A composite column apparatus and method for use in the extraction of acetone / methyl acetate / ethyl formate mixtures

Abstract

This invention discloses a composite tower apparatus and method for extracting a mixture of acetone, methyl acetate, and ethyl formate. The feed liquid enters from the bottom of the tower, while pure water enters from the top. The feed and water undergo countercurrent contact between several layers of sieve-packed composite tower plates. Gas enters from the bottom of the composite tower apparatus, and after passing through a gas distributor, forms a uniform gas flow within the tower, continuously impacting and agitating the liquid phase to enhance interphase mass transfer. After the extraction process is completed between the plates, the gas and liquid phases at the top of the tower are separated by a three-phase separator. The ester phase flows out from the top of the tower, yielding high-purity methyl acetate and ethyl formate, while the gas is discharged from the top. The aqueous phase flows out from the bottom of the tower after clarification in the lower clarification section. The extraction method described in this invention exhibits excellent hydrodynamic performance, with uniform gas-liquid phase distribution, which enhances the contact and mass transfer between the two phases, helps eliminate "dead zones" and channeling within the packing, and significantly improves the mass transfer efficiency of the extraction process.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification in the chemical industry, specifically relating to a composite tower device and method for the extraction of a mixture of acetone / methyl acetate / ethyl formate. Background Technology

[0002] Acetone is a representative low-boiling-point, fast-drying polar solvent. It has strong dissolving power and is also soluble in water. Besides being used as a solvent for coatings, varnishes, and nitrocellulose lacquer, it is also used as a solvent and paint remover in the manufacture of cellulose, cellulose acetate, and photographic film. Acetone can extract various vitamins and hormones and dewax petroleum. Acetone is also an important chemical raw material used in the manufacture of acetic anhydride, methyl methacrylate, bisphenol A, isopropyl acetone, and methyl isobutyl ketone. Methyl acetate is mainly used in the production of acetic anhydride, which is then used to prepare cellulose acetate, or as an acetylation agent in pharmaceuticals, dyes, fragrances, and organic synthesis. It is also used in the manufacture of artificial leather and fragrances, as an oil extractant, and as a standard substance and solvent for chromatographic analysis. Ethyl formate is used as a solvent for nitrocellulose and cellulose acetate, and as a bactericide, larvicidal agent, and fumigant in food, cigarettes, grains, and dried fruits. Ethyl formate is used as a flavoring agent to blend the aromas of peaches, bananas, and apples, and it can also be used as a flavoring agent in butter, brandy, and other products. It is also an intermediate in organic synthesis. In industrial production, a mixture of acetone, methyl acetate, and ethyl formate is produced. These three compounds have relatively close boiling points (acetone 56.1℃, methyl acetate 57.1℃, ethyl formate 54.4℃). Furthermore, acetone and methyl acetate form an azeotrope with an azeotropic composition of 57.9 mol% acetone. Conventional distillation methods are insufficient to separate the esters from the acetone in this mixture.

[0003] There are many methods for separating near-boiling point and azeotropic mixtures, and liquid-liquid extraction is a commonly used method. Liquid-liquid extraction is a separation and purification method that uses two immiscible (or partially miscible) liquids to transfer a component of a mixture from one liquid to the other. The processing capacity and efficiency of the extraction equipment are two important indicators for evaluating its performance. Pulse packed towers and pulse sieve plate towers are highly efficient but have low throughput, limiting their application. Patent 200410081600.1 discloses a production process and equipment for purifying wet-process phosphoric acid, in which the extraction process is carried out in a rotating vibrating sieve plate tower, which can reduce energy consumption and production costs. Patent 201610270076.5 provides a wet-process phosphoric acid extraction device that can form an impinging flow to shorten the reaction time and reduce extraction energy consumption. However, both of these devices suffer from mechanical vibration and wear, placing special requirements on mechanical strength and equipment safety, and also posing difficulties for large-scale design and maintenance.

[0004] No literature reports exist regarding the separation of acetone / methyl acetate / ethyl formate mixtures. Therefore, providing a separation device and method for acetone / methyl acetate / ethyl formate mixtures that has a large processing capacity, simple and safe structure, low cost, and is easy to manufacture and install is a problem worthy of research. Summary of the Invention

[0005] The purpose of this invention is to provide a separation apparatus and method for a mixture of acetone, methyl acetate, and ethyl formate.

[0006] A separation device for a mixture of acetone / methyl acetate / ethyl formate is a bubbling sieve plate packed composite extraction tower, comprising a tower body, a feed liquid inlet at the bottom, an ester phase liquid outlet and a pure water inlet at the top, a three-phase separator, a wire mesh demister, and an aqueous phase outlet at the bottom. A gas inlet is also located at the bottom of the tower, along with a gas distributor connected to the gas inlet within the tower, and a gas outlet is located at the top. Several through-flow sieve plates and a packing layer are arranged within the tower between the gas distributor and the pure water inlet.

[0007] When the feed liquid inlet and the gas inlet are the same, and a liquid distributor connected to it is installed inside the column, during extraction, the gas is first mixed with the feed liquid before entering the column, and then both are evenly introduced into the lower part of the extraction column through the liquid distributor via the same inlet. The liquid distributor can be a pipe-type liquid distributor.

[0008] It also includes several trays, which consist of a cross-flow sieve plate and a thin layer of packing material located below the cross-flow sieve plate with a layer height of 40 to 120 mm. The plate spacing is 200 to 400 mm. There are no downcomers, and the gas and liquid flow in countercurrent.

[0009] The diameter of the sieve holes in the flow-through sieve plate is 10-15 mm, and the opening rate is 35-50%.

[0010] The packing includes various bulk packings, structured packings, composite packings, mixed packings, etc. Of course, various high-efficiency packings are preferred, and different types of packings can also be mixed and packed in a specified manner and proportion.

[0011] Another object of the present invention is to provide a method for extracting a mixture of acetone / methyl acetate / ethyl formate. The method includes the following steps: Step ①: The feed liquid enters through feed inlet 12 of the bubbling sieve plate packed composite tower body 13, and pure water enters through pure water inlet 4 at the top of the tower. The feed and water undergo countercurrent contact between several layers of crossflow sieve plates 8 and packing 7 composite tower plates. Since methyl acetate and ethyl formate are both slightly soluble in water, an aqueous phase and an ester phase are formed. Acetone has a higher solubility in water, so a large amount of acetone is transferred to the aqueous phase, while the ester phase contains less acetone and water. Step 2: Gas enters from gas inlet 11 at the bottom of the tower, and after passing through gas distributor 9, it forms a uniform gas flow in the tower, continuously impacting and agitating the liquid phase to enhance interphase mass transfer. Step 3: After the extraction process is completed between the trays, the gas and liquid phases at the top of the column are clarified in the upper clarification section 5 and then separated by the three-phase separator 6. The ester phase flows out from the ester phase outlet 2 at the top of the column to obtain high-purity methyl acetate and ethyl formate. The gas passes through the wire mesh demister 3 and is discharged from the gas outlet 1 at the top of the column. The aqueous phase is clarified in the lower clarification section 14 and flows out from the aqueous phase outlet 10 at the bottom of the column to obtain an acetone aqueous solution.

[0012] According to another preferred embodiment of the present invention, in the separated acetone / ethyl formate / methyl acetate mixture, the molar fraction of acetone is 5%-25%, and the remainder is ethyl formate and methyl acetate, which can be in any proportion.

[0013] The gas mentioned in step ② can be air or an inert gas, such as nitrogen.

[0014] According to another preferred embodiment of the present invention, the gas velocity in the empty tower is 5 to 15 mm / s.

[0015] The beneficial effects of the present invention are as follows: 1. The extraction method of the bubble sieve plate packing composite tower of the present invention has the following advantages: During the rapid rise of the gas in the tower, on the one hand, it strongly impacts and agitates the liquid layer, and continuously breaks up the dispersed phase droplets and renews the surface, thereby strengthening the contact and mass transfer between the two phases and significantly improving the mass transfer efficiency of the extraction process; on the other hand, the rising impact of the gas drives the raw material liquid to overcome the surface tension and pass smoothly through the sieve holes and packing. At the same time, the gas agitation also helps to eliminate the "dead corners" and channels in the packing, thereby significantly increasing the processing capacity of the bubble sieve plate packing composite extraction tower.

[0016] 2. The composite tower tray of this invention, featuring a bubbling sieve plate and packing, exhibits excellent hydrodynamic performance and uniform gas-liquid phase distribution. The through-flow sieve plate acts as a liquid redistributor within the packing layer, uniformly distributing the liquid phase. The packing layer ensures uniform gas distribution, improving the distribution of the bubbling gas phase on the tray and preventing short-circuiting by concentrating the gas phase through the central sieve holes, thus enhancing the mass transfer effect of the bubbling layer. The packing layer essentially eliminates the entrainment problem between trays, resulting in excellent hydrodynamic performance and a small tray spacing. The composite tower tray eliminates the need for downcomers, increasing gas throughput and reducing tray pressure drop.

[0017] 3. The three-phase separator at the top of the extraction tower in this invention can effectively separate the gas phase, ester phase, and aqueous phase, thereby improving the mass transfer efficiency of the extraction tower. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the overall structure of a bubble sieve plate-packed composite extraction tower used for the extraction of a mixture of acetone, methyl acetate, and ethyl formate. Explanation of reference numerals in the attached diagram: 1 Gas outlet; 2 Ester phase outlet; 3 Wire mesh demister; 4 Pure water inlet; 5 Upper clarification section; 6 Three-phase separator; 7 Packing layer; 8 Through-flow sieve plate; 9 Gas distributor; 10 Aqueous phase outlet; 11 Gas inlet; 12 Raw material liquid inlet; 13 Tower body; 14 Lower clarification section. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] A composite tower device for the extraction of a mixture of acetone / methyl acetate / ethyl formate includes a tower body 13. The lower part of the tower body 13 has a feed liquid inlet 12 and a lower clarification section 14. The upper part of the tower body 13 has an upper clarification section 5, a three-phase separator 6, and an ester phase outlet 2. Below the ester phase outlet 2, a pure water inlet 4 is provided, and at the bottom of the tower body 13, an aqueous phase outlet 10 is provided. A gas inlet 11 is also provided at the lower part of the tower body 13, along with a gas distributor 9 connected to the gas inlet 11 and located within the tower. A gas outlet 1 is provided at the top of the tower body 13. A wire mesh demister 3 for capturing and recovering light phase droplets is installed within the tower between the ester phase outlet 2 and the gas outlet 1. Between the gas distributor 9 and the pure water inlet 4, several flow-through sieve plates 8 without downcomers and a packing layer 7 are provided within the tower.

[0021] When the raw material inlet 12 and the gas inlet 11 at the bottom of the tower body 13 are the same inlet, a liquid distributor connected to the raw material inlet 12 and the gas inlet 11 is provided inside the tower. During extraction, the gas is first mixed with the raw material before entering the tower body 13, and then they enter the lower part of the extraction tower evenly from the bottom of the tower body 13 through the liquid distributor through the same inlet. The liquid distributor is a pipe-type liquid distributor.

[0022] Example 1: A method for extracting a mixture of acetone / methyl acetate / ethyl formate, wherein the feed contains 10% acetone by molar fraction, Pall ring packing is used, and the through-flow sieve plate 8 has a sieve aperture diameter of 10 mm and an open area ratio of 48%. (See attached image) Figure 1 Taking the process as an example: the acetone / methyl acetate / ethyl formate mixture enters the extraction tower from the feed liquid inlet 12, and exits the extraction tower from the ester phase outlet 2 after extraction; pure water enters the extraction tower from the pure water inlet 4, and after countercurrent contact and mass transfer with the acetone / methyl acetate / ethyl formate mixture, it exits the extraction tower from the aqueous phase outlet 10. The molar ratio of water to the acetone / methyl acetate / ethyl formate mixture is 3:1. Nitrogen gas used for stirring enters from the gas inlet 11 and exits the extraction tower from the gas outlet 1. The nitrogen gas velocity in the empty tower is 11 mm / s. Calculations show that the purity of the esters in the ester phase reaches 90.1%.

[0023] Example 2: A method for extracting a mixture of acetone / methyl acetate / ethyl formate, wherein the feed contains 5% acetone by molar fraction, Raschig ring packing is used, and the through-flow sieve plate 8 has a sieve aperture diameter of 12 mm and an open area ratio of 45%. (See attached image) Figure 1 Taking the process as an example: the acetone / methyl acetate / ethyl formate mixture enters the extraction tower from the feed liquid inlet 12, and exits the extraction tower from the ester phase outlet 2 after extraction; pure water enters the extraction tower from the pure water inlet 4, and after countercurrent contact and mass transfer with the acetone / methyl acetate / ethyl formate mixture, exits the extraction tower from the aqueous phase outlet 10. The molar ratio of water to the acetone / methyl acetate / ethyl formate mixture is 2:1. Nitrogen gas used for stirring enters from the gas inlet 11 and exits the extraction tower from the gas outlet 1. The nitrogen gas velocity in the empty tower is 5 mm / s. Calculations show that the purity of the esters in the ester phase reaches 94.3%.

[0024] Example 3: A method for extracting a mixture of acetone / methyl acetate / ethyl formate, wherein the acetone molar fraction in the feed is 15%, the packing material is corrugated structured packing, the through-flow sieve plate 8 has a sieve aperture diameter of 15 mm and an open area ratio of 50%. (Appendix) Figure 1 Taking the process as an example: the acetone / methyl acetate / ethyl formate mixture enters the extraction tower through feed liquid inlet 12, and exits the extraction tower from ester phase outlet 2 after extraction; pure water enters the extraction tower through pure water inlet 4, and after countercurrent contact and mass transfer with the acetone / methyl acetate / ethyl formate mixture, exits the extraction tower from aqueous phase outlet 10. The molar ratio of water to the acetone / methyl acetate / ethyl formate mixture is 4:1. Air used for agitation enters through gas inlet 11 and exits the extraction tower from gas outlet 1. The nitrogen air velocity is 15 mm / s. Calculations show that the ester purity in the ester phase reaches 92.2%.

[0025] Example 4: A method for extracting a mixture of acetone / methyl acetate / ethyl formate, wherein the feed contains 20% acetone by molar fraction, Pall ring packing is used, and the through-flow sieve plate 8 has a sieve aperture diameter of 13 mm and an open area ratio of 35%. (See attached image) Figure 1 Taking the process as an example: the acetone / methyl acetate / ethyl formate mixture enters the extraction tower through feed liquid inlet 12, and exits the extraction tower from ester phase outlet 2 after extraction; pure water enters the extraction tower through pure water inlet 4, and after countercurrent contact and mass transfer with the acetone / methyl acetate / ethyl formate mixture, exits the extraction tower from aqueous phase outlet 10. The molar ratio of water to the acetone / methyl acetate / ethyl formate mixture is 5:1. Air used for agitation enters through gas inlet 11 and exits the extraction tower from gas outlet 1. The nitrogen air velocity is 13 mm / s. Calculations show that the ester purity in the ester phase reaches 91.1%.

[0026] Example 5: A method for extracting a mixture of acetone / methyl acetate / ethyl formate, wherein the acetone molar fraction in the feed is 25%, the packing material is corrugated structured packing, the through-flow sieve plate 8 has a sieve aperture diameter of 9 mm and an open area ratio of 40%. (Appendix) Figure 1 Taking the process as an example: the acetone / methyl acetate / ethyl formate mixture enters the extraction tower from the feed liquid inlet 12, and exits the extraction tower from the ester phase outlet 2 after extraction; pure water enters the extraction tower from the pure water inlet 4, and after countercurrent contact and mass transfer with the acetone / methyl acetate / ethyl formate mixture, exits the extraction tower from the aqueous phase outlet 10. The molar ratio of water to the acetone / methyl acetate / ethyl formate mixture is 5:1. Air used for agitation enters from the gas inlet 11 and exits the extraction tower from the gas outlet 1. The nitrogen air velocity is 9 mm / s. Calculations show that the ester purity in the ester phase reaches 90.4%.

Claims

1. A composite column apparatus for use in the extraction of an acetone / methyl acetate / ethyl formate mixture, characterized by: The column body (13) is provided with a raw material liquid inlet (12) at the lower part, an ester phase outlet (2), a pure water inlet (4), a three-phase separator (6), a wire mesh demister (3) at the upper part, and a water phase outlet (10) at the bottom; a gas inlet (11) is provided at the lower part of the column body (13), and the column body (13) is provided with a gas distributor (9) connected with the gas inlet (11), and a gas outlet (1) is provided at the top of the column body (13); the upper and lower parts of the column body (13) are respectively provided with an upper clarification section (5) and a lower clarification section (14).

2. The composite column apparatus for use in the extraction of acetone / methyl acetate / ethyl formate mixture according to claim 1, characterized in that: When the raw material liquid inlet (12) and the gas inlet (11) at the lower part of the column body (13) are the same inlet, a liquid distributor connected with the raw material liquid inlet (12) and the gas inlet (11) is arranged in the column; during extraction, the gas is mixed with the raw material liquid before entering the column body (13), and then enters the lower part of the column body (13) through the liquid distributor from the same inlet.

3. The composite column apparatus for use in the extraction of acetone / methyl acetate / ethyl formate mixture as claimed in claim 1, wherein: A plurality of trays are further included, the tray includes a flow-through sieve plate (8) and a filler (7) located below the flow-through sieve plate (8) and having a layer height of 40-120 mm, the tray spacing is 200-400 mm, no downcomer is arranged, and the gas and liquid flow in countercurrent.

4. The composite column apparatus for use in the extraction of acetone / methyl acetate / ethyl formate mixtures according to claim 3, characterized in that: The flow-through sieve plate (8) is provided with sieve holes, the sieve hole diameter is 10-15 mm, and the opening rate of the sieve holes on the flow-through sieve plate (8) is 35-50%.

5. A method for the extraction of acetone / methyl acetate / ethyl formate mixtures, characterized in that: The method comprises the following steps: Step 1: the raw material liquid enters from the raw material liquid inlet (12) of the column body (13) of the bubble sieve plate filler combined column, the pure water enters from the pure water inlet (4) at the top, the raw material and the water are countercurrently contacted between the several trays, since the methyl acetate and the ethyl formate are slightly soluble in water, the water phase and the ester phase are formed, and the acetone is transferred to the water phase; Step 2: the gas enters from the gas inlet (11) at the bottom, is uniformly formed into a gas flow in the column after passing through the gas distributor (9), constantly impacts and agitates the liquid phase, and strengthens the mass transfer between phases; Step 3: after the extraction process is completed between the trays, the gas-liquid phase at the upper part of the column body (13) is clarified in the upper clarification section (5), is separated through the three-phase separator (6), the ester phase flows out from the ester phase outlet (2) at the upper part of the column body (13) to obtain high-purity methyl acetate and ethyl formate, the gas passes through the wire mesh demister (3) and is discharged from the gas outlet (1) at the top, and the water phase is clarified in the lower clarification section (14) and is discharged from the bottom (10) to obtain an acetone aqueous solution.

6. The method for application to the extraction of acetone / methyl acetate / ethyl formate mixture according to claim 5, characterized in that: In the separated acetone / ethyl formate / methyl acetate mixture, the molar fraction of the acetone is 5%-25%, and the rest is ethyl formate and methyl acetate.

7. The method for application to the extraction of acetone / methyl acetate / ethyl formate mixture according to claim 5, characterized by: The gas in step 2 is air or inert gas.

8. The method for application to the extraction of acetone / methyl acetate / ethyl formate mixture according to claim 5, characterized by: The empty column gas velocity of the gas is 5-15 mm / s.

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