MSW is a poor-quality fuel and its pre-processing is necessary to prepare fuel pellets to improve its consistency, storage and handling characteristics, combustion behaviour and calorific value. Technological improvements are taking place in the realms of advanced source separation, resource recovery and production/utilisation of recovered fuel in both existing and new plants for this purpose. There has been an increase in global interest in the preparation of Refuse Derived Fuel (or RDF) containing a blend of pre-processed MSW with coal suitable for combustion in pulverised coal and fluidised bed boilers.
Pelletization of Urban Wastes
Pelletization of municipal solid waste involves the processes of segregating, crushing, mixing high and low heat value organic waste material and solidifying it to produce fuel pellets or briquettes, also referred to as Refuse Derived Fuel (RDF) or Process Engineered Fuel (PEF) or Solid Recovered Fuel (SRF). The process is essentially a method that condenses the waste or changes its physical form and enriches its organic content through removal of inorganic materials and moisture. The calorific value of RDF pellets can be around 4000 kcal/ kg depending upon the percentage of organic matter in the waste, additives and binder materials used in the process.
The calorific value of raw MSW is around 1000 kcal/kg while that of fuel pellets is 4000 kcal/kg. On an average, about 15–20 tons of fuel pellets can be produced after treatment of 100 tons of raw garbage. Since pelletization enriches the organic content of the waste through removal of inorganic materials and moisture, it can be very effective method for preparing an enriched fuel feed for other thermo-chemical processes like pyrolysis/ gasification, apart from incineration.
Pellets can be used for heating plant boilers and for the generation of electricity. They can also act as a good substitute for coal and wood for domestic and industrial purposes. The important applications of RDF in the Middle East are found in the following spheres:
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