Inventor Baddour Disk, doughnut, no channeling
June 28, 1965, page 46). It is now working with about a dozen companies on client-paid piloting programs which should lead eventually to plant production units. For many cases, gas chromatography already appears to be directly competitive with distillation, especially for separating heatsensitive materials or those with low relative volatilities. The Baddour patent casts a shadow on other efforts in large-scale preparative chromatography where column internals are employed. F & M Scientific (a division of Hewlett-Packard), for example, is now marketing a preparative chromatograph based on technology developed by Continental Oil. Conoco has licensed F & M to manufacture and market the units, which use columns up to 4 inches in diameter, and has applied for patents of its own. The internals used in Conoco's approach are of a somewhat different design than those used by Abcor. What effect the Baddour patent will have on the preparative gas chromatography field is yet to be seen. In any event, the patent, because of its breadth, is a significant factor. Various efforts at scaling up chromatographic columns directly from the small 1/4-inch columns used in laboratory instruments have run headon into a major problem. In the small columns, nonuniform flow or channeling, if it exists, is insignificant. In large columns, however, channeling keeps components from separating into sharp fractions. The gross effect is a loss of resolving power. In the approach described in the Baddour patent, channeling is eliminated by using baffles to promote radial mixing. Different designs are possible, but essentially two types of
baffles are used in combination—one a disk with diameter less than the inside diameter of the column, and the other a doughnut form having a hole in the center. They alternate down the length of the column with packing between them. As gas flows down the column, it first hits the disk baffle and is directed toward the column wall. As it continues to flow, it hits the doughnut baffle, which directs flow toward the center. This way, flow is continually alternating first toward the wall and then toward the center. Slits or holes can also be arranged around the periphery of the baffles to help promote radial mixing. The area of the hole in the doughnut baffle can be designed to hold pressure drop in the column to a minimum. Also, by keeping the area of the hole and that of the annular space around the disk baffle about the same, flow rate through the column can be made constant. Preventing channeling by using the baffles is by far the biggest single item in designing a successful large-scale system, Abcor says. But other parts of the system are important, too. In taking an engineering approach to chromatograph system design, the company has also developed injection, collection, and carrier gas recycle techniques. At present, the company says, it is carrying on licensing discussions with some analytical equipment manufacturers concerning use of its technology in small lab-scale units. For its own part, the company is primarily interested in adapting the technology to custom-engineered processes.
Thermal HDA economics emerge Details of the economics of thermal hydrodealkylation are beginning to emerge as commercial experience is gained with the HDA process of Hydrocarbon Research and Atlantic Refining. Dealkylation costs drop to 1.7 cents per gallon when plant size is extrapolated to 340,000 gallons per day of product benzene from a unit which is fed 10,000 barrels per stream day of toluene. On-site investment for a 10,000 barrel-per-day unit will total $5 million, Stanford Feigelman of Hydrocarbon Research told the American Petroleum Institute's division of refining last week in Houston, Tex. On-site investment for a unit to be charged with 1000 barrels per stream day of toluene will be $930,000. These figures are based on a Gulf Coast location; utilities at 0.53 cent per gallon of benzene; labor, overhead, and supervision at 0.13 cent per
gallon; maintenance, insurance, and taxes at 0.25 cent per gallon; interest and depreciation at 0.54 cent per gallon; and running royalty at 0.25 cent per gallon. The HDA unit's onstream efficiency is conservatively estimated at 350 days per year, Mr. Feigelman claims. A hypothetical HDA unit charging 2000 barrels per stream day of toluene will show an after-tax profitability (sometimes called a profitability index) of 26.4%. This unit is assumed to be fed toluene valued at 13 cents per gallon and to produce benzene that's sold for 23 cents per gallon. If toluene goes to 15 cents per gallon, the after-tax profitability drops to 16.8%. The hypothetical plant would cost $1.4 million and would be completed in a year. During the second year, the plant is assumed to run at 50% of capacity. Working capital at $1 million is charged in the second year, and an investment credit of 7% ($98,000) is taken after the second year. The third year the plant is assumed to run at 75% of capacity and at 100%? during the fourth and subsequent years of a 20-year life. After the sixth year, the royalty is fully paid.
Process bonds PVC to wire A continuous wire coating process which chemically bonds a plastic to metal has been developed by Anchor Post Products, Inc. The Baltimore, Md., company is using the process, called Permafused, to coat steel wire with polyvinyl chloride in the production of chain-link fencing. Because the coating is chemically bonded to the wire, it will not crack or slough off, even under severe bending at subfreezing temperatures. And since the coating is thinner than conventional extruded coatings, wire coated to gage contains more steel and thus is stronger. The process involves drawing a heated wire, which has been coated with a bonding agent, through a solid bed of PVC powder. Wire drawn to a desired gage passes through a cleaning machine, where grease and dirt are removed by bombarding the wire with minute metal particles. Cleaned wire passes through a liquid bonding bath, which deposits on the wire a thin film of a liquid bonding agent, or primer. This primer is an epoxy-acrylic-phenolic combination blended with other ingredients so that it takes quick heating without blistering. Primer-coated wire then enters an induction heating assembly, which cures the bonding agent and raises the temperature of the wire to a preMAY 16, 1966 C&EN
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