Filter press and use of an electromagnetically operating sensor in the same

Abstract

Filter press for solid-liquid separation of suspensions comprising several plate-shaped filter elements (2; 20; 30) connected in series and clamped together at their edges, with a press wall (21), a plate frame (22) and a filter medium (23), a suspension inlet (5) and a filtrate outlet (6, 7), wherein cake spaces (8) are provided between each pair of adjacent and neighboring filter elements (2; 20; 30), in which filter cakes (9) are formed during operation, characterized by a sensor (18) assigned to at least one press wall (21), operating electromagnetically with a measuring frequency in a range of 300 MHz and 1.5 GHz and having two spaced-apart conductor electrodes (18a), which determines the dielectric constant of a filter cake (9) formed during operation, and from this determines a water content value and optionally a conductivity value via an evaluation device (19).

Description

[0001] The invention relates to a filter press for the solid-liquid separation of suspensions, comprising several plate-shaped filter elements arranged in series and clamped together at the edges, with a press wall, a plate frame, and a filter medium, such as a fabric or membrane, a suspension inlet, and a filtrate outlet. Cake spaces are provided between each two adjacent filter elements, in which filter cakes build up during operation. The invention also relates to the use of an electromagnetically operating sensor in the filter press. Filter presses of this type are discontinuously operating pressure filters.

[0002] From DE 38 31 377 C1 a filter plate for filter elements of a filter press is known, which is a chamber filter press.

[0003] From DE 41 19 166 A1 a filter element for a filter press of the above-mentioned type is known, which is a so-called membrane filter press.

[0004] US 2011 / 0203999 A1 describes a filter press assembly that heats the filter cake using electromagnetic radiation. For this purpose, the assembly comprises parallel electrodes arranged outside the filter plate stack and perpendicular to the plane of the filter plates. Each pair of electrodes is connected to a radio frequency generator and excited by electromagnetic radiation to heat the filter cake in the plate stack.

[0005] EP 0 478 815 B1 and EP 1 359 410 B1 disclose devices for measuring material moisture and devices for determining the moisture content of a substrate. Electromagnetic measuring probes or sensors are used. These sensors each detect and determine the dielectric constant of a material. From this dielectric constant, the moisture content or water content of a material under investigation, such as a substrate, screed, or the like, is determined via appropriate electronic processing devices.

[0006] DE 10 2011 056 548 A1 describes a measuring device and a method for determining the moisture content of a material. The measuring device comprises a capacitive moisture sensor with two spaced-apart conductor electrodes fixed in a moisture-permeable base material. The capacitance measured between the electrodes directly determines the moisture content of the material under test.

[0007] From DE 101 53 353 A1 a device for determining the residual liquid content of solid cakes in centrifuges is known, which has two electrodes for conductivity or capacitance measurement.

[0008] To optimize the process operation of filter presses for the solid-liquid separation of suspensions of the type mentioned above and to ensure process-economical operation of the same, a great deal of extensive experience is required on the part of the operating personnel, in particular to estimate the moisture value or the water content value and, if applicable, the composition of the filter cake built up in the filter press during operation, so that the filter cakes can then be discharged, for which purpose such a filter press must be switched off.

[0009] KR 101 308 170 B1 discloses a filter press for dewatering sludge, which has a moisture sensor for measuring the moisture content of the sludge during the dewatering process. The moisture sensor is arranged on a dewatering plate within the receiving space for the sludge to be dewatered in order to measure the moisture content of the dewatered sludge.

[0010] US Pat. No. 4,627,914 A describes an automatic control system for a chamber filter press. The control system serves to determine the duration of a dehydration process for a suspension. A capacitive sensor, located in a discharge line for the filtrate of the chamber filter press downstream of the chamber filter press, serves to determine the end point of the dehydration process.

[0011] The invention aims to design a filter press of the aforementioned type in such a way that filter presses of this type can be operated as efficiently as possible and largely free of malfunctions. The invention also aims to provide the use of an electromagnetic sensor in such a filter press for the solid-liquid separation of suspensions.

[0012] On the one hand, a filter press for the solid-liquid separation of suspensions is provided for this purpose, comprising a plurality of plate-shaped filter elements connected one behind the other and clamped together at the edges, with a press wall, a plate frame and a filter medium, such as fabric or membrane, a suspension inlet and a filtrate outlet, wherein cake spaces are present between each two adjacent and neighbouring filter elements, in which filter cakes build up in the operating state, wherein the filter press is characterized in that at least one press wall is assigned a sensor which operates electromagnetically with a measuring frequency in a range of 300 MHz and 1.5 GHz and has two spaced-apart conductor electrodes, wherein the sensor determines the dielectric constant of a filter cake formed in the operating state and, from this, determines a water content value and, if appropriate, a conductivity value via an evaluation device.

[0013] The sensor provided according to the invention, which operates electromagnetically with a measuring frequency in the range of 300 MHz to 1.5 GHz and features two spaced-apart conductor electrodes, can thus reliably, promptly, in real time, and during filter press operation, measure the water content and moisture content of the filter cake formed during operation, and, if applicable, its conductivity, via the dielectric constant of the filter cake. This allows the process parameters of the filter press to be recorded independently of experience, and the operating sequence of the filter press or the filter process can thus be optimized and controlled economically.

[0014] Preferably, the evaluation device performs temperature compensation for the measured dielectric constant so that the operating temperatures are also taken into account.

[0015] Preferably, the sensor is arranged approximately centrally in the press wall so that it can reliably detect in particular the central region of the filter cake on both sides of the press wall and the two spaced conductor electrodes are arranged in particular at the critical point of the filter cake structure.

[0016] In another preferred embodiment, the sensor's conductor electrode(s) can be integrated directly into the press wall. This avoids additional processing, such as drilling a hole into the press wall into which the electromagnetic sensor is then pressed. This also effectively prevents material weakening of the press wall.

[0017] Furthermore, according to the invention, a use of a sensor operating electromagnetically with a measuring frequency in a range of 300 MHz and 1.5 GHz, having two spaced-apart conductor electrodes, is provided, which is characterized in that the sensor is used in a filter press for the solid-liquid separation of suspensions, wherein the filter press has several plate-shaped filter elements connected in series and clamped together at the edges, with a press wall, a plate frame and a filter medium, a suspension inlet and a filtrate outlet, wherein cake spaces are present between each two adjacent and neighbouring filter elements, in which filter cakes build up in the operating state, wherein the sensor is used to detect the dielectric constants of filter cakes formed between the filter elements of the filter press in the operating state,and the sensor determines a water content value and optionally a conductivity value of the filter cake(s) from the dielectric constant, and wherein the sensor is assigned to at least one press wall of the filter element,

[0018] Such use of an electromagnetically operating sensor having two spaced-apart conductor electrodes with a discontinuously operating filter press in the form of a pressure filter enables the filter press to be operated under optimized operating conditions and correspondingly process-economical process parameters, and operational disturbances can be effectively avoided.

[0019] According to the invention, the sensor is assigned to at least one press wall of the filter element. In particular, the sensor can be arranged approximately centrally in the press wall of the filter element. This allows the water content values ​​and, if applicable, the conductivity values ​​to be reliably determined, particularly in the critical central region of the filter cake formed during operation.

[0020] In summary, it is essential according to the invention that in a reliable and experience-independent manner and with structurally relatively simple and failure-resistant means, in particular the moisture content or the water content of the filter cake built up during the operating state of a filter press can be detected and, depending on this, corresponding process parameters can be influenced and controlled if necessary.

[0021] The invention will be explained in more detail below with reference to the accompanying drawings using preferred but non-limiting embodiments. In these drawings: Fig. 1 a schematic diagram of a filter press of conventional design, Fig. 2 is a schematic view of a preferred embodiment of a filter press according to the invention, Fig. 3a and Fig. 3b each shows a sectional view of an individual filter element in the form of a chamber filter element of a filter press, Fig. 4 a schematic sectional view of several chamber filter elements arranged side by side and a sensor according to the invention, Fig. 5 an enlarged detail view of the Fig. 4 area marked A, Fig. 6 a schematic sectional view of a single membrane filter element before filter cake formation, Fig. 7 a schematic sectional view of several membrane filter elements arranged side by side or connected in series to illustrate the assignment of the sensor according to the invention, and Fig. 8 a schematic sectional view of several membrane filter elements connected in series according to Fig. 7 with filter cake build-up and change in the position of the elastic press membrane.

[0022] In the figures of the drawing, identical or similar parts are provided with the same reference symbols.

[0023] In Fig. Figure 1 shows a schematic sectional view of a conventionally designed filter press, designated overall by 1. This filter press 1 comprises several plate-shaped filter elements 2 connected one behind the other, clamped together at the edges, which are arranged between a counter-holder plate 3 and a pressure plate 4. Furthermore, the illustrated filter press 1 for the solid-liquid separation of suspensions comprises a suspension inlet 5, which is arranged centrally and centrally in the illustrated embodiment, and a filtrate outlet 6 and a filtrate outlet 7, which are arranged at the outer edge region of the filter elements 2 and are connected to the filter elements 2 via channel systems (not shown in detail).

[0024] Cake spaces 8 are formed between adjacent and neighbouring filter elements 2, in which schematically indicated filter cakes 9 can build up when the pressure plate 4 is pressed hydraulically and / or mechanically against the counter-holder plate 3 during operation of the filter press 1.

[0025] In Fig. 2 shows a schematic representation of a filter press, which is designated therein as a whole by 1'. The basic structure of the filter press 1' with regard to the filter elements and other details corresponds to the design of the filter press 1 according to Fig. 1. Therefore, these details will not be explained again. As also schematically shown in Fig. 1, the filter cake chambers 8 are sealed by means of corresponding seals 10. In Fig. 2 further shows a variant of the embodiment to illustrate the possibility of ejecting the filter cake 9 built up in the cake chambers 8 either manually or, if necessary, automatically, as shown by an arrow 11 to indicate the filter cake ejection.

[0026] The filter press 1' according to the invention also comprises Fig. 2 an electromagnetically operating sensor 18, which in the example shown has two spaced-apart conductor electrodes 18a, wherein the sensor 18 is arranged approximately centrally in a press wall 21 of the filter element 2. This sensor 18 determines the dielectric constant of the filter cake 9 formed on both sides of the press wall 21 of each filter element 2. A water content value and, if applicable, a conductivity value are determined from this via an evaluation device 19. The evaluation device 19 can, if necessary, perform temperature compensation. The measuring frequency lies in a range of 300 MHz and 1.5 GHz in order to minimize interference from disturbances such as electrical conductivity, temperature, etc., when determining the dielectric constant.

[0027] Although not shown in detail, the conductor electrode(s) 18a of the sensor 18 can also be integrated directly into the press wall 21.

[0028] The moisture values ​​determined by means of the sensor 18 and the evaluation device 19 and, if applicable, corresponding values ​​for the conductivity of the filter cake 9 are used to influence the control of the filter press 1' in a suitable manner in order to optimize the process parameters of the same. Fig. As can be seen from Figure 2, the evaluation device 19 comprises a sensor evaluation device 19a, a control device 19b and a display and monitoring device 19c.

[0029] The Fig. 3a and Fig. The filter element 2 shown in Figure 3b is designed as a chamber filter element 20. The filter element 20 comprises a press wall 21, a plate frame 22 and a filter medium 23, which may be a fabric or a membrane, as shown in Fig. 3 is shown schematically in broken lines. Via bores 24, the filtrate from the individual filter elements 2, 20 can be conveyed from a channel system 25 (not shown in detail) in the area of ​​the extension of the press wall 21 to the filtrate outlet 6 or 7 to Fig. 1 or, as in Fig. 3, with the filtrate outlet 6. A filter cake 9 then builds up in the cake spaces 8 formed at the end walls of the filter element 2, 20. Above the channel system 25 of the chamber filter element 20 to Fig. 3, a filter medium, such as a filter membrane or a filter cloth, is stretched. The seals 26 between adjacent filter elements 2 are in Fig. 3. Additionally, a seal 10 for the filter medium 23, such as the filter membrane, is also indicated.

[0030] Fig. 3b shows a variation of Fig. 3a a chamber filter element 20 in which the two conductor electrodes 18d of the sensor 18 are spatially separated and separately assigned to the press wall 21.

[0031] With reference to Fig. Figure 4 illustrates an arrangement of several adjacent chamber filter elements 20. This shows that an electromagnetically operating sensor 18 having two spaced-apart conductor electrodes 18a determines the dielectric constant of the filter cakes 9 formed on both sides of the press wall 21 of each filter element 20. From this, the corresponding values ​​of two adjacent filter cakes 9 are then determined using at least one single sensor 18, and from these, the water content value and, if applicable, a conductivity value are determined using the evaluation device 19.

[0032] Fig. 5 shows an enlarged section of area A in Fig. 4. A filter plate 27 of the filter element 20 has protruding nubs 28 against which the filter medium 21, such as a filter cloth, rests. A distance, designated 29, from the conductor electrode 18a of the probe 18 to the base of the nubs 28 of the filter plate 27 is preferably 1.5 mm to 10 mm, more preferably 2 to 4 mm. It has also been shown that the longer the probe 18 is in its axial extension, the better the measurement quality. These length values ​​are, for example, 100 mm to 400 mm, and preferably a length in a range of 200 mm to 300 mm.

[0033] With reference to Fig. 6 illustrates a further embodiment of the filter element 2, which is designed in the form of a membrane filter element 30. The same or similar parts as in the filter element 2, 20, which were previously described under Fig. 3 are explained in Fig. 6 are provided with the same reference numerals and will not be explained in more detail again. In a membrane filter 30, a flexible or elastic press membrane 31 is additionally provided, which presses the filter cake 9 building up in the cake chambers 8 in such a way that the filter cake 9 formed can be further pressed after filtration with the aid of the press membrane 31. The sensor 18 with its two spaced-apart conductor electrodes 18a is arranged approximately centrally in the press wall 21 and - as schematically indicated - is connected via corresponding lines to the evaluation device 19 (not shown in more detail) (see Fig. 2) connected.

[0034] In Fig. Figure 7 shows a schematic sectional view of an arrangement of several membrane filter elements 30 arranged side by side. This shows that the electromagnetically operating probe 18 can measure the dielectric constant of filter cakes 9 in cake chambers 8 constructed by adjacent filter elements 30. All further details in Fig. 7 essentially corresponding to those which in Fig. 6 are shown.

[0035] Fig. 8 finally shows in a schematic sectional view starting from Fig. 7, in which the membrane filter elements are illustrated in the basic state without the built-up filter cake 9, the membrane filter elements 30 in an operating state, wherein with the filter cake 9 building up in the cake space 8, the position starting from the position of the press membrane 31 in Fig. 7 before the filter cake formation, divide it into Fig. 8 and, as indicated there by force arrows 32, is elastically pressed in the direction of the press wall 21, so that the filter cake 9 built up in the cake chamber 8 is pressed again by means of elastic press membranes 31. With the help of the electromagnetically operating sensor 18, the dielectric constant in the two adjacent, built-up filter cakes 9 is then recorded, from which the evaluation device 19 in Fig. 2 corresponding water content values ​​and, if applicable, conductivity values ​​of the filter cake 9 are determined.

[0036] In the illustrated embodiments, the sensor 18 according to the invention is pressed into a bore 40 formed in the press wall 21. Alternatively, the sensor 18 can also be integrated directly into the press wall 21 by embedding the spaced-apart conductor electrodes 18a directly into the material of the press wall.

[0037] Although the invention has been explained above with reference to preferred embodiments, the electromagnetically operating sensors 18 can be assigned to one or more filter elements 2, 20, 30, or the sensor 18 can also be used and arranged in preferred critical areas of the filter press 1, 1'.

[0038] If necessary, at least one contactless sensor for detecting the press wall load can be arranged on at least one filter element in addition to or in combination with this.

[0039] The invention is therefore not limited to the preferred embodiments shown, but the number, position and arrangement of the sensor 18 can be selected as required.

[0040] As can further be seen from the figures of the drawing, the invention also provides the use of a sensor 18 operating electromagnetically with a measuring frequency in a range of 300 MHz and 1.5 GHz and having two spaced conductor electrodes 18a, with the proviso that the sensor 18 is used in a filter press 1' for the solid-liquid separation of suspensions to detect the dielectric constant of is inserted between the filter elements 2, 20, 30 of the filter press 1, 1' in the operating state of the filter cake 9, and the sensor 18 determines the water content value and optionally a conductivity value of the filter cake(s) from the dielectric constant, wherein the sensor is assigned to at least one press wall of the filter element. List of reference symbols 1 filter press in total in Fig. 1 1' filter press in total in Fig. 2 2 filter element 3 Counterholder plate 4 pressure plate 5 Suspension inlet 6 Filtrate outlet (top) 7 Filtrate outlet (bottom) 8 cake rooms 9 filter cakes 10 seals in Fig. 1 11 Filter cake ejection 16 bending zone of the filter element 2 18 electromagnetic sensor 18a two spaced conductor electrodes 19 Evaluation device 19a Sensor evaluation electronics 19b Regulation 19c Display and monitoring device 20 chamber filter element in the Fig. 3 to 5 21 Press wall 22 plate frames 23 Filter medium 24 holes 25 Gutter system 26 Seal for filter medium 23 27 Filter plate 28 studs 29 Distance in Fig. 5 30 membrane filter elements in total in the Fig. 6 - 8 31 Press membrane 32 power arrows 40 Hole for sensor 18

Claims

[1] Filter press for the solid-liquid separation of suspensions comprising a plurality of plate-shaped filter elements (2; 20; 30) connected one behind the other and clamped together at the edges, with a press wall (21), a plate frame (22) and a filter medium (23), a suspension inlet (5) and a filtrate outlet (6, 7), wherein cake spaces (8) are present between each two adjacent and neighbouring filter elements (2; 20; 30), in which filter cakes (9) build up in the operating state, characterized by a sensor (18) associated with at least one press wall (21), operating electromagnetically with a measuring frequency in a range of 300 MHz and 1.5 GHz and having two spaced-apart conductor electrodes (18a), which determines the dielectric constant of a filter cake (9) formed in the operating state and, therefrom, determines a water content value and, if appropriate, a conductivity value via an evaluation device (19). [2] Filter press according to claim 1, characterized by that the evaluation device (19) carries out temperature compensation. [3] Filter press according to claim 1 or 2, characterized by that the sensor (18) is arranged approximately centrally in the press wall (21). [4] Filter press according to one of claims 1 to 3, characterized by that the conductor electrode(s) (18a) of the sensor (18) is / are integrated into the press wall (21). [5] Use of a sensor (18) operating electromagnetically with a measuring frequency in a range of 300 MHz and 1.5 GHz and having two spaced-apart conductor electrodes (18a), wherein the sensor (18) is used in a filter press (1') for the solid-liquid separation of suspensions, wherein the filter press has a plurality of plate-shaped filter elements (2; 20; 30) connected one behind the other and clamped together at the edges, with a press wall (21), a plate frame (22) and a filter medium (23), a suspension inlet (5) and a filtrate outlet (6, 7), wherein cake spaces (8) are present between each two adjacent and neighbouring filter elements (2; 20; 30), in which filter cakes (9) build up in the operating state, wherein the sensor is used to detect the dielectric constant of the liquid between the filter elements (2; 20;30) of the filter press (1, 1') in the operating state, and the sensor (18) determines a water content value and optionally a conductivity value of the filter cake(s) (9) from the dielectric constant, and wherein the sensor (18) is assigned to at least one press wall (21) of the filter element (2; 20; 30); [6] Use according to claim 5, characterized by that the sensor (18) is arranged approximately centrally in the press wall (21) of the filter element (2; 20; 30).

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