KR20070006584A - Remanufacturing method for the aged scr de-nox catalyst - Google Patents

Abstract

Provided is a method for preparing a used SCR de-NOx catalyst, comprising recovering a used SCR de-NOx catalyst of which service life is substantially terminated, cleaning and rinsing the recovered catalyst, performing performance inspection of the catalyst, acid-treating the performance inspection finished catalyst, correcting performance of the acid-treated catalyst, and heat-treating the catalyst. A method for preparing a used SCR de-NOx catalyst comprises: a contaminant cleaning step of removing contaminants presenting on a surface of a recovered SCR(selective catalytic reduction) catalyst using compressed air; an ultrasonic rinsing step of rinsing the cleaning step finished catalyst using ultrasonic waves; a catalyst inspection step of inspecting performance of the rinsing step finished catalyst; an acid-treating step of acid-treating the inspection step finished catalyst; a performance correcting step of correcting performance of the acid-treating step finished catalyst; and a heat-treating step of heat-treating the performance correcting step finished catalyst. The ultrasonic rinsing step is performed by rinsing the catalyst using ultrasonic waves for 30 minutes after injecting the recovered SCR catalyst and water into a reactor having an ultrasonic equipment.

Description

Remanufacturing method for the Aged SCR De-Nox Catalyst

1 is a flow chart showing a method for remanufacturing a waste denitrification SCR catalyst according to the present invention;

2 is a view showing the configuration of a waste SCR catalyst activity measuring apparatus for evaluating the performance of the catalyst remanufactured by the remanufacturing method according to the present invention.

The present invention relates to a method for remanufacturing a waste denitrification SCR catalyst, and more particularly, when the life of the catalyst used in the selective catalytic reduction (SCR) applied to remove the nitrogen oxides is substantially terminated, The present invention relates to a method for remanufacturing a waste denitrification SCR catalyst through recovery, washing, catalyst performance inspection, and catalyst performance correction.

Exhaust gases from coal-fired power plants, coal-fired power plants, and / or incinerators generally contain large amounts of harmful substances such as hydrochloric acid, sulfur oxides, nitrogen oxides, and dioxins. The selective catalytic reduction method (SCR) using NH ₃ as a reducing agent has been widely applied as a method for removing.

In particular, the nitrogen oxide discharge facilities such as coal-fired power plants, coal-fired power plants, and incinerators in Korea have already installed or installed the above-described SCR denitrification facilities, and the emission regulations in the air required by the government and environmental organizations are more stringent. As it disappears, cases of applying SCR denitrification facilities to satisfy such emission regulations are increasing rapidly, and most of the catalysts used in the SCR denitrification facilities are imported from foreign countries.

On the other hand, the catalyst is installed to remove the nitrogen oxide in the SCR denitrification process using a catalyst prepared by adding a small amount of vanadium (V ₂ O ₅ ) and tungsten (WO ₃ ) using a titanium dioxide (TiO ₂ ) as a carrier. As such, the SCR denitrification catalyst is contaminated by a large amount of impurities and contaminants contained in the exhaust gas in the process of being installed and used in the SCR denitrification process, and thus the activity of the catalyst decreases over time. On average, after two to three years, the performance of the catalyst is substantially degraded or terminated.

Therefore, considering the general lifespan of the SCR catalyst mounted in the SCR denitrification facility to discharge the nitrogen oxide below the regulated value, from the next three to five years, including the present, the life of the catalyst is substantially terminated. Tens to millions of tonnes of waste denitrification SCR catalysts that have been installed and operated will continue to be generated.

Therefore, there is a need for a method for remanufacturing the waste denitrification SCR catalyst which re-manufactures the waste denitrification SCR catalyst so that the performance of the catalyst can be restored and reused. In view of this, it is an urgently needed catalyst remanufacturing technology.

Thus, the present inventors objectively check the state of the catalyst through the step of recovering the waste denitrification SCR catalyst substantially end of life during the continuous research to solve the above-mentioned problems and undergoes a physical washing step and then inspect the catalyst performance. The present invention was completed by devising a remanufacturing method that can be used as an SCR catalyst after chemically cleaning and restoring a catalyst which has been found to be inferior in performance after chemical cleaning and performance restoration.

The present invention was derived in order to solve the above-mentioned problems, and the performance of the waste denitrification SCR catalyst which has substantially expired is recovered, washed and washed, and then tested for performance, and the acid treatment of the finished catalyst has been subjected to acid treatment and acid treatment. There is a technical problem to provide a method for remanufacturing a waste denitrification SCR catalyst comprising correcting the performance of the prepared catalyst and then performing heat treatment.

The present invention is a contaminant washing step of removing contaminants present on the surface of the recovered SCR catalyst using compressed air; An ultrasonic cleaning step of ultrasonically cleaning the catalyst in which the washing step is completed; A catalyst inspection step of examining the performance of the catalyst in which the washing step is completed; An acid treatment step of acid treatment of the catalyst in which the inspection step is completed; A performance correction step of correcting the performance of the catalyst in which the acid treatment step is completed; And a heat treatment step of heat treating the catalyst on which the performance correction step is completed.

Substantially end-of-life catalysts, in particular SCR catalysts, according to the present invention are subjected to prolonged exposure to impurities and contaminants contained in the exhaust gas during the application and use of SCR denitrification equipment for removing nitrogen oxides. It means that the activity of is reduced to less than 70% of the performance of the new SCR catalyst, which can be commonly referred to as waste denitrification SCR catalyst, in the present invention the waste denitrification SCR catalyst is substantially end of life or It can be regarded as the same as the catalyst with significantly reduced activity, ie SCR catalyst.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, the following description is only for explaining the present invention specifically, and is not limited to the scope of the present invention by the following description.

1 is a flow chart illustrating a method for remanufacturing a waste denitrification SCR catalyst according to the present invention.

As shown in FIG. 1, in the method for remanufacturing the waste denitrification SCR catalyst according to the present invention, the catalyst is remanufactured according to a remanufacturing procedure defined in the remanufacturing industry, and more specifically, the waste denitrification SCR catalyst is physically produced. Physical remanufacturing methods for remanufacturing, catalyst inspection methods for measuring the performance of catalysts, chemical remanufacturing methods for chemical remanufacturing, and / or performance correction methods for impregnating catalyst active ingredients.

At this time, the remanufacturing order of the physical remanufacturing method and the chemical remanufacturing method is not particularly limited, but preferably, the chemical remanufacturing method is completed by a catalyst in which the physical remanufacturing method is completed.

Thus, looking at the method for remanufacturing the waste denitrification SCR catalyst in more detail, first, the physical remanufacturing method of the waste denitrification SCR catalyst according to the present invention is to remove contaminants present on the surface of the recovered SCR catalyst using compressed air. Removing pollutants; And an ultrasonic cleaning step for ultrasonically cleaning the catalyst in which the contaminant washing step is completed.

Here, the contaminant washing step is typically for removing contaminants present on the surface of the waste denitrification SCR catalyst at a high pressure, for example, at a pressure of 0.1 to 0.5 kg / cm ² , and the ultrasonic cleaning step includes: After filling the reactor with the recovered catalyst, preferably the SCR catalyst and water, preferably distilled water, and washing the catalyst using ultrasonic waves of 15,000 to 24,000 MHz frequency for 5 to 30 minutes.

On the other hand, the catalyst inspection step of examining the performance of the catalyst according to the present invention is to determine whether to prepare a test by examining the performance of the substantially end-of-life denitrification SCR catalyst recovered from the SCR facility, i) waste Measuring the denitrification SCR catalyst with an inductively coupled plasma spectrometer to evaluate the loss rate of the active ingredient constituting the catalyst and the heavy metal content deposited on the catalyst surface; Ii) X-ray diffractometer measurement of the waste denitrification SCR catalyst of step iii) to evaluate the crystal structure of the catalyst; Iii) measuring the waste denitrification SCR catalyst of step ii) with a specific surface area analyzer and a pore distribution analyzer to evaluate specific surface area reduction rate and pore distribution of the catalyst; Iii) evaluating the thermal stability of the catalyst by measuring the waste denitrification SCR catalyst of step iv) with a thermogravimetric analyzer; Iii) evaluating the NOx conversion activity of the waste denitrification SCR catalyst of step iv) with a catalytic performance measurement device.

Here, each step constituting the inspection step is not particularly limited in order, it is possible to determine the order in accordance with the user's selection, the X-ray diffractometer (XRD) as the preferred measurement conditions Is measured in the range of 5 ^o to 90 ^o , and in order to check the surface state of the catalyst, SEM (scanning electron microscopy) is observed at a magnification of 10,000 to 50,000 times, and a thermogravimetric analyzer (TGA) ) Is the catalyst thermal stability measurement in the 150 to 600 ℃ range.

In addition, the step of evaluating the NOx conversion activity of the waste denitrification SCR catalyst of step iii) as a catalyst performance measuring device is configured to measure the catalytic activity after configuring the catalytic activity measuring device capable of measuring the reaction activity of the catalyst by simulating the exhaust gas. Measuring the catalytic activity by installing a catalyst in the device and exposing the simulated off-gas; After the catalyst is installed in the SCR facility may be composed of the step of measuring the reaction activity of the catalyst under the condition that the SCR facility is running or a combination thereof.

On the other hand, in the catalyst inspection step according to the present invention, if the waste denitrification SCR catalyst analyzed in any one of the steps iii) to iii) does not satisfy the desired conditions, the waste denitrification SCR without proceeding to the next step Discarding the catalyst, the desired conditions are the loss rate and heavy metal content of the active ingredient of step iii) less than 5% loss rate, less than 10% heavy metal content; The crystal structure of the catalyst of step ii) is in the anatase form; The specific surface area reduction rate and pore distribution of step iii) are within 30% of reduction rate, and the rate of change of micropore distribution in pore distribution is within 50%; The thermal stability of step iii) is within 5% of the total weight loss within the analysis temperature of 600 ° C .; The NOx conversion in step iii) is at least 70% catalytic activity.

The chemical remanufacturing method of the waste denitrification SCR catalyst according to the present invention includes an acid treatment step of acid-treating the catalyst having a substantially end of life, in particular the waste denitrification SCR catalyst, wherein the acid treatment step is provided with an ultrasonic apparatus. The reactor was charged with an SCR catalyst, specifically a waste denitrification SCR catalyst and a solution of sulfuric acid, nitric acid or a mixture thereof maintained at pH 1 to 5, followed by acid treatment by washing the catalyst using ultrasonic waves for 5 to 30 minutes, The acid treated catalyst is washed with water for 5 to 10 minutes and then dried at a temperature of about 150 ° C. for about 2 hours.

Here, the acid treatment step may be an acid treatment directly without treating the catalyst which has been substantially end of life without a physical remanufacturing method, but is preferably an ultrasonic cleaning step as a post-process of the ultrasonic cleaning step included in the physical remanufacturing method. Acid treatment of the finished catalyst is preferred.

On the other hand, the performance correction step according to the present invention is impregnated on the surface of the spent SCR catalyst catalyst vanadium, tungsten or a mixture thereof, and dried for about 2 hours at about 150 ℃, the dried catalyst at about 500 ℃ about 3 Firing for time.

Here, the impregnated vanadium is impregnated up to 1.5% by weight based on the weight of the catalyst, tungsten impregnated is impregnated up to 0.5% by weight relative to the weight of the catalyst.

In the heat treatment step according to the present invention, after filling the waste SCR catalyst in the heatable heating device, the air is flowed at a space velocity of 5,000 to 10,000 hr ^−1, and the temperature of the heating device is heated to 450 to 550 ° C., followed by 2 to 2 conditions. Maintaining for 3 hours to oxidize and remove contaminants deposited on the catalyst.

On the other hand, the physical remanufacturing method, the chemical remanufacturing method and the catalyst performance correction according to the present invention are contaminated with the contaminated waste denitrification SCR catalyst and the required remanufacturing performance conditions, for example, 90% of the performance of the new catalyst. Its application depends on the conditions of remanufacturing.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only for illustrating the present invention in detail and do not limit the scope of the present invention by these examples.

<Example>

First, the waste denitrification SCR catalyst whose life was substantially terminated was separated from the catalyst holder of the SCR plant to recover the catalyst.

At this time, the recovered catalyst is a honeycomb catalyst of 46 cpsi (cell per square inch), the catalyst at a position up to 1,500 cm from the exhaust gas inlet of the cogeneration plant deteriorates and heavy metals are deposited to cause severe color deformation. It was dark brown, and the self-reaction test showed that the catalytic activity was maintained at 60 to 70% of the unused new catalyst over the temperature range 350 to 600 ° C.

The catalyst recovered from the SCR reactor was then washed using 0.3 kg / cm ² of compressed air.

Then, the washed catalyst was filled in a reactor equipped with a 410 mm x 410 mm x 590 mm forged ultrasonic generator [UIL-600W, Ultrasonic Wave, Korea], filled with distilled water, and then ultrasonically cleaned at 24,000 Hz for 15 minutes. And the ultrasonic cleaning was completed, the catalyst was dried at 150 ℃ for 3 hours.

Then, the dried catalyst was charged into a reactor equipped with a 410 mm x 410 mm x 590 mm forged ultrasonic generator [UIL-600W, Ultrasound, Korea], and then filled with a sulfuric acid solution prepared to have a pH of 24,000. Ultrasonic washing was performed for 15 minutes at Hz, and the catalyst after the ultrasonic washing was dried at 150 ° C. for 3 hours.

In the method, the first washed catalyst was visually inspected, and then, after determining the performance of the catalyst according to the remanufacturing step, the performance and condition of the catalyst were examined to apply the catalyst remanufacturing step.

At this time, the inspection method of the catalyst was selected in addition to the method of visual inspection, the catalyst was randomly selected from the first re-produced catalyst, and then the catalyst property measurement and the performance test of the catalyst were performed to evaluate the performance of the catalyst.

As the method used for the evaluation, XRD (X-ray Diffractometer) [Rigaku Dmax II, Rigaku Co., Japan] was used to confirm the crystal structure of the catalyst after remanufacturing, and BET (Brunauer Emmett Teller) [ASAP 2010, Micromeritics , United States] to compare the specific surface area of the catalyst, to confirm the thermal behavior of the remanufactured catalyst using the Thermogravimetric Analyzer (TGA) [Shimadzu TG-9, Shimadzu, Japan], ICP (Inductively Coupled Plasma) [Optima 2100 DV, Perkin Elmer Co.] was used to confirm the removal of heavy metals accumulated on the catalyst surface after use.

In addition, scanning electron microscopy (SEM) [JEOL 5600, Jeol. co. ltd, Japan] and EDS (energy dispersive spectrometer) [Stereo scan 440 / Link ISIS, Leica Cambridge Ltd.] analyzes were performed to observe the surface state of the remanufacturing catalyst.

The performance of the catalyst was evaluated after the first wash and catalyst performance test. Catalytic reactor used to evaluate the performance of the catalyst is a continuous flow atmospheric pressure reactor shown in Figure 2 to simulate the exhaust gas of the commercial SCR catalytic reactor of the cogeneration plant, the flow of all the gases used in the NOx reduction reaction experiment is MFC (Mass Flow Controller) [F-100C, Bronkhorst Co.] is controlled by the Gas Analyzer [Greenline D max. II, 9000, EUROTRON] and a gas analyzer [Hewlett Packard 9000, Hewlett Packard, USA]. The volume of the continuous flow atmospheric reactor was 45 cm ³ (3 cm x 3 cm x 5 cm), and the PID controller was used to adjust the temperature of the continuous flow atmospheric reactor in the range of 250 to 400 ° C.

The activity of the catalyst was evaluated by comprehensively analyzing the characteristics of the commercial SCR catalyst and the NOx conversion reaction experiment of the regenerated cogeneration plant.

The results are shown in Table 1, and the conversion rate was calculated by the following equation.

As shown in Table 1, the activity of the catalyst and the spent catalysts treated with primary washing, drying, etc., carried out with varying temperature and varying space velocity, were compared.

Here, the reason for changing the temperature and space velocity is the case of the commercial SCR catalyst applied to the actual cogeneration plant according to the installation location or design conditions, etc. This is to simulate the space velocity depending on the number of catalysts due to.

In order to calibrate the performance of the catalyst after the physical re-manufacturing, which is 90% lower than that of the new catalyst in the low temperature range and high space velocity, vanadium, which is a catalytically active ingredient, is used in the dried catalyst. vanadate, Junsei Chemical, Japan] 3 g / ft ³ (catalyst carrier) and tungsten [Ammonium tungstate hydrate, Junsei Chemical, Japan] 5 g / ft ³ (catalyst carrier) were impregnated and dried at 150 ° C. for 3 hours.

The dried catalyst was then calcined at 500 ° C. for 2 hours to remanufacture the performance of the spent catalyst. The catalyst was then reassembled in a commercial SCR catalytic reactor to complete the catalyst remanufacturing procedure.

The catalyst performance was measured using the same catalytic reactor as in the first wash of the remanufactured catalyst, which is shown in Table 2.

As shown in Table 2, since most of the catalysts that have undergone chemical treatment were found to have a catalyst performance of more than 90% based on the new catalyst, the performance of the catalysts re-produced through this remanufacturing procedure was superior to that of the new catalysts. It confirmed that it was shown.

As described above, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, the exemplary embodiments described above are to be understood as illustrative in all respects and not as restrictive. The scope of the present invention should be construed that all changes or modifications derived from the meaning and scope of the appended claims and their equivalents, rather than the detailed description, are included in the scope of the present invention.

The present invention is to recover the SCR catalyst of the SCR process for removing nitrogen oxides used in incinerators, cogeneration plants or coal-fired power plants, such as washing, inspection, performance correction and assembly to reduce the amount of waste of the catalyst is discarded entirely In addition to reducing waste disposal costs and preventing environmental pollution, it is possible to replace waste denitrification SCR catalysts at low cost.

Claims (9)

A contaminant washing step of removing contaminants present on the surface of the recovered SCR catalyst using compressed air; An ultrasonic cleaning step of ultrasonically cleaning the catalyst in which the washing step is completed; A catalyst inspection step of examining the performance of the catalyst in which the washing step is completed; An acid treatment step of acid treatment of the catalyst in which the inspection step is completed; A performance correction step of correcting the performance of the catalyst in which the acid treatment step is completed; And Method for re-manufacturing the waste denitrification SCR catalyst comprising a heat treatment step of heat-treating the catalyst is completed the performance correction step. The method of claim 1, The ultrasonic cleaning step is a method for re-manufacturing the waste denitrification SCR catalyst, characterized in that to clean the catalyst by using ultrasonic waves for 30 minutes SCR catalyst and water recovered in the reactor equipped with the ultrasonic device. The method of claim 1, Wherein the catalyst inspection step iii) measuring the waste denitrification SCR catalyst with an inductively coupled plasma spectrometer to evaluate the loss rate of the active ingredient constituting the catalyst and the heavy metal content deposited on the catalyst surface; Ii) X-ray diffractometer measurement of the waste denitrification SCR catalyst of step iii) to evaluate the crystal structure of the catalyst; Iii) measuring the waste denitrification SCR catalyst of step ii) with a specific surface area analyzer and a pore distribution analyzer to evaluate specific surface area reduction rate and pore distribution of the catalyst; Iii) evaluating the thermal stability of the catalyst by measuring the waste denitrification SCR catalyst of step iv) with a thermogravimetric analyzer; Iii) evaluating the NOx conversion activity of the waste denitrification SCR catalyst of step iii) with a catalytic performance measurement device. The method of claim 3 If the waste denitrification catalyst analyzed in any one of steps iii) to iii) does not satisfy the desired conditions, the waste denitrification SCR catalyst re-manufacturing is characterized in that the waste denitrification catalyst is discarded without proceeding to the next step. Way. The method of claim 4, wherein The desired condition is that the loss rate and heavy metal content of the active ingredient of step iii) is less than 5% loss, less than 10% heavy metal content; The crystal structure of the catalyst of step ii) is in the anatase form; The specific surface area reduction rate and pore distribution of step iii) are within 30% of reduction rate, and the rate of change of micropore distribution in pore distribution is within 50%; The thermal stability of step iii) is within 5% of the total weight loss within the analysis temperature of 600 ° C .; A process for producing a waste denitrification SCR catalyst, wherein the NOx conversion in step iii) is at least 70% catalytic activity. The method of claim 3, wherein The step of evaluating the NOx conversion activity of the waste denitrification SCR catalyst of step iii) as a catalyst performance measuring device constitutes a catalytic activity measuring device capable of measuring the reaction activity of the catalyst by simulating the exhaust gas and then into the catalytic activity measuring device. Measuring the catalytic activity by installing a catalyst and exposing the simulated exhaust gas; A method for re-manufacturing a waste denitrification SCR catalyst comprising measuring the reaction activity of the catalyst under a condition in which the SCR facility is operated after installing the catalyst in the SCR facility or a combination thereof. The method of claim 1, After the acid treatment step is filled with the recovered SCR catalyst and a solution of sulfuric acid, nitric acid or a mixture thereof maintained at pH 1 to 5 in the reactor equipped with an ultrasonic device for 5 to 30 minutes by washing the catalyst using ultrasonic waves to acid And a process for washing the acid treated catalyst with water for 5 to 10 minutes and then drying at a temperature of about 150 ° C. for about 2 hours. The method of claim 1, The performance correction step includes impregnating the surface of the catalyst with vanadium, tungsten or a mixture thereof, and then drying at about 150 ° C. for about 2 hours, and calcining the dried catalyst at about 500 ° C. for about 3 hours. A method for remanufacturing a waste denitrification SCR catalyst. The method of claim 1, After the heat treatment step fills the recovered SCR catalyst in the heatable heating device, the air is flowed at a space velocity of 5,000 to 10,000 hr ^−1, and the temperature of the heating device is heated to 450 to 550 ° C., and this state is maintained for 2 to 3 hours. A method for remanufacturing a waste denitrification SCR catalyst, wherein the denitrification SCR catalyst is maintained by oxidizing to remove the contaminants deposited on the catalyst.

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