Abstract:
A filtering apparatus is described which is designed to reduce or completely eliminate dripping losses and in which fitting or exchanging filtering elements can be carried out in a simpler manner. The filtering apparatus is characterized in that there is provided, between the end plate and the pressure plate, at least one filter carriage mounted for displacement on the cross beams and having a compression-proof outer wall and exhibiting at least one chamber for the accommodation of at least one filter module composed of filtering elements.

Description:
[0001]     This application is a continuation application of pending international application No. PCT/EP03/03743, filed Apr. 10, 2003, which is incorporated herein by reference in its entirety and for all purposes.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a filtering apparatus, especially a filter press, having a support extending along a lengthwise direction of the filtering apparatus, a pressuring device comprising a stationary head mounted at one end of said support and a movable head which is movably supported on said support and spaced apart from said stationary head. The movable head and/or the stationary head comprise connector elements for feed and filtrate. In the space being provided between the movable head and the stationary head filtering elements are accommodated. The invention also relates to a filter carriage and to a supplementary set or retrofit kit for filtering apparatus.  
         [0003]     Such filtering apparatus are also known as filter presses because the filtering elements are pressed against each other by means of the pressing device prior to filtration. A horizontal filter press  1 ′ of the prior art is illustrated diagrammatically in  FIG. 1 .  
         [0004]     On a rack provided with a pillar  8  there is disposed a displaceable movable head or pressure plate  2  and a stationary head or end plate  4 , between which filter plates  5  and filter frames  6  are provided in an alternating sequence. Filtering elements, particularly layers of filtering material, are clamped between the filter plates  5  and the filter frames  6 . The filter plates  5  and filter frames  6  are displaceably mounted on two cross beams  3  disposed between the pressure plate  2  and the end plate  4  so that they can be pressed together by means of the pressing device, which in the embodiment shown here comprises a spindle  9  and a handwheel  10 . Between the stack comprising filter plates and filter frames and the respective end plate or the pressure plate there is provided an adapter in the form of plate  7 , which adapter plate forms a link to the filtrate and feed (or non-filtrate) connector elements in or on the end plate  4  or pressure plate  2  respectively.  
         [0005]     These filter presses are used for clarifying, degerminating, or declouding filtration of liquids and are used, for example, in the chemical and pharmaceutical industries and the beverage industry.  
         [0006]     The advantages of these sheet filter presses consist in that the construction of the racks is simple, that the filtering apparatus can be arbitrarily enlarged or diminished in size by changing the number of filter plates so as to afford easy adaptation to the particular filtration task, that the filtering device can be readily degassed and emptied, and that the filter plates are readily accessible for changing the filtering elements.  
         [0007]     This is offset by a number of drawbacks, however. For example, the filtering elements also serve as a seal between the filter plates and filter frames so that by-passes are inevitable on account of the porosity of the filtering materials. The undesirable leakage of feed or filtrate is referred to in the art as dripping losses. In addition, the fluid can be impaired by materials that diffuse in or diffuse out. In the case of filtration of fluids containing toxic ingredients there is the risk of these passing into the environment via the by-passes.  
         [0008]     Various attempts have hitherto been made to provide a remedy for this. DE 35 20 171 A1 discloses a device of the type, in which the filter stack formed by a horizontal row of in-line filtering elements including its support means is surrounded by a protective covering. This protective covering prevents material leaking from the filter stack during filtration from disturbing the operator(s) or contaminating the filter stack. The protective covering can be completely removed, at least from the region of the filtering elements of the filter stack, when the filter press is opened, particularly for work on the filtering elements, for unhindered exchange of the filtering elements, and for the removal of filter cakes to be recovered or discarded. The drawback of this device consists in that considerable space is necessary and that this device is not capable of being retrofitted.  
         [0009]     WO 99/17861 discloses a filter press in which a special layer of wax is provided between the layers of filtering material to provide a seal and to avoid dripping losses.  
         [0010]     Elaborate sealing means are disclosed in DE 39 068 16 C3.  
       SUMMARY OF THE INVENTION  
       [0011]     It is an object of the present invention to reduce or entirely avoid dripping losses in a filtering device and to simplify equipping the filtering device and exchanging the filtering elements. In particular, existing filtering devices can be retrofitted due to the improvements afforded by the invention so that the existing racks and pressing devices and the movable heads (pressure plates) and stationary heads (end plates) and their associated connections can still be used in unchanged form.  
         [0012]     This object is achieved with a filtering device defined in claim 1.  
         [0013]     The provision of the invention is that between the end plate (stationary head) and the pressure plate (movable head) there is provided at least one filter carriage which is displaceably mounted on the support and has a compression-proof outside wall and which exhibits at least one chamber for accommodation of at least one filter module composed of filtering elements.  
         [0014]     Preferably the support comprises two cross beams.  
         [0015]     Any arrangement of filtering elements is regarded as a filter module in which the filtering elements are integrated to form a stack which can be handled as a unit and the non-filtrate should impinge on the filter module from the outside, and the interior of the module should exhibit at least one filtrate interceptor. Exemplary filter modules which can be used in connection with the filtering device of the invention, are described, for example, in DE 198 372 57 A1, DE 197 058 56 A1, and DE 197 058 55 A1. In the case of these known filter modules, it suffices when the individual filtering elements are locked together for transportation purposes only but can otherwise be interconnected so as to be displaceable in the longitudinal direction with respect to each other so that the filter module can be compressed when in the filtering device. Alternatively, precompressed modules can be used, such as are described in DE 100 299 60 A1.  
         [0016]     Although the device of the present invention basically may comprise only one filter carriage having one chamber and one filter module, the filtering device will preferably be equipped with a number of filter carriages, each having a number of chambers accommodating a number of filter modules. The embodiments of the filter carriage that are preferred will be described below.  
         [0017]     Instead of the filter plates and filter frames conventionally provided, the filter carriages are mounted on the support, e.g., cross beams designed to accept the filter carriages for displacement thereon. Equipping of the filtering device is carried out by releasing the pressing device and moving the filter carriages away from each other so that the chamber(s) of the carriages become accessible and can be filled with the prepared filter modules. Once the filter carriage has been equipped with the filter modules these are merely moved together and the pressing device applies the pressure necessary to press the filter modules with their filtrate interceptors against the corresponding filtrate orifices in the corresponding feed and filtrate means. Simultaneously, the filter carriages are pressed against each other, seals being preferably provided between the filter carriages to prevent fluid from escaping. Within the filter carriages, i.e., their chambers, pressure filtration is carried out, and the resulting filtrate is removed through the filtrate interceptors of the filter modules via the filtrate outlets present in the adapter or the end plate or the pressure plate.  
         [0018]     Existing filtering devices can be retrofitted by the filter carriages of the invention. Retrofitting can be carried out cheaply because no modification of the existing connections is necessary. Retrofitting can be carried out without loss of time because only the filter plates and filter frames have to be replaced by the filter carriages. Furthermore, the user can return to the old system at any time.  
         [0019]     Due to the fact that a closed system is made available, there are no losses of product and there is no contamination of the environment, and gasses cannot diffuse into the filtering device from the environment.  
         [0020]     Furthermore, only a few gaskets are necessary because gaskets are only required, if at all, between the filter carriages and between the filter carriages and the adapter or the end plate or pressure plate. The chambers of the filter carriages are easier to clean and sterilize and the exchange of filter modules takes place faster than an exchange of individual filter plates or filtering elements present in the filter plates, particularly when these are layers of filtering material. Following filtration the filter modules are disposed of as complete units so that very little effort is required to equip the filtering device with fresh filter modules. There is distinct overall improvement in filtration and handling.  
         [0021]     In order to accelerate changing of the filter modules even more, a lifting device can be additionally provided, by means of which the filter carriages can be lifted out from the space between the pressure plate and the end plate so that the faces of the first and last filter carriages become open to access. When retrofitting is carried out, fresh filter modules are pushed into the chambers with the result that the spent filter modules are simultaneously knocked out at the opposite end. Thus very little effort is necessary to effect retrofitting. The filter carriages are then lowered by means of the lifting device and come to rest on the cross beams of the filtering device.  
         [0022]     Preferably, the longitudinal axis of the chambers runs parallel to the support (e.g., cross beams). This has the advantage that when a number of filter carriages are disposed in line the filter modules disposed in the chambers are also in line and thus the number of filter carriages and filter modules in the filtering device is freely selectable.  
         [0023]     The filter carriages are preferably open at one or both ends so that the filter modules can be introduced into the filter carriage. When the filter carriage is open at one end only, it possesses, at the opposite end, an end wall having filtrate orifices and feed orifices to match the filter module. These end walls can be releasably connected to the filter carriage (e.g., by screws or pins) or they can be welded thereto. This embodiment is of advantage when a large number of filter carriages are disposed successively in a row and there is the risk that the row comprising a large number of filter modules might sag following compression, as a result of which leakage might occur, particularly in the region of adjacent filtrate channels of the filter modules. The use of filter carriages which are closed at one end provides a greater-degree of overall stability as regards positioning of the filter modules.  
         [0024]     Preferably, the filter carriage is rectangular in cross-section. The filter chamber(s) may thus also be rectangular in shape so that filter modules that are rectangular in cross-section can be used.  
         [0025]     Since the feed (or non-filtrate) is forced into the filter chamber, during filtration, at a pressure of up to 10 bar, the outer wall of the filter carriage must be capable of withstanding this pressure. Depending on the size of the filter carriage and the chambers disposed in the filter carriage, it may be necessary to provide at least one horizontal and/or vertical tension strut. The said strut or struts are preferably arranged such that they delimit said chamber or chambers. These struts can be in the form of a stiffening cross or as partitions containing passages for the feed. The struts can be formed in such a manner that they delimit the chambers leak-sealingly or non-leak-sealingly.  
         [0026]     To guarantee unproblematic retrofitting of existing filtering devices, which are generally available in three standard sizes, it is an advantage when the filter carriage has one, four, or nine chambers, whose cross-sections conform to specific modular dimensions. The chambers are preferably arranged in juxtaposed and superposed relationship within the filter carriage. In this case the carriages are preferably square in cross-section and have edge lengths of 400 mm, 600 mm, and 1000 mm. These exterior dimensions permit an arrangement of chambers having interior dimensions of ca 280 mm so that one and the same type of module can be used in all three sizes of filter carriage without further modification.  
         [0027]     Advantageously, the carriage has along its longitudinal axis at least two chambers disposed in line and separated from each other by a vertical partition having filtrate orifices and feed orifices. It is thus possible to make relatively long carriages so that a few carriages will suffice for one filtering device. The number of points to be sealed is thus considerably reduced.  
         [0028]     To ensure that the filter modules can be compressed when the pressing device is actuated, the length L 1  of the chamber is less than L 2 , L 2  being the length of the filter module to be placed in the chamber.  
         [0029]     According to another advantageous embodiment, intermediate plates of similar cross-section are disposed between two filter carriages, said plates having filtrate orifices and feed orifices. These intermediate plates have the same function as the end walls of the filter carriage open at one end. The interposition of intermediate plates serves to increase the stability of the filter module configuration.  
         [0030]     These intermediate plates are preferably also slidably mounted on the cross beams so that the intermediate plates cannot fall down when the filter carriages are moved away from each other.  
         [0031]     Between the pressure plate and the adjacent filter carriage and/or between the end plate and the adjacent filter carriage there is preferably provided an adapter having means for feeding in the feed and means for removing the filtrate.  
         [0032]     The adapter preferably comprises a perforated plate adjacent the filter carriage and an adapter frame disposed between the perforated plate and the end plate or pressure plate. The perforated plate can be releasably attached to the adapter frame, e.g., by means of screws or a pin-and-socket connection, or it can alternatively be welded. The adapter serves for adaptation to the existing connections on the pressure plate or end plate and the filter modules used.  
         [0033]     The perforated plate preferably has filtrate and feed orifices or openings.  
         [0034]     The adapter frame connects the connections for filtrate and feed in the pressure plate and/or end plate to the filter module or filter modules to give one or more filtering circuits.  
         [0035]     According to one embodiment, the adapter frame has a partition which divides the space delimited by the frame into a filtrate chamber and a feed chamber, these two chambers being connected to the filtrate and feed connector elements on the pressure plate or end plate. The filtrate chamber is connected, via filtrate conduits disposed in the feed chamber, to the filtrate orifices in the perforated plate, or the feed chamber is connected, via feed conduits disposed in the filtrate chamber, to the filtrate orifices in the perforated plate.  
         [0036]     According to another embodiment, the adapter frame has connecting means for feeding in feed and removing filtrate, and the filtrate connecting means are connected, via filtrate conduits, to the filtrate orifices in the perforated plate, or the feed connecting means are connected, via feed conduits, to the feed orifices in the perforated plate.  
         [0037]     Preferably, the filtering device comprises filter modules equipped with filtering elements which are attached to each other and can be displaced, relatively to each other, along the longitudinal axis of the filter module so that when the pressing device is actuated, the filtering elements and the filter modules can be compressed such that the necessary seal both between the filter modules and between the filtering elements and the filter modules and the intermediate plates or adapters can be achieved.  
         [0038]     To ensure that the filter module can be installed in the filter chamber with all its sides at the same distance therefrom, the filter module possesses projecting spacing elements around its perimeter. An alternative possibility is to provide these spacing elements in the filter chamber.  
         [0039]     The invention also relates to filter carriages for filter presses, which are characterized in that they exhibit a compression-proof outer wall, which surrounds at least one chamber for the accommodation of a filter module composed of filtering elements, said filter carriages being open at one or both ends for the introduction of the filter modules and are provided with rolling or sliding means on said outside wall. These rolling or sliding means are preferably adapted to the design of the cross beams of existing filter presses so that retrofitting of existing filtering devices can be carried out in without any problems.  
         [0040]     The length of the filter carriages is preferably between 10 cm and 1 m. The filter carriage preferably comprises a bundle of rectangular pressure tubes, which, for example, are welded to each other or braced together. Particular embodiments of the filter carriages have already been described in connection with the filtering device.  
         [0041]     The retrofit kit (supplementary set) of the invention for a filtering device, in particular a filter press, having a pressure plate mounted on a support on which it can be moved by a pressing device, and having a stationary end plate connected to the pressure plate via said support, which pressure plate and/or end plate have connections for feed and filtrate, whilst space is provided between the pressure plate and the end plate for the accommodation of filtering elements, contains at least one such filter carriage. Exemplary embodiments of the invention are illustrated below with reference to the drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]      FIG. 1  shows a filtering device according to the prior art;  
         [0043]      FIG. 2  is a section through a device of the invention comprising a filter carriage;  
         [0044]      FIG. 3   a  illustrates the filtering device shown in  FIG. 2  in the opened state;  
         [0045]      FIG. 3   b  is a perspective view of a filter carriage;  
         [0046]      FIG. 3   c  is a perspective view of a filter module;  
         [0047]      FIG. 4  shows a filtering device according to another embodiment;  
         [0048]      FIG. 5  shows a filtering device according to another embodiment;  
         [0049]      FIGS. 6, 7 ,  8   a ,  8   b,    9   a,    9   b,    9   c  are plan views of the end faces of filter carriages according to various embodiments;  
         [0050]      FIG. 10  is a plan view of a backing plate;  
         [0051]      FIG. 11 a  top view of an adapter frame;  
         [0052]      FIG. 12  is a vertical cross section through an adapter with filter carriage and end plate taken along the line A-A in  FIG. 13 ; and  
         [0053]      FIG. 13  is a plan view of an adapter frame according to another embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0054]      FIG. 2  illustrates a filtering device  1 , which, as already explained in connection with  FIG. 1 , exhibits a rack having pillars  8 , a pressure plate  2 , an end plate  4 , and a pressing device  10  comprising a handwheel and a spindle  9 . Between the pressure plate  2  and the end plate  4  there are displaceably mounted three filter carriages  20  on the cross beams  3  forming part of a support. To this end, the filter carriages  20  possess external rollers  11 . Between the filter carriage  20  and the pressure plate  2  or the end plate  4  there is disposed, in each case, an adapter  60 , which is explained in greater detail in connection with FIGS.  12  to  15 .  
         [0055]     The middle carriage is shown as a cross-section so that the superposed filter modules  40  disposed in the interior of the filter carriage  20  can be seen.  
         [0056]      FIG. 3   a  shows the filtering device  1  in the opened state. The pressing device  10  has been opened by turning the handwheel  13  to cause the pressure plate  2  to be withdrawn and to afford accessibility to the interior of the filter carriages  20 .  
         [0057]     As shown in  FIG. 3   b,  the filter carriages are rectangular in cross-section and enclose a total of four juxtaposed and superposed chambers  25 . The outer wall  21  is compression-proof. For reinforcement, internal horizontal struts  23  and internal vertical struts  24  are provided, which together form a stiffening cross. These struts  23  and  24  are arranged in such a manner that they delimit the chambers  25 . In each chamber there is a filter module  40 , whose axial length L 1  is greater than the length of the filter carriage  20 , designated by L 2 . By reason of these different lengths, the filter module  40  projects beyond the end faces of the filter carriage so that when the filtering device  1  is closed by means of the pressing device  10 , the filter modules  40  are pressed against each other.  
         [0058]     As shown in  FIG. 3   c,  each filter module possesses in its interior two filtrate interceptors  41   a  and  41   b.  The filter modules are placed in the filter chambers  25  such that the two filtrate interceptors  41   a  and  41   b  are superposed. The aim of this arrangement is to afford unproblematic deaeration of the filter module through the filtrate interceptor  41   a  when the filter module is filled. Filtrate interceptor  41   b  is provided to make it possible to empty the filter module completely after filtration. More than two filtrate interceptors may be present, if desired.  
         [0059]      FIG. 4  illustrates another embodiment, in which filter carriages  20  are provided with a vertical partition  26 . This means that a total of eight chambers, i.e., four+four chambers, are formed in each filter carriage  20 , into which filter modules  40  can be inserted. The partition  26  has feed or non-filtrate orifices and filtrate orifices so that unhindered change of non-filtrate is possible and the filtrate interceptors of adjacent filter modules can communicate with each other.  
         [0060]      FIG. 5  illustrates another embodiment, in which intermediate plates  50  are disposed between the filter carriages  20 . These intermediate plates  50  serve to stabilize the filter module configuration. Due to the fact that the filter modules  40  are not directly juxtaposed but each rests with its end face against the intermediate plate  50 , sagging of the chain of filter modules is prevented. These intermediate plates are explained in greater detail in connection with  FIG. 11 .  
         [0061]      FIG. 6  shows a plan view of the end face of a filter carriage which is square in cross-section and has four filter modules  40  inserted therein. To the outer wall  21  of the filter carriage  20  there is fixed, on both sides, a bearing element  27 , by means of which the filter carriage  20  rests on the two cross beams  3 . The filter modules  40  in the quadratic filter chambers  25  are set at a distance from the outer wall  21  and the horizontal and vertical struts  23 ,  24  so that the feed chamber  28  is formed between the filter modules and the chamber delimiting means.  
         [0062]      FIG. 7  is a plan view of the end face of a similarly square filter carriage  20  composed of rectangular tubes welded to each other.  
         [0063]      FIGS. 8   a  and  8   b  show two further embodiments,  FIG. 8   a  depicting the smallest variant having one chamber and one filter module  40 . The filter module  40  illustrated in  FIG. 8   a  is provided with spacing elements  42  around its perimeter to ensure that the filter module  40  can be set at a distance from the filter carriage  20  on all sides.  FIG. 8   b  shows another embodiment having a total of nine filter chambers, these being formed by horizontal struts  23  and vertical struts  24 . The filter carriages  20  according to  FIGS. 8   a  and  8   b  and also  6  comply with specific modular dimensions so that a regular distribution of the filtrate chambers is possible, and filter modules of the same sectional area can be used.  
         [0064]     In  FIGS. 9   a  to  9   c  there are shown corresponding arrangements involving square tubes and corresponding chambers. The tubes are interconnected by braces  80 . The square outline corresponds to the dimensions of the square filter carriage  20  according to  FIGS. 6 and 8   a ,  8   b.  In this embodiment it is again possible to accommodate one, four, or nine chambers  20  by reason of their modular dimensions.  
         [0065]      FIG. 10  is a plan view of an intermediate plate  50 , which can be disposed between filter carriages according to  FIG. 8   b.  The intermediate plate  50  is basically a perforated plate exhibiting rows  52  of filtrate orifices  51  and rows  54  of non-filtrate orifices  53 . The filtrate orifices  51  are arranged in such a manner that they are opposite to the filtrate channels  41   a,    41   b.  The feed orifices  53  are disposed between the rows  52  in such a manner that all filtrate chambers are supplied with feed as evenly as possible. In addition, two rows of feed orifices  53  are further provided at the outer edge in the vicinity of the outer wall  21 .  
         [0066]     The perforated plate  61  as a component of the adapter  60  corresponds to the intermediate plate  50  and can exhibit, in the four corner regions, feed orifices and filtrate orifices which cooperate with the corresponding orifices  76  and  77  in the adapter frame  70 , as illustrated in  FIG. 11 . The adapter frame  70  possesses a vertical separating wall  71  so that the interior of the adapter frame is divided into a feed chamber  72  and a filtrate chamber  73 . Since, by reason of the arrangement of the filter modules, the filtrate interceptors open into the region of the feed chamber  72 , filtrate connections  74  and corresponding filtrate pipes  75  are provided in this region, which pipes extend in a horizontal direction and open into the filtrate chamber  73  at the separating wall  71 .  
         [0067]      FIG. 12  is a cross-section illustrating the cooperation between perforated plate  61  and adapter frame  70 . The two filter modules  40  shown rest against the perforated plate  61  in such a manner that the filtrate interceptors  41   a ,  41   b  bear sealingly against the filtrate orifices  62 . The opposite side of the perforated plate  61  is adjoined by filtrate connections  74  and filtrate pipes  75 . The adapter frame  70  also possesses non-filtrate orifices  76 , which supply non-filtrate chamber  72  via the non-filtrate inlets  12  in the end plate  4 .  
         [0068]      FIG. 13  shows another embodiment of the adapter frame  70 . In the embodiment shown here there is only one feed chamber  72 , in which a piping system comprising filtrate pipes  75  is disposed, which piping system is connected to the filtrate orifices  77  and interconnects all of the filtrate connections  74 .  
         [0069]     The terms “vertical” and “horizontal” refer to the horizontal filtering device described above by way of example. The filtering device can also be vertically oriented, in which case the rolling and sliding means of the filter carriage will have to be modified appropriately.  
         [0070]     In the Figures the chamber  28  is designated as the feed chamber. Alternatively, the filter module can be operated inversely, i.e., employing a reversed direction of flow so that the chamber  28  will then form the filtrate chamber. Similar considerations apply to the orifices  41   a,    41   b.