less ▁steel , ▁glass - lined ▁steel , ▁glass ▁or ▁ex otic ▁al loy . ▁Li qu ids ▁and ▁sol ids ▁are ▁usually ▁charged ▁via ▁connections ▁in ▁the ▁top ▁cover ▁of ▁the ▁re actor . ▁ ▁V ap ors ▁and ▁g ases ▁also ▁dis charge ▁through ▁connections ▁in ▁the ▁top . ▁Li qu ids ▁are ▁usually ▁dis charg ed ▁out ▁of ▁the ▁bottom . ▁ ▁The ▁advantages ▁of ▁the ▁batch ▁re actor ▁lie ▁with ▁its ▁vers at ility . ▁A ▁single ▁vessel ▁can ▁carry ▁out ▁a ▁sequence ▁of ▁different ▁operations ▁without ▁the ▁need ▁to ▁break ▁contain ment . ▁This ▁is ▁particularly ▁useful ▁when ▁processing ▁to xic ▁or ▁highly ▁pot ent ▁comp ounds . ▁ ▁Ag itation ▁ ▁The ▁usual ▁ag it ator ▁arrangement ▁is ▁a ▁cent r ally ▁mounted ▁driv esh aft ▁with ▁an ▁overhead ▁drive ▁unit . ▁Imp eller ▁bl ades ▁are ▁mounted ▁on ▁the ▁sh aft . ▁A ▁wide ▁variety ▁of ▁bla de ▁designs ▁are ▁used ▁and ▁typically ▁the ▁bl ades ▁cover ▁about ▁two ▁third s ▁of ▁the ▁diameter ▁of ▁the ▁re actor . ▁Where ▁vis c ous ▁products ▁are ▁handled , ▁anchor ▁sh aped ▁p add les ▁are ▁often ▁used ▁which ▁have ▁a ▁close ▁clear ance ▁between ▁the ▁bla de ▁and ▁the ▁vessel ▁walls . ▁ ▁Most ▁batch ▁react ors ▁also ▁use ▁b aff les . ▁These ▁are ▁station ary ▁bl ades ▁which ▁break ▁up ▁flow ▁caused ▁by ▁the ▁rot ating ▁ag it ator . ▁These ▁may ▁be ▁fixed ▁to ▁the ▁vessel ▁cover ▁or ▁mounted ▁on ▁the ▁interior ▁of ▁the