Patent ID: 6319362
Filing Date: 2001-11-20
Classification: D21G,D21H,G01N,Y10S

Abstract:
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.