Lignocellulosic biomass treatment method

A process for treating a lignocellulosic biomass comprising a solids content of not more than 90% by weight, said process comprising

• feeding the lignocellulosic biomass to an impregnation reactor (9) via a first feeder (6) wherein said first feeder is a plug screw feeder
• increasing the pressure between a biomass inlet and a biomass outlet of the first feeder (6), and
• wherein the second feeder (6) is washed by circulation of a washing fluid between a washing inlet (7) and a washing outlet (8), and
• wherein at least a portion of the washing fluid exiting the washing outlet of the first feeder (6) is reintroduced into the washing inlet (7),
• wherein the process additionally comprises:
• a) preparing an impregnation liquor (4) containing a chemical catalyst (2) suitable for impregnation of the lignocellulosic biomass (5), wherein the chemical catalyst (2) is an acid catalyst, a basic catalyst or an oxidizing catalyst, in a preparation zone (3),
• b) introducing the lignocellulosic biomass (5), which is milled, via an inlet of the impregnation reactor (9) by the first feeder (6), the first feeder being washed by circulation of a first washing fluid between an inlet and an outlet of the first feeder (6),
• c) introducing the impregnation liquor into the impregnation reactor (9) via a first impregnation liquor inlet of the impregnation reactor (9),
• d) draining and transferring the resultant impregnated biomass (10), from an impregnation reactor outlet to an inlet of a cooking pretreatment reactor (14), the introduction into the cooking reactor (14), which is a cooking pretreatment reactor, and which is a steam explosion reactor, taking place via a second feeder (11), the second feeder (11) being washed by circulation of a second washing fluid between an inlet and an outlet of the second feeder (11),
• e) pretreating the biomass (10) in the cooking reactor (14), which is,
• f) reintroducing at least a portion of the first and/or of the second washing fluid leaving the fluid outlet of said first or of said second feeder (6), (11) into a washing inlet of the first feeder (6) and/or of the second feeder (11).