On the operation of the stripping tower in gasoline hydrogenation units
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I have some questions regarding the operation of the stripping tower in gasoline hydrogenation units, and I’d like to discuss them with all of you here: 1. What is the purpose of the stripping tower? I think the purpose is simply to further remove hydrogen sulfide gas from the hydrogenated products. 2. Is it necessary to use steam? I’ve always thought that if the goal is merely to remove hydrogen sulfide, could other media that cannot be liquefied be considered? Such as dry gas, etc., to save steam. 3. Will the use of steam stripping cause water to be carried over in the product? I think using steam as the stripping gas source will cause severe water contamination in the product. Once there are residual hydrogen sulfide levels, it causes severe corrosion to the equipment. 4. Regarding the tower top reflux, is full reflux possible? I think that since the goal is to remove hydrogen sulfide, all the material in the top reflux tank of the stripping tower should be recycled. Taking the above points into consideration, I believe that for processes using steam stripping, the feed temperature should be as high as possible, so that a portion of the oil phase can vaporize immediately after feeding, thereby removing hydrogen sulfide. The operating pressure of the tower should also be reduced as much as possible. If other non-liquefiable gases are used for stripping, it doesn’t make much difference. Mainly, all the gas-phase load can be fully supplied from the bottom of the tower. I’m a beginner, so there might be mistakes in what I say; I hope all fellow sailors can be understanding. If anyone has different opinions, feel free to share them. Discuss with each other! Thank you!
Indeed, that is true； However, during steam stripping, if the feed temperature is too high, the negative load on the top reflux pump increases, requiring a larger pump model. In this case, with full reflux, water will inevitably enter the bottom of the tower due to the low top temperature.
I’m very curious to know if there are any companies that use non-condensable gas as a stripping medium
Regarding the restoration of the operation of the stripper in the gasoline hydrogenation unit: 1. What is the purpose of the stripper? I think the purpose is simply to further remove hydrogen sulfide gas from the hydrogenated products. Right. 2. Is it necessary to use steam? I’ve always thought that if the goal is merely to remove hydrogen sulfide, could other media that cannot be liquefied be considered? Such as dry gas, etc., to save steam. No, dry gas dissolving in gasoline results in an unsatisfactory vapor pressure of the gasoline. 3. Will using steam stripping cause water to be present in the product? I think using steam as the stripping gas source will cause severe water contamination in the product. Once there are residual hydrogen sulfide levels, it causes severe corrosion to the equipment. Relatively speaking, the product does not contain water, so it does not cause severe corrosion to the equipment; the corrosion rate is within acceptable limits. 4. Regarding the reflux at the top of the tower, is it possible to use full reflux? I think that since the goal is to remove hydrogen sulfide, all the material in the top reflux tank of the stripping tower should be recycled. Generally, it is designed for full reflux; the feed temperature should be as high as possible. The material should be fed before cooling following the reaction, as it’s not possible to separate the recycled hydrogen ； The device design generally adopts heat exchange before entry!
H2S can be separated using dry gas stripping, but what about after that? How should the separated H2S be handled? Burn it along with the dry gas? Should it be vented together with dry gas and H2S? Isn’t it a waste?
1. The purpose of the gasoline hydrodesulfurization stripping tower is to strip out hydrogen sulfide, along with the hydrogen gas and unsaturated hydrocarbon gases present in the hydrogenated gasoline. A laboratory analysis can be conducted to compare the sulfur content of gasoline before and after stripping, thereby determining the extent to which the stripping tower is effective. 2. If dry gas is used, the result will be as the user above mentioned: it increases the content of unsaturated hydrocarbon compounds, and such gasoline will not resist combustion well; similarly, it leads to higher fuel consumption, which reduces the engine’s performance. 3. Our stripping tower is equipped with a bottom reboiler, using medium-pressure steam as the heat source. Steam does not come into direct contact with the oil to prevent water contamination, and the heat source is sufficient. 4. The tower top can be operated in full reflux mode; if the liquid level in the reflux tank is high, the oil can be drained to an underground tank through the bottom of the tank for recovery.
Reply 1# aattop: The feed temperature is too high; could the heavier components be carried to the top of the tower during distillation?
If the stripping process carries water, a reboiler can be considered; additionally, the feed temperature should not be too high
Question: If full reflux is possible at the tower top, can the liquid taken from the reflux drum be discharged together with the product at the tower bottom (mixed into the product)? . In this way, the liquid yield is still high to some extent;; will it affect the saturated vapor pressure?
The purpose of blowing steam is to reduce the oil and gas partial pressure at the bottom of the tower, which facilitates the separation of hydrogen sulfide. When using dry gas for stripping, the flash point of the product drops significantly, making it difficult to achieve acceptable standards. Using waste hydrogen for stripping increases the gas-phase load on the tower and is not economical.
The issue of reflux at the tower top: if full reflux occurs at the top of the tower, there is essentially no means to control the temperature there. The amount of reflux is determined by the liquid level in the reflux drum at the top, which makes it difficult to ensure the flash point of the product at the bottom of the tower.