Patent DE-102007027269-A1 (DE)
Title: Control of the undulating tendency of a paper-making fiber web in a paper/cardboard machine, comprises determining specified moisture content behind the drying section, and measuring mass per unit area and moisture content of the fiber web
Inventor: JUPPI KARI
IPC: D21F5/18
Filed: 2007-06-11
Abstract: The control of the undulating tendency of a paper-making fiber web in a paper/cardboard machine having first and second drying section, comprises determining the specified moisture content PM0 behind the second drying section, measuring the moisture content PM1, the mass per unit area BW and the waviness coefficient K1 of the paper-making fiber web behind the second drying section, and determining the partial energies required for the drying process in each of the drying sections or the total energy E required for the drying process of the drying sections. The control of the undulating tendency of a paper-making fiber web in a paper/cardboard machine having first and second drying section, comprises determining the specified moisture content PM0 behind the second drying section, measuring the moisture content PM1, the mass per unit area BW and the waviness coefficient K1 of the paper-making fiber web behind the second drying section, and determining the partial energies required for the drying process in each of the drying sections or the total energy E required for the drying process of the drying sections using the formula E = BW.S.L.dPM, where S stands for the production speed of the machine, L stands for the width of the paper-making fiber web and dPM stands for the targeted change in moisture content in the each of the drying sections or in the drying sections as a whole. In the first drying section, the energy needed for the drying process is generated by a cylinder drying mechanism and is directed towards the first surface of the paper-making fiber web. The second drying section follows the first drying section and in which energy needed for drying is generated by means of impact flow drying process and is directed towards the second surface of the paper-making fiber web that is placed facing the first surface of the paper-making fiber web. The ratio of the drying energy produced by the first drying section is regulated to the drying energy produced by the second drying section on the basis of the waviness coefficient K1 that is measured on the fabricated paper-making fiber web, according to the formula E pp= k.E s, where E ppand E sstand for the drying energy produced by the first and second drying section respectively, and k stands for a factor that is experimentally determined for every type of paper-making fiber web. The impact flow drying of the drying energy is regulated by the regulation of the gas flow of the burner that produces the heating energy for the speed of rotation of the blower, which transfers the hot gas flow produced by the burner to the paper-making fiber web. The drying energy produced by the drying cylinder (20) in the first drying section is recalculated through regulation of the pressure of the steam to be supplied to the drying cylinders. The difference between the specified moisture content and the measured moisture content is used as the target change in moisture content. The ratio of the drying energy of the drying sections is regulated based on the waviness coefficient. The moisture content of the paper-making fiber web is measured between the first and the second drying sections, and the total drying energy in the second drying section is determined. The specified moisture content behind the first drying section is determined based on the total energy.