Systems and methods for determining amount of reductant deposits in aftertreatment systems

A method for estimating an amount of reductant deposits formed in an aftertreatment system comprising a reductant injector and a SCR unit located downstream of the reductant injector, the method comprising:

• receiving, by a controller, a first NOx amount signal from a first NOx sensor indicative of an amount of NOx gases at a location upstream of the reductant injector;
• receiving, by the controller, a second NOx amount signal from a second NOx sensor indicative an amount of NOx gases at a location downstream of the SCR unit;
• determining, by the controller, an amount of reductant that has been inserted into the aftertreatment system by the reductant injector;
• determining, by the controller, an estimated amount of reductant deposits formed in the aftertreatment system based on at least the first NOx amount, the second NOx amount, and the amount of reductant that has been inserted into the aftertreatment system;
• and
• adjusting, by the controller, an amount of reductant to be inserted into the aftertreatment system based on the estimated amount of reductant deposits formed in the aftertreatment system.

A method for estimating an amount of reductant deposits formed in an aftertreatment system comprising a reductant injector and a SCR unit located downstream of the reductant injector, the method comprising:

• determining, by a controller, an average NOx amount over time of NOx gases included in an exhaust gas flowing through the aftertreatment system downstream of the SCR unit;
• determining, by the controller, whether the average NOx amount is equal to or greater than a threshold;
• in response to the average NOx amount being equal to or greater than the threshold, determining, by the controller, that ammonia slip is occurring;
• determining, by the controller, an ammonia slip parameter;
• estimating, by the controller, an amount of reductant deposits formed in the aftertreatment system based on at least an amount of NOx gases measured at the location upstream of the reductant injector, an amount of NOx gases measured at the location downstream of the SCR unit, an amount of reductant that has been inserted into the aftertreatment system by the reductant injector, and the ammonia slip parameter;
• and
• adjusting, by the controller, an amount of reductant to be inserted into the aftertreatment system based on the estimated amount of reductant deposits formed in the aftertreatment system.