Story by: Tyler Campbell, Managing Editor, H2Tech

The energy transition will require various innovations, such as sustainable aviation fuel, automation and hydrogen (H₂). Although much attention has been given to green H₂, blue H₂ development will be crucial and may make more sense depending on the sector (e.g., refining). At Honeywell Users Group 2023, Naved Reza, Director, Business Development Sustainable Technology Solutions for Honeywell UOP, delivered a presentation titled “Powering the CO₂ countdown with blue H₂.”

Honeywell UOP has been developing H₂ processing solutions for decades. The company does not make electrolyzers but does produce catalytic-coated membranes for the electrolyzer stack. However, this presentation is focused on UOP’s blue H₂ purification and carbon capture methods. A blue H₂ process takes the CO₂ traditionally emitted into the atmosphere, purifies it, and either stores it underground through industrial carbon capture and storage (CCS) or transports it for utilization in another industrial process. According to Reza, of the 40 million tons (MMt) of CO₂ captured, 15 MMt (approximately 38%) were captured by UOP's technology. The company intends to be carbon neutral in its operations by 2035.

Today, about 50 billion tons per year (Btpy) of greenhouse gas (GHG) is emitted. Nearly half comes from power generation, refining, steel and cement. CCS has the potential to decarbonize these hard-to-abate segments. According to the International Energy Agency, by 2050, 660 MMtpy of H₂ will be needed, accounting for approximately 22% of the global energy demand. Gray H₂ is currently the primary type of H₂ produced, but Reza notes a Hydrogen Council study predicting that by 2050 there will be no gray H₂, and the energy mix will be dominated by blue (approximately 300 MMtpy) and green H₂ (approximately 200 MMtpy).

To meet these projections, UOP has several purification and carbon capture processes highlighted in the presentation revolving around steam methane reforming (SMR) and autothermal reforming (ATR). “Today, SMR is the primary method for producing gray H₂,” Reza said. “However, we see that for new projects like the ExxonMobil Baytown project, they will use ATRs for H₂ generation, and decarbonize it using carbon capture, resulting in a very low carbon intensity (CI) H₂.”

SMRs contain two streams for the CO₂ to come through. One is the CO₂ produced during combustion, about 40% and 60% is present in the synthetic gas (syngas)—carbon monoxide (CO) and H₂. SMRs have pre and post combustion—pre combustion is capturing the CO₂ before combustion is completed. In ATR, the methane (CH₄) is combusting with oxygen in a controlled environment. In this circumstance, all the CO₂ produced comes through one stream.

UOP has multiple carbon capture and pressure swing absorption (PSA) technologies for SMR and ATR based H₂ production processes that are slightly different. In the first ATR configuration, the syngas—40%−50% H₂, the remainder is CO₂—goes through a H₂ PSA system, separating the H₂ and pushing the CO₂ through the tail gas. The CO₂ is then compressed, dried and passes through UOP’s CO₂ fractionation system, removing the CO₂, liquefying it and sending it to the pipeline for storage or utilization.

According to Reza, the process will have some off-gas. “There will be CO₂ and CH₄, and you will recycle it and go through the same process,” he said. “At the end, you should be able to capture most of the CO₂.” The ATR has a preheater upstream that uses CH₄ as fuel to burn. The ATR-fired fuel contains a small amount of H₂ and will be sent to the preheater to be used as fuel for the combustion process, further reducing the CI and purging the argon and nitrogen.

In the second ATR configuration, carbon-free fuel gas (ATR-fired fuel) is produced. This ATR-fired fuel has no CO₂, thus lowering the CI of the combustion process in the preheater, enabling Scope 1 emissions reduction of the whole process to <0.1 kilograms (kg) of CO₂ per kg of H₂ produced. The process is mostly the same as the first configuration; however, the capital expenditure (CAPEX) is 2%−5% greater due to a much larger PSA. The ExxonMobil Baytown facility is using this configuration with minor variation.

Regarding the SMR processes, methane in natural gas is heated with steam in the presence of a catalyst to produce syngas (mixture of CO and H₂), which then goes through the water gas shift (WGS) process. The WGS process produces H₂ and CO₂, and the Polybed H₂ PSA separates them. Once again, UOP’s CO₂ fractionation system recycles the CO₂ and CH₄ into the system. In this process, 90% of the H₂ in the tail gas is captured and added to the main H₂ stream, resulting in an additional 20% H₂ yield with about 99.9% purity.

The second SMR carbon capture process presented uses a Polybed CO₂ PSA, and the H₂ purity is not as high, at about 95%; however, according to Reza, it has the lowest CAPEX and operational costs (OPEX) of all systems previously mentioned. The 90%−98% of CO₂ recovered from the PSA tail gas in this process results in a 50%−60% CO₂ emissions reduction compared to existing SMR processes without carbon capture.

The Amine Guard^TM FS is the third solution for CO₂ capture that UOP offers. Everything in this system is the same, except the CO₂ exported from the WGS reactor is passed through the Amine Guard system upstream of the H₂ PSA, where the CO₂ capture takes place—the H₂ is separated with the Polybed H₂ PSA.

The final SMR carbon capture solution is the advanced solvent for carbon capture. According to Reza, more than 95% of CO₂ can be captured with this process. In this process, the CO₂ and CH₄ in the tail gas are recycled into the H₂ production process.

“All the CO₂ is passed through the flue gas, and we put our advance solvent carbon capture solution to capture the CO₂,” Reza said. “With this, greater than 95% of carbon capture is possible in an SMR, whereas in the previous examples, it was about 50%−60%.”