KR20230108747A - Methods for capturing greenhouse gas and preparing precipitated calcium carbonate by using flyash generated from household waste incinerators - Google Patents

Abstract

The present invention is intended to provide environmentally friendly treatment of fly ash containing calcium chloride generated from a domestic waste incinerator. The present invention is about a method of selectively extracting useful components from fly ash and using the useful components as a medium for greenhouse gas capture while simultaneously producing light calcium carbonate and ammonium chloride, which are high value-added products, to improve economic efficiency and profitability.

Description

Methods for capturing greenhouse gas and preparing precipitated calcium carbonate by using flyash generated from household waste incinerators}

The present invention relates to a technology capable of environmentally friendly and stable treatment of flyash generated in a domestic waste incineration plant, and to a process of permanently capturing greenhouse gases using the same. More specifically, it is a technology for permanently capturing carbon dioxide by utilizing calcium chloride (CaCl ₂ xH ₂ O), the main component of fly ash, and a process for producing light calcium carbonate and ammonium chloride as a result.

Flyash generated from domestic waste incinerators is classified as designated waste as of 2021 and is being disposed of in a landfill. Fly ash is composed of calcium _chloride x hydrate (CaCl ₂ xH ₂ O), calcium hydroxide (Ca ₍ OH) ₂ ), and calcium carbonate (CaCO ₃ ). It is absorbed into the soil and causes environmental problems such as groundwater contamination. In addition, harmful dust generated during the landfill process has a negative impact on residents near the landfill site. Therefore, a technical solution to solve this problem is required.

According to Patent Publication No. 10-0749344, in order to fundamentally block harmful dust generated in the process of treating fly ash, a facility that turns fly ash into sludge has been developed. Although the problem caused by dust generated during the landfill process of fly ash has been solved, the problem of soil acidification and groundwater contamination due to the elution of calcium chloride contained in fly ash still remains. In addition, there is no change in the amount of landfill itself, so the task of securing a landfill has not been solved, and there is a problem that greenhouse gases are generated by the energy source used to generate steam used during the process.

According to Patent Publication No. 10-2313785, a melt processing method for modifying and reducing the generated fly ash was developed. However, during this process, basic components (FeO, MnO, CaO, MgO) and additives (Sb ₂ O ₅ ), which are additionally added in the process of heating water and adjusting basicity, are additionally added, while recycling as aggregate Due to the value of the final product, it is unlikely to benefit from an economic point of view.

On the other hand, calcium oxide (CaO) is used as a raw material for producing precipitated calcium carbonate. This calcium oxide is produced by calcining ingots mined from high-grade limestone mines or fine powder obtained by pulverizing them at a high temperature (850 ° C or higher). As fuel is used in this process, greenhouse gases are generated.

The net reaction for producing quicklime from limestone is as follows.

CaCO ₃ (s) -> CaO (s) + CO ₂ (g) ( 850℃)

According to Patent Publication No. 10-1656035, a technique for producing precipitated calcium carbonate using dolomite dust was developed. Deforestation due to limestone mining can be suppressed by using dolomite dust, which is treated as waste powder, instead of high-grade limestone used in the past.

1. Korean Intellectual Property Office Registration No. 10-0749344 2. Korean Intellectual Property Office Registration No. 10-2313785 3. Korean Intellectual Property Office Registration No. 10-1656035

The present invention was made to solve the above-mentioned conventional problems, and aims to solve problems such as landfill shortage and soil contamination by reducing the landfill amount of fly ash. In addition, it is intended to realize high added value in terms of environmental and economic aspects by replacing the commercial process that generates greenhouse gases when manufacturing precipitated calcium carbonate with a new process that captures greenhouse gases.

Specifically, useful components that can permanently capture greenhouse gases are selected among fly ash, and carbon dioxide (CO ₂ , carbon dioxide) is permanently captured and solidified to produce calcium carbonate (CaCO ₃ , precipitated calcium carbonate, PCC) and ammonium chloride ( A process for producing NH ₄ Cl, ammonium chloride) was developed.

On the other hand, the technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems that are not mentioned will become clear to those skilled in the art from the description below. You will be able to understand.

One embodiment of the present invention, a method for collecting greenhouse gases using fly ash generated in a municipal waste incinerator, selectively elutes CaCl ₂ xH ₂ O among the components constituting the fly ash, and then uses a filter paper to remove insolubles and CaCl ₂ xH ₂ O Step 1 of completely separating the solution; a carbonation reaction of producing PCC(s) and NH ₄ Cl(aq) by giving carbon dioxide and ammonia to the eluted solution and a second step of separating PCC(s) and NH ₄ Cl(aq); It may include; a third step of solidifying NH ₄ Cl (aq).

The first step includes process water, ground water, tap water, distilled water, deionized water, acetic acid, alcohol, etc. capable of dissolving CaCl ₂ xH ₂ O as eluents, and sufficiently elutes CaCl ₂ xH ₂ O even at room temperature However, heating and cooling processes may be included to increase the dissolution rate and efficiency. In the form of CaCl _{2 2} H ₂ O in fly ash, one or more of _{CaCl 2} 0H ₂ O, CaCl ₂ 1H ₂ O, and _{CaCl 2 2H 2} O can coexist. When exposed, 1 water of crystallization is lost and becomes CaCl ₂ .1H ₂ O. When CaCl ₂ 2H ₂ O is exposed to 100℃, 2 water of crystallization is lost and becomes CaCl ₂ 0H ₂ O.

For the insoluble matter that has not been dissolved through the first step, it is okay to use various filtration facilities such as a pressure-reducing filter, compression type filtration facility (filter press), and centrifugal dehydrator among conventional filtration facilities. The filtered insoluble matter is finally discharged in the form of a cake containing moisture, so that dust is not generated so that transportation and landfill processes can be smoothly performed.

The net reaction equation for elution of CaCl ₂ ·xH ₂ O is as follows.

CaCl ₂ xH ₂ O(s) + H ₂ O(l) -> CaCl ₂ xH ₂ O(aq)

The second step is _ammonia (NH ₃ , ammonia) is given, which is to give a counter ion to combine with chloride (Cl ^- ) in the elution solution so that Ca ²⁺ can react with CO ₂ dissolved in the aqueous solution. NH ₃ given in the second step may be added to the elution solution after the first step before CO ₂ is added, or together with CO ₂ , or CO ₂ may be added first. NH ₃ can be used regardless of the form and concentration, such as an aqueous solution, a liquefied form, a high-pressure gas, nitrogen, helium, argon, or a mixture of one or more of these. As the CO ₂ used in the second step, it is okay to use up to CO ₂ composed of a mixture and purified high-purity CO ₂ . Commonly, flue gas generated from boilers using solid fuel contains 10~25 vol% CO ₂ , 60~70 vol% N ₂ , 4~6 vol% H ₂ O, 3~5 vol% O ₂ , several vol.ppm NOx, It is composed of SOx and CO. Flue gas generated from boilers using non-solid liquid fuel contains 5-10 vol% CO ₂ , and gaseous fuel boiler processes in which one or more of C ₁ ~ C ₆ s are mixed are 1-7 vol% It contains CO ₂ . The concentration of CO ₂ generated from the waste incinerator is 5-10 vol%. On the other hand, the concentration of CO ₂ from petrochemical processes other than boilers/incinerators is higher. CO ₂ generated in the reforming process to produce blue hydrogen is 30~70 vol% CO ₂ , and the process of producing ethylene oxide and ethylene glycol from ethylene is finally discharged at around 90 vol% CO ₂ . CO ₂ generated from boilers, waste incinerators, and petrochemical processes using the above-described solid, liquid, and gaseous fuels, and flue and process gases containing them are all effective components in achieving the second step.

The net reaction formula and unit reaction formula of the two-step process are as follows.

Net reaction: CaCl ₂ xH ₂ O(aq) + 2NH ₄ ⁺ (aq) + CO ₃ ^2- (aq) -> CaCO ₃ (s) + 2NH ₄ Cl(aq)

Unit Reaction 1: CaCl ₂ xH ₂ O(aq) -> Ca ²⁺ (aq) + 2Cl ^- (aq)

Unit Reaction 2: NH ₃ (g) + H ₂ O(l) -> [ NH ₄ ⁺ (aq) + OH ^- (aq) ] or [ NH ₄ OH(aq) ]

Unit reaction 3: CO ₂ (g) + H ₂ O (l) -> [ 2H ⁺ (aq) + CO ₃ ^2- (aq) ] or [ H ₂ CO ₃ (aq) ]

The two-step process proceeds at room temperature and pressure, but the temperature of the reaction atmosphere is lowered and the pressure is increased to promote the reaction of unit reaction 3, or the temperature is increased to promote the combination of Ca ²⁺ and CO ₃ ^2- Even if it is increased, the net reaction proceeds without change.

There are no restrictions on the filtration equipment for separating PCC(s) and NH ₄ Cl(aq). Conventional filtration facilities, that is, pressure-reducing filters, compression filtration facilities (filter press), and filtration facilities of various methods such as centrifugal dehydrators may be used. Filtered PCC(s) can be provided to industrial groups that are applied in various forms such as liquid slurry and solid content.

The third step is a process of preparing NH ₄ Cl(s) in the form of NH ₄ Cl(aq) by removing the solvent. NH ₄ Cl in solution is difficult to transport and store, so the solvent is evaporated and powdered for efficient treatment. In order to evaporate the solvent, a heat source that enables this must be used, but if the boiler, incinerator, and flue gas generated in the petrochemical process described in step 2 are used, NH ₄ Cl (aq) can be powdered without additional energy cost. Boilers and incinerators are operated at 800℃ or higher, and petrochemical processes are operated at 200℃ or higher, so the generated flue gas also has corresponding heat. Using this, it is possible to powderize NH ₄ Cl (aq). Directly inject flue gas into the solution to raise the temperature of the solvent to vaporize it, or introduce a spray dryer facility for uniform powderization. Flue gas can be used as a heat source.

According to the present invention, environmental pollution caused by CaCl ₂ xH ₂ O (x = 0, 1. 2) eluted from landfill fly ash is blocked at the source, and the amount of landfill is reduced, thereby solving the social problem of landfill site selection. . It is an eco-friendly technology that can manufacture PCC while capturing greenhouse gases by replacing the PCC manufacturing technology that generates greenhouse gases using high-quality limestone as a raw material, which is a conventional technology. At the same time, it is a technology that can create high added value that is part of strengthening national competitiveness by manufacturing NH ₄ Cl, which is highly dependent on imports, replacing imports and localizing it. In particular, if the invented process is installed in an incinerator generating fly ash, it is possible to simultaneously treat fly ash and greenhouse gas generated from the incinerator, enabling the construction of an eco-friendly incinerator.

On the other hand, the effects obtainable in the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

Figure 1 shows an example of the results of X-ray diffraction analysis of fly ash samples and insolubles carried out according to Example 1.
2 shows an example of the result of X-ray diffraction analysis of PCC finally obtained according to Examples 1, 2, 3, 4, 5, and 6.
FIG. 3 shows an example of the result of X-ray diffraction analysis of the solid content remaining after evaporation of the NH ₄ Cl solution finally obtained according to Example 1. FIG.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclatures used herein are those well known and commonly used in the art.

Throughout the present specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

The present invention relates to environmentally friendly treatment of fly ash generated in a domestic waste incineration plant, and particularly to a process for developing high value-added products.

Specifically, the first step of eluting CaCl ₂ ·xH ₂ O (x=0, 1, 2) and separating from insoluble content in fly ash; Step 2 of giving CO ₂ and NH ₃ to the eluted solution to produce PCC(s) and NH ₄ Cl(aq) and separating PCC(s) and NH ₄ Cl(aq); 3 steps of solidifying NH ₄ Cl (aq);

Stage 1: CaCl in fly ash ₂ ·xH ₂ O(x=0, 1, 2)) elution and separation from insolubles

Elution of CaCl ₂ ·xH ₂ O (x=0, 1, 2) in the fly ash may proceed by mixing with a solvent.

First, distilled water is prepared, and the fly ash is mixed and stirred so that it is sufficiently mixed. The amount of distilled water used is not limited, but it should be sufficiently dissolved in consideration of the solubility of CaCl ₂ ·xH ₂ O (x = 0, 1, 2) in the solvent. If the amount of solvent is insufficient, CaCl ₂ xH ₂ O (x=0, 1, 2) in the fly ash will not be sufficiently dissolved, resulting in a decrease in process efficiency. Economic feasibility may be difficult. 50 to 10,000 parts by weight of the solvent may be applied to 100 parts by weight of the fly ash, preferably 100 to 5,000 parts by weight. The dissolution rate of CaCl ₂ xH ₂ O (x=0, 1, 2) in fly ash is determined by X-ray diffraction analysis of insoluble matter after the elution process to determine if there is a peak corresponding to CaCl ₂ xH ₂ O (x=0, 1, 2). The dissolution rate of CaCl ₂ ·xH ₂ O (x=0, 1, 2) can be determined by analysis.

After eluting CaCl ₂ ·xH ₂ O (x=0, 1, 2), there is no limit to the equipment for separation from insolubles. In the present invention, a vacuum filtration facility mainly used on a laboratory scale was used, and the same results were obtained when a compression type filtration facility (filter press) was used.

Step 2: CO in the eluted solution ₂ and NH ₃ By giving PCC(s) and NH ₄ Cl(aq) production and separation

PCC and NH ₄ Cl may be produced using the CaCl ₂ ·xH ₂ O (x=0, 1, 2) eluate prepared in the first step and CO ₂ . According to the net reaction equation described above, NH ₃ is used in addition to CO ₂ to produce PCC and NH ₄ Cl. This is to give a counter ion capable of bonding with Cl ⁻ present in the eluate, and the reaction proceeds in the following manner.

NH ₄ ⁺ (aq) + Cl ^- (aq) -> NH ₄ Cl(aq)

In the second stage reaction, the chemical reaction proceeds only when CaCl ₂ ·xH ₂ O (x=0, 1, 2) eluent, CO ₂ , and NH ₃ are present in the reactor, regardless of the order in which they are given, and the reactants Regardless of the injection rate, PCC and NH ₄ Cl can be produced in all cases.

In the present invention, while sufficiently stirring the eluate of CaCl ₂ xH ₂ O (x=0, 1, 2) in the reactor, NH ₃ is first given and then CO ₂ is applied, and CaCl ₂ xH ₂ O (x =0, 1, 2) While sufficiently stirring the eluate in the reactor, CO ₂ was first applied and then NH ₃ was applied separately.

The amount of NH ₃ used is not limited. Stoichiometrically, when Ca ²⁺ in CaCl ₂ xH ₂ O (x=0, 1, 2) is greater than the amount of NH ₃ used, NH ₃ acts as a limiting reactant and used NH ₃ will mostly participate in the carbonation reaction, and vice versa, NH ₃ will remain in the reaction solution even after the carbonation reaction due to excess reactants.

Furthermore, when CO ₂ was first added in the reactor and then NH ₃ was added, the pH of the carbonation solution was analyzed in real time to adjust the rate of addition, and the carbonation reaction proceeded in a range exceeding pH 8.5, preferably exceeding pH 8.9. can The higher the pH is, the faster the carbonation reaction rate is, and it is advantageous to reach a high conversion rate and PCC selectivity.

The reaction can be accelerated or delayed by changing the reactor pressure. When the pressure in the reactor is applied, the amount of CO ₂ dissolved in the solution increases and more CO ₂ is converted to H ₂ CO ₃ for reaction, so the area capable of reacting with Ca ²⁺ increases. Since the conversion rate increases as the pressure increases, the reactor pressure is not limited.

In the present invention, the pressure was maintained at 2 bar.g or less, and the same results were obtained even when the invention was performed at a pressure higher or lower.

Equipment for separating PCC(s) and NH ₄ Cl(aq) after completion of the carbonation reaction is not limited.

In the present invention, a vacuum filtration facility mainly used on a laboratory scale was used, and the same results were obtained when a compression type filtration facility (filter press) was used.

Step 3: NH ₄ Cl(aq) solidification

This is a process for evaporating and solidifying the solvent in NH ₄ Cl (aq) separated through the above two steps. In the industrial group, NH ₄ Cl is used in a solid state or dissolved in a solvent (mainly water) to suit the purpose, but it is preferable to solidify it for economic reasons such as storage and transportation. To remove the solvent, a method of vaporizing the solvent by giving a temperature is adopted. Energy is usually used to give temperature, but when using waste heat generated from boilers/incinerators/petrochemical processes, no separate energy costs are incurred. However, since NH ₄ Cl has the property of sublimating at 337.6 ° C @ 1 atm, it is necessary to control the temperature in the drying process so that the solidified NH ₄ Cl is not exposed to this temperature. In the present invention, each NH ₄ Cl powder was obtained by heating the solution on a hot plate or by spraying the solution on a spray dryer in which a heat source is injected at 300 ° C., and the results were the same.

[Example 1]

20 g of fly ash was mixed with 1,000 g of deionized water and dissolved at room temperature. Next, the eluate was separated using a vacuum filtration facility, and only the filtrate was collected. The separated filtrate was mixed with 130 g of 28wt% NH ₄ OH solution, and carbonation was performed by supplying a pressure of 2 bar.g while injecting 99 vol% CO ₂ gas into the solution. Finally, PCC was generated and precipitated. PCC and the solvent were separated using a vacuum filtration facility. The separated solvent was removed using a spray dryer, and the temperature of the hot air introduced into the spray facility was adjusted to 300 ° C.

[Example 2]

The manufacturing method is the same as in Example 1, and 20 g of deionized water was used instead of 1,000 g.

[Example 3]

The manufacturing method is the same as in Example 1, and 520 g of 28 wt% NH ₄ OH solution was added instead of 130 g.

[Example 4]

20 g of fly ash was mixed with 1,000 g of deionized water and dissolved at room temperature. Next, the eluate was separated using a vacuum filtration facility, and only the filtrate was collected. While injecting the separated 99% CO ₂ gas into the solution, a pressure of 2 bar.g is provided, and a carbonation reaction is performed by injecting 28wt% NH ₄ OH solution to maintain 10.5 while analyzing the pH of the solution in real time. Finally, PCC was generated and precipitated. PCC and the solvent were separated using a vacuum filtration facility. The separated solvent was removed using a spray dryer, and the temperature of the hot air introduced into the spray facility was adjusted to 300 ° C.

[Example 5]

The manufacturing method is the same as in Example 4, and the pH of the solution is maintained at 9.0 instead of 10.5.

[Example 6]

The manufacturing method is the same as in Example 1, and the CO ₂ used is 15vol% CO ₂ - 85vol% N ₂ instead of 99vol%

The results of Examples 1, 2, 3, 4, 5, and 6 are shown through FIGS. 1, 2, and 3.

1 shows a comparison of the X-ray diffraction analysis results for fly ash generated in a municipal waste incineration plant and insoluble matter obtained through Example 1. According to FIG. 1, it was confirmed that CaCl ₂ ·2H ₂ O analyzed in fly ash was not included in insoluble matter. Through this, it was confirmed that CaCl ₂ ·2H ₂ O was all dissolved by the solvent.

Figure 2 shows the results of X-ray diffraction analysis of PCC obtained through Examples 1, 2, 3, 4, 5, and 6. According to FIG. 2, it was confirmed that PCC was prepared through Examples 1, 2, 3, 4, 5, and 6.

FIG. 3 shows the results of X-ray diffraction analysis for NH ₄ Cl(s) obtained in Example 1. FIG. According to FIG. 3, as the peak corresponding to NH ₄ Cl was mainly analyzed, it was confirmed that NH ₄ Cl(s) was finally prepared.

Effect according to the present invention

As described above, it is possible to partially solve the social problem of landfill by treating the fly ash generated in the domestic waste incineration plant, and solve the global warming problem by permanently capturing the generated carbon dioxide. In addition, it is a technology that can protect the country by replacing the PCC process produced from high-grade limestone, which is a conventional technology, and it is a technology that can be part of strengthening national competitiveness by localizing NH ₄ Cl, which depends on imports.

On the other hand, the effects obtainable in the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

Claims (9)

A first step of selectively extracting and separating available calcium compounds from fly ash generated in a municipal waste incineration plant;
a carbonation reaction of preparing precipitated calcium carbonate and aqueous ammonium chloride solution by applying carbon dioxide and ammonia to the separated calcium compound, and a second step of separating the precipitated calcium carbonate from the aqueous ammonium chloride solution; and
A method for producing light calcium carbonate and ammonium chloride using fly ash generated in an incinerator comprising a; third step of removing the solvent from the aqueous ammonium chloride solution to prepare ammonium chloride powder. According to claim 1,
In the first step,
The solvent used to selectively extract the calcium compound is at least one of process water, ground water, tap water, distilled water, deionized water, acetic acid, and alcohol,
The calcium compound includes at least one of calcium chloride 0 hydrate, calcium chloride 1 hydrate, and calcium chloride 2 hydrate,
The first step is
Step 1-1 of eluting calcium chloride x hydrate (x = 0, 1, 2) using 50 to 10,000 parts by weight of a solvent based on 100 parts by weight of the fly ash; and
A method for producing light calcium carbonate and ammonium chloride using fly ash generated from an incineration plant, including steps 1 and 2 of separating the calcium chloride x hydrate aqueous solution and insoluble matter according to the calcium chloride x hydrate elution. According to claim 1,
In the second step,
In order to carry out the carbonation reaction using the separated calcium chloride x hydrate aqueous solution, a carbonation reaction is performed using 88 to 374 parts by weight of ammonia and carbon dioxide in 100 parts by weight of the fly ash raw material constituting the calcium chloride x hydrate aqueous solution to obtain the light calcium carbonate and the above Step 2-1 of preparing an aqueous ammonium chloride solution; and
A method for producing light calcium carbonate and ammonium chloride using fly ash generated in an incinerator comprising a step 2-2 of separating the light calcium carbonate and the aqueous ammonium chloride solution. According to claim 3,
The ammonia used in the carbonation reaction is generated in an incinerator used in the form of one or more of the form of aqueous solution, form of liquefaction, form of high-pressure gas, nitrogen, helium, argon, or a mixture mixed with one or more of them. Method for producing light calcium carbonate and ammonium chloride using fly ash. According to claim 3,
The carbon dioxide used in the carbonation reaction is
In an incineration plant performed by selectively applying at least one of carbon dioxide with a composition of 3 to 99% generated in a boiler using one or more of solid fuel, liquid fuel, and gas fuel, a reforming process for producing hydrogen, and a process for manufacturing ethylene oxide Method for producing light calcium carbonate and ammonium chloride using generated fly ash. According to claim 3,
In the 2-1 step,
Production of light calcium carbonate and ammonium chloride using fly ash generated from an incineration plant performed by mixing the ammonia with the calcium chloride x hydrate aqueous solution and then injecting the carbon dioxide into the mixed solution in mixing the calcium chloride x hydrate aqueous solution, ammonia and carbon dioxide method. According to claim 3,
In the 2-1 step,
In mixing the calcium chloride x hydrate aqueous solution, ammonia and carbon dioxide, the carbon dioxide is mixed with the aqueous solution and the ammonia is added to the mixed solution at the same time. According to claim 1,
The third step,
It is carried out using at least one of the methods of spray drying and boiling to remove the solvent among the components constituting the aqueous ammonium chloride solution,
The temperature at which ammonium chloride is exposed to prevent sublimation of ammonium chloride is a method for producing light calcium carbonate and ammonium chloride using fly ash generated in an incinerator performed by maintaining the temperature at 337.6 ° C or lower. Precipitated calcium carbonate and ammonium chloride prepared according to the method according to any one of claims 1 to 8.