CN103002977B

CN103002977B - For chemicals being mixed into the method and apparatus in process streams

Info

Publication number: CN103002977B
Application number: CN201180033333.9A
Authority: CN
Inventors: T.贾欣斯基
Original assignee: Voith Paper Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2010-05-05
Filing date: 2011-04-14
Publication date: 2015-11-25
Anticipated expiration: 2031-04-14
Also published as: EP2566607A1; CN103002977A; EP2566607B1; WO2011138143A1; DE102010028577A1

Abstract

The present invention relates to a kind of method and apparatus be mixed into by liquid chemicals by mixing apparatus (10,200) in process streams, described mixing apparatus comprises: the especially housing of mixing tube (20), at least one fluid inlet opening (30), chemicals inlet opening (14), diluted fluid inlet opening (18), and at least one leads to the outflow opening (60) of process streams (70).Feature according to method of the present invention is, by the chemicals stream from chemicals inlet opening (14) be mixed into fluid stream from the diluted fluid stream of diluted fluid inlet opening (18), and after chemicals stream and the mixing of diluted fluid stream fluid flowed through and flow out opening (60) and be particularly supplied to process streams (70) post by nozzle, be preferably injected in described process streams (70).

Description

Method and apparatus for mixing chemicals into a process stream

Technical Field

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

Background

Special requirements are placed on the dosing and subsequent mixing-in of chemicals, for example in paper-making processes, in particular with regard to efficient mixing-in and on-demand dosing of chemicals. Dosing on demand refers to the addition of chemicals in the process flow of a paper machine, for example, in the paper making process, depending on the amount of fibers. By such measures, the amount of added chemicals can be reduced significantly in the paper making process. Another reason for the efficient use of chemicals is that the heating of fresh water to dissolve or dilute the process chemicals requires a large amount of energy. Such heating is advantageous to avoid thermal shock when mixing chemicals into fresh water. By providing an efficient method of dosing and mixing chemicals into a process stream, in particular when manufacturing fibrous and/or non-woven webs, it is possible to a significant extent to reduce not only the consumption of process chemicals and functional chemicals but also the use of fresh water as dilution medium in the preparation of the chemicals.

A number of methods and devices for mixing a chemical stream into a process stream are known from the prior art. EP- ｃA-1219344 thus provides ｃA method for mixing ｃA liquid chemical into ｃA process liquid stream, wherein the chemical and ｃA second liquid are substantially mixed with each other if the chemical and the second liquid are introduced into the process stream from ｃA mixing nozzle at high velocity.

EP- ｃA-1064427 describes ｃA method and an apparatus for mixing ｃA liquid chemical stream into ｃA second liquid stream in ｃA mixing device, wherein the chemical stream is mixed with the second liquid stream substantially simultaneously in ｃA further fourth liquid stream, in particular ｃA process stream, as the chemical is evolved in the second liquid stream.

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

A disadvantage of the apparatus 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 stream and thus not A completely mixed fluid stream, chemical stream and dilution water stream is injected into the process stream, but the mixing of the chemical stream and the dilution water stream takes place separately from the fluid stream.

From WO91/02119 an apparatus is known in which additives are mixed into an aqueous fiber suspension for the production of paper.

In the configuration according to WO91/02119, the two separately guided streams are mixed outside the process stream and the mixed stream is injected transversely to the process stream after complete mixing. A disadvantage of WO91/02119 is that accelerated injection is not achieved in the process stream.

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

All the aforementioned methods and apparatuses furthermore have the disadvantage that deposits form in the inflow line and also in the mixing apparatus, in particular in the nozzle itself, during longer-term operation. The formation of such deposits is critical, in particular in the region of the mixing device, for example in the form of a nozzle, since the cross section of the channel is small, and small amounts of deposits can already significantly influence the incorporation of chemicals into, for example, the process stream as a result of said small cross section.

Deposits can occur even in the event of an unplanned sudden production stop, where chemicals remain in the inflow lines and mixing equipment, especially in the nozzles. The deposits can not only affect the mixing process as described before, but also fall off when the production process is started after the machine has stopped. The deposits lead, for example, to holes in the paper web or to deposits on the screen, which in turn leads to expensive cleaning shutdowns. This problem is particularly pronounced in the dosing after the screening apparatus in the paper machine, since undissolved chemicals, in particular undissolved polymers, cannot be removed from the fibre suspension.

In order to avoid deposits during continuous operation, it is advisable in the prior art to select the line cross section of the inflow line and the line cross section in the region of the mixing device to be sufficiently large so that such deposits are largely avoided. This of course results in the cross section of the inflow line or the nozzle of the mixing device being dimensioned such that sufficiently high flow velocities cannot be achieved in order to prevent such deposits. If the cross section is reduced, however, this can lead to blockages and thus to a malfunction of the mixing device, in particular of the nozzle, which leads to production stoppages and to replacement of the entire nozzle or the inflow line.

Disclosure of Invention

The technical problem underlying the present invention is therefore to avoid the disadvantages of the prior art.

In particular, a method and a device for dosing or mixing a fluid or a liquid, in particular a liquid containing a chemical or a liquid chemical itself, into a process flow for producing a fibrous or nonwoven web are provided, wherein a homogeneously mixed chemical fluid fiber mixture is injected into the process flow and mixed therewith as far as possible. Furthermore, stoppages, which may result in deposits and deposits falling off of holes in the fibrous web, for example when the production process is restarted, should also be avoided.

According to the invention, this object is achieved by a method for mixing a liquid chemical into a process stream by means of a mixing device comprising a housing, in particular in the form of a mixing tube, a fluid inlet opening, a chemical inlet opening, a dilution fluid inlet opening, and at least one outlet opening to the process stream. The method is characterized in that a chemical flow from the chemical inflow opening and a dilution fluid flow from the dilution fluid inflow opening are mixed into the fluid flow, and the fluid flow is supplied to the process flow, preferably sprayed, accelerated through the outflow opening, in particular through the nozzle, after the at least one chemical flow and the dilution fluid flow have mixed.

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

By achieving a strong mixing of the fluid stream with the dilution fluid and the chemical, an overall mixing with the fluid stream can be achieved to a large extent, and then the homogeneously mixed chemical fluid stream fiber solution is dosed into the process stream through the outflow opening and mixed therewith there.

The chemicals to be dosed are in particular polymers, for example adhesives added to the process stream in a paper making process. Examples of such chemicals or polymers are Polyacrylamide (PAM), Polyethyleneimine (PEI), polyallylamine (PAAm), crosslinkable polyallylamine resins, polydimethyldiallylammonium chloride, polyvinylamine (PVAm), polyethylene oxide (PEO). As an alternative to the aforementioned polymers, the dosed chemical may also be micro-or nanoparticles, such as bentonite or silicate. Furthermore, the chemical to be dosed may be 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 dose mineral substances, for example calcium carbonate, titanium dioxide, also in the form of a suspension, into the second liquid or into the process stream.

It is particularly preferred that the dosing of the chemical is not directly added from the chemical nozzle into the process stream, but takes place after the liquid chemical has been mixed with the dilution liquid and the fluid stream. The dilution liquid and/or the fluid stream 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, in the manufacture of a fibrous web, the circulating liquid is white water, clear filtrate, turbid filtrate or another suitable non-pure liquid occurring in the paper making process. But also clear water or clear filtrate primary ultra-clear filtrate comprising micro-suspension (DAF), e.g. ultra-clear filtrate of a disc filter, is conceivable. The dilution liquid and/or fluid may also be process water from a waste water cleaning plant, i.e. using so-called biological water. The process stream may preferably be the added chemical, such as a fibre suspension flowing into the paper machine with which the retention chemical will react.

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

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

In particular, in an expanded embodiment, it is achieved that the chemical stream and the dilution fluid stream are substantially mixed with one another before being mixed into the fluid stream. In particular, the method also enables the adjustment of the chemical concentration within the fluid stream by the amount of dilution fluid added. To this end, the relationship of the pipe diameter of the dilution fluid flow to the pipe diameter of the chemical flow may for example be varied, preferably in the range of 1:1 to 20:1, preferably in the range of 5:1 to 10:1, i.e. the pipe diameter of the inflow pipe of the dilution fluid flow is in the limit case 20 times larger than the pipe diameter of the inflow pipe of the chemical flow.

Preferably, the supply of the chemical flow and the supply of the dilution flow to the fluid flow and possibly the supply of the further chemical or the further fluid flow to said fluid flow take place at an angle to the housing wall, in particular at an angle with respect to the symmetry axis of the mixing tube.

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.

It is particularly preferred to take measures in the region of the housing or the mixing tube, so that turbulence is generated or increased in the flow provided to the process stream. This can be done, for example, by means of an impact surfaceAnd (5) realizing.

Alternatively, a swirling flow may be created such that the mixing exits the nozzle as a centrifugal flow as long as it exits the nozzle into the process flow. In this way, the penetration depth of the jet with the mixed-in chemical and dilution fluid in the process flow increases. Furthermore, the introduction of the impact surface not only enables a turbulent flow, but also a dosing of the chemical and/or dilution stream.

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

The separation of the mixing device from the process stream, which separation is effected for example in such a way that the mixing device is received by the receiving means, wherein the mixing device is arranged in the receiving means in a cleaning step to form a cleaning chamber, enables a process-stream-independent cleaning of the mixing device. A cleaning liquid, for example fresh water, can be supplied into the cleaning chamber, with which the inflow lines and the nozzles are rinsed. By flushing the mixing device and the inflow line, deposits are removed therefrom and thus clogging of the mixing device and the feed piece by deposits is largely avoided.

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

To guide the mixing device within the receiving means, a joint may be provided. Preferably, a slide can be integrated in the receiving device, for example, which slide is moved manually, pneumatically, electrically or hydraulically into the receiving device. The slide is a separating device for separating the cleaning space if the slide is mounted over the entire cross section of the receiving device.

In addition to the aforementioned method of mixing a liquid chemical into a process stream by means of a mixing device, the present invention also provides a device for mixing a liquid chemical into a process stream. In order to be able to select the flow velocity in the mixing device or in the feed device to be high so that no or only very low deposits are formed during continuous operation, the small line cross section at the inflow line of the fluid chemical is correspondingly selected so that the flow velocity reaches a range of 0.05 m/s to 20 m/s, preferably 0.1 m/s to 10 m/s, and in particular 0.1 m/s to 5 m/s.

To prevent adhesion to the pipeline wall, the flushing process is carried out with a small pipeline cross section resulting in a high flow velocity. It is particularly preferred to form the device such that no ball valve or further shut-off device is provided to the inflow line. Thus, the possibility of deposit formation at the narrow profile edge of the ball valve or shut-off device is prevented. Furthermore, the production is simplified, since the processing of such components is expensive, in particular the electrolytic polishing must be carried out.

In order to place the mixing device in the process flow and to remove it therefrom, it may be advisable to form the mixing device so as to be 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 the chemical supply system is characterized in that the means for supplying chemicals to the process stream comprise a mixing apparatus according to the invention. In an expanded embodiment, it can be provided that the device is connected to a process water recovery device via a line in order to use the process water as the second liquid and/or dilution liquid.

Drawings

The invention is described below by way of example and without limitation in the figures of the accompanying drawings.

The figures are as follows:

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

fig. 2a to 2b show further configurations of a dosing nozzle according to the invention with an offset supply opening;

fig. 3 shows a feeding device with opposed feeding openings and turbulence generators;

FIG. 4 shows opposite feed openings with turbulence generators for the chemical flow and the dilution liquid;

FIG. 5 shows an apparatus according to the invention with a tilted nozzle;

FIG. 6 shows a mixing apparatus with an inclined feed device and further feed lines according to the invention;

figure 7 shows a mixing device with an inclined feeding means and a turbulence generator according to the invention;

figure 8 shows a mixing device with an inclined nozzle and a cleaning device.

Detailed Description

In fig. 1 a mixing device 10 according to the invention is shown, said mixing device 10 comprising a chemical inflow tube 12 with a chemical inflow opening 14 and a dilution fluid inflow tube 16 with a dilution fluid inflow opening 18. The chemical inflow conduit 18 and the chemical inflow conduit 12 open 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 flow is mixed with the dilution fluid and then from the mixing zone into the fluid supplied through the inflow opening 30. Below the mixing zone, a fluid stream comprising the fluid, the dilution fluid, and the chemical is introduced as a mixed stream from the mixing tube into the nozzle 50. By forming the mixing tube as a nozzle within the region 50, the mixed flow may be accelerated and provided to the process flow 70 through the outflow opening 60.

In particular, a practically complete mixing of the fluid flow and the chemical flow and the dilution flow is achieved by the device according to the invention, so that the homogeneously mixed chemical fluid fiber mixture is dosed into the process flow through the outflow opening 60 and can be mixed with said process flow.

By forming the outflow opening as a nozzle, an acceleration of the mixed flow and thus a deep intrusion of the mixed flow within 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,the cross section has a diameter d in the region of the outflow opening₄. In general, d₄Is less than d₃I.e. the mixing tube is formed as a nozzle in the region of the outflow opening.

Preferably, the flow velocity of the fluid stream within the mixing tube is dependent on the diameter d₄Or d₃The selection is such that preferably turbulent flow characteristics are formed. The length of the turbulence or the type of flow, i.e. whether turbulent or laminar within the mixing tube, can be described by the reynolds number. The flow type or reynolds number may in particular be influenced by the volumetric flow rate of the fluid flow provided before the dilution fluid and the chemical are mixed.

If the mixing tube has a stepped and discontinuous diameter reduction as illustrated, the outflow opening may not be formed in the form of a nozzle as illustrated, but rather in the form of a nozzle with a diameter d₄A simple cylindrical hollow body.

It is particularly preferred that the diameter d of the dilution tube₁Diameter d of chemical tube₂Is from 1:1 to 20:1, preferably from 5:1 to 10: 1. I.e. d₁:d₂In the range of 1:1 to 20: 1.

As illustrated in fig. 1, the dilution pipe projects into the mixing pipe at an angle α 1=90 ° relative to the housing wall 55 and the chemical pipe projects into the mixing pipe at an angle α 2=90 ° relative to the housing wall 55.

Furthermore, it can be seen that the distance AB between the supply opening 18 for the dilution fluid and the supply opening 14 for the chemical is small, and preferably between 1mm and the diameter d of the mixing tube₃1/4.

If the supply openings for the dilution fluid stream and the chemical stream are in close proximity, the dilution fluid may mix with the chemical stream and be thoroughly mixed into the fluid stream. In the embodiment of fig. 1, the mixing of the chemical stream and the diluting fluid stream is therefore carried out before introduction into the fluid stream.

The mixing relationship or chemical concentration before the mixed stream is mixed into the fluid stream and finally introduced into the process liquid can be adjusted by corresponding dimensioning of the pipe diameter of the dilution water stream and the pipe diameter of the chemical stream. Preferably, the pressure difference P of the dilution fluid with respect to the fluid flow is in the range of 0.5 to 5bar, preferably in the range of 1 to 2bar, and the pressure difference of the chemical flow with respect to the fluid flow is in the range of-0.25 to 0 bar.

A slightly modified configuration of the feed device according to fig. 1 is illustrated in fig. 2. The same components as in fig. 1 have the same reference numerals in fig. 2a and 2 b. The significant difference to the embodiment in fig. 1 is that the supply lines for the dilution fluid flow and the chemical flow are not arranged opposite one another in the same plane, but are arranged offset from one another in the mixing tube at a distance from the ABS.

The embodiment according to fig. 2a is further characterized in that impact surfaces 100.1, 100.2 are provided in the mixing tube, which impact surfaces serve to deflect the dilution fluid flow, for example a dilution water flow, and the chemical flow, which exit the dilution tube 16 or the chemical tube 12 on the one hand, and to increase the turbulence of the flow, so that a swirling flow is generated and so that the mixture, which comprises the dilution fluid flow and the chemical flow and the fluid flow, exits the nozzle, for example in a centrifugal flow, when it exits the mixing tube from the nozzle into the process flow. An advantage of such an apparatus is that the depth of penetration of the beam exiting the nozzle is increased.

The mixing tube 20 has a mixing space or mixing zone 25 (the boundaries are illustrated in dashed lines). In an embodiment that is not shown, the mixing space 25 can preferably extend over the entire length L_mischAnd is formed as a diffuser. In an alternative embodiment, it is provided that only the part of the chemical tube 12 behind the chemical feed opening 14 is used as the length L_CHEMFormed as a diffuser (not shown). Such a diffuser may be realized by providing the mixing tube with a step, i.e. the preferably cylindrical inner cross-section of the mixing tube 20 has a step widening. Such a step-like widening of the cross-section leads to an increase in the turbulence of the flow and thus to a stronger mixing of the fluid stream, for example the fiber stream, in particular to a strong mixing of the fiber fraction stream with the diluting fluid stream and/or the chemical stream.

Generally, in case the cross-section of the mixing tube is constant, the degree of turbulence may also be influenced by increasing the volumetric flow velocity, for example by increasing the volume of the fluid flow fed to the mixing device.

In an alternative configuration of the mixing device of the invention, the mixing tube is formed as an ejector or as a multi-stage ejector. In fig. 2b a mixing tube formed as an ejector in the form of an ejector pump is shown. The same components as in fig. 1 and 2a are indicated with the same reference numerals. In fig. 2b, the mixing tube 20 is configured in the form of a jet pump 2000. First, mixer 20 is driven from diameter d within region 2010₃Reduced to diameter d_Fluid. After the mixing tube 20 has been narrowed in the region 2010, the mixing tube has again a diameter d in the supply region of the dilution fluid line 16₃Is enlarged. In the embodiment according to fig. 2b, the dilution fluid and the chemical are again supplied one after the other, i.e. the dilution fluid supply opening 18 is at a distance ABS from the chemical supply opening 14. The mixing zone is marked with 25. After the dilution fluid and chemical supply, the mixing tube narrows continuously again in the region 2020. Within section 2030, the internal cross-section of the mixing tube increases continuously again. This configuration of the mixing tube is also referred to as an ejector. 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 ejector.

Furthermore, the chemical fluid dosing and/or the dilution fluid dosing can also be achieved by the impact surface. This is particularly the case in the embodiment according to fig. 3. The same components as those shown in fig. 1 and 2 are denoted by the same reference numerals. The embodiment according to fig. 2 and 3 differs in that the inflow conduits for the dilution fluid and the chemical are essentially opposite. In the embodiment according to fig. 3, impact surfaces 100.1, 100.2 are also provided, with which the flow can be deflected or turbulence can be introduced into the flow. The injection into the fluid flow is effected by means of opposing supply lines for the chemical flow and the dilution fluid flow.

In the embodiment according to fig. 3, in addition to the impact surfaces already shown in fig. 2, further impact surfaces 100.3, 100.4, 100.5, 100.6 are provided for generating a swirling flow, so that the mixture leaves in the centrifugal flow when it leaves the nozzle into the process flow and furthermore a dosing of the chemical and/or the dilution fluid is achieved.

The embodiment shown in fig. 4 is similar to the embodiment according to fig. 3, i.e. the supply opening 18 for the dilution fluid and the supply opening 14 for the chemical are opposite one another, but has a similar narrow distance a as shown in fig. 1, preferably at 1mm and the diameter D of the mixing tube, compared to the embodiment according to fig. 3₃1/4 so that to a large extent complete mixing of the dilution fluid and the chemical is achieved before entry into the fluid stream. In all the embodiments described so far, a mixing space or mixing zone 25 (the boundary is indicated by a dashed line) is formed in the mixing tube 20 in which the dilution fluid and the chemical flow and the fluid flow are mixed with one another, so that at the outflow opening 60 to the process flow 70 there is a strong and virtually completely mixed mixing flow comprising the fluid flow, the dilution fluid flow and the chemical flow.

This mixed stream can be accelerated and injected into the process stream by the nozzle device before the mixture reaches the nozzle device. The amount of dilution fluid determines the concentration of chemicals within the fluid stream.

In all the exemplary embodiments according to fig. 1 to 4, the angle α 1 of the dilution feed line or the angle α 2 of the chemical feed line is 90 °, whereas the embodiments according to fig. 5, 6 and 7 show configurations according to the invention in which the angle of the feed line is less than 90 °, i.e. preferably in the range from 60 ° to 45 ° relative to the axis of symmetry 201 of the housing wall of the mixing tube or the mixing tube.

Mixing can be achieved by an inclination in the range of 60 ° to 45 ° without the flow having to be deflected very strongly in the direction away from the opening. The same components as in fig. 1 to 4 are again denoted by the same reference numerals.

In the configuration according to fig. 5, between the chemical supply opening 14 and the dilution fluid supply opening 18The distance between them is small, i.e. between 1mm and the diameter D of the mixing tube₃1/4 so that strong mixing of the chemical stream and the diluting fluid stream and hence concentration regulation is achieved before injection into the fluid stream.

In the configuration according to fig. 6, in addition to the dilution line and the chemical line shown in fig. 5, further supply lines are provided. Additional fluid may be injected into the fluid flow within the mixing tube 20 from additional supply lines 300. For example, the further fluid may be a further chemical stream or also a supply of filler-slurry. The supply lines 300 are also arranged at an angle α 3 in the range of 60 ° to 45 ° as are the supply angles α 1 and α 2 of the chemical lines and the dilution fluid supply lines.

Fig. 7 shows a combination of a supply line for dilution fluid 16 or chemical 12 and an impact surface 100.3, 100.4, 100.5, 100.6 for generating turbulence or chemical dosing and/or fluid dosing arranged in an angular range of 60 ° to 45 °.

Particularly preferred is the embodiment according to fig. 8, in which the mixing device is movable in the axial direction within the receptacle in addition to the supply line. The same components as in fig. 6 have the same reference numerals. In the configuration according to fig. 8, the mixing chamber can simultaneously serve as a cleaning chamber. For this purpose, a supply of the second liquid in the process stream is effected. The end portion 54 may vary in its length so that it is adjustable whether the second liquid stream supplied through the second flow path exits simultaneously with, before or after the chemical stream or the first fluid stream supplied through the first flow path 12.

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

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

In fig. 8, the mixing device 200 is led out of the process flow in direction 222 within the receptacle 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. Mixing apparatus 200 is separated from process stream 70 by a 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 area.

To start cleaning, fresh water may be supplied, for example, in the chemical supply line as a replacement for the chemical flow. Of course, it may also be supplied via the dilution supply line or another supply line.

Fresh water supplied via, for example, the 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. The medium along which the supply is made to flow is thereby pressed out by fresh water or fluid cleaning medium. The nozzles and lines, in particular the mixing device, can be cleaned of the chemicals contained therein, in particular the deposition of the chemicals, as illustrated, by such a cleaning step. Thus, clogging of the mixing device and the supply caused by deposits is actively handled independently of the process flow at shutdown.

The chemicals to be dosed are in particular polymers, for example adhesives added to the process stream in a paper making process. Examples of such chemicals or polymers are Polyacrylamide (PAM), Polyethyleneimine (PEI), polyallylamine (PAAm), crosslinkable polyallylamine resins, polydimethyldiallylammonium chloride, polyvinylamine (PVAm), polyethylene oxide (PEO). As an alternative to the aforementioned polymers, the dosed chemical may also be micro-or nanoparticles, such as bentonite or silicate. Furthermore, the chemical to be dosed may be 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 dose mineral substances, for example calcium carbonate, titanium dioxide, also in the form of a suspension, 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 practically 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 entering the process flow and thus a great penetration depth in the process flow.

Claims

1. A method of mixing a fluid or a liquid itself into a process stream by means of a mixing device (10, 200) comprising: 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),

wherein a chemical flow from the chemical inflow opening (14) and a diluting fluid flow from the diluting fluid inflow opening (18) are mixed into the fluid flow and the fluid flow is fed into the process flow (70) with acceleration through the outflow opening (60) after the mixing of the chemical flow and the diluting fluid flow,

characterised in that an additional chemical or an additional fluid stream is supplied to the fluid stream.

2. The method of claim 1, wherein the fluid or liquid is a chemical-containing liquid or liquid chemical.

3. Method according to claim 1, characterized in that the outflow opening (60) is a nozzle.

4. The method of claim 1, wherein the fluid stream is injected into the process stream (70).

5. The method of claim 1, wherein the chemical stream and the diluting fluid stream are substantially mixed with each other prior to being mixed into the fluid stream.

6. The method of claim 1 or 5, wherein the concentration of the chemical in the fluid stream is adjusted by the amount of dilution fluid added.

7. Method according to claim 1 or 5, characterized in that the chemical inflow opening and/or the dilution fluid inflow opening are inclined with respect to the housing wall of the mixing tube.

8. Method according to claim 7, characterized in that the angle (α 1, α 2, α 3) by which the chemical inflow opening and/or the dilution fluid inflow opening is inclined with respect to the housing wall of the mixing tube is between 10 ° and 90 °.

9. A method according to claim 1 or 5, characterized in that filler-slurry is supplied to the fluid flow as a further chemical or a further fluid flow.

10. Method according to claim 1 or 5, characterized in that the chemical flow and/or the dilution fluid flow and/or the fluid flow is influenced before and/or after mixing such that a turbulent flow is fed to the process flow (70) through the outflow opening (60).

11. The method according to claim 1 or 5, characterized in that the method comprises a cleaning step in addition to a mixing step in which liquid chemicals are fed to the fluid flow, and in that the mixing device (200) is separated from the process flow (70) in said cleaning step, so that the mixing device (200) can be cleaned independently of the process flow (70).

12. An apparatus for mixing a liquid chemical into a process stream (70), the apparatus comprising a housing, at least one fluid inflow conduit (30), a chemical inflow conduit (12), a dilution fluid inflow conduit (16) and an outflow conduit (60),

wherein,

at least the chemical inflow line (17) and the dilution fluid inflow line (16) are arranged such that a mixing region (25) is formed within the housing, wherein the chemical flow and the dilution fluid flow are introduced into the fluid flow and the resulting well-mixed flow is introduced from the outflow opening (60) into the process flow (70),

it is characterized in that the preparation method is characterized in that,

the chemical inflow conduit (12) and the dilution fluid inflow conduit (16) are in close spatial proximity to each other such that the flow of chemical out of the chemical inflow opening and the flow of dilution fluid out of the dilution fluid inflow opening are largely mixed with each other with the fluid flows before mixing, the distance AB between the chemical inflow opening (14) of the chemical inflow conduit (12) and the dilution outflow opening (18) of the dilution fluid inflow conduit (18) being between 1mm and 100 mm.

13. The apparatus according to claim 12, characterized in that at least one chemical inflow line (12) and/or dilution fluid inflow line (16) is inclined with respect to the housing wall.

14. The apparatus according to claim 13, characterized in that the at least one chemical inflow conduit (12) and/or dilution fluid inflow conduit (16) is inclined with respect to the housing wall by an angle (α 1, α 2) between 90 ° and 10 °.

15. The apparatus according to claim 12 or 13, characterized in that the distance AB between the chemical inflow opening (14) of the chemical inflow conduit (12) and the dilution outflow opening (18) of the dilution fluid inflow conduit (18) is between 1mm and a quarter of the diameter (d3) of the mixing tube (20).

16. The device according to claim 15, characterized in that the pressure difference (p) between the diluting fluid and the fluid flow exiting the diluting outflow opening (18) is between 0.5bar and 5bar and/or the pressure difference (p) between the chemical flow exiting the chemical outflow opening (14) with respect to the diluting flow exiting the diluting outflow opening (18) is between-0.2 bar and 0 bar.

17. The apparatus according to claim 13, characterized in that the ratio between the pipe inner diameter of the dilution fluid inflow conduit (16) and the pipe inner diameter of the chemical inflow conduit (12) is in the range between 1:1 and 20: 1.

18. Device according to claim 12, characterized in that the housing comprises an impact surface (100.1, 100.2, 100.3, 100.4, 100.5, 100.6) for generating turbulence and/or for chemical dosing and/or dilution fluid dosing.

19. The apparatus of claim 12, wherein the housing is formed in the form of a nozzle.

20. A chemical supply system for use in an inflow system of a paper machine, characterized in that the means for supplying chemicals into the process flow comprise an apparatus according to one of claims 12 to 19.

21. A chemical supply system according to claim 20, wherein the apparatus is connected to a process water recovery device by a pipe to use process water as the second liquid.