7.2. Modification requirements
Co-firing can be carried out in any furnace system,
although some modifications may be necessary in order to
accommodate the nature of combustion of the agricultural
residues. An important factor of consideration is the residue
feeding system. Due to their low bulk densities, biomasses
are generally difficult to feed. This is particularly valid in
small-scale combustion units. There are problems of blockage
and discontinuous dosing if screw feeders are used. In
such cases, pneumatic feeding systems may be considered.
For pulverized coal combustion units, the biomass may
require milling and then premixing with coal before being
fed pneumatically. However, problems of segregation of the
biomass in the fuel silo may also be experienced [15].
For all types of fluidized beds the modifications which
may be required include