Continuous processes for hydrolyzing hemicelluloses from ligocellulosic materials with cleaning system

A continuous process for producing hemicellulose sugars from a biomass extraction liquor, said process comprising:

• (a) providing or obtaining a biomass extraction liquor containing water, hemicellulose oligomers, and dissolved or suspended lignin;
• (b) optionally introducing an acid catalyst to said biomass extraction liquor;
• (c) for a first period of time, feeding said biomass extraction liquor through a first hydrolysis reactor under effective hydrolysis reaction conditions to hydrolyze said hemicellulose oligomers into hemicellulose monomers;
• (d) at a first switching time, diverting said biomass extraction liquor from said first hydrolysis reactor to a second hydrolysis reactor;
• (e) for a second period of time, feeding said biomass extraction liquor through said second hydrolysis reactor under said effective hydrolysis reaction conditions;
• (f) during said second period of time, cleaning said first hydrolysis reactor by introducing a cleaning agent selected from the group consisting of steam, an alkaline solution, an organic solvent, and combinations thereof, wherein said cleaning agent is effective to dissolve precipitated lignin formed from said lignin under said effective hydrolysis reaction conditions;
• (g) at a second switching time, diverting said biomass extraction liquor from said second hydrolysis reactor back to said first hydrolysis reactor or to a third hydrolysis reactor for hydrolyzing said hemicellulose oligomers into hemicellulose monomers, while concurrently cleaning said second hydrolysis reactor by introducing said cleaning agent to dissolve said precipitated lignin;
• and
• (h) repeating steps (c) to (g) a plurality of times, thereby continuously producing hemicellulose sugars from said biomass extraction liquor.