Method for resource utilization of amino acid mother liquor

Abstract

This invention relates to the field of amino acid mother liquor resource utilization technology, specifically disclosing a method for the resource utilization of amino acid mother liquor. Specifically, the method involves: treating the amino acid mother liquor by electrodialysis to obtain an inorganic salt solution and desalted material; using the inorganic salt solution as an inorganic salt supplement for reuse in the amino acid fermentation production process; concentrating, crystallizing, and separating the desalted material to obtain crude amino acids and final mother liquor; and spray-granulating the final mother liquor to produce organic fertilizer. Compared with existing ion exchange and chromatographic separation technologies, the process provided by this invention has significant advantages such as simple flow, stable operation, no need for acid-base regeneration, and low equipment investment and operating costs. It achieves both amino acid resource recovery and the resource utilization of inorganic salt impurities, realizing a balance between clean production and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of amino acid mother liquor resource utilization technology, and specifically to a method for utilizing amino acid mother liquor resources. Background Technology

[0002] In the industrial production of amino acids, the residual mother liquor after crystallization and separation, known as amino acid mother liquor, has a complex composition, containing various inorganic salts, pigments, and organic impurities. This mother liquor is characterized by high salt content, high chemical oxygen demand (COD), and a dark brown color. Its subsequent treatment has long been a technical challenge in the amino acid industry. The conductivity of this mother liquor can reach tens of thousands, its COD value can be hundreds of thousands, and it still contains a large amount of amino acids, making it unsuitable for direct discharge into wastewater systems and requiring further treatment.

[0003] Several technologies have been attempted in the industry for treating mother liquor, but all have significant drawbacks. For example, while ion exchange or chromatographic separation techniques can recover some amino acid products, the equipment investment is too high. The cost of a complete chromatographic system, including specialized resins, is typically over 2 million yuan. Furthermore, the high impurity content in the mother liquor easily leads to resin clogging and contamination, resulting in a very short continuous operating cycle for the system, generally requiring shutdown and regeneration after only about a week. Simultaneously, the high concentrations of calcium and magnesium salts in the mother liquor can cause resin transformation and decreased stability, necessitating frequent alkali regeneration, leading to high operating costs. Taking threonine mother liquor as an example, even if the amino acid yield from chromatographic separation reaches 90%, the total cost of treating one ton of mother liquor still exceeds 8,000 yuan after considering equipment depreciation, resin replacement, energy consumption, and regeneration costs, making it uneconomical for industrial application. Another common approach is to use the mother liquor directly as inexpensive fertilizer, for example, by producing solid fertilizer through spray granulation. However, this method not only produces products with extremely low added value and a selling price of only a few hundred yuan per ton, making it difficult to cover processing costs, but also generates a strong odor during the granulation process, leading to secondary environmental pollution problems. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for the resource utilization of amino acid mother liquor.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for the resource utilization of amino acid mother liquor, comprising the following steps: electrodialysis treatment of amino acid mother liquor to obtain inorganic salt solution and desalted material; the inorganic salt solution is used as inorganic salt supplement and recycled in the fermentation production process of amino acids; the desalted material is concentrated, crystallized and separated to obtain crude amino acid and final mother liquor; the final mother liquor is spray-granulated to produce organic fertilizer.

[0007] Preferably, the temperature for electrodialysis is 15℃~40℃, the current is 10~105A, and the treatment time is 12~16h.

[0008] Preferably, the conductivity of the inorganic salt solution is 30–100 mS / cm, and the conductivity of the desalted material is less than 10 mS / cm.

[0009] Preferably, when the inorganic salt solution is reused in the fermentation production process of amino acids, it can replace 50% to 70% of the amount of fresh inorganic salt added in the fermentation production process.

[0010] Preferably, the concentration is carried out under reduced pressure, with a vacuum degree of -0.09MPa to -0.07MPa and a temperature of 50℃ to 80℃.

[0011] Preferably, the desalted material is concentrated to a dry matter content of 55% to 80%.

[0012] Preferably, the crystallization is by cooling, and the cooling temperature is 10℃~40℃.

[0013] Preferably, the volume of the final mother liquor is 5% to 10% of the volume of the amino acid mother liquor. When the volume of the final mother liquor is <5%, the concentration factor is too high and the material is too viscous to be separated; when the volume is >10%, the volume of the final mother liquor is too large and the crystallization yield is low.

[0014] Preferably, the conductivity of the amino acid mother liquor is 40–80 mS / cm.

[0015] Preferably, the separation is performed by centrifugal separation or plate and frame filtration.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] The process provided by this invention solves the problem of separating salt and organic matter through precise electrodialysis, and enables the recycling of salt; it efficiently recovers the main amino acid product through concentration and crystallization; and finally, it reduces the volume and recovers the resources of the residual liquid. The entire process does not require the use of ion exchange resins or chromatographic columns, thus eliminating problems such as resin clogging, pollution, and frequent regeneration. It has comprehensive advantages such as simple process, stable operation, low investment and operating costs, and high resource recovery rate, while achieving both environmental compliance and economic benefits. Compared with existing amino acid mother liquor treatment schemes, this invention uses electrodialysis to separate three products of different values: high-salt water, crude amino acids, and final mother liquor. In terms of environmental performance, the volume of the final mother liquor is reduced to 5%–10% of the original mother liquor, and the COD load is reduced by more than 90%. In terms of process steps, the electrodialysis system is simple to operate, highly adaptable, and the process water consumption is only about 10% of that of traditional ion exchange or chromatographic separation processes, and no acid-base regeneration is required. This system maintains stable operation even with mother liquors exhibiting high conductivity (up to 105 μS / cm) and high chemical oxygen demand (hundreds of thousands of mg / L), whereas traditional ion exchange or chromatography processes are prone to resin clogging and poisoning under such high-load conditions, making sustained stable operation difficult. In terms of economic benefits, the process of this invention simultaneously achieves the resource recovery of both the main amino acid product and by-product inorganic salts, with the recovered inorganic salts directly reused in the amino acid fermentation process. In contrast, existing processes typically discharge inorganic salts as impurities into the wastewater system, increasing the wastewater treatment load and resulting in significant resource waste.

[0018] This invention develops a simple and low-cost mother liquor treatment process that effectively extracts amino acids while recovering and recycling a large amount of inorganic salts. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a process flow diagram for the resource utilization of amino acid mother liquor. Detailed Implementation

[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0022] A method for the resource utilization of amino acid mother liquor, such as Figure 1 As shown, it includes the following steps:

[0023] A high-concentration amino acid mother liquor with a conductivity of 40–80 mS / cm (the mother liquor is the residual liquid material after primary crystallization and separation of feed-grade amino acids, with a dry matter content of 20–50%) is fed into an electrodialysis system. Under the action of a DC electric field, inorganic salt ions in the mother liquor selectively migrate through the ion exchange membrane, thereby separating from most organic molecules such as amino acids. The electrodialysis treatment temperature is 15–40℃, preferably 15–35℃. Too low a temperature results in a slow processing speed, while too high a temperature damages the membrane material. The operating current can reach over 90A to ensure a high ion migration rate. Too high an operating current can lead to over-polarization or a sharp increase in energy consumption. The inorganic salts and organic matter in the amino acid mother liquor are separated by the electric field, yielding a high-salt solution (inorganic salt solution) and the desalted material.

[0024] The conductivity of the high-concentration brine obtained by electrodialysis is 30–100 mS / cm. If the conductivity is too high, there is a risk of salt precipitation. This portion of salt is mainly recycled for use as inorganic salts added during the fermentation process. For example, based on ions, it may include 40% magnesium salts, 40% potassium salts, 10% ammonium salts, and 10% sodium salts. The high-concentration brine can be directly or, after appropriate adjustments, returned to the fermentation process for recycling, replacing approximately 50%–70% of the fresh inorganic salt added, thus saving on the use of inorganic salts in fermentation and achieving closed-loop utilization of inorganic salts. Economic calculations show that the operating cost of recycling one ton of salt is approximately 500 yuan, while the cost of purchasing one ton of similar industrial salt exceeds 4000 yuan, demonstrating significant economic benefits.

[0025] After electrodialysis treatment, over 90% of the inorganic salts in the amino acid mother liquor are removed. The conductivity of the desalted material decreases to below 10 mS / cm, preferably below 5 mS / cm. When the conductivity is below 5 mS / cm, the current drops to about 15% of its peak value, and the ion migration rate decreases significantly. Then, the desalted material, mainly containing organic matter, is concentrated using vacuum concentration at a vacuum degree of -0.09 to -0.07 MPa and a temperature of 50 to 80°C until the dry matter content is 55 to 80%. The concentration is then reduced to 10 to 40°C, preferably 25°C, utilizing the change in solubility to induce the crystallization of a large amount of solid amino acids. The slurry containing crystals undergoes solid-liquid separation, which can be performed using a centrifuge or a plate and frame filter, preferably a plate and frame filter. After feeding, further filtration with press water can be used to reduce the moisture content of the resulting amino acid filter cake to below 30%. The amino acid filter cake is dried, preferably by flash drying, with an inlet air temperature of 140℃ and an outlet air temperature of 90℃, controlling the final product moisture content to below 5% (more preferably below 3%), thus obtaining crude amino acids. This crude amino acid mainly contains glutamic acid, threonine, and various other amino acids, and can be used as amino acid feed. Taking threonine mother liquor as an example, the above process can yield 90% pure threonine, with approximately 5% being polysaccharides and approximately 5% being other amino acids. The processing cost per ton of crude amino acid is approximately 1000 yuan, while the market price for similar single-product amino acids is over 8000 yuan / ton, making it significantly more economical.

[0026] The final mother liquor produced after solid-liquid separation has a dry matter content of 30-50%, a residual amino acid content of approximately 20% (dry basis), a chemical oxygen demand of approximately 100,000 mg / L, and an electrical conductivity of approximately 10 mS / cm. Preliminary screening showed that the contents of key heavy metals such as arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), and mercury (Hg) were significantly lower than the limits specified in the "Organic Fertilizer" (NY525-2021) standard. The main components of the final mother liquor are organic matter such as amino acids and proteins, which can be spray-granulated to produce organic fertilizer.

[0027] After the above-described complete process, the final amount of mother liquor requiring discharge or fertilizer treatment is only 5% to 10% of the original mother liquor mass, greatly reducing the end-of-pipe treatment load. Meanwhile, over 90% of the economically valuable amino acid components in the mother liquor have been extracted and recovered.

[0028] Example 1

[0029] A method for the resource utilization of amino acid mother liquor includes the following steps:

[0030] A high-concentration threonine mother liquor with a conductivity of 67.5 mS / cm was fed into an electrodialysis system. This mother liquor contained 50% dry matter and 15 g / L of potassium salt, 15 g / L of magnesium salt, 4 g / L of ammonium salt, 4 g / L of sodium salt, and trace amounts of inorganic salts such as calcium and iron. The electrodialysis system used a homogeneous membrane, initially operating at a constant voltage of 400V, automatically switching to constant current control mode when the current exceeded 100A. The processing temperature ranged from 15 to 35℃, with a maximum operating current of 102A. An electric field was used to separate the inorganic salts from the amino acid mother liquor, yielding a high-concentration brine solution and the desalted material.

[0031] The concentrated water (inorganic salt solution) obtained by electrodialysis, also known as high-salt water, has a conductivity of 67.8 mS / cm. It can be directly or after appropriate adjustment returned to the fermentation process for recycling, replacing 50% of the fresh inorganic salt addition.

[0032] After electrodialysis treatment, 92.3% of the inorganic salts in the threonine mother liquor were removed, resulting in an amino acid yield of 99.16%. The conductivity of the desalted material decreased to 5.2 mS / cm, and then it was concentrated using vacuum concentration at -0.07 MPa and 80℃ until the dry matter content reached 60%. The concentration was then lowered to 25℃, causing the amino acid solids to crystallize out. Solid-liquid separation was performed using a plate and frame filter press, resulting in an amino acid filter cake with 30% moisture content. This cake was then flash-dried at an inlet air temperature of 140℃ and an outlet air temperature of 90℃, with an outlet moisture content below 3%, yielding crude threonine with a threonine content of 90% and a total amino acid content of 95%.

[0033] The final mother liquor produced after solid-liquid separation has a dry matter content of 50%, a residual amino acid content of about 20% of the dry basis of the mother liquor, and a chemical oxygen demand of 110,000 mg / L. It is then spray-granulated to produce organic fertilizer.

[0034] The electrodialysis results of the threonine mother liquor are shown in Table 1.

[0035]

[0036] Note: Salts in the mother liquor enter the other side of the membrane, i.e., the concentrated aqueous phase, under the influence of the electric field. A small amount of amino acids also enter; this portion represents the yield loss. Top water is the flushing water after the mother liquor has been discharged following treatment.

[0037] As shown in Table 1, the initial mother liquor conductivity was 67.5 ms / cm, which decreased to 5.2 ms / cm after electrodialysis, with a desalination rate of 92.3% and a yield of 99.16%. This portion of salt entered the concentrate, with a conductivity of 67.8 ms / cm.

[0038] Example 2

[0039] A method for the resource utilization of amino acid mother liquor includes the following steps:

[0040] An isoleucine mother liquor with a conductivity of 43.9 mS / cm was fed into an electrodialysis system. This mother liquor, with a dry weight of 40%, contained 13 g / L potassium salt, 16 g / L magnesium salt, 5 g / L ammonium salt, 5 g / L sodium salt, and other trace inorganic salts. The electrodialysis system used a homogeneous membrane and an initial constant voltage control mode of 400 V. The processing temperature ranged from 15 to 30 °C, and the maximum operating current was 51.8 A. An electric field was used to separate the inorganic salts from the amino acid mother liquor, yielding a high-salt solution and the desalted product.

[0041] The concentrated water obtained by electrodialysis, also known as high-salt water, has a conductivity of 32.8 mS / cm. It can be directly or after appropriate adjustment returned to the fermentation process for recycling, replacing 50% of the fresh inorganic salt addition.

[0042] After electrodialysis treatment, 93.4% of the inorganic salts in the isoleucine mother liquor were removed, resulting in an amino acid yield of 99.26%. The conductivity of the desalted material decreased to 2.9 mS / cm, and then it was concentrated using vacuum concentration at -0.08 MPa and 65℃ until the dry matter content reached 55%. The concentration was then lowered to 25℃, causing the amino acid solids to crystallize out. Solid-liquid separation was performed using a plate and frame filter press, resulting in an amino acid filter cake with 25% moisture content. This cake was then flash-dried at an inlet air temperature of 140℃ and an outlet air temperature of 90℃, with an outlet moisture content below 3%, yielding crude isoleucine with a total amino acid content of 90%.

[0043] The final mother liquor produced after solid-liquid separation has a dry matter content of 50%, a residual amino acid content of about 15% of the dry basis of the mother liquor, and a chemical oxygen demand of 100,000 mg / L. It is then spray-granulated to produce organic fertilizer.

[0044] The electrodialysis results of the isoleucine mother liquor are shown in Table 2.

[0045]

[0046] As shown in Table 2, the initial mother liquor conductivity was 43.9 ms / cm, which decreased to 2.9 ms / cm after electrodialysis, with a desalination rate of 93.4% and a yield of 99.26%. This portion of salt entered the concentrate, with a conductivity of 32.8 ms / cm.

[0047] To verify the feasibility of reusing high-salt water recovered from electrodialysis in the fermentation process, a 5L scale isoleucine fermentation pilot was conducted. The experiment systematically investigated the effects of the recycled salt on key indicators of the fermentation process by adjusting the proportion of recycled salt added and correspondingly reducing the amount of fresh magnesium, potassium, and ammonium salts added.

[0048] The experimental results showed that when the proportion of recycled salt was 50% and the corresponding amount of fresh magnesium potassium ammonium salt was halved, the sugar-acid conversion rate of the experimental group was 30.2%, which was not significantly different from the control group (30.1%) that used fresh inorganic salt throughout the process. This indicates that at this proportion, the recycled salt did not inhibit cell growth and product synthesis. When the recycling ratio was increased to 70% and the corresponding amount of fresh salt was reduced to 30%, the sugar-acid conversion rate of the experimental group decreased to 29.2%, showing a slight inhibition compared to the control group (30.3%) that used fresh inorganic salt throughout the process. When the recycling ratio was further increased to 80% and the amount of fresh salt was reduced to only 20%, the sugar-acid conversion rate of the experimental group decreased significantly to 25.3%, which was significantly different from the control group (30.2%) that used fresh inorganic salt throughout the process, indicating that it had substantially inhibited fermentation metabolism.

[0049] Based on the above data, the maximum permissible safe reuse ratio of electrodialysis recovered salt in isoleucine fermentation in the process of this invention is determined to be 50% to 70%, preferably 50%. At this ratio, both effective recycling of inorganic salt resources and cost savings can be achieved, while ensuring stable fermentation performance.

[0050] Compared with existing ion exchange, chromatographic separation and other treatment technologies, the treatment process provided by this invention has significant advantages such as simple process, stable operation, no need for acid and alkali regeneration, and low equipment investment and operating costs. While realizing the recovery of amino acid resources, it also realizes the resource utilization of inorganic salt impurities, achieving a unity of clean production and economic benefits.

[0051] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the inventive concept of the present invention, can make other changes and modifications to these embodiments, all of which fall within the scope of the present invention.

[0052] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for the resource utilization of amino acid mother liquor, characterized in that, Includes the following steps: The amino acid mother liquor was subjected to electrodialysis to obtain an inorganic salt solution and desalted material; Inorganic salt solution is used as an inorganic salt supplement and recycled in the fermentation production process of amino acids; The desalted material is concentrated, crystallized, and separated to obtain crude amino acids and final mother liquor; the final mother liquor is then spray-granulated to produce organic fertilizer.

2. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, The temperature for electrodialysis treatment is 15℃~40℃, and the current is 10~105A.

3. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, The conductivity of inorganic salt solutions is 30–100 mS / cm, while the conductivity of the desalted material is less than 10 mS / cm.

4. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, When inorganic salt solutions are reused in the fermentation production process of amino acids, they can replace 50% to 70% of the amount of fresh inorganic salts added in the fermentation production process.

5. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, The concentration is carried out under reduced pressure, with a vacuum degree of -0.09MPa to -0.07MPa and a temperature of 50℃ to 80℃.

6. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, The desalted material is concentrated to a dry matter content of 55%–80%.

7. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, Crystallization occurs through cooling, with the cooling temperature ranging from 10℃ to 40℃.

8. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, The final mother liquor volume is 5% to 10% of the amino acid mother liquor volume.

9. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, The conductivity of the amino acid mother liquor is 40–80 mS / cm.

10. The method for resource utilization of amino acid mother liquor according to claim 1, characterized in that, Separation is achieved through centrifugal separation or plate and frame filtration.

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