Benzene contains some non-aromatic impurities
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Benzene is drawn off via the side line, and it always contains some trace amounts of non-aromatic impurities; overhead benzene is also withdrawn in large quantities continuously, yet this has not improved the situation. Moreover, the amount of benzene-containing wastewater is also higher than before. How should this be adjusted?
During the benzene extraction process, it is normal for the resulting benzene to contain small amounts of impurities. Since non-aromatic compounds are also in equilibrium with the extraction solvent, and an evaporation equilibrium exists during distillation as well, these trace impurities are inevitable. As long as the trace impurities present do not affect the product quality, that is sufficient. Is the increase in the amount of benzene-containing wastewater related to the solvent regeneration process?
However, these non-aromatic impurities affect benzene, preventing the purity from reaching 99.9%; moreover, the amount of benzene-containing wastewater is also higher than before. At present, the solvent regeneration tower has not been put into use
It is recommended to adjust the operation of the extraction towers No. 2 to ensure that the content of non-aromatic compounds in the mixed aromatics is within acceptable limits. With a large amount of benzene-containing wastewater, first, check for any leaks in the heat exchangers and water coolers; second, properly control the level in the recovery tank to prevent water from being carried along with the oil.
It generally still depends on the operation of the extraction distillation tower. The solvent ratio, the bottom temperature of the tower, and whether the temperature of the sensitivity plate are within normal ranges; these values can be increased slightly if necessary. When the water content is high, more drainage is needed from the extraction feed buffer tank; if there is also a benzene tower feed buffer tank, more drainage should be carried out there as well. The level levels of the solvent recovery column reflux tank, the extraction column reflux tank, and the benzene reflux tank must be maintained at normal levels.