Abstract:
The invention relates to a line element for handling fluids, in particular for digestion or for synthesis of substances in chemical process engineering, said line element comprising at least one temperature-resistant and pressure-resistant support element ( 15 ) that has a first interior in which an inner line ( 14 ) made of a plastic material resistant to chemicals is arranged, at least one free end of the line element being provided with a connector element ( 16 ) that has a second interior into which the inner line ( 14 ) extends, the line element according to the invention being characterized in that the support element ( 15 ) and/or the connector element ( 16 ) has at least one relief opening ( 25, 26 ) which ensures a communicating link between the first interior of the support element ( 15 ), or second interior of the connector element ( 16 ), and the environment.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to a line element for handling fluids for high-pressure and high-temperature applications with high chemical resistance, in particular for digestion or for synthesis of substances in chemical process engineering, the line element comprising at least one temperature-resistant and pressure-resistant support element that has a first interior in which an inner line made of a plastic material resistant to chemicals is arranged, at least one free end of the line element being provided with a connector element that has a second interior into which the inner line extends.  
       BACKGROUND OF THE INVENTION  
       [0002]     Line elements are known in chemical process engineering and are used, for example, for transporting a wide variety of fluids, in particular liquids, gases, solids and mixtures thereof, between storage vessels, collection vessels, reactors, cooling or heating elements, etc. These line elements can also be used for carrying out chemical or physical processes with the fluids contained in them, that is to say the line elements can also serve as reaction chambers or analysis chambers, for example in continuous-flow or stopped-flow processes. Chemical processes often involve aggressive substances, so that the line elements used in process engineering have to be resistant to the chemicals used in the respective processes. Chemical processes of this kind are also often carried out at high temperatures and/or high pressures. There is therefore a need for line elements for chemical process engineering which are resistant to a large number of aggressive substances and which can be used at temperatures of 300° C. and more and at pressures of several hundred bar.  
         [0003]     A wide variety of line systems for carrying out analysis and synthesis processes at a laboratory scale are described in the prior art. For example, documents U.S. Pat. No. 5,215,715 and U.S. Pat. No. 5,314,664 disclose devices for carrying out chemical reactions by means of microwave heating, in which tube lines are used that are made of fluoroplastics resistant to chemicals. However, plastic tubes of this kind can be used only at very low pressures and low temperatures, well below the temperature and pressure ranges cited above.  
         [0004]     U.S. Pat. No. 5,672,316 discloses a microwave-heatable pressure reactor into which a tube element made of a fluoroplastic extends. The interior of the reactor is pressurized by an external gas pressure supply, such that a pressure equilibrium essentially exists between the interior and the tube opening into this interior. The plastic tube system can therefore be used at temperatures of up to 260° C. and at pressures of up to 100 bar. However, the way in which the tube system is supported via the internal pressure in the reactor is complicated because of the required external gas pressure source, and it can accordingly be used only for relatively short line elements. In addition, the application of this technology is limited to processes in which the line element opens with its free end into the interior of the reactor.  
         [0005]     European Patent EP-B-0 750 746 describes a device for handling liquids for analytical purposes, in which the lines that are used consist of platinum/iridium capillaries. However, capillaries of this kind are very expensive, and they can also be attacked by substances such as hot aqua regia or by phosphorus corrosion in the incineration of organic substances. Moreover, platinum/iridium capillaries are available only up to a length of 1.5 m. As alternatives to platinum/iridium capillaries, EP-B-0 750 746 also mentions tubes made of polytetrafluoroethylene (PTFE) that are encased by a steel cloth or a high-pressure capillary of special steel. However, in order to attach such lines to the components that are to be connected, metal flanges are used which in many applications are disadvantageous because of their limited resistance to chemicals. Moreover, there are no commercially available lines with which it is possible to obtain capillaries having small internal diameters of less than 3 mm. Moreover, when using inner lines made of fluoroplastics, substances may diffuse through the jacket of the inner tube and into the area between support jacket and inner tube at high temperatures and pressures. This can lead to a collapse of the inner tube, with the result that the tube is partly or even completely occluded.  
         [0006]     Therefore, the technical problem addressed by the invention is that of making available a line element for handling fluids which is temperature-resistant and pressure-resistant and is also resistant to a large number of chemicals and can be produced inexpensively in large lengths. The line element according to the invention should in particular be able to be produced as a capillary line with an internal diameter of less than 3 mm.  
         [0007]     This technical problem is solved by the line element according to Claim 1. Advantageous developments of the line element according to the invention are the subject of the dependent claims.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention accordingly relates to a line element for handling fluids which is of the type described in the introduction and which is characterized in that the support element and/or the connector element has at least one relief opening which ensures a communicating link between the first interior of the support element, or second interior of the connector element), and the environment.  
         [0009]     By way of the relief opening provided according to the invention, substances diffusing through the inner line can escape outward from the interspace between the inner line and the support element, with the result that a collapse of the inner line is effectively avoided. Any desired number and size of the relief openings can be chosen, as long as the support function of the support element is not impaired. If so required, the relief openings can also be used for flushing the support element. The line element according to the invention can be produced particularly inexpensively, even in quite considerable lengths, for example of several metres, whereas platinum/iridium capillaries are commercially available only up to a length of 1.5 m. The inner line can be formed on the inside wall of the support element by injection moulding, for example. However, it is particularly cost-effective to mechanically insert a plastic tube serving as inner line into the support element, for example by pushing the tube in, or by blowing the tube in by means of a gas or a liquid. The tube in this case has an external diameter slightly smaller than the internal diameter of the interior of the support element. On the initial application of pressure and/or temperature, the inner line then moulds itself onto the inside wall of the support element. Depending on the material used, the inner line can mould itself permanently onto the support element or can detach itself from the support element again after the pressure has lowered. In the latter case, especially if the inner line has a certain elasticity, this moulding takes place each time after application of the operating pressure. For maintenance work, for example for cleaning purposes, the inner tube can again be removed from the support element, and afterwards reinserted again, either pneumatically, hydraulically or, if appropriate, by mechanical pulling or pressing.  
         [0010]     According to one embodiment of the invention, at least the connector element has a relief opening. Particularly in the case of fairly long line elements, one or more relief openings can also be formed in the support element.  
         [0011]     In known plastic tube systems, a problem arises in providing the tube ends with suitable connector elements that ensure a reliable join between the connector element and the inner line under the conditions in question, in particular at temperatures of up to 300° C. and at pressures of several hundred bar. Proposed solutions involving adhesively bonded connector elements have proven disadvantageous in practice, because of the poor adherence of the fluoroplastics that are preferably used on account of their resistance to chemicals. In purely mechanical clamp connections, the problem is that, on the one hand, a firm and leaktight connection has to be ensured also at high pressures, and, on the other hand, the inner line should not be clamped shut. To solve this problem, the present invention proposes that the free end of the line element is sealed by means of at least one preferably conical clamp. A particular advantage of the solution according to the invention is that only a primary seal is needed, since, when the pressure in the system increases, the inner line is pressed more firmly onto the sealing cone and therefore remains leaktight. The mechanical fixing of the inner line is in this case provided for by the connector element in conjunction with the mechanically securely connected support element serving as support jacket, via static friction between inner line and the support element. In addition, a light clamping can be provided. The inner line is thus held securely even at very high pressures and upon heating of the system, without any danger of constriction by a sealing and retaining cone. The mechanical fixing of the support element in the connector element can be effected for example by clamping sleeves, threads or adhesive bonds.  
         [0012]     According to a first variant, the connector element has a connector piece which can interact with complementary connector bushings provided on the components to which the line element according to the invention is to be attached. For example, the connector piece can be designed as a screwed connection with a conical sealing surface which can interact with a complementary sealing surface of a component that is to be connected to the line element. According to one embodiment of the invention, the inner line extends into the connector piece and, when screwed into the corresponding mating piece, is compressed such that the connector piece is sealed against the inner line only upon screwing.  
         [0013]     According to a second variant, the support element comprises at least two support tube portions which are connected releasably to one another via a connector element designed as joining element. Here too, the mechanical fixing of the support element in the connector element can be effected via clamping sleeves, threads or adhesive bonds.  
         [0014]     In both variants, the construction of the connector element ensures that the tube cannot emerge from the connector piece at high pressures or be squeezed together by liquid that diffuses out.  
         [0015]     The inventive design of the connector elements permits a considerable lengthening of the working life of the line element. If the line has to be made shorter, for example because of ageing or soiling in the connector pieces, it is not necessary to exchange the entire line element. After dismantling of the support line, all that needs to be done is to cut off the soiled end portion of the line element. A shorter support tube or the shortened support tube is then fitted over the old inner line.  
         [0016]     According to an advantageous embodiment of the line element according to the invention, the inner line is made of a fluoroplastic resistant to chemicals, for example of polytetrafluoroethylene (PTFE), polytetrafluoroethylene compounds, that is to say PTFE with suitable fillers such as glass fibres, charcoal, bronze, molybdenum disulphide or special steel, perfluoroalkoxy copolymers (PFA), polychloro-trifluoroethylene or polyvinylidene fluoride. In addition, however, the inner line can also be made of high-performance plastics such as polyether ether ketone (PEEK), polyoxymethylene or polyamide.  
         [0017]     Advantageously, the support element comprises a support tube which surrounds the inner line and which is preferably made of metal, for example titanium or special steel, a ceramic material or a temperature-resistant and pressure-resistant plastic, for example polyether ether ketone. The support tube can in particular be designed as a flexible metal wire mesh or metal wire cloth. Particularly as a wire mesh, the support tube can be designed such that, on the one hand, the necessary support function is ensured and, on the other hand, the mesh already provides the required relief openings for release of the substances diffused through the inner line.  
         [0018]     The support element can also comprise a support body which surrounds the inner line and which is made of a cured or dried moulding compound. The production of the support body by means of a curing or drying moulding compound permits particularly good flexibility in the shaping of the support body. The support element can also be made up of two or more solid elements which form a hollow space for receiving the inner tube and which are resistant, at least for a certain duration, to the reagents that are used. Optionally, the support body or the multi-part support element can also be surrounded by a housing, preferably a metal or plastic housing, which further increases the stability of the arrangement.  
         [0019]     The internal diameter of the inner line of the line element according to the invention preferably lies in the range of 0.5 to 5 mm, and particularly preferably in the range of 1 to 3 mm.  
         [0020]     The line element according to the invention can also be temperature-controlled. For example, the support element can be heated by electric resistance heating or by inductive or resistive heating to temperatures of over 300° C. By mounting Peltier elements in or on the support element, the latter can also be cooled to temperatures far below 0° C. Of course, it is also possible to lead the line element through a temperature-control medium which is heated or cooled to the desired temperature via a secondary circuit.  
         [0021]     In addition to its use purely for transporting substances, the line element according to the invention can also be used as a reactor for chemical or physical processes. The invention accordingly also relates to the use of the described line element for physical and/or chemical treating or influencing of fluids contained in the inner line of the line element. The corresponding physical and/or chemical processes can be realized, for example, as continuous-flow processes or as stopped-flow processes. For example, the line element according to the invention or segments of several line elements according to the invention can be divided into zones in which energy is delivered or removed, for example by cooling, heating or irradiating. The line system according to the invention can also be used for mixing and, if appropriate, subsequent reaction of different substances, and the materials involved can also be present in different states of aggregation. Typical areas of application of the line element according to the invention also lie in chemical analysis, for example continuous-flow digestion, high-pressure chromatography or gas chromatography. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The invention is explained in more detail below with reference to the illustrative embodiments depicted in the attached drawings, in which:  
         [0023]      FIG. 1  shows a schematic representation of an analysis device in which a first embodiment of the line element according to the invention serves as a connecting line between two components of the device;  
         [0024]      FIG. 2  shows a detailed view of one end of the line element from  FIG. 1 , with a connector element for connection to one of the components of the device;  
         [0025]      FIG. 3  shows a further embodiment of the line element from  FIGS. 1 and 2  with a modified support element;  
         [0026]      FIG. 4  shows a modified embodiment of the line element from  FIG. 3  with a further variant of the support element;  
         [0027]      FIG. 5  shows a further embodiment of the line element according to the invention from  FIG. 2 , in which a connector element is designed for attachment to a second line element; and  
         [0028]      FIG. 6  shows an example of a device for chemical reaction in which the individual segments of the device are connected by line elements according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]      FIG. 1  is a schematic representation of a device intended to serve as an example of the use of the line element according to the invention as a connecting line between two components of the device. The device, designated overall by reference number  10 , is made up of a first component  11 , which for example can be a sample source or a device for preparing a sample, and of a second component  12 , which for example can be a detection means, for instance a gas chromatograph. The two components  11 ,  12  are connected to one another via a line element according to the invention, designated overall by reference number  13 , so that fluids can be transferred from component  11  to component  12 . The line element  13  according to the invention comprises an inner line  14 , which is indicated only schematically in  FIG. 1  and which is made, for example, of a fluoroplastic such as polytetrafluoroethylene and is surrounded by a temperature-resistant and pressure-resistant support tube  15 . In the example in  FIG. 1 , both the inner line  14  and the support tube  15  are flexible. The support tube  15  can, for example, be configured as a metal wire mesh. However, the support tube  15  can also be a rigid tube, for example a tube made of special steel or titanium. At its two ends, the line element  13  according to the invention has connector elements  16 ,  17  for connecting the line element  13  to corresponding connector bushings  18 ,  19  provided on the components  11 ,  12 .  
         [0030]     The left-hand end of the connecting line  13  from  FIG. 1 , with the connector element  16 , is shown in greater detail in  FIG. 2 . For the sake of clarity, the connector element  16  in  FIG. 2  is shown in the free state in which it is therefore not located in the corresponding connector bushing  18  of the component  11  from  FIG. 1 . In the example shown, the connector element  16  is in several parts and is made up of a connector  20 , which is shaped such that it can be fitted tightly into the corresponding connector bushing  18  (cf.  FIG. 1 ) of the component that is to be connected. The connector elements  16 ,  17  according to the invention have a cylindrical thread area  21  and a cone-shaped end area  22 . The cone  22  of the connector  20  is pressed together when screwed into the part  18  and forms a seal against the polytetrafluoroethylene tube  14 . When high pressures arise in conventional connectors, there is a danger of the tube slipping out of the connector; this can no longer be compensated for by tightening the connector, because otherwise the tube would be squeezed off in the area of the cone. In the connector element  16  according to the invention, however, static friction of the inner tube  14  in the connector  20  and in the support tube  15  is able to prevent it from slipping axially out of the sealing cone  22 . For this purpose, the support tube  15  is fixed securely in the connector  20  by means of a clamping ring  24  and the hollow screw  23 . The clamping ring consists of a metal ring  24   a  and of a sealing cone  24   b . Upon assembly, the hollow screw  23  presses the metal ring  24   a  onto the sealing cone  24   b  and the latter is thereby squeezed permanently onto the support tube  15 . However, because of the mechanical stability of the support tube  15 , there is no appreciable constricting of the tube  15  and of the inner tube  14  extending therein. The static friction resulting from the inner tube  14  moulding onto the support tube  15 , which is also no longer movable after the clamping, avoids any slipping movement of the inner tube relative to the support tube. All of the components of the connector element  16  can be produced free of metal, for example from polyether ether ketone (PEEK). The clamping ring  24  in particular can also be made of metal, for example titanium, or, since the clamping ring does not come into contact with aggressive substances, of special steel. A relief opening  25 , which is designed as a drainage bore in the example shown, is formed in the connector element according to the invention. Substances diffusing through the PTFE tube  14  can escape outwards through the relief opening  25  into the environment, with the result that no overpressure arises between the inner tube  14  and the support tube  15 , which overpressure would otherwise lead to collapse of the inner tube  14 . For longer line elements, as shown schematically in  FIG. 2 , further relief openings  26  can also be provided in the support tube  15 .  
         [0031]      FIG. 3  shows a variant of the line element according to the invention in which the support element consists of a mechanically stable support body  30 , at least in a partial area of the line. In the example in  FIG. 3 , the support body consists of two connectable parts  31 ,  32 , but it can also comprise more than two parts. Such support bodies can be used in a wide variety of ways to physically influence the fluids transported in the inner tube  14 . For example, the support body  30  can serve as a heat exchanger for controlling the temperature of the transported fluids. For this purpose, the support body itself can be temperature-controlled via a heat exchange medium, for example water, circulating in a secondary circuit (not shown). In the case of metal support bodies, it is also possible to heat the support body by inductive or resistive direct heating or to cool it via Peltier elements integrated into the support structure or secured on its outside surface. If the fluids transported in the inner tube  14  are to be heated via microwave heating (also not shown), the support body is preferably made of a microwave-transparent material, for example a plastic or ceramic material. However, in the case of microwave heating, the support body  30  can also contain microwave-absorbing substances, for example soot particles, such that the whole support body serves as a heating bath.  
         [0032]      FIG. 4  shows a variant of the support body  30  from  FIG. 3 . The support body  33  shown in  FIG. 4  is made in one piece and is shaped from a curing casting compound. Depending on the pressure that the support body has to withstand, it can additionally be provided with a housing  34  that increases the stability of the support body.  
         [0033]     Also in the variants shown in  FIGS. 3 and 4  with support body, a part of the support element is advantageously designed as a support tube  15  protruding out of the support body  30  or  33 , its ends again being provided with the connector elements  16 ,  17  already mentioned in connection with  FIGS. 1 and 2 .  
         [0034]      FIG. 5  shows a variant of the line element from  FIG. 2  in which one end of the line element  13  is provided with the connector element  16  already described in  FIG. 2 . In this variant, the support tube  15  consists of a first support tube  15   a  and of a second support tube  15   b  which are connected to one another by a connector element  40 . The connector element  40  is designed as a cylindrical connector  41 , into whose end openings  42 ,  43  the ends of the support tubes  15   a  and  15   b , respectively, extend. The two ends of the support tubes  15   a  and  15   b  are once again fixed in the cylindrical connector  41  by hollow screws  23  and two-part clamping rings  24 . Like the conical connector  20 , the cylindrical connector  41  can also have a relief opening  27 . In the cylindrical connector  41 , the two support tubes abut one another in the contact area  44 . The contact area  44  should as far as possible be gap-free in order not to impair the support action. In this area, however, no sealing of the inner tube  14  is needed. Usually, a slight leakage is even desired in order to ensure a pressure relief of the diffusing substances.  
         [0035]     If the inner tube  14  were to become blocked at its end area  45  as a result of soiling or mechanical defects, it is possible, in the variant in  FIG. 5 , to cut the tube end  45  off to the required length and either to shorten the support tube  15   b  too or replace it by a shorter support tube  15   c . The line element  13  can thus continue to be used. In the event of blockage of the inner line, it is therefore not necessary to dispose of the entire line element  13 .  
         [0036]      FIG. 6  shows a device  50  for carrying out high-temperature and high-pressure reactions in which use is made of line elements according to the invention which, in the device shown, are used as reactor  51  and cooler  52  in order to carry out reactions with different starting materials  53 ,  54  with different substances (here a first acid  55  and a second acid  56 ).  
         [0037]     The reactor  51  and the cooler  52  can, for example, be designed in accordance with the variants shown in  FIGS. 3 and 4  and can be provided with the heating or cooling means explained in connection with  FIGS. 3 and 4 .  
         [0038]     The device  50  works as follows: To prepare for the reactions, pumps  57 ,  58  and multi-way valves  59 ,  60 ,  61 ,  62  fill all the lines of the system with a carrier liquid  63 , which at the same time can also be reagent or substrate. At the same time an HPLC pump  64  builds up the system pressure in the reactor  51  and in the cooler  52  counter to the resistance of the restrictor  65 . The restrictor  65  can either be a thin capillary or a pressure control valve. After the system pressure has been built up, the reactor  51  is heated to the desired operating temperature. As soon as the operating temperature is reached, the pump  57  suctions one or more starting materials  53 ,  54  via the valves  59  and  61 , while the pump  58  suctions one or more reagents  55 ,  56  via the valves  60  and  62 . The starting materials and the reagents are then metered through a T-piece  66  and valve  67  into a sample loop  68  and mixed. Alternatively, the sample loop  68  can be filled directly in the bypass from a process or by any desired other filling method. The valve  67  is then switched so that the content of the sample loop  68  can be introduced into the reaction system  51 ,  52 . After the fluids have been heated and the desired reactions have been carried out in the reactor  51 , and after subsequent cooling in the cooler  52 , the end product can be collected via a controllable valve  69  into different vessels  70  or can be delivered directly to a measurement device (not shown), for example via a line  71  branching off from the valve.  
         [0039]      FIG. 6  also shows a collecting vessel  72  in which, before and after the filling of the sample loop  68 , irrigation liquids for cleaning the lines and/or sample and reagent solutions can be collected during filling of the lines. A pressure gauge  74  is also shown with which the pressure in the line  73  between HPLC pump  64  and restrictor  65  can be monitored. The temperature in the reactor  51  and in the cooler  52  is monitored by means of temperature probes  75 ,  76 .  
         [0040]     Several high-pressure reaction systems of this kind can be arranged in parallel or in series, in order to increase the throughput or to execute different treatment steps one after another.