EP1846144B1 - Device for the creation of the largest possible interface in order to continuously and very efficiently mix different fluids in gas-liquid mixtures - Google Patents

Abstract

Apparatus for continuous mixing of fluids comprises an optionally heated or cooled mixing vessel under adjustable pressure; nozzle(s) for spraying liquid into the top of the container; a cone (optionally with an axial hole) below each nozzle and firmly connected to the nozzle at a defined spacing; tubes, open at the top and closed up to a hole in the bottom, below and aligned with each nozzle; and a liquid outlet below the tube in the base of the mixing vessel.

Description

The invention relates to a technically particularly simple and space-saving design for generating a maximum phase interface for the mass transfer in the continuous mixing of fluids in gas-liquid mixtures. At the same time a particularly high efficiency of the homogenization of the mixture is achieved with relatively low energy input and prevents foaming automatically.

A similar device is off WO 2004/000447 A2 for gas saturation of a fluid under pressure and in combination with a pressure release device for introducing the expanded fluid into a flotation cell, but without a device for automatically preventing foaming, whereby the range of use is limited to low or low foaming systems known. Therefore, this device has hitherto been used only in combination of a gas (air or nitrogen) with a liquid (water or wastewater) in Druckentspannungsflotation but never in the reaction, stirring or mixing technique or for mixing several gas or liquid phases Service. Another similar device is off FR-A-1 285 644 known.

• Aufwendige Rührerkonstruktionen und Auswahl der für den Anwendungsfall jeweils geeigneten Form des Rührers.
• Einbau von Stromstörern in den Behälter zur Erzeugung von Turbulenzen.
• Ausbildung von Bereichen unterschiedlicher Strömungsintensität im Behälter.
• Bereitstellung eines ausreichend großen Behältervolumens für eine geeignete Strömungsführung.
• Energiezufuhr zum Antrieb und relativ hoher Energieeintrag in den Behälter.
• Mechanischer Antrieb des Rührers, verbunden mit einer Dichtungsanforderung an der Durchführung der Welle in den Behälter und ggf. einzuhaltenden Ex-Richtlinien für el. Antriebe nach DIN EN 50014 ff sowie 1127-1, 13237-1.
• Zugabe von chemischen Entschäumem oder Schaumverhütem bei Schaumbildungsneigung.

The most common way of mixing fluids by stirring them in a container has the following disadvantages:

• Elaborate stirrer designs and selection of the appropriate form of the stirrer for the application.
• Installation of baffles in the tank to generate turbulence.
• Formation of areas of different flow intensity in the container.
• Provision of a sufficiently large container volume for a suitable flow guidance.
• Energy supply to the drive and relatively high energy input into the container.
• Mechanical drive of the stirrer, combined with a seal requirement for the passage of the shaft into the container and, if applicable, Ex guidelines for el. Drives to DIN EN 50014 ff as well as 1127-1, 13237-1.
• Addition of chemical defoamers or anti-foaming agents with foaming tendency.

Also known from the prior art are conventional injection mixers, but these tend when used in comparable systems, greatly foaming, causing them in certain areas, eg. As the wastewater technology, so far find little application.

The object of the invention is therefore to provide a structurally particularly simple, space-saving and particularly energy-saving device for the continuous mixing of fluids in gas-liquid mixtures, preferably for foaming, in particular strongly foaming, mixtures which does not have the disadvantages of the systems of the prior art ,

It became now. Surprisingly found that such a device is very easy to implement.

• einen Mischbehälter entsprechend den gestellten Druckanforderungen und ggf. mit Heizungs- oder Kühlungsmöglichkeit,
• eine oder mehrere Düsen zur Eindüsung von Flüssigkeit in den Mischbehälter am Kopf des Mischbehälters,
• je einen Kegel mit oder ohne axialer Bohrung unmittelbar unter jeder Düse und in definiertem Abstand fest mit dieser verbunden,
• je ein oben offenes und unten, bis auf eine Bohrung im Boden, verschlossenes Rohr, das unterhalb jeder Düse im Mischbehälter angeordnet ist,
• einen Flüssigkeitsaustritt unterhalb der Rohre am Boden des Mischbehälters.

The present invention therefore relates to a device for continuously mixing fluids

• a mixing container according to the set pressure requirements and possibly with heating or cooling possibility,
• one or more nozzles for injecting liquid into the mixing container at the head of the mixing container,
• one cone each with or without axial bore immediately below each nozzle and fixedly connected to it at a defined distance,
• depending on a top open and bottom, except for a hole in the bottom, closed tube, which is arranged below each nozzle in the mixing container,
• a liquid outlet below the tubes at the bottom of the mixing container.

The introduction of the liquid which is to be mixed with the gas takes place at the top of the mixing container via one or more nozzles, preferably conventional plain-jet nozzles. These can be screwed into the lid of the mixing container. The pressure loss at the nozzles should be less than 2 bar under operating conditions, preferably between 1 bar and 0.4 bar.

The nozzles generally have diameters of 2 to 50 mm, preferably at their narrowest flow cross-sections diameter greater than 4 mm, whereby a blockage by fine particles can be excluded. In addition, the nozzles can be protected by upstream, backwash filter filters.

The stream of liquid supplied, can be previously divided into individual feed pipes. The liquid flow through the individual nozzles can preferably be controlled separately for each nozzle by upstream or downstream shut-off valves z. B. by a battery of shut-off valves. Thereby, the amount of liquid supplied to the mixing container can be adjusted according to need.

The injection of the liquid takes place at a speed of more than 3 m / s, preferably more than 6 m / s. The choice of the speed of the injection depends on the conversion rate or the diffusion rate or the concentration gradient to the thermodynamic or physical-chemical equilibrium of the material system. In order to influence the equilibrium in the tube reactor to produce a desired turnover or concentration gradient, it may be helpful to specify pressure and temperature accordingly.

In the mixing container, the liquid jet of each nozzle first strikes the cone, which is arranged with the tip upwards in the gas space, with or without an axial through-bore. The axes of the nozzle bore and cone are exactly the same. The distance of the cone to the nozzle is 10-100 mm, preferably 20-50 mm. The diameter of the axial bore through the cone is 0.5-5 mm, preferably 1-2 mm smaller than the diameter of the liquid jet or the nozzle. As a result, the full beam can not pass through the conical bore. The outer edge of the jet is peeled off annularly and fanned along the conical surface, after which it flows in the form of a thin liquid film downwards and continues the conical surface until it enters the liquid level at the container wall.

In foaming mixtures, which are preferably the focus of the fluid mixing devices of the present invention, the sharp liquid film, prior to entering the liquid collected below, cuts the foam bubbles piling up above the interface so that undesirable foaming will automatically occur without further physical or chemical counteraction is prevented.

The jet flowing through the conical bore penetrates the gas cushion in the space between cones and the tubes located in the liquid space in the form of a free jet and then enters the tube arranged below. The distance between each of the tubes and the associated nozzle is in the range of 100-400 mm, preferably in the range of 150-250 mm.

In the pipes, the liquid is swirled and a short time later emerges from the top of the pipe again. As a result of the liquid flowing in continuously from each nozzle, the respectively assigned pipe is always filled with liquid. Due to the free jet of liquid through the gas cushion gas molecules are entrained and entered in the form of gas bubbles in the interior of the tube. Due to the high shear forces and turbulences in the tube, there is an intensive contact of gas and liquid as a result of which a concentration balance or a material flow can be established. Ascending gas bubbles are divided by the liquid flowing from above into the pipe and conveyed downwards again.

The residence time of the liquid in the tubes depends on the one hand on the speed of the injection and on the other hand on the ratio of the diameter of the tubes to the diameter of the associated nozzle at the liquid outlet of the nozzle. In this case, the larger the ratio of the diameter of the tubes to the diameter of the associated nozzles, the greater the residence time. As the velocity of the injection increases, the residence time decreases while the ratio of the diameter of the tubes to the diameter of the associated nozzle remains the same. Preferably, the ratio of the diameter of the tube to the diameter of the associated nozzle at 3 to 8, preferably 3 to 5, more preferably it is 4. When using a nozzle of 10 mm diameter at the liquid outlet so a tube with 40 mm diameter is used advantageously.

The residence time of the liquid in the tubes is according to the invention less than 10 s, preferably less than 5 s, more preferably less than 2.5 s.

Preferred, particularly preferred or very particularly preferred are embodiments which make use of the parameters, compounds, definitions and explanations mentioned under preferred, particularly preferred or very particularly preferred.

However, the general or preferred definitions, parameters, compounds and explanations given in the description can also be combined with one another as desired, ie between the respective ranges and preferred ranges.

The liquid flows out of the tubes and accumulates or accumulates in the lower part of the container, where it can escape through the liquid outlet below the tubes at the bottom of the container. The liquid outlet at the bottom of the mixing container is dimensioned so that the outflow velocity of the liquid from the mixing container in the range between 50 and 150 m / h, preferably in the range of 70 and 90 m / h.

The liquid stored in the container has the function of a bubble filter. Larger bubbles (d> 100 microns) can not get into the liquid outlet, as they rise faster than the liquid moves down. The control of the level in the mixing tank is done by regulating the gas supply.

The level of the liquid in the tank can be controlled by a level gauge. Preferably, for this purpose, a vertical pipe outside the mixing vessel communicating with the container interior connected. A float in the pipeline indicates the level. Preferably, the float is magnetically detectable and activates a minimum and maximum circuit. In the min case, the supply of gas is automatically stopped. In the max case, the supply of gas is opened. The maximum pressure in the tank can be adjusted by a pressure reducing valve in the gas supply line.

The level meter in combination with the min. And max. Circuit not only regulates the level of the mixing container with the liquid, but also ensures that the mixing container is sufficiently supplied with gas. The liquid is automatically fed in this way as much gas as is consumed by the mass transfer.

An advantage of the devices according to the invention for the continuous mixing of fluids is that even before the nozzle metered additives in the form of liquids in the range of aqueous viscosities can be mixed in easily.

The mass transfer or the solution of gases takes place in the inventive devices for continuous mixing of fluids with a particularly high space-time yield, because with short residence times in the tubes (less than 10 seconds) z. B. for a water-air mixture over 90% relative saturation can be achieved.

The devices according to the invention for the continuous mixing of fluids work very energy-efficiently, because the pump pressure generated is converted by the combination of nozzles and mixer geometry into virtually pure flow energy and thus in a mixture-promoting manner. In contrast to conventional Rührbehältertechnik no additional drive unit is used to generate a rotational movement, wherein energy is dissipated in frictional heat. In addition, the device is constructed of very simple components and can thus be manufactured extremely inexpensively.

An advantage of the devices according to the invention for the continuous mixing of fluids is also that by the connection and disconnection of individual nozzle elements, the liquid flow rate and thus the gas input can be flexibly controlled.

1. 1. die Reaktionsgeschwindigkeit so groß ist, dass die Verweilzeit im kleinen Volumen des Mischbehälters bei den verfahrensbedingt hohen Strömungsgeschwindigkeiten noch ausreicht und
2. 2. die Viskosität der Fluide klein genug ist, um die erforderlichen Turbulenzen zu erzeugen.
3. 3. ein ggf. exothermer Reaktionsverlauf beherrschbar bleibt, indem der Wärmestrom z. B. konvektiv mit dem Flüssigkeitsstrom abgeführt wird, da sonst zur Wärmeübertragung nur die zum Volumenstrom verhältnismäßig kleine Behälterwand zur Verfügung steht.

The device according to the invention is suitable, for example, for carrying out mixing or dissolution processes of fluid components as multiphase mixtures with more than one liquid and / or gaseous phase, oxidation reactions with gaseous oxidizing agents as well as other chemical or physical reactions, taking care that

1. 1. The reaction rate is so great that the residence time in the small volume of the mixing container at the high flow velocities due to the method is still sufficient and
2. 2. the viscosity of the fluids is small enough to produce the required turbulence.
3. 3. a possibly exothermic reaction process remains manageable by the heat flow z. B. is discharged convective with the liquid flow, otherwise only the volume flow for relatively small container wall is available for heat transfer.

It is preferably suitable for physical reactions, in particular, for example, solution of gases in liquid, chemical reactions, in particular, for example, hydrogenation, oxidations, and sufficiently fast phase boundary reactions.

Figures and examples

Fig. 1

Mischbehälter mit Einbauten

Fig. 2

Glattstrahldüse mit Kegel

Fig. 3

Anlagenfließbild

Fig. 4

Fotoreihe zur Schaumbekämpfung

The figures show

Fig. 1

Mixing container with internals

Fig. 2

Smooth jet nozzle with cone

Fig. 3

Plant flow

Fig. 4

Photo series for foam control

Fig. 1 shows an exemplary construction of a mixing container 1 with internals. The introduction is flow-controlled at the head of the mixing container via one or more conventional smooth-jet nozzles 2, which are screwed into the container lid 3. The flow of the supplied liquid is previously divided into individual feed pipes 4. In the mixing container 1, the liquid first passes through the gas cushion 5 in the form of a free jet and then impinges on the cone 6. While a portion of the liquid flows along the shell of the cone 6 and continues downward, the remaining jet flows through the conical bore and enters the underlying tube 7 a. There, the liquid is vortexed and mixed with gas bubbles and emerges a short time later up again. The water flows out of the tubes 7 and accumulates or accumulates in the lower region 8 of the container 1. The liquid exits through the liquid outlet 9 at the bottom of the container 1.

Fig. 2 shows a nozzle unit 3 with the firmly connected cone 6 in a detailed view.

example 1

In an attempt to sulfite oxidation, a plastic container was made according to the Fig. 3 integrated into a pilot plant. It was a 1500 mm long, vertical standing, 190 mm inside diameter tubular reactor. The reactor was suspended concentrically with a 500 mm long, bottom-terminated tube attached to four steel bars, the distance between the top of the tube and the lid being 150 mm.

In between was a cone with an axial bore. The liquid entering the container as a free jet first hit the cone, where it was divided into a cone and a free jet. The free jet was generated by a smooth jet nozzle. The flow area at the outlet of the nozzle was circular and 8 mm in diameter. The diameter of the conical bore was 7 mm. While the free jet, which has been reduced by the cone jet, has hit the tube below, the cone jet strikes near the vessel wall directly on the liquid reservoir in the lower part of the container. The level in the tank was regulated to 150 mm below the top of the pipe.

At the top of the container an oxygen supply was connected, the pressure from the leased line was lowered by means of a conventional pressure reducing valve to 1 barÜ. In addition, a solenoid valve was connected between the pressure reducing valve and the reactor, which opened when the max level was reached and closed at the min level. The pressure in the container was thus almost constant at 1 bar.

Example 2

An experiment similar to Example 1 was carried out, whereby a specific energy input of 0.019 kWh / m ^{3 was} determined. Comparative figures for a conventional injector are 0.075 kWh / m ³ .

Example 3

An experiment was carried out according to Example 1 but with an air-water mixture, with a concentration compensation up to 95% bez. could be achieved on the solution balance. It was also shown by varying different nozzle-cone combinations that only by using the cone foaming can be controlled safely (see also photo series in Fig. 4 ).

Claims (9)

1. Device for the continuous mixing of fluids, comprising

   - a mixing container (1) according to the set pressure requirements and optionally having a heating or cooling facility,

   - one or more nozzles (2) for spraying liquid into the mixing container at the top of the mixing container,

   - one cone (6) each with or without axial bore, immediately below each nozzle (2) and connected firmly thereto at a defined distance,

   - tubes (7) which are open at the top and, apart from a bore in the bottom, closed at the bottom and which are arranged below each nozzle in the mixing container, a nozzle (2) being assigned to each tube,

   - a liquid outlet (9) below the tubes at the bottom of the mixing container.
2. Device according to Claim 1, characterized in that the nozzles are smooth jet nozzles.
3. Device according to either of Claims 1 and 2, characterized in that the pressure drop at the nozzles under operating conditions is less than 1 bar.
4. Device according to any of Claims 1 to 3, characterized in that the nozzles have a diameter of 2 to 50 mm.
5. Device according to any of Claims 1 to 4, characterized in that the liquid is sprayed in at a velocity of more than 3 m/s.
6. Device according to Claim 5, characterized in that the ratio of the diameter of the tube to the diameter of the assigned nozzle is in the range from 3 to 8.
7. Device according to any of Claims 1 to 6, characterized in that the distance between each of the tubes and the assigned nozzle is in the range of 100-400 mm.
8. Device according to any of Claims 1 to 7, characterized in that the residence time of the liquid in the tubes is less than 10 s.
9. Use of the device according to any of Claims 1 to 8 for physical reactions and chemical reactions and for phase interface reactions.

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