Aftertreatment systems for dual-fuel engines
Systems and methods for an aftertreatment system configured for use with a dual-fuel engine system are described. The method comprises determining an operating mode of the dual-fuel engine. Upon determining that the dual-fuel engine is operating in a dual-fuel mode or a natural gas mode, the dual-fuel engine operates in a stoichiometric operating condition, and the exhaust is received into a three-way catalyst communicatively connected to a selective catalytic reduction catalyst. Upon determining that the dual-fuel engine is not operating in the dual-fuel mode or the natural gas mode, the engine operates in a lean operating condition.
1. A method of treating exhaust from a dual-fuel engine, comprising:
determining an operating mode of the dual-fuel engine;
upon determining that the dual-fuel engine is operating in a dual-fuel mode or a natural gas mode:
operating the dual-fuel engine at or near a stoichiometric operating condition, and
receiving the exhaust into a three-way catalyst communicatively connected to a selective catalytic reduction catalyst, and operating the three-way catalyst at a temperature of 500 degrees Celsius or greater to facilitate desulfation of the selective catalytic reduction catalyst; and
upon determining that the dual-fuel engine is not operating in the dual-fuel mode or the natural gas mode, operating the engine in a lean operating condition.
2. The method of claim 1 , further comprising disabling urea dosing when the dual-fuel engine is operating in the dual-fuel mode or the natural gas mode.
3. The method of claim 1 , further comprising enabling urea dosing when the dual-fuel engine is not operating in the dual-fuel mode or the natural gas mode.
4. The method of claim 1 , wherein the three-way catalyst is configured to reduce nitrogen oxide, carbon monoxide, and hydrocarbons when the dual-fuel engine is operating at or near the stoichiometric operating condition and operating in the dual-fuel mode or the natural gas mode.
5. The method of claim 1 , further comprising using the selective catalytic reduction catalyst to reduce nitrogen oxide when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
6. The method of claim 1 , wherein the selective catalytic reduction catalyst is positioned downstream of the three-way catalyst.
7. The method of claim 6 , further comprising using the selective catalytic reduction catalyst to store potential ammonia slip from the three-way catalyst when the dual-fuel engine is operating at or near the stoichiometric operating condition and operating in the dual-fuel mode or the natural gas mode.
8. The method of claim 6 , further comprising using the three-way catalyst to oxidize nitrogen oxide to nitrogen dioxide and reduce hydrocarbons and carbon monoxide when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
9. The method of claim 6 , wherein the three-way catalyst is configured to oxidize nitrogen oxide, carbon monoxide, and hydrocarbons when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
10. The method of claim 1 , wherein the selective catalytic reduction catalyst is positioned upstream of the three-way catalyst.
11. The method of claim 10 , further comprising using the three-way catalyst to reduce ammonia, carbon monoxide, and hydrocarbons exiting the selective catalytic reduction catalyst when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
12. The method of claim 1 , further comprising operating the dual-fuel engine in a diesel mode when the dual-fuel engine is not operating in the dual-fuel mode or the natural gas mode.
13. A controller for use in an aftertreatment system that is configured to be used with a dual-fuel engine that is operable in a plurality of operating modes and that comprises a three-way catalyst positioned configured to receive exhaust from the dual-fuel engine, and a selective catalytic reduction catalyst communicatively connected to the three-way catalyst and positioned downstream of the dual-fuel engine, the controller comprising:
a determination module configured to determine an operating mode of a dual-fuel engine;
an operation module configured to operate the dual-fuel engine at or near a stoichiometric operating condition when the dual-fuel engine is operating in a natural gas mode or a dual-fuel mode, and to operate the dual-fuel engine in a lean operating condition when the dual-fuel engine is not operating in the dual-fuel mode or the natural gas mode;
a dosing module configured to control the injection of urea into exhaust downstream from the dual-fuel engine, the dosing module communicating with the operation module to determine when to allow the injection of the urea; and
a fuel injection module configured to control an air-fuel ratio in the dual-fuel engine based upon the operating mode of the dual-fuel engine,
wherein the controller is configured to control the three-way catalyst to operate at a temperature of 500 degrees Celsius or greater to facilitate desulfation of the selective catalytic reduction catalyst when the dual-fuel engine is operating at or near the stoichiometric operating condition and operating in the dual-fuel mode or the natural gas mode.
14. The controller of claim 13 , wherein the dosing module prevents the injection of the urea into the exhaust when the dual-fuel engine is operating at or near the stoichiometric operating condition and operating in the natural gas mode or the dual-fuel mode.
15. The controller of claim 13 , wherein the dosing module enables the injection of the urea into the exhaust when the dual-fuel engine is operating in the lean operating condition and is not operating in the natural gas mode or the dual-fuel mode.
16. The controller of claim 13 , wherein the dosing module enables the injection of the urea into the exhaust when the dual-fuel engine is operating in the lean operating condition and is operating in a diesel mode.
17. The controller of claim 13 , wherein the fuel injection module creates a lean air-fuel ratio in the dual-fuel engine when the dual-fuel engine is not operating in the dual-fuel mode or the natural gas mode.
18. An aftertreatment system configured to be used with a dual-fuel engine operable in a plurality of operating modes, the aftertreatment system comprising:
a three-way catalyst positioned downstream of the dual-fuel engine, the three-way catalyst configured to receive exhaust from the dual-fuel engine;
a selective catalytic reduction catalyst communicatively connected to the three-way catalyst and positioned downstream of the dual-fuel engine; and
a controller configured to determine the operating mode of the dual-fuel engine,
wherein the controller operates the dual-fuel engine at or near a stoichiometric operating condition when the dual-fuel engine is in a dual-fuel mode or a natural gas mode, and wherein the controller operates the dual-fuel engine in a lean operating condition when the dual-fuel engine is not in the dual-fuel mode or the natural gas mode, and
wherein the three-way catalyst is configured to operate at a temperature of 500 degrees Celsius or greater to facilitate desulfation of the selective catalytic reduction catalyst when the dual-fuel engine is operating at or near the stoichiometric operating condition and operating in the dual-fuel mode or the natural gas mode.
19. The aftertreatment system of claim 18 , further comprising a doser configured to inject urea into the exhaust, wherein the selective catalytic reduction catalyst uses the urea injected by the doser to reduce nitrous oxide emissions exiting the three-way catalyst when the dual-fuel engine is operating in the lean operating condition and operating in a diesel mode.
20. The aftertreatment system of claim 18 , wherein the three-way catalyst is configured to oxidize nitrous oxide exiting the dual-fuel engine into nitrogen dioxide when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
21. The aftertreatment system of claim 18 , wherein the three-way catalyst is configured to reduce carbon monoxide and hydrocarbons exiting the dual-fuel engine when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
22. The aftertreatment system of claim 18 , wherein the three-way catalyst is positioned downstream of the selective catalytic reduction catalyst.
23. The aftertreatment system of claim 22 , wherein the three-way catalyst is configured to reduce ammonia, carbon monoxide, and hydrocarbons slipping from the selective catalytic reduction catalyst when the dual-fuel engine is operating in the lean operating condition and is not operating in the dual-fuel mode or the natural gas mode.
24. The aftertreatment system of claim 18 , wherein the three-way catalyst is positioned upstream of the selective catalytic reduction catalyst.