System and method for producing battery-grade sodium carbonate from food-grade sodium bicarbonate

Abstract

The invention provides a system and method for producing battery-grade sodium carbonate from food-grade sodium bicarbonate, and relates to the technical field of chemical production. The system comprises the following components: a dissolving unit, an impurity removal unit, a pulse heating reaction unit, a microreactor unit, a crystallization unit, a separation unit, a calcination unit, a pulverizing unit, a ferromagnetic removal unit, a carbonization unit, a baking soda preparation unit, and a material circulation unit. The invention realizes precise control of the decomposition reaction of sodium bicarbonate by introducing pulse heating technology and microreactor technology. The pulse heating technology effectively avoids local overheating and side reactions caused by too fast reaction by precisely regulating the frequency, intensity and duration of pulses, and also solves the problem that too slow reaction affects production efficiency. The microreactor technology optimizes the reaction process of converting sodium bicarbonate into sodium carbonate by virtue of its high surface area-to-volume ratio and good mass transfer and heat transfer performance.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and particularly relates to a system and a method for producing battery-grade sodium carbonate from food-grade sodium bicarbonate. Background Art

[0002] With the increasing global attention to clean energy and sustainable development, the new energy industry has ushered in unprecedented development opportunities. As the core component in the new energy field, the performance and quality of lithium-ion batteries directly determine the market competitiveness of new energy products. Battery-grade sodium carbonate, as a key raw material for the production of lithium-ion batteries, has a vital impact on the performance of batteries due to its purity and particle size. In recent years, with the continuous expansion of the new energy market, the demand for battery-grade sodium carbonate has also shown a rapid growth trend.

[0003] The traditional battery-grade sodium carbonate production process mainly relies on a combination of chemical reactions and physical treatment steps, but in actual operation, there are many limitations. On the one hand, the traditional process is not precise enough in reaction control, resulting in poor product quality consistency and large batch differences, which is difficult to meet the needs of the high-end market. On the other hand, the traditional process is inefficient in impurity removal and purification, requires a large amount of energy and raw materials, and the generated wastewater, waste gas and other pollutants are difficult to treat, which is not conducive to environmental protection. In addition, most of the equipment in the traditional process are large reactors and crystallizers, which make it difficult to achieve precise temperature, pressure and residence time control, resulting in product purity and particle size distribution. It is difficult to achieve an ideal state, especially for the conversion of food-grade sodium bicarbonate to battery-grade sodium carbonate. The traditional process has problems such as low conversion efficiency and unstable product quality.

[0004] In view of the above problems, it is necessary to optimize the existing food-grade sodium bicarbonate production battery-grade sodium carbonate system and method thereof. By introducing pulse heating technology and microreactor technology, precise control of the decomposition reaction of sodium bicarbonate can be achieved, and the purity and particle size uniformity of the product can be improved. At the same time, by optimizing the steps of impurity removal, crystallization, calcination, etc., energy consumption and pollutant emissions are reduced. Therefore, it is of great significance to develop a food-grade sodium bicarbonate production battery-grade sodium carbonate system and method thereof that can comprehensively realize the above characteristics. Summary of the invention

[0005] The purpose of the present invention is to make up for the shortcomings of the prior art and provide a system and method for producing battery-grade sodium carbonate from food-grade sodium bicarbonate. The system can automatically adapt to different medical environments and lighting conditions through the high-resolution, low-light camera in the image acquisition module, combined with the scene analysis capability. At the same time, the environment and privacy management module automatically adjusts the camera parameters according to the privacy level and monitoring strategy to ensure the acquisition of clear and usable video images. The data monitoring module encrypts the video image data and displays the processed images in real time to facilitate viewing and supervision by monitoring personnel. The facial recognition module adopts a facial recognition algorithm to realize dynamic facial recognition of personnel entering the medical data management area to improve security. The privacy display control module flexibly controls the display degree of the privacy area according to the personnel role and authority to effectively protect the patient's privacy.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: on the one hand, a food-grade sodium bicarbonate production battery-grade sodium carbonate system, the system includes the following components: a dissolution unit, an impurity removal unit, a pulse heating reaction unit, a microreactor unit, a crystallization unit, a separation unit, a calcination unit, a crushing unit, a ferromagnetic removal unit, a carbonization unit, a baking soda preparation unit and a material circulation unit;

[0007] The dissolving unit comprises a dissolving tank, which is equipped with a stirring device and a heating device to fully dissolve the food-grade sodium bicarbonate to form a sodium bicarbonate solution;

[0008] The impurity removal unit is composed of an ion exchange column and a filter device, the ion exchange column is used to remove specific metal ion impurities in the solution, and the filter device further filters out suspended impurities in the solution;

[0009] The pulse heating reaction unit adopts a pulse heating device to control the rate of sodium bicarbonate decomposition reaction through pulse heating technology. During the reaction process, the frequency, intensity and duration of the pulse are controlled to match the kinetic requirements of the reaction.

[0010] The microreactor unit comprises a microreactor, into which the sodium bicarbonate solution and the reaction reagent are introduced at a small flow rate, and rapid mixing and reaction are performed in the microchannel, and the reaction conditions are precisely controlled to optimize the reaction process;

[0011] The crystallization unit adopts a crystallizer, which uses vacuum cooling crystallization technology to promote the precipitation of sodium carbonate crystals by regulating crystallization temperature, pressure and solution concentration parameters;

[0012] The separation unit uses a centrifugal separator, adjusting the rotation speed between 1000-5000 rpm to separate the crystallized sodium carbonate crystals from the mother liquor;

[0013] The calcination unit is a drying furnace, which calcines food-grade sodium bicarbonate in a specific environment of 160-200° C. to completely convert it into sodium carbonate, preliminarily meeting the basic index requirements of battery-grade sodium carbonate;

[0014] The pulverizing unit uses a jet mill system to finely pulverize the calcined material to meet the product particle size requirements of battery-grade sodium carbonate;

[0015] The iron and magnetic removal unit adopts an iron and magnetic material removal device, and the magnetic field strength is controlled at 5000-20000 Gauss, which is used to completely remove impurities mixed in the material during the transportation process, so that it meets the quality standards of battery-grade sodium carbonate;

[0016] The carbonization unit includes a carbonization tower, which is used to make a Na2CO3 solution by mixing the hot alkali solution sent from the calcination process with the low-salt heavy ash filtrate, which enters the carbonization tower after clarification and filtration, and reacts with the CO2 gas sent from the soda ash process to generate a NaHCO3 solution, which is then cooled to obtain NaHCO3 crystals;

[0017] The baking soda preparation unit comprises a separator, a dryer, a cyclone separator and a cooling alkali machine. The NaHCO3 crystals separated from the carbonization unit are separated by the separator and then enter the dryer. The dried baking soda enters the cooling alkali machine through the cyclone separator for cooling and then enters the packaging warehouse for packaging;

[0018] The material circulation unit includes a filtrate barrel and a delivery pump. The filtrate after separating the NaHCO3 solid enters the filtrate barrel and is pumped back to the hot alkali liquid tower of the calcination process to absorb furnace gas dust to form hot alkali liquid, which is then sent to the baking soda for recycling.

[0019] Furthermore, the dissolution unit includes a dissolution tank, which is equipped with a stirring device and a heating device. According to the volume of the dissolution tank and the required stirring intensity, the speed of the stirring device is set to 60-300 rpm, and the temperature of the dissolution tank is set to 40-60°C. By comparing with the set temperature, the heating device automatically determines whether to heat.

[0020] Furthermore, during the reaction process, the pulse heating reaction unit matches the kinetic requirements of the reaction by controlling the frequency, intensity and duration of the pulse, wherein the pulse frequency can be adjusted between 1-100 Hz, the pulse intensity can be adjusted between 10%-100% of the rated power, and the pulse duration can be adjusted between 1-60 seconds.

[0021] Furthermore, the pulse heating reaction unit matches the kinetic requirements of the reaction. Specifically, the target reaction rate of the sodium bicarbonate decomposition reaction is set to v r The activation energy of the reaction is E a, the ideal gas constant is R, the reaction temperature is T, and the reaction rate constant is A is the pre-exponential factor, assuming that the heat provided by pulse heating has a linear relationship with the reaction rate v r =k1×Q, k1 is the proportionality coefficient, single pulse heat Q=P×t, P is the pulse intensity or power, t is the pulse duration, pulse frequency f and average reaction rate v avg The relationship is v avg =k1×Q×f=k1×P×t×f, according to v avg Adjust the pulse frequency f so that the average reaction rate v avg Approaching the target reaction rate v τ , thereby matching the kinetic requirements of the reaction.

[0022] Furthermore, the microreactor unit includes a microreactor, which is made of stainless steel or silicon carbide material to form a microchannel plate laminated structure, the size of the microchannel is between 100-1000 microns, and its feeding system includes a metering pump and a flow controller, which are respectively used to introduce sodium bicarbonate solution and reaction reagents into different feeding ports of the microreactor at a small flow rate, the reaction reagent selects the solution, and the flow controller is linked with the pressure sensor and temperature sensor in the microreactor to adjust the feed flow rate in real time according to the reaction conditions to ensure that the reaction is carried out in a stable state, and the microreactor is equipped with a heat exchange system, by introducing a cooling medium into the jacket or microchannel, the reaction temperature is accurately controlled, the heat exchange system is connected to the temperature controller, the reaction temperature is set to 50-80°C, and the flow rate of the cooling medium is automatically adjusted by comparing with the set temperature, so that the reaction reaches a balanced state in an instant and maintains stability.

[0023] Furthermore, in the microreactor unit, the feed flow rate is adjusted in real time according to the reaction conditions, the designed flow rate of the pump is Q, the speed of the pump is n, and the displacement of the pump is D, and the relationship is Q=D×n. The feed flow rates of the two solutions are controlled by adjusting the speed of the pump, and the reaction temperature is accurately controlled by introducing a cooling medium into the jacket or microchannel. Specifically, the reaction temperature in the microreactor is set to T, and the target temperature is set to T set , the flow rate of the cooling medium is q, and the specific heat capacity of the cooling medium is C p The heat transfer coefficient between the microreactor and the cooling medium is h, the heat transfer area is A, and according to the heat balance equation q×C p ×(TT in )=h×A×(TT set ), where T in is the inlet temperature of the cooling medium, from which the adjustment formula of the cooling medium flow rate can be obtained: When T>T set When q increases, when T <T setWhen q is reduced, the reaction temperature is controlled near the target temperature.

[0024] Furthermore, the crystallization unit adopts a crystallizer, and the crystallizer uses vacuum cooling crystallization technology to regulate crystallization temperature, pressure and solution concentration parameters. The crystallization temperature is controlled at 30-40°C, the pressure is controlled at 1-10 kPa, and the solution concentration should be close to saturation or supersaturation.

[0025] Furthermore, the pulverizing unit adopts a jet mill system to finely pulverize the calcined material. A fluidized bed jet mill is used, and a pulverizing chamber and a classifying wheel are arranged inside. The diameter of the pulverizing chamber is 0.5-1 meter, and the height is 1-2 meters. The rotation speed of the classifying wheel can be adjusted between 1000-10000 rpm. By adjusting the rotation speed of the classifying wheel, the particle size of the product can be accurately controlled. The material is accelerated by the high-speed airflow and collides with each other in the jet mill main unit and pulverized. The pulverized material enters the classifying wheel with the airflow for particle size classification. The product that meets the particle size requirements is discharged from the discharge port of the jet mill main unit and enters the ferromagnetic removal unit. The coarse particle material that does not meet the particle size requirements returns to the pulverizing chamber for further pulverization, forming a closed cycle pulverizing process.

[0026] Furthermore, the baking soda preparation unit includes a separator, a dryer, a cyclone separator and a cooling alkali machine. The separator is a centrifugal separator made of stainless steel with a special surface treatment. The drum diameter is between 0.3-1.5 meters and the rotation speed is between 800-4000 rpm. The feed port of the separator is connected to the discharge port of the carbonization unit. The discharge port is divided into a solid phase discharge port and a liquid phase discharge port. The solid phase discharge port is connected to the dryer, and the liquid phase discharge port is connected to the material circulation unit. The dryer adopts a fluidized bed dryer, and the drying temperature is adjusted between 80-150°C. The flow rate and temperature of the heating medium are controlled by the temperature controller and the temperature sensor installed in the dryer. The cyclone separator is made of stainless steel. The dust-containing gas enters from the tangential direction of the top side of the cyclone separator and rotates at high speed in the separator. Due to the action of centrifugal force, the baking soda particles are thrown to the wall of the device and fall along the wall to the bottom discharge port and enter the cooling alkali machine, while the purified air is discharged from the air outlet at the top.

[0027] On the other hand, a method for producing battery-grade sodium carbonate from food-grade sodium bicarbonate comprises the following specific steps:

[0028] Sodium bicarbonate dissolution: Add food-grade sodium bicarbonate into the dissolution tank of the dissolution unit, add an appropriate amount of deionized water, turn on the stirring device and the heating device to fully dissolve the sodium bicarbonate, control the solution temperature at 40-60°C, and obtain a sodium bicarbonate solution;

[0029] Solution impurity removal: pass the sodium bicarbonate solution into the ion exchange column of the impurity removal unit to remove the metal ion impurities in the solution, and filter out the suspended impurities in the solution through the filtering device to obtain the purified sodium bicarbonate solution;

[0030] Pulse heating reaction step: feeding the purified sodium bicarbonate solution into a pulse heating device of a pulse heating reaction unit, performing a sodium bicarbonate decomposition reaction by controlling the frequency, intensity and duration of the pulse to obtain a preliminarily converted sodium carbonate solution;

[0031] Micro-reaction: The initially converted sodium carbonate solution and the reaction reagents are introduced into the microreactor of the microreactor unit at a small flow rate, and quickly mixed and reacted in the microchannel, and the temperature, pressure and residence time are precisely controlled to improve the purity and particle size uniformity of the sodium carbonate;

[0032] Vacuum cooling crystallization step: the solution treated by the microreactor is sent to the crystallizer of the crystallization unit, and the vacuum cooling crystallization process is used to accurately control the crystallization temperature at 30-40°C and the pressure at 5-10 kPa to promote the precipitation of sodium carbonate crystals;

[0033] Centrifugal separation: The centrifugal separator of the separation unit is used to efficiently separate the crystallized sodium carbonate crystals from the mother liquor, and the separated mother liquor is partially returned to the dissolution unit for recycling;

[0034] Calcination: The separated sodium carbonate crystals are sent to the drying furnace of the calcination unit and calcined at a temperature range of 160-200°C to completely convert the sodium bicarbonate into sodium carbonate, preliminarily meeting the index requirements of battery-grade sodium carbonate;

[0035] Crushing: The calcined sodium carbonate material is sent to the closed circulation air flow mill system of the crushing unit for crushing to make its particle size meet the requirements of battery-grade sodium carbonate;

[0036] Iron and magnet removal: The crushed materials enter the iron and magnet removal device of the iron and magnet removal unit to remove impurities brought in during the material transportation process and obtain the preliminarily processed sodium carbonate product;

[0037] Carbonization: The hot alkali solution from the calcination process and the low-salt heavy ash filtrate are made into Na2CO3 solution, which is clarified and filtered before entering the carbonization tower of the carbonization unit to react with the CO2 gas from the soda ash process to form NaHCO3 solution, which is cooled and precipitated into NaHCO3 crystals;

[0038] Preparation of baking soda: The NaHCO3 crystals separated from the carbonization unit are separated by the separator of the baking soda preparation unit and then enter the dryer. The dried baking soda is cooled by the cyclone separator and then enters the packaging warehouse for packaging;

[0039] Material circulation: The filtrate after separation of NaHCO3 solid enters the filtrate barrel of the material circulation unit and is pumped back to the hot alkali liquid tower of the calcination process to absorb furnace gas dust and produce hot alkali liquid with relatively high concentration, which is sent to the baking soda for recycling.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention achieves precise control of the decomposition reaction of sodium bicarbonate by introducing pulse heating technology and microreactor technology. The pulse heating technology effectively avoids local overheating and side reactions caused by too fast reaction by precisely controlling the frequency, intensity and duration of pulses, and also solves the problem of too slow reaction affecting production efficiency. The microreactor technology optimizes the reaction process of converting sodium bicarbonate into sodium carbonate by virtue of its high surface area-to-volume ratio and good mass transfer and heat transfer performance, thereby producing a battery-grade sodium carbonate product with higher purity and more uniform particle size distribution.

[0042] (2) The present invention greatly shortens the production cycle and improves the output per unit time by accurately controlling the reaction conditions and optimizing the process flow. At the same time, the system also focuses on the recycling of resources. For example, the filtrate after separating the NaHCO3 solid is returned to the hot alkali liquid tower of the calcination process to absorb furnace gas dust and produce hot alkali liquid with relatively high concentration, which is then sent to baking soda for recycling. This not only reduces the emission of waste and environmental pollution, but also saves the cost of raw materials and improves the overall economic benefits.

[0043] Other advantages, objectives and features of the present invention will be set forth in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 Schematic diagram of the system flow for producing battery-grade sodium carbonate from food-grade sodium bicarbonate;

[0046] Figure 2 Flowchart of a process for producing battery grade sodium carbonate for food grade sodium bicarbonate. DETAILED DESCRIPTION

[0047] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0048] Embodiment 1:

[0049] 300 kg of food-grade sodium bicarbonate was added into a dissolution tank with a volume of 2 cubic meters, and deionized water was added at the same time. The stirring device was turned on, the power of the stirring motor was set to 8 kilowatts, the speed was adjusted to 120 rpm, and the heating device was jacketed with steam to control the solution temperature at 42°C to fully dissolve the sodium bicarbonate to obtain a sodium bicarbonate solution.

[0050] The sodium bicarbonate solution is passed through an ion exchange column with a diameter of 0.8 meters and a height of 2.5 meters, which is filled with strong acidic cation exchange resin to a filling height of 2 / 3 of the column height. After ion exchange to remove metal ion impurities such as calcium and magnesium, the solution enters a bag filter with a filtration accuracy of 20 microns to filter out suspended impurities to obtain a purified sodium bicarbonate solution.

[0051] The purified sodium bicarbonate solution was fed into a pulse heating reaction unit container with a volume of 0.8 cubic meters. The power of a single heating tube of the pulse heating device was 2 kW, the pulse frequency was set to 15 Hz, the pulse intensity was 3 kW, and the pulse duration was 20 seconds. k1, A, and E were determined based on the reaction kinetics theory and experimental data. a By monitoring the reaction temperature T and using v r = k1 × Q to calculate the required pulse heat Q, and then further determine the combination of pulse intensity P and duration t through Q = P × t. avg = k1×P×t×f Adjust the pulse frequency f so that the average reaction rate v avg Approaching the target reaction rate v r , so that the reaction proceeds stably and a preliminary converted sodium carbonate solution is obtained.

[0052] For feed flow control, the relationship between the flow rate Q of the metering pump and the pump speed n and the pump displacement D is Q = D × n, the metering pump accuracy is ± 0.196, the sodium carbonate solution flow rate is 15 ml / min, and the sodium hydroxide solution flow rate is 4 ml / min, which is precisely controlled by the flow controller. The micro-channel size of the micro-reactor is 600 microns, and the material is stainless steel. The micro-channel has a special shape to enhance the mixing effect. The micro-reactor is equipped with an efficient heat exchange system, using jacketed heat exchange. The reaction temperature in the micro-reactor is set to T, and the target temperature is set to T set , the flow rate of the cooling medium (such as water or ethylene glycol aqueous solution) is q, and the specific heat capacity of the cooling medium is C pThe heat transfer coefficient between the microreactor and the cooling medium is h, the heat transfer area is A, and according to the heat balance equation: q×C p ×(TT in )=h×A×(TT set ), where T in is the inlet temperature of the cooling medium, from which the adjustment formula of the cooling medium flow rate can be obtained: When T>T set When q increases, when T <T set When q is reduced, the reaction temperature is set to 55°C, the pressure is stabilized at 7 kPa, the temperature is controlled by adjusting the cooling medium flow rate, and the residence time is about 2.5 minutes, which further improves the quality of sodium carbonate.

[0053] The solution treated by the microreactor enters the crystallizer, which is a vacuum cooling crystallizer. The vacuum pump in the connected vacuum unit is a water ring vacuum pump. The vacuum degree is adjusted to 7 kPa. Chilled water is introduced into the cooling coil to control the crystallization temperature at 32°C to promote the precipitation of sodium carbonate crystals. The solution is kept slowly stirred during the crystallization process.

[0054] A three-legged centrifuge is used with a drum diameter of 0.8 meters and a rotation speed of 1800 rpm to efficiently separate the crystallized sodium carbonate crystals from the mother liquor. The separated mother liquor is partially returned to the dissolution unit for recycling.

[0055] The separated sodium carbonate crystals are sent to a rotary drying furnace with a length of 8 meters, a diameter of 1.5 meters and an inclination angle of 1.5 degrees. It is heated by gas. The burner burns the coal gas to produce high-temperature flue gas that flows in the opposite direction of the material. The temperature controller is linked to the temperature sensor in the furnace to accurately control the temperature in the furnace at 170°C. The calcination time is 1.8 hours, so that the sodium bicarbonate is completely converted into sodium carbonate, which preliminarily meets the battery-grade sodium carbonate index requirements.

[0056] The calcined sodium carbonate material enters the closed circulation air flow mill system. The diameter of the crushing chamber of the air flow mill main engine is 0.6 meters, the height is 1.2 meters, the speed of the grading wheel is 4000 rpm, and the air compressor of the air source system provides 0.8 MPa high-pressure air, which enters the main engine after heating. The material is transported to the feed port of the main engine by a screw feeder. The material is crushed and graded in the main engine, and the product that meets the particle size requirements is discharged, and the coarse particle material returns to the crushing chamber for further crushing.

[0057] The crushed material first passes through an electromagnetic iron remover with a magnetic field strength of 8000 Gauss, which is installed above the material conveying pipeline to remove ferromagnetic impurities, and then passes through a magnetic rod filter with a filtration accuracy of 30 microns. The magnetic rod is made of neodymium iron boron magnets to further remove magnetic substances and obtain a preliminarily processed sodium carbonate product.

[0058] The hot alkali liquid from the calcination process is mixed with the low-salt heavy ash filtrate in a mixing tank and then transported to the top feed port of the carbonization tower with a height of 15 meters and a diameter of 2 meters through a feed pump with a flow rate of 3 cubic meters per hour. The carbon dioxide gas from the soda ash process enters from the bottom air inlet of the carbonization tower and is evenly distributed through a porous plate gas distributor. Temperature sensors are installed at different heights of the carbonization tower, and cooling water is introduced through the cooling jacket outside the tower body to control the reaction temperature at 35°C.

[0059] The NaHCO3 crystals separated from the carbonization unit are separated by a centrifugal separator (drum diameter 0.4 meters, rotation speed 1200 rpm) and then enter the fluidized bed dryer. Hot air is introduced into the heat exchange coil in the dryer, and the drying temperature is controlled at 90°C through the temperature controller and the temperature sensor in the dryer. The hot air is sent to the bottom of the dryer by the fan and evenly distributed through the gas distribution plate to fluidize and dry the baking soda crystals. The dried baking soda is separated by a cyclone separator with a diameter of 0.8 meters. The baking soda particles are cooled by a cooling alkali machine and then enter the packaging warehouse for packaging.

[0060] The filtrate after separation of NaHCO3 solid enters the filtrate barrel and is pumped back to the hot alkali liquid tower of the calcination process to absorb furnace gas dust and make hot alkali liquid with higher concentration, which is then sent to baking soda for recycling. The final battery-grade sodium carbonate product is tested to have a purity of 99.55%, and its particle size, iron and magnetic material content and other indicators all meet the quality requirements of battery-grade sodium carbonate.

[0061] Embodiment 2:

[0062] 600 kg of food-grade sodium bicarbonate was put into a dissolution tank with a volume of 4 cubic meters, and an appropriate amount of deionized water was added. The motor power of the stirring device was 12 kW and the speed was 250 rpm. The jacket of the heating device was passed with heat transfer oil. The solution temperature was maintained at 55°C to fully dissolve the sodium bicarbonate to obtain a sodium bicarbonate solution.

[0063] The sodium bicarbonate solution is passed through an ion exchange column with a diameter of 1.2 meters and a height of 3.5 meters, and filled with strong acid cation exchange resin to 3 / 4 of the column height. After ion exchange and impurity removal, the solution enters a bag filter with a filtration accuracy of 8 microns to remove suspended impurities and obtain a purified sodium bicarbonate solution.

[0064] The purified sodium bicarbonate solution enters a pulse heating reaction unit container with a volume of 1.5 cubic meters. The power of a single heating tube of the pulse heating device is 4 kilowatts, the pulse frequency is 25 Hz, the pulse intensity is 5 kilowatts, and the pulse duration is 12 seconds. The stirring paddle in the reaction container stirs the reaction to ensure efficient and stable reaction, thereby obtaining a preliminarily converted sodium carbonate solution.

[0065] The initially converted sodium carbonate solution and sodium hydroxide solution are introduced into a microreactor. The microchannel size of the microreactor is 400 microns. The material is silicon carbide. The microchannel design is conducive to mixing. The metering pump accuracy is ±0.1%. The flow rate of the sodium carbonate solution is 25 ml / min, and the flow rate of the sodium hydroxide solution is 6 ml / min. The flow controller precisely controls the heat exchange system. The heat exchange system is microchannel type, and ethylene glycol aqueous solution is passed. The reaction temperature is 65°C, the pressure is 9 kPa, and the residence time is 1.2 minutes, which improves the quality of sodium carbonate.

[0066] The solution treated by the microreactor enters the crystallizer. The vacuum cooling crystallizer is connected to a vacuum unit composed of a Roots vacuum pump. The vacuum degree is 9 kPa. Chilled water is passed through the cooling coil. The crystallization temperature is controlled at 36°C to promote the precipitation of sodium carbonate crystals. The solution is slowly stirred during crystallization.

[0067] A horizontal spiral unloading centrifuge with a drum diameter of 1.2 meters and a rotation speed of 3500 rpm is used to separate the crystallized sodium carbonate crystals from the mother liquor, and part of the mother liquor is returned to the dissolution unit for recycling.

[0068] The separated sodium carbonate crystals are sent to a rotary drying furnace with a length of 12 meters, a diameter of 2 meters and an inclination angle of 2.5 degrees. It is electrically heated and heated by electric heating rods in the furnace. The temperature controller and temperature sensor are linked to accurately control the temperature in the furnace at 195°C. It is calcined for 1.2 hours to completely convert sodium bicarbonate into sodium carbonate, meeting the preliminary index requirements.

[0069] The calcined sodium carbonate material enters the closed circulation air flow mill system. The diameter of the crushing chamber of the air flow mill main engine is 0.9 meters, the height is 1.8 meters, the speed of the grading wheel is 6000 rpm, and the air compressor of the air source system provides 1.3 MPa high-pressure air. After heating, it enters the main engine. The pneumatic conveying device is used to send the material to the main engine feed port. The material is crushed and graded in the main engine. Qualified products are discharged and unqualified products are returned to the crushing chamber.

[0070] The crushed material is first passed through an electromagnetic iron remover with a magnetic field strength of 15,000 Gauss to remove ferromagnetic impurities, and then passed through a magnetic rod filter (magnetic rod neodymium iron boron magnet) with a filtration accuracy of 15 microns to remove magnetic substances to obtain a preliminarily processed sodium carbonate product.

[0071] After the hot alkali liquid in the calcination process is mixed with the low-salt heavy ash filtrate, it is transported to the top feed port of the carbonization tower with a height of 22 meters and a diameter of 3.5 meters by a feed pump with a flow rate of 6 cubic meters per hour. The carbon dioxide gas from the soda ash process enters from the bottom air inlet and is distributed through a nozzle-type gas distributor. Temperature sensors are installed at different heights of the carbonization tower, and chilled water is passed through the cooling coil in the tower to control the reaction temperature at 45°C.

[0072] The NaHCO3 crystals separated from the carbonization unit are separated by a centrifugal separator (drum diameter 0.8 meters, rotation speed 2500 rpm) and then enter the fluidized bed dryer. The heat exchange coil of the dryer is passed through steam, and the temperature controller is linked to the temperature sensor in the dryer to control the drying temperature at 110°C. Hot air is sent to the bottom of the dryer by the fan and evenly distributed through the gas distribution plate to fluidize and dry the baking soda crystals. The dried baking soda is separated by a cyclone separator with a diameter of 1.2 meters. The baking soda particles are cooled by a cooling alkali machine and then enter the packaging warehouse for packaging.

[0073] The filtrate after separation of NaHCO3 solid enters the filtrate barrel and is pumped back to the hot alkali liquid tower of the calcination process to absorb furnace gas dust and make hot alkali liquid with higher concentration, which is then sent to baking soda for recycling. The final battery-grade sodium carbonate product is tested to have a purity of 99.68%, and indicators such as particle size, iron and magnetic material content all meet the quality requirements of battery-grade sodium carbonate.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate, characterized in that: The system includes the following components: a dissolution unit, an impurity removal unit, a pulse heating reaction unit, a microreactor unit, a crystallization unit, a separation unit, a calcination unit, a pulverization unit, a ferromagnetic removal unit, a carbonization unit, a baking soda preparation unit and a material circulation unit; The dissolving unit comprises a dissolving tank, which is equipped with a stirring device and a heating device to fully dissolve the food-grade sodium bicarbonate to form a sodium bicarbonate solution; The impurity removal unit is composed of an ion exchange column and a filter device, the ion exchange column is used to remove specific metal ion impurities in the solution, and the filter device further filters out suspended impurities in the solution; The pulse heating reaction unit adopts a pulse heating device to control the rate of sodium bicarbonate decomposition reaction through pulse heating technology. During the reaction process, the frequency, intensity and duration of the pulse are controlled to match the kinetic requirements of the reaction. The microreactor unit comprises a microreactor, into which the sodium bicarbonate solution and the reaction reagent are introduced at a small flow rate, and rapid mixing and reaction are performed in the microchannel, and the reaction conditions are precisely controlled to optimize the reaction process; The crystallization unit adopts a crystallizer, which uses vacuum cooling crystallization technology to promote the precipitation of sodium carbonate crystals by regulating crystallization temperature, pressure and solution concentration parameters; The separation unit uses a centrifugal separator, adjusting the rotation speed between 1000-5000 rpm to separate the crystallized sodium carbonate crystals from the mother liquor; The calcination unit is a drying furnace, which calcines food-grade sodium bicarbonate in a specific environment of 160-200° C. to completely convert it into sodium carbonate, preliminarily meeting the basic index requirements of battery-grade sodium carbonate; The pulverizing unit uses a jet mill system to finely pulverize the calcined material to meet the product particle size requirements of battery-grade sodium carbonate; The iron and magnetic removal unit adopts an iron and magnetic material removal device, and the magnetic field strength is controlled at 5000-20000 Gauss, which is used to completely remove impurities mixed in the material during the transportation process, so that it meets the quality standards of battery-grade sodium carbonate; The carbonization unit includes a carbonization tower, which is used to make a Na2CO3 solution by mixing the hot alkali solution sent from the calcination process with the low-salt heavy ash filtrate, which enters the carbonization tower after clarification and filtration, and reacts with the CO2 gas sent from the soda ash process to generate a NaHCO3 solution, which is then cooled to obtain NaHCO3 crystals; The baking soda preparation unit comprises a separator, a dryer, a cyclone separator and a cooling alkali machine. The NaHCO3 crystals separated from the carbonization unit are separated by the separator and then enter the dryer. The dried baking soda enters the cooling alkali machine through the cyclone separator for cooling and then enters the packaging warehouse for packaging; The material circulation unit includes a filtrate barrel and a delivery pump. The filtrate after separating the NaHCO3 solid enters the filtrate barrel and is pumped back to the hot alkali liquid tower of the calcination process to absorb furnace gas dust to form hot alkali liquid, which is then sent to the baking soda for recycling.

2. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 1, characterized in that: The dissolving unit comprises a dissolving tank, which is equipped with a stirring device and a heating device. According to the volume of the dissolving tank and the required stirring intensity, the speed of the stirring device is set to 60-300 rpm, and the temperature of the dissolving tank is set to 40-60°C. By comparing with the set temperature, the heating device automatically determines whether to heat.

3. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 1, characterized in that: During the reaction process, the pulse heating reaction unit matches the kinetic requirements of the reaction by controlling the frequency, intensity and duration of the pulse, wherein the pulse frequency can be adjusted between 1-100 Hz, the pulse intensity can be adjusted between 10%-100% of the rated power, and the pulse duration can be adjusted between 1-60 seconds.

4. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 3, characterized in that: The pulse heating reaction unit matches the kinetic requirements of the reaction. Specifically, the target reaction rate of the sodium bicarbonate decomposition reaction is set to v r The activation energy of the reaction is E a , the ideal gas constant is R, the reaction temperature is T, and the reaction rate constant is A is the pre-exponential factor, assuming that the heat provided by pulse heating has a linear relationship with the reaction rate v r =k1×Q, k1 is the proportionality coefficient, single pulse heat Q=P×t, P is the pulse intensity or power, t is the pulse duration, pulse frequency f and average reaction rate v avg The relationship is v avg =k1×Q×f=k1×P×t×f, according to v avg Adjust the pulse frequency f so that the average reaction rate v avg Approaching the target reaction rate v τ , thereby matching the kinetic requirements of the reaction.

5. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 1, characterized in that: The microreactor unit includes a microreactor, which is made of stainless steel or silicon carbide material to form a microchannel plate laminated structure, and the size of the microchannel is between 100-1000 microns. Its feeding system includes a metering pump and a flow controller, which are respectively used to introduce sodium bicarbonate solution and reaction reagents into different feeding ports of the microreactor at a small flow rate. The reaction reagent selects the solution. The flow controller is linked with the pressure sensor and the temperature sensor in the microreactor to adjust the feed flow rate in real time according to the reaction conditions to ensure that the reaction is carried out in a stable state. The microreactor is equipped with a heat exchange system, and the reaction temperature is accurately controlled by introducing a cooling medium into the jacket or the microchannel. The heat exchange system is connected to the temperature controller, and the reaction temperature is set to 50-80°C. By comparing with the set temperature, the flow rate of the cooling medium is automatically adjusted, so that the reaction reaches a balanced state in an instant and maintains stability.

6. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 5, characterized in that: In the microreactor unit, the feed flow rate is adjusted in real time according to the reaction conditions. The designed flow rate of the pump is Q, the speed of the pump is n, and the displacement of the pump is D, and the relationship is Q=D×n. The feed flow rates of the two solutions are controlled by adjusting the speed of the pump, and the reaction temperature is accurately controlled by introducing a cooling medium into the jacket or microchannel. Specifically, the reaction temperature in the microreactor is set to T, and the target temperature is set to T set , the flow rate of the cooling medium is q, and the specific heat capacity of the cooling medium is C p The heat transfer coefficient between the microreactor and the cooling medium is h, the heat transfer area is A, and according to the heat balance equation q×C p ×(TT in )=h×A×(TT set ), where T in is the inlet temperature of the cooling medium, from which the adjustment formula of the cooling medium flow rate can be obtained: When T>T set When q increases, when T <T set When q is reduced, the reaction temperature is controlled near the target temperature.

7. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 1, characterized in that: The crystallization unit adopts a crystallizer, and the crystallizer uses vacuum cooling crystallization technology to regulate crystallization temperature, pressure and solution concentration parameters. The crystallization temperature is controlled at 30-40°C, the pressure is controlled at 1-10 kPa, and the solution concentration should be close to saturation or supersaturation.

8. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 1, characterized in that: The pulverizing unit adopts a jet mill system to finely pulverize the calcined material. A fluidized bed jet mill is used, and a pulverizing chamber and a classifying wheel are arranged inside. The diameter of the pulverizing chamber is 0.5-1 meter, and the height is 1-2 meters. The rotation speed of the classifying wheel can be adjusted between 1000-10000 rpm. By adjusting the rotation speed of the classifying wheel, the particle size of the product can be accurately controlled. The material is accelerated by the high-speed airflow in the jet mill host and pulverized by mutual collision. The pulverized material enters the classifying wheel with the airflow for particle size classification. The product that meets the particle size requirements is discharged from the discharge port of the jet mill host and enters the ferromagnetic removal unit. The coarse particle material that does not meet the particle size requirements returns to the pulverizing chamber for further pulverization, forming a closed cycle pulverizing process.

9. The system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to claim 1, characterized in that: The baking soda preparation unit comprises a separator, a dryer, a cyclone separator and a cooling alkali machine. The separator is a centrifugal separator made of stainless steel with a special surface treatment. The diameter of the drum is between 0.3 and 1.5 meters and the rotation speed is between 800 and 4000 rpm. The feed port of the separator is connected with the discharge port of the carbonization unit. The discharge port is divided into a solid phase discharge port and a liquid phase discharge port. The solid phase discharge port is connected to the dryer, and the liquid phase discharge port is connected to the material circulation unit. The dryer adopts a fluidized bed dryer. The drying temperature is adjusted between 80 and 150° C. The flow rate and temperature of the heating medium are controlled by the temperature controller and the temperature sensor installed in the dryer. The cyclone separator is made of stainless steel. The dust-containing gas enters from the tangential direction of the top side of the cyclone separator and rotates at a high speed in the separator. Due to the action of centrifugal force, the baking soda particles are thrown to the wall of the device and fall along the wall to the bottom discharge port and enter the cooling alkali machine, while the purified air is discharged from the air outlet at the top.

10. A method for producing battery-grade sodium carbonate from food-grade sodium bicarbonate, the method being applicable to the system for producing battery-grade sodium carbonate from food-grade sodium bicarbonate according to any one of claims 1 to 9, characterized in that: The method comprises the following specific steps: Sodium bicarbonate dissolution: Add food-grade sodium bicarbonate into the dissolution tank of the dissolution unit, add an appropriate amount of deionized water, turn on the stirring device and the heating device to fully dissolve the sodium bicarbonate, control the solution temperature at 40-60°C, and obtain a sodium bicarbonate solution; Solution impurity removal: pass the sodium bicarbonate solution into the ion exchange column of the impurity removal unit to remove the metal ion impurities in the solution, and filter out the suspended impurities in the solution through the filtering device to obtain the purified sodium bicarbonate solution; Pulse heating reaction step: feeding the purified sodium bicarbonate solution into a pulse heating device of a pulse heating reaction unit, performing a sodium bicarbonate decomposition reaction by controlling the frequency, intensity and duration of the pulse to obtain a preliminarily converted sodium carbonate solution; Micro-reaction: The initially converted sodium carbonate solution and the reaction reagents are introduced into the microreactor of the microreactor unit at a small flow rate, and quickly mixed and reacted in the microchannel, and the temperature, pressure and residence time are precisely controlled to improve the purity and particle size uniformity of the sodium carbonate; Vacuum cooling crystallization step: the solution treated by the microreactor is sent to the crystallizer of the crystallization unit, and the vacuum cooling crystallization process is used to accurately control the crystallization temperature at 30-40°C and the pressure at 5-10 kPa to promote the precipitation of sodium carbonate crystals; Centrifugal separation: The centrifugal separator of the separation unit is used to efficiently separate the crystallized sodium carbonate crystals from the mother liquor, and the separated mother liquor is partially returned to the dissolution unit for recycling; Calcination: The separated sodium carbonate crystals are sent to the drying furnace of the calcination unit and calcined at a temperature range of 160-200°C to completely convert the sodium bicarbonate into sodium carbonate, preliminarily meeting the index requirements of battery-grade sodium carbonate; Crushing: The calcined sodium carbonate material is sent to the closed circulation air flow mill system of the crushing unit for crushing to make its particle size meet the requirements of battery-grade sodium carbonate; Iron and magnet removal: The crushed materials enter the iron and magnet removal device of the iron and magnet removal unit to remove impurities brought in during the material transportation process and obtain the preliminarily processed sodium carbonate product; Carbonization: The hot alkali solution from the calcination process and the low-salt heavy ash filtrate are made into Na2CO3 solution, which is clarified and filtered before entering the carbonization tower of the carbonization unit to react with the CO2 gas from the soda ash process to form NaHCO3 solution, which is cooled and precipitated into NaHCO3 crystals; Preparation of baking soda: The NaHCO3 crystals separated from the carbonization unit are separated by the separator of the baking soda preparation unit and then enter the dryer. The dried baking soda is cooled by the cyclone separator and then enters the packaging warehouse for packaging; Material circulation: The filtrate after separation of NaHCO3 solid enters the filtrate barrel of the material circulation unit and is pumped back to the hot alkali liquid tower of the calcination process to absorb furnace gas dust and produce hot alkali liquid with relatively high concentration, which is sent to the baking soda for recycling.

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