(631a) Continuous Wire Embedded 3D Printed Sorbent Structures

Zeolites with their structured micropores have found widespread use for over 100 years in adsorption, separations, and catalysis in applications such as oil and gas upgrading, air purification, CO₂ capture, and biomass conversion. One common application is using the zeolite as an adsorbent for a contaminant, which is then expelled by heating, regenerating the zeolite for reuse. In general, zeolites are formed into beads or pellets of different sizes and packed into a bed to achieve high mass transfer, but at the expense of an increased pressure drop and non-uniform heating. This can be especially problematic in applications that are power limited and require large thermal energy to regenerate the adsorbent.

Mainstream Engineering has developed a process of fabricating advanced sorbent beds with a 6-degree-of-freedom additive manufacturing (AM)/3D printing process. We have developed a zeolite-based paste that can be deposited and sintered into complex shapes that allow us to optimize the structure for a specific application. Using this paste, we have begun fabricating and testing complex sorbent bed designs optimized for physical size, adsorption, and pressure drop. Additionally, we are continuing to develop our continuous-wire embedding mechanism and process, that allows us to embed thin (30-40 AWG), high-resistivity wires directly into the printed roads. This process eliminates the need for external heaters, as we can electrify the embedded wires for highly-uniform and efficient heating of the sorbent structure.

Mainstream will discuss and present data on paste formulation, AM bed printing with integrated wire, and device adsorption and thermal profiles for a targeted application of CO₂ removal from sealed environmental systems, such as the Internal Space Station (ISS). To maintain an earth-like atmosphere in sealed environments, several different systems generate oxygen and remove unwanted gases. Specifically, CO2 removal is critical for air revitalization. Zeolite molecular sieves are used as a sorbent for CO2, water, and other trace contaminants; the zeolite cyclically adsorbs contaminants that are then expelled by heating. Currently, these beds are fabricated from loose zeolite beads with cartridge heaters and conductive fins embedded for heating. While cartridge heaters are a reliable and proven technology, the use of these heaters for heating a bed of discrete spherical beads leads to high thermal resistance, extended heat-up/desorption time, and local hotspots. Mainstream 3D printed a complex zeolite monolith with a tortuous path and embedded heating elements that can be heated from room temperature to 200°C in under 10 minutes with no degradation of the structure or its adsorption capacity.

Figure caption: 10"-diameter cylinder printed during Phase I—a) Showing the structure while printing, b) showing 2.7 kΩ resistance in a single wire embedded layer (post-sintering)