Thermo-fluid-mechanical numerical simulations of surface subsidence at the site of underground coal gasification

2021 ◽  
pp. qjegh2020-106
Author(s):  
Yury Derbin ◽  
James Walker ◽  
Liphapang Khaba
Keyword(s):  
Coal Combustion ◽  
Coal Gasification ◽  
Complex Geometry ◽  
Surface Subsidence ◽  
Three Dimensions ◽  
Successful Implementation ◽  
Underground Coal Gasification ◽  
Model Surface ◽  
Fluid Analysis ◽  
Upper Aquifer

This work deals with modelling surface subsidence that aims to help industrialize Underground Coal Gasification (UCG). UCG is a long-known, but poorly industrialized method of energy extraction from coal. Risks of surface subsidence and groundwater pollution are two main hurdles that are affecting the potential industrialization of UCG. The particular challenge is the existence of groundwater because of implications to both its pollution and its influence on surface subsidence. Additionally, the coal combustion and the complex geometry of the UCG reactors impacts surface subsidence. To meet these challenges, the thermal and fluid analyses should be included in the model and surface subsidence should be modelled in three dimensions to capture the collapsed shape of the UCG reactor. Based on nature of these challenges and an earlier successful implementation, the commercial software FLAC3D by Itasca with the intrinsic thermal and fluid models is chosen to model surface subsidence.This study discovers that the inclusion of fluid analysis improves the predictions of surface subsidence when compared with measurements at the highly watered Shatsk UCG site. In turn, thermal analysis mildly influences the modelled surface subsidence. The fluid analysis shows that the flow in the upper aquifer influences surface subsidence more greatly than the flow in the lower aquifers. High temperature causes an upward flow in the lower aquifer located above the UCG reactor, but does not change the flow pattern in the upper aquifer. The fluid analysis also reveals that if the UCG reactor is filled with water, the surface subsidence does not occur.

scholarly journals Valorization of non-balanced coal reserves in Serbia for underground coal gasification

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 4067-4081
Author(s):  
David Petrovic ◽  
Lazar Kricak ◽  
Milanka Negovanovic ◽  
Stefan Milanovic ◽  
Jovan Markovic ◽  
...  
Keyword(s):  
Coal Combustion ◽  
Fossil Fuels ◽  
Coal Gasification ◽  
Solar Photovoltaic ◽  
Underground Coal Gasification ◽  
Gas Combustion ◽  
Available Energy ◽  
Gasification Process ◽  
Gas Generators ◽  
Coal Reserves

In the name of a better and safer energy future, it is our responsibility to focus our knowledge and activities to save on imported liquid and gas fossil fuels, as well as coal on which energy security of Serbia is based. The rationalization in the use of available energy resources certainly positively affects economy and the environment of a country. This paper indicates motivations for the application of the underground coal gasification process, as well as surface gasification for Serbia. The goal is to burn less coal, while simultaneously utilizing more gas from the onsite underground coal gasification, or by gasification in various types of gas generators mounted on the surface. In both cases, from the obtained gas, CO2, NOx, and other harmful gases are extracted in scrubbers. This means that further gas combustion byproducts do not pollute the atmosphere in comparison with traditional coal combustion. In addition, complete underground coal gasification power requirements could be offset by the onsite solar photovoltaic power plant, which furthermore enhances environmental concerns of the overall coal utilization.

scholarly journals Subsidence and heat propagation modeling on the underground coal gasification (Case study at Muara Enim Formation, South Sumatera)

2020 ◽  
Vol 23 (2) ◽  
pp. 83-98
Author(s):  
Zulfahmi Zulfahmi ◽  
◽  
Ildrem Syafri ◽  
Abdurrokhim Abdurrokhim ◽  
Ridho Wattimena ◽  
...  
Keyword(s):  
Coal Gasification ◽  
Mechanical Characteristics ◽  
Heat Propagation ◽  
Surface Subsidence ◽  
Underground Coal Gasification ◽  
Propagation Modeling ◽  
External Conditions ◽  
Cap Rock ◽  
Physical And Mechanical Characteristics

One of the important issues to study underground coal gasification (UCG) is the prediction of surface subsidence. Several parameters that influence these conditions are the thickness of cap rock, the physical and mechanical characteristics, the structure condition, the minerals composition of the rock, and external conditions. This study had been carried out simulation and modeling to determine the level of surface subsidence risk and the effect of high temperatures due to the activities. The modeling results show that the thickness of the rock above the UCG coal seam greatly affects the surface subsidence. The depth is more than 200 m and found that the SF value is 1.59 which indicates UCG reactor depth of ≥ 200 m is safe from the risk of subsidence. From the characteristic aspect of the cap rock, the claystone types which not contain kaolinite minerals are more prone to collapse than those of contain kaolinite minerals. From this models, the gasifier at 150 m depth was estimated that there will be a decline of -7.23 m, and the minimum subsidence is at 275 m about 0.1 m. The heat propagation modeling results show that at 50 m the temperature is estimated to be 213- 289°C, but if the thickness of the cap rock is > 200 m depth, the temperature is around 29-28°C.

Possibility of accelerating coal combustion in underground coal gasification

1995 ◽  
Vol 31 (2) ◽  
pp. 154-155
Author(s):  
A. A. Myasnikov ◽  
S. N. Lazarenko ◽  
L. V. Presler
Keyword(s):  
Coal Combustion ◽  
Coal Gasification ◽  
Underground Coal Gasification

scholarly journals Soviet experience of underground coal gasification focusing on surface subsidence

2015 ◽  
Vol 16 (10) ◽  
pp. 839-850 ◽  
Author(s):  
Yury Derbin ◽  
James Walker ◽  
Dariusz Wanatowski ◽  
Alec Marshall
Keyword(s):  
Coal Gasification ◽  
Surface Subsidence ◽  
Underground Coal Gasification ◽  
Soviet Experience

Finite Element Analysis of the Subsidence of Cap Rocks during Underground Coal Gasification Process

2013 ◽  
Vol 859 ◽  
pp. 91-94
Author(s):  
Xiao Xiong Zha ◽  
Hai Yang Wang ◽  
Shan Shan Cheng
Keyword(s):  
Finite Element ◽  
Coal Seam ◽  
Coal Gasification ◽  
Feasibility Studies ◽  
Element Model ◽  
Numerical Results ◽  
Surface Subsidence ◽  
Underground Coal Gasification ◽  
Element Analysis ◽  
Gasification Process

This paper discusses the possible surface subsidence and deformation of the overlying rock during the underground coal gasification (UCG) process, which is an important part of feasibility studies for UCG operations. First coal seam roof movement and surface subsidence in the shallow UCG process were simulated by a finite element model coupled with heat transfer module in COMSOL. Numerical results from this model were compared with and in good agreement to the existing studies. This was followed by the development of model for deeper coal seam cases. The comparison of the numerical results from two models shows that surface uneven settlement in deep underground coal gasification is only 7% of that in shallow underground coal gasification.

Evaluation Method of Surface Subsidence Degree for Underground Coal Gasification without Shaft

2020 ◽  
pp. 1-14
Author(s):  
Huaizhan Li ◽  
Jianfeng Zha ◽  
Guangli Guo ◽  
Hongzhen Zhang ◽  
Youyou Xu ◽  
...  
Keyword(s):  
Coal Gasification ◽  
Evaluation Method ◽  
Surface Subsidence ◽  
Underground Coal Gasification

Experimental Study on the Environmental Behaviors of Poisonous Trace Elements in Post-Gasified Residues

2013 ◽  
Vol 805-806 ◽  
pp. 1478-1483 ◽  
Author(s):  
Bing Xu ◽  
Lun Jian Chen ◽  
Bao Lin Xing ◽  
Gui Yun Yi ◽  
Long Li
Keyword(s):  
Trace Elements ◽  
Groundwater Quality ◽  
Coal Combustion ◽  
Inductively Coupled Plasma ◽  
Coal Gasification ◽  
Combustion Process ◽  
Quality Standard ◽  
Enrichment Factors ◽  
Underground Coal Gasification ◽  
Potential Threat

Pyrolysis chars at 500°C, 700°C, 900°C and coal combustion ashes were prepared to simulate the three zones residues of underground coal gasification. The contents of trace elements in solid residues, such as chromium, manganese, arsenic, cobalt, nickel and lead, were determined by using inductively coupled plasma mass spectroscopy (ICP-MS) and the enrichment factors were also calculated. By immersing the pyrolysis chars and coal combustion ashes in weakly acidic leaching liquid (pH=4, 5, 6), the leaching features of above trace elements and their potential threat on groundwater were characterized. Compared with the enrichment feature of Fe, the results indicate that CrMnCo stably exist in pyrolysis and combustion process; Ni and As get depleted in low-temperature pyrolysis chars, while enriched in 900°C chars and coal combustion ashes; Pb becomes enriched in ash, but gets depleted with the increase of pyrolysis temperature. The concentration of As in ash leachate is higher than the 5thclass of groundwater quality standard which may cause serious pollution; the concentration of Ni is below the 4thclass and may contaminate the groundwater; other elements in leachate have little influence on groundwater because of low concentrations below the 3rdclass of groundwater quality standard.

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