KR102572208B1 - 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 REGENERATING IRON 2,3-DIMERCAPTO-1-PROPANESULFONIC ACID ABSORBENT BY ELECTROCHEMICAL REACTION USING ACTIVATED CARBON}

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

Industrial exhaust gases from the combustion process of fossil fuels may contain excessive amounts of 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 between nitrogen and oxygen contained in the excess air supplied, and the reaction between the nitrogen component contained in the fuel and the oxygen contained in the excess air. Nitrogen oxide is a precursor of fine dust and 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, sulfur oxides generated in the combustion process are mostly sulfur dioxide (SO ₂ ), which is mainly produced by the reaction of sulfur-containing fossil fuels and oxygen contained in excess air. Because sulfur dioxide is highly water-soluble, most of it is absorbed into the body by breathing and irritates mucous membranes such as the bronchi, eyes, and nose. In addition, chronic exposure to sulfur dioxide can cause 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 rear end of a boiler or furnace. The selective catalytic reduction method can effectively remove nitrogen oxides, but increases equipment costs and power consumption. In the case of the selective non-catalytic reduction method, equipment costs are low and power consumption is low, but it may be difficult to secure a denitrification efficiency of 50% or more.

Sulfur oxides are mostly removed through flue gas desulfurizer (FGD), and flue gas desulfurization facilities are largely divided into wet and dry desulfurization methods. About 87% of them are operated as wet desulfurization facilities worldwide. This process is operated by cleaning and absorbing sulfur oxides contained in exhaust gas with an alkaline solution. It is highly efficient and easy to operate, but the installation cost is high and wastewater secondary pollutants such as

In addition, a technology that can simultaneously remove nitrogen oxides and sulfur oxides in one facility is being developed, and oxidizing agents, adsorbents, and absorbents are used. The exhaust gas removal process using an oxidizing agent is efficient, but a continuous supply of the oxidizing agent is essential. Processes using adsorbents require regeneration of the adsorbent. The process using an absorbent is highly efficient and it is easy to convert the captured nitrogen oxides into other materials for recycling, but it is essential to regenerate the absorbent oxidized by the exhaust gas.

Recently, as the emission standards for soluble harmful gases included in exhaust gas have been strengthened, field application of 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, it is essential to reuse the absorbent, and accordingly, it is necessary to develop an absorbent regeneration technology for 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.

An apparatus for regenerating an absorbent according to an embodiment of the present invention is for continuously using the absorbent used in the treatment of industrial exhaust gas by reducing the oxidized absorbent while absorbing soluble harmful gases in order to reuse the absorbent semi-permanently.

An apparatus for regenerating an absorbent according to an embodiment of the present invention is for increasing the redox potential of the absorbent by means of activated carbon.

An apparatus for regenerating an absorbent according to an embodiment of the present invention is for separating the absorbent into iron and a chelate compound using activated carbon.

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

An apparatus for regenerating an absorbent according to an embodiment of the present invention is a filter for filtering finely powdered activated carbon and is for locally adjusting pH.

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

An apparatus for regenerating an absorbent according to an embodiment includes a reaction tank containing activated carbon, regenerating the absorbent and locally increasing the pH of the solution through a reduction electrode of the reaction tank, adjusting the pH of the absorbent by an oxidation electrode, The absorbent discharged from the absorption tower flows into the reaction tank and reacts, and the sulfur oxides absorbed in the absorption tower exist as sulfur trioxide ions (SO ₃ ^2- ) and flow into the reaction tank to be 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 electrical energy to increase the reduction rate, and the pH is adjusted by a micro-sized filter between the outlet and the reaction tank. It can be locally polarized, and 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 flow from the absorption tower, a reaction tank filled with activated carbon, a reduction electrode inside the reaction tank, and an outlet through which the regenerated absorbent is re-supplied to the absorption tower, in the form of fine particles. A micro-size filter capable of filtering phosphorus activated carbon may be included, and an anode may be included opposite 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 ^° C. or higher.

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

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

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

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

Inside the reactor, sulfur trioxide ions act as a reducing agent under activated carbon catalyst to convert ferric and ferric-2,3-dimercapto-1-propanesulfonic acid into ferrous and ferrous-2,3-dimercapto- It can be reduced to the 1-propanesulfonic acid form to produce sulfate.

Inside the reactor, sulfur trioxide ions act as a reducing agent under the activated carbon catalyst to reduce ferrous-2,3-dimercapto-1-propanesulfonic acid containing disulfide bonds and generate sulfate.

Absorbed sulfur oxides exist in the form of sulfur trioxide ions in the solution, act as a reducing agent, and are converted to sulfate, and can continuously absorb sulfur oxides in the absorption tower.

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

Water decomposition may occur by the reduction electrode, 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 hydrogen ions may be consumed to locally increase the pH of the solution inside the micro-size filter.

Water decomposition may occur by the anode, and the pH of the solution outside the micro-size filter may locally decrease due to consumption of hydroxide ions.

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

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

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

Concentration of the absorbent, pH, size of the reaction tank, and particle size of the activated carbon may be adjusted in response to the regeneration rate of the absorbent.

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

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

1 is a schematic diagram showing a regeneration reactor for an electrochemical-based absorbent according to an embodiment.
2 is an electrochemical oxidation of ferrous iron and ferric 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 pH change.

With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein. In order to clearly describe 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 widely known known technologies, detailed descriptions thereof will be omitted.

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

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 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 flows, a mesh network 20, activated carbon 30, a reducing electrode 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 detail with reference to FIG. 1 .

In the electrochemical-based absorbent regenerator 100, the reduction electrode 40 and the oxidation electrode 60 can transfer electrons by the power supply 70, and the spontaneous reaction between sulfur trioxide present in the solution and the oxidized absorbent The absorbent can be regenerated by Sulfur trioxide is above about 0.5 M, and the concentration can be increased up to the solubility of sulfur trioxide. 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 oxidation-reduction reaction rate, so using the highest concentration as possible can increase the reaction efficiency. The absorbent may contain a high concentration of sulfur trioxide, greater than about 0.5 M, and about 0.1 M iron-2.3-dimercapto-1-propanesulfonic acid. The electrochemical-based absorbent regeneration apparatus 100 may be used to regenerate an absorbent used in treating industrial exhaust gas. In addition, the electrochemical-based absorbent regenerator 100 can be used in a process associated with processing industrial exhaust gas. When the electrochemical-based absorbent regenerator 100 has a form in which the absorbent flows in a vertical direction, it may be advantageous to uniform fluid movement.

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

The mesh network 20 has pores having a particle size smaller than that of the activated carbon 30, and may include a metal material such as SUS 316, which is high-strength and less corrosive and can withstand the weight of the activated carbon and the fluid.

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 and the movement of the fluid is slow and a pressure drop may occur, activated carbon 30 having a large particle size may be used instead. Since the diameter of the mesh network 20 is sufficiently large, the fluid moves quickly and the pressure drop is not observed, but when the reaction rate is slow due to the reduced specific surface area, activated carbon 30 having a small particle size can be used instead.

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

The standard oxidation-reduction potential of sulfur trioxide 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)

As the pH of the absorbent is more acidic, the standard oxidation-reduction potential of sulfur trioxide ion compared to the standard hydrogen electrode is closer to about 0.172V, and as it is more basic, it is closer to about -0.93V. The theoretical potential difference between reduction of ferric iron bound to ferric-2,3-dimercapto-1-propanesulfonic acid is about 1.26V when the pH is basic.

The activated carbon 30 may separate ferric-2,3-dimercapto-1-propanesulfonic acid into ferric iron and 2,3-dimercapto-1-propanesulfonic acid, respectively.

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

Fe ³⁺ + e ^- → Fe ²⁺ (E ⁰ /V = 0.771)

Ferric iron, which may be present separately under the activated carbon 30 catalyst, may be spontaneously reduced by sulfur trioxide ions. When the pH is basic conditions, the theoretical potential difference for reducing ferric iron is about 1.701 V, and the reaction can occur at a faster rate than in the case of reducing ferric-2,3-dimercapto-1-propanesulfonic acid. . The reduced ferric iron escapes from the influence of the activated carbon 30 catalyst and escapes through the outlet 80, recombines 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 reduction electrode 40 is a negative electrode, and includes a porous metal material, and may be used in a multi-stage type inside a reaction vessel containing activated carbon. The absorbent can easily pass through the reduction electrode (40). The absorbent contacts activated carbon with a large surface area to separate ferric iron and 2,3-dimercapto-1-propanesulfonic acid, and the redox reaction can be maximized.

When voltage is applied between the reduction electrode 40 and the oxidation electrode 60 by the power supply 70, hydroxide ions (OH ^- ) can be generated around the reduction electrode 40, and the pH of the absorbent is may increase negatively. The cathode 40 may include one or more of titanium (Ti), chromium (Cr), copper (Cu), carbon-based, platinum-based metal materials, and the like, which are less corrosive. 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 flowing into the reaction tank filled with the activated carbon 30 may have a local pH, and when it exits the outlet 80, the water decomposition reaction around the oxidation electrode 60 pH can be neutralized by hydrogen ions generated 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 with 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.

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

When a voltage is applied between the reduction electrode 40 and the oxidation electrode 60 by the power supply 70, the following reaction may occur around the reduction electrode 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 voltage is applied to the reduction electrode 40 and the oxidation electrode 60 by the power supply 70, the following reaction may occur around the oxidation electrode 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 reduction of ferric iron, reduction of iron may occur around the reduction electrode 40, and decomposition of water may occur around the oxidation electrode 60.

When a voltage of about 2.058 V or higher is applied to locally maintain the pH of the absorbent in a basic condition, hydroxide ions due to decomposition of water are generated around the reduction electrode 40 and hydrogen due to decomposition of water around the oxidation electrode 60 ions can be formed.

The electrochemical-based absorbent regeneration device 100 converts ferric-2,3-dimercapto-1-propanesulfonic acid contained in the absorbent by activated carbon 30 into ferric and 2,3-dimercapto- Separation into 1-propanesulfonic acid, respectively, can be made so that the reduction of ferric iron can occur at a high rate by using sulfur trioxide ion as a reducing agent. In addition, the electrochemical-based absorbent regeneration device 100 can make 2,3-dimercapto-1-propanesulfonic acid containing a disulfide bond reduced 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 embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also made according to the present invention. falls within the scope of the rights of

100: absorbent regeneration device 10: inlet
20: mesh net 30: activated carbon
40: reduction electrode 50: micro size filter
60: oxidation electrode 70: power supply
80: outlet

Claims (14)

A reaction tank in which an absorbent is introduced and activated carbon is filled therein;
A porous reduction electrode located inside the reaction tank and in contact with the activated carbon,
A porous oxidation electrode separated from the inside of the reaction vessel;
A micro-size filter located between the reduction electrode and the oxidation electrode and separating the oxidation electrode and the reduction electrode, and
A power supply device for supplying electric energy to the reduction electrode and the oxidation electrode
including,
Regenerating ferric and ferric-2,3-dimercapto-1-propanesulfonic acid by an electrochemical redox reaction using the activated carbon as a catalyst,
The reduction electrode includes a first reduction electrode and a second reduction electrode connected to each other in a multi-stage structure, the second reduction electrode is located on the first reduction electrode, and the micro-size filter is located on the second reduction electrode ,
The first reduction electrode and the second reduction electrode regenerate the absorbent in contact with the activated carbon inside the reaction tank.
In paragraph 1,
The reduction electrode located inside the reaction vessel includes a porous metal through which fluid can pass,
Absorbent regeneration device further comprising a mesh network having pores smaller than the particle size of the activated carbon.
In paragraph 1,
The micro-size filter includes a micro-size pore through which the fluid passes, and the absorbent regeneration device separates the inside and the outside of the reaction tank.
In paragraph 1,
An apparatus for regenerating an absorbent in which the external pH of the reaction tank separated by the micro-size filter is locally reduced by hydrogen ions supplied by the anode.
In paragraph 1,
An absorbent recycling device in which the oxidized absorbent flowing into the reactor is reduced before passing through the micro-size filter.
In paragraph 1,
An absorbent regeneration device in which ferric-2,3-dimercapto-1-propanesulfonic acid is separated into ferric iron and 2,3-dimercapto-1-propanesulfonic acid, respectively, by the activated carbon.
In paragraph 6,
An apparatus for regenerating an absorbent in which the standard redox potential of iron separated by the activated carbon is increased and the absorbent is regenerated through a redox reaction with sulfur trioxide present in the absorbent.
In paragraph 6,
An absorbent regeneration device in which the standard oxidation-reduction potential of iron separated by the activated carbon increases.
delete In paragraph 1,
The absorbent regeneration device, wherein the reduction electrode located inside the reaction tank contains at least one of titanium (Ti), chromium (Cr), copper (Cu), a carbon-based metal, or a platinum-based metal.
In paragraph 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 reduction electrode.
A reactor into which an absorbent containing iron-2,3-dimercapto-1-propanesulfonic acid is introduced,
A reduction electrode in contact with activated carbon filled in the reaction tank;
An oxidation electrode that is separated from the inside of the reaction tank and adjusts the pH of the absorbent;
A micro-size filter positioned between the reduction electrode and the oxidation electrode to locally polarize the pH, and
A power supply for supplying electric energy to the cathode and the anode;
including,
The sulfur oxides flowing into the reactor exist as sulfur trioxide ions (SO ₃ ^2- ) and are used as a reducing agent, and the oxidized ferric (Fe ³⁺ )-based absorbent is reduced to a ferrous (Fe ²⁺ ) absorbent,
The reduction electrode includes a first reduction electrode and a second reduction electrode connected to each other in a multi-stage structure, the second reduction electrode is located on the first reduction electrode, and the micro-size filter is located on the second reduction electrode ,
The first reduction electrode and the second reduction electrode regenerate the absorbent in contact with the activated carbon inside the reaction tank.
In paragraph 12,
Water decomposition occurs by the reduction electrode, hydroxide ions are generated to locally increase the pH of the solution inside the micro-size filter, and hydrogen ions are consumed to locally increase the pH of the solution inside the micro-size filter. playback device.
In paragraph 12,
Water decomposition occurs by the anode, 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. A device for regenerating the absorbent.