| JP01231910 | PRECIPITATOR |
| JP52109664 | SUCTION TYPE CYCLONE |
| JP08024884 | SUPERNATANT WATER DRAWING DEVICE OF BATCH TREATMENT TANK |
TUOMIKOSKI, Pekka (Valtakatu 4 A 11, Rauma, FI-26100, FI)
| Claims : 1. An apparatus for removal of surface scum, particularly in a circular processing space (1) such as a clarification tank or the like, said apparatus comprising mechanical processing means (2) making use of a surface skimming assembly (4) for the removal of surface scum floating to a surface (np) of liquid present in the processing space, by means of one or more surface scrapers (2a) rotating (w) around the center of the process space, and whereby the surface scraper (2a) , which is included in the processing means (2), has an element (2b) thereof, which is used for skimming surface scum to an outlet opening (4a) included in the surface skimming assembly (4), adapted to be rotatable (z) around a longitudinal axis (si) for scraping the surface scum along a baffle arrangement (op) , which controls movement of the skimming element (2b) in connection with the surface skimming assembly (4) and extends above the liquid surface (np) , in a manner that enables the rotating motion (w) of the surface scraper (2a) on a substantially constant level (t) , characterized in that the surface scum skimming element (2b) is provided with a flushing trough (2b2), which is provided with an inlet opening (A) extending in its standby position (I), prior to making contact with the baffle arrangement (op) , substantially below the liquid surface (np) , and which, while passing along a flushing chute (opl) of the baffle arrangement, assumes an inclined position (y) and delivers flushing liquid onto the flushing chute (opl) for facilitating the passage of surface scum to the outlet opening (4a) of the surface skimming assembly. 2. An apparatus as set forth in claim 1, char- acterized in that the surface skimming element (2b) comprises a skimmer surface (2bl) , extending continuously in its longitudinal direction and having its bottom end fitted with the flushing trough (2b2) in a manner rotatable (y) around a longitudinal axis (s2) and comprising bottom (pp) , front (es), rear (ts) and side walls (ss) . 3. An apparatus as set forth in claim 1 or 2, characterized in that, in the standby condition (I), the flushing trough (2b2) has its rear edge (At) below the liquid surface (np) for collecting surface liquid present in the processing space (1) into the flushing trough. 4. An apparatus as set forth in any of preceding claims 1-3, characterized in that, while passing along the flushing chute (opl) of the baffle arrangement, the flushing trough (2b2) is adapted to bring liquid therein to flow over a front edge (Ae) of the inlet opening. 5. An apparatus as set forth in any of preceding claims 1-4, characterized in that it includes an inclination control arrangement (3) for controlling a tilting movement (y) in connection with the baffle arrangement (op), such that, in the surface scum flushing sequence, the flushing trough (2b2) assumes a sufficient inclination for draining liquid therein onto the flushing chute (opl) , and in the surface scum expulsion sequence, a further advanced inclination for draining the surface scum present in the flushing trough into the outlet opening (4a) . 6. An apparatus as set forth in claim 5, characterized in that the inclination control arrangement (3) is implemented by the collaboration of curved baffle surfaces (3a) present on the opposite sides of the baffle arrangement (op) and an curved complementary surface (3b) established by a front wall (es) of the flushing trough. 7. An apparatus as set forth in any of preced- ing claims 1-6, characterized in that in connection with the flushing trough (2b2), such as at the upper edge of its front wall (es) and/or at the front edge of its bottom (pp) , are provided actuators (5) for keeping the baffle arrangement's flushing chute (opl) clean and/or for blocking the backward return of surface scum. 8. An apparatus as set forth in claim 7, characterized in that the actuators (5) comprise e.g. a ribbing that extends continuously in a longitudinal direction (s) . 9. An apparatus as set forth in claim 7 or 8, characterized in that the actuators (5) comprise a wiper that extends continuously in the longitudinal direction (s) and is made in a flexible material, such as rubber, plastics, silicone and/or the like. 10. An apparatus as set forth in any of preceding claims 1-9, characterized in that the' skimmer plate (2bl) and/or the flushing trough (2b2) are made in a substantially inflexible material, such as met- al, glass fiber, carbon fiber, plastics and/or the like . |
The invention relates to an apparatus for removal of surface scum, particularly in a circular processing space such as a clarification tank or the like, said apparatus comprising mechanical processing means making use of a surface skimming assembly for the removal of surface scum floating to a surface of liquid present in the processing space, by means of one or more surface scrapers rotating around the center of the process space. The surface scraper, which is included in the processing means, has an element thereof, which is used for skimming surface scum to an outlet opening included in the surface skimming assembly, adapted to be rotatable around a longitudinal axis for scraping the surface scum along a baffle arrangement, which controls movement of the skimming element in connection with the surface skimming assembly and extends above the liquid surface, in a manner that enables the rotating motion of the surface scraper on a substantially constant level.
Circular clarification tanks as described above have a long history of service with quite traditional en- gineering solutions. Hence, first of all, the clarification tank generally has its floor sloping towards its center, whereby a bottom sludge draining channel is located at the center of a clarification tank. On the other hand, the mechanical processing means em- ployed in traditional clarification tanks of the foregoing type are constructed e.g. by providing a clarification tank with one or more surface scrapers, rotating around the center of said clarification tank and being connected, e.g. by way of rigid shafts, to a bottom scraper for working the latter in synchronization with the surface scraper. In particular, the removal of surface scum in clarification tanks has been conventionally performed by using a skimming element rotating around a longitudinal axis as described above, its purpose being to draw surface scum with flushing water along a flush- ing chute extending above the water level and included in the surface skimming assembly, i.e. a so- called scum box, for enabling its removal to an outlet opening present in the middle of the scum box. However, the skimming elements of currently available surface scrapers have involved operational problems, resulting occasionally even from ordinary liquid tank surface level fluctuation. The reason for this is that, as the liquid level falls below a certain limit, the surface scum builds up on the flushing chute because the skimming element is not able to collect a sufficient quantity of flushing water along with surface scum for carrying it to the outlet opening. As a consequence, the surface scum dries, thus forming lumps and building up on scraper and scum box struc- tures and further in a discharge pipe system.
It is an objective of the apparatus according to the present invention to provide a decisive improvement in terms of the above-described problem and to there- by upgrade substantially the existing prior art. In order to achieve this objective, the apparatus according to the invention is principally characterized in that the surface scum skimming element is provided with a flushing trough, which is provided with an inlet opening extending in its standby position, prior to making contact with the baffle arrangement, substantially below the liquid surface, and which, while passing along a flushing chute of the baffle arrangement, assumes an inclined position and delivers flushing liquid onto the flushing chute for facilitating the passage of surface scum to the outlet opening of the surface skimming assembly. The volume of a flushing trough is determined by the quantity of flushing liquid, such as flushing water, necessary for the removal of surface scum in such a way that the surface scum passes quickly, without forming lumps and without freezing, out of the scum box and discharge pipe systems (approximately 8 to 12 liters) .
The most important benefits gained by an apparatus of the invention notably include the simplicity, working reliability and efficiency of its construction, assembly and operation, because, first of all, it enables ensuring the efficient and functionally reliable removal of surface scum from a circular processing space, such as a clarification tank, while at the same time minimizing in this respect the overhaul and maintenance demand of the discussed process apparatus. By virtue of a surface scum skimming element, configured according to the invention, the expulsion of surface scum from a process space is enhanced as both said element and the surface skimming assembly's flushing chute retain optimal moisture. Irrespective of liquid level fluctuations, the surface scum skimming element, configured according to the invention, always carries a sufficient quantity of flushing water along with surface scum, preventing, first of all, too much surface scum from accumulating on the liquid surface and, secondly, preventing it also from forming lumps. In a preferred embodiment, the surface scum skimming element comprises a longitudinally continuous skimmer surface, having its bottom end fitted with a flushing trough, which is rotatable around a longitudinal axis and comprises bottom, front, rear and side walls, and which, being suspended on a principle extremely simple in technical sense, in a so- called double link fashion, is able to moisten the flushing chute while carrying surface scum along the same .
Preferred embodiments for an apparatus of the inven tion are presented in relevant dependent claims .
The invention will be discussed in detail in the sub sequent specification with reference to the accompa nying drawings, in which fig. 1
shows in an overhead view a surface scraper according to the invention just approaching the location of a surface skimming assembly in a circular processing space, fig . 2
shows in an enlarged detail the head of a surface scraper of fig. 1, and show in perspective views a string of illustrations depicting sequential stages for one preferred surface scum skimming element, configured according to the invention, during its process of scraping surface scum into a surface skimming assembly.
The invention relates to an apparatus for removal of surface scum, particularly in a circular processing space 1 such as a clarification tank or the like. The apparatus comprises mechanical processing means 2 making use of a surface skimming assembly 4 for the removal of surface scum floating to a surface np of liquid present in the processing space, by means of one or more surface scrapers 2a rotating w around the center of the process space. The surface scraper 2a, which is included in the processing means 2, has an element 2b thereof, which is used for skimming sur- face scum to an outlet opening 4a included in the surface skimming assembly 4, adapted to be rotatable z around a longitudinal axis si for scraping the surface scum along a baffle arrangement op, which controls movement of the skimming element 2b in connec- tion with the surface skimming assembly 4 and extends above the liquid surface np, in a manner that enables the rotating motion w of the surface scraper 2a on a substantially constant level t, as shown in principle e.g. in fig. 3a. The surface scum skimming element 2b is provided with a flushing trough 2b2, which is provided with an inlet opening A extending in its standby position I, e.g. in a condition visualized in fig. 3a, prior to making contact with the baffle ar- rangement op, substantially below the liguid surface np, and which, while passing along a flushing chute opl of the baffle arrangement, as depicted e.g. in figs. 3b, 3c, assumes an inclined position y and de- livers flushing liquid onto the flushing chute opl for facilitating the passage of surface scum to the outlet opening 4a of the surface skimming assembly.
In a preferred embodiment, particularly in reference to figs. 3a-3f, the surface scum skimming element 2b comprises a skimmer surface 2bl, extending continuously in its longitudinal direction and having its bottom end fitted with a flushing trough 2b2 which is rotatable y around a longitudinal axis s2 and com- prises bottom p, front es, rear ts and side walls ss. In a standby condition I, shown e.g. in figs. 2 and 3a, the inlet opening of the flushing trough 2b2 has its rear edge At below the liquid surface np for collecting surface liquid present in the processing space 1 into the flushing trough.
In a further preferred embodiment, particularly in reference to figs. 3b and 3c, the flushing trough 2b2 is adapted, while passing along the flushing chute opl of the baffle arrangement, to bring liquid present therein to flow over a front edge Ae of the inlet opening.
Particularly in reference to a preferred embodiment depicted in the sequence of illustrations 3a-3f, the apparatus according to the invention further includes an inclination control arrangement 3 for controlling a tilting motion y of the flushing trough 2b2 in con- nection with the baffle arrangement op, such that, in the surface scum flushing sequence (figs. 3b, 3c), the flushing trough 2b2 assumes a sufficient inclination for draining liquid present therein onto the flushing chute opl and, in the surface scum expulsion sequence (figs. 3d, 3e) , a further advanced inclinatio for draining surface scum present in the flushing trough into the outlet opening 4a. In a return sequence, as shown in fig. 3f, the flushing trough 2b2 has a return to its standby position I "calmed down" by avoiding abrupt movements in a tilt rectification sequence which is somewhat quieter than the flushing sequence. In a further preferred embodiment, referring e.g. to fig. 3c, the inclination control arrangement 3 is implemented by the collaboration of curved baffle surfaces 3a present on the opposite sides of the baffle arrangement op and an curved complementary surface 3b established by a front wall es of the flushing trough.
In a further preferred embodiment, referring particularly to fig. 3a, in connection with the flushing trough 2b2, such as at the upper edge of its front wall es and/or at the front edge of its bottom pp, are provided actuators 5 for keeping the baffle arrangement's flushing chute opl clean and/or for blocking the backward return of surface scum. The ac- tuators 5 comprise e.g. a ribbing that extends continuously in its longitudinal direction and/or a wiper made in a flexible material, such as rubber, plastics, silicone and/or the like. It is understood that the invention is not limited to the embodiments illustrated or described above, but it lends itself to variations within the basic inven- tive concept according to any given conditions and application demands. Thus, first of all, it is clear that, depending on the size of a process tank, it is possible to employ one or several surface scrapers designed according to the invention, wherein the sur- face scum skimming element is made from any of a most diverse range of manufacturing materials, by using a most diverse range of manufacturing techniques, and having been assembled by a range of optional methods highly diverse in technical sense. Hence, e.g. the skimmer surface can be partly or completely made from a flexible material, whereby it is not absolutely necessary to connect it to the head of a surface scraper or to the flushing trough by means of a coupling that enables rotation around a longitudinal axis. Re- spectively, the mechanical processing means can be implemented in a highly diverse existing ways in terms of their mobility in a process space, although the embodiment shown e.g. in fig. 1, wherein the movement of a surface scraper is designed to be ef- fected by a chain running along the edges of a clarification tank, is preferred for practical reasons, especially because the chain is capable of being manufactured from plastics, which is another factor contributing to the optimally low overhaul and mainte- nance demand for an apparatus of the invention.
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