Problem about low capacity of VRM for coal

Dear Expert!

can anyone hepl us. our coal mill (VRM of Loesch) just running after maintenance, but when restart we can not increase the capacity (now the capacity is about 10 T/h - design: 20 T/h of anthracite). the VRM when running is not vibration, the layer of material between roller and table quite stable and low (we had adjusted the clearance between roller and table to minimum), the power consumption of Motor for coal mill low ( ~200 kw - design: 400 kw). the difference pressure of the mill high (raw coal fall to the box under table a lot). we checked the chute of material to the table, is ok (type of feed material is screw- design: material feed at the edge of table, between rollers, but now we modified to expend the feed near the center of table), adjust the operation mode (the draft of mill fan, classifier, hydraulic pressure of roller, mill feed...) but the vibration of VRM still not high and quite stable.(the finess of product adjust easy by adjusted the speed of classifier).

What is the problem? Any one have solution for this matter?

thank you.