Please give the possible causes of increased pressure drop in middle and lower catalyst beds in VGO Hydrotreater main reactor. What solutions could be implemented to prevent pressure drop events?
Answers
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08/07/2013
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Saleh Daryabari, Senior Process Engineer of RCD and RFCC, Arak Refinery, daryabari@gmail.com
As mentioned in previous comments the pressure drop increase may have several causes. If you do not have plugging in the reactor, my conclusion for your case is: in middle and lower catalyst beds you have higher temperature (due to exothermic reactions) and lower H2 partial pressure (due H2 consumption in upper bed and more vapor products), so chance for coke formation is higher. You should optimize temperature profile in the reactor and minimize coke precursor in the feed to prevent accelerated coke formation.
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02/04/2013
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Keng Chung, Well Resources Inc., kengchung@hotmail.com
You would expect that to certain extent, due to exothermic reactions and more vapor products (check reactions and flash calculations along the bed). However, if you have excessive pressure drop that is non reversible (i.e., independent of reaction parameters), then you have a bed plugging problem. You have to do a few tests to nail down the causes.
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02/04/2013
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Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
As mentioned in previous comment, there are several potential causes---depending in part on the performance capabilities of the VGO Hydrotreater Unit and the amount of entrainment allowed in upstream processing units [CDU+VDU and Coker] and crude slate.
Each refinery situation is different---so really need to have refining / hydroprocessing specialist experts make an assessment.
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02/04/2013
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keith bowers, B and B Consulting, kebowers47@gmail.com
The pressure drop increase may have several causes. The most likely are:
a) asphaltene precipitation as Watson K factor increases down the reactor.
b) Metals deposition as de-metalization reactions occurs.
The above presume the top beds incorporate means to remove fine solids entrained in the feed.
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