Abstract
The invention relates to a water treatment line and a process for removing suspended solids, such as ferrous scale, and in particular also oils and greases, from cooling waters of metallurgical or steel processing. A sedimentation tank is included in which there is a lamellar pack filter with inclined sedimentation surfaces comprising a plurality of adjacent, essentially parallel and inclined tubular profiles, in particular with an angle of inclination with respect to the bottom of said tank of 50-65?. The application of the laminar packs in the tank which separate suspended solids, in particular ferrous scale, by sedimentation avoids the use of sand filters or the like.
Claims
1) A water treatment line comprising: (a) a device for removing suspended solids from liquids, in particular from water comprising: (a-1) a sedimentation tank with a solids collection sector; (a-2) in said tank a lamellar pack filter with sedimentation surfaces inclined with respect to the bottom of said tank; (a-3) in said tank a system for conveying the solids leaving said lamellar pack filter into said collection sector; and (a-4) a device configured to extract the solids from said solids collection sector, (b) upstream of said sedimentation tank one or more pre-treatment tanks for separating solids by gravity, optionally provided with one or more devices configured to extract solids, in particular one or more magnetic devices, and/or one or more oil skimmers, and (c) metal processing plants, in particular rolling mills or casting machines, quenching or tempering machines, pre-finishing or finishing machines, wherein preferably the cooling fluid is directly sprayed on the metal material, and wherein said metal processing plants feed said water treatment line and are located upstream of said device for the removal of suspended solids from liquids and of said one or more pre-treatment tanks; wherein the lamellar pack filter comprises a plurality of adjacent, essentially parallel and inclined tubular profiles.
2) The water treatment line according to claim 1, wherein said plurality of tubular profiles in cross-section corresponds to a honeycomb structure in which each tubular profile has a V shape.
3) The water treatment line according to claim 1, wherein the hydraulic radius is in the range between 1.5 and 3 cm.
4) The water treatment line according to claim 1, wherein the sedimentation surface is in the range between 6.25 and 13 m.sup.2/m.sup.3.
5) The water treatment line according to claim 1, wherein the lamellar packs do not have any magnetic elements or surfaces.
6) The water treatment line according to claim 1, wherein said device for the removal of suspended solids from liquids further comprises one or more oil skimmers arranged in the upper part of said sedimentation tank.
7) The water treatment line according to claim 1, wherein said lamellar packs are composed of modular units with an assembly of a given number of tubular profiles.
8) The water treatment line according to claim 1, wherein said device configured to extract solids from said solids collection sector is a magnetic device.
9) The water treatment line according to claim 1, wherein said sedimentation tank is connected downstream to a basin for redistributing of the liquids leaving said sedimentation tank to users using the purified liquid without further passage through cleaning devices.
10) The water treatment line according to claim 1, wherein said water treatment line excludes filter media through which fluids are guided to separate solids, in particular said water treatment line excludes sand filters.
11) A process for removing suspended solids from treatment waters comprising the following steps: (I) pre-treating treatment waters from metallurgical or steel plants or processes to remove solids, in particular metal scale, by gravity and/or magnetic effect and optionally to remove oils and greases; (II) passing the pre-treated waters through a lamellar pack filter with inclined sedimentation surfaces, within the water treatment line according to claim 1; and (III) directly returning the waters leaving the lamellar pack filter to said metal processing plants.
12) A method of using lamellar pack filters with inclined sedimentation surfaces, wherein each lamellar pack filter comprises a plurality of adjacent, essentially parallel and inclined tubular profiles, in particular with an angle of inclination with respect to the bottom of said sedimentation tank of 50-65? for separating ferrous scale and ferrous oxides from cooling waters or from lubricants coming from steel or metallurgical processes, comprising the steps of: pre-treating treatment waters from metallurgical or steel plants or processes to remove solids, including metal scale, by gravity and/or magnetic effect and to remove oils and greases; and passing the pre-treated waters through said lamellar pack filters with inclined sedimentation surfaces, wherein the waters leaving the lamellar pack filters are directly returned to said metal processing plants.
13. The water treatment line according to claim 1, wherein the plurality of inclined tubular profiles have an angle of inclination with respect to the bottom of said sedimentation tank of 50-65?.
14. The process of claim 11, wherein the step of passing further comprises subjecting the pre-treated waters to magnetic and/or oil and grease separations, before and/or after the passing of the pre-treated waters through the lamellar pack filters.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] FIG. 1 depicts an embodiment of a sedimentation tank with lamellar packs according to the invention in a longitudinal section.
[0065] FIG. 2 depicts two embodiments of configurations for one or more sedimentation tanks in a plant for removing suspended solids and oils/greases from treatment waters in top view.
[0066] FIG. 3 depicts in a perspective view an embodiment of a lamellar pack for the sedimentation tank according to the invention.
[0067] FIG. 4 depicts three embodiments of layouts for the tubular profiles which are components of the lamellar pack according to FIG. 3 in cross-sections.
[0068] FIG. 5 illustrates a plant for removing suspended solids and oils/greases from treatment waters in a metallurgy/steel plant according to the state of the art.
[0069] FIG. 6 illustrates an embodiment of a plant for removing suspended solids and oils/greases from treatment water in a metallurgy/steel plant according to the invention.
DETAILED DESCRIPTION
[0070] FIG. 1 depicts in longitudinal section an embodiment of a sedimentation tank 10 with lamellar packs 12. Below the lamellar packs 12 is a transport system, preferably a scraper belt 14 for removing solids separated from the lamellar packs 12 towards a conveying area, preferably lowered in the form of a pit 16 arranged in the bottom of the tank 10. A second conveyor system, preferably a belt 18, can optionally be provided above the lamellar packs 12 for conveying oils and/or greases to the oil skimmer 20, alternatively the tank 10 uses only the skimmer 20. The solids accumulated in the pit 16 consist mainly of metal scale which is extracted with a hoist 22 provided with a bucket 24. The scale accumulates in the pit 16 also by gravity when the water containing the suspended solids comes from different sources 26 in the tank 10. The water after the passage of the lamellar packs 12 and the removal of lighter oils and greases from the water from the surface 28 of the fluid is transferred through a weir 31 with siphon effect from a first chamber 10A to a second chamber 10B of the tank 10. From this chamber 10B, the clean water can be discharged at different levels 30a, 30b and 30c to be released into the ground or be pumped to further treatments and/or reuse as a cooling fluid in the metal processing plants from which the water being treated in the tank 10 originated. A level gauge 32 serves to indicate the water level in the tank 10.
[0071] FIG. 2 depicts two configurations for one or more sedimentation tanks as can be included in a plant for removing suspended solids and oils/greases from treatment waters in top view. Such configurations can respond to different capacity needs and/or spaces available within the plants with the use of cooling water which must then be subjected to treatment in the tanks. On the left is a series of sedimentation tanks 110 made of metallic carpentry and arranged in parallel with the relative lamellar packs 112 and the pits 116 for the collection of the separated scale. In the image on the right, instead, a single elongated tank 210 made of reinforced concrete with relative pit 216 and lamellar packs 212 can be seen. The variation of the geometry of the configurations, the number and dimensions of the tanks is facilitated by the fact that the lamellar packs can be assembled in modular form by a plurality of lamellar pack base units.
[0072] FIG. 3 depicts a perspective view of a lamellar pack 312 for a sedimentation tank. The lamellar pack 312 is composed of a plurality of adjacent profiles 311 which share a same wall along adjacent surfaces. The individual profiles 311 are combined without gaps between one profile and the other; each profile represents a channel for the passage of the fluid being settled.
[0073] FIG. 4 depicts three exemplary layouts for the profiles 311 a-c, which compose a lamellar pack according to FIG. 3, in cross-sections. All the profiles 311 a-c have in a preferential shape a V section which mimics a slide and favours the directing of the solids towards the tip of the V and in accordance with the more or less inclined arrangement of the profiles 311 a-c with respect to the bottom of the tank a downwards sliding thereof. The individual profiles from top to bottom are distinguished by the distance d between the walls and the maximum width 1 of the profiles 311 a-c, allowing to vary the number of profiles per sectional area and the surface available for sedimentation per m.sup.3. Obviously it is also possible to vary the length of the profiles 311 a-c and therefore the height of the relative lamellar pack.
[0074] FIG. 5 shows a plant for removing suspended solids and oils/greases from treatment waters which can be integrated in a metallurgy/steel plant according to the state of the art. From different metal processing plants, for example but not exclusively a bar quenching and tempering plant 434, a rod quenching and tempering plant 436, a reheating furnace 438 and a rolling mill 440, but also casting machines or other, cooling fluids emerge, in particular water dirty with oils and greases from lubrication and scale from the surface oxidation of metal objects, such as strips, bars, slabs, wires, rods etc.; the scale concentrates in particular in the cooling waters which are directly sprayed on the metal objects or on components in contact therewith such as the laminating rollers. From the processing devices 434 and 436 the dirty water with fine scale is directed to a recovery tank 442 with a water level meter 444 where the fine scale remains suspended in the tank 442 and recovered together with the water to the next tank 460B for the sand filtration treatment 478. The treatment waters from the processing devices 438 and 440 instead reach a pre-treatment tank 446 divided into two chambers 446A and 446B separated by a weir 448. A level gauge 450 detects the water level in the tank 446B. In the first chamber 446A, the largest scale that can be withdrawn with a relative electro-hydraulic bucket 452 fall by gravity. In the second chamber 446B, an oil skimmer 454 removes the oil from the surface. A first pump 456 withdraws water to be reintroduced to a new treatment in the first chamber 446A. A second pump 458 withdraws water to feed a longitudinal sedimentation tank 460, also divided into a first chamber 460A and a second chamber 460B connected by a weir 462 which allows a passage of surface water thus avoiding the passage of heavier elements possibly contained in the water which descend by gravity towards the bottom. In the first chamber 460A the heavier solids are deposited on the bottom. A translatable scraping device 464 scrapes the solids from the bottom and pushes them into the pit 466. An oil skimmer 468 removes oils and greases from the water. An electro-hydraulic bucket 470 removes the ferrous solids from the pit 466. The water thus deprived of oils and greases and of the larger scale passes to the surface, thus without heavy solids descending, through the weir 462 in the second chamber 460B. A level gauge 472 is included in the second chamber 460B. As described for the tank of FIG. 1, the water can be withdrawn from the second chamber at different levels 474 a-c, to be used for different applications or destinations. In the specific case, the bottom water still comprising sludge, i.e., finer solids which could not be separated in the longitudinal tank 460 are pumped with a relative pump 476 into a set of sand filters 478 to be filtered. The filtered water is conveyed with a relative network of pipes 484 leading to different applications or further processing, as it can be intended for the soil. For example, it can also be returned to the starting devices where it is again used to cool metal objects. The sand filters 478 become clogged over time due to the fouling which forms on the sand. They require a regeneration which occurs by introducing rinsing water through a relative supply network 486 from the bottom to the top, it is also possible to introduce an airflow 482. The washing water is then removed from the filters 478 through a relative drainage network 480 and can be subjected to cleaning steps, such as sludge treatment. The water thus cleaned can for example also be used for backwashing and introduced through relative lines 486 into the filters 478.
[0075] From the pre-treatment tank 442 the water can be directly passed with a relative pump 443 into the second chamber 460B of the longitudinal sedimentation tank 460.
[0076] FIG. 6 illustrates a plant for removing suspended solids and oils/greases from treatment waters from metallurgy/steel plants according to the invention. The left part of the plant corresponds to that of the state of the art of FIG. 5, equal reference numbers describe equal elements. Unlike the state-of-the-art system, the set of sand filters is completely missing, resulting in a huge saving of space. Also the sedimentation tank 10, which here corresponds to the one depicted in FIG. 1, has changed, it can be made with smaller dimensions with respect to that 460 of FIG. 5. There is always the hoist 22 with the electro-hydraulic bucket 24 which withdraws metallic/ferrous solids accumulated in the pit 16, there is an oil skimmer 20, the division of the tank 10 into two chambers 10a and 10B with a level meter 32. The two chambers 10a, 10B communicate through a weir 31. But unlike the longitudinal sedimentation tank of FIG. 5, the first chamber is not a simple gravity sedimentation chamber, but comprises the lamellar packs 12 which separate solids suspended in the water by sedimentation as described. The settled solids leaving the lamellar packs fall on the scraper belt 14 which transports them into the pit 16, as described above. The water leaving the water recovery tank 442 with fine scale here is not directed to the second chamber of the sedimentation tank 10B, but subjected to the treatment with lamellar packs 12 in the chamber 10a. The water deprived of solids in the tank 10 unlike the tank 460 can be directly reused in metallurgical plants 434, 436, 438, 440 or introduced into the ground or intended directly for other applications without further treatment; it is possible to completely avoid further treatment with sand filters.
