What is Downcomer clearance?
An early indication of flooding in a distillation column is loss of liquid level in the bottom of the column. • If the downcomer clearance—which means the distance between the bottom edge of the downcomer and the tray below—is too great, the downcomer becomes unsealed.
What is the purpose of Downcomers?
Downcomers are pipes leading from the top to the bottom of the boiler. Downcomers carry the water from steam drum to the bottom part of the boilers where it enters the distribution headers to be heated in the combustion zone.
What is Downcomer in evaporator?
Downcomers are tubes that start from the steam drum and supply water to the lowest points of the furnace walls and boiler banks. From: Steam Generation from Biomass, 2017.
What is the function of weir and Downcomer?
The gas flows through the holes, and the downcomer ensure the flow of the liquid down from one plate to the other. The weir is the element which retains a liquid quantity on the plate in order to ensure the contact between the two phases before flow into the next plate.
What is weeping in distillation column?
Weeping/Dumping This phenomenon is caused by low vapour flow. The pressure exerted by the vapour is insufficient to hold up the liquid on the tray. Therefore, liquid starts to leak through perforations. Excessive weeping will lead to dumping.
Why is circulation ratio kept over 6?
The value of circulation ratio varies from 6 to 30 in industrial boilers. Circulation ratio for utility high pressure boilers is between 6 to 9. Circulation ratio is higher side as the density difference between steam & water is high. Medium pressure industrial boilers adopted higher circulation ratio.
What is natural circulation evaporator?
Natural circulation in an evaporator is caused by the thermal difference between the heating medium and the liquid. The mixture of vapor and liquid merges from the tubes and enters the upper chamber from which it passes through a short connection into the vapor separator.
Which tray type is the cheapest and has the lowest pressure drop?
The tray pressure drop will depend on the detailed design of the tray, but in general, sieve trays give the lowest pressure drop, followed by valves, with bubble-caps giving the highest.
What is Seal pan in column?
Seal pan. The primary purpose of a seal pan in a distillation column is to prevent up-flowing vapour from bypassing through the downcomer. Overflowing liquid from the seal pan provides sealing for the tray downcomer.