A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water

Abstract

The present invention relates to the technical field of corn soaking water recycling and treatment, and in particular to a process method for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate using corn soaking water, comprising the following steps: (1) the supernatant after the corn soaking water is settled is fed into a cationic resin column, and the collected effluent is used for standby; (2) the cationic resin column is rinsed in reverse flow with purified water, and then the cationic resin column is rinsed in forward flow with phosphoric acid, and the collected effluent is used for standby; (3) the standby effluent in step (2) is taken, concentrated, pH adjusted, heated, and after white solid suspension is precipitated, the mixture is kept warm and stirred for a period of time, then cooled, filtered, and the filtrate and precipitate are collected respectively; (4) the filtrate in step (3) is taken, phosphoric acid is added to adjust the pH, vacuum concentrated and crystallized, cooled, centrifuged, and the collected filter cake is rinsed and dried to obtain a potassium dihydrogen phosphate product. Potassium dihydrogen phosphate and magnesium hydrogen phosphate products can be obtained by the above process method.

Description

Technical Field

[0001] The invention relates to the technical field of corn soaking water recovery and processing production, and in particular to a process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by utilizing corn soaking water. Background Art

[0002] In the production process of corn starch wet milling, corn soaking water is the main production wastewater, in which the solid content is about 10-12%, mainly containing 5-6% protein, 2-3% lactic acid, 1% phytic acid, 1% sugar, 0.5% potassium ion and 0.1% magnesium ion and a small amount of starch residue and other substances. At present, most of the treatment processes for these components in corn soaking water are to recover phytic acid. Although cationic resin columns are used to adsorb potassium ions and then hydrochloric acid is used to desorb potassium ions, calcium and magnesium ions are also entrained at the same time. The desorption, concentration, and concentration cost are high, and the value of the obtained potassium salt is low. In addition, potassium, calcium, and magnesium ions are not easy to separate, and the processing cost is high. Therefore, in view of the above problems, a process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate using corn soaking water is explored and studied. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in view of the deficiencies in the prior art, a process method for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water is provided, the potassium and magnesium ions can be recovered by using the process method, and high-value potassium dihydrogen phosphate products and magnesium hydrogen phosphate products can be obtained.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water, the process comprising the following steps:

[0006] (1) The supernatant after the corn soaking water settles enters the cationic resin column in countercurrent, and the effluent is collected for later use;

[0007] (2) flushing the cationic resin column in step (1) with purified water in a countercurrent manner until the protein content in the effluent is less than 0.1 w / v%, then flushing the cationic resin column with phosphoric acid in a forward flow, and collecting the effluent for later use;

[0008] (3) taking the reserved effluent in step (2), concentrating it, adding potassium hydroxide, stirring and mixing, adjusting the pH, heating, and after the white solid suspension is precipitated, keeping warm and stirring for a period of time, then cooling, filtering, and collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product;

[0009] (4) taking the filtrate described in step (3), adding phosphoric acid to adjust the pH, vacuum concentrating and crystallizing, cooling, centrifugal filtering, eluting, and drying the collected filter cake to obtain a potassium dihydrogen phosphate product.

[0010] As an improved technical solution, the resin in the cationic resin is a strong acid cationic resin ZG-1.

[0011] As an improved technical solution, the supernatant in step (1) enters the cationic resin column in countercurrent at a flow rate of 0.5-5 BV / h.

[0012] As an improved technical solution, the purified water in step (2) enters the cationic resin column in countercurrent at a flow rate of 1-10 BV / h.

[0013] As an improved technical solution, in step (2), the phosphoric acid flows into the cationic resin column at a flow rate of 0.2-2.0 BV / h, and the concentration of the phosphoric acid is 5-20 w / v%.

[0014] As an improved technical solution, the effluent in step (3) is concentrated to 30-35 pmol, solid sodium hydroxide is added to adjust the pH to 4.3-9.5, heated to 80-90°C, and after the white solid suspension is precipitated, kept warm for 1.5-3h and cooled to 55-65°C.

[0015] As an improved technical solution, 80-88 w / v% phosphoric acid is added in step (4), the pH is adjusted to 2.0-5.0, vacuum concentrated and crystallized, and then the temperature is reduced to 25-35°C.

[0016] After adopting the above technical solution, the beneficial effects of the present invention are:

[0017] The present invention allows the supernatant after corn soaking water sedimentation to flow into a cationic resin column in reverse flow, potassium ions and magnesium ions are adsorbed by the resin column, the resin column is first rinsed with purified water, and then with phosphoric acid, the collected desorption liquid contains potassium dihydrogen phosphate and magnesium hydrogen phosphate, and then the desorption liquid is concentrated, the pH is adjusted to 4.3-9.5, the temperature is first raised, and after white solid suspension is precipitated, the temperature is kept and stirred, and then the temperature is lowered, and a filtrate and a precipitate (dried to obtain a magnesium hydrogen phosphate product) are obtained by filtering; then phosphoric acid is added to the filtrate, the pH is adjusted, concentrated and crystallized, the temperature is lowered and centrifuged, and the filter cake obtained is then rinsed and dried to obtain a potassium dihydrogen phosphate product. The above-mentioned process method is adopted to realize the recovery of potassium ions and magnesium ions, and the products of potassium dihydrogen phosphate and magnesium hydrogen phosphate are also obtained, which increases economic benefits for enterprises and avoids waste of resources. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail in conjunction with the following embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Example 1

[0020] A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water comprises the following steps:

[0021] (1) After the corn soaking water settles, 46 L of supernatant is countercurrently fed into a cationic resin column (filled with 8 L of strong acid cationic resin ZG-1) at a flow rate of 0.5 BV / h, and the collected effluent is reserved for later use;

[0022] (2) flushing the cationic resin column in step (1) with purified water at a flow rate of 1 BV / h in reverse flow until the protein content in the effluent is less than 0.1 w / v%, and then flushing the cationic resin column with 5 w / v% phosphoric acid at a flow rate of 0.2 BV / h in forward flow, and collecting the effluent for later use;

[0023] (3) taking the reserved effluent in step (2), concentrating it to 30 ppm, adding solid potassium hydroxide, stirring and mixing, adjusting the pH to 4.3, heating to 80° C., and after the white solid suspension precipitates, keeping the temperature and stirring for 1.5 h, then cooling to 55° C., filtering, collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product;

[0024] (4) Take the filtrate in step (3), add 80w / v% phosphoric acid to adjust the pH to 2, and stir the kettle at 50°C under vacuum at -0.07-0.09Mpa. When a small amount of solid is precipitated, start vacuum cooling, continue cooling to 25°C with cooling water, vacuum concentrate and crystallize, centrifuge, filter, rinse, and dry the collected filter cake to obtain the potassium dihydrogen phosphate product.

[0025] Example 2

[0026] A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water comprises the following steps:

[0027] (1) After the corn soaking water settles, 46 L of supernatant is countercurrently fed into a cationic resin column (filled with 8 L of strong acid cationic resin ZG-1) at a flow rate of 1 BV / h, and the collected effluent is reserved for later use;

[0028] (2) flushing the cationic resin column in step (1) with purified water at a flow rate of 3 BV / h in reverse flow until the protein content in the effluent is less than 0.1 w / v%, and then flushing the cationic resin column with 12 w / v% phosphoric acid at a flow rate of 0.5 BV / h in forward flow, and collecting the effluent for later use;

[0029] (3) taking the reserved effluent in step (2), concentrating it to 31 mmol, adding solid potassium hydroxide, stirring and mixing, adjusting the pH to 5.5, heating to 83° C., and after the white solid suspension precipitates, keeping the temperature and stirring for 1.8 h, then cooling to 58° C., filtering, collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product;

[0030] (4) Take the filtrate described in step (3), add 83w / v% phosphoric acid to adjust the pH to 2.5, stir and evaporate water at a kettle temperature of 55°C under vacuum at -0.07-0.09Mpa, and when a small amount of solid is seen to precipitate, start to cool to 50°C under vacuum, and continue to cool to 28°C with cooling water to vacuum concentrate and crystallize, centrifuge, filter, rinse, and dry the collected filter cake to obtain the potassium dihydrogen phosphate product.

[0031] Example 3

[0032] A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water comprises the following steps:

[0033] (1) After the corn soaking water settles, 46 L of supernatant is countercurrently fed into a cationic resin column (filled with 8 L of strong acid cationic resin ZG-1) at a flow rate of 2.5 BV / h, and the collected effluent is reserved for later use;

[0034] (2) flushing the cationic resin column in step (1) with purified water at a flow rate of 6 BV / h in reverse flow until the protein content in the effluent is less than 0.1 w / v%, and then flushing the cationic resin column with 15 w / v% phosphoric acid at a flow rate of 1 BV / h in forward flow, and collecting the effluent for later use;

[0035] (3) taking the reserved effluent in step (2), concentrating it to 32 ppm, adding solid potassium hydroxide, stirring and mixing, adjusting the pH to 6.5, heating to 85° C., and after the white solid suspension precipitates, keeping the temperature and stirring for 2.5 hours, then cooling to 60° C., filtering, collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product;

[0036] (4) Take the filtrate in step (3), add 85w / v% phosphoric acid to adjust the pH to 3.5, stir and evaporate water at a kettle temperature of 65°C under vacuum at -0.07-0.09Mpa, and when a small amount of solid is seen to precipitate, begin to cool to 58°C under vacuum, and continue to cool to 30°C with cooling water to vacuum concentrate and crystallize, centrifuge, filter, rinse, and dry the collected filter cake to obtain the potassium dihydrogen phosphate product.

[0037] Example 4

[0038] A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water comprises the following steps:

[0039] (1) After the corn soaking water settles, 46 L of supernatant is countercurrently fed into a cationic resin column (filled with 8 L of strong acid cationic resin ZG-1) at a flow rate of 4 BV / h, and the collected effluent is reserved for later use;

[0040] (2) flushing the cationic resin column in step (1) with purified water at a flow rate of 8 BV / h in reverse flow until the protein content in the effluent is less than 0.1 w / v%, and then flushing the cationic resin column with 18 w / v% phosphoric acid at a flow rate of 1.5 BV / h in forward flow, and collecting the effluent for later use;

[0041] (3) taking the reserved effluent in step (2), concentrating it to 30 ppm, adding solid potassium hydroxide, stirring and mixing, adjusting the pH to 8.5, heating to 88° C., and after the white solid suspension precipitates, keeping the temperature and stirring for 2.8 hours, then cooling to 63° C., filtering, collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product;

[0042] (4) Take the filtrate described in step (3), add 85w / v% phosphoric acid to adjust the pH to 4.3, stir and evaporate water at a kettle temperature of 75°C under vacuum at -0.07-0.09Mpa, and when a small amount of solid is seen to precipitate, start to cool to 50°C under vacuum, and continue to cool to 33°C with cooling water to vacuum concentrate and crystallize, centrifuge, filter, rinse, and dry the collected filter cake to obtain the potassium dihydrogen phosphate product.

[0043] Example 5

[0044] A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water comprises the following steps:

[0045] (1) After the corn soaking water settles, 46 L of supernatant is countercurrently fed into a cationic resin column (filled with 8 L of strong acid cationic resin ZG-1) at a flow rate of 5 BV / h, and the collected effluent is reserved for later use;

[0046] (2) flushing the cationic resin column in step (1) with purified water at a flow rate of 10 BV / h in reverse flow until the protein content in the effluent is less than 0.1 w / v%, and then flushing the cationic resin column with 20 w / v% phosphoric acid at a flow rate of 2 BV / h in forward flow, and collecting the effluent for later use;

[0047] (3) taking the reserved effluent in step (2), concentrating it to 35 ppm, adding solid potassium hydroxide, stirring and mixing, adjusting the pH to 9.5, heating to 90° C., and after the white solid suspension precipitates, keeping the temperature and stirring for 3 hours, then cooling to 65° C., filtering, collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product;

[0048] (4) Take the filtrate in step (3), add 88w / v% phosphoric acid to adjust the pH to 5, stir and distill water at 80°C under vacuum at -0.07-0.09Mpa, and when a small amount of solid is seen to precipitate, start to cool to 60°C under vacuum, and continue to cool to 35°C with cooling water to vacuum concentrate and crystallize, centrifuge, rinse, and dry the collected filter cake to obtain the potassium dihydrogen phosphate product; the filtrate collected by centrifugation contains calcium ions and a small amount of protein.

[0049] In order to better prove that the process method of the present invention has a good technical effect, 8 comparative examples are given with reference to Example 3, as shown in Table 1 for details.

[0050] Comparative Example 1

[0051] The difference from Example 3 is that the resin in the cationic resin column is D001;

[0052] Comparative Example 2

[0053] The difference from Example 3 is that in step (2), a 20 w / v% phosphoric acid positive flow is used to flush the cationic resin column, and the remaining operations are the same.

[0054] Comparative Example 3

[0055] The difference from Example 3 is that in step (2), a 5 w / v% phosphoric acid positive flow is used to flush the cationic resin column, and the remaining operations are the same.

[0056] Comparative Example 4

[0057] The difference from Example 3 is that in step (3), the pH is adjusted to less than 4.3, and the remaining operations are the same.

[0058] Comparative Example 5

[0059] The difference from Example 3 is that in step (3), the pH is adjusted to be greater than 9.5, and the remaining operations are the same.

[0060] Comparative Example 6

[0061] The difference from Example 3 is that in step (4), the pH is adjusted to less than 2, and the remaining operations are the same.

[0062] Comparative Example 7

[0063] The difference from Example 3 is that in step (4), the pH is adjusted to be greater than 5, and the remaining operations are the same.

[0064] Table 1

[0065]

[0066] It can be found from the data in Table 1 that the process method of the present invention can obtain potassium dihydrogen phosphate products and magnesium hydrogen phosphate products with high yield, high yield and high purity; although the yield of potassium dihydrogen phosphate in Comparative Example 4 is higher than that in Example 4, because too much potassium hydroxide and phosphoric acid are used when adjusting the pH in Comparative Example 4, thereby increasing the yield of potassium dihydrogen phosphate, the actual yield is lower than that in Example 4. In summary, the process method of the present invention uses the supernatant of corn soaking water as a raw material, and after treatment, potassium dihydrogen phosphate and magnesium hydrogen phosphate products can be obtained, and the potassium ions and magnesium ions in the corn soaking water can be recovered.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate using corn soaking water, characterized in that The process comprises the following steps: (1) The supernatant after corn soaking water sedimentation, countercurrent into the cationic resin column, the effluent collected for later use; the cationic resin resin is a strong acid cationic resin ZG-1; (2) flushing the cationic resin column in step (1) with purified water in a countercurrent manner until the protein content in the effluent is less than 0.1 w / v%, then flushing the cationic resin column with phosphoric acid in a forward flow, and collecting the effluent for later use; (3) taking the reserved effluent in step (2), concentrating it, adding potassium hydroxide, stirring and mixing, adjusting the pH, heating, and after the white solid suspension precipitates, keeping warm and stirring for a period of time, cooling, filtering, collecting the filtrate and the precipitate respectively, wherein the precipitate is dried to obtain a magnesium hydrogen phosphate product; the effluent is concentrated to 30-35 ppm, adding solid potassium hydroxide to adjust the pH to 4.3-9.5, heating to 80-90°C, and after the white solid suspension precipitates, keeping warm for 1.5-3h, and cooling to 55-65°C; (4) Take the filtrate in step (3), add 80-88 w / v% phosphoric acid to adjust the pH to 2.0-5.0, vacuum concentrate and crystallize, cool to 25-35° C., centrifuge and rinse, and collect the filter cake and dry to obtain the potassium dihydrogen phosphate product.

2. The process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water according to claim 1, characterized in that: The supernatant in step (1) enters the cationic resin column in a countercurrent flow at a flow rate of 0.5-5 BV / h.

3. The process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water according to claim 1, characterized in that: In step (2), the purified water enters the cationic resin column in a countercurrent flow at a flow rate of 1-10 BV / h.

4. The process for preparing potassium dihydrogen phosphate and magnesium hydrogen phosphate by using corn soaking water according to claim 1, characterized in that: In step (2), the phosphoric acid flows into the cationic resin column at a flow rate of 0.2-2.0 BV / h, and the concentration of the phosphoric acid is 5-20 w / v%.

Images