Moving bed biomass fractionation system and method

Abstract

Countercurrent extraction of lignocellulosic biomass such as trees, grasses, shrubs, and agricultural residues or waste involves the separation of cellulose fibers from other constituents, for subsequent use in the manufacture of paper, plastics, ethanol, and other industrial chemicals. Systems and methods involve continuous, multiple processing steps that may include chemical reactions with mixing at elevated temperature and/or pressure, efficient reagent or solvent utilization, filtration at elevated temperature and/or pressure, controlled discharge of liquid and solid products, and energy recuperation.

1 . A continuous, countercurrent process of one or more stages for the fractionation of a lignocellulosic biomass feedstock, comprising:
 feeding the biomass feedstock into a first stage of a pressurized reaction vessel;   injecting a first wash liquid into the first stage countercurrently to the biomass feedstock;   discharging the first wash liquid from the first stage; and   discharging a solid biomass product from the reaction vessel in slurry form.   
   
   
       2 . The process of  claim 1 , further comprising conveying a first stage biomass product from the first stage to a second stage of the reaction vessel, injecting a second wash liquid into the second stage countercurrently to the first stage biomass product, and discharging the second wash liquid from the second stage. 
   
   
       3 . The process of  claim 1 , wherein the first wash liquid comprises water or a solution of water and a mineral acid for hemicellulose hydrolysis, and the second wash liquid comprises water and a sodium or ammonium hydroxide base for lignin hydrolysis. 
   
   
       4 . The process of  claim 3 , wherein the second wash liquid comprises about 40% to about 60% ethanol by weight. 
   
   
       5 . The process of  claim 1 , wherein the first wash liquid comprises a water rinse and a concentrated chemical reagent that mix to form the first wash liquid. 
   
   
       6 . The process of  claim 1 , wherein the first wash liquid provides optimal recovery of oils, proteins, and other extractives. 
   
   
       7 . The process of  claim 1 , further comprising maintaining a temperature of at least one of the stages in a range from about 190° C. to about 240° C. 
   
   
       8 . A continuous, countercurrent system of one or more stages for the fractionation of a lignocellulosic biomass, the system comprising:
 means for feeding the biomass into an elongated, pressurized reaction vessel;   means for conveying the biomass through the length of the reaction vessel;   means for discharging a processed biomass from the reaction vessel;   means for injecting a counter-flow of pressurized wash liquid into each stage of the reaction vessel;   means for discharging the wash liquid from each stage of the reaction vessel;   means for separating liquids from solids in each stage of the reaction vessel prior to discharging the wash liquid;   means for maintaining a desired temperature in each stage of the reaction vessel;   means for transferring heat from the liquid being discharged to the liquid being injected; and   means for controlling pressure throughout each stage of the reaction vessel such that boiling nowhere occurs, separate countercurrent flows are established in each stage where desired, and mixing of liquids between stages is minimized.   
   
   
       9 . The system of  claim 8 , wherein the pressurized reaction vessel comprises an elongated barrel accommodating twin screws for conveying the biomass, the screws being driven by a gearbox and motor. 
   
   
       10 . The system of  claim 8 , wherein the means for discharging a processed biomass from the reaction vessel comprises a processed biomass discharge progressive cavity pump configured to reduce pressure while avoiding clogging from liquid-solid separation, and the means for discharging the wash liquid from each stage of the reaction vessel comprises a wash liquid discharge progressive cavity pump configured to reduce pressure while avoiding clogging from liquid-solid separation. 
   
   
       11 . The system of  claim 8 , wherein the means for separating liquids from solids in each stage of the reaction vessel prior to discharging the wash liquid comprises at least one twin-screw extruder configured to force solids back into the reaction vessel. 
   
   
       12 . A simulated moving bed (SMB) system of one or more stages for the countercurrent fractionation of lignocellulosic biomass, the system comprising:
 a plurality of elongated, pressurized reactors interconnected with a plumbing system for controlling and directing one or more fluid flows;   means for sequential loading of the plurality of reactors with a biomass feedstock and for sequential unloading of a processed biomass;   means for injecting countercurrently a pressurized wash liquid into each stage of the simulated moving bed system;   means for discharging the wash liquid from each stage of the simulated moving bed system;   means for separating liquids from solids prior to discharging the wash liquid and transferring the wash liquid between reactors;   means for maintaining a desired temperature in each of the plurality of reactors of the simulated moving bed system;   means for transferring heat from the wash liquid being discharged to the wash liquid being injected;   means for controlling a pressure in each of the plurality of reactors to prevent boiling and to maintain a desired liquid flow throughout the simulated moving bed system; and   means for sequential switching of a plurality of valves to create a desired countercurrent, moving bed simulation.   
   
   
       13 . The system of  claim 12 , wherein the means for sequential loading of the plurality of reactors with a biomass feedstock and for sequential unloading of a processed biomass comprises:
 one or more augurs configured to load the biomass feedstock into the plurality of reactors; and   means for slurrying and washing out the processed biomass with water.   
   
   
       14 . The system of  claim 12 , wherein the means for sequential loading of the plurality of reactors with a biomass feedstock and for sequential unloading of a processed biomass comprises a plurality of baskets. 
   
   
       15 . The system of  claim 12 , wherein the means for discharging the wash liquid from each stage of the SMB comprises a wash liquid discharge progressive cavity pump configured to reduce pressure while avoiding clogging from liquid-solid separation. 
   
   
       16 . The system of  claim 12 , wherein the means for separating liquids from solids in each stage of the SMB prior to discharging the wash liquid comprises at least one twin-screw extruder configured to force solids back into the reaction vessel. 
   
   
       17 . The system of  claim 12 , wherein the means for sequential switching of a plurality of valves to create a desired countercurrent, moving bed simulation comprises an electronic computer. 
   
   
       18 . The system of  claim 12 , wherein the plumbing system for controlling and directing one or more fluid flows comprises a first reactor outlet port coupled with a second reactor inlet port. 
   
   
       19 . The system of  claim 18 , wherein the first reactor outlet port is coupled with the second reactor inlet port via a heat exchanger. 
   
   
       20 . The system of  claim 12 , wherein the means for sequential loading of the plurality of reactors with a biomass feedstock and for sequential unloading of a processed biomass comprises a common feedstock hopper in operative association with the plurality of elongated, pressurized reactors.