KR20040087050A - The synthesis method of cubical precipitated calcium carbonate using the limestone washing process sludge - Google Patents

Abstract

PURPOSE: A method for preparing a cubic precipitated calcium carbonate and a cubic precipitated calcium carbonate prepared by the method are provided, to obtain a cubic precipitated calcium carbonate having a size of 0.1-0.9 micrometers with a low cost by using limestone sludge. CONSTITUTION: The method comprises the steps of calcining the limestone sludge whose quicklime (calcium oxide) content is 45-55 wt% at a constant temperature for a specific time; pulverizing the calcined lime; mixing the quicklime powder with water to hydrate it; filtering the obtained slaked lime (calcium hydroxide) suspension, drying the filtered one at a temperature of about 95 deg.C and washing the dried one; blowing out carbon dioxide to the calcium hydroxide suspension; and filtering and drying the calcium carbonate obtained by the carbonation to prepare a cubic precipitated calcium carbonate. Preferably the calcination is carried out at 1,000-1,200 deg.C for 1-3 hours; the calcined lime is pulverized into a size of 200 mesh or less; the suspension has a concentration of 4.0-8.0 wt%, the flow rate of carbon dioxide is 0.2-2.0 L/min and a stirring velocity is 500-1,000 rpm in the carbonation; and the carbonation is carried out at 10-20 deg.C.

Description

The synthesis method of cubical precipitated calcium carbonate using the limestone washing process sludge}

The present invention relates to calcium carbonate used as a filler or thickener in the field of paints, pigments, paper, and plastics. In particular, the calcium hydroxide suspension obtained by calcining and pulverizing limestone sludge produced in steel mills and reacting with water It relates to a cubic precipitated calcium carbonate made of limestone sludge as a raw material so as to obtain calcium carbonate powder by a carbonation reaction, and a method for producing the same.

In general, calcium carbonate has high whiteness and is physically and chemically stable, and thus is widely used as a filler or a thickener in paper, plastic, and rubber, and recently, its use range has increased with white pigments, pharmaceuticals, chemicals, and adsorbents. .

The calcium carbonate manufacturing method according to the prior art is a manufacturing method using a chemical precipitation reaction, there are an aqueous solution method, carbonation method, etc. The aqueous solution method is a mixture of an aqueous solution in which a salt containing a carbonic acid dissolved and an aqueous solution in which calcium salt is dissolved As a method for producing, the resulting particle size is about 4 to 5㎛.

In addition, as a method for the carbonate speech is produced by blowing a carbon dioxide gas to the calcium hydroxide suspension, in the case where the use of water as a solvent for calcium hydroxide suspension 10 is in accordance with the synthesis ^conditions or the fine powder having a particle diameter of 0.5 to 2 units ²㎛ A powder having a size of about μm is obtained.

However, the carbonation method using water as a calcium hydroxide suspension is not impossible to prepare a powder having a particle size of 10 ^- ¹ μm, but can be produced only when the concentration of the suspension is very low, and the distribution of the particle size is uneven, which makes it unsuitable for commercialization. There is a problem.

In addition, the aqueous solution method can control the particle size of the calsite powder by the change of the supersaturation of the solution and various other reaction conditions, but the production of powder having a particle size of 1㎛ or less has not been reported.

In addition, the carbonation method and the aqueous solution method has a problem that it is difficult to reduce the cost required for the production of calcium carbonate because a separate manufacturing process is required to supply the quicklime used in the production of calcium carbonate in addition to the problems described above. In particular, the aqueous solution method has a problem that it takes a relatively higher cost compared to the carbonation method.

The present invention has been made to solve the above problems of the prior art, by applying the limestone sludge generated in the steel mill to the carbonation method for the production of calcium carbonate, a separate process for the production of quicklime used for the production of calcium carbonate is It is an object of the present invention to provide a cubic precipitated calcium carbonate made of limestone sludge as a raw material and a method for producing the same, so that the cost and time required for the production of calcium carbonate can be reduced.

In addition, the present invention by recycling the limestone sludge generated in the steel mill for additional purposes, it is possible to reduce both the plant wastewater generated during the production of limestone, the exhaust gas of the limestone kiln, slurry generated in the wet dust collector, so that the environmentally friendly manufacturing method The purpose is to be able to produce calcium carbonate by.

1 is a process diagram showing a method for producing a cubic precipitated calcium carbonate based on limestone sludge according to the present invention;

Figure 2 is a cross-sectional view showing the main part of the cubic precipitated calcium carbonate production apparatus using the limestone sludge according to the present invention,

3 is a graph showing the results of thermal analysis of cubic precipitated calcium carbonate using limestone sludge as a raw material according to the present invention;

4 is a graph showing the results of X-ray rotation analysis of cubic precipitated calcium carbonate using limestone sludge as a raw material according to the present invention;

FIG. 5 is a photograph showing a scanning electron microscope result of a cubic precipitated calcium carbonate based on limestone sludge according to the present invention.

<Explanation of symbols on main parts of the drawings>

10: thermostat tank 20: carbon dioxide inlet pipe

30: stirrer 40: electrical conductivity electrode

50: thermometer

Cubic precipitated calcium carbonate manufacturing method using the limestone sludge according to the present invention for solving the above problems is a calcining step of heating the limestone sludge having a quick lime content of 45 to 55% by weight under a certain temperature condition;

A grinding step of crushing the quicklime supplied in the firing step into powder having a predetermined size or less;

A hydration step of mixing the quicklime powder supplied in the crushing step with water into a calcium carbonate production apparatus and mixing the water;

Preparing a step of washing the calcined lime suspension supplied in the hydration step, and drying at a temperature of about 95 ° C .;

A carbonation reaction step of blowing carbon dioxide into the slaked lime suspension supplied in the preparation step;

The calcium carbonate is produced by filtering and drying the calcined lime supplied in the carbonation reaction step to produce a cubic precipitated calcium carbonate.

In addition, the cubic precipitated calcium carbonate as a raw material of limestone sludge according to the present invention is produced by the calcium carbonate production method, characterized in that the particle size is 0.1 ~ 0.9 micrometers.

Hereinafter, an embodiment of a cubic precipitated calcium carbonate manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a process chart showing a cubic precipitated calcium carbonate manufacturing method using the limestone sludge according to the present invention.

Cubic precipitated calcium carbonate manufacturing method using the limestone sludge raw material according to the present invention is a calcining step of heating the limestone sludge generated in a steel mill for a certain time under a certain temperature condition, and the quicklime supplied in the calcining step is below a certain size The crushing step of crushing the powder, the hydrating step of mixing the quicklime powder supplied in the crushing step with water into the calcium carbonate production apparatus, and mixing the hydrated lime suspension supplied from the hydration step, the temperature of about 95 ℃ After the drying step in the washing step, the carbonation reaction step of blowing carbon dioxide into the slaked lime suspension supplied in the preparation step, and the calcined lime supplied in the carbonation step is filtered and dried to form cubic precipitated calcium carbonate Calcium carbonate production step is included.

Here, the calcination step is generated in a steel mill, and the limestone sludge having a quicklime content of 45 to 55% by weight into the calcination furnace for heating, the reaction scheme is the same as in Scheme 1 described below, limestone sludge is sufficiently burned Heating the temperature of the furnace for 1 to 3 hours while maintaining the temperature of 1000 ~ 1200 ℃ so that it can be easily crushed, limestone sludge in the grinding step when the temperature is 1000 ℃ or less, or when the time is fired to 1 hour Since the lime is not pulverized below a certain size, a problem arises in that the quicklime powder is not uniformly mixed with water in the hydration step.

Scheme 1

CaCO₃ → CaO + CO₂

The chemical composition of the limestone sludge generated in the steel mill is made as shown in Table 1, the limestone sludge is a high-grade fine powder calsite different from the general toxic sludge of the inorganic system according to the high quality quality of quicklime required for the steelmaking process to be.

Table 1

Chemical species CaO MgO SiO2 Al2O3 Fe2O3 Na2O K2O Ig-loss Content (weight percent) 52.1 0.8 2.3 1.2 0.3 0.07 0.22 43.1

In addition, the limestone sludge produced in steel mills has the properties of ordinary calcium carbonate treated with gemstones physically except for the problem of water content of about 20 to 30%. There are several times the added value.

Therefore, since the annual average sludge quality is 51% by weight of quicklime, and the particle size range is homogeneous at 15 to 22 micrometers, the potential is very high as an effective resource.

The grinding step is a step of breaking the quicklime supplied from the firing step into a grinder to form a powder having a predetermined size or less. When the grinding step is pulverized to 200 mesh or less, it may be easily mixed with water in the next step of hydration.

The hydration step is a step of adding the quicklime powder obtained in the crushing step to the calcium carbonate production apparatus, supplying and mixing water, the reaction scheme is the same as in Scheme 2 described below, the calcium carbonate production apparatus shown in FIG. Is installed on the inner wall of the cylindrical case forming the appearance, made of a certain thickness, made of a porous material and the thermostat tank 10 for generating the effect of the insulation of the buffer and sound insulation, and inserted into the thermostat tank 10 A carbon dioxide inlet tube 20, an agitator 30 inserted into the thermostat tank 10, rotated by a driving means to mix quicklime powder and water, and a liquid inserted into the thermostat tank 10 and fresh water It includes an electrode 40 for sensing the electrical conductivity and the pH (PH) of the, and the thermometer 50 is inserted into the thermostat tank 10 to sense the temperature.

As a result, the quicklime powder and water are added to the thermostatic tank 10, and the stirrer 30 is driven, whereby the hydration step is performed. The stirrer 30 is maintained at room temperature for about 30 minutes while the stirrer 30 is driven. To prepare a hydrated lime suspension in which the quicklime powder is completely mixed with water.

Scheme 2

CaO + H ₂ O → Ca (OH) 2

In addition, the hydration step to control the powder size and characteristics of the calcium carbonate by adjusting the concentration of hydrated lime, in which the suspension concentration of hydrated lime is adjusted to 4.0 to 8.0% by weight, preferably 5.0% by weight The carbonation reaction step is carried out at a reaction temperature of 10 ~ 20 ℃ by adjusting to.

The carbonation reaction step is a step of reacting the calcium hydroxide suspension obtained in the hydration step with carbon dioxide, the reaction scheme is the same as in Scheme 3 described below, the particle size by maintaining the flow rate of carbon dioxide flowing into the reactor 0.2 to 2.0 liters per minute Allow cubic precipitated calcium carbonate to be produced with 0.1 to 0.9 micrometers.

Scheme 3

Ca (OH) ₂ + CO₂ → CaCO₃

Figure 3 is a graph showing the thermal analysis results of the cubic precipitated calcium carbonate as a raw material limestone sludge according to the present invention, Figure 4 is an X-ray rotation analysis of the cubic precipitated calcium carbonate as a raw material limestone sludge according to the present invention 5 is a photograph showing a scanning electron microscope result of a cubic precipitated calcium carbonate based on limestone sludge according to the present invention.

Cubic precipitated calcium carbonate manufacturing method using the limestone sludge according to the present invention is made by the process as described above, and thermal analysis and X-ray to confirm the formation of cubic precipitated calcium carbonate after the calcium carbonate production step As a result of performing diffraction analysis and scanning electron microscope analysis, it can be seen from the thermal analysis results shown in FIG. 3 that calcitic precipitated calcium carbonate is produced without the formation of amorphous calcium carbonate indicating the presence of amorphous calcium carbonate.

In addition, as a result of the X-ray diffraction analysis of Figure 4 it can be confirmed that the calcium carbonate composed of the calsite phase, the scanning electron microscope analysis of Figure 5, the cubic calcium carbonate was not synthesized when the concentration of the slaked lime in the sludge is 2.5% by weight. In a suspension concentration of 5.0% by weight, cubic precipitated calcium carbonate was synthesized.

Cubic precipitated calcium carbonate based on the limestone sludge according to the present invention configured as described above and a method for producing the same are carbonated by blowing carbon dioxide after firing and pulverizing limestone sludge generated in a steel mill and mixing with water. By undergoing the reaction, cubic precipitated calcium carbonate is prepared in which particles of a certain size are formed, thereby reducing the cost and time required for preparing calcium carbonate.

In addition, the cubic precipitated calcium carbonate manufacturing method based on the limestone sludge according to the present invention can be used to produce environmentally friendly calcium carbonate by recycling the limestone sludge that was previously buried, and at the same time to prevent environmental pollution. There is an advantage to this.

In addition, the method for producing a cubic precipitated calcium carbonate using limestone sludge as a raw material according to the present invention controls the cubic precipitated calcium carbonate by controlling the amount of a substance contained therein, namely, water and carbon dioxide, during a hydration reaction and a carbonation reaction. It is possible to control the particle shape and size of the technology can be spread to the field that requires it, can be used as a filler or thickener in a variety of products there is an advantage that can achieve the quality of each product.

Claims (6)

In a method for producing calcium carbonate; A calcining step of heating the limestone sludge having a quicklime content of 45 to 55% by weight under a predetermined temperature condition for a specific time; A grinding step of crushing the quicklime supplied in the firing step into powder having a predetermined size or less; A hydration step of mixing the quicklime powder supplied in the crushing step with water into a calcium carbonate production apparatus and mixing the water; Preparing a step of washing the calcined lime suspension supplied in the hydration step, and drying at a temperature of about 95 ° C .; A carbonation reaction step of blowing carbon dioxide into the slaked lime suspension supplied in the preparation step; A method for producing cubic precipitated calcium carbonate using limestone sludge as a raw material, characterized in that it comprises a calcium carbonate generating step of filtering and drying the calcined lime supplied in the carbonation reaction step to produce cubic precipitated calcium carbonate. The method of claim 1; The firing step is cubic precipitated calcium carbonate based on limestone sludge, characterized in that the heating furnace is heated for 1 to 3 hours while maintaining the temperature of the furnace 1000 to 1200 ℃ so that the sludge is sufficiently combusted and easily comminuted. Manufacturing method. The method of claim 1; The pulverizing step is a cubic precipitated calcium carbonate production method using a limestone sludge as a raw material, characterized in that the quicklime is pulverized to a particle size of 200 mesh or less. The method of claim 1; The hydration step is to achieve a calcium hydroxide suspension concentration of 4.0 to 8.0% by weight, the feed flow rate of carbon dioxide is 0.2 to 2.0 liters per minute, the speed of the stirrer to maintain the cube settling using limestone sludge, characterized in that to maintain 500 ~ 1000rpm Method for preparing calcium carbonate. The method of claim 1; The carbonation reaction step is a cubic precipitated calcium carbonate production method using a limestone sludge as a raw material, characterized in that to maintain a reaction temperature of 10 ~ 20 ℃. The method of claim 1; A cubic precipitated calcium carbonate prepared by the method for producing calcium carbonate and having a limestone sludge as a raw material, the particle size of which is 0.1 to 0.9 micrometers.