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 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) 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) optionally, recovering the biogenic reagent continuously or periodically during step (d), or ultimately after step (d), thereby generating a recovered biogenic reagent, wherein recovered biogenic reagent is activated carbon.   
     
     
         2 . The process of  claim 1 , wherein step (d) is conducted at a reaction temperature selected from about 300° C. to about 1200° C. 
     
     
         3 . The process of  claim 1 , wherein step (e) is conducted at a reduction temperature selected from about 500° C. to about 2000° C. 
     
     
         4 . The process of  claim 1 , wherein the biomass feedstock comprises softwood chips, hardwood chips, timber harvesting residues, tree branches, tree stumps, leaves, bark, sawdust, corn, corn stover, wheat, wheat straw, rice, rice straw, sugarcane, sugarcane bagasse, sugarcane straw, energy cane, sugar beets, sugar beet pulp, sunflowers, sorghum, canola, algae, miscanthus, alfalfa, switchgrass, fruits, fruit shells, fruit stalks, fruit peels, fruit pits, vegetables, vegetable shells, vegetable stalks, vegetable peels, vegetable pits, grape pumice, almond shells, pecan shells, coconut shells, coffee grounds, food waste, commercial waste, grass pellets, hay pellets, wood pellets, cardboard, paper, paper pulp, paper packaging, paper trimmings, food packaging, construction or demolition waste, railroad ties, lignin, animal manure, municipal solid waste, municipal sewage, or a combination thereof. 
     
     
         5 . The process of  claim 1 , wherein the biogenic reagent comprises at least 50 wt % carbon. 
     
     
         6 . The process of  claim 1 , wherein the biogenic reagent comprises at least 50 wt % fixed carbon. 
     
     
         7 . The process of  claim 1 , wherein the selected metal oxide comprises iron oxide, copper oxide, nickel oxide, magnesium oxide, manganese oxide, aluminum oxide, tin oxide, zinc oxide, cobalt oxide, chromium oxide, tungsten oxide, molybdenum oxide, or a combination thereof. 
     
     
         8 . The process of  claim 1 , wherein the selected metal oxide comprises iron ore. 
     
     
         9 . The process of  claim 8 , wherein the iron ore comprises hematite, magnetite, limonite, taconite, or a combination thereof. 
     
     
         10 . The process of  claim 1 , wherein the reduced form of the selected metal oxide is a fully reduced metal. 
     
     
         11 . The process of  claim 1 , wherein the reduced form of the selected metal oxide is a second metal oxide having a lower oxidation state than the selected metal oxide. 
     
     
         12 . The process of  claim 1 , wherein the reducing gas comprises at least 10 mol % hydrogen. 
     
     
         13 . The process of  claim 1 , wherein the reducing gas comprises at least 10 mol % carbon monoxide. 
     
     
         14 . The process of  claim 1 , the process further comprising increasing hydrogen content of the reducing gas via the water-gas shift reaction. 
     
     
         15 . The process of  claim 1 , the process further comprising separating hydrogen from the reducing gas and recovering the hydrogen. 
     
     
         16 . The process of  claim 15 , the process further comprising separating the hydrogen from the reducing gas, wherein the separating is achieved using pressure-swing adsorption, molecular-sieve membrane separation, or cryogenic distillation. 
     
     
         17 . The process of  claim 1 , wherein the pyrolysis off-gas is partially oxidized, thereby generating additional reducing gas and the heat, and optionally wherein step (e) further comprises chemically reducing the selected metal oxide in the presence of the additional reducing gas. 
     
     
         18 . The process of  claim 1 , the process further comprising separating converting the pyrolysis off-gas to additional reducing gas. 
     
     
         19 . The process of  claim 18 , wherein the additional reducing gas comprises at least 20 mol % hydrogen. 
     
     
         20 . The process of  claim 18 , wherein the additional reducing gas comprises at least 20 mol % carbon monoxide. 
     
     
         21 . The process of  claim 1 , the process further comprising recovering the reduced form of the selected metal oxide. 
     
     
         22 . The process of  claim 1 , wherein the process is co-located at a metal-oxide mine. 
     
     
         23 . The process of  claim 1 , wherein the process is co-located at a metal-oxide processing plant. 
     
     
         24 . The process of  claim 23 , wherein the metal-oxide processing plant comprises a steel mill, a taconite plant, or a direct reduced-iron plant. 
     
     
         25 . The process of  claim 1 , wherein step (e) is conducted in a metal ore furnace or is conducted upstream of a metal ore furnace. 
     
     
         26 . The process of  claim 25 , wherein the metal ore furnace comprises a blast furnace, a direct-reduced-metal furnace, a top-gas recycling blast furnace, a shaft furnace, a reverberatory furnace, a crucible furnace, a muffling furnace, a retort furnace, a flash furnace, a Tecnored furnace, an Ausmelt furnace, an ISASMELT furnace, a puddling furnace, a Bogie hearth furnace, a continuous chain furnace, a pusher furnace, a rotary hearth furnace, a walking beam furnace, an electric arc furnace, an induction furnace, a basic oxygen furnace, a puddling furnace, a Bessemer furnace, or a combination thereof. 
     
     
         27 . The process of  claim 1 , wherein step (b) and step (e) are conducted at the same site. 
     
     
         28 . The process of  claim 1 , wherein all process steps are conducted at a single site. 
     
     
         29 . The process of  claim 1 , wherein step (f) is conducted. 
     
     
         30 . The process of  claim 29 , wherein at least 10 wt % of the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         31 . The process of  claim 30 , wherein at least 50 wt % of the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         32 . The process of  claim 31 , wherein at least 90 wt % of the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         33 . The process of  claim 29 , wherein at least 50 wt % of the fixed carbon within the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         34 . The process of  claim 33 , wherein at least 90 wt % of the fixed carbon within the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         35 . The process of  claim 34 , wherein essentially all of the fixed carbon within the biogenic reagent generated in step (b) is recovered as the activated carbon in step (f). 
     
     
         36 . The process of  claim 1 , wherein at least 50 wt % of the volatile carbon within the biogenic reagent generated in step (b) is directed to the reducing gas. 
     
     
         37 . The process of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 500. 
     
     
         38 . The process of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 1000. 
     
     
         39 . The process of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 2000. 
     
     
         40 . The process of  claim 1 , wherein the activated carbon is characterized as fully renewable activated carbon as determined from a measurement of the  14 C/ 12 C isotopic ratio of the activated carbon.