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A Super Simple Sour Gas Boiler

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So in the course of my crusade to extract as much water out of my asteroid as humanly possible i looked into the many, many sour gas boiler designs floating round the forums and the internet, and yet very little of it struck me as practical. Most designs have some special feature focus such as trying to make the system (up to natural gas output, usually ignoring pumps and always ignoring natural gas generators) as compact as possible, or making use of fancy tricks and clever exploits to the point of obscure and inexplicable build contortions and small easily-missed hidden items that the entire build will explode without.

I did not want any of that. And so, i took all of these designs, both crude and refined, and i boiled them down to the simplest most straightforward sour gas cooker i could condense. The natural output was a nice, self-contained little hotbox that pumps in one oil well worth of crude (i.e. 3333g/s), and churns out around 1650g/s of water and 18kW of constant power, along with the less desirable trace amounts of dirt, 555g/s of CO₂, and 1111g/s of sulphur. Of the output water, 1kg/s will usually be sent back to the oil well, leaving 650g/s net.


As simple and straightforward as this is, some pieces will be non-obvious to those not already familiar with sour gas boiler design, and so i will annotate the pieces and then go over them clearly one by one.


Stage 1: Oil Boiler

Crude oil is input at (1). Input oil temperature is not greatly important, and will here be assumed to be 95°C. This oil comes out of the vent as drips (magical items not yet part of the physical world), which are forced to turn into beads (physical tiles of liquid that can be seen in the materials overlay) by the mesh floor at (2). Oil beads travel past the heat exchanger at (3) before being boiled into 550°C sour gas on the diamond heat plate (4). This sour gas then rises, exchanging heat with the falling oil and arriving at (8) at around 150°C.

This combined system can be referred to as a bead pump heat exchanger. The thermal interface medium (3) consists of automation ribbon, radiant liquid pipes, and radiant gas pipes. The materials are not greatly important, but the higher the thermal conductivity, the better. Here i used steel for the radiant gas pipes, and copper for the automation ribbon and radiant liquid pipes. This is an effective combination which uses minimal material. The falling oil beads will actively pump sour gas out of this section, creating a high pressure area at (8).

Stage 2: Sour Gas Condenser

The airlock doors at (8) are player-operated, and can be used to clear natural gas if it forms in the condenser. This does not happen under normal operation, but can be caused by player interference, impatience during startup, or build mistakes. Under normal operation about 100kg per tile of sour gas will accumulate here, flowing slowly down the heat exchanger (9) before being directly condensed into ⅔ liquid methane and ⅓ sulphur by radiant pipes at (10). Sulphur is picked up by the auto sweeper and passed back up the heat exchanger column (9). Liquid methane is pumped to the other side of the heat exchanger where it immediately boils into natural gas at (11). This natural gas rises exchanging heat via (9) until it reaches the pumping area (12).

The heat exchanger here uses conveyor bridges to share heat between incoming sour gas and outgoing natural gas. Diamond window tiles separated by insulated tiles assist heat conduction horizontally while impeding it vertically. The material of the conveyor bridges is not greatly important and even copper ore will work, but here i used steel for generally good thermal conduction.

Both heat exchangers (3) and (9) could be made much shorter with the addition of more thermal exchange media and the use of more highly conductive materials, but this form factor fits well, is easy to construct and explain, looks good, and is mostly clear at a glance.

Stage 3: Power and Output

Natural gas is pumped by steel pumps at (12) to the 25 natural gas generators in the main steam room (13). It is not strictly necessary to have these all in a big steam room. But it is both simple and effective, and so i consider it 20t of steel well spent. Average generator use is about 24.7 out of 25, giving 19.75kW of gross power and creating around 1666g/s polluted water which is allowed to fall into the steam room. Heat from the generators will eventually rise to a point where this water is boiled immediately, turning into 99% steam and 1% dirt. The dirt is collected by auto-sweepers and shipped out. The steam is processed by two mostly-self-cooled steam turbines (14) before either being recycled to maintain steam pressure at around 10kg/tile, or sent directly out. Of this 1650g/s of eventual water, 1kg/s can be sent back to cover the operation of the input oil well, leaving 650g/s net water gain.

Heating and Cooling

Both heating and cooling are provided by a thermium aquatuner at (5). Supercoolant is used for the coolant loop. Aquatuner uptime should be stable at around 40%. If the coolant gets too cold (-182°C which will freeze methane), it is heated by the supercoolant-immersed tepidizer at (6). If the aquatuner chamber gets too hot (630°C or so) heat is dumped into the main steam chamber via the thermal interface plates at (7). The aquatuner is enabled both to ensure the coolant stays cold enough to condense sour gas into methane (-168°C), and the boiling plate is producing sour gas (550°C). With both of the safety features (6) and (7), there is very little that can go wrong. In practical usage the tepidizer (6) is only used when initializing, and for normal operation only the heat dump (7) is occasionally used.

Two self-cooled steam turbines is not quite enough to handle the heat output of 25 natural gas generators along with the occsional dumped heat from the aquatuner, so the briefly-mentioned sulphur from sour gas condensation is passed through the turbine chamber before being ejected. During stable operation this raises the sulphur from around -70°C at the top of (9) to a nice tepid 25-30°C at output. The two self-cooled turbines could be replaced by one turbine and one steel aquatuner, but it looks neater this way and if you are playing Spaced Out that sulphur will be easier to use at room temperature.


An auxiliary power source will be needed to run the aquatuner during initialization. This can be plugged straight into the main natural gas generator grid.

Option 1:

Before use, the walls of the condenser should first be cooled so as to avoid flaking liquid methane into natural gas. This is the reason for the very important radiant pipe segments inside the insulated walls at the lowest level of the condenser. This will dump a lot of heat into the main steam chamber, which should either be primed with steam, or have a temporary heat dump of some sort touching the thermal interface plate.

Once the condenser is cooled, some oil should be allowed in to boil. Once it boils into sour gas, normal operation can immediately commence.

Option 2:

For the lazy and impatient, the condenser can be cooled and the oil can be boiled at the same time. A hydrosensor at (4) blocks oil input when 200kg of oil is waiting to boil. An atmo sensor in (10) blocks the oil input when 10 kg/tile of sour gas is waiting to condense. This will create more excess cooling than heat, and thus minimal heat will be dumped into the main steam chamber. As such you can just straight up start shoving oil into the thing from cold and it should eventually work. But it may produce a lot of natural gas inside the condenser while starting up, and some may need to be crushed using the door crusher at (8) if it refuses to clear once the condenser cools enough to start recondensing it.

Failure Cases

There's not actually much that can go wrong. If the input oil is interrupted (which it will be as oil wells need pressure relieved) the large mass of sour gas will simply condense more and more slowly as pressure decreases. It can go up to a cycle with no input before power generation drops to a point where it needs to be jump started.

If it is stalled for longer, power generation may cease thus causing the aquatuner to stall. Simply add power to restart it.

During initizlization sulphur may melt as it travels up the heat exchanger (9). This is not a huge problem as it simply falls back down into the condenser. It may boil some methane and produce natural gas, which can either be crushed at (8) or avoided by disabling the conveyor loader until operation is stable.

If a gas lighter than steam is caught in the steam chamber, it can interfere with the pressure sensor, causing steam to build up forever. Well... just don't let this happen. If the possibility worries you, you can add a gas element sensor next to it and attach it to an alarm for if it ever fails to say "steam". It's also possible to put the atmo sensor near the bottom of the steam chamber where there is some free space.

Hidden tricks

I don't think i used any but let me know if something isn't obvious. I did put one tempshift plate in the main steam chamber touching the thermal interface plate (7). This was useful to spread heat during testing, but may be irrelevant during normal operation.

The vent in the steam chamber drips onto a heavi-watt plate. This is useful to keep the lower half of the chamber nice and hot for boiling the polluted water which all drips down there. An alternative could be to drip it next to the thermal interface plate to help that stay cool. The whole row of insulated tiles under the gas pumps is just space-filler, so the vent can go anywhere there.


Full overlays follow in spoilers.




  • Nat gas pump atmo sensor (12): enables pumps only if pressure is over 3kg
  • Door crusher switch (8): manually controlled
  • Input oil vent (1): closed if over 200kg of liquid on the boiling plate (4) or over 10kg of gas in the condenser chamber (10).
  • condenser pump (10): enabled when liquid methane is over 10kg/tile
  • aquatuner (5): enabled if boiler temperature below 820K (547°C) or coolant temperature above 105K (-168°C)
  • aquatuner heat dump (7): enabled if aquatuner chamber above 900K (627°C)
  • coolant heater (6): enabled if coolant below 90K (-183°C)
  • steam recycling vent (top of 13): open if steam pressure is less than 10kg
  • the automation ribbon (3) is used exclusively for heat transfer, not automation




The transformers at the bottom of the chamber feed three internal circuits. One for the tepidizer, one for the aquatuner and condenser, and one for the pumps and declogger. As the pumps are running most of the time, they are supplemented by the steam turbine output, which will be about 700W under stable operation.




  • A supercoolant loop (note the radiant pipes inside two insulated walls, these must be cooled) runs from bottom to top of the condenser.
  • Water from steam turbines self-cools a little, then is either recycled to maintain steam chamber pressure or ejected.
  • The radiant pipe at (3) is used solely for heat exchange.




Sulphur gets sent up the heat exchange column (9), then further used to help cool the steam turbines (14). Dirt is just sent out. Conveyor bridges are solely for heat exchange.




Natural gas goes to natural gas generators. CO₂ goes out. The radiant gas pipe at (3) is used for heat exchange.



"But what if i don't have thermium and supercoolant???", you ask?

Well the easy answer there is that you should go and get some. But i did actually manage to make a pre-space version using a magma spike for boiling the oil and liquid methane inside a two-aquatuner coolant loop for condensing the sour gas. I needed to prime it using 10% water packets to condense the initial 500kg of liquid methane. Flush the 10% water, replace with the methane, et voilà, liquid-methane-condensed liquid methane. Maybe i'll polish it later and do a writeup. And on my second try, i only broke two pipes!


In conclusion, while this isn't the most compact, the most efficient, the highest volume, the most material-lean, etc etc etc, this is a very simple and straightforward boiler. I hope it helps explain the concepts to some who maybe haven't tried to make one of these or were driven off by the complexity of other designs. It nicely creates a closed system with a single oil well, and all you need are the materials to make it and some patience to deal with putting it all together and fixing what few small problems can crop up. Let me know if you have anything to add, or know of some other good simple designs!

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very nice design, especially nice idea to chill steam turbines with sulfur. But,

1. I can't believe natural gas is not going top, for sure it could be fixed with door pump and automation, but anyway

2. I can't understand why people immerse tepidizer into super coolant, you can achieve same effect with water or petroleum or any other liquid. Just lay pipes inside of doors, and make this doors "touch" liquid.

3. Are conveyor range long enough to get all chill back from sulfur? Most probably you throw it outside with -100C.



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19 minutes ago, degr said:

1. I can't believe natural gas is not going top, for sure it could be fixed with door pump and automation, but anyway

Up top where? It sometimes can form in the condenser during startup, but it just floats to the little notch in the top left and then doesn't get in the way after that. If it's ever a problem, the doors there can be used to crush it. During normal operation it never forms.

21 minutes ago, degr said:

2. I can't understand why people immerse tepidizer into super coolant, you can achieve same effect with water or petroleum or any other liquid. Just lay pipes inside of doors, and make this doors "touch" liquid.

In this case it's just because the coolant needs to be kept above -180°, so the pool is being heated to -180°. A different solution could be used to save the supercoolant sure, but as it's already using supercoolant for the cooling loop i didn't worry about it.

26 minutes ago, degr said:

3. Are conveyor range long enough to get all chill back from sulfur? Most probably you throw it outside with -100C.

Nowhere near it :grin:. It could be improved to exchange more heat there, but would have to have some kind of loop. Indeed it outputs between -100 and -70°C if not being used to cool the steam turbines. But after cooling turbines it outputs between 0 and 30°C.

It could be made more efficient by cycling the cold sulfur until it warms more, like how ghkbrew did it here. But i like outputing at near room temperature for potential use in Spaced Out.

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Very well engineered. And very well written. I also like the methane loop version a lot.

One thing I'd explore is getting rid of the tepidizer. I thought of that while designing a petroleum boiler. Do I have anything hot around here? Yes, the outgoing petroleum. It's a bit tricky (petroleum might freeze) but if you're not too aggressive with radiant pipes (and never let the petroleum flow come to a halt of course), it's totally doable.

In your case, you could use the nat gas to dump a little heat into the cool box where the tepidizer is now.  But also, you have a steam room close by. Just as you occasionally dump heat into it from the AT, you could drain some to keep the supercoolant from getting too cold. Conceptually there isn't much difference, heat in the steam chamber comes mostly from the nat gas anyway.
Also, it doesn't buy you anything. The tepidizer is super convenient, and the power cost is minimal. It's one of those things you do just because you can. And it removes an unnecessary buiding. The hard part is to get the right amount of radiant pipe, even one segment might be enough, or even a regular granite pipe.

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15 hours ago, TheMule said:

One thing I'd explore is getting rid of the tepidizer.

Yeah the tepidizer could definitely be removed/replaced with some more clever tricks. It's not quite so simple as dumping cold into the steam room or nat gas, as the tepidizer is almost exclusively used when boiling the initial oil when there's nothing in the condenser. At that point there's also probably no steam in the steam room, but perhaps some initial water could soak up enough of the cold to work.

It's a little dangerous to be playing around with the coolant temperature, as there's only 20°C of leeway for condensing methane without freezing it. So the tepidizer is sort of the safe choice requiring no extra thought. The tepidizer bath also provides a significant thermal buffer, keeping the coolant temperature stable.

But i kind of like that there's room to improve the design in a lot of little ways :). Judging by other designs, it should be possible to get the aquatuner usage down to less than 33% just by improving the efficiency of the various components individually. Removing the tepidizer would mean the heat exchangers could be longer, improving efficiency.

I'm not even 100% sure the tepidizer is necessary for this design at all. Freezing the methane at startup should recover over time. But as a base for other designs, or showing others how this sort of thing works, it's pretty foolproof.

16 hours ago, TheMule said:

I also like the methane loop version a lot.

Yeah i was impressed with how well it worked when i tried it. I was planning on doing a version without the big steam chamber, so the nat gas gens can be made of something other than steel. I think steel usage could be reasonably minimized to just the aquatuners and gas pumps, so under 5t. I haven't gotten around to it yet though, and already have supercoolant and thermium in my current game, so i'm not sure if i will. It would also need a dedicated boiler for the p-water, or some other filtration system.

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This is probably one of the best designs for one new to Sour Gas Boilers.  It's a simple and elegant approach to it.

It's also awesome that it is imperfect so others can still improve on the design in multiple ways, but these changes aren't necessary to make it function, just make it more efficient.  This is kind of neat because players will try building this because they can improve on it.

I try to make my own builds too perfect perhaps.

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