AU4149299A - Method for regenerating used infusorial earth and uses for filtering beer - Google Patents

Description

WO 99/65603 PCT/FR99/01413 PROCESS FOR REGENERATING SPENT INFUSORIAL EARTH, AND USES FOR FILTERING BEER The present invention relates to a process for 5 regenerating spent infusorial earth, which is used as a filtering aid, as well as to an installation for regenerating spent infusorial earth. Infusorial earth, also known as kieselguhr, is a variety of pulverulent silica formed from microscopic 10 carapaces of very small animals, fossil Infusoria, which are known as diatoms. The shells which form kieselguhr have very varied shapes (circular, elliptical, rectangular, lozenge-shaped), since there are 5000 different species of diatom. Infusorial earth, 15 which is chalky and whitish in appearance, is of low density. It is very porous and is capable of absorbing large amounts of liquid. It is used widely in industry as an absorbent, a support for catalysts, an abrasive agent and a filling material, but especially as a 20 filtering aid. In the beermaking industry, beer must usually be obtained in the form of a clear uncloudy product whose appearance is acceptable to consumers. It is thus necessary to remove the colloids and yeasts responsible 25 for the cloudiness of beer, by means of a filtration step at the end of fermentation. Currently, this filtration is carried out in closed chambers comprising filtering interfaces (filtration supports), infusorial earth being used as a 30 filtration adjuvant. Its role is to increase the total surface area for filtration. On account of its porosity of the order of a micron, it also allows the use of filtration grates with a less tight mesh (typically, the size of the grating is about 70 tm + 30 tm), 35 resulting in less loss of pressure. Gradually as the filtration proceeds, the infusorial earth retains colloids, yeasts and other waste, mainly of organic nature. It becomes RA& increasingly loaded with organic residues, resulting in

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-2 a loss of pressure and thus requiring an increase in pressure at the filter inlet. It then becomes necessary to remove the spent infusorial earth from the filtration supports, either to replace it with fresh 5 infusorial earth or to regenerate it so that it can be re-used. Significant industrial costs are entailed in removing the spent infusorial earth. Specifically, it is unacceptable, and consequently not permitted on 10 clearly appreciable environmental grounds, to discard it down the drain without processing it. Spent infusorial earth should thus be processed, for example, in a purification plant in which it will be dehydrated and processed so as to 15 upgrade it, thus making it suitable for use, for example, as a support for crops, by agricultural spreading. Another solution consists in incinerating spent infusorial earth, as described in European patent 20 EP 0 418 847. However, considerable energy consumption is involved in combusting organic waste at a temperature of about 600 0 C. None of these solutions is suitable in practice. This is because very substantial expenses are 25 involved, in particular the costs associated with reprocessing the spent infusorial earth. As regards calcination, this does not produce a regenerated infusorial earth whose quality is equivalent to that of fresh infusorial earth. It is thus necessary to replace 30 the spent infusorial earth with fresh infusorial earth, thereby incurring additional expenses. It has thus been proposed to process spent infusorial earth by unloading it into a tank which can be heated and which is fitted with a stirring device, 35 followed by treating it with a 2 to 8% caustic soda solution at a reaction temperature of from 60 to 90 0 C, for 30 to 120 minutes (European patent EP 0 253 233) and then passing it through a filtration mat for neutralization and rinsing. Ao'- -3 The use of this process requires considerable investment in terms of associated installations, in the brewery itself. It has also been proposed to make layers of 5 infusorial earth in a filter press, and then to introduce the beer to be filtered therein. When this infusorial earth is spent, it is regenerated in situ by introducing a caustic soda solution into the filter (GB patent application 2 190 603) ; after suitable rinsing 10 of the filter, filtration of the beer is resumed. When this in situ process no longer enables correct regeneration of the spent infusorial earth, this earth is extracted from the filter and transferred into a regeneration vessel. 15 Patent application EP 0 255 696 proposes a similar process, i.e. a regeneration process which is carried out in the filter itself, but which is adapted to the regeneration of another type of filtering aid, namely an aluminium oxide powder. 20 The aim of the present invention is thus to propose a process for regenerating a spent infusorial earth, which is more able to satisfy the practical requirements than the processes known previously, in particular in that the process according to the 25 invention: - is more economical than the processes of the prior art, - does not involve immobilization of the filter for any longer than in the previously-existing 30 processes, - entails less polluting waste than in the known processes, - constitutes effective reprocessing of spent infusorial earth, the infusorial earth thus regenerated 35 being able to be re-used as a filtering aid in at least one new cycle of filtration, by being introduced into the filter at the same time as the beer to be filtered. The subject of the invention is a process for regenerating a spent infusorial earth, the said -4 infusorial earth being used as a filtering aid and being held in a filter chamber, the said process comprising a step of introducing an alkaline solution into the filter chamber, with placing of the said 5 solution in contact with the infusorial earth to be regenerated, characterized in that the said process is followed by a step of recovery, outside the filter chamber, of the regenerated infusorial earth so that it can be re-used, in a subsequent filtration of beer, as 10 a filtering aid, the said regenerated infusorial earth being introduced into the filter chamber in the form of a mixture with the beer to be filtered. The regeneration described above is carried out by removing the organic waste accumulated in the 15 infusorial earth during the filtration. In the context of the beermaking industry, the organic waste accumulated in the infusorial earth during the filtration is, for example, proteins, yeasts, tannins, polyphenols and various colloids present in beer after 20 it has been fermented. According to one advantageous arrangement of the process according to the invention, the recovery, outside the filter chamber, of the regenerated infusorial earth comprises a step of opening the filter 25 chamber. Any filter whose chamber is capable of chemically withstanding contact with an alkaline solution can be used to carry out the process according to the present invention. Mention may be made, as non 30 limiting examples, of metal multiple-tube filters or metal chamber filters. According to one preferred arrangement of the invention, the said filter is a multiple-tube filter. According to one advantageous embodiment of the 35 invention, the process for regenerating the spent infusorial earth comprises the following steps: (a) rinsing the filter retaining the spent infusorial earth with water at a temperature of between * 35 and 95 0 C, preferably about 75 0 C, ofJ -5 (b) introducing an alkaline solution into the filter chamber, and placing the said solution in contact with the infusorial earth to be regenerated, (c) rinsing the filter with water at a 5 temperature of between 35 and 95 0 C, preferably about 70-C, (d) rinsing the filter with an acidic solution, these steps being followed by a step of recovering the regenerated infusorial earth so that it 10 can be re-used as a filtering aid, the said regenerated infusorial earth being introduced into the filter chamber in the form of a mixture with the beer to be filtered. The rinsing of the filter with water at the 15 temperature indicated in step (a) makes it possible in particular to remove some of the organic material accumulated in the infusorial earth and to make this earth less compact, and thus more permeable. As regards step (c), this makes it possible to remove the alkaline 20 solution introduced into the filter chamber during step (b) and the silicates formed by the attack in alkaline medium of the silica constituting the infusorial earth. Step (d) of rinsing the filter with an acidic solution makes it possible firstly to neutralize the 25 infusorial earth in the filter chamber by reacting with the residual alkaline solution, and secondly to hydrolyse any polysaccharides which may still be present in the infusorial earth. Preferably, the said acidic solution is 30 carbonated de-aerated water. For the purposes of the present invention, the term "de-aerated" means a water which contains no dissolved oxygen in gaseous form. Such a water can be obtained, for example, by passing carbon dioxide 35 through counter-currentwise to the flow of water. Typically, this operation is carried out in a de aeration column. It produces a water from which dioxygen gas has been removed and which contains

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dissolved carbon dioxide, this water being known as carbonated de-aerated water. Advantageously, the process according to the present invention comprises, between steps (b) and (c), 5 a step (e) of recycling, in a closed circuit, a volume of alkaline solution equal to the internal volume of the filter minus the volume occupied by the infusorial earth. As a variant, the said process comprises, 10 between steps (e) and (c) , a step (f) of introducing into the filter a fresh volume of alkaline solution equal to the internal volume of the filter minus the volume occupied by the infusorial earth. The expression "fresh volume of alkaline 15 solution" means a volume of "fresh" alkaline solution which has not been subjected to the recirculation in a closed circuit as described above. The said alkaline solution is, for example, introduced at a temperature of from 35 to 95 0 C, 20 preferably about 75 0 C. Such a temperature promotes the protein hydrolysis reactions and makes the degradation of the organic matter present in the infusorial earth more efficient. In addition, it may allow the one-step regeneration and sterilization of the infusorial earth. 25 The said alkaline solution is, for example, a 0.1 to 15%, preferably about 1% (V/V), sodium hydroxide solution. In a particularly advantageous manner, the process as described above effectively makes it 30 possible, by means of in situ processing of the spent infusorial earth, to regenerate this earth at reduced cost and without immobilizing the filter for longer than in the previously known processes (masked time). Specifically, the process according to the present 35 invention allows the one-step regeneration of the infusorial earth and sterilization of the filter. Furthermore, the expenses involved in transporting the spent infusorial earth or in the associated plants required for the processing are avoided. Such a process -7 also makes it possible to avoid discharging the spent infusorial earth in a purification plant or in a calcination plant and turns out to be less polluting to the environment. 5 The efficacy of the process in accordance with the invention also makes it possible to re-use the regenerated infusorial earth at least once as a filter aid, in a new filtration cycle, the regenerated infusorial earth being introduced into the filter 10 chamber in the form of a mixture with the beer to be filtered. A subject of the present invention is thus also a process for filtering beer using an infusorial earth as a filtering aid, characterized in that it comprises 15 the following steps: - filtration of the beer, an infusorial earth/beer to be filtered mixture being introduced into the filter chamber, - regeneration of the spent infusorial earth 20 in situ in the said filter chamber, - recovery of the regenerated infusorial earth, - reintroduction of a regenerated infusorial earth/beer to be filtered mixture into the filter chamber. 25 In addition, a subject of the present invention is a device for filtering beer, comprising a chamber in which are located means capable of retaining infusorial earths used as a filtration adjuvant and filtration residues, means for conveying into the chamber an 30 alkaline solution to react with the said filtration residues, and means for removing the said alkaline solution charged with at least some of the said filtration residues, characterized in that the said device also comprises means for introducing an 35 infusorial earth/beer to be filtered mixture, the said infusorial earth being an infusorial earth which has been regenerated by the process described above. According to one advantageous arrangement of the device according to the invention, the said means -8 capable of retaining infusorial earths used as filtration adjuvant and filtration residues consist of a multiple-tube filter. According to another advantageous arrangement 5 of the device according to the invention, this device also comprises means for circulating, in a closed circuit, the alkaline solution through the said chamber. In addition to the preceding arrangements, the 10 invention also comprises other arrangements which will emerge from the description which follows, which refers to implementation examples of the present invention, as well as to the attached drawing, which represents an installation in accordance with the present invention. 15 It should be clearly understood, however, that these examples are given purely for the purposes of illustrating the subject of the invention, of which they in no way constitute a limitation. Figure 1 is a diagrammatic view of an 20 installation for filtering beer, in accordance with the invention. Figure 1 shows an installation according to the present invention for filtering beer, comprising means for the in situ regeneration of the filtration 25 adjuvants, in particular infusorial earth. The installation comprises a filter 1, for example a chamber filter or, advantageously, a multiple-tube filter with, for example, a volume of 4 m3 and a surface area for filtration of 80 m 2 (388 filtering 30 tubes), allowing from 5.5 x 10-3 to 11 x 10-3 m 3 /s of beer to be filtered, for a maximum pressure difference of 5 x 105 Pa. An inlet 3 of the filter 1 is connected, via a valve 5, to a pipe 7 for conveying the beer to be filtered, this pipe being fitted with a device 9 for 35 distributing infusorial earth, an infusorial earth/beer to be filtered mixture thus being introduced into the inlet 3 of the filter 1. In the filter described above, the maximum amount of infusorial earth injected is * 320 kg. An outlet 11 of the filter 1 is connected, via

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-9 a valve 13 and a pipe 15, to an inlet 17 of a buffer tank 19, allowing any pressure surges to be avoided. A valve 21 mounted on an outlet 23 of the tank 19 makes it possible either to send the filtered beer, via a 5 valve 22, to a reservoir (not represented in Figure 1), from which the beer will be withdrawn for packaging, or to recycle the beer into the filter, via a valve 24 whose outlet is connected to the inlet of the valve 5. This recirculation intervenes, for example, in the 10 event of an incident arising on the filtration line, such as a deficiency detected in the quality of the filtered beer. The installation according to the present invention also comprises means for regenerating spent 15 infusorial earth, i.e. earth which is excessively charged with filtration residues and which consequently induces excesses loss of pressure. The preferred installation embodiment illustrated in Figure 1 comprises a tank 25 of carbonated de-aerated water 20 connected, via a valve 27, to the outlet 11 of the filter 1 and, via a valve 26, to the inlet 3 of the filter 1, a tank 29 of alkaline reagent, advantageously sodium hydroxide, connected, via valve 31, to the inlet 3 of the filter 1, a tank 33 for recovering alkaline 25 reagents, connected, via a valve 35, to the inlet 3 of the filter 1 and, via a valve 37, to the outlet 11 of the filter 1, and a tank 39 of hot water connected, via 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 30 discharged to the drain, to a storage vat or to a purification plant. A pipe 47 and a valve 49 allow the contents of the filter, for example the regenerated filtering aid, to be discharged into a preparation tank 55, as will be described in greater detail below. The 35 installation can also comprise tanks for recovering hot water or de-aerated water (not shown), thus allowing these fluids to be circulated in a closed circuit through the filter 1. The installation also comprises equipment not shown, such as heating means, thermal -10 insulation means, pumping means for circulating the desired fluids, and means for remote control, from a control room, of the beermaking with the valves 5, 13, 21, 22, 24, 26, 27, 31, 35, 37, 41, 45 and 49, pumping 5 means and heating means for ensuring the desired circulation of the various fluids at set temperatures. Advantageously, the device also comprises safety means or a programmable robot for controlling the installation, preventing an accidental command to 10 open a valve leading to an unwanted circulation of fluid. During the filtration of the beer, the valves 5, 13, 21 and 22 are open while the other valves are closed. 15 At the end of the filtration cycle, all or some of the beer present in the filter 1 is recovered by exerting pressure on it with de-aerated water. During the pressure-exertion step, the valves 13, 21, 22 and 26 are open while the other valves are closed. 20 During the rinsing with hot water, the valves 41 and 45 are open, while the other valves are closed. During the circulation of sodium hydroxide in an open circuit, the valve 31 and/or the valve 35 are open, as is the valve 45, while the other valves are 25 closed. During the circulation of sodium hydroxide in a closed circuit in the filter 1, the valves 31 and/or 35 and the valve 37 are open, while the other valves are closed. 30 During the introduction of de-aerated water, via the outlet 11 of the filter 1, the valve 27 is open and the mixture of de-aerated water (or other fluid present at that moment in the filter 1)/regenerated infusorial earth is recovered via the pipe 47 and the 35 valve 49. The carbonated de-aerated water from the tank 25 fills the internal volume of the filter 1 at the end of the regeneration process, so as to avoid the presence of 02 molecules in the filter chamber during k e the next filtration cycle, which would entail the risk -11 of comprising the quality of the beer. The recovered infusorial earths are stored in the container 55 for subsequent use and/or are directly loaded into the device 9 for distribution. 5 In accordance with the invention, at the end of filtration, the beer is pushed from the filter with cold (for example about 4 0 C) de-aerated water. It is then conveyed to a PVPP (polyvinylpyrrolidone) processing plant, this processing retaining the tannins 10 present in the beer. The filter, which still contains the spent infusorial earth, is rinsed with hot water (step (a)) at between 35 and 95 0 C, preferably about 75 0 C. By way of example, for a filter with a volume of 4 M 3 , the hot 15 water delivery rate is about 17 x 10-3 m 3 /s and the volume of water used is 12 M 3 . An alkaline solution is then introduced into the filter chamber (step (b)). Typically, this is a 0.1 to 15% (V/V), preferably about 1%, sodium hydroxide 20 solution, but may be any other alkaline solution, for example a potassium hydroxide solution or commercial alkaline solutions based on sodium hydroxide, such as the solutions PE 1700 or PE 1900 sold by Henkel, Galor 8/74 or Galor C7 sold by CFPI. 25 The temperature of the alkaline solution is between 35 and 95 0 C, preferably about 75 0 C. The delivery rate can be adjusted to 22 x 10-3 m 3 /s, for example. Introduction of the sodium hydroxide solution is terminated if (for example and in a non-limiting 30 manner) the volume introduced is greater than 15 M 3 , 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 recycling the sodium hydroxide into 35 the filter (step (e)) can then be carried out, for example for 30 minutes, the recycling flow rate possibly being adjusted to about 22 x 10-3 m 3 /s. If the brightness of the solution leaving the * filter (indicator of the progress of the regeneration -12 of the infusorial earth) is found to be greater than a predetermined threshold, advantageously between 0.04 and 0.1 ebc, for example 0.06 ebc, after 30 minutes, a further volume of fresh sodium hydroxide (for example 5 about 4 M 3 ) is introduced into the filter. In the contrary case, the recycling step is terminated. The sodium hydroxide solution used for the recycling can be recovered for subsequent re-use in step (b) of another regeneration cycle. 10 Optionally, a small volume (< 4 M 3 ) of fresh sodium hydroxide is introduced into the filter in order to optimize the regeneration efficiency (step (f)). After these various treatments in alkaline medium, the filter is rinsed with hot water (step (c)) 15 at a temperature of between 35 and 95 0 C, preferably about 70 0 C. The volume of water is, for example, 8 M 3 , with a delivery rate of 24 x 10- m 3 /s. A final rinsing operation of the filter is then carried out with an acidic solution (step (d)), 20 typically with de-aerated water saturated with carbon dioxide, of pH 4.5 and at a temperature of about 4 0 C. Its delivery rate is, for example, 24 x 10-3 m 3 /s. The final rinsing with de-aerated water saturated with carbon dioxide is terminated if the 25 following two cumulative conditions are satisfied: the volume of water sent into the filter is greater than or equal to a given volume (for example 8 M 3 ) and the pH of the solution leaving the filter is less than 6. The regeneration of the infusorial earth is 30 then terminated. This earth is recovered by passing de aerated water through the filter backwards (unclogging of the filter tubes), for example for about 90 seconds. The regenerated infusorial earth is characterized by an organic matter content of less than 35 or equal to 5% by weight. It can be re-used as a filtering aid, after cleaning the filter tubes of the filter in an identical manner to a conventional flushing operation. The regenerated infusorial earth is then, for example, reintroduced into the device 9 for n -13 distributing infusorial earth, via the pipes 47 and 57 and the valve 49, another valve, not shown in Figure 1, being provided on the pipe 57. However, since the degree of recovery of the 5 infusorial earth is about 75% by weight relative to the infusorial earth used, it is preferable to reconcentrate it by adding a small amount of fresh infusorial earth. In this case, the regenerated infusorial earth is recovered in the preparation tank 10 55, which has a volume, for example, of 4 M 3 , via the pipes 47 and 51 and the valve 49, another valve, not shown in Figure 1, being provided on the pipe 51; fresh infusorial earth is added to the regenerated infusorial earth in the tank 55, in order to reconcentrate the 15 regenerated infusorial earth; the mixture of regenerated infusorial earth/fresh infusorial earth is then introduced into the device 9 for distributing infusorial earth, via the pipe 53. All the solutions described above for rinsing 20 the filter and regenerating the infusorial earth are sent to the drain in order to be conveyed to a purification plant, apart from the sodium hydroxide solution used in step (e) , which is recovered for subsequent use. In the case of the sodium hydroxide 25 solutions used in steps (b) and (f) , they are stored beforehand in a waiting basin which collects various factory wastes (from processes other than the one described above), thus allowing the pH to be renormalized before these solutions are sent down the 30 drain. As emerges from the text hereinabove, the invention is not limited in any way to its modes of implementation, preparation or application which have just been described in greater detail; on the contrary, 35 it embraces all the variants which may occur to a person skilled in the art, without departing from the context or scope of the present invention.

Claims (5)

1. Process for regenerating a spent infusorial earth, the said infusorial earth being used as a 5 filtering aid and being held in a filter chamber, the said process comprising a step of introducing an alkaline solution into the filter chamber, with placing of the said solution in contact with the infusorial earth to be regenerated, characterized in that the said 10 process is followed by a step of recovery, outside the filter chamber, of the regenerated infusorial earth so that it can be re-used, in a subsequent filtration of beer, as a filtering aid, the said regenerated infusorial earth being introduced into the filter 15 chamber in the form of a mixture with the beer to be filtered.

2. Process according to Claim 1, characterized in that the said recovery, outside the filter chamber, of the regenerated infusorial earth comprises a step of 20 opening the filter chamber.

3. Process according to Claim 1 or 2, characterized in that the said filter is a multiple tube filter.

4. Process according to any one of Claims 1 to 3, 25 characterized in that it comprises the following steps: (a) rinsing the filter retaining the spent infusorial earth with water at a temperature of between 35 and 95 0 C, preferably about 75 0 C, (b) introducing an alkaline solution into the 30 filter chamber, and placing the said solution in contact with the infusorial earth to be regenerated, (c) rinsing the filter with water at a temperature of between 35 and 95 0 C, preferably about

70-C, 35 (d) rinsing the filter with an acidic solution, these steps being followed by a step of recovering the regenerated infusorial earth so that it can be re-used as a filtering aid, the said regenerated infusorial earth being introduced into the filter -15 chamber in the form of a mixture with the beer to be filtered. 5. Process according to Claim 4, characterized in that the said acidic solution is carbonated de-aerated 5 water. 6. Process according to Claim 4 or Claim 5, characterized in that it comprises, between steps (b) and (c) , a step (e) of recycling, in a closed circuit, a volume of alkaline solution equal to the internal 10 volume of the filter minus the volume occupied by the infusorial earth. 7. Process according to Claim 6, characterized in that it comprises, between steps (e) and (c) , a step (f) of introducing into the filter a fresh volume of 15 alkaline solution. 8. Process for filtering beer using an infusorial earth as a filtering aid, characterized in that it comprises the following steps: - filtration of the beer, an infusorial 20 earth/beer to be filtered mixture being introduced into the filter chamber, - regeneration of the spent infusorial earth in situ in the said filter chamber, - recovery of the regenerated infusorial earth, 25 - reintroduction of a regenerated infusorial earth/beer to be filtered mixture into the filter chamber. 9. Device for filtering beer, comprising a chamber in which are located means capable of retaining 30 infusorial earths used as a filtration adjuvant and filtration residues, means (3, 29, 31, 33, 35) for conveying into the chamber an alkaline solution to react with the said filtration residues, and means (11, 43, 45) for removing the said alkaline solution charged 35 with at least some of the said filtration residues, characterized in that the said device also comprises means (3, 5) for introducing an infusorial earth/beer to be filtered mixture, the said infusorial earth being -16 an infusorial earth which has been regenerated by the process according to any one of Claims 1 to 7. 10. Device according to Claim 9, characterized in that the said means capable of retaining infusorial 5 earths used as filtration adjuvant and filtration residues consist of a multiple-tube filter. ' 11. Device according to Claim 9 or Claim 10, characterized in that it also comprises means (37) for circulating, in a closed circuit, the alkaline solution 10 through the said chamber. OR