lack of publicity and promotion, but it is also manifest outside the U.S. In its second annual review of electric vehicles around the world, a group from Jet Propulsion Laboratory ( JPL) has described the status as of the end of 1978. One of the major findings is that electric vehicles are used to any extent only in England and Japan, and there only because of special local conditions. In England, home milk deliveries have been made for many years with electric vehicles. In Japan, a publisher operates a similar fleet of delivery trucks. In both cases the overriding consideration is for quiet operation in a populated region in the early morning hours. The only U.S. electric vehicle fleet of major size is that operated by the Postal Service. Auto and truck makers perpetually express interest in electric vehicles, but there is, in fact, only limited development in progress. This is usually attributed to the lack of a perceived market. Even so, DOE is exerting great pressure to develop electric vehicles, market or no market, and the lack of any organization to service them notwithstanding. At present, the typical electric vehicle maker in the U.S. is a small company that has been in business for three or four years and makes only a few units per year. The vehicles are usually small passenger cars and/or delivery vans. According to the J P L survey, the manufacturers are "machine oriented" and few of them have a real appreciation of potential markets or eventual electric vehicle requirements. Not everyone agrees with that assessment but it does seem to be widespread. Most electric vehicle development so far has been an attempt to adapt the conventional gasoline-powered vehicle to battery power, rather than starting from scratch. This has been the approach of American Motors in adapting the Jeep to electric drive for the Postal Service, which now has about 350 vehicles in operation. This is the largest electric vehicle fleet in the U.S. and provides operating data for DOE. Elsewhere in the world, the experience with electric vehicles closely parallels that in the U.S. In England the milk delivery vans have been operating for about 40 years and remain cost-effective, according to operators. However, the market appears to be limited to about 1500 vehicles per year, a demand easily satisfied by three manufacturers. Japan probably has the largest electric vehicle program in the R&D stage. This program includes small cars and vans and some 30,000-lb passenger buses. D 28
C&EN Sept. 10, 1979
Coal cuts energy use in metal electrowinning
be extracted in large amounts from aqueous solutions by electrowinning. Electrowinning is already an important source of much U.S. chromium, cobalt, nickel, copper, zinc, and cadmium. Energy savings arise from the low voltage needed to oxidize carbon to carbon dioxide in water solution compared with the voltage for oxidation of water to oxygen. In terms of standardized laboratory conditions, the reversible thermodynamic potential for carbon oxidation is only 0.21 volt, compared to 1.23 volts for water. The number of amperes required for a given weight of metal remains the same because the same number of coulombs is needed. Volts times amperes is watts, however, which is power, and lowering the voltage reduces power consumption. With the assistance of senior chemical engineering student Larry Veneziano, Coughlin and Farooque plated copper from a solution of copper sulfate in dilute sulfuric acid at 60° C using platinum gauze anodes and cathodes. A magnetic stirring bar was used to stir a slurry of pulverized North Dakota lignite coal. Purity of deposited copper was more than 99% as measured by atomic absorption spectroscopy. Use of lignite or presence of its ash in the electrolyte did not seem to affect purity. In addition to platinum gauze, graphite rods and felt also were successful as anodes. Copper plates performed well as alternate cathodes.
Smelting metals at the expense of oxidizing carbon is as old as the Bronze Age. Something newer is electrolytic reduction of metals in a cell that uses coal or lignite as reducing agent in a medium no hotter than warm water. Chemical engineers at the University of Connecticut, Storrs, who developed the coal-based electrowinning process, say the technique cuts electric power consumption two thirds compared with customary electrolytic refining based on parallel oxidation of water alone [Nature, 280, 666 (1979)]. Even when alternative use of the coal or lignite to generate electricity is considered, the engineers say, power use is half that of usual methods. Chemical engineering professor Robert W. Coughlin and postdoctoral student Mohammad Farooque developed coal-based electrowinning of metals out of their process of coalassisted electrolysis of water—a kind of room-temperature coal gasification (C&EN, June 25, page 33). In this process, hydrogen is produced at the cathode and carbon dioxide containing 3 to 7% carbon monoxide at the anode. The Connecticut investigators cite chromium, manganese, cobalt, nickel, copper, zinc, gallium, cadmium, indium, and thallium as metals that can
Coal-metal redox couple saves energy by reducing voltage Cathode gas outlet Anode gas outlet
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Supporting electrolyte
Cathode Platinum anode Fritted-glass separator
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- 2Cu
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The investigators are confident that results from their copper electrowinning studies also will show re ductions in energy when applied to other aqueous cation solutions. Without the coal, depending only on water oxidation, the cell potential was 1.65 volts at 5.9 milliamp and 1.73 volts at 12 milliamp. These potentials were lowered about 1.1 volts during oxidation of coal. Based on weights of deposited copper, Coughlin and Farooque calculate power consump tion of 1.622 kwh per kg without coal and 0.552 kwh per kg with coal at 12 milliamp, amounting to a 66% re duction in power used. Results are similar at 5.9 milliamp. Assuming 35% efficiency in con verting coal to electricity, the Con necticut engineers calculate that the coal used in electrowinning consti tutes a 0.3 kwh-per-kg debit. Even taking this into consideration, how ever, coal-based electrowinning uses 45% less energy than the usual tech nology. Turning to current dollar costs, Coughlin and Farooque assume 2 cents per kwh for electricity and $35 per ton of coal containing 75% carbon. They calculate that the conventional process produces copper at 3.1 cents per kg, compared with 1.5 cents per
kg for coal-based electrowinning—a cost saving of 50%. One difficulty in the new process is the presence of 12.5% ferric oxide in ash of North Dakota lignite coal. This amounts to 14 kg of ferric oxide in 1 metric ton. Ferric iron would waste electricity through reduction to the ferrous state. The investigators rec ommend removing ferric oxide from coal slurries as well as from copper ores in continuous processes, possibly by oxidation with oxygen and pre cipitation as the hydroxide. For the future, Coughlin and Farooque cite four barriers to com mercial coal-based electrowinning that must be overcome. First, current densities must be increased from the maximum 12 milliamp used in labo ratory evaluations to levels that give economical capital costs. The second is ability to use total coal carbon content for the process. Third, influ ence of particular coal characteristics and ash content on reaction rates and deposited metal morphology must be explored. Finally, buildup of other cations, such as ferric iron, which might compete with target metal ions for consumption of current, must be prevented by devising schemes for their continuous removal from coal slurries and ores. D
Device lessens pipe noise caused by valves Laminar fluid flow through a pipe can be practically noiseless. But put a control valve or pressure regulator in the line and quite a racket can re sult. A new approach to reducing that noise has been developed by engi neers at Pennsylvania State Univer sity, University Park. It is a device that fits into the pipeline just down stream from the valve and cancels out a significant part of the noise caused by the valve. Although the device resembles a muffler, it is not a muffler, notes me chanical engineering professor Ger hard Reethof, director of Penn State's noise control laboratory. Working with Reethof on the device were re search associate Oliver H. McDaniel and mechanical engineering professor Jeremy L. Walter. Current methods of reducing noise include low-noise valves and multi ple-chamber, reverse-flow mufflers. A disadvantage of the mufflers, which aren't used to any great extent, is that they cause a high pressure drop. The low-noise valves cost three to 10 times more than standard valves and be-
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