LOW-TEMPERATURE MULTIBED SCR PROCESS FOR TAIL GAS TREATMENT IN NITRIC-ACID PLANT

A four bed catalytic system for the control of NO(x). emissions in stack gases from nitric acid plant is described. The process has been designed for the selective catalytic reduction of nitrogen oxides with ammonia at low temperatures. Two catalysts fill consecutive beds along the longitudinal axis of the reactor; one is prepared by impregnation of colloidal platinum of gamma-alumina, while the other consists of copper and nickel oxides supported on gamma-alumina. The essential feature of this multibed system is the combination of the performance of the above mentioned catalysts in such a way that a high efficiency of nitrogen oxides reduction is obtained, maintaining the ammonia slip at the exit gas below 50 ppm. The comparison of the NO(x), conversion obtained at industrial scale and that obtained at laboratory scale shows a good parity.