Diesel aftertreatment systems

• US 6,895,747 B2
• Filed: 11/21/2002
• Issued: 05/24/2005
• Est. Priority Date: 11/21/2002
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Ruona, William Charles, van Nieuwstadt, Michiel J., Upadhyay, Devesh, Goebelbecker, Michael
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): TRAN, DIEM T
• Application Number:
  US10/301,077
• Publication Number:
  US 20040098971A1
• Time in Patent Office: 915 Days
• Field of Search: 602/74, 602/86, 602/99, 603/01, 603/03, 423/212, 423/235, 423/352, 423/239.1
• US Class Current: 60/286
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2240/16 an electric heater, i.e. a resistance heater
• CPC Class Codes: F01N 2240/20 a flow director or deflector
• CPC Class Codes: F01N 2240/40 a hydrolysis catalyst
• CPC Class Codes: F01N 2250/02 filtering and catalytic conversion
• CPC Class Codes: F01N 2370/04 Zeolitic material
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/08 with prior mixing of the substances with a gas, e.g. air
• CPC Class Codes: F01N 2610/10 the substance being heated, e.g. by heating tank or supply line of the added substance
• CPC Class Codes: F01N 2610/107 using glow plug heating elements
• CPC Class Codes: F01N 2610/1453 Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: F01N 3/2896 Liquid catalyst carrier
• CPC Class Codes: F01N 3/32 using air pump using jet air pumps F01N3/34; pumps in general F04
• CPC Class Codes: F02B 2075/125 Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A method and a system for improving conversion efficiency of a urea-based SCR catalyst coupled downstream of a diesel or other lean burn engine is presented. The system includes an electrically heated vaporizer unit into which a mixture of reductant and air in injected. The mixture is vaporized in the unit and introduced into the exhaust gas prior to its entering the SCR catalyst. Introducing the reductant mixed with air into the reductant delivery system prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process thus reducing system response delays and improving the device conversion efficiency. The reductant delivery system is further improved by adding a hydrolyzing catalyst to it, and by isolating the reductant and air mixture from the heating element.

Claims

1. A method for controlling a reductant delivery system having at least a heating element and a mixing unit, the delivery system coupled upstream of an SCR catalyst, the method comprising:

injecting air into the mixing unit;

injecting reductant into the mixing unit;

providing an operating temperature for the heating element; and

directing a spray of a mixture of said air and reductant from said mixing unit onto said heating element, said heating element vaporizing said spray into an exhaust gas mixture from an internal combustion piston engine, said

exhaust gas mixture entering the SCR catalyst, wherein said reductant includes urea.

2. The method as set forth in claim 1 wherein the heating element is housed inside a housing, and said mixture spray is injected into said housing, and subsequently comes into contact with a surface of the heating element.

3. The method as set forth in claim 2 wherein the heating element is an electrically heated heating element.

4. The method as set forth in claim 2 wherein an inner surface of said housing is coated with a hydrolyzing catalyst.

5. The method as set forth in claim 2 wherein a hydrolyzing catalyst is placed in the path of said vaporized mixture of said reductant and said air.

6. The method as set forth in claim 1 wherein the heating element is housed inside a housing, wherein the housing deflects part of the directed mixture spray.

7. The method as set forth in claim 1 wherein said directed mixture spray impinges on a heated surface of the heating element.