Problems with the alkali solution used for desulfurization and alcohol removal in liquefied gas treatment
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Dear experts from Haichuan, do you have any systems that use low-sulfur gasoline for back-extraction of the alkali solution after its regeneration in liquefied gas alkaline washing desulfurization units? How is it working? What is the concentration of the alkaline solution? How often should the alkali be replaced? Where does the extracted oil end up? The total sulfur content in the gas after treatment by our liquefied gas alkali washing unit is always unstable, ranging from 30 at times to just over 10 at other times. We plan to install an alkali liquid back-extraction unit. Also, what is the concentration of the alkali solution you are using? Is it possible to separate disulfides? We use a 10% alkali solution, and we have never been able to separate disulfides. I hear that there is a method that uses coal to coagulate disulfides; if anyone knows anything about this, I would be very grateful.
We installed this device on our unit; the liquefied gas production was satisfactory, but the gasoline obtained after extraction could not be utilized as it contained about 2% sulfur. It was discontinued after a few days of use.
We have conducted some experiments; the extraction efficiency of disulfides from the regenerated alkaline solution using hydrogenated gasoline back-extraction is generally between 20-30%. As mentioned above, it is rare for the sulfur content in gasoline to reach 2%. In ordinary circulating gasoline. When the total sulfur content exceeds 0.6%, the extraction efficiency becomes very poor, and it is no longer possible to ensure an effective desulfurization effect using alkaline solutions. If the landlord requires that the total sulfur content in refined liquefied gas be no more than 30 ppm, the back-extraction process is unlikely to yield good results, unless the amount of sulfur-containing gasoline discharged is increased. Sulfur-containing gasoline needs to be washed to remove trace amounts of alkali, dehydrated, and then sent to a gasoline hydrogenation unit for further treatment.
The coagulation and separation of disulfides in regenerated alkali liquor using anthracite yields relatively limited results. We conducted experiments using anthracite as a filter media for filtration and adsorption; as a result, the level of disulfides in the regenerated alkaline solution was reduced from around 8000 ppm to around 7000 ppm. No liquid disulfides were observed to have been separated through coagulation, and the filter media became saturated very quickly.
The concentration of the alkali solution is generally around 18%; the alkali solution needs to be replaced every half month. A catalyst is added during replacement, and 2/3 of the existing alkali solution is replaced each time. Atmospheric direct-current gasoline is used for extraction; it comes out of the outlet of the atmospheric gasoline pump, and after extraction it returns to the inlet of the gasoline pump in the atmospheric unit. The results are excellent – the total sulfur content in the liquefied gas after treatment is generally below 20 ppm, and the amount of alkali solution required is also very low.
Haiyou on the 5th floor: Will the return of sulfur-containing gasoline to the atmospheric and vacuum distillation units increase the total sulfur content in the final gasoline product? Affects gasoline product quality? I’ve sent you an in-app message to ask for your advice. Thank you.
Hello, we are currently developing a technology for the separation of disulfides from the alkaline solution used in liquefied gas desulfurization and alkylation processes. The goal is to remove the emulsified oil and solids present in this circulating alkaline solution. However, we still have some questions, and we hope to get your answers: 1. To what extent is the emulsification problem caused by the sodium hydroxide solution used in these processes serious? Can neither the improved Melox process nor the fiber membrane process solve this issue? 2. The emulsification of disulfides in alkaline solutions may be due not only to the small density difference, but also to the synergistic effect of organic substances such as thiol compounds and catalysts present in the alkaline solution, which leads to enhanced emulsification of the disulfides Our experimental tests showed that when dimethyl disulfide is mixed with alkali solutions of different concentrations and shaken, the emulsification effect is not very good; after about 2 hours, the oil and water separate completely, and the higher the concentration of the alkali solution, the faster this separation occurs. 3. Disulfides have a certain solubility in alkaline solutions; if the emulsified form of disulfides is completely removed, will the dissolved disulfides affect the reuse of the alkaline solution? Is it still necessary to use the subsequent hydrogenated reformate for extraction, even after the emulsified disulfides have been completely removed?