# US 7,849,674 B2 · Exhaust emission purifying apparatus for engine

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- Number: US 7,849,674 B2
- Document ID: US7849674B2
- Status: Granted
- Kind: B2
- Application number: 10/572,558
- Filed: 2004-09-02
- Published: 2007-08-09
- Granted: 2010-12-14
- Earliest claimed: 2003-09-19
- Assignees: Nissan Diesel Motor Co., Ltd.
- Inventors: Kouji Masuda; Kiminobu Hirata; Hisashi Akagawa; Shuichi Nakamura; Hiroki Ueno; Ikuo Sakai
- Web page: https://patentgrep.com/patent/US7849674B2

## CPC

- F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent}
- B01D 53/9409: {Nitrogen oxides}
- F01N 3/105: {General auxiliary catalysts, e.g. upstream or downstream of the main catalyst}
- F01N 3/106: {Auxiliary oxidation catalysts}
- F01N 3/206: {Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents}
- F01N 11/002: {the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus}
- F01N 13/009: {having two or more separate purifying devices arranged in series}
- F01N 13/0097: {the purifying devices are arranged in a single housing}
- B01D 2251/2062: Ammonia
- F01N 2610/02: the substance being ammonia or urea
- F01N 2610/08: with prior mixing of the substances with a gas, e.g. air
- F01N 2610/10: the substance being heated, e.g. by heating tank or supply line of the added substance
- F01N 2610/1406: Storage means for substances, e.g. tanks or reservoirs
- F01N 2610/1486: Means to prevent the substance from freezing
- Y02T 10/12: Improving ICE efficiencies
- Y02T 10/40: Engine management systems
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A NOx reduction catalyst and an ammonia slip oxidation catalyst are disposed in an exhaust system in this order, and also, an electric fan is disposed on piping which communicates an upper space of a storage tank storing therein a reducing agent with the exhaust upstream of the NOx reduction catalyst. Then, when the temperature of the ammonia slip oxidation catalyst reaches or exceeds the temperature for activating a catalyst thereof, the electric fan is operated for a predetermined period of time, so that the gas (ammonia series gas) in the upper space of the storage tank is forcibly discharged to the upstream side of the NOx reduction catalyst. Further, a discharge-forcing device, such as an electric fan or the like, forcibly discharging the gas in the upper space of the storage tank, an adsorbing device temporarily adsorbing thereto the forcibly discharged gas and an oxidation catalyst oxidizing the gas desorbed from the adsorbing device, may be disposed to the storage tank in this order.

## Claims

### Claim 1

An exhaust emission purifying apparatus for an engine, comprising:
a reduction catalyst disposed in an engine exhaust system, for reductively purifying nitrogen oxides with a reducing agent;
a reducing agent oxidation catalyst disposed on an exhaust downstream side of said reduction catalyst, for oxidizing the reducing agent passed through said reduction catalyst;
a storage tank for storing therein the reducing agent;
a reducing agent supply device for supplying the reducing agent from said storage tank to said reduction catalyst;
a first discharge-forcing device for forcibly discharging a gas in an upper space of said storage tank to an intake system or said exhaust system on an upstream side of said reducing agent oxidation catalyst;
a temperature detecting device for detecting a temperature of said reducing agent oxidation catalyst; and
a first operation control device for operating said first discharge-forcing device when the temperature detected by said temperature detecting device reaches an activating temperature for said reducing agent oxidation catalyst or above.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein said first operation control device is configured to operate said first discharge-forcing device for a predetermined period of time.

### Claim 3 (depends on 1)

The apparatus according to claim 1, wherein said first discharge-forcing device is an electric fan disposed on piping which communicatively connects the upper space of said storage tank to the intake system or the exhaust system on the upstream side of said reducing agent oxidation catalyst.

### Claim 4 (depends on 3)

The apparatus according to claim 3, wherein said piping is disposed with a check valve which is configured to be opened only in a direction in which the gas in the upper space of said storage tank is discharged to the intake system or the exhaust system.

### Claim 5 (depends on 1)

The apparatus according to claim 1, wherein said first discharge-forcing device comprises: a venturi disposed in the intake system or the exhausted system, on the upstream side of said reducing agent oxidation catalyst; and a switching valve disposed on piping for providing a fluid communication between the upper space of said storage tank and said venturi, and said first operation control device for opening said switching valve when the temperature detected by said temperature detecting device reaches the activating temperature for said reducing agent oxidation catalyst or above.

### Claim 6 (depends on 1)

The apparatus according to claim 1, wherein said temperature detecting device is configured to detect the temperature of said reducing agent oxidation catalyst indirectly via the exhaust emission temperature on the upstream side of said reducing agent oxidation catalyst.

### Claim 7

An exhaust emission purifying apparatus for an engine, comprising:
a reduction catalyst disposed in an engine exhaust system, for reductively purifying nitrogen oxides with a reducing agent;
a storage tank for storing therein the reducing agent;
a reducing agent supply device for supplying the reducing agent stored in said storage tank to said reduction catalyst;
a second discharge-forcing device for forcibly discharging the gas in an upper space of said storage tank;
an adsorbing device for temporarily adsorbing thereto the gas forcibly discharged by said second discharge-forcing device; and
an oxidation catalyst for oxidizing the gas desorbed from said adsorbing device,
wherein said second discharge-forcing device, said adsorbing device and said oxidation catalyst are disposed on a top wall of the storage tank,
wherein after passing through the oxidation catalyst, the gas is to be discharged into an atmosphere.

### Claim 8 (depends on 7)

The apparatus according to claim 7, further comprising:
a reducing agent temperature detecting device for detecting the temperature of the reducing agent in said storage tank; and
a second operation control apparatus for operating said second discharge-forcing device when the temperature of the reducing agent detected by said reducing agent temperature detecting device is equal to or higher than the first predetermined temperature.

### Claim 9 (depends on 8)

The apparatus according to claim 8, wherein said second operation control device is configured to operate said second discharge-forcing device for a predetermined period of time.

### Claim 10 (depends on 7)

The apparatus according to claim 7, further comprising:
a catalyst temperature detecting device for detecting the temperature of said oxidation catalyst; and
a catalyst activating device for activating said oxidation catalyst based on the catalyst temperature detected by said catalyst temperature detecting device.

### Claim 11 (depends on 10)

The apparatus according to claim 10, further comprising;
a heating device for heating said oxidation catalyst,
wherein said catalyst activating device is configured to control said heating device so that the catalyst temperature detected by said catalyst temperature detecting device reaches the activating temperature for said oxidation catalyst or above.

### Claim 12 (depends on 11)

The apparatus according to claim 11, wherein said catalyst activating device is configured to stop an operation of said heating device when the catalyst temperature detected by said catalyst temperature detecting device reaches the second predetermined temperature or above.

### Claim 13 (depends on 7)

The apparatus according to claim 7, wherein said adsorbing device is mordenite, cobalt-supported mordenite or activated carbon.

### Claim 14 (depends on 7)

The apparatus according to claim 7, wherein said oxidation catalyst is an electrically heated honeycomb catalyst.

### Claim 15

An exhaust emission purifying apparatus for an engine, comprising:
a reduction catalyst disposed in an engine exhaust system, for reductively purifying nitrogen oxides with a reducing agent;
a storage tank for storing therein the reducing agent;
a reducing agent supply device for supplying the reducing agent stored in said storage tank to said reduction catalyst;
a heating device for circulating a heating medium heated by said engine, within said storage tank, to heat said reducing agent stored in said storage tank;
a blocking device for blocking a passage which leads said heating medium into said storage tank;
a heating medium temperature detecting device for detecting the temperature of said heating medium; and
first control means for controlling said blocking device to block said passage, when the heating medium temperature detected by said heating medium temperature detecting device is higher than the third predetermined temperature.

### Claim 16 (depends on 15)

The apparatus according to claim 15, further comprising: a reducing agent temperature detecting device for detecting the temperature of the reducing agent stored in said storage tank; and second control means for controlling said blocking device to block said passage, when the reducing agent temperature detected by said reducing agent temperature detecting device is equal to or higher than the fourth predetermined temperature.

### Claim 17 (depends on 15, 16)

The apparatus according to claim 15 or claim 16, further comprising: third control means for controlling said blocking device to forcibly cancel the blocking of said passage for a predetermined period of time, immediately after an operation of said engine is started, and also, when the heating medium temperature detected by said heating medium temperature detecting device is higher than the freezing temperature of the reducing agent.

### Claim 18 (depends on 15)

The apparatus according to claim 15, wherein said blocking device is manually controllable, to cancel the blocking of said passage.