Dear kalsegowda,

Question: What is the effect of lining wearing on mill motor power,grinding media motion,flow of material and grindability?

Answer: I will try to break it down in parts:

1. Liner configurations do alter the grinding behavior of SAG,AG and Ball Mills including all your points.

2. There are other factors, associated with liner wear, that produce more or less effect on the grinding outcome such as: ■

sorry - must have hit a bad key - continuing



- a) ball size distribution

- b) feed size distribution

- c) mill end configuration

- d) slurry properties

- e) mill speed

- f) liner material properties

- g) initial liner-lifter shape

- h) product breakage properties

Breakage in Ball Mills is dependent on compression fracture and niping of product between balls and balls with walls. Product comminution can be improved by increasing the circulation rate of the product in the radial direction (ie. more probability of contacts between product and balls, and walls. This is often refered to as the Selection Function in the Population Balance Model per:

Metso Minerals Optimization Services:

http://www.metsominerals.com/

JKTech's JKSimMet:

http://www.jktech.com.au/

The initial shape of the liner is very important to grinding rate, power, and life, et al. Some compromises are necessary to obtain the best overall performance by selecting the initial shape that metamorphsis over its wear life in a predictable manner to optimize the objectives you stated.

Thus, I claim the liner wear can improve performance and it depends on many conditions some of which are noted above.

Unfortunately, the problem is complex and cannot be easily treated in this space. We have applied DEM (discrete Element Modeling) to classify the Selection Function of many mills and can identify the benefits of of the contributing attributes and their correlations with performance.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Dear Kalsegowda,

Liner wear will almost always reduce mill performance. In case of lifting liners the lift will be deminished, in case of classifying liners the media classification will be less effective.

It really depends upon the mill system: Wet or dry? SAG? Two-compartment? Type of grinding media?

Mill motor power goes down, grindability (or better: specific power consumption)goes up.

Regards ■