Extreme energy, supercritical water, nanostuff and biofuels

November 5, 2013 |
The Sandia Lab's Z Machine

The Sandia Lab’s Z Machine

At the frontier of exotic temperature and pressures, even everyday materials like water begin to act strangely in ways that can drive energy transformation.

New work in nanocatalysts may make those frontiers more accessible, and those energy systems more affordable.

OK – try this one for size.  Water ice that checks in at 1300 degrees F – um, that’s hot enough to melt glass. Ice that melts glass? What strange world have we entered, exactly?

It’s the Digest Cinematic Universe of water under exotic temperature and pressure. Where water begins to act like a metal – and in a superionic state, driving magnetic fields on Uranus and Neptune.

At the supercritical barrier – a realm of high temps and high pressures where the barrier between steam and liquid water begins to get decidedly fuzzy and water begins acting like an acid and a base, at the same time – well, that’s where biofuels come in.

We start the tale at that exotic center of fusion research known as the Sandia National Lab’s Z Machine, which provides the fastest, most accurate, and cheapest method to determine how materials will react under high pressures and temperatures.

The Z concentrates electrical energy and turns it into short pulses of enormous power — for an instant, it generates more electric energy than all other systems on earth, combined.

One of the byproducts of so much work on the science of high-temperature and high-pressure — naturally, that is found deep inside large gas-giant planets and the Sun itself and important to the study of fusion — is some work on the exotic behavior of water under extreme conditions.

As is not commonly discussed around the breakfast table, water has far more than the three traditional phases we know from life (ice, liquid water and steam). In fact, science has presented us with fifteen distinct phases, to date.

Water that acts like metal, water that drives magnetic fields?

Just to add complete weirdness to the mix — at temperatures and pressures not present on earth, there’s a theoretical stage where water acquires metallic properties.

Another state — at temperatures so high that the boundary between solid and liquid water becomes less well-defined, superionic water is now credited with driving a measurable portion of the magnetic field of Uranus and Neptune. In case you are flying by sometime and your magnetics-influenced instruments do not calibrate properly.

Another boundary that becomes ill-defined under sufficient temperature and pressure — and that impacts the here and now of biofuels — that’s the gas-liquid boundary.

Supercritical water and biofuels

At a well-known “supercritical” point – at 374 degrees Celsius and 221 atmospheric pressures – the boundary between liquid water and steam becomes ill-defined and “supercritical water” begins to act as excellent solvent for cellulose — separating C6 sugars from lignin in seconds, compared to the hours or days associated with enzymatic systems.

The exploration of supercritical water as a biofuels technology is at the heart, as it happens, of the Renmatix Plantrose system — producing a stream of C5 and C6 sugars, plus a lignin fraction — at what it believes, at scale, will be industry-transforming low costs. Renmatix is building towards that scale right now.

Now, there’s much more to the Plantrose system than simply bathing biomass in supercritical water. For one, the relatively easy-to-extract C5 sugars (xylose) are extracted from hemicellulose in a separate pre-process — and there’s are entire biomass-handling and lignin recovering processes that are a part of the overall system. But supercritical is at the heart of it.

But even when the science is done — there’s the cost of creating all that energy and pressure. Now, lignin contributes to providing that, through combustion of that residual fraction — that’s part of why Renmatix is looking at transformatively low-cost sugars with its system.

But, with high temperature and pressure, you not only have operating costs to consider in terms of delivering system energy — you have capital costs associated with materials that can withstand high temps and pressures. Not every steel alloy can handle it, plastics are a no-no, and valves and flanges will generally need to be of the high-performance type.

Not exactly building the Space Shuttle, but it’s a walk down the Deadly Path of High Cost, for sure.

The opportunities with nanocatalysts

But it turns out — there might be another route, as it were, to the summit. And here, we begin to look at another emerging area of materials science, the advancements in what are known as nanocatalysts.

One group, ECR Renewable Fuels and Georgia Alternative Fuels, has been pursuing nanocatalysts and their effect on supercritical boundaries for several years. The goal? To reduce the temperature and pressure barrier at which liquids begin to demonstrate supercritical properties — using catalysis to reduce the energy levels.

“Our cellulosic ethanol process uses the supercritical heterogeneous catalytic process to pretreat cellulose,” said Alan Lawson, who heads the group. At a pilot and lab-scale, the technology is modeling along exciting lines.

“Supercritical fluid operating heat and pressures are now much lower due with the advanced catalysis technology. The critical point for our system is now less than 25 psi and 170F.”

As seen at lab and pilot-scale, Lawson says, “The process lowers our costs significantly to make a small scale system produce a very nice profit. We can now compete with mid-west ethanol on the East Coast. Our per pound sugar cost using biomass is about $0.04 per pound verses $0.125 per pound for corn ethanol. Our model is small cellulosic ethanol plants highly distributed over the East, at less than 10 million gallons per year.”

The practical effect of using supercritical to replace enzymes in the process and going smaller-scale? Lower costs, if the system develops towards scale as hoped.

“Small scale production costs are currently less than $1.40 per ethanol gallon. Using local market sources within a couple miles of the plant, we project to rubber stamp the small scale plants for sale to co-op farmers that can fund our small scale plants, with about a 1.5 year payback.”

Ethanol, yes — but biodiesel and drop-in fuels, too

There are applications for supercritical liquids on the biodiesel and drop-in fuel side, as well, according to Lawson.

“Our company was able to reduce the critical point for producing pure biodiesel and pure glycerin without transesterification,” Lawson adds. “The process only uses oil and alcohol, so the biodiesel quality is exceptional. We are in discussions with several biodiesel plants to cost effectively retrofit them with to produce SCF (super critical fluids, SCF) catalysis systems.”

On the drop-in side? “We are now looking into using waste coal from exiting slurry ponds,” Lawson says, adding that “gas well liquids, biomass, waste solids from cities and other sources” are options as well.

How does it work? “We would install a small commercial pilot system (proof of concept) design to convert coal and biomass into drop in renewable (gasoline and diesel) that is >30% renewable (biomass) and >70% fossil fuel. We are looking at per gallon break even at about <$0.60 per fuel gallon. This technology will use our SCF process to directly convert biomass into hydrocarbons using our SCF hydro-treating and hydro-cracking process using power plant waste heat.

Again, early-stage, but highly promising if scalable.

Supercritical biodiesel and the saga of BioFuelBox

Now, you might be thinking to yourself…supercritical biodiesel….that rings a bell. And you’d be right. BioFuelBox jumped up in the go-go biodiesel years in 2006-2009 with just such a technology — and got as far as a 1 million gallon demonstration of the technology before running out of money.

The promise at the time was that BioFuelBox could develop systems that could handle the really exotic feedstocks, with 85 percent free fatty acids or higher — and thereby access a low-cost feedstock not available to competitors.

Another system, called InProTek, which also languished, targeted operating cost savings of up to $140 per ton from catalyst savings and yield improvements.

And neither reached scale and commercial success. Could be a victim of bad timing.

After all, BioFuelBox once picked up a Technology Pioneer Award at the World Economic Forum — a distinction that companies like Google and PayPal landed, and look what became of them.

So — caution, supercritical is no gold rush. Or, maybe it is, offering success to just a handful of the prospectors who crowd in to stake their claim. One thing is sure — the technologies are still early-stage, but there definitely is gold in “them thar hills”. Whether it is cellulose or high-FFA feedstocks, everyone agrees that they are potential gold mines for biofuels.

Something that was known for a long time with tight oil and gas. And then along came the right set of technologies.

It’s been a while since the groups involved have disclosed their advances via the patent process, but you can read up on the progress through the mid-2000s, here.

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