Hi Samuel - welcome to 911,

Turbo Pulp Lifters have been shown to be effective at discharging slurry where other designs have failed.  I believe the Cortez gold mine had success with this design after struggling many years with slurry pooling in their SAG mill.

You will only achieve gains if your mill is suffering from ineffective discharge behavior, so it is important to evaluate fully what is the problem:

• If you currently have radial pulp lifters and you have a large diameter mill and/or are operating your mill at high speed (>80% C.S.) you may be unable to fully discharge your pulp lifters.
• If you are operating your mill with excessively low pulp density, there may be too much volume for your system to discharge (pump).  At ~75% solids, approximately half of the volume you discharge is water.
• If your grates are poorly designed, you may not be able to fill your pulp lifters - for example, if your grate features a tall "lifter", that "lifter" could be preventing slurry from contacting your grate surface (presumably to prevent wear and/or impact breakage).
• If your grate slots are too small, it could restrict discharge.  If slots are too large or too long, excessive reversion may be occurring.
• If your pulp lifters narrow to too small of an opening near the center, they may be getting blocked with coarse material.  If your pulp lifters are not deep enough, they may not have sufficient volume to carry the discharge amount required.

If you are able to share some of your operating parameters, we may be able to offer you advice more specific to your issue:  grate/pulp lifter designs (drawing or really good description); mill diameter and operating speed (rpm or %C.S.); typical pulp density (total feed/(total feed + water)); a description of the mill behavior that has you interested in the TPL system.

There may be a simpler (and cheaper) solution to the problems you are experiencing - we would be happy to help you evaluate.

Cheers, Craig

Hi Samuel,

Craig's information above is great and I would just like to add a comment based on our experience as a manufacturer of radial pulp lifters (Turbo Pulp I believe is a trademarked name for radial lifters).

Modelling is a very worthwhile exersize because in some cases the radial lifters actually evacuate too much slurry from the mill and as a result cause excessive wear on the lining and other issues.

Perhaps have as Craig has suggested provide detailed operating parameters and have DEM (Discrete Element Modelling) and FEA (Finite Element Analysis) done which will show the evacuation as well as expected wear points on the pulp lifters.

Cheers

Jim

Here is a good paper by OK on TPL.  Obviously they sell TPL's so it may not be completely objective but worth reading to gain some additional knowledge.

http://millingsolutions.com/wp-content/uploads/ccs/case-studies/CMP-2007_Latchireddi-on-Turbo-Pulp-Lifter-TPLTM-An-Efficient-Discharge.pdf

Regards

Samuel, here is an excerpt of a paper by https://www.linkedin.com/in/david-royston-02765013/

Modern Semi-Autogenous (SAG) Grinding Mills can be up to 12 metres in diameter (absorbing up to 20 MW of power) and need to discharge over 2500 tonnes per hour of solids via pulp lifters.

Pulp lifters take the form of a radial array of “box-section” channels mounted inside the discharge end wall of the mill. The number of pulp lifters used in conventional mill design is equal to the number of feet in the measure of the mill diameter.

Ground material flows into the pulp lifters via grates mounted on the outer part of the pulp lifter channels. As these channels rotate with the mill, they collect, lift and direct the captured “charge” towards the mill-centre and out through the external discharge trunnion, Figure 1.

Interpretation of Charge Motion in Pulp Lifters

Denlay et al (1997) reviewed the motion of the outer solid charge along a pulp lifter during a mill rotation cycle. The motive force is the component of the gravitational force acting radially inwards, it is opposed by the centrifugal force acting radially outwards. Friction opposes motion and is a function of the normal components of centrifugal force and gravity acting on the lifter and both static and dynamic friction factors. Discharge motion is initiated at points where the inward gravitational force exceeds opposing forces. The locus of all such points is a circle. For a mill operating at around 76% of critical speed, this circle has a diameter similar to the diameter of the mill. (Mill speed is expressed as percent of the critical speed at which outer layers of rocks in the mill would begin to centrifuge). From initiation of motion to TDC, i.e. the first stage of motion, the inward-discharging force is that of gravity opposed by both friction and centrifugal force. After TDC, the second stage of motion is entirely ballistic i.e. controlled by gravity alone. The third stage of motion follows the re-contact of the charge with the opposite side of the pulp lifter, motion from this point to discharge is promoted by gravity and opposed only by friction. The stages in the motion of the outer solid charge are shown in Figure 2.

This interpretation of solid motion indicates that, for straight radial pulp lifters, a significant part of the solid motion occurs after mill top dead centre (TDC). This contrasts with the more fluid components where (due to initial segregation and displacement of the liquid charge) the motion of liquids to the discharge trunnion can be complete around TDC.

Curved Pulp lifters assist the movement of the charge to the centre by initiating motion of the charge earlier than is the case with straight lifters. This moves the charge towards the centre of the mill where, relative to straight pulp lifters, it can be subject to earlier and stronger application of the inward motion gravity forces. In this action the curved lifter enables solids motion to imitate the levelling action of a fluid charge. The overall motion for curved pulp-lifters is illustrated in Figure 3.

This interpretation of solid charge flow is supported by field observation, including video of the discharge flow into trunnions of operating mills, and by the wear patterns due to slurry and solid flow in pulp lifters. The wear data from both curved and straight radial pulp lifters was reviewed by Royston et al (1998).