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Hydrogen blending is gaining momentum as a method to reduce greenhouse gas emissions and transition towards cleaner energy sources.
Naturally available, raw natural gas is composed of primarily Methane of approximately 75 – 95% by volume.
The world’s natural gas (~ 90-95% Methane gas, further refined on raw natural gas) infrastructure has grown into a sprawling network over decades, has built vast networks spanning hundred thousands of kilometers, often referred to as transmission pipelines. They transport natural gas over long distances at high pressures (can vary depending on the pipeline) and large diameters (often exceeding one meter).
Methane is a much stronger greenhouse gas than carbon dioxide (CO2). Over a 20-year time frame, it traps over 72 to 80 times more heat than CO2. Dual contribution to global warming, firstly by burning natural gas, CO2 is released and other through leaks (from pipelines, agriculture, landfills) it reaches atmosphere directly.
Hence natural gas decarbonization is the second most priority after CO2 emission.
Hydrogen burns in clean way, only water vapor and heat released. No carbon based emissions. (small Nox is possible).
As hydrogen is playing a crucial role in the energy transition and decarbonization, it is natural to think why not use a low mixture of hydrogen and natural gas together towards the path of decarbonizing natural gas burning, by taking advantage of the vast pipelines of existing natural gas infrastructure.
Achieving carbon neutrality demands a shift from fossil fuels to clean alternatives. While transitioning directly to pure hydrogen might seem ideal, a more practical approach could involve an incremental blending of hydrogen with existing natural gas.
This blending strategy offers a seamless transition by leveraging existing infrastructure. By gradually increasing the hydrogen content (from 5% to final target < 40%), disruptions to public power and heating distribution networks can be minimized. This smoother path paves the way for a successful transition towards clean energy.
Here comes hydrogen blending!
Hydrogen blending is the controlled introduction of a specific proportion of hydrogen gas into an existing gas stream, typically natural gas. This creates a blended fuel with a lower carbon footprint compared to the original gas.
Mixing vs. Blending: Blending is a controlled and precise process, ensuring a consistent and well-defined hydrogen concentration within the final mixture. Mixing, on the other hand, can be less precise and might involve combining different gases without strict control over the final composition.
Infrastructure: Hydrogen blending leverages existing natural gas infrastructure like pipelines, compressor stations, and storage facilities. This significantly reduces the cost and time needed for widespread hydrogen adoption compared to building entirely new infrastructure for pure hydrogen.
Blending is primarily used for large-scale applications, such as decarbonizing the natural gas grid for power generation and industrial processes.
Main reason for adopting the blending:
- Approach for achieving near-term emissions reductions
- Early market access for hydrogen technologies
- Blending would primarily require minimal modifications to the existing fuel delivery infrastructure – pipeline networks
- Least or no changes to the appliances used by the consumers
- No need for a huge substantial investment costs for creating dedicated hydrogen transmission and distribution infrastructure which is still in the early stages
Blending ratio:
Hydrogen embrittlement: It is well known that the presence of hydrogen causes cracking in commonly used pipeline solid metals and hydrogen also affects the fatigue properties of steels.Hence blend ratio depend on the design and condition of current pipeline materials, pipeline infrastructure equipment, and end user applications that utilize natural gas.
Learning and fine tuning the blending and outcome will open up new areas of using Hydrogen as a fuel with large blending ratio.
Most common blending of hydrogen with natural gas is 5% by volume.
For CNG vehicles, the current value for the proportion of hydrogen used is only 2 vol%, depending on the materials built in.
Range of Blending Ratios
Studies and trials suggest that blending up to 20% hydrogen by volume into natural gas pipelines might be technically feasible without requiring major infrastructure changes.
Researchers are studying how mixing hydrogen with methane (natural gas) affects the gas’s properties. This includes density, flow behavior (viscosity), how the gases mix (phase interactions), and the amount of energy it can hold (energy density).
- The goal is to understand if these blended fuels can be safely transported through pipelines and used in existing appliances like engines, burners, and fuel cells, potentially with some modifications.
- While hydrogen is a clean energy source, safety concerns exist when transporting the blended gas. These include potential for leaks and pressure build-up in pipelines.
Numerous challenges and uncertainties complicate blending approach to natural gas decarbonization.
The blending ratio of hydrogen in natural gas is currently a topic of research and development, with ongoing discussions about safety, infrastructure, and effectiveness. There isn’t a single universally accepted ratio.
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