Preparation of high purity calcium carbonate_industrial additives

Preparation background and overview of high-purity calcium carbonate

Calcium carbonate is one of the most widespread inorganic compounds and one of the most important basic raw materials for inorganic chemicals. It has the characteristics of low price, abundant raw materials, non-toxicity, simple production process and stable performance. It is added in rubber and plastic processing. An appropriate amount of calcium carbonate can improve the rigidity, wear resistance, hardness, heat resistance, dimensional stability and other properties of the product. In recent years, with the rapid development of science and technology, the requirements for calcium carbonate in various industries are increasingly moving towards high purity and high yield. Therefore, how to prepare high-purity calcium carbonate with high purity and high yield has become an urgent issue. question.

Preparation of high-purity calcium carbonate

Preparation Report of High Purity Calcium Carbonate 1.

A method for refining calcium carbonate from sulfate bamboo wood mixed pulping green liquor includes the following steps:

(1) Silicon removal from green liquor: Add 20 mL of aluminum sulfate with a mass fraction of 10% to 1L of green liquor, and stir to convert the silicates in the green liquor into aluminosilicates and precipitate;

(2) Green liquor flocculation: Add 4g of crushed quicklime to the green liquor, stir, add 10mg of anionic polyacrylamide, continue stirring, stir at a fast and then slow speed, and let stand for 20 minutes;

(3) Green liquor purification: Add 20 mL of 10% triethanolamine to the flocculated green liquor, stir gently, then add 5 mL of 10% disodium ethylenediaminetetraacetate, stir, and let stand for 10 minutes;

(4) Green liquor filtration: filter the flocculated and purified green liquor to obtain clear green liquor;

(5) Green liquor concentration: The main components of the processed green liquor: 15.19g NaOH, 14.26g Na₂S, 91.76g Na₂CO₃, the total alkali content is 120.21g (all calculated as Na₂O), the green liquor is heated and concentrated until the total alkali content of the green liquor is 132.8g (all calculated as Na₂O) Na₂O), the main components of the concentrated green liquor are 16.3g NaOH, 15.8g Na₂S and 100.7g Na₂CO₃;

(6) Quicklime quality screening: The screened quicklime has an effective calcium oxide of 88.7%, a whiteness of 76.6%, magnesium oxide of 1.2%, and iron oxide of 0.11%;

(7) Quicklime crushing: crush the screened quicklime into small particles of quicklime ≤10cm through a crusher;

(8) Digestion of quicklime: Use hot water above 90℃ to digest quicklime;

(9) Preparation of milk of lime: pass the digested milk of lime through a 200-mesh screen to remove coarse residue and impurities, then put the milk of lime into a centrifuge for centrifugal discharge to further remove fine impurities and obtain high-quality Lime emulsion, adjust the concentration of lime emulsion, and detect calcium hydroxide to be 16.17%;

(10) Lime milk purification: Weigh 390g of the lime milk obtained in step (9), add 5 mL of 10% triethanolamine, stir, and then add 2 mL of 10% ethylenediaminetetraacetic acid diacetate. Sodium;

(11) Green liquor causticization: Turn on the mixer, stir the lime milk, control the rotation speed at 300r/min, and keep the water bath at 90°C. Take 0.5L of the purified green liquor and add it to the lime milk, and control the flow rate At 20mL/min, causticization reaction takes 2 hours;

(12) Solid-liquid separation: Separate the white liquor from the white mud. The main components of the white liquor are analyzed to be 79.1g NaOH, 13.1g Na₂S, and 9.9g Na ₂CO₃, the total alkali content is 102.1g (all calculated as Na₂O), which is the standard white liquid for pulping and cooking;

(13) White mud washing: Wash the white mud with water to wash out the residual alkali in the white mud;

(14) White mud stabilization treatment: Add water to the white mud to prepare a turbid liquid of about 30%, add 30 mL of 10% sodium carbonate with a mass fraction of 10%, and keep stirring at 60°C for 10 minutes;

(15) Oxidative whitening of white mud: add 0.5mL of hydrogen peroxide with a mass fraction of 27.5%;

(16) pH adjustment of white mud: Use phosphoric acid to adjust the pH of white mud to 9.5;

(17) Directional grinding of white mud calcium carbonate: Prepare a solution with a concentration of white mud calcium carbonate of 72%, add 0.3% dispersant (the amount of dispersant is 0.3% of the absolute dry amount of calcium carbonate), stir, and grind for 5 seconds. The grinders are connected in series to obtain ground high-purity calcium carbonate.

High purity calcium carbonate indicators: whiteness 94.2%, calcium carbonate content 97.8%, sedimentation volume: 2.8mL/g.

Preparation Report 2 of High Purity Calcium Carbonate,

A preparation process for high-purity calcium carbonate, which uses highly active calcium oxide and high-purity carbon dioxide as raw materials, and uses a carbonization tower as reaction equipment to react;

The preparation process includes the following steps:

(1) Mix and digest calcium oxide and water in a mass percentage of 1:3, and sift to obtain lime milk;

(2) Place the milk of lime in the slurry tank and let it stand in the slurry tank for 36 hours. After the standing milk of lime undergoes secondary hydrocyclone separation, it enters the slurry mixing tank to adjust the concentration of the milk of lime. When the temperature reaches 15 degrees Baume, add the crystal form control agent to obtain the initial slurry;

(3) The measured initial slurry enters the metering tank for measurement;

(4) Pump the initial slurry into carbonized carbon, and pass the high-purity carbon dioxide according to the concentration of the initial slurry to perform a carbonization reaction;

(5) In the early stage of carbonization of 5-15 minutes, the carbon dioxide input amount is 30-80 cubic meters/minute, and then the amount of bromomethylbenzeneborate pinacol ester is 10-60 cubic meters/minute, and the carbonization reaches 80-80 cubic meters/minute. 90%, turn to 5-40 cubic meters/minute, and stop carbonization when the pH value of the slurry reaches 6.7-7.0;

(6) Filter, wash and dry the final reaction slurry to obtain high-purity calcium carbonate.

Among them, the specific process of mixing and digesting calcium oxide and water in a mass percentage of 1:3 in step (1) is: placing quicklime in a slurry digester.At the feeding platform of the machine; heat the water to a temperature of 50°C; turn on the paddle digester; add warm water to the paddle digester to carry out the digestion reaction.

Wherein, the calcium oxide and water are mixed in a mass percentage of 1:4 for digestion reaction.

Wherein, the added amount of the crystal form control agent in step (2) is 0.4-0.8% of the dry basis mass of calcium hydroxide in the magnesium carbolic acid ash milk.

Wherein, the crystal form control agent is a mixture of barium chloride and malic acid with a mass ratio of 1:1.

Wherein, the carbonization reaction temperature in step (4) is 22°C.

Wherein, the drying in step (6) adopts microwave radiation drying, and the process is as follows: place the washed calcium carbonate in a microwave radiation reaction furnace, introduce nitrogen at a speed of 50 mL/min, and microwave the calcium carbonate. Radiation drying treatment; the conditions for the microwave radiation drying treatment are: microwave radiation frequency is 2450MHz, microwave radiation unit power is 0.10-1.00w/g, microwave radiation time is 30min, and microwave radiation temperature is 50°C.

References

[1][China invention, China invention authorization] CN201810870248.1 A method for refining high-purity calcium carbonate by causticizing green liquor

[2][China Invention] CN201810459389.4 A preparation process of high-purity calcium carbonate