WO2010136347A1

WO2010136347A1 - Microfluidic separator for liquid mixtures

Info

Publication number: WO2010136347A1
Application number: PCT/EP2010/056709
Authority: WO
Inventors: Hans-Richard Kretschmer; Oliver Lade
Original assignee: Siemens Aktiengesellschaft
Priority date: 2009-05-29
Filing date: 2010-05-17
Publication date: 2010-12-02
Also published as: DE102009024801A1

Abstract

The invention relates to a microfluidic separator for liquid mixtures (31) having different boiling points. According to the invention, a head (17) and a bottom (14) are formed in a separating channel (11) for the liquid mixture, and a temperature control device, consisting of temperature control elements (34) that preferably can be actuated individually, is provided in a thermally conductive manner over the entire length of the separating channel. It is thus advantageously possible to rectify the liquid mixture by way of the separator, wherein individual fractions of the liquid mixture (31) can be withdrawn by way of the outlets (33). This allows for a continuous operation of the separator while simultaneously achieving highly efficient separation.

Description

description

Microfluidic separator for liquid mixtures

The invention relates to a microfluidic separation device for liquid mixtures of liquids with different boiling point. This has an inlet for the liquid mixture and outlets for the separated substances, which are connected by a channel system. In addition, a tempering device is provided on the separating device, which is thermally conductively connected to the channel system.

A microfluidic separation device of the type described above is known for example from the abstract to JP 2007-136280 A. This separator operates on the principle of distillation. It has an inlet for the liquid mixture, which is separated in an elongated channel such that the more volatile substance is evaporated by heating the liquid mixture. This can then be taken from a dedicated outlet of the separator, while the less volatile liquid remains in the system and can be removed through another outlet. The microfluidic separator is made of a layered component of several layers.

Another method of separating liquid mixtures is described in US 5,441,719. In contrast to distillation, this process, referred to as rectification, can be operated continuously, the separation effect for the components contained in the liquid mixture being many times higher than for distillation. In this case it is necessary, the contact surface between the vapor and liquid phase by suitable internals such as bubble trays, Packages or other fillers in a separation channel to increase in a suitable manner. These internals stand as flow obstacles in the rectification column thus formed and thereby improve the separation of the individual components of the liquid mixture. At least one more volatile component of the liquid mixture then collects at the upper end of the separation channel, referred to as the head, and a less volatile component at the lower end of the separation channel, referred to as the sump.

In micro-technology, it is known from DE 101 62 801 A1 that structural measures to increase the interface can also be carried out in reactions between gases and liquids in the microreactor.

The object of the invention is to provide a microfluidic separation device with which a separation of liquid mixtures comparatively efficient, d. H. in a comparatively short time and with a comparatively high throughput.

This object is achieved according to the invention with the microfluidic separation device specified at the outset in that the channel system has a separation channel whose end regions forming a head and a sump for rectification

Seen in terms of gravity are at different height levels and that the tempering over the entire length of the separation channel is thermally conductively connected thereto. As a result, according to the invention, two prerequisites are fulfilled, so that the separation channel can permit a process of rectification at all. For the separation channel to be able to form a head and a sump, it is necessary for the end regions to be at different height levels. Only in this way can it be ensured that the more volatile substances of the liquid mixture move towards the head and accumulate there, while the less volatile substances flow into the sump. This gravity must be exploited. Another essential prerequisite for the successful use of the rectification process is that vapor and liquid are as close as possible to the thermodynamic equilibrium in the entire separation channel. In ordinary rectification columns (for example according to US Pat. No. 5,441,719), this is achieved by the design conditions in the rectification column. A suitable column surface is provided in addition to the column outer wall, the system being capable of achieving the desired equilibrium with time in operation and subsequently operating continuously. However, in microfluidic channel structures, other conditions prevail with regard to the surface-volume ratio of the channel, so that the achievement of a thermodynamic equilibrium can only be achieved on condition that the separation channel is specifically tempered over the entire length in order to set the required temperature profile in the separation channel. Therefore, the tempering must be present over the entire length of the separation channel, which must be dimensioned so that the present liquid mixture can be effectively separated. This means that, as already explained, the thermodynamic equilibrium at the interface between the liquid and gaseous phase must at least largely be maintained within the entire separation channel.

If the abovementioned requirements are met, the microfluidic separation device can advantageously be used to effect a comparatively efficient separation of the components of the liquid mixture. In particular, a continuous mode of operation of the separating device is possible, whereby can be increased enormously by the mass flow rate of the microfluidic separation device according to the invention in relation to their size. Advantageously, it is also possible to separate a plurality of components of a liquid mixture in a single separation device, which in particular reduces the complexity of components (a microfluidic rectification column instead of a plurality of distillation units), which also enables more economical solutions.

According to an advantageous embodiment of the invention it is provided that the tempering device has individual tempering, which are distributed over the length of the separation channel and are individually controllable. In view of the above-explained need to set as far as possible thermodynamic equilibrium in the entire separation channel, this embodiment has the advantage that the microfluidic separation device can be optimally adapted to different liquid mixtures to be separated. With the help of individually controllable tempering can be seen from the sump to the head of the separation channel set any temperature profile, which is not linear or dependent on the conditions of the separator (geometry, wall thickness, heat capacity) dependent. Depending on requirements, it can be heated with heating elements over the length of the separation channel and cooled with cooling elements. in the

Sump of the separation channel is always heated to vaporize the liquid located there, and in the head of the separation channel is cooled to liquefy the gaseous phase located there.

With regard to the individual tempering, it is particularly advantageous if temperature sensors over the entire length of the separation channel are thermally conductively connected thereto. In this way, it is advantageous to monitor the Temperature profile over the length of the separation channel possible. With the individually controllable tempering can then be responded to a possible shift of the temperature profile and the optimum temperature profile by appropriate control of the tempering be forced. This ensures that the microfluidic separation device always operates at the optimum operating point.

It is particularly advantageous if in each case one temperature sensor is provided for each tempering element, which is thermally conductively connected to the separation channel in the thermal influence region of the respective tempering element. In this case, it is particularly easy to establish a relation, on the one hand, between the temperature in the separating channel present at a tempering element and, on the other hand, the heating or cooling power introduced into the separating channel by the tempering element. On a deviation of this range of the separation channel of the target temperature can then be reacted in a suitable manner by controlling the tempering. This is particularly easy if the associated ones

Temperature control elements and temperature sensors are integrated in control circuits. This has the advantage that a particularly rapid reaction of the temperature control to the detected sensor signals is possible.

According to a particularly advantageous embodiment of the separating device according to the invention it is provided that the temperature control are designed as Peltier elements. This has the advantage that both a heating and a cooling of the separation channel can be carried out with the tempering element. The cost of components can thus advantageously be kept low, without sacrificing a far-reaching control possibility, ie both heating and cooling. It is also advantageous if flow obstacles for the liquid mixture are provided in the separation channel. These obstacles increase, as already explained, the inner surface in the separation channel, which also increases the interface between the liquid and the gaseous phase. As a result, the efficiency of the separation can be further increased, whereby the optimum operating point can always be set by the possibility of being able to set the desired temperature at any point of the separation channel. Thus, it is not necessary to re-optimize the inner surface of the separation channel for each liquid mixture.

It is advantageous if the channel structure is embodied by a multilayer structure consisting of individual layers. The channels are formed by depressions in the respective surfaces of the layers and through holes connecting through these recesses. This is advantageously a structure with which the channel structure can be manufactured with high precision. Due to the multi-layer structure, even complex channel structures can be constructed with simple manufacturing steps. In particular, an evaporator layer having a channel structure for evaporating the liquid mixture, a separating layer containing the separating channel and a collecting layer having at least one channel structure for condensing a separated substance can advantageously be provided. These layers are connected to one another in a suitable manner, the fluidic connection permitting a transfer of the liquid mixture into the individual subregions of the separating device. Due to the modular structure, it is advantageously possible to provide a modular system for microfluidic separation devices. For example, several evaporators can be stored, with the most favorable ones for the intended application. is selected and then joined together with the Verdampfanläge and the collecting layer.

It is also advantageous if the layers are aligned vertically in the intended operating position of the separator. This allows a production of the separation channel in the surface of one of the layers, which is then vertically aligned in the operating position, ie the orientation of the separator during operation.

The tempering is advantageously mounted on the back and / or the front of the separator. Here is a relatively large area available, which is easily accessible for the production of tempering. In addition, maintenance and a possible replacement of defective temperature control is simplified.

In order to further increase the efficiency of the rectification process, it can be advantageously provided that a condensate trap with a cooler and a return channel for the condensate obtained is provided at the top, which opens into the separation channel. The liquid mixture collected at the head in the condensate trap can then be fed again to the rectification process, since this is normally not pure in real rectification processes. However, by adding it back to the rectification process, it does not have to be discarded, but is further split into the continuous rectification process.

It is also advantageous if more than two outlets for the separated substances are present. This can be separated with the separation device and liquid mixtures, which consist of more than two components. For each substance to be separated an outlet must be provided, this one must be in the appropriate temperature range for the substance to be separated. Therefore, it is particularly advantageous if in each case a tempering is provided for each outlet. This can be achieved by the forced setting of a temperature profile at each of the

Outlets the required temperature for the substance to be separated there is present. This again makes the advantage of the microfluidic separation clear, since the geometry of the separation channel does not have to be adapted for a successful performance of the separation process. It is only necessary to set a suitable temperature profile.

Further details of the invention are described below with reference to the drawing. Identical or corresponding drawing elements are each provided with the same reference numerals and will only be explained several times as far as there are differences between the individual figures. Show it

FIG. 1 shows a first exemplary embodiment of the separating device according to the invention, it being possible to see a plan view of the position of the multilayer component containing the separating channel,

Figure 2 shows a section through the assembled separation device according to Figure 1 and

Figure 3 shows another embodiment of a separating device according to the invention in section.

FIG. 1 shows a separating device, wherein it has a separating channel 11. This has an inlet 12 for a liquid mixture which passes in the separation channel flow obstacles 13 and collected in a sump 14 becomes. In the separation channel 11 a more volatile substance is separated and leaves through a first outlet 15, the separator. In the sump 14, the less volatile liquid collects and can be removed through a second outlet 16 of the separator. A portion of the liquid mixture evaporates completely and collects in a head 17 of the separation channel 11, where the liquid mixture condenses and can be fed through a return channel 18 to the separation channel 11 again.

FIG. 2 shows, in addition to the layer 19 shown in FIG. 1, a second layer 20, which is similar to a cover on the separating channel 11 produced in the surface of the layer 19 sitting. In the position 20 is also the head 17, the return channel 18, the inlet 12 and the outlets 15, 16 are formed (therefore, these elements are shown in Figure 1 only in dashed lines). The outlets 15, 16 and the inlet 12 are realized by pipe sockets 21, which are fitted in suitable through-holes of the layer 20. These can serve as connections for hoses, for example.

On a side surface 22 of the separating device, which is formed by the outer side of the layer 19, a tempering device 23 is formed. This consists of a Peltier element 24 on the head 17 and a heating coil 25 in the region of the remaining separation channel 11 including the sump 14. The distances between the turns of the heating coil are closest in the region of the sump 14, since evaporation of the liquid mixture takes place here and therefore the largest heat input is required. On the other hand, the separation channel must be less heated in relation to this, so the distance between the turns in this area increases continuously from bottom to top. With the heating coil 25 can be produce an approximately linear temperature profile in the separation channel, wherein the linear slope of the temperature profile can be adjusted by the controllable heat output to the heating coil. Likewise, the cooling performance of the Peltier element 24 can be controlled.

The separating device according to FIG. 3 has an evaporator layer 26, a separating layer 27, an intermediate layer 28 covering the separating channel 11 and a collecting layer 29, which are stacked on top of one another in the listed sequence.

The evaporator layer has the inlet 12 and also a cavity 30, which serves as a storage space for the liquid mixture to be evaporated. In addition, a heating coil 25 is provided on the side surface of the separating device formed by the evaporator layer 26, with which heat energy can be introduced into the liquid mixture 31, which collects in the cavity 30. The vaporizing liquid mixture passes through a passage 32a into the separation channel formed in the separation layer 27. Here are as with the

Separating device according to Figure 1 flow obstacles 13 is provided. In addition, the sump 14 of the separation channel 11 is connected to the cavity 30 via a passage 32b. The head 17 of the separation channel is connected via a passage 32 c to a condensate trap 33, which is realized by the collecting layer 29. The passage 32c is located in the intermediate layer which separates the separation channel 11 in the separation layer 27 from the condensate trap 33 in the collecting layer 29. On the side surface of the separating device formed by the collecting layer 29, a Peltier element 24 is provided as a cooler, whereby the formation of the condensate in the condensate trap 33 is promoted. The return channel 18 is connected via a passage 32d to the separation channel 11, so that the collected condensate can be fed back to the rectification process. The intermediate layer 32 is formed of a good thermal conductivity material, such as aluminum nitride, and has four outlets 33 in the region of the separation channel 11, can be removed through the individual substances of the liquid mixture of the separator. Each of these outlets 33 is provided with an annular Peltier element 34, wherein these Peltier elements are individually controllable. As a result, a temperature profile desired for the present rectification task can be set in the separation channel 11, which does not necessarily have to be linear. In order to adjust the temperature profile and also to keep it during the course of the rectification, a temperature sensor 35 is arranged in the separating layer in the head 17, in the sump 14 and in the region of each outlet 23, their electrical contacting being effected via printed conductors (not shown) the side surface 36 of the separating layer 27 are formed.

The geometrical relationships of the separating device shown in Figure 3 need not correspond to reality. In particular, the distances between the individual outlets 33 can be chosen much larger, in order to ensure a more accurate adjustment of the desired temperature profile in the separation channel. Also, the flow obstacles 13 can be assigned directly to the individual outlets 33, thus in this

Areas of efficient collection of each condensing in the area of the outlet substance of the liquid mixture is possible.

Claims

claims

1. Microfluidic separation device for liquid mixtures of liquids with different boiling points, exhibiting

• an inlet (12) for the liquid mixture and outlets (15, 16) for the separated substances, which are connected by a channel system and

A tempering device (23), which is thermally conductively connected to the duct system, that is to say that

The channel system has a separation channel (11) whose end regions (14), which form a head (17) and a sump (14) for rectification, lie at different height levels in the direction of gravity and

• the temperature control device (23) over the entire length of the separation channel (11) is thermally conductively connected thereto.

2. Separating device according to claim 1, characterized in that the tempering device (11) individual tempering (34), which are distributed over the length of the separation channel (11) and are individually controllable.

3. Separating device according to claim 2, characterized in that temperature sensors (35) over the entire length of the separation channel (11) are thermally conductively connected thereto.

4. Separating device according to claim 2, characterized a temperature sensor (35), which is thermally conductively connected to the separation channel (11) in the thermal influence region of the respective tempering element (34), is provided for each tempering element (34).

5. Separating device according to claim 4, characterized in that the mutually associated tempering elements (34) and temperature sensors (35) are integrated into control loops.

6. Separating device according to one of the preceding claims, characterized in that the tempering elements (34) are designed as Peltier elements.

7. Separating device according to one of the preceding claims, characterized in that flow obstacles (13) for the liquid mixture are provided in the separation channel (11).

8. Separating device according to one of the preceding claims, characterized in that the channel structure by a multilayer structure consisting of individual layers (19, 20) is executed, wherein the channels formed by depressions in the respective surfaces of the layers and through these recesses connecting through holes are.

9. Separating device according to claim 9, characterized in that an evaporator layer (26) having a channel structure for vaporizing the liquid mixture, a separation channel (11) containing separating layer (27) and a collecting layer (29) at least one channel structure for condensing a separated substance are provided.

10. Tennis device according to one of claims 8 or 9, characterized in that the layers (19, 20) are vertically aligned in the intended operating position of the separating device.

11. Separating device according to one of the preceding claims, characterized in that the tempering device (23) on the back and / or the front of the separating device are mounted.

12. Separating device according to claim 1, wherein a condensate trap (33) with a cooler and a return channel (18) for the obtained condensate is provided at the head (17), which opens into the separating channel (11).

13. Separating device according to one of the preceding claims, characterized in that more than two outlets (15, 16) are provided for the separated substances.

14. Separating device according to claim 13, characterized in that in each case one tempering element (34) is provided for each outlet (15, 15).

16) is provided.