report one,
A method of utilizing industrial wet purification of phosphoric acid to manufacture food-grade disodium hydrogen phosphate, the steps of which are:
(1) Dilute with water to take the qualified product and the industrial wet purification phosphoric acid with a mass percentage concentration of 85% in accordance with HG/T4069-2008 “Industrial Wet Purification of Phosphoric Acid” in an acid-resistant container. Under the condition of stirring, add its mass The reverse osmosis method pure water with a multiple of 1.12 times was continuously stirred for 0.5 hours to obtain an industrial wet purification phosphoric acid diluent with a mass percentage concentration of 40%. During the whole process of controlling this step, the stirring speed is 100rpm.
(2) Neutralization reaction and defluorination and sulfur removal step (1) 1.85kg of industrial wet purification phosphoric acid dilution solution with a concentration of 40% by mass was placed in an acid-resistant container, and under constant stirring, 0.5% by mass of barium carbonate was added. As a desulfurizing agent, continue stirring for 4.5 hours until no bubbles (carbon dioxide) are generated, so that the barium carbonate is fully dissolved and fully reacted with the fluoride ions and sulfate radicals in the phosphoric acid diluent to obtain a reaction mixture; The sodium hydroxide solution with a concentration of 45% neutralizes the reaction mixture to a pH of 4.2, and continues to stir for 7 hours to obtain a neutralization solution; the temperature of the neutralization solution is controlled to 30 ° C, and the membrane material is silicon carbide, and the membrane pores are 0.04 μm and 0.04 μm. The microporous membrane equipment in the form of the membrane module is a honeycomb-type inner tubular membrane to filter it precisely, to separate barium sulfate, barium fluorosilicate and other solid particles, and to obtain a precision-filtered neutralization solution for use. During the whole process of controlling this step, the stirring speed is 145rpm.
(3) Oxidative removal of arsenic, slightly alkaline removal of heavy metals and membrane filtration, under the condition of constant stirring, use sodium hydroxide solution with a mass percentage concentration of 45% to adjust the pH of the precision-filtered neutralization solution obtained in step (2) to 7.5, Add bleaching powder with a mass fraction of 1% of the neutralization solution as an oxidant, heat the temperature of the mixture to 85 °C and maintain it at 85 °C, and keep it under reflux for 4.5 hours under stirring. After oxidation, turn on the cooling water to reduce the temperature of the mixture to 40 °C, and continue After stirring for 5 hours, it was precisely filtered with a microporous membrane device with a membrane material of silicon carbide, a membrane pore of 0.04 μm and a membrane module form of a honeycomb-type inner tubular membrane to separate barium arsenate, sodium arsenate, lead oxide and oxide Cadmium and other insolubles, the micro-alkaline heavy metal removal and oxidative arsenic removal solution are used for use. During the whole process of controlling this step, the stirring speed is 115rpm.
(4) pH adjustment and concentration Under the condition of constant stirring, with the sodium hydroxide solution whose mass percentage concentration is 45%, the pH of the slightly alkaline de-heavy metal and oxidative de-arsenic solution obtained in step (3) is adjusted to 9.3 to obtain disodium hydrogen phosphate solution With rotary evaporation vacuum concentration method, under the condition that vacuum tightness is 0.95MPa and temperature is 95 ℃, the disodium hydrogen phosphate solution is concentrated to mass percent concentration is 50.5%, obtains disodium hydrogen phosphate concentrated solution for subsequent use. The stirring speed of this step is controlled to be 145 rpm.
(5) Cooling and Crystallization Transfer the concentrated solution of disodium hydrogen phosphate obtained in step (4) into the crystallization equipment, and after cooling to 30 ° C for 10 hours to crystallize disodium hydrogen phosphate, reduce its temperature to 5 ° C at a cooling rate of 1.5 ° C/hour, and continue Crystallization for 30 hours, until no crystallization is generated; the crystallization mixture obtains the wet crystallization of disodium hydrogen phosphate and the crystallization mother liquor of disodium hydrogen phosphate through solid-liquid separation (the crystallization mother liquor of disodium hydrogen phosphate can be obtained by concentration-crystallization or concentration-spray drying. Agricultural grade disodium hydrogen phosphate, used as agricultural sodium phosphate fertilizer), take disodium hydrogen phosphate wet crystallization for use.
(6) Crystallization and drying: Wet crystallization of disodium hydrogen phosphate obtained in step (5), and use hot air with a temperature of 105 ° C, a speed of 3.5 m/s and a relative humidity of 70% to dry to the mass percentage of moisture < 2%, and then cool to obtain Food grade disodium hydrogen phosphate product 0.97kg.
After determination, the obtained food grade disodium hydrogen phosphate is white crystalline powder or granules; disodium hydrogen phosphate content (Na2HPO4) (on a dry basis, mass percentage, %)≧98.0, water insoluble matter≤0.2, Arsenic (As, mg/kg)≤3, heavy metal (calculated as Pb, mg/kg)≤10, lead (Pb, mg/kg)≤4, fluoride (calculated as F, mg/kg)≤50, pH (10g/L) is 8.8～9.2, drying weight loss (mass percentage, %)≤2.0. All physical and chemical indicators meet or exceed the requirements of the national food safety standard GB25568-2010 “Food Additive Disodium Hydrogen Phosphate”.
report two,
A method of utilizing wet-process dilute phosphoric acid to manufacture food-grade disodium hydrogen phosphate, the steps of which are:
(1) Membrane filtration: take 1.85kg of wet dilute phosphoric acid (aqueous solution) with a phosphoric acid content of 40% (mass fraction), a sulfate content of 1.5% (mass fraction) and a fluoride ion content of 0.5% (mass fraction) in acid-resistant In the container, use a microporous membrane device with a membrane material of silicon carbide, a membrane pore of 0.04 μm and a membrane module form of a honeycomb-type inner tubular membrane to filter it precisely to separate pigment particles, suspended solids and solid particles, etc., to obtain precise filtration. Wet-process dilute phosphoric acid for use.
(2) Neutralization reaction and simultaneous defluorination and desulfurization: take the precision-filtered wet dilute phosphoric acid obtained in step (1) in an acid-resistant container, and under constant stirring, add barium carbonate with a mass fraction of 4.1% as a defluorination and desulfurization agent, and continue to stir For 4.5 hours, until no bubbles (carbon dioxide) are generated, the barium carbonate is fully dissolved and fully reacted with fluoride ions and sulfate radicals in the precision-filtered wet-process dilute phosphoric acid to obtain a reaction mixture; maintain stirring, with a mass percentage concentration of 45% The sodium hydroxide solution was used to neutralize the reaction mixture to a pH of 4.2, and continued stirring for 7 hours to obtain a neutralization solution; the temperature of the neutralization solution was controlled to 30°C, and the membrane material was silicon carbide, the membrane pore was 0.04 μm, and the membrane module was in the form of The microporous membrane equipment of the honeycomb type inner tubular membrane is used for precision filtration, and the barium sulfate, barium fluorosilicate and other solid particles are separated, and the precision-filtered neutralization solution is obtained for use. During the whole process of controlling this step, the stirring speed is 145rpm.
(3) Oxidative removal of arsenic, slightly alkaline removal of heavy metals and membrane filtration: under constant stirring, use sodium hydroxide solution with a concentration of 45% by mass to adjust the pH of the precision-filtered neutralization solution obtained in step (2) to 7.5 , adding hydrogen peroxide with a mass fraction of 4% of the neutralization liquid as an oxidant, heating the temperature of the mixture to 85 ° C and maintaining it at 85 ° C, under the condition of stirring, reflux for 4.5 hours, and then turn on the cooling water to reduce the temperature of the oxidizing liquid to 40 ° C , continue to stir for 5 hours, and use the microporous membrane equipment whose membrane material is silicon carbide, the membrane pore is 0.04 μm and the membrane module form is honeycomb type inner tubular membrane to be finely filtered to separate barium arsenate, sodium arsenate and lead oxide. and cadmium oxide and other insolubles, the micro-alkaline heavy metal removal and oxidative removal of arsenic solution should be used for use. During the whole process of controlling this step, the stirring speed is 115rpm.
(4) pH adjustment and concentration: under the condition of constant stirring, use the sodium hydroxide solution with a mass percentage concentration of 45% to adjust the pH of the slightly alkaline de-heavy metal and oxidative de-arsenic solution obtained in step (3) to 9.3 to obtain dihydrogen phosphate. Sodium solution; use rotary evaporation vacuum concentration method under the condition that vacuum degree is 0.95MPa and temperature is 95 ℃, the disodium hydrogen phosphate solution is concentrated to the mass percentage concentration of disodium hydrogen phosphate is 50.5%, obtains disodium hydrogen phosphate Reserve liquid concentrate. The stirring speed of this step is controlled to be 145 rpm.
(5) Cooling and crystallization: transfer the concentrated disodium hydrogen phosphate obtained in step (4) into the crystallization equipment, cool down to 30 ° C for 10 hours to crystallize disodium hydrogen phosphate, and reduce its temperature to 5 ° C at a cooling rate of 1.5 ° C/hour, Continue to crystallize for 30 hours, until no crystals are formed; the crystallization mixture obtains the wet crystallization of disodium hydrogen phosphate and the crystallization mother liquor of disodium hydrogen phosphate through solid-liquid separation (the crystallization mother liquor of disodium hydrogen phosphate can be obtained by concentration-crystallization or concentration-spray drying. Obtain agricultural grade disodium hydrogen phosphate, used as agricultural sodium phosphate fertilizer), take disodium hydrogen phosphate wet crystallization for use.
⑹Crystallization and drying: Wet crystallization of sodium dihydrogen phosphate obtained in step ⑸, and dry it with hot air with a temperature of 105°C, a speed of 3.5m/s and a relative humidity of 70% to the mass percentage content of moisture < 2%, and then the solution is cooled. 0.97kg of food grade disodium hydrogen phosphate product was obtained.
After determination, the obtained food grade disodium hydrogen phosphate is white crystalline powder or granules; disodium hydrogen phosphate content (Na2HPO4) (on a dry basis, mass percentage, %)≧98.0, water insoluble matter≤0.2, Arsenic (As, mg/kg)≤3, heavy metal (calculated as Pb, mg/kg)≤10, lead (Pb, mg/kg)≤4, fluoride (calculated as F, mg/kg)≤50, pH (10g/L) is 8.8～9.2, drying weight loss (mass percentage, %)≤2.0. All physical and chemical indicators meet or exceed the requirements of the national food safety standard GB25568-2010 “Food Additive Disodium Hydrogen Phosphate”.
report three.
The sodium carbonate solution with a mass concentration of 10% was slowly added to 200 mL of dilute phosphoric acid with a specific gravity of 1.13, and neutralization was carried out. After the solution was concentrated by evaporation, disodium hydrogen phosphate crystals were obtained. After analysis and testing, the product meets the index requirements of the national standard GB1909-1987 for food additive disodium hydrogen phosphate dodecahydrate.
