Process for recovering acetone from tablet acetone coating waste gas

Abstract

The invention belongs to the field of medicine manufacturing, and particularly relates to a process for recovering acetone from acetone coating waste gas. The acetone in the tablet coating waste gas is absorbed by water, the acetone is liquefied into the acetone aqueous solution, the acetone aqueous solution is separated and recovered to obtain the acetone with high purity, the recovery rate of the acetone can reach 70% or above, the purity of the recovered acetone reaches 99.6%, and the recovered acetone can be continuously used as a solvent of a tablet coating solution. The acetone is recycled in the tablet coating process, so that the utilization rate of the acetone in the tablet coating process is increased, and the material cost of the acetone is reduced.

Description

Technical Field

[0001] The invention relates to a process for recovering acetone from waste gas of tablet acetone coating, belonging to the field of medical technology, in particular to the field of medicine manufacturing. Background Art

[0002] Acetone is a colorless and transparent liquid with a boiling point of 56.5°C. It is often used as a volatile organic compound in the pharmaceutical production process, especially as a solvent for tablet coating liquid. During the coating process, acetone is vacuumed away to become organic waste gas. The most common method for treating acetone organic waste gas is combustion, which allows the mixture of acetone and air to be directly burned in the airflow. Although this method has high purification efficiency, it causes a great waste of resources, increases the production and operation costs of enterprises, and has low economic benefits. In addition, the main methods of recycling research at home and abroad are adsorption, absorption, condensation and membrane separation. Among them, the industrialized technologies are adsorption, absorption and condensation. The membrane separation method is a developing technology that needs further research and improvement. The adsorption method is mainly activated carbon adsorption. This method is only suitable for the treatment of low-concentration acetone waste gas. The condensation method, combustion method and membrane separation method are only suitable for the treatment of high-concentration acetone waste gas. In contrast, the absorption method is suitable for the treatment of acetone waste gas of various concentrations and is more universal in industry. Summary of the invention

[0003] The invention aims to recover acetone in tablet coating waste gas, realize the recycling of acetone, avoid waste of resources and reduce production and operation costs. 1. In order to achieve the above object, the present invention provides a process for recovering acetone from tablet acetone coating waste gas, and the specific process steps are as follows: a. Use a solvent with low volatility and high solubility in acetone as an absorbent to absorb acetone in tablet coating waste gas to obtain acetone absorption liquid. b. Separate the acetone absorption liquid obtained in step a to purify the acetone. 2. Preferably, in the above process for recovering acetone by acetone coating, in step a, the absorbent is Purified water, water temperature controlled within the range of 10-15℃. 3. A device for absorbing acetone in coating waste gas, comprising: an acetone waste gas condenser, an absorption tower, an absorption liquid pump, a reflux cooler, a water condenser, and an acetone absorption liquid storage tank. The acetone waste gas condenser is connected to the bottom of the absorption tower, and the tablet coating acetone waste gas is cooled through the acetone waste gas condenser and enters the bottom of the absorption tower. The purified water passes through the water condenser and enters the absorption tower above the absorption tower. A portion of the absorption liquid enters the reflux condenser from the bottom of the absorption tower, and the other portion enters the acetone absorption liquid storage tank. 4. The device for absorbing acetone in exhaust gas, the absorption tower is a packed tower, and the reflux ratio of the absorption tower is 0.5. 5. Preferably, the acetone waste gas passes through a condenser to room temperature (about 25° C.) and enters an absorption tower. 6. The ratio of the acetone waste gas flow rate to the purified water flow rate is 1:1.4. 7. The device for separating and purifying the acetone absorption liquid in step b comprises: a centrifugal pump, an acetone distillation tower, a tower bottom reboiler, a tower top reflux device, an acetone product tank and a condenser. The centrifugal pump is connected to the acetone storage tank and the tower bottom of the acetone distillation tower, and the acetone absorption liquid enters the tower bottom of the acetone distillation tower for refining. 8. The device for separating and purifying acetone absorption liquid, the acetone distillation tower is a packed tower, and the reflux ratio at the top of the packed tower is 2. 9. After adopting the above technical scheme, the acetone in the coating waste gas is absorbed into purified water, which reduces the difficulty of liquefying the acetone in the waste gas. The absorption liquid is distilled to obtain acetone with a purity of 99.6%, which can continue to be used as a solvent for coating, realizing the recycling of acetone, reducing the production cost of the enterprise, and reducing the risk of environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 It is a process flow chart of acetone absorption purification of the present invention. DETAILED DESCRIPTION

[0005] The present invention is further described below in conjunction with embodiments: Embodiment 1: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m 3 / h, passes through the acetone waste gas condenser to cool the acetone waste gas to 25℃, and the cooled acetone waste gas enters the acetone absorption tower from the bottom, and purified water with a temperature of 10-15℃ enters from the top of the absorption tower, and the purified water flow rate is 150kg / h. The acetone waste gas contacts with the purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection tank. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the refluxed absorption liquid to the flow rate discharged into the absorption liquid collection tank is 1:2. The acetone absorption liquid in the collection box is poured into the distillation bottle for distillation operation. The distillation column uses glass springs as fillers to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation tower at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 2: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m 3 / h, passes through the acetone waste gas condenser to cool the acetone waste gas to 25℃, and the cooled acetone waste gas enters the acetone absorption tower from the bottom, and purified water with a temperature of 10-15℃ enters from the top of the absorption tower, and the purified water flow rate is 210kg / h. The acetone waste gas contacts with purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection tank. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the refluxed absorption liquid to the flow rate discharged into the absorption liquid collection tank is 1:2. The acetone absorption liquid in the collection box is poured into the distillation bottle for distillation operation. The distillation column uses glass springs as fillers to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation tower at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 3: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m 3 / h, passes through the acetone waste gas condenser to cool the acetone waste gas to 25℃, and the cooled acetone waste gas enters the acetone absorption tower from the bottom, and purified water with a temperature of 10-15℃ enters from the top of the absorption tower. The purified water flow rate is 270kg / h. The acetone waste gas contacts with the purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection tank. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the refluxed absorption liquid to the flow rate discharged into the absorption liquid collection tank is 1:2. Pour the acetone absorption liquid in the collection box into the distillation bottle for distillation operation. Use glass springs as fillers in the distillation column to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation column at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 4: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m 3 / h, the acetone waste gas is not cooled, the temperature of the acetone waste gas is about 35℃, and it enters the acetone absorption tower from the bottom. Purified water with a temperature of 10-15℃ enters from the top of the absorption tower. The purified water flow rate is 210kg / h. The acetone waste gas contacts with purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection box. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the reflux absorption liquid to the discharge into the absorption liquid collection box is 1:2. The acetone absorption liquid in the collection box is poured into the distillation bottle for distillation operation. The distillation column uses glass springs as fillers to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation column at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 5: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m3 / h, passes through the acetone waste gas condenser to cool the acetone waste gas to 15℃, and the cooled acetone waste gas enters the acetone absorption tower from the bottom, and purified water with a temperature of 10-15℃ enters from the top of the absorption tower. The purified water flow rate is 210kg / h. The acetone waste gas contacts with the purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection tank. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the refluxed absorption liquid to the flow rate discharged into the absorption liquid collection tank is 1:2. The acetone absorption liquid in the collection box is poured into the distillation bottle for distillation operation. The distillation column uses glass springs as fillers to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation tower at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 6: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m 3 / h, passes through the acetone waste gas condenser, cools the acetone waste gas to 25℃, and enters the acetone absorption tower from the bottom. Purified water with a temperature of 15-20℃ enters from the top of the absorption tower. The purified water flow rate is 210kg / h. The acetone waste gas contacts with purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection tank. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the refluxed absorption liquid to the flow rate discharged into the absorption liquid collection tank is 1:2. The acetone absorption liquid in the collection box is poured into the distillation bottle for distillation operation. The distillation column uses glass springs as fillers to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation tower at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 7: The coating waste gas extracted from the coating machine, the acetone waste gas flow rate is 150m 3 / h, after passing through the acetone waste gas condenser, the acetone waste gas is cooled to 25℃ and enters the acetone absorption tower from the bottom. Purified water with a temperature of 20-25℃ enters from the top of the absorption tower. The purified water flow rate is 210kg / h. The acetone waste gas contacts with purified water, and the acetone is absorbed by the water and enters the acetone absorption liquid collection tank. Part of the acetone absorption liquid refluxes into the absorption tower, and the ratio of the refluxed absorption liquid to the flow rate discharged into the absorption liquid collection tank is 1:2. The acetone absorption liquid in the collection box is poured into the distillation bottle for distillation operation. The distillation column uses glass springs as fillers to purify the acetone absorption liquid. Acetone is extracted from the top of the distillation tower at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation column at a reflux ratio of 2:1. The acetone is collected in a round-bottom flask. Embodiment 8: According to the process parameters obtained from the comparative experiments of Examples 1 to 7 (Table 1 to Table 6), the temperature of the acetone coating waste gas entering the absorption tower is 25°C, the ratio of the absorbent purified water flow rate to the acetone coating waste gas flow rate is 1.4, the absorbent purified water temperature is 10-15°C, the distillation tower reflux ratio is 2, and the tower top extraction temperature is 55-60°C, and industrial scale expansion verification is carried out. The flow rate of acetone waste gas extracted from the coating machine is 2000m 3 / h, after passing through the acetone waste gas condenser, the acetone waste gas is cooled to 25℃ and enters the acetone absorption tower from the bottom. Purified water with a temperature of 20-25℃ enters the absorption tower from the top of the absorption tower. The purified water flow rate is 2800kg / h. The acetone waste gas contacts the purified water, and the acetone is absorbed by the water. The acetone absorption liquid is discharged from the bottom of the absorption tower. Part of the absorption liquid enters the absorption tower after cooling, and the remaining absorption liquid enters the absorption liquid storage tank. The mass flow ratio of the refluxed absorption liquid to the absorption liquid storage tank is 1:2. The acetone absorption liquid in the storage tank is pumped into the distillation tower kettle through a centrifugal pump, heated for distillation, and the acetone absorption liquid is purified. Acetone is extracted from the top of the distillation tower at a temperature of 55-60°C. Part of the acetone is cooled and refluxed into the distillation tower, and the remaining acetone enters the acetone product tank. The flow ratio of refluxed acetone to that entering the acetone tank is 2:1. After the liquid in the tower kettle drops to room temperature, it is discharged into the sewage treatment station for centralized treatment. Table 1 Effect of liquid-gas ratio (purified water flow rate to acetone waste gas flow rate ratio) on acetone content in absorption liquid Table 2 Effect of acetone waste gas temperature on acetone content in absorption liquid Table 3 Effect of purified water temperature on acetone content in absorption liquid Table 4 Recovery of acetone at different purified water flow rates Table 5 Recovery of acetone at different acetone waste gas temperatures Table 6 Recovery of acetone at different acetone waste gas temperatures Table 7 Process scale-up verification It can be seen from Table 1 that the flow rate of absorbent purified water is related to the degree of acetone absorption, and a low flow rate of absorbent purified water is not conducive to the absorption of acetone. It can be seen from Table 2 that the present invention can better absorb acetone in the coating waste gas. The degree of acetone absorption is related to the temperature of the acetone waste gas entering the absorption tower. Acetone waste gas with a higher temperature is not conducive to the absorption of acetone by purified water. When the temperature of the acetone waste gas is below 25°C, the absorption effect of acetone is not much different. It can be seen from Table 3 that the absorption degree of acetone in the present invention is related to the temperature of the absorbent purified water entering the absorption tower. The lower the temperature of the purified water, the better the absorption effect of acetone. The purified water temperature is selected to be 10-15°C. It can be seen from Table 4, Table 5 and Table 6 that the present invention can separate and purify the acetone absorption liquid well, the recovery rate of acetone can reach more than 70%, and the purity of acetone can reach 99.6%, and there is very little acetone in the distillation tower bottom. It can be seen from Table 7 that the industrial scale-up of the acetone recovery process from acetone coating waste gas has an acetone recovery rate of 76.4% and a product purity of 99.6%, which can achieve good acetone recovery effects. Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications resulting from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A process for recovering acetone from tablet acetone coating waste gas, the specific steps are as follows: a. Use a solvent with low volatility and high solubility in acetone as an absorbent to absorb acetone in tablet coating waste gas to obtain acetone absorption liquid. b. Separate the acetone absorption liquid obtained in step a to purify the acetone.

2. In step a, the absorbent is purified water, and the water temperature is controlled within the range of 10-15°C.

3. The device for absorbing acetone in the waste gas in step a comprises: Acetone waste gas condenser, absorption tower, absorption liquid pump, reflux cooler, water condenser and acetone absorption liquid storage tank. The acetone waste gas condenser is connected to the bottom of the absorption tower. The tablet coating acetone waste gas is cooled through the acetone waste gas condenser and enters the bottom of the absorption tower. The purified water passes through the water condenser and enters the absorption tower above the absorption tower. Part of the absorption liquid enters the reflux condenser from the bottom of the absorption tower, and the other part enters the acetone absorption liquid storage tank.

4. The device for absorbing acetone in exhaust gas, the absorption tower is a packed tower, and the reflux ratio of the absorption tower is 0.

5.

5. According to the device for absorbing acetone in waste gas of claim 3, the acetone waste gas passes through a condenser to room temperature (25°C) and enters an absorption tower.

6. According to claim 3, the ratio of acetone waste gas flow rate to purified water flow rate is 1:1.

4.

7. The device for separating and purifying the acetone absorption liquid in step b comprises: Centrifugal pump, acetone distillation tower, tower bottom reboiler, tower top reflux device, acetone product tank and condenser. The centrifugal pump connects the acetone storage tank and the tower bottom of the acetone distillation tower, and the acetone absorption liquid enters the tower bottom of the acetone distillation tower for refining.

8. The device for separating and purifying acetone absorption liquid according to claim 6, wherein the acetone distillation is a packed tower with a top reflux ratio of 2.

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