Influence of Powder Type on Aerosol Emissions in Powder-Binder Jetting with Emphasis on Lunar Regolith for In Situ Space Applications

• Published in: ACS ES&T engineering Vol. 1; no. 2; pp. 183 - 191
• Main Authors: Hayes, Austin C, Osio-Norgaard, Jorge, Miller, Shelly, Vance, Marina E, Whiting, Gregory L
• Format: Journal Article
• Language: English
• Published: American Chemical Society 12.02.2021
• Subjects: Particulate Matter; Emission Rate; Additive Manufacturing; Powder-Binder Jetting
• ISSN: 2690-0645; 2690-0645
• DOI: 10.1021/acsestengg.0c00045

Powder-binder jetting is an additive process with applications for manufacturing complex geometric structures, such as lightweighting, mold making, and in situ resource utilization (ISRU) for space applications. With this technique, a powder feedstock is spread across a bed during which aerosol may be released leading to human health implications. This study characterizes airborne powder emissions for three powders of varying particle diameters and composition: Hydroperm gypsum plaster, Lunar Highland Simulant regolith (LHS-1, a lunar soil simulant), and Zeolite 13X (a molecular sieve). Bulk powder D 50 values were 22 μm for Hydroperm, 304 μm for LHS-1, and 3.85 μm for Zeolite. Total particle emission rates were (5.4 ± 0.96) × 105 min–1 for Hydroperm, (1.0 ± 0.28) × 106 min–1 for Zeolite, and (2.2 ± 0.82) × 107 min–1 for LHS-1. An emission factor was developed normalized to the volume of powder spread resulting in emission factors of 2.8 ± 0.85 min–1 mm–3 for Hydroperm, 220 ± 72 min–1 mm–3 for LHS-1, and 5.0 ± 0.24 min–1 mm–3 for Zeolite. This indicates that particle emissions from powder-binder jetting machines with a constant spreading mechanism can vary widely depending solely on powder type. In the experimental enclosure where testing took place, LHS-1 PM 10 concentrations exceeded 8 h TWA PEL OSHA standards for crystalline silica by sixfold, indicating that air quality should be a strong design consideration for 3D printing for lunar ISRU. With lower gravitational settling effects, Lunar particulate concentrations 20 m away from the printer were modeled to be 330% higher than on Earth. This study suggests that powder size, morphology, and composition should be considered holistically when determining emission concerns for new powders in powder-binder jetting. This study also suggests particular attention should be paid to aerosol emissions in a Lunar environment.