工业级水平管粉煤气力输送的最小压降速度和稳定性

采用压缩空气作为输送介质,在工业级水平管(内径50 mm)上开展了粉煤密相气力输送实验研究。在实验获得最小压降速度基础上,通过电容层析成像系统观察到,随着表观气速降低而存在分层流、沙丘流、移动床流以及栓塞流4种流型。不同流型压力信号的概率密度分布和功率谱密度分析表明,压力信号的波动特征与流型紧密联系;由于流动形态的变化,存在由稳定输送过渡到不稳定输送的临界气速,且该速度小于最小压降速度。

Minimum pressure drop velocity and stability analysis in pneumatic conveying of pulverized coal in commercial-scale horizontal pipe

Dense-phase pneumatic conveying of pulverized coal was investigated in an commercial-scale horizontal pipe (50 mm I.D.) by using compressed air as carrier gas.Minimum pressure drop velocity was obtained from the Zenz-type phase diagram, which was influenced by solids mass flux significantly.Based on electrical capacitance tomography (ECT) system, the flow in the experimental range was classified into four regimes:stratified flow, dune flow, moving bed flow and slug flow.Using probability density function (PDF) and power spectral density (PSD) function to analyze the pressure signals of typical cases, pressure fluctuations were well correlated with flow patterns.The relative stability characteristics of different operating conditions showed that the critical velocity between stable and unstable conveying was smaller than minimum pressure drop velocity due to the transitions of flow patterns.