Note: Descriptions are shown in the official language in which they were submitted.
- iO7~870
The invention relates generally to the production of gase-
ous mixtures which may be used in the synthesis of ammonia,
The production of ammonia synthesis gas from low-boiling
point, gaseous or liquid hydrocarbons, particularly natural gas,
refinery gas and naptha, is known. These substance may be trans-
formed into a crude synthesis gas using the so-called steam reform-
ing method which involves catalytic cracking in the presence of
water vapor. After suitable further processing, the thus-obtained
crude synthesis gas may be utilized for the synthesis of ammonia.
The above-mentioned starting substances are relatively
easy to process. However, they are not everywhere available and,
in addition, have of late been in markedly short supply and have
also undergone marked increases in cost. Thus, methods by which
ammonia synthesis gas is obtained by the gasification of solid or
difficult-to-volatilize hydrocarbons have again become of interest.
In these gasification methods, the use of coal as a starting mater-
ial is of special significance. In particular, those types of coal
such as, for instance, crude lignite and coal of high ash content,
having low calorific values are preferred as starting materials.
The use of crude lignite as a starting material is of
especially great interest since such coal may, in most instances,
be found in large deposits located near the surface and, according-
ly, may be mined in a particularly expedient fashion using open pit
mining techniques. However, crude lignite generally contains be-
tween 50 and 60 percent by weight of water. Thus, it has been the
practice heretofore to subject the crude lignite to a drying opera-
tion prior to the gasification. This, however, adds to the produc- -
tion costs of the ammonia synthesis gas generatéd from the crude
lignite.
It is a general object of the invention to provide a pro-
- 2 - ~
1071870
cess whLch enables gaseous mixtures suitable for the synthesis of
ammonia to be produced from solid and difficult-to-volatilize fuels,
e.g., solid and difficult-to-volatilize hydrocarbons, in a more
economical manner than heretofore.
A more particular object of the invention is to provide
an improved process for the production of ammonia synthesis gas from
crude lignite which enables a preliminary drying of the coal to be
eliminated and which also provides additional processing advantages
by means of which the production costs for the manufactured ammonia
synthesis gas may be reduced so that the production of ammonia from
crude lignite may be effected more economically than heretofore.
These objects, as well as others which will become appar-
ent hereinafter, are achieved in accordance with the invention. One
aspect of the invention provides a process for the production of
gaseous mixtures suitable for the synthesis of ammonia wherein a
solid fuel, e.g., carbonaceous substances such as coal and other
hydrocarbons, is gasified togehher with the inherent water content
thereof to thereby form a crude gas containing hydrogen and other
gaseous components. The crude gas is purified and then dissociated
to obtain a hydrogen-rich fraction and another fraction. A portion
of the hydrogen-rich fraction is combusted in the presence of air
to form a combustion product which includes water vapor and nitro-
gen. The water vapor is condensed from the combustion product to
obtain a nitrogen-rich gas and the latter is combined with the re-
mainder of the hydrogen-rich fraction to obtain a gaseous mixture
rich in nitrogen and hydrogen.
A favorabl~ embodiment of the invention contemplates for
the portion of the hydrogen-rich fraction which is combusted to be
combusted in the presence of such a quantity of air that the nitro-
gen present, that is, the nitrogen in the air quantity, is suffic-
-- 3 --
107~3'70
ient to constitute, in the nitrogen-rich and hydrogen-rich gaseous
mixture, the proportion of nitrogen requLred in an ammonia synthesLs
gas.
Another aspect of the invention provides a process for
the production of gaseous mixtures suitable for the synthesis of
ammonia wherein a solid fuel is again gasified together with the
inherent water content thereof to thereby form a crude gas contain-
ing hydrogen and other gaseous components The crude gas is puri-
fied and a first portion of the purified crude gas is dissociated
to obtain a hydrogen-rich fraction and another fraction. A second
portion of the purified crude gas is combusted in the presence of
air to form a combustion product which includes water vapor and
nitrogen. The water vapor is condensed from the combustion product
to obtain a nitrogen-rich gas and the latter is combined with the
hydrogen-rich fraction to obtain a gaseous mixture rich in nitrogen --
and hydrogen.
H~re also, a favorable embodiment of the invention con-
templates for the portion of the crude gas which is combusted to
be combusted in the presence of such a quantity of air that the
amount of nitrogen in the air quantity is sufficient to constitute,
in the nitrogen-rich and hydrogen-rich gaseous mixture, the propor-
tion of nitrogen required in an ammonia synthesis gas.
The novel features which are considered as characteristic
for the invention are set forth in particular in the appended claims.
The invention itself, however, both as to its construction and its
method of operation, to~ether with additional objects and advantages
thereof, will be best understood from the following description of
specific embodiments when read in connection with the accompanying
drawing.
FIG. 1 diagrammatically represents one form of an arrange-
-- 4 --
`- 1071870
ment in accordance with the invention which may be used for carry-
ing out a process according to the invention; and
FIG. 2 diagrammatically represents another form of an ar-
rangement in accordance with the invention which may be used for
carrying out a process according to the invention.
In a preferred aspect, the invention relates to a process
for the production of ammonia synthesis gas by the gasification of
crude lignite.
Altho~gh the description herein will be confined to crude
lignite since this substance may be mined quite expediently and is,
therefore, of great interest, it will be understood that the process
of the invention may be applicable to other solid and difficult-to-
volatilize fuels, e.g., other carbonaceous substances such as dif-
ferent types of coal and other hydrocarbons.
According to a preferred embodiment of the invention, the
objects of the invention are achieved through a process for the pro-
duction of ammonia synthesis gas by the gasification of crude lignite
which is characterized by a combination of the following process
steps:
(a) Crude lignite, which has been comminuted to a parti-
cle size of less than 6 millimeters, is gasified together with its
inherent water content at temperatures of up to 1150C. The gasifi-
cation is carried o~t in an externally heated gasifier which is in
the form of a tubular oven, that is, an ov~n provided with a plural-
ity of tubes the interior of each of which constitutes at least one
heating zone or gasification zone.
(bl) The crude gas obtained from the gasification is cool-
ed to below the water dew point and simultaneously washed with re-
cycled condensed water derived from other stages of the process.
Subsequently, the crude gas is desulfurized and subjected to a car-
-- 5 --
107~870
bon dioxide (C02) scrub.
OR
(b2) The crude gas obtained from the gasification is cool-
ed to below the water dew point and simultaneously washed with re-
cycled condensed water derived from other stages of the process.
Subsequently, a first portion of the crude gas is desulfurized and
subjected to a carbon dioxide (CO2) scrub whereas a second portion
of the crude gas is desulfurized.
(cl) The crude gas treated in accordance with step (bl)
is subjected to low-temperature dissociation and a hydrogen fraction
is separated out.
OR
(c2) The first portion of the crude gas treated in accord-
ance with step (b2) is subjected to low-temperature dissociation
and a hydrogen fraction is separated out.
(dl) A portion of the hydrogen fraction obtained in step
(cl) is branched off and combusted in the presence of air. The
quantity of air used for the combustion is selected to be so large
that it contains all of the nitrogen necessary for a subsequent
synthesis of ammonia using the remainder of the hydrogen fraction
obtained in step (cl).
OR
(d2) The second portion of the crude gas treated in ac-
cordance with step (b2) is branched off and combusted in the pres-
ence of air. The quantity of air used for the combustinn is select-
ed to be so large that it contains all of the nitrogen necessary
for a subsequent synthesis of ammonia using the hydrogen fraction
obtained in step (c2).
(el) The nitrogen-rich gas derived from step (dl) is cool-
ed to below the water dew point so that the water vapor present
~ 1071870therein i9 condensed out. Traces of oxygen and carbon dLoxide whLch
may stLll be present in the gas are removed.
- OR
(e2) The nitrogen-rich gas derived from step (d2) is cool-
ed to below the water dew point so that the water vapor present there-
in is condensed out. Traces of oxygen and carbon dioxide which may
still be present in the gas are removed.
(fl) The nitrogen-rich gas recovered from step (el) is
mixed with that portion of the hydrogen fraction obtained from step
(cl) which was not combusted. The resulting gaseous mixture may,
after suitable fur~her processing and compression, be conveyed to
an ammonia synthesizing apparatus.
OR
(f2) The nitrogen-rich gas recovered from step (e2) is
mixed with the hydrogen fraction obtained from step (c2). The re-
sulting gaseous mixture may) after suitable further processing and
compression, be conveyed to an ammonia synthesizing apparatus.
Thus, in a process according to the invention, the crude
lignite with its inherent water content is gasified essentially in
accordance with the following overall reaction:
C + H2O ~ CO + H2 H = 38.9 kilocalories
per mole pre C
The energy req-nrea is preferably, in kno~n manner, supplied to the
tubular oven gasifier from externally thereof.
The crude gas or product gas may be subjected to a conver-
sion reaction where sppropriate or desirable so that hydrogen is
generated according to the following overall reaction:
C + 2H2O = CO2 + 2H2 H s 39.5 kilocarlLes
per mole per C
In accordacne with an advantageous embodiment of the in-
vention, the gasification is carried out in a manner kn~wn per se
107~870
in that the comminuted crude lLgnite is initially admitted into a
fluidized bed and then conveyed into the tubular oven gasifier from
the fluidized bed. The tubes of the tubular oven gasifier are favor-
ably either substantially horizontally oriented or slightly inclined
to the horizontal. In order to increase and/or regulate the quanti-
ties of coal entering the tubes of the gasifier, it is possible to
subject the fluidized bed to pressure impulses which propagate into
the tubes. For the purpose of maintaining the fluidized bed, it is
possible to utilize the carbon dioxide (CO2) which is washed out of
the crude gas derived from the gasification in later stages of the
processing sequence. However, it is also possible to use other gas-
es such as, for example, water vapor, hydrogen and methane, which
favorably influence the gasification.
Although it is particularly favorable for the gasification
of the crude lignite to be sffected in a tubular oven gasifier the
tubes of which are substantially horizontally oriented or slightly
inclined to the horizontal, it is nevertheless possible for the gasi-
fication to be carried out in known manner in a tubular oven gasifier
the tubes of which are substantially vertically arranged. Here, how-
ever, it is preferred that the inner diameters of the tubes not ex-
ceed a value Gf 80 millimeters.
In order to incréase the surface area available for heat-
exchange to occur, the tubes of the tubular oven gasifier may be
provided with fins.
Several possibilities exist for heating the tubular oven
gasifier. Thus, the heating may, for instance, be accomplished in --
known manner via the flue gas obtained by combustion of a portion
of the crude gas generated in the tubular oven gasifier. It is
likewise possible to use the waste heat from nuclear processes for
the purpose of heating the tubular oven gasifier. In addition,
~71870
there exists a new and favorable possibility in the present instance
for heating the tubular oven gasifier. This resides in combusting
the so-called resLdual gas fraction which remains behind after sep-
aration of the hydrogen fractLon from the crude gas in the low-tem-
perature dissociation stage (according to steps (cl) and (c2) above)
and using the flue gas obtained fr~m this combustion for he~ting the
tubular oven gasifier. This residual gas fraction will usually con-
sist essentially of a mixture of carbon monoxide (C0), methane (CH4)
and nitrogen (N2).
Different embodiments of the process according to the in-
vention will now be described with reference to the drawings. The
drawings illustrate only those apparatus elements which are import-
ant in one or another and do not show auxiliary devices.
With reference to FIG. 1 of the drawings, one aspect of
the process according to the invention operates as follows:
Crude lignite which has been comminuted in a crushing de-
vice is fed into a fluidized bed 2 via suitable conveying devices 1.
The fluidiæed bed 2 is maintained in operation by means of carbon
dioxide (C02) or another gaseous medium which favorably influences
the gasification to be effected in the tubes 5 of a tubular oven
gasifier. The fluidizing gas is admitted into the fluidized bed 2
via a blower 4 and a conduit 3.
From the fluidized bed 2, the crude lignite enters the
tubes 5 of the tubular oven gasifier. It will be noted that the
crude lignite is not subjected to a drying operation prior to enter-
ing the tubes 5 of the tubular oven gasifier. In the tubes 5 of
the tubular oven gasifier, there occurs a transfDr~ation of the crude
lignite with its inherent water content to crude gas.
This gasification may be effected at super-atmospheric
pressure where appropriate or desirable. Preferably, the pressure
_ g _
- ~07~870
`during the gasifica~ion does not exceed a value of about 80 bars
It is particularly advantageous for the gasification to be effected
at pressures between about 20 and 40 bars.
The crude gas generated in the tubes 5 of the tubular oven
gasifier enters a collecting space 6 in which the gasification resi-
dues are, at least for the most part, separated out. From the col-
lecting space 6, the gas travels to a waste-heat boiler 8 via a con-
duit 7. In the waste-heat boiler 8, the sen~ible heat of the crude
gas is utilized for the generation of steam to as great an extent
as possible. Concomitantly, the crude gas is cooled.
The gas nQw passes to a cooling washer 10 via a conduit 9.
In the cooling washer 10, the gas is further cooled by directly
spray.ng water therein and, at the same time, the gas is washed with
recycled condensed water obtained from other stages of the process.
In particular, the gas is washed with water which has been condensed
out of preceding quantities of gas in later stages of the process
and recycled to the cooling washer 10, e.g., condensed water obtain-
ed from a carbon dioxide (C02) scrubber 16 and a condenser 29.
Thus, in the cooling washer 10, so-called inherent or in-
trinsic condensate, that is, condensate derived from the process it-
self, is used as wash water either alone or together with water de-
rived from other sources. The condensed water obtained from the
carbon dioxide scrubber 16 and the condenser 29 is collected and
used again. The quantity of water admitted into the cooling washer
10 should be sufficiently large to insure that the gas is cooled
and that, at the same time, an effective separation of dust from
the gas is achieved. Under appropriate circumstances, water from
other sources will be admitted into the cooling washer 10 together
with the intrinsic condensate in order to permit removal from the
system of the dust washed out of the gas. Thus, the use of water
- 10 -
" 107~870
which is additional to the intrinsLc condensate enables a portion
of the dust-loaded wash water stream derived from the cooling wash-
er 10 to be continuously branched off and discharged from the system.
It is favorable for the gas to be cooled to temperatures
below the water dew point in the cooling washer 10.
In cases where it may be necessary, the gas which has
been washed in the coDling washer 10 may be further purified by means
of an elect~ofilter or in a disintegrator such as, for example, a
disintegrator of the character referred to as a disintegrator scrub-
ber in Perry's Chemical Engineer's Handbook, 1973 edition Section 20
and, in particular, of the character illustrated in Figures 20-123
of this Handbook. These apparatus, that is, the electrofilter and
the disintegrator, have not, however, been shown in the drawings.
The gas leaving the cooling washer 10 travels through a
conduit 11 to a compressor 12 in which it is compressed to the ex-
tent which may still be necessary, for instance, to a pressure of
30 bars. Subsequently, the gas is conveyed to a desulfurizing ap-
paratus 14 via a cDnduit 13. In the desulfurizing apparatus 14,
the sulfur-containing components of the gas such as H2S and COS
are washed out with suitable washing agents in accordance with known
methods.
The desulfurizing apparatus 14 is favorably constructed
in the form of an absorption and regeneration installation. In
other words, the desulfurizing apparatus 14 is favorably construct-
ed in such a manner that the washing solution is regenerated after
use within the framework of the process and then once more utilized
for the washing out of sulfur-containing components.
After the sulfur-containing components have been washed
out of the gas, the latter flows through a conduit 15 to the carbon
dioxide (C02) scrubber 16. Where appropriate or desirable, a non-
1071870illustrated conversion apparatus may be arranged in the vLcinity of
the conduit 15 in which, prior to entering the carbon dioxide scrub-
ber 16, the gas is subjected to a conversion reaction or shift con-
version according to the following equation:
~ H20 ~ --- C2 ~ H2
In the carbon dioxide scrubber 16, the carbon dioxide (C02) present
in the gas is removed therefrom. As is the case for the desulfur-
izing apparatus 14, known absorption and regeneration procedures
may be used in the carbon dioxide scrubber 16 for removing ~arbon
dioxide from the gas.
From the carbon dioxide scrubber 16, the gas which has
been preheated as above now flows to a gas dissociation apparatus
18 via a conduit 17. Gas dissociation apparatus are generally known
and described in the literature such as, for example, in Perry's
Chemical Engineer's Handbook, 1963 edition, Section 12, particular-
ly Figures 12-30 of this Handbook.
In the gas dissociation apparatus 18, the crude gas is
decomposed or dissociated into two or more fractions at low tempera-
tures of down to -200C for the purpose of separating out the hydro-
gen. When the gas is dissociated into only two fractions, substan-
tially pure hydrogen is obtained as one fraction. The other frac-
tion is a mixture of carbon monoxide (C0), methane (CH4) and nitro-
gen (N2). Where appropriate or desirable, this other fraction or
mixture (residual gas) may be further decomposed or dissociated in-
to its components.
In the gas dissociation apparatus 18, thP crude gas en-
tering the same is cooled to liquefactive temperature in a heat-
exchanger system. The gas subsequently flow to a distillation sys-
tem in which it is decomposed into the individual fractions. The
ao fraction constituted by substantially pure hydrogen leaves the gas
- 12 -
` 1071870
dissociation apparatus 18 via a conduit 19 whereas the other frac-
tion leaves the gas dissociation apparatus 18 as residual gas via
a conduit 20.
In the just-mentioned heat-exchanger system, the two frac-
tions are heated while, simultaneously, the gas entering the gas
dissociatLon apparatus 18 is cooled.
The residual gas fraction leaving the gas dissociation
apparatus 18 via the conduit 20 travels through the latter to a
combustion chamber 21 in which it is combusted with air. The flue
gas which is thus generated is, in the present instance, utilized
for heating the tubes 5 of the tubular oven gasifier. Thus, the
flue gas generated by combustion of the residual gas fraction pass-
es through a conduit 22 to the tubular oven gasifier. The cooled
flue gas leaves the tubular oven gasifier via a conduit 23. The
combustion air required for combustion of the residual gas fraction
is conveyed to the combustion chamber 21 via a conduit 24.
In the embodiment of the invention under consideration, a
portion of the hydrogen fraction leaving the gas dissociation appa-
ratus 18 through the conduit l9 is branched off from the latter via
a conduit 25. This portion of the hydrogen fraction travels through
the conduit 25 to a combustion cha~r 26. In the combustion cham-
ber 26, combustion is effected with an appropriate quantity of air
so that a mixture of water vapor and nitrogen is obtained. The air
required for the combustion is admitted into the combustion chamber
26 via a conduit 30. The quantity of air conveyed into the combus-
tion chamber 26 through the conduit 30 is selected to be so large
that the nitrogen content of the nitrogen-water vapor tN2/H20) mix-
ture formed by the combustion suffices to provide the required pro-
portion of nitrogen (N2) in the ammonia synthesis gas to be formed~
In other words, the quantity of air conveyed into the combustion
- 13 -
`-` 1071870
chamber 26 via the conduit 30 should be selected Ln such a manner
that the nitrogen (N2) content thereof amounts to 33 percent by vol-
ume or more ~ the quantity of non-combusted hydrogen.
The sensible heat of the nitrogen-water vapor (N2/H20) mix-
ture produced during the combustion in the combustion chamber 26 is
utilized for the generation of steam in a waste-heat boiler 27. As
a result, the mixture is cooled. Subsequently, the mixture is con-
veyed to the condenser 29 via a conduit 28. In the condenser 29,
the mixture is further cooled and the water vapor formed by the com-
bustion in the co~bustion chamber 26 condenses out.
The steam generated in the waste-heat boiler 27 is convey-
ed off through a conduit 31.
It is possible to build in a fuel cell instead of the com-
bustion chamber 26 and the waste-heat boiler 27. In such an event,
electrical energy may be generated by direct transformation of the
hydrogen through reaction with atmospheric oxygen.
The nitrogen-rich gas which has been cooled in the con-
denser 29 is sucked in by a compressor 32 via a conduit 33. In the
compressor 32, the nitrogen-rich gas is compressed to a pressure
which corresponds to the hydrogen pressure at the exit from the gas
dissociation apparatus 18 Subsequently, the nitrogen-rich gas may
be canveyed to a deoxidizing apparatus, which is not illustrated in
the drawings, for the purp~se of removing traces of oxygen which may
be present in the nitrogen-rich gas. The thus-purified nitrogen-
rich gas passes through a conduit 34 and is admixed with the pure
hydrogen in the conduit 19
It is pointed out that the nitrogen-rich gas may also be
treated at some point between the condenser 29 and the conduit 19
in order to remove traces of carbon dioxide which may be present in
<the nitrogen-rich gas.
- 14 -
1071870
The admixture of the purified nitrogen-rich gas from the
conduit 34 with the pure hydrogen in the conduit 19 result~ in the
formation of a gaseous mixture suitable for use in the synthesis of
ammonia. The synthesis gas produced by admixture of the nitrogen-
rich gas from the conduit 34 with the hydrogen in the conduit 19 is
conveyed to a compressor 36 via a conduit 35. The synthesis gas
contains the components hydrogen and nitrogen in a proportion of
about 3:1 by volume so that it may, in known manner, be transformed
into ammonia under pressure and in the presence of a suitable cata-
lyst according to the following equation:
3 -- 2NH3
In the preceding embodiment of the invention, the amount
of hydrogen branched off from the conduit 19 via the conduit 25 is
favorably between about 5 and 15 percent by volume of the hydrogen
stream flowing through the conduit 19. It is particularly advantage-
ous when about 8 percent by volume of the hydrogen stream flowing
through the conduit 19 is branched off through the conduit 25.
Another advantageous possibility for obtaining the nitro-
gen re~uired for the synthesis of ammonia is illustrated in FIG. 2
of the drawings
In FIG. 2, the same reference numerals as in FIG. 1 have
been used to identify like components.
The embodiment of FIG. 2 differs from that of FIG. 1 chief-
ly in that the conduit 25 is eliminated and in that a conduit 25a,
which branches off from the conduit 15 and leads to the combustion
chamber 26, is substituted for the conduit 25.
Thus, in the embodimeht of FIG. 2 a portion of the desul-
furized crude gas travelling through the conduit 15 is branched off
from the latter via the conduit 25a and conveyed to the combustion
chamber 26. The remainder of the desulfurized crude gas travelling
1071870
through the conduit 15 is processed in the same manner as in the
embodiment of F~G. 1 except that no portion of the hydrogen fraction
generated in the gas dissociation device 18 is branched off from the
conduit 19.
The amount of desulfurized crude gas branched off from
the conduit 15 via the conduit 25a depends upon the nitrogen con-
tent of the stream which is branched off. Favorably, however, the
amount of desulfurized crude gas branched off from the conduit lS
via the canduit 25a is between about 5 and lS percent by volume of
the crude gas stream flowing through the conduit 15.
The desulfurized crude gas admitted into the combustion
chamber 26 via the conduit 25a is combusted in the presence of air
conveyed into the combustion chamber 26 through the conduit 30. As
before, the quantity of air admitted into the combustion chamber 26
via the conduit 30 is so selected that it contains all of the nitro-
gen required for the synthesis of ammonia.
The heat generated by the combustion in the combustion
chamber 26 may here also be used for the generation of steam Thus,
the nitrogen-containing mixture obtained in the combustion chamber
2~ 26 is admitted into the waste-heat boiler 27. From the waste-heat
boiler 27, the mixture is conveyed into the condenser 29. The
nitrogen-rich gas which leaves the condenser 29 is, as in the em-
bodiment of FIG. 1, drawn into the compressor 32. However, FI~. 2
shows that the nitrogen-rich gas may pass through a carbon dioxide
scrubbing device 45 prior to entering the compressor 32 in order
to remove carbon dioxide which may be present in the nitrogen-rich
gas. From the compressor 32, the nitrogen-rich gas is admitted in-
to the conduit 19 via the conduit 34 for admixture with the hydro-
gen flowing through the conduit 19. Where appropraite or desirable,
the nitrogen-rich gas may be purified in a deoxidizing apparatus
107~870
.
prior to admission into the conduit 19 for the purpose of removing
traces of oxygen which may be present in the nitrogen-rich gas.
The embodiment of FIG. 2 possesses the advantages that
the combustion which is effected in the combustion chamber 26 so as
to obtain the nitrogen required for the synthesis of ammonia is car-
ried out with gas which has un~ergone relatively littLe pretreatment
and that smaller losses of hydrogen may be achieved.
In both the embodiment of FIG. 1 and the embodiment of
FIG. 2, the synthesis gas obtained in the conduit 35 is compressed
to the synthes~is pressure in the compressor 36 and mixed with the
circulating gas of the ammonia (NH3) synthesis operation. The re-
sulting gaseous mixture travels to a compressor 37 which circulates
the gas of the ammonia (NH3~ synthesis operation. The compressor
37 conveys the gaseous mixture to an ammonia (NH3) synthesizer 39
via a conduit 38.
Since the ammonia (NH3) synthesis per se does not form a
direct part of the process according to the invention, it is not
necessary here to go into the details of this synthesis.
The steam generated in the waste-heat boilers 8 and 27,
as well as in the ammonia (NH3) synthesizer 39, is collected in a
conduit 40 and conveyed away. The water for the steam generation
is supplied via a conduit 41 from which conduits 42 and 43 branch
off to the waste-heat boilers 8 and 27, respectively, and from which
a conduit 44 branches off to a waste-heat boiler in the ammonia
(NH3) synthesizer 39.
The-f~llowing Example is intended to further illustrate
the invention and is not to be construed as limiting the same in
any manner:
EXAMPL~
195 tons per hour of crude lignite having a water content
``` 107~870
of 59 percent by volume is comminuted to a particle size of less
than 6 millimeters. The comminuted coal is admitted into a fluidiz-
ed bed and, from the latter, into a tubular oven gasifier the tubes
of which are arranged horizontally. The coal is gasified in the
tubular oven gasifier at a temperature of 800C and under a pressure
of 40 bars. The gasification yields 250,000 normal cubic meters per
hour of crude gas having the following composition:
H2 44.5 percent by volume -
CO 18.6 percent by volume
C2 11.7 percent by volume
CH4 2.1 percent by volume
N2 1.3 percent by volume
H20 21.7 percent by volume
H2S ~ COS 0.1 percent by volume
This crude gas is treated in the manner described with
reference to FIG. 1, namely, by passing it through a collecting
space where the gasification residues are separated out at least
for the mOSt part; then conveying it through a waste-heat boiler
wherein it is initially cooled; next passing it through a cooling
washer for the nemoval of dust and for further cooling; subsequent-
ly compressing it; thereafter desulfurizing it to remove sulfur-
containing gases; and finally subjecting it to a carbon dioxide
(C02) scrub to remcve carbon dioxide. The thus-treated crude gas
is then admitted into a low-temperature dissociation apparatus. In
the low-temperature dissociation apparatus, approximately 101,415
normal cubic meters per hour of pure hydrogen are separated out of
the crude gas at a temperature of about -200C. 15,540 normal cubic
meters per hour of this hydrogen fraction are branched off from the
main body of the h~drogen fraction and combusted in a combustion
chamber with 37,000 normal cubic meters per hour of air. The com-
- 18 -
107~8'70
bustion yLelds a nitrogen-rich gas having the followLng composition:
N2 22.7 percent by volume
H2 66.7 percent by volume
H20 10.6 percent by volume
After the water vapor and the residual oxygen have been
removed from this nitrogen-rich gas, the nitrogen-rich gas is com-
bined with the remainder of the hydrogen fraction in an amount of
about 28,625 normal cubic meters per hour. Thereis thus obtained
114,500 normal cubic meters per hour of ammonia syn~hesis gas which
may be conveyed to a synthesis installation for further processing.
During the production of the synthesis gas, 51 tons per
hour of steam is generated. The steam has a temperature of 312C
and a pressure of 105 bars and may be conveyed away for use outside
of the framework of the process according to the invention.
The process in accordance with the invention exhibits the
following basic advantages as opposed to the known processing se-
quences for the production of ammonia (NH3) from crude lignite:
(1) Free oxygen is not required for the gasification.
In addition, when a shift conversion or conversion reaction of the
crude gas is omitted, no externally supplied steam is required. Con-
sequently, no air dissociation apparatus is necessary and, where a
shift conversion of the crude gas is omitted, there is no need for
a steam generator to generate process steam for the conversion of
the crude gas.
(2) The crude lignite is not pre-dried. Hence, no dry-
ing apparatus is required.
(3) The crude lignite need only be comminuted to a part-
icle size of less than 6 millimeters and need not be finely ground.
Accordingly, fine grinding and sieving are not necessary.
(4) Where a shift conversion of the crude gas is omitted,
- 19 -
` ~L071870
there is no need to provide an apparatus for carryLng out a shift
conversLon.
A process calculation whLch has been carried out showed
that, when the process of the invention is used, about 11 , 106
kilocalories are required per ton of ammonia manufactured when op- -
erating at low pressure. On the other hand, when the known process-
i~ sequences are used, the energy required for producing a ton of
ammonia from crude lignite amounts to approximately 14.5 , 106 kilo-
calories.
The teechnical advance achievable with ~he process accord-
ing to the invention should accordingly be absolutely clear.
- 20 -
