The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3 m high rectangular fluidized be...The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3 m high rectangular fluidized bed dryer of cross sectional area of 0.15 m×0.61 m at different operating conditions using paddy, a group D particle, as the fluidizing material. The results of the study showed that the fluidized bed dryer system with vertical internal baffles gave better particle mixing effect in the bed of particles than that without vertical internal baffles. This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking up the large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bed of particles before finally erupting at the bed surface. This improves the contacting efficiency and enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate was obtained in the falling rate period because the higher contacting efficiency increases the evaporation rate at the particle surface. However, the drying rate in the diffusion region shows little improvement because the moisture diffusivity does not depend on the contacting efficiency. The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapid drying stage in a two stage drying strategy for paddy. The insertion of vertical internal baffles into a fluidiz ed bed system improves the processing of Group D particles in a fluidized bed system especially if the system is large in scale.展开更多
The large-scale integration of new energy generation has put forward higher requirements for the peak-shaving capability of thermal power.The circulating fluidized bed(CFB)depends on the advantages of a wide load adju...The large-scale integration of new energy generation has put forward higher requirements for the peak-shaving capability of thermal power.The circulating fluidized bed(CFB)depends on the advantages of a wide load adjustment range and low cost of pollutant control to become a good peak shaving power supply.However,the large delay and inertia caused by its unique combustion mode make it very difficult to change the load quickly.To further understand the factors that affect the load change of CFB,and explore the method of increasing CFB load change rate,the load change experiment on the combustion side was carried out in the 0.1 MW CFB experiment platform.The influence law of bed material amount and fuel particle size on load change of CFB combustion side was revealed for the first time.The results indicated that the increase of bed material amount was beneficial to improve the load change rate on the combustion side of CFB and reduce the carbon content of fly ash,but had no obvious effect on NO_(x)emission.When the bed height at rest increased from 200 mm to 400 mm,the load change rate of the CFB combustion side load from 50%to 75%increased from 0.78%/min to 1.14%/min,and the carbon content of fly ash at 75%load decreased from 26.6%to 24.9%.In addition,the reduction of fuel particle size positively improved the load change rate on the combustion side of the CFB and reduced NO_(x)emission but had a negative effect on reducing the carbon content of fly ash.When the fuel particle size decreased from 0-1 mm to 0-0.12 mm,the load change rate of CFB combustion side load from 50%to 75%increased from 0.78%/min to 1.09%/min,and the NO_(x)emission and carbon content of fly ash at 75%load decreased from 349.5 mg/m^(3)to 194.1 mg/m^(3)and increased from 26.6%to 31.8%,respectively.展开更多
为数众多的计算颗粒初始流态化速度的公式大体上分为三类:第一类以Ergun公式为基础,引入经验系数加以修正;第二类以某种流体力学关系为基础;第三类属于纯经验公式。这三种类型中,以第一类式子有较大范围之Ar适应性,比较适用。本文提出...为数众多的计算颗粒初始流态化速度的公式大体上分为三类:第一类以Ergun公式为基础,引入经验系数加以修正;第二类以某种流体力学关系为基础;第三类属于纯经验公式。这三种类型中,以第一类式子有较大范围之Ar适应性,比较适用。本文提出的计算式子也属于Ergun型,从目前掌握的实验数据看来,比工程界广泛应用的Wen and Yu式子用于计算液-固流态化系统有更高的精确性,而且对球形与非球形颗粒都适用。展开更多
文摘The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3 m high rectangular fluidized bed dryer of cross sectional area of 0.15 m×0.61 m at different operating conditions using paddy, a group D particle, as the fluidizing material. The results of the study showed that the fluidized bed dryer system with vertical internal baffles gave better particle mixing effect in the bed of particles than that without vertical internal baffles. This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking up the large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bed of particles before finally erupting at the bed surface. This improves the contacting efficiency and enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate was obtained in the falling rate period because the higher contacting efficiency increases the evaporation rate at the particle surface. However, the drying rate in the diffusion region shows little improvement because the moisture diffusivity does not depend on the contacting efficiency. The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapid drying stage in a two stage drying strategy for paddy. The insertion of vertical internal baffles into a fluidiz ed bed system improves the processing of Group D particles in a fluidized bed system especially if the system is large in scale.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21040100)。
文摘The large-scale integration of new energy generation has put forward higher requirements for the peak-shaving capability of thermal power.The circulating fluidized bed(CFB)depends on the advantages of a wide load adjustment range and low cost of pollutant control to become a good peak shaving power supply.However,the large delay and inertia caused by its unique combustion mode make it very difficult to change the load quickly.To further understand the factors that affect the load change of CFB,and explore the method of increasing CFB load change rate,the load change experiment on the combustion side was carried out in the 0.1 MW CFB experiment platform.The influence law of bed material amount and fuel particle size on load change of CFB combustion side was revealed for the first time.The results indicated that the increase of bed material amount was beneficial to improve the load change rate on the combustion side of CFB and reduce the carbon content of fly ash,but had no obvious effect on NO_(x)emission.When the bed height at rest increased from 200 mm to 400 mm,the load change rate of the CFB combustion side load from 50%to 75%increased from 0.78%/min to 1.14%/min,and the carbon content of fly ash at 75%load decreased from 26.6%to 24.9%.In addition,the reduction of fuel particle size positively improved the load change rate on the combustion side of the CFB and reduced NO_(x)emission but had a negative effect on reducing the carbon content of fly ash.When the fuel particle size decreased from 0-1 mm to 0-0.12 mm,the load change rate of CFB combustion side load from 50%to 75%increased from 0.78%/min to 1.09%/min,and the NO_(x)emission and carbon content of fly ash at 75%load decreased from 349.5 mg/m^(3)to 194.1 mg/m^(3)and increased from 26.6%to 31.8%,respectively.
文摘为数众多的计算颗粒初始流态化速度的公式大体上分为三类:第一类以Ergun公式为基础,引入经验系数加以修正;第二类以某种流体力学关系为基础;第三类属于纯经验公式。这三种类型中,以第一类式子有较大范围之Ar适应性,比较适用。本文提出的计算式子也属于Ergun型,从目前掌握的实验数据看来,比工程界广泛应用的Wen and Yu式子用于计算液-固流态化系统有更高的精确性,而且对球形与非球形颗粒都适用。
