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Title:Separation of solvents from selected biopolymeric matrixes and aqueous mixtures by ultrasound
Author(s):Kahraman, Ozan
Director of Research:Feng, Hao
Doctoral Committee Chair(s):Padua, Graciela Wild
Doctoral Committee Member(s):Engeseth, Nicki; Lee, Youngsoo
Department / Program:Food Science & Human Nutrition
Discipline:Food Science & Human Nutrition
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Ultrasound technology
Drying
Separation
Azeotropic Mixtures
Abstract:Distillation, one of the oldest separation processes, is of central importance in the chemical and process industries due to its ability to separate ideal, non-ideal, homogeneous, heterogeneous, and azeotropic mixtures in industrial-scale operations. It is the most commonly employed method for liquid-liquid separation applications. Distillation accounts for ~95% of the total separation energy used in the refining and chemical-processing industries (Leeson et al., 2017). Unfortunately, the energy efficiency of a commercial distillation column is fairly low, with a typical thermodynamic efficiency of less than 10% (Rush, 1980). There are two main reasons for its low efficiency. First, there are large irreversible heat-transfer losses in the phase-change processes of boiling a liquid and then condensing the vapor. Second, a significant fraction of energy is used to overcome the azeotropic bottleneck in azeotrope-forming systems (e.g., ethanol + water). While a few conventional distillation technologies and new separation approaches have been developed for azeotropes, they rely largely on separation via phase equilibrium, or involve large capital, energy, or other operating costs. Like distillation, drying is an energy-intensive process which removes the moisture content from biopolymer matrixes such as food products, for the purposes of reducing the costs of transportation and packaging, and for food preservation. The thermal energy that is required in a drying process, plus the fact that water removal in the falling-rate period is difficult, cause the drying foods to be exposed to elevated temperatures for a long time. Drying is thus a process that is known to degrade the product quality, especially the nutritional quality. Hence, ways are being sought to dry foods with heat-sensitive nutrients at low temperatures. Indeed, there is a crucial need to develop a new food-drying method that can preserve food quality and reduce energy consumption. In this project, a new approach has been proposed and tested for liquid-liquid and solid-liquid separations using ultrasonic waves at different frequencies. First, power ultrasound was used to separate ethanol from an ethanol-water mixture, with a focus on prototype development and optimization of process parameters, including the initial ethanol concentration, carrier gas-flow rate, temperature, and mist collection time. Additionally, the physicochemical properties of the ethanol-water mixture were investigated to gain a better understanding of ethanol and water interactions, which may provide insights for the selection of process parameters. The results showed that the ultrasound-mediated ethanol separation at low temperatures was effective in enriching ethanol in the ultrasound-generated mist. The volumetric flow rate of the carrier air was found to be an important parameter affecting the ethanol concentration in the mist. More importantly, this non-thermal, non-equilibrium separation method was able to break the ethanol-water azeotrope, showing promise for reducing energy consumption in the ethanol-production process. With regard to water removal from biomaterials (solid-liquid separation), a novel use of power ultrasound was tested for drying fabrics and apple slices with no or minimal application of heat. For drying the apple slices, the performance of ultrasonic drying was compared with those of two commonly used methods, freeze drying and hot-air drying. The effects of the non-thermal ultrasonic drying method on the drying kinetics, product-quality attributes, and microstructures of the apple slices were evaluated. The results obtained for the fabric drying showed that, regardless of the fabric type, room-temperature ultrasound drying with a high-frequency transducer significantly reduced the drying time compared to ultrasound drying by a low-frequency mesh transducer or a hot-air drying method. The time needed to dry apples to a 5% moisture content (wet basis) was 81% faster for the ultrasonic contact-drying method than the hot-air drying method at 60±1oC. The apple slices processed by the ultrasound also maintained a significantly higher rehydration ratio, antioxidant capacity, total phenol content, better color, and microstructure than the hot-air-dried samples. Overall, the novel ultrasonic, non-thermal, solvent-separation schemes proposed and tested in this study demonstrated a significant improvement over the current technologies in ethanol-enrichment and food dehydration processes. The information obtained in this study will provide important guidelines for the future development of pilot scale and industrial scale operations.
Issue Date:2019-06-19
Type:Text
URI:http://hdl.handle.net/2142/105867
Rights Information:©2019 Ozan Kahraman
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08


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