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The Next Generation of Blue Hydrogen Technologies

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Schalk Cloete's picture
Research Scientist Independent

My work on the Energy Collective is focused on the great 21st century sustainability challenge: quadrupling the size of the global economy, while reducing CO2 emissions to zero. I seek to...

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  • Mar 18, 2020
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Introduction

Hydrogen is currently enjoying an unprecedented surge in attention. Several countries and regions have issued formal hydrogen roadmaps, including the EU, the US, the UK, and Australia. In addition, the International Energy Agency has developed a comprehensive report assessing all elements of the hydrogen value chain.

One of the key findings of the report is that blue hydrogen (natural gas or coal with CCS) is likely to remain cheaper than green hydrogen (electrolysis from renewables) in several word regions.

As shown below, this includes regions like Australia, Europe, Japan, the Middle East and the US. In China, India and North Africa, long-term blue and green hydrogen costs are very similar.

However, there are two important considerations that could shift the balance further towards blue hydrogen:

  1. The costs related to the intermittent nature of hydrogen production from renewables is not accounted for
  2. The potential of next generation CCS technologies to considerably reduce the cost of blue hydrogen is not considered 

As a rough estimate, these considerations will move the green bars in the figure above up by about $0.4/kg and the yellow and grey bars down by about $0.4/kg, making blue hydrogen the lowest-cost long-term option in all regions. 

This article will review two blue hydrogen technologies that can facilitate such cost reductions.


Chemical looping technology

The next generation of blue hydrogen technologies is based on the principle of chemical looping. This technology uses an oxygen carrier material (metal oxide powder) to transport oxygen from an air stream to a fuel stream, allowing for fuel combustion with integrated CO2 capture at almost no energy penalty.

For hydrogen production, chemical looping reforming can be employed. This technology works on the same principle, but the oxygen carrier also acts as a catalyst for the steam methane reforming reaction. In this way, the heat requirement of the endothermic (heat consuming) reforming reactions can be satisfied by burning waste fuel from the pressure swing adsorption (PSA) hydrogen separation unit with integrated CO2 capture.

One of the key practical challenges with the scale-up of chemical looping technology is the need to circulate the oxygen carrier material between two different reactors where it can be separately contacted with air and fuel. This is particularly challenging at the high pressures and temperatures required for high hydrogen production efficiency from natural gas reforming.

To address this challenge, we have been working on two concepts that keep the oxygen carrier material in a single reactor, eliminating this important scale-up challenge.


Gas switching reforming (GSR)

The first of these technologies, GSR, keeps the oxygen carrier material in a single reactor where it is periodically exposed to three different gas streams (as illustrated in the image below).

  1. An air stream that oxidizes the oxygen carrier and releases heat, producing a hot depleted air stream with almost no CO2.
  2. A low-grade fuel stream from the PSA hydrogen separation unit that reduces the oxygen carrier once again, producing a stream of CO2 and H2O from which CO2 can easily be separated.
  3. A stream of natural gas and steam that is reformed to syngas (mainly H2 and CO) over the oxygen carrier that also acts as a catalyst.

This dynamic operation of the reactor requires a cluster of several coordinated reactors to operate as a steady state processing unit.

Simple schematic of the GSR reactor operation (source).

When deployed for hydrogen production, the GSR concept functions just like the fired tubular reformer used in conventional steam methane reforming that is responsible for the majority of global hydrogen production today.

This process layout is illustrated below.

Process integration of the GSR reactors for hydrogen production. Orange blocks are GSR and blue blocks are conventional commercially available process units.

Membrane-assisted autothermal reforming (MA-ATR)

The second alternative, MA-ATR, relies on hydrogen perm-selective membranes to continuously extract the hydrogen produced during the reforming reactions.

These reactions are equilibrium limited (not all the fuel can be converted), but the continued extraction of the hydrogen product overcomes this equilibrium limitation to achieve higher fuel conversion at milder temperatures. In addition, direct extraction of pure hydrogen avoids the need for downstream water-gas shift and PSA units for extracting hydrogen from the syngas (as in the figure above).

This concept was first proposed as membrane-assisted chemical looping reforming, which faces the challenge of circulating an oxygen carrier material between two reactors at high temperatures and pressures. We have therefore simplified the concept to avoid the need for oxygen carrier circulation, using a conventional air separation unit, as shown below.

Illustration of the functionality of the membrane assisted autothermal reforming concept operating using a nickel oxide (NiO) oxygen carrier material (source). Reactions taking place in different reactor regions are also shown. 

In the lower reactor regions, methane (CH4) is reformed to hydrogen (H2) over the nickel (Ni) catalyst, with the hydrogen continuously being extracted. Directly above the membranes, any fuel that slipped past the membranes is converted to CO2 and H2O by reducing the oxygen carrier material (NiO). In the upper reactor regions, high purity oxygen is injected to oxidize the oxygen carrier and release heat. This heat is then carried down to the membrane region by the good mixing in the fluidized bed reactor to supply the heat needed by the endothermic reforming reactions. Hence, separate high-purity streams of H2 and CO2 are produced from a single reactor.


Cost assessment

We have recently published two peer-reviewed papers to assess the costs of hydrogen production from these two concepts (GSR and MA-ATR). The main results are shown below.

Comparison of hydrogen production costs from SMR (without CO2 capture) to GSR and MA-ATR (with CO2 capture). Natural gas (€6/GJ) and electricity (€60/MWh) prices relevant to Europe are used.

As can be seen, hydrogen from GSR and MA-ATR is only slightly more expensive than conventional steam methane reforming (SMR) without CO2 capture.

A key feature of both concepts is that they consume considerably less natural gas than SMR, but require significant electricity consumption. This fits well with a future scenario of clean electricity and scarcer natural gas resources. CO2 transport and storage is the most important "other" cost.

The CO2 avoidance cost is about €12/ton, implying that these technologies will slot in below the lower edge of the red bars (SMR with a CO2 price of $25/ton) in the figure from the IEA report at the top of this article.


Scale-up considerations

Both concepts have been successfully demonstrated in the lab (GSR and two membrane concepts: MA-GSR and MA-CLR), showing their practical feasibility.

Following these demonstrations and the promising techno-economic assessment results discussed above, we are now working on proposals for scale-up projects. The key elements to be demonstrated are the longevity of the oxygen carrier material, high temperature outlet valves (for GSR) and membranes (for MA-ATR) at larger scales.

Once these demonstrations are successfully completed, commercialization can proceed rapidly. Both reactor concepts are attractively simple and unlikely to pose complications when going to commercial scales.

In addition, a promising business case exists where the plants can first be constructed without capturing CO2.

In this case, the pressurized CO2 stream can be expanded for some extra power production and vented to the atmosphere, avoiding the need for CO2 compression, transport and storage. Without CO2 capture, both the GSR and MA-ATR concepts become cheaper than conventional SMR, minimizing investment risk related to uncertain CO2 markets and CO2 infrastructure buildouts.

Then, once CO2 prices rise and CO2 transport and storage infrastructure gets established, these plants can easily be retrofitted for CO2 capture by simply adding a CO2 compression train.

Through this business model, we are hopeful that the GSR and MA-ATR technologies can accelerate the advent of the hydrogen economy, helping to decarbonize sectors other than electricity (which still account for 80% of global final energy consumption) at a reasonable cost.


This is the original version of an article recently published on Energy Post.

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Matt Chester's picture
Matt Chester on Mar 18, 2020

Through this business model, we are hopeful that the GSR and MA-ATR technologies can accelerate the advent of the hydrogen economy, helping to decarbonize sectors other than electricity (which still account for 80% of global final energy consumption) at a reasonable cost.

Hydrogen, blue or green, can do much for these non-power sectors; then green hydrogen seems poised to benefit the strategy of scaling up generation beyond demand as a form of energy storage-- that would be unique to green and not a blue function, right? Could this lead to two different streams and business models regarding hydrogen that aren't necessarily competitors but just fit into different areas? 

Schalk Cloete's picture
Schalk Cloete on Mar 24, 2020

Green hydrogen for productively utilizing excess renewables is an intuitively attracgive idea, but it is not particularly economical. The problem with only using peak wind and solar for hydrogen is the low capacity factors of the electrolysers, hydrogen transmission lines and hydrogen storage infrastructure. Due to its low energy density, hydrogen is actually relatively expensive to transmit and store, so this capital under-utilization is quite costly. Blue hydrogen can be produced in line with demand to avoid these costs. 

In cases where lots of renewable energy has to be spilled so that electrolysers can use low-cost electricity at relatively high capacity factors, it could be better, but that would of course be bad for the wind/solar producers. However, in the windiest and sunnyest regions in the world, wind/solar costs could be low enough for this to work. 

As the first graph in this article shows, the attractiveness of blue and green hydrogen varies considerably by region, so there should be applications for both. 

William Hughes-Games's picture
William Hughes-Games on Mar 20, 2020

If I understand correctly, Hydrogen for transport is a non-starter.  It is more economic energy wise and financially to simply send the electricity by the existing grid to a battery in a car or truck.  However, it does have considerable value in producing very high temperatures, especially when you re-combine the hydrogen and oxygen produced from electrolysis.  Even higher temperatures can be obtained by splitting the molecules of Hydrogen and molecules of Oxygen before re-combining them.  This, of course, has uses in metalurgy, and glass and cement production.  Hopefully, we will soon have the technology to use Hydrogen to reduce metalic ores and especially iron ores.  Another potential use of electrolysis is in energy storage when excess energy is being produced in excess by wind and solar. Consideration should be given to low pressure storage in tanks such as used to be used for Producer Gas.  Compressing or liquifying Hydrogen uses a lot of energy.  I haven't yet heard a financial treatment of the economics of the by product of electrolysis, namely Oxygen.  Surly if we are electrolyzing water, we have to factor in the financial benefit of producing Oxygen in a very pure form for all sorts of uses. Lastly, surly it would be wise to simply get away from the use of any fossil fuel.  We are simply perpetuating the use of gas by providing a market for a product that should be simply left in the ground.

Schalk Cloete's picture
Schalk Cloete on Mar 24, 2020

From an economic point of view, hydrogen use in long-distance transport is substantially more attractive than use in metallurgy. See the IEA report linked above. 

As mentioned in my reply to Matt above, the problem with using electrolysis for utilizing wind/solar peaks is the low capacity utilization of several elements of the system, substantially increasing full system costs. System complexity also increases, leading to further unforeseen costs and a higher accident rate. 

See my discussions with Roger in the earlier article about the challenge with intermittent oxygen production. Oxygen is valuable, but much less so than hydrogen, so added costs for intermittency quickly make venting the most economic option. 

The whole debate about just addressing climate change or doing away with fossil fuels alltogether can quickly become very philosophical. But I'm of the opinion that it is unethical to pursue an uneconomic solution when so many global citizens are still below decent living standards. As long as blue hydrogen is significantly cheaper and more practical than green (from a full system perspective), it should be pursued. 

Bob Nikon's picture
Bob Nikon on Mar 23, 2020

Hi Schalk, You can't call it next generation for hydrogen extrated from natural gas. There is no future on that route. It's totally wrong for two reasons:

- We can't extricate out of fossil fuel codependency forever.

- What kind of sense does this make to produce clean fuel by burning more fossil    fuels (dirty fuels) emtting more green house gases to pollute environment.

The one and only sensible way to produce hydrogen is to electrolyse water. The biggest problem is there is no right energy to do it....so far. It is nothing to do with costs in the process. It is the accountibily instead. Because all known renewables simply can't do it. The only renewable that can do this is Hydro-Electrenergy. Because this system can induce electric current unconditionally around the clock. That is the accountibity we need to porduce a significant amount of hydrogen. It will be a while for this project to be launched. Until then the hope for hydrogen is up in the thin air. 

Schalk Cloete's picture
Schalk Cloete on Mar 24, 2020

Next generation implicitly means that it's a transient thing - i.e. that there will be many more generations following the next one. Hence, blue hydrogen is not touted as a solution until the end of time. It is touted as a more cost effective and practical way to get the hydrogen economy on its feet.

To your second point, almost all the CO2 is captured and stored, so greenhouse gas emissions are much lower than the fuels currently responsible for 80% of our final energy consumption. 

As outlined in the replies above, I agree that the intermittency of wind and solar is detrimental to the green hydrogen story. However, it does not make green hydrogen unworkable, just more expensive and less practical than proponents believe. 

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