FR2788761A1 - Drying of pig slurry on a hot surface, after spreading as a foam to give a thin layer - Google Patents

Abstract

Pig slurry (M) is dried by spreading in a thin layer onto a hot surface (10). Water and other volatile materials are thus quickly evaporated (E). The dry material remaining is crushed (3) and scraped (4) off the surface. Formation of a thin layer is helped by a rapid expansion of the slurry into a foam, just before application to the hot surface. An independent claim is given for a machine to carry out the above process.

Description

The present invention relates to a method and a machine for extracting,

  by evaporation, solid residues in suspension and / or in solution in a

  fluid material containing volatile substances, and in particular an aqueous material.

  It has already been proposed to spread the material to be treated in the form of a thin layer on the smooth and hot face of a heat exchange wall which is heated to a temperature sufficient to achieve rapid evaporation of the water. and / or other volatile substances contained in the material, this hot wall being movable along a closed cyclic trajectory, then crushing the layer of material against this hot face to level it and favor its crumbling and spreading, and finally to recover by scraping, at the end of the cycle, the solid and dry residues which are formed on said hot face. A process of this kind is the subject of document WO 93/16005, to which

can refer to if necessary.

  The machine described in this document comprises a series of horizontal, coaxial and parallel discs, which are carried by a common rotary shaft, each of these discs constituting the movable wall, and its upper face constituting the hot face.

  on which the material is treated.

  In this known embodiment, the spreading of the material on the rotary disc is done by means of an oscillating arm which carries a material distribution duct opening near the upper face of the disc. The crushing of the material layer is carried out, in the embodiment described, by means of a series of crushing rollers. The scraping at the end of the cycle is carried out by a scraper associated with a small brush, which are advantageously carried by the swinging arm ensuring spreading; the scraper and the

  small broom expels dry residue outwards.

  In the method and the machine of WO 93/16005, the discs and their shaft are hollow, their interior spaces communicating with each other to form a so-called condensation enclosure, and this set of discs is mounted inside a so-called enclosure evaporation, the machine being equipped with a system for taking off the vapor produced in the evaporation enclosure, for mechanical compression of this vapor, and for introducing the compressed steam into the condensation enclosure, the substances noncondensable being eliminated from the vapor, before its recompression, by a physicochemical treatment.

  Thanks to this arrangement, the amount of heat which is released by condensa-

  tion of the vapor inside the discs is transmitted to the material by conduction through the heat exchange wall on the upper face of the disc, and this quantity of heat will be used to evaporate an equivalent volume of liquid found in the layer

  of material to be treated, which is spread over this upper face.

  Thus, the heat emitted by the condensation is recovered for evaporation, which makes it possible to work with a low energy input, corresponding to

  roughly the mechanical energy required to compress the vapor.

  This process and the machine which makes it possible to implement it are particular-

  suitable for the treatment of farmed manure, and in particular pig manure; one then works at a pressure of approximately 1 bar and at a temperature of the order of 100 C in the evaporation enclosure, and at a pressure of approximately 1.4 bar and a temperature of

  the order 110 C in the condensation enclosure.

  Although the present invention is also adapted to be implemented in a similar installation, in which the heat generated by the condensation on one side of the heat exchange face is used to cause the evaporation of

  the other side of this wall, it is not limited to such an installation.

  It is in fact transposable to heated evaporation surfaces o this principle of mechanical compression of the vapor is not implemented; in this case the process is significantly more expensive than that which requires mechanical vapor recompression; it may however be suitable for certain materials and / or for applications in which energy consumption is not a prohibitive constraint. Whether working with a dehydrating surface heated normally (for example by Joule effect), or according to the principle of vapor recompression, it is very important that the material to be dehydrated is spread in the form of a very thin layer.

  thin and very even on a smooth and clean surface.

  However, the experiments carried out by the applicant have shown that this apparently simple objective is extremely difficult to achieve, with certain materials such as animal manure from the farm, sludge from treatment plants, and

  numerous rejections from agro-food factories.

  Such releases have many things in common. They contain a lot

  of water (around 85 to 98%), are relatively fluid, heterogeneous and sedimentable.

  Their vapor is chemically very charged. They pose major problems of corrosion and of behavior of materials in general, as well as problems related to clogging and

  plugging in the lines of the valves and pumps fitted to the machine.

  Optimally, the thickness of the layer of material deposited on the

  heating surface must be less than 1 mm and preferably of the order of 0.5 mm.

  However, the physical nature of the products to be dehydrated makes it impossible to use the usual solutions such as nozzles, pierced booms, distributing slots, or in particular a capillary coating. It is practically impossible to spread the products

  in the form of such a thin liquid.

  The objective of the present invention is to solve this difficulty.

  For this, the method according to the invention, which repeats the various steps set out above, is remarkable by the fact that, just before spreading the material on the hot face of the heat exchange wall, one causes a significant volume expansion of this material, to give it the consistency of a foam, so that it is this foam which is spread in the form of a thin layer on the hot face. Advantageously, the spreading is carried out at a thickness of less than 1 mm

  approximately, and preferably of the order of 0.5 mm.

  This volume expansion is preferably carried out with a factor

between 20 and 100.

  According to a possible additional characteristic, which is particularly advantageous, the undesirable particles which have remained adhered to the face are eliminated.

  hot after the scraping operation, to prevent them from entering the spreading area

foaming.

  Indeed, the presence of residual particles in the foam formation zone would risk clogging the expansion device and counteract the formation of

the foam.

  Such a method is particularly suitable for treating farmed manure, and

especially pig manure.

  The extraction machine according to the invention, which is of the general type below

  above mentioned, is remarkable in that the means for feeding and spreading the material are adapted to cause a significant volume expansion of this material, and to give it the consistency of a foam just before its spreading, and for

  deposit this foam on the hot side, in the form of a thin layer.

  Furthermore, according to a certain number of additional, non-limiting characteristics of this machine: - said hot face is flat and horizontal, and the volume expansion means of the material comprise a housing placed above this hot face, which is open both downwards and to the side, in the direction of the direction of advance of the movable wall, as well as means for bringing the material to be treated into the housing, this housing delimiting an expansion chamber of the material the bottom of which is constituted by said movable hot face;

  - the material is brought into the housing by means of a volumetric pump

  that, via an Archimedes screw constituted by a brush rotatably mounted in a supply duct; - The housing has a bottom, the bottom face of which is flat, horizontal and parallel to the hot face, this bottom being movable in the vertical direction so that it can be lowered and applied (periodically) against said hot face in order to clean it; the machine includes means for simultaneously causing the temporary stoppage of said pump and the lowering of the bottom of the housing to apply it against the

  hot side, cyclically, the raising of this bottom being then carried out automatically

  only by elastic return members; - the housing has, seen from above, a flared outline, the opening of which is directed in the direction of advance of the movable wall, and the supply of the material takes place at the upstream part of the housing, in its narrow zone ; - Said crushing means comprise at least one flexible sheet which is applied against the material by elastic means such as a leaf spring; - Said flexible sheet is animated by an oscillating back-and-forth movement of small amplitude; - Said sheet is made of polytetrafluoroethylene; said scraping means comprise a battery of scrapers working in cascade, and driven by a cyclic movement with a substantially elliptical trajectory; - Said heat exchange wall is a rotating disc with a vertical axis, the upper face of which constitutes said hot face, while said scrapers are arranged to gradually transfer the residues towards the outside of the disc, and make them fall into a collecting well vertical; - The machine includes an additional scraper capable of scraping the edge of the disc; - It comprises a fixed side wall in an arc of a circle arranged at the edge of the disc, just downstream of the means for spreading the material on the disc, and intended to prevent the escape of the foam towards the outside; - It includes means for mechanically removing the particles remaining adhering to said hot face, these means being located downstream of said scraping and recovery means and upstream of the spreading means; - Said means for removing the particles comprise a collecting sheet associated with at least one evacuation endless screw; - Said means for removing particles are adapted to evacuate the latter towards the outside of the disc; - The machine comprises a set of identical horizontal discs, slightly spaced and coaxial, which rotate as a block around their vertical axis, this machine further comprising a heated annular pickup track arranged at the base of the machine, directly above the edge of discs; - It includes a set of scrapers which rotates in synchronism with the set of discs inside the pickup track, and are adapted to transfer the particles which are there towards a discharge hole located at the base of the collector well; - it includes scrapers adapted to scrape deposits adhering to the

  underside of the discs, and to drop them onto the upper side of the disc

  jacent and / or in the pickup track; - The set of discs is hollow and are carried by a tubular shaft whose interior space communicates with the interior space of each disc, these spaces constituting a so-called condensation enclosure, said assembly being mounted inside a so-called evaporation enclosure, the machine comprising a system for withdrawing the vapor produced in the evaporation enclosure, for mechanical compression of this vapor, and for introducing the compressed steam into the condensation enclosure; - The machine includes a device for extracting and compacting all of the residues, such as a pair of endless heated mobile belts; - The machine comprises means for washing with hot water said hot face. Other characteristics and advantages of the invention will become apparent from the

  description which will now be made of it, with reference to the appended drawings, which

  represent - by way of nonlimiting example - a possible embodiment.

  In these drawings: - Figure 1 is a simplified diagram illustrating the process forming the subject of the invention; - Figure 1A is a detail of Figure 1, which shows the bottom of the foam forming housing in the low position, suitable for cleaning the hot face; - Figure 2 is a schematic front view of the lower part of an extraction machine comprising a stack of hollow discs; - Figure 3 is a schematic top view of a disc; - Figure 4 is a detail showing the feed pump fitted to the machine; - Figure 4A is a detail of the camshaft controlling the pump; - Figure 5 is a schematic top view of the material expansion housing, which generates the foam; - Figure 6 is a view cut by a broken vertical plane referenced VI-VI of Figure 5; - Figure 7 is a schematic and partial view of the disc, which shows the crushing means constituted by a flexible sheet; - Figure 8 is a schematic side view of these same means; - Figure 9 is a partial top view of the disc, intended to show the structure of the scraping means and to illustrate their operation; - Figure 10 is a partial schematic view showing the system for controlling the elliptical movement of the scrapers;

  - Figures 11 and 12 are schematic views from above and, respectively-

  lying, from the front, with a scraper; - Figure 13 shows schematically, in cross section, a possible embodiment of the mechanical particle removal means; - Figure 14 is a partial top view of the disc, which shows both the scraping means, the means for removing small remaining particles, and the material supply means and foam formation; - Figure 15 is a schematic sectional view of the lower portion of the machine, at the base of the collection well and at the inlet of the residue extraction and compacting device; - Figure 15A is a side view of one of the scrapers which run along the pickup track, just at the entrance of the discharge hole; - Figure 16 is a general top view of the lower disc and the discharge system; - Figure 17 shows, in section, the device for extracting and compacting residues; - Figure 18 is a detail of Figure 17, showing a drive cylinder of the belt; - Figure 19 is a top view of the discharge and compacting device, with cut parts; - Figure 20 is a top view of a side panel provided at the edge of a disc; - Figure 21 is a cross section corresponding to the section plane

vertical XXI-XXI of figure 20.

  With reference to Figure 1, we will first describe the principle

  general of the process which is the subject of the invention.

  The material to be treated is for example pig manure.

  The material is dehydrated on a heat exchange wall 1, which is heated to a temperature sufficient to achieve rapid evaporation of the water

  and / or other volatile substances that are contained in the material.

  The upper face 10 of this wall is smooth and flat.

  The wall 1 is movable. It moves from left to right if we consider Figure 1, this displacement being symbolized by the arrow R.

  It is preferably a displacement at constant speed.

  As will be seen later, in the case where the surface 10 is the upper face of a disc, the movement R is a rotational movement at continuous speed

and slow.

  It is therefore a cyclic movement, the deposition of the material on the hot face 10 being done at the start of the cycle, and the removal of the various residues at the end of the cycle, so that the face 10 is clean when it represents himself at the spreading station of

the material to be treated.

  As will be seen below, this item 2 affects the general shape of a box whose bottom is referenced 20. It is a box open both downwards and on one side, in this case downstream, on the side corresponding to the direction of advance R. The material is brought into this housing by means which will be described later, comprising an Archimedes screw 21 rotatably mounted in a tube. The section

  of the material supply duct is relatively small compared to the available volume

  ble for the material inside the space of the housing 2. This is why there is a partial vaporization and rapid expansion of the material, which becomes

  emulsion and takes the consistency of a foam.

  Depending on the nature of the product, the foam is more or less dense. The housing is shaped and dimensioned in such a way that the expansion takes place in a ratio of between 20 and 100. This means that the volume of the foaming material formed in the housing is 20 to 100 times greater than that of the volume of material which is introduced into it by Archimedes' screw 21. As a result of the gradual evaporation of this emulsion, which is symbolized by the arrows E in FIG. 1, an increasingly dry layer is obtained

and less and less thick.

  This meets crushing means 3, the role of which is to promote the crumbling and spreading of the layer of material against the hot face, in order to make this layer homogeneous by flattening the small craters which have formed, which has the effect of considerably improving the quality of the heat exchange of the hot face

with matter.

  These crushing means will be described later, with particular reference

in Figures 7 and 8.

  At the end of the dehydration, the layer is formed of dry residues, or practically dry. This is where the scraping means 4 come into play, which have the function of scraping these residues r in order to expel them from the surface 10, towards collecting means. These scraping means will be described later, with particular reference

in Figures 9 and 10.

  Despite this operation, there are still small particles p on the face

hot 10.

  Indeed, certain residues inevitably escape the action of the scraping means, in particular because they adhere strongly to the hot face. Other particles p are residues which have been well captured by the scraper members but which are

are detached.

  It is important to remove these unwanted particles p so that they do not get into the foaming housing, as they would clog it

  quickly and would counteract the phenomenon of expansion.

  To this end, there are provided, between the scraping members 4 and the housing 2,

  means 5 intended to remove these particles p to drive them from the hot face 1.

  These means will be described later, with particular reference to the figures.

13 and 14.

  As shown in FIG. 1A, it is possible periodically to clean the face 10 by lowering the bottom 20 of the housing to press it with a certain force against the face 10. This action has the effect of destructuring the agglomerates being formed, agglomerates which consist of heavy sediments or partially dried products which adhere very strongly to the face 10. FIG. 2 very schematically and partially represents a machine

  dehydration with rotating discs of the same general type as that described in WO-

93/16005 already cited.

  This machine comprises a tank 6, with isothermal walls 60, of shaped

  general cylindrical, with vertical axis Z Z ', supported by a base 61 fixed to the ground.

  Inside the tank 6 is mounted a stack of hollow discs 1,

  arranged horizontally, and mounted on the same tubular shaft 100, of axis Z Z '.

  This assembly is guided in rotation in a guide device 101 carried

through the bottom 62 of the tank.

  The interior space of the tubular shaft 100 and the hollow disks constitute a condensation enclosure, while the space exterior to the disk and interior to the tank

  constitutes an evaporation chamber.

  The vapor taken from the evaporation enclosure is recovered, mechanically compressed by means not shown, and introduced into the

  condensation, as symbolized by the arrow a.

  The condensate is collected in a receptacle 63 mounted at the base of the shaft

  tubular 100, and is periodically discharged as symbolized by the arrow b.

  As an indication, a set of 20 to 30 discs is planned and these have

a diameter of the order of 2 m.

  The hollow shaft 100 is driven in rotation by appropriate means (not shown), at relatively slow uniform and continuous speed, of the order of 0.33

revolution / minute for example.

  When observing FIG. 2, it will be noted that there is an annular track 7, which is fixed inside the tank, on the bottom 62. This track has the shape of a circular channel of cross section "U", the opening of which is directed upwards and is located at

  plumb with the edge of the stack of discs.

  We understand that the products chased outside of each disc are

  likely to fall by gravity into runway 7.

  Inside the track 7 is mounted a plurality of scraper members 71.

  These are regularly angularly spaced and carried by an additional disc 72

  also rotating around the axis Z Z '.

  Advantageously, this lower disc 72 is integral with the hollow shaft 100, so that it rotates at the same time as the discs. On the left of FIG. 2, there is an electric geared motor 48,

  whose output shaft is referenced 47.

  As will be seen below, this rotary shaft makes it possible to drive, in an oscillating movement back and forth, a pair of arms 44, 44 'carrying the means of

scraping mentioned previously.

  The general top view which is the subject of FIG. 3, makes it possible to locate the location of the different stations on each disk 1, the direction of rotation of which is symbolized by the arrow R. In this figure, we see a pump 213 supplying the material to the Archimedes 21 screw, the foam expansion unit 2, the crushing means 3, the

  scraping means 4, and means 5 for removing the unwanted residual particles

  wheat. There is also an annular track 7 which is traversed by the set of scrapers 71, as well as a small brush 710 whose function is to clean the top of these

scrapers each time they pass.

  In this figure 3 there is also a vertical collecting well 8 and

  a drop side 12 whose functions will be explained later.

  FIG. 4 shows the device for supplying the material to be treated, which is at a temperature close to its dehydration temperature, ie for

  slurry a temperature close to 100 C.

  Advantageously, the slurry has in fact been heated beforehand by the distillate resulting from the evaporation treatment, by passage through an exchanger in which

  both slurry and distillate flow against each other.

  An exchanger suitable for carrying out such preheating is the subject of patent application N * 99 00655 of January 14, 1999, to which reference may be made to

need.

  This material is brought in by a positive displacement pump 213, the characteristics of which, and in particular the flow rate, are chosen to be compatible with the drying area and the nature of the material; for slurry, a pump can be used

  eccentric rotor type, the flow rate of which is between approximately 25 and 50 liters / hour.

  The Archimedes screw 21 which has the function of introducing the material into the housing 2 comprises a tube 218 in which rotates a helical brush 217, which constitutes the screw proper; this solution is particularly suitable to avoid

fouling and clogging.

  The pump 213 is supplied by a material inlet pipe 210, via a three-way valve 212. In fact, the device also includes a hot water inlet 211 and, by actuating the valve 212, it is possible to '' selectively supply the material to be treated or hot water to the pump (for a cleaning sequence). The pump 213 is driven in rotation from a pinion 216, itself driven by a motor not shown, via a clutch. This one

  includes a drive dog biased by a helical compression spring 215.

  It is possible to disengage the pump with respect to the drive pinion 216 by rotation of a camshaft 200, the disengagement being achieved when the cam 201 of the camshaft comes to push a rod 217 secured to the dog clutch. This allows

  cyclically control the stop of the material supply to the housing 2.

  As shown in FIG. 4A, the tree 200 carries a certain number of

  cams 201 angularly offset, regularly distributed in the longitudinal direction

  nale of the tree. A pump is associated with each disc, the stop of which is controlled by one of these cams. The angular offset makes it possible to shift the cleaning cycles from one disc to another, so that dehydration takes place overall in a homogeneous manner

in the machine.

  Archimedes' screw 21 opens inside the housing 2, which is

  illustrated in detail in Figures 5 and 6.

  This housing 2 consists of a frame 22 which seen from above has a flared shape. It is a vertical partition, and which is in contact with the hot face 10 by

through a deputy 23.

  The box has a horizontal wall 20, called "bottom" (because the box is upside down, opening facing down), located at a certain distance from the face 10,

  the assembly being made of a thermally insulating material.

  The underside 2000 of this bottom is flat and smooth, parallel to the face 10.

  This plate 20 is held in the high position by springs constituted by elastic wires or blades 25, which apply it upwards against stops 24; these are plates with a semicircle contour regularly distributed and fixed

on top of frame 22.

  A flexible membrane 26, one of the edges of which is fixed in the upper part of the frame 22, and the other to the adjacent lower edge of the bottom 2, provides sealing at this level.

  In top view, the partition 22 has an approximate symmetrical shape-

  ment in the shape of a "V" whose branches diverge in the direction of advance R. The branches of this "V" are slightly arched, their convexity being directed inwards

of the housing.

  The feed screw 21 opens into the narrow zone 23, corresponding

at the top of this "V".

  The relatively dense material, which is driven back by Archimedes' screw 21 in the area 29 of the shoemaker, therefore arrives at the entrance to a flared space, delimited upwards by the bottom 20, on the sides by the partitions divergent 22, and downwards by the movable hot face 10, this space being open on the other side, in the direction of advance R. As can be seen in FIG. 3, the mouth of this case in "V "extends substantially radially, over the entire surface of the disc, between the central shaft 100

and the edge of the disc.

  As a result of the instantaneous partial vaporization resulting from the heat of the face 10, the increase in the available volume, and the decrease in pressure, the material M becomes an emulsion, with generation of bubbles, and takes on a consistency.

frothy.

  This foam is spread over the entire radius of the moving disc.

  On the top of the bottom plate 20 is fixed a pair of tabs 28. These constitute counter-cams with which come into contact, at each turn, cams 282, which are fixed against the underside of the disc located just above, come to bear against the cleats 28, in order to move the bottom 20 downwards

  (arrow P) to press it against the surface 10.

  After passage of this cam 280, the elastic members 25 cause the automatic raising of the plate 20, which abuts against the tabs 24,

returning to its normal position.

  The stop command of the pump by the cams 201 mentioned above is naturally synchronized with the lowering of the housing bottom 20, so that the supply of material is stopped during the period of time during which the

  plate 20 rubs against surface 10.

  We thus perform a cleaning of the disc at each turn, that is to say all

  three minutes, the duration of this cleaning being a few seconds.

  In addition to these frequent cleanings, it is possible to provide an additional cleaning with hot water, every three to six hours for example, by substituting hot water for the material to be dried, or selectively disc by disc by means three-way valve 212, or collectively for all the discs. This additional cleaning with hot water advantageously lasts for 1 to 2 turns, that is to say

  for a duration of between 3 and 6 minutes.

  The cleaning action done separately disc by disc disturbs the

  overall operation of the machine.

  Such cleaning is also carried out at each start and at each stop.

of the machine.

  Cleaning with hot water is required to remove the fouling which inevitably forms with certain particularly difficult to treat products, which form on the disc, after a few hours, a deposit of very thin film but

  sufficient to significantly degrade the effectiveness of dehydration.

  At the outlet of the housing 2, it is necessary to prevent the foaming material from

escapes around the edges of the disc.

  For this, a drop side is provided, positioned immediately at the exit of the

housing 2.

  With reference to FIGS. 20 and 21, it can be seen that the side panel 13 is formed of a pair of rods in an arc of a circle, concentric with the disc, which enclose a flexible strip 12. This is applied to the edge of the disc and constitutes a sealing flap, which prevents material from overflowing out of the disc. The drop side is carried by a pin 140 disposed at the end of an elastic blade 14, the other end of which is supported by a fixed part. The elastic blade 14 applies the seal 12 against the upper face of the disc with a certain force. The flap 12 is made of synthetic material

  flexible which resists corrosion of the material.

  This drop side extends over a sector of limited circumference, because its presence

  is not necessary once the material has been channeled and has started to dehydrate

  ter. With reference to FIGS. 7 and 8 we will now describe a mode of

  advantageous production of the crushing means 3.

  These means include a section 30 of "V" section, which is fixed to one end of a bending blade 34, of relatively great stiffness; the blade 34 extends approximately mid-radius of the disc, and is oriented in the general direction of advance of the disc in this zone. It can flex in a horizontal plane. The other end of the blade 34 is fixed to a support 33 secured to a fixed part 400. This has the function of ensuring guiding in translation, but with a certain freedom of angular movement, of an arm 40 constituting the scraping means 4 which will be described later. The arm 40, which is symbolized by broken lines in FIG. 7, is driven by an oscillatory movement of small amplitude d, centered at the level of the part 400. The “V” profile 30, the edge of which is turned upwards, has a vertical wing, while its other wing is inclined downwards and downstream (if we consider the

direction of advance R of the disc).

  Under the inclined wing is fixed a strip of elastic stainless steel sheet

  ble 31, which partially covers a large sheet 32 of P.T.F.E (polytetrafluoroethy-

lene).

  This sheet is applied with force against the upper face of the disc.

  The sheet metal strip 31 and the sheet 32 have an elongated rectangular shape,

  whose long side corresponds to the length of the section 30 which supports them.

  This large side 32 forms a slight acute angle and with respect to the radial direction. It is a re-entrant angle relative to the central zone of the disc, which tends to direct the material rather towards the inside of the disc and not towards the outside, in which case it

  may partially escape.

  At the end of the profile 30 which is oriented towards the inside of the disc is fixed a cam 35 which is normally in contact with the swing arm 40 mentioned above. The oscillatory movement is therefore transmitted by this cam 35 to the flexible sheet 32, which also describes a back-and-forth movement. The amplitude of this movement is, for information, of the order of 10 to 30 mm. The reminder of sheet 32 is

  produced as a result of the elasticity of the blade 34.

  The large sheet of P.T.F.E in motion crushes the craters and other roughness of the material, flattens them, and makes it possible to obtain a thin and regular layer over the whole width of the disc, which allows to obtain a good thermal transfer and a

excellent drying.

  With particular reference to 9 to 12, we will now

  describe the structure and operation of the scraping means.

  These means include a set of scrapers which, in the example illustrated, are four in number and are referenced 41a, 41b, 41c, 41d. The scrapers are regularly spaced and arranged in a line close to the radial direction, the first scraper 41a being located in the central area (near the hub 100), while the last scraper 41d is located in the edge region of the disc. Each scraper is mounted at the end of a spring leaf 43 carried by the

arm 40 above.

  It is a bent horizontal arm whose free end extends beyond the central part of the disc and is guided in translation, with a certain angular freedom,

in organ 400 already cited.

  The bend of the opposite end referenced 44, is extended by a connecting rod

  the movement of which is controlled by an eccentric pinion 46b.

  This is engaged with a drive pinion 46a carried by a shaft

motor 47.

  The latter is rotated, at continuous and uniform speed by the

  motor 48 mentioned above, with reference to FIG. 2.

  Each scraper 41 is applied against the upper face 10 of the disc by

its blade comes out 43.

  The blade presses strongly on the scraper using a welded 430 ball

under the leaf spring.

  In the example illustrated (Figures 11-12), the scraper 41 is provided with two

side scraping blades 42.

  Preferably these blades are made of very hard metal having a good coefficient of

  friction, such as tungsten carbide for example.

  The position of the scraper relative to the leaf spring 43 is adjustable, by a connecting finger, for example threaded 431 (whose axis only is shown in Figure 12). Thanks to this arrangement, in which the ball 430 acts as a ball joint, it is possible to apply the scraping blades suitably against the surface.

  disc, even if it has some flatness defects.

  As seen in Figure 9, the various scrapers are arranged along a line which forms an angle relative to the strictly radial direction of the disc. The external scraper 41d is located further downstream of the disc than the scraper

  previous 41c, and so on until the internal scraper 41a.

  Due to the movement generated by the rod / crank system 41b / 45, each scraper follows an oval closed trajectory, approximately elliptical, which is shown in fine lines in FIG. 9. The different trajectories ta, tb, tc, td are

  nested one inside the other so that the scrapers work in cascade.

  Thus, the residues which are peeled off by the first scraper 41a, over the entire trajectory of this scraper, are transmitted to the following scraper 41b; the latter transmits to the following scraper 41c the cumulation of its own residues and those from the first scraper,

  and so on, until the last scraper 41d.

  This drives them out of the disc, in a vertical well 8, of

  semi-cylindrical section, located at the edge of the disc, opposite the scraper 41d.

  Each disc is associated with such a battery of scrapers, the last of which

  are all next to well 8.

* All the residues taken from the different discs are therefore discharged into this vertical well 8, which collects them; they fall to the base of the well by

gravity.

  As can be seen in FIG. 10, the same pinion 46b drives two arms, namely the arm 44 which has just been mentioned and the arm 44 'of the disc which is located

just above.

  The two connecting rods corresponding to the arms 44 and 44 'are articulated at diametrically opposite points on the drive pinion 46b, so as to balance

  correctly the forces at the hubs of the gears 46a, 46b.

  This is the case for all discs, a drive mechanism

  unique being associated with a pair of scraping sets.

  It will be noted in FIG. 9 that the arm 40, 44 carries elements referenced

  441, also four in number.

  These carry upward-facing scrapers, which may have a

  configuration similar to that of the scrapers which have just been described.

  They are located slightly upstream of the scrapers 41.

  Their role is to scrape the underside of the disc located just above, on which deposits of material also form, due to the large volume of foam which leaves the housing at the start of the cycle, this abundant foam being susceptible

  to come into contact with the top disc.

  The residues scraped by these scrapers 441 fall onto the disc, and are incorporated into all of the residues discharged by the scrapers 41 into the well.

collector 8.

  Note that there is in particular provided, just upstream of the collection well 8, a scraper blade 80, which is applied against the cylindrical edge - or edge - of the disc. These deposits are removed by the blade 80 and fall by gravity into the underlying track 7. It should be noted that the deposits present on the underside of the discs and on their edges have a different chemical composition from the base material; the bubbles that cause these deposits do not contain sediment; on the other hand there are

  soluble substances, in particular sodium and potassium chlorides.

  As the deposits thicken, their drying becomes impossible; they remain under the discs and on the edges in a wet phase, likely to

  quickly corrode stainless steel.

  The secondary cleanings carried out by the scrapers 441 and 8 make it possible to maintain the layers of chloride at very small and dry thicknesses, and therefore not

corrosive.

  At the exit of the scraping assembly 4, all the dry residues were not perfectly recovered. There remain on the disc small particles of undesirable residues, more or less sticky, some of them having detached from the scrapers. These

  particles must be removed and directed to the collection path 7.

  Otherwise, the back of the foam generator box would be completely

  dirty after a few hours of work.

  To solve this problem, the machine is equipped with means intended to

  remove these particles, means which are shown in FIGS. 13 and 14.

  These means 5 comprise a thin, hard and elastic sheet 50.

  It is an elongated sheet which is roughly folded transversely-

  in the shape of a "U", the opening of which faces laterally upstream, and which

  extends substantially parallel to the line of the scrapers 41, just downstream of this line.

  The lower branch of this "U", referenced 500, is applied with precision on the face 10 and plays the role of a shovel-knife which picks up the particles as they go.

as they arise.

  The sheet 50 constitutes a kind of cover, in which a conveyor endless screw 51 is mounted, the rotation of which is controlled by an end pinion 53, engaged with a suitable motor pinion not shown. This worm is guided to

  its ends in parts forming bearings integral with the housing 2 (neighbor).

  The worm is made of stainless steel and has a very smooth thread; his

  direction of rotation and as it conveys particles outside the disks

  ted by the "shovel-knife" 500, and retained by the cover 50.

  Preferably, two reverse worms nested one inside the other 51, 51 ′ are used, as shown in FIG. 13. The particles conveyed by this device are transferred outside the

  disc and also fall by gravity into the annular track 7.

  As seen in Figure 15, the collection well 8 opens at its

  base in a circular opening 81 which is formed in the bottom wall of this track.

  Under this hole 81 is installed a device 9 for extracting and compacting all of the residue which has been removed from the discs by the various means described above. FIG. 15A represents, seen from the side, one of the scrapers 71 which turns in

permanence in runway 7.

  It is an elastic blade, for example made of spring steel, the upper part of which is integral with a mounting part 710 fixed under the drive disc 72. The blade 71 is inclined downwards and towards the upstream, and its lower free end is folded at a right angle, so as to scrape the various particles p which are on the track, and to bring them to the hole 81, by which they fall at

  the inlet of the extraction device 9.

  Because the scrapers 71 periodically cross the collection well, they have been contaminated by the residues falling into this well, which explains the presence of the small

  cleaning brush 710 mentioned above, with reference to FIG. 3.

  The extraction and compacting device 9 comprise a pair of belts, 91. These are endless bands, arranged horizontally. The lower belt is longer than the carpet 91, and the portion of its upper strand which is not

  covered by the carpet 91 passes under the hole 81.

  The two endless belts 90, 91 are metallic belts which are driven on the downstream side, by drive cylinders 900, 910, respectively; the upstream side return cylinders are respectively referenced 901, 911, their direction of rotation being symbolized

  by the arrows m, respectively n.

  These mats rub on heating insulating plates 95, respectively-

  ment 96, which are capable of withstanding high pressures, so as to ensure the

  compacting and extraction of the collected residues, while completing their drying.

  The tensile forces applied to each of the belts can exceed 1000 daN. This is why the metallic carpets are mesh carpets, the cylinders 900

  and 910 being fitted with peripheral pins 913 capable of engaging in these meshes.

  The drive cylinders 910, 900 carry end gears 931 (see FIGS. 18 and 19) which are engaged with one another in order to ensure that the two belts move in synchronism, at the same speed; mat training is

  controlled by a gear motor 94, the output shaft 93 of which carries a drive pinion

  ely engaged with the engine cylinders, via a 930 transmission chain.

  The two mats can either be parallel - as shown in

  the figures - either be slightly convergent to narrow towards the exit in compact -

both the product.

  After compaction, the residues exit in the form of a cake through a

  adjustable die 950, called knife-die.

  The carpet device is installed in a box referenced 97; sealing

  of the die-knife relative to this box is provided by seals 951.

  Sealing with respect to the evaporation enclosure of the dehydrating tank

  tion is ensured by the dried product itself, because this product is sufficiently compacted

  in the die to ensure this essential seal.

  It goes without saying that the diameter of the rollers 910, 900, 911 901, the space between the two belts, their inclination, their width and the speed of their movement are adapted to

  the nature and at the rate of the material to be extracted.

  The purpose of this extraction device is to evacuate all of the residues having passed through the opening 81, to compact them and take them out outside the machine while ensuring vapor tightness, since the enclosure d evaporation, in which the temperature is for example of the order of 102 C, is in overpressure relative to the external atmospheric pressure, the value of this overpressure being for information only

between 50 and 100 Pascal.

  The process, the machine and the installation which have just been described are

  particularly suitable for the treatment of liquid manure, in particular pig breeding.

  It goes without saying, however, that they can be transposed to various different applications, for the treatment of various materials, such as for example

  sewage treatment plant sludge and agro-food plant discharges.

Claims (18)

  1. Method for extracting, by evaporation, solid residues which are in suspension and / or in solution in a fluid material containing volatile substances, and in particular of an aqueous material, according to which: a) the material (M) is spread to be treated in the form of a thin layer on the smooth and hot face (10) of a heat exchange wall (1) which is heated to a temperature sufficient to achieve rapid evaporation of the water and / or other volatile substances contained in the material, this hot wall (1) being movable along a closed cyclic path; b) the layer of material (M) is crushed against said hot face (10) to level it and promote its crumbling and spreading; c) the solid and dry residues (2) which are formed on this hot face are recovered by scraping, at the end of the cycle; characterized in that, just before its spreading, a significant volume expansion of the material is caused, to give it the consistency of a foam, so that it is this foam which is spread in the form of a layer thin on the hot side.   2. Method according to claim 1, characterized in that the expansion   volume is carried out with a factor between 20 and 100.   3. Method according to claim 1 or 2, characterized in that the particles (p) remaining adhering to said hot face are eliminated after the scraping operation,   to prevent them from entering the foam spreading area.   4. Method according to one of claims 1 to 3, characterized in that   the material (M) treated is farmed manure, in particular pig manure.   5. Machine for extracting solid residues which is in suspension and / or in solution in a fluid material containing volatile substances and in particular of an aqueous material, which comprises: a) a heat exchange wall (1) having a smooth and hot face (10) which is heated to a temperature sufficient to achieve rapid evaporation of water and / or other volatile substances contained in the material, this wall being movable along a closed cyclic path; b) means (21, 2) for supplying and spreading the material to be treated on this hot face, at the start of the cycle, in the form of a thin layer; c) crushing means (3) capable of promoting the crumbling and spreading of the layer of material on this hot face (10); d) means (4) for scraping and recovering at the end of the cycle the solid residues (r) which have formed; characterized in that said supply and spreading means (21, 2) are adapted to cause a significant volume expansion of the material (M) and give it the consistency of a foam just before its spreading, and to deposit this   foam on the hot side (10), in the form of a thin layer.   6. Machine according to claim 5, wherein said hot face (10) is planar and horizontal, characterized in that the volume expansion means of the material comprise a housing (2) placed above this hot face, which is open both downwards and to the side, towards the direction of advance of the movable wall, as well as means (21) for bringing the material to be treated into the housing, this housing delimiting a chamber expansion of the material, the bottom of which is constituted by said hot face mobile (10).   7. Machine according to claim 6, characterized in that the material (M) is brought into the housing (2) by means of a positive displacement pump (213), via an Archimedes screw constituted by a brush (217) rotating rise in a duct supply (218).   8. Machine according to claim 6 or 7, characterized in that the housing (2) has a bottom (20) whose lower face (2000) is flat and horizontal and is parallel to the hot face (10), this bottom being movable in a vertical direction so that   be able to be lowered and applied against said hot face (10) in order to clean it.   9. Machine according to claims 7 and 8 taken in combination,   characterized in that it comprises means (200, 201, 216, 214, 215; 28, 280) for simultaneously causing the temporary stopping of said pump (213) and the lowering of the bottom of the housing (20) to apply it against the hot face, in a cyclic manner, the raising of this bottom (20) then being carried out automatically, by means of elastic return (25).   10. Machine according to one of claims 6 to 9, characterized in that   that said housing (2) has, seen from above, a flared outline, the opening (O) of which is directed in the direction of advance (R) of the movable wall (1), and that the supply of the material is   made at the upstream part of the housing, in its narrow zone (29).   1 1. Machine according to one of claims 5 to 10, characterized in that   that said crushing means (3) comprise at least one flexible sheet (32) which is   applied against the material (M) by elastic means such as a leaf spring (3).   1 2. Machine according to claim 11, characterized in that said flexible sheet (32) is driven by an oscillating back-and-forth movement (d) of low amplitude. 1 3. Machine according to claim 11 or 12, characterized in that   said flexible sheet (32) is made of polytetrafluoroethylene.   1 4. Machine according to one of claims 5 to 13, characterized in that   that said scraping means (4) comprise a battery of scrapers (41a, 41b, 41c, 41d) working in cascade, and animated by a cyclic movement with a substantially trajectory elliptical (ta., tb, tó, td) -   15. Machine according to one of claims 5 to 14, wherein said   heat exchange wall (1) is a rotating disc with vertical axis (ZZ '), the upper face (10) of which constitutes said hot face, characterized in that said scrapers (41) are arranged to gradually transfer the residues ( r) out of   disc, and drop them into a vertical collecting well (8).   1 6. Machine according to claim 15, characterized in that it   comprises an additional scraper (80) capable of scraping the edge (11) of the disc.   17. Machine according to claim 15, characterized in that it comprises a fixed side wall in an arc of a circle (12) disposed at the edge of the disc (1), just downstream of the means (2) for spreading the material ( M) on the disc (1), and intended for   prevent the foam from escaping to the outside.   1 8. Machine according to one of claims 5 to 16, characterized in that   that it comprises means (5) for mechanically removing the particles remaining adhering to said hot face (10), these means being located downstream of said means of   scraping and recovery (4) and upstream of the spreading means (2).   1 9. Machine according to claim 18, characterized in that said means (5) for removing the particles comprise a collecting sheet (50) associated with   at least one endless screw (51) for evacuation.   20. Machine according to claims 15 and 18, taken in combination,   characterized in that said particle removal means (5) are adapted   to evacuate the latter towards the outside of the disc (1).   21. Machine according to claim 15, comprising a set of identical horizontal discs, slightly spaced and coaxial (1), which rotate as a block around their vertical axis (XX '), characterized in that it comprises a pickup track heated ring (7) arranged at the base of the machine, directly above the edge discs (1).   22. Machine according to claim 21, characterized in that it comprises a set of scrapers (71) which rotates in synchronism with the set of discs inside the pickup track (7), and are adapted for transfer the particles therein to a discharge hole (81) located at the base of the well manifold (8).   23. Machine according to claim 21 or 22, characterized in that it comprises scrapers (440, 441) adapted to scrape the deposits adhering to the underside (1 ') of the discs, and to make them fall on the face upper (10) of the disc   (1) underlying and / or in the collection path (7).   24. Machine according to one of claims 21 to 23, wherein   all the discs (1) are hollow and are carried by a tubular shaft (100), the interior space of which communicates with the interior space of each disc (1), these spaces constituting a so-called condensation enclosure, said assembly being mounted inside an enclosure (6) called evaporation, the machine comprising a system for drawing off the vapor produced in the evaporation enclosure, for mechanical compression of this   steam, and introduction of the compressed steam into the condensation enclosure (6).   2 5. Machine according to one of claims 5 to 24, characterized in that   that it includes a device (9) for extracting and compacting all of the   residue, such as a pair of heated mobile endless belts (90, 91).   26. Machine according to one of claims 5 to 25, characterized in that   that it comprises means (211, 212, 213) for washing said face with hot water hot (10).