The invention relates to a method and an apparatus for removal of surface scum according to the preambles of the independent claims related thereto. The invention is meant to be utilized particularly with an apparatus in a circular processing space, such as a in a clarification tank or the like.
Circular clarification tanks have a long history of service with quite traditional engineering 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. The mechanical processing means for their part, being employed 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 scraper part that exists at an end of a surface scraper and that rotates in an essentially vertical plane, which makes possible rotating movement of the surface scraper in a same level in a direction of height of the processing space. The purpose of the scraper part is to draw surface scum together with escort water along an escort chute of a surface scraper arrangement, i.e. a so-called scum box, reaching above the water surface; so that it can be removed to an outlet opening present in the the scum box. However, the scraper parts 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 escort chute because the scraper part is not able to collect a sufficient quantity of escort water along with the surface scum for carrying it to the outlet opening. As a consequence, the surface scum dries, thus forming lumps and building up on the scraper and the scum box structures and further in a discharge pipe system. The above problems are emphasized particularly under cold circumstances due to freezing, in which case the adverse effect of the small quantity of escort water is further emphasized.
It is an objective of the method and the apparatus for removal of surface scum according to the present invention to provide a decisive improvement in terms of the above-described problems and to thereby upgrade substantially the existing prior art. In order to achieve this objective, the method and the apparatus according to the invention are principally characterized by what has been presented in the characterizing parts of the independent claims related thereto.
The most important benefits gained by the method and the apparatus according to the invention notably include the simplicity, working reliability and efficiency of the constructions applicable for the same as well as assembly and operation thereof in practise, which is particularly thanks to the removal of surface scum being carried out in a differing manner, when compared to so called traditional way of thinking, whereby the surface scum is being flushed to the outlet opening of the surface scum removal arrangement by using an adequately large quantity of surface water of the processing space. Thus, by virtue of the invention, first of all, ensuring the efficient and functionally reliable removal of surface scum from a circular processing space, such as a clarification tank, can be ensured, while at the same time minimizing in this respect the overhaul and maintenance demand of the discussed process apparatus. By an adequately strong flushing of the surface scum, the surface scum is not able to get collected in the surface scum removal arrangement, thanks to which it is not able to form lumps, either. This has been carried out by using a closing arrangement, when viewed in the rotating direction of the surface scraper, at a front edge of the surface scum removal arrangement, so that it is being opened and closed essentially before the guide part of the surface scraper enters at the point of the front edge of the surface scum removal arrangement. The invention furthermore enables operation of a block plate of the closing arrangement in a so called self operated manner, so that it is being controlled mechanically by using mutual driving means between the surface scraper and the closing arrangement, which is carried out profitably by co-operation of a counterpart, existing at an end of the surface scraper; and a guide element, being coupled with the block Plate, the guide element getting back to its stand-by position and returning the block plate to its closing position profitably in a gravity operated manner.
Other preferred embodiments for the method and the apparatus according to the invention are presented in the dependent claims related thereto.
The invention will be discussed in detail in the subsequent specification with reference to the accompanying drawings, in which
a-3f show in front and side views the removal of surface scum operating according to the invention in succesive phases, while the surface scraper rotates in the processing space, while the head of the surface scraper moves over the surface scum removal arrangement.
The invention relates first of all to a method for removal of surface scum by means of an apparatus particularly in a circular processing space 1, such as a clarification tank as shown e.g. in
As an advantageous embodiment of the method according to the invention, the closing arrangement 4, when viewed in the rotating direction w of the surface scraper 2a, at a front edge 3a1 of the surface scum removal arrangement 3 is being opened o and closed s essentially before the guide part 2a; 2a1 of the surface scraper enters the point of the front edge 3a1 of the surface scum removal arrangement.
Furthermore as an advantageous embodiment Of the method according to the invention, operation of the closing arrangement 4, such as a block plate 4a being arranged movable essentially in the direction of height h, is being controlled mechanically by using mutual driving means between the surface scraper 2a and the closing arrangement 4, such as by a co-operation as shown in
Furthermore as an advantageous embodiment of the method, an opening advance timing of the closing arrangement 4 is being set by adjusting a distance e of the counterpart 2a3 at the end of the surface scraper suitable in respect with the guide part 2a1 of the surface scraper.
Furthermore as an advantageous embodiment of the method, the closing arrangement's 4 opening movement, such as its duration and movement speed in the direction of height h, is being regulated by changing a shape or length of the guide element 4a1 or in a corresponding manner.
The invention relates on the other hand also to an apparatus for removal of surface scum particularly from a circular processing space 1, such as a clarification tank as shown in
As an advantageous embodiment of the apparatus according to the invention, the closing arrangement 4 arranged, when viewed in the rotational direction w of the Surface scraper 2a, a front edge 3a1 of the surface scum removal arrangement 3 comprises a block plate 4a or like that is arranged movable essentially in the direction of height h by a slide rail arrangement 4b or in a corresponding manner.
As a furthermore advantageous embodiment of the apparatus according to the invention, the opening and closing movements o, s of the closing arrangement 4 are arranged mechanically by using mutual driving means between the surface scraper 2a and the closing arrangement 4, such as by a co-operation as shown in
Furthermore as an advantageous embodiment of the apparatus according to the invention, the guide element 4a1 is arranged to get back to its stand-by position I and to return the block plate 4a to its closing position in a gravity operated manner.
The driving means being carried out according to
Furthermore as an advantageous embodiment of the apparatus according to the invention, the closing arrangement 4 is adjustable for the part of its opening advance timing by making the distance e of the counterpart 2a3 at the end of the surface scraper in respect with the guide part 2a1 of the surface scraper adjustable and/or for the part of the closing arrangement's 4 opening movement, such as regarding its duration and movement speed in the direction of height h, by changing a shape or length of the guide element 4a1 or in a corresponding manner.
It is to be understood that the invention is not limited to the embodiments illustrated or described above, but it lends itself to variations within the basic inventive 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 surface scum scraping parts are 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. Respectively, the mechanical processing means utilized in the invention 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
Number | Date | Country | Kind |
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20135330 | Apr 2013 | FI | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FI2014/050202 | 3/19/2014 | WO | 00 |