Experimental equipment for simulation of press nip in tissue paper machine : Prestudy and concept generation

Sammanfattning: During manufacturing of tissue paper, large amounts of energy could be saved with an optimized press nip. In the press nip, water is pressed out of the paper and depending on both machine and paper parameters, the dewatering effect will vary. The dewatering process is however, a complex process which is not fully understood. With the facility to simulate different tissue machine concepts in a lab-testing machine, theoretical models of the dewatering process could be tested and evaluated. Karlstad university has started a three-year project with the purpose of building a lab-test equipment for simulation of pressing of paper, and one of their partners during this project is the company Valmet AB. This master thesis was a part of this three-year project and was carried out in collaboration with Valmet AB. The aim of the master thesis was to determine important parameters affecting the pressing process and the requirements to be considered during the design of the lab-test equipment. The goal was also to develop some concrete concept proposals. During the literature study it was found that the most important parameters of the equipment affecting the result were nip pressure, duration time and process temperature. Paper parameters with the biggest effect on the result were compressibility resistance, flow resistance, ingoing moisture and temperature stability. After discussion with the engineers at Valmet AB, customer requirements of the equipment were determined and these, in combination with the information gathered from the literature study, were used in order to determine the product requirements of the equipment. The most important product requirements turned out to be load capacity, changeable load, process time, distance between upper and lower plate and incorporation of load cells. Several different concept proposals were developed and four of them where evaluated further. The biggest challenge in designing a lab-test equipment for simulation of pressing of paper is the short duration time in combination with high loads, and therefore, all concepts were evaluated according to this as a first step. Plenty of work still needs to be done before any of the generated concepts are finished, but three of them, Three weight, Profile and Electromagnet are seen as potential solutions.