Serial Hybrid Modelling for a Gold Cyanidation Leaching Plant

Abstract

In this paper, a serial hybrid model of a gold cyanidation leaching process is proposed. The serial hybrid model consists of mass conservation equations of gold and cyanide as well as two kernel partial least square (KPLS) models, which are used as the estimators of the unknown kinetic reaction rates without the complicated kinetic model structures considered. The proposed serial hybrid model makes full use of both the a priori process knowledge and the ability of a data-driven model to discover the information behind data sets. Moreover, before training the KPLS models, the proposed estimation strategy based on Tikhonov regularization is used to estimate the kinetic reaction rates, which can mitigate the effect of measurement noise on the estimation results effectively. The proposed serial hybrid model has been applied to a gold cyanidation leaching plant to predict the gold leaching rate. The prediction results show that the proposed serial hybrid model can track the real leaching rate of gold closely and has the best prediction accuracy at both dynamic and steady states compared with the pure KPLS and mechanistic models, thereby laying an important foundation for the successful implementation of optimization and control of the leaching process.Keywords: leaching process, mechanistic model, hybrid model, kinetic rate, Tikhonov regularization INTRODUCTION C yanidation has been the main method to recover gold from ores, concentrates, and tailings for the past century. It has the advantages of being a mature technology, having high gold recovery, having a low production cost, and being applicable to a diverse variety of ore types. [1,2] Usually, a gold cyanidation leaching process occurs in an aerated continuous stirred tank reactor (CSTR) containing a solution of sodium cyanide and oxygen. The undissolved gold in the solid is transformed into the easy-to-dissolve gold cyanide complex by means of reaction with both sodium cyanide and oxygen. [2,3] In practice, a cascade of leaching tanks in series are configured in order to increase the residence time of slurry and hence ensure a longer reaction time. [4] As the most important procedure in hydrometallurgy, the performance of the leaching process has a significant impact on the subsequent procedures and ultimately determines the gold recovery. The most important quality index for the leaching process is the leaching rate, which is directly related to gold recovery, production efficiency, and overall yield. The ideal leaching rate of 100 % is required in all plants, however this is not realistic in practice due to the impossibilities of infinitely small ore particles, infinitely long residence time, and complete reaction. [5] In industrial applications, the lowest production cost is usually required under the condition that the leaching rate is ensured to be equal to or greater than the index determined by the plant-wide decision. The above optimal operation can usually be obtained by solving the model-based optimization problem of the leaching process -namely, dete...

Comparison of Alternative Strategies Estimating the Kinetic Reaction Rate of the Gold Cyanidation Leaching Process

“…Then, the leached ore pulp overflows into the two-stage thickener, and after washing, the pregnant solution is stored in a pregnant solution tank and gradually pumped into the subsequent process of gold recovery by zinc. 9−11…”

“…6−8 Therefore, under the condition that the quality of the leaching products is ensured, reasonable distribution of raw materials and then reduction of the total consumption, production cost, and improvement of economic efficiency have become serious problems that need to be solved urgently in hydrometallurgy industrial processes, which are solved based on the online prediction of key variables and process optimization. 9−13…”

Two‐level multi‐block operating performance optimality assessment for plant‐wide processes

“…The replacement production unit turns the liquid pregnant solution with abundant gold complex into solid gold in the gold mud, where zinc powder is an important additive during the replacement reaction. The details of the process description are well explained in Zhang et al…”

Plant‐wide optimization for gold hydrometallurgy based on the fuzzy qualitative model and interval number

“…It is worth mentioning that for different pulp discharge volumes, through the frequent adjustment of the mixing water, the pulp density can be measured by field workers' offline test for many times, and the actual values of pulp density can be obtained under different levels. In the previous literatures regarding modeling and optimization for the hydrometallurgy process, scholars usually assume that the pulp density is uniform in the beginning stage of the leaching process and can be assumed to be a constant . Unfortunately, due to the changing actual environment and some interference factors, the off‐line assayed data are usually not accurate and not consistent with the actual plant study.…”

“…In recent years, some scholars carried on related researches on uncertainty optimization methods for metallurgical processes . For instance, to solve the model mismatch problems of model parameter uncertainty and structure uncertainty, Zhang et al put forward a kind of modifier adaptation real‐time optimization strategy for the gold cyanidation leaching process.…”