A control system for NOx reduction in a power plant, the control system comprising: a model predictive controller; where the model predictive controller is adapted to control overall system constraints including outlet NOx, ammonia slip, reaction zone temperature distribution level(s), furnace load demand, or a combination thereof and to generate manipulated variables including urea flow distribution, total carrier water flow, injection height(s) of nozzles, water pulsation rate/magnitude, amount of NOx, amount of excess oxygen, the main burner zone stoichiometry, windbox/furnace differential pressure, or a combination thereof; a plurality of proportional integral differential controllers (108, 110, 122, 124) and/or adaptive controllers (308, 310, 322, 324) subordinated to and in operative communication with the model predictive controller, each of which being in a feedback loop with a pressure gauge or a flow measurement device and with a valve; a NOx reduction system comprising a NOx reducing agent supply tank, a water supply tank and lines that carry water and NOx reducing agent and that are fitted with the pressure gauge or the flow measurement device and with the valve; and a furnace for combusting a fuel; where the furnace lies downstream of the NOx reduction system and where the furnace is provided with a plurality of nozzles that are in fluid communication with the NOx reduction system; where the control system is configured to determine an amount of NOx reducing agent and water introduced into the furnace from the NOx reducing agent supply tank and the water supply tank respectively and to deliver intermittently NOx reducing agent and water to the furnace. a model predictive controller; where the model predictive controller is adapted to control overall system constraints including outlet NOx, ammonia slip, reaction zone temperature distribution level(s), furnace load demand, or a combination thereof and to generate manipulated variables including urea flow distribution, total carrier water flow, injection height(s) of nozzles, water pulsation rate/magnitude, amount of NOx, amount of excess oxygen, the main burner zone stoichiometry, windbox/furnace differential pressure, or a combination thereof; a plurality of proportional integral differential controllers (108, 110, 122, 124) and/or adaptive controllers (308, 310, 322, 324) subordinated to and in operative communication with the model predictive controller, each of which being in a feedback loop with a pressure gauge or a flow measurement device and with a valve; a NOx reduction system comprising a NOx reducing agent supply tank, a water supply tank and lines that carry water and NOx reducing agent and that are fitted with the pressure gauge or the flow measurement device and with the valve; and a furnace for combusting a fuel; where the furnace lies downstream of the NOx reduction system and where the furnace is provided with a plurality of nozzles that are in fluid communication with the NOx reduction system; where the control system is configured to determine an amount of NOx reducing agent and water introduced into the furnace from the NOx reducing agent supply tank and the water supply tank respectively and to deliver intermittently NOx reducing agent and water to the furnace.