Effect of impeller type and baffle presence on ion exchange in batch reactor : diploma thesis

U ovom radu istraživan je utjecaj tipa miješala i prisutnosti razbijala virova na ionsku izmjenu bakra na zeolitu NaX u kotlastom reaktoru. Eksperimenti su provedeni pojedinačno u kotlastom reaktoru s i bez razbijala virova korištenjem tri tipa miješala: turbinsko miješalo s ravnim lopaticama (SBT), turbinsko miješalo s lopaticama nagnutim pod kutom od 45° (PBT) i turbinsko miješalo s diskom i ravnim lopaticama (Rushtonova turbina, RT) s ciljem dobivanja uvida u utjecaj geometrije na hidrodinamiku sustava, a time i na proces ionske izmjene. Ispitivanje je provedeno s česticama zeolita veličine od 40 do 50 µm i otopine bakrova(II) nitrata početne koncentracije 7·10 -3 mol L -1 . Za svaku geometrijsku konfiguraciju reaktora i miješala određena je minimalna brzina vrtnje miješala (N JS ) pri kojoj se postiže stanje potpune suspenzije temeljem Zwieteringovog kriterija "1s", kao i utrošak snage miješala (P JS ) . Dobiveni rezultati parametara miješanja pokazali su veće vrijednosti prilikom korištenja razbijala virova. Izučavanjem kinetike ionske izmjene pokazalo se da tijekom prvog perioda procesa, količina izmijenjenog bakra naglo raste, nakon čega nagli rast prelazi u postepeni sve do postizanja ravnotežnog stanja. Provedena je i kinetička analiza eksperimentalnih podataka nelinearnom i linearnom regresijom korištenjem Ritchievog i Weber-Morrisovog modela kako bi se utvrdilo koji od procesa kontrolira kinetiku izmjene. Ritchiev model je pokazao najbolje slaganje s eksperimentalnim podacima i time je utvrđeno da ukupnu brzinu kemijske reakcije kontrolira proces ionske izmjene. Osim toga, proces ionske izmjene je brži u reaktoru s razbijalima virova za svaki tip miješala.In the present paper the influence of the impeller type, as well as the presence of baffles on the ion exchange of copper at zeolite NaX was investigated within a batch reactor. The experiments in the batch reactor were conducted separately with and without the presence of baffles using three types of impellers: straight blade turbine (SBT), pitch blade turbine (PBT) and Rushton turbine (RT), with the goal of obtaining an insight into the influence of geometry on hydrodynamics and on ion exchange kinetics, as well. The study was conducted with zeolite particles ranging from 40 to 50 µm and a copper (II) nitrate solution with initial concentration of 7·10 -3 mol L -1 . For each geometrical configuration of reactor and impeller used, just suspended impeller speed (N JS ) responsible for obtaining the state of complete suspension was determined based on the Zwietering's criterion "1s". Also, the value of power consumption (P JS ) was found. The obtained results show higher values when reactors with baffles were used. Study of ion exchange rate revealed that during the first part of process, the amount of copper exchanged increases fast whereupon that rapid growth gradually reaches the equilibrium state. Kinetic analysis of experimental results was carried out using non-linear and linear regression using Ritchie's and Weber-Morris models in order to determine which of the processes controls the exchange kinetics. Ritchie's model exhibited the best fitting with the experimental data, thus leading to a conclusion that overall reaction rate is controlled by the ion exchange process itself. Besides, the ion exchange process is faster in a reactor with baffles for all impeller types