Patent ID: 8033096
Filing Date: 2011-10-11
Classification: B01D,F01N,F02D,Y02T

Abstract:
1. An engine exhaust gas purifying apparatus for reducing NOx in an exhaust gas from an engine by adding a reducing agent for NOx to the exhaust gas, comprising: a storage tank for storing the reducing agent for NOx or a precursor thereof to be added to the exhaust gas in a state of aqueous solution; a concentration detecting unit for detecting a concentration of the reducing agent or the precursor contained in the aqueous solution stored in the storage tank, the concentration detecting unit including: a first temperature sensing body having a property that an electric characteristic value changes according to a temperature and arranged to be in direct or indirect contact with the aqueous solution; and a heater thermally connected to the first temperature sensing body, the concentration detecting unit driving the heater and outputting an electric characteristic value of the first temperature sensing body heated by the heater as the concentration of the reducing agent or the precursor; a control unit which is connected to the concentration detecting unit to detect a predetermined abnormality concerning the aqueous solution based on the concentration detected by the concentration detecting unit, the control unit including: a state determining portion for determining whether or not the temperature of the aqueous solution is substantially in an equilibrium state; and an abnormality detecting portion which, when the detected concentration is in an abnormal area other than a predetermined area specified to be a normal area of concentration, detects the predetermined abnormality based on a concentration detected at a time period of temperature equilibrium during which it is determined that the temperature of the aqueous solution is in the equilibrium state; and a tank heater provided on the storage tank, wherein the control unit detects the predetermined abnormality with the abnormality detecting portion according to a result of the determination by the state determining portion at the time of heating by the tank heater.