WO2011081254A1

WO2011081254A1 - Method and apparatus for removing carbon dioxide from combustion exhaust gases using alkalized seawater

Info

Publication number: WO2011081254A1
Application number: PCT/KR2010/001812
Authority: WO
Inventors: 박원용; 박주용
Original assignee: (주) 오씨아드
Priority date: 2009-12-30
Filing date: 2010-03-24
Publication date: 2011-07-07
Also published as: KR100944539B1

Abstract

The present invention relates to a safe and economical method for removing carbon dioxide (CO₂) discharged in combustion gases, and particularly, to a method and apparatus for: condensing carbon dioxide through a reverse osmosis membrane; reacting the condensed CO₂ with ingredients in alkalized seawater through water-splitting electrodialysis (WSED) employing a bipolar membrane and ion exchange membrane and drying the reacted components via a spray-drying process; removing moisture for recovery in the form of crystallized carbonate and salt; and using the moisture removed in the drying process and seawater filled with residual carbon dioxide so as to be condensed and recovered as freshwater. The present invention also relates to an apparatus for separating, using a particle size separator or the like, carbon dioxide into crystallized states of calcium carbonate, sodium carbonate, magnesium carbonate, iron carbonate, salt, etc., and to a method for manufacturing the apparatus.

Description

Method and apparatus for removing carbon dioxide from combustion flue gas using alkaline seawater

The present invention relates to a method of recovering crystals by reacting carbon dioxide contained in a large amount of combustion exhaust gas with cations contained in a large amount of seawater and crystallizing it through a spray drying process. The present invention relates to a method for recovering carbon dioxide in a combustion exhaust gas, including a separation extraction process by separation, as carbonate crystals without being discharged into the air.

More specifically, it refers to the recovery of carbon dioxide (CO ₂ ) by crystallization such as calcium carbonate, magnesium carbonate, iron carbonate, sodium carbonate by combining with cations such as calcium ions, magnesium ions, iron ions and sodium ions contained in seawater. . In this case, in order to react carbon dioxide more efficiently and economically, it is necessary to go through a concentration process of seawater through RO membrane (reverse osmosis membrane) and an alkalizing process through a hydrolysis electrodialysis apparatus using bipolar membrane and ion exchange membrane. This process is necessary because carbon dioxide reacts with the cation components in seawater, so that the anions in the seawater, such as sulfate ions (SO ₄ ^2- ) and chlorine ions (Cl ⁻ ), must be blocked with cations. Bipolar membranes and electrodialysis (ion exchange membrane) H ⁺ and OH to decompose the water sea water in the through a combination of ^- making the combine them with sea water in the composition through the electrodialysis (ion exchange membrane), one is OH ^- ions and cationic Combined to make alkaline seawater containing a large amount of sodium hydroxide (NaOH), etc. The other side combines H ⁺ ion with sulfate anion and chlorine ion to make acidic seawater, and then increase the reactivity with carbon dioxide using alkaline seawater. It is to increase the amount drastically. In this case, the amount of carbon dioxide combined with the seawater and the reaction rate increase dramatically, and the target carbon dioxide removal amount is increased, and the input of the seawater and the spray drying amount can be reduced to increase energy and equipment efficiency in the whole process.

The reduction and removal of carbon dioxide has become a global concern beyond individuals, companies and countries, and the world is working to solve the problem.

At present, the development of technology to control carbon dioxide is focused on the development of technology to capture and store permanently, and part of it is gathered to study how to throw it into the ocean. In general, sea water contains a large amount of material, and new substances are continuously dissolved, and conversely, by repeating the process of releasing substances dissolved in sea water into the air or as crystals, the sea water continues to equilibrate its components. have.

Sea water accounts for two-thirds of the earth's surface area, and the amount is enormous, which is an absolute influence on the maintenance of the global ecosystem.

Carbon dioxide is an important resource that is absolutely necessary for life on earth. That is, it functions as a key raw material for photosynthesis, which is the basis for most living things. Plants use water (H ₂ O) and carbon dioxide (CO ₂ ) as basic raw materials to produce various organic materials using solar energy, and these organics are used as the starting point of the food chain to make the food chain of life on this planet function. do. In other words, most life on earth has been using carbon dioxide as an important means of maintaining life.

However, as industrialization progressed, the use of fossil fuels increased, and carbon dioxide released into the air in large quantities exceeded the appropriate amount and became infamous as the main culprit of global warming. have. Therefore, it is no exaggeration to say that the survival of mankind now depends on the reduction of carbon dioxide.

The present invention relates to a method for recovering carbon dioxide from burning fossil fuel by crystallization using alkaline seawater. Current methods for solving the carbon dioxide problem have been devised, such as a solution through complete combustion, a chemical solution using a catalyst, a method of collecting and storing in a permanent storage facility, dissolved in sea water and thrown into the sea. . However, currently devised methods suffer from large facility or disposal costs, secondary byproducts as sources of pollution, stability problems and environmental degradation from different angles. For example, the capture technology has a problem of permanently storing the captured carbon dioxide somewhere, and the method of dissolving carbon dioxide in seawater has the problem of marine pollution and marine ecosystem destruction, and solves it through complete combustion. Has created an irony that uses the enormous energy produced by generating carbon dioxide for complete combustion to reduce carbon dioxide, and the energy and equipment costs associated with it are also a serious problem.

As such, the currently developed method has significant problems due to cost and side effects, and requires considerable research and sealing in the future before securing stability and economic feasibility.

The present invention has been made in accordance with the above requirements, and by reacting carbon dioxide with a large amount and properties of the cation contained in the alkaline seawater recovered in crystals economically and effectively solve the problem that carbon dioxide contained in the exhaust gas is released into the air It is an object of the present invention to provide an alkaline seawater production method, a method of reacting carbon dioxide in a large amount with alkaline seawater, and a method for recovering it as crystals at an economic energy cost and an apparatus thereof.

In order to solve the above problems, the present invention is a seawater alkali through the hydrolysis electrodialysis apparatus using a bipolar membrane (Bipolar Membranes) and ion exchange membrane and the concentration process through the RO membrane (reverse osmosis membrane) in order to promote and massify the reaction with carbon dioxide The amount of cations contained in the seawater is increased by using the ignition process, and the seawater is alkalined, and then reacted and dried by spray drying using heat energy contained in the exhaust gas discharged by containing carbon dioxide to react and dry the water contained in the seawater. Removal and recovery in crystallized form, residual water and carbon dioxide are recovered to condensed fresh water using the low temperature of the seawater, and the resulting crystals are separated by type through a particle size separator.

According to the present invention, it is possible to safely extract and remove carbon dioxide at an economic cost, thereby preventing environmental destruction that is caused by the discharge of carbon dioxide in the exhaust gas as well as various carbonates, salts, and fresh water as by-products.

1 shows a water decomposition process by bipolar membrane.

2 shows a water decomposition process by an electrode.

3 shows a water decomposition process by bipolar membrane.

4 shows an alkalizing process of seawater by bipolar membrane.

5 is an overall process diagram showing a carbon dioxide removal process of the present invention.

6 is a photograph of a device for concentrating and desalting seawater using a RO membrane (reverse osmosis membrane) facility.

7 is a photograph of an apparatus for alkalizing seawater using a water decomposition electrodialysis apparatus using a bipolar membrane and an ion exchange membrane.

8 is an actual spray dryer picture.

9 is an actual vibration screen picture.

The present invention for achieving the above object

1) preparing seawater and demineralized water (fresh water) by passing seawater through a first RO membrane (reverse osmosis membrane) after pretreatment;

2) converting the seawater into alkaline water by passing the concentrated water through a hydrolysis electrodialysis apparatus using a bipolar membrane and an ion exchange membrane;

3) crystallizing carbonates and salts through a drying process by spraying the alkaline concentrated seawater with hot air containing carbon dioxide and reacting with ions contained in the carbon dioxide and the concentrated water;

4) collecting the crystals produced by the dry crystallization and separating through a particle size separator;

5) securing the condensed liquefied fresh water by cooling the clean gas containing moisture discharged after the dry crystallization process using the cold temperature of the sea water;

And 6) reacting residual carbon dioxide with water in the liquefaction process to recover the dissolved carbon dioxide in a dissolved state in water.

In the carbon dioxide crystallization process of the present invention, the pretreatment of step 1) may be performed through sand filtration, rapid filtration membrane, micro filter (MF), or ultra filter (UF) filtration, but is not limited thereto.

In the spraying process of the present invention, it is preferable to promote the reaction and increase the efficiency of drying by making the concentrated water in a fine mist state when spraying.

The particle size separator of step 4) of the present invention may be a vibration screen of 20 to 500 mesh.

Separation extraction of step 4) of the present invention may be performed according to the difference in solubility and specific gravity, not the particle size separator.

The present invention also provides a pretreatment apparatus for removing impurities from seawater; A concentrating device for separating and producing concentrated water and demineralized water by passing pretreated seawater through a reverse osmosis membrane; An apparatus for converting the concentrated water into alkaline water by interposing a hydrolysis electrodialysis apparatus using a bipolar membrane and an ion exchange membrane; A blower for spraying the alkaline concentrated water together with hot air containing carbon dioxide; A spray crystallization apparatus which crystallizes through drying while reacting ions contained in the sprayed carbon dioxide and the alkaline concentrated water; A crystal separation extracting device for collecting and separating the crystals produced by dry crystallization; And a condensation apparatus for cooling the air containing moisture discharged through the drying process to liquefy condensation by dehydration by cooling the cold temperature of seawater, and recovering the remaining carbon dioxide in the dissolved state by reacting residual carbon dioxide with water. The present invention relates to a carbon dioxide removal apparatus in combustion exhaust gas using alkaline seawater.

The pretreatment device of the present invention may be one or a combination of sand filtration, rapid filtration membrane, micro filter or ultra filter.

In addition, the crystal separation extracting apparatus of the present invention is preferably a particle size separator, an example of a vibration screen of 20 to 500 mesh.

According to the present invention, the carbon dioxide reduction and removal process of the present invention is made in the seawater desalination process and the process of crystallizing the various minerals contained in the seawater is possible with low cost and simple equipment, salt and various carbonates (calcium carbonate, Magnesium carbonate, iron carbonate, sodium carbonate, etc.) is also an efficient way to produce a variety of products, such as by-products.

Seawater is concentrated and desalted through RO membranes (reverse osmosis membranes) to produce fresh water, while the saltwater of seawater, etc., is concentrated to twice the concentration. The obtained fresh water is utilized for various purposes as fresh water, and the concentrated water is alkalinized by passing through a hydrolysis electrodialysis apparatus using bipolar membranes and ion exchange membranes. The reason why the seawater is alkaline is because the water is decomposed by the bipolar membrane to generate OH ^- ions and these ions are bonded to the cations in the seawater.

Concentrated and alkaline seawater is injected into the hot air of a flue gas containing carbon dioxide. In this process, ions in seawater are actively reacted with carbon dioxide, dried and extracted as crystals. Since the sprayed seawater is sprayed in a fine mist state, it starts to crystallize through the evaporation process when hot air is blown over 60 ° C. In general, the evaporation of seawater is effective at high temperature, but due to the wind and fine particles, it is effectively dried even in the hot air of about 60 ° C lower than that in the spray drying process. Of course, if the temperature is higher than that can be crystallized faster.

When spraying seawater, it is important to split the seawater finely and spray, but in the present invention, if it can be sprayed in the state of fine particles such as rotary disk, pressure nozzle type does not matter the type. However, in the case of a large capacity, the rotary disk type is efficient.

The sprayed seawater is not dried at a high temperature and has a large amount of spray, and is dried while floating in the air in a fog state for a certain time. At this time, the carbon dioxide reacts with the components in the mist of seawater and crystallizes into carbonate and is accumulated on the floor. In other words, carbon dioxide is combined with cations such as calcium, magnesium, iron, and sodium contained in concentrated seawater and crystallized into calcium carbonate, magnesium carbonate, iron carbonate, sodium carbonate, etc. Will fall.

The present invention is safe because carbon dioxide is recovered as carbonate crystals in the final process, and does not require extra energy because it uses energy contained in the exhaust gas of fossil fuel. In addition, since the reactivity is increased through the concentration process and alkalinization of seawater, the reaction is fast and the amount of carbon dioxide that is crystallized by bonding with cations in the seawater is greatly increased. And since carbonates and salts are produced as final products, these carbonates and salts can be used for various purposes.

Through spray drying, most of the minerals in seawater crystallize into salts and carbonates and fall to the bottom, and the water is discharged with water as air. The discharged air contains a significant amount of water and some carbon dioxide that has not been crystallized, which is then liquefied through cold water and temperature exchange to recover fresh water. At this time, most of the remaining carbon dioxide is dissolved in water. Through this process, the air discharged into the air becomes a clean state in which most substances such as moisture and carbon dioxide are removed.

Hereinafter, the present invention will be described in more detail.

The flow of the whole process of the present invention is pre-treatment (filtered by sand filtration, rapid filtration membrane, micro filter (MF), ultra filter (UF), etc.) and then passed through the RO membrane (reverse osmosis membrane) concentrated water and demineralized water (fresh water) ), And the prepared concentrated water is alkalized by passing through a hydrolysis electrodialysis apparatus using a bipolar membrane and an ion exchange membrane.

Bipolar membranes break down water⁺ And OH^- Divide by ions In addition, the ion exchange membrane installed together collects ions of concentrated seawater according to electrical characteristics. Na gathered like this⁺,Ca²⁺,K⁺, Mg²⁺Such asCation is OH^- By combining with ions, sodium hydroxide, calcium hydroxide, potassium hydroxide, magnesium hydroxide and the like become alkaline. Most cations are OH^-In combination with alkali to form Cl^-EtcAnion is H⁺It is combined with ions and acidified.

The concentrated and alkaline seawater is sprayed in a fine fog state into the combustion exhaust gas hot air containing carbon dioxide. The temperature of the exhaust gas, which is hot air, is appropriate if it is 60 ° C. or higher, but if it is too high, sea water may crystallize even before completion of the reaction with carbon dioxide. Of course, some exothermic reactions occur in the course of the reaction, so the temperature may rise above that. If the temperature rises too high, it is necessary to adjust the temperature through cold seawater. As such, the seawater that has risen in temperature during liquefaction of seawater or evaporated seawater used for temperature control helps to increase the efficiency of the RO membrane (reverse osmosis membrane).

Most of the exhaust gas has a considerable amount of heat and exothermic reactions occur during the reaction, so it is hardly necessary to supply additional energy to increase the temperature of the exhaust gas.

During spray drying, the carbon dioxide contained in the off-gas reacts with various cations contained in seawater and crystallizes to fall to the bottom. Alkalineization process removes most of the chlorine and sulfate ions contained in the sea water and is alkaline because the reaction proceeds quickly and in large quantities. In this way, the salts and carbonates accumulated in the crystals may be separated by a particle size separator, etc., and used according to the purpose, or may be used as it is.

The air discharged after the drying process contains both the water contained in the seawater and the water generated during the reaction process. It is liquefied by temperature exchange using cold seawater and recovered as fresh water. In this process, the remaining amount of carbon dioxide is dissolved in the liquefaction process and recovered as fresh water.

The energy used in the present invention is the degree necessary to apply pressure for passing seawater through various membranes and the energy used in the electrodialysis apparatus. Water dissociation electrodialysis using bipolar membranes consumes very little energy because water dissociation utilizes the properties of the membrane rather than the power of electricity. The heat required in the drying process uses its own heat of the exhaust gas containing carbon dioxide. Most of the exhaust gases have a high temperature, and this drying process only needs to secure a temperature of 60 ° C or higher, so there is no need to add a separate heating system.

The present invention makes it possible to secure various by-products with high economical efficiency such as production of fresh water, production of salt, and production of carbonate, rather than merely to remove or reduce carbon dioxide.

In order to improve the quality and expand the use of carbonates and salts produced through this device, pretreatment of exhaust gases including carbon dioxide is required. In general, the combustion gas discharged on a large scale currently goes through a pollution prevention device, a centrifugal separator, a scrubber, a desulfurization facility, and a denitrification facility. In order to improve the quality and utilization of the by-products, it is necessary to secure the cleanliness of the exhaust gases by utilizing these facilities in the pretreatment stage before the spray drying process of the exhaust gases.

Table 1

Seawater

division	Seawater conditions			Content of seawater-containing substances
division	Volume ml	Density	Weight g	Iron oxideFe ₂ O ₃	Calcium Carbonate CaCO ₃	Calcium SulfateCaSO ₄	Sodium chlorideNaCl ₂	Magnesium Sulfate MgSO ₄	Magnesium Chloride MgCl ₂	Sodium bromide NaBr	Potassium Chloride KCl	Total g
content	1000	1.0245	1025	0.0012	0.1143	1.3196	25.8120	2.0826	3.4462	0.1028	0.7121	33.5908

* Source: Seawater Content Analysis Experiment (Marine Chemistry, Donghae University Press)

Of course, if you are not only removing carbon dioxide, but also want to crystallize and remove nitrogen oxides, sulfur dioxide, etc. contained in the exhaust gas, the waste gas is put into the exhaust gas without additional pretreatment to remove it and reacted with alkaline seawater, such as carbon dioxide removal, to recover as crystals. It is possible to do

In this case, the recovered crystals are mixed with carbonate (sodium carbonate, calcium carbonate, potassium carbonate, etc.) crystals, sulfate (sodium sulfate, calcium sulfate, potassium sulfate, etc.) crystals, nitrate (calcium nitrate, potassium nitrate, iron nitrate, sodium nitrate, etc.) crystals. It may be difficult to separate and use because it exists. However, it is possible to avoid the hassle of having to install a separate facility in order to remove each material, and there is an advantage of saving a lot of facility costs because there is no need for a separate facility. Furthermore, operating costs can also be reduced. However, even when using this method, it is good to ensure the cleanliness of salts produced by removing soot and dusts using a dust collecting facility.

As can be seen in Table 1, seawater contains a large amount of material and is dissolved in an ionic state. Of course, a number of substances that are not shown in Table 1 are also melted together, and the kinds of the substances are known to be more than 80 kinds. It is a natural phenomenon to keep an eye on the development of resources dissolved in seawater, as materials buried on land are gradually bottoming out due to long mining activities, and mining costs are increasing. Researchers around the world are currently working on developing extraction methods for gold, lithium, and tritium dissolved in seawater, and the results are becoming more visible.

The present invention also proposes a method for recovering various substances dissolved in seawater at an economic cost. In general, materials dissolved in seawater by evaporation of seawater require a lot of energy and special equipment to crystallize.

However, the present invention produces a variety of economical materials while minimizing this energy. The first material produced is fresh water. That is, clean fresh water is produced in the process of passing RO membrane (reverse osmosis membrane) for economical evaporation. The produced fresh water can be supplied as tap water, deuterium water, or water required for various facilities, and can be used as a raw material for drinking water. Carbonates and salts which are crystallized and recovered during spray drying can be used for various purposes. It can be separated by a particle separator (vibration screen) or the like, or used as a whole carbonate and salt without separation.

Currently, 2.5 million tons of salt is imported into Korea annually. Of the total 3 million tons, 2.5 million tons are imported every year except 500,000 tons of domestic production, and most of them are used for chemical industry and snow removal agent. Therefore, in these cases, even if the product contains a small amount of other substances, there is no problem in use. When the facility is installed and operated according to the present invention, most of the annually imported salt can be covered by the production of cheap carbon dioxide removal process, and it is considered to be possible to export.

In addition, if the carbonate (calcium carbonate, magnesium carbonate, sodium carbonate, iron carbonate, etc.) of a specific component of high purity is separated through a particle size separator, etc., it may be used for a much more expensive use.

TABLE 2

Type of particle separator (separation net size of vibration screen)

NO (Identification Number)	Mesh	Wire Dia (mm)	Screen Opening (㎛)
4	4	1.60	4,750
5	5	1.08	4,000
6	6	0.88	3,350
7	7	0.83	2,800
8	8	0.82	2,360
9	9	0.82	2,000
10	10	0.84	1,700
12	12	0.72	1,400
14	14	0.63	1,180
16	16	0.59	1,000
20	20	0.42	850
25	24	0.35	710
30	28	0.31	600
35	32	0.29	500
40	35	0.30	425
45	42	0.25	355
50	48	0.23	300
60	60	0.17	250
70	65	0.18	212
80	80	0.14	180
100	100	0.10	150
120	115	0.10	125
140	150	0.06	106
170	170	0.06	90
200	200	0.05	75
230	250	0.04	63
270	270	0.04	53
325	325	0.03	45
400	400	0.03	38
500	500	0.02	26
635	635	0.02	20

Separation net size of the particle size separator is present in a variety as shown in Table 2, the material produced in the sea water by the present invention is able to separate and extract most of the material if the size of 20 ~ 500Mesh.

In addition, when the membrane of the electrodialysis device (ion exchange membrane) is selectively used in the alkaline process, the component of the alkaline water can be adjusted. When using this method, it is possible to make the crystallized component into almost one component. That is, sodium carbonate, magnesium carbonate, calcium carbonate, potassium carbonate and the like can be selectively produced.

The heat source used in the spray drying process uses the heat source of the exhaust gas containing carbon dioxide as it is. Carbon dioxide emitted through the combustion process contains considerable heat energy because it contains heat generated during the combustion process. It is used as a heat source required for spray drying. The heat source used for spray drying is suitable if it is a hot wind having a temperature of 60 to 100 ° C., and no separate energy supply is required except for the heat energy included in the exhaust gas. Of course, the pretreatment process to remove various foreign matters contained in the exhaust gas may reduce the temperature slightly, but it is not a problem because the residual heat is enough.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are merely illustrative of the present invention, and the content of the present invention is not limited by the following Examples.

<실시예 1> 바이폴라막(Bipolar Membranes)을 이용한 물 분해Example 1 Water Degradation Using Bipolar Membranes

Water decomposition by bipolar membrane was carried out. Recently, water-splitting electrodialysis (WSED) has attracted attention as an efficient process for producing acids / bases. The bipolar membrane is a type of membrane combined with a cation exchange layer and an anion exchange layer and plays a key role in the hydrolysis electrodialysis process. Bipolar membranes have unique electrochemical properties that decompose water molecules into hydrogen and hydroxide ions under reverse bias conditions. Thus, chemical and biological processes can produce acids / bases without the generation of by-products.

The bipolar film production method can be divided into four types. The first method is to combine a commercially available cation / anion exchange membrane, and the second method is to prepare a bipolar membrane in the form of a single sheet. The third method is casting on the existing commercial film. Finally, it can be divided into manufacturing method by continuous coating method.

The first method was attempted early in the development of bipolar membrane, and it can be divided into loose overlapping method and hot pressing or introduction of adhesive polymer.However, bipolar membrane manufactured by this method has low physicochemical stability and resistance to water decomposition. It has a high disadvantage and is rarely used at present. Recently, second and third single-sheet bipolar membranes and bipolar membranes manufactured by casting have been mainly developed, and polymer catalysts (eg, Carboxylic acid, Secondary / tertiary amines) and Research into the introduction of inorganic catalysts (eg metal hydroxide / oxide) is underway.

As can be seen in Figure 1, the bipolar membrane can decompose water into H ⁺ and OH ^- by applying more than 0.83V, the theoretical decomposition voltage of water. The bipolar membrane is a membrane in which a cation and an anion exchange layer are combined to reverse bias, that is, the water molecules are hydrogen ions (H ⁺ ) while the cation exchange layer of the bipolar membrane faces the cathode and the anion exchange layer faces the anode. and hydroxide ions (OH ^-) is digested with. The water decomposition process using bipolar membrane is more effective than the existing electrolytic water dissociation method used to generate acid / base. Conventional electrolytic processes using water decomposition reactions at the electrodes require very large electrode areas, resulting in low current efficiency and low energy efficiency. On the other hand, the water decomposition process using bipolar membrane is easy to scale up and has much lower energy consumption than electrolytic method.

Example 2 Comparison of Energy Efficiency and Process Difference Between Bipolar Membrane and Electrolysis Process

The water decomposition process using a bipolar membrane and the water decomposition process by an electrode were compared.

In the case of producing sulfuric acid and sodium hydroxide through a water decomposition process made by the electrode is as shown in FIG.

Water splitting processes by the electrode is water-splitting consists in the cathode and the anode, wherein protons (H ⁺⁾ and hydroxyl ions (OH ^-), which occurs in conjunction with the positive and negative ions that has transmitted through the ion exchange membranes made of materials aiming To me. As shown in FIG. 2, oxygen and hydrogen are generated by water decomposition at the positive electrode, and hydrogen and hydroxide ions are generated at the negative electrode. Sodium sulfate is melted and the water ions (Na ⁺⁾ is (+) - hydroxyl ions (OH ^-) produced by the water-splitting in the pole by pole reversal in combination with the ion to produce sodium hydroxide (NaOH). The reaction also occurs in the (+) electrode. Hydrogen ions (H ⁺ ) produced by water decomposition at the (+) electrode combine with sulfate ions (SO ₄ ^2- ), which have migrated through an anion exchange membrane, to form sulfuric acid (H ₂ SO ₄ ). Make it up The energy value used at this time is ΔU = 2.056V, ΔG = 0.0551kwh / mol.

The process of producing the same material through the water decomposition process by the bipolar membrane is as shown in FIG.

The major difference is that the decomposition of water is caused by bipolar membranes, not electrodes. Therefore, the contamination problem of the electrode which occurs when water is decomposed by the electrode does not occur, and a large electrode area is not required. In particular, even when a plurality of membranes are stacked, the number of electrodes can be drastically reduced because the electrodes do not need to be installed, but the electrodes can be installed at both ends after installing several membranes.

In particular, the electrical efficiency is remarkably high because the decomposition of water is made by the bipolar membrane, not the power of electricity. As described in FIG. 3, the energy values of the water decomposition process by the electrode and the water decomposition process by the bipolar membrane are compared as follows.

TABLE 3

Comparison of energy between water decomposition by electrode and water decomposition electrodialysis apparatus by bipolar membrane

division	△ U-Electric Voltage Difference	ΔG-reversible free enthalpy required for water decomposition
Water decomposition by electrode	ΔU = 2.056 V	ΔG = 0.0551kwh / mol
Water decomposition by bipolar membrane	ΔU = 0.828 V	ΔG = 0.0221 kwh / mol

<실시예 3> 바이폴라막에 의한 해수의 알카리화 공정Example 3 Alkalization of Seawater by Bipolar Membrane

Alkalization of seawater was carried out using a hydrolysis electrodialysis apparatus using a bipolar membrane and an ion exchange membrane.

When the seawater is flowed into the hydrolysis electrodialysis apparatus using the bipolar membrane and the ion exchange membrane as shown in FIG. 4, the seawater is divided into alkaline water seawater and acidic seawater. When the seawater flows, the hydrogen ions and the hydroxyl ions generated by the decomposition of water by the bipolar membrane react with the cations and anions contained in the seawater and are separated into acidic seawater and alkaline seawater. In this case, if the ion exchange membrane and the bipolar membrane are installed in multiple stages, the process can be performed more efficiently. Fresh water is generally used on both sides of the bipolar membrane, but sea water may be used. When seawater is used, there may be some problems in the purity of the material produced, but it may be better to use seawater to increase the amount of reaction in the reaction process or to reduce the amount of fresh water used.

Example 4 Separation of Crystallized Carbonate and Salt by Type Using a Particle Size Separator

In order to selectively separate and extract the crystallized material, it was separated using a vibration screen according to the particle size. 9 is an actual vibration screen picture. Using a vibrating screen, carbonates, salts, etc. were separated according to the particle size of the crystal salt (Table 4). The average particle size of magnesium salt was 263 μm, the average particle size of sodium chloride salt was 175 μm, and the average particle size of calcium salt was 7.73 μm. Magnesium salts, sodium chloride salts and calcium salts were separated using multiple vibrating screens having pore sizes of 180 μm, 125 μm, and 38 μm using the average particle size difference of these mineral salts.

Table 4

Particle Size and Mesh Size of Minerals

division	Particle size (㎛)	Mesh size	Remarks
Magnesium salt	263.23	80	180 μm
Sodium chloride salt	175.08	115	125 μm
Calcium salt	7.73	500	26 μm

* In the case of calcium, it is possible to extract with a net of 26㎛ because the mass is larger than the individual particle size due to the tangling and bonding property.

Claims

1) preparing seawater and demineralized water by passing seawater through a first reverse osmosis membrane after pretreatment;

2) converting the concentrated water into alkaline concentrated water by passing it through a hydrolysis electrodialysis apparatus using a bipolar membrane and an ion exchange membrane;

3) spraying the alkaline concentrated water with the hot air containing carbon dioxide and reacting with the ions contained in the carbon dioxide and alkaline concentrated water to crystallize through drying;

4) collecting the crystals produced by the dry crystallization and separating through a particle size separator, or separated by solubility or specific gravity;

5) securing fresh water by cooling the air containing moisture discharged through the drying process using a cold temperature of sea water to liquefy condensation;

6) a method of removing carbon dioxide from combustion exhaust gas using alkaline seawater, characterized in that it comprises a step of recovering the remaining carbon dioxide in the dissolved state in the water by reacting the residual carbon dioxide in the liquefaction process.

The method of claim 1, wherein the pretreatment of step 1) is carried out using at least one selected from a sand filtration, a rapid filtration membrane, a micro filter, or an ultra filter. .

The method of claim 1, wherein the particle size separator of step 4) is a vibration screen of 20 to 500 mesh, and carbon dioxide is removed in combustion exhaust gas using alkaline seawater.

A pretreatment apparatus for removing impurities from seawater; A concentrating device for separating and producing concentrated water and demineralized water by passing pretreated seawater through a reverse osmosis membrane; An apparatus for alkalizing the concentrated water by interposing a hydrolysis electrodialysis apparatus using a bipolar membrane and an ion exchange membrane; A blower for spraying the alkaline concentrated water together with hot air containing carbon dioxide; A spray crystallization apparatus which crystallizes through drying while reacting ions contained in the sprayed carbon dioxide and the alkaline concentrated water; A crystal separation extracting device for collecting and separating the crystals produced by dry crystallization; And a condensation apparatus for cooling the air containing moisture discharged through the drying process to liquefy condensation by dehydration by cooling the cold temperature of seawater, and recovering the remaining carbon dioxide in the dissolved state by reacting residual carbon dioxide with water. Carbon dioxide removal apparatus in combustion exhaust gas using alkaline seawater.

5. The apparatus for removing carbon dioxide in combustion exhaust gas using alkaline seawater according to claim 4, wherein the pretreatment device is a combination of at least one selected from sand filtration, rapid filtration membrane, micro filter or ultra filter.

5. The apparatus for removing carbon dioxide in combustion exhaust gas using alkaline seawater, according to claim 4, wherein the crystal separation extracting device is a particle size separator.

7. The apparatus for removing carbon dioxide in combustion exhaust gas using alkaline seawater, wherein the particle size separator is a vibration screen of 20 to 500 mesh.