Patent Application
20180030870
The present application claims priority to and the benefit of Korean Patent Application No. 10-2016-0094741 filed on Jul. 26, 2016, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of manufacturing a catalyzed particulate filter. More particularly, the present invention relates to a method of manufacturing a catalyzed particulate filter including at least one porous wall defining a boundary between at least one inlet channel and at least one outlet channel and a support located within at least one among the at least one inlet channel and the at least one outlet channel, the method being related to effectively coating a catalyst on the at least one wall and the support.
An exhaust gas from internal combustion engines such as diesel engines or a variety of combustion equipment contains particulate matter (PM). Such PMs can cause environmental pollution when emitted into the atmosphere. For this reason, gas exhaust systems are equipped with a particulate filter for capturing PM.
The particulate filter may be categorized as a flow-through particulate filter or a wall-flow particulate filter depending on a flow of fluid.
In the flow-through particulate filter, a fluid flowing into a channel flows only within this channel without moving to another channel. This helps minimize an increase in back pressure, but necessitates a means for capturing particulate matter in the fluid and may result in low filter performance.
In the wall-flow particulate filter, a fluid flowing into a channel moves to an adjacent channel and is then discharged from the particulate filter through the adjacent channel. That is, a fluid flowing into an inlet channel moves to an outlet channel through a porous wall and is then discharged from the particulate filter through the outlet channel. When a fluid passes through the porous wall, particulate matter in the fluid is captured without passing through the porous wall. The wall-flow particulate filter is effective at removing particulate matter, although it may increase the back pressure to some extent. Hence, wall-flow particulate filters are primarily used.
A vehicle is equipped with at least one catalytic converter, along with a particulate filter. The catalytic converter is designed to remove carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx).
The catalytic converter may be physically separated from the particulate filter, or combined with the particulate filter by coating a catalyst in the particulate filter. The particulate filter coated with a catalyst may be called a catalyzed particulate filter (CPF).
In the CPF, the catalyst is coated on the porous wall that separates the inlet channel and the outlet channel from each other, and the fluid passes through the porous wall and contacts with the catalyst coating. There is a pressure difference between the inlet channel and outlet channel separated by the porous wall. This allows the fluid to pass fast through the porous wall. Accordingly, the contact time between the catalyst and the fluid is short, which makes it hard for a catalytic reaction to occur efficiently.
Also, a thick catalyst coating on the porous wall allows the catalyst to block the micropores on the wall, and this may disturb the flow of the fluid from the inlet channel to the outlet channel. Accordingly, the back pressure increases. To minimize the increase in back pressure, a catalyst is thinly coated on the walls in the CPF. Thus, an amount of catalyst coating in the CPF may be insufficient for the catalytic reaction to occur efficiently.
To overcome this problem, the surface area of walls to be coated with the catalyst may be increased by increasing the number (density) of inlet channels and outlet channels (hereinafter, collectively referred to as ‘cells’). However, the increase in cell density in the limited space reduces the wall thickness. The reduction in wall thickness may deteriorate the filter performance. Therefore, the cell density should not be increased to more than the density limit.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Various aspects of the present invention are directed to providing a method of manufacturing a catalyzed particulate filter having advantages of minimizing an increase in back pressure and increasing catalyst loading.
Another exemplary embodiment various aspects of the present invention are directed to providing a method of manufacturing a catalyzed particulate filter having advantages of increasing entire catalyst loading coated in the particulate filter but minimizing catalyst loading coated on a porous wall by disposing a support on which much catalyst is coated in inlet channels and outlet channels.
A method of manufacturing a catalyzed particulate filter according to an exemplary embodiment of the present invention may include: preparing a bare particulate filter including at least one inlet channel which may have a first end being open and a second end being blocked, at least one outlet channel which may have a first end being blocked and a second end being open and which is positioned alternately with the at least one inlet channel, at least one porous wall which defines a boundary between adjacent inlet and outlet channels, and a support which is located within at least one among the at least one inlet channel and the at least one outlet channel; injecting a catalyst slurry into the at least one inlet channel and the at least one outlet channel; discharging a portion of the catalyst slurry by blowing gas into or drawing the gas from the at least one inlet channel or the at least one outlet channel; and drying/calcining the particulate filter from which the portion of the catalyst slurry is discharged.
The at least one inlet channel, the at least one outlet channel, the at least one porous wall, and the support may extend in a same direction.
An amount of the catalyst slurry removed from the at least one porous wall may be larger than that of the catalyst slurry removed from the support in the discharging a portion of the catalyst slurry.
An amount of a catalyst coated on the at least one porous wall may be controlled by adjusting a pressure of the gas which is blown or drawn.
In one aspect, the support and the at least one porous wall may include a same material.
In another aspect, the support and the at least one porous wall may include different materials from each other.
A viscosity of the catalyst slurry may be smaller than or equal to 200 cpsi.
The viscosity of the catalyst slurry may be controlled according to content of solid particle, pH of the catalyst slurry, and particle size of the solid particle.
A lean NOx trap (LNT) catalyst or a selective catalytic reduction (SCR) catalyst may be coated on the at least one porous wall and the support.
As described above, increase in back pressure may be minimized and entire catalyst loading may be increase by disposing a support within at least one among at least one inlet channel and at least one outlet channel and coating much catalyst on the support to reduce catalyst loading on a porous wall.
In addition, sufficient filter performance and catalyst performance can be achieved since larger catalyst loading and a larger contact area (time) between a fluid and the catalyst are provided while keeping the wall thickness.
The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.
In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.
Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.
An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.
A catalyzed particulate filter according to an exemplary embodiment of the present invention can be configured for use in variety of devices, as well as vehicles, that get energy by burning fossil fuels and emit gases produced in the burning process into the atmosphere. Although this specification illustrates an example of a catalyst particulate filter configured for use in a vehicle, the present invention should not be construed as limited to this example.
The vehicle is equipped with an engine for generating power. The engine converts chemical energy into mechanical energy by the combustion of a fuel-air mixture. The engine is connected to an intake manifold to draw air into a combustion chamber, and connected to an exhaust manifold where an exhaust gas produced during combustion is collected and emitted out. Injectors are mounted at the combustion chamber or intake manifold to spray fuel into the combustion chamber or intake manifold.
The exhaust gas produced from the engine is emitted out of the vehicle via an exhaust system. The exhaust system may include an exhaust pipe and exhaust gas recirculation (EGR) apparatus.
The exhaust pipe is connected to the exhaust manifold to emit the exhaust gas out of the vehicle.
The exhaust gas recirculation apparatus is mounted on the exhaust pipe, and the exhaust gas emitted from the engine pass through the exhaust gas recirculation apparatus. Also, the exhaust gas recirculation apparatus is connected to the intake manifold and mixes some of the exhaust gas with air to control the combustion temperature. The combustion temperature may be regulated by controlling ON/OFF of an exhaust gas recirculation (EGR) valve in the exhaust gas recirculation apparatus. That is, the amount of exhaust gases supplied to the intake manifold is adjusted by controlling the ON/OFF of the EGR valve.
The exhaust system may further include a particulate filter that is mounted on the exhaust pipe and captures particulate matter in the exhaust gas. The particulate filter may be a catalyzed particulate filter according to an exemplary embodiment of the present invention that removes harmful substances as well as particulate matter in exhaust gases.
Hereinafter, a catalyzed particulate filter according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As illustrated in
In this specification, the inlet channel 10 and the outlet channel 20 may be collectively referred to as ‘cells’. Although, in this specification, the housing has a cylindrical shape and the cells have a rectangular shape, the housing and the cells are not limited to such shapes.
Referring to
The outlet channel 20 extends along the flow of the exhaust gas, and may be placed parallel to the inlet channel 10. At least one inlet channel 10 is located around the outlet channel 20.
For example, when the cells have a rectangular shape, each outlet channel 20 is surrounded by walls 30 on four sides. At least one of the four sides is located between each outlet channel 20 and an adjacent inlet channel 10. When the cells have a rectangular shape, each outlet channel 20 may be surrounded by four adjacent inlet channels 10 and each inlet channel 10 may be surrounded by four adjacent outlet channels 20, but the present invention is not limited thereto.
Since the front end of the outlet channel 20 is blocked by a second plug 22, the exhaust gas does not flow into the particulate filter 1 through the outlet channel 20. The rear end of the outlet channel 20 is open so that the exhaust gas in the particulate filter 1 flows out of the particulate filter 1 through the outlet channel 20.
A wall 30 is placed between adjacent inlet and outlet channels 10 and 20 to define the boundary between them. The wall 30 may be a porous wall 30 with at least one micropore therein. The porous wall 30 allows the adjacent inlet and outlet channels 10 and 20 to fluidly communicate with each other. Thus, the exhaust gas introduced into the inlet channel 10 may move to the outlet channel 20 through the porous wall 30. Moreover, the porous wall 30 does not cause particulate matter in the exhaust gas to pass therethrough. When the exhaust gas moves from the inlet channel 10 to the outlet channel 20 through the porous wall 30, the particulate matter in the exhaust gases is filtered by the porous wall 30. The porous wall 30 may be made from aluminum titanate, codierite, silicon carbide, etc.
The porous wall 30 may be coated with a catalyst 50. The catalyst 50 coated on the porous wall 30 is not limited to particular ones. In other words, the wall 30 may be coated with a variety of catalysts 50 including a lean NOx trap (LNT) catalyst, a three-way catalyst, an oxidation catalyst, a hydrocarbon trap catalyst, a selective catalytic reduction (SCR) catalyst, etc., depending on the design intent. Moreover, at least two types of catalyst 50 may be coated on the wall 30. For example, the LNT catalyst may be coated on an inside surface of the inlet channel 10 and the SCR catalyst may be coated on an inside surface of the outlet channel 20, but the present invention is not limited thereto.
The support 40 may be located within at least one among the at least one inlet channel 10 and the at least one outlet channel 20. The support 40 may be located within the at least one inlet channel 10 or within the at least one outlet channel 20. Although
The support 40 is coated with a catalyst 50. The catalyst 50 coated on the support 40 is not limited to particular ones. In other words, the support 40 may be coated with a variety of catalysts 40 including a lean NOx trap (LNT) catalyst, a three-way catalyst, an oxidation catalyst, a hydrocarbon trap catalyst, a selective catalytic reduction (SCR) catalyst, etc. depending on the design intention. Moreover, at least two types of catalyst 50 may be coated on the support 40. For example, the LNT catalyst and the SCR catalyst may be sequentially coated on the support 40, but the present invention is not limited thereto. Furthermore, different types of catalyst 50 may be coated on a first side and a second side of the support 40. Also, the catalyst 50 coated on the support 40 may be a same type as or a different type from the catalyst 50 coated on the wall 30.
Meanwhile, the support 40 is provided to hold the catalyst 50 in place, rather than serving as a filter. Thus, the support 40 is not necessarily made from a porous material. That is, the support 40 may be made from a same material as the porous wall 30 or a different material. Even in the case that the support 40 is made from a porous material, the exhaust gas mostly moves along the support 40 and wall 30 without passing through the support 40, because there is little difference in pressure between the two parts of the channel 10 or 20 separated by the support 40. Also, the support 40 does not need to be thick since it is not required to serve as a filter. That is, the support 40 may be thinner than the wall 30, which minimizes an increase in back pressure. When the support 40 is made from a porous material, the catalyst 50 is coated on a surface of the support 40 and on the micropores in the support 40. On the contrary, when the support 40 is made from a non-porous material, the catalyst 50 is coated on the surface of the support 40.
As mentioned previously, the catalyst 50 may be coated on both the support 40 and the porous wall 30. In the instant case, an amount of catalyst 50 coated on the support 40 may be greater than that coated on the porous wall 30. The catalyst 50 may be thinly coated on the porous wall 30 since the porous wall 40 serves as a filter. On the contrary, the catalyst 50 may be thickly coated on the support 40 since the support 40 is not required to serve as a filter. Accordingly, the amount of catalyst coating in the particulate filter 1 may be increased. Here, the amount of catalyst 50 refers to the amount of catalyst coating per unit length or unit area.
Operation of the catalyzed particulate filter according to the exemplary embodiment of the present invention will be described below.
Referring to
Referring to
The X-axis in
In
Referring overall to
On the other hand, in the case of the flow-through carrier, the increase in back pressure is small even with an increase in the amount of catalyst coating, and there is no need to achieve sufficient filter performance. Thus, the number of cells can be increased a lot by making the walls sufficiently thin. As mentioned previously, the support 40 according to the present exemplary embodiment is not required to function as a filter but only serves as a carrier for holding the catalyst 50. Accordingly, the support 40 according to the present exemplary embodiment performs the same function as the flow-through carrier. Consequently, the increase in back pressure is minimized even with an increase in the number of supports 40. Moreover, a sufficient number of supports 40 can be mounted in the particulate filter 1 since the supports 40 can be made thin. In addition, the support 40 allows for an increase in the amount of catalyst 50 supported on it and a longer contact time (larger contact area) between the catalyst 50 and the exhaust gas, thereby improving the nitrogen oxide reduction.
As shown in
If the bare particulate filter is manufactured at the step S100, a catalyst slurry 52 is injected into the at least one inlet channel 10 and the at least one outlet channel 20 at step S110. In the instant case, the at least one inlet channel 10 and the at least one outlet channel 20 are filled with the catalyst slurry 52.
Herein, making the catalyst slurry will be briefly described.
Firstly, a catalyst solid particle having a same ingredients as a target catalyst is prepared. For example, when the target catalyst is an LNT catalyst, the catalyst solid particle including Al2O3, CeO2, Ba, Pt, Pd, Rh, etc. is prepared. In addition, when the target catalyst is an SCR catalyst, the catalyst solid particle including zeolite, Cu, etc. is prepared.
After that, the catalyst solid particle is mixed with water to wet-grind the catalyst solid particle. At this time, content of the catalyst solid particle is approximately 20 wt %-40 wt %. Herein, the catalyst solid particle wet-grinded and mixed with the water is called the catalyst slurry.
In addition, pH of the catalyst slurry can be adjusted by adding acid component such as acetic acid into the catalyst slurry, and a viscosity of the catalyst slurry can be changed by the pH of the catalyst slurry. That is, the viscosity of the catalyst slurry is controlled according to content of the solid particle, the pH of the catalyst slurry, and particle size of the solid particle. According to the present exemplary embodiment, the viscosity of the catalyst slurry 52 is controlled to be smaller than or equal to 200 cpsi to prevent the catalyst slurry from blocking the micropores on the porous wall.
After the step S110 is performed, gas is blown into or is drawn from the at least one inlet channel 10 or the at least one outlet channel 20 so that a portion of the catalyst slurry 52 is discharged from the channels 10 and 20 at step S120. For example, a blower is connected to any one channel 10 (inlet channel 10 in
When the gas is blown into or drawn from the channel 10 or 20 at the step S120, a pressure difference between the inlet channel 10 and the outlet channel 20 is generated. The gas passes through the inlet channel 10 and is then discharged from the outlet channel 20 or passes through the outlet channel 20 and is then discharged from the inlet channel 10 by the pressure difference. At this time, the portion of the catalyst slurry 52 filling the inlet channel 10 or the outlet channel 20 is discharged from the outlet channel 20 or the inlet channel 10 with the gas.
Since the pressure difference between the inlet channel 10 and the outlet channel 20 across the porous wall 30 is greatly generated, the gas passes through the porous wall 30 relatively quickly at the step S120. Therefore, a substantial amount of the catalyst slurry 52 on the porous wall 30 is removed from the porous wall 30 and is discharged from the outlet channel 20 or the inlet channel 10.
As described above, since any one support 40 is located within any one channel 10 or 20, a pressure difference between two parts of the channel 10 or 20 divided by the support 40 is hardly generated. Therefore, the gas hardly passes through the support 40 and moves along the support 40 and the wall 30. Therefore, a little amount of the catalyst slurry 52 on the support 40 is removed from the support 40 and is discharged from the outlet channel 20 or the inlet channel 10.
When the gas is blown into or drawn from the inlet channel 10 or the outlet channel 20 filled with the catalyst slurry 52, an amount of the catalyst slurry 52 removed from the porous wall 30 is larger than that of the catalyst slurry 52 removed from the surface of the support 40. Resultantly, the catalyst loading coated on the porous wall 30 is small and the catalyst loading coated on the support 40 is large. The increase in the back pressure when using the CPF may be suppressed by reducing the catalyst loading coated on the porous wall 30, but the entire catalyst loading in the CPF may be increased by increasing the catalyst loading coated on the support 40. In addition, the catalyst loading coated on the porous wall 30 can be controlled by adjusting a pressure of the gas which is blown into or drawn from the channel 10 or 20. When the pressure of the gas is high, the catalyst loading coated on the porous wall 30 decreases. When the pressure of the gas is low, on the contrary, the catalyst loading coated on the porous wall 30 increases. At this time, the catalyst loading coated on the support 40 is hardly dependent upon the pressure of the gas which is blown into or drawn from the channel 10 or 20.
After that, the particulate filter from which the portion of the catalyst slurry 52 is discharged is dried/calcined at step S130 so that the catalyzed particulate filter 1 is manufactured.
When the CPF is manufactured through the manufacturing method according to the exemplary embodiment of the present invention, the same type of the catalyst is coated on the porous wall 30 and the support 40. In addition, the catalyst loading on the porous wall 30 serving as a filter is small so that the increase in the back pressure may be suppressed. Further, much of the catalyst can be coated on the support 40 which does not serve as a filter and only supports the catalyst. Therefore, performance of the catalyst may be improved.
For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”, “upper”, “lower”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “interior”, “exterior”, “inner”, “outer”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2016-0094741 | Jul 2016 | KR | national |
