Modeling fine particles and alkali metal compound behavior in a kraft recovery boiler

Abstract

Under certain conditions, ash in black liquor forms a locally corrosive environment in a kraft recovery boiler. The ash also might cause efficiency losses and even boiler shutdown because of plugging of the flue gas passages. The most troublesome compounds in a fuel such as black liquor are potassium and chlorine because they change the melting behavior of the ash. Fouling and corrosion of the kraft recovery boiler have been researched extensively, but few computational models have been developed to deal with the subject. This report describes a computational fluid dynamics-based method for modeling the reactions between alkali metal compounds and for the formation of fine fume particles in a kraft recovery boiler furnace. The modeling method is developed from ANSYS/FLUENT software and its Fine Particle Model extension. We used the method to examine gaseous alkali metal compound and fine fume particle distributions in a kraft recovery boiler furnace. The effect of temperature and the boiler design on these variables, for example, can be predicted with the model. We also present some preliminary results obtained with the model. When the model is developed further, it can be extended to the superheater area of the kraft recovery boiler. This will give new insight into the variables that increase or decrease fouling and corrosion

CFD-modeling of fume formation in kraft recovery boilers

“…In our previous paper [10], we introduced a model that incorporates equilibrium chemistry and fine particle formation into CFD simulations to gain insight into fouling and corrosion in kraft recovery boilers. However, the earlier model covered only the furnace area of the boiler.…”

Combustion Performance of Agropellets in an Experimental Fixed Bed Reactor versus a Commercial Grate Boiler. Validation of Ash Behavior

“…The P-XRD results already seem to confirm these findings (you can compare the results of the deposits in the boiler case, as shown in Table 10 , with those of the reactor case, as shown in ref ( 36 )). This difference in behavior may be related to the fact that a greater excess of air was used in the boiler, which implies lower combustion temperatures and, therefore, a lower release of Cl and a higher release of S. 41 …”

Optimizing the heat transfer performance of the recovery boiler superheaters using simulated annealing, surrogate modeling, and computational fluid dynamics

“…Most of the recent research has been connected to the furnace. The main topics have been the combustion of black liquor [20,21], furnace processes and combustion [22][23][24], char bed processes [25][26][27][28], fume formation and emissions [29][30][31], and injection of combustion air [32,33]. Another focal research area has been the superheater region.…”

“…Several researchers have also published data measured from recovery boilers and contributed to validation work of the CFD models [23,24,28,34,[46][47][48]. However, the amount of published measurement data and validation work of recovery boiler CFD models is limited, since full-scale measurements on a Introduction Leppänen et al [30] Modeling fume formation in the furnace Jukola et al [31] Modeling sodium release from the black liquor char…”