The rise of food deserts, areas in which affordable and nutritious food is hard to find, prompted this project to design and build a compact and efficient hydroponic system housed within a shipping container that can be transported to such areas. The constrained area of the shipping container led to a design using two high-density growth hydroponic systems covering 200 square feet, in which Butterhead lettuce was grown in deep flow and nutrient film technique systems. Development of specifications and design of the lighting, nutrient, and growth system was based on research by the agricultural and biosystems engineering department and consultation with engineering experts. This mobile engineered system gives food desert communities the power to end the drought.

Potting protects electronics components from shock, vibration, and moisture by encapsulating them in substances like epoxies, silicones and urethanes, but vacuum impregnation is superior because it removes air and allows the potting material to fill micropores and channels. The goal of this project is to design a vacuum impregnation system that protects capacitors against corrosion by water. The system consists of a vacuum chamber connected to a sealed rotary vane pump. Capacitors and a range of potting agents are placed under vacuum at -15 inches of mercury, which degasses them, and the capacitors are coated with potting material. Vacuum is released and reapplied several times to ensure that voids in the capacitors are degassed and filled with potting material. Potted components are cured in an oven and kept in a humidity chamber for a week at 100 percent humidity and 90 degrees Celsius. Capacitance is monitored during this period; changes in capacitance are directly correlated to water corrosion in the capacitors.

Vehicles powered by hydrogen fuel cells store hydrogen as a cooled liquid at 20 degrees kelvin or a compressed gas at 10,000 pounds per square inch. An alternative that eliminates the need for these extremes of temperature and pressure is to heat a compound containing covalently bonded hydrogen, causing it to release the hydrogen to the fuel cell. Ammonia borane, which is stable at ambient conditions, requires minimal energy for dehydrogenation, and is rich in hydrogen, is a possible storage medium for hydrogen. If a viable storage system could be engineered, demand for ammonia borane as a source of hydrogen would increase. The goal of this project is to develop a processing plant and to optimize design specifications for scaling up processing of ammonia borane through the metathesis reaction pathway. Optimization of individual unit operations was determined using quality-by-design concepts, which allowed the team to confirm scalability, design limitations, and competitive market pricing. The final design involves the application of two mixers, two reactors, and four separators. The plant design should yield 99 percent pure ammonia borane.

The objective of this project was to design a chemical plant that uses cultivated algae, a sustainable energy source, grown on-site to produce carbon-neutral biofuel. The design includes a supercritical carbon dioxide extractor for the triglycerides in the algae cells, base-catalyzed transesterification in continuously stirred reactors in series, and final separation processes to produce a high-grade biofuel. The environmental considerations of the design include using carbon dioxide for algae growth and the solid-extraction process, and using methanol for the transesterification and liquid extraction, which made recycling easy and further reduced the fuel’s environmental footprint.

The goal of this project is to design a modification enabling a plant that produces ethanol for E85 fuel to switch production to spirits such as whiskey. The Pinal Energy ethanol plant in Maricopa, Arizona, was used as a basis for modeling ethanol production. The design uses a new and proprietary technology that pumps ethanol through flavor additives such as oak chips, using a packed-bed reactor, to age whiskey about 120 times faster than standard barrel aging. During normal ethanol production, denaturant is added in the final step to avoid alcohol taxation. The modified plant design removes this last step and includes piping to the new whiskey-aging vessels. The whiskey produced would be roughly 80-120 proof. Other byproducts that could be sold are carbon dioxide and dried distiller’s grain. The plant would be modified for two months of the year for whiskey production. Ethanol would be produced for eight months, with two months set aside for the plant to change processes. The ethanol plant produces 50 million gallons of ethanol per year. The modified plant would produce approximately 33 million gallons per year of ethanol and 16 million gallons per year of whiskey.

Coastal desalination plants can release waste brine to the ocean, but inland plants are left with a generally unprofitable byproduct that can be costly to dispose of. The Kay Bailey Hutchison inland plant in El Paso, Texas, treats brackish groundwater, which is too salty for potable use but less salty than seawater, using reverse osmosis to produce 15.5 million gallons per day of potable water and 3 million gallons per day of brine waste. The purpose of this project is to design a membrane distillation desalination method to reduce this brine waste and increase the plant’s output of potable water. Membrane distillation involves heating feed water to evaporation and running it along one side of a membrane. On the other side is flowing air, which causes pure water vapor to move through the membrane, leaving the salts and other dissolved solids behind. Modeling was used to design and optimize the membrane distillation process specifications and units, based on water composition and a conscious effort to minimize energy demands. Membrane distillation is typically a standalone process, often solar-powered, and this project determines the viability of using it on an industrial scale to further treat brine waste from reverse osmosis.

The University of Arizona biodiesel pilot plant converts waste cooking oil from student union restaurants into biodiesel to fuel campus vehicles. With community partner Grecycle, students have built a 100-gallon single-reactor plant and quality-testing laboratory to convert the waste oil into biodiesel that meets quality standards of the American Society for Testing and Materials.

The goal of this project was to optimize separation of the biodiesel byproduct stream to recover methanol for recycling and separate water and glycerin, thus creating products of higher purity and value. The team used Aspen and ChemCAD software to simulate a pilot-scale divided-wall column separation method, and is developing a process template for future pilot- and large-scale biodiesel operations.

The goal of this project is to design a process to produce 90-proof corn whiskey using solar energy. The project is located in Yuma, Arizona, which experiences the nation’s highest direct normal irradiance. Solar energy is gathered using a series of rotating parabolic mirrors that reflect light onto a tube located at the foci. The tube is transparent, vacuum-sealed, and contains a heat-transfer fluid designed to absorb solar energy, which is transferred to a series of two distillation columns. After dilution of the purified ethanol, the final product is 90-proof corn whiskey.

The University of Arizona is nationally recognized for its central cooling system, but the three cooling sites on campus use 1,1,1,2-tetrafluoroethane, or HFC-134a, a known greenhouse gas that is likely to be banned in the future. The goal of this project is to find a refrigerant that could replace HFC-134a and determine what changes would need to be made to existing cooling sites to accommodate its use. A mathematical model of the entire refrigeration cycle was created to experiment with different refrigerants and determine the best replacement. Another objective of the project was to determine how choice of power source affects greenhouse gas emissions from the refrigeration process.

When the EPA reduced the sulfur content allowable in diesel fuel to 15 ppm in 2010, many refineries had to upgrade their hydrodesulfurization units to meet the new limit. The objective of this project is to design an upgraded catalytic hydrodesulfurization unit that can treat 35,000 barrels per stream day of liquid feedstock containing 1.9 percent sulfur by weight. Performance data from an existing catalytic hydrodesulfurization unit was used to predict the performance of the upgraded unit. ChemCAD software was used for process calculations and the feed was modeled using boiling curve data. The desulfurization reaction kinetics were based on the reduction of dibenzothiophene. The project goals are 99 percent recovery of diesel fuel and a sulfur content below 15 ppm. To achieve these recovery levels the liquid feedstock is run through a catalyst-filled packed-bed reactor, where the sulfur compounds react with hydrogen gas to form hydrogen sulfide gas. The reactor effluent is run through a distillation column to separate the diesel fuel from the naphtha. More volatile and noncondensible compounds, such as butane, propane, nitrogen, and carbon dioxide, are run through an amine process to remove the hydrogen sulfide from the hydrogen recycle stream. Hydrogen is provided from a nearby hydrogen plant.