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With the chemical value of hydrogen (H₂) increasing, what are the best options for extracting H₂ from fuel gas?

Jan-2024

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Cristian Spica, Oli Systems, Cristian.Spica@olisystems.com

Hydrogen is an integral part of the modern energy industry and plays a crucial role in the path to net zero. Despite the strong momentum behind ‘green’ hydrogen, to stay on track for achieving net zero emissions by 2050, we will need more than a doubling of the announced investments by 2030. These investments must mature and be put into action.

Therefore, considering their significant economic advantages and as part of the short- to mid-term strategy to support the development of a clean hydrogen economy, we should make use of ‘grey’, ‘turquoise’, and especially ‘blue’ hydrogen production methods. Industrial technologies currently employed for grey hydrogen production include:
• Catalytic steam methane reforming (SMR)
• Dry reforming (DR)
• Catalytic partial oxidation (CPO)
• Autothermal reforming (ATR)
• Tri-reforming (TR)
• Coal/petroleum coke gasification/pyrolysis.

Blue hydrogen also relies on hydrocarbons but is combined with carbon capture, utilisation, and storage (CCUS) technology, which helps mitigate its environmental impact but may require additional investments.

Turquoise hydrogen is produced through methane thermal pyrolysis. Each of these technologies has its own set of advantages and disadvantages based on the unique characteristics of the process.

While SMR is one of the most established and widely used technologies for grey hydrogen production, it is also one of the most energy and capital-intensive processes. This is because the endothermic reaction in SMR requires heat, and the catalyst can suffer from deactivation if the fuel gas is not properly desulphurised.

Additionally, in an SMR plant, there are two sources of CO₂ emissions: one from the oxidation of carbon atoms in the feedstock during reforming and shift reactions and the other from combustion in the reformer furnace. To capture all the CO₂, a post-combustion plant is required, as pre-combustion capture can only capture the CO₂ in the syngas.

Despite these challenges, SMR is still considered one of the most efficient methods for producing grey hydrogen, especially when heat integration is part of the process design. The same efficiency advantage applies to DR, but it also faces the drawback of coke deposition on the catalyst surface. In the case of CPO, the partial oxidation of CH₄ and other hydrocarbons in the fuel gas is a slightly exothermic reaction, making it less capital-intensive than SMR. However, it initially produces less hydrogen and CO₂ per unit of input fuel compared to SMR. To produce high-purity H2, pure oxygen or an air separation unit (ASU) is needed.

ATR generates syngas by partially oxidising a hydrocarbon feedstock with oxygen and steam, along with subsequent catalytic reforming. Unlike SMR, the heat for the reaction is provided within the reaction vessel, eliminating the need for an external furnace. This method allows up to 99% of carbon removal directly from the syngas, resulting in lower carbon capture costs. ATR, when combined with CO-shift and carbon capture technology, is one of the most cost-effective solutions for large-scale low-carbon hydrogen production.

TRM is a combination of SMR, CO₂ reforming, and PCO in a single reactor for efficient syngas production. The inclusion of oxygen in the reaction generates in-situ heat, which can enhance energy efficiency. However, it may present challenges in terms of heat transfer and temperature uniformity in the catalyst bed.

The choice of the best production process depends on several factors affecting both capital and operational expenditures, including hydrogen yield, purity, energy efficiency, flexibility, plant complexity, and raw material availability. ATR combines the advantages of both SMR and partial oxidation, offering a high hydrogen yield, rapid reaction kinetics, and reduced reactor number and size.

OLI Systems provides unique tools for designing and safely operating grey and blue hydrogen facilities. These tools encompass a wide range of capabilities, including modelling for various production processes (SMR, ATR, TRM, CPO) for hydrogen storage, transportation, and CCUS. These tools offer rigorous mass balance, corrosion, and scaling risk assessment, considering the reactivity and phase equilibria of impurities and their potential negative impacts on plant safety and reliability. Hydrogen as well as CO₂ dense phase, especially when containing impurities, can promote corrosion in materials such as steel, pipelines, and storage tanks. Impurities like water vapour, oxygen, sulphur compounds, nitrogen compounds, and carbon monoxide can react with hydrogen to form corrosive substances, making the selection of corrosion-resistant materials essential for hydrogen transportation infrastructure.

Jan-2024
Neeraj Tiwari, Honeywell UOP, Neeraj.Tiwari@Honeywell.com

High-yield byproducts generated by the refinery process for motor fuel, diesel or aromatics production can be high-value secondary revenue. The typical composition of fuel gas contains H2 as ~30-50 mol%, and other major components are LPG range material. To monetise the benefit of these high-value byproducts and increase the overall profitability, a novel concept involving a dual sponge absorber can be applied to the off-gas stream (routed to fuel gas header) to recover the majority of LPG range material along with light naphtha, if any.
The application of a novel dual sponge absorber will improve the hydrogen composition in off-gases to a high level (such as 70-85 mol%). This high-purity gas can then be routed to PSA to recover hydrogen efficiently having a purity of 99.9 mol%. In catalytic reforming, secondary byproducts generated include H₂, LPG, and fuel gas. Of these byproducts, the lowest value byproduct is generally fuel gas.

UOP’s proprietary RecoveryMax system allows 95% recovery of hydrogen, >85% LPG recovery, and nearly 100% reformate recovery by purifying more of these byproducts and not diverting them to fuel gas. Alternative options are being explored based on where hydrogen is being used as one of the raw materials.
One option is to contact the feed stream or any hydrocarbon stream with hydrogen-rich fuel gas that will absorb the hydrogen; then, the absorbed hydrogen can be used during the reaction process.

Concern with this option is that it can also absorb impurities from fuel gas (such as C1, C2), which may not be desirable in the process.

Jan-2024