I&EC REPORTS & COMMENTS
Austrians Design New NHaConverter Indirect h a t cxchangc and close l e m j n a hac conhol promise h i g h ammonia viddsfcr unit of reactor volume
Continuing pressure on profit margins means that even workhorse processes of long standing get continuing engineering attention. Latest case in point is ammonia synthesis, with which the chemical industry has more than 40 years experience. An Austrian company by applying computer technique? now has come up with a new reactor design promising longer catalyst life and a higher ammonia output per unit volume. 6stemichische Stickstoffwerke, Linz, Austria, feels that each of the c u m t reactor designs has at least one significant disadvantage. Example: Some need too much costly heat exchange capacity; others have hot spots leading to reduced catalyst life; and some dilute the reaction gases to maintain temperature conh 1 . In its new design, the Austrian company thinks it has avoided all these problems. The new design divides the reactor into three catalyst zones separated by heat exchange zones. Heat exchange is indirect to avoid dilution of the gas stream leaving the reactor. Fccd gas, flowing countercurrent to the reaction gas, cools the gas between the catalyst zones, is itself heated to reaction temperature on its way to the first catalyst zone. Cold feed gas is also added aft& the first heat exchange zone. Since optimum reaction conditions for ammonia synthesis dictate that reaction temperature go down as ammonia content goes up, this countercurrent system means that, with the proper design, reaction gas temperature can follow closely the
optimum conditions for each ammonia content. And this is where the computer entered the picture-it calculates the optimum dimensions of each catalyst section, the necessary heat exchange capacity between them, and the amount of cold feed gas to add as supplementary temperature control medium.
Ostcwcic&che Stickstofwuke A.-G.’s MW ahlmonio converter. Fccd gas enters converter at top lcff, J%WS &wn fhc oursi& of the rcactor to thc boftom heat exchange WOMwherc it cwls the d i n g reaction gas and is ilssrf heated. It thenfiws to on annular sIof in the middle, upward to the middle heat exchange zone, where it is furthn healed whilc cooling the reaction gas Itacing the recod catolysf mm. Liknvisr IO the third hear exchange WOMand thence to the fop of the reackw and into theJird rcnction ZOOM, wherc it bccmncr the reaction gas. Cold gascntersaf the bottom and mixer with fced gas after fhe latkr has passrd through fhc fist k o f exchange wnt
The result, OSAG says, is a converter that, according to calculations, will yield 156 tons of ammonia per day with a maximum catalyst temperature of 525’ C. Converter dimensions: about 40 feet high, and 31.5 inches in inside diameter. Other conditions: 2.47 million cubic feet of feed gas per hour at 315 atm. Feed gas composition: 1.9 volume % ammonia, 4.0% argon, 4.0% methane, 4 p.p.m. carbon monoxide, with the rest nitrogen and hydrogen at a mole ratio of one to three. Other calculations show, OSAG says, that three catalyst zones are best. Adding more means that too much space in the converter is taken up by mechanical catalyst supports, thus reducing the production per unit volume .of converter. Fewer means that the temperature profile strays too far from the optimum. Osterreichische Stickstoffwerke has patented the new converter in most of the industrialized countries of the world. The company figures the design will lead to a “very economical” plant, particularly where it is necessary to get a high production rate per unit volume of pressure vessel. The relatively low maximum temperature (525” C.)also will lead to a considerably longer catalyst life than in many converters, OSAG adds.
Rare EaHh Catalysts Boom Rare earth catalysts are about to make the big jump from R & D to commercial application. Quite a stir was created by a recent announcement -that Socony Mohil is about to use their Durabead 5 cracking catalyst on a large scale. Why the stir? Socony is said to he VOL 54
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I&EC REPORTS
remaking the cata1)st and now using cerium as the active cracking agent. Some 2 million pounds per year of cerium might end up in this application. Another source describes the 2 million figure as conservative. For Socony’s part-they aren‘t saying, except that large scale commercial tests indicate that Durabead 5 will produce from 5 to lOYc more gasoline from a barrel of oil than any catalyst now in commercial use. Socony considers the application of Durabead 5 to catalytic cracking a breakthrough in petroleum refining. Catalytic activity has been associated with ~ a r i o u s rare earth elements and compounds since the late 19th century. Cerium and mixtures of rare earth elements were among the first investigated. But it wasn‘t until after If’orld \Var I1 that rare earth elements became available in any quantity suitable for commercial usage. \.\‘ith increased use of atomic piles and expanding titanium production, rare earth elements became more abundant. The ion exchange technology of Spcdding and Powell at Iowa State College provided the key for obtaining rare earth elements in their pure form. Systematic catalytic studies ha\ e shown that some of the rare earths show definite indications of high selectivity as compared with the action of mixed rare earth catalysts or promoters. They have been shown to be effective in hydrogenation and dehydrogenation, cracking and conversion, polymerization, oxidation reactions, hydration and dehydration, halogenation, and, more recently, as effective tracers in cancer research. An I&EC Report on rare earths in December 1954 suggested that the development of an oversupply of rare earths and the stimulus that always accompanies such a situation could be expected to shift rare earth research into high gear. And 12
indeed it did-but commercial application did not keep pace. Apparantly our chemist and chemical engineering counterparts in East Germany and Russia were able to bridge the gap quicker than we. An I&EC April feature points out what has been done with rhenium catalysts and what some of the more interesting potential applications might be. An equally interesting potential use turned up during the Symposium on Photochemistry in Industrial iipplication at the recent ACS meeting in \Vashington. R . J. Marcus suggested that a light absorber can be used to photocatalyze a particular reaction. The example he gave was the oxidation of xylene to form phthalic acid. The ceric ion was the light absorber in this case. The photocatalytic agent also produced an atom of oxygen which make this particular reaction go. A rare earth catalyst could do the job Socony claims for their Durahead 5. Conjecture among catalyst manufacturers is that the catalyst is a microsieve with added rare earths. It is thought that back-added fines replace chromium with about 2% cerium. Increase in gasoline yield would be due to better combustibility of the gas oil feed. An added credit would be due to the better regenerability of the catalyst. There would be a significant reduction in fines formation and a slightly lower loss in actilrity with each regeneration. Socony makes the catalyst themselves. Cerium is obtained probably as the chloride from Lindsay Chemical, a Division of American Potash 8: Chemical Corp., located in Chicago. The current supply of rare earths as by-products from atomic piles and titanium production can hardly be expected to satisfy demand once the ball gets rolling. What other sources are there? Perhaps the quiet research in minerals extraction
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
from sea water and the sandy beaches of North and South Carolina will provide the answer. But whatever the source, this much is certainrare earths are destined to play a major role in chemicals processing and not in the too distant future.
CSto C ~ N-Paraffins Z by IsoSiv After five years of development, Linde’s IsoSiv process has gained commercial status. T h e first commercial IsoSiv installation produces normal paraffins from pentane to dodecane at the South Hampton Co. plant at Silsbee, Tex., in a 1000 barrel-per-day charge capacity unit. A molecular sieve adsorption process, IsoSiv originally was developed to improve naphtha feed stocks by removing normal paraffins. It is a pressure-swing adsorption process which requires pressures and temperatures within the range of those used in most refineries. T h e molecular sieves used in the process have pores of about 5 A. in effective diameter which admit normal paraffins but exclude other isometric and cyclic hydrocarbons. Behind the interest in the process to recover n-paraffins is increased jet fuels, industrial solvents, raw materials for “biologically soft” de-
Cycling of two sieve beds through adsorpion and desorption steps using valves actuated by an automatic sequence control permits continuous operation. Linde has made process improvements which haoe ended the need f o r a third bed, used when frequent burnoff of the adsorbent was necessary
,. * *
tergents, and cracking stocks to make olefins. Other smaller uses include making chlorinated petroleum waxes, lubricants, plasticizers, flame-proofing agents, and extracting vegetable oils. I n the South Hampton plant several different charge stocks have been processed. One example is a 350° F. end point stock which contains 27.7 liquid volume % C4 to. CI3 n-paraffins. Normal pentane and higher n-paraffins are recovered as the product containing 95.8% liquid. T h e nonnormal stream contains less than 0.1 liquid volume 7. n-pentane and no detectable trace of higher n-paraffins. Linde's W, F. Avery and M. N. Y. Lee prepared cost estimates for a 1000 barrel-per-day unit for a paper given at the April National Petroleum Refiners Association Meeting. They based cost estimates on a feed stock with a 360° F. end point and containing about 28 liquid volume 7.n-paraffins. Investment costs for a 1000 barrel-per-day unit built on the gulf coast and feeding a 360" F. end point stock containing 28 liquid volume yo n-paraffins looks like this: Major process equipment Other indirect materials and adsorbent Total direct materials Direct labor Indirect labor and materials Contractors' charges Total labor and indirect costs" Grand tota I
$ 71,000
113,000 $184,000 $38,000 28,000 45,000 $111.000
$295,000
Estimated as a function of process equipment costs. a
T h e authors caution that investment cost is estimated a n d not a n actual cost from competitive bidding. Actual investment cost will vary depending on individual circumstances. Operating costs also will vary significantly because of the large part that fixed charges have
in these costs. Based on' the charge, operating costs are 25.2 cents per barrel. Based on n-paraffin products, operating costs are 91.7 cents per barrel. Estimated Operating Costs $/Calendar Day
Utilities and adsorbent Operating labor" Fixed charges Total
53 34
165
$252;
Q Lower in a fully integrated unit. process license fee.
b Excluding
U. S. Industry in the 'Common Market I n recent years some European governments have shown an eagerness to attract foreign investments. Many nations have encouraged industrial and commercial firms from outside to build plants and set up operations within their borders. The rise of the European Economic Community (Common Market) has already played a strong role in convincing U. s. chemical makers to send capital into the EEC countries, establishing partially or wholly owned subsidiary companies and building plants behind the tariff barriers. Lower wage rates and reduced operating costs are added inducement. I n the March 1962 issue (p. 34) I&EC began a series of articles on costs of building plants outside the United States. Over the years between 700 and 800 companies dealing in chemicals in Western Europe have become partly or completely U. S. controlled. About 500 of these are in the six Common Market countries and the United Kingdom. Since 1958, over 600 U. S. enterprises have been set up in European Common Market countries (I&EC March 1962, Trends). T h e most interesting investments for American companies seem to be in chemicals, nonelectrical machinery, electronics, transportation equip-
ment, precision instruments, and metallurgy. France leads with 145 widely diversified industries. West Germany has now taken the lead in total number of U. S. controlled chemical firms. Great Britain, because of the common language and similar ways of doing business, attracted the most American capital over the years. Recently, however, the Common Market countries have been receiving the bigger share of U. S. investments. Rumblings of concern are beginning to be heard from European manufacturers as they see Americanowned companies and plants moving in on their domestic markets. European chemical makers may soon be putting a 'good bit of pressure on some of their governments to halt or at least slow the rate of U. S. entry into their industries. A cutback in the incentives offered to foreign investors may be the result. A special case is in the Ruhr region where government agencies are promoting new investment by industrial firms regardless of nationality. The situation there and in other European coal mining centers is similar to the economic slump suffered in U. S. coal areas of West Virginia, Kentucky, and Pennsylvania. Inroads made by oil and gas have hurt the coal industry, and governments are anxious to bring in new industry to take up the slack. I&EC International Edition in November 1961 (p. 12A) told of efforts by the West German state of North Rhine Westphalia. At that time the North Rhine-Westphalian Industrial Development Company (IDC) had just been formed in Dusseldorf. Judging from recent announcements, the state-owned agency has rolled into high gear in its program to persuade foreign and domestic firms to build plants and start operations in North RhSne Westphalia. I D C reports that 250 industrial sites in the Ruhr area ,are ready for establishing new plants. VOL. 5 4
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