## chapter 20 modelling of mills and milling circuits - sciencedirect

This chapter provides an overview of the existing mathematical models for the simulation of grinding and classification in millclassifier circuits not only for ball mills but also for other mill types. Examples of the simulation of closed circuits are divided according to the mill type and the level of sophistication introduced into the models. Milling circuits are used in various industrial sectors to achieve desired product size distributions and product properties. The optimization and control of milling circuits is of high technological importance. Various models of mills and milling circuits are published in the literature with different precision and degree of sophistication. Mostly the grinding and classification are investigated separately and then both unit operations are connected into a mathematical model by the recirculation feed. To provide cost and time savings as well improvement of productivity through optimization of a grinding circuit a mathematical simulation of the process can be applied.

## measurement system of the mill charge in grinding ball mill circuits - sciencedirect

Investigation of a dry fine grinding circuit has shown significant influence of the mill load (powder filling) on the production capacity. To improve the circuit performance at industrial scale, alternative ways of mill load measurement were investigated. Detection of strain changes in the mill shell during mill rotation, by using a piezoelectric strain transducer, provided very interesting results, allowing evaluation of the weight of the mill charge and control of the powder filling to obtain an optimal level. Power draw has thus been increased by about 5% compared to the old configuration where mill motor power input was used to control the mill charge. By measuring mechanical vibration with the transducer, additional useful information has been obtained about the behavior of the cataracting and cascading balls inside the mill shell. Finally an important factor was simplicity and low investment cost of the total installation, as many fine grinding mills operate in relatively small circuits that do not warrant large investment for alternative measurement methods.

## control of a grinding mill circuit using fractional order controllers - sciencedirect

Control of a grinding mill circuit using fractional order SISO controllers is addressed.A continuous time dynamic phenomenological non-linear population balance model is used to describe and simulate the circuit.Designed controllers can achieve similar or better results to that achieved using linear model predictive control, which is an advanced multivariable control techniques.Controllers are tested in the presence of disturbances and process noise.

This paper presents the design and application of fractional single-inputsingle-output (SISO) controllers to a grinding mill circuit, which is a multiple-inputmultiple-output (MIMO) process. Two kinds of controllers are presented: fractional order proportional-integral (FOPI) controllers, and a combination of FOPI and fractional order model reference adaptive controllers (FOMRAC). The parameters of the controller are tuned using off-line particle swarm optimization. In the presence of disturbances and process noise, the SISO fractional controllers achieve similar or better performance compared to linear model predictive control (LMPC).

## grinding mill circuits - a survey of control and economic concerns - sciencedirect

A worldwide survey on grinding mill circuits in the mineral processing industry was conducted. The aims of this survey are to determine how milling circuits are currently controlled, and to find out how key process variables are linked to economic benefits. The survey involves background information on the circuits, the choice of controlled and manipulated variables, the economic impact of the controlled variables, adopted control technologies, and assessment of control performance. 68 responses were received as a whole. Survey results are contrasted to the milling control literature.

## disturbance rejection of ball mill grinding circuits using dob and mpc - sciencedirect

Ball mill grinding circuit is essentially a multivariable system with couplings, time delays and strong disturbances. Many advanced control schemes, including model predictive control (MPC), adaptive control, neuro-control, robust control, optimal control, etc., have been reported in the field of grinding process. However, these control schemes including the MPC scheme usually cannot achieve satisfying effects in the presence of strong disturbances. In this paper, disturbance observer (DOB), which is widely used in motion control applications, is introduced to estimate the disturbances in grinding circuit. A compound control scheme, consisting of a feedforward compensation part based on DOB and a feedback regulation part based on MPC (DOBMPC), is thus developed. A rigorous analysis of disturbance rejection performance is given with the considerations of both model mismatches and external disturbances. Simulation results demonstrate that when controlling the ball mill grinding circuit, the DOBMPC method possesses a better performance in disturbance rejection than that of the MPC method.

In the grinding process, disturbances severely influence the control performance of the closed-loop system. The purpose of this paper is to study the disturbance rejection performance of the ball mill grinding circuit by using a proposed compound control scheme consisting of a feedforward compensation part based on disturbance observer (DOB) and feedback regulation part on model predictive controller (MPC) (DOBMPC).Download : Download full-size image

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