Development of an Optimization Model for the Design of Mechanical Treatment Processes Under Final Product Constraints

The model serves as an analysis tool to study the production of a refuse derived fuel [RDF] from a waste stream collected at are cycling sorting plant located in Montreal, Quebec. The objective was to define the optimal mechanical sequence i.e. the most cost effective solution that allows the production of RDF that conforms to the quality requirements for waste co-processing in cement plants. Characterization of the raw waste found that both the chlorine content and the moisture content exceeded the maximum allowable limits whilst the calorific value was below the minimum limit. We proved the validity of the model by evaluating successfully the technical and economic feasibility of implementing a mechanical waste treatment unit. We obtained the optimal line configuration of equipment (enumerated in order) as: shredder, trommel screen, NIR optical sorter(1), magnetic separator and NIR opticalsorter(2). The total cost per tonne of waste treated was estimated to 86 Can$, a Price about 23% higher than the landfill tipping fee in the City of Montreal.