| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device for a gas engine that can supply urea in accordance with an NOx concentration in exhaust gas without depending on changes over time of a NOx sensor.SOLUTION: An exhaust emission control device for a gas engine includes: an NOx removal catalyst 2 provided in an exhaust gas flow passage L1 for reducing NOx by using urea water 6 sprayed from a spray section 8; an NOx measurement section 3 having an NOx sensor 5 for measuring an NOx concentration in exhaust gas G1; and an urea water supply amount control section 4 for controlling the amount of the urea water 6 to be supplied by the spray section 8 to the exhaust gas flow passage L1 on the basis of the NOx concentration measured by the NOx sensor 5. The NOx measurement section 3 includes: a sampling flow passage L2 branched from the exhaust gas flow passage L1 and communicated with the NOx sensor 5; and an air flow passage L3 communicated with the NOx sensor 5 from an outer space. The exhaust emission control device is configured to enable switching between an exhaust gas mode m1 of measuring the NOx concentration of the exhaust gas G1 flowing in the sampling flow passage L2 and a calibration mode m3 of measuring the NOx concentration of outside air flowing in the air flow passage L3.SELECTED DRAWING: Figure 1 |
