Raw ACM syngas is upgraded to PEM-fuel-cell-compatible purity through a multi-stage industry-standard cleanup train. Target purity: >99.99% H2 with <5 ppm CO — well below PEM catalyst poisoning threshold. The cleanup approach uses well-characterized industrial unit operations arranged in a Carbotura-specific sequence for the ACM syngas chemistry.
Engineering Detail
The cleanup train is a multi-stage sequence — stage names only (no vendor / chemistry detail):
- Hot cyclones — particulate and solids carryover removed from raw vapor.
- CRSCU (plasma cracker) — 1,300–1,800 °C plasma with no catalyst. Cracks CH4, tars and light hydrocarbons to H2/CO, AND simultaneously drives sulfur, chlorine and nitrogen contaminants to water-soluble species (HCl, NH3, dissolved sulfides). Pristine carbon recovered via dedicated cyclone downstream of the quench boiler.
- HRSG + condenser — heat recovered to steam loop; gas cooled from ~200 → ~40 °C. Water condenses out carrying dissolved contaminants (HCl, NH3, sulfides) with it.
- Oil–water separation — bulk contaminant path: organics + moisture partition; the aqueous phase (with dissolved acids, ammonia, sulfides) routes to Water MAX where NH4Cl / (NH4)2S / metals precipitate out as salt cake (see Section 4 Q12). Organics route to Aromatics MAX.
- Water-gas shift (WGS) — CO + H2O → CO2 + H2 over Fe/Cr at ~250 °C (~75% CO conversion in the modeled case). Gas stream at this point is already low in sulfur / chloride because CRSCU + OWS did the bulk removal upstream.
- PSA cascade — zeolite 5A + self-produced activated carbon (from Carbon MAX). H2 enriched to 4–5 nines (99.99%–99.999%).
- Trace polish + OEM acceptance — self-produced activated-carbon guard beds catch residual trace S / Cl / siloxane / alkali / Hg (small quantities remaining after upstream water-path removal); online analytical monitoring; ISO 14687 verification before PEM entry.
Key architectural insight: the CRSCU (1,300–1,800 °C plasma) does the heavy chemistry — at those temperatures sulfur, chlorine and nitrogen species convert to water-soluble ionic forms (H2S → dissolved sulfide; Cl → HCl aq; N → NH3 aq). These partition to the aqueous phase in OWS and leave via the water path, where Water MAX crystallizes them as salt cake product (NH4Cl / (NH4)2S; ~50.7 kg/h dry basis at 100 TPD). Downstream gas-phase steps (guard beds, PSA sorbent) handle trace polish only — a small fraction of what a conventional pyrolysis-cleanup train would need to remove. All guard-bed and PSA sorbent is self-produced on-site by Carbon MAX (module MAX-CRB-003).