Murray told the Division of Fuel Chemistry at a symposium on desulfurization of coal and coal char that macroscopic pyrite occurs in coal in veins (usually in thick films along vertical joints), in geologic lenses, in nodules, and in aggregates. Since coal is diamagnetic and pyrite is paramagnetic, the two can be separated, if the coal is crushed fine enough to liberate the pyrite. A variation of the process involves exposure of the ground coal to iron carbonyl vapor, which deposits a thin magnetic skin on the pyrite and ash but not on the coal. This permits the simultaneous removal of pyrite and ash. In experiments conducted by Murray, pyrite from various coals was separated in both dry and wet systems using Frantz screens (made from thin ribbons of Type 430 magnetic stainless steel). Up to 93% of the pyrite was removed in the most successful runs, with removal effectiveness depending on retention time in the magnetic separator and on the amount of recycle. There also was significant removal of ash. For a 500 ton-per-hour plant, Murray estimates that the cost of operating a separator would be about 37 cents per ton, including the cost of installed separators amortized over 10 years. This cost is substantially less than that of conventional methods of mechanical coal cleaning, which may run as high as $1.25 per ton. He is presently substantiating preliminary results with further tests. One ol the drawbacks of magnetic separation is that it removes only minor amounts of chemically bound sulfur. Bound sulfur must be removed by chemical means, and a familiar way is controlled oxidation. Dr. Sidney Friedman of the Energy Research & Development Administration's Pittsburgh Energy Center thinks that the most promising method involves contacting an aqueous slurry of pulverized coal with air at pressures up to 1000 psig and temperatures between 140° and 200° C. This method removes more than 90% of the pyritic sulfur and up to 40% of the organic sulfur from a wide variety of coals. Losses in fuel values, he claims, are less than 10%. Preliminary estimates indicate that sulfur removal by air oxidation in this manner would cost from $3.50 to $5.00 per ton. Another oxidation technique is an ammonia/oxygen system developed at Kennecott Copper Corp. Kennecott's Dr. S. S. Sareen says that this system removes virtually all the pyritic sulfur and 25% of the organic sulfur, with carbon losses being slightly higher than for oxygen/ steam systems. These three systems, and others as well, all attack the problem of sulfur removal at the source, namely in the coal. They are claimed to be more attractive than the alternative of stack gas scrubbing, which is often considered unreliable. If so, it would seem that coal consumers would opt for coal desulfurization, on economic and technical grounds. Since not all systems remove all types of sulfur, however, it follows that some kind of composite system probably would be adopted. •
Science Data revealed on Venusian surface, atmosphere 3oth hard data and speculative ideas about the earth's moon, planets and their moons (if any), and the solar system are expanding rapidly. This increasing pace of information development ranges from newly discovered kinds of basalts in lunar samples to proposals on the use of asteroids as building materials for space stations and as living quarters in space. These diverse topics were covered at the 8th Lunar Science Conference held at the National Aeronautics & Space Administration's Johnson Space Center. One example of nonlunar science at the conference was technical data about the surface and atmosphere of Venus, together with just-released photographs of the surface divulged in a paper authored by several Soviet scientists and one from the U.S. The Soviet probes of Venus, called Veneras, revealed significantly different surface features at the different landing sites. Extensive surface reworking is apparent, says Dr. C. P. Florensky of the V. I. Vernadsky Institute of Geochemistry & Analytical Chemistry of the Soviet Academy of Sciences. To account for such reworking, Florensky and his coworkers in a paper presented by Dr. L. B. Ronca of Wayne State University suggest chemical transformations. The wide variations in temperature of ±25° C at about 450° C and in pressure of ±20 atm at about 80 atm over an altitude change of 5 to 6 km could stimulate surface chemical reactions. In another nonlunar paper, the possible structure of a cryolithosphere on Mars was delineated by Dr. R. O. Kuzmin of the Vernadsky Institute. His structure is based on data and photographs obtained by both Soviet and U.S. Martian probes. He estimates the permafrost as varying in thickness along a meridional equator-pole section from 1 to more than 4 km. Soviet scientists delivered, in addition
to photographs of the Venusian surface, parts of the sample returned from Mare Crisium by Lunar 24, the latest unmanned probe of the moon by Soviet scientists. Because the sample was taken on Aug. 18, 1976, only preliminary studies have been done on it. These studies have turned up a new variety of lunar basalt, according to Dr. V. L. Barsukov, director of the Vernadsky Institute. In a special evening session at the conference, the use of asteroids was proposed as a way to overcome the extremely high cost of launching materials from earth into space. The availability of many thousands of asteroids 100 m or more in diameter became apparent from studies of the distribution of craters on the moon, Mars, Mercury, and the earth as well as recently initiated astronomical surveys. The basic idea of recovering and using asteroids comes from Dr. Brian J. O'Leary of Princeton University. Other contributors to the concept include Dr. Eugene M. Shoemaker of California Institute of Technology, who has begun telescopic surveys to estimate the potential population of asteroids, and Dr. David R. Criswell of the Lunar Science Institute, who has made some estimates of cost savings in the possible use of asteroids as material sources and, if tunneled into, living quarters. Recovery of asteroids whose orbits pass at one time or another between the earth's orbit and the sun would require 10 to 100 times less energy than to recover asteroids from the main belt of asteroids between Mars and Jupiter. The method proposed to move asteroids to convenient locations—generally at least as far away as the earth's moon—is a mass-driver based on the law of action-reaction. A solar-powered device would break up an asteroid and eject the pieces in a direction opposite to the direction of desired travel. •
Computer-enhanced TV pictures taken by Soviet probes show Venusian landscape on a steep slope from 0.9 m above ground (top) and on a plain (bottom) March 28, 1977 C&EN
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