Combustion and heat transfer characteristics at the combustion chamber of an oxy-fuel boiler for CO_2 capturing: a numerical simulation

摘要

A 0.5 MW class-oxy-fuel boiler was developed to capture CO_2 from the exhaust gas. Flue gas recirculation (FGR) was adopted to make it possible to retrofit existing facility by changing its burner. A co-axial burner was devised to support three combustion modes, which are conventional air combustion, oxy-fuel combustion and oxy-fuel combustion with FGR. Numerical simulations were conducted for the three combustion modes to study the detailed physics inside the combustion chamber of the boiler. The temperature field obtained from the simulation reproduces the flame structures in general, while the results under-predict the spanwise mixing for the air and FGR modes. The FGR combustion yields similar heat transfer characteristics with the conventional air combustion, which implies the possibility to have a CO_2-free boiler by retrofitting the burner while keeping other parts of the boiler.