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Future Fuels & CO2 - Questions Answered [Ask the Experts]

Originally published by Pipeline Technology Journal, March 2024.*

What are the primary challenges in establishing a regulatory and technical framework for hydrogen pipelines?

Victoria Monsma: The worldwide ambition is to shift to clean energy sources to reduce our CO2 footprint. However, national safety regulators will require evidence to demonstrate that the operators are “hydrogen-ready”. To achieve "hydrogen readiness," a pipeline operator must guarantee that their infrastructure, operations, and personnel are fully equipped to manage hydrogen transportation with the same target safety level as natural gas. This involves a few key elements:

  • Technical Compatibility: The operator's pipeline infrastructure, including pipelines and equipment, must be compatible with hydrogen transportation. 
  • Regulatory Compliance: Pipeline operators must comply with regulatory and code requirements related to hydrogen transportation, including safety, environmental, and operational standards.

Handling hydrogen comes with some challenges that are different from natural gas. This requires adapting existing operations, practices, and organizations, and developing new strategies to ensure safe and efficient transportation. For many years, pipeline operators have effectively operated and managed high-pressure, long-distance oil and natural gas pipelines, relying on their experience and comprehensive safety and integrity data. However, the transportation of hydrogen through similar pipelines poses new challenges in terms of design and operation, integrity, and risk management.

The lack of extensive historical data and operational experience with hydrogen pipelines poses a significant challenge in establishing regulatory standards and technical requirements. Current industry codes and standards for repurposing existing pipelines for hydrogen transport are prescriptive and generally not practical for conversion of pipelines built to natural gas standards. Multiple ongoing efforts are under development by Codes and Standards organizations to provide updates to these requirements.

Additionally, the legal and regulatory framework for H2 transportation is still evolving in most nations. This is one of the greatest challenges faced by the energy sector, the lack of a clear legal and regulatory framework for hydrogen transportation. The safety of such pipelines is regulated using approaches developed for natural gas, which is being debated by industry and regulators.

What are the challenges for integrating Hydrogen into existing pipeline operations, and how can these challenges be addressed?

Tim Illson: For most regions, it will be challenging to manufacture enough hydrogen to operate an entire pipeline system with 100% hydrogen, and there may be insufficient widespread demand initially for a pure hydrogen network to be required. Pipeline network operators have to plan for operating with blends of hydrogen and natural gas or running a hydrogen network in parallel with a natural gas network. These options have different challenges; for blends, the main issue is that not all gas users will require hydrogen but still need natural gas. This may be mitigated by the use of deblending technology, which separates the hydrogen and natural gas after offtake from the pipeline. 

A UK deblending test has been approved as part of the FutureGrid programme. The main challenge with operating parallel hydrogen and natural gas networks is that many facilities would be shared (e.g., compression). The mitigation is careful network planning so that the hydrogen network uses spare capacity in the facilities; for example, a site with multiple compressors could dedicate some to hydrogen and the rest to natural gas. Then, as demand for hydrogen increases, more facilities can be dedicated to the hydrogen network.

In addition, the integrity management system for hydrogen will be different than for natural gas and needs to be suitable for hydrogen.

Kevin Hemingway: Operators encounter significant challenges when integrating alternative gases, such as hydrogen, into existing gas infrastructure. One of the primary challenges stems from the inherent differences in calorific value and thermal content between these alternative gases and traditional natural gas. Hydrogen has a significantly lower thermal content volumetrically, necessitating the combustion of larger volumes to meet the same energy requirements. 

Furthermore, most existing equipment and appliances within the gas distribution network and end-user facilities are optimized for natural gas, posing compatibility issues with alternative gases. Gas operators must ensure blended gases, including those containing hydrogen, remain safe for transport and compatible with various customer appliances such as stoves, heaters, and boilers. This requires comprehensive risk assessments, compatibility studies, potential retrofitting of equipment, and the utilization of robust gas quality tracking systems supported by advanced analytical techniques. By addressing these challenges, gas operators can facilitate the successful integration of hydrogen while maintaining reliable service for customers amidst the transition to decarbonized energy sources.

We are looking to accurately measure and monitor the flow of hydrogen in pipelines. Are there technologies we can rely on to improve this?

Kevin Hemingway: Hydrogen has a low density and high diffusivity, which can complicate traditional measurement methods designed for denser gases like natural gas. As a result, accurately quantifying hydrogen flow rates becomes more challenging, potentially leading to inaccuracies in measurement data.

To address these challenges, various technologies, such as ultrasonic flow meters, advanced computational fluid dynamics (CFD) simulations, and hydraulic modelling software solutions, are being developed to improve the accuracy and reliability of hydrogen flow measurements. 

While ultrasonic flow meters utilize sound waves to measure the velocity of hydrogen flowing through the pipeline, advanced computational fluid dynamics (CFD) simulations model the behaviour of hydrogen within the pipeline, considering factors such as pressure, temperature, and flow dynamics. By simulating different scenarios, operators can better understand hydrogen flow behaviour and optimize pipeline performance.

Advanced hydraulic modelling software solutions are another important tool for improving hydrogen flow measurement accuracy. A powerful tool, such as Synergi Gas, is great for system planning and can be used to size main extensions and replacements for economy and performance, and create long-term strategic plans that maximize gas network infrastructure.  It can also help make daily operating decisions for load approval, compressor operations, and other operational support challenges. Hydraulic models help monitor pipeline conditions, including flow rates, pressures, and temperatures and provide feedback to operators where SCADA may not be available. Furthermore, by integrating data from sensors with hydraulic models, operators can detect anomalies promptly and validate measurement data through virtual simulations.

What are the key factors we should consider when repurposing existing infrastructure for carbon capture and storage (CCS) initiatives?

Kevin Heminway: Repurposing existing infrastructure for carbon capture and storage (CCS) initiatives requires careful consideration of various factors to ensure the safety, reliability, and efficiency of CCS systems. One critical aspect is assessing the structural integrity and suitability of the existing infrastructure for CO2 transportation. This involves conducting thorough evaluations of pipelines and facilities to determine their capacity to safely transport CO2 and implementing necessary upgrades or retrofits as needed to meet CCS requirements.

Managing the potential risks associated with CO2 transportation is another key consideration. Challenges such as fracture control, corrosion, and impurity control must be effectively managed to mitigate risks and ensure the long-term integrity of the CCS system. Implementing strategies to prevent system overpressurization and equipment damage is essential for maintaining safe and reliable operations.

Sophisticated modelling techniques also play a crucial role in addressing challenges associated with repurposing existing infrastructure for CCS initiatives. By utilizing advanced hydraulic modelling solutions, operators can assess the dynamic behaviour of CO2 flow and predict and mitigate transient pressure surges effectively. Designing surge mitigation measures based on these simulations is critical to ensuring system reliability and preventing equipment damage.

Furthermore, implementing robust leak detection solutions is essential for maintaining the integrity and safety of CCS systems. Continuous monitoring of pressures, inventories, and flows enables early detection of leaks or anomalies, allowing prompt response and mitigation measures to prevent environmental risks.

Victoria Monsma: Carbon dioxide (CO2) can be transported via pipelines in different states, such as gaseous, liquid, or dense phase, depending on temperature and pressure. Gaseous CO2 provides less transport capacity because of the lower density of the product and associated frictional pressure drop. Transporting gaseous CO2 would typically be limited to moderate pipeline lengths and transfer rates. Liquid CO2 can provide higher transfer capacity; however, for the existing natural gas pipeline, there might be some potential process and operating challenges. For example, in the case of liquid CO2, one of the key considerations is a ductile running fracture. To prevent ductile running fractures, the decompression speed of the fluid needs to be higher than the fracture propagation speed of the pipeline wall. This shall be considered when assessing the existing pipelines for CO2 transport. If pipe properties cannot arrest cracks, then the operator will need to consider the installation of crack arrestors.

Furthermore, when repurposing existing pipelines for CO2 transport, the topography of the pipeline route becomes crucial. It can present significant challenges, particularly with varying elevations along the route.  The transportation of CO2 demands careful consideration to address the complexities imposed by diverse topographical conditions. Additionally, in the event of a CO2 release, the topographical features pose an additional concern. Due to its density, CO2 has a tendency to flow downhill from elevated areas such as hillsides to lower-lying regions like valleys, where populations often reside

How can we optimize the integration of renewable natural gas (RNG) into existing natural gas systems?

Kevin Hemingway: Renewable natural gas (RNG), also known as biomethane, is produced by upgrading biogas to remove contaminants like CO2 and N2, resulting in a high-BTU gas predominantly composed of methane. RNG sources are characterized by small but consistent flow rates, necessitating flow control rather than pressure regulation. The thermal (energy) value of RNG may vary but is often slightly lower than that of natural gas, although it can occasionally be enriched with propane to align with customary gas energy values.

The proposed thermal value of RNG compared to natural gas is a critical consideration, as a lower value means a larger volume of RNG is required to provide the same energy output. Enforced specifications for RNG system entry are advantageous in ensuring compatibility with existing natural gas infrastructure and operations.

Modelling the integration of RNG into natural gas systems involves assessing whether there is sufficient pipe capacity to accommodate RNG during peak load periods, which is typically the biggest challenge. Conversely, ensuring the system can absorb RNG throughout the year, particularly during periods of low demand, presents another significant challenge. By addressing these differences and challenges comprehensively, integrating RNG into existing natural gas systems can contribute to a more sustainable and diversified energy supply.

When blending hydrogen or any other future fuel, how can we prepare for variations in energy supply and demand?

Kevin Hemingway: Modeling variations in energy supply and demand plays a pivotal role in facilitating the integration of hydrogen blending into existing energy systems. Using advanced modelling techniques, energy planners can analyze the dynamic interactions between hydrogen production, storage, distribution, and consumption alongside traditional energy sources. This enables the identification of optimal blending ratios and operational strategies to maximize the benefits of hydrogen integration while ensuring system stability and reliability.

Moreover, sophisticated modelling tools such as Synergi Gas allow for the simulation of different scenarios, including variations in hydrogen availability, demand patterns, and renewable energy generation. By forecasting future trends and assessing potential challenges, stakeholders can proactively design infrastructure upgrades, grid reinforcements, and market mechanisms to effectively accommodate hydrogen blending.

Additionally, modeling enables the evaluation of hydrogen blending's impact on overall energy system performance, including factors such as grid flexibility, emissions reduction, and cost-effectiveness. This holistic approach aids in developing policies and regulations that incentivize hydrogen adoption and support its role in achieving decarbonization goals.


The Experts

Kevin Hemingway, Product Manager – Synergi Gas and Synergi Liquid, DNVkevin hemingway

Kevin holds business and engineering degrees from Drexel University and Temple University, respectively. He has served the international natural gas and water utility industries for over 20 years by providing computer-based modelling tools, consulting services, client support, and professional training.

Kevin joined DNV in 1996 and has served in client-facing roles focused on gas and liquid hydraulic modelling throughout his tenure. Currently, he is the Product Manager for Synergi Gas and Synergi Liquid, where he continues to collaborate with customers and help DNV better meet its clients' needs through software and service offerings. When not evangelizing for DNV’s modellers or modelling software, he can be found hiking the trails of Pennsylvania with his family, both two-legged and four-legged. 

Victoria Monsma, Principal Integrity Specialist, DNVvictoria monsma

Victoria Monsma, a Principal Pipeline Specialist at DNV with more than 15 years of experience. She is currently engaged in consulting on a broad spectrum of Energy Transition projects. Victoria is a Subject Matter Expert in a field of reuse of existing natural gas network for transport hydrogen. As a SME she is involved in the developing of the company hydrogen service portfolio, methodology, guidelines, service specification. Using her expertise, she is supporting different clients such as gas TSO’s and DSO’s, authorities and other in making them an informed decision with regards to the conversion of their assets to hydrogen.

Tim Illson, Principal Integrity Specialist – Hydrogen and Carbon Transport, DNVTim Illson

Tim Illson has worked in industrial corrosion control for more than 
35 years and is presently involved in consultancy for a wide range of hydrogen and CCUS activities, and renewables infrastructure. Specific areas of technical expertise include pipeline repurposing studies (H2/CO2), corrosion control and materials selection for hydrogen and CO2 pipelines, test programme development for validating hydrogen materials, corrosion of wind turbine structures, cathodic protection of monopile interiors, and offshore and onshore coating systems.


Find out more about Synergi Gas.

 

*To view the original article, visit Pipeline Technology Journal