Numerical investigation of combustion optimization in a tangential firing boiler considering steam tube overheating

• Published in: Applied thermal engineering Vol. 154; pp. 87 - 101
• Main Authors: Yu, Cong, Xiong, Wei, Ma, Huan, Zhou, Jianxin, Si, Fengqi, Jiang, Xiaoming, Fang, Xuwen
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 25.05.2019; Elsevier BV
• Subjects: Aerodynamics; Boiler tubes; Boilers; Combustion; Combustion efficiency; Computational fluid dynamics; Computer simulation; Coupled simulation; Finite element method; Fluid dynamics; Full load; Heat flux; Heating; Hydraulic models; Hydraulics; Mapping; Mathematical models; Matlab; Nitrogen oxides; NOx emission; Numerical analysis; Optimization; Organic chemistry; Overheating; Steam tube overheating; Tangential firing boiler; Three dimensional models; Wall temperature; Steam tube overheating; NOx emission; Tangential firing boiler; Combustion efficiency; Coupled simulation
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2019.03.074

•A comprehensive boiler model that coupled the furnace and steam sides was developed.•A detailed mapping method was provided for the grid systems of different models.•The effects of the SOFA tilt angle on boiler efficiency and NOx emissions were studied.•The effects of the SOFA tilt angle on the tube outer surface temperature were studied.•Combustion optimization was conducted under the constraint of tube overheating. A comprehensive numerical study of the combustion optimization of a 660-MW tangentially fired boiler under the constraint of steam tube overheating is presented. To obtain the chemical products and the heat flux at the heating surfaces, a three-dimensional (3D) combustion model was established using computational fluid dynamics (CFD) software. In addition, a 1D + 1D thermal hydraulic model was developed using MATLAB to describe the heating process inside the tubes. Detailed mapping methods were also provided to connect the mesh systems in CFD and MATLAB. As a result, the tube wall temperature can be calculated by considering the coupled heat transfer on the gas and steam sides. The simulation results reveal that under full load conditions, the upward tilting of the separated over-fire air (SOFA) burners can reduce the formation of CO and NOx, which helps achieve higher boiler efficiency. However, when the SOFA tilt angle increases from +20° to +30°, 0.16% of the outer surfaces of the final re-heater would exceed the allowable temperature of the TP347H material; additionally, the improvement in the boiler efficiency and decrease in NOx formation are much less. Thus, considering the unit’s safe operation, the optimal SOFA tilt angle for combustion optimization should be +20°.