====GeneralThe considerationsDTB on crystallizersCrystallizer====
[[Image:DTB_Xls.png|frame|left|DTB Crystallizer]]
Whichever the form of the crystallizer, to achieve an effective process control it is important to control the retention time and the crystal mass, to obtain the optimum conditions in term of crystal specific surface and the fastest possible growth.. CiòThis siis ottieneachieved realizzandoby unaa zonaseparation di- separazioneto deiput cristalliit dallasimply massa- liquidathe crystals from the liquid mass, solitamentein perorder to manage the two flows in a different way. The practical way is to perform a gravity [[sedimentazionesettling]] naturale.to Inbe genereable ito cristalliextract vengono(and riciclatipossibly nellarecycle massaseparately) the (almost) clear liquidaliquid, mentrewhile lamanaging soluzionethe chiarificatamass (edflow esausta)around vienethe estratta.crystallizer Unto casoobtain tipicoa diprecise applicazioneslurry èdensity ilelsewhere. cristallizzatoreA tipotypical example is the DTB (''Draft Tube and Baffle'') crystallizer, ideatoan daidea of Richard Chisum Bennett allaat the fineend degliof annithe '5050s. (sirumors narrasay anzithe chename ilderives nomefrom derivithe dainitial quelloof dell'inventore,the dettoinventor - Dick Bennett, manessuno- habut maimistery trovatostill lasurrounds ragionethe dellaletter T). NelThe DTB crystallizer (vedisee figuraimages) lahas circolazionean èinternal assicuratacirculator, datypically unan elicaaxial flow mixer - yellow - pushing upwards in a flussodraft assialetubewhile outside the crystallizer there ia a settling area (in giallo)an intubataannulus; chein spingeit versothe l'altoexhaust solution moves upwards at a very low velocity, mentreso all'esternothat dellarge cristallizzatorecrystals verosettle e- proprioand vireturn èto unathe coronamain circolarecirculation in- cuiwhile laonly soluzionethe esaustafines, risalebelow a bassagiven velocità[[granulometry]] are extracted and eventually destroyed by increasing or decreasing temperature, consentendothus lacreating sedimentazioneadditional deisupersaturation. cristalliA quasi-perfect control of all parameters is achieved. This crystallizer, cheand vengonothe risucchiatiderivate dalmodels flusso(Krystal, CSC, discendenteetc.) Sicould ottienebe cosìthe unultimate controllosolution quasiif not for a major limitation in the evaporative capacity, due to the limited diametre of the vapour head and the relatively low external circulation not allowing large amounts of perfettoenergy dito tuttibe isupplied parametrito dellathe cristallizzazionesystem.
