Control scheme for rapid pulp delignification and bleaching
First Claim
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1. A coupled control method for controlling a continuous ozone bleaching process for paper pulp to a desired degree of bleaching, which comprises:
- (a) adding feed ozone at a desired amount to the pulp;
(b) passing the pulp continuously into and out of a bleaching reactor;
(c) measuring ingoing pulp brightness between successive ingoing pulp K number measurements; and
(d) adjusting the quantity of feed ozone required to reach a desired degree of bleaching in response to the measured brightness and K number values.
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Abstract
A process control for adjusting bleaching agent application in response to the pulp brightness and/or K number is realized by utilizing a coupled control feedforward and/or feedback control system or combination thereof wherein brightness measurements are made between successive K number measurements and adjustments made to the bleaching agent application in response to a comparison value.
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Citations
16 Claims
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1. A coupled control method for controlling a continuous ozone bleaching process for paper pulp to a desired degree of bleaching, which comprises:
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(a) adding feed ozone at a desired amount to the pulp; (b) passing the pulp continuously into and out of a bleaching reactor; (c) measuring ingoing pulp brightness between successive ingoing pulp K number measurements; and (d) adjusting the quantity of feed ozone required to reach a desired degree of bleaching in response to the measured brightness and K number values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A coupled control method for controlling a continuous ozone bleaching process for paper pulp to a desired degree of bleaching, which comprises:
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(a) adding feed ozone at a desired amount to the pulp; (b) passing the pulp continuously into and out of a bleaching reactor; (c) measuring the brightness value of the pulp between successive K number measurements; and (d) adjusting the quantity of feed ozone required to reach a desired degree of bleaching in response to the measured brightness and K number values; wherein the measured pulp property is an ingoing pulp property; and the adjusting step comprises; (e) periodically measuring the K number of the incoming pulp as it passes into the reactor and adjusting the amount of feed ozone to obtain the desired degree of bleaching; (f) measuring the pulp brightness between periodic K number measurements, and making a moving average of several pulp brightness measurements; (g) comparing the moving average brightness measurement with the brightness representing the K number for that period prior to the next K number measurement to initiate a change in feed ozone; and (h) adjusting the quantity of feed ozone in response to the comparison value. - View Dependent Claims (14, 15, 16)
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Specification