Method of removing nitrogen oxides from flue gases
For the catalytic removal of nitrogen oxides ( 2 ) from flue gases of combustion furnaces ( 1 ) which use hydrogen (H 2 ) is used as reducing agent and the reaction is conducted at a temperature of below 150° C.
1 . In a method for the selective catalytic removal of nitrogen oxides from oxygen-containing flue gas of a combustion furnace in the presence of a reducing agent, the improvement wherein the reducing agent is hydrogen, and the catalytic removal is conducted at a temperature below 150° C. in contact with a hydrogen reduction catalyst.
2 . A method according to claim 1 , wherein the catalytic removal of the nitrogen oxides is carried out directly at an exit waste heat flue of the combustion furnace.
3 . A method according to claim 1 , wherein the catalytic removal of the nitrogen oxides is conducted in a separate reactor downstream of the waste heat flue.
4 . A method according to claim 1 , wherein flue gases of at least two combustion furnaces are combined and together are freed from nitrogen oxides.
5 . A method according to claim 1 , wherein in at least one combustion furnace in an olefin plant, a hydrogen plant, or a synthesis gas plant in which hydrogen is a process gas, and the latter hydrogen is used as the reducing agent for nitrogen oxide removal.
6 . A method according to claim 5 , wherein the hydrogen used as reducing agent is cleaned up downstream of the catalytic nitrogen oxide removal via a membrane method and/or a pressure-swing adsorption method, reused and/or fed to the nitrogen oxide removal.
7 . A method according to claim 1 , conducted under the following operating conditions
Range
Catalyst volume-
40,000-160,000 l/h
related flue gas
velocity:
Temperature:
120-150° C.
NO x :
75-2500 ppmV
O 2 :
1.7-5.5% by
volume
H 2 :
500-10,000 ppmV
NO x conversion:
80-99%
8 . A method according to claim 7 , conducted at 135-145° C.
9 . A method according to claim 7 , wherein said catalyst volume-related flue gas velocity is 40,000-100,000 l/h.
10 . A method according to claim 8 , wherein said catalyst volume-related flue gas velocity is 40,000-100,000 l/h.
11 . A method according to claim 7 , wherein the catalyst comprises platinum or palladium on a substrate.
12 . A method according to claim 7 , wherein the catalyst comprises platinum on a substrate.
13 . A method according to claim 12 , wherein the substrate comprises MgO—CeO.
14 . A method according to claim 10 , wherein the catalyst comprise platinum on a substrate.
15 . A method according to claim 14 , wherein the substrate comprises MgO—CeO.
16 . A method according to claim 15 , wherein the catalytic removal of the nitrogen oxides is carried out directly at an exit waste heat flue of the combustion furnace.
17 . An integrated plant comprising means for providing hydrogen, a combustion chamber, means for containing catalyst located downstream and integral with said combustion chamber and conduit means connecting said means for producing hydrogen with said means for containing catalyst.