CN104587834A - Device and method for separating and recovering high-boiling-point organic matter from low-concentration aqueous solution - Google Patents

Abstract

The invention discloses a device and a method for separating and recovering high-boiling point and water-soluble organic matter from low-concentration aqueous solution and directly obtaining high-purity liquid organic matter by utilizing a pervaporation-staged condensation coupling process. First, a vacuum pump is used to form a low-pressure atmosphere downstream of the pervaporation membrane, and the pervaporation membrane is used as a mass transfer separation medium to selectively enrich the high-boiling point organics in the dilute solution, and then the pervaporation membrane is enriched on the downstream side of the membrane The low-pressure mixed steam is condensed in stages; the high-boiling organic vapor is first trapped in the first-stage condenser to generate high-purity liquid organic matter, and the uncondensed water vapor and a small part of organic vapor are trapped in the second-stage condenser. Pump back into raw material tank. The invention adopts pervaporation-staged condensation coupling process without adding chemical reagents, eliminates secondary pollution, is not limited by gas-liquid balance, is simple, fast and efficient to operate, and can directly obtain high-boiling liquid organic matter with a purity greater than 99.9wt%.

Description

A device and method for separating and recovering high-boiling-point organic matter from low-concentration aqueous solution

technical field

The invention relates to a device and method for separating and recovering high-boiling-point organic matter from low-concentration aqueous solution, and belongs to the technical field of chemical engineering separation.

Background technique

The recovery of high-boiling point organics from dilute solutions has a wide range of applications in the fields of biomass fuel extraction and wastewater purification. Furfural and aniline are one of the most representative high-boiling point organic compounds of amines and furan ring systems respectively, and it is of great value to directly obtain high-purity furfural and aniline from dilute solutions.

The production of furfural (scientific name: furan formaldehyde) is obtained by acid hydrolyzing the hemicellulose material in the raw material of biomass (corncob, cottonseed hull, etc.). The mass percentage of furfural in the hydrolyzed solution after hydrolysis is about 2~8 wt%. At present, domestic furfural factories use distillation to separate and purify furfural from the hydrolyzed solution. The first time is primary rectification, which can increase the concentration of furfural to 90 wt%~92 wt% (concentration at the constant boiling point of water and furfural), and then use multi-stage rectification to refine furfural. The rectification process consumes a large amount of steam, so energy consumption accounts for a large proportion of furfural production cost. How to reduce the energy consumption of furfural separation and recovery is a research hotspot.

Chinese patent CN103214439A discloses a fixed bed filled with non-polar macroporous adsorption resin to absorb furfural in the hydrolyzate, and then desorb the eluent to obtain a higher concentration of furfural eluate, and finally obtain The target product of furfural, the adsorption-desorption process is cumbersome and requires a large investment in equipment. Chinese patent CN103254158A discloses a method and device for producing furfural using biomass hydrolysis coupled with pervaporation separation: the pervaporation membrane has high adsorption selectivity for furfural in the hydrolyzate, and when the membrane adsorption is balanced, the downstream of the membrane is vacuumed to remove the furfural in the membrane. The preferentially adsorbed furfural and a small amount of water are desorbed in the form of low-pressure mixed steam, and finally the furfural and water vapor are condensed and collected. The furfural collected by this process still needs to be further refined, and the refining process of furfural consumes a lot of energy.

Aniline is one of the important intermediates in the chemical industry. It is widely used in dyestuffs, pesticides, rubber additives and other industries. The content of aniline in wastewater is relatively high (mass fraction 1wt%~3wt%). Currently, aniline wastewater treatment commonly used in industry Methods include extraction and adsorption. The adsorption method is not suitable for treating high-concentration aniline wastewater, and the regeneration of the adsorbent is difficult. After several regenerations, the adsorption capacity will be greatly lost. Extraction method (CN1600696A, CN102936079A) is easy to cause secondary pollution of water body, requires multi-stage extraction, equipment investment is large, and it is difficult to obtain high-purity aniline that can be reused.

Contents of the invention

Aiming at the current situation that the production of furfural consumes a lot of energy and the treatment process of aniline wastewater is cumbersome, the present invention aims to provide a pervaporation-staged condensation coupling device with low energy consumption and simple flow process, and the process separates and recovers high boiling point and water solubility in low-concentration aqueous solution. Organic matter - furfural and aniline.

The present invention provides a device for separating and recovering high-boiling-point organics from low-concentration aqueous solutions, including a pervaporation section and a graded condensation section. The pervaporation section includes a raw material storage tank, a material-liquid circulation pump, a pervaporation tank, and a pervaporation tank There is a pervaporation membrane module inside; the graded condensation section includes a first-stage condenser and a second-stage condenser, the first-stage condenser and the second-stage condenser are connected in series, and the end of the second-stage condenser is connected to a vacuum pump, The lower end of the first-stage condenser is connected to the first storage tank, the lower end of the second-stage condenser is connected to the second storage tank, and the second storage tank is connected to the raw material storage tank through a circulation pump.

A method for separating and recovering high-boiling-point organics from low-concentration aqueous solutions provided by the invention comprises the following steps:

(1) Pass the aqueous solution of low-concentration organic matter into the pervaporation tank, and fully contact the pervaporation membrane with the function of selectively separating organic matter on the upstream side of the membrane to achieve adsorption dynamic equilibrium;

(2) A vacuum pump is used to generate a low-pressure vacuum downstream of the pervaporation membrane, so that the high-boiling organic matter-water adsorbed on the surface of the membrane on the upstream side is vaporized, and desorbed through the membrane on the downstream side of the pervaporation membrane to form organic matter-water low-pressure mixed steam ;

(3) Pass the organic matter-water low-pressure mixed steam enriched on the downstream side of the membrane into two series-connected condensers in sequence, select the temperature range of the first condenser according to the absolute pressure value, and obtain high purity in the first-stage condenser Liquid high-boiling organic matter with a purity greater than 99.9wt%;

(4) The uncondensed water vapor and a small part of organic vapor are trapped in the second-stage condenser, and the second-stage condenser is connected to the pervaporation tank, and a small part of organic vapor is sent to the pervaporation tank for secondary separation Recycle.

In the above scheme, the low-concentration aqueous solution is an aqueous solution with an organic concentration in the range of 0.1 to 8 wt%.

In the above scheme, the high-boiling-point organic matter is an amine and a furan ring system room-temperature liquid organic matter with a boiling point in the range of 150-230°C.

In the above scheme, the high-boiling organic matter is furfural or aniline. The concentration of the furfural aqueous solution is: 1wt%-8wt%; the concentration of the aniline aqueous solution is: 0.1wt%-4wt%.

In the above solution, the pervaporation membrane with the function of selectively separating organic matter is a polyether block polyamide membrane.

In the above scheme, the low-pressure vacuum condition downstream of the pervaporation membrane is: the absolute pressure is in the range of 30-2000 Pa.

In the above scheme, the temperature of the first stage condenser is controlled at -30~30°C; the temperature of the second stage condenser is -200~-50°C.

In the above scheme, the initial temperature of the aqueous solution of low-concentration organic matter is 30-95°C.

Because the pervaporation membrane separation process provided by the present invention has the advantages of high separation efficiency, low energy consumption, simple process, and no secondary pollution, and: (1) aniline is a high-boiling, water-soluble organic substance that can be condensed through pervaporation-gradation The coupling process directly recovers high-purity colorless aniline liquid from the low water solution; (2) furfural is a water-soluble organic compound with a high boiling point (161.7°C), and the furfural in the hydrolyzed solution can be recovered to high Purity colorless furfural liquid, this method reduces the energy consumption of separating and recovering furfural from dilute hydrolyzate, has very important industrial application value.

The working principle of the present invention: because the pervaporation membrane separation has the advantage of not being limited by the vapor-liquid equilibrium, it has high adsorption selectivity. The pervaporation membrane preferentially adsorbs organic matter in low-concentration aqueous solution, and then the other side of the membrane is vacuumed to make the adsorbed organic matter Vaporize with a small amount of water, and finally condense the low-pressure organic vapor enriched by the film (organic matter has a higher boiling point) and water vapor in stages. The easily condensed organic vapor is first trapped in the first-stage condenser, and the uncondensed water Vapor and a small part of organic vapor are trapped in the second stage condenser. Through the pervaporation-fractional condensation process, the high-boiling, water-soluble aniline and furfural are extracted from their respective low-concentration aqueous solutions, and the purity of the recovered furfural and aniline is greater than 99.9wt%.

Beneficial effects of the present invention:

(1) High-purity and high-boiling-point liquid organic compounds can be directly separated from low-concentration aqueous solutions through the pervaporation-staged condensation coupling process;

(2) There is no need to add chemical reagents during the separation process, and there is no secondary pollution;

(3) During the separation process, the temperature of the raw material liquid is controlled at a relatively low temperature (less than 95°C), with low energy consumption and high separation efficiency;

(4) The coupling process is simple and easy to operate, and the obtained high-purity organic matter does not need further purification;

(5) For the first time, the staged condensation process is applied to the pervaporation method to recover high-boiling organic matter, and a second-stage condenser is added to increase the recovery rate of aniline or furfural products.

Description of drawings

Fig. 1 is a schematic flow chart of the pervaporation-fractionated condensation process of the present invention.

In the figure: 1-raw material storage tank; 2-material liquid circulation pump; 3-pervaporation tank; 4-first-stage condenser; 5-second-stage condenser; 6-vacuum pump; 7-valve, 8-first Storage tank; 9-the second storage tank; 10-residual liquid circulation pump.

Detailed ways

The present invention is further illustrated by the following examples, but not limited to the following examples.

Embodiment 1: The device that separates and recovers high-boiling-point organic matter from low-concentration aqueous solution

As shown in Figure 1, it includes a pervaporation section and a graded condensation section. The pervaporation section includes a raw material storage tank 1, a feed liquid circulation pump 2, and a pervaporation tank 3, and a pervaporation membrane module is arranged in the pervaporation tank 3; The graded condensation section includes a first-stage condenser 4 and a second-stage condenser 5, the first-stage condenser 4 and the second-stage condenser 5 are connected in series, and the second-stage condenser 5 is connected with a vacuum pump 6, that is, in two stages The end of the condenser is connected to a vacuum pump, the lower end of the first-stage condenser 4 is connected to the first storage tank 8 through a valve 7, the lower end of the second-stage condenser 5 is connected to the second storage tank 9 through a valve, and the second storage tank 9 passes through the residual liquid The circulation pump 10 is connected to the raw material storage tank 1 . After condensation, the product enters into the storage tank through valve control.

The technological process of adopting the above-mentioned device to separate and recover high-boiling point organic matter is as follows:

Because pervaporation membrane separation has the advantage of not being limited by vapor-liquid equilibrium, it has high adsorption selectivity. Pervaporation membrane preferentially adsorbs organic matter in low-concentration aqueous solution, and then the other side of the membrane is vacuumed to vaporize the adsorbed organic matter and a small amount of water, and finally The low-pressure organic vapor (organic matter has a higher boiling point) enriched by the membrane is condensed in stages with water vapor. The organic vapor that is easy to condense is first trapped in the first-stage condenser, and then enters the first storage tank after condensation. The condensed water vapor and a small part of organic vapor are trapped in the second-stage condenser and enter the second storage tank after condensation. The liquid in the second storage tank enters the raw material storage tank through the raffinate circulation pump. Through the pervaporation-fractional condensation process, the high-boiling, water-soluble aniline and furfural are extracted from their respective low-concentration aqueous solutions, and the purity of the recovered furfural and aniline is greater than 99.9wt%.

Embodiment 2: Separation and recovery of high boiling point furfural from low concentration aqueous solution

(1) Heat the furfural aqueous solution with a concentration of 2 wt% to 80°C, and circulate the furfural aqueous solution into the pervaporation tank at a flow rate of 120 L/h through the feed liquid circulation pump, so that the membrane adsorption reaches equilibrium, and the pervaporation in the membrane module The area of the membrane is 20.4 cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is evacuated to maintain the pressure downstream of the membrane at an absolute pressure of 30 Pa;

(3) Introduce the low-pressure mixed steam of furfural and water into the first-stage condenser with a temperature of -29°C and a heat exchange area of 0.1 m ² , and introduce the low-pressure mixed steam of furfural and water that has not been condensed into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C;

(4) The purity of furfural collected in the first-stage condenser was 99.92 wt%, and the collection rate was 240 g/(m ² h) measured by Karl Fischer moisture meter; the purity of furfural collected in the second-stage condenser was 25 wt%, the collection rate is 610 g/(m ² ·h).

Embodiment 3: Separation and recovery of high boiling point furfural from low concentration aqueous solution

(1) Heat the furfural aqueous solution with a concentration of 3 wt% to 60 °C, and circulate the furfural aqueous solution into the pervaporation membrane module at a flow rate of 120 L/h with a pump, so that the membrane adsorption reaches equilibrium, and the pervaporation membrane in the membrane module The area is 20.4cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is vacuumed to maintain the pressure downstream of the membrane at an absolute pressure of 250 Pa;

(3) Introduce the low-pressure mixed steam of furfural and water into the first-stage condenser with a temperature of -8°C and a heat exchange area of 0.1 m ² , and introduce the low-pressure mixed steam of furfural and water that has not been condensed into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C.

(4) The purity of furfural collected in the first-stage condenser was 99.94 wt%, and the collection rate was 270 g/(m ² h) as measured by Karl Fischer moisture meter; the purity of furfural collected in the second-stage condenser was 27 wt%, the collection rate is 320 g/(m ² ·h).

Embodiment 4: Separation and recovery of high boiling point furfural from low concentration aqueous solution

(1) Heat the furfural aqueous solution with a concentration of 5 wt% to 70 °C, and circulate the furfural aqueous solution into the pervaporation membrane module at a flow rate of 120 L/h with a pump, so that the membrane adsorption reaches equilibrium, and the pervaporation membrane in the membrane module The area is 20.4cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is vacuumed to maintain the pressure downstream of the membrane at an absolute pressure of 1000 Pa;

(3) Introduce the low-pressure mixed steam of furfural and water into the first-stage condenser with a temperature of 10 °C and a heat exchange area of 0.1 ^m2 , and introduce the low-pressure mixed steam of furfural and water that has not been condensed into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C.

(4) The purity of furfural collected in the first-stage condenser was 99.95 wt%, and the collection rate was 492 g/(m ² h) measured by Karl Fischer moisture meter; the purity of furfural collected in the second-stage condenser was 29 wt%, the collection rate is 510 g/(m ² ·h).

Embodiment 5: Separation and recovery of high boiling point aniline from low concentration aqueous solution

(1) Heat the aniline aqueous solution with a concentration of 1 wt% to 80°C, and use a pump to circulate the aniline aqueous solution into the pervaporation membrane module at a flow rate of 120 L/h, so that the membrane adsorption reaches equilibrium, and the pervaporation membrane in the membrane module The area is 20.4cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is evacuated to maintain the pressure downstream of the membrane at an absolute pressure of 50 Pa;

(3) Introduce the low-pressure mixed steam of aniline and water into the first-stage condenser with a temperature of -25°C and a heat exchange area of 0.1 m ² , and introduce the low-pressure mixed steam of uncondensed aniline and water into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C.

(4) The purity of the aniline collected in the first-stage condenser was 99.91 wt%, and the collection rate was 395 g/(m ² h) as measured by the Karl Fischer moisture meter; the purity of the aniline collected in the second-stage condenser was 1 wt%, the collection rate is 410 g/(m ² ·h).

Embodiment 6: Separation and recovery of high boiling point aniline from low concentration aqueous solution

(1) Heat the aniline aqueous solution with a concentration of 0.2 wt% to 70°C, and circulate the aniline aqueous solution into the pervaporation membrane module at a flow rate of 120 L/h with a pump, so that the membrane adsorption reaches equilibrium, and the pervaporation membrane in the membrane module The area is 20.4cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is evacuated to maintain the pressure downstream of the membrane at an absolute pressure of 500 Pa;

(3) Introduce the low-pressure mixed steam of aniline and water into the first-stage condenser with a temperature of 3°C and a heat exchange area of 0.1 m ² , and introduce the low-pressure mixed steam of uncondensed aniline and water into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C.

(4) The purity of the aniline collected in the first-stage condenser was 99.94 wt% measured by Karl Fischer moisture meter, and the collection rate was 50 g/(m ² h); the purity of the aniline collected in the second-stage condenser was 10 wt%, the collection rate is 400 g/(m ² ·h).

Embodiment 7: Separation and recovery of high boiling point aniline from low concentration aqueous solution

(1) Heat the aniline aqueous solution with a concentration of 3 wt% to 60°C, and circulate the aniline aqueous solution into the pervaporation membrane module at a flow rate of 120 L/h with a pump, so that the membrane adsorption reaches equilibrium, and the pervaporation membrane in the membrane module The area is 20.4cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is evacuated to maintain the pressure downstream of the membrane at an absolute pressure of 1200 Pa;

(3) Introduce the low-pressure mixed steam of aniline and water into the first-stage condenser with a temperature of 13°C and a heat exchange area of 0.1 m ² , and introduce the low-pressure mixed steam of uncondensed aniline and water into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C.

(4) The purity of the aniline collected in the first-stage condenser was 99.93 wt%, and the collection rate was 90 g/(m ² h) as measured by the Karl Fischer moisture meter; the purity of the aniline collected in the second-stage condenser was 12 wt%, the collection rate is 380 g/(m ² ·h).

Embodiment 8: Separation and recovery of high boiling point aniline from low concentration aqueous solution

(1) Heat the aniline aqueous solution with a concentration of 2 wt% to 50°C, and circulate the aniline aqueous solution into the pervaporation membrane module at a flow rate of 120 L/h with a pump, so that the membrane adsorption reaches equilibrium, and the pervaporation membrane in the membrane module The area is 20.4cm ² ;

(2) On the downstream side of the membrane, the end of the two-stage condenser is vacuumed to maintain the pressure downstream of the membrane at an absolute pressure of 250 Pa;

(3) Introduce the low-pressure mixed steam of aniline and water into the first-stage condenser with a temperature of 20°C and a heat exchange area of 0.1 m ² , and introduce the low-pressure mixed steam of uncondensed aniline and water into the first-stage condenser In the second-stage condenser connected in series, the temperature of the second-stage condenser is -196°C.

(4) The purity of the aniline collected in the first-stage condenser was 99.96 wt%, and the collection rate was 104 g/(m ² h) as measured by the Karl Fischer moisture meter; the purity of the aniline collected in the second-stage condenser was 47 wt%, the collection rate is 395 g/(m ² ·h).

Claims (9)

1. A device for separating and recovering high-boiling-point organics from low-concentration aqueous solutions, characterized in that: it includes a pervaporation section and a graded condensation section, and the pervaporation section includes a raw material storage tank, a material-liquid circulation pump, a pervaporation tank, and a pervaporation section. The vaporization tank is provided with a pervaporation membrane module; the graded condensation section includes a first-stage condenser and a second-stage condenser, the first-stage condenser and the second-stage condenser are connected in series, and the second-stage condenser is connected to a vacuum pump . 2. A method for separating and recovering high-boiling point organics from low-concentration aqueous solution, characterized in that: comprising the following steps: (1) Pass the aqueous solution of low-concentration organic matter into the pervaporation tank, and fully contact the pervaporation membrane with the function of selectively separating organic matter on the upstream side of the membrane to achieve adsorption dynamic equilibrium; (2) A vacuum pump is used to generate a low-pressure vacuum downstream of the pervaporation membrane, so that the high-boiling organic matter-water adsorbed on the surface of the membrane on the upstream side is vaporized, and desorbed through the membrane on the downstream side of the pervaporation membrane to form a low-pressure mixed steam; (3) Pass the low-pressure mixed steam enriched on the downstream side of the membrane into two series-connected condensers in turn, select the temperature range of the first condenser according to the absolute pressure value, and obtain a high-purity liquid with a high boiling point in the first-stage condenser Organic matter, the purity is greater than 99.9wt%; (4) The uncondensed water vapor and a small part of organic vapor are trapped in the second-stage condenser, and the second-stage condenser is connected to the pervaporation tank, and a small part of organic vapor is sent to the pervaporation tank for secondary separation Recycle. 3. the method for separating and recovering high-boiling organic matter from low-concentration aqueous solution according to claim 2, is characterized in that: described low-concentration aqueous solution is the aqueous solution of organic matter concentration in the scope of 0.1～8 wt%. 4. The method for separating and recovering high-boiling point organics from low-concentration aqueous solution according to claim 2, characterized in that: said high-boiling point organics are amines and furan ring system room temperature liquid organics with boiling points in the range of 150 to 230 °C. 5. The method for separating and recovering high-boiling-point organic matter from low-concentration aqueous solution according to claim 4, characterized in that: the high-boiling-point organic matter is furfural or aniline. 6. The method for separating and recovering high-boiling-point organic matter from low-concentration aqueous solution according to claim 2, characterized in that: the pervaporation membrane with the function of selectively separating organic matter is a polyether block polyamide membrane. 7. The method for separating and recovering high-boiling-point organic matter from low-concentration aqueous solution according to claim 2, characterized in that: the low-pressure vacuum condition downstream of the pervaporation membrane is: the absolute pressure is in the range of 30-2000 Pa. 8. The method for separating and recovering high-boiling point organic matter from low-concentration aqueous solution according to claim 2, characterized in that: the temperature of the first-stage condenser is controlled at -30~30°C; the temperature of the second-stage condenser is -200~-50°C. 9. The method for separating and recovering high-boiling point organic matter from low-concentration aqueous solution according to claim 2, characterized in that: the initial temperature of the aqueous solution of low-concentration organic matter is 30-95°C.