A Low Energy Consumption and Low Loss Vinyl Chloride Distillation Process

Abstract

The invention discloses a low-energy consumption low-loss vinyl chloride rectifying technology. The technology comprises the steps that 1, two stages of condensation liquefying is performed on most crude vinyl chloride gas through circulating water and chilled water respectively, and liquid enters a first water separator to be pumped to the upper middle portion of a low boiling tower for feeding; 2, uncondensed gas enters a tail gas condenser for deep condensation, condensate enters a second water separator and self flows to the upper portion of the low boiling tower to be charged, and non-condensable gas is delivered to a tail gas treatment device; 3, the tower top gas of the low boiling tower returns to a conversion unit, and crude vinyl chloride liquid at the tower bottom enters a high boiling tower; 4, a vinyl chloride product is obtained on the top of the high boiling tower, and high boiling residues generated at the tower bottom is delivered to a residue treatment device. The technology has the advantages that due to the fact that oxygen in the light components is effectively removed by adopting two stages of condensation, the tower top gas of the lower boiling tower can be circulated to the front-end conversion unit to be directly reused, material circulation is reduced, and material and energy consumption is reduced; the amount of water entering a rectifying tower can be effectively decreased, and the self-polymerization degree of the vinyl chloride in the rectifying tower is reduced; the rectifying efficiency is improved, the yield is increased, and the huge economic and environment-friendly value is achieved.

Description

technical field [0001] The invention relates to a rectification process for vinyl chloride with low energy consumption and low loss, in particular to a rectification process for reducing energy consumption and loss of vinyl chloride and acetylene in the process of producing vinyl chloride by calcium carbide method. Background technique [0002] Vinyl chloride (referred to as VCM) is the raw material for the production of polyvinyl chloride (referred to as PVC), and is mass-produced due to the wide application of PVC materials. There are two main methods for producing vinyl chloride, ethylene oxychlorination method and acetylene method. The acetylene method is also called calcium carbide method. Domestic PVC manufacturers generally use calcium carbide method to produce vinyl chloride. The crude vinyl chloride gas obtained by the calcium carbide method often contains light and heavy impurities such as acetylene, acetaldehyde, nitrogen, oxygen, dichloroethylene, dichloroethane,...

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Problems solved by technology

[0004] Although this rectification process is the most widely used in domestic PVC production enterprises, there are some unreasonable problems that lead to high energy consumption, high loss of vinyl chloride and acetylene, etc.:

[0005] (1) The total condenser completely uses 5°C chilled water for condensation, which consumes a large amount of chilled water, which is not conducive to energy saving. As it rises, it increases, so less water is separated by the water separator, and more water enters the rectification tower, which intensifies the degree of self-polymerization of vinyl chloride in the tower;

[0006] (2) Condensing most of the vinyl chloride into a liquid in one device will cause more acetylene, inert gas and other gases entrained in the liquid, and participate in the low boiling tower-tail gas condenser-water separator-low boiling tower The amount of recycled vinyl chloride and other components also increases, increasing the production load and affecting product quality;

[0007] (3) Since the composition and temperature of the condensate of the tail gas condenser and the crude vinyl chloride liquid are different, they enter the low-boiling tower after mixing, which reduces the rectifying efficiency of the low-boiling tower and increases energy consumption;

[0008] (4) The tail gas discharged from the tail gas condenser contains acetylene and a large amount of vinyl chloride. Although some enterprises have adopted pressure swing adsorption or other methods for recovery, the recovery efficiency is low due to various conditions, and a lot of energy is wasted. , also makes a large amount of acetylene and vinyl chloride discharged into the atmosphere, which not only causes great economic losses to the enterprise, but also pollutes the environment

The above-mentioned first patent only improved the low-boiling column from the perspective of adjusting the reflux ratio, and failed to optimize the existing rectification process as a whole; the second patent used a completely different method to purify vinyl chloride monomer, However, during the operation process, the conditions are harsh, the energy consumption is high, the residence time is long, and the utilization rate of the equipment is low, so it is not suitable for industrialized continuous mass production.

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