DE4142612A1 - Filtering aq. suspensions in filter column - with closed backflushing circuit fed with filtered liq., used for treating contaminated aq. solns., coolants and lubricants from metal machining, etc. - Google Patents

Abstract

Treatment of aq. media, contaminated with fine particles and sludges from machining or cleaning processes, involves passing the liq. from a dirty water tank through a labyrinthine filter column (filled with quartz sand, glass beads or the like) to a clean liq. tank. the column is periodically cleaned by back-flushing. Liq. is withdrawn from the clean liq. tank for back-flushing the column in a closed circuit. The contaminated back-flushing liq. is passed from the column to an additional bag filter. The cleaned back-flushing liq. is returned to the clean liq. tank. The contaminants, remaining in the filter bag are disposed of separately. A filter unit for carrying out the process is also claimed. USE/ADVANTAGE - The process is useful for treating contaminated aq. solns., coolant/lubricants, etc. from metal machining and cleaning processes. It provides optimal cleaning of the aq. media, recovers the back-flushing liq. as clean liq. and produces waste only in the form of dry particles which can be easily disposed of or opt. reused.

Description

The invention relates to a method and a filter system for the treatment of contaminated liquids after The preamble of claim 1 and 7 respectively.

State of the art

In metalworking processes such. B. grinding, Eroding, electrochemical removal or the like, as well as in all Metal cleaning process in industrial manufacturing fine particles and sludges are created by means of aqueous Solutions, cooling lubricants or the like must be removed.

EP 02 75 819 A2, for example, describes a Labyrinth filter for separating the smallest removal particles from Spark erosion machines have become known. This well-known  Filter is designed as a kind of sand bed filter, with a Filling from fine filter grains from quartz sand or the like. Maze filters or sand filters are used in industrial Manufacturing used for a variety of cleaning purposes. For example, sand filters are used for cleaning Swimming pools, chemical plants, municipal sewage treatment plants or the like used, the cleaning mechanical, biological or can run off chemically. For purely mechanical cleaning the dirt particles are attached to the Bound filter sand. Technically, these filters are called Columns with different diameters and heights and with quartz sand or quartz balls in a defined grain size filled. The one to be filtered is pumped Liquid pressed through the sand filter (labyrinth filter). So that the filter grains remain in the filter column are in usually at both ends of retaining elements fine-meshed wire or sieves. The passage width the wire mesh filter must be smaller than that Grain diameter of the filter medium, but larger than that too filtering dirt particles.

In addition to the physical effect of the adhesion of the Dirt particles enter the filter grains mechanically A filter effect caused by the build-up of dirt particles is effected. Crucial for one therefore, the filtering effect is satisfactory Flow speed in the filter column, for one should this be as slow as possible due to the adhesion to the others, however, should be as high as possible to achieve a satisfactory Achieve throughput. This discrepancy can be overcome by suitable selection of the filter column diameter in Connect the connection to a certain labyrinth height.  

The have a further influence on the filtering effect Viscosity of the medium to be filtered and the order of magnitude the dirt particles normal grinding particles in the order of 2 to 10 µ diameter, with fine grinding from 1 to 3 µ, with Eroding from 1 to 100 µ, during electrochemical removal from 1 to 2 µ and in industrial metal washing plants each depending on the application from 1 to 500 µ.

The well-known labyrinth filters / sand filters are based on declining cleaning effect through a backwashing process cleaned. The filter is usually passed through Acting in reverse flow direction with Clean liquid cleaned, the dirt particles from the Filter grains are detached and removed. The Filter cleaning by loosening the filter sand be supported by agitators or compressed air is achieved.

The soiled by the filter cleaning Backwash liquid is in turn in known systems separate settling tanks or into the sewage system guided. The disposal of the backwash liquid therefore makes again problems because they may have to be treated as hazardous waste is. Plants are also known in which the complete Filter medium, d. H. the filter grains replaced and is disposed of.

The invention has for its object a method and a filter system to treat the dirty To propose liquids, which one for one of the cleaning effects of the liquid is optimized. On the other hand, the problem of the disposal of the  Backwashing impurities in an environmentally friendly manner be solved.

This task is based on a process of introductory telling type by the characterizing Features of the method or device claim solved.

In the subclaims are advantageous and expedient Developments of the invention included.

Advantages of the invention

The method according to the invention with the associated system has the advantage that, in particular during the backwashing process Labyrinth filter / sand filter the backwash liquid in is fully recovered and not the sewer system or must be brought to a special landfill. As a result of that the backwash liquid in a closed circuit the sand filter to another downstream additional filter supplied, can be cleaned by the additional filter Backwash liquid recovered as pure liquid will. There is an additional filter for the Backwash liquid from a reusable Filter bag, which after blowing out with compressed air from the dirt particles can be freed. In the end remains therefore only dried dirt and abrasion left easily disposed of and reused if necessary can.  

Further details of the invention are in the following Description given and in connection with the Drawings explained in more detail. Show it

Fig. 1 shows a schematic structure of a filter unit,

Fig. 2 shows a schematic structure of the labyrinth filter / sand filter.

Description of the invention

The filter system 1 shown schematically in FIG. 1 is used for cleaning aqueous media, in particular liquids 2, such as those obtained in metalworking processes and cleaning processes. The contaminated liquid 2 is fed to a container 3 via a feed line 4 from the processing station, the container 3 being divided into a dirty liquid tank 5 and a clean liquid tank 6 . The contaminated liquid 2 is fed by means of a pump 7 via a line 8 to a labyrinth filter column 9 , which can be designed, for example, as a sand filter with a quartz sand filling or glass ball filling. An electromagnetic valve 10 serves to shut off the inlet line 8, in particular during the backwashing process.

The liquid cleaned in the filter column 9 reaches the clean liquid tank 6 via a line 11 with a solenoid valve 12 . The cleaned liquid 13 is removed from the pure liquid tank 6 via a line 14 and conveyed back into the machine circuit 16 or to the processing station by means of a pump 15 .

The labyrinth filter or sand filter 9 is shown in FIG. 2 and its structure is explained in more detail.

The labyrinth filter 9 is constructed as a filter column and consists of a cylindrical housing 17 with an upper end cover 18 with inlet connection 19 and a lower end cover 20 with outlet connection 21 . Inside the housing 17 is the filter medium 22 , consisting of quartz sand, glass balls or the like. The filter medium 22 is mounted on a lower retaining element 23 , which is designed as a type of sieve plate. The filter medium 22 itself occupies a filling volume with the height H _L and the diameter D within the housing 17 . Above the upper surface 24 of the filter medium 25 there remains a chamber volume with the height H _W, which serves as an additional swirl 25th The lower end cover 20 has an additional connecting piece 26 for compressed air. In the backwashing process to be explained, the compressed air supply 26 supports the fluidized bed formation of the filter medium, so that the entire height H _L and H _W serves as a swirling space. For the inclusion of the filter medium 22 within the housing 17 , an upper retaining element 27 for the filter medium is therefore provided in the upper region thereof.

Because of the very differently large diameter ranges of the dirt particles described above, the geometric ratio of the labyrinth filter column 9 must be optimized. Experimental research results have shown that a dimension ratio H _L : D = 2: 1 is selected as the optimal geometry ratio for labyrinth filtering, regardless of the grain size of the quartz sand or glass balls used. This also enables an optimal adaptation of the system to coarser dirt particles in connection with larger mesh sizes of the retaining elements 23 , 27 . The mesh size is always chosen so large that the filter grains of the filter medium 22 cannot pass through the retaining elements 23 , 27 .

The flow rate at the dimensional ratios mentioned strongly depends on the delivery capacity of the feed pump 7 . The volume flow of the liquid 2 to be cleaned can be throttled by means of the pump 7 or the valve 10 such that a flow rate of preferably 0.6 to 0.8 m / min. however max. 1 m / min. is achieved. Higher flow speeds reduce the adhesion effect within the labyrinth filter 9 and thus the purity of the filtered liquid.

Another process parameter is the inlet pressure. This must not be higher than 0.5 to 0.8 bar, which is explicitly the Volume flow corresponds to that Flow velocity maintained.

The dirt particles of the contaminated liquid 2 accumulate in the labyrinth filter 9 due to an adhesive effect on the quartz sand or the like and form a kind of precoat, especially in the upper inlet area, which gradually leads to an increase in the pump pressure of the pump 7 or a gradual reduction in the Throughput leads.

The labyrinth filter column 9 must therefore be subjected to a cleaning process from time to time. This is done by means of a backwashing process known per se, in which the filter medium 22 is cleaned by reversing the liquid flow within the labyrinth filter. For this purpose, cleaned liquid 13 is removed from the pure liquid tank 6 by means of the pressure pump 15 and fed via a branch line 28 with a control valve 29 in turn via line 11 to the lower connection 21 of the labyrinth filter 9 . In this position, the valve 12 in the feed line 11 to the tank 6 is closed. Similarly, a further valve 30 is closed to the consumer within the line 14 following the branch point 31 , so that the backwashing liquid only reaches the filter 9 .

The backwashing for cleaning the filter medium 22 within the labyrinth filter 9 therefore takes place via the line 14 , 28 , 11 , ie by reversing the liquid flow. The quartz sand grains or the glass balls are whirled up so that they occupy the entire interior of the cylindrical housing 17 between the retaining elements 23 , 27 . The quartz sand grains or the like rub against each other and release the dirt particles adhering to them to the backwashing liquid. The whirling up of the grains can be accelerated in a manner known per se by adding compressed air via the connecting line 26 into the filter column 9 , an intermittent addition of the compressed air having proven to be particularly efficient with regard to separating the dirt particles from the filter grains. A solenoid valve 32 is used to control the addition of the compressed air.

The backwashing process or the fluidized bed created by compressed air support leads to the longitudinal expansion of the filter medium 22 over the height H _L + H _W , ie up to the upper retaining element 27 . This larger space is needed for the intensive swirling and cleaning of the grains. D = 1: as the optimum aspect ratio for this swirl chamber 25, the ratio of H _W 1 has been shown, wherein _W H the height of the chamber 25 and D is the diameter of the filter column 9 is.

According to the invention, the backwashing process and thus the cleaning of the labyrinth filter column 9 takes place via an additional filter 33 . For this purpose, the backwashing liquid emerging from the upper connection piece 19 is fed via a node 34 to a line 35 with a solenoid valve 36 and was introduced into the additional filter 33 . The filter 33 has a fine-pored filter bag 37 in its interior, which is supported on a support basket 38 . The backwash liquid from the labyrinth filter 9 , which is cleaned in the additional filter 33 by means of the filter bag 37 , is then fed back to the clean liquid tank 6 via the line 39 , so that a closed circuit exists with respect to the backwash liquid. The filter bag 37 can consist of a fine-pored, disposable material. However, it is preferably designed as a reusable filter bag in order to generate the lowest possible environmental impact. For this purpose the valve 36 in the feed line 35 is closed after the backwashing process has taken place, so that the additional filter 33 can run empty. Via an additional supply line 40 in the upper region of the additional filter 33 with a corresponding control valve 41 , compressed air is pressed into the interior of the filter of the additional filter 33 and thus the dirt mass adhering to the filter bag 37 is dried. The filter bag can thus be removed from the filter 33 in the event of excessive contamination and the dirt particles can be disposed of in a dry form. As a result, the filter bag 37 is used as a reusable part. To carry out the backwashing process, the solenoid valve 10 between the dirty liquid tank 5 and the labyrinth filter 9 within the line 8 is closed, so that the backwashing liquid can be fed to the additional filter 33 in a closed circuit via the line 35 .

The backwashing liquid from the labyrinth filter 9 can also be temporarily stored or buffered in an intermediate tank, not shown; it is then fed from this intermediate tank to the additional filter 33 with filter bag 37 by means of a separate, preferably pressure booster pump.

The invention is not based on that shown and described Embodiment limited, but rather includes all professional training and improvements in the frame of the idea of the invention.

Reference list

1 filter system
2 aqueous media, liquids
3 containers
4 feed line
5 dirty liquid tank
6 pure liquid tank
7 pump
8 line
9 labyrinth filter column
10 Electr. Solenoid valve
11 line
12 Magnetic valve
13 cleaned liquid
14 line
15 pump
16 machine cycle
17 cylindrical housing
18 upper end cover
19 inlet supports
20 lower end cover
21 drain connector
22 filter medium
23 retaining element
24 top surface of 22 25 swirl chamber
26 connection supports for compressed air
27 retaining element
28 branch line
29 control valve
30 valve
31 balancing point
32 electric magnetic valve
33 filters
34 node
35 line
36 Magnetic valve
37 filter bags
38 support basket
39 discharge line
40 supply line for compressed air
41 control valve

Claims (9)

1. A process for the treatment of aqueous media which are contaminated with fine particles and sludges by ablative machining processes or cleaning processes, the liquid being fed from a dirty water tank to a labyrinth filter column filled with quartz sand, glass balls or the like and subsequently a pure liquid tank and the labyrinth Filter column is subjected to a backwashing process for cleaning from time to time, characterized in that during the backwashing process of the labyrinth filter column ( 9 ) in a closed circuit, the backwash liquid is removed from the clean liquid tank ( 6 ), so that the backwashing liquid contaminated during backwashing from the labyrinth filter column ( 9 ) is fed to a downstream additional filter ( 33 ) with a filter bag ( 37 ) and that the backwashing liquid cleaned in the additional filter ( 33 ) is returned to the clean liquid container ( 6 ) and remains in the filter bag ( 37 ) ibend pollution is disposed of separately. 2. The method according to claim 1, characterized in that the retained in the filter bag ( 37 ) of the additional filter ( 33 ) particles and sludge dried by means of compressed air and removed from the filter bag dried for further use. 3. The method according to claim 1 or 2, characterized in that the filter bag ( 37 ) is designed as a reusable bag which is carried within the additional filter ( 33 ) by means of a support basket ( 38 ). 4. The method according to claim 1, characterized in that the filter column diameter (D) of the filter medium ( 22 ) in the labyrinth filter column ( 9 ) is dimensioned such that in the labyrinth filter column ( 9 ) a flow rate ≦ 1 m / min . preferably 0.6 to 0.8 m / min. sets and that the inlet pressure is in particular about 0.5 to 0.8 bar. 5. The method according to one or more of the following claims, characterized in that during backwashing of the labyrinth filter columns ( 9 ) compressed air is supplied at intervals to achieve a fluidized bed. 6. The method according to one or more of the preceding claims, characterized in that the contaminated backwashing liquid is collected in an intermediate tank and is conveyed through the additional filter ( 33 ) by means of a booster pump. 7. Filter system for performing the method according to one or more of the preceding claims and in particular for the treatment of contaminated liquids according to the preamble of claim 1, characterized in that a dirty liquid tank ( 5 ) for the contaminated liquid, a labyrinth filter column ( 9 ) and this a clean liquid tank ( 6 ) is connected downstream and which is followed by an additional filter ( 33 ) with filter bag ( 37 ), the outlet of which is connected to the clean liquid tank ( 6 ) in order to carry out a backwashing process for cleaning the labyrinth filter column ( 9 ). 8. Filter system according to claim 6, characterized in that the height H _{L of} the filter medium ( 22 ) in the labyrinth filter ( 9 ) corresponds to twice the column diameter (D) of the filter medium ( 22 ). 9. Filter system according to claim 7 or 8, characterized in that above the surface ( 24 ) of the filter medium ( 22 ) a free volume is provided as an additional swirl chamber ( 25 ) with a height (H _W ), the height (H _W ) corresponds approximately to the diameter (D) of the filter medium ( 22 ).