Methods and systems for promoting hydrogen gas distribution within cellulosic biomass solids during hydrothermal digestion

A method comprising:

• providing cellulosic biomass solids in a hydrothermal digestion unit, a first portion of the cellulosic biomass solids being contacted by a continuous liquid phase and a second portion of the cellulosic biomass solids being contacted by a continuous gas phase;
• wherein a slurry catalyst capable of activating molecular hydrogen is present in the continuous liquid phase;
• supplying an upwardly directed flow of molecular hydrogen through the cellulosic biomass solids;
• heating the cellulosic biomass solids and the continuous liquid phase in the presence of the molecular hydrogen, thereby forming an alcoholic component derived from the cellulosic biomass solids;
• conveying at least a portion of the continuous liquid phase and at least a portion of the slurry catalyst through a fluid conduit external to the hydrothermal digestion unit to a location within the continuous gas phase that is above at least a portion of the cellulosic biomass solids;
• and
• after conveying the continuous liquid phase and the slurry catalyst, releasing them such that they migrate downward through the second portion of cellulosic biomass solids as a discontinuous phase within the continuous gas phase.

A biomass conversion system comprising:

• a hydrothermal digestion unit having a first zone and a second zone, the first zone being located below the second zone;
• wherein the first zone is configured to contain a continuous liquid phase and the second zone is configured to contain a continuous gas phase;
• wherein the continuous liquid phase contains a slurry catalyst therein;
• a fluid conduit external to the hydrothermal digestion unit configured to convey the continuous liquid phase from the first zone to the continuous gas phase in the second zone;
• and
• an inlet configured to provide upwardly directed gas flow in the first zone.