Vaporization model for arsenic during single-particle coal combustion: Model development

Abstract

The kinetic parameters for chemical reactions associated with the vaporization of arsenic species are rarely reported due to the difficulties in obtaining suitably purified arsenic compounds as well as the issues associated with the extreme toxicity of many arsenic species. Here, we used a single-particle coal combustion model combined with a vaporization yield model of arsenic fitted by experimental data, which was used to determine the activation energy and frequency factor of the oxidation/decomposition reactions of arsenic species in this work, namely: As-org, FeAsS, FeAsO4 and Ca3(AsO4)2. The combustion kinetics of volatile/char and arsenic thermodynamic properties were used to model the vaporization zone and intensity of emissions for arsenic compounds. The results show that the reaction kinetic parameters of these arsenic species could be determined within an order of magnitude despite the variation of compositions in the coal sample and temperature, and this approach provides a new method to determine the reaction kinetics of hazardous elements such as As. Combining the vaporization yield and reaction kinetics of arsenic species with the single-particle coal combustion model, a novel vaporization model of arsenic was developed. With this model, the temporal evolution of combustion parameters (temperature, conversion ratio of coal, particle porosity, flue gas concentration) as well as arsenic vaporization ratio and As2O3(g) concentration can be predicted at the microscopic level. Model applications and predictions can be found in Part 2 of this work [Vaporization model of arsenic during single-particle coal combustion: Part 2. Numerical simulation].

Formation and Reduction of NO2 in Fixed Bed Combustion of Coal Char under Oxy–Fuel Conditions: Experimental and Density Functional Theory Analysis

“…Synthetic gas mixtures O 2 , CO 2 , and H 2 O were injected into the furnace at a constant flow rate of 2.67 L/min, which not only eliminate the influence of external diffusion, but also avoid any sample thermal agglomeration during the combustion . In terms of the test results, the heating rate of char was estimated to be in the range of 5 × 10 3 to 10 4 K/s, which is closer to the heating rate for practical combustion in contrast to the TGA method. A number of previous studies have demonstrated that the isothermal combustion system can be successfully used to study char combustion and pollutant release.…”