DE29723682U1 - Device for cleaning liquid waste from printing works - Google Patents

Description

*. Dr, Pieter Weber

Kläüs ^; Seiffert&ogr;,

Dr. Winfried Lieke

Dipl.-Phys.

Patent attorneys

Weber, Seiffert, Lieke ■ Patent attorneys ■ PO Box 6145 ■ 65051 Wiesbaden

Gustav-Freytag-Strasse 25

German Patent Office 65189 Wiesbaden

Zweibrückenstr. 12 PO Box 6145 · 65051 Wiesbaden

Telephone 06 11/37 27 20 and 37 25

r^oo-, &kgr; u Fax 0611/372111

' ⁸⁰²⁹⁷ Munich _E . _mail: wSL-Patent@t-online.de

Date:

12 October 1998 L/kr anm\müller97.G01

Müller Printing Technology GmbH On the Langwies, 65510 Hünstetten

Device for cleaning liquid waste from printing works

The present invention relates to a device for cleaning liquid waste from printing works, namely for cleaning contaminated waste water and contaminated solvent from printing works.

A state of the art technology that comes close to this is currently not known, since up to now these liquid wastes have been disposed of as hazardous waste and incinerated in particular in waste incineration plants.

The disadvantage of this state of the art technology is the effort involved in transporting it to incineration plants, especially since this liquid waste must be treated as hazardous waste. Since this type of hazardous waste cannot be safely disposed of in every waste incineration plant, long journeys to suitable waste incineration plants often have to be accepted.

Postgiro: Frankftirt/M 6763-602 Bank: Dresdner Bank AG, Wiesbaden Account 27680700 (bank code 51080060)

In addition, the printing companies must have adequate storage capacity for the temporary storage of the collected liquid waste. A costly supply of fresheners must also be kept on hand at all times. If this supply fails due to external circumstances, the printing company cannot continue to operate.

In addition, this transport of solvents is declared as "dangerous goods transport" and causes relatively high costs.

In terms of costs, the fact that the burned solvent must be replaced with new solvent and is not reused also has an impact, which also has a negative environmental impact.

Compared to this state of the art, the present invention is based on the object of creating a device for treating liquid waste from printing works, which is able to adequately process this waste on site in the printing works so that it no longer has to be disposed of as hazardous waste. In particular, the waste water used should be able to be processed in such a way that it can flow directly into the sewer system and the liquid solvent should be able to be recovered if possible.

This task is solved by the combination of the following facilities:
a sedimentation tank,

Facilities for the separate removal of an upper and a lower fraction from the sedimentation tank,
a filter system for the upper fraction,
a collecting container for the solvent obtained by filtering the upper fraction,

a flocculation tank for the lower fraction,

a filter device for the waste water treated with a reaction separating agent in the collecting tank and

an outlet device for the filtered waste water.

Preferably, the device has an automatic electronic control system which carries out the individual steps of collecting and distributing the liquids as well as the (possibly only partial) emptying of the containers and filters in a time-controlled manner or depending on various measuring parameters (fill level).

• ■···

Further advantageous embodiments of the device according to the invention are set out in claims 2 to 7. In particular, an embodiment of the invention is preferred in which a micropore filter or a microfilter system is provided for the upper fraction from the sedimentation container, which essentially consists of contaminated solvent, through which this upper fraction is passed. Such a filter system can also retain very small solid particles, such as those present in the form of color pigments and the like. Therefore, practically only liquids pass through this micropore filter, in this case almost pure solvent, which may, however, still contain a certain amount of water.

In the preferred embodiment of the invention, it is therefore also provided that for the solvent or the upper fraction after passing through the micropore filter, a residual water separator is initially provided, where the water present in the lower part of the container settles solely by sedimentation due to gravity and can be drained into a residual water container via a corresponding valve. The remaining part of the solvent remaining in the residual water separator is then directed into a solvent collection container and is available for reuse.

According to the invention, a further container is provided for the lower fraction, namely a so-called flocculation container, into which this lower fraction can be fed or transferred and mixed with a reactant. The reactant binds any residues of the solvent that may still be present and also the solids contained in the lower fraction, which consists mainly of water, such as paper dust and printing ink. Because these substances are bound to the flocculation, a relatively simple filter, such as a filter cloth or filter bag provided on or in this container, can be used to retain the flocculated residues on the filter cloth or filter bag, while the water flows through such a filter cloth or filter bag and is then of sufficient quality to be fed into a normal sewer as waste water.

The position of the boundary layer between the upper and lower fractions is recorded by suitable devices provided on or in the sedimentation tank, such as a float whose weight lies between its buoyancy in the lower fraction (water) and that in the upper fraction (solvent), or by a conductivity probe, which records the position of the change in conductivity at the transition from the lower to the upper fraction.

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- 4-

The advantage of such a system is that printing companies are largely self-sufficient, i.e. they can process the liquid waste themselves and - as far as waste water is concerned - dispose of it themselves, without having to have large storage capacities for liquid waste and without having to rely on the punctual and regular removal of this liquid waste. This of course eliminates the high costs of transport and the even higher costs of incineration as hazardous waste. In addition, considerable costs are saved by the fact that the solvent used is recovered and can be reused. Only the filter residues have to be collected and disposed of from time to time. The residual water from the residual water separator, which may still contain solvent, is also expediently fed into the flocculation tank so that any organic substances it may still contain are bound and retained by the reactant. The filter residues that still accrue from this process and the corresponding device only amount to a small fraction in terms of volume and weight, in the order of 5% or less, of the original liquid waste that was previously disposed of as hazardous waste. These filter residues can be collected with a relatively small storage capacity and only need to be transported away at very long intervals. The disposal costs are then only the remaining volume of 5% and are therefore extremely low.

The cost advantages that can be achieved with this device are so great that a corresponding system pays for itself within just a few months, not to mention the resulting benefits for the environment.

In the sedimentation tank, a thick layer of solids can accumulate between the lower fraction and the upper fraction. It is therefore advisable if the sedimentation tank is emptied in a controlled manner by removing the lower fraction, so that the removal of the lower fraction is stopped as soon as material from the thick layer comes out of the sedimentation tank and the material contained in this thick layer is then collected separately and, for example, after being filtered through a filter cloth, is added to the remaining filter residues without first entering the flocculation tank.

A single recycling plant can easily process the liquid waste from several printing machines.

Further advantages, features and possible applications of the present invention will become clear from the following description of a preferred embodiment and the associated figures. They show:

Figure 1 shows a schematic overview of the entire disposal facility,

Figure 2 a detailed view of the flocculation tank and

Figure 3 shows a floor plan of the flocculation tank.

Figure 1 shows a processing plant for liquid waste from printing works, which is essentially only shown schematically. 20 refers to printing machines, which are only shown as blocks, which must be cleaned continuously or regularly, with both water and organic solvents being used as cleaning agents. The main contaminants in the solvent and in the waste water are printing inks, paper dust, oils and greases from the printing machines, as well as any abrasion from rubber rollers.

All liquid waste is collected together and transferred via a line 21 to a sedimentation tank 3. Since the organic solvents usually used are not or only slightly water-soluble and generally also have a lower density than water, over time the water-solvent mixture in the sedimentation tank 3 separates into a light upper fraction 1 and a heavier lower fraction 2, with the lighter fraction 1 essentially consisting of contaminated solvent and the heavier fraction 2 generally consisting of contaminated water, although both fractions can still contain certain amounts of the other liquid, since the solvent is mixed with emulsifiers.

A so-called "thick layer" 14 of contaminants, in which, for example, paper dust and printing ink are concentrated, often settles at the interface between the upper fraction 1 and the lower fraction 2.

A lifting device 4, the depth of which can be adjusted into the sedimentation tank 3 and thus into the upper fraction 1, extends with its suction opening into the upper fraction 1, so that the upper fraction 1 can be transferred to a filter system 6 via the line 18. In order to prevent the suction line 4 from sucking in water, the sedimentation tank is equipped with a device that detects the solvent level and the water level. This detection can be carried out via the conductivity of both media or via two floats with different volumes. The filter system 6 is also shown in Figure 1.

only shown roughly schematically, but if possible it has a micropore filter, which retains practically all particle contamination in the upper fraction 1, so that the solvent emerging from the filter system 6 is practically free of solid contamination. However, the filtered solvent or the filtered upper fraction 1 can still contain a certain amount of water, so that a residual water separator 12 is provided after the filter system 6, in which, similar to the sedimentation tank 3, the solvent 8 is separated from the residual water, which collects at the lower end of the residual water separator 12 and is drained via a valve 17 into a residual water tank and is collected there as residual water 2'. This accumulated residual water 2' can then be added from time to time to the flocculation tank 9, which will be described in more detail later.

The valve 17 is a two-way valve, so that after draining the water accumulating in the lower area of the residual water separator 12, the valve 17 can be switched so that the cleaned solvent 8 can be fed into the collecting container 7. From there it is available for reuse for cleaning printing rollers and the like.

In the lower area of the sedimentation tank 3, a drain valve 5 is provided through which the lower fraction 2 can flow out or be pumped out of the sedimentation tank. In the example shown, a canister 15 or the like is shown into which the lower fraction 2 can be drained from the sedimentation tank 3 in batches and poured into the flocculation tank 9. The lower fraction can also be automatically transferred into the reaction tank via a second suction line. The reaction tank 9 is shown in more detail in Figures 2 and 3 and is therefore also described with reference to these figures. In addition to the contaminated water, which forms the lower fraction 2 in the sedimentation tank 3, a reaction or flocculating agent is added to the flocculation tank 9, which forms an insoluble chemical bond with the remaining solvent in the lower fraction 2 and also with the contaminants, such as the printing ink and the paper dust, and thus flocculates. The residual water 2' from the residual water separator 12 is also added to the flocculation tank 9 so that the remaining solvent contained therein can also be separated from the water by reacting with the aforementioned reaction or reaction separating agent. When the substances contained in the lower fraction 2 have reacted with the reaction agent and flocculated, the liquid can be filtered out through a filter bag 10 and the purified water is then collected in a clear water tank 16 and can be discharged into the sewer system via the drain 11.

·

The filter cake accumulating in the filter bag 10 and also any filter residues from the filter system 6 plus the thick sludge are the only residual materials that still have to be disposed of, but their amount, based on the total amount of liquid waste that was previously disposed of as hazardous waste, is less than 5%.

In detail, the flocculation tank 9, which can be seen in a side view in Figure 2 and in a view from above in Figure 3, consists of an upper tank with a funnel 19 attached to it and a lid 23, a housing or frame 26 which carries the upper tank with the funnel 19 and the filter bag 10 hanging from it, a front lid 25 in order to have access to the filter bag 10 and to be able to change and empty it, and the clear water tank 16 arranged underneath. In addition, a power supply unit for the system is provided in the rear area on top of the flocculation tank 19, from which all electrically operated parts, such as pumps and the filter system 6, are supplied with power and controlled.

Another design variant would be to create a complete circuit in which the contaminated solvent flowing from the printing machine is automatically fed into the sedimentation tank, then automatically to the filter system, then to the residual water separator system, then to the filtrate tank and back to the printing machine.

Claims (7)

-8- "&Rgr;- ■» 4-ffl nforderungen 1. Device for cleaning liquid waste from printing works, in particular contaminated waste water and contaminated solvent, characterized by: a sedimentation tank (3), Devices (4, 5) for the separate removal of an upper (1) and a lower (2) fraction from the sedimentation tank (3), a filter system (6) for the upper fraction (1), a collecting container (7) for the solvent (8) obtained by filtering the upper fraction (1), a flocculation tank (9) for the lower fraction (2), a filter device (10) for the waste water treated with a reaction separating agent in the collecting container (9) and an outlet device (11) for the filtered waste water. 2. Device according to claim 1, characterized in that the filter system (6) for the upper fraction (2) is a micropore filter. 3. Device according to claim 1 or 2, characterized in that a residual water separator (12) is provided between the filter system (6) and the collecting container (7) for filtered solvent (8). 4. Device according to one of claims 1 to 3, characterized in that the filter device (10) for the waste water treated with a reaction separating agent is a filter cloth or filter bag. 5. Device according to one of claims 1 to 4, characterized in that a collecting trough (13) is provided, the base area of which is sufficient to accommodate the entire device and the capacity of which is at least the sum of the capacity of the sedimentation container (3), the collecting container (7) and the flocculation container (9). 6. Device according to one of claims 1 to 5, characterized in that a device for automatically detecting the boundary layer between the upper and lower fractions in the sedimentation container (3) is provided. 7. Device according to one of claims 1 to 6, characterized in that a automatic electronic control is provided.