CN103002977A - Process and apparatus for addition of a chemical to a process stream - Google Patents

Abstract

The present invention relates to a method and apparatus for mixing liquid chemicals into a process flow using a mixing device (10, 200), the mixing device comprising: in particular a housing of a mixing tube (20), at least one fluid inlet opening (30), a chemical inlet opening (14), a diluent inlet opening (18), and at least one outlet opening (60) leading to a process flow (70). The method according to the invention is characterized in that a chemical flow from the chemical inlet opening (14) and a diluent flow from the diluent inlet opening (18) are mixed into the fluid flow, and after the chemical flow and the diluent flow are mixed, the fluid flow is acceleratedly supplied to the process flow (70) through the outlet opening (60), particularly through a nozzle, preferably injected into the process flow (70).

Description

Method and apparatus for mixing chemicals into process streams

technical field

The invention relates to a method of mixing liquid chemicals into a process stream by means of a mixing device, as well as to a device for mixing liquid chemicals into a process stream and a chemical supply system comprising such a device.

Background technique

The dosing and subsequent dosing of chemicals (for example in the paper manufacturing process) imposes special requirements, especially with regard to the efficient dosing and dosing of chemicals on demand. Dosing on demand means, for example, in the papermaking process that chemicals are added to the process flow of the paper machine according to the amount of fiber. By means of such measures, the amount of added chemicals can be significantly reduced in the papermaking process. Another reason for efficient use of chemicals is the high energy required to heat fresh water to dissolve or dilute the process chemicals. Such heating is beneficial to avoid thermal shock when mixing chemicals into fresh water. By providing an efficient method of dosing and mixing chemicals into process streams, especially in the manufacture of fibrous and/or nonwoven webs, not only process chemicals but also functional chemical consumption of chemicals and also reduces the use of fresh water used as a dilution medium during chemical preparation.

A number of methods and devices for mixing chemical streams into process streams are known from the prior art. EP-A-1219344 therefore provides a method for mixing a liquid chemical into a process liquid stream, wherein the chemical and the second liquid are mixed together if they are introduced into the process stream at high speed from a mixing nozzle. basically mixed with each other.

EP-A-1064427 describes a method and apparatus for mixing a liquid chemical stream into a second liquid stream in a mixing device, wherein the chemical stream is substantially separated from the second liquid stream when the chemical is precipitated in the second liquid stream. while mixing in an additional fourth liquid stream, in particular a process stream.

WO-A-2005/32704 shows a method and apparatus for providing chemicals into a liquid stream, wherein the chemical is introduced into the liquid stream by means of a mixer, wherein the chemical is mixed in the mixing space, for example with mixing water or The liquids circulating in the paper machine are mixed to form a mixed liquid which is then introduced into a liquid stream, in particular into a process stream.

A disadvantage of the device according to WO-A-2005/32704 is that on the one hand a separate mixing space in the form of a mixing chamber has to be provided, on the other hand the mixing chamber is separated from the fluid flow and therefore does not combine a completely mixed fluid flow, chemical flow and The dilution stream is injected into the process stream, but the mixing of the chemical and dilution streams is done separately from the fluid stream.

An apparatus is known from WO 91/02119 in which additives are mixed into an aqueous fiber suspension for papermaking.

In the embodiment according to WO 91/02119, the two separately conducted streams are mixed outside the process flow and the mixed stream is injected transversely to the process flow after complete mixing. A disadvantage of WO91/02119 is that no accelerated injection is achieved within the process stream.

Additionally, the chemical and dilution water streams are introduced directly into the process stream rather than into the fluid stream.

All the aforementioned methods and devices also have the disadvantage that deposits form during longer-term operation in the inflow line and also in the mixing device, in particular in the nozzles themselves. Especially in the area of mixing devices, e.g. Mixins within a process flow.

Deposits can occur even in the event of an unplanned sudden production stop where chemicals remain in the inflow lines and mixing equipment, especially nozzles. Deposits can not only affect the mixing process as previously described, but also come off when starting the production process after a machine stop. The deposits lead, for example, to holes in the paper web or to deposits on the screen, which in turn lead to costly cleaning stops. This problem is especially pronounced in dosing after screening equipment in paper machines, since undissolved chemicals, especially undissolved polymers, cannot be removed from the fiber suspension.

In order to avoid deposits during continuous operation, it can be proposed in the prior art to select the line cross-sections of the inflow lines and also in the area of the mixing device sufficiently large, so that this is largely avoided. class deposition. This of course leads to dimensioning the cross-section of the inflow line or the nozzles of the mixing device in such a way that a sufficiently high flow velocity cannot be achieved in order to prevent such deposits. On the other hand, if the cross-section is reduced, this can lead to clogging and thus to a malfunction of the mixing device, especially the nozzle, which leads to a production stop and replacement of the entire nozzle or inflow line.

Contents of the invention

Therefore, the technical problem to be solved by the present invention is to avoid the disadvantages of the prior art.

In particular, a method and a device for dosing or mixing fluids or liquids, in particular chemical-containing liquids or liquid chemicals themselves, into a process flow for producing a fibrous or nonwoven web are given, wherein As far as possible, the homogeneously mixed chemical fluid fiber mixture should be sprayed into the process stream and mixed with it. Furthermore, downtimes such as the deposition and detachment of deposits which may lead to holes in the fibrous web when the production process is restarted should also be avoided.

According to the invention, this technical problem is solved by a method for mixing a liquid chemical into a process flow by means of a mixing device comprising a housing in particular in the form of a mixing tube, a fluid inflow opening, a chemical inflow opening, a dilution A fluid inflow opening, and at least one outflow opening to process flow. The method is characterized in that a chemical stream from a chemical inflow opening and a dilution fluid stream from a dilution fluid inflow opening are mixed into the fluid streams and the fluid stream is passed through the outflow opening after at least one chemical stream and the dilution fluid stream are mixed In particular, it is accelerated by means of nozzles to the process flow, preferably sprayed into said process flow.

The fluid stream may be any process water commonly used or available in the production of fibrous or nonwoven webs. In particular, the fluid stream may be an aqueous fibrous suspension, wherein the fibrous material is preferably cellulose fibres.

Total mixing with the fluid stream can be achieved to a large extent by achieving strong mixing of the fluid stream with the diluent fluid and the chemical, and then dosing the uniformly mixed chemical fluid stream fiber solution through the outflow opening into the process stream and at This is mixed with it.

The chemicals to be dosed are in particular polymers such as adhesives which are added to process streams in papermaking processes. Examples of such chemicals or polymers are polyacrylamide (PAM), polyethyleneimine (PEI), polyacrylamine (PAAm), crosslinkable polyacrylamine resins, polydimethyldiallyl chloride ammonium chloride, polyvinylamine (PVAm), polyethylene oxide (PEO). As an alternative to the aforementioned polymers, the dosing chemicals can also be microparticles or nanoparticles, such as bentonite or silicates. Furthermore, the chemical to be dosed may be a starch or a biocide or a pigment or a brightener. Further possible chemicals are neutral binders such as AKD (alkyl ketone dimer) or ASA (alkenyl succinic anhydride). Furthermore, the method according to the invention makes it possible to also meter minerals in the form of a suspension, eg calcium carbonate, titanium dioxide, into the second liquid or into the process stream.

It is particularly preferred that the dosing of the chemical is not added directly into the process flow from the chemical nozzle, but after the liquid chemical is mixed with the diluent liquid and the fluid flow. The dilution liquid and/or fluid flow may be fresh water. Alternatively, the second liquid may be a circulating liquid. In principle, every liquid or fluid used in the process can be considered. In particular, during the manufacture of the fibrous web, the circulating liquid is white water, clear filtrate, turbid filtrate or another suitable impure liquid occurring in the papermaking process. However, clean water or clear filtrate primary ultra-clean filtrates, for example ultra-clean filtrates of disc filters, including micron suspended solids (DAF), are also conceivable. The dilution liquid and/or fluid can also be process water from waste water cleaning plants, ie so-called biological water is used. The process stream may preferably be the added chemical, eg the fiber suspension flowing into the paper machine with which the chemical is left to react.

Preferably, within the mixing device, the liquid or liquid chemical is provided in the first chemical stream and the dilution fluid is provided in the dilution fluid stream.

According to the invention it is proposed that a dilution fluid flow, for example of a fresh water flow or a recirculation water flow, is mixed with the chemical of the chemical flow to be dosed, for example in a mixing region, before being supplied to the process flow.

In particular, in an extended embodiment it is achieved that the chemical stream and the diluent fluid stream are substantially mixed with one another before being mixed into the fluid stream. In particular, the method also enables adjustment of the chemical concentration within the fluid stream through the addition of dilution fluid. For this, the relationship of the diameter of the dilution fluid flow to the diameter of the chemical flow can be varied, preferably in the range of 1:1 to 20:1, preferably in the range of 5:1 to 10:1 In the extreme case, the pipe diameter of the inflow line for the dilution fluid flow is 20 times larger than the pipe diameter of the inflow line for the chemical flow.

Preferably, the supply of the chemical stream to the fluid stream and the supply of the diluent stream to the fluid stream and possibly the supply of further chemical or further fluid streams to said fluid stream take place at an angle to the housing wall, in particular with respect to the mixing tube The axis of symmetry is supplied at an angle.

The angle at which the addition of the chemical stream and/or dilution stream is carried out may be in the range of 90° to 10°, preferably in the range of 60° to 65°. Such angles ensure strong mixing of the chemical and dilution fluid streams.

实现。Particularly preferably, measures are taken in the region of the housing or of the mixing tube in order to generate or increase turbulence in the flow supplied to the process flow. This can be done, for example, by means of the impact surface

accomplish.

Alternatively, a swirl can be created such that the mixing exits the nozzle in a centrifugal flow as soon as it exits the nozzle into the process flow. As a result, the penetration depth of the jet with entrained chemicals and dilution fluid into the process flow is increased. Furthermore, the introduction of the impingement surface enables not only a turbulent flow, but also a dosing of the chemical and/or dilution flow.

It is particularly preferred that the method comprises a cleaning step in addition to the mixing step in which the liquid chemical is added to the fluid stream. During the cleaning step, the mixing device is separated from the process flow, so that the mixing device can be cleaned independently of the process flow.

The separation of the mixing device from the process flow enables cleaning of the mixing device independently of the process flow, for example by having the mixing device received by a receiving device in which the mixing device is arranged in a cleaning step To form a clean room. A cleaning liquid, such as fresh water, can be supplied into the cleaning chamber with which the inflow lines and nozzles are flushed. By flushing the mixing device and the inflow line, the deposits are removed from them, and clogging of the mixing device and the supply with deposits is thus largely avoided.

It is preferred to have the mixing chamber at the same time as a clean room or clean area. If the mixing device can be arranged directly above the process flow, eg in the receiving device, it is advantageous if the mixing device is formed movable in the receiving device to form a clean room. To clean the mixing device, the mixing device is moved into the receiving device and removed from the process flow, for example by manual, pneumatic, hydraulic or electric means. By being removed from the process flow within the receiving unit, a clean room is provided.

In order to guide the mixing device in the receiving device, a connection can be provided. Preferably, for example a slide can be integrated in the receiving device, which is moved manually, pneumatically, electrically or hydraulically into the receiving device. The slider is a separating device for separating the cleaning space, if it is installed over the entire cross-section of the receiving device.

In addition to the aforementioned method of mixing liquid chemicals into a process stream by means of a mixing device, the present invention also provides a device for mixing liquid chemicals into a process stream. In order to be able to select the flow speed in the mixing device or in the supply device so high that no or only low deposits occur during continuous operation, the small pipes at the inflow lines of the fluid chemicals are selected accordingly The cross-section of the road is such that the flow speed reaches the range of 0.05 m/s to 20 m/s, preferably reaches the range of 0.1 m/s to 10 m/s, and especially reaches the range of 0.1 m/s to 5 m/s within range.

To prevent adhesions on the pipe walls, the flushing process is carried out with small pipe cross-sections resulting in high flow velocities. It is particularly preferred to form the device such that no ball valve or another shut-off device is provided to the inflow line. Thus, the possibility of deposits forming at the narrow profile edges of ball valves or shut-off devices is prevented. In addition, production is simplified, since such components are expensive to machine, in particular electropolishing must be carried out.

For placing and removing the mixing device in the process flow, it may be proposed to make the mixing device movable within the receptacle.

In addition to the apparatus according to the invention, the invention also provides a chemical supply system for use in a paper machine, wherein said chemical supply system is characterized in that the means for supplying chemicals to a process flow comprises a chemical supply system according to Mixing device of the present invention. In a further embodiment, it can be proposed to connect the device via a line to a process water recovery in order to use process water as the second liquid and/or dilution liquid.

Description of drawings

The invention is described below by way of example and non-limitatively with reference to the drawings.

Each picture is:

Figure 1 shows a first configuration of a dosing nozzle according to the invention;

Figures 2a-2b show further configurations of dosing nozzles according to the invention with offset feed openings;

Figure 3 shows a feed device with opposing feed openings and turbulence generators;

Figure 4 shows opposing supply openings with turbulence generators for chemical flow and dilution liquid;

Figure 5 shows a device according to the invention with an inclined nozzle;

Figure 6 shows a mixing device according to the invention with inclined feed means and additional feed lines;

Figure 7 shows a mixing device according to the invention with an inclined supply device and a turbulence generator;

Figure 8 shows a mixing device with inclined nozzles and cleaning devices.

Detailed ways

In FIG. 1 a mixing device 10 according to the invention is shown which comprises a chemical inflow pipe 12 with a chemical inflow opening 14 and a dilution fluid inflow pipe 16 with a dilution fluid inflow opening 18 . The chemical inflow line 18 and the chemical inflow line 12 open out in a housing which is preferably formed as a mixing tube 20 of the mixing device 10 . The mixing tube 20 is supplied with a fluid flow through the fluid inflow opening 30 . In the region of the mixing zone 40 the chemical stream is mixed with the dilution fluid and then mixed from the mixing zone into the fluid supplied through the inflow opening 30 . Below the mixing zone, a fluid flow comprising fluid, dilution fluid and chemicals is introduced from the mixing tube into the nozzle 50 as a mixed flow. By forming the mixing tube as a nozzle in region 50 , the mixed flow can be accelerated and provided to process flow 70 through outflow opening 60 .

In particular, a practically complete mixing of the fluid stream and the chemical stream as well as the dilution stream is achieved by the device according to the invention, so that a homogeneously mixed chemical fluid fiber mixture is dosed into the process stream through the outflow opening 60 and can be combined with all Mixing of the process streams described above.

By forming the outflow opening as a nozzle, an acceleration of the mixed flow and thus a deep penetration of the mixed mixed flow into the process flow can be achieved.

The outflow opening 60 is preferably formed by a preferably cylindrical inner cross section of the mixing tube 20 , which has a diameter d ₄ in the region of the outflow opening. In general, d ₄ is smaller than d ₃ , ie the mixing tube is formed as a nozzle in the region of the outflow opening.

Preferably, in the mixing tube, the flow velocity of the fluid flow is selected as a function of the diameter d ₄ or d ₃ such that a turbulent flow characteristic is preferably formed. The length of the turbulent flow or the type of flow, i.e. whether it is turbulent or laminar in the mixing tube, can be described by the Reynolds number. The flow type or Reynolds number can be influenced in particular by the volumetric flow rate of the fluid flow provided before the dilution fluid and chemical mix.

If the mixing tube, as shown, has a stepped and discontinuous diameter reduction, the outflow opening can be formed not in the form of a nozzle as shown, but as a simple cylindrical hollow body with a diameter _d4 .

It is particularly preferred that the ratio of the diameter d ₁ of the dilution pipe to the diameter d ₂ of the chemical pipe is 1:1 to 20:1, preferably 5:1 to 10:1. That is, d ₁ :d ₂ is in the range of 1:1 to 20:1.

As shown in FIG. 1 , the dilution pipe projects into the mixing pipe at an angle α1=90° and the chemical pipe at an angle α2=90° relative to the housing wall 55 .

Furthermore, it can be seen that the distance AB between the supply opening 18 of the dilution fluid and the supply opening 14 of the chemical is small and preferably between 1 mm and 1/4 of the diameter d ₃ of the mixing tube.

If the supply openings of the dilution fluid stream and the supply openings of the chemical stream are in close proximity, the dilution fluid can mix with the chemical stream and be mixed completely into the fluid stream. In the embodiment of FIG. 1 , the mixing of the chemical stream and the diluent fluid stream therefore takes place before introduction into the fluid stream.

The mixing relationship or chemical concentration prior to mixing the mixed stream into the fluid stream and eventual introduction into the process liquid can be adjusted by corresponding sizing of the pipe diameter of the dilution water stream and the pipe diameter of the chemical stream. Preferably, the pressure difference δP of the dilution fluid relative to the fluid stream is in the range of 0.5 bar to 5 bar, preferably in the range of 1 bar to 2 bar, and the pressure difference of the chemical stream relative to the fluid stream is -0.25 bar to 0bar range.

A slightly modified configuration of the feeding device according to FIG. 1 is illustrated in FIG. 2 . Components that are the same as in Figure 1 have the same reference numerals in Figures 2a and 2b. A clear difference from the embodiment in FIG. 1 is that the supply lines for the dilution fluid flow and the chemical flow are not situated opposite each other in the same plane, but are arranged offset from one another in the mixing tube at a distance ABS.

Furthermore, the embodiment according to FIG. 2a is characterized in that impact surfaces 100.1, 100.2 are provided in the mixing tube, which are used on the one hand to divert the dilution fluid flow, for example the dilution water flow, coming out of the dilution line 16 or the chemical line 12. And the chemical stream deflects and increases the turbulence of the flow so that a swirl is created and the mixture comprising the diluent fluid stream and the chemical stream and the fluid stream exits the nozzle eg in a centrifugal flow as it exits the mixing tube from the nozzle into the process stream. The advantage of such devices is to increase the penetration depth of the jet leaving the nozzle.

The mixing tube 20 has a mixing space or zone 25 (boundary shown in dashed lines). Preferably, in an embodiment not shown, the mixing space 25 can be formed as a diffuser over the entire length L _misch . In an alternative embodiment, it is realized that only the part of the chemical pipe 12 behind the chemical supply opening 14 is formed as a diffuser (not shown) as a length L _CHEM . Such a diffuser can be realized by having a mixing tube with steps, ie the preferably cylindrical inner cross-section of the mixing tube 20 has a stepped widening. Such a stepwise widening of the cross-section leads to an increase in the turbulence of the flow and thus to a stronger mixing of the fluid flow, such as the fiber flow, in particular to the fiber part flow with the dilution fluid flow and/or the chemical flow. Strong mix.

In general, with a constant cross-section of the mixing tube, the degree of turbulence can also be influenced by increasing the volumetric flow velocity, for example by increasing the volume of the fluid flow supplied to the mixing device.

In an alternative configuration of the mixing device according to the invention, the mixing tube is formed as an injector or as a multi-stage injector. In Fig. 2b a mixing tube formed as an injector in the form of an injector pump is shown. The same components as in Figures 1 and 2a are indicated with the same reference numerals. In FIG. 2 b , the mixing tube 20 is configured in the form of a jet pump 2000 . First, the mixer 20 narrows in region 2010 from diameter d ₃ to diameter d _Fluid . After the mixing tube 20 narrows in the region 2010 , the mixing tube again has an enlargement to the diameter d ₃ in the supply region of the dilution fluid line 16 . In the embodiment according to FIG. 2 b , the dilution fluid and the chemical are again supplied successively, ie the dilution fluid supply opening 18 is at a distance ABS from the chemical supply opening 14 . The mixed zone is marked with 25. After the dilution fluid and chemical supply, the mixing tube narrows again continuously in region 2020 . In section 2030, the inner cross-section of the mixing tube increases continuously again. This configuration of mixing tubes is also known as an injector. The turbulence and thus the mixing efficiency can be influenced by the geometry and course of the preferably cylindrical cross-section of the diffuser or injector.

Furthermore, chemical fluid dosing and/or diluent fluid dosing can also be achieved via the impact surface. This is especially the case in the embodiment according to FIG. 3 . The same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals. The embodiment according to FIGS. 2 and 3 differs in that the inflow lines for the dilution fluid and the chemical are substantially opposite. Also in the embodiment according to FIG. 3 , impact surfaces 100 . 1 , 100 . 2 are again provided, with which the flow can be deflected or turbulence can be introduced into the flow. The injection into the fluid stream takes place via opposing supply lines for the chemical stream and the diluent fluid stream.

In the embodiment according to FIG. 3, in addition to the impact surfaces already shown in FIG. While in the process flow exits in the centrifugal flow and additionally enables dosing of chemicals and/or diluent fluids.

The embodiment shown in FIG. 4 is similar to the embodiment according to FIG. 3 in that the supply opening 18 for the dilution fluid and the supply opening 14 for the chemical are located opposite each other, but compared to the embodiment according to FIG. A similarly narrow distance A as shown in Figure 1, preferably between 1 mm and 1/4 of the diameter _D3 of the mixing tube, enables the dilution fluid and chemicals to be largely Complete mixing before entering the fluid stream. In the mixing tube 20 , in all the embodiments described so far, a mixing space or mixing zone 25 is formed in which the dilution fluid and the chemical stream and the fluid stream mix with each other (the border is indicated by a dotted line), so that in the outflow to the process stream 70 There is a strong and virtually complete mixed flow at the opening 60 comprising the fluid flow, the dilution fluid flow and the chemical flow.

Before this mixture reaches the nozzle device, the mixed flow can be accelerated by the nozzle device and injected into the process flow. The amount of dilution fluid determines the chemical concentration within the fluid stream.

In all the embodiments according to FIGS. 1 to 4 , the angle α1 of the dilution supply line or the angle α2 of the chemical supply line is 90°, while the embodiments according to FIGS. 5 , 6 and 7 show where the supply In the configuration according to the invention, the angle of the lines is less than 90°, ie the angle is preferably in the range of 60° to 45° relative to the housing wall of the mixing tube or the axis of symmetry 201 of the mixing tube.

By means of an inclination in the range of 60° to 45°, mixing can be achieved without strongly deflecting the flow in the direction away from the opening. Components that are the same as in FIGS. 1 to 4 are again designated with the same reference numerals.

In the configuration according to FIG. 5 , the distance between the chemical supply opening 14 and the dilution fluid supply opening 18 is again very small, namely between 1 mm and 1/4 of the diameter D ₃ of the mixing tube, so that after spraying into the fluid Intense mixing of the chemical stream and the diluent fluid stream and thus concentration regulation is achieved beforehand within the stream.

In the configuration according to FIG. 6 , in addition to the dilution and chemical lines shown in FIG. 5 , further supply lines are provided. Additional fluid can be injected into the fluid flow within the mixing tube 20 from an additional supply line 300 . For example, the additional fluid may be an additional chemical flow or also a feed of filler-slurry. Feed angles α1 and α2 like the chemical line and dilution fluid supply line The supply line 300 is also arranged at an angle α3 in the range of 60° to 45°.

FIG. 7 shows the supply lines for the dilution fluid 16 or the chemical 12 and the impact surfaces 100.3, 100.3, A combination of 100.4, 100.5, 100.6.

Particularly preferred is the embodiment according to FIG. 8 , in which, apart from the supply line, the mixing device is movable in the axial direction within the receptacle. The same components as in Fig. 6 have the same reference numerals. In the configuration according to FIG. 8 the mixing chamber can simultaneously be used as a clean chamber. To this end, the supply of the second liquid in the process stream is effected. The end portion 54 can be varied in its length so that it can be adjusted whether the second liquid stream fed through the second flow channel exits at the same time as the chemical stream fed through the first flow channel 12 or the first fluid stream, or before the latter Or leave later.

In the embodiment according to FIG. 8 , the mixing device 200 is movable in the axial direction 222 within the receiving housing 220 or receptacle.

In addition to the configuration illustrated in FIGS. 1 to 7 , the receiving device 220 includes a cut-off slide 230 . The stop slide 230 is designed to be movable in a direction 232 . The mixing device 200 or the dosing nozzle can be guided through the shown open shut-off slide.

In FIG. 8 , the mixing device 200 is led out of the process flow in direction 222 within the receiving piece or receiving housing when the valve 230 is opened, for example pneumatically, hydraulically or electrically.

To start the cleaning process, in the position of the mixing device 200 according to FIG. 8 , the valve 230 can be introduced over the entire cross-section of the receiving device 220 . The mixing device 200 is separated from the process flow 70 by the closed shut-off valve 230 . Between the mixing device 200 and the shut-off valve 230 a clean space 400 is formed, which preferably coincides with the mixing zone.

To start the cleaning, fresh water can be supplied, for example, in the chemical supply line instead of the chemical flow. Of course, it can also be supplied through a dilution supply line or another supply line.

Fresh water supplied via, for example, a chemical supply line impinges on the closed shut-off device 230 during the cleaning step and can be supplied in the two further supply lines 16 , 300 . In this case, the medium that follows in this supply is squeezed out by fresh water or fluid cleaning medium. Nozzles and lines, in particular mixing devices, can be cleaned of chemicals contained therein, especially deposits of chemicals, as illustrated by such cleaning steps. Thus, blockages of mixing equipment and supplies caused by deposits are actively addressed during shutdowns independently of the process flow.

The chemicals to be dosed are in particular polymers such as adhesives which are added to process streams in papermaking processes. Examples of such chemicals or polymers are polyacrylamide (PAM), polyethyleneimine (PEI), polyacrylamine (PAAm), crosslinkable polyacrylamine resins, polydimethyldiallyl chloride ammonium chloride, polyvinylamine (PVAm), polyethylene oxide (PEO). As an alternative to the aforementioned polymers, the dosing chemicals can also be microparticles or nanoparticles, such as bentonite or silicates. Furthermore, the chemical to be dosed may be a starch or a biocide or a pigment or a gloss enhancer. Further possible chemicals are neutral binders such as AKD (alkyl ketone dimer) or ASA (alkenyl succinic anhydride). Furthermore, the method according to the invention makes it possible to also meter minerals in the form of a suspension, eg calcium carbonate, titanium dioxide, into the second liquid or into the process stream.

The use of the device according to the invention and the method according to the invention gives a method and a device to achieve virtually complete mixing of the chemical stream with the dilution fluid stream and the fluid stream fed into the process stream. In particular, a swirling flow is also generated by means of the impact surface, so that the mixed flow has a centrifugal flow when it enters the process flow and thus has a great penetration depth into the process flow.

Claims (19)

1. A method for mixing fluids or liquids, in particular chemical-containing liquids or liquid chemicals themselves, into a process flow by means of a mixing device (10, 200), comprising, in particular, a mixing tube (20) a housing, at least one fluid inflow opening (30), a chemical inflow opening (14), a dilution fluid inflow opening (18), and at least one outflow opening (60) to a process stream (70), It is characterized in that the chemical flow from the chemical inflow opening (14) and the dilution fluid flow from the dilution fluid inflow opening (18) are mixed into the fluid flow, and the fluid flow is passed through the outflow after the chemical flow and the dilution fluid flow are mixed. The openings ( 60 ), in particular via nozzles, are accelerated into the process flow ( 70 ), preferably sprayed into said process flow ( 70 ). 2. The method of claim 1, wherein the chemical stream and the dilution fluid stream are substantially mixed with each other before being mixed into the fluid stream. 3. A method according to claim 1 or 2, characterized in that the concentration of the chemical in the fluid stream is adjusted by the amount of dilution fluid added. 4. Method according to one of claims 1 to 3, characterized in that the chemical inflow opening and/or the dilution fluid inflow opening are inclined at an angle relative to the housing wall, in particular relative to the axis of symmetry of the mixing tube (201) Tilted at an angle. 5. Method according to claim 4, characterized in that said angles (α1, α2, α3) are between 10° and 90°, preferably between 45° and 60°. 6. Method according to one of claims 1 to 5, characterized in that a further chemical or a further fluid flow, in particular a filler slurry, is supplied to the fluid flow. 7. The method according to one of claims 1 to 6, characterized in that the chemical stream and/or the dilution fluid stream and/or the fluid stream are influenced before and/or after the mixing in such a way that the especially The centrifugal flow is fed to the process flow (70) through the outflow opening (60). 8. The method according to one of claims 1 to 7, characterized in that it comprises a cleaning step in addition to the mixing step in which liquid chemicals are supplied to the fluid flow, and in said cleaning step the mixing device ( 200 ) is separated from the process stream ( 70 ) so that the mixing device ( 200 ) can be cleaned independently of the process stream ( 70 ). 9. Apparatus for mixing liquid chemicals into a process stream (70), said apparatus comprising a housing, in particular a mixing tube (20), at least one fluid inflow line (30), and the chemical inflow line (12), dilution fluid inflow line (16) and outflow line (60), It is characterized in that, At least the chemical inflow line (17) and the dilution fluid inflow line (16) are arranged such that a mixing area (25) is formed in the housing, in particular in the mixing tube, wherein the At least one of the chemical stream and the dilution fluid stream is introduced into the fluid stream such that after the mixing zone the chemical stream, the dilution fluid stream and the fluid stream are largely mixed such that the resulting well mixed flow exits the outflow opening (60 ) is introduced into the process flow (70). 10. Device according to claim 9, characterized in that at least one chemical inflow line (12) and/or dilution fluid inflow line (16) is inclined at an angle (α1, α2) relative to the housing wall , especially at an angle relative to the axis of symmetry of the mixing tube. 11. Device according to claim 10, characterized in that the angles (α1, α2) are between 90° and 10°, preferably between 60° and 45°. 12. Device according to one of claims 9 to 11, characterized in that the chemical inflow line (12) and the dilution fluid inflow line (16) are spatially adjacent to each other such that from the chemical inflow opening The exiting chemical stream and the dilution fluid stream exiting the dilution fluid inflow opening are largely intermixed with the fluid stream prior to mixing. 13. The device according to claim 12, characterized in that the gap between the chemical inflow opening (14) of the chemical inflow line (12) and the dilution outflow opening (18) of the dilution fluid inflow line (18) The distance AB is between 1 mm and 100 mm, preferably between 1 mm and a quarter of the diameter (d3) of the mixing tube (20). 14. Apparatus according to claim 12 or 13, characterized in that the pressure difference (δp) between the dilution fluid and the fluid flow coming out of the dilution outflow opening (18) is between 0.5 bar and 5 bar, preferably between Between 1 bar and 2 bar, and/or the pressure difference (δp) between the chemical flow coming out of the chemical outflow opening (14) relative to the dilution flow coming out of the dilution outflow opening (18) is between -0.2 bar and 0 bar between. 15. The device according to one of claims 10 and 14, characterized in that the ratio between the inside diameter of the dilution fluid inflow line (16) and the inside diameter of the chemical inflow line (12) is 1: 1 to 20:1, preferably 5:1 to 10:1. 16. Device according to one of claims 9 and 15, characterized in that the housing comprises impact surfaces (100.1 , 100.2, 100.3, 100.4, 100.5, 100.6). 17. Apparatus according to one of claims 9 and 16, characterized in that the housing is formed in the form of a nozzle such that the mixture comprising the fluid stream, the dilution fluid stream and the chemical is accelerated before being injected into the process stream. 18. A chemical supply system for use in a paper machine inflow system, characterized in that the means for supplying chemicals into a process flow comprises an apparatus according to one of claims 9 to 17. 19. The chemical supply system according to claim 18, wherein the device is connected to a process water recovery device through a pipe to use the process water as the second liquid.

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