Suspension firing

RDF-3 is intended for use as a supplement with coal for semisuspension or suspension firing or for use by itself in similar boilers. d-RDF is intended as a supplement with stoker coal or for use by itself in stoker boilers. Several methods and alternatives for producing RDF-3 or d-RDF have been described (25). 

Ptilverizers The pulverizer is the heart of any solid-fuel suspension-firing system. Air is used to dry the coal, transport it through the pulverizer, classify it, and transport it to the burner, where the transport air provides part of the air for combustion. The pulverizers themselves... 

Conceptually speaking, the technology for combustors is similar to that used for coal combustion (see Chapter 9) if solid biomass fuels are used. Typically used configurations for biomass combustion include [41] (1) pile-burned, (2) stoker-fired, (3) suspension-fired, and (4) fluidized-bed combustors. 

The suspension-fired boilers are similar to the pulverized coal firing technology and involve combusting the fuel in the form of small particles as they are fed into the boiler. A great deal of pretreatment is required of the fuel, which is a potential disadvantage. However, the higher boiler efficiency is an advantage. 

Suspension firing 20 Chips, shavings, and Sander dust Low High Suspension... 

TABLE 6.2 Typical Moisture Contents and Heating Values of Waste Biomass for Combustion in Fluid-Bed, Grate, and Suspension Firing Units... 

A demonstration unit sponsored by the Environemtal Protection Agency (EPA) to produce RDF at St. Louis proved the basic feasibility of mechanical separation processes, transport and storage techniques, and combustion of fluff RDF to replace 5 to 27 percent of the pulverized coal used in suspension-fired utility boilers. However, the refinement of equipment components and the technical and economic optimization of the basic technology still require a great deal of work. 

It is practical to suspension over-fire a dutch oven or grate system with residues but characteristically higher emissions from suspension firing must be considered. The higher percentage (4-6 ) of low-melting ash in ag-residues poses special grate problems vis-a-vis wood at 1. ... 

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