Why is sulfolane not prone to decomposition when operated under negative pressure?
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This post was last edited by sdwfsgyykai on 2019-9-13 07:50. I read an article earlier stating that the decomposition temperature of sulfolane is 220°C and its boiling point is 280°C. I’m wondering whether, when operating under positive pressure, it would be possible to not keep the temperature at 220°C or even lower it to 160°C Why is it operated under negative pressure? If the pressure is reduced, will its decomposition temperature change? I only know that its boiling point changes
You mean the recovery tower and the solvent regeneration tower, right? Although the decomposition temperature of sulfolane stated in the data is 220°C, this refers to the temperature at which rapid decomposition occurs significantly. In fact, during the continuous operation of the device, a small amount of decomposition of the sulfolane solvent occurs at around 170°C, and the decomposition loss increases as the temperature rises. Therefore, in the sulfolane extraction process, the bottom temperatures of the recovery tower and the solvent regeneration tower are typically controlled at around 170°C, with a maximum not exceeding 170°C; accordingly, the operating condition for the top pressure is negative pressure.
Negative pressure operation is used to lower the boiling point and thus reduce the operating temperature; the decomposition temperature, however, remains unchanged. Generally, the temperature should not exceed 180, and the temperature of the reboiling steam also needs to be strictly controlled. If the steam temperature is too high, local overheating can occur – the apparent temperature may not exceed 180, but the actual local temperature can still be above 180, posing a risk of degradation~
The decomposition temperature of sulfolane is 220, while the safe operating temperature is below 180; therefore, during normal operation, the temperature at the bottom of the tower is generally kept between 168 and 172. To ensure that the aromatic compounds dissolved in sulfolane can be completely vaporized at the top of the tower, negative pressure is used to lower the boiling points of these aromatic compounds and water, thereby maintaining acceptable levels of water and aromatic compounds in the sulfolane at the bottom of the tower under normal operating conditions
If it is at positive pressure, it is not possible to separate the aromatics from the solvent at low temperatures; separation is possible only when the temperature is around 174 degrees under negative pressure. Since it is at positive pressure, the temperature must be higher than that, and the decomposition temperature should remain unchanged
Our operating temperature is between 172 and 178 degrees. The main purpose of negative pressure operation is to reduce the hydrocarbon partial pressure, so that the hydrocarbons in the solvent-rich mixture can be distilled and separated efficiently. In the long term, this helps to prevent decomposition due to excessively high solvent temperatures.
Oxygen content is very crucial. Under negative pressure conditions, systems are generally well-sealed, oxygen-free, and have relatively low temperatures.