Method for recovering polyether-containing defoaming agent in fermentation wastewater

Abstract

The invention discloses a method for recovering a polyether-containing defoaming agent in fermentation wastewater, which comprises the following steps of: adding acetone into the wastewater, stirring and dissolving, filtering through a ceramic membrane, and separating out phospholipid-cell residue to obtain an acetone wastewater solution containing the defoaming agent; adding activated carbon powder to adsorb pigments and small molecular impurities in the wastewater, and filtering the decolorized mixed solution through a plate frame to obtain a clarified acetone-defoaming agent solution; and then three-stage gradient distillation is adopted to finally obtain the regenerated defoaming agent, so that accurate separation and recovery of a target product are realized. A silane coupling agent is added into the regenerated defoaming agent to repair the surface activity, so that the recovery rate of the defoaming agent is greater than 93%, and the cyclic utilization rate of acetone is greater than 98%. The method is suitable for treating the fermentation wastewater containing the polyether defoaming agent, and has the advantages of high resource utilization rate, good selectivity, low cost, no secondary pollution, resourceful byproducts and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment technology, and specifically relates to a method for recovering polyether defoamers in fermentation wastewater, and is particularly suitable for separating and regenerating polyether defoamers from biomass residues in the fermentation process of high value-added products such as coenzyme Q10. Background Art

[0002] During the fermentation of microorganisms such as coenzyme Q10, it is necessary to continuously add silicone or polyether defoamers to inhibit foam generation. After the fermentation is completed, the residual defoamer concentration in the wastewater is generally between 100-200 mg / L, forming a stable suspension system with broken cells (containing phospholipids, proteins, etc.) and metabolic byproducts (organic acids, alcohols, carbon sources, nitrogen sources). The traditional treatment method has the following defects: (1) Waste of resources: The cost of defoamers accounts for 5-8% of the total cost of the fermentation process, and direct decomposition leads to huge losses; (2) Low treatment efficiency: Cell fragments adsorb defoamers, and the conventional filtration recovery rate is less than 50%; (3) Secondary pollution: Incineration produces toxic gases such as dioxins, and chemical decomposition requires the addition of strong oxidants (such as ozone), which increases treatment costs.

[0003] In addition, fermentation wastewater often contains complex components such as phospholipids and proteins, which are difficult to degrade by conventional biological methods. The recovery technology of valuable substances in wastewater (such as residual defoamers and phospholipids) is not yet mature, and the resource utilization rate is low, resulting in waste and secondary pollution risks. Although physical and chemical methods (such as adsorption, coagulation, and membrane separation) can remove some pollutants, there are problems such as high treatment costs and easy generation of secondary pollution (such as waste residues and waste membranes). Biological methods (such as activated sludge method and anaerobic digestion) have limited treatment effects on difficult-to-degrade organic matter and toxic substances, and microorganisms are easily affected by shock loads, resulting in unstable treatment efficiency. Although high-temperature incineration can decompose difficult-to-degrade organic matter, its operating energy consumption is high and it is impossible to achieve resource recycling, so its economic efficiency is poor. Summary of the invention

[0004] The purpose of the present invention is to provide an efficient method for recovering polyether defoamers in fermentation wastewater based on acetone selective extraction and activated carbon decolorization, in order to address the technical difficulties of existing technologies for recovering polyether defoamers in fermentation wastewater, such as low resource utilization rate, high treatment cost, high operating energy consumption, unstable treatment efficiency, and easy secondary pollution.

[0005] To achieve the above-mentioned object of the present invention, a method for recovering polyether defoaming agent contained in fermentation wastewater of the present invention comprises the following steps:

[0006] S1 acetone gradient extraction

[0007] Add 0.5 to 1 times the volume of acetone with a mass concentration of 98.5% to 99.5% to the wastewater, first stir at a low speed of 200-300 rpm for 10 to 30 minutes to fully dissolve the defoamer, then switch to a high-speed stirring of 800 to 1000 rpm for 5 to 10 minutes, use shear force to break up cell clumps and release the encapsulated defoamer; then filter through a 1 to 5 μm ceramic membrane to separate the phospholipid-cell residue (retained phase) to obtain an acetone wastewater solution containing the defoamer (permeated phase);

[0008] S2 activated carbon in situ decolorization

[0009] Under high-speed stirring, 0.3% to 0.7% of the mass of the acetone wastewater solution containing the defoamer is added with activated carbon powder to adsorb the pigments and small molecular impurities in the wastewater. After decolorization, the mixed solution is filtered through a plate and frame to obtain a clear acetone-defoamer solution;

[0010] S3 vacuum distillation regeneration

[0011] The clarified acetone-defoaming agent solution obtained in step S3 is subjected to three-stage gradient distillation: the first stage is 50-55°C / -0.08MPa to recover 90-95% of acetone, the second stage is 60-65°C / -0.09MPa to purify the defoaming agent, and the third stage is 70-75°C / -0.095MPa to remove trace water, and finally a regenerated defoaming agent is obtained; and 0.1wt%-0.5wt% of a regenerated defoaming agent is added to the regenerated defoaming agent to repair the surface activity.

[0012] Preferably, the activated carbon that adsorbs pigments and small molecular impurities in the wastewater in step S2 is regenerated by microwave irradiation, with an irradiation power of 700 to 900 W and a time of 4 to 6 minutes.

[0013] Preferably, in step S2, the particle size of the activated carbon powder added is in the range of 100 to 200 mesh, and the iodine value is ≥800 mg / g.

[0014] Preferably, in step S3, the added silane coupling agent is KH-550 or KH-792.

[0015] Preferably, in step S1, the amount of acetone added to the wastewater is 0.7 to 0.8 times the volume of the wastewater.

[0016] Preferably, the amount of activated carbon powder added is 0.4% to 0.6% by mass of the acetone wastewater solution containing the defoaming agent.

[0017] Preferably, in step S3, 0.2 wt % to 0.4 wt % of the amount of the regenerated defoamer is added to the regenerated defoamer to repair the surface activity.

[0018] Compared with the prior art, the method for recovering polyether defoamers in fermentation wastewater of the present invention has the following beneficial effects:

[0019] (1) Highly selective separation

[0020] The solubility difference between acetone and phospholipids (defoaming agent solubility> 95%, phospholipid solubility< 5%) is utilized to achieve accurate separation and recovery of the target product.

[0021] (2) High resource utilization

[0022] The entire process achieves closed-loop resource utilization, with an acetone recycling rate of >98% and a surface tension recovery rate of the regenerated defoamer of ≥99%.

[0023] (3) Added value from by-products

[0024] The retained cells (containing phospholipids, proteins, etc.) have a purity of >85% after drying and can be sold as feed additives, and the by-products can be used for value-added purposes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a process flow chart of a method for recovering polyether defoaming agents contained in fermentation wastewater. DETAILED DESCRIPTION

[0026] To describe the present invention, the following is a further detailed description of a method for recovering polyether defoamers in fermentation wastewater according to the present invention in combination with an embodiment. However, the present invention is not limited to the embodiment, and any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0027] The upper and lower limits and interval values ​​of the raw materials and process parameters involved in the present invention can all achieve the product of the present invention, and are not listed here one by one.

[0028] Depend on Figure 1 As shown in the process flow chart of the present invention, the method of the present invention is implemented by the following steps:

[0029] S1 acetone gradient extraction

[0030] Add 0.5 to 1 times the volume of acetone with a mass concentration of 98.5% to 99.5% to the wastewater, first stir at a low speed of 200-300 rpm for 10 to 30 minutes to fully dissolve the defoaming agent, then switch to a high-speed stirring of 800 to 1000 rpm for 5 to 10 minutes, use shear force to break up cell agglomerates and release the encapsulated defoaming agent; then, filter through a 1 to 5 μm ceramic membrane to separate the phospholipid-cell residues to obtain an acetone wastewater solution containing the defoaming agent.

[0031] S2 activated carbon in situ decolorization

[0032] Under high-speed stirring, 0.3% to 0.7% of the mass of the acetone wastewater solution containing the defoamer is added simultaneously to adsorb the pigment and small molecular impurities in the wastewater. After decolorization, the mixed solution is filtered through a plate and frame to obtain a clear acetone-defoamer solution; the particle size of the activated carbon powder is between 100 and 200 meshes, and the iodine value is ≥800 mg / g. The activated carbon adsorbing the pigment and small molecular impurities in the wastewater is regenerated by microwave irradiation, with an irradiation power of 700 to 900 W and a time of 4 to 6 minutes.

[0033] S3 vacuum distillation regeneration

[0034] The clarified acetone-defoaming agent solution obtained in step S3 is subjected to three-stage gradient distillation: the first stage is 50-55°C / -0.08MPa to recover 90-95% of acetone, the second stage is 60-65°C / -0.09MPa to purify the defoaming agent, and the third stage is 70-75°C / -0.095MPa to remove trace water, and finally a regenerated defoaming agent is obtained; 0.1wt%-0.5wt% of a regenerated defoaming agent is added to the regenerated defoaming agent to repair the surface activity; the added silane coupling agent is KH-550 or KH-792.

[0035] In the embodiment of the present invention, coenzyme Q10 fermentation wastewater is treated.

[0036] Raw materials: wastewater pH = 6.8, defoamer (propylene glycol polyoxyethylene polyoxypropylene ether) concentration 158 mg / L, phospholipid content 3.2 g / L, chromaticity (ADMI) 350;

[0037] Process parameters:

[0038] 98.5% acetone (mass fraction) added amount: 0.8 times the wastewater volume;

[0039] 100 mesh iodine value 800mg / g activated carbon powder dosage: 0.5wt%; microwave regeneration conditions: 800W / 5min;

[0040] Distillation conditions: first stage 50℃ / -0.08MPa, second stage 60℃ / -0.09MPa, third stage 70℃ / -0.095MPa.

[0041] Table 1 Experimental results

[0042] index Numeric Defoamer recovery rate 94.2％ Acetone recovery 98.5％ Decolorization rate 91.3％ Phospholipid retention rate 96.8％

[0043] Table 2 Example repeatability verification (5 batches)

[0044] batch Defoamer recovery rate (%) Acetone recovery rate (%) 1 93.5±0.8 98.2±0.3 2 94.1±0.6 98.5±0.2 3 92.9±1.0 98.0±0.4 4 93.8±0.7 98.3±0.3 5 94.0±0.5 98.6±0.2

[0045] The present invention utilizes the difference in solvent polarity to achieve precise separation of defoamer-phospholipids, the equipment modification cost is 30% lower than that of the traditional solution, and there is no risk of secondary pollution.

Claims

1. A method for recovering polyether defoamers in fermentation wastewater, characterized in that This is done using the following steps: S1 Acetone Gradient Extraction Add 0.5 to 1 times the volume of acetone with a mass concentration of 98.5% to 99.5% to the wastewater, first stir at a low speed of 200-300 rpm for 10 to 30 minutes to fully dissolve the defoamer, then switch to a high speed of 800 to 1000 rpm for 5 to 10 minutes to break up the cell clumps by shear force to release the encapsulated defoamer; then filter through a 1 to 5 μm ceramic membrane to separate the phospholipid-cell residues to obtain an acetone wastewater solution containing the defoamer; S2 activated carbon in situ decolorization Under high-speed stirring, 0.3% to 0.7% of the mass of the acetone wastewater solution containing the defoamer is added with activated carbon powder to adsorb the pigments and small molecular impurities in the wastewater. After decolorization, the mixed solution is filtered through a plate and frame to obtain a clear acetone-defoamer solution; S3 vacuum distillation regeneration The clarified acetone-defoaming agent solution obtained in step S3 is subjected to three-stage gradient distillation: the first stage is 50-55°C / -0.08MPa to recover 90-95% of acetone, the second stage is 60-65°C / -0.09MPa to purify the defoaming agent, and the third stage is 70-75°C / -0.095MPa to remove trace water, and finally a regenerated defoaming agent is obtained; and 0.1wt%-0.5wt% of a regenerated defoaming agent is added to the regenerated defoaming agent to repair the surface activity.

2. The method for recovering polyether defoamers in fermentation wastewater according to claim 1, characterized in that: The activated carbon that adsorbs pigments and small molecular impurities in the wastewater in step S2 is regenerated by microwave irradiation, with an irradiation power of 700 to 900 W and a time of 4 to 6 minutes.

3. The method for recovering polyether defoamers in fermentation wastewater according to claim 1, characterized in that: In step S2, the particle size of the activated carbon powder added is in the range of 100 to 200 meshes, and the iodine value is ≥800 mg / g.

4. The method for recovering polyether defoamers in fermentation wastewater according to claim 1, characterized in that: In step S3, the added silane coupling agent is KH-550 or KH-792.

5. The method for recovering polyether defoamers in fermentation wastewater according to claim 2, characterized in that: In step S2, the particle size of the activated carbon powder added is in the range of 100 to 200 meshes, and the iodine value is ≥800 mg / g; in step S3, the silane coupling agent added is KH-550 or KH-792.

6. The method for recovering polyether defoamers in fermentation wastewater according to claim 1, 2, 3, 4 or 5, characterized in that: In step S1, the amount of acetone added to the wastewater is 0.7 to 0.8 times the volume of the wastewater.

7. The method for recovering polyether defoamers in fermentation wastewater according to claim 6, characterized in that: In step S2, the amount of activated carbon powder added is 0.4% to 0.6% of the mass of the acetone wastewater solution containing the defoaming agent.

8. The method for recovering polyether defoamers in fermentation wastewater according to claim 7, characterized in that: In step S3, 0.2 wt% to 0.4 wt% of the regenerated defoamer amount of silane coupling agent is added to the regenerated defoamer to repair the surface activity.

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