WO2022223868A1

WO2022223868A1 - Reactor arrangement and use thereof

Info

Publication number: WO2022223868A1
Application number: PCT/FI2021/050287
Authority: WO
Inventors: Marko Latva-Kokko; Ville STRÖMMER; Jiliang Xia
Original assignee: Metso Outotec Finland Oy
Priority date: 2021-04-19
Filing date: 2021-04-19
Publication date: 2022-10-27
Also published as: EP4326427A1; CN115212828A; CN218222402U

Abstract

A reactor arrangement (100) and uses thereof. The arrangement (100) comprises a reactor tank (10), a draft tube (1) arranged in the reactor tank (10), and an impeller (8) arranged in the immediate vicinity of a lower end (6) of the draft tube (1). The wall (2) of the draft tube comprises openings (3) through said wall so that the total surface area of the openings (3) as a percentage of the total outside surface area of the draft tube (1) is 4 % at most.

Description

REACTOR ARRANGEMENT AND USE THEREOF

BACKGROUND

The invention relates to a reactor arrangement.

The invention further relates to uses of the reactor ar rangement.

In leaching of concentrate and minerals from slurry, such as for example metal concentrate, the participatory oxygen needed in the leaching process is introduced in the form of oxygen or gas containing oxygen and dissolved into the solid-containing slurry, so that the oxygen can partici pate in the leaching reactions of the solid matter. A high reactor provided with a draft tube is used for the disso lution of the oxygen, whereupon a high hydrostatic pres sure, such as 1.5-3.0 atm i.e. 0.15-0.30 MPa, is formed at the bottom of the reactor. Said high hydrostatic pressure promotes the dissolving of the oxygen in the slurry.

A problem arises if the free surface of the slurry falls under an upper end of the draft tube. Then, the slurry may not flow in the draft tube. This may cause mechanical stress and vibration of the draft tube, and the safe oper ation of the reactor may be jeopardized.

BRIEF DESCRIPTION

Viewed from a first aspect, there can be provided a reac tor arrangement, comprising a reactor tank, a draft tube arranged in the reactor tank, and an impeller arranged in the immediate vicinity of a lower end of the draft tube, wherein, the wall of the draft tube comprises openings through said wall, and wherein the total surface area of the openings as a percentage of the total outside surface area of the draft tube is 4 % at most. Thereby a reactor arrangement that can be run safely also during situations where slurry level is on lower level than the upper end of the draft tube without sacrificing the reactor performance during normal operation may be achieved.

The arrangement and the method are characterised by what is stated in the independent claims. Some other embodi ments are characterised by what is stated in the other claims. Inventive embodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of sever al separate inventions, especially if the invention is ex amined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups. Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be ap plied to other embodiments.

In one embodiment, the total surface area of the openings as a percentage of the total outside surface area of the draft tube is in range of 0.5 % - 4 %. In one embodiment, the total surface area of the openings is in range of 0.5 % - 2 %.

An advantage is that the reactor performance during situa tions where slurry level is lower than draft tube height may be optimized without sacrificing the reactor perfor mance during normal operation.

In one embodiment, at least one of the openings is round. An advantage is that the relation of flowing capacity of the opening is maximised in relation to the circumference thereof.

In one embodiment, the width of the opening as a percent age of the outer diameter of the draft tube is in range of 5 % - 30 %, preferably 10 % - 20%.

An advantage is that a proper flow in the draft tube may be achieved without jeopardizing mechanical strength thereof.

In one embodiment, the openings are arranged in opening groups comprising at least two openings and arranged suc cessively in longitudinal direction of the draft tube, and wherein in longitudinal direction of the draft tube, a distance between adjacent opening groups is larger than between the openings arranged in a same opening group.

An advantage is that flow in the draft tube may be en hanced on those sections of the draft tube comprising said opening groups.

In one embodiment, the openings are evenly spaced between an opening closest to an upper end of the draft tube and an opening closest to a lower end of the draft tube.

An advantage is that a steady flow in the draft tube inde pendent from the level of free surface may be achieved.

In one embodiment, the openings are of a quantity and po sition such that a fluid is capable to flow through the openings in the draft tube along substantially the entire length of the draft tube between the opening closest to a upper end of the draft tube and the opening closest to a lower end of the draft tube. An advantage is that a steady flow in the draft tube inde pendent from the level of free surface may be achieved. In one embodiment, there is a lengthwise section in the draft tube extending from the opening closest to the upper end to the opening closest to the lower end, and wherein the total area of the openings arranged in a upper half of said lengthwise section closest to the upper end is at least 50 % of total area of all the openings arranged in the lengthwise section.

An advantage is that the flowing capacity of the openings is concentrated to the upper sections of the draft tube where hydrostatic pressure is low, and thus a satisfactory flow in those sections in the draft tube may be ensured.

In one embodiment, the total area of the openings arranged in the upper half of said lengthwise section is at least 60 %.

An advantage is that the satisfactory flow in the upper sections of the draft tube may be ensured even more. In one embodiment, at the upper end of the draft tube there is arranged an upper conical extension for slurry inflow, the diameter of which upper conical extension ta pers towards the draft tube. An advantage is that the slurry inflow may be intensified.

In one embodiment, there is a first clearance without openings between the opening closest to the upper end and said upper end, the first clearance being not more than the draft tube diameter. In one embodiment, the first clearance is in range of 0.5 x D - l x D. An advantage is that an undisturbed slurry inflow at the upper end of the draft tube may be ensured. In one embodiment, at a lower end of the draft tube there is arranged a lower conical extension for accommodating an impeller, the diameter of which lower conical extension tapers towards the draft tube. An advantage is that the diameter of the impeller may be larger than the draft tube, and thus a more effective pumping may be achieved.

In one embodiment, the inner surface of the draft tube is provided with one or more blocking elements, such as baf fles, that is/are arranged to extend in the direction of the longitudinal direction.

An advantage is that the downward flow in the draft tube may be controlled.

In one embodiment, the draft tube is arranged concentri cally with the reactor tank. An advantage is that a radially symmetric and uniform mix ing in the reactor tank may be achieved.

In one embodiment, there is a bottom clearance between a median level of the impeller and a bottom of the reactor tank, the bottom clearance being in range of 0.8D - 1.5D.

An advantage is that an optimized room between the impel ler and the bottom of the reactor tank for creating an op timized slurry flow that enhances dissolving gas into the slurry may be achieved. In one embodiment, the distance between the median level of the impeller and the lower end of the draft tube is 0.5 X D at most. In one embodiment, the distance between the median level of the impeller and the lower end of the draft tube is 0.25 X D at most.

An advantage is that dissolving gas into the slurry may be enhanced.

In one embodiment, the impeller is arranged partly inside of the draft tube.

An advantage is that the flowing capacity of the draft tube may be enhanced.

In one embodiment, the impeller is arranged completely outside of the draft tube.

An advantage is that dissolving gas into the slurry may be enhanced.

In one embodiment, the arrangement comprises only one im peller.

An advantage is that a high local mixing power intensity is obtained at the bottom of the reactor where gas feed is arranged, and thus gas to liquid mass transfer may be en hanced.

In one embodiment, there is a top clearance between the upper end of the draft tube and an overflow, the top clearance being 1.0D at most.

An advantage is that the length of the draft tube may be optimized without jeopardizing the normal operation of the arrangement. In one embodiment, the inner wall of the reactor tank is cylindrical having an inner diameter, and the ratio of said inner diameter to the outer diameter of the draft tube, that is R/D, is selected in range of 2 - 4.

An advantage is that the flowing capacity of the draft tube may be optimized in relation to the volume of the re actor tank.

In one embodiment, an inner height of the reactor tank is at least 10 m.

An advantage is that high hydrostatic pressure that pro- motes the dissolving of the oxygen in the slurry may be achieved.

In one embodiment, at least one blocking element, such as a baffle, is arranged to an inner wall of the reactor tank.

An advantage is that an effective structure for working the flow pattern in the reactor tank may be achieved. In one embodiment, the impeller is arranged for creating a downward directed suck in the draft tube.

An advantage is that the flowing capacity of the draft tube may be enhanced.

In one embodiment, the impeller is arranged at least part ly outside of the draft tube.

An advantage is that the flow pattern in the reactor tank and outside the draft tube may be effectively influenced by the impeller. In one embodiment, the impeller is arranged for creating a radially directed flow in the reactor tank. An advantage is that an effective dispersion of gas in the slurry may be achieved.

In one embodiment, there is a second clearance between the opening closest to the lower end and the lower end, the second clearance being 1 - 2 times of the draft tube diam eter.

An advantage is that impairing of the pumping efficiency of the impeller caused by the openings may be alleviated.

BRIEF DESCRIPTION OF FIGURES

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which

Figure 1 is a schematic side view of a reactor arrangement in partial cross-section,

Figure 2 is a schematic side view of a draft tube,

Figure 3 is a schematic side view of another draft tube,

Figure 4 illustrates some embodiments of openings, and Figure 5 is a schematic view of a detail of a draft tube.

In the figures, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures. DETAILED DESCRIPTION

Figure 1 is a schematic side view of a reactor arrangement in partial cross-section. The reactor arrangement 100 com prises a reactor tank 10, a draft tube 1 arranged in the reactor tank 10, and an impeller 8 that is arranged in the immediate vicinity of a lower end 6 of the draft tube 1. According to an aspect, said immediate vicinity of the im peller may guarantee a downward directed suck of slurry in the draft tube.

The reactor arrangement can be used for mixing gas, such as oxygen or oxygen containing gas mixture, in slurry e.g. for leaching sulfidic material containing iron, nickel, cobalt, zinc and/or copper.

The wall 2 of the tube has typically a circular cross- section. The wall 2 comprises plurality of openings 3 that extends through said wall, i.e. are through-holes. The to tal surface area of the openings 3 as a percentage of the total outside surface area of the draft tube 1 is 4 % at most. In one embodiment, said percentage is in range of 0.5 % - 4 %. In one embodiment, said percentage is in range of 0.5 % - 2 %. Said total area of the openings en sures a satisfactory inflow in the draft tube 1 when the slurry falls under the upper end 4 of the draft tube, but, on the other hand, prevents an excessive outflow out from the draft tube 1 under normal working conditions when the slurry inflow takes place through the upper end 4. According to an idea, the mass flow rate through the open ings 3 is not more than 30 % of the pumping mass flow rate of the impeller 8 during a normal operation of the ar rangement 100 when the slurry level is above the upper end 4 of the draft tube 1. In one embodiment, said percentage is not more than 10 %. In one embodiment, such as shown in Figure 1, all the openings 3 has a round shape. In other embodiments, not all but at least one of the openings is round. In one em bodiment, at least half of the openings 3 have a round shape.

In one embodiment, the inner wall of the reactor tank 10 is cylindrical having an inner diameter R. However, the reactor tank 10 may have another shape, too.

In the embodiment shown in Figure 1, the reactor tank 10 has a semi-ellipsoidal shape at its lower end. However, the lower end may also be shaped to e.g. a flat or a coni cal shape.

In one embodiment, the draft tube 1 is arranged concentri cally with the reactor tank 10. However, this is not al ways necessary.

In one embodiment, the reactor tank 10 is cylindrical and the ratio of its inner diameter R to the outer diameter D of the draft tube, that is R/D, is selected in range of 2 - 4. In one embodiment, said ratio is in range of 2.5 -

3.5.

In one embodiment, an inner height of the reactor tank 10 is at least 10 m. This order of height makes it possible to reach high hydrostatic pressure in lower parts of the reactor tank and quicken dissolving of the oxygen in the slurry.

In one embodiment, the draft tube 1 is attached to the re actor tank 10 by at least one tube support 13. The tube support may comprise e.g. a bar-like or a plate-like structure. There is a bottom clearance BC between a median level ML of the impeller 8 and a bottom of the reactor tank 10. The median level ML is defined by the upmost and lowermost edges of the blades of the impeller in the longitudinal direction of the draft tube L. In one embodiment, the im peller 8 and the draft tube 1 are positioned in the reac tor tank 10 so that the bottom clearance BC is in range of 0.8D - 1.5D, wherein the D is the outer diameter of the draft tube.

In one embodiment, the impeller 8 is positioned such that when measuring in the longitudinal direction of the draft tube L, there is a distance between the median level ML of the impeller 8 and the lower end 6 of the draft tube that is 0.5 X D at most. In one embodiment, said distance is 0.25 X D at most. The median level ML is defined by the upmost and lowermost edges of the blades of the impeller in the longitudinal direction of the draft tube L.

In one embodiment, the impeller 8 or its blades situate(s) completely outside of the draft tube 1.

In one embodiment, there is a top clearance TC between an upper end 4 of the draft tube and an overflow 14, such as a launder, a chute, a channel or a duct. The overflow 14 may define a free surface FS of slurry during normal oper ation of the arrangement 100. In one embodiment, the top clearance TC being 1.0D at most, wherein the D is the out er diameter of the draft tube.

In one embodiment, there is at least one blocking element 9 is arranged to an inner wall of the reactor tank 10. The blocking element 9 may be or comprise a baffle, for in stance. The blocking element 9 may be arranged to extend in the direction of the longitudinal direction L. The blocking element 9 may be arranged parallel to L or to a position that deviates from the longitudinal direction L. In one embodiment, there is at least one blocking element 9 in an upper half of the reactor tank 10. In one embodi ment, there is at least one blocking element 9 in a lower half of the reactor tank 10. In one embodiment, such as shown in Figure 1, there are blocking elements 9 in the upper half as well as in the lower half of the reactor tank 10.

In one embodiment, an inner surface of the wall 2 of the draft tube is provided with one or more blocking elements 9. Said blocking element 9 may be or comprise a baffle that is arranged to extend in the direction of the longi tudinal direction L. The blocking element 9 may be ar ranged parallel to L or to a position that deviates from the longitudinal direction L.

In one embodiment, such as shown in Figure 1, the arrange ment comprises only one impeller 8.

The impeller 8 is arranged to create a downward directed suck in the draft tube 1, i.e. moving slurry inside the draft tube 1 towards the lower end 6. This kind of suck may be provided e.g. with suitably shaped curved impeller blades (not shown) creating axially downwards directed flow.

In one embodiment, such as shown in Figure 1, the impeller 8 is arranged partly outside and partly inside of the draft tube 1. In one embodiment, the impeller 8 is ar ranged to create at least partly radially (i.e. horizon tally) directed flow in the reactor tank 10. The radially directed flow may be created e.g. by straight blades or turbine blades (not shown) of the impeller. The radially directed flow disperses effectively gas fed underneath the impeller in the slurry. In one embodiment, the impeller 8 comprises a first set of blades arranged in its upper part for creating axially downwards directed flow, whereas in a lower part of the impeller there is a second set of blades for creating at least partly radially directed flow.

In one embodiment, the impeller 8 is arranged completely outside of the draft tube 1.

Figure 2 is a schematic side view of a draft tube. In one embodiment, such as shown in Figure 2, the openings 3 are arranged in opening groups 11. The opening group 11 may include two or more openings. The opening groups 11 are arranged successively in longitudinal direction L of the draft tube 1 so that a distance between adjacent opening groups 11 is larger than between the openings arranged in a same opening group 11. In one embodiment, the number of opening groups 11 is 4 - 10 groups. In one embodiment, the number of the openings 3 in one opening group 11 is selected in range of 2 - 6. It is to be noted that the number of the openings may be equal in all the opening groups 11; however, this is not necessary. Furthermore, the shape, size, placing and total area of the openings may be identical in every opening groups 11, or, alternatively, there may be variations in said variables. In one embodiment, the openings 3 are evenly spaced be tween an opening closest to an upper end 4 of the draft tube 1 and an opening closest to a lower end 6 of the draft tube 1. In one embodiment, such as shown in Figure 5, the openings 3 are of a quantity and position such that slurry or liq- uid is capable to flow through said openings in the draft tube 1 along substantially the entire length of a length wise section 12 that situates between the opening closest to a upper end 4 of the draft tube and the opening closest to a lower end 6 of the draft tube. Thus, the lower edge of an opening positioned higher may situate at the same height position H or lower than an upper edge of another opening positioned lower. In Figure 5 said lower and upper edges are positioned on the same height position H.

In one embodiment, such as shown in Figure 2, the upper end 4 of the draft tube 1 is provided with an upper coni cal extension 5. The diameter of the upper conical exten sion 5 tapers towards the draft tube 1. The upper conical extension 5 may promote slurry inflow in the draft tube 1.

There is a first clearance Cl in the draft tube between the opening 3 closest to the upper end 4 and said upper end 4. In other words, the first clearance Cl is devoid of openings. In one embodiment, the first clearance Cl is not more than the draft tube diameter D. In one embodiment, the first clearance Cl is in range of 0.5 x D - l x D.

In one embodiment, there is a second clearance C2 between the opening 3 closest to the lower end 6 and the lower end devoid of the openings, the second clearance C2 being 1 - 2 times of the draft tube diameter D, i.e. 1 x D - 2 x D.

In one embodiment, a lower conical extension 7 tapering upwards is provided at the lower end 6 of the draft tube. In one embodiment, the impeller 8 is arranged partly in side the lower conical extension 7. In another embodiment, the impeller 8 is arranged below and close proximity of the lower conical extension 7. Figure 3 is a schematic side view of another draft tube. In one embodiment, the openings 3 are arranged in the lengthwise section 12 in the draft tube so that the total area of the openings 3 in an upper half 12a of said lengthwise section 12, i.e. the half-length of the length wise section 12 closest to the upper end 4, is at least 50 % of total area of all the openings 3 arranged in the lengthwise section 12. In other words, majority of the to tal area of the openings is situated in the upper half 12a. In one embodiment, at least 60 % of said total area of the openings 3 is arranged in the upper half 12a.

Figure 4 is illustrating some embodiments of the openings. As shown in Figures 1 - 3, the opening 3 may have a round shape.

In one embodiment, at least one of the openings 3 is poly gon, such as triangular, quadrangular, etc.

In one embodiment, at least one of the openings 3 has an oblong form, such as oval, oviform or rectangle. In one embodiment, the longitudinal direction of the oblong shaped opening is arranged at least essentially parallel with the longitudinal direction L of the draft tube. In one embodiment, said longitudinal direction of the oblong shaped opening is arranged at least essentially to a per pendicular direction with the longitudinal direction L. In one embodiment, said longitudinal direction is arranged at an angle between the longitudinal direction and the per pendicular direction.

In one embodiment, the width w, i.e. dimension perpendicu lar to the longitudinal direction L, of the opening 3 de fined as a percentage of the outer diameter D of the draft tube is in range of 5 % - 30 %. In one embodiment, said percentage is 10 % - 20%. In one embodiment, the width w is selected in range of 5 cm - 100 cm. In one embodiment, the width w is selected in range of 10 cm - 60 cm. In one embodiment, the width w is selected in range of 15 cm - 20 cm.

In one embodiment, the height of the opening 3, i.e. its dimension perpendicular to the width w, is selected in range of 5 cm - 75 cm. In one embodiment, the height of the opening is selected in range of 10 cm - 60 cm. In one embodiment, the height of the opening is selected in range of 15 cm - 20 cm.

The invention is not limited solely to the embodiments de scribed above, but instead many variations are possible within the scope of the inventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conjunction with or replace the attributes of another embodiment or application.

The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the inventive idea de fined in the following claims.

REFERENCE SYMBOLS

1 draft tube

2 wall 3 opening

4 upper end of the draft tube

5 upper conical extension

6 lower end of the draft tube 7 lower conical extension 8 impeller

9 blocking element

10 reactor tank 11 opening group 12 lengthwise section 12, b half-section

13 tube support

14 overflow

100 arrangement

Cl first clearance

C2 second clearance

BC bottom clearance

D outer diameter of the draft tube FS free surface

H height position

L longitudinal direction of the draft tube

ML median level of the impeller

R inner diameter of the reactor TC top clearance w width

Claims

1. A reactor arrangement (100), comprising

- a reactor tank (10),

- a draft tube (1) arranged in the reactor tank (10), and

- an impeller (8) arranged in the immediate vicinity of a lower end (6) of the draft tube (1), wherein the wall (2) of the draft tube comprises

- openings (3) through said wall, and wherein

- the total surface area of the openings (3) as a percent age of the total outside surface area of the draft tube (1) is 4 % at most.

2. The arrangement as claimed in claim 1, wherein

- said total surface area of the openings (3) as a per centage of the total outside surface area of the draft tube (1) is in range of 0.5 % - 4 %.

3. The arrangement as claimed in claim 1, wherein

- said total surface area of the openings (3) as a per centage of the total outside surface area of the draft tube (1) is in range of 0.5 % - 2 %.

4. The arrangement as claimed in any of the preceding claims, wherein

- at least one of the openings (3) is round.

5. The arrangement as claimed in any of the preceding claims, wherein the width (w) of the opening (3) as a percentage of the outer diameter (D) of the draft tube is in range of 5 % - 30 %, preferably 10 % - 20%.

6. The arrangement as claimed in any of the preceding claims, wherein

- the openings (3) are arranged in opening groups (11) comprising at least two openings and arranged successively in longitudinal direction (L) of the draft tube (1), and wherein

- in longitudinal direction (L) of the draft tube (1), a distance between adjacent opening groups (11) is larger than between the openings arranged in a same opening group (4).

7. The arrangement as claimed in any of claims 1 - 5, wherein

- the openings (3) are evenly spaced between an opening closest to a upper end (4) of the draft tube (1) and an opening closest to a lower end (6) of the draft tube (1).

8. The arrangement as claimed in claim 7, wherein

- the openings (3) are of a quantity and position such that a fluid is capable of flow through the openings (3) in the draft tube (1) along substantially the entire length of the draft tube between the opening closest to a upper end (4) of the draft tube (1) and the opening clos est to a lower end (6) of the draft tube (1).

9. The arrangement as claimed in any of the preceding claims, wherein

- there is a lengthwise section (12) in the draft tube (1) extending from the opening closest to the upper end (4) to the opening closest to the lower end (6), and wherein

- the total area of the openings (3) arranged in a upper half (12a) of said lengthwise section (12) closest to the upper end (4) is at least 50 % of total area of all the openings (3) arranged in the lengthwise section (12).

10. The arrangement as claimed in claim 9, wherein

- said total area of the openings (3) arranged in the up per half (12a) of said lengthwise section (12) is at least 60 %.

11. The arrangement as claimed in any of the preceding claims, wherein

- at the upper end (4) of the draft tube (1) there is ar- ranged an upper conical extension (5) for slurry inflow, the diameter of which upper conical extension (5) tapers towards the draft tube (1).

12. The arrangement as claimed in any of the preceding claims, wherein

- there is a first clearance (Cl) without openings between the opening (3) closest to the upper end (4) and said up per end (4), the first clearance being not more than the draft tube diameter (D).

13. The arrangement as claimed in claim 12, wherein

- the first clearance (Cl) is in range of 0.5 x D - l x D.

14. The arrangement as claimed in any of the preceding claims, wherein

- at a lower end (6) of the draft tube (1) there is ar ranged a lower conical extension (7) for accommodating an impeller (8), the diameter of which lower conical exten sion (7) tapers towards the draft tube (1).

15. The arrangement as claimed in any of the preceding claims, wherein

- the inner surface of the draft tube (1) is provided with one or more blocking elements (9) that is/are arranged to extend in the direction of the longitudinal direction (L).

16. The arrangement as claimed in any of the preceding claims, wherein

- the draft tube (1) is arranged concentrically with the reactor tank (10).

17. The arrangement as claimed in any of the preceding claims, comprising

- a bottom clearance (BC) between a median level (ML) of the impeller (8) and a bottom of the reactor tank (10), the bottom clearance (BC) being in range of 0.8D - 1.5D.

18. The arrangement as claimed in any of the preceding claims, comprising

- a top clearance (TC) between the upper end (4) of the draft tube and an overflow (14), the top clearance (TC) being 1.0D at most.

19. The arrangement as claimed in any of the preceding claims, wherein

- the inner wall of the reactor tank is cylindrical having an inner diameter (R), and

- the ratio of said inner diameter (R) to the outer diame ter (D) of the draft tube, that is R/D, is selected in range of 2 - 4.

20. The arrangement as claimed in any of the preceding claims, wherein

- an inner height of the reactor tank (10) is at least 10 m.

21. The arrangement as claimed in any of the preceding claims, wherein

- at least one blocking element (5) is arranged to an in ner wall of the reactor tank (10).

22. The arrangement as claimed in claim 15 or 21, wherein

- the blocking elements (5) comprise a baffle.

23. The arrangement as claimed in any of the preceding claims, wherein the impeller (8) is arranged for creating a downward di rected suck in the draft tube (1).

24. The arrangement as claimed in any of the preceding claims, wherein

- the impeller (8) is arranged at least partly outside of the draft tube (1).

25. The arrangement as claimed in claim 24, wherein

- the impeller (8) is arranged partly inside of the draft tube (1).

26. The arrangement as claimed in any of claims 1 - 24, wherein

- the impeller (8) is arranged completely outside of the draft tube (1).

27. The arrangement as claimed in any of the preceding claims, comprising

- only one impeller (8).

28. The arrangement as claimed in any of the preceding claims, wherein

- the distance between the median level (ML) of the impel ler and the lower end of the draft tube is 0.5 X D at most.

29. The arrangement as claimed in claim 28, wherein

- the distance between the median level (ML) of the impel ler and the lower end of the draft tube is 0.25 X D at most.

30. The arrangement as claimed in any of the preceding claims, wherein

- the impeller (8) is arranged for creating a radially di rected flow in the reactor tank (10).

31. The arrangement as claimed in any of the preceding claims, comprising a second clearance (C2) between the opening (3) closest to the lower end (6) and the lower end (6), the second clearance (C2) being 1 - 2 times of the draft tube diameter (D).

32. Use of the arrangement as claimed in any of the pre ceding claims for mixing gas in slurry.

33. Use of the arrangement as claimed in any of claims 1 - 31 for leaching sulfidic material containing iron.

34. Use of the arrangement as claimed in any of claims 1 - 31 for leaching sulfidic material containing nickel.

35. Use of the arrangement as claimed in any of claims 1 - 31 for leaching sulfidic material containing cobalt.

36. Use of the arrangement as claimed in any of claims 1 -

31 for leaching sulfidic material containing zinc.

37. Use of the arrangement as claimed in any of claims 1 - 31 for leaching sulfidic material containing copper.