Abstract
Coals are invariably associated with mineral matter, which makes it unsuitable for efficient utilisation. For difficult-to-wash coals, advanced coal beneficiation technologies like chemical leaching methods are under development. In this paper, kinetic equations using different methods have been evolved, and related parameters have been estimated, using the experimental results obtained during coal leaching process. As coal is a heterogeneous rock, three different methods namely (i) parametric estimation through rate equation, (ii) non-linear regression and (iii) parametric estimation through shrinking core model have been developed and validated to check the minimum level of permitted error tolerance. Experiments were designed, using full factorial design with three variables, which are sensitive to the process. Values of activation energy and k0 obtained, using the parametric estimation of rate equation and shrinking core model, are almost in the same range. The order of the reaction for silica and alumina is two, using rate equation method. The parametric data obtained from the polynomial regression method were compared with the actual data. The exponential polynomial provides a better fit for the chemical leaching process of coal.
Nomenclature
- t
Reaction time (min)
- Δt
Time interval for reaction (min)
- R0
initial coal particle size (mm)
- R
coal particle size at time “t” (mm)
- φC
fraction of the reactive minerals in the solid
- ρC
Density of silica/alumina containing mineral (kg/m3)
- kc
Reaction constant
- n, m
Rate of reaction of pure components
- x
weight of ash in grams after time “t” (g)
- x0
initial weight of ash in grams (g)
- i
Stoichiometric coefficient
Concentration of silica/alumina at time t (g/g)
Concentration of silica/alumina at time t – Δt (g/g)
- CB
Concentration of solvent (%)
- T
Reaction temperature (K)
- Ea
Activation energy (J/K)
- A, B, a–j
constants
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