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.

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.