retrieve the grains gone with the hulls and the bran

In the US the hulls or chaff is removed by the combine in the field. Where it is ether tilled under or collected and milled for animal feed. As I understand the equipment involve to mill it and its value is not to profitable. So what little grain is left in it lends to its nutritional value as feed. I do not think that there is enough grain in it to warrant expending resources to clean it again. If there is that much grain in the chaff that you customer believes he can profit from the re-cleaning I would look at the machinery that is doing the initial cleaning.

Most of these machines separate the chaff and the bran with blowers. Both of which are lighter than the grain. May be able to replace the blower motor with a variable speed to control the amount of grain blown it to these.

you can use flour milling machine to retrieve the grains gone with the hulls and the bran.

Sure there is. You need a sorter. Talk to Satake. http://www.satake-usa.com/