LU85336A1 - EXTRACTION METHOD AND DEVICE - Google Patents

Description

9 * Descriptive memory in support of a patent application for:

EXTRACTION METHOD AND DEVICE

The present invention relates to a method and a device for extracting a liquid contained in a non-gaseous aggregate, by evaporation and entrainment in a gas flow.

More particularly the invention relates to the separation of the at least partially evaporated liquid from the gas flow using a nozzle.

According to one form of application of the invention, the separation in the nozzle of the at least partially evaporated liquid takes place in the form of condensate by an adiabatic expansion in the upstream part of the nozzle. This expansion produces a high speed flow of the gas which contains condensate in the form of droplets. The separation in the nozzle is done by barodiffusion of said droplets through the gas flow streams at high speed. In the downstream part of the nozzle, the gas separated from the condensate is adiabatically recompressed. According to an advantageous form of application of the invention, a portion of the droplets separated by barodiffusion rises the pressure gradient within the main flow of the gas flow to a permeable wall through which they are sucked.

The invention can advantageously be used for drying an aggregate containing water.

By way of example and in no way limiting, the method according to the invention and an implementation device are described below using a. application to the drying of an aggregate by means of a flow of hot air.

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In the known methods of drying by means of hot air, the water is evaporated and entrained by the current of hot air obtained by heating outside air. This heating is carried out either by direct combustion of gas or of fuel oil in said outside air, or by passage of said outside air in one or more heat exchangers where walls separate this air from the heating fluid. According to known methods, the heating fluid is combustion gas, and there is or there is no heat recovery.

According to elaborate processes, the heat contained in the humid air is extracted by heat pumping.

Heat recovery by these methods requires installations and equipment of a certain complexity, such as recovery heat exchangers, heat pumping installations comprising at least - a condenser, an evaporator, and a mechanical or thermal compressor.

These processes therefore entail investment, operating and maintenance costs, which depend on the size, complexity, and energy consumption of the installations required.

The method and the device according to the invention are both very efficient in terms of energy and inexpensive in terms of investment and maintenance costs.

FIG. 1 illustrates a case of drying application according to the invention. The operation is carried out in an enclosure 1 in which an aggregate, for example germinated barley 2 sip of water is placed on a rack 3.

The fan 4 operates at the same time as the burner 5 supplied with combustion air 6 and with fuel 7, producing combustion gases 8 which are mixed with the drying air 9. The burner 5 is adjusted so as to maintain in the lower part 10 of the enclosure 1 the temperature of the drying air at the desired level.

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Said air then passes through the wet barley bed 2 and leaves it in the upper part 11 of the enclosure 1 at a temperature which varies during the drying operation, "but which is lower by 20 ° to 30 ° C to that in 10.

The moist air sucked in 11 by the fan 4 is blown in 12 in a duct 13 which brings it to the aerodynamic separator 14. The latter separates the incoming flow of humid air into a main flow 22 of hot air depleted in vapor of water and an extracted flow 20, essentially composed of cold water, which is discharged through the conduit 21. The main flow is brought through the conduit 23 to 9 where it begins the course of the drying cycle again. A valve 25 is provided in the duct 23 to allow the addition of fresh air to compensate for air leaks or losses from the entire installation to the outside.

FIG. 2 shows the same example but in the aerodynamic separator 14 the main flow 15 of air depleted in water vapor is brought by a pipe 16 to a heat exchanger-recuperator 17. The flow 18 enriched in water vapor, extracted by the separator 14, is brought by a conduit 19 to the exchanger 17, where it transfers its heat through the heat exchange walls to the main flow 15. The extracted flow 18 is thus cooled, the vapor it contains being largely condensed, and is discharged at 20 through line 21. The main flow leaves at 22 after reheating in the exchanger-recuperator 17.

As shown in the diagrams of Figures 1 and 2, the method according to the invention is characterized by great simplicity. In operation, the energy required for the operation of the process is provided essentially in mechanical form by the fan 4.

In addition, the burner 5 requires fuel consumption, but this is reduced to a small fraction of that which would be necessary if the fan 4 discharged the flow 12 into the atmosphere and if the air flow entering 9 was all fresh outside air. By comparison with known methods, the method according to the invention allows maximum energy saving, without requiring high investment and maintenance costs. Indeed, the rotating machines,% * 4.

or the burner 5 and the fan 4, are necessary in all known methods of the type described. If used, the exchanger 17 is an apparatus common to all known methods which recover part of the heat.

! Its investment and maintenance costs are very moderate.

The aerodynamic separator 14 is itself an essentially static device, and therefore of a very moderate investment and maintenance cost.

According to a particularly advantageous form of the invention, the aerodynamic separation, according to FIG. 1, between on the one hand the main flow of air depleted in humidity, and on the other hand the extracted flow composed essentially of cold water, can be done as described below:

The flow of moist air to be separated is introduced into a fixed nozzle in the first part of which it undergoes adiabatic expansion. Said moist air * is thus accelerated at a speed of up to several hundred meters per second. This expansion is pushed to the point where the desired fraction of the vapor condenses. This condensation takes place from nucleation centers which have appeared spontaneously and / or created artificially within said flow before or during expansion. The droplets thus condensed within the gas flow at high speed tend, due to their high density with respect to the gaseous medium which surrounds them, to follow a rectilinear trajectory, from which they only deviate slightly due to the drag that they undergo within the gaseous medium. The shape of the upstream part of the nozzle is designed so that, during expansion and at the end of it, the trajectories of the condensed droplets diverge from the trajectories of the gaseous threads, which makes it possible to collect said droplets and separate them from the gas stream which continues to flow at high speed. This current î! thus freed from the condensed water is then subjected to an adiabatic recompression by transformation of its kinetic energy in the second part of the separation nozzle. After this recompression, the pressure of the gas flow rose to a level close to - · M>

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pressure level at the inlet of the nozzle; and its temperature is significantly higher than that at the inlet of the nozzle. Indeed, we find at the end of the recompression an enthalpy per kg of dry air very close to that in the gas flow at the inlet of the nozzle, since the enthalpy of cold water separated by the nozzle is almost negligible compared to the enthalpy that said water had when it was in the state of vapor before its condensation.

The aerodynamic separation process described above allows maximum performance to be obtained. Indeed, it achieves full recovery of the heat contained at the start of the cycle in the drying air, using a fully static separator whose investment and maintenance costs are very moderate.

By way of example and not limitation, Figure 3 illustrates this aerodynamic separation. The separation is done in a vertical nozzle 26 which has the general shape of a convergent-divergent circular section. In the axis of the nozzle 26 is a cylindrical manifold 27 of small diameter. The flow of moist air, driven at a speed parallel to the axis of the nozzle, enters the upper space 28 of the nozzle, where it can be subjected to any known means capable of creating within it nucleation. These means can consist of a fine and homogeneous spraying of water or any other element stimulating nucleation, and / or sonic and / or ultrasonic waves, and / or electromagnetic waves of sufficient frequency (for example ultraviolet rays, laser rays , ionizing rays, radar waves), and / or electrostatic fields. The flow of moist air then enters the converging part 29 of the nozzle 26, where the expansion takes place accompanied by condensation in the form of droplets which are projected onto the external surface of the manifold 27 and onto the internal surface of the neck of the nozzle. , surrounded by a collection chamber 30. Said surfaces are made, over the entire height of the collector 30, of porous material (or having any other known permeable structure) through which the condensate formed by the droplets is sucked into the collector 27 and in the collection chamber 30, from which it is discharged outside the main circuit by ^ any known means.

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The flow of air freed from the droplets of condensate at the outlet from the neck of the nozzle 26 enters the divergent part thereof where it undergoes * an adiabatic recompression which reduces its pressure to a level close to that which prevails at 28, and which raises its temperature to a level higher than that of the temperature at 28. The throat of the nozzle has a constant section over a length sufficient to allow efficient collection of the condensate.

The velocity at any point of the main flow in the nozzle 26 has only axial and radial components, with the exclusion of tangential component. As a variant, a fin can be provided at the inlet of the nozzle 26 which induces a free vortex which is superimposed on the axial and radial flow. This free vortex, the amplitude of which can remain small compared to the axial and radial components of the main flow, promotes the projection of the condensate droplets onto the interior surface of the collection chamber 30 and can thus improve the efficiency of the separation of said droplets.

Among the multiple possible variants of application of the method and of the device according to the invention, mention should be made of those illustrated by FIGS. 4 and 5.

FIG. 4 represents a particular variant of the upper part of the nozzle 26 illustrated in FIG. 3. In this variant, the upper space 28 and the converging part 29 of the nozzle are separated by a central body 35 and a grid d 'fins 36. Said fin grid gives the vertical flow of the main flow a tangential component * it creating within this flow a free vortex of moderate amplitude. Due to the particular shape of the converging part of the nozzle represented in FIG. 4, the axial component of the flow gradually disappears along the fluid threads, and is gradually replaced by a centripetal radial component, thus sparing a zone in which the tangential component of the speed of the condensate droplets orients them horizontally towards the external wall of the converging part 29 of the nozzle, making them 7.

4 * raise the pressure gradient of the main flow. The condensate reaching the wall is sucked by a collector in a similar manner to that described with reference to FIG. 3. This arrangement is likely to improve the efficiency of the separation of said droplets during expansion. At the end of the latter, the centripetal radial flow is deflected as shown in FIG. 4 to become again axial with a view to its recompression in the divergent part of the nozzle.

FIG. 5 represents a particular variant of application of the method and of the device according to the invention in which the main circuit is open instead of being closed as described above. The main stream, consisting of fresh outside air, is drawn in at 37 in a countercurrent exchanger 38, where it is heated by the stream of dehumidified hot air 22 coming from the nozzle 26. The main stream of the fresh air thus heated in the exchanger 38 is brought through a pipe 39 to the fan 4, which injects it at 9 into the drying enclosure 1. The main stream of hot and humid air 12 coming from the drying chamber then enters the aerodynamic separation nozzle 26, from which the extracted stream composed mainly of condensate leaves at 20, the main stream 22 of hot air dehumidified being introduced into the countercurrent exchanger 38 where it is cooled to a temperature close to that of the ambient air and from which it leaves in the atmosphere at 40. The variant of the invention shown in FIG. 5 can compare to that of Figure 1, supplemented by the addition of an exchanger. The open circuit operation of the method according to the invention allows permanent renewal of the air passing through the drying chamber, at the cost of a slight increase in energy consumption. This increase is due on the one hand to the additional power of the fan 4 which corresponds to the pressure drops in the exchanger 38, and on the other hand to the additional heat to be supplied by the burner 5, which must compensate a part the temperature difference of the main flow between its inlet at 37 and its A outlet at 40.

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Although the description of the methods and devices according to the invention has been made for the particular application to drying malt, the same methods and devices are applicable to all cases of drying and in particular to plastering, stationery and cardboard mills.

In fact, the invention can be applied in general to any non-gaseous aggregate, solid or liquid, or solid saturated with liquid. The aggregate can be a mixture or combination of different chemical or isotopic elements in any proportions. The liquid to be extracted can be a single body or a mixture or combination of different chemical or isotopic elements in any proportions. As for the components of the gaseous fluid, they can be generally any in any proportions.

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Claims (6)

1. Method for extracting a liquid from a non-gaseous aggregate by evaporation and entrainment of the at least partially evaporated liquid in a gas flow characterized in that the at least partially evaporated liquid is separated from the gas flow using a nozzle in which the energy of the gas is used to effect the * separation. 2. Method according to claim 1. characterized in that the separation in the nozzle of the at least partially evaporated liquid takes place in the form of condensate by an adiabatic expansion in the upstream part of the nozzle, producing a high speed flow of the gas containing in the form of droplets, the condensate and a separation in the nozzle by barodiffusion of said droplets through the gas flow streams at high speed, and a recompression, in the downstream part of the nozzle, of said gas flow separated from said condensate. 3. Method according to claim 2, characterized in that at least a portion of the droplets separated by barodiffusion go up the pressure gradient within the main flow of the gas flow to a permeable wall through which they are sucked . 4. Method according to claim 1, characterized in that the method is used to dry an aggregate containing water. 5. Method according to any one of claims 1 to 4, characterized in that the gas circulates in a closed circuit through the aggregate to be dried and the nozzle which separates the at least partially evaporated liquid from the gas. 6. Device using the method according to claims 1 to 5.