METHOD OF CONTROLLING THE CHEMICAL BALANCE OF A PULP MILL

摘要

A method to optimize the chemical balance at a sulfate pulp mill, which produces at least pulp bleached with chlorine dioxide and has a chlorine dioxide plant using at least chlorate, methanol and sulfuric acid for making chlorine dioxide. The method includes: a) gases from the mill's concentrated non-condensable gas system are incinerated in order to form a gas containing sulfur dioxide, which is treated to produce concentrated sulfuric acid, and b) raw methanol from the mill processes is purified to produce methanol, and c) side streams containing sodium compounds and/or sulfur compounds produced by mill processes are used as make-up chemicals, wherein the production of chlorine dioxide uses the sulfuric acid produced in step a) and methanol purified in step b), with a sulfuric acid concentration of 94-99%, preferably 95-98%, and using in step c) sesquisulfate or sodium sulfate produced during the production of chlorine dioxide.