DE102010028577A1 - Method for adding a chemical to a process stream - Google Patents

Abstract

The invention relates to a method for admixing a liquid chemical to a process stream by means of a mixing device (10, 200), comprising a housing, in particular a mixing tube (20), at least one fluid inlet opening (30), a chemical inlet opening (14), a dilution fluid inlet opening (18) ) and at least one drain opening (60) to a process stream (70). The method according to the invention is characterized in that a chemical flow from the chemical inlet opening (14) and a dilution fluid flow from the dilution fluid inlet opening (18) are mixed into a fluid flow and the fluid flow, after the chemical flow and the diluting fluid flow have been mixed in, is a process flow (70) ), in particular accelerated by a nozzle, supplied, preferably injected.

Description

The invention relates to a method for admixing a liquid chemical to a process stream by means of a mixing device and to a device for admixing a liquid chemical to a process stream and a chemical feed system, comprising such a device

Special requirements are placed on the metering and subsequent incorporation of chemicals, for example in the papermaking process, in particular with a view to efficient mixing and on-demand metering of the chemicals. In the case of a papermaking process, demand-oriented metering means, for example, an addition of chemicals to a process stream of a paper machine that depends on the amount of pulp. Such a measure can significantly reduce the added amounts of chemicals in the papermaking process. Another reason for the efficient use of the chemicals is the high amount of energy needed to heat the fresh water for dissolution or dilution of the process chemicals. Such heating is advantageous in order to avoid a thermal shock in the mixing of the chemicals in the fresh water. By providing an efficient method for metering and mixing chemicals into a process stream in the process stream, particularly a process stream in the production of a fiber and / or nonwoven web, the consumption of process and functional chemicals, but also the use of fresh water as a diluent be reduced to a considerable extent in the treatment of chemicals.

From the prior art, a number of methods and apparatus for mixing a chemical service stream into a process stream have become known. This is how the EP-A-1 219 344 a method for admixing a liquid chemical in a process liquid stream, wherein the chemical and a second liquid are substantially brought into communication with each other when chemical and second liquid from a mixer nozzle are introduced into a process stream at high speed.

The EP-A-1 064 427 describes a method and apparatus for mixing a liquid stream of chemical into a second stream of liquid in a mixing device, wherein the stream of chemical mixed with the second stream substantially simultaneously with the application of the chemicals in the second liquid into a further fourth stream of liquid, in particular a process stream becomes.

The WO-A-2005/32704 shows a method and apparatus for feeding a chemical into a liquid stream wherein the chemical is introduced into the liquid stream by means of a mixer, the chemical being mixed into the mixing space, for example, with mixed water or a liquid circulating in the paper machine to form an admixing liquid before it is introduced into a liquid stream, in particular a process stream.

A disadvantage of the arrangement according to the WO-A-2005/32704 was that on the one hand a separate mixing chamber in the form of a mixing chamber had to be provided, on the other hand, the mixing chamber was separated from the fluid flow and so no complete mixture of fluid flow, chemical flow and dilution water stream was injected into the process stream, but the mixture of chemical stream and Dilution water flow is separate to the fluid flow.

From the WO 91/02119 For example, there has been known an apparatus in which additives are mixed in an aqueous fiber suspension solution used for the production of paper.

In the embodiment according to the WO 91/02119 two separately supplied streams are mixed outside of a process stream and injected the mixed stream across the process stream after complete mixing. A disadvantage of the WO 91/02119 was that there was no accelerated injection into a process stream.

Furthermore, the chemical stream and the dilution water stream were introduced directly into the process stream, but not into a fluid stream.

All of the aforementioned methods and devices also have the disadvantage that, during prolonged operation, deposits are formed in the supply lines and also in the mixing device, in particular the nozzle itself. In particular, in the area of the mixing device, for example in the form of a nozzle, the formation of such deposits is critical, since the cross sections of the channels are small and even small deposits due to the small cross sections can significantly influence the interference of the chemical, for example in a process stream.

Even with unplanned, sudden production stoppages, in which the chemicals remain in the supply lines and the mixing device, in particular the nozzle, deposits can occur. Deposits can not only affect the mixing process, as described above, but also detach upon ingestion of the production process after a machine downtime. They then lead for example, to holes in a paper web or deposits on screens, which in turn leads to a costly cleaning shutdown of the machine. These problems are favored above all in the case of metered addition to a sorting unit in a paper machine, since undissolved chemicals, in particular undissolved polymers, can not be removed from the pulp suspension.

In order to prevent deposits from taking place during ongoing operation, it may be provided in the prior art to select the line cross-sections of the supply lines and in the area of the mixing device so large that such deposits are largely avoided. However, this then has the consequence that, in order to prevent such deposits, the cross sections of the supply lines or nozzles of the mixing device are dimensioned so that no sufficiently high flow velocities are achieved. If, however, the cross section is reduced, the result may be blockages and thus malfunctions of the admixing device, in particular the nozzle, which lead to a production stoppage and to the replacement of the complete nozzle or supply lines.

The object of the invention is to avoid the disadvantages of the prior art.

In particular, a method and a device for metering or mixing a fluid or a fluid, in particular a fluid containing a chemical or even a liquid chemical itself, preferably in a process stream, in particular a process stream to produce a fiber or nonwoven web, are specified , Where possible, a homogeneously mixed chemical-fluid-fiber mixture is metered into a process stream and mixed with this. Furthermore, shutdowns due to deposits and the detachment of deposits should also be avoided, which can lead to holes in the fibrous web, for example, when the production process is resumed.

According to the invention this object is achieved in that in a method for admixing a liquid chemical to a process stream by means of a mixing device, wherein the mixing device at least one housing, in particular in the form of a mixing tube, a fluid inlet, a chemical inlet, a dilution fluid inlet and at least one drain opening to a Process stream has. The method is characterized in that a chemical stream from the chemical feed opening and a dilution fluid stream from the dilution fluid inlet opening is mixed into a fluid stream and the fluid stream is fed in, in particular injected, after admixing at least the chemical stream and dilution fluid stream via a drain opening to a process stream, in particular accelerated by a nozzle.

The fluid stream may be any process water that is commonly used or is available in the production of a fibrous or nonwoven web. In particular, it may be an aqueous pulp suspension, wherein the pulp is preferably cellulose fibers.

The fact that an intensive mixing of a fluid flow with the dilution fluid and the chemical takes place, a total mixing with the fluid flow can be largely achieved and then metered a homogeneous mixed chemical fluid-fiber solution via a drain opening in a process stream and thereby mixed with this.

The chemicals to be metered are, in particular, polymers, for example adhesives, which are added to the process stream in the papermaking process. Examples of such chemicals or polymers are polyacrylamide (PAM), polyethyleneimine (PEI), polyamidoamine (PAAm), crosslinkable polyamidoamine resins, polydadmac, polyvinylamine (PVAm), polyethylene oxide (PEO). As an alternative to the aforementioned polymers, the dosing chemicals may also be microparticles or nanoparticles, for example bentonite or a silicate. Further, the chemicals to be dosed may be starch or a biocide or a dye or an optical brightener. Other possible chemicals are neutral size such. B. AKD (Acrylketendimer) or ASA (alkenylsuccinic anhydride). Next, it allows the inventive method, and mineral substances such. As calcium carbonate, titanium dioxide in the form of a suspension in a second liquid or the process stream to dose.

It is particularly preferred that the metered addition of the chemicals does not take place from the chemical nozzle directly into the process stream, but after the liquid chemical has been mixed with a dilution liquid and a 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, any liquid or fluid used in the process is conceivable. In particular, in a manufacturing process for a fibrous web, the circulating liquid may be white water, clear filtrate, cloudy filtrate or another suitable non-pure liquid obtained in the papermaking process. Are conceivable but also clear water from the microflotation (DAF), or clear filtrate or super clear filtrate, for example, a disc filter. As a dilution liquid and / or fluid and the process water from a wastewater treatment plant, so-called bio-water can be used. The process stream is preferably a pulp suspension flowing to a paper machine, with which the supplied chemical, in particular the retention chemical, should react.

Preferably, in the mixing device, the liquid or liquid chemical in a stream of chemical and the dilution fluid in a dilution fluid stream are provided.

According to the invention, it is provided that the dilution fluid stream, for example the fresh water stream or the circulating water stream, is mixed with the chemical to be metered in the chemical stream before being fed to the process stream, for example in a mixing zone.

In particular, in a further developed embodiment it is possible for the chemical stream and the dilution fluid stream to be substantially mixed with one another prior to admixing with the fluid stream. In particular, the method also makes it possible to adjust the concentration of chemicals in the fluid stream by adding the amount of diluent fluid. For this purpose, for example, the ratios of the tube internal diameter for the dilution fluid flow to the tube internal diameter for the chemical stream can be varied, preferably in the range from 1: 1 to 20: 1, preferably from 5: 1 to 10: 1, d. H. the tube inner diameter of the feed line for the dilution fluid is in extreme cases 20 times greater than the inner tube diameter of the feed line for the flow of chemicals.

Preferably, the supply of the chemical stream and the dilution stream and any other chemicals or other fluid streams to the fluid flow at an angle to the housing wall, in particular at an angle relative to the axis of symmetry of the mixing tube.

The angle at which the supply of the chemical stream and / or the dilution stream takes place can be in the range of 90 ° to 10 °, preferably at an angle of 60 ° to 65 °. Such an angle guarantees intensive mixing of chemical stream and dilution fluid stream.

It is particularly preferred if measures are taken in the region of the housing or mixing tube so that turbulence in the flow which is supplied to the process flow is generated or increased. This can be done for example by means of baffles.

Alternatively, a swirl may be generated so that the mixture exits the nozzle in a centrifugal flow as soon as it leaves the nozzle in the process stream. As a result, the penetration depth of the jet with admixed chemical and dilution fluid in the process stream is increased. Furthermore, the penetration of baffles not only allows a turbulent flow, but also a chemical and / or dilution fluid dosing.

It is particularly preferred if, in addition to a mixing step in which a liquid chemical is supplied to the fluid stream, the method comprises a purification step. In the cleaning step, the mixing device is separated from the process stream, such that the mixing device can be cleaned independently of the process stream.

The separation of the mixing device from the process stream, which enables independent cleaning of the mixing device from the process stream, is achieved, for example, by receiving the mixing device from a receiving device, wherein the mixing device is arranged in the receiving device in the cleaning step such that a cleaning chamber is formed. In the cleaning chamber cleaning fluid, such as fresh water, can be supplied, with which the supply lines and the nozzles is rinsed. By rinsing the mixing device and the feeders they are cleaned of deposits and so clogging of the mixing device and the feeders by deposits largely avoided.

Preferably, it is preferred if the mixing area simultaneously also represents the cleaning chamber or the cleaning area. Can the mixing device directly above the process stream z. B. are arranged in a receiving device, it is advantageous if the mixing device is designed to be displaceable in the receiving device for forming the cleaning chamber. To clean the mixing device, the mixing device in the receiving device is then moved away from the process stream, for example by means of manual, pneumatic, hydraulic or electromotive devices. By moving within the receiving device away from the process stream then a cleaning chamber is provided.

To guide the mixing device in the receiving device may be provided a sleeve. For example, a slide can be integrated in the receiving device, which can be manually, is moved pneumatically, by electric motor or hydraulically in the receiving device. If the slide is spent over the complete cross section of the receiving device, then the slide is the separating device for separating the cleaning chamber.

In addition to the method described above for adding a liquid chemical to a process stream by means of a mixing device, the invention also provides a device for adding a liquid chemical to a process stream. In order to be able to select the flow velocity in the mixing device or in the feed devices so high that no or only a few deposits form during operation, correspondingly small line cross sections are selected at the feed lines of the fluid chemicals, so that flow rates in the range of 0, 05 to 20 m / sec, preferably in the range of 0.1 to 10 m / sec and especially in the range of 0.1 to 5 m / sec can be achieved.

In order to prevent buildup on the duct walls, flushing operations are performed on the small duct cross-sections leading to the high flow rates. It is particularly preferred if the device is designed such that no ball valves or other shut-off devices are provided to the supply lines. Thus, the possibility of the formation of deposits on the edges of the narrow contour of the ball valves or shut-off devices is prevented. In addition, the production is simplified because such components processed consuming, in particular must be electropolished.

In order to bring the mixing device to the process stream and to move away from it, provision can be made for the mixing device to be displaceable within the receptacle.

In addition to the device according to the invention, the invention also provides a chemical feed system for use in a paper machine, the chemical feed system being characterized in that the means for feeding the chemicals into the process stream comprise a mixing device according to the invention. In a further developed embodiment it can be provided that the device is connected via a pipe to process water recovery means in order to use process water as second liquid and / or dilution liquid.

The invention will be described below by way of example with reference to the drawings, in which:

1 : a metering nozzle according to the invention in a first embodiment

2a B shows a further embodiment of a metering nozzle according to the invention with staggered supply openings

3 : Feeder with opposite feed ports and turbulizers

4 : opposite supply ports for chemical flow and dilution liquid with turbulizer

5 : Device according to the invention with oblique injection

6 : Mixing device according to the invention with oblique feed and further feed line

7 : Mixing device according to the invention with oblique feed and turbulence generator

8th : Mixing device with inclined injection and cleaning device

In 1 is a mixing device according to the invention 10 shown comprising a chemical feed pipe 12 with a chemical inlet 14 and a dilution fluid inlet tube 16 with dilution fluid inlet port 18 , Both the chemical supply line 18 like the chemical dilution feed line 12 open into a housing, preferably as a mixing tube 20 the mixing device 10 educated. The mixing tube 20 is through a fluid inlet opening 30 charged with a fluid stream. In the area of the mixing zone 40 the chemical stream is mixed with the dilution fluid and then from the mixing zone to the via inlet port 30 supplied fluid mixed. Below the mixing zone, a fluid stream comprising the fluid, the dilution fluid and the chemical is mixed flow from the mixing tube into a nozzle 50 initiated. Due to the design of the mixing tube in the area 50 as a nozzle, the mixed flow can be accelerated and over the drain opening 60 the process stream 70 be supplied.

In particular, it is achieved by the arrangement according to the invention that a virtually complete mixing of fluid stream and chemical stream and dilution stream is achieved in order to obtain a homogeneously mixed chemical-fluid-fiber mixture via the discharge opening 60 can be metered into the process stream and mixed with this.

By forming the drain opening as a nozzle, an acceleration of the mixed flow be reached and so a deep penetration of the mixed stream mixed into the process stream.

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

Within the mixing tube, the flow velocity of the fluid flow is preferably to be selected as a function of the diameter d ₃ or d _{4 in} such a way that preferably a turbulent flow characteristic is formed. The degree of turbulence or the type of flow, ie whether a turbulent or a laminar flow is present in the mixing tube can be described by the Reynolds number. The type of flow or the Reynolds number can be influenced, in particular, by the volume flow of the fluid flow supplied before admixing dilution fluid and chemical.

If the mixing tube has a step change and no continuous decrease in the diameter as shown, then it is possible to form the drain opening not in the illustrated nozzle shape but as a simple cylindrical hollow body with a diameter d ₄ .

It is particularly preferred if the diameter d1 of the dilution tube to the diameter d2 of the chemical tube is in a ratio of 1: 1 to 20: 1, preferably 5: 1 to 10: 1. So d1: d2 is in the range 1: 1 to 20: 1.

As in 1 shown, both the dilution tube at an angle α1 = 90 ° as well as the chemical inlet pipe at an angle α2 = 90 ° occurs relative to the housing wall 55 into the mixing tube.

Furthermore, it can be seen that the distance AB between the feed opening 18 for the dilution fluid and the feed port 14 is very low for the chemicals and preferably between 1 mm and ¼ of the diameter d3 of the mixing tube.

When the dilution fluid stream and chemical stream supply ports are very close together, the dilution fluid may be mixed with the chemical stream and then mixed into the fluid stream completely mixed. In the embodiment in 1 Thus, a mixing of chemical flow and dilution fluid flow takes place before being introduced into the fluid flow.

By appropriate dimensioning of the pipe diameter of the dilution water stream to the pipe diameter of the chemical stream, the mixing ratios or the concentration of the chemical can be adjusted before the mixed stream is added to the fluid stream and finally introduced into the process liquid. The pressure difference ΔP of the dilution fluid with respect to the fluid flow is preferably in the range from 0.5 to 5 bar, preferably in the range from 1 to 2 bar, and the pressure difference between the chemical flow with respect to the fluid flow in the range from -0.25 to 0 bar.

In 2 is a slightly modified embodiment of a feed according to 1 shown. Same components as in 1 are in 2a and 2 B with the same reference numerals. As a major difference from the embodiment in 1 is to be considered that the supply lines for the dilution fluid flow and the chemical flow are not opposite in the same plane, but offset by a distance ABS in the mixing tube to each other.

Furthermore, the embodiment is characterized according to 2a characterized in that in the mixing tube baffles 100.1 . 100.2 are provided, which serve for a dilution fluid stream, for example, the dilution water stream and the flow of chemicals from the dilution tube 16 or the chemical tube 12 exit, divert and increase the turbulence of the flow so as to create a swirl and exit the mixture of dilution fluid stream and chemical stream as well as fluid stream as it leaves the mixing tube from the nozzle into the process stream, for example in a centrifugal flow from the nozzle. The advantage of such an arrangement is that the penetration depth of the jet from the nozzle is increased.

The mixing tube 20 has a mixing space or a mixing zone 25 (Borders are shown in phantom). Preferably, in an embodiment, not shown, the mixing space 25 over the entire length L _{mixing be designed} as a diffuser. In an alternative embodiment, it is possible that only the portion after the chemical supply opening 14 of the chemical tube 12 as L _{CHEM is designed} as a diffuser (not shown). Such a diffuser can be realized in that the mixing tube a step change, ie a sudden expansion of the preferably cylindrical inner cross section of the mixing tube 20 having. Such an abrupt extension of the cross section leads to an increase in the turbulence of the flow and thus to a more intensive mixing of the fluid stream, for example of the pulp stream, in particular of the pulp partial stream with the dilution fluid stream and / or the chemical stream to mix more intensively.

In general, even with a constant cross-section of the mixing tube, it is possible to influence the degree of turbulence, for example by increasing the volume of the fluid flow supplied to the mixing device, by increasing the volume flow rate to influence the turbulence degree.

In an alternative embodiment of a mixing device of the invention, the mixing tube is designed as an ejector or multi-stage ejector. in 2 B an embodiment of the mixing tube is shown as ejector in the form of a jet pump. Same components as in 1 and 2a are marked with the same reference numbers. In 2 B is the mixing tube 20 in the form of a jet pump 2000 designed. At first, the mixing tube narrows 20 in the area 2010 from the diameter d ₃ to the diameter d _fluid . After narrowing the mixing tube 20 in the area 2010 the mixing tube again experiences an expansion to the diameter d ₃ in the region of the feed of the dilution fluid line 16 , having. In the embodiment according to 2 B Dilution fluid and chemical are re-sequenced, ie the dilution fluid delivery port 18 has a distance ABS to the chemical supply port 14 on. The mixing zone is with 25 designated. After supplying both the dilution fluid and the chemical, the mixing tube again narrows continuously in the area 2020 , In the section 2030 The inner cross-section of the mixing tube expands continuously. In such a configuration of Msichrohres one speaks of an ejector. The turbulence and thus the mixing efficiency can be influenced by the geometry and the course of the vorzugswesie cylindrically shaped cross section of the diffuser or ejector.

Furthermore, by the baffles also a chemical and / or dilution fluid metering done. This is in particular gem in the embodiment. 3 the case. Again, the same components, as in the 1 and 2 marked with the same reference numerals. The difference of the embodiment according to 2 and 3 is to be seen in that the supply line for the dilution fluid and the chemical are substantially opposite. Also in the embodiment according to 3 are again baffles 100.1 . 100.2 provided, with which the flow can be deflected or introduced into the flow turbulence. The injection into the fluid stream takes place through opposing supply lines for the chemical stream and the dilution fluid stream.

About the already in 2 shown baffles are in the embodiment according to 3 further baffles 100.3 . 100.4 . 100.5 . 100.6 intended to create a swirl so that as soon as the mixture discharges the nozzle into the process stream, the mixture exits in a centrifugal flow and further allows a chemical and / or dilution fluid dosage.

4 shows an embodiment of the embodiment according to 3 is similar, ie the feed opening 18 for the dilution fluid and the delivery port 14 for the chemical are opposite to each other, but have contrary to the embodiment according to 3 a similarly close distance A as in 1 which is preferably between 1 mm and ¼ of the diameter D3 of the mixing tube, so that a largely complete mixing of dilution fluid and chemical takes place before it enters the fluid stream. In the mixing tube 20 In all embodiments described so far, a mixing chamber or mixing zone 25 (Borders are dash-dotted) formed in the dilution fluid and chemical flow and fluid flow are mixed together, so that at the drain port 60 to the process stream 70 an intense and practically completely mixed mixed flow of fluid stream, dilution fluid stream and chemical stream is present.

Before this mixing achieved before the nozzle assembly can be accelerated by the nozzle assembly of this mixed stream and injected into the process stream. The amount of dilution fluid determines the chemical concentration in the fluid stream.

While in all embodiments according to the 1 to 4 the angle α1 and the angle α2 of the diluent supply line and the chemical supply line is 90 °, the embodiments according to the 5 . 6 and 7 Embodiments of the invention, in which the angle of the supply lines is less than 90 °, ie preferably in an angular range of 60 ° to 45 ° relative to the housing wall of the mixing tube or the axis of symmetry 201 the mixing tube is located.

By tilting in the range 60 ° to 45 °, a mixture can be done without the current must be deflected very strongly in the direction of the outlet opening. Again, the same components as in 1 to 4 , same reference numerals.

In the embodiment according to the 5 again, is the distance between the chemical feed opening 14 and the dilution fluid supply port 18 very low, ie in the range 1 mm to ¼ of the diameter D3 of the mixing tube, so that prior to injection into the fluid flow intensive mixing of chemical flow and dilution fluid flow and thus concentration adjustment is achieved.

In the embodiment according to 6 is in addition to the dilution lines and the Chemical lines in 5 are shown, another feed line 300 intended. From the additional supply line 300 may be another fluid in the fluid flow in the mixing tube 20 be injected. For example, this could be another stream of chemicals or even the supply of filler slurry. Also the supply line 300 is at an angle α3, which is in the range 60 ° to 45 °, as the supply angles α1 and α2 for the chemical line and the Verdünnungsfluidzuführleitung is located.

7 shows a combination of dilution fluid supply lines at an angle in the range of 60 ° to 45 ° 16 or the chemical 12 with baffles 100.3 . 100.4 . 100.5 . 100.6 , which serve the turbulence generation or the chemical and / or fluid dosing.

Particularly preferred is an embodiment according to 8th in which, in addition to the feed lines, the mixing device can be moved within a receptacle in the axial direction. Same components as in 6 are assigned the same reference numbers. In the embodiment according to 8th the mixing chamber can also be used as a cleaning chamber. For this purpose, the supply of the second liquid into the process flow has taken place. The end section 54 can be varied in its length, so that it can be adjusted whether the second liquid flow supplied through the second flow channel at the same time, before or after via the first flow channel 12 supplied chemical stream or first liquid flow emerges.

In the embodiment according to 8th can the mixing device 200 inside a receptacle housing 220 or a recording in the axial direction 222 to be moved.

In addition to the in 1 - 7 illustrated embodiment, the receiving device comprises 220 a gate valve 230 , The gate valve 230 is in the direction 232 movably designed. The mixing device 200 or metering nozzle can be guided through the gate valve shown open.

In 8th is the mixing device 200 within the receptacle or the receiving housing in the direction 222 from the process stream with the slide open 230 , z. B. pulled out pneumatically, hydraulically or by electric motor.

To start the cleaning process, the slider can 230 over the entire cross section of the receiving device 220 at a position of the mixing device 200 according to 8th be introduced. Through the closed gate valve 230 becomes the mixing device 200 from the process stream 70 separated. Between the mixing device 200 and the gate valve 230 becomes a cleaning room 400 formed, which preferably coincides with the mixing area.

To start the cleaning, for example, fresh water can be fed into the chemical supply line instead of a chemical stream. Of course, the feed would also be possible via the dilution feed line or the further feed line.

The fresh water supplied via, for example, the chemical supply line impinges on the closed shut-off device in the cleaning step 230 and can in the other two supply lines 16 . 300 be guided. In this case, media that are contained in these feeds, displaced by the fresh water or the fluid cleaning medium. The nozzles and the feeders, in particular the mixing device, can be represented by such a cleaning step, be cleaned by the chemicals contained therein, in particular their deposits. Thus, clogging of the mixing device and the feeds is actively counteracted by deposits at standstill, regardless of the process stream as dosing chemicals, in particular polymers, such as adhesives, which are added to the process stream in the papermaking process, can be used. Examples of such chemicals or polymers are polyacrylamide (PAM), polyethyleneimine (PEI), polyamidoamine (PAAm), crosslinkable polyamidoamine resins, polydadmac, polyvinylamine (PVAm), polyethylene oxide (PEO). As an alternative to the aforementioned polymers, the dosing chemicals may also be microparticles or nanoparticles, for example bentonite or a silicate. Further, the chemicals to be dosed may be starch or a biocide or a dye or an optical brightener. Other possible chemicals are neutral size such. B. AKD (Acrylketendimer) or ASA (alkenylsuccinic anhydride). Next, it allows the inventive method, and mineral substances such. As calcium carbonate, titanium dioxide in the form of a suspension in a second liquid or the process stream to dose.

With the device according to the invention and the method according to the invention, a method and a device is provided, with which a virtually complete mixing of a chemical stream with a dilution fluid flow and a fluid flow is achieved, which is supplied to a process stream. In particular, with the help of baffles, a swirl is generated, so that the mixed flow, when in the process stream occurs, has a centrifugal flow and thereby a very large penetration depth into the process stream.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1219344A [0003]
• EP 1064427A [0004]
• WO 2005/32704 A [0005, 0006]
• WO 91/02119 [0007, 0008, 0008]

Claims (19)

Method for admixing a fluid, in particular a liquid containing a chemical or a liquid chemical itself, to a process stream by means of a mixing device ( 10 . 200 ), comprising a housing, in particular a mixing tube ( 20 ), at least one fluid inlet opening ( 30 ), a chemical feed opening ( 14 ), a dilution fluid inlet port ( 18 ) and at least one drain opening ( 60 ) to a process stream ( 70 ), characterized in that a chemical stream from the chemical feed opening ( 14 ) and a dilution fluid stream from the dilution fluid inlet port ( 18 ) is admixed into a fluid stream and the fluid stream after admixing of the chemical stream and dilution fluid stream via a drain opening ( 60 ), a process stream ( 70 ), in particular accelerated by a nozzle, fed, preferably injected. A method according to claim 1, characterized in that the chemical stream and the dilution fluid stream is mixed with each other before admixing to the fluid flow substantially. Method according to one of claims 1 or 2, characterized in that the chemical concentration is adjusted in the fluid stream by the addition of the amount of dilution fluid. Method according to one of claims 1 to 3, characterized in that the chemical inlet opening and / or the dilution fluid inlet opening at an angle relative to the housing wall, in particular at an angle relative to the axis of symmetry ( 201 ) of the mixing tube is (are) inclined. A method according to claim 4, characterized in that the angle (α1, α2, α3) is between 10 ° and 90 °, preferably between 45 ° and 60 °. Method according to one of claims 1 to 5, characterized in that a further chemical or other fluid stream, in particular a filler slurry is supplied to the fluid stream. Method according to one of claims 1 to 6, characterized in that the chemical flow and / or the dilution fluid flow and / or the fluid flow before and / or after admixture is influenced such that a turbulent, in particular a centrifugal flow through the drain opening ( 60 ) the process stream ( 70 ) is supplied. Method according to one of claims 1 to 7, characterized in that the method comprises a cleaning step in addition to a mixing step in which a liquid chemical is supplied to the fluid stream, and in the cleaning step, the mixing device ( 200 ) from the process stream ( 70 ), such that the mixing device ( 200 ) independent of the process stream ( 70 ) can be cleaned. Device for adding a liquid chemical to a process stream ( 70 ), comprising a housing, in particular a mixing tube ( 20 ), at least one fluid feed ( 30 ), a chemical feed ( 12 ) as well as a dilution fluid feed ( 16 ) and a fluid flow sequence ( 60 ), characterized in that at least the chemical feed ( 17 ) and the dilution fluid feed ( 16 ) are arranged such that in the housing, in particular in the mixing tube, a mixing area ( 25 ) is formed, wherein in the mixing area ( 25 ) at least one chemical stream and a dilution fluid stream are introduced into the fluid stream in such a way that, after the mixing zone, the chemical stream, dilution fluid stream and fluid stream are largely mixed in such a way that the resulting mixed stream flows out of the discharge opening (FIG. 60 ) into the process stream ( 70 ) is introduced. Device according to claim 9, characterized in that at least the chemical feed ( 12 ) and / or the dilution fluid feed ( 16 ) at an angle (α1, α2) with respect to the housing wall, in particular at an angle with respect to the axis of symmetry of a mixing tube, is (are) inclined. Apparatus according to claim 10, characterized in that the angle (α1, α2) between 90 ° and 10 °, preferably 60 ° and 45 °. Device according to one of claims 9 to 11, characterized in that the chemical feed ( 12 ) and the dilution fluid feed ( 16 ) are so close together that the chemical stream leaving the chemical feed and the dilution fluid stream exiting the diluent fluid feed are substantially mixed together prior to mixing with the fluid stream. Apparatus according to claim 12, characterized in that the distance AB between the chemicals inlet opening ( 14 ) of the chemical feed ( 12 ) and dilution feed port ( 18 ) of dilution fluid inlet ( 18 ) between 1 mm and 100 mm, preferably between 1 mm and quarter of the diameter (d3) of the mixing tube ( 20 ) lies. Device according to one of claims 12 and 13, characterized in that the pressure difference (δp) between that from the dilution fluid inlet opening (δp) 18 ) exiting dilution fluid and the fluid flow in the range 0.5 to 5 bar, preferably 1 to 2 bar, and / or the pressure difference (δp) of the from the chemical feed opening ( 14 ) chemical flow with respect to that from the dilution feed port ( 18 ) is in the range -0.2 to 0 bar. Device according to one of claims 10 to 14, characterized in that the ratio of a tube inner diameter of the dilution fluid inlet ( 16 ) to the pipe inside diameter of the chemical feed ( 12 ) in the range 1: 1 to 20: 1, preferably 5: 1 to 10: 1. Device according to one of claims 9 to 15, characterized in that the housing baffles ( 100.1 . 100.2 . 100.3 . 100.4 . 100.5 . 100.6 ), in particular for turbulence generation and / or chemical dosing and / or dilution fluid dosing. Device according to one of claims 9 to 16, characterized in that the housing is formed in a nozzle shape, such that the mixture of fluid flow, dilution fluid flow and chemical is accelerated before being injected into the process stream. Chemical feed system for use in a paper machine feed system, characterized in that the means for feeding the chemicals into the process stream comprises a device according to one of claims 9 to 17. The chemical feed system of claim 18, wherein the device is connected to the process water recovery means via a pipe to use the process water as the second liquid.

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