I S D l - S T R I A L A-YD El-GIJTEERISGCHEMISTRY
AIlqUit. -- 1925
Catalyst Testing-The
'is9
Basis of New Industries'
By D. H. Killeffer, Associate Editor I!) E. 24In St.,
NEW
YORK, N.Y.
I T T H E T I C ammonia has not been America's forte, but there are many indications that leadership in this field, as in many others, may be acquired by the cooperation of American brains, American capital, and Ameriran technical skill. The latest entrant into this field is Lazote, Incorporated, an organization formed by E. I. du Pont de A-emours and Company, together with other interests, which has acquired the North American patent rights to the Claude process for the ammonia synthesis, and will develop it under American conditions. Lazote, Incorporated, has a 25-ton per day plant now under construction a t Charleston, K. 1-a.
testing of the same or ten different catalysts a t once under :I variety of conditions of pressure, temperature, and gas flow. The plant is particularly adapted to carry out catalyst testing for ammonia synthesis, but it may easily be converted to thc testing of catalysts for other gas reactions. The accompanying flow' sheet of the catalyst-testing plant, (Figure 1) will make clear its method of operation. The principles employed in its construction and operation follow those developed in catalyst testing a t the Fixed Xitrogen Research Laboratory. The Lazote staff expressed cordial appreciation of the generous assistance rendered by the laboratory in Washington.
Purpose of Plant
Raw Materials
In order to study the various catalytic problems which are peculiar to the synthetic ammonia process, Lazote has installed a catalyst laboratory a t the Experimental Station of E. I. du Pont de Xemours and Company a t Wilniington, Del., which embodies many interesting features, and is, in many respects, unique in its field. A principal part of this laboratory is the high-pressure catalyst-testing plant, the purpose of which is to test a wide variety of catalysts for the reaction between nitrogen and hydrogen under a diversity of conditions. I t is occupied principally in determining the actiyity and longevity of these materials under variations of conditions which parallel as closely as possible those met in commercial operation. The chief operating variables which this installation is equipped to study are temperature, pressure, gas flow, and purity of the gas mixture. It is possible to use reaction temperatures up to 800" C., and the pressure may be varied from atmospheric pressure to 1000 atmospheres or above. The present installation permits gas flows as high as 2,000,000 space velocity (space velocity being defined as unit volumes of gas, measured a t one atmosphere pressure
The mixed hydrogen and nitrogen are supplied through a train of apparatus shown in Figure 2. The first operation is the decomposition of ammonia, which gives a t once a nitrogen-hydrogen mixture in the ratio of 1 :3. Liquid ammonia is supplied from three cylinders connected to a header in such a way that any or all of then1 may be brought into the systein as desired and for convenience in replacement of empty cylinders. From the cylinders the liquid is conducted to a steam-heated expansion chamber consisting of a 76-nllll. (3-inch) iron pipe surrounded by a steam jacket. Thi. ia done to prevent cooling the lines to such an extent that liquid ammonia instead of gaseous ammonia would pas3 through the expansion valve. This expanded ammonia is then passed through an orifice flommeter to the ammonia cracker.
S
Ammonia Decomposition
The ammonia cracker consists of three concentric iron cylinders connected in such a way that gas passing tliroiigli them must pass longitudinally through each in turn. The
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HIGH P e m m
smeaqc
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J AMOSPHLLIC PPE55UeLI
Figure 1-Flow
and 0" C., passing through unit volume of catalyst per hour). Special arrangements are made for the introduction into the synthesis system of the gaseous impurities most often met in practice, such as carbon monoxide and methane. The installation is equipped with ten catalyst furnaces, which may be operated either in parallel or in series, thus permitting the Received June 3, 1926
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Sheet
whole is carefully jasketed to reduce radiation losses and id heated by a coiled nichrome wire in the center of the conibination. The ammonia is first passed up through the outer cylinder to preheat it, then downward through the cracking catalyst, and finally upward past the heated nichrome wire in the center cylinder. The cracking cata1y.t consists of porous iron. The temperature of the iron catalyst
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
is about 600" C , , arrd tliat of t,he nicliromc wire heater over which the gas pasaes out, about 101H)" C. In passing through this cracker t.hc aminonia is a t approximately atmospheric grersurc, and is decomposed alniost cntircly. The gases passing out of t,he cracker contain lesx tlran I pw cent of anm~o~iia, and flow next tlirnugli a water scruliber, where tiria residual animonia is removed.
Pieure I-Lon-Rfesnure P ~ r i I i e ~ f Train i ~ n Showing Ammonia Cracker. Water Scrubber, and Deoxidizer
The gas is then passed through a deoxidizer, which is similar to the ammonia cracker in all respects except that the flow of gas through it is reversed and iron is replaced onehalf by ropper and the other half by nickel. The copper is iir the. form of turnings; the nickel is in the form of a methanation catalyst. The materials in the deoxidizer convert any free oxygcn in the gases to water; the nickel catalyst serves to meblianate any carbon monoxide or carbon dioxide that might be present..
Vol. li, KO. 8
vaciiiim alarm is placed in the line from the gas holders to this compressor to warn the operator in cwe the supply line, is not clear. The high-pressure storage consists of sixteeii gas cylinders, each of 28.3 liters (1 cubic foot) vapacity. These are arranged on four headers of four cylinders each, which makes it possible to uae thein in blocks of four. This high-pressure storage supplies gas at 3(H) atmospheres to thr hypr-pressure system. (The term "liyper-pressure" was first used by Claude to describe the pressure iindcr which his synthesis operates.) This hyper-pressure system makes it possible to compress the gas to 1000 atmo..;plieresand ~IXJTY:. The method of producing these high pressures co rimning gas a t 301) atmospheres into a forged steel and then pumping water into the bottom of the cylinder until tlie desired pressure in obtained. Maintenance of pressnrc during witlidrawal of the hyper-comprrssed gas is cariirrl out in the same way. Two compression cyliuders are pr,!vided so that they may be used alternately, thus permittiii(: regulation of the gas pressure and contintlous flow of tlie Iiyjrw-compressed gas. They are mounted on a solid stccl Iilock in which arc machined channels for watrr flow and i n Xvliich valvcs are mounted so that water frnin the Iiydrairlic system map be pumped into either one, arrd by which eitlicr cylinder or the hydraulic pump itself may be connected to the drain. Connections are made to tha tops of t,tiese cyliriders KJ that either or b0t.h may he coniiectrd a t will to tlie highi)rcssure storage or to the hyper-pressure storage. The hyper-prcssure storage consists of two similar
