DE2643456A1 - CATALYTIC DRY REDUCTION AND DENITRATION PROCESS - Google Patents

Description

PATENT LAWYERS! 2 6 4 ν

SHIP ν. FÜNER STREHL SCHÜBEL-HOPF EBBINGHAUS

MUNICH 9O, MARIAHILFPLATZ 2 & 3 POST ADDRESS: D-8 MÜNCHEN 95, POSTFACH 95 O1 6O

HITACHI, LTD. and

BABCOCK-HITACHI KABUSHIKI KAISHA O-7 ο + v irwi

September 27, 1976

DA-12 280

Catalytic dry reduction and denitration

procedure

The invention relates to a catalytic dry reduction and denaturation process for the decomposition of gases contained in gas mixtures Nitrogen oxides to nitrogen and water. In particular, it relates to a dry process for removing nitrogen oxides (hereinafter referred to as NO), which in gas

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shaped mixtures or gas mixtures, such as combustion exhaust gases or process gases are included. More specifically, the invention is directed to a method of reducing nitrogen oxides with the aid a solid catalyst directed to nitrogen and water, in this way the nitrogen oxides into non-toxic materials to convert.

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The main source of nitrogen oxides are gases containing NO the combustion exhaust gases from thermal power plants that use fossil fuels, the exhaust gases from coke ovens and sintering furnace in the steel industry as well as exhaust gases produced in processes for treating metal surfaces, in heating furnaces and in Nitric acid forming processes occur in metal finishing plants and chemical plants. NO amounts are also due the exhaust gases from internal combustion engines or internal combustion engines are released. The nitrogen oxides NO are for living organisms

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toxic and cause a photochemically formed smog, so that there is a strong need for the disposal of these products consists.

It is well known that the nitrogen oxides NO with a reducing Gas such as carbon monoxide, hydrogen or ammonia and using an oxidation catalyst such as platinum, palladium, Copper, vanadium, molybdenum, titanium, tungsten, manganese, cobalt or chromium, decomposed reductively to nitrogen, carbon dioxide and / or water can be. (In this regard, reference can be made to US Patents 2,975,025 and 3,008,796 and JA-OS 13002/1969 will). However, the combustion exhaust gases generally contain excess amounts of oxygen and are thus oxidizing The atmosphere. It is therefore necessary to remove the nitrogen oxides NO

to reduce under such oxidizing conditions.

The reaction of NO with hydrogen can be expressed by the following equation be clarified:

2N0 + 2H ₂ → N ₂ + 2H ₂ O.

The reaction of NO with carbon monoxide proceeds according to the following

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the reaction equation:

2N0 + 2C0 Ϊ N, + 2CO ₀ ,

while NO with ammonia is subject to the following reaction sequence:

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6N0 + 4NH ₃ > 5N ₂ + 6H ₃ O.

Since the exhaust gases contain oxygen, in addition to the reduction reaction of the nitrogen oxides, NO as side reactions, oxidation

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reactions of the reducing agents with the oxygen present according to the following equations:

2H ₉ + O ₉ > 2H ₉ O,

2CO + O ₉ p- 2CO ₉ ,

4NH ₃ + 3O ₂ > 2N ₂ + 6H ₂ O.

If the exhaust gases are reacted with hydrogen and carbon monoxide, the reaction rates of the secondary oxidation reactions are greater than those of the desired reduction reactions, so that the desired reduction reactions only take place when the side reactions have expired and large amounts of the available oxygen are used up. When hydrocarbons (CH) or other organic compounds, such as alcohols, are used as reducing agents are used, one observes the same phenomena. As a result, this method is a nonselective one catalytic reduction reaction uses, not economical, since large amounts of the reducing agent are uselessly consumed. On the other hand, the reaction of NO with ammonia is faster than the oxidation reaction of ammonia, so this reaction proceeds preferentially, so that this reaction can be referred to as a selective catalytic reduction reaction.

Thus, on an industrial scale, it is catalytic Reduction with ammonia is the most advantageous method for the following reasons:

(1) It is economical because the undesired consumption of ammonia due to its oxidation with oxygen is very low is and

(2) ammonia is cheap and easy to use.

In the presence of a catalyst, the reaction of the nitrogen oxides NO with ammonia generally takes place in a temperature range from 250 to 450 ^° C. If the reaction ^{temperature is above 450 °} C., the reaction rate of the oxidation of the ammonia increases, so that predominantly the oxidation of the ammo -

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ORIGINAL INSPECTED

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niaks is favored over the reduction of nitrogen oxides NO, which leads to a reduction in the denitration efficiency. When the reaction temperature 250 ⁰ C is lower than the speed of the reduction of the nitrogen oxides NO is slowed down, which reduces also the efficiency of denitration. Therefore, it is quite common practice to allow the reaction to the catalytic reduction and denitration process run using a temperature in the range from 250 ⁰ C to 450 ⁰ C. If the method is used to treat boiler exhaust gases, these exhaust gases emerging from the economizer (exhaust gas preheater or feedwater preheater) are subjected to the reduction treatment, since the temperature of the exhaust gases in the vicinity of the economizer outlets is 270 to 400 ^° C. So that the reduction reaction of nitrogen oxides NO with ammonia can proceed, it is necessary to keep the gases to be treated in a catalyst layer in the presence of ammonia for a predetermined period of time, it being customary to carry out the reduction reaction in such a way that the gases are passed through leads a certain amount of the catalyst, which is in the form of a catalyst layer. It is possible to build more economical plants with which dust removal and desulfurization can be achieved more economically and at a lower temperature, in order to make the process more economical by denitrating the purified gas that is produced after the desulfurization step, which has a low temperature, without heating it again. However, the reduction should be carried out at a temperature of more than 30 ⁰ C and preferably at a temperature in the range of 50 to 250 ⁰ C.

However, the denitration reaction cannot be carried out at such a low temperature by the usual dry denitration methods.

The object of the invention is thus to create a catalytic dry reduction and denxtrxerungsverfahren that within a wide temperature range and in particular can also be carried out at low temperature.

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ORIGINAL INSPECTED

2B43456

This object is achieved by the inventive catalytic dry reduction and denitration process for the decomposition of nitrogen oxides contained in gas mixtures into nitrogen and water, which is characterized in that a gas mixture containing nitrogen oxides is mixed with a reducing agent selected from the group consisting of NH ₂ Amines containing groups or NH groups and _{amides containing CONH 2} groups, and a catalyst is brought into contact.

Thus, in the process according to the invention, one or more amines with NH ~ groups or NH groups or amides with CONH ₉ groups are used as reducing agents and the nitrogen oxides NO are reduced in contact with a catalyst with said reducing agent.

Examples of amines containing NH ^ groups, which are used in the invention Processes that can be used are: hydrazine, ethylenediamine, triethylenetetramine, monoethanolamine, methylamine, Ethylamine, propylamine, isopropylamine, butylamine, amylamine, hexylamine, Heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, Cetylamine, allylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, Cyclohexylamine, aniline, toluidine, benzylamine, and naphthylamine.

Examples of amines with NH groups are dimethylamine, diethylamine, Dipropylamine, diisopropylamine, dibutylamine, diamylamine, diallyl amine and methylethylamine.

Examples of amides with CONHj groups which are suitable according to the invention are urea, formamide, acetyl semicarbazide, acetamide, ethyl urea, ethylene urea, caprylamide, capronamide, diacetamide, Cyanoacetamide, nicotinamide, naphthylacetamide and butylamide.

If one hydrazine is used as reducing agent, so it is preferably 0.5 to 10 moles of hydrazine per mole of NO, and executes the reduction at a temperature by which extends from room temperature to 500 ⁰ C.

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ORIGINAL INSPECTED

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If urea is used, the reduction reaction can be carried out at a temperature from room temperature to 800 ^° C. with the addition of 0.5 to 10 mol of urea per mol of NO.

If one of the other reducing agents is used, the reduction reaction can be carried out at a temperature which extends from room temperature to 500 to 800 ^° C., with the addition of 0.5 to 10 mol of the reducing agent per mol of NO.

In the catalyst of the present invention, as the catalyst, any Metal oxide catalyst can be used. It is believed that the amino groups and the imino groups, respectively consist of one nitrogen atom and two or fewer hydrogen atoms are more active than the ammonia molecule, which consists of one Nitrogen atom and three hydrogen atoms, so these Compounds at lower temperature act as catalytic agents for reducing nitrogen oxides NO. Particularly effective

Reducing agents are hydrazine (NH.) And urea (CO (NH ₂ ) ₂ ) · The reducing agent can be added to the exhaust gas and then reacted with the catalyst, or the reducing agent can also be combined with the catalyst first.

Further embodiments, objects and advantages of the invention emerge from the further description and the examples in which reference is made to the accompanying drawings is.

In the drawings show:

Fig. 1 is a flow chart illustrating an embodiment based on a diagram of the method according to the invention, which is applied to a boiler exhaust gas;

Fig. 2 is a graph showing the experimental results of an example of the invention, the graph showing the denitration rate is plotted against the reaction temperature;

3 shows a curve similar to that shown in FIG. 2, which shows the experimental results of a further example

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ORIGINAL INSPECTED

game of the invention illustrates; and

Fig. 4 is a flow diagram illustrating a further embodiment of the method according to the invention, which is also is applied to a boiler exhaust.

In the following the invention will be explained further by means of examples, in which boiler exhaust gases are treated.

Referring to FIG. 1, a combustion exhaust gas from a boiler 1 is introduced into an air preheater 2 for heat recovery. A reducing agent is then fed into the gas emerging from the air preheater from a reducing device 6, whereupon the mixture formed is transferred to the NO reduction reactor or the denitration reactor 3. Both anhydrous hydrazine (N ₀ H) and water-containing hydrazine (N ₂ H.-HO) are liquid at room temperature and at atmospheric pressure. This liquid hydrazine can be uniformly mixed with the exhaust gas by injecting the liquid reducing agent through a nozzle inserted into a chimney, as is conventionally practiced for uniformly mixing a liquid with a gas. In this case it is desirable to atomize the liquid droplets as small as possible in order to disperse the liquid more evenly in the gas. It is also possible to introduce the liquid into the chimney in gaseous form by heating it, or it is also possible to bring the gas into direct contact with the liquid if a liquid with a high vapor pressure is used as the reducing agent. If you use a reducing agent in solid form, you can use it in the. Dissolve water to form an aqueous liquid, which is treated for uniform mixing with the exhaust gas as well as the liquid reducing agent, or the solid reducing agent can be sublime and supplied in the form of a gas. The combustion exhaust gas is in contact with a catalyst in the denitration reactor 3 brought by passing the gas through a fixed catalyst bed. After denitration in the denitration reactor 3, the exhaust gas is passed into a desulfurization device 4 or the SO -

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Reduction reactor 4 transferred, where the gas is desulfurized, whereupon it is discharged through a chimney 5. However, one can also dispense with the desulfurization device 4 and discharge the exhaust gas directly from the denxtration reactor, if that Gas contains only small amounts or no sulfur oxides (SO). Furthermore, you can the embodiment shown, in the the gas is desulfurized after the end of the denitration, also reverse, and the gas only after the end of the desulfurization denitrate. This latter embodiment is preferred if the concentration of sulfur oxides is high or the dust content of the gas is high. The reaction of the reducing agent with the nitrogen oxides NO is explained below with reference to the reaction of hydrazine with NO. This reaction can be represented by the following reaction equation:

N ₂ H ₄ + 2NO> N ₂ + H ₂ O

As can be seen from the above equation, 0.5 mole of hydrazine reacts with 1 mole of NO. Hence it is required at least Add 0.5 mole of hydrazine per mole of NO to allow the reaction to proceed. The most preferred amount of hydrazine added extends from the chemically equivalent amount up to 10 moles based on 1 mole of NO. If you have the gas with an amount of hydrazine added, which is greater than the chemically equivalent amount, so this does not have the consequence that hydrazine in the process is released as the excess hydrazine through the action of the existing oxygen to nitrogen and water is implemented.

In the following example, the denitration is carried out at a low temperature of about 150 ⁰ C in the vicinity of the air preheater. The inventive method is not limited to this example, so that the denitration can be performed even at a high temperature of about 350 ⁰ C at a point of the process sequence, which is located in front of the air preheater. However, the reaction temperature is selected based on economic considerations.

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The space velocity in the solid catalyst bed can range from 1,000 volumes / volume / hour to 100,000 Volume / volume / hour.

The reaction between urea and NO can be represented by the following reaction equation:

+ ■ 2NO + 1/2 O ₃ > 2N ₂ + 2H ₃ O +

₂ + 2H ₃

As can be seen from the above reaction equation, 2 moles of NO are reacted with 1 mole of urea and decomposed to nitrogen and water or carbon dioxide. Since oxygen is also involved in the reaction, the denitration efficiency is reduced if the oxygen concentration is less than O ₇ 5%. The most preferred amount of hydrazine added ranges from the chemically equivalent amount up to 10 moles based on 1 mole of NO. The reduction reaction of NO with urea is carried out at a temperature of more than 30 ⁰ C, where the efficiency of the denitration increases with increasing temperature. In the following example, the denitration is carried out at a temperature in the range of about 150 ⁰ C in the vicinity of the outlet of the air preheater 2, although the reaction can be performed at a location and at a temperature in the range of about 350 ⁰ C, which located in front of the air preheater 2. In this embodiment of the process according to the invention, too, the denitration temperature can be selected taking into account economic reasons, so that the claimed process is not restricted to this lower temperature range.

example 1

This example concerns the selective reduction of nitrogen oxides, which are contained in a gas mixture which is contained in a gas cylinder or in the gas cylinder, using of hydrazine. Hydrazine is mixed with a gas mixture containing 2.5% by volume of oxygen, 205 ppm (by volume

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ORIGINAL INSPECTED

2 ^Γ Α 3 4 5 G -> er -

drawn) NO and the remainder nitrogen. The gas mixture mixed with hydrazine is then passed through a glass tube with a diameter of 14.5 mm serving as a reactor. The glass tube reactor is filled with a catalyst, which mainly consists of titanium, iron and vanadium. One works at a gas space velocity of 14500 volume / volume / hour. The reaction temperature is varied in a range from 30 ⁰ C to 150 ⁰ C while maintaining an added amount of hydrazine of 1000 ppm (by volume), and calculates the Denitrierungsraten at the respective temperatures from the results obtained by determining the NO concentration at the Establishes inlet and outlet of the reactor tube, for which purpose an NO catalyst (of the Kemilumi type) is used. The denitration rate is defined by the following equation:

Denitration rate =

it ΝΟ ,, - concentration at the outlet of the reactor tube . _inn "

NO concentration at the inlet of the reactor tube

The results obtained are summarized in Table I below:

Table I.

Temperature ( ⁰ C) Denitration Rate (%)

30 20

50 25

100 47

120 80

150 100

As can be seen from Table I above, the denitration reaction is already running off at a low temperature of 30 ⁰ C to obtain achieved with increasing temperature higher denitration rate and a higher percentage denitration.

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ORSGlNAL! NSPECTED

At 150 ⁰ C, the denitration rate substantially reaches the value of 100%. ■

Example 2

Under similar conditions as described in Example 1, determining the Denitrierungsraten, with the difference that maintaining a reaction temperature of 120 ⁰ C and changing the concentration of the added hydrazine. The results obtained are shown in Table II below.

Table II

-N ₂ H ₄ / NO denitration rate (%)

0.5 27

1 ■ 50

2 67 5 80

10 90

As can be seen from Table II above, the denitration rate improves with increasing N ₃ H./NO molar ratio. It is preferable to work with a molar ratio of N _? H. to NO (N ₂ H./NO molar ratio) from 0.5 to

Example 3

Hydrazine is mixed with a gas mixture that is 2.5% by volume Oxygen, 200 ppm NO and the remainder nitrogen contains and leads the gas through a glass reactor tube with a diameter of 14.5 mm. The reactor tube is made with activated alumina filled as a catalyst. A space velocity of 68600 h (or V / V / h) is used. The amount of hydrazine added is held constant at 1000 ppm, whereupon the denitration

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rates determined / by determining the NO concentration at the inlet and outlet of the reactor at varying reaction temperatures from 30 to 500 ⁰ C and calculating the denitration rate with the help of the following equation:

Denitration rate =

NO concentration at the outlet of the reactor tube ¹ NO concentration at the inlet of the reactor tube ' ^X *'

The results thus obtained are summarized in Fig. 2, it can be seen from that one already achieved even at a low temperature of 30 ⁰ C a high denitrification rate. When carrying out the denitration at a temperature of 100 to 200 ⁰ C, the total available nitrogen oxides are reduced substantially, so that a denitration rate and a reduction percentage of NO of 98% is obtained. At temperatures of more than 200 ⁰ C a reduction in the denitration rate and the NO reduction occurs.

Example 4

Under similar conditions as described in Example 3, determines the Denxtrierungsraten, maintaining in this case the Reaktxonstemperatur at 200 ⁰ C and changes the oxygen concentration. The results obtained are shown in Table III below.

Table III

Oxygen Concentration (%) Denitration Rate (%)

0 51

3 93

10 93

15 93

It can be seen that the

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denitration rate achievable with the system is lower than the one obtained in a system that contains oxygen. Furthermore, one achieves under the conditions of this example in the presence of oxygen, a constant denitration rate which is independent of changes in the oxygen concentration.

Example 5

The denxtrusion rates are determined under conditions which are similar to those of Example 3, with the difference that the reaction ^{temperature is kept at 200 °} C. and the amount of hydrazine added is changed. The results obtained are shown in Table IV below.

Table IV

./NO molar ratio denitration rate (%)

0.5 32

1 56

2 81 5 93

It can be seen from the numerical values given in Table IV above that, despite a decrease in the denitration rate with decreasing amount of hydrazine, a denitration rate of 32% is achieved if only 0.5 mol of hydrazine per mol of NO (N ₂ H ₄ / NO molar ratio = 0.5) begins.

Example 6

Under conditions similar to those described in Example 1, the determination of the denxtration rates is carried out, 1000 ppm urea being added as a reducing agent instead of hydrazine. The results obtained are in the Table V below.

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Table V

Temperature ( ⁰ C) Denitration Rate (%)

30 11

50 30

100 41

120 . 53

150 100

As can be seen from the above Table V, the denitration reaction proceeds even at low temperature of 30 ⁰ C, and will result in higher with increasing reaction temperature Denitrierungsraten. This behavior is in agreement with the results of the investigations in which hydrazine is used as a reducing agent, in which case the efficiency of the denitration is shifted towards the higher temperatures.

Example 7

An aqueous solution of urea is mixed by atomization with a gas mixture containing oxygen, NO and nitrogen, and the mixture is then passed through a glass reactor tube with a diameter of 14.5 mm. The reactor tube is packed with activated alumina as a catalyst. Is carried out at a space velocity of 14500 h (v / v / h) and applies a reaction temperature in the range of 200 to 800 ⁰ C., while maintaining the added amount of urea constant at 1500 ppm. The concentration of oxygen in the gas mixture is also varied and is 0%, 2.5% and 15%, respectively.

The results of this study are shown in Fig. 3, from which it can be seen that the denitration can be carried out at a lower temperature when the system contains oxygen as compared with a system containing no oxygen. It can also be seen that a denitration rate of 70 to 80% at 500 to 700 ⁰ C and in the presence of oxygen is achieved

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aims to reduce the rate of denitration in the absence of oxygen increases with increasing temperature.

Example 8

The denitration rates are determined under conditions similar to those described in Example 6, the amount of urea added being changed and the oxygen concentration being kept at 15% and the reaction ^{temperature at 600 °} C. as a change. The results of this investigation are as follows
Table VI compiled.

Table VI

CO (NH ₂ ) "/ NO molar ratio Denitration rate (%)

1 54

2 68
5 79

From the results shown in Table VI above, it can be seen that the denitration rate under the conditions
this investigation increases with the molar ratio. A molar ratio of 1 results in a denitration rate of 54 I,
while a molar ratio of 5 to a denitration rate of
79% leads.

The following is a further embodiment of the invention Method explained with reference to FIG.

As shown in FIG. 4, the combustion exhaust gas becomes
of a boiler 1 through an air preheater 2, in which the existing heat is recovered, into the denitration reactor or the NO reduction reactor 3. The denitration reactor 3 comprises

holds a solid support layer 13, a catalyst layer 14 and a spray nozzle 16 for spraying a reducing agent. The Ver-

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Combustion exhaust gas is first passed through the solid support layer 13 and then passed through the catalyst 14, the spray nozzle 16 being above the solid support layer 13, in the direction of flow seen, is arranged. The reducing agent supplied from a reducing agent container with the aid of a pump 17 is over the spray nozzle 16 is injected. The injected reducing agent meets the solid support layer 13, on which the main amount the reducing agent sticks. The adhering reducing agent evaporates or sublimates under the action of those in the exhaust gas existing heat and mixes evenly with the exhaust gas, whereupon the gas mixture passed through the catalyst shaft 14 in which the nitrogen oxides are decomposed into nitrogen and water. This procedure can be particularly effective on one System can be used in which a reducing agent is used which cannot easily be vaporized, for example urea. If an easily evaporable reducing agent such as hydrazine is used, the solid support layer 13 is not required, since this reducing agent can easily be mixed evenly with the combustion gases.

Alternatively, the substance, which is not easily evaporated, can first be sprayed onto the catalyst layer 14. In this case however, when designing the reactor, account must be taken of the fact that the liquid substance temporarily acts as the catalyst covered and thus impaired its effectiveness.

As the solid support material, any heat-resistant support material with high strength, such as alumina, alumina-silica, can be used and use silica. Instead of spraying the reducing agent onto the apply solid support material; for example, a fluid bed or a fluidized bed made of the solid support material can be used use and gradually remove the solid support from the denitration reactor peel off and reintroduce it into the denitration reactor. Especially when in the combustion exhaust If large amounts of dust are present, the solid support can serve as a prefilter to filter off this dust. According to the denitrie

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If necessary, the combustion exhaust gas is reneged in the desulphurisation device 4 desulfurized and then discharged through the chimney 5 as a clean gas.

In the embodiment shown, the gas is after The denitration step is desulfurized, although one involves a process in which both denitration and desulfurization should be carried out, you can also do the reverse order can apply. The last-mentioned method is then preferred, when the concentration of the sulfur oxides present in the exhaust gas is high, since these substances are removed by the preferred step can be.

Example 9

This example illustrates the selective reduction of nitrogen oxides contained in a gas mixture supplied via a gas bomb using urea. A catalyst, which consists essentially of titanium, vanadium and iron, is immersed in a 5% urea solution for 1 hour, and the impregnated catalyst is transferred to a vessel which is kept at a constant temperature of 100 ^° C., which temperature is lower than the melting temperature of urea to evaporate the water and then introduces the catalyst into a glass reactor tube. Then, in order to bring about contact with the catalyst, a gas mixture containing 300 ppm (based on volume) NO, 2.5% by volume O ₂ and nitrogen as a resist is introduced into the glass reactor tube. From the results of the determination of the NO concentrations at the inlet and at the outlet of the reactor tube

ter using a suitable analyzer (of the type Kemilumi) calculated one, aiüe be achieved if won the gas at a reaction temperature supplies the Denitrierungsraten 30 to 150 ⁰ C and with a space velocity of 14500 V / W / h. The results obtained are shown in Table VII below.

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Table VII

Temperature ( ⁰ C) Denitration Rate (%)

30 11

50 30

100 41

120 53

150 100

As can be seen from Table VII above, NO can be reduced at a low temperature when urea is on the surface of the catalyst is present.

Furthermore, the Denitrierungsraten be determined, resulting in a change in the oxygen concentration of 0 to 15 volume%, the reaction temperature Meantime constant at 150 ⁰ C is maintained. These results are summarized in Table VIII below.

Table VIII

Oxygen Concentration (%) Denitration Rate (%)

0

1 5

15th

As can be readily seen from Table VIII above, oxygen will participate in the reaction and the reaction will proceed successfully when oxygen is present in an amount greater than about 0.5 percent or more. It can therefore be assumed that the oxygen increases the reactivity of the urea. The results of this example are consistent with the findings obtained in those experiments

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in which the urea is injected into the gas, and serve to further illustrate the advantageous effects of the method according to the invention.

Example 10

A glass reactor tube with a diameter of 14.5 mm, which is divided into two stages, is used. A gas mixture is first passed through a layer of a solid support material and then through the catalyst layer. Inactive aluminum oxide is used as the solid support material. The urea is supplied in such a way that it is previously sprayed onto the solid support material, using a ratio of 2 moles of urea per mole of NO. One works at a space velocity in the solid support material layer of 10,000 V / V / h. The denitrification rate is 100% at 150 ⁰ C, which is consistent with the study, in which the urea is applied to the catalyst.

Example 11

Example 10 is repeated, with the difference that 2 moles of hydrazine per mole of NO are used instead of urea by atomization with a denitration rate of 100%.

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Claims (10)

2 B 4 3 4 5 8 claims 1. Catalytic dry reduction and denitration process for the decomposition of nitrogen oxides contained in gas mixtures to nitrogen and water, characterized in that a gas mixture containing nitrogen oxides is mixed with a reducing agent selected from the group consisting of the NH ₂ groups or NH groups comprising amines and amides containing CONH groups, and brings them into contact with a catalyst. 2. The method according to claim 1, characterized in that a reducing agent selected from the group the amines and CONH groups containing the NEU groups or NH groups containing amides, mixed with a gas mixture containing nitrogen oxides and then the formed Bringing mixture into contact with a catalyst. 3. The method according to claim 1, characterized in that a gas containing nitrogen oxides is brought into contact with a catalyst to which a reducing agent adheres which is selected from the group consisting of _{amines containing NH 2} groups or NH groups and CONH ₂ -Group containing amides. 4. The method according to claim 1, characterized in that the _{amines containing NH 2} ~ groups are hydrazine, ethylenediamine, triethylenetetramine, monoethanolamine, methylamine, ethylamine, propylamine, isopropylamine, butylamine, amylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, andecylamine , Dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine, allylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, aniline, toluidine, benzylamine and / or naphthylamine are used. 5. The method according to claim 1, characterized / that the amines containing NH groups are dimethylamine, diethylamine, dipropylamine, Diisopropylamine, dibutylamine, diamylamine, diallylamine and / or methylethylamine are used. 6. The method according to claim 1, characterized in that the amides containing CON ^ groups are formaldehyde, urea, Acetyl semicarbazide, acetamide, ethyl urea, ethylene urea, Caprylamide, capronamide, diacetamide, cyanoacetamide, Nicotinamide, naphthylamide and / or butylamide are used. 7. The method according to claim 1, characterized in that one carries out the reaction at a temperature ranging from room temperature to 800 ⁰ C. 8. The method according to claim 1, characterized in that a metal oxide is used as the catalyst. 9. The method according to claim 1, characterized in that a nitrogen oxides-containing gas at a temperature in the range from room temperature to 500 ⁰ C with hydrazine, which is added in a molar ratio of 0.5 to 10 moles of hydrazine per mole of NO, and a Bringing catalyst into contact. 10. The method according to claim 1, characterized in that a nitrogen oxides-containing gas is brought ^{into contact with urea at a temperature in the range from room temperature to 800 °} C., which the gas in a molar ratio of 0.5 to 10 mol of urea per mol of NO is admitted. 709813/0798