Project Case Study
Liquid H2S Scavenger Project
Triazine Atomizer Technology
Triazine and Iron oxide (Fe₂O₃) pellets
H2S Scavenger capable of scrubbing H2S gas from 500pm to 10ppm
Certified & High Capacity
CE/UKCA & ATEX certified; processes 50 Nm³/hr at 200psi for safe and efficient gas management.
Delivered in 18 Weeks
Strict timeline met by collaborating with suppliers to tailor equipment and integrate with existing infrastructure.
Overview
This case study focuses on a Liquid H₂S Scavenger system that Kapwell designed for a natural gas processing application. The client was dealing with raw gas containing high levels of hydrogen sulfide (H₂S) – around 500 ppm – which needed to be reduced to very low levels (approximately 10 ppm) to meet safety and export specifications. Instead of installing a large amine treating unit, the client sought a compact scavenger-based solution. The project’s objective was to implement a chemical scavenger system that could reliably scrub out H₂S from the gas stream. The system had to be skid-mounted, automated, and compliant with CE/ATEX standards, and it needed to be delivered quickly to address the sour gas issue in a timely manner.
Solution
Kapwell provided a triazine-based H₂S scavenger system combined with an iron oxide polishing stage – a hybrid approach to maximize H₂S removal. The solution works in two stages: 1. Triazine Atomization: A liquid scavenger (triazine chemical) is injected into the gas stream through a special atomizer, allowing it to rapidly react with H₂S. The triazine chemically binds with H₂S, forming a non-volatile compound and thus removing H₂S from the gas phase. 2. Iron Oxide (Fe₂O₃) Pellet Bed: After the triazine stage, the gas passes through a vessel packed with iron oxide pellets (often known as iron sponge). These pellets adsorb any remaining H₂S, pulling the concentration down to virtually zero. They act as a backup to catch what the triazine might miss, ensuring the H₂S is reduced from 500 ppm to about 10 ppm or lower.
The entire setup was contained on a skid, which included chemical storage and dosing pumps for the triazine, the contactor (mixing) section, and the iron oxide absorber vessel. Kapwell designed the system for a flow of 50 Nm³/hr of gas at up to 200 psi operating pressure[29]. All components like pumps, valves, and the vessel were CE marked and ATEX rated, ensuring safe operation with the toxic and potentially explosive sour gas. The system also featured automation to control the dosing rate of triazine based on H₂S levels and to monitor the saturation of the iron oxide bed.
Key
Features
Hybrid Scavenger Process
Combines liquid triazine injection and dry iron-oxide adsorption to achieve deep H₂S removal. This dual method ensures high effectiveness – the triazine reacts quickly with most H₂S, and the iron sponge polishes the rest, achieving outlet H₂S levels ~10 ppm.
Certified & High-Pressure Design
The unit is CE/UKCA & ATEX certified, designed for 50 Nm³/hr gas flow at 200 psi operating pressure. It can safely handle high-pressure sour gas, and the certification means it meets all relevant European Pressure Equipment Directive and explosive atmosphere requirements.
Automated Chemical Dosing
Features an automated scavenger dosing system that adjusts triazine injection rates based on real-time H₂S measurements or flow rate. This optimizes chemical usage, ensuring enough scavenger is injected to remove H₂S without wastage. It also provides alarms when the chemical storage is low or if H₂S breakthrough is detected, making the system largely self-regulating.
Fast Deployment Skid
The scavenger system was fabricated and delivered in 18 weeks, a rapid timeline compared to large-scale amine units. The skid came pre-assembled with all piping and wiring, allowing quick on-site installation. This fast-track deployment was essential for the client to quickly mitigate the H₂S issue in their gas.
Challenges & Innovation
A significant challenge was achieving a large H₂S reduction (500→10 ppm) in a single pass, which typically would require substantial contact time or large equipment. The innovative hybrid approach addressed this by using two complementary scavenger techniques: the fast-reacting liquid triazine handles the bulk H₂S, and the solid iron oxide bed provides a long-lasting polishing capability. This innovation meant the system could be relatively compact yet highly effective. Another challenge was managing the by-products of H₂S scavenging – triazine reactions produce spent chemicals that needed to be handled, and iron oxide eventually becomes spent sulfur compounds. Kapwell innovated by incorporating an efficient contactor design (for thorough mixing of triazine with gas) and designing the iron oxide vessel for easy media replacement. They also provided guidance on spent scavenger disposal as part of the solution. Lastly, working under a tight timeframe (18 weeks) forced innovation in project execution; Kapwell pre-procured some standard components and used modular construction so that chemical skid and absorber vessel fabrication occurred in parallel, compressing the schedule.
Client Benefit
Effective H₂S Removal
The client’s gas is now treated from 500 ppm H₂S down to ~10 ppm, ensuring the gas meets safety and pipeline specifications. This protects downstream equipment and pipelines from H₂S corrosion and avoids health hazards. The client can now sell or use the gas confidently without H₂S-related issues.
Improved Safety and Compliance
Removing H₂S dramatically improves site safety – workers are not exposed to high H₂S levels, and the risk of toxic releases is minimized. The client also stays in compliance with environmental and occupational regulations regarding H₂S emissions and exposure.
Cost Savings vs. Alternatives
The scavenger approach provided a cost-effective and quick solution compared to installing a full amine sweetening unit. Capital and operating costs are lower, especially for the scale of 50 Nm³/hr. The quick deployment (18 weeks) meant the client could resolve their sour gas problem faster, possibly avoiding production shut-ins or penalties.
Operational Flexibility
The system is modular and can be adjusted (e.g., by changing chemical dose or adding more iron oxide) if H₂S levels fluctuate. The client benefits from this flexibility – if their gas throughput or H₂S content changes, they can adapt the scavenging rate accordingly. Additionally, maintenance is straightforward (replacing the iron oxide periodically and refilling chemical), which can be done without major downtime.
Timeline
Delivered in 18 weeks. This fast delivery allowed the client to start gas treatment almost 4–5 months from project kick-off. The timeline was met by parallelizing engineering and fabrication and close coordination with component suppliers, enabling on-time commissioning and quick H₂S mitigation.