Issues related to the regeneration of sulfolane in aromatic extraction
Thread Content
After operating for a period of time, the solvent generates certain degradation products. These impurities not only cause blockages and corrosion in the equipment but also reduce the performance of the solvent, leading to fluctuations in product quality. So, generally, a small amount of solvent is taken out for on-line regeneration. The process I’m familiar with involves using a steam stripping tower to regenerate the solvent, with the stripping water being sent directly back to the tower where the solvent is separated from the aromatics. I would like to ask everyone for their opinions. What are the solvent degradation products? What causes this degradation? Why is the stripping water returned to the tower, and what is the purpose of this return? What is the principle behind using water to regenerate solvents? Thank you all:time:
The solvent decomposes to form polymers and salts. The low-pressure steam generated by the wash tower reboiler is injected into the regeneration tower to reduce the partial pressure of the solvent, allowing it to evaporate at a relatively low temperature.
Sulfolane is formed by the reaction of butadiene with sulfur dioxide under certain conditions to yield cyclobutenesulfone, which then reacts with hydrogen to produce sulfolane. The process can be expressed as follows: C4H6 + SO2 → C4H6SO2 + H2 → C4H8SO2. During production, sulfolane typically exhibits acidic properties, as it decomposes in the presence of oxygen at high temperatures, resulting in the formation of sulfur dioxide. To ensure optimal solubility and selectivity of sulfolane during production, the circulating solvent must maintain a certain water content, usually between 0.4–0.6%. However, local areas with higher water content can inevitably lead to the hydrolysis of sulfolane, producing highly corrosive sulfonic acids. It is caused by highly corrosive acids and weakly acidic polymers.
What should be returned to the solvent regeneration tower is stripping gas rather than stripping water, right? The regenerated solvent is recovered by using stripping gas to carry it into the solvent aromatic separation tower (which we call the recovery tower). Solvent that cannot volatilize at the bottom of the regeneration tower is considered waste solvent, and it must be discharged regularly.
Sulfolane has good thermal stability, with a decomposition temperature of 220°. At this temperature, sulfolane can decompose into sulfur dioxide and unsaturated, polymerizable substances, and the substances produced can give the product a brown color. As an additional note, sulfolane decomposes more rapidly in the presence of oxygen; the decomposition products include aldehydes, SO2, acidic polymers, and others. In the presence of oxygen, sulfolane can also undergo hydrolysis to produce corrosive sulfonic acids; these sulfonic acids react with ethanolamine to form salts, which affect the efficiency of heat exchange equipment and trays. Therefore, it is very important to ensure the airtightness of the system. The reason why the stripping water is returned to the tower is that it exists in the form of steam inside the tower, which can reduce the partial pressure of hydrocarbons at the bottom of the tower and thus make the separation of the solvent from the aromatics easier.
Thank you all for your help, I’ve learned something :)
Thank you all for your help, I’ve learned something :)
There is little need to regenerate sulfolane; its usage is already low, and its price is relatively low