The dynamic simulation of carbon-in-pulp systems: A review of recent developments
Despite major advances in the practical use of the carbon-in-pulp (CIP) process, the dynamics of this process are still poorly understood by operating staff. Moreover, the many features of existing models for the CIP process are frequently not appreciated by production personnel. It is the aim of this paper to review and compare existing empirical and fundamental models, and to identify areas for further development work. Empirical methods, such as the classic and widely used Fleming & Nicol model, are conceptually simple but rather limited in their applicability. Also, it is sometimes impossible to attach any practical significance to the values of their parameters. On the other hand, the more rigorous fundamental models are computationally more complex, but more generally based. Most of these models involve the simultaneous solution of initial value or boundary value problems. In pulps with a low concentration of gold or silver, a simple film diffusion model may be adequate. However, if the process is characterised by incomplete leaching, severe preg-robbing, fouling of the carbon by organics and inorganic precipitates, competitive adsorption by base metal cyanides, or high loadings of gold or silver, then a more complex model may be required. This paper explains how these phenomena could be accounted for in material balance equations. Relatively simple models, however, could be used to study the interaction between the leaching, adsorption, elution and regeneration sections with a view to determine optimal operating conditions. As in the case of adsorption models, such scope still exists for R&D on elution and the development of simulation models for desorption. The transport phenomena associated with the pre-treatment step in AARL elution deserves special attention in this regard. Furthermore, very little work has been published on the modelling of the regeneration step in a CIP circuit. With the development of knowledge-based system (KBS) modelling, new avenues have been opened to the simulation of complex adsorption processes. © 1991.