A hot syngas purification system integrated with downdraft gasification of municipal solid waste. (1st March 2019)

• Record Type: Journal Article
• Authors: Chan, Wei Ping; Veksha, Andrei; Lei, Junxi; Oh, Wen-Da; Dou, Xiaomin; Giannis, Apostolos; Lisak, Grzegorz; Lim, Teik-Thye
• Is Part Of: Applied energy. Volume 237(2019)
• Page Start: 227
• Page End: 240
• Publication Date: 2019-03-01
• Subjects: Syngas purification -- Municipal solid waste -- Catalytic tar reforming -- Nickel catalyst -- Ni-Zn nanocomposite -- Sulfur removal; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2019.01.031
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Demonstrated feasibility of MSW gasification with a hot syngas purification system. Produced hot and clean syngas through downward cascading of system temperatures. Removed up to 90% of tar compounds and sulfur species (H2 S and COS). Demonstrated operational stability of Ni/Al2 O3 catalyst for over 20 h on stream. Demonstrated reliable performance of NiZn-28-HC sorbent with real MSW syngas. Abstract: Gasification of municipal solid waste (MSW) with subsequent utilization of syngas in gas engines/turbines and solid oxide fuel cells can substantially increase the power generation of waste-to-energy facilities and optimize the utilization of wastes as a sustainable energy resources. However, purification of syngas to remove multiple impurities such as particulates, tar, HCl, alkali chlorides and sulfur species is required. This study investigates the feasibility of high temperature purification of syngas from MSW gasification with the focus on catalytic tar reforming and desulfurization. Syngas produced from a downdraft fixed-bed gasifier is purified by a multi-stage system. The system comprises of a fluidized-bed catalytic tar reformer, a filter for particulates and a fixed-bed reactor for dechlorination and then desulfurization with overall downward cascading of the operating temperatures throughout the system. Novel nano-structured nickel catalyst supported on alumina and regenerable Ni-Zn desulfurization sorbent loaded on honeycomb are synthesized. Complementary sampling and analysis methods are applied to quantify the impurities and determine their distribution at different stages. Experimental and thermodynamic modeling results are compared to determine the kinetic constraints in the integrated system. The hot purification system demonstrates up to 90% of tar and sulfur removal efficiency, increased total syngas yield (14%) and improved cold gas efficiency (12%). The treated syngas is potentially applicable in gas engines/turbines and solid oxide fuel cells based on the dew points and concentration limits of the remaining tar compounds. Reforming of raw syngas by nickel catalyst for over 20 h on stream shows strong resistance to deactivation. Desulfurization of syngas from MSW gasification containing significantly higher proportion of carbonyl sulfide than hydrogen sulfide, traces of tar and hydrogen chloride demonstrates high performance of Ni-Zn sorbents.