Journal
ENERGY
Volume 244, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.energy.2021.122722
Keywords
Supercritical water gasification; Heat integration; Direct mass transfer; Exergy efficiency; Sensitivity analysis
Categories
Funding
- Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foun-dation of China [51888103]
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This paper proposes an optimized direct mass transfer design for the supercritical water gasification system, which uses recycled product gas to improve energy efficiency and reduce oxygen consumption. The study shows that the optimized design has higher efficiency and significantly alters mass and energy flow.
Supercritical water gasification (SCWG) is a promising clean technology for coal utilization due to high chemical reactivity and no tar emission. However, the wall-type heat exchange in the SCWG system demands a large heating surface area and an extreme high-temperature heat source. This paper puts forward an optimized design, namely direct mass transfer, in which the final product gas is partially recycled back into the gasification reactor to supplement the gasification agent and provide sensible heat energy. A whole system simulation was established to analyze the mass flow and exergy efficiency in the reference design and the optimized design. The process analysis shows that the optimized design has higher exergy efficiency (85.6%) than that (72.5%) of the reference design. In the optimized system, direct mass transfer significantly alters the mass flow and exergy flow, with less influent water (33.3%), less heat transfer rate (30.5%), and less oxygen consumption (51.5%). Furthermore, sensitivity analysis shows that increasing circulation ratio, feedstock concentration, and preheating temperature can reduce oxygen consumption and improve gas output and efficiency. The study indicates that direct mass transfer has the potential superiority to solve the challenge of heat integration and facilitate the application of the industrial-scale SCWG system.
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