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.

The International Energy Agency predicts that hybrid electric vehicles will account for 20 percent of global lithium sales by 2050, and lithium carbonate batteries are in demand for their higher voltages, energy content, chemical stability, long storage life, and good ionic conduction at ambient temperatures. The goal of this project is to design a production plant for lithium carbonate extracted from McDermitt clay found in Nevada and Oregon. The plant is expected to produce 56 tons of lithium carbonate per year from a feed of 2,000 tons of McDermitt clay per day. Key factors analyzed include a clay-gypsum-limestone feed ratio of 5:2:2, power costs for kiln and roaster, and crystallization parameters for glaserite and Glauber’s salt byproducts.

The sponsor makes water-soluble mandrels to create products ranging from musical instruments to aerospace modules. The mandrels are composed of silica and alumina cenospheres, polyvinylpyrrolidone, and sodium silicate, which are formed into blocks and solidified, or cured, using carbon dioxide, microwave radiation, and convective heating. Mandrels can shear and crack, causing product loss, so the sponsor charged the team with finding a cost-effective and feasible solution to overcome compromised mandrel strength. The team analyzed the production process and investigated three potential sources of product damage. First, material composition was analyzed for any inconsistency, impurity, or noninteractivity that might cause weakness. Second, various curing methods were explored, such as carbon dioxide curing of sodium silicate for structure, and microwaving and using a constant-temperature convection oven to dehydrate and strengthen the mandrel. Third, transportation was investigated as a potential source of mandrel stress and rupture.

The purpose of this project was to design a mobile hazardous compound disinfection truck to treat medical waste for proper disposal while extracting recyclable material from it. The design uses of a continuous system that breaks down, disinfects, and stores many types of medical waste. An industrial-grade shredder reduces the volume of waste, which is then disinfected in an autoclave. This operation includes an optical sorting system that separates white paper and other cellulosic solids from medical waste for recycling. The design was based on extensive research and tours of recycling and trash facilities.

The National Helium Reserve is dwindling and new methods of helium extraction are required to meet global demand. The goal of this project is to design a system to produce helium with purity greater than 99 percent from industrial carbon dioxide pipelines with high helium concentrations. The team’s solution is to feed the pipeline gas through a catalytic converter and pressure swing adsorption unit to remove most of the water and hydrogen sulfide. A compressor and condenser then remove carbon dioxide and hydrocarbons, leaving mostly helium and nitrogen, which is further compressed and condensed until liquefied. The stream then enters two distillation columns in series, which separate the helium from the nitrogen. The final product is high-grade helium, which is liquefied ready for transportation, and a separate stream of hydrocarbons and carbon dioxide that can be fed back into the pipeline.

The objective of this project was to develop a method to process an industrial waste stream consisting of methyl ethyl ketone and water. Distillation at various temperatures and pressures removes the bulk of the methyl ethyl ketone. Simulations and lab experiments were conducted to model the most effective conditions for removal and, to reduce costs, the remaining wastewater is processed using air stripping and thermal oxidation. This makes the water disposable by Pima County standards and removes sufficient methyl ethyl ketone to make the water reusable in the industrial process.