Monitoring and Control of Paper Web Moisture

Abstract

Product quality is a key indicator of the positive outcome of pulp and paper production. Moisture content is one of the main paper quality characteristics. The moisture profile across the paper web width shows possible shortcomings of the process equipment which, if corrected, will improve the consumer properties of paper and enhance economic efficiency. The research aims to assess whether the moisture content measurement results meet the requirements of the process regulations in the steady-state and transient modes of paper machine operation as well as the uniformity of the moisture profile in the cross direction. Data from the scanning device at high and low resolution were processed using statistical methods in order to assess the quality of the automatic paper web moisture control system. It was determined that in the steady-state mode of paper machine operation the moisture content meets the requirements of the regulations with a confidence probability of 0.95; in the transient mode of operation it exceeds the upper limit by 6 %. It has been found that the automated moisture control system eliminates this fault in 340 s. The coefficient of variation was used as a criterion for evaluating the uniformity of the moisture profile across the paper web width. The hypothesis of a trend line in the moisture profile across the paper web width was confirmed and a trend line equation was obtained using regression analysis techniques. The moisture profile was modeled while eliminating the technological factor that systematically affects the uniformity. It is proven that the elimination of the fault will reduce the coefficient of variation and therefore improve the uniformity of the profile by 41.2 % in the steady-state mode of paper machine operation. In the transition mode of operation the moisture profile improves slightly. The proposed algorithm for studying the moisture profile of paper, its modeling after corrections of the control object can be used in systems for controlling the quality of paper in the transverse direction. For citation: Koryakovskaya N.V., Bederdinova O.I. Monitoring and Control of Paper Web Moisture. Lesnoy Zhurnal [Russian Forestry Journal], 2022, no. 1, pp. 188–204. DOI: 10.37482/0536-1036-2022-1-188-204