Browsing by Subject "Process Optimization"
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Item A Systems-Integration Approach to the Optimal Design and Operation of Macroscopic Water Desalination and Supply Networks(2012-02-14) Atilhan, SelmaWith the escalating levels of water demand, there is a need for expansion in the capacity of water desalination infrastructure and for better management and distribution of water resources. This dissertation introduces a systems approach to the optimization of macroscopic water desalination and distribution networks to tackle three problems: 1. Optimal design of desalination and allocation networks for a given demand, 2. Optimal operation of an existing infrastructure of water desalination, distribution, and storage, 3.Optimal planning for expanding the capacity of desalination plants to meet an increasing water demand over a time horizon. A source-interception-sink representation was developed to embed potential configurations of interest. Mathematical programming was used to model the problem by studying different objective functions while accounting for constraints the supply, demand, mass conservation, technical performance, and economic aspects. Such approach determines the type of technologies to be selected, the location and capacity of the desalination plants, and the distribution of the desalinated water from sources to destinations. For the operation and planning problems, the planning horizon was discretized into periods and a multi-period optimization approach was adopted with decisions made for each period. Short- and long-term water storage options (e.g., in storage tanks, aquifers) were included in the optimization approach. Water recycle/reuse was enhanced via the use of treated water and its utilization was improved by minimizing the losses observed in discharged water resulting from the linkage of power plants and thermal desalination plants and the lack of integration between water production and consumption. Several case studies were solved to demonstrate the applicability of the devised approaches.Item Optimal Scheduling for Biocide and Heat Exchangers Maintenance Towards Environmentally Friendly Seawater Cooling Systems(2012-10-19) Binmahfouz, AbdullahUsing seawater in cooling systems is a common practice in many parts of the world where there is a shortage of freshwater. However, biofouling is one of the major operational problems associated with the usage of seawater in cooling systems. Microfouling is caused by the activities of microorganisms, such as bacteria and algae, producing a very thin layer that sticks to the inside surface of the tubes in heat exchangers. This thin layer has a tremendously negative impact on heat transferred across the heat exchanger tubes in the system. In some instances, even a 250 micrometer thickness of fouling film can reduce the heat exchanger's heat transfer coefficient by 50 percent. On the other hand, macrofouling is the blockage caused by relatively large marine organisms, such as oysters, mussels, clams, and barnacles. A biocide is typically added to eliminate, or at least reduce, biofouling. Typically, microfouling can be controlled by intermittent dosages, and macrofouling can be controlled by continuous dosages of biocide. The aim of this research work is to develop a systematic approach to the optimal operating and design alternatives for integrated seawater cooling systems in industrial facilities. A process integration framework is used to provide a holistic approach to optimizing the design and operation of the seawater cooling system, along with the dosage and discharge systems. Optimization formulations are employed to systematize the decision-making and to reconcile the various economic, technical, and environmental aspects of the problem. Building blocks of the approach include the biocide water chemistry and kinetics, process cooling requirements, dosage scenarios and dynamic profiles, biofilm growth, seawater discharge, and environmental regulations. Seawater chemistry is studied with emphasis on the usage of biocide for seawater cooling. A multi-period optimization formulation is developed and solved to determine: * The optimal levels of dosing and dechlorination chemicals * The timing of maintenance to clean the heat-exchange * The dynamic dependence of the biofilm growth on the applied doses, the seawater-biocide chemistry, the process conditions, and seawater characteristics for each time period. The technical, economic, and environmental considerations of the system are accounted for and discussed through case studies.Item Optimization of hybrid dynamic/steady-state processes using process integration(2009-06-02) Grooms, Daniel DouglasMuch research in the area of process integration has focused on steady-state processes. However, there are many process units that are inherently unsteady-state or perform best when operated in an unsteady-state manner. Unsteady-state units are vital to chemical processes but are unable to be included in current process optimization methods. Previous methods to optimize processes containing unsteady-state units place restrictions or constraints on their use. This optimization still does not give the best system design because the solution found will only be the best out of the available options which likely excludes the true optimal design. To remedy this, a methodology was created to incorporate unsteady-state process units into process optimization analysis. This methodology is as general as possible. Unlike many existing unsteadystate optimization methods, it determines all three main components of process design: the network configuration, sizes of units, and operation schedule. This generality ensures that the truly optimal process design will be found. Three problems were solved to illustrate the solution methodology. First, a general mass exchange network was optimized. The optimization formulation resulted in a mixed-integer nonlinear program, and linearization techniques were used to find the global solution. A property interception network was also optimized, the first work done using property integration for systems with unsteady-state behavior. Finally, an industrial semi-batch water purification system was optimized. This problem showed how process integration could be used to optimize a hybrid system and gain insights into the process under many different operating conditions.Item Preparation and Characterization of Chitosan-Alginate Nanoparticles for Trans-Cinnamaldehyde Entrapment(2014-11-04) Loquercio, Andre STrans-cinnamaldehyde incorporated chitosan and alginate nanoparticles were synthesized using the ionic gelation and polyelectrolyte complexation technique. Alginate, chitosan, calcium chloride, and trans-cinnamaldehyde at predetermined concentrations were complexed electrostatically to optimize size and loading efficiency (i.e. preliminary study). A final extrapolated methodology using optimized processing parameters (e.g. stirring, homogenization, and equilibration time; droplet size) was developed and utilized for controlled release, morphological, thermal, antioxidant, and antimicrobial studies. The best working alginate to chitosan mass ratio was determined to be 1.5:1 at a pH dispersion of 4.7. Particle size (166.26 nm) and encapsulation efficiency (73.24%) were further optimized at this mass ratio using an alginate:calcium chloride mass ratio of 4.8:1, alginate:trans-cinnamaldhyde mass ratio of 37.5:1, 18 gauge syringe needle, stirring times of 90 minutes, 15 minutes of homogenization, and equilibration time of 24 hours. Optimized nanoparticles showed increased shelf life (6 weeks) and translucency in solution. Release tests showed trans-cinnamaldehyde release from loaded nanoparticles best followed the bioexponential model; a burst release function (32.5% cumulative release) followed by a sustained release function (62.31% final cumulative release). Differential scanning calorimetry confirmed inclusion of oil into nanoparticles by indirectly comparing thermal stability of free trans-cinnamaldehyde with loaded trans-cinnamaldehyde in the inclusion complex. Nanoparticles resembled a spherical shell and core type arrangement (i.e. spherical, distinct, and regular) and were in the size range of 10-100 nm. The final radical scavenging effect of loaded particles in apple juice was 62% and trans-cinnamaldehyde was just as available to react in free form as it was in inclusion complexes. Minimum inhibitory concentration values (MIC) for trans-cinnamaldehyde loaded nanoparticles was 7,031.25 ?g/ml for Escherichia coli O157:H7 and 14,062.5 ?g/ml for Listeria monocytogenes. The concentration of trans-cinnamaldehyde in the inclusion complexes corresponded to a MIC of approximately 730 and 1,4062 ?g/ml of free trans-cinnamaldehyde for E. coli O157:H7 and L. monocytogenes, respectively. Results indicated that L. monocytogenes was more tolerant to the inhibition by trans-cinnamaldehyde inclusion complex in comparison to E. coli O157:H7. Overall, results suggest that the application of antimicrobial polymeric nanoparticles optimized for essential oil loading in food systems may be effective at inhibiting specific pathogens.