| 1. |
- Alipour, Yousef, 1979-, et al.
(författare)
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The analysis of furnace wall deposits in a low-NOx waste wood-fired bubbling fluidised bed boiler
- 2012
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Ingår i: VGB PowerTech Journal. - : VGB Power Tech. - 1435-3199. ; 92:12, s. 96-100
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Increasing use is being made of biomass as fuel for electricity production as the price of natural wood continues to rise. Therefore, more use is being made of waste wood (recycled wood). However, waste wood contains more chlorine, zinc and lead, which are believed to increase corrosion rates. Corrosion problems have occurred on the furnace walls of a fluidised bed boiler firing 100 % waste wood under low-NOx conditions. The deposits have been collected and analysed in order to understand the impact of the fuel.
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| 2. |
- Eldensten, L., et al.
(författare)
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Introduction of co-combustion of coal and biomass in a 315 MWth CFB boiler
- 2005
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Ingår i: VGB PowerTech. - 1435-3199. ; 85:8, s. 60-62+6
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Elektrocieplownie Warszawskie S.A, has tested various mixtures of coal with biomass. This has been done both as full-scale trials and in separate lab-scale investigations. The main goal of the measurement program, during full-scale trials, was to evaluate influence of co-combustion on emissions, overall efficiency and full load of boiler.
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| 3. |
- Henderson, Pamela, et al.
(författare)
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In-situ fireside corrosion testing of superheater materials with coal, wood and straw fuels for conventional and asvanced steam temperatures
- 2005
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Ingår i: VGB PowerTech. - Essen, Germany : VGB PowerTech eV. - 1435-3199. ; 84:6, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- An increase in the steam temperature of a power station increases the electrical efficiency of the turbine. This in turn leads to a reduction in the cost of electricity and in environmental emissions produced per unit of electricity generated. However, higher steam temperatures give rise to more aggressive corrosive environments and the choice of material becomes more important. In addition, the aggressiveness of the fuels also depends on their chemical compositions. As part of a European research programme (COST 522) fireside corrosion tests of superheater and waterwall materials have been performed in-situ in industrial boilers or combustion test facilities, simulating conventional and higher steam temperatures. The fuels used were, straw, wood (logging residues) and coal. Goals were set at different maximum steam temperatures and lifetimes according to the fuel. The targets were: coal 650°C/100,000 h, wood 580°C/40,000 h and straw 580°C/20,000 h .A wide range of materials was tested. An overriding constraint was that the materials must be economically viable and not impose exceptional fabrication requirements. Some materials were tested in a number of combustion environments, allowing useful comparisons to be made. The results showed that for a given superheater alloy, temperature and fuel, the corrosion rate depended on the alloy’s position in a superheater bank. Tubes on the outside, exposed to the flue gas, corroded faster than those positioned deeper in a bank. Tubes experiencing a greater heat flux will corrode more rapidly. Poorly controlled combustion will also increase corrosion. Straw was much more corrosive than wood (logging residues). The difference in corrosiveness increased with increasing temperature above a metal temperature of about 520°C. The corrosion rates of the alloys tested during wood-firing were only a little higher than those from firing coal with a medium to high chlorine content. Straw and wood are often collectively known as “biomass”, but the corrosion they cause can vary by a factor of 5 or more. No difference could be found in the fireside corrosion rates of the steels TP 347H and TP 347HFG, when tested under similar conditions. Esshete 1250 also showed similar fireside corrosion rates to347 instraw and wood boilers and at temperatures below 650°Cin coal boilers. Several alloys were identified to resist corrosion in coal-fired plant at metal temperatures of680°C(steam temperatures650°C) and high heat fluxes. Adequate high temperature creep strength remains more problematic. At lower heat fluxes (resulting in lower corrosion rates) more candidate alloys exist. It is expected that the goals set can be achieved with the use of suitable alloys in the case of wood, waste and coal. For wood (logging residues) TP347, Esshete 1250 and 50Ni50Cr coatings showed sufficient corrosion resistance at the target temperatures. In the coal case HR3C fulfills the requirements of strength and corrosion resistance with a high heat flux and Super 304H and SAVE 25 if the heat flux is low. HR11N and IN671 are suitable for use as claddings on a substrate with the appropriate creep strength. The goal set for straw firing was ambitious, a steam temperature of580°C, and in this case a combination of material, combustion technology and boiler design are needed.
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| 4. |
- Henderson, Pamela, et al.
(författare)
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The use of fuel additives in wood and waste wood fired boilers to reduce corrosion and fouling problems
- 2004
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Ingår i: VGB PowerTech. - Essen : VGB PowerTech e.V.. - 1435-3199. ; 84:6, s. 58-62
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Tidskriftsartikel (refereegranskat)abstract
- One of the major drawbacks to the implementation of 100% biomass in conventional power station boilers is the increase in the fouling and corrosion of superheaters. Rapid corrosion of superheaters leads to increased maintenance costs while fouling caused by widespread deposit formation gives rise to a decrease in efficiency of the turbine and an increase in unplanned outages. The purpose of this paper is to report on the effects of fuel additives to change the biofuel chemistry, thus making the fuel less problematic and reducing corrosion and fouling problems. Full-scale trials have been carried out in 35MWth and 105 MWth combined heat and power stations. Most biomass fuels have a high content of alkali metals and sometimes high chlorine levels, but they contain very little sulphur compared to fossil fuels. It is thought that the addition of sulphur to the fuel could help to reduce corrosion since a deposit containing only alkali sulphates has a higher first melting point than deposits containing alkali chlorides. Molten phases increase the corrosion and fouling rates and in this sense, sulphates are preferred to chlorides in the deposits. To investigate the effect fuel additives, trials were initially performed in a 35 MWth wood-fired circulating fluidised bed boiler, adding controlled amounts of sulphur and a newly developed compound additive, called ChlorOut, to the 100% wood fuel feed or flue gases. It was found that the compound additive, ChlorOut, had a greater effect in removing KCl from the flue gases that pure sulphur, whilst having only a marginal effect on the SO2 content of the flue gas and sulphate content and pH of the flue gas condensate. Long term tests with ChlorOut were then repeated in a 105 MWth boiler and in addition corrosion probe testing of superheater steels was performed with and without ChlorOut. The results showed that the ChlorOut additive effectively reduced KCl levels in the flue gas at the superheaters, removed chlorides from the deposits, reduced fouling problems and reduced the corrosion rates by about 50%.
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| 5. |
- Johnsson, Filip, 1960, et al.
(författare)
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An experimental study of in-furnace processes and dynamic behaviour of a 235 MWe CFB boiler
- 2004
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Ingår i: VGB PowerTech. - 1435-3199. ; 84:3, s. 82-87
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Tidskriftsartikel (refereegranskat)abstract
- In a project funded by the 5th Framework Programme of the European Union, a 235 MWe Circulating Fluidized Bed (CFB) boiler is investigated with respect to in-furnace processes and dynamic response to load changes. The purpose of the project is to assess the insufficiently known features of large-scale CFB boilers. The furnace of the boiler has a cross-section of 21 x 10 meters and a height of 44 meters. The boiler is located in Turow, Poland, and is operated on a local brown coal.The project is unique in that several measurement ports were opened in the walls of the large CFB furnace for measurements in various locations inside the furnace. Also, a number of techniques were employed with new probes developed for this type of measurements to form a basis for studies of hydrodynamic processes as well as local variations in gas components (such as O2, CO, THC) and solid bed materials. The paper describes the measurement techniques and provides examples of results obtained from the in-situ measurements and from the dynamic response study.
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