Category Archives: Hydrogen

The chemistry of sewage treatment

6 Replies

The first thing to know about sewage is that it’s mostly water and only about 250 ppm solids. That is, if you boiled down a pot of sewage, only about 1/40 of 1% of it would remain as solids at the bottom of the pot. There would be some dried poop, some bits of lint and soap, the remains of potato peelings… Mostly, the sewage is water, and mostly it would have boiled away. The second thing to know, is that the solids, the bio-solids, are a lot like soil but better: more valuable, brown gold if used right. While our county mostly burns and landfills the solids remnant of our treated sewage, the wiser choice would be to convert it to fertilizer. Here is a comparison between the composition of soil and bio-solids.

The composition of soil and the composition of bio-solid waste. biosolids are like soil, just better.

The composition of soil and the composition of bio-solid waste. biosolids are like soil, just better.

Most of Oakland’s sewage goes to Detroit where they mostly dry and burn it, and land fill the rest. These processes are expensive and engineering- problematic. It takes a lot of energy to dry these solids to the point where they burn (they’re like really wet wood), and even then they don’t burn nicely. As shown above, the biosolids contain lots of sulfur and that makes combustion smelly. They also contain nitrate, and that makes combustion dangerous. It’s sort of like burning natural gun powder.

The preferred solution is partial combustion (oxidation) at room temperature by bacteria followed by conversion to fertilizer. In Detroit we do this first stage of treatment, the slow partial combustion by bacteria. Consider glucose, a typical carbohydrate,

-HCOH- + O2 –> CO2 + H2O.    ∆G°= -114.6 kcal/mol.

The value of ∆G°, is relevant as a determinate of whether the reaction will proceed. A negative value of ∆G°, as above, indicates that the reaction can progress substantially to completion at standard conditions of 25°C and 1 atm pressure. In a sewage plant, many different carbohydrates are treated by many different bacteria (amoebae, paramnesia, and lactobacilli), and the temperature is slightly cooler than room, about 10-15°C, but this value of ∆G° suggests that near total biological oxidation is possible.

The Detroit plant, like most others, do this biological oxidation treatment using either large stirred tanks, of million gallon volume or so, or in flow reactors with a large fraction of cellular-material returning as recycle. Recycle is needed also in the stirred tank process because of the low solid content. The reaction is approximately first order in oxygen, carbohydrate, and bacteria. Thus a 50% cell recycle more or less doubles the speed of the reaction. Air is typically bubbled through the reactor to provide the oxygen, but in Detroit, pure oxygen is used. About half the organic carbon is oxidized and the remainder is sent to a settling pond. The decant (top) water is sent for “polishing” and dumped in the river, while the goop (the bottom) is currently dried for burning or carted off for landfill. The Holly, MI sewage plant uses a heterogeneous reactors for the oxidation: a trickle bed followed by a rotating disk contractor. These have higher bio-content and thus lower area demands and separation costs, but there is a somewhat higher capital cost.

A major component of bio-solids is nitrogen. Much of this in enters the form of urea, NH2-CO-NH2. In an oxidizing environment, bacteria turns the urea and other nitrogen compounds into nitrate. Consider the reaction the presence of washing soda, Na2CO3. The urea is turned into nitrate, a product suitable for gun powder manufacture. The value of ∆G° is negative, and the reaction is highly favorable.

NH2-CO-NH2 + Na2CO3 + 4 O2 –> 2 Na(NO3) + 2 CO2 + 2 H2O.     ∆G° = -177.5 kcal/mol

The mixture of nitrates and dry bio-solids is highly flammable, and there was recently a fire in the Detroit biosolids dryer. If we wished to make fertilizer, we’d probably want to replace the drier with a further stage of bio-treatment. In Wisconsin, and on a smaller scale in Oakland MI, biosolids are treated by higher temperature (thermophilic) bacteria in the absence of air, that is anaerobically. Anaerobic digestion produces hydrogen and methane, and produces highly useful forms of organic carbon.

2 (-HCOH-) –> CO2 + CH4        ∆G° = -33.7 Kcal/mol

3 (-HCOH-) + H2O –> -CH2COOH + CO2 +  2 1/2 H2        ∆G° = -21.9 kcal/mol

In a well-designed plant, the methane is recovered to provide heat to the plant, and sometimes to generate power. In Wisconsin, enough methane is produced to cook the fertilizer to sterilization. The product is called “Milorganite” as much of it comes from Milwaukee and much of the nitrate is bound to organics.

Egg-shaped, anaerobic biosolid digestors.

Egg-shaped, anaerobic biosolid digestors, Singapore.

The hydrogen could be recovered too, but typically reacts further within the anaerobic digester. Typically it will reduce the iron oxide in the biosolids from the brown, ferric form, Fe2O3, to black FeO.  In a reducing atmosphere,

Fe2O3 + H2 –> 2 FeO + H2O.

Fe2O3 is the reason leaves turn brown in the fall and is the reason that most poop is brown. FeO is the reason that composted soil is typically black. You’ll notice that swamps are filled with black goo, that’s because of a lack of oxygen at the bottom. Sulphate and phosphorous can be bound to ferrous iron and this is good for fertilizer. Generally you want the reduction reactions to go no further.

Weir dam on the river dour. Used to manage floods, increase residence time, and oxygenate the flow.

Weir dam on the river Dour in Scotland. Dams of this type increase residence time, and oxygenate the flow. They’re good for fish, pollution, and flooding.

When allowed to continue, the hydrogen produced by anaerobic digestion begins to reduce sulfate to H2S.

NaSO4 + 4.5 H2 –>  NaOH + 3H2O + H2S.

I’m running for Oakland county, MI water commissioner, and one of my aims is to stop wasting our biosolids. Oakland produces nearly 1000,000 pounds of dry biosolids per day. This is either a blessing or a curse depending on how we use it.

Another issue, Oakland county dumps unpasteurized, smelly black goo into Lake St. Clair every other week, whenever it rains more than one inch. I’d like to stop this by separating the storm and “sanitary” sewage. There is a capital cost, but it can save money because we’d no longer have to pay to treat our rainwater at the Detroit sewage plant. To clean the storm runoff, I’d use mini wetlands and weir dams to increase residence time and provide oxygen. Done right, it would look beautiful and would avoid the flash floods. It should also bring natural fish back to the Clinton River.

Robert Buxbaum, May 24 – Sept. 15, 2016 Thermodynamics plays a big role in my posts. You can show that, when the global ∆G is negative, there is an increase in the entropy of the universe.

New REB hydrogen generator for car fueling, etc.

3 Replies

One of my favorite invention ideas, one that I’ve tried to get the DoE to fund, is a membrane hydrogen generator where the waste gas is burnt to heat the reactor. The result should be exceptional efficiency, low-cost, low pollution, and less infrastructure needs. Having failed to interest the government, I’ve gone and built one on my own dime. That’s me on the left, with Shua Spirka, holding the new core module (reactor, boiler, purifier and purifier) sized for personal car fueling.

Me and Shua and our new hydrogen generator core

Me and Shua and our new hydrogen generator core

The core just arrived from the shop last week, now we have to pumps and heat exchangers. As with our current products, the hydrogen is generated from methanol water, and extracted 99.99999% pure by diffusion through a metal membrane. This core fit in a heat transfer pot (see lower right) and the pot sits on a burner for the waste gas. Control is tricky, but I think I’ve got it. If it all works like it’s supposed to, the combination should be 80-90% energy-efficient, delivering about 75 slpm, 9 kg per day. That’s the same output as our largest current electrically heated generators, with a much lower infrastructure cost. The output should be enough to fuel one hydrogen-powered automobile per day, or keep a small fleet of plug-in, hydrogen-hybrids running continuously.

Hydrogen automobiles have a lot of advantages over Tesla-type electric automobiles. I’ll tell you how the thing works as soon as we set it up and test it. Right now, we’ve got other customers and other products to make.

Robert Buxbaum, February 18, 2016. If someone could supply a good hydrogen compressor, and a good fuel cell, that would be most welcome. Someone who can supply that will be able to ride in a really excellent cart of the future at this year’s July 4th parade.

The Hindenburg: mainly the skin burnt

4 Replies

The 1937 Hindenburg disaster is often mentioned as proof that hydrogen is too flammable and dangerous for commercial use. Well hydrogen is flammable, and while the Hindenburg was full of hydrogen when it started burning, but a look at a color photograph of the fire ( below), or at the B+W  Newsreel film of the fire, suggests that it is not the hydrogen burning, but the skin of the zeppelin and the fuel. Note the red color of the majority flame, and note the black smoke. Hydrogen fires are typically invisible or very light blue, and hydrogen fires produce no smoke.

Closeup of the Hindenburg burning. It is the skin that burns, not the gaseous hydrogen

Closeup of the Hindenburg burning. It is the skin and gasoline that burns, not the gaseous hydrogen.

The Hindenburg was not a simple hydrogen balloon either. It was a 15 story tall airship with state-rooms, a dining room and an observation deck. It carried 95 or so passengers and crew. There was plenty of stuff to burn besides hydrogen. Nor could you say that a simple spark had set things off. The Hindenburg crossed the ocean often: every 2 1/2 days. Lightning strikes were common, as were “Saint Elmo’s fire,” and static electricity discharges. And passengers smoked onboard. Holes and leaks in the skin were also common, both on the Hindenburg and on earlier airships. The hydrogen-filled, Graf Zeppelin logged over 1 million flight miles and over 500 trips with no fires. And it’s not like helium-filled zeppelins and blimps are much safer. The photo below shows the fire and crash of a helium-filled Goodyear blimp, “Spirit of Safety”, June, 2011. Hydrogen has such a very high thermal conductivity that it is nearly as hard to light as helium. I recently made this video where I insert a lit cigar into a balloon filled with hydrogen. There is no fire, but the cigar goes out.  In technical terms, hydrogen is said to have a low upper combustion limit.

Helium-filled goodyear blimp catches fire and burns to destruction.

Helium-filled goodyear blimp “spirit of safety” catches fire and burns before crashing. It’s not the helium burning.

The particular problem with the Hindenburg seems to have been its paint, skin and fuel, the same problems as caused the fire aboard the “Spirit of Safety.” The skin of the Hindenburg was cotton, coated with a resin-dope paint that contained particles of aluminum and iron-oxide to help conduct static electricity. This combination is very flammable, essentially rocket fuel, and the German paint company went on to make rocket fuel of a similar composition for the V2 rockets. And the fuel was flammable too: gasoline. The pictures of the Hindenburg disaster suggest (to me) that it is the paint and the underlying cotton skin that burned, or perhaps the fuel. A similar cause seems to have beset the “Spirit of Safety.” For the Hindenburg’s replacement, The Graf II, the paint composition was changed to replace the aluminum powder with graphite – bronze, a far less flammable mixture, and more electrically conductive. Sorry to say, there was no reasonably alternative to gasoline. To this day, much of sport ballooning is done with hydrogen; statistically it appears no more dangerous than hot air ballooning.

It is possible that the start of the fire was a splash of gasoline when the Hindenburg made a bumpy contact with the ground. Another possibility is sabotage, the cause in a popular movie (see here), or perhaps an electric spark. According to Aviation Week, gasoline spoiled on a hot surface was the cause of the “Spirit of Safety fire,” and the Hindenburg disaster looks suspiciously similar. If that’s the case, of course, the lesson of the Hindenburg disaster is reversed. For safety, use hydrogen, and avoid gasoline.

Dr. Robert E. Buxbaum, January 8, 2016. My company, REB Research, makes hydrogen generators, and other hydrogen equipment. If you need hydrogen for weather balloons, or sport ballooning, or for fuel cells, give us a call.

Highest temperature superconductor so far: H2S

Leave a reply

The new champion of high-temperature superconductivity is a fairly common gas, hydrogen sulphide, H2S. By compressing it to 150 GPa, 1.5 million atm., a team lead by Alexander Drozdov and M. Eremets of the Max Planck Institute coaxed superconductivity from H2S at temperatures as high as 203.5°K (-70°C). This is, by far, the warmest temperature of any superconductor discovered to-date, and it’s main significance is to open the door for finding superconductivity in other, related hydrogen compounds — ideally at warmer temperatures and/or less-difficult pressures. Among the interesting compounds that will certainly get more attention: PH3, BH3, Methyl mercaptan, and even water, either alone or in combination with H2S.

Relationship between H2S pressure and critical temperature for superconductivity.

Relation between pressure and critical temperature for superconductivity, Tc, in H2S (filled squares) and D2S (open red). The magenta point was measured by magnetic susceptibility (Nature)

H2S superconductivity appears to follow the standard, Bardeen–Cooper–Schrieffer theory (B-C-S). According to this theory superconductivity derives from the formation of pairs of opposite-spinning electrons (Cooper pairs) particularly in light, stiff, semiconductor materials. The light, positively charged lattice quickly moves inward to follow the motion of the electrons, see figure below. This synchronicity of motion is posited to create an effective bond between the electrons, enough to counter the natural repulsion, and allows the the pairs to condense to a low-energy quantum state where they behave as if they were very large and very spread out. In this large, spread out state, they slide through the lattice without interacting with the atoms or the few local vibrations and unpaired electrons found at low temperatures. From this theory, we would expect to find the highest temperature superconductivity in the lightest lattice, materials like ice, boron hydride, magnesium hydride, or H2S, and we expect to find higher temperature behavior in the hydrogen version, H2O, or H2S than in the heavier, deuterium analogs, D2O or D2S. Experiments with H2S and D2S (shown at right) confirm this expectation suggesting that H2S superconductivity is of the B-C-S type. Sorry to say, water has not shown any comparable superconductivity in experiments to date.

We have found high temperature superconductivity in few of materials that we would expect from B-C-S theory, and yet-higher temperature is seen in many unexpected materials. While hydride materials generally do become superconducting, they mostly do so only at low temperatures. The highest temperature semiconductor B-C-S semiconductor discovered until now was magnesium boride, Tc = 27 K. More bothersome, the most-used superconductor, Nb-Sn, and the world record holder until now, copper-oxide ceramics, Tc = 133 K at ambient pressure; 164 K at 35 GPa (350,000 atm) were not B-C-S. There is no version of B-C-S theory to explain why these materials behave as well as they do, or why pressure effects Tc in them. Pressure effects Tc in B-C-S materials by raising the energy of small-scale vibrations that would be necessary to break the pairs. Why should pressure effect copper ceramics? No one knows.

The standard theory of superconductivity relies on Cooper pairs of electrons held together by lattice elasticity. The lighter and stiffer the lattice, the higher temperature the superconductivity.

The standard theory of superconductivity relies on Cooper pairs of electrons held together by lattice elasticity. The lighter and stiffer the lattice, the higher temperature the superconductivity.

The assumption is that high-pressure H2S acts as a sort of metallic hydrogen. From B-C-S theory, metallic hydrogen was predicted to be a room-temperature superconductor because the material would likely to be a semi-metal, and thus a semiconductor at all temperatures. Hydrogen’s low atomic weight would mean that there would be no significant localized vibrations even at room temperature, suggesting room temperature superconductivity. Sorry to say, we have yet to reach the astronomical pressures necessary to make metallic hydrogen, so we don’t know if this prediction is true. But now it seems H2S behaves nearly the same without requiring the extremely high pressures. It is thought that high temperature H2S superconductivity occurs because H2S somewhat decomposes to H3S and S, and that the H3S provides a metallic-hydrogen-like operative lattice. The sulfur, it’s thought, just goes along for the ride. If this is the explanation, we might hope to find the same behaviors in water or phosphine, PH3, perhaps when mixed with H2S.

One last issue, I guess, is what is this high temperature superconductivity good for. As far as H2S superconductivity goes, the simple answer is that it’s probably good for nothing. The pressures are too high. In general though, high temperature superconductors like NbSn are important. They have been valuable for making high strength magnets, and for prosaic applications like long distance power transmission. The big magnets are used for submarine hunting, nuclear fusion, and (potentially) for levitation trains. See my essay on Fusion here, it’s what I did my PhD on — in chemical engineering, and levitation trains, potentially, will revolutionize transport.

Robert Buxbaum, December 24, 2015. My company, REB Research, does a lot with hydrogen. Not that we make superconductors, but we make hydrogen generators and purifiers, and I try to keep up with the relevant hydrogen research.

Chemical engineers and boilers, ‘I do anything’

1 Reply

One of the problems I run into trying to hire chemical engineers is that their background is so varied that they imagine they can do anything. Combine this with a willingness to try to do anything, and the job interview can go like this.

Me: You have a great resume. I suppose you know that our company is a leader in hydrogen engineering (in my case). Tell me, what do you see yourself doing at our company?

Engineer: I don’t know. I do anything and everything.

Me: That covers a lot of ground. Is there something that you do particularly well, or that you would particularly like to do here?

Engineer.: Anything, really.

Me: Do you see yourself making coffee?

Engineer: I could do that, but was thinking of something with more … responsibility.

Me: OK. Could you design and build a 5 kW, gas-fired boiler?

Engineer: Himm. How much coffee did you say you guys drink?

Current version of our H2 generators (simplified) and the combustion-heated modification I'm working on.

Current version of our H2 generators (simplified) and the combustion-heated modification I’m working on.

Not quite where I was going with that. The relevance of this joke is that I’m finally getting around to redesigning our hydrogen generators so that they are heated by waste-gas combustion instead of electricity. That was the plan originally, and it appears in almost all of my patents. But electricity is so easy to deal with and control that all REB generators have been heated this way, even the largest.

The current and revised processes are shown in the figure at right. Our general process is to make ultra pure hydrogen from methanol and water in one step by the following reaction:

CH3OH + H2O –> CO2  + 3 H2.

done in a membrane reactor (see advantages). My current thought is to make the first combustion heated hydrogen generator have an output about 2/3 as large as our largest. That is, to produce 100 scfh, or 50 slpm, or 6 kg of H2/ day. This could be advantageous for people trying to fuel fork lifts or a hybrid, fuel cell car; a car could easily carry 12 kg of hydrogen, allowing it to go an extra 300 miles.

The generator with this output will need a methanol-water feed rate of about 2/3 gal per hour (about 80¢/worth pre hour), and will need a heat rate of 2.5 to 3 kW. A key design issue is that I have to be sure not to extract too much energy value from the feed because, if there’s not enough energy in the waste gas, the fire could go out. That is, nearly pure CO2 doesn’t burn. Alternately, if there is too much flow to the flame or too much energy content, there might be over-heating. In order to avoid the flame going out, I have a pilot flame that turns off the flow if it goes out. I also plan to provide 30% or so of the reactor heat about 800 W, by burning non-wast gas, natural gas in this iteration. My plan is to use this flow to provide most of the temperature control, but to provide secondary control by (and safety) by venting some of the off-gas if the reactor gets hotter than a set limit. Early experiments suggest it should work.

The business side of this is still unknown. Perhaps this would provide military power or cabins in the woods. Perhaps ship-board auxiliary power or balloons, or hydrogen fueling stations, or perhaps it will be used for chemical applications. With luck, it’ll sell to someone who needs hydrogen.

Robert E. Buxbaum. December 4, 2015. By the way, hydrogen isn’t as flammable as you might think.

Air swimmer at REB Research

Leave a reply

Birds got to swim and fish got to fly. Gonna love that hydrogen till the day I die. Here’s a movie of our hydrogen-filled air swimmer, a fish-blimp at REB Research. My hope is that this thing will help us sell hydrogen generators — perhaps to folks who fly military balloons, or those who fly hydrogen balloons for sport. On the other hand, the swimmer is a lot of fun to play with — and I got to show it off to a first grade class!

Aside from balloon fliers, military and otherwise, the sort of customers I’d hoped to attract were those building fueling stations for fuel cell cars or drone airplanes, and those running multiple gas chromatographs or adding hydrogen to car or diesel engine. Even small amounts of hydrogen added to a standard engine will reduce pollution significantly, add raise mileage too: a plus for a company like VW.

Dr. Robert E. Buxbaum, December 2, 2015. I should mention that hydrogen balloons are no where near as unsafe as people think. Here’s a movie I made of lighting a hydrogen filled balloon with a cigar.

My latest invention: improved fuel cell reformer

1 Reply

Last week, I submitted a provisional patent application for an improved fuel reformer system to allow a fuel cell to operate on ordinary, liquid fuels, e.g. alcohol, gasoline, and JP-8 (diesel). I’m attaching the complete text of the description, below, but since it is not particularly user-friendly, I’d like to add a small, explanatory preface. What I’m proposing is shown in the diagram, following. I send a hydrogen-rich stream plus ordinary fuel and steam to the fuel cell, perhaps with a pre-reformer. My expectation that the fuel cell will not completely convert this material to CO2 and water vapor, even with the pre-reformer. Following the fuel cell, I then use a water-gas shift reactor to convert product CO and H2O to H2 and CO2 to increase the hydrogen content of the stream. I then use a semi-permeable membrane to extract the waste CO2 and water. I recirculate the hydrogen and the rest of the water back to the fuel cell to generate extra power, prevent coking, and promote steam reforming. I calculate the design should be able to operate at, perhaps 0.9 Volt per cell, and should nearly double the energy per gallon of fuel compared to ordinary diesel. Though use of pure hydrogen fuel would give better mileage, this design seems better for some applications. Please find the text following.

Use of a Water-Gas shift reactor and a CO2 extraction membrane to improve fuel utilization in a solid oxide fuel cell system.

Inventor: Dr. Robert E. Buxbaum, REB Research, 12851 Capital St, Oak Park, MI 48237; Patent Pending.

Solid oxide fuel cells (SOFCs) have improved over the last 10 years to the point that they are attractive options for electric power generation in automobiles, airplanes, and auxiliary power supplies. These cells operate at high temperatures and tolerate high concentrations of CO, hydrocarbons and limited concentrations of sulfur (H2S). SOFCs can operate on reformate gas and can perform limited degrees of hydrocarbon reforming too – something that is advantageous from the stand-point of fuel logistics: it’s far easier to transport a small volume of liquid fuel that it is a large volume of H2 gas. The main problem with in-situ reforming is the danger of coking the fuel cell, a problem that gets worse when reforming is attempted with the more–desirable, heavier fuels like gasoline and JP-8. To avoid coking the fuel cell, heavier fuels are typically reforming before hand in a separate reactor, typically by partial oxidation at auto-thermal conditions, a process that typically adds nitrogen and results in the inability to use the natural heat given off by the fuel cell. Steam reforming has been suggested as an option (Chick, 2011) but there is not enough heat released by the fuel cell alone to do it with the normal fuel cycles.

Another source of inefficiency in reformate-powered SOFC systems is basic to the use of carbon-containing fuels: the carbon tends to leave the fuel cell as CO instead of CO2. CO in the exhaust is undesirable from two perspectives: CO is toxic, and quite a bit of energy is wasted when the carbon leaves in this form. Normally, carbon can not leave as CO2 though, since CO is the more stable form at the high temperatures typical of SOFC operation. This patent provides solutions to all these problems through the use of a water-gas shift reactor and a CO2-extraction membrane. Find a drawing of a version of the process following.

RE. Buxbaum invention: A suggested fuel cycle to allow improved fuel reforming with a solid oxide fuel cell

RE. Buxbaum invention: A suggested fuel cycle to allow improved fuel reforming with a solid oxide fuel cell

As depicted in Figure 1, above, the fuel enters, is mixed with steam or partially boiled water, and heated in the rectifying heat exchanger. The hot steam + fuel mix then enters a steam reformer and perhaps a sulfur removal stage. This would be typical steam reforming except for a key difference: the heat for reforming comes (at least in part) from waste heat of the SOFC. Normally speaking there would not be enough heat, but in this system we add a recycle stream of H2-rich gas to the fuel cell. This stream, produced from waste CO in a water-gas shift reactor (the WGS) shown in Figure 1. This additional H2 adds to the heat generated by the SOFC and also adds to the amount of water in the SOFC. The net effect should be to reduce coking in the fuel cell while increasing the output voltage and providing enough heat for steam reforming. At least, that is the thought.

SOFCs differ from proton conducting FCS, e.g. PEM FCs, in that the ion that moves is oxygen, not hydrogen. As a result, water produced in the fuel cell ends up in the hydrogen-rich stream and not in the oxygen stream. Having this additional water in the fuel stream of the SOFC can promote fuel reforming within the FC. This presents a difficulty in exhausting the waste water vapor in that a means must be found to separate it from un-combusted fuel. This is unlike the case with PEM FCs, where the waste water leaves with the exhaust air. Our main solution to exhausting the water is the use of a membrane and perhaps a knockout drum to extract it from un-combusted fuel gases.

Our solution to the problem of carbon leaving the SOFC as CO is to react this CO with waste H2O to convert it to CO2 and additional H2. This is done in a water gas shift reactor, the WGS above. We then extract the CO2 and remaining, unused water through a CO2- specific membrane and we recycle the H2 and unconverted CO back to the SOFC using a low temperature recycle blower. The design above was modified from one in a paper by PNNL; that paper had neither a WGS reactor nor a membrane. As a result it got much worse fuel conversion, and required a high temperature recycle blower.

Heat must be removed from the SOFC output to cool it to a temperature suitable for the WGS reactor. In the design shown, the heat is used to heat the fuel before feeding it to the SOFC – this is done in the Rectifying HX. More heat must be removed before the gas can go to the CO2 extractor membrane; this heat is used to boil water for the steam reforming reaction. Additional heat inputs and exhausts will be needed for startup and load tracking. A solution to temporary heat imbalances is to adjust the voltage at the SOFC. The lower the voltage the more heat will be available to radiate to the steam reformer. At steady state operation, a heat balance suggests we will be able to provide sufficient heat to the steam reformer if we produce electricity at between 0.9 and 1.0 Volts per cell. The WGS reactor allows us to convert virtually all the fuel to water and CO2, with hardly any CO output. This was not possible for any design in the PNNL study cited above.

The drawing above shows water recycle. This is not a necessary part of the cycle. What is necessary is some degree of cooling of the WGS output. Boiling recycle water is shown because it can be a logistic benefit in certain situations, e.g. where you can not remove the necessary CO2 without removing too much of the water in the membrane module, and in mobile military situations, where it’s a benefit to reduce the amount of material that must be carried. If water or fuel must be boiled, it is worthwhile to do so by cooling the output from the WGS reactor. Using this heat saves energy and helps protect the high-selectivity membranes. Cooling also extends the life of the recycle blower and allows the lower-temperature recycle blowers. Ideally the temperature is not lowered so much that water begins to condense. Condensed water tends to disturb gas flow through a membrane module. The gas temperatures necessary to keep water from condensing in the module is about 180°C given typical, expected operating pressures of about 10 atm. The alternative is the use of a water knockout and a pressure reducer to prevent water condensation in membranes operated at lower temperatures, about 50°C.

Extracting the water in a knockout drum separate from the CO2 extraction has the secondary advantage of making it easier to adjust the water content in the fuel-gas stream. The temperature of condensation can then be used to control the water content; alternately, a separate membrane can extract water ahead of the CO2, with water content controlled by adjusting the pressure of the liquid water in the exit stream.

Some description of the membrane is worthwhile at this point since a key aspect of this patent – perhaps the key aspect — is the use of a CO2-extraction membrane. It is this addition to the fuel cycle that allows us to use the WGS reactor effectively to reduce coking and increase efficiency. The first reasonably effective CO2 extraction membranes appeared only about 5 years ago. These are made of silicone polymers like dimethylsiloxane, e.g. the Polaris membrane from MTR Inc. We can hope that better membranes will be developed in the following years, but the Polaris membrane is a reasonably acceptable option and available today, its only major shortcoming being its low operating temperature, about 50°C. Current Polaris membranes show H2-CO2 selectivity about 30 and a CO2 permeance about 1000 Barrers; these permeances suggest that high operating pressures would be desirable, and the preferred operation pressure could be 300 psi (20 atm) or higher. To operate the membrane with a humid gas stream at high pressure and 50°C will require the removal of most of the water upstream of the membrane module. For this, I’ve included a water knockout, or steam trap, shown in Figure 1. I also include a pressure reduction valve before the membrane (shown as an X in Figure 1). The pressure reduction helps prevent water condensation in the membrane modules. Better membranes may be able to operate at higher temperatures where this type of water knockout is not needed.

It seems likely that, no matter what improvements in membrane technology, the membrane will have to operate at pressures above about 6 atm, and likely above about 10 atm (upstream pressure) exhausting CO2 and water vapor to atmosphere. These high pressures are needed because the CO2 partial pressure in the fuel gas leaving the membrane module will have to be significantly higher than the CO2 exhaust pressure. Assuming a CO2 exhaust pressure of 0.7 atm or above and a desired 15% CO2 mol fraction in the fuel gas recycle, we can expect to need a minimum operating pressure of 4.7 atm at the membrane. Higher pressures, like 10 or 20 atm could be even more attractive.

In order to reform a carbon-based fuel, I expect the fuel cell to have to operate at 800°C or higher (Chick, 2011). Most fuels require high temperatures like this for reforming –methanol being a notable exception requiring only modest temperatures. If methanol is the fuel we will still want a rectifying heat exchanger, but it will be possible to put it after the Water-Gas Shift reactor, and it may be desirable for the reformer of this fuel to follow the fuel cell. When reforming sulfur-containing fuels, it is likely that a sulfur removal reactor will be needed. Several designs are available for this; I provide references to two below.

The overall system design I suggest should produce significantly more power per gm of carbon-based feed than the PNNL system (Chick, 2011). The combination of a rectifying heat exchange, a water gas reactor and CO2 extraction membrane recovers chemical energy that would otherwise be lost with the CO and H2 bleed steam. Further, the cooling stage allows the use of a lower temperature recycle pump with a fairly low compression ratio, likely 2 or less. The net result is to lower the pump cost and power drain. The fuel stream, shown in orange, is reheated without the use of a combustion pre-heater, another big advantage. While PNNL (Chick, 2011) has suggested an alternative route to recover most of the chemical energy through the use of a turbine power generator following the fuel cell, this design should have several advantages including greater reliability, and less noise.

Claims:

1.   A power-producing, fuel cell system including a solid oxide fuel cell (SOFC) where a fuel-containing output stream from the fuel cell goes to a regenerative heat exchanger followed by a water gas shift reactor followed by a membrane means to extract waste gases including carbon dioxide (CO2) formed in said reactor. Said reactor operating a temperatures between 200 and 450°C and the extracted carbon dioxide leaving at near ambient pressure; the non-extracted gases being recycled to the fuel cell.

Main References:

The most relevant reference here is “Solid Oxide Fuel Cell and Power System Development at PNNL” by Larry Chick, Pacific Northwest National Laboratory March 29, 2011: http://www.energy.gov/sites/prod/files/2014/03/f10/apu2011_9_chick.pdf. Also see US patent  8394544. it’s from the same authors and somewhat similar, though not as good and only for methane, a high-hydrogen fuel.

Robert E. Buxbaum, REB Research, May 11, 2015.

How do technology companies sell stuff?

1 Reply

As the owner of a technology company, REB Research, hydrogen generators and hydrogen purifiers, I spend a fair amount of time trying to sell my stuff, and wondering how other companies connect to potential customers and sell to them. Sales is perhaps the most important area of business success, the one that makes or breaks most businesses — but it was sadly ignored in my extensive college education. Business books are hardly better: they ignore the salesmen (and women); you’re left to imagine sales and profit came of themselves by the insight of the great leader. The great, successful internet companies are applauded for giving away services, and the failed interned companies are barely mentioned. And hardly any book mentions smaller manufacturing businesses, like mine.

So here are some sales thoughts: things I tried, things that worked, and didn’t. I started my company, REB Research, about 20 years ago as a professor at Michigan State University. I figured I knew more about hydrogen purifiers than most of my colleagues, and imagined this knowledge would bring me money (big mistake: I needed customers and profitable sales). My strategy was to publish papers on hydrogen and get some patents as a way to build credibility (worked reasonably well: I write well, do research well, and I’m reasonably inventive). Patents might have been a better strategy if I had not then allowed my patents to be re-written by lawyers. I built the company. while still a professor (a good idea, I think).

When I realized I needed sales, I decided to use trade fairs, conferences, and ads as the big companies did. Most of my budget went for ads in The Thomas Register of American Manufacturing, a fantastically large compendium of who did or sold what (it worked OK, but was since rendered obsolete by the internet). I bought $1500 worth of ads, and got 2 small lines plus a 1/8 page. That’s where I got my sales until the internet cam along. In retrospect, I suspect I should have bought more ads.

William Hamilton cartoon from the new-yorker. I sure wish I could make deals.

William Hamilton cartoon from the new-yorker.

My other big expense was trade fairs. Many big companies sold at trade fairs, events that are widely attended in my field. Sorry to say, I never found customers at these fairs, even when the fairs were dedicated to hydrogen, everyone who’d come by was was selling, and no one was buying, as best I could tell.Somehow, my bigger competitors (also at the fairs) seemed to get interest but I’m not sure if they got sales there. They seem to find sales somewhere, though. Is it me? Am I at the wrong fairs, or are fairs just a scam where no one wins but the organizers? I don’t know. Last month, I spent $2000 for a booth in Ann Arbor, MI, including $350 for inclusion into the promoter’s book and $400 for hand-out literature. As with previous events, few people came by and none showed anything like interest, I got no e-mail addresses and no sales. Some hungry students wandered the stalls for food and freebees, but there was not one person with money in his/her pocket and a relevant project to spend it on. I doubt anyone read the literature they took.

To date, virtually all of my sales have come from the internet. I got on the internet early, and that has helped my placement in Google. I’ve never bought a google ad, but this may change. Instead I was lucky. About 20 years ago, 1994?, I attended a conference at Tufts on membrane reactors, and stayed at a bed-and-breakfast. After the conference let out, the owner of the BnB suggested I visit something that was new at Harvard; a cyber cafe, the second one in the US. They had Macintosh computers and internet explorer a year before the company went public. I was hooked, went home, learned html, and wrote a web-site. I bought my domain name shortly thereafter.

The problem, I don’t know the next big thing. Twitter? Facebook? LinkedIn? I’m on 2 of these 3, and have gotten so sales from social media. I started a blog (you’re reading it), but I still wonder, why are the bigger companies selling more? The main difference I see is they attend a lot more product fairs than I do, have slicker web-sties (not very good ones, I think), and they do print advertising. Perhaps they match their fairs to their products better, or have a broader range of products. People need to see my products somewhere, but where? My latest idea: this week I bought HydrogenPurifier.com. Send me advice, or wish me luck.

Robert E. Buxbaum, flailing entrepreneur, September 10, 2014. Here’s a feedback form, the first time I’m adding one. 

Getting rid of hydrogen

4 Replies

Though most of my company’s business is making hydrogen or purifying it, or consulting about it, we also provide sorbers and membranes that allow a customer to get rid of unwanted hydrogen, or remove it from a space where it is not wanted. A common example is a customer who has a battery system for long-term operation under the sea, or in space. The battery or the metal containment is then found to degas hydrogen, perhaps from a corrosion reaction. The hydrogen may interfere with his electronics, or the customer fears it will reach explosive levels. In one case the customer’s system was monitoring deep oil wells and hydrogen from the well was messing up its fiber optic communications.

img505

Pd-coated niobium screws used to getter hydrogen from electronic packages.

For many of these problems, the simplest solution is an organic hydrogen getter of palladium-catalyst and a labile unsaturated hydrocarbon, e.g. buckminsterfullerene. These hydrogen getters are effective in air or inert gas at temperatures between about -20°C and 150°C. When used in an inert gas the organic is hydrogenated, there is a finite amount of removal per gram of sober. When used in air the catalyst promotes the water-forming reaction, and thus there is a lot more hydrogen removal. Depending on the organic, we can provide gettering to lower temperatures or higher. We’ve a recent patent on an organo-palladium gel to operate to 300°C, suitable for down-well hydrogen removal.

At high temperatures, generally above 100*C, we generally suggest an inorganic hydrogen remover, e.g. our platinum ceria catalyst. This material is suitable for hydrogen removal from air, including from polluted air like that in radioactive waste storage areas. Platinum catalyst works long-term at temperatures between about 0°C and 600°C. The catalyst-sorber also works without air, reducing Ce2O3 to CeO and converting hydrogen irreversibly to water (H2O). As with the organo-Pd getters, there is a finite amount of hydrogen removal per gram when these materials are used in a sealed environment.

Low temperature, Pd-grey coated, Pd-Ag membranes made for the space shuttle to remove hydrogen from the drinking water at room temperature. The water came from the fuel cells.

Low temperature, metal membranes made for NASA to remove H2 from  drinking water at room temperature.

Another high temperature hydrogen removal option is metallic getters, e.g. yttrium or vanadium-titanium alloy. These metals require temperatures in excess of 100°C to be effective, and typically do not work well in air. They are best suited for removing hydrogen a vacuum or inert gas, converting it to metallic hydride. The thermodynamics of hydriding is such that, depending on the material, these getters can extract hydrogen even at temperatures up to 700°C, and at very low hydrogen pressures, below 10-9 torr. For operation in air or at 100-400°C we typically provide these getters coated with palladium to increase the hydrogen sorption rate. A fairly popular product is palladium-coated niobium screws 4-40 x 1/4″. Each screw will remove over 2000 sec of hydrogen at temperatures up to 400°C. We also provide oxygen, nitrogen and water getters. They work on the same principle, but form metallic oxides or nitrides instead of hydrides.

Our last, and highest-end, hydrogen-removal option is to provide metallic membranes. These don’t remove the hydrogen as such, but transfer it elsewhere. We’ve provided these for the space shuttle, and to the nuclear industry so that hydrogen can be vented from nuclear reactors before it has a chance to build up and case damage or interfere with heat transfer. Because nothing is used up, these membranes work, essentially forever. The Fukushima reactor explosions were from corrosion-produced hydrogen that had no acceptable way to vent.

Please contact us for more information, e.g. by phone at 248-545-0155, or check out the various sorbers in our web-site. Robert Buxbaum, May 5, 2014.

Nuclear fusion

5 Replies

I got my PhD at Princeton University 33 years ago (1981) working on the engineering of nuclear fusion reactors, and I thought I’d use this blog to rethink through the issues. I find I’m still of the opinion that developing fusion is important as the it seems the best, long-range power option. Civilization will still need significant electric power 300 to 3000 years from now, it seems, when most other fuel sources are gone. Fusion is also one of the few options for long-range space exploration; needed if we ever decide to send colonies to Alpha Centauri or Saturn. I thought fusion would be ready by now, but it is not, and commercial use seems unlikely for the next ten years at least — an indication of the difficulties involved, and a certain lack of urgency.

Oil, gas, and uranium didn’t run out like we’d predicted in the mid 70s. Instead, population growth slowed, new supplies were found, and better methods were developed to recover and use them. Shale oil and fracking unlocked hydrocarbons we thought were unusable, and nuclear fission reactors got better –safer and more efficient. At the same time, the more we studied, the clearer it came that fusion’s technical problems are much harder to tame than uranium fission’s.

Uranium fission was/is frighteningly simple — far simpler than even the most basic fusion reactor. The first nuclear fission reactor (1940) involved nothing more than uranium pellets in a pile of carbon bricks stacked in a converted squash court at the University of Chicago. No outside effort was needed to get the large, unstable uranium atoms split to smaller, more stable ones. Water circulating through the pile removed the heat released, and control was maintained by people lifting and lowering cadmium control rods while standing on the pile.

A fusion reactor requires high temperature or energy to make anything happen. Fusion energy is produced by combining small, unstable heavy hydrogen atoms into helium, a bigger more stable one, see figure. To do this reaction you need to operate at the equivalent of about 500,000,000 degrees C, and containing it requires (typically) a magnetic bottle — something far more complex than a pile of graphic bricks. The reward was smaller too: “only” about 1/13th as much energy per event as fission. We knew the magnetic bottles were going to be tricky, e.g. there was no obvious heat transfer and control method, but fusion seemed important enough, and the problems seemed manageable enough that fusion power seemed worth pursuing — with just enough difficulties to make it a challenge.

Basic fusion reaction: deuterium + tritium react to give helium, a neutron and energy.

Basic fusion reaction: deuterium + tritium react to give helium, a neutron and energy.

The plan at Princeton, and most everywhere, was to use a TOKAMAK, a doughnut-shaped reactor like the one shown below, but roughly twice as big; TOKAMAK was a Russian acronym. The doughnut served as one side of an enormous transformer. Hydrogen fuel was ionized into a plasma (a neutral soup of protons and electrons) and heated to 300,000,000°C by a current in the TOKOMAK generated by varying the current in the other side of the transformer. Plasma containment was provided by enormous magnets on the top and bottom, and by ring-shaped magnets arranged around the torus.

As development went on, we found we kept needing bigger and bigger doughnuts and stronger and stronger magnets in an effort to balance heat loss with fusion heating. The number density of hydrogen atoms per volume, n, is proportional to the magnetic strength. This is important because the fusion heat rate per volume is proportional to n-squared, n2, while heat loss is proportional to n divided by the residence time, something we called tau, τ. The main heat loss was from the hot plasma going to the reactor surface. Because of the above, a heat balance ratio was seen to be important, heat in divided by heat out, and that was seen to be more-or-less proportional to nτ. As the target temperatures increased, we found we needed larger and larger nτ reactors to make a positive heat balance. And this translated to ever larger reactors and ever stronger magnetic fields, but even here there was a limit, 1 billion Kelvin, a thermodynamic temperature where the fusion reaction went backward and no energy was produced. The Princeton design was huge, with super strong, super magnets, and was operated at 300 million°C, near the top of the reaction curve. If the temperature went above or below this temperature, the fire would go out. There was no room for error, but relatively little energy output per volume — compared to fission.

Fusion reaction options and reaction rates.

Fusion reaction options and reaction rates.

The most likely reaction involved deuterium and tritium, referred to as D and T. This was the reaction of the two heavy isotopes of hydrogen shown in the figure above — the same reaction used in hydrogen bombs, a point we rarely made to the public. For each reaction D + T –> He + n, you get 17.6 million electron volts (17.6 MeV). This is 17.6 million times the energy you get for an electron moving over one Volt, but only 1/13 the energy of a fission reaction. By comparison, the energy of water-forming, H2 + 1/2 O2 –> H2O, is the equivalent of two electrons moving over 1.2 Volts, or 2.4 electron volts (eV), some 8 million times less than fusion.

The Princeton design involved reacting 40 gm/hr of heavy hydrogen to produce 8 mol/hr of helium and 4000 MW of heat. The heat was converted to electricity at 38% efficiency using a topping cycle, a modern (relatively untried) design. Of the 1500 MWh/hr of electricity that was supposed to be produced, all but about 400 MW was to be delivered to the power grid — if everything worked right. Sorry to say, the value of the electricity did not rise anywhere as fast as the cost of the reactor and turbines. Another problem: 1100 MW was more than could be easily absorbed by any electrical grid. The output was high and steady, and could not be easily adjusted to match fluctuating customer demand. By contrast a coal plant’s or fuel cell’s output could be easily adjusted (and a nuclear plant with a little more difficulty).

Because of the need for heat balance, it turned out that at least 9% of the hydrogen had to be burnt per pass through the reactor. The heat lost per mol by conduction to the wall was, to good approximation, the heat capacity of each mol of hydrogen ions, 82 J/°C mol, times the temperature of the ions, 300 million °C divided by the containment time, τ. The Princeton design was supposed to have a containment of about 4 seconds. As a result, the heat loss by conduction was 6.2 GW per mol. This must be matched by the molar heat of reaction that stayed in the plasma. This was 17.6 MeV times Faraday’s constant, 96,800 divided by 4 seconds (= 430 GW/mol reacted) divided by 5. Of the 430 GW/mol produced in fusion reactions only 1/5 remains in the plasma (= 86 GW/mol) the other 4/5 of the energy of reaction leaves with the neutron. To get the heat balance right, at least 9% of the hydrogen must react per pass through the reactor; there were also some heat losses from radiation, so the number is higher. Burn more or less percent of the hydrogen and you had problems. The only other solution was to increase τ > 4 seconds, but this meant ever bigger reactors.

There was also a material handling issue: to get enough fuel hydrogen into the center of the reactor, quite a lot of radioactive gas had to be handled — extracted from the plasma chamber. These were to be frozen into tiny spheres of near-solid hydrogen and injected into the reactor at ultra-sonic velocity. Any slower and the spheres would evaporate before reaching the center. As 40 grams per hour was 9% of the feed, it became clear that we had to be ready to produce and inject 1 pound/hour of tiny spheres. These “snowballs-in-hell” had to be small so they didn’t dampen the fire. The vacuum system had to be able to be big enough to handle the lb/hr or so of unburned hydrogen and ash, keeping the pressure near total vacuum. You then had to purify the hydrogen from the ash-helium and remake the little spheres that would be fed back to the reactor. There were no easy engineering problems here, but I found it enjoyable enough. With a colleague, I came up with a cute, efficient high vacuum pump and recycling system, and published it here.

Yet another engineering challenge concerned the difficulty of finding a material for the first-wall — the inner wall of the doughnut facing the plasma. Of the 4000 MW of heat energy produced, all the conduction and radiation heat, about 1000 MW is deposited in the first wall and has to be conducted away. Conducting this heat means that the wall must have an enormous coolant flow and must withstand an enormous amount of thermal stress. One possible approach was to use a liquid wall, but I’ve recently come up with a rather nicer solid wall solution (I think) and have filed a patent; more on that later, perhaps after/if the patent is accepted. Another engineering challenge was making T, tritium, for the D-T reaction. Tritium is not found in nature, but has to be made from the neutron created in the reaction and from lithium in a breeder blanket, Li + n –> He + T. I examined all possible options for extracting this tritium from the lithium at low concentrations as part of my PhD thesis, and eventually found a nice solution. The education I got in the process is used in my, REB Research hydrogen engineering business.

Man inside the fusion reactor doughnut at ITER. He'd better leave before the 8,000,000°C plasma turns on.

Man inside the fusion reactor doughnut at ITER. He’d better leave before the 8,000,000°C plasma turns on.

Because of its complexity, and all these engineering challenges, fusion power never reached the maturity of fission power; and then Three-mile Island happened and ruined the enthusiasm for all things nuclear. There were some claims that fusion would be safer than fission, but because of the complexity and improvements in fission, I am not convinced that fusion would ever be even as safe. And the long-term need keeps moving out: we keep finding more uranium, and we’ve developed breeder reactors and a thorium cycle: technologies that make it very unlikely we will run out of fission material any time soon.

The main, near term advantage I see for fusion over fission is that there are fewer radioactive products, see comparison.  A secondary advantage is neutrons. Fusion reactors make excess neutrons that can be used to make tritium, or other unusual elements. A need for one of these could favor the development of fusion power. And finally, there’s the long-term need: space exploration, or basic power when we run out of coal, uranium, and thorium. Fine advantages but unlikely to be important for a hundred years.

Robert E. Buxbaum, March 1, 2014. Here’s a post on land use, on the aesthetics of engineering design, and on the health risks of nuclear power. The sun’s nuclear fusion reactor is unstable too — one possible source of the chaotic behavior of the climate. Here’s a control joke.