Circulating fluidized bed boiler with improved NOx reduction

摘要

The combustion area (1) is connected to a separation cyclone (11) by a pipe (9) carrying a flow of particles and gas containing nitrogen oxides (NOx). A reactant is injected into the flow, to reduce the NOx emissions, using at least one tubular rod (21) in the top of the combustion area which extends into the pipe to inject the reactant in the direction of flow of the fluid A second rod mounted in the top of the pipe near the combustion area also injects reactant in the direction of fluid flow. An external exchanger with dense fluidized bed connects the separation cyclone to the combustion area and the top of this forms a pipe for the flow, with a third tubular rod in the top of the exchanger injecting reactant into the flow. Each tubular rod contains at least one injection nozzle for the reactant and can be moved in a direction perpendicular to the longitudinal axis of the pipe. Each tubular rod has a cooling circuit containing water and is coated with tungsten carbide or chromium carbide to resist the abrasion of the flow. The reactant is gaseous ammonia or droplets of ammonia in solution, or an ammonia compound such as urea, sprayed by air.