A few days ago, I started a new playthrough of Factorio with nine planet mods installed: Corrundum, Muluna, Secretas&Frozeta, Cerys, Igrys, Maraxsis, Moshine, Muluna, and Paracelsin. I also installed Mineral Chemistry, as it is a recommended dependency of Corrundum. I installed no other mods (other than the required dependencies of these mods, of course). The only changes I made to the mod setup settings were to turn on Mineral Chemistry's options, except "Jump start initial research to chemical science". I turned on the Mineral Chemistry settings so that Nauvis would be more interesting, but also because this seems to be your recommended way of playing the mod.

I'm at a point now where I'm producing red and green science packs, and I've just researched "Expert Mineral Processing", "Advanced Pressure Oxidation", "Blasting and Charcolation", "Froth Floatation and Soaponification", and "Fluorination and Pressure Washing". These appear to unlock all of the recipes for disposing of slag that are available before leaving Nauvis. So I decided to try to figure out how to dispose of slag.

It looks like the main recipe for destroying slag is "Slag destruction", which requires hydrofluoric acid. The alternate recipes also consume hydrofluoric acid. There's just one recipe for making hydrofluoric acid, and it produces the waste product calcium sulfate. At this point in the game, there is only one recipe that consumes calcium sulfate, the recipe "Calcium sulfate destruction", which produces the waste product sulfur dioxide. The only recipe available that consumes sulfur dioxide is "sulfur reduction", which requires hydrogen sulfide. The only recipe for making hydrogen sulfide requires the Catalytic Chemical Plant, which can't be built before visiting Corrundum.

So it looks like, no matter what I do, I'll end up with a waste product that I can't automatically destroy: either slag, calcium sulfate, or sulfur dioxide.

Is my analysis correct?

Hmmm. You're partially correct. I should adjust this. Thank you for the feedback.

Calcium sulfate should be able to be destroyed in the dangerous cryogenic plant. Slag too. Sulfur dioxide is awkward and I should add a vent recipe.

I just want to comment that I'm running into the same issue, both with and without Corrundum installed. I'd like to be able to void slag in an automated way before going off of Nauvis, ideally without causing explosions.

Without Corrundum installed:

• I can use Hydrofluoric acid to delete slag. The only other recipes that consume slag aren't possible. First, there is the Slag recycling recipe, but I cannot produce any machine to do this (they are locked behind other planets - either Cerys, Fulgora, or Secretas). I can technically do this recipe by hand but that's not automatable. Second, there are the Fluoro slag destruction and Dangerous fluoro slag destruction recipes, both of which require Fluorine, which has a chance of causing an explosion when created from Hydrofluoric acid.
• To produce Hyrofluoric acid, I require fluorite and sulfuric acid (both fine), and produce both calcium sulfate and Hydrofluoric acid.
• To get rid of the Calcium sulfate, I can use the Calcium Sulfate destruction recipe, which takes solid fuel and calcium sulfate, but produces sulfur dioxide. No other recipe that uses Calcium sulfate is available on Nauvis.
• To get rid of the sulfur dioxide, I have several options. First, there are voiding recipes (options appear on Maraxis (hydro plant), Linox (outlet), and Cerys (flare stack)), but all require going off of Nauvis. Second, there is a recipe for calcium sulfate creation, but this both causes a loop and also requires fresh calcite as an ingredient (and also actually increases the amount of calcium sulfate). Third, there is what I believe is the intended path of using the Sulfur Destruction recipe, but this requires Hydrogen sulfide, which has no recipe to create it (only to unbarrel it, and the hydrogen sulfide barrel can only be created by filling the barrel in the first place).
• So without Corrundum installed, I cannot progress in deleting slag unless I'm willing to allow explosions, due to the lack of a hydrogen sulfide creation recipe, or any other use for sulfur dioxide.

With Corrundum installed:

• I can use Hydrofluoric acid to delete slag. The only other recipes that consume slag aren't possible. First, there is the Slag recycling recipe, but I cannot produce any machine to do this (they are locked behind other planets - either Cerys, Fulgora, or Secretas). I can technically do this recipe by hand but that's not automatable. Second, there are the Fluoro slag destruction and Dangerous fluoro slag destruction recipes, both of which require Fluorine, which has a chance of causing an explosion when created from Hydrofluoric acid. (Same as without Corrundum)
• To produce Hyrofluoric acid, I require fluorite and sulfuric acid (both fine), and produce both calcium sulfate and Hydrofluoric acid. (Same as without Corrundum)
• To get rid of the Calcium sulfate, I can use the Calcium Sulfate destruction recipe, which takes solid fuel and calcium sulfate, but produces sulfur dioxide. No other recipe that uses Calcium sulfate is available on Nauvis. (Same as without Corrundum)
• To use Sulfur dioxide, things are different with Corrundum. First, there are the same voiding recipes, but those are locked behind other planets (Maraxis (hydro plant), Linox (outlet), or Cerys (flare stack)). Second, there are two recipes for sulfonated plastic, but both are locked behind Corrundum and its Sulfonated plastic technology. Third, there is the calcium sulfate production recipe, but that requires calcite (and also actually increases the amount of calcium sulfate). Fourth, there's a Sulfurous oxidation recipe from Corrundum's Sulfur Redox 2 technology that creates sulfuric acid, but that's locked behind Corrundum. Fifth and finally, there's a Sulfur reduction recipe (unlocked by both Corrundum and by Mineral Chemistry's Advanced pressure oxidation technology) that takes sulfur dioxide and hydrogen sulfide and creates sulfur and water. The problem with this fifth option is that creating Hydrogen sulfide requires Sulfur Redox 1 technology, from Corrundum.
• So with Corrundum installed, I cannot progress in deleting slag unless I'm willing to allow explosions, due to the lack of a Nauvian hydrogen sulfide creation recipe, or any other use for sulfur dioxide.

If the intent is to force us to use the dangerous plant with its explosion recipes, that's fine, I understand. However, the sheer cost of the dangerous cryogenic plant (seven ingredients including processing units, batteries, and electric engine units) prevents me from seeing "allow explosions and rebuild the machine if it explodes" as a viable option for me personally.

For now in this playthrough, I'll just stockpile calcium sulfate, as this is 10x denser than storing slag (300 Hydrofluoric acid makes 3 calcium sulfate, but can delete 30 slag, with identical stack sizes). Then eventually I can send calcium sulfate to space and throw it overboard (each rocket represents 10,000 slag deleted, which isn't a horrible cost). My suggestion for fixing this deadlock on Nauvis itself (feel free to ignore this suggestion) would be:

• With Corrundum present, unlock the hydrogen sulfide recipe with this mod's Fulorination and pressure washing technology. Allow it to be made in the dangerous cryogenic plant.
• Without Corrundum present, either provide a hydrogen sulfide recipe or allow venting of sulfur dioxide.

As an unrelated side note, since the dangerous cryogenic plant requires lubricant and sulfuric acid in its production chain, it would make sense to me if the "fluorination and pressure washing" technology was moved behind chemical science (or possibly advanced oil processing), to help hint to the player that this building is not available until starting chemical science (and thus they should find a temporary solution for slag).