A FluidBedIncinerator is a highly efficent form of incinerator. Basically, it a bed of sand, through which you pump air. If you pump air fast enough the sand and air mix and produces a highly fluid base. If the sand is hot enough, then any flammible material dropped onto the sand will burn rapidly and completely. This in turn proudces more heat which keeps the sand hot.
As far as I know, the main advantage of these incinerators is that they can be relatively small compared to a more traditional incinerator.