Device and method for eliminating NOx and N2O

Patent metadata

Field	Value
Publication number	US-9238196-B2
Application number	US-201214365949-A
Country	US
Kind code	B2
Filing date	Dec 8, 2012
Priority date	Dec 16, 2011
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

Disclosed herein is a device and method for lowering the content of NO X and N 2 O in gases. The device comprises a container having therein two reaction steps connected in series. The first step removes NO X (DeNO X stage) by reducing NO X with a nitrogen-containing reducing agent. Downstream thereof, the second step removes N 2 O by catalytic decomposition of N 2 O to N 2 and O 2 (DeN 2 O stage). Each step comprises one or more catalyst beds through which flows gas to be purified. The catalyst bed of the DeNO X stage containing zeolites doped with transition metals, including lanthanides. The at least one catalyst bed of the DeN 2 O-stage contains one or more catalytically active compounds of elements selected from groups 5 to 11 of the Periodic Table, but not iron-doped zeolites. A device for introducing a nitrogen-containing reducing agent into the stream of the NO X and N 2 O-containing gas is further disposed upstream of the DeNO X stage.

First claim

The invention claimed is:

1. An apparatus for lowering the content of NO X and N 2 O in gas to be cleaned, comprising:
a vessel having an interior cavity defining a gaseous flow direction from a gas inlet of said vessel to a gas outlet of said vessel, said vessel configured to permit a gas to be cleaned to flow there through from said inlet to said outlet and reduce the amount of NO X and N 2 O contained in the gas to be cleaned;
an reducing-agent feed apparatus configured to introduce of a nitrogen-containing reducing agent into a stream of the gas to be cleaned;
a deNO X reaction stage through which the gas to be cleaned may flow, said deNOx reaction stage being disposed within the interior cavity of said vessel and downstream of said reducing-agent feed apparatus and configured to reduce the amount of NO X gas present in the gas to be cleaned, said deNO X stage including at least one catalyst bed, said at least one catalyst bed including at least one NO X removal catalyst bed containing a nitrogen-containing reducing agent for the reduction of NO X , the nitrogen-containing reducing agent containing zeolites doped with transition metals including the lanthanides; and
a deN 2 O reaction stage through which the gas to be cleaned may flow, said deN 2 O reaction stage being disposed within the interior cavity of said vessel and downstream of and in gaseous communication with the deNO X stage and configured to reduce the amount of N 2 O gas present in the gas to be cleaned, said deN 2 O stage including at least one catalyst bed, said at least one catalyst bed including at least one N 2 O removal catalyst bed containing a catalyst configured to remove N 2 O by catalytic breakdown of N 2 O into N 2 and O 2 , the catalyst in the at least one N 2 O removal catalyst bed containing less than 15% by weight of zeolites and further containing one or more catalytic active compounds of elements selected from groups 5 to 11 of the Periodic Table of the Elements, excluding iron-doped zeolites.

2. The apparatus of claim 1 , further comprising:
a mixer in gaseous communication with said vessel and disposed upstream of the deNO X stage, said mixer configured to mix the gas to be cleaned and the nitrogen-containing reducing agent, and thereafter pass the mixed gas into the deNO X stage.

3. The apparatus of claim 1 , further comprising:
a plurality of measuring devices in gaseous communication with said vessel and configured to take measurements of at least one of a flow rate of the gas to be cleaned, a volume of the gas to be cleaned, a concentration of NO X in either of a gas to be cleaned or partially cleaned gas, and a concentration of one of the individual components of NO X in either of a gas to be cleaned or partially cleaned gas, said measuring devices being disposed in at least one of a location upstream of the deNOx stage, downstream of the deNO X stage but upstream of the deN 2 O stage, or downstream of the deN 2 O stage.

4. The apparatus of claim 3 , wherein one of said measuring devices is positioned upstream of the deNO X stage in the inlet of said vessel.

5. The apparatus of claim 3 , wherein a measuring device configured to determine an amount of reducing agent to be fed to said vessel is controllably coupled to an adjustment device configured to adjust the amount of the reducing agent flowing through said reducing-agent feed apparatus.

6. The apparatus of claim 1 , wherein at least one catalyst bed in each of said deNO X and deN 2 O reaction stages is a hollow cylinder such that the gas to be cleaned flows through said cylindrical catalyst beds in a radial direction.

7. The apparatus of claim 6 , wherein the catalyst beds of said deNO X and deN 2 O reaction stages are a pair of concentric hollow cylinders, wherein an outer hollow cylinder contains a catalyst for NO X reduction with catalyst particles having an equivalent diameter of about 2 to 5 mm, and wherein an inner hollow cylinder contains a catalyst for N 2 O breakdown with catalyst particles having an equivalent diameter of about 1 to 4 mm.

8. The apparatus of claim 1 , wherein the at least one catalyst bed in said deNO X stage includes at least one of Co-, Cu-, or Fe-doped zeolites.

9. The apparatus of claim 1 , wherein the at least one catalyst bed in said deN 2 O stage includes at least one of catalytic active compounds of elements selected from groups 9 to 11 of the Periodic Table of the Elements.

10. The apparatus of claim 9 , wherein the catalytic active compounds are present in deN 2 O catalysts in pure form.

11. A method for lowering the content of NO X and N 2 O in gases, comprising:
adding nitrogen-containing reducing agent to a gas stream containing N 2 O and NO X to reduce the NO X ;
passing the gas stream containing N 2 O, NO X , and reducing agent through at least one deNO X stage catalyst bed containing a catalyst for the reduction of NO X by the reducing agent, the catalyst containing zeolites doped with transition metals, including lanthanides, with conversion of NO X occurring by a reduction of NO X with the nitrogen-containing reducing agent; and
passing the gas stream that is leaving the deNOx stage through at least one catalyst bed of a deN 2 O stage that contains a catalyst for the breakdown of N 2 O to N 2 and O 2 , the deN 2 O stage catalyst being selected from the group of the catalysts containing one or more catalytic active compounds of elements selected from groups 5 to 11 of the Periodic Table of the Elements, excluding iron-doped zeolites, with conversion of N 2 O by catalytic breakdown of N 2 O to N 2 and O 2 .

12. The method of claim 11 , wherein an amount of the reducing agent is selected such that it is converted in the deNO X stage so as to result in a slippage of less than 25 ppmv of the reducing agent from the deNO X stage into the deN 2 O stage.

13. The method of claim 11 , wherein the reducing agent for NO X is ammonia, and which is added in such an amount as to result in, based on the NH 3 and NO X components at the inlet of the deNO X stage, a molar NH 3 /NO X ratio of 0.8 to 3.

14. The method of claim 11 , wherein the nitrogen-containing reducing agent is added to the gas stream containing N 2 O and NO X in such an amount that the decomposition level of NO X , based on the inlet concentration of NO X , is more than 70%, and in the deN 2 O stage, space velocity, temperature, and pressure are selected such that the gas at the output of the deN 2 O stage has an N 2 O content of less than 100 ppmv.

15. The method of claim 11 , further comprising:
measuring the NO X content of gas exiting the deN 2 O stage by a measuring device disposed at an outlet thereof;
regulating the amount of reducing agent added for NO X based on the measured NO X content of gas exiting the deN 2 O stage, said regulating occurring by use of a regulation unit to control an adjustment device for dosage of the reducing agent, such that the desired NO X content is established at the outlet of the deN 2 O stage.

16. The method of claim 11 , wherein the temperature in the deNO X stage and in the deN 2 O stage is between 300 and 600° C., and wherein the difference between the temperature of the deN 2 O stage and the temperature of the deNO X stage is no greater than 50° C., and wherein the pressure in each of the deNO X stage and the deN 2 O stage is in the range from 1 to 50 bara, and wherein the process is conducted in the deNO X stage at space velocities of 5,000 to 200,000 h −1 .

17. The method of claim 11 , wherein the process is conducted in the deN 2 O stage at space veloci

Assignees

• Schwefer Meinhard
• Siefert Rolf
• Pinnow Stefan
• Thyssenkrupp Ind Solutions Ag

Inventors

• Schwefer Meinhard
• Siefert Rolf
• Pinnow Stefan

Classifications

• B01D2255/1025

  Rhodium · CPC title

• B01D53/8631 Primary

  Processes characterised by a specific device · CPC title

• B01D53/8696

  Controlling the catalytic process · CPC title

• Y02C20/10

  of nitrous oxide (N2O) · CPC title

• B01D53/8628

  Processes characterised by a specific catalyst · CPC title