Exhaust purification system and method for controlling exhaust purification system

Abstract

Provided is an exhaust purification system capable of clearing a blockage of a reducing agent injection valve caused by solidification of an aqueous urea solution soon after starting an engine and preventing degradation in exhaust purification efficiency when starting an internal combustion engine. An exhaust purification system with a DPF, a reducing agent injection valve, and an SCR catalyst in order from the exhaust upstream side includes: an operation state detecting unit capable of detecting starting and stopping of the internal combustion engine; a forced regeneration control unit which performs forced regeneration of the DPF; a condition establishment determining unit which determines whether there is a possibility of solidification of the aqueous urea solution when the operation state detecting unit detects that the internal combustion engine is stopped; a data storage unit which stores the determination result of the condition establishment determining unit as data; and a blockage-clearing control unit which controls a temperature raising unit for raising the temperature of the reducing agent injection valve so as to raise the temperature of the reducing agent injection valve based on the data when starting the internal combustion engine.