Method for separating a mixture

Abstract

The invention relates to a method for separating a mixture comprising a liquid phase and a gas phase, wherein the mixture is introduced in a free-flowing manner through a mixture inlet (9) into a closed container (1), in which the liquid phase sinks and is discharged from the container (1) through a liquid outlet (10) at a lower side (4) that closes the container (1) at the bottom, and the gas phase rises and is discharged from the container (1) through a gas outlet (12) at an upper side (3) that closes the container (1) at the top, wherein, apart from the mixture inlet (9), the liquid outlet (10), and the gas outlet (12), the container (1) is closed, a feed line (17) extending from the mixture inlet (9) projects into the container (1), and a vertical component of a flow direction of the mixture upon introduction into the container (1) is greater than or equal to a horizontal component of the flow direction. In order to reduce the size of the container (1) while maintaining consistently large material flows, according to the invention an end (18) of the feed line (17) which is open towards the container (1) is flared in the shape of a funnel and / or is surrounded radially by a tubular guide plate that is preferably provided with vertical slots.

Description

[0001] Method for separating a mixture

[0002] The invention relates to a method for separating a mixture of a liquid phase and a gas phase, wherein the mixture is introduced in free flow through a mixture inlet into a closed container, in which the liquid phase sinks and is discharged from the container through a liquid outlet at a bottom end closing off the container, and the gas phase rises and is discharged from the container through a gas outlet at a top end closing off the container, wherein the container is closed except for the mixture inlet, the liquid outlet and the gas outlet, a feed line extending from the mixture inlet projects into the container and a vertical component of a flow direction of the mixture when introduced into the container is greater than or equal to a horizontal component of the flow direction.

[0003] Methods of the aforementioned type are known, for example, from JP201363374A3 for separating a mixture of an electrolysis fluid and hydrogen and / or oxygen gas produced in an electrolyzer. In the known methods, the mixture is fed into a container in which the bubbles of the gas phase rise to the surface of the slowly horizontally flowing liquid phase and are deposited there. At the end of the container, the liquid phase, separated from the gas phase, is drawn off.

[0004] In known processes, the minimum container size is determined by the rising velocity of the slowest bubbles to the surface—i.e., the smallest bubbles—in the gas phase and the horizontal flow velocity of the liquid phase. These known processes utilize horizontal cylindrical containers with a diameter of 0.4 to approximately 3 meters and a length several times greater than their diameter.

[0005] Task

[0006] The invention is based on the objective of reducing the size of the container while maintaining consistently large material flows. Solution

[0007] Based on known methods, the invention proposes that a vertical component of a flow direction of the mixture when introduced into the container is greater than or equal to a horizontal component of the flow direction.

[0008] The invention is based on the understanding that reducing the size of the container necessitates an acceleration of the rise of gas-phase bubbles in the liquid phase. The vertical component of the flow accelerates the rise of the bubbles into the gas phase towards the surface of the liquid phase, thus accelerating the separation of the gas phase. In a process according to the invention, the flow direction is inclined at a maximum angle of 45° to the vertical. At least 70% of the kinetic energy of the mixture then supports the vertical rise of the bubbles. The container for carrying out the process according to the invention can be built proportionally up to an order of magnitude smaller and correspondingly more cost-effective compared to the prior art, in proportion to the accelerated separation of the phases.

[0009] In the method according to the invention, a feed line extending from the mixture inlet projects into the container. The mixture is thus introduced above the bottom into the liquid phase located in the container, and turbulence of the liquid phase below the inlet cross-section is prevented.

[0010] In the method according to the invention, in a first embodiment, the end of the supply line open towards the container is widened in a funnel shape. The average flow velocity of the mixture is thus reduced proportionally to the widening. If the widening is, for example, twice the cross-section, the average flow velocity is halved.

[0011] In a second or additional variant, the end of the feed line is radially enclosed by a tubular guide plate. Such a guide plate evens out the radial flow of the mixture into the liquid phase. Preferably, this guide plate is vertically slotted, perforated, or otherwise open. The evenness of the radial flow can thus be regulated so that the liquid phase is calmed but does not overflow the upper edge of the guide plate. The guide plate can also be open on its underside. Depending on the flow conditions from the end of the feed line, gas plugs can escape and simultaneously carry liquid with them. The openings prevent liquid from entering the gas space above the surface uncontrollably and carrying the gas back down.

[0012] The method according to the invention is characterized by increased flow velocities compared to the known prior art. In the method according to the invention, the flow direction and extent must be controlled to prevent the formation of flow acceleration zones within the liquid. In particular, minute gas bubbles with a diameter below 500 pm must not enter such an acceleration zone because their buoyancy is insufficient to resist the downward flow of the liquid (drag force). In such a zone, the smallest gas bubbles would flow downwards with the liquid without the desired separation occurring.

[0013] In a method according to the invention, the funnel-shaped widened end of the feed line preferably has an opening angle of 5 to 10° and / or the mixture is introduced centrally. This evens out the deceleration of the mixture.

[0014] In a method according to the invention, flat perforated plates are preferably arranged at the outlet cross-section of the supply line and / or below the outlet cross-section. This decelerates the flow.

[0015] In a method according to the invention, at least one vertically oriented guide plate is preferably arranged in the supply line. Depending on the cross-section of the supply line, several such guide plates can be arranged on the supply line. These ensure a swirl-free and uniform flow into the container across the cross-section of the supply line. In a method according to the invention, at least one guide plate, vertically oriented in the mixture, is preferably arranged above the outlet cross-section of the supply line. Depending on the cross-section of the container, several such guide plates can be arranged in the mixture. These prevent, particularly in the case of off-center inflow, an annular flow around the outlet cross-section, which makes determining the liquid level difficult.

[0016] In a method according to the invention, the mixture preferably flows freely into the container at a flow velocity of at most 2 m / s, preferably at less than 1 m / s. The flowing mixture then does not escape into the gas space above the liquid phase in a fountain-like jet.

[0017] In a process according to the invention, the mixture is preferably introduced into the container below the surface of the liquid phase. The mixture then flows into the liquid phase, which continuously decelerates the vertical component of the flow up to the surface. More preferably, the mixture is introduced between 30 mm and 200 mm, particularly between 100 mm and 200 mm, or alternatively up to 350 mm below the surface. This range has proven effective experimentally for separating a mixture of an electrolysis liquid and hydrogen and / or oxygen gas produced by one of the known electrolysis processes. The process according to the invention works best when the distance to the surface is as small as possible without a fountain forming at the surface.

[0018] Furthermore, one or more guide plates running in the direction of flow can be arranged at the end of the inlet pipe to force a largely directed flow and thus further promote the separation of the phases.

[0019] In a method according to the invention, the supply line within the container is preferably branched to several ends, and the mixture is distributed to these ends. In such a method according to the invention, the introduced mixture is distributed more evenly across the surface of the container, particularly in large containers. In such containers, up to 8,000 Nm³ can be achieved. 3 / h hydrogen or oxygen is separated from the liquid phase.

[0020] In a method according to the invention, the volume enclosed by the surface and the top side is preferably less than 0.1 m³. 3. If the volume of gas phase enclosed between the surface and the top surface ignites, then the immediate consequences are limited to the equivalent of this confined gas space.

[0021] In a process according to the invention, the gas phase preferably consists of water vapor with molecular hydrogen and / or oxygen. Such mixtures are produced as an intermediate product in the production of hydrogen gas by electrolysis. Alkaline electrolysis or polymer electrolyte membrane (PEM) electrolysis are particularly suitable electrolysis processes.

[0022] In a method according to the invention, the container is preferably under an internal pressure of 1 to 200 bar. The known electrolysis processes are carried out within this pressure range.

[0023] In a process according to the invention, the liquid phase preferably consists of distilled water or an aqueous potassium or sodium hydroxide solution. Such liquid phases are used in known electrolysis processes.

[0024] In such a process, the mixture is preferably produced by electrolysis and the liquid phase is recycled back into the electrolysis process. Recycling the liquid phase is a proven method in known electrolysis processes.

[0025] In a process according to the invention, the container is preferably filled at the bottom with a bed of packing material. Any gas phase bubbles remaining in the liquid phase are deposited on the packing material, preventing damage to the pump during the pumping of the liquid phase. In known electrolysis processes, Pall rings made of stainless steel or equivalent packing material have proven particularly suitable. The packing height can extend to the end of the feed line. Alternatively, the container can be filled with a structured packing material in the area of ​​the shell.

[0026] The expansion angle is between 3 and a maximum of 10°. The funnel-shaped expansion of the inlet has a perforated plate at the outlet cross-section with an open area of ​​between 20% and 40% to ensure maximum uniformity of the mixing phase's entry into the liquid phase, thereby preventing flow acceleration zones. The perforated plate prevents the formation of a flow acceleration zone both in the inlet and in the funnel area. Without the perforated plate, the following would not be possible:

[0027] Flow acceleration zones are created in the liquid phase of the apparatus, which hinder the separation of the two phases.

[0028] In a process according to the invention, the gas phase is preferably dried and / or filtered after being removed from the container. Drying and filtration, in particular of the hydrogen gas produced by known electrolysis processes, are known and proven, for example, in gas purification units and droplet separators.

[0029] In a method according to the invention, the shell of the container preferably has a material grade of SA 316L or DIN 1 .4404 or equivalent. The liquid outlet preferably has a nominal diameter of DN25, DN80 or DN300.

[0030] Examples of implementation

[0031] The invention is explained below with reference to exemplary embodiments. These show

[0032] Fig. 1 shows a first container for carrying out a method according to the invention,

[0033] Fig. 2 shows the internal structure of the first container,

[0034] Fig. 3 shows a detail of a second container,

[0035] Fig. 4 shows a detail of a third container, Fig. 5 a detail of a fourth container, Fig. 6 the internal structure of a fifth container and

[0036] Fig. 7 shows the internal structure of a sixth container.

[0037] The container 1 shown in Figures 1 and 2 has a cylindrical shell 2, which is closed at a top 3 and a bottom 4 by dished ends. The shell 2 is made of austenitic stainless steel of grade SAE 316L, is supported on four feet 5, and has a height 6 of 780 mm, an inner diameter 7 of 800 mm, and a total volume of 0.51 m³ between the dished ends. 3 on.

[0038] On the outside of the casing 2 there is an inspection opening 8, on the underside 4 a mixture inlet 9 and a liquid outlet 10, each with a nominal diameter of DN80, and a water inlet 11, on the top side 3 a gas outlet 12, a

[0039] A safety valve 13 and a lifting eye 14 are attached. In addition, a connection 15 for measuring a liquid level is attached to the casing 2 and to the top 3, as well as one reserve connection 16 on the underside 4 and two on the top 3.

[0040] Inside the casing 2, a tubular supply line 17 (not shown to scale) leads vertically upwards from the mixture inlet 9. The upper end 18 of the supply line 17, which points into the container 1, is conically flared. The underside 4 is covered with a bed 19 of Pall rings.

[0041] For commissioning according to a method according to the invention, the container 1 is purged with gas, then filled through the water inlet 11 with a 30% potassium hydroxide solution until its surface 20 is above an outlet cross-section 19 at the end 18 of the supply line 17, and finally the container 1 is placed under an internal pressure of 45 bar.

[0042] To carry out the process according to the invention, a mixture produced by electrolysis consisting of 60 vol% of potassium hydroxide solution as liquid phase and 40 vol% hydrogen and oxygen gas as gas phase is continuously supplied to the container 1 at a mean flow rate of 3 m / s in the mixture inlet 9.

[0043] The funnel reduces the average flow velocity of the mixture to 1 m / s. At surface 20, the gas phase, consisting of hydrogen and oxygen gas, separates from the liquid phase and is drawn off via the gas outlet 12. The liquid phase initially spreads radially from the funnel across surface 20 and then flows vertically downwards. In the bed 19 of Pall rings, the smallest remaining gas phase bubbles coalesce into larger bubbles, rise to surface 20, and are deposited there. The liquid phase, purified of the gas phase, is drawn off via the liquid outlet 10.

[0044] Under normal operating conditions, the container 1 is closed during the process according to the invention, except for the mixture inlet 9, the liquid outlet 10, and the gas outlet 12. A small compensating flow of the liquid phase, two orders of magnitude below the mixture flow, is added or removed via the water inlet 11 as needed to regulate the process, in particular the concentration of the liquid phase in the container 1. The gas phase is released into the environment of the container 1 via the safety valve 13 if a limit pressure is exceeded.

[0045] Figure 3 schematically shows a detail of a second container (not shown) for carrying out a method according to the invention. The second container differs from the first container 1 only in that the upper end 22 of the supply line 23 is enclosed by a tubular guide plate 24 made of perforated sheet metal. During the method according to the invention, the guide plate 24 projects above the surface (not shown here), and the guide plate 24 accelerates the deflection of the flow of the remaining liquid phase vertically downwards.

[0046] Figure 4 schematically shows a detail of a third container (not shown) for carrying out a method according to the invention. The third container differs from the first container 1 only in that the outlet cross-section 25 is located above the surface 26 of the liquid phase and a downwardly funnel-shaped guide plate 27 is connected to the outlet cross-section 25. During the method according to the invention, the guide plate 27 distributes the remaining liquid phase radially around the supply line 28, thus increasing the exchange surface between the gas phase and the liquid phase to such an extent that even the smallest gas bubbles escape from the liquid phase much more quickly. The mixture containing the gas bubbles flows over the guide plate 27 into the container. The low height of the liquid film on the guide plate 27 promotes the degassing of the gas phase.Bubbles of the gas phase rising from the packing of Pall rings are directed upwards through the guide plate 27.

[0047] Figure 5 schematically shows a horizontal section through a fourth container 29 (not shown) for carrying out a method according to the invention. The fourth container 29 differs from the first container 1 in that its diameter 30 is 2,400 mm and its height is 90 cm. The fourth container 29 thus has a total volume of 7.7 m³. 3 The supply line branches out from the mixture inlet within the fourth container 29 to four funnel-shaped widened ends 31, and a mixture flow of up to 8,000 Nm 3 / h hydrogen gas and up to 640 m 3 Potassium hydroxide solution and divided into four approximately equal partial streams to the ends 31. The mixture inlet and the supply line below the ends 31, as well as the mixture itself, are not shown.

[0048] The fifth container 32, shown in simplified form in Figure 6, differs from the first container 1 by two horizontally arranged, flat perforated plates 34 below the outlet cross-section 33. The perforated plates 34 prevent the formation of flow acceleration zones and ensure complete separation of the gas and liquid phases for gas bubbles larger than 650 pm and fractional separation for smaller bubbles. The liquid flows through the perforated plates 34 in a largely vertical downward direction. The flow straightening effect can be improved by an additional layer of Pall rings (not shown) between the two perforated plate planes, which contribute to further agglomeration of gas bubbles.

[0049] The sixth container 35, shown in simplified form in Figure 7, differs from the first container 1 by a flat perforated plate 37 arranged horizontally above the outlet cross-section 36, which further decelerates the flow.

[0050] The seventh container 38, shown in simplified form in Figures 8a and b, differs from the first container 1 by two vertically positioned guide plates 40 arranged in the inlet 39, which ensure a swirl-free inflow.

[0051] The eighth container 41, shown in simplified form in Figures 9a and b, differs from the first container 1 by means of vertically positioned guide plates 43 arranged above the outlet cross-section 42, which prevent a circular flow around the inlet 45 on the surface 44.

[0052] The additional features of the second to eighth containers can also be combined with each other in other methods according to the invention.

[0053] In another method according to the invention, the gas phase consists of hydrogen or oxygen gas.

[0054] The volume fractions of the liquid phase and the gas phase can vary considerably in other processes according to the invention. A mixture produced by alkaline hydrolysis (also: alkalesis) contains significantly more potassium hydroxide solution, while a mixture produced in a PEM contains no potassium hydroxide solution, but rather pure water.

[0055] The characters are

[0056] 1 container

[0057] 2 coats

[0058] 3 Top

[0059] 4 Underside

[0060] 5 feet

[0061] 6 Height

[0062] 7 diameters

[0063] 8 Revision opening

[0064] 9 Mixture intake

[0065] 10 Liquid outlet

[0066] 11 Water inlet

[0067] 12 Gas outlet

[0068] 13 Safety valve

[0069] 14 Lifting eye

[0070] 15 Connection for measuring a liquid level

[0071] 16 spare connection

[0072] 17 Supply line

[0073] 18 upper end

[0074] 19 Fill

[0075] 20 surface

[0076] 21 Outlet cross-section

[0077] 22 upper end

[0078] 23 Supply line

[0079] 24 guide plate

[0080] 25 Outlet cross-section

[0081] 26 surface

[0082] 27 Guide plate

[0083] 28 Supply line

[0084] 29 containers

[0085] 30 Diameter End

[0086] container

[0087] Outlet cross-section

[0088] Perforated sheet

[0089] container

[0090] Outlet cross-section

[0091] Perforated sheet

[0092] container

[0093] supply line

[0094] Guide plate

[0095] container

[0096] Outlet cross-section

[0097] Guide plate

[0098] surface

[0099] supply line

Claims

Patent claims 1. Method for separating a mixture of a liquid phase and a gas phase, wherein • the mixture is introduced freely through a mixture inlet (9) into a closed container (1 , 29) in which • the liquid phase sinks and is discharged from the container (1 , 29) through a liquid outlet (10) at a bottom end (4) of the container (1 , 29), and • the gas phase rises and is discharged from the container (1, 29) through a gas outlet (12) at a top surface (3) that closes off the container (1, 29), wherein the container (1, 29) is closed except for the mixture inlet (9), the liquid outlet (10) and the gas outlet (12), a supply line (17, 23, 28, 39) extending from the mixture inlet (9) projects into the container (1, 29) and a vertical component of a flow direction of the mixture when introduced into the container (1, 29) is greater than or equal to a horizontal component of the flow direction, characterized in that an open to the container (1, 29) The end (18, 22, 31) of the supply line (17, 23, 28, 39) is widened in a funnel shape and / or is enclosed radially by a tubular, preferably vertically slotted guide plate (24).

2. Method according to the preceding claim, characterized in that the funnel-shaped widened end (18, 22, 31) of the The supply line (17, 23, 28, 39) has an opening angle between 5 and 10°.

3. Method according to one of the preceding claims, characterized in that the mixture is introduced centrally.

4. Method according to one of the aforementioned claims, characterized by perforated plates (37) at the outlet cross-section (36) of the supply line (17, 23, 28, 39).

5. Method according to one of the preceding claims, characterized by one or two flat perforated plates (34) below the outlet cross-section (33) of the supply line (17, 23, 28, 39).

6. Method according to one of the preceding claims, characterized by at least one guide plate (40) standing vertically in the supply line (39).

7. Method according to one of the preceding claims, characterized by at least one guide plate (43) positioned vertically in the mixture above the outlet cross-section (42) of the supply line (45).

8. Method according to one of the preceding claims, characterized in that the mixture flows freely into the container (1 , 29) at a flow velocity of at most 2 m / s, preferably at less than 1 m / s.

9. Method according to one of the preceding claims, characterized in that the mixture is placed below, preferably between 30 mm and 200 mm, in particular between 100 mm and 200 mm, alternatively up to 350 mm below a surface (20) of the liquid phase into the container (1 , 29).

10. Method according to one of the preceding claims, characterized in that the supply line within the container (29) is branched to several ends (31) and the mixture is distributed to the ends (31).

11. Method according to one of the preceding claims, characterized in that a volume enclosed by the liquid phase and the top surface (3) is less than 0.1 m³ 3 is.

12. Method according to one of the preceding claims, characterized in that the gas phase consists of molecular hydrogen and / or oxygen saturated with water vapor.

13. Method according to one of the preceding claims, characterized in that the container (1 , 29) is under an internal pressure of 1 to 200 bar.

14. Method according to one of the preceding claims, characterized in that the liquid phase consists of distilled water or an aqueous potassium or sodium hydroxide solution.

15. Method according to the preceding claim, characterized in that the mixture is produced in an electrolysis and the liquid phase is returned to the electrolysis.

16. Method according to one of the preceding claims, characterized in that the container (1 , 29) is filled on the underside (4) with a structured packing or a bulk (19) of packing materials.

17. Method according to one of the preceding claims, characterized in that the gas phase is dried and / or filtered after being removed from the container (1 , 29).

Images