Method and apparatus for cleaning reusable beverage containers

Abstract

Method for cleaning reusable beverage containers (1), comprising the step of applying an aqueous solution containing alkali chlorite and / or chlorine dioxide to the containers (1) at ambient temperature in a region (3) sealed against gas exchange with the environment, and device for cleaning reusable beverage containers (1) having a region (3) sealed against gas exchange with the environment, which contains an aqueous solution containing alkali chlorite and / or chlorine dioxide, and means (6, 7, 8) by which the containers (1) can be applied to the solution in the region (3) at ambient temperature.

Description

The present invention relates to a method and an apparatus for cleaning reusable beverage containers.Very long reusable containers, in particular reusable bottles, are already used for beverages. For a number of years, plastic bottles made of polyethylene terephthalate, so-called PET bottles, have also become established in addition to glass bottles. Glass bottles have hitherto been cleaned for reuse generally with about 2% sodium hydroxide solution at temperatures of 80 to 90° C., usually with the addition of additives such as defoamers. The alkaline washing solution is intended to remove mineral deposits and organic residues and additionally to remove labels of a wide variety of types. An example of such washing liquors is given in DE 696 30 407 T2.In PET bottles, lower temperatures and caustic concentrations are used to minimize material deformation and plastic attack. However, the cleaning effect deteriorates.A particular problem with all containers and bottle types is mould, which is why the temperatures are often selected to be even higher. It has also already been proposed to pretreat the threaded region with special disinfecting solutions, see for example DE 101 41 239 A1.A disadvantage is above all the huge energy requirement in order to heat the bottles to, for example, 80° C. If, for example, 60,000 glass bottles per hour are cleaned in a cleaning device, then approximately 50 tons of glass per hour must be heated to 80° C. for this purpose. Cleaning devices often run in a stratified operation for 24 hours. Heat recovery, as described inter alia in DE 32 05 956 A1, also does not solve this problem sufficiently.There is therefore a great need for a method and a device with which reusable beverage containers made of glass and plastic can be cleaned.Surprisingly, it has now been found that an aqueous solution comprising alkali chlorite and / or chlorine dioxide achieves a better cleaning result even at ambient temperature than the sodium hydroxide solution used since, optionally with additives. Because of the toxicity of chlorine dioxide, the cleaning device is sealed against gas exchange with the environment when it is used.The above-mentioned procedure is described. The object is also achieved by a device for cleaning reusable beverage containers, which has a region which is sealed against gas exchange with the environment and contains an aqueous solution containing alkali chlorite and / or chlorine dioxide at ambient temperature, and means by which the containers can be acted upon with the solution in the region at ambient temperature.A problem which has not been solved up to now in bottle cleaning is container equipment with labels. There are no regulations at all for releasable labels and adhesives. A variety of water-insoluble adhesives and water-impermeable label materials make label removal difficult or impossible at the same time as cleaning.The present invention therefore proposes, in a preferred embodiment, removing the labels from the containers prior to cleaning.Labels which are adhesively bonded overlapping at a narrow location or tubular plastic labels can be removed mechanically, for example with high-pressure water jets, before the actual cleaning and then possibly even disposed of in a single type. Labels which have been bonded on with water-insoluble adhesives can optionally be removed with the aid of solvents or high-pressure water jet. An important advantage of this prior removal is that the labels and adhesive residues do not contaminate the cleaning solution, such as the casein adhesives and paper labels often used for beer bottles. These cause a high chemical oxygen (COD) requirement in the waste water when the cleaning solution is discharged from the apparatus. In addition, they consume a lot of cleaning chemistry and cause high waste water costs.Despite a possibly required redesign of the device in comparison with the conventional cleaning devices since then, the new method and the new device are located within the shortest time due to the energy saved. The other advantages, lower wear of the containers and increased cleaning effect also against moulds, lower waste water costs and highest microbiological safety result.In particular, the prior removal of the labels is advantageous since all the introduced contaminants would consume the oxidizing agent chlorine dioxide and / or alkali chlorite and thus a substantially higher consumption of the cleaning chemicals would be expected.Due to the very mild conditions in the cleaning according to the invention, it is alternatively conceivable not to remove labels made of plastic, such as plastic banderols, at all, or to use permanently printed containers. As far as the containers are sorted before cleaning and they are filled with the same contents as before, the label can remain on the container. In contrast to the hitherto customary cleaning with alkali at 80° C., it is to be expected that alkali chlorite and / or chlorine dioxide normally does not significantly attack either the plastic label material or the printing at ambient temperature. The minimum date of durability can be identified either elsewhere than the label, for example on the bottleneck. Or, printing is carried out with an oxidation-labile ink which is removed by the cleaning of the invention.In a first step, a pre-flushing of the containers with a pre-flushing liquid, preferably water, preferably under high pressure, can remove liquid residues and coarse and loosely adhering contaminants. As in the case of the present cleaning methods, the final rinse water is expediently used for prewashing. The prewash water thereby produced is generally discharged from the device. The pre-rinse water can also be at least partially circulated. In this case, filtering is preferably carried out in order to separate off solid contaminants.The cleaning of the containers is effected according to the invention by applying the aqueous solution of chlorine dioxide and / or alkali chlorite at ambient temperature, preferably by spraying / spraying and spraying / spraying or foaming of the containers. When the solution contains chlorine dioxide and preferably generally, the exposure is in a region sealed against gas exchange with the environment. Filling with 2% alkali since then customary in bottles and treatment in alkali baths of more than 20 m 3 content would require the handling of very large amounts of non-harmless chlorine dioxide and / or alkali chlorite if the alkali was replaced by the cleaning solution used according to the invention. Therefore, according to the invention, it is preferably provided to spray and expel the containers and / or spray and expel them or foam them. The effluent solution is preferably filtered off and, after being supplemented with fresh solution or alkali chlorite / chlorine dioxide, is recycled into the purification.According to the invention, the cleaning solution contains relatively high concentrations of alkali chlorite and / or chlorine dioxide. Chlorine dioxide is preferably released from alkali chlorite by addition of acid. This release of chlorine dioxide is effected by mixing alkali chlorite with acid. In the device according to the invention, it can take place in the region sealed against gas exchange with the environment. For this purpose, the acid is introduced into the region separately from the solution containing alkali chlorite. The liberation can alternatively or additionally be effected by mixing alkali chlorite and acid in a premixing vessel. Other methods for generating chlorine dioxide, e.g., reduction of chlorate with hydrogen peroxide and acid, are also possible, but less preferred. These processes can also be carried out in the apparatus itself or take place in a separate premixing vessel or reactor. The latter corresponds to the use of a "finished" chlorine dioxide solution. The high chlorine dioxide concentrations required do not, however, make it useful to transport corresponding chlorine dioxide solutions. The production directly in or in the immediate vicinity of the device according to the invention is significantly more expedient. If chlorine dioxide is generated outside the device according to the invention, this should be done at a matched rate to the requirement, optionally using an intermediate container.The aqueous solution comprising alkali chlorite is used with concentrations of alkali chlorite of ≥0.05 mol per liter of solution, preferably of 0.5 to 5 mol per liter of solution, particularly preferably of 1 to 3.5 mol per liter of solution.According to the invention, concentrations of chlorine dioxide in the range from 50 to 25000 mg / liter, preferably from 50 to 15000 mg / liter, are adjusted in the cleaning solution. Suitable concentrations of alkali chlorite for releasing the same by addition of acid thereto are likewise from ≥0.05 mol / liter, preferably from 0.5 to 5 mol / liter, particularly preferably from 1 to 3.5 mol / liter of solution.Preferred acids for releasing chlorine dioxide are oxidation-stable acids such as, for example, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, phosphonobutanetricarboxylic acid, carbonic acid, and polyacrylic acid or mixtures thereof, hydrochloric acid being particularly preferred. However, the use of other acids is not excluded. The amount of acid required will depend on the acid used and its concentration and can be readily calculated.The aqueous solution comprising alkali chlorite and / or chlorine dioxide can also contain, as is known per se, one or more additives, for example oxidation-stable surfactants, complexing agents and / or defoamers, of which mixtures are also possible in each case. A low pH value, for example ≤3 or ≤2 or ≤1, in the cleaning solution promotes dissolution and dissolution of salts or prevents precipitation of water hardness during cleaning.Preferred surfactants are short-chain organic sulfonates, sugar surfactants and amine oxides; preferred complexing agents phosphonobutane tricarboxylic acid, polycarboxylic acids, maleic acid and citric acid and salts thereof; and preferred defoamers are end group-capped block polymers.Chlorine dioxide is sometimes already used at present for disinfection in the fresh water area after the main cleaning in cleaning devices for reusable beverage containers. This is described, for example, in a catalog of Calvatis GmbH retrievable under: www.calvatis.com / fileadmin / content / 03_products / fruit juice_ und_Weinbau_2017.pdf on page 16 below or in the Flyer Bottle Cleaning of Fink Tec GmbH retrievable under: www.finktec.de / company / downloads?file=files / cto_ layout / downloads / de / gest%C3%A4nke industry / Flyer%20-%20 bottle Cleaning.pdf. Because chlorine dioxide is outgassed from about 5 ppm, only a few ppm are possible for this purpose in the final flushing operation, and the concentration of chlorine dioxide must not exceed the concentrations prescribed by the drinking water treatment of at most 0.2 to 0.4 ppm at the end. Concentrations of 0.2 to 0.8 ppm of active substance are mentioned in the flyer on page 5. However, these concentrations are by far insufficient for the cleaning of the containers according to the invention. For this purpose, the concentrations must be more than 0.5% by weight for sodium chlorite and more than 50 ppm for chlorine dioxide. In this respect, the known application and the application according to the invention differ considerably both in the purpose-on the one hand disinfection and on the other hand cleaning-and in the required concentrations.The use of alkali chlorite or combinations thereof with sodium hydroxide solution is conceivable in known cleaning devices without major alterations. However, at low temperatures, no detachment of labels is possible and the consumption of cleaning solution is insense high due to the large amount of soiling. Because of the gas formation, the use of solutions containing chlorine dioxide is only possible if the cleaning region is isolated from the environment both at the container inlet into the device and at the container outlet from the device. This is preferably also effected in the case of cleaning solutions which contain only alkali chlorite. It is important that the region in which the treatment of the containers takes place is designed such that no relevant gas exchange with the environment takes place when chlorine dioxide is used according to the invention.For this purpose, the inlet and outlet section of the device, where the containers are transported into and out of the treatment area, can be designed, for example, as a siphon. The siphon keeps gases within the region shut off from the ambient air. Alternatively, a liquid or spray mist curtain or a lock is conceivable. Other embodiments such as slides, flaps, doors, etc. are also possible; the air can also be respectively suctioned off and cleaned by filters. The aforementioned methods and devices can also be combined with one another, for example a liquid curtain in the inlet section with a lock or a siphon in the outlet section, or a siphon in the inlet section with a liquid curtain in the outlet section, etc. A foam lock likewise prevents outgassing into the ambient air. Other techniques may also be used as long as they reliably prevent amounts of chlorine dioxide that exceed the maximum allowable workplace concentration from entering the environment from the cleaning area.If provided, the label is removed and / or a pre-rinsing of the containers is carried out before cleaning.In a preferred embodiment, the device according to the invention is secured in the inlet and outlet section by siphons against gas exchange with the environment. For this purpose, liquid reservoirs are arranged in each case in the inlet and outlet section, through which the containers must be dipped. In a further preferred embodiment, a siphon is provided at the inlet section and a liquid curtain is provided at the outlet section.The containers pass--optionally after the label removal and / or pre-rinsing--through the siphon in the inlet section or another means for sealing the region in which the application takes place, and are acted upon in the region with the container opening downwards both on the outside and on the inside with the cleaning solution, preferably sprayed therewith or sprayed and sprayed out or sprayed out. To increase the throughput, many spraying and / or spraying positions can be provided one after the other and the containers can each advance one position further. The transport into and through the device and out of it takes place as is known per se, for example with the aid of conveyor belts or-preferably-solely by the force of gravity. The chemistry used in the cleaning solution according to the invention dissolves mold and soils and the solution drained from the containers carries away the soils. Preferably, the solution runs into collecting channels or tubes and is passed to a filter. As far as the filter is outside the gas exchange sealed area, pipes are used outside. The filtrate is preferably circulated. The separated dirt is discharged-optionally after reduction of chlorine dioxide present, for example by the addition of sodium sulfite.Following the cleaning, a rinsing step is expediently carried out, preferably by multiple spraying / spraying with final rinse water. This final rinse water can also be used as a barrier liquid of the siphon at the outlet section, i.e. at the end of the cleaning and / or as a pre-rinse water.According to the invention, the purification is carried out at ambient temperature, i.e. the aqueous solution containing alkali chlorite and / or chlorine dioxide is not heated or even heated to 60° C., 80° C. or even more. Ambient temperatures of 10 to 40° C., usually of 15 to 35° C., are safe and complete purification with the method according to the invention or the device according to the invention in the case of the cleaning solution used according to the invention, i.e. the aqueous solution containing ≥0.05 mol / liter of alkali chlorite and / or chlorine dioxide in a concentration of at least 50 ppm.Typical exposure times of the aqueous solution comprising alkali chlorite and / or chlorine dioxide liberated therefrom by addition of acid are from 1 to 60 minutes, preferably from 5 to 20 minutes, particularly preferably from 10 to 15 minutes. These times are also sufficient for effective cleaning at temperatures of 15 to 35° C. Even particularly problematic dirt such as mold is completely removed. Due to the germicidal effect of chlorine dioxide and alkali chlorite, the containers are simultaneously disinfected according to the invention.Drying the bottles is neither necessary nor meaningful. The final rinse water quantity is usually dimensioned such that the drinking water limit values for ClO 2 of 0.2 to 0.4 ppm are not exceeded.The invention is to be explained with reference to the following figures and examples, without however being restricted to the specifically described embodiments. Unless otherwise indicated or unless the context dictates otherwise, percentages refer to the weight, in doubt to the total weight of the mixture. The invention also relates to all combinations of preferred embodiments, provided they are not mutually exclusive. The terms "about" or "about" in connection with a numerical indication mean that higher or lower values are included at least by 10%, or higher or lower values are included by 5%, and higher or lower values are included in each case by 1%.The figures show: FIG. 1 is a schematic view of a device according to the invention, FIG. 2 is a schematic diagram of an alternative apparatus according to the invention, FIG. 3 is a photograph of an untreated bottle; and FIG. 4 is a photograph of the same bottle after cleaning.FIG. 1 illustrates the sequence of a cleaning of reusable bottles according to the invention in a schematically illustrated apparatus. The bottles 1 are--as a rule after a pre-rinsing, not shown--introduced into the apparatus with the opening 2 downwards through a siphon 4. This is preferably done by conveying the bottles with the aid of a bottle guide 5 and by gravity. Label removal is also preferably carried out before the bottles enter the gas-tight region 3 of the cleaning device. This preferred label removal is not shown in Figure 1.After the optionally pre-flushed bottles 1 have been introduced through the siphon 4 into the gas-tight region 3 of the cleaning device, the bottles 1 are ejected / sprayed with the cleaning solution used according to the invention, containing alkali chlorite and / or chlorine dioxide, through a plurality of nozzles. The supply of the cleaning solution 6 is ensured from a circulating vessel 8 by a pump. The cleaning liquid running off from the region 3 passes through the filter 7 before it reaches back into the vessel 8, so that coarse dirt can be discharged. Subsequently, the bottles 1 pass through an area without treatment as a drip zone, in which still adhering cleaning solution drips. This is followed by spraying / spraying and optionally also spraying / spraying with fresh water as final rinse water, which is conveyed by the fresh water pump 9. A water curtain 10 isolates the region 3 in the outlet section from gas exchange with the environment. The water curtain 10 can be generated, for example, by the fresh water pump 9, as shown. Preferably, this water is also at least partially used for pre-rinsing and is supplied for this purpose to the pre-rinsing via a line 11. The cleaned bottles 1 are then removed from the apparatus by means of a control 12 for the bottle outlet and are generally supplied directly to the filling system, which is not shown here.In FIG. 2, an alternative device is schematically shown, in which the region 3 is sealed against gas exchange with the environment by means of a foam layer 13. The bottles 1 are fed with the opening 2 downwards to the device. The opening 2 and a part of the bottle 1 are dipped into the foam layer 13. The circulation vessel 8 with pump for the cleaning solution is here part of the region 3. In the region in which no nozzles are arranged, the solution flows and drips back into the circulating vessel 8 through the foam layer 13. Subsequently, the bottles are ejected with fresh water, which is supplied by a fresh water pump 9. The injected final rinse water flows and drops back into a collecting container in the region in which no nozzles are arranged, from which the pump 9 sprays it again into the bottles 1. A portion of the water is constantly discharged and replaced by fresh water, which is not shown in FIG. 2. The discharged water is suitable for replenishing the cleaning solution, a part of which is likewise constantly discharged and replaced by fresh solution, which is also not illustrated in FIG. 2. After the bottles 1 have left the area 3, a further fresh water pump 9 is used to flush them with fresh water from the outside. The water running off there is conducted into the preliminary flushing, not shown in FIG. 2.Example 1Into the mold-grown beverage bottle shown in Figure 2, 12.5 ml of a 7.5% NaClO 2 and 12.5 ml of a 9% HCl solution were charged. After 10 minutes, 75 ml of water were added to make up a solution containing about 5000 ppm of chlorine dioxide. The bottle was allowed to stand at ambient temperature of 20°C for 20 minutes, after which the solution was poured out and then rinsed 3 times with 50 ml of fresh water. Figure 3 shows the bottle after this treatment. It is clear that the cleaning solution according to the invention could completely remove the mold in a short time at ambient temperature.List of reference characters1 Bottle 2 Opening 3 Gas-tight region of the cleaning device 4 Siphon 5 Bottle guide 6 Application of cleaning solution 7 Filter 8 Circulation vessel with pump for the cleaning solution 9 Fresh water pump for the final rinsing 10 Water curtain 11 Rinsing water for the primary rinsing 12 Control of the bottle outlet 13 Foam layerReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 696 30 407 T2

[0002] DE 101 41 239 A1

[0004] DE 32 05 956 A1

[0005]

Claims

A method for cleaning reusable beverage containers (1), comprising the step of applying an aqueous solution containing alkali chlorite in a concentration of at least 0.05 mol / litre of solution and / or chlorine dioxide in a concentration of 50 to 25000 mg / litre of solution to the containers (1) at ambient temperature, wherein the application of the solution containing chlorine dioxide takes place in a region (3) sealed against gas exchange with the environment.Method according to claim 1, characterised in that labels are removed from the containers (1) before cleaning.Method according to claim 1 or 2, characterised in that after the cleaning a rinsing step with final rinsing water takes place, preferably until a concentration of chlorine dioxide ≤ 0.4 ppm is reached, and / or before the cleaning a pre-rinsing takes place, preferably with high pressure and / or a final rinsing water removed from the rinsing step.Method according to one of Claims 1 to 3, characterized in that the application of the solution is effected by spraying or spraying the solution onto the containers (1) and / or spraying or spraying the containers (1) with the solution or by foaming the containers (1) with the solution.Process according to any of Claims 1 to 4, characterized in that the solution contains from 0.5 to 5 mol / litre, preferably from 1 to 3.5 mol / litre, of alkali chlorite and / or from 50 to 15000 mg / litre of solution of chlorine dioxide.Process according to one of Claims 1 to 5, characterized in that sodium chlorite and / or potassium chlorite, preferably sodium chlorite, is used as alkali chlorite.Method according to one of claims 1 to 6, characterised in that chlorine dioxide is released from the alkali chlorite by mixing with acid, preferably with hydrochloric acid, nitric acid, sulphuric acid, phosphoric acid, phosphonobutane tricarboxylic acid, carbonic acid and / or polyacrylic acid, particularly preferably with hydrochloric acid, within the region (3) sealed against gas exchange with the environment and / or in a premixing container.Process according to one of Claims 1 to 7, characterized in that the solution comprising alkali chlorite and / or chlorine dioxide is circulated, the solution preferably being purified via a filter and / or supplemented with fresh solution.Device for cleaning reusable beverage containers (1), which has a region (3) which is sealed against gas exchange with the environment and contains an aqueous solution containing alkali chlorite and / or chlorine dioxide, and means (6, 7, 8) by means of which the containers (1) can be acted upon with the solution in the region (3) at ambient temperature.Device according to claim 9, characterised in that the means for applying the solution to the containers (1) are formed by a plurality of spray nozzles and / or spray nozzles.Device according to claim 9 or 10, characterised in that the area (3) is sealed against gas exchange with the environment by means which are arranged at the inlet and outlet section of the device and which are selected independently of one another from a liquid reservoir forming a siphon, a liquid curtain, a spray curtain, a lock, a slide, a flap and a door.Apparatus according to claim 9 or 10, wherein during the cleaning process the bottles are guided with the opening (2) downwards in a foam layer (13) which prevents outgassing of chlorine dioxide.Device according to one of Claims 9 to 12, characterized in that the containers (1) are guided through the region (3) without drive and only by gravity, and / or in that they are sprayed with the solution on the inside and the solution runs off from the containers (1) into a collecting trough.

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