Comprehensive Model of Single Particle Pulverized Coal Combustion Extended to Oxy-Coal Conditions

Abstract

Oxy-fired coal combustion is a promising potential carbon capture technology. Predictive CFD simulations are valuable tools in evaluating and deploying oxy-fuel and other carbon capture technologies either as retrofit technologies or for new construction. However, accurate predictive simulations require physically realistic submodels with low computational requirements. In particular, comprehensive char oxidation and gasification models have been developed that describe multiple reaction and diffusion processes. This work extends a comprehensive char conversion code (CCK), which treats surface oxidation and gasification reactions as well as processes such as film diffusion, pore diffusion, ash encapsulation, and annealing. In this work several submodels in the CCK code were updated with more realistic physics or otherwise extended to function in oxy-coal conditions. Improved submodels include the annealing model, the swelling model, the mode of burning parameter, and the kinetic model, as well as the addition of the chemical percolation devolatilization (CPD) model. Results of the char combustion model are compared to oxy-coal data, and further compared to parallel data sets near conventional conditions. A potential method to apply the detailed code in CFD work is given.

Adjoint-based sensitivity analysis of char combustion surface reaction kinetics

“…Despite well-known weaknesses of the onestep heterogeneous model analysed here, it is commonly used in literature to give a quantitative description of different experimental or fuel-dependent parameters on the resulting reactivity, motivating its use in the experimental and numerical investigations here. However, a variety of other char combustion models exist, many of them consider more physical and chemical effects than the one-step kinetics model, which has been applied here (for example, the CBK model family [10,20], and Senneca's model [26], to name a few). Although different in their overall structures, these models all consider multiple chemical reactions for char conversion, coupled serially and/or in parallel.…”

Review of Carbonaceous Annealing Effects on O2 and CO2 Coal Reactivity

“…Later, these sets of oxidation and gasification reactions were combined by Shurtz 41 in the Carbon Conversion Kinetics (CCK) model, which is also employed in the Carbon Conversion Kinetics for oxy-coal combustion code (CCK/oxy). 42 Liu and Niksa, 39 in particular, noted that their model could not match an extensive compilation of coal combustion rate data unless they allowed for a distinct activated complex for each primary gasification agent (i.e., one C(O) for O 2 , another for CO 2 , and another for H 2 O). Senneca et al 21 further observed that annealing appeared to decrease both the adsorption and desorption preexponential factors for char combustion.…”

“…For example, Liu and Niksa , used five reaction steps for gasification and an additional three steps for O 2 char oxidation. Later, these sets of oxidation and gasification reactions were combined by Shurtz in the Carbon Conversion Kinetics (CCK) model, which is also employed in the Carbon Conversion Kinetics for oxy-coal combustion code (CCK/oxy) . Liu and Niksa, in particular, noted that their model could not match an extensive compilation of coal combustion rate data unless they allowed for a distinct activated complex for each primary gasification agent (i.e., one C­(O) for O 2 , another for CO 2 , and another for H 2 O).…”

A Predictive Physico-chemical Model of Biochar Oxidation

“…The most advanced char conversion models available consider a limited degree of complexity in chemical kinetics. − A more complex chemical description was formulated by Haynes and co-workers, , defining the concepts of turnover models for char oxidation, and explaining how surface reactions expose unreactive carbon to the gaseous environment. In this case the reactivity of different structures is described by means of a continuous distribution of activation energies.…”