Medium-load power generating station with an integrated coal gasification plant

Medium-load power generating station with an integrated coal gasification plant, a gas turbine power generating station part connected to the coal gasification plant, a steam power generating station part connected to the raw gas heat exchanger plant of the coal gasification plant, a methanol synthesis plant having a plurality of modules connected in parallel to each other, and a purified gas distribution system which connects the methanol synthesis plant to the gas turbine power generating station part and which includes a purified gas continuous flow interim storage plant and is connected on the gas side to the raw gas heat exchanger plant. The methanol synthesis plant is associated, for hydrogen enrichment, to a "cooler-saturator loop" which is connected to the raw gas heat exchanger plant and consists of the saturator, a converting plant, cooler and following gas purification plant. In one mode of operation, a water electrolysis plant is associated with the methanol synthesis plant and its hydrogen line is connected to the methanol synthesis plant, and its oxygen line is connected to the coal gasifier.

CROSS-REFERENCE TO RELATED APPLICATION 
The following application, assigned to Kraftwerk Union Aktiengesellschaft, 
a German corporation, the assignee of the present application is hereby 
incorporated by reference; Application Ser. No. 614,470, filed for Konrad 
Goebel, Rainer Muller and Ulrich Schiffers, inventors, on May 25, 1984. 
BACKGROUND OF THE INVENTION 
FIELD OF THE INVENTION 
The invention relates to a medium-load power generating station with an 
integrated coal gasification plant, with a gas turbine generating station 
part connected to the coal gasification plant with a steam power 
generating station part connected to the raw gas heat exchanger plant of 
the coal gasification plant, with a methanol synthesis plant consisting of 
several parallel-connected modules, and with a purified gas distribution 
system which connects the methanol synthesis plant to the gas turbine 
power generating station part and which includes a purified gas 
continuous-flow interim storage plant and is connected on the gas side to 
the raw gas heat exchanger plant. 
The subject of our related application referred to above, is a medium-load 
power generating station for generating electric power and methanol, in 
which a combination gas turbine/steam power generating station and a 
methanol synthesis plant having a plurality of modules which modules can 
be added into the stream separately, is connected via a purified gas 
distribution system, to a coal gasification plant. The waste heat of the 
raw gas is fed to the steam power generating station part via a raw gas 
heat exchanger plant and is utilized there. In this medium-load power 
generating station, the generated electric power can be adapted quickly to 
the instantaneous power demands of the electric network without the need 
of employing a further expensive secondary fuel for load peaks and without 
the need that in the event of a sudden load reduction or even load 
shedding due to a disturbance, a loss of fuel has to be tolerated. 
Instead, methanol is produced to a larger degree in this medium-load power 
generating station at times of reduced demand of electric power and 
excesses as well as shortfalls of pure gas are buffered by the purified 
gas continuous flow interim storage plant which is associated with the 
pure gas distribution system. 
Therefore, the relatively move sluggish coal gasification plant can 
continue to be operated with constant output independently of the 
prevailing load demands of the electric network. Because the composition 
of the purified gas flowing toward the methanol synthesis plant is far 
from the stoichiometric ratio required for the methanol synthesis, the 
synthesis gas returned in the methanol synthesis reactors of the 
individual modules must be enriched with hydrogen in times of reduced 
energy demand to utilize the not completely reacted synthesis gas which 
can no longer be burned in the combustion chamber of the gas turbine. This 
hydrogen enrichment could be achieved by external feeding-in of hydrogen. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide in a medium-load power generating 
station of the type mentioned at the outset, the hydrogen required for the 
hydrogen enrichment of the synthesis gas of the methanol synthesis plant 
from the power generating station itself in a most economical manner. 
With the foregoing and other objects in view, there is provided in 
accordance with the invention a medium-load power generating plant with an 
integrated coal gasification plant comprising 
(a) a coal gasification plant for producing raw hot fuel gas-containing 
carbon monoxide and hydrogen, 
(b) a raw gas heat exchanger installation having a first raw gas heat 
exchanger for indirect heat exchange between the hot raw gas from the coal 
gasification plant with feedwater to generate steam, 
(c) a gas purifier for purifying the raw gas, 
(d) a central purified gas distribution system, 
(e) a purified gas supply line connected to the raw gas heat exchanger 
installation and passing into the central purified gas distribution 
system, 
(f) a purified gas continuous-flow interim storage plant connected in 
parallel to the purified gas supply line, 
(g) a gas turbine power generating plant connected to the coal gasification 
plant to receive fuel via the purified gas supply line, 
(h) a methanol synthesis plant having parallel-connected modules for 
converting CO and H.sub.2 into methanol connected to the gas turbine power 
generating plant via the central purified gas distribution system, the 
combination therewith of 
(i) a cooler-saturator loop connected to the methanol synthesis plant for 
treating methanol exhaust gas therefrom containing carbon monoxide and 
converting it into a gas richer in hydrogen, comprising a saturator 
wherein the gas is saturated with moisture, a converter wherein at least 
part of the carbon monoxide in the gas saturated with moisture is 
converted to hydrogen and carbon dioxide; a cooler for cooling the 
products from the converter, a gas purification plant for the removal of 
carbon dioxide and hydrogen sulfide, if any, from the gas from the cooler, 
and connecting means for passing said purified gas to the methanol 
synthesis plant for hydrogen enrichment of synthesis gas to be converted 
into methanol. 
In accordance with the invention, there is provided a medium-load power 
generating plant with an integrated coal gasification plant comprising 
(a) a coal gasification plant for producing raw hot fuel gas-containing 
carbon monoxide and hydrogen, 
(b) a raw gas heat exchanger installation having a first raw gas heat 
exchanger for indirect heat exchange between the hot raw gas from the coal 
gasification plant with feedwater to generate steam, 
(c) a gas purifier for purifying the raw gas, 
(d) a central purified gas distribution system, 
(e) a purified gas supply line connected to the raw gas heat exchanger 
installation and passing into the central purified gas distribution 
system, 
(f) a purified gas continuous-flow interim storage plant connected in 
parallel to the purified gas supply line, 
(g) a gas turbine power generating plant connected to the coal gasification 
plant to receive fuel via the purified gas supply line, 
(h) a methanol synthesis plant having parallel-connected modules for 
converting CO and H.sub.2 into methanol connected to the gas turbine power 
generating plant via the central purified gas distribution system, the 
combination therewith of 
(i) a water electrolysis plant, adapted to utilize electrical power from 
the combination power station containing the gas turbine power generating 
station part and the steam power generating station part, to convert water 
into oxygen and hydrogen, hydrogen connecting means for transferring the 
hydrogen from the electrolysis plant to the methanol synthesis plant for 
hydrogen enrichment of synthesis gas to be converted into methanol, and 
oxygen connecting means for transferring the oxygen from the electrolysis 
plant to the coal gasifier. 
In an embodiment of the invention hot water is supplied to the saturator by 
indirect heat exchange between the raw gas and water in the third raw gas 
heat exchanger in the raw gas heat exchange plant to heat the water and 
connecting means through which the saturator can be supplied with hot 
water from the third heat exchanger. 
In another embodiment of the invention, steam is supplied to the saturator 
by indirect heat exchange between the raw gas and water in the first raw 
gas heat exchanger in the the raw gas heat exchange plant to heat the 
water to form steam and connecting means through which the saturator can 
be supplied with the steam from the first heat exchanger. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
medium-load power generating station with an integrated coal gasification 
plant, if is nevertheless not intended to be limited to the details shown, 
since various modifications may be made therein without departing from the 
spirit of the invention and within the scope and range of equivalents of 
the claims.

DETAILED DESCRIPTION OF THE INVENTION 
The invention relates to a medium-load power generating station with an 
integrated coal gasification plant with a gas turbine power generating 
station part connected to the coal gasification plant, with a steam power 
generating station part connected to the raw gas heat exchanger plant of 
the coal gasification plant and with a methanol synthesis plant. In such a 
medium-load power generating station, more methanol is generated in times 
of reduced power demand. The remaining synthesis gas which is now no 
longer burned in the gas turbine, has a composition far short of that 
desired and the objective is to bring the composition closer to the 
stoichiometric ratio required for the methanol synthesis. To this end, the 
methanol synthesis plant is associated for the purpose of hydrogen 
enrichment, with a so-called cooler-saturator loop which is connected to 
the raw gas heat exchanger plant and includes a saturator, a converting 
plant, coolers and a gas purification plant connected thereto. 
Furthermore, a water electrolysis plant can also be associated with the 
methanol synthesis plant with a hydrogen line from the electrolysis plant 
connected via a compressor to the methanol synthesis plant. Fossil fuels 
are suitable for use with a medium-load power generating station according 
to the invention. 
In a medium-load power generating station of the type mentioned at the 
outset, the methanol synthesis plant, according to the invention, is 
therefore associated for the hydrogen enrichment with a so-called 
"cooler-saturator loop" which is connected to the raw gas heat exchanger 
plant and consists of saturator, conversion plant, cooler and a following 
gas purification plant. In such a cooler-saturator loop hydrogen and 
carbon dioxide are generated by introduction of steam into the synthesis 
gas and subsequent conversion of the synthesis gas/steam mixture. After 
separating the carbon dioxide, the remaining synthesis gas, enriched with 
hydrogen, is returned to the methanol synthesis plant. 
As an alternative, a water electrolysis plant in which water is converted 
to hydrogen and oxygen by electrolysis, the hydrogen is connected by a 
hydrogen line to the methanole synthesis plant and the oxygen by an oxygen 
line to the coal gasification plant, thereby associating the water 
electrolysis plant with the medium-load power generating station and with 
the methanol synthesis plant. In such an arrangement, the electric power 
generated in excess at times of reduced power demands, can be utilized in 
the water electrolysis plant for generating hydrogen and oxygen gases. The 
hydrogen can be used immediately for the enrichment of the synthesis gas 
of the methanol synthesis plant. The simultaneously generated oxygen can 
be fed to the coal gasifier. The oxygen there substitutes for a part of 
the oxygen which would otherwise be supplied by the air separation plant, 
reducing the output of the latter and thereby saving energy. 
Further details of the invention will be explained with the aid of two 
embodiment examples shown in the drawings. 
In the presentation of FIG. 1, the superimposed assemblies of the 
medium-load power generating station 1 are framed by dashed lines. These 
are coal gasifier 2, a raw gas heat exchanger plant 3, a gas purification 
plant 4, a central purified gas distribution system 5 with an integrated 
pressurizer and storage plant (not shown here for the sake of clarity), a 
combination power generating station 8 consisting of a gas turbine power 
generating station part 6 and a steam power generating station part 7, and 
a methanol synthesis plant 9. The coal gasification plant 2 includes a 
coal gasifier 10, and air separation plant 11 with at least one additional 
air compressor 12 preceding the air separation plant, and a further oxygen 
gas compressor 14 which is arranged in the oxygen line 13 leading from the 
air separation plant 11 to the coal gasifier 10. The raw gas heat 
exchanger plant 3 arranged in the gas stream from the coal gasifier 10 
includes a first heat exchanger 15 for generating high-pressure steam, a 
second raw gas/purified gas heat exchanger 16 and a third heat exchanger 
17 for generating low-pressure steam. Finally, a control cooler 18 is 
provided in the raw-gas heat exchanger plant 3. The gas purification plant 
4 following the raw gas heat exchanger plant includes a raw gas scrubber 
19 as well as a hydrogen sulfide absorption and sulfur extraction plant 
20. To the purified gas line 21 leaving the hydrogen sulfide absorption 
and sulfur extraction plant 20 are connected the purified gas distribution 
system 5, the methanol synthesis plant 9 and, via the raw gas/purified gas 
heat exchanger 16, the gas turbine power generating plant part 6. 
The gas turbine power generating station part 6 includes a combustion 
chamber 22, a gas turbine 23 and one generator 24 and one air compressor 
25 driven by the gas turbine 23. 
The exhaust gas line 26 of the gas turbine 23 is connected to a waste heat 
boiler 27. Its steam line 28 is connected to the high-pressure part 29 of 
a steam turbine 31 consisting of a high-pressure part 29 and a 
low-pressure part 30. A generator 32 is coupled to the steam turbine 31. 
The low-pressure part 30 of the steam turbine 31 is followed by a 
condenser 33, a condensate pump 34, a feedwater tank 35 as well as several 
feedwater pumps 36, 37, 38, 39. The combustion chamber 22 of the gas 
turbine as well as the air separation plant 11 of the coal gasification 
plant 2 are connected to the air compressor 25 driven by the gas turbine 
23. A water electrolysis plant 40, wherein water is converted to oxygen 
and hydrogen, is associated with the coal gasification plant. The oxygen 
line 41 of the electrolysis plant 40 is connected in parallel to the 
oxygen line 13 of the air separation plant 11 to the coal gasifier 10. The 
hydrogen line 42 of the water electrolysis plant 40 is connected via a 
hydrogen gas compressor 43 to the methanol synthesis plant 9. 
In the operation of the medium-load power generating station 1, the air 
separation plant 11 is supplied with air by the air compressor 25 driven 
by the gas turbine 23 as well as by the supplemental air compressor 12. 
The oxygen of the air separation plant is forced into the coal gasifier 10 
by the gas compressor 14. Coal is gasified with oxygen and fed-in process 
steam in the coal gasifier 10 to form raw gas. The hot raw gas discharged 
from gasifier 10 at a temperature of 800.degree. to 1600.degree. C. gives 
off its heat in the heat exchanger plant 3, being utilized in part to 
generate high-pressure steam in the first heat exchanger 15. In the second 
raw gas/purified gas heat exchanger 16, the purified gas flowing toward 
the combustion chamber 22 of the gas turbine power generating plant part 6 
is preheated by the raw gas. In the third heat exchanger 17, additional 
heat from the raw gas is utilized to generate low-pressure steam which can 
be fed to the low pressure part 30 of the steam turbine 31 or can be used 
as process steam. The control cooler 18 cools the raw gas to a defined 
temperature before it enters the raw gas scrubber 19. The pressure 
maintenance which takes place in the purified gas line 21 leaving the gas 
purification plant 4 is accomplished via the purified gas distribution 
system 5 with an integrated purified gas continuous flow interim storage 
plant. 
The methanol synthesis plant 9, which is subdivided into several modules 
which can separately be cut-in or cut-out of operation, remains 
switched-on in the operation of the medium load power generating station 1 
at nominal load with at least one module which operates in continuous flow 
operation. At so-called low-load times when less electric power is given 
off to the network, the gas turbine power generating station part 6 is cut 
back first. The excess purified gas is consumed by running the modules of 
the methanol synthesis plant 9 which happened to be in operation at higher 
capacity, or by adding further modules. Thus, the coal gasification plant 
2 can be continued to be operated in the optimum range for gasification of 
coal. The water electrolysis plant 40 can be set in operation with part of 
the excess steam while the output of the gas turbine power generating 
station part is reduced at the same time. The hydrogen produced by 
electrolysis can be fed through line 42 into the methanol synthesis plant 
9 by means of the compressor 43. Thereby, the composition of the pure gas 
fed into the methanol synthesis plant or of the synthesis gas 
recirculating in the methanol synthesis plant is brought closer to the 
stoichiometric ratio required for the methanol synthesis. The oxygen 
produced at the same time in the water electrolysis plant 40 is fed to the 
coal gasifier 10. This oxygen substitutes for part of the oxygen from the 
air separation plant 11. As a result, the output of the air separation 
plant 11 can be reduced. In this manner, the quantity of methanol 
generated in times of reduced power demand can be increased by modifying 
the synthesis gas composition normally going to the methanol synthesis 
plant to a composition closer to the stoichiometric ratio by the addition 
of hydrogen generated by excess electric power. By this procedure the 
entire amount of active constituents, namely carbon monoxide and hydrogen 
in the purified gas generated at nominal load of the coal gasifier 10 
which is not needed by the gas turbine power generating station part 6 is 
completely converted into methanol. 
A further increase in methanol quantity is produced if additionally, 
hydrocarbon containing gas from an external source (not shown) is cracked 
to form synthesis gas and this gas is fed into the methanol synthesis 
plant. In this case, the entire electric power of the network can be fed 
to the water electrolysis plant 40 in an extreme case of complete 
separation of the medium/low power generation station 1 from this network. 
Since in this mode of operation of the medium/low power generating 
station, only a small amount of the purified gas generated by the coal 
gasifier is available for methanol synthesis, there is inadequate hydrogen 
to effect complete reaction of the carbon monoxide in the purified gas to 
methanol by methanol synthesis, and this hydrogen is available from the 
hydrocarbon containing gas fed-in from the external source to 
substantially complete the methanol synthesis. The coal gasification plant 
2 is continued to be operated at nominal load regardless of whether the 
combination power generating station 8 consisting of a gas turbine part 6 
and a steam generating station part 7 is continued to be operated at 
nominal load at times of reduced power demands or whether its output is 
reduced in such times. The purified gas produced in excess and/or at the 
same time, synthesis gas from the cracking of additional hydrocarbon 
containing gas is converted into methanol. 
The medium-load power generating station 44 of the embodiment example shown 
in FIG. 2 consists of a coal gasification plant 45, a raw gas heat 
exchanger plant 46, a gas purification plant 47, a combination power 
generating station 48 including a gas turbine power generating station 
part and a steam power generating station part, a methanol synthesis plant 
49 and a central purified/gas distribution system 50 with a purified gas 
continuous-flow interim storage plant (not shown here for the sake of 
clarity) connected in parallel to the purified gas line 51. The coal 
gasification plant 45 includes a coal gasifier 52, and air separation 
plant 53, a supplemental air compressor 54 preceding the air separation 
plant 53, and an oxygen gas compressor 56 arranged in the oxygen line 55 
to the coal gasifier 52. Also, the raw gas heat exchanger plant 46 
associated with the raw gas stream issuing from the coal gasifier 52 
includes a heat exchanger 57 for generating steam, a raw gas/purified gas 
heat exchanger 58, a heat exchanger 59 for generating hot water, and a 
control cooler 60. The gas purification plant 47 following the raw gas 
heat exchanger plant 46 includes a raw gas scrubber 61 and a hydrogen 
sulfide absorption and sulfur extraction plant 62. 
The purified gas line 51 leaving the gas purification plant 47 is 
connected, similar to the embodiment example of FIG. 1, to the central 
purified gas distribution system 50, the methanol synthesis plant 49 and, 
via the purified gas/raw gas heat exchanger 58, to the combination power 
generating station 48. The latter is designed as shown in detail in the 
embodiment example of FIG. 1. 
In a modification of the embodiment example of FIG. 1, a so-called 
"cooler-saturator loop" 63 is connected to the methanol synthesis plant 
49. The loop includes a saturator 64, a converter 65, a heat exchanger 66, 
a cooler 67 and a gas purification plant 68. The synthesis gas enriched in 
the cooler-saturator loop with hydrogen is returned via a recirculation 
line 69 to the methanol synthesis plant 49 and is fed to the synthesis 
reactor (not shown for clarity) of the methanol synthesis plant. 
In the operation of the medium-load power generating station 44 raw gas is 
generated in the coal gasifier 52 with the oxygen of the air separation 
plant 53 and with steam in a manner similar to that described in 
connection with embodiment example of FIG. 1. Raw gas issuing from coal 
gasifier 52 is cooled in the following raw gas heat exchanger plant 46 and 
is purified in the gas purification plant 47. The combination power 
generating station 48 including a gas turbine power generating station 
part and a steam power generating station part is operated by burning in 
the gas turbine the purified gas from the gas distribution system 50 after 
first preheating the purified gas in the raw gas/purified gas heat 
exchanger 58. Also, the high-pressure steam generated in the first heat 
exchanger 57 of the raw gas heat exchanger plant 46 is fed to the steam 
turbine of the steam power generating station part. The synthesis gas 
partially reacted in the modules of the methanol synthesis plant 49, but 
which gas contains unreacted carbon monoxide, is conducted into the 
saturator 64 with steam by means of hot water which is taken from the 
third heat exchanger 59 of the raw gas heat exchanger plant 46, thereby 
saturating the synthesis with moisture. The mixed gas obtained in this 
manner is converted in the following converting plant 65 by reaction of 
the carbon monoxide with water to give carbon dioxide and hydrogen. The 
exhaust gas of the converting plant 65 is cooled in a first heat exchanger 
66, where the cooling water warmed up in this exchanger is fed for further 
heating into the third heat exchanger 59 of the raw gas heat exchanger 
plant 46. The thus precooled exhaust gas of the converting plant 65 is 
further cooled in a cooler 67 connected to the cooler loop 70 and the 
cooled exhaust gas from cooler 67 introduced into the gas purification 
plant 68. In this gas purification plant, the carbon dioxide is washed out 
and the remaining gas enriched with hydrogen is returned as synthesis gas 
via the recirculation line 69 to the methanol synthesis plant 49. There, 
it is fed to a synthesis reactor which is in operation. 
If desired, the exhaust gas of the converting plant may be treated in a gas 
separation plant to obtain a fraction rich in hydrogen by liquidfication 
of the less volatile gaseous constituents. Also, the purified gas flowing 
initially into the methanol synthesis plant may be enriched with hydrogen 
via the cooler-saturator loop instead of making synthesis gas from the 
synthesis reactor of the methanol synthesis plant, in order that the 
synthesis gas approach a stoichiometric ratio for the methanol generation. 
This synthesis gas enriched with hydrogen could then be fed to the methanol 
synthesis plant and recirculated there through the individual synthesis 
reactors until it is completely reacted to methanol, except, of course, 
for the inert gas residues. The connection of the methanol synthesis plant 
71 for this type of pre-enrichment of the purified gas with hydrogen is 
shown in the embodiment example of FIG. 3. It is seen here that the 
purified gas line 72 is first fed to the otherwise unchanged 
cooler-saturator loop 73 and only the exhaust gas which is enriched with 
hydrogen and freed of carbon dioxide is fed to the converting plant behind 
the gas purification plant via the recirculating line 74 into the methanol 
synthesis plant 71. 
The output of the gas turbine can also be reduced or the turbine can be 
switched off at times when less power is fed into the electric network. 
The purified gas which under these conditions is available in larger 
quantity, can be converted via the methanol synthesis plant into methanol 
while the synthesis gas is enriched with hydrogen. The heat produced in 
larger quantity in the third heat exchanger 59 of the raw gas heat 
exchanger plant 46 can be utilized for further saturation of the pure gas 
and in some circumstances, for the additional decomposition of externally 
introduced hydrocarbon containing gas. Due to the increase of the 
synthesis gas production, more methanol can be produced.