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Post by eclipse on Oct 30, 2023 11:15:58 GMT 9.5
A butcher must buy a whole beef carcass - and then aims to cut it up into as many marketable products as he can. But if his customers suddenly only want his best tenderloin fillet steaks, and refuse to buy the other cuts like chuck, rib, brisket or short loin - that butcher is in trouble. He still has to buy the whole cow, but can’t afford to only sell 6% of the cow.
In the same way an oil refinery refines crude oil into the various products we normally buy. Gasoline and diesel make about 70%, heavy fuel for ocean liners is 5%, asphalt is 4%, light fuels for domestic heating is 3%, and various plastics and cooking gases etc make up 12%. All of these, more or less, have alternative energy or material products that can scale up as the oil industry winds down. All of them except one - the last 6% I haven’t mentioned yet that we use for jet fuel. The airline industry does not have a clear energy succession plan. All the alternatives are too expensive - at this stage. Hydrogen requires much larger fuel tanks and would squeeze down the number of seats per flight, increasing costs. Manufactured ‘e-fuels’ like synthetic fuel made from hydrogen and capturing CO2 to add to the mix to make real jet fuel is too energy intense, and too expensive.
So what can we do in coming decades as we wean off oil but have no plan for airlines yet? The oil refinery MUST buy a whole tanker of crude for say $200 million. But we’ll have alternatives to petroleum and diesel and asphalt - and only want 6% of their product - the jet fuel. Yet it still takes the other 94% of the crude oil just to refine out that 6%.
It seems to me we need to have the brute force of laws that mandate airlines wean off oil by a given date, or they won’t take action and we’ll be left with the refinery version of this Butcher’s Dilemma above. Any other ideas?
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Post by David B. Benson on Oct 30, 2023 13:19:15 GMT 9.5
Jet engines can be engineered to run on hydrogen so the issue is being able to store the hydrogen at the same energy density as jet fuel, i.e., kerosene.
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Post by cyrilr on Oct 30, 2023 18:05:04 GMT 9.5
From a refining viewpoint this isn’t a big problem, with the advent of fluid catalytic cracking.
From a sustainability viewpoint it is more difficult. In the near term some green hydrogen could be produced and used to upgrade oil, effectively flying on clean hydrogen, at least on the margin.
Longer term high temp nuclear reactors can make synfuel. I think hydrogen is too heroic for aviation, heck even Musk thinks we should use methane for rockets.
Really longer term, batteries could get good enough for longer and longer flights. Boeing had a great stepping stone approach with the development of 4 engined aircraft with one engine electric, presumably moving to more engines electric over time. Sadly they cancelled the project.
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Post by eclipse on Oct 31, 2023 4:35:39 GMT 9.5
I'm no chemist, but the wiki seems to indicate jet fuel is in the middle length of the carbon chain potential in crude. EG: "Kerosene-type jet fuel (including Jet A and Jet A-1, JP-5, and JP-8) has a carbon number distribution between about 8 and 16 (carbon atoms per molecule); wide-cut or naphtha-type jet fuel (including Jet B and JP-4), between about 5 and 15.[2][3]"
So in the short term as the oil industries scale back, say most gasoline and diesel are replaced by EV's (whenever). That's 70% of the crude product, gone. Say the oil industry finally sees the writing on the wall but has a last decade in which to supply jet fuel.
How much of a tanker of average crude could be turned into jet fuel? Half? 3/4? 90%? Would the rest find alternative markets in less harmful stuff - because we really need to lower emissions.
Obviously, the lower the ratio of tanker load turned into jet-fuel exclusively - the more the oil industry must dispose of or divert into other uses. EG: Could a refinery be fine tuned to make a good portion jet fuel, and dump the rest into something nasty like asphalt?
Also, how much would it cost to refit a refinery from a normal mix of products to selling mostly jet-fuel? Like, another 10% of the refinery's value? 50%? When is that old refinery basically just junk, and we're looking at a completely different structure anyway?
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Post by Roger Clifton on Oct 31, 2023 16:32:55 GMT 9.5
So what can we do in coming decades as we wean off oil but have no plan for airlines yet? ... we’ll have alternatives to petroleum and diesel and asphalt - and only want 6% of their product - the jet fuel. Hi Eclipse, it's good to hear from you again! Today, most transport fuel is not found in the "beast", but is created by cracking heavier chemicals. It needn't always be so. A modern fuel refinery is a hotbed of chemistry, with long or flat molecules been broken up, impurities removed, and designer cross-links inserted. Any hydrocarbon can be made from the mix of carbon, hydrogen and oxygen, at the expense of enough energy. A big refinery inputs about 5 GW of crude oil, of which about 1 GW is used to create power, heat, pressure – and hydrogen. Some of the heat value is dumped along with so-called lean gas, which is mainly CO2 along with nitrogen and odds-and-ends chemicals that are too much bother to recycle. Fuel refineries are good at evolving, and are certainly capable of gradually increasing their non-fossil energy content – starting with that 1 GW. As well as generating clean electricity, nukes can be built to generate the high-grade heat and hot hydrogen needed by the refineries. At the same time, byproduct CO2 could be recycled back into hydrocarbon fuels when they have enough non-fossil hydrogen. In some green future, I imagine that a fuel refinery would have no fossil inputs at all, just CO2 captured from the air or sea, and copious amounts of cheap non-fossil power. Recycling CO2 back into jet fuel is theoretically well based. No doubt you remember the earlier BNC discussion: bravenewclimate.com/2013/01/16/zero-emission-synfuel-from-seawater/While interest continues, the technology improves – www.newscientist.com/article/2394108-jet-fuel-made-with-captured-co2-and-clean-electricity-set-for-take-off/ |
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Post by eclipse on Oct 31, 2023 17:08:27 GMT 9.5
So a refinery could hypothetically mix in half crude AND half hydrogen & CO2 from greener sources? I did not know that. That means they're a lot more flexible than the peak oil doomer was saying.
But how much does a regular refinery have to be 'tweaked' to go from the regular mix of products to a much higher percent of jet fuel? Could there be one of our hybrid refineries taking in half crude, half green stuff that produces a majority airline product with whatever else being diverted into whatever niche chemical, plastics and bitumen markets there still are after most ground transport is electric?
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Post by Roger Clifton on Oct 31, 2023 18:27:14 GMT 9.5
how much does a regular refinery have to be 'tweaked' to go from the regular mix of products to a much higher percent of jet fuel? Well, fuel refineries evolve gradually, rather than get replaced 50-50. Initially, fuel refineries would easily accept non-fossil electricity, saving them from burning their feedstock. With more nonfossil power, electrolytic or thermolytic hydrogen would become available. Hydrogen would be easily incorporated into their processes, especially hot hydrogen. Hydrogen is particularly welcome, because it allows low-hydrogen feedstock to be cracked into high-hydrogen products such as jet fuel. (Jet fuel must be high-hydrogen to ensure that it does not gel and clog up aircraft fuel lines.) Conventionally, hydrogen is generated by partial burning of feedstock, with the implied oxides being eventually dumped as CO2 into the atmosphere. With extra hydrogen available, more of the carbon in the feedstock is converted to valuable hydrocarbons. In the future, we don't want them to dump CO2 at all, but react it with hydrogen to create hydrocarbons directly. See Wikipedia for the Fischer-Tropsch process, for example. en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process |
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Post by eclipse on Oct 31, 2023 19:27:38 GMT 9.5
Thanks guys! Chemistry broken down into English and metaphors I can understand. Cheers!
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Post by eclipse on Nov 2, 2023 11:34:01 GMT 9.5
From a refining viewpoint this isn’t a big problem, with the advent of fluid catalytic cracking. Hi again, I finally had time to check the wiki and it seems to be mainly gasoline and diesel? en.wikipedia.org/wiki/Fluid_catalytic_crackingThe wiki then put me onto hydrocracking which seems to be more about kerosene. |
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Post by cyrilr on Nov 3, 2023 0:17:22 GMT 9.5
Yes, sorry, I tend to lump in all cracking as FCC, but that's not really accurate, as hydrogen demand for hydrocracking is actually quite big.
Not entirely sure why hydrocracking for gasoline isn't more popular. You'd need more hydrogen for it compared to kerosine, but other than that I can't think of a technical reason it isn't done?
Once we have high temperature nuclear reactors commonly available, the hydrocracking route becomes much more attractive, since the added hydrogen energy is clean. Flying on hydrocracked kerosine would then become partly flying on nuclear power.
I'm not as sanguine about near term reductions of petroleum demand. Gasoline is probably the one big guy to drop, with electric and hybrid vehicles taking over the world by storm. But diesel is much harder to replace, being used mostly for large machinery and long haul transport, which are tough to provide with batteries. And bunker oil for shipping is even harder to do with batteries. Natural gas could take over a lot of these markets though, in which case there'd be a big drop in oil demand for these. Plastics are tough to replace, there isn't enough biomass to make all PE and PP and so on sustainably.
The only realistic near term alternative to shipping, aviation and long haul road transport is natural gas, mostly as LNG for transport and low pressure NG for plastics production. Along with the need for large amounts of natural gas to balance out wind and solar heavy grids, it means that natural gas is the quiet winner in all this. This is what I would expect to play out over the coming decades. Gasoline demand plummets from electric vehicles, with heavier fractions and plastics increasingly replaced with natural gas. It'll be interesting to see how the refiners would respond to this. Natural gas needs little refining.
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