Can you think of a configuration in a mill where gravity could be employed to save the mill energy?

In my column last week, our survey asked, "Can you think of a configuration in a mill where gravity could be employed to save the mill energy?"

Responses:

If we know what a pump of a certain size costs - say ten-year cost,for everything: base, wiring, motor, pump, inspection and maintenance, drive energy - maybe engineers who can't imagine a project without pumps would be motivated (or forced by the owner) to use gravity (and accurate sizing) to minimize the number (and size) of pumps in a project. Modern fluid mechanics modeling and variable speed motors allow precise pump design - a rarity in pulp and paper mills where I'd venture >75% of pumps are at least 30% oversize.

First thought - gravity was used in virtually all wind powered grinding mills. Green-field sites should be located on the valley sides above the water source. Gravity will assist the pumping of stock and transfer water well but serious consideration must be given to solids settlement when velocities are low.

Sedimentation tank

You may take this week's quiz here.