KR102266542B1 - Method for manufacturing nano calcium carbonate using waste concrete and apparatus thereof - Google Patents

Abstract

The nano calcium carbonate manufacturing method and apparatus of the present invention disclosed herein utilize waste resources by using waste concrete, and can efficiently produce calcium carbonate and simultaneously remove carbon dioxide.

Description

Nano calcium carbonate manufacturing method and device using waste concrete {METHOD FOR MANUFACTURING NANO CALCIUM CARBONATE USING WASTE CONCRETE AND APPARATUS THEREOF}

Disclosed herein is a method for manufacturing nano calcium carbonate using waste concrete and an apparatus therefor.

Carbon dioxide is the most important factor influencing global warming. The concentration of carbon dioxide in the atmosphere has steadily increased, reaching 405.5 ppm in 2017, an increase of about 46% compared to pre-industrial times (before 1750). Therefore, many scholars and researchers are looking for ways to reduce carbon dioxide emissions, and one promising option is mineral carbonation, that is, the storage and utilization of mineral carbonates and silica through carbonates of natural silicate minerals such as calcium and magnesium silicates. will do

Waste concrete is a construction waste, and it has the advantage of being easily supplied and supplied in large quantities during urban redevelopment, highway, bridge construction, and dismantling or new construction of buildings such as apartments. However, since the recycling rate is not high because of mixed discharge at the construction site, an efficient system has not been established.

On the other hand, fine-grained calcium carbonate classified as nano calcium carbonate or light calcium carbonate is widely used in various fields such as building materials, paints, paper, medicine, cosmetics, and plastics. The market is estimated to be around 10 trillion won. In order to preoccupy the market expansion according to the demand for high-end products in the future, it is necessary to secure price competitiveness by securing high-quality nano calcium carbonate production and process yield.

In addition, microbubbles mean microbubbles with a bubble diameter of 50 μm or less. In water, the buoyancy is smaller than that of general bubbles, so they are reduced and converted into nano-sized bubbles, and then completely dissolved as they disappear, so the contact area of the bubbles and the amount of dissolution are increased. It can be generated in various ways, such as a turning method. Currently, it is widely used in various industries and environmental fields, and the application field is further expanding.

According to the conventional method for producing precipitated calcium carbonate using recycled aggregate and carbon dioxide gas (Korean Patent No. 10-0803706), in the process of improving the quality by removing the lime component of the recycled aggregate, the precipitated calcium carbonate is produced by supplying washing water and carbon dioxide gas. will produce However, according to this, construction waste and waste wood must be incinerated, and in this process, it does not help to reduce the concentration of carbon dioxide in the atmosphere, so a limit occurs in terms of carbon dioxide reduction.

Therefore, it is necessary to commercialize nano calcium carbonate manufacturing technology by converting carbon dioxide present in the atmosphere from construction waste generated in large quantities.

Korean Registered Patent No. 10-0803706

In one aspect, an object of the present invention is to economically and efficiently produce nano-calcium carbonate having a higher utility value than general calcium carbonate by recycling waste concrete, which is a construction waste.

In one aspect, in the present specification, the steps of recovering and pulverizing the waste concrete; adding the waste concrete to an acidic solution to produce an elution solution containing divalent or trivalent cations; removing impurities by adding a basic solution to the elution solution; and supplying carbon dioxide in the form of microbubbles to the elution solution from which the impurities are removed to produce nano-sized calcium carbonate.

In another aspect, in the present specification, as an apparatus for producing nano calcium carbonate, an extraction tank for supplying an acidic solution, eluting divalent or trivalent cations in waste concrete to produce an elution solution; a neutralization tank connected to the extraction tank and supplying a basic solution to neutralize the elution solution; a precipitation tank connected to the neutralization tank and recovering impurities precipitated in the neutralization process; one or more reaction tanks connected to the precipitation tank and reacting the elution solution from which impurities are removed and carbon dioxide; and a microbubble device connected to the one or more reaction tanks and supplying carbon dioxide in the form of microbubbles to the one or more reaction tanks.

According to the present specification, it is possible to extract divalent or trivalent cations from waste concrete containing various ions, and selectively precipitate impurities in the form of hydroxide compounds to produce high-purity nano calcium carbonate.

The nano calcium carbonate prepared by the manufacturing method disclosed herein is of high quality and can be used as building materials, paints, paper, medicine, cosmetics, plastics, and the like. In other words, it means that high concentrations of carbon dioxide and waste resources in the atmosphere can be converted into usable resources to produce added value.

In addition, the manufacturing method disclosed herein supplies carbon dioxide in the form of microbubbles to produce nano-sized high-quality calcium carbonate, thereby securing competitiveness and preoccupying the market.

In addition, by using the manufacturing apparatus of the present specification, by designing and building a continuous automated process program, it is possible to secure economic feasibility with features such as efficient production environment establishment, labor cost reduction, production yield improvement, and mass production of equal quality.

^{1 is a graph showing the extraction efficiency of Ca 2+} of a solution in which HCl is mixed with waste concrete according to an embodiment of the present specification, ICP-OES analysis results for each HCl concentration.
Figure 2 shows an apparatus for manufacturing nano calcium carbonate using waste concrete, according to an embodiment of the present specification.
3 is a photograph showing the results of SEM analysis of the nano calcium carbonate produced according to an embodiment of the present specification.
4 is an EDS analysis graph of nano calcium carbonate produced according to an embodiment of the present specification.
5 is a result showing the mineral content by XRD and XRF analysis of the waste concrete used according to an embodiment of the present specification.

Term Definition

In the present specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

exemplary of embodiments Explanation

Hereinafter, the present invention will be described in detail.

Nano calcium carbonate manufacturing method

In exemplary embodiments of the present specification, the steps of recovering and pulverizing the waste concrete; adding the waste concrete to an acidic solution to produce an elution solution containing divalent or trivalent cations; removing impurities by adding a basic solution to the elution solution; and supplying carbon dioxide in the form of microbubbles to the elution solution from which the impurities are removed to produce nano-sized calcium carbonate.

The nano calcium carbonate manufacturing method disclosed in the present specification is a technology for generating nano calcium carbonate by reacting calcium ions extracted from pulverized waste concrete with micro-sized carbon dioxide bubbles, and is a circulating environmental technology in which carbon dioxide is not emitted at all in the carbonation step. to be.

Specifically, in the case of using microbubbles, the particle shape of calcium carbonate is formed in a spherical shape rather than an aragonite shape, and the size of the particles can be reduced from several micrometers to several tens of nanometers by controlling the flow rate of the microbubbles, The reaction time can be about 20 to 45% faster in the carbonation process than when using normal bubbles.

In addition, in the present specification, the supply of the microbubbles may be sequentially and continuously reacted using one or more, preferably two or more reaction tanks to further improve the reaction rate. For example, as shown in FIG. 2 , when the solution in the reactor 1 is injecting carbon dioxide through the microbubble device, the reactor 2 recovers the generated nano calcium carbonate, and this process may be repeated every 30 minutes.

In one embodiment, when the waste concrete is analyzed by X-ray flourescence spectrometry (XRF), the Ca content may be 60% or more based on the mass of the total metal or metalloid element.

Wherein the waste concrete is Al ^{3 +} with a calcium ion (Ca ^2+), Mg ^{+ 2,} Fe ^{+ 3,} etc. There are many elements are contained, in the case of the addition of the acid solution with waste concrete also the element according to the pH value An elution solution can be produced by extraction.

During extraction, an acidic solution is used, and various conditions such as optimum concentration, reaction time, temperature, and RCF value can be considered.

Then, the number of divalent or trivalent adding a basic solution to the eluted solution containing the cation, by the precipitation of elements other than the Ca ^{2 +} in the form of hydroxide compounds can be removed of impurities.

In this case, it is preferable to perform a process of filtering the impurities, and the filtering process is not limited thereto as long as it is a method capable of separating impurities other than calcium ions.

Thereafter, carbon dioxide is supplied in the form of microbubbles to the elution solution from which impurities have been removed. Since the carbon dioxide microbubbles are smaller than normal bubbles, they stay in water for a long time and are completely dissolved until they are reduced and disappear. As such, carbon dioxide in the form of microbubbles acts as a microreactor and reacts with calcium hydroxide to produce nano-sized calcium carbonate.

In one embodiment, the content of calcium ions in the waste concrete may be 60% or more.

In one embodiment, the waste concrete may be pulverized to a size of 150 μm or less. After the pulverization process, a sieving step may be additionally performed to form a powder, and it may be filtered through a 100 mesh sieve to provide a powder with a uniform particle size and increased specific surface area, thereby efficiently generating a reaction between the elution solution and carbon dioxide, which will be described later. .

In one embodiment, the diameter of the microbubbles may be 50 μm or less.

In an embodiment, the waste concrete and the acidic solution may be mixed at a solid-liquid ratio (S/L) of 50 to 150 g/L. When the solid-liquid ratio is less than 50 g/L, there is a problem in that the process cost is increased by excessively including an acidic solution, and when the solid-liquid ratio is more than 100 g/L, the calcium carbonate yield may not increase proportionally.

In one embodiment, the concentration of the acidic solution may be 0.1 to 1 M, for example, 0.2 M or more, 0.5 M or more, or 0.7 M or more, and 1 M or less, 0.9 M or less, or 0.8 M or less. . When the concentration of the acidic solution is less than 0.1M, it is difficult to sufficiently extract calcium ions, and when it is more than 1M, the extraction efficiency of calcium ions decreases, and economical efficiency in terms of the cost of the acidic solution may be lowered. Therefore, it is efficient to extract calcium ions at a concentration of 0.1M or more and 1M or less.

In one embodiment, the acidic solution may be at least one selected from the group consisting of hydrochloric acid, ammonium salt solution, ammonium acetate solution, and ammonium chloride solution, and if it is an acidic solution containing chloride ions capable of eluting calcium ions, it is limited thereto. doesn't happen

Thereafter, carbon dioxide is supplied to the elution solution from which the impurities are removed to produce calcium carbonate. As a mineral carbonation reaction, the carbon dioxide reacts with calcium ions contained in the elution solution to produce calcium carbonate.

In one embodiment, the generating of the nano-sized calcium carbonate may be carried out at a pH of 9 to 12.5, and preferably may be carried out at a pH of 12.5 by additionally injecting a base solution into the reaction tank.

All ions other than calcium ions are precipitated at pH 11 or pH 11.5, and only calcium ions are not precipitated and it can be confirmed that they exist in ionic form, so that high purity calcium carbonate is prepared after all impurities are precipitated Calcium carbonate can be produced at the above pH in order to do so.

Specifically, by adding a basic solution to create a pH 12.5 condition, CO ₂ can be injected until the pH is reduced to 8 to prepare nano-sized calcium carbonate.

In one embodiment, in the step of generating the nano-sized calcium carbonate, the carbon dioxide in the form of microbubbles may be supplied using a microbubble pump or a pressure dissolution microbubble device.

There are two methods for supplying carbon dioxide in the form of microbubbles: a microbubble pump type and a method of installing a microbubble generator at the bottom of the reactor.

First, the microbubble pump is a revolving microbubble device, which generates a vortex in an aqueous solution to suck gas with a difference in atmospheric pressure, and when the vortex collapses, the rotational force of the bubbles released is changed to collision energy, and the bubbles are refined by impact. to be.

In this method, microbubbles are generated when the vortex of the liquid containing bubbles is collapsed, and Ca(OH) ₂ of pH 11.5 in the reactor is injected into the pump to create a vortex and mix the carbon dioxide gas and aqueous solution in the pump. way. The reaction chemical formula of calcium carbonate is as shown in Equation (2) below.

Ca(OH) ₂ +CO ₂ →CaCO ₃ +H ₂ O (2)

That is, it can be seen that 1 M carbon dioxide reacts to produce 1 M calcium carbonate.

As a second method, by installing a pressure dissolution type microbubble device at the bottom of the reactor, the amount of gas dissolved in proportion to the pressure is also increased according to Bernoulli's Law PV=P'V'. The pressure dissolution method uses this characteristic to dissolve carbon dioxide in an aqueous solution and then reduce pressure to create supersaturation conditions, and it can be designed to automatically shut off when a specific pH is reached, such as pH 8, through a pH meter. The time to reach a specific pH may vary depending on the condition of the flow rate, and may be set so that a continuous process can be performed. In addition, it can be seen that the pressure melting method is inversely proportional to the pressure and flow rate based on PV = nRT.

In one embodiment, the nano-sized calcium carbonate may have a size of 50 to 200 nm. Since calcium carbonate with a size of several tens to hundreds of nanometers can be used as high-grade calcium carbonate, the size of the particles is one of the important determining factors of quality.

In one embodiment, the produced nano-sized calcium carbonate may be recovered using a centrifuge. When using a centrifuge, it is effective to recover a large amount of calcium carbonate, and it is more efficient than using a filter or drying because it is faster and the recovery amount is also higher.

In exemplary embodiments of the present invention, there is provided a nano-sized calcium carbonate prepared according to the above-described method for producing nano calcium carbonate.

Nano calcium carbonate manufacturing device

Hereinafter, an apparatus for producing nano calcium carbonate of the present specification will be described with reference to FIG. 2 .

In exemplary embodiments of the present specification, as the nano calcium carbonate manufacturing apparatus 100, the extraction tank 101 for supplying an acidic solution, eluting divalent or trivalent cations in the waste concrete to produce an elution solution; a neutralization tank 102 connected to the extraction tank and supplying a basic solution to neutralize the elution solution; a precipitation tank 103 connected to the neutralization tank and recovering impurities precipitated in the neutralization process; one or more reaction tanks 104 connected to the precipitation tank and reacting the elution solution from which impurities are removed and carbon dioxide; and a microbubble device 105 connected to the one or more reaction tanks and supplying carbon dioxide in the form of microbubbles to the one or more reaction tanks.

In one embodiment, the nano calcium carbonate manufacturing apparatus, connected to the one or more reaction tanks, recovery unit 106 for recovering the wastewater remaining after the reaction; may further include. The wastewater can be designed as a continuous process that can minimize environmental pollution in connection with the recycling process through electrolysis.

In one embodiment, the nano calcium carbonate manufacturing apparatus may further include a filter 107 connecting the precipitation tank and one or more reaction tanks to each other, and the filter removes the sediment from the middle of the solution moving from the precipitation tank to the reaction tank It plays a role in removing impurities, that is, precipitates.

In one embodiment, the pH in the reaction tank may be 9 to 12.5, preferably pH 12.5.

In one embodiment, the microbubble device may be a microbubble pump or a pressure dissolution type microbubble device.

Hereinafter, the present invention will be described in more detail through the following examples. However, the following examples are provided only for the purpose of illustration to help the understanding of the present invention, and the scope and scope of the present invention are not limited thereto.

Example

Example One: from waste concrete Ca ^{2 +} extraction of

Waste concrete was pulverized to a size of 150 μm or less using a Boll-mill. Then, 0.5 M of HCl was added and reacted for 30 minutes, followed _{by extraction in the form of CaCl 2} , and the mechanism is as shown in Equation (1) below.

CaO+2HCl→CaCl ₂ +H ₂ O (1)

That is, through the equation (1) within the waste concrete is Ca ^{2 +} HCl in a 1: It can be seen that the reaction rate by two.

Figure 1 shows the extraction efficiency of a mixed solution of Ca ^{2 +} in the HCl waste concrete showing an ICP-OES analysis by HCl concentration in the graph. Specifically, the S/L ratio of waste concrete with a particle size of 150 μm or less and HCl is 10 g/100 mL, and the HCl concentration is 0.1 M, 0.25 M, 0.5 M, 0.75 M, 1 M, 1.5 M, 2 M days. When Ca ^{2 +} extraction amount was plotted through ICP-OES analysis.

Referring to FIG. 1 , as the concentration of HCl increases, the elution amount of calcium ions increases, but does not increase further after 1.5 M, so it is considered that it is not economically efficient to increase the concentration any more. This seems to be because most of the Ca ions already present in the waste concrete have been eluted, so no further elution proceeds.

In addition, Figure 5 is a result showing the mineral content by XRD, XRF analysis of the waste concrete used in accordance with an embodiment of the present specification. In the case of calcium ions, it was confirmed that the content was about 60% or more (60.5%). Based on this, the injection amount of the hydrochloric acid solution can be titrated.

Example 2: Impurity removal through NaOH injection

In order to remove elements other than ^{Ca 2 +} , NaOH was injected and precipitated in the form of _{M(OH) x and removed.} At this time, the precipitation formation of ions by pH was analyzed to evaluate the conditions under which each element was precipitated.

As a result, Fe ^{+ 3} was showed the precipitate formed is completely at pH 3 or more, in the case of pH 5.8 ^{+ 3} Al, Mg ^{+ 2} was confirmed to be completely precipitated from the pH 11. In the case of Ca ^{2 +} is present in the soluble ionic form at pH 11, it was confirmed that present in ionic form in the pH 11.5. Therefore, in this example, the supernatant was separated through a filter after injection until pH 11 was reached.

At this time, it is necessary to quantitatively calculate and inject the amount of NaOH required to reach a constant pH condition for a continuous process, and thus, the pH change according to the NaOH injection amount in the HCl extract for quantification was observed.

As a result, when NaOH of 1/3 of the HCl content was injected, pH 11 was reached, and precipitation occurred in the order of ^{Fe 3+} >Al ³⁺ >Mg ²⁺ >Ca ^2+. Thus, Ca ^{+ 2} before the ions are precipitated ^{Al 3 +, Fe 3+, Mg} 2 + ion is confirmed to be removed first. After the filter, 2/3 was injected and reacted with carbon dioxide at pH 11.5 to prepare calcium carbonate.

Example 3: Micro bubble form of carbon dioxide injection

Calcium carbonate was prepared by injecting 99% carbon dioxide into a calcium hydroxide reactor in the form of microbubbles at a fixed flow rate (0.1 L/min to 3 L/min flow rate, here 1 L/min), and reacting until the pH decreased to 8. Here, it was induced to generate calcium carbonate with a nano-sized particle size through the use of microbubble-shaped air bubbles.

In this Example 3, a pressure-dissolving microbubble device was used, and the time to reach pH 8 was set to 30 minutes, so that a continuous process could be performed. Specifically, referring to FIG. 2 , the injection of carbon dioxide is stopped in Reactor 1 having reached pH 8 and moves to a calcium carbonate storage tank through a pipe, and at this time, carbon dioxide is injected into Reactor 2 again. That is, the reaction tank in which carbonation proceeds and the reaction tank discharged are crossed and proceeded.

In Example 3, since the particles of calcium carbonate are fine at several tens to several hundreds of nm, and good mobility when mixed with a solution, it is considered that it is not necessary to consider the amount of bubbles and clogging by foreign substances.

Example 4: Recovery and analysis of the produced nano calcium carbonate

3 is a photograph showing the results of SEM analysis of the nano calcium carbonate produced according to an embodiment of the present specification. It was confirmed that the spherical calcium carbonate particles had a size of several tens of nanometers, and that the square particles formed a particle size of several hundred nanometers.

The produced nano calcium carbonate was separated from the supernatant and nano calcium carbonate using a centrifuge, and after removing the supernatant, it was recovered by drying at 40° C. for 8 hours.

4 is an EDS analysis graph of nano calcium carbonate produced according to an embodiment of the present specification. The components of the produced nano calcium carbonate were Na 1.04% and Cl 1.08%, and _{it was confirmed that the purity of CaCO 3} was about 98% or more (the content of Na and Cl was about 2%, and the purity of calcium carbonate was 98%).

5 is a result showing the mineral content by XRD and XRF analysis of the waste concrete used according to an embodiment of the present specification. In the case of calcium ions, it was confirmed that the content was about 60% or more. Based on this, the injection amount of the hydrochloric acid solution can be titrated.

100: nano calcium carbonate manufacturing device
101: extraction tank
102: neutralization tank
103: sedimentation tank
104: reactor
104a, 104b: Reactors 1 and 2
105: micro bubble device
106: recovery unit (Waste water)
107: Filter

Claims (14)

recovering and pulverizing waste concrete;
adding the waste concrete to an acidic solution to produce an elution solution containing divalent or trivalent cations;
removing impurities by adding a basic solution to the elution solution; and
Including; supplying carbon dioxide in the form of microbubbles to the elution solution from which the impurities have been removed to produce nano-sized calcium carbonate;
In the step of producing the nano-sized calcium carbonate, the reaction is continuously made in one or more reaction tanks,
A method for producing nano calcium carbonate in which the carbon dioxide in the form of microbubbles is supplied using a pressure dissolution method microbubble device. According to claim 1,
The content of calcium ions in the waste concrete is 60% or more, nano calcium carbonate manufacturing method. According to claim 1,
The method for producing nano calcium carbonate by grinding the waste concrete to a size of 150 μm or less. According to claim 1,
The diameter of the microbubbles is 50 ㎛ or less, nano calcium carbonate manufacturing method. According to claim 1,
The waste concrete and the acid solution will be mixed in a solid-liquid ratio (solid-liquid ratio, S/L) of 50 to 150 g / L, nano calcium carbonate manufacturing method. According to claim 1,
The concentration of the acidic solution is 0.1 to 1 M, nano calcium carbonate manufacturing method. According to claim 1,
The acidic solution is at least one selected from the group consisting of hydrochloric acid, ammonium salt solution, ammonium acetate solution, and ammonium chloride solution, nano calcium carbonate manufacturing method. According to claim 1,
The step of producing the nano-sized calcium carbonate is to be carried out at a pH of 9 to 12.5, nano calcium carbonate production method. delete According to claim 1,
The size of the nano-sized calcium carbonate is 50 to 200 nm, nano calcium carbonate manufacturing method. As a nano calcium carbonate manufacturing apparatus,
an extraction tank for producing an elution solution by supplying an acidic solution and eluting divalent or trivalent cations in the waste concrete;
a neutralization tank connected to the extraction tank and supplying a basic solution to neutralize the elution solution;
a precipitation tank connected to the neutralization tank and recovering impurities precipitated in the neutralization process;
one or more reaction tanks connected to the precipitation tank and reacting the elution solution from which impurities are removed and carbon dioxide; and
a microbubble device connected to the one or more reaction tanks and supplying carbon dioxide in the form of microbubbles to the one or more reaction tanks;
A continuous process is made in the one or more reaction tanks,
The microbubble device is a pressure dissolution type microbubble device, a nano calcium carbonate manufacturing device. 12. The method of claim 11,
The nano calcium carbonate manufacturing apparatus,
It is connected to the one or more reaction tanks, and a recovery unit for recovering the wastewater remaining after the reaction; will further include, the nano calcium carbonate manufacturing apparatus. 12. The method of claim 11,
The pH in the reaction tank is 9 to 12.5, nano calcium carbonate manufacturing apparatus. delete

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