Method and equipment for controlling properties of paper
AssigneeMetso Paper Automation Oy
InventorsTaisto Huhtelin, Risto Kuusisto, Lin Tian, Timo Rantala, Jukka Nokelainen
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Abstract
The invention relates to a method and equipment for controlling properties of paper, which method comprises modelling the effect of the flow of retention agent (Fra) both on the amount of filler in the white water and on the paper ash content (ASH), and the effect of the flow of filler (Ffi) both on the paper ash content (ASH) and on the amount of filler in the white water. The fulfilled modelling is used to adjust the amount of filler in the white water and the paper ash content (ASH) by controlling simultaneously the flow of retention agent (Fra) and the flow of filler (Ffi).
Claims16
A method for controlling properties of paper produced by a paper making machine, said method comprising supplying paper stock into a headbox, conveying the paper stock from the headbox to a former section in which a paper web is produced and from which white paper is expelled, producing paper from the paper web, measuring properties of the paper, combining the white water into the paper stock, the white water, the paper stock and the paper having respective amounts of ash content, measuring a variable describing the amount of the filler in the white water and the ash content in the paper, in the headbox or both, said method comprising a control system including a dynamic model and control variables, said model relating the effect of the flow retention agent on the amount of filler in the white water and on the paper ash content, and the effect of the flow of filler on the paper ash content and on the amount of filler in the white water and the paper ash content by simultaneously controlling the flow of retention agent and the flow of filler,
- the control system comprising predictor and optimization steps, in which the predictor step takes into account the opereating variables and said model and provides a prediction on the basis thereof, and the optimization step utilizes the prediction produced in the predictor step to optimize the control variables.
Equipment for controlling properties of paper produced by a paper making machine comprising a headbox into which paper stock is supplied and from which the paper stock is supplied to former section which produces a paper web from the stock, said web being supplied as paper to a measuring beam, said former section having an outlet for white water expelled during production of the paper web, means for combining the white water into the paper stock, means for adding a flow of filler to the paper stock, means for adding a flow of retention agent to the paper stocl, the white water, the paper stock and the paper having respective amounts of ash content, said equipment comprising means for measuring a variable relating the amount of filler in the white water, means for measuring ash content in the paper, or ash content in the paper stock in the headbox or both, a control system including a model and control variables relating the flow of retention agent on the amount of filler in the white water and on the ash content of the paper, and of the flow of filler on the ash content of the paper and on the amount of filler in the white water, means for controlling simultaneously, on the basis of said model, the flow of retention agent and the flow of filler in order to adjust the amount of filler in the white water and the ash content of the paper, the control system further including a predictor means and an optimization means, the predictor means comprising means for taking into account said model and operating variables for providing a prediction output, the optimization means comprising means for utilizing said prediction output produced by the predictor means for optimizing the control variables and the process of producing the paper.
Dependencies are inferred from the claim text.