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- Boman, Christoffer, et al.
(författare)
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Development of innovative small(micro)-scale biomass-based CHP technologies
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To enhance the overall efficiency of the use of biomass in the energy sector in Europe, the large electricity production potential from small-scale biomass heating systems should be utilised. So far, no technologically sound (in terms of efficiency and reliability) and economically affordable micro- and small-scale biomass CHP technologies are, however, available. Therefore, the present ERA-NET project (MiniBioCHP) aimed at the further development and test of new CHP technologies based on small-scale biomass combustion in the electric capacity range between some W and 100 kW. Within the project, an international consortium consisting of 12 partners from 4 countries, including university institutions, institutes and industry (both engineering and manufacturing), collaborated closely to perform high level R&D on three promising micro/small-scale biomass based CHP technologies which are covering a broad range of applications in the residential heating sector. The Austrian engineering company BIOS, coordinated the international project. The project was based on earlier basic research and development work related to these promising new technologies and aimed at the achievement of a technological level which allows a first (commercial) demonstration after the end of the project. The three CHP concepts included in the MiniBioCHP project were;1. Pellet stoves with a thermoelectric generator (TEG)2. Small-scale biomass boilers (10-30 kWth) with a micro-ORC process3. High temperature heat exchanger (HT-HE) for an externally fired gas turbine (EFGT)The Swedish part of the project was focused on the development of the concept of biomass based EFGT with dedicated R&D activities related to the development of the HT-HE system. The Swedish project consisted of the research partners Umeå University (project leader), Luleå University of Technology, Chalmers University of Technology and RISE Research Institutes of Sweden, together with the industrial partners Enertech AB/Osby Parca and Ecergy. The expertise of the Swedish partners regarding ash related problems, grate boiler combustion and modelling, deposit formation and high temperature corrosion, were combined with the know-how of a Polish partner regarding HT-HE design, construction, testing and optimisation.The HT-HE is the most crucial component in EFGT processes significantly influencing the investment costs, availabilities as well as the efficiencies that can be achieved. With a thermal capacity from several hundred kW up to 2-3 MWth) the CHP technology based on a biomass boiler and an EFGT is suitable for district heating systems, or process heat consumers. The electricity produced by the gas turbine (up to some 100 kWel) can be used to cover the own electricity consumption of a company and/or fed into the grid. Even though the concept of biomass based EFGT has been an interesting alternative for small-scale CHP production for some decades, and R&D activities have been undertaken, tackling both economic and technical aspects, only a few pilot-plants have been in operation and no initiative has so far reached the level of commercial implementation. Thus, the concept of EFGT fed with biomass is still considered to be in a rather early development stage and the main technical challenges are related to alkali deposit induced corrosion and thermal stress of the HT-HE material, turbine design/operation and system integration.Within the present project, a HT-HE prototype aimed for an EFGT system was therefore designed, constructed and successfully tested at flue gas temperatures up to 900°C. Thus, appropriate guidelines for a compact design of the HT-HE and recommendations have been worked out to minimize thermal stresses as well as ash related problems regarding ash deposit formation and high temperature corrosion in a biomass boiler system. Furthermore, different concepts for the overall biomass based EFGT system have been worked out and evaluated. The outcome of the project will hopefully be used in the further development work and form the basis for a first testing and demonstration plant within the coming years.
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| 5. |
- Kivumbi, Bernard, et al.
(författare)
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Techno-economic assessment of municipal solid waste gasification for electricity generation: a case study of Kampala City, Uganda
- 2015
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Ingår i: CIGR Journal. - : Int. Comm. of Agricultural and Biosystems Engineering. - 1682-1130. ; 17:4, s. 141-155
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Tidskriftsartikel (refereegranskat)abstract
- This study was aimed at assessing the techno-economic potential of municipal solid waste (MSW) generated in Kampala City for electricity production through gasification. The quantity, characteristics and gasification parameters were determined. In addition, the gasifier- engine system components were sized, and an economic analysis was conducted to obtain the net present value (NPV) and the payback period. This study found that 523 t/d of MSW is collected in Kampala City. The biomass component of MSW was found to be 459.5 t/d with moisture content of 71.09% on as-received basis. The physical characteristics of the gasified biomass included 11.8% moisture content, 88.2% total solids, 25.9% ash content and 57.7 kg/m3 bulk density. The resulting normalized producer gas constituted 11.64% H2, 13.70% CO, 16.09% CO2, 54.12% N2, 4.45% CH4 and lower heating value (LHV) of 4.75 MJ/Nm3. The design fuel flow rate of 0.23 kg/s, specific gasification rate (SGR) of 5089.29 kg h-1 m-2 and specific energy demand of 42.75 GJ m-2 h-1 were obtained. This yields a net electrical power output of 425.17 kW with an overall efficiency of 15.6%. The net annual electricity generation from a single gasifier-engine system was found to be 2.97 GWh/a. The economic analysis for this system worth $887 333 of investment cost yielded a payback period of 6.57 years while the NPV at 6% interest rate was found to be nine years with a value of $316 47.
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| 6. |
- Menya, Emmanuel, 1982-, et al.
(författare)
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Assessment of pollution levels resulting from biomass gasification
- 2014
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 2:3, s. 1228-1235
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Tidskriftsartikel (refereegranskat)abstract
- In biomass gasification process the producer gas generated can be cleaned by water scrubbing. Some of the organic compounds generated are entrained together with other flue gas dust particles in to the cooling stream. The treatment/disposal of this waste stream remains a challenge because some of the compounds are toxic to humans and the environment. The objective of this study was to assess pollution levels resulting from organic constituents of flue gas filtration in a downdraft gasifier. The study involved assessment of the concentration of polycyclic aromatic hydrocarbons (PAHs) in the liquid effluence. The impacts on human health and environment are also discussed and recommendations on measures to minimize the pollution levels are provided. A downdraft gasifier fed with maize cobs was used and condensates were collected by cooling of producer gas. Samples were preserved in a cooler at about 2 degrees C for 24 h before analysis using a capillary gas chromatographer connected to a mass spectrometer (GCMS). The results were that concentrations of: naphthalene was 204.3 mg/m, benzene 17.92 mg/m(3), toluene 182.94 mg/m(3), ethylbenzene 202.43 mg/m(3), 1,2-dimethyl benzene 359.28 mg/m(3) and 1,3+1,4-dimethyl benzene 1016.18 mg/m(3). It was observed that the concentrations of naphthalene and xylene were considerably higher than the recommended permissible exposure limits (PELs) on both human health and the environment. On the other hand, the concentrations of benzene, toluene, and ethylbenzene were below the PEL. Generally this study indicated that the liquid effluent meets regulatory standards, but it would be interesting to carryout tests with different biomass fuel types which this study recommends.
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- Olwa, Joseph
(författare)
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Investigation of thermal biomass gasification for sustainable small scale rural electricity generation in Uganda
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the increasing need for renewable energy technologies in the world, biomass fuel transformation technology is growing towards meeting that need, among others. Challenges remain certain and new innovations are being tested in bid to overcome them with the application of biomass as energy source. This report presents some studies carried out into understanding the potential and challenges associated with utilization of biomass fuel, especially for technologies that are appropriate for rural applications. Utilization of biomass gasification technologies is in the focus of this study. The great potential biomass fuel provide to Uganda for possible energy production in small scale application is presented. This study was carried out to understand the possibility of using biomass as fuel in electricity power generation in Uganda. It takes into consideration the use of biomass gasification technology in energy production. Challenges related to the application of biomass fuels are discussed, mostly with tar and alkali metal compounds in the gas stream. Suggested methods to combat some of the challenges with biomass fuels are pointed out in this study. Application of externally fired gas turbine (EFGT) system is a particular approach discussed and its technical performance analyzed. The analysis revealed that efficiency of the EFGT system is greatly dependent on the heat exchanger effectiveness and on turbine inlet temperature. Optimum performance can be realized with air compression ratio of 3.4. It is also noted that fouling and deposition in the heat exchanger can affect its performance. A related study carried out was on the retention of alkali metals in an updraft gasifier. The gasifier was chosen for possible integration with the EFGT system. Finding was that about 99% of the alkali metals are retained in the gasifier. It is anticipated that this would reduce on the deposition in the heat exchanger, reducing on maintenance time. A need is identified to determine the level of deposition mentioned. A simple thermodynamic modeling of the alkali metals condensation reaction on a high temperature heat exchanger surface was conducted. The results showed that with appropriate quantity of S in the raw fuel, alkali metals bounding with Cl are greatly reduced. Cl is passed out as gaseous HCl, leaving deposition of none corrosive sulphates. Recommendation is made to study this phenomenon in an experimental setting. Biomass gasification technology integration with an internal combustion (IC) engine is also studied. Here requirements for the producer gas quality have been discussed. Some tests carried out with wood pellets and wood cylinders compared the yield of tar from the two physically different fuels. Wood pellets were found to yield more tar than wood cylinders. Economic analysis of biomass gasifier integrated with an IC engine running a generator of 100 kWe was carried out. Comparison with a diesel electricity generator of similar capacity was made for a scenario in Uganda over a project life of 20 years. Different Plant Capacity Factors (PCF) and fuel costs including subsidies were considered. The analysis showed that over long period of time biomass power plant was more beneficial than the diesel power plant at PCF over 40%. This is more pronounced with unsubsidized diesel fuel.
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| 8. |
- Olwa, Joseph, et al.
(författare)
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Potassium retention in updraft gasification of wood
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 27:11, s. 6718-6724
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Tidskriftsartikel (refereegranskat)abstract
- The release of compounds of K with producer gas during biomass gasification is known to play significant roles in fouling and high-temperature corrosion in boilers and high-temperature heat exchangers as well as blades in gas turbines that use producer gas as fuel. These phenomena are a major setback in the application of biomass fuel in combination with advanced process conditions. Updraft gasification provides gas filtering by the fuel bed with a gas cooling effect, conditions anticipated to create an avenue for K retention in the gasifier. The objective of this study was to determine the K retention potential of such gasifiers during wood gasification. Samples for the determination of the fate of K compounds included in the feedstock were collected from the generated producer gas using Teflon filters and gas wash bottles and also from wall deposits and ash residues. Analyses of samples were carried out using inductively coupled plasma-atomic emission spectrometry/mass spectrometry and X-ray diffraction methods. The finding was that about 99% of K was retained in the gasifier. K was found in the ash samples as a crystalline phase of K 2Ca(CO3)2(s) (fairchildite). A possible reaction mechanism leading to the formation of K2Ca(CO 3)2 is discussed in the paper. The 1% K understood as released, equivalent to 1200 ppbw content of K entrained in the producer gas stream, exceeds a known limit for application of the gas in conventional gas turbines. This would suggest application of the gas in an externally fired gas turbine system, where some limited K and other depositions in the heat exchanger can be relatively easy to handle.
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