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A Novel Two-Stage Gasification Reactor for Generating H2-Rich High Calorific Value Gas by Low-Grade Coals

Sharma, SK and Shivapuji, AM and Dasappa, S (2022) A Novel Two-Stage Gasification Reactor for Generating H2-Rich High Calorific Value Gas by Low-Grade Coals. In: 39th Annual International Pittsburgh Coal Conference, PCC 2022, 19 - 22 September 2022.

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High ash content in coal, by virtue of potential ash fusion and agglomeration, renders conventional gasification approaches either impractical OR prohibitively expensive. Ash agglomeration and clinker formation, primarily due to high localized temperatures, are required to be addressed through appropriate technological interventions to enable the gasification of high ash coal. In the current work, the challenge of high ash coal gasification has been addressed by separating the exothermic high-temperature combustion zone and endothermic gasification zone in two-stage gasification. The high-temperature zone has the feed coal in a highly mobile phase. In contrast, the gasification zone has the char in the form of the packed bed, collectively enabling the handling of high ash coal without facing any ash fusion issues. The two separate but connected stages enable independent control over combustion and gasification. A pilot scale gasification system of 150 kW thermal gasification capacity has been designed and tested with a range of high ash Indian coal. In stage one, coal is fed into the mobile phase reactor with air as the carrying media, where mostly devolatilization and volatile combustion takes place. Appropriate mechanisms enable controlling the residence time of the coal in the mobile phase. The devolatilized char generated is subsequently transferred to the second stationary bed reactor for Oxy-steam gasification. The process parameters are optimized for high carbon conversion and cold gas efficiency without clinker formation. The typical volume percentage of CO, CO2, CH4, and H2 are 30-40%, 15-20%, 0.5-2%, and 40-50%, respectively, yielding a syngas of calorific value of 11.2 MJ/kg. Carbon conversion greater than 80% has been achieved.

Item Type: Conference Paper
Publication: 39th Annual International Pittsburgh Coal Conference, PCC 2022
Publisher: International Pittsburgh Coal Conference
Additional Information: The copyright for this article belongs to the International Pittsburgh Coal Conference.
Keywords: Agglomeration; Calorific value; Carbon; Coal combustion; Gasification; Packed beds, 'current; Ash agglomeration; Ash contents; Ash fusion; Carbon conversions; High-ash coals; High-calorific-value; Localized temperature; Low-grade coal; Mobile phasis, Coal
Department/Centre: Division of Interdisciplinary Sciences > Interdisciplinary Centre for Energy Research
Division of Mechanical Sciences > Centre for Sustainable Technologies (formerly ASTRA)
Date Deposited: 13 Jul 2023 09:43
Last Modified: 13 Jul 2023 09:43
URI: https://eprints.iisc.ac.in/id/eprint/82429

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