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I’m in a pinch to finish up my story’s cover art and I don’t know if my train has a smokestack, logically.

This train runs in the planet Hell (see note) and uses liquid sulphur for the steam cycle. Traditional trains were an open steam cycle and carried their water behind them in a tender, blowing the steam out the smoke stack. My sulphur would also be liquid at ambient temperatures, it could follow the same scheme technically. But I think our decision not to use a closed cycle was because the earth has a natural water cycle that brings the steam back to us in rain. It was technically a closed cycle with weather completing the loop, and water towers lined the tracks to refill engines en route. Hell doesn’t rain brimstone… as poetic as that sounds, I think it’s implausible. I think? I’m in a quandary.

So if sulphur needs to be made from sulphuric acid or mined, a closed steam cycle may make more sense, sending the condensed liquid sulphur back to the tanks.

Yes, I still need to boil my sulphur with a moderate heat source, or run it at a slight vacuum, which water steam didn’t need. I’m working on that too.

Does a brimstone train in Hell need a smokestack?

Note: Climate on Hell

  • Average temperature: 420°C
  • Atmospheric content: Nitrogen and CO$_2$
  • Terrain: Volcanic wastes
  • Biology: None
sphennings
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Vogon Poet
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    It sounds like the real question is can a steam engine possibly work without releasing the steam at the end. – Daron Mar 16 '22 at 16:57
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    Venting steam out into the atmosphere and topping up from an external water reservoir is pretty much the definition of an open cycle. – sphennings Mar 16 '22 at 16:57
  • So what is the atmosphere? Burning sulphur with oxygen produces sulphur dioxide, a poison gas. Is the sulphur burned? What is your heat source? – DWKraus Mar 16 '22 at 16:59
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    And wouldn't it be called a steamstack? – Daron Mar 16 '22 at 17:00
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    On a conventional 'steam engine' locomotive, what comes out the top stack is more the smoke from the combustion of the wood or coal. The steam from the cylinders is released down by the wheels themselves, directly out of the cylinders. The steam/water and the combustion chamber are completely separate. The smoke stack depends on how you produce the heat. Electrical heaters do not use combustion. – Justin Thyme the Second Mar 16 '22 at 17:08
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    The reason why these steam engines used an open cycle system is that the steam could not be cooled fast enough to be functionally re-used. – Justin Thyme the Second Mar 16 '22 at 17:14
  • @JustinThymetheSecond I wasn’t sure about that, or sure it was always done that way. Yes now the stack seems to relate to a heat source, which isn’t decided yet. There is no oxygen (because no plants), and no one will be breathing anything from outside. – Vogon Poet Mar 16 '22 at 18:31
  • @Daron your electricity comes from a closed rankine cycle steam engine today, it’s the most common application. – Vogon Poet Mar 16 '22 at 19:20
  • @VogonPoet Nope it comes out of this silly hole in the wall called a plug socket. – Daron Mar 16 '22 at 19:24
  • @Daron that’s weird? – Vogon Poet Mar 16 '22 at 19:27
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    Only part of the steam from a terrestrial steam engine is vented near the pistons, and that's largely accidental. Most is vented into the stack to create a draft to improve the combustion of the coal. – Monty Wild Mar 16 '22 at 20:47
  • Do consider the ambient temperature. The steam cycle works because the steam is at a considerably higher temperature than the water it is made from, which is at ambient temperature. As such, it is thermodynamically feasible for it to transmit energy to its surroundings, namely the pistons. In Hell, given the normal tourist information available, the situation may be considerably different--perhaps a system designed on cooling heat absorbed from the surroundings, i.e., a heat pump, would be more effective, though you'd still have a problem with waste heat; so possibly load up with bags of ice? – nzaman Mar 17 '22 at 03:14
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    @JustinThymetheSecond : some of the steam is intentionally directed towards the smokestack in order to create more air draft. Smoke isn't just pouring out slowly when more power is needed, but blown out with considerable force. Of course, when there is enough pressure for the current power need, then it can be closed to conserve steam, and then smoke is indeed just slowly pouring out. – vsz Mar 17 '22 at 05:09
  • @nzaman The train is condenser driven by endothermic cooling, per the linked question. That cycle wouldn't involve a smokestack, so it wan't put in. But boiling sulphur is something new I was directed to because of this near boiling point. No heat source was originally designed, and maybe I can just run at a vacuum instead. It was water steam until... well, brimstone? You just can't say no to that. – Vogon Poet Mar 17 '22 at 05:23
  • @ Monty Wild And your point? No smoke, no need for the steam to go out the stack. Most of what cones out of the smoke stack is smoke, not steam. The heat from the steam is what goes out the smoke stack along with the heat from the combustion. You can tell if it is an oil fired burner or a wood fired burner by the color - white or back - of the smoke. – Justin Thyme the Second Mar 18 '22 at 03:55
  • I think the people waiting on a platform were also considered when deciding where to blow out hot anything. It had always been my assumption that most everything just went up rather then blowing over anything they pass—horses at crossroads, cattle, platforms, etc. – Vogon Poet Mar 18 '22 at 04:45

6 Answers6

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Yes!

Because it is art! It is a locomotive. It needs a smokestack. And it needs condenser coils coming down from the smoke stack like a moonshine still. The coils will be copper stained blue from the copper sulfate.

Willk
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@MontyWild's right, but let's be more clear.

The smoke stack's primary purpose was to vent the exhaust from burning coal and/or wood.

From a basic point of view, it doesn't have anything to do with water (or sulfur, in your case). If you need a stack (aka, an exhaust pipe), then it's due to whatever you're using to change the temperature of the sulfur. If that doesn't cause an exhaust, then you don't need a smoke stack because the sulfur (a consequence of the valve actions around the pistons) could be either evicted to the side or simply sent back to what a traditional steam engine would call a boiler.

Monty's perspective is important for the same reason that modern 95%+ efficiency furnaces need an exhaust fan. After sucking so much heat out of the combustion to heat the water, the remaining heat wasn't enough to lift the exhaust. The heat from the expelled steam helped lift the exhaust out and away from the engine.

enter image description here
Image courtesy ThreeRiversRambler.com. See website for details of operation.

Why couldn't the exhaust simply have been shunted down to the tracks? Ignore wood for a moment and remember most trains were driven using coal. And coal ash is a big problem. Tossed down onto the tracks (like modern combustion engines drop it onto the road) would cause the ash to be stirred up, seriously degrading the passenger experience and potentially harming goods such as food and animals. In the early days of steam, train cars were not hermetically sealed by any stretch of the imagination (compared to modern passenger cars, they might as well have not had windows).

If you've never had the chance to ride an old steam engine, add it to your bucket list. Even with that big stack the ash is a problem. Having traveled on such trains a couple of times it's easy to realize why they want to push it as high into the air as possible.

TL;DR... So, do you need a stack?

No...

Frankly, you haven't given us enough information to answer that question. Steam isn't the primary reason (or the primary component) of what travels through a traditional steam engine's smoke stack. Therefore, talking about the sulfur is kinda irrelevant — unless you need to vent the sulfur for the same reason to vent coal ash, to not kill or damage what you're dragging behind the engine.

However, the smoke stack works because of rising heat. I haven't taken the time to read through all your posts, but originally you were looking for an endothermic process. If that's the case, no way on earth would you have a smoke stack.

In fact, what you'll likely need is an auger. Cooled sulfur is a solid. But that might be a false perception because I haven't followed your complete design.

JBH
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    Not at 420°C. Sulphur is a liquid at that temperature. – Monty Wild Mar 17 '22 at 01:21
  • Nitpick: It's not the heat of the waste steam that's used to lift the smoke out of the chimney, it's the momentum of the steam that's blown into the bottom of the chimney that mechanically sucks in the surrounding smoke and pushes it out of the top. It's the same effect that any gas appliance uses to mix the gas with the surrounding air before it enters the burner. – cmaster - reinstate monica Mar 17 '22 at 11:48
  • You are correct about the ash. I rode one steam pulled train and afterwards, my jacket was speckled with ash from the time when I was in the open rail car. The ash might be a good reason why most passenger rail cars were covered even the observation cars. – David R Mar 17 '22 at 14:23
  • @cmaster - reinstate monica I doubt that the steam would have a lot of mechanical energy left after pushing the piston and then expanding in the stack. It would be the heat and expanding gas being 'lighter than air' that causes the air to rise, just like in any fire tornado. – Justin Thyme the Second Mar 18 '22 at 04:03
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    @JustinThymetheSecond Well, your doubt is mistaken. Unfortunately, there is preciously little on the physics of the blastpipe in the wikipedia (https://en.wikipedia.org/wiki/Blastpipe). However, the article does mention that the blast pipe did create back pressure on the pistons (which was the aim of later developments to reduce). This back pressure is required to accelerate the exhaust steam upwards, so that it can suck the surrounding smoke with it. Also consider the speed at which the steam/smoke exits the chimney when the locomotive is working, that's not the result of buoyancy. – cmaster - reinstate monica Mar 18 '22 at 07:24
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    @ cmaster - reinstate monica The LAST thing you want is back pressure in a piston engine. Back pressure prevents the complete evacuation of the cylinder on the exhaust stroke. That is the bane of mufflers on cars - they reduce the efficiency of the piston engine by inhibiting the exhaust gas pressure from escaping the cylinder. The BEST outlet for a piston engine is 'discharge into a vacuum', so the exhaust gases are evacuated from the cylinder using the least amount of energy. All energy used in expelling the gases from the cylinder is energy lost to the mechanical output. – Justin Thyme the Second Mar 18 '22 at 14:48
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I think your train does need a smoke stack to vent the pressure of the expanding sulphur. This is the case even if you don't have a closed loop in the environment.

Water steam does need to be boiled with a heat source, which is what the coal is for.

However, sulphur burns. Not sulphuric acid but pure sulphur. So it can be both the heat source and also the gas which expands to run the engine. That would be like gasoline.

Burning sulphur does go into the atmosphere as sulphuric acid. It comes down in acid rain. (I'm talking about our earthly environment here.)

The only thing missing in the loop is returning the sulphur to a higher chemical potential for the energy to be released when burned in the train engine.

Marlin Pierce
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    That’s a logical argument, but the plant doesn’t have atmospheric oxygen to burn the sulfur (there are no plants in hell) So that would be another thing that they would have to carry. I didn’t put that in the question because I wasn’t really considering the heat source at this point. – Vogon Poet Mar 16 '22 at 18:02
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    You don't want to vent the pressure of expanding sulfur--that's what drives the engine! Venting it would be pointless--what you vent is depressurized gas, which has already expanded in a cylinder. – Logan R. Kearsley Mar 16 '22 at 21:58
  • The smoke stack would be for the exhaust of the spent sulfur. There might be venting when the pressure is too high as happens for steam engines. However the smoke stack is for exhaust. – Marlin Pierce Mar 17 '22 at 13:55
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It's going to depend upon your heat source.

If you're burning something in some sort of oxidiser, then your combustion products are probably going to be gaseous, and you'd want to vent them. That means having a smoke stack, as combustion products are rarely transparent. Carbon disulfide is commercially useful, but I don't know how you'd condense it in such a hot atmosphere.

If you burn hydrocarbons in sulphur (it's Hell... Sulphur would be common, wouldn't it?), you'll get carbon disulfide and hydrogen sulfide. Carbon disulfide is a neurotoxin, which would make the exhaust even more hellish... but people aren't going to be exposed to the outside air anyway, are they?

Of course, you could use an atomic reactor, and that wouldn't require a smoke stack, just heat sinks, but I'm not sure if the OP would want that.

Monty Wild
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  • H2S is also rather nasty - when you stop smelling it (without getting away from it) you're already poisoned – Chris H Mar 17 '22 at 15:08
  • @ChrisH You're assuming demons have the same oxygen-based body chemistry as us. :) With a different body chemistry, perhaps oxygen is actually toxic to them. Hence haemoglobin is a mild toxin for them with fun side-effects, on the same level as a shot of whiskey. Which explains why they want humans in the first place - we're small mobile distilleries! – Graham Mar 18 '22 at 10:13
  • @Graham I was only really following on from the toxicity of CS2 – Chris H Mar 18 '22 at 11:43
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    @ChrisH I know, but demons drinking our blood like fine wine seems like a suitably Hellish result. :) – Graham Mar 18 '22 at 14:28
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In a closed system you may instead be looking for a condenser and/or heat exchange system

In a normal train, as you mentioned the typical steam system is closed when the environment and rain cycle is included, refilling water reserves along the trip.

It would take more infrastructure to have liquid sulfur refill stations, than to have a locomotive which recycled it's resources rather than spew them out. It may have a smokestack look, but really it's a cooling tower/condenser, which may use another fluid to cool the surfer gas enough for reuse, even recycling that heat back into the system via heat exchange to concentrate and be used in reheating the liquid sulfur on the next cycle.

What that transnational fluid would be made of though, I have not the time to research.

Danger Lake
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I'll answer the question of where to vent the steam/gas. A smokestack seems illogical as the air would slowly contain more and more sulphur, which causes problems for a variety of reasons. A more logical solution would be to pump it out near to the wheels of the train. This would allow it to return to the ground more quickly, where it can be more easily collected (assuming this is a concern). This would also minimize the amount of gas falling on the rest of the train as sulphur, unlike steam, is heavier than air.

fallstorm05
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  • I haven’t figured out if the sulphur steam is heavier than the atmosphere here, but if it fell on the train it would condense to a liquid and bead off. There’s no water or oxygen so corrosion shouldn’t be a problem. – Vogon Poet Mar 16 '22 at 19:27
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    There could be waste sulfur collection troughs along the tracks – Atog Mar 16 '22 at 20:05
  • @Atog Yeah I have to figure out if it rises or falls as a fog. It will eventually precipitate either way at 420C. – Vogon Poet Mar 16 '22 at 21:45