Steam generation plant and method for operating same

Abstract

The invention relates to a steam generation plant (1) comprising at least one steam generator (2) and a compressor (4) with several successive compressor stages (10, 11, 12), characterised in that a thermal energy storage system (5) is provided which is designed to selectively extract steam at several different pressure levels from the compressor (4) after several compressor stages (10, 11, 12), in particular after each compressor stage (10, 11, 12), to store extracted steam at several different pressure levels and to selectively supply stored steam to the compressor (4) at a suitable pressure level before and / or after several compressor stages (10, 11, 12), and in that the thermal energy storage system (5) is designed to selectively supply stored steam to the compressor (4) at a suitable pressure level after the last compressor stage (12). The invention further relates to a method for operating a steam generation plant (1) of this kind.

Description

[0001] Description

[0002] Steam generation plant and method for operating such a plant

[0003] The present invention relates to a steam generation system comprising at least one steam generator and one compressor with several successive compressor stages. Furthermore, the present invention relates to a method for operating such a steam system.

[0004] Various industrial processes require process steam at different pressure levels. Examples of such industries include the paper, food, and chemical industries, as well as oil and gas refineries.

[0005] Steam generation plants of the type mentioned above are used to generate process steam at medium and high pressure levels. The steam generated in the steam generator is compressed in the compressor to the required pressure level. Compressors in such steam generation plants are now being designed or arranged in multiple stages, with the steam being taken off downstream of the individual compressor stages as precisely as possible, i.e. at the pressures required from a process perspective. The mass flow requirements of the individual compressor stages can differ and fluctuate independently of one another. This results in different and independently fluctuating mass flow requirements for each compressor stage. Against this background, the permissible mass flow can be exceeded or undershot in one or more compressor stages, which must be avoided.If the mass flow rate is too low and the pressure ratio is too high, the flow can detach from the compressor blades when the so-called surge limit is reached, interrupting the pumping process. If the mass flow rate is too high and the pressure ratio is too low, the so-called absorption limit is reached, which defines the maximum possible throughput of the compressor stage. If the surge or absorption limit is exceeded, the compressor is shut down, meaning that the processes requiring the steam can no longer be served.

[0006] Until now, steam was vented or extracted via a condenser when the load requirement was not met. However, it would be desirable to avoid such steam disposal, as it is noisy and energy-intensive. Water conservation is also important.

[0007] To avoid exceeding the surge limit, the steam can be recirculated around the compressor. However, this is not energy efficient.

[0008] Based on this prior art, it is an object of the present invention to provide a steam generation plant of the type mentioned at the outset with an improved structure and a more efficient method for operating such a steam generation plant.

[0009] To achieve this object, the present invention creates a steam generation plant of the type mentioned at the outset, which is characterized in that a thermal energy storage system is provided which is designed to selectively withdraw steam at several different pressure levels from the compressor after several compressor stages, in particular after each compressor stage, to store withdrawn steam at several different pressure levels and to selectively supply stored steam to the compressor at a suitable pressure level before and / or after several compressor stages, and in that the thermal energy storage system is designed to selectively supply stored steam at a suitable pressure level to the compressor after the last compressor stage. The storage of steam in the thermal energy storage device can take place in the vaporous and / or liquid state.Therefore, when reference is made to "storage of steam" below, this does not refer to the aggregate state, unless explicitly stated otherwise. Furthermore, the thermal energy storage device can also be designed so that water or steam can be added to and removed from a separate source, for example to refill the energy storage device or to remove excess water or steam and, if necessary, use it for another purpose.

[0010] Thanks to the thermal energy storage system according to the invention, it is possible to optimally adjust or regulate the mass flow through each individual compressor stage according to demand. This means that the correct mass flows at the correct pressure according to the requirements of the consumers assigned to the individual compressor stages can be made available, with the involvement of the energy storage system, if the mass flow coming from the steam generator or the previous compressor stage is insufficient. Excess steam can be removed and stored in the thermal energy storage system if the mass flow coming from the steam generator or the previous compressor stage is too high. In this way, each compressor stage can be kept within its operating range without the need to shut down or recirculate steam.Furthermore, the steam quantity can be adjusted so that the mass flow is optimized in order to increase the efficiency of the steam generation plant. This is possible because the efficiency of a compressor stage depends on the mass flow and the differential pressure of the compressor stage. The setting or regulation of the mass flow through the individual compressor stages is naturally carried out using a suitably designed evaluation and control unit as well as suitable sensors, which record in particular the mass flows in the lines, especially in the lines to the consumers, and control devices such as valves, flaps and the like.

[0011] The thermal energy storage system is designed to selectively supply stored steam at a suitable pressure level to the compressor after the last compression stage. This allows sufficient steam to be made available at the compressor outlet if the upstream steam generator is producing too little steam, for example, during the start-up phase of the steam generation plant.

[0012] According to the invention, the thermal energy storage system can comprise a Ruths storage system. Such a Ruths storage system enables direct steam injection without the need for an intermediate circuit and associated heat exchangers and additional pumps, thus achieving an overall cost-effective design.

[0013] Alternatively or additionally, the thermal energy storage system can have at least one feedwater tank with thermal degassing. Such a feedwater tank requires steam to ensure degassing from the feedwater. This steam supply leads to heating of the feedwater, which is normally a boiling liquid. A feedwater tank is also designed for a certain operating range which allows flexibility in terms of fill volume and pressure / temperature. If the compressor stage exceeds the absorption limit, the steam quantity could be reduced by reducing or switching off the steam supply to the feedwater tank, which brings the corresponding compressor stage back into its operating range. If the steam quantity via the compressor stage is too low, a higher steam flow into the feedwater tank can stabilize the compressor stage.Overall, this reduces the equipment and thus the material and energy costs required for production. Furthermore, the space requirement is reduced, thereby increasing the chances of retrofitting a thermal energy storage system according to the invention into existing systems with limited space.

[0014] According to a further embodiment of the present invention, the thermal energy storage system can alternatively or additionally comprise a condensate tank. A condensate tank can increase the amount of steam through the compressor stage by heating the condensate without the steam having to be vented. This can reduce the system's water loss.

[0015] Alternatively or additionally, the thermal energy storage system according to the invention can comprise a large water boiler. As in the feedwater tank, the water reservoir in the large water boiler can be used as a storage reservoir, particularly for preheating in heat-maintenance mode, which can be switched on or off depending on the operating state of the compressor stage.

[0016] According to one embodiment of the present invention, the thermal energy storage system has at least one heat source which is designed to heat stored steam. With such a heat source, it is possible to bring steam stored in the energy storage system to the desired temperature / pressure levels. The at least one heat source is preferably an electrically operated heat source, such as an electrode boiler or a heating rod, which enables the heat generator to make optimal use of the supply of electricity from fluctuating renewable energies. The fact that the electricity supply of individual consumers can be aligned with the supply of electricity from fluctuating renewable energies thereby facilitates its integration into power grids.Thus, at least one heat source can be used to directly provide a steam source via the thermal energy storage system when the compressor starts up, for example, if the steam generator has not yet fully started up. Furthermore, if an increased steam demand arises, the additional heat source can be used to replenish the required steam or to fill the thermal energy storage system.

[0017] Advantageously, the at least one steam generator is a high-temperature heat pump, which is operated, for example, using waste heat from one or more processes that are supplied with steam via the steam generation system and / or using waste heat from an external process. It should be noted, however, that in addition to such a high-temperature heat pump, other steam generators can also be used, which can be used together with or alternatively to the high-temperature heat pump. High-temperature heat pumps have the advantage over conventional steam generators that they can be operated completely CCp-neutrally by utilizing existing waste heat and electricity from renewable energies.

[0018] The thermal energy storage system is advantageously designed to supply stored steam to the evaporator of the high-temperature heat pump at a suitable pressure level. Accordingly, steam stored in the thermal energy storage system can be used, for example, to start up the heat pump when the process is not yet ready as a heat source.

[0019] To achieve the object stated at the outset, the present invention further provides a method for operating a steam generation plant, in particular a steam generation plant according to the invention, comprising at least one steam generator and one compressor with a plurality of successive compressor stages, in which method the operating states of the individual compressor stages are monitored, wherein, when a compressor stage approaches its individual surge limit, a steam mass flow is extracted immediately downstream of this compressor stage until a proper operating state is reached and the extracted steam is stored in a thermal energy storage system, and, when a compressor stage approaches its individual absorption limit, a steam mass flow of a suitable pressure level is supplied from the thermal energy storage system immediately downstream of this compressor stage until a proper operating state is reached.In this case, a steam mass flow of suitable pressure level is optionally supplied from the thermal energy storage system after the last compressor stage, particularly when the upstream steam generator produces too little steam, for example during the start-up phase of the steam generation plant.

[0020] According to one embodiment of the present invention, steam stored in the thermal energy storage system is selectively heated by at least one heat source. Advantageously, the at least one steam generator is a high-temperature heat pump, the evaporator of which is selectively operated, in particular, by steam stored in the thermal energy storage system.

[0021] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

[0022] Figure 1 is a schematic view of a steam generating plant according to an embodiment of the present invention and

[0023] Figure 2 is a schematic view of a steam generating plant according to a further embodiment of the present invention.

[0024] The same reference numerals refer to the same or similar components hereinafter.

[0025] Figure 1 shows a steam generation plant 1 according to an embodiment of the present invention, which comprises as main components at least one steam generator 2, a compressor 4 connected to the steam generator 2 via a line 3, a thermal energy storage system 5, and an evaluation and control unit 6. The compressor 4 has several successive compressor stages 10, 11, and 12 connected by lines 7, 8, and 9, which compress the steam generated by the steam generator 2 to different pressure levels. In the example shown, the steam generated in the steam generator 2 is fed to the compressor 4 and thus to the first compressor stage 10 at a pressure of 1.6 bar, from where it is then further compressed in the individual compressor stages 10, 11, and 12 to pressures of 2.8 bar, 5.0 bar, and 9.0 bar, respectively. It should be understood that the number of compressor stages and the respective pressures can vary fundamentally.From lines 3, 7, and 9, i.e., between the steam generator 2 and the compressor 4 and between the respective compressor stages 10, 11, and 12, and from line 13 coming from the last compressor stage 12, lines 14, 15, 16, and 17 branch off, via which the steam is supplied at the appropriate pressure level to various consumers 18, 19, 20, and 21. Further lines 22, 23, and 24 branch off from lines 7 and 9 between the compressor stages 10, 11, and 12 and from line 13 leading from the last compressor stage 12, which lead to the thermal energy storage device 5. The thermal energy storage device 5 is designed to store steam at different pressure levels. Alternatively, several thermal energy storage devices can be provided for this purpose, although not shown here.Further lines 25, 26 and 27 lead from the thermal energy storage device 5 back to lines 3 and 7, optionally a further line 28, shown here in dashed lines, to line 13. The lines 22, 23, 24, 25, 26, 27 and 28 are each provided with control elements 29, which in this case can be controlled by a motor via the evaluation and control unit 6. Furthermore, in the present exemplary embodiment, all lines 7, 9, 13, 14, 15, 16, 17, 22, 23, 24, 25, 26, 27 and 28 are provided with sensors 30 which record the steam mass flows conducted through lines 7, 9, 13, 14, 15, 16, 17, 22, 23, 24, 25, 26, 27 and 28 and transmit the recorded measured values ​​to the evaluation and control unit 6. It should be clear that in addition to the control elements 29 shown, further control elements can be provided and / or some of the sensors 30 can be omitted, since the mass flows can in principle also be calculated on the basis of the measured values ​​from fewer sensors.The thermal energy storage system 5 can have at least one Ruths storage tank and / or at least one feedwater tank with thermal degassing and / or at least one condensate tank and / or at least one large water boiler. The respective advantages were already explained at the beginning, which is why they will not be discussed again here to avoid repetition. The thermal energy storage system 5 can have one or more additional heating sources 31 for heating the steam stored therein, for example, electrical heating sources.

[0026] During operation of the steam generation plant 1, the consumers 18, 19, 20 and 21 create a varying demand for steam mass flows at the different pressure levels, which must be covered by the steam generated by the steam generator 2. The evaluation and control unit 6 balances the mass flows of each individual compressor stage 10, 11 and 12 based on the measured values ​​provided by the sensors 30 and compares these with corresponding operating ranges of the compressor stages 10, 11 and 12 stored in the evaluation and control unit 6.If it is determined that predefined limit values ​​have been exceeded towards the surge or absorption limit of the respective compressor stage 10, 11, 12, countermeasures are taken by releasing steam via one or more of the lines 22, 23, 24 and storing it in the thermal energy storage device 5 or by supplying steam from the thermal energy storage device 5 via one or more of the lines 25, 26, 27. If a compressor stage 10, 11, 12 approaches its individual surge limit, a steam mass flow is extracted immediately behind this compressor stage 10, 11, 12 until a proper operating state is reached and the extracted steam is stored in the thermal energy storage device 5.If a compressor stage 10, 11, 12 approaches its individual capacity limit, a steam mass flow of a suitable pressure level is supplied from the thermal energy storage device 5 immediately downstream of this compressor stage 10, 11, 12 until a proper operating state is reached. In this way, shutdown of the corresponding compressor stage 10, 11, 12 can be reliably prevented. Preferably, the respective mass flows are maintained at an optimal level that optimizes the efficiency of the steam generation system 1.

[0027] When the steam generation plant 1 is started up, as long as the steam generator 2 is not producing enough steam, steam can also be taken from the thermal energy storage device 5, thereby minimizing the start-up time. If more steam is temporarily required by the consumers 18, 19, 20 and 21 than the steam generator 2 can produce, this additional mass flow can also be provided via the thermal energy storage device 5. A control system that reacts to the electricity, fuel and / or CCp price is also possible. For example, when electricity prices are low or even negative, particularly when there is a high supply of electricity from renewable energies, more steam than required by the consumers 18, 19, 20 and 21 can be produced in the steam generator 2 and the excess steam can then be stored in the thermal energy storage device 5. In times of high electricity prices, the steam can then be provided from the thermal energy storage device 5.Of course, it is also possible to provide several different steam generators 2, for example a steam boiler and / or a cogeneration and / or a solar thermal and / or a geothermal steam generator, thus enabling reliable and cost-effective steam generation even in times of high energy prices. The steam generation plant 1 can also have additional electrical or thermo-mechanical energy storage devices with or without reconversion to electricity.

[0028] Figure 2 shows a steam generation plant 1 according to a further embodiment of the present invention, the structure and mode of operation of which is largely similar to the steam generation plant 1 shown in Figure 1 and described above. In the steam generation plant 1 shown in Figure 2, however, the steam generator 2 is formed by a high-temperature heat pump which, in a known manner, has an evaporator 32, a compressor 33, a condenser 34 and a throttle 35. In this case, the evaporator 32 is supplied with process waste heat via a line 36 and / or with the energy required to evaporate the refrigerant via a line 37 connected to the thermal energy store 5. The feed water supplied via a line is evaporated in the condenser 34 and fed to the compressor 4.

[0029] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0030] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

Claims

Patent claims 1. Steam generation plant (1) comprising at least one steam generator (2) and one compressor (4) with a plurality of successive compressor stages (10, 11, 12), characterized in that a thermal energy storage system (5) is provided which is designed to selectively withdraw steam at a plurality of different pressure levels from the compressor (4) after a plurality of compressor stages (10, 11, 12), in particular after each compressor stage (10, 11, 12), to store withdrawn steam at a plurality of different pressure levels and to selectively supply stored steam to the compressor (4) at a suitable pressure level before and / or after a plurality of compressor stages (10, 11, 12), and in that the thermal energy storage system (5) is designed to selectively supply stored steam at a suitable pressure level to the compressor (4) after the last compressor stage (12).

2. Steam generation plant (1) according to claim 1, characterized in that the thermal energy storage system (5) has at least one Ruths storage.

3. Steam generation plant (1) according to one of the preceding claims, characterized in that the thermal energy storage system (5) has at least one feed water tank with thermal degassing.

4. Steam generation plant (1) according to one of the preceding claims, characterized in that the thermal energy storage system (5) has at least one condensate tank.

5. Steam generation plant (1) according to one of the preceding claims, characterized in that the thermal energy storage system (5) has at least one large water boiler.

6. Steam generation plant (1) according to one of the preceding claims, characterized in that the thermal energy storage system (5) has at least one heating source (31) which is designed to heat stored steam.

7. Steam generation plant (1) according to one of the preceding claims, characterized in that the at least one steam generator (2) is a high-temperature heat pump.

8. Steam generation plant (1) according to claim 7, characterized in that the thermal energy storage system (5) is designed to supply stored steam to the evaporator (32) of the high-temperature heat pump at a suitable pressure level.

9. Method for operating a steam generation plant (1) comprising at least one steam generator (2) and one compressor (4) with several successive compressor stages (10, 11, 12), in which the operating states of the individual compressor stages (10, 11, 12) are monitored, wherein, when a compressor stage (10, 11, 12) approaches its individual surge limit, a steam mass flow is extracted immediately behind this compressor stage (10, 11, 12) until a proper operating state is reached and the extracted steam is stored in a thermal energy storage system (5), and when a compressor stage (10, 11, 12) approaches its individual absorption limit, a steam mass flow of suitable pressure level is supplied from the thermal energy storage system (5) immediately upstream of this compressor stage (10, 11, 12) until a proper operating state is reached, wherein a steam mass flow of suitable pressure level is optionally supplied from the thermal energy storage system (5) downstream of the last compressor stage (12).

10. The method according to claim 9, wherein steam stored in the thermal energy storage system (5) is selectively heated by at least one heat source (31).

11. Method according to one of claims 9 or 10, wherein the at least one steam generator (2) is a high-temperature heat pump whose evaporator (32) is selectively operated via steam stored in the thermal energy storage system (5).

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