U.S. patent number 3,873,845 [Application Number 05/398,543] was granted by the patent office on 1975-03-25 for method of producing electric energy including coal gasification.
This patent grant is currently assigned to Heinrich Koppers Gesellschaft mit beschrankter Haftung. Invention is credited to Kaspar Heinrich Osthaus.
United States Patent |
3,873,845 |
Osthaus |
March 25, 1975 |
METHOD OF PRODUCING ELECTRIC ENERGY INCLUDING COAL GASIFICATION
Abstract
Chunk coal is comminuted to form coal dust, or existing coal
dust is utilized. The coal dust is advanced in concurrent flow with
a stream of heated air, and is gasified at atmospheric pressure and
at a temperature of substantially 1,500.degree.C. The resulting
combustion gases are cooled by admitting them to a waste-heat
boiler, to substantially 150.degree.C and concurrently with this
cooling effect steam is produced by heat exchange with the gases.
At least some of the thus produced steam is utilized to generate
electric energy at such times as the electric energy which can be
generated with the aid of the steam is sufficient to meet demands.
The cooled gases have dust electrostatically removed from them, and
are thereupon compressed to a pressure of between 20-50
atmospheres, whereupon they are de-sulphurized. Some or all of the
thus de-sulphurized compressed gases are used to generate
additional electric energy, but only at such times as the demand
for electric energy exceeds the amount which can be generated with
the aid of the steam produced by the combustion gases. Any
compressed and desulphurized gases which are not used for the
production of additional electric energy are subjected to further
processing.
Inventors: |
Osthaus; Kaspar Heinrich
(Essen, DT) |
Assignee: |
Heinrich Koppers Gesellschaft mit
beschrankter Haftung (Essen, DT)
|
Family
ID: |
5856992 |
Appl.
No.: |
05/398,543 |
Filed: |
September 18, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Sep 21, 1972 [DT] |
|
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2246407 |
|
Current U.S.
Class: |
290/2; 48/76;
60/39.12; 60/690; 48/203; 60/39.182 |
Current CPC
Class: |
C10J
3/00 (20130101); F01K 23/067 (20130101); C10J
3/84 (20130101); F02C 3/28 (20130101); C10J
2300/1671 (20130101); C10J 2300/1606 (20130101); C10J
2300/1253 (20130101); C10J 2300/1846 (20130101); Y02E
20/18 (20130101); C10J 2300/0909 (20130101); C10J
2300/1884 (20130101); Y02E 20/32 (20130101); Y02P
20/129 (20151101); C10J 2300/0946 (20130101); C10J
2300/0956 (20130101); C10J 2300/0976 (20130101); C10J
2300/1892 (20130101); C10J 2300/093 (20130101) |
Current International
Class: |
F02C
3/26 (20060101); F01K 23/06 (20060101); C10J
3/00 (20060101); F02C 3/28 (20060101); C10j
003/00 () |
Field of
Search: |
;60/64,39.12 ;48/203,76
;290/2,40,52 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simmons; G. R.
Attorney, Agent or Firm: Striker; Michael S.
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims:
1. In a differential-cycle method of producing electric energy for
peak and off-peak demand conditions, the steps of advancing coal
dust in concurrent flow with a stream of heated air, and effecting
its gasification at atmospheric pressure and at a temperature of
substantially 1,500.degree.C; cooling the resulting gases in a
waste-heat boiler to substantially 150.degree.C and concurrently
producing steam by heat exchange with said gases; using only the
thus produced steam to generate electric energy at such times as
the electric energy which can be generated with the aid of the
steam is sufficient to meet off-peak demands; removing dust
electrostatically from the cooled gases, thereupon compressing the
latter to a pressure of between substantially 20 - 50 atmospheres,
and finally desulphurizing the compressed gases; and using at least
some of the de-sulphurized compressed gases to generate additional
electric energy only at such times as the peak demand for electric
energy exceeds the amount thereof which can be generated with the
aid of the steam produced by cooling said combustion gases.
2. In a method as defined in claim 1, the preliminary step of
producing said coal dust by subjecting coal chunks to a grinding
and drying operation.
3. In a method as defined in claim 1; and further comprising the
step of converting that amount of the compressed and de-sulphurized
gas which is not required for generating of said additional
electric energy, into hydrogen.
4. In a method as defined in claim 1; and further comprising the
step of converting that amount of the compressed and de-sulphurized
gas which is not required for generating of said additional
electric energy, into ammonia-synthesis gas.
5. In a method as defined in claim 1; and further comprising the
step of converting that amount of the compressed and de-sulphurized
gas which is not required for generating of said additional
electric energy, into hydrogen and ammonia-synthesis gas.
6. In a method as defined in claim 1; and further comprising the
step of converting that amount of the compressed and de-sulphurized
gas which is not required for generating of said additional
electric energy, into a methane-rich gas.
7. In a method as defined in claim 1, wherein the step of using
said steam to produce electric energy comprises driving a turbine
with said steam, and driving a generator with said turbine.
8. In a method as defined in claim 1, wherein the step of using
said compressed and de-sulphurized gases to generate electric
energy comprises admitting said gases under pressure into a
combustion chamber, combusting the gases to produce gaseous
combustion products at substantially 1,500.degree.C, admixing
pressurized air with said combustion products to form therewith a
mixture having a temperature of substantially 820.degree.C, and
driving with said mixture a turbine which is coupled with a
generator.
9. In a method as defined in claim 1; further comprising using that
amount of the steam which is not required for generating of
electric energy, in one of the succeeding steps.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method of producing electric
energy, and more particularly to a method of producing electric
energy based upon the partial oxidation of coal dust. Still more
specifically, the present invention relates to the production of
electric energy using hot gases which are obtained by the partial
oxidation of coal dust.
It is well known that every producer of electric energy for
household, commercial and other purposes is faced with the problem
that the energy demand differs at different times of the day. Thus,
the highest energy demand of the day may come in the summertime
around noon, when a large number of airconditioners and other
devices is in operation. During the night when the temperature
drops somewhat, less energy will be required for airconditioners,
and of course, also for other purposes, since many businesses are
closed at night-time and since the household consumption of
electric energy also decreases. The producer must be ready to meet
both types of demand, that is either the low demand at night (or in
another comparable time period when low demand occurs) and the peak
demand. On the other hand, he cannot produce electric energy
constantly at the peak-demand level, because this type of electric
energy cannot effectively be stored. It is hardly necessary to
point out that this problem is highly disadvantageous in terms of
the economy of electric energy production.
The prior art has made various attempts to overcome the problem.
One of these has been to create power grids, where different
power-consuming areas are linked with one another, and one area can
draw upon extra electric energy of another area. This is effective
to a certain extent if the areas have different peak demand times,
for instance if they are far apart so that due to an existing time
differential, peak demand occurs in the various areas at different
times. Thus, an area having a peak demand period can draw upon the
excess electric energy of a producer who is associated with the
grid and is located in an area where at this same time there is a
low demand. However, for various reasons this solution also is not
fully effective, and the industry continues to actively seek better
solutions, especially solutions which provide improved operating
economy.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to
provide such an improved solution.
More particularly, it is an object of the present invention to
provide an improved method of producing electric energy.
Still more particularly, an object of the present invention is to
provide an improved method of producing electric energy by
utilizing hot gases obtained by the partial axidation of coal
dust.
In keeping with these objects, and with others which will still
become apparent hereafter, one feature of the invention resides in
a method of producing electric energy, in the steps of advancing
coal dust in concurrent flow with a stream of heated air, and
effecting its gasification at atmospheric pressure and at a
temperature of substantially 1,500.degree.C. The resulting
combustion gases are cooled in a waste-heat boiler to substantially
150.degree.C. and concurrently steam is produced by heat exchange
with the gases. At least some of the thus produced steam is
utilized to generate electric energy at such times as the electric
energy which can be generated with the aid of the steam is
sufficient to meet demands. The cooled combustion gases have dust
electrostatically removed from them, and are thereupon compressed
on a pressure of between substantially 20 - 50 atmospheres, and
finally de-sulphurized. At least some of the de-sulphurized
compressed gases are used to generate additional electric energy
only at such times as the demand for electric energy exceeds the
amount thereof which can be generated with the aid of the steam
produced by cooling the combusion gases.
To operate with the method of the present invention, the coal dust
oxidation installation is so dimensioned that the heat which can be
reovered by heat exchange in the waste-heat boiler from the
combustion gases produced by the partial oxidation of the coal
dust, is at least sufficient to generate that amount of electric
energy which is necessary to meet the basic energy demand, that is
to produce the amount of electric energy which the producer can
sell on 24-hour basis. The gases, however, which produce the steam
required for generating the basic amount of energy, are utilized
for producing additional electric energy at the peak demand
periods, that is to produce the amount of energy which must be
added to the basic amount produced by the steam in order to meet
the peak energy demand. Evidently, there will be circumstances
and/or time periods when it is not necessary to produce additional
electric energy, because a peak demand does not exist. Then again,
there will be circumstances when the additional energy which must
be produced with these gases in order to meet the peak demand, does
not require that all of the gases be utilized for energy
production. Any gases which are not required for the production of
additional electric energy can, in accordance with the present
invention, be utilized for other purposes so as not to be wasted.
In particular, these gases can be converted into a methane-rich
gas, into hydrogen and/or a so-called ammonium-synthesis gas. Two
or more of these conversions can be carried out simultaneously, by
allocating appropriate parts of the available gases to the
different conversion methods. It is evidently also possible to
convert the gases for other purposes, which will suggest themselves
to those skilled in the art.
The coal dust required for the present invention can be produced by
a so-called comminuting or grinding drying process, which will be
described subsequently. In this case, chunk coal is converted into
coal dust. There will, however, be many instances when sufficient
coal dust is already available as a waste product of normal coal
production, particularly if the coal is produced under certain
production conditions. Evidently, if the coal dust is already
available, it need be merely dried, not comminuted.
An essential feature of the present invention is the fact that the
gasification or partial oxidation of the coal dust is carried out
at normal pressure, that is at atmospheric pressure. Heretofore, it
has always been an aim of the industry to operate coal dust
gasifying equipment at increased pressure levels, during
gasification of the coal at temperatures of approximately
1,500.degree. C. which are above the slag melting point. However,
the introduction of the quantities of which are required for
carrying out the method of the present invention, for instance on
the order of 500 tons per hour, creates certain problems if the
gasification equipment operates at super-atmospheric pressure. It
is for this reason, that the present invention proposes to subject
the gases produced during the coal dust gasification to an
electrostatic dust-removal operation, and thereupon to compress
them at pressures of between substantially 20 - 50 atmospheres.
Since the present invention requires the use of air in conjunction
with the coal dust during the gasification of the latter, the
advantage which exists in certain prior-art gasification proposals,
namely to operate the gasification equipment at higher pressure
levels in order to eliminate or reduce the necessity for subsequent
compression of the gas, does not exist in any case, but its absence
is far outweighed by the advantages obtainable with the present
method.
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 opertion, together with additional objects and advantages
thereof, will be best understood from the following description of
specific embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINg
The single FIGURE is a flow diagram which illustrates, by way of
example, how the present invention operates.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The example illustrated in the drawing is based upon the conversion
of chunk coal into coal dust, that is, it assumes that coal dust is
not already available in dust form or is not being used in the
initial step. The term chunk coal used herein should be understood
not merely to refer to large-size coal pieces, but also to
relatively coarse granules of coal as opposed to mere coal
dust.
With the aforementioned comments in mind, it will be seen that the
coal to be gasified, either soft coal or hard coal, is admitted
from the coal bunker 1 through a conduit 2 into a drying tube 3 the
upper end of which is divergent as shown, and which operates as an
air-dryer. At the same time, coal dust is combusted in a furnace or
combustion chamber 4 and the hot combustion gases are admitted at
approximately 800.degree.C. temperature through the conduit 5 into
the lower end of the conduit 3, to rise herein. The coarse coal
particles admitted from the bunker 1 are removed from the rising
gas stream at the upper diverging part of the conduit 3, whereas
the fine coal dust which is carried along by the upwardly moving
gas stream enteres the cyclone 7, where it is separated from the
gas stream in dry condition. The vapors which develop during this
drying operation for the coal dust are withdrawn through the
conduit 6, after they have passed through a cooling and scrubbing
stage 8.
The coarse coal particles which have been retained in the upper
divergent part of the conduit 3, are admitted via conduit 9 into
the grinder or comminuter 11 in which they are comminuted to form
coal dust. This dust is returned via conduit 12 into the lower part
of the drying conduit 3. As this takes place, the coal dust which
has been recovered and returned in the cyclone 7 flows via the
conduit 10 to an intermediate storage bunker 13, from where it is
fed into the conduit 14 through which the air flow that is required
for the desired coal dust gasification.
This air has previously been pressurized in blower 15, and
pre-heated to approximately 600.degree. C. in an air heater 16. The
mixture of air and coal dust enteres the gasification unit 17 which
is of completely conventional construction, as described in
Ullmann's Encylklopadie de Scchnischen Chemie Vol. 10, 1958, page
412-413 (Berlin-Mandren) and is gasified therein at a temperature
of approximately 1,500.degree. C. The molten slag which results
during gasification is withdrawn in molten condition through the
conduit 10, and is subsequently subjected to a granulation step.
Since the gasification takes place at normal pressure, that is at
atmospheric pressure, the unit 17 must be appropriately
large-dimensioned. To retard as much as possible the heat energy
radiation, the unit 17 must be provided with an effective thermal
insulation, and it will be noted that the wasteheat boiler 20 is
located not in the unit 17 itself, but is arranged separate from
the same.
Assuming, by way of example, that the unit 17 receives 100 tons of
coal dust per hour, then during each hour approximately 400,000
Mm.sup.3 of a gas are produced, having the following
composition:
3.4 % by volume CO.sub.2
26.0% by volume CO.sub.2,
9.4% by volume H.sub.2,
0 % by volume CH.sub.4,
61.0% by volume N.sub.2,
0.2% by volume of sulphur compounds.
This gas if of course hot. It is admitted via the conduit 19 into
the waste-heat boiler 20, where it is cooled from approximately
1,500.degree.C. to approximately 150.degree.C. The heat exchange
which makes this cooling possible, results in the production of
high pressure steam at a pressure of 120 atmospheres, and a
temperature of 520.degree.C. This steam is furnished via the
conduit 21 to a turbine 22 which is coupled with a generator 23,
capable of producing the normally required amount of electrical
energy, that is the amount of electric energy which can be sold on
a 24-hour basis. This, in other words, is the amount of energy that
can be sold around the clock.
The steam which has been expanded and cooled in the turbine 22, is
furnished via the conduit 24 into the condenser 25. Cooling water
required for the operation of the condenser 25 is supplied to the
same via conduit 28 from a cooling tower 27, and after it has been
heated up in the condenser 25 it is recirculated to the cooling
tower 27 via a conduit 26. The condensate produced by condensing of
the steam in the condenser 25 is returned via the conduit 29 into
the waste-heat boiler 20 for the production of additional
steam.
If the amount of high pressure steam produced in the boiler 20 is
not required in its entirety for driving the generator 23 via the
turbine 22 in order to produce the normally required amount of
energy which can be sold on a 24 hour basis, that is the base
amount of energy, the excess steam can be vented via the conduit 30
and supplied to the subsequently following gas processing stations,
which will now be described.
The gas, which has been cooled in the boiler 20 to a temperature of
approximately 150.degree.C., is vented from the boiler 20, and
supplied to an electrostatic dust separator 32, wherein it is freed
of dust particles. From there, it passes via the conduit 31 to the
compressor 33 where it may be compressed to a pressure of between
substantially 30-50 atmospheres, depending upon requirements. In
the present example it is assumed that a pressure of approximately
30 atmospheres is sufficient. The thus compressed gas is then
passed on through the conduit 34 into the de-sulphurizing unit 35,
where it is scrubbed of the sulphur compounds, particularly the
H.sub.2 S, by treating it in known manner with a known solution or
substance, which flows through the unit 35 in downward direction,
that is in counterflow to the gas which rises upwardly through the
unit 25. During this flow, the solution becomes enriched with the
sulphur compounds, and is discharged into the scrubber 37 via the
conduit 36 where it becomes re-generated. Scrubbed-out H.sub.2 S is
supplied via the conduit 38 into the Claus oven 39, where it is
combusted to form elementary sulphur which is vented out of the
installation via the conduit 40. During this time the regenerated
solution is pumped out of the scrubber 37, and via the conduit 41
back to the top of the unit 35.
At this point in time, the compressed and desulphurized gas is
advanced via the conduit 42 to the distributor (e.g. valve) 43,
where it can be split up into partial streams. That amount of gas
which is to be used for producing additional electric energy to
meet peak energy demand, is advanced via the conduit 44 into a
pressure burner 45 in which it is combusted at for instance
approximately 1,500.degree. C and 30 atmospheres pressure. The
combustion air required for this purpose is pressurized in the
device 71 and blown under pressure through the conduit 46 into the
unit 45. The hot combustion gases produced in the unit 45 are
vented via the conduit 47, and are admixed with compressed air
which is supplied by a bypass conduit 48. This results in a cooling
of the thus-created mixture to approximately 820.degree.C., and the
thus produced cooled mixture is admitted to the turbine 49 which it
drives, during which operation it becomes expanded. The expanded
gas issues from the turbine 49 at a temperature of approximately
150.degree.C., and is vented via the conduit 50 to the chimney. The
turbine 49 is coupled with a generator 51 which produces the
necessary amount of electrical energy to meet the peak demand, that
is, it produces an amount of electrical energy equal to the
difference between the peak demand and the amount of energy
produced by the generator 23.
Any compressed and de-sulphurized gas which is not required for
producing electric energy via the generator 51, can be processed
for different purposes and in a different manner. In the
illustrated embodiment, it is split up at the point 43 into two
partial streams, one of which is supplied via the conduit 52 into a
methane producing installation 53, in which the gas is converted at
a temperature of approximately 400.degree. C. in the presence of an
appropriate catalyst, for instance an iron catalyst well known in
the art, to form a methane rich gas. The water vapor necessary for
this conversion can be supplied via the conduit 54 which
communicates with the unit 53 and with the conduit 30. If no vapor
or steam can be supplied via the conduit 30, then it is of course
necessary to derive the vapor or steam from an external source. The
methane-rich gas produced in the unit 53 and vented therefrom
through the conduit 55, has the following composition:
22.8% by volume CO.sub.2,
9.7% by volume CH.sub.4,
67.5% by volume N.sub.2,
traces of H.sub.2, CO, and H.sub.2 O.
This gas which has been thus produced is admitted into a
heat-exchanger 57 where it is cooled in heat exchange with a gas
stream which comes from a gas separating unit 57. CO.sub.2 is
separated from the gas and vented out of the installation via the
conduit 58. In the gas separating unit 57, CH.sub.4 and N.sub.2.
Ch.sub.4 are withdrawn via the conduit 59 which passes the heat
exchanger 57. N.sub.2 is similarly withdrawn via the conduit
60.
The second partial stream of compressed and de-sulphurized gas
which is branched off at the point 43, is admitted via the conduit
61 into a converting unit 62 which receives steam from conduit 30
via a conduit 63 or via an external source of steam. The gas is
converted in known manner, that is either by way of high
temperature conversion or low temperature conversion, by contact
with catalysts which are known in the art. The gas which is
produced by conversion and which is vented from the unit 62 via the
conduit 64, has the following composition:
23.4% by volume CO.sub.2,
28.2% by volume H.sub.2,
48.4% by volume N.sub.2,
traces of CO and H.sub.2 O.
This gas is passed via the heat exchanger 65 into a gas separating
unit 66. In the heat exchanger 65 it undergoes cooling, resulting
in a separation of CO.sub.2 from the gas, which CO.sub.2 is
withdrawn via the conduit 67. The gas which is derived after
treatment in the installation 66, and which is withdrawn therefrom
via conduit 68, contains N.sub.2 and H.sub.2 in a ratio of 1 : 3;
this gas is therefore suitable for further processing to produce an
ammonium-synthesis gas. Excess H.sub.2 is withdrawn via conduit 69
and heat exchanger 65, whereas excess N.sub.2 is withdrawn via
conduit 70 and heat exchanger 65, to be furnished to the conduit 60
and united with the N.sub.2 which is already present in the
same.
It should be clearly understood that no attempt has been made in
the flow diagram to illustrate or describe components, equipment,
or processes which are already well known to those skilled in the
art, for instance, the construction and operation of the heat
exchangers, gas separating units, or the like. Similarly, such
necessary but conventional parts of the installation as valves,
pumps and the like, whose presence and location will be readily
apparent to those conversent with the field have not been shown or
described.
The present invention presents a method of producing electric
energy which permits a heretofore unequaled flexibility in the
production of electric energy that is a flexibility in the
accommodation of the energy production to peak and off-peak
demands. Moreover, the economy of energy production is not merely
significantly improved over the prior art, but is guaranteed,
because of the possibility afforded by the present invention, of
converting the gas not required for the production of additional
electric energy into other useful and economically valuable
products, as part of the energy-production cycle.
It will be understood that each of the elements described above, or
two or more together, may also find a useful application in other
types of applications differing from the types described above.
While the invention has been illustrated and described as embodied
in a method of producing electric energy, it is not intended to be
limited to the details shown, since various modifications and
structural changes may be made without departing in any way from
the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge readily adapt it for various applications without
omitting features that, from the standpoint of prior art, fairly
constitute essential characteristics of the generic or specific
aspects of this invention and, therefore, such adaptations should
and are intended to be comprehended within the meaning and range of
equivalence of the following claims.
* * * * *