The Fate of Ashes and Inorganics in a Two-stage Fluid Particle System for Waste Valorization

Abstract

This paper reviews the most recent results obtained at the Gasplasma pilot plant for gasification of municipal solid wastes in the UK. The two-stage system involves the combination of a fluidized bubbling bed and a single carbon electrode plasma converter. Bed particles of mullite (3Al2O3-2SiO2) with coarse particle size (1-2mm) are applied as solid inventory in the fluidized bed system. The waste is thermally decomposed within the fluidized bed to produce a crude syngas, containing residual tars, unconverted char and entrained ash particles. The crude syngas is then sent to the plasma cyclone converter where all the inorganic material (particulates and heavy metals components) are captured and immobilized into a vitrified slag. Experimental test runs with RDF waste were conducted by varying the operating conditions and contaminants quantity. The results are presented according to solid samples composition, gas composition, and further specific data (e.g., carbon conversion efficiency, leaching test, etc). Particulate loading data and materials mass balance suggested from 40 to 90% of non-volatile metals (e.g. chromium) and other heavy metals (e.g. vanadium) were incorporated within the slag where they are rendered non-leachable. The work demonstrates the ability to process highly heterogeneous material achieving high energy conversion (87-94%), high material recovery, and virtually complete carbon conversion, producing a very clean syngas capable of being used for power generation or as a chemical feedstock.