Bei hydrolysis process system an improved process for the continuous hydrolysis saccharification of ligno-cellulosics in a two-stage plug-flow-reactor system

• US 5,411,594 A
• Filed: 07/08/1991
• Issued: 05/02/1995
• Est. Priority Date: 07/08/1991
• Status: Expired due to Term

• Current Assignee: Brelsford Engineering, Inc.
• Original Assignee: Donald L. Brelsford
• Inventors: Brelsford, Donald L.
• Primary Examiner(s): RICE, KENNETH R
• Assistant Examiner(s): Hailey, P. L.
• Application Number:
  US07/736,949
• Time in Patent Office: 1,394 Days
• Field of Search: 127/37, 127/1, 127/2
• US Class Current: 127/37
• CPC Class Codes: B01J 19/242 in series
• CPC Class Codes: B01J 2219/00114 involving reactant slurries
• CPC Class Codes: B01J 2219/00159 controlling multiple zones along the direction of flow, e.g. pre-heating and after-cooling
• CPC Class Codes: B01J 2219/00162 controlling the pressure
• CPC Class Codes: B01J 2219/00164 controlling the flow
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32

Abstract

An improved two-stage dilute-acid hydrolysis process and apparatus the continuous saccharification of ligno-cellulosic biomass, or other cellulosic material feedstocks, with higher efficiency and better economics than known art, is disclosed. It comprises two double-tube heat-exchanger and plug-flow-reactor systems, in series. The improved process is primarily by reverse interstage transfer-flow, opposite to biomass, of second-stage surplus of: 1. process heat, 2. dilute- acid and 3. ingredient and solution water, all in an alpha cellulose hydrolysate, dilute-acid solution. It also comprises recycle of a fraction of unhydrolyzed alpha-cellulose hydrolysis residue, thereby achieving higher hydrolysis conversion of alpha-cellulose to glucose; and providing: 1. lower hydrolysate sugar decomposition, 2. reduced reaction time and 3. increased reactor processing capacity, without increased dimensions. The process is ideal for process control to efficiently produce a primary final liquid product, which is the combined hydrolysate sugars into a single solution, including pentose, hexose and glucose sugars, which are readily fermented into Ethanol and/or Torula Yeast. The secondary final solid product is the resulting net unhydrolyzed lignin residue solids.

Claims

1. A two-stage dilute-acid hydrolysis process for the continuous saccharification of ligno-cellulosic biomass feedstock to produce hydrolysate sugars, comprising the following steps:

(a) substantially continuously admixing, in a first-stage, a lignocellulosic biomass feedstock and a dilute mineral acid to form an aqueous preheated feedstock slurry, of about 10 to 20 wt % solids, whereas said dilute mineral acid is in a hot pressurized aqueous solution, supplied by reverse interstage transfer from a second stage, said dilute mineral acid consisting of an alpha cellulose hydrolysate and dilute mineral acid in aqueous solution;

(b) introducing said preheated feedstock slurry into one end of a first tubular reactor and constricting the other end of said reactor so as to develop a back pressure therein;

(c) receiving indirectly into said aqueous feedstock slurry sufficient process heat supplied-by reverse inter-stage transfer of said second-stage flash-steam to heat and maintain said slurry at a pressure ranging from about 45 to 200 psia and at a temperature ranging from about 135°

to 195°

C. saturated steam equivalent;

(d) passing said heated feedstock slurry of step (c) into and through a reaction zone in said first tubular reactor, the length of said reaction zone and the flow rate of said heated slurry introduction being so selected as to afford an average reaction zone detention time of about 1.0 to 20 minutes;

(e) producing hemicellulose hydrolysate sugars in said reacting slurry;

(f) substantially continuously discharging and flashing said reacting slurry, thereby cooling by reducing the pressure and temperature of said reacting slurry, and also substantially continuously generating a first stage flashed steam supply;

(g) thereafter separating said flashed slurry into;

1.) a combined hydrolysate solution, and 2.) an unhyrolyzed hemicellulose hydrolysis residue;

(h) recovering said combined hydrolysate solution, which includes therein said hemicellulose hydrolysate sugars, said alpha cellulose hydrolyzate sugars, and said dilute-acid, thereby producing a single-solution final product of said saccharification.

(i) admixing, within said second stage, a blend of said unhydrolyzed hemicellulose hydrolysis residue, and of a recycled up-to 50 wt % fraction of an unhydrolyzed alpha cellulose hydrolysis residue, with a fresh preheated dilute mineral acid solution, to form a partially heated aqueous alpha cellulose hydrolysis slurry, of about 10 to 20 wt % solids, whereas said dilute acid is continuingly preheated by a first stage flash steam supply;

(j) introducing said aqueous preheated slurry into one end of a second tubular reactor and constricting the other end of said reactor so as to develop a back pressure therein;

(k) receiving indirectly into said aqueous alpha cellulose hydrolysis slurry, suficient process heat, by way of a high temperature fresh process heat supply, to heat and maintain said aqueous slurry at a pressure ranging from about 100 to 200 psia and to a temperature ranging from about 165°

to 260°

C. saturated steam equivalent;

(l) passing said heated slurry into and through a reaction zone in said tubular reactor, the length of said reaction zone and the flow-rate of said heated slurry introduction being so selected as to afford an average reaction zone detention time of about 0.5 to 20 minutes;

(m) producing alpha cellulose hydrolysate sugars in said heated slurry in the presence of said dilute acid;

(n) there after continuously discharging and flashing said reacting slurry, thereby cooling and reducing it'"'"'s pressure and temperature and generating a second stage flashed steam supply.

(o) separating said flashed slurry into;

1.) a hot reduced pressure alpha cellulose hydrolysate and dilute acid solution, and 2.) an unhydrolyzed alpha cellulose and lignin residue solids;

(p) recovering said hydrolysate and dilute acid solution, whereupon continuously transferring said solution to said first stage for admixing to slurry;

(q) recovering said unhydrolyzed alpha cellulose and lignin residue, whereupon continuously fractionating said residue, thereby an up to 50 wt % fraction is recycled within second stage and blended with said unhydrolyzed hemicellulose hydrolysis residue from said first stage, thereafter admixing said blend to said second stage slurry, whereby said remaining fraction is a unhydrolyzed alpha cellulose lignin residue and is the final solid product of said saccharification.

2. Process according to claim 1 wherein said first stage flashed steam supply is generated with a pressure of about 15 to 30 psia and a temperature of about 100°

to 120°

C. saturated steam equivalent.

3. Process according to claim 1 wherein said second stage flashed steam supply is generated with a pressure of about 45°

to 200 psia and at a temperature of about 135°

to 200°

C. saturated steam equivalent.

4. Process according to claim 3 further comprising continuously supplying said hemicellulose hydrolysis processing process heat by reverse interstage transfer to said first stage by continuously adding the flashed steam supply of step (n).

5. Process according to claim 1 wherein said dilute mineral acid is selected from the group consisting of sulfuric acid, sulfurous acid, and phosphoric.

6. Process according to claim 1 wherein said feedstock is selected from the group consisting of ligno-cellulosic biomass, soft wood, hard wood, wood wastes, logging slash, crop residues, sugar cane baggase, and rice hulls.

7. Apparatus for a two-stage dilute-acid hydrolysis process for the continuous saccharification of feedstocks selected from the group consisting of lignocellulosic biomass and cellulosic materials to produce monosaccharide hydrolysate sugars, wherein the first stage comprises:

(a) admixing means for a fresh feedstock and a hot, pressurized dilute-mineral-acid solution, forming a preheated aqueous fresh feedstock slurry, wherein said dilute acid solution consists of a hot pressurized alpha cellulose hydrolysate and a dilute-acid in-water solution, being supplied by a reverse interstage transferring means from said second stage;

(b) pumping and pressurizing means for the introduction of said feedstock slurry into one end of an inner tube of a plug flow reactor in a double-tube, heat-exchanger, plug-flow-reactor system, wherein said inner-tube has a constricting means at the other end, so as to develop a back pressure therein;

(c) indirect process heating means for whereby supplying second stage flashed steam, by a reverse, interstage transferring means, indirect heat transferring means for heating said pressurized slurry, thereby sufficiently providing for hemicellulose hydrolysis processing, at a saturated pressure ranging from about 45 to 200 psia and at a temperature ranging from about 135°

to 195°

C., within said plug flow reactor, and with a pumping rate control means for meeting the required flow rate of said heated slurry within the said plug flow reactor, thereby meeting the required reacting slurry detention time;

(d) reacting slurry discharging and flashing means for cooling by reducing said reacting slurry pressure and temperature and for generating said first stage flashed steam supply;

(e) flashed slurry separating means for providing recovery of;

1.) a combined hydrolysates single-solution final product and 2.) an unhydrolyzed hemicellulose hydrolysis residue;

(f) means for supplying said unhydrolyzed hemicellulose residue into said second stage, means for blending, an up-to 50 wt % fraction of said unhydrolyzed alpha cellulose residue, and said unhydrolyzed hemicellulose for admixing a fresh pre-heated dilute-acid in-water solution, and said unhydrolyzed hemicellulose thereby forming an alpha cellulose hydrolysis feedstock slurry;

(g) slurry pumping and pressurizing means for introducing said alpha cellulose hydrolysis feedstock slurry, into an inner tube of a plug flow reactor;

(h) high temperature process heat supplying means and an indirect heat exchanging means, for providing sufficient indirect process heat to said alpha cellulose hydrolysis slurry;

(i) partially flashing and reduced pressurizing means for reacting slurry, and said generated flashed steam and a recovering means for said reduced pressure and temperature slurry;

(k) separating and recovering means for said slurry as a reduced-pressure alpha cellulose hydrolysate and dilute-acid solution and an unhydrolyzed alpha cellulose lignin residue solids;

(l) pressurized slurry pumping means for reverse inter stage transfering of said reduced pressure alpha cellulose hydrolysate and dilute-acid solution.

8. Apparatus according to claim 7, further including a surplus flashed steam recovering means, in each stage separately, and also including a pressurized slurry flashing tank means connected by a blow-pipe means.

9. Apparatus in claim 7, wherein further including a centrifugal slurry separating means for removal and recovery of unhydrolyzed solids residue.

10. Apparatus according to claim 7 further including a second stage recovering and means for the unhydrolyzed alpha cellulose unhydrolysis residue, and a fractionation means, and further comprising a conveying means.