Provided are embodiments for apparatuses, systems and methods for reducing emissions in an exhaust gas flow of an engine, the apparatus comprising: a reactor vessel positioned externally from the exhaust gas flow, the reactor vessel comprising an inlet and an outlet, the outlet in communication with the exhaust gas flow; an injector positioned within the reactor vessel, the injector receiving a reductant flow from the inlet of the reactor vessel and combining the reductant flow with a pressurized gas flow to generate a reductant spray; and an ammonia generation means within the reactor vessel, the ammonia generation means generating a gaseous reductant flow from the injected reductant flow, the gaseous reductant flow transmitted into the exhaust gas flow via the outlet of the reactor vessel.