A double-belt system for processing viscous melts includes a driven upper belt having a lower working run, and a driven lower belt having an upper working run spaced beneath the lower working run to form a gap therewith for receiving a viscous melt. A gap-adjusting mechanism includes upper rollers engaging an upper surface of the lower working run, and lower rollers engaging a lower surface of the upper working run. A distance between the upper rollers and lower rollers is adjustable to vary a size of the gap. A compensation mechanism is disposed over the lower working run to apply an upward force thereto for pulling the lower working run against the upper rollers, thereby resisting sagging of the lower working run. At least one delivery mechanism applies a temperature-controlled liquid across an entire width of the lower working run for controlling a temperature thereof. The liquid is extracted by an extraction mechanism disposed downstream of the delivery mechanism. Vertically adjustable stops are provided for determining a vertical position of respective ones of the upper rollers.