Several questions regarding the purge distillation system
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The distillation column in our facility is of the floating valve type. We now want to use stripping steam for cleaning, but some people say there is a risk that the floating valves might be flipped over. I would like to ask whether there is a mechanism for controlling the movement of these valves, so that they can only move up and down and cannot be flipped over Also, I have a steam evacuator installed at the outlet of the liquid separation tank at the hydrogen circulation inlet; it is connected to the inlets of two new hydrogen compressors. What is the function of this evacuator? Some say it is to create negative pressure in the system, and argue that negative pressure is also a pressure level related to airtightness. There are also claims related to the compressor. Additionally, the lead seals on the manual valves before and after the two safety valves at the high-pressure end are different: one safety valve has its lead seal removed, while the other one has its lead seal intact. Is this correct? I hope an expert can provide an answer
1. Floating valves have limitations – their lift distance is fixed – but an excessive gas flow rate can also cause backflow in the tray. 2. Creating a negative pressure is generally not suitable for ensuring airtightness; it is used during nitrogen purging of the system. However, it is generally not necessary; just perform several more pressing and replacement operations. 3. The lead seals on the front and rear manual valves of the safety valve should be removed, while those on the double-line valve should remain in place. This post was last edited by chengkang on 2009-2-24 at 19:02
I haven’t heard of any cases where trays were overturned due to excessive steam during line cleaning; there’s no need to worry too much.
The floating valve cannot be blown over, as it is fixed to the tray and can only rise or fall. High pressure might blow over the tray, but the vacuum pump is certainly used to create a vacuum; its purpose is to remove air from the system and keep the oxygen level low enough
How are the tray plates fixed? On the images I found on Baidu, I saw holes at the edges of the trays; are they fixed using bolts?
The tray is fixed with bolts. The floating valve tray is fixed to the tray.
The evacuator is used during startup to carry out purging, so as to bring the oxygen content to an acceptable level and create conditions suitable for introducing hydrogen. During purging, it must be isolated from the compressor to prevent damage to the seals
The distillation tower is purged with steam, and this does not cause the floating valves to be displaced. The tower has a large diameter, and there are many floating valves on each tray; when steam enters the tower, both the pressure and the linear velocity decrease significantly, so the floating valves are not displaced.
As long as the tray clamps are secure, the tray cannot be blown over. Moreover, the floating valves on the tray, regardless of their design, can only move up and down, and they have stop flanges; under normal circumstances they cannot be blown off or get stuck. The owner is worrying needlessly!
Please have the thread owner take a look at the introductions to various tray types: Catalytic Cracking Technician Training Manual – Fractionation System Lecture Notes http://bbs.hcbbs.com/viewthread.php?tid=148742
Only the tray can be blown over; the floating valve cannot