KR101734943B1 - Separation method and equipment of liquid carbon dioxide preparation for utilization of carbon dioxide in emission gas from power generation plant - Google Patents

Abstract

According to the present invention, a method to separate carbon dioxide from exhaust gas includes: a step of generating sulfate ions and nitrate ions from sulfurous acid gas and nitrogen oxide contained in exhaust gas of a power plant by manufacturing an absorption solution mixed with iron ions and then making the exhaust gas penetrate the absorption solution after the addition of hydrogen peroxide, and collecting and removing the sulfate ions and the nitrate ions from the absorption solution by increasing solubility by oxidizing the sulfate ions and the nitrate ions at room temperature and normal pressure; a step of removing reactionless nitrogen oxide and carbon monoxides by using an absorbent after the removal of moisture to process gas which is passed without being absorbed by liquid due to low solubility; and a step of separating carbon dioxide by maintaining the carbon dioxide in a liquid or solid state and nitrogen and oxygen in a gas state by concentrating the carbon dioxide of the processed gas through a selective permeable membrane and then using a difference in the boiling point of the gas.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for separating carbon dioxide from an exhaust gas for utilization of carbon dioxide in a power plant exhaust gas,

The present invention relates to a method and apparatus for separating carbon dioxide from exhaust gas for utilization of carbon dioxide in a power plant exhaust gas. More particularly, the present invention relates to a method for separating carbon dioxide contained in a gas discharged from a thermal power plant into the atmosphere, Liquefied carbon dioxide, which is used for cultivation of crops, for various purposes such as beverage additions and welding, is manufactured and replaced by a manufacturing method using fossil fuels at present chemical plants, which ultimately contributes to the reduction of carbon dioxide emitted from the thermal power plant to the atmosphere .

Various substances emitted by human industrial activities not only pollute the environment, but also change the climate of the earth, leading to global warming. In particular, carbon dioxide, ozone, methane, nitrous oxide, and hydrogen fluoride gas absorb almost all the sunlight in the atmosphere, absorb infrared rays emitted from the earth, prevent the earth's heat from escaping into space, . Based on scenarios prepared by the IPCC (International Panel on Climate Change), we estimated the temperature rise as follows, assuming that the rate of increase in greenhouse gas emissions does not decrease and gradually decreases. Unless the greenhouse gas emissions are reduced, the temperature will rise to 1.5 to 4.5 ° C by mid-21st century, and the temperature will rise at 0.2 to 0.5 ° C per decade. It is estimated that if the emission of greenhouse gases is gradually reduced, the temperature rise rate will be 0.1 ~ 0.2 ℃ every 10 years. As a result of various environmental changes such as climate change, carbon dioxide has been pointed out and many studies have been carried out to reduce carbon dioxide emissions, or to collect, store and use them as useful resources. The use of fossil fuels has been the most important factor in releasing carbon dioxide, which has been stored in the form of coal, oil, and natural gas, to the atmosphere for a long time.

In addition to the reduction of carbon dioxide emissions through the application of various policies to reduce carbon dioxide and the development of technologies and the diversification of energy sources, it is necessary to capture the carbon dioxide that can inevitably be generated in each process and utilize or store it appropriately The development of technologies that can be used also plays an important role in reducing CO2 emissions.

The technologies to reduce and reduce CO2 emissions include energy saving, high efficiency energy utilization technology, non-fossil fuel use such as new energy and clean energy, conversion technology between renewable energy and fossil fuel, carbon dioxide capture and sequestration technology (CCS, ), Forest sinks, and ecological or biological treatment technologies. Among them, CCS technology refers to all the technologies that capture, recover and isolate carbon dioxide from the combustion or treatment of fossil fuels used to obtain energy, rather than releasing it to the atmosphere. These CCS technologies are divided into a capture technique for capturing carbon dioxide from a carbon dioxide emission source and a storage technique for storing the captured carbon dioxide in the ground or the ocean. In terms of cost, the capture technology cost accounts for about 70 to 80% of the total CCS cost. However, the current technology for storing carbon dioxide in underground or deep water has not been realized internationally due to the opposition to environmental impacts.

On the other hand, the thermal power plant is a power generation source that accounts for about 70% (as of 2008) of Korea's electricity production, but it is also pointed out as a major greenhouse gas emission source. However, in such a thermal power plant, since sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), and the like are contained in the exhaust gas in addition to reducing and utilizing carbon dioxide from the exhaust gas, problems arise.

Accordingly, the present inventors have found that by effectively removing sulfur dioxide (SO 2), nitrogen oxides (NO x), and carbon monoxide (CO), which are problems in utilizing carbon dioxide emitted from a power plant, And a separating device for separating the waste water.

It is another object of the present invention to provide a method for cultivating crops by effectively removing the above-mentioned gas from the exhaust gas of a thermal power plant and then injecting the purified carbon dioxide into a gardening facility for agriculture.

The method for separating carbon dioxide from exhaust gas for utilization of carbon dioxide in a power plant exhaust gas according to the present invention comprises the steps of preparing an absorption liquid in which iron ions are dissolved and adding hydrogen peroxide to pass the exhaust gas of the power plant through the absorption liquid, And a step of oxidizing the sulfuric acid ions and the nitric acid ions from the nitrogen oxides by oxidizing the sulfuric acid ions and the nitric acid ions at normal temperature and pressure to increase the solubility and collecting the sulfuric acid ions and the nitric acid ions in the absorption liquid and neutralizing them to remove the liquid, Removing unreacted nitrogen oxides and carbon monoxide by using an adsorbent after removing moisture to treat the gas that has not been absorbed by the adsorbent; treating the purified gas with a selective permeable membrane to concentrate the carbon dioxide, The difference between the boiling point of And separating the nitrogen and oxygen in a liquefied or solid state while keeping the nitrogen and oxygen in a gaseous state.

The absorbing solution is characterized in that the concentration of iron ion is maintained and the concentration of the absorbing solution is adjusted to 5.5 to 9.0 by using Na ₂ CO ₃ .

Further, ozone is added to the absorption liquid as an oxidation promoting agent.

In addition, the absorbing solution is characterized by maintaining an acidity in the range of 5.5-9.0 with an alkali solution in which NaOH is dissolved to adjust the pH.

The method may further include removing unreacted nitrogen oxides and carbon monoxide by using an adsorbent after removing moisture to treat the passed gas without being absorbed into the liquid phase due to its low solubility in the absorbing solution.

The adsorbent is an adsorbent produced by supporting manganese oxide on activated carbon.

Further, it is characterized in that moisture is removed using silica gel or zeolite in the gas that is passed through without being absorbed by the absorption liquid.

The reactor includes a reactor into which exhaust gas of a power plant is injected to remove sulfurous acid gas and nitrogen oxides contained in the exhaust gas of a power plant. Inside the reactor, four columns are formed by three valve plates, A gas outlet is formed at the upper end of the reactor. An exhaust gas from the power plant is injected into the lower portion of the first column to cause the injected gas to rise together with the liquid catalyst inside the reactor in the form of bubbles. The liquid phase catalyst is lowered in the second column beyond the upper end of the valve plate and then moved to the third column through the lower side of the second valve plate to move up and down in the fourth column beyond the upper end of the third valve plate, And then flows back to the first column to circulate the liquid phase catalyst.

Further, air is injected into the lower portion of the third column in the form of bubbles to facilitate mixing and circulation of the liquid catalyst.

Also, the cross sectional area ratio between the first column and the second column is 2: 1, and the cross sectional area ratio between the third column and the fourth column is 2: 1.

Further, the precipitate produced in the lower part of the reactor is introduced into the filter and removed.

Further, the selective permeation membrane is used to concentrate the concentration of carbon dioxide to 20% to 100%.

Further, the present invention is characterized in that the liquefied or solid carbon dioxide is used for food, welding, or cooling preservation.

The carbon dioxide separator in the exhaust gas for utilization of carbon dioxide in the power plant exhaust gas according to the present invention comprises a gas compressor for pressurizing the remaining carbon dioxide and nitrogen in the exhaust gas of the power plant at a constant pressure, A gas compressor for compressing the gas containing carbon dioxide and nitrogen enriched in the carbon dioxide concentrator; an intermediate cooler for cooling the gas compressed by the gas compressor; And a carbon dioxide separator for separating carbon dioxide from the remaining gas by liquefying the carbon dioxide by cooling with a coolant using the boiling point of the gas, characterized in that the carbon dioxide separator The carbon is concentrated, and then the concentrated carbon dioxide is separated from the remaining gas by the liquefaction separator.

Further, in the carbon dioxide concentration apparatus, a plurality of filters and a gas dryer are further provided between the gas compressor and the membrane tower to remove moisture in the gas.

According to the present invention, it is possible to effectively remove sulfur dioxide (SO 2), nitrogen oxides (NO x), and carbon monoxide (CO), which are problems in utilizing carbon dioxide emitted from a power plant, A method and a separation device are provided. Also, there is provided a method of effectively removing the above-mentioned gas from the exhaust gas of such a thermal power plant and then feeding the purified carbon dioxide to an agricultural horticultural facility to cultivate the crop.

FIG. 1 is a view showing a reactor of a plant exhaust gas purifying apparatus for utilization of carbon dioxide in the present invention,
FIG. 2 is a graph showing the results of an adsorption experiment of activated carbon adsorbed on a NO standard gas,
3 is a graph showing the results of an experiment of adsorption of activated carbon on a CO standard gas,
4 is a phase diagram of the temperature of the CO ₂ -N ₂ mixture and the mole fraction of CO ₂ ,
FIG. 5 is a graph showing the degree of separation of CO 2 by pressure based on the phase-equilibrium graph of FIG. 4,
Figure 6 is a device for the carbon dioxide thickening process of the present invention,
Figure 7 is a device for the carbon dioxide separation process of the present invention,
8 is a graph showing the amount of total biomass in atmospheric and CO ₂ cultivated crops.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method and apparatus for separating carbon dioxide from exhaust gas for utilization of carbon dioxide in a power plant exhaust gas according to a preferred embodiment of the present invention will be described in detail.

The method for separating carbon dioxide from exhaust gas for utilization of carbon dioxide in a power plant exhaust gas according to the present invention comprises the steps of: S1) preparing an absorption liquid in which iron is dissolved, adding hydrogen peroxide to pass the exhaust gas of the power plant through the absorption liquid, Sulfur dioxide and nitrate ions from sulfur dioxide and nitrogen oxides and oxidizing the sulfuric acid ions and nitric acid ions at normal temperature and pressure to increase the solubility and collecting the sulfuric acid ions and nitric acid ions in the absorption liquid and neutralizing them to remove them; S2) Removing unreacted nitrogen oxides and carbon monoxide by using an adsorbent after removing moisture to treat the passed gas without being absorbed by the liquid phase due to its low solubility, and S3) purifying the purified gas after the step S2 by a selective permeable membrane After concentrating carbon dioxide, it compresses and cools it, And separating the carbon dioxide by keeping it in a liquefied or solid state, and keeping nitrogen and oxygen in a gaseous state.

In addition, the above step S1 includes the following steps.

1) Forced suction of exhaust gas at the end of flue gas desulfurization (FDG) using a gas blower creates negative pressure in the gas transfer path, and the exhaust gas moves due to the pressure difference to introduce the gas Step,

2) In the step 1), the exhaust gas contains moisture, and since the temperature is generally higher than room temperature, condensation water is generated due to cooling during the passage through the gas introduction facility. If the condensation water is not removed, Clogging of the catalyst, deterioration of the service life of the catalyst, etc., so that the condensed water is treated using a heat exchanger,

3) removing the sulfurous acid gas and the nitrogen oxide through the chemical reaction of the gas absorbed in the reactor through the reactor for absorbing the gas introduced from the step 2); and

4) an adsorption process for removing the insoluble gas in the carbon dioxide separated from the step 3).

More specifically, in steps 3) and 4), the gas absorbed in the reactor in step 3) is subjected to the following chemical reaction to remove sulfur dioxide and nitrogen oxides. The exhaust gas of the power plant injected into the reactor has a carbon dioxide concentration of about 10% to 30% by volume, a sulfur dioxide concentration of 20 ppm to 100 ppm, a nitrogen oxide concentration of 20 ppm to 200 ppm, a carbon monoxide concentration of 1 ppm to 200 ppm, %, And less than 10% oxygen (approximately 1% to 10%).

[Absorption step of sulfur dioxide and nitrogen oxide ]

SO ₂ (gas) + H ₂ O -------> SO ₂ (liq) + H ₂ O ---------------- (1)

NO ₂ (gas) + H ₂ O -------> NO ₂ (liq) + H ₂ O - (2)

When the mixed gas such as the exhaust gas is injected, the water-soluble gas such as the dioxide gas and the nitrogen oxide is absorbed into the aqueous solution, so that the water-soluble carbon dioxide is not absorbed but concentrated.

[Oxidation Step of Sulfuric Acid Gas]

SO ₂ + H ₂ O ₂ <-------> HSO ₃ ^- + H + ^- (3)

HSO ₃ - <-------> SO ₃ ^{2 -} + H + ^- (4)

NO ₂ ^- + H ₂ O ₂ -------> NO ₃ ^- + H + ^- (5)

Hydrogen peroxide and nitrogen oxides absorbed in aqueous solution are present in the form of sulfite and nitrite ions by hydrogen peroxide and Fe-EDTA and produce proton (H +).

SO ₃ ² - + H + + 2OH - + Fe ^{3 +} + ^- chelate S ^- + H ₂ O + 2Fe ^{2 +} + chelate (6)

NO ₃ ^- + H ⁺ + OH - + Fe ^{3 +} + ^- chelate ---- N ^- + H ₂ O + Fe ^{2 +} + chelate (7)

The primary dissociated sulfur oxides and nitrogen oxide ions produce radical ions and Fe-EDTA sulfur and nitrogen ions, where the Fe-EDTA serves to lower the electron supply and reaction activation energies. Proton (H +) is consumed in this reaction. The ions in the aqueous solution are supplied with electrons from the trivalent catalyst and oxidized and precipitated as solid sulfur. Reduced iron is converted into a bivalent form.

2Fe ^{2 +} + 1/2 O ₂ + H ₂ O <--------> 2Fe ^{3 +} + 2OH -------------- (8)

Reduced bivalent iron is oxidized by trivalent iron through regeneration process with oxygen.

In the present invention, an internally circulating multi-membrane bubble column reactor for separating carbon dioxide from a power plant discharge gas is shown in FIG. 1, the interior of the reactor 100 for separating carbon dioxide in the present invention is constituted by three plate membranes 10, 11 and 12, and a space between the plate membranes 10, The first column 20, the second column 30, the third column 40 and the fourth column 50 were named as the first column 20, the second column 30, the third column 40 and the fourth column 50. In order to efficiently maintain the absorption and regeneration reactions, ), The third column 40, the second column 30 and the fourth column 50 for circulation are set to a ratio of 2: 1 (the first column 20 and the third column 50 40 are the same, and the sectional areas of the second column 30 and the fourth column 50 are the same). The inner circulation type multi-membrane bubble column reactor 100 is configured such that the exhaust gas of the power plant is injected into the lower part of the first column 20 through the exhaust gas inlet 21 and the mixing and circulation is facilitated in the lower part of the third column 40 Air is injected in the form of a bubble through the air inlet 41. [ The injected bubble rises in the liquid phase catalyst, thereby causing the liquid phase catalyst to rise together. As a result, the liquid catalyst having risen is lowered in the second column 30 and the fourth column 50. The liquid catalyst that descends in the second column 30 moves to the third column 40 and moves up through the lower side of the second plate 11 and the liquid catalyst that descends in the fourth column 50 flows into the reactor 100, And then moves back to the first column 20 via the lower end thereof, and is then raised to thereby circulate the liquid catalyst in the reactor 100 in its entirety. The injected gas flows into the gas outlet 62 at the upper portion of the third column 40 and the fourth column 50 to the gas outlet 61 at the upper portion of the first column 20 and the second column 30 Respectively. As a result of investigating the flow characteristics of the reactor according to the present invention, the pilot scale reactor was manufactured and examined. As a result, the circulation rate of the liquid phase catalyst was measured between the first column 20 and the second column 30, between the third column 40 and the fourth column (OFLH) based on the upper end point of the separation membrane between the column 50 and the amount of the aeration gas. As a result of experiments, it has been found that when the liquid level (OFLH) exceeds 40 mm, There was no significant change in the rate of circulation, and the circulation time of the fluid showed the fastest rate. That is, when the liquid level (OFLH) is 40 mm, the circulation rate is slightly increased when the air injection rate is increased to 20 L / min or more.

On the other hand, Na ₂ SO ₄ and Na ₂ NO ₃ are continuously generated in the absorption liquid of the liquid catalyst due to the neutralization reaction between SO ₃ and NO ₃ of NaOH and the absorption liquid used for controlling the pH and solids such as dust. When the solid content of the precipitate reaches a predetermined concentration, the precipitate is introduced into a filter (not shown) connected to the lower end of the reactor 100 to facilitate the removal.

The preparation of the liquid phase catalyst used in the reactor 100 and the oxidation reaction

After completely dissolving the iron salt [Fe (NO ₃ ) ₃ 9H ₂ O], the chelate Na ₂ EDTA was added to form iron chelate complex of Fe-EDTA. Na ₂ CO ₃ was added to adjust the pH of the solution, Was used as a catalyst for the reaction. The pH of the solution is adjusted to 5.5-9.0, more preferably 6.0-9.0. Use reagents Fe (NO ₃ ) ₃ 9H ₂ O and Na ₂ CO ₃ are dissolved using distilled water. In the case of the field-installed reactor 100, industrial grade reagents and city water are used in view of economical efficiency. The Fe concentration to be used in the reaction was prepared based on 0.1 mol / L, and iron chelate and Na ₂ EDTA were prepared in a ratio of 1: 2.5 mol. The constituents of the catalyst composition were 4.04 kg / ton of Fe (NO ₃ ) ₃ , 3.7 kg / ton of 4Na-EDTA, 1.15 kg / ton of Na ₂ S ₂ O ₃ , 1.15 kg / ton of Na ₂ CO ₃ , 0.23kg / ton and 989.73kg / ton of water. The addition concentration of hydrogen peroxide as a catalyst aid was 27.009 kg / ton as compared with the catalyst injection amount.

Hydrogen peroxide and ozone are added to the liquid catalyst as oxidation promoting agents. Hydrogen peroxide and ozone are strong oxidizing power of OH generated by reaction with metal ions, and oxidize HSO ₃ -, SO ₃ ^{2 -} , NO ₃ - dissolved in absorbing solution. Hydrogen peroxide is generally supplied in a weakly acidic state because it decomposes more at pH 6 and above and increases at higher pH. Hydrogen peroxide is mainly used for the oxidation reaction. It is easy to think that oxygen is generated in the molecule because the oxygen or the active oxygen is in the molecule. However, the two oxygen atoms in the molecule of hydrogen peroxide practically have no distinctive property. The reason for the excellent reactivity between hydrogen peroxide and ozone is that the binding force of OO in the molecule is weak. It acts as an oxidizing agent in reactions with ions. Hydrogen peroxide and ozone oxidize and decompose various substances because the OO bond is destroyed and the radical is generated when the metal catalyst exists. In particular, hydrogen peroxide is relatively environmentally safe because it is relatively non-toxic, easy to handle and has no byproducts generated during the oxidation reaction. In addition, it is water and oxygen when it decomposes spontaneously and it is advantageous in terms of environmental safety, ease of use and selective oxidation reaction compared with other oxidizing agents. As for the properties of hydrogen peroxide, hydrogen peroxide is very stable because the following equilibrium reaction proceeds only in the forward direction in an acidic solution.

H ₂ O ₂ + OH ^- > HOO ^- + H ₂ O

Further, hydrogen peroxide reacts with hydrogen ions to produce oxonium.

H ₂ O ₂ + H ^{+ -} & gt ^; HOOH ₂ ⁺

These oxonium ions increase the stability of hydrogen peroxide by making hydrogen peroxide molecules electrophilic.

In an alkaline solution, hydrogen peroxide reacts with OH- to form HO2- (perhydroxyl ion).

H ₂ O ₂ + OH ^- > HOO ^- + H ₂ O (pH) = 16.6 (20 ° C.)

This equilibrium reaction proceeds as the alkalinity increases. Since HOO- is more than 200 times more reactive than OH-, decomposition reaction of hydrogen peroxide occurs.

^{_{HOO - + H 2 O 2 →}} H 2 O + OH - + O 2

Therefore, the presence of organic compounds that can attack HOO ^- in alkaline solutions occurs competitively in the above reactions, thus accelerating the decomposition of hydrogen peroxide. Hydrogen peroxide, on the other hand, has the property of generating free radicals in the presence of metal ions of low oxidation state in acidic or neutral state. When hydrogen peroxide is activated, OH and HO2 are formed, and their redox potentials are as high as 2.8 V, which allows oxidative decomposition of the electrophilic organic compounds.

Meanwhile, in order to control the pH of the absorption liquid solution of the liquid catalyst, the pH can be adjusted to 5.5-9.0 with an alkali solution in which NaOH is selectively dissolved instead of Na ₂ CO ₃ . When an alkaline solution in which NaOH is dissolved is used, as described above, the neutralization reaction between NaOH and the SO ₃ and NO ₃ generated in the absorption liquid continuously generates Na ₂ SO ₄ and Na ₂ NO ₃ , and a solid solution such as dust When the solid content of the precipitate reaches a certain concentration, the product is introduced into the filter connected to the lower end of the reactor 100 and removed.

Step 4) Adsorption process for removing the insoluble gas in the separated carbon dioxide

In this step, moisture is removed to treat the passed gas without being absorbed into the liquid because the solubility of the absorbent is low, and then the unreacted nitrogen oxides and carbon monoxide are removed using an adsorbent.

First, manganese-deposited activated carbon prepared by removing moisture by using silica gel or zeolite in a gas that is not absorbed by the absorption liquid and supporting manganese oxide on activated carbon is used as an adsorbent for removing non-spurious gas. The manganese-deposited activated carbon has a pore size of 4.28 nm, a pore volume of 0.336 cm ² / g, a surface area of 303.4 m ² / g, and a manganese content of 19.0 atomic%. The activated activated carbon is chemisorbed and adsorbs and removes a gas to be removed together with a neutralization reaction, a chemical reaction and a catalytic reaction.

NO and CO removal using manganese deposition activated carbon

The activated carbon containing manganese deposit had a pore size of 4.28 nm, a pore volume of 0.336 cm 2 / g, a surface area of 303.4 m 2 / g, and manganese containing 19.0 atomic%. NO was 23 ppm and CO was 919 ppm using NO standard gas (23 ppm) and CO standard gas (919 ppm), and then passed through a glass tube having a height of 130 mm and an inner diameter of 10 mm at 20 cc / min. As a result of calculating the adsorption amount and adsorption rate of activated carbon adsorbed on 10 g of manganese oxide by measuring the concentration of the adsorbed NO, the adsorbed amount of NO was 173.2 mg when the NO standard gas was adsorbed for 8 hours and the adsorption rate was 64.7% . When the CO standard gas was adsorbed for 12 hours, the total adsorbed amount was 14,661.8 mg and the adsorption rate was 97.9%.

NO standard gas (23 ppm) was adsorbed on the activated carbon, it was confirmed that the initial concentration increased from 0 ppm to 15 ppm and the adsorption rate was 64.7% (see FIG. 2 NO 2) ).

As the CO standard gas (919 ppm) adsorbed on the activated carbon, it was confirmed that the passing time was maintained and the initial concentration was reduced from 26 ppm to 16 ppm at 12 hours of analysis, and the adsorption rate was 97.9% (see FIG. 3 Test of Carbon Standard Gas Deposition Activated Carbon Adsorption) ).

As described above, the remaining gas after the adsorption process for removing the insoluble gas in the separated carbon dioxide is composed of carbon dioxide and most of nitrogen (including a small amount of oxygen). Here, the characteristics of the gas of the remaining gas for separating carbon dioxide are as follows.

The physical properties of CO ₂ are summarized as follows: Molecular Formula is CO ₂ , Molecular Weight is 44.01 g / gmol, Critical Temperature is 31.0 ° C, Critical Pressure is 75.3 g / ml and specific gravity is 1.529 (Air = 1) for gas and 0.93 (0 ℃ Water = 1) for liquid. Temperature of triple point is -56.6 ℃ and pressure is 5.28kg / abs. At temperatures and pressures below the triple point, CO ₂ becomes solid or gas. The solid is sublimated into the gas at -78.5 ° C and atmospheric pressure without going through the liquid state. At this time, the dry ice absorbs the sublimation heat of 150K Call / Kg and shows a strong cooling effect. When the solid carbonic acid sublimes to a pressure lower than atmospheric pressure, the temperature will be lower.

At temperatures and pressures above the triple point and below 31.1 ° C, the liquid and gas may be in equilibrium in a closed container of CO ₂ .

When the critical temperature (31.0 ℃) or more CO ₂ can not be present in the liquid regardless of the pressure solubility in water (Solubility In Water, v / v at 20 ℃) 0.90, sublimation point (Sublimation Point at 101.325 kpa) Lt; / RTI &gt;

In order to design the liquefaction process of carbon dioxide, the following properties are summarized. Figure 4 is a phase diagram of the temperature of the CO ₂ -N ₂ mixture and the mole fraction of CO ₂ . If the concentration of CO ₂ in the purified gas from the stack is 17%, it can be seen that the equilibrium condition required for liquefaction should be about 60 atm -120 ° C. Also, in the state of CO ₂ mixture, CO ₂ is equilibrated on the gas phase even in the liquefaction, so that only a certain amount of CO ₂ is liquefied. FIG. 5 shows the result of estimating the degree of separation at a CO ₂ concentration of 80% based on the phase-equilibrium graph. When the concentration is 80% of the CO ₂ gas mixture temperature and pressure of the CO ₂ separation according to (15bar, 30bar, 60bar) it has shown that the more the high concentration and the temperature of CO ₂ at low temperatures bunriyul is high.

 Based on these results, it can be seen that the mass separated by liquefaction according to the concentration of carbon dioxide is determined by the function of the concentration, pressure and temperature of carbon dioxide, and it is necessary to derive the separation conditions according to these conditions.

5 is a kind of mixture gas that is, nitrogen, oxygen, argon, hydrogen, etc. is inde graph showing the purity of the road and liquefied CO ₂ separation of CO ₂ according to the pressure when they are mixed wherein the purity is in the liquefied CO ₂ itself Purity "means the gas purity in the gas-liquid separator to be liquefied. As can be seen from this graph, increase the degree of separation The higher the liquid pressure during the CO _2, but shows that the purity of the CO ₂ is not a significant change in around 95%, depending on the pressure.

Therefore, in order to increase the efficiency of liquefaction separation of carbon dioxide in order to separate the carbon dioxide from the remaining gas after the adsorption process for removing the non-dissolved gas in the separated carbon dioxide as described above, the concentration of carbon dioxide before liquefaction is separated and separated. Since the concentration of carbon dioxide and nitrogen in the liquefaction process influences the liquefaction equilibrium in the liquefaction process as described above, in the present invention, the concentration of the carbon dioxide is appropriately concentrated, and then, in the separation process, the liquefied carbon dioxide is separated from nitrogen (oxygen) The efficiency of separation is increased. Of course, the liquefaction of 100% of carbon dioxide is the least cost of concentration, but since the concentration cost of the separation membrane and the cost required for liquefaction are in conflict with each other, the carbon dioxide is suitably concentrated and separated by liquefaction to achieve the most efficient separation at low cost.

The carbon dioxide separation apparatus for separating carbon dioxide from the purified gas in the present invention comprises a concentration apparatus 200 and a liquefaction separation apparatus 300.

6 is a device for the carbon dioxide concentration process of the present invention. The carbon dioxide concentration apparatus 200 includes a gas compressor 210 for compressing carbon dioxide and nitrogen remaining after the adsorption process, an aftercooler 220, a prefilter 230 (prefilter), a gas dryer 240, an activated carbon tower 250, an after filter 260, and a membrane tower 270 for concentrating the concentration of carbon dioxide using a selective permeable membrane.

The gas compressor 210 is a device for compressing the purified gas to about 6 to 7 bar in order to concentrate the purified gas. The aftercooler 220 is a cooler for preventing overheating and overloading of the continuously operated gas compressor 210. The prefilter 230, the after filter 260, the activated carbon tower 250, and the gas dryer 240 for drying the purified gas using the moisture adsorbent are installed at the front end or the rear end of the equipment, By removing the moisture of the compressed gas, the life of the separation membrane of the membrane tower 270 and the efficiency of carbon dioxide concentration can be increased.

The selective permeable membrane of the membrane tower 270 is composed of a membrane having a mesh of a predetermined size to allow the nitrogen gas to pass through and the carbon dioxide to pass through, thereby concentrating the carbon dioxide.

After the carbon dioxide concentration process is performed, a separation process of carbon dioxide and nitrogen due to the liquefaction process is performed.

As shown in FIG. 7, the liquefying and separating apparatus 300 of the present invention used in the separation process comprises a gas compressor 310 (gas compressor) and an oil separator (340) for cooling the gas in the piping by using the cooling water, and a cooler (340) for liquefying the carbon dioxide by cooling with the coolant using the boiling point of the gas And a carbon dioxide separator 350 for separating the carbon dioxide gas from the nitrogen gas.

The gas compressor 310 is a compressor for pressurizing CO 2 in a lower critical region, and is a device for raising low-temperature low-pressure CO 2 to a certain pressure and temperature.

The air-cooled intercooler 330 by the cooling fan is composed of an air pin cooler (SUS 316) which can withstand high pressure in the present embodiment.

The carbon dioxide separator 350 is a storage device for separating the two-phase gas (CO ₂ , N ₂ ) supplied to the apparatus and recovering the liquid CO ₂ to the storage tank. In order to maintain the supercritical state, . The operating pressure is 100 bar or more, and a heat exchanger for liquefying CO ₂ of high temperature and high pressure is attached. As the coolant, dry ice is used. In addition, cooling water is injected and cooled to about -40 ° C. The upper part of the carbon dioxide separator 350 has a vapor recovery port and the lower part thereof has a liquid recovery port and a pressure gauge. All piping is constructed of stainless steel, piping diameter is determined so that 100 bar CO ₂ can flow safely, and piping is insulated with insulation.

Therefore, the carbon dioxide separator of the liquefying and separating apparatus 300 of the present invention liquefies carbon dioxide to separate it from the remaining nitrogen and oxygen gas.

[Test Example] Plant cultivation using carbon dioxide fertilizer using pretreated exhaust gas

A greenhouse for carbon dioxide fertilization was constructed to utilize carbon dioxide separated from the pretreated exhaust gas through the above process for plant cultivation. The carbon dioxide green glasshouse can be divided into a comprehensive general greenhouse system, an exhaust gas supply, and a CO2 concentration measurement and control unit.

The temperature of the exhaust gas is about 85 ° C, the water content is about 4%, and the carbon dioxide concentration is about 17%. In the present invention, an exhaust gas cooling heat exchanger utilizing a cooling medium produced in a water-removing chiller is installed without introducing an additional cooling device, so that the temperature of the exhaust gas flowing into the glass greenhouse can be lowered to 30 ° C or less.

In order to examine the effect of plant growth on CO ₂ concentration, CO ₂ fertilizer was set to 800 ppm to 1200 ppm during the growth period of the crop (24 hours a day). The temperature was maintained at 25 캜 through a temperature device.

The irrigation water for the cultivated crops was set so that 200 cc was supplied to the crops for 1 minute per one pot (piping supplying water to the roots of each plant), once at 09:00, at 11:00 A total of 1,600 cc per port is set to be supplied every 8 times per day, once per hour from 12:00 to 17:00.

The atmospheric cultivation room was cultivated with tomato, cucumber, zucchini and pepper in an atmosphere similar to the normal atmospheric condition (300 ~ 400ppm). The CO ₂ cultivation room was fed with purified CO ₂ in the pretreatment facility, and CO ₂ concentration (800 ppm to 1,200 ppm) Tomatoes, cucumbers, zucchini and peppers were grown in an environment where they were maintained.

The concentration of CO ₂ in the atmosphere cultivation chamber is about 300 ~ 400ppm, CO ₂ concentration of the CO ₂ culture chamber was determined by the number and fresh weight of the fruit after the growing and harvesting of crops by setting to about 800 ~ 1200ppm. Cucumber, pepper, and pumpkin were grown for 3 weeks in each greenhouse. Tomatoes were removed and the weight of biomass including fruit was measured.

Atmospheric and CO2 growing crops
Total biomass (in g) Atmospheric cultivation
(300 to 400 ppm) CO2 growing
(800 to 1200 ppm)
leaf
cucumber 315.5 340.5 pepper 318 648 squash 627 695.5
stem
cucumber 306.5 312 pepper 275.5 746 squash 704 725
Root
cucumber 521 627 pepper 298 473.5 squash 36.5 46

division Cucumber (in g) pepper squash Atmospheric cultivation
(300 to 400 ppm)
1142
891.5
1367.5 CO2 growing
(800 to 1200 ppm)
1279.5
1867.5
1466.5

The results of cultivating crops for each greenhouse for 70 days are shown in Tables 1 and 2 and FIG. In the case of cucumber, the total weight was 1143g for 300 ~ 400ppm, and 1279.5g for 800 ~ 1200ppm. In the case of pepper, it increased from 891.5g at 800 ~ 1200ppm to 1867.5g at 800 ~ 1200ppm, and in the case of squash, it showed about 6.8% weight gain from 300 ~ 400ppm at 1367.5g and 800 ~ 1200ppm at 1466.5g. Cucumber, red pepper and zucchini all showed the tendency of increasing biomass when grown at carbon dioxide concentration of 800 ~ 1200ppm.

Therefore, according to the present invention, it is possible to effectively remove sulfur dioxide (SO ₂ ), nitrogen oxides (NO x), carbon monoxide (CO) and the like, which are problems in utilizing carbon dioxide emitted from a power plant, And separate liquefied or solid carbon dioxide can be used for other food, welding, or cooling preservation. In addition, it can reduce air pollution and can be very useful for mitigating global warming.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken as limitations Changes and modifications will be possible.

10, 11, 12: valves 20, 30, 40, 50:
21: gas inlet 41: air inlet
61, 62: gas exhaust port 100: reactor
200: Condenser 300: Liquefying separator

Claims (8)

S1) an iron ion absorbing solution is prepared and hydrogen peroxide is added to pass the exhaust gas of the power generation plant through the absorption liquid to generate sulfate ion and nitrate ion from the sulfur dioxide gas and nitrogen oxide contained in the exhaust gas of the power generation plant, Oxidizing the ions at room temperature and normal pressure, increasing the solubility, collecting the ions in the absorbing solution, neutralizing and removing the ions,
S2) removing unreacted nitrogen oxides and carbon monoxide by using an adsorbent after removing moisture to treat the passed gas without being absorbed into the liquid phase due to its low solubility in the absorption liquid,
S3) Concentrating carbon dioxide in the remaining gas after the step S2 by compressing and cooling the carbon dioxide by a selective permeable membrane, separating carbon dioxide into liquid or solid state while keeping nitrogen and oxygen in a gaseous state Wherein the carbon dioxide is separated from the exhaust gas. The method according to claim 1,
Wherein the carbon dioxide is concentrated from 20% to 100% by using the selective permeable membrane in the step S3). The method according to claim 1,
Wherein the ozone is added to the absorption liquid in the step S1) as an oxidation promoting agent. The method according to claim 1,
Wherein the absorbing solution is maintained in the range of 5.5-9.0 pH with an alkaline solution in which NaOH is dissolved to adjust the acidity (pH) of the carbon dioxide. The method according to claim 1,
Wherein the adsorbent is an adsorbent produced by supporting manganese oxide on activated carbon. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt; The method according to claim 1,
Wherein the carbon dioxide separated in the liquefied or solid state is used as carbon dioxide for food, welding, or cooling preservation. delete delete

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