SYSTEM FOR FILTERING AN AEROSOL BY MEANS OF A MULTIPLE OF SEPARATORS BY CYCLE EFFECT AND CORRESPONDING FILTERING METHOD

Description

Technical field

[0001] The invention relates to a filtration system and a filtration method. State of the art

[0002] In many technical fields, it is known to inject oil to facilitate a cutting, engraving, cooling, or surface treatment operation. The injected oil is often in the form of droplets that saturate the atmosphere of the cutting, engraving, cooling, or surface treatment equipment. These oil-laden atmospheres are called oil mists.

[0003] It is of particular interest to recover the oil in order to reuse and / or recycle it and thus maintain a healthy atmosphere. There is therefore an interest in filtering the atmosphere loaded with oil droplets in order to separate the gaseous part and the liquid part. The oil mist is transferred to a filtration device which is configured to separate the carrier gas and the oil droplets.

[0004] Filtration systems that perform filtration by cyclone effect are known. Cyclone separation allows for separation of carrier gas and oil droplets without using one or more filters that become clogged and therefore need to be cleaned regularly.

[0005] Separation efficiency depends on the centrifugal acceleration experienced by the droplets, the number of revolutions made in the cyclone, their density and their size. There is therefore an interest in finding a cyclone configuration that is best suited to oil droplets.

[0006] Generally speaking, the higher the speeds or the greater the number of cyclones, the greater the filtration efficiency. An optimum balance must therefore be found between the complexity of the implementation and energy consumption.

[0007] Document US2009 / 0139192 A1 describes a system for filtering an aerosol using a plurality of cyclone separators. Statement of the invention

[0008] An object of the invention is to provide a filtration system which has a better ratio between energy consumption and its compactness while maintaining the provision of good separation between the particles and the gaseous medium of the aerosol.

[0009] These drawbacks tend to be solved by means of a filtration system which includes. a feed channel having a first end intended to be connected to a delivery member configured to deliver an aerosol to be treated; a plurality of cyclone separators, each cyclone separator having an inlet opening into the feed channel.

[0010] Several cyclone separators of the plurality of cyclone separators and their respective inlets are arranged consecutively along the feed channel and on the same side of the feed channel. Two consecutive inlets of two cyclone separators of the plurality of cyclone separators on the same side of the feed channel are arranged at different heights and / or have different cross-sections. According to one aspect of the invention, the feed channel is obstructed or reduced by a plurality of flow diverters, each flow diverter being configured to divert a portion of a flow of the atmosphere laden with oil droplets towards one of the corresponding cyclone separators.

[0011] Preferably, the feed channel is connected to N cyclone separators and in which each flow diverter diverts 1 / N of the initial section of the feed channel to a corresponding cyclone separator and reduces the section of the feed channel by a value equal to 1 / N for the cyclone separators to follow according to the direction of advancement of the aerosol flow.

[0012] Advantageously, the filtration system consists of only two parts, a first part defining the lower part of the cyclone separators, the lower part of the feed channel and possibly the flow separators if necessary, the second part forming a cover closing the feed channel and closing the cyclone separators.

[0013] The invention also relates to a filtration method which is efficient and simple to use.

[0014] This result is achieved by means of a process of filtration of an aerosol comprising particles and a gaseous medium comprising the following steps: provide a filtration system according to any of the preceding configurations; feed the filtration system with an aerosol; recover the particles at the outlet of the separators by cyclone effect.

[0015] Preferably, the aerosol is an oil mist and oil is recovered at the outlet of the separators by cyclone effect. Description of the drawings

[0016] Other advantages and characteristics will emerge more clearly from the following description of particular embodiments and implementations of the invention given as non-limiting examples and represented in the appended drawings, in which: there figure 1, schematically illustrates a sectional view of a filtration system according to a first embodiment; the figure 2 , schematically illustrates one of the sides of the filtration system according to the first embodiment in the direction of the inlet of the supply channel; the figure 3 , schematically illustrates a section of the inlet of the feed channel; the figure 4 , schematically illustrates a section of the feed channel between the first separators and the second cyclone separators; the Figure 5 , schematically illustrates a section of the feed channel between the second separators and the third cyclone separators; the figure 6 , schematically illustrates a section of the feed channel between the third separators and the fourth cyclone separators. Detailed description

[0017] The filtration system is a system for filtering an aerosol. The aerosol is formed by a set of particles in the solid or liquid state that are suspended in a gaseous medium. For example, the filtration system is a system for filtering an atmosphere loaded with oil droplets. The filtration system is configured to separate the oil present in the atmosphere in the form of droplets and the carrier gas, which may be air. The carrier gas supports the oil droplets. The filtration system is configured to facilitate the recovery of the particles, and more particularly the oil.

[0018] The particles are discharged through a first outlet 2. The carrier gas is discharged through another outlet 3 and may also be discharged in part through the first outlet. Advantageously, the particles are discharged through a lower outlet while the carrier gas is discharged through an upper outlet to take advantage of the difference in density between these two components. The lower outlet is at a lower altitude than the upper outlet.

[0019] The filtration system 1 comprises a supply channel 4 having a first end intended to be connected to a supply member configured to supply an aerosol to be treated which is for example the source of an atmosphere loaded with oil droplets. The supply channel 4 receives a mixture containing a carrier gas and particles, for example droplets. If the aerosol is an oil mist, the latter can be supplied from equipment using the oil and forming the oil mist. Alternatively, the aerosol is supplied by a reservoir receiving the atmosphere to be treated. The arrow illustrated in figure 1represents the direction of flow of an oil mist in the supply channel 4. The aerosol is set in motion by means of a ventilation system, for example a fan. Depending on the configuration, the ventilation system is arranged upstream and / or downstream of the filtration system 1 so that the aerosol enters the filtration system 1 with a certain speed.

[0020] The feed channel 4 is connected to a plurality of cyclone separators 5. A cyclone separator 5 has an inlet 5a receiving the mixture to be separated and it has two separate outlets. Each cyclone separator 5 has a first outlet 2 for recovering the aerosol particles, preferably the oil, and a second outlet 3 for recovering the carrier gas that is free of oil or has an oil content lower than the oil content at the inlet 5a. The cyclone separator 5 takes advantage of the effect of gravity to separate the particles and the carrier gas.

[0021] The inlet 5a of each cyclone separator 5 is connected to the feed channel 4 so that each cyclone separator 5 receives a fraction of the flow of the atmosphere to be treated. The cyclone separators 5 are not connected in series but in parallel. The cyclone separators 5 receive the same atmosphere to be treated or substantially the same atmosphere to be treated at their inlets 5a.

[0022] A cyclone separator 5 is a separator that has an inlet 5a engaging in a cone or in a structure having substantially the shape of a cone. In the illustrated embodiment, the upper part of the cyclone separator 5 has a circular cylindrical section while the lower part has a conical and more particularly frustoconical section. The lower end of the cyclone separator 5 is open so as to form the outlet 2 intended for the extraction of the oil. The upper part of the cyclone separator 5 is covered by a cover 6 which defines a through opening. The through opening forms the outlet 3 for the carrier gas having a low oil content. Preferably, the cyclone separators are identical.

[0023] In order to increase the efficiency of the separation between the carrier gas and the particles, particularly the oil, it is advantageous to have a cyclone effect separator 5 having a small diameter. The smaller the diameter, the greater the centrifugal effect for a given speed of the atmosphere to be treated in the feed channel 4. It is therefore advantageous to have a reduction in the section of the conical part to increase the circulation speed of the gas and thus better separate the oil.

[0024] However, the smaller the diameter of the cyclone separator 5, the smaller the volume of gas treated. There is therefore an advantage in feeding several cyclone separators 5 connected in parallel so as to increase the quantity of carrier gas treated for a given time.

[0025] In order to facilitate the feeding of the cyclone separators 5, it is advantageous to mount the cyclone separators 5 consecutively along the feed channel 4. The inlets 5a of the cyclone separators 5 are arranged consecutively along the feed channel 4. It is also advantageous to have a straight or slightly curved feed channel 4 to limit the pressure drop along the feed channel 4. The feed channel 4 is divided into multiple portions which each feed a cyclone separator 5.

[0026] Preferably, the filtration system 1 has an even number of cyclone separators 5. The cyclone separators 5 are distributed symmetrically with respect to the longitudinal direction of the feed channel 4 so as not to disturb the flow of the particle-laden atmosphere. It is advantageous to take two identical portions of the carrier gas flow symmetrically with respect to the median longitudinal plane of the feed channel 4 so as not to disturb the flow and to facilitate obtaining a controlled flow in the cyclone separator 5. In other words, the same quantity of flow is taken from the right side and the left side of the feed channel 4.

[0027] In order to form a compact filtration system, it is advantageous to offset the cyclone separators 5 transversely to the feed channel 4, i.e. along the width direction of the feed channel 4. The separators are arranged in a staggered manner. In this way, with the same length of feed channel 4, it is possible to connect more cyclone separators 5 without increasing the width of the filtration system too much.

[0028] Advantageously, two consecutive inlets 5a of two cyclone separators 5 of the plurality of cyclone separators 5 on the same side of the feed channel 4 are arranged consecutively and at different heights. The two inlets 5a are arranged at different levels. For example, the first inlet 5a is at a lower level of the feed channel 4 and the second inlet 5a is at a higher level of the feed channel 4. The offset of the inlets 5a over the height of the feed channel 4 makes it possible to improve the capture of the carrier gas flow by limiting the disturbances on the flow for the other inlets to follow. The height is measured in a vertical direction.

[0029] A plurality of flow diverters 7 are present which divert the flow of carrier gases towards the cyclone separator inlets 5. Depending on the configurations the diverters are installed in the feed channel 4 or they are formed by the side wall 4a of the feed channel. In the embodiment illustrated in figure 1 , the diverters are formed by the side wall 4a of the feed channel 4. The flow diverters 7 obstruct or reduce the active section of the feed channel 4 to divert a part of the flow towards the cyclone separator 5 to be fed and reduce the section of the feed channel 4 for the cyclone separators 5 to follow in the longitudinal direction of the feed channel 4.

[0030] Preferably, the flow separators 7 define a curved wall so as to shift the direction of the carrier gas flow between the feed channel 4 and the cyclone separator 5 so that the carrier gas flowing in the longitudinal direction flows tangentially in the cyclone separator 5. This allows for more efficient separation.

[0031] In an advantageous embodiment, the filtration system 1 has a first number of cyclone separators 5, for example N cyclone separators 5, arranged on one side of the feed channel 4. The inlets 5a of the cyclone separators 5 are distributed in the height direction over the first number of stages, i.e. N stages. In other words, the N inlets 5a define N different stages for capturing the carrier gas flow. The carrier gas flow is diverted in each of the cyclone separators 5 by means of said first number of flow diverters 7, i.e. N flow diverters 7. The N flow diverters 7 are arranged consecutively along the longitudinal axis of the feed channel and the N flow diverters reduce the cross-section of the feed channel by a value equal to 1 / N.Each flow diverter feeds a cyclone separator 5 with a gas flow that represents 1 / N of the initial flow that fills the feed channel. Preferably, each flow diverter 7 obstructs or reduces the cross-section of the feed channel 4 by a value equal to 1 / N for the remainder of the feed channel. In other words, the active cross-section of the feed channel 4 decreases each time a portion of the carrier gas flow is diverted to a cyclone separator 5.

[0032] Each inlet 5a has a height h which corresponds to H / N with H the initial height of the supply channel 4.

[0033] There figure 2represents the distribution of the different flow diverters 7 in the feed channel 4. The eight flow diverters 7 corresponding to the eight cyclone separators 5 have a total deflection section which is equal to the initial section of the feed channel 4. The series of flow diverters 7 extend from the side walls towards the center of the feed channel 4. In a series, the flow diverters are arranged one above the other.

[0034] There figure 3 , represents a section of the inlet of the supply channel 4 which defines the value of the initial section of the supply channel 4. The figure 4 represents a sectional view of the feed channel at the start-up of the first two flow diverters intended to feed the first two cyclone separators 5. The Figure 5represents a sectional view of the feed channel at the start-up of the two second flow diverters intended to feed the two second cyclone separators 5. The feed channel has been reduced in section by the first two flow separators.

[0035] In another embodiment, the filtration system 1 has a first number of cyclone separators 5, for example N cyclone separators 5, arranged on one side of the feed channel 4. The number of cyclone separators 5 is an even number. The inlets of the cyclone separators 5 are distributed over a second number of stages which corresponds to half of the first number, i.e. N / 2 stages. The carrier gas flow is diverted in each of the cyclone separators 5 by means of said first number of flow diverters 7, i.e. N flow diverters 7. The N flow diverters 7 are arranged consecutively along the longitudinal axis of the feed channel 4 and the N flow diverters reduce the active cross-section of the feed channel 4 by a value equal to 1 / N.Each flow diverter 7 feeds a cyclone separator 5 with a gas flow which represents 1 / N of the initial flow which fills the feed channel 4.

[0036] The N flow diverters 7 are divided into two series of second number of flow diverters 7, i.e. N / 2. Each of the series extends from one end to the other according to the height of the feed channel 4. Each of the two series of flow diverters 7 defines N / 2 stages. The section of the feed channel 4 is divided into two equal portions according to the height, i.e. in a direction parallel to the central axis. Advantageously, each inlet series captures a section of the initial flow from one side wall of the feed channel to the opposite side wall.

[0037] There figure 1illustrates a configuration of filtration system 1 with eight cyclone separators 5. Only the four cyclone separators on the left side are shown. The four inlets 5a are divided into two sets of two inlets 5a. The figure 2 illustrates a view of the various flow diverters 7 in the feed channel 4. The eight flow diverters 7 occupy a section equal to the section of the feed channel 4 to divert all the flow towards the cyclone separators 5.

[0038] In another embodiment, the filtration system 1 has a first number of cyclone separators 5, for example N cyclone separators 5, arranged on one side of the feed channel 4. The inlets of the cyclone separators 5 are distributed in n series of inlets with n series of flow diverters 7. Each of the n series of inlets has N / n inlets with N / n flow diverters 7.

[0039] Each flow diverter 7 feeds a cyclone separator 5 with a gas flow which represents 1 / N of the initial flow which fills the feed channel 4. Each series of flow diverters 7 occupies 1 / n of the cross-section of the feed channel 4 with respect to the initial cross-section of the feed channel 4. The carrier gas flow is diverted in each of the cyclone separators 5 by means of said first number of flow diverters 7, i.e. N flow diverters 7. The N flow diverters are arranged consecutively along the longitudinal axis of the feed channel 4 and the N flow diverters 7 reduce the cross-section of the feed channel 4 by a value equal to 1 / N. The operation is identical to that of the previous embodiment

[0040] In a particular embodiment, the filtration system has 2N cyclone separators. The 2N cyclone separators are divided into N cyclone separators on the right side of the feed channel 4 and N separators on the left side of the feed channel 4. Depending on the configurations, the N inlets 5a and the N flow separators are distributed in n series, with n a non-zero integer, for example 1, 2 or 3. N is also a non-zero integer.

[0041] In a particular embodiment, the different cyclone effect separators 5 all have the same deflection section value.

[0042] Such a configuration makes it possible to optimize the section of the feed channel to feed each of the cyclone effect separators 5.

[0043] Preferably, the deflection section defined by a flow deflector 7 has a height h which is greater than the width, preferably the height h is at least twice the width.

[0044] In order to have a height which is greater than the width of the deflection section, it is advantageous to choose the number of series of cyclone separators 5 as well as the number of cyclone separators 5 in each series. In the embodiment illustrated in figure 1, the filtration system 1 has eight cyclone separators with four cyclone separators on each side of the feed channel. Such a configuration allows for a section close to the square which is preferential for feeding the cyclone separators 5. Depending on the constraints imposed, the number of separators to be used and their distribution define the section of the feed channel 4 or the section of the feed channel defines the number of cyclone separators 5 to be used.

[0045] In a particularly advantageous embodiment, the filtration system 1 is formed by only two parts made of polymer material and which can be obtained by injection. The first part defines the feed channel 4 as well as the cyclone separators 5 and the flow diverters 7 if applicable. The second part forms the cover 6 with the outlet orifice 3 for the carrier gas. It is then particularly economical to form a high-performance separation system 1 for the separation of air and oil from an oil mist.

[0046] The filtration of an oil mist and more generally of an aerosol is carried out by injecting the mist at the inlet of the supply channel 4. The flow of oil mist is divided into a plurality of elementary flows which each feed a cyclone separator 5. Each cyclone separator 5 carries out the filtration to extract the oil which comes out through a dedicated outlet.

[0047] The multiple cyclone separators 5 are mounted in parallel and are compactly integrated into the filtration system, which allows for a small yet highly efficient filtration system.

[0048] Although the exemplary embodiments describe the separation of an oil mist, the separation system may be used to separate particles from an aerosol, wherein the aerosol may contain particles in a solid state and / or particles in a liquid state.

Claims

1. Filtration system (1) for an aerosol containing a carrier gas and particles comprising : - a feed channel (4) having a first end designed to be connected to a supply member configured to supply the aerosol; - a plurality of cyclone separators (5), each cyclone separator (5) having an inlet (5a) opening into the feed channel (4); wherein several cyclone separators (5) of the plurality of cyclone separators (5) and their respective inlets (5a) are arranged consecutively along the feed channel (4) and on the same side of the feed channel (4); - flow diverters (7) are arranged in the feed channel (4) to divert part of a flow of the droplet-laden atmosphere towards one of the corresponding cyclone separators (5), wherein the cross-section of the feed channel (4) decreases in a direction away from the first end towards the plurality of cyclone separators (5); filtration system (1) characterized in that flow diverters (7) are arranged in the feed channel (4) to monotonically reduce the effective cross-section of the feed channel (4), the effective cross-section of the feed channel (4) decreasing each time a portion of the carrier gas flow is diverted to a cyclone separator by one of the flow diverters ; and in that two consecutive inlets of two cyclone separators (5) of the plurality of cyclone separators (5) on the same side of the feed channel (4) are arranged at different heights.

2. Filtration system (1) according to claim 1 wherein two consecutive flow diverters have the same thickness and are arranged at different heights which respectively correspond to the height of the corresponding flow diverter.

3. Filtration system (1) according to one of claims 1 and 2 wherein the feed channel (4) is connected to N cyclone separators and wherein each flow diverter (7) diverts 1 / N from the initial cross-section of the feed channel (4) to a corresponding cyclone separator and reduces the cross-section of the feed channel by a value equal to 1 / N for the cyclone separators to follow according to the direction of advance of the aerosol flow.

4. System according to any one of the preceding claims wherein the plurality of cyclone separators (5) is divided into two series of cyclone separators facing each other perpendicularly to an aerosol flow axis and wherein two inlets facing each other perpendicularly to the aerosol flow axis are at the same height.

5. System according to any one of the preceding claims consisting of only two parts, a first part defining the lower part of the cyclone separators (5), the lower part of the feed channel (4) and possibly the flow diverters (7), the second part forming a cover closing the feed channel (4) and closing the cyclone separators (5).

6. System according to any one of the preceding claims wherein said two consecutive inlets of two cyclone separators (5) of the plurality of cyclone separators (5) on the same side of the feed channel (4) have different cross-sections.

7. Filtration method comprising the following steps: - providing a filtration system according to any one of the preceding claims; - feeding an aerosol to the filtration system; - collecting particles at an outlet of the cyclone separator (5).

8. Filtration method according to the preceding claim wherein the aerosol is an oil mist and oil is collected at the outlet of the cyclone separators (5).