Numerical simulation of co-combustion of pulverized coal

refuse derived fuel (RDF) and thermal decomposition of calcium carbonate was carried out aiming at an actual precalciner with swirl type prechamber. The predicted burn-off rates of pulverized coal and RDF were 99% and 100% respectively

and the predicted decomposing rate of calcium carbonate was 95%

being in accordance with engineering data actually measured. The results show that the fuel and raw meal are carried by gas stream to rise spirally. The pulverized coal stream starts to burn soon when injected into the furnace from the top of the prechamber

and then burns rapidly

being dominated by char combustion

when rising into the cone section and the column section above the prechamber

forming a violent combustion region. The RDF starts to burn soon

being dominated by volatile combustion

when blown into the furnace horizontally from the lower part of the column section of the precalciner

forming a main combustion zone

and then rises spirally intertwining with the pulverized coal stream. The calcium carbonate begins to whirl in the prechamber

being decomposed by absorbing the heat of high-temperature gas stream

when falling into the furnace from the top of the prechamber

and then is further decomposed in the main combustion zone of coal and RDF on the way up. As a result of the coupling of co-combustion and decomposition

there is a uniform and steady temperature field in the column section of the precalciner.