BIOMASS PYROLYSIS INTEGRATED WITH BIO-REDUCTION OF METAL ORES, HYDROGEN PRODUCTION, AND/OR ACTIVATED-CARBON PRODUCTION
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.
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 .