Method of improving combustion in a system having a circulating fluidized bed, and a corresponding system

The invention relates to a method of improving combustion in a combustion system having a circulating fluidized bed. It also relates to systems for implementing the method. The method is applicable to a combustion system of the circulating fluidized bed type which system includes a hearth and a cyclone, and operates using fuel that is inserted into the bottom of the hearth, where a reducing atmosphere is created and where the fuel undergoes pyrolysis with separation into two phases, namely a solid phase made up of grains of coke, and a gaseous phase containing volatile matter. Provision is made for a primary air injection, secondary air injections, and a late air injection to be performed at different levels. The late air injected between the top of the hearth and the inlet of the cyclone is used to increase the efficiency with which the cyclone collects the particles that reach the top of the hearth unburnt, and thus to increase the combustion efficiency of the system. The system includes air injection means making it possible to implement the method.