US20150023843A1

US20150023843A1 - Reductant supply system

Info

Publication number: US20150023843A1
Application number: US14/510,141
Authority: US
Inventors: James J. Driscoll; Brian M. Cole; Jinhui Sun
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2014-10-09
Filing date: 2014-10-09
Publication date: 2015-01-22
Also published as: CN205047281U

Abstract

An aftertreatment system is disclosed. The aftertreatment system includes an exhaust conduit and a selective catalytic reduction module. The aftertreatment system also includes a reductant supply system. The reductant supply system includes a reductant tank, a reductant injector, and a pump assembly. The pump assembly includes a reversing valve assembly and a pump unit. The pump assembly also includes a plurality of check valves, a pressure sensor, and a filter. Further, the reductant supply system includes a back flow valve assembly. The reductant supply system also includes at least two header units associated with the pump assembly. The at least two header units include a reductant draw conduit and at least one heat exchanger. The at least two header units also include a bag filtration assembly.

Description

TECHNICAL FIELD

The present disclosure relates to an aftertreatment system, and more particularly to a reductant supply system for the aftertreatment system.

BACKGROUND

An aftertreatment system is associated with an engine system. The aftertreatment system is configured to treat and reduce NOx and/or other compounds of the emissions present in an exhaust gas flow, prior to the exhaust gas flow exiting into the atmosphere. In order to reduce NOx, the aftertreatment system may include a Selective Catalytic Reduction (SCR) module and a reductant delivery module.
The reductant delivery module may include a tank for storing a reductant, a pump unit, reductant delivery lines, and a reductant injector. The reductant from the reductant tank may be delivered to the reductant injector via the pump unit. For large engine systems, reductant dosing may be increased as compared to that required by smaller engine systems. Sometimes, in the large engine systems the load on the reductant delivery module may increase due to thawing time required at engine startup.
U.S. Pat. No. 8,586,895 describes a plastic vehicle tank for an aqueous urea solution used for reducing the hydrogen oxide content in exhaust gases of an internal combustion engine. The tank comprises a functional unit comprising at least one pump, at least one pressure control valve, at least one internal container provided with an internal electrical heating and at least one suction line. The functional unit is preferably mounted in the form of a lid on the container opening for closing it.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, an aftertreatment system is disclosed. The aftertreatment system includes an exhaust conduit. The aftertreatment system also includes a selective catalytic reduction module configured to receive an exhaust gas flow from the exhaust conduit. The aftertreatment system also includes a reductant supply system configured to supply a reductant into the exhaust conduit upstream of the selective catalytic reduction module. The reductant supply system includes a reductant tank. The reductant supply system also includes a reductant injector. The reductant supply system further includes a pump assembly provided in fluid communication with the reductant tank and the reductant injector. The pump assembly includes a reversing valve assembly. The pump assembly also includes a pump unit. The pump assembly further includes a plurality of check valves associated with the pump unit. The pump assembly includes a pressure sensor. The pump assembly also includes a filter. The reductant supply system includes a back flow valve assembly provided in fluid communication with the pump assembly and the reductant tank. The reductant supply system also includes at least two header units associated with the pump assembly. The at least two header units include a reductant draw conduit configured to supply the reductant from the reductant tank to the pump assembly. The at least two header units also include at least one heat exchanger. The at least two header units further include a bag filtration assembly provided on each of the at least two header units.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary engine system including an aftertreatment system, according to one embodiment of the present disclosure;

FIG. 2 is a schematic view of a reductant supply system of the aftertreatment system, according to one embodiment of the present disclosure;

FIG. 3 is cross-sectional view of a reductant tank including two header units, according to one embodiment of the present disclosure; and

FIG. 4 is a perspective view of one of the two header units, according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts. Referring to FIG. 1, a block diagram of an exemplary engine system 100 is illustrated, according to one embodiment of the present disclosure. The engine system 100 includes an engine 102, which may be an internal combustion engine, such as, a reciprocating piston engine or a gas turbine engine. According to one embodiment of the disclosure, the engine 102 is a spark ignition engine or a compression ignition engine, such as, a diesel engine, a homogeneous charge compression ignition engine, or a reactivity controlled compression ignition engine, or other compression ignition engines known in the art. The engine 102 may be fueled by gasoline, diesel fuel, biodiesel, dimethyl ether, alcohol, natural gas, propane, hydrogen, combinations thereof, or any other combustion fuel known in the art.
The engine 102 may include other components, such as, a fuel system, an intake system, a drivetrain including a transmission system, and so on. The engine 102 may be used to provide power to any machine including, but not limited to, an on-highway truck, an off-highway truck, an earth moving machine, an electric generator, and so on. Further, the engine system 100 may be associated with an industry including, but not limited to, transportation, construction, agriculture, forestry, power generation, and material handling.
The engine system 100 includes an exhaust aftertreatment system 104 fluidly connected to an exhaust manifold of the engine 102. The aftertreatment system 104 is configured to treat an exhaust gas flow exiting the exhaust manifold of the engine 102. The exhaust gas flow contains emission compounds that may include Nitrogen Oxides (NOx), unburned hydrocarbons, particulate matter and/or other combustion products known in the art. The aftertreatment system 104 may be configured to trap or convert NOx, unburned hydrocarbons, particulate matter, combinations thereof, or other combustion products in the exhaust gas flow before exiting the engine system 100.
In the illustrated embodiment, the aftertreatment system 104 includes a first module 106 that is fluidly connected to an exhaust conduit 108 of the engine 102. During engine operation, the first module 106 is arranged to internally receive engine exhaust gas from the exhaust conduit 108. The first module 106 may contain various exhaust gas treatment devices, such as, a Diesel Oxidation Catalyst (DOC) 110 and a Diesel Particulate Filter (DPF) 112, but other devices may be used. The first module 106 and the components found therein are optional and may be omitted for various engine applications in which the exhaust treatment function provided by the first module 106 is not required.
In the illustrated embodiment, the exhaust gas provided to the first module 106 by the engine 102 may first pass through the DOC 110 and then through the DPF 112 before entering a transfer conduit 114. The aftertreatment system 104 includes a reductant supply system 116. A reductant is injected into the transfer conduit 114 by a reductant injector 118. The reductant may be a fluid, such as, Diesel Exhaust Fluid (DEF). The reductant may include urea, ammonia, or other reducing agent known in the art.
Referring to FIG. 2, the reductant is contained within a reductant tank 120 (see FIG. 2). Parameters related to the reductant tank 120 such as size, shape, location, and material used may vary according to system design and requirements. Further, the reductant injector 118 may be communicably coupled to a controller 212. Based on control signals received from the controller 212, the reductant from the reductant tank 120 is provided to the reductant injector 118 by a pump assembly 122. In one embodiment, the reductant supply system 116 may include two or more reductant injectors 118. The number of the reductant injector 118 may vary based on the type of application. Various components of the reductant supply system 116 will be explained in detail in connection with FIGS. 2-4.
As the reductant is injected into the transfer conduit 114, the reductant mixes with the exhaust gas passing therethrough, and is carried to a second module 124. Further, the transfer conduit 114 is configured to fluidly interconnect the first module 106 with the second module 124, such that, the exhaust gas from the engine 102 may pass through the first and second modules 106, 124 in series before being released at a stack 126 connected downstream of the second module 124. The second module 124 encloses a Selective Catalytic Reduction (SCR) module 128 and an Ammonia Oxidation Catalyst (AMOX) 130. The SCR module 128 operates to treat exhaust gases exiting the engine 102 in the presence of ammonia, which is provided after degradation of a urea-containing solution injected into the exhaust gases in the transfer conduit 114. The AMOX 130 is used to convert any ammonia slip from the downstream flow of the SCR module 128 before exiting the exhaust gas through the stack 126.
Further, in order to promote mixing of the reductant with the exhaust gas, a mixer 132 may be disposed along the transfer conduit 114. The mixing of the reductant with the exhaust gas is not limited to a separate mixer 132 but may be accomplished with other known techniques, such as, a curved transfer conduit 114. The amount of the reductant that may be injected into the transfer conduit 114 may be appropriately metered based on engine operating conditions.
The aftertreatment system 104 disclosed herein is provided as a non-limiting example. It will be appreciated that the aftertreatment system 104 may be disposed in various arrangements and/or combinations relative to the exhaust manifold. These and other variations in aftertreatment system design are possible without deviating from the scope of the disclosure.
FIG. 2 is a schematic view of the reductant supply system 116. According to an exemplary embodiment, the reductant tank 120 of the reductant supply system 116 includes two or more header units. In the illustrated embodiment, the reductant tank 120 includes a first header unit 202 and a second header unit 302. In one embodiment, the reductant tank 120 may include three or more such header units based on the type of application. The first and second header units 202, 302 may be threadably coupled with a top portion of the reductant tank 120. Alternatively, the first and second header units 202, 302 may be welded, bolted, or brazed to the reductant tank 120.
As shown in FIGS. 2 and 3, each of the first and second header units 202, 302 include a reductant draw conduit 206, 306. The reductant draw conduits 206, 306 extend into the reductant tank 120. The reductant draw conduit 206, 306 is arranged and configured to draw the reductant present within the reductant tank 120.
Further, a heat exchanger 210, 310 is provided in association with each of the first and second header units 202, 302. The heat exchanger 210, 310 is configured to receive a coolant flow from a coolant system. The coolant may be any engine coolant that is configured to cool the engine 102. The coolant is generally at a temperature which is higher than that of the reductant, due to heat transfer between the coolant and various engine parts.
A coolant flow valve (not shown) may be associated with the coolant system and may be communicably coupled to the controller 212. Based on an actuation signal received from the controller 212, the coolant flow valve may be actuated and the coolant may flow into the heat exchanger 210, 310 via a coolant inlet line 214, 314 associated with the first and second header units 202, 302. The coolant flow through the first and second header units 202, 302 is configured to exchange heat with the reductant present within the reductant tank 120, thereby increasing the temperature of the reductant in the reductant tank 120. Further, after passing through the heat exchanger 210, 310 the coolant may flow out of the first and second header units 202, 302 through a coolant outlet line 216, 316 respectively. A coolant pump (not shown) may be provided in fluid communication with the coolant system. The coolant pump is configured to pump and deliver the coolant from a source such as a coolant tank (not shown) to various components of the aftertreatment system 104.
Further, each of the first and second header units 202, 302 may also include a level sensor 218, 318 (see FIG. 3). As shown in the accompanying figures, the level sensor 218, 318 is positioned along the reductant draw conduit 206, 306 of the first and second header units 202, 302 respectively. The level sensor 218, 318 is configured to determine an amount or quantity of the reductant present within the reductant tank 120. The level sensor 218, 318 may be embodied as a float operated sensor or any other sensor known in the art to detect a level of the reductant in the reductant tank 120.
Each of the first and second header units 202, 302 may include a temperature sensor 219, 319. The temperature sensors 219, 319 may be configured to determine a temperature of the reductant present within the reductant tank 120. The level sensors 218, 318 and the temperature sensors 219, 319 may be communicably coupled to the controller 212 (see FIG. 2). The reductant draw conduits 206, 306 of the first and second header units 202, 302 respectively may include a pick-up screen (not shown). The pick-up screen may be configured to restrict an entry of ice into the reductant draw conduits 206, 306. This ice may be formed due to freezing of the reductant present in the reductant tank 120. One of ordinary skill in the art would understand that various additional components may be added or certain components could be removed depending on the application of the header unit 202, 302.
Each of the first and second header units 202, 302 may additionally include a bag filtration assembly 220, 320. FIG. 4 shows a perspective view of the bag filtration assembly 220, 320 of the first or second header unit 202, 302 respectively. The bag filtration assembly 220, 320 is embodied as a sock filter. The bag filtration assembly 220, 320 is a high surface area porous filter, and is configured to protect the pick-up screen from debris that may be present within the reductant tank 120. The bag filtration assembly 220, 320 is further configured to enclose and protect the reductant draw conduit 206, 306, the heat exchanger 210, 310, and any other allied components of the first and second header units 202, 302 from exposure to debris present within the reductant tank 120.
Referring to FIG. 3, the reductant tank 120 may also include an opening 222 for receiving a supply of the reductant from an external source (not shown). The opening 222 may be closed using a cap member 224. The opening 222 may be provided with a strainer (not shown) in order to restrict debris present in the incoming reductant from entering into the reductant tank 120.
Referring now to FIG. 2, each of the reductant draw conduits 206, 306 may be fluidly coupled to a supply conduit 226. The supply conduit 226 is configured to fluidly couple the reductant draw conduit 206, 306 with the reductant injectors 118, via the pump assembly 122. The pump assembly 122 includes a reversing valve assembly 228. In one embodiment, the reversing valve assembly 228 may be pressure controlled.
The reversing valve assembly 228 may be communicably coupled with the controller 212. Based on control signals received from the controller 212, the reversing valve assembly 228 may operate in a first position or a second position. In the accompanying figures, the reversing valve assembly 228 is shown in the first position. The reversing valve assembly 228 includes a first flow passage 230 and a second flow passage 232. The first flow passage 230 of the reversing valve assembly 228 is configured to fluidly couple the reductant draw conduit 206, 306 to a first check valve 234. The first check valve 234 is provided downstream of the reversing valve assembly 228. The first check valve 234 is configured to restrict a reverse flow of the reductant flowing therethrough.
The pump assembly 122 also includes a pump unit 236 provided downstream of the first check valve 234. The pump unit 236 is fluidly coupled to the reversing valve assembly 228, via the first check valve 234. The pump unit 236 is configured to pump and pressurize the reductant from the reductant tank 120 and supply the pressurized reductant to the reductant injector 118. A second check valve 238 is provided downstream of the pump unit 236. The second check valve 238 is configured to restrict a reverse flow of the reductant towards the pump unit 236. The first and second check valves 234, 238 may be embodied as one way or non-return valves that allow fluid to flow in a single direction only.
The reductant exiting the pump unit 236 is configured to flow through the second check valve 238 and the second flow passage 232 of the reversing valve assembly 228. Further, the pump unit 236 also includes an in-line filter 240. More particularly, the in-line filter 240 is positioned between the reversing valve assembly 228 and the reductant injector 118. The in-line filter 240 disclosed herein may be any type of known filter.
The pump assembly 122 also includes a pressure sensor 242. The pressure sensor 242 may be communicably coupled to the controller 212. The pressure sensor 242 may be provided downstream of the in-line filter 240. Under certain operating conditions, the amount of the reductant delivered by the pump unit 236 may exceed a reductant flow demand from the reductant injectors 118. In such a situation, the excess amount of the reductant supplied by the pump unit 236 may be recirculated to the reductant tank 120 via a reductant return conduit 244.
The reductant return conduit 244 fluidly connects the supply conduit 226 with the reductant tank 120. A back flow valve assembly 246 may be provided in the reductant return conduit 244. A portion of excess reductant not required by the reductant injector 118 may be recirculated from the supply conduit 226 to the reductant tank 120, through the back flow valve assembly 246. The back flow valve assembly 246 may be communicably coupled to the controller 212. Regulation of the back flow valve assembly 246 by the controller 212 may be based on the pressure sensed by the pressure sensor 242.
The illustrated back flow valve assembly 246 is an electrically controlled diaphragm valve; however, alternative embodiments may include configurations wherein the back flow valve assembly 246 may include other valve mechanisms, such as, angle valves, piston valves, ball valves, rotary valves, sliding cylinder valves, etc. Further, while the back flow valve assembly 246 is electronically controlled, one of ordinary skill in the art would appreciate that other methods of controlling valves, e.g., pneumatically, or hydraulically controlled valves, may alternatively be used.
It should be noted that the reductant supply system 116 illustrated in the accompanying figures includes a single pump assembly 122 and a single reductant injector 118. However, based on the type of application, the reductant supply system 116 may include multiple pump assemblies and multiple reductant injectors without deviating from the scope of the present disclosure.

INDUSTRIAL APPLICABILITY

Reductant supply system associated with aftertreatment systems of large diesel engines may require a comparatively greater amount of the reductant to be injected into the exhaust gas flow, due to high power requirements and higher NOx reduction requirements. In these systems an increase in demand in the reductant injection may in turn be affected by factors like filtration capacity of the reductant tank and thaw time during dosing, in order to meet the injection requirements.
The present disclosure relates to the reductant supply system 116 provided with at least two header units 202, 302 per pump assembly 122. The number of header units per pump assembly may be varied based upon the size of the engine 102 and also the operating environment of the engine 102. The multiple header units may be retrofitted to an existing reductant tank 120 of the reductant supply system 116.
The working of the system will now be described in detail. During a dosing operation of the reductant, the controller 212 may send control signals to the reversing valve assembly 228 in order to actuate and operate the reversing valve assembly 228 in the first position. The controller 212 may then send control signals to actuate the pump unit 236. On actuation of the pump unit 236, the reductant from the reductant tank 120 may flow towards the pump unit 236, via the reductant draw conduits 206, 306, the supply conduit 226, the first flow passage 230 and the first check valve 234. From the pump unit 236, the reductant may flow towards the reductant injectors 118, via the second check valve 238, the second flow passage 232, and the in-line filter 240. The reductant may then be injected into the exhaust gas flow by the reductant injectors 118.
The first and second header units 202, 302 include the bag filtration assembly 220, 320. The bag filtration assembly 220, 320 may increase the surface area to which the reductant may be exposed for filtration, thereby improving the filtration capabilities of the reductant supply system 116. The bag filtration assembly 220, 320 also protects the various components of the first and second header units 202, 302 from the debris present within the reductant tank 120, thus improving a service life of the components. Further, each of the first and second header units 202, 302 also include individual heat exchangers 210, 310 associated therewith. During an operation of the engine 102, the heat exchangers 210, 310 may help keep the reductant within the reductant tank 120 in a thawed condition.
Accordingly, the reductant supply system 116 disclosed herein may meet the dosing requirements of the large engine systems. In some embodiments, the reductant supply system 116 may assist in improving servicing intervals, dosing duration, and dosing requirements by almost twice to that of existent systems.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof

Claims

What is claimed is:

1. An aftertreatment system comprising:

an exhaust conduit;

a selective catalytic reduction module configured to receive an exhaust gas flow from the exhaust conduit; and

a reductant supply system configured to supply a reductant into the exhaust conduit upstream of the selective catalytic reduction module, the reductant supply system comprising:

a reductant tank;

a reductant injector;

a pump assembly in fluid communication with the reductant tank and the reductant injector, the pump assembly comprising:

a reversing valve assembly;

a pump unit;

a plurality of check valves associated with the pump unit;

a pressure sensor; and

a filter;

a back flow valve assembly in fluid communication with the pump assembly and the reductant tank;

at least two header units associated with the pump assembly, each of the at least two header units comprising:

a reductant draw conduit configured to supply the reductant from the reductant tank to the pump assembly; and

at least one heat exchanger; and

a bag filtration assembly provided on each of the at least two header units.