scholarly journals Experimental Study on the Fractal Features and Permeability Characteristics of Low Metamorphic Coal Pore Structure under Thermal Damage

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhen Liu ◽  
Mingrui Zhang ◽  
Shijian Yu ◽  
Lin Xin ◽  
Gang Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Pore Structure ◽  
Coal Gasification ◽  
Thermal Damage ◽  
Fractal Model ◽  
Utilization Efficiency ◽  
Heating Process ◽  
Underground Coal Gasification ◽  
External Temperature ◽  
Permeability Characteristics

Underground coal gasification and exploitation of geothermal mine resources can effectively improve coal conversion and utilization efficiency, and the basic theory of the above technologies generally relies on the change law of the coal pore structure under thermal damage. Therefore, the influence mechanism of the development of the coal pore structure under thermal damage is analyzed by the nuclear magnetic resonance experiment, and the temperature-permeability fractal model is created. The results show that compared with microtransitional pores, the volume of meso-macropores in the coal body is more susceptible to an increase in temperature, which was most obvious at 200-300°C. During the heating process, the measured fractal dimension based on the T2 spectral distribution is between 2 and 3, indicating that the fractal characteristics did not disappear upon a change in external temperature. The temperature has a certain negative correlation with DmNMR, DMNMR, and DNMR, indicating that the complexity of the pore structure of the coal body decreased gradually with the increase of the temperature. Compared with the permeability calculated based on the theoretical permeability fractal model, the permeability obtained from the temperature-permeability fractal model has a similar increasing trend as the permeability measured by the NMR experiment when the temperature increases. The experimental study on pore structure and permeability characteristics of the low metamorphic coal under thermal damage provides a scientific theory for underground coal gasification and geothermal exploitation.

scholarly journals Gas Permeability Model for Porous Materials from Underground Coal Gasification Technology

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4462
Author(s):  
Grzegorz Wałowski
Keyword(s):  
Reynolds Number ◽  
Flow Resistance ◽  
Gas Flow ◽  
Coal Gasification ◽  
Gas Permeability ◽  
Resistance Coefficient ◽  
Underground Coal Gasification ◽  
Permeability Model ◽  
Permeability Characteristics

Underground coal gasification (UCG) technology converts deep coal resources into synthesis gas for use in the production of electricity, fuels and chemicals. This study provides an overview of the systematic methods of the in situ coal gasification process. Furthermore, the model of the porous structure of coal has been presented and the gas movement taking place in the carbon matrix—which is part of the bed—has been described. The experimental tests were carried out with the use of air forced through the nozzle in the form of a gas stream spreading in many directions in a porous bed under bubbling conditions. The gas flow resistance coefficient was determined as a function of the Reynolds number in relation to the diameter of the gas flow nozzle. The proprietary calculation model was compared to the models of many researchers, indicating a characteristic trend of a decrease in the gas flow resistance coefficient with an increase in Reynolds number. The novelty of the study is the determination of the permeability characteristics of char (carbonizate) in situ in relation to melted waste rock in situ, taking into account the tortuosity and gas permeability factors for an irregularly shaped solid.

scholarly journals Measurements of Gasification Characteristics of Coal and Char in CO2-Rich Gas Flow by TG-DTA

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Zhigang Li ◽  
Xiaoming Zhang ◽  
Yuichi Sugai ◽  
Jiren Wang ◽  
Kyuro Sasaki
Keyword(s):  
Flue Gas ◽  
Gas Flow ◽  
Coal Gasification ◽  
Heating Temperature ◽  
Heating Process ◽  
Carbon Oxidation ◽  
Underground Coal Gasification ◽  
Basic Reference ◽  
Gasification Reaction ◽  
Physical And Chemical

Pyrolysis, combustion, and gasification properties of pulverized coal and char in CO2-rich gas flow were investigated by using gravimetric-differential thermal analysis (TG-DTA) with changing O2%, heating temperature gradient, and flow rate of CO2-rich gases provided. Together with TG-DTA, flue gas generated from the heated coal, such as CO, CO2, and hydrocarbons (HCs), was analyzed simultaneously on the heating process. The optimum O2% in CO2-rich gas for combustion and gasification of coal or char was discussed by analyzing flue gas with changing O2from 0 to 5%. The experimental results indicate that O2% has an especially large effect on carbon oxidation at temperature less than 1100°C, and lower O2concentration promotes gasification reaction by producing CO gas over 1100°C in temperature. The TG-DTA results with gas analyses have presented basic reference data that show the effects of O2concentration and heating rate on coal physical and chemical behaviors for the expected technologies on coal gasification in CO2-rich gas and oxygen combustion and underground coal gasification.

scholarly journals Experimental study of underground coal gasification (UCG) of a high-rank coal using atmospheric and high-pressure conditions in an ex-situ reactor

Fuel ◽  
2020 ◽  
Vol 270 ◽  
pp. 117490 ◽  
Author(s):  
Renato Zagorščak ◽  
Sivachidambaram Sadasivam ◽  
Hywel Rhys Thomas ◽  
Krzysztof Stańczyk ◽  
Krzysztof Kapusta
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
Coal Gasification ◽  
High Rank ◽  
Ex Situ ◽  
Underground Coal Gasification

scholarly journals Model-Free Control of UCG Based on Continual Optimization of Operating Variables: An Experimental Study

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4323
Author(s):  
Ján Kačur ◽  
Marek Laciak ◽  
Milan Durdán ◽  
Patrik Flegner
Keyword(s):  
Experimental Study ◽  
Coal Gasification ◽  
Calorific Value ◽  
Ex Situ ◽  
Underground Coal Gasification ◽  
Water Steam ◽  
Operating Variables ◽  
Model Free ◽  
Optimization Task ◽  
Model Free Control

The underground coal gasification (UCG) represents an effective coal mining technology, where coal is transformed into syngas underground. Extracted syngas is cleaned and processed for energy production. Various gasification agents can be injected into an underground georeactor, e.g., air, technical oxygen, or water steam, to ensure necessary temperature and produce syngas with the highest possible calorific value. This paper presents an experimental study where dynamic optimization of operating variables maximizes syngas calorific value during gasification. Several experiments performed on an ex situ reactor show that the optimization algorithm increased syngas calorific value. Three operation variables, i.e., airflow, oxygen flow, and syngas exhaust, were continually optimized by an algorithm of gradient method. By optimizing the manipulation variables, the calorific value of the syngas was increased by 5 MJ/m3, both in gasification with air and additional oxygen. Furthermore, a higher average calorific value of 4.8–5.1 MJ/m3 was achieved using supplementary oxygen. The paper describes the proposed ex situ reactor, the mathematical background of the optimization task, and results obtained during optimal control of coal gasification.

Experimental study on evaluation of underground coal gasification with a horizontal hole using two different coals

Fuel ◽  
2021 ◽  
Vol 305 ◽  
pp. 121556
Author(s):  
Akihiro Hamanaka ◽  
Fa-qiang Su ◽  
Ken-ichi Itakura ◽  
Kazuhiro Takahashi ◽  
Jun-ichi Kodama ◽  
...  
Keyword(s):  
Experimental Study ◽  
Coal Gasification ◽  
Underground Coal Gasification
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