A METHOD FOR TREATING CIRCULATION WATERS

摘要

The present invention relates a method for the treating of circulation waters in papermaking processes wherein a stream of process water separated from an aqueous cellulosic pulp suspension of the papermaking process is provided, said separated process water having an elevated level of free calcium ions. A pH of not less than pH 9 is provided in the process water. Gaseous carbon dioxide is distributed in the process water in an amount sufficient for precipitating a substantial part of the calcium ions as solid calcium carbonate in the water and for obtaining a decreased level of free calcium ions in the water. The calcium ion depleted process water is returned to the papermaking process, thereby reducing or preventing the accumulation of calcium ions circulating in the process.