519 / 2018-12-31 21:00:36

Effects of thermal load on performance of large-scale wall-fired lignite boiler

Lignite boiler,wall-fired,boiler thermal load,in-service burners' location,numerical simulation

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Operating characteristics of wall-tangentially fired lignite boiler under various boiler thermal load (BTL) were studied with a previously established and validated three-dimensional lignite boiler model. To be more suitable for combustion simulation of high moisture lignite, coal particle properties are defined by the simplified coal compositions method. 5 combustion scenarios were investigated where BTL in the former 3 cases is 660MW, 550MW and 440MW respectively. In the latter two cases, BTL is kept the same as case 3, but the location of in-service burners and nozzles (LBNs) differs among them. Results show that BTL and LBNs have significant impacts on coal combustion process and boiler performance. With BTL decreasing, the in-furnace coal combustion behavior deteriorates and thus results in decreases of combustion temperature and heat absorption on heating surfaces. Meanwhile, unburnt particles’ mass concentration and NO emission increase. Furthermore, LBNs significantly affects the patterns of coal combustion behavior and heat transfer process, and an optimal arrangement of LBNs ensures lowest NO emission. Findings of this work can serve as guidance in practical operation of lignite boilers.