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I'm seeing on TV senior politicians, including the Liberal PM and involved Labor Victorians (bi-partisan), gathering in Morwell in Victoria to announce that jobs in the Latrobe Valley have been saved by a Japanese consortium that will build a pilot plant to convert brown coal to hydrogen. Read Here...

I had to pinch myself to check that our screen had not somehow turned itself into Lewis Carroll's looking glass and sucked me through to the other side.

Fans of the Reverend Dodgson's (Lewis Carroll's) work will recall some 'weird shit' in Wonderland like: Alice growing and shrinking; a disembodied cat coming and going; and babies turning into pigs.  But these adventures are put into the shade by Alice's subsequent experiences: Through the Looking-Glass

Hydrogen from coal (carbon) - really?  Surely they mean hydrogen from water. 

You know:   HO + C   H + CO 

Fortunately water and carbon do not spontaneously combine like this, otherwise there would be no coalmines; and no carbon cycle; and no life on Earth..  The reaction consumes/requires a lot of energy to proceed.

 

Back in the Rev's day, right through to my young adulthood, this was done in a great many places called 'gasworks'. All the reaction needed was a lot more carbon and oxygen from the air:  2C + O 2CO + heat (energy).  As Eliza Doolittle opined:  "Lots of coals makin' lots of 'eat, wouldn't it be lover-ly"  

The principal product of the reaction: CO, carbon monoxide, is poisonous.  That's why we have catalytic converters in our car exhausts to convert the CO to CO (carbon dioxide) by sucking in some of that good old O from the air.   

In Eliza's day this was not a problem. Pipes were laid in the street and the mixture of hydrogen and the carbon monoxide was distributed to peoples' homes to light their mantles; provide room and water heating; and to use in their gas oven - principally to cook their meals.  It also provided a convenient suicide means when it all got too much - just put one's head in the oven.    

But this poisonous component was soon removed by burning it, consuming oxygen, in the home, to convert the 'town gas' into relatively harmless CO (carbon dioxide) and H₂O (water).

Even though it's yet another century, like Alice, I'm starting to feel a bit weird - disoriented. 

Didn't we decide way back in the fifties that if we burnt the coal near the mine and produced electricity instead, it would be more useful and a lot less messy?  And if our power station was more efficient than a gasworks we would not have to consume as much carbon to get equivalent utility.   For example, might electric lamps be more efficient than gas mantles?  Might microwave or even electric ovens be more efficient than gas ovens?  Not to mention that it's a bit hard to power a radio or IBM 360 with gas.

But times change and we're about to close the very large coal burning Loy Yang Power Station power-station, constructed as recently as 1985, because it produces too much carbon dioxide for each MWh of electricity produced.   

I haven't seen Kawasaki Heavy Industries proposed design but I'm guessing it's based on well established coal gasifier technology where burning coal is treated with steam and controlled amounts of air or pure oxygen, under high pressure, to produce a mixture of carbon monoxide and hydrogen - a sort of upgrade on the old gasworks we learnt about in high school chemistry. 

There's no particular mystery to making and separating hydrogen this way.  The room I'm in is a kind of town-gas separator.  It once had a gas mantle lamp plumbed into the wall.  If a careless person left the gas on, the carbon monoxide sank to the floor and the hydrogen potentially filled the upper part of the room where it became an explosion hazard.  As a result of several such disasters those cunning government officials at the turn of the 19th century required that ventilators shall be installed near the ceiling in Australian gas-lit homes to avoid a repetition.  Today the lamps are LED but the ventilators,  prettily decorated in Art Nouveau style, still look down on me as I write.

Sure, the old processes were inefficient and seriously polluting, in addition to being financially challenged by newer technologies. But the chemistry remains unchanged. So how will a gas plant, in which the carbon dioxide is a huge by-product in the reduction of relatively modest amounts of hydrogen, produce less carbon dioxide from a similar amount of coal?  

In this 21st century version, instead of piping the gas out to Alice and Eliza, or producing electricity locally, the hydrogen is to be separated and compressed for shipment to Japan. 

Yet efficiency, cost and impact on the environment remain significant hurdles.

And if it's so good why not just gasify the coal like this then turn the hydrogen into electricity in big fuel-cells locally, like Elon Musk's big battery in South Australia, thus avoiding all that compression and shipment to Japan for use in fuel cells in Japanese cars? 

Wait a minute, that's not a new idea.  Isn't that sort of what what happens in modern combined-cycle thermal power stations?  And aren't there an awful lot of failed combined-cycle thermal power stations?  See Here...

In particular, isn't the high capital and maintenance cost of these often uncompetitive with modern super-critical designs?  The latter are quite a bit cheaper to build and run; achieve similar overall efficiency and produce a similar amount of CO for each MWh of electricity generated - quite a bit less than older designs like Loy Yang.

Like Alice Through the Looking-Glass we seem to be back at square one.  We would get more, lower cost, electricity per tonne of CO if we just build a modern super-critical thermal electricity generation plant.  Oh, I remember that's no good - that's where we began.  So how's this thing any better?

If you've been paying attention you know the mantra - clean coal.  Here comes CCS, carbon capture and storage, again.  Just dump the nicely separated CO into the depleted Bass Straight oil fields - "come to my arms, my beamish boy!"

Yet there are one or two problems with this. Tweedledum and Tweedledee have been spruiking carbon capture and storage for years and, as ever, the problem is not the technical practicality of doing this. The problems are of scale including: capital cost; energy cost; the massive volumes of COproduced when coal is burnt; as well as serious environmental and safety concerns.

Yet for me the main disjunction is that this pilot 'coal to hydrogen' plant is being spruiked by our pollies as the start of a trillion dollar industry employing thousands. Surely, in this event, the new industry will release far more carbon than Loy Yang ever did.

Read More about CCS...

 

 


 

Technical Footnote

 Assuming full carbon oxidisation:  2HO + 2C + O  2H + 2CO 

And to provide the energy required for the reaction (> 131 kJ/mol) let's burn some more carbon:  2C + 2O₂ →  2CO 

Combined: 2HO + 4C + 3O  2H + 4CO  = (8O; 4C; 4H)/4 = 2O; 1C; 1H

Thus two Oxygen atoms and one Carbon atom are required to liberate each Hydrogen atom. 

The atomic weight of common Carbon is 12; that of Oxygen 16; and that of Hydrogen 1.

Thus to produce one tonne of hydrogen for export will create at least 44 tonnes of CO (12+16x2) to be disposed of - and probably a lot more - to make up for thermal inefficiency.

This is before additional fuel and/or electricity is consumed for compression of the gasses; required for transport and for injection of the by-product CO into an oilwell.

Given that the by-product carbon dioxide is by far the heaviest and most voluminous material to be dealt with, logistically the best location for the plant could be on an oil platform in Bass Straight. 

At about half the weight of the CO produced and much easier to store, transporting the coal to the plant is the least problematic of the materials handling issues.  Maybe the best solution would be to export the coal to Japan?
 

 

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