Selective catalytic reduction in a rotary air heater (RAH-SCR)

Abstract

The paper investigates SCR (Selective Catalytic Reduction) in a RAH (Regenerative Air Heater). A method of using the air heater as a SCR reactor and its expected benefits are presented. In this method, catalytic elements are used as both catalyst carriers and heating surfaces. An analysis of the heat transfer and NOx reduction of the catalytic elements is presented along with an error analysis. Three catalysts (with 0.5% of Cu and 1.5% of Mn; with 0.5% of Cu; and with 0.5% of Mn) were chosen. Using a semi-industrial research scale on prototype catalytic elements, the maximum NOx reduction by 40% was achieved. This can be satisfactory for many industrial applications, in particular in hybrid systems consisting of an efficient low-NOx furnace and RAH-SCR. These results support the usefulness of the RAH-SCR method. The tests of ceramic elements in the RAH of real coal-fired boilers confirmed their resistance to cyclic temperature changes and erosive wear. However, the use of this method is only safe and profitable when all of the operating/process factors that appear during operation of the real device are considered. Therefore, to evaluate the multifaceted efficiency of NOx reduction for RAH-SCR systems, further investigations under real industrial conditions are necessary.