Abstract
Oxygen is a harmful substance in many processes because it can bring out corrosion and oxidation of food. This study aimed to enhance the removal of dissolved oxygen (DO) from water by employing a novel rotor–stator reactor (RSR). The effectiveness of the nitrogen stripping coupled with vacuum degassing technique for the removal of DO from water in the RSR was investigated. The deoxygenation efficiency (η) and the mass transfer coefficient (KLa) were determined under various operating conditions for the rotational speed, liquid volumetric flow rate, gas volumetric flow rate, and vacuum degree. The nitrogen stripping coupled with vacuum degassing technique achieved values for η and KLa of 97.34% and 0.0882 s−1, respectively, which are much higher than those achieved with the vacuum degassing technique alone (η = 89.95% and KLa = 0.0585 s−1). A correlation to predict the KLa was established and the predicted KLa values were in agreement with the experimental values, with deviations generally within 20%. The results indicate that RSR is a promising deaerator thanks to its intensification of gas–liquid contact.
Highlights
IntroductionOxygen is a harmful substance and removal of dissolved oxygen (DO) from water is an essential step carried out in power plants in order to prevent corrosion in boilers and pipes, improve heat transfer and enhance plant efficiency [3,4,5]
Oxygen plays a key role in the treatment of wastewater [1,2]
Both η and KL a increased from 96.32% and 0.0803 s−1 to 97.34% and 0.0882 s−1, respectively, with an increase in rotational speed from 200 to 600 rpm, beyond which both η and KL a showed little change with increasing rotational speed
Summary
Oxygen is a harmful substance and removal of dissolved oxygen (DO) from water is an essential step carried out in power plants in order to prevent corrosion in boilers and pipes, improve heat transfer and enhance plant efficiency [3,4,5]. This operation is adopted in the power industry but is necessary in the semiconductor, pharmaceutical, biotechnology and food industries, which have stringent requirements for DO levels in water [6,7]. Coupled techniques, such as thermal degassing with vacuum degassing or thermal degassing with nitrogen stripping, are promising means for DO removal [8,9]
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