Showing papers by "Sanjoy Banerjee published in 2018"

Chemical hydrodynamics of a downward microbubble flow for intensification of gas-fed bioreactors

Abstract: Bioreactors are of interest for value-upgrading of stranded or waste industrial gases. Reactor intensification requires development of low cost bioreactors with fast gas–liquid mass transfer rate. Here we assess published reactor technology in comparison with a novel downward bubble flow created by a micro-jet array. Compared to known technology, the advanced design achieves higher volumetric gas transfer efficiency (kLa per power density) and can operate at higher kLa. We measure the effect of four reactor heights (height-to-diameter ratios of 12, 9, 6, and 3) on the gas transfer coefficient kL, total interfacial area a, liquid residence time distribution, energy consumption, and turbulent hydrodynamics. Leading models for predicting kL and a are appraised with experimental data. The results show kL is governed by “entrance effects” due to Higbie penetration dominate at short distances below the micro-jet array, while turbulence dominates at intermediate distances, and finally terminal rise velocity dominates at large distances. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1399–1411, 2018

Hydrodynamics under the jet-array of a downflow microbubble column: Performance intensification

Abstract: Development of low-cost, ambient pressure, gas-liquid contactors with fast mass transfer (high k L a ) and low energy consumption are key for industrial chemical processing technologies. A recently published reactor design comprised an array of downward-pointing micro-jets at the top of the vessel to create a downflow of microbubbles. Performance showed high k L a and low power usage. However, the most stable hydrodynamic mode under a jet array includes a large and persistent eddy, likely similar to the “Coanda effect” reported much earlier. Here we test swirling hydrodynamics to prevent momentum positive feedback that hypothetically creates this backmixing. Particle imaging velocimetry (PIV), salt-pulse tracking residence time distribution (RTD), and k L a data are collected from the swirl and non-swirl case. The data confirm the hypothesis about the hydrodynamic origin of the eddy, and suggests that it must be considered during reactor design. The data further show that swirl shifts the overall reactor hydrodynamics closer to plug flow, creates more tanks in series, more homogenous turbulence, greater k L a , and greater k L a per power usage (an increase by 40%). A physical understanding is given by measurements of residence time distribution that create more efficient contact of gas and liquid phases.

Cycling protocol for alkaline batteries

Abstract: A method of operating a battery comprises discharging a cathode comprising manganese dioxide to within a 2 nd electron capacity of the manganese dioxide at a C-rate of equal to or slower than C/10, recharging the battery, and cycling the battery during use a plurality of times. The cathode is in a battery, and the battery comprises the cathode, an anode, a separator disposed between the anode and the cathode, and an electrolyte. The cathode comprises the manganese dioxide and a conductive carbon. The anode comprises: a metal component and a conductive carbon. The metal component can be a metal, metal oxide, or metal hydroxide, and the metal of the metal component can be zinc, lithium, aluminum, magnesium, iron, cadmium and a combination thereof.

Stabilized birnessite cathode for high power and high energy density applications

Abstract: A battery comprises a housing, an electrolyte disposed in the housing, an anode disposed in the housing, a stabilized cathode disposed in the housing and comprising a cathode material. The cathode material comprises a composition selected from birnessite or layered-polymorph of manganese dioxide (δ-MnO2), the composition being stabilized by bismuth and copper ions, a conductive carbon, and a binder. The anode can be at least 50% (m/m) lithium, magnesium, aluminum, or zinc.