CA1064225A - Process for removing nox from a flue gas by selective reduction with nh3 - Google Patents
Process for removing nox from a flue gas by selective reduction with nh3Info
- Publication number
- CA1064225A CA1064225A CA232,942A CA232942A CA1064225A CA 1064225 A CA1064225 A CA 1064225A CA 232942 A CA232942 A CA 232942A CA 1064225 A CA1064225 A CA 1064225A
- Authority
- CA
- Canada
- Prior art keywords
- flue gas
- catalyst
- gas
- amount
- ppm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
Landscapes
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
A B S T R A C T
A process for removing NOx from an oxygen-containing flue gas, which is substantially free from SO2, by reacting NOx with NH3, in the presence of a catalyst, NH3 being introduced for this purpose in the flue gas, in which process a catalyst is used comprising one or more metal sulphates, and wherein an amount of up to 700 ppm by volume of SO2 is added to the flue gas prior to contacting the same with the catalyst.
A process for removing NOx from an oxygen-containing flue gas, which is substantially free from SO2, by reacting NOx with NH3, in the presence of a catalyst, NH3 being introduced for this purpose in the flue gas, in which process a catalyst is used comprising one or more metal sulphates, and wherein an amount of up to 700 ppm by volume of SO2 is added to the flue gas prior to contacting the same with the catalyst.
Description
10~4ZZ5 The present invention relates to a process for re ving N0x from an oxygen-containing flue gas which is substantially free from S02.
Several processes for the selective reduction of nitrogen oxides in oxygen-containing waste gas with ammonia have already been proposed, which processes mainly differ in the catalyst that is used. The earlier catalysts were easily poisoned by sulphur oxides which are generally present in a flue gas and accordingly sulphur-resistant catalysts were developed. Examples of the former catalysts are noble metals, an example of the latter catalyst is for instance copper oxide.
The above selective reduction converts the nitrogen oxides into harmless nitrogen and a limited excess of ammonia is also converted. The reduction of N0x i8 selective in that oxygen, mostly present in flue gases in amounts far greater than the amount of nitrogen oxides, does not preferentially convert the -ammonia. This is contrary to the non-selective N0x-reduction processes in which, apart from the nitrogen oxides, also the oxygen will be taken away by the reducing agent.
There are waste gases that will never contain sulphur oxides, such as the waste gases from nitric acid manufacturing processes or flue gases from boilers which are fired with natural gas. For these waste gases a sulphur-resistant catalyst ~ .
is in principle not needed though they will be less expensive than - -the proposed noble metal-based catalysts. With other waste gases, sulphur oxides are sometimes present and sometimes not;
depending on, for example, whether the fuel used in the combustion process, whence the flue gas in question originates, contains sulphur or not. In such cases for the N0x-conversion a catalyst is needed that is sulphur-resistant, notwithstanding the fact that for long periods of time there may be no sulphur oxides present at all in the flue gas.
Many catalysts for the conversion of N0x in flue gases with NH3 have been developed that contain one or more metal oxides~ However, ~
most of these catalysts are poisoned easily by sulphur oxides~ -~ '`.
~ .
_..... , - - . . . - - - - ., .
",. .. . .
~ . . : ., . . :
10~42Z5 It has now been found, that at certain conditions the initial activity of N0 -conversion catalysts that contain one or more metal sulphates on a carrier is higher than the activity of the catalyst that contains the corresponding metal oxides. It was further found that a major drawback of these cstalysts based on metal sulphates, is that their activity tends to decrease. This decrease especially occurs when the flue gases contain no sulphur oxides.
Apart from proposing the above catalysts, the present invention aims at providing means to prevent this decrease in activity.
Moreover the invention aims at providing a process for converting N0x with NH3 in oxygen-containing flue gases which are free from sulphur oxides while using the above catalysts of high initial activity without a subsequent decrease in activity.
Accordingly the present invention provides a process for removing N0x from an oxygen-containing flue gas which is substan-A tially free from S02~by reacting N0 with NH3 in t~e~presence of a catalyst, NH3 being introduced for this purpose ~Y~ the flue gas, , in which process a catalyst is used comprising one or more metal --sulphates and wherein an amount of up to 700 ppm by volume of S02 is added to the flue gas prior to contacting the same with the catalyst.
The deliberate introduction of S02 in the flue gas is effected in order to keep the activity of the catalyst at its high initial level. An amount of 700 ppm S02 is more than sufficient for this ~ :
purpose and it will be clear that it is not advantageous to introduce more S02 into the flue gas than strictly necessary.
The mechanism according to which the catalysts slowly lose activity when the S02 partial pressure in the waste gas treated is below a certain minimum value is not fully known. It could be possible that the metal sulphates are slowly converted into a less active form, for example by reaction with the alumina that is generally -used as a carrier. Another possibility is that the active compounds `~
in the catalyst such as copper- and/or aluminium sulphate slowly decompose in the flue gas at the relatively high temperatures whereat the N0x-conversion is generally carried out.
" .~. ~.... ' '.
... ..
Though temperatures of above 500 C or below 200C may be applied while still removing a considerable amount of N0 from the gas treated, the process of the present invention is mainly developed for the removal of N0x from flue gases having a temperature between 200 and 500C.
The advantage of being able to remove the N0x at these temperatures is that the flue gases do not have to be cooled nor to be reheated before and after removal of N0x or vice ver~a and that the flue ga~es can directly be sent to the stack after removal of the N0x. For disposal of a flue gas through a stack a sufficiently high temperature is required to guarantee that the flue gas has the neces~ary buoyancy for rising from the stack.
A particularly preferred embodiment of the invention makes use of temperatures between 350 and 450C. In this temperature range the proposed catalysts have a high activity, do not decompose or lose their strength and a high conversion rate of both N0x and a possible excess of NH3 is obtaiDed. `
Both for practical reasons and in order to arrive at a design --of a reactor with reasonable dimensions, the process according to ~ -the invention is preferably carried out at conditions whereby the linear velocity of the flue gas while in contact with the catalyst is between 10 and 30 m/sec. These gas velocities are very suitable for application in a parallel passage type of reactor wherein the :
gas flows through void gas channels having gas permeable walls behind which the catalyst is freely accessible to the gas components by diffusion.
In fixed bed application the hourly space velocity of the flue gas, while in contact with the said catalyst, is between 500 and 25,000 Nm3 gas per m3 catalyst per hour.
A preferred catalyst, according to the invention, comprises copper sulphate supported on a carrier. Although other metal sulphates, such as iron sulphate, cobalt sulphate, nickel sulphate, aluminium sulphate, chromium sulphate, molybdenum sulphate, vanadium `;
sulphate and wolfram sulphate also have a certain catalytic activity for the conversion of N0 with NH3, copper sulphate is preferred since it both has a high activity and a high thermal stability, ,1,. . . : . :. :
- . .:
10~;4225 whereas it is not easily stripped to copper oxide. A catalyst comprising copper sulphate on alumina can be readily made in the usual way and is not very expensive.
According to a preferred embodiment of the invention the catalyst comprises copper sulphate in an amount of 0.5-20% by weight, calculated as metal.
The process of the invention will be most economical for treating flue gas comprising between 10-4000 ppm by volume of N0 , though it is suitable for flue gases having a N0x content beyond this range.
Although it is in principle possible to supply the required S2 discontinuously to the flue gas, i.e. when the need arises, it is considered prudent to supply at least 10 ppm by volume of S0~ constantly to the flue gas. Such a constant but small supply will in principle already be sufficient to obtain the S02-partial pressure in the flue gas that is required to keep the active components of the catalyst in the sulphate form.
In general a supply in amounts of from 10 to 100 ppm by volume f S2 will be sufficient for the purpose of the invention and such a supply will not cause any air pollution nor corrosion problems.
Amounts of 20-50 ppm by volume of S02 are much preferred.
With the N0x-conversion according to the invention it is preferred to introduce an amount of NH3 ranging from the amount that is stoichio-metrically required to twice this amount. In this range most of the '`~
N0x is converted and no substantial NH3-slip occurs. More preferably 1.2 to 1.5 times the stoichiometrically required amount of NH3 is supplied.
According to a preferred embodiment of the process of the invention the catalyst is present in a reactor behind gas-permeable walls of void gas channels that extend through the reactor from the gas inlet to the gas outlet thereof. An advantage of the use of such a special reactor (parallel passage type) is that flue gases can be processed that contain an amount of particulate matter, such as fly ash or soot, without the catalyst becoming clogged therewith.
The flue gases pass along the catalyst beds, whereas with a conventional fixed catalyst bed the gases would pass through the bed. While passing through the gas channels the gases reach the catalyst by diffusion , .~"~ 7 jS, ~ 7~7 ~ ,'7~tA 7~ `. 7'~` ' ` ~ `
10~4225 through the permeable walls. ~he latter may, for example, consist of sheets of gauze that have been properly mounted in the reactor.
An important economic advantage connected with the use of this special reactor is the fact that a lower pressure drop occurs over the reactor than if a fixed cataly~t bed would have been applied. Accordingly, there is also an incentive to use the specisl resctor if particulate matter is absent in the flue gas.
Preferred catalysts for the NOx-conversion according to the present invention may be obtained by impregnating a refractory carrier material with 1-25% by weight of a metal compound, by calcining the impregnated material and subsequently, if necessary, by treating the calcined material to convert the deposited metal co~pound to the sulphate form.
According to an embodiment of the present invention NH3 i9 introduced in the flue gas by injecting a NH3-precur~or into the ~ -flue gas duct, Examples of such precursors are an aqueous ammonia ~ ~ -solution, urea, hydrazine, ethylene diamine, hexamethylene tetramine and an aqueous solution of ammoniumcarbonate, or of ammonium sulphite.
Under certain circumstances it will be an advantage to make u~e of such a precursor7 because handling a liquid is more simple than handling gaseous NH3, An aqueous solution of ammonium-sulphite is a particularly preferred precursor because by introducing this solution NH3 and S02 are simultaneously introduced into the flue gas to be treated.
The invention will be further elucidated by means of the following Example.
EXAMPLE
A synthetic flue gas, comprising 86 vol.% N2, 5 vol.g 2' and 11 vol.~ H20 to which 450 ppm by vol. of NO w~e added, was passed through a tubular reactor having a void channel of 1.5 m length formed by a gauze cylinder contained in the reactor. Between the inner wall of the reactor and the outer surface of the said gauze cylinder catalyst particles were present. The catPlyst consisted of alumina particles on which copper nitrate had been deposited by impregnation and which copper nitrate had subsequently been decomposed .
into copper oxide by calcination in a stream Or hot air.
The synthetic flue gas was passed at a gas hourly space velocity of 8000 Nl/l/h through the reactor at a temperature of 350C while the catalyst was successively in oxide and sulphate form.
The sulphate form was obtained by treating the catalyst for an hour at 400 C with a gas comprising nitrogen and 5 vol.% S02, after which the copper oxide had been completely converted to copper sulphate. Each separate test lasted for a full 24 hours and was repeated at different levels of NH3 and S02 injection as indicated in the table below. The amount of N0 in the gases that originated from the reactor was determined after 24 hours of operation. From the results it can be concluded that copper sulphate is a better catalyst than copper oxide and that the addition of some sulphur dioxide does help to lower the amount of N0x in the treated gas on the long run. From separate measurements at the initial stage of each test it appeared that for copper sulphate no significant difference in the degree of N0x-conversion exists with or without S2 addition to the flue gas.
Condition Amount of Amount of Amount of -of catalyst NH in flue S02 in flue N0 in reactor -gas3 in gas in off-gas in --ppm/vol ppm/vol ppm/vol ____________ _____________ _ _________ ______________ ... -CuO o o 450 CuO 600 0 110 :-CuS04 0 0 450 -~
CuS04 500 0 100 CuS04 500 90 20 CuS04 900 90 35 . ~
Several processes for the selective reduction of nitrogen oxides in oxygen-containing waste gas with ammonia have already been proposed, which processes mainly differ in the catalyst that is used. The earlier catalysts were easily poisoned by sulphur oxides which are generally present in a flue gas and accordingly sulphur-resistant catalysts were developed. Examples of the former catalysts are noble metals, an example of the latter catalyst is for instance copper oxide.
The above selective reduction converts the nitrogen oxides into harmless nitrogen and a limited excess of ammonia is also converted. The reduction of N0x i8 selective in that oxygen, mostly present in flue gases in amounts far greater than the amount of nitrogen oxides, does not preferentially convert the -ammonia. This is contrary to the non-selective N0x-reduction processes in which, apart from the nitrogen oxides, also the oxygen will be taken away by the reducing agent.
There are waste gases that will never contain sulphur oxides, such as the waste gases from nitric acid manufacturing processes or flue gases from boilers which are fired with natural gas. For these waste gases a sulphur-resistant catalyst ~ .
is in principle not needed though they will be less expensive than - -the proposed noble metal-based catalysts. With other waste gases, sulphur oxides are sometimes present and sometimes not;
depending on, for example, whether the fuel used in the combustion process, whence the flue gas in question originates, contains sulphur or not. In such cases for the N0x-conversion a catalyst is needed that is sulphur-resistant, notwithstanding the fact that for long periods of time there may be no sulphur oxides present at all in the flue gas.
Many catalysts for the conversion of N0x in flue gases with NH3 have been developed that contain one or more metal oxides~ However, ~
most of these catalysts are poisoned easily by sulphur oxides~ -~ '`.
~ .
_..... , - - . . . - - - - ., .
",. .. . .
~ . . : ., . . :
10~42Z5 It has now been found, that at certain conditions the initial activity of N0 -conversion catalysts that contain one or more metal sulphates on a carrier is higher than the activity of the catalyst that contains the corresponding metal oxides. It was further found that a major drawback of these cstalysts based on metal sulphates, is that their activity tends to decrease. This decrease especially occurs when the flue gases contain no sulphur oxides.
Apart from proposing the above catalysts, the present invention aims at providing means to prevent this decrease in activity.
Moreover the invention aims at providing a process for converting N0x with NH3 in oxygen-containing flue gases which are free from sulphur oxides while using the above catalysts of high initial activity without a subsequent decrease in activity.
Accordingly the present invention provides a process for removing N0x from an oxygen-containing flue gas which is substan-A tially free from S02~by reacting N0 with NH3 in t~e~presence of a catalyst, NH3 being introduced for this purpose ~Y~ the flue gas, , in which process a catalyst is used comprising one or more metal --sulphates and wherein an amount of up to 700 ppm by volume of S02 is added to the flue gas prior to contacting the same with the catalyst.
The deliberate introduction of S02 in the flue gas is effected in order to keep the activity of the catalyst at its high initial level. An amount of 700 ppm S02 is more than sufficient for this ~ :
purpose and it will be clear that it is not advantageous to introduce more S02 into the flue gas than strictly necessary.
The mechanism according to which the catalysts slowly lose activity when the S02 partial pressure in the waste gas treated is below a certain minimum value is not fully known. It could be possible that the metal sulphates are slowly converted into a less active form, for example by reaction with the alumina that is generally -used as a carrier. Another possibility is that the active compounds `~
in the catalyst such as copper- and/or aluminium sulphate slowly decompose in the flue gas at the relatively high temperatures whereat the N0x-conversion is generally carried out.
" .~. ~.... ' '.
... ..
Though temperatures of above 500 C or below 200C may be applied while still removing a considerable amount of N0 from the gas treated, the process of the present invention is mainly developed for the removal of N0x from flue gases having a temperature between 200 and 500C.
The advantage of being able to remove the N0x at these temperatures is that the flue gases do not have to be cooled nor to be reheated before and after removal of N0x or vice ver~a and that the flue ga~es can directly be sent to the stack after removal of the N0x. For disposal of a flue gas through a stack a sufficiently high temperature is required to guarantee that the flue gas has the neces~ary buoyancy for rising from the stack.
A particularly preferred embodiment of the invention makes use of temperatures between 350 and 450C. In this temperature range the proposed catalysts have a high activity, do not decompose or lose their strength and a high conversion rate of both N0x and a possible excess of NH3 is obtaiDed. `
Both for practical reasons and in order to arrive at a design --of a reactor with reasonable dimensions, the process according to ~ -the invention is preferably carried out at conditions whereby the linear velocity of the flue gas while in contact with the catalyst is between 10 and 30 m/sec. These gas velocities are very suitable for application in a parallel passage type of reactor wherein the :
gas flows through void gas channels having gas permeable walls behind which the catalyst is freely accessible to the gas components by diffusion.
In fixed bed application the hourly space velocity of the flue gas, while in contact with the said catalyst, is between 500 and 25,000 Nm3 gas per m3 catalyst per hour.
A preferred catalyst, according to the invention, comprises copper sulphate supported on a carrier. Although other metal sulphates, such as iron sulphate, cobalt sulphate, nickel sulphate, aluminium sulphate, chromium sulphate, molybdenum sulphate, vanadium `;
sulphate and wolfram sulphate also have a certain catalytic activity for the conversion of N0 with NH3, copper sulphate is preferred since it both has a high activity and a high thermal stability, ,1,. . . : . :. :
- . .:
10~;4225 whereas it is not easily stripped to copper oxide. A catalyst comprising copper sulphate on alumina can be readily made in the usual way and is not very expensive.
According to a preferred embodiment of the invention the catalyst comprises copper sulphate in an amount of 0.5-20% by weight, calculated as metal.
The process of the invention will be most economical for treating flue gas comprising between 10-4000 ppm by volume of N0 , though it is suitable for flue gases having a N0x content beyond this range.
Although it is in principle possible to supply the required S2 discontinuously to the flue gas, i.e. when the need arises, it is considered prudent to supply at least 10 ppm by volume of S0~ constantly to the flue gas. Such a constant but small supply will in principle already be sufficient to obtain the S02-partial pressure in the flue gas that is required to keep the active components of the catalyst in the sulphate form.
In general a supply in amounts of from 10 to 100 ppm by volume f S2 will be sufficient for the purpose of the invention and such a supply will not cause any air pollution nor corrosion problems.
Amounts of 20-50 ppm by volume of S02 are much preferred.
With the N0x-conversion according to the invention it is preferred to introduce an amount of NH3 ranging from the amount that is stoichio-metrically required to twice this amount. In this range most of the '`~
N0x is converted and no substantial NH3-slip occurs. More preferably 1.2 to 1.5 times the stoichiometrically required amount of NH3 is supplied.
According to a preferred embodiment of the process of the invention the catalyst is present in a reactor behind gas-permeable walls of void gas channels that extend through the reactor from the gas inlet to the gas outlet thereof. An advantage of the use of such a special reactor (parallel passage type) is that flue gases can be processed that contain an amount of particulate matter, such as fly ash or soot, without the catalyst becoming clogged therewith.
The flue gases pass along the catalyst beds, whereas with a conventional fixed catalyst bed the gases would pass through the bed. While passing through the gas channels the gases reach the catalyst by diffusion , .~"~ 7 jS, ~ 7~7 ~ ,'7~tA 7~ `. 7'~` ' ` ~ `
10~4225 through the permeable walls. ~he latter may, for example, consist of sheets of gauze that have been properly mounted in the reactor.
An important economic advantage connected with the use of this special reactor is the fact that a lower pressure drop occurs over the reactor than if a fixed cataly~t bed would have been applied. Accordingly, there is also an incentive to use the specisl resctor if particulate matter is absent in the flue gas.
Preferred catalysts for the NOx-conversion according to the present invention may be obtained by impregnating a refractory carrier material with 1-25% by weight of a metal compound, by calcining the impregnated material and subsequently, if necessary, by treating the calcined material to convert the deposited metal co~pound to the sulphate form.
According to an embodiment of the present invention NH3 i9 introduced in the flue gas by injecting a NH3-precur~or into the ~ -flue gas duct, Examples of such precursors are an aqueous ammonia ~ ~ -solution, urea, hydrazine, ethylene diamine, hexamethylene tetramine and an aqueous solution of ammoniumcarbonate, or of ammonium sulphite.
Under certain circumstances it will be an advantage to make u~e of such a precursor7 because handling a liquid is more simple than handling gaseous NH3, An aqueous solution of ammonium-sulphite is a particularly preferred precursor because by introducing this solution NH3 and S02 are simultaneously introduced into the flue gas to be treated.
The invention will be further elucidated by means of the following Example.
EXAMPLE
A synthetic flue gas, comprising 86 vol.% N2, 5 vol.g 2' and 11 vol.~ H20 to which 450 ppm by vol. of NO w~e added, was passed through a tubular reactor having a void channel of 1.5 m length formed by a gauze cylinder contained in the reactor. Between the inner wall of the reactor and the outer surface of the said gauze cylinder catalyst particles were present. The catPlyst consisted of alumina particles on which copper nitrate had been deposited by impregnation and which copper nitrate had subsequently been decomposed .
into copper oxide by calcination in a stream Or hot air.
The synthetic flue gas was passed at a gas hourly space velocity of 8000 Nl/l/h through the reactor at a temperature of 350C while the catalyst was successively in oxide and sulphate form.
The sulphate form was obtained by treating the catalyst for an hour at 400 C with a gas comprising nitrogen and 5 vol.% S02, after which the copper oxide had been completely converted to copper sulphate. Each separate test lasted for a full 24 hours and was repeated at different levels of NH3 and S02 injection as indicated in the table below. The amount of N0 in the gases that originated from the reactor was determined after 24 hours of operation. From the results it can be concluded that copper sulphate is a better catalyst than copper oxide and that the addition of some sulphur dioxide does help to lower the amount of N0x in the treated gas on the long run. From separate measurements at the initial stage of each test it appeared that for copper sulphate no significant difference in the degree of N0x-conversion exists with or without S2 addition to the flue gas.
Condition Amount of Amount of Amount of -of catalyst NH in flue S02 in flue N0 in reactor -gas3 in gas in off-gas in --ppm/vol ppm/vol ppm/vol ____________ _____________ _ _________ ______________ ... -CuO o o 450 CuO 600 0 110 :-CuS04 0 0 450 -~
CuS04 500 0 100 CuS04 500 90 20 CuS04 900 90 35 . ~
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for removing NOx from an oxygen-containing flue gas, which is substantially free from SO2, by reacting NOx with NH3 in the presence of a catalyst, NH3 being introduced for this purpose into the flue gas, in which process a catalyst is used comprising one or more metal sulphates, and wherein an amount of up to 700 ppm by volume of SO2 is added to the flue gas prior to contacting the same with the catalyst.
2. A process as claimed in Claim 1, in which the temperature of the flue gas during the said reaction is between 200 and 500°C.
3. A process as claimed in Claim 1, in which the temperature of the flue gas during the said reaction is between 350 and 450°C.
4. A process as claimed in Claim 2, in which the linear veloci-ty of the flue gas while in contact with the said catalyst is between 10 and 30 m/sec.
5. A process as claimed in Claim 1, 2 or 3, in which the hour-ly space velocity of the flue gas, while in contact with the said catalyst, is between 500 and 25,000 Nm3 gas per m3 catalyst per hour.
6. A process as claimed in Claim 1, 2 or 3, in which the said catalyst comprises copper sulphate supported on a refractory carrier.
7. A process as claimed in Claim 1, 2 or 3, in which the cata-lyst comprises copper sulphate in an amount of from 0.5-20% by weight, calcu-lated as metal, supported on a refractory carrier.
8. A process as claimed in Claim 1, 2 or 3, in which the flue gas comprises between 10-4,000 ppm by volume of NOx.
9. A process as claimed in Claim 1, 2 or 3, in which at least 10 ppm by volume of SO2 is constantly supplied to the flue gas.
10. A process as claimed in Claim 1, 2 or 3, in which from 10 to 100 ppm by volume of SO2 is constantly supplied to the flue gas.
11. A process as claimed in Claim 1, 2 or 3, in which an amount of NH3 is supplied ranging of from the amount that is stoichiometrically re-quired to twice this amount.
12. A process as claimed in Claim 1, 2 or 3, in which the said catalyst is present in a reactor behind gas-permeable walls of void gas chan-nels that extend through the reaction from the gas inlet to the gas outlet thereof.
13. A process as claimed in Claim 1, 2 or 3, in which NH3 is introduced into the flue gas by injection of a NH3-precursor, the said precur-sor being chosen from the group comprising urea, hydrazine, ethylene diamine, hexamethylene tetramine, an aqueous solution of ammonium carbonate and an aqueous ammonia solution.
14. A process as claimed in Claim 1, 2 or 3, in which NH3 and SO2 are introduced simultaneously by injecting an aqueous solution of ammonium sulphite.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4150574A GB1523726A (en) | 1974-09-24 | 1974-09-24 | Process for removing no from a flue gas by selective reduction with |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064225A true CA1064225A (en) | 1979-10-16 |
Family
ID=10420007
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA232,942A Expired CA1064225A (en) | 1974-09-24 | 1975-08-06 | Process for removing nox from a flue gas by selective reduction with nh3 |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5837009B2 (en) |
| AT (1) | AT357993B (en) |
| CA (1) | CA1064225A (en) |
| DE (1) | DE2542204C2 (en) |
| FR (1) | FR2285922A1 (en) |
| GB (1) | GB1523726A (en) |
| IT (1) | IT1042887B (en) |
| NL (1) | NL181846C (en) |
| SE (1) | SE413887B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7601371A (en) * | 1976-02-11 | 1977-08-15 | Shell Int Research | PROCEDURE FOR THE SIMULTANEOUS REMOVAL OF NITROGEN OXIDES AND SULFUR OXIDES FROM A GAS FLOW. |
| JPS5314189A (en) * | 1976-07-26 | 1978-02-08 | Hitachi Zosen Corp | Denitration catalyst supporting copper sulfate |
| DE3701527A1 (en) * | 1987-01-21 | 1988-08-04 | Metallgesellschaft Ag | METHOD FOR SIMULTANEOUS NICKELING AND DESULFURATION OF AN OXYGEN-EXHAUST GAS |
| ES2022607B3 (en) * | 1988-01-22 | 1991-12-01 | Metallgesellschaft Ag | PROCEDURE FOR THE CATALYTIC REDUCTION OF NO. |
| DE3830045C2 (en) * | 1988-09-03 | 1993-09-30 | Bayer Ag | Process for the reduction of nitrogen oxides contained in exhaust gases by means of a zeolite-containing catalyst |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5515247B2 (en) * | 1974-06-11 | 1980-04-22 |
-
1974
- 1974-09-24 GB GB4150574A patent/GB1523726A/en not_active Expired
-
1975
- 1975-08-06 CA CA232,942A patent/CA1064225A/en not_active Expired
- 1975-09-19 IT IT2746275A patent/IT1042887B/en active
- 1975-09-22 JP JP50113795A patent/JPS5837009B2/en not_active Expired
- 1975-09-22 DE DE19752542204 patent/DE2542204C2/en not_active Expired
- 1975-09-22 AT AT724175A patent/AT357993B/en not_active IP Right Cessation
- 1975-09-22 SE SE7510605A patent/SE413887B/en not_active IP Right Cessation
- 1975-09-22 NL NL7511144A patent/NL181846C/en not_active IP Right Cessation
- 1975-09-22 FR FR7528949A patent/FR2285922A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5837009B2 (en) | 1983-08-13 |
| NL181846B (en) | 1987-06-16 |
| JPS5157676A (en) | 1976-05-20 |
| DE2542204A1 (en) | 1976-04-08 |
| NL7511144A (en) | 1976-03-26 |
| FR2285922B1 (en) | 1978-04-07 |
| FR2285922A1 (en) | 1976-04-23 |
| GB1523726A (en) | 1978-09-06 |
| SE7510605L (en) | 1976-03-25 |
| NL181846C (en) | 1987-11-16 |
| ATA724175A (en) | 1980-01-15 |
| SE413887B (en) | 1980-06-30 |
| AT357993B (en) | 1980-08-11 |
| IT1042887B (en) | 1980-01-30 |
| DE2542204C2 (en) | 1987-02-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US3279884A (en) | Selective removal of oxides of nitrogen from gas mixtures containing oxygen | |
| US4912776A (en) | Process for removal of NOx from fluid streams | |
| JP4313213B2 (en) | Method for removing nitrogen oxides | |
| US4107272A (en) | Process for removing nitrogen oxides using ammonia as a reductant and sulfated metallic catalysts | |
| US4089930A (en) | Process for the catalytic reduction of nitric oxide | |
| US4251496A (en) | Process for the removal of SOx and NOx from gaseous mixture containing the same | |
| CA2193638C (en) | Exhaust gas treating systems | |
| CZ34494A3 (en) | Supported catalyst containing silver and process of selective catalytic decomposition of nitrogen monoxide | |
| US5132103A (en) | Process for the removal of nitrogen oxides from offgases from turbines | |
| JPS5915022B2 (en) | Catalyst for removing nitrogen oxides from exhaust gas | |
| US4853193A (en) | Process for removing NOx and SOx from a gaseous mixture | |
| RU1837957C (en) | Catalyst for treatment of sulfur-containing gases | |
| CA1261591A (en) | Process for the removal of nitrogen oxides and sulphur oxides from flue gases | |
| CA1036794A (en) | Removal of nitrogen oxides from exhaust gases and catalyst therefor | |
| US5505919A (en) | Method for the denitration of exhaust gas | |
| CA1064225A (en) | Process for removing nox from a flue gas by selective reduction with nh3 | |
| US6106791A (en) | Exhaust gas treating systems | |
| IE64035B1 (en) | Method by reduction of nitrogen oxide | |
| US3872213A (en) | Method for removing harmful components from exhaust gases | |
| US4695437A (en) | Selective catalytic reduction catalysts | |
| WO1992004968A1 (en) | Catalytic decomposition of cyanuric acid and use of product to reduce nitrogen oxide emissions | |
| US6814948B1 (en) | Exhaust gas treating systems | |
| US4695438A (en) | Selective catalytic reduction catalysts | |
| Blanco et al. | Selective reduction of nitric oxide on nickel oxide-copper oxide supported catalysts | |
| US4003987A (en) | Waste stream treatment |