US20100186389A1

US20100186389A1 - Reductant Insulating System

Info

Publication number: US20100186389A1
Application number: US12/360,605
Authority: US
Inventors: Jinhui Sun; Yong Yi
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2009-01-27
Filing date: 2009-01-27
Publication date: 2010-07-29

Abstract

A reductant insulating system configured to prevent a flow of reductant used by an engine's selective catalytic reduction (SCR) device from overheating.

Description

TECHNICAL FIELD

The present disclosure relates to the supply of reductant for selective catalytic reduction systems, and more particularly to thermally managing the supply of the reductant.

BACKGROUND

Selective Catalytic Reduction (SCR) systems may be included in an aftertreatment system for a power system to remove or reduce nitrous oxide (NOx or NO) emissions coming from an engine. The SCR systems may include the introduction of a reductant, such as urea, to the exhaust stream. Thermal management of the reductant may be needed for proper operation of the SCR system.
U.S. Pat. No. 5,976,475 discloses that coolant can be passed in heat exchange contact with a urea injector.

SUMMARY

In one aspect, the present disclosure provides a reductant insulating system comprising an insulating line thermally associated with a flow of reductant used by a selective catalytic reduction (SCR) device. The insulating line is configured to maintain the reductant below a temperature limit.
In another aspect, the present disclosure provides a method for maintaining a flow of reductant used by a selective catalytic reduction (SCR) below a temperature limit. The method comprises passing the flow of reductant through an insulating line thermally associated with the flow of reductant and passing a coolant through the insulating line. In yet another aspect, the coolant is hotter than the flow of reductant.
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 diagrammatic view of a power system including an engine, an aftertreatment system, and a reductant insulating system;

FIG. 2 is a cross-sectional view of an insulating line used in the reductant insulating system;

FIG. 3 is a cross-sectional view of an insulating line used in the reductant insulating system; and

FIG. 4 is a cross-sectional view of an insulating line used in the reductant insulating system.

DETAILED DESCRIPTION

As seen in FIG. 1, a power system 10 includes an engine 12 and an aftertreatment system 14 to treat an exhaust stream 13 produced by the engine 12. The engine 12 may include other features not shown, such as fuel systems, air systems, insulating systems, peripheries, drivetrain components, turbochargers, etc. The engine 12 may be any type of engine (internal combustion, gas, diesel, gaseous fuel, natural gas, propane, etc.), may be of any size, with any number of cylinders, and in any configuration (“V,” in-line, radial, etc.). The engine 12 may be used to power any machine or other device, including on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, locomotive applications, marine applications, pumps, stationary equipment, or other engine powered applications.
The aftertreatment system 14 includes pre-SCR components 16, an SCR system 18, post-SCR components 20, and an exhaust pipe 22. The exhaust stream 13 exits the engine 12, passes through the pre-SCR components 16, then passes through the SCR system 18, and then passes through the post-SCR components 20 via the exhaust pipe 22. The pre-SCR and post-SCR components 16 and 20 may include devices such as regeneration devices, heat sources, oxidation catalysts, diesel oxidation catalysts (DOCs), diesel particulate filters (DPFs), additional SCR systems, lean NOx traps (LNTs), mufflers, or other devices needed to treat the exhaust stream 13 before and after the SCR system 18 and before exiting the power system 10. The pre-SCR and post-SCR components 16 and 20 may or may not be needed.
The SCR system 18 includes a reductant system 24, mixer 26, and a Selective Catalytic Reduction (SCR) 28 device. The reductant system 24 introduces or supplies a reductant 30 into the exhaust stream 13. The mixer 26 may be included to mix the reductant 30 with the exhaust stream 13 and introduce the mixture to the SCR 28. The reductant 30 may be urea, ammonia, diesel fuel, other hydrocarbon, or chemical used by the SCR 28 to reduce or otherwise remove NOx or NO emissions from the exhaust stream 13.
The reductant system 24 is shown to include a reductant source 32, pump 34, valve 36, injector 38, and reductant line 40. The reductant flow 31 originates from the reductant source 32. The reductant source 32 may be a tank, vessel, absorbing material, or other device capable of storing and releasing the reductant 30. The reductant line 40 transports the reductant 30 from the reductant source 32 to the exhaust stream 13 of the engine 12 via the injector 38.
The pump 34 is an extraction device capable of pulling the reductant 30 from the reductant source 32, generating a reductant flow 31. The valve 36 may be included to help regulate or control the delivery of the reductant 30. The injector 38 is a device capable of creating a reductant spray or otherwise introducing the reductant 30 in the exhaust stream 13. The injector 38 may be designed to introduce the reductant 30 in the exhaust stream 13 with or without the aid of compressed air.
The reductant system 24 may also include a flushing or purging system. The purging system may flush reductant 30 from the pump 34, valve 36, injector 38, or reductant line 40. The reductant 30 may be flushed back to the reductant source 32 or into the exhaust stream 13 through the injector 38. The purpose of the purging system may be to protect the reductant system 24 from freezing of the reductant 30. The purging system may include an air compressor or other source of compressed fluid, valves, and extra reductant lines.
The SCR 28 includes a catalyst facilitating the reaction, reduction, or removal of NOx emissions from the exhaust stream 13 as it passes through the SCR 28. The SCR 28 body may be a honeycomb or other structure made from or coated with an appropriate material. The material may be an oxide, such as vanadium oxide or tungsten oxide, coated on an appropriate substrate, such as titanium dioxide.
As shown in FIG. 1, the engine 12 and aftertreatment system 14 are contained or located inside an engine compartment 42. The engine compartment 42 defines an engine compartment interior space 44 inside. The engine compartment 42 may be the machine's hood or engine's enclosure. The engine compartment 42 may include vents for ventilation and other components not shown. Components shown to be inside the engine compartment 42 may alternatively be located outside the engine compartment 42 and components shown to be outside the engine compartment 42 may alternatively be located inside the engine compartment 42. The reductant source 32 is located outside or otherwise thermally insulated from the engine compartment 42.
FIG. 1 also shows a reductant insulating system 46 coupled to a heat exchanging system 48. The heat exchanging system 48 may embody the engine's cooling system, as illustrated, or may embody another heat exchanging system in the power system 10. The heat exchanging system 48 is shown to include a radiator 50, radiator inlet line 52, radiator outlet line 54, and a fan 56. The radiator 50 is fluidly coupled to the engine 12 by the radiator inlet line 52 and radiator outlet line 54. The engine 12 or another power source may drive the fan 56. The fan 56 pulls air 58 from outside the engine compartment 42 through a core 60 of the radiator 50.
A pump pulls a coolant 62 through the core 60 where it is cooled by the air 58. The coolant 62 next passes through the radiator outlet line 54 and an engine coolant flow 64 portion of the coolant 62 is circulated through the engine 12. The engine coolant flow 64 portion is next pumped back to the radiator 50 through the radiator inlet line 52.
The reductant insulating system 46 is shown to include a feed line 66, insulating line 68, and a return line 70. The feed line 66 is fluidly coupled to the radiator outlet line 54 at one end and the insulating line 68 at the opposite end. The return line 70 is fluidly coupled to the radiator inlet line 52 at one end and the insulating line 68 at the opposite end.
A reductant coolant flow 72 portion of the coolant 62 is pumped from the radiator 50 through the feed line 66. The reductant coolant flow 72 next passes through the insulating line 68 and back to the radiator 50 through the return line 70.
The insulating line 68 is in contact with an insulated portion 74 of the reductant line 40. The insulated portion 74 may be the portion of the reductant line 40 located in the engine compartment interior space 44. The insulating line 68 is also shown to be in contact with the valve 36 and injector 38. In an alternative embodiment, the insulating line 68 may also be in contact with the pump 34 if the pump 34 were relocated to be in the engine compartment interior space 44.
FIGS. 2-4 illustrate alternative embodiments of the insulating line 68. The insulating line 68 is in heat exchange contact or thermally associated with portions the reductant line 40 to achieve heat transfer between the reductant coolant flow 72 and the reductant flow 31.
FIG. 2 shows the insulating line 68 may include an outer pipe 76 surrounding the insulated portion 74 of the reductant line 40. The reductant coolant flow 72 passes in a space 78 defined between the outer pipe 76 and the insulated portion 74 of the reductant line 40. Fins or additional material may also be added to the outside of the insulated portion 74 of the reductant line 40 to aid in heat transfer.
FIG. 3 shows the insulating line 68 may include one or more contact pipe(s) 80. The reductant coolant flow 72 passes through the contact pipe(s) 80. A contact portion 82 of the contact pipe(s) 80 is in contact with the insulated portion 74 of the reductant line 40. The shape of the contact pipe(s) 80 or the insulated portion 74 of the reductant line 40 may also be modified to increase the size of the contact portion 82. The contact pipe(s) 80 may also be designed to wrap about the insulated portion 74 of the reductant line 40 in a helical fashion along the length.
FIG. 4 shows the insulating line 68 may include a conduit pipe 84. The conduit pipe 84 may include one or more cooler orifice(s) 86 through which the reductant coolant flow 72 passes. The conduit pipe 84 may also include a reductant orifice 88 to form the insulated portion 74 of the reductant line 40.
Additional alternative embodiments of the insulating line 68 are also possible. Additional designs may be used to achieve a thermal or heat exchange connection between the reductant coolant flow 72 and the reductant flow 31. The pipes are shown in FIGS. 2-4 to be circular, but may be any shape. The embodiments shown in FIGS. 2-4 may also be combined. Insulation may also be added to the outside of the insulating line 68. Insulation may also be added to the feed line 66 or return line 70.

INDUSTRIAL APPLICABILITY

The reductant insulating system 46 is configured to maintain the reductant 30 below a predetermined temperature limit. Said another way, the reductant insulating system 46 prevents the reductant 30 from overheating. The reductant insulating system 46 insulates the reductant 30 from the temperatures in the engine compartment interior space 44. The temperatures in the engine compartment interior space 44 may be especially high because of the aftertreatment system 14 components added to comply with new emissions standards. Because of packaging and space constraints, these aftertreatment system 14 components may be located in the engine compartment 42 thereby raising the temperature in the engine compartment interior space 44.
The reductant 30 may have a predetermined temperature limit at which point the reductant 30 is adversely impacted. This predetermined temperature limit may be reached because of temperatures in the engine compartment interior space 44.
A common reductant 30 is urea, which may begin to crystallize or otherwise hydrolyze such that solids precipitate at temperatures above about 90-95 degrees Celsius. This temperature may represent a predetermined temperature limit. This crystallization may cause plugging or blocking in the reductant system 24 and may negatively impact the operation of the SCR 28.
Temperatures in the engine compartment interior space 44 may reach about 150-160 degree Celsius during steady state operation of the power system 10. The coolant 62 may reach temperatures of about 95-105 degrees Celsius. The reductant source 32 may be located outside the engine compartment 42 to maintain the supply of reductant 30 below its temperature limit.
Without the reductant insulating system 46, the 150-160 degree Celsius temperature in the engine compartment interior space 44 may cause the temperature of the reductant 30 to rise above its limit. While the coolant 62 may be hotter than the reductant 30 temperature limit, the coolant 62 is cooler than the temperatures in the engine compartment interior space 44. Accordingly, the reductant insulating system 46 helps prevent the reductant 30 from reaching the temperature limit as it passes through the engine compartment interior space 44.
The injector 38 may be hotter than the rest of the reductant system or the engine compartment interior space 44 because of its direct contact with the exhaust stream. Therefore, the reductant insulating system 46 may cool the injector 38 and not only insulate it.
The reductant insulating system 46 provides a method for insulating the reductant flow 31 and preventing it from overheating. The method includes passing the reductant flow 31 through the insulating line 68. The insulating line 68 is thermally associated with the reductant flow 31 through the insulated portion 74 of the reductant line 40. The coolant 62 is passed through the insulating line 68. The method may also involve the insulating line 68 being thermally associated with the injector 38 and valve 36.
Another feature of the method includes the coolant 62 being hotter than the reductant flow 31 and the coolant 62 being cooler than the engine compartment interior space 44. The reductant flow 31 may be cooler because the reductant source 32 is located outside the engine compartment 42.
In another aspect, the reductant insulating system 46 may also help cool injector 38 and valve 36. The injector 38 will be especially hot because of its proximity to the exhaust stream 13. The flow of coolant 62 in the reductant insulation system 46 may provide a degree of cooling in addition to insulating the reductant 30 as it passes through the insulated portion 74 of the reductant line 40.
In yet another aspect, the reductant insulating system 46 may also help heat the reductant 30 to a desired temperature. The reductant 30 may be below the desired temperature. The temperature of the reductant 30 may be associated with the environment surrounding the reductant source 32, which may be ambient temperatures. The reductant insulating system 46 may help heat the reductant 30 as it passes through.
The temperatures provided above are exemplary of temperatures during steady state operation of the power system 10. Actual temperatures may be higher or lower depending on the power system 10 and operating conditions. The steady state operation of the power system 10 may be considered the time when the temperature in the engine compartment interior space 44 has reached a substantially constant temperature.
Although the embodiments of this disclosure as described herein may be incorporated without departing from the scope of the following claims, it will be apparent to those skilled in the art that various modifications and variations can be made. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A reductant insulating system comprising:

an insulating line thermally associated with a flow of reductant used by a selective catalytic reduction device associated with an engine wherein the insulating line is configured to maintain the reductant below a temperature limit.

2. The insulating system of claim 1 wherein a flow of coolant passes through the insulating line.

3. The insulating system of claim 2 located at least partially inside an engine compartment.

4. The insulating system of claim 3 wherein the temperature of the coolant exceeds the temperature of the reductant flow at steady state operation of the engine.

5. The insulating system of claim 4 wherein the temperature inside the engine compartment exceeds the temperature of the coolant at steady state operation of the engine.

6. The coolant system of claim 5 wherein the flow of reductant originates from a source outside the engine compartment.

7. The insulating system of claim 6 wherein the flow of coolant is supplied from a radiator used to cool the engine.

8. The insulating system of claim 1 wherein the insulating line is thermally associated with a valve used to control the flow of reductant.

9. The insulating system of claim 2 wherein the insulating line is thermally associated with a reductant line used to transport the reductant from a reductant source to the exhaust of the engine.

10. The insulating system of claim 9 wherein the insulating line includes an outer pipe configured to allow the flow of coolant to pass through the outer pipe and around the reductant line.

11. The insulating system of claim 9 wherein the insulating line includes a contact pipe configured to be in contact with the reductant line.

12. The insulating system of claim 9 wherein the insulating line includes a conduit pipe surrounding the reductant line and configured to allow the flow of coolant to pass through.

13. A method for maintaining a flow of reductant used by a selective catalytic reduction device below a temperature limit comprising:

passing the flow of reductant through an insulating line thermally associated with the flow of reductant; and

passing a coolant through the insulating line wherein the coolant is hotter than the flow of reductant.

14. The method of claim 13 wherein the coolant is cooler than the space containing the insulating line.

15. The method of claim 13 further including:

supplying the flow of coolant from a radiator used to cool the engine.

16. The method of claim 13 further including:

passing the flow of reductant through a reductant line to transport the reductant from a reductant source to the exhaust of the engine.

17. The method of claim 14 wherein the space containing the insulating line is the space inside an engine compartment.

18. The method of claim 17 further including:

locating a source of reductant outside the engine compartment.

19. A power system including:

an engine contained inside an engine compartment;

a selective catalytic reduction device in the exhaust of the engine;

a reductant system configured to supply a reductant to the exhaust for use in the selective catalytic reduction device;

a reductant insulating system configured to maintain the reductant below a temperature limit.

20. The power system of claim 19 wherein a flow of coolant passes through the reductant insulating system and the coolant is hotter than the reductant and cooler than the temperature inside the engine compartment.