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- Ajdari, Sima, 1985, et al.
(författare)
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Formation and Control of NOx and SOx in Pressurized Oxy-Combustion Systems
- 2015
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Ingår i: The Proceedings of the 40th International Technical Conference on Clean Coal & Fuel Systems, 31 May-4 June 2015, Clearwater, Florida, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation and control of NOx and SOx in pressurized oxy-fuel combustion systems is discussed in the present work. The chemistry of nitrogen and sulfur species under pressurized conditions and the experiences gained from operating atmospheric oxy-fuel combustion pilot plants are reviewed in brief. In a conventional combustion and gas cleaning process, SO2 and NO are the principle NOx and SOx species. However, the oxidation of NO to NO2 and SO2 to SO3 is favored by low temperature and high pressure. In the present paper we will make a first modelling based of the altered oxidation conditions during both high and low temperature conditions in pressurized oxy-combustion. Besides the gas-phase oxidation, the liquid-phase N-S interactions will further enhance the formation of acids in the flue gas condensate. Thus, these low and high temperature processes will be discussed in the present work due to their relevance for the design of the flue gas compression and gas cleaning system in pressurized oxy-combustion.
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| 4. |
- Ajdari, Sima, 1985, et al.
(författare)
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NOx AND SOx CHEMISTRY IN PRESSURIZED FLUE GAS SYSTEMS: IMPORTANCE FOR CHEMICAL LOOPING COMBUSTION
- 2014
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Ingår i: 3rd International Conference on Chemical Looping, 9-11 September 2014, Gothenburg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The control of NOx and SOx in chemical-looping combustion systems is discussed with the focus on the importance of the pressurized flue-gas train. The chemistry of nitrogen and sulfur under pressurized conditions and the experiences gained from operating oxy-fuel combustion pilot plants that pertain to chemical looping are reviewed. In the flue gases from the combustion process, SO2 and NO are the principle NOx and SOx species. The oxidation of NO to NO2 is favored by low temperature and high pressure and is enhanced during the compression of flue gases. The oxidation of NO to NO2 in the flue-gas train is significant at pressures >15 bar. The solubilities of NO2 and SO2 in water are high and results in the formation of acids. Once NOx and SOx are absorbed, the liquid-phase N-S interactions lead to the formation of sulfuric and nitric acids. Thus, the chemistry of NOx and SOx is of importance for flue-gas conditioning of chemical-looping combustion systems. Similar to oxy-fuel combustion, the conditions in the chemical-looping flue-gas train offer new opportunities for the design of NOx and SOx removal processes.
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| 7. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Investigation of the Behavior of Alkali Chlorides during Sulfur Recirculation in a Waste-to-Energy Facility
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- High temperature corrosion related issues are known problems for Waste-to-Energy facilities where the formation of alkali chlorides is among the most problematic species formed during the combustion. Sulfur Recirculation is a novel technology developed to reduce the chlorine content in the ash and in that way also the corrosivity of the ash. This concept has been installed at the Maabjerg Energy Center (MEC) in Denmark. This work aims to take a first step towards a reaction kinetics based model that can describe systems like the MEC boiler and to evaluate the impact of Sulfur Recirculation. This is done by implementing a plug flow reactor model in the software Chemkin. Previously obtained data from on-site experiments and CFD simulations is used as input to the model. The model is focused on describing the sulfation of alkali chlorides and the result from the model is compared to experiments. The model is able to predict the degree of sulfation with less than 10% deviation from the experimental results. Both the experiment and the model show a clear benefit from implementing sulfur recirculation which lowers the chlorine content in the up to as much as 70%. It is, however, also shown that the results are sensitive towards several of the assumptions made. Even though there is a relatively good agreement in final sulfation between model and experiments the model is not able to represent the detailed chemistry in a realistic way in its current state; further development is required.
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| 8. |
- Allgurén, Thomas, 1986, et al.
(författare)
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NO formation during co-combustion of coal with two thermally treated biomasses
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The behavior of biomass as a fuel varies a lot. Not only between different sources of raw material, but also depending on if they have been pre-treated, and if so, also depending on the type of treatment. Two types of thermal pre-treatments of woody biomass used for combustion in suspension systems are torrefaction and steam explosion. These two types of pre-treated biomass were investigated in this work with focus on the nitrogen chemistry, and were investigated both experimentally in a 1.5MWth combustion unit and by performing detailed reaction simulations. Three different cases have been investigated. One case with 100% Utah Sufco coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Even though only 15% of the coal has been substituted there is a clear difference in the amount of NO formed between the cases. The pure coal had the highest amount of NO formed which was expected due to the higher amount of fuel-bound nitrogen in the coal compared to the biomasses. The fuel analyses indicate that the nitrogen content is the same in the two investigated bio fuels. Despite this fact, the amount of NO formed was when coal was co-fired with torrefied biomass than with steam exploded biomass. The gas composition data from the in-flame measurements show that the concentration of volatile nitrogen species (HCN and NH3) varies between the cases, which is suggested as the reason for the difference in the NO formation. The importance of when and where the nitrogen species are released is also shown in the modelling work, supporting what was observed experimentally.
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| 10. |
- Allgurén, Thomas, 1986, et al.
(författare)
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The Influence of Alkali, Chlorine and Sulfur on Aerosol Formation
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of low-quality fuels in power generation is typically motivated by a potential reduction in fuel costs or CO2 emissions, the latter in case the fuel is based on biomass. These features make low quality fuels attractive at the same time as such fuels are usually problematic to use in power generation due to fuel composition. One of the main issues is deposition of aerosols upon heating surfaces reducing heat transfer and causing high-temperature corrosion (HTC). The later most often related to alkali chlorides, and these are formed from alkali species and chlorine when released during the combustion process. The present work aims to investigate how the gas phase chemistry are connected to the formation aerosols and their characteristics. This is an ongoing work why only part of the preliminary results is presented focusing on the interaction between alkali, sulfur and chlorine in the gas phase. The results presented here indicate a clear correlation between the S/Cl ratio and the formation of alkali sulfates over chlorides. It is also indicated that the local conditions at which the species are released and available in the gas phase is important for the resulting formation of alkali sulfates.
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