Abstract: Methods for continuous drying of sludges. Large scouring particles are added to a sludge to be dried to create a mixture which is passed through a rotary screw type indirect heat exchanger. The scouring particles are large relative to the particulates of suspended and dissolved solids which result from drying in the heat exchanger. During the process of drying and conveying the mixture through the heat exchanger the scouring particles continuously remove the particulate residue from the surfaces of the heat exchanger. It also appears that the particles assist in the actual heat transfer between the heat exchanger surfaces and the sludge by absorbing and subsequently releasing heat through relatively large surface areas. The scouring particles can be consumptive, that is, consumed in processes during subsequent handling of the residue, or nonconsumptive.