Biomass pyrolysis integrated with bio-reduction of metal ores, hydrogen production, and/or activated-carbon production

Abstract

Improved processes and systems are disclosed for producing renewable hydrogen suitable for reducing metal ores, as well as for producing activated carbon. Some variations provide a process comprising: pyrolyzing biomass to generate a biogenic reagent comprising carbon and a pyrolysis off-gas; converting the pyrolysis off-gas to additional reducing gas and/or heat; reacting at least some of the biogenic reagent with a reactant to generate a reducing gas; and chemically reducing a metal oxide in the presence of the reducing gas. Some variations provide a process for producing renewable hydrogen by biomass pyrolysis to generate a biogenic reagent, conversion of the biogenic reagent to a reducing gas, and separation and recovery of hydrogen from the reducing gas. A reducing-gas composition for reducing a metal oxide is provided, comprising renewable hydrogen according to a hydrogen-isotope analysis. Reacted biogenic reagent may also be recovered as an activated carbon product. Many variations are disclosed.

What is claimed is: 
     
         1 . An activated carbon product produced by a process comprising:
 (a) providing a biomass feedstock;   (b) pyrolyzing the biomass feedstock, thereby generating a biogenic reagent, wherein the biogenic reagent comprises carbon, and a pyrolysis off-gas;   (c) optionally, oxidizing the pyrolysis off-gas, thereby generating heat;   (d) reacting the biogenic reagent with a selected reactant, thereby generating a reducing gas;   (e) optionally, chemically reducing a selected metal oxide in the presence of the reducing gas from step (d), thereby generating a reduced form of the selected metal oxide; and   (f) recovering the biogenic reagent continuously or periodically during step (d), or ultimately after step (d), thereby generating a recovered biogenic reagent, wherein the recovered biogenic reagent is activated carbon.   
     
     
         2 . The activated carbon product of  claim 1 , wherein step (b) is conducted at a pyrolysis temperature of at least about 250° C. to at most about 1250° C.\ 
     
     
         3 . The activated carbon product of  claim 1 , wherein the pyrolysis temperature is at least about 300° C. to at most about 700° C. 
     
     
         4 . The activated carbon product of  claim 1 , wherein step (b) is conducted for a pyrolysis time of at least about 10 seconds to at most about 24 hours. 
     
     
         5 . The activated carbon product of  claim 1 , wherein step (d) is conducted at a reaction temperature of at least about 300° C. to at most about 1200° C. 
     
     
         6 . The activated carbon product of  claim 5 , wherein the reaction temperature is at least about 400° C. to at most about 1000° C. 
     
     
         7 . The activated carbon product of  claim 1 , wherein step (d) is conducted for a reaction time of at least about 1 second to at most about 1 hour. 
     
     
         8 . The activated carbon product of  claim 1 , wherein the biogenic reagent comprises at least about 50 wt % carbon. 
     
     
         9 . The activated carbon product of  claim 1 , wherein the biogenic reagent comprises at least about 75 wt % carbon. 
     
     
         10 . The activated carbon product of  claim 1 , wherein the biogenic reagent comprises at least about 50 wt % fixed carbon. 
     
     
         11 . The activated carbon product of  claim 1 , wherein the biogenic reagent comprises at least about 75 wt % fixed carbon. 
     
     
         12 . The activated carbon product of  claim 1 , wherein the reducing gas comprises at least about 10 mol % hydrogen. 
     
     
         13 . The activated carbon product of  claim 1 , wherein the reducing gas comprises at least about 25 mol % hydrogen. 
     
     
         14 . The activated carbon product of  claim 1 , wherein the reducing gas comprises at least about 10 mol % the carbon monoxide. 
     
     
         15 . The activated carbon product of  claim 1 , wherein the reducing gas comprises at least about 25 mol % the carbon monoxide. 
     
     
         16 . The activated carbon product of  claim 1 , wherein the process further comprises increasing hydrogen content of the reducing gas via the water-gas shift reaction. 
     
     
         17 . The activated carbon product of  claim 1 , wherein the selected reactant in step (d) is water. 
     
     
         18 . The activated carbon product of  claim 1 , wherein the selected reactant in step (d) is oxygen, and wherein the oxygen is comprised within air, pure oxygen, enriched oxygen, ozone, or a combination thereof. 
     
     
         19 . The activated carbon product of  claim 1 , wherein the selected reactant in step (d) comprises a combination of water and oxygen. 
     
     
         20 . The activated carbon product of  claim 1 , wherein at least about 10 wt % of the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         21 . The activated carbon product of  claim 1 , wherein at least about 50 wt % of the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         22 . The activated carbon product of  claim 1 , wherein at least about 90 wt % of the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         23 . The activated carbon product of  claim 1 , wherein at least about 50 wt % of the fixed carbon within the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         24 . The activated carbon product of  claim 1 , wherein at least about 90 wt % of the fixed carbon within the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         25 . The activated carbon product of  claim 1 , wherein essentially all of the fixed carbon within the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         26 . The activated carbon product of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 500. 
     
     
         27 . The activated carbon product of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 1000. 
     
     
         28 . The activated carbon product of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 1500. 
     
     
         29 . The activated carbon product of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 2000. 
     
     
         30 . The activated carbon product of  claim 1 , wherein the activated carbon is characterized by a renewable carbon content of at least about 90% as determined from a measurement of the  14 C/ 12 C isotopic ratio of the activated carbon. 
     
     
         31 . The activated carbon product of  claim 1 , wherein the activated carbon is characterized as consisting essentially of renewable activated carbon as determined from a measurement of the  14 C/ 12 C isotopic ratio of the activated carbon.