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Characterisation of the contaminants generated from a large-scale ex-situ underground coal gasification study using high-rank coal from the South Wales coalfield

Sadasivam, Sivachidambaram ORCID:, Zagorscak, Renato ORCID:, Thomas, Hywel Rhys ORCID:, Kapusta, Krzysztof and Stańczyk, Krzysztof 2020. Characterisation of the contaminants generated from a large-scale ex-situ underground coal gasification study using high-rank coal from the South Wales coalfield. Water, Air, and Soil Pollution 231 , 519. 10.1007/s11270-020-04888-1

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Abstract This paper presents an analysis of contaminants generated from large-scale, laboratory-based, underground coal gasification (UCG) experiments using a high-rank coal from the South Wales Coalfield. The experiments were performed at atmospheric and elevated pressures (30 bar) by varying the oxidants’ composition. The experiments were designed to predict the amount of produced water and contaminants generated at each stage of the operating conditions. The mass balance of water supplied and produced in the experiments was accounted for. Chemical analyses of produced water, char and ash contents were performed to quantifytheinorganicandorganicchemicalparameters. Mostof the contaminant concentrationsinthe produced water from the 30-bar pressure experiment were lower than the concentrations generated from the atmospheric pressure experiment. The measured concentrations of theinorganicchemicalspeciesandtheinorganicparameters of the coal seam water from the South Wales Coalfieldwereusedintheoreticalcalculationstopredict the dominant equilibrium species concentrations in a hypothetical scenario of effluent contaminated groundwater.Thebiodegradationoforganiccontaminantssuch as phenol, benzene and sorbed fractions of inorganic contaminants from the produced water on iron oxide in theashresiduewaspredictedusingexistingbiotransformation kinetics and surface complexation models, respectively. The biodegradation of phenol and benzene would be a slow process even at optimum conditions and the iron oxide left in the cavity can act as a sorbent for a few inorganic species. The evidence from the present study suggests future work towards (i) developing an appropriate water treatment process during gas cleaning, (ii) operational procedure (pressure and proportions of oxidant) and (iii) developing UCG-specific experimental prediction of contaminant transportation and transformation kinetics. Keywords High-rankcoal.Undergroundcoal gasification.Highpressure.Producedwater.Inorganic organiccontaminants.Ash

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Engineering
Publisher: Springer Verlag (Germany)
ISSN: 0049-6979
Date of First Compliant Deposit: 5 October 2020
Date of Acceptance: 24 September 2020
Last Modified: 24 Aug 2023 20:30

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