Modeling the Vaporization of Inorganic Matter from a Single Coal Char Particle Burning in an O₂/CO₂ Atmosphere

Abstract

The present work aims to model ash vaporization from a burning char particle during pulverized coal combustion in an oxygen-enriched O 2 /CO 2 atmosphere. The modeling development was to apply the classic ash vaporization model of Quann and Sarofim to cover oxy-coal combustion over a wide range of O 2 concentrations by coupling it with the double-film char burning submodel to properly describe the burning process of a single char particle. The model was extensively validated with literature data on the vaporization of SiO 2 , MgO, and CaO in both O 2 /N 2 and O 2 /CO 2 atmospheres. The model was proved to be able to predict the vaporization behavior of SiO 2 during char conversion stages in both atmospheres, covering the effects of coal type, particle size, and O 2 concentration. The model predicts the vaporization of MgO and CaO during char combustion of bituminous coal, but improvement is required to describe the vaporization of MgO and CaO during char combustion of lower-rank coals by considering the occurrence of Mg and Ca in the coals and their interactions with other included minerals at high temperatures. The model validations demonstrated the importance of considering CO homogeneous oxidation in the boundary layer to reasonably predict the char particle burning process and ash vaporization in both O 2 -enriched O 2 /N 2 and O 2 /CO 2 atmospheres.

Correlation of the Sub-micrometer Ash Yield from Pulverized Coal Combustion with Coal Ash Composition

“…However, as stated in the Introduction, PM 1 formation depends upon combustion conditions. For example, low NO x combustion, such as air staging, which is common for modern industrial furnaces, increases PM 1 formation from lower rank coals. , Oxygen-enriched combustion promotes PM 1 formation through enhancing refractory oxide/element vaporization. ,, Oxyfuel combustion at the same oxygen concentration generally lowers PM 1 formation compared to air firing. − Fortunately, the effects of these conditions on PM 1 formation can be well-described by modeling. − …”

“…The effects of combustion conditions on PM 1 formation are generally predictable . Fine mode ash formation can be well-described with theoretical models of the vaporization, nucleation, condensation, and coagulation, ,,,− which can be integrated into the computational flow dynamics model to predict ash vaporization as well as sub-micrometer ash formation in pulverized coal-fired furnaces. − With the char morphology and appropriate ash formation mechanisms considered, central mode ash formation is also likely to be predicted with models. , However, the nature of high variability in coal properties, especially the occurrence and distribution of inorganic matter, leads to the greatest difficulty in predicting PM 1 yields from various coals. For example, the sizes of major mineral inclusions have to be specified empirically ,,, to predict the vaporization of refractory oxides/elements and the formation of the fine mode ash for different coals.…”

6th Sino-Australian Symposium on Advanced Coal and Biomass Utilisation Technologies

“…Wu et al () study the impacts of oxy-fuel conditions on ash properties and sintering behavior from the combustion of a pulverized sub-bituminous coal at 1300 °C in a drop-tube furnace. Chen et al () simulate the vaporization of inorganic matter from the combustion of a single coal char particle under oxy-fuel conditions. Li et al () report the effect of acidic gases (NO x and SO 2 ) on the removal of Hg 0 in an oxy-fuel CO 2 compression process.…”

“…Chen et al (10.1021/acs.energyfuels. 7b03171)30 simulate the vaporization of inorganic matter h i b i t e d .…”