C hementato R
Using DME (Continued from p. 14) vapor by depressurization. In laboratory trials using blue-green algae (a mixture of microalgae, including the genus Microcystis), the DME-based extraction was shown to be 60 times more efficient at extracting oil than traditional methods. The
product “green crude oil” was subsequently shown to have a molecular weight of 200–400 and a calorific value of 10,950 cal/g (which is below that of dry wood). The researchers are further optimizing the extraction process with other algae, and plan to scale up the process with commercial partners.
Forward osmosis moves a step closer to commercialization
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asys Water Inc. (Cambridge, Mass.; www. oasyswater.com) has commercialized a forward-osmosis (FO) membrane as the next step toward introducing its lower-cost desalination and water-reuse technology. The membrane, developed by Professor Menachem Elimelech, chair of chemical engineering at Yale University (New Haven, Conn.; www.yale.edu), is a polyamide thinfilm composite that can be produced on conventional manufacturing lines, says Lisa Sorgini, vice president of markets and strategy at Oasys Water. “The Oasys membrane is roughly 60% thinner than standard reverse-osmosis (RO) membranes thereby reducing resistance to water passage without reducing salt rejection,” she says. As in RO, FO uses a semi-permeable membrane to separate fresh water from dissolved solutes, with the separation driven by an osmotic pressure gradient. In FO, a salt solution of higher concentration draws purified water from the (lower concentration) feed stream through the membrane. Purified water is then obtained by evapo-
rating away the salt of the “draw” solution. The Oasys Engineered Osmosis (EO) process uses a patented ammonium-carbonate draw solution that, at high concentrations, can provide osmotic pressures in excess of 400 atm making it possible to treat high-salinity feeds that are infeasible for RO, says Sorgini. Unlike RO, which requires high hydraulic pressure to counteract the osmotic pressure and drive separation, EO operates at atmospheric pressure with less expensive materials of construction, she adds. The EO process uses low-temperature (40–50°C) heat to evaporate the draw solutes. Oasys plans to incorporate full-scale membranes (manufactured by a third party partner) with the patented EO process to produce a system for waters with salinities of 10,000 to over 150,000 mg/L of dissolved solids. Sorgini estimates that the Engineered Osmosis process will be 40–80% more cost effective than traditional seawater reverse-osmosis systems. The first commercial system is scheduled for release in June, 2011.
Energy efficiency prize for alumina production
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t the Hannover Messe 2010, Alumina do Norte do Brasil S.A. (Alunorte; Barcarena, Brazil; www.alunorte.net) and Outotec Oyj (Espoo, Finland; www.outotec.com) received the X Prize (special recognition) for energy efficiency in alumina production. The award, part of the German Energy Agency’s (dena; Berlin, Germany; www.dena.de) Initiative EnergieEffizienz, was bestowed to Alunorte for using an energy efficient calcination process developed by Outotec. To make alumina (Al2O3), bauxite is first digested in sodium hydroxide, which recovers aluminum as aluminum hydroxide. The Al(OH)3 is then calcined to form Al2O3. In the calcination process, Al(OH)3 is first mixed in two preheating stages with the hot waste gas from the calcining stage, predried and partially calcined. The mixture between gas and solid is carried out in a venturi dryer, followed downstream by a cyclone, 16
where gas and solids are separated. The final calcination is performed at 970°C in a circulating fluidized-bed (CFB) reactor. The hot alumina is discharged from the CFB and cooled in a two-stage, fluidized-bed cooler by preheating the combustion air. Using simulations, Outotec developed a procedure that improves the efficiency of cyclone separation, which considerably reduces the amount of solids remaining in the gas, thereby improving the heat transfer while reducing the pressure losses in the process. Using this procedure, Alunorte has been able to reduce specific energy consumption for calcination from 3,000 kJ/kg to 2,790 kJ/kg — an annual energy saving of about 56-million kWh, and a reduction of CO2 emissions of approximately 18,000 m.t./yr. The €100,000 investment led to a operating-cost reduction of €1,360,000/yr. ■
Chemical Engineering www.che.com June 2010
Fuel-cell catalyst Chemists at Brookhaven National Laboratory (Upton, N.Y.; www.bnl.gov) have received three patents for catalysts and their production methods, which have the potential to reduce the amount of platinum needed for fuel cells. Two of the patents were awarded for catalysts that speed up oxygen reduction — one is composed of a thin layer of Pt on palladium nanoparticles; and the other includes metal oxides, such as those of niobium and ruthenium, with a thin layer of Pt on the metal-oxide catalysts. The third patent covers a process for adding gold clusters to Pt-based catalyst, which is said to improve the performance of fuel cells during acceleration. The catalysts and technology are available for licensing.
Zeptomole detection The latest triple-quadrapole, LC/MS (liquid-chromatography mass-spectrometer) system from Agilent Technologies Inc. (Salt Lake City, Utah; www.agilent.com) has a 10-fold increase in sensitivity over its predecessors, enabling the instrument to detect molecules at the zeptamole (10–12 mol) level. Incorporating iFunnel technology, the system covers a linear dynamic range over six orders of magnitude.
Washdown motors At Interphex (New York; April 20–22), Stainless Motors, Inc. (Rio Rancho, N.M.; www.stainlessmotors.com) launched what is claimed to be the first washdown-duty stainless-steel motors approved for use in hazardous locations. The motors are UL-approved for use in Class I, Div. 1, Groups C and D and Class II, Div. 1, Groups F and G environments. They are highly resistant to caustic liquids, vapors and dust, making them suitable for applications requiring safety, cleanliness and wash-down tolerance, says the manufacturer. ❏