Manufacture and control of quality in band of paper, requires sensors at headbox discharge, and locations throughout plant, measurements being computer coordinated and used in control model

摘要

Zonal sensors located transversely, near the papermaking machine headbox discharge (10), provide measurement data resolved in position, concerning one or more properties of the material. This is evaluated with other data from sensors at locations (14, 16, 17-21) ahead of, and/or following the discharge (10). An Independent claim is included for corresponding equipment to carry out the method. Preferred features: Sensors at the headbox number 10, preferably 100, each allocated a specific measurement zone. All data is entered into a predictive model. Output data controls the process, especially when changing the type of feed and/or product. Further variation of process magnitudes takes place in this case, at the former, the pressing unit (17) and/or the drying stretch (21) following the feed box. Steam flow into the press (17) steam boxes, steam flow into a drying cylinder, humidifiers and/or drying equipment, preferably infra red dryers; all are controlled as described. Rapidly-acting control actuators in the machine, in e.g. the preceding sections, are controlled. Further equipment in the line is controlled for the purpose of rapid change, e.g. stretching, smoothing or glazing and/or winding equipment is included, preferably using feed-forward control. For direct control of manufacture using the predictive model, merely the headbox feed data are employed, and the model is fitted to data from the further sensors. Head box data sensors are used in monitoring and control of the feed systems (14, 16). The method is further detailed, taking into account process speed and synchronization of measurements. Further sensors are operated at comparatively low speeds of e.g. 0.1-10 cm/s. Further sensors over the entire band width are employed, each covering limited width of e.g. 1 m, preferably 10-30 cm. Such measurements are brought into time and/or spatial synchronism with those from the zonal sensors. The data are employed in cross correlation, identifying zones of measurement from the zonal sensors.