Canadian International Paper Company

Murray J McLeod

John A Histed

William H Lawford

A method and apparatus are provided for automatically and simultaneously controlling the solution viscosity and degree of brightness of a pulp during a bleaching process which employs a sequence of chlorination, hypochlorite and chlorine dioxide bleaching reagents. The pulp is monitored during the bleaching sequence by employing an optical device utilizing reflected light of one or two wavebands. The optical monitoring device electronically feeds a control signal to a regulator or computer which regulates the input of one or more of the bleaching reagents. The amounts of reagents added are based upon and made possible by relationships which have now been determined between the light reflectance values of the pulp at various stages of the process and desired viscosity and brightness values. The viscosity is controlled by controlling the hypochlorite addition and the brightness of the fully bleached pulp is controlled by chlorine dioxide addition.

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Hawkesbury, Canada

Murray J McLeod