CHLORIDE AND POTASSIUM CONTROL IN CLOSED KRAFT MILL LIQUOR CYCLES

Chloride and potassium are two problematic minor components which can accumulate in kraft pulping chemical recovery cycles. There is an enri chment of these two elements in recovery boiler electrostatic precipit ator dust and so this is a good point from which to remove them. The m ass flow rate of the electrostatic precipitator dust has been quantifi ed in two field studies, and the effect of four different boiler opera ting parameters on this mass flow rate has been evaluated. The results show that the recycle dust varies between 3.5 to 10% of the as-fired black liquor solids content. A process for selectively removing chlori de and potassium from electrostatic precipitator dust has been develop ed.