Continuously fed biomass pretreatment process for a packed bed reactor

Abstract

Biomass pretreatment using anhydrous ammonia is effective in a static reactor vessel when the ammonia can penetrate through the biomass particles or pieces in vapor state, and when biomass is continuously fed and moved through the reactor. To achieve this condition, total system moisture content is kept below 40 weight % based on total mass in the system. The pretreated biomass product is effectively saccharified to produce fermentable sugars for biocatalyst production of a product.

1 . A process for treating biomass to produce a pretreated biomass product comprising:
 a) providing biomass with dry matter content of at least about 60%;   b) charging a static pretreatment vessel with the biomass of (a) by continuous feeding whereby the charged biomass in the vessel moves through the vessel;   c) contacting the charged biomass of (b) as it moves through the pretreatment vessel with at least about 4% anhydrous ammonia measured as a function of dry weight of the biomass in the vessel, under conditions whereby the total moisture content in the vessel remains below 40 weight % measured as a function of total mass in the vessel; whereby a majority of the biomass is permeated by ammonia vapor; and   d) exiting the biomass from the pretreatment vessel;   wherein the biomass exiting the vessel is pretreated biomass product.   
     
     
         2 . The process of  claim 1  wherein after exiting of (d), vapors are separated from the pretreated biomass product. 
     
     
         3 . The process of  claim 2  wherein vapors comprise ammonia vapor which is recovered and recycled to the pretreatment vessel or to an ammonia vapor handling system. 
     
     
         4 . The process of  claim 1  wherein after step (d) the pretreated biomass product is recovered. 
     
     
         5 . The process of  claim 1  wherein at step (c) the charged biomass moves through the pretreatment vessel with a residence time of between about 10 minutes and about 5 hours. 
     
     
         6 . The process of  claim 1  wherein where the anhydrous ammonia is in contact with the biomass for less than about 5 hours. 
     
     
         7 . The process of  claim 1  wherein the temperature of the biomass in the vessel is at least about 70° C. 
     
     
         8 . The process of  claim 1  wherein the temperature of the vessel is raised to at least about 70° C. prior to step (b). 
     
     
         9 . The process of  claim 8  wherein the temperature prior to step (b) is between about 70° C. and about 190° C. 
     
     
         10 . The process of  claim 8  wherein the temperature is raised directly by injecting hot gas or indirectly by application of heat to the vessel. 
     
     
         11 . The process of  claim 1  wherein the concentration of anhydrous ammonia at step (c) is less than about 20% measured as a function of dry weight of the biomass in the vessel. 
     
     
         12 . The process of  claim 1  wherein pressure in the vessel is between about 0 and 20 atmosphere gauge over steps (b) through (d). 
     
     
         11 . The process of  claim 1  wherein the biomass of (a) is mechanically size-reduced biomass. 
     
     
         12 . The process of  claim 1  wherein the biomass is cellulosic biomass comprising cellulose, hemicellulose and lignin. 
     
     
         13 . The process of  claim 12  wherein the biomass is selected from the group consisting of corn cobs, corn husks, corn stover, grasses, wheat straw, barley straw, oat straw, canola straw, hay, rice straw, switchgrass, miscanthus, cord grass, reed canary grass, waste paper, sugar cane bagasse, sorghum bagasse or stover, soybean stover, components obtained from milling of grains, trees, branches, roots, leaves, wood chips, sawdust, shrubs and bushes, vegetables, fruits, flowers and animal manure.