What to do if the gasoline-hydrogenated blend has a high olefin content?
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In gasoline hydrogenation units, the olefin content in the mixed oil is high; the specified limit is no more than 26%, although in practice it can reach up to 28%. How should this be addressed? At the current cutting ratio, heavy gasoline accounts for 57%, and the reaction temperature has also increased significantly? Dear sea friends, is there any other way?
Return the hydrogenated gasoline to the mixed fuel tank to dilute the mixture, or add a line directly to the feed pipeline for dilution.
This post was last edited by qugd on 2018-6-25 at 15:35. It is advisable to analyze the composition of the olefins; if it consists of only single olefins, appropriate dilution followed by hydrogenation should pose no problems, but care must be taken to ensure that the temperature rise does not exceed limits； If the diene content is high, strict attention must be paid, as dienes tend to cause carbon deposition on the catalyst, leading to a decrease in its activity. It is best to separate the dienes (such as by extracting them). Or, a pre-hydrogenation reactor can be added before the main hydrogenation reactor to specifically treat certain components prone to carbon deposition. It is estimated that a certain proportion of the crude oil consists of coker gasoline products; these fractions have a high content of dienes, which can lead to the formation of gums and precipitates, thereby having an impact on hydrogenation catalysts.
After cutting, does a 57% content of heavy gasoline refer to the olefin content or the proportion of the fractions?
Fraction ratio. We perform light, medium, and heavy fractionation on the crude oil, with the fractionation ratios being 22:21:57.
After the feed oil enters, it first passes through the pre-hydrogenation reactor, where light sulfur is converted into heavy sulfur and dienes are hydrogenated and saturated.
There’s no problem with this ratio; your cutting temperature is likely only around 80-90°C. The sulfur content in heavy oil is relatively high, so the reaction temperature increases. You can switch to a catalyst with a better hydrogenation depth. Is the middle fraction among you used for desulfurization?
To reduce olefins, it is possible to increase the hydrogen-to-oil ratio and appropriately lower the reaction temperature
Process adjustment plan for excessive olefin content in refined gasoline. Recently, two batches of gasoline have shown an olefin content that exceeds the national standards (19). The process adjustment plans for the gasoline hydrogenation unit are as follows: 1. Brief introduction: The selective hydrogenation unit for gasoline utilizes Beijing Annejie’s catalytic ALG technology for selective hydrogenation and desulfurization of gasoline. The three hydrogenation reactors are used for the following processes: (1) R-101 for full-range pre-hydrogenation (selective removal of dienes from the feedstock, along with partial isomerization of olefins and conversion of light thiols)； (2) The R-102 hydrodesulfurization reactor (AGP series catalyst) is primarily used for selective hydrodesulfurization; this catalyst has a low degree of olefin saturation ； (3) The APT-21 catalyst in the R-103 hydrodesulfurization of alcohols exhibits excellent alcohol desulfurization capabilities without causing olefin saturation reactions ； 2. Adjustments due to high olefin content: Option 1: Increase the temperature at the inlet of the pre-reactor (currently 140°C) and the temperature at the outlet of the second reactor (currently 302°C). In recent days, the reaction temperature in the gasoline hydrogenation unit R-101 has increased by about 5°C compared to before, indicating an increase in the content of dienes (olefins) in the feed gasoline. Increasing the temperature of the pre-hydrogenation reaction appropriately facilitates the hydrogenation and saturation of olefins (current reactor inlet temperature: 140°C, outlet temperature: 150°C) ； The R-102 hydrodesulfurization reactor: Hydrodesulfurization is the target reaction; increasing the overall temperature rise in the reactor can promote the saturation of olefins (the current overall temperature rise is 47°C), but this results in a significant loss of gasoline octane number ； Plan 2 for pre-fractionation tower: Cut 15% of the light gasoline. While maintaining the existing operating parameters, temporarily modify part of the internal circulation in order to increase the depth of the hydrogenation reaction (hydrogenation saturation of olefins). This reduces the temperature rise in the second reactor; the inlet temperature of this reactor is increased along with the injection of quench hydrogen, thereby adjusting the reaction depth and reducing the load on the heater as well as the inlet temperature of the third reactor. The sulfur content can be kept under control, and mercaptans can be managed successfully (as confirmed by experiments conducted by Dr. Bo) ； Under these conditions of excessive olefin content, partially increasing the internal circulation in the short term can enhance the reaction depth. Option 3: Control the olefin content in the crude gasoline at the upstream stage.
I think it’s possible to blend them together; oils with a high olefin content can be mixed with oils having a low olefin content in certain proportions, and the blending ratio can be determined based on the feed rate of the facility.