Engine exhaust gas treatment system and exhaust gas treatment process

• US 20050013756A1
• Filed: 05/27/2004
• Published: 01/20/2005
• Est. Priority Date: 05/28/2003
• Status: Active Grant

• Current Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Inventors: Yokota, Hiroshi, Kusumoto, Hiroshi, Mukai, Toshifumi, Amou, Kiyoshi, Yamakado, Makoto, Hamada, Ikuhisa, Nagano, Masami
• Granted Patent: US 7,509,799 B2
• Time in Patent Office: Days
• US Class Current: 423/239.100
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: B01F 23/2132 using nozzles
• CPC Class Codes: B01F 25/10 Mixing by creating a vortex flow, e.g. by tangential introduction of flow components
• CPC Class Codes: B01F 25/32 wherein the additional components are added in a by-pass of the main flow
• CPC Class Codes: F01N 13/08 Other arrangements or adaptations of exhaust conduits pipes, joints or supports therefor in general F16L; collecting or removing exhaust gases of vehicle engines in workshops B08B15/00, on highways E01C1/005
• CPC Class Codes: F01N 2470/24 Concentric tubes or tubes being concentric to housing, e.g. telescopically assembled
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2560/07 the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters
• 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 2610/102 after addition to exhaust gases, e.g. by a passively or actively heated surface in the exhaust conduit
• CPC Class Codes: F01N 2610/1426 Filtration means
• CPC Class Codes: F01N 2610/146 Control thereof, e.g. control of injectors or injection valves
• CPC Class Codes: F01N 2610/1473 Overflow or return means for the substances, e.g. conduits or valves for the return path
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: F01N 3/2892 Exhaust flow directors or the like, e.g. upstream of catalytic device
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

To provide an engine exhaust gas treatment system that can efficiently reduce and remove NOx using easy-to-handle urea as the reducing agent, regardless of the engine operating conditions. An exhaust gas denitration system in which an exhaust gas is introduced into the denitration catalyst reactor 5 provided in the exhaust gas flue 3, where NOx is reduced and removed in the presence of the denitration catalyst, wherein a diversion means provided in the exhaust gas flue 3 introduces part or all of the exhaust gas into a urea solution injection evaporator having a heating means by the heater 30, and the heat from the exhaust gas and the heat from the heater serve to generate ammonia that is then circled and mixed with the exhaust gas and introduced into the denitration catalyst reactor 4.

Claims

1. An exhaust gas treatment system in which an exhaust gas is introduced into a denitration catalyst reactor provided in an exhaust gas flue, where nitrogen oxide is reduced in a presence of the denitration catalyst, comprising:

an exhaust gas diversion passage portion provided in the exhaust gas flue;

a urea solution injection valve, which is provided in said exhaust gas diversion passage portion and in which part or all of the exhaust gas is introduced, for injecting a urea solution into the introduced exhaust gas;

an ammonia generation portion, which has heating means by a heater, for decomposing particulate droplets of the urea solution and urea to generate ammonia by one or both of heat from the exhaust gas and heat from the heater;

a mixing portion for mixing the gene rated ammonia with the exhaust gas; and

said denitration catalyst reactor in which a mixed gas of the ammonia and exhaust gas is introduced.

3. An exhaust gas treatment system according to claim 1, wherein

said exhaust gas diversion passage portion comprises an exhaust flow control valve which changes a diversion amount of the exhaust gas into the urea solution injection valve depending on output from part or all of an exhaust gas temperature sensor, an exhaust gas flow rate sensor, and a nitrogen oxide sensor.

4. An exhaust gas treatment system according to claim 1, wherein

said mixing portion is provided in said exhaust gas diversion passage portion.

5. An exhaust gas treatment system according to claim 1, wherein

said mixing portion is provided in said exhaust gas flue.

6. An exhaust gas treatment system according to claim 1 or 2, wherein

said ammonia generation portion comprises a urea decomposition catalyst reactor.

7. An exhaust gas treatment system according to claim 1 or 2, further comprising a urea solution injection device including said urea solution injection valve, wherein

said urea solution injection device comprises a urea solution injection amount control device which changes an amount of the injected urea solution depending on output from part or all of an exhaust gas temperature sensor, an exhaust gas flow rate sensor, and a nitrogen oxide sensor.

8. An exhaust gas treatment system according to claim 1 or 2, comprising a heater temperature control device which changes an amount of heat generated depending on output from part or all of an exhaust gas temperature sensor, an exhaust gas flow rate sensor, and a nitrogen oxide sensor.

9. An exhaust gas treatment system according to claim 8, said heater temperature control device comprises a heat amount change pattern for changing the amount of heat generated according to a previously stored heat generation pattern depending on an engine operating condition.

10. An exhaust gas treatment system according to claim 9, said heat amount change pattern is that a smaller amount of heat is generated for higher temperatures and a greater flow rate of the exhaust gas.

11. An exhaust gas treatment system according to claim 1 or 2, wherein

circling means mixes the particulate droplets of the urea solution and ammonia with the exhaust gas.

2. An exhaust gas treatment system in which an exhaust gas is introduced into a denitration catalyst reactor provided in an exhaust gas flue, where nitrogen oxide is reduced in a presence of the denitration catalyst, comprising:

a urea solution injection valve for injecting a urea solution into part of the exhaust gas introduced from the exhaust gas flue;

an ammonia generation portion, which has heating means by a heater, for decomposing particulate droplets of the urea solution and urea to generate ammonia by at least heat of said heater;

a mixed gas carrier portion, which has another heating means by a heater, for decomposing particulate droplets of a residual urea solution and urea, and for mixing the generated ammonia with the exhaust gas, and for carrying a mixed gas; and

said denitration catalyst reactor in which the mixed gas of the heated ammonia and exhaust gas is introduced.

12. An exhaust gas treatment system in which an exhaust gas is introduced into a denitration catalyst reactor provided in an exhaust gas flue, where nitrogen oxide is reduced in a presence of the denitration catalyst, comprising:

a urea solution injection valve for injecting a urea solution into part of the exhaust gas introduced from the exhaust gas flue;

a first ammonia generation portion, which has heating means by a heater, for decomposing particulate droplets of the urea solution and urea to generate ammonia by at least heat of said heater;

a second ammonia generation portion, which has another heating means by a heater, for decomposing particulate droplets of a residual urea solution and urea to generate ammonia;

a mixed gas carrier portion for mixing the generated ammonia with the exhaust gas by circling means, and for carrying a mixed gas of the heated ammonia and exhaust gas with allowing its temporal dwelling between a plurality of restrictions; and

said denitration catalyst reactor in which said mixed gas is introduced.

13. An exhaust gas treatment process in which an exhaust gas is introduced into a denitration catalyst reactor provided in an exhaust gas flue, where nitrogen oxide is reduced in a presence of the denitration catalyst, comprising the steps of:

introducing part or all of the exhaust gas from an exhaust gas diversion passage portion provided in the exhaust gas flue, and injecting a liquid reducing agent into the introduced exhaust gas from a liquid reducing agent injection device;

having heating means by a heater and decomposing particulate droplets of the liquid reducing agent and the liquid reducing agent to generate ammonia by one or both of heat from the exhaust gas and heat from the heater;

mixing the generated ammonia with the exhaust gas; and

introducing a mixed gas of the ammonia and exhaust gas into said denitration catalyst reactor.