Numerical analysis of the combustion and fluid flow in a carbon monoxide boiler

Poor performance of a carbon monoxide (CO) boiler can have a detrimental influence on the operation and production of petrochemical industry, steel and iron industry and relevant industries. In this paper, the combustion and fluid flow in a carbon monoxide boiler is examined. Influences of some important parameters related to the geometry and operation of a CO boiler are discussed, including refractory thickness, insertion of an ellipsoidal cone, inlet air flowrate and inlet flue gas flowrate. It is found that when the refractory is thickened, the skin friction coefficient in the DeNOx section increases and arises later in the flow direction. Temperature and NO concentration increase in the DeNOx section and the larger the ellipsoidal cone angle is, the larger the skin friction coefficient will be. Compared with the original CO boiler, refractory thickening alleviates the temperature and NO rise in the DeNOx section. For moderate ellipsoidal cone angles, insertion of an ellipsoidal cone can alleviate the temperature rise in the DeNOx section and this leads to a lower NO emission. On the other hand, as the ellipsoidal cone angle becomes very large, the temperature rise in the DeNOx section is severer than for smaller ellipsoidal cone angles, leading to higher NO emission. A lower excess air flowrate can reduce the skin friction coefficient, NO formation and CO concentration, but the temperature increases. A higher flue gas flowrate can reduce the NO formation and the CO concentration, but the temperature and the skin friction coefficient increase. On the other hand, when the flue gas flowrate is reduced, the temperature and the skin friction coefficient decrease, but the NO formation and CO concentration in the product increase.