Regeneration method of solvent used for separating styrene through extractive distillation

Abstract

The invention discloses a regeneration method of a solvent used by separating styrene through extractive distillation. The regeneration method comprises the steps that: a hydrocarbon mixture containing styrene is introduced into the middle of an extractive distillation tower, an extractive distillation solvent is introduced into the upper part of the extractive distillation tower for extractive distillation, a rich solvent rich in the styrene is discharged from the bottom of the extractive distillation tower and enters a solvent recovery tower, one part of lean solvent flowing out from the solvent recovery tower returns to the extractive distillation tower, the other part of lean solvent is introduced into a heat exchange pipe of a falling film evaporator, the solvent and a low-boiling-point material are evaporated through decompression falling film evaporation to enter a solvent regeneration tower, high-boiling-point impurities are discharged from a bottom pipeline in a liquid state and a gas-phase regeneration solvent is discharged from a top pipeline in the solvent regeneration tower, the pressure in the heat exchange pipe of the falling film evaporator is 10-30kPa, and the temperature of the heat exchange pipe of the falling film evaporator is 120-145 DEG C. According to the regeneration method, the high-boiling-point impurities in the lean solvent can be effectively removed at lower temperature, the high-temperature polymerization of the styrene is prevented, and the operation period of a styrene extractive distillation separation device is prolonged.

Description

technical field [0001] The invention relates to a method for regenerating a solvent used for extracting, rectifying and separating hydrocarbon products, in particular to a method for regenerating a solvent used for extracting, rectifying and separating styrene. Background technique [0002] Extraction and extractive distillation are widely used to separate aromatics (benzene, toluene, xylenes), styrene and butadiene from hydrocarbon mixtures. It is very important to maintain the quality of the extraction solvent during the extraction process to improve the purity of the separated and recovered product, the recovery rate and the long-term stable operation of the device. [0003] The feasible way to separate styrene from unhydrogenated pyrolysis gasoline is to use extractive distillation. There are two technical keys to the extractive distillation process. One is the solvent. The performance of the solvent includes selectivity, boiling point, thermochemical stability, and the...

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Problems solved by technology

[0004] In the process of extraction or extractive distillation of aromatic hydrocarbons and styrene, the method commonly used to remove high-boiling impurities in solvents is to use vacuum distillation. The specific operation method is: pass the solvent and water vapor to be regenerated into a device Decompression evaporation regeneration is performed in a container with a plug-in reboiler. Since the plug-in reboiler is prone to fouling and affects the heating effect, once the fouling needs to be stopped and cleaned, it is not only troublesome, but also affects the long-term stable operation of the entire device.

Especially for heat-sensitive and easy-to-polymerize materials such as styrene, if the high-boiling-point polymer in the solvent cannot be continuously removed, it will force the entire extraction and distillation unit to fail to operate normally.

[0005] CN1077560C discloses a method for reclaiming styrene from pyrolysis gasoline by extractive distillation, which is characterized in that water is added to the extraction solvent, and its solvent regeneration method is the common vacuum distillation that adds water vapor. The influence of the pressure of the static liquid column at the bottom of the regeneration tower causes the temperature at the bottom of the regeneration tower to be high, and the heater is prone to fouling, which affects the regeneration ability of the solvent and the long-term operation of the device

This method is more suitable for removing oligomers in poor solvents, and the removal effect for high polymers and highly water-soluble impurities is relatively poor

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