A process of both milling and drying a solvent-moist material (e.g., water-moist methylhydroxyethylcellulose) is described. The process includes, (a) providing a mill-dryer (100) which includes, in series, a heat exchanger (1), a mill (2) and a particulate separating apparatus (105) connected by conduits (8), (9) and (11, 12), which together define a mill-dryer circuit (103). The mill-dryer (100) also includes a bypass conduit (14), which provides optionally at least partial gaseous bypass of the heat exchanger (1). The process further includes: (b) introducing the solvent-moist material into the mill (2); (c) circulating a vapor stream (e.g., a steam/air stream) throughout the mill-dryer circuit (103); (d) heating the vapor stream by means of passage through the heat-exchanger (1); (e) forwarding milled particulate material from the mill (2) to the particulate separating apparatus (105) by means of conduit (9); (f) separating the particulate material from the vapor stream in the particulate separating apparatus (105); (g) forwarding the vapor stream from the particulate separating apparatus (105) through conduits (11, 12); and (h) controlling the temperature of the vapor stream by optionally forwarding at least some of the vapor stream through the bypass line (14).