Method for recovering concentrated hydrolysate after hydrolysis of cellulose material

A batch process for recovering concentrated hydrolysate after hydrolysis of lignocellulose material in batch digesters comprising the following stages in sequence;

• a. Subjecting the lignocellulose material to a steam phase hydrolysis wherein (1) the resulting total L/W ratio formed by steam condensate and lignocellulose moisture do not exceed 1.5 if the lignocellulose material only contains natural lignocellulose moisture before the steam phase hydrolysis or (2) the resulting total L/W ratio does not exceed 2.5 if the lignocellulose material has been subjected to washing or any corresponding liquid treatment with subsequent draining before the steam phase hydrolysis, and wherein the lignocellulose material is subjected to a first P-factor exposure during the steam phase hydrolysis resulting in a packing degree increase of at least 20%;
• b. Subjecting the lignocellulose material to a liquid phase hydrolysis by adding hydrolysis liquid covering the packed lignocellulose material from the steam phase hydrolysis wherein the total L/W ratio formed by a liquid content comprising steam condensate, lignocellulose moisture and added hydrolysis liquid does not exceed a range of from 2.5-3.5, and wherein the lignocellulose material is subjected to a second P-factor exposure during the liquid phase hydrolysis, and
• c. Recovering a hydrolysate after the liquid phase hydrolysis which hydrolysate corresponds to a volume of from 0.5-2.0 in total L/W ratio and which is diluted only by the added hydrolysis liquid;
• wherein total P-factor established in the steam phase hydrolysis and the liquid phase hydrolysis lies in the range of from 200-1500, and the first P-factor exposure is 50-95% of the total P-factor and the second P-factor exposure is 5-50% of the total P-factor.