Abstract: The present invention is characterized in that in a simulation for predicting a steam pressure setpoint after grade change, an initial moisture percentage is evaluated from differences between bone-dry basis weights and between machine speeds before and after grade change; the bone-dry coated weight of a size is evaluated from the flow rate and concentration thereof; and then the dryer inlet moisture percentage of a web after a size press is calculated from the coated weight. Thus, the invention intends to improve the quality of products through precise dryer control, as well as reduce the time required for grade change, by precisely predicting the web's initial moisture percentage at the dryer inlet after grade change and precisely and quickly controlling dryer steam pressure during grade change.

Abstract: The present invention is characterized in that in a simulation for predicting a steam pressure setpoint after grade change, an initial moisture percentage is evaluated from differences between bone-dry basis weights and between machine speeds before and after grade change; the bone-dry coated weight of a size is evaluated from the flow rate and concentration thereof; and then the dryer inlet moisture percentage of a web after a size press is calculated from the coated weight. Thus, the invention intends to improve the quality of products through precise dryer control, as well as reduce the time required for grade change, by precisely predicting the web's initial moisture percentage at the dryer inlet after grade change and precisely and quickly controlling dryer steam pressure during grade change.

Abstract: A paper-making process control system is provided for a paper making machine to simulate a web drying operation performed by the drying sections of the paper machine, in order to enhance the reliability of controlling operation in the web product grade change and to reduce the time necessary for the grade change. In the control system, when a web product change is carried out during the paper-making process by passing a web (WE) along with a canvas belt (14b) around a steam-heated drums (14a) for the drying of the web (WE), the control system describes heat balance among the steam-heated drums(14a), the web (WE), and the canvas belt (14b) by heat balance equations on an assumption that there is no temperature differential in the temperature of the circumferential portion of each steam-heated drum (14a), and adjustably regulates supply of steam to the respective steam-heated drums (14a) on the basis of the heat balance equations to thereby bring a moisture content of the web (WE) to a desired value.