Energy-saving methyl acetate production process method

Abstract

The invention discloses an energy-saving methyl acetate production process method, which comprises the following steps: carrying out reactive distillation on methanol and an acetic acid raw material solution through a reactive distillation tower, sequentially purifying through a first refining tower and a second refining tower, extracting refined methyl acetate from tower kettles of the first refining tower and the second refining tower, mixing, and extracting as a product. And returning the methyl acetate methanol solution at the tower top to the reactive distillation tower. The production amount of the methyl acetate product is increased through pressurization, and the amount of circulating methyl acetate is reduced, so that the steam consumption is reduced. Compared with an existing device, the energy consumption can be reduced by 10%-30%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical environmental protection, and in particular relates to a production process device and method for methyl acetate. Background Art

[0002] Methyl acetate is an important chemical raw material and organic solvent. The production process of methyl acetate uses acetic acid and methanol as raw materials, and finally obtains high-purity methyl acetate products through reaction and distillation separation. At present, in the distillation and separation process of methyl acetate, due to the azeotropic reaction of methyl acetate and methanol, a large amount of steam will be consumed. The energy consumption of the distillation process has a great impact on the production cost of methyl acetate, and there is still room for improvement in energy saving and recovery. Summary of the invention

[0003] Purpose of the invention: In view of the above existing problems and shortcomings, the purpose of the present invention is to provide an energy-saving methyl acetate production process.

[0004] Technical solution: In order to solve the above technical problems, the present invention adopts the following technical solution: an energy-saving methyl acetate production process method, comprising a reaction distillation tower, a first refining tower, a second refining tower and a recovery tower, wherein the bottoms of the reaction distillation tower, the first refining tower, the second refining tower and the recovery tower are respectively provided with a first reboiler, a second reboiler, a third reboiler and a fourth reboiler, and the production process of methyl acetate comprises the following steps: S1, using methanol and acetic acid as raw material liquid, feeding them from the middle and upper section of the reaction distillation tower to undergo esterification reaction, the top temperature of the reaction distillation tower is 50-60°C, the bottom temperature is 90-100°C, and the tower is operated at normal pressure; the gas phase reaction product of the reaction distillation tower is taken out from the top of the tower, cooled, partly refluxed to the reaction distillation tower, and the rest is sent to the first refining tower; S2, the light component reaction product sent to the first refining tower is subjected to primary distillation purification, the operating pressure in the first refining tower is 0.5-0.6MPaG, the tower top temperature is 110-115°C, the gas phase of the first purified component at the top of the tower is cooled by heat exchange in the first reboiler, part of it is refluxed to the first refining tower, and the rest is sent to the second refining tower; S3, the primary purified product sent to the second refining tower is subjected to secondary distillation purification, the operating pressure in the second refining tower is 0.8-0.9MPaG, the tower top temperature is 125-130°C, the gas phase secondary purified product at the top of the tower is cooled by the fourth reboiler, part of it is refluxed to the second refining tower, and the rest is sent to the reactive distillation tower; S4, extract part of the liquid reaction product from the bottom of the reaction distillation tower, part of it is refluxed to the reaction distillation tower, and the rest is sent to the recovery tower, and a mixed light component of methanol and water is obtained at the top of the recovery tower. After condensation, part of the mixed light component is refluxed to the recovery tower, and the rest is sent to the reaction distillation tower as a reaction raw material; the wastewater extracted from the bottom of the recovery tower is sent to a sewage treatment device; the top temperature of the recovery tower is 60-70°C, and the bottom temperature is 100-110°C; The first reboiler, the second reboiler, the third reboiler and the fourth reboiler provide heat to the bottom liquid of each tower to boil and vaporize it, and the vaporized material reacts with the material flowing down from the upper part of the tower to separate the materials while the materials react. Reaction products are respectively taken out from the bottom of the first refining tower and the bottom of the second refining tower to obtain methyl acetate products with different concentrations.

[0005] Preferably, the reflux ratio at the top of the reactive distillation tower, the first refining tower, the second refining tower and the recovery tower is in the range of (0.5, 1).

[0006] Preferably, the reflux ratio of the bottom of the first refining tower is (0.5, 1), and the reflux ratio of the bottom of the second refining tower is (0.5, 1).

[0007] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) By adding a pressurized distillation tower and adjusting the operating parameters of each tower, energy recovery can be achieved, thereby reducing steam consumption. Although the equipment investment will increase, the operating cost will be reduced and the investment cost can be recovered within one year.

[0008] (2) Refined methyl acetate is extracted from the first refining tower and the second refining tower, and then mixed and extracted as the product. The methyl acetate methanol solution at the top of the tower is returned to the reactive distillation tower. By increasing the pressure, the extraction of methyl acetate products is increased, the amount of circulating methyl acetate is reduced, and thus the steam consumption is reduced. Compared with the existing device, the energy consumption can be reduced by 10%-30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The figure is a schematic diagram of the structure of the energy-type methyl acetate production process device of the present invention.

[0010] Among them, there are a reactive distillation tower 1, a first refining tower 2, a second refining tower 3, a recovery tower 4, a condenser 5, a first reboiler 6, a second reboiler 7, a third reboiler 8, and a fourth reboiler 9. DETAILED DESCRIPTION

[0011] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0012] like Figure 1 As shown, the energy-saving methyl acetate production process of the present invention has the following specific production process: raw materials methanol and methyl acetate enter from the middle and upper part of the reaction distillation tower, and the top gas is condensed by the condenser, and a part of it is refluxed, and a part of it is sent to the first refining tower. The methanol solution in the bottom of the tower is sent to the recovery tower. The reaction distillation tower is operated at normal pressure, the top temperature is 50-60°C, and the bottom temperature is 90-100°C.

[0013] The operating pressure of the first refining tower is 0.5-0.6MPaG, the gas temperature at the top of the tower is 110-115℃, and the reflux ratio is 0.5-1. The gas at the top of the tower goes to the hot side of the reboiler of the reaction feed tower. After condensation, part of it is refluxed and part of it is sent to the second refining tower. The bottom of the tower is methyl acetate, which is sent out as a product after cooling.

[0014] The operating pressure of the second refining tower is 0.8-0.9MPaG, the gas phase temperature at the top of the tower is 125-130℃, and the reflux ratio is 0.5-1. The gas phase at the top of the tower is used to recover the hot side of the tower kettle reboiler. Part of the condensed methyl acetate methanol solution is refluxed, and part is sent to the reactive distillation tower. The tower kettle is methyl acetate, which is sent out as a product after cooling. The concentration of the product methyl acetate can reach 99-99.5%.

[0015] The recovery tower is operated at normal pressure, with a top temperature of 60-70°C and a bottom temperature of 100-110°C. After the gas at the top of the tower is condensed by the condenser, part of the methanol solution is refluxed and part is sent to the reactive distillation tower. The waste water from the bottom of the tower is sent to the sewage treatment device.

[0016] The present invention matches the appropriate heat recovery temperature by controlling the operating pressures of the reaction distillation tower, the first refining tower, the second refining tower and the recovery tower, requiring that the gas phase temperature at the top of the first refining tower is 10°C higher than the temperature of the reactor of the reaction distillation tower, and the gas phase temperature at the top of the second refining tower is 10°C higher than the temperature of the reactor of the recovery tower.

Claims

1. An energy-saving methyl acetate production process, characterized in that: The process comprises a reaction distillation tower, a first refining tower, a second refining tower and a recovery tower, wherein the bottoms of the reaction distillation tower, the first refining tower, the second refining tower and the recovery tower are respectively provided with a first reboiler, a second reboiler, a third reboiler and a fourth reboiler, and the production process of methyl acetate comprises the following steps: S1, using methanol and acetic acid as raw material liquid, feeding them from the middle and upper section of the reaction distillation tower to undergo esterification reaction, the top temperature of the reaction distillation tower is 50-60°C, the bottom temperature is 90-100°C, and the tower is operated at normal pressure; the gas phase reaction product of the reaction distillation tower is taken out from the top of the tower, cooled, partly refluxed to the reaction distillation tower, and the rest is sent to the first refining tower; S2, the light component reaction product sent to the first refining tower is subjected to primary distillation purification, the operating pressure in the first refining tower is 0.5-0.6MPaG, the tower top temperature is 110-115°C, the gas phase of the first purified component at the top of the tower is cooled by heat exchange in the first reboiler, part of it is refluxed to the first refining tower, and the rest is sent to the second refining tower; S3, the primary purified product sent to the second refining tower is subjected to secondary distillation purification, the operating pressure in the second refining tower is 0.8-0.9MPaG, the tower top temperature is 125-130°C, the gas phase secondary purified product at the top of the tower is cooled by the fourth reboiler, part of it is refluxed to the second refining tower, and the rest is sent to the reactive distillation tower; S4, extract part of the liquid reaction product from the bottom of the reaction distillation tower, part of it is refluxed to the reaction distillation tower, and the rest is sent to the recovery tower, and a mixed light component of methanol and water is obtained at the top of the recovery tower. After condensation, part of the mixed light component is refluxed to the recovery tower, and the rest is sent to the reaction distillation tower as a reaction raw material; the wastewater extracted from the bottom of the recovery tower is sent to a sewage treatment device; the top temperature of the recovery tower is 60-70°C, and the bottom temperature is 100-110°C; The first reboiler, the second reboiler, the third reboiler and the fourth reboiler provide heat to the bottom liquid of each tower to boil and vaporize it, and the vaporized material reacts with the material flowing down from the upper part of the tower to separate the materials while the materials react. Reaction products are respectively taken out from the bottom of the first refining tower and the bottom of the second refining tower to obtain methyl acetate products with different concentrations.

2. The energy-saving methyl acetate production process according to claim 1, characterized in that: The reflux ratio range of the top of the reactive distillation tower, the first refining tower, the second refining tower and the recovery tower is (0.5, 1).

3. The energy-saving methyl acetate production process according to claim 1, characterized in that: The reflux ratio of the bottom of the first refining tower is (0.5, 1), and the reflux ratio of the bottom of the second refining tower is (0.5, 1).

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