Metcom Grinding Process Management System

This module will introduce you to rod mill, ball mill, and AG/SAG mill power draw. Please note, that this module was originally created for plants with rod and ball mills. Those types of mills are very similar in that the steel media dominate their power draw characteristics. Rod and ball mill power draw calculations are covered in Parts I and II. Subsequently, AG/SAG mill power draw calculations were added, and presented in Part III.

At the end of this module, you will be able to: 

• Differentiate between "energy consumed" and "power drawn" by grinding mills. 
• Calculate the approximate power draw of operating mills given basic design and operating conditions. 
• Calculate the approximate power draw of operating AG/SAG mills given basic
• design and operating conditions, with emphasis on the relative proportion of slurry, rock, and balls in the mill. 
• Specify practical means (and limitations) to increase the power draw of operating rod mills and ball mills in the plant. 

There is no prerequisite to this module. The estimated time to complete this module is 2.5 hours.

In this module, you will learn about Work Index calculations for evaluating grinding circuit efficiency, as developed by Mr. Fred Bond.

After completing this module, you will be able to:

• Identify the boundaries of various grinding circuit arrangements.
• Calculate the operating Work Index of a grinding circuit.
• Calculate the Work Index efficiency of a grinding circuit.
• State the accuracy of comparative Work Index efficiencies.
• Calculate the operating Work Index and Work Index efficiency of various grinding circuit arrangements.

Note that this module was originally produced for sponsoring companies that used only rod and ball mills. These are covered in the first three sections of the module. Work Index analysis of SAG-ball milling circuits was subsequently added as the fourth section of this module.

The estimated time to complete this module is 3.5 hours.

In this module, you will learn how to relate grinding efficiency to grinding costs and estimate the value of the grinding circuit product in your plant.  You will then be able to evaluate the effects of changes in plant tonnage and grind, and different ways of exploiting improvements in grinding efficiency.

At the end of the module, you will be able to:

• Identify the two major direct operating costs and the major source of indirect grinding costs in a flotation concentrator.
• Estimate the grinding cost savings and payback period on expenditures required for improving grinding efficiency.
• Calculate the value of the grinding circuit product in terms of recoverable minerals.
• Compare the economic benefits of various options for exploiting improvements in grinding efficiency.

The estimated time to complete this module is 3 hours.

The objective of this module is for you to familiarize yourself with hydrocyclone adjustments.  Specifically, you will learn how to:

• Select the diameter of the hydrocyclone apex to handle the slurry flow rate to underflow at an acceptable % solids and discharge pattern.
• Characterize the relationships between hydrocyclone feed pressure, capacity, and number of operating units.
• Characterize the relationships between the corrected cut-size, dimensions, and feed conditions of hydrocyclone installations in both open and closed circuit.

The estimated time to complete this module is 4 hours.

In this module, you will find a summary of the existing and required information you need on the grinding circuit in your plant to achieve improvements in grinding performance.  In particular, you will learn how to compile relevant existing data on grinding circuits and identify the data required from grinding circuit surveys.

This module is relatively short.  However, you will spend considerable time compiling information on the grinding circuit(s) in your plant for further use.  If you read this module attentively, information searching will be more productive, and you won’t waste time looking for information you don’t need.

If you are a metallurgist, you should have completed the following modules before completing this one:

• Introduction to the Metcom System
• Power and Charge Level Measurements
• Functional Performance of Ball Milling
• Grinding and Plant Economics
• Hydrocyclone Performance
• Slurry Pumping

If you are a technician, you should have completed the first module listed; you may have completed some or all of the other modules.

The estimated time to complete this module is 1 hour.

In this module you will learn how to handle and analyse ore and slurry samples.  At the end of this module you will be able to:

• Determine the % solids by weight of slurry samples.
• Prepare samples for further analysis.
• Divide samples.
• Conduct size analyses.
• Calculate size distributions.
• Plot sieve analysis results.
• Calculate the 80% passing size, K80, of a sample.
• Determine solids density.

There is no prerequisite to this module.  To complete the exercises, you will need a calculator that can perform logarithmic calculations. The estimated time to complete this module is 3.5 hours.

The objective of this module is for you to be able to perform Bond rod mill and ball mill grindability tests.

At the end of this module, you will be able to:

• Identify the apparatus for rod mill and ball mill tests and operate them correctly.
• Select the test control size.
• Prepare the test feed from the sample you collected.
• Calculate the test feed characteristics.
• Determine test parameters.
• Perform the work index tests.
• Calculate the grindability and Bond work index of the test feed.

The prerequisite to performing the Bond tests is the module entitled "Sample Handling and Analysis". The estimated time to complete this module is 2.5 hours.

In this module you will learn how to mass balance grinding circuit survey data using the Metcom Mass Balance Computer Program.

The prerequisite to this module is the module entitled “Plant Sampling Guide and Circuit Surveys”. The estimated time to complete this module is 1 hour.

Once you have completed this module, you will be able to evaluate existing and alternative ball mill circuit design and operating variables in terms of their effects on the classification system efficiency of a ball mill circuit.

In particular, you will learn:

• A strategy for making adjustments to the classification system of a ball mill circuit based on the functional performance equation.
• How to select hydrocyclone process design characteristics in order to improve classification system efficiency.
• How to estimate the increase in classification system efficiency that you will achieve from specific adjustments to the classification system.

The prerequisites to this module are the following:

• "Functional Performance of Ball Milling" (Module 5)
• "Hydrocyclone Performance" (Module 7)
• "Hydrocyclone Adjustments" (Module 8)
• "Slurry Pumping" (Module 9)

In addition to the above prerequisites, see “Grinding and Plant Economics” (Module 6) to determine the economic benefits of increased classification system efficiency. The estimated time to complete this module is 2.5 hours.

Once you have completed this module, you will be able to evaluate existing and alternative grinding circuit arrangements in terms of their effect on grinding circuit efficiency.

In particular you will learn:

• The relative advantages/disadvantages of selecting a rod mill versus a ball mill for the first stage of grinding following the crushing plant.
• The relative advantages/disadvantages of ball mill grinding to a desired product size in one versus two stages of grinding.
• How to identify and estimate the potential advantage of adjusting the grind size between stages of grinding.
• The relative advantages/disadvantages of using two-stages of hydrocycloning in a closed ball milling circuit.

Before doing this module, be sure you have previously completed:

• “Introduction to the Metcom System”
• “Rod and Ball Mill Power Draw”
• “Work Index Efficiency”
• “Functional Performance of Ball Milling”
• “Grinding and Plant Economics”
• “Evaluation of Rod Milling”
• “Evaluation of Circuit Classification”
• “Evaluation of Ball Mill Grinding”

The estimated time to complete this module is 4 hours.

This module will present to you the Metcom methodology for AG/SAG circuit processing performance evaluation and improvement.

When you have completed this module, you will be able to:

• Calculate the approximate power draw of AG/SAG mills given basic design and operating conditions. (Preface 1)
• Determine volumetric loading of an AG/SAG mill, and the relationship between power draw and volumetric loading of ore and balls. (Preface 2)
• Determine the Work Index efficiency of AG/SAG – ball mill circuits, as well as that of each stage of these circuits. (Preface 3)
• Define and use terminology specific to AG/SAG; outline common circuit arrangements; and describe two key findings from early development of AG/SAG technology.
• Describe and utilize a ‘framework’ for evaluating AG/SAG circuit performance.
• List circuit design and operating variables and describe experts’ recommendations regarding each.
• Plan and conduct evaluations of your circuit using the methods presented and following the examples provided.

The estimated time to complete this module is 4 hours.

Este módulo lo introducirá al tema de la demanda de potencia de molinos de barras y molinos de bolas. Please note, that this module was originally created for plants with rod and ball mills. Those types of mills are very similar in that the steel media dominate their power draw characteristics. Rod and ball mill power draw calculations are covered in Parts I and II. Subsequently, AG/SAG mill power draw calculations were added, and presented in Part III.

 Al final de éste módulo, usted será capaz de:

• Diferenciar entre el “consumo de energía” y la “demanda de potencia” en los molinos.
• Calcular la demanda de potencia aproximada en molinos de barras y en molinos de bolas dados los diseños básicos y las condiciones de operación.
• Especificar significados prácticos (y limitaciones) para incrementar la demanda de potencia de los molinos de barras y molinos de bolas en la planta.
• Specify practical means (and limitations) to increase the power draw of operating rod mills and ball mills in the plant.

En este modulo no tiene pre-requisitos y lo único que necesita es una calculadora científica para hacer los cálculos.

Este módulo contiene dos revisiones: una después de la introducción y la otra al finalizar el módulo. El tiempo estimado para completar este módulo es dos horas. Esto incluye los dos repasos.

En este módulo, usted aprenderá sobre cálculos de índices de trabajo para evaluar la eficiencia de los circuitos de molienda que están basados en el método desarrollado por el Señor Fred Bond.

Después de completar este módulo, usted podrá:

• Identificar los límites de los diferentes modelos de circuitos de moliendas.
• Calcular el índice de trabajo operacional de un circuito de molienda.
• Calcular la eficiencia del índice de trabajo de un circuito de molienda.
• Indicar la exactitud de eficiencias comparativas en el índice de trabajo de circuitos de molienda.
• Calcular el índice de trabajo operacional y la eficiencia del índice de trabajo de molienda con los diferentes tipos de circuitos.

El pre-requisito para este modulo es “Introducción al Sistema Metcom”. Para completar el módulo, usted necesitará una calculadora científica. El tiempo estimado para completarlo es de dos horas y media. Esto incluye un repaso al final del modulo.

English version:

Note that this module was originally produced for sponsoring companies that used only rod and ball mills. These are covered in the first three sections of the module. Work Index analysis of SAG-ball milling circuits was subsequently added as the fourth section of this module.

The estimated time for completion three and a half hours

En este módulo, usted aprenderá como relacionar eficiencia de molienda con costos de molienda y estimar los valores del producto del circuito de molienda en su planta. Usted podrá evaluar los efectos de cambios en el tonelaje de la planta, la molienda, y sobre las diferentes maneras de aprovechar las mejoras en la eficiencia de molienda.

Al final del módulo, usted podrá: 

• • Identificar los dos costos directos de operación mayores y la mayor fuente de costos de molienda indirectos en un concentrador de flotación. 

• • Estimar los ahorros de los costos de molienda y los periodos de reembolso en gastos requeridos para mejorar la eficiencia de molienda. 

• • Calcular el valor del producto del circuito de molienda en términos de minerales recuperables. 

• • Comparar los beneficios económicos presentados por las diversas opciones para sacarle provecho al incremento en eficiencia de molienda.

El módulo prerrequisito para este módulo es “Introducción al Sistema Metcom”

Al final de este modulo encontrará un Repaso, usted necesitará una calculadora científica para completar el modulo. El tiempo estimado para completar el módulo es de tres horas, esto incluye el repaso.

El objetivo de este módulo es que usted se familiarice con los ajustes del hidrociclón. Específicamente, usted aprenderá como:

• • Seleccionar el diámetro del ápex del hidrociclón para manejar la velocidad del flujo de la pulpa a bajoflujo en un  % de sólidos aceptable y patrones de descarga.
  • Caracterizar la relación entre la presión de alimentación del hidrociclón, la capacidad, y el número de unidades en operación.
  • Caracterizar la relación entre el tamaño de corte correcto, las dimensiones, y las condiciones de alimentación de las instalaciones del hidrociclón en circuito abierto y cerrado.