Study On Choking Phenomenon Of Downcomer In Tray Column

The downcomer directly influences the operating stability and efficiency of the tray. Some principal theory and experimental research have been developed on the vapor-liquid phase flow in the downcomer, and the downcomer entrance was not considered. When a large amount of liquid is set on the downcomer entrance, the entrance is choked. As a result, the liquid level on the tray ascends sharply and tray pressure drop increases rapidly, causing the tray column flood. The dissertation describes a series of experiments about choking phenomena on some downcomer s of vary width sub-commercial scale, and try to find out the discipline of liquid loading intensity and liquid head over the weir all the round. The experiment results show that:1. Under the condition of a single liquid phase, carried out researches to 12 rectangle downcomers of different size( width :60> 80 > 100mm, weir length: 600 > 500 ^ 400 > 300mm), the following concludes was obtained.I. Before the choking occurred, the amended correlation of the liquid headover the weir to liquid loading intensity is:II. After the choking was occurred, the liquid head over the weir is not proportion to the square of liquid loading intensity, but to over-square, which was not the ordinary pipe entrance flow.III. As the choking occurred, the impact to critical liquid loading intensity from the width(B) of downcomer is not symmetry to the length(A)., as shown below:2. Under the condition of a single liquid phase, carried out researches to 3 arced downcomers of different size(arc height :60, 80, 100mm,weir lengm:600mm)and find out that the discipline about liquid head over the weir to liquid loading intensity is nearly similar to that of rectangle downcomer. However, the critical liquid loading intensity of former is less than that of the latter. The predict expression at equivalentwidth condition of the latter is: ic = l.39EA0.1464(2B)0.6003,E = 0.7942 . (E is shrinkingcoefficiency)3. Under the condition of vapor-liquid phases flow, the experiments were carried out on 3 rectangle downcomers of different size(width :60, 80, 100mm,weir length: 600mm)and find out that pressure slowly ascend as the increase of liquid loading intensity before choking phenomena occurred and rapidly ascend after that. Another outcome of the experiment is that the wider the downcomer was, the later the choking occurred. The critical liquid loading intensity can be calculated by the correlation, and then times 0. 6.