System and method for mixing two fluids
Patent Information
- Application Number
- PCT/EP2025/053321
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-05
- Filing Date
- 2025-02-07
- Publication Date
- 2025-10-02
AI Technical Summary
Existing systems for mixing methanol and water in methanol reformers are bulky, costly, and lack effective control mechanisms to maintain optimal mixing ratios, leading to inefficiencies and potential catalyst degradation.
A system comprising pumps, a recirculation line with a concentration sensor, and a controller to adjust pump speeds based on real-time feedback, combined with static mixers and pressure control valves to ensure precise mixing and stable pressure, allowing for continuous operation and efficient mixing.
Achieves precise control of mixing ratios with ±0.5 wt-% accuracy, reduces system size and cost, and enhances efficiency by compensating for pump fluctuations and maintaining consistent quality, suitable for space-constrained environments like ships.
Smart Images
Figure EP2025053321_02102025_PF_FP_ABST
Abstract
Description
Description TITLE Plant and method for mixing two fluids TECHNICAL FIELD
[0001] The invention relates to a system for mixing two fluids, in particular for mixing methanol and water for methanol reformers. The invention further relates to a corresponding method. BACKGROUND
[0002] Methanol reformers play a central role in hydrogen production for fuel cells. They use methanol, a liquid alcohol that is easy to transport and handle, as a source of hydrogen.
[0003] The combination of methanol and water is a key aspect of this process. Within a methanol reformer, the mixture of methanol and water is heated and passed through a catalyst. This method, also known as steam reforming, produces pure hydrogen from a methanol-water mixture, releasing carbon dioxide.
[0004] The mixing of methanol and water must be carefully controlled to achieve an optimal ratio for steam reforming. A ratio of water that is too high can reduce hydrogen yield and waste energy, while a ratio that is too low can promote the formation of carbon deposits on the catalyst, which can reduce reformer efficiency.
[0005] State-of-the-art systems use a combination of two pumps, static mixers, tanks, and mass flow controllers. Composition control is achieved by measuring the density with three Mass flow controllers are used. Despite their effectiveness, these systems are bulky in both physical size and cost.
[0006] An alternative method for mixing the two reactants could be the use of pumps with a constant target speed or flow rate. This approach allows for direct mixing of the substances. However, this solution also has disadvantages. It offers no way to compensate for mixing errors through variable pump control. Furthermore, it cannot compensate for changes in pump flow rates that can occur over time due to aging. SUMMARY OF THE INVENTION
[0007] The invention is based on the object of providing an improved system for mixing two fluids. A further object of the invention is to provide a corresponding method.
[0008] The object directed to the system is achieved by a system for mixing two fluids, comprising a first pump for a first fluid and a second pump for a second fluid, wherein a first outlet of the first pump and a second outlet of the second pump open into a main line which leads into a container, wherein the container has a fill level sensor and a recirculation line branches off from the container and leads back into it, wherein a third pump and a concentration sensor are connected into the recirculation line and a consumer line branches off from the recirculation line, the system further comprising a controller which is configured to process signals from the fill level sensor and the concentration sensor for controlling the first pump and the second pump.
[0009] The advantages over similar state-of-the-art systems are, on the one hand, quality control by the concentration sensor in the recirculation line, not in the tank, and, on the other hand, improved homogenization of the mixture through recirculation. Regarding the arrangement of the concentration sensor in the recirculation line, there are various Possibilities: The concentration sensor does not necessarily have to be located upstream of the consumer line branch; positioning it downstream is also conceivable. It may also be necessary to severely restrict the flow for the sensor. The sensor could then be installed in a dedicated bypass line to the recirculation line.
[0010] It is advantageous to install a pressure control valve in the consumer line. The pressure control valve can be a safety valve, a pressure relief valve, or an overflow valve, for example. It protects downstream systems or equipment from excessive pressure by limiting the maximum pressure flowing through the line to a safe value. Furthermore, the pressure control valve ensures a stable, constant pressure in the consumer line, regardless of fluctuations in the upstream recirculation line. This can help improve the performance and efficiency of downstream equipment.
[0011] Alternatively or additionally, it may be advantageous if a pressure control valve is arranged in the recirculation line.
[0012] In an advantageous embodiment of the invention, a first static mixer is arranged in the main line. It can contribute to improved mixing of the fluids involved and utilizes the energy loss that normally occurs in the line to achieve efficient mixing. Static mixers have no moving parts and are low-maintenance and relatively less susceptible to mechanical failure. Furthermore, they enable continuous operation, which can enable a higher production rate and greater efficiency. On the other hand, by controlling the first and second pumps, the production of a defined mixture with an accuracy of ± 0.5 wt-% is possible without costly mass flow controllers. If greater accuracy is not absolutely necessary, the mixer could be omitted.This would result in a reduced number of components, thus enabling a more compact and cost-effective design. This would be particularly advantageous for the Use on ships where space is limited and green methanol is currently gaining importance as a climate-neutral fuel of the future.
[0013] In a further advantageous embodiment of the invention, a second static mixer is arranged in the recirculation line. This allows homogenization of the mixture to be restored more quickly after extended downtimes.
[0014] It is advantageous if the supply valves are arranged downstream of the first and second pumps because they allow the quantities of the first and second fluids provided to be regulated reliably and quickly when there is a corresponding control requirement.
[0015] It can be advantageous to have mass flow controllers downstream of the first and second pumps. Mass flow controllers enable precise control of flow rates, independent of changes in pressure and temperature. This can improve process accuracy and efficiency. Mass flow controllers allow flow rates to be adjusted quickly and easily to respond to changes in requirements or conditions. Furthermore, by maintaining a constant flow, mass flow controllers can protect pumps from potentially damaging conditions such as cavitation.
[0016] In an advantageous embodiment of the invention, a shut-off valve is arranged in the consumer line. Control: A shut-off valve allows the flow of fluid to the consumer to be completely stopped. This can be useful when maintenance work needs to be performed or when the consumer does not require fluid for some reason. A shut-off valve in the consumer line provides protection for downstream devices by stopping the flow of a faulty mixture as soon as the concentration sensor detects deviations. Due to its placement in the consumer line, it can quickly and efficiently prevent the inflow of undesired mixtures.
[0017] It is useful if the first fluid is water and the second fluid is methanol. The mixture of water and methanol is used in a number of industrial applications, including, in addition to fuel cells, as an antifreeze and as a solvent in chemical processes.
[0018] The object directed to a method for mixing two fluids is achieved by a method in which a first fluid and a second fluid are brought together and a mixture resulting therefrom is passed into a container, wherein the mixture is recirculated by continuously removing the mixture from the container and at least partially returning it to it, and at least a portion of the recirculated mixture is delivered to a consumer, wherein a fill level in the container is measured and a concentration of the recirculated mixture is determined and wherein the first and second fluids are provided as a function of the fill level measured in the container and the concentration of the recirculated mixture.
[0019] It is advantageous to determine a mixing ratio to be fed into the tank based on a control deviation of the concentration of the recirculated mixture. Target speeds of the first and second pumps are calculated from this mixing ratio and a control deviation of the tank fill level. This ensures that the final product always has the correct mixing ratios and thus guarantees consistent quality, even when rapid response to changes is required and the pump outputs must be adjusted accordingly to achieve the optimal mixing ratio and pump speeds.
[0020] It is particularly useful if, when concentration threshold values for the first fluid or the second fluid are exceeded or undershot (for example, ± 0.3 wt%), the excess fluid is stopped and only the other fluid is fed into the container so that equilibrium can be restored as quickly as possible. By interrupting By pumping the excess fluid and exclusively supplying the other fluid, the efficiency of the mixing process can be improved. This can lead to a reduction in energy consumption and operating costs.
[0021] In order to reach a concentration setpoint as quickly as possible after a deviation of an actual concentration value, it is advantageous if the other fluid is fed to the container with the aid of a characteristic curve that depends on a concentration control deviation.
[0022] Furthermore, it is advantageous if, in the event of a deviation from the setpoint, the delivery of the excess fluid is stopped by switching off the corresponding first or second pump or closing a supply valve.
[0023] It is advantageous if, when an incorrect mixture is detected, its delivery to the consumer is stopped by means of a shut-off valve in the consumer line.
[0024] A key aspect of the invention is that the consumer is supplied not from the container, but from the recirculation circuit with the concentration sensor. The circuit mixes the water-methanol mixture to be mixed, ensures the correct pre-pressure for the consumer(s), and by supplying the consumers directly after the concentration sensor, it is ensured that the correct quality always reaches the consumers, for example, mixture-sensitive methanol reformers. With direct extraction from the container, one would never know what quality would reach the consumer.
[0025] A setup according to the invention could also serve as evidence in the event of damage to a consumer (e.g., a methanol reformer or fuel cell). Should a fuel cell module be damaged and the cause is incorrectly attributed to a faulty mixture, the concentration sensor's recording would allow documentation of the actual quality of the mixture used. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG 1 shows a system for mixing two fluids according to the invention,
[0027] FIG 2 shows an alternative embodiment of the inventive system with a modified arrangement of a pressure control valve,
[0028] FIG 3 shows a further alternative embodiment of the inventive system with a static mixer in the main line,
[0029] FIG 4 shows a further alternative embodiment of the inventive system with a static mixer in the recirculation line,
[0030] FIG 5 shows a further alternative embodiment of the inventive system with supply valves,
[0031] FIG 6 shows a further alternative embodiment of the inventive system with mass flow controllers and
[0032] FIG 7 shows a further alternative embodiment of the inventive system with a shut-off valve in the consumer line. DESCRIPTION OF THE EMBODIMENTS
[0033] FIG. 1 shows a simplified schematic embodiment of the system 1 according to the invention for mixing two fluids. The system 1 comprises a first pump 2 for a first fluid and a second pump 3 for a second fluid, wherein a first outlet 4 of the first pump 2 and a second outlet 5 of the second pump 3 open into a main line 6 leading into a container 7. According to the invention, the container 7 has a fill level sensor 8. In addition, a recirculation line 9 branches off from the container 7 and is fed back into it. A third pump 10 and a concentration sensor 11 are connected to the recirculation line 9. A consumer line 12 branches off from the recirculation line 9 and leads to a consumer 17 not shown in FIG. 1, for example, a methanol reformer. In the embodiment of FIG. 1, A pressure control valve 15 is arranged in the consumer line 12. FIG. 1 does not show that, depending on the design of the pressure control valve 15, a line back into the container 7 is required. A controller 13 is configured to process signals from the level sensor 8 and the concentration sensor 11 to control the first pump 2 and the second pump 3.
[0034] FIG 2 shows an alternative embodiment of the inventive system 1 with a pressure control valve 15 in the recirculation line 9.
[0035] FIG 3 shows a further alternative embodiment of the inventive system 1 with a first static mixer 14 arranged in the main line 6. The first static mixer 14 intensifies the mixing that already takes place in the main line 6 and thus optimizes the homogeneity of the mixture before it is fed into the container 7.
[0036] FIG 4 shows an alternative embodiment of the inventive system 1 with a second static mixer 19 arranged in the recirculation line 9, with which homogenization of the mixture can be restored more quickly after longer downtimes.
[0037] FIG 5 shows two supply valves 18 arranged in the two lines leading from the first pump 2 and the second pump 3, which control the quantities of the first and second fluids provided when there is a corresponding control requirement, but in particular reliably and quickly stop the supply of the corresponding fluid when limit values are significantly exceeded or undershot.
[0038] FIG. 6 shows a further alternative embodiment of the inventive system 1, in which mass flow controllers 16 are arranged downstream of the first pump 2 and the second pump 3 in the flow direction of the corresponding fluid. The use of mass flow controllers 16 is a way to ensure that a desired mixing ratio is achieved quickly and as precisely as possible with minimal control effort with respect to the first and second pumps 2, 3, particularly during load changes.
[0039] FIG. 7 shows another alternative embodiment of the inventive system with a shutoff valve 20 in the consumer line 12. The shutoff valve 20 is connected to the controller 13. It protects downstream consumers from excessively deviating mixing ratios by stopping the inflow as soon as the concentration sensor 11 detects excessive deviations outside the tolerance range. Due to the arrangement of the consumer line 12 directly downstream of the concentration sensor 11 and not at the tank 7, the inflow of a potentially harmful mixture to the consumer 17 can be prevented with a very high degree of reliability and speed. LIST OF REFERENCE SYMBOLS 1 system 2 first pump 3 second pump 4 first outlet 5 second outlet 6 Main line 7 containers 8 Level sensor 9 Recirculation line 10 third pump 11 Concentration sensor 12 Consumer line 13 Control 14 first static mixer 15 Pressure control valve 16 mass flow controllers 17 consumers 18 Supply valve 19 second static mixer 20 Shut-off valve
Claims
Claims What is claimed:
1. A system (1) for mixing two fluids, comprising a first pump (2) for a first fluid and a second pump (3) for a second fluid, wherein a first outlet (4) of the first pump (2) and a second outlet (5) of the second pump (3) open into a main line (6) leading into a container (7), characterized in that the container (7) has a fill level sensor (8) and a recirculation line (9) leading away from the container (7) and back into it, wherein a third pump (10) and a concentration sensor (11 ) are connected to the recirculation line (9) and a consumer line (12) branches off from the recirculation line (9), the system (1) further comprising a controller (13) which is configured to process signals from the level sensor (8) and the concentration sensor (11) for controlling the first pump (2) and the second pump (3).
2. The system (1) according to claim 1, wherein a pressure control valve (15) is arranged in the consumer line (12).
3. The system (1) according to one of claims 1 or 2, wherein a pressure control valve (15) is arranged in the recirculation line.
4. The system (1) according to one of the preceding claims, wherein a first static mixer (14) is arranged in the main line (6).
5. The system (1) according to one of the preceding claims, wherein a second static mixer (19) is arranged in the recirculation line (9).
6. The system (1) according to one of the preceding claims, wherein supply valves (18) are arranged downstream of the first (2) and the second pump (3).
7. The system (1) according to one of the preceding claims, wherein mass flow controllers (16) are arranged downstream of the first (2) and the second pump (3).
8. The system (1) according to one of the preceding claims, wherein a shut-off valve (20) is arranged in the consumer line (12).
9. The plant (1) according to any one of the preceding claims, wherein the first fluid is water and the second fluid is methanol.
10. A method for mixing two fluids, wherein a first fluid and a second fluid are brought together and a mixture resulting therefrom is fed into a container (7), characterized in that the mixture is recirculated by continuously removing the mixture from the container (7) and at least partially returning it to it, and at least part of the recirculated mixture is delivered to a consumer (17), wherein a fill level in the container (7) is measured and a concentration of the recirculated mixture is determined and wherein the first and the second fluid are provided as a function of the fill level measured in the container (7) and the concentration of the recirculated mixture.
11. Method according to claim 10, wherein a mixing ratio to be supplied to the container (7) is determined from a control deviation of the concentration of the recirculated mixture, wherein target speeds of the first pump (2) and the second pump (3) are calculated from this mixing ratio and a control deviation of a container fill level.
12. Method according to one of claims 10 or 11, wherein when concentration threshold values for the first fluid or the second fluid are exceeded or undershot, delivery of the excess fluid is interrupted and only the other fluid is supplied to the container (7).
13. The method according to claim 12, wherein the other fluid is supplied to the container (7) with the aid of a characteristic curve dependent on a concentration control deviation.
14. Method according to one of claims 12 or 13, wherein the delivery of the excess fluid is stopped by switching off the corresponding first or second pump (2, 3) or closing a supply valve (18).
15. Method according to one of claims 10 to 14, wherein upon detection of an incorrect mixture, its delivery to the consumer is stopped.