A method for co-producing baking soda and battery-grade soda ash

Abstract

The present invention belongs to the technical field of inorganic compound preparation, and specifically discloses a method for co-producing baking soda and battery-grade soda ash, which comprises the following steps: (1) refining brine to absorb ammonia to obtain ammonia brine, and after the ammonia brine is carbonized, sodium bicarbonate slurry is obtained; (2) washing, drying and packaging a part of the sodium bicarbonate slurry obtained in step (1) to obtain the product baking soda; (3) washing and purifying the remaining sodium bicarbonate slurry in step (1), and calcining, and no purification is required after calcination to obtain the product battery-grade soda ash. The present invention does not change the original baking soda and soda production equipment, but only adds branch washing, calcining, drying and packaging steps to achieve flexible production of battery-grade soda ash and baking soda products; at the same time, the battery-grade soda ash product obtained by the present invention has a purity of more than 99.9%, and the chloride ion content in the product is less than 20ppm. The obtained product can be used in the fields of sodium ion batteries, reagent-grade soda ash, etc., greatly improving the competitiveness and market influence of enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic compound preparation, relates to the preparation of baking soda and soda ash, and specifically relates to a method for co-producing baking soda and battery-grade soda ash. Background Art

[0002] Baking soda, as an important chemical product, is widely used in the fields of chemical industry, food, medicine, etc. The main methods for producing baking soda include synthesis method, double decomposition method, natural alkali method, etc. The synthesis method is also called soda method, that is, soda carbonization method. At present, the domestic synthesis carbonization method for making baking soda is basically matched with the soda production process. The high-temperature and low-concentration alkali dust from the calcination system in the soda production process is directly collected, and the baking soda is produced through the processes of alkali, concentration, purification, carbonization, thickening, centrifugation, drying, and cooling.

[0003] The baking soda production device installed in the soda ash production system can effectively utilize a small amount of alkali dust in the exhaust gas of the calcining furnace, avoid environmental pollution caused by waste discharge, and reduce resource waste. However, during the production process of this method, due to the low concentration of the collected soda ash, the production waste alone is not enough to form a production line, and finished soda ash needs to be added for alkali concentration. The baking soda products produced not only increase energy consumption but also increase production costs. At the same time, the natural alkali method for producing baking soda has significant cost advantages, which are unmatched by the synthesis method and the double decomposition method for producing baking soda.

[0004] Therefore, if the soda ash waste generated by the calciner exhaust gas can be collected and used to produce products with higher added value, it will not only avoid the competitive pressure from baking soda, but also turn waste into treasure, greatly improving the utilization value of waste liquid, while entering the high-end product market and improving corporate competitiveness and market influence.

[0005] With the rapid development of the electronics industry, as an important raw material for sodium-ion batteries, the purity requirements of soda ash are getting higher and higher, especially the salt content in soda ash. During the production process, soda ash companies generally require the salt content of soda ash products to be controlled at around 0.3wt%, but sodium-ion battery-grade soda ash requires the chloride ion content to be ≤100ppm, or even lower to 10-20ppm.

[0006] To prepare ultra-low salt soda ash, the brine is purified from the source, mainly through the two-alkali method, and flocculants are added. However, the impurity content in the brine refined by this method is still high, and the expected purity cannot be achieved, so further purification is required. The traditional method of refining soda ash is mainly to use the produced industrial-grade soda ash to physically wash or chemically remove impurities such as chloride ions, calcium and magnesium, and then obtain soda ash with higher purity through processes such as recrystallization and drying. However, this type of method generally has cumbersome procedures, and the method of washing soda ash with water has a high solid loss rate, while increasing energy consumption, or destroying the water balance of the system, greatly increasing costs, and the acquisition rate of high-purity soda ash is low.

[0007] Therefore, based on the existing technology of soda ash enterprises, developing a method for co-producing baking soda and battery-grade soda ash will have important driving significance for the production of both soda ash and baking soda. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for the co-production of baking soda and battery-grade soda ash. On the basis of the original synthesis process for producing baking soda, it is only necessary to add washing, centrifugation, calcination, drying and packaging steps after the sodium bicarbonate slurry is obtained to achieve the co-production of baking soda and battery-grade soda ash.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for co-producing baking soda and battery-grade soda ash comprises the following steps:

[0011] (1) Using the low-concentration alkali dust waste in the calcination furnace gas during the soda ash production process, the sodium bicarbonate slurry is produced through the processes of collection, concentration, heating, filtration, purification, and carbonization;

[0012] (2) partially dethickening, centrifuging, drying, sieving, and packaging the sodium bicarbonate slurry obtained in step (1) to obtain the product baking soda;

[0013] (3) The remaining sodium bicarbonate slurry in step (1) is washed and purified multiple times, and then calcined to obtain battery-grade soda ash.

[0014] A further improvement of the present invention is:

[0015] The specific process of step (1) is as follows: in the soda ash production process, the furnace gas containing a small amount of alkali dust from the calcining furnace enters the alkali dust washing tower, is washed with soft water, and the washing liquid is pumped into the hot alkali liquid tank for collection, and then sent to the ammonia distillation tower to evaporate the ammonia and carbon dioxide gas therein. The obtained hot alkali liquid is pumped into the alkali barrel by the hot alkali liquid pump, and the finished soda ash is added to the alkali barrel. After the alkali liquid concentration in the alkali barrel reaches 70-88tt, it is pumped into the clarification barrel for clarification. The alkali liquid in the clarification barrel is continuously clarified, and the clear liquid overflows from the top to the clear alkali liquid barrel. The clear alkali liquid is pumped into the bottom of the PE microporous filter by the clear alkali liquid pump, and then pumped into the alkali liquid storage barrel. The temperature of the alkali liquid in the alkali liquid barrel is controlled, and the alkali liquid is pumped into the carbonization tower by the alkali liquid pump to react with CO2 for carbonization, and carbonization and crystallization are carried out inside the carbonization tower to generate sodium bicarbonate slurry.

[0016] Furthermore, the washing and purification in step (3) includes a primary washing and a secondary washing.

[0017] Furthermore, the one-time washing process is as follows: thickening the sodium bicarbonate slurry to a crystal content of 40-50%, entering the centrifuge for centrifugal separation, and adding washing water to the centrifuge to wash the salt and impurities in the crystals to obtain wet sodium bicarbonate;

[0018] Furthermore, the secondary washing process is as follows: the wet sodium bicarbonate obtained by the primary washing is sent into a storage barrel through a feeding auger for slurry adjustment. During slurry adjustment, the solid-liquid ratio is controlled to be (1-4):1. After slurry adjustment, the solid-liquid slurry is then sent to a secondary washing device for washing to obtain ultra-pure wet sodium bicarbonate.

[0019] Furthermore, the secondary washing is performed by vacuum washing with a belt filter, the length and width of the belt filter are (15~30):1, the vacuum degree is -0.04~-0.08MPa, and 2~5 washing waters are used.

[0020] Furthermore, the calcination process in step (3) is as follows: the obtained ultrapure damp sodium bicarbonate is sent to a steam calcining furnace for calcination, the calcined product is cooled by a powder flow cooler, and then packaged to obtain battery-grade soda ash.

[0021] Furthermore, the steam temperature entering the steam calcining furnace is 280-350° C., and the air inlet pressure in the furnace is 2.2-3.2 MPa.

[0022] The present invention does not change the original production device of baking soda and soda ash by the synthesis method, but only adds branch washing, centrifugation, calcination, drying and packaging processes. The output of baking soda products and battery-grade soda ash can be adjusted according to market conditions and soda ash output, thereby realizing flexible production of baking soda products and battery-grade soda ash.

[0023] The present invention can share the problem of excessive hot alkali solution caused by the continuous increase in soda ash production capacity, reduce the production load of baking soda, and achieve alkali solution balance in the system;

[0024] The present invention is combined with the existing soda ash production device, and the washing water (filtrate) used for washing sodium bicarbonate in the production can be recycled in the ammonia-soda process of soda ash production, without increasing waste liquid discharge, maintaining system water balance, and reducing energy consumption;

[0025] The present invention takes a unique approach to wash and purify sodium bicarbonate slurry to obtain ultra-pure sodium bicarbonate, which is then directly calcined for production. The obtained sodium carbonate does not need to be washed, and is ultra-low salt high-purity soda ash. The purity of the product is above 99.9%, the chloride ion content in the product is less than 20ppm, and other indicators can also meet the chemical purity standard requirements of GB / T 639-2008 "Chemical Reagent Sodium Carbonate". The obtained product can be used in the fields of sodium ion batteries, reagent-grade soda ash, etc.

[0026] The present invention collects the soda ash waste generated by the calciner tail gas to produce products with higher added value, which can not only avoid the competitive pressure of baking soda, but also turn waste into treasure, greatly improve the utilization value of waste liquid, and at the same time enter the high-end product market, thereby improving the competitiveness and market influence of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the process flow chart for this application. Implementation

[0028] The present invention is described in detail below in conjunction with specific embodiments. Example

[0029] A method for producing ultra-low salt high-purity soda ash for sodium ion batteries: In the soda ash production process, furnace gas containing a small amount of alkali dust from a calcining furnace enters an alkali dust washing tower, is washed with soft water, and the washing liquid is pumped into a hot alkali liquid tank for collection. The collected hot alkali liquid (Na2CO3 concentration is 50-70tt, NH3≤30tt) is then sent to an ammonia distillation tower (steam pressure≤1.6MPa, middle section temperature 90°C), ammonia and carbon dioxide gas therein are evaporated, and the obtained hot alkali liquid is pumped into an alkali barrel by a hot alkali liquid pump, and finished soda ash is added to the alkali barrel. After the alkali liquid concentration in the alkali barrel reaches 70-88tt, it is pumped into a clarification barrel for clarification for 0.5h, the alkali liquid in the clarification barrel is continuously clarified, and the clear liquid overflows from the top to the clear alkali liquid barrel, and is pumped into a PE microporous filter (Ø1400×3000, maximum output 38m 3 / h) at the bottom, filtered and pumped into the alkali liquid storage barrel, the alkali liquid in the alkali liquid barrel is controlled at 78℃, and is pumped into the carbonization tower by the alkali liquid pump to undergo carbonization reaction with CO2 (volume concentration 38%) (tower top working pressure 0.05MPa, tower inlet alkali liquid temperature 76℃, tower pressure 0.18MPa), carbonized and crystallized inside the carbonization tower (the temperature in the middle of the carbonization tower is controlled at 84℃, and the tower pressure is controlled at 0.22MPa) to generate sodium bicarbonate slurry.

[0030] According to production requirements, the sodium bicarbonate slurry is divided into two parts, one part enters the original baking soda thickening, centrifugation, drying, screening and packaging line to obtain the baking soda product.

[0031] The other part of the sodium bicarbonate slurry (alkali concentration of 65) is placed in a thickener to thicken (the slurry contains 40% water), and then enters the centrifuge for centrifugal separation. After washing water is added to the centrifuge to wash the salt and impurities in the crystals (washing water volume 1.5m 3 / h), the wet sodium bicarbonate is sent to the wet material auger, and then to the slurry mixing barrel for slurry mixing (for example, solid: washing water = 2:1). After slurry mixing, the solid-liquid slurry is poured into the belt filter for vacuum washing. The length and width of the belt filter can be made into 15:1-30:1, the vacuum degree is -0.05MPa, and there are 3 washing water. After washing, the loss rate of solid materials is 5%. The wet sodium bicarbonate after vacuum washing is sent to the steam calcining furnace, the steam temperature entering the furnace is 280℃, and the inlet pressure in the furnace is 2.4MPa. The obtained sodium carbonate is sent to the powder flow cooler by pneumatic conveying, and packaged after cooling. The packaging temperature is 22℃ to obtain sodium ion battery grade soda ash (ultra-low salt high purity soda ash). Example

[0032] A method for producing ultra-low salt high-purity soda ash for sodium ion batteries: In the soda ash production process, furnace gas containing a small amount of alkali dust from a calcining furnace enters an alkali dust washing tower, is washed with soft water, and the washing liquid is pumped into a hot alkali liquid tank for collection. The collected hot alkali liquid (Na2CO3 concentration is 50-70tt, NH3≤30tt) is then sent to an ammonia distillation tower (steam pressure≤1.6MPa, middle section temperature 95°C), ammonia and carbon dioxide gas therein are evaporated, and the obtained hot alkali liquid is pumped into an alkali barrel by a hot alkali liquid pump, and finished soda ash is added to the alkali barrel. After the alkali liquid concentration in the alkali barrel reaches 70-88tt, it is pumped into a clarification barrel for clarification for 0.5h, the alkali liquid in the clarification barrel is continuously clarified, and the clear liquid overflows from the top to the clear alkali liquid barrel, and is pumped into a PE microporous filter (Ø1400×3000, maximum output 38m 3 / h) at the bottom, filtered and pumped into the alkali liquid storage barrel, the alkali liquid in the alkali liquid barrel is controlled at 78℃, and is pumped into the carbonization tower by the alkali liquid pump to undergo carbonization reaction with CO2 (volume concentration 40%) (tower top working pressure 0.05MPa, tower inlet alkali liquid temperature 78℃, tower pressure 0.20MPa), carbonized and crystallized inside the carbonization tower (the temperature in the middle of the carbonization tower is controlled at 84℃, and the tower pressure is controlled at 0.22MPa) to generate sodium bicarbonate slurry.

[0033] According to production requirements, the sodium bicarbonate slurry is divided into two parts, one part enters the original baking soda thickening, centrifugation, drying, screening and packaging line to obtain the baking soda product.

[0034] The other part of the sodium bicarbonate slurry (alkali concentration of 70tt) is placed in a thickener to thicken (the slurry contains 45% water), and then enters the centrifuge for centrifugal separation. After washing water is added to the centrifuge to wash the salt and impurities in the crystals (washing water volume 2.0m 3 / h), the wet sodium bicarbonate is sent to the wet material auger, and then to the slurry mixing barrel for slurry mixing (for example, solid: washing water = 2:1). After slurry mixing, the solid-liquid slurry is poured into the belt filter for vacuum washing. The length and width of the belt filter can be made into 15:1-30:1, the vacuum degree is -0.06MPa, and there are 4 washing water. After washing, the loss rate of solid materials is 6%. The wet sodium bicarbonate after vacuum washing is sent to the steam calcining furnace, the steam temperature entering the furnace is 285℃, and the air inlet pressure in the furnace is 2.5MPa. The obtained sodium carbonate is sent to the powder flow cooler by pneumatic conveying, and packaged after cooling. The packaging temperature is 25℃ to obtain sodium ion battery grade soda ash (ultra-low salt high purity soda ash). Example

[0035] A method for producing ultra-low salt high-purity soda ash for sodium ion batteries: In the soda ash production process, furnace gas containing a small amount of alkali dust from a calcining furnace enters an alkali dust washing tower, is washed with soft water, and the washing liquid is pumped into a hot alkali liquid tank for collection. The collected hot alkali liquid (Na2CO3 concentration is 50-70tt, NH3≤30tt) is then sent to an ammonia distillation tower (steam pressure≤1.6MPa, middle section temperature 100°C), ammonia and carbon dioxide gas therein are evaporated, and the obtained hot alkali liquid is pumped into an alkali barrel by a hot alkali liquid pump, and finished soda ash is added to the alkali barrel. After the alkali liquid concentration in the alkali barrel reaches 70-88tt, it is pumped into a clarification barrel for clarification for 0.5h, the alkali liquid in the clarification barrel is continuously clarified, and the clear liquid overflows from the top to the clear alkali liquid barrel, and is pumped into a PE microporous filter (Ø1400×3000, maximum output 38m 3 / h) at the bottom, filtered and pumped into the alkali liquid storage barrel, the alkali liquid in the alkali liquid barrel is controlled at 78℃, and is pumped into the carbonization tower by the alkali liquid pump to undergo carbonization reaction with CO2 (volume concentration 42%) (tower top working pressure 0.05MPa, tower inlet alkali liquid temperature 80℃, tower pressure 0.22MPa), carbonized and crystallized inside the carbonization tower (the temperature in the middle of the carbonization tower is controlled at 84℃, and the tower pressure is controlled at 0.22MPa) to generate sodium bicarbonate slurry.

[0036] According to production requirements, the sodium bicarbonate slurry is divided into two parts, one part enters the original baking soda thickening, centrifugation, drying, screening and packaging line to obtain the baking soda product.

[0037] The other part of the sodium bicarbonate slurry (alkali concentration of 75tt) is placed in a thickener to thicken (the slurry contains 50% water), and then enters the centrifuge for centrifugal separation. After washing water is added to the centrifuge to wash the salt and impurities in the crystals (washing water volume 2.5m 3 / h), the wet sodium bicarbonate is sent to the wet material auger, and then sent to the slurry mixing barrel for slurry mixing (for example, solid: washing water = 2:1). After slurry mixing, the solid-liquid slurry is poured into the belt filter for vacuum washing. The length and width of the belt filter can be made into 15:1-30:1, the vacuum degree is -0.07MPa, and 5 washing waters are washed. After washing, the loss rate of solid materials is 7%. The wet sodium bicarbonate after vacuum washing is sent to the steam calcining furnace. The steam temperature entering the furnace is 280-350℃, and the inlet pressure in the furnace is 2.6MPa. The obtained sodium carbonate is sent to the powder flow cooler by pneumatic conveying, and packaged after cooling. The packaging temperature is 28℃ to obtain sodium ion battery grade soda ash (ultra-low salt high purity soda ash).

[0038] The test results of the products of Examples 1-3 are as follows:

[0039] Test items GB / T 639-2008 "Chemical Reagent Sodium Carbonate" Chemically Pure Example 1 Example 2 Example 3 Sodium carbonate / % ≥99.8% 99.94 99.92 99.93 chloride / % ≤0.005% 0.0016 0.0014 0.0013 Sulfur compounds / % ≤0.01% 0.0016 0.0017 0.0018 Silicon dioxide / % ≤0.013% 0.0028 0.0024 0.0019 lead / % ≤0.001% 0.0001 0.0002 0.0002 aluminum / % ≤0.01% 0.0065 0.0052 0.0055 magnesium / % ≤0.005% 0.0026 0.0024 0.0033 iron / % ≤0.001% 0.0006 0.0007 0.0007 Potassium / % ≤0.02% 0.0078 0.0069 0.0066

[0040] As can be seen from the above table, the purity of the sodium ion battery-grade soda ash obtained by the present invention reaches more than 99.9wt%, the chloride content is lower than 0.002wt%, and other indicators can meet the chemical purity standard requirements of GB / T 639-2008 "Chemical Reagent Sodium Carbonate".

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for co-producing baking soda and battery-grade soda ash, characterized in that: The following steps are involved: (1) Using the low-concentration alkali dust waste in the calcination furnace gas during the soda ash production process, the sodium bicarbonate slurry is obtained through the collection, concentration, heating, filtering, purification and carbonization processes; (2) partially dethickening, centrifuging, drying, sieving, and packaging the sodium bicarbonate slurry obtained in step (1) to obtain the product baking soda; (3) The remaining sodium bicarbonate slurry in step (1) is washed and purified, and then calcined to obtain battery-grade soda ash; The washing and purification in step (3) includes a primary washing and a secondary washing; The one-time washing process is as follows: thickening the sodium bicarbonate slurry to a crystal content of 40-50%, entering the centrifuge for centrifugal separation, and adding washing water to the centrifuge to wash the salt and impurities in the crystals to obtain wet sodium bicarbonate; The secondary washing process is as follows: the wet sodium bicarbonate obtained from the primary washing is sent into a storage barrel through a feeding auger for slurry mixing, and the solid-liquid ratio is controlled to be (1-4):1 during slurry mixing. After slurry mixing, the solid-liquid slurry is then sent to a secondary washing device for washing to obtain ultra-pure wet sodium bicarbonate.

2. A method for co-producing baking soda and battery-grade soda ash according to claim 1, characterized in that: The specific process of step (1) is as follows: in the soda ash production process, the furnace gas containing a small amount of alkali dust from the calcining furnace enters the alkali dust washing tower, is washed with soft water, and the washing liquid is pumped into the hot alkali liquid tank for collection, and then sent to the ammonia distillation tower to evaporate the ammonia and carbon dioxide gas therein. The obtained hot alkali liquid is pumped into the alkali barrel by the hot alkali liquid pump, and the finished soda ash is added to the alkali barrel. After the alkali liquid concentration in the alkali barrel reaches 70-88tt, it is pumped into the clarification barrel for clarification. The alkali liquid in the clarification barrel is continuously clarified, and the clear liquid overflows from the top to the clear alkali liquid barrel. The clear alkali liquid is pumped into the bottom of the PE microporous filter by the clear alkali liquid pump, and then pumped into the alkali liquid storage barrel. The temperature of the alkali liquid in the alkali liquid barrel is controlled, and the alkali liquid is pumped into the carbonization tower by the alkali liquid pump to react with CO2 for carbonization, and carbonization and crystallization are carried out inside the carbonization tower to generate sodium bicarbonate slurry.

3. The method for co-producing sodium bicarbonate and battery-grade soda ash according to claim 1, characterized in that: The secondary washing adopts a belt filter for vacuum washing, the belt filter has a length-to-width ratio of (15-30):1, a vacuum degree of -0.04-0.08MPa, and 2-5 wash waters.

4. The method for co-producing sodium bicarbonate and battery-grade soda ash according to claim 1, characterized in that: The calcination process in step (3) is as follows: the obtained ultrapure damp sodium bicarbonate is sent to a steam calcining furnace for calcination, the calcined product is cooled by a powder flow cooler, and then packaged to obtain battery-grade soda ash.

5. A method for co-producing baking soda and battery-grade soda ash according to claim 4, characterized in that: The steam temperature entering the steam calcining furnace is 280-350° C., and the air pressure in the furnace is 2.2-3.2 MPa.

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