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 system comprising:
 a first reactor configured for pyrolyzing a biomass feedstock and generating a biogenic reagent, wherein the biogenic reagent comprises carbon, and a pyrolysis off-gas;   a second reactor configured for reacting the biogenic reagent with a selected reactant, thereby generating reducing gas, wherein the second reactor is optionally configured for continuously, periodically, or ultimately removing activated carbon from the second reactor; and   a third reactor configured for chemically reducing a selected metal oxide in the presence of the reducing gas, thereby generating a reduced form of the selected metal oxide,   wherein optionally the system further comprises a heating unit in thermal communication with the first reactor, the second reactor, or the third reactor, and wherein the heating unit is configured for oxidizing the pyrolysis off-gas, thereby generating heat.   
     
     
         2 . The system of  claim 1 , wherein the first reactor is configured for operating at a pyrolysis temperature of at least about 250° C. to at most about 1250° C. 
     
     
         3 . The system of  claim 2 , wherein the pyrolysis temperature is at least about 300° C. to at most about 700° C. 
     
     
         4 . The system of  claim 1 , wherein the first reactor is configured for operating at a pyrolysis time of at least about 10 seconds to at most about 24 hours. 
     
     
         5 . The system of  claim 1 , wherein the second reactor is configured for operating at a reaction temperature of at least about 300° C. to at most about 1200° C. 
     
     
         6 . The system of  claim 5 , wherein the reaction temperature is at least about 400° C. to at most about 1000° C. 
     
     
         7 . The system of  claim 1 , wherein the second reactor is configured for operating at a reaction time of at least about 1 second to at most about 1 hour. 
     
     
         8 . The system of  claim 1 , wherein the third reactor is configured for operating at a reduction temperature of at least about 500° C. to at most about 2000° C. 
     
     
         9 . The system of  claim 8 , wherein the reduction temperature is at least about 700° C. to at most about 1800° C. 
     
     
         10 . The system of  claim 1 , wherein the third reactor is configured for operating at a reduction time of at least about 30 minutes to at most about 48 hours. 
     
     
         11 . The system 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. 
     
     
         12 . The system of  claim 1 , wherein the 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. 
     
     
         13 . The system of  claim 12 , wherein the metal oxide is iron ore selected from hematite, magnetite, limonite, taconite, or a combination thereof. 
     
     
         14 . The system of  claim 1 , wherein the reduced form of the selected metal oxide is a fully reduced metal. 
     
     
         15 . The system 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. 
     
     
         16 . The system of  claim 1 , wherein the system comprises a heating unit in thermal communication with the first reactor. 
     
     
         17 . The system of  claim 1 , wherein the system comprises a heating unit in thermal communication with the second reactor. 
     
     
         18 . The system of  claim 1 , wherein the system comprises a heating unit in thermal communication with the third reactor. 
     
     
         19 . The system of  claim 1 , wherein the second reactor is configured to increase hydrogen content of the reducing gas via the water-gas shift reaction. 
     
     
         20 . The system of  claim 1 , the system further comprising an additional reactor in flow communication with the second reactor, wherein the additional reactor is configured to increase hydrogen content of the reducing gas via the water-gas shift reaction. 
     
     
         21 . The system of  claim 1 , the system further comprising a separation unit configured for separating hydrogen from the reducing gas. 
     
     
         22 . The system of  claim 21 , wherein the separation unit comprises a pressure-swing adsorption unit, a molecular-sieve membrane, or a cryogenic distillation unit. 
     
     
         23 . The system of  claim 1 , wherein the second reactor is a fixed-bed reactor or a rotary kiln. 
     
     
         24 . The system of  claim 1 , wherein the second reactor is a fluidized-bed reactor. 
     
     
         25 . The system of  claim 1 , the system further comprising an off-gas reactor configured to partially oxidize the pyrolysis off-gas, thereby generating additional reducing gas. 
     
     
         26 . The system of  claim 25 , wherein the off-gas reactor is in flow communication with the third reactor. 
     
     
         27 . The system of  claim 1 , wherein the second reactor is further configured for receiving and converting the pyrolysis off-gas to additional reducing gas. 
     
     
         28 . The system of  claim 1 , wherein the system further comprises an outlet from the third reactor configured for recovering the reduced form of the selected metal oxide. 
     
     
         29 . The system of  claim 1 , wherein the system is co-located at a metal-oxide mine. 
     
     
         30 . The system of  claim 1 , wherein the system is co-located at a metal-oxide processing plant. 
     
     
         31 . The system of  claim 30 , wherein the metal-oxide processing plant is selected from a steel mill, a taconite plant, or a direct reduced-iron plant. 
     
     
         32 . The system of  claim 1 , wherein the third reactor is a metal ore furnace. 
     
     
         33 . The system of  claim 1 , wherein the third reactor is upstream of a metal ore furnace. 
     
     
         34 . The system of  claim 32 , wherein the metal ore furnace is selected from 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. 
     
     
         35 . The system of  claim 1 , wherein the first reactor and the third reactor are co-located at the same site. 
     
     
         36 . The system of  claim 1 , wherein the system is entirely located at a single site. 
     
     
         37 . The system of  claim 1 , wherein the second reactor is configured for continuously or periodically removing activated carbon from the second reactor. 
     
     
         38 . The system of  claim 1 , wherein the second reactor is configured for ultimately removing activated carbon from the second reactor. 
     
     
         39 . The system of  claim 1 , wherein the activated carbon is characterized by an Iodine Number of at least about 500. 
     
     
         40 . The system 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.