不同含水率褐煤粉的输送流动特性及稳定性

Flow Characteristics and Stability of Lignite Powder with Different Moistures in Pneumatic Conveying

在高压浓相输送实验台上利用氮气进行了褐煤粉输送实验,考察了褐煤粉含水率对输送压损特性、质量流量及稳定性的影响,采用小波分析理论对输送压损信号进行了分析,根据差压波动不同频率段的能量、波幅和方差等特征参数,并结合褐煤粉不同含水率下的输送特性及煤粉的表观形貌分析,进行系统输送稳定性判别.结果表明,随煤含水率增大,其输送压损和质量流量减小,输送稳定性明显下降,压损呈周期脉冲.含水率低于5.36%时,系统输送特性良好,含水率为5.36%~8.56%时,系统不稳定,含水率超过8.56%时,系统稳定性急剧下降,并经常堵塞.差压信息的小波分析结果显示,在不同含水率褐煤粉的输送过程中,当差压信号的能量、波幅和方差主要分布在低频段时,输送过程较稳定,当这些特征参数向高频段转移时,输送稳定性随之下降.

Pneumatic conveying experiments of lignite powder with various moisture contents using nitrogen were carried out with an experimental facility under high conveying pressure. The effects of moisture content on pressure drop, mass flow rate and stability were investigated. The wavelet theory was applied to analyze pressure drop signal of horizontal pipe. Fluctuation amplitude, energy and standard deviation of different frequency regions were extracted to distinguish the stability of conveying process with conveying characteristic and apparent morphology. Lignite powder mass flow rate and pressure drop decreases, conveying stability falls and pressure drop shows periodic fluctuation with the increase of moisture content. The transmission characteristic is good with moisture content below 5.36%, the instability appears when the moisture content between 5.36% and 8.56~A, when the moisture content is greater than 8.56%, the flow in the pipe becomes very difficult and blockage often happens, the system stability falls down sharply and there are not stable delivery conditions. In the conveying process of lignite powder with various moisture contents, the process is stable when fluctuation, energy and standard deviation mainly distribute in low frequency regions. As those of characteristic parameters transfer to high frequency regions, the flow becomes unstable.