Abstract: The air cooling of exothermic reaction vessels is improved by providing a cooling air recirculation loop wherein substantial amounts of the cooling air are recycled through the system with but a small fraction thereof being discharged to ambient, and after the condensable/soluble off-gases are depleted therefrom and with addition thereto of but minor amounts of additional feed air. Such technique is well suited for controlling the temperature of the digestion of phosphate rock with sulfuric acid, in the known wet-process for the production of phosphoric acid.

Abstract: Liquid/solids feed to be filtered is uniformly distributed over a filter surface by (i) initially, continuously introducing said liquid/solids feed into the feeder compartment of a compartmentalized, partitioned feed-distribution box, said feeder compartment having a volume such that no decantation results, (ii) continuing such feed as to effect an overflow of feed from said feeder compartment into a second, distribution compartment, over a partition or common wall member therebetween, via a plurality of outlet openings shaped into the top of said partition along the length thereof and being sufficiently few in number such that the rate of flow of the liquid/solids stream flowing through each opening is high, and (iii) thence uniformly cascading the entire flow of liquid/solids stream to be filtered onto suitable filter surface, advantageously after a change in the downward direction thereof.