scope:

Considerable research and operating experience have established industry acceptance that limiting chloride and potassium concentrations in the pulping and recovery cycle liquors is necessary to achieve recovery boiler capacity and high availability. Limiting these non-process elements can result in ash deposits on boiler heat transfer surfaces that are controllable by sootblower operation. This Technical Information Paper (TIP) will provide an understanding of the sources of chloride and potassium in the mill cycle and their effect on carryover particles and fume in the recovery boiler, the steps that can be taken to develop a mill material balance and determine the maximum acceptable concentration of these in the precipitator ash, and the various approaches that can be applied to limit the concentrations. Ash produced in many recovery boilers contains alkali carbonate compounds, in addition to the sulfates, and their effect is also addressed. Note that there are many other factors that contribute to recovery boiler fouling such as: high carryover, low ash pH, and poor sootblower operation. These issues are not covered in this document. Processes are described that are available and are being developed to remove chloride and potassium from the cycle with sufficient detailed information to permit an operating mill to make a preliminary evaluation of the most suitable process (1).