Abstract: The invention is directed to a process and apparatus for drying a slurry, particularly a sludge, such as sewage sludge, in which a sludge mixture of recycled dried sludge and wet sludge is fed to a drier. The quantity of wet sludge or recycled dried sludge supplied to the drier is controlled based upon drier inlet temperature. In this way, the evaporation rate of the drier is kept substantially constant.