COMPUTER CONTROL OF PARALLEL PAPER MILL REFINERS FOR CONTROLLING THE FREENESS OF STOCK BY CONTROLLING THE STOCK TEMPERATURE RISE THROUGH EACH REFINER

摘要

Apparatus is disclosed for controlling freeness of stock from parallel refiners by controlling the rise in temperature of stock through each refiner. The DELTA T setpoint for each refiner is adjusted to compensate for: variations in consistency of stock; maximum power rating of the refiner; weighted average freeness of stock from all refiners; and the composite frheness of stock delivered to a paper machine. Error in the desired temperature rise of a given refiner is employed to control its disc or plug operation. An on-line analyzer is employed to monitor composite freeness. Couch or flatbox vacuum is employed as an alternative measure of composite freeness, but only if intentional paper machine changes which would affect vacuum have not been made. Operator control of composite freeness is also permitted. The composite freeness setpoint is adjusted to maintain a desired paper bursting strength. Power checks are made and instructions are automatically given to adjust flow rate to an individual refiner in order to keep it operating within its maximum power limit and to add or delete refiners for optimum efficiency.