Method for operating a compressor system

Abstract

The invention relates to a method for operating a compressor system, wherein the compressor system has at least one first compressor (1), wherein the compressor (1) is designed to compress a flow medium, wherein the flow medium comprises hydrogen, wherein the compressor is operated in diverter mode, wherein a substance for increasing the molecular weight of the flow medium is supplied to the compressor (1) on the suction side (2).

Description

2024PF00430 1 Description TITLE L Method for operating a compressor plant TECHNICAL BOROUGH

[0001] The invention relates to a method for operating a compressor system, wherein the compressor system has at least one first compressor, wherein the compressor is designed to compress a flow medium, the flow medium comprising hydrogen, and wherein the compressor is operated in recirculation mode.

[0002] Furthermore, the invention relates to a compressor system. BACK ROUND

[0003] The importance of hydrogen has increased significantly and it is of great relevance as a future technology. The hydrogen density in the atmosphere is approximately 90 g / m³. 3very low. Therefore, hydrogen must be compressed to achieve a usable energy density. Compressors designed for hydrogen compression are essential for realizing a future-oriented hydrogen economy.

[0004] The operating principle of compressors, such as turbo compressors used for hydrogen compression, presents challenges. Due to hydrogen's relatively low molecular weight, the possible pressure ratio per compressor stage is very low. For single-shaft compressors, for example, the pressure ratio is essentially 1.05 per stage. Therefore, achieving a high final pressure requires a very large number of stages.

[0005] Efforts to reduce the number of stages required for hydrogen compression could increase the enthalpy input per stage. 2024PF00430 2. However, this requires an increase in the impeller peripheral speeds and thus the rotational speeds.

[0006] However, increasing the impeller peripheral speeds and rotational speeds could lead to insufficient material strength in the impeller material in combination with hydrogen.

[0007] The hydrogen produced in water electrolysis exists as saturated hydrogen with an extremely high water content in the form of water vapor. At low pressure and saturation with water vapor, the molecular weight increases from approximately 2 g / mol to approximately 3 g / mol. Such an increase in molecular weight simplifies compression and increases the achievable pressure.

[0008] Typically, two compressor housings are used for such compression tasks. A reduction in water loading leads to a reduction in molecular weight and a drop in the achievable final pressure, which can no longer be compensated for within the two compressor housing stages.

[0009] The compression process in a turbo compressor inevitably increases not only the pressure but also the temperature of the hydrogen stream being compressed. Therefore, the temperature must be reduced by recooling before the subsequent compressor or process stage.

[0010] Since hydrogen's water-holding capacity decreases significantly at higher pressures, a considerable amount of liquid condensate is removed during cooling between the compressor stages. This reduction in water content occurs both during cooling between the compressor stages and in the aftercooler downstream of the final compressor stage.

[0011] Due to the resulting change in the process gas composition (hydrogen and water content), the molecular weight is reduced from approximately 3 g / mol to a minimum of 2 g / mol. 2024PF00430 3. When designing the compressor stages, the change in molecular weight due to intercooling is taken into account.

[0013] Varying process conditions require the compressor to operate at different flow rates. A reduction in the flow rate of turbo compressors is generally possible down to 70% of the design rate. If the flow rate is too low, damaging pump surges or other problems can occur. Pressure fluctuations within the compressor, which should be avoided.

[0014] To ensure that this minimum permissible process gas quantity at the compressor inlet is not undershot, the individual compressor stages are equipped with so-called bypass lines. A bypass line connects the suction side to the pressure side of the compressor. This quantity is also the minimum process gas quantity that can be operated without bypassing.

[0015] To further reduce the delivery rate, the compressor is operated in so-called bypass mode. The difference between the minimum delivery rate and the reduced delivery rate is returned to the suction side of the compressor via a control valve, also known as a surge control valve, located behind the pressure-side cooler. This process is also referred to as bypass mode. Bypass mode may also be necessary in the event of process-related malfunctions if the process downstream of the compressor cannot accept any or only a small delivery rate.

[0016] Cooling the returned flow rate during recirculation is essential to prevent the temperature on the suction side from rising unacceptably high.

[0017] By recirculating the cooled and pressure-throttled hydrogen mass flow with a significantly reduced molecular weight, which corresponds to a lower water content after recooling, hydrogen with a high water content mixes, in which the 2024PF00430 4 molecular weight is approximately 3 g / mol and hydrogen has a low molecular weight. Water loading where the molecular weight is at least 2 g / mol.

[0018] Due to the reduction in molecular weight after the mixing of both hydrogen streams before the compressor stage, the original final pressure of the compressor stage can usually no longer be achieved.

[0019] To increase the operating range with respect to mass flow variability, such as fluctuations in the regeneratively generated electricity for electrolysis, two identical compressor trains are provided in parallel operation.

[0020] When hydrogen production is reduced, one compressor train can be shut down and is thereby sealed off on both the suction and pressure sides. During standstill, the hydrogen present in the connecting pipes equalizes between the suction and pressure sides, and this also leads to a reduction in molecular weight.

[0021] When a compressor is started from such a standstill condition, the current pressure of the running compressor can no longer be reached. The newly started compressor train therefore cannot pump gas into the shared process gas line with the compressor running in parallel. SUMMARY OF THE INVENTION

[0022] This is where the invention comes in.

[0023] The object of the invention is to provide a suitable method for the compression of hydrogen.

[0024] This problem is solved by a method for operating a compressor plant, wherein the compressor plant has at least one first compressor, wherein the compressor is designed to compress a flow medium, wherein the flow medium comprises hydrogen, wherein the 2024PF00430 5 The compressor is operated in recirculation mode, whereby a substance is supplied to the compressor on the suction side to increase the molecular weight of the flow medium.

[0025] Furthermore, the task is solved by a compressor system designed to carry out the process. DESCRIPTION OF THE INVENTION

[0026] A key aspect of the invention is that a substance is specifically added to the hydrogen mass flow during recirculation operation, which counteracts the reduction of the molecular weight, thereby allowing the compressor discharge pressure to be maintained.

[0027] Advantageous embodiments are the subject of the dependent claims.

[0028] The dependent claims list further advantages that can be combined in any way to achieve further advantages.

[0029] In an advantageous design, a stoichiometric amount of nitrogen is added to the hydrogen mass stream in a downstream ammonia synthesis to produce ammonia.

[0030] Therefore, a targeted and minimally necessary addition of nitrogen on the suction side of the compressor train is unproblematic and rather beneficial.

[0031] The advantage of minimally targeted nitrogen addition to the compression process, compared to complete stoichiometric mixing, would be twofold. First, the stoichiometric mixture would require a significantly larger amount of nitrogen compared to hydrogen. This would necessitate comparatively large storage volumes. Second, the energy losses during the compression process would be reduced. 2024PF00430 6 Throttle the total amount of nitrogen from the pressure level of an air separation unit to the suction pressure level of the hydrogen compressor.

[0032] A targeted, minimal addition of nitrogen to the hydrogen inlet mass flow can be achieved in various ways. Firstly, the final pressure drop caused by the bypass operation can be detected, and as soon as predefined limits are exceeded, nitrogen is added to the hydrogen mass flow upstream of the compressor suction port or the knock-out drum until the final pressure returns to and / or remains within the permissible range. Secondly, the addition is based on calculated proportions, such as the hydrogen volume flow rate, pressure, temperature, nitrogen measurement via a pressure differential, and calculation of the molecular weight.

[0033] By combining both methods, the driving style can be improved even further in order to correct any further deviations in final pressure by adding the calculated quantities and by slightly changing the amount of nitrogen.

[0034] Nitrogen can be obtained from two sources. Firstly, from an air separation plant. Typically, ammonia plants located nearby have an air separation plant from which the required nitrogen is drawn. Secondly, barrier gas can be used. This barrier gas is used to seal the compressor shaft ends with dry gas seals, and nitrogen is used for this purpose. The barrier gas is then fed back into the compressor on the suction side. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] An embodiment of the invention will be explained in more detail below with reference to the following figure. 2024PF00430 7

[0036] The properties, features and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more easily understood in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings.

[0037] Identical components or components with the same function are marked with the same reference numerals.

[0038] Exemplary embodiments of the invention are described below with reference to the drawings. These drawings are not intended to be drawn to scale; rather, where helpful for explanation, they are presented in a schematic and / or slightly distorted form. For further details regarding the teachings directly apparent from the drawings, reference is made to the relevant prior art.

[0039] They show:

[0040] FIG 1 a schematic representation of a compressor DESCRIPTION OF THE EXECUTION FORM EN

[0041] Figure 1 shows a schematic representation of a compressor 1, which can be used in a compressor system according to the invention. The compressor system can have more than one compressor, so that the compressor shown in the figure can also be referred to as the first compressor 1. The compressor 1 comprises a suction side 2, into which a fluid medium flows via an inlet line 3. A flow channel is formed in the compressor 1, through which the fluid medium flows and which is designed such that the pressure and temperature of the fluid medium are increased. The fluid medium comprises hydrogen (H2).

[0042] At one outlet of compressor 1 is an outlet line 4. The outlet of compressor 1 is also referred to as the pressure side 5. The fluid flows through outlet line 4 to a further process. 2024PF00430 8

[0043] The suction side 2 is fluidically connected to the pressure side 5 via a bypass line 6. A valve 7 is located in the bypass line 6. As soon as the valve 7 is open during operation, the operation is also referred to as bypass operation.

[0044] During recirculation operation, the molecular weight of the fluid on the suction side 2 may decrease to such an extent that sufficient pressure can no longer be achieved in the outlet line 4. In this case, a substance is added to the compressor on the suction side 2 to increase the molecular weight of the fluid. The substance is supplied via an access line 8.

[0045] The substance contains nitrogen (N2).

[0046] According to the invention, the pressure of the flow medium is determined at the pressure side 5 of the first compressor 1 and as soon as a limit value is exceeded, the substance is supplied in a certain quantity.

[0047] The substance is added until the pressure is back within an acceptable range. Physical parameters are determined to calculate the required amount of the substance. The compressor system can include a second compressor (not shown). During operation, the two compressors would run in parallel, with each compressor handling 50% of the incoming fluid. However, situations can arise where the flow rate of the incoming fluid is reduced. In this case, one compressor is effectively shut down or blocked. The compressor system therefore has a second compressor that is operated in parallel to the first compressor 1, with the compressor system having a common outlet line for the compressed flow medium. 2024PF00430 9

[0050] The fluid flowing from the compressor system, which is mixed with the substance, can be fed into an ammonia plant.

[0051] The substance can be supplied via an inlet line downstream of the compressor system to obtain a stoichiometric amount of nitrogen for ammonia synthesis.

[0052] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples and other variants can be derived by a person skilled in the art without leaving the scope of protection of the invention.

Claims

2024PF00430 10 Claims 1. Method for operating a compressor plant, wherein the compressor plant has at least one first compressor (1 ), wherein the compressor (1 ) is designed to compress a flow medium, wherein the flow medium comprises hydrogen, wherein the compressor is operated in recirculation mode, characterized in that a substance to increase the molecular weight of the flow medium is supplied to the compressor (1) on the suction side (2).

2. The method of claim 1, wherein the substance comprises nitrogen.

3. Method according to claim 1 or 2, wherein the pressure of the flow medium is determined at the pressure side (5) of the first compressor (1) and as soon as a limit value is exceeded, the substance is supplied in a certain quantity.

4. The method of claim 3, wherein the substance is supplied until the pressure is again within an acceptable range.

5. Method according to claim 3 or 4, wherein the quantity of the substance is supplied according to physical parameters.

6. The method according to claim 5, wherein the physical parameters include the volume flow rate of the flow medium, pressure, temperature and / or molecular weight. 2024PF00430 11 7. Method according to one of the preceding claims, wherein the compressor system has a second compressor which is operated in parallel to the first compressor (1), wherein the compressor system has a common outlet line for the compressed flow medium.

8. Method according to one of the preceding claims, wherein the flow medium compressed in the compressor system is fed to an ammonia synthesis.

9. The method of claim 8, wherein a stoichiometric amount of nitrogen is supplied to the flowing medium for ammonia synthesis.

10. Compressor system, configured to carry out a process according to one of the preceding claims.

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