Q & A

Welcome to ePTQ's Q&A: the technology Q&A for the refining, gas, biofuels and petrochemical processing industries. You can browse existing questions and answers by topic or date or carry out a freetext search.

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This face to face interactive event features experts from leading European refineries and technology providers; engineers have the chance to hear unparalleled knowledge through interactive discussions such as fishbowl panels, Q&A Panels and Poster Sessions. Learn more at: asktheexperts.wraconferences.com  


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Recent Questions
Date  Replies
06/02/2021 Q: We have recently commissioned a 0.74 MMTPA RFCCU with mainly reduced crude oil (85%) and coker gas oils (10-12 %) as feed. We are getting a very high benzene content (~ 2-3%) in our light cycle naphtha (LCN), leading to problems in the finished MS pool due to a benzene limit of 1%. The downstream naphtha hydrotreater unit is only able to desulfurize the LCN with no benzene saturation. What methods will control the formation of benzene in the reactor, by either a change in feed composition or the operating parameters?  
04/02/2021 Q: What is the mechanism for mercury desorption from crude oil pipelines during emergency shutdowns upstream? Does it effect the normal mercury concentration after resuming t operations?  
04/02/2021 Q: I work in a UOP licensed DHDS unit. It has one HP amine absorber to absorb H2S from recycle gas. At thr top of the column, a water wash facility with level tray is installed to wash lean amine from recycle gas. We are experiencing foaming. The water tray level quickly fills and goes to the next recycle gas knockout drum. Delta pressure of the column is also increasing and the level increases suddenly in the water tray even after isolating fresh water. The delta temperature between amine and process gas is 12oC. Drained liquid is milky in colour. Please suggest a remedy.

 
29/01/2021 Q: This is about a LPG Merox unit in our refinery. Since the content of RSH(mercaptan) in the feedstock has more than doubled, this makes it difficult to regenerate the caustic. The content of mercaptide and disulphide in regenerated caustic has greatly increased. Frequent replacement of caustic and increased air flow and temperature in the oxidizer doesn't solve the problem. How can we solve the problem if we can not change the feedstock?
 
26/01/2021 Q: Does high water and salts in crude oil feed cause high gum in kerosene oil?

 
Recently Answered Questions
Date  Replies
25/12/2020 Q: What should be the maintenance and inspection schedule for underground storage tanks for petroleum. (1)
13/12/2020 Q: In our DHDS plant (Axens licensor, revamped in January 2018 ) with both a hot high pressure separator and cold high pressure separator, we are facing several tube leaks(A179-CS tubes ) in our stripper feed/stripper bottom exchangers (life three years).Corrosion is mainly on the stripper feed side and corrosion is due to localised under-deposit corrosion on the OD side of tubes near the floating head tubesheet, probably due to carry over of water and salts from upstream separators. Our hot separator is operating at 40 ksc and 90 degC operating temperature against the design 100 degC. In the same plant we are facing severe choking issues in our stripper overhead fin fan coolers where a complete header box was found choked with deposits. Around 76 % of the foulant collected is iron, and ammonia is also present. Has anyone faced such issues? Is operating the hot seperator at lower temperature the cause ? Has anyone used Alloy 825 tubes for stripper feed /stripper bottom exchangers?

(6)
25/12/2020 Q: How to handle ethanol above ground storage tank drainage? (1)
19/09/2020 Q: We are operating an aromatic recovery unit producing benzene and toluene. The extraction section uses Sulfolane as solvent. The extract is stored in a charge day tank and is used for charging the benzene column. To remove olefins from the feed, there is a clay tower prior to the benzene column that operates at at inlet temp of 170 deg C and a pressure of 13 kg/cm2. There is an exchanger for heating the clay tower feed (tube side). We are observing a frequent issue of plugging in this exchanger. This leads us to shut down the fractionation section for almost a day every five months for cleaning/replacing the tube bundle. The olefin content in the light reformate feed varies between 5% and 7%. Is there any way this issue can be resolved? Is the olefinic content in the feed too high? The plugging material seems black in colour. Is there any method that can be used for identifying the fouling type? Is is it due to polymerisation of olefins? Any solution to avoid such frequent plugging in this exchanger? (10)
23/11/2020 Q: Our company has two serial desalters. Wash water at pH 7-7.5 level is injected, and brine of pH 6 is released. Not long ago, Brazilian crude(Lula) was mixed at about 30 percent, and the pH dropped to 4.5. The TAN value of Lula is low at 0.3 level. I cut naphtha and checked for organic acids, but this isn't a particularly large amount. Our chemical vendor gave the opinion that this was because there were a lot of salts crystallized in the crude oil. However, even after analyzing metal and ash, there was not much. We need to analyze the cause; does someone have similar experience? (4)
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