Analysis of CO2Scrubbers for the Plant Generic Bioprocessing Apparatus(PGBA)Peter Journeay Kaler Space Payload DesignASEN 5519Plants: Daytime versus Nighttime• During the day:Photosynthesis converts CO2, Light and H2O into O2and SugarPlants: Daytime versus Nighttime• During the night: Respiration converts O2, H2O and Sugar into CO2and plant growthPlants in Space• Spaceflight requires that plants are kept in a Sealed Environment•A Constant Level of CO2simplifies scientific analysis of plant growth• Daytime: CO2injection to support photosynthesis• Nighttime: Removal of respired CO2(Scrubbers)PGBA: Atmospheric Control System (ATS)• Nominal:•CO2within set parameters• Plant growth chamber (PGC) air is internally circulatedPGBA: Atmospheric Control System (ATS)• Daytime Photosynthesis:•CO2bellow set parameter•CO2rich cabin air is injected• Cabin air acts as unlimited CO2sourcePGBA: Atmospheric Control System (ATS)• Nighttime Respiration:•CO2above set parameters• Internal air is diverted to CO2scrubber •CO2chemically converted to H2O vapor•CO2removal is limited by amount and quality of scrubberCO2Scrubbers1. Amsrob2. Medisorb3. Divesorb Dive Drager4. Divesorb Pro5. Dragersorb 4006. Sodasorb7. Sodalime8. Baralyme• These scrubbers are a mixtures of various hydroxides • Ca(OH)2,• Ba(OH)2, • NaOH •KOH• Eight commercially available scrubbers were testedChemical absorption of CO2CO2+ Ca(OH)2→ CaCO3+ H2OGoals of Scrubber Analysis• Identify the “best” scrubber– Highest ratio of absorbed to injected CO2– Highest total mass of CO2absorbed– Longest “effective” operation time (> 33% absorption)– Highest packing density– Minimal dusting and breakup• Balance “realistic” experiment with feasible run time– 8 gram scrubber samples– 1.0 Liter per minute constant flow rateScrubber Experiment Setup• Known CO2input concentration • Control over CO2input pressure and flow rate• Computer recorded flow rate and CO2output concentration • Scaled down cartridge and flow rate to reduce run timeExperiment Data: Passed CO2vs. Time CO2 Scrubber Test 28g samples 1.0 L/m01002003004005006007008000 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Elapsed Time (min)C02 (ppm)AmsorbMedisorbDivesorb DDDivesorb ProDragersorb 400SodasorbSodalimeBaralymeScrubber Performance Analysis • Scrubber considered effective down to 33% CO2absorption• The total mass of CO2injected was calculated usingmCO2total= FR * Teff* ρCO2• FR = flow rate, Teff= time to reach 33% CO2absorption • ρCO2= density of CO2at 12.2psi (correcting for reduced atmos pressure)• The total mass of CO2absorbed was calculated usingmCO2abs= Aint* mCO2total•Aint= integrated area between 1000ppm and output CO2concentrationScrubber Analysis Results8g samples 1.0 L/m flow rate 33% Min. AbsorptionAmsorbMedisorbDiversorb Dive DragerDivesorb ProDragersorb 400SodasorbSodalimeBaralymeRatio Absorbed to Injected CO20.61 0.620.850.8 0.77 0.75 0.73 0.75Total Mass of Absorbed CO2 (g)0.1045 0.1312 0.1734 0.1617 0.163 0.1739 0.17230.2075Elapsed Time for 33% Absorption (min)105.5 128.5 125.5 124.5 129 137.75 139.75170.5Packing Density (g/mL)0.732 0.848 0.85 0.8 0.854 0.838 0.8420.892Cost ($/kg)13.76NANANA4.753.567.33 10.26• Baralyme was the best performer in three categories• Lower absorbed to injected ratio resulted from long “tale” of low absorptionFuture Work • Add equipment to test for back pressure buildup • Retest best performing scrubbers in a more realistic setup– Larger sample size– Higher flow rate– Longer test time– Full test in PGBAAcknowledgements• Dr. Alex Hoehn: Advisor• Juniper Jairala: Researched and Purchased Scrubbers • Hans Seelig: Labview Software• Jeff Sweet & Anand Satyamoorthy: Hardware and ElectronicsReferences: Scrubber Product Inforamtion• 1. Allied Healthcare Products, Inc. "Baralyme Brochure." • 2. Allied Healthcare Products, Inc. "Carbolime Brochure." • 3. Armstrong Medical, Ltd. "Amsorb Brochure." • 4. Datex-Ohmeda, Inc. "Medisorb Brochure." • 5. Diver Supply, Inc. "Sodasorb Brochure." • 6. How Stuff Works, March 10, 2003. "The Sofnolime Pages." http://www.metacut.com/rebreathers/sofnolime.htm.• 7. "A Comparitive Study of Draegersorb, LimePak, and HP Sodasorb Carbon Dioxide absorbents within the MK 15 Mod 0 Underwater Breathing Apparatus." NEDU Test Plan 87-01, Navy Experimental Dive Unit, 1998.• 8. Pulmonary Therapy Supplies, March 7, 2003. "Ascarite." http://www.a-msystems.com/pulmonary/products/absorbents/ascarite.asp.• 9. January 17, 2003. "Life Support." http://members.aol.com/beanstalkr/elevatorclub/lifesupport.htm.• 10. Dosch, M. P., Crna Ms. (2002). "The Anesthesia Gas Machine."• 11. Higuchi, H., Adachi, Y., Arimura, S., Kanno, M., and Satoh, T. (2001). "The Carbon Dioxide Absorption Capacity of Amsorb(R) is Half That of Soda Lime." Anesth Analg, 93(1), 221-225.• 12. Lawrence J. Baudendistel, P., M.D. (1987). "Performance Comparison BetweenPrepacked Cannisters of Sodasorb Versus Baralyme." St. Louis University School of Medicine, Department of Anesthesiology.• 13. Simske, S. "RE: CO2 Removal." E-mail to J. Jairala,References: Experiment Procedures1. A scrubber cartridge was weighed using a digital scale (including filters and rubber stopper)2. 8 grams (+/- .01g) of scrubber was weighed out using a digital scale3. The scrubber was loaded into the cartridge with filters at the entrance and exit points4. The cartridge was loaded into the Scrubber Testing Apparatus as illustrated in Fig. 15. The valve was set to bypass the cartridge6. The regulator on the 1000ppm CO2cylinder was set to 10 PSI injection pressure and flow was started7. The N052 – 075T flow tube was used to adjust the flow rate to 1.0 L/m (This was checked using the analog output from the 100-7 flow meter with Vout= 2.46V)8. The Labview VI was activated and began to record the analog outputs of the CO2transmitter and the flow meter.9. The bypass valve was turned to direct flow into the scrubber cartridge10. The flow rate was monitored and if necessary was adjusted to keep it constant a 1.0 L/m for the entire data collection period. (Vout= 2.46V +/- 0.05V)11. The VI collected data until the scrubber was allowing 700 ppm CO2to pass through. (This ensured that the 33% absorption point of 666 ppm was reached)12. Flow was stopped and the valve reset to bypass13. The cartridge was removed and weighed14. Steps 1 through 13