Process for removing nitrogen oxides from flue gases

US6117405A · kind A · utility

Assignee

• Von Roll Umwelttechnik AG · DE

Inventors

• Rudolf Frey · Illnau, CH
• Felix Koller · Brugg, CH

Key dates

• Filing date: Jun 22, 1998
• Grant date: Sep 12, 2000
• Expiry date: Jun 22, 2018

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F23J2219/40
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

A process is provided for removing contaminants, such as nitrogen oxides, out of exhaust gases, such as gases emitted from an incineration plant. Ammonia or a reducing agent producing ammonia is added to the exhaust gases at a point where the exhaust gases are at a temperature ranging from 700 to 900.degree. C. so that ammonia reacts with and removes nitrogen oxides out of the gases; the gases are passed into a boiler where they are cooled to a temperature ranging from 200 to 350.degree. C. and additional ammonia or reducing agent is injected into the gases; the gases are removed from the boiler and alkaline sorbents, such as alkali metal compounds or alkaline earth metal compounds are injected into the gases, and the gases are passed through a catalyst/filter element coated with a catalytically active oxide or salt of vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, tungsten and molybdenum for catalyzing the reduction of residual nitrogen oxides in the flue gases. The gases discharged from the catalyst/filter element may be subjected to a wet scrubbing step to remove sulfur dioxide and/or hydrochloric acid out of the gases.