Preparation method of silica for feed additive

Abstract

The invention discloses a preparation method of silica white for feed additives: B1. Water glass is added with water to be prepared into a solution with a concentration of 1.0 - 2.0 mol / L, a composite flocculant is added, stirred and then left to stand, and high-purity water glass liquid is obtained by plate-frame filtration; B2. Water and calcium chloride are added to the reaction kettle, stirred and dissolved, heated to 30 - 45 °C, and then the water glass liquid is added dropwise. After a white jelly-like substance is formed, the addition is stopped and stirring and aging are carried out; B3. The water glass liquid is added, kept warm at 30 - 45 °C, concentrated sulfuric acid is added dropwise, and the addition of acid and stirring are stopped when the pH reaches 6.0 - 7.0, and left to stand to form a gel; B4. Stir, add water to raise the temperature of the liquid material to 65 - 80 °C, and at the same time add the water glass liquid and concentrated sulfuric acid dropwise, control the pH at 6.0 - 7.0, stop adding the water glass after reacting for 50 - 70 min, continue to add acid to make the reaction complete, stir and adjust the pH of the suspension to 3.0 - 3.5, and then age to obtain a silica slurry; B5. The subsequent treatment of the slurry is to make the content of soluble dissociation salts in the filter cake after pressure filtration and washing less than 0.6%, and the solid content is 18% - 20%; B6. Spray drying is carried out to obtain silica particles. The invention solves the problems of long production cycle, low yield and environmental impact.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation methods of precipitated silica, and particularly relates to a preparation method of silica for feed additives. Technical Background

[0002] Precipitated hydrated silica, also known as silica white, belongs to the field of inorganic silicides and is an important inorganic chemical raw material. Due to its special surface structure and unique physical and chemical properties, silica white has a very wide range of applications. As a reinforcing agent for rubber (including silicone rubber) products, it is mainly used in the shoe industry, tires and other light-colored rubber products; it is used as a carrier or flow agent in industries such as pesticides and feeds; it is used as a friction agent and thickener in toothpaste; it is used as a dispersant, anti-settling agent or matting agent in the paint industry; it is also widely used as an adsorbent in industries such as medicine and food.

[0003] Although the amount of silica white used as a feed additive is small, the role it plays in feed is irreplaceable. It can balance the nutritional components of feed, enhance the nutritional value of basic feed, improve animal production performance, ensure animal health, and improve the utilization rate of feed. Due to the good adsorption and fluidity of silica, when silica feed additive is used in feed, it can significantly improve the quality of feed additive, form a powder that is easy to flow, and can be evenly dispersed in feed to improve feed utilization rate, thereby reducing feed consumption and lowering production costs. The main role of silica in the field of feed additives is: it is a good carrier for various vitamins, flavoring agents, allicin, anti-enzymatic agents, sour agents, antioxidants, etc., and has an antioxidant and freshness preservation effect, and the granulation drying time is relatively reduced by 2 / 3; adding this product to the anti-caking agent has good dispersibility, and is especially suitable for the finished products of water-soluble antibiotics, vitamins, protease, and polysaccharase that are prone to moisture absorption and caking. It can be quickly dried, anti-caking, and can quickly return to its original state, and is not easy to get damp after being made into finished products. However, conventional silica has a smaller particle size and a lower pore volume, resulting in poor adsorption performance of silica particles, and less active ingredients can be carried when applied to the preparation of feed, thus affecting its application.

[0004] Chinese Patent CN 113264531 A discloses a preparation method of granular feed additive silica. The invention adopts a three-step synthesis, three-step cooling, and three-step aging method, and adds a modifier such as cetyltrimethylammonium bromide or cetyltrimethylammonium chloride, and then adds polyacrylamide, sodium polyacrylate or a combination thereof as a water-soluble polymer stabilizer to the slurry. The defects of this method are long production cycle, low efficiency, adding a variety of organic solvents in the reaction process, and greater environmental impact during the production process.

[0005] Therefore, it is necessary to develop a production method of silica with high yield, environmental protection in production, high oil absorption value, high strength, and low heavy metal content. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method of silica white for feed additives with a short production cycle, high production efficiency and little environmental impact, and to solve the problems of long production cycle, low yield and large environmental impact in the prior art.

[0007] To achieve the above object, a preparation method of silica white for feed additives of the present invention includes the following steps:

[0008] Step 1: Take water glass with a modulus of 3.30 - 3.60 and add water to prepare a solution with a concentration of 1.0 - 2.0 mol / L. In the prepared water glass solution, add a composite flocculant prepared from aluminum sulfate, polyaluminum chloride and polyacrylamide with a mass concentration of 0.3% - 0.5%. After uniformly stirring for 0.5 - 1.0 h, let it stand for 3.0 - 6.0 h, and remove the impurities precipitated in the water glass solution through plate-frame filtration to remove the impurities and heavy metals in the solution, and obtain a high-purity water glass solution;

[0009] Step 2: Add water and calcium chloride to a glass reaction kettle with high-speed stirring. The mass ratio of water to calcium chloride added is 1000:(0.5 - 1). Start stirring to fully dissolve calcium chloride, start heating to a temperature of 30 - 45 °C, and dropwise add the water glass solution prepared in Step 1 to the reaction kettle. The dropping time is 30 - 50 min. Stop dropping when a white gel-like substance is formed, and stir and age for 20 - 30 min;

[0010] Step 3: Add the water glass solution prepared in Step 1 to the reaction kettle. The volume ratio of the water glass solution to the water in Step 2 is (5 - 15):100. Keep the temperature at 30 - 45 °C, and dropwise add concentrated sulfuric acid with a mass concentration of 98%. Stop adding acid and stop stirring when the pH reaches 6.0 - 7.0, and let it stand for 15 - 30 min to make the solution completely gel-like;

[0011] Step 4: Start stirring, add water at 90 - 95 °C to the reaction kettle to raise the temperature of the liquid material to 65 - 80 °C. At the same time, dropwise add the water glass solution prepared in Step 1 and concentrated sulfuric acid with a mass concentration of 98%. Control the pH during the reaction process to be 6.0 - 7.0. After reacting for 50 - 70 min, stop adding the water glass, continue to add concentrated sulfuric acid to completely react the water glass in the reaction kettle, stir until a uniform suspension is obtained, and adjust the pH value of the suspension to 3.0 - 3.5 and then continue to age for 10 - 30 min to obtain a silica slurry;

[0012] Step 5: Wash, solid-liquid separate and pulp the silica slurry prepared in Step 4 to make the content of soluble dissociation salts in the filter cake after pressure filtration and washing less than 0.6%, and the solid content of the filter cake is 18% - 20%;

[0013] Step 6: Spray drying treatment is carried out to obtain silicon dioxide particles, and the spray drying temperature is 600 - 650 °C.

[0014] Furthermore, in Step 1, the composite flocculant is prepared from aluminum sulfate: polyaluminum chloride: polyacrylamide according to a mass ratio of (1 - 2):(2 - 4):(0.15 - 0.25).

[0015] Furthermore, in Step 2, the dropping flow rate of sodium silicate is 0.3 - 0.6 mL / s.

[0016] Furthermore, in Step 3, the dropping flow rate of concentrated sulfuric acid is 0.05 - 0.08 mL / s.

[0017] Furthermore, in Step 4, the dropping flow rate of sodium silicate is 2.0 - 2.5 mL / s.

[0018] The preparation method of silica for feed additive of the present invention has the following technical features and beneficial effects:

[0019] 1. The composite flocculant prepared from aluminum sulfate, polyaluminum chloride (inorganic flocculant) and polyacrylamide (organic flocculant) is used to purify sodium silicate. The composite flocculant can quickly and effectively remove impurities and heavy metals in the solution, and obtain a high-purity sodium silicate solution.

[0020] 2. Silica gel is formed under weakly acidic conditions, and calcium silicate is introduced before the formation of silica gel. The calcium silicate is restricted within its three-dimensional space network by the silica gel, thus forming a silica crystal nucleus encapsulating calcium silicate. The calcium silicate inner core has a higher atomic packing density than silica. Therefore, the prepared silica has more excellent particle strength performance, and has the beneficial effect of higher particle strength than the silica prepared by the ordinary precipitation method, providing a silica product with more excellent particle strength performance for the application field of feed additives.

[0021] 3. The pH of the precipitation reaction is controlled at 6.0 - 7.0. Under this weakly acidic and nearly neutral condition, the acid-base neutralization rate in the reaction system is relatively high, and the crystal grains grow rapidly, which is beneficial to improving the porosity of silica. As a result, the feed particles processed from silica have a large pore volume and strong adsorption, effectively avoiding the situation that the pore volume of some feed additives made of silica is small and the adsorption is not strong after being added to the feed.

[0022] 4. The prepared silica has a high oil absorption value, high strength, good fluidity, low heavy metal content, and uniform particle size distribution. Specific Embodiments

[0023] The following further elaborates in detail on the preparation method of silica for feed additive of the present invention in combination with specific embodiments.

[0024] Example 1

[0025] 1. Take water glass with a modulus of 3.45 and add water to prepare a solution with a concentration of 1.23 mol / L. In the prepared water glass solution, add a composite flocculant prepared from aluminum sulfate, polyaluminum chloride, and polyacrylamide with a mass concentration of 0.45%. The mass ratio of aluminum sulfate, polyaluminum chloride, and polyacrylamide is 1.5:2.5:0.2. After stirring evenly for 0.6 h, let it stand for 4.0 h, and filter out the precipitated impurities in the water glass solution with a plate and frame to remove the impurities and heavy metals in the solution, obtaining a high-purity water glass solution;

[0026] 2. Add 8.0 L of water to a 50 L glass reactor with high-speed stirring, and at the same time add 6.50 g of calcium chloride. Start stirring to fully dissolve the calcium chloride. Start heating to a material temperature of 40 °C, and drip the water glass solution prepared in step 1 into the reactor. The dripping rate of the water glass is 0.4 mL / s, and the dripping time is 30 min. Stop dripping after forming a white gel-like substance, and stir and age for 30 min;

[0027] 3. Add 0.8 L of the water glass solution prepared in step 1 to the reactor, keep the temperature at 40 °C, and drip concentrated sulfuric acid with a mass concentration of 98%. The dripping rate is 0.065 mL / s. Stop adding acid and stop stirring when the pH reaches 6.7, and let it stand for 20 min to make the solution completely gel-like;

[0028] 4. Start stirring, and at the same time add a certain amount of 90 °C water to the reactor to raise the material temperature to 75 °C. At the same time, drip the water glass solution prepared in step 1 and concentrated sulfuric acid with a mass concentration of 98%. The dripping rate of the water glass is 2.2 mL / s, control the pH of the reaction process to 6.7, stop adding the water glass after the reaction time reaches 60 min, continue to add concentrated sulfuric acid to react the water glass in the reactor completely, stir to a uniform suspension, and adjust the pH value of the suspension to 3.2 and then continue to age for 20 min to obtain a silicon dioxide slurry;

[0029] 5. Wash, solid-liquid separate, and make a slurry of the silicon dioxide slurry prepared in step 4, so that the content of soluble dissociation salts (such as sulfates) in the filter cake after pressure filtration and washing treatment is below 0.6%, and the solid content of the filter cake is 19.5%;

[0030] 6. Spray drying treatment, the spray drying temperature is 620 °C, and silicon dioxide particles are obtained.

[0031] Example 2

[0032] 1. Take sodium silicate with a modulus of 3.60 and add water to prepare a solution with a concentration of 2.0 mol / L. In the prepared sodium silicate solution, add a composite flocculant with a mass concentration of 0.5%. The mass ratio of aluminum sulfate, polyaluminum chloride, and polyacrylamide in the composite flocculant is 2.0:4.0:0.25. After stirring evenly for 0.5 h, let it stand for 3.0 h, and filter out the precipitated impurities in the sodium silicate solution with a plate and frame to remove the impurities and heavy metals in the solution, obtaining a high-purity sodium silicate solution;

[0033] 2. Add 9.0 L of water to a 50 L glass reaction kettle with high-speed stirring, and at the same time add 7.25 g of calcium chloride. Start stirring to fully dissolve the calcium chloride. Start heating to a material temperature of 45 °C, and drip the sodium silicate solution prepared in step 1 into the reaction kettle. The dripping rate of sodium silicate is 0.60 mL / s, and the dripping time is 40 min. Stop dripping when a white gel-like substance is formed, and stir and age for 25 min;

[0034] 3. Add 1.0 L of the sodium silicate solution prepared in step 1 to the reaction kettle, keep the temperature at 45 °C, and drip concentrated sulfuric acid with a mass concentration of 98%. Stop adding acid and stop stirring when the dripping rate is 0.08 mL / s until the pH is 6.9, and let it stand for 15 min to make the solution completely gel;

[0035] 4. Start stirring, and at the same time add a certain amount of water at 95 °C to the reaction kettle to raise its temperature to 80 °C. At the same time, drip the sodium silicate solution prepared in step 1 and concentrated sulfuric acid with a mass concentration of 98%. The dripping rate of sodium silicate is 2.5 mL / s, control the pH of the reaction process to be 6.9, stop adding sodium silicate after the reaction proceeds for 70 min, continue to add concentrated sulfuric acid to react the sodium silicate in the reaction kettle completely, stir to a uniform suspension, and adjust the pH value of the suspension to 3.5 and then continue to age for 30 min to obtain a silicon dioxide slurry;

[0036] 5. Wash, separate solid and liquid, and make pulp of the silicon dioxide slurry prepared in step 4, so that the content of soluble dissociation salts (such as sulfates) in the filter cake after pressure filtration and washing treatment is below 0.6%, and the solid content of the filter cake is 20.0%;

[0037] 6. Spray drying treatment, the spray drying temperature is 650 °C, and silicon dioxide particles are obtained.

[0038] Example 3

[0039] 1. Prepare a solution by adding water to sodium silicate with a modulus of 3.30 to form a solution with a concentration of 1.0 mol / L. In the prepared sodium silicate solution, add a composite flocculant with a mass concentration of 0.3%. The mass ratio of aluminum sulfate, polyaluminum chloride, and polyacrylamide in the composite flocculant is 1.0:2.0:0.25. After stirring evenly for 1.0 h, let it stand for 6.0 h, and filter out the precipitated impurities in the sodium silicate solution with a plate and frame to remove impurities and heavy metals in the solution, obtaining a high-purity sodium silicate solution;

[0040] 2. Add 6.5 L of water to a 50 L glass reactor with high-speed stirring, and at the same time add 5.23 g of calcium chloride. Start stirring to fully dissolve the calcium chloride. Start heating to a material temperature of 35 °C, and drip the sodium silicate solution prepared in step 1 into the reactor. The dripping rate of the sodium silicate is 0.3 mL / s, and the dripping time is 50 min. Stop dripping after forming a white gel-like substance, and stir and age for 20 min;

[0041] 3. Add 0.6 L of the sodium silicate solution prepared in step 1 to the reactor, keep the temperature at 35 °C, and drip concentrated sulfuric acid with a concentration of 98%. The dripping rate is 0.05 mL / s. Stop adding acid and stop stirring after the pH reaches 6.1, and let it stand for 30 min to make the solution completely gel;

[0042] 4. Start stirring, and at the same time add a certain amount of water at 90 °C to the reactor to raise the material temperature to 65 °C. At the same time, drip the sodium silicate solution prepared in step 1 and concentrated sulfuric acid with a concentration of 98%. The dripping rate of the sodium silicate is 2.0 mL / s, control the pH of the reaction process to 6.1, stop adding the sodium silicate after the reaction proceeds for 70 min, continue to add concentrated sulfuric acid to completely react the sodium silicate in the reactor, stir until a uniform suspension is formed, and adjust the pH value of the suspension to 3.0 and then continue to age for 10 min to obtain a silicon dioxide slurry;

[0043] 5. Wash, separate solid and liquid, and make pulp of the silicon dioxide slurry obtained in step 4, so that the content of soluble dissociation salts (such as sulfates) in the filter cake after pressure filtration and washing treatment is below 0.6%, and the solid content of the filter cake is 18.0%;

[0044] 6. Conduct spray drying treatment at a spray drying temperature of 600 °C to obtain silicon dioxide particles.

[0045] Comparative Example 1

[0046] Differing from Example 1, in step 1, an inorganic flocculant mixture of aluminum sulfate and polyaluminum chloride is used alone to purify sodium silicate, and other conditions are the same as in Example 1.

[0047] Comparative Example 2

[0048] Different from Example 1, in Step 1, the sodium silicate was purified using only the organic flocculant polyacrylamide, and other conditions were the same as in Example 1.

[0049] Comparative Example 3

[0050] Different from Example 1, in Step 2, calcium chloride was not added, and only the bottom water was added to the reaction kettle, and other conditions were the same as in Example 1.

[0051] Comparative Example 4

[0052] Different from Example 1, Step 3 in Example 1 was cancelled, and other conditions were the same as in Example 1.

[0053] Comparative Example 5

[0054] Different from Example 1, the pH of the reaction process was controlled at 8.5 in Step 4, and other conditions were the same as in Example 1.

[0055] The technical indexes of the white carbon black products prepared in the above examples and comparative examples are listed in the following table:

[0056]

[0057] It can be seen from the table that the oil absorption value of the silica prepared in Examples 1-3 of the present invention is 2.9-3.1 cm 3 / g, the pore volume is 2.3-2.5 ml / g, and the heavy metal content (calculated as Pb) ≤ 0.4 mg / Kg. Compared with the comparative examples, the various performances are improved significantly. Among them, the comprehensive technical indexes of Example 1 are the best, and it is the best example.

[0058] It should be noted that the above examples are not used to limit the protection scope of the present invention. For those skilled in the art, they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of silica white for feed additive, characterized in that: It includes the following steps: Step 1: Take sodium silicate with a modulus of 3.30 - 3.60 and add water to prepare a solution with a concentration of 1.0 - 2.0 mol / L. In the prepared sodium silicate solution, add a composite flocculant prepared from aluminum sulfate, polyaluminum chloride, and polyacrylamide with a mass concentration of 0.3% - 0.5%. After uniformly stirring for 0.5 - 1.0 h, let it stand for 3.0 - 6.0 h, and remove the impurities precipitated in the sodium silicate solution through plate-and-frame filtration to remove impurities and heavy metals in the solution, obtaining a high-purity sodium silicate solution; the composite flocculant is prepared according to the mass ratio of aluminum sulfate: polyaluminum chloride: polyacrylamide of (1 - 2):(2 - 4):(0.15 - 0.25); Step 2: Add water and calcium chloride to a glass reaction kettle with high-speed stirring. The mass ratio of water to calcium chloride added is 1000:(0.5 - 1). Start stirring to fully dissolve calcium chloride, start heating to a temperature of 30 - 45 °C, and drip the sodium silicate solution prepared in Step 1 into the reaction kettle. The dripping time is 30 - 50 min. Stop dripping when a white gel-like substance is formed, and stir and age for 20 - 30 min; Step 3: Add the sodium silicate solution prepared in Step 1 to the reaction kettle. The volume ratio of the sodium silicate solution to the water in Step 2 is (5 - 15):

100. Keep the temperature at 30 - 45 °C, and drip concentrated sulfuric acid with a mass concentration of 98%. Stop adding acid and stop stirring when the pH reaches 6.0 - 7.

0. Let it stand for 15 - 30 min to make the solution completely gel-like; Step 4: Start stirring, add water at 90 - 95 °C to the reaction kettle to raise the temperature of the liquid material to 65 - 80 °C. At the same time, drip the sodium silicate solution prepared in Step 1 and concentrated sulfuric acid with a mass concentration of 98%. Control the pH during the reaction process to be 6.0 - 7.

0. Stop adding the sodium silicate solution after reacting for 50 - 70 min, continue to add concentrated sulfuric acid to completely react the sodium silicate in the reaction kettle, stir until a uniform suspension is formed, and adjust the pH value of the suspension to 3.0 - 3.5 and then continue to age for 10 - 30 min to obtain a silica slurry; Step 5: Wash, separate solid and liquid, and make pulp of the silica slurry prepared in Step 4, so that the content of soluble dissociable salts in the filter cake after pressure filtration and washing treatment is below 0.6%, and the solid content of the filter cake is 18% - 20%; Step 6: Conduct spray drying treatment to obtain silica particles. The spray drying temperature is 600 - 650 °C.

2. The preparation method of the silica white for feed additive as described in claim 1, characterized in that: The dropping flow rate of sodium silicate in Step 2 is 0.3 - 0.6 mL / s.

3. The preparation method of the silica for feed additive according to claim 1, characterized in that: The dropping flow rate of concentrated sulfuric acid in Step 3 is 0.05 - 0.08 mL / s.

4. The preparation method of the silica for feed additive according to claim 1, characterized in that: The dropping flow rate of sodium silicate in Step 4 is 2.0 - 2.5 mL / s.

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