Reductant injecting device, exhaust gas processing device and exhaust gas processing method

A reductant injecting device, comprising:

• a honeycomb structure comprising:
• a pillar shaped honeycomb structure portion having a partition wall that defines a plurality of cells each extending from a fluid inflow end face to a fluid outflow end face;
• and
• at least one pair of electrode portions being configured to heat the honeycomb structure portion by conducting a current, the pair of the electrode portions being arranged on a side surface of the honeycomb structure portion, the honeycomb structure being configured to be able to decompose urea in an aqueous urea solution in the honeycomb structure portion heated by conducting the current to generate ammonia;
• an outer cylinder having an inlet side end portion and an outlet side end portion, the inlet side end portion comprising a carrier gas introduction port being configured to introduce a carrier gas, the outlet side end portion comprising an injection port being configured to inject ammonia, wherein the outer cylinder houses the honeycomb structure, and a first flow path through which a fluid can flow through the plurality of cells and a second flow path through which the fluid can flow from the inlet side end portion to the outlet side end portion without passing through the plurality of cells are provided in the outer cylinder;
• a urea sprayer being configured to spray the aqueous urea solution into the first flow path or the second flow path on an inflow side of the fluid, the urea sprayer being arranged at one end of the outer cylinder;
• and
• a spray direction switcher configured to be able to switch a spray direction of the aqueous urea solution to the first flow path or the second flow path depending on temperatures of an exhaust gas.