Computational fluid dynamics modelling and optimisation of a new Ecotube air system for clean combustion of coal in a grate fired boiler

The computational fluid dynamics (CFD) technique together with a black-box bed model are used to simulate and optimise the performance of a 25-MW indu strial travelling grate fired boiler for coal combustion. A new advanced se condary/over-fire air (SOFA) system using an Ecotube technique is studied a nd five different air configurations are comprehensively calculated to opti mise the SOFA configuration in the boiler. The results of the numerical mod elling show that the Ecotube system can generate a local strong mixing zone , which produces good mixing and enhances the residence time. Results show that the Ecotube technique is quite effective in distributing the secondary /over-fire air, in improving the grate combustion and in reducing CO and NO x emissions. Complete combustion can be achieved by using the low position Ecotube air configuration, whereas NOx can be reduced by about 35% by using the upper position Ecotube air configuration in the boiler. Therefore, for grate combustion, the Ecotube system is effective and has a potential for future application in industry.