초록 ▼

Filtrates from bleach plants for cellulosic (paper) pulp non-chlorine bleaching sequences are treated to minimize the consumption of ozone in ozone bleaching stages. Organic material in the filtrate used in a washer just prior to an ozone stage is oxidized to make the organic material less attractiv

Filtrates from bleach plants for cellulosic (paper) pulp non-chlorine bleaching sequences are treated to minimize the consumption of ozone in ozone bleaching stages. Organic material in the filtrate used in a washer just prior to an ozone stage is oxidized to make the organic material less attractive to the ozone. It may be oxidized by indirectly heating the filtrate, and then reacting it with oxygen gas in a reactor. Alkali may be added to the filtrate in the reactor. Metallic ions are also removed from the system by applying an electrical potential either to the filtrate, an entire washer prior to the ozone stage, or to the pulp line prior to the ozone stage. All of the wash filtrates are treated and recirculated so as not to discharge any wash filtrates into the environment, or so that the only wash filtrate discharged from the washing system of the bleaching plant is a small stream used for smelt dissolution. A typical non-chlorine bleaching sequence utilized may be OAZEZP.

대표청구항 ▼

[ What is claimed is:] [1.] A method of treating filtrates from bleach plants for bleaching cellulosic pulp, including utilizing at least one ozone bleaching stage, comprising the steps of:(a) washing the pulp in a washer with a wash liquid prior to the ozone bleaching stage, the wash liquid includi

[ What is claimed is:] [1.] A method of treating filtrates from bleach plants for bleaching cellulosic pulp, including utilizing at least one ozone bleaching stage, comprising the steps of:(a) washing the pulp in a washer with a wash liquid prior to the ozone bleaching stage, the wash liquid including filtrate from another washing stage of a bleaching stage;(b) oxidizing the organic material in the filtrate used as wash liquid in step (a) prior to its use in step (a) in order to make the organic material less attractive to ozone in the ozone bleaching stage; and(c) ozone bleaching the washed pulp in said at least one ozone bleaching stage.