The sorbent structure and the flow structure don't have to be the same physical object.
- Every current contactor treats the sorbent-containing geometry as the airflow geometry — the pellets, fibers, or monolith walls that hold the sorbent ARE the structures that define the flow channels.
- This couples void fraction to sorbent density through a single geometric parameter.
- But if you separate these functions — use one structure (macro-channels) for airflow and a different structure (thin sorbent coatings on those channel walls) for CO₂ capture — you can independently optimize each.
- The macro-void fraction controls ΔP; the micro-scale sorbent thickness controls diffusion path length and capacity.
- The Ergun equation still governs the macro-channels, but now ε is set by channel geometry, not by sorbent packing density.
- All five targets are individually achievable with proven physics; the challenge is simultaneous integration in a single architecture at the cost target, which requires the hierarchical decoupling of flow and sorbent geometry validated here.
If you prioritize speed to a working prototype and operational learning, start with the desiccant wheel swap (sol-support-1) in parallel with sorbent sheet development. If you prioritize meeting all five targets in a single architecture, invest in the cross-corrugated sheet contactor (sol-primary). If your deployment model is centralized at >1,000 tCO₂/yr, the Ljungström rotary (innov-recommended) should be your 18–36 month moonshot.
Cross-Corrugated Sorbent Sheet Contactor
Slot-die coat PEI-silica onto Al foil, corrugate, cross-stack — 40–120 Pa ΔP, 0.84–1.27 kgCO₂/m³/hr, $100–250/m³ structure cost. Blocking question: coating adhesion under 10,000+ TVSA cycles.
Ljungström-Derived Rotary DAC Contactor
Adapt 100-year-proven rotary preheater architecture with sorbent sheet packing and atmospheric steam regeneration — eliminates vacuum sealing, enables continuous operation, but requires Howden/Balcke-Dürr partnership and $3–10M pilot investment.
If this were my project, I'd start two parallel tracks this week and spend less than $10K in the first month. Track 1 is the slurry formulation test — order the materials (SBA-15, PEI, CMC, SBR, Al foil), mix the slurry, measure viscosity. This takes 1–2 weeks and costs $2–5K. If the slurry is coatable, you've unlocked the entire portfolio. If it gels, try PVA binder or the two-step approach. This is the single highest-leverage experiment in the entire program because it gates everything downstream. Track 2 is the Munters phone call. Literally call their technical sales team and ask about custom sorbent chemistry for their HCU platform. Request uncoated substrate samples. This costs nothing and could get you a working rotary DAC prototype in 6–12 months — invaluable operational data while the primary concept develops. Once the slurry works (and I'm confident it will — at least one of the three approaches), coat Al foil coupons and start TVSA cycling. This is the $30–80K, 8–12 week experiment that answers the adhesion question. Run it in parallel with corrugation trials on a few meters of coated foil. I would NOT pursue the freeze-cast concept, the avian cross-flow concept, or the resistive heating concept as standalone development tracks. The freeze-cast has a fatal ΔP problem; the avian cross-flow has a fatal sealing problem; the resistive heating has a fatal cost problem. But I'd extract the useful principles from each — the embedded heating idea from concept-6 should be integrated into the Al foil substrate design as supplementary zone heating, and the cross-flow geometry from concept-9 is already captured by the cross-corrugation.
- Week 1–2 — Order materials, mix slurry, measure viscosity ($2–5K)
- Week 2–4 — Doctor-blade coat coupons, measure initial CO₂ uptake ($5–10K)
- Week 4–12 — TVSA cycling durability test, 1,000 cycles ($20–50K)
- Month 1 — Call Munters, request substrate samples ($0)
- Month 3–6 — Toll-coat sorbent sheets at battery electrode service ($30–80K)
- Month 6–12 — Build 10 cm³ test contactor, measure ΔP and CO₂ uptake ($50–100K)
The Ljungström concept is the 18–36 month moonshot. Don't start the partnership conversation until you have validated sorbent sheet data — you need credibility before approaching Howden. But start the heat recovery analysis now (CFD modeling, $20–50K) so you have the technical brief ready when the sorbent data comes in.