A boiler or other fired vessel includes a housing with a burner at one end, a furnace downstream of the burner, a convection section downstream of the furnace and a flue gas outlet downstream of the convection section. A first means for loading a reducing agent comprising at least two injectors is located downstream of the furnace. A second means for loading a reducing agent is located downstream of the first means for loading a reducing agent. A selective catalytic reduction catalyst is located either downstream of the second means for loading a reducing agent or adjacent the second means for loading a reducing agent such that the catalyst is provided to the boiler or other fired vessel approximately simultaneously with the reducing agent from the second means for loading the reducing agent.