FR2833853A1 - Evaporator for separating effluent phases has diffuser to disperse effluent in droplets in heated chamber - Google Patents

Abstract

The evaporator (1), designed to separate an effluent into a vapor phase and a liquid and/or solid phase, consists of a heated chamber (2) with an inlet for the effluent, a outlet channel (15) for the vapor phase and an outlet aperture (7) for the liquid/solid phase. The evaporator (1), designed to separate an effluent into a vapor phase and a liquid and/or solid phase, consists of a heated chamber (2) with an inlet for the effluent, a outlet channel (15) for the vapor phase and an outlet aperture (7) for the liquid/solid phase. The effluent is fed into the chamber through a diffuser (9) that disperses it in droplets inside the chamber and towards a heater, while the chamber is maintained at a pressure below atmospheric. The heater is formed by tubes (4) carrying a heating agent inside the wall of the chamber, with the diffuser spraying the effluent towards the wall's inner surface (2b) which can have lengthwise fins to increase its heat exchange area. The chamber has a mesh filter (21) between the diffuser and its base (2a) which is inclined to promote the flow of the liquid phase towards its outlet (7).

Description

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 The technical field of the invention is that of evaporators making it possible to separate a fluid into at least two phases, a vapor phase and a liquid and / or solid phase.

 GB419566 discloses an evaporator in which a liquid which must be separated into several phases (or distilled) is spread over the external surface of a heated cylindrical body. The liquid is then placed in a thin layer on this heated wall and the vapor and gas phases are separated from the liquid phases.

 Such an evaporator has a low yield and it is ill-suited for the distillation of highly viscous fatty liquids.

 Indeed in this case the flow on the heating body is too slow and the layers obtained are not thin enough.

 In addition, the solid impurities which are possibly included in the effluents to be separated may agglomerate on the heating body and disturb the phase separation step while fouling the evaporator.

 It is the object of the invention to propose an evaporator which does not have such drawbacks.

 Thus, the evaporator according to the invention allows rapid and efficient separation of the vapor and liquid phases from an effluent, in particular from a fatty effluent.

 Furthermore, the evaporator according to the invention makes it possible to avoid the accumulation of solid residues liable to clog the evaporator and it ensures the separation of these solid residues from the liquid phase.

 Thus, the subject of the invention is an evaporator intended to separate an effluent into a vapor phase and a liquid and / or solid phase, and comprising a heated tank comprising means for introducing the effluents to be separated, a pipe for discharging the vapor phase and at least one discharge opening for the liquid and / or solid phases, evaporator characterized in that the introduction means comprise a diffuser ensuring dispersion of

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 the effluent in droplets inside the tank, the tank also being kept under vacuum.

 The diffuser will preferentially disperse the effluent towards a heating means.

 The heating means may comprise a wall of the tank heated by pipes carrying a heat transfer fluid and arranged in the wall, the diffuser dispersing the effluents towards the wall of the tank.

 The wall of the tank may carry at least two longitudinal fins making it possible to increase a heat exchange surface between tank and effluents.

 The diffuser may be in the form of a toric pipe.

 The tank may include at least one filtering screen disposed between the diffuser and a bottom of the tank where the openings for discharging the liquid and / or solid phases are arranged.

 Advantageously, the bottom of the tank may be inclined so as to favor the flow of a liquid phase towards a first discharge opening for the liquid phase.

 The filter screen may have a substantially conical profile so as to promote the evacuation of solid or muddy residues towards a second evacuation opening disposed substantially axially.

 The invention also relates to an installation for separating an effluent in several phases, installation using such an evaporator and ensuring efficient separation of effluents (in particular fatty effluents) in several phases while reducing the fouling of the evaporator and facilitating cleaning and maintenance.

 This separation installation may include a diffuser supplied with effluents which are pressurized by a first pump.

 The diffuser can be connected on one side to a pressurized effluent supply and on the other to a filtering means.

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 The diffuser may be connected to the filtering means by a return pipe on which at least one pressure regulator will be placed.

 The filtering means may comprise at least one filtering screen, the effluents intended for the evaporator being introduced upstream of the screen and in parallel with those coming from the return pipe, a second pump being provided between the diffuser and the filter to ensure an overpressure relative to the effluent inlet pressure.

 The separation installation according to the invention may comprise at least one device for injecting water and or steam under pressure which may be connected to the disperser and / or to the tank by means of a valve, injection which will be used to clean the disperser and / or the tank.

 Other advantages of the invention will appear on reading the description which follows of a particular embodiment, description made with reference to the accompanying drawings and in which: - Figure 1 is a schematic view in longitudinal section of an evaporator according to the invention, - Figure 2 is a cross-sectional view of this evaporator, section taken along the plane whose trace AA is visible in Figure 1, - Figure 3 is an enlarged detail view of the diffuser, - Figure 4 is a block diagram of a separation installation according to the invention.

 Referring to FIG. 1, an evaporator 1 according to the invention comprises a substantially cylindrical tank 2 comprising a bottom 2a and closed at the top by a cover 3.

 The cover 3 carries means for introducing the effluents to be separated which comprise a pipe 5 ensuring the conduct of the effluents (introduced at E into the installation). This pipe is closed by a

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 first valve 6. The effluents here comprise an oily or oily phase mixed with water which it is necessary to eliminate in order to allow the reuse or subsequent treatment of the oily phase.

 The bottom 2a carries an opening 7, arranged in an offset manner, and allowing the evacuation of a liquid phase.

This discharge opening is closed by a second valve 8.

 The cylindrical wall 2b of the tank of the evaporator is hollow and contains tubes 4, regularly distributed angularly (see also Figure 2), connected to each other and which extend over substantially the entire height of the wall 2b. These pipes make it possible to heat the wall which thus constitutes a means of heating the tank.

 For this purpose they transport a heat transfer fluid, for example hot water, which is supplied by a heat source S not shown here in detail (for example a boiler or a heat exchanger).

 For the separation of a fatty effluent (such as used oil or animal or vegetable fat) into a water vapor phase and a liquid phase, the heating means will be defined so as to ensure a temperature in the evaporator between 80 and 95 C.

 Furthermore, the effluents will advantageously be preheated before their introduction into the tank in order to provide them with sufficient fluidity facilitating their dispersion.

 Pressurization will be obtained using a pump 19.

For fatty effluents it is possible to preheat to 90 C and introduce the effluents at a pressure of the order of 0.4 MPa.

 According to an essential characteristic of the invention, the introduction means comprise a diffuser 9 which is connected to the pipe 5. The diffuser 9 consists of a metal tube (for example made of stainless steel) of toric shape having for axis the axis 10 of the tank 2.

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 This tube is pierced with holes 11 which have axes oriented in the direction of an internal surface 12 of the wall 2b of the tank 2.

 The holes are regularly distributed angularly around the axis 10 of the diffuser 9. FIG. 3 shows in an enlarged manner the arrangement of the holes 11 relative to the wall 12 of the tank 2. Some holes have an axis a perpendicular to the wall 12 , other holes have an axis a2 which is inclined relative to the wall 12 and oriented towards a lower part of the tank 2.

 The result of this configuration is a dispersion of the effluents along a toroidal shower, oriented towards the wall 12, and having in longitudinal section an opening angle a which is delimited by the directions a 1 and a 2.

 The diffuser 9 is disposed at a distance d from the wall 12. It is possible, for example, to produce a toric diffuser in the form of a tube 30 mm in external diameter (with a thickness of the order of 2 mm). The diameter of the torus itself will be chosen so as to ensure a distance d between the diffuser and the wall which is between 50 and 100 mm.

 The opening angle a of the spray pattern will be of the order of 20 to 40 and the diameter of the holes 11 will be of the order of 1 mm.

 Such a diffuser ensures dispersion of the effluent in the form of fine droplets which are deposited in a thin layer on the heated wall 12 of the tank, a wall which ensures the separation between the liquid and vapor phases.

 Due to its toric shape, the diffuser does not hinder the evacuation of the vapors V generated by the heated wall.

These vapors move from the wall 12 of the tank to a pipe 15 allowing the evacuation of the vapor phase and pass through the torus 9.

 In order to increase the heat exchange surface between the effluents and the wall of the tank, longitudinal metal fins 13 will advantageously be available.

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 on the internal surface 12 of the tank. This improves the efficiency of the evaporator.

 The diffuser 9 will preferably be placed in the upper half of the tank. The effluents can thus be distributed by trickling over a larger surface of the wall 12 of the tank and the yield is improved.

 In order to facilitate the separation of phases, the tank 2 will also be kept under vacuum thanks to a vacuum pump 14. This is connected to the tank by the pipe 15 which opens at the level of the cover 3 of the tank. A valve 16 allows the opening or closing of this pipe. A condenser 17 ensures the cooling of the water vapor obtained. This water is stored in a tank 18.

 To allow the formation of droplets, the effluents introduced into the installation at E are supplied to the diffuser 9 under pressure, the pressurization is ensured by a first pump 19 or feed pump.

 According to another characteristic of the invention, the diffuser 9, which is connected on one side by the pipe 5 to the effluent supply, is connected on the other side by a return pipe 40 to a filtering means 20.

 Thus the toroid of the diffuser 9 is not closed. The effluents circulate continuously in the torus between the first pump 19 and the filter 20 and only part of the effluents is diffused in the tank 2 through the diffuser 9.

 Such an arrangement makes it possible to reduce the risk of clogging of the holes 11 of the diffuser. The solid impurities are not pressed by the pressure into the holes 11 but are naturally entrained by the first pump 19 towards the filter 20.

 In order to ensure the dispersion of the effluent by the diffuser 9 through the holes 11, a regulator 37 with adjustable section by an actuator 39 (such as a flywheel) will be provided on the pipe 40. The effluents are introduced into the tank at a pressure of the order of 0.4 MPa. We will settle

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 the regulator 37 in order to ensure in the return pipe 40 a pressure of the order of 0.2 Mpa. A pressure gauge 38 will make it possible to control the pressure of effluents in the return pipe 40. Such an arrangement makes it possible to ensure a pressure of 0.2 Mpa for the evacuation of effluents through holes 11.

 It is possible as a variant not to provide a return pipe 40. In this case a supply pressure of the diffuser of 0.2 Mpa is sufficient. The risk of clogging of the diffuser holes increases but may be acceptable for certain types of effluent to be dehydrated (paint solutions, industrial oils, etc.). Advantageously, the filter 20 will be connected to the effluent supply circuit E upstream of the first pump 19. The filter 20 contains one or more filter screens 35. It will be able to receive the effluents E upstream of the screen 35 which will then provide a pre-filtration of these latter.

A second pump 36 makes it possible to give the effluents coming from the return pipe 40 an overpressure relative to the pressure of arrival of the effluents at E. Such an arrangement makes it possible to avoid a direct passage of the effluents introduced at E into the pipe of return.

 It is possible as a variant to dissociate the supply E of effluents and the filter 20. In this case it will be useless to provide a second pump 36 to ensure a back pressure. The tank 2 also includes a filter screen 21 which is interposed between the diffuser 9 and the bottom 2a of the tank where the discharge opening 7 of the liquid phase is located. This sieve is formed by a metal grid made for example of stainless steel. The mesh size of the sieve is of the order of 1 mm.

 The purpose of the filtering screen 21 is to retain the solid residues and thus ensures that a filtered liquid phase 22 is obtained which can be discharged through the valve 8 to a storage tank 23.

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 The bottom 2a of the tank is inclined so as to promote the flow of the liquid phase towards the first discharge opening 7.

 The filter screen 21 has a conical profile centered on the axis 10 of the tank 2. It is connected to a bowl 24 which ensures the reception of solid or muddy residues. The bowl 24 is connected to a second discharge opening 25 which is arranged substantially axially and closed by a valve 26.

 The conical profile of the screen 21 ensures a natural evacuation by gravity of the solid residues towards the bowl 24 and the evacuation opening 25.

 The solid residues 27 obtained are stored in a container 28 before being eliminated, for example by incineration.

 As a variant, it is of course possible to define an evaporator comprising a disperser having a different structure. For example formed of a single nozzle pierced with several holes and disposed at the level of the cover 3 of the tank, or also comprising several nozzles regularly distributed angularly and oriented so as to direct the effluents towards the wall of the tank. These nozzles will be connected to each other by pipes. In all cases it will be advantageous to avoid clogging of the disperser to provide a return pipe 40 leading the effluents to a filter.

 The evaporator according to the invention has been described in an application for the separation of water and a fatty phase from an effluent. It can of course be adapted to other types of phase separation: desalination of seawater, dehydration of hydrocarbons, dehydration of industrial effluents (water / paint mixtures for example), treatment of industrial oils ...

 FIG. 4 shows a separation installation 29 according to the invention. This installation comprises a separator 1 incorporating a toric disperser 9 supplied with effluents which are pressurized by a first pump 19.

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 This figure also diagrams by S the heating means to which the heating pipes 4 of the tank 2 are connected.

 The filter 20 which is shown schematically comprises a filter screen 35 (or more). The effluent inlet is shown diagrammatically by E and is carried out in the upper part of the filter. The feed pump 19 is connected at the bottom of the filter. The pipe 40 which brings back the effluents coming from the disperser 9 is connected in the upper part of the filter by means of a second pump 36 ensuring a back pressure to the supply of effluents E. Thus the effluents circulate continuously from the filter 20 at the disperser 9 and the solid residues are retained by the screen 35.

 This separation installation also comprises a device 30 making it possible to generate water and / or steam under pressure. This device can be connected to the disperser 9 or else to the tank 2 via a three-way valve 31. Another valve 32 makes it possible to isolate the water or steam generator from the separator 1.

 A channel of the valve 31 is connected to a pipe 33, carried by the cover 2 of the tank. Another way of the valve 31 is connected to the effluent introduction pipe 5.

 This device is used to clean the tank or the disperser 9.

To carry out such cleaning, the first pump 19 will be stopped and the effluent inlet valve 6 will be closed.
The isolation valve 32 will then be opened and the injection of water or steam under pressure by the device 30 will then be controlled by the device 30 towards the introduction pipe 5 by positioning the three-way valve appropriately.

 Such an injection through the pipe 5 and the diffuser 9 will allow the opening of the holes 11 of the diffuser

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 and push any residues accumulated in the diffuser towards the filter 20.

 If the three-way valve 31 is controlled so as to direct the water or the steam under pressure directly to the tank 2, the inside of the latter will be cleaned.

 The distribution of water or steam in the tank may be favored by having a diffusion ramp (not shown) on the internal face of the cover and connected to the pipe 33.

 Of course, the various valves 6,8, 16, 26, 31 and 32 will all be remotely controlled by an electronic control unit 34. This will also group together the controls for the other elements of the installation: pump 19, cleaning device by water or steam 30. It will also control the various parameters of the installation: regulation of the tank temperature, flow of pumps 19 and 36 ...

 As a variant, it is of course possible to define an installation comprising several evaporators 1 arranged in parallel. This will allow cleaning of an evaporator without stopping the operation of the installation.

Claims (14)

 CLAIMS 1-Evaporator (1) intended to separate an effluent into a vapor phase and a liquid and / or solid phase, and comprising a heated tank (2) comprising means for introducing the effluents to be separated, a pipe (15) d evacuation of the vapor phase and at least one opening (7) for evacuation of the liquid and / or solid phases, evaporator characterized in that the introduction means comprise a diffuser (9) ensuring dispersion of the effluent in droplets inside the tank (2), the tank also being maintained in depression.  2-evaporator according to claim 1, characterized in that the diffuser (9) disperses the effluent to a heating means.  3-evaporator according to claim 2, characterized in that the heating means comprises a wall (2b) of the tank heated by pipes (4) transporting a heat transfer fluid and arranged in the wall, the diffuser (9) dispersing the effluents towards the wall (2b) of the tank.  4-evaporator according to claim 3, characterized in that the wall (2b) of the tank carries at least two longitudinal fins (13) allowing to increase a heat exchange surface between tank (2) and effluents.  5-Evaporator according to one of claims 3 or 4, characterized in that the diffuser (9) has the shape of a toric pipe.  6-evaporator according to one of claims 1 to 5, characterized in that the tank (2) comprises at least one filter screen (21) disposed between the diffuser (9) and a bottom of the tank where the openings are arranged (7 , 25) evacuation of the liquid and / or solid phases.  7-evaporator according to claim 6, characterized in that the bottom (2a) of the tank is inclined so as to promote the flow of a liquid phase to a first opening (7) for discharging the liquid phase. <Desc / Clms Page number 12>  8-evaporator according to claim 6, characterized in that the filter screen (21) has a substantially conical profile so as to favor the evacuation of solid or muddy residues towards a second opening (25) evacuation disposed substantially axially.  9-Installation for separating an effluent in several phases, characterized in that it comprises at least one evaporator (1) according to one of the preceding claims.  10-Separation installation according to claim 9, characterized in that the diffuser (9) is supplied with effluents which are pressurized by a first pump (19).  11-Separation installation according to claim 10, characterized in that the diffuser (9) is connected on one side to an effluent supply (E) under pressure and on the other to a filtering means (20).  12-Separation installation according to claim 11, characterized in that the diffuser (9) is connected to the filtering means (20) by a return pipe (40) on which is disposed at least one regulator (37).  13-Separation installation according to claim 12, characterized in that the filtering means (20) comprises at least one filtering screen (35), the effluents intended for the evaporator being introduced upstream of the screen and in parallel with those from from the return pipe (40), a second pump (36) being provided between the diffuser and the filter (20) to ensure an overpressure relative to the effluent inlet pressure (E).  14-Separation installation according to one of claims 9 to 13, characterized in that it comprises at least one device (30) for injecting water and or steam under pressure which can be connected to the disperser (9) and / or to the tank (2) via a valve (31), an injection device which is used to clean the disperser (9) and / or the tank (2).