Featured Project: Permanent H2S & Aerosol Control on Cold Feed Storage Tank – Midwest Refinery (State Air Permit & EPA MACT Compliance)
An Illinois refinery faced a hard regulatory deadline to reduce H2S emissions from a large cold feed tank that routinely vented >1,000 ppm H2S plus heavy aerosol/oily mist. Previous single-stage scrubbers failed repeatedly due to clogging, breakthrough, and seasonal temperature swings.
The state agency mandated >99% H2S removal + zero visible aerosols or the unit would be shut down.
The Challenge
- High-volume vent (up to 2,000 scfm) with oily mist & aerosols
- H2S spikes from 500 ppm to >10,000 ppm
- Winter temperatures down to −20 °F (risk of freezing)
- No room for downtime or equipment failure
- Must meet state permit limits and EPA MACT 40 CFR Part 63 Subpart CC (Refinery MACT 1)
Envent’s Engineered Multi-Stage Solution
Envent’s chemical & mechanical engineers co-developed a bulletproof, high-reliability system with the plant:
| Stage | Equipment & Purpose |
|---|---|
| 1 – Aerosol / Oil Knockout | Heated knockout pot + demister pads |
| 2 – Primary H2S Removal | Two ESCRUB-3000P passive scrubbers in parallel with VapoScrub H2S5 |
| 3 – Polishing & Surge Protection | ESCRUB-6000 recirculating scrubber (caustic/oxidizer blend) |
| 4 – Final Safety | Dual 10K carbon polishers + continuous H2S/LEL analyzers |
Key Design Features
- Redundant blowers with auto-switchover
- Heated lines & vessels for sub-zero weather
- PLC-controlled pH/ORP, level, and pressure monitoring
- Remote telemetry + on-site Envent technician 24/7 during startup
Result: >99.9% H2S removal, zero visible aerosols, zero downtime for the entire multi-month project.
Proven Benefits – Deadline Met, Plant Saved
| Benefit | Delivered Outcome |
|---|---|
| H2S Removal | >99.9% (10,000+ ppm inlet → <5 ppm outlet) |
| Aerosol / Oil Carryover | 100% eliminated — no downstream fouling |
| Regulatory Compliance | Met state deadline — unit stayed online |
| Reliability | Zero failures despite winter extremes |
| Knowledge Transfer | Plant engineers now run optimized scrubber SOPs |
| Long-Term Savings | Avoided $10M+ shutdown + multimillion-dollar fines |
This system is now the facility’s permanent H2S control standard and has been replicated at sister plants. → Learn more about Envent’s turnkey scrubber systems → Download our H2S Scrubber Selection Guide
Facing an H2S deadline on a cold feed, sour crude, or slop tank? Get your Free Multi-Stage Scrubber Design & Quote today. Call Envent at 888-997-9465 or email [email protected] — we turn impossible deadlines into guaranteed compliance.
