Systems and methods for control of engine NOx emissions using liquid and dry reductant sources

A method, comprising:

• producing an exhaust gas in an exhaust flow path including a selective catalytic reduction (SCR) catalyst and at least one of an oxidation catalyst or a diesel particulate filter, wherein producing the exhaust gas includes operating an internal combustion engine;
• determining a temperature condition of the exhaust gas;
• determining an engine start-up condition;
• and
• selectively providing one of a gaseous reductant released from a dry reductant storage source and a liquid reductant from a liquid reductant source to the exhaust flow path upstream of the SCR catalyst and downstream of the at least one of the oxidation catalyst or the diesel particulate filter in response to the temperature condition of the exhaust gas;
• wherein providing the gaseous reductant released from the dry reductant source is in response to the engine start-up condition before operating the internal combustion engine to produce the exhaust gas.

A system, comprising:

• an internal combustion engine operable to produce an exhaust stream, the exhaust stream including an amount of NOx emitted into an exhaust flow path;
• a first reductant source that stores a NOx reductant in a solid storage media and a second reductant source that stores the NOx reductant in a liquid medium;
• a selective catalytic reduction (SCR) conversion catalyst and at least one of an oxidation catalyst or a diesel particulate filter in the exhaust flow path, wherein the first reductant source and the second reductant source are each connected to the exhaust flow path upstream of the SCR catalyst and downstream of the at least one of the oxidation catalyst or the diesel particulate filter to provide the NOx reductant to the SCR catalyst;
• and
• a controller connected to one or more sensors associated with the exhaust stream operable to indicate a temperature condition of the exhaust stream, wherein the controller is configured to control the first reductant source to dose the NOx reductant in a gaseous form from the solid storage media into the exhaust stream in response to a first temperature condition of the exhaust stream and the internal combustion engine being in a post-shutdown condition, and the controller is further configured to control the second reductant source to dose the NOx reductant from the liquid medium in a liquid form in response to a second temperature condition of the exhaust stream and the internal combustion engine being in a pre-shutdown condition.

An apparatus, comprising:

• an electronic controller structured to receive operating parameters from at least one sensor associated with an exhaust system that is connected with a first reductant source for storing a gaseous reductant in a solid storage media and a second reductant source for storing a liquid reductant in a liquid storage medium, wherein the controller includes:
• an exhaust system temperature condition module structured to determine a temperature condition associated with the exhaust system and to determine the temperature condition in response to a startup condition of an internal combustion engine connected to the exhaust system;
• and
• a reductant source selection module structured to selectively dose gaseous reductant from the first reductant source and liquid reductant from the liquid reductant source in response to the temperature condition and to provide gaseous reductant from the first reductant source in response to the startup condition before operating the internal combustion engine to produce the exhaust gas,
• wherein the exhaust system comprises a selective catalytic reduction (SCR) conversion catalyst and at least one of an oxidation catalyst or a diesel particulate filter in the exhaust flow path, the liquid reductant and the gaseous reductant is selectively dosed upstream of the SCR catalyst and downstream of the at least one of an oxidation catalyst or a diesel particulate filter.