Method for continuous hydrolysis of pentose containing material and apparatus for implementing the method

Claim 2

Method for the continuous acid hydrolysis of pentosan-containing material in a hydrolysis vessel at a temperature between 80° C. and 120° C. and at a pH lower than 5 comprising recirculating at least two portions of the hydrolysate withdrawn from the hydrolysis vessel back into said vessel, said hydrolysate portions differing from one another in their respective acid concentrations, said portions of recirculated hydrolysate entering the hydrolysis vessel at the same or different levels and wherein a said hydrolysate portion having a lower acid concentration is supplemented with additional acid before returning to said vessel.

Claim 3

Method according to claim 1, wherein the pentosan-containing material is bagasse which is depithed by the hydrolysis, whereby the pith is detached from the fibres.

Claim 4

Method according to claim 1, wherein the solid, insoluble residue material is converted into cellulose, animal fodder or monosaccharides.

Claim 5

Method according to claim 1, wherein part of the departing hydrolysate is returned to the hydrolysis vessel at a point closer to the feed-in than to the feed-out of the raw material.

Claim 6

Method according to claim 1, wherein washing fluid is recirculated into the hydrolysis vessel together with the feed-in of raw material in a concurrent method or in the immediate vicinity of the feed-out in a countercurrent method.

Claim 7

Method according to claim 1, wherein the replacement of losses of fluid and acid takes place by additions to the washing fluid prior to its entry into the hydrolysis vessel.

Claim 8

Method according to claim 1, wherein the temperature is 100° C.

Claim 9

Method according to claim 1 wherein the solid residue resulting from the hydrolysis is subjected to further hydrolysis at a temperature between 140° C. and 180° C. whereby difficultly hydrolyzable pentosans are solubilized and pentose is converted to furfural.

Claim 10

Apparatus for the continuous hydrolysis of pentosan-containing material at a temperature between 60° and 120° C. and at a pH lower than 5 comprising a hydrolysis vessel with a feed-in means at one end and a feed-out means at the other end and a drain for hydrolysate, means for recirculation of concentrated hydrolysate at a point between the feed-in and feed-out of the raw material, and closer to the feed-in, means for returning of weaker hydrolysate, washing fluid, at a point immediately adjacent to the feed-in of the raw material in concurrent operation and immediately adjacent to the feed-out in countercurrent operation, wherein the feed-out means has been constructed so that the hydrolysis fluid is prevented from flowing out by a continuous plug formation from the hydrolyzed, solid matter.

Claim 11

Apparatus for the continuous hydrolysis of pentosan-containing material at a temperature between 60° and 120° C. and at a pH lower than 5 comprising a hydrolysis vessel with a feed-in means at one end and a feed-out means at the other end and a drain for hydrolysate, means for recirculation of concentrated hydrolysate at a point between the feed-in and feed-out of the raw material, and closer to the feed-in, means for returning of weaker hydrolysate, washing fluid, at a point immediately adjacent to the feed-in of the raw material in concurrent operation and immediately adjacent to the feed-out in countercurrent operation, wherein the feed-out means has been constructed so that the hydrolysis fluid is prevented from flowing out by a continuous plug formation from the hydrolyzed, solid matter.