Systems and techniques for heating urea injection systems

A system, comprising:

• an exhaust system for receiving an exhaust gas produced from operation of an internal combustion engine;
• a reductant delivery system that includes a reductant storage tank and a reductant doser, wherein the reductant storage tank stores a reductant that is provided to the doser for delivery to the exhaust system for treatment of the exhaust gas produced by operation of the internal combustion engine;
• a heat exchange system including a heat exchange circuit configured to provide a flow path for a heat exchange fluid to heat the reductant, wherein the flow path is arranged to circulate the heat exchange fluid to thermally contact heated heat exchange fluid with the reductant in the doser and reductant in the reductant storage tank, wherein the heat exchange system further includes a control valve in the flow path to control a flow of the heat exchange fluid in the flow path;
• a controller connected to the control valve that is operable to open and close the control valve to control circulation of the heat exchange fluid in the flow path, wherein the controller is configured to:
• initiate a first circulation period of the heated heat exchange fluid in the flow path through the doser and then through the reductant storage tank to increase a temperature of the reductant in the doser and the reductant storage tank when the temperature of the reductant in at least one of the doser and the reductant storage tank is less than a predetermined minimum temperature;
• terminate the first circulation period of the heat exchange fluid when the temperature of the reductant in the doser reaches an upper temperature limit;
• and
• initiate a second circulation period of the heat exchange fluid in the heat exchange circuit after the first circulation period when the temperature of the reductant in the doser reaches a lower temperature limit to increase the temperature of the reductant in the doser and the reductant storage tank.