FR2690164A1 - Edible oil and fat prodn. powder treatment for recovery and cleaning - by mixing with hot alkaline water, settling and decanting phases, for decolourising, filtration or dewaxing food oils and fats - Google Patents

Abstract

Powders (T) are treated after use. The powders are mixed with hot water (5) at ca. 90 deg.C, up to a concn. of 35% solids. An alkaline liq. (7) is added to form the pH of the mixt. to ca. 9. After sepn. of the three phases of oil, water, and powder, by density the powders (53) may be collected separately. USE/ADVANTAGE - Recovery and cleaning of powders used for decolourising, filtration, or dewaxing of food oils and fats. The treatment reduces the level of oil in the powder to less than 1%, allowing them to be reused in agriculture. Oils removed from the powder may be reused directly as they are not denatured. The treatment is simple, free from pollution risks, and may treat a reasonable tonnage at acceptable cost.

Description

 The present invention relates to the treatment of soils used in the production of edible oils or fats.

 The term "land" used in the context of the invention relates to several types of land, which are inscribed in different stages of production.

 First there are the bleaching earths, with which the oils and greases are mixed to lighten the color, and to carry out a coarse filtration stopping impurities by absorption. A mass of bleaching earth or cake comprising oil with a high content (generally from 15 to 50%) is then recovered, after passage through filters. There are also the filtration earths which are then added to the liquid thus cleared, these earths having a very small particle size. In some cases, dewaxing (or "winterization") earth is also used to remove the wax from the oil.

 The treatment of these different soils to remove the oil is currently the subject of much research, both for the recovery of the oil they contain, and for the reuse of the so treated earth.

 Indeed, these soils saturated with fatty matter and often flammable (especially when they contain phosphoric acid used during production for degumming) are considered as waste generating nuisances, and must be eliminated. As the dumping of such substances in landfills is often prohibited by regulations, the only authorized solution is incineration in an approved center, at a very high cost.

 The problem with these soils is that they contain excessive amounts of fat, which must first be extracted and then eliminated.

 Mechanical pressing techniques have thus been used, with a turbo-circulator associated with a filter press, which have the advantage of simplicity, but which in reality remain ineffective: the oil content of the pressed earth is indeed still relatively low. high (between 15 and 30% in general), which requires subsequent treatment of incineration to comply with pollution regulations, resulting in a high overall cost.

 As a result, research has rather turned to essentially chemical treatments.

 Mention may be made in this connection of the use of salt water as a washing means, which is circulated on the filter containing the bleaching earth cake, the oil then being separated by sedimentation. The oil content of the bleaching earth cake still remains relatively high (10 to 15% in general). In addition, the oil recovered is of poor quality, and denaturation also affects residual water and soil, which are therefore not directly reusable. We also used different solvents (gasoline, hexane, or perchlorethylene in particular), this which has made it possible to lower the oil content of the treated earth to a value approaching 5%, but, in addition to the dangers which these treatments entail, it then becomes necessary to carry out a subsequent distillation treatment to separate the oil, which is complex, bulky and expensive.

 Finally, the various methods currently used do not make it possible to remove enough fat from the earth to make it inert, or to remove this fat at an economically acceptable cost. In most cases, the residual soil and the fat obtained are polluted by the separating agents, and are difficult to recover.

 The object of the invention is precisely to solve this problem, by carrying out a treatment method which does not have the above-mentioned drawbacks and / or limitations.

 The subject of the invention is therefore a process for treating the soil which is both efficient, by succeeding in particular in lowering the oil content below a value of 1%, and in recovering oil that is sufficiently little denatured for be reusable directly, but which is also free from risks of pollution or other dangers.

 The subject of the invention is also a treatment process suitable for a wide variety of soils, whether they are bleaching, filtration or dewaxing soils, these soils being able to be further reusable in agriculture thanks to their very low content in oil.

It is more particularly a process for treating the earth used in the production of edible oils or fats, characterized in that
- the earth is mixed with hot water in a treatment tank, with a proportion of earth essentially below 35%, to obtain a homogeneous mud maintained at a temperature close to 900C;
- basic liquid is added to this homogeneous mud to bring its pH to a value close to 9
- After separation of the three oil-earth phases by difference in densities, the earth thus treated is recovered separately.

 The aforementioned term "mud" is intended to represent a relatively thick and viscous liquid mixture. This term will be repeated below without further details.

 Preferably, the homogeneous mud comprises a proportion of earth close to 30%.

 Advantageously still, the temperature of the homogeneous mud is maintained between 880C and 920C, and the pH of the homogeneous mud is essentially maintained between 9 and 9.5.

In particular, the basic liquid used so that the pH of the homogeneous mud is at the desired value can be a sodium hydroxide solution, preferably titrated between 45% and 50%.

 It may, in certain cases, be advantageous to add to the homogeneous sludge a dewaxing agent, for example sodium carbonate.

 In accordance with a particular embodiment of the process, the separation of the three oil-earth phases is carried out by natural decantation in the treatment tank, preferably for a period of between 4 and 6 hours, so as to recover the two liquid phases oil and water before recovering the soil treated at the bottom of the tank.

 The recovery of the two oil and water liquid phases can then be carried out by pumping into each of the liquid layers, or by natural flow at suitable heights. As a variant, this recovery can be carried out by pumping the two layers of liquid or by natural flow at an adequate height, then by separation of the two phases from the liquid thus recovered.

 According to another embodiment, the separation of the three oil-water-earth phases is carried out by centrifugation in a separator provided downstream of the treatment tank.

 Advantageously finally, the water recovered at the end of the land treatment undergoes a subsequent treatment in a settling-settling tank, in order to be able to recover the fat and the residual land.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawings, illustrating particular modes of implementation of the treatment method, with reference to the figures where
- Figure 1 schematically illustrates a land treatment process according to the invention, with an installation for implementing this process
- Figure 2 illustrates a variant of the process, according to which, after natural decantation of the homogeneous mud in the treatment tank, the recovery of the two liquid phases oil and water is carried out by natural flow (this recovery was carried out by pumping with installation of figure 1)
- Figure 3 illustrates a variant of the treatment tank used for the implementation of the process, according to which permanent stirring and heating are provided by a single means, here produced in the form of a ramp of hot compressed air
- Figure 4 illustrates another variant of the process, according to which the separation of the three oil-earth phases is carried out, no longer by natural decantation as was shown diagrammatically in Figures 1, 2 and 3, but directly by centrifugation in a separator
- Figure 5 illustrates a subsequent treatment of batten recovered in a settling-settling tank.

 FIG. 1 schematically illustrates an installation for implementing the treatment method according to the invention, making it possible to treat soil used in the production of edible oils or fats. The earths to be treated are here represented in the form of heap T, and it is understood that they may also be bleaching, filtration or dewaxing earths, or even mixtures of such earths. Usually, manufacturers of edible oils or fats know the starting oil content of the soil to be treated with fairly good precision: this content is generally in the range of 10 to 40% (by weight) to plus or minus 2%. The earths T can be brought, by mechanical means of conventional type, shown diagrammatically by the arrow 10, into a treatment tank 20. Before admitting the earths in this treatment tank, a certain amount of material has however been introduced into said tank beforehand. quantity of hot water, from a tank 6 containing hot water 5, as shown diagrammatically by the arrow 11. The tank 6 will be equipped with heating means of known type (not shown here), such as a oil burner or electric resistors, making it possible to maintain the water 5 contained therein at a predetermined temperature, preferably in the vicinity of 950C for reasons which will be explained below.

 In accordance with an essential characteristic of the invention, the earths T are mixed with hot water 5 in the treatment tank 20, with a proportion of earths substantially less than 35%, in order to have a homogeneous mud 50 maintained at a temperature close to 900C.

 The homogeneity of the mud 50 is ensured by a stirring system equipping the treatment tank 20, this system being illustrated here in the form of a rotary agitator 22. Maintaining the temperature of the mud thus permanently stirred can be provided by a casing 23 disposed inside the treatment tank 20, preferably in the vicinity of the interior walls thereof, this casing being supplied with hot compressed air or hot water vapor by a boiler 26 which is connected to the casing by associated pipes 24 and 25.

Thus, depending on the tonnage of earth to be treated, there is a predetermined volume of preheated water in the treatment tank 20 so as to respect a proportion of earth essentially below 35% for the sludge which is stirred in the treatment tank. . If the proportion exceeds a value of 35%, the excess of soils does not make it possible to obtain sufficient washing thereof, and consequently satisfactory de-oiling. If this proportion falls below 25%, the treatment process becomes less profitable, since the tonnage of treated land is relatively low compared to the treatment costs. In practice, a satisfactory value for the proportion of land will be around 30
The temperature at which the homogeneous mud 50 must be maintained will be chosen as close as possible to 90 "C., being in particular maintained between 88 and 920 C. In fact, if the temperature of the mud is too much lower than 90, we will have an insufficient separation of the oil, and consequently a poor yield of the process. A temperature which is too high above 90 "would have even greater disadvantages, insofar as one would initiate an exothermic reaction with an overflow, This is both dangerous and highly polluting. It is for this reason that the temperature of the homogeneous mud will preferably be maintained between 88 and 920C, around the preferred value of 900C.

 One could naturally mix the earth and the water cold, and then proceed to heat the mud stirred in the treatment tank. It is however more rational to mix the earths with water previously heated, so that the drop in temperature caused by the injection of the earths in hot water quickly leads to a temperature close to the desired value of 900C. . This is why a value of 950C for the hot water with which the earths are mixed will give good results, when the proportion of earths is close to 30%.

 The foregoing means thus make it possible to have a homogeneous sludge maintained, throughout the treatment tank, at a value close to 90 "C.

 In accordance with another characteristic of the process, basic liquid is added to this homogeneous slurry to bring its pH to a value close to 9. A tank 8 containing a basic liquid 7 is thus distinguished, with a supply pipe 12 allowing inject a predetermined volume of this liquid into the treatment tank 20. For example, it is possible to use a sodium hydroxide solution, preferably titrated between 45 and 50%. Too strong a titration could indeed accentuate a phenomenon of agglomeration of the mud, and to produce a paste difficult to decompose.

 The pH value of the homogeneous slurry is an important parameter of the treatment process, and care must be taken to maintain this pH at the desired value. In fact, if the pH drops below 9, there is a risk of insufficient soil washing, and if the pH exceeds a value of 9.5, there is a risk of creating soaps, which implies using a acid, such as sulfuric acid, to treat these soaps (it goes without saying that such an addition of acid would prohibit food use of the recovered oil). Consequently, the pH of the homogeneous mud 50 will essentially be maintained between 9 and 9.5.

 In practice, there will be a sensor 27.1 for the temperature and a sensor 27.2 for the pH in the treatment tank, these sensors being connected to a control box 28 outside the treatment tank, and possibly itself connected to a unit. control center. It will naturally be possible to have a plurality of temperature and / or pH sensors distributed over the height of the treatment tank, in order to verify the homogeneity of these parameters in the volume of homogeneous mud which is constantly stirred.

 In some cases, it may turn out that the soil to be treated has a greater or lesser amount of wax, depending on the types of seeds used. In this case, it is planned to add a de-waxing agent to the homogeneous mud. There have thus been illustrated blocks or bags of such a dewaxing agent 9, for example consisting of powdered sodium carbonate, which can be brought as shown diagrammatically by the arrow 13 in the treatment tank 20. The sodium carbonate is particularly effective in activating detachment and providing the desired dewaxing action. Preferably, a small amount of sodium carbonate will be used, representing a percentage by weight of between 0.125 and 0.375% of the total mixture.

 It goes without saying that the injection of basic liquid, like the possible injection of a dewaxing agent, into the homogeneous mud stirred, can produce a slight lowering of the temperature of this mud, so that the heating means associated with the treatment tank must react accordingly in order to bring the temperature of this sludge to the desired value close to 900C.

 The various means which precede thus make it possible to avoid the formation of agglomerates, and then to ensure the good distribution of the necessary additional products, until complete recovery of the fat on the surface. As such, it should be noted that the use of hot water for the initial mixture of soil and water not only makes it possible not to delay the process, but also avoids interfering with the takeoff of the fat from the soil.

 Finally, after separation of the three oil-water-soil phases by difference in densities, the soil thus treated is recovered separately.

 With the installation shown in Figure 1, the three oil-water-soil phases are separated by natural decantation in the treatment tank 20, preferably for a period of between 4 and 6 hours, so as to recover the two phases liquids oil and water before recovering the soil treated at the bottom of the tank. Illustrated here, in dotted lines, the line 54 of separation between the upper layer of oil 51 and the lower layer of water 52, and the line of separation 55 between this layer of water 52 and the layer of earth 53 which rests on the bottom 21 of the treatment tank 20. Thus, when the operator has observed the rise in fat content on the surface, he allows the mixture to stand for a period of 4 to 6 hours for natural decantation. If the level reached is abnormally lower than what he can expect, this means that the treated earth still contains wax to be removed, and it can then trigger an additional injection of dewaxing agent: by adding a few doses of sodium carbonate, we arrive thus to accelerate the reaction, and to obtain a complete rise in fat content on the surface. The three oil-water-soil phases are, at the end of this settling time, clearly separated, so that it is easy to extract the two liquid phases to access the soil to be recovered which has deposited at the bottom of the treatment tank.

 In FIG. 1, the recovery of the two liquid oil and water phases is carried out by pumping into each of the layers of liquid: there is a pipe 30 fitted with a pump 31 (comprising an integrated filter), and the end of which dips in the homogeneous mud 50 just above the level 54 of separation between the two liquid phases, as well as a pipe 32 equipped with a pump 33 (also with integrated filter), the end of which plunges into the homogeneous mud 50 just above the level 55 of separation between water and land to be recovered. We then start by recovering the oil on the surface over the entire height of the corresponding layer 51, by actuating the associated pump 31, then the water over the entire height of the corresponding layer 52 by actuating the associated pump 33.

By having pumped first the oil which floats, then the intermediate water, we have access to the earth 53 which has settled to the bottom, and this earth can then be recovered by scraping, or any other equivalent means, using example an articulated lower hatch 34, the recovery of the earth being shown here schematically by an outlet pipe 35.

 The oil recovered at the surface is therefore of very good quality, and the soil recovered at the bottom of the treatment tank has an oil content which can drop to the level of 1%, which allows this land to be reused, for example in the agriculture, without having to provide for incineration.

 FIG. 1 also shows the presence of a recovery tank, illustrated in dashed lines, this tank referenced 29 supplementing the equipment of the treatment tank 20 as safety in the event of overflow.

 In practice, a treatment tank with a volume of around 20 m3 will treat a tonnage of around 5 to 7 tonnes of soil in a time of 4 to 6 hours.

 As illustrated in FIG. 2, the recovery of the two oil and water liquid phases can be carried out by natural flow at suitable heights. The treatment tank 20 is then equipped with two pipes 36 and 38, provided at the level of the separation lines 54 and 55, and each equipped with an associated valve 37 and 39. This type of recovery may however pose some problems, in the extent that the product flowing through the upper line 36 may contain a mixture of oil, water and earth, since the levels of separation in the treatment tank are not always known in advance with a very high precision. This drawback can be overcome by providing a plurality of pipes fitted with valves, regularly distributed (for example every 50 cm) over the entire height of the treatment tank 20.

 Alternatively, the two oil and water liquid phases can be recovered by first pumping the two layers of liquid (for example by actuating only the pump 33 with the installation of FIG. 1), or by natural flow at a adequate height (for example by opening the valve 39 with the modified tank of FIG. 2), then, in a second step, by separating the two phases from the liquid thus recovered, this separation being able to be carried out by centrifugation, according to a technique already known.

 The treatment tank 20 of FIG. 2 comprises, as before, heating means using a casing 23, and stirring means symbolized by a rotating agitator 22. It is however possible, as illustrated in FIG. 3, d '' ensure by a single means the permanent mixing and heating of the homogeneous mud 50: the tank 20 thus modified indeed has, in the vicinity of its bottom 21, a ramp 40 which is connected to an external compressor 42 by an associated pipe 41 , this ramp making it possible to expel hot compressed air, the corresponding jets carrying out the desired permanent mixing.

 Alternatively, it is possible to carry out the separation of the three oil-water-soil phases by centrifugation in a separator provided downstream of the treatment tank.

 FIG. 4 illustrates such a mode of separation and recovery. The homogeneous sludge then leaves the treatment tank 20 via a lower pipe 60, to reach, after having been filtered by an adequate filtration assembly 61, in a tank 62 equipped with a stirring system shown here by two rotary agitators 63. This tank 62 actually constitutes a buffer tank associated with the three-phase separator 70 arranged downstream of said tank. The filtered sludge 50 is in fact sucked through a pipe 64, by means of a pumping and filtration assembly 65, to reach the inlet of the separator 70. A deflection member 66, associated with a return pipe 67, prevents any jamming of the machine and preserves the homogeneity of the mixture, which ensures that the soil does not fill up with oil before being recovered. The separator 70 is of known design, being equipped with a drive motor 71 and a conical screw 72 which are shown here in dashed lines in FIG. 4. Such a three-phase separator is already known, and the only the corresponding outlet lines have been shown, with a line 73 for the recovery of oil, a line 74 for the recovery of water, and a line 75 for the recovery of land. Depending on the case, it may be a counter-current or single-current system.

 It is also advantageous for the water recovered at the end of the treatment of the earth to undergo, before being discharged, a subsequent treatment in a settling-settling tank in order to be able to recover the fat and the residual earth.

 FIG. 5 schematically illustrates an installation which allows such subsequent treatment of the recovered water.

 A tank 80 for decanting and settling is thus distinguished, into which the recovered water 90 has been brought in. This tank is equipped with a stirring system shown diagrammatically by a rotary agitator 82. In addition, a tank 85 containing a volume 84 of acid , for example sulfuric acid, allows an injection of acid via an associated pipe 86, into the recovered water 90, in order to adjust the pH thereof. The fat then rises to the surface and forms a layer 91, while the residual earth is deposited on the bottom 81 of the tank 80, to form a layer 92. The water thus neutralized can then be pumped through a line 87, by means of a treatment system 88, for example a methanization system, downstream of which the treated water leaves through a line 89 so as to be able to be discharged without risk of pollution in the wastewater network.

It is thus sufficient to recover the fatty substances on the surface by removing the layer 91 by any suitable pumping or scraping means, then to pump the neutralized water 90, in order to finally be able to recover by scraping (or by any equivalent means) the layer of earth 92 deposited on the bottom 81, for example by means of a lower manhole 83.

 We have thus managed to carry out a soil treatment process capable of lowering the oil content to a value of 1%, and sometimes even less, and of recovering an oil which is not sufficiently denatured to be reusable directly. The recovery of the separate oil-earth phases is also free from risks of pollution or other dangers. The treatment process finally makes it possible to obtain a reasonable tonnage under acceptable cost conditions while retaining great flexibility as to the nature of the soil to be treated, whether it is discoloration, filtration or dewaxing soil, or a mixture of these, these soils can in particular be reusable in agriculture because of their very low oil content.

 The invention is not limited to the embodiment which has just been described, but on the contrary encompasses any variant incorporating, with equivalent means, the essential characteristics set out above.

Claims (11)

 1. A method of treating soil used in the production of edible oils or fats, characterized in that  - the earth (T) is mixed with hot water (5) in a treatment tank (20), with a proportion of earth essentially below 35%, to obtain a homogeneous slurry (50) maintained at a close temperature 90 "C;  - basic liquid (7) is added to this homogeneous mud to bring its pH to a value close to 9;  - After separation of the three oil-earth phases by difference in densities, the earth (53) thus treated is recovered separately.  2. Method according to claim 1, characterized in that the homogeneous mud (50) comprises a proportion of earth close to 30%.  3. Method according to claim 1 or 2, characterized in that the temperature of the homogeneous mud (50) is maintained between 880C and 920C.  4. Method according to one of claims 1 to 3, characterized in that the pH of the homogeneous mud (50) is essentially maintained between 9 and 9.5.  5. Method according to claim 4, characterized in that the basic liquid (7) used so that the pH of the homogeneous mud (50) is at the desired value is a sodium hydroxide solution, preferably titrated between 45% and 50 %.  6. Method according to one of claims 1 to 5, characterized in that a dewaxing agent (9), for example sodium carbonate, is added to the homogeneous mud (50).  7. Method according to one of claims 1 to 6, characterized in that the separation of the three oil-water-soil phases is carried out by natural decantation in the treatment tank (20), preferably for a period of between 4 and 6 hours, so as to recover the two liquid oil and water phases before recovering the treated earth (53) at the bottom of the tank.  8. Method according to claim 7, characterized in that the recovery of the two oil and water liquid phases is carried out by pumping in each of the liquid layers, or by natural flow at suitable heights.  9. Method according to claim 7, characterized in that the recovery of the two liquid oil and water phases is carried out by pumping the two layers of liquid or by natural flow at an adequate height, then by separation of the two phases from the liquid thus recovered.  10. Method according to one of claims 1 to 6, characterized in that the separation of the three oil-water-earth phases is carried out by centrifugation in a separator (70) provided downstream of the treatment tank (20).  11. Method according to one of claims 1 to 10, characterized in that the water recovered at the end of the treatment of the earth undergoes a subsequent treatment in a settling tank - settling (80), in order to be able to recover the materials oily (91) and residual soils (92).