WO2011020787A1

WO2011020787A1 - Device for processing wet biomass by frying

Info

Publication number: WO2011020787A1
Application number: PCT/EP2010/061818
Authority: WO
Inventors: Didier Lecomte; Anwar Hamasaiid; Jean-Claude Poussin; Bernard Auduc; Bruno Ladevie; Med Hedi Romdhana
Original assignee: Ecole Nationale Supérieure Des Techniques Industrielles Et Des Mines D'albi-Carmaux
Priority date: 2009-08-18
Filing date: 2010-08-13
Publication date: 2011-02-24
Also published as: CN102597674A; FR2949256B1; FR2949256A1; ES2428750T3; TN2012000066A1; MA33532B1; EP2467661B1; PT2467661E; EP2467661A1

Abstract

The invention relates to a device for processing wet biomass by frying, comprising a first tank (1) containing a first oil bath (108) that is kept at a temperature for frying the biomass, a means for feeding the biomass into said first tank, a second tank (2) containing a second oil bath (211) at a temperature lower than said frying temperature, the first and second tank being communicating spaces, a means (3) for transferring fried solid material from the first tank into the second tank, and a means (210) for discharging the fried solid material out of the second tank. A means for keeping the oil in the first bath at a temperature for frying the biomass comprises a means (401) for collecting oil from the second tank, a means for heating the collected oil, and a means (412) for injecting the heated oil into the first tank.

Description

DEVICE FOR TREATING WET BIOMASS BY FRYING

The invention is in the field of moist biomass treatment by frying technology. It relates more particularly to a device for such treatment.

In the present description by biomass is meant any material of organic type containing a high water content, especially at least 50% by weight, regardless of its origin. The biomass to which the invention applies may, for example, be a sludge, originating, for example, from purification plants, a waste from the paper industry, slaughterhouses, agriculture, etc., or a waste material. vegetable origin, a food, a biological waste or a sedimentary material such as lignite or peat.

A preferred, although not limiting, field of application of the invention, which will be more particularly described in the present description, is that of the manufacture of solid fuel from biomass, by dehydration of the latter by frying. The invention also applies in a manner similar to frying food or hygienization, for example medical biological waste, or any other type of treatment to obtain, after frying, a final material that is particularly solid , storable and transportable.

It has been proposed in the prior art solid fuel fabrication devices from wet biomass, using the so-called frying dehydration technology. Such technology is already known in itself. By bringing moist biomass into contact with oil at an appropriate temperature, it can significantly increase the Lower Heating Value, or ICP, of the fried biomass to about 15-20 MJ / kg. This is particularly due to the combined effect of drying and impregnation of the oil in the biomass during frying. The solid material obtained is hygienized, storable, transportable and recoverable as a source of energy. By way of example of prior art, reference may be made to the document WO 2009/03825, which describes a device comprising a dehydration unit containing an oil bath heated by a burner, into which the material to be fried is introduced, and a fuel cooling unit obtained. A control of the residence time of the biomass in the oil is carried out by means of a worm or a conveyor belt driving the material to be fried inside a cylindrical drum filled with oil. Such a device has the particular disadvantage of requiring a significant energy input to achieve the frying to form the fuel.

The present invention aims to overcome the disadvantages of existing wet biomass frying treatment devices, particularly those described above, by proposing a device that requires a low energy input for its operation, and therefore has a cost of reduced operation, while allowing to obtain a solid material, separated from the frying oil, water content perfectly controlled.

A frying wet biomass treatment device according to the invention, in particular for forming a solid fuel from this biomass, comprises a first frying tank, containing a first oil bath, means capable of maintaining the oil of this first bath at a so-called frying temperature for frying the biomass, that is to say at a significantly higher temperature, for example at least 5 ° C, at the boiling temperature of the water, and means for introducing the biomass into this first tank.

This device is characterized in that it comprises a second tank, said separation, forming separation means by gravitational settling of the solid material fried in the first oil bath and oil, the second tank containing a second oil bath temperature lower than the frying temperature. The first tank and the second tank are communicating volumes, so that the respective oil bath they contain are naturally in hydraulic communication one with the other. The device according to the invention further comprises means for transferring the solid fried material, obtained from the biomass, from the first tank to the second tank, more specifically from the first oil bath in the second oil bath. and means for discharging the solid fried material, which has been separated from the oil by gravity settling, out of the second tank. The means capable of maintaining the oil of the first bath at a frying temperature of the biomass, defined and controlled, comprise means for sampling oil in the second tank, means for heating the oil thus taken and means for injection of the oil thus heated in the first tank.

Here, the term "oil" includes any fluid fatty substance, and more generally any fluid having the characteristics of being immiscible with water, stable at a temperature above the boiling point of water, and of high power. heat. Particularly preferred in the context of the invention, for an implementation for the manufacture of solid fuel from wet waste, oils and fats obtained from agro-food waste plants and animals, fats or waste wastewater treatment plants that have been previously heated and rendered liquid. According to the invention, frying of the biomass itself is carried out in the first tank, in which the oil bath is at a temperature sufficient to ensure this frying. It produces, in a conventional manner in itself, a dehydration of the biomass by frying. This dehydration causes the release of steam in the first tank, above the oil bath. The solid fuel thus obtained has, in a manner known per se, a high calorific value.

In preferred embodiments of the invention, the oil bath of the first tank occupies about a quarter of the height of the latter.

In the second tank, the fried solid material and the bath oil are separated. This separation is advantageously facilitated by the lower temperature of the oil in the second bath, which allows stopping the boiling of the water emerging from the biomass.

Most advantageously, in the second oil bath, a transfer of the heat stored in the fried solid material to the oil takes place, which is allowed in particular by the relatively long residence time of the solid fried material in the second oil bath where the separation by gravitational settling occurs, which is known to involve by nature a residence time of the solid in the fluid of a certain duration, in any case sufficient to ensure this heat transfer. In addition, the first and second oil bath being in hydraulic communication with each other, the respective temperatures of these baths remain close. The oil of the second bath being used to replenish the oil bath of the first tank, after heating, and therefore already having a relatively high temperature, the external energy input to provide to bring it to a temperature adequate to fry the biomass before injecting it into the first tank is low. The recovery of the heat of the fried material occurring in the oil bath of the second tank thus advantageously reduces the energy consumption required for frying.

The residence time of the fried material in the second oil bath, which determines in particular the heat transfer occurring therein, is also advantageously partly controlled by the speed of operation of the means for discharging the solid material. fried out of the tank.

The frying and separation tanks operating in communicating vessels, the loss of the oil taken from the second tank is compensated by a supply of oil occurring at the same time spontaneously from the first tank. The volumes of oil in each of the tanks thus remain substantially constant. The invention also advantageously provides means for maintaining the overall volume of oil contained in the two tanks at a substantially constant value throughout the operation of the device. In addition, the energy performance of the device according to the invention is further improved by the advantageous choice, in order to ensure separation of the fried material and the oil, from the gravitational settling technique, based on the sedimentation phenomenon, which, in addition to the fact that it ensures a residence time of the fried material in the oil sufficiently long to allow the heat transfer mentioned above, does not in itself require any input of energy to achieve the separation.

The oil taken from the second bath to be reinjected, after heating, in the first bath, is further clarified in the second bath, that is to say largely free of solid particles, before its circulation in the heating circuit.

An additional advantage of the decantation technique is the mechanical simplicity of the equipment used, which does not involve any moving parts, so that the device according to the invention has a reduced manufacturing cost, a high mechanical strength, and it requires only a few maintenance operations.

In addition, according to an advantageous characteristic of the invention, the means for heating the oil taken from the second tank comprise means for extracting the water vapor released in the first tank during frying, and means for heat exchange between the oil taken from the second tank and the water vapor taken from the first tank.

The frying tank preferably comprises, in an upper part upstream of a steam extraction opening, demisters capable of removing oil residues from the water vapor escaping above the first oil bath when frying.

In preferred embodiments of the invention, the device further comprises means for mechanically compressing the water vapor released during frying, upstream of the heat exchange means between the vapor thus compressed and the oil. driven in circulation of the second tank to the first tank.

The device according to the invention therefore advantageously has a relatively low energy requirement. After an initial heating of the oil in the first oil bath so as to give it a suitable temperature for frying, this device requires, in order to maintain its operation, a very small external energy input, realized in particular by means of a heating element disposed on the oil circulation circuit between the second tank and the first tank, preferably at the level of the heat exchange means with the steam. At the outlet of the device according to the invention, a fried material separated from the oil is obtained, this with a limited energy requirement, much lower than that of the devices of the prior art.

The operation of the device according to the invention, in particular the circulation of oil between the two baths, is advantageously implemented continuously, allowing maximum energy efficiency.

The means for injecting biomass into the first tank, the means for transferring the fried material into the second tank, and the means for discharging this material out of the latter are also advantageously able to be operated continuously. As part of the implementation of the device according to the invention for the manufacture of a solid fuel, it achieves a global energy balance quite advantageous, since it is possible to manufacture, by means involving a low consumption of energy, a solid fuel with a high calorific value. The device according to the invention makes it possible to obtain a ratio between the energy consumed and the energy theoretically necessary to manufacture the fuel, linked to the latent heat of vaporization of the water contained in the biomass, which can be as low as 0 , 4, whereas in the industrial drying processes proposed by the prior art, this ratio is generally between 1, 25 and 2.5. According to an advantageous characteristic of the invention, the device further comprises means for controlling the residence time of the biomass in the first oil bath, allowing the control of the final water content of the fried material, and its oil impregnation rate. In particularly preferred embodiments of the invention, these control means comprise a rotating vane wheel arranged in the first oil bath and capable of displacing the biomass from a zone for introducing said biomass into the first vat. an outlet window to the second vessel, which is preferably formed in a bottom wall of the first vessel. Such an embodiment offers the advantage of a very well controlled control of the water content of the final fuel. The wheel preferably forms, between rotary blades and a perforated upper frame that it comprises, receiving and transport compartments of biomass, substantially identical shapes and reduced volumes.

In preferred embodiments of the invention, the means for controlling the residence time of the biomass in the oil bath comprise at least one, preferably a plurality, of blades which are secured by an internal lateral edge of a central shaft articulated in rotation on itself and disposed in the first vessel substantially perpendicular to a lower wall thereof. These blades extend, from the bottom wall, into an internal volume for receiving the oil bath from the tank, and they substantially reach, by an opposite outer lateral edge, the peripheral wall of the tank also delimiting this internal volume. The device according to the invention also comprises means for controlling the rotation of this central shaft.

Preferably, the wheel comprises a plurality of blades arranged at regular intervals from each other, and defining between them compartments of substantially triangular section. The device according to the invention preferably further comprises means for driving the wheel in discrete rotational movements, advantageously allowing better control of the rate of dehydration of the biomass. These means comprise for example a set of cams operable in translation in a direction transverse to the blade (or central shaft) of the wheel, alternately in opposite directions, these cams being arranged and configured so that their translational movement causes the discrete rotation of a solidary disc in rotation with the blade of the wheel by the ad hoc engagement of the cams successively with each of a set of rollers fixed to the disc.

According to an advantageous characteristic of the invention, the solid fried material transfer means of the first tank in the second tank consist of a conduit operating by gravity and also carrying out the communication between the first oil bath and the second oil bath. 'oil. Such a characteristic confers in particular on the device a simple structure, since the same element, that is to say the duct, ensures at the same time on the one hand the hydraulic communication between the first and the second tank, and on the other hand the transfer of the fried material between the two tanks, from one bath to another. In addition, such a transfer, operating solely by gravity, does not in itself require any input of energy. This duct preferably has a sufficiently small length to minimize the bulk generated by the device according to the invention, but large enough to allow a slight cooling of the oil circulating in its interior between the first and the second tank, so that blocking the boiling of the oil flowing to the second bath and thereby ensuring that the settling separation of the fried solid and the oil in the second oil bath occurs optimally, such a characteristic makes it possible in particular to achieve a further objective of the invention which is to ensure, by simple means of easy implementation, a good separation of the solid fried material and the oil.

In such an embodiment, in order to achieve all the better this objective, the device is preferably dimensioned so as to ensure a significant decrease in the hydraulic drive speed of the fried material and oil from the first bath on their arrival in the second bath, so that the separation by settling gravity in the second bath is improved. Preferably, the ratio between the volume of the second bath and the volume of the first bath is between 1, 5 and 4, and preferably about 2.

In preferred embodiments of the invention, the second tank is placed under the first tank, the pipe connects a lower wall of the first tank and an upper portion of the second tank, and the means for discharging the fried material. solid out of the second vessel operate at an opposite bottom portion of the second vessel. Such characteristics particularly advantageously promote the phenomenon of settling of the solid material occurring in the second tank. Such characteristics of the device according to the invention are furthermore quite advantageously combined with the particular embodiment of the means for controlling the residence time of the biomass in the first oil bath recommended by the invention, and in which a rotating vane wheel is provided to drive the biomass from an introduction zone in the first vessel to an exit window to the second vessel. This window is then advantageously arranged in a lower wall of the tank, directly above the duct, which directly and rapidly transfers the fried material to the second tank.

In preferred embodiments of the invention, the conduit opens into an upper part of the second tank and extends inside the latter by a dip tube reaching an opposite lower part, preferably close to an opening for discharging solid material fried out of the second tank. According to an advantageous characteristic of the invention, this dip tube is provided with fins inclined towards the lower part of the second tank, so as to prevent the solid material to go up towards the upper part of the tank, thus advantageously favoring the settling.

In preferred embodiments of the invention, aimed at achieving a temperature between the oil in the second vessel which is favorable to optimum operation of the device according to the invention, in terms of energy efficiency and settling performance, it is provided at the conduit connecting the two tanks to each other oil cooling means. These means may have any form known in itself to those skilled in the art, for example a water exchanger. In general, the device according to the invention is advantageously configured and operated so as to obtain an adequate temperature of the oil in the second tank, that is to say a temperature sufficiently low to stop the boiling of the water biomass from the first tank and thus promote the settling phenomenon, and at the same time high enough to ensure the lowest possible external energy consumption to maintain the operation of the device ..

Preferably, the second tank also has a high height and is substantially completely filled with oil, which also promotes obtaining a suitable temperature difference between the oil located in the upper part of the tank, which is at a temperature substantially equal to that of the first oil bath contained in the first tank, and the oil located in its lower part, at the discharge opening of the solid material. The device according to the invention is preferably configured and implemented so as to ensure a difference in temperature of the oil between the lower part and the upper part of the second tank which is between 2 and 5 ° C. The difference in pressure between the lower part of the second tank, where it is slightly higher, and its upper part, where it is lower, furthermore makes it possible to stop the boiling when the fried material reaches this lower part. . According to an advantageous characteristic of the invention, the device further preferably comprises means for placing under reduced pressure inside the first tank, for example so as to obtain a pressure of about 0.5 bar therein. This advantageously results in a lowering of the temperature necessary to cause boiling of the oil in this tank. These means for placing under reduced pressure are in particular advantageously constituted by the mechanical vapor compressor which is provided according to the invention in the circuit for recovering the energy of the water vapor released during frying. In such embodiments, the device advantageously comprises means capable of sealing the low-pressure device, in particular at the level of the means for introducing the biomass into the first tank and means for evacuating the material. fried out of the second tank. These sealing control means may for example be in the form of locks associated with feeding systems and / or screw extraction.

Preferably, the circulation of oil and the circulation of the water vapor takes place in very distinct circuits.

In preferred embodiments of the invention, the device comprises means for maintaining a substantially constant oil level in the first tank, preferably at about 25% of the internal volume of the tank, by introducing oil. cold in the second tank. This introduction of cold oil is preferably slaved to an oil level indicator disposed in the first tank, and is preferably performed in a lower portion of the second tank, preferably near the outlet port. fried material, so as to help stop boiling.

Preferably, the means for introducing the biomass into the first vessel comprise an extrusion die disposed through a wall of this first vessel and having cutting zones on a rear face. opposed to the first oil bath, as well as feed means for this biomass die.

The invention will now be more specifically described in the context of preferred embodiments, which are in no way limiting, represented in FIGS. 1 to 9, in which:

Figure 1 shows a perspective view of a device according to the invention;

FIG. 2 shows a detailed view of the means for controlling the residence time of the biomass in the oil of a device according to the invention;

- Figure 3 shows a partial sectional view of a separation tank of a device according to the invention;

Figure 4 shows a schematic view of a device according to the invention illustrating a circulation path of the oil;

FIG. 5 represents, in plan view, means for controlling the rotation of a rotating vane wheel of a device according to the invention;

Figure 6 shows in more detail in plan view the cam system means for controlling the rotation of a rotating blade wheel of Figure 5;

Figure 7 illustrates in side view the control means of Figure 5;

FIG. 8 represents a front face of an extrusion die of a device according to the invention;

and FIG. 9 shows a sectional view along plane A-A of the die of FIG. 9.

A frying wet biomass treatment device according to the invention is shown in Figure 1, in its normal position of use. This figure in dotted lines, for the sake of clarity of explanation, is represented in the elements inside the tanks forming part of the constitution of this device.

This device consists essentially of elements formed of metallic material. It comprises a first tank, said frying 1, which preferably has a substantially cylindrical shape, and an internal volume is delimited in its bottom by a lower wall 101, and laterally by a peripheral wall 102. At an upper end opposite to the lower wall 101, the vessel is closed by a lid 103, which is secured to it by attachment, and which preferably has a conical shape. An opening 104 is pierced in this cover, preferably substantially at its center, at the top of the cone.

The tank 1 contains in its bottom an oil bath 108, which can for example reach a height between one quarter and one third of the height of the tank. The upper level of this oil bath is designated 107 in the figure.

The tank 1 comprises means for controlling the residence time of the biomass in the oil. These means may be of any type known to those skilled in the art. In preferred embodiments of the invention shown in the figures, they comprise a rotating vane wheel system disposed in the bottom of the tank 1, in the oil bath 108. This system will be described in more detail in FIG. reference to Figure 2 further in the description.

The tank 1 is supplied with biomass by introduction means which comprise, for example, in the embodiment shown in the figure, a feed hopper 1 January 1 connected to means 1 12 biomass thrust through a extrusion die 1 13 disposed in an opening provided for this purpose in the peripheral wall 102 of the vessel 1, preferably at the bottom of the latter. All means of thrusting the biomass in the tank 1 conventional in themselves are within the scope of the invention. The introduction of biomass may also, for example, alternatively be effected by an opening in the bottom of the vessel 1, through the bottom wall 101.

The tank 1 is further provided in its lower wall 101 with a window 105 which preferably defines an angular sector of the wall. As can be seen in more detail in FIG. 2, the window 105 is slightly peripherally offset in the tank with respect to the biomass introduction opening, illustrated by the reference numeral 106 in the figure, of an angle about 30 to 90 degrees.

A rotating central shaft 122 is disposed in the center of the vessel 1, so as to extend from the bottom of the vessel substantially perpendicularly to the bottom wall 101. The tank 1 is associated with controlled drive means of the rotating shaft on itself, an embodiment of which will be described in more detail further in the present description.

In the bottom of the tank 1, at least one blade 121 is fixed on the shaft 122, by a so-called internal lateral edge 141, so as to be integral in rotation. This blade 121 is disposed in the tank so as to extend, above the lower wall 101, substantially perpendicular to this wall, towards the top of the tank, and so that it comes substantially, by a opposite outer side edge 142, substantially against the peripheral wall 102 of the vessel. Here is meant by substantially the fact that the blade 121 is able to move inside the tank, driven by the rotary shaft 122 which it is integral, without exerting friction against the one hand the peripheral wall 102 and on the other hand the lower wall 101 of the tank, and while being sufficiently close to these respective walls so that there is no gap between them that is large enough to let the biomass circulate.

In Figure 2, for clarity, the shaft 122 has not been shown, but is illustrated by its receiving cavity 143 formed between the blades in the center of the bottom of the tank.

In preferred embodiments of the invention, the device comprises a plurality of blades 121. In the example shown in the figures, these blades are eight in number, such a number is however not limited to the invention. These blades 121 are arranged at regular angular intervals from one another, and they define between them section compartments of substantially triangular shape 144. The opening 106 for introducing the biomass into the vessel 1 is disposed below the upper level of the compartments 144. A wire frame, which is not shown in the figures, is preferably disposed just above the blades 121, so as to delimit the compartments 144 in their upper part, and maintain the biomass in these compartments in the bottom of the tank 1, immersed in the oil bath 108.

An indicator of the oil level, which is not shown in the figures, is arranged in the tank 1. This indicator is conventional in itself, and can take any form known to those skilled in the art.

Deesiculators, which have not been shown in the figures for the sake of clarity, are arranged in the vessel 1, in an upper part of the latter. These strippers can take any form known to those skilled in the art, for example knits or metal mattresses. They make it possible to eliminate the oil residues from the water vapor forming during the frying in the tank 1 and going towards the top of the latter, to escape through the opening 104.

With reference to FIG. 1, the device comprises, under the tank 1, means 3 for transferring the biomass to a second tank 2, called a separator, placed under the first tank 1. These means are in the form of a duct 31, preferably substantially rectilinear, connecting the window 105 of the first tank 1 to the second tank 2.

The duct 31 may be associated with means for cooling the oil circulating in its interior, for example in the form of a heat exchanger schematically illustrated in the figure and designated by the reference 32.

The separation vessel, or separator 2 preferably has a substantially cylindrical shape of large diameter. It is delimited at an upper end by an upper wall 201 and at a lower end opposite by a bottom wall in the form of a funnel 202 delimiting in its inside a substantially conical contour volume 203 in the bottom of the separator.

The separator 2 is shown in more detail in FIG. 3. In its interior, the duct 31 is extended, through the upper wall 201, by a dip tube 204 which extends substantially vertically in the separator, until it reaches the lower conical volume 203 by an open lower end 205.

On the outer peripheral surface of the dip tube 204 are fixed fins 206, which have for example a substantially triangular flat shape flaring away from the tube 204 and inclined, from their zone of attachment to the latter, towards the lower volume 203 of the separator, at an angle which may be for example, as illustrated in the figure, approximately equal to 45 degrees. These fins are preferably dimensioned so as to extend substantially to a peripheral wall 207 delimiting the separator 2. In the particular example illustrated in the figures, the separator comprises three rows each comprising four fins 206, arranged in addition to such that the fins of a first row are offset angularly with respect to the fins of a second row, and so on, so as to occupy together ultimately the entire circular surface of the separator. These fins advantageously prevent any solid material contained in the bottom of the separator back to its upper part.

The invention is not however limited to such a number and to such an arrangement of the fins, any other configuration also falling within the scope of the invention insofar as it makes it possible to achieve the aforementioned result.

At the lower end 208 of the separator 2, substantially corresponding to the apex of the cone formed by the bottom wall 202, there is formed in this wall an opening 209 allowing the passage of solid material to means for continuous evacuation of this material, which are designated overall by reference 210 in Figure 1. These means evacuation can be of any type. This is for example a sealed extrusion mechanism, for example an endless screw equipped at its end with an airlock for discharging the fried biomass while maintaining a reduced pressure in the system.

The separator 2 contains an oil bath 21 1, which preferably fills substantially all of its internal volume, and which communicates with the first oil bath 108.

A reservoir 51 containing cold oil is connected to a pipe 52 which opens, at an opposite end 53, into the lower volume 203 of the separator. The pipe 52 is associated, between the tank 51 and the separator 2, with a valve 54. This valve is preferably automatically controlled in opening and closing, by conventional means in themselves, depending on the information reported by the level indicator disposed in the vessel 1.

The device according to the invention is further provided with continuous oil circulation means in a closed circuit connecting the vessel 1 and the separator 2 in the manner described below.

One embodiment of this oil circulation circuit is shown schematically in FIG. 1, and in a more detailed manner in FIG. 4.

A first pipe 401 opening through a first end 402 inside the separator 2, in an upper internal volume of the latter, is connected by a second opposite end 403 to a second pipe 404 in a median portion thereof.

The first pipe 401 is associated with a pump 405 ensuring the circulation of oil in its interior. This pump is preferably chosen at a variable rate.

The second pipe 404 opens at a first end 406 in a lower part of a buffer tank filled with oil 407. From this first end 406, beyond the zone of intersection with the first duct 401, this second duct 404 passes through heating means of the oil circulating in its interior, for example in the form of a heat exchanger 408, before coming out, by a second end 409 opposite the first end 406 in an upper part of the buffer tank 407.

The circulation of oil in the second pipe 404 is provided by a pump 410, conventional in itself, and which is preferably chosen to have a high flow rate.

The heat exchanger 408 is preferably associated with a heating element 408 ', which constitutes an additional source of energy for heating the oil circulating in the second pipe 404. This heating element can be of any type, being understood that it is preferred in the context of the invention the implementation of inexpensive means of energy supply. For example, it will be preferred to supply this heating element with solar energy sources.

Means 41 1 for preheating the oil circulating in the second pipe 404 in order to initially start the device, arranged between the first end 406 of this pipe and the heat exchanger 408, may also be included in the device according to the invention.

A third pipe 412 connects, by a first end 413, an upper end of the buffer tank 407, to the tank 1 in which it opens by an opposite second end 414. A flow meter 415 is disposed on the third pipe 412.

The direction of displacement of the oil in this double circuit is indicated by the arrows corresponding to the following references in FIG. 4. The oil extracted from the separator 2 is fed, in the direction 416, through the first pipe 401, up to the second pipe 404, at a preferably slow speed. It flows in the latter in the direction 417, that is to say from the bottom of the buffer tank 407, through the heat exchanger 408 associated with the heating element 408 ', to an upper part of the buffer tank 407. Its circulation speed in this pipe 404 is preferably fast, so as to promote heat exchange at the exchanger 408. In the third pipe 412, the oil finally circulates, preferably at low speed, in direction 418, from the upper end of the buffer tank 407 to the frying tank 1.

The third pipe 412 preferably opens into the tank 1 flush with the inner surface of the peripheral wall 102 of the latter, so that the oil injected into the tank through this pipe falls there by forming a film on the inner surface of this peripheral wall, and therefore does not disturb the surface of the oil bath 108 by creating eddies.

A tube 420 is fixed, by a first end 421, on the opening 104 formed at the top of the tank 1, above the mistletters. This tube is intended to bring the water vapor released during the frying of the biomass in the tank 1, to a mechanical steam compressor 422, for example a lobe compressor, which compresses it, then up to heat exchanger 408 where it can be used to transfer its energy to the oil flowing in the line 404. In such an embodiment, the heating element 408 'is preferably a liquid water collection tank from the compressor 422 through the pipe 420, and provided with a heating resistor capable of heating the water to provide additional energy for the heating of the oil. This tank can be equipped with an overflow system to evacuate the excess water that it could receive.

The circulation of water vapor in the tube 420 is effected in the direction indicated at 423 in FIG. 4, from the top of the vessel 1 to the heat exchanger 408.

The supply of cold oil from the tank 51 to the separator 2 takes place in the direction indicated at 55 in this figure.

The device according to the invention comprises means for placing under reduced pressure in the frying tank 1, preferably but not Limitatively advantageously constituted by the compressor 422 also involved in the system for recovering water vapor released during frying. It is also provided with means for sealing at low pressure.

Preferred means for rotating the central shaft 122 of the vessel 1 are shown very schematically in FIG. 1 and in more detail in FIGS. 5 to 7.

These means are for example, mainly for reasons of space, arranged in the upper part of the tank 1.

A slider 123 is disposed in the tank, substantially perpendicular to the central shaft 122, which is located by the reference 124 in Figure 5. This shaft 122, which is not shown for reasons of clarity , extends rearward perpendicularly to the plane of this figure. The slider 123 is able to be displaced in translation, in a direction perpendicular to the axis of the shaft 122, by a piston 125 actuated by a jack, for example a pneumatic cylinder, shown in FIG. The sliding is carried out along a rail 126 supported by a ring 127, illustrated in Figures 5 and 7. This ring 127 is fixed to the peripheral wall 102 of the vessel 1, by conventional means in themselves.

On an upper face directed towards the top of the tank 1, the slider 123 carries two cam protruding respectively 128 and 129, whose profiles are illustrated in Figure 6.

The first cam 128, disposed at a so-called front end of the slide located opposite the rotary shaft 122, against a first lateral edge of the slide, has a rear edge 130 bevelled widening towards said first lateral edge . The second cam 129, disposed on its opposite end opposite the slider, against a second opposite lateral edge thereof, has a front edge 131 also bevelled substantially perpendicularly to the rear edge 130 of the first cam 129. These cams apparently determine a path 132 on the upper face of the slide 123, as illustrated in FIG. 6.

The slider 123 is associated with a rotating disc 133 fixed around the shaft 122 so as to be integral in rotation. The slider is disposed under a lower face 134 of the disc facing the bottom of the tank, so that the cams 128, 129 are able to interact with rollers 135 carried on the underside of the disk 133. In FIG. For the sake of clarity, a single roller 135 is shown. The disk actually comprises a plurality of rollers, which are arranged circularly over its entire periphery at regular intervals from one another. Each roller is identified in FIG. 5 by a pin 136 ensuring its attachment to the disk, and opening on the upper face 137 of the disk opposite to the lower face 134.

The pitch between the rollers 135 is fixed, in connection with the dimensions and the relative position of the cams 128 and 129 relative to each other, to a value such that each translational movement of the slide 123, in a perpendicular direction to the axis of the shaft 122, in one direction or the other, causes the displacement of a roller along the path 132 formed by the cams 128 and 129, and thereby a rotational movement, according to the direction indicated at 138 in FIG. 5, of the disk 133. This rotation drives, via the shaft 122, the displacement of the blades 121 which are integral with it in the vessel 1. By choosing the rate and the speed of movement of the slide 123, the speed of movement of the blades 121 in the vessel 1 is thereby advantageously determined, and thereby the residence time of the biomass in this vessel. Any other means of controlling the residence time of the biomass in the tank 1 in general, or of controlling the speed of the rotation of the blades 121 more particularly, known per se to those skilled in the art, also falls within the scope of the invention.

A preferred, but in no way limiting embodiment of the invention, of an extrusion die 1 13 through which the biomass is introduced into the vessel 1, is shown in FIGS. 8 and 9.

This die 1 13 is in the form of a disk pierced in its center of a plurality of extrusion orifices 1 14. A front face 1 15 of this disc, facing the inside of the vessel 1, is shown in plan in FIG. 8.

At the rear of the extrusion orifices 1 14, at a rear face 1 17 opposite to the front face 1 15, the die preferably has cutting edges 1 16 for cutting the biomass before its introduction into the tank 1. Such an embodiment is particularly advantageous in cases where the biomass is in filamentous form, so that it can not be satisfactorily crushed before its introduction into the frying tank.

The invention does not exclude the fact that the introduction of the biomass into the tank is carried out through an extrusion die of any other form, especially of conventional form in itself, that is to say without cutting areas, or even directly through the opening 106 formed in the peripheral wall 102 of the vessel 1, without any extrusion die.

In general, the dimensions of the device according to the invention, in particular of the tank 1 and the separator 2, are determined according to the type and amount of biomass to be treated, its water content, the heating value desired for the fried material and oil used, according to calculations within the skill of the art.

For example, the vessel 1 may have a diameter of 0.90 m and a height of 1.40 m, and the blades 121 have a height, measured between their lower edge vis-à-vis the wall lower 101 of the tank and their opposite upper edge, about 20 cm. The separator 2 may have a height of 1.30 m, for a diameter of about 0.90 m. The conduit 31 may have a length of about 50 cm.

The device according to the invention is for example implemented as follows.

Here again, the operation parameters are chosen generally according to calculations within the reach of the person skilled in the art, depending not only on the nature of the biomass to be treated but also the desired water content for the fried material, directly related to its calorific value, and the target energy efficiency during these processing operations. Values of the operation parameters are given below by way of example only, without being in any way limiting to the invention.

An oil, or any other fluid defined in accordance with the invention, which has been previously heated to a temperature at least 10 ° C higher than the boiling point of the water by the preheating means 41 1, is poured into the tank 1. This fluid may for example emanate from fish or meat fat waste, which have been melted beforehand. It can also be recycled oil.

The oil poured into the tank 1 flows naturally through the window 105 formed in the bottom of the tank, through the conduit 31, to fill the separator 2. Once it is filled, the oil level increases in the tank 1 as and when pouring. The oil is poured in such an amount that it completely covers the blades 121 disposed at the bottom of the tank 1, and that its level exceeds 1.5 to 2 times the height of these blades in the tank. By way of example, for a tank 1 and a separator 2 of dimensions given above, approximately in the device is poured an amount of oil of between 1 and 2 m ³ , which is distributed between the tank 1, for a volume of about 0.2 m ³ , the separator 2, for a volume of about 0.7 m ³ , and the oil circulation circuit.

Once the device has been hermetically sealed, a reduced pressure is applied to the tank 1 by means of the compressor 422. Any other means known per se for placing under reduced pressure also falls within the scope of the invention. The operating pressure is preferably selected to be about 0.5 atm. The decrease in the pressure in the tank 1 causes the decrease in the temperature necessary for the boiling of the water contained in the biomass that will be introduced into the oil bath. The device according to the invention can however also be operated at atmospheric pressure. Due in particular to the differences in volume between the oil bath 108 of the tank 1 and the oil bath 21 1 of the separator 2, added to the cooling means of the conduit 31 connecting the tank and the separator, one to the other, the temperature of the oil in the latter becomes during operation slightly lower than that of the tank.

For example, for optimum operation of the device, the temperature difference of the oil between the bottom of the separator 2 and the tank 1 is at least 10 ° C.

The movement of the blades 121 is initiated by the driving means of the rotary central shaft 122. With each movement of the piston 125 driving the slide 123 in translation, it is printed on the shaft 122 a rotational movement on itself. same, which causes the blades to move in the tank 1. The rotation is effected in the direction inducing the longest path of movement of the blades between the opening 106 for introducing the biomass into the vessel 1 and the window 105 formed in its lower wall 101.

The biomass is introduced into the tank 1 by the introduction means, in particular such as those described above by way of example. From the feed hopper 1 1 1, it is for example extruded directly into the tank through the extrusion die 1 13, in the form of cords segments.

The invention does not exclude the fact that the biomass is introduced into the tank 1 in any other way. For example, depending on its physico-chemical properties, the biomass can be milled and introduced into the tank without any other operation, including extrusion, the general objective of the invention being to bring into the tank small elements obtained from the initial wet biomass, and having a large contact surface with the oil contained in the tank.

The wet biomass is introduced into the tank through the opening 106 directly into the oil bath, into one of the compartments 144 formed between two neighboring blades 121. The biomass stuck in this compartment is then driven by the blade 121 delimiting the rear of the compartment, defined in the direction of advance of the blades, until it finally reaches the window 105 through which it falls, under the effect of its weight, in direction of the separator 2.

During this course in the tank 1, the biomass is dehydrated by frying, according to a phenomenon known per se, to form a material, for example a fuel, which is solid and of reduced water content relative to the initial biomass.

The rate of introduction of the biomass into the tank 1, the operating pressure, the quantity and the temperature of the fluid in the latter, as well as the rotational speed of the shaft 122, which determines the residence time of the material in the oil bath, are set according to each other, in connection with the dimensions of the tank, by calculations within the reach of the skilled person, so as to obtain the water content, and therefore Lower Calorific Value, desired for the final product, also depending on the initial water content of the wet biomass. The device according to the invention can achieve a very low water content of the final solid material, only a few percent.

For example, in connection with the particular parameters defined above, the shaft 122 is printed with a slow rotation speed of 1 revolution in 5 to 20 minutes.

Any means of controlling the residence time of the biomass in the frying tank 1 known to those skilled in the art, for example a worm transporting the biomass in the oil bath at a controlled rate, also enters the scope of the invention. The preferred embodiment incorporating a rotary vane wheel that is the subject of the figures and described above is however particularly advantageous, particularly in that it allows precise control of the residence time of the biomass in the oil. , that it requires little maintenance because of its simple constitution, and that it allows the reduced pressurization of the tank, since only must be ensured a seal at the passage of the piston 125 through the wall of the tank. In addition, the use of the rotary blade system in accordance with the invention makes it possible to obtain a large contact surface of the biomass with the oil, and a good control of the heat transfer occurring in the bath, as a result of a relatively low biomass / fluid mass ratio. This results in a very great control of the water content of the fried material.

During frying, steam is evolved in the tank 1, above the oil bath 108, from the dehydration of the biomass.

The fried material reaching the window 105 formed in the lower wall 101 of the tank 1 is driven by the gravity and the forced circulation of the oil, in the pipe 31 and then in the dip tube 204, in the lower part of the separator 2 It accumulates there and is naturally separated, by a phenomenon of gravitational decantation, from the oil of the bath 21 1 which tends to rise above it. The presence of the fins 206 advantageously prevents the solid material from rising towards the upper part of the separator, even in the presence of eddies created in the latter during the fall of the material.

The slightly cooler temperature of the oil in the separator relative to that of the vessel 1, in particular in the lower part thereof, if necessary in combination with the cooling means arranged at the level of the conduit 31, advantageously allows blocking the boiling of the biomass inside the separator, thereby improving the settling of the solid in the separator.

At the same time, the oil contained in the separator 2 recovers the heat stored in the fried material that reaches it. It creates inside the separator 2 a temperature gradient between the oil located in its bottom, cooler, and that located in its upper part, warmer.

The fried material is discharged from the separator by the evacuation means 210, through the opening 209 provided for this purpose at the bottom of the separator. The speed of extraction of the fried material is determined, according to calculations within the reach of those skilled in the art, so as to ensure a time of the residence of this material in the separator 2 sufficient to allow the transfer of the heat it has stored when frying to the oil.

The operation of the device according to the invention is advantageously operated continuously, both for the introduction of the biomass in the tank 1 and for the rotation of the blades 121 and the evacuation of the solid material as it accumulates in the the bottom of the separator 2.

Furthermore, the oil contained in the device is also circulated continuously between the separator 2 and the vessel 1, via the double circulation closed circuit, under the action of the pumps 405 and 410. The flow rates of these pumps are determined according to calculations within the skill of those skilled in the art, in order firstly to maintain the equilibrium of the thermal differences between the oil contained in the tank 1 and the separator 2, and secondly to allow optimum operation of the heat exchanger 408. The oil taken from the upper part of the separator 2 advantageously has a high temperature, partly due to the heat it has recovered from the fried material, and only a small contribution of energy is required to bring it to a boiling point at the pressure applied in the vessel 1.

This energy input is partly ensured by the heat exchanger 408 which operates from the energy of the water vapor released during frying.

When the level indicator disposed in the tank 1 indicates an insufficient oil level in the latter, a supply of cold oil emanating from the tank 51 is automatically carried out in the separator 2. This supply makes it possible to increase the level of oil. oil in the tank 1, by the effect of the communication of the internal volumes of the separator 2 and the tank 1 by the conduit 31. The introduction of cold oil is preferably carried out in the lower part of the separator, so as to maintain an optimum temperature gradient therein and to stop the boiling of the fried material as soon as it arrives in the bottom of the separator.

The cumulative effects of the recovery of water vapor energy released during frying to heat the oil extracted from the separator 2 before reinjecting it into the tank 1, and the recovery in the oil of the separator 2 from the heat of the fried material, advantageously provide a high energy efficiency of the device . After the initial energy input to heat the oil, the device operates almost autonomously, only a contribution of a small amount of additional external energy being necessary, at the level of the heating element 408 'associated with the heat exchanger 408 for its operation.

For a low operating cost, the device according to the invention as described above advantageously makes it possible to manufacture up to 80 kg / h of a fuel that can have a lower heating value of up to 20 MJ / kg.

The above description clearly illustrates that by its different characteristics and advantages, the present invention achieves the objectives it has set for itself. In particular, it provides a device for treating biomass by frying, in particular to form a solid fuel, which requires only a small contribution of external energy for its operation and which makes it possible, for a low cost price, to form a fuel with high calorific value, water content very well controlled. This device is an effective tool for the recovery of wet waste.

Claims

1. Device for treating moist biomass by frying, comprising a first tank (1) containing a first oil bath (108), means able to maintain the oil of said first bath at a frying temperature ensuring the frying of the biomass and means for introducing the biomass into said first tank, characterized in that said device comprises means (3) for transferring solid fried material from said first tank into separation means by gravitational decantation of said fried material and oil, in the form of a second tank (2) containing a second oil bath (21 1) having a temperature lower than said frying temperature and in hydraulic communication with said first oil bath, and means ( 210) for discharging the solid fried material from said second tank, said means being able to maintain the oil of said first bath at a frying temperature of the biomass comprising means (401) for lèvement oil in said second tank, the oil heating means removed and means (412) for injecting the oil thus heated into said first tank.

2. Device according to claim 1, characterized in that the heating means of the sampled oil comprise means (422) for extracting the water vapor released into the first tank (1) during frying, and means (408) for heat exchange between the oil taken from the second tank (2) and said water vapor taken from said first tank

(1) -

3. Device according to any one of claims 1 to 2, characterized in that the transfer means (3) solid fried material of the first vessel (1) in the second vessel (2) are constituted by a conduit (31). ) operating by gravity and providing communication between the first oil bath (108) and the second oil bath (21 1).

4. Device according to claim 3, characterized in that said second vessel (2) is disposed under the first vessel (1), said conduit (31) connects a bottom wall (101) of said first vessel and an upper portion of said second tank, and the discharge means (210) of the solid fried material out of the second tank (2) operate at an opposite lower portion (202) of said second tank.

5. Device according to claim 3 or 4, characterized in that said duct (31) opens into an upper part of the second tank (2) and extends inside said second tank by a dip tube (204). reaching an opposite lower portion (202), said dip tube being preferably provided with fins (206) inclined towards said lower portion of the second tank.

6. Device according to any one of claims 1 to 5, characterized in that it comprises means for controlling the residence time of the biomass in the first oil bath (108).

7. Device according to claim 6, characterized in that the means for controlling the residence time of the biomass in the first oil bath (108) comprise a rotating blade wheel disposed in said first oil bath and adapted to moving the biomass from an introduction zone of said biomass into the first vessel (1) to an exit window (105) to the second vessel (2), preferably formed in a bottom wall (101) of said first tank.

8. Device according to claim 7, characterized in that it comprises means for driving said wheel in discrete rotational movements.

9. Device according to any one of claims 1 to 8, characterized in that it comprises means for maintaining a substantially constant oil level in the first tank (1), by introducing cold oil in the second tank (2).

10. Device according to any one of claims 1 to 9, characterized in that it comprises means for placing under reduced pressure inside the first vessel (1).

11. Device according to any one of claims 1 to 10, characterized in that the first tank (1) comprises in an upper part of the winders capable of removing oil residues from the steam escaping from the water. above the first oil bath (108) during frying.

12. Device according to any one of claims 1 to 1 1, characterized in that the means for introducing the biomass into the first vessel (1) comprises an extrusion die (1 13) disposed through a wall ( 102) of said first tank and having cutting areas (1 16) on a rear face (1 17) opposite to the first oil bath (108), and means for supplying said die with biomass.