Note: Descriptions are shown in the official language in which they were submitted.
^- ~118178
The invention relates to a method, and an appli-
ance for carrying out the method, for generating ga~es
for operating a gas turbine in a combined gas turbine
and ~team turbine power station, in which fine-grained
to pulverized coal ic almost completely burned at a
pres~ure greater than 1 bar and a temperature greater
than 1000 C with air, with air enriched with oxygen or
with pure oxygen alone or mixed with recirculated
exhaust gas in each case to form a combustion gas which
consists essentially of C02 and steam and, when air is
used, also of ni~rogen, and which i8 subsequently
cleaned at least from dust including alkali metal
compounds and possibly from S02 and N0x, which
combustion gas flows in sequence through a gas turbine
and a waste heat steam generator in whiah water for
operating a steam turbine is preheated, evaporated and
superheated at one or a plurality of pressure stages.
Such installations have become known from the
journal VGB Xraftwerkstechnik (70) 1990, No. 5,
Pages 399-406, inter alia. The gases generated contain
pollutant materials which would damage the gas turbine
and a gas cleaning system is therefore absolutely
necessary. Because it is scarcely possible to carry
out effectivè cleaning of such hot, pollutant-laden
gases with temperatures above the permissible entry
: 21182178
temperature of modern gas turbine~, i.e. above 1200 C,
the temperature of the gases must be reduced to a level
of approximately 650-950 C co that the gas cleaning
can be carried out by known and tested methods. Thi~
temperature level i8, in partiaular, also decisive for
the dry additive method (desulphurization by spraying
in lime dust) and the selective non-catalytic reduction
- SNCR - method (reduction of the oxide~ of nitrogen by
ammonia or a catalyzer). In order to achieve this tem~
perature level, heat is generally removed in a steam
:: ~ .
power process or the sy3tem i~ operated with a very
high level of excess air.
In the known method - removing heat in a steam
: . . -:
process or operating with a high level of excess air -
disadvantageous features are the 1088 of efficiency due
to the heat transfer to the steam process at a rela-
tively low temperature or due to the reduced gas tur-
bine inlet temperature in the ca~e of a high level of
excess air and the increased exhaust gas lo~ses. The
coupling of gas turbine operation and waste heat boiler
operation is also disadvantageous.
As a consequence of the discussion ahout the
climate, of environmental protection and of the preser-
vation of resources, the not unsubstantial increase in
efficiency due to the method proposed and the appliance
proposed have gained great importance, particularly in
recent years.
The objec~ of the invention i8 to create a method
of the type de~cribed at the beginning and the
2118178
associated appliance in which the disadvant2ges
described are avoided and a decisive improvement to the
efficiency i8 aahieved in the generation of electrical
current from coal. This object is achieved by means of
the characterizing part of Patent Claim 1.
Advantageous embodiments of the invention may be
taken from the su~-claims 2 to 9.
The following advantages relative to the known
prior art are achieved by mean~ of the measures accord-
ing to the invention:
1) Higher clean gas temperatures (1200-1400 C) can
be achieved 80 that gas turbine~ can be operated
with higher inlet temperatures and correspondingly
higher efficiency.
2) The heat losses relative to the prior art are
smaller due to the raw gas/clean gas heat exchange
and the efficiency of the overall installation is
improved by this means.
3) The gas turbine can be operated with its own chim-
ney independently of the waste heat boiler.
.5 4) The internal insulation of the pressure ves3elsand the connecting conduits, which are necessary
in any case, is simultaneously used as a heat
exchanger and the temperature of the pressure ves-
sels and the connecting conduit walls is reduced
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for the same in~ulation thickne~s. Under certain
circumstances, it is possible to dispense with the
separate heat exchanger (15 in Figure 2).
.
The invention is explained in more detail using
the description and Figures 1 and 2.
Figure 1 show3 a combined gas turbine and steam
turbine power station which includes the installation
complex 31-37, namely the compressor for exhaust gas
31, the compressor for air or for air enriched with
oxygen or for pure oxygen 32, the combu~tion chamber
33, the heat exchanger 34, the gas cleaning system 35,
the gas turb,ine ~with electrical generator) 36 and the
wa~te heat steam generator (including steam turbine and
electrical generator) 37.
Figure 2 shows the installation parts 33, 34 and
35, fine-grained to pulverized coal under pressure, for
example 16 bar, together with air or with air enriched
with oxygen ox with pure oxygen alone or with recircu-
lated exhaust gas in each case being supplied via theconnecting piece 11 to the combustion chamber 27 and
'being burned in the latter. The combustion then takes
place either at a temperature at which the ash remains
solid or at a temperature at which the ash can be witih-
drawn in the molten state. The combustion temperaturecan be adjusted by the selection of the air excess
and/or oxygen excess and~or exhaust gas recirculation.
The combustion chamber 27 is of cyclone type 90 that a
major proportion of the ash can be precipitated and
: --- 211817~
extracted via the connecting piece 14. If the combus-
tion temperature in the combustion chamber is above the
ash melting point, the combustion gas at the outlet
connecting piece of the combustion chamber 12 is cooled
to a temperature below the a h melting point by admix-
ture of recirculated exhaust gas or a gas similar to
that used for combustion (via the connecting piece 25)
in order to avoid slagging of the subsequent conduit
and of the heat exchanger. In both cases (solid or
molten ash in the combu~tion chamber), the combustion
gases (~ raw gases) then flow through the connecting
conduits 2, which are configured as a heat exchanger~
and - if necessary - via the raw gas inlet connecting
piece 16 through the heat exchanger 15, which i8
arranged for cooling the raw gases and heating the
clean gases in the heating surface space 22 of the heat
exchanger pressure vessel 3.
The raw gases leave the heat exchanger pressure
vessel via the raw gas outlet 17 and flow via the con-
necting conduit 4, which i8 provided with insulation 7only, and via the raw gas inlet 18 into the gas clean-
ing pressure vessel 5, recirculated exhaust gas or a
gas similar to that used for combustion being mixed via
the connecting piece 30 with the raw gases, which have
already been cooled by giving up heat to the clean gas,
that they are cooled to a temperature between
approximately 650 to 950 C. At this temperature, the
raw ga~es can have dust (including alkali metal com-
pounds) removed by known methods, such as cyclones,
~. ~118178 :~ ~
- 6
ceramic filter tubes 24 etc. and are, furthermore,
desulphurized by likewise known method~, for example
the dry additive method, i.e. by spraying in lime dust,
and are freed from oxides of nitrogen by, for example,
the selective non-catalytic reduction - SNCR - method,
i.e. by spraying in ammonia. These gas cleaning meth-
ods 35 are arranged in a vessel 5 from which fly ash
and other residue~ such as gypsum can be withdrawn via
the outlet 20. The supply of the additives take~ place
via the connecting piece 28. The cleaned combustion
gases (~ clean gases) then flow via the clean gas out-
let 19, the connecting conduit 6 - which is only pro-
vided with insulation 7 - and the connecting piece 23
back to the heat exchanger pressure vessel 3. The
clean gas then flows through the heat exchanger 15
and/or the ducts 10, 9 and 8, which are configured as
heat exchangers, of the heat exchanger pressure vessel
3, of the connecting conduit 2 and of the combustion
chamber pressure vessel 1, taking up heat from the
uncleaned combustion gaseE (= raw gases) in the process
and leaving the combustion chamber pressure vessel via
the connecting piece 13 at the permissible gas turbine
inlet temperature. The clean gas then flows sequen-
tially through the gas turbine 36 in Figure 1 and the
waste heat steam generator 37 in Figure 1. In this
waste heat steam generator 37, water for operating a
steam turbine is preheated, evaporated and superheated
at one or a plurality of pre~sure stages (a possible
cycle with three pre~sure stages is represented in
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Figure 1). Water can also be tapped off for heating
purposes.
After the exhaust heat boiler, part of the exhaust
gases can be recirculated by means of a compressor 31
driven by the ga~ turbine, see Figure 1, to the pos-
itions-ll, 26 and 30 listed above. The rest can - if
this is necessary or has not already occurred - be
cleaned in known manner to permissible emi~sion figures
and leaves the power station via a chimney. If pure
oxygen i8 used as the oxidizing agent, a gas mixture
which consists almost exclusively of C02 and steam
occurs - as already mentioned - as the exhaust gas.
With appropriate further cooling, stéam condenses first
and finally the C02 with the residual gas traces also
becomes fluid or freezes. This produces a power
station which i8 free of exhaust gas, if the nitrogen
separated from the air during the production of the
oxygen is ignored. In addition, the compressor for air
or for air enriched with oxygen or for pure oxygen 32 -
see Figure 1 - is also driven by the gas turbine 36.
The combustion chamber pressure vessel 1, the con-
necting conduit 2 and the heat exchanger pres~ure ves-
sel 3 are constructed in such a way that the pre3sure-
carrying wall is located on the outside. Insulation !7~
ducts 8, 9 and 10 in which clean gas flows and a jacket
21, which is heat conducting, substantially impermeable
to gas and fire-resistant, follow in sequence towards
the inside. It is only within this jacket that raw gas
flows.
