Systems and methods for step grinding

A system for grinding a particulate material, the system comprising:

• a roller mill apparatus including a pair of rotatable grinding mill rolls to grind the particulate material, the pair of mill rolls being positioned adjacent to each other in a manner defining an adjustable gap therebetween for the passage of the particulate material therethrough, the roller mill apparatus including at least one roller mill motor connected to at least one of the mill rolls to rotate the mill roll;
• a hammermill apparatus including a rotatable rotor and a plurality of hammers mounted on the rotor to shred the particulate material passing through the hammermill apparatus, the hammermill apparatus including a hammermill motor connected to the rotor to rotate the rotor and the hammers;
• and
• a control apparatus controlling operation of elements of the roller mill apparatus and the hammermill apparatus, the control apparatus is configured to:
• adjust a feed rate of particulate material to the roller mill apparatus to cause power consumption by operation of the roller mill apparatus to move toward a target power consumption for the roller mill apparatus;
• and
• adjust a gap between the mill rolls of the roller mill apparatus until the power consumption by operation of the hammermill apparatus achieves a target power consumption for the hammermill apparatus.