Production method of instant sodium pyrophosphate

Abstract

The invention provides a production method of instant sodium pyrophosphate. The production method comprises the following steps: neutralizing, spray-drying, polymerizing, pre-hydrating, cooling and screening to obtain the instant sodium pyrophosphate. Food phosphoric acid and sodium carbonate are neutralized to obtain disodium hydrogen phosphate slurry, the pH is controlled to be 8.8-9.2, and the specific gravity is 1.4-1.5 g / ml; conveying the neutralized slurry to a pressure spray drying tower, and controlling the temperature of the tower bottom to be 120-150 DEG C; after drying, the mixture enters a dynamic polymerization furnace, the polymerization time is 30-40 min, the furnace tail temperature is 180-210 DEG C, and a sodium pyrophosphate semi-finished product is obtained. The semi-finished product passes through a cooling roller, water mist is sprayed at an inlet of the roller for pre-hydration, and meanwhile cooling is conducted; and sieving the product to obtain the instant sodium pyrophosphate.

Description

Technical Field

[0001] The invention relates to a method for producing instant sodium pyrophosphate, in particular to the production of an instant sodium pyrophosphate product. Background Art The solubility of sodium pyrophosphate in 100g water at 20℃ is 6.23g, and the pH value of 1% aqueous solution is about 10. In food processing, sodium pyrophosphate has a stronger ability to adjust the pH of meat tissue system; and pyrophosphate has an ATP-like effect, which can dissociate actomyosin into actin and myosin, which helps to extract salt-soluble protein, thereby improving water retention. Sodium pyrophosphate is the monomer phosphate with the highest water retention efficiency among phosphates. In the processing of meat and aquatic products, phosphates are usually configured into low-temperature pickling solutions, and gradually penetrate into muscle tissue through soaking, rolling, injection, etc., to exert effects on meat protein. The solubility of sodium pyrophosphate is 6.23g, which is half lower than that of sodium tripolyphosphate 13.5g; the main content of conventional commercial sodium pyrophosphate is more than 96%, in fine powder form, with a density of about 0.9. It is easy to form hard lumps when dissolved at low temperature, difficult to stir and melt, and inconvenient to use. When used, it may clog the injection needle hole or attach small pieces of white phosphate to the surface of the food, affecting customer sensory perception. Another side effect of agglomeration is that the active ingredients are not completely dissolved, cannot fully exert their effects, and cannot achieve the desired effect; therefore, the poor solubility of conventional sodium pyrophosphate on the market limits its use, and it is necessary to develop instant sodium pyrophosphate. Domestic patents are mostly focused on methods for producing sodium pyrophosphate using byproducts or crude sodium pyrophosphate, disodium hydrogen phosphate and other industrial-grade raw materials. There are few studies on the production process of instant sodium pyrophosphate. Only patent CN104891466B uses a crystallization method to produce sodium pyrophosphate decahydrate, and then dries to obtain an anhydrous product. The process is relatively complicated and cannot be continuously industrialized. The present invention uses a continuous phosphate production device to obtain a large-particle porous product through a special spray drying and polymerization process; pre-hydration and cooling are carried out on a cooling drum, and the product is directly sieved without crushing to remove the part above 40 mesh, retaining a specific large particle shape. The obtained sodium pyrophosphate does not agglomerate when dissolved, and is completely dissolved within 3 minutes of stirring, and the dissolution rate is fast. Summary of the invention

[0002] The present invention provides the following technical scheme: a method for producing instant sodium pyrophosphate, comprising the following steps: neutralization, drying, polymerization, prehydration, cooling, screening and packaging.

[0003] The neutralization process comprises: mixing phosphoric acid, water and alkali and heating the mixture to obtain a neutralized slurry of disodium hydrogen phosphate; In some embodiments, 7000L of 85% food phosphoric acid, water and 9.9 tons of sodium carbonate are added to a neutralization pot for reaction at a temperature of 90-100°C, and the end point is controlled to be a pH value of 8.9-9.2 and a specific gravity of 1.4-1.5g / ml to obtain a disodium hydrogen phosphate slurry.

[0004] Preferably, the pH value of the neutralization process is controlled at 9.0-9.1.

[0005] The spray drying process: the neutralized slurry is pumped into a spray drying tower through a high-pressure pump, and anhydrous disodium hydrogen phosphate is obtained by pressure spray drying; In some preferred embodiments, the sodium hydrogen phosphate solution is pumped into a spray drying tower through a high-pressure pump, the tower bottom temperature is 120° C. to 150° C., and anhydrous sodium hydrogen phosphate is obtained by pressure spray drying.

[0006] Preferably, the spray drying tower adopts pressure spraying, and the spray nozzle is specially designed. The nozzle part includes a disc core, a distributor and a nozzle. Six diversion holes are arranged around the disc core disk; the distributor has a sealed top, an internal hollow structure, a single oblique hole on the side, and an open bottom. The sealed top of the distributor is connected to the disc core, and the lower opening is matched and connected to the nozzle. The nozzle is inclined at an angle of 30-45 degrees up and down. The liquid flows down through the small holes in the disc core in the spray gun, swirls into the inside of the distributor through the small holes on the side of the distributor, and then reaches the nozzle. The diameter of the diversion hole is 2.5-3.0mm; the aperture of the distributor opening is 1.5-2mm.

[0007] The nozzle significantly increases the volume of atomized droplets and the spray angle by reducing the number of flow guide ports in the core of the flower disc while increasing the aperture; and by opening oblique holes on the side of the distributor, so that the dried sodium dihydrogen phosphate has a fluffy large particle structure.

[0008] More preferably, the spray drying tower adopts downstream drying, with a drying pressure of 4-6 MPa and a nozzle spray angle of 30-45 degrees. The bottom temperature of the spray drying tower is 120°C to 150°C.

[0009] The polymerization process is as follows: anhydrous sodium dihydrogen phosphate is fed into the polymerization furnace, the temperature at the end of the polymerization furnace is ensured to be 180°C to 210°C, and the powder reacts in the polymerization furnace for 30 to 40 minutes. The material coming out of the polymerization furnace is sampled to determine the main content, and crude sodium pyrophosphate is obtained.

[0010] Preferably, the polymerization process is carried out in a dynamic polymerization furnace, so that the polymerization is more complete and uniform.

[0011] The pre-hydration and cooling process: the semi-finished sodium pyrophosphate flows into the cooling drum at high temperature, the atomizing nozzle at the head of the drum is turned on to spray water mist on the material, the water molecules on the surface of the material are pre-hydrated, and the material is turned over in the drum for cooling before flowing out; In some embodiments, the high-temperature material (about 200°C) at the end of the polymerization furnace flows out into the cooling drum. An atomizing nozzle is installed at the head of the drum to spray water mist on the material. The water temperature is 30-50°C, and the spray volume accounts for 1-5% of the powder mass. The granular material absorbs water to pre-hydrate, and gradually cools down as the cooling drum rotates. The residence time on the cooling drum is maintained for 30 minutes.

[0012] The screening and packaging process is as follows: the cooled sodium pyrophosphate is passed through a 40-mesh sieve and then packaged. The particle size of the final product is: all passed through a 40-mesh sieve, the residue on a 60-mesh sieve is ≥50%, the residue on an 80-mesh sieve is ≥60%, and the residue on a 100-mesh sieve is ≥70%.

[0013] Preferably, the particle size of the final product is: 60 mesh sieve residue ≥ 40%, 80 mesh sieve residue ≥ 55%, 100 mesh sieve residue ≥ 80%.

[0014] Compared with the prior art, the present invention provides a method for producing large-particle instant sodium pyrophosphate, which has the following beneficial effects: (1) The present invention changes the nozzle so that fluffy granular disodium hydrogen phosphate is obtained during the drying process, and the sodium pyrophosphate obtained by subsequent polymerization also presents fluffy large particles and a porous structure. When dissolved, the sodium pyrophosphate particles have a larger specific surface area in contact with water, and there are more channels for water molecules to enter the particles, so the dissolution rate is fast. Compared with fine powder, the particle morphology is less likely to stick and clump, and the caking situation is improved.

[0015] (2) Pre-hydration reduces the agglomeration of sodium pyrophosphate. A small amount of anhydrous sodium pyrophosphate molecules pre-absorb water, forming a small amount of hydrated sodium pyrophosphate mixed in the product. Hydrated sodium pyrophosphate is easily soluble, which hinders the mutual adsorption and agglomeration caused by the large amount of heat released by anhydrous sodium pyrophosphate in water, thereby improving solubility. (3) The present invention adopts a continuous phosphate production device, which has achieved large-scale continuous production. The process is easy to operate and has strong production guidance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of a traditional nozzle, where 1' is the core of the flower plate, 2' is the distributor, and 3' is the nozzle.

[0017] Figure 2 It is a top view and a front view of a part of the structure of a conventional nozzle, wherein 1' is the core of the flower plate, 2' is the distributor, and 3' is the nozzle.

[0018] Figure 3 Schematic diagram of the nozzle structure of the present invention, wherein 1 is the core of the flower disc, 2 is the distributor, and 3 is the nozzle.

[0019] Figure 41 is a top view and a front view of the nozzle structure of the present invention, wherein 1 is a faceplate core, 2 is a distributor, and 3 is a nozzle.

[0020] Figure 5 The microstructure of the product particles obtained in Example 1 and Comparative Example 1, wherein a is Comparative Example 1 and b is Example 1. Figure 6 The product appearance diagrams of Example 1, Comparative Example 1 and Comparative Example 2 are shown.

[0021] Figure 7 The following are appearance pictures of the products obtained in Example 1, Comparative Example 1 and Comparative Example 2 after standing and agglomerating.

[0022] Figure 8 The residue after stirring the products obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 for 3 minutes DETAILED DESCRIPTION The technical solution of the present invention will be described in detail below in conjunction with the embodiments of the present invention.

[0023] It should be noted that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The protection scope of the present invention shall be subject to the content of the claims. Any modification or equivalent substitution made by those skilled in the art without creative work on the premise of fully understanding the technical solution of the present invention shall fall within the protection scope of the present invention.

[0024] The nozzle part of the present application includes a flower disc core, a distributor and a nozzle. Six guide holes are set around the flower disc core disc; the diameter of the guide hole is 2.5mm; the distributor is sealed on the top, with a hollow structure inside, a single hole obliquely opened on the side, and an open bottom. The sealed top of the distributor is connected to the flower disc core, and the lower opening is connected to the nozzle. The nozzle is inclined at 45 degrees up and down. The slurry flows down through the small holes in the flower disc core in the spray gun, swirls through the small holes on the side of the distributor into the inside of the distributor, and then reaches the nozzle. The aperture of the distributor measuring hole is 2mm; if Figure 2 shown.

[0025] The nozzle part of the spray drying tower of the commonly used technology includes a flower plate core, which is provided with 8 diversion holes, each with a diameter of 1.5mm, connected to the distributor; the distributor is a solid cylindrical type, with an oblique groove structure at the bottom, connected to the nozzle. The nozzle adopts an angle of 45 degrees up and down; Figure 1 shown.

[0026] Example 1 S1. Neutralization: Add 7000L of 85% food phosphoric acid, 9.9 tons of sodium carbonate and water into a neutralization pot for reaction at a temperature of 90-100°C. The end point is a pH value of 9.0-9.1 and a specific gravity of 1.4-1.5g / ml to obtain disodium hydrogen phosphate slurry.

[0027] S2. Spray drying: The neutralized slurry is pumped into the spray drying tower through a high-pressure pump. The pressure spray tower uses a special nozzle (such as Figure 3 , 4 As shown), the tower bottom temperature is 140°C to 150°C, and anhydrous disodium hydrogen phosphate particles are obtained.

[0028] S3, polymerization: anhydrous disodium hydrogen phosphate is fed into a dynamic polymerization furnace, the temperature at the end of the polymerization furnace is 200℃~210℃, and the material reacts in the polymerization furnace for 30 minutes. Samples are taken from the material at the end of the furnace, and the main content is determined to be 96% or more, to obtain semi-finished sodium pyrophosphate.

[0029] S4, pre-hydration and cooling: The high-temperature material (200-210℃) at the tail of the furnace flows into the cooling drum. The atomizing nozzle at the head of the drum is turned on to spray water mist on the material. The water mass is 4% of the weight of the semi-finished sodium pyrophosphate. The water temperature is 30-50℃. The material absorbs water molecules for local pre-hydration and flows out after cooling in the drum.

[0030] S5, screening and packaging process: the cooled material is passed through a 40-mesh sieve and then packaged.

[0031] Fluidity test method: weigh 3g of the sodium pyrophosphate prepared above and pour it into a beaker containing 100ml of distilled water (20℃). After standing for a period of time (3min), gently shake the beaker to observe the fluidity and use a glass rod to feel the agglomeration.

[0032] Dissolution rate test method: Add 100 mL of distilled water (20°C) into a beaker, place it on a magnetic stirrer for stirring, weigh 3 grams of sodium pyrophosphate, press the stopwatch and quickly pour the sample into the beaker in the form of quicksand, and record the residue after 3 minutes and the time it takes for the sample to be completely dissolved.

[0033] Final product determination: main content is 96.8%, pH 10.2; the product has a large particle appearance ( Figure 6 ), microporous structure ( Figure 5 ). The residue on 60 mesh is 54%, the residue on 80 mesh is 69%, the residue on 100 mesh is 83%, and the apparent density is 0.49g / ml.

[0034] from Figure 5 It can be seen that the sodium pyrophosphate particles obtained in Example 1 have a larger particle size, more pores on the surface, and are more fluffy inside. The specific surface area in contact with water during dissolution is larger, and the dissolution speed is faster.

[0035] from Figure 6 It can be seen that the material particles obtained by using the special nozzle in Example 1 are the largest, the particles obtained by the conventional nozzle are the second largest, and the material crushed by using the conventional nozzle is the most powdery.

[0036] The product has good fluidity and does not agglomerate when placed in water ( Figure 7 ); fast dissolving speed, stirring for 3 minutes to completely dissolve, ( Figure 8 ).

[0037] Example 2 The amount of water mist sprayed in step S4 of Example 1 was changed to 2% of the weight of the crude sodium pyrophosphate, and the rest remained unchanged; Final product determination: main content is 96.8%, pH 10.2; product has large particle appearance, microscopic porous structure. 60 mesh sieve residue is 54%, 80 mesh sieve residue is 69%, 100 mesh sieve residue is 83%, apparent density is 0.49g / ml.

[0038] The solubility of the final product was measured: the product had good fluidity and did not clump when left standing in water; it dissolved quickly and dissolved completely after stirring for 4 minutes.

[0039] Comparative Example 1 The pressure spray in step S2 of Example 1 is carried out using a conventional nozzle ( Figure 1 , 2 ), the rest remain unchanged.

[0040] Product measurement: The particle size of the product is smaller than that of the embodiment, with 14% on 60 mesh, 30% on 80 mesh, and 43% on 100 mesh. The apparent density is 0.65 g / ml. The product partially lumps when left standing in water, and needs to be stirred for 7 minutes to completely dissolve.

[0041] Comparative Example 2 S1. Neutralization: Add 7000L of 85% food phosphoric acid, water and 9.9 tons of sodium carbonate into a neutralization pot for reaction at a temperature of 90-100°C. The end point is controlled to be a pH value of 9-9.1 and a specific gravity of 1.4-1.5g / ml to obtain disodium hydrogen phosphate slurry.

[0042] S2, spray drying: The neutralized slurry is pumped into the spray drying tower through a high-pressure pump, and a conventional spray nozzle ( Figure 1 , 2 ), the tower bottom temperature is 140°C to 150°C, and anhydrous disodium hydrogen phosphate powder is obtained.

[0043] S3, polymerization: the anhydrous disodium hydrogen phosphate powder is fed into a dynamic polymerization furnace, the temperature at the end of the polymerization furnace is 200℃~210℃, and the powder reacts in the polymerization furnace for 30 minutes. The material at the end of the furnace is sampled, and the main content is determined to be qualified, and the semi-finished sodium pyrophosphate is obtained.

[0044] S4. Pre-hydration cooling: The high-temperature material at the tail of the furnace flows into the cooling drum. The atomizing nozzle at the head of the drum is turned on to spray water mist on the material. The water spray mass is 2% of the weight of the crude product. The material absorbs water molecules for pre-hydration and flows out after cooling in the drum.

[0045] S5. After cooling, the material is crushed by a pulverizer to obtain conventional commercial sodium pyrophosphate powder with a density of 0.9 g / ml, passed through a 40-mesh sieve, and then packaged.

[0046] Product determination: main content is 96.8%, pH 10.2; particle size: 60 mesh sieve residue 7%, 80 mesh sieve residue 13%, 100 mesh sieve residue 20%. Apparent density 0.9g / ml.

[0047] Solubility test of the final product: severe lumps were observed when standing in water and stirring was required for 12 minutes to completely dissolve.

[0048] Comparative Example 3 In Example 1, S4 is changed to only undergo cooling: the high-temperature material at the furnace tail flows into the cooling drum, and flows out after being cooled in the drum. The rest remains unchanged.

[0049] Final product determination: Sodium pyrophosphate particle size 60 mesh sieve residue 54%, 80 mesh sieve residue 69%, 100 mesh sieve residue 83%, apparent density 0.49g / ml. It basically does not clump when standing in water, dissolves quickly, and dissolves completely in 4.5 minutes.

[0050] from Figure 7 It can be seen that Example 1 does not clump, the bottom material is in the form of quicksand, is uniform and smooth, and has the best fluidity; Comparative Example 1 has a small amount of clumps locally; Comparative Example 2 has a large amount of clumps.

[0051] from Figure 8 It can be seen that after stirring for 3 minutes, Example 1 was completely dissolved; a very small amount of Example 2 was not dissolved, a large amount of Comparative Example 1 was not dissolved, and a large amount of Comparative Example 2 was not dissolved and agglomerated.

[0052] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing instant sodium pyrophosphate, characterized in that: The following steps are involved: S1, neutralization: mixing phosphoric acid, water and alkali and heating the mixture to obtain a neutralized slurry of disodium hydrogen phosphate; S2, spray drying: the neutralized slurry is pumped into a spray drying tower through a high-pressure pump, and anhydrous disodium hydrogen phosphate is obtained by pressure spray drying; S3, polymerization: subjecting anhydrous disodium hydrogen phosphate to polymerization to obtain semi-finished sodium pyrophosphate; S4, pre-hydration and cooling: the semi-finished sodium pyrophosphate flows into the cooling drum at high temperature, and the atomizing nozzle at the head of the drum is turned on to spray water mist on the material, so that the water molecules on the surface of the material are pre-hydrated, and the material is turned over in the drum for cooling before flowing out; S5, screening and packaging process: the cooled material is passed through a 40-mesh sieve and then packaged.

2. The production method of instant sodium pyrophosphate according to claim 1, characterized in that In step S1, the reaction temperature is 90-100° C., the pH value of the neutralization solution is controlled to be 8.8-9.2, and the specific gravity is 1.4-1.5 g / ml.

3. The production method of instant sodium pyrophosphate according to claim 1, characterized in that In step S2, the spray drying tower has a bottom temperature of 120°C to 150°C.

4. The production method of instant sodium pyrophosphate according to claim 3, characterized in that The nozzle part of the spray drying tower for spraying includes a disc core, a distributor and a nozzle; 6 guide holes are arranged around the disc core disk, with a diameter of 2.5-3.0 mm; the distributor has a sealed top, a hollow structure inside, a single hole obliquely opened on the side, and an open bottom; the sealed top of the distributor is connected to the disc core, and the open bottom is matched and connected to the nozzle, and the nozzle is obliquely angled 30-45 degrees up and down.

5. The production method of instant sodium pyrophosphate according to claim 4, characterized in that The diameter of the single hole on the side of the distributor is 1.5-2 mm; the spray drying pressure is 4-6 MPa, and the nozzle spray angle is 30-45 degrees.

6. The production method of instant sodium pyrophosphate according to claim 1, characterized in that In step S3, the polymerization reaction temperature is 180° C. to 210° C., and the polymerization reaction time is 30 to 40 minutes.

7. The production method of instant sodium pyrophosphate according to claim 1, characterized in that The water mist temperature in step S4 is 30-50°C, and the mass of the mist is 1-5% of the mass of the semi-finished sodium pyrophosphate. The residence time on the cooling drum is maintained at 30 minutes.

8. The method for producing instant sodium pyrophosphate according to any one of claims 1 to 7, characterized in that: The particle size of instant sodium pyrophosphate is: all pass through the standard 40-mesh sieve, the residue on the 60-mesh sieve is ≥40%, the residue on the 80-mesh sieve is ≥55%, and the residue on the 100-mesh sieve is ≥70%; it is in the form of quicksand after being dissolved.

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