Determining the Bond Efficiency of Industrial Grinding Circuits

Working Group: Mineral Processing
Status: Current

This guideline describes the Bond method for quantifying and comparing the relative energy efficiency of most industrial comminution circuits.

The objective of this guideline is to provide a benchmark metric for the specific energy requirements of an industrial grinding circuit, in comparison with a standard circuit designed with a set of standardized laboratory tests. Additionally, the actual plant circuit and can deploy any type of size reduction equipment, allowing this tool to be used by operators and designers to benchmark the energy efficiency of any size reduction circuit, over the applicable size reduction range, that exists in the industry. Examples of calculation of the Actual Operating Bond Work Index (WioACT) and Wi Efficiency Ratio for different industrial circuits are provided.

This document also intends to provide guidelines to standardize Bond test equipment and procedures to minimize the testing experimental error, minimizing plant Bond Efficiency measurement error and maximize the usefulness of this efficiency value for performance benchmarking and process improvement.

The guideline provides further explanation on:

  • The Work Index (Wi), defined by Bond as the comminution circuit equipment’s needed specific energy input (W, in kWh/t) to reduce ore from a very large size (80% passing, or an F80 of infinity) to a circuit product size of 80% passing (a P80 of) 100 μm. Bond’s work index equation then relates all size reduction processes back to this value based on the observation that specific energy is related to the inverse of the square root of the circuit feed and product sizing.
  • The design energy (W) input delivery requirements for new plants and the laboratory tests that were developed and scaled to a large database of plant (crushing, rod, and ball milling) equipment specific energy usages along with the outcome of these tests such as the Standard Circuit Bond Work Index (WiSTD) values for various equipment including ore crushers, rod milling, and ball milling.