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BASF Cracker Makes Ethylene from Crude Oil

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Major components of the process are housed in this structure

26 A INDUSTRIAL AND ENGINEERING CHEMISTRY

German unit avoids reactor-regenerator dupli­cation, gives high yields of olefins and few by-products

M ORE DETAILS about the newer European processes for petrochemical olefin product ion continue to become available. Latest case in point is the fluidizcd bed crude oil cracking proc­ess developed by Badische Anilin- & Soda-Fabrik, Ludwigshafen, West Germany {C&EN, Nov. 9, 1959, p . 50). Badische has been running its unit nonstop for more than two years now, and has accumulated sufficient confidence in its design to begin talk­ing in more depth about it.

Significance of its new process, Badische points out, lies in its ability to handle a wide variety of crude and residual oils, its high yield of ethylene, propylene, and Cj's, and its operat ing ease. And as a result of the operat ing knowledge it has gained, Badische can increase capac­ity—i.e., one unit can process 200,000 metric tons per year of crude to 50,-000 tons of ethylene, 30,000 tons of propylene, and more than 12,000 tons of C^s. Like fluid coking, this BASF process is basically a daughter of the Winkler process, developed by Badische in the twenties and com­mercialized by Esso Research and Engineering in the U. S. Badische has some 40 years experience wi th fluidized bed roasting, best exempli­fied by its application to pyrites roast­ing ( I / E C , October 1958, p . 1500). I t differs from fluid coking in that it uses only one vessel for both crack­ing and regenerat ion and tha t it is aimed at making gaseous olefins in­stead of liquid products. T h u s it operates at considerably higher tem­peratures.

Many ideas and projects—big and little—can influence you, give you ideas for use in your work, and provide useful information for "current awareness." Each month I/EC's field editors and Washington staff select for detailed report and analysis, designed for easy reading, some of the most timely, in research and commercial development, process design, engineering, production, and marketing areas in the chemical process industries. We present also our comments on other interesting happenings of business and professional interest.

The Chemical World Today H o w It Works

In to a fluidized bed of petroleum coke at about 750° C. go steam, oxy­gen, and the crude oil. The steam and oxygen enter below the bed; the oil goes in about 2 feet above the grid fixed at the lower level of the bed.

In the lower par t of the bed, some of the coke is burned in the steam-oxygen stream to provide heat for the endothermic cracking reaction. The heated coke particles rise in the bed to the reaction zone, where they yield their heat. Circulation is so good that the temperature of the bed (within the limits of measurement) is uniform from top to bottom, Badische says.

All the oxygen is used up in the combustion process by the time the gas stream reaches the height where crude oil enters. Hence, the crack­ing reactions are not complicated by oxidation reactions, the company points out. Cracking time, con­trolled by the flow rate of steam plus oxygen, is more than one second—a long time for a cracking reaction. It is closely interrelated with cracking temperature which, at around 750° C , is lower than most cracking proc­esses. Changing the oxygen rate changes the cracking temperature .

Under these conditions—one sec­ond contact time at 720° to 750° C — the main cthylcne-forming fractions are "correctly cracked," as Badische puts it. Smaller molecules won't crack optimally, but in crude oil they are present only in small quantities. Some larger molecules undergo secondary reactions to yield soot and asphalts. These mostly stick to the coke particles in the bed, though, and are carried back down to the oxidiz­ing zone and burned off to supply some of the heat of reaction.

Contact time and bed temperature can be varied widely. Thus, crude oils from many different sources demand ing different conditions for opt imum cracking can be readily processed, BASF has found. T h e

These Are Typical Yields when 1 Ton of a Minas Crude Oi l Is Fed to the

BASF Cracker

(Using about 10,000 cu. ft. of Oxygen per ton)

1,1).

Ethylene 507 Propylene 276 C4's 132 Hydrogen 18 Methane 265 Ethane 99 Propane 15 Acetylene 2

co2 871

CO 220 Light oil 309 Aromatic fraction 88 Coke 99

unit can even handle oil fractions as light as straight naphthas and as heavy as the heaviest residual oils.

After Cracking

Cracked gases, containing some soot, tars, oils and other contaminants, enter a cyclone directly after leav­ing the cracking zone. There any entrained coke particles arc separated and returned to the coke bed. Next, the gases flow to a quencher, where they are cooled to about 300 e C. as they flow through a spray of recir­

culated "column sump oil." The quenching also removes most of the residual carbon dust and asphaltic constituents, so that the gases are rela­tively clean when they leave.

The 300° C. gas stream goes next to a fractionating column with a head temperature maintained at about 100° C. Oils boiling above 100° C. are condensed and fraction­ated, yielding a high-boiling cut (column sump oil) taken from the bottom of the column and a highly aromatic cut taken from about the middle.

T h e column sump oil not used in the quencher is recycled directly back into the coke bed, sticks to the coke particles, is carried down into the oxidation area, and burned. The aromatic fraction, rich in naphthalene, is an end product.

Oils boiling below 100° C. go over­head with the gases, arc condensed with the steam in a cooler, and arc separated as a light oil fraction, part of which goes back to the top of the fractionating column, the excess being drawn off as an end product .

Uncondensed gases leaving the cooler contain hydrogen, carbon monoxide and dioxide, methane,

Simplified flow d iagram shows basic steps in process

VOL. 53, NO. 11 · NOVEMBER 1961 2 7 A

ORTHO-ANISALDEHYDE... which you may also know as O-Mcthoxy Benzaldehyde... is one of those little-known, little-discussed chemicals which on first look appears to have very limited application. However, its unusually promising physical properties seem to oiler exciting possibilities—especially in organic synthesis or as a pharmaceutical intermediate. ANSUL is in a position to supply it in quantities at an extremely reasonable price. We'd like to work with you in developing additional use information. Write us for samples and complete technical information. ANSUL CHEMICAL COMPANY, MARINETTE, WISCONSIN.

PHYSICAL PROPERTIES

ORTHO-ANISALDEHYDE MOLECULAR WEIGHT... 136.14 BOILING POINT (at 760 mm Hg).. .238°C MELTING POINTS*...(1) 38-39"C

(2) 3"C SPECIFIC GRAVITY (liquid) 25° 126".. .1.1274 SPECIFIC GRAVITY (solid) 25°/25°.. . 1.258 REFRACTIVE INDEX η 20°/D.. .1.5608 ODOR. . .Burned, slightly phenolic SOLUBILITY in H20-Slightly soluble APPEARANCE... White to light tan solid

*Exists in two crystalline forms

ethylene, ethane, a trace of acetylene, propylene, propane, and the C4 fraction. Processing of this stream is conventional—CO2 absorption fol­lowed by low temperature fractiona­tion to give a synthesis gas (hydro­gen, C O , and methane) plus the desired ethylene, propylene, and Cj's as separated products.

Engineering Advantages

In this crude oil cracker, BASF has been able to keep undesirable and unusable by-products to a min imum. All the soot and tars, for example, (which don ' t crack to ethylene and are a nuisance besides) are recycled to the fluidized coke bed and burned to provide some of the heat needed lor cracking. With the two-zone bed, it dispenses with a regenerator.

T h e coke particles in the bed are 8 0 % between 0.1 and 0.5 m m . in diameter and can be modified by catalysts if desired. Grains below 0.1 m m . don ' t remain in the bed. Since there are no small coke par­ticles, Badische has been able to de­sign its cyclone with somewhat lower efficiency and a correspondingly better aerodynamic pat tern to pre­vent coking of solid particles.

Column sump oil is used as quench­ing fluid. It is injected in coarse sprays rather than a mist, so that it can penetrate the gas stream enough to wash and cool it. This in turn

eases greatly the problem of nozzle pluggage.

Burning in the cracker does lead to a dilution of the final gas stream with CO2, but this can be easily absorbed. The extra cost for this, Badische points out, is less than a second generator would be.

T h e final by-products—synthesis gas, light oil, naphthalene-rich oil, and a small amount of petroleum coke—can all be used to economic advantage.

Other European Crude Oil Crackers

BASF is not the only German com­pany to turn to crude oil itself—in addit ion to various oil fractions—as a source for its light olefins. Hoechst at Frankfurt has a pebble cracker, called the Hoechs tcoker ,andErdoe lChemie at Dormagen (jointly held by Ba­yer and British Petroleum) uses the sand cracker developed by Lurgi, one of the largest Ge rman engineering firms, in collaboration with Ruhrgas and Bayer. Both of these two proc­esses use a moving bed of carefully sized solids (sand and pebbles) to carry the heat supply to the cracking zone, but they both use two genera­tors— heating and cleaning of soot in one and cracking in the other. Fur­ther, Badische says, its process gives a very high yield of C2-C4 olefins per ton of crude, and fewer and more useful by-products.

Wet Chemistry Enriches Iron Ore

For French deposits, physical treatment costs too much

INORGANIC CHEMISTRY is by no means dead, despite all the at tention organic gets these days. In the iron ore area of France 's Lorraine basin, for example, chemists are hot on the trail of an inorganic chemical method of enriching siliceous ores. If success­ful, the technique would make avail­able for economic exploitation large deposits of such ores. S tandard physical methods—e.g., flotation or magnetic roasting and separat ion— are not economical.

T h e new route is now going into semiworks trials at Société des

Aciéries de Pompey, at Pompcy in northeastern France. According to the company 's scientific director, Dr . Eugene Herzog, the process not only increases the iron content of the ore but also renders three fourths of it magnetic , whereas it is all nonmag­netic when taken from the mine.

T h e approach : Dr . Herzog's process, still very tentative, consists basically of boiling for a half hour or so the crushed iron ore (containing abou t 3 0 % Fe) in 40 or 5 0 % caustic soda. T h e caustic is decanted, taking with it 50 to 8 0 % of the silica, all the alumina, 8 0 % of the phos­phates, and only 2 to 3 % of the iron. Remain ing behind are a t least 9 7 % of the iron, the calcium, and the magnesium, plus some 10 to 2 0 % of

Circ le No. 18 on Readers' Serv ice Card

2 8 A INDUSTRIAL A N D ENGINEERING CHEMISTRY

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