Effects of momentum ratio and velocity difference on combustion performance in lignite-fired pulverized boiler

Abstract

To study the effects of momentum ratio and velocity difference between primary and secondary air flow on boiler performance, simulation work was conducted on a lignite-fired boiler within a three dimension computational fluid dynamics model. Within the model, 8 cases were simulated where momentum ratio and velocity difference vary among cases. The distributions of combustion temperature, radiative heat flux, gas species concentration and residual particles’ concentration were analyzed. Results show that momentum ratio of primary and secondary air flow significantly determines coal combustion behavior and boiler performance, and a reasonably small momentum ratio is beneficial for boiler performance. The velocity difference between primary and secondary air also affects coal combustion performance, and a relatively large velocity difference is favorable in boiler operation. These findings reveal the effects of momentum ratio and velocity difference on boiler performance, and can be helpful in guiding the actual operation of lignite-fired boiler to avoid the unfavorable boiler performance degradation.