Performance of a dual helical ribbon impeller in a two-phase (gas-liquid) stirred tank reactor
Maryam Amiraftabi, Mehdi Khiadani, Hussein A. Mohammed
Abstract
The performance of a dual helical ribbon impeller in a gassed stirred tank reactor filled with a shear-thinning polymer has been investigated experimentally in this study. Sodium carboxymethyl cellulose with different concentrations were applied to change the viscosity and rheological behaviour of working fluid. Titration reaction between HCl and NaOH then took place inside the reactor under controlled pH, evaluating the influence of a dual helical ribbon impeller on the performance of a two-phase agitated reactor. The impact of impeller rotational speed, gas flow rate, viscosity, and clearance to the bottom on power uptake and mixing time are explored. The results thus reveal that the presence of bubbles reduces both required power uptake and mixing time to reach an endpoint reaction. Contrary to expectations, this study indicates that increasing the impeller's speed beyond a certain level, not only fails to further reduction in mixing time, whilst the power uptake increases exponentially. Furthermore, for the first time, this study suggest that power number is inversely proportional to the square root of Reynolds number when systems are equipped with a dual helical ribbon impeller. The response surface method and quadratic numerical models are applied to suggest models in order to calculate the mixing time and power consumption.