Power plants – Internal combustion engine with treatment or handling of... – Methods
Reexamination Certificate
1998-10-23
2001-03-13
Chapman, Jeanette (Department: 3711)
Power plants
Internal combustion engine with treatment or handling of...
Methods
C060S276000, C060S277000, C060S285000, C060S301000, C060S303000, C060S295000
Reexamination Certificate
active
06199372
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus and a method for regenerating NO
X
catalyst for a diesel engine, and the invention particularly relates to an apparatus and a method for regenerating NO
X
catalyst for a diesel engine which has lower performance.
BACKGROUND ART
Conventionally, Japanese Laid-open Patent No. 4-330314 describes a catalyst type exhaust emission control device for a diesel engine, which reduces and decomposes NO
X
contained in the exhaust emissions from a diesel engine. According to Japanese Laid-open Patent No. 4-330314, the device is composed of a copper-zeolite NO
X
catalyst provided in an exhaust path of a diesel engine, a hydrocarbon sensor for detecting the hydrocarbon concentration in the exhaust emissions, and a fuel spraying means which is provided in the exhaust path at the upstream side of the hydrocarbon sensor and which sprays fuel into the exhaust path to control the hydrocarbon concentration in the exhaust emissions within a predetermined range. According to the aforesaid configuration, based on a detected value of the hydrocarbon concentration, fuel is appropriately sprayed into the exhaust path from the fuel spraying means, and the hydrocarbon concentration in the exhaust emissions is kept within the predetermined range. The fuel sprayed from the fuel spraying means acts as a hydrocarbon reductant, and activates the copper-zeolite NO
X
catalyst in association with oxygen contained in the exhaust emissions from the diesel engine. Thus, it is proposed that the reduction of NO
X
in the exhaust emissions is promoted. However, the copper-zeolite NO
X
catalyst has a low performance in controlling NO
X
.
Accordingly, in order to obtain a higher performance in controlling NO
X
, a large quantity of hydrocarbon for reduction is necessary, and this is disadvantageous in the operational cost of the catalyst.
On the other hand, an NO
X
catalyst containing an alkali-earth or a rare-earth oxide and a precious metal, and an NO
X
catalyst having silver as an active component show a higher efficiency of controlling NO
X
with a smaller quantity of reductant hydrocarbon as compared with a copper-zeolite catalyst.
However, the high-performance NO
X
catalyst containing an alkali-earth or a rare-earth oxide and a precious metal, and the NO
X
, catalyst having silver as an active component enable highly efficient control of NO
X
, but have a disadvantage in that they have a lower durability against SO
x
, and therefore it is difficult to put them into practical use.
SUMMARY OF THE INVENTION
The present invention is made to mitigate the aforesaid disadvantages, and its object is to provide an apparatus and a method for regenerating the NO
X
catalyst having a low performance as a result of SO
x
being accumulated in the NO
X
catalyst due to sulfur in the fuel supplied to a diesel engine. The NO
X
catalyst applied to the present invention is not limited to the NO
X
, catalyst containing an alkali-earth or a rare-earth oxide and a precious metal, or the NO
X
catalyst having silver as an active component, as described above, but any NO
X
catalyst can be applied if it is an NO
X
catalyst which is generally deteriorated by SO
x
in the exhaust emissions in a short time.
In order to attain the aforesaid object, a first aspect of an apparatus for regenerating an NO
X
, catalyst for a diesel engine according to the present invention is an NO
X
catalyst device for a diesel engine, which reduces and controls NO
X
in exhaust gas by adding into an exhaust pipe a quantity of diesel fuel, such as kerosene, as a reductant fuel being a reductant hydrocarbon, and by using an NO
X
catalyst which is disposed in the exhaust pipe and the performance of which is easily lowered by absorbing SO
x
, characterized by including: a reductant fuel adding nozzle, for adding a reductant fuel into the exhaust pipe;
a flow rate control valve, for controlling a feed rate of the reductant fuel to the reductant fuel adding nozzle; an NO
X
catalyst inlet temperature sensor, disposed at an upstream side of the NO
X
catalyst; and a regeneration control unit, for computing the quantity of SO
x
taken into the NO
X
catalyst during a period of time, in which a signal from the NO
X
catalyst inlet temperature sensor indicates that the inlet temperature of the NO
X
catalyst is not higher than a predetermined value and an instruction of a zero feed rate is given to the flow rate control valve based on the quantity of the diesel fuel supplied to the diesel engine during the period of time of zero feed rate of the reductant fuel, and when the inlet temperature exceeds a predetermined value and the reductant fuel is started to be added, for outputting to the flow rate control valve an instruction for supplying a quantity of reductant fuel which is larger than a quantity which is suitable for the current operational condition of the diesel engine, and is characterized by the apparatus regenerating the NO
X
catalyst, which has low performance due to SO
x
, by adding the quantity of the reductant fuel which is larger than the quantity which is suitable for the current operational condition.
A second aspect of the invention, based on the first aspect of the invention of the apparatus for regeneration, is characterized by including either a selector switch, for indicating the kind of diesel fuel for the diesel engine, or a component sensor, for detecting the sulfur content in the diesel fuel, and characterized by the regeneration control unit computing the quantity of SO
x
discharged from the diesel engine from the feed rate of the diesel fuel to the diesel engine and a signal sent from either the selector switch or the component sensor; and when the inlet temperature becomes a predetermined value or over and the reductant fuel is started to be added, outputting to the flow rate control valve an instruction to supply a quantity of the reductant fuel which is larger than a predetermined quantity which is suitable for the operational condition of the diesel engine.
A third aspect of the invention of the apparatus for regeneration is an NO
X
catalyst device for a diesel engine, which reduces and controls NO
X
in the exhaust gas by adding into an exhaust pipe a predetermined quantity of diesel fuel, such as kerosene, as a reductant fuel being a reductant hydrocarbon, and by using an NO
X
catalyst which is disposed in the exhaust pipe and which has a performance which is easily lowered by absorbing SO
x
, characterized by including; a reductant fuel adding nozzle, for adding a reductant fuel into the exhaust pipe at an upstream side of the NO
X
catalyst; a flow rate control valve, for controlling a feed rate of the reductant fuel to the reductant fuel adding nozzle; an NO
X
catalyst inlet temperature sensor, disposed at an upstream side of the NO
X
catalyst; a hydrocarbon concentration sensor, disposed at a downstream side of the NO
X
catalyst; and a regeneration control unit; and is characterized by the regeneration control unit outputting to the flow rate control valve an instruction, for adding a quality of the reductant fuel which is larger than a predetermined quantity which is suitable for the operational condition of the diesel engine, when a signal from the NOx catalyst inlet temperature sensor indicates that the inlet temperature of the NO
X
catalyst is higher than a predetermined value, and a signal from the hydrocarbon concentration sensor indicates that the hydrocarbon concentration at the downstream side of the NO
X
catalyst is greater than a predetermined value, to regenerate the NO
X
catalyst which has a low performance due to SO
x
.
A first aspect of the invention of a method for regenerating an NO
X
catalyst for a diesel engine relates to a NO
X
catalyst device for a diesel engine, which reduces and controls NO
X
in the exhaust gas by adding into an exhaust pipe a predetermined quantity of diesel fuel, such as kerosene, as a reductant fuel being a reductant hydrocarbon, and by using an NO
X
catalyst which is disposed in the exhaust pipe and whic
Chapman Jeanette
Komatsu Ltd.
Sidley & Austin
Varma Sneh
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