WASTE TYPES MUNICIPAL SOLID WASTE
RDF is made from domestic waste which includes biodegradable material as well as plastics, and has a lower calorific value than solid recovered fuel. It is basically a processing method for mixed MSW, which can be very effective in preparing an enriched fuel feed for thermal processes like or for use in industrial . It is a fuel produced by shredding municipal solid waste (MSW) or steam pressure treating in an autoclave. RDF consists largely of organic components of municipal waste such as plastics and biodegradable waste compressed into pellets, bricks, or logs. Noncombustible materials such as glass and metals are removed during the post treatment processing cycle with an air knife or other mechanical separation processing. The production of Refuse Derived Fuels involves the mechanical processing of household waste using screens, shredders and separators to recover recyclable materials and to produce a combustible product. Systems involve the removal of inert and compostable materials followed by pulverization to produce a feedstock which can be incinerated in power stations, pyrolysis and gasification systems, or co-incinerated in other industrial combustion processes.
Several fuel recovery facilities where waste is sorted both mechanically and by hand to extract recyclable material. The remaining material is then used to produce refuse derived fuel and solid recovered fuel. The RDF can be used alongside traditional sources of fuel in coal power plants, kiln industry, plasma arc gasification modules, pyrolysis plants etc. RDF is capable of being combusted cleanly and can provide a funding source where unused carbon credits are sold on the open market via a carbon exchange.
Solid recovered fuel is produced using mainly with additional processing to improve quality and value. After initial sorting, the material is shredded, passed through a trommel (a cylindrical screening unit that separates material by rotation), picked over by hand and then shredded again. The resulting material is then blended with other materials to increase the calorific value. All RDF processes typically begin with shredding MSW to a finer size; many then separate the fuel fraction from the residue. In plants where no additional preparation is included, the operation is called a "shred-and-burn" RDF facility. Frequently, however, the separated fuel fraction is further processed to recover metals and sometimes glass. The normal sequence of RDF preparation is shredding, air classifying/screening, magnetic separation, and sometimes eddy current separation for nonferrous metal recovery. Many variations of the process have been developed, each of which has certain advantage.
One of the most dangerous problems in preparation of RDF is the possibility of an explosion during shredding. Process and equipment improvements have significantly reduced the severity of the problem, but not eliminated it. Improved designs for commonly used shredders and their enclosures have been able to minimize the number of explosions and reduce their destructiveness. Explosion-suppression systems have been effective in preventing many solvent ignition and dust explosions.
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