Regarding hydrogen sulfide in recycled hydrogen.
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I’m talking about normal production times. After passing through the high-pressure amine absorption tower, it enters the compressor as quench hydrogen and mixed hydrogen; at this point, it contains a certain amount of hydrogen sulfide.
In our residue hydrogenation process, the sulfur content after desulfurization is 10PPM
This can be adjusted; we can control the concentration between 100 and 500 PPM
Cyclic sulfur dehydrogenation – in our case, it has persisted for a year or two due to problems with the amine-rich liquid pump; each time it stops, it lasts for half a month, and no issues seem to arise.
Our gasoline hydrogenation unit controls the hydrogen sulfide content to no more than 40 ppm, with evaluation based on product quality.
For general diesel hydrogenation or the hydroprocessing of heavy oils, catalyst manufacturers typically require a hydrogen sulfide level in the recycle hydrogen of over 500 PPM. In the case of gasoline hydrogenation, high levels of hydrogen sulfide in the recycle hydrogen can affect the test results related to gasoline quality; therefore, this level is usually kept below 50 PPM
In our facility, the hydrogen used in the diesel hydrodesulfurization process has a hydrogen sulfide content of 50–100 ppm
4000 ppm for diesel hydrogenation, below 50 for gasoline hydrogenation
There are no specific requirements for this; based on the experience of various refineries, diesel hydrogenation is kept within the range of 50–500 ppm, while gasoline hydrogenation is maintained between 10–20 ppm. These values are not absolute – as long as the level remains above 1 ppm over the long term, it is acceptable.
In diesel hydrogenation units, a certain level of sulfur content is required in the recycle hydrogen; if this level exceeds the limit, a lean liquid pump is used for desulfurization. However, the sulfur content requirement in gasoline hydrogenation units is strict.
The diesel hydrogenation process isn’t running, and our gasoline hydrogenation level is also below 10; this is adjusted based on the quality of the product!