Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
  • B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
  • B01D65/102—Detection of leaks in membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
  • B01D63/02—Hollow fibre modules
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2311/00—Details relating to membrane separation process operations and control
  • B01D2311/06—Specific process operations in the permeate stream
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2313/00—Details relating to membrane modules or apparatus
  • B01D2313/90—Additional auxiliary systems integrated with the module or apparatus
  • B01D2313/903—Integrated control or detection device
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
  • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
  • G01N15/082—Investigating permeability by forcing a fluid through a sample
  • G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change

Definitions

• the invention relates to a method for testing the integrity of filtration membranes, namely ultrafiltration, microfiltration, nanofiltration or hyperfiltration membranes, of tubular geometry, implemented in a module composed of a casing grouping a set of hollow fibers.
• a lack of integrity of the membrane can nevertheless lead to pollution of the filtered water circuit which then becomes re-contaminated.
• the need to control the integrity of the physical barrier constituted by the membrane has therefore naturally imposed itself.
• Another method known as the "pressure decay test" provides an answer by isolating a face of the previously pressurized membrane at a gas pressure lower than its bubbling pressure. The procedure then consists in measuring the evolution of the pressure on the side of the pressurized side for a determined duration, generally from 5 to 15 minutes. The diffusion of gas within the liquid generates a slight decrease in pressure, which is defined as a loss of pressure maximum acceptable for a specified period of time. A decrease in pressure above this reference value means a gas leak interpreted as a lack of integrity.
• WO 2005/077499 applies "pressure decay test" to hollow fiber type filtration membranes subjected to backwashing under gas pressure.
• the test is conducted after a backwash which is usually the phase where damage can be caused to the membranes.
• the inner portion of the hollow fibers is pressurized with gas and isolated, and the pressure decrease in the inner portion of the hollow fibers is measured and analyzed.
• the sensitivity of the test remains very dependent on the duration of the test and, when this duration is of the order of one minute as announced in this document, the sensitivity needs to be improved.
• this static test requiring the isolation of the inner parts of the membranes is very sensitive to valve leakage, which disrupts the results.
• the object of the invention is, above all, to provide a filtration membrane integrity test method which, using a gas pressure, takes place in a reduced time of the order of a few minutes or less, while giving reliable results, insensitive to valve leaks.
• the sequencing of the process is as follows:
• an integrity test method applied to hollow fiber type filtration membranes mounted inside a liquid filtration assembly, with compartment delineation.
• concentrate where the retained materials accumulate, both in suspension and on the membranes, and a permeate compartment collecting the filtered liquid comprises a step of pressurizing with a gas, in particular air, the inner part of the hollow fibers of the membranes under a pressure lower than the bubbling pressure of the membrane and greater than the pressure of the part outside the fibers, and is characterized in that - the test is carried out on membranes of the internal skin type, the compartment being concentrated constituted by the inner part of the hollow fibers, the permeate compartment consisting of the part outside the hollow fibers, the pressurized gas is circulated in the concentrated compartment for the emptying of the hollow fibers which are open at their ends,
• the permeate compartment is left in the atmosphere to allow the liquid on the membrane surface to migrate through the membrane;
• the pressure increase in the permeate compartment caused by the circulation of gas in the concentrated compartment and the passage of gas towards the permeate compartment are measured; and after a definite time, the pressure increase is compared to that observed when using an intact membrane.
• an integrity test method applied to hollow fiber type filtration membranes, mounted inside a liquid filtration assembly, with compartment delineation. concentrate where the retained materials accumulate, both in suspension and on the membranes, and a permeate compartment collecting the filtered liquid comprises a step of pressurizing with a gas, in particular air, the inner part of the hollow fibers of the membranes under a pressure lower than the bubbling pressure of the membrane and greater than the pressure of the part outside the fibers, and is characterized in that:
• the test is carried out on membranes of the internal skin type, the concentrate compartment being constituted by the inner part of the hollow fibers, the permeate compartment being constituted by the outer part of the hollow fibers, the gas under pressure being circulated in the concentrated compartment for the emptying of hollow fibers which are open at their ends,
• the permeate compartment is left in the atmosphere, in particular with a purge of gas at a high point of this compartment, to allow the liquid on the membrane surface to migrate through the membrane;
• the liquid quality of the permeate compartment in particular that present at the purge of gas at the high point of the permeate compartment, is compared with that observed during the use of an integral membrane.
• the presence of a diphasic gas / water mixture demonstrates a non-integral membrane.
• the test of the invention is dynamic since the gas flows continuously through the compartment concentrate during the test.
• the measurement of the pressure increase in the permeate compartment is insensitive to possible leakage of an isolation valve due to a continuous supply of circulating pressurized gas.
• the quality of the liquid present in the permeate compartment, in particular the purge of gas is almost independent of an undesirable liquid flow.
• the present invention makes it possible to associate the measurement of integrity with a two-phase air-plus-water wash by reducing the test duration to less than a few minutes; it also makes it possible to apply tests during the filtration and then allows the localization of the faulty modules.
• the concentrate compartment can be filled with backwashing or filtration.
• the integrity test can take place during each backwash, or cyclically after a number of backwashes, or cyclically during filtration.
• the detection of the water quality can be carried out by a conductimetric measurement, or by a passage detection measurement, or by a visual measurement (video image analyzer). ).
• the invention also relates to an integrity test device applied to hollow fiber type filtration membranes, mounted inside a liquid filtration assembly, with delimitation of a concentrated compartment where accumulate the retained materials, both in suspension and on the membranes, and a permeate compartment collecting the filtered liquid, comprising means for pressurizing by a gas, in particular air, the inner part of the hollow fibers of the membranes under a lower pressure at the bubbling pressure of the membrane and greater than the pressure of the part outside the fibers, this device being characterized in that it comprises a booster, in particular a blower, means for connecting the outlet of the fan to the compartment concentrate formed by the internal parts of hollow-skin type membranes with internal skin, means for isolating the permeate compartment, draining means compartment concentrat to allow a flow of gas delivered by the booster, and means for measuring
• the measuring means may comprise a pressure gauge, sensitive to the pressure of the permeate compartment, and / or a bubble detector at the top of the permeate, and / or a conductivity meter for measuring the conductivity of the permeate, and / or a pass detector, and / or a video image analyzer.
• the booster is advantageously constituted by a fan with a high air flow at a pressure of the order of 0.5 bar.
• the flow rate of the blower is in particular provided to ensure at the top of the module (reduced to the free section of the hollow fibers) an air flow rate of the order of 0.4 to 1.5 m / s.
• Fig. 1 is a diagram of a filtration installation implementing a method according to the invention.
• Fig. 2 is a schematic of a hollow fiber type membrane module with internal skin.
• Fig. 3 is a large scale schematic axial vertical section of an integrated filtration membrane subjected to the test according to the first aspect of the method.
• Fig. 4 is a schematic axial section on a large scale of a damaged, unhealthy filtration membrane subjected to the test according to the first aspect of the process.
• Fig. 5 is a diagram illustrating the evolution of the pressure in the permeate, expressed in bars and range on the ordinate, as a function of time in seconds, carried on the abscissa, in the case of an intact membrane and a damaged membrane, according to the first aspect of the process.
• Fig. 6 is a schematic diagram of implementing the second aspect of the method with measurement of the liquid quality of the permeate compartment of a module.
• Fig. 7 is a schematic large-scale axial section of a damaged filtration membrane, with air bleed at the high point of the permeate compartment, for a test according to the second aspect of the process, and
• FIG. 8 is a diagram illustrating the evolution of the conductivity in the permeate, plotted on the ordinate, as a function of time in seconds, carried on the abscissa, in the case of an intact membrane and a damaged membrane.
• FIG. 1 can be seen a filtration installation of the type described in the application FR 2 867 394 (04 02492) in the name of the same applicant company, implementing the method of the invention.
• a module composed of a casing C shown schematically, groups together a set M (FIG. 2) of hollow fiber filtration membranes F with internal skin.
• Each module M comprises several thousand hollow fibers F, arranged in parallel between two ramps G, H distribution or collection in the direction of flow.
• the casing C has two orifices E1, E2, respectively low and high, which can serve as outputs and / or inputs.
• the orifices E1, E2 are connected to the concentrate compartment J formed by the interior space of the hollow fibers. Inside the housing, the space around the membranes, and between them, forms the permeate compartment K which has an output A.
• the installation comprises a feed pump 1 of the liquid to be filtered, the discharge of which is connected, via a supply valve 2, to the orifice E1.
• a drain connection between the valve 2 and the orifice E1 is provided with a drain valve 3.
• the pipe located downstream of the valve 3 opens into a device B discharge discharges.
• a head-up backwash rejection valve 4 is connected to the orifice E2 of the casing C.
• a duct downstream of the valve 4 opens into the evacuation device B.
• a valve 5 is mounted on a pipe connecting a booster 6 of gas, in particular air, to the orifice E2.
• the booster 6 is advantageously constituted by a fan S giving a high air flow, under a pressure of the order of 0.5 bar.
• the flow rate of the blower is provided to ensure at the top of the module (reduced to the free section of the hollow fibers) an air flow rate of the order of 0.4 to 1.5 m / s.
• a leak created by one or more non-intact membranes causes virtually no pressure drop of the air flowing in the hollow fibers.
• a backwashing valve 7 is disposed on a pipe connecting the outlet of a backwashing pump 8 to the orifice A.
• the suction of the pump 8 is connected to a reservoir 9 of filtered liquid.
• Another pump 10 has its suction connected to a tank 11 containing an adjuvant, for example a disinfectant, oxidizing solution (for example, hypochlorite, di-oxide, etc.), or an acidic or even basic chemical compound.
• the discharge of the pump 10 is connected to a portion of pipe located between the valve 7 and the inlet A, with the interposition of a valve 10a.
• a manometer 12 is disposed on a pipe connected to the orifice A. The manometer 12 thus measures the pressure in the permeate compartment K.
• a detector 13 of the permeate quality is disposed on a gas purge pipe 14 connected to the part high compartment permeate.
• the outlet A is located in the upper part of the permeate, and the pipe 14 is connected to the outlet A.
• a valve 15 is disposed on the pipe 14 upstream of the detector 13.
• This detector can be for example, a bubble detector 16 (FIG. 6) or a conductivity meter measuring the conductivity of the permeate.
• a pipe 17 provided with a valve 18 connects the outputs of the valves 2 and 4.
• pump 1 In filtration mode, pump 1 is in action and valves 2 and 7 are open while all other valves are closed.
• the liquid to be treated enters the orifice E1 and the filtered liquid (permeate) leaves through the orifice A to be directed towards the reservoir 9.
• valves 2 and 4 are closed, while valve 3 is open for emptying.
• the valve 5 of the booster 6 is open and the booster is turned on to send air under pressure in the inner part of the hollow fibers and accelerate the emptying. The air circulates continuously and escapes through the open ends of the fibers and the valve 3 open.
• the valve 7 is open and the pump 8 is turned on to send, through the inlet A, the backwashing liquid. Thanks to two-phase backwashes (air and water), as described in patent FR 0402492, it is possible to implement an integrity test according to the invention when using backwashing phases with gas alone.
• the permeate side K previously purged is filled with water, and the concentrated side J of the membrane is pressurized by a gas below the bubbling pressure.
• the permeate side K first left to the atmosphere to allow the membrane surface liquid to migrate through the membrane.
• the permeate side K is then closed, ie isolated, by closing the various valves 7, 15, 10a connected to the outlet A (Fig.1).
• Fig.3 the compartment K is shown closed schematically.
• the concentrate side J of the membrane is pressurized by a gas below the bubbling pressure.
• the valve 4 is closed while the valve 5 is open and the fan 6 is turned on.
• the gas the air in the example considered, while circulating continuously in the concentrate compartment J will migrate in part by diffusion through the membrane F and cause a slow increase in the pressure of the permeate compartment K.
• the increase in pressure will be faster.
• the pressure value is read and compared to the value expected when the equipment was intact.
• FIG. 5 illustrates the evolution of the pressure of the permeate compartment plotted on the ordinate, and expressed in bars, as a function of the time plotted on the abscissa and expressed in seconds in the case of an integral module (curve 19) and in the case of a module with a broken fiber (curve 20). It appears that the difference can be detected very quickly, in a few seconds.
• the implementation, according to this first aspect, is therefore the following:
• the permeate compartment K remains open to the atmosphere, for example by a gas purge 21 (Figs 6 and 7) in the upper part of the permeate, equipped with a bubble detector 16.
• An air purge of the permeate portion K is carried out by filtration or backwashing, then stopping filtration or backwashing, while leaving the permeate compartment in the atmosphere.
• Pressurization is provided in dynamics of the concentrate J portion of the membranes obtained by circulating a gas under pressure less than the bubbling pressure, in particular a pressure of about 0.1 bar. If a fiber Fd is not integral with a tear R as illustrated in FIG. 7, air passes into the permeate compartment K in the form of bubbles, detected for example by a bubble detector 16.
• the quality of the liquid present at the air purge at the high point of the module is compared with that observed during the use of integral membrane.
• Fig. 8 illustrates the conductivity variations plotted on the ordinate, as a function of time, in seconds, plotted on the abscissa in the case of an integral module (curve 22), a module with a broken fiber (curve 23) and a module with five broken fibers (curve 24).
• the concentrate can be filled with backwash or filtration.
• the integrity control method according to the present invention has many advantages: the measurement of the integrity detection can be done online, associated with the backwashing or the filtration, at a frequency such that it can appear as continuous, with minimal production interruptions; the accuracy of the measurement is adjustable by modifying the thresholds and test times; the technology and the setting device. described by the present invention are particularly simple. The result is an economical device, both in investment costs and in operation, which can be multiplied to refine the identification of non-intact membranes.
• the method of the invention can be applied simultaneously to the modules of the block and makes it easy to locate the module (s) defective among the 10 to 50 modules present on a filtration unit.
• a brief integrity test can thus be performed dynamically during the short backwashing sequence or during filtration.
• the duration of the integrity test procedure is significantly shortened compared to the usual tests.
• Integrity tests can then be initiated very frequently, during backwashing or even during filtration with minimal water loss and non-production times. They can be managed at the request of an operator or an operator.
• An integrity test according to the invention is rapid thanks to the use of a circulation of gas under pressure, preferably coming from an external booster, to accelerate the emptying phase, to accelerate the equilibrium phase of the compressed air allowing the test.
• the gain in duration also results from the integration of the test with backwashing.
• the phases of production stoppage, filling and return to production would have been performed anyway during a two-phase backwashing (air + water).
• An industrial example concerns a water production unit of 24 modules each containing 35,000 fibers of internal diameter of 0.93 mm. The total section at the top of the module is 0.59 m 2 (24 x 35000 x internal section of a fiber).
• the blower then provides an air flow of 1050 Nm 3 / h (for an air speed of 0.5 m / s) or 3150 Nm 3 / h (for an air velocity of 1, 5 m / s).

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

Applications Claiming Priority (2)

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• 2005
  • 2005-12-20 FR FR0512954A patent/FR2894843B1/fr not_active Expired - Fee Related
• 2006
  • 2006-12-13 WO PCT/FR2006/002720 patent/WO2007080260A1/fr active Application Filing
  • 2006-12-13 EP EP06841924A patent/EP1971846A1/de not_active Withdrawn
  • 2006-12-13 CN CN200680047966.4A patent/CN101341389A/zh active Pending

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