The axial pressure drop profile and the radial solids distribution were measured in a circulating fluidized bed for evaluating the effects of return gas-solids stream position on the riser flow properties.The saturati...The axial pressure drop profile and the radial solids distribution were measured in a circulating fluidized bed for evaluating the effects of return gas-solids stream position on the riser flow properties.The saturation carrying capacity of gas for Geldart B typed particles and the flow mode of return gas-solids stream in the bed were discussed.It was found that arranging the inlet at a higher position of the riser would make the bottom bed leaner when U0 was high and Gs was low.When Gs increased,the longer influenced region of return particles and a small air-staging through lifting the loosening air injection position made the bottom bed become denser significantly.The deceleration and residence of return particles caused a relatively denser but asymmetrical region in the vicinity of inlet.But much more symmetrical solids distribution profile was found in the upper and lower regions far away from the inlet.The effects of inlet height on the flow properties of the riser with air-staging also were analyzed.The secondary air injection below the solids inlet could not cut off the solids exchange in the bed.The bed solids concentration increased when the particles inlet moved to a higher position of the bed when air-staging was adopted.Using CO2 as tracer,the dispersion of the loop-seal-fluidizing air for transmitting the return particles was investigated.It was found that the loop-seal fluidizing air dispersion rate was low but can be enhanced by the secondary air injection.展开更多
By using a cold CFB model, the effect of horizontal orifice areas of Loop Seal with side aeration air on operational property was studied in detail.The results showed that the horizontal orifice area had a great effec...By using a cold CFB model, the effect of horizontal orifice areas of Loop Seal with side aeration air on operational property was studied in detail.The results showed that the horizontal orifice area had a great effect on its stable operation and regulation of the recirculation rate.Under a certain range of the horizontal orifice area,the stable flow of solid particles through Loop Seal could be obtained and recirculation rate of solid particles could be well regulated and controlled through changing external aeration.The flow resistance properties across the horizontal orifice were given and an empirical equation of the pressure drop of horizontal orifice and solid circulating flow rate was proposed and a new orifice discharge coefficient was defined.The expression’s were in good agreement with the experimental data.展开更多
Loop seals are among the most common non-mechanical valves used in circulating fluidized bed sys- tems. In the present work. a fundamental study is conducted of a fluidized loop seal, which consists of a fluidized sta...Loop seals are among the most common non-mechanical valves used in circulating fluidized bed sys- tems. In the present work. a fundamental study is conducted of a fluidized loop seal, which consists of a fluidized standpipe, a fluidized supply chamber, and a fluidized recycling chamber. Based on the princi- ples of momentum, mass. and energy conservation, a hydrodynamic model for a loop seal is established, consisting of 13 equations. The effects of operating conditions such as the bottom aeration rate, total solid inventory, and fluidizing gas velocity in the riser on the solids flow rate and the performance of the loop seal are studied by a combination of model analysis and experiments. The experiments are carried out in a circulating fluidized bed with silica gel particles （Geldart group A）. The model predictions show good agreement with the experimental data.展开更多
文摘The axial pressure drop profile and the radial solids distribution were measured in a circulating fluidized bed for evaluating the effects of return gas-solids stream position on the riser flow properties.The saturation carrying capacity of gas for Geldart B typed particles and the flow mode of return gas-solids stream in the bed were discussed.It was found that arranging the inlet at a higher position of the riser would make the bottom bed leaner when U0 was high and Gs was low.When Gs increased,the longer influenced region of return particles and a small air-staging through lifting the loosening air injection position made the bottom bed become denser significantly.The deceleration and residence of return particles caused a relatively denser but asymmetrical region in the vicinity of inlet.But much more symmetrical solids distribution profile was found in the upper and lower regions far away from the inlet.The effects of inlet height on the flow properties of the riser with air-staging also were analyzed.The secondary air injection below the solids inlet could not cut off the solids exchange in the bed.The bed solids concentration increased when the particles inlet moved to a higher position of the bed when air-staging was adopted.Using CO2 as tracer,the dispersion of the loop-seal-fluidizing air for transmitting the return particles was investigated.It was found that the loop-seal fluidizing air dispersion rate was low but can be enhanced by the secondary air injection.
文摘By using a cold CFB model, the effect of horizontal orifice areas of Loop Seal with side aeration air on operational property was studied in detail.The results showed that the horizontal orifice area had a great effect on its stable operation and regulation of the recirculation rate.Under a certain range of the horizontal orifice area,the stable flow of solid particles through Loop Seal could be obtained and recirculation rate of solid particles could be well regulated and controlled through changing external aeration.The flow resistance properties across the horizontal orifice were given and an empirical equation of the pressure drop of horizontal orifice and solid circulating flow rate was proposed and a new orifice discharge coefficient was defined.The expression’s were in good agreement with the experimental data.
基金The authors wish to gratefully acknowledge the financial sup- port from the State Key Development Program for Basic Research of China （973 Program） under Grant No. 2015CB251402 and from the National Natural Science Foundation of China under Grant Nos. 21325628 and 91334108.
文摘Loop seals are among the most common non-mechanical valves used in circulating fluidized bed sys- tems. In the present work. a fundamental study is conducted of a fluidized loop seal, which consists of a fluidized standpipe, a fluidized supply chamber, and a fluidized recycling chamber. Based on the princi- ples of momentum, mass. and energy conservation, a hydrodynamic model for a loop seal is established, consisting of 13 equations. The effects of operating conditions such as the bottom aeration rate, total solid inventory, and fluidizing gas velocity in the riser on the solids flow rate and the performance of the loop seal are studied by a combination of model analysis and experiments. The experiments are carried out in a circulating fluidized bed with silica gel particles （Geldart group A）. The model predictions show good agreement with the experimental data.
