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  Cross flow filter device with concentric filter elementsRelated Patent Categories: Liquid Purification Or Separation, Serially Connected Distinct Treating With Or Without Storage Units, One Unit Inside AnotherThe Patent Description & Claims data below is from USPTO Patent Application 20080000824. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to a cross flow filter device provided for filtering a raw material comprising particles in a medium, said cross flow filter device comprising: [0002] a longitudinal first filter element having a first width and a longitudinal central axis, [0003] a longitudinal second filter element having a second width, smaller than said first width, and being longitudinally installed substantially concentrically inside said first filter element, [0004] a housing surrounding said first filter element, said cross flow filter device having respectively a raw material inlet, a concentrate outlet provided to exit a concentrate being said raw material substantially enriched in particles, and a first filtrate outlet provided to exit a filtrate being said medium substantially depleted in particles, said filtrate outlet being connected to said first filter element. [0005] In the art of filter devices, several types of filter devices are known. The two major types of filter devices are the dead end filter device and the cross flow filter device. [0006] Traditionally, filter devices are used to filter a raw material comprising particles in suspension in a medium which can be liquid or gaseous. After filtration, or ultrafiltration, depending of the cut-off of the filter elements, and as aforementioned, a filtrate being the raw material depleted in particles, a concentrate being the raw material enriched in particles are both obtained. Depending on the application, the product of interest is either the filtrate or the concentrate. [0007] The most important difference between these two types of filter devices, is as follows: [0008] the dead end filter device comprises a raw material inlet and a filtrate outlet, the concentrate being generally maintained inside the device, [0009] the cross flow filter device comprises a raw material inlet, a filtrate outlet and a concentrate outlet. [0010] A dead end filter device is for example known from DE 38 05 361 which discloses several embodiments of the dead end filter device. The device according to DE 38 05 361 comprises for example two or more concentric filter elements, an external compartment being between the housing of the device and the most external filter element and a central compartment, being inside the most internal concentric filter elements. The device also comprises a raw material inlet and a filtrate outlet. The raw material inlet is in direct communication with the external compartment and the filtrate outlet is in direct communication with the central compartment. The filter elements are provided for retaining particles with a predetermined particle size and to allow the passage of the particles which present a particle size smaller than the predetermined particle size through the filter element. Therefore, the raw material comprising particles in suspension in a medium enters the filter device in the external compartment, the particles having a particle size greater than the predetermined particle size are retained upstream and the medium with the particles having a particle size smaller than the predetermined particle size passes through the filter element. The same applies to all concentric filter elements. [0011] Thus, the particles having a size greater than the predetermined particle size of the filter element downstream and a size smaller than the predetermined particle size of the filter element upstream are retained between two filter elements. Further, the filter device comprises a cleaning device to harvest or to remove the concentrate and the particles being retained between each filter element. [0012] The cross flow filter devices always comprise a concentrate outlet to harvest or to remove the concentrate and the particles. But generally, a cleaning device is still needed because of particle deposition and clogging of the filter element. [0013] Such a cross-flow filter device, as mentioned in the preamble of claim 1, is known, for example, from DE 197 03 877 which describes an assembly to clean a filter membrane of a cross flow filter. A layer of sedimentary deposits is rinsed off by fluid directed at the deposits from a nozzle a short distance away. In the filter device according to DE 197 03 877, there is a concentric positioning of multiple filter membranes with sufficient space between the membranes for having inside cleaning nozzles that clean the surface of the filter media like a jet washer. [0014] Generally, and as it is the case in DE 197 03 877 (see drawings), the ratio between the second and the first filter membrane width is around 0.55. [0015] Unfortunately, such a cross flow filter device is very difficult to manufacture and to operate and does not prevent or reduce the accumulation of sediments at the surfaces of the filter element. [0016] It is an object of the invention to palliate at least some of these drawbacks by providing a cross flow filter device which is easy to manufacture, easy to carry out while providing better performance by improving the filtration effect due to a reduction of the membrane clogging and particle deposition and an increase of the filtration surface of a given space requirement. [0017] To this end, the invention provides a cross flow filter device according to the preamble of claim 1, characterised in that the ratio between the second width and the first width is 65%, preferably at least 70% and more preferably about 75%. [0018] It has been surprisingly found that the ratio between the second width and the first width of at least 65% substantially reduced the clogging and the particle deposition. Indeed, the presence of such a little space between the two filter elements involves an increased velocity for raw material while substantially reducing or preventing particle deposition or membrane clogging. Indeed at a constant flow rate of the raw material, if the space between the two filter elements is reduced, the velocity of the raw material will increase. Thus it is desirable to reduce the space between the two filter elements by adjusting the ratio between the second width and the first width to at least 65%, preferably to least 70% and more preferably to about 75% to reduce or prevent permanent particle deposition and membrane clogging without requiring any cleaning device between the two filter elements (like jet washers, scrapers or the like). [0019] Preferably, the ratio between the second width and the first width is at most 95% for allowing a predetermined flow rate of the raw material and to avoid an overpressure effect at the raw material inlet. [0020] Another advantage of the device according to the invention is that the first filter element and the second filter element are two separate filter elements having each their own filtrate outlet being different from each other, the filtrate outlet of the first filter element being said first filtrate outlet and the filtrate outlet of the second filter element being a second filtrate outlet. [0021] With two different filtrate outlets, the device according to the invention is a more flexible device allowing to use the device with only one filter element when required by blanking the outlet of the concerned filter element, for example, when the concerned filter element is accidentally perforated. [0022] Advantageously, the raw material inlet and the concentrate outlet are substantially aligned, in particular, aligned with said longitudinal central axis. [0023] It is advantageous that the raw material inlet and the concentrate outlet are aligned with the longitudinal central axis as this is the direction of the raw material flow. Such configuration allows the flow to remain a substantially laminar flow without substantial perturbation and the raw material (concentrate) passes with a higher efficiency tangentially to the surface of the filter element. [0024] In a particular embodiment, the first and the second filtrate outlets are respectively prolonged by a first and a second nozzle which are ended respectively by a first and a second valves, each valve having at least an open position and a closed position and being separately controlled. [0025] This is also a characteristic which allows a more flexible device as mentioned before. When the filtrate outlets present a nozzle ended by a valve, when it is required, it is possible, to blank an outlet. One valve being optionally controlled independently from the other or both valves being controlled together. Moreover, one filter element can be in operation while the other could be in a cleaning cycle. Indeed, by having two concentric filter elements, they present different diameters implying that the surface of the first filter element is different than the surface of the second element and the two filter elements should then be in a cleaning cycle at different moment. Indeed, with two different surfaces, since each filter element can manage a certain quantity of particles, they do not necessarily need to be cleaned at the same moment. [0026] Preferably, each filter element comprises a filter media, each filter media of each filter element having its own cut-off, said cut-off of the filter media of the first filter element being substantially different or similar from said cut-off of the filter media of the second filter element. [0027] The device according to the invention allows to collect two qualities of filtrates as the cut-off of the first filter media can be different of the second filter media. The device according to the invention comprises in an advantageous embodiment, two independent filtrate outlets allowing to collect the two filtrates with respectively their own qualities. [0028] It can be preferred to have, depending on the application to which the device is dedicated, the same cut-off for the two filter elements. [0029] Moreover, each filter media being manufactured in a material selected in the group consisting of metallic material, organic material or inorganic material. Continue reading... Full patent description for Cross flow filter device with concentric filter elements Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Cross flow filter device with concentric filter elements patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Cross flow filter device with concentric filter elements or other areas of interest. ### Previous Patent Application: Fine bubble airlift device Next Patent Application: Underdrain system Industry Class: Liquid purification or separation ### FreshPatents.com Support Thank you for viewing the Cross flow filter device with concentric filter elements patent info. 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