WO1999051530A1

WO1999051530A1 - Flocculator apparatus

Info

Publication number: WO1999051530A1
Application number: PCT/NO1998/000118
Authority: WO
Inventors: Odd Paulsboe
Original assignee: Kvaerner Technology & Research Ltd.
Priority date: 1996-10-18
Filing date: 1998-04-07
Publication date: 1999-10-14
Also published as: NO964426D0; NO304880B1; NO964426L

Abstract

Flocculator apparatus in treatment plants with biological and/or chemical coagulation for treatment of waste water, comprising two concentric chambers (1, 1A, 2), of which an inlet chamber (1, 1A) has a lower, tangential inlet (4) causing rotation of the water in the chamber at the same time as the water moves upwards therein, and an immediately adjacent, second chamber (2), which on top receives water from the inlet chamber, whereby the water in part during continued rotation moves downwardly in the second chamber. The inlet chamber (1, 1A) is surrounded by the second chamber (2) and comprises a lower rotation chamber part (1A) and above this a flocculation chamber part (1). The flocculation chamber part (1) is widened generally conically upwards, and the second chamber (2) is a contact chamber where outflow of water at a lower portion (10) takes place at a minimum of rotational and sinking velocity.

Description

FLOCCUATOR APPARATUS.

This invention relates to a flocculator apparatus in treatment plants with biological and/or chemical coagulation for treatment of waste water. One of the necessary conditions for obtaining good purification results in treatment plants by e.g. chemical coagulation, is an optimal effect of coagulation chemicals being added. Traditional solutions in this connection have comprised special flocculation basins being subdivided into chambers, e.g. two to four chambers. In each chamber there is provided a mechanical stirring device, e.g. in the form of a gate or propeller. Specific detention times in such a flocculation basin based on common dimensional criteria, can be from 20-40 minutes. This detention time is related to the number of chambers. Such detention times in the traditional basins are generally too long and there will easily occur too much mechanical wear of the floes . This often leads to poor sedimentation properties and thereby an increased risk of sludge loss from subsequent separation steps. A proposal for an arrangement aiming at a more effective flocculation process, is described in International patent publication W093/17773. In replacement of conventional flocculation basins as discussed above, this patent publication comprises at static flocculator operating with significantly shorter detention times (4-8 minutes) than what was mentioned above. Shorter detention times involve savings both with respect to investment costs and operational costs.

The known arrangement just mentioned above, is designed for disposition immersed in a basin. The arrangement is divided into two chambers, of which an outer chamber constitutes an inlet chamber and has the highest water velocity. The inlet takes place at the lower edge of the chamber. The water is transferred to an inner chamber without bottom, where the water velocity is reduced. According to the patent publication this water transfer between the two chambers takes place by means of an upper horizontal slot at the water surface. This leads to sedimentation problems in the outer chamber at low hydraulic loads. In actual practice 2 this known arrangement is modified at this point, since the water transfer takes place through a vertical slot extending over the whole height of the outer chamber. This in turn as the drawback that short-circuit flows can occur between the two chambers, i.e. an uncontrolled flow having an unfavourable effect on the detention time.

The present invention aims at an improvement of the flow conditions compared to the previously known arrangement referred to above, in particular for obtaining a flow pattern being better controlled, where the various steps in the treatment process will have more favourable conditions, with a terminating, quiet outflow of water without any significant rotation and having a low sinking velocity.

Thus, on the above background the invention takes as a starting point an apparatus comprising two concentric chambers, of which an inlet chamber has a lower, tangential inlet causing rotation of the water in the chamber at the same time as the water moves upwards therein, and an immediately adjacent, second chamber which on top receives water from the inlet chamber, whereby the water in part during continued rotation moves downwardly in the second chamber. What is novel and specific in the apparatus according to the invention in the first place consist therein that the inlet chamber is surrounded by the second chamber and com- prises a lower rotation chamber part and above this a flocculation chamber part, that the flocculation chamber part is widened generally conically upwards, and that the second chamber is a contact chamber where outflow of water at a lower portion takes place at a minimum of rotational and sinking velocity.

The solution presented here results in a flow cross section in the total and general water flow path, increasing more or less regularly from the rotation chamber part upwards through the flocculation chamber part and then down- wards through the second chamber.

In an advantageous embodiment according to the invention the flocculation chamber part is provided on top with at least one, preferably tangentially directed, slot-shaped outlet for transferring water to the contact chamber, 3 whereby the outlet is directed in correspondence with the rotational direction of the water. Preferably according to the invention there are provided two or more pairs of diametrically opposed, slot-shaped outlets, being regularly distributed around the flocculation chamber part, namely at the upper portion thereof.

Transfer of water between the two main parts of the apparatus through tangential outlet slots as described here, contributes to a substantial degree to a favourable water flow through the whole apparatus.

The apparatus according to the invention will be explained more closely below with reference to the drawing, wherein: Fig. 1 shows a schematic and axial vertical section through the apparatus, i.e. according to the line

B-B in Fig. 2, and Fig. 2 shows the apparatus in Fig. 1 from above.

The exemplary embodiment in the drawing shows a structure having two main components, i.e. an inlet chamber con- sisting of a lower rotation chamber part 1A and immediately above this, a flocculation chamber part 1, and surrounding this a second, outer chamber 2. Chamber 2 is cylindrical and has a common axis with inlet chamber 1,1A. Due to the relative height dimensions between the two chambers, the upper perimeter 5 of the flocculation chamber part 1 lies lower than the upper edge 3 of the outer chamber 2 , and on the other hand a lower end portion of the rotation chamber part 1A is located below the downward limitation of chamber 2. An inlet 4 is directed tangentially into the rotation chamber part 1A at the lowermost portion thereof, for supplying water to be treated. Flocculation chamber part 1 has an upwardly conical widened shape, as indicated with a conicity angle 9, being in this example of a magnitude of 15°. It is obvious that the conicity can vary from plant to plant, but in most cases it is preferred that the conicity angle 9 is within a range from 10-30°, preferably between 15 and 20°.

For transferring water which during decreasing rotation moves upwards through flocculation chamber 1, to the second or outer chamber 2, there are formed two slot-shaped outlets 4 -

11 and 12, as will be seen in particular from Fig. 2. These outlet slots 11 and 12 are directed substantially tangen- tially from the upper portion of chamber part 1, so that the rotating flow pattern will be disturbed to a smallest pos- sible degree during transfer to the outer chamber 2. See in this connection the arrows denoted Rl, R2 and R3 for indicating the rotational direction of the water when flowing through the chambers which constitute the whole apparatus in the figures of drawings. According to the invention it is a great advantages to have two or more pairs of diametrically opposed outlet slots 11 and 12, these being in the case of several pairs of slots, regularly distributed around the circumference.

As a result of the tangential inlet pipe 4 the water is brought to rotate in the cylindrical rotation chamber 1A, and then the water rises up through the conical flocculation chamber 1, whereby the rotational velocity of the water gradually decreases upwards. This has to do with the conical widening of chamber 1 in the upward direction. When the water has been conveyed out through slots 11 and 12 it will sink through the outer chamber 2, at the same time as the rotational velocity continues to decrease, while the same rotational direction in maintained. Also the flow cross section as seen in the downward direction in chamber 2, expands in view of the conical shape of chamber l being located inwardly of chamber 2. The result of this design or configuration will be that vertical outflow of water, as indicated with arrow 10, takes place at a minimum of rotational and sinking velocity. Accordingly optimal sedimen- tation conditions will be obtained in the mass of water underneath the flocculator apparatus. Thus, it is here a precondition that the apparatus is located and immersed in a common sedimentation basin, which can have a rectangular, square or round main shape. Accordingly, the second or outer chamber 2 has no bottom, so that the complete circular flow cross section is at disposal for the downward water outflow as mentioned above, and as indicated with arrow 10.

In the case of installation of such an apparatus outside a common sedimentation basin as mentioned above, i.e. 5 - when it is arranged in dry surroundings, e.g. for use in front of a filter or similar separation equipment, there will normally be provided a bottom in chamber 2, with an associated outlet device, e.g. quite simply an outlet pipe (not shown) , which is preferably oriented tangentially. Fig. 1 shows supports 8 adapted to keep the inlet chamber parts 1 and 1A in position within the outer chamber 2. Such supports or suspension elements can also advantageously be located in the upper portion of the apparatus instead of a lower portion as in Fig. 1. Moreover, such elements should be shaped so as to influence at a smallest possible degree, the flow pattern of the water.

As a possible modification there is indicated in Fig. 1 with dashed lines 22, that the outer chamber 2 is not cylindrical, but downward conical. Such a design will further enhance the effect of a downward expanding flow cross section in chamber 2. The conicity angle 19 shown for chamber wall 22 can of course be varied, and in many cases it can preferably be equal to the conicity angle 9 of floc- culation chamber 1. Another variant, being of interest in particular in a dry arrangement of the apparatus without a bottom, consists in an inverse conicity of what is explained above, i.e. with a downward narrowing shape of the outer chamber 2. As a consequence of the process steps taking place in the apparatus as described, it is obvious that the second or outer chamber 2 can rightly be denoted contact chamber, since the floes being the result of the process in flocculation chamber 1, are here brought into contact with impurities in the water, namely in particular contamination particles, so that these can be collected and bound to the floes. This takes place in a very efficient manner in the apparatus described here.

In the case of a dry arrangement or embodiment of the apparatus, i.e. with a bottom in chamber 2 and an associated outlet, sedimentation in chamber 2 may occur, so that there should be provided a drain tap for necessary removal of sediments .

As regards the conical chamber shapes being discussed 6 above, it is obvious that the conicity can vary in the height direction, so that partially it can have a certain, given angle, whereas over other portions there can be a different conicity or possibly a cylindrical shape. This latter alternative applies in particular to the outer chamber wall 2.

Claims

7C l a i m s

1. Flocculator apparatus in treatment plants with biological and/or chemical coagulation for treatment of waste water, comprising two concentric chambers (1,1A,2), of which an inlet chamber (1,1A) has a lower, tangential inlet (4) causing rotation of the water in the chamber at the same time at the water moves upwards therein, and an immediately adjacent, second chamber (2) which on top receives water from the inlet chamber, whereby the water in part during continued rotation moves downwardly in the second chamber, c h a r a c t e r i z e d in that the inlet chamber (1,1A) is surrounded by the second chamber (2) and comprises a lower rotation chamber part (1A) and above this a flocculation chamber part (1) , that the flocculation chamber part (1) is widened generally conically upwards, and that the second chamber (2) is a contact chamber where outflow of water at a lower portion (10) takes place at a minimum of rotational and sinking velocity.

2. Apparatus according to claim 1, c h a r a c t e r i z e d in that the flocculator chamber part (1) at the upper portion is provided with at least one preferably tangentially directed, slot-shaped outlet (11,12) to the contact chamber (2) , oriented in accordance with the rotational direction (R2) of the water.

3. Apparatus according to claim 2 , c h a r a c t e r i z e d in the provision of two or more pairs of diametrically opposed, slot-shaped outlets (11,12) being regularly distributed around the upper portion of the flocculation chamber part (1) .

4. Apparatus according to claim 2 or 3 , c h a r a c t e r i z e d in that the upper circumferential edge (5) of the flocculation chamber part (1) is lower than the upper edge (3) of the contact chamber (2) . 8

5. Apparatus according to any one of claims 1-4, c h a r a c t e r i z e d in that the rotation chamber part (1A) is cylindrical.

6. Apparatus according to any one of claims 1-5, c h a r a c t e r i z e d in that the contact chamber (2) is cylindrical.

7. Apparatus according to any one of claims 1-5, c h a r a c t e r i z e d in that the contact chamber (22) is widened at least piecewise, in general conically downwards .

8. Apparatus according to any one of claims 1-7, c h a r a c t e r i z e d in that the conicity angle (9) of the flocculation chamber part (1) is within the range 10- 30┬░, preferably between 15┬░ and 20┬░.

9. Apparatus according to claim 7 and 8 , c h a r a c t e r i z e d in that the conicity angle (19) of the contact chamber (22) is substantially ec╧Çial to the conicity angle (9) of the flocculation chamber part (1) .

10. Apparatus according to any one of claims 1-9, c h a r a c t e r i z e d in that a lower end portion of the rotation chamber part (1A) extends below the contact chamber, and that the tangential inlet (4) is located at this lower end portion.