LPG desulfurization
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How is dimethyl disulfide formed in coker liquefied gas? And how to remove it? We only have the desulfurization alcohol process.
Thiethers are not produced during liquefied gas desulfurization or in liquefied gas dewaxing units; they are formed through catalysis earlier in the process.
What is your content level? Are there any requirements for this parameter? Is the total sulfur level excessive after desulfurization?
The dialkyl sulfides present in liquefied gas before amine washing can be reduced by adjusting absorption stability, typically by lowering the C5+ content. After alkaline washing, the dithiethers in liquefied gas are mainly generated during the regeneration of the alkaline solution; they are drawn back into the liquefied gas. Improving the quality of alkaline solution regeneration is key.
The C5 content in the liquefied gas before desulfurization is kept quite low, sometimes almost absent; however, after desulfurization but before dewaxing, the dimethyl disulfide content in the liquefied gas is around 1000 mg/m3. What is the reason for this?
After desulfurization, the level of dimethyl disulfide is between 600 and 800 mg/m3, while after dewaxing, the total sulfur content in the refined hydrocarbons remains above 400 mg/m3.
1. What is the specific control value for C5+? ≯ 0.5%, or ≯ 0.1%? 2. How is dimethyl disulfide in liquefied gas determined qualitatively and quantitatively after amine washing? 3. If possible, conduct a quantitative analysis of the sulfur content in the liquefied gas before amine treatment and after amine treatment, and compare the levels of dimethyldisulfide. If the difference is significant, try using an amine solution. This situation is very rare, but it is possible. During the regeneration of the amine solution, in the presence of oxygen, some of the methanethiol removed by the amine is oxidized to dimethyl disulfide, and this compound then enters the liquefied gas after the amine solution is recycled.
The C5+ content that we control generally does not exceed 0.5%, and sometimes it is absent. Dimethyl disulfide was quantitatively analyzed. We analyzed and compared that both the desulfurized liquefied gas and the desulfurized alcoholized liquefied gas have high levels of dimethyl disulfide.
In fact, dimethyl disulfide cannot be reduced in the desulfurization and hydrodesulfurization processes. You can analyze the content of dimethyl disulfide in the raw materials; if it is also at a high level, then it is necessary to improve the precision of raw material sorting, or use a tower for separating light and heavy tetrahydrocarbons. If there’s no problem, then it’s an issue with the amine solution; let’s analyze it.
The raw materials are cut quite well. What is the normal concentration of dimethyl disulfide in the amine solution?
What is the acceptable normal level for the disulfide content in the amine solution?