Device and method for generating steam

Abstract

The invention relates to a device for generating steam, comprising a heat source (17) for heating water, a first flash device (1) in which water heated by transferring heat from the heat source (17) is partly evaporated, and at least one compressor (23) having at least one compression stage (25.1,25.2) for compressing steam, the compressor being connected to a steam chamber in the first flash device (1) via a first steam line (21). A second flash device (9) is included which is connected to the first flash device (1) via a first connecting line (7) and a second connecting line (13) in such a way that non-evaporated water is conducted from the first flash device (1) into the second flash device (9) through the first connecting line (7) and non-evaporated water is conducted from the second flash device (9) into the first flash device (1) via the second connecting line (13), the second connecting line (13) being equipped with the heat source (17) and a pump (15) by means of which the pressure of the water can be increased. A second steam line (27) branches off from the second flash device (9) and opens into the first steam line (21) upstream of the at least one compressor (23), and at least one compensation compressor (29) is provided in the second steam line (27). The invention also relates to a method for generating steam in such a device.

Description

[0001] 240546W001

[0002] Device and method for steam generation

[0003] Description

[0004] The invention relates to a device for steam generation comprising a heat source for heating water, a first flash apparatus in which water heated by heat transfer from the heat source is partially evaporated, and at least one compressor with at least one compression stage for steam compression, which is connected via a first steam line to a steam space in the first flash apparatus. The invention further relates to a method for steam generation in such a device.

[0005] Steam is an important energy carrier in industry, particularly in the chemical industry. Currently, steam is typically produced using fossil fuels, which is associated with significant carbon dioxide emissions. To reduce these emissions, heat pumps can be used, which require considerably less electrical energy compared to purely electric heating systems and, especially when using electricity from renewable sources, produce virtually no additional carbon dioxide emissions.

[0006] To heat water to the temperature required for steam generation in a heat pump, heat generated during process cooling is preferably used. Since the temperature of the coolant flows used for cooling or of the process flows to be cooled can vary depending on the type of process and environmental influences, and since the coolant flows or process flows themselves can also fluctuate, particularly in an open-vent heat pump where steam is generated by flash evaporation, either a fluctuating amount of steam is produced at a constant pressure (to which it is expanded in the flash unit) due to the temperature or volume of the coolant or process flow, or the pressure in the flash unit must be adjusted to maintain a constant evaporation rate.Furthermore, current systems are not designed to efficiently respond to steam pressure fluctuations on the compressor outlet side due to changing consumer demand.

[0007] However, this has the disadvantage that fluctuating steam quantities are generated and, due to fluctuating steam quantities, compression becomes less efficient as soon as the pressure ratio between the inlet and outlet of the compressor and / or the steam volume flow rate deviates from the values ​​for which the compressor was designed.

[0008] Therefore, the object of the present invention is to provide a device and a method for steam generation in which fluctuations in the heat source and the 240546W001

[0009] 2. They wished to have as little impact as possible on the efficiency of steam production by the steam pressure to be generated and / or to expand the possible operating range with regard to tolerable deviations from the design values ​​for the temperature and heat quantity of the heat source.

[0010] This problem is solved by a steam-generating device comprising a heat source for heating water, a first flash apparatus in which water heated by heat transfer from the heat source is partially evaporated, and at least one compressor with at least one compression stage for steam compression, which is connected via a first steam line to a steam space in the first flash apparatus, wherein a second flash apparatus is included, which is connected to the first flash apparatus via a first connecting line and a second connecting line such that unevaporated water from the first flash apparatus is passed through the first connecting line into the second flash apparatus, and unevaporated water from the second flash apparatus is passed into the first flash apparatus, wherein the second connecting line contains the heat source and a pump with which the pressure of the water can be increased.and wherein a second steam line branches off from the second flash apparatus and opens upstream of the at least one compressor into the first steam line, and at least one compensating compressor is arranged in the second steam line.

[0011] By using the second flash unit, it is possible to minimize the energy required for steam generation, since the at least one compressor with at least one compression stage can be operated at its optimal operating point as long as sufficient heat is introduced into the overall system. This is because the pressure ratio between the steam supplied to and extracted from the compressor can be adjusted by the second flash unit and the compensating compressor. A further advantage is that the device according to the invention, with a first and a second flash unit, makes it possible to directly provide the steam pressure required for feeding into a steam network. No exergy-wasting pressure-reducing valves are needed when the pressure in the steam network is low or the evaporation temperature or pressure is high.Furthermore, it is not necessary for all the steam to be compressed across the entire pressure range from the lowest evaporation pressure to the pressure of the steam generated in the at least one compressor with at least one compression stage, since some of the water evaporates at a higher pressure in the first flash unit and some of the water evaporates at a lower pressure in the second flash unit. If more heat is available than is required to generate the desired amount of steam, the amount of steam generated in the first flash unit can be increased up to the desired amount. In this case, it is possible to generate or compress less or even no steam in the second flash unit and in the compensating compressor, thus reducing energy consumption, especially electricity consumption. Heat not used for steam generation can be dissipated in another way, for example, via an additional cooler. 240546W001.

[0012] 3

[0013] Another advantage is the ability to generate significantly larger quantities of steam with a single system, provided sufficient heat is supplied to the overall system. The delivery volume flow rate of the at least one compressor with at least one compression stage is the decisive limiting factor in the scalability and space requirements of the system; that is, the higher pressure in the first flash tank allows for the compression of a larger quantity of steam at the maximum possible flow rate. Additional advantages include a wider operating window for the at least one compressor due to the lower stage pressure ratio and specifically lower mechanical losses due to the more compact design of the compressors.

[0014] In order to keep the pressure ratio between the steam supplied to the at least one compressor with at least one compression stage and the compressed steam as constant as possible for high efficiency, the inventive method for steam generation comprises:

[0015] (a) Heating water by heat transfer from a heat source;

[0016] (b) Supply of the heated water to the first flash apparatus, whereby part of the water is evaporated by expansion and a first vapor stream is obtained;

[0017] (c) Supply of the water not evaporated in step (b) from the first flash apparatus to the second flash apparatus, the pressure in the second flash apparatus being controlled by the compensating compressor depending on the evaporation rate in the first flash apparatus so that enough water evaporates in the second flash apparatus that the total amount of steam produced in the first flash apparatus and in the second flash apparatus is essentially constant;

[0018] (d) Compressing the vapor produced in the second flash apparatus in the compensating compressor to form a second vapor stream which is at substantially the same pressure as the first vapor stream;

[0019] (e) Combining the first steam stream and the second steam stream into a single combined steam stream;

[0020] (f) Compressing the total steam flow in at least one compressor with at least one compression stage;

[0021] (g) Taking out unevaporated water from the second flash apparatus, increasing the pressure of the unevaporated water and returning the water to step (a).

[0022] To achieve optimal efficiency of the process, the process is preferably operated in such a way that during normal operation, i.e., the operation in which the amount of heat transferred is that for which the device is designed and in which the process is used most of the time, 240546W001

[0023] 4. Preferably, more than 50% of the operating time is spent in the first flash apparatus, 20 to 80% of the steam is generated in the first flash apparatus, more preferably 30 to 70% of the steam is generated in the first flash apparatus, and in particular 48 to 52% of the steam, for example 50% of the steam, is generated in the first flash apparatus. The remaining steam is then generated in the second flash apparatus.

[0024] In addition to using two flash units, it is also possible to use a cascade with at least three flash units. In this case, the flash units are connected in series, and the operating pressure decreases from one flash unit to the next in the direction of water flow. Steam is drawn from each flash unit and compressed by a compensating compressor to the pressure at which the steam is supplied to the at least one compressor with at least one compression stage. If more than two flash units are involved, it is further preferred to operate the process such that the amount of steam generated in one flash unit does not deviate by more than 20% from the amount of steam generated in the other flash units.However, if a larger quantity of heat than in the design case is available, it is advantageous to generate a larger quantity of steam in the first flash apparatus and less or no steam in the subsequent flash apparatuses, which are operated at lower pressure.

[0025] With a higher heat input, for example, if the heat source has a higher temperature or a higher mass flow rate, more heat is supplied to the water at a higher temperature level before the first flash unit. Thus, at a constant pressure in the first flash unit, a larger quantity of water is evaporated, generating more steam. The compensating compressor is then preferably operated in such a way that the pressure in the second flash unit increases, thereby generating less steam in the second flash unit, and the total quantity of steam supplied to the at least one compressor with at least one compression stage remains constant. Discarding heat at a lower temperature level makes the process more efficient and thus reduces the specific power consumption.

[0026] Accordingly, with a lower heat input, resulting, for example, from a lower temperature or a smaller mass flow rate of the heat source, less water is evaporated at constant pressure due to the colder water supplied to the first flash unit, and the amount of steam produced decreases. To maintain a constant total steam output, the compensating compressor is operated in this case in such a way that the pressure in the second flash unit drops further, thus causing a larger amount of water to evaporate there.

[0027] Even if less steam is required than could be generated with the heat transferred from the heat source to the water, it is advantageous to generate the steam at a higher temperature, preferably in the first flash evaporator, and to discard the unused heat at a lower temperature. Energy savings are thus possible through the appropriate operation of the two flash units and the compensating compressor. 240546W001

[0028] 5

[0029] The first flash apparatus is preferably operated at a pressure of 100 mbar(abs) to 1.5 bar(abs), more preferably in a range of 150 to 800 mbar(abs), and particularly in a range of 200 to 500 mbar(abs). The temperature of the supplied water is preferably selected such that the evaporation rate in the first flash apparatus is in a range of 0 to 10 wt.%, more preferably in a range of 0.2 to 7 wt.%, and particularly in a range of 0.5 to 5 wt.%.

[0030] The heat source used to heat the water is, for example, a heat exchanger through which a heat transfer medium flows, transferring heat to the water. The heat exchanger in which the water is heated can be any type of heat exchanger known to experts. Common heat exchangers include shell and tube heat exchangers, plate heat exchangers, and spiral heat exchangers.

[0031] The heat transfer medium can be any liquid or gaseous medium capable of transferring heat to the water. Suitable liquid heat transfer media include water, thermal oils, alcohols, and mixtures of alcohol (such as glycol) and water. Gaseous heat transfer media that condense upon heat transfer are particularly suitable, such as methanol, ethanol, benzene, or steam. Furthermore, gases like air or exhaust gases, especially combustion gases, can also be used as heat transfer media.

[0032] In addition to the aforementioned heat transfer media, it is also possible to use any other heat transfer medium known to those skilled in the art. Particularly when the device is used in an industrial plant, it is also possible to use a process stream as the heat transfer medium, for example, a mass stream to be cooled from a chemical reaction, distillation, condensation, absorption, adsorption, crystallization, or extraction. The process stream can be liquid, gaseous, or two-phase, i.e., partly liquid and partly gaseous.

[0033] As an alternative to a heat exchanger, the heat source can also be any process step, for example, a step in a chemical process where the water being heated is used as a cooling medium. In this case, heat transfer to the heat transfer medium, which then transfers the heat to the water, is unnecessary. Such process steps include, for example, a phase transition, such as condensation, resublimation, or crystallization.

[0034] Besides cooling process steps, water can also be used to cool equipment such as motors, generators, or batteries. Here, too, the water acts directly as a cooling medium for the equipment, absorbing heat by cooling it.

[0035] The water that did not evaporate in the first flash device is fed into the second flash device. 240546W001

[0036] 6

[0037] Since the pressure ratio between the suction and discharge sides of a compressor, as designed for an open-circuit heat pump, can often only be adjusted to a limited extent during operation, resulting in efficiency losses, the pressure at which the first flash unit operates depends on the pressure to which the vapor is compressed. Preferably, the first flash unit is operated at a pressure where the pressure ratio before and after each compression stage deviates by no more than 5% from the design pressure ratio. The pressure at which the second flash unit operates is preferably in the range of 80 to 1200 mbar (abs), more preferably in the range of 90 to 500 mbar (abs), and particularly in the range of 100 to 400 mbar (abs).It is preferred that the pressure in the first flash apparatus is 20 to 120% above the pressure in the second flash apparatus, more preferably in the range of 30 to 80% above the pressure in the second flash apparatus and particularly in the range of 40 to 60% above the pressure in the second flash apparatus.

[0038] The evaporation rate in the second flash apparatus is preferably in a range of 0 to 10 wt.%, more preferably in a range of 0 to 7 wt.% and in particular in a range of 0 to 4 wt.%.

[0039] By configuring the system with at least two flash units, it is possible to efficiently adjust for changing conditions, such as an increased target vapor pressure.

[0040] The pressure and evaporation rate in the second flash apparatus are preferably chosen such that, when the evaporation rate in the first flash apparatus changes, the total amount of vapor produced in the first flash apparatus and in the second flash apparatus remains essentially constant.

[0041] In this context, "essentially constant" means that the total amount of steam decreases by no more than 10%, preferably by no more than 5%, and in particular by no more than 3%, and increases by no more than 5%, preferably by no more than 2%, and in particular by no more than 1%. It is especially preferred that the total amount of steam remains constant even when the amounts of steam generated in the first and second flash apparatus change.

[0042] According to the invention, the pressure in the second flash apparatus is controlled by the compensating compressor. To control the pressure in the second flash apparatus with the compensating compressor, at least one speed-controlled blower is preferably used as the compensating compressor, since these have a large operating range with respect to pressure ratio and volume flow. If more than one speed-controlled blower is used, they are preferably connected in parallel. Due to the variable pressure in the second flash apparatus and the variable amount of vapor generated in the second flash apparatus, it is further preferred if the at least one speed-controlled blower has a large operating range.

[0043] To increase the amount of steam to be generated, it is preferred to provide a return line downstream of the compensating compressor, through which the 240546W001 compressed in the compensating compressor is returned.

[0044] 7

[0045] Steam can be returned to the second flash vessel. By returning the superheated steam, additional energy is introduced into the second flash vessel, thus increasing the total amount of steam generated there. Since the steam at the outlet of the compensating compressor has a higher pressure than in the second flash vessel, an expansion device, such as a throttle, is incorporated in the return line. Preferably, the expansion device is located at the point where the return line connects to the second flash vessel.

[0046] By increasing the amount of steam generated in the second flash tank, through the return of some of the steam compressed in the compensating compressor to the second flash tank, it is possible to avoid prematurely shutting down the compressor due to insufficient steam flow rates or putting it into a recycling mode, in which at least some of the compressed steam is returned to its inlet. This ensures that efficient compressor operation is maintained for as long as possible, even with decreasing heat output from the heat source.

[0047] The first and second flash apparatus can each be any flash apparatus known to those skilled in the art, operating independently of one another. Common flash apparatuses are, for example, containers or columns with an expansion valve at the inlet for the liquid to be evaporated. To allow for level control in the second flash apparatus, it is further preferred that the expansion element through which the unevaporated water supplied to the second flash apparatus is adjustable. The pressure in the second flash apparatus is then regulated by the compensating compressor.

[0048] Furthermore, it is preferable if the expansion device, through which the water supplied to the first flash apparatus is depressurized, is also adjustable in order to regulate the flow into the first flash apparatus. The pressure in the first flash apparatus can be regulated by the amount of steam extracted and compressed.

[0049] As an alternative to two separate devices, it is also possible to combine the first and second flash apparatuses as two separate chambers within a single unit. For example, a column can be divided into the two chambers by a tray, with the chamber above the tray forming either the first or the second flash apparatus, and the chamber below the tray forming the other. If the chamber above the tray contains the first flash apparatus, a pressure relief valve can be provided in the tray, allowing the unevaporated water to flow into the lower chamber, which forms the second flash apparatus. Alternatively, a pipeline can be provided from the upper chamber to the lower chamber, with the pressure relief valve preferably located at the end of the pipeline opening into the lower chamber. The pipeline can run inside or outside the unit.In addition to placing the pressure relief device at the end of the pipeline, it can also be placed at any other position along the pipeline. 240546W001.

[0050] 8

[0051] Since only a portion of the water in the first and second flash apparatus evaporates and a large portion remains liquid, the non-evaporated water is removed from the second flash apparatus and returned to step (a) in order to minimize the amount of fresh water required for steam production and to utilize the residual heat of the water.

[0052] To ensure the water evaporates upon entering the first flash apparatus, the pressure of the returned water is increased. Any pump capable of increasing the water pressure can be used for this purpose. Suitable pumps include centrifugal pumps.

[0053] The pressure to which the water is pressurized by the pump is preferably in the range of 0.5 to 20 bar(abs). More preferably, the pressure of the water is increased to 0.5 to 8 bar(abs) and particularly to 1 to 2 bar(abs).

[0054] In particular, to prevent contamination of the water by the heat source, it is preferred if the water has a pressure that is higher than the pressure of the heat source.

[0055] After the pressure increase, the water is fed to the heat source, where it absorbs heat and is warmed.

[0056] The steam generated in the first flash apparatus is drawn off as the first steam stream via the first steam line, and the steam generated in the second flash apparatus is drawn off via the second steam line and compressed in the compensating compressor contained in the second steam line, so that the second steam stream obtained in this way has essentially the same pressure as the first steam stream.

[0057] "Essentially the same pressure" here means that the pressure of the second steam stream deviates from the pressure of the first steam stream by no more than 100 mbar; preferably, the pressure of the second steam stream deviates from the pressure of the first steam stream by no more than 80 mbar; and particularly, the pressure of the second steam stream deviates from the pressure of the first steam stream by no more than 50 mbar, whereby, in the event of a pressure deviation, the second steam stream may have a lower or higher pressure than the first steam stream. Most preferably, the first and second steam streams have the same pressure. Pressure deviations can result, for example, from pressure losses in pipelines and equipment.

[0058] The first steam stream and the second steam stream, pre-compressed in the compensating compressor, are combined into a single steam stream and then fed to at least one compressor with at least one compression stage for further compression. 240546W001

[0059] 9

[0060] The pressure to which the total steam flow is compressed in the at least one compressor with at least one compression stage depends on the intended use of the steam. The steam can be supplied directly to a consumer or fed into a steam network that supplies various consumers. Steam networks typically distinguish between low-pressure, medium-pressure, and high-pressure steam. To prevent reverse flow, the steam fed into the network has a pressure higher than the pressure already present in the network.

[0061] Depending on the consumer for whom the steam is used, or the type of steam network, low-pressure steam, medium-pressure steam, or high-pressure steam can be generated by compression in at least one compressor with at least one compression stage. It is also possible to first compress all the steam to low-pressure steam, provided the pressure in the steam generation facility is below that of low-pressure steam, then to further compress at least a portion of the low-pressure steam to medium-pressure steam, and finally at least a portion of the medium-pressure steam to high-pressure steam.

[0062] In the context of the present invention, low-pressure steam is understood to mean steam having a pressure in the range of 0.9 to 4 bar(abs), preferably in the range of 1 to 2 bar(abs) and particularly in the range of 1.2 to 1.5 bar(abs) and a temperature in the range of 96 to 160 °C, more preferably in the range of 99 to 140 °C and particularly in the range of 104 to 120 °C.

[0063] Medium-pressure steam within the scope of the present invention is steam with a pressure in the range of 4 to 8 bar(abs), preferably in the range of 4.5 to 7 bar(abs) and particularly in the range of 5 to 6 bar(abs) and a temperature in the range of 143 to 220 °C, more preferably in the range of 147 to 210 °C and particularly in the range of 151 to 200 °C.

[0064] High-pressure steam within the scope of the present invention is steam with a pressure in the range of 8 to 40 bar(abs), preferably with a pressure in the range of 10 to 30 bar(abs) and in particular with a pressure in the range of 16 to 20 bar(abs) and a temperature in the range of 170 to 280 °C, more preferably in the range of 180 to 260 °C and in particular with a temperature in the range of 201 to 240 °C.

[0065] It is preferred to compress the steam to a pressure in the range of 1 to 20 bar(abs) and it is particularly preferred to generate steam that is preferably compressed to a pressure in the range of 4 to 7 bar(abs) in order to then be able to feed it into a steam network with the overpressure required for injection.

[0066] The at least one compressor with at least one compression stage can be any compressor suitable for compressing steam. Preferably, the total steam flow is compressed in a compressor cascade comprising at least two compressors, or in a single compressor 240546W001

[0067] 10. Compressed with at least two compression stages. If a compressor cascade is used for compression, compressors with only one compression stage or compressors with more than one compression stage can be used. It is also possible that the compressor cascade comprises at least one compressor with one compression stage and at least one compressor with at least two compression stages. The use of a compressor with at least two compression stages, for example a geared turbo compressor, particularly preferably a radial geared turbo compressor, or several blowers connected in series, is particularly preferred.

[0068] Regardless of whether a single compressor, a compressor cascade, or a compressor with at least two compression stages is used to compress the total steam flow, it is preferred to perform intercooling between the individual compression stages.

[0069] For intercooling, fresh water, in particular demineralized and degassed water, for example boiler feedwater, is preferably injected into the steam. If thermally degassed fresh water is used for intercooling, it generally has a higher temperature than the water returned to the first flash unit. The injection can take place either directly into the impeller of a compression stage and / or downstream of a compressor port between two compression stages or downstream of the last compression stage. It is particularly preferred to select the injection method such that the lowest possible superheat is achieved before entering the next compression stage.

[0070] Due to the superheating of the compressed steam, at least some of the injected fresh water evaporates, cooling the steam and simultaneously increasing the steam volume. To ensure that the injected fresh water evaporates as completely as possible before subsequent compression in a further compression stage, and that as little condensate as possible is separated, the finest possible atomization and a sufficiently long evaporation path must be provided.

[0071] Since the liquid water content decreases due to steam extraction, it is necessary to replenish fresh water for continuous operation. The fresh water can, for example, be mixed into the water returned to the first flash unit, or alternatively or additionally into the first flash unit, the second flash unit, or the connecting line from the first flash unit to the second flash unit. However, it is preferable to mix the fresh water into the water returned to the first flash unit.

[0072] To mix the fresh water into the water returned to the first flash unit, it is particularly advantageous if a fresh water inlet opens into the second connecting line. The fresh water inlet can open into the second connecting line at any point, whereby, in the case of thermally degassed fresh water, the inlet for the 240546W001

[0073] 11

[0074] Fresh water is preferably arranged downstream of the heat source, since the water taken from thermal degassing generally has a higher temperature than the water heated in the heat source and returned to the first flash unit. The mixing temperature is therefore above the temperature of the water heated in the heat source, thus increasing efficiency.

[0075] To minimize the risk of corrosion in the pipelines through which the steam flows, and to further prevent damage to equipment and pipelines through which the steam flows, the water used for steam generation and supplied to the process as fresh water is preferably demineralized and degassed water.

[0076] An embodiment of the invention is shown in the figure and is explained in more detail in the following description.

[0077] The single figure shows a flowchart of a possible embodiment of the method according to the invention.

[0078] A steam-generating device comprises a first flash apparatus 1, to which heated water is supplied via an inlet 3. At the inlet to the first flash apparatus 1, the inlet 3 includes an expansion element 5, for example, a throttle. As the heated water flows through the throttle, it expands, causing some of the water to evaporate upon entering the first flash apparatus 1. This partial evaporation results in the formation of a gas phase containing vapor and a liquid phase containing unevaporated water within the first flash apparatus 1.

[0079] In order to always generate the desired total amount of steam as efficiently as possible with the device, even under fluctuating conditions, for example fluctuations in temperature or quantity of heated water supplied to the first flash apparatus 1, the unevaporated water is supplied to a second flash apparatus 9 via a first connecting line 7.

[0080] If the amount of steam generated in the first flash apparatus 1 already corresponds to the desired total amount of steam, the pressure in the second flash apparatus 9 is set to match the pressure in the first flash apparatus 1, so that no water evaporates upon entering the second flash apparatus 9. If the amount of steam generated in the first flash apparatus 1 is less than the desired total amount of steam, the pressure in the second flash apparatus 9 is adjusted so that enough steam is generated in the second flash apparatus 9 for the total amount of steam generated in the first flash apparatus 1 and the second flash apparatus 9 to equal the desired total amount of steam.To prevent more steam than the desired total amount of steam from being generated in the first flash apparatus 1, the pressure in the first flash apparatus 1 is preferably set so that, regardless of the temperature and amount of water supplied, the amount of water evaporated is always no more than is required for the desired total amount of steam. 240546W001.

[0081] 12

[0082] To enable some of the water supplied to the second flash apparatus 9 via the first connecting line 7 to evaporate, an adjustable pressure relief valve 11 is arranged in the second connecting line 7. As shown here, the adjustable pressure relief valve 11 is preferably located at the end of the first connecting line 7 at the inlet to the second flash apparatus 9. If the pressure in the second flash apparatus 9 is lower than the pressure in the first flash apparatus 1, some of the water supplied to the second flash apparatus 9 via the first connecting line 7 evaporates. If the pressure in the first flash apparatus 1 and the second flash apparatus 9 is the same, no water evaporates.

[0083] The unevaporated water from the second flash apparatus 9 is returned to the first flash apparatus 1 via a second connecting line 13.

[0084] To allow the water to expand upon entering the first flash apparatus 1, it is necessary, regardless of whether the pressure in the first flash apparatus 1 and the second flash apparatus 9 is the same or lower than the pressure in the first flash apparatus 1, to increase the water pressure sufficiently to overcome any height differences and ensure that the pressure at the inlet to the first flash apparatus, upstream of the expansion device, is higher than the pressure in the first flash apparatus 1. For this purpose, a pump 15 is installed in the second connecting line 13. Any pump capable of increasing the water pressure and pumping the water into the first flash apparatus 1 can be used as pump 15.

[0085] In order to evaporate the water supplied to the first flash evaporator 1, it is also necessary to heat the water. For this purpose, a heat source 17 is arranged in the second connecting line 13. The heat source can be any heat source, for example, an apparatus to be cooled or, as shown here, a heat exchanger 19 in which a heat transfer medium is cooled. The heat transfer medium can be a coolant used to cool a process step or apparatus, or, preferably, a process stream that needs to be cooled, for example, a stream from a distillation, rectification, extraction, crystallization, absorption, adsorption, or chemical reaction.

[0086] In the embodiment shown here, the heat source 19 is located downstream of the pump 15 to prevent water from evaporating due to heating in the heat source 19.

[0087] The steam generated in the first flash evaporator 1 is extracted via a first steam line 21 and fed to a compressor 23 with at least one compression stage 25.1, 25.2. In the embodiment shown here, two compression stages 25.1, 25.2 are included, whereby it is possible either to use one compressor with at least two compression stages 23, for example a geared turbo compressor, in particular a radial geared turbo compressor, or several compressors, each with one compression stage. The use of one compressor 23 with at least two compression stages 25.1, 25.2 is preferred. (See also 240546W001)

[0088] 13. In addition to using only one compressor 23 with at least two compression stages 25.1, 25.2, depending on the pressure to which the steam is to be compressed, it is also possible to use several compressors with multiple compression stages. Furthermore, at least one compressor with one compression stage and at least one compressor with multiple compression stages can also be used to compress the steam.

[0089] The steam generated in the second flash evaporator 9 is extracted via a second steam line 27 and fed to a compensating compressor 29 located in the second steam line 27.

[0090] The compensating compressor 29 adjusts the pressure in the second flash evaporator 9 so that enough water is evaporated to ensure that the sum of the steam volumes generated in the first flash evaporator 1 and the second flash evaporator 9 corresponds to the desired steam volume. Preferably, this is the volume flow rate for which the compressor was designed. The compensating compressor 29 can be operated in a steam reuse mode via a return line 31 to supply additional energy to the system and thus generate steam. This is advantageous when more steam is required than the heat source can actually provide. In some cases, this can also prevent the compressor from shutting down or entering recycle mode due to insufficient steam volume flow rates.For this purpose, part of the steam compressed in the compensating compressor 31 is fed to the compressor 23 and part is returned to the second flash tank 9 in order to increase the amount of steam generated in the second flash tank 9.

[0091] Since the pressure downstream of the compensating compressor 29 is higher than the pressure in the second flash apparatus 9, a further expansion element 33 is incorporated in the return line 31, through which the returned vapor is expanded. Preferably, the further expansion element 33 is located at the inlet to the second flash apparatus 9.

[0092] Since steam is drawn from the first flash apparatus 1 and the second flash apparatus 9, a supply of fresh water is necessary for continuous operation. The fresh water is preferably supplied via a fresh water inlet 35. The fresh water inlet preferably opens, as shown here, downstream of the heat source 17 into the second connecting line 13.

[0093] Since the steam is strongly superheated during compression in the at least one compressor 23 with at least one compression stage 25.1, 25.2, it is usually cooled. For cooling, fresh water is injected into the steam via a fresh water injection system 37.1, 37.2, 37.3. Because a large portion of the injected fresh water evaporates, the injection of fresh water has the additional advantage of increasing the steam volume.

[0094] The fresh water injection 37.1, 37.2, 37.3 can be either upstream or downstream of a

[0095] Compression stage 25.1, 25.2, preferably if upstream of each 240546W001

[0096] 14

[0097] Compression stage 25.1, 25.2 or downstream of each compression stage 25.1, 25.2 a fresh water injection 37.1, 37.2, 37.3 is provided.

[0098] The supplied fresh water, which is introduced into the second connecting line 13, and the fresh water, which is introduced into the steam via the fresh water injection 37.1, 37.2, 37.3, is usually demineralized and degassed water.

Claims

240546W001 15 Patentansprüche 1. Device for steam generation, comprising a heat source (17) for heating water, a first flash apparatus (1) in which water heated by heat transfer from the heat source (17) is partially evaporated, and at least one compressor (23) with at least one compression stage (25.1, 25.2) for steam compression, which is connected via a first steam line (21) to a steam space in the first flash apparatus (1), characterized in that a second flash apparatus (9) is included, which is connected to the first flash apparatus (1) via a first connecting line (7) and a second connecting line (13) such that unevaporated water from the first flash apparatus (1) is passed through the first connecting line (7) into the second flash apparatus (9), and unevaporated water from the second flash apparatus (9) is passed through the second connecting line (13) into the first flash apparatus (1).wherein the heat source (17) and a pump (15) with which the pressure of the water can be increased are included in the second connecting line (13), and wherein a second steam line (27) branches off from the second flash apparatus (9) and opens upstream of the at least one compressor (23) into the first steam line (21) and at least one compensating compressor (29) is arranged in the second steam line (27).

2. Device according to claim 1, characterized in that an inlet for fresh water (35) opens into the second connecting line (13), wherein the inlet for fresh water (35) is preferably arranged downstream of the heat source (17).

3. Device according to claim 1 or 2, characterized in that upstream and / or downstream of at least one compression stage (25.1 , 25.2) a fresh water injection (37.1 , 37.2, 37.3) is included.

4. Device according to one of claims 1 to 3, characterized in that the at least one compressor (23) with at least one compression stage (25.1 , 25.2) is a geared turbo compressor.

5. Device according to one of claims 1 to 4, characterized in that the first flash device (1) and the second flash device (9) are connected as two separate chambers in one unit.

6. Device according to one of claims 1 to 5, characterized in that the heat source (17) comprises a heat exchanger (19) through which a heat transfer medium flows, which transfers heat to the water. 240546W001 16 7. Device according to one of claims 1 to 6, characterized in that a return line (31) is arranged downstream of the compensating compressor (29), through which steam compressed in the compensating compressor (29) can be directed back into the second flash apparatus (9).

8. Method for generating steam in a device according to any one of claims 1 to 7, comprising: (a) Heating water by heat transfer from a heat source (17); (b) Supply of the heated water into the first flash apparatus (1), whereby part of the water is evaporated by expansion and a first vapor stream is obtained; (c) Supply of the water not evaporated in step (b) from the first flash apparatus (1) to the second flash apparatus (9), wherein the pressure in the second flash apparatus (9) is controlled by the compensating compressor depending on the evaporation rate in the first flash apparatus (1) such that enough water evaporates in the second flash apparatus (9) that the total amount of steam produced in the first flash apparatus (1) and in the second flash apparatus (9) is essentially constant; (d) Compressing the vapor produced in the second flash apparatus (9) in the compensating compressor (29) to form a second vapor stream which has essentially the same pressure as the first vapor stream; (e) Combining the first steam stream and the second steam stream into a single combined steam stream; (f) Compressing the total steam flow in at least one compressor (23) with at least one compression stage (25.1 , 25.2); (g) Taking out unevaporated water from the second flash apparatus (9), increasing the pressure of the unevaporated water and returning the water to step (a).

9. Method according to claim 8, characterized in that the first flash apparatus (1) is operated at a pressure in a range of 100 mbar(abs) to 1.5 bar(abs) and the evaporation rate in the first flash apparatus (1) is in a range of 0 to 10 wt.%.

10. Method according to claim 8 or 9, characterized in that the second flash apparatus (9) is operated at a pressure in a range of 80 to 1200 mbar(abs) and 240546W001 17 the evaporation rate in the second flash apparatus (9) is in a range of 0 to 10 wt.%.

11. Method according to one of claims 8 to 10, characterized in that the pressure of the water in step (d) is increased to 0.5 to 20 bar(abs).

12. Method according to one of claims 8 to 11, characterized in that the water in the heat source is heated to a temperature in the range of 50 to 95 °C.

13. Method according to one of claims 8 to 12, characterized in that fresh water is injected into the steam upstream or downstream of at least one compression stage (25.1 , 25.2).

14. Method according to one of claims 8 to 13, characterized in that the steam is compressed to a pressure in the range of 1 to 20 bar(abs).

15. Method according to one of claims 8 to 14, characterized in that fresh water is mixed into the water returned to the first flash apparatus (1).

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