Reaction of Hydrogen Chloride Gas with Sodium Carbonate and Its Deep Removal in a Fixed-Bed Reactor

• Published in: Industrial & engineering chemistry research 2014-12, Vol.53 (49), p.19145-19158
• Main Authors: Hartman, Miloslav, Svoboda, Karel, Pohořelý, Michael, Šyc, Michal, Skoblia, Siarhei, Chen, Po-Chuang
• Format: Article
• Language: English
• Subjects: Chloridizing; Hydrogen chlorides; Integrals; Mathematical analysis; Mathematical models; Reactors; Sodium; Sorbents
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie503480k

The chloridization rates of sodium hydrogen carbonate calcines were determined using both a differential fixed-bed reactor and an integral fixed-bed, flow-through reactor at ambient pressure and a temperature of 500 °C. In the course of the reaction with hydrogen chloride gas, monoclinic or hexagonal Na2CO3 was transformed into cubic NaCl. The expansion of the volume of the solid phase, because of the reaction, was described by means of a simple structural model. The reacted solids remained quite porous (∼29%), having decreased from an initial porosity of 45%. Up to advanced stages of the reaction, the rate-decaying behavior of the chloridization reaction can be approximated by first-order kinetics as a function of either the solids conversion or the elapsed time of reaction. The reaction between hydrogen chloride gas and the Na2CO3-based sorbents is rapid, and a high degree of sorbent utilization can be attained. The unsteady-state sorption of hydrogen chloride gas in a column packed with reactant solids can be described by a pair of partial differential equations, and their analytical, closed-form solution is presented in terms of three dimensionless variables. Unsteady-state experimental runs were carried out in a small integral fixed-bed reactor (14-mm i.d.) with spherical alumina particles having an average diameter of 1.5 mm, impregnated with NaHCO3 and packed to a depth of 6.5 cm. The effective reaction rate constants inferred from the experimental breakthrough curves in accordance with the model were found to be in reasonable agreement with those determined from the experiments executed in the differential mode of reaction. The presented, tractable expressions can readily serve as a rational basis for the conceptual design and effective operation of packed-bed reactors for the deep removal of hydrogen chloride gas from hot producer gas.