Abstract: Oxidized white liquor is heat treated to increase the concentration of polysulphide measured at 285 or 286 nm (PSUV) or measured at 416 nm (PSVIS) and the PSUV/PSGR or PSVIS/PSGR ratio, whereby the content of active polysulphide in the total polysulphide is increased which active polysulphide can be exploited to increase pulp yield in Kraft pulping.

Abstract: A method and an apparatus for optimizing the combustion air system in a power boiler or chemical recovery boiler by improving fluid flow and gas mixing are disclosed, whereby one can increase boiler capacity and combustion uniformity and reduce particulate and gaseous emissions. The method involves interlacing of the secondary and, where applicable, the tertiary air supply through opposing air ports on all four walls of the boiler, and is implemented by alternately opening wide or partially closing a port damper on one side, while partially closing or opening wide a port damper on the opposite side, such that a 70-100% open damper on one side opposes a partially closed (10-40% open) damper on the other and vice versa in an alternating fashion, along opposing walls.