CN1053642C

CN1053642C - Process for preparing calcium carbonate

Info

Publication number: CN1053642C
Application number: CN95117940A
Authority: CN
Inventors: 于惠生; 熊海宁
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-11-02
Filing date: 1995-11-02
Publication date: 2000-06-21
Anticipated expiration: 2015-11-02
Also published as: CN1150125A

Abstract

The present invention relates to a process for producing flaky superfine calcium carbonate. The process uses the carbonate of liquefied ammonia as double decomposition agents to carry out double decomposition reactions to prepare flaky superfine calcium carbonate, and the ammonia can be circularly used or made into corresponding ammonia compounds used as byproducts to be sold. The present invention is characterized in that the process does not use carbon dioxide and directly carbonizes lime cream, so the whole operation is simple and stable, and has high selectivity, and the process can be used for producing flaky products, and can produce various products with the granularity of 0.01 to 2 micrometers according to requirements.

Description

Preparation method of calcium carbonate

The invention relates to a preparation method of carbonate, in particular to amethod for preparing calcium carbonate by a double decomposition method.

Prior to the present invention, there were five general methods for chemically preparing calcium carbonate:

① carbonization method:

the limestone is used as a raw material to be prepared by the following chemical reaction processes:

② Solvay method:

the method is a byproduct method in the process of preparing the sodium carbonate, and the reaction process comprises the following steps:

③ Cogeneration method:

lime slag and hydrochloric acid are used as raw materials, and the chemical reaction formula is as follows:

④ causticizing method:

the byproduct method for preparing sodium hydroxide from sodium carbonate has a reaction formula as follows:

⑤ calcium chloride-soda process:

the product is mainly used for medicine, and the reaction formula is as follows:

among the various methods described above, the only industrial scale process is the carbonization process. Is the main method for producing calcium carbonate in various countries in the world at present.

The method adopts the basic operation of introducing carbon dioxide gas into lime milk slurry, and the greatest defects of the carbonization mode are that the gas cannot be instantly and uniformly mixed with the slurry, the reaction is carried out on the surface of bubbles, the reaction speed is slow, the generated calcium carbonate particles are not uniform, and the crystal form is difficult to control. In order to solve this problem, it is necessary to add various surfactants, crystal modifiers, which cause difficulties in handling and troubles in product selectivity in industry.

The invention aims to provide a novel method for manufacturing flaky superfine calcium carbonate, which has simple process, easy operation and stable product quality.

The present invention uses limestone as raw material, also can use quicklime as raw material, and uses limestone as raw material, and makes them undergo the process ofcalcination to produce calcium oxide and carbon dioxide, then the calcium oxide can be reacted with water to obtain calcium hydroxide slurry, and the carbonate of ammonia, for example ammonium hydrogen carbonate, ammonium carbonate or carbonized ammonia water, etc. can be added into the slurry instead of adding it in the form of carbon dioxide gas as in the previous carbonization method, so that the reaction can be quickly and stably carried out, and said reaction can be used for conveniently and accurately controlling crystal form and grain fineness, and can obtain the invented superfine flaky calcium carbonate.

The present invention features that the double decomposition reaction of ammonia carbonate and calcium hydroxide emulsion to produce calcium carbonate and ammonia or ammonia compound, and the ammonia may be reused or made into corresponding ammonia compound for sale.

The invention aims to prevent primary particles from aggregating or add a surfactant, such as benzene sulfonate, polyacrylate, a coupling agent and the like according to the requirements of different purposes.

The double decomposition reaction temperature is 30-100 ℃, the reaction time is 30 minutes to 10 hours, and the material ratio is CaO to CO in mol₃ ^-2∶NH₄ ⁺＝1∶0.5～2.0∶0.5～4.0。

The carbonate of ammonia used in the present invention is both a metathesis and a crystal modification agent. In order to obtain calcium carbonate with different crystal forms and different fineness in the carbonization method, different surfactants, crystal form modifiers, modifiers and the like must be added, and the addition of the substances not only increases the cost, but also reduces the product purity, and some substances can enter waste water to pollute the environment. The invention overcomes the problems, the reaction by-product can be recovered and recycled, and the product and the environment can not be polluted.

In order to overcome the problems of the prior carbonization process, the calcium carbonate manufacturing process provided by the invention is characterized in that a new reactant, namely, the carbonate of ammonia and calcium hydroxide slurry are subjected to double decomposition reaction, so that the selectivity, stability and uniformity of the product quality are easily met. The carbonate of ammonia is also an excellent crystal shape modifier for realizing the manufacture of the flaky calcium carbonate, is a control agent for causing an ultra-fine environment, is a surface modifier for forming flaky crystals, and is a carrier of carbon dioxide.

The process has the other characteristic that various process configurations can be formed according to the market requirements, and the matching between the main product and the by-product can be optimized.

The product prepared by the process has stable quality and strong selectivity, and can obtain products with required specifications, such as flaky calcium carbonate with different fineness, which is incomparable with a carbonization method and is especially important for paper making and ink industries, as long as the reaction conditions are slightly changed, and the superfine flaky calcium carbonate can improve the printing brightness, the flatness, the coverage rate, the whiteness, the printing surface strength, the ink absorption performance and the like of paper, so the method of the invention can promote the process of converting acid sizing into neutral sizing and alkaline sizing of coated paper.

The process of the method of the invention can be illustrated by means of two flow charts shown in FIG. 1.

FIG. 1 shows a process flow diagram of the process of the present invention.

FIG. 2 shows the result of electron microscopic photography of the product of example 1.

FIG. 3 shows the result of electron microscopic photography of the product of example 2.

FIG. 4 shows the result of electron microscopic photography of the product of example 3.

FIG. 5 shows the result of electron microscopic photography of the product of example 4.

Examples

1. Weighing 1,000 g of quicklime, adding the quicklime into 5,000 ml of hot water, digesting for 30 minutes, filtering by a 325-mesh fine sieve to remove coarse particles in the emulsion, putting the mixture into a 10,000 ml three-neck bottle, quickly adding 1,500 g of ammonium bicarbonate under the condition of starting stirring, heating to 80 ℃ for reaction for 2 hours, allowing ammonia gas to escape from one end of the three-neck bottle, cooling by a cooler, receiving into an ammonium hydroxide bottle, filtering the slurry after the reaction is finished to obtain 3,400 g of wet filter cake, and drying to obtain 1,780 g of calcium carbonate product.

The product is subjected to various index measurement, the crystal form is flaky, the particle size is 0.13 micron, and the result of electron microscope photography is shown in figure 2.

2. The same operation as in example 1 was carried out, except that ammonium bicarbonate was replaced by liquid ammonium carbonate in an amount of 1: 1 (molar ratio) with respect to CaO and the reaction temperature was 40 ℃.

The crystal form of the obtained calcium carbonate product was flaky and the particle size was 0.06 μm as a result of measurement of various indices, and the resultof electron microscopic photography is shown in fig. 3.

3. 1,000 g of quicklime is weighed and added into 4,000 ml of hot water, and after digestion is finished, coarse particles are removed by filtration to obtain lime milk slurry for later use. Then preparing a mixed solution of ammonium hydroxide and ammonium carbonate with a prepared concentration of NH₄ ⁺：20％，CO₃ ^-2: 30 percent. Mixing the above ash emulsion slurry and prepared ammonia-carbon solutionThen adding the calcium carbonate into a 10,000 ml three-mouth bottle, wherein the reaction temperature is initial 30 ℃, the reaction temperature is final 90 ℃, removing clean ammonia, standing for 5 hours, filtering and drying to obtain 1,800 g of calcium carbonate product, and the measurement result of each index of the product shows that the crystal form is sheet-shaped, the particle size is 0.1 micron, and the result of electron microscope photography is shown in figure 4.

4. The same procedure as in example 3 was used, except that lime milk was added to the ammonia carbonate liquor, and CO in the ammonia carbonate liquor₃ ^-2The amount ratio of CaO to CaO is equimolar.

The crystal form of the obtained calcium carbonate product is flaky and the particle size is 0.05 microns as a result of various index measurements, and the result of electron microscope photography is shown in figure 5.

5. The device is a continuous reaction device and mainly comprises a reactor, a deamination device and an aging device.

Slowly and continuously adding lime milk and ammonium carbonate solution into a reactor with a stirrer according to an equal molar ratio for reaction, and then, feeding into a deamination device for deamination; the reaction solution flows into an aging device to be placed for about 3 hours, and the product is obtainedby filtering and drying, and the crystal form of the product is quadrilateral flake and the primary particle size is 0.06 micro

Claims

1. A method for preparing superfine flaky calcium carbonate is characterized in that carbonate of ammonia reacts with calcium hydroxide to generate calcium carbonate and ammonia or an ammonia compound, wherein the reaction conditions are as follows: the material ratio is CaO to CO in mol₃ ^2-∶NH₄ ⁺The reaction time is 0.5-10 hours at 30-100 ℃ and 1.0: 0.5-2.0: 0.5-4.0.

2. The method of claim 1, wherein a surfactant is added, said surfactant being selected from the group consisting of a benzenesulfonate, a polyacrylate, and a coupling agent.

3. The method of claim 1, wherein the calcium hydroxide is prepared by calcining limestone, slaking limestone or slaking quicklime.

4. The production method according to claim 1, wherein the carbonate of ammonia is ammonium bicarbonate, ammonium carbonate, or carbonized aqueous ammonia.