Thermal Treatment

Types of MSW combustion systems

Municipal Solid Wastes (MSW) combustion systems can be divided into mass burning type and refuse-derived-fuel (RDF) burning type, depending on the fuel preparations steps and the way the refuse is combusted.

Mass burning
For this type of system, the refuse is combusted on a hearth or stoker as it is received, without the preparation step. Stokers are designed to include drying, burning and ash burnout sections, with each of these sections requiring different combustion air quantities.

Owing to the heterogeneity of the refuse, the furnace combustion environment must be designed to cater for very different combustion characteristics of the refuse constituents. On the other hand, combusting unprocessed refuse obviates the need for the extra land area for refuse preparation as in the case of the RDF burning systems. Furthermore, mass burning can produce a small total residue.

Refuse-derived-fuel (RDF) burning
For this type of system, a more homogenous fuel is derived from MSW for the combustion process by separating the combustibles with non-combustibles. Hence part of the useful materials can be recycled.

With a more homogenous fuel, the cost of the combustion furnace for RDF burning can be lowered. Besides, flue gas quantities are reduced and hence the cost for air pollution control equipment can be lowered.

However, RDF burning requires additional capital investment and land area for RDF preparation. The mass and volume of residues that need to be landfilled are higher than that of the mass burning process.