Analysis and simulation of K and Cl in electrostatic precipitator ash and black liquor of an operating kraft recovery boiler

Abstract

Non-process elements such as potassium (K) and chlorine (Cl) are commonly found in the recovery cycle of kraft mills and are capable of forming highly soluble compounds. These elements, in high concentrations, can lead to the corrosion of process equipment or to the plugging of recovery boilers. The behaviour of these elements throughout the liquor cycle is often a direct result of variables related to the operation of the process. An unusual cyclical trend was observed in the Cl content of the electrostatic precipitator (ESP) ash produced in the recovery boiler of a Canadian kraft mill. Analysis of the ash and liquor samples during a 390-day sampling period found that the Cl enrichment factor (EFCl) varied significantly between 1.2 to 3.9, whereas the EFK stayed fairly constant at ~ 1.4. [...]