school energy&environment

Refuse derived fuel

In the context of the waste-to-energy strategy, we find the so-called refuse derived fuel (RDF) obtained from non-dangerous waste, and used to recover energy in incineration plants (also known as Waste to Energy systems). The range of waste materials that are used is very large and includes the residues which have been excluded from the recycling processes, waste from the industries and the distribution networks, muds from water purification systems, dangerous industrial waste, discarded biomass materials, etc. … These must be treated suitably in order to comply with the criteria, regulations and industrial specifications in order to reach a suitable heat producing potential.
One of the least costly methods, which is most widespread, for the production of RDF, is mechanical biological pre-treatment, MBT. In a MBT plant, metals (which are recycled) and inert materials (e.g. glass), and organic fractions (that are sent to the composting plants, with or without an anaerobic digesting phase) are separated from the MSW, and fractions with a higher heat producing power for the production of RDF, are chosen. Other solutions, besides MBT, are bio-stabilization and bio-drying of materials from which metals and inert materials have been removed beforehand, in which the organic fraction is stabilized and loses a part of the humidity, thus obtaining a final fraction with a higher heat producing power, that is suited for combustion, and consisting of paper and cardboard, wood, plastic and textiles that can be burnt directly. The total quantity of RDF produced from MSW in the European Union is estimated around 3 million tons. The Italian production amounts to 200,000 tons with a yield of 300 kg per ton of MSW. The characteristics that are necessary for the product that is obtained with the treatments to be used as RDF are many, and include a heat producing power of at least 15 MJ and 25% humidity.
Which are the current uses of RDF? There are numerous possibilities, which include: Waste to Energy systems, cement plants, thermal energy plants for district heating, steel plants, coal thermo-electric power plants etc. and, depending on the plant, they are uses as the only fuel or as an auxiliary fuel.