L-valve之壓力擾動分析

Abstract

本實驗採用內徑 80mm 之壓克力圓管，製成水平長度為 380 mm 之 L-valve 。而下降管長度為 1760mm。 所使用之固體粒子為平均粒徑 193.5µm ( B 類 )，及用平均粒徑 936.5 µm ( D類 )，兩者密度均為 2635kg/m3的砂。以測量固體流量及壓力擾動訊號，來探討不同上升床速、通氣位置、通氣方向和不同成分比例混合對 L-valve 性能之影響。 實驗結果顯示，不同通氣方向對於固體流量的差異僅在較低通氣位置會有影響。若在高位置通氣時， L-valve 水平段所測得壓力在高通氣量時，壓力值會趨於定值 (12500 Pa)，此時已達 L-valve 水平段所能承受之最大壓力值，固體流量將不再增加。由混合不同比例的 B 類與 D 類粒子可以發現，對使用 D 類粒子而言，若增加 B 類粒子的比例可以降低 L-valve 所需之門檻通氣量，使 L-valve 能在較低通氣量時即可操作；對使用 B 類粒子而言，若增加 D 類粒子時，因為下降管會發生有渠道效應，因此在高通氣量時不易產生大型氣泡與駐塞，而固體流量會因為 D 類粒子的增加而減少。

The experimental apparatus consist of L-valve and downcomer, which is made by the transparent Plexiglas columns, 80 mm i.d. The B group sand particles with mean particle size 193.5µm was used in the experiment. The D group sand particles with mean particle size 936.5 µm was used in the experiment. The density of B and D group solid were both 2635kg/m3. The influence of the riser velocity, aeration tap location, aeration direction and components were determined by the measurement of solid flow rate and pressure fluctuations at various pressure probes. The results show that the solid flow rate of L-valve in different aeration direction had differences in lower aeration tap location only. The pressure of the horizontal section of L-valve was constant in high aeration. At the time, it had reached the largest pressure (12500 Pa) that the horizontal section of L-valve could support, and the solid flow rate would not increase any more. By mixing different proportion of B group and D group solid, we can discover that if we increase the proportion of B group for using D group solid, we could decrease the threshold aeration of L-valve, and the L-valve could be operated in lower aeration. Because of the channel effect, there would have the difficulty to occur large bubbles and slugging in the downcomer if we increase D group solid for using B group solid. But the solid flow rate will decrease because of increasing D group solid.