Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a process for supplying
fuel for a gas-steam turbine power station providing peak
current generation on a basis of coal, preferably bituminous
coal, wherein the fuel is generated by the autothermic
pressure gasification of prepared run-of-mine coal with
a mixture of steam and oxygen and with air, respectively.
Furthermore, the invention relates to a plant for carry-
ing out this process.
Generally, peak current is generated in older
coal-fired power stations in which the heat is provided
by the direct burning of the coal used and is employed for
generating steam for the steam turbines, by which generators
for producing current are driven. The use of older power
stations is due to the relatively short duration of the
peak loading, and to the consideration that the relatively
poor efficiency of the old power stations can be accepted
under such conditions. However, the use of such power
stations manifests itself in the
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increased costs of the peak current. There are also
disadvantages for the enviro~nent, because in the older
coal-fired power stations, mostly only inadequate measures
can be taken against environmental pollution. In partic-
ular, emissions of injurious materials such as carbonmonoxide, oxides of nitrogen, smoke, ashes and drainage
waters in considerable quanti-ties have to be reckoned
with.
As opposed to this, gas-steam turbine power
stations,of the type mentioned in the introduction, offer
considerable advantages. Principally, they are based on
pressure gasification, the gas being fed into so-called
combi-blocks. A plant of this kind has/pressure-fired
steam generator in which the gasification gas is burned.
The heat released by this drives a steam turbine which is
coupled to a generator which serves to produce the current.
The partly cooled combustion gases are delivered to the
expansion stage of a further gas turbine with a coupled
generator and are reduced in this to atmospheric pressure.
Combi-blocks of this kind have the advantage of a good
degree of efficiency.
For some time, such gas-turbine power stations
have been erected in the immedia-te vicinity of the pressure
gasifier and its coupled gas scrubbing plant. Since, on
the other hand~ it is most practical to erect the pressure
gasification at the locality of the power station and
the coal delivery plant respectively, it au-tomatically
results that the gas-steam turbine power station is
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located in the immediate vicinity of the stora~e sites.
Thus, the generated current has to be conveyed to distant
consumers. However, it is well known that the conveying
of current involves considerable expense. Also, the
number of gasification plants per power station unit
forms a bottle-neck. As the gasification plant is
located directly before the combi-block, the gasification
plant can only be run at an output corresponding to the
offtake of current. This means an irregular method of
operating which also leads to a multiplicat~on of gasifi-
cation plants. Thus, hitherto, the described gas-steam
turbine power stations have not been suitable for the
generation of peak current.
The essential object of the invention is to
exploit the advantages of these gas-steam turbine power
stations for the generation of peak current by achieving
especially, in spite of the differing operatlon of the
combi-blocks on account of the peak loadings, a regular
operation of the gas generating plant and a constant
optimum gas product.
According to one aspect of the present invention
there is provided a method for matching the generally
constant output of a coal gasification process with a
gas-steam turbine power station intermittently operable
to accommodate peak loadings, said power plant being
coupled to a gas supply utility system, said process com~
prising the steps of: generating a supply gas of auto-
thermic pressure gasification of coal with steam and oxygen;
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obtaining from the supply gas, methane gas and, selectively,
a synthetic gas of lower heating content and methanol;
storing the methanol so obtained; supplying the methane
gas to the gas supply utility system as a storage means;
intermittently supplylng at ].east one of the stored
methanol and synthetic gas to the power stat~on as a
fuel for peak loading conditi.ons; and intermittently with-
drawing gas from the gas supply utility system for supply
to the po~er station for peak loading conditions.
The balancing of the peaks between the power
station and the gas production is carried out according
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to the invention by storing the energy con-tained in the
gasification gas in the form of materials which are
produced in the periods in which the power offtake either
does not take place at all, or only attains a fraction of
the full load of the power station. For this reason the
generation of gas need not be matched to the current
offtake. If the current offtake reaches peak proportions,
which demands the employment of more energy than that made
available in the synthetic gas, then the previously
produced and stored methanol can be employed and thus the
necessary additional energy obtained.
The pure methane (natural gas quality) obtained
in both cases with a calorific value of e.g. 8.330 kcal/Nm3
(as opposed to the calorific value of C0 ~ H2 ~ synthetic
gas with 2.750 kcal/Nm' and a calorific value of 4660
kcal/kg of the methanol in the example selected) can also
be employed for use in the generation of the peak currents
if it is fed in as a replacement gas in an available
natural gas supply system.
The invention has, inter alia, the advantage
that it enables the power station to be erected in the
vicinity of the consumer, and also at any required distance
from the gas producing plant and the storage areas, because
the conveying of methanol is, of course, without problems,
and a gas pipe of a relatively small diameter is sufficient ;
for piping the synthetic gas owing to the gas pressure
which is produced in the generation of the gasification
gas. This gas pressure enables, on its part, gas storage
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which can be exploited to maintain a constant supply on
the gas side.
The following is a more detailed description of
an embodiment of the invention, reference being made to
the accompanying drawings in which:
Figure 1 is a schematic representation of a
plant for carrying out a process according to the invention,
with a gasifier and several power stations,
Figure 2 is a schematic representation of a
plant for the conversion of coal into synthet~c gas or
methanol, and methane,
Figure 3 shows details of a coal pressure gasification
process and methanol synthesis,
Figure 4 is a gas progress chart showing the
process from the pressure gasification to the synthesis
of the methanol, and
Figure 5 sets out the energy supply for the
pressure gasification and synthesis.
According to Figure 1 long-flame gas coal,
of run-of-mine quality, is processed. This takes place
in conventional pressure gas reactors which are only
schematically shown at 1 in Figure 1 but which is shown
in greater detail in Figure 2 through 5. In these vessels
the fuel, together with oxygen and steam as gasification
agents, is gasified as well as being pyrolytically split.
The operational pressure is around 40 bar or greater.
The generated gasification gas (at a temperature
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oE 550C to 600C) goes through a scrubber cooler in the
form of a quench cooler and subsequently a waste-heat
boiler (5 bar, or greater, saturated steam) and emerges
into the indirect condensation stages at about 140C.
Up to about 120C, each of the condensation stages,
water and tar are precipitated; below 120C to about 5C
above the cooling water temperature, water and oils separate
out.
The li~uid condensates are separated after prior
releasing of pressure by a parallel plate separator (CPI)
into oil, water and tar. A part of the tar is recycled
to the gas generator, the remainder can be used incident
ally, in the preparation of fuel, as a binder for agglom-
erating the small grade granules (0 to 3 mm) of the raw coal,
but is also available as a fuel for the generation of
steam, whereas KW gas corresponds to HC gas and HU denotes
calorific value.
After passing through the condensation stages the
gas has the composltion in Figure 4.
The supplied raw coal is first graded in a sieving
device to a grain size of above 3 mm.
The material passing through the sieve goes to an
agglomerating device (for making into pellets or briquettes)
and is agglomerated into particles of 10 to 20 mm grain
size by means of tar from the pressure gasification and
sulphite waste liquors.
; The agglomerated material then passes through a hard-
~ ening process which takes place at 150C in a stream of
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nitrogen. The nitrogen comes from the decomposition of
air and is heated by means of steam. The residues from
the sieve as well as the agglomerated undersize granules
are stored in the day bunker. In this respect, according
to requirements, separate or common storage may be employed.
The crude gas is then washed with methanol at 230
to 205 K. Thus, all the impurities in the gas such as
gas benzene, crude benzole, ammonia, hydrocyanic acid,
organic sulphur components, hydrogen sulphide, carbonic
acid and also resin formants and steam are absorbed.
In different stages rege~erationof methanol then takes
place by releasing from pressure, evacuating and heating.
The hydrocarbon fraction contains the hy~rocarbons and
other impurities, the H2S fraction passes to the Claus
oven. The separated C02 is released into the atmosphere.
This so-called rectisol plant is integrated in the coal
part of the gas splitting area in order to improve the
economies of the process which can be seen from Column
B of Figure 4.
For splitting the gas from the rectisol plant, a iow
temperature separating plant is provided wherewith the
H2 fraction is washed with liquid methane. In this manner
the operation can be carried out in temperature ranges
around 100K.
The CH4 fraction has a natural gas quality, a part
of which is fed to the internal heating gas system, as
indicated at E and F respectively in Figure 4.
By way of the methane washing, the required
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--~ C0-H2 ratio of 1:2 is adjusted by regulation of the mixed
gases; the final mixing takes place in the live gas
compressing which follows. The hydrogen fraction leaves
the gas separating plant at a pressure of 30 atmospheres
whilst the C0 fraction, the CH4 and residual gas fractions
occur under normal pressure and slightly increased pressure
respectively; they are shown at C in Figure 4.
For the synthesis of methanol the described
embodiment employs a known process which works at
approximately 60 atmospheres.
The compressing of live gas and circulation gas
is combined in one plant.
The heat of reaction from the synthesis reactor
is used for the production of steam for gasification.
The condensed-out crude methanol goes to a
storage tank which supplies the two stage associated
distillation.
The residual gas from the reactor, and also the
residual distillation gases, are fed into the internal hot
gas system. The pure methanol comes from the distillation
and is fed to the tank storage for the finished product
or the pipe line. The synthesis is shown in D of Figure
4.
The oxygen necessary for -the gasification con-
sisting of 96% 2 is generated in a conventional airdecomposition plant.
All residual gases are used for the generation
of steam which is based on a live steam condition of 116
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bar and 525C. Air compressors, 2 compressors,
refrigerating machines, synthetic gas compressors and
the charging gas compressor are driven by steam. The
back steam, at 35 bar, 241C, serves as gasification steam
and the still remaining residue as processing steam for
the distillation, coal preparation and for dealing with
the drainage waters as well as other auxiliary equipment.
The feed water is obtained partly from the
preparation of the drainage water and partly from con-
ventional sources.
The H2S fraction from the rectisol plant is
converted to elemental sulphur by a Claus plant.
The steam generated in the Claus boiler is fed
to the low pressure steam processing system.
For reasons of cost, the retrieving of the
materials contained in the drainage waters is to a great
extent dispensed with in the described embodiment. The
organic components are separated and biologically broken
down respectively according to known processes.
The inorganic components still remain in the
drainage water and are retrieved as firm residues
thermically.
The purified drainage water then passes to the
feed water preparation. The following results from the
material and heat balance sheets Example I and II.
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Applied heat 1,166,08 Gcal/h
Direct employable heat from products
(summary of the stated positions) 836,27 Gcal/h
or 71.7%
From the material and heat balance sheet of the
methanol procedure which is shown in ~xample II the
following results:
Applied heat 1,166,08 Gcal/h
Direct employable heat from products
(summary of the stated positions) 749,16 Gcal/h
or 64.2%
In the embodiment there are yearly approximately
1.6 million tons of coal prepared inthree thousand work-
ing hours for a 640 M~ unit.
The coal conversion plant is to a great extent
self-supplying with regard to energy, ie., it generates
steam for driving and processing by way of its own steam
generation from residual gases.
The gasification plant is indicated generally
at 1 in Figure 1. Its details emerge from the above
description of Figures 2 to 5. Several supply pipe lines
2, 3, 4 lead from the gasification plant 1 to individual
power stations 5, 6, 7. The power stations are similar
to each other so that it is sufficient to describe only
power station 6 in greater detail:
The synthetic gas which comes from the pipe 3,
by way of a slide valve 45, is fed to an expansion turbine
10 which reduces the pressure of the gas to the working
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pressure of the so-called pressure fired steam generator
12. The gas is burnt in this steam generator 12. With
the heat thus generated high pressure s-team is collected
in a heat exchanger sys-tem 13, which steam drives a
steam turbine 14 which is coupled to a generator 15 used
for producing current. The partly cooled flue gases
arrive in an expansion stage l6 of a gas turbine and are
there reduced to atmospheric pressure.
The expansion stage-16 of the gas turbine drives
a gas turbine-air compressor 17 which delivers the
necessary combustion air to the combustion chamber of the
steam generator 12. In the embodiment a generator 18 is
driven with the excess power of the gas turbine 16,17
which generator serves for the generation of current.
The plant components which have been described
so far form a so-called combi-block. As long as no
synthetic gas is in the gas pipe 3, methanol can be taken
from the schematically shown tank storage 46 and burnt
instead of the synthetic gas.
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Material and Heat balance for Synthetlc ~aæ Route:
INPU~:
Crude coal -1 97J20 t/h = 1.104,33 ~ca~/h
O~cyge~ 86, 04 t/h _ _ _
Stea~ 249 9 94 t/h _ _ _
Briquetted materiala 11,00 t/h = 61,75 Goal/:h
( own tar and sulphlte liquor)
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. Total Input 544~18 t/h = 1.166~08 Gcal/h
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OUTPUT
A~h 47,33 t/h
Tar and oil rrom condensation 3,00 t/h = ?700 Gcal/h
PS-Residual gas rro~ Rectisol 4,57 t/h = ~ cal/h
C2 re~idual gas ~ro~ Rectisol 185,43 t/h = 0,28 Gcal/h
~ rro~ Claus Plant 2,27 t/h = 5~03 ~cal/h
Clau~ residual gas 9, 58 t/h _ _ _
CH4 fraction ~ro~ æpl~tting 21, 21 t/h - ~ ~cal/h
CO~H2 fraction rrom splitting 87,39 t/h = ~00~_ GcaL~h
Residual gas rro~ splittlng2917 t/h = 14t~4 ~cal/h
Organic and i~organic materials
fron gas water 3,80 t/h = 13~20 t~cal~h
Pure water rro~ waste water1 6g, 56 $/h _ _ _
Losæes 7987 t/h =31 1"30 Gc~l/h~
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Total Output 544,18 t/h -=1 .166908 acal/h
Renarks:
Heat input. 1.1 66,o8 Gcal/h
Direct e~Loyable heat fro~ products
( total Or defiIIed positions) 836,27 Gcal/h~
7 ?7 %
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2. Materlal ~d Heat Balanc~ for the hlethanol Route
INPUT a ~ 1.
OUTPUT:
A~h 47,33 t~
Tar and oil ~ro~ conden&-
ation 3~00 t/h = ?7.00 ~cal~h
PS-Res~dual ga~ ~rom Rectisol 4,57 t/h = 43,29 ~cal/h
C~2 residual gas ~ro~
Rectisol 185,43 ~h c0,28 ~cal/h
8 from Clau~ plant 2,27 t/h =5,03 Gcal/h
Claus re6idual gas 9,58 t/h ~ _
CH4 fraction ~rom ~plitting 21, 21 t~h = ~ cal/h
Residual gas rrom splitting 2917 t/h = 14.~4 ~cal~h
Methanol from synthe~is 83,66 t/h ~ Gca~/h
Re~idual gas rro~ synthesi~ 3,73 t/h - ? ~ ~cal/h
Organic and Inorganic
materlals ~ro~ gas ~ater 3,80 t/h = i5,00 Gcal/h
Pure ~ater and ~a~te water 169,56 t/h ~
Lo88~8 7,87 t/h =396,61 ~cal~h
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- Total Output 544,18 t/h = 1 o1 66po8 ~cal/h
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Remark~:
Heat input 1.166908 Gcal~h
Direct employable heat from products
(total o~ de~ined po8ition8) -749~16 Gcal~h
or 64,2 %
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