Provided is an apparatus for digesting cellulosic material that includes a vessel containing a digestion chamber and having an opening that provides access to the digestion chamber. A container for holding the cellulosic material is located within the digestion chamber. A closure interfaces with the vessel opening to form a seal against a predetermined digestion pressure and temperature within the chamber. A fluid-transporting system directs digestion fluids from a supply in the digestion chamber through a port and the container toward any cellulosic material therein. Digestion fluid distributed from the port through the container soaks the cellulosic material. Also provided are processes for digestion cellulosic material.