Research On Control Of The Thickening Process In Hydrometallurgy

There are lots of deposits of low-grade non-ferrous metal resources in our country, with the rapid growth of the national economy, and steady progress of industrialization, it is very important for sustainable development strategy of our country to use such resources effectively and economically. As one of the two extractive metallurgy technologies, the remarkable advantages of hydrometallurgy are high comprehensive recovery rates of valuable metals in raw materials, benefit for environmental protection, and easy fulfillment of continuous and automated production processes, therefore it is more suitable to recover low-grade metal resources. Thickening process is an important unit operation that is widely used in hydrometallurgy. Thickener is the key equipment for the thickening process and the underflow concentration of thickener is the key quality index. However, at present, most thickening processes are still in manual operation state, making its concentration and flow fluctuate largely, and influencing subsequent production index. Due to the harsh working conditions and other factors, the large time-delay and the slow time-varying, so the automatic control of thickening process has been a difficult problem.Aiming to overcome the difficulties in the thickening underflow concentration control, and based on the deep insight of the hydrometallurgy procedure, this thesis puts forward a control strategy of the thickening process based on multiple model and dynamic matrix control (DMC). The main content of this thesis is as following:1. Firstly, the operational and dynamics characteristics of the thickening process are analyzed. And based on the review of the control strategies for the thickening process, the problems and difficulties in the actual production process which is the basis for the proposed control approach in the paper are analyzed.2. In consideration of the thickening process control problem with high nonlinear and large variation of working condition, the control strategy based on multiple model structure and dynamic matrix control is applied. In the control strategy, the global operation spaces are divided into several different operation spaces while a linear sub-model and a dynamic matrix controller are established for each operation space. Then the global controller output is a weighted average of the multiple linear DMC controllers. The capabilities of the control strategy are investigated through computer simulations3. Taking a thickening section in a hydrometallurgy plant as a research example, the computer simulation platform is established. Under the support of computer simulation platform, based on the above theory studies, optimal operating system software of thickening section is designed and developed; optimal control for underflow concentration of thickening process is achieved.At last, the thesis is concluded with a summary and the problems which need further research are also discussed.