AMF #19 - Fuel Reforming Technology in Marine Applications: Technical Considerations

1. Introduction

Fuel reforming is a process that enables the chemical transformation of primary fuels such as ammonia, methanol, or liquid organic hydrogen carriers (LOHCs) into secondary fuels that are better suited to specific onboard energy applications. This conversion typically occurs within a dedicated unit, often called a fuel reformer or fuel cracker. Through a combination of controlled thermochemical reactions, catalytic materials, and precise temperature management, the reformer breaks down the original fuel into hydrogen-rich gases or other compounds. These reformed fuels can then be directed to advanced propulsion systems or power generators, including fuel cells and hydrogen-fueled engines, providing a more efficient and environmentally conscious energy source for maritime use.

The appeal of fuel reforming in marine applications lies in its ability to optimize the energy density, emissions profile, and operational flexibility of alternative fuels. For example, hydrogen generated from ammonia cracking can be used as a zero-carbon energy source, while methanol reforming can provide a stable hydrogen supply that potentially can be integrated with onboard carbon capture systems (OCCS) as long as technology and value chain are in place. LOHC-based reforming offers the advantage of storing hydrogen safely in a liquid carrier, releasing it only as needed, which can significantly simplify onboard hydrogen handling.

Each reforming method comes with its own set of technical considerations, challenges, and benefits. The choice of catalyst, the operating temperature range, the efficiency of the conversion process, and the management of by-products such as CO2 or nitrogen are all critical factors that must be carefully engineered and managed. Furthermore, integrating reformers into shipboard energy systems requires detailed planning to ensure compatibility with existing propulsion equipment, regulatory compliance, and minimal impact on vessel operations.

2. Ammonia Cracking to Hydrogen and Nitrogen

One notable application of fuel reforming is the cracking of ammonia. By decomposing ammonia into hydrogen (H?) and nitrogen (N?), shipboard systems can produce a hydrogen-rich fuel stream suitable for various advanced propulsion and power generation systems. Hydrogen generated through ammonia cracking can be directed to fuel cells with already available technology in the market, enabling the use of proton exchange membrane (PEM), solid oxide, or alkaline fuel cells, depending on the specific design criteria.

• Catalysis and Thermal Requirements: Ammonia cracking often utilizes a metal-based catalyst to facilitate the decomposition reaction at lower temperatures than would otherwise be required. Typical operating temperatures range from 400°C to 600°C, depending on the catalyst material and the desired hydrogen yield.
• Integration with Fuel Cells: Hydrogen derived from ammonia can be fed into fuel cells for direct electricity generation. Alternatively, it may serve as a pilot fuel in dual-fuel ammonia engines, ensuring stable ignition and reducing or eliminating CO? emissions.
• System Complexity: While the use of hydrogen offers flexibility in selecting fuel cell technologies, the additional cracking equipment adds complexity to the system design. Considerations include thermal management, catalyst longevity, and the handling of nitrogen as a non-reactive by-product.

3. Reforming of Liquid Organic Hydrogen Carriers (LOHCs)

LOHC-based reforming technologies offer a viable pathway for storing and transporting hydrogen in a liquid form that can be converted back to hydrogen on demand. This approach enhances safety in handling and storage while ensuring a consistent supply of hydrogen for fuel cells or other consumers.

• Dehydrogenation Process: The reforming of LOHCs involves the release of hydrogen through endothermic dehydrogenation reactions. These reactions typically require elevated temperatures, often exceeding 200°C, and may utilize specialized catalysts to optimize the rate of hydrogen release. Effective catalyst selection is crucial for maximizing efficiency and minimizing energy input.
• Thermal and Energy Balances: Given that the dehydrogenation process consumes heat, integrating waste heat recovery systems can significantly enhance overall system efficiency. Optimizing the thermal cycle and ensuring steady-state operation are critical for maintaining consistent hydrogen output.
• Impact on Fuel Cell Performance: The purity of hydrogen produced from LOHCs has a direct impact on fuel cell performance. Contaminants or incomplete conversion can necessitate additional purification stages, thereby increasing system complexity and potentially affecting overall efficiency.

4. Methanol Reforming

Methanol is another candidate for onboard reforming due to its relatively simple chemical structure, availability, and well-established handling infrastructure. Reforming methanol to produce hydrogen and carbon dioxide (CO?) can support marine power systems while enabling future potential integration with carbon capture technologies.

a) Reforming Reactions: Common methods for methanol reforming include steam reforming and autothermal reforming.

• Steam Reforming (SR): Methanol and water are converted into hydrogen and CO? via endothermic reactions facilitated by a catalyst, typically operating at temperatures between 200°C and 300°C.
• Autothermal Reforming (ATR): ATR combines partial oxidation with steam reforming in a single unit, balancing endothermic and exothermic reactions. This approach simplifies thermal management and reduces the need for external heat sources.

b) CO? Management: The pure CO? by-product can be captured and stored onboard potentially contributing to compliance with future greenhouse gas reduction regulations.

5. Technological and Operational Considerations

• Catalyst Selection and Longevity: The choice of catalyst materials (e.g., nickel-based, noble metals) affects reformer efficiency, operating temperature, and lifecycle. Proper selection and maintenance of catalysts are critical to ensuring consistent hydrogen production over long service intervals.
• Thermal Management Systems: Given the high-temperature requirements of many reforming processes, effective thermal insulation, heat recovery systems, and cooling circuits must be incorporated into the design.
• System Scalability: Future ship designs may include modular reforming systems that allow for capacity scaling as fuel demand increases. This approach can also accommodate changes in fuel availability or shifting regulatory requirements.
• Integration with Onboard Carbon Capture Systems (OCCS): For fuels like methanol that produce CO? as a by-product, integrating reformers with OCCS units can help reduce net emissions, aligning with emerging industry standards for decarbonization.

6. Risks and Hazards

The risks and hazards associated with fuel reforming depend significantly on the types of fuels involved, including both the primary fuels (such as ammonia, LOHC, or methanol) and the reformed fuels (typically hydrogen and by-products like CO2 or nitrogen). For example:

• Ammonia-to-Hydrogen Reforming: Ammonia is toxic, and leaks can lead to significant safety hazards for crew and equipment. Hydrogen is flammable and poses explosion risks, requiring careful management of leak detection, ventilation, and spark prevention systems.
• LOHC-to-Hydrogen Reforming: LOHCs are generally safer to handle than compressed hydrogen, but the reforming process can produce high temperatures and hazardous by-products that need proper containment. The release of hydrogen must be controlled to prevent accumulations in enclosed spaces.
• Methanol-to-Hydrogen Reforming: Methanol is flammable, and its vapors can form explosive mixtures with air. The reforming process generates both hydrogen and CO2, necessitating robust systems for CO2 handling and hydrogen storage.

In all cases, reformers must be designed with proper shielding, safety valves, continuous monitoring systems, and emergency shutdown procedures to mitigate risks. Refer to fuel-specific risk tables for detailed hazard profiles and mitigation strategies.

7. Existing Guidance Documents and Standards

Currently, the primary guidance for fuel reforming within marine applications is found in MSC.1/Circ.1647, the Interim Guidelines for the Safety of Ships Using Fuel Cell Power Installations. This document outlines general safety considerations, system requirements, and definitions for components such as fuel reformers, reformed fuels, and the associated piping and storage systems.

According to guidelines, a fuel reformer encompasses all equipment necessary for processing gaseous or liquid primary fuels into reformed fuel suitable for fuel cells. The system can be configured either as an integrated component within the fuel cell system or as a standalone unit connected to fuel cells via reformed fuel piping.

The implementation of fuel reformers requires careful consideration of dual safety requirements, as spaces housing these units must comply with safety protocols for both primary and reformed fuels. The reformed fuel piping systems must adhere to strict safety standards, including prohibition of routing through enclosed spaces outside designated fuel cell areas, requirement for full welding wherever practically possible, and minimization of connection points to reduce potential leak sources. Fixed hydrogen detection systems must be installed at critical points such as valves, flanges, and seals.

Safety monitoring in fuel reforming systems encompasses several critical parameters, including potential cross-contamination between air and fuel systems, system pressures and temperatures, and automated sequences for containing or managing reaction propagation. Notably, current maritime safety guidelines specifically exclude provisions for reformed fuel storage, focusing instead on the immediate production and utilization of reformed fuel within the system.

The fuel reforming system integrates into the vessel's overall safety architecture, working in conjunction with emergency shutdown procedures, ventilation requirements, gas detection systems, and fire safety measures. This comprehensive approach ensures that the reformation process maintains the high safety standards required in maritime applications while effectively supporting the fuel cell power installation's operation.

While it provides a foundational framework, these guidelines are primarily focused on fuel cell systems and do not comprehensively address all potential reformer applications or the full range of fuels that might be utilized.

Gaps in Guidance and Standards

Fuel reforming is not yet comprehensively addressed in maritime regulations. While MSC.1/Circ.1647 introduces the concept of reforming fuel cell systems, there are significant gaps:

• Applications Beyond Fuel Cells: No detailed guidance exists for reformers used in internal combustion engines (ICEs) that rely on reformed fuels, such as hydrogen produced from ammonia or LOHC. Systems that may generate pilot fuel (e.g., hydrogen for ammonia engines) lack dedicated standards.
• Risk Management: Fuel-specific risk assessments are not fully incorporated into existing guidelines. For example, the unique hazards of ammonia reforming and LOHC dehydrogenation are not separately treated.
• Operational Procedures and Maintenance Standards: There is limited regulatory clarity on how to maintain and inspect reformers, manage catalyst replacement, or handle unexpected system shutdowns.

8. Further Adoption

The primary roadblock to more widespread use of fuel reformers in marine applications is the absence of comprehensive guidelines and regulations. Without clear, internationally recognized standards, there is uncertainty in system design, certification, and compliance. This lack of regulation results in:

• Inconsistent Safety Practices: Operators must rely on manufacturer recommendations or ad hoc safety measures, which may vary widely in quality and thoroughness.
• Hesitancy to Invest: Delay in adopting reformer technologies due to uncertainty about future regulatory requirements, potential retrofitting costs, and the complexity of integrating reformers into existing propulsion systems.
• Limited Vendor Accountability: With no unified standard, equipment manufacturers are not uniformly held to the same performance and safety benchmarks, may increase the risk of design flaws or suboptimal installations.

9. Final Thoughts and Key Takeaways

Fuel reforming holds promise as a transformative technology for the marine industry, offering a pathway to integrate alternative fuels into advanced power systems while addressing the pressing need to decarbonize shipping operations. By converting primary fuels such as ammonia into application-specific fuels most notably hydrogen, fuel reforming enables the use of cleaner energy sources in fuel cells, hydrogen engines, and other innovative propulsion systems. This process not only improves emissions performance but also increases fuel flexibility, enabling safer, more efficient vessel designs.

However, challenges remain. Existing guidance documents only partially cover the range of reforming applications, leaving gaps in standards for certain configurations and fuels. The lack of comprehensive regulations and clear operational guidelines creates hurdles. Furthermore, the complexity of reforming technologies, including catalyst selection, thermal management, and by-product handling, necessitates careful engineering and robust safety protocols.

In summary, fuel reforming emerges as a key driver of cleaner and more adaptable maritime energy strategies. Despite ongoing challenges, its potential to facilitate decarbonization, improve fuel flexibility, and accelerate the adoption of innovative propulsion technologies establishes it as an important part of future sustainable ship designs.

Disclaimer: This article reflects the author's personal views and does not represent ABS in any way. It is not official communication from ABS, and the information here should not be taken as professional or legal advice.