The Characteristics And Optimization Of Discharging Process Of Typical Industrial Powder From Hopper

The industrial powders' flowability during aerated discharging was investigated by using atmospheric pressure plexiglass hopper discharging system for the application of lock hopper in the feeding system of entrained flow pulverized coal pressurized gasification technology.The physical properties of three typical industrial powders:Jincheng coal,Yangchangwan coal and petroleum coke were measured by using the FT4,particle sizer,etc.The results show that the industrial powders have poor fluidity and strong adhesion.After comprehensive comparison,it is found that the HR index,Carr index and shear characteristic are the effective parameters to predict the flow of the powder in the bin.The material characteristics of different powders were summarized by using weighing module,pressure sensor and ECT.It is found that the sedimentation time had a great influence on grativity discharging after analysing the change of the received mass.Aeration was more effective in promoting the discharging of smaller particle size and stronger adhesion powders.For the powder of good fluidity,the pressure of the wall surface of the silo was higher at the initial stage of the discharging,and the continuous negative pressure state would exist near the surface of the cone mouth.It was found that the flow pattern of the powders in the pipe was generally in the form of central flow,which was in good continuous for the powder of bigger particle size.The movement was not easy to be affected by the aeration after analysing the change of ECT signal.The flow pattern in the pipe was generally in form of central flow,the movement of the powders with bigger particle size showed good continuity,and was not easy to be affected by the aeration.The switch of the whole flow pattern in the vertical pipe can be found in the adherent powders.The property of powder and the phenomenon of discharging had showed the truth that there was a critical accumulation strength during discharging.The discharging happened only if the overall accumulation strength was less than the critical strength.The one effect of aeration was to reduce the accumulation strength of the powders in the bin before discharging.A partition model was developed to describe the falling motion of the particles in the view of the gas phase motion by using the bubble theory in the fluidized bed.The model explains the phenomena of the arch curve of air flow rate and air pressure balance arch.Based on the experimental data,the relationship between the bubble size and the aeration height,aeration rate was calculated,the optimal relative aeration height H/D=12.25 and the optimal aeration gas velocity U_g=1.58 m·s^-1,?2.4Umf?are calculated by the partition model,respectively.The calculated results are in good agreement with the experimental values.In the range of 5.56<H/D<18 and U_g>Umf,the calculated deviation of the dischargine flow rate is less than 20%.The effectiveness of the optimization method is proved.