DE102008017921B3 - Bubble mixer for mixing two liquids, which are not miscible with one another and have different density, useful as reactor for washing process, comprises vertical cylindrical pipe, whose lower end is closed and equipped with emptying line - Google Patents

Abstract

The bubble mixer for mixing two liquids, which are not soluble into one another and have different density, comprises a vertical cylindrical pipe, whose lower end is closed and equipped with an emptying line with drain valve (V), by which the outlet for the produced mixture (M) is arranged in the upper portion and which has a gas-discharge opening within the upper portion, and a cylindrical immersion tube (T) for supplying the liquids. The gas (G) such as nitrogen needed for mixing is added over a gas-dip tube above the phase forming within the lower region of the mixer. The bubble mixer for mixing two liquids, which are not soluble into one another and have different density, comprises a vertical cylindrical pipe, whose lower end is closed and equipped with an emptying line with drain valve (V), by which the outlet for the produced mixture (M) is arranged in the upper portion and which has a gas-discharge opening within the upper portion, and a cylindrical immersion tube (T) for supplying the liquids. The gas (G) such as nitrogen needed for mixing is added over a gas-dip tube above the phase forming within the lower region of the mixer, where the phase is enriched with liquid with higher density, so that the gas bubbles hit on the surface of the phase and the small droplets of the liquid with higher density deposit themselves on the gas bubbles. The liquid of lower density rises upward to the outlet due to the density variation. The liquid of higher density is carried upwardly with the gas bubbles in the form of fine cup. The immersion tube is placed more deeply into the mixer than a gas-immersion tube (GT), so that no gas bubbles rise upward by the immersion tube. The ratio between the immersion tube diameter to the mixer diameter is 0.3-0.7. The ratio between the gas-immersion tube diameter to the mixer diameter is 0.2-0.8. The height of the immersion tube over the mixer is large so that in case of failure of the gas supply, the liquid, which ascends due to the density variation in the immersion tube, does not overflow from the immersion tube during the operation of the mixer. The diameter of the outlet mixture is large so that the total produced mixture and the gas run over the mixture without back pressure and gas release is needed through a separator. The lower end of the mixer is flat and runs conical to the drain valve. The mixer is equipped with a cooling jacket lying outside. The different liquids are mixed, where a phase with lower and a phase with higher density are developed.

Description

The The invention relates to a bubble mixer for mixing at least two liquids, not soluble in each other are and have a different density, according to the preamble of claim 1.

For mixing of substances according to the prior art mechanical stirrer and, alternatively, pneumatically operated mixing apparatus are used.

Pneumatic Operated mixing apparatuses have compared to the mechanically operated the advantage that usually no shear forces occur, so this Technology also for sensitive energetic materials such as explosives, can be used.

In the US 2007 0 182 033 A1 For example, the prior art for pneumatic mixers is described as follows. A pneumatic mixer consists of a vertical tube, at the lower end of which the substances to be mixed are added. At the lower end of the tube is also the gas bubble inlet. The gas bubbles are generated in a separate gas bubble generator and must have a certain optimum size, as only in the tube a plug flow is generated, with which the liquids to be mixed are pumped together with a piston of gas from bottom to top through the pipe and to mix by it.

In the KR 10 2002 0 074 659 A (Abstract) A multi-stage pneumatic mixer-settler unit is described in which the mixing effect is improved by pulsing the gas flow. Again, a special device for generating a uniform distribution of the gas bubbles will be described.

The EP 1 679 112 A1 describes a pneumatic mixer in which fine gas bubbles are generated with a nozzle. The substances to be mixed are fed directly below the nozzle and conveyed in cocurrent with the air bubbles through a static mixer from bottom to top to achieve a uniform mixing. Here also the use of an additional static mixer in the gas inlet nozzle is described, through which the mixing effect is improved.

In the DE 16 67 231 B2 describes an apparatus for carrying out a mass transfer between gas and liquid phases, in which a dip tube is used, wherein the gas and the liquid are mixed in the upper region of the dip tube and flow together through the dip tube.

The DE 1 026 283 A refers to a device for producing emulsions by circulating liquids by means of gas supply, wherein the gas is injected at the bottom of the container.

The FR 1 529 536 A proposes a device for mixing two immiscible liquids using a dip tube in which gas is used as the transport medium, wherein the gas is also introduced at the bottom of the container and the liquids circulate in the container.

All according to the prior art described pneumatic mixer have in common that they are a costly metering for the gas need and that partially extra Internals for the achievement of the desired mixing quality needed become.

Of the The invention described here was based on the idea of a simple one pneumatic mixer to be used in the washing of organic compounds that are not water-soluble, are used can and in addition has the following properties. The gas task should be easy too be governed. about the gas quantity should be the quality of mixing can be adjusted well. The mixer should be operated continuously. As well as sensitive, less stable substances such as explosives are mixed should the mixer be easy and quick to empty completely. The mixer should, if possible, contain no internals where shear forces can occur and the one complete Make emptying difficult. The mixer should be used for mixing smaller quantities can be used in the laboratory.

to solution these specifications, the bladder mixer is provided according to claim 1. Advantageous embodiments are the subject of the dependent claims.

First, a prior art mixer consisting of a vertical cylindrical tube was tested. The two liquids to be mixed were added to the lower part of the mixing tube. The gas was bubbled in the lower part of the mixing tube below the liquid inlets by means of a pervator, a fine-pored glass structure specially used for producing small gas bubbles. Although a sufficient mixing quality could be achieved with this mixer, this construction did not fulfill the other criteria. A complete emptying was not possible because the liquids accumulated in the fine-pore aerator and not completely removed even by prolonged blowing of gas could.

With The same construction could be done without a pervator, just with a dipped one Gas inlet, no sufficient mixing quality can be achieved.

Around Achieving sufficient mixing quality without an aerator was a very good idea thin and several meters long mixing tube necessary. This construction let yourself for reasons of space do not use in a laboratory.

To Trial of several different constructions became surprisingly relatively simple construction for the bubble mixer according to the invention found that meets all requirements.

The operation of the bubble mixer according to the invention is in 1 shown. The bubble mixer B according to the invention consists of a vertical cylindrical tube. The lower end is closed and equipped with a drain line with drain valve V. In the pictures, the lower end of the bubble blender is flat. This embodiment is the simplest. For optimal emptying of this conclusion may also taper conically to the drain valve. In the bladder mixer, a cylindrical dip tube T is installed, through which the low-density liquid ND and the higher-density liquid HD are supplied at position 1 in the bladder mixer of the present invention. The gas G required for mixing is added at position 2 into a gassing tube GT and passed into the bubble mixer according to the invention. In the upper region of the bladder mixer according to the invention is the outlet for the generated mixture M, which exits at position 3 from the bladder mixer according to the invention. The bubble mixer according to the invention furthermore has a gas outlet GA, from which the mixed gas leaves the bubble mixer again at position 4. During operation of the mixer, different phases are formed in the partial regions of the bubble mixer according to the invention. In the lower part, a phase is formed which is enriched with liquid of higher density HD (shown in black). In the upper part of the dip tube T, a phase is formed, which is enriched with liquid of lower density ND (shown in light). The low-density incoming liquid ND mixes directly with the phase as it strikes the surface, while the higher-density liquid HD drops (shown in black) descend through the sub-dip phase T and contact the immersion tube according to residence time with the liquid of lower density ND. As the droplets of the higher density liquid HD impinge on the higher density phase at the bottom of the mixer, they mix directly with the phase. The mixed gas G exits above the higher-density phase from the gaseous exhaust pipe GT. The gas bubbles (shown in white) impinge on the surface of the higher density phase where small droplets of the higher density liquid HD are deposited on the gas bubbles. The lower density liquid rises upward due to the density difference up to the outlet, while the higher density liquid is carried up with the gas bubbles in the form of fine pots. As the gas bubbles rise, they become larger due to the decreasing hydrostatic pressure. By contact with other gas bubbles, gas bubbles can also unite. The entrained fine droplets of the higher density liquid HD may also detach from the gas bubbles during the ascent and then float in the lower density liquid ND. Also, droplets of the higher density liquid HD can combine to form larger drops and sink back down. Higher density liquid droplets of HD floating in the lower density liquid ND can be captured by rising gas bubbles and carried upwards. Gas bubbles reaching the upper phase boundary (liquid boundary) leave the liquid and the adhering droplets of the higher density liquid HD remain in the liquid. With this technique, a very good mix M of the two liquids ND and HD is achieved, which then runs out of the mixer at position 3. The mixed gas is discharged via the gas outlet GA at position 4 from the mixer. Surprisingly, it was found that when using the bubble mixer according to the invention even with low gas quantities significantly better mixing qualities up to emulsions are achieved, compared with the bubble mixers according to the prior art, in which both liquids are conveyed together with the gas through the mixer. Even with the use of a pervator for the fine distribution of the gas, a higher amount of gas was required for comparable mixing quality.

When constructing the bladder mixer according to the invention, care should be taken that the dip tube T dips deeper into the mixer B than the gas immersion tube GT, to ensure that no gas bubbles through the dip tube T rise up, otherwise the uniform drop of the liquid drops higher density HD is disturbed. Furthermore, it is important to ensure that the gas immersion tube GT ends according to the invention above the forming phase with higher density, so that the gas bubbles impinge on the surface of the phase and there accumulate fine liquid droplets to the gas bubbles. When immersing the gas immersion tube GT in the phase with liquid of higher density HD, a poorer mixing quality is surprisingly achieved, compared with the arrangement according to the invention. This effect was unexpected, as it ent According to the state of the art, it is as far as possible prevented that a phase of only one liquid is formed, and ideally the gas is passed from below through the liquid in order to mix the fluids generated by the turbulence and order to produce a plug flow to convey both liquids. The surprisingly newly found principle underlying the bubble mixer according to the invention that a significantly better mixing quality is achieved by the formation of a phase and the entrainment of very fine droplets of the phase boundary with the gas bubbles, also has the significant advantage over the bladder mixers according to the prior art in that the gas is introduced via a simple dip tube and no complex gas distribution is required.

For the structural Optimization of the blender mixer were mixed trials with the following Systems performed: Water / dichloromethane, water / nitrobenzene, water / nitrotoluene, water / chloroform.

In 2 the construction of the bladder mixer according to the invention is shown. For all experiments, a bubble blender made of glass with a diameter DB of 5 cm was used. Dip tubes with diameter DT 1 cm, 1.5 cm, 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm and 4.5 cm were used. Further, gastight tubes with diameter DGT 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm; 3.5 mm, 4 mm, 4.5 mm and 5 mm. Bladder mixers with a height HB of 30 cm, 50 cm and 100 cm were used. The amounts of liquid examined were 10 ml / min and 100 ml / min, with the same amount of liquid being used for both liquids HD and ND. As gas G air and nitrogen were used for the experiments. The amounts of gas examined were 1 l / min, 5 l / min, 10 l / min and 20 l / min.

It the following was found. For All investigated systems yielded similar mixed grades same operating conditions. There was no difference be between air and nitrogen as gas. With a gas quantity of 10 l / min and higher became one with all constructions and all liquid combinations Emulsion produced. At a gas volume of 1 l / min was only a small Blending effect achieved. With 5 l / min gas quantity could for all systems a good mixing can be achieved. The best mixing at a gas volume of 5 l / min was at dip tube diameters DT between 1.5 cm and 3.5 cm; d. H. at a ratio DT / DB between 0.3 and 0.7; and at a gullet diameter DGT between 1 mm and 4 mm; d. H. at a ratio DGT / DB between 0.02 and 0.08.

at a quantity of liquid of 10 ml / min and a gas volume of 5 l / min, the blender mixer height HB of 30 cm to create a good mix. For a quantity of fluid of 100 ml / min and a gas volume of 5 l / min, the bubble mixer height HB should be at least 50 cm.

Farther was found in the experiments that when stopping the gas supply due to the difference in density of the liquid level in dip tube T about the fluid level in the bubble mixer B increases. To prevent failure in case of failure Gas supply during the operation of the mixer overflows the liquid from the dip tube, the Height H of the dip tube over be selected accordingly high the mixer. The distance HT between the lower end of the blender mixer B and the lower end of the dip tube T influences the mixing quality not, as long as a phase is formed, in which the liquid higher Density of HD enriches. The distance HGT between the lower end the bladder mixer B and the lower end of the gastro-tube GT must be chosen be that the escaping gas bubbles on the surface of the Phase in which the liquid higher Density HD enriched, impact. The distance HGT must be in be bigger in any case as the distance HT, to prevent gas bubbles in the dip tube T ascend.

Of the Diameter of the mixing sequence must be chosen so that the entire produced mixture without backwater can expire. The diameter of the gas outlet GA must be chosen so that all the gas can escape easily. Alternatively, the Diameter of the mixing sequence are chosen so large that the gas above the running mixture can easily escape here. In this case a separate gas outlet can be omitted.

There the bubble mixer according to the invention no additional Contains internals, he can easily over the drain valve V are emptied quickly and completely.

When mixing substances, especially if additional chemical reactions take place, such as neutralization reactions, mixing heat and heat of reaction can arise. For many chemical products, however, an increase in temperature can lead to undesired reactions. In order to keep the temperature constant in the bubble mixer according to the invention, the heat produced can preferably be removed via a cooling jacket. In 3 the bubble mixer according to the invention with external cooling jacket K is shown. In terms of process technology, it usually makes sense to carry the coolant in countercurrent to the process media, ie the coolant occurs at the top End of bladder mixer at position KME in the cooling jacket K, absorbs the energy and leaves it on the opposite side down in position KMA. For different processes, a DC driving mode may be useful. This is possible with the specified construction. Then the coolant is passed through the cooling jacket in opposite directions.

Of the Installation of cooling coils or cold plates in the bladder mixer is also possible. Here, however, should be on it be taken to ensure that these installations can influence the quality of mixing. Farther Care should be taken that the internals are drained do not influence. Which construction is chosen depends only on the respective mixing task and can be chosen freely. The specified options are intended as examples only and are intended to be used the bubble mixer according to the invention do not restrict.

With leave the bubble mixer according to the invention mix several different liquids, as long at least one lower and one higher density phase arise.

When Mixed gas can be used in principle any gas, as long as the droplets the liquid with higher Attach density to the gas bubbles. For cost reasons, air is preferred. If oxygen with the liquids or their components undesirable Nitrogen or other non-reactive Gas to be selected.

The indicated dimensions refer to one for use In a laboratory imaginary bladder mixer and intended to use the Bladder mixer according to the invention do not restrict. The mixing principle can also be applied to larger bubble mixers for the industrial Transfer operation become. The one for it required Dimensions need if necessary be adapted experimentally.

Of the Bubble mixer according to the invention can be used as a reactor, for example, for a nitration reaction in which a non-acid soluble organic Compound such as toluene with nitrating acid, a Mixture of sulfuric acid and nitric acid, is nitrided. Also for the laundry of crude products from nitration processes, the bubble mixer according to the invention be used. With the bubble blender according to the invention can acid residues washed out of the crude organic product with water or with neutralized alkaline solution become. Also dissolved in an organic liquid salts can for example, with water with the bladder mixer according to the invention from the organic liquid be washed out, if not or only to a small extent Part soluble in water is and the density varies accordingly.

Of the Bubble mixer according to the invention Can also be used as a quench for rapid dilution or neutralization of a reaction solution be used.

All specified applications are intended only as examples and limit the use of the bladder mixer according to the invention not a.

Claims (14)

Bladder mixer for mixing at least two liquids that are not soluble in each other and have a different density, consisting of a vertical cylindrical tube whose lower end is closed and equipped with a discharge line with a drain valve, wherein the outlet for the mixture produced in the upper area is arranged and has a gas outlet in the upper region, characterized in that a. in the bladder mixer, a cylindrical immersion tube is installed, through which the liquids are supplied; b. the gas needed for mixing is added via a gas immersion pipe above the phase forming in the lower part of the bubbler which is enriched with higher density liquid so that the gas bubbles hit the surface of the higher density phase and there are smallest droplets of the liquid Add higher density liquid to the gas bubbles, c. the lower density liquid alone rises due to the difference in density up to the outlet, d. the liquid of higher density is carried upwards with the gas bubbles in the form of fine pots, e. and thereby forms a very good mixture of the two liquids, which then runs out of the mixer, f. the immersion tube is immersed deeper into the mixer than the gas immersion tube, so that it is ensured that no gas bubbles rise through the dip tube upwards Bladder mixer according to claim 1, characterized that the ratio from dip tube diameter to bubble mixer diameter between 0.3 and 0.7 A bladder mixer according to claim 1, characterized in that the ratio of the gastro-tube diameter to the bladder mixer diameter between 0.02 and 0.08 Bladder mixer according to claim 1, characterized that the height of the dip tube above the Mixer chosen so high is that in case of failure of the gas supply during the operation of the mixer the Liquid, which does not rise due to the density difference in the dip tube overflows from the dip tube, Bladder mixer according to claim 1, characterized that the diameter of the mixing process is so great that the entire mixture produced and the gas over the effluent mixture without backwater can expire and thereby a separate gas outlet is needed. Bladder mixer according to claim 1, characterized that the lower end of the bladder mixer is flat. Bladder mixer according to claim 1, characterized the lower end of the bladder mixer is tapered to the drain valve tapers. Bladder mixer according to claim 1, characterized that the bubble mixer with an external cooling jacket equipped is Bladder mixer according to claim 1, characterized that several different liquids be mixed, with at least one phase with lower and a phase with higher Dense arise. Bladder mixer according to claim 1, characterized that air is used as mixed gas. Bladder mixer according to claim 1, characterized that nitrogen is used as mixed gas. Bladder mixer according to claim 1, characterized that the bubble mixer is used as a reactor. Bladder mixer according to claim 1, characterized that the bladder mixer to the laundry of Raw products from nitration processes is used. Bladder mixer according to claim 1, characterized that the bubble mixer for washing salts of organic liquids is used.