Thank you for this interesting application. We talked with some delumper experts first and all agreed if a high speed hammer or tooth hits the large lumps they will tend to disintegrate to their elemental size. We believe the simplest solution would be a jaw crusher type mill set slightly larger than pea size. You would still get some fines but not nearly as many.

A more elegant but more expensive solution with a near 100% yield would be to delump the material and then pass it through a granulator to compact it all to a uniform pea size. Good luck with your project.