DE20122446U1 - Catalytically converting nitrogen oxide in exhaust gas stream mixed with ammonia to form water and nitrogen comprises feeding gas stream together with added catalytically active substance to reaction chamber - Google Patents

Abstract

Catalytically converting a nitrogen oxide in an exhaust gas stream mixed with ammonia to form water and nitrogen comprises feeding the gas stream (A) together with an added catalytically active substance (S) to a reaction chamber (2). Independent claims are also included for the following: (a) a process for reacting a catalyst module (3) produced by depositing a catalytically active material in or on a catalyst substrate (31) comprising wetting the catalyst module with a catalytically active substance; (b) a fuel for burning in a combustion process containing the catalytically active substance; and (c) an exhaust gas purification device for a power station or a vehicle combustion engine comprising an injection device for injecting the catalytically active substance into the fuel.

Description

The Invention is in the field of catalysts.

The The invention relates to an emission control system of the first type, in particular for one Combustion plant of a power plant or for an internal combustion engine Motor vehicle, in which an emerging during combustion exhaust stream for converting a pollutant contained therein by a catalyst module guided That is by depositing a catalytic conversion of the Pollutant-promoting catalytically active material on or in a catalyst substrate is produced, wherein in particular nitrogen oxide contained in the exhaust stream convertible according to the principle of selective catalytic reduction is, according to the preamble of claim 1.

The The invention also relates to an exhaust gas purification system second Type, especially for an incinerator of a power plant or an internal combustion engine of a motor vehicle in which one from the combustion of a fuel emerging exhaust gas stream for the conversion of a pollutant contained therein passed through a catalyst module That is by depositing a catalytic conversion of the Pollutant-promoting catalytically active material on or in a catalyst substrate is produced, wherein in particular nitrogen oxide contained in the exhaust stream convertible according to the principle of selective catalytic reduction is, according to the preamble of claim 3.

Out For example, WO-A-9728358 is a diesel engine with a particulate filter known in which oxidizable exhaust gas constituents both accumulated as well as catalytically oxidized. To the particle filter in one To operate at equilibrium, i. in a state in which the rate of accumulation of oxidizable exhaust constituents in the particulate filter the rate of degradation of the oxidizable exhaust gas constituents in the particle filter corresponds, is the feed catalytically more effective, the degradation of oxidizable gas constituents in Particle filter supportive Substances provided in the intake and / or exhaust tract of the diesel engine.

Out US-A-5322671 discloses a catalyst system which comprises at least having two chambers, which by at least one opening having Plate, which allows a flow of gas, are separated. In the Catalyst system is by pumping or spraying a solution with catalytically active Material can be introduced.

Out US-A-3168368 discloses a method in which a fuel for one Internal combustion engine catalytically active substances are supplied, which, for example, vanadium, chromium, manganese, iron, cobalt, nickel, Copper or other metals.

Out DE-A-19800873 is a catalyst solution for reducing emissions of harmful substances in case of burns and / or drying and / or thermal processes of carbonaceous material known. A pollutant-reducing effect should thus, for example, in a Sinterband plant for be achievable a blast furnace.

One A process for regenerating a honeycomb catalyst is, for example known from EP-A-0974397. In addition to cleaning the catalyst with a cleaning solution is also the impregnation provided with catalytically active material.

In the oxidic combustion of fossil fuels, substances or pollutants that pollute the environment are produced in the exhaust gas or flue gas. For example, nitrogen oxides, for example NO or NO ₂ , are contained in the flue gases which are produced in waste incineration plants, power plants, smelting furnaces or heating plants. An exhaust gas or fluid stream of a similar nature also arises in the combustion of diesel fuel or other fuels in the internal combustion engines of motor vehicles.

For the conversion of unwanted nitrogen oxides is a known under the name "selective catalytic reduction (SCR)" method, for example, in a prospectus of Siemens AG with the order number A96001-U11-A294-V1 from 1996, or from the German patent DE 24 58 888 known. The nitrogen oxides are catalytically converted into harmless nitrogen and water vapor in this process by the addition of ammonia. For this purpose, the flue gas or exhaust gas at a temperature between 300 and 500 ° C is passed through a catalyst or through a catalyst module. The catalyst module consists of a ceramic matrix or a ceramic catalyst substrate, on which a catalytically active material is deposited, which causes or promotes the conversion of the nitrogen oxides into nitrogen and water vapor. Such a catalytic material are, for example, the oxides of titanium, vanadium and / or the Tungsten and / or molybdenum.

It it is known that SCR catalysts dependent on deactivate the smoke gas ingredients during their operation. The causes for the deactivation are e.g. chemically grounded, i. that the catalytic effective material will enter into compounds that do not participate in the SCR process can. But it can also be that in the During operation, the catalytically active material from the flowing exhaust gas stream is transported out of the catalyst module out. This occurs in particular then, if the catalytically active material contained in the exhaust Halogens volatile Metal-halogen compounds are received.

The Deactivation of SCR catalysts has been compensated by that extra catalyst volume or other catalyst modules were added. This approach is expensive and expensive. When carrying out the SCR in the automotive sector it is technically feasible only at unreasonable expense. At the Use in the power plant area is a power plant shutdown required.

It There is therefore a need, the deactivation of the catalytic effective material through other measures. The invention the object is to provide a device for this purpose.

The Task is based on the aforementioned emission control system first type according to the invention solved by an emission control system with an injection device, with the one substance in the flow direction is fed into the exhaust gas before the catalyst module, wherein the Substance for the conversion of a pollutant present in the exhaust gas catalytically effective material is or contains or from the substance catalytically active material can be deposited is. A downstream of the catalyst module separation device is for the separation of catalytically active material from the exhaust stream intended. Preferably, the injection device to a reservoir for Absorption of the substance.

The Task is based on the aforementioned emission control system second type according to the invention solved by an emission control system with a feed device, by means of which a substance can be added to the fuel, wherein the Substance catalytically active material is or contains or From the substance catalytically active material is deposited. To the feeder a return line is connected by which separated from the exhaust stream catalytically active material can be fed into the fuel.

Preferably the feeding device has a storage container for receiving the substance on.

The Emission control systems of both types are to carry out a suitable in the following method. The related apply to the advantages mentioned with the method described below for the Exhaust gas purification systems analog. The facilities are responsible for the implementation of the Process suitable trained.

At the Operation of the emission control system is the exhaust gas flow to the reaction space supplied a substance, the catalytically active material is or from the catalytic Effective material is bildbar. In a downstream of the reaction space Separator is catalytically active material from the Gas stream separated.

Preferably the substance is added continuously. But it is also one discontinuous addition possible.

The Arrangement of a catalyst module is not necessarily required. The catalytic conversion of the pollutant in the exhaust gas can alone be done by such catalytic effective material that the Reaction space is supplied in the form of the substance. This catalytic effective material can be fed continuously or discontinuously.

To In a preferred embodiment, the gas stream is through, in particular arranged in the reaction space, catalyst substrate or on a passed such over.

Preferably the substance is the gas flow in the flow direction in front of the catalyst substrate added.

Especially the substance is homogeneously dispersed upon addition to the gas stream or atomized.

Prefers is or is the substance admixed with a fuel in which Combustion of the substance contained in the gas stream is produced as exhaust gas.

With particular advantage is in or on the catalyst substrate, a catalytic conversion of the material promoting catalytically active Material stored or deposited a catalyst module forming. The Catalyst module was so for example by deposition of the catalytic effective material in a separate manufacturing process prior to the implementation of the Produced method according to the invention.

If such a catalyst module is completely or partially deactivated, is it possible with this method to regenerate it quasi in situ. The catalyst module must therefore for Regeneration is not necessarily taken out of service, i.e. In particular, a power plant does not necessarily have to be out of service walk. When a fresh or unused catalyst module is already using this method of deactivation of Initially counteracted.

To a preferred embodiment is the catalytically active material, that supplied with the gas stream or from the substance is formed, the same as the catalytic effective material used in the preparation of the catalyst module was deposited or deposited. As a result, the catalyst module in Regenerated particularly efficient way.

It also works the catalytic material added to or formed in the gas stream itself catalytic, so that itself in the event of regeneration of the catalyst module not taking place Increasing the catalytic efficiency would be possible.

to Increasing the regeneration effect has that before the catalyst module added catalytically active material or from the substance formed catalytically active material the property of being on the Deposit catalyst module.

Also with particular advantage is by storage or deposition of the catalytic effective material of the gas stream in or on the catalyst substrate a catalyst module is formed.

With This method is in fact in a particularly advantageous manner possible, in the gas stream inert or catalytically inactive catalyst substrate to bring. The catalyst module is then gradually formed by deposition or incorporation of the substance formed or contained in the substance catalytically active material.

• a) Dem Gasstrom wird eine Substanz beigemischt, die katalytisch wirksames Material ist oder enthält oder aus der katalytisch wirksames Material abscheidbar ist.
• b) Der Gasstrom wird anschließend durch oder über ein Katalysatorsubstrat geführt.
• c) Durch Ab- oder Einlagerung des katalytisch wirksamen Materials auf dem bzw. in das Katalysatorsubstrat wird das Katalysatormodul gebildet.

The preparation of the catalyst module takes place in particular in the following steps:

• a) The gas stream is admixed with a substance which is or contains catalytically active material or can be separated from the catalytically active material.
• b) The gas stream is then passed through or over a catalyst substrate.
• c) By depositing or storing the catalytically active material on or in the catalyst substrate, the catalyst module is formed.

at an alternative method, the catalyst module with a Wets substance for the conversion of a substance present in a gas stream catalytically effective material is or contains or can be separated from the catalytically active material. In a the separator downstream of the catalyst module is catalytically active material separated from the gas stream. It will for example, in or on the catalyst substrate of the catalyst module, after the catalyst module for longer time in operation, again catalytically active material on or introduced.

Especially is the catalytically active material of the substance in or on the preparation caused existing catalytically active material deposited and / or deposited.

With particular advantage is the catalytically active material of the substance the same as the catalytically active material used in the manufacture the catalyst module was deposited or deposited.

According to a particularly preferred embodiment, the substance is supplied to the catalyst module during the catalyst operation. Such an online operation has the particular advantage that the catalyst module for regeneration must not be taken out of service and therefore no interruption the catalytically influenced process must take place.

Preferably the substance is mixed with a substance belonging to the catalyst module to promote the Conversion of the substance supplied becomes. It is therefore advantageously no separate stream to the catalyst module required because the substance is mixed with the substance will be, the operational according anyway supplied to the catalyst module becomes.

To the Wetting the catalyst module, the substance is preferably in vaporized or gaseous Condition before.

To In a preferred variant, the substance is or will become a fuel admixed with the combustion of which a substance is produced as exhaust gas, the catalyst module for promotion fed to the conversion of the substance becomes.

Preferably the substance content in the fuel is between 10 mg / kg Fuel and 200 mg / kg of fuel.

Especially the content of the fuel of catalytic material is one Value between 50 mg / kg fuel and 100 mg / kg fuel.

The Substance, and in particular the catalytically active material is preferably in dissolved or dispersed form contained in the fuel or is it in soluble or dispersing form.

The Catalytically active material is preferably suitable for Conversion to promote the combustion of pollutant.

To a particularly preferred embodiment has the catalytically active Material the property, nitric oxide according to the principle of selective to convert catalytic reduction, which in the case of combustion resulting exhaust gas is included.

at contains all the above-mentioned procedures the catalytically active material is preferably atoms of one of the elements Vanadium, titanium, tungsten, iron and / or molybdenum, and the catalytically active In particular, material is an oxide of one of these metals. Also mixtures the said elements are possible.

Six embodiments of a device according to the invention are described below with reference to FIG 1 to 6 explained in more detail. Show it:

1 A first embodiment of an exhaust gas purification system according to the invention,

2 a second embodiment relating to the implementation of a method according to the invention,

3 A third embodiment relating to a method according to the invention,

4 A fourth embodiment relating to a method according to the invention,

5 A fifth embodiment relating to a method according to the invention,

6 A sixth embodiment relating to a device and a method according to the invention,

7 a first measurement result obtained by the method according to the second embodiment, and

8th a second measurement result obtained by the method of the second embodiment.

1 shows a line 1 in which a reaction space 2 is formed. In the reaction room 2 is a catalyst device comprising three catalyst modules 3 arranged. The catalyst modules 3 be in the flow direction 5 by a fluid or gas A, which is an exhaust gas or flue gas flows through. The exhaust gas A contains a substance or pollutant, namely nitric oxide NO (NO _x ). To reduce the nitrogen oxides according to the principle of selective catalytic reduction (SCR) is the gas A with the pollutant NO by means of a line 1 opening first feedline 7 Ammonia NH (NH ₃ reducing agent fed in. The nitrogen oxides NO enter the catalyst modules together with the admixed ammonia NH 3 in the reaction room 2 , There is a conversion of the nitrogen oxide NO in nitrogen (N ₂ ) and water vapor (H ₂ O) instead, so that after the catalyst modules 3 emerging gas stream has a greatly reduced nitrogen oxide content.

The exhaust A comes from, for example, the firing system of a gas, oil or coal-fired power plant. The catalyst modules 3 contain as catalytically active material K vanadium, molybdenum, tungsten and / or titanium, in particular in oxidic form. In the preferred temperature range from 300 ° C. to 450 ° C., the catalytically active materials K used for the SCR process operate in a highly selective manner, so that undesirable side reactions are largely prevented.

The catalyst modules 3 can partially or completely deactivate after prolonged operation. Possible deactivation causes are the action of dust or the action of chemical compounds, for example halogens contained in the exhaust gas A, on the catalytically active material K.

For in-situ regeneration of the deactivated catalyst modules 3 becomes the exhaust gas A in the flow direction 5 in front of the catalyst modules 3 by means of an injection device 8th fed new or fresh catalytically active material KU. Instead of catalytically active material KU can by means of the injection device 8th Also, a substance S are supplied, from which, for example, only in the exhaust stream A, the catalytically active material KU forms. The added or formed catalytically active material KU is the same or has a composition similar to that of the catalytically active material K present in the catalyst modules 3 already exists or was originally available.

The injection device 8th has a reservoir 11 for receiving the substance S or the catalytically active material KU. From the reservoir 11 starting from a second feed line opens 9 in the exhaust A leading line 1 , The second feedline 9 is configured at its mouth so that the substance S or the catalytically active material KU when entering the line 1 is dispersed or atomized.

The administration 1 , the catalyst modules 3 and the first feeder 7 form together with the injection device 8th an emission control system 13 , which is used both stationary for an incinerator of a power plant and mobile for an internal combustion engine of a motor vehicle.

This in 2 illustrated second embodiment of a method according to the invention differs from the first embodiment essentially in that the substance S or the fresh catalytically active material KU is admixed with a fuel B, from the combustion in a combustion chamber 15 the exhaust A first arises. In the illustrated embodiment, the fuel B, the substance S or the catalytically active material KU is added in dissolved or dispersed form, by means of a fuel line 17 into the combustion chamber 15 promoted. To promote the fuel B from a tank 21 is a pump 19 available. The fuel B contains the substance S or the catalytically active material KU with a share between 10 mg / kg fuel and 200 mg / kg fuel.

In the combustion chamber 15 the fuel B is burned, whereby nitric oxide-containing exhaust gas A is formed. For example, forms in the combustion chamber 15 from the substance S, the new catalytically active material KU. From the combustion chamber 15 out the exhaust gas A passes with the nitrogen oxide NO and the new catalytically active material KU through the line 1 to the catalyst modules 3 in the reaction room 2 , In the flow direction 5 in front of the catalyst modules 3 is like the first embodiment via the first feed line 7 Ammonia NH added.

The combustion of the substance B or catalytically active material KU offset fuel B for an extended period of time, the catalyst modules 3 regenerated.

This regeneration is from the in 7 shown first measurement result. In the underlying experiment, catalytically active material KU was added to fuel B of a refinery power plant as a mixture of vanadium V and iron Fe. 102 mg of vanadium and 252 mg of iron per kg of fuel B were added. During the combustion of the fuel B, an exhaust gas flow with a volume flow in the humidity of 150,000 m ³ / h was generated. The vanadium content in the exhaust gas A or flue gas was 316 ppm. This was based on a moist smoke gas density of 1.31 kg / m ³ . The operating temperature of the catalyst modules 3 was 370 ° C.

In the table below the vanadium content V205 (content of vanadium oxide V ₂ O ₅ ) at the beginning of the combustion of the fuel B (t = 0h) and after about 6000 h, respectively measured on the upstream side and on the downstream side the multi-layer catalyst modules 3 :

In the diagram of 7 is on the left ordinate the vanadium content V205 in the catalyst modules 3 Plotted in percent. The abscissa shows the time t in hours (h).

The vanadium content V205 in the partially deactivated catalyst modules 3 was at the beginning of the regeneration measure (t = 0h) about 0.4%. After 6000 hours of operation, the vanadium content V205 was measured by RFA (= X-ray fluorescence analysis), whereby a dust deposit had previously been removed.

The graph shows that the vanadium content V205 increased to about 1.3%. As a result, the nitrogen oxide specific catalytic activity K-NOx of the catalyst modules increased 3 from initially about 41.5 m / h to about 48.5 m / h after 6000 operating hours (right ordinate).

In 8th the oxidation rate K-SOx for the oxidation reaction of SO ₂ to SO _{3 is} plotted on the right ordinate. This increased during the 6000-hour observation phase from initially 200 m / h to about 550 m / h.

This in 3 illustrated third embodiment differs from that in 2 illustrated second embodiment, first, characterized in that the substance S or the fresh catalytically active material KU the fuel B in the tank 21 not already mixed, but from a separate container 25 is added to the fuel B only after this from the tank 21 is encouraged. In the example shown, the substance S or the catalytically active material KU from the container 25 by means of a supply line 27 the fuel line 17 supplied so that the fuel B mixed with the substance S or the fresh catalytically active material KU - as in the embodiment of 2 - in the combustion chamber 15 arrives. This variant of the fuel supply to the combustion chamber 15 can also in the embodiment of 2 be realized. The container 25 and the supply line 27 form a feed facility 28 ,

The embodiment of 3 differs from the embodiment of 2 further characterized in that no catalyst modules 3 available. The catalytic conversion of the resulting during combustion nitrogen oxides NO in the exhaust stream A happens in this embodiment solely by the action of the fuel B mixed catalytically active material KU on the nitrogen oxides NO, in particular in the reaction space 2 ,

This in 4 illustrated fourth embodiment of a method according to the invention is used to reactivate an at least partially deactivated catalyst module 3 , The reactivation takes place ex-situ in the example shown, ie in a state in which the catalyst modules 3 not used for the catalytic conversion of the substance NO. The deactivated catalyst modules 3 are for this purpose in the reaction space 2 are arranged and wetted with a substance S, which is or contains new or fresh catalytically active material KU or from which such catalytically active material KU is deposited. The fresh catalytically active material KU is deposited here in or on a catalyst substrate 31 in or on, already in the preparation of the catalyst modules 3 catalytically active material K was deposited or deposited. The catalyst modules 3 are regenerated in this way.

At the in 5 illustrated fifth embodiment is of a first inert catalyst substrate 33 went out. This catalyst substrate 33 is acted upon by a gas stream or exhaust stream A, which arises for example in the combustion of a fuel. The gas stream A is either in the 2 or 3 analogous way (in 5 not explicitly shown) or by means of a Lei tung 1 opening branch 29 a substance S is added, which is or contains catalytically active material K or from the catalytically active material K is formed. According to the in 5 illustrated embodiment is thus by introducing the inert catalyst substrate 33 in the flowed through by the exhaust gas A line 1 a catalyst module 3 produced.

In the 6 as a sixth embodiment shown exhaust gas purification system 41 includes, like that in 3 illustrated third embodiment, a feed device 28 , In contrast to 3 are however in the in 6 illustrated embodiment, as well as in the execution example of 2 , Catalyst modules 3 in the reaction room 2 present, by depositing or depositing a catalytically active material K in or on a catalyst substrate 31 have been produced. At the in 6 illustrated embodiment, therefore, the catalyst modules 3 by means of the feed device 28 added new or fresh catalytically active material KU, or by means of the substance S, "in situ" or "online" regenerated.

The catalyst modules 3 in the flow direction 5 downstream is a separation device 49 in which for the regeneration of the catalyst modules 3 Not required catalytically active material KU, ie, such that in the exhaust stream A after the catalyst modules 3 is still contained, is separated. From the separator 49 leads a return line 51 - If necessary, via a concentrator, not shown - to the feed device 28 , In this way, fed but not needed catalytically active material KU can be used again for feeding into the fuel B. As a result, the cost of catalytically active material KU are significantly reduced.

Claims (4)

Emission control system ( 13 ), in particular for an incinerator of a power plant or for an internal combustion engine of a motor vehicle, in which an exhaust gas stream (A) arising during the combustion is converted by a catalyst module (A) for converting a pollutant (NO) contained therein. 3 ) by depositing a catalytic conversion of the pollutant (NO) promoting catalytically active material (K) on or in a catalyst substrate ( 31 ), wherein nitrogen oxide contained in particular in the exhaust gas stream (A) can be converted according to the principle of selective catalytic reduction, an injection device ( 8th ) is provided, with a substance (S) in the flow direction ( 5 ) in front of the catalyst module ( 3 ) can be fed into the exhaust gas and wherein the substance (S) for the conversion of existing in the exhaust stream (A) pollutant (NO) is catalytically active material (KU) or from the substance (S) catalytically active material (KU) can be deposited is characterized by a the catalyst module ( 3 ) downstream deposition device ( 49 ) for the separation of catalytically active material (KU) from the exhaust stream (A). Emission control system according to claim 1, characterized by a to the separation device ( 49 ) connected return line ( 51 ), through which in this from the exhaust stream (A) separated catalytically active material (KU) upstream of the catalyst module ( 3 ) can be supplied to the exhaust gas flow (A). Emission control system ( 41 ), in particular for an incinerator of a power plant or an internal combustion engine of a motor vehicle, in which an exhaust gas stream (A) resulting from the combustion of a fuel (B) is converted by a catalyst module (A) into a pollutant (NO) contained therein 3 ) by depositing a catalytic conversion of the pollutant (NO) promoting catalytically active material (K) on or in a catalyst substrate ( 31 ), wherein nitrogen oxide contained in particular in the exhaust stream (A) is convertible according to the principle of selective catalytic reduction, wherein a feed device ( 28 ), by means of which a substance (S) can be added to the fuel (B), wherein the substance (S) for the conversion of the pollutant (NO) present in the exhaust gas flow (A) is or contains catalytically active material (KU) the substance (S) catalytically active material (KU) is deposited, characterized by a to the feed device ( 28 ) connected return line ( 51 ), through which the exhaust stream (A) downstream of the catalyst module ( 3 ) separated catalytically active material (KU) in the fuel (B) can be fed. Exhaust gas purification system according to claim 3, characterized in that the feed device ( 28 ) has a storage container for receiving the substance (S).