A method for preparing spherical large-particle sodium bicarbonate crystals

Abstract

The application discloses a crystallization method for preparing spherical large-particle sodium bicarbonate by adding one or a mixture of several additives of sodium polyacrylate, polyacrylamide, hydroxymethyl cellulose and sodium tartrate into a brine solution, adding ammonium bicarbonate into the brine solution with the additives to perform reaction crystallization, and obtaining large-particle spherical sodium bicarbonate. After adding the additives in the preparation process, the obtained spherical sodium bicarbonate particles are not easy to break, have high bulk density, large particle size, and the main particle size can reach 200-600 microns. The production method of the spherical sodium bicarbonate product obtained by the method is simple, the product has high purity, low ammonium salt content, is easy to filter and dry, has a Karl index less than 25%, has good fluidity, is beneficial to storage and transportation, and greatly improves the market competitiveness of the product.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering crystallization technology, specifically relating to a method for preparing large-particle spherical sodium bicarbonate by adding a certain ingredient. Background Technology

[0002] Sodium bicarbonate (NaHCO3), also known as baking soda, is a commonly used inorganic salt compound. It exists as white crystalline powder, appearing as fine crystals. The crystals are odorless, non-toxic, and have a salty taste. It is readily soluble in water, with solubility increasing with temperature. Its solubility in water is less than that of sodium carbonate, resulting in a weakly alkaline solution. It is insoluble in organic solvents such as ethanol and acetone. Sodium bicarbonate is stable at room temperature but unstable under heat, readily decomposing. It is highly hygroscopic and slowly decomposes in humid air. The solid begins to gradually decompose above 50°C, producing sodium carbonate, carbon dioxide, and water, and completely decomposes at 270°C. Sodium bicarbonate is an acidic salt and can undergo hydrolysis. In aqueous solution, it reacts with acids to produce the corresponding salt, water, and carbon dioxide; it also reacts with bases to produce the corresponding carbonate and water.

[0003] Sodium bicarbonate is an important chemical raw material with wide applications in many fields. It can be used in the production of acid-base fire extinguishers and foam fire extinguishers, in rubber and sponge production, as a flux in casting steel ingots and a molding aid in casting steel (sand casting) molds, and in the dyeing process to prevent color spots on yarn bobbins. It can also be used as a wool detergent. As a weak alkali, sodium bicarbonate can be used to care for the acidic environment of the oral cavity and digestive tract, alleviate adverse reactions caused by other drug treatments or diagnostic techniques, and play an important role in key stages of many surgeries. In daily life, sodium bicarbonate is commonly used as a leavening agent for foods such as steamed buns, fried dough sticks, biscuits, and bread, and in kitchen cleaning. It can also be used to produce soda water.

[0004] Currently, the main industrial methods for producing sodium bicarbonate include the soda ash carbonation method, waste alkali recovery method, natural alkali method, and metathesis method. Among these, the soda ash carbonation method involves reacting soda ash (sodium hydroxide) with carbon dioxide to produce sodium bicarbonate; however, this method is costly and energy-intensive. The waste alkali recovery method utilizes carbonates in industrial waste alkali to produce sodium bicarbonate through a reaction. While this method can solve some of the waste alkali recovery and reuse issues, it still suffers from energy consumption and complex processes. The natural alkali method involves extracting sodium bicarbonate from natural alkali ore; however, natural alkali ore resources are relatively limited, and mining costs are high, thus limiting its industrial application. The metathesis method, also known as the natural brine method, utilizes abundant raw salt ore and inexpensive ammonium fertilizer as the main raw materials to produce sodium bicarbonate. In this process, sodium chloride in the brine undergoes a metathesis reaction with ammonium bicarbonate in the ammonium fertilizer. Due to the low solubility of sodium bicarbonate, it precipitates directly from the solution, forming the target product, sodium bicarbonate. This production process does not generate waste or cause environmental pollution, and is one of the effective ways to utilize abundant natural raw salt resources. However, the metathesis production method generally has disadvantages such as unstable quality, uneven particle size, and susceptibility to nucleation. CN112919502A discloses a method for preparing food-grade sodium bicarbonate by metathesis, but the obtained sodium bicarbonate product is powdery, with small particles and uneven particle size distribution; CN104136372B discloses a method using soda ash carbonation to improve the sodium bicarbonate crystallization process with a polycarboxylic acid and / or its salt additive, but the equipment is complex, the operation is relatively cumbersome, and the final particles are also small.

[0005] Therefore, it is essential to provide a new method for preparing large-particle sodium bicarbonate crystals.

[0006] Generally speaking, spherical crystal products have more obvious advantages over non-spherical crystal products (needle-shaped, rod-shaped, etc.), such as high bulk density and good flowability. During the crystallization process, adding specific trace amounts of additives can significantly control the crystal morphology. The influence of additives on the morphology during the crystallization process can be mainly divided into the following two functions: (1) inhibiting crystal nucleation; (2) changing the crystal shape through surface-specific adsorption. After adding trace amounts of additives to the brine, adding ammonium bicarbonate can induce the formation of large spherical sodium bicarbonate particles, which can effectively solve the problems of small sodium bicarbonate particles, poor flowability, and high ammonium salt content obtained by metathesis method. Summary of the Invention

[0007] This invention discloses a crystallization method for preparing large-particle spherical sodium bicarbonate by adding one or more of the following additives: sodium polyacrylate, polyacrylamide, hydroxymethyl cellulose, and sodium tartrate. The resulting spherical sodium bicarbonate particles are not easily broken, have high bulk density, and large particle size, with a main particle size of 200–600 μm. Furthermore, the spherical sodium bicarbonate product obtained by this method is easy to filter and dry, has good flowability, and is conducive to storage and transportation, thus significantly improving the product's market competitiveness.

[0008] To achieve this objective, the present invention adopts the following technical solution: One of the objectives of this invention is to provide a method for preparing large-particle spherical sodium bicarbonate crystals. The method includes: adding ammonium bicarbonate to a brine solution containing additives and reacting and crystallizing to obtain large-particle spherical sodium bicarbonate. The additives include any one or a combination of at least two of sodium polyacrylate, polyacrylamide, hydroxymethyl cellulose, or sodium tartrate.

[0009] Preferably, the method for preparing the brine solution includes: dissolving an additive in the brine under stirring conditions at a temperature of 10-40°C to obtain a brine solution containing the above-mentioned additive.

[0010] Preferably, the sodium chloride content in the brine is 300-400 g / L; Preferably, the content of Ca ions and Mg ions in the brine is both less than 150 mg / L.

[0011] Preferably, the number-average molecular weight of the sodium polyacrylate is 0.6-3000 W; Preferably, the number-average molecular weight of the polyacrylamide is 0.6-3000 W; Preferably, the viscosity of the hydroxymethyl cellulose is in the range of 600-100000 mPa·s.

[0012] Preferably, the mass ratio of the additive to ammonium bicarbonate is 1:(20000-2000); Preferably, the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.1-1.5.

[0013] Preferably, the reaction crystallization temperature is 20℃~40℃.

[0014] Preferably, the reaction crystallization is carried out under stirring conditions.

[0015] Preferably, the ammonium bicarbonate is added at a time of 0.5-4 h.

[0016] Preferably, the preparation method further includes sequentially performing solid-liquid separation, washing, and drying on the mixture obtained after reaction crystallization; Preferably, the solid-liquid separation method is filtration; Preferably, the cleaning process includes washing the solid obtained from solid-liquid separation sequentially with brine, saturated baking soda solution, and clean water.

[0017] The second objective of this invention is to provide a preparation method as described in the first objective to prepare large-particle spherical sodium bicarbonate crystals.

[0018] Preferably, the large-particle spherical sodium bicarbonate has a main particle size greater than 200 μm and an ammonium content of less than 900 ppm.

[0019] Preferably, the Karl Fischer index of the large spherical sodium bicarbonate particles is less than 25%.

[0020] The third objective of this invention is to provide an application of large-particle spherical sodium bicarbonate crystals as described in objective two as a raw material in food and chemical industries.

[0021] Technical features and beneficial effects of the present invention: (1) This invention obtains spherical sodium bicarbonate crystals with a specific morphology by adding one or a mixture of sodium polyacrylate, polyacrylamide, hydroxymethyl cellulose, and sodium tartrate during the preparation of baking soda. These crystals are not easily broken during the preparation process, and the particles are intact and dense, with a bulk density of 1.26 g / cm³. 3 The particle size is large, with the main particle size of the product reaching 200–600 μm.

[0022] (2) The spherical sodium bicarbonate crystals prepared by this invention are easy to filter and dry. Compared with commercially available powdered sodium bicarbonate, the Karl Fischer index is less than 25%, the fluidity is good, the anti-caking ability is strong, and the storage and transportation are convenient. Compared with sodium bicarbonate particles obtained without additives, the fluidity, bulk density and particle size are significantly improved, which greatly enhances the product's market competitiveness. Attached Figure Description

[0023] Figure 1 Electron micrograph of sodium bicarbonate product without additives; Figure 2 This is an electron microscope image of the sodium bicarbonate product obtained in Example 4 of the present invention; Figure 3 These are electron microscope (EM) images of the sodium bicarbonate products obtained in Examples 6 and 7 of the present invention; wherein, the left side is an EEM image of the product obtained using hydroxymethyl cellulose, and the right side is an EEM image of the product obtained using sodium tartrate. Detailed Implementation

[0024] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0025] Example 1 Add 0.0483g of sodium polyacrylate to 300g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, the mass ratio of sodium polyacrylate to ammonium bicarbonate is 1:2000, and the molecular weight of sodium polyacrylate is 3000w). Stir at 35℃, uniformly controlling the ammonium bicarbonate addition time to 1h. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40℃ for 4h. The obtained spherical sodium bicarbonate product has a main particle size D50 of 576μm, a bulk density of 1.26g / mL, a Karl ellipse index of 8%, and an ammonium salt content of 589ppm. Compared with sodium bicarbonate without additives (D50 of 170μm, ammonium salt content of 1384ppm, bulk density of 0.53g / mL, and Karl ellipse index of 38%), the sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0026] Example 2 Add 0.02416 g of sodium polyacrylate to 300 g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, the mass ratio of sodium polyacrylate to ammonium bicarbonate is 1:4000, and the molecular weight of sodium polyacrylate is 2000w). Stir at 20℃, uniformly controlling the ammonium bicarbonate addition time to 1 hour. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40℃ for 4 hours. The obtained spherical sodium bicarbonate product has a main particle size D50 of 438 μm, an ammonium salt content of 569 ppm, a bulk density of 1.26 g / mL, and a Karl Fischer index of 9%. Compared with sodium bicarbonate without additives (D50 of 170 μm, ammonium salt content of 1384 ppm, bulk density of 0.53 g / mL, and Karl Fischer index of 38%), the sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0027] Example 3 Add 0.0097g of sodium polyacrylate to 300g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, the mass ratio of sodium polyacrylate to ammonium bicarbonate is 1:10000, and the molecular weight of sodium polyacrylate is 10w). Stir at 20℃, uniformly controlling the ammonium bicarbonate addition time to 3h. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40℃ for 4h. The obtained spherical sodium bicarbonate product has a main particle size D50 of 424μm, an ammonium salt content of 607ppm, a bulk density of 1.26g / mL, and a Karl Fischer index of 9%. Compared with sodium bicarbonate without additives (D50 of 170μm, ammonium salt content of 1384ppm, bulk density of 0.53g / mL, and Karl Fischer index of 38%), the sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0028] Example 4 Add 0.0048g of sodium polyacrylate to 300g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, the mass ratio of sodium polyacrylate to ammonium bicarbonate is 1:20000, and the molecular weight of sodium polyacrylate is 6k). Stir at 25℃, uniformly controlling the ammonium bicarbonate addition time to 2 hours. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40℃ for 4 hours. The resulting spherical sodium bicarbonate product (see...) Figure 2 The main particle size D50 is 272 μm, the ammonium salt content is 542 ppm, the bulk density is 1.26 g / mL, and the Karl Fischer index is 8%. Compared to sodium bicarbonate without additives (see...), Figure 1 (D50 is 170 μm, ammonium salt content is 1384 ppm, bulk density is 0.53 g / mL, and Karl index is 38%). The sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0029] Example 5 Add 0.0097g of polyacrylamide to 300g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, the mass ratio of polyacrylamide to ammonium bicarbonate is 1:10000, and the molecular weight of polyacrylamide is 3000w). Stir at 20℃, uniformly controlling the ammonium bicarbonate addition time to 1h. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40℃ for 4h. The obtained spherical sodium bicarbonate product has a main particle size D50 of 440μm, an ammonium salt content of 542ppm, a bulk density of 1.25g / mL, and a Karl elliptic index of 9%. Compared with sodium bicarbonate without additives (D50 of 170μm, ammonium salt content of 1384ppm, bulk density of 0.53g / mL, and Karl elliptic index of 38%), the sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0030] Example 6 Add 0.0970 g of hydroxymethyl cellulose (HMC) to 300 g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, the mass ratio of HMC to ammonium bicarbonate is 1:1000, and the viscosity of HMC is 1200 mPa·s). Stir at 20°C, uniformly controlling the ammonium bicarbonate addition time to 1 hour. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40°C for 4 hours. The obtained spherical sodium bicarbonate product has a main particle size D50 of 550 μm, an ammonium salt content of 720 ppm, a bulk density of 1.21 g / mL, and a Karl Fischer index of 10%. Compared to sodium bicarbonate without additives (D50 of 170 μm, ammonium salt content of 1384 ppm, bulk density of 0.53 g / mL, and Karl index of 38%), the sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0031] Example 7 Add 0.0970 g of sodium tartrate to 300 g of brine (the molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.3:1, and the mass ratio of sodium tartrate to ammonium bicarbonate is 1:1000). Stir at 20°C, uniformly controlling the ammonium bicarbonate addition time to 1 hour. After the ammonium bicarbonate addition is complete, filter the crystal slurry, wash it sequentially with brine, saturated sodium bicarbonate, and deionized water, and dry it in a forced-air oven at 40°C for 4 hours. The resulting spherical sodium bicarbonate product has a main particle size D50 of 180 μm, an ammonium salt content of 810 ppm, a bulk density of 1.2 g / mL, and a Karl elliptic index of 10%. Compared to sodium bicarbonate without additives (D50 of 170 μm, ammonium salt content of 1384 ppm, bulk density of 0.53 g / mL, and Karl elliptic index of 38%), the sodium bicarbonate particles obtained by this method are spherical, have a uniform particle size distribution, low ammonium salt content, high bulk density, and good flowability.

[0032] Figure 3 These are electron microscope (EM) images of the sodium bicarbonate products obtained in Examples 6 and 7 of the present invention; wherein, the left side is an EEM image of the product obtained using hydroxymethyl cellulose, and the right side is an EEM image of the product obtained using sodium tartrate.

[0033] It must be emphasized that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to completely limit the implementation. Those skilled in the art can make other variations based on the above description. It is neither possible nor necessary to provide examples for all implementations here, but obvious variations derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing spherical large-particle sodium bicarbonate crystals, characterized in that, The preparation method includes: dissolving in... Ammonium bicarbonate is added to the brine solution of the additive to react and crystallize, resulting in spherical large-particle sodium bicarbonate. The additive is hydroxymethyl cellulose or sodium tartrate; The mass ratio of hydroxymethyl cellulose to ammonium bicarbonate is 1:1000; The mass ratio of sodium tartrate to ammonium bicarbonate is 1:1000; The molar ratio of sodium chloride to ammonium bicarbonate in the brine is 1.1-1.5; The crystallization temperature of the reaction is 20-40℃; The reaction crystallization was carried out under stirring conditions.

2. The preparation method according to claim 1, characterized in that, The method for preparing the brine solution includes: stirring... Under stirring conditions, additives are dissolved in the brine at a temperature of 10-40℃ to obtain a brine solution containing the additives.

3. The preparation method according to claim 2, characterized in that, The sodium chloride content in the brine is 300-400 g / L.

4. The preparation method according to claim 2, characterized in that, The content of Ca ions and Mg ions in the brine is both less than 150 mg / L.

5. The preparation method according to claim 1, characterized in that, The viscosity range of the hydroxymethyl cellulose is 600-100000 mPa·s.

6. The preparation method according to claim 1, characterized in that, The ammonium bicarbonate is added over a period of 0.5-4 hours.

7. The preparation method according to claim 1, characterized in that, The preparation method further includes obtaining the product after reaction crystallization. The mixture is then subjected to solid-liquid separation, washing, and drying in sequence.

8. The preparation method according to claim 7, characterized in that, The solid-liquid separation method is filtration.

9. The preparation method according to claim 7, characterized in that, The cleaning process involves sequentially washing the solid obtained from solid-liquid separation with brine, saturated baking soda solution, and clean water.

10. The method for preparing spherical large-particle sodium bicarbonate crystals according to claim 1, characterized in that, The spherical large-particle sodium bicarbonate has a main particle size of 200-600 μm and an ammonium content of less than 900 ppm. The Karl Fiber index of the spherical large-particle sodium bicarbonate is 8-10%. The bulk density of the spherical large-particle sodium bicarbonate is 1.2-1.3 g / mL.

Images