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 . A renewable hydrogen 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) separating hydrogen from the reducing gas, optionally wherein the separating is achieved using pressure-swing adsorption, molecular-sieve membrane separation, or cryogenic distillation;   (f) recovering a renewable hydrogen product, wherein the renewable hydrogen product comprises the hydrogen; and   (g) optionally, 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 renewable hydrogen product of  claim 1 , wherein the hydrogen is characterized as at least about 50% renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         3 . The renewable hydrogen product of  claim 1 , wherein the hydrogen is characterized as at least about 90% renewable hydrogen. 
     
     
         4 . The renewable hydrogen product of  claim 1 , wherein the hydrogen is characterized as at least about 95% renewable hydrogen. 
     
     
         5 . The renewable hydrogen product of  claim 1 , wherein the hydrogen is characterized as fully renewable hydrogen. 
     
     
         6 . The renewable hydrogen product of  claim 1 , wherein the selected reactant in step (d) is water. 
     
     
         7 . The renewable hydrogen 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. 
     
     
         8 . The renewable hydrogen product of  claim 1 , wherein the selected reactant in step (d) comprises a combination of water and oxygen. 
     
     
         9 . The renewable hydrogen product of  claim 1 , wherein the reducing gas comprises at least about 10 mol % the hydrogen. 
     
     
         10 . The renewable hydrogen product of  claim 1 , wherein the reducing gas comprises at least about 25 mol % the hydrogen. 
     
     
         11 . The renewable hydrogen product of  claim 1 , wherein the reducing gas comprises at least about 10 mol % the carbon monoxide. 
     
     
         12 . The renewable hydrogen product of  claim 1 , wherein the process further comprises increasing hydrogen content of the reducing gas via the water-gas shift reaction. 
     
     
         13 . The renewable hydrogen product of  claim 1 , wherein the pyrolysis off-gas is partially oxidized, thereby generating additional reducing gas and the heat. 
     
     
         14 . The renewable hydrogen product of  claim 1 , wherein the separating is achieved using pressure-swing adsorption. 
     
     
         15 . The renewable hydrogen product of  claim 1 , wherein the separating is achieved using molecular-sieve membrane separation. 
     
     
         16 . The renewable hydrogen product of  claim 1 , wherein the separating is achieved using cryogenic distillation. 
     
     
         17 . The renewable hydrogen product of  claim 1 , wherein the hydrogen product comprises at least about 50 mol % hydrogen. 
     
     
         18 . The renewable hydrogen product of  claim 1 , wherein the hydrogen product comprises at least about 90 mol % hydrogen. 
     
     
         19 . The renewable hydrogen product of  claim 1 , wherein the hydrogen is characterized as fully renewable hydrogen, and wherein residual carbon comprised within the hydrogen product is essentially fully renewable carbon as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         20 . The renewable hydrogen product of  claim 1 , wherein the hydrogen product is substantially free of nitrogen. 
     
     
         21 . A reducing-gas composition for reducing a metal oxide, wherein the reducing-gas composition comprises at least about 25 mol % hydrogen, and wherein the hydrogen is at least about 50% renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         22 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition comprises at least about 50 mol % hydrogen. 
     
     
         23 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition comprises at least about 75 mol % hydrogen. 
     
     
         24 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition comprises at least about 90 mol % hydrogen. 
     
     
         25 . The reducing-gas composition of  claim 21 , wherein the hydrogen is characterized as at least about 80% renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         26 . The reducing-gas composition of  claim 21 , wherein the hydrogen is characterized as at least about 90% renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         27 . The reducing-gas composition of  claim 21 , wherein the hydrogen is characterized as fully renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         28 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition further comprises carbon-containing gases, wherein the carbon-containing gases comprise CO, CO 2 , or CH 4 , and wherein the carbon-containing gases are at least about 50% renewable as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         29 . The reducing-gas composition of  claim 28 , wherein the carbon-containing gases are at least about 90% renewable as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         30 . The reducing-gas composition of  claim 28 , wherein the carbon-containing gases are fully renewable as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         31 . The reducing-gas composition of  claim 30 , wherein the hydrogen is characterized as at least about 90% renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         32 . The reducing-gas composition of  claim 30 , wherein the hydrogen is characterized as fully renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         33 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition further comprises carbon monoxide, and wherein the carbon monoxide is at least about 50% renewable as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         34 . The reducing-gas composition of  claim 33 , wherein the carbon monoxide is at least about 90% renewable as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         35 . The reducing-gas composition of  claim 33 , wherein the carbon monoxide is essentially fully renewable as determined from a measurement of the  14 C/ 12 C isotopic ratio. 
     
     
         36 . The reducing-gas composition of  claim 35 , wherein the hydrogen is characterized as at least about 90% renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         37 . The reducing-gas composition of  claim 35 , wherein the hydrogen is characterized as fully renewable hydrogen according to a hydrogen-isotope  2 H/ 1 H analysis. 
     
     
         38 . The reducing-gas composition of  claim 33 , wherein the molar ratio of the hydrogen to the carbon monoxide is at least about 2. 
     
     
         39 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition comprises at most about 1 mol % N 2 . 
     
     
         40 . The reducing-gas composition of  claim 21 , wherein the reducing-gas composition is essentially free of N 2 .