Investigation on the radiation heat transfer in dilution zone of a 100 kWth oxy-fuel pressurized circulating fluidized bed

Abstract

Due to high pressure, complicated flue gas components and high particle concentration in dilute phase region, radiation heat transfer in the oxy-fuel combustion pressurized circulating fluidized bed (PCFB) is complex. To indicate the radiation heat transfer, both experiments and numerical simulations were carried out, where the Computational Fluid Dynamics (CFD) modelling was based on the full spectrum correlated k-distribution model (FSCK) combined with Mie theory. The multiphase flow behaviors, combustion reactions and radiation heat transfer of the PCFB under oxy-fuel combustion at 0.6 MPa were revealed with good agreement between the simulated result and the experimental data. The predictions of radiation heat transfer were accomplished under different oxygen concentration and operating pressure. The results illustrated that the existence and accumulation of particles lead to the increase of flue gas optical thickness, which hinders more radiation energy transmitted to the wall. Various oxygen concentration leads to the different distribution of temperature and radiative medium concentration, which all have an impact on total radiation intensity. Compared with temperature, particle radiation and gas radiation have less effect on radiation heat transfer under different atmosphere. In addition, the operating pressure affected the flue gas temperature as well as particle concentration and radiative gas concentration in the dilution zone, and the combustion atmosphere also has an influence on the above characteristics. Complicated thermodynamic states lead to dissimilar thermal radiation characteristics under different operating condition.