Aug-2023

Opportunities for decarbonising existing hydrogen production

Decarbonising existing SMR-based hydrogen production units is possible, and each solution has advantages and disadvantages related to the required modifications.

Omar Bedani
Wood

Article Summary

The effects of climate change are becoming increasingly apparent. As a result, the energy and materials industries have been given a strong mandate to take clear and decisive actions to reduce dependency on oil and cut greenhouse gas emissions to mitigate the effects of climate change.

Hydrogen can be a key enabler of the transition to a lower carbon future for heavy industry. With minimal modifications to existing assets, hydrogen can be used as a fuel with zero carbon dioxide (CO₂) emissions. It can also be used as a means for low-carbon energy storage, and new value chains are emerging for the transportation and consumption of hydrogen, including ammonia, methanol, and methane.

However, the hydrogen available to us naturally is bound to other elements, for example, oxygen in water or carbon in hydrocarbons. Hydrogen production via water electrolysis is costly as it needs power, and these power sources must be produced renewably if we want to really consider our hydrogen as low or zero carbon emitting. While electrolysis has been in existence for a long time, it can be argued that the process is not yet technologically or commercially mature at the scale required to provide the huge amount of energy we currently use, despite several gigawatt-scale projects planned globally.

Extracting hydrogen from hydrocarbons using a process called reforming is less energy intensive, but the primary by-product of this process is CO2, which we want to avoid. Therefore, for this process to be reasonably sustainable, the CO2 must be recovered from the process and then either stored or reused.

Reforming has been proven at scale for decades within the refining and chemical sectors. However, the amount of CO₂ produced by this process is large: each steam reforming unit produces in the range of 8.5-10 tons of CO₂ for each ton of hydrogen product.

To achieve the full promise and scale of hydrogen using steam reforming in the near to medium term, there is no doubt that new assets must be coupled with a carbon capture system. The low-carbon hydrogen produced through the combination of these technologies is often called blue hydrogen.

What about existing hydrogen production facilities?
In 2021 alone, the world produced 94 million tons of hydrogen – 74 million tons as pure hydrogen and 20 million tons as hydrogen mixed with other gases (IEA, 2022). More than 50% of this hydrogen was produced via steam reforming, resulting in approximately 900 million tons of CO₂ emissions. To put this into perspective, the total CO₂ emissions of Spain, Italy, and France combined in the same year equalled 850 million tons (European Commission, 2022). These economies collectively represent nearly 1/12th of the global GDP.

This example shows both the magnitude of the challenge and the potential benefit of reducing CO₂ emissions from hydrogen production via decarbonising existing steam methane reforming (SMR) facilities.

Hydrogen production unit under consideration
Given its significant near-term positive potential, this article focuses on four options that Wood has developed for decarbonising an existing hydrogen production unit based on steam reforming.

The unit on which this analysis has been performed was designed by Wood in 2017 and has been operational since 2020. It is designed to produce 80,000 Nm³/h (approximately 173 TPD) of hydrogen at 99.9% purity by reforming natural gas and does not have a pre-reforming section or any provision for carbon capture installation. It works on high-temperature (HT) shift and is equipped with an HT combustion air pre-heating system.

In each of the four cases, reduction in CO₂ emissions/carbon impact, capital expenditure, operational expenditure, and project implementation time are compared with a reference case. The reference case is the revamp of the existing unit by adding a post-combustion carbon capture system.

To better understand the solutions in this article, it is important to properly define some terms that will be used:
λ    Post-combustion carbon capture: this refers to a solvent-based carbon absorption system added to the flue gas stream leaving the hydrogen production unit by means of the stack installed on top of the furnace.
λ    Pre-combustion carbon capture: this refers to a carbon removal system installed on the syngas stream leaving the reaction section of the hydrogen unit (meaning, it removes the CO2 before the syngas enters the final purification section).
λ    Gas heated reformer: a convection-type steam reforming reactor in which the process heat required is provided by cooling down the syngas leaving the steam reforming furnace.
λ    Carbon impact: is the parameter used by UK regulations to measure the CO₂ footprint of the facility under assessment.

For the purpose of this article, Wood has considered both the carbon capture options to be a solvent-based absorption system.
The results described are not fully exhaustive of the options available on the market, and each unit will have its own unique characteristics.