LABORATORY EVALUATION OF WASHING CHARACTERISTdCS OF BROWN STOCK

Abstract

A brown stock washing is the most important operation in the pulp mill controlling on one hand, the cleanliness of the pulp for bleaching and reducing bleach demand and on the other hand going black liquors of acceptable concentration on for further processing in recovery plant. To control and to optimize the various process variables of a washer in the industry one can study the parameters on laboratory vacuum filters continently industry filters are not amenable for experimentation and cannot provide data for rational analysis so easily. Institute of Paper Technology has an EMICO-KCP vacuum drum washer of size 18" x 12" ( 45cm x 30 cm). The system was not in running condition. The system has to be installed after making the modification in the setup as some of the components are•missing/not supplied originally. Therefore the installation and commissioning of the equipment was the first major step of the work. The installation required modification of some components and assembly of various sections. The modification includes wash liquor shower system, vacuum gauge setting, seal-water arrange-ment in vacuum pump, exhaust snubber arrangement to vacuum pump, receiving line installation to vacuum. receiver, filter cloth installation on drum, feed pump connection and electrical connec-tion. The systenrwas commissioned and tr~a..tls are taken with the water and lime sludge. All .these activities took the major part of the time. Experiments were planned for conducting washing ttals with brown stock obtained from a nearby paper mill. The experi-ments includes variation of wash water flow rate, drum speed, vat consistency and drum submergence. Only limited data could be taken due to paucity of time. The experimental data is analyzed. -Simultaneously the operating data of brown stock system of a nearby mill ( 3- stage counter current brown stock washing on rotary vacuum drum filter) is taken and analyzed. Using the Perkin's method, Equivalent displacement,ratio method. Norden factor method and the funda-mental methods. The comparison are presented in the report.