Efficient energy use in different applications
Abstract: There is a steadily growing awareness for environmental issues caused by the increased energy use, mainly in the industrial world. The use of fossil fuels has reached the point where it can not be looked at as an endless source, the resources are decreasing at a pace where alternative energy sources will be a necessity for this and future generations. Global warming, due to increased concentration of greenhouse gases in the atmosphere, has become one of the most important issues on the political agenda at all levels. A widespread opinion is that energy conservation technologies are needed and a shift towards renewable energy sources is required to attain a sustainable development of our society and a progress in the developing countries. This thesis is focusing on two different energy conservation technologies in different applications. The open absorption system, a modification of an absorption heat pump is a promising technique in moist air processes, recovering the latent heat in the air and decreasing the total heat demand. The technology has been tested in two full scale pilot plants at a sawmill operating four timber dryers and another unit installed at an indoor swimming pool. The technique has had positive outcomes in both operational energy conservation respects. It has been shown that the energy demand was decreased considerably in both applications. The investment cost has proved to be relatively high, but optimization of operational parameters shows a potential to decrease the initial investment and make the technology more competitive. Pressurized entrained-flow high temperature black liquor gasification (PEHT- BLG), developed by Chemrec AB, is another novel technique presented in this thesis. Black liquor is an important by-product in the papermaking process. Chemicals and energy is recovered in the conventional recovery boiler where superheated steam is produced to generate electricity and process heat. The cooking chemicals are recovered from the smelt in the bottom of the boiler in a separate recovery cycle. By introducing PEHT-BLG, a synthesis gas is obtained that can be used to generate electricity or be reformed into alternative automotive fuels. A demonstration plant, constructed by Chemrec AB, has been running periodically since late 2005. The plant is located at the Kappa Smurfit mill in conjunction with the Energy Technology Centre in Piteå, Sweden. In this thesis CFD models of the quench and counter current condenser have been performed and presented. The long term objectives with the CFD models are to create a tool that can be an aid in future scale-ups and for optimisation purposes. Since PEHT-BLG enhances the flexibility of the black liquor recovery cycle it is a promising alternative for future industrial commercialization if the remaining issues can be overcome.
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