Method of countercurrent acid hydrolysis of comminuted cellulosic fibrous material

  • US 4,668,340 A
  • Filed: 03/20/1984
  • Issued: 05/26/1987
  • Est. Priority Date: 03/20/1984
  • Status: Expired due to Fees
First Claim
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1. A method of prehydrolyzing comminuted cellulosic fibrous material to remove hemi-cellulose and sugars therefrom, and utilizing a generally vertical substantially liquid-filled vessel, comprising the steps of:

  • (a) feeding comminuted cellulosic fibrous material suspended in liquid to a top portion of the vessel;

    (b) effecting countercurrent acid hydrolysis in a top zone of the vessel, as the material passes downwardly in the vessel;

    (c) withdrawing liquid containing hydrolysate, including hemi-cellulose and sugars, from the top of the acid hydrolysis zone of the vessel, and recirculating the liquid to be fed back to the top of the vessel in step (a);

    (d) diverting a part of the liquid, containing hydrolysate, withdrawn in step (c);

    (e) flashing the diverted liquid from step (d) to produce steam and a high concentration hydrolysate liquid;

    (f) effecting countercurrent washing of the material after the acid hydrolysis zone;

    wherein the washing takes place in the vessel in a washing zone below the acid hydrolysis zone; and

    wherein step (d) is practiced by;

    withdrawing liquid from a central portion of the vessel, between the hydrolysis reaction zone and the washing zone thereof;

    adding fresh mineral acid to the liquid withdrawn at the central portion of the vessel;

    heating the withdrawn liquid; and

    reintroducing the withdrawn liquid in the vessel at the interface between the hydrolysis reaction zone and the wash zone, so that the acid flows upwardly in the hydrolysis reaction zone, countercurrent to the material.

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