VCM purification hydrochloric acid full-resolution device and process

Abstract

The invention relates to a VCM purification hydrochloric acid full-resolution device and process. The VCM purification hydrochloric acid full-resolution device comprises a concentrated hydrochloric acid resolution system and a dilute hydrochloric acid vacuum concentration system, wherein the concentrated hydrochloric acid resolution system comprises a two-way heat exchanger, a concentrated hydrochloric acid resolution tower, a first-stage hydrogen chloride cooler, a second-stage hydrogen chloride cooler and an acid mist separator which are in communication with each other in sequence, and thelower part of the two-way heat exchanger is in communication with a dilute acid intermediate tank through a dilute acid cooler; the dilute hydrochloric acid vacuum concentration system comprises a dilute hydrochloric acid concentration tower, a water vapor condenser, a waste water intermediate tank and a waste water cooler, the dilute acid intermediate tank is in communication with the dilute hydrochloric acid concentration tower, the bottom of the dilute hydrochloric acid concentration tower is in communication with the concentrated hydrochloric acid resolution tower, and the dilute hydrochloric acid concentration tower is connected with the water vapor condenser and the waste water intermediate tank sequentially, and the waste water intermediate tank is in communication with the dilute hydrochloric acid concentration tower and the waste water cooler. The VCM purification hydrochloric acid full-resolution device is free of waste liquid containing mercury-diluted calcium chloride, andhas the advantages of low failure rate, long-term continuous operation, short process flow, small occupied area and small investment and the like.

Description

technical field [0001] The invention belongs to the technical field of hydrochloric acid analysis, and in particular relates to a VCM purification hydrochloric acid full analysis device and process. Background technique [0002] As of December 2017, the total domestic production capacity of polyvinyl chloride is about 23 million tons per year, of which about 83% are based on calcium carbide raw material process routes, and the rest are ethylene-based devices. In the production device of the raw material route of the calcium carbide method, the hydrochloric acid recovered by VCM purification cannot be discharged due to mercury elements (mercuric chloride is a catalyst for conversion into VCM), so the hydrochloric acid recovered by VCM purification adopts hydrochloric acid analysis technology, recovery Hydrogen chloride recycling, in order to solve the problem of water balance, most hydrochloric acid analysis devices are divided into two parts: conventional analysis of concent...

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Problems solved by technology

[0003] (1) Due to the high process temperature of the calcium chloride dilute hydrochloric acid full analysis device (the temperature of the tower kettle is 120 ° C ~ 135 ° C), the steam pressure used by the reboiler is high (≧0.6MPa (G)), resulting in the failure rate of the device High, especially for graphite reboilers

[0004] (2) Due to the characteristics of high-concentration calcium chloride aqueous solution, it is easy to scale on the hole wall of the reboiler, resulting in a decrease in its heat transfer efficiency, and the acid content in the wastewater exceeds the standard; especially the dilute hydrochloric acid entering the system is composed of iron, zinc, etc. The chloride formed by metal ions has a flocculation effect on the calcium chloride solution, which gradually causes the calcium chloride solution to gradually scale in the reboiler tube side, first causing the acid content in the wastewater to exceed the standard, and finally causing the reboiler to fail to work normally; Therefore, in actual industrial operation, the service life of the reboiler is about 2 to 3 years, and it needs to be overhauled (return to the factory for re-drilling)

The typical method is that the calcium chloride deep analysis device replaces the calcium chloride in the system once a quarter, and replaces it about 4 times a year. The disadvantage of this is that the device must discharge mercury-containing dilute calcium chloride waste liquid, and the device cannot achieve real "zero emission

Moreover, the total amount of mercury-containing dilute calcium chloride waste liquid discharged annually is quite a lot. Taking a typical 300,000-ton PVC plant as an example, the annual discharge volume reaches 20-25 tons of mercury-containing dilute calcium chloride waste liquid. waste liquid requires high treatment costs

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