煤粉外水含量对上出料式发送罐供料特性的影响

摘要

Experimental investigations on the discharge characteristics of pulverized coal with different external moisture content were carried out in a dense-phase pneumatic conveying facility of top discharge blow tank. The effects of external moisture content on solid discharge rate, solid loading ratio and discharge stability were investigated. The limit and the best values of external moisture content for Neimenggu lignite used in the experiments were obtained. Combined with flowability analysis of the pulverized coal, the discriminate methods of limit and the best external moisture content for discharge process were discussed. The results showed that for pulverized coal with original external moisture content of 3.3%, an obvious electrostatic discharge phenomenon could be observed near the wall of the top discharge blow tank and the riser inlet during the discharge process. When the pulverized coal external moisture content was increased to 10%, arching phenomenon would appear in the top discharge blow tank. The limit external moisture content for Neimenggu lignite was in the range of 8.7%—10%, and its best external moisture content was about 4% corresponding to the maximum solid discharge rate and solid loading ratio, and to the best discharge stability. When the external moisture content was 4%, equal to the best external moisture content obtained by discharge experiments, the flow function reached the maximum value, the cohesion reached the minimum value and the pulverized coal flowability became the best. When the external moisture content was increased from 8.7% to 10%, the pulverized coal flowability turned from the easy flow region to cohesive region and the flowability became worse. When the external moisture content was 10%, the pulverized coal was in the cohesive region which meant difficult to flow. Compared with discharge experiments, the flow function and cohesion obtained by the shear tests could be used as preliminary criterion to judging the limit and best values of external moisture content pulverized coal in industrial applications more conveniently.%在上出料式发送罐密相气力输送实验台上，研究了外水含量对煤粉供料质量流率、固气比以及供料稳定性的影响，获得了内蒙古褐煤的极限供料外水含量和最佳供料外水含量，并结合煤粉流动特性分析，探讨了煤粉极限供料外水含量和最佳供料外水含量的判别方法。结果表明：在初始外水含量为3.3%条件下，在上出料式发送罐壁面以及提升管入口处能够观察到明显的静电放电现象；当外水含量增加至10%时，发送罐内会出现煤粉结拱现象；实验所用内蒙古褐煤的极限供料外水含量在8.7%～10%之间，其最佳供料外水含量大约为4%，在最佳供料外水含量下煤粉供料质量流率和固气比均达到最大值，且供料稳定性最好；当外水含量为供料实验获得的最佳外水含量4%时，煤粉的流动函数达到最大值，同时黏附力达到最小值，煤粉的流动性也达到最佳。在外水含量由8.7%增加至10%的过程中，煤粉流动性由容易流动区域转为有黏性区域，流动性变差。当外水含量为10%时，煤粉处于有黏性区域，流动困难。与供料实验相比，通过剪切实验获得煤粉的流动函数和黏附力，可以作为工业应用中初步判别煤粉极限供料外水含量和最佳供料外水含量的便捷方法。