Improving the energy efficiency in the fresh water system at Skärblacka paper mill

The purpose of this master thesis was to study the water system for mechanically cleaned water at Skärblacka mill, in order to find and evaluate possibilities of using energy more efficiently. The thesis also includes an evaluation of the software tool “Pumpanalys” Skärblacka mill produces pulp and paper. The large amount of water required is cleaned mechanically through filters and called mechanically cleaned water (MR0). The MR0 water is pumped out to the factory by four crude water pumps. During normal conditions there are only three pumps in use. With regard to the water flow only two pumps would be sufficient during a large part of the year. But because of the head loss in the water system, a third pump has to be used to keep the pressure at the right level. The result of the investigation showed that 514 000 kWh/year can be saved with a new strategy for operating the crude water pumps. The new strategy implies that only two pumps should be in operation, during November to April when the water consumption is under 4000 m3/h. To facilitate for the new strategy some of the weak links, like the air compressor and an evaporation plant, number 3, need to be reinforced. A new pipe for cooling water to the air compressors should be installed and evaporation plant, number 3 needs to be complemented with a reinforcement pump. To optimize the operation strategy the crude water pumps need to be equipped with a long-distance control system. The evaluation of the computer program “Pumpanalys” showed that the program was not suitable to use in this thesis work. But by making a different choice of system to investigate, the program could be used at Skärblacka mill