Collaborative simulations and experiments for a novel yield model of coal devolatilization in oxy-coal combustion conditions

Abstract

Oxy-coal combustion is an emerging low-cost "clean coal" technology for emissions reduction and Carbon Capture and Sequestration (CCS). The use of Computational Fluid Dynamics (CFD) tools is crucial for the development of cost-effective oxy-fuel technologies and the minimization of environmental concerns at industrial scale. The coupling of detailed chemistry models and CFD simulations is still challenging, especially for large-scale plants, because of the high computational efforts required. The development of scale-bridging models is therefore necessary, to find a good compromise between computational efforts and the physical-chemical modeling precision. This work presents a procedure for scale-bridging modeling of coal devolatilization, in the presence of experimental error, that puts emphasis on the thermodynamic aspect of devolatilization, namely the final volatile yield of coal, rather than kinetics. The procedure consists of an engineering approach based on dataset consistency and Bayesian methodology including Gaussian-Process Regression (GPR). Experimental data from devolatilization tests carried out in an oxy-coal entrained flow reactor were considered and CFD simulations of the reactor were performed. Jointly evaluating data and simulations, a novel yield model was validated against the data via consistency analysis. In parallel, a Gaussian-Process Regression was performed, to improve the understanding of the uncertainty associated to the devolatilization, based on the experimental measurements. Potential model forms that could predict yield during devolatilization were obtained. The set of model forms obtained via GPR includes the yield model that was proven to be consistent with the data. The overall procedure has resulted in a novel yield model for coal devolatilization and in a valuable evaluation of uncertainty in the data, in the model form, and in the model parameters.

Large‐eddy simulation of coal combustion in 15 MW pilot‐scale boiler‐simulation facility

“…The posterior impact factor colored in green is significantly reduced via the verification and uncertainty quantification (V/UQ) approach, which uses the bound‐to‐bound approach to estimate the range of uncertainty of simulation and experimental data 45,74 . More details about this analysis are presented in publications of other group member 43,74 . Even V/UQ technique dramatically reduces the impact factor for most of the model parameters colored in green.…”

“…The maximum volatile yield is a function of the particle temperature and increases when increasing the particle temperature. Parameters in the ultimate volatile yield equation are fitted with the CPD model 43,44 …”

“…These two mixture fractions also relate the products of devolatilization and char oxidation from the coal particles to the gas phase. Further details may be found in other studies utilizing the current approach 37,42,43,47 …”

Application of cassava harvest residues (Manihot esculenta Crantz) in biochemical and thermochemical conversion process for bioenergy purposes: A literature review

“…In addition, coal oxy-fuel combustion makes it possible to capture and sequester carbon, using technology already available in conventional pulverized coal boilers, and to capitalize on the enormous quantities of money invested in the existing boilers (Riaza et al, 2012). Some researchers (Sengupta and Basu, 1991;Stenseng et al, 1995;Iavarone et al, 2017;Gaikwad et al, 2017) focused their attentions on the development of mathematical models to predict coal combustion, gaseous emissions and combustion chambers performance. It was observed that biomass oxygen emissions are not extensively investigated and applications of oxyfuel combustion using cassava residues were not found.…”

Bayesian calibration of a methane-air global scheme and uncertainty propagation to flame-vortex interactions

“…Recently, Enderle et al [36] investigated the uncertainties arising from spray boundary conditions specifications in an ethanol flame using detailed chemistry. Despite uncertainties from the calibration of global chemistry models have been characterized in some studies ( [19][20][21]37]), their forward propagation through computational fluid dynamics (CFD) of combustion applications remains to be investigated.…”