the feed and makeup hydrogen are preheated together and quenched with a part of the recycle gas, Fran cois Audibert of IFP explains. The stream is then passed through a fixedbed reactor where the rest of the re cycle gas is used as a quench. Efflu ent from the reactor heats the feed/ hydrogen stream and is sent to a highpressure separator. Gas from the sep arator goes to purge or to the recycle gas compressor. The heavier liquid hydrocarbon product is separated into various products by distillation. Catalysts. IFP has developed pro prietary catalysts for its process, as have other process developers. The catalysts all aim at giving long onstream times, high yields of quality products, and optimum costs, but they encounter substantial problems. Be sides having a high viscosity, which causes problems in handling, resids contain high amounts of carbon, met als (nickel and vanadium), nitrogen, and sulfur, which tend to poison cata lysts. After pilot plant runs of several thousand hours, IFP engineers found that vanadium compounds deposit on catalyst particles as a layer 20 microns thick. Vanadium diffuses into parti cles up to 650 microns, and nickel even farther. During regeneration, sulfur is oxidized and metallic sulfates form which combine with metallic ox ides, mostly vanadium, to cause changes in the catalyst texture. IFP engineers have used detailed catalyst studies to achieve required activities and regeneration properties in poten tial adaptations of the process. Partial oxidation. Making hydro gen by partial oxidation of the residue from the Η-Oil process can be attrac tive when the residue is small relative to refinery throughput and its incre mental value is low, J. E. Papso of Hydrocarbon Research, Inc., says. The situations where this use of the residue as a source of hydrogen is profitable are those where disposal of heavy pitches is a problem and where natural gas is expensive. In most hydroprocessing the hydro gen comes from steam reforming of methane or as a coproduct from other operations such as catalytic reforming of naphthenes. Usually, if hydrogen is made for upgrading resids in a re finery, additional hydrogen is also made for processing light fuel prod ucts to improve their qualities. Mr. Papso and A. R. Johnson, R. F. Hippeli, and G. Nongbri of HRI have worked out an example illustrating the integration of the Η-Oil process in two refinery schemes, each with feed of 25,000 barrels per day of vacuum dis tillation bottoms. They estimate that partial oxidation of the Η-Oil pitch (fraction boiling above 1050° F.) to
Lunar wheel research spawns earth version Glass-fiber-reinforced plastic wheels with a radically new open cone shape have been developed for off-the-road vehicles by Grumman Aerospace Corp. at its Bethpage, N.Y., laboratory. Dubbed the "Markow wheel" after its developer, Grumman engineer Edward G. Markow, the tire's wide tread gives it maximum contact with sand, mud, or swampy ground, fitting it for use on jeeps, beach buggies, tractors, snowmobiles, and amphibious sports vehicles. An adaptation of wheels de signed originally for a lunar roving vehicle, the noninflated wheel bears a 3 /4-inch-thick tread coating of 30-durometer polyurethane rubber, cured in
make hydrogen would require a $4.2 million investment more than the orig inal $25 million investment if hydro gen were made by steam reforming of gas. Operating costs are $4636 more for each on-stream day. In each case, 38 million cu. ft. per day of hydrogen are made for the Η-Oil unit and another 27 million cu. ft. for other uses in the refinery. Slightly more sulfur is produced using partial oxidation, since sulfur in the pitch is recovered in the auxiliary sul fur plant along with sulfur from hy drogen sulfide from the Η-Oil unit. Break-even values between methane and pitch depend on oxygen value. Flexibility. Growing use of hydrocracking by refiners adds emphasis to economic comparisons of the process with catalytic reforming and fluid cat alytic cracking. Studies of the eco nomics of various refinery situations by engineers at Chevron Research and at M. W. Kellogg lead to about the same conclusion: a need for flexibil ity to meet increased demands for jet engine fuels and to meet changes in gasoline components if lead alkyls are reduced or eliminated.
place, bonded to a 7ie-inch-thick shell made from epoxy laminating resin re inforced with glass fiber. On the lunar vehicle prototype—beaten out in com petition by a Boeing design—titanium V-cleats were bolted on a similar coni cal base instead of rubber treads. The Markow wheel has been tested successfully on a jeep over sand and mud, and will now be tested on recre ational vehicles. Mr. Markow hopes to finish tests and start marketing the wheel in about a year. Grumman is also studying the equipping of Markow-wheeled vehicles with a TV cam era and remote-control system for unmanned duties.
Complexities in such economic com parisons develop from the specific uses possible for products from each of the processes. Hydrocracking makes products high in saturated par affins. Reforming makes highly aro matic products. Catalytic cracking makes highly olefinic products. Economic studies by M. S. Michaelian, R. J. Shlegeris, and N. J. Haritatos of Chevron Research in cluded tangible variables such as type of feedstock, octane level of gasoline, and severity of operation. They also included intangibles such as possible future marketing objectives that would lead to greater jet-fuel produc tion and to production of unleaded gasolines. Optimum investment prof itability, according to the Chevron en gineers, involves low hydrocracker se verity coupled with reforming. According to J. R. Murphy, M. R. Smith, and C. H. Viens of Kellogg, who compared catalytic cracking with hydrocracking, catalytic cracking with the newer zeolite catalysts is favored when the primary product is gasoline. If jet fuel or middle distillates are the prime targets, hydrocracking is best. MAY 25, 1970 C&EN 45
