Adsorption tower for recycling organic ester in industrial wastewater and process method

Abstract

The invention relates to the technical field of adsorption separation, in particular to an adsorption tower for recycling organic ester in industrial wastewater and a process method. Comprising a tower kettle (1), a stirring device (2), an adsorbent (3) and a communicating device (4), the stirring device (2) is arranged inside the tower kettle (1); the adsorbent (3) is fixedly arranged in the tower kettle (1) and is positioned below the stirring device (2); and the communicating devices (4) are respectively arranged at the side part and the bottom of the tower kettle (1) and are used for exchanging substances inside and outside the kettle. In the whole process, the number of the adsorption towers and the connection mode between the adsorption towers can be adjusted and controlled to meet different actual requirements, a single-tower mode is suitable for intermittent operation, a double-tower series connection mode and a three-tower series connection mode are suitable for continuous operation, and under the three-tower series connection operation mode, the concentration of organic ester in outlet waste liquid can be reduced to 1000 ppm or below.

Description

Technical Field

[0001] This invention relates to the field of adsorption separation technology, specifically to an adsorption tower and process for recovering organic esters from industrial wastewater. Background Technology

[0002] Butyl acetate, an important chemical raw material, is widely used in coatings, printing, food, and other fields. Due to its good solubility in some organic substances, it is often used as an industrial solvent and is a commonly used extractant in penicillin production. However, the emulsification phenomenon during the extraction process can lead to trace amounts of butyl acetate remaining in the wastewater. Because the concentration of butyl acetate in the wastewater is extremely low, traditional azeotropic distillation is not only costly but also prone to causing equipment corrosion. Therefore, new recovery technologies are urgently needed.

[0003] Chinese utility model patent CN206660878U discloses a method for recovering organic esters from gas using activated carbon as an adsorbent. The specific steps are as follows: gas containing organic esters is introduced into an activated carbon filter using an induced draft fan until adsorption saturation; the adsorbed activated carbon is transferred to a treatment tank; the treatment tank is heated with steam to cause the organic ester vapors to volatilize; finally, the organic ester vapors are passed into a condenser for condensation and recovery. This method utilizes the abundant pore structure of activated carbon to effectively adsorb trace amounts of organic esters in gas, but it suffers from insufficient adsorption selectivity, leading to frequent activated carbon regeneration and difficulty in guaranteeing the purity of the recovered product.

[0004] Chinese invention patent CN101973875B discloses a method for recovering organic esters using hydrocarbon extractants. The process involves selecting one or more of liquid paraffin, high-boiling-point solvent oil, light diesel oil, and heavy diesel oil as extractants, mixing them with organic ester wastewater in a specific ratio for extraction; mixing the separated organic phase with an aqueous solution containing organic esters for further extraction; distilling the repeatedly extracted organic phase to extract low-boiling-point organic ester components; and regenerating the extractant through alkaline washing. While this method yields good results, the operation is cumbersome, and the alkaline washing regeneration process generates new wastewater, increasing the burden on subsequent treatment. Summary of the Invention

[0005] The first aspect of the present invention provides an adsorption tower for the recovery of organic esters from industrial wastewater, comprising a tower bottom, a stirring device, an adsorbent, and a communication device; the stirring device is disposed inside the tower bottom; the adsorbent is fixedly disposed inside the tower bottom and located below the stirring device; the communication device is disposed on the side and bottom of the tower bottom for material exchange between the inside and outside of the tower.

[0006] The upper and lower parts of the tower are cylindrical, and the middle part is conical. The upper, middle and lower parts are fixedly connected. The connecting device is respectively installed on the upper side wall, the lower side wall and the bottom of the tower.

[0007] The ratio of the diameter of the upper and lower cylinders of the tower is (1.2-3):1.

[0008] Optionally, the ratio of the diameter of the upper and lower cylinders of the tower is (1.5-2):1.

[0009] The diameter of the cylindrical part at the bottom of the tower is 1-5cm.

[0010] Optionally, the diameter of the cylinder at the bottom of the tower is 1-3 cm.

[0011] The stirring device includes a stirring shaft and stirring paddles. The stirring shaft extends to the lower part of the tower, and stirring paddles are arranged at intervals at the end of the stirring shaft.

[0012] The number of stirring paddles is 2-5, with a distance of 30-60cm between each two adjacent stirring paddles.

[0013] Optionally, the number of stirring paddles is 2-3, wherein the distance between any two adjacent stirring paddles is 40-50cm.

[0014] The adsorbent is an organic or inorganic particle containing polar functional groups such as F, Cl, Br, I, -CHO, -NH2, and -NO2, with a particle diameter of 0.5-2 mm.

[0015] The density of the adsorbent is 0.5-1.2 g·cm³. -3 .

[0016] The connecting device at the bottom of the tower has a dispersion plate composed of fine quartz sand, which can filter millimeter-sized solid impurity particles and other viscous substances in the raw material liquid; it is also equipped with a high-pressure steam cleaning pipeline and nozzle for reverse cleaning of the dispersion plate.

[0017] A second aspect of this invention provides a process for recovering organic esters from industrial wastewater using an adsorption tower, comprising the following steps: Industrial wastewater is transported into the tower bottom through the connecting device at the bottom of the tower. The stirring device is turned on, and the industrial wastewater is adsorbed by the adsorbent. The adsorbed wastewater is discharged from the lower side wall of the tower bottom through the connecting device at the bottom of the tower for collection. After the adsorbent becomes saturated, the industrial wastewater in the bottom of the column is discharged and collected through the connecting device at the bottom of the column. Steam is introduced into the column through the connecting device at the bottom of the column to regenerate the adsorbent. At the same time, the water-ester mixture is condensed and collected through the connecting device on the upper side wall of the column, and the organic ester is obtained after separation and recovery.

[0018] The adsorption towers used in the organic ester recovery process include a single adsorption tower or 2-5 adsorption towers connected in series.

[0019] Optionally, the adsorption tower used in the organic ester recovery process includes a single adsorption tower or two to three adsorption towers connected in series; wherein the single adsorption tower mode is suitable for batch operation, and the dual-tower and triple-tower series modes are suitable for continuous operation.

[0020] Each adsorption tower has its own independent feed pipe, discharge pipe, and corresponding valves, allowing it to be used independently without affecting each other.

[0021] The industrial wastewater undergoes a settling process to remove impurities before entering the reactor.

[0022] The steam temperature is 100-110℃.

[0023] The pressure inside the regeneration tower is 0.1-1 MPa during the regeneration process.

[0024] Optionally, the pressure inside the regeneration tower is 0.1-0.18 MPa during the regeneration process.

[0025] The regeneration process takes 60-240 minutes.

[0026] Optionally, the regeneration process takes 90-240 minutes.

[0027] The temperature of the industrial wastewater entering the reboiler is 10-40℃, the pressure inside the reboiler is 0.1-1 MPa, and the feed space velocity is 20-30 m / s. 3 ·h -1 ·t -1 .

[0028] Optionally, the temperature of the industrial wastewater entering the reboiler is 15-20℃, the pressure inside the reboiler is 0.1-0.5MPa, and the feed space velocity is 20-25m / s. 3 ·h -1 ·t -1 .

[0029] The steam feed space velocity is 0.2-2 m / s. 3 ·h -1 ·t -1 .

[0030] Optionally, the steam feed space velocity is 0.5-1.5 m / s. 3 ·h -1 ·t -1 .

[0031] Optionally, the wastewater temperature during the adsorption process is 20℃, the adsorption pressure is 0.1MPa, and the feed space velocity is 20m. 3 ·h -1 ·t -1The steam temperature during regeneration is 105℃, the regeneration pressure is 0.1MPa, and the steam flow rate is 1 m³ / s. 3 ·h -1 ·t -1 Regeneration time ≥ 90 min.

[0032] Working principle: The adsorbent can adsorb organic ester compounds in solution at low temperatures. When heated to provide the energy required for desorption, the organic esters precipitate from the adsorbent. During regeneration, the steam velocity in the lower cylindrical structure is greater than the minimum fluidization velocity of the adsorbent, thus keeping the adsorbent in suspension. After the adsorbent leaves the lower cylindrical structure, the increased pipe diameter causes the steam velocity to fall below the fluidization velocity of the adsorbent, causing the adsorbent to return to the lower part.

[0033] Beneficial effects 1. The adsorption tower of the present invention is suitable for various operating modes such as single tower, double tower in series, and triple tower in series. The single tower is suitable for intermittent operation, while the double tower and triple tower in series can realize continuous production.

[0034] 2. The adsorption tower equipment of this invention is structurally designed to be suitable for large-scale production and can be stably adapted to organic ester wastewater treatment scenarios in multiple fields such as coatings, printing, and penicillin production.

[0035] 3. The process of this invention can achieve the adsorption and recovery of organic esters in wastewater by periodically adjusting the valves of each pipeline on the adsorption tower.

[0036] 4. The process of this invention achieves efficient purification of organic esters by optimizing adsorption parameters and using a multi-tower series design.

[0037] 5. The three-tower series mode of the present invention can reduce the concentration of organic esters in the effluent to below 1000 ppm. Under optimal process conditions, the concentration of organic esters in the purified wastewater is as low as 805 ppm, which can meet the subsequent fermentation treatment and environmental emission standards, and solves the problem that traditional processes are difficult to treat low-concentration organic ester wastewater. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the adsorption tower in Example 1.

[0039] Figure 2 This is a schematic diagram of the recovery of organic esters from industrial wastewater using a single adsorption tower in Example 1, where a, b, c, d, and e all represent valves.

[0040] Figure 3 This is a schematic diagram of the recovery of organic esters from industrial wastewater using two adsorption towers connected in series in Example 2, where a, b, 1a, 1b, 1c, 1d, 1e, 2a, 2b, 2c, 2d, and 2e all represent valves.

[0041] Figure 4 This is a schematic diagram of Example 3, which uses three adsorption towers connected in series to recover organic esters from industrial wastewater. In this diagram, a, b, 1a, 1b, 1c, 1d, 1e, 1f, 2a, 2b, 2c, 2d, 2e, 2f, 3a, 3b, 3c, 3d, 3e, and 3f all represent valves.

[0042] The components include: 1. Tower bottom; 2. Stirring device; 3. Adsorbent; 4. Connecting device; 21. Stirring shaft; 22. Stirring paddle; 5. Raw material liquid; 6. Steam; 7. Condenser; 8. Storage tank; Figure 2-4 The line segments in the diagram represent pipes. Detailed Implementation

[0043] Example 1 An adsorption tower for recovering organic esters from industrial wastewater, such as Figure 1 As shown, it includes a column reactor 1, a stirring device 2, an adsorbent 3, and a connecting device 4; the stirring device 2 is disposed inside the column reactor 1; the adsorbent 3 is fixedly disposed inside the column reactor 1 and located below the stirring device 2; the connecting device 4 is disposed on the side and bottom of the column reactor 1, respectively, for the exchange of substances inside and outside the reactor.

[0044] The upper and lower parts of the tower vessel 1 are cylindrical structures, and the middle part is a conical structure. The upper, middle, and lower parts are fixedly connected. The connecting device 4 is respectively installed on the upper side wall, lower side wall, and bottom of the tower vessel 1. The diameter ratio of the upper and lower cylinders of the tower vessel 1 is 1.8:1. The diameter of the lower cylinder of the tower vessel 1 is 2cm. The stirring device 2 includes a stirring shaft 21 and stirring paddles 22. The stirring shaft 21 extends to the lower part of the tower vessel 1, and stirring paddles 22 are arranged at intervals at the end of the stirring shaft 21. There are 3 stirring paddles 22, and the distance between each two adjacent stirring paddles 22 is 45cm.

[0045] The adsorbent was prepared in-house using the following steps: Using 99.9% pure HCl and phenethyl alcohol as raw materials, 180g of phenethyl alcohol was first placed in a flask and heated to 45°C. Then, 70g of HCl solution was slowly added dropwise, and the mixture was heated to 80°C. This temperature was maintained while stirring the solution. After stirring for 2 hours, the solution was cooled to room temperature, ice water was added, and NaOH was added to adjust the pH to 7. After filtering out solid impurities, the remaining solution was heated and distilled in a flask, and the fraction collected at 180-190°C was collected. The collected fraction was reacted with potassium persulfate as an initiator at 220°C. After reacting for 1 hour, the solution was filtered, the solid product was collected, and dried at 60°C to obtain the adsorbent.

[0046] The connecting device 4 at the bottom of the tower 1 has a dispersion plate composed of fine quartz sand, which can filter millimeter-sized solid impurity particles and other viscous substances in the raw material liquid; it is also equipped with a high-pressure steam cleaning pipeline and nozzle for reverse cleaning of the dispersion plate.

[0047] Working principle: The adsorbent can adsorb organic ester compounds in solution at low temperatures. When heated to provide the energy required for desorption, the organic esters precipitate from the adsorbent. During regeneration, the steam velocity in the lower cylindrical structure is greater than the minimum fluidization velocity of the adsorbent, thus keeping the adsorbent in suspension. After the adsorbent leaves the lower cylindrical structure, the increased pipe diameter causes the steam velocity to fall below the fluidization velocity of the adsorbent, causing the adsorbent to return to the lower part.

[0048] A process for recovering organic esters from industrial wastewater using adsorption towers is disclosed. Each adsorption tower has its own independent inlet and outlet pipes, as well as corresponding valves, allowing for independent operation without interference. The process flow is as follows: Figure 2 As shown in Table 1, the relevant process parameters are as follows: Industrial wastewater is transported from the connecting device 4 at the bottom of the tower 1 through valve a and pipeline into the tower 1. The stirring device 2 is turned on, and the industrial wastewater is adsorbed by the adsorbent 3. The adsorbed wastewater is discharged from the connecting device 4 at the bottom of the tower 1 and collected at the lower side wall of the tower 1, and enters the liquid storage tank. After the adsorbent 3 is saturated, valves a and d are closed, and valve c is opened to discharge the industrial wastewater in the bottom of the column 1 through the connecting device 4 at the bottom of the column 1 for collection. Then, valve c is closed, valve b is opened, and steam is introduced into the column 1 through the connecting device 4 at the bottom of the column 1 to regenerate the adsorbent 3. At the same time, valve e is opened to condense and collect the water-ester mixture from the connecting device 4 on the upper side wall of the column 1 into a condenser tank, where the organic ester is recovered through separation.

[0049] Table 1

[0050] Example 2 A process for recovering organic esters from industrial wastewater using adsorption towers is disclosed. The adsorption towers used consist of two towers connected in series (the structures of towers 1 and 2 are the same as in Example 1). Each tower has independent inlet and outlet pipes and corresponding valves, allowing for independent operation without interference. The process flow is as follows: Figure 3As shown in Table 1, 1a and 2a are connected to the communication device (4) at the bottom of the adsorption tower (1); 1d and 2d are connected to the communication device (4) on the lower side wall of the adsorption tower (1); 1e and 2e are connected to the communication device (4) on the upper side wall of the adsorption tower (1). The process parameters involved are shown in Table 1. The steps are as follows: First, open valve a to introduce the raw material liquid. At this time, open valve 1a to allow the raw material liquid to enter the adsorption tower #1 for adsorption treatment. The treated solution enters the liquid storage tank through valve 1d. After the adsorbent is saturated, close valves 1a and 1d. At this time, open valve 2a to allow the raw material liquid to enter the adsorption tower #2 for adsorption treatment. The treated solution enters the liquid storage tank through valve 2d. The adsorbent in adsorption tower #1 is regenerated. Valve 1b is opened to release the remaining solution in adsorption tower #1. After the solution in adsorption tower #1 is released, valve 1b is closed and valve 1c is opened to introduce steam. At this time, valve 1e is opened to introduce the water-ester mixed steam obtained from the regeneration into the condenser for recovery, thus obtaining the organic ester.

[0051] Example 3 A process for recovering organic esters from industrial wastewater using adsorption towers is disclosed. The adsorption towers used consist of three towers connected in series (the structures of towers 1, 2, and 3 are the same as in Example 1). Each tower has independent inlet and outlet pipes and corresponding valves, allowing for independent operation without interference. The process flow is as follows: Figure 4As shown in Table 1, valves 1a, 2a, and 3a are connected to the communication device (4) at the bottom of the adsorption tower (1); valves 1e, 2e, and 3e are connected to the communication device (4) on the lower side wall of the adsorption tower (1); and valves 1f, 2f, and 3f are connected to the communication device (4) on the upper side wall of the adsorption tower (1). The process parameters involved are shown in Table 1, and the steps are as follows: valve a is opened to introduce the raw material liquid. At this time, valve 1a is opened to allow the raw material liquid to enter the adsorption tower 1 first. At this time, valves 2a and 3a are closed. The solution from the adsorption tower 1 enters the adsorption tower 2 through valve 1e, and then enters the liquid storage tank through valve 2d. At this time, the adsorption tower 3 is not used. When the adsorbent in the adsorption tower 1 is saturated, valves 1a and 1e are closed. Valve 2a is opened to allow the raw material liquid to enter the adsorption tower 2 first, then enter the adsorption tower 3 through valve 2e, and finally enter the liquid storage tank through valve 3d. Simultaneously, the adsorbent in adsorption tower #1 is regenerated. Valve 1b is opened to release the remaining solution in the tower. After the solution is completely released, valve 1b is closed. Steam is introduced through valve 1c, and valve 1f is opened to input the regenerated water-ester mixed steam into the condenser for recovery. After regeneration, valves 1c and 1f are closed. The regenerated adsorbent in adsorption tower #1 can be considered fresh adsorbent, and adsorption tower #1 is used as a standby unit. When the adsorbent in adsorption tower #2 becomes saturated, valves 2a and 2e are closed. Valve 3a is opened to allow the feed liquid to first enter adsorption tower #3, then through valve 3e into adsorption tower #1, and finally through valve 1d into the liquid storage tank. The adsorbent in adsorption tower #2 is then regenerated. When the adsorbent in adsorption tower #3 becomes saturated, the above method is repeated. At this point, the entire system has completed one cycle, yielding the organic ester.

[0052] Comparative Example 1 The specific implementation method is the same as in Example 1; the difference is that the regeneration pressure was changed in Comparative Example 1, as shown in Table 1.

[0053] Comparative Example 2 The specific implementation method is the same as in Example 1; the difference is that the regeneration time was changed in Comparative Example 2, as shown in Table 1.

[0054] Comparative Example 3 The specific implementation method is the same as in Example 1; the difference is that the temperature of the steam was changed in Comparative Example 3, as shown in Table 1.

[0055] Performance testing methods The wastewater and recovered organic esters from the liquid storage tanks recovered in the examples and comparative examples were tested, and the test data are listed in Table 2.

[0056] 1. Detect the concentration of organic esters in the wastewater after purification (ppm).

[0057] 2. Recovery rate of regenerated organic esters % = (Regenerated organic esters / Theoretical organic ester content in industrial wastewater) × 100%.

[0058] Performance test data Table 2

[0059] As shown in Table 2, the concentration of wastewater at 15°C in Example 1 after purification by the adsorbent was 1263 ppm, while the concentrations in Example 2 and Comparative Examples 1, 2, and 3 were 867 ppm, 805 ppm, 841 ppm, and 797 ppm, respectively. This result indicates that increased temperature accelerates the movement rate of ester molecules, which is beneficial for the adsorption of esters by the adsorbent. However, considering that the wastewater temperature in actual industrial production is generally around 20°C, 20°C is considered a more optimal adsorption temperature. In Example 3, the feed space velocity was increased. The increased space velocity, i.e., the reduced adsorption time, led to an increase in the concentration of organic esters in the wastewater after purification by the adsorbent, reaching 1037 ppm. In Examples 1, 2, and 3, the recovery rates of regenerated organic esters were 97.3%, 98.1%, and 97.5%, respectively. However, in Comparative Example 2, where the regeneration time was shortened, the recovery rate was only 88.9%, a decrease of nearly 10 percentage points compared to Examples 1, 2, and 3. This indicates that the 60-minute regeneration time was too short to completely desorb the esters from the adsorbent, thus requiring a further extension of the regeneration time. In Comparative Example 1, the regeneration pressure was increased to 0.2 MPa, but the recovery rate was only 85%, indicating that increasing the pressure inhibits the desorption of esters from the adsorbent and is detrimental to ester recovery. In Comparative Example 3, the regeneration steam temperature was reduced to 90°C (hot water), and no esters were recovered under this condition. This indicates that a temperature of 90°C cannot provide sufficient energy for adsorbent regeneration, and the actual temperature required for the regeneration process is higher than 90°C.

Claims

1. An adsorption tower for recovering organic esters from industrial wastewater, characterized in that, It includes a tower (1), a stirring device (2), an adsorbent (3), and a connecting device (4); the stirring device (2) is located inside the tower (1); the adsorbent (3) is fixedly located inside the tower (1) and below the stirring device (2); the connecting device (4) is located on the side and bottom of the tower (1) respectively, for material exchange between the inside and outside of the tower.

2. The adsorption tower for organic ester recovery from industrial wastewater according to claim 1, characterized in that, The upper and lower parts of the tower (1) are cylindrical structures, and the middle part is a conical structure. The upper, middle and lower parts are fixedly connected. The connecting device (4) is respectively installed on the upper side wall, the lower side wall and the bottom of the tower (1).

3. The adsorption tower for organic ester recovery from industrial wastewater according to claim 2, characterized in that, The ratio of the diameter of the upper and lower cylinders of the tower (1) is (1.2-3):1; the diameter of the lower cylinder of the tower (1) is 1-5cm.

4. The adsorption tower for organic ester recovery from industrial wastewater according to claim 2, characterized in that, The stirring device (2) includes a stirring shaft (21) and a stirring paddle (22). The stirring shaft (21) extends to the lower part of the tower (1), and the stirring paddle (22) is arranged at intervals at the end of the stirring shaft (21).

5. The adsorption tower for organic ester recovery from industrial wastewater according to claim 4, characterized in that, The number of stirring paddles (22) is 2-5, and the distance between any two adjacent stirring paddles (22) is 30-60cm.

6. A process for recovering organic esters from industrial wastewater using the adsorption tower according to any one of claims 2-5, characterized in that, The process includes the following steps: industrial wastewater is transported from the bottom of the adsorption tower (1) to the bottom of the tower (1) via the connecting device (4), the stirring device (2) is turned on, and the industrial wastewater is adsorbed by the adsorbent (3). The adsorbed wastewater is discharged from the bottom side wall of the tower (1) via the connecting device (4) for collection. After the adsorbent (3) is saturated, the industrial wastewater in the tower (1) is discharged from the bottom side wall of the tower (1) via the connecting device (4) for collection. Steam is introduced into the tower (1) through the bottom side wall of the tower (1) via the connecting device (4) to regenerate the adsorbent (3). At the same time, the water-ester mixture is condensed and collected from the connecting device (4) on the upper side wall of the tower (1), and the organic ester is obtained by separation and recovery.

7. The process method for recovering organic esters from industrial wastewater using the adsorption tower according to claim 6, characterized in that, The adsorption towers used in the organic ester recovery process include a single adsorption tower or 2-5 adsorption towers connected in series.

8. The process method for recovering organic esters from industrial wastewater using the adsorption tower according to claim 7, characterized in that, The steam temperature is 100-110℃.

9. The process method for recovering organic esters from industrial wastewater using the adsorption tower according to claim 7, characterized in that, The pressure inside the regeneration tower (1) is 0.1-0.18 MPa during the regeneration process.

10. The process method for recovering organic esters from industrial wastewater using the adsorption tower according to claim 7, characterized in that, The regeneration process takes 65-240 minutes.

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