Method for recovering dichloroethane through two-stage vacuum rectification

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a method for recovering dichloroethane through two-stage vacuum rectification. The method comprises the following steps: a material from the bottom of a high-boiling tower is enabled to pass through the middle part of a first-section vacuum rectifying tower; when the first-section vacuum rectifying tower and a second-section vacuum rectifying tower are used at the same time, a material with the dichloroethane content of 25%-35% is extracted from the bottom of the first-section vacuum rectifying tower and fed into the middle of the second-section vacuum rectifying tower, and a material with the dichloroethane content of 10%-15% is extracted from the bottom of the second-section vacuum rectifying tower and is taken as a byproduct to be fed into a storage tank to be stored; dichloroethane products are extracted from the top of the first-section vacuum rectifying tower and the top of the second-section vacuum rectifying tower; and when only the first-section vacuum rectifying tower is used, a material with the dichloroethane content of 10-15% is extracted from the bottom of the first-section vacuum rectifying tower, the material is stored as a byproduct in a storage tank, and a dichloroethane product is extracted from the top of the first-section vacuum rectifying tower. The invention provides a method for recovering dichloroethane through two-stage vacuum rectification, which is not easy to coke.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for recovering dichloroethane through two-stage vacuum rectification. Background technique [0002] The bottom material of the high boiling tower of the ethylene method vinyl chloride plant and the bottom stripping tower of the quenching tower contains about 5% of heavy components and 95% of ethylene dichloride (EDC), and the ethylene dichloride can be further recovered by the vacuum tower. Heavy fractions are concentrated. Through vacuum rectification, 85% to 90% of heavy components and 10% to 15% of EDC are contained in the bottom material of the vacuum tower, and the bottom material is treated as waste liquid for incineration. [0003] The vacuum column operates under vacuum, and its operating conditions should be as mild as possible to avoid coking of heavy components in the reboiler at the bottom of the column. Some heavy components, especial...

AI Technical Summary

Problems solved by technology

If the concentration of heavy components in the bottom material is too high, the vacuum tower reboiler will coke, and some heavy components together with solids and iron will enter the EDC product, which will cause coking in the EDC cracking furnace evaporator and cracking furnace tubes, affecting the entire VCM unit stable operation of

[0004] The vacuum rectification of the existing ethylene-based vinyl chloride plant is one-stage vacuum rectification, and the operation is difficult to control due to the large difference between the composition of the feed and the composition of the bottom of the tower

In the actual operation process, the reboiler of the vacuum tower is often severely coked due to the high content of heavy components, and the maintenance cycle of the tower is extremely short, so it cannot operate stably, and more materials are sent to incineration, which has a great impact on environmental protection

Images