Questions regarding the pre-hydrogenation outlet pressure difference and temperature difference! I would like to ask for advice
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1. Normal production. The hydrogenation reaction takes place in the pre-hydrogenation reactor; impurities such as S, N, O, and Cl present in the hydrogen and oil react to form gases like H2S. I believe that this results in an increase in volume, which in turn leads to an increase in outlet pressure, so the outlet pressure is higher than the inlet pressure! If the catalyst cokes, the reaction decreases relatively, so the increase in outlet pressure is reduced as well, and thus the pressure difference becomes smaller! Is that the correct way to understand it? 2. The same principle applies to temperature differences: normally, the outlet temperature should increase! If the cat cokes, the reaction decreases and the temperature rise becomes smaller! Is that the correct way to understand it? So, if there is a decrease in outlet temperature (due to heat dissipation), does that indicate severe coking, or very low impurity content?
The hydrogenation unit consumes hydrogen, causing a temperature rise!
No, it’s clogged; there’s no smooth flow, so the pressure difference increases
To understand this in the simplest way possible: water flows from higher to lower levels. If the pressure at the outlet of the reactor increases (in other words, the outlet pressure is higher than the inlet pressure), can the reactants and hydrogen pass through the reactor? If coking occurs, the inlet pressure must be higher than the outlet pressure under normal conditions. When the reactor cokes or the processing volume increases, the pressure difference in the reactor rises (i.e., the resistance increases). The impurities present in naphtha are at the PPM level; by how much can the volume of the reaction products increase?
The first question is that, generally speaking, the pressure on the back side is lower than the inlet pressure; therefore, even in a case where the volume increases, there will still be a pressure drop, meaning the outlet pressure is lower than the inlet pressure. Otherwise, flow would not be possible on the back side. Changes in pressure difference can be caused not only by catalyst coking, but also by the catalyst being damaged as a result of exposure to high-water content feedstocks, or by the formation of ammonium salts in the pipelines of the downstream system, as well as by changes in the feed conditions and the conditions in the downstream section. The second issue is that the hydrogenation activity of the catalyst decreases after coking, but this understanding is not comprehensive enough, as changes in the feed composition and reaction temperature can also lead to changes in temperature rise. A temperature drop does not necessarily indicate severe coking or a low impurity content; it could also be due to a low outlet temperature of the inlet heater, resulting in incomplete reaction of the oil product in the reactor.
Pre-hydrogenation is a hydrogen-consuming reaction that uses hydrogen gas, so the system pressure definitely decreases, resulting in a pressure drop.