METHOD OF TREATING A COOLING CIRCUIT WATER CONTAMINATED WITH ORGANIC SUBSTANCES AND INORGANIC PARTICLES

Abstract

A method of treating cooling circuit water of industrial plants (2) contaminated with organic substances and inorganic particles, comprises the following steps: a) separating the organic substances and inorganic particles from the cooling circuit water to obtain precleaned cooling circuit water; b) cooling the precleaned cooling circuit water by an open cooling tower (11) to obtain cooled precleaned cooling circuit water; c) desalinating at least a partial volume flow of the cooled precleaned cooling circuit water by an desalination plant (14) to obtain cleaned cooling circuit water; and d) adding bacteria capable of degrading organic substances present in the cooling circuit water. The bacteria are added to the cooling circuit water before the separation in accordance with step a), before the cooling in accordance with step b) and/or before the desalination in accordance with step c), to form a biological cleaning stage.

Claims

1.-14. (canceled)

15. A method of treating cooling circuit water of industrial plants (2), in particular of a hot rolling mill (2), contaminated with organic substances and inorganic particles, comprising the following steps: a) separating the organic substances and the inorganic particles from the cooling circuit water so as to obtain a precleaned cooling circuit water; b) cooling the precleaned cooling circuit water by an open cooling tower (11) so as to obtain a cooled precleaned cooling circuit water; c) desalinating at least a partial volume flow of the cooled precleaned cooling circuit water by an at least one-stage desalination plant (14) so as to obtain a cleaned cooling circuit water; and d) adding bacteria capable of degrading organic substances present in the cooling circuit water, wherein the bacteria are added to the cooling circuit water before the separation in accordance with step a), before the cooling in accordance with step b) and/or before the desalination in accordance with step c), so as to form a biological cleaning stage.

16. The method according to claim 15, further comprising a step b1): separating, prior to step c), a residual amount of the organic substances and/or the inorganic particles contained in the partial volume flow of the cooled precleaned cooling circuit water.

17. The method according to claim 16, wherein separating in accordance with step b1) is carried out gravimetrically.

18. The method according to claim 16, wherein the inorganic particles are ferromagnetic, and wherein separating in accordance with step b1) is carried out by magnetic separation.

19. The method according to claim 15, wherein nutrients that promote growth of the added bacteria are added to the cooling circuit water before the separation in accordance with step a), before the cooling in accordance with step b), and/or before the desalination in accordance with step c), and wherein a ratio of added bacteria to added nutrients is reduced over time.

20. The method according to claim 19, wherein the bacteria and/or the nutrients are provided in the form of a granulate and are added to the water of a cooling circuit in the form of an aqueous solution, and wherein the bacteria in the granulate are lyophilized bacteria.

21. The method according to claim 15, wherein the cooling circuit water contaminated with the organic substances and the inorganic particles in accordance with step a) is passed through a settling basin (6), a clarifying basin (7) and/or a filtration purification device (8).

22. The method according to claim 15, wherein the cooling circuit water cleaned in accordance with step c) is fed to the industrial plant (2), if necessary after conditioning.

23. The method according to claim 15, wherein the desalination in accordance with step c) is carried out by reverse osmosis, by capacitive deionization or by thin film evaporation.

24. The method according to claim 15, wherein the bacteria are added only to the partial volume flow of the cooled precleaned cooling circuit water.

25. The method according to claim 24, wherein the partial volume flow is passed over a reactor (21) used to form the biological cleaning stage before the desalination in accordance with step c).

26. A plant (1) for treating cooling circuit water of industrial plants (2), in particular of a hot rolling mill (2), contaminated with organic substances and inorganic particles, comprising: a) a separation device (5) for separating the organic substances and the inorganic particles from the cooling circuit water in order to obtain precleaned cooling circuit water; b) an open cooling tower (11) through which the precleaned cooling circuit water can be cooled; c) an at least one-stage desalination plant (14), by means of which at least a partial volume flow of the cooled precleaned cooling circuit water can be desalinated, in order to obtain cleaned cooling circuit water; and d) a dosing device (16, 17, 18, 20) for adding bacteria capable of degrading the organic substances present in the cooling circuit water, wherein the dosing device (16, 17, 18, 20) is arranged upstream of the separation device (5), upstream of the cooling tower (11) and/or upstream of the desalination plant (14), so as to obtain a biological cleaning stage.

27. The plant (1) according to claim 26, wherein the dosing device (16, 20) is arranged in a bypass line (13) connecting the cooling tower (11) with the at least one-stage desalination plant (14).

28. The plant (1) according to claim 27, further comprising a reactor (21) arranged in the bypass line (13) and upstream of the at least one-stage desalination plant (14) and provided for forming the biological cleaning stage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a schematic illustration of a plant for treating cooling circuit water contaminated with organic substances and inorganic particles in accordance with a first embodiment,

[0039] FIG. 2 is a schematic illustration of a plant for treating cooling circuit water contaminated with organic substances and inorganic particles in accordance with a second embodiment,

[0040] FIG. 3 is a schematic illustration of a plant for treating cooling circuit water contaminated with organic substances and inorganic particles in accordance with a third embodiment, and

[0041] FIG. 4 is a schematic illustration of a plant for treating cooling circuit water contaminated with organic substances and inorganic particles in accordance with a fourth embodiment.

DETAILED DESCRIPTION

[0042] In the embodiment shown here, the plant 1 shown in FIG. 1 comprises a hot rolling mill 2 that is adjoined by a cooling circuit 3. The cooling circuit 3 comprises a plurality of aggregates, each of which is fluidically interconnected and will be explained in more detail below.

[0043] As shown, the hot rolling mill 2 is initially coupled to the cooling circuit 3, such that cooling circuit water that has been consumed in the hot rolling mill 2 and contaminated with organic substances, such as oils and greases, along with inorganic particles, such as scale in particular, is treated by the aggregates arranged in the cooling circuit 3 to such an extent that it can be fed directly back to the hot rolling mill 2. If the quantity of water of the cooling circuit should fall below a specific volume, additional fresh water can be added to the cooling circuit 3 via a fresh water inlet 4. If necessary, biocides, hardness stabilizers, flocculants and precipitating agents and other additives can be added to this.

[0044] The plant 1 shown in FIG. 1 initially comprises a separation device 5 for separating the organic substances and the inorganic particles from the water of the cooling circuit of the hot rolling mill 2, such that precleaned water of the cooling circuit is obtained. As can be seen from FIG. 1, the separation device 5 comprises a plurality of components connected in series. In the present embodiment shown, the separation device 5 comprises a settling basin 6 for separating a coarse fraction of a mixture of organic substances and inorganic particles, a clarifying basin 7 for separating an average size of the mixture of organic substances and inorganic particles, along with a filtration device 8, which generally comprises a plurality of filtration units. It should be noted that, in the present embodiment, only two filtration units 9, 10 of the plurality of filtration units of the filtration device 8 connected in parallel are shown as examples. In both filtration units 9, 10, a fine fraction of the mixture of organic substances and inorganic particles is separated. Each of the two filtration units 9, 10 of the filtration device 8 is in the form of a gravel filter in the present embodiment.

[0045] Furthermore, the plant 1 shown in FIG. 1 comprises an open cooling tower 11, via which the precleaned water of the cooling circuit can be cooled. In the cooling tower 11, the precleaned cooling circuit water is sprayed such that an aerosol is formed, which then condenses and cools down in the process. The cooled precleaned cooling circuit water then obtained (so-called blowdown water) is divided into a main volume flow and a partial volume flow. The main volume flow is fed to the hot rolling mill 2 via a main line 12. The partial volume flow is fed via a bypass line 13 to an at least one-stage desalination plant 14 and desalinated in order to obtain cleaned cooling circuit water, which is then fed to the hot rolling mill 2 via a return line 15. This results in a high savings of water. Another advantage is that the plant 1 can also be operated in regions that have little groundwater or river water in the immediate vicinity.

[0046] Desalination is preferably carried out according to the principle of reverse osmosis, capacitive deionization or thin film evaporation.

[0047] Within the cooling circuit 3, the plant 1 further comprises a dosing device 16 for adding bacteria that are suitable for degrading the organic substances present in the water of the cooling circuit. In the present case, the bacteria are formed as lyophilized bacteria. The dosing device 16 can be arranged upstream of the separation device 5, upstream of the cooling tower 11 and/or upstream of the desalination plant 14.

[0048] Alternatively, the dosing device 16 can also be arranged within the separation device 5 upstream of the settling basin 6, upstream of the clarifying basin 7 and/or upstream of the filtration device 8 (not shown).

[0049] In the embodiment shown here (FIG. 1), the plant 1 comprises a first dosing device 17 arranged upstream of the separation device 5 and a second dosing device 18 arranged upstream of the cooling tower 11, via which the bacteria are added to the cooling circuit 3.

[0050] The addition of the bacteria to the cooling circuit water significantly increases the service life of the membranes (not shown) used in the desalination plant 14. This is due to the fact that the organic substances, in particular oils and greases, and inorganic particles, in particular scale, which consists predominantly of iron (II,III) oxide, contained in the cooling circuit water form highly adhesive fine agglomerates, which cannot be completely removed by means of the separation device 5. The bacteria added to the cooling circuit 3 break down or metabolize the organic substances, in particular the oils and greases, which are responsible for the adhesive property of the fine agglomerates, such that the scale particles then bare in the cooling circuit water can no longer block the membranes due to the lack of adhesive property. When the bacteria are added throughout the entire cooling circuit 3, as shown in the present case, there is also the advantage that any aggregates of the cooling circuit 3 remain largely free of the sticky deposits that would normally have to be removed from the entire cooling circuit 3 at regular intervals and disposed of separately. The removal of such deposits, which include the organic substances along with the inorganic particles, can thus be additionally saved, which has a beneficial effect on the ongoing operating costs of the plant 1. In such embodiment, a biocide addition to the cooling circuit water is excluded, since the biocide would then destroy the biocoenosis formed by the bacteria in the settling basin 6, in the clarifying basin 7, in the filtration device 8, in the cooling tower 11 as well as in the respective lines.

[0051] Nutrients that promote the growth of the added bacteria are also added to the cooling circuit 3 via the two dosing devices 17, 18. The added nutrients promote the formation of a biocenosis by the bacteria and further favor their long-term existence. Preferably, it is thereby provided that the ratio of added bacteria to added nutrients is reduced over time. In this connection, it is particularly preferred that the bacteria are added as a function of the formation of a biocenosis. For the initial formation of a biocenosis in the cooling circuit 3, a higher concentration of bacteria is beneficial. A particularly preferred mixture of added bacteria and added nutrients contains 1% by weight of bacteria and 99% by weight of nutrients. On the other hand, to maintain an already formed biocenosis, an increased nutrient concentration is beneficial. Thus, the concentration of added bacteria decreases below 1% by weight with increasing application time, while simultaneously adding over 99% by weight of nutrients. The bacteria and the nutrients are provided in the form of a granulate and added to the cooling circuit water within a cooling circuit 3 in the form of an aqueous solution via the two dosing devices 17, 18.

[0052] The bacteria added to the water of the cooling circuit have different environmental requirements. Thus, the settling basin 6 is operated anaerobically, the clarifying basin 7 is operated anaerobically or aerobically, the filtration device 8 is operated anoxically and aerobically and the cooling tower 11 is operated aerobically.

[0053] FIG. 2 shows a second embodiment of the plant 1. In contrast to FIG. 1, the plant 1 comprises a second separation device 19, which is arranged between the cooling tower 11 along with the desalination plant 14 in the bypass line 13. If the concentration of the released solid scale particles in the blowdown water is too high for subsequent desalination, they can advantageously be separated initially by means of the second separation device 19. Since the scale particles have ferromagnetic properties, the separation can be carried out by magnetic separation in addition to the usual sedimentation. By separating the scale particles beforehand, the desalination membranes are protected and can be used longer, which has a beneficial effect on operating costs.

[0054] FIG. 3 shows a third embodiment of the plant 1. In contrast to the embodiment shown in FIG. 1, the bacteria are added locally to the cooling circuit water via a third dosing device 20. As shown, the bacteria in accordance with the present embodiment are only added to the partial volume flow of the blowdown water in order to dissolve the highly adhesive fine agglomerates formed from the organic substances, in particular oils and greases, and inorganic particles, in particular scale, which consists predominantly of iron (KIM oxide, for the downstream desalination. For this purpose, the plant 1 comprises a reactor 21 located downstream of the third dosing device 20, in which the biocoenosis is formed. The reactor 21 in the present embodiment is a biological fixed-bed reactor.

[0055] Since the cooling circuit formed upstream of the third dosing device 20 is thus not subject to biological purification, biocides and other additives are added via the two dosing devices 17, 18 in the embodiment shown here. Thereby, the biocides are added to the cooling circuit at intervals. In order to avoid inhibition of the biocenosis in the reactor 21, the bypass line 13 and the return line 15 are advantageously blocked via a shut-off valve (not shown) until the concentration peak has distributed in the system after approximately 3 hours and has reached a stable value.

[0056] Finally, FIG. 4 shows a fourth embodiment of the plant 1 which, in contrast to the previous embodiment (FIG. 3), comprises a second separation device 19, analogous to the embodiment shown in FIG. 2, for removing the inorganic scale constituents, which is arranged in the bypass line 13 downstream of the reactor 21 and serves to relieve the desalination stages.

LIST OF REFERENCE SIGNS

[0057] 1 Plant [0058] 2 Industrial plant/hot rolling mill [0059] 3 Cooling circuit [0060] 4 Fresh water inlet [0061] 5 Separation device [0062] 6 Settling basin [0063] 7 Clarifying basin [0064] 8 Filtration device [0065] 9 Filtration unit [0066] 10 Filtration unit [0067] 11 Cooling tower [0068] 12 Main line [0069] 13 Bypass line [0070] 14 Desalination plant [0071] 15 Return line [0072] 16 Dosing device [0073] 17 First dosing device [0074] 18 Second dosing device [0075] 19 Second separation device [0076] 20 Third dosing device [0077] 21 Reactor