Space Resources Roundtable VII (2005) …

Space Resources Roundtable VII (2005)                                                                                                                2069.pdf




           CARBON MONOXIDE SILICATE REDUCTION SYSTEM. Mark Berggren, Robert Zubrin, Stacy Carrera,
           Heather Rose, and Scott Muscatello, Pioneer Astronautics, 11111 W. 8th Ave., Unit A, Lakewood, CO 80215,
           mberggren@pioneerastro.com


               Introduction: The Carbon Monoxide Silicate Re-                             leverage (mass of oxygen recovered divided by mass of
           duction System (COSRS) is a novel technology for                               carbon lost to the residue) on the order of 25 was
           recovering large amounts of oxygen from lunar soils.                           achieved in each case. COSRS was successfully inte-
           Soils are sequentially subjected to iron oxide reduction                       grated with an RWGS-electrolysis system during iron
           by carbon monoxide, in-situ deposition of carbon                               oxide reduction of lunar soil simulant. The integrated
           throughout the soil by carbon monoxide dispropor-                              system produced the desired solids product and dem-
           tionation catalyzed by metallic iron, and finally high-                        onstrated that minor gas constituents stabilize at very
           temperature reduction of silicates by the deposited car-                       low concentrations after extended periods in the closed
           bon. Figure 1 shows the process schematic.                                     RWGS loop.
                                                          Lunar                               Carbothermal reduction residues contained spheres
             O2             H2                CO2          Soil                           of iron and silicon metal above a glassy oxide matrix.
                                                                                          Figure 2 shows the metallic and oxide phases in JSC-1
                                                                   CO                     carbothermal reduction residue. Electron microprobe
                                                     Partial                   High
                                  RWGS              Reduction/             Temperature    analysis of the residue confirmed distinct separation of
             Electrolyzer
                                  Reactor            Carbon                Carbothermal   the metal and oxide phases, opening the possibility of
                                                    Deposition    Solids    Reduction
                                                                                          byproduct separation and recovery.

                                 Condenser/                                Metallic and
                     H2O         Separator      CO                           Oxide
                                                                            Residue

                      Figure 1: COSRS process schematic.

                Approximately 2 kilograms of oxygen per 100
           kilograms of soil are recovered by the initial iron oxide
           reduction step. Up to an additional 28 kilograms of
           oxygen per 100 kilograms of feed soil are recovered
           during the carbothermal reduction step. Process gases
           are fed to a Reverse Water Gas Shift (RWGS) unit for
           regeneration of carbon monoxide and recovery of oxy-
           gen by electrolysis from the resulting water. The
           COSRS-RWGS-electrolysis is a closed system with                                   Figure 2: JSC-1 carbothermal reduction residue.
           only small losses of carbon to the spent soil. The me-
           tallic and oxide slag residues have value for in-situ                              The Phase I results demonstrated oxygen recoveries
           resource utilization.                                                          of five times that possible using hydrogen as a reduc-
                A six-month, NASA SBIR Phase I COSRS pro-                                 tant. Up to ten times more oxygen than could be recov-
           gram was conducted in 2005. Each unit operation was                            ered by hydrogen reduction is possible by increasing
           separately demonstrated in the laboratory using both                           the mass of carbon deposited before carbothermal re-
           JSC-1 lunar and JSC Mars-1 soil simulants. A final                             duction. Further trade studies are needed to optimize
           integrated, closed-loop, COSRS-RWGS-electrolysis                               the carbon:silicate ratio with respect to oxygen recov-
           experiment produced oxygen from JSC-1 lunar soil                               ery and leverage.
           simulant.                                                                          Acknowledgement: This work was conducted un-
                Program Accomplishments: Thermodynamic                                    der NASA Small Business Innovation Research (SBIR)
           evaluations led to selection of a substoichiometric car-                       funding. Kris Lee was the NASA JSC Contracting Of-
           bon:silicon dioxide ratio to minimize carbon losses to                         ficer's Technical Representative (COTR).
           the carbothermal reduction residue. Under conditions
           selected for Phase I demonstration, about 15 kilograms
           of oxygen per 100 kilograms of soil were recovered
           from both lunar and Mars soil simulants using the
           COSRS process at temperatures up to 1,600oC. Process