Systematic evaluation of gasifiers driven by the high-enthalpy plasma supply

The study overviews gasifiers driven by thermal and microwave plasma which primarily produce hydrogen and carbon monoxide. Industrially available plasma generation methods are described. Analysis of plasma gasification systems revealed eight distinct designs and their features. Counter current systems matured to industrial scale (up to 7000 kg/h of municipal solid waste), though tar cracking is not forced by plasma integration. The cold gas efficiency (∼61%) is similar to the autothermal industrial systems. Cross current systems reached technology readiness levels of 4-5 (up to 60 kg/h) but require long-term testing for stationary state balancing. In co-current downdraft systems wood and low-ash, plastic-rich municipal solid waste were processed (<110 kg/h). The drawback is that plasma temperature is limited by ash melting. A horizontal co-current design was proven at feeding rates of 400 kg/h in a 12 months’ run on municipal solid waste with slagging ash discharge, whereas cold gas efficiencies of ∼ 53% were reached that are comparable to conventional gasifiers. Entrained flow designs require good plasma-feedstock mixing, which is hard to ensure at throughputs far below 90 kg/h of coal. Arc and microwave discharge integrated solutions suffer from the feeding-caused instabilities of the discharge and require high energy consumption (>10 kWh/kg). The furnace-like designs, which have a throughput of up to 437 kg/h, also suffer from arc instabilities resulting in energy consumptions of > 4 kWh/kg due to a poor energy distribution. A counter current design was determined to be the most mature one, while horizontal co-current designs promise better performance.