System and method for providing steam in a urea production plant, and urea production plant

Abstract

The invention relates to a system (10) for providing steam in a urea production plant (100), having: - at least one first steam drum (11), which is adapted so as to receive steam at a first pressure level (D1) and to supply same to a stripper (101) for the urea synthesis; and - at least one second steam drum (12) which is connected downstream of the first steam drum (11) in the flow direction (SR) and is connected thereto in order to transfer steam condensate (DK1, DK3), the second steam drum (12) being adapted so as to contain steam (D2) and / or steam condensate (DK2) at a second lower pressure level. The system (10) also has - at least one compressor unit (13) which is connected to the second steam drum (12) and is adapted so as to increase the pressure of the steam (D2) at the second pressure level to the first higher pressure level by compressing the steam, the compressor unit (13) being connected upstream of the first steam drum (11) in the flow direction (SR); and / or - at least one heat transfer unit which is connected upstream of the at least one second steam drum (12) and is adapted so as to transfer heat to the steam condensate (DKS) from a collecting container (16) of the system (10) in such a way that steam (D2) at the second pressure level is produced for further use.

Description

[0001] System and method for providing steam in a urea production plant, as well as urea production plant

[0002] Description

[0003] The invention relates to a system and a method for providing steam in a urea production plant, as well as a urea production plant with such a system.

[0004] In general, there is a drive to make production facilities that use fossil fuels as an energy source more environmentally friendly. This also applies to the production of urea, which is known to be produced by a urea synthesis process. Urea is synthesized by the reaction of ammonia (NH3) and carbon dioxide (CO2). An example of urea production is known from EP 3 656 759 Al, which uses a stripping process in which a carbamate-containing solution of urea exiting a reactor is processed in a steam-heated stripper.

[0005] To operate a urea production plant, it must be supplied with steam. In existing urea plants, a natural gas-fired steam generator, such as a boiler, is often used to provide the necessary steam for the plant and for the energy required during product processing. This steam is typically used in a high-pressure synthesis process for a stripper, such as an NH3 or CC stripper. However, burning natural gas to generate steam has the disadvantage of releasing a large amount of CO2.

[0006] A significant disadvantage of older, existing urea plants lies in the untapped potential for heat recovery. For example, urea plants are equipped with a cooling system because they require large amounts of cooling capacity, typically around 630 kilowatts per ton of product. In such existing plants, unused energy is usually released into the environment via cooling towers.

[0007] The invention is therefore based on the objective of providing a system for supplying steam in a urea production plant in which CO2 emissions are at least reduced and which exhibits increased efficiency through heat recovery for steam generation. The invention is further based on the objective of providing a urea production plant with such a system, as well as a method for supplying steam in a urea production plant.

[0008] According to the invention, this problem is solved with regard to the system by the subject matter of claim 1. With regard to the urea production plant and the process, the aforementioned problem is solved by the subject matter of claim 12 (urea production plant) and claim 13 (process), respectively.

[0009] Specifically, the task is solved by a system for providing steam in a urea production plant, in particular for urea synthesis, wherein the system comprises the following:

[0010] - at least one first steam drum adapted to receive steam of a first pressure level and supply it to a stripper, in particular an NH3 or CO2 stripper, for urea synthesis; and

[0011] - at least a second steam drum, which is connected downstream of the first steam drum in the direction of flow and to it for transferring steam condensate, wherein the second steam drum is adapted to contain steam and / or steam condensate of a second, lower pressure level, wherein the system further comprises:

[0012] - at least one compressor unit connected to the second steam drum and adapted to increase the steam of the second pressure level to the first, higher pressure level by compression, with the compressor unit being located upstream of the first steam drum in the direction of flow; and / or

[0013] - at least one heat transfer unit, in particular a heat pump, which is connected upstream of at least one second steam drum and is adapted to transfer heat, in particular from at least one cooling water circuit and / or at least one media flow, to steam condensate from a collection tank of the system in such a way that steam of the second pressure level is produced for further use.

[0014] A key advantage of the invention is that the compressor unit uses and compresses steam from a lower, second pressure level, resulting from the urea synthesis process, to raise it to a higher, first pressure level. For this purpose, the compressor unit is connected to the second steam drum, which contains the steam from the second pressure level. The compressed steam from the first pressure level is then fed to the first steam drum, which in turn supplies the stripper for a stripping process. This corresponds to the normal operation of the system, in which the urea production plant is preferably operating at full capacity.

[0015] During the start-up phase, it may be necessary to supply the system with externally generated steam to enable regular operation. Therefore, the system may be temporarily connected to an external steam generator, which is then switched off after the start-up phase or once the urea production plant has been ramped up. Additionally or alternatively, the system may draw steam from an ammonia production plant during the start-up phase, for example, until the urea production plant is fully operational.

[0016] The compressor unit is preferably designed to generate steam of a first pressure level with an absolute pressure of 12 bar a to 20 bar a, more preferably an absolute pressure of 15 bar a to 19 bar a. The compression ratio is preferably 1:4. The steam of the second pressure level, which the compressor unit draws from the second steam drum and compresses to steam of the first pressure level, preferably has an absolute pressure of 2.5 bar a to 6 bar a, in particular 3 bar a to 5 bar a, more preferably approximately 4 bar a. The steam of the second pressure level is conventionally referred to as low-pressure steam.

[0017] The compression process also increases the temperature of the steam at the second pressure level. After compression, steam, particularly superheated steam, at the first, higher pressure level is present. This steam is then fed to the first steam drum, where it exists as saturated steam.

[0018] Preferably, the compressor unit is configured such that the compression of the steam at the second pressure level to steam at the first pressure level is carried out by several compressor stages. The compressor unit can therefore comprise several, in particular at least two, preferably at least three, and most preferably at least four, steam compressors, which are, for example, connected in series. Alternatively, it is possible for the steam compression to be carried out in a single stage, namely by a single steam compressor.

[0019] The compression unit and the use of steam generated in the urea synthesis process eliminate the need for an external steam generator, which, as is known from the prior art, is powered by the combustion of natural gas. This has the significant advantage of drastically reducing or even completely eliminating CC emissions associated with steam generation. Furthermore, the system's efficiency is increased by reusing steam generated in the process.

[0020] Additionally or alternatively, the system includes a heat transfer unit that transfers heat from a fluid stream of the urea production plant to steam condensate from a collection tank of the system to generate steam at the second pressure level. The heat transfer unit is preferably configured to extract heat from at least one cooling water circuit and transfer it to steam condensate from the system's collection tank to generate the steam at the second pressure level. For this purpose, the system can be coupled to at least one cooling water circuit of the urea production plant via the heat transfer unit, which preferably includes at least one heat pump. The cooling water circuit comprises cooling water used for cooling in the urea synthesis process.The cooling water serves as a heat transfer medium. Following a cooling process in urea synthesis, during which the cooling water is heated, the heat transfer unit extracts heat from the cooling water and transfers this heat to steam condensate, which, for example, has a temperature of approximately 99°C, from a collection tank. The heat transfer unit thus heats the steam condensate to such an extent that steam at the second pressure level is produced. It is possible for the heat transfer unit to be coupled to several cooling water circuits, which, for example, operate at different temperature levels within the urea production plant. The system can, for example, have several heat transfer units coupled to several cooling circuits, which, for example, operate at different temperature levels within the urea production plant, for heat transfer to the steam condensate from the collection tank.

[0021] Additionally or alternatively, the heat transfer unit can be coupled to at least one condensate system carrying process condensates from the urea plant and / or to at least one media system carrying media flows from the urea plant in order to transfer heat to the steam condensate from the collection tank for the formation of the steam at the second pressure level. The heat transfer unit can therefore be adapted to extract heat from at least one condensate system and / or at least one media system of the urea production plant and transfer it to steam condensate from the system's collection tank for the formation of the steam at the second pressure level.

[0022] The heat transfer unit preferably comprises at least one heat pump. The heat pump can include at least one water heat exchanger on the cooling water circuit side, particularly on the condensate system and / or the media system, to extract heat from the cooling water and transfer it to a heat transfer medium of the heat pump. The heat pump can include a further (water) heat exchanger that transfers the absorbed heat to the steam condensate from the collection tank in such a way that it evaporates into steam at the second pressure level. Furthermore, the heat pump can have at least one compressor for compressing the heat transfer medium and at least one expansion valve for reducing the pressure of the heat transfer medium.

[0023] As described above, the heat transfer unit is located upstream of the second steam drum, so that the steam generated by the heat transfer at the second pressure level is fed into the second steam drum. The heat transfer unit thus recovers heat, which is used to provide low-pressure steam for other consumers or for the compressor unit. This reduces energy loss in the urea production plant and significantly increases the system's efficiency, particularly because additional quantities of low-pressure steam are generated that can be used throughout the entire urea production plant. This has a positive impact on CC emissions, among other benefits.

[0024] Another advantage of the invention is that the compressor unit and / or the heat transfer unit can be integrated into existing plants, i.e., into existing urea production plants, with minimal effort, without requiring any significant modification of the plants or the synthesis process.

[0025] Preferred embodiments of the invention are specified in the dependent claims.

[0026] In a preferred embodiment, the compressor unit comprises at least one steam compressor, and in particular several steam compressors, driven by an electric motor, which uses, and preferably exclusively uses, electricity from renewable energy sources for its operation. In other words, the electric motor of the steam compressor is preferably powered by electricity generated from renewable energy sources. For example, the electric motor is powered by electricity from solar energy, wind energy, and / or hydropower, in particular from run-of-river power plants and / or pumped-storage power plants. Additionally or alternatively, the electric motor can be powered by electricity from marine energy, such as wave and / or tidal power plants. By using renewable energy sources for electricity generation, CO₂ emissions are further reduced.

[0027] For example, the power input for a urea production plant with a production volume of 3900 tons per day is approximately 18.4 megawatts, i.e., approximately 114 kilowatts per ton of product (urea) produced, to provide a required steam quantity of approximately 129 tons per hour at an absolute pressure of 19 bar. Preferably, the compressor unit with its electrically driven steam compressor is designed accordingly to generate the required steam quantity. In a further preferred embodiment, the heat transfer unit, in particular the heat pump, uses, and especially exclusively uses, electricity from renewable energy sources for its operation. For example, the heat transfer unit is operated with electricity from at least one or more of the renewable energy sources described above, which further reduces carbon dioxide emissions.

[0028] Preferably, the first steam drum is adapted to collect steam condensate from the stripper and make it available for further use. Preferably, the first steam drum is further adapted to saturate the (superheated) steam of the first pressure level before it is fed to the stripper. The steam condensate has a first pressure level and is made available for further processing by a downstream unit, in particular a third steam drum. Additionally or alternatively, a further steam drum can be provided and adapted to collect steam condensate of a first pressure level from the stripper and make it available for further use.

[0029] The collected steam condensate can be partially evaporated by pressure reduction, particularly expansion, to provide steam for other steam consumers. The (respective) steam drum is preferably connected to the stripper via a supply line for steam and / or a return line for the steam condensate.

[0030] Preferably, the second steam drum is adapted to receive steam of the second pressure level and / or steam condensate and to reduce the pressure level of the steam condensate, in particular to expand it, so that steam of the second pressure level is produced. In other words, the steam drum reduces the pressure such that a portion of the received steam condensate evaporates. Preferably, this results in steam of the second pressure level, which is then compressed by the compressor unit to supply steam to the stripper. The second steam drum preferably has at least one first connection for receiving steam of the second pressure level and a second connection for receiving steam condensate from an upstream unit, in particular the third and / or first steam drum.For steam generation to supply the stripper, condensate from the system itself is used, without obtaining steam from an external steam generator.

[0031] In one embodiment, at least two first steam drums and / or at least two second steam drums can be provided. In the variant with at least two second steam drums, a heat transfer unit, particularly of the type described above, can be connected upstream of each second steam drum. The two second steam drums can operate at the same pressure level. It is possible for the two second steam drums to be identical.

[0032] Preferably, at least the first and second steam drums and the compressor unit form a closed circuit, particularly during normal operation. The second steam drum provides steam at the second pressure level, i.e., low-pressure steam. The compressor unit is located downstream of the second steam drum and connected to it for steam extraction, for example, via a steam line. Furthermore, the compressor unit is located upstream of the first steam drum and connected to it for steam supply, for example, via a line. During normal operation, the compressor unit extracts steam at the second pressure level from the second steam drum and increases its pressure, so that the compressor unit supplies steam at the first pressure level to the first steam drum.

[0033] The first steam drum supplies the stripper with compressed steam at the first pressure level and directs the steam condensate generated during heat transfer at the stripper towards the second steam drum. This can be done directly, i.e., without an intervening third steam drum, or indirectly with an intervening third steam drum. Through appropriate expansion of the steam condensate in the second steam drum, low-pressure steam is produced again, which is then recirculated as described above. Therefore, no external steam generators are necessary to supply the stripper with sufficiently compressed steam.

[0034] Thus, steam flows as the medium from the second steam drum to the compressor unit and from the compressor unit to the first steam drum, in particular exclusively, and steam condensate flows between the steam drums, in particular exclusively.

[0035] In a preferred embodiment, the second steam drum is coupled, or can be coupled, to a urea synthesis condenser, in particular a carbamate condenser, such that the condenser evaporates at least a portion of the steam condensate contained in the second steam drum into steam at the second pressure level, which is then returned to the second steam drum. This allows the remaining steam condensate in the second steam drum, after expansion, to be fed to the condenser and used to generate low-pressure steam. This increases the efficiency of steam supply in the system. The evaporation of the remaining steam condensate preferably occurs through exothermic heat of reaction from the condenser.

[0036] The collection tank is preferably connected to the second steam drum by a pipe, with the heat transfer unit arranged between the second steam drum and the collection tank. The heat transfer unit is coupled to the cooling water circuit on one side and to the steam condensate line from the collection tank on the other. The heat transfer unit is particularly preferably integrated into the pipe near the second steam drum to feed the generated low-pressure steam into the second steam drum with minimal loss.

[0037] It is advantageous to have at least one third steam drum arranged between the first and second steam drums and connected to them for transferring or receiving steam condensate. This third steam drum is designed to receive steam condensate from the first steam drum and reduce its pressure, in particular by expanding it, to produce steam at a third pressure level. The third steam drum facilitates the utilization of the steam condensate from the first steam drum, forming an intermediate stage. The steam condensate from the first steam drum is thus expanded stepwise before reaching the second steam drum. This allows for improved utilization of the steam condensate at the first pressure level. For example, the third steam drum can expand the steam condensate from the first steam drum to produce steam at an absolute pressure of approximately 9 bar a.Other pressure ranges between 19 bar a and 4 bar a are possible.

[0038] The second and / or third steam drum can each be connected to at least one steam consumer unit, in particular a heat exchanger, with the steam consumer unit(s) being connected to a collection tank for draining steam condensate. The steam drums thus supply steam at different pressure levels to the corresponding steam consumers of the urea production plant. The resulting steam condensate from the steam consumers is collected in the collection tank and fed to the heat transfer unit for steam generation. The steam condensate from the other steam consumers in the plant is also used to generate low-pressure steam for the compression unit or other consumers.

[0039] In a preferred embodiment, the system comprises at least one further compressor unit connected to the second steam drum and adapted to increase a portion of the steam contained therein at the second pressure level by compression to a fourth, higher pressure level and to supply it for further use to at least one external steam consumer, in particular one independent of the urea production plant. This makes it possible to compress the low-pressure steam from the second steam drum and supply it to further steam consumers outside the urea production plant.

[0040] In one embodiment, the additional compressor unit can be arranged downstream of the compressor unit in the direction of flow, in particular downstream of it, and increase a diverted partial flow of the compressed steam to a further pressure level.

[0041] According to a secondary aspect, the invention relates to a urea production plant with at least one system of the type described above, wherein the urea production plant comprises at least one stripper, in particular an NH3 or CC stripper, or a recirculation heater for heating recycled carbamate, at least one reactor in which ammonia (NH3) and carbon dioxide (CO2) react at a specific reaction pressure to form an aqueous urea solution, and at least one condenser for condensing a gaseous phase, wherein the stripper, the reactor and the condenser form a synthesis cycle.

[0042] The recirculation heater preferably heats the recycled carbamate before it is fed to the reactor or the carbamate condenser. In one embodiment, the reactor and the condenser can form a single unit. This may be the case, in particular, for some, e.g., smaller, plant types.

[0043] According to a further subordinate aspect, the invention relates to a method for providing steam in a urea production plant, in particular for urea synthesis, in which

[0044] - a stripper, in particular an NH3 or CO2 stripper, for urea synthesis, is supplied with steam of a first, in particular high, pressure level, which is used for a stripping process;

[0045] - by utilizing the steam of the first pressure level, steam condensate of a first, in particular high, pressure level is produced, wherein the first pressure level of the steam condensate is reduced in such a way that steam of a second, lower pressure level is produced, wherein the process further

[0046] - the steam of the second pressure level is compressed by at least one compressor unit to steam of the first, in particular higher, pressure level, which in turn is fed to the stripper for the stripping process; and / or

[0047] - Heat is transferred by at least one heat transfer unit, in particular a heat pump, to steam condensate from a collection tank of the urea production plant in such a way that steam of the second pressure level is produced, which in turn is made available for further use, in particular the compression unit and / or other steam consumers.

[0048] In a preferred embodiment, the process is carried out using a system of the type described above. The process is then preferably carried out such that at least one first steam drum receives steam of a first pressure level and supplies it to a stripper, in particular an NH3 or CC stripper, for urea synthesis;

[0049] - at least a second steam drum, which is connected downstream of the first steam drum in the direction of flow and receives steam condensate from the first and / or a further, in particular third, steam drum, wherein the second steam drum contains steam and / or steam condensate of a second, lower pressure level, wherein the method further

[0050] - at least one compressor unit increases the steam of the second pressure level from the second steam drum to the first, higher pressure level by at least one compression step and supplies this to the first steam drum for the steam supply of the stripper; and / or

[0051] - at least one heat transfer unit, in particular a heat pump, transfers heat to steam condensate from a collection tank of the urea production plant in such a way that steam of the second pressure level is produced, which in turn is fed to the second steam drum for further use.

[0052] In one embodiment, the heat transfer unit extracts heat from a cooling water circuit and / or at least one media stream, in particular process condensates and / or process streams, of the urea production plant and transfers this heat to the steam condensate from the collection tank to form steam of the second pressure level.

[0053] The advantages of the urea production plant and the process are described in the section on the system. In addition, the urea production plant and the process may alternatively or additionally exhibit one or a combination of several of the features previously mentioned in relation to the system.

[0054] The invention is explained in more detail below with reference to the single accompanying drawing. The illustrated embodiment represents an example of how the system according to the invention can be configured. In this embodiment, Fig. 1 shows a process flow diagram of a system 10 for providing steam in a urea production plant 100 according to a preferred embodiment of the invention.

[0055] In the following description, the same reference numbers are used for identical or equivalent parts.

[0056] Specifically, Fig. 1 shows a part of a urea production plant 100 with a system 10 according to the invention, which relates to the steam management in the plant 100. The urea production plant 100, hereinafter referred to as urea plant 100, comprises a stripper 101, in particular an NH3 or CO2 stripper, a reactor (not shown) in which ammonia NH3 and carbon dioxide CO2 react at a specific reaction pressure to form an aqueous urea solution, and a condenser 103, in particular a carbamate condenser, for condensing a gaseous phase, wherein the stripper 101, the reactor, and the condenser 103 form a synthesis cycle. The prevailing condensation pressure in the condenser 103 is between 120 bar and 180 bar, preferably between 130 bar and 160 bar. In urea synthesis, the processes are preferably isobaric.

[0057] To supply the stripper 101 with steam, in particular saturated (drive) steam at a specific pressure level required for urea synthesis, as well as other steam consumers with steam at different pressure levels, the urea plant 100 comprises system 10. System 10 serves to provide steam in the urea plant 100 without using a natural gas-powered steam generator, in particular a natural gas-powered boiler, for steam generation.

[0058] Furthermore, system 10 is optimized such that, through heat recovery from a cooling water system 102, in particular a residual heat distribution system or a cooling water system (102) and a process condensate collection system, steam condensate from system 10 is evaporated from the urea plant 100, thereby generating steam of a further specific pressure level, in particular low-pressure steam, for further use in the urea plant 100 or in external steam consumers independent of the urea plant 100. System 10 comprises a first steam drum 11, which receives steam D1 of a first pressure level and supplies it to the stripper 101 for urea synthesis. The first steam drum 11 also collects steam condensate DK1 (of a first pressure level) generated in or at the stripper 101 and makes it available for further use in system 10. The vapor condensate DK1 is formed by heat transfer from the vapor Dl to the stripper 101.To supply the steam Dl and to collect the steam condensate DK1, the first steam drum 11 is connected to the stripper 101 by a supply line 22 and a return line 23.

[0059] The vapor Dl of the first pressure level is preferably a saturated vapor with an absolute pressure of 12 bar a to 20 bar a, preferably an absolute pressure of 15 bar a to 19 bar a.

[0060] System 10 comprises a compressor unit 13 for compressing low-pressure steam, or steam D2 of a second pressure level, which is located upstream of the first steam drum 11 in the flow direction SR. The compressor unit 13 is connected to the first steam drum 11 by a first steam line 26, preferably directly. The compressor unit 13 is designed to generate steam D1 of a first pressure level with an absolute pressure of 12 bar a to 20 bar a, preferably an absolute pressure of 15 bar a to 19 bar a. The compression ratio is preferably 1:4. The steam D2 of the second pressure level, which the compressor unit 13 draws from a second steam drum 12 and compresses to the first pressure level to form steam D1, has an absolute pressure of 2.5 bar a to 6 bar a, preferably 3 bar a to 5 bar a, and preferably substantially 4 bar a. The steam D2 of the second pressure level is referred to as low-pressure steam.The second steam drum 12 and the generation of steam D2 (low-pressure steam) will be discussed in more detail later.

[0061] During the compression process by the compressor unit 13, the temperature of the steam D2 at the second pressure level is also increased. After the compression process, steam, in particular superheated steam, at the first, increased pressure level is present. This steam is then fed to the first steam drum 11 and is present there as saturated steam. The compressor unit 13 is adapted such that the compression of the steam D2 from the second pressure level to the first pressure level is carried out by several compressor stages. The compressor unit 13 can therefore comprise several, in particular at least two, preferably at least three, and most preferably at least four, steam compressors, which are, for example, connected in series. Alternatively, it is possible for the steam compression to be carried out in a single stage, namely by a single steam compressor. The steam compressors each have an electric motor as a drive.

[0062] System 10 comprises two further steam drums 12, 17, which are connected downstream of the first steam drum 11 in the flow direction SR. Specifically, as can be seen in Fig. 1, system 10 has a second steam drum 12 and a third steam drum 17, which is arranged between the first and the second steam drums 11, 12. The first steam drum 11 is connected to the second steam drum 12 via the third steam drum 17 for the purpose of transferring steam condensate.

[0063] Thus, the third steam drum 17 is directly connected downstream of the first steam drum 11 in the flow direction SR, with the first steam drum 11 being connected to the third steam drum 17 by a first condensate line 24 for transferring the steam condensate DK1 of the first pressure level collected in the first steam drum 11. The steam condensate DK1 of the first pressure level has, for example, a pressure of 10 bar to 20 bar, in particular from 12 bar to 19 bar or from 14 bar to 16 bar.

[0064] The steam condensate DK1 from the first steam drum 11 is gradually depressurized, i.e., the pressure of the steam condensate DK1 is progressively reduced to provide steam D2, D3 at different pressure levels for further use in the urea plant 100. This process is also referred to as pressure depressurization.

[0065] For example, the pressure of the steam condensate DK1 of the first pressure level in the third steam drum 17 is reduced such that the steam condensate DK1 partially evaporates. This produces steam D3 of a third, lower pressure level, which is collected in the third steam drum 17 and supplied to at least one further steam consumer 18, e.g., a heat exchanger, of the urea plant 100. The steam D3 of the third pressure level is preferably steam with an absolute pressure of 6 bar a to 12 bar a, in particular 8 bar a to 10 bar a, but preferably of approximately 9 bar a. The third steam drum 17 is further adapted to collect the steam condensate DK3 remaining after the pressure reduction of the steam condensate DK1 from the first steam drum 11, which has a lower, third pressure level than the steam condensate DK1 from the first steam drum 11.

[0066] As described above, the second and third steam drums 12, 17 are connected to each other for transferring the steam condensate DK3 of the third pressure level. Specifically, the second steam drum 12 is directly downstream of the third steam drum 17 in the flow direction SR, with the third being connected to the second steam drum 17, 12 by a second condensate line 25 for transferring the steam condensate DK3 of the third pressure level collected in the third steam drum 17. In other words, the second steam drum 12 is indirectly downstream of the first steam drum 11 in the flow direction SR.

[0067] The second steam drum 12 is adapted to reduce the pressure of the absorbed steam condensate DK3 of the third pressure level such that the steam condensate DK3 partially evaporates. This produces steam D2 of a second pressure level, which is lower than the third pressure level of the steam condensate DK3 from the third steam drum 17. The steam D2 of the second pressure level is preferably steam with an absolute pressure of 2 bar a to 6 bar a, in particular 3 bar a to 5 bar a, but preferably of approximately 4 bar a.

[0068] It is generally possible that the reduction of the pressure levels of the steam condensate DK1, DK3 can be carried out alternatively or additionally by pressure relief valves, e.g. in the condensate lines 24, 25.

[0069] The remaining steam condensate DK2 in the second steam drum 12 is collected. Steam condensate DK2 has a second pressure level that is lower than the pressure level of steam condensate DK3 from the third steam drum 17.

[0070] The second steam drum 12 is heat-coupled to the condenser 103 of the urea plant 100. Specifically, the second steam drum 12 is connected to the condenser 103 in such a way that the steam condensate DK2 collected in the steam drum 12 at the second pressure level is fed to the condenser 103. The supplied steam condensate DK2 is evaporated by exothermic reaction heat from the condenser 103, producing steam D2 at the second pressure level, which is then returned to the second steam drum 12. This results in a particularly high utilization rate for the steam condensate DK1, DK2, and DK3 produced in system 10. A pump 104 is provided between the steam drum 12 and the condenser 103 to extract the remaining steam condensate DK2 from the second steam drum 12.

[0071] As already mentioned, the compressor unit 13 draws steam D2 of the second pressure level from the second steam drum 12 in order to compress it to steam D1 of the first pressure level, i.e., to increase its pressure level to the first pressure level, and supply it to the first steam drum 11. The compressor unit 13 can extract at least a portion of the steam D2, or low-pressure steam, contained in the second steam drum 12 to generate the necessary motive steam, i.e., the steam D1 of the first pressure level. For this purpose, the compressor unit 13 is connected to the second steam drum 12 by a second steam line 33, in particular directly. The compressor unit 13 is thus located downstream of the second steam drum 12 in the flow direction SR and upstream of the first steam drum 11 in the flow direction SR. In other words, the compressor unit 13 is arranged between the second and first steam drums 11, 12.

[0072] The steam drums 11, 12, 17 and the compressor unit 13 thus form a closed circuit, in particular a steam circuit, to supply the stripper 101 for the stripping process with steam D1, which is generated exclusively from steam D2 from the system 10.

[0073] Fig. 1 further shows that the system 10 has a collection tank 16 for steam condensate DK. V This includes the steam generated in further steam consumers 18. Fig. 1 shows that, in addition to the compressor unit 13, at least one further steam consumer 18 is or can be supplied with low-pressure steam, with the resulting steam condensate DK V The condensate is drained into the collection tank 16 via a third condensate line 27. Alternatively, several steam consumers 18 can be supplied with the low-pressure steam. The steam condensate DK is also... Vfrom one or more other steam consumers 18, which is supplied with steam D3 by the third steam drum 17, is connected to the collection tank 16 via a third condensate line 27 to collect the resulting steam condensate DK V to derive.

[0074] System 10 further comprises a heat transfer unit 14, which includes a heat pump 15. The heat pump 15 is coupled to a cooling water circuit 102 of the urea plant 100. The cooling water circuit 102 contains cooling water that is used for cooling in the urea synthesis process. The cooling water serves as a heat transfer medium, whereby the heat pump 15 extracts heat from the cooling water after a cooling process in the urea synthesis, during which the cooling water is heated, and transfers this heat to the vapor condensate DK. V , e.g., at a temperature of approximately 99°C, is transferred from the collection tank 16. The heat pump 15 thereby heats the steam condensate DK. Vsuch that steam D2 of the second pressure level is generated. Additionally or alternatively, the heat pump 15 can be coupled to at least one condensate system carrying process condensates from the urea plant 100, and / or to at least one media system carrying media flows from the urea plant 100, in order to transfer heat to the steam condensate DK. V to be transferred from the collection vessel 16 to form the steam D2 of the second pressure level.

[0075] The heat pump 15 comprises at least one first (water) heat exchanger 28 on the side of the cooling water circuit 102 in order to extract heat from the cooling water and transfer it to a heat transfer medium of the heat pump 15. The heat pump 15 has a second (water) heat exchanger 29, which transfers the absorbed heat to the vapor condensate DK. VThe heat transfer medium is transferred from the collection tank 16 in such a way that it is evaporated to form steam D2 of the second pressure level, i.e., low-pressure steam. Furthermore, the heat pump 15 has a compressor 31 for compressing the heat transfer medium and an expansion valve 32 for expanding the heat transfer medium. Since the basic principle of a heat pump is generally known, it will not be discussed in detail here.

[0076] The heat pump 15 is connected upstream of the second steam drum 12, so that the steam D2 generated by heat transfer at the second pressure level is fed into the second steam drum 12. The collection tank 16 is connected to a line 21 for the steam condensate DK. Vconnected to the second steam drum 12, with which the second heat exchanger 29 of the heat pump 15 is coupled for heat transfer. The heat pump 15 thus recovers heat from the cooling water circuit 102, which is used to provide low-pressure steam for other consumers or for the compressor unit 13.

[0077] Figure 1 shows a further compressor unit 19, depicted in dashed lines. This unit is connected to the second steam drum 12 for steam transfer. The further compressor unit 19 is designed to compress a portion of the quantity of steam D2 of the second pressure level contained in the second steam drum 12 and to supply it for further use to at least one external steam consumer, in particular one independent of the urea plant 100. It is possible that the further compressor unit 19, like the compressor unit 13, comprises one or more steam compressors driven by an electric motor.

[0078] It is possible that the further compressor unit 19 is arranged in the flow direction SR after the compressor unit 13, in particular that it may be downstream of it, and increases a diverted partial flow of the compressed steam Dl of the first pressure level to a further pressure level.

[0079] In System 10, a key aspect is that the electric motor of the respective steam compressor is powered by electricity from renewable energy sources. The same applies to the operation of the heat pump 15. Thus, System 10 not only saves CO₂ emissions by eliminating the need for natural gas-powered steam generators, but also, and in particular, through the exclusive use of green electricity from renewable energy sources.

[0080] List of reference signs

[0081] 10 System

[0082] 11 first steam drum

[0083] 12 second steam drum

[0084] 13 Compressor unit

[0085] 14 Heat transfer unit

[0086] 15 Heat pump

[0087] 16 collection containers

[0088] 17 third steam drum

[0089] 18 steam consumer units

[0090] 19 additional compressor units, 21 lines

[0091] 22 Lead line

[0092] 23 Return line

[0093] 24 first condensate line

[0094] 25 second condensate line

[0095] 26 first steam line

[0096] 27 third condensate line

[0097] 28 first heat exchanger

[0098] 29 second heat exchanger

[0099] 31 Compressor

[0100] 32 Expansion valve

[0101] 33 second steam line

[0102] 100 urea production plants

[0103] 101 Strippers

[0104] 102 Cooling water circuit

[0105] 103 Capacitor

[0106] 104 Pump

[0107] The steam of a first pressure level

[0108] D2 Steam of a second pressure level

[0109] D3 Steam of a third pressure level

[0110] DK1 Vapor condensate of a first pressure level

[0111] DK2 Vapor condensate of a second pressure level

[0112] DK3 Vapor condensate of a third pressure level

[0113] DK V Steam condensate from the consumer SR flow direction

Claims

Claims 1. System (10) for providing steam in a urea production plant (100), in particular for urea synthesis, comprising: - at least one first steam drum (11) adapted to receive steam (Dl) of a first pressure level and supply it to a stripper (101), in particular an NH3 or CO2 stripper, for urea synthesis; and - at least a second steam drum (12) which is connected downstream of the first steam drum (11) in the direction of flow (SR) and to which it is connected for transferring steam condensate (DK1, DK3), wherein the second steam drum (12) is adapted to contain steam (D2) and / or steam condensate (DK2) of a second, lower pressure level, wherein the system (10) further - comprising at least one compressor unit (13) connected to the second steam drum (12) and adapted to increase the steam (D2) of the second pressure level to the first, higher pressure level by compression, the compressor unit (13) being positioned upstream of the first steam drum (11) in the flow direction (SR); and / or - comprising at least one heat transfer unit (14), in particular a heat pump (15), which is connected upstream of at least one second steam drum (12) and adapted to transfer heat, in particular from at least one cooling water circuit and / or at least one media stream, to steam condensate (DK) S ) from a collection container (16) of the system (10) in such a way that steam (D2) of the second pressure level is produced for further use.

2. System (10) according to claim 1, characterized in that the compressor unit (13) has at least one with an electric motor has a steam compressor, in particular several such steam compressors, which uses electricity from renewable energy sources for its operation, in particular exclusively.

3. System (10) according to claim 1 or 2, characterized by the fact that the heat transfer unit (14), in particular the heat pump (15), uses electricity from renewable energy sources for operation, in particular exclusively.

4. System (10) according to one of the preceding claims, characterized by the fact that the first steam drum (11) is adapted to collect steam condensate (DK1) of a first pressure level from the stripper (101) and make it available for further use and / or a further steam drum is provided and adapted to collect steam condensate (DK1) of a first pressure level from the stripper (101) and make it available for further use.

5. System (10) according to one of the preceding claims, characterized by the fact that the second steam drum (12) is adapted to receive steam (D2) of the second pressure level and / or steam condensate (DK1, DK3) and to reduce the pressure level of the steam condensate (DK1, DK3) such that steam (D2) of the second pressure level is produced.

6. System (10) according to one of the preceding claims, characterized by the fact that at least the first and second steam drum (11, 12) and the compressor unit (13), in particular during normal operation, form a closed steam circuit.

7. System (10) according to one of the preceding claims, characterized by the fact that the second steam drum (12) is equipped with a condenser (103) for urea synthesis, in particular a carbamate condenser, such that coupled or can be coupled such that the condenser (103) evaporates at least a part of the steam condensate (DK2) contained in the second steam drum (12) to steam (D2) of the second pressure level, which is then returned to the second steam drum (12).

8. System (10) according to one of the preceding claims, characterized by the fact that the collection container (16) is connected to the second steam drum (12) by a line (21), wherein the heat transfer unit (14) is arranged between the second steam drum (12) and the collection container (16).

9. System (10) according to one of the preceding claims, characterized by the fact that at least one third steam drum (17) is arranged between the first and the second steam drum (12) and is connected to them for transferring or receiving steam condensate (DK1, DK3), wherein the third steam drum (17) is adapted to receive steam condensate (DK1) from the first steam drum (11) and to reduce the pressure level of the steam condensate (DK1) so that steam (D3) of a third pressure level is produced.

10. System (10) according to one of the preceding claims, in particular according to claim 9, characterized in that the second and / or the third steam drum (12, 17) are each connected to at least one steam consumer unit (18), in particular a heat exchanger, in a steam-transferring manner, wherein the steam consumer unit (18) is connected to a collection container (16) for draining steam condensate (DK). V ) is / are connected.

11. System (10) according to one of the preceding claims, characterized by the fact that at least one further compressor unit (19) is provided which is connected to the second steam drum and is adapted to extract a portion of the quantity of steam (D2) contained therein from the second to increase pressure levels by compression to a fourth, higher pressure level and to make available for further use to at least one external steam consumer, in particular independent of the urea production plant (100).

12. Urea production plant (100) comprising at least one system (10) according to one of the preceding claims, at least one stripper (101), in particular an NH3 or CO2 stripper, or a recirculation heater for heating recycled carbamate, at least one reactor in which ammonia (NH3) and carbon dioxide (CO2) react at a specific reaction pressure to form an aqueous urea solution, and at least one condenser (103) for condensing a gaseous phase, wherein the stripper (101) or the recirculation heater, the reactor and the condenser (103) form a synthesis cycle.

13. Method for providing steam in a urea production plant (100), in particular for urea synthesis, wherein - a stripper (101), in particular an NH3 or CO2 stripper, for urea synthesis, is supplied with vapor (Dl) of a first, in particular high, pressure level, which is used for a stripping process; - by utilizing the steam (D1) of the first pressure level, steam condensate (DK1) of a first, in particular high, pressure level is produced, wherein the first pressure level of the steam condensate (DK1) is reduced in such a way that steam (D2) of a second, lower pressure level is produced, wherein the process further - the steam (D2) of the second pressure level is compressed by at least one compressor unit (13) to steam (D1) of the first, in particular higher, pressure level, which is then supplied to the stripper (101) for the stripping process; and / or - Heat is transferred to steam condensate (DK) by at least one heat transfer unit (14), in particular a heat pump (15). V ) from a collection tank (16) of the urea production plant (100) is transferred in such a way that steam (D2) of the second pressure level is produced, which in turn is made available for further use, in particular by the compression unit (13) and / or other steam consumers.

14. Method according to claim 13, characterized in that the heat transfer unit (14) extracts heat from a cooling water circuit (102) and / or at least one media stream, in particular process condensates and / or process streams, of the urea production plant (100) and transfers it to the Steam condensate (DK) V ) from the collection vessel (16) to form steam (D2) of the second pressure level.

Images