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Method of Operating a Pulp Bleaching Plant

IP.com Disclosure Number: IPCOM000096102D
Original Publication Date: 1964-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Nabavian, KJ: AUTHOR

Abstract

The preparation of wood pulp for a paper making machine involves a bleaching process as shown. Raw pulp is added to storage tank F, and subsequently fed through chlorine tower Cl2, washer W, alkali extraction tower E, and subsequent stages to be held in storage tank H until needed by the paper machine.

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Method of Operating a Pulp Bleaching Plant

The preparation of wood pulp for a paper making machine involves a bleaching process as shown. Raw pulp is added to storage tank F, and subsequently fed through chlorine tower Cl2, washer W, alkali extraction tower E, and subsequent stages to be held in storage tank H until needed by the paper machine.

Any number of other bleaching stages, such as hypochlorite and chlorine dioxide towers, can be included in the sequence. The towers can be upflow or downflow, but should not have much longitudinal mixing. The latter towers should be kept full all the time. Such towers behave as batch reactors and merely provide residence time for the bleaching reactions.

This method of operation assumes that the reaction rates in the bleaching units are known from an independent kinetic study, or a statistical relation between the output and input variables of each unit is available. The feed rate to the chlorine tower is planned for T minutes ahead of the present time to. This planned rate is followed if at all possible. In case of an event at time t that requires a modification of the average production rate, the desired change is obtained by appropriate scheduling of the feed rate for the time after t+ T. For best results, T should be equal to or larger than the throughput time of the chlorine tower under current operating conditions. The considerations involved in scheduling of the feed rate to the chlorine tower are maintaining the desired average production rate, if possible, and minimizing the probability of running out of pulp or pulp storage before or after the bleaching plant.

The residence time theta of the pulp in a tower is calculated before...