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  • 1.
    Johansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Efficient energy use in different applications2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 2. Johansson, Lars
    The open absorption system: energy savings in different applications2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The open absorption system is a technique that makes it possible to recover energy in different processes using moist air. In most applications the latent heat in moist air is difficult to recover because of the low temperature. Processes using outdoor air to carry away moisture therefore have high energy demands. The open absorption system makes it possible to recover the latent heat and therefore decrease the outdoor air flow and the total energy demand. Two different pilot plants with an open absorption system have been realized in the northern part of Sweden. One is located at a sawmill where four timber dryers and one bio-fuel dryer have been operating. The other one is a pilot plant in a public swimming pool. In this thesis these pilot plants are described in detail and the energy savings when using the open absorption system are evaluated. The specific heat demand for a conventional drying system at the sawmill was about 5970 kJ/kg of evaporated water. When the open absorption system was installed the heat demand was reduced to approximately 1400 kJ/kg of evaporated water. At the same time, an additional 360 kJ/kg of electricity has to be supplied. 45 000 m3 per year of dried bio-fuel has been sold on the market as a result of the decreased heat demand in the wood dryers at the sawmill. Compared to other drying techniques the investment cost is high due to large airflows and therefore large apparatus. The main part of the investment cost, i.e. about 70% originate from the bio fuel dryer and the absorbers. In order to decrease the initial cost a parameter study has been made to investigate the possibilities to reduce the airflow of the drying process, i.e. bio fuel dryer and absorber. Parameters studied were, drying temperature, salt concentration and cooling of the airflow during the absorption process. The results show that it is possible to decrease the airflow by 31% when using a higher drying temperature. Higher salt concentration decreases the airflow by approximately 32% and cooling during absorption makes it possible to decrease the airflow by 50%. In order to minimize the airflow the three parameters were combined. In this case it is possible to decrease the airflow by approximately 60%. The energy demand for the conventional ventilation technique in indoor swimming pools has also been compared to two different heat recovery techniques, the mechanical heat pump and the open absorption system. The mechanical heat pump is the most widely used technique in Sweden today. The open absorption system is a new technique in this application. Calculations have been carried out on an hourly basis for the different techniques. Measurements from an absorption system pilot plant installed in an indoor swimming pool in the northern part of Sweden have been used in the calculations. The results show that with the mechanical heat pump, the electrical input increases with 63 MWh/year and with the open absorption system 57 MWh/year. However, both a mechanical heat pump and an open absorption system decrease the annual energy demand from 611 MWh to 528 and 484 MWh respectively, which corresponds to a decrease of approximately 14 and 20% respectively. The electricity input will increase when using the heat recovery techniques. Changing the climate in the facility has also been investigated. An increased temperature decreases the energy demand when using the conventional ventilation technique. However, when the mechanical heat pump and the open absorption system is used the energy demand is increased when the temperature is increased. In order to make the open absorption technique competitive the thesis shows that there is need for designing optimised systems that can be produced in large numbers, all in order to decrease the production costs and lower necessary investment. Another potential advantage with this system is that it does not require electricity as the driving energy. It seems reasonable to conclude however that the price difference between electricity and fuels must be very large before a new system like open absorption technology will be able to penetrate a market dominated by an established technology, like the mechanical heat pump.It appears that the most interesting market for the open absorption technology would be larger installations at industrial plants. If the reductions of the investment estimated in paper B can be realised and if fuel prices increase, the open absorption process would be more competitive with conventional drying technologies. For large installations, mass production is not essential for achieving competitive manufacturing costs and the risks taken by the companies that decide to introduce the system on the market would therefore not be so large.

  • 3. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    An open absorption system installed at a sawmill: Description of pilot plant used for timber and bio-fuel drying2000In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 25, no 11, p. 1067-1079Article in journal (Refereed)
    Abstract [en]

    This work describes a pilot plant and its different parts in a system used for bio-fuel drying and timber drying with an open absorption process. This technique has not been used previously in Sweden in this application. The open absorption system has been installed on four timber dryers and one bio-fuel dryer at a sawmill located in the northern part of Sweden. The annual energy demand for the dryers has decreased considerably. The specific heat demand for a conventional drying system is about 5970 kJ/kg of evaporated water. For the open absorption system, the corresponding value is a heat demand of approximately 1400 kJ/kg of evaporated water. At the same time, an additional 360 kJ/kg of electricity has to be supplied. Here, 45,000 m3 per year of dried bio-fuel has been sold on the market as a result of the decreased heat demand in the wood dryers at the sawmill. The plant has been working well and has had a high availability. The pay-off time for the investment will be approximately 3 years for nondiscounted cash-flows

  • 4. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    CFD modeling of the quench in a pressurized entrained flow black liquor gasification reactor2006In: CHISA 2004: 16th International Congress of Chemical and Process Engineering, 22 - 26 August 2004, Prague, Czech Republic, Prague, 2006, p. 11399-11409Conference paper (Refereed)
    Abstract [en]

    Black liquor, a biomass-based fuel formed in the papermaking process has traditionally been burned in recovery boilers to generate steam and electricity and recover the inorganic chemicals. Pressurized black liquor gasification offers an attractive alternative to the recovery boiler that has the potential to add a net electrical power of the order of 1000 MW to the Swedish power grid at full integration. Chemrec AB, one of the leading actors has developed an entrained down flow reactor. A development plant has been designed and is to be taken into operation during 2004, At the laboratory of Energy Technology Centre (ETC) in Pitea, Sweden. The plant will operate at 30 bar (a) and 30 tons/day black liquor will be gasified. The entrained flow reactor consists of two parts. In the gasification reactor black liquor is supplied together with an oxidant. Combustible fuel gases and inorganic smelt is formed. The smelt and fuel gases are transported to the quench cooler in the lower part where it is rapidly cooled by spray nozzles. The smelt is separated from the fuel gases by gravitation. At LTU a CFD model of the quench has been developed using the commercial code FLUENT 6. The simulations were performed in steady state using the segregated solver. A non structured mesh with approximately 48000 cells was used in the study. The results show that the model is predicting the flow pattern, velocity field and temperature field. The separation of smelt from the gas flow shows that droplets larger then 100 μm will be collected in the bottom of the quench but smaller droplets will travel with the gas flow to the quench outlet. Further work is required in order to make the model more complete. Radiation needs to be included as well as important chemical reactions. The model also needs to be validated against measurement data when the development plant is in operation.

  • 5. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Energieffektiv biobränsletorkning med öppen absorptionsprocess: beskrivning av befintligt system samt parameterstudie som underlag till systemförbättringar1999Report (Other academic)
    Abstract [sv]

    Denna rapport beskriver ingående en befintlig torkanläggning vid ett sågverk, Martinsons Trä, beläget i Västerbotten. Anläggningen bygger på en teknik, sk öppet absorptionssystem, vilken ej tidigare i Sverige utnyttjats i torksammanhang.För att belysa möjligheterna att vidareutveckla tekniken har en parameterstudie genomförts. Variabler såsom torktemperatur, absorptionslösningens koncentration samt kylning vid absorption har undersökts. Som jämförelse utnyttjas dagens anläggning, ett lågtemperatursystem, (torktemperatur 78°C).Resultaten visar att lufttemperaturen i torksystemet skall vara så hög som möjligt för att minimera erforderlig luftmängd. Det är möjligt att reducera luftflödet med ca 30% vid bibehållen torkkapacitet genom att höja torktemperaturen till 140°C.En kylning av luften vid passage genom absorbatorn minskar även erforderlig luftmängd. För att detta skall vara ett alternativ måste det finnas avsättning för den bortförda värmemängden från luftkretsen. Detta avser såväl temperaturnivå som energimängd. En kylning med 5°C jämfört med dagens anläggning minskar luftflödet med ca 50% vid bibehållen avfuktnings-kapacitet.Hög saltkoncentration bör eftersträvas för att minimera biobränsletork och absorbator. En begränsade faktor utgör kristallisationsproblem för absorptionslösningen. En saltkoncentration på 85 viktsprocent för lösningen i absorbatorn reducerar luftflödet med ungefär 30% av referensfallet.Studien visar att det är möjligt att reducera den befintliga anläggningens

  • 6. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Energy efficient bio fuel drying with an open absorption system1999In: Applied Modelling and Simulation, International conference, 1999Conference paper (Refereed)
  • 7. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Energy efficient bio fuel drying with an open absorption system: parameter study in order to reduce investment costs2000In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 67, no 3, p. 231-244Article in journal (Refereed)
    Abstract [en]

    A pilot plant using the open absorption system for drying of timber and bio fuel has been realized at a sawmill located in the northern part of Sweden. The technique decreases the energy demand for the dryers considerably and the system has an availability of about 8000 h per year. Compared with other drying techniques, the investment cost is high due to large airflow and therefore large apparatus. The main part of the investment cost, i.e. about 70% originates from the bio fuel dryer and the absorbers. In order to decrease the initial cost a parameter study has been made to investigate the possibilities to reduce the airflow of the drying process, i.e. bio fuel dryer and absorber. Parameters studied are drying temperature, salt concentration and cooling of the airflow during the absorption process. Measured values from the pilot plant have been used as a reference case. The results show that it is possible to decreases the airflow by 31% when using a higher drying temperature. Higher salt concentration decreases the airflow by approximately 32% and cooling during absorption makes it possible to decrease the airflow by 50%. In order to minimize the airflow, the three parameters were combined. In this case it is possible to decrease the airflow by approximately 60%. The electrical input for the plant is also high due to large air and solution flows. By decreasing the airflow, the required electrical input will also decrease since the fan power is proportional to the volume airflow. The results clearly show that it is possible to reduce the airflow and therefore the investment costs compared with the pilot plant.

  • 8. Johansson, Lars
    et al.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Energy savings in indoor swimming-pools: comparison between different heat-recovery systems2001In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 70, no 4, p. 281-303Article in journal (Refereed)
    Abstract [en]

    In indoor swimming-pool facilities, the energy demand is large due to ventilation losses with the exhaust air. Since water is evaporated from the pool surface, the exhaust air has a high water content and specific enthalpy. Because of the low temperature, the heat from the evaporation is difficult to recover. In this paper, the energy demand for the conventional ventilation technique in indoor swimming pools is compared to two different heat-recovery techniques, the mechanical heat pump and the open absorption system. The mechanical heat-pump is the most widely used technique in Sweden today. The open absorption system is a new technique in this application. Calculations have been carried out on an hourly basis for the different techniques. Measurements from an absorption system pilot-plant installed in an indoor swimming pool in the northern part of Sweden have been used in the calculations. The results show that with the mechanical heat pump, the electrical input increases by 63 MWh/year and with the open absorption system 57 MWh/year. However, a mechanical heat-pump and an open absorption system decrease, the annual energy demand from 611 to 528 and 484 MWh respectively, which correspond to decreases of approximately 14 and 20% respectively. The electricity input will increase when using heat-recovery techniques. Changing the climate in the facility has also been investigated. An increased temperature decreases the energy demand when using the conventional ventilation technique. However, when either the mechanical heat-pump or the open absorption system is used, the energy demand is increased when the temperature is increased. Therefore increasing the temperature in the facility when using the conventional technique should be considered the first measure to reduce the energy demand.

  • 9. Westerlund, Lars
    et al.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Johansson, Lars
    Theoretical investigation of the heat demand for public baths1996In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 21, no 7-8, p. 731-737Article in journal (Refereed)
    Abstract [en]

    Public baths normally use outdoor air to remove moisture from the building. This procedure results in large heating demands. A theoretical hour-based method for estimation of the heating demand has been developed. The method allows for dynamic behaviour with correct time periods for each mass-transfer level. Results of predictions with this method have been compared with yearly estimates of the heating demand based on actual measurements in a public bath. The difference is 3%. A parametric study shows that the air temperature and relative humidity in the building strongly influence the heating demand. Comparisons with other prediction methods based on use of the duration curve or mean annual outdoor temperature show differences less than 5% from results obtained with the hour-based method. The simpler approaches (use of a duration curve or mean value) fail when minimum outdoor airflow must be considered, as will be the case, for instance, when comparing different energy-saving systems or design of components for the climate system.

  • 10.
    Westerlund, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Johansson, Lars
    Modelling gas cooling in black liquor gasification2011In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 31, no 16, p. 3176-3181Article in journal (Refereed)
    Abstract [en]

    Pressurized Entrained Flow High Temperature Black Liquor Gasification (PEHT-BLG) is a new technology not yet commercialized. The technology has the potential to improve the efficiency of energy and chemical recovery in the pulping industry. It also enables new processes, i.e. production of renewable motor-fuels from the syngas. The technology is not yet fully developed and interest in computer models for scale-up and optimization of the process in combination with experiments is favourable in the development process. A demonstration plant has been in operation since late 2005, in Pitea, Sweden. At Lulea University of Technology (LTU), a CFD model of a vertical tube in the counter current condenser has been developed using the commercial code FLUENT 6. The geometry is consistent with the demonstration plant and input data of the design has been used as boundary conditions for the model. The objective is to create a CFD model that can be used as a designing tool for the technology developer in future scale-up and for commercialized units. The model predicts the condensation process very well and shows that the major part of the condensation takes place in the first quarter of the tube under the given conditions. The heat transfer through the tube wall has been modeled based on results from the literature. The results show the importance of accurate heat transfer coefficients. Compared to designing data, the heat transfer through the wall and the condensate rate show good agreement. However, these results need to be validated against experimental data for different conditions

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