Design And Application Of A Grinding And Classification Automatic Control System For Mineral Processing Plants

This thesis analysis the grinding and classification control process of mineral processing plants, presents the design and implementation of a multivariable control system utilizing fuzzy control strategy. The task of the thesis is based on a control system design project in Gongchangling Mineral Processing Plants.Ensuring of the mineral size requirement, the control objective of the Mineral grade milling process focuses on the increase of handling capacity of the mill machine, namely try to improve the milling efficiency of the production as high as possible. After detailed analysis of Gongchangling milling classification situation as well as grinding and classification requirements, the automatic control system is designed as a Fieldbus control system, including three subsystems: mill feed control subsystem, mill feed density control subsystem and classification overflow density control subsystem. Each subsystem achieves a specific objective of regulation, while cascade control and optimal control methods are performed in the system.Since the grinding and grading production is a multi-parameter, time-varying, non-linear system with large lag, it is difficult to establish a precise mathematical model. Traditional PID control performed on grinding control classification process failed to achieve stable operation behavior, couldn't meet desired control effect.Considering the grinding process of automatic classification, Fuzzy + PID control is used in three subsystems. Whole system is divided into several control modules: fuzzy control module of grinding capacity, Fuzzy analysis module of ore feature, monitoring and control module of grinding concentration etc. Practical running proved that the designed fuzzy + PID control strategies have realized steady operation and satisfied control result. The new control system possess several advantages from both methods: good stability, no-stable error characteristics comes from PID control, good dynamic behavior as well as flexibility to parametric variation and nonlinear feature comes from Fuzzy control. Moreover, a "Step-by-step search for self-optimizing" approach is utilized during ore feed control of the grinding process to achieve optimal control. The designed control system has been implemented in Gongchangling Mineral Processing Plants successfully. This thesis also analyze certain practical data related quality and productivity, such as mill feed amount and grain size of the overflow. The result shows that the designed automatic system reaches considerable improvement on desired characteristics of Grinding and Classification control system.