An energy balance analysis for current and future production of paper at Mondi Dynäs paper mill : A development project of current and future scenarios for the steam and condensate network with proposals for enhanced utilization of energy

Abstract: Mondi Dynäs is a pulp and paper producer in the north of Sweden close to the town Kramfors. Last year Mondi Dynäs produced 231,404 tons of Kraft paper. In order to increase their production to 300,000 tons of paper per year this study was done in order to investigate how the increased biomass flow would affect the generation of steam along with the steam and condensate balance. This study started with a mapping of the current steam and condensate balance for one winter period January – Mars and one summer period July – September 2015. The resulting balance is used as reference period for the development of the future steam and condensate scenario where Mondi Dynäs will achieve the targeted production of 300,000 tons of paper per year. The future model shows that the future production of paper will give an abundance of biomass since the generation of steam will be more than sufficient. For the winter period the venting of steam over roof could be derived to 11.9 tons per hour and 34.4 tons per hour during the summer period. This can be compared to the current situation where the winter period gave an average steam blow out of 8.7 tons per hour and for the summer period 13.1 tons per hour. To utilize the accumulated energy from these energy streams, three different scenarios was studied. The first scenario were a future installation of a backpressure turbine along with a condensing turbine section. The new turbine would be attached to the highest pressure level at 65.5 bar and have a backpressure exhaust at 20 bar which will give a power of 7.6 MWe. The second scenario included the implementation of a new condensing turbine with the current system design for the steam network and boilers. This turbine would be attached to the 3.5 bar network and give the electricity power of 1.9 MWe. The third scenario included the installation of a new bark dryer. This would give Mondi Dynäs the possibility to sell bark to an external actor on the energy market. From derived figures in the future scenario model it would be possible to sell 108,144 MWh of bark while running the bark boiler. Mondi Dynäs AB is recommended to add a new condensing turbine to their steam network. The new turbine would be able to produce 1.9 MWe and need a cooling water flow of 190 tons of water per hour. Derived figures for the investment shows a NPV of 0.6 MEUR and the IRR value of 31 %