Using Waste Heat to Dry RDF: a Technical and Environmental Assessment of the Low Temperature Belt Dryer Technology

Abstract

In 2015, the Portuguese cement production company Cimpor modified the alternative fuel supply operation of refuse derived fuel (RDF) co-processing in the main burner of one of its cement kilns in Souselas. This modification resulted in the installation of an RDF drying unit with low temperature belt dryer (LTBD) technology that uses cascading energy available in Souselas cement plant. Implementation of the dryer project improves production and efficiency of the industrial process, while also resulting in environmental benefits as it decreases moisture and increases the lower calorific value of RDF, improving its quality. This paper intended to determine these environmental benefits and the added value that the project brings to the industry by presenting an energy balance and environmental assessment. This methodology allowed to compare the use of available heat as an energy source for the dryer instead of fossil fuels, such as natural gas or coal, which concluded that the waste heat available at the cement plant for the dryer would allow the saving of 75 to 84 kg of CO₂-eq per tonne of wet RDF to be dried. Projects such as this one may greatly help address the main barriers of using RDF from municipal solid waste and other waste streams with high moisture content.