Abstract: A continuous hydrolysis process for the hydrolysis of wood and wood derived products into sugars and other products, wherein woodchip or other feedstock is formed into a slurry which is acidified, pressurized and heated before being hydrolyzed in reactors J. Three heat exchangers L1, L2 and L3 form a closed circuit in which exchanger L2 recovers heat from the slurry, L1 returns heat to the slurry and L3 makes up lost heat. The slurry is cooled before pressure reduction by pressure reducing means N and separation of the solids and liquid. The cooling prevents flashing to steam of part of the liquid in the slurry so that the process is single phase where generation of steam is avoided. After separation the solids can proceed to further processing or to discharge as lignin as indicated by arrow B. The liquid can proceed to further processing or discharge as indicated by arrow D.