United States Patent [19]
Stephens, Jr.
[11]
[45]
4,257,781
* Mar. 24, 1981
[73] Assignee:
[.] Notice:
[54] PROCESS FOR ENHANCING THE FUEL
VALUE OF LOW BTU GAS
[75] Inventor: Frank M. Stephens, Jr., Lakewood,
Colo.
U.S. PATENT DOCUMENTS
2,409,235 10/1946 Atwell 260/449.6
2,537,496 1/1951 Watson 260/449.6
2,562,806 7/1951 Mayer 260/449.6
2,589,925 3/1952 Cain et al. ~ 260/449.6
2,601,121 7/1902 Mattox 260/449.6
[57] ABSTRACT
2,686,819 8/1954 Johnson 260/449 M
2,694,624 11/1954 Sweetsen 260/449 M
2,819,283 1/1958 Montgomery 260/449.6
3,031,287 4/1962 Benson et al. 48/197 R
4,005,996 2/1977 Hausberger 260/449 M
4,134,907 1/1976 Stephens 48/197 R
Primary Examiner-Peter F. Kratz
Attorney, Agent, or Firm-Sheridan, Ross, Fields &
McIntosh
34 Claims, 3 Drawing Figures
In the field of chemical fuels, prior art coal gasification
.produces a fuel value of a mixture of carbon monoxide
and hydrogen which has a lower BTU than methane.
The present process uses coal resources more economically
for industry by converting part of the hydrogen
and part of the carbon in the carbon monoxide of the
gas mixture to methane, by continuously introducing
the gas mixture into a fluid bed in the presence of iron
under conditions of pressure and temperature which
promote the reduction of carbon monoxide to carbon,
the formation of iron carbide from the iron and carbon,
and the formation of methane and iron from iron carbide
and hydrogen, and continuously removing from
the fluid bed a methane enriched gas mixture including
carbon monoxide and hydrogen having a substantially
increased fuel value over the gas mixture introduced
into the fluid bed.
Related U.S. Application Data
Continuation-in-part of Ser. No. 817,576, Jul. 21, 1977,
Pat. No. 4,134,907.
Int. C1.3 CI0K 3/04
U.S. C1 48/197 R; 260/449.6 M;
585/733
Field of Search 48/197 R; 260/449 M,
260/449.6 M, 676 R, 449.6 R; 585/733
References Cited
Hazen Research, Inc., Golden, Colo.
The portion of the term of this patent
subsequent to Jan. 16, 1996, has been
disclaimed.
[21] Appl. No.: 2,956
[22] Filed: Jan. 12, 1979
[63]
[56]
[51]
[52]
[58]
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4,257,781
DISCLOSURE OF THE INVENTION
A process for increasing the fuel value of a gas mixture
of carbon monoxide and hydrogen by converting 55
part of the hydrogen, and part of the carbon in the
carbon monoxide of the gas mixture to methane, which
comprises continuously introducing the gas mixture
into a fluid bed in the presence of a mixture of iron and
iron carbide under conditions of pressure and tempera- 60
ture which promote the reduction of carbon monoxide
to carbon along with the formation of iron carbide by
the reaction of iron and carbon followed by the formation
of methane and iron by the reaction of iron carbide
with hydrogen, while continuously removing from the 65
fluid bed a gas mixture including methane, carbon monoxide
and hydrogen having a· substantially increased
fuel value over the gas mixture introduced into the fluid
BEST MODE FOR CARRYING OUT THE
INVENTION
The invention is based on establishing and maintaining
conditions in a fluid bed which promote the following
three reactions:
(1) CO+H2-C+H20
(2) C+3Fe_Fe3C
(3) Fe3C+2H2-3Fe+CH4
These reactions will proceed under atmospheric pressures,
although slightly elevated pressures may be preferred.
In the fluid bed reaction, the iron acts as an acceptor
of carbon in reaction (2) and as a donor of carbon in
reaction (3). It will be noted that iron is reformed or
regenerated in reaction (3) and that the iron carbide is
reformed or regenerated in reaction (2) so that after the
first addition of iron and iron carbide they are always
present in the reaction zone without further additions.
Reaction (3) can be made to proceed to the right
either by the addition of hydrogen or the removal of
methane. Hydrogen and carbon monoxide are being
continuously added in reaction (1) and methane, along
with the carbon monoxide and hydrogen not converted,
is being continuously removed as part of the enriched
fuel gas.
The reactions can be made to proceed and controlled
by controlling the ratio of the various gases present,
that is, the ratio of methane to hydrogen, water to hydrogen,
carbon dioxide to carbon monoxide, etc. Charts
will be described hereinafter illustrating how control of
these ratios results in the reactions proceeding in the
required manner.
The fluidized bed reactor referred to herein is of the
conventional type in which finely divided feed material
on a grate or perforate support is fluidized by upwardly
flowing gases which may include or entirely comprise
the reactant gases. Auxiliary equipment includes heating
and temperature control and monitoring equipment,
heat exchangers, scrubbers, cyclones, gas cycling equipment
and other conventional equipment which is used
to remove solids from the off-gas stream and to remove
water and C02 from a recycle gas loop to shift the gas
system equilibrium.
The reactants introduced into the reactor after the
initial charge of iron carbide and iron are the low Btu
coal gasification gases containing carbon monoxide and
hydrogen.
By proper balancing of the ratios of the hydrogen and
carbon bearing materials in accordance with the stability
diagrams, it is possible to make the hydrogen serve a
reducing function to reduce the carbon monoxide to
carbon, and the carbon serve a carburizing function as
iron carbide is formed. As stated previously, conditions
2
bed. The gas mixture removed has a Btu value of about
600 on the average and is a suitable industrial or utility
fuel. If methane alone is required it can be recovered
from the gas mixture removed from the fluid bed by
5 conventional procedures.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1-3 are stability diagrams indicating the gas
phase relationships between iron carbide and the hydro-
10 gen-carbon-oxygen system. The symbol aC refers to
the activity of carbon in the system. The symbol "P"
represents partial pressure. The amounts of gases are
essentially directly related to the partial pressures.
1
PROCESS FOR ENHANCING THE FUEL VALUE
OF LOW BTU GAS
DESCRIPTION
This application is a continuation-in-part of my copending
application, U.S. Ser. No. 817,576, filed July
21, 1977 now U.S. Pat. No. 4,134,907.
TECHNICAL FIELD
The need to use the extensive coal resources in this
country as a source of fuel gas is now quite evident in
view of the rapid depletion of other sources. Accordingly,
it has become essential to develop processes for
the economic production of fuel gas for industrial uses 15
from coal.
Atmospheric coal gasification processes are well
known and well developed. Typical of these proven
processes are the Koppers-Totzek, Winkler, WellmanGalusha,
Woodall-Duckman, and others. The gas pro- 20
duced from these gasification processes is a low BTU
gas comprising a mixture of carbon monoxide and hydrogen.
This gas mixture has a low fuel value of about
300 Btu/ft3or less, on the average, which is too low for
most industrial uses. 25
The fuel value of the gas produced by the atmospheric
coal gasification processes can be enhanced
with the use of high temperatures and pressures, sometimes
accompanied by the use of oxygen and/or catalysts,
to make the hydrogen and carbon monoxide pres- 30
ent react to produce methane. Methane has a heat of
combustion of 1013 Btu/ft3, whereas carbon monoxide
and hydrogen has Btu's of about 322 and 325, respectively.
The chief disadvantage, of course, of these procedures
for enhancing the fuel value of the low Btu gas 35
is the expense involved. The expense is so great that low
Btu gas enhanced in this manner is not competitive with
other fuels available for industrial uses.
So-called intermediate Btu gas is suitable for industrial
uses, this gas having a Btu value of 450 Btu/ft3or 40
more. It will burn well in existing gas burner equipment
in power plants and other industrial applications with
only minor modification in the burner head. The Btu
value is high enough so that its use does not result in loss
ofboiler efficiency and, further, this gas can be econom- 45
ically piped moderate distances, which is not true for
low Btu gas.
Accordingly, it is an object of this invention to provide
a relatively inexpensive process for enhancing the
fuel value of the low Btu gas produced by coal gasifica- 50
tion processes.
4,257,781
3
are established and maintained so that iron serves both
a carbon acceptor function and a carbon donor function.
Additionally, reaction conditions are adjusted so
that hydrogen performs an additional reducing function
in reducing iron carbide to iron and forming methane 5
with the released carbon.
Because of the equilibrium conditions involved in
hydrogen-carbon-oxygen gas systems, the required hydrogen-
carbon ratios will automatically require that
methane be present in the gas system. The quantity of 10
methane present or produced will be a function of carbon
to hydrogen ratios, as well as temperature and
pressure conditions, and all of these can be controlled.
FIGS. 1, 2 and 3 are stability diagrams indicating the
gas phase relationships between iron carbide and the 15
hydrogen-carbon-oxygen system at temperatures of
1160·, 1070· and 1250· F., respectively. The stability
diagrams indicate the relationship between log plots of
partial pressure ratios of the various gas components
which are in equilibrium with iron carbide in the pres- 20
ent process. These illustrate that definite amounts of
methane will exist in the system in the presence of the
iron carbide, and that the amount of methane present or
produced can be controlled by controlling the other
variables in the system. These stability diagrams show 25
that for any given temperature and pressure there is a
fixed relationship between the gas components and the
solid reactants iron and iron carbide thus indicating that
4
sures of up to about 10 atmospheres are also suitable.
Higher pressures are uneconomical.
The iron to iron carbide ratio in the reaction area can
vary between about 10 percent iron carbide to 96 percent
or more iron carbide. Iron may be added in metallic
form or supplied from various sources, including
iron oxide. Some carbon dioxide can be used in the feed
gas as a source of carbon. It is an advantage of the
process that oxygen is removed from the process in the
form of water which is easily recovered. Hany methane
is fed into the reactor, it is unreacted and recovered
with the product gas.
A 50 percent mixture of methane with carbon monoxide
and hydrogen gives a gas mixture of 600 Btu. As can
be seen from the examples below, this intermediate fuel
gas is easily produced by the process of the invention.
EXAMPLE I
Using the stability diagrams, a computer program
was constructed which gives the equilibrium gas composition
expected for the process when various hydrogen
and carbon bearing gases are contacted with ironiron
carbide mixtures at various temperatures. Table I
below shows examples of results obtained from this
computer program under varying conditions of inlet gas
composition, temperature and pressure under which the
process is performed within the favorable methane production
gas ratios illustrated in FIGS. 1-3.
TABLE 1
Equilibrium Shift Calculations for Fe3C System
Pres- Btu/scf
Temp sure _--:;I:.:.:nlc:.et:....G=as:.:.:,-,V-"o",lu:.:.:m",e:...;P:...;e:.:.:rc::.:e:.:.:n:.:.:t_ __.:::O"'ff.-.g.."'a::.:s,_V:...;o::.:.lu::.:m;.:.e;:...::..P::.:er.:::c::.:en;.:.t Inlet Ofr
OF. Atm HZ HZO CO COZ CH4 NZ HZ HZO CO COZ CH4 NZ Gas Gas
9.7 1.7 38.0 37.5 8.6 292
9.0 4.5 35.6 34.7 8.3 292
8.5 9.7 30.9 30.0 7.8 292
8.0 17.1 24.2 23.6 7.2 292
7.1 25.2 17.0 16.3 6.5 292
5.9 32.1 10.8 9.7 5.8 292
4.6 36.8 6.7 4.9 5,4 292
750 48.0 2.0 39.0 5.0
840 48.0 2.0 39.0 5.0
930 48.0 2.0 39.0 5.0
1020 48.0 2.0 39.0 5.0
1110 48.0 2.0 39.0 5.0
1200 48.0 2.0 39.0 5.0
1290 48.0 2.0 39.0 5.0
750 53.0 1.0 31.0 1.0
840 53.0 1.0 31.0 1.0
930 53.0 1.0 31.0 1.0
930 I 48.0 2.0 39.0 5.0
930 5 48.0 2.0 39.0 5.0
930 10 48.0 2.0 39.0 5.0
Section I
1.0 5.0 4.6
1.0 5.0 8.0
1.0 5.0 13.0
1.0 5.0 19.8
1.0 5.0 27.9
1.0 5.0 35.6
1.0 5.0 41.6
Section 2
13.0 1.0 7.7 16.4
13.0 1.0 12.7 14.0
13.0 1.0 19.3 11.4
Section 3
1.0 5.0 13.0 8.5
1.0 5.0 6.3 10.0
1.0 5.0 4.6 10,4
0.9 19,4 54.0 1.7 400
2.5 18.9 50.0 1.6 400
5.9 17.0 44.9 1.5 400
9.7 30.9 30.0 7.8 292
4.6 35.4 35.3 8,4 292
3.3 36.5 36.7 8.5 292
434
422
405
382
356
331
312
674
638
595
405
-129
435
fixed gas compositions will be obtained if mixed gases
are contacted with iron carbide. Furthermore, the equi- 50
librium gas composition can be altered at any given
temperature and pressure by removal of one or more
reaction products from the system. For example, if
water vapor and/or carbon dioxide are continuously
removed by scrubbing in the recycle gas loop, then the 55
quantity of methane will continue to increase in the
reaction zone. The charts indicate the operative range
of variables at specified temperatures for insuring that
Fe3C is present in the fluid bed. They also show the
effect of temperature on the production of methane and 60
Fe3C when the other variables for insuring the presence
of Fe3C in the fluid bed are maintained substantially
constant.
A feasible temperature range for the process is about
600· F. to about 1200· F., preferably about 600· F. to 65
about 950· F. Temperatures outside these ranges are not
economically feasible. Atmospheric pressures can be
used and are preferred, although slightly elevated pres-
The results recorded in section 1 of Table I show the
theoretical change in composition resulting when a gas
having a composition similar to commercially produced
"blue water gas" is subjected to the computerized program.
The results is section 2 of the Table show the theoretical
change in composition obtained when a gas having
a composition similar to gas produced by the Lurgi
oxygen-pressure gasification is subjected to the computerized
process. The large increase in yields of methane
within a well defined temperature range graphically
illustrates the critical effect of temperature on the yield
of methane.
The results in section 3 of the Table show the theoretical
effect of pressure on the yield of methane when the
computerized process is applied to the same gas used for
the section 1 tests. Methane yield is increased from 30
volume percent to 36.7 volume percent by increasing
4,257,781
5
the pressure from one to ten atmospheres. Increased
pressures would probably show slight increase in methane
production but such pressures become uneconomic.
6
Analyses were made of the off-gas taken at half-hour
intervals for a 12 hour period, the results of which are
presented in Table 3.
EXAMPLE 2 TABLe 3
5
In order to further illustrate the operativeness of the Pilot Plant Gas Composition Data Reactor Products-Solid, Gas
invention and to illustrate the correlation between the Ratio
results obtained by the computer application of the Off Gas COl H21 H21 process and actual operation of the process, bench scale Time H2O CO2 CO N2 H2 CH4 CO2 H2O CH3 tests were made of the process. The tests were run in 10
accordance with previously described procedure. Ade- 2400 1.2 4.5 3.9 8 35 44 0.9 29.2 0.8
0030 1.2 4.5 3.9 8 33 44 0.9 27.5 0.8
quate iron and iron carbide were present in the fluid bed 0100 1.0 4.5 3.9 8 35 44 0.9 35.0 0.8
to start the reaction. No further addition of these com- 0130 1.0 4.8 4.2 8 35 43 0.9 35.0 0.8
ponents was necessary. Results from actual tests are 0200 1.0 4.8 4.2 8 35 44 0.9 35.0 0.8
recorded in each section with results from the comput- 15 0230 1.0 4.8 4.2 8 35 44 0.9 35.0 0.8
0300 1.0 4.8 4.0 8 34 42 0.8 34.0 0.8
erized test under identical conditions. The results are 0330 1.0 4.8 4.2 8 34 43 0.9 34.0 0.8
recorded in Table 2. 0400 1.0 4.8 4.2 8 34 43 0.9 34.0 0.8
TABLE 2
Experimental Shift Data for Pe3C System
Btu/scf
Temp Pressure Inlet Gas, Volume Percent Off-gas, Volume Percent Inlet Off-
'P. Atm H2 H2O CO CO2 CH4 N2 H2 H2O Cll CO2 CH4 N2 Gas Gas
Section I
Actual 1020 65.0 2.0 33.0 0 0 0 60.7 2.5 12.6 2.4 21.8 0 317 461
Computer 1020 65.0 2.0 33.0 0 0 0 38.8 1.7 10.5 17.2 31.8 0 317 481
Section 2
Actual 1020 22.0 1.7 17.7 13.3 7.8 37.5 30.2 1.1 13.0 4.8 12.5 38.4 207 264
Computer 1020 22.0 1.7 17.7 13.3 7.8 37.5 15.9 1.9 16.2 5.7 13.3 47.0 207 239
The results recorded in section 1 of Table 2 are from
a test program using a 3:1 mixture of hydrogen to carbon
monoxide as the inlet gas, this gas representing a
gasification process working with oxygen. At 1020· F. 35
the actual test produced a gas with a 21.8 percent methane
and a Btu value of 461 as compared to the predicted
values of31.8 percent methane and 481 Btu's.
The results recorded in section 2 of Table 2 show the
change in composition obtained by the process in a 40
representative gas containing relatively large amounts
of inert nitrogen, this gas representing a gasification
process working with air. The actual test produced a
gas with 12.5 percent methane and a Btu value of 264 as
compared to a predicted methane content of 13.3 per- 45
cent and a Btu value of 239. An increase in Btu value of
over 30 percent was obtained in both instances.
The test results established the operativeness of the
process for producing methane, and prove the validity
of the stability diagrams of FIGS. 1-3 for use in select- 50
ing conditions for operative and feasible production of
methane.
EXAMPLE 3
Various gases were fed at a rate of 200 cubic feet per 55
minute to a two foot diameter fluidized-bed reactor
containing sufficient iron and iron carbide to start the
reaction. No further addition of these materials was
necessary. The inlet gases consisted of hydrogen, carbon
monoxide and carbon dioxide introduced in 60
amounts conforming to favorable methane production
ratios illustrated in FIGS. 1-3. A temperature of930· F.
and atmospheric pressure were used for all the tests.
The inlet gas had it composition of approximately 82
percent hydrogen, 8 percent carbon dioxide and 10 65
percent methane with a Btu value of about 370. The
ratio of iron carbide to iron varied from a ratio of about
73/27 percent to 96/4 percent.
0430 1.0 5.5 4.2 8 35 43 0.8 35.0 0.8
0500 1.0 5.5 4.0 8 35 43 0.7 .35.0 0.8
0530 1.0 6.7 4.8 8 35 40 0.7 35.0 0.9
0600 1.0 6.2 4.8 8 35 40 0.8 35.0 0.9
0630 1.0 6.2 4.8 8 35 41 0.8 35.0 0.9
0700 1.0 6.2 5.0 8 35 40 0.8 35.0 0.9
0730 1.0 6.7 5.1 8 35 40 0.8 35.0 0.9
0800 2.4 7.5 7.9 7 35 40 1.1 14.6 0.9
0830 2.4 7.75 8.25 6.5 35 39 1.1 14.6 0.9
0900 2.4 8.6 8.9 7 34 38.3 1.0 14.2 0.9
0930 2.4 5.3 6.6 7 38 40 1.3 15.8 1.0
1000 2.3 4.4 4.5 5.5 41 33.5 1.0 17.8 1.2
1030 2.3 3.6 4.5 5.5 40 40 1.3 17.4 1.0
1100 2.4 4.5 5.2 7 39 41.5 1.2 16.3 0.9
1130 2.3 4.8 6.5 7 37 41.5 1.4 16.1 0.9
The average methane content of the off-gas during
the 12-hour period exceeded 40 percent and the off-gas
had a Btu average value ofabout 560 as compared to the
Btu value of only 370 for the inlet gas.
Again, the results of the table show the feasibility of
the process for strongly enhancing the Btu value of a
gas, including one containing methane. The results illustrate
the feasible time period for the enhancement. Further,
the results show that large amounts of methane are
produced with large percentages of iron carbide to iron
present in the fluid bed. For example, at 1000 the percentage
of iron carbide to iron in the bed was about 96
percent. The results further establish the validity of the
stability diagrams of FIGS. 1-3 for use in selecting
favorable operating conditions for the process.
EXAMPLE 4
Gases containing hydrogen and carbon monoxide in a
ratio of three parts of hydrogen to one part of carbon
monoxide were fed at a rate of 200 cubic feet to a twofoot
diameter fluidized-bed reactor containing sufficient
iron and iron carbide to start the reaction. No further
addition of these materials was necessary. A temperature
of 840· F. and atmospheric pressure were used for
all tests. After the system reached equilibrium with
4,257,781
7
respect to off-gas composition, a portion of the off-gas
was taken through a water scrubbing step to remove the
water formed in the reaction and this scrubbed gas was
substituted for part of the incoming hydrogen and carbon
monoxide feed gas. As predicted from the stability 5
diagrams, this removal of water shifted the equilibrium
and permitted additional quantities of hydrogen and
carbon monoxide to react and form methane. Analysis
of the off-gas taken at half-hour intervals for a period of
twelve hours are presented in Table 4. 10
TABLE 4
8
4. The process of claim 1 wherein the reaction is
conducted at a pressure 'of from about I to about 10
atmospheres.
5. The process of claim 1 wherein methane is recovered
in continuous fashion from the reactor.
6. The process of claim 1 wherein carbon dioxide is
added to the reactor as a source of carbon.
7. The process of claim 1 wherein water is removed
from the reactor via a recycle gas stream.
8. The process of claim 7 wherein the water is contin-
Pilot Plant Gas Composition Data
for Reactor Products with Water Scrub Circuit
Off·gas Recycle Gas Ratio
Time H2O CO2 CO N2 H2 CH4 H2O CO/CO2 H2/H20 Hz/CH4
1800 8 6 4 10 32 40 3 0.7 4.0 0.8
1900 8 6 4 8 31 42 3 0.7 3.9 0.7
2000 8 6 5 7 29 44 3 0.9 3.6 0.7
2100 8 6 5 5 26 48 3 0.9 3.3 0.5
2200 8 6 5 3 24 52 3 0.9 3.0 0.5
2300 8 6 5 4 24 52 3 0.9 3.0 0.5
2400 7 4 5 4 22 56 2 1.3 3.1 0.4
0100 7 4 4 4 20 60 2 1.0 2.9 0.3
0200 6 5 5 4 22 58 2 1.0 3.7 0.4
0300 7 4 4 4 20 60 2 1.0 2.9 0.3
0400 6 4 3 4 20 62 2 0.8 3.3 0.3
0500 6 5 3 3 20 62 2 0.6 3.3 0.3
0600 6 5 3 3 20 62 2 0.6 3.3 0.3
50
30 uously removed.
9. The process of claim 1 wherein carbon dioxide is
removed via a recycle gas stream.
10. The process of claim 9 wherein the carbon dioxide
is continuously removed.
11. The process of claim 2 wherein the reaction is
conducted at a pressure of from about I to about 10
atmospheres.
12. The process of claim 2 wherein methane is recovered
in continuous fashion from the reactor.
13. The process of claim 2 wherein carbon dioxide is
added to the reactor as a source of carbon.
14. The process of claim 2 wherein water is removed
from the reactor via a recycle gas stream.
15. The process of claim 2 wherein the water is continuously
removed.
16. The process of claim 2 wherein carbon dioxide is
removed via a recycle gas stream.
17. The process of claim 16 wherein the carbon dioxide
is continuously removed.
18. The process of claim 4 wherein methane is recovered
in continuous fashion from the reactor.
19. The process of claim 4 wherein the water and/or
carbon dioxide is removed during the reaction by means
of a recycle gas stream.
20. The process of claim 4 wherein carbon dioxide is
added to the reactor as a source of carbon.
21. The process of claim 4 wherein water is removed
from the reactor via a recycle gas stream.
22. The process of claim 21 wherein the water is
60 continuously removed.
23. The process of claim 4 wherein carbon dioxide is
removed via a recycle gas stream.
24. The process of claim 23 wherein the carbon dioxide
is continuously removed.
25. A process for converting a first gas mixture containing
carbon monoxide and hydrogen into a second
gas mixture of methane, carbon monoxide and hydrogen
having a substantially increased fuel value over said
The average methane content of the gas increased
from 42 percent at the beginning of the run to a value of
62 percent at the end of the run to give an increased Btu
value of 690 as compared to the 300 Btu value of the
inlet gas. By shifting the equilibrium through the re- 35
moval of water vapor, the methane content was increased
as indicated by the stability diagrams.
Similar results were obtained when the equilibrium
was shifted by removing C02 from the recycle gas
through the addition of caustic to the water scrub recy- 40
cle loop. These results further establish the validity of
the stability diagrams of FIGS. 1-3 for use in selecting
favorable operating conditions for the process.
I claim:
1. A process for producing methane in a single reac- 45
tion zone in the presence of iron, Fe3C, carbon monoxide,
carbon dioxide, hydrogen and water comprising:
(a) maintaining in a fluidized bed, iron and Fe3C in a
single reactor without substantial further additions
of iron and/or Fe3C to the reactor;
(b) introducing a gas mixture containing carbon monoxide
and hydrogen into the reactor;
(c) reacting the iron and Fe3C with the carbon monoxide
and hydrogen and balancing the ratio of
carbon monoxide, hydrogen, carbon dioxide, water 55
and methane under conditions such that a portion
of the carbon monoxide is reduced to carbon, iron
is reacted with the carbon to produce Fe3C, and
the Fe3C is reacted with hydrogen to form methane
and reform iron;
(d) removing water and/or carbon dioxide; via a
recycle gas stream; and
(e) recovering methane from the reactor.
2. The process of claim 1 wherein the reaction is
conducted at a temperature of from about 600· F. to 65
about 1200· F.
3. The process of claim 1 wherein the reaction is
conducted from about 600· F. to about 950· F.
4,257,781
9
first gas mixture in a single reaction zone which comprises,
(a) maintaining iron and Fe3C in a fluidized bed in the
reaction zone without substantial further additions 5
of iron and/or Fe3C to the reaction zone;
(b) continuously introducing said first gas mixture
into said fluidized bed in the reaction zone;
(c) adjusting gas compositions in the reaction zone by 10
a circulating gas stream which removes water and/
or carbon dioxide so as to maintain mixtures of
carbon monoxide, carbon dioxide, hydrogen, water
and methane which are thermodynamically favor- 15
able for maintaining the presence of Fe3C and the
formation of methane;
(d) continuously removing from said reaction zone as
a product said second gas mixture of methane, 20
carbon monoxide and hydrogen having an increased
fuel value.
10
26. The process of claim 25 wherein the reaction is
conducted at a temperature of from about 6000 F. to
about 12000 F.
27. The process of claim 25 wherein the reaction is
conducted at a temperature of from about 6000 F. to
about 9500 F.
28. The process of claim 25 wherein the reaction is
conducted at a pressure of from about 1 to about 10
atmospheres.
29. The process of claim 25 wherein methane is recovered
in continuous fashion from the reactor.
30. The process of claim 25 wherein carbon dioxide is
added to the reactor as a source of carbon.
31. The process ofclaim 25 wherein water is removed
from the reactor via a recycle gas stream.
32. The process of claim 25 wherein the water is
continuously removed.
33. The process ofclaim 25 wherein carbon dioxide is
removed via a recycle gas stream.
34. The process of claim 25 wherein the carbon dioxide
is continuously removed.
* * * * *
25
30
35
40
45
50
55
60
65
ly:"4̘sNPA@s,"serif";mso-fareast-font-family: HiddenHorzOCR'>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