Reclaim belt feeders can produce feed from back or front of the hopper depending on the pressure exerted by the charge above the exit plane.

In most cases we see rear end recovery, as wished to prolong belt life, minimize power, and maintain a tendency toward mass flow.

Long slot feeders tend to recover from the front if there is insufficient pressure on the rear zone of the charge to gain traction. When this occurs, power and belt wear degrade the expectations. When ore is reclaimed from the front much of the ore in the rear zone slips on the belt surface in preference to the ore feeding from the front.

So a question can be asked, how to achieve sufficient pressure to provide more uniform mass flow or flow from the rear? This is a topic of good feeder design. As you suggest, how does one pick the slot length, slot tapers, exit height, belt width, belt speed, skirt design, et al. ■

The last time I looked up Shamlou's book he had gathered about 7 slightly different equations for discharge through hopper outlets. All could be right or all could be wrong. Evidence is that if the choice of slot size, for the required discharge, is reasonably correct then the extraction should be from the back. Otherwise why have a slot at all?

Exigent material expands as it leaves the slot under gravity & this reduces the stiction effect. If the feeder is extracting from the front then the slot isn't working because it's too near the belt. ■