EP0264596B1 - Method of disposing with lye leaving cleaning machines - Google Patents

Abstract

1. Process for disposal of caustic solution from cleaning machines, in particular bottle cleaning machines (11, 12, 13, 14), by draining the caustic solution intermittently into associated setting tanks (21, 22, 23, 24), settling of the suspended solids taking place after several hours so that about 90% of the sediment is precipitated from the caustic solution after which the caustic solution cleaned to a very large extent is returned to the cleaning machines, while the highly alkaline sludge left as a residue is further treated, characterized in that the sludge and part of the caustic solution remaining in the settling tank (21, 22, 23, 24) are drawn off and passed to a sludge thickening system (30) in which the sludge is further concentrated, that the clarified clean caustic solution accumulating in the upper part of the thickening tower (31) is continuously drawn off and after intermediate storage in a clean caustic solution tank (32) led to a settling tank (21, 22, 23, 24) or a manipulation tank (27), that the sludge accumulating in the sludge thickening tower (31) is passed through a downstream flocculant station (39) in which a flocculant is added to the sludge, and that the sludge is subsequently dewatered in a screening container (37, 40).

Description

The invention relates to a method for disposing of lye from cleaning machines, in particular bottle cleaning machines, by the lye being emptied discontinuously into associated sedimentation tanks, with sedimentation of the floating parts being caused after several hours, so that approximately 90% of the sediment is deposited from the lye, whereupon the largely cleaned lye is pumped out of the upper part of the sedimentation tanks and fed back to the cleaning machines, while the remaining highly alkaline sludge is disposed of.

DE 27 23 004 A1 discloses a method for increasing the lye service life in cleaning machines in which the objects to be cleaned are passed through at least one cleaning bath containing lye and kept at an elevated temperature, the lye from the first cleaning bath holding the objects to be cleaned Dirt is removed in a continuous circulation via separators, so that the amount of lye flow conducted via a circuit containing the separator corresponds to an hourly conversion of approximately the total amount of lye in the first cleaning bath up to a multiple of this total amount and the concentration of the cleaned part of the lye before Reintroducing into the first cleaning bath to control the addition of detergent to this bath is continuously measured and the replenishment of the amount of liquid by introducing liquid into the first cleaning bath under control by measuring the suds level in this bath leads. The known method has the disadvantage that the use of a separator in the cleaning system does not ensure that the alkali loss is kept as low as possible.

Furthermore, DE 27 25 562 A1 also states that the amount of alkali flow in the circuit containing the separator is reduced to a value which corresponds to an hourly conversion of only a fraction, preferably one third, of the total amount of alkali in the first cleaning bath. This known method also has the disadvantage that the loss of alkali is not particularly important.

In addition, DE 29 20 737 A1 discloses a method for cleaning and recovering working liquids drained from bottle washing machines, in which an oxidizing agent is added to the wash liquor in the pre-soak and then the oxidized pollutant particles are separated out by filtration so that those still remaining in the liquor Pollutants are selectively flocculated by a flocculant added to the wash liquor and then filtered out, whereupon the so washed wash liquor is returned to the bottle washing machine. The known method specifies measures for cleaning the wash liquor, but the process has the disadvantage that the disposal of the resulting contaminants in the wash liquor is not taken into account.

The invention is based on the object of specifying a method for disposing of alkali from cleaning machines, in which the alkali loss during the discharge of the resulting contaminants is kept as low as possible.

The object is achieved in a generic method by the characterizing features of claim 1. The use of a thickening system ensures that the entire dirt and sediment portion is concentrated, which can then be disposed of as puncture-proof sediment. Due to the strong concentration of the dirt and sediment in the thickener, the alkali loss is kept low, because the thick sludge that is collected hardly contains any detergent solution.

The neutralization system provided according to claim 2 also ensures that the puncture-proof sediment finally obtained is disposed of to the extent that it can be stored as normal waste in any landfill.

An embodiment of the invention is shown in the single drawing and is explained in more detail below.

The wash liquors from four simultaneously operated bottle cleaning machines 11, 12, 13, 14 of the cleaning system 10 with lye baths of different sizes are discharged into sedimentation tanks 21, 22, 23, 24 of the sedimentation system 20 arranged for this purpose at the end of the shift.

The sedimentation tanks 21, 22, 23, 24 have a cylindrical-conical design and are provided with an approximately 100 mm thick thermal insulation under VA sheet.

Since one of the systems mainly cleans reusable aluminum-foil bottles, the so-called alkali exchanger principle is used in the exemplary embodiment.

In such systems, the aluminum-loaded alkali is only run in the system for one day and used in a normal / Euro bottle system the next day.

The lye filling of the individual bottle cleaning machines 11, 12, 13, 14 is emptied via shut-off valves, not shown, which are provided with feedback for the open and closed position of the valves. The sedimentation tank 21, 22, 23, 24 is selected by the operating personnel via an on-site control box on the respective bottle cleaning machine 11, 12, 13, 14, which is also not shown, and which is to be assigned to the corresponding bottle cleaning machine, the associated electro-pneumatic valve being opened that is also not shown.

Some of the bottle washers can now only carry lightly soiled lye with small particles, while other bottle washers carry considerable dirt loads up to large pieces of broken glass, bottle caps and labels.

In the exemplary embodiment shown, belt sieve dirt discharge systems 15, 16, 17, 18 are exemplary wise chain conveyor systems, built directly next to the bottle cleaning machines 11, 12, 13, 14, to which the lye flows by gravity in order to keep coarse dirt carried away from the sedimentation tanks 21, 22, 23, 24. When quick release valves, not shown, are opened, the respective belt sieve dirt discharge system is switched on by the respective on-site switch boxes in order to discharge the existing coarse dirt. The corresponding sedimentation tank must be selected beforehand using the corresponding on-site control box so that the valves are open.

The bottle washers are emptied one after the other since only one drain rail 19 is available. The total drainage time is about 120 minutes, depending on the volume of the lye in the bottle washers, which can vary depending on the machine.

When the first bottle washer is empty of the suds, a flashing light can illuminate in the on-site control box via an empty sensor, not shown. The shut-off valve is then to be closed by the operating personnel, the limit switches attached to the valve switching off the flashing light (not shown). The other bottle washers can now be emptied one after the other in the same way.

After emptying the bottle cleaning machines 11, 12, 13, 14 into the preselected sedimentation tanks 21, 22, 23, 24, the sedimentation process of the contaminants begins in the cone area of the sedimentation tanks. Depending on the shift operation on such a cleaning system 10, the cleaning solution now remains in the sedimentation tanks, namely for about 6 hours. The lyes are returned and exchanged in good time before the shift starts as follows. At the on-site switch box (not shown) of each bottle washing machine 11, 12, 13, 14, the operating personnel preselects the volume of the detergent solution and determines which bottle cleaning machine is to be filled with which liquor from the sedimentation tanks 21, 22, 23, 24. This is followed by the release of a return pump, which is not shown. The lye is fed to the bottle cleaning machine selected first, the pump delivering until the preselected lye holding volume of the corresponding bottle cleaning machine is reached. For this purpose, a probe is advantageously attached to each bottle washer, which indicates the level of the caustic solution and emits a signal when the preselected caustic level is reached, so that the filling valve (not shown) is switched off and at the same time the next bottle washer is released for filling by opening the corresponding filling valve.

The filling is carried out as described above via a filler rail 25 and ends when the respective target eye level is reached. In such a cleaning system 10, it is advantageously provided that the return pump is switched off when a minimum fill level in the corresponding sedimentation tank is reached and the corresponding fill valve on the bottle washer is closed in order to prevent the return pump from running dry.

After completion of the refilling process, about 7 cbm of residual liquor with the sedimented contaminants remain in the cones of the respective sedimentation tanks.

The remaining sediments are withdrawn tank-wise via a discharge rail 26 during the working shift in which the cleaning liquors are located in the bottle cleaning machines 11, 12, 13, 14 and are fed to a thickening system 30 with a thickening tower 31 by means of a pump, for example a diaphragm pump, which is also not shown. The thickening tower 31 is also essentially a cylindrical-conical tank container. The incoming sediment is led to the bottom area of the container via internal internals and then led upwards again via an inner pipe. The overflow is located on the side in the upper area of the tank.

A further sedimentation in the cone area of the thickening tower 31 is achieved via the displacement flow caused. The overflowing liquor is fed to a cleaning liquor tank 32. From there, the cleaned lye is pumped back into the sedimentation tank with the largest usable volume. The essentially cleaned lye collected here is used for the next return of the lye to the bottle cleaning machines to supplement the sediment losses.

The highly alkaline sludge that collects in the cone area of the thickening tower 31 is drawn off once a week, so that the entire alkali cycle only has to be supplemented by this volume.

The sludge collecting in the thickening tower 31 is conveyed once a week into a neutralization container 33 with the aid of a thick matter pump (not shown). The neutralization container is provided with a cold water connection 34 and an agitator in order to thin out the thick mass and lower the temperature accordingly. The process step serves to relieve the downstream neutralization pump, which is also not shown.

The thinned sludge is neutralized in the pumping process via downstream pipe loops of a pipe reactor 35 with controlled addition of CO ₂ gas via a pipe 36. The initial pH of approximately 13.7 is brought to a pH of by adding CO ₂ 9 reduced. The pH value is reduced by automatic control via a conductivity measuring station, not shown. After neutralization and cooling, the sludge is prepared for subsequent disposal. The processed thin sludge in the neutralization container 33 is disposed of via a three-way valve to sieve containers 37. A coagulator 38 for the addition of flocculant is installed in the pipeline required for this.

The flocculant, a polymeric electrolyte, is previously prepared in a flocculant dissolving station 39 with the proportional addition of water and mixed uniformly by means of an agitator. The flocculant is processed at the same time as the neutralization phase, so that disposal in the sieve containers 37, 40 can take place immediately after the neutralization of the thinned sludge has ended. The flocculant is metered by means of a metering pump (not shown) proportional to the amount of neutralized sludge to be disposed of.

The sludge mixed with the flocculant is then fed directly to the sieve container 37. The sieve container is a standardized waste container with a water-permeable lining on the inside. In the container, the solid and liquid phases are separated by gravity. The solid phase is retained in the sieve container, while the liquid phase, namely neutralized, relatively clean waste water, passes through the lining and is fed to the sewage system via a drain.

The sludge remaining in the container becomes puncture-proof within 24 hours and can be disposed of in a normal landfill.

Flocculation of the sludge in the highly alkaline range, that is to say without upstream neutralization, is also technically feasible, but the sludge then obtained must be disposed of in a special waste landfill.

In addition to the four sedimentation tanks 21, 22, 23, 24 of the sedimentation system 20 mentioned above, a further tank of the same design is installed as a manipulation and neutralization tank 27. The main functions of this tank are as follows; it serves as a replacement tank if a sedimentation tank fails; it also serves as a disposal tank for the rapid disposal of a complete caustic bath in a bottle washer in the event of overdosing or excessive soiling; it also serves for the possible absorption of pure liquor from the clean liquor container 32, which is connected downstream of the thickening tower 31.

In order to avoid faulty switching when emptying the bottle washer, the lye is first drained into a pre-selected sedimentation tank. The manipulation tank can then be filled with a recirculation rail 28 using the lye return pump. This pumping-over process is a manual process and, for safety reasons, cannot be carried out via the automatic system.

If the alkali in the manipulation tank 27 is to be discarded, neutralization is initially provided. It is carried out as described above in the pump-around process via a tubular reactor 29 with the controlled addition of CO ₂ gas. By adding cold water, the temperature is reduced according to the intended limits, so that wastewater disposal can then be carried out without any problems.

The sediment remaining in the container is then disposed of via the thickening tower.

Since the manipulation tank has only a limited volume, the entire disposal may be carried out gradually using the upstream sedimentation tanks.

A freely programmable system can be used for regulating and controlling the cleaning system 10. The individual regulation and control circuits can be divided into three operating levels, namely on-site control boxes for the bottle washers; Main switch boxes for the sedimentation tank system; Switch boxes for the thickening system.

Fully automatic operation with the establishment of a central operating and monitoring unit is also technically easy to implement.

Claims (4)

1. Process for sidposal of caustic solution from cleaning machines, in particular bottle cleaning machines (11, 12, 13, 14), by draining the caustic solution intermittently into associated settling tanks (21, 22, 23, 24), settling of the suspended solids taking place after several hours so that about 90% of the sediment is precipitated from the caustic solution after which the caustic solution cleaned to a very large extent is returned to the cleaning machines, while the highly alkaline sludge left as a residue is further treated, characterized in that the sludge and part of the caustic solution remaining in the settling tank (21, 22, 23, 24) are drawn off and passed to a sludge thickening system (30) in which the sludge is further concentrated, that the clarified clean caustic solution accumulating in the upper part of the thickening tower (31) is continuously drawn off and after intermediate storage in a clean caustic solution tank (32) led to a settling tank (21, 22, 23, 24) or a manipulation tank (27), that the sludge accumulating in the sludge thickening tower (31) is passed through a downstream flocculant station (39) in which a flocculant is added to the sludge, and that the sludge is subsequently dewatered in a screening container (37, 40).

2. Process according to Claim 1 characterized in that the sludge accumulating in the sludge thickening tower (31) is first passed to a neutralization tank (33) in which the sludge is diluted with water and after addition of C0₂ gas neutralized in a tubular reactor (35), and that the sludge is then led through a downstream flocculant station (39).

3. Process according to Claim 1, characterized in that the cleaning machines (11, 12, 13, 14) are filled with cleaned caustic solution on the exchanging principle.

4. Process according to Claim 1, characterized in that the sludge in the screening container (37, 40) is dewatered after a given dewatering time to such an extent that the dewatered sludge is spadable.

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