TRIGLAVCANIN, Richard (10 Watkins Road, Dalkeith, Western Australia 6009, AU)
CLAIMS
1. An apparatus (1) for removing the surface material (2, 3) in connection with clarifying and/or thickening a solids-containing solution, whereby the apparatus comprises a clarification and/or settling tank (4), which is equipped with a feedwell (5) for the slurry to be settled, and discharge ports (6) for removing the thickened slurry and a rake (7) rotating on its drive shaft (8), which rake is for moving the underflow from the edges of the tank to the centre, at least one outer collection launder (9) adjacent periphery (10) of the tank (4), characterised in that, there is at least one radial element (11) at least partly inside the feedwell (5), which radial element is for supporting the feedwell and for guiding the surface material outside the feedwell (5) and outside the tank (4), when there is at least one scraping element (12), which is supported from above, to be movable in radial direction in relation to the radial element (11) for moving at least part of the surface material (2,3) of the feedwell and the thickener tank into the radial element (11).
2. An apparatus according to claim 1 , characterised in that, the radial element (11) comprises of at least one launder for guiding the surface material outside the feedwell.
3. An apparatus according to claim 1 , characterised in that, the scraping element (12) is connected to the drive shaft (8).
4. An apparatus according to claim 1 or 3, characterised in that, the scraping element (12) has scraping means (13) for moving at least part of the surface material (2, 3).
5. An apparatus according to claim 4, characterised in that, the scraping means (13) comprises of at least one scraping blade (14) inside the feedwell for removing the surface material outside the feedwell.
6. An apparatus according to claim 4 or 5, characterised in that, the scraping means (13) comprise of at least one scraping blade (14) inside the feedwell for removing the surface material outside the feedwell and at least one scraping blade (15) outside the feedwell (5).
7. An apparatus according to claim 5 or 6, characterised in that, at least part of the scraping blade (14, 15) is made of flexible material, such as rubber.
8. An apparatus according to claim 5, 6 or 7, characterised in that, the scraping blade (14, 15) is hinged in terms of the scraping element (12).
9. An apparatus according to claim 1 , 3 or 4, characterised in that, the scraping element (12) is as long as the tank radius (16).
10.An apparatus according to claim 1 or 2, characterised in that, the radial element (11) extends from periphery (10) of the tank towards the centre of the tank (4) inside the feedwell.
11.An apparatus according to claim 1 , characterised in that, the apparatus comprises of two scraping elements (12) and four radial elements (11).
12. A method for removing the surface material (2, 3) in connection with clarifying and/or thickening a solids-containing solution by an apparatus, which apparatus (1) comprises a clarification and/or settling tank (4), which is equipped with a feedwell (5) for the slurry to be settled, and discharge ports (6) for removing the thickened slurry and a rake (7) rotating on its drive shaft (8), which rake is for moving the underflow from the edges of the tank to the centre, at least one outer collection launder (9) adjacent periphery (10) of the tank (4), characterised in that, there is at least one radial element (11) at least partly inside the feedwell (5), which radial element supports the feedwell and guides the surface material outside the feedwell (5) and outside the tank (4), when there is at least one scraping element (12), which is supported from above, moving in radial direction in relation to the radial element (11) and moving at least part of the surface material (2,3) of the feedwell and the thickener tank into the radial element (11).
13. A method according to claim 12, characterised in that, the surface material (2) is firstly removed outside the feedwell (5) and then removed outside the tank (4).
14. A method according to claim 12, characterised in that, the scraping element (12) has scraping means (13), which moves at least part of the surface material.
15. A method according to claim 12, characterised in that, two scraping elements (12) move the surface material (2, 3) into four radial elements (11).
16. A method according to claim 12, characterised in that, the radial element (11) extends from periphery (10) of the tank towards the centre of the tank (4) inside the feedwell when the radial element supports the feedwell and guides the surface material outside the tank. |
THICKENER
This invention relates to an apparatus and method for removing the surface material in connection with clarifying and/or thickening a solids-containing solution.
The clarifying and thickening apparatus comprises a tank, into which the slurry to be clarified is fed via a feedwell, which is located in the centre of the clarification tank, generally in its upper section. The purpose of the feedwell is to ensure relatively uniform distribution and to prevent turbulence from the incoming feed liquid from disturbing the settling process taking place within the surrounding tank. When the term clarification is used later in the specification of the invention, it is used however to refer also to thickening, since the methods and apparatus described can usually be applied for both purposes. In addition to the slurry a flocculant used in clarification is fed into the feedwell. The flocculant is often mixed into the slurry while it is being fed into the feedwell. The clarification or thickening tank may be equipped with a rake operating near the bottom, or function without one. The clarified liquid, or overflow, is removed from the clarification tank as an overflow and the thickened slurry, or underflow, is removed from the central part of the tank bottom, to where it has been moved by the rake arms. The bottom of a thickening tank is usually inclined, i.e. sloping down towards the centre, whereby the removal of solids is made easier. The number of arms in the rake can be varied depending on the design solution.
In case where the feed liquid is partially aerated, the air bubbles, if allowed to pass from the feedwell into the main tank, tend to produce a considerable amount of relatively stable froth on the surface of both the feedwell and the thickener. This froth can contain a significant proportion of entrained solids and thereby tends to reduce the separation efficiency of the thickener. In addition, air bubbles can become trapped in the sludge, resulting in slower settling rates and lower underflow densities, both of which reduce separation efficiency further still.
Sometimes there are problems in clarifying slurries, for example thickening oil sands slurries; surface bitumen build-up becomes a process problem similar to that of froth in other applications. This becomes a critical issue in oil sands thickening where the build-up of bitumen eventually plugs the feedwell and restricts feed flocculation. Bitumen in oil sands is a product and as such its collection is of value. The feedwell is the first point of froth generation, because this is where the feed first enters. Logically this is where most of the air with attached particles hence froth is released from the feed. For normal concentrate duties these air bubbles with attached particles can also easily exit the feedwell or be released from the feed stream once the slurry has exited the feedwell. Hence froth build-up in the main body of thickener as well. The bigger problem is in oil sands where its not necessarily air bubbles with attached particles but oil or bitumen being part of the feed stream. This oil and bitumen builds up in the feedwell and eventually becomes a large layer in the feedwell causing thickener process issues.
The purpose of the present invention is to provide an apparatus and method for removing the surface material in connection with clarifying and/or thickening a solids-containing solution. Furthermore the object is to provide a more effective way to remove the surface material by providing in connection with the apparatus at least one radial element being at least partly inside the feedwell, when there are means for moving at least part of the surface material into the radial element and means for guiding the surface material outside the feedwell. According to the embodiment of the invention there is at least one scraping element to be movable in radial direction in relation to the radial element for moving the surface material into the radial element. There are many advantages for the invention. According to the apparatus and method of the invention the harmful surface material, such as buildups of oil and bitumen can be advantageously removed from the surfaces of both the feedwell and the tank. The essential features of the invention become evident from the appended claims.
In the following the preferred embodiments are described in more details with reference to the accompanying drawings, where
Fig. 1 is a side view illustration of a preferred embodiment of the invention Hg. 2 is a top view of Fig 1 in a direction A
Figures 1 and 2 show an apparatus 1 for removing the surface material 2, 3 in connection with clarifying and/or thickening a solids-containing solution such as finely ground ore suspended as pulp in a suitable liquid medium, such as water. The apparatus 1 comprises a clarification and/or settling tank 4 for containing liquid pulp, which tank has right cylindrical sidewalls defining a periphery 10 and centrally downwardly sloping floor. The drive shaft 8 is centrally rotatably mounted within the tank 4. In the tank 4 there is recycled some of the dilute liquid (liquor) overflow from the top of the thickener tank 4 back to the feedwell 5 in order to dilute the inflowing pulp. A feedwell 5 is for the slurry to be settled. The feedwell 5 is located centrally in the tank 4, and the feedwell is supplied via a feed line. The feedwell has a restricted bottom opening in fluid communication with the tank, and through which a liquid pulp in the feedwell can flow into the tank. There are discharge ports 6 for the settled solids or underflow in the centre of the settling space where the thickened pulp is drawn off. There is at least one outer collection launder 9 adjacent periphery 10 of the tank 4, where the excess overflow ends and is discharged from there on to a discharge pipe 17. Outer collection launder 9 could reach the whole periphery of the tank or part of it. Outer collection launder is fixed outside or inside of the periphery of the tank. Also there is a rake 7 rotating on its drive shaft 8, which rake is for moving the underflow from the edges of the tank to the centre. A flocculant agent is added and mixed into the suspension. In normal operation the flocculation takes place in the feedwell 5, whereby a bed of thickened pulp settles to displace an upper layer of relatively dilute liquid towards the top of the tank. The thickened slurry is removed from below through discharge ports 6 like underflow withdrawal pipes.
According to the invention there is at least at least one radial element 11 being at least partly inside the feedwell 5, when there are means for moving at least part of the surface material 2, 3 into the radial element and means for guiding the surface material outside the feedwell 5. Radial element means that it extends radially in the tank 4 or inside the feedwell 5. The radial element could only reach a little way inside the feedwell. According to the example of invention there are four radial elements 11 extending from periphery 10 of the tank towards the centre of the tank 4 at least partly inside the feedwell 5. Radial element according to this example also supports the feedwell 5 and guides at least part of the surface material 2 and 3 outside the feedwell and when needed outside the tank 4. When the support is given by the radial element, there is not needed any extra support systems from above for the feedwell. The removal of the surface material can be highly improved by using four radial elements. The radial element extends inside the feedwell, collects the surface material, such as froth inside feedwell and then froth flows down the radial elements 11 , such as launder or pipe out of the feedwell, which launder or pipe could extend to the periphery of the tank and further to a discharge pipe 17 outside of the main body of thickener. The surface material 2 of the feedwell could be firstly removed outside the feedwell 5 and then removed outside the tank 4. According to this example the radial element 11 is connected at its one end into the periphery 10 of the tank and extends inwards in the tank there from. The radial element 11 has an overflow lip 18, which defines the level of the surface material 2 and 3, such as froth, bitumen, oil or other harmful material. The radial element is connected to the feedwell 5 by any attaching means. The number of radial elements 11 could be changed, but at least one is needed in order to support the feedwell 5 and for collecting the harmful surface material. According to the example there are four radial elements 11 , which all function both as a support for the feedwell and collect the surface material. It also could be so, that two of them just supports the feedwell.
According to the invention there is at least one scraping element 12 to be movable in radial direction in relation to the radial element 11 and for moving the surface material into the radial element. Means for moving the surface material inside into the radial element could also be a pump located under the surface material. According to the embodiment of the invention the scraping element 12 is connected to the drive shaft 8 above the radial element. According to the example there are two scraping elements 12 connected to the drive shaft 8, which elements 12 move in radial direction in relation to the four radial elements 11. The scraping element 12 has scraping means 13, for moving at least part of the surface material 2, 3, such as into the radial elements. The scraping element 12 rotates axially around the drive shaft 8 and scrapes the surface material 2, 3 by using its scraping means 13 over the overflow lip 18 of the radial element 11 such as launder. The scraping means 13 consist of at least one scraping blade 14 inside the feedwell and at least one scraping blade 15 outside the feedwell 5, which means the tank 4 area outside the feedwell. According to the example of the invention the scraping blades 14, 15 are made of flexible material, such as rubber. The scraping blades 14, 15 could be hinged in relation to the scraping element 12, whereby they could pivot under the scraping element 12 when moving the surface material into the radial element 11. The scraping element 12 and the radial element 11 are made of any resistant material such as steel. According to the invention the harmful material from the surfaces both from the feedwell and thickener tank can considerably be removed. The scraping element could for example only be used for scraping the surface of the feedwell or only the surface of the tank. The scraping element 12 extends radially for example from the tank periphery 10 into the drive shaft 8 or is as long as the tank radius 16.
The radial elements 11 according to this example extend from periphery 10 of the tank towards the centre of the tank 4 inside the feedwell. The radial element 11 consists of at least one launder or of many launders connected to each other in radial direction or pipes, collection boxes that then transport the material outside the thickener tank and same time support the feedwell. There could be
mounted as many radial elements as needed, when different radial elements are mounted circumferentially, advantageously at even distances around the drive shaft.
While the invention has been described with reference to its preferred embodiments, it is to be understood that modifications and variations will occur to those skilled in the art. Such modifications and variations are intended to fall within the scope of the appended claims.