KR102558190B1 - Method for regenerating waste plate type SCR catalyst - Google Patents

Abstract

The present invention relates to a method for regenerating a waste plate-type SCR catalyst, comprising c) a second washing step of washing the waste plate-type selective catalytic reduction (SCR) catalyst with an aqueous solution containing an ammonium-based compound.

Description

Method for regenerating waste plate type SCR catalyst}

The present invention relates to a method for regenerating a waste plate type SCR catalyst.

Nitrogen oxides mainly mean NO and NO ₂ and are expressed as NOx. NO is a colorless, odorless gas that is readily converted to yellow-brown NO ₂ in the air. It also causes acid rain, and generates various oxidants such as O ₃ , HCHO, and PAN (peroxyacetyl nitrate) to cause secondary pollution and photochemical smog. N ₂ O is the most emitted component after CO ₂ and CH ₄ , which are representative greenhouse gases, and its global warming effect is 310 times higher than that of CO ₂ molecules.

Accordingly, various techniques for removing nitrogen oxides have been developed. Among them, selective catalytic reduction (SCR) catalyst technology is currently the only technology that can remove more than 90% of nitrogen oxides emitted from stationary sources.

As the SCR catalyst, a catalyst in which metals such as vanadium pentoxide (V ₂ O ₅ ) and tungsten oxide (WO ₃ ) are supported by using titanium dioxide (TiO ₂ ) as a support is widely used. Since vanadium and tungsten are expensive metals, it is necessary to regenerate and reuse an already used SCR catalyst in consideration of economic aspects while solving environmental pollution problems.

In order to regenerate and reuse the SCR catalyst, a process of removing inactive materials including fly ash, heavy metals such as arsenic, alkali metals, alkaline earth metals, and dust deposited on the catalyst body and imparting catalytic activity again is required.

Patent Document 1 (Korean Registered Patent Publication No. 10-0668936) discloses an SCR catalyst regeneration method for cleaning and eluting fly ash and alkali metals by flowing a mixed solution containing ammonium metavanadate solution, ammonium paratungstate, and sulfuric acid solution into a waste catalyst and generating bubbles, and at the same time supplementing catalytic activity.

However, according to Patent Document 1, a problem may occur that the active ingredient coats the inactive material by the mixed solution even before the inactive materials are removed, and a side reaction between the inactive material and the mixed liquid may cause salt to be generated. Moreover, there is also a problem that it is uneconomical because the inactive material is removed with a mixture containing expensive vanadium and tungsten.

Republic of Korea Patent Registration No. 10-0668936 (2007.01.08)

In order to solve the above problems, an object of the present invention is to provide a method for regenerating a waste plate-type SCR catalyst that can recover the activity of a waste catalyst whose catalytic activity has decreased due to physical poisoning such as plugging, masking, blocking, etc., and chemical poisoning by arsenic, alkali metal, alkaline earth metal, phosphorus, sulfur compound component, etc. to 90% or more of that of the new catalyst.

However, the above purpose is exemplary, and the technical spirit of the present invention is not limited thereto.

One aspect of the present invention for achieving the above object relates to a method for regenerating a waste plate-type SCR catalyst, including c) a secondary washing step of washing the waste plate-type selective catalytic reduction (SCR) catalyst with an aqueous solution containing an ammonium-based compound.

In the above aspect, the ammonium-based compound may be at least one selected from the group consisting of an ammonium carbonate-based compound, an ammonium bicarbonate-based compound, and an ammonium carbamate-based compound.

In the above aspect, the ammonium carbonate-based compound is ammonium carbonate, ethylammonium ethyl carbonate, isopropylammonium isopropylcarbonate, n-butylammonium n-butylcarbonate, isobutylammonium isobutylcarbonate, t-butylammonium t-butylcarbonate, 2-ethylhexylammonium 2-ethylhexylcarbonate, 2-methoxyethylammonium 2-methoxyethylcarbonate, octadecylammonium octadecylcarbonate, dibutylammonium dibutylcarbonate, dioctadecylammonium di It may be at least one selected from the group consisting of octadecyl carbonate, methyldecyl ammonium, methyldecyl carbonate, and triethylenediaminium isopropyl carbonate.

In the above aspect, the ammonium bicarbonate-based compound may be at least one selected from the group consisting of ammonium bicarbonate, isopropylammonium bicarbonate, t-butylammonium bicarbonate, 2-ethylhexylammonium bicarbonate, 2-methoxyethylammonium bicarbonate, dioctadecylammonium bicarbonate, and triethylenediaminium bicarbonate.

In one aspect, the ammonium carbamate-based compound is ammonium carbamate, ethylammonium ethyl carbamate, isopropylammonium isopropyl carbamate, n-butylammonium n-butyl carbamate, isobutylammonium isobutyl carbamate, t-butylammonium t-butyl carbamate, 2-ethylhexylammonium 2-ethylhexylcarbamate, octadecylammonium octadecylcarbamate, 2-methoxyethylammonium 2-methoxyethyl It may be at least one selected from the group consisting of carbamate, dibutyl ammonium dibutyl carbamate, dioctadecylammonium dioctadecylcarbamate, methyldecylammonium methyldecylcarbamate, and triethylenediaminium isopropyl bicarbamate.

In the above aspect, the concentration of the aqueous solution containing the ammonium-based compound may be 0.01 to 1 M.

In the above aspect, the method for regenerating the waste plate-type SCR catalyst may further include, before the second washing step, a) a physical cleaning step of supporting the waste SCR catalyst in a cleaning solution and injecting and bubbling air into the waste SCR catalyst.

In the above aspect, the cleaning solution may be deionized water, purified water, or industrial water.

In the above aspect, the method for regenerating the waste plate-type SCR catalyst may further include b) a first washing step of washing the cleaned waste plate-type SCR catalyst with pure water before and after the second washing step.

In the above aspect, the regeneration method of the waste plate-type SCR catalyst may include, after the second washing step, d) drying the second-washed waste plate-type SCR catalyst; and e) an activity recovery step of coating an active component on the dried waste flat plate-type SCR catalyst.

The method for regenerating the waste plate-type SCR catalyst according to the present invention has the advantage of being able to regenerate the catalyst so that it has a relative activity ( _KR /K ₀ ) of 0.94 or more and an SO ₂ conversion rate of less than 1% compared to the new catalyst by washing the waste plate-type SCR catalyst with an aqueous solution containing an ammonium compound.

1 is a flowchart illustrating a method for regenerating a waste plate-type SCR catalyst according to an embodiment of the present invention.
2 is a real picture of a sample of waste catalyst (used catalyst) before regeneration (Hadong Units 7 and 1) according to an example of the present invention.
3 is an X-ray diffraction analysis (XRD) result of waste catalyst samples (Hadong Units 7 and 1) before regeneration according to an example of the present invention.
4 is a real picture showing a state in which waste catalyst samples (Hadong Units 7 and 1) are fixed to a micro-reactor for performance evaluation.
5 is a result of analysis of the specific surface area (unit 1) of the new catalyst before use, the used catalyst, and the cleaned waste catalyst.
6 is a result of analysis of the specific surface area of the new catalyst before use, the spent catalyst used, and the cleaned waste catalyst (Unit 7).
7 shows the results of pore volume analysis (Unit 1) of the new catalyst before use, the used catalyst, and the cleaned waste catalyst.
8 shows the results of pore volume analysis (Unit 7) of the new catalyst before use, the used catalyst, and the cleaned waste catalyst.
9 shows the results of pore size analysis (Unit 1) of the new catalyst before use, the used catalyst, and the cleaned waste catalyst.
10 shows the results of pore size analysis (Unit 7) of the new catalyst before use, the used catalyst, and the cleaned waste catalyst.
11 is a result of analyzing the content of poisonous substances (Na ₂ O, K ₂ O, P ₂ O ₅ , As ₂ O ₃ , MgO) before and after cleaning of the spent catalyst and the cleaned waste catalyst (Unit 1).
FIG. 12 shows the results of analyzing the content of poisonous substances (Na ₂ O, K ₂ O, P ₂ O ₅ , As ₂ O ₃ , MgO) before and after cleaning of the spent catalyst and the cleaned waste catalyst (Unit 7).
13 is a result of analyzing the content of poisonous substances (SO ₃ , CaO, SiO ₂ , Al ₂ O ₃ ) of used and cleaned waste catalysts before and after cleaning (Unit 1).
14 shows the results of analyzing the content of poisonous substances (SO ₃ , CaO, SiO ₂ , Al ₂ O ₃ ) in the spent catalyst and the cleaned waste catalyst before and after cleaning (Unit 7).
15 is a result of analyzing the content of catalyst materials (V ₂ O ₅ , WO ₃ , MoO ₃ ) before and after cleaning of the spent catalyst and the cleaned waste catalyst (Unit 1).
FIG. 16 shows the analysis results (Unit 7) of catalyst material (V ₂ O ₅ , WO ₃ , MoO ₃ ) content of used and cleaned waste catalysts before and after cleaning.
17 is data showing the NOx removal efficiency and activity of the waste catalyst taken out from Unit 7, the regenerated catalyst and the new catalyst.
18 is data showing the SO _x conversion rates of the spent catalyst withdrawn from Unit 7, the regenerated catalyst obtained by regenerating the same, and the new catalyst.
19 is data showing the NOx removal efficiency and activity of the waste catalyst taken out from Unit 1, the regenerated catalyst and the new catalyst.
20 is data showing the SO _x conversion rates of the waste catalyst withdrawn from Unit 1, the regenerated catalyst obtained by regenerating the same, and the new catalyst.

Hereinafter, a method for regenerating a waste plate-type SCR catalyst according to the present invention will be described in detail. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Therefore, the present invention may be embodied in other forms without being limited to the drawings presented below, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, unless there is another definition in the technical terms and scientific terms used, they have meanings commonly understood by those of ordinary skill in the art to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings. Descriptions of known functions and configurations that may unnecessarily obscure will be omitted.

One aspect of the present invention relates to a method for regenerating a waste plate-type selective catalytic reduction (SCR) catalyst, comprising a second washing step of washing the waste plate-type selective catalytic reduction (SCR) catalyst with an aqueous solution containing an ammonium-based compound.

As such, the method for regenerating the waste plate-type SCR catalyst according to the present invention has the advantage of regenerating the catalyst so that the waste plate-type SCR catalyst has a relative activity ( _KR /K ₀ ) of 0.94 or more and a SO _x conversion rate of less than 1% compared to the new catalyst by washing the waste plate-type SCR catalyst with an aqueous solution containing an ammonium compound. At this time, in the relative activity ( _KR /K ₀ ), _KR is the activity of the regenerated waste catalyst, and K ₀ is the activity of the new catalyst.

For example, the ammonium-based compound may be at least one selected from the group consisting of an ammonium carbonate-based compound, an ammonium bicarbonate-based compound, and an ammonium carbamate-based compound. As a more specific example, the ammonium carbonate-based compound is ammonium carbonate, ethylammonium ethyl carbonate, isopropylammonium isopropylcarbonate, n-butylammonium n-butylcarbonate, isobutylammonium isobutylcarbonate, t-butylammonium t-butylcarbonate, 2-ethylhexylammonium 2-ethylhexylcarbonate, 2-methoxyethylammonium 2-methoxyethylcarbonate, octadecylammonium octadecylcarbonate, dibutylammonium dibutylcarbonate, dioctadecylammonium dioxane It may be at least one selected from the group consisting of tadecyl carbonate, methyldecylammonium methyldecyl carbonate, and triethylenediaminium isopropyl carbonate, and the ammonium bicarbonate-based compound may be at least one selected from the group consisting of ammonium bicarbonate, isopropylammonium bicarbonate, t-butylammonium bicarbonate, 2-ethylhexylammonium bicarbonate, 2-methoxyethylammonium bicarbonate, dioctadecylammonium bicarbonate, and triethylenediaminium bicarbonate, and the ammonium Carbamate compounds include ammonium carbamate, ethylammonium ethyl carbamate, isopropylammonium isopropylcarbamate, n-butylammonium n-butylcarbamate, isobutylammonium isobutylcarbamate, t-butylammonium t-butylcarbamate, 2-ethylhexylammonium 2-ethylhexylcarbamate, octadecylammonium octadecylcarbamate, 2-methoxyethylammonium 2-methoxyethylcarbamate, dibutyl ammonium dibutyl carbamate It may be at least one selected from the group consisting of barmate, dioctadecylammonium dioctadecylcarbamate, methyldecylammonium methyldecylcarbamate, and triethylenediaminium isopropyl bicarbamate. Preferably, in terms of securing better regeneration efficiency, the ammonium-based compound may be an ammonium carbonate-based compound.

In addition, the concentration of the ammonium-based compound-containing aqueous solution may be 0.01 to 1 M, more preferably 0.05 to 0.8 M, and more preferably 0.1 to 0.5 M. Regeneration efficiency may be more excellent in this range.

Meanwhile, in the method for regenerating a waste plate-type SCR catalyst according to an embodiment of the present invention, a cleaning step and a first washing step may be further performed before the second washing step, and a drying step and an activation step may be further performed after the second washing step.

As a specific example, the method for regenerating the waste plate-type SCR catalyst may further include, before the second washing step, a) a physical cleaning step of supporting the waste SCR catalyst in a cleaning solution and injecting and bubbling air into the waste SCR catalyst.

This step is a physical cleaning step for removing inactive substances such as fly ash, dust, heavy metals, alkali metals and alkaline earth metals, and sulfur compounds deposited on the waste catalyst. After supporting the waste SCR catalyst in the cleaning solution, it can be physically cleaned by air bubbling. In this case, the cleaning solution may be deionized water, purified water, or industrial water, and the temperature of the cleaning solution may be 20 to 40°C. The cleaning time is not particularly limited, and the cleaning may be performed until the slope of the graph does not change by measuring the pH and electrical conductivity of the cleaning solution.

Next, before the second washing step and after the washing step, b) a first washing step of washing the cleaned waste plate type SCR catalyst with pure water may be further performed. The first washing step is a step for removing inactive substances remaining in the waste catalyst, and can be washed using pure water such as deionized water or purified water.

Next, the above-described second washing step may be performed. After the second washing step, d) a drying step of drying the secondly washed waste plate-type SCR catalyst; and e) an activity recovery step of coating an active component on the dried waste plate-type SCR catalyst.

The drying step may be performed through methods and conditions commonly used in the art, and specifically, for example, drying may be performed at room temperature for 10 to 60 minutes.

Thereafter, an active component may be coated on the dried waste plate-type SCR catalyst to supplement the catalytically active component, thereby improving catalytic efficiency. The active component may be coated using an active solution, and the active solution may be a regeneration vandium-oxide mixing solution (RVMS) prepared by mixing VOS (Vanadyl Oxalate Solution), CeS (Cerium Nitrate Solution), SiS (Silicon binder Solution), and deionized water in consideration of the composition and desired catalyst concentration of the SCR catalyst.

Hereinafter, a method for regenerating a waste plate-type SCR catalyst according to the present invention will be described in more detail through examples. However, the following examples are only one reference for explaining the present invention in detail, but the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is merely to effectively describe specific embodiments and is not intended to limit the present invention. In addition, the unit of additives not specifically described in the specification may be % by weight.

1) Physical property analysis of waste catalyst:

go. Acquisition of catalyst samples for development of regeneration technology

In order to develop a regeneration technology for high-efficiency plate-type catalysts, waste plate-type SCR catalysts (Fig. 2) discarded after use in Hadong Thermal Power Plant Units 1 and 7 were procured, and physicochemical properties and catalyst performance were analyzed.

All of the waste catalysts were manufactured by Nano Co., Ltd. and installed and used in 2018, and the waste catalyst for Unit 7 was withdrawn in March 2020 and the waste catalyst for Unit 1 was withdrawn in November 2020. The waste catalyst of Unit 7 was taken out by 10 sheets each from more than 15 waste modules, and was mainly used for basic tests for the development of high-efficiency flat-plate regeneration technology. For Unit 1 waste catalyst, 2 small boxes (about 150 sheets) were taken out from one module and used to verify the developed regeneration technology.

For the data on the new catalyst for each unit, the quality data provided at the time of catalyst supply were referred to, and the NOx removal efficiency, SO _x conversion rate, and NH ₃ slip of the catalyst were referred to the official test evaluation result data.

me. Waste Catalyst Physical Property Analysis

While the high-efficiency plate-type catalyst was installed and operated in the SCR denitration system, the catalyst surface characteristics and chemical composition were analyzed to confirm the deterioration of the catalyst due to the operating environment and the physical and chemical changes caused by poisonous substances. For surface characterization, changes in the specific surface area, pore volume, and average pore size of the catalyst were measured through BET experiments, and changes in the composition of the catalyst were measured by X-ray fluorescence analysis. In addition, the degree of deactivation of the catalyst was examined by measuring the NOx removal efficiency of the waste catalyst.

a. Surface Characterization Analysis: The surface characteristics of the catalyst were analyzed using a surface characterization analyzer (Tristar II 3020 Micromeritics, USA) capable of analyzing the specific surface area and pore distribution characteristics.

In detail, 0.5 g of the sample prepared by cutting the waste catalyst sheet except for the upper edge hardening portion, pulverizing the catalyst material separated from the metal support with a mortar, and sieving into powder having a size of 80 to 300 μm was inserted into the cell and mounted. Mounted on the analyzer, the temperature was raised to 300 ° C., maintained for about 3 hours, and a de-gassing process was performed to desorb the adsorbed gas. As for the analysis conditions, 17 adsorption/desorption points were measured by nitrogen adsorption/desorption method. The surface characterization results of the spent catalyst are shown in Table 1 below.

exhalation Catalyst type specific surface area
(㎡/g) void volume
(cm3/g) pore size
(nm) Unit 1 new catalyst 71.5 0.26 12.73 waste catalyst 57.8 0.23 13.71 Unit 7 new catalyst 70.04 0.26 13.67 waste catalyst 52.58 0.23 16.06

Referring to Table 1, a decrease in specific surface area and pore volume, and an increase in average pore size were commonly observed in the waste catalyst taken out from all units compared to the new catalyst. The decrease in the specific surface area and pore volume is the result of the particle growth of relatively small particles of the catalyst carrier TiO ₂ and the blocking of the pores of the catalyst by fly ash or poisonous substances as the catalyst is exposed to a high temperature of 300 ° C or higher during use.

b. Chemical composition and phase analysis: The chemical composition of the waste catalyst was analyzed using an X-ray fluorescence spectrometer (Axios PANanlytical, Nederland) to investigate the correlation between the degradation of the waste catalyst and poisoning by the chemical composition.

While Nano Co., Ltd. has been carrying out the catalyst regeneration business for many years, compared to sites using oil or biomass as fuel, sites using coal as fuel have experienced that fly ash in exhaust gas stabilizes toxic components such as alkali metals or phosphorus in the boiler, and that catalyst deactivation by ionized alkali or phosphorus on the catalyst is relatively small. As a result of analyzing the crystal phase with an X'Pert PRO PANalytical, Netherlands, in order to confirm the crystal phase of the catalyst carrier material TiO ₂ , as shown in FIG. 3, it was found that the waste catalysts of Units 1 and 7 maintained the same anatase phase as the new catalyst.

For the sample for chemical composition analysis, the catalyst material was separated from the metal support (mesh), pulverized in a mortar, and sieved into powders of 80 μm or less, and then the powder was placed in an aluminum cup and compressed at a pressure of 15 ton for 40 seconds to prepare a pellet specimen. After analyzing the chemical components of the catalyst using X-ray fluorescence spectrometry, alkali metals, phosphorus, and arsenic, which are poisonous substances detected in trace amounts, were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP) by requesting an external institution. Table 2 shows the chemical composition analysis results of the new catalyst and the spent catalyst.

division ingredient
(weight%) new catalyst waste catalyst Unit 7 Unit 4 Unit 1 Unit 7 Unit 4 Unit 1 carrier TiO ₂ 81.40 81.69 81.55 77.09 78.82 78.05 Catalyst V ₂ O ₅ 1.83 2.65 2.56 1.70 2.16 2.13 WO ₃ 3.04 0.78 0.93 2.80 0.61 0.79 MoO ₃ 1.98 2.29 2.38 1.78 1.83 2.03 main
poisonous substance Na ₂ O 0.12 0.13 0.13 0.30 0.25 0.31 _K2O 0.04 0.04 0.05 0.08 0.05 0.13 P ₂ O ₅ 0.08 0.08 0.06 0.11 0.18 0.23 As ₂ O ₃ - 0.02 - 0.28 0.11 0.14 SO ₃ 0.78 0.77 0.89 1.65 2.35 2.58 CaO 1.62 1.63 1.58 2.60 2.18 2.23 MgO 0.24 0.23 0.23 0.62 0.54 0.49 etc SiO ₂ 6.49 7.30 7.21 7.54 7.81 7.78 Al ₂ O ₃ 2.02 2.01 2.10 2.82 2.49 2.46 Fe ₂ O ₃ 0.25 0.26 0.22 0.53 0.51 0.49 Cl 0.11 0.12 0.11 0.10 0.11 0.16

Referring to Table 2, the contents of TiO ₂ , V ₂ O ₅ , WO ₃ , and MoO _{3 ,} which are the main components of the new catalyst, tended to decrease in the waste catalyst compared to the new catalyst, and alkali metal oxides such as Na ₂ O and K ₂ O, alkaline earth metal oxides such as CaO and MgO, phosphorus oxide (P ₂ O ₅ ), arsenic oxide (As ₂ O ₃ ), and SO ₃ components, which are classified as major toxic components. has increased relatively. Components with a relatively large increase were identified as SO ₃ and Na ₂ O components. The decrease in the contents of carrier material TiO ₂ and catalytic material V ₂ O ₅ , WO ₃ , and MoO ₃ in the spent catalyst is not a change in the absolute amount of these materials, but a result of a decrease in the relative content due to an increase in poisoning materials.

c. Waste Catalyst Performance Evaluation

In order to evaluate the performance of the waste catalysts of Units 1 and 7, samples were taken from a portion of the catalyst sheet without bending in the middle after cleaning the surface of the catalyst sheet with compressed air. The performance test was evaluated under the Test-I condition of the high-efficiency plate-type catalyst performance evaluation test method. In general, since the SO _x conversion rate depends on the V ₂ O ₅ content of the main catalyst and the surface dispersion state, the waste catalyst is known to be lower than the SO _x conversion rate of the new catalyst, so only the NOx removal efficiency was measured in the waste catalyst state. The micro reactor used in the performance evaluation is equipped with a reactor tube made of STS 316 inside an electric heating type electric furnace, and an electric furnace made of individual heating zones divided into three parts so that the temperature difference between the front and rear ends of the catalyst can be adjusted to ± 1 ° C for accurate analysis. The test evaluation procedure applied the procedure presented in the VGB Guideline for the purpose of testing catalyst performance, and the flat plate portion was cut and processed with a cutter to avoid the bent portion of the catalyst according to the test conditions (face velocity and exhaust gas composition) presented. In order to fix the catalyst in the reactor, a separate plate-type catalyst performance evaluation jig was used, and the processed specimen and loading state of the catalyst are shown in FIG. 4.

After processing the catalyst sample and loading the reactor, the reactor was installed in an electric furnace, the temperature was set to the analysis temperature, and the concentration of exhaust gas at the inlet was adjusted by injecting the simulated gas required for analysis with the MFC (Mass flow controller). Then, H ₂ O and NH ₃ were injected, and the NOx concentration at the front and outlet of the catalyst was read after 2 hours, and the NOx concentration was measured. The catalyst activity was calculated from the NOx removal efficiency of the measured waste catalyst using Equation 1 below, and the relative activity compared to the activity of the new catalyst was calculated using Equation 2. The results are shown in Table 3 below.

(Calculation 1) Catalytic activity (Activity, K) = -(Face velocity)×ln(1-η)

In Equation 1, η is the NOx removal rate [(NOx _inlet concentration-NOx _outlet concentration)/NOx _inlet concentration].

(Calculation 2) Relative activity = K _t /K ₀

In Equation 2, K _t is the activity of the waste catalyst after the usage time (t), and K ₀ is the activity of the new catalyst.

exhalation catalyst type NOx removal efficiency Catalytic activity relative activity Unit 1 new catalyst 71.4 63.8 0.71 waste catalyst 58.7 45.1 Unit 7 new catalyst 67.2 56.9 0.83 waste catalyst 60.5 47.4

2) Regeneration of spent catalyst:

go. Regeneration device: The laboratory-scale regeneration device is designed to enable air bubbling cleaning and ultrasonic cleaning used in Nano's ART (Advanced Regeneration Tech.) process. The frequency of ultrasonic waves is 40 KHz, and the output is designed to be adjusted in 3 steps, and the amount of air input for bubbling can be adjusted in the same way as the existing ART process. In addition, a cleaning solution heating function was added to check the cleaning function according to the temperature of the cleaning solution. The regeneration device is separated into a regeneration treatment tank and an active solution storage tank, and after cleaning of the waste catalyst is completed, the active solution stored in the active solution storage tank is supplied to the regeneration treatment tank so that a re-coating process can be performed. The size of the regeneration treatment tank was manufactured to a size capable of simultaneously regenerating 10 flat catalyst sheets, and the inside was configured in the form of a metal mesh so that water could be easily drained after cleaning and the interval between the catalyst sheets could be adjusted. The material was made of SUS 304 in consideration of the acidity of the active solution and the cleaning experiment using weak acid and weak base.

me. Cleaning efficiency according to cleaning conditions

The cleaning step for regeneration of the high-efficiency plate-type catalyst is divided into ① a physical cleaning step of removing particulate matter between catalyst sheets and on the surface of the catalyst using compressed air or a vacuum cleaner, and ② a wet cleaning step of removing poisonous substances by precipitating waste catalyst in general water, deionized water (hot water or cold water), weak acid, or weak base solution. In this study, an experiment was conducted using a catalyst sheet in which dust adhered to the catalyst sheet was removed with compressed air. First, an experiment was conducted on two types of cleaning methods, an air bubbling method and an ultrasonic method, to select a method suitable for a high-efficiency plate-type waste catalyst, and then experiments with different cleaning solutions were conducted.

Through a literature review, many studies have used various variables such as the weight of waste catalyst before and after cleaning and the analysis of components leached into the filtered regeneration solution. As a result, it was confirmed that the catalyst regeneration efficiency is most affected by the state of the initial catalyst and the poisoning state of the waste catalyst. Therefore, in this cleaning efficiency study, since the goal was to secure a cleaning technology suitable for high-efficiency plate-type catalysts, the cleaning stage was judged based on the recovery level of the specific surface area of the catalyst before and after cleaning and the removal level of poisonous substances.

a. Cleaning efficiency test according to cleaning method

The comparison of cleaning efficiency using the ultrasonic method and the air bubbling method was conducted using deionized water at 25 ° C instead of general water to minimize variables. As mentioned above, the cleaning time was set as the time until the pH and the electrical conductivity gradient of the cleaning solution did not change. The cleaned catalyst was washed twice with deionized water, dried at room temperature for 30 minutes, cut samples, dried in a dryer at 80 ° C for 10 hours, and analyzed for specific surface area and major poisoning components.

In the case of ultrasonic cleaning, the initial pH decrease and the increase in electrical conductivity increased rapidly, but the width of the slope decreased over time, so the cleaning time was delayed by more than 5 minutes on average compared to the air bubbling method. When the temperature of the deionized water is raised to 35°C, the cleaning time is similar to that of the air bubbling method, which is considered to be a result of the ions eluted by ultrasonic waves not being sufficiently diffused from the catalyst surface to the outside.

Compared to the ultrasonic method, the air bubbling cleaning showed a slightly lower rate of initial pH decrease and electrical conductivity increase, but active mixing of the cleaning solution made it easier for ions to diffuse on the catalyst surface, resulting in a shorter cleaning time. The average specific surface area of the catalyst cleaned by ultrasonic method was 59.6 m 2 /g, and the average specific surface area of catalyst cleaned by air bubbling method was 60.3 m 2 /g. No significant difference occurred.

As a result of examining the removal efficiency of major poisoning substances according to the cleaning method, the removal efficiency of alkali components and SO ₃ was almost the same in the two cleaning methods, but the removal rate of alkaline earth components, phosphorus oxide, and alumina and silica components was found to be about 10% greater by the ultrasonic method.

After cleaning with different cleaning methods, the NOx removal efficiency of the regenerated catalyst was measured after an activation recovery process in which two samples were washed with deionized water and immersed in 1.9 wt% vanadium oxalate active solution for 20 minutes.

Ultrasonic cleaning is considered to be effective for regeneration of catalysts used in sites using heavy oil or biomass as fuel, which are highly inactivated by phosphorus due to high removal efficiency of alkaline earth components and phosphorus oxide. In addition, when the output is increased to reduce the cleaning time during ultrasonic cleaning, a problem occurs in which the catalyst supported on the metal support is partially separated, so when cleaning the flat catalyst by ultrasonic method in the future, the catalyst material is not released from the metal support.

In this study, as the existing air bubbling cleaning method of Nano Co., Ltd. showed similar cleaning efficiency compared to ultrasonic waves, an air bubbling method that can be used without changing the ART process was adopted and subsequent experiments were conducted.

b. Cleaning efficiency test according to cleaning solution

In the experiments with the cleaning solution, the temperature of the deionized water was changed to 25℃ and 45℃, the condition of weakly acidic aqueous solution of sulfuric acid (0.1M, 0.2M) and aqueous nitric acid (0.1M, 0.2M), the condition of weakly basic aqueous solution of monoethanolamine (MEA, 0.1M, 0.2M) and aqueous solution of sodium hydroxide (0.1M, 0.2M), and general industrial water were used as the target materials, and the cleaning method was air. A bubbling method was used. The cleaning efficiency according to the cleaning solution was analyzed for the same items as the cleaning method test, and the significance of the cleaning solution was confirmed. Table 4 compares the cleaning efficiency according to the cleaning solution.

cleaning solution cleaning time specific surface area
recovery rate poisonous substance
removal efficiency note deionized water 25℃ ○ ○ ○ standard 45℃ ◎ ◎ ◎ V dissolution problem, low workability weakly acidic 0.1M sulfuric acid ○ △ △ V elution problem, increase in SO ₃ concentration 0.2M sulfuric acid ◎ ◎ ○ 0.1M nitric acid ○ ○ △ V Dissolution problem, no discrimination from deionized water 0.2M nitric acid ○ ○ ○ Weak base 0.1M MEA △ △ △ Sediment formation, low cleaning effect 0.2M MEA △ △ △ 0.1 M NaOH ◎ ◎ x Excellent cleaning efficiency, increased Na ₂ O component 0.2 M NaOH ◎ ◎ x industrial water 25℃ △ ○ ○ late cleaning

In an experiment with deionized water, it was confirmed that the cleaning solution in which the deionized water temperature was 45° C. completed cleaning in a time less than twice as short. However, the higher the temperature, the higher the elution of vanadium, the main catalyst material, and the workability problem due to the high cleaning temperature. When applying the process, it was concluded that the higher the temperature of the cleaning solution is, the better it is under the condition that it does not exceed 30 ℃.

It was also confirmed that the regeneration time was shortened in the weak acid test, and there was a problem that a lot of the main catalyst material escaped compared to deionized water. In addition, even after washing with deionized water, SO ₄ ^2- ions remaining in the pores were not completely removed, so it was found that the concentration of SO ₃ increased during the component analysis after washing.

In the case of the weak base test, it was confirmed that a white salt was generated and precipitated in the washing solution after the washing process. In particular, in the case of sodium hydroxide, it was determined that it was not suitable as a regeneration solution because Na ⁺ ions remained in the pores even after washing with deionized water.

Compared to deionized water, industrial water has a slightly slower elution rate of poisonous substances, and the pH decrease and electrical conductivity increase are small even after final cleaning. However, the specific surface area after washing was within 2% of the sample washed with deionized water. Considering the economic aspect of applying a large amount of cleaning solution as deionized water, it is judged that a method to increase cleaning efficiency with industrial water is needed.

The ART regeneration process is designed so that the cleaning process, washing process, drying process, and active recovery process proceed continuously, so the problem of the delay in cleaning time due to the use of industrial water can act as a bottleneck process. In this study, a method to increase the cleaning efficiency was reviewed. In the cleaning process of the ART process, Lab. After applying the scale regenerator to the industrial water washed 2-3 times, the waste catalyst was put in and the time required for pH and electrical conductivity to stabilize was measured. As a result, it was confirmed that the cleaning time was reduced similarly to 0.2 M sulfuric acid solution. This is considered to be due to the reduction of the cleaning time as the pH of the catalyst was reduced similarly to that of a dilute sulfuric acid solution due to the elution of SO ₄ ^2- ions, which are poisonous substances on the catalyst, in the previous cleaning. In addition, when using industrial water, a cleaning experiment was conducted by raising the temperature of the cleaning solution by 30 ℃, and it was confirmed that the cleaning time was similar to that of 25 ℃ deionized water. When using industrial water, the components of industrial water must be analyzed to confirm the concentration of components that affect catalytic activity, such as alkali and alkaline earth components in the water.

all. active recovery process

In the regeneration process of high-efficiency plate-type catalyst waste catalyst, the activity recovery process is an important process that determines the performance of the final catalyst. As the active solution used in the active recovery process of this experiment, RVMS (Regeneration Vandium-oxide Mixing Solution) solution, which is an active stock solution used in the ART process of Nano Co., Ltd., was used. RVMS is prepared by mixing deionized water with RVMS prepared by mixing VOS (Vanadyl Oxalate Solution), CeS (Cerium Nitrate Solution), and SiS (Silicon Binder Solution) in the form of RVDS (Regeneration Vanadium Diluted Soluton), which is an active solution having a desired catalyst material concentration. If necessary, a cocatalyst component may be supplemented by using AMT (Ammonium Meta-Tungstate) or a MoO ₃ precursor. As a result of the cleaning process of the high-efficiency plate-type waste catalyst, the elution of WO ₃ and MoO ₃ components, which are cocatalysts, was very low, and the supporting process of AMT and MoO ₃ precursors was excluded in this study.

A RVDS was prepared with the goal of supporting 110% of the V ₂ O ₅ content of the new catalyst on a catalyst sheet that had undergone cleaning, washing, and drying processes, and after being supported for 20 minutes, it was drawn out, dried naturally, and X-ray fluorescence analysis was used to confirm the supported amount of the catalyst material. The NOx removal efficiency and _SOx conversion rate of the catalyst sample loaded with the catalyst material at the desired concentration were measured using a microreactor in the same way as the waste catalyst. The SO _x conversion rate is confirmed through Equation 3 by measuring the concentrations of SO ₂ at the inlet and SO ₃ at the outlet of the reactor.

(Calculation 3) SO _x conversion rate (%) = (SO _{3 outlet} concentration / SO _{2 inlet} concentration) × 100

The SO ₂ concentration at the inlet of the reactor was measured using a continuous SO ₂ gas analyzer, and the SO ₃ concentration was converted after the concentration of SO ₄ ^2- ions was measured using ion chromatography by dissolving the SO ₃ adsorbed in the SO ₃ collection bottle in distilled water by inhaling the exhaust gas at constant speed at the outlet of the reactor.

la. High-efficiency plate type catalyst regeneration test result

In order to secure regeneration technology for high-efficiency plate-type catalysts, an economical regeneration method suitable for regeneration of high-efficiency plate-type catalysts was designed as follows through research on cleaning methods and cleaning efficiencies for each cleaning solution.

① The cleaning solution uses industrial water of 25℃ or higher and cleans the waste catalyst in two steps by air bubbling cleaning method. ② The cleaned catalyst is washed twice with deionized water, and then moisture is removed from the surface by air blowing. ③ The catalyst from which moisture has been removed is immersed in the active solution RVDS for 20 minutes and dried naturally. ④The regeneration catalyst after drying is measured for NOx removal efficiency and _SOx conversion rate using a micro-reactor evaluation device to determine whether or not regeneration is successful.

a. Surface Characteristics Analysis

After cleaning the waste catalyst taken out from Units 1 and 7 by applying the above ① cleaning process, the change in specific surface area before and after cleaning (FIGS. 5 and 6), change in pore volume (FIGS. 7 and 8), and change in pore size (FIGS. 9 and 10) are shown. The specific surface area, which was reduced to 70% compared to the new catalyst, was recovered by more than 85% after cleaning. In addition, a slight increase in pore volume and a decrease in average pore size were also confirmed.

b. Changes in major toxic substances

Changes in major toxic components included in the catalyst before and after the cleaning process were measured by X-ray fluorescence spectrometry and ICP method. Changes in Na ₂ O, K ₂ O, P ₂ O ₅ , As ₂ O ₃ , and MgO (FIGS. 11 and 12), which show a content of 1% or less among toxic components, and changes in SO ₃ , CaO, SiO ₂ , and Al ₂ O ₃ components with relatively high contents (FIGS. 13 and 14) are shown graphically. Through the cleaning process, it was found that alkali metal components, Na ₂ O, K ₂ O, and SO ₃ components, which are easily eluted as ions, were significantly reduced, and other P ₂ O ₅ , As ₂ O ₃ , CaO, MgO, SiO ₂ , Al ₂ O ₃ and the like were not significantly changed.

c. Changes in catalytically active substances

15 and 16 show changes in the content of V ₂ O ₅ as a main catalyst material and WO ₃ and MoO ₃ as co-catalyst materials in addition to the main toxic components in the cleaning step. As a result of the analysis, it was confirmed that the elution of the cocatalysts WO ₃ and MoO ₃ was insignificant in the cleaning process, but some of the main catalyst material V ₂ O ₅ was eluted and escaped.

d. Catalyst performance change before and after regeneration

The NOx removal efficiency of the regenerated catalyst samples that went through the above steps ① to ④ using the waste catalyst taken out from Unit 7 was measured according to Test-I condition, which is a severe condition among the denitrification catalyst performance evaluation methods of the Hadong Thermal Power Plant Headquarters, and the SO _x conversion rate was measured according to the Test-II condition, which is an actual application condition among the denitration catalyst performance evaluation methods of the Hadong Thermal Power Plant Headquarters. The reason for applying different performance evaluation methods for NOx removal efficiency and _SOx conversion rate is that the evaluation method enhances the discrimination power in the confirmation of each performance under harsh conditions for each item. At this time, the reason why the relative activity ( _KR /K ₀ ) standard of the regenerated catalyst is set to 0.94 or higher is that the level that satisfies the guarantee value of the new catalyst of Hadong Thermal Power Plant is 0.94.

The results of measuring NOx removal efficiency, activity, and _SOx conversion rate by dividing into new catalyst, waste catalyst, and regenerated catalyst are shown in FIGS. 17 and 18, respectively.

When the V ₂ O ₅ content of the regenerated catalyst was maintained at the same level as the new catalyst (Regenerated Catalyst-A) and when the V ₂ O ₅ content was increased by 0.15% by weight compared to the new catalyst (Regenerated Catalyst-B), the relative activity ( _KR /K ₀ ) of the regenerated catalyst compared to the new catalyst was lower than 0.94, and the V ₂ O ₅ content was increased to increase the relative activity to 0.94 or higher. When supported by increasing 0.3% by weight compared to each sheet (regenerated catalyst-C), a problem occurred in which the SO _x conversion rate exceeded the target of 1.0% or more. When the same amount of catalyst material is supported on a regenerated catalyst with a relatively reduced specific surface area compared to the new catalyst, it is judged that the efficiency of the denitrification reaction, which is a surface reaction, is lowered due to fewer acid sites than in the new catalyst state. When the content of V ₂ O ₅ , which is the main catalyst, is increased to compensate for insufficient acid sites, the denitration efficiency increases, but the SO _x conversion rate, which is influenced by the V ₂ O ₅ content of the entire catalyst, also increases.

Additional research was conducted to solve this trade-off phenomenon. As a way to solve the problem of activity deterioration due to the reduced specific surface area, a method of activating the surface in the cleaning process after cleaning was applied. For the purpose of further activating the pores and surface of the catalyst, in step ②, the cleaned catalyst was washed once with deionized water instead of twice with deionized water and then washed a second time with a 0.5 M aqueous solution of ammonium carbamate (AC). It was changed to a process (regenerated catalyst-D). As a result of evaluating the performance of the regenerated catalyst in which the waste catalyst was regenerated by the modified process, the regenerated catalyst in which the V ₂ O ₅ content was increased to 0.1% by weight compared to the new catalyst showed a relative activity of 0.94 or more and a SO _x conversion rate of less than 1% compared to the new catalyst. Results were obtained.

In addition, using the waste catalyst taken out from Unit 1, the performance of the regenerated catalyst sample that went through the steps ① to ④ was measured according to the performance evaluation method of the regenerated catalyst (Test-I condition). The results of measuring NOx removal efficiency, activity, and _SOx conversion rate by dividing into new catalyst, waste catalyst, and regenerated catalyst are shown in FIGS. 19 and 20, respectively.

As in Unit 7, when the V ₂ O ₅ content of the regenerated catalyst was maintained at the same level as the new catalyst (Regenerated Catalyst-A) and when the _{V 2} O ₅ content was increased by 0.15% by weight compared to the new catalyst (Regenerated Catalyst-B), the relative activity ( _KR /K ₀ ) of the regenerated catalyst compared to the new catalyst showed lower activity than 0.94, and V 2 to raise the relative activity to 0.94 or higher When the O ₅ content was increased by 0.3% by weight compared to the new catalyst (regenerated catalyst-C), a problem occurred in which the SO _x conversion rate exceeded the target of 1.0% or more.

② In the process, when the cleaned catalyst was washed once with deionized water instead of twice with deionized water and then washed a second time with a 0.5 M aqueous solution of ammonium carbamate (AC) (Regenerated Catalyst-D), the regenerated catalyst in which the V ₂ O ₅ content was increased to 0.1% by weight compared to the new catalyst resulted in a relative activity of 0.94 or more and a SO _x conversion rate of less than 1% compared to the new catalyst.

evaluation items
evaluation sample Test-Ⅰ Test-Ⅱ NOx removal efficiency Catalytic activity relative activity SO _x conversion rate Unit 1 new catalyst 71.4 63.83 - 0.88 Regeneration Catalyst-A 68.6 59.07 0.92 0.98 Regeneration Catalyst-B 69.1 59.89 0.93 1.03 Regenerative Catalyst-C 73.4 67.53 1.05 1.13 Regeneration Catalyst-D (Example 1) 70.8 62.78 0.98 0.67 Unit 7 new catalyst 67.2 56.85 - 0.71 Regeneration Catalyst-A 63.9 51.96 0.91 0.84 Regeneration Catalyst-B 64.7 53.10 0.93 0.93 Regenerative Catalyst-C 66.9 56.38 0.99 1.05 Regeneration Catalyst-D (Example 2) 66.1 55.16 0.97 0.69

In addition, in order to optimize the molar ratio of the AC aqueous solution used in the secondary washing process, the molar ratio of the AC aqueous solution was changed from 0.1 to 1.0 M to confirm the change in performance.

e. Prototype production of regenerative catalyst and official test evaluation

10 sheets of prototype high-efficiency flat-type regenerated catalysts were manufactured by applying the high-efficiency plate-type regeneration technology established by using waste catalysts disposed of after use at the Hadong Thermal Power Plant Headquarters. The trial product was evaluated by Test-I (severe conditions) and Test-II (practical application conditions) by applying _the same performance test conditions as the high-efficiency plate-type new catalyst at the Korea Institute of Industrial Technology, an authorized testing institute. Table 7 below shows the performance test methods of Test-I and Test-II.

Test Items
Exam conditions denitrification efficiency
(%) activity
(m/h) SO _x conversion rate
(%) NH ₃ slip
(ppm) note Test-Ⅰ 69.8 61.06 - - Satisfaction of guarantee New Catalyst Guarantee Value ≥ 69.0 ≥ 59.80 - - Satisfaction of guarantee Test-Ⅱ 93.4 - 0.70 1.94 Satisfaction of guarantee New Catalyst Guarantee Value ≥ 93.3 - ≤ 1.0 ≤ 2.0 Satisfaction of guarantee

exhalation Performance test method Units 1 to 6 Test-Ⅰ guaranteed value
1. NOx removal efficiency ≥ 69.0%
2. SO _x conversion rate ≤ 2.1% Test-II guaranteed value
1. NOx removal efficiency ≥ 93.3%
2. SO _x conversion rate ≤ 1.0%
3. NH ₃ slip ≤ 2.0 ppm test requirements
1. Temperature (℃): 350
(For NOx removal efficiency test)
2. Temperature (℃): 380
(When examining the SO ₂ /SO ₃ conversion rate)
3. AV(m/hr) : 51
(For NOx removal efficiency test)
4. AV(m/hr) : 6
(When examining the SO ₂ /SO ₃ conversion rate)
5. NH ₃ /NOx molar ratio: 1.2 test requirements
1. Temperature (℃): 359
(When NOx removal efficiency test and SO ₂ /SO ₃ conversion rate test)
2. AV(m/hr) : 5.2
(For NOx removal efficiency test)
3. AV(m/hr) : 13
(When examining the SO ₂ /SO ₃ conversion rate)
4. NH ₃ /NOx molar ratio: 0.941 test gas composition
1. NO (ppm, O ₂ 6%) : 200
2. NH ₃ (ppm, O ₂ 6%) : 240
3. SO ₂ (ppm, O ₂ 6%) : 500
4. _CO2 (vol%): 12
5. O ₂ (vol %, dry) : 3
6. H ₂ O (vol %) : 12
7.N ₂ (vol%): balance test gas composition
1. NO (ppm, O ₂ 6%) : 220
2. NH ₃ (ppm, O ₂ 6%) : 207
3. SO ₂ (ppm, O ₂ 6%) : 740
4. _CO2 (vol%): 15.57
5. O ₂ (vol %,dry) : 3.68
6. H ₂ O (vol %) : 8.41
7.N ₂ (vol%): balance Units 7~8 Test-Ⅰ guaranteed value
1. NOx removal efficiency ≥ 65.0%
2. SO _x conversion rate ≤ 2.0% Test-II guaranteed value
1. NOx removal efficiency ≥ 90.0%
2. SO _x conversion rate ≤ 1.0%
3. NH ₃ slip ≤ 2.0 ppm Same as Units 1 to 6 conditions test requirements
1. Temperature (℃): 359
(In case of NOx removal efficiency test and SO ₂ /SO ₃ conversion rate test)
2. AV(m/hr) : 7.3
(For NOx removal efficiency test)
3. AV(m/hr) : 7.3
(When examining the SO ₂ /SO ₃ conversion rate)
4. NH ₃ /NOx molar ratio: 0.914 test gas composition
1. NO (ppm, O ₂ 6%) : 150
2. NH ₃ (ppm, O ₂ 6%) : 137
3. SO ₂ (ppm, O ₂ 6%) : 837
4. _CO2 (vol%): 14.84
5. O ₂ (vol %,dry) : 2.54
6. H ₂ O (vol %) : 8.48
7.N ₂ (vol%): balance

Although the present invention has been described through specific details and limited examples as described above, this is only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. Those skilled in the art can make various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the present invention.

Claims (10)

a) a physical cleaning step of supporting the waste SCR catalyst in a cleaning solution and injecting and bubbling air into the cleaning solution;
b) a first washing step of washing the cleaned waste plate type SCR catalyst with pure water;
c) a second washing step of washing the waste plate-type selective catalytic reduction (SCR) catalyst with an aqueous solution containing an ammonium-based compound;
d) a drying step of drying the secondly washed waste plate type SCR catalyst; and
e) an active recovery step of coating an active component on the dried waste plate-type SCR catalyst;
The ammonium-based compound is an ammonium carbamate-based compound, a method for regenerating a waste plate-type SCR catalyst. delete delete delete According to claim 1,
The ammonium carbamate compounds include ammonium carbamate, ethylammonium ethyl carbamate, isopropylammonium isopropylcarbamate, n-butylammonium n-butylcarbamate, isobutylammonium isobutylcarbamate, t-butylammonium t-butylcarbamate, 2-ethylhexylammonium 2-ethylhexylcarbamate, octadecylammonium octadecylcarbamate, 2-methoxyethylammonium 2-methoxyethylcarbamate, dibutyl A method for regenerating a waste plate-type SCR catalyst comprising at least one selected from the group consisting of ammonium dibutyl carbamate, dioctadecylammonium dioctadecylcarbamate, methyldecylammonium methyldecylcarbamate, and triethylenediaminium isopropyl bicarbamate. According to claim 1,
The concentration of the aqueous solution containing the ammonium-based compound is 0.01 to 1.0 M, a method for regenerating a waste plate-type SCR catalyst. delete According to claim 1,
The cleaning solution is deionized water, purified water or industrial water. delete delete