Continuous Flowing Pre-Treatment System with Steam Recovery

• US 20080064906A1
• Filed: 09/30/2005
• Published: 03/13/2008
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: Iogen Energy Corporation (Iogen Corporation)
• Original Assignee: Iogen Energy Corporation (Iogen Corporation)
• Inventors: Rea, David, Anand, Vijay, Foody, Brian
• Granted Patent: US 8,017,820 B2
• Time in Patent Office: Days
• US Class Current: 585/242
• CPC Class Codes: C12P 19/02 Monosaccharides 2-ketogulonic acid C12P7/60
• CPC Class Codes: C12P 19/14 produced by the action of a carbohydrase (EC 3.2.x), e.g. by alpha-amylase , e.g. by cellulase, hemicellulase
• CPC Class Codes: C12P 2201/00 Pretreatment of cellulosic or lignocellulosic material for subsequent enzymatic treatment or hydrolysis
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

The present invention is directed to a continuous process for pretreating a lignocellulosic feedstock. A feedstock slurry is provided, which has a solids concentration of 10% to 33% by weight. The feedstock slurry is pumped through a heating train of at least two stages, each stage including a pump to increase stage pressure and a direct steam injection to heat the feedstock slurry. Acid is also added to the feedstock slurry prior to the heating train, during a heating stage, or after leaving the heating train; the acid is added at a concentration of 0% to 12% weight of acid on weight of initial feedstock. A heated, acidified feedstock slurry is thus produced. The heated, acidified feedstock slurry is flowed through a pre-treatment reactor at a temperature of 160° C. to 280° C. for a time sufficient to increase efficiency of conversion of cellulose in the feedstock to glucose using cellulase enzymes. After the slurry exits the pre-treatment reactor, it is cooled using two, or more than two flashing stages at successively lower pressures, without intermittent increases in pressure. The steam energy, at or near its flash temperature, from two or more than two of the flashing stages is used to heat the feedstock slurry in the heating train.

Claims

1. A continuous process for pre-treating a lignocellulosic feedstock, comprising:

(a) providing a feedstock slurry having a solids concentration of 8% to 30% by weight;

(b) pumping the feedstock slurry through a heating train of two, or more than two heating stages, each heating stage including a pump to increase heating stage pressure and a direct steam injection to heat the feedstock slurry;

(c) adding acid to the feedstock slurry prior to the heating train, during a heating stage, or after leaving the heating train, the acid added at a concentration of 0% to 12% weight of acid on weight of initial feedstock, to produce a heated, acidified feedstock slurry;

(d) flowing the heated, acidified feedstock slurry through a pre-treatment reactor at a temperature of 160°

C. to 280°

C. for a time sufficient to increase efficiency of conversion of cellulose in the feedstock to glucose using cellulase enzymes;

(e) cooling the slurry after the slurry exits the pre-treatment reactor, using two, or more than two flashing stages at successively lower pressures, without intermittent increases in pressure;

(f) using steam energy from two or more than two of the flashing stages, at or near its flash temperature, to heat the feedstock slurry in the heating train.

2. The process of claim 1, wherein in the step of providing (step a), the feedstock is selected from the group consisting of agricultural waste, corn stover, wheat straw, oat straw, barley straw, canola straw, and soybean stover;

grass, switch grass, miscanthus, cord grass, and reed canary grass.

3. The process of claim 1, wherein in the step of providing (step a) the feedstock is slurried in water.

4. The process of claim 3, wherein in the step of pumping (step b) the heating train consists of 3 to 8 heating stages.

5. The process of claim 4, wherein the step of cooling (step e), comprises 3 to 8 flashing stages.

6. The process of claim 5, wherein the slurry is cooled from about 30°

C. to about 70°

C. after a final flashing stage.

7. The process of claim 1, wherein in the step of adding (step c), the acid is selected from the group consisting of sulphuric acid, sulfurous acid, and sulfur dioxide.

8. The process of claim 1, wherein in the step of adding (step c) the acid is added to the feedstock slurry prior to the heating train.

9. The process of claim 1, wherein in the step of adding (step c) the acid is added to the feedstock slurry after the heating train.

10. The process of claim 1, wherein in the step of adding (step c) the acid is added to the feedstock slurry in a final heating stage.

11. The process of claim 1, wherein after the step of providing (step a) and before the step of pumping (step b), the feedstock slurry is reacted at a temperature of less than about 170°

C. in the present of about 0.5% to about 3% sulfuric acid to hydrolyze the hemicellulose.

12. The process of claim 1, wherein after the step of cooling (step e), the slurry is submitted to enzymatic hydrolysis.