KR101550289B1 - Simultaneous Removal Method of Nitrous Oxide and Nitrogen Monoxide from Exhausted Gas with Catalytic Reactior - Google Patents

Abstract

The present invention relates to a method for simultaneously removing nitrous oxide and nitrogen monoxide in a chemical plant exhaust gas using a catalyst, wherein ammonia is used as a reducing agent in a catalytic reactor including a zeolite catalyst impregnated with iron ions, By controlling the operating conditions under which the gas is supplied, nitrous oxide and nitrogen monoxide can be simultaneously reduced at a low reaction temperature of 300 to 400 ° C in the exhaust gas discharged from a chemical production process such as nitric acid, adipic acid or caprolactam The present invention provides a simultaneous abatement method capable of simplifying an existing multistage exhaust gas reduction process in which the nitrous oxide removal step and the nitrogen monoxide removal step are separately performed.

Description

TECHNICAL FIELD The present invention relates to a method for simultaneously removing nitrous oxide and nitrogen monoxide from a chemical plant exhaust gas using a catalyst,

The present invention relates to a method for simultaneously reducing nitrous oxide and nitrogen monoxide in an exhaust gas discharged from a chemical production process such as nitric acid, adipic acid or caprolactam using a catalytic reactor including a zeolite catalyst impregnated with iron ions Which can replace the conventional catalytic process using an ammonia reducing agent requiring a high reaction temperature of 400 ° C or higher and integrating the processes in which nitrous oxide and nitrogen monoxide proceed through separate removal processes, The present invention relates to a method for simultaneously removing N ₂ O under an Nox reduction operation using an ammonia reducing agent under operating conditions.

In the zeolite catalyst impregnated with iron ions used in the present invention, the zeolite is subjected to water pretreatment by supplying steam for 0.1 to 2 hours in a nitrogen atmosphere, and the pretreated zeolite is reacted with iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O in the presence of iron ions and then drying in air at a temperature of 100 to 120 ° C for 5 to 24 hours and then at a temperature of 400 to 600 ° C for 1 to 5 hours .

Approximately 25% of the nitrous oxide released into the atmosphere is emitted in the form of exhaust gas from fixed sources such as manufacturing plants in various chemical industries. The nitrous oxide released is usually present with nitrogen monoxide in an oxygen-rich atmosphere. In particular, nitric acid (HNO ₃ ), which is mainly used in the fertilizer industry, produces undesirable by-products such as nitrous oxide (N ₂ O) during the production process. This global nitrous oxide has a global-warming potential of 310 . Global nitric acid production plants produce about 400,000 tons of nitrous oxide annually. Reduction of these greenhouse gas emissions due to implementation of emission trading system, clean development system and joint implementation system based on the Kyoto Protocol is an important technical task .

The nitrogen monoxide discharged from the fixed source is removed by selective catalytic reduction (SCR) using a reducing agent such as ammonia or hydrogen or carbon monoxide. Numerous catalysts have been developed to apply the technique over a wide range of temperature ranges, of which the catalyst system of the V ₂ O ₅ -TiO ₂ series is commercialized and is mainly used with ammonia reducing agents.

In order to reduce nitrous oxide, iron-impregnated zeolite catalysts are mainly used. As the reducing agent, hydrocarbons such as methane or propane or ammonia are used.

When hydrocarbon is used as the reducing agent, the removal or reduction of nitrous oxide can be performed at a temperature of less than 400 ° C. However, when ammonia is used as the reducing agent, a temperature of 400 ° C. or more is required to achieve the same reduction of nitrous oxide. Therefore, there is still a difficulty in securing the simultaneous reduction technology of nitrous oxide and nitrogen monoxide using a single reducing agent.

In U.S. Patent No. 5,198,403, catalysts were prepared by mixing oxides in W, Si, B, Al, P, Zr, Ba, Y, La and Ce with oxides in Y, Nb, Mo, Fe and Cu in titanium oxide , Ammonia was used as a reducing agent for selective reduction of nitrogen monoxide. At this time, 50% to 99% of the prepared catalyst was composed of titanium oxide, and in the temperature range of 360 to 500, 81.1% to 94.3% of nitrogen monoxide was reduced and removed.

U.S. Patent Application Publication No. 2002/0127163 discloses a method for selectively reducing nitrogen monoxide using ammonia by adding Fe, Cu, Co, Ce, Pt, Rh, Pd, Ir, Mg, etc. to zeolites such as BETA, ZSM, MORD, To prepare a catalyst. In this catalyst, selective reduction of nitrogen monoxide and nitrous oxide by selecting a catalyst having activity in the selective reduction of nitrous oxide and conversion of nitrous oxide at the temperatures of 450 and 500 ° C were 80% and 99%, respectively, Respectively.

US Patent No. 6,682,710 discloses a method for removing nitrous oxide and nitrogen monoxide using a catalyst obtained by ion exchanging iron ions with FER zeolite, and U.S. Patent No. 6,872,372 discloses a zeolite catalyst containing iron ions It is suggested that nitrous oxide can be selectively reduced at a temperature of 350 or less when palladium, rhodium, gold, or the like is added, wherein the reducing agent used was a saturated hydrocarbon such as methane or propane.

In Japanese Patent Application Laid-Open No. 2006-281026, titanium oxide and at least one element selected from the group consisting of Cr, Mg, Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, In, , Au, Pb and one of these oxides.

These conventional patent documents show that when hydrocarbon is used as a reducing agent, nitrous oxide can be reduced at a temperature of 350 ° C or lower. However, when ammonia is used as the reducing agent, the catalysts used in the above-mentioned patents require a high temperature of 360 ° C or higher in order to reduce nitrous oxide alone.

Also, when ammonia is used as the reducing agent, the techniques used in the above conventional patent documents are required to have a high temperature of 400 ° C or higher in order to simultaneously reduce nitrogen monoxide and nitrous oxide.

The high temperature treatment and operation of the exhaust gas necessarily brings about a problem of a high operating cost. In addition to nitrogen monoxide and nitrous oxide, which are substances to be removed, other substances such as moisture, oxygen and sulfur dioxide are contained in the exhaust gas, It is necessary to remove the nitrogen monoxide first using ammonia as a reducing agent as shown in FIG. 1 in a conventional chemical plant, and then to remove the nitrous oxide by using a hydrocarbon reducing agent at a high temperature of 500 ° C or higher A multi-stage removal system for removing nitrogen is used.

Therefore, while using ammonia as a reducing agent, the reaction temperature is lowered to the level when the hydrocarbon is used as a reducing agent (that is, the temperature is lower than 400 ° C), and nitrogen monoxide and nitrous oxide are simultaneously reduced in the exhaust gas generated in various chemical manufacturing plants An economical method is essential.

United States Patent No. 5,198,403 U.S. Published Patent Application 2002/0127163 U.S. Patent No. 6,682,710 U.S. Patent No. 6,872,372 Japanese Patent Laid-Open No. 2006-281026

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems in the prior art by using ammonia as a reducing agent in a catalytic reactor including a zeolite catalyst impregnated with iron ions, It is possible to simultaneously reduce nitrous oxide and nitrogen monoxide at a low reaction temperature of 300 to 400 ° C in the exhaust gas discharged from a chemical production process such as nitric acid, adipic acid or caprolactam, The present invention is to provide a simultaneous abatement method capable of simplifying an existing multi-stage exhaust gas abatement process in which nitrogen monoxide removal steps are separately performed.

The present invention relates to a method for simultaneous removal of nitrous oxide and nitrogen monoxide in a chemical plant exhaust gas using a catalyst, the method comprising the steps of: i) discharging an exhaust gas containing nitrous oxide (N ₂ O) and nitrogen oxide (NO _x ) To a catalytic reactor in the range of from < RTI ID = 0.0 > And ii) the catalytic reactor comprises a zeolite catalyst impregnated with iron ions, wherein the space velocity in the catalytic reactor of the exhaust gas is maintained in a range of 20,000 to 25,000 hr ^-1 to effect catalytic reaction, In the reaction step, ammonia is supplied as a reducing agent at a concentration of 1100 to 3300 ppm, and nitrous oxide and nitrogen monoxide are simultaneously removed from the exhaust gas by a zeolite catalyst impregnated with iron ions in the catalytic reactor.

The iron ion-impregnated zeolite catalyst used in the catalytic reactor of the present invention is selected from the group consisting of (A) BEA, MFI, MOR and FER having an Al ₂ O ₃ / SiO ₂ mole ratio of 5 to 100 Subjecting at least one or more zeolites to steam pretreatment by supplying water vapor for 0.1 to 2 hours in a nitrogen atmosphere; (B) impregnating the water-pretreated zeolite with iron ions using iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O); (C) drying the iron-ion-impregnated zeolite at a temperature of 100 to 120 ° C in air for 5 to 24 hours; And (E) calcining the dried iron ion-impregnated zeolite at a temperature of 400 to 600 ° C for 1 to 5 hours in air.

The cation in the zeolite is preferably at least one selected from the group consisting of sodium, ammonium and hydrogen. The iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) used for impregnating the zeolite with iron ions, Is preferably in the range of 0.001 to 1.0 M. [

In addition, in order to control the amount of iron ions impregnated into the zeolite, the steps (B) and (C) are preferably repeated a plurality of times in a range of at least 2 to 10 times, Is 400 占 폚 or lower, more specifically 300 占 폚 to 400 占 폚.

The present invention relates to a method and apparatus for effectively and simultaneously reducing nitrous oxide and nitrogen monoxide in an exhaust gas discharged from a chemical production process such as nitric acid, adipic acid or caprolactam using a catalytic reactor including a zeolite impregnated with iron ions We suggest a method.

Further, the present invention can decompose and / or reduce nitrous oxide and nitrogen monoxide simultaneously at a low reaction temperature of 300 to 400 ° C., even though ammonia is used as a reducing agent in the catalytic reactor, The operation cost of the nitrogen removal process can be reduced.

The use of a zeolite-impregnated zeolite catalyst together with an ammonia reducing agent makes it possible to remove nitrous oxide and nitrogen monoxide from the exhaust gas discharged during the production process of nitric acid or caprolactam through conventional processes, Is carried out simultaneously through one catalytic reactor, the exhaust gas treatment process is simplified, the operation cost is reduced, and the economical effect is obtained, and the removal efficiency is also high.

FIG. 1 schematically shows a process for separately removing nitrous oxide and nitrogen monoxide from the exhaust gas of a conventional nitric acid manufacturing plant.
FIG. 2 is a graphical representation of the simultaneous removal of nitrous oxide and nitrogen monoxide in the exhaust gas by a zeolite catalyst impregnated with iron ions in the catalytic reactor of the present invention.
3 shows the result of measuring the N ₂ O conversion of the present invention according to the change in space velocity with respect to the nitric acid process exhaust gas (catalyst layer inlet temperature = 250 ° C.)
4 shows the result of measuring the conversion of N ₂ O according to the change in the inlet temperature of the catalyst layer to the nitric acid process gas (space time = 20000 hr ^-1 )
5 shows the result of measuring the simultaneous conversions of N ₂ O and NO according to the present invention for the nitric acid process gas (space time = 20000 hr ^-1 , catalyst layer inlet temperature = 350 ° C.)

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

As shown in FIG. 2, the present invention is a method of removing nitrous oxide and nitrogen monoxide from exhaust gas discharged from a chemical production process such as nitric acid, adipic acid, or caprolactam by using a catalyst and reducing reaction using a reducing agent The present invention is characterized in that ammonia is used as a reducing agent in a catalytic reactor including a zeolite catalyst impregnated with iron ions.

Specifically, the method for preparing a zeolite catalyst impregnated with iron ions used in the present invention comprises the steps of: (A) pre-treating zeolite at a high temperature with water; (B) impregnating the zeolite pretreated in the step (A) with iron ions as a precursor solution of iron ions; (C) filtering and drying the zeolite particles impregnated with iron ions in the step (B); (D) repeating steps (B) and (C) for increasing the iron content of the powder dried in the step (C); And (E) firing the catalyst prepared in the step (D) in air.

More specifically, the processes of each of the above steps will be described as follows.

The step (A) is a step of preparing a zeolite for iron ion impregnation by water treatment, wherein the zeolite used is one of Beta (BEA), ZSM-5 (MFI), Mordenite (MOR) and Ferrierite And one of the zeolite in which the Al ₂ O ₃ / SiO ₂ mole ratio is 5 to 100 and the cationic form in the zeolite is sodium, ammonium or hydrogen is used.

Outside the range of the mole ratio of Al ₂ O ₃ / SiO ₂ of the zeolite, the impregnation amount of the iron ion is extremely small and it is difficult to exert its effect as a catalyst. In addition, since the ionic form in the zeolite is impregnated into the zeolite by the ion exchange method, the ion exchange performance with the iron ion is lower than that of the cation form presented.

The prepared zeolite is heated to 400 to 600 ° C, and 0.1 to 5 times as much moisture as the weight of the zeolite is supplied for 0.1 to 2 hours in a nitrogen atmosphere. In order to obtain the water treatment effect of the zeolite, it is preferable to carry out the water treatment in the range of the numerical limit conditions.

The step (B) is a step of preparing an iron ion solution and impregnating the zeolite with iron ions. The iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) is used as a precursor material of the iron ion and the concentration is 0.001 To 1.0 molar. This range of concentrations is intended to inhibit excessive iron ion impregnation while providing the impetus for iron ions to be ion-exchanged into the zeolite.

The zeolite hydrated in step (A) is added to the solution of the iron precursor material at a weight ratio of 0.1 to 3.0, and the mixture is stirred at a temperature of 10 to 35 ° C for 5 to 30 hours. This range of conditions is intended to maximize the ion exchange capacity of the iron ions to increase the amount of iron ions impregnated in the zeolite.

In the step (C), the zeolite slurry of step (B) is filtered and the obtained cake is washed with 500 to 2000 ml of deionized distilled water. In this step, the iron ions in the non-ion-exchanged solution in the zeolite are removed by filtration and the excess iron ions around the zeolite particles are removed by washing. Limiting the amount of distilled water for washing is to minimize the loss of iron ions impregnated into the zeolite while increasing the removal effect of excess iron ions.

The iron ion-containing zeolite obtained after washing is dried in air at a temperature of 100 to 120 ° C. for 5 to 24 hours. The limitation of the drying temperature and time is to remove moisture contained in the zeolite to enhance the effect of further ion exchange and firing in the next step.

In the step (D), the step (C) is repeated 2 to 5 times in the step (B), and the number of repetitions is such that the amount of iron ions impregnated in the zeolite is maximized, To prevent them from being generated.

In the step (E), the zeolite having been subjected to the step (D) is calcined in air at a temperature of 400 to 600 ° C for 1 to 5 hours. The range of temperature and time is to remove the impurities contained in the catalyst.

In addition, the present invention provides an exhaust gas discharged from the production process of chemical substances such as nitric acid, adipic acid or caprolactam to a catalytic reactor comprising iron ion-impregnated zeolite produced according to the above-mentioned method for producing a catalyst, A method of simultaneously reducing nitrous oxide and nitrogen monoxide in the exhaust gas by using ammonia to control the space time to maintain the supply temperature of the exhaust gas to be supplied in the range of 300 to 400 ° C, The nitrogen conversion rates could be maintained at 90% and 95%, respectively.

[Example 1]

8 g of Al ₂ O ₃ / SiO ₂ mole ratio of 25 was heated to 500 ° C. while feeding 1 liter / min of nitrogen, and deionized distilled water was passed through a syringe pump at a flow rate of 0.5 ml / min For 1 hour. After the distilled water was supplied, the temperature was cooled to room temperature at the same flow rate of nitrogen to prepare a water-treated BEA zeolite (A).

The iron ion solution (B) was prepared by dissolving 1.6 g of iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) in 1 liter of deionized distilled water. 8 g of the water-treated BEA zeolite (A) was dispersed in 1 liter of the prepared iron ion solution (B) and stirred at a temperature of 21 for 24 hours. The stirred zeolite slurry was filtered to obtain a zeolite cake impregnated with iron ions, and the cake was washed with 1 liter of deionized distilled water. The washed cake was dried in air at a temperature of 105 ° C for 12 hours. The dried zeolite was again added to the above iron ion solution, and iron ion was ion-exchanged and dried twice. The final dried iron ion impregnated zeolite was calcined at 500 ° C in air for 4 hours.

[Comparative Example]

For comparison with the catalyst in Example 1 above, BEA zeolite impregnated with iron ions not containing a water treatment process was prepared. Except for the moisture pretreatment process, the remaining production method is the same as in [Example 1], and the concrete steps thereof are as follows.

The iron ion solution (B) was prepared by dissolving 1.6 g of iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) in 1 liter of deionized distilled water. 8 g of BEA zeolite having an Al ₂ O ₃ / SiO ₂ mole ratio of 25 was dispersed in 1 liter of the prepared iron ion solution (B), and the mixture was stirred at a temperature of 21 for 24 hours.

The stirred zeolite slurry was filtered to obtain a zeolite cake impregnated with iron ions, and the cake was washed with 1 liter of deionized distilled water. The washed cake was dried in air at a temperature of 105 ° C for 12 hours. The dried zeolite was again added to the iron ion solution, and the iron ion was ion-exchanged and dried twice. The final dried iron ion impregnated zeolite was calcined at 500 ° C in air for 4 hours.

[Example 2]

In order to compare the basic performances of the catalysts prepared in [Example 1] and [Comparative Example], 0.4 g of each catalyst prepared was placed in the center of a 1/2 "stainless steel tube reactor. At a rate of 4 / min to 350 < 0 > C.

Nitrous oxide was supplied at a concentration of 400 ppm, and 400 ppm ammonia reducing agent was used. The oxygen concentration in the reaction gas was adjusted to 3,000 ppm. The total flow rate of the reaction gas was fixed at 0.4 l / min using nitrogen and the space velocity (GHSV) was maintained at 20,000 hr ^-1 . After the reaction, the concentration of nitrous oxide was analyzed using an on-line gas analyzer (SIEMENS) to analyze the gas components. The results are shown in the table below.

The nitrous oxide conversion of the catalyst prepared in [Example 1] and [Comparative Example] was measured to be 89% and 31% at a reaction temperature of 350 ° C, respectively. From these results, it was found that the catalysts impregnated with iron ions in the water- treated BEA zeolite It was confirmed that the conversion of nitrous oxide was significantly improved as compared with the BEA zeolite impregnated with iron ions which had not been treated with water at all. In the following, the iron ion-impregnated zeolite produced by the method of [Example 1] was used in the catalytic reactor.

In the case of the catalyst of the present invention, the conversion rate of nitrous oxide is significantly improved as compared with BEA zeolite impregnated with iron ions not subjected to pretreatment with water. In the zeolite catalyst of the present invention in which iron ion is impregnated by ion exchange, The reduction reaction of N ₂ O by the following reaction pathway.

N ₂ O + * N ₂ + O *

N ₂ O + O * N ₂ + O ₂ +

2O * O ₂ + 2 *

_{3O * + 2NH 3 N 2 +} 3H 2 O + 3 *

Here, when the active point represented by * is binuclear Fe and the zeolite is ZSM-5, O * generated by the decomposition of N ₂ O is referred to as a-oxygen, and O ₂ is adsorbed on Fe / ZSM- The chemistry is different from the chemical species. Also, when the zeolite is BEA, the reaction takes place in a similar path as ZSM-5, and these reactions are rearranged as follows.

N ₂ O + Fe ^II N ₂ + Fe ^III -O reduction of N ₂ O

2 / 3NH ₃ + Fe ^III -O 1 / 3N ₂ + Fe ^II + H ₂ O oxidation of NH ₃

Fe ^II + aNH ₃ Fe ^II (NH ₃ ) _a adsorption of NH ₃

Thus, Fe ^II is considered as the active site for the reduction of N ₂ O. It is judged that these active sites are improved in N ₂ O reducing ability at low temperature by the water treatment of the zeolite catalyst. In the case of zeolite Y, when the water treatment is performed at a temperature of 500 ° C. or higher, a dealumination process occurs in which the aluminum in the zeolite skeleton out of the skeleton as shown below occurs. As a result, a defect point called "hydroxyl nest" And it is believed that the process of dealumination of the Fe-impregnated zeolite of the present invention occurs during the water pretreatment process of the Fe-impregnated zeolite of the present invention, and the defect point thus generated is considered to be related to the low temperature activity of Fe ^{II as} the active site.

[ Example  3]

In order to confirm the removal efficiency of nitrous oxide and nitrogen monoxide using the catalyst of the present invention from the exhaust gas generated in an actual manufacturing plant, exhaust gas from a nitric acid production plant was used as a raw material gas, and through the iron ion-impregnated zeolite reactor of the present invention The removal efficiency of nitrous oxide and nitrogen monoxide was observed.

The iron ion-impregnated zeolite used in this example was prepared in the same manner as in [Example 1], and in order to allow a sufficient amount of Fe ions to be ion-exchanged and impregnated into the zeolite, impregnation and filtration , Washing, and drying were repeated three times in total. The final dried catalyst was calcined in an atmosphere at 500 DEG C for 4 hours.

Generally, it is known that the composition of the exhaust gas discharged from the nitric acid production process is about [NO] several hundred ppm, [N ₂ O] thousands of ppm, [O ₂ ] less than 5%, [H ₂ O] less than 1% Is about 345 ° C.

Particularly, the amount of nitrous oxide contained in the exhaust gas is about 1000 to 3000 ppm, and is contained in an average concentration of about 2000 ppm. In the case of NO, which is a nitrogen oxide, the NO is distributed in a range of about 100 to 300 ppm, .

In order to confirm the efficiency of the simultaneous removal method of nitrous oxide and nitrogen monoxide according to the present invention under the condition of introducing the raw material gas, a process as shown in FIG. 2 was carried out.

The exhaust gas 10 is supplied to the catalytic reactor 600 through the heat exchanger 200 to be supplied to the catalytic reactor at a temperature ranging from 300 to 400 ° C while maintaining the temperature of the exhaust gas 10 discharged during the nitric acid production process. The ammonia 800 used as a reducing agent is supplied to the catalytic reactor 600 through a separate feed line and is supplied to the catalytic reactor 600 through the catalytic cracked zeolite impregnated with the iron- Line analyzer 700 to analyze the composition in real time.

In the catalytic reactor 600, zeolite impregnated with Fe ions prepared in [Example 1] was pelletized to maintain a space velocity of 20000 hr < ^-1 >. In the exhaust gas supplied from the nitric acid production process The concentration of N ₂ O was about 6 times higher than that of NO.

3 shows the results of measurement of the conversion of N ₂ O when the inlet temperature of the catalyst bed was fixed at about 250 ° C and the space velocity was varied by varying the flow rate. It can be seen that the conversion rate of N ₂ O tends to decrease with increasing space velocity.

The same experiment was carried out at a space velocity of 20000 hr ^-1, and the conversion rate of N ₂ O was measured while changing the feed temperature at the inlet of the catalytic reactor from 210 ° C to 350 ° C. The results are shown in FIG.

As can be seen from the results of FIG. 4, the conversion rate of N ₂ O increased from about 35% to 90% as the feed temperature at the inlet of the catalytic reactor increased from 210 ° C. to 350 ° C., The NO conversion was found to be 100% in the range of inlet temperature and space velocity of the reactor. Considering the conversion of N ₂ O, it can be seen that the inlet temperature of the catalytic reactor is preferably maintained at 300 ° C. or higher.

5 shows the results of operating the simultaneous conversions of N ₂ O and NO in the exhaust gas for about 100 hours. By adjusting the flow rate of the exhaust gas generated from the nitric acid production process with 100 l / min, and maintaining a space velocity of 20000 hr ^-1, and, while maintaining constant the inlet temperature of the catalyst layer to 350 ℃ N ₂ O for 100 hours NO , It was confirmed that the conversion of N ₂ O and NO according to the present invention was maintained at a high and stable value of about 90% and 95%, respectively.

At this time, when the operation is temporarily stopped or the supply of the ammonia reducing agent is changed during the operation of the catalytic reactor for 100 hours, the conversion rate of N ₂ O and NO temporarily drops sharply due to the change of the operating parameters, , The conversion of N ₂ O and NO is restored to the range of about 90% and 95%, respectively.

10: nitric acid product supply part including exhaust gas component
11: process water supply unit 12: nitric acid product discharge unit
13: Cooling water line 100: Absorption tower for nitric acid production
200: Heat exchanger 300: Carbon monoxide removal unit
400: nitrous oxide removal unit 500: air exhaust line
600: catalytic reactor 700 of the present invention: exhaust gas analysis unit
800: reducing agent (NH ₃ ) supplying part 900: flow adjusting part

Claims (6)

A method for simultaneous removal of nitrous oxide and nitrogen monoxide in a chemical plant exhaust gas using a catalyst,
i) supplying an exhaust gas containing nitrous oxide (N ₂ O) and nitrogen oxide (NOx) to a catalytic reactor at a temperature ranging from 300 to 400 ° C; And
ii) the catalytic reactor comprises a zeolite catalyst impregnated with iron ions, wherein the space velocity in the catalytic reactor of the exhaust gas is maintained in the range of 20000 to 25000 hr <" ¹ &
In the catalytic reaction step, ammonia is supplied as a reducing agent at a concentration of 1100 to 3300 ppm, and nitrous oxide and nitrogen monoxide are simultaneously removed from the exhaust gas by a zeolite catalyst impregnated with iron ions in the catalytic reactor,
The simultaneous removal of nitrous oxide and nitrogen monoxide in the exhaust gas of a chemical plant using a catalyst, wherein the catalytic reactor temperature in the catalytic reaction step is 400 DEG C or less The method according to claim 1,
The iron-ion-impregnated zeolite catalyst is prepared by mixing at least one zeolite selected from the group consisting of (A) Al ₂ O ₃ / SiO ₂ mole ratio of 5 to 100, BEA, MFI, MOR, Supplying water vapor in an atmosphere for 0.1 to 2 hours to pretreat water; (B) impregnating the water-pretreated zeolite with iron ions using iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O); (C) drying the iron-ion-impregnated zeolite at a temperature of 100 to 120 ° C in air for 5 to 24 hours; And (E) calcining the dried iron-ion-impregnated zeolite at a temperature of 400 to 600 ° C for 1 to 5 hours. Simultaneous removal of nitrogen and nitrogen monoxide 3. The method of claim 2,
Wherein the cation in the zeolite is at least any one selected from the group consisting of sodium, ammonium and hydrogen, a method for simultaneously removing nitrous oxide and nitrogen monoxide in a chemical plant exhaust gas using a catalyst 3. The method of claim 2,
Wherein the concentration of the ferric nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) is in the range of 0.001 to 1.0 M. The method for simultaneous removal of nitrous oxide and nitrogen monoxide in a chemical plant exhaust gas using a catalyst 3. The method of claim 2,
(B) and (C) are repeated a plurality of times in order to control the amount of iron ions impregnated into the zeolite, characterized in that the method of simultaneous removal of nitrous oxide and nitrogen monoxide in a chemical plant exhaust gas using a catalyst delete

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