Development of an innovative 3-stage steady-bed gasifier for municipal solid waste and biomass

Gasification of biomass, municipal solid waste, waste-derived fuels and residues has been lately gaining in attractiveness as an alternative thermal treatment method to produce power and heat. Presented in this paper is a new, recently patented, 3-stage gasification scheme, designed for all aforementioned types of fuels and for producing a synthesis gas free of tar and dioxins. The proposed 3-stage gasification scheme comprises of three stages: i) pyrolysis, ii) combustion and iii) gasification. The proposed 3-stage gasification scheme is valid for municipal solid waste and any type of biomass despite differences in chemical composition. The innovation of this 3-stage gasification scheme is based on the fact that the transition between normal and reverse operation and vice versa is achieved only by the proper rotation settings of four air blowers, thus creating a new model of gaseous flow management between the three aforementioned stages. The presented model can achieve a safe industrial-scale operation while producing a gas free of harmful components. The proposed gasification model is validated as suitable for small-to-medium scale capacities, achieving an overall electrical efficiency of 30% and minimum environmental impacts well below all existing thresholds, including those set by the Directive 2000/76/EC on solid waste incineration. (C) 2011 Elsevier B.V. All rights reserved.