Relating the Deactivation Potential of SCR Catalysts to Fuel Properties and Firing Conditions

摘要

Forms of As, P, Na, K, and Camay deactivate SCR catalysts depending on fuel quality, furnace staging in the burner zone, and flame temperatures.We combined thermochemical equilibrium calculations and finite-rate reaction mechanisms to estimate deactivation potentials of particular coals and blends given fuel properties, the stoichiometric ratio (S. R.) in the primary flame zone, and maximum flame temperature. Estimated extents of poison vaporization in the furnace vary significantly with S. R. for P and As, whereas scavenging and sequestration of poisons by molten mineral phases in the upper furnace elevations is important for all poisons except P.Condensation of poisons into aerosol or onto flyash through superheaters and the economizer is inevitable for Na, K, and Ca; unimportant for As; and the key factor in the deactivation potential of P species. The most effective means to lower poison precursor concentrations into an SCR are (1) scavenging of As species by Ca-minerals; (2) condensation of P species onto flyash upstream of the SCR inlet; and (3) scavenging of Na, K, and Ca species by aluminosilicates upstream of the furnace exit before they condense into sulfates.