Patent ID: 9260818
Filing Date: 2016-02-16
CPC Classification: D21C

Claim Text:
1. A method to produce pulp from cellulosic material comprising: introducing cellulosic material to an upper inlet of a pressurized reaction vessel; adding pressure and heat energy to the vessel; hydrolyzing the cellulosic material in a hydrolysis zone of the reaction vessel, wherein a temperature in the hydrolysis zone is at least 150 degrees Celsius; extracting hydrolysate and liquid from the cellulosic material through a hydrolysate and liquid extraction screen below the hydrolysis zone and above a cooling zone of the vessel; introducing a cooling liquid to the cooling zone, wherein the cooling liquid suppresses hydrolysis of the cellulosic material in the cooling zone and the cooling liquid is essentially sulfur free, and wherein at least a portion of the cooling liquid flows upward through the cellulosic material to and is extracted by the extraction screen; digesting the cellulosic material in a cooking zone below the cooling zone by injecting a cooking liquor in the cooking zone, wherein the cooking liquor includes sulfur containing chemicals and the cooking liquid is not introduced into the vessel in the hydrolysis zone or the cooling zone; discharging the digested cellulosic mater from a discharge port of the vessel wherein the port is below the cooking zone, and wherein the cooling liquid is a mixture of water and at least one of sodium hydroxide and essentially sulfur free white liquor.