Catalyst bed and method for reducing nitrogen oxides
A catalyst bed comprising a ceramic or metallic foam comprising one or more NO x reduction catalysts is described. A method for reducing the concentration of NO x in a dust containing gas stream comprising: a) passing a first gas stream containing NO x into a contacting zone; b) contacting the first gas stream with a ceramic or metallic foam catalyst bed having one or more flow paths through the catalyst bed wherein the ceramic or metallic foam comprises a NO x reduction catalyst to produce a second gas stream with a reduced NO x concentration; and c) passing the second gas stream out of the contacting zone wherein the first gas stream has a dust concentration of at least 5 mg/Nm 3 and the pressure drop of the foam catalyst bed increases by 300% or less relative to the initial pressure drop of the foam catalyst bed due to dust accumulation, measured under the same conditions is also described.
1. A method for reducing a concentration of NO in a dust containing gas stream comprising:
a. passing a first gas stream containing NO into a contacting zone;
b. contacting the first gas stream with a catalyst bed having one or more flow paths through the catalyst bed, wherein the catalyst bed comprises a ceramic or metal foam catalyst having a NO x reduction catalyst configured to produce a second gas stream with a reduced NO x concentration, and wherein the NO x reduction catalyst comprises a bimodal pore distribution with more than 90% of a pore volume present in pores having a diameter of at most about 100 nanometers (nm); and
c. passing the second gas stream out of the contacting zone, wherein the first gas stream has a dust concentration of at least 5 mg/Nm 3 and a pressure drop of the catalyst bed increases by 300% or less relative to an initial pressure drop of the catalyst bed due to dust accumulation, measured under the same conditions.
2. The method of claim 1 , wherein the first gas stream has a dust concentration of at least 10 mg/Nm 3 .
3. The method of claim 1 , wherein the pressure drop of the catalyst bed increases by 200% or less relative to the initial pressure drop of the catalyst bed due to dust accumulation, measured under the same conditions.
4. The method of claim 1 , wherein the contacting occurs at a temperature in the range of from 100 to 250° C.
5. The method of claim 1 , wherein the ceramic or metallic foam catalyst has in the range of from about 5 to about 50 pores per inch.
6. The method of claim 1 , wherein the ceramic or metallic foam catalyst has an interconnected internal tortuous pore structure providing flow paths through the catalyst bed that have a tortuosity of greater than 1.0.
7. The method of claim 1 , wherein the ceramic foam catalyst comprises cordierite, titanium oxide or alumina.
8. The method of claim 1 , wherein the metallic foam catalyst comprises nickel, iron or alloys thereof.
9. The method of claim 1 , wherein the NO x reduction catalyst comprises vanadium, molybdenum, tungsten or mixtures thereof.
10. The method of claim 1 , wherein the ceramic or metallic foam catalyst further comprises a binder material.
11. The method of claim 1 , wherein the second gas stream comprises at least 50% of an amount of dust in the first gas stream.
12. The method of claim 1 , wherein the second gas stream comprises at least 80% of an amount of dust in the first gas stream.
13. The method of claim 1 , wherein a density range of the ceramic or metallic foam catalyst is between 0.4 to 0.75 grams/cubic centimeter (g/cm 3 ).
14. The method of claim 1 , wherein the contacting occurs at a pressure range of from 0 kilopascals (kPa) to 1200 kPa.
15. The method of claim 1 , wherein the NO x reduction catalyst has a surface area of between approximately 70 square meters/gram (m 2 /g) and approximately 150 m 2 /g.
16. The method of claim 1 , wherein the pore volume is present in pores having a diameter of between approximately 1 nm and approximately 104 nm.
17. A method for reducing a concentration of NO x in a dust containing gas stream comprising:
a. passing a first gas stream containing NO x into a contacting zone;
b. contacting the first gas stream with a catalyst bed having one or more flow paths through the catalyst bed, wherein the catalyst bed comprises a ceramic or metal foam catalyst having a NO x reduction catalyst configured to produce a second gas stream with a reduced NO x concentration, and wherein a pore volume of the NO x reduction catalyst is present in pores having a diameter of between approximately 1 nm and approximately 104 nm; and
c. passing the second gas stream out of the contacting zone, wherein the first gas stream has a dust concentration of at least 5 mg/Nm 3 and a pressure drop of the catalyst bed increases by 300% or less relative to an initial pressure drop of the catalyst bed due to dust accumulation, measured under the same conditions.
18. The method of claim 17 , wherein the second gas stream comprises at least 50% of an amount of dust in the first gas stream.
19. The method of claim 17 , wherein the NO x reduction catalyst has a surface area of between approximately 70 square meters/gram (m 2 /g) and approximately 150 m 2 /g.