Method and device for introducing liquid into an exhaust-gas purification system

US5884475A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Lothar Hofmann · Burgkunstadt, DE
• Ronald Neufert · Aichach, DE
• Wieland Mathes · Aichach, DE

Key dates

• Filing date: Mar 13, 1997
• Grant date: Mar 23, 1999
• Expiry date: Mar 13, 2017

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02T10/12
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

Nitrogen oxides emitted by an internal-combustion engine operated with excess air are normally converted by the method of selective catalytic reduction by bringing the nitrogen oxides, together with ammonia, into contact with a selective catalyst. Due to the dangers associated with the use of ammonia, in a motor vehicle ammonia should only be carried in the form of a substance which liberates ammonia, generally an aqueous urea solution. A method and a device for introducing liquid into an exhaust-gas purification system according to the invention avoids frost damage to sections of the system during shutdown times and permits operation of the system at temperatures below the freezing point of the reducing agent solution being used. The method and device include a (thermally insulated) reservoir for the reducing agent liquid and a liquid supply line which is connected thereto and terminates in an outlet opening for the liquid. The reservoir and the liquid supply line can be heated. Furthermore, a heater is provided for liquefying a starting volume which is small as compared with the volume of the reservoir. The liquid supply line may also have a back-flush valve to which a gas that i…