Optimal control in selective catalytic reduction using linear quadratic regulator

Abstract

In current scenario, it is significant to have harmful emissions under control and supervision by deploying control technology is indispensable. In the thermal power plants, diesel engine industries hazardous gases are being emitted and Nitric Oxide gases (represented by NOx) are one among them. Thus, (EPA) Environmental Protection Agency has set standards where the industry has to pertain to it in order to minimize the level of NOx to a certain level. Selective Catalytic Reduction (SCR) means converting nitrogen oxides [NOx] with the aid of a catalyst into nitrogen and water using a reducing agent ammonia (NH3) in this example. In the existing system, the two classical Proportional Integral Derivative controllers (cascade controller) is employed to reduce the NOx value by predicting the set point of ammonia. In this process, we get higher cost, increased peak overshoot and more settling time, which caused time delay affecting the process to a certain extent. In the proposed system, we are incorporating Linear Quadratic Regulator in place of two PID controllers, where we optimize the system to get a constant feedback which overcomes the existing disadvantages of the existing system. The LQR technique minimizes the energy of the system by giving minimum cost which is lesser than that of nominal cost of the system. This also gives low cost, faster setting time and less peak overshoot when compared to PID controller.