KR20220139663A - Apparatus and method for regenerating iron 2,3-dimercapto-1-propanesulfonic acid absorbent by electrochemical reaction using activated carbon - Google Patents

Abstract

An apparatus and method capable of regenerating an absorbent capable of simultaneously absorbing nitrogen oxides and sulfur oxides using electrochemical-based activated carbon are provided. Absorbent components that can be oxidized can be regenerated through activated carbon and electrochemical reactions. When nitrogen oxides and sulfur oxides contained in exhaust gas are treated based on an absorbent, nitrogen oxides and sulfur oxides can be removed through a continuous process.

Description

Apparatus and method for regeneration of iron-2,3-dimercapto-1-propanesulfonic acid absorbent by electrochemical reaction using activated carbon ACTIVATED CARBON}

An apparatus and method for regenerating an absorbent that is oxidized during treatment of soluble harmful gas contained in industrial exhaust gas are provided.

Industrial exhaust gases from the combustion process of fossil fuels may contain excess nitrogen oxides and sulfur oxides. Nitrogen oxides generated in the combustion process are mostly nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ). These nitrogen oxides are mainly produced by the reaction of nitrogen and oxygen contained in the excess air supplied, and the reaction of nitrogen contained in the fuel with oxygen contained in the excess air. Nitrogen oxide is a precursor of fine dust that causes respiratory and cardiovascular diseases, reacts with water to produce nitric acid, and is a major cause of acid rain, which can cause dermatitis and hair loss.

In addition, most of the sulfur oxides generated in the combustion process are sulfur dioxide (SO ₂ ), which is mainly produced by the reaction of sulfur-containing fossil fuels with oxygen contained in excess air. Since sulfur dioxide is highly water-soluble, most of sulfur dioxide is absorbed into the human body by respiration and irritates the mucous membranes of the bronchi, eyes, and nose. In addition, chronic exposure to sulfur dioxide causes the onset of diseases such as pneumonia, bronchitis, asthma, and emphysema.

Currently, most of the nitrogen oxides emitted are removed through a post-combustion removal process. For example, selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) is mostly used at the downstream stage of a boiler or combustion furnace. The selective catalytic reduction method can effectively remove nitrogen oxides, but increases equipment cost and power consumption. In the case of the selective non-catalytic reduction method, although the equipment cost is low and the power consumption is small, it may be difficult to secure a denitration efficiency of 50% or more.

Most of the sulfur oxides are removed through flue gas desulfurizers (FGDs), and flue gas desulfurization facilities are largely divided into wet and dry desulfurization methods. About 87% of the world is operated as wet desulfurization facilities, and this process is operated by cleaning and absorbing sulfur oxides contained in exhaust gas with an alkaline solution. Secondary pollutants such as

In addition, a technology that can simultaneously remove nitrogen oxides and sulfur oxides in one facility is under development, and oxidizing agents, adsorbents, and absorbents are used. The exhaust gas removal process using an oxidizing agent is efficient, but continuous supply of the oxidizing agent is essential. Processes using adsorbents require regeneration of adsorbents. The process using the absorbent has excellent efficiency and is easy to use as a resource by converting the collected nitrogen oxides into other materials, but regeneration of the absorbent oxidized by exhaust gas is essential.

Recently, as the emission standards for soluble harmful gases included in exhaust gas have been strengthened, the field application of the simultaneous treatment and removal technology for nitrogen oxides and sulfur oxides is urgently needed, but commercialization is non-existent. In order to commercialize an efficient and easy-to-apply absorbent-based exhaust gas treatment process, the reuse of the absorbent is essential. Accordingly, it is necessary to develop an absorbent regeneration technology for the continuous use of the absorbent.

Spray absorption and electrochemical reduction of nitrogen oxides from flue gas. Environ. Sci. Technol., 2013, 476(16), 9514-9522. Kinetics of the [Fe(III)-EDTA]-reduction by sulfite under the catalysis of activated carbon. Energy Fuels., 2011, 25.10: 4248-4255. Integrated tests for removal of nitric oxide with iron thiochelate in wet flue gas desulfurization systems. Environ. Sci. Technol, 1996, 30.11: 3371-3376.

The apparatus for regenerating an absorbent according to an embodiment of the present invention is to reduce the oxidized absorbent while absorbing the soluble harmful gas in order to semi-permanently reuse the absorbent used in the treatment of industrial exhaust gas to continuously use it.

The apparatus for regenerating the absorbent according to an embodiment of the present invention is to increase the redox potential of the absorbent by activated carbon.

The apparatus for regenerating the absorbent according to an embodiment of the present invention is to separate the absorbent into iron and a chelate compound by activated carbon, respectively.

The apparatus for regenerating an absorbent according to an embodiment of the present invention is to increase the regeneration rate of the absorbent by an electrochemical reaction.

The apparatus for regenerating the absorbent according to an embodiment of the present invention is to locally adjust the pH with a filter for filtering fine powder activated carbon.

In addition to the above problems, the embodiment according to the present invention may be used to achieve other problems not specifically mentioned.

The apparatus for regenerating the absorbent according to an embodiment includes a reaction tank containing activated carbon, and locally increases the regeneration and solution pH of the absorbent through the cathode of the reaction tank, and adjusts the pH of the absorbent by the anode, The absorbent discharged from the absorption tower flows into the reaction tank and reacts, and the sulfur oxide absorbed in the absorption tower exists as sulfur trioxide ions (SO ₃ ^2- ), flows into the reaction tank and is used as a reducing agent, and oxidized ferric iron (Fe ³⁺ ) )-based absorbent is reduced to a ferrous (Fe ²⁺ ) absorbent, and the reduction rate of ferric iron is increased by using electric energy to increase the reduction rate, and the pH is adjusted by a micro-size filter between the outlet and the reaction tank. It can be locally polarized, the oxidized chelate compound is regenerated into a reduced chelate compound, and the regenerated absorbent is re-introduced into the absorption tower and circulated.

The reaction tank includes an inlet through which a reducing agent and an oxidized absorbent are introduced from the absorption tower, a reaction tank filled with activated carbon, a reduction electrode inside the reaction tank, an outlet through which the regenerated absorbent is re-supplied to the absorption tower, fine particle form It may include a micro-size filter capable of filtering phosphorus activated carbon, and an anode opposite to the micro-size filter.

The absorbent supplied from the absorption tower may react with the high temperature exhaust gas to maintain a temperature of about 60 ^o C or higher.

The absorbent may include iron-2,3-dimercapto-1-propanesulfonic acid.

The oxidized absorbent may comprise ferric-2,3-dimercapto-1-propanesulfonic acid, or ferric-2,3-dimercapto-1-propanesulfonic acid comprising disulfide bonds.

Ferric-2,3-dimercapto-1-propanesulfonic acid is separated into ferric iron and 2,3-dimercapto-1-propanesulfonic acid, respectively, so that the oxidation-reduction potential of the separated ferric iron is increased. can

The absorbent is ferrous-2,3-dimercapto-1-propanesulfonic acid, ferric-2,3-dimercapto-1-propanesulfonic acid, ferrous-2,3- containing disulfide bonds. Dimercapto-1-propanesulfonic acid, ferrous-2,3-dimercapto-1-propanesulfonic acid-nitrous oxide, nitrous oxide, sulfur trioxide ions present by dissolving sulfur oxides, and sulfur trioxide ions in an oxidized form Sulfate (SO ₄ ^2- ) may be included.

In the reactor, sulfur trioxide ions act as reducing agents under activated carbon catalyst to convert ferric and ferric-2,3-dimercapto-1-propanesulfonic acid into ferrous and ferrous-2,3-dimercapto- Reduction to the form of 1-propanesulfonic acid can form sulfate salts.

In the reaction tank, sulfur trioxide ions act as a reducing agent under an activated carbon catalyst to reduce ferrous-2,3-dimercapto-1-propanesulfonic acid containing a disulfide bond, thereby generating sulfate.

The absorbed sulfur oxides exist in the form of sulfur trioxide ions in the solution, act as a reducing agent, are converted into sulfates, and can continuously absorb sulfur oxides in the absorption tower.

Ferric separated from ferric-2,3-dimercapto-1-propanesulfonic acid by the cathode may be reduced to ferrous iron.

Water decomposition may occur by the cathode, and hydroxide ions may be generated to locally increase the pH of the solution inside the micro-size filter.

Water decomposition may occur by the cathode, and the pH of the solution inside the micro-size filter may increase locally as hydrogen ions are consumed.

Water decomposition may occur by the anode, and hydroxide ions may be consumed, so that the pH of the solution outside the micro-size filter may decrease locally.

Water decomposition may occur by the anode, and hydrogen ions may be generated to locally decrease the pH of the solution outside the micro-size filter.

Sulfur trioxide may be oxidized in the form of sulfate by the anode.

The pH of the absorbent may be slightly basic between pH 8-9.

The concentration of the absorbent, the pH, the size of the reactor, and the particle size of the activated carbon may be adjusted in response to the regeneration rate of the absorbent.

The voltage between the anode and cathode may be adjusted in response to the regeneration rate of the absorbent.

The apparatus for regenerating the absorbent according to an embodiment of the present invention can regenerate the absorbent oxidized in the absorption tower through a reaction tank filled with activated carbon, and increase the oxidation-reduction potential of the absorbent by using the activated carbon, the anode electrode The absorbent can be regenerated by the voltage supplied between the anode and the cathode, the pH of the absorbent can be locally increased and decreased, and the concentration, pH, voltage between the anode and the cathode, and the particle size of the activated carbon can be changed. The regeneration rate can be adjusted, the sulfur oxides contained in the exhaust gas can be finally converted to sulfate and removed, and the absorbent can be used semi-permanently.

1 is a schematic diagram showing a regeneration reaction tank of an electrochemical-based absorbent according to an embodiment.
Figure 2 is an electrochemical oxidation of ferrous and ferrous iron present in ferrous-2,3-dimercapto-1-propanesulfonic acid and ferric-2,3-dimercapto-1-propanesulfonic acid; It is a graph showing the reduction potential.
3 is a graph showing the redox potential of ferric-2,3-dimercapto-1-propanesulfonic acid containing a disulfide bond according to a change in pH.

With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of a well-known known technology, a detailed description thereof will be omitted.

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

Then, an apparatus and method for regenerating an absorbent containing iron-2,3-dimercapto-1-propanesulfonic acid by an electrochemical reaction using activated carbon according to an embodiment will be described in detail.

1 is a view showing a reaction tank based on electrochemistry for the regeneration of ferric-2,3-dimercapto-1-propanesulfonic acid according to an embodiment.

Referring to FIG. 1 , the electrochemical-based absorbent regeneration apparatus 100 according to the embodiment includes an inlet 10 through which the absorbent is introduced, a mesh network 20, activated carbon 30, a cathode 40, and a micro-size filter. 50 , an anode 60 , a power supply 70 , and an outlet 80 .

A process of regenerating the absorbent will be described in more detail with reference to FIG. 1 .

In the electrochemical-based absorbent regeneration device 100, the anode 40 and the anode 60 can transfer electrons by the power supply device 70, and in the spontaneous reaction of the oxidized absorbent with sulfur trioxide present in the solution. The absorbent can be regenerated by Sulfur trioxide is about 0.5M or more, and the concentration can be increased up to the solubility of sulfur trioxide. The iron-2,3-dimercapto-1-propanesulfonic acid is about 0.1 M or more, and the concentration can be increased up to the solubility of iron-2,3-dimercapto-1-propanesulfonic acid. The higher the concentration of sulfur trioxide and iron-2,3-dimercapto-1-propanesulfonic acid, the faster the redox reaction rate. The absorbent may contain a high concentration of about 0.5 M or more of sulfur trioxide and about 0.1 M of iron-2.3-dimercapto-1-propanesulfonic acid. The electrochemical-based absorbent regeneration apparatus 100 may be used for regeneration of an absorbent used in the treatment of industrial exhaust gas. In addition, the electrochemical-based absorbent regeneration apparatus 100 may be used for processing industrial exhaust gas and related processes at the same time. When the electrochemical-based absorbent regenerating apparatus 100 has a form in which the absorbent is introduced in a vertical direction, it may be advantageous for uniform fluid movement.

The inlet 10 may be uniformly supplied in the direction in which the activated carbon 30 is present. At this time, using a mesh network having a smaller void than the activated carbon 30, the fluid may pass through, but the activated carbon may have a structure that does not settle in the inlet 10 direction by gravity.

The mesh network 20 has pores having a smaller particle size than the activated carbon 30 , and may include a metal material such as SUS 316 with high strength capable of withstanding the weight of activated carbon and fluid and less corrosive.

The activated carbon 30 may have a uniform particle size of about 4 to 8 mesh sizes. When the diameter of the mesh network 20 is sufficiently small, the movement of the fluid is slow and the pressure drop can appear, it can be replaced with the activated carbon 30 having a large particle size. Since the diameter of the mesh network 20 is sufficiently large, the fluid movement is fast and the pressure drop is not observed, but when the reaction rate is slow due to a decrease in specific surface area, it can be used instead of activated carbon 30 having a small particle size.

The oxidation-reduction potential of iron bound to ferrous-2,3-dimercapto-1-propanesulfonic acid and ferric-2,3-dimercapto-1-propanesulfonic acid is based on the results of FIG. 2 . It is about 0.11V compared to the electrode (Ag/AgCl) and about 0.33V compared to the standard hydrogen electrode.

The standard redox potential of sulfur trioxide ions present in the absorbent is as follows compared to the standard hydrogen electrode.

SO ₄ ^2- + H ₂ O + 2e ^- → SO ₃ ^2- + 2OH ^- (E ⁰ /V = -0.93)

SO ₄ ^2- + 4H ⁺ + 2e ^- → H ₂ SO ₃ + H ₂ O (E ⁰ /V = 0.172)

The more acidic the pH of the absorbent, the closer the standard redox potential of sulfur trioxide ions compared to the standard hydrogen electrode is about 0.172V, and the more basic it is, the closer to about -0.93V. When the pH is basic, the reduced theoretical potential difference of ferric iron bound to ferric-2,3-dimercapto-1-propanesulfonic acid is about 1.26V.

Activated carbon 30 can separate ferric-2,3-dimercapto-1-propanesulfonic acid into ferric and 2,3-dimercapto-1-propanesulfonic acid, respectively.

The standard oxidation-reduction potentials of ferrous and ferric iron are as follows compared to the standard hydrogen electrode.

Fe ³⁺ + e ^- → Fe ²⁺ (E ⁰ /V = 0.771)

The ferric iron that may exist separately under the activated carbon 30 catalyst may be spontaneously reduced by sulfur trioxide ions. When the pH is a basic condition, the theoretical potential difference at which ferric iron is reduced is about 1.701 V, and the reaction can occur at a faster rate than when ferric-2,3-dimercapto-1-propanesulfonic acid is reduced. . The reduced ferric iron escapes the influence of the activated carbon 30 catalyst and exits the outlet 80, and is recombined with 2,3-dimercapto-1-propanesulfonic acid, and ferric-2,3-dimer It can be regenerated in the form of capto-1-propanesulfonic acid.

The cathode 40 is a cathode, and includes a porous metal material, and may be used in a multi-stage type inside a reaction tank containing activated carbon. The absorbent can easily pass through the cathode 40 . The absorbent is contacted with activated carbon having a large surface area to separate ferric iron and 2,3-dimercapto-1-propanesulfonic acid, and the redox reaction can be maximized.

When a voltage is applied between the cathode 40 and the anode 60 by the power supply device 70, hydroxide ions (OH ⁻ ) may be generated around the cathode 40, and the pH of the absorbent is local. may increase exponentially. The cathode 40 may include one or more corrosive titanium (Ti), chromium (Cr), copper (Cu), carbon-based, platinum-based metal materials, and the like. The point where the reduction reaction of the solution occurs is inside the activated carbon 30 separated by the micro-size filter 50 , and the point where the oxidation reaction occurs is around the outlet 80 separated by the micro-size filter 50 . Since the fluid is continuously circulated, the absorbent introduced into the reaction tank filled with the activated carbon 30 may have a basic pH locally, and when exiting the outlet 80 , the water decomposition reaction around the anode 60 The pH can be neutralized by hydrogen ions produced by

Oxidized 2,3-dimercapto-1-propane bound to ferrous-2,3-dimercapto-1-propanesulfonic acid and ferric-2,3-dimercapto-1-propanesulfonic acid The sulfonic acid may be in the form of 2,3-dimercapto-1-propanesulfonic acid containing a disulfide bond, and may be reduced under basic conditions having a pH of 9 or higher. The oxidation-reduction potential is about -0.73V compared to the reference electrode (Ag/AgCl) and about -0.51V compared to the standard hydrogen electrode according to the results of FIG. 3 .

The more acidic the pH of the absorbent, the closer the standard redox potential of sulfur trioxide ions compared to the standard hydrogen electrode is about 0.172V, and the more basic it is, the closer to about -0.93V. The pH can be locally increased by water decomposition around the reduction electrode 40, and when the pH is a basic condition, 2,3-dimercapto-1-propanesulfonic acid including a disulfide bond is reduced theoretically The phosphorus potential difference is about 0.42V. Sulfur trioxide ions present in the absorbent can serve as a reducing agent for 2,3-dimercapto-1-propanesulfonic acid containing a disulfide bond, and is slower than the reduction rate of ferric iron but contains a disulfide bond. 3-dimercapto-1-propanesulfonic acid can be reduced spontaneously.

When a voltage is applied between the anode 40 and the anode 60 by the power supply device 70, the following reaction may occur around the cathode 40.

Fe ³⁺ + e ^- → Fe ²⁺ (E ⁰ /V = 0.771)

H ₂ O + e ^- → ½ H ₂ + OH ^- (E ⁰ /V = -0.829)

When a voltage is applied to the cathode 40 and the anode 60 by the power supply device 70 , the following reaction may occur around the anode 60 .

O ₂ + 4H ⁺ + 4e ^- → 2H ₂ O (E ⁰ /V = 1.229)

When a voltage of about 0.46 V or more is applied for the reduction of ferric iron, reduction of iron may occur around the cathode 40, and decomposition of water may occur around the anode 60.

In order to maintain the pH of the absorbent in a local basic condition, when a voltage of about 2.058 V or more is applied, hydroxide ions due to decomposition of water around the cathode 40, and hydrogen due to decomposition of water around the anode 60 Ions may be formed.

The electrochemical-based absorbent regenerating device 100 uses activated carbon 30 to convert ferric-2,3-dimercapto-1-propanesulfonic acid contained in the absorbent with ferric and 2,3-dimercapto- By separating each 1-propanesulfonic acid, the reduction of ferric iron using sulfur trioxide ion as a reducing agent can be made to occur at a high rate. In addition, the electrochemical-based absorbent regeneration device 100 can be made to reduce 2,3-dimercapto-1-propanesulfonic acid including a disulfide bond by using sulfur trioxide ion as a reducing agent, and the electrochemical reaction Through this, the reduction rate of ferric iron can be maximized.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

100: absorbent regeneration device 10: inlet
20: mesh network 30: activated carbon
40: cathode 50: micro-size filter
60: anode 70: power supply
80: outlet

Claims (14)

Reactor tank in which absorbent is introduced and activated carbon is filled inside;
A porous reduction electrode located inside the reactor and in contact with the activated carbon,
A porous anode separated from the inside of the reaction tank,
A micro-size filter that is positioned between the cathode and the anode and separates the cathode and the anode;
A power supply for supplying electrical energy to the cathode and the anode, and
Mesh network having pores smaller than the particle size of the activated carbon
including,
An absorbent regeneration device for regenerating ferric iron and ferric-2,3-dimercapto-1-propanesulfonic acid by electrochemical redox reaction using the activated carbon as a catalyst.
In claim 1,
The regenerating device of the absorbent comprising a porous metal through which the cathode located inside the reaction tank can pass a fluid.
In claim 1,
The micro-size filter includes micro-sized pores through which the fluid passes, and the absorbent regeneration device separates the inside and the outside of the reactor.
In claim 1,
An absorbent regeneration device for recovering the pH by locally reducing the external pH of the reaction tank separated by the micro-size filter by the hydrogen ions supplied by the anode.
In claim 1,
An absorbent regeneration device for reducing the oxidized absorbent flowing into the reaction tank before it exits through the micro-size filter, and recovering the pH after it exits.
In claim 1,
An apparatus for regenerating an absorbent in which ferric-2,3-dimercapto-1-propanesulfonic acid is separated into ferric iron and 2,3-dimercapto-1-propanesulfonic acid by the activated carbon, respectively.
In claim 6,
An absorbent regeneration device in which the absorbent is regenerated through a redox reaction with sulfur trioxide present in the absorbent by increasing the standard redox potential of iron separated by the activated carbon.
In claim 6,
An absorbent regeneration device in which the regeneration rate of the absorbent is increased by receiving electrons supplied from the anode by increasing the standard oxidation-reduction potential of iron separated by the activated carbon.
In claim 6,
The standard oxidation-reduction potential of iron separated by the activated carbon increases and the absorbent is regenerated through a redox reaction with sulfur trioxide present in the absorbent, and the absorbent regeneration rate increases by receiving electrons supplied from the anode Device.
In claim 1,
The regenerating device of the absorbent wherein the cathode located inside the reaction tank includes one or more titanium (Ti), chromium (Cr), copper (Cu), carbon-based metal, or platinum-based metal.
In claim 10,
An absorbent regeneration device in which the internal pH of the reaction tank separated by the micro-size filter is locally increased by the hydroxide ions supplied by the cathode.
a reactor into which an absorbent containing iron-2,3-dimercapto-1-propanesulfonic acid is introduced;
a cathode in contact with the activated carbon filled in the reaction tank;
an anode separated from the inside of the reaction tank and controlling the pH of the absorbent;
A micro-size filter that is located between the cathode and the anode and locally polarizes the pH, and
a power supply for supplying electrical energy to the cathode and the anode;
including,
The sulfur oxide introduced into the reaction tank exists as sulfur trioxide ions (SO ₃ ^2- ) and is used as a reducing agent, and the oxidized ferric (Fe ³⁺ )-based absorbent is a ferrous (Fe ²⁺ ) absorbent that is reduced to a ferrous (Fe 2+) absorbent. playback device.
In claim 12,
Water decomposition occurs by the cathode, and hydroxide ions are generated to locally increase the pH of the solution inside the micro-size filter, and hydrogen ions are consumed to increase the pH of the solution inside the micro-size filter. playback device.
In claim 12,
Water decomposition occurs by the anode, and hydroxide ions are consumed to locally decrease the pH of the solution outside the micro-size filter, and hydrogen ions are generated to locally decrease the pH of the solution outside the micro-size filter. Absorbent regeneration device.

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