FR2779665A1 - METHOD FOR REGENERATING AN EXHAUSTED INFUSORY EARTH AND DEVICE FOR CARRYING OUT THIS METHOD - Google Patents

Abstract

The invention mainly concerns a method for regenerating used infusorial earth, said infusorial earth being used as filtering auxiliary and being retained in a filter chamber (1), said method comprising a step which consists in introducing an alkaline solution inside the filter chamber, while contacting said solution with the infusorial earth to be regenerated. The invention is characterised in that said method is followed by a step which consists in recuperating, outside the filter chamber, regenerated infusorial earth for reuse when subsequently filtering beer, as filtering auxiliary, said regenerated infusorial earth being introduced in the filter chamber in the form of a mixture with the beer to be filtered. The invention also concerns a beer filtering method using infusorial earth as filtering auxiliary and a beer filtering device.

Description

METHOD FOR REGENERATING AN EXHAUSTED INFUSORY LAND

  AND DEVICE FOR CARRYING OUT THIS METHOD

  The present invention relates to a method for regenerating spent diatomaceous earth, used as a filtration aid, as well as to an installation for regenerating spent diatomaceous earth. The diatomaceous earth, also known as kieselguhr, is a variety of powdery silica formed from microscopic shells of very small animals, fossil diatomaceous earths, known as diatoms. The shells that form the kieselguhr have very varied shapes (circular, elliptical, rectangular, lozenge-shaped), since there are 5,000 different species of diatom15. With a chalky appearance and a whitish color, the diatomaceous earth has a low density. Very

  porous, it is capable of absorbing large quantities of liquid. It is widely used in industry as an absorbent, catalyst support, abrasive, filler, but above all as a filter aid.

  In the brewing industry, beer must most often be obtained in the form of a limpid and clear product, of appearance acceptable to the consumer. It is therefore necessary to eliminate the colloids and yeasts which are responsible for the cloudiness of the beer, by a filtration stage at the end of fermentation. Currently, this filtration is carried out in closed enclosures comprising filtering interfaces (filtration media), the diatomaceous earth being used as a filtration aid. Its role is to increase the total filtration area. It also allows, by its porosity on the order of 35 micrometers, to use less tight mesh filtration grids (typically, the mesh size is of the order of 70 pm 30 pm) which result in less

pressure drop.

  As filtration progresses, the diatomaceous earth retains colloids, yeasts and other wastes, mainly of an organic nature. It becomes more and more loaded with organic residues, which leads to a pressure drop and therefore requires an increase in the pressure at the inlet of the filter. It then becomes necessary to remove the exhausted diatomaceous earth from the filtration media, either to replace it with virgin diatomaceous earth, or to regenerate it for reuse. The disposal of spent diatomaceous earth has significant industrial costs. Indeed, it is not acceptable, and therefore unauthorized, for understandable environmental reasons, to reject it as it is in the sewer. It is therefore advisable, for example, to treat spent diatomaceous earth in a treatment plant in which it will be dehydrated and treated in a way

  to develop it, for example by making it usable as a crop support, by agricultural spreading.

  Another solution consists in incinerating the spent diatomaceous earth, as described in European patent EP 0 418 847. However, the energy consumption involved in the combustion of organic waste at a temperature of the order of 600 C is considerable. . In practice, none of these solutions is satisfactory. The costs involved, in particular the costs linked to the reprocessing of the exhausted diatomaceous earth, are very significant. As for calcination, it does not make it possible to obtain a regenerated diatomaceous earth of quality equivalent to a virgin diatomaceous earth35. It is therefore necessary to replace the exhausted diatomaceous earth with virgin diatomaceous earth, a source of additional expense. It has therefore been proposed to treat the spent diatomaceous earth by discharging it into a tank which can be heated and which is provided with a stirring device, then to treat it using a 2 to 8% sodium hydroxide solution. at a reaction temperature of 60 to 90 ° C., for 30 to 120 minutes (European patent EP 0 253 233) and then to pass it over a filter mat

for neutralization and rinsing.

  The implementation of this process requires significant investments in additional facilities, in the brewery itself. The aim of the present invention is therefore to design a process for the regeneration of exhausted diatomaceous earth which better meets the needs of the practice than the previously known processes, in particular in that the process according to the invention: is more economical than the processes of the prior art, - does not imply a longer immobilization of the filter than in the processes existing previously, results in less polluting releases than the known processes, - constitutes an effective reprocessing of the earth diatomaceous spent, diatomaceous earth as well

  regenerated being able to be reused as a filtration aid in at least one new filtration cycle.

  These aims are achieved by the use of the filter enclosure as a reactor for cleaning the spent diatomaceous earth, by elimination of the organic waste accumulated in the diatomaceous earth35 during filtration, this cleaning being carried out by means of an alkaline solution introduced into the filter enclosure and brought into contact with the diatomaceous earth to be regenerated. The subject of the invention is a method of regenerating a spent diatomaceous earth, said diatomaceous earth being used as a filtration aid and being retained in the enclosure of a filter,

  characterized in that said method comprises a step of introducing an alkaline solution inside the enclosure of the filter, with bringing said solution into contact with the diatomaceous earth to be regenerated.

  Any filter whose enclosure is capable of chemically withstanding contact with an alkaline solution can be used to carry out the method according to the present invention. Mention may be made, by way of nonlimiting examples, of metal filters

with candles or trays.

  According to a preferred arrangement of the invention, said filter is a candle filter.

  According to a preferred embodiment of the invention, the regeneration is carried out by elimination of the organic waste accumulated in the diatomaceous earth during filtration. In the brewing industry, the organic waste accumulated in the diatomaceous earth during filtration is for example proteins, yeasts, tannins, polyphenols and various colloids present in beer following its fermentation. According to an advantageous embodiment of the invention, the method for regenerating the spent diatomaceous earth comprises the following steps: (a) rinsing the filter retaining the spent diatomaceous earth with water at a temperature between 35 and 95 C, preferably about 70 C, (b) introduction into the filter enclosure of an alkaline solution, with bringing said solution into contact with the diatomaceous earth to be regenerated, (c) rinsing the filter with water at a temperature between 35 and 95 C, preferably about 70 C. Rinsing the filter with water at the temperature indicated in step (a) makes it possible in particular to remove part of the organic matter accumulated in the diatomaceous earth and make it less compact, therefore more permeable. As for step (c), it makes it possible to eliminate the alkaline solution introduced into the enclosure of the filter during step (b) and the silicates formed by the attack in an alkaline medium of the silica constituting the earth d 'Infusoria. Advantageously, the method according to the present invention comprises, between steps (b) and (c), a step (d) of recirculation, in a closed circuit, of a volume of alkaline solution equal to the internal volume of the filter minus the volume occupied by the diatomaceous earth. As a variant, said method comprises, between steps (d) and (c), a step (e) of introducing into the filter a new volume of alkaline solution equal to the internal volume of the filter minus the volume occupied by the earth diatom. "New volume of alkaline solution" means a volume of "virgin" alkaline solution, which

  has not been subjected to recirculation in a closed circuit as described above.

  According to a preferred arrangement of the invention, said alkaline solution is introduced at a temperature of 35 to 95 ° C., preferably around 70 ° C. This temperature makes it possible to favor the reactions of protein hydrolysis and to make more efficient the degradation of organic matter present in the diatomaceous earth. In addition, it can possibly ensure, in a single step, the regeneration of the diatomaceous earth and its sterilization. According to another preferred arrangement of the invention, said alkaline solution is a sodium hydroxide solution of 0.1 to 15%, preferably about 1% (V / V). According to an advantageous embodiment of the invention, the method comprises, after step (c), a

  step (f) of rinsing the filter with an acid solution.

  This acid solution makes it possible on the one hand to neutralize the diatomaceous earth in the enclosure of the filter by reacting with the residual alkaline solution, and on the other hand to hydrolyze the polysaccharides which would possibly be still present in the diatomaceous earth . Preferably, said acid solution is

  deaerated water containing dissolved carbon dioxide.

  For the purposes of the present invention, the term "deaerated" means water which does not contain oxygen

  dissolved in gaseous form. Such water can be obtained, for example, by passing carbon dioxide against the flow of water. Typically, this operation is carried out in a deaeration column.

  It makes it possible to obtain water in which the gaseous dioxygen has been removed and which contains dissolved carbon dioxide. 25 According to another advantageous embodiment of the invention, the method also comprises a step of opening the filter enclosure to recover the regenerated diatomaceous earth. In a particularly advantageous manner, the method as described above effectively allows, by an in situ treatment of the spent diatomaceous earth, to regenerate the latter at a lower cost and without immobilizing the filter for longer than in the previously known methods. (masked time). Indeed, the method according to the present invention makes it possible to ensure, in a single step, the regeneration of the diatomaceous earth and the sterilization of the filter. In addition, the costs associated with transporting the depleted diatomaceous earth or the ancillary facilities required to process it are avoided. Such a process also makes it possible to avoid the rejection of the soil of diatomaceous earth exhausted in a purification station or in a calcination installation and proves to be less polluting for the environment. The efficiency of the process according to the invention also makes it possible to reuse the diatomaceous earth

  regenerated at least once as a filtration aid, in a new filtration cycle.

  The present invention therefore also relates to a process for filtering beer using a diatomaceous earth as a filter aid, characterized in that said diatomaceous earth is a diatomaceous earth regenerated by the method described above. In addition, the subject of the present invention is a beer filtration device comprising an enclosure in which are arranged means capable of retaining diatomaceous earth used as a filter aid and filtration residues, characterized in that it comprises means for supplying an alkaline solution to the enclosure in order to react with said filtration residues and means for discharging said alkaline solution charged with at least part of said filtration residues. According to an advantageous arrangement of the present invention, said beer filtration device further comprises means for circulating in a closed circuit the alkaline solution, in particular sodium hydroxide, through said enclosure. In addition to the foregoing provisions, the invention also comprises other provisions which

  will emerge from the description which follows, which

  refers to examples of implementation of the present invention, as well as to the accompanying drawing, which represents an installation in accordance with the present invention. It should be understood, however, that these examples are given solely by way of illustration of the subject of the invention, of which they do not in any way constitute a limitation. Figure 1 is a schematic view of a beer filtration installation according to the invention.10 In Figure 1, one can see an installation according to the present invention of beer filtration comprising means for in situ regeneration of the adjuvants filtration, especially of diatomaceous earth. The installation comprises a filter 1, for example a tray filter or, advantageously, a candle filter having for example a volume of 4 m3 and making it possible to filter approximately 11.10-3 m3 / s of beer for a maximum pressure difference of 5.105 Pa. An inlet 3 of the filter 1 is connected by a valve 5 to a pipe 20 7 for supplying the beer to be filtered equipped with a device 9 for distributing diatomaceous earth. An outlet 11 of the filter 1 is connected by a valve 13 and a pipe to an inlet 17 of a buffer tank 19, making it possible to avoid pressure surges. A valve 21 mounted at an outlet 23 of the tank 19 makes it possible either to send the filtered beer, by a valve 22, to a tank (not shown in FIG. 1), from which the beer will be drawn off for its packaging, either to recirculate the beer on the filter, via a valve 24, the outlet of which is connected to the inlet of the valve 5. This recirculation takes place, for example, in the event of an incident on the filtration line, such as '' a deficiency detected in the quality of filtered beer. The installation according to the present invention further comprises means for regenerating spent diatomaceous earth, that is to say too loaded with filtration residues and consequently inducing excessive pressure drops. The preferred embodiment of installations illustrated in FIG. 1 comprises a tank 25 of deaerated water connected by a valve 27 to the outlet 11 of the filter 1 and by a valve 26 to the inlet 3 of the filter 1, a tank 29 of alkaline reagent, advantageously sodium hydroxide, connected by a valve 31 to the inlet 3 of the filter 1, a tank 33 for recovering alkaline reagent connected by a valve 35 to the inlet 3 of the filter 1 and by a valve 37 at the outlet 11 of the filter 1 and a hot water tank 39 connected by a valve 41 to the inlet 3 of the filter 1. A pipe 43 and a valve 45 allow the contents of the filter 1 to be evacuated to the sewer, to a storage bath, or to a treatment plant.15 The installation may also include hot water or deaerated water recovery tanks (not shown) allowing these fluids to circulate in a closed circuit filter 1. The installation also includes equipment not shown s such as heating means, thermal insulation means, pumping means for ensuring the circulation of the desired fluids and remote control means from a control room of the valve brewery 5, 13, 21, 22, 24, 26, 27, 31, 35, 25 37, 41, 45, pumping means and heating means for ensuring the desired circulation of the various fluids at set temperatures. Advantageously, the device further comprises safety means or a programmable automaton for controlling the installation preventing an accidental command to open a valve causing an undesired circulation of fluid. When filtering the beer, the valves 13, 21 and 22 are open while the other valves

are closed.

  At the end of the filtration cycle, all or part of the beer present in filter 1 is recovered.

  pushing it with deaerated water. During the pushing step, the valves 13, 21, 22 and 26 are open while the other valves are closed.

  During the rinsing with hot water, the valves 41 and 45 are open, the other valves being closed.

  When circulating soda in open circuit, the valve 31 and / or the valve 35 as well as the valve

  45 are open, the other valves being closed.

  During circulation in the filter 1, in a closed circuit of the sodium hydroxide, the valves 31 and / or 35 and the valve 37 are open, the other valves being closed. When introducing the deaerated water, via the outlet 11 of the filter 1, the valve 27 is open and the mixture of deaerated water (or other fluid present at this time in the filter 1) / regenerated diatomaceous earth is recovered via the pipe 43 and the valve 45. The deaerated water coming from the tank 2520 fills the internal volume of the filter 1 at the end of the regeneration process so as to avoid the presence of the molecules of 02 in the enclosure filter during the next filtration cycle, which could compromise the quality of the beer. The diatomaceous earth recovered25 is stored for later use and / or directly loaded into the device 9 for its distribution. According to the invention, at the end of filtration, the beer is pushed from the filter by cold deaerated water (around 4 ° C., for example). She will then be guided to a PVPP treatment station

  (polyvinylpyrrolidone), treatment that will retain the tannins present in beer.

  The filter, which still contains the diatomaceous earth used, is rinsed with hot water (step (a)) between 35 and 95 C, preferably around 70 C. For example, for a filter having a volume of 4 m3,

  the flow rate for sending hot water is approximately 17.10-3 m3 / s and the volume of water used is 12 m3.

  An alkaline solution is then introduced into the filter enclosure (step (b)). Typically, it is a soda solution of 0.1 to 15% (V / V), preferably about 1%, but it can be any other alkaline solution, for example a solution of potassium hydroxide or alkaline commercial solutions based on sodium hydroxide, such as the solutions PE 1700 or PE 1900 marketed by HENKEL, GALOR 8/74 or GALOR C7 marketed by CFPI. The temperature of the alkaline solution is between 35 and 95 C, preferably about 70 C. The flow rate can be regulated at 24.10-3 m3 / s, for example. The introduction of the soda solution ends

  if (for example and without limitation) the volume introduced is greater than or equal to 15 m3, or if the brightness of the solution measured at the filter outlet is less than 0.06 ebc (units of the European Brewery Convention).

  A step of recirculating the soda on the filter (step (d)) can then be implemented, by

  example for 30 minutes, the recirculation rate25 can be regulated at around 22.10-3 m3 / s.

  If the brightness of the solution at the outlet of the filter (indicator of the progress of the regeneration of the diatomaceous earth) proves to be greater than a predetermined threshold, advantageously between 0.04 and 30 0.1 ebc, for example 0 , 06 ebc, at the end of 30 minutes, a new volume of fresh soda (about 4 m3 per

  example) is introduced into the filter. Otherwise, the recirculation step ends. The sodium hydroxide solution used for recirculation can be recovered for later use during step (b) of another regeneration cycle.

  Optionally, a small volume (<4 m3) of fresh soda is introduced into the filter to

  optimize the efficiency of regeneration (step (e)).

  After these various treatments in an alkaline medium, the filter is rinsed with hot water (step (c)) at a temperature between 35 and 95 C, preferably about 70 C. The volume of water is for example

  of 8 m3 with a flow rate of 24.10-3 m3 / s.

  Next, the filter is rinsed with an acid solution (step (f)), typically deaerated water saturated with carbon dioxide of pH = 4.5 and at a temperature of around 4 C. shipment is for example 24.10-3 m3 / s. The final rinse with deaerated water saturated with carbon dioxide ends if the following two cumulative conditions are met: the volume of water sent to the filter is greater than or equal to a given volume (8 m3 for example) and the pH of the solution at the filter outlet is less than 6.20 The regeneration of the diatomaceous earth is then complete. The latter is recovered by sending deaerated water upside down on the filter (unclogging the candles) for about 90 seconds for example. The regenerated diatomaceous earth is characterized by a rate of organic matter less than or equal to% by weight. It can be reused as a filter aid, after cleaning the filter plugs in the same way as a classic settling. However, the recovery rate of the diatomaceous earth30 being around 75% by weight relative to the diatomaceous earth used, it should be reconcentrated by adding a small amount of new diatomaceous earth . All the solutions described above for rinsing the filter and regenerating the diatomaceous earth are put in the sewer to be conveyed to a purification station, except the sodium hydroxide solution used during step (d), which is retrieved for later use. In the case of the sodium hydroxide solutions used during steps (b) and (e), these5 are previously stored in a parking basin where various plant wastes are collected (from processes other than that described above ), thus allowing a renormalization of the pH before putting these solutions in the sewer.10 As appears from the above, the invention is in no way limited to those of its modes of implementation, embodiment and application which have just been described more explicitly; on the contrary, it embraces all the variants which may come to the mind of the technician in the matter, without departing from the scope or the scope of the present invention.

Claims (14)

  1. A method of regenerating spent diatomaceous earth, said diatomaceous earth being used as a filtration aid and being retained in the enclosure of a filter, characterized in that said method comprises a step of introducing of a solution   alkaline inside the filter enclosure, with contacting said solution with the diatomaceous earth to be regenerated.   2. Method according to claim 1, characterized in that said filter is a candle filter. 3. Method according to claim 1 or 2, characterized in that the regeneration is carried out by   elimination of organic waste accumulated in the diatomaceous earth during filtration.   4. Method according to any one of the preceding claims, characterized in that it   includes the following steps: (a) rinsing the filter retaining the spent diatomaceous earth with water at a temperature between 35 and 95 C, preferably about 70 C, (b) introduction into the filter enclosure of an alkaline solution, with bringing said solution into contact with the diatomaceous earth to be regenerated, (c) rinsing the filter with water at a temperature between 35 and 95 C, preferably about 70 C. 5. Method according to claim 4, characterized in that it comprises, between steps (b) and (c), a step (d) of recirculation, in closed circuit, of a volume of alkaline solution equal to the internal volume of the filter minus the volume occupied by the diatomaceous earth. 6. Method according to claim 5, characterized in that it comprises, between steps (d) and (c), a step (e) of introducing into the filter a   new volume of alkaline solution.   7. Method according to any one of the preceding claims, characterized in that said   alkaline solution is introduced at a temperature of 35   at 95 C, preferably around 70 C.   8. Method according to any one of the preceding claims, characterized in that said   alkaline solution is a soda solution of 0.1 to 10 15%, preferably about 1% (V / V).   9. Method according to any one of claims 4 to 6, characterized in that it comprises,   after step (c), a step (f) of rinsing the filter with an acid solution. 10. Method according to claim 9, characterized in that said acid solution is water   deaerated carbonated. 11. Method according to any one of the preceding claims, characterized in that it   further includes a step of opening the filter enclosure to recover the regenerated diatomaceous earth.   12. Beer filtration process using diatomaceous earth as a filtration aid,   characterized in that said diatomaceous earth is diatomaceous earth regenerated by the method according to any one of the preceding claims.   13. Beer filtration device comprising an enclosure in which are arranged means capable of retaining diatomaceous earth30 used as filter aid and filtration residues, characterized in that it comprises   means (3, 29, 31, 33, 35) for supplying an alkaline solution to the enclosure to react with said filtration residues and means (11, 43, 45) for discharging said charged alkaline solution at least part of said filtration residue.   14. Beer filtration device according to claim 13, characterized in that it further comprises means (37) for circulating in a closed circuit the alkaline solution, in particular sodium hydroxide, through said enclosure.