Process for extracting ammonium sulfate from amino acid fermentation wastewater

Abstract

A process for extracting ammonium sulfate from amino acid fermentation wastewater, comprising: S1. using a sodium polyacrylate flocculant to extract a microbial protein and performing filtration to obtain the microbial protein and filtrate; S2. using an ultrafiltration membrane to filter the filtrate, allowing ammonium sulfate to pass through, so as to obtain an ultrafiltration permeate; S3. filtering the ultrafiltration permeate by means of a reverse osmosis membrane to obtain an ammonium sulfate solution; and S4. crystallizing the ammonium sulfate solution obtained in step S3 to obtain a finished ammonium sulfate product. In the extraction process, using the sodium polyacrylate flocculant to extract the microbial protein can increase the protein yield, reduce organic matter components in the waste liquid, and improve the purity and yield of the extracted ammonium sulfate. In the extraction process, by using the ultrafiltration membrane filtration and reverse osmosis filtration treatment sequentially, the purity of the finally obtained finished ammonium sulfate product is 98.4-98.7%, that is, the purity is relatively high.

Description

A process for extracting ammonium sulfate from amino acid fermentation wastewater Technical Field

[0001] The present application belongs to the field of amino acid fermentation technology, and specifically relates to a process for extracting ammonium sulfate from amino acid fermentation wastewater. Background Art

[0002] Currently, amino acids are typically mass-produced using biofermentation or chemical synthesis. During the production process, mother liquor wastewater or cleaning wastewater is generated, which together constitute amino acid fermentation wastewater. Currently, this wastewater is directly evaporated and concentrated to be used as agricultural fertilizer. This wastewater contains large amounts of protein, inorganic salts, organic acids, and ammonium sulfate. Long-term use can cause soil compaction and affect crop growth. Therefore, when utilizing amino acid fermentation wastewater, it is necessary to extract the ammonium sulfate. This not only reduces its impact on soil quality, but also allows for the recovery of ammonium sulfate, achieving resource reuse. Chinese patent CN 109988724A provides a combined process for resource utilization of amino acid fermentation broth. The process first extracts bacterial protein from the fermentation broth, then concentrates and crystallizes the ammonium sulfate and mother liquor to collect it. Dry lime is added to neutralize the residual ammonium sulfate in the mother liquor, and the ammonium sulfate is converted into calcium sulfate, which is then removed by filtration. Although this process removes ammonium sulfate, it introduces another substance, dry lime, and the ammonium sulfate is finally separated as calcium sulfate. If high-purity ammonium sulfate is required, additional processing steps are required.

[0003] Summary of the Invention

[0004] The present application provides a process for extracting ammonium sulfate from amino acid fermentation wastewater, which provides a simple process, does not introduce other substances, and the extracted ammonium sulfate has a high purity.

[0005] The present application provides a process for extracting ammonium sulfate from amino acid fermentation wastewater, which comprises the following steps:

[0006] S1: Extract bacterial protein using sodium polyacrylate flocculant, and obtain bacterial protein and filtrate after filtration;

[0007] S2: Filter the filtrate through an ultrafiltration membrane, pass ammonium sulfate through it, and obtain an ultrafiltration permeate;

[0008] S3: filtering the ultrafiltration permeate through a reverse osmosis membrane to obtain an ammonium sulfate solution; and

[0009] S4: crystallizing the ammonium sulfate solution obtained in step S3 to obtain finished ammonium sulfate.

[0010] Furthermore, the method for extracting bacterial protein in step S1 is: adjusting the pH of the fermentation broth waste liquid to 3.0-3.5, heating it to 65-72°C, adding 0.05-0.1‰ of flocculant sodium polyacrylate, stirring for 28-32 minutes, and then standing for 10-12 minutes, using a plate and frame filter press to perform solid-liquid separation to obtain bacterial protein and filtrate.

[0011] Furthermore, the ultrafiltration membrane in step S2 has a molecular weight cutoff of 3000Da, an operating pressure of 0.3-0.6Mpa, an operating temperature of 37-40°C, and a concentration multiple of 5-7 times; the retentate in this step is composed of impurities such as miscellaneous proteins and pigments, wherein the organic matter content in the retentate is 2.0-2.5%, and the retentate passes through the ammonium sulfate solution.

[0012] Furthermore, in step S3, the operating pressure of the reverse osmosis membrane is 0.8-1.0 MPa, the operating temperature is 37-40° C., the concentration multiple is 5-7 times, the permeate is deionized water, and the retentate is ammonium sulfate solution.

[0013] Furthermore, the crystallization process in step S4 includes: adjusting the pH of the ammonium sulfate solution to 5.0-6.0, preheating the solution, passing the solution into a pre-crystallization tank, and then crystallizing the solution through a crystallization device.

[0014] Furthermore, the deionized water produced in step S3 and the finished ammonium sulfate crystallized in step S4 can be used as nutrients for the fermentation medium.

[0015] Furthermore, the bacterial protein produced in step S1 and the retentate obtained in step S2 are used as raw materials for processing fertilizers.

[0016] Compared with the prior art, this application has the following beneficial effects:

[0017] (1) This application uses sodium polyacrylate flocculant to extract bacterial protein. This flocculant can increase protein yield, reduce the organic content in the wastewater, and improve the purity and yield of ammonium sulfate extraction. Ultrafiltration membrane filtration and reverse osmosis filtration are used successively to obtain a solution with an ammonium sulfate concentration of 32-35%. Finally, crystallization is performed to obtain an ammonium sulfate product. The purity of the finished ammonium sulfate product is 98.4-98.7%, which is relatively high.

[0018] (2) The process provided in this application is simple to operate, does not introduce other substances, and the extracted ammonium sulfate has high purity and can be used as a nutrient component of the fermentation medium. DETAILED DESCRIPTION

[0019] The present application is further described below with reference to the following embodiments. The present application includes but is not limited to the following embodiments.

[0020] Example 1

[0021] This embodiment provides a process for extracting ammonium sulfate from amino acid fermentation wastewater, which comprises the following steps:

[0022] (1) Extraction of bacterial protein: The pH of the fermentation waste liquid was adjusted to 3.2 and heated to 70°C. 0.1‰ of flocculant (sodium polyacrylate) was added. After stirring for 30 minutes, the mixture was allowed to stand for 10 minutes. Solid-liquid separation was performed using a plate and frame filter press to obtain bacterial protein and filtrate.

[0023] (2) filtering the filtrate through an ultrafiltration membrane, wherein the retentate is composed of miscellaneous proteins and pigment impurities, and passing through ammonium sulfate to obtain an ultrafiltration permeate;

[0024] The molecular weight cut-off of the ultrafiltration membrane is 3000 Da, the operating pressure is 0.3 MPa, the operating temperature is 38° C., and the concentration ratio is 5. The main components of the retentate in this step are organic matter, N, P, and K, wherein the organic matter content is 2.0%.

[0025] (3) filtering the ultrafiltration permeate through a reverse osmosis membrane, wherein the permeate is deionized water and the retentate is ammonium sulfate solution;

[0026] The operating pressure of the reverse osmosis membrane is 0.8Mpa, the operating temperature is 38℃, and the concentration ratio is 6 times.

[0027] (4) The pH of the ammonium sulfate solution obtained in (3) is adjusted to 5.0-6.0, preheated, passed into a pre-crystallization tank, and then crystallized by a crystallization device. After crystallization, the ammonium sulfate product is obtained by centrifugation.

[0028] (5) The deionized water obtained in (3) and the ammonium sulfate obtained in (4) can be used as nutrients for the fermentation medium; the bacterial protein produced in step (1) and the retentate produced in step (2) are processed into fertilizer.

[0029] The amino acid fermentation wastewater tested in the present embodiment has a sugar content of 2.0-2.2%, an ammonia nitrogen content of 2.5-3%, an organic content of 6-7%, and a pH of 3.2-3.4. The amino acid fermentation wastewater contains a large amount of protein, inorganic salts, organic acids, etc.; In the present embodiment, a sodium polyacrylate flocculant is selected to extract bacterial protein. This flocculant can increase protein yield and reduce the organic composition in the wastewater (the organic content in the original amino acid fermentation wastewater is 6-7%, and the organic content after the bacterial protein extraction is 2.0), and improve the purity and yield of ammonium sulfate extraction. The present embodiment adopts an ultrafiltration membrane to ultrafilter the filtrate after the bacterial protein extraction, which can further remove impurities such as foreign proteins and colloids in the filtrate. The concentration of ammonium sulfate in the ultrafiltrate is 8%, and then deionized water reverse osmosis filtration is used. The trapped liquid is a sodium sulfate solution, wherein the concentration of ammonium sulfate is 32%. Finally, crystallization is carried out to obtain an ammonium sulfate product. After testing, the purity of the ammonium sulfate finished product is 98.7%.

[0030] Example 2

[0031] This embodiment provides a process for extracting ammonium sulfate from amino acid fermentation wastewater, which comprises the following steps:

[0032] (1) Extraction of bacterial protein: The pH of the fermentation broth wastewater was adjusted to 3.2 and heated to 65°C. 0.08‰ of flocculant (sodium polyacrylate) was added. After stirring for 30 minutes, the mixture was allowed to stand for 12 minutes. Solid-liquid separation was performed using a plate and frame filter press to obtain bacterial protein and filtrate.

[0033] (2) filtering the filtrate through an ultrafiltration membrane, wherein the retentate is composed of miscellaneous proteins and pigment impurities, and passing through ammonium sulfate to obtain an ultrafiltration permeate;

[0034] The molecular weight cut-off of the ultrafiltration membrane is 3000Da, the operating pressure is 0.5MPa, the operating temperature is 38°C, and the concentration ratio is 7. The main components of the retentate in this step are organic matter, N, P, and K, of which the organic matter content is 2.2%.

[0035] (3) filtering the ultrafiltration permeate through a reverse osmosis membrane, wherein the permeate is deionized water and the retentate is ammonium sulfate solution;

[0036] The operating pressure of the reverse osmosis membrane is 1.0 MPa, the operating temperature is 38°C, and the concentration ratio is 6 times.

[0037] (4) The pH of the ammonium sulfate solution obtained in (3) is adjusted to 5.0-6.0, preheated, passed into a pre-crystallization tank, and then crystallized by a crystallization device. After crystallization, the ammonium sulfate product is obtained by centrifugation.

[0038] (5) The deionized water obtained in (3) and the ammonium sulfate obtained in (4) can be used as nutrients for the fermentation medium; the bacterial protein produced in step (1) and the retentate produced in step (2) are processed into fertilizer.

[0039] The amino acid fermentation wastewater tested in this embodiment has a sugar content of 2.0-2.2%, an ammonia nitrogen content of 2.5-3%, an organic matter content of 6-7%, and a pH of 3.2-3.4. In this embodiment, the filtrate after extracting bacterial protein is ultrafiltered using an ultrafiltration membrane to further remove impurities such as foreign proteins and colloids in the filtrate. The concentration of ammonium sulfate in the ultrafiltrate is 12%. The ultrafiltrate is then subjected to reverse osmosis filtration using deionized water. The retentate is a sodium sulfate solution in which the concentration of ammonium sulfate is 35%. Finally, crystallization is performed to obtain an ammonium sulfate product. Testing shows that the purity of the finished ammonium sulfate product is 98.9%.

[0040] Example 3

[0041] This embodiment provides a process for extracting ammonium sulfate from amino acid fermentation wastewater, which comprises the following steps:

[0042] (1) Extraction of bacterial protein: The pH of the fermentation broth waste liquid was adjusted to 3.5 and heated to 72°C. 0.08‰ of flocculant (sodium polyacrylate) was added. After stirring for 32 minutes, the mixture was allowed to stand for 12 minutes. Solid-liquid separation was performed using a plate and frame filter press to obtain bacterial protein and filtrate.

[0043] (2) filtering the filtrate through an ultrafiltration membrane, wherein the retentate is composed of miscellaneous proteins and pigment impurities, and passing through ammonium sulfate to obtain an ultrafiltration permeate;

[0044] The molecular weight cut-off of the ultrafiltration membrane is 3000Da, the operating pressure is 0.4 MPa, the operating temperature is 40°C, and the concentration ratio is 6. The main components of the retentate in this step are organic matter, N, P, and K, of which the organic matter content is 2.5%.

[0045] (3) filtering the ultrafiltration permeate through a reverse osmosis membrane, wherein the permeate is deionized water and the retentate is ammonium sulfate solution;

[0046] The operating pressure of the reverse osmosis membrane is 0.9 MPa, the operating temperature is 38°C, and the concentration ratio is 5 times.

[0047] (4) The pH of the ammonium sulfate solution obtained in (3) is adjusted to 5.0-6.0, preheated, passed into a pre-crystallization tank, and then crystallized by a crystallization device. After crystallization, the ammonium sulfate product is obtained by centrifugation.

[0048] (5) The deionized water obtained in (3) and the ammonium sulfate obtained in (4) can be used as nutrients for the fermentation medium; the bacterial protein produced in step (1) and the retentate produced in step (2) are processed into fertilizer.

[0049] The amino acid fermentation wastewater tested in this embodiment has a sugar content of 2.0-2.2%, an ammonia nitrogen content of 2.5-3%, an organic matter content of 6-7%, and a pH of 3.2-3.4. The amino acid fermentation wastewater contains a large amount of protein, inorganic salts, organic acids, etc. In this embodiment, the filtrate after extracting bacterial protein is ultrafiltered using an ultrafiltration membrane to further remove impurities such as foreign proteins and colloids in the filtrate. The concentration of ammonium sulfate in the ultrafiltrate is 10%. The ultrafiltrate is then filtered through reverse osmosis with deionized water. The retentate is a sodium sulfate solution in which the concentration of ammonium sulfate is 33%. Finally, crystallization is performed to obtain an ammonium sulfate product. After testing, the purity of the finished ammonium sulfate product is 98.4%.

[0050] The above embodiment is only one of the preferred implementation methods of the present application and should not be used to limit the scope of protection of the present application. Any changes or modifications that are made to the main design concept and spirit of the present application and have no substantive significance, as long as the technical problems they solve are still consistent with those of the present application, should be included in the scope of protection of the present application.

Claims

1. A process for extracting ammonium sulfate from amino acid fermentation wastewater, comprising: S1: extract bacterial protein with sodium polyacrylate flocculant, and obtain bacterial protein and filtrate after filtration; S2: filtering the filtrate with an ultrafiltration membrane, passing ammonium sulfate through it, and obtaining an ultrafiltration permeate; S3: filtering the ultrafiltration permeate through a reverse osmosis membrane to obtain an ammonium sulfate solution; and S4: crystallizing the ammonium sulfate solution obtained in step S3 to obtain a finished ammonium sulfate product.

2. The process for extracting ammonium sulfate from amino acid fermentation wastewater according to claim 1, wherein: The method for extracting bacterial protein in step S1 is as follows: adjusting the pH of the fermentation broth waste liquid to 3.0-3.5, heating it to 65-72° C., adding 0.05-0.1‰ of a flocculant sodium polyacrylate, stirring for 28-32 minutes, and then standing for 10-12 minutes, and performing solid-liquid separation with a plate and frame filter press to obtain bacterial protein and filtrate.

3. The process for extracting ammonium sulfate from amino acid fermentation wastewater according to claim 1, wherein: The ultrafiltration membrane in step S2 has a molecular weight cutoff of 3000Da, an operating pressure of 0.3-0.6Mpa, an operating temperature of 37-40°C, and a concentration multiple of 5-7 times; the retentate in this step is impurities of proteins and pigments, wherein the organic matter content in the retentate is 2.0-2.5%; the retentate passes through the ammonium sulfate solution.

4. The process for extracting ammonium sulfate from amino acid fermentation wastewater according to claim 1, wherein: The operating pressure of the reverse osmosis membrane in step S3 is 0.8-1.0 MPa, the operating temperature is 37-40° C., the concentration multiple is 5-7 times, the permeate is deionized water, and the retentate is ammonium sulfate solution.

5. The process for extracting ammonium sulfate from amino acid fermentation wastewater according to claim 4, wherein: The crystallization process in step S4 includes: adjusting the pH of the ammonium sulfate solution to 5.0-6.0, preheating it, then passing it into a pre-crystallization tank, and then crystallizing it through a crystallization device.

6. The process for extracting ammonium sulfate from amino acid fermentation wastewater according to claim 5, wherein: The deionized water produced in step S3 and the ammonium sulfate product crystallized in step S4 can be used as nutrients for the fermentation medium.

7. The process for extracting ammonium sulfate from amino acid fermentation wastewater according to claim 6, wherein: The bacterial protein produced in step S1 and the retentate obtained in step S2 are used as raw materials for processing fertilizers.