| 1. |
- Azis, Muhammad Mufti, 1983, et al.
(författare)
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The Effect of Bituminous and Lignite Ash on the Performance of Ilmenite as Oxygen Carrier in Chemical‐Looping Combustion
- 2013
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Ingår i: Chemical Engineering and Technology. - : Wiley. - 0930-7516 .- 1521-4125. ; 36:9, s. 1460-1468
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Tidskriftsartikel (refereegranskat)abstract
- The influence of ash in chemical-looping combustion (CLC) has been studied in a lab-scale fluidized bed reactor. The oxygen carrier, ilmenite, was investigated with German lignite coal, Chinese bituminous coal, Mexican pet coke, wood char, and methane. Lignite ash and ash from gasified Chinese bituminous coal were compared in this study. Up to 50 wt % and 33.3 wt % loadings of ash from the combustion of lignite and ash from the gasification of coal were added. The gas conversion was clearly affected by the addition of ash, and very similar results were seen both for methane conversion and for CO conversion in the solid fuel tests. Thus, both ashes showed initial decrease in gas conversion with the addition of some ash due to the presence of inert/deactivating material in the ashes. At higher ash loading, a beneficial effect of ash could be seen. Furthermore, no negative effect of ash addition on the fluidizability of the bed material could be seen.
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| 2. |
- Balksten, Kristin, et al.
(författare)
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The influence of particle size and structure in hydrated lime on the properties of the lime putty and lime mortar
- 2010
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Ingår i: International journal of architectural heritage. - Philadelphia : Taylor & Francis. - 1558-3058 .- 1558-3066. ; 4:2, s. 86-101
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this work, scanning electron microscopy (SEM) analysis of lime slaked in different ways and analysis of thin section of lime putty and mortar specimens by light microscopy was combined with practical tests and field studies to evaluate the impact of the slaking technique on the properties of the lime putty as well as the structure of the fresh and carbonated mortar. The lime slaking methods studied were wet slaking and earth slaking, giving lime putties with very different consistency and workability. The aim of this work was to use microscopy techniques to explain these differences in properties and to investigate if it is possible to use these analytical methods to recognize the lime-slaking technique used in a historical lime mortar. The results obtained by SEM show significant differences in structure between the lime putties. The earth-slaked lime consists of relatively large particles that are packed in a porous system compared with the wet-slaked lime with very small particles closely packed in a dense structure. After storing, the wet-slaked lime gives a putty that has a dense and clearly defined stratified structure, whereas the earth-slaked lime is porous and has no stratification.
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| 3. |
- Elled, Anna-Lena, 1975, et al.
(författare)
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Composition of agglomerates in fluidized bed reactors for thermochemical conversion of biomass and waste fuels Experimental data in comparison with predictions by a thermodynamic equilibrium model
- 2013
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 111, s. 696-708
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Tidskriftsartikel (refereegranskat)abstract
- Controlled combustion tests of biomass were performed in the 12 MWth circulating fluidized bed (CFB) boiler located on the campus of Chalmers University of Technology. The aim was twofold: to investigate the composition of agglomerated material and also to highlight the reasons for sintering and agglomeration during thermochemical conversion of biomass and wastes in fluidized bed reactors using quartz sand as bed material. Bed ash from three different tests regarding fuel or fuel mixtures (wood with straw, bark, and bark with refused derived fuel) was analysed to determine the ash elements using: (a) inductive coupled plasma (ICP) equipped with optical emission spectroscopy (OES) and (b) scanning electron microscopy equipped with an electron dispersive X-ray spectrometer (SEM-EDX). Chemical equilibrium calculations were also performed to support the interpretation of the experimental findings. It was found that the combination of (i) well controlled full-scale tests in a fluidized bed boiler, (ii) the use of line-scans by the EDX spectrometer of the SEM on bed samples and (iii) thermodynamic equilibrium modelling is a powerful tool in understanding the phenomena of bed agglomeration using quartz sand.
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| 4. |
- Karlfeldt Fedje, Karin, 1977, et al.
(författare)
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Element associations in ash from waste combustion in fluidized bed
- 2010
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 30:7, s. 1273-1279
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Tidskriftsartikel (refereegranskat)abstract
- The incineration of MSW in fluidized beds is a commonly applied waste management practice. The composition of the ashes produced in a fluidized bed boiler has important environmental implications as potentially toxic trace elements may be associated with ash particles and it is therefore essential to determine the mechanisms controlling the association of trace elements to ash particles, including the role of major element composition. The research presented here uses micro-analytical techniques to study the distribution of major and trace elements and determine the importance of affinity-based binding mechanisms in separate cyclone ash particles from MSW combustion. Particle size and the occurrence of Ca and Fe were found to be important factors for the binding of trace elements to ash particles, but the binding largely depends on random associations based on the presence of a particle when trace elements condensate in the flue gas. (C) 2009 Elsevier Ltd. All rights reserved.
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| 5. |
- Karlfeldt Fedje, Karin, 1977, et al.
(författare)
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Initial studies of the recovery of Cu from MSWI fly ash leachates using solvent extraction
- 2012
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Ingår i: Waste Management and Research. - 1096-3669 .- 0734-242X. ; 30:10, s. 1072-1080
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Tidskriftsartikel (refereegranskat)abstract
- Large volumes of ash from combustion of municipal solid waste are produced and most of it is landfilled. As this type of ash contains significant amounts of metal compounds the landfilling strategy is not optimal when considered from a resource conservation perspective. A better situation would be created if metals were recovered from the ash. In the present study leaching and solvent extraction was applied for release and separation of copper from municipal solid waste combustion fly ashes. The results showed promising results with Cu yields of 50-95%. The yield was heavily dependent on the efficiency of the initial leaching of Cu from the ash.
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| 6. |
- Karlfeldt Fedje, Karin, 1977, et al.
(författare)
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Removal of hazardous metals from MSW fly ash-An evaluation of ash leaching methods
- 2010
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 1873-3336 .- 0304-3894. ; 173:1-3, s. 310-317
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Tidskriftsartikel (refereegranskat)abstract
- Incineration is a commonly applied management method for municipal solid waste (MSW). However, significant amounts of potentially hazardous metal species are present in the resulting ash, and these may be leached into the environment. A common idea for cleaning the ash is to use enhanced leaching with strong mineral acids. However, due to the alkalinity of the ash, large amounts of acid are needed and this is a drawback. Therefore, this work was undertaken in order to investigate some alternative leaching media (EDTA, ammonium nitrate, ammonium chloride and a number of organic acids) and to compare them with the usual mineral acids and water. All leaching methods gave a significant increase in ash specific surface area due to removal of soluble bulk (matrix) compounds, such as CaCO3 and alkali metal chlorides. The use of mineral acids and EDTA mobilised many elements, especially Cu, Zn and Pb, whereas the organic acids generally were not very effective as leaching agents for metals. Leaching using NH4NO3 was especially effective for the release of Cu. The results show that washing of MSW filter ash with alternative leaching agents is a possible way to remove hazardous metals from MSW fly ash.
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| 7. |
- Karlsson, Sten, 1951, et al.
(författare)
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What is required for the viability of metal recovery from municipal solid-waste incineration fly ash? - Design and assessment of a process plant for copper extraction
- 2010
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Ingår i: Proceedings of LINNAEUS ECOTECH'10 Nov 22-24, 2010, Kalmar, Sweden. ; , s. 463-474
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The incineration of municipal solid waste produces large amounts of fly ashes, today in Sweden around 200 000 tons/yr. The ashes normally contain a considerable amount of valuable and hazardous metals. To fulfil the environmental regulations, most of these fly ashes can be deposited only in specific sites. This handling costs, requires energy and leads to emissions in the transportation to the deposit site. This work, taking departure in laboratory experiments for crucial steps, discusses possible chemical processing schemes and from this develops an overall design of a plant for the extraction and production of copper from the fly ash generated in a fluidized bed waste incineration plant. It also addresses the economic viability and environmental impact of the suggested processing in comparison to current handling, which involves transport to and disposal of the fly ash in Norway. The proposed process involves a leaching step, a solvent extraction process, a stripping step where the copper is transferred to an aqueous phase and finally electrolysis. By quantitative modelling and cost estimates of the processing steps of the proposed plant we identify the most important factors for the economics and environmental impact of the plant. In addition, we quantify the necessary recycling rates of the different process chemicals for achieving profitability. We conclude that a crucial factor is the recycling rate of the used organic solvent. Important parameters are also the handling costs and transportation needs of the rest products. For instance, a major benefit of the process is if treated fly ash can be reclassified such that it is allowed to be disposed into the own close-up hazardous waste landfill thus lowering the costs and environmental impacts. An extension of the process to include also the extraction of metals other than copper, for instance zinc, should be an interesting further development to consider.
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| 8. |
- Kassman, Håkan, 1962, et al.
(författare)
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Two Strategies to Reduce Gaseous KCl and Chlorine in Deposits during Biomass Combustion - Injection of Ammonium Sulphate and Co-Combustion with Peat
- 2013
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 105, s. 170-180
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Tidskriftsartikel (refereegranskat)abstract
- Combustion of a biomass with an enhanced content of chlorine can result in operational problems including deposit formation and superheater corrosion. The strategies applied to reduce such problems include co-combustion and the use of additives. In this work a mixture of wood pellets and straw pellets was fired in a circulating fluidised bed boiler. Two strategies were applied to decrease the risk of superheater corrosion by reducing gaseous KCl and content of chlorine in deposits: sulphation of KCl by injection of ammonium sulphate and co-combustion with peat. During co-combustion of biomass with peat both sulphation of KCl and capture of released potassium in ash components can be of importance. The results were evaluated by means of IACM (on-line measurements of gaseous KCl), deposit probe measurements (chemical composition in collected deposits, initial corrosion) and ash analysis (chemical composition in fly ashes). The best overall performance was achieved with ammonium sulphate, which significantly reduced KCl. Meanwhile almost no chlorine was found in the deposits. Only a minor reduction of gaseous KCl was obtained during co-combustion although the chlorine content in the deposits was greatly reduced. The resistance to initial corrosion was improved during both injection of ammonium sulphate and co-combustion with peat.
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| 9. |
- Knutsson, Pavleta, 1980, et al.
(författare)
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Effect of bed materials mixing on the observed bed sintering
- 2014
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Ingår i: 11th International Conference on Fluidized Bed Technology, CFB 2014; Beijing; China; 14 May 2014 through 17 May 2014. ; , s. 655-660
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Konferensbidrag (refereegranskat)abstract
- The most widely used bed material in the existing fluidized bed systems is silica sand. Upon burning fuels with high alkali content, such as biomass, in a bed of silica sand, alkali silicates are formed as molten glassy phase that easily stick and form agglomerates, defluidization of the reactor and unplanned operational stops. Several materials have been tested as alternative bed materials, often containing aluminate minerals. Due to the relatively high cost of such bed materials the most dominant practice is still the use of silica sand even with high alkali fuels and the bed sintering is controlled by continuous replacement of the bed material. The present study investigates the possibility of mixing bed materials and thereby optimizing the existing process by combining the low cost of silica sand with the sintering inhibiting properties of bauxite. Silica sand and bauxite were mixed in different ratios in a series of tests and were exposed to alkali compounds in a 12 MW boiler as well as in simplified experiments in a lab-scale furnace. The performance of the mixture of bed materials was then evaluated based on the tendency to chemically interact with the alkali compounds, the formation of agglomerates and the effect on the overall performance of the reactor. Thermodynamic predictions of the expected compounds at the given conditions were also used to compare with the experimentally obtained results. It was observed that mixing bed materials led to change in the observed mechanism of agglomeration and is beneficial for the fluidization. Furthermore, when calcium was present the amount of the formed alkali silicates and thereby the amount of agglomerates was decreased. It could be therewith shown that a significant improvement can be reached with existing bed materials.
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| 10. |
- Knutsson, Pavleta, 1980, et al.
(författare)
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Use of natural ores and waste materials as oxygen carriers for chemical-looping combustion
- 2014
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Ingår i: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM. - 1314-2704. ; 1:4, s. 597-604
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Konferensbidrag (refereegranskat)abstract
- The increasing CO2 levels in the atmosphere require an immediate action in order to avoid irreversible climate changes. Chemical-looping combustion (CLC) is an innovative technology that provides an energy and cost-effective separation of CO2 for further capture and storage and thereby helps to mitigate the anthropogenic CO2 emissions from thermochemical fuel conversion. The solid oxygen carrier is a core component of every CLC system and the choice of the oxygen carrier depends on the fuel and operation conditions. Low-cost oxygen carriers tend to be more suitable for the process as the lifetime of the oxygen carrier material is often limited by side reactions with fuel ash, or by carryover losses in the ash separation. A series of natural ores and waste products have been investigated as potential oxygen cares, such as Mn-ore, Fe-ore, ilmenite. The materials are chosen based on their content of oxides that have proven to have promising oxygen transporting capabilities. The results lead to summary of criterion for further screening of the existing materials for more reactive and better suited candidates for the process.
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