What are the reasons for the difference in pH values between the wash water from the recovery tower and the water in the stripping reflux tank of the aromatic hydrocarbon extraction water system?
Thread Content
This post was last edited by Green Lotus on 2019-3-2 at 10:56. I have a question that has been bothering me for a long time. Here’s what happened: last year, in March, I increased the feed load to its maximum designed value one day; as a result, the interface level in the extraction tower kept dropping, and the liquid level in the recovery tower also kept falling. Due to these large fluctuations in levels, I reduced the load again, and both the interface level and the liquid level returned to normal. However, two days later, the water from the wash towers of the recovery tower in the aromatic hydrocarbon extraction water system, the water from the wash towers used for washing the raffinate oil, and the water from the reflux tank of the stripping unit all suddenly became acidic (with a pH as low as 3), while the pH of the solvent remained normal (around pH 7). Prior to this, the pH of the water system was fine. System oxygen leakage has been ruled out, and the raw materials contain no chloride ions. The current corrective measure is to add monoethanolamine regularly, but the pH of the water system still drops after about 2 months, while the pH of the solvent remains normal. I would like to ask what causes the pH of only the water system to drop suddenly, while the pH of the solvent remains normal? Thank you so much
Could it be that the negative pressure is too low, or that the temperature in the regeneration tower is too high? If system oxygen leakage and the presence of chloride ions in the raw materials are ruled out, it seems there’s nothing that could make the system acidic
Consider chloride ions introduced due to internal leakage in the heat exchanger, or the oxidation of olefins in the raw materials, or the high-temperature degradation of cyclobutene
Secondly, reduce the temperature of the poor solvent entering the tower, strengthen solvent analysis, and prevent excessive oxygen from being introduced into the system when adding solvents
Thank you; the temperature of the regeneration tower isn’t high
The heat exchanger should have no leaks, and the water system is well-balanced； What do you mean by the oxidation of that raw material, olefin? Thank you
What solvent are you using? Has there been any change in the sulfur content of the product? We used sulfolane before; it decomposes under high temperatures or in the presence of oxygen, and water circulation causes the environment to become acidic
Thank you very much. We are using sulfolane; the sulfur content in the raw material is not high, and there is no oxygen leakage. No issues were detected even at high temperatures. After all, the water system became acidic suddenly after the load was increased, but the pH value of the solvent remained normal. I don’t quite understand why, if the solvent decomposes, only the water-based system becomes acidic while the pH of the solvent remains normal
Possible reason: Local overheating occurs after increasing the load, leading to solvent degradation
Thank you. Local high-temperature degradation is possible, but why is the pH value low in the water system, while the pH value of the solvent is fine?
Thank you, but why is the pH of the water system low, while the pH of the solvent is normal?