Flexibly operable power plant and method for the operation thereof

Abstract

One embodiment relates to a power plant having a large steam generator, which is equipped with hydrocarbon-fired burners and/or with a gas turbine and which has a water/steam circuit connected thereto, and comprising at least one device for generating a CO.sub.2-rich gas flow, wherein the electrical power output of the electricity-generating part, of the power plant to the electrical grid is subject to power regulation controlled, at the power grid side. Some embodiments relate to a flexible operating method for the power plant that is fired with hydrocarbon-containing fuel, which operating method permits in particular a rapid adaptation of the power plant output to the power demands from the grid.

Claims

1. A power plant which has a large-scale steam generator which is equipped with carbon-fired burners and/or a gas turbine and has a connected water/steam circuit comprising at least one steam-charged turbogenerator comprising at least one connected generator, wherein a CO.sub.2-containing offgas stream is produced in the large-scale steam generator equipped with the carbon-fired burners, and which comprises at least one unit for production of a CO.sub.2-rich gas stream, and which is connected by its power-generating component comprising the at least one generator to a public power grid which provides control power, wherein the release of electrical power by the power-generating component of the power plant to the power grid is subject to power control on the power grid side, wherein the power plant comprises at least one electrolysis plant for preparation of hydrogen (H.sub.2) and at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least CO.sub.2 components of the CO.sub.2-rich gas stream and the hydrogen produced in the electrolysis plant, and wherein the at least one unit for production of a CO.sub.2-rich gas stream and the at least one electrolysis plant for preparation of hydrogen (H.sub.2) and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least CO.sub.2 components of the CO.sub.2-rich gas stream and the hydrogen produced in the electrolysis plant are connected and interconnected physically and electrically to one another in terms of conduction via current-conducting and via media-conducting lines to form a group in such a way that the power generated on the power plant side in the course of operation of the power plant is utilizable wholly or partly, as required, for operation of one, more than one or all of this group of units and plants comprising the at least one unit for production of a CO.sub.2-rich gas stream, the at least one electrolysis plant for preparation of hydrogen (H.sub.2) and the at least one synthesis plant for preparation of methanol and/or methanol conversion products.

2. The power plant as claimed in claim 1, wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or a plurality of electrolysis plants for preparation of hydrogen (H.sub.2) is/are designed and set up on the power plant side in terms of their current/power consumption capacity and their hydrogen production capacity so as to be controllable in such a way that the current/power consumption and hydrogen production thereof can be run up or down within 5 minutes, in response to a grid-side power control demand on the power plant.

3. The power plant as claimed in claim 1, wherein the at least one unit for production of a CO.sub.2-rich gas stream or a plurality of units for production of a CO.sub.2-rich gas stream and/or the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or a plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream is/are designed and set up on the power plant side in terms of their current/power consumption capacity and their production or conversion capacity so as to be controllable in such a way that their respective current/power consumption and production or conversion output can be run up or down within 5 minutes, in response to a grid-side power control demand on the power plant.

4. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are designed and connected to one another for control purposes on the power plant side in terms of their respective current/power consumption capacity and their respective production or conversion output in such a way that they can be run up or down in response to a grid-side power control demand on the power plant in the integrated system, each in terms of their respective current/power consumption and production or conversion output, within 5 minutes, that the power plant, in the case of a grid-side power control demand, can be adjusted to the altered power demand in terms of output by way of a change in load with a load change gradient in the range of 3%/min-30%/min.

5. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream is/are designed in terms of their respective current/power consumption and/or their respective production or conversion output in such a way that it/they can be subjected, in response to a grid-side power control demand on the power plant, for short periods within a period of up to 30 minutes, to a current/power consumption of 100%-300% of the standard design or standard operating value for the particular plant or unit.

6. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are configured to be able to be actuated and controlled individually in terms of their respective current/power consumption and their respective production or conversion output.

7. The power plant as claimed in claim 1 wherein the at least one synthesis plant for preparation of methanol and/or methanol conversion products or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products is/are designed overall in terms of capacity such that it/they can be used to convert 10%-50% by weight of the CO.sub.2 which forms at full load of the power plant and is present in the CO.sub.2-containing offgas stream to methanol and/or a methanol conversion product.

8. The power plant as claimed in claim 1 wherein the at least one synthesis plant for preparation of methanol and/or methanol conversion products or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products is/are designed overall with regard to their current/power consumption capacity and the production or conversion output possible in each case, in terms of capacity, such that not more than the total amount of electrical power that can be generated by the power plant at full load and/or maximum power thereof can be utilized for the preparation of methanol and/or methanol conversion products.

9. The power plant as claimed in claim 1 wherein the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream comprise(s) or consist(s) of at least one CO.sub.2 separation plant, and/or one or more burner(s) or burner device(s), operated by the oxyfuel process, of the large-scale steam generator having a dedicated CO.sub.2 separation plant.

10. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are designed with regard to their current/power consumption and production or conversion output overall in such a way that, in the course of operation thereof, the power plant can be operated in operation with its minimum load necessary for the purposes of the plant without feeding power into the power grid.

11. The power plant as claimed in claim 1 wherein the power plant takes the form of a power sink for the connected public power grid, in which case the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are designed in terms of their current/power consumption and production or conversion output overall and are connected to the power grid in such a way that they can be operated with the surplus power drawn from the power grid.

12. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are connected physically and electrically to the public power grid as a load that can be switched off.

13. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products are conductively connected in terms of waste heat that arises in the operation of these plant(s) and/or unit(s) in the range of 30-400 C. via at least one waste heat-conducting conduit to a preheater of the feed water of the water/steam circuit and/or a preheater of a CO.sub.2 separation plant, and/or a preheater of at least one of the in reactants used and/or products generated in the power plant.

14. The power plant as claimed in claim 1 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.z) is/are designed in terms of their production and/or conversion capacity in such a way that the amount of hydrogen that can be produced can be used to convert the entire CO.sub.2 content of the offgas stream that forms in the burners of the large-scale steam generator in the course of combustion of carbonaceous fuel and/or the total amount of CO.sub.2 separated out in the at least one CO.sub.2 separation plant to methanol or a methanol conversion product in the synthesis plant(s) for preparation of methanol and/or methanol conversion products.

15. The power plant as claimed in claim 1 wherein each of the units or plants from the group of the at least one unit for production of a CO.sub.2-rich gas stream, the at least one electrolysis plant for preparation of hydrogen (H.sub.2) and the at least one synthesis plant for preparation of methanol and/or methanol conversion products has at least one dedicated reactant and/or product storage component, and the electrolysis plant has a dedicated hydrogen storage component and/or an oxygen storage component and the unit for production of a CO.sub.2-rich gas stream has a dedicated CO.sub.2 storage component.

16. A method of flexibly operating a power plant as claimed in claim 1 wherein the at least one unit for production of a CO.sub.2-rich gas stream and the at least one electrolysis plant for preparation of hydrogen (H.sub.2) and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least CO.sub.2 components of the CO.sub.2-rich gas stream and the hydrogen produced in the electrolysis plant have been and are connected and interconnected physically and electrically to one another in terms of conduction by current-conducting and media-conducting lines to form a group such that the power generated on the power plant side in the course of operation of the power plant is utilized wholly or partly, as required, for operation of one, more than one or all of this group of units and plants comprising the unit for production of a CO.sub.2-rich gas stream, the electrolysis plant for preparation of hydrogen (H.sub.2) and the synthesis plant for preparation of methanol and/or methanol conversion products.

17. The method as claimed in claim 16, wherein the current/power consumption and the hydrogen production in the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) is run up or down within 5 minutes, on the power plant side in response to a grid-side power control demand on the power plant.

18. The method as claimed in claim 16 wherein the respective current/power consumption and production or conversion output of the at least one unit for production of a CO.sub.2-rich gas stream or a plurality of units for production of a CO.sub.2-rich gas stream and/or the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or a plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream is run up or down within 5 minutes, on the power plant side in response to a grid-side power control demand on the power plant.

19. The method as claimed in claim 16 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are actuated and controlled individually in terms of their respective current/power consumption and their respective production or conversion output.

20. The method as claimed in claim 16 wherein the at least one electrolysis plant for preparation of hydrogen (H.sub.2) or the plurality of electrolysis plants for preparation of hydrogen (H.sub.2) and the at least one unit for production of a CO.sub.2-rich gas stream or the plurality of units for production of a CO.sub.2-rich gas stream and the at least one synthesis plant for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream or the plurality of synthesis plants for preparation of methanol and/or methanol conversion products from at least portions of the CO.sub.2-rich gas stream are operated as a load connected physically and electrically to the public power grid that can be switched off.

21. A power plant comprising: a steam generator configured to produce electricity and a CO.sub.2-containing offgas stream; a first current-conducting line configured to conduct the electricity produced by the steam generator to a power grid, the conduction of electricity to the power grid subject to control from the power grid; a CO.sub.2 separation unit configured to process the CO.sub.2-containing offgas stream to produce a CO.sub.2-rich gas stream; a first media-conducting line conducting the CO.sub.2-containing offgas stream from the steam generator to the CO.sub.2 separation unit; a second current-conducting line configured to conduct electricity produced by the steam generator to the CO.sub.2 separation unit; a synthesis plant for production of at least one of methanol and methanol conversion products from hydrogen (H.sub.2) and the CO.sub.2-rich gas stream, the synthesis plant also producing water; a second media-conducting line conducting the CO.sub.2-rich gas stream from the CO.sub.2 separation unit to the synthesis plant; a third current-conducting line configured to conduct electricity produced by the steam generator to the synthesis plant; an electrolysis plant configured to produce hydrogen (H.sub.2) from water; a third media-conducting line conducting water from the synthesis plant to the electrolysis plant; a fourth media-conducting line conducting hydrogen (H.sub.2) from the electrolysis plant to the synthesis plant; and a fourth current-conducting line configured to conduct electricity produced by the steam generator to the electrolysis plant, wherein the electricity generated by the steam generator is conducted to one or more of the electrolysis unit, the synthesis unit, and the CO.sub.2 separation unit, based on the control from the power grid, for operation of one or more of the electrolysis unit, the synthesis unit, and the CO.sub.2 separation unit.

22. The power plant of claim 21, wherein the power plant is configured to adjust the power consumption of the electrolysis plant, in response to control from the power grid, to increase or decrease the power provided to the power grid by the power plant.

23. The power plant of claim 1, wherein the power plant is configured to adjust the power consumption of the at least one electrolysis plant in response to a grid-side power control demand on the power plant from the power grid.

Description

(1) The invention is elucidated in detail by way of example hereinafter with reference to a drawing. This shows, in

(2) FIG. 1: in schematic form, a plant flow diagram of a power plant of the invention and, in

(3) FIG. 2: likewise in schematic form, the interconnection of a power plant of the invention with dedicated components.

(4) FIG. 1 shows, in schematic form, a power plant 51 fired with brown coal 50, which comprises a large-scale steam generator 1 with a connected water/steam circuit 54. The flue gas 53 formed in the firing of the brown coal 50 in the burners of the large-scale steam generator 1 is fed in a conduit to an air preheater 2 to which is fed, in countercurrent, the combustion air 52 which is supplied through a conduit and is preheated in the air preheater 2. Thereafter, the flue gas 53 is fed to a heat displacement system 3 and heat which is extracted from the flue gas 53 is provided to the feed water preheater of the water/steam circuit 54. Thereafter, the flue gas 53, in terms of conduction, is passed into a flue gas desulfurization plant 4 where it is substantially freed of SO.sub.2 (sulfur dioxide) and SO.sub.3 (sulfur trioxide). The flue gas 53 cleaned in this way leaves the flue gas desulfurization plant 4 with a temperature of 40-90 C. In order to achieve and to assure high availability and high separation rates in the post-combustion capture (PCC) CO.sub.2 separation plant 5 connected downstream of the steam generator 1, the flue gas 53 is first subjected to a fine purification in a fine purification plant 6. The fine purification plant 6 takes the form of a flue gas cooler with a dedicated NaOH (sodium hydroxide) pre-scrubber in which scrubbing of the flue gas 53 with an NaOH solution takes place and the flue gas 53 is cooled to a temperature of 30-50 C. At the same time, the SO.sub.2/SO.sub.3 concentration of the flue gas 53 is lowered further.

(5) From the fine purification plant 6, the cooled flue gas 53 is introduced into an absorber 7 of the post-combustion capture (PCC) plant 5 and contacted therein, in countercurrent, with a scrubbing agent which leaches the CO.sub.2 out of the gas stream. The CO.sub.2 scrubbing agent in the working example is an aqueous amine solution which takes the form of a simple monoethanolamine solution, such that the energy demand in the downstream desorption in the desorber 8 is 3.2-3.8 MJ/kg of carbon dioxide removed. Alternatively, it is also possible to use a CO.sub.2 scrubbing agent which is optimized in relation to the energy demand necessary in the desorption such that only an energy demand in the range of 2.4-2.8 MJ/kg of carbon dioxide removed is now required therein. Departing from the absorber are firstly a cleaned gas 55 and secondly the CO.sub.2-saturated CO.sub.2 scrubbing agent solution, which is fed via a conduit 56 to the desorber 8 which likewise takes the form of a constituent of the post-combustion capture (PCC) plant 5. The heat required for the desorption in the desorber 8 is provided and supplied in the form of steam in a customary manner in a reboiler 9. In the working example, this steam is taken from the water/steam circuit 54 at a temperature of 110 C. and 200 C. as bleed steam 12 between a medium-pressure turbine 10 and a low-pressure turbine 11 of the turbogenerator 58 disposed in the water/steam circuit 54 and fed via a conduit 57 to the reboiler 9. The condensate that arises in the reboiler 9 in the reboiler heating is recycled via a conduit 13 into the preheating zone of the water/steam circuit 54. Departing from the desorber 8 are firstly the scrubbing agent which has been freed of CO.sub.2 and is typically recycled in the circuit to the absorber 7, and secondly a mixture of carbon dioxide (CO.sub.2) and steam. This carbon dioxide/steam mixture, after a cooling and re-scrubbing operation 14 which is disposed in the exit region of the desorber 8, is fed to a compressor stage 15. The cooling in the top region of the desorber 8 is effected with the aid of a heat exchanger 16b, and the re-scrubbing 14 is preferably effected with the aid of an acidic medium. In the compressor stage 15, the carbon dioxide/steam mixture is compressed to a pressure of above 20 bar, preferably to a pressure between 30-60 bar. The tangible heat of the carbon dioxide/steam mixture leaving the desorber 8 and the compressor stage 15 and also some of the heat of condensation of the water present therein is withdrawn or decoupled in a heat exchanger 16a which is connected downstream of the compressor stage and through which the carbon dioxide/steam mixture flows, and the dedicated heat exchanger 16b of the exit region of the desorber 8. The thermal energy withdrawn or decoupled here is fed, for example via heat exchangers 17a, 17b, 17c, 17d for the low-pressure preheater (17b) of the water/steam circuit 54, for the combustion air preheater (17a) or for reactant preheaters (17c, 17d) in the region of the reactors (27, 31) for the methanol synthesis and the distillation of a synthesis plant 60 for preparation of methanol and/or methanol conversion products. In the compressor plant which, in the working example, comprises several compressor stages 15, the heat exchanger 16a is disposed between the first and last compressor stages 15. The CO.sub.2-rich gas stream 59 leaving the last compressor stage 15 is fed to a storage means 18 and thence to the synthesis plant 60 for preparation of methanol and/or methanol conversion products. Upstream of the entrance into the storage means 18, the CO.sub.2-rich gas stream once again passes through a heat exchanger 19 in which this gas stream is cooled further. After leaving the storage means 18 and before entering the methanol synthesis reactor 27 of the synthesis plant 60 as well, the CO.sub.2-rich gas stream flows through a further heat exchanger 20, by means of which heat is introduced into the CO.sub.2-rich gas stream, in order to bring the CO.sub.2-rich gas stream which enters the methanol synthesis reactor 27 as reactant to a reactor or reaction temperature in the range of 100-400 C., preferably of 150-300 C. The heat required for the purpose is fed to the heat exchanger 20 as bleed steam which is taken from the turbogenerator 58, or in the form of waste heat that arises in other processes.

(6) In the methanol synthesis reactor, the CO.sub.2 supplied in the CO.sub.2-rich gas stream is reacted with hydrogen to give methanol. The hydrogen is prepared in an electrolysis plant 61 which, in the working example, is an alkaline water electrolysis. An alternative option is to employ other electrolyzer types such as polymer electrolyte membrane (PEM) electrolyzers or solid oxide electrolyzer cells (SOEC) or a chlor-alkali electrolysis.

(7) The alkaline water electrolysis in the working example comprises an electrolysis cell 21 in which water 34 supplied is broken down electrolytically at a temperature between 50 and 100 C., preferably between 70 and 90 C., into its hydrogen and oxygen constituents. In this electrolysis, the temperature of the electrolysis cell 21 itself is controlled by means of a heat exchanger 22b and that of the water supplied by means of a heat exchanger 22a, such that the electrolysis at any time is within the optimal operating temperature range and can undergo changes in load rapidly, more particularly including those up to higher loads. The alkaline electrolysis can be operated within wide pressure ranges, especially employing pressures above 15 bar, preferably pressures in the range from 20 bar to 60 bar. Alternatively or additionally, the synthesis plant 61 is equipped with a hydrogen compressor 23 to which the hydrogen produced in the electrolysis cell 21 is fed prior to entry thereof into the methanol synthesis reactor 27. Such a hydrogen compressor 23 is appropriate especially because it has a dedicated hydrogen storage means 24 in which hydrogen produced can be stored. The intermediate storage means 24 is firstly a product storage means, since the hydrogen produced by means of the electrolysis plant 61 is stored therein. Secondly, however, it is also a reactant storage means since the hydrogen stored therein constitutes one starting material for the methanol synthesis. In order to cool the hydrogen compressed in the hydrogen compressor 23 prior to the intermediate storage thereof, a heat exchanger 25 disposed between the hydrogen compressor 23 and the intermediate storage means 24 can be used to extract or withdraw thermal energy from the hydrogen stream. In order to bring the hydrogen stream which leaves the intermediate storage means 24 at a later stage to a sufficiently high reaction temperature prior to entry thereof into the methanol synthesis reactor 27, a further heat exchanger 26 is provided, by means of which heat is introduced again into the hydrogen stream, for which purpose the heat needed may originate from the bleed steam that originates from the water/steam circuit 54 or from the waste heat from the methanol synthesis reactor 27. The rest of the waste heat that arises in the methanol synthesis can be removed via the heat exchangers or cooling units 28a, 28b, 28c which are connected downstream of the methanol synthesis reactor 27 or integrated therein. The heat exchanger 28a conducts its heat away to the preheating zone of the water/steam circuit 54, although it is also possible to conduct the heat removed away to the reboiler 9 of the post-combustion capture (PCC) plant 5 and/or to various reactant preheaters, i.e. the preheating in the power plant of the invention to give starting materials to be processed/converted. Since the conversion of the carbon dioxide (CO.sub.2) and hydrogen (H.sub.2) reactants supplied which is achieved in the methanol synthesis reactor 27 is not very high but is only in the range of 10%-35%, in the working example, the cooler 28a, 28b, 28c which is connected downstream and comprises the heat exchangers/cooling units is designed in such a way that a phase separation of the methanol product produced in the methanol synthesis reactor 27 is effected in a vessel 29 and the gaseous constituents removed are recycled wholly or partly via a recycle line 30 back into the methanol synthesis reactor 27. In the recycle line 30, heat is again supplied to the recycled gaseous constituents by means of the heat exchanger 17c.

(8) The liquid phase removed in the vessel 29 is fed to a distillation or rectification reactor 31 in which water, but if desired also higher-boiling alcohols when a relatively high purity of the methanol product to be produced is desired, are separated from the liquid phase. The heat required for the distillation or rectification is appropriately provided by heat exchangers which can be supplied with lower-value bleed steam from the water/steam circuit 54 and/or from the waste heat of the reboiler 9, or else thermal energy extracted from other process steps. Departing from the distillation and/or rectification reactor 31 is a gaseous methanol (CH.sub.3OH) stream 35, a particular possibility being that of extracting the heat of evaporation thereof in two subsequent cooling steps (32a, 32b) by means of heat exchangers 32a, 32b into the preheating zone of the water/steam circuit 54 and/or a reactant preheater.

(9) The water 33 removed from the distillation and/or rectification reactor 31 can be fed to a special water processing plant and/or the feed water processing plant of the water/steam circuit 54 and then fed as reactant (water 34) to the electrolysis plant 61.

(10) The oxygen formed in the electrolysis can be compressed, liquefied if desired, and sent to a use.

(11) FIG. 2 shows a schematic of the assignment and interconnection of the individual units and plants of the power plant of the invention.

(12) The power generated by means of a generator 70 with an optionally dedicated transformer in the power plant 51 can firstly be fed into the connected public power grid 71, or alternatively to the electrolysis plant 61, the electrolysis plant 61 additionally having dedicated batteries 72 and transformers 73 which enable storage and transformation of the power supplied. Alternatively, the power generated by the generator 70 can also be used to supply an electrically heated heat storage means 74 which produces district heat, for example, which can be supplied to a district heating grid 75. The heat storage means 74 can additionally be supplied with steam 76 originating from the water/steam circuit 54 or thermal energy extracted therefrom. The power generated by means of the generator 70 can alternatively be fed to an oxygen compression or liquefaction plant 77 in which oxygen 78 formed in the electrolysis 61 is processed. The compressed or liquefied oxygen can then be stored in an oxygen storage means 79 or alternatively sent to a further use 80. The oxygen 78 produced in the electrolysis plant 61 can alternatively be fed to the steam generator 1 as oxidizing agent. The individual plants or units 61, 72, 74, 77 and 80 supplied with the power generated by the generator 70 can alternativelyeven though this is not shown in FIG. 2all be supplied with power drawn from the power grid 71, especially when it provides surplus power. More particularly, the units/plants shown are interconnected to one another in such a way that the power generated by means of the generator 70 or drawn from the power grid 71 can be distributed flexibly between the individual units/plant components. The priority, however, is with the methanol production, especially with the methanol production by means of the synthesis plant 60, and so the electrolysis plant 61 is basically the plant that reacts in a flexible, timely and rapid manner to grid-side power control demands with changes in load.

(13) The electrolysis plant 61 and the synthesis plant 60 have a dedicated water purifier 81 in which the water to be supplied to the electrolysis plant 61 and the synthesis plant 60 is purified beforehand in accordance with the desired requirements.

(14) Both the methanol production by means of the methanol synthesis reactor 27 and the production plant for production of methanol conversion products 82 have dedicated storage means, the synthesis plant 60 having a dedicated methanol storage means 83 and the production plant 82 having a dedicated methanol conversion product storage means 84. The waste heat that arises in the methanol production in the synthesis plant 60 and that which arises in the CO.sub.2 separation in the post-combustion capture plant 5 is introduced back into the water/steam circuit 54, as indicated by the arrows 85 and 86.

(15) Overall, the power plant 51 of the invention, by virtue of the current-conducting and media-conducting connecting conduits shown in FIGS. 1 and 2, is flexibilized with regard to modes of operation that can thus be realized and production or conversion outputs that can be established or production or conversion products that can be produced. The current consumptions or current/power consumptions of the individual plant components, especially of the electrolysis plant 61, also contribute to this by enabling ways of running or modes of operation of the power plant 51 that can be adjusted to different power demands and power control demands for flexibilization. For instance, the CO.sub.2 separation by means of the PCC plant 5 and/or the hydrogen production by means of the electrolysis plant can be controlled in such a way that the minimum load of the power plant 51 and the power feed-in into the power grid 71 can be reduced down to 0 MW.sub.el. If power is then additionally drawn from the power grid 71, the grid feed-in of the power plant 51 then even becomes negative overall.

(16) The electrolysis plant 61 can additionally be designed in such a way that the power drawn for hydrogen production is five to ten times higher than the current output of the generator 70 at each present load state of the power plant 51.

(17) It is also possible for the CO.sub.2 separation plant 5 to be designed such that up to 95% of the carbon dioxide or carbon dioxide stream produced with the flue gas 53 is separated out and, at the same time or with a time delay after intermediate storage in a CO.sub.2 storage means 18, is supplied to chemical reactors, especially the methanol synthesis reactor 27 for preparation of methanol or methanol conversion products.

(18) The storage means provided, CO.sub.2 storage means 18, hydrogen storage means 24, methanol storage means 83, oxygen storage means 79 and methanol conversion product storage means 84, take the form of buffer storage means in order to be able to intermediately store the products stored therein as reactants for the downstream further processing. In this case, the hydrogen storage means 24 and/or the CO.sub.2 storage means 18 and/or the oxygen storage means 79 preferably take the form of pressurized storage means and all storage means are equipped with a capacity to store the amounts of products required for the further processing, such that they can be stored for short or longer periods, but can also, if desired, be provided at short notice to the assigned production process.

(19) In addition, the electrolysis plant 61 and/or the CO.sub.2 separation plant 5 or the unit for production of a CO.sub.2-rich gas stream and/or the chemical reactors, especially the methanol synthesis reactor 27, promote the flexible operation of the power plant by the provision of a rapid change in load, in such a way that the entire control capacity, especially the primary and secondary control of the power plant, is improved in relation to a power feed-in or a power consumption. The effect of the load change capacity provided by these plants, but especially the electrolysis plant 61, is that the power plant 51 can then be operated with a load change gradient of 3%/m to 10 to more than 20%/m. Of course, it is also possible to additionally provide plants in the power plant that generate renewable energy, such as photovoltaic plants or wind power plants, which then likewise provide the power generated to the overall process.

(20) The process heat that arises or process heat required in each of the plants detailed in the individual processes can be provided by appropriate conduit interconnection of the individual plants or process components. For instance, it is possible to use process heat, especially in the range from 30 to 150 C., which is withdrawn as waste heat from the post-combustion capture plant 5 and/or as bleed steam from the water/steam circuit 54, for preheating of process streams for an electrolyzer, especially for the electrolysis plant 61, and/or for trace heating thereof and/or for preheating of reactants to be converted in the methanol synthesis reactor 27 and/or for feed water preheating in the water/steam circuit 54 and/or in the distillation and/or rectification reactor 31. It is also possible to feed waste heat which originates from the cooling of products in the reactant preheating for the electrolysis, from reactors or from the purification of products back to the overall process. It is also possible to feed the water 33 obtained in the distillation or rectification or any water obtained elsewhere in the overall process, preferably after treatment in a water purifier 81, back to the electrolysis plant 61. The oxygen formed in the electrolysis of water can be fed at least partly to an adjacent industrial operation and reduce the capacity utilization of air fractionation plants therein. Alternatively, it is possible to at least partly compress the oxygen formed in the electrolysis of water and to dispense it into pressure vessels or at least into an oxygen storage means 79 and/or liquefy it by a refrigeration process.

(21) The dimensions of the hydrogen production and/or other plant components, especially electrical plant components, are such that it is possible to increase the electrical consumption to more than 100% of the design value, preferably to more than 120% to 200%, at least over a short period in the range of minutes, preferably up to more than 30 minutes. In addition, the dimensions of the additionally installed batteries 72 are such that it is possible to increase the electrical consumption or the electrical feed-in to more than 100% of the design value, preferably to more than 150% to 300%, at least over a short period in the range of seconds, preferably even up to more than 15 minutes.

(22) In addition, it may be the case that an electrical water heater and/or steam generator installed in the overall process or in the power plant 51 firstly makes a contribution in relation to its power consumption to the flexibilization of the power plant, and the heat generated thereby (hot water or steam) can be fed to one or more heat storage means. More particularly, it is therefore also the case that heat storage in the form of water, steam or solids or liquids such as salts is integrated within the power plant. It is also possible for the heat generated or stored to be utilized for the drying of the fuel used, especially the brown coal envisaged in the working example, by using waste heat from the component processes or turbine bleeding (turbogenerator) for drying of brown coal or other fuels.

(23) FIG. 1 includes the following abbreviations: GP=gas phase, FP=liquid phase, HDV=high-pressure preheater, NDV=low-pressure preheater, HD=high-pressure turbine, MD=medium-pressure turbine and ND=low-pressure turbine.

(24) Finally, it may also be the case that some of the reaction products produced, especially with the synthesis plant 60, i.e. methanol or a methanol conversion product, are stored at the power plant site and supplied at least temporarily as starter fuel and/or as support fuel and/or as main fuel to the burners of the steam generator 1 and combusted therein.

(25) A CO.sub.2-rich gas stream in the context of this application is understood to mean one having a proportion of at least 12, especially at least 30, percent by weight or percent by volume of CO.sub.2.

(26) In summary, it can be stated that the invention proceeds from the consideration that, in the case of power plants that would otherwise have to be run down, the increase in the internal demand for energy by means of the CO.sub.2 separation 5 (especially demand for steam for the heating of the reboiler 9) and by means of a methanol preparation by a synthesis plant 60 (demand for power for the electrolysis) can increase the exploitation of the existing power plant capacities by making it possible to operate the power plant with a higher load even in periods of weak demand than would be necessary for pure power generation. The ultimate outcome is that the power plant can then be operated with a higher number of full-load hours, since it is not just designed for power production but also for methanol production or the production of methanol conversion products. In addition, the invention is based on the consideration that the higher speed of change in the load of the electrolysis plant 61 compared to the possible speed of change in the load of the power plant can be utilized in order to offer a much quicker control service to the connected public power grid. In the event of power control or a power control demand from the power grid side, the electrolysis plant 61 can be run up or run down relatively quickly and at short notice, such that the steam generator or the power plant overall is given more time to undertake a change in load, or there is even avoidance of any need for a change in load of the actual power plant component, i.e. an adjustment of the output of the steam generator 1. Finally, the invention proceeds from the consideration that it is possible with the invention to avoid the need to shut down the power plant entirely in times of weak demand. It can still be designed such that the electrolysis plant 61 and the methanol production 60 draw or consume sufficient power at minimum load of the power plant and no power release to the grid becomes necessary.

(27) Marginal cases for the inventive design of a power plant are firstly brown coal power plants which currently (still) generate electrical power very inexpensively. Such a power plant can still be run at 100% load (full load) with the invention, even when the power grid does not consume the electrical power generated in the form of power. The unconsumed power can be utilized in the electrolysis plant 61 for production of hydrogen. The other marginal case is that of hard coal power plants which nowadays have to be run with a minimum load since they would otherwise take too long to restart, or which have to keep a specific generator output available for control purposes. In the case of hard coal power plants equipped in accordance with the invention, the minimum load can now be (over-)absorbed and the power generated can be utilized for the hydrogen production in the electrolysis plant 61 without any need to remove the power plant from the grid, such that the high-inertia rotating mass thereof (especially that of the generator) is still available to the grid for control support.

(28) In this respect, flexibilization of the mode of operation of a power plant is enabled, since the actual power plant 51 can still gradually change its load, but the load utilized by the electrolysis plant 61 and the synthesis plant 60 is available for control.

(29) Overall, the aforementioned control options can improve the economic viability of a power plant (more full-load hours, constantly available grid services, additional fuel product (methanol and methanol conversion products)).

(30) It is advantageous in the case of the present invention that there is no need for prior gasification of products for preparation of methanol or methanol conversion products; instead, the combustion of carbonaceous fuel in the steam generator 1 of a/the power plant 51 is utilized. The invention features low capital costs in the retrofitting of existing power plants, an increase in the economic viability of existing plants in the case of retrofitting and high operational safety and reliability of the methanol synthesis which uses CO.sub.2 formed in the combustion in the steam generator 1 and H.sub.2 produced by electrolysis. Even in the case of new constructions, the inventive solution constitutes an improvement in flexibility, plant exploitation time and economic viability.

(31) In the power plant shown in schematic form in FIG. 1, for example, in the operation of a 670 MWel power plant at 30% load, 45 kg/s of fuel (calorific value 10.5 MJ/kg) are required, 190 Mel of power are generated, 15% of the CO.sub.2 present in the flue gas is separated out and 1.1 kg/s of hydrogen are produced electrolytically. From the latter are produced about 6 kg/s of methanol, which corresponds to a carbon conversion efficiency of the fuel to the methanol product of about 27% and an efficiency of more than 60% (power to calorific value of the methanol).

(32) If these product volumes were produced in each of 90% of the annual operating hours of such a power plant, assuming fuel costs of 10 /t and sales of 400 /t of methanol, it would be possible to achieve a turnover of million Euros. In addition, the power plant may generate additional sales through higher power production, and primary/secondary control for virtually the whole year. Finally, sales are also possible through demand-side management by means of the electrolysis plant 61. More particularly, the electrolysis plant 61 itself can at any time run loads between 0 and up to more than 200 MW, in some cases up to 400 MW (overloads only briefly), much more quickly than the power plant, and so it is possible to provide additional grid services.

(33) It is apparent from this that the inventive flexibilization of the power plant 51 has a positive influence on the operation of the power plant 51 both in technical and economic terms.