Product distribution and process performance in single-, two- and three-stage pyrolysis/gasification of RDF

For RDF gasification, a unit composed of three stages: pyrolysis, coke gasification, and tar decomposition, was employed. Effect of involvement of individual unit stages on product distribution, producer gas composition, and unit performance was investigated. Separate experiments considering just pyrolysis, pyrolysis plus coke gasification, pyrolysis plus tar decomposition, and with all three stages involved were performed. Compared to the RDF pyrolysis experiment, introduction of coke gasification stage primarily affected the product distribution, CO and hydrocarbons content in the producer gas as well as its lower heating value and hydrogen-to-carbon monoxide ratio. Coupling of the pyrolysis and tar catalytic decomposition stages of the gasification unit reduced the tar yield and slightly improved the process efficiency compared to the RDF pyrolysis experiment. In case that all three stages of the gasification unit were active in experiments, product distribution was similar to that achieved when just pyrolysis and coke gasification stages were involved. Changes in the producer gas composition and process efficiency parameters clearly reflected a synergy effect of both the coke gasification and the tar decomposition stages. To conclude, coke gasification stage conditions the RDF gasification unit performance, whilst the operation of the tar decomposition stage modifies the producer gas composition.