Guest post by Ryan Richter
At this point I hope we have all imagined the possibility of a future with economic prosperity and without fossil carbon-based motor fuels. You can use electricity and renewable sources for most things. OK, but what about everything else? Motor fuels and fossil carbon electricity generation aren’t the whole story by a long shot. There’s steel and aliminum, oh and also cement. And then there’s organic chemistry more generally – can’t you do that without burning the oil? Well, no, not today you can’t. This is what I want to take the knife to. We have the tools, but I don’t hear many people talking about how to really use them to full effect.
I’m talking about nuclear power of course. We certainly want to take the fullest advantage of solar power and other renewable sources as well. I want to additionally propose the use of radioisotope heater units to replace a number of unobvious carbon sources in today’s heavy industry. Nuclear advocates have recommended the reprocessing of fuel to extend the nuclear fuel cycle in the past, but relatively little has been done so far. This lackadasical effort needs to end yesterday, of course. I fully recommend an expanded nuclear fuel cycle including reprocessing and fast breeder reactors, and maybe also a thorium cycle. But in addition to that, I want to re-propose an old idea (I don’t know where it originates) in a new context – not only extracting and fully using the actinides in the fuel cycle, but also extracting the fission products to make Fission Product Radioisotope Heater Units, FPRHUs.
Now let me change tack for a bit and talk about some very nasty fossil CO2 sources in heavy industry today. We use coal to make iron and steel. We use petroleum coke to make aliminum. We have lime kilns which release the CO2 from carbonate rocks, which is perhaps the very worst. And then there’s the awful oil-powered oil refinery. If you’re not familiar with the industry (I have never been any part of it), you may not have heard any of the details, so let me try to explain from what I’ve been able to piece together.
My explanation of the oil refinery will focus on what I consider to be the two fundamental processes in a refinery that’s not dedicated to motor fuels, which is a difficult thing to imagine based on what engineers build today. One is called the hydrotreater, which is an industry name for the high-pressure hydrogenation of hydrocarbons[1][3][4][5]. The so-called naphtha hydrotreater seems to operate somewhere around 100 atmospheres and maybe 300-400 celcius ([1][3][5] – this is difficult. According to [1] and [3] the hydrocarbons are pressurized to ~40atm and by [5] the H2 to ~200atm, which makes sense as H2 is cheaper to compress. A similar process is Hydrocracking [9] which is around 120atm). There is also a diesel or lube oil hydrotreater which operates at more extreme conditions [5] and processes a smaller feed. These hydrotreaters are fed with hydrogen from a reaction which overall is basically
CH4 + 2 H2O -> 4 H2 + CO2 (where does the CH4 come from? – not natural gas)
The second fundamental process is called the olefins unit pyrolysis furnace [8], which operates at more like 30 atmospheres and maybe 800 celsius. This is simply the thermal decomposition of hydrocarbons, in this case only the lighter naphtha mixture. The feeds to both of the fundamental precesses are highly miscellaneous mixtures of hydrocarbons, although not exactly the same. The hydrotreater in effect comes first, after the main fractionation (called the crude unit [1][2][7]). The feed from the crude unit typically still includes organic sulfur and nitrogen, and the hydrotreater is the sledgehammer for dealing with that, as sulfur comes out as H2S and N as NH3. But the other effect of the hydrotreater is to add hydrogen across carbon-carbon double bonds to make single bonds, although this makes it sound far more surgical than it is. On the other hand, the pyrolysis furnace in effect cooks hydrogen out – how many things can a hydrocarbon decompose to? So in that one you make double bonds, and also triple bonds, and some coke too no doubt, and some hydrogen, and also some methane. Well, more than a little bit in fact. The hydrotreater is also a prodigious producer of methane, being a hydrogenator after all. So that’s where the methane comes from. As it happens, only a little of it is needed to make the hydrogen that’s needed. A third process is called Hydrocracking [9], essentially a combination of the above two in one reactor, said to occur around 450 Celsius and 120 atmospheres.
So neither of the fundamental processes is especially chemically efficient. And if you’ve looked at the reaction conditions you can see that some thermal and mechanical power inputs are required also, not a small amount. What a horrible mess. How can you ever make money doing something like that – OH WAIT. You can burn the methane. So at the inlet to the hydrotreater there’s a jet engine the size of a large truck burning, in effect, the same methane that’s cooking out of the reaction. The naphtha hydrotreater at a medium size refinery costs over 200 megawatts to run (I swear I saw this number somewhere but now I can’t find it again) – but not in money. The pyrolysis furnace is a very similar story. This is where ethylene for plastics comes from. And the big embarrasment is that you have to send the same oil to the hydrotreater fisrt even though the pyrolysis furnace undoes the single bond-double bond thing. The cruse unit – the tallest tower – also has a house-sized burner fed by the so-called refinery fuel gas mix. All the other hundreds of other smaller towers also have their fuel gas-powered preheaters or compressors. It’s said that you can turn crude oil into anything, but it you want to turn all of it into polyethylene you have to, basically, burn half or more of it first, counting carbon atom by carbon atom. But in every case what you need is a concentrated heat source, and so I propose the FPRHU. There is a question about the effect of ionizing radiation on the chemical process, but I have a surprising answer for that.
What’s needed is a convenient high-temperature heat transfer material, and I have no idea what chemical engineers would propose based on that criterion alone. But I will propose the use of molten silicates for another reason. The Radioisotope Silicate Foundry (RSF) can be the basis of a carbon-free construction industry. The idea is that the RSF is located at a nucear fuel reprocessing facility and uses its freshest isotopes to produce both a high-temperature heat source for co-located heavy industry and a precast building material to replace concrete. This may not sound remotely believable based on the scale of recently-imagined nuclear reprocessing efforts, but I propose a great increase in that. Another benefit here is that all of this activity, together with the complete nuclear fuel cycle for actinides, reduces the final amount of nuclear waste produced for each ton of uranium mined.
It starts to become clearer what the overall picture looks like. Let me say a little bit about the metals first before sharpening the chemistry picture a little more. You need a reducing agent to make metals. One possibility is a electrical/nuclear biomass charcoal furnace. What biomass you would want and how much would be available is an interesting question I don’t know much about, as the chemical quality of the charcoal is important. An interesting alternative is hydrogen produced either by electrolysis of water or the pyrolysis of fossil carbon methane, not yet fully developed.
The steel mill coke ovens also produce a coal gas which is now called coke oven gas [6], and is used in the steel mill to het furnaces much the same as the oil refinery fuel gas. This would also be replaced by FPRHU/RSF. Preparing aluminum ore is mainly mechanical and wet chemistry, but iron ores are roasted and that’s a nut to crack. Heat is no problem with abundant FPRHUs, but some carbonates are decomposed here also. This may be on a scale that can be accepted if all other main sources of fossil CO2 are really eliminated. The other possibility is to treat carbonates with a wet chemistry, i.e. to use an acid to release CO2 and then a mineral base to absorb it. That would require support from the chloralkali process, more or less.
Finally, what would carbon chemistry look like? You will still need things like oil and coal to produce a number of things including asphalt and lubricants. Polymers and chemical feedstocks are also needed. Some of this can come from biomass, e.g. you can easily make ethylene from ethanol, although competing with food sources is not necessarily a good idea. Some real new chemical enginnering is needed, to say the least. I would presume butadiene still comes out of oil and coal. You can picture a refinery that processes heavy inputs with FPRHU/RSF heating, and which uses pyrolysis to destroy the methane which is the ultimate waste product. The hydrogen can be used liberally for anything, making iron, whatever. The carbon black has to end up in steel, tires, carbon fibre materials, and on printed pages I guess. There’s another interesting engineering question as to the overall balance between electricity usage and FPRHU, the point of which is that the FPRHUs need to be available on a real market. So in a little more detail, in a nuclear powered oil refinery the compressors would be powered by electricity but the feed preheat would be done by direct radioisotope heating. As I understand, the rule of thumb is that the fission products release about 10% of the heat that the original reactor produced. The thermal efficiency into electricity at a large reactor is around 40%. Waste heat at a power reactor is in the form of low-temperature steam, although some fast breeders may allow for something better – I’m not really sure.
OK, so I hope I’ve shown that it’s basically possible to do things this way, and emit only the smallest amount of fossil CO2 while making all the things we expect to make and have. The extensive handling of radioisotopes within the heavy manufacturing centers will necessitate an increase in automation, but the industry was really heading in that direction anyway. The big question is the capital expenditure. Of course the answer to that is state involvement to some degree – it’s just a question, politically, of what kind of future we want.
My data source for petrleum industry stuff are the reports of the CSB (which has an annoyingly long name), which investigates fatal accidents in the chimical industry in the US. They were created out of the EPA in the Clinton years with a subpoena power to reveal industry secrets. I downloaded personal copies of these when Trump was elected, having seen previous EPA reports disappear under Bush. This turned out to be a good idea, as the older reports are no longer linked from the main page. Other people have made archives. Report number 1 is particularly revealing. If you read only one report about a fatal accident at an oil refinery, make it that one. Number 2 is really shocking in the details and has a hilarious photo. 6 and 7 are weirdly macabre, seeming to describe the same accident at two different places.
[1] BP-Husky Toledo Refinery 2022
[2] Husky Superior Refinery 2018
[3] Tesoro Anacortes Refinery 2010
[4] Silver Eagle Woods Cross Refinery 2009
[5] BP Texas City Refinery 2005 (RHU Unit)
[6] Bethlehem Steel Chesterton 2001
[7] Tosco Avon Refinery 2001
[8] Shell Chemical Deer Park 1997
[9] Tosco Avon Refinery 1997
