Why not several pressuried exits, that then could cool or be heated to the next stage for the chemical mixing? I'm just seat of my pants guessing about all of this. I'm no engineer and only made it through 400 level chemistry college classes. I never went on to seek masters or further in it. Seems a combo of endothermic and exothermic mixing chambers would help to solve many of the problems. Then if you are not mixing the big batches this could all be scaled down to a smaller operation. Again pure speculation.