Premium
Initial kinetics of the direct sulfation of limestone
Author(s) -
Hu Guilin,
Shang Lei,
DamJohansen Kim,
Wedel Stig,
Hansen Jens Peter
Publication year - 2008
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.11570
Subject(s) - calcite , chemistry , activation energy , sulfation , nucleation , carbonate , diffusion , thermal diffusivity , kinetics , mineralogy , calcium carbonate , reaction rate , porosity , chemical engineering , thermodynamics , catalysis , organic chemistry , biochemistry , physics , quantum mechanics , engineering
The initial kinetics of direct sulfation of Faxe Bryozo, a porous bryozoan limestone was studied in the temperature interval from 873 to 973 K in a pilot entrained flow reactor with very short reaction times (between 0.1 and 0.6 s). The initial conversion rate of the limestone—for conversions less than 0.3%—was observed to be significantly promoted by higher SO 2 concentrations and lower CO 2 concentrations, whereas O 2 showed negligible influence. A mathematical model for the sulfation of limestone involving chemical reaction at calcite grain surfaces and solid‐state diffusion of carbonate ions in calcite grains is established. The validity of the model is limited to the initial sulfation period, in which nucleation of the solid product calcium sulphate is not started. This theoretical reaction‐diffusion model gives a good simulation of the initial kinetics of the direct sulfation of Faxe Bryozo. The intrinsic rate of the direct sulfation of the limestone is estimated to have an activation energy of about 25 kJ/mol and reaction orders of about 0.9 and −0.75 for SO 2 and CO 2 , respectively. The diffusivity of carbonate ions in the surface layer of the calcite grain is estimated to be about three orders of magnitude higher than the diffusivity of carbonate ions in the inner lattice of calcite grain and have an activation energy of about 202 kJ/mol. © 2008 American Institute of Chemical Engineers AIChE J, 2008