Filtration of chromium from flue gas in furnace stacks

A system for treating a flue gas, comprising:

• a furnace environment comprising a fuel inlet, a combustion zone, a flue gas flow path, and a flue gas outlet;
• and
• a catalyst bed that defines at least a portion of the flue gas flow path, the catalyst bed comprising a Group 5 metal, a Group 6 metal, a Group 8-11 metal, or a combination thereof to form a treated flue gas, the catalyst bed comprising a bed height of 0.8 m to 2.0 m,
• wherein the furnace environment comprises one or more surfaces comprising a Cr-containing metal.

A steam cracker furnace decoking process, comprising:

• contacting accumulated coke in at least one furnace tube of a steam cracker furnace with steam and/or air at a temperature in a range of from 600° C. to 900° C. to produce a decoke effluent, conducting at least a portion of the decoke effluent into the steam cracker furnace, and at least partially-converting the decoke effluent in the steam cracker furnace to produce a flue gas;
• exposing at least a portion of the flue gas to one or more surfaces comprising a Cr-containing metal to form a Cr-containing flue gas;
• exposing the Cr-containing flue gas to a catalyst bed comprising a Group 5 metal, a Group 6 metal, a Group 8-11 metal, or a combination thereof to form a treated flue gas, wherein the catalyst bed comprises a bed height of 0.8 m to 2.0 m, and wherein the flue gas is at a temperature in the range of from 100° C. to 590° C. during exposure to the catalyst bed;
• and
• conducting a treated flue gas away from the catalyst bed and away from an outlet of the steam cracker furnace.