United States Patent [19]
Ruskin et at
[11]
[45]
4,250,157
Feb. 10, 1981
Attorney, Agent, or Firm-Dennis K. Shelton; Bruce G.
Klaas; Jerry W. Berkstresser
[54] METHOD AND APPARATUS FOR
ENRICHING THE IRON CARBONYL
CONTENT OF A RECYCLE GAS STREAM
[57] ABSTRACT
[75] Inventors: Richard P. Ruskin, Houston, Tex.;
Humayon Z. Zafar, Wichita, Kans.;
Duane N. Goens, Golden, Colo.;
David E. Hyatt, Wheatridge, Colo.;
Charlie W. Kenney, Lakewood, Colo.
[73] Assignee: Pentanyl Technologies, Inc., Arvada,
Colo.
760,852
1,841,973
2,780,553
3,595,965
4,045,541
Appl. No.: 139,422
References Cited
U.S. PATENT DOCUMENTS
A method and apparatus for enriclhing the iron carbonyl
content of a recycle gas stream produced in an iron
carbonyl decomposition or reaction process to enable
reuse of the recycle gas stream in the iron carbonyl
decomposition or reaction process by cooling the recycle
gas stream, adding carbon monoxide to the recycle
gas stream, compressing the recycle gas stream to a
pressure of about 20 to about 38 atmospheres under
conditions suitable to prevent substantial decomposition
of residual iron carbonyl, and contacting the compressed
gas stream at a temperature ofabout 65 to about
160· C. with a reduced iron containing material in the
presence of hydrogen sulfide under conditions suitable
to produce substantially condensed iron carbonyl. In a
particularly preferred embodiment, the recycle gas
stream is initially split into first and second portions, the
first portion of the recycle gas stream is cooled, enriched
with carbon monoxide, compressed and contacted
with the reduced iron containing material to
produce substantially condensed iron carbonyl, and at
least a portion of the condensed iron carbonyl is vaporized
and then combined with the second portion of the
recycle gas stream to produce an iron carbonyl enriched
gas stream. The iron carbonyl enriched gas
stream may then be reintroduced into the iron carbonyl
decomposition or reaction process.
Dewar 423/417
Naumann 423/417
Pawlyk 252/372
Franz 423/417
Mercer 423/417
Apr. 11, 1980
5/1904
111932
2/1957
7/1971
8/1977
Int. CI,3 COlG 49/16; C21B 15/04
U.S. Cl 423/417; 252/372;
423/149; 75/0.5 BA; 44/1 R; 48/210; 208/244;
252/372
Field of Search 423/149, 417;
75/0.5 BA; 252/372
Filed:
[56]
[58]
[21]
[22]
[51]
[52]
Primary Examiner-Brian E. Hearn 15 Claims, 1 Drawing Figure
46
//5
//2 //4 /06 '--__E~7,;.r~8--~---- ------
2
velocities are utilized in conjunction with lower reaction
temperature and pressure conditions. U.S. Pat. No.
1,828,376 also utilizes high gas velocities to produce
iron carbonyl by passing carbon monoxide at a pressure
5 of between 50 and 120 atmospheres over porous iron
lumps at a temperature betweeIl 90° and 100° C.
Other attempts at the efficient production of iron
carbonyl have utilized modified reaction materials. For
example, U.S. Pat. No. 2,086,88] discloses a process for
producing iron and nickel carbonyl from sulfur bearing
matte materials preferably between 140° and 300° C.
and at pressures preferably of 50, 100 or 200 atmospheres
or even more. U.S. Pat. No.3, 112, 179 discloses
a process for preparing iron and nickel carbonyl by
mixing nickel oxide powder with sponge iron to form a
mixture containing 50 to 98% by weight of sponge iron
and 50 to 2% by weight of nickel oxide powder, pelletizing
the mixture, reducing the oxides in the pellets, and
then passing a stream of carbon monoxide through the
pellets at a temperature of 70° to 170° C. while maintaining
the carbon monoxide pressure at a sufficiently high
level to prevent substantial decomposition of nickel
carbonyl.
Still other attempts at efficiently producing iron carbonyl
have suggested that the presence of sulfur in an
active form may increase the efficiency of iron carbonyl
production. However, the form of the sulfur bearing
material utilized in such a process appears to be critical
in determining efficiency of iron carbonyl production.
For example, as disclosed in U.S. Pat. No. 2,378,053, ..
... although as has been recognized, sulfur in the form
of sulfides such as nickel sulfide is effective to increase
the velocity of the reaction involved in the production
of nickel carbonyl from reduced nickel, nevertheless
the addition of solid sulfides to reduced iron such as
described hereinbefore is not effective. Futhermore,
gaseous sulfides have been found to be ineffective also
in view of the fact that there is an excessive local action
near the inlet port for the gaseous sulfides and relatively
ineffective action at points remote from the gas inlet.
Thus, it is manifest that sulfides are not effective in
increasing the velocity of the reaction between iron
and carbon monoxide to produce iron carbonyl". U.S,
Pat. No. 2,378,053 then discloses that the reaction
between reduced iron and carbon monoxide can be
accelerated by treating the iron containing material
with a soluble solution of heavy metal sulfates prior to
reduction of the iron containing material.
While the basic reaction of carbon monoxide gas with
reduced iron containing material to form iron carbonyl
has been known for many years, the prior art processes
for production of iron carbonyl have not proceeded
with sufficient efficiency to enable substantial commer-
55 cial production, or have entailed economically prohibitive
reaction conditions or material treatment prior to
production. Thus, several proposed industrial processes
involving the decomposition or reaction of iron carbonyl,
as heretofore described, have not been commercially
feasible.
It has now been determined that iron carbonyl may
be produced in a highly efficient manner enabling its use
on a commercial scale in an iron carbonyl decomposition
or reaction process by cooling a recycle gas stream
produced in an iron carbonyl decomposition or reaction
process to a temperature of about 5° to about 15° C.,
adding carbon monoxide to the cooled gas stream to
produce a carbon monoxide enriched gas stream, com-
4,250,157
1
BACKGROUND AND SUMMARY OF THE
INVENTION
METHOD AND APPARATUS FOR ENRICHING
THE IRON CARBONYL CONTENT OF A
RECYCLE GAS STREAM
This invention relates to a method and apparatus for
enriching the iron carbonyl content of a recycle gas
stream, and more particularly to a method and appara- 10
tus for receiving a recycle gas from an iron carbonyl
decomposition or. reaction process and enriching the
iron carbonyl content with the gas to enable reuse of the
gas stream in the iron carbonyl decomposition or reaction
process. 15
It has previously been suggested that highly pure
metallic iron may be produced under the proper conditions
by passing carbon monoxide over reduced iron
containing material to form iron carbonyl, and then
decomposing the iron carbonyl to deposit iron and re- 20
lease the carbon monoxide. More recently, it has been
suggested that iron carbonyl decomposition or reaction
processes may be useful in the desulfurization of hydrocarbons
such as disclosed in U.S. Pat. No. 2,756,182, in
the removal of sulfur during the gasification of coal, 25
such as disclosed in U.S. Pat. No. 2,691,573, in the desulfurization
of petroleum crude and primary refinery
products, such as disclosed in U.S. Pat. No. 3,996,130, in
the removal of pyrite and ash from coal, such as disclosed
in U.S. Pat. No. 3,938,966, and in the removal of 30
organic sulfur from coal, such as disclosed in U.S. Pat.
No. 4,146,367.
A typical process for producing a metallic carbonyl
entails passing carbon monoxide, or gases containing a
substantial portion of carbon monoxide, over the metal 35
of which the carbonyl is to be formed. The metal to be
acted upon by carbon monoxide is typically obtained by
gaseous reduction of an oxide of the metal. Although
other carbonyls may be formed in this manner, substantial
commercial production appears to have been lim- 40
ited to nickel carbonyl, since the reaction may take
place at relatively low pressure and temperatures, as for
example at atmospheric pressure and a temperature of
about 40° C. to about 50° C. Iron carbonyl, on the other
hand, is much more difficult to form, and is typically 45
produced by the reaction of carbon monoxide with iron
generally obtained by the reduction of iron ore, but at
temperatures and pressures much higher than are required
for the production of nickel carbonyl from reduced
nickel. For example, temperatures on the oder of 50
175° C. or higher and pressures in the range of from 100
to 200 atmospheres, or even as high as 2,000 atmospheres,
have been employed in attempts to make the
reaction proceed sufficiently rapidly to make iron carbonyl
production efficient.
Several attempts have been made to efficiently produce
iron carbonyl by modifying reaction conditions.
For example, U.S. Pat. No. 1,614,625 discloses a process
for producing iron carbonyl by passing carbon monoxide
under a pressure of about 200 atmospheres over iron 60
metal at a temperature of about 200° C. U.S. Pat. No.
1,759,268 discloses a process for producing iron carbonyl
by passing carbon monoxide at a pressure of
about 50 atmospheres or more over reduced oxides of
iron at a temperature of about 100° to about 200° C. at 65
a sufficient velocity to prevent deposition of jron carbonyl
on the iron oxide material. U.S. Pat. No.
1,783,744 discloses a similar process wherein higher gas
4,250,157
3
pressing the carbon monoxide enriched gas stream to a
pressure of about 20 to about 38 atmospheres under
conditions suitable to prevent the decomposition of
substantial amounts of iron carbonyl in the carbon monoxide
enriched gas stream, and contacting the compressed
gas stream at a temperature of about 65° to
about 160° C. with a reduced iron containing material in
the presence of an iron carbonyl production enhancing
amount of hydrogen sulfide under conditions suitable to
producing substantially condensed iron carbonyl. Pref· 10
erably, the recycle gas stream is split into first and second
portions, the first portion is cooled, enriched with
carbon monoxide, compressed and contacted with the
reduced iron containing material to produce substan·
tially condensed iron carbonyl, and at least a portion of 15
the condensed iron carbonyl is vaporized and combined
with the second portion of the recycle gas stream to
produce an iron carbonyl enriched recycle gas stream.
The iron carbonyl enriched recycle gas stream may
then be reintroduced into the iron carbonyl decomposi- 20
tion or reaction process.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic drawing of the process and
apparatus of an illustrative embodiment of the present 25
invention.
DESCRIPTION OF THE PRESENTLY
PREFERRED EMBODIMENTS
As used herein, the term "iron carbonyl" means iron 30
compounds containing a plurality of carbonyl groups.
Although it is presently thought that the predominate
form of iron carbonyl produced by the process of the
invention and present in the recycle gas stream is iron
pentacarbonyl, Fe(CO)s, it is further expected that 35
lesser amounts of other iron carbonyls, such as iron
butacarbonyl, Fe(CO)4, iron nonacarbonyl, Fe2(C0)9,
iron dodecacarbonyl, Fe3(CO)12, etc., may be present
both in the condensed iron carbonyl and in the recycle
gas stream. All such compounds are intended to be 40
included in the term "iron carbonyl". Although it is not
fully understood at this time, it may be possible that the
equilibrium existing between various iron carbonyl
forms under the process conditions disclosed herein
may contribute to both enhanced iron carbonyl yields 45
ad effectiveness of the recycle gas stream in the iron
carbonyl decomposition or reaction process.
Recycle gas to be treated according to the process of
the present invention can be any by-product gas produced
as a result of an iron carbonyl reaction or decom- 50
position process. For example, the recycle gas may be
produced by reacting iron carbonyl with iron disulfide
to produce "iron-rich disulfide" in the coal beneficiating
process disclosed in U.S. Pat. no. 3,938,966 of Kindig
et aI., by reacting the iron carbonyl with coal to 55
obtain organic sulfur removal, or from other processes
in which iron carbonyl is reacted or decomposed to
form iron or iron compounds and carbon monoxide. A
typical recycle gas stream suitable for use in connection
with the inventive concepts comprises residual, unre- 60
acted or undecomposed iron carbonyl, carbon monoxide
produced in the iron carbonyl reaction or decomposition
process, and possibly other by-product or leakage
gases such as nitrogen, carbon dioxide, hydrogen and
water vapor. The recycle gas stream may comprise, for 65
example, about 0.0 to about 10%, more preferably about
1 to about 8%, and most preferably about 4 to about 6%
by volume residual iron carbonyl.
4
Although the recycle gas stream may be processed as
a whole in accordance with the inventive concepts, it is
a presently particularly preferred embodiment to initially
split the recycle gas stream into at least first and
second portions, to treat one portion to produce iron
carbonyl and then to recombine the separate portions of
the recycle gas stream. Thus, although the inventive
concepts are hereinafter described in connection with a
split recycle gas stream, it is to be understood that the
recycle gas stream may also be processed as a whole. In
accordance with the foregoing, the recycle gas stream is
initially split into two portions, a first portion of which
is processed, as hereinafter further described, to produce
additional iron carbonyl, and a second portion
which is enriched with vaporized iron carbonyl and
returned directly to the· iron carbonyl reaction or· decomposition
process.
The first portion of the recycle gas stream is treated
by cooling the first portion to a temperature of about 5°
to about 15° C., preferably about 10° C. During cooling,
a portion of the iron carbonyl and water in the gas
stream is condensed, and the liquid iron carbonyl is
recovered and stored for subsequent use. Carbon monoxide
is then added to the cooled gas stream to form a
carbon monoxide enriched recycle gas stream.
The carbon monoxide enriched gas stream is compressed
to a pressure of about 20 to about 38 atmospheres,
more preferably about 27 to about 36 atmospheres,
and most preferably about 30 to about 34 atmospheres,
under conditions suitable to prevent the decomposition
of a substantial amount of the iron carbonyl
remaining in the gas stream. Iron carbonyl in the
carbon monoxide enriched gas stream may decompose
under certain combinations of gas stream temperature,
pressure and iron carbonyl content. In particular, decomposition
of iron carbonyl may occur during compression
of the carbon monoxide enriched gas stream
due to a temperature rise resulting from the adiabatic
heat of compression and/or the heat of mechanical
inefficiency of the compressor. However, it has been
found that iron carbonyl decomposition can be substantially
reduced by compressing the gas stream in multiple
stages with interstage cooling of the gas stream to a
temperature of about 5° to about 15° C. In a presently
particularly preferred embodiment, the gas stream is
compressed to the desired degree in four separate stages
with relatively low initial stage compression ratios and
with interstage cooling to a temperature of about 100 C.
After compression, the first portion of the recycle gas
stream is contacted with an activated, reduced iron
containing material at a temperature of about 65 to
about 160° c., more preferably about 1250 to about 1500
C., and most preferably about 1300 to about 135° C.
Suitable iron containing materials include all iron containing
materials in which the iron is capable of being
reduced to a high degree. For example, sponge iron has
been found to be particularly well suited as an iron
containing material in the process of the invention due
to its partially prereduced condition and commercial
availability, although other iron containing materials
may be employed.
In order to activate the sponge iron, or other iron
containing material, the sponge iron is charged into a
sealable vessel and the vessel is sealed and evacuated or
purged, such as with a steam ejector, vacuum device,
suitable purge gas or the like. The sponge iron is then
preheated to a temperature of about 600° to about 760°
c., preferably to about 6500 C. at a pressure of about 2
6
TABLE 1
4,250,157
Fe+5CO.=Fe(CO)s
It ha~ been found that a majority of the iron carbonyl
formed in the vessel condenses under the foregoing
reaction conditions providing a driving force for the
forward iron carbonyl generation reaction, while not
substantially impeding the kinetic mechanism which is
generally thought to require migration of carbon monoxide
to active iron sites. The reaction vessel is preferably
sized and designed so that substantially all of the
carbon monoxide in the compressed gas stream is converted
to iron carbonyl. After contacting the compressed
gas stream with sponge iron in the reaction
vessel, the gas stream, comprising various inert gases,
carbon monoxide and iron carbonyl is cooled, such as in
a tail gas cooler, to condense and recover additional
iron carbonyl.
The activity of the iron containing material in the
reaction vessel has been found to decrease over time
due to phenomena which are not completely understood,
but which may result from reaction of iron in the
iron containing material with trace quantities of oxygen
in the compressed recycle gas stream, from a build-up of
carbon on the iron bed, or from the physical blocking of
active iron sites by substances such as hydrocarbon
material which are typically present in carbon monoxide
containing synthesis gas. It has been determined that
any such decrease in iron activity can be at least partially
reversed by the presence ofiron carbonyl production
enhancing amounts of hydrogen sulfide during the
carbonylation reaction. Enhancing amounts of hydrogen
sulfide may be maintained in the reaction vessel by
the intermittent or continuous injection of hydrogen
sulfide into the compressed recycle gas stream or by the
45 utilization of trace hydrogen sulfide and other effective
sulfur containing gases which may be present in the
The exothermic heat of reaction formed during iron carbon monoxide synthesis gas. In extreme cases where
carbonyl production is removed to maintain the sponge the carbonylation reaction has resulted in substantial
iron at the desired temperature level. deactivation of the iron containing material, it has been
It is critical to the· efficient operation of the present 50 determined that restoration of activity may be obtained
process that the operating carbonylation temperature by further reduction of the iron containing material
for any given pressure be maintained at a level less than with reducing gas, as hereinbefore described, followed
that at which phase equilibria and chemical equilibria by reactivation with hydrogen sUllfide.
commonly exist. If the operating temperature exceeds The condensed iron carbonyl produced according to
this critical level, a reverse carbonylation reaction may 55 the foregoing process is then vaporized and combined
occur. If the operating temperature is approximately with the second portion of the recycle gas stream to
equal to this critical level, the forward carbonylation provide an iron carbonyl enriched gas stream comprisreaction
will proceed until iron carbonyl gas saturation ing, for example, about 5 to about 20%, more preferably
is obtained, at which point chemical equilabria is about 6 to about 14%, and most preferably about 8 to
reached and the forward reaction will substantially 60 about 12%, by volume iron carbonyl, for reuse in the
stop. If the operating temperature is maintained below iron carbonyl reaction or decomposition process. Vathis
critical level, the forward carbonylation reaction porization of the condensed iron carbonyl may be obproceeds,
iron carbonyl gas saturation is Ultimately tained, for example, by heating the condensed iron carreached,
and thereafter iron carbonyl condenses, favor- bonyl to a temperature of about 1050 to about 1400 C.
ing continuation of the forward reaction since chemical 65 under a pressure of, for example, about 32 atmospheres,
equilibria is not obtained. Based upon current informa- and thereafter reducing the pressure to about 1 atmotion,
it appears that the critical temperature levels for sphere while introducing the iron carbonyl into the
various given pressure levels are as follows: second portion of the recycle gas stream, whereby the
5
to about 3 atmospheres, such as by passing heated nitrogen
through the sealed vessel. When the sponge iron Critical
has been preheated to the desired temperature level, a Pressure Temperature
reducing gas, such as hydrogen, carbon monoxide or (Atmospheres) (c. 0)
mixtures thereof, is slowly passed through the column 20 132
to further reduce the sponge iron and to activate the 27 146
sponge iron for subsequent reaction with the com-;~ :~~
pressed recycle gas stream. Due to its greater ability to 36 158
reduce iron at a given temperature level, hydrogen, and 10 ...3:.8;.. 159 _
reducing gases comprising a relatively large hydrogen
concentration, are the presently preferred reducing gas
for use in connection with the present invention. Water
vapor and other gaseous materials produced during
sponge iron reduction, together with unconsumed hy- 15
drogen, are purged from the top of the sealed vessel.
When the purged gas stream no longer evidences the
production of additional water vapor or carbon dioxide,
the sponge iron is cooled to the desired reaction temperature
of about 650 to about 1600 C., more preferably 20
about 1250 to about 1500 C., and most preferably to
about 1300 to about 1350 C., under a protective blanket
of the reducing gas or other inert gas to prevent oxidation
of the reduced sponge iron. Final activation of the
sponge iron is then obtained by charging the sponge 25
iron in the vessel with an iron carbonyl production
exhancing amount of hydrogen sulfide. Effective
amounts of hydrogen sulfide have been found to be
about 0.2% to about 0.4%, preferably about 0.3%, of
sulfur per unit of sponge iron in the vessel, when di- 30
luted, for example, in the cooling blanket of reducing or
inert gas. The activated, reduced sponge iron, or other
iron containing material is then contacted with the compressed,
carbon monoxide enriched recycle gas stream
at a temperature of about 650 to about 1600 C., more 35
preferably about 1250 to about 1500 C., and most preferably
about 1300 to about 1350 C., and at a pressure of
about 20 to about 38 atmospheres, more preferably
about 27 to about 36 atmospheres, and most preferably 40
about 30 to about 34 atmospheres, by slowly passing the
compressed recycle gas stream over the sponge iron to
produce iron carbonyl, predominately by the reaction:
4,250,157
8
duit means 44 at a temperature of about 185° to about
190° C.
Cooling means 46 is provided in the system for receiving
the compressed carbon monoxide enriched recycle
gas stream from the compressor means 42 through
conduit means 44 and for cooling the recycle gas stream
to the desired carbonylation temperature of about 65° to
about 160° C. After cooling, the recycle gas stream is
transferred through conduit means 48 to an activated
reduced iron containing material filled reaction chamber
means formed by a suitable reaction vessel, such as
reaction vessel 50, for carrying out the carbonylation
reaction.
In the illustrative, presently preferred embodiment of
FIG. 1, the system comprises three separate reaction
chamber means formed by reaction vessels 50, 52, 54,
with the reaction vessels 50, 52 being shown on stream
in the production of iron carbonyl, and the reaction
vessel 54 being shown as used for iron containing material
reduction, as is hereinafter further described. In this
manner, the production of iron carbonyl according to
the present invention may be operated continuously by
simultaneously activating and reducing iron containing
material in, for example, reaction vessel 54, while carrying
out iron carbonyl production in, for example, reaction
vessels 50, 52. Then, when the reduced iron content
of, for example, reaction vessel 50 becomes substantially
depleted, the reaction vessel 50 may be taken off stream,
the functional position of reaction vessel 52 can be
shifted to that previously occupied by reaction vessel
50, the reaction vessel 54 containing newly reduced iron
containing material may be placed on stream in the
functional position previously occupied by reaction
35 vessel 52, and the reaction vessel 50 may be filled with
fresh iron containing material and placed in the reduction
cycle in the functional position previously occupied
by reactor vessel 54. Although illustrative embodiment
of FIG. 1 is presently particularly preferred in that
it permits continuous operation of the system by rotation
of the functional position of reaction vessels 50, 52,
54, it is contemplated that the inventive concepts may
be employed in a batch or continuous system utilizing
one or two reaction vessels, or in a batch or continuous
45 system utilizing four or more reaction vessels.
From foregoing, it is apparent that the system of the
invention further comprises means, such as reaction
vessels 50, 52, for receiving compressed carbon monoxide
enriched recycle gas from cooler means 46 and for
providing a reaction chamber containing activated,
reduced iron containing material wherein the iron containing
material is contacted with the compressed recycle
gas at a temperature of about 65° to about 160° C.,
more preferably about 125° to about 150° c., and most
preferably about 130° to about 135° C., and at a pressure
of about 20 to about 38 atmospheres, more preferably
about 27 to about 36 atmospheres, and most preferably
about 30 to about 34 atmospheres. The reaction vessels
50, 52, 54 are preferably of vertically oriented, cylindrical
design so as to form reaction columns. For example,
the reaction columns may be about 3 feet in diameter,
about 22 feet in length, provided with coils or the like
adapted for the passage of steam or water therethrough
to cool the reduced iron containing material and to
maintain the reaction temperature within desired limits,
as hereinafter further described, and adapted to withstand
both the reduction and carbonylation temperature
and pressure conditions of the process. .
7
iron carbonyl is simultaneously vaporized and combined
with the second portion of the recycle gas stream.
The foregoing process may be more fully understood
in connection with FIG. 1, which is a schematic drawing
of a presently preferred embodiment of the appara- 5
tus of the invention. A by-product gas stream produced
by an iron carbonyl reaction or decomposition process
and to be treated by the system of the present invention
is introduced into the treatment system through recycle
gas input conduit means 10. The recycle gas is split into 10
a first portion which is transferred to cooling means 12
through conduit means 14, and a second portion which
is transferred to iron carbonyl vaporization means 16
through conduit means 18.
Cooling means 12 for cooling the first portion of the 15
recycle gas stream to a temperature of about 5° to about
15° c., preferably about 10° C., may comprise two or
more separate gas coolers 20, 22, as shown in FIG. 1, or
may comprise a single gas cooler. In the illustrative
embodiment of FIG. 1, cooling means 12 is particularly 20
adapted to receiving an input recycle gas stream at
temperatures on the order of 185° C., or higher, and
cooling the gas stream to temperatures on the order of
50° C. in the first gas cooler 20 and to the desired tem- 25
perature of about 5° to about 15° C. in the second gas
cooler 22. During cooling of the recycle gas, a portion
of the iron carbonyl in the recycle gas will condense in
the coolers 20, 22. Any such condensed iron carbonyl is
recovered from the coolers 20, 22 and transferred 30
through conduit means 24, 26, respectively, and conduit
means 28 to intermediate iron carbonyl collection
means 30, and through conduit means 32 to iron carbonyl
storage means 34 for subsequent use, as will be
hereinafter further described.
After cooling to the desired temperature, the cooled
recycle gas is transferred out of gas cooler 22 through
conduit means 36. A.. carbon monoxide containing gas is
introduced into the cooled recycle gas stream from
carbon monoxide source 38 through conduit means 40 40
to produce a carbon monoxide enriched recycle gas
stream in the conduit means 36. The carbon monoxide
enriched recycle gas stream is then transferred through
the conduit means 36 to recycle gas compressor means
42.
The system further comprises recycle gas compressor
means 42 for compressing the carbon monoxide enriched
recycle gas to a pressure of about 20 to about 38
atmospheres under conditions suitable to prevent the
decomposition of a substantial amount of iron carbonyl 50
in the carbon monoxide enriched recycle gas stream. As
previously set forth, iron carbonyl decomposition is
minimized by compressing the recycle gas stream in
multiple stages with interstage cooling of the partially
compressed gas stream. In a presently particularly pre- 55
ferred embodiment, recycle gas compressor means 42
comprises a four stage recycle gas compressor having a
relatively low first stage compression ratio of, for example,
about 1.6, a relatively high last stage compression
ratio of, for example about 3.9, and incrementally in- 60
creasing intermediate stage compression ratios of, for
example, about 2.1 and 2.8, respectively. The compressor
means 42 further comprises three interstage gas
coolers (not shown) adapted to cool the partially compressed
recycle gas stream to a temperature of about 5° 65
to about 15° C. between the individual stages of the
recycle gas compressor, the recycle gas stream being
transferred out of the compressor means through con4,250,157
10
removed from the condenser means 79 such as through
conduit means 83 for subsequent treatment prior to
discharge into the atmosphere. Upon determination that
no iron carbonyl remains in the reaction vessel 54, the
spent iron containing material is discharged from the
vessel and the vessel is filled with suitable, fresh iron
containing material, such as sponge iron or the like. The
filled vessel is then sealed and air is evacuated from the
vessel through conduit means 78, such as by introducing
steam through conduit means 80 into ejector means
82.
The system further comprises heater means, such as
nitrogen supply source 84, heater 86 and interconnecting
conduit means 88, 90, for heating the iron containing
material to a temperature sufficient for enabling efficient
reduction of the iron containing material. It has
been found that the iron containing material may be
efficiently reduced at temperatures of about 6200 to
about 7600 c., preferably about 6500 C. In the illustrative
embodiment of FIG. 1, nitrogen from nitrogen
supply source 84 is transferred through conduit means
88 into heater 86 and then through conduit means 90
into reaction vessel 54, where the heated. nitrogen heats
the iron containing material to tthe desired temperature
level. In order to conserve nitrogen, nitrogen recycle
means 91 may additionally be provided for recycling
the nitrogen from the vessel through the heater and
back into the vessel. In the illustrative embodiment of
FIG. 1, the nitrogen recycle means comprises pump
means 92, nitrogen cooler means 94 for receiving heated
nitrogen from the vessel 54 and cooling the nitrogen
during the last portions of the heating cycle to a temperature
within the operating limits of the pump means 92,
and conduit means 96, 86 and 100 operativelyinterconnecting
vessel 54, nitrogen cooler means 94, pump
means 92 and heater 86. When the iron containing material
has been heated to the desired level, the nitrogen
supply is closed off and a reducing gas, such as hydrogen,
heated to a temperature of about 6200 to about 7500
c., preferably about 6500 C., is introduced into the
vessel 54, such as from hydrogen supply source 102,
through conduit means 104, lheater 86 and conduit
means 90, to reduce the iron in the iron containing
material to a highly metalized state. Water vapor produced
during iron reduction, and unconsumed hydrogen,
are purged from the reaction vessel 54, such as
through conduit means 78. When the desired degree of
iron reduction has been obtained in reaction vessel 54,
the vessel 54 is ready to be used for the production of
50 iron carbonyl, as heretofore described.
From the foregoing, it is apparent that the system of
the invention provides for continuous production of
iron carbonyl by utilizing two reaction vessels, such as
vessels 50, 52 for iron carbonyl production while simultaneously
reducing fresh iron containing material in a
third reaction vessel, such as reaction vessel 54. In this
manner, when the metalized iron content of the material
in one carbonylation vessel, such as vessel 50, becomes
substantially depleted, it may be pulled off-line from the
carbonylation process, replaced in functional position
by the second carbonylation vessel, such as vessel 52,
while the newly reduced reaction vessel, such as vessel
54, is brought in line in the carbonylation process in the
functional position formerly held by the vessel 52, all
without substantial interruption of the iron carbonyl
production process.
The apparatus further comprises vaporization means
16 for vaporizing the condensed iron carbonyl and re-
9
The temperature of vessels 50, 52 is adjusted, for
example, to about 65 0 C. to about 1600 C. at a pressure
of about 20 to about 38 atmospheres by passing steam
through coils in the reaction vessels, and then an iron
carbonyl production enhancing amount of hydrogen 5
sulfide from hydrogen sulfide supply source 56 is introduced
into the vessels 50, 52 through conduit means 58,
60. The compressed, carbon monoxide enriched gas is
then introduced into the top of reaction vessel 50
through conduit means 48 and allowed to pass slowly 10
downwardly through the reaction vessel where it
contacts the activated, reduced iron containing material
and reacts with the material to form iron carbonyl.
Excess heat produced by the exothermic heat of reaction
is removed from the reaction vessel, such as by 15
passing water or the like through the coils in the reaction
vessel. A majority of the iron carbonyl formed in
reaction vessel 50 condenses under the foregoing carbonylation
conditions, and is removed from reaction vessel
50 through conduit means 62. Any unreacted gas, 20
vaporized iron carbonyl, and other tail gases, are removed
from the bottom of reaction vessel 50 and transferred
to the top of reaction vessel 52 through conduit
means 64. The tail gases from reaction vessel 50 are then
passed slowly downwardly through reaction vessel 52 25
where they are allowed to contact the activated, reduction
iron containing material in reaction vessel 52 under
the same reaction conditions and react with the material
to form additional iron carbonyl. Similarly to reaction
vessel 50, excess heat produced by the exothermic heat 30
of reaction is removed from reaction vessel 52. A majority
of the newly formed iron carbonyl condenses in
the reaction vessel 52 and is removed from the bottom
of the reaction vessel 52 through conduit means 66. The
apparatus may further comprise tail gas cooler means 68 35
for receiving tail gas from reaction vessel 52, such as
through conduit means 69 and cooling the tail gas to
condense additional iron carbonyl. Uncondensed gases
are transferred away from cooler means 68 through
conduit means 70 for subsequent treatment prior to 40
discharge or disposal, while condensed iron carbonyl is
recovered and removed from the cooler means through
conduit means 72.
Condensed iron carbonyl recovered from reaction
vessels 50, 52 and tail gas cooler means 68 is transferred 45
through conduit means 62, 66, 72 and received by receiver
means 74 for receiving the condensed iron carbonyl
and maintaining the iron carbonyl at a temperature
and pressure level about equal to that within reaction
vessels 50, 52.
The presently preferred, illustrative embodiment
shown in FIG. 1 further comprises reaction vessel 54,
which is shown as used for iron containing material
reduction in FIG. 1. The reaction vessel 54, having been
previously utilized in the carbonylation cycle for the 55
production of iron carbonyl, contains material having a
substantially reduced metallic iron content The reaction
vessel 54 is depressurized and slowly and carefully
purged with air from air supply means 76 to deactivate
the iron heel, to destroy residual iron carbonyl, and to 60
cool the iron heel in the reaction vessel. The purged
gases are removed from the vessel through conduit
means 78 and passed through condenser means 79 for
condensing any residual iron carbonyl from the purge
gas stream. Any condensed iron carbonyl is transferred 65
from condensor means 79 to iron carbonyl collection
means 30 such as through conduit means 81, while the
substantially iron carbonyl free purge gas stream is
* * * * *
12
contacting the compressed gas stream at a temperature
of about 65 0 to about 1600 C. with a reduced
iron containing material in the presence of an iron
carbonyl production enhancing amount of hydrogen
sulfide to produce substantially condensed iron
carbonyl.
2. The process of claim 1 which further comprises
splitting the iron carbonyl lean recycle gas stream into
a first portion and a second portion, and wherein the
first portion of the recycle gas stream is cooled, enriched
with carbon monoxide, compressed, and contacted
with the reduced iron containing material to
produce the substantially condensed iron carbonyl.
3. The process of claims 1 or 2 wherein the iron containing
material is reduced by heating the iron containing
material to a temperature of about 6500 C. and then
passing a reducing gas over the iron containing material
in the absence of oxygen.
4. The process of claims 1 or 2 wherein the compressed
gas stream is contacted with the reduced iron
containing material by passing the compressed gas
stream downwardly through a first reaction vessel containing
a first portion of the reduced iron containing
material and then passing the compressed gas stream
downwardly through a second reaction vessel containing
a second portion of the reduced iron containing
material, and which further comprises recovering condensed
iron carbonyl from the first and second reaction
vessels.
5. The process of claims 1 or 2 wherein the carbon
monoxide enriched gas stream is compressed in at least
three stages, and which further comprises cooling the
carbon monoxide enriched gas stream to a temperature
less than about 75 0 C. between the separate stages.
6. The process of claims 1 or 2 wherein the carbon
monoxide enriched gas stream is compressed to a pressure
of about 30 to about 34 atmospheres.
7. The process of claims 1 or 2 wherein the compressed
gas stream is contacted with the reduced iron
containing material at a temperature of about 1250 to
about 1500 C.
8. The process of claims 1 or 2 wherein the compressed
gas stream is contacted with the reduced iron
containing material at a temperature of about 1300 to
about 1350 C.
9. The process of claim 2 which further comprises
vaporizing at least a portion of the condensed iron carbonyl
and combining the vaporized iron carbonyl with
the second portion of the recycle gas stream to produce
an iron carbonyl enriched recycle gas stream.
10. The process of claim 9 which further comprises
introducing the iron carbonyl enriched recycle gas
50 stream into the iron carbonyl decomposition process.
11. The process of claim 9 wherein sufficient vaporized
iron carbonyl is combined with the second portion
of the recycle gas stream to produce an iron carbonyl
enriched gas stream comprising about 5 to about 20%
by volume of iron carbonyl.
12. The process of claim 3 wherein the reducing gas
is hydrogen.
13. The process of claim 3 wherein the reducing gas
is carbon monoxide.
14. The process of claim 4 which further comprises
reducing iron containing material in a third reaction
vessel simultaneously with contacting the compressed
gas stream with reduced iron containing material in the
first and second reaction vessels.
15. The process of claim 14 wherein the carbon monoxide
enriched gas stream is compressed in four separate
stages and is cooled to about 500 C. between the
separate stages.
4,250,157
11
combining the vaporized iron carbonyl with the second
portion of the recycle gas stream to produce an iron
carbonyl enriched gas stream for use in the iron carbonyl
decomposition or reaction process. As shown in
FIG. 1, condensed iron carbonyl recovered from reac- 5
tion vessels 50, 52 and collected in receiver means 74 is
transferred from the receiver means to the vaporization
means 16 through conduit means 106, 108. Vaporization
means 16 comprises heater means, such as heater 110, in
the conduit means 108 for preheating the condensed 10
iron carbonyl to a temperature of about 1050 to about
1400 C., at a pressure of about 20 to about 38 atmospheres,
and vaporization column means 111 for receiving
iron carbonyl from heater 110, reducing the pressure
of the iron carbonyl to about 1 atmosphere to va- 15
porize the iron carbonyl and combining the vaporized
iron carbonyl with the second portion of the recycle gas
stream. Preheated iron carbonyl from heater 110 is
introduced into the vaporization column means and is
vaporized therein. The second portion of recycle gas is
simultaneously introduced into the vaporization column 20
means through conduit means 18 and is combined with
the vaporized iron carbonyl in any desired proportions
to produce an iron carbonyl enriched gas stream. The
enriched gas stream, comprising, for example, 10% iron
carbonyl, is transferred out of vaporization means 16 25
through conduit means 113 and is recycled to the iron
carbonyl decomposition or reaction process. Any iron
carbonyl which condenses in vaporization column
means 111 is collected in a bottom portion thereof and
is transferred to iron carbonyl collection means 30 such 30
as through conduit means 115.
During periods of excess iron carbonyl production or
vaporization means shut-down, condensed iron carbonyl
is transferred from receiver means 74 through
conduit means 106, 112 to iron carbonyl storage means 35
34. Cooling means, such as cooler 114, are preferably
provided in the conduit means 112 for cooling the iron
carbonyl to a temperature less than about 900 C. prior to
transferring the iron carbonyl to the storage means.
During periods of iron carbonyl production storage, 40
make-up iron carbonyl is transferred from storage
means 32 to vaporization means 16 through conduit
means 106, 108 is required.
While the foregoing process and apparatus have been
described in connection with various presently pre- 45
ferred and illustrative embodiments, various modifications
may be made without departing from the inventive
concepts. All such modifications are intended to be
within the scope of the appended claims, except insofar
as limited by the prior art.
What is claimed is:
1. A process for enriching the iron carbonyl content
of a recycle gas stream comprising carbon monoxide
and produced in an iron carbonyl decomposition or
reaction process to enable reuse of the recycle gas
stream in the iron carbonyl decomposition or reaction 55
process, comprising:
cooling an iron carbonyl lean recycle gas stream
produced in an iron carbonyl decomposition process
to a temperature of about 50 to about 150 C.;
adding carbon monoxide to the cooled recycle gas 60
streilm to produce a carbon monoxide enriched gas
stream;
compressing the carbon monoxide enriched gas
stream to a pressure of about 20 to about 38 atmospheres
under conditions suitable to prevent the 65
decomposition of substantial amounts of the iron
carbonyl in the carbon monoxide enriched recycle
gas stream; and
PATENT NO. :
DATED
INVENTOR(S) :
UNITED STATES PATENT AND TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
4,250,157
February 10, 1981
Richard P. Ruskan, Humayon Z. Zafar, Duane N.
Goens, David E. Hyatt, Charlie W. Denney
It is certified that error appears in the above-identified patent and that said Letters Patent
are hereby corrected as shown below:
On the Abstract page, in the listing of the inventors,
"Ruskin" should read --Ruskan--.
~igncd and ~calcd this
El611111 Da'I of /J«-.1Hr I'll
ISEALI
GERALD J. MOSSINGHOFF
A"atllwO/fItw Commissioner ofPtJfents tJnd T1tJdemiJ1ks