CA1258773A - Medium-load power generating station with an integrated coal gasification plant - Google Patents

Abstract

Abstract of the Disclosure:

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 gen-erating 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.

Description

Background of the Invention Field of the Invention This application is a division of our Canadian Patent Appli-cation Serial -l~O. 455,348 filed May 29, 1984.
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-connect-ed 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 con-tinuous-flow interim storage plant and is connected on the gas side to the raw gas heat exchanger plant.
The subject of a related:development by the applicant is a medium-load power generating station for generating electric ~2S~3 power and methanol, in which a combination gas turbine/steam power generati~g station and a methanol synthesis plant having a plurality of modu]es 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 ~dium-load power generating station, the generated electric power can be a~apted quic~ly to the instantaneous power demands of the elec~ric 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 tol-exated. Instead, methanol is produced to a larger degree in this medium-load power generating station at times oE reduced demand of electric power and excesses as well as shortfalls of pure gas are buffered by the p~rified gas continuous flow interim storage plant which is associated with the pure gas distribution system;

There~ore, the relatively more 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 ~e enriched with hydrogen in times o~ reduced energy ~emand to utilize the not completely reacted syn-thesis gas which can no longer be burned in the combustion chamber oE
the qas turbine. This hydrogen enrichment could be achieved by external feeding-in oE hydrogen.

Summax of the Invention Y

~n object of t~e invention is to provide in a medium-load power generating station of .the type mentioned at the outset, the hydxogen required for the hydrogen enrichment of the synthesis gas o the methanol synthesis plant from the power generating station itself in a most economical manner.

Wi~l 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 ins-tallation having a first xaw qas heat exchanger for indirect heat exchange between the hot raw gas rom 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, ~2S8773 20365-2401D

e) a purified gas supply line connected to the raw gas heat ex-changer 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 each with a reactor for converting CO and H2 into methanol con-nected 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 tur-bine power generating station part and the steam power generating station part, to convert water into oxygen and hydrogen, hydro-gen connecting means for transferring the hydrogen from the elec-trolysis plant to the methanol synthesis plant for hydrogen en-richment of synthesis gas to be coverted into methanol, and oxygen connecting means for transferring the oxygen from the electrolysis plant to the coal gasifier.

1258~73 20365-2401D

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, it is nevertheless not in-tended to be limited to the details shown, since various modi-fications may be made therein without departing from the spirit of the invention and within the scope and range of equivalents o the claims.
Brief Description of the Drawings ...... .
The invention, however, together with the additional objects and advantages thereof will be best understood from the following description when read in connection with the accompanying draw-ings, in which:
Figure 1 is a schematic presentation of a medium-load power generating station with an integrated coal gasification plant and a water electrolysis-plant associated-with theimethanol synthesis plant, '~
" ' ' ' ~2587173 FIG. 2 is a dif~erent medium-load power genexating station with an integrated coal gasification plant and a so-called "cooler-saturator loop" associated with the methanol synthesis plant, and FIG. i is a variant for connecting the methanol synthesis plant of FIG.2 to the so-called "cooler-saturator loop".

Detailed Description of the Invention Thè inve~ltion relates to a medium-load power genera-ting station with an integrated coal gasification plant with a gas turbine power generating station par-t connected to the coal gasification plant, with a steam power generatillg station part connected to the raw gas heat exchanger plant o~ the coal gasification plant and with a methanol syntllesis plant. In such a medium-load power generating station, more methanol is generated in times of reduced power demand. The remaining syntllesis gas which is now no longer burned in the gas -turbine, has a composition ~ar short of tha-t 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 connectèd to the raw gas heat excha,nger plant and includes a saturator, a converting plant, coolers and a gas puriEication plant connected thereto. Furt:hermore, a water electrolysis plant can also be as;sociated with the methanol syn-thesis plan-t 12~8773 with a hydrogen line ~rom 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 xaw gas heat exchanger plant and consis-ts of saturator, conversion plant, cooler and a following gas purification plant. In such a cooler-saturator loop hydrogen and carbon di~xide are generated by introduction of steam into the synthe-sis gas and subsequent conversion of the synthesis gas/steam ~ixture. ~fter separating the carbon dioxide, the remaining synthesis gas, enriched with hydrogen, is returned to the methanol synthesis plant.

~s an alternative, a water electrolysis plant in which wa-ter is converted to hydrogen and oxygen by electrolysis, the hydrogen is connected by a hydxogen line to the methanol synthesis plant and the oxygen by an oxygen line to the coal gasification ~lant, tllereby associating the water electrolysis plant with the medium-load power gellerating 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 q Z5~773 utilized in the water electrolysis plant for generating hydro-gen and oxygen gases. The hydrogen can be used immediately or the enrichment of the synthesis gas of the rnethanol synthesis `plant. The simultaneously generated oxygen can be fed to the coal gasifier. The oxygen there substitutes for a part oE -the oxygen ~hich would otherwise be supplied by the air separation plant, xeducing the output of the la-tter and thereby saving en~rgy.

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 l are framed by dashed lines. These are coal gasifier 2, a raw gas heat exchanger plant 3, a ~as purification plant 4, a central purified gas distxibution system S 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 tuxbine 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 ll with at least one additional air compressor 12 precedlng 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 1~58~3 gasifier lO. The raw gas heat exchanger plant 3 arranged in the ~as 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 con-trol 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 hydrogell sulfide absorption and sulfur extraction plant 20. To the purified gas line 21 leaving the hydrogen sul~ide absorp-tion and sulfur extraction plant 20 are connected the purified gas distribution system 5, the me-thanol synthesis plant 9 and, via ~lle raw gas/puri~ied 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 ~4 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 }ligh-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 il. l'he 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 tu~bine as well as the air separation plant 11 of the coal gasification ylant 2 are connected to the air compressor 25 driven by the gas turbine 23. A water elec-trolysis plant 40, wherein water is converted to oxygen and hydrogen, is associated with the coal gasification plan-t. The oxygen line ~l o the electrolysis plant 40 is connec-ted in parallel to the oxygen line 13 of the.air separation plant 11 to the coal gasi~ier 10. The hydrogen line 42 of the water electrolysis plant 40 is connected ~-ia a hydrogen gas compressor 43 to the ~ethanol synthesis plant 9.

.
In the operation of the medium-load power generating station 1, th~ 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 sepa-ration plant is forced into tile coal gasifier 10 by the gas compressor 14. Coal is gasified with oxygen and fed-in process steam in the coal gasifier lO to form raw gas. The hot raw gas discharged from gasifier 10 at a temperature of 800 to 1600C
gives o 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, ' ` ' ' ~' ~ ' ' ' ' 8~7;;~

additional lleat 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 mainte-nance which takes place in the purified gas line 21 leaving the yas puri~ication plant 4 is accomplished via the purified gas distribution system 5 with an integrated purified gas continu-ous 10w interim storage plant.

The methanol synthesis plant 9, which is subdivided into several mod`ules whlch can separately be cut-in or cut~out of operation, remains switched-on in the operation of the medium load power generating station l 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 ~irst. The excess purified gas is consumed by xullning the modules of the methanol synthesis plant 9 which happened to be in operation at higher capacity, or by adding ~uxth~r modules. Thus, the coal gasification plant 2 can be .
contin~ed to be operated in the opkimum range for gasification o~ coal. The water electrolysis plant 40 can be set in opera-tion witll 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 ' '.

~%587~3 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 synthe-sis~ The oxygen produced .at the same time in the water electrolysis plant 40 is fed to the coal gasifier 10. This o~gen substitutes for part of the oxygen from the air sepa-~ation plant 11. ~s 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 syntl-esis plant to a composition closer ~o tlle stoichiometric ratio by the addition of hydrogen gen-erated 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 me~hanol~

. . .
A further increase in methanol ~uantity is produced if addi-tionally, 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 elect~ic power of the network can be fed to the water . : , .

~;~S8773 e`lectrolysis plant 40 in an extreme case of complete separation of the mediulm/low power generation station 1 from this network.
Since in this mode of opexation o~ the medi~m/low power gen-erating station, only a small amount of the purified gas generated- b~r the coal gasifier is available for meth~nol 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 Erom the h~ydrocarbon containing gas fed-in from the external source to s~bstantially complete -the methanol synthesis. The coal gasiEication plant 2 is continued to be operated at nominal load regardless of whether the combination power generating station 8 c~nsisting 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 o~ additiona1 hydrocarbon containing gas is converted into n~e-thanol .

The n~edium-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`includiny a gas turbine power generating station part and a steam power gen-erating station part, a methanol synthesis plant 49 and a ~2S1~773 central purified/gas distribution system 50 with a purified yas continuous-flow interim storage plant (not shown here for the sake of clarity~ connected in parallel to the purified gas line 51. The coal gasifica-tion plant 45 includes a coal gasifier 52, and air separation plant 5i, a supplemental air compressor 54 preceding the air separation plant 53, and an oxygen gas compxessor 56 arranged in the oxygen line 55 to the coal gasi~ier 52. Also, the raw gas heat exchanger plant 46 associ-ated 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 puri-~ication plant 47 following the raw gas heat exchanger plant 46 illcludes a raw gas scrubber 61 and a hydrogen sulfide absorp-tio~ and sulfur extraction plant 62.

To 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 excbanger 58, to the combination power generating station 48. The latter 'is desig'ned'as'shown in detail in the embodi-ment example of FIG. 1.

In a modification of the embodiment example of FIG. l, a so-called "cooler-saturator loop" 63 is connected to the ~ ' ' ~ , ' ' ' .

la~S8773 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 enrichecl in the cooler-saturator loop with hydrogen is returned via a recircu-lation line 69 to the methanol synthesis plant ~9 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 ~ollowing xaw gas heat exchanger plant 46 and is purified in the gas purification plant 47. The combination power generat-ing station 48 including a gas turbine power generating station part and a steam power generating station part is operated by buxning 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 5~. Also, the high-pressure steam generated in the first heat exchanger 57 o~
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 -- `~
~;258~3 water wl~ich is taken from the third heat exchanger 59 of the raw gas heat exchanger plant 46, thereby saturating the synthe-sis 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 Eirst 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 prlecooled 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 caxbon dioxide is washed out and the remaining gas enriched with hydrogen is returned as synthesis gas via the recircu-lation line 69 to the methanol synthesis plant 49. There, it is fed to a synthesis reactor whjch is in operation.

IE desired, the exhaust gas of the converting plant may be ~reated in a gas separation plant to obtain a fraction rich in ~drogen. ~lso, the purified gas flowing initially into the ~et~lanoL 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, A in order that the synthesis gas approach a stoichiometric ratio ~or the methanol generation.

, ` ' , . ' ' . ~' . , ~ ' , .

.

~5~3773 This synthesis gas enriched with hydrogen could th~n be fed to the methanol syn-thesis 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 irst fed to the otherwise unchanged coolex-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 o~ 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 s~nthesis gas is enriched with hydrogen. The~heat produced in larger quantity in the third heat exchanger 58 o~ 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.

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A medium-load power generating plant with an inte-grated 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 gen-erate 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 con-nected 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 mod-ules each with a reactor for converting CO and H2 into methanol connected to the gas turbine power generating plant via the cen-tral 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 tur-bine 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 electrol-ysis plant to the methanol synthesis plant for hydrogen enrichment of synthesis gas to be converted into methanol, and oxygen con-necting means for transferring the oxygen from the electrolysis plant to the coal gasifier.

2. Medium-load power generating station according to claim 1, wherein the coal gasifier operates at the same pressure as the water electrolysis plant and wherein one compressor is in-terposed in the purified gas feedline leading to the methanol synthesis plant and another compressor is interposed in the hydro-gen line from the electrolysis plant to the methanol synthesis plant.

3. Medium-load power generating station according to claim 1, wherein the coal gasifier operates at the same pressure as the methanol synthesis reactor, and wherein a compressor is interposed in the oxygen line between the water electrolysis plant and the coal gasifier and another compressor interposed in the hydrogen line to the methanol synthesis reactor.

4. Medium-load power generating station according to claim 1, wherein the hydrogen line from the electrolysis plant is connected to the purified gas line leading to a module of the methanol synthesis plant.