After a UOP hydrotreating catalyst changeover an issue was observed in the product colour which became 15 instead of 30 while no particulates were present. I am seeking any explanation and solution.
Answers
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13/10/2020
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keith bowers, B and B Consulting, kebowers47@gmail.com
What is the root cause of colour drop? A high resolution mass spec to identify the particular molecular species will help identify the culprit--assuming you have a retain sample of the previous 30 colour product to compare against.
Leaking feed/effluent heat exchangers are often overlooked, but a common cause of colour and sulphur spec degradation.
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17/04/2020
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Robert Stults, Eurecat US, bstults@eurecat.com
If the catalyst was pre-activated, some technologies use lube oil for catalyst treatment or passivation, which can create color issues. For those units with product color sensitivity, Eurecat uses a activation process that minimizes any color bodies due to catalyst activation.
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14/04/2020
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Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
Some colour precursors are not removed while hydrotreating, mostly basic nitrogenous compounds or aryl alcohols. Also tertiary mercaptans of high molecular weight contribute to colour . Check for the intensity of hydrotreating. Also perform this test - UOP 793 - Colour Stability of Petroleum Distillates. This test can provide guidance on the nature of the product. No data is available for support.
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13/04/2020
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
If the crude quality changed or the feed end point got higher after the catalsyst change out that could explain things. Poor reactor loading with the new catalyst could allow channeling to occur, which effectively allows some of the feed to bypass part of the reactor. If there was a problem in the presulfiding step that could also cause catalyst performance problems leading to increased color. Last and least likely possibility is a problem with the quality of the catalyst received from UOP.
Without understanding how the ability to meet other specs such as product sulfur (and what those specs are), it is hard to get more specific.
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13/04/2020
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Steve Mayo, Eurecat US Inc, smayo@eurecat.com
Color issues are often difficult to troubleshoot because they can have many different causes. The manifestation of color can also vary substantially. Most color bodies are associated with aromatic and/or nitrogen ring species. The former is the most common type of color and often observed immediately after a catalyst change. In that case the cause is typically related to low H2 partial pressure at reactor outlet, low mass flux, or maldistribution. High initial catalyst activity exacerbates color as higher hydrogen consumption reduces outlet ppH2. In general, maximizing gas rate and hydrogen purity have the most positive effect. Both increasing and decreasing temperature can have a positive effect depending on the root cause of the issue. Decreasing temperature reduce catalytic hydrogen consumption as well as decreasing vaporization, at the risk of increasing sulfur. Increasing temperature can remove more nitrogen, if the cause of color is caused by nitrogen compounds. Color problems associated with a catalyst change tend to reduce over time as the catalyst is broken in.
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