We have been really enjoying the mod and would like to be able to start from scratch on Corrundum,
but there seems to be no automated way to make iron without productivity modules.

Chalcopyrite -> Mixed sulphate
100 Mixed sulphate + 1 iron plate -> 1 copper ore + 100 iron sulphate
100 iron sulphate + 1 iron plate -> 2 iron ore

So this process turns 2 iron plates into 2 iron ore (plus copper): no extra iron is produced.
The "mixed sulphate" contains iron: so where does this iron go?

Without productivity modules, the loop is iron-neutral.

You're right. I should update the recipe. Mixed sulphate should have more iron as it already contains iron. One moment please...

Funny how minds converge. I was briefly play testing some set ups so I could get some screenshots for the image gallery. And then I realized it was impossible to get iron in the early game or Corrundum only starts. I had originally locked the planet behind Vulcanus, and envisioned using the 50% productivity bonus from the foundry to aid in Chalcopyrite processing. But I moved the planet to no longer require Vulcanus.

No productivity bonus from many recipes to balance around recrystalization recipes and foundry. You can efficiently recycle parts to get sulfate solutions, and then use quality modules to get better ores. Notably, you can use productivity on the ores in the furnace to get more plates.

Now it is 200 Mixed Sulphate, 1 iron plate -> 2 copper ore + 200 Iron sulphate. This should reduce the pressure on iron.

Great minds think alike: that was the same idea I had, but I also changed the iron sulphate processing to 200 iron sulphate + 1 iron plate -> 4 iron ore. So that the total cycle gives 4 iron ore and 2 copper ore from 2 iron plates.

I want to keep 100 Copper sulfate solution to 1 Copper ore, and 100 Iron Sulfate to 1 Iron Ore ratios. But 200 Iron sulfate + 1 iron plate --> 3 iron ore is reasonable. That will likely the next change, but I want to finish a bit more play testing before I throw out another patch. I felt fixing that one recipe was worth its own hotfix because gameplay is important.

For example, I want another Sulfuric acid concentration recipe that works faster but doesn't give you steam.

I also think you don't get enough CO2 fast enough from petrol, but it isn't a big deal as that is just initial power. But it could be an issue for ice-boxes. Forgot which setting I have to tweak and I'll have to look back at the documentation. There are a bunch of steps to even get sulfuric acid, and you are power constrained at the start. More CO2 production could help with this. Gleba does give a heating tower, which is easy to power with water.

And I need to test the current iteration of the platinum thruster.

Also want to stress test the new lab.

Hope you've been enjoying this planet.

We are having a great time with the planet! :-)

Something else I noticed was that the steam from dilute sulphuric acid is only 15 degrees C: not hot enough for power.
How can water form steam at only 15C when the atmospheric pressure is so high? :-/

Dilute sulphuric acid seems to need a huge number of chemical plants to get rid of
Thermoelectric engines seem to need a huge number of red boilers to get any amount of power.

We managed to make red and green science and research sulphonated plastic :-)
We have 478 red boilers and 90 chemical plants to supply one red and two green science assemblers.

I'll have to update the recipes. Not sure why red boilers are so inefficient. Might be that 0.2 number. I'll further nerf the time requirements for sulfuric acid concentration. The catalytic chem plant does have double speed, so I would suggest using that.

I'll look into the steam from dilute sulfuric acid. Probably forgot a temperature modifier. Patch will come soon. Thanks for the input.

The catalytic chem plant does have double speed, so I would suggest using that.

They are all catalytic chem plants! :-)

Can't see the image. But I did add recipes to address red-boiler speed, and dilute sulfuric acid build up. You can now neutralize dilute sulfuric acid to 100C water. Should make it much easier to manage.