KR102054855B1 - Method for Simultaneous Treating Nitrogen Oxides and Sulfur Oxides using Iron Ethylene diamine tetraacetic acid - Google Patents

Abstract

The present invention relates to a method for simultaneously recovering nitrates and sulfates in the form of fertilizers by simultaneously reducing nitrogen oxides (NO _X ) and sulfur oxides (SO _X ) contained in the exhaust gas of a power plant. By converting to a fertilizer form through a simple electrochemical device that collects and consumes less space, it has a high removal efficiency, is economical, and is close to commercialization in consideration of initial equipment investment cost and ease of operation.

Description

Method for Simultaneous Treating Nitrogen Oxides and Sulfur Oxides using Iron Ethylene diamine tetraacetic acid}

The present invention relates to a power plant exhaust gas treatment method, and more particularly, to a method of recovering nitrogen oxides (NO _X ) and sulfur oxides (SO _X ) contained in the power plant exhaust gas at the same time to recover as fertilizer form nitrate and sulfate. It is about.

In the combustion process of fossil fuel using facilities such as power plants, industrial boilers, and incineration plants, and automobile engines, a large amount of nitrogen oxides are generated that are harmful to the human body. It is even considered to be the main cause of fine dust.

Processes for removing this include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), electron beam using process, and pulse corona discharge injecting a reducing agent (NH ₃ ) into the catalyst. Processes and the like have been researched and developed. Nitrogen oxide emissions have been slightly reduced in recent decades with the development of nitrogen oxide abatement technologies, but about 30 million tonnes of nitrogen oxides are emitted annually in the United States alone, and the most widely used selective catalytic reductin, SCR) requires an astronomical amount of about $ 24 billion.

Sulfur oxide can be treated through various processes such as dry and wet desulfurization, and the most commercialized process is flue gas desulfurization (FGD) which removes sulfur oxide using calcium or lime. . However, the calcium sulfide collected as the final product has a low degree of recycling and uses a toxic heavy metal such as mercury during the process, thereby causing secondary environmental problems (Non-Patent Document 2).

Recently, as environmental standards are strengthened due to concerns caused by fine dust, interest in reducing nitrogen oxides and sulfur oxides is increasing, and research on the effective treatment at the same time is being conducted, but there are no commercialized processes. Document 1, Patent Document 1). In particular, considering the space velocity and the gas flow rate of the power plant exhaust gas, it is necessary to develop a technology that is excellent in the field application.

Therefore, the present inventors have made diligent efforts to develop a method for efficiently and economically treating nitrogen oxides and sulfur oxides simultaneously. As a result, by using an integrated scrubber in the exhaust gas of a power plant, the present inventors simultaneously collect nitrogen oxides and sulfur oxides, When converted to fertilizer form of nitrate and sulphate, it was confirmed that nitrogen oxide and sulfur oxide can be efficiently removed at the same time, the present invention was completed.

Apparatus for improving the performance of electrochemically mediated oxidation processes for the treatment of NOX, SOO and dioxins (application number: 10-2008-0008837)

 The Chemical Behaviors of Nitrogen Dioxide Absorption in Sulfite Solution. Appl. Sci. 7: 377, 2017.  Simultaneous removal of NOx and SO2 from flue gas using combined Na2SO3 assisted electrochemical reduction and direct electrochemical reduction. J. Hazard. Mater. 276: 371, 2014.

It is an object of the present invention to provide a method for efficiently and economically treating nitrogen oxides and sulfur oxides present in exhaust gas simultaneously.

Another object of the present invention is to provide an apparatus for efficiently and economically treating nitrogen oxides and sulfur oxides present in exhaust gas simultaneously.

In order to achieve the above object, the present invention comprises the steps of: (a) simultaneously absorbing nitrogen oxides and sulfur oxides with an absorbent based on iron and ethylenediaminetetraacetic acid; (b) regenerating the absorbent liquid generated by absorbing nitrogen oxide and sulfur oxide in the absorbent in an electrochemical cell having an electrode structure of fine pores; And (c) applying the regenerated absorbent liquid to an electrochemical cell comprising an anion exchange membrane to produce nitrates and sulfates, and further regenerating the absorbent liquid. Nitrogen oxides and sulfur oxides using iron-ethylenediaminetetraacetic acid. Provides a simultaneous processing method.

The present invention also includes: (i) a scrubber comprising iron and an ethylenediaminetetraacetic acid-based absorbent and simultaneously absorbing nitrogen oxides and sulfur oxides; (ii) an electrochemical cell having a microporous electrode structure for regenerating the absorbent liquid absorbed by the scrubber; And (iii) an apparatus for simultaneously treating nitrogen oxides and sulfur oxides using iron-ethylenediaminetetraacetic acid comprising an electrochemical cell comprising an anion exchange membrane to produce nitrates and sulfates in the absorbent liquid regenerated in the electrochemical cell. .

By using the simultaneous treatment of nitrogen oxides and sulfur oxides according to the present invention, it is possible to simultaneously convert nitrogen oxides and sulfur oxides, which could not be treated simultaneously in the prior art, to nitrates and sulfates in the form of fertilizers, and have high removal efficiency. Low initial equipment investment cost, easy operation, and easy commercialization.

1 shows an apparatus for simultaneously treating nitrogen oxide and sulfur oxide using iron-ethylenediaminetetraacetic acid according to the present invention.

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 nomenclature used herein and the experimental methods described below are well known and commonly used in the art.

In the present invention, iron-ethylenediaminetetraacetic acid is used as an absorbent to simultaneously absorb nitrogen oxides and sulfur oxides, and then to develop a process for converting fertilizers such as nitrates and sulfates through electrochemical treatment. Integral scrubber using tetraacetic acid as an absorbent can remove nitrogen oxide and sulfur oxide at the same time, so it can use the form of scrubber used in the existing flue gas desulfurization process. This can be greatly improved. In addition, the nitrogen oxides and sulfur oxides of the flue gas can be utilized as a high-purity fertilizer instead of waste or untreated by-products. Accordingly, it is expected to provide technology that is close to commercialization and has excellent field applicability.

Therefore, in one aspect, the present invention comprises the steps of: (a) simultaneously absorbing nitrogen oxides and sulfur oxides with iron and ethylenediaminetetraacetic acid based absorbents; (b) regenerating the absorbent liquid generated by absorbing nitrogen oxide and sulfur oxide in the absorbent in an electrochemical cell having an electrode structure of fine pores; And (c) applying the regenerated absorbent liquid to an electrochemical cell comprising an anion exchange membrane to produce nitrates and sulfates, and further regenerating the absorbent liquid. Nitrogen oxides and sulfur oxides using iron-ethylenediaminetetraacetic acid. It relates to the simultaneous processing of.

In addition, the present invention in another aspect, (i) a scrubber containing iron and ethylenediaminetetraacetic acid-based absorbent, and simultaneously absorbs nitrogen oxide and sulfur oxide; (ii) an electrochemical cell having a microporous electrode structure for regenerating the absorbent liquid absorbed by the scrubber; And (iii) an apparatus for simultaneous treatment of nitrogen oxides and sulfur oxides using iron-ethylenediaminetetraacetic acid comprising an electrochemical cell comprising an anion exchange membrane to produce nitrates and sulfates in the absorbent liquid regenerated in the electrochemical cell. .

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 shows a nitrogen oxide and sulfur oxide simultaneous treatment apparatus using iron-ethylenediaminetetraacetic acid according to the present invention.

Specifically, step (a) of FIG. 1 is a scrubber in which exhaust gas is absorbed, and the exhaust gas inlet is generally used in a process of supplying gas to a liquid phase, and may be supplied using a pump or a venturi from an exhaust gas generating point. Can be.

The inside of the scrubber is filled with a mixture of trivalent iron and ferric ethylenediaminetetraacetic acid of pH 6-8. The concentration of iron-ethylenediaminetetraacetic acid in the scrubber may range from 0.1M to 1M. In addition, the ratio of the ferric-ethylenediaminetetraacetic acid in the total iron-ethylenediaminetetraacetic acid is maintained at 70-90%.

Under the above-mentioned conditions, absorption of nitrogen oxides and sulfur oxides takes place inside the scrubber. First of all, ferric-ethylenediaminetetraacetic acid has a very high adsorption capacity for nitrogen monoxide and thus can be absorbed, and sulfur oxides are basically very well soluble in bases. If the scrubber pH is 7 or less, solubility is high, and thus absorption is relatively easy. Nitrogen oxide and sulfur oxide absorption reaction is as follows.

Fe ²⁺ -EDTA + NO → Fe ²⁺ -EDTA-NO

^{_{SO 2 + 2OH - → SO 3}} 2- + H 2 O

In the step (a) scrubber of the present invention, the sulfur oxide is converted to the sulfate by the residual oxygen in the exhaust gas or trivalent-ethylenediaminetetraacetic acid.

The absorbent of step (a) is preferably ammonium iron-ethylenediaminetetraacetic acid (Ammonium iron EDTA) having an ammonium ion as a cation source.

In the present invention, the absorbent may be characterized in that ammonium iron-ethylenediaminetetraacetic acid (Ammonium iron EDTA) having an ammonium ion as the cation source.

In the present invention, the concentration of the absorbent in step (a) is 0.1 M ~ 1M, pH may be characterized in that 6 to 8.

In the present invention, the ratio of divalent iron-ethylenediaminetetraacetic acid in the total iron-ethylenediaminetetraacetic acid contained in the absorbent may be 70 to 90%.

Step (b) of FIG. 1 is a step of flowing the absorbent liquid generated in the above (a) through an electrochemical cell having an electrode structure of fine pores and regenerating the absorbent liquid. In flowing liquid through the microporous electrode structure, the anode first passes through the anode and then passes through the cathode. By sequentially passing the cathode after the anode, the reaction taking place inside the reactor is as follows.

_{H 2 O → 1/2 O 2 +} 2H + + 2 e - ( anode reaction)

Fe ²⁺ -EDTA-NO → Fe ³⁺ -EDTA + e- + NO (anode reaction)

Fe ²⁺ -EDTA-NO + _1/2 O ₂ + 2H ⁺ → Fe ³⁺ -EDTA + H ₂ O + NO

2NO + O ₂ → 2NO ₂

3NO ₂ + H ₂ O → 2HNO ₃ + NO

Fe ³⁺ -EDTA + e- → Fe ²⁺ -EDTA (cathode reaction)

Specifically, electrochemical oxidation takes place at the anode first. When a high overvoltage is applied, water is decomposed to generate oxygen, or the ferric-ethylenediaminetetraacetic acid is converted into trivalent-ethylenediaminetetraacetic acid. When the overvoltage is low, the ferric-ethylenediaminetetraacetic acid is trivalent-ethylenediamine. Only reactions oxidized to tetraacetic acid occur. Eventually, if the oxidizing atmosphere is maintained, the ratio of trivalent ethylene-diaminetetraacetic acid increases, and this form is desorbed because the ability to adsorb nitrogen oxides further decreases.

When the overvoltage is low, only desorbed nitrogen oxides can be collected in high concentration and pure, and reacted with oxygen, water and ammonia in the general atmosphere to convert to ammonium nitrate. The nitrogen oxide collecting port is usually used in a process for collecting a general gas, and may be further provided with a pump if necessary.

When the overvoltage is high, the desorbed nitrogen oxides are present in the form of nitrogen dioxide by reacting with the oxygen generated by water decomposition, and the nitrogen dioxide reacts with water to be converted directly into nitrate form, so that the product is converted only in solution without generating nitrogen-based gas.

In the cathode of step (b), trivalent-ethylenediaminetetraacetic acid is reduced to divalent-ethylenediaminetetraacetic acid to regenerate the absorbent liquid.

In the operation of step (b), the anode may be selected from the group consisting of platinum, titanium, or dimensionally stable anode (DSA), or the anode used in a typical chloro-alkali process may be used as it is. have. The cathode may be a noble metal such as platinum, palladium, rudenium, gold, silver, or a transition metal such as manganese, cobalt, nickel, copper, or zinc, or a cathode used in a typical chloroalkali process.

In the operation of step (b), when it is desired to capture high-purity nitrogen oxides without generating oxygen, the applied voltage is preferably 0.7 V or less, and the oxygen is generated to be oxidized to nitrate and dissolved in the solution. In this case, the applied voltage is preferably 1V or more.

In the present invention, the electrochemical device of step (b) is characterized in that the nitrogen oxides are trapped by applying an applied voltage of 0.1 ~ 0.7V, the applied voltage is set to 1V ~ 10V in the electrochemical device of step (b) And it can be characterized in that the conversion to the nitrate to be dissolved in the absorbent liquid.

Step (c) of FIG. 1 is a step of separating the nitrates and sulfates generated in steps (a) and (b) using an electrochemical cell including an anion exchange membrane to generate fertilizer and further regenerating the absorbent solution. When a voltage is applied externally, nitrates and sulfates are moved through the anion exchange membrane from the cathode to the anode by the electric field. The anode chamber is supplied with ammonia continuously, and the ammonia is a cation source, and nitrates and sulfates from the cathode act as an anion source, so that fertilizers of ammonium nitrate and ammonium sulfate can be collected as final products. The reaction that takes place inside the reactor is shown below.

_{H 2 O → 1/2 O 2 +} 2H + + 2 e - ( anode reaction)

^{_{SO 3 2- + 2OH- → SO 4}} 2- + 2e - + H 2 O ( anode reaction)

Fe ³⁺ -EDTA + e- → Fe ²⁺ -EDTA (cathode reaction)

^{_{2H 2 O + 2e - → H}} 2 + 2OH - ( cathode reaction)

The reaction that occurs mainly in the anode of step (c) is a reaction in which water is decomposed to generate oxygen, or if the entire sulfur oxide is present as some sulfite without changing to sulfate during the steps (a) and (b). , Sulfites act as electron donors and oxidize. In addition, in the cathode of step (c), water is decomposed basically to generate hydrogen. However, when trivalent-ethylenediaminetetraacetic acid is present in the chamber, additionally, it is converted to divalent-ethylenediaminetetraacetic acid to regenerate additional absorption liquid. This is done. The solution passed through the cathode of step (c) can be recycled to the absorbent liquid of step (a).

In operation (c), the anode may be selected from the group consisting of platinum, titanium, or dimensionally stable anode (DSA), or the anode used in a conventional chloro-alkali process may be used as it is. have. The cathode may be a noble metal such as platinum, palladium, rudenium, gold or silver, or a transition metal such as manganese, cobalt, nickel, copper or zinc, or a cathode used in a typical chloroalkali process.

In the operation of step (c), the applied voltage is preferably 1.23 ~ 5.0V.

In the operation of step (c), as the available anion exchange membrane, a conventional anion exchange membrane can be used as it is, for example, SELEMION AMV, SELEMION AMT, SELEMION DSV, SELEMION AAV, SELEMION ASV, SELEMION AHD, SELEMION APS4 , Neosepta AMX, Fumasep FAS, Fumasep FAB, Fumasep FAD, Fumasep FAP, Fumasep FAA-3, etc. may be used, but is not limited thereto.

As described above in detail specific parts of the present invention, it will be apparent to those skilled in the art that these specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. will be. Therefore, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (16)

Simultaneous treatment of nitrogen oxides and sulfur oxides with iron-ethylenediaminetetraacetic acid comprising the following steps:
(a) simultaneously absorbing nitrogen oxides and sulfur oxides with an ammonium iron EDTA absorbent having ammonium ions as the cation source;
(b) regenerating the absorbent liquid generated by absorbing nitrogen oxide and sulfur oxide in the absorbent in an electrochemical cell having an electrode structure of fine pores; And
(c) applying the regenerated absorbent liquid to an electrochemical cell comprising an anion exchange membrane to produce nitrates and sulfates, and further regenerating the absorbent liquid.
delete The method of claim 1, wherein the concentration of the absorbent in step (a) is characterized in that 0.1M ~ 1M.
The method according to claim 1, wherein the pH of the absorbent liquid is 6-8.
The method of claim 1, wherein the ratio of divalent iron-ethylenediaminetetraacetic acid in the total iron-ethylenediaminetetraacetic acid contained in the absorbent is 70 to 90%.
The method of claim 1, wherein the anode of the electrochemical cell is selected from the group consisting of platinum, titanium or Dimensionally stable anode (DSA), and the cathode of the electrochemical cell is platinum, palladium, ruthenium, gold, silver, manganese, cobalt At least one alloy selected from the group consisting of nickel, copper and zinc.
The method of claim 1, wherein in the electrochemical cell of step (b), the nitrogen oxides are collected at an applied voltage of 0.1 to 0.7V.
The method of claim 1, wherein in the electrochemical cell of step (b), the applied voltage is set to 1V to 10V and converted to nitrate to dissolve in the absorbent liquid.
The method of claim 1, wherein the applied voltage in the electrochemical cell comprising the anion exchange membrane of step (c) is 1.23 ~ 5.0 V.
The method of claim 1, wherein the anion exchange membrane used in the electrochemical cell comprising the anion exchange membrane of step (c) is SELEMION AMV, SELEMION AMT, SELEMION DSV, SELEMION AAV, SELEMION ASV, SELEMION AHD, SELEMION APS4, Neosepta AMX, Fumasep FAS, Fumasep FAB, Fumasep FAD, Fumasep FAP, and Fumasep FAA-3.
Simultaneous treatment of nitrogen oxides and sulfur oxides using iron-ethylenediaminetetraacetic acid comprising:
(i) a scrubber comprising an ammonium iron EDTA absorbent having ammonium ions as a cation source and simultaneously absorbing nitrogen oxides and sulfur oxides;
(ii) an electrochemical cell having a microporous electrode structure for regenerating the absorbent liquid absorbed by the scrubber; And
(iii) an electrochemical cell comprising an anion exchange membrane to produce nitrates and sulfates in the absorbent liquid regenerated in the electrochemical cell.
delete The apparatus of claim 11, wherein the concentration of the absorbent is between 0.1 M and 1 M, and the pH is between 6 and 8. 13.
12. The apparatus according to claim 11, wherein the proportion of divalent iron-ethylenediaminetetraacetic acid in the total iron-ethylenediaminetetraacetic acid contained in the absorbent is 70 to 90%.
The method of claim 11, wherein the anode of the electrochemical cell is selected from the group consisting of platinum, titanium or Dimensionally stable anode (DSA), wherein the cathode of the electrochemical cell is platinum, palladium, rudennium, gold, silver, manganese, cobalt At least one alloy selected from the group consisting of nickel, copper and zinc.
The method of claim 11, wherein the anion exchange membrane used in the electrochemical cell including the anion exchange membrane is SELEMION AMV, SELEMION AMT, SELEMION DSV, SELEMION AAV, SELEMION ASV, SELEMION AHD, SELEMION APS4, Neosepta AMX, Fumasep FAS, Fumasep FAB , Fumasep FAD, Fumasep FAP and Fumasep FAA-3.

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