibility study and evaluation of the UCG site.

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Stability analysis of hyperbolic coal pillars with peeling and high temperature effects

Energy Exploration & Exploitation ◽

10.1177/0144598720933515 ◽

2020 ◽

Vol 38 (5) ◽

pp. 1574-1588

Author(s):

Youyou Xu ◽

Huaizhan Li ◽

Guangli Guo ◽

Xiaopeng Liu

Keyword(s):

High Temperature ◽

Bearing Capacity ◽

Temperature Effects ◽

Coal Gasification ◽

Coal Pillar ◽

Industrial Test ◽

Test Area ◽

Underground Coal Gasification ◽

Coal Pillars ◽

The Stability

In this present study, a twice-peeling model was established to analyze the hyperbolic coal pillars stability in underground coal gasification and then propose the concept of stripping degree to show model details for numerical simulation. The data shows that hyperbolic coal pillars stability can be analyzed through the twice-peeling model. Considering the coal pillars peeling and high temperature effects, one side of coal pillars will decrease 3 m, and the stability coefficient is 1.6 which has enough bearing capacity. When the arch depth ratio is 0.6, the critical condition for the coal pillar instability is reached. In this paper, underground coal gasification industrial test area still had strong bearing capacity after twice stripping, and there was no sudden instability. The research results can provide reference for the gasifier design and the stability of non-uniform coal pillars in the future.

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Thermo-mechanical coupling numerical simulation method under high temperature heterogeneous rock and application in underground coal gasification

Energy Exploration & Exploitation ◽

10.1177/0144598719888981 ◽

2020 ◽

Vol 38 (4) ◽

pp. 1118-1139

Author(s):

Xiaopeng Liu ◽

Guangli Guo ◽

Huaizhan Li

Keyword(s):

Mechanical Properties ◽

Numerical Simulation ◽

Rock Mass ◽

High Temperature ◽

Coal Gasification ◽

Geotechnical Engineering ◽

Simulation Method ◽

Underground Coal Gasification ◽

Strata Movement ◽

Mechanical Coupling

The heterogeneity of a rock mass under high temperature and its thermo-mechanical coupling characteristics are difficult problems to investigate. This situation brings considerable difficulties to the study of underground coal gasification under thermo-mechanical coupling. The development of a numerical simulation method for the thermo-mechanical coupling of heterogeneity rock mass under high-temperature burnt conditions can provide an important foundation for related research. On the basis of the variation of mechanical properties of rock mass with temperature, a thermo-mechanical coupling simulation method, which considers the heterogeneity of a rock mass under high temperature, is proposed in this study. A test block experiment is implemented and then applied to the strata movement and failure of underground coal gasification. The results are as follows: (1) The proposed method can truly reflect the heterogeneity of a rock mass under high-temperature environment, providing an effective method for the numerical simulation of geotechnical engineering in high-temperature conditions. (2) The variation of mechanical properties of rock mass after an increase in temperature is the main reason for the change law of strata movement and failure of underground coal gasification. These factors should be considered in the investigation of underground gasification strata movement and failure. The present study can provide an important means for the research on geotechnical engineering in high-temperature environments.

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Numerical Study on Convection Diffusion for Gasification Agent in Underground Coal Gasification (UCG). Part II: Determination of Model Parameters and Results Analysis

Energy Sources Part A Recovery Utilization and Environmental Effects ◽

10.1080/15567030701527723 ◽

2009 ◽

Vol 31 (4) ◽

pp. 318-324

Author(s):

L. H. Yang ◽

Y. M. Ding

Keyword(s):

Coal Gasification ◽

Numerical Study ◽

Model Parameters ◽

Underground Coal Gasification ◽

Convection Diffusion

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Determination of random pore model parameters for underground coal gasification simulation

Energy ◽

10.1016/j.energy.2018.10.156 ◽

2019 ◽

Vol 166 ◽

pp. 972-978 ◽

Cited By ~ 10

Author(s):

Sebastian Iwaszenko ◽

Natalia Howaniec ◽

Adam Smoliński

Keyword(s):

Coal Gasification ◽

Model Parameters ◽

Underground Coal Gasification ◽

Pore Model ◽

Random Pore Model

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The Thermal and Structural Properties of a Hanna Basin Coal

Journal of Energy Resources Technology ◽

10.1115/1.3231050 ◽

1984 ◽

Vol 106 (2) ◽

pp. 266-271 ◽

Cited By ~ 5

Author(s):

R. E. Glass

Keyword(s):

Structural Properties ◽

Coal Gasification ◽

Cavity Growth ◽

Underground Coal Gasification ◽

Growth Mechanisms ◽

Hanna Basin ◽

The Town ◽

Thermomechanical Effects

In an effort to understand the cavity growth mechanisms occurring during an Underground Coal Gasification (UCG) test, a study of the thermomechanical effects has been initiated at Sandia National Laboratories. The first phase of this study has been the determination of the intrinsic thermal and structural properties of the Hanna Basin Coal that was utilized in a series of four UCG tests near the town of Hanna, Wyoming. The result of this study is a consistent set of thermal and structural properties of a Hanna Basin coal. This set has been used in a model that successfully simulated the growth of the cavity observed during the Hanna II UCG test.

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