Numerical investigation on oxy-combustion characteristics of a 200 MW e tangentially fired boiler Junjun Guo a , Zhaohui Liu a,⇑ , Peng Wang a,b , Xiaohong Huang a , Jing Li a , Ping Xu a , Chuguang Zheng a a State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China b Shenhua Guohua Electric Power Research Institute, Beijing 100025, People’s Republic of China highlights  A CFD model is developed to investigate the oxy-fuel combustion in a 200 MW e boiler.  A compatible burner design for air-fired and oxy-fuel combustion is proposed.  A high CO concentration appears in burner region due to chemical effect of CO 2.  Only slight increase in total heat transfer was observed with O 2 content increased.  The full load of a boiler will decrease by 5–10% under oxy-fuel combustion. article info Article history: Received 23 June 2014 Received in revised form 26 August 2014 Accepted 25 September 2014 Available online 18 October 2014 Keywords: Oxy-fuel combustion Chemical effect Radiative heat transfer Numerical simulation abstract In recent years, oxy-fuel combustion in coal-fired plants has become one of the most promising technologies for carbon capture and storage (CCS). Compared with air-fired combustion, high concentrations of CO 2 and H 2 O in the flue gas cause a remarkable change in the pulverized coal combustion and heat transfer characteristics in furnace. In this study, improved models for the gas radiative properties and chemical reaction mechanisms were incorporated into the computational fluid dynamics (CFD) code to simulate a 200 MW e tangentially fired utility boiler, which is expected to operate at full load under both conven- tional air-fired and oxy-fuel combustion. Different flue gas recycle patterns: dry recycle and wet recycle, were also investigated. The results indicate that, stable combustion is achieved by a compatible burner design in both air-fired and oxy-fuel combustion. In the oxy-fuel combustion, the flue gas peak temper- ature and wall heat flux decrease and high CO concentration appears in the burner region, resulted from higher heat capacity of CO 2 and chemical effect of CO 2 (Liu et al., 2003, Glarborg and Bentzen, 2008). Based on the comparison of the wet recycle and dry recycle, it shows the wet recycle has more advanta- ges than dry recycle. This study indicates a slight increase in total heat transfer, when the oxygen concen- tration in oxidant increases from 23% to 29%, consistent with the results of Vattenfall and Callide pilot scale oxy-combustion plant. Thus, compared with air-fired combustion, the full load of a boiler may decrease by 5–10% under oxy-fuel combustion. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The problem of CO 2 emissions is becoming increasingly serious. Oxy-fuel combustion is one of the most feasible CCS technologies. In this combustion, oxygen is diluted with recycled flue gas (RFG) instead of air, where carbon dioxide is highly concentrated. Several investigations on oxy-fuel combustion have been reported the flame stability and temperature were greatly changed [1,2]. During the boiler design for oxy-fuel combustion, it is essen- tial to consider both the heat transfer and combustion quality. If an existing boiler is retrofitted with this technique, it should be assured that the heat transfer in furnace and heat exchange in the convective pass match with that of air-fired. A significant increase of oxygen concentration in oxidant is expected to achieve temperature levels similar to air-fired flame without significant changes in the flame aerodynamics [3]. However, recent experi- ences from large pilot oxy-combustion facility, such as Callide 30 MW e [4] and Schwarze Pumpe 30 MW th [5], show lower radiant heat transfer in wide oxygen concentration scopes. As it remains questionable whether observation gained from small or large pilots is universal, detailed investigations on the temperature and heat transfer properties in a large-scale furnace are highly expected. http://dx.doi.org/10.1016/j.fuel.2014.09.125 0016-2361/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +86 13971078291. E-mail address: zliu@hust.edu.cn (Z. Liu). Fuel 140 (2015) 660–668 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel