Optimization and innovation of process for preparing vinyl acetate by ethylene method

Abstract

The invention relates to the technical field of preparation of vinyl acetate by an ethylene method, and discloses an optimized and innovative process for preparation of vinyl acetate by an ethylene method, the optimization and innovation of the process mainly relate to a gas-liquid treatment process, and the process comprises the following steps: pumping out a kettle liquid part of an acetic acid evaporator to prevent accumulation of a reaction byproduct high-boiling residue; part of gas is extracted for refining to maintain the ethylene concentration while a small part of refined gas is discharged to a ground torch for burning in order to prevent inert gas accumulation, and the optimized procedures are innovatively applied to the production process, so that the production is continuously, stably and efficiently operated, and the operation cost is lower; and each path of tail gas is sent to a regenerative thermal oxidation furnace to be treated, so that pollution gas emission is reduced, and green and pollution-free production is realized. Through the optimized and innovative process, the production operation is simpler and more efficient, the production cost is lower, more energy-saving and environment-friendly effects are achieved, the purity of the produced product is higher, the produced product vinyl acetate meets the quality requirement of a vinyl acetate product and the quality requirement of a special-grade vinyl acetate product, and the lowest purity is larger than 99%.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing vinyl acetate by the ethylene method, and relates to the optimization and innovation of the process for preparing vinyl acetate by the ethylene method. Background Art

[0002] VAC is the abbreviation of vinyl acetate. Currently, the mainstream international production uses ethylene, acetic acid, and oxygen as basic raw materials and is produced by a synthesis method. Since vinyl acetate is one of the largest organic chemical products in the world in terms of production volume and is also one of the 50 most important organic chemical raw materials with large consumption in the world. Vinyl acetate can be used to produce a series of chemical fiber and chemical products such as adhesives, sizing agents, vinylon, films, vinyl copolymer resins, etc., and is widely used in fields such as textiles, machinery, construction, automobiles, light industry, food, cigarettes, furniture, printing, dyeing and printing, papermaking, aviation, water conservancy, agriculture, fishery, communication, biology, packaging, etc. At present, the market development and application potential of vinyl acetate are huge. The current production volume cannot meet the demand, and many production processes are relatively backward, with low production capacity, discontinuous production, high energy consumption and large pollution in production costs, and poor product quality. Therefore, the process for preparing vinyl acetate needs to be optimized and innovated. Summary of the Invention

[0003] The purpose of the present invention is to provide an optimized design and innovation for the process of preparing vinyl acetate by the ethylene method, so as to solve the problems of many existing production processes being relatively backward, having low production capacity, being discontinuous, having high energy consumption and large pollution in production costs, and having poor product quality as mentioned in the above background art.

[0004] To achieve the above purpose, the present invention provides the following optimized design and innovation:

[0005] Optimization and Innovation 1: To prevent the accumulation of high-boiling by-products in the reaction, a part is drawn from the bottom liquid of the acetic acid evaporator and sent to the rectification residue system to remove high-boiling substances. This makes it so that high-boiling substances do not accumulate during the production process, and the operation is simple, having a certain degree of innovation in this process.

[0006] Optimization and Innovation 2: By maintaining a constant ethylene concentration in the gas purification and holding system, and at the same time discharging a small part of the purified gas to the flare for burning to prevent the accumulation of inert gases, the production can run continuously, stably and efficiently, and the operating cost is relatively low.

[0007] Optimization and Innovation 3: After collecting the tail gas, it is sent to a regenerative thermal oxidizer for treatment by a tail gas blower, reducing the emission of polluting gases, lowering the energy consumption, and achieving high efficiency, economy and environmental protection in tail gas treatment.

[0008] Compared with the prior art, the beneficial effects of the present invention:

[0009] (1) The innovation of the process makes the production operation simpler, saves labor costs, enables the production to run efficiently, stably and for a long time, avoids the impact on production caused by the accumulation of high-boiling substances and inert gases, improves production efficiency, and the product quality is very high, with the minimum purity being greater than 99%.

[0010] (2) The tail gas is discharged after being treated by a regenerative thermal oxidizer, making the production process more environmentally friendly and saving energy, which conforms to the concept of green production. Specific implementation manners

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0013] Example 1: The rectified acetic acid with a flow rate of about 30 m 3 / h sent out by the bottom liquid pump of the first rectification tower is circulated together with the bottom liquid of the acetic acid evaporator through the acetic acid circulation pump. The circulating acetic acid enters the upper part of the evaporator after being heated by the acetic acid heater. The liquid level of the acetic acid evaporator is adjusted to 0.8 meters by the liquid level regulator. In addition, spray acetic acid is added to the top of the evaporator, and the flow rate is controlled at 2 - 5 m 3 / h. The circulating ethylene gas entering from the lower part of the acetic acid evaporator is in countercurrent contact with the heated circulating acetic acid in the upper part and the new acetic acid sprayed from the top in the packing of the acetic acid evaporator. The circulating gas is saturated with acetic acid and then comes out from the top. The steam amount of the acetic acid heater is adjusted to control the temperature of the gas at the outlet of the acetic acid evaporator at 95 - 120 °C. In addition, to prevent the accumulation of high-boiling by-products in the reaction, 3 m 3 / h is drawn out from the bottom liquid of the acetic acid evaporator and sent to the rectification residue system to remove the high-boiling substances in the circulating acetic acid.

[0014] Example 2: Since the concentration of the main by-products CO2 generated during the reaction and inert components such as N2 in the system continuously accumulates and increases, the ethylene concentration in the system decreases, affecting the smooth progress of the reaction. In order to keep the ethylene concentration in the system and the CO2 concentration in the circulating gas constant, part of the gas needs to be drawn out for purification to remove part of the CO2. The purified gas is returned for synthesis use. At the same time, in order to prevent the accumulation of inert gases, a small part of the purified gas is discharged to the ground flare for burning.

[0015] Example 3: After the synthesis system operates normally, the ethylene seal gas of the circulating gas compressor, the tail gas of the third rectification tower, the tail gas of the VAC exhaust condenser, and the tail gas of the low-boiling liquid tank are respectively collected into the tail gas buffer tank, and then sent to the regenerative thermal oxidizer for treatment through the tail gas blower.

[0016] It should be noted that:

[0017] (1) In the process description, the abbreviation VAC represents the product vinyl acetate, HAC represents acetic acid, and Ald represents aldehydes, including acetaldehyde, etc.

[0018] (2) Vinyl acetate is also known as vinyl acetate ester. These are different names for the same substance. At the same time, it has two English abbreviations, including VAC and VAM.

[0019] (3) Whether it is a liquid or a gas, some components accumulate due to reasons such as difficulty in evaporation or reaction. The accumulation of these components will affect normal production. Therefore, by removing part of the liquid or gas or through refining methods, the accumulation of these components is reduced, enabling the production to proceed efficiently and orderly. This process operation has a relatively low cost and is applied for the first time in this process.

[0020] (4) The regenerative thermal oxidizer, also known as RTO, is an efficient, economical and environmentally friendly tail gas treatment method and is one of the most widely accepted air pollution control technologies in the industry today. The regenerative thermal oxidizer uses the ceramic bed heated in the previous oxidation cycle to preheat the input gas, partially oxidize it, and the preheated gas enters the combustion chamber for combustion to generate gas that is pollution-free to the air.

[0021] The above shows and describes the basic principles, main features and advantages of the present invention. Technical staff in this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

[0022] The orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is only a simplified description for facilitating the description of the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the protected content of the present invention.

[0023] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. It relates to the optimization and innovation of the process for preparing vinyl acetate by the ethylene method, characterized in that Adopt an optimized and innovative gas-liquid treatment process to achieve stable and continuous production, with higher product purity, and achieve the production goal of being green and pollution-free.

2. According to the optimized and innovative design of the process described in claim 1, to prevent the accumulation of high-boiling by-products in the reaction, part of the liquid from the bottom of the acetic acid evaporator is withdrawn to the rectification residue system to remove high-boiling substances, which makes the high-boiling substances not accumulate during the production process, and the operation is simple, the production cost is lower, and the production runs continuously and stably.

3. According to the optimized and innovative design of the process described in claim 1, by keeping the ethylene concentration constant in the gas purification and holding system, and discharging a small part of the purified gas to the flare to prevent the accumulation of inert gases, the production runs continuously, stably and efficiently, and the operating cost is relatively low.

4. According to the optimized and innovative design of the process described in claim 1, after the synthesis system operates normally, the tail gas generated by various devices is finally sent to the regenerative thermal oxidizer for treatment by the tail gas blower, thereby reducing the emission of polluting gases, lowering the energy consumption, being more environmentally friendly and green, and achieving the high efficiency and economy of tail gas treatment.