Hydrogen sulfide (H2S) is a toxic and corrosive gas prevalent in oil and gas operations, requiring efficient removal technologies. The Valkyrie Liquid Redox process (Streamline Innovations) and the LO-CAT process (Merichem Technologies) are advanced liquid redox systems that convert H2S into elemental sulfur and water. While both share similar chemical principles, they differ significantly in chemistry, operational design, automation, applications, and environmental impact. This article explores these differences to guide operators in selecting the optimal technology.

Chemistry and Catalyst

Both processes use chelated iron to oxidize H2S, but their catalyst formulations diverge:

  • Valkyrie: Employs TALON® chemistry, a biodegradable, proprietary chelated iron solution that generates hydroxyl radicals to treat H2S and other sulfur compounds (e.g., mercaptans, thiophenes). This modern formulation enhances efficiency and environmental sustainability.
  • LO-CAT: Uses a traditional chelated iron solution (e.g., EDTA-based) to stabilize iron ions. While effective, this older formulation is less optimized for complex gas streams and lacks biodegradability.

Difference: Valkyrie’s TALON chemistry is biodegradable and tailored for broader sulfur compound treatment, giving it an edge in sustainability and versatility over LO-CAT’s conventional chemistry.

Reaction Mechanism

Both processes follow similar redox reactions, but their documentation differs in granularity:

Valkyrie Reactions

  1. H2S Oxidation:
    H2S + 2Fe3+ → S↓ + 2Fe2+ + 2H+
  2. Catalyst Regeneration:
    2Fe2+ + ½O2 + H2O → 2Fe3+ + 2OH–
  3. Net Reaction:
    H2S + ½O2 → S↓ + H2O

LO-CAT Reactions

  1. H2S Absorption:
    H2S (gas) + H2O (liquid) → H2S (aq) + H2O (aq)
  2. H2S Ionization:
    H2S (aq) → H+ + HS–
  3. Sulfide Oxidation:
    HS– + 2Fe3+ → S↓ + 2Fe2+ + H+
  4. Oxygen Absorption:
    ½O2 (gas) + H2O (liquid) → ½O2 (aq) + H2O (aq)
  5. Iron Oxidation:
    ½O2 (aq) + H2O + 2Fe2+ → 2OH– + 2Fe3+
  6. Net Reaction:
    H2S + ½O2 → S↓ + H2O

Difference: Valkyrie simplifies the reaction description for practical application, while LO-CAT provides a detailed, five-step breakdown, reflecting its longer history of technical refinement.

Operational Design and Automation

The operational setups differ in automation and system design:

  • Valkyrie: Features skid-mounted, modular units with advanced automation via the Valkyrie Intelligence Platform (VIP). Offers single-button startup, SCADA integration, and remote monitoring, ideal for decentralized operations.
  • LO-CAT: Uses a traditional absorber-oxidizer setup with robust but less advanced automation. Focuses on reliability for industrial-scale operations, with manual-compatible controls.

Difference: Valkyrie’s cutting-edge automation and modularity enhance user-friendliness and remote operation, while LO-CAT prioritizes proven, stable performance with basic automation.

Sulfur Product Characteristics

Both produce elemental sulfur, but their properties vary:

  • Valkyrie: Yields organic-certified sulfur (Simple Elemental Sulfur™), high-purity, and marketable for agricultural use.
  • LO-CAT: Produces 99+% pure sulfur (8–45 microns) as a filter cake, soft-textured, and free of trapped H2S vapors, suitable for soil applications.

Difference: Valkyrie emphasizes organic certification for commercial value, while LO-CAT focuses on technical purity and safety in handling.

Applications and Market Focus

The processes target different market segments:

  • Valkyrie: Focuses on sustainability-driven markets like biogas, renewable natural gas (RNG), and upstream oil and gas (e.g., Permian Basin). Offers configurations like ECO FLEX for low-pressure biogas and TGTU for tail gas treating.
  • LO-CAT: Serves a broader industrial base, including wastewater treatment, petrochemicals, and specialty gases (e.g., coke oven gas). Established in large-scale applications for over 35 years.

Difference: Valkyrie aligns with emerging, green markets, while LO-CAT excels in traditional industrial and specialty applications.

Performance and Efficiency

Both achieve high H2S removal, but their operational envelopes differ:

  • Valkyrie: Infinite turndown, no pressure loss, handles pressures up to 1,400 psig and flows of 0.1–50 MMSCFD. Ideal for low-pressure biogas applications.
  • LO-CAT: 100% turndown, >99.9% removal efficiency, suitable for sulfur loads up to 20 tons/day across any gas stream.

Difference: Valkyrie’s no-pressure-loss design suits low-pressure systems, while LO-CAT’s single-stage treatment optimizes industrial-scale efficiency.

Environmental and Economic Considerations

Both are environmentally friendly, but their economic profiles vary:

  • Valkyrie: Biodegradable chemistry reduces flaring emissions. Automation lowers OPEX, and modular design cuts CAPEX for small-scale operations.
  • LO-CAT: Produces no toxic byproducts, with low OPEX compared to scavengers and lower CAPEX than Claus plants. Proven reliability minimizes maintenance costs.

Difference: Valkyrie’s automation and green chemistry enhance sustainability and cost savings, while LO-CAT’s long-term reliability ensures economic stability.

Comparison Table

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Aspect Valkyrie Process LO-CAT Process
Chemistry TALON® biodegradable chemistry; treats multiple sulfur compounds. Traditional chelated iron; older formulation.
Automation Advanced (VIP, SCADA, single-button startup). Basic; manual-compatible controls.
Sulfur Product Organic-certified, high-purity sulfur. 99+% pure, 8–45 micron sulfur;
no H2S vapors.
Applications Biogas, RNG, upstream oil/gas. Wastewater, petrochemicals,
specialty gases.
Performance Infinite turndown; no pressure loss;
up to 1,400 psig.		 100% turndown; >99.9% efficiency;
up to 20 tons/day.
Environmental Biodegradable; reduces flaring emissions. No toxic byproducts;
regulatory compliance.
Economic Low OPEX via automation;
modular CAPEX savings.		 Low OPEX vs. scavengers;
reliable CAPEX.

Conclusion

The Valkyrie and LO-CAT processes are effective liquid redox solutions for H2S removal, but they cater to different needs. Valkyrie’s biodegradable TALON chemistry, advanced automation, and focus on green markets like biogas make it ideal for sustainable, decentralized operations. LO-CAT’s proven reliability, broad industrial applications, and robust performance suit large-scale, traditional facilities. Operators should choose based on their operational scale, gas stream characteristics, and environmental priorities.

References

  • Streamline Innovations. (2024). Valkyrie H2S Treating Solutions. Retrieved from streamlineinnovations.com.
  • Merichem Technologies. (2020). LO-CAT Sulfur Recovery Solution. Retrieved from merichemtech.com.
  • Digital Refining. (2022). LO-CAT: A Flexible Hydrogen Sulphide Removal Process. Retrieved from digitalrefining.com.
  • Chemical Online. (n.d.). LO-CAT Process Overview. Retrieved from chemicalonline.com.

tion; modular CAPEX savings. Low OPEX vs. scavengers; reliable CAPEX.