the invention concerns a method for separating solid and liquor components of a process slurry comprising solid material entrained in a liquor , said method comprising : a pre - treatment step of adding a flocculent to the process slurry and mixing the flocculent and the slurry by selecting a higher extent of mixing in an early stage of said step than in a later stage of said step , and a solid / liquor separation step of allowing separation of solid material , including aggregates of solid material , and liquor of said process slurry to produce process outputs of a clarified liquor and solid material with some entrained liquor . the invention also concernes a method and an apparatus for adding a flocculent to a process slurry .