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26/05/2016
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Patrick Bullen, UOP, patrick.bullen@uop.com
As Ravi stated in his answer, there are many variables that affect the coking rate on the catalyst. One can adjust these variables to some extent, but typically are restrained by either the unit design or the feedstock used or the target product quality.
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19/05/2016
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Sampath Attuluri, Reliance Industries Limited-Jamnagar, sampath.attuluri@ril.com
As a temporary measure we tried decreasing PCE injection rate. Because of this, more acid sites are formed in the catalyst which will lead to more acid function leading to hydrocracking reactions. It worked ,Leading to less than 5% wt of coke on spent catalyst. Thanks for the replies
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19/05/2016
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
The activity of the acid sites is maintained by chloride injection. If the activity is too high, the ratio of hydrocracking to the other reactions will increase. C5+ yield will decrease and light ends will increase. Coke laydown will increase. Excessive chloride injection will over-activate the acid sites. So will excessive water in the feed.
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18/05/2016
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Sampath Attuluri, Reliance Industries Limited-Jamnagar, sampath.attuluri@ril.com
Ralph: In the general UOP manual it was asked to maintain a proper H2/HC ratio(WT%). We were maintaining at a ratio of 2.6, still the required KPI of Coke on spent catalyst is not achievable, Value going to higher range 5.5%..PCE is meant to maintain proper chloride content, reactivate the catalyst, in details how does this help in reducing the coke content on spent catalyst. Can you explain?
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17/05/2016
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Ravi Kiran Kandikatla, Process Engineer, ravikiran204@gmail.com
Various parameters like Recycle ratio, feed quality (% N, %P, Sulfur and FBP), Catalyst circulation rate, and catalyst chloride content contribute to coke laydown on catalyst. One should cross check all these parameters with design to identify the possible reasons for higher coke laydown.
To limit coke on catalyst, recycle ratio and cat circulation rate are to be increased. Sudden ingress of sulfur and Nitrogen, higher chloride levels on catalyst will also increase coke on catalyst.
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16/05/2016
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Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
To limit the coke content in catalyst , following precautions needs to be taken, FBP of feed naphtha to be controlled, presence of metals, high moisture content in recycle gas, prevent leak of seal oil into recycle gas stream.
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14/05/2016
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Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
You should 1) reduce recycle gas moisture content (trim water injection into Platformer feed if in service or increase NHT stripper base temperature if water injection not in service), 2) maximise H2/HCBN ratio (recycle gas flowrate), 3) increase average reactor pressure (raise product separator pressure controller set point), 4) reduce reactor severity (reduce reactor inlet temperatures) and 5) reduce final boiling point of Platformer feed (increase CDU internal reflux).
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14/05/2016
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Coke on catalyst is inevitable. Excessive hydrocracking results in excessive coke. Maintain the proper acidity of the catalyst by correct chloride injection.
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