Aerosol dynamics using the quadrature method of moments: comparing several quadrature schemes with particle-resolved simulation

Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition

Absorption by black carbon strongly affects regional and global climate. Yet, large discrepancies between standard model predictions and regionally specific observations—often with observed absorption lower than expected—raise questions about current understanding of black carbon absorption and its atmospheric impacts. Through a combination of measurement and modeling, our analysis resolves the discrepancy by showing that particular laboratory designs or atmospheric conditions engender distinct compositional heterogeneity among particles containing black carbon. Lower-than-expected absorption results largely from increased heterogeneity, although slightly lowered absorption occurs even in a purely homogeneous system. This work provides a framework that explains globally disparate observations and that can be used to improve estimates of black carbon’s global impact.

Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC’s radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model–measurement differences. We show that accounting for these two effects—variability in per-particle composition and deviations from the core-shell approximation—reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC’s radiative effect on climate.

Application of the Numerical Techniques for Modelling Fluidization Process Within Industrial Scale Boilers

The numerical simulation of the large scale industrial circulating fluidized bed (CFB) boilers, working under air- and oxy-fuel combustion are presented in this paper. Moreover, two-dimensional experimental rig used for numerical model validation is described. For three-dimensional numerical simulations two industrial compact CFB boilers were selected installed in Polish Power Plants. Numerical simulations were carried out using three-dimensional model where the dense particulate transport phenomenon was simultaneously modelled with combustion process. The fluidization process was modelled using the hybrid Euler-Lagrange approach. Within the paper, readers can find information about used computational technique and a number of reference to specific work. The impact of radiative heat transfer on predicted temperature profile within the CFB boiler was investigated in presented work. Moreover, the novel model for retrieving radiative properties of gases under oxy-fuel combustion process was used. The evaluated temperature and pressure profiles during numerical simulations were compared against measured data collected during boiler air-fuel operation. Collected data was also used for validating numerical model of the oxy-fuel combustion model. Stability of the model and its sensitivity on changes of composition of the oxidizer were studied. This simulations were evaluated to check the response of the numerical model on changing the combustion conditions from air- to oxy-fuel combustion process. The comparison of the pressure and temperature profiles for all considered cases gave comparable trends in contrary to measured data.