THE TECHNOLOGY OF AMMONIA PRODUCTION AT THE LEUNA WORKS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600350118-2
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 8
• Document Creation Date: December 22, 2016
• Document Release Date: August 19, 2011
• Sequence Number: 118
• Publication Date: October 3, 1950
• Content Type: REPORT

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In the synthesis of ammonia, a mixture of hydrogen and nitrogen is cata-
lyzed under high pressure, part of the gases combining to. form ammonia. The
hydro;,...i is made from water gas, the nitrogen from generator gas. Both are
produced by the gasification of solid fuels such as bituminous coke, or coke
derived from the distillation of lignite, or from dried lignite.
Since the resumption of production at the Leuna Works in 1945, lignite
coke has been used in production of the 'synthesis gas instead of bituminous
coke, because the latter originates in the Western Zone e.d is now difficult
to obtain. This has caused a change in the composition df the gases, which
is shown in +'-t following.table:
COUNTRY Soviet Zone Germany
SUBJECT Scientific - Chemistry
Production of Ammonia
HOW
PUBLIS~ED Monthly periodical
WHERE
PUBLISHED Berlin
DATE
PUBLISHED Apr 1950
LANGUAGE German
TKIS DOCYnNR C0$tAJ00 uroRUTION QnmIS 7111 NATIONAL WORM
Or Till UNITED STUNS ?17110 7O1 NUNOOS OF Ur1011A011 ACT $0
0. 1. .21 A110 NS.AS ANU011. 10 TOMOISINOS OR 100 ONSNSAtl011
Or ITS C011Ti1171 10 YT 11A1111NS TO AN 00ASTO0111110 r11S011 IS PO0-
UISlTlO.ST LAW. U1,6000CIO4 or T919 room IS ro00111T10.
SOURCE Chemische Technik, Vol II,No 4, 1950.
Typt bf
Composition in percent of volume
Gr
of
ams
S per
Cu
m of gas
Gas
CO
COZ
CMHI
HMS
cu
m.:of N
_ pe
r..ton N
Bit
uminous
Coke
Water gas 4
9.0 38.
0
6.0
6.3
0.5
0.2
3.0
2,862
Generator gas
5.0 30.
0
57.0
7.0
6.5
0.3
4.3
1,343
Mixture
2.13:1 3
5.0 35.
4
22.3
6.5
0.23
3.4
4,205
Water gas
41.0 32.
Lig
9,
nite Dis
1.2
tillatio
23.1
n Coke
1.5
1.2
17.2
3,235
Generator gas
9.0 27.
0 1
54.0
9.1
0.5
0.5
7.2
1,662
Mixture
1.95:1
30.2 30.
3
19.1
18.3
1.2
0.97
De !!ac_. Jho . Dr Paul Koppe
CLASSIFICATION CONFIDENTIALCUNFI!1 NTLAL
CENTRAL INTELLIGENCE AGENCY REPORT
INFORMATION FROM
FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO.
DATE OF
INFORMATION
DATE DIST. 3 04 1950
NO. OF PAGES a
SUPPLEMENT TO
REPORT NO.
THIS IS UNEVALUATED INFORMATION
THE TECHNOLOGY OF AMMONIA PRODUCTION AT THE LSJN/L WORKS
CLASSIFICATION co1FIDZEIAL
STATE MAw I X; MRS DISTRIBUTION
ARMY AIR 1XI FBI
CONFIRNTIAL
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Water gas and generator gas are mixed in sucha proportion that the gas
mixture will supply, after further reaction and cleaning stages, a very pure
mixture suitable for ammonia synthesis, consisting of about 75 percent hydro-
gen and 25 percent nitrogen. As the analysis shows, the gas mixture obtained
from the lignite contains less hydrogen and less carbon monoxide, but more car-
bon dioxide and more methane, and a great deal more hydrogen sulfide than the
gas obtained from bituminous coke. The high C02 content of the mixture is a
disadvantage for the conversion of CO, because the carbon dioxide already pres-
ent in the original gas requires an additional high excess of stern in this
equilibrium reaction. The gases made from lignite also contain small amounts
of compounds which form resins and other organic impurities. The amounts of
these impurities are only a few milligrams per cubic meter of gas, but they
are catalyst poisons and very difficult to remove completely.
The changes in composition of the gas have had an effect on the process-
ing of the gas mixture. Because the content of hydrogen and carbon monoxide
is now lower, the amaunt of crude gas required for the produc*ion,of one ton
of ammonia nitrogen is much greater than it was before, a fact which has, of
cburse? affected the capacity of the plant very unfavorably.
Both components of the gas mixture are made by continuous ge.sification
of lignite distillation coke in Winkler generators, at temperatures between
900 and 10000 C. The heat of the gas is 3ed for steam generation in a heat
exchanger.
The sulfur is then removed. Because the sulfur content is very high,
this is done in two stages, a so-celled "coarse sulfur removal" by means of
the Alkazid process, and then a "fine sulfur removal" by means of active car-
bon. Application of both processes yields very pure elemental sulfur.
Most of the carbon monoxide is then removed by conversion. it is con-
verted into carbon dioxide and hydrogen by means of steam at 450 to 5000C in
presence of a catalyst. A remainder of 4 to 5 percent of carbon monoxide and
30 percent of carbon dioxide are left.
The first three stages of five-stage compressors then put the gas under a
pressure of 26 to 27 atmospheres. After the third compression stage, it is
washed with water to remove the carbon dioxide, leaving a residual content of
1 or 2 percent. The fourth and fifth stages then compress the gas to about 250
atmospheres.
The compressed mixture is washed with an ammon.i,acal copper solution and
then washed a second time with an aqueous ammonia solution to remove the last
residua of carbon monoxide and dioxide. The copper solution is regenerated and
used again. The gas fo: the synthesis is finally cleaned catalytically to re-
The Winkler Generator
Recently, an innovation has been introduced at Leuna, in the form of a
Winkler generator which has no grate and no stirring arm. The cylindrical
shaft is closed at the bottom by a slender cone. The material for gasifica-
tion is injected into the shaft about 2 meters above the point of the cone by
mena of nozzles. Fuel feed is the same as in the old-type generators. The
fuel parts are circulated much more efficiently than in the grate-type genera-
tors, forming a fountain which reaches half-way up the generator. The contact
time is therefore longer. Furthermore, the new construction is slightly supe-
rior in respect to consumption figures and the quality of the gas, and it does
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CoI CONFIDENTIAL
away precisely with those parts which are most susceptible to breakdowns,
namely the grate and the agitation mechanism. New Winkler generators, there-
fore, will be built only in this version.
Oxygen and Nitrogen Production
The oxygen required for the production of water gas from lignite distilla-
tion coke is made by liquefaction and fractionation of air by the Linde-Fraenkl
process. The process is shown in the schematic diagram below;
Os)
Air N ? (O. _ 1 ' ) _
200 otn,'(youge)~---- -
0.3
atm. (yn,
Mfev!
The process uses cold acci;.aulators.opprating alternately in place of the
tubular cold exchangers used previously. The cold exchangers are 4 to 5 meters
high, about one meter in diameter, and contain a cold-storing mass of maximum
surface. They are alternately charged with the air to be fractionated,'and its
fractionation products, nitrogen and oxygen. Valves operated by compressed air
serve for regulating or reversing the direction of flow. These values are at-
tached to the top of the vessels. The bottom of the vessel is fitted with auto-
matic check valves. Two accumulators each operate together, one pair serving
for cold exchange between air and the oxygen which is produced, the other pair
for cold exchange between air and nitrogen.
The cold-accumulators make pre-cleaning of the air which is to be frac-
tionated unnecessary. Water vapo:: nd carbon dioxide from the air condense
on the cold hurdles during passage through the accumulator, and are carried
off again when the accumulators are filled with oxygen and nitrogen.
OOnrIUMIAL
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1LIGEN
ATION
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iia, a
.t of t
is, the
)f soli
product
In of
Lnates
change
le:
in per
ainous
5.0
T.0
1.2
I.0
The reversal occurs every 3 minutes. The timing is arranged in such a
manner that a reversal takes place every 90 seconds.
The refrigeration required for covering losses is provided by decom-.??
pression of about 5 to 10 percent of the air, which is under a pressure of
about 200 atmoshperes, and by decompression of part of the gaseous nitrogen
in a decompression turbine.
The Linde-Fraenkl process effects a great saving in energy and thus
lowers the production costs of oxygen considerably. Originally, however,
this process could produce, in addition to the 98 to 99 percent pure oxy-
gen, only very impure nitrogen which contained 3 to 4 percent oxygen. Since
pure nitrogen is needed at Leuna for scavenging and compression of high-pres-
sure apparatus, especially in ammonia production, a number of small Linde ap-
paratuses, operating on the old Linde process, had to be retained. They are
much less economical, howevc;, and the Leuna Works rebuilt the Linde-Fraenkl
installations for the simultaneous production of pure nitrogen.
This modification, previously suggested for use in standard Linde ap-
paratus by Lachmann, consists of the attachment of a gas tap in the middle
of the upper portion of the column which removes a relatively small part of
the oxygen-nitrogen mixture present at this point in the rectification column.
The ratio of liquid to gas thus becomes greater above the tap, facilitating
rectification in the upper portion of the column, so that both oxygen and
nitrogen can be obtained in a very pure state. The amount of gas removed is
about 5 or 6 'ercent of the total. Its _ow temperature is used for precooling
of the high-pressure air in the counter-current precooler. The amount of air
under high pressure to be used must be slightly increased to make up for re-
frigeration losses and in order to obtain the same quantities of oxygen as be-
fore. This additional quantity of air also supplies sufficient oxygen and
nitrogen for removal of impurities from the cold accumulators. The energy
consumption, however, is not higher than it is in apparatus which does not
produce nitrogen because the total yield of oxygen is higher, and the speci-
fic energy consumption, i.e. the consumption of energy per equal quantity of
100 percent pure oxygen, has not increased. The new method thus not only
eliminates the necessity of operating a special Linde apparatus for producing
nitrogen, but is also more economical.
TheLinde-Fraenkl apparatus, depending on its size, can supply 2500 to
3400 cubic meters of pie oxygen per hour, and 9000 to 1_,000 cubic meters of
nitrogen, which contain less than 0.5 percent oxygen per hour.
The hurdles in the cold accumulators are made of ribbed aluminum ribbon
25 millimeters wide wound to form a flat disc. Lately, iron ribbons coated
with an aluminum film to prevent corrosion have been used instead. While the
specific heat of iron is lower than that of aluminum, the specific weight is
higher and t`^ heat capacity therefore almost as great.
Sulfur Removal and Carbon Monoxide Conversion
The removal of sulfur from the gas for synthesis used to be carried out
exclusively with active carbon, since the gas produced from bituminous coke
contains only 3 to 4 grams of sulfur per cubic meter in the form of hydro-
gen sulfide. The gas made from lignite coke, however, has a sulfur content
of approximately 15 grams per cubic meter, and the active carbon process
alone was not sufficient for iemoval. The ao-called "alkazid" method, which
is widely known and used, had to be introduced as a preliminary step to treat-
ment with active carbon. It is based on the property of solutions of the al-
kali salts of weak organic acids to absorb hydrogen sulfide at normal tempera-
tures and to release it again when heated. Salts like potassium aminopropicc9te
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cOID IAZ CONFIDENTIAL
are suitable for this purpose. The "Alkazid" liquids can be loaded with very
large quantities of hydrogen sulfide, and then regenerate by simple steam heat-
ing. The sulfur yielded by this process is highly pure, containing only 0.02
to 0.03 percent moisture, catalyst dust, and bituminous impurities, and is
light yellow in color.
The question of materials caused difficulties for years. All cold parts
of the apparatus could usually be built of iron, but if hot liquids were used,
the iron had to be protected by brickwork. For all apparatus transferring heat,
aluminum could generally be used, but serious corrosion would occasionally ap-
pear, quite suddenly and often only after the part had been in operation for a
long time. It was finally possible to eliminate these difficulties by careful
analysis of the "Alkazid" liquid and by adding a carefully controlled amount
of silicic acid in the form of water glass. V2A steel would be even better
than aluminum, because it is absolutely corrosion proof against Alkazid.
The Alkazid process reduces the hydrogen sulfide content of the mixture
gas to 3 or 4 grams per cubic meter.
The process is followed by the active carbon treatment. It consists of
a catalytic oxidation of the hydrogen sulfide to elemental sulfur which is
adsorbed in?the pores of the active carbon. When the carbon is saturated,
the sulfur is dissolved by ammonium sulfide solution, forming ammonium poly-
sulfide. This is steam boiled under pressure, and pure, elemental sulfur is
obtained. The vapors are cooled and condensed, and the ammonium sulfide solu-
tion is recovered. The carbon is cleaned with water and steam, and used again.
Small quantities of ammonia in the gas expedite oxidation of the hydrogen sul-
fide.
The carbon monoxide in the gas from which the sulfur has been removed is
converted by water vapor in ttie presentee of a catalyst to carbon dioxide and.
hydrogen. The carboj monoxide thus serves for the production of hydrogen, how-
ever, for reasons of economy not all of it is converted, bpt 4 or 5 percent of
the carbon monoxide remain, and are removed at a later stage by washing under
pressure with copper solution. The catalyst is iron oxic36, mixed with chrom-
ium oxide; the reaction takes place at temperatures between 400 and 5000C.
This stage of the production has been very badly affected by the conver-
sion fror bituminous to lignite coke. The high carbon dioxide content re-
quires a high excess-of steam for conversion of the carbon monoxide, because
this is An equilibrium reaction; the results are higher steam losses and a
greater steam consumption. The additional consumption of steam, in terms of
ammonia produced, amounts to 50 percent or more.
Gas Compression
The compression of the converted gas takes place in five-stage piston
compressors, driven partly by steam, partly by gas, and partly by electricity.
The first three stages compress the gas to 26 or 27 atmospheres. It is washed
under this pressure to remove the carbon dioxide, and then compressed to 250
atmospheres in the two last stages. Intermediate cooling is carried out after
each stage. The condition of the cooling water is important, both for the life
of the cooling tubes and for the efficiency of the operation. It has been found
that the carbonate hardness can be as low as 30 at temperatures of 35 to 40oC,
without any occurrence of corrosion but the water will cause neither corrosion
nc- sediments in the tubes if the carbonate hardness is between 7.2 to 7.40.
The longevity of the tubes is increased from 2 years to 6 to 8 years by forma-
tion of a protective film due to the use of water having an appropriatedegree
-of hardness. V
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Reaoval of Carbon Dioxide
The gas is washed under a pressure of 25 to 26 atmospheres to remove the
carbon dioxide. Washing takes place in high cylindrical towers filled with
earthenware rings. The water is supplied from the low-pressure water system
of the plant, brought to the required pressure by centrifugal pumps, and pumped
into the scrubbing towers which are connected in parallel.
The potential energy if the water, which is charged with carbon dioxide,
is recovered and used for feeding water into the tower against the gas pres-
sure. For that purpose it is decompressed to almost atmospheric pressure in
Pelton turbines. The Pelton turbines are coupled with the centrifugal pumps,
and about 50 or 55 percent of the total energy requirements for pressure water
can be obtained by this method.
Instead of water under pressure, chemical absorption can be used for the
removal of carbon dioxide at atmospheric pressure. This method has the advan-
tage that th- carbon dioxide to be removed does not have to be compressed to
a pressure corresponding to that of the scrubbing water, so that considerable
expense for the compression process is eliminated.
At Leuna, part of the converted gas is treated with ammonia for the re-
moval of carbon dioxide. This yields ammonium carbonate, which is used for
the manufacture of ammonium sulfate by double decomposition with either gypsum
or ankydrite.
Both gases, one scrubbed with water under pressure, and the other treated
with ammonia at normal pressure, are compressed separately to 250 atmospheres
and then combined. The high-pressure lines behind the junction point showed
bad corrosion effects which became more and more alarming. At the same time
sediments of sludge were noticed. The substance responsible for the corrosion
and sludge formation was hydrogen sulfide in the gas, present in a quantity of
about 200 milligrams per cubic meter. Only after the hydrogen sulfide content
had been reduced to less than 0.1 milligram per cubic meter was it possible to
prevent corrosion and sludge formation almost completely. It was found that
these corrosion effects in iron apparatus and pipelines will always occur when-
ever hydrogen sulfide, oxygen, and-r.)isture are present at the same time. At
Leuna, a check is made on corrosion by the insertion of test sections into
susceptible high-pressure lines. The sections whose eight is known are peri-
odically removed and weighed. Corrosion effects can be determined after an
exposure as short as 2 or 4 weeks.
Copper Washing
The carbon monoxide and c=roon dioxide still present in the gas must be
removed. This is carried out by washing with an ?oniscal solution of copper
carbonate under 240 to 250 atmospheres pressure. The copper solution is re-
generated and used again.
The use of gases made from lignite created an unforeseen difficulty.
The copper solution will occasionally foam while in the scrubbing towers.
Part of the solution is carried out with the purified gas, thus reducing the
degree of purity of the gas and the efficiency of the scrubbers. It is there-
fore necessary to prevent foam formation. At the beginning, small quantities
of castor oil were added to the copper solution during the regeneration process.
After the outbreak of the war castor oil became unobtainable, and an oil for
corrosion prevention made by Rhenania of Hamburg was used instead, a machir-e
oil containing a naphthene sulfonic acid as emulsifior. Since it could not
be obtained in uniform quality, and therefore turned out to be unreliable,
other means were tested for foam prevention. Of the many substances investi-
gated, alcohols having more than 12 carbon atoms, preferably 15 or 16, or
Ca rI r rIne CC~ CA-rIC TI a 1
C aI- riuD
.
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hydrocarbon mixtures of the synol synthesis with boiling points between 220
and 260?C were found to be the most effective. These anti-foaming agents are
used in small quantities, only 1 or 2 liters per day for 500 cubic meters of
copper solution.
Catalytic Gas Purification
This process serves to remove the last traces of impurities which might
poison the catalyst, by turning the residua of carbon monoxide and dioxide into
methane, and by eliminating the sulfur still present in the form of organic sul-
fur compounds..
Most other ammonia synthesis plants use a nickel catalyst. Since this
catalyst is very sensitive to sulfur, it is preceded by a copper and iron cat-
alyst. The temperature is 300 to 3500c, and the pressure is the same as that
used in the synthesis stage.
Lewis employs a different system. The temperature is only 200 to 220?C,
and the catalyst is the reduced catalyst of the ammonia synthesis. It con-
sists mostly of pure iron, with small amounts of aluminum oxide and potassium
oxide added because of their promotion effect. At a temperature of 2006C, when
ammonia synthesis will not yet take place, this catalyst has a high purfication
effect and long life. The purification effect is lowered only at higher tem-
peratures when the formation of ammonia begins to take place. This catalyst
has an advantage over nickel, because the regeneration of an exhausted nickel
catalyst is a laborious process, while the iron catalyst merely has to be melted
down in the presence of oxygen and then reduced in order to be ready for use
again.
The catalyst converts the carbon monoxide and dioxide and the unsaturated
hydrocarbons still present into methane and ethane to the extent of 90 percent.
The carbon dioxide content is reduced from 0.03 percent to 0.003-0.005,pprcent.
The Ammonia Synthesis
The most importr,nt part of the synthesis apparatus is, of course, the cat-
alyst furnace which has undergone a number of changes and impro.-ements. Most
of these changes were made on the interior equipment of the furnace. The Leuna
furnaces are built on the tube principle. The catalyst tubes form a bundle,
with the tubes touching each other. Space is well utilized. The preheated
gas flows past these tubes, entering the space at the tapered end of the tubes,
then flows upward, and back down through the catalyst tubes. The high velocity
of the flow effects good heat transfer and high efficiency. At a pressure of
230 atmospheres, 10 percent by volume of the gas leaving the furnace has been
converted to ammonia, or 20 percent of a quantity of gas is turned into ammonia
during one passage of the gas through the furnace. Because of this high effi-
c'ency, each Leung catalyst furnace can produce 30 to 35 tons of nitrogen in
the form of ammonia per day.
Removal of Foreign Gases From the Gas Cycle
Despite the catalytic purification, the gas does not consist only of pure
hydrogen and nitrogen. The other components methane and argon, are not catalyst
poisons, but simply do not take part in the reaction. The percentages are about
1.3 percent methane and 0.3 to 0.4 percent orgon.
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Removal would be a difficult and expensive job, and therefore is not
carried out. The two gases are carried along into the gas cycle. To prevent
them from accumulating there and thereby impairing the efficiency of the am-
monia catalyst furnaces,.part of the gas in the cycle is always decompressed,
in such quantities that the content of foreign gas remains low. If the con-
tent of foreign gas is high, this also means high losses of hydrogen and re-
duced efficiency. This was prevented at Leuna by a special method of arrang-
ing the gas intake and exhaust. This innovation did not require any new ap-
paratus, it consisted merely in a change of the intake and exhaust controls
of the cycle.
The entire cycle arrangement consists of the catalyst furnaces and their
auxiliary equirment in parallel arrangement, and the'circulation pumps, also
in :parallel arrangement. Furnaces and pumps are connected by joint high-
pressure lines. The incoming gas used to be distributed to all furnaces,
and the removal of foreign gases by decompression of part of the gas also
took place as evenly as possible at several points. The entire apparatus
was a uniform cycle, with the gas having the same composition at all furnace
points. Now, however, the incoming gas is supplied only to a part of the '-
furnace battery, about the. first third. The gas to be exhausted from the cy-
cle is decompressed at the other end.- Thus, the gas of the cycle moves to
the end of the furnace battery, and the content of foreign gases increases
toward that direction.' Since only that part is decompressed, the foreign
gases are removed from there as a higly concentrated mixture. This is easily
explained by the fact that the quantity of synthesis gas becomes smaller and
smaller as it goes from one oven to the next, while the quantity of the fore-
ign gases which take no part in the reaction remains constant, until it is
removed at the end point of the cycle.
Only in the final stage is there any effect on the efficiency of the
catalyst furnaces. However, this final stage consists of only two furnaces
out of a total of more than 20, so that the loss of efficiency, as far as
the entire plant is concerned.is very slight.