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

• Published in: Fuel (Guildford) Vol. 270; p. 117490
• Main Authors: Zagorščak, Renato, Sadasivam, Sivachidambaram, Thomas, Hywel Rhys, Stańczyk, Krzysztof, Kapusta, Krzysztof
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.06.2020; Elsevier BV
• Subjects: Anthracite; Atmospheric pressure; Calorific value; Coal; Coal gasification; Energy efficiency; Flow rates; Flow velocity; Gas composition; Gas production; High pressure; In-situ laboratory tests; Oil and gas production; Oxygen; Oxygen enrichment; Reactors; Syngas; Synthesis gas; Underground coal gasification; In-situ laboratory tests; Anthracite; Underground coal gasification; Coal; High pressure; Syngas
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.117490

•High-rank coal samples are used in large-scale ex-situ UCG experiments.•Two multi-day trials are conducted under atmospheric and high pressure conditions.•Overall, high pressure gasification produces more CH4 and CO2, but less H2 and CO.•Energy efficiency of the high pressure gasification is higher than the atmospheric.•Temperatures up to 1250 °C are recorded in the gasification channel and roof strata. This paper presents the results of an extensive experimental analysis of underground coal gasification (UCG) using large bulk samples in an ex-situ reactor under atmospheric and high-pressure (30 bar) conditions. The high-rank coal obtained from the South Wales (UK) coalfield is employed for that purpose. The aim of this investigation is to define the gas production rates, gas composition, gas calorific value, process energy efficiency and temperature changes within the UCG reactor during the gasification process based on the pre-defined reactants and flow rates. Two UCG trials, each lasting 105 h, consisted of six stages where the influences of oxygen, water, air and oxygen enriched air (OEA) under different flow conditions on the gasification process were investigated. Based on the results of two multi-day experiments, it is demonstrated that the gasification under high pressure conditions produces syngas with higher average calorific value (8.49 MJ/Nm3) in comparison to syngas produced at atmospheric pressure conditions (6.92 MJ/Nm3). Hence, the overall energy efficiency of the high-pressure experiment is higher compared to the atmospheric pressure test, i.e. 57.67% compared to 51.72%. This is related to the fact that the high-pressure gasification produces more methane (11.97 vol%) than the atmospheric pressure gasification (2.30 vol%). Under elevated pressure, the temperatures recorded in the roof strata are about 100 °C higher compared to the UCG process under atmospheric pressure conditions. This work provides new insights into the gasification of carbon-rich coals subject to different gasification regimes and pressures.