CaCO3–CO2–H2O system in falling film on a bank of horizontal tubes: Model verification

The purpose of this work is to model the CaCO3–CO2–H2O system in falling film on a bank of horizontal tubes. The model was applied on a 5-effects reference thermal vapor compression multiple-effect distiller (MED-TVC) operating at top brine temperatures (TBT) of 60–70 °C. The model can predict pH values, CaCO3 deposition and fouling resistance with greater accuracy. Through the MED stages, the HCO3− and CO2 concentrations slightly increased while the CO32− concentration slightly decreased. The pH decreased from 8.8 in the first stage to 8.4 in the 5th stage. The CO2 release rates as well as the CaCO3 deposition rates increase with increasing top brine temperature (TBT). CO2 release rates decrease from 36.4 g/t feed water in the first stage to 32.5 g/t in the last stage. The specific CaCO3 deposition decreases from 127.3 g/t feed water in the first stage to 100.1 g/t in the last stage.