The Experience of ECF Bleaching Plant Operation

Abstract

Hokuetsu Paper Niigata Mill started up in June 1998 its third coated paper machine (PM8) with a capacity of 240, 000tpy. For the purpose of not having to purchase as much market pulp for this machine and other upgraded machines, the increase of pulp production capacity and the modernization of the plant were planned are carried out before the machine's start up.Many facilities such as a recovery boiler, a recausticizing plant including lime kiln, a bleach chemical preparation plant, a chip handling system and a fiber line have been installed one after another according to three-year program which was completed by March 1998.This fiber line with 1, 200tpd of hardwood bleached pulp is now running satisfactorily and achieved the expected results, meeting demands of quality and quantity for the paper machines of our four mills.This article describes operation experience of our new fiber line and influence of its perfoemance upon environmental aspects.Hokuetsu paper Niigata Mill's new fiber line produces about 400, 000 admtpy of hardwood ECF bleached kraft pulp. This is the first full scale ECF bleach plant in Japan. The fiber line consists of ITC (Isothermal Continuous Cooking) digester, two stages oxygen MC delignification stage, and D0-E/O-DnD1 bleaching sequence, Even if pulp and paper production are increased, to keep of rather than to low level of environmental loads, a wastewater treatment system was additionally introduced. The sysrem configuration is primary sedimantation and activated sludge treatment that uses oxygen gas aeration.At the stage of wiriting this, AOX (absorbable organic halogen) at treated wastewater are 0.04kg /ADMt, respectively. Especially. effluent color is drastically improved and is almost clear, so, we call it as “white wine”.