ES2898393T3 - Mixing system for the introduction of chemical substances in a fluid to be treated - Google Patents

Abstract

Mixing system (10) for the introduction of chemical substances in a fluid to be treated, comprising: - a container (11) comprising an external wall (12), an internal wall (13), a bottom (14) and a lid (15), - at least two concentric mixing chambers, a first central chamber (16) defined inside said internal wall (13) and a second chamber (17) defined outside said internal wall (13), being said first chamber (16) and said second chamber (17) in communication with each other, - an inlet conduit (19) for a fluid to be treated, configured for the introduction of said fluid from the outside into said first chamber (16 ), - an outlet conduit (20) for said treated fluid, configured for the outlet of said fluid from said second chamber (17) to the outside of said container (11), said inlet conduit (19) being configured, first chamber (16), second chamber (17) and outlet duct (20) to define a path labyrinthine mixing (30), - stirring blades (18) positioned inside said first chamber (16), operated by drive means through a rotation shaft (21), - at least one injection passage (22) for the introduction of a chemical additive at one or more points of said labyrinthine mixing path (30), said inlet conduit (19) being positioned below said outlet conduit (20) with respect to a configuration of use of said system of mixing (10), - said agitator blades (18) comprising at least a first group of blades (18a), - said first group of blades (18a) being positioned below said inlet conduit (19) with respect to a configuration of use of the mixing system (10), characterized in that said at least one injection passage (22) comprises: - a first injection pipe (22a) directly connected to said inlet duct (19); - a second injection pipe (22b) directly connected to said first chamber (16); - a third injection pipe (22c) directly connected to said second chamber (17).

Description

DESCRIPTION

Mixing system for the introduction of chemical substances in a fluid to be treated

The invention relates to a mixing system designed to introduce chemical substances into a fluid to be treated.

Today, clean water is considered a valuable resource that should be conserved and used only when consumption is absolutely necessary.

For example, the paper industry has always used large amounts of fresh water, that is, new water, in order to obtain high-quality products. However, in recent years, environmental regulations and greater environmental awareness worldwide have increasingly led people to reduce water consumption.

Today, for example, paper sludge is increasingly important and is increasingly used for the production of other papers, in the cement and tile industry, in environmental restoration projects, to cover landfills and in construction mixes. Some stages of a process for the treatment of wastewater from a paper mill include the use of a polyelectrolyte, for example a cationic flocculant powder, or even, for example, a cationic polyacrylamide, suitable to be applied in the clariflocculation of water. containing organic substances, in sludge thickening treatments, in sludge dewatering processes and also in other processes carried out in paper mills, such as froth flotation.

During these process steps it is necessary to maximize the yield of the polymer, i.e. the cationic flocculant, to improve the quality of the dry residue in the case of sludge or to improve froth flotation in the case of a froth flotation stage.

To be activated, these polymers need to be premixed with water at a preset concentration.

Currently, said premixing stage is carried out in static mixing tanks, in which the polymer is introduced after being extracted from a small storage container; These polymers are normally ^{diluted in solutions between 0.2 % and 1 %, so they are very demanding in terms of water use.}

In the static mixing tank, the mixture is obtained from the simple turbulence of the water. Subsequently, an auxiliary pump introduces the water with the polymer into a pipe that leads to a tank or canal for the treatment of residual sludge.

Thus, as already mentioned, these systems that use a cationic flocculant, although they are widely used and appreciated, require the use of considerable amounts of water and specific mixing equipment, together with the corresponding preparation lines for their use and for introduction into a sludge treatment line.

Another limitation of currently known sludge treatment systems is that polyelectrolytes are culture media for bacteria, so a polymer that remains in a storage tank for a long time is very likely to favor the proliferation of bacteria.

Patent document US53 140 76 describes a system for mixing two fluid phases, more specifically for mixing a treatment fluid with a fluid to be treated; said system comprises two concentric chambers that communicate with each other at least at their ends, the central chamber being provided with two turbines whose axis of rotation is equal to the axis of symmetry of the installation. In this technical solution known in the art, the fluid to be treated flows from above, exits from below and the turbines are interposed between the inlet and the outlet.

Patent document US 20 12/0 19 9524 describes a clarifying silo comprising a closed vessel with an internal mixer surrounded by a diffuser with a cylindrical tube.

The diffuser and mixer define three internal chambers that overlap in the vertical direction, an upper chamber, a central chamber and a lower chamber, as well as an external annular region. Each of the three internal chambers is in fluid communication with the annular region.

Even in this technical solution known in the art, the fluid to be treated flows from above, exits from below, and the turbines are interposed between the inlet and the outlet.

Even in the mixer described in patent document US3392963, the fluid to be treated enters from the top, exits from the bottom and the turbines are interposed between the inlet and the outlet.

Patent documents US2577856 and US3737288, on the other hand, describe mixing equipment in which the fluid to be treated flows in from the bottom and flows out from the top, and a propeller is interposed between the inlet and the exit. The mixers and equipment described in the aforementioned patent documents cannot overcome the drawbacks and limitations illustrated above.

Document GB-A-2 13 6304 describes a mixing system according to the preamble of claim 1. The object of the present invention is to provide a mixing system for the introduction of chemical substances into a fluid to be treated, which can overcome the aforementioned drawbacks and limitations of the prior art. More specifically, it is an object of the invention to provide a mixing system that drastically reduces the use of water for the preparation of a polyelectrolyte suitable for being introduced into the residual fluid flow to be treated.

Another object of the invention is to provide a mixing system that favors the reduction of energy consumption in wastewater treatment processes.

Another object of the invention is to provide a mixing system that improves the water retention of the sludge, thus increasing the amount of dry product that can be obtained from the sludge.

Another object of the invention is to provide a mixing system that can reduce waiting times for the start of the action of the polymer in solution on the fluid to be treated, consequently improving the effectiveness of the polymer itself.

Another object of the invention is to provide a mixing system that is compact and can be easily installed also in already existing sewage treatment or purification plants or sludge drying plants.

Another object of the invention is to provide a mixing system that limits the proliferation of bacteria in the same polyelectrolytes.

The task and the objects illustrated above are fulfilled by a mixing system for the introduction of ^{chemical substances in a fluid to be treated according to claim} 1 ^.

Other features of the mixing system according to claim 1 are described in the dependent claims.

The aim and objects illustrated above, together with the advantages described below, are highlighted in the description of two embodiments of the invention, which are given by way of non-limiting example with reference to the accompanying drawings, in which:

Figure 1 shows a schematic side sectional view of a first embodiment of a mixing system according to the invention;

Figure 2 shows a schematic side sectional view of a second embodiment of a mixing system according to the invention.

With reference to Figure 1, in the context of a first embodiment, a mixing system according to the invention is indicated by the number "10" .

Said mixing system 10 comprises:

- a container 11 comprising an external wall 12 , an internal wall 13 , a bottom 14 and a lid 15 ,

- two concentric mixing chambers, a first central chamber 16 defined inside the internal wall 13 and a second chamber 17 defined outside the internal wall 13 , the first chamber 16 and the second chamber 17 being in communication with each other,

- an inlet conduit 19 for a fluid to be treated, configured to introduce said fluid from the outside into said first chamber 16 ,

- an outlet conduit 20 for the treated fluid, said outlet conduit 20 being configured to allow said fluid to exit from said second chamber 17 to the outside of said container 11 , said inlet conduit 19 being configured, first chamber 16 , second chamber 17 and outlet duct 20 to define a labyrinthine mixing path 30 ,

- stirring blades 18 located inside the first chamber 16 , operated by drive means through a rotation shaft 21 ,

- at least one injection passage 22 for the introduction of a chemical additive at one or more points of the labyrinthine mixing path 30 .

In the present exemplary embodiment, it should be understood that the second chamber 17 is ring-shaped.

The labyrinthine mixing path 30 is indicated by arrows showing schematically the possible paths of the fluid being treated between the inlet conduit 19 and the outlet conduit 20 .

The drive means comprise, for example and not exclusively, a motor 35 configured to configure the rotary axis 21 to rotate.

Said axis of rotation 21 carries the stirring blades 18 .

The axis of rotation of the axis of rotation 21 is parallel to the direction of extension of the inner wall 13 .

More specifically, in the present non-limiting example of embodiment of the invention, the external wall 12 has a cylindrical shape.

In the present non-limiting example of embodiment of the invention, the internal wall 13 also has a cylindrical shape. More specifically, the second chamber 17 surrounds the first chamber 16 . More specifically, the second chamber 17 is concentric and coaxial with the first chamber 16 .

The inlet duct 19 is located below the outlet duct 20 with respect to a use configuration of the mixing system 10 .

The stirring blades 18 comprise a first group of blades 18a positioned at the lower end of the axis of rotation 21 .

More specifically, said first group of blades 18a is positioned below the inlet duct 19 with respect to a use configuration of the mixing system 10 .

It should be understood that said first group of blades 18a can also be arranged in another position along the axis of rotation 21 .

It should be understood that the agitator blades 18 may be made up of a single group of blades 18a .

In said exemplary embodiment, the stirring blades 18 also comprise a second group of blades 18b positioned in a central area of the axis of rotation 21 .

More specifically, said second group of blades 18b is positioned above the inlet duct 19 with respect to a use configuration of the mixing system 10 . The first chamber 16 and the second chamber 17 are in communication with each other through at least one passage opening 37 defined at one end of the internal wall 13 .

More specifically, but not exclusively, in said embodiment, a first passage opening 37 is defined by a lower recirculation space between a lower end 13a of the internal wall 13 and the bottom 14 . More specifically, but not exclusively, in said embodiment, a second passage opening 38 is defined by an upper recirculation space between an upper end 13b of the internal wall 13 and the lid 15 . In a variant embodiment, not illustrated for reasons of simplicity, the first chamber 16 and the second chamber 17 are in communication only through a lower passage opening 37 ; in said variant the upper end 13b of the internal wall 13 is in contact with the cover 15 and there is no opening 38 for upper passage.

In another embodiment variant, also not illustrated for reasons of simplicity, the first chamber 16 and the second chamber 17 are in communication only through an upper passage opening 38 ; in said variant the lower end 13a of the internal wall 13 is in contact with the bottom 14 and there is no opening 37 for lower passage.

In said additional embodiment variant, the inlet duct 19 and the outlet duct 20 are both advantageously positioned near the bottom 14 with respect to a use configuration of the mixing system 10 .

Mixing system 10 comprises a flow diversion element 40 configured to divert fluid flowing out of first chamber 16 into second chamber 17 .

Said flow diversion element 40 is located at the bottom 14 .

Said flow diversion element 40 is constituted by a body in the form of a cone or truncated cone, configured to deflect the flow outwards in a radial direction, where the term 'radial' is understood with respect to an axial direction of the axis of symmetry of the internal wall 13 , where the flow flows downwards from the first chamber 16 . The at least one injection passage 22 comprises a first injection pipe 22a connected directly to the inlet duct 19 .

Said at least one injection passage 22 further comprises a second injection pipe 22b ^{directly connected to the first chamber} 16 ^.

Said at least one injection passage 22 comprises, in addition to the first injection pipe 22a and the second injection pipe 22b , a third injection pipe 22c directly connected to the second chamber 17 .

A second embodiment of a mixing system is shown schematically in Figure 2 and is indicated therein by the number 110 .

The specific feature of the mixing system 110 is that the container 111 , which comprises an external wall 112 , an internal wall 113 , a bottom 114 and a lid 115 , also comprises an intermediate wall 150 .

Said intermediate wall 150 defines, together with the external wall 112 and the internal wall 113 , three concentric mixing chambers, a first central chamber 116 defined within the internal wall 113 , a second intermediate chamber 117 surrounding the first chamber 116 and a external third chamber 153 surrounding the second chamber 117 .

In said second embodiment of the mixing system 110 according to the invention:

- the first chamber 116 and the second chamber 117 are in communication with each other through at least one passage opening 137 defined at the level of one end of the internal wall 113 and, at the same time,

- the second chamber 117 and the third chamber 153 are in communication with each other through at least one passage opening 154 defined at one end of the intermediate wall 150 .

More specifically, but not exclusively, in said embodiment, a first passage opening 137 between the first chamber 116 and the second chamber 117 is defined by an upper recirculation space between an upper end 113a of the internal wall 113 and the cover 115 .

More specifically, but not exclusively, in said embodiment, a second passage opening 138 between the first chamber 116 and the second chamber 117 is defined by a lower recirculation space between a lower end 113b of the internal wall 113 and the bottom 114 .

More specifically, but not exclusively, in said embodiment, a first passage opening 154 between the second chamber 117 and the third chamber 153 is defined by a lower recirculation space between a lower end 150a of the intermediate wall 150 and the bottom 114 .

More specifically, but not exclusively, in said embodiment, a second passage opening 155 between the second chamber 117 and the third chamber 153 is defined by an upper recirculation space between an upper end 150b of the intermediate wall 150 and the cover 115 .

In a variant embodiment, not illustrated for reasons of simplicity, the first chamber 116 and the second chamber 117 are in communication only through an upper passage opening 137 , and the second chamber 117 and the third chamber 153 are in communication only. through a lower passage opening 154 .

In another embodiment variant, also not illustrated for reasons of simplicity, the first chamber 116 and the second chamber 117 are in communication only through a lower passage opening 138 , and the second chamber 117 and the third chamber 153 are in communication only. through an upper passage opening 155 .

In said additional embodiment variant, the inlet duct 119 and the outlet duct 120 are both advantageously positioned near the bottom 114 with respect to a use configuration of the mixing system 110 .

Mixing system 110 comprises a flow diversion element 140 configured to divert fluid flowing out of first chamber 116 or second chamber 117 into third chamber 153 .

Said flow diversion element 140 is located at the bottom 114 .

Said flow diversion element 140 is constituted by a body in the shape of a cone or truncated cone, configured to deflect the flow outwards in a radial direction.

Analogous to what has been described above with reference to the first embodiment of the invention, the mixing system 110 comprises an injection passage 122 for the introduction of a chemical additive at one or more points of the labyrinthine mixing path 130 .

According to its first embodiment illustrated in Figure 1, the mixing system 10 works in such a way that the fluid to be treated, for example the sludge, flows into the first chamber 16 through the inlet duct 19 and, thanks to the gravity and to the action of the stirring blades 18 , it flows downwards, towards the passage opening 37 , where it deflects upwards into the second chamber 17; while flowing upwards along the second chamber 17 the treated fluid meets the outlet conduit 20 and is conveyed to it.

A chemical additive, for example cationic polyacrylamide, is injected into the fluid to be treated during its passage through said labyrinthine mixing path 30 .

According to its second embodiment illustrated in Figure 2, the mixing system 110 operates in such a way that the fluid to be treated flows into the first chamber 116 through the inlet duct 119 and is transported upwards thanks to the action of the 118 stirring blades.

Successively, the fluid follows a labyrinthine mixing path 130 in which it passes through the three chambers, the first 116 , the second 117 and the third 153 and, from the latter, passes to the outlet duct 120 .

It has practically been shown that the mixing system 10 and 110 according to the invention fulfills its task and achieves the stated objectives.

In fact, the invention provides a mixing system thanks to which the fluid to be treated and the chemical additive are mixed without the need to prepare the chemical additive, that is, to dilute it, previously in expensive and voluminous water tanks, drastically reducing the water consumption.

The chemical additive, for example a cationic flocculant polymer, is activated when it comes into direct contact with a fluid to be treated, and this occurs directly inside the first, second and, if necessary, the third chamber. In addition, the invention provides a mixing system that, thanks to the stirring effect produced by the stirring blades, improves the effectiveness and efficiency of the chemical additive; for example, in the case of organic sludge, in which the sludge has a nonpolar surface membrane, the strong action of agitation favors the rupture of said membrane and makes available anionic sites; the introduction and mixing with a cationic polyelectrolyte cause the anionic sites to react with the cationic polyelectrolyte, releasing water molecules, which favors a greater separation of the solid fraction of the fluid to be treated from the liquid fraction.

Therefore, the invention provides a mixing system that makes it possible to drastically reduce the use of water in the preparation of a polyelectrolyte destined to be introduced into a residual fluid flow that it is desired to treat.

In addition to the above, the invention provides a mixing system that favors the reduction of energy consumption in wastewater treatment processes, since it is no longer necessary to manage a mixing and storage tank and the efficiency in terms of separation of the dry fraction of the liquid fraction is improved compared to known treatment systems.

In fact, the invention provides a mixing system that improves the water retention of the sludge, thus increasing the amount of dry product that can be obtained.

In addition, the invention provides a mixing system that is capable of reducing waiting times before the start of the action of the polymer in solution on the fluid to be treated, consequently improving the efficiency of the polymer itself; This has been obtained by introducing the chemical additive directly into the fluid to be treated and subjecting both to a mixing action produced by the agitator blades.

Furthermore, the invention provides a compact mixing system that can be easily installed also in existing sewage treatment or purification systems or sludge drying systems.

In addition, the invention provides a mixing system that limits the proliferation of bacteria on the polyelectrolytes themselves, thanks to the direct introduction of said polyelectrolytes directly into the fluid to be treated, without foreseeing a storage period before use.

In practice, any component and any material can be used, as long as it is compatible with the intended use, and any shape and size can be selected, according to the needs and the state of the art.

When the characteristics and techniques mentioned in any of the claims are followed by reference signs, it should be understood that these reference signs are used solely for the purpose of facilitating the understanding of the claims, so that these reference signs have no effect. limitative. on the interpretation of each element identified by way of example by the aforementioned reference signs.

Claims (7)

1. Mixing system (10) for the introduction of chemical substances in a fluid to be treated, comprising: ^{- a container (} 11 ^{) comprising an external wall (12), an internal wall (13), a bottom (14) and a lid (15),} - at least two concentric mixing chambers, a first central chamber (16) defined inside said internal wall (13) and a second chamber (17) defined outside said internal wall (13), said first chamber (16) being and said second chamber (17) in communication with each other, - an inlet conduit (19) for a fluid to be treated, configured for the introduction of said fluid from the outside into said first chamber (16), ^{- an outlet conduit (} 20 ^{) for said treated fluid, configured for the outlet of said fluid from said} second chamber (17) to the outside of said container (11), said inlet conduit (19) being configured, first chamber ( 16), second chamber (17) and outlet duct (20) to define a labyrinthine mixing path (30), - stirring blades (18) positioned inside said first chamber (16), operated by drive means through a ^{rotation shaft (} 21), ^{- at least one injection passage (22) for the introduction of a chemical additive at one or more points of said} labyrinthine mixing path (30), said inlet duct (19) being positioned below said ^{outlet duct (} 20) ^{with respect to a configuration of use of said mixing system (} 10 ^), - said agitator blades (18) comprising at least a first group of blades (18a), - said first group of blades (18a) being positioned below said inlet duct (19) with respect ^{to a configuration for use of the mixing system (} 10 ^{), characterized in that said at least one injection passage (} 22 ⁾ comprises: - a first injection pipe (22a) directly connected to said inlet duct (19); ^{- a second injection pipe (} 22 ^{b) directly connected to said first chamber (16); - a third injection pipe (} 22 ^{c) directly connected to said second chamber (17).} Mixing system according to claim 1, characterized in that said drive means comprise a motor (35) configured to rotate said rotation shaft (21), wherein said rotation shaft (21) carries said blades (18) agitators. Mixing system according to one or more of the preceding claims, characterized in that said first chamber (16) and second chamber (17) are in communication with each other through at least one passage opening (37) defined at the level of one end of said internal wall (13). Mixing system according to claim 3, characterized in that a first passage opening (37) is defined by a lower recirculation space between a lower end (13a) of said internal wall (13) and said bottom (14). Mixing system according to one or more of claims 3 and 4, characterized in that a second passage opening (38) is defined by an upper recirculation space between an upper end (13b) of said internal wall (13) and said lid (15). 6 ^{. Mixing system according to one or more of the preceding claims, characterized in that it comprises a} flow diversion element (40) configured to divert said fluid leaving said first chamber (16) towards said second chamber (17). 7. Mixing system according to one or more of the preceding claims, characterized in that said container (111) comprising an external wall (112), an internal wall (113), a bottom (114) and a lid (115) comprises also an intermediate wall (150), said intermediate wall (150) defining, together with said external wall (112) and with said internal wall (113), three concentric mixing chambers, a first central chamber (116) defined within said internal wall (113), a second intermediate chamber (117) surrounding said first chamber (116) and a third external chamber (153) surrounding said second chamber (117).