| 1. |
- Blasiak, Wlodzimierz, et al.
(författare)
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Reforming Of Biomass Wastes Into Fuel Gas With High Temperature Air And Steam
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The presented work aims to provide information on solid biomass conversion into fuel gas as a result of air and steam gasification process. In contrary to the conventional gasification in this work highly preheated air and steam is used as a gasifying agent. Preheat of air and steam is realised by means of the high-cycle regenerative air/steam preheater. Use of highly preheated gasifying media provides additional energy into the gasification process that enhances the thermal decomposition of the gasified solids. The objective of this work is to provide information on the process of biomass wastes reforming to fuel gas using high temperature air and steam gasification.High Temperature Air/Steam Gasification of biomass wastes has very clear economical and environmental benefits. It will increase consumption of biomass thus decreases CO2 emissions. Apart from CO2 reduction possibility, the new process, High Temperature Gasification has the following advantages:- Clean fuel gas for production of heat or electricity,- No need to treat ashes from gasification since there is no ash or at least no carbon in the ash produced,- No need to landfill since the produced slag can be used for example as a building material.In this work high temperature air and steam gasification of charcoal and wood pellets in a fixed bed updraft gasifier is tested. The following conclusions were found out:• For both charcoal and wood pellets gasification cases it was seen that an increase of steam molar fraction in the feed gas decreases the temperature of the gasification, the gasification rate, the mass yield of the fuel and molar fraction of carbon monoxide but increases molar fraction of hydrogen,• An increase of the feed gas temperature reduces production of tars, soot and char residue as well as increases calorific value of the fuel gas produced,• Preheating of the feed gas obtains a higher gasification efficiency and a higher gasification rate,• High temperature air and mixture of air and steam used as feed gas in a fixed bed gasifier shows the capability of this technology of maximising the gaseous product yield,• High lower heating value of fuel gas and high molar fraction of hydrogen and hydrocarbons obtained by using high temperature air and steam gasification technology increase the technical possibility of the application of fuel gas produced.
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| 2. |
- Flamme, Michael, et al.
(författare)
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Radiant Tube Burners
- 2010
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Ingår i: Industrial Combustion Testing. - : Taylor & Francis Group. ; , s. 487-504
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Li, Jun, et al.
(författare)
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CFD Approach for Unburned Carbon Reduction in Pulverized Coal Boilers
- 2012
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 26:2, s. 926-937
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Tidskriftsartikel (refereegranskat)abstract
- Low-NO, technologies are widely used in pulverized coal boilers, but they usually produce high levels of carbon in the fly ash. High levels of unburned carbon represent fuel loss, so the overall boiler efficiency is reduced. Additionally, the higher carbon content affects the suitability of fly ash for cement applications. The purpose of this paper is to provide a CFD approach for unburned carbon reduction by optimizing operating conditions. In this paper, three different boiler loads were simulated: 200 MW, 170 MW, and 140 MW. The air supply System was simulated previously for preparing as precise as possible boundary conditions. At last, the unburned carbon level of every burner was investigated, and the effects of residue residence time and the local fuel air momentum ratio are discussed in detail. According to the predicted results, operating conditions and the residence time of the coal particles affects the unburned carbon level in fly ash. Operating conditions play a more significant role during the combustion process, while the residence time affects char burnout only when the burner's location is low. Therefore, it is concluded that a cost-effective method could be developed for reducing the unburned carbon level in ash and correspondingly, the loss on ignition level. First, it is necessary to determine which burners are operating under poor conditions through CFD analysis. Then, the fuel air momentum ratios of those burners should be modified by changing the operating conditions, meanwhile increasing the residence time of coal particles to ensure complete combustion.
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| 4. |
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| 5. |
- Lucas, Carlos, et al.
(författare)
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High-temperature air and steam gasification of densified biofuels
- 2004
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Ingår i: BIOMASS BIOENERG. - : Elsevier BV. ; , s. 563-575
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Konferensbidrag (refereegranskat)abstract
- An experimental study was carried out to investigate gasification of densified biofuels using highly preheated air and steam as a gasifying agent. Preheat of air and steam is realised by means of the newly developed high-cycle regenerative air/steam preheater. Use of highly preheated feed gas provides additional energy into the gasification process, which enhances the thermal decomposition of the gasified solids. For the same type of feedstock the operating parameters, temperature, composition and amount of gasifying agent, were varied over a wide range. Results of experiments conducted in. a high-temperature air/steam fixed bed updraft gasifier show the capability of this technology of maximising the gaseous product yield as a result of the high heating rates involved, and the efficient tar reduction. Increase of the feed gas temperature reduces production of tars, soot and char residue as well as increases heating value of the dry fuel gas produced. Overall, it has been seen that the yield and the lower heating value of the dry fuel gas increase with increasing temperature.
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| 6. |
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| 7. |
- Rafidi, Nabil, et al.
(författare)
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Increase of the Effective Energy from the Radiant Tube Equipped with Regenerative System in Comparison with Conventional Recuperative System
- 2005
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Ingår i: IFRF Combustion Journal. - 1562-479X. ; :03, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the experimental results of High Temperature Air Combustion (HiTAC)investigations with the use of a radiant tube, in order to compare the Regenerative System (RS)with a conventional recuperative system.For this work a semi-industrial HiTAC test furnace was equipped with the W-shape RadiantTube. The working length of this tube was around 7,0 m and the diameter was 0,195 m. Theradiant tube was operated in sequence with a conventional recuperative system and aRegenerative System. The recuperative burner was mounted in the upper end of the tube. TheRS consisted of two burners, equipped with honeycomb ceramic regenerators, mounted to bothends of the radiant tube. The temperature profile of the tube wall was monitored by 74thermocouples located along the tube. Additional temperatures, flow rates and pressures weremeasured to assess and compare the energy balance of both systems. Pollutant emissions,including NOx and CO, as well as the exhaust gas composition were measured. The tests werecarried out over a wide range of parameters: firing power from 75 kW to 155 kW, furnacetemperature from 670°C to 950°C and an oxygen molar fraction in the exhaust gases set at 3%.LPG was used as a fuel in all tests.Test results show that the temperature profiles along the tube were more uniform when theregenerative system was used. The cross-sectional temperature distribution for the tube wasalso more uniform. Because of the relatively flat temperature distribution along the tube, moreenergy from the radiant tube can be emitted using RS in comparison with the conventionalrecuperative burner, for the same maximum temperatures of the tube. In certain conditions, theincrease of energy release can be up to 100%.Energy balance calculations show that the efficiency of the Regenerative System can be up to25% higher than that of the recuperative system, mainly due to very low temperature of fluegases for RS operation. Although, the preheated air temperature used for combustion wasmuch higher in the case of the regenerative system (in some tests as high as 960°C), the NOxemission was found to be almost the same in both cases.
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