To study the effect of inert dust on gas explosion suppression mechanism,SiO_2 fine powders were sprayed to suppress premixed CH_4-Air gas explosion in a 20 L spherical experimental system.In the experiment,high speed...To study the effect of inert dust on gas explosion suppression mechanism,SiO_2 fine powders were sprayed to suppress premixed CH_4-Air gas explosion in a 20 L spherical experimental system.In the experiment,high speed schlieren image system was adopted to record explosion flame propagation behaviors,meanwhile,pressure transducers and ion current probes were used to clearly record the explosion flame dynamic characteristics.The experimental results show that the SiO_2 fine powders suppressed evidently the gas explosion flame,and reduced the peak value of pressure and flame speed by more than 40%.The ion current result shows that the SiO_2 super fine powders were easy to contact with and absorb free radicals near the combustion reaction region,which greatly reduced the combustion reaction intensity,and in turn influenced the flame propagation and pressure rising.展开更多
First, the characteristics of low-velocity conveying of particles having different hardness are experimentally investigated in a horizontal pipeline in terms of flow pattern and pressure drop to show that the slug flo...First, the characteristics of low-velocity conveying of particles having different hardness are experimentally investigated in a horizontal pipeline in terms of flow pattern and pressure drop to show that the slug flow can be classified into two types depending on the settling of particles along the pipeline, and the period is small for slug flow without the settled layer, which is called solitary slug flow. The pressure drop for soft particles is shown to be larger than that for hard particles. Then, experimental results are presented on horizontal fluidized-bed conveying of fine powders to show that air release from the top surface of the conveying channel is an imnortant factor for high mass flow rate of particles.展开更多
The reduction-degree of the sample increases and the utilization ratio of gas decreases when the reaction lasts longer time,which indicates that the reaction is faster at the beginning of reduction,while it becomes sl...The reduction-degree of the sample increases and the utilization ratio of gas decreases when the reaction lasts longer time,which indicates that the reaction is faster at the beginning of reduction,while it becomes slower in subsequent process.The higher the reaction temperature,the higher the utilization ratio of gas and the reduction-degree are,but the difference of utilization ratio among the different temperatures becomes smaller with time.The utilization ratio of gas can reach about 8% and the reduction-degree is 80% for 20 min reduction at 850 ℃,indicating that the reduction reaction by CO is very fast at high temperature.The higher the reaction temperature,the higher the apparent reaction rate constant is,but the difference of apparent reaction rate constant among the different temperatures becomes bigger.The apparent activation energy is about 59.11 kJ/mol in the fluidized bed experiment.The increase of reduction-degree with gas velocity shows quite good linearity,indicating that at high temperature even higher velocity of reducing gas can be used to improve the productivity of reactor when CO is used as reducing gas.With the increase of charge height,the metallization ratio and the reduction-degree decrease,but the utilization ratio of gas increases.展开更多
基金supported by the National Natural Science Foundation of China(50804038)Specialized Research Fund for the Doctoral Program of Higher Education of China (200804971055)Open Foundation of State Key Lab of Explosion Science and Technology(KFJJ 07-06)
文摘To study the effect of inert dust on gas explosion suppression mechanism,SiO_2 fine powders were sprayed to suppress premixed CH_4-Air gas explosion in a 20 L spherical experimental system.In the experiment,high speed schlieren image system was adopted to record explosion flame propagation behaviors,meanwhile,pressure transducers and ion current probes were used to clearly record the explosion flame dynamic characteristics.The experimental results show that the SiO_2 fine powders suppressed evidently the gas explosion flame,and reduced the peak value of pressure and flame speed by more than 40%.The ion current result shows that the SiO_2 super fine powders were easy to contact with and absorb free radicals near the combustion reaction region,which greatly reduced the combustion reaction intensity,and in turn influenced the flame propagation and pressure rising.
文摘First, the characteristics of low-velocity conveying of particles having different hardness are experimentally investigated in a horizontal pipeline in terms of flow pattern and pressure drop to show that the slug flow can be classified into two types depending on the settling of particles along the pipeline, and the period is small for slug flow without the settled layer, which is called solitary slug flow. The pressure drop for soft particles is shown to be larger than that for hard particles. Then, experimental results are presented on horizontal fluidized-bed conveying of fine powders to show that air release from the top surface of the conveying channel is an imnortant factor for high mass flow rate of particles.
基金Item Sponsored by National Natural Science Foundation of China(50474006)National Key Technology Research and Development Programin 11th Five-Year Plan of China(2006BAE03A12,2006BAE03A05)
文摘The reduction-degree of the sample increases and the utilization ratio of gas decreases when the reaction lasts longer time,which indicates that the reaction is faster at the beginning of reduction,while it becomes slower in subsequent process.The higher the reaction temperature,the higher the utilization ratio of gas and the reduction-degree are,but the difference of utilization ratio among the different temperatures becomes smaller with time.The utilization ratio of gas can reach about 8% and the reduction-degree is 80% for 20 min reduction at 850 ℃,indicating that the reduction reaction by CO is very fast at high temperature.The higher the reaction temperature,the higher the apparent reaction rate constant is,but the difference of apparent reaction rate constant among the different temperatures becomes bigger.The apparent activation energy is about 59.11 kJ/mol in the fluidized bed experiment.The increase of reduction-degree with gas velocity shows quite good linearity,indicating that at high temperature even higher velocity of reducing gas can be used to improve the productivity of reactor when CO is used as reducing gas.With the increase of charge height,the metallization ratio and the reduction-degree decrease,but the utilization ratio of gas increases.
