Pyroflux dousing should use raw vulcanite ore, not the processed one (in the box). The reason is it blocks Core Mining on original planet. In standard Space Exploration Core Mining was producing fluid vulcanite that could be used for pyroflux dousing. Now it gives vulcanite ore, and there is no way to use it anyhow till much later!

I'm still on blue/black science, working on orange right now (I'm playing on Rampant but without it's Arsenal submod so it's pretty tough to advance) and I'm core mining for quite long already, it was essential due to how difficult solo Rampant expansion can be. I was always using pyroflux dousing to keep the Drill working, right now I realised that achieving meaningful progress on solo Rampant SE is gonna take half of my lifetime, I added your mod, but my crushers started to produce ore instead of red liquid! Processing vulcanite is hidden behind 2 more science tiers, orange and first space. So loong time still for me to get it, and I already have 6 biggest AAI warehouses full of raw vulcanite and it's still going. Also there was only a little bit of pyroflux generated from crushers, there is much more raw ore, maybe too much.

tl;dr Please make pyroflud dousing use raw vulcanite ore instead of processed vulcanite cause it's unusable for very long time and blocks core mining on original planet.

For those who encountered this problem while Core Mining on Nauvis you can make my proposed fix yourself until mod author decides how to go about it. I think my way is reasonable as it's a minimal change and producing mass amounts of unusable resource that you have to store in order to keep Core Drill working is not the Factorio way.

In \AppData\Roaming\Factorio\mods find a mod seoh_0.3.5.zip (for current version), open it, and edit /prototypes/phase-1/resources.lua file.
In line 59, change "se-vulcanite-block" to "se-vulcanite". You also need to change the value from 1 to much higher, as the recipe uses 2k water for 2 vulcanite. I believe somewhere between 5 and 20 will be the best but I will test it out.

So change:
data_util.change_ingredients("se-pyroflux-steam", {"se-pyroflux"}, {{"se-vulcanite-block", 1}})
to:
data_util.change_ingredients("se-pyroflux-steam", {"se-pyroflux"}, {{"se-vulcanite", 5}})

Hope it helps someone who is starting new game with the mod, as it helped me.

Good value for vulcanite ore use per 2k water seems to be about 2-5. I overestimated at first due to my huge vulcanite storage.

Hi Podtxt,
Sorry for the late reply.
I've been meaning to check the balancing on this. Thanks for finding a fix for me. I'll go ahead and apply it in the next update.

Thanks, I'm glad I could help. Great mod for solo SE.