A riser with high density has unique behavior as compared with conventional circulating fluidized bed. With increase of cross-sectional solids fraction, the radial profiles of solids fraction,and particle velocity bec...A riser with high density has unique behavior as compared with conventional circulating fluidized bed. With increase of cross-sectional solids fraction, the radial profiles of solids fraction,and particle velocity become significantly non-uniform. The objective of this paper is to develop unique internals that can improve the poor distribution of solids fraction and particle velocity. The experiments are conducted at a high-density riser with 0.186 m ID and 9.0 m in height. FCC particle with particle density 1398 kg·m -3 and average particle size of 54 μm as fluidized material. The apparatus was operated under typical conditions of high-density riser. Two-dimensional LDV and optical fiber density sensor are used to measure the particle velocity and solids concentration in the high-density riser. The radial solids concentration profile in the high-density riser is significantly changed with internals added in the riser. The solids concentration profile downstream the bluffs is much flatter than without internals case. The particle measurement shows that the core-annular structure is destroyed. Transient signal analysis shows that the particle turbulent intensity increases several times near the wall region. The addition of internals reduces the average solids concentration near the internals, while the solids circulating rate changes insignificantly with the addition of internals. The internals can make the radial solids concentration and particle velocity profile uniform downstream the riser, but the length that shows improvement of gas-solids flow in the riser by the internals is about 0.8 m.展开更多
A liquid-solid fluidized bed separator, used for the separation of coarse slime, was developed. Test parti- cles sized in the range from 0.25 to 0.5, 0.5 to 1.0, and 0.25 to 1.0 mm were separated in the liquid-solid f...A liquid-solid fluidized bed separator, used for the separation of coarse slime, was developed. Test parti- cles sized in the range from 0.25 to 0.5, 0.5 to 1.0, and 0.25 to 1.0 mm were separated in the liquid-solid fluidized bed. Beds with column heights of 1200, 1500, and 1800 mm were tried. The clean coal and the railings were subsequently analyzed by float-sink testing. The results showed that the ash and yield of clean coal both decreased with increasing column height, for all three size fractions, and that the ash of the clean coal obtained from tests on the broader size fraction was less than that from the narrower sized fractions. The separation density decreased with increasing column height. The lowest E value was seen for a column height of 1500 ram, for which conditions the separation density was 1.45 g/cm3. The E value was 0.084 for the 0.25-0.5 mm fraction but the corresponding separation density was 1.48 g/cm3, and the E value 0.089, for the broader 0.25-1.0 mm fraction.展开更多
The first micro-segregation under conditions of twin roll strip casting was simulated.The relationship between the temperature and solid fraction in the mushy zone was given.The temperatures such as ZDT,LIT were got f...The first micro-segregation under conditions of twin roll strip casting was simulated.The relationship between the temperature and solid fraction in the mushy zone was given.The temperatures such as ZDT,LIT were got from this simulation.Then using the turbulent model,the flow field and thermal field in the pool of twin-roll strip caster was simulated.The speed and temperature at different casting speed was given,and the results were also explained.By these two simulations,the appropriate casting speed can be found.These simulations can provide effective data for controlling the twin-roll strip casting process.展开更多
文摘A riser with high density has unique behavior as compared with conventional circulating fluidized bed. With increase of cross-sectional solids fraction, the radial profiles of solids fraction,and particle velocity become significantly non-uniform. The objective of this paper is to develop unique internals that can improve the poor distribution of solids fraction and particle velocity. The experiments are conducted at a high-density riser with 0.186 m ID and 9.0 m in height. FCC particle with particle density 1398 kg·m -3 and average particle size of 54 μm as fluidized material. The apparatus was operated under typical conditions of high-density riser. Two-dimensional LDV and optical fiber density sensor are used to measure the particle velocity and solids concentration in the high-density riser. The radial solids concentration profile in the high-density riser is significantly changed with internals added in the riser. The solids concentration profile downstream the bluffs is much flatter than without internals case. The particle measurement shows that the core-annular structure is destroyed. Transient signal analysis shows that the particle turbulent intensity increases several times near the wall region. The addition of internals reduces the average solids concentration near the internals, while the solids circulating rate changes insignificantly with the addition of internals. The internals can make the radial solids concentration and particle velocity profile uniform downstream the riser, but the length that shows improvement of gas-solids flow in the riser by the internals is about 0.8 m.
基金supports for this work provided by the National Natural Science Foundation of China (No. 50974120)the Fundamental Research Funds for the Central Universities (No.2010QNB08)
文摘A liquid-solid fluidized bed separator, used for the separation of coarse slime, was developed. Test parti- cles sized in the range from 0.25 to 0.5, 0.5 to 1.0, and 0.25 to 1.0 mm were separated in the liquid-solid fluidized bed. Beds with column heights of 1200, 1500, and 1800 mm were tried. The clean coal and the railings were subsequently analyzed by float-sink testing. The results showed that the ash and yield of clean coal both decreased with increasing column height, for all three size fractions, and that the ash of the clean coal obtained from tests on the broader size fraction was less than that from the narrower sized fractions. The separation density decreased with increasing column height. The lowest E value was seen for a column height of 1500 ram, for which conditions the separation density was 1.45 g/cm3. The E value was 0.084 for the 0.25-0.5 mm fraction but the corresponding separation density was 1.48 g/cm3, and the E value 0.089, for the broader 0.25-1.0 mm fraction.
基金Item Sponsored by National Natural Science Foundation(59995440)
文摘The first micro-segregation under conditions of twin roll strip casting was simulated.The relationship between the temperature and solid fraction in the mushy zone was given.The temperatures such as ZDT,LIT were got from this simulation.Then using the turbulent model,the flow field and thermal field in the pool of twin-roll strip caster was simulated.The speed and temperature at different casting speed was given,and the results were also explained.By these two simulations,the appropriate casting speed can be found.These simulations can provide effective data for controlling the twin-roll strip casting process.
