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Danish team electrifies steam-methane reforming for greener approach to hydrogen production

Researchers from the Technical University of Denmark and Haldor Topsoe, with colleagues from the Danish Technological Institute and Sintex have developed a “disruptive approach to a fundamental process” by integrating an electrically heated catalytic structure directly into a steam-methane–reforming (SMR) reactor for hydrogen production. A paper describing their approach is published in the journal Science.

Intimate contact between the electric heat source and the reaction site drives the reaction close to thermal equilibrium, increases catalyst utilization, and limits unwanted byproduct formation. The integrated design with small characteristic length scales allows compact reactor designs, potentially 100 times smaller than current reformer platforms. Electrification of SMR offers a strong platform for new reactor design, scale, and implementation opportunities. Implemented on a global scale, this could correspond to a reduction of nearly 1% of all CO2 emissions.

—Wismann et al.

Esmr

Heating principles. (A) Conventional fired reactor. (B) Electric resistance–heated reactor. Characteristic radial length scales and temperature profiles are shown across the heat source, reactor wall (gray), and catalyst material (green). In (B), the heat source and reactor wall are one. Illustrations are not to scale. Wismann et al.


Steam methane reforming (SMR) is the most common process used to produce hydrogen on a large industrial scale. Using very high temperatures and steam, SMR reformers convert methane into carbon dioxide and hydrogen. However, this widely used method also has a significant CO2 footprint; not only is the greenhouse gas produced as a byproduct of the reaction, fossil-fuel burning furnaces are used to supply the heat required to drive the reactions.

While SMR generates nearly 50% of the global supply of hydrogen, it’s estimated that the process accounts for nearly 3% of global CO2 emissions, and despite decades of research into improving the efficiency of the process, no lower-emission alternatives have been implemented at an industrial scale, the authors say.

We see the electrified reformer as the next logical step in the chemical industry because in this way we can transform the industry going towards greener processes, but [with] processes that are at the same time feasible so ... we don’t have to increase the production prices.

—co-author Peter Mortensen

The electrically-driven version of methane reforming uses an AC current and direct electrical resistance to heat the reactors. Unlike conventional SMR, the electrified process supplies heat uniformly across the reactor. The integrated heating also allows for exceptionally compact reactor designs.

The electrification, uniform heating, and potential for exceptionally compact reactors present a disruptive approach to resolving CO2 emission issues and current constraints regarding design, operation, and process integration for hydrogen production by SMR. In addition to reducing CO2 emissions, implementation of the resistance-heated reactor into existing plants could offer alternative operation conditions, reducing the steam-to-carbon ratio, or operate at increased methane conversion, typically limited by carbon deposition and temperatures (i.e., material constraints). High methane conversion coupled with an alternative purification technology could even provide a local source of CO2 for other processes.

With less need for heat recovery, resistance-heated reforming is efficient and applicable at many different sizes, promoting delocalization designs by using the existing and well-developed infrastructure of natural gas and potentially also biogas. Low thermal mass can also lead to reformers optimized for intermittent operation, following the fluctuations in availability of excess renewable energy with possible startup times in seconds. The operating costs for an electrified reformer are directly related to the cost of electricity, natural gas, and CO2 taxes. Preliminary estimates indicate that a resistance-heated reformer would be on par with current fired reformers in regions with a high production of renewable electricity.

—Wismann et al.

Resources

  • Sebastian T. Wismann, Jakob S. Engbæk, Søren B. Vendelbo, Flemming B. Bendixen, Winnie L. Eriksen, Kim Aasberg-Petersen, Cathrine Frandsen, Ib Chorkendorff, Peter M. Mortensen (2019) “Electrified methane reforming: A compact approach to greener industrial hydrogen production” Science Vol. 364, Issue 6442, pp. 756-759 doi: 10.1126/science.aaw8775

Comments

Davemart

Since they are talking about reducing GHG emissions by using it, presumably it is a lot more efficient.
It would be good if they provided figures for that.

And also it is more compact.

So how compact is that?

Compact enough to fit on a garage forecourt?

Engineer-Poet

Colorado School of Mines calculates 77% efficiency for conventional SMR (p. 11).  Given external process heat and 100% conversion, that efficiency could be as high as 129%.  Ergo, it appears that the methane input required could decrease by just over 40%.  Just how efficient this process could be depends on the magnitude of the losses.

Remember that we've already seen a superior method for doing this.  It uses a high-temperature PEM membrane and electrically separates, purifies and compresses the H2 while the steam + methane on the input side is driven to pure CO2 by removal of the hydrogen (and presumably an excess of steam to prevent coking).

gryf

@Davemart
Remember the GCC post about the SMR system suited for distributed applications, a team from Georgia Tech in 2014 proposed the sorption-enhanced CO2/H2 Active Membrane Piston reactor (CHAMP-SORB).
Check the comments.

Davemart

Thanks gryf.

I had forgotten all about that one!

There is so much happening in the fields of hydrogen and fuel cells that it is impossible to keep up, especially with my 68 year old memory!

Just trying to find out more about your link, I stumbled upon another new one, using sound waves to dissociate hydrogen and produce water.

DevinSerpa

This will never be a better efficiency than putting that electricity into a battery.

So why do it?

Engineer-Poet

Actually, it WILL be better efficiency than putting electricity into a battery.

1 kg methane has a LHV of 50 MJ.  Converting 1 kg via CH4 + 2 H2O -> CO2 + 4 H2 creates 1/2 kg H2 with a LHV of about 60 MJ.  If you can get this for the difference between 77% efficiency and 129% efficiency (52%) you are getting 60 MJ of hydrogen for 26 MJ of electricity, more or less (not counting the methane and assuming LHV throughout).

If the converter can tolerate fast power cycling, this is one way to soak up unreliable power from wind and PV and store it in a useful form.  If CO2 is captured then it can be pumped into deep, unmineable coal seams or other reservoirs.  Used with biogas, this has the potential to be carbon-negative.

Davemart

Video of the process here:
https://techxplore.com/news/2019-05-electrified-methane-reformer-carbon-dioxide.html

In the illustration they give the height of the new reformer at 4 metres, by what looks like 1 metre.

That would fit on a garage forecourt, although it is not clear to me at least what quantities of hydrogen we are talking about - maybe too much for a single filling station?

If methane generated from renewables were used, this should be more or less carbon neutral

HarveyD

Interesting to see that better/cleaner ways exist to produce H2 for future FCEVs and other uses.

SJC

Using waste heat can help processes become more efficient.

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