Coking fractionation tower vent hole
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What is the structure of the rising vapor holes in a coking distillation tower? What is its purpose?
The vent holes you mentioned are probably the vent holes in the oil collection tank. Their function is to serve as channels for gas to pass through, and they also help with the distribution of gas. Their shape is usually square or circular, and the area of these openings typically accounts for 15-30% of the total area of the tower.
15-30% might be a bit low; it’s usually around 40%.
What is the opening rate of your tray? 20% is considered pretty high, right? As long as the gas collection area of the tank is larger than the opening area of the tray plates, there should be no issues. As for pressure drop, such gas lift pipes result in a pressure increase of only a few hundred pascals per hundred meters, so the increase is not significant. For some trays with a low open area, an open area of 15% for the oil collection tank is also sufficient.
That makes sense too. The area of the gas lift pipe generally needs to be larger than the opening ratio of the tray, to leave sufficient margin; this way, no changes will be necessary to the gas lift tray in the future!
If the rising gas area is too large, the liquid volume in the oil collection tank will decrease. With the same residence time, the height of the rising gas pipe will increase, causing the overall oil collection tank to become heavier; this results in material waste and wasted space, which is highly inefficient.