Publication Type |
journal article |
Research Institute |
Institute for Clean and Secure Energy (ICSE) |
Author |
Davis, Sheldon B.; Wendt, Jost O. L. |
Title |
Mechanism and kinetics of lead capture by kaolinite in a downflow combustor |
Date |
2000 |
Description |
An 18 kW, 6 m long, gas-fired downflow combustor was used to examine the postflame reaction between lead vapor and kaolinite. Since the focus of this work was to evaluate the reaction with lead vapor, samples were extracted at a temperature above the metal dew point. The sample was rapidly diluted with nitrogen such that lead vapor homogeneously nucleated to form small particles in the presence of a pre-existing particle population. These small lead particles were easily distinguished from lead reacted to large sorbent particles; hence, multicomponent particle size distributions were used to determine the extent of lead capture. A parametric study was conducted in which sorbent/metal molar ratio and sorbent injection temperature were controlled. Temperatures and residence times were varied by changing the sorbent injection point in the combustor, which had the approximate time and temperature profile of practical scale units. The effect of chlorine was evaluated by doping chlorine gas into the flame. Results show that lead capture by kaolinite was reduced at higher temperatures and in the presence of chlorine. A two-reaction mechanism is proposed to model the apparent temperature inhibition. In the primary capture reaction, lead oxide reacts with activated kaolinite and forms a lead aluminosilicate product. Subsequently, a reaction between this product and activated kaolinite acts to inhibit further lead capture. First-order rate expressions are proposed for each reaction, and kinetic parameters are estimated from experimental results. The primary capture reaction appears to have an activation energy that is approximately zero. The inhibition reaction has an activation energy of -102 kJ mol-1. To model the effect of chlorine, the reaction scheme is modified to account for the partitioning of lead between lead oxide and lead chloride. Based on experimental results, the concentration of lead chloride vapor in the system is significantly higher than predicted by equilibrium calculations. |
Type |
Text |
Publisher |
Elsevier, Inc. |
Subject |
mechanism and kinetics; lead capture; kaolinite; downflow combustor; postflame reaction; lead vapor |
Language |
eng |
Bibliographic Citation |
Davis, S. B.; Wendt, J. O. L. (2000). Mechanism and kinetics of lead capture by kaolinite in a downflow combustor. Proceedings of the Combustion Institute, 28. pp. 2743-2749. |
Relation Has Part |
Proceedings of the Combustion Institute; vol 28, pp. 2743-2749 (2000) |
Rights Management |
(c)Elsevier, Inc. |
Format Medium |
application/pdf |
Format Extent |
179,434 bytes |
Identifier |
ir-eua/id/2110 |
Source |
DSpace at ICSE |
ARK |
ark:/87278/s6m64jbs |
Setname |
ir_eua |
ID |
213315 |
Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6m64jbs |