KR101256807B1 - the limestone forming materials using waste lime powder and a method of therof - Google Patents

Abstract

In the present invention, limestone of 20 mm or less, which is generated and discarded during the crushing process of limestone or used as a low-cost cement material, is made into a powder, recycled into a high-grade lime resource through a molding and firing process, and is a method of improving value added. The present invention relates to a method for producing and calcining a molded body using low limestone powder and using it as a raw material of Precipitated Calcium Carbonate.

Description

Lime shaped compact using low utilization limestone powder and its manufacturing method and hard calcium carbonate using the same {the limestone forming materials using waste lime powder and a method of therof}

The present invention relates to a method for producing quick-lime molded body using a low utilization limestone powder and a method for producing hard calcium carbonate using the same, and more particularly, to form and calcinate low-utility powder limestone, dust, sludge, etc. using a divalent metal chloride. The present invention relates to a method for producing a quicklime molded body and a method for producing hard calcium carbonate using the molded body.

In general, the mined limestone has a large particle shape of about 700 ~ 1000㎜ size. Since it is difficult to put in the kiln, it is crushed by using a grinder such as jaw crusher, classified into a certain size, and sorted again and put into the kiln, depending on the method of the kiln, 60 to 80 mm, 40 to 60 mm, 20 It is classified into ˜40 mm and fed into quicklime kiln. When the stone is crushed for size classification, a large amount of powder is generated, and about 30 to 35% is generated. The quality of the small particles and powder generated at this time has the same level of ingredients as the raw materials, but is extremely limited as a raw material for ground reinforcement, soil improving agent and cement.

As a prior art utilizing a low utilization of the limestone powder, Patent No. 10-134862 discloses a method for utilizing waste limestone sludge, but the patent is to produce a sulfur oxide (SO ₂ ) absorber in four processes. Patent Document No. 10-158267 discloses an alternative snow removing agent using a low-grade limestone or waste cement material and a manufacturing method thereof, wherein the CaCO ₃ purity of limestone generated during the demolition of a concrete building is 85%. Lower limestones are used. On the other hand, Patent Publication No. 1998-44849 discloses a method for producing slag deoxidation using limestone sludge, although limestone sludge generated in the limestone firing process is used, the dried waste sludge is dried and aluminum flakes and aluminum The present invention relates to a method for producing a deoxidizer formed by mixing, drying and curing with cement.

Another publication No. 1998-51226 discloses a method for preparing a wet flue gas desulfurization absorber using steelworks Busan limestone sludge, but relates to a flue gas desulfurization absorber for reducing the emission concentration of sulfur dioxide. In addition, Korean Patent No. 10-213466 discloses a method of recycling the limestone sludge produced when washing limestone ore and the quicklime (CaO) contained in cyclone dust, which is a waste generated when calcining limestone. It is characterized by the control of the sludge's water content and the use of coagulants to provide pellets that can be recycled into the material. In addition, there are patents using low-grade limestone, such as Patent Nos. 10-270094 and 10-538774, but these patents all relate to a method of manufacturing cement and cement components using low-grade limestone and limestone by-products. On the other hand, Patent No. 10-586316 discloses a method for preparing powdered lime using limestone sludge and fine-grained limestone, but it seems to be characterized by a rotary drying furnace for executing the method rather than the method of manufacturing powdered lime.

The present invention solves the problems of the prior art as described above, and, unlike the prior art, high-quality through the molding and baking process by making the limestone of 20 mm or less, which is generated or broken at the time of crushing or used as a low-cost cement raw material, as a powder Its purpose is to provide a method for producing hard calcium carbonate (Precipitated Calcium Carbonate) that is recycled to lime resources and is a value-added improvement method using the molded product.

In order to accomplish the object of the present invention as described above,

95% to 99wt% of limestone powder and 1 ~ 5wt% divalent metal chloride produced from limestone, dust, sludge, or limestone powder produced in the mining process after mining. Provided is a quicklime molded body using a low utilization limestone, characterized in that it comprises.

In the above, limestone powder is preferably 200 mesh or less, divalent metal chloride may be used at least one of calcium chloride (CaCl ₂ ), magnesium chloride (MgCl ₂ · 6H ₂ O).

When the powder is 200 mesh or more, the impurities are excessive, resulting in problems in physical properties such as plastic strength of the product.

The present invention is also added to 95 ~ 99wt% limestone fine powder of 200 mesh or less, 1-5wt% divalent metal chloride aqueous solution of 40-50% concentration and mixed for 5-10 minutes and then mixed 100kgf / Provided is a quicklime molded product manufacturing method for molding at a pressure of 2 cm 2 or more.

If the mixing time is short, the mixing is not made well, if it is longer than 10 minutes, the production yield is lowered because there is no further meaning as described above.

In addition, the pressure is intended to have an appropriate strength, the higher the pressure is increased in strength.

The present invention also provides a method for producing hard calcium carbonate using the molded article prepared as described above.

According to the present invention, by increasing the mining yield and producing high value-added hard calcium carbonate by reusing the powder generated in the limestone crushing process, there is an effect of increasing the economic benefits through the recycling of resources. In particular, it can be applied to the treatment of all the dust and sludge generated in the quicklime manufacturing process using divalent metal chloride, which has the effect of adopting a method to increase the utilization of incidentally, and in the case of existing limestone powder Rotary Kiln) was processed through a limited firing method, but due to the present invention, there is a feature that can be fired without limitation of the firing method of the kiln, such as a shaft kiln, a chamber kiln.

1 is a SEM image of hard calcium carbonate prepared by the present invention.
Figure 2 is a manufacturing process of the present invention.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

The following examples are provided to assist those skilled in the art in practicing the present invention, but not to limit the present invention.

In general, limestone is calcined at 950-1,300 ° C, where carbon dioxide decarbonizes and exhibits a weaker strength.

This property is known to be due to the anisotropy of limestone. In other words, when the limestone is calcined, the expansion occurs. Since the thermal expansion coefficients are different according to the direction of the crystal axis of the limestone, internal stress necessarily occurs due to anisotropic expansion. In this case, when the anisotropic thermal expansion coefficient is relatively large and the porosity is low, the internal stress is large, so that it is easy to differentiate. Therefore, even if it is composed of molded particles, it should be able to absorb the thermal expansion to some extent by the voids and the like around the particles. At the same time, the physical and chemical properties such as activity, whiteness, etc., affecting the production of hard calcium carbonate, should be maintained at a level similar to that of raw stone products.

The present invention is made of limestone, dust, sludge or limestone crushing process generated in the limestone processing process as described above limestone of less than 20㎜ in powder form to form the briquettes and then calcined, the limestone calcined product It is a raw material processing method for maintaining strength and physical properties similar to those of In particular, the present invention has a limitation of the application of the product after the firing process of the rotary kiln type (powder-type firing method in the form of a powder form of the firing furnace, in order to improve this problem, Finely divided limestone of 20 mm or less, and adding _divalent metal chlorides (CaCl ₂ , MgCl _{2 ·} 6H ₂ O) to form briquettes and calcining them to produce products of a similar level to that of limestone fired products. It relates to a method for producing.

When the inorganic matter in powder form is produced in a predetermined form by using a compression method, it should be molded using a binder. Generally, binders are classified into inorganic binders and organic binders. When inorganic binders such as water glass (Na ₂ SiO ₃ ) and cement (3CaO · SiO ₂ ) are used, the binder is composed of SiO ₂ , and the quicklime of the present invention is used. In the manufacturing method, since it acts as an impurity, it is difficult to apply to the production of high purity hard calcium carbonate, and in the case of cement, when the addition amount is 5% or less, the molding strength is maintained to some extent, but briquettes are easily collapsed and powdered after firing. On the other hand, organic binders such as molasses, CMC (Carboxymethyl Cellulose) and starch can be used at room temperature or low temperature, but they can be burned at the calcined calcining temperature of 1000 ° C or higher, and thus cannot maintain their strength. Inadequate

In the present invention, the divalent metal chloride has a high solubility in water, a phase change occurs in a relatively low temperature region, changes to an anhydride form at about 300 ° C, and solidifies solidly. . In detail, the divalent metal chloride has high degradability, so that it is melted with soluble chloride to surround the limestone particles, and is fixed in the form of dense chloride to have high forming strength. In this case, since the molded product to which the divalent metal chloride is added is heated in a molten state and dried, even if a dehydration phase transition reaction occurs in which the hydrate is released, the molded product has a relatively uniform internal stress so that dry cracking does not occur. . In addition, it has the advantage that the strength can be maintained in a certain form even after firing and easy handling, and the reason why the selective use of CaCl ₂ and MgCl _{2 ·} 6H ₂ O is mainly used as the main component of this chloride This is because (Ca) and magnesium (Mg) components are the same as the main components of quicklime, which is more advantageous to use.

As described above, since a small amount of divalent metal chloride is mixed and prepared in a range where physical and chemical properties do not change significantly, briquettes in the form of briquettes having excellent physical properties can be produced.

[ Example  One]

In the present invention, by utilizing the feature that the uniform fine powder during molding is stronger, the limestone of 20 mm or less was processed into a powder of 200% or more 70% using a mill (Mill). The processed limestone fine powder was put in a 95 ~ 99wt% in a paddle mixer (Paddle Mixer), 1-5wt% of a 40-50% divalent metal chloride solution was added, and mixed evenly for 5-10 minutes. Thereafter, the mixed limestone was molded into briquettes having a size of 30 × 40 mm at a pressure of 100 kgf / cm 2 or more. The manufactured briquettes were dried using a net type drying furnace utilizing the gas discharged from the lime-fired furnace at a temperature of 150 ~ 200 ℃, and some of them were used for firing experiments with general electric furnaces. For example, a rotary kiln of 50 Ton / day scale was used.

Table 1 shows the forming and plastic strengths of limestone briquettes according to the amount of CaCl ₂ and MgCl _{2 ·} 6H ₂ O additions.

Strength by CaCl ₂ and MgCl ₂ · 6H ₂ O Addition division Dry strength
(Kgf / cm2) Plastic strength
(Kgf / cm2) Remarks 5% cement 5 powder Universal testing machine CaCl ₂ 1% 26 30 〃 CaCl ₂ 1.5% 32 43 〃 CaCl ₂ 2% 43 55 〃 CaCl ₂ 3% 64 72 〃 MgCl _{2 ·} 6H ₂ O 1% 23 27 〃 MgCl _{2 ·} 6H ₂ O 1.5% 29 39 〃 MgCl _{2 ·} 6H ₂ O 2% 38 46 〃 MgCl _{2 ·} 6H ₂ O 3% 56 68 〃 CaCl ₂ 1.5% + MgCl _{2 ·} 6H ₂ O 1.5% 58 67 〃

In general, moldings of inorganic materials are easy to transport and transfer when the compressive strength of at least 30 kgf / cm 2 or more is expressed. Particularly, in the present invention, when briquettes are collapsed or cracked during the formation of limestone, powdering occurs during the calcination process, and thus the combustion air is blocked to prevent combustion, which may cause problems such as incomplete calcination. Therefore, molding and plastic strength, which is directly related to the quality of quicklime, should be maintained at least 30 kgf / cm 2 or more.

In the present invention, as a result of measuring the molding strength and the plastic strength while changing the addition amount of CaCl ₂ and MgCl _{2 ·} 6H ₂ O was able to obtain a surprisingly high value.

According to the experimental results shown, the higher the added amount of CaCl ₂ and MgCl _{2 ·} 6H ₂ O, which is a divalent metal chloride, the higher the strength, CaCl ₂ has a higher strength value than MgCl _{2 ·} 6H ₂ O. Particularly, in the present invention, when the amount of CaCl ₂ added is 3% or more, it has surprisingly excellent molding strength and plastic strength, in which a high strength of 70 kgf / cm 2 or more is expressed, and the obtained quicklime briquettes are easily handled.

This is because, as described above, since the divalent metal chloride is dried and calcined in the molten state, the internal stress is uniformly distributed and is maintained in a constant form even after firing, so that the strength can be expressed.

However, when 5% or more of divalent metal chloride is added, it acts as a quicklime impurity, and especially MgCl _{2 ·} 6H ₂ O has a large aspect ratio in the form of hard calcium carbonate. Since it is difficult to manufacture a spindle type hard calcium carbonate that is deformed into a (Stick) form, it is desirable to regulate it within 5%.

In the present invention, the addition amount of 2 to 5% could obtain the most effective tendency.

[ Example  2]

On the other hand, the measure of quicklime reactivity is described as activity, and this activity is of paramount importance in the production of hard calcium carbonate. In particular, the activity of quicklime is closely related to the temperature of calcareous oil, which directly affects the shape and size of crystal grains formed after recarbonation. Therefore, the proper calcination and activity of quicklime are the most basic items in the manufacture of hard calcium carbonate.

Activity indicates the rate at which quicklime reacts with the material. The higher the value, the faster the reaction rate and the higher the reaction efficiency. The reactivity of quicklime is assessed by measuring its activity by neutralization titration as follows. In detail, a quicklime sample is classified into 1-5 mm, 50 g is used as a measurement sample, 2 L of water is put in a beaker, it heats at 40 degreeC, and 10 ml of phenolphthalein indicators are added dropwise. Using 3 propeller stirrers, while stirring at a speed of 500 rpm, 4N-HCl is placed in a 500 ml burette and zero is set. 50g of sample is added at once and time is measured. 4N-HCl is added dropwise. At this time, the value of dividing the consumption amount of 4N-HCl consumed for 10 minutes to the consumption time (10min) is the activity, and the value is shown in Table 2.

Comparison of Activity According to Metal Chloride Treatment and Whiteness of Manufacture of Hard Calcium Carbonate division Active castle
(Ml / min) Whiteness (L) in the manufacture of calcium carbonate Remarks 5% cement 277 97.54 Activity (neutrality titration method) CaCl ₂ 1% 334 97.61 CaCl ₂ 1.5% 329 97.67 CaCl ₂ 2% 317 97.58 CaCl ₂ 3% 312 97.59 MgCl _{2 ·} 6H ₂ O 1% 345 97.75 MgCl _{2 ·} 6H ₂ O 1.5% 341 97.63 MgCl _{2 ·} 6H ₂ O 2% 337 97.71 MgCl _{2 ·} 6H ₂ O 3% 332 97.69 CaCl ₂ 1.5% + MgCl _{2 ·} 6H ₂ O 1.5% 326 97.62

ㆍ Whiteness measurement: using D65 light source of minolta CR-400

As shown in the experimental results, it can be seen that quicklime treated with MgCl _{2 ·} 6H ₂ O showed higher activity value than quicklime treated with CaCl ₂ . In other words, quicklime treated with MgCl ₂ .6H ₂ O is more advantageous for hard calcium carbonate production than quicklime treated with cement and CaCl ₂ .

Hard calcium carbonate consists of the following six steps.

(I) CaO (s) + H ₂ O → Ca (OH) ₂ (s)

_{(Ⅱ) Ca (OH) 2} (s) → Ca 2+ (aq) + 2OH - (aq)

(III) CO ₂ (g) → CO ₂ (aq)

_{(Ⅳ) CO 2 (aq)} + OH - (aq) → HCO 3 2- (aq)

^{_{(Ⅴ) HCO 3 2- (aq}} ) + OH - (aq) → H 2 O + CO 3 2- (aq)

(VI) Ca ²⁺ (aq) + CO ₃ ^2- (aq) → CaCO ₃ (s)

The steps of (V) and (VI) are instantaneous, and the control step of the reaction is the dissolution step of (II) Ca (OH) ₂ and the absorption reaction step of (III) CO ₂ .

In the above reaction, quicklime added with MgCl _{2 ·} 6H ₂ O has high activity in the reactions of (II) and (III), so it is reacted in the slaker process of making quicklime into calcareous oil in the manufacturing process of hard calcium carbonate. The reaction between CaO and water is relatively fast, and Ca (OH) _{2 is} formed in a short time, and the formation of (II) and (III), which is the rate step, is promoted, so that hard calcium carbonate with a uniform particle size can be obtained. It has merit.

On the other hand, hard calcium carbonate hard calcium carbonate obtained by treating with divalent metal chloride in the present invention was prepared. In the method of preparing hard calcium carbonate, 300 g of quicklime was added to water at 30 ° C., stirred at 300 rpm, and hydrated for 1 hour, and immediately screened using a 60 mesh sieve. 750 g of Ca (OH) ₂ slurry was aliquoted, placed in a reactor, and 750 g of 50 ° C water was added to adjust the solid content to 9 to 10%, followed by stirring at 600 rpm. When the internal temperature reached 55 to 60 ° C., the CO ₂ was blown at 1 NL / min to be synthesized, and then the reaction was terminated when the pH was changed from pH 13 to pH 7. The hard calcium carbonate thus obtained was removed using an 325 mesh sieve to remove impurities, and then dried in a 200 ° C. dryer for 1 hour. The dried hard calcium carbonate powder was measured using a whiteness meter, and the whiteness meter used was measured using a D65 light source of Minolta CR-400. The measured whiteness values are shown in Table 2.

According to the experimental results, the change in the whiteness of the hard calcium carbonate according to the addition amount of the _divalent metal chloride CaCl ₂ and MgCl _{2 ·} 6H ₂ O is not significantly different, it can be seen that the effect on the whiteness is insignificant.

This reason is believed that the divalent metal chloride is partially volatilized during the calcining process of limestone, and the remaining chloride in the process of producing hard calcium carbonate is released into the aqueous solution and does not significantly affect the whiteness.

[ Example  3]

In the following examples, quicklime was calcined by briquetting with a high molding and plastic strength and a composition of divalent metal chloride.

A) Specifications of main facilities

1. Molding Equipment

1) Molding machine production capacity: 100Ton / day

2) Product size: 30 × 40㎜

3) Compression pressure: 100㎏f / ㎠

2. Kiln facility

1) Firing Furnace Type: Rotary Kiln

2) Production capacity: 50Ton / day

3) Internal standard: 2.4M × 6.2M

4) Fuel used: Refined oil

5) Firing time: 12 hours

Firing Conditions and Results division Firing temperature
(℃) Firing time
(hr) Plastic strength
(Kgf / cm2) Activity
(Ml / min) Whiteness
(L) CaCl ₂ 3% 1,200 12 75 329 97.59 MgCl ₂ 6H ₂ O 3% 1,200 12 69 337 97.61 CaCl ₂ 1.5% + MgCl ₂ 6H ₂ O 1.5% 1,200 12 66 331 97.59

In the actual manufacturing industry, the limestone treated as a result of the operation was able to obtain quick lime having uniform plasticity due to briquetting of a certain size, and showed high reproducibility of plastic strength, activity and whiteness. In addition, fusiform-type hard calcium carbonate to be obtained was stably obtained using quicklime treated with divalent metal chloride. As a result of preparing and comparing the quicklime formed by adding a divalent metal chloride, the uncalcined quicklime circuit, and the hard calcium carbonate, there were no changes in physical properties such as shape and whiteness. The scanning electron micrograph of the manufactured hard calcium carbonate is shown in FIG.

Claims (5)

95 to 99wt% of limestone powder and calcium chloride (CaCl ₂₎ , which is a powder of limestone of 20 mm or less generated in the process of particle size classification after limestone, dust, sludge or mine mining ), Quicklime formed using limestone with low utilization limestone, characterized in that it comprises 1 to 5wt% of at least one of magnesium chloride (MgCl ₂ · 6H ₂ O). 2. The quicklime molded body using low limestone according to claim 1, wherein the limestone powder is 200 mesh or less. delete To 95 to 99 wt% of limestone fine powder of 200 mesh or less, add 1 to 5 wt% of one or more aqueous solutions of calcium chloride (CaCl ₂ ) and magnesium chloride (MgCl ₂ ㆍ 6H ₂ O), which are 40 to 50% in concentration. After mixing 5-30 minutes to form a quick-lime molded body for molding the mixed limestone at a pressure of 100kgf / ㎠ or more. Hard calcium carbonate, characterized in that the molded body according to any one of claims 1 and 2.

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