Characteristics Of Powder Material Discharging From Conical Hopper

Efficient large-scale coal gasification technology is the foundation and key technology of IGCC power generation, multi-generation, hydrogen, fuel cells and other process industries. The Pulverized Coal Pressurized Dense Transport Bed Gasifier can adapt to coal of low rank coal, high-ash and high ash melting point in china. Stable and good regulating performance of pulverized coal feeding ensures the stable operation and regulation of gasifier, which makes it become a key technology of Dense Transport Bed Gasification technology.Based on the evaluation of the powder material flow ability, research of gravity discharge from hopper, research of discharge from downward blowing tank and pneumatic conveying system design, we do a lot of job on the work performance and design principle of downward discharge hopper and pneumatic conveying system. The main work is as follows:(1) Based on the test of basic physical properties of different size, moisture content and different types of materials (7kinds of sand, one kind of coal and γ-Al2O3), we used five evaluation models to predict the flow ability of powder materials. The result showed that as the sand particle type changed from Geldart A to Geldart B, the flow function significantly increased, and further to Geldart D, stable flow ability of easy flow was obtained. In the range of external water0-10.6%, the flow ability of pulberized coal with400μm particle size decreased with the moisture content increasing. Jenike Flow Function evaluation method and CFI evaluation method were more pervasive effect.(2) The gravity discharge characteristics of sand, coal and γ-Al2O3form nine different size conical hoppers were investigated. These characteristics included the discharge stability and the effect of the packing head, outlet diameter, particle size and the hopper half-angle for gravity discharge. A serial of validation and comparation had also been made among typical discharge rate predication models. The study found that the mass flow had good process and repeat stability, there exited a particle size range for maximum discharge rate as the influence of interstitial pressure gradient and empty ring effect, the impact of hopper half-angle for discharge was restrained by the particle size and hopper outlet diameter, for Geldart B paticles, increase in pressure would increase the interstitial pressure gradient, and then reduced the discharge rate, Brown model and Beverloo model both had good predictive accuracy.(3) The discharge characteristics of coal form hoppers in the combination conditions of hopper different pressure and fluidizing gas were investigated. We found that the repeat stability was poor than conditions of gravity discharge, with the hopper different pressure increasing, the discharge rate increased linearly with the gas flow rate, the slope showed a decreasing trend with the gas flow rate increasing, and became stable at0.1～0.2m/s, when hopper different pressure was small (3000-6000Pa), the discharge flow mainly controlled by the hopper inflation, while it mainly controlled by hopper different pressure when hopper different pressure was lagrge (15000～20000Pa).(4) The pneumatic conveying system design was summarized. The pressure drop characteristics of Geldart B pulverized coal with wide particle size distribution were obtained. Based on the energy model, the conditional extremum method was adopted to obtain the optimal pipe diameter and conveying gas velocity, which was validated by experiments.