Low energy consumption method for electrolytic synthesis of l-cysteine hydrochloride monohydrate

Abstract

The application discloses a low-energy-consumption electrolytic synthesis method of L-cysteine hydrochloride monohydrate, and belongs to the technical field of preparation of amino acids and derivatives thereof. The synthesis method comprises the following steps: raw material pretreatment, electrolytic tank feeding, asymmetric pulse electrolytic reduction, stirring and bubble cooperative treatment, product purification and slurry adjustment, gradient temperature reduction crystallization, solid-liquid separation and washing, and vacuum low-temperature drying. In the application, the asymmetric pulse electrolytic reduction is implemented, compared with the traditional constant-voltage and constant-current electrolysis mode, the electrochemical activity window of the cathode can be accurately controlled, the invalid side reactions such as hydrogen ion reduction and hydrogen evolution are effectively inhibited, and the power consumption of the electrolysis process is greatly reduced. The moving frame of the stirring mechanism drives the cleaning mechanism to realize horizontal reciprocating movement, simultaneously drives the moving wheel to roll along the V-shaped groove support table, realizes lifting reciprocating movement, mechanically peels the bubbles on the surface of the cathode sheet and the anode sheet from multiple angles, greatly reduces the accumulation of the gas film on the electrode surface, and improves the electrolysis current efficiency.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of amino acids and their derivatives, and particularly relates to a low-energy-consumption electrolytic synthesis method of L-cysteine ​​hydrochloride monohydrate. Background Technology

[0002] L-cysteine ​​hydrochloride monohydrate, as an important amino acid derivative containing thiol groups, is widely used in food processing, pharmaceutical preparations, daily chemical skin care, feed additives and other fields due to its unique physicochemical activity. It is an essential raw material in the fine chemical industry, and the optimization and upgrading of its synthesis process has always been a research focus in this field.

[0003] The synthesis technology of this product has gone through the development process of hair hydrolysis-chemical reduction method, enzyme catalytic synthesis method and electrochemical reduction synthesis method. Among them, the electrochemical reduction synthesis method uses L-cysteine ​​as raw material. In the hydrochloric acid aqueous solution system, the disulfide bond is broken by cathodic reduction to generate L-cysteine. After crystallization and drying, the monohydrate product is obtained. This process does not require the use of toxic chemical reducing agents, the product has high purity, and the production process has low emissions of waste. It has become the mainstream technology for the current industrial preparation of L-cysteine ​​hydrochloride monohydrate.

[0004] The current industrial-scale electrolytic synthesis process of L-cysteine ​​hydrochloride still has the following shortcomings: Firstly, existing electrolysis processes mostly adopt traditional constant voltage or constant current electrolysis modes, which cannot precisely control the electrochemical activity window of the cathode. Ineffective side reactions such as hydrogen ion reduction and hydrogen evolution are difficult to suppress effectively, resulting in low current efficiency in the electrolysis process and high energy consumption per unit product, which contradicts the industrial development needs of low energy consumption. Secondly, during the electrolysis process, bubbles easily adhere to the surfaces of the anode and cathode and form a gas film. Existing methods for cleaning bubbles mostly involve fixed scrapers, which are not thorough. The gas film will exacerbate electrode polarization and further reduce electrolysis efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate, which solves the technical problems in the prior art where existing electrolytic processes mostly adopt traditional constant voltage or constant current electrolysis modes, which cannot accurately control the electrochemical activity window of the cathode, resulting in low current efficiency in the electrolysis process; and the incomplete cleaning of the gas film attached to the anode and cathode surfaces, which reduces the electrolysis efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate includes the following steps: Step 1: Add L-cysteine ​​to an aqueous hydrochloric acid solution and stir until L-cysteine ​​is completely dissolved to form a mixture. Then, the mixture is subjected to constant-temperature stirring and dissolution, activated carbon decolorization and impurity removal, and filtration to obtain the electrolyte stock solution; Step 2: Add the electrolyte stock solution to the cathode chamber of the electrolytic cell, and inject the aqueous hydrochloric acid solution into the anode chamber of the electrolytic cell; Step 3: Connect the electrolytic cell to a power source and perform asymmetric pulse electrolytic reduction; control the pulse frequency to 10-1000Hz, the pulse duty cycle to 10%-60%, the average current density to 10-100mA / cm², and the cell voltage to 2.0-2.6V; Step 4: Start the drive mechanism in the electrolytic cell. The drive mechanism drives four sets of stirring mechanisms to operate synchronously. The stirring mechanisms respectively stir the cathode and anode chambers... The electrolyte undergoes mass transfer enhancement stirring; simultaneously, the stirring mechanism is linked with four sets of cleaning mechanisms to perform reciprocating motion, enabling the cleaning mechanisms to remove air bubbles from both sides of the cathode and anode plates; Step 5: After electrolysis, the electrolytic product solution in the cathode chamber is exported from the electrolytic cell, and then the electrolytic product solution is desalted and purified by nanofiltration membrane to obtain a purified product solution; concentrated hydrochloric acid is added to the purified product solution to adjust the pH to 1.0-1.5, and the slurry is prepared by constant temperature stirring to obtain a crystallization solution; Step 6: The crystallization solution is sent to a jacketed continuous crystallizer, and a gradient cooling crystallization process is adopted. L-cysteine ​​hydrochloride monohydrate seed crystals are added to grow crystals and crystallization continues; Step 7: The crystallization slurry is separated into solid and liquid by a horizontal screw centrifuge to obtain wet crystals, and then the wet crystals are washed with purified water; Step 8: The washed wet crystals are dried under vacuum at low temperature until the water content is ≤0.5% to obtain the L-cysteine ​​hydrochloride monohydrate finished product.

[0007] Preferably, in step one, the conditions for constant temperature stirring and dissolution are: temperature 40℃-50℃, stirring speed 80-120r / min, stirring time 30-60min; activated carbon addition is 0.5%-1.0% of the initial solution mass; and the constant temperature stirring time for decolorization and impurity removal is 20-30min.

[0008] Preferably, in step eight, the process parameters for vacuum low-temperature drying are: vacuum degree 0.08-0.09 MPa, temperature 40℃-45℃, and drying time 2-3 hours.

[0009] Preferably, the electrolytic cell in step two includes: a cell body with a sealing cap installed on its top; a cation exchange membrane installed in the cell body, dividing the interior of the cell body into a cathode chamber and an anode chamber, wherein a cathode plate and an anode plate are respectively installed in the cathode chamber and the anode chamber; four sets of stirring mechanisms symmetrically arranged on both sides of the cathode plate and the anode plate, used to enhance the mass transfer stirring of the electrolyte in the corresponding chambers; four sets of cleaning mechanisms corresponding to the four sets of stirring mechanisms, respectively located on both sides of the cathode plate and the anode plate, used to remove bubbles from the reaction surfaces of the cathode plate and the anode plate; and a drive mechanism installed on the bottom surface of the cell body, forming a transmission connection with all four sets of stirring mechanisms, used to provide synchronous driving force for the four sets of stirring mechanisms.

[0010] Preferably, the electrolytic cell further includes: a first discharge pipe installed on the bottom surface of the cell and communicating with the interior of the cathode chamber; a second discharge pipe installed on the bottom surface of the cell and communicating with the interior of the anode chamber; a first metal connecting plate fixedly connected to the cathode plate and extending above the sealing cover; and a second metal connecting plate fixedly connected to the anode plate and extending above the sealing cover.

[0011] Preferably, the stirring mechanism includes: a vertical rod that passes through the bottom surface of the tank and is rotatably connected to the tank; a second bevel gear that is installed at the lower end of the vertical rod; and multiple stirring racks that are located inside the tank and are equidistantly installed on the circumferential surface of the vertical rod.

[0012] Preferably, the stirring mechanism further includes: two guide rails, both installed on the inner bottom surface of the tank; a movable frame, slidably connected to the two guide rails, having a through groove on it; and a cam, located in the through groove and fixedly sleeved on the vertical rod.

[0013] Preferably, the cleaning mechanism includes: a mounting plate with a connecting frame mounted on its bottom surface, the connecting frame passing through the movable frame and slidably connected to the movable frame; multiple drainage channels, all formed on the mounting plate; multiple horizontal scrapers, all mounted on the mounting plate; multiple vertical scrapers, all mounted on the mounting plate; multiple movable wheels, all mounted on the bottom surface of the connecting frame; and multiple support platforms, all mounted on the inner bottom surface of the channel, the top surface of each support platform having a V-shaped groove, and the movable wheels located within the V-shaped groove.

[0014] Preferably, the drive mechanism includes: a mounting box, mounted on the bottom surface of the groove; a crossbar, rotatably connected to the inner wall of the mounting box; a plurality of first bevel gears, all fixedly sleeved on the crossbar and respectively meshing with a plurality of second bevel gears; and a motor, mounted inside the mounting box, with a third bevel gear mounted on its power output shaft, the third bevel gear meshing with any of the first bevel gears.

[0015] Preferably, the electrolytic cell further includes: a first feed pipe installed on the top surface of the sealing cover and communicating with the interior of the cathode chamber; a second feed pipe installed on the top surface of the sealing cover and communicating with the interior of the anode chamber; two exhaust valves, both installed on the top surface of the sealing cover and communicating with the interiors of the cathode chamber and the anode chamber respectively; and a display controller installed on the front of the cell.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The present invention implements asymmetric pulsed electrolytic reduction, which, compared with the traditional constant voltage and constant current electrolysis mode, can precisely control the electrochemical activity window of the cathode, effectively suppress ineffective side reactions such as hydrogen ion reduction and hydrogen evolution, and significantly reduce the power consumption of the electrolysis process.

[0017] 2. The electrolytic cell in this invention is equipped with a driving mechanism and a stirring mechanism. By activating the driving mechanism, the stirring mechanism and the cleaning mechanism are driven to operate, thereby eliminating the concentration gradient near the electrode, avoiding the re-decomposition reaction caused by the local enrichment of L-cysteine ​​on the electrode surface, and ensuring the yield of electrolytic products.

[0018] 3. The electrolytic cell in this invention is equipped with a stirring mechanism. The moving frame of the stirring mechanism drives the cleaning mechanism to move horizontally back and forth. At the same time, the moving wheels are driven to roll along the V-shaped groove support to achieve lifting and reciprocating movement, forming a multi-dimensional reciprocating scraping of the cathode and anode plates. This can mechanically peel off the air bubbles on the surface of the cathode and anode plates from multiple angles, greatly reducing the accumulation of gas film on the electrode surface, structurally reducing electrode polarization, and improving electrolysis current efficiency. 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 The three-dimensional electrolytic cell in this invention Figure 1 ; Figure 2 The three-dimensional electrolytic cell in this invention Figure 2 ; Figure 3 This is a schematic diagram of the assembly structure of the tank and the drive mechanism in this invention; Figure 4 This is a schematic diagram of the assembly structure of the tank, cation exchange membrane, cathode plate, anode plate, stirring mechanism and cleaning mechanism in this invention; Figure 5This is a schematic diagram of the assembly structure of the cathode plate, anode plate, stirring mechanism, and cleaning mechanism in this invention; Figure 6 This is a schematic diagram of the assembly structure of the stirring mechanism and the cleaning mechanism in this invention. Figure 1 ; Figure 7 This is a schematic diagram of the assembly structure of the stirring mechanism and the cleaning mechanism in this invention. Figure 2 ; Figure 8 This is a perspective view of the cleaning mechanism in this invention; Reference numerals: 100, Electrolytic cell; 101, Cell body; 1011, Cathode chamber; 1012, Anode chamber; 1013, First discharge pipe; 1014, Second discharge pipe; 102, Sealing cover; 1021, First feed pipe; 1022, Second feed pipe; 1023, Exhaust valve; 103, Cation exchange membrane; 104, Cathode plate; 1041, First metal connecting plate; 105, Anode plate; 1051, Second metal connecting plate; 106, Handle; 107, Display controller; 110, Stirring Mixing mechanism; 111, guide rail; 112, moving frame; 113, through groove; 114, vertical rod; 115, second bevel gear; 116, mixing rack; 117, cam; 120, cleaning mechanism; 121, mounting plate; 122, drainage trough; 123, horizontal scraper; 124, vertical scraper; 125, connecting frame; 126, moving wheel; 127, support platform; 130, drive mechanism; 131, mounting box; 132, crossbar; 133, first bevel gear; 134, motor; 135, third bevel gear. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] This invention is described in detail with reference to the accompanying drawings. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not to scale. Furthermore, the accompanying drawings are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0025] Furthermore, it should be noted in the description of this invention that the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Example 1: As Figures 1 to 8 As shown, a low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate includes the following steps: Step 1: Add L-cysteine ​​to a 10% hydrochloric acid aqueous solution and stir initially until no obvious solid particles of L-cysteine ​​are visible, forming a mixture. Transfer the mixture to a constant temperature stirring dissolving tank and stir at a constant temperature to dissolve. After dissolution, add activated carbon to the mixture for decolorization and impurity removal. After decolorization, filter using a 5μm precision filter to remove activated carbon and insoluble impurities from the mixture, obtaining an impurity-free and uniformly colored electrolyte stock solution. Temporarily store the electrolyte stock solution in a constant temperature storage tank for later use, with the storage temperature controlled at 40℃. Step 2: The electrolyte stock solution prepared in Step 1 is pumped into the cathode chamber 1011 of the electrolytic cell 100 through the first feed pipe 1021, with the feed rate being 90%-95% of the effective volume of the cathode chamber 1011; simultaneously, a hydrochloric acid aqueous solution with a mass concentration of 5%-8% is pumped into the anode chamber 1012 of the electrolytic cell 100 through the second feed pipe 1022, with the feed rate being 90%-95% of the effective volume of the anode chamber 1012; Step 3: Connect the first metal connecting plate 1041 of the electrolytic cell 100 to the negative terminal of the power supply and the second metal connecting plate 1051 to the positive terminal of the power supply. Turn on the power supply and set the electrolysis process parameters to implement asymmetric pulse electrolysis reduction. Specifically, control the pulse frequency to 10-1000Hz, the pulse duty cycle to 10%-60%, and the average current density to 10-100mA / cm². The cell voltage of the electrolytic cell 100 is stably controlled at 2.0-2.6V. The voltage, current, and temperature parameters during the electrolysis process are monitored in real time through the display controller 107 on the front of the cell 101 to ensure that the electrolysis parameters are within the set range. Step 4: Simultaneously with starting electrolysis, activate the drive mechanism 130 on the bottom of the electrolytic cell 100. This drive mechanism 130 transmits power to the four stirring mechanisms 110, causing them to operate synchronously. The stirring mechanisms 110 stir the electrolyte in the cathode chamber 1011 and the anode chamber 1012, respectively. At the same time, the operation of the stirring mechanisms 110 drives the four cleaning mechanisms 120 to reciprocate synchronously. The cleaning mechanisms 120 continuously clean the two sides of the cathode plate 104 and the two sides of the anode plate 105, promptly removing air bubbles attached to the electrode surfaces. During the electrolysis process, the exhaust valve 1023 can discharge a small amount of gas accumulated in the cathode chamber 1011 and the anode chamber 1012 to ensure pressure balance within the chambers; Step 5: When the electrolysis reaction reaches its endpoint as monitored by the display controller 107, i.e., the L-cysteine ​​conversion rate in the cathode chamber 1011 is ≥98% and the L-cysteine ​​concentration reaches 80-100g / L, turn off the power supply and drive mechanism 130, stop electrolysis and stirring cleaning; open the valve of the first discharge pipe 1013 on the bottom of the tank 101 to discharge the electrolysis product liquid in the cathode chamber 1011 through the first discharge pipe 1013; The electrolyte product solution is then transported to a nanofiltration membrane separation device, where it is desalted and impurities removed by the nanofiltration membrane. This process removes chloride ions and unreacted trace inorganic salts from the product solution, resulting in a purified product solution. The dilute solution retained by the nanofiltration membrane is returned to the constant temperature stirring dissolution tank in step one via pipeline and recycled as water for preparing hydrochloric acid aqueous solution. The purified product solution is then transferred to a mixing tank, and concentrated hydrochloric acid is slowly added while stirring. The pH value of the purified product solution is adjusted to 1.0. After adjustment, the mixture is stirred at a constant temperature for 10 minutes to obtain a uniform crystallization solution. Step Six: The crystallization solution prepared in Step Five is transported to a jacketed continuous crystallizer through pipelines. The stirring and jacket heat exchange functions of the crystallizer are turned on, and a gradient cooling crystallization process is adopted for crystallization. First, the temperature of the crystallization solution is reduced to 20℃-25℃ at a rate of 1℃ / h. L-cysteine ​​hydrochloride monohydrate seed crystals are added to the crystallizer at a rate of 0.1% of the mass of the crystallization solution. The crystals are kept at a constant temperature for 2 hours. Then, the temperature of the solution is reduced to 10℃-15℃ at a rate of 0.5℃ / h, and crystallization continues for 6 hours. During the crystallization process, the condensate from the crystallizer is returned to the constant temperature stirring and dissolving tank in Step One through pipelines. Step 7: After crystallization, the slurry is transported to a horizontal screw centrifuge. The centrifuge is turned on to perform solid-liquid separation. The centrifuge speed is controlled at 2000-2500 r / min and the separation time is 5-8 min to obtain wet crystals of L-cysteine ​​hydrochloride monohydrate. The separated mother liquor is transported to a vacuum concentration device through pipeline. After vacuum concentration, it is returned to the constant temperature stirring and dissolving tank in Step 1 as a solvent for raw material preparation and recycling. Then, add purified water to the wet crystals in the centrifuge to wash them and remove the residual mother liquor on the surface of the crystals. After washing, start the centrifuge again to separate the solid and liquid. Step 8: Transfer the washed L-cysteine ​​hydrochloride monohydrate wet crystals to a vacuum dryer, turn on the vacuum system and heating system, set the vacuum drying process parameters, and perform vacuum low-temperature drying until the moisture content of the wet crystals is ≤0.5%, to obtain the finished L-cysteine ​​hydrochloride monohydrate product.

[0028] In step one above, the specific process conditions for constant temperature stirring and dissolution are as follows: the temperature of the constant temperature stirring and dissolution tank is controlled at 40℃-50℃, the stirring speed is controlled at 80-120r / min, and the constant temperature stirring and dissolution time is 30-60min, so that L-cysteine ​​is completely dissolved in the hydrochloric acid aqueous solution without any solid particles remaining; the specific parameters for activated carbon decolorization and impurity removal are as follows: the amount of activated carbon added is 0.5% of the mass of the initial solution, after adding activated carbon, stirring is continued at a constant temperature of 40℃, the constant temperature stirring time for decolorization and impurity removal is 20min, after stirring is completed, it is allowed to stand for 5min, and then filtered.

[0029] In step eight above, the specific process parameters for vacuum low-temperature drying are as follows: the vacuum degree of the vacuum dryer is controlled at 0.08 MPa, the drying temperature is controlled at 40℃, the vacuum low-temperature drying time is 2 hours, and the moisture content of the crystal is monitored in real time by an online moisture content detector during the drying process. When the moisture content is ≤0.5%, the vacuum system and heating system are turned off, the drying is stopped, and the dried crystal is taken out.

[0030] Example 2: While all other parts are the same as in Example 1, the difference between this example and Example 1 is as follows: In step one, the hydrochloric acid aqueous solution has a mass concentration of 15%, and the temperature of the constant temperature storage tank is controlled at 50℃. The amount of activated carbon added is 1.0% of the mass of the initial solution. After adding the activated carbon, the mixture is stirred at a constant temperature of 50℃ for 30 minutes to remove color and impurities.

[0031] In step five, the purified product solution is transferred to a mixing tank, and concentrated hydrochloric acid is slowly added while stirring. The pH value of the purified product solution is adjusted to 1.5. After adjustment, the mixture is stirred at a constant temperature for 15 minutes.

[0032] In step six, the amount of seed crystal added is 0.2% of the mass of the crystallization solution, and the crystals are grown at a constant temperature for 3 hours; then the temperature of the solution is reduced to 10℃-15℃ at a rate of 0.5℃ / h, and crystallization continues for 8 hours.

[0033] In step eight, the vacuum degree of the vacuum dryer is controlled at 0.09 MPa, the drying temperature is controlled at 45°C, and the vacuum low-temperature drying time is 3 hours.

[0034] Example 3: As Figure 1 , Figure 4 and Figure 5 As shown, while all other parts are the same as in Example 1, the difference between this example and Example 1 is that: The electrolytic cell 100 used in step two above includes a cell body 101, a sealing cover 102, a cation exchange membrane 103, a cathode plate 104, an anode plate 105, four sets of stirring mechanisms 110, four sets of cleaning mechanisms 120, and a drive mechanism 130.

[0035] The top of the tank 101 is open, and two handles 106 are installed on the side of the tank 101. The sealing cover 102 is installed on the top of the tank 101 by bolts to achieve a seal. The cation exchange membrane 103 is vertically installed in the center of the tank 101 and is sealed to the inner wall of the tank 101 by a sealing strip, dividing the internal space of the tank 101 into independent cathode chambers 1011 and anode chambers 1012 at equal intervals, preventing the electrolyte in the cathode chambers 1011 and anode chambers 1012 from mixing. The cathode plate 104 is vertically installed in the center of the cathode chamber 1011, and the anode plate 105 is vertically installed in the center of the anode chamber 1012. Both the cathode plate 104 and the anode plate 105 are titanium-based inert electrodes coated with precious metals, which can ensure the conductivity and corrosion resistance of the electrodes. Two sets of stirring mechanisms 110 are symmetrically arranged on both sides of the cathode plate 104, and another two sets of stirring mechanisms 110 are symmetrically arranged on both sides of the anode plate 105; four sets of cleaning mechanisms 120 correspond one-to-one with the four sets of stirring mechanisms 110, and are also divided into two sets symmetrically arranged on both sides of the cathode plate 104, and another two sets symmetrically arranged on both sides of the anode plate 105. The four sets of cleaning mechanisms 120 are used to remove bubbles from the reaction surfaces on both sides of the cathode plate 104 and the reaction surfaces on both sides of the anode plate 105, respectively. The drive mechanism 130 is connected to the four mixing mechanisms 110. The drive mechanism 130 is used to provide power to the four mixing mechanisms 110 and drive the four mixing mechanisms 110 to run synchronously.

[0036] Specifically, the cation exchange membrane 103 in the electrolytic cell 100 is a proton-selective permeable membrane that allows only hydrogen ions and metal cations to pass through while preventing anions and large organic molecules from passing through. This effectively separates the cathode chamber 1011 and the anode chamber 1012, ensuring that the reduction reaction at the cathode and the oxidation reaction at the anode proceed independently, and preventing the anode reaction products from diffusing into the cathode chamber 1011 and causing side reactions. In operation, the drive mechanism 130 activates four sets of stirring mechanisms 110, which simultaneously stir the electrolyte in the cathode chamber 1011 and anode chamber 1012 to enhance mass transfer. Simultaneously, the four stirring mechanisms 110 also activate four sets of cleaning mechanisms 120, which clean air bubbles from the reaction surfaces on both sides of the cathode plate 104 and the anode plate 105. Furthermore, the operation of both the stirring mechanisms 110 and the cleaning mechanisms 120 is driven by the drive mechanism 130, reducing the need for a separate power source and lowering energy consumption and maintenance costs.

[0037] like Figures 1 to 3 As shown, the electrolytic cell 100 also includes a first discharge pipe 1013, a second discharge pipe 1014, a first metal connecting plate 1041, and a second metal connecting plate 1051. The first discharge pipe 1013 is installed on the left side of the bottom surface of the cell 101 by welding. The upper end of the first discharge pipe 1013 is connected to the bottom of the cathode chamber 1011, and the first discharge pipe 1013 is used for the discharge of electrolytic product liquid in the cathode chamber 1011. The second discharge pipe 1014 is installed on the right side of the bottom surface of the cell 101 by welding. The upper end of the second feed pipe 1014 is connected to the bottom of the anode chamber 1012. The second feed pipe 1014 is used to discharge the waste electrolyte in the anode chamber 1012. The first metal connecting plate 1041 is made of copper. One end of the first metal connecting plate 1041 is fixedly connected to the top of the cathode plate 104. The other end of the first metal connecting plate 1041 extends vertically upward, passes through the sealing through hole on the sealing cover 102, and extends to the top of the sealing cover 102. The first metal connecting plate 1041 is used to connect to the negative terminal of the power supply. The second metal connecting plate 1051 is also made of copper. One end of the second metal connecting plate 1051 is fixedly connected to the top of the anode plate 105, and the other end of the second metal connecting plate 1051 extends vertically upward, passes through another sealing through hole on the sealing cover 102, and extends to the top of the sealing cover 102 for connection with the positive terminal of the power supply. An insulating sealing sleeve is provided in the sealing through hole to ensure sealing performance and prevent leakage caused by contact between the metal connecting plate and the sealing cover 102.

[0038] like Figures 1 to 3 As shown, the electrolytic cell 100 also includes a first feed pipe 1021, a second feed pipe 1022, two exhaust valves 1023, and a display controller 107. Both the first feed pipe 1021 and the second feed pipe 1022 are made of stainless steel and are symmetrically installed on the top surface of the sealing cover 102 by welding. The lower end of the first feed pipe 1021 communicates with the interior of the cathode chamber 1011 and is used to supply the electrolyte to the cathode chamber 1011. The lower end of the second feed pipe 1022 communicates with the interior of the anode chamber 1012 and is used to supply hydrochloric acid aqueous solution to the anode chamber 1012. The two exhaust valves 1023 are symmetrically installed on the top surface of the sealing cover 102 and are respectively connected to the interior of the cathode chamber 1011 and the anode chamber 1012. The two exhaust valves 1023 are used to discharge fluid from the chambers. The gas generated during electrolysis ensures pressure balance within the chamber. Temperature, current, and voltage sensors are installed inside the tank 101 (not shown in the diagram). The display controller 107 is a touchscreen intelligent controller, bolted to the front of the tank 101. The display controller 107 contains a PLC control system and is electrically connected to the temperature, current, and voltage sensors of the electrolytic cell 100. The display controller 107 can monitor and display the temperature, current, and voltage parameters during electrolysis in real time. Simultaneously, electrolysis process parameters can be set via the touchscreen, enabling precise parameter control.

[0039] like Figures 5 to 7 As shown, the stirring mechanism 110 includes a vertical rod 114, a second bevel gear 115, and multiple sets of stirring racks 116. The vertical rod 114 is made of stainless steel and vertically penetrates the bottom surface of the tank 101. It is rotatably connected to the tank 101 via bearings. A sealing gasket is provided at the connection between the bearings and the tank 101 to ensure the sealing performance of the tank 101 and prevent electrolyte leakage. The second bevel gear 115 is fixedly installed at the lower end of the vertical rod 114. The second bevel gear 115 is located below the tank 101 and is connected to the drive mechanism 130 for transmission. The second bevel gear 115 is used to receive the power transmitted by the drive mechanism 130. The multiple sets of stirring racks 116 are made of polypropylene and are resistant to acid corrosion. The multiple sets of stirring racks 116 are equidistantly fixed on the circumferential surface of the vertical rod 114.

[0040] Specifically, when the drive mechanism 130 is running, it drives the vertical rod 114 to rotate through the second bevel gear 115, which in turn drives multiple sets of stirring racks 116 to rotate, thereby stirring the electrolyte in the cathode chamber 1011 and the anode chamber 1012 and reducing the concentration gradient near the electrodes.

[0041] like Figures 6 to 8 As shown, the cleaning mechanism 120 includes a mounting plate 121, multiple drainage channels 122, multiple horizontal scrapers 123, multiple vertical scrapers 124, a connecting frame 125, multiple casters 126, and multiple support platforms 127. The mounting plate 121 is made of polypropylene and is vertically positioned above the movable frame 112. The mounting plate 121 is parallel to the surfaces of the cathode plate 104 and the anode plate 105. Multiple drainage channels 122 are formed through the mounting plate 121. The multiple horizontal scrapers 123 and multiple vertical scrapers 124 are all made of polytetrafluoroethylene, and the horizontal scrapers 123 and vertical scrapers 124 are interlaced to form a grid structure. The free ends of the horizontal scraper 123 and the vertical scraper 124 are in contact with the electrode surface; the connecting frame 125 is made of stainless steel, and the upper end of the connecting frame 125 is fixedly connected to the bottom surface of the mounting plate 121 by bolts. The connecting frame 125 is slidably connected to the moving frame 112; multiple moving wheels 126 are evenly installed on the bottom surface of the connecting frame 125 through rotating shafts; multiple support platforms 127 are fixedly installed on the inner bottom surface of the tank 101. The multiple support platforms 127 are located below the multiple moving wheels 126 respectively. The top surface of the support platform 127 is provided with a V-shaped groove, and the moving wheels 126 are located in the V-shaped groove. The moving wheels 126 can roll along the V-shaped groove.

[0042] Specifically, when the moving frame 112 moves horizontally back and forth along the guide rail 111, it can drive the connecting frame 125 to move, which in turn drives the mounting plate 121 to move, and then drives the horizontal scraper 123 and the vertical scraper 124 to move horizontally. When the moving frame 112 moves, it will also drive multiple moving wheels 126 to move along the V-shaped groove. The undulation of the V-shaped groove causes the moving wheels 126 to move back and forth while moving horizontally, which in turn drives the connecting frame 125 and the mounting plate 121 to move back and forth, and then drives the horizontal scraper 123 and the vertical scraper 124 to move up and down back and forth. When the horizontal scraper 123 and the vertical scraper 124 move back and forth, the friction between their free ends and the cathode plate 104 and the anode plate 105 will directly destroy the gas-liquid interface film on the electrode surface, forcibly peeling off the bubbles attached to the electrode surface. The peeled bubbles accumulate at the top of the chamber with the flow of electrolyte and are discharged through the exhaust valve 1023, which greatly reduces the accumulation of gas film on the electrode surface.

[0043] like Figures 5 to 7As shown, the stirring mechanism 110 also includes two guide rails 111, a movable frame 112, a through groove 113, and a cam 117. The two guide rails 111 are made of stainless steel and are fixedly installed parallel and symmetrically on the inner bottom surface of the tank 101. The movable frame 112 is made of polypropylene and has a sliding groove on its bottom surface that matches the guide rails 111. The movable frame 112 is slidably connected to the two guide rails 111 through the sliding groove and can move horizontally back and forth along the guide rails 111. The through groove 113 is a rectangular through hole and is opened at the center of the movable frame 112. The cam 117 is made of stainless steel and its rim extends into the through groove 113. The cam 117 slides in contact with the inner wall of the through groove 113.

[0044] Specifically, when the vertical rod 114 drives the cam 117 to rotate in a circular motion, the rim of the cam 117 generates a horizontal thrust on the inner wall of the through groove 113, which pushes the moving frame 112 to move horizontally back and forth along the guide rail 111.

[0045] The two parallel guide rails 111 can guide and position the moving frame 112, ensuring that the reciprocating movement of the moving frame 112 is in the horizontal direction without deviation or jamming, while reducing the friction between the moving frame 112 and the bottom surface of the tank 101.

[0046] Working principle: In actual use, the electrolyte in the constant temperature storage tank is first pumped into the cathode chamber 1011 through the first feed pipe 1021, and the 5%-8% hydrochloric acid aqueous solution is pumped into the anode chamber 1012 through the second feed pipe 1022, and the feed rate is controlled to be 90%-95% of the effective volume of the anode chamber 1012.

[0047] The first metal connecting plate 1041 is then connected to the negative terminal of the power supply, and the second metal connecting plate 1051 is connected to the positive terminal of the power supply. The process parameters of asymmetric pulse electrolysis are then set through the display controller 107: pulse frequency 10-1000Hz, pulse duty cycle 10%-60%, average current density 10-100mA / cm², and cell voltage 2.0-2.6V. At the same time, the parameter monitoring threshold of the display controller 107 is set, and the real-time parameter monitoring function is enabled.

[0048] The power is turned on by the display controller 107, and the asymmetric pulse electrolysis reduction reaction is started. L-cysteine ​​in the cathode chamber 1011 undergoes a reduction reaction on the surface of the cathode plate 104 to generate L-cysteine, and water in the anode chamber 1012 undergoes an oxidation reaction to generate oxygen. During the electrolysis process, the display controller 107 monitors parameters such as voltage, current, and temperature in real time. If the parameters deviate from the set range, they are adjusted in time via the touch screen.

[0049] Then, by starting the motor 134, the crossbar 132 is driven to rotate through the meshing of the third bevel gear 135 and the first bevel gear 133. The crossbar 132, through the meshing of the first bevel gear 133 and the second bevel gear 115, synchronously drives the vertical rod 114 of the four sets of stirring mechanisms 110 to rotate, thereby driving the stirring frame 116 and the cam 117 to rotate synchronously. The rotating stirring frame 116 will stir the electrolyte in the cathode chamber 1011 and the anode chamber 1012, reducing the concentration gradient near the electrode.

[0050] When the cam 117 rotates, the rim of the cam 117 exerts a horizontal thrust on the inner wall of the through groove 113, pushing the moving frame 112 to reciprocate horizontally along the guide rail 111. The moving frame 112 drives the connecting frame 125 to move, which in turn drives the mounting plate 121 to move, which in turn drives the horizontal scraper 123 and the vertical scraper 124 to move horizontally. When the moving frame 112 moves, it also drives multiple moving wheels 126 to move along the V-shaped groove. The undulations of the V-shaped groove cause the moving wheels 126 to reciprocate while moving horizontally. The lifting motion drives the connecting frame 125 and the mounting plate 121 to reciprocate, which in turn drives the horizontal scraper 123 and the vertical scraper 124 to move up and down. When the horizontal scraper 123 and the vertical scraper 124 reciprocate, the friction between their free ends and the cathode plate 104 and the anode plate 105 will directly destroy the gas-liquid interface film on the electrode surface, forcibly peeling off the bubbles attached to the electrode surface. The peeled bubbles accumulate at the top of the chamber with the flow of electrolyte and are discharged through the exhaust valve 1023, greatly reducing the accumulation of gas film on the electrode surface.

[0051] When the display controller 107 detects that the L-cysteine ​​conversion rate in the cathode chamber 1011 is ≥98% and the L-cysteine ​​concentration reaches 80-100g / L, the display controller 107 first turns off the power to stop the electrolysis reaction, then turns off the motor 134, and stops the operation of the stirring mechanism 110 and the cleaning mechanism 120.

[0052] Finally, the electrolyte solution in the cathode chamber 1011 is discharged through the first discharge pipe 1013.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0054] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate, characterized in that, Includes the following steps: Step 1: Add L-cysteine ​​to hydrochloric acid aqueous solution and stir until L-cysteine ​​is completely dissolved to form a mixture. Then, stir the mixture at a constant temperature to dissolve it, decolorize and remove impurities with activated carbon, and filter it to obtain the electrolyte stock solution. Step 2: Add the electrolyte stock solution to the cathode chamber of the electrolytic cell, and inject hydrochloric acid aqueous solution into the anode chamber of the electrolytic cell; Step 3: Connect the electrolytic cell to a power source and perform asymmetric pulse electrolytic reduction; control the pulse frequency to 10-1000Hz, the pulse duty cycle to 10%-60%, the average current density to 10-100mA / cm², and the cell voltage to 2.0-2.6V. Step 4: Start the drive mechanism in the electrolytic cell. The drive mechanism drives four sets of stirring mechanisms to run synchronously. The stirring mechanisms respectively perform mass transfer enhancement stirring of the electrolyte in the cathode chamber and anode chamber. At the same time, the stirring mechanisms are linked with four sets of cleaning mechanisms to perform reciprocating motion synchronously, so that the cleaning mechanisms remove air bubbles from both sides of the cathode and anode plates. Step 5: After electrolysis is completed, the electrolytic product solution in the cathode chamber is exported from the electrolytic cell, and then the electrolytic product solution is desalted and purified by nanofiltration membrane to obtain purified product solution. Concentrated hydrochloric acid was added to the purified product solution to adjust the pH to 1.0-1.5, and the mixture was stirred at a constant temperature to obtain the crystallization solution. Step 6: The crystallization liquid is fed into a jacketed continuous crystallizer, and a gradient cooling crystallization process is adopted. L-cysteine ​​hydrochloride monohydrate seed crystals are added to grow crystals and crystallization continues. Step 7: Separate the crystallization slurry into solid and liquid phases using a horizontal screw centrifuge to obtain wet crystals, and then wash the wet crystals with purified water; Step 8: The washed wet crystals are dried under vacuum at low temperature until the water content is ≤0.5% to obtain the L-cysteine ​​hydrochloride monohydrate product.

2. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 1, characterized in that, In step one, the conditions for constant temperature stirring and dissolution are: temperature 40℃-50℃, stirring speed 80-120r / min, stirring time 30-60min; the amount of activated carbon added is 0.5%-1.0% of the initial solution mass, and the constant temperature stirring time for decolorization and impurity removal is 20-30min.

3. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 1, characterized in that, In step eight, the process parameters for vacuum low-temperature drying are: vacuum degree 0.08-0.09 MPa, temperature 40℃-45℃, and drying time 2-3 hours.

4. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 1, characterized in that, The electrolytic cell in step two includes: The tank body has a sealing cover installed on its top; A cation exchange membrane is installed in the tank, dividing the interior of the tank into a cathode chamber and an anode chamber, wherein a cathode plate and an anode plate are respectively installed in the cathode chamber and the anode chamber. Four sets of stirring mechanisms are symmetrically arranged on both sides of the cathode plate and both sides of the anode plate to enhance mass transfer stirring of the electrolyte in the corresponding chambers. Four sets of cleaning mechanisms are arranged one-to-one with the four sets of stirring mechanisms, located on both sides of the cathode plate and both sides of the anode plate, respectively, for removing bubbles from the reaction surfaces of the cathode plate and the anode plate; The drive mechanism is installed on the bottom surface of the tank and forms a transmission connection with the four sets of stirring mechanisms, and is used to provide synchronous driving force for the four sets of stirring mechanisms.

5. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 4, characterized in that, The electrolytic cell also includes: The first discharge pipe is installed on the bottom surface of the tank and communicates with the interior of the cathode chamber; The second feed pipe is installed on the bottom surface of the tank and communicates with the interior of the anode chamber; A first metal connecting plate is fixedly connected to the cathode plate and extends above the sealing cover; The second metal connecting plate is fixedly connected to the anode plate and extends above the sealing cover.

6. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 4, characterized in that, The stirring mechanism includes: A vertical rod passes through the bottom surface of the tank and is rotatably connected to the tank. The second bevel gear is installed at the lower end of the vertical rod; Multiple sets of stirring racks are located inside the tank and are equidistantly installed on the circumferential surface of the vertical rod.

7. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 6, characterized in that, The stirring mechanism also includes: Both guide rails are installed on the inner bottom surface of the groove; The movable frame is slidably connected to the two guide rails and has through slots on it. The cam is located in the through groove and is fixedly sleeved on the vertical rod.

8. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 7, characterized in that, The cleaning mechanism includes: The mounting plate has a connecting frame installed on its bottom surface, and the connecting frame passes through the movable frame and is slidably connected to the movable frame. Multiple drainage channels are provided on the mounting plate; Multiple transverse scrapers are mounted on the mounting plate; Multiple vertical scrapers are mounted on the mounting plate; Multiple casters are mounted on the bottom surface of the connecting frame; Multiple support platforms are installed on the inner bottom surface of the groove, and a V-shaped groove is opened on the top surface of the support platform. The moving wheel is located in the V-shaped groove.

9. The low-energy-consumption electrolytic synthesis method for L-cysteine ​​hydrochloride monohydrate according to claim 6, characterized in that, The drive mechanism includes: The mounting box is installed on the bottom surface of the groove. The crossbar is rotatably connected to the inner wall of the mounting box; Multiple first bevel gears are fixedly sleeved on the crossbar and respectively mesh with multiple second bevel gears; The motor is installed in the mounting box, and a third bevel gear is mounted on its power output shaft. The third bevel gear meshes with any of the first bevel gears.

10. The low-energy-consumption electrolytic synthesis method of L-cysteine ​​hydrochloride monohydrate according to claim 4, characterized in that, The electrolytic cell also includes: The first feed pipe is installed on the top surface of the sealing cover and communicates with the interior of the cathode chamber; The second feed pipe is installed on the top surface of the sealing cover and communicates with the interior of the anode chamber; Two exhaust valves are installed on the top surface of the sealing cover and are respectively connected to the inside of the cathode chamber and the anode chamber; The display controller is mounted on the front of the tank.

Images