The Experts below are selected from a list of 326136 Experts worldwide ranked by ideXlab platform
Arthu F Stam - One of the best experts on this subject based on the ideXlab platform.
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superheater fouling in a bfb boiler firing wood based Fuel blends
Fuel, 2014Co-Authors: Arthu F Stam, Kees HaasnooAbstract:Four different Fuel blends have been fired in a 28 MWel BFB. Wood pellets (test 0) were not problematic for about ten years, contrary to a mixture of demolition wood, wood cuttings, compost overflow, paper sludge and roadside grass (test 1) which caused excessive fouling at a superheater bundle after already a few weeks. Two week tests with the test 2 blend (wood chips and cuttings, compost overflow and paper sludge) and test 3 blend (wood chips, demolition wood and wood cuttings) showed that, based on air cooled probe tests, fouling was slightly higher with test 3 compared to test 2. The bulk of the deposits consisted of a mixture of CaSO4 and K2SO4 (with minor amounts of Na2SO4). The occurrence of alkali sulfates is explained by a combination of 4 different deposition mechanisms. Gaseous alkali chlorides that condense, either as chlorides or sulfates and form aerosols, that deposit, especially initially, by thermophoresis (1), and, in the more mature deposit, by eddy diffusion and Brownian diffusion (2). The gaseous alkalis can also condense directly on the tube surface or on, or in the deposit (3). Gaseous alkalis can also condense on larger particle surfaces that deposit by inertial impaction (4). Whether gaseous alkalis have sulfatized during transport or after deposition, or both, could not be determined. CaSO4 is formed by sulfation of Ca-containing particles (not being silicates or slag) that cause the deposits to be sintered modestly (tests 2 and 3) or to a large extent (test 1, matured deposit). A molten K–Na–SO4–Cl salt is thermodynamically stable at the temperature range of tube surface +40 K to local flue gas temperature, and may also have contributed to sintering when reactive Ca is present locally in only low concentrations. Thermodynamic calculations predict fouling tendency as test 3 > test 2 > test 1 > test 0. The total amount of molten salt seemed a better predictor for fouling than the amount of salt as a percentage of total ash
Kees Haasnoo - One of the best experts on this subject based on the ideXlab platform.
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superheater fouling in a bfb boiler firing wood based Fuel blends
Fuel, 2014Co-Authors: Arthu F Stam, Kees HaasnooAbstract:Four different Fuel blends have been fired in a 28 MWel BFB. Wood pellets (test 0) were not problematic for about ten years, contrary to a mixture of demolition wood, wood cuttings, compost overflow, paper sludge and roadside grass (test 1) which caused excessive fouling at a superheater bundle after already a few weeks. Two week tests with the test 2 blend (wood chips and cuttings, compost overflow and paper sludge) and test 3 blend (wood chips, demolition wood and wood cuttings) showed that, based on air cooled probe tests, fouling was slightly higher with test 3 compared to test 2. The bulk of the deposits consisted of a mixture of CaSO4 and K2SO4 (with minor amounts of Na2SO4). The occurrence of alkali sulfates is explained by a combination of 4 different deposition mechanisms. Gaseous alkali chlorides that condense, either as chlorides or sulfates and form aerosols, that deposit, especially initially, by thermophoresis (1), and, in the more mature deposit, by eddy diffusion and Brownian diffusion (2). The gaseous alkalis can also condense directly on the tube surface or on, or in the deposit (3). Gaseous alkalis can also condense on larger particle surfaces that deposit by inertial impaction (4). Whether gaseous alkalis have sulfatized during transport or after deposition, or both, could not be determined. CaSO4 is formed by sulfation of Ca-containing particles (not being silicates or slag) that cause the deposits to be sintered modestly (tests 2 and 3) or to a large extent (test 1, matured deposit). A molten K–Na–SO4–Cl salt is thermodynamically stable at the temperature range of tube surface +40 K to local flue gas temperature, and may also have contributed to sintering when reactive Ca is present locally in only low concentrations. Thermodynamic calculations predict fouling tendency as test 3 > test 2 > test 1 > test 0. The total amount of molten salt seemed a better predictor for fouling than the amount of salt as a percentage of total ash
Ari Erkkila - One of the best experts on this subject based on the ideXlab platform.
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natural drying treatments during seasonal storage of wood for bioenergy in different european locations
Biomass & Bioenergy, 2011Co-Authors: Dominik Roser, Blas Molayudego, Lauri Sikanen, Robert Prinz, David Gritten, B Emer, Kari Vaatainen, Ari ErkkilaAbstract:Research into the methods of producing high quality wood chips for a rapidly growing energy sector is becoming increasingly important. For example, small wood chip heating plants require high quality wood chips to ensure efficient operation, thereby minimizing maintenance costs. Moisture content is considered to be an important quality parameter regarding wood based Fuels. The objective of this study is to investigate methods to promote the natural drying of wood for bioenergy purposes. The effects on the drying process through covering the wood piles and partial debarking of stems were tested in order to identify methods to reduce the moisture content of the woody material in the storage. Drying trials were established in Finland, Italy and Scotland, utilizing tree species typically used for energy purposes in each area. The results show that natural drying is a viable and effective method to enhance the energy efficiency of wood based Fuel products in all the regions studied. Furthermore, by adapting current harvesting methods and storage procedures even better results can be achieved. In addition, the results also indicate that broadleaved trees dry more effectively, if some partial debarking is carried out and that covering of piles is of utmost importance in Scotland and Finland.
S Grundvig - One of the best experts on this subject based on the ideXlab platform.
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compositional constraints on slag formation and potassium volatilization from rice straw blended wood Fuel
Fuel Processing Technology, 2006Co-Authors: B M Jenkins, Charles E. Lesher, S GrundvigAbstract:Abstract Experimental melting of biomass ash blends demonstrates that the addition of rice straw to a dominantly Wood-Based Fuel causes a marked freezing point depression in the liquidus temperature of the inorganic slag from well above 2000 °C to a minimum of about 1260 °C. The minimum temperature is achieved for ash blends with about 30% rice straw ash. The melting interval (liquidus to solidus) for the ash blends is typically 100–200 °C. The solidus shows a systematic decrease from about 1350 °C to as low as 800 °C for pure rice straw ash. Potassium is completely lost from slag for blends with less than 30% rice straw ash content. The addition of more than 30% rice straw ash results in an enhanced retention of potassium in the solid slag. Potassium loss for Fuel blends with above 30% rice straw ash is further positively correlated with melting temperature. As the temperature approaches the solidus, potassium is increasingly bound in the melt as well as in potassium–aluminum silicate minerals (leucite) and, therefore, partially retained in the slag. There are indications that melting temperatures above the ‘true’ liquidus for rice straw-rich blends cause partial potassium loss and consequently a rise in the liquidus. This will result in an apparent extending of the melting interval for blends with above 30% rice straw ash. The liquidus silicate mineralogy of the slag changes as a function of increasing rice straw ash from larnite, to akermanite, wollastonite, and diopside. This mineralogical sequence reflects an increase in the Si/Ca ratio and polymerization of the melt. The experimental slag shows favorable similarities to the mineralogy and composition of slag formed in commercial biomass-Fueled boilers, suggesting that the simplified conditions of the experimental melting study can be used to predict combustion conditions in commercial biomass-Fueled boilers. Thus, small additions of straw to a predominantly wood Fuel should have the effect of lowering slag melting temperature and relatively reducing potassium loss to the flue gas. If combustion temperature can be controlled to within, or below, the melting interval of the ash (
Blas Molayudego - One of the best experts on this subject based on the ideXlab platform.
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natural drying treatments during seasonal storage of wood for bioenergy in different european locations
Biomass & Bioenergy, 2011Co-Authors: Dominik Roser, Blas Molayudego, Lauri Sikanen, Robert Prinz, David Gritten, B Emer, Kari Vaatainen, Ari ErkkilaAbstract:Research into the methods of producing high quality wood chips for a rapidly growing energy sector is becoming increasingly important. For example, small wood chip heating plants require high quality wood chips to ensure efficient operation, thereby minimizing maintenance costs. Moisture content is considered to be an important quality parameter regarding wood based Fuels. The objective of this study is to investigate methods to promote the natural drying of wood for bioenergy purposes. The effects on the drying process through covering the wood piles and partial debarking of stems were tested in order to identify methods to reduce the moisture content of the woody material in the storage. Drying trials were established in Finland, Italy and Scotland, utilizing tree species typically used for energy purposes in each area. The results show that natural drying is a viable and effective method to enhance the energy efficiency of wood based Fuel products in all the regions studied. Furthermore, by adapting current harvesting methods and storage procedures even better results can be achieved. In addition, the results also indicate that broadleaved trees dry more effectively, if some partial debarking is carried out and that covering of piles is of utmost importance in Scotland and Finland.
