Förfarande för förebyggande av kalciumoxalatutfällning

摘要

The magnesium ions are added to the process flow in a quantity sufficient for prevention of precipitation of calcium oxalate under ruling conditions. The amount of magnesium added is within the range of /=0.5 to /=5 kg per ton of pulp. The magnesium is added to a process flow the pH of which is in the range of /=pH 2 to /=pH 9, suitably /=pH 3 to /=pH 7 and most suitable /=pH 5. The process flow is one involving oxidative bleaching of the paper pulp, or where a complex former is added to the pulp. Where oxidative bleaching is used, the bleaching filtrate from a washing stage is at least partly fed back to earlier process stages. Where a complex former is added, the bleaching filtrate is also fed back from a washing stage at least partly to earlier process stages.