HK1167360B - Metering ring - Google Patents

Description

Metering ring

Technical Field

A metering device for a free-flowing medium or gas and the use thereof.

Background

(meth) acrylic acid and (meth) acrylic esters are important products of the chemical industry, which are used as starting materials for many important products. Therefore, maximum yields, particularly high purities and low preparation costs are necessary for an economic success of the preparation process of such important products. Relatively small improvements in yield, equipment life, or similar process characteristics have resulted in significant advances in the amount of undesirable by-products and manufacturing costs.

The methacrylamide used for the preparation of methacrylic acid can preferably be obtained by the so-called ACH process. Starting from hydrocyanic acid and acetone, acetone cyanohydrin is prepared in a first step and is then converted into methacrylamide. These steps are described in particular in US 7,253,307, EP-A-1666451 and PCT/EP 2007059092.

Acetone cyanohydrin is prepared by known processes (see, for example, Ullmanns)der technischen Chemie, 4 th edition, volume 7). The reactants frequently used here are acetone and hydrocyanic acid. The reaction is exothermic. In order to counteract the decomposition of the acetone cyanohydrin formed in this reaction, the heat of reaction is generally conducted away by means of a suitable apparatus. The reaction can in principle be carried out here as a batch process or as a continuous process, if a continuous mode of operation is preferred, the reaction is frequently carried out in correspondingly arranged loop reactors.

Acetone cyanohydrin, prepared by different known preparation processes, is generally subjected to distillative workup. In this case, the stabilized crude acetone cyanohydrin is freed of low-boiling components by means of a corresponding column. Suitable distillation processes can be carried out, for example, via only one column. However, it is also possible to use a combination of two or more distillation columns in the case of a corresponding purification of the crude acetone cyanohydrin, even in combination with a falling-film evaporator. It is additionally possible to combine two or more falling-film evaporators or two or more distillation columns with one another.

The crude acetone cyanohydrin is typically transferred from the storage device to distillation at a temperature of about 0 ℃ to about 15 ℃, for example about 5 ℃ to about 10 ℃. In principle, the crude acetone cyanohydrin can be introduced directly into the column. However, it has been found in some cases to be useful when the crude, cold acetone cyanohydrin first absorbs a portion of the heat of the product which has been purified by means of distillation by means of a heat exchanger. Thus, in another embodiment of the process described herein, the crude acetone cyanohydrin is heated to a temperature of about 60-80 ℃ by means of a heat exchanger.

The distillative purification of acetone cyanohydrin is carried out by means of a distillation column having more than 5 and preferably more than 10 trays or by means of a cascade of two or more correspondingly suitable distillation columns. The bottom of the column is preferably heated with steam. It was found to be advantageous when the bottom temperature does not exceed a temperature of 140 ℃; good yields and good purification can be achieved when the bottom temperature is no greater than about 130 ℃ or no greater than about 110 ℃. The temperature data is here based on the wall temperature at the bottom of the column.

Crude acetone cyanohydrin is fed into the column at the upper third of the column. The distillation is preferably carried out under reduced pressure, for example at a pressure of from about 50 to about 900 mbar, in particular from about 50 to about 250 mbar, with good results between 50 and about 150 mbar.

At the top of the column, gaseous impurities, in particular acetone and hydrocyanic acid, are discharged and the separated gaseous substances are cooled by means of a heat exchanger or a cascade of two or more heat exchangers. In this context, preference is given to using brine cooling with a temperature of from about 0 to about 10 ℃. Where the gaseous components of the vapor are given the opportunity to condense. The first condensation stage can be carried out, for example, at atmospheric pressure. However, it is also possible and in some cases found to be advantageous when the first condensation stage is carried out under reduced pressure, preferably under the pressure present in the distillation. The condensate is further conducted to a cooled collection vessel and collected there at a temperature of about 0 to about 15 c, in particular about 5 to about 10 c.

The gaseous compounds which are not condensed in the first condensation step are removed from the low-pressure space by means of a vacuum pump. In principle, any vacuum pump can be used here. However, it was found to be advantageous in many cases when using a vacuum pump which, due to its design, does not lead to the introduction of liquid impurities into the gas stream. It is therefore preferred here to use, for example, a dry-running vacuum pump.

The gas stream escaping at the pressure side of the pump is guided through a further heat exchanger which is preferably cooled with brine at a temperature of about 0 to about 15 ℃. The condensed components are likewise collected in a collection container, which collects the condensate that has been obtained under vacuum. The condensation on the pressure side of the vacuum pump can be carried out, for example, by means of a heat exchanger, but also with a cascade of two or more heat exchangers arranged in series and in parallel. The gaseous material remaining after this condensation step is discharged and sent to any further utilization, such as heat utilization.

The collected condensate may also be further utilized in any manner. However, it was found to be extremely advantageous from an economic point of view to recycle the condensate to the reaction for preparing acetone cyanohydrin. This is preferably done at one or more locations where the passage into the loop reactor can be effected. The condensates may in principle have any composition, as long as they do not interfere with the preparation of acetone cyanohydrin. However, in many cases, the major amount of condensate will consist of acetone and hydrocyanic acid, for example in a molar ratio of from about 2: 1 to about 1: 2, often in a ratio of about 1: 1.

The acetone cyanohydrin obtained from the bottom of the distillation column is first cooled via a first heat exchanger from the cold crude acetone cyanohydrin fed to a temperature of about 40 to about 80 ℃. Subsequently, the acetone cyanohydrin is cooled by means of at least one further heat exchanger to a temperature of about 30 to about 35 ℃ and optionally intermediately stored.

In another process element, acetone cyanohydrin is subjected to hydrolysis. In this case, methacrylamide is formed as product after a series of reactions at various temperature levels.

The conversion is brought about by reaction between concentrated sulfuric acid and acetone cyanohydrin in a manner known to the person skilled in the art. The reaction is exothermic and therefore the heat of reaction can be removed from the system in an advantageous manner.

Here, the conversion can also be carried out again in a batch process or in a continuous process. The latter has proven advantageous in many situations. The use of a loop reactor has been found to be useful if the reaction is carried out in a continuous process. Loop reactors are known in the art. These can be configured in particular in the form of a tubular reactor with recirculation. The reaction can, for example, be carried out in only one loop reactor. However, it may be advantageous when the reaction is carried out in a cascade of two or more loop reactors.

Suitable loop reactors in the context of the process have one or more feed points for acetone cyanohydrin, one or more feed points for concentrated sulfuric acid, one or more gas separators, one or more heat exchangers and one or more mixers. The loop reactor may comprise further components, such as transfer means, pumps, control elements, etc.

As already described, the hydrolysis of acetone cyanohydrin with sulfuric acid is exothermic. Several side reactions occur in parallel with the main reaction, which results in a reduction in yield. In the preferred temperature range, the decomposition of acetone cyanohydrin, which is also an exothermic and rapid reaction, plays a significant role. However, the heat of reaction generated in the reaction must be at least substantially removed from the system, since the yield decreases with increasing operating temperature and increasing residence time. Although in principle a rapid and complete removal of the heat of reaction can be achieved with corresponding heat exchangers. However, too great a cooling of the mixture before the metering in of acetone cyanohydrin can also be disadvantageous, since high turbulence is required both for the mixing and for efficient heat removal. Since the viscosity of the stirred mixture increases significantly with decreasing temperature, the flow turbulence decreases correspondingly in some cases up to the lamellar region, which leads to less effective heat removal in the heat exchanger and to slower and less homogeneous mixing when acetone cyanohydrin is metered in.

Rapid mixing of acetone cyanohydrin and reaction mixture is required because acetone cyanohydrin should be reacted before it is decomposed by heating. The fine dropletization of the reactants-which means a large specific interfacial area, results in the desired reaction on the droplet surface being favored over the heating of the droplet volume, which is followed by decomposition. A fine distribution of acetone cyanohydrin was found to be advantageous because the reaction takes place on the surface of the droplets.

In addition, too low a temperature in the reaction mixture may cause the components of the reaction mixture to crystallize on the heat exchanger. Thereby further deteriorating heat transfer, which may cause a significant decrease in yield. Furthermore, the loop reactor cannot be charged with an optimal amount of reactants, so the efficiency of the process as a whole suffers.

Disclosure of Invention

It is therefore an object of the present invention to improve the supply and fine distribution of free-flowing media or gases in a pipeline or tubular reactor, ideally also improving the mixing operation.

This object is achieved by a device for metering a free-flowing medium or gas, characterized in that one or more metering loops with a metering point 11, which are equipped in a pipeline, a tubular reactor or a loop reactor, are used.

It has surprisingly been found that the use of the metering ring enables a free-flowing medium or gas to be supplied and finely distributed over the entire tube circumference or the cross-section of the tube, so that the mixing operation is significantly improved. Large amounts can be mixed over short paths.

The metering ring of the present invention may have a variety of different embodiments. For example, many small metering points 11 may be introduced into the ring, or a few large metering points may be introduced into the ring (fig. 1). The metering point may also protrude through the small tube 13 into the interior of the tube (fig. 2), and in certain embodiments there are also small tubes of various lengths.

The metering ring may be cooled or heated depending on the metering task.

Here, a further advantage of the externally located ring of the invention is that it is not heated by the surrounding medium, such as a metering lance inserted into the pipe. In addition, acetone cyanohydrin can be cooled through the ring, which can be much more complicated in terms of construction, for example in metering lances.

A particular embodiment is a metering ring in which the metering is carried out under overpressure.

The device may take any suitable three-dimensional shape, preferably it is constructed in the form of a ring. Bicyclic or polycyclic rings may also be used here.

The metering ring is particularly suitable for continuous processes. The metering ring is preferably used for the continuous preparation of methacrylamide by hydrolysis of acetone cyanohydrin with sulfuric acid. Another field of application is, for example, the preparation of acetone cyanohydrin from acetone and hydrocyanic acid.

According to the invention, the reaction is carried out continuously in a tubular reactor or in a loop reactor. The terms "continuous" and "tubular reactor" are known in the art. "continuous reaction" is understood to mean, in particular, a reaction in which the reactants are added over a relatively long period of time and the product is removed from the reaction mixture. The tubular reactor comprises at least one tubular zone in which the reaction can be carried out. These reactors are generally of relatively simple construction and therefore have relatively low capital costs.

The reactants may be introduced into the tubular reactor by means of a pump. In order to prevent an interruption of operation caused by maintenance, two or more pumps may also be provided, which may be connected in parallel. The mixing of the reactants with the metering ring can expediently take place upstream of the pump, i.e. on the suction side of the pump, as seen in the flow direction, wherein the apparatus is particularly preferably free of any further internals for mixing in the region between the pump and the tube reactor. However, the metering ring can also be an integral part of the pump and can be integrated into the pump housing. By these measures, surprising advantages can be achieved in terms of operational reliability and service life of the plant, and in relation to yield and purity of the product.

The components of the plant which come into contact with corrosive substances, in particular the tube reactor, the pump and the phase separator, are composed of suitable materials, for example acid-resistant metals, such as zirconium, tantalum, titanium or stainless steel, or coated metals, for example with an enamel or zirconium layer. In addition, plastic, for example PTFE-coated components, graphitized modules or workpieces made of graphite, in particular in pumps, can also be used.

In one design of the process, a partial volume flow, preferably from about two-thirds to about three-quarters, is introduced from the acetone cyanohydrin stream into the first loop reactor. The first loop reactor preferably has one or more heat exchangers, one or more pumps, one or more mixing elements and one or more gas separators. The circulation flow through the first loop reactor is preferably in the range of about 50 to 650m³H, more preferably 100-³H and further preferably about 150-450m³H is used as the reference value. In at least one further loop reactor downstream of the first loop reactor, the circulation flow is preferably in the range of about 40 to 650m³H, more preferably 50 to 500m³H and, in addition, preferably from about 60 to 350m³H is used as the reference value. In addition, the preferred temperature difference across the heat exchanger is about 1-20 deg.C, with about 2-7 deg.C being particularly preferred.

The supply of acetone cyanohydrin through the metering ring according to the invention can in principle be carried out at any point in the loop reactor. It was found, however, to be advantageous when the supply to the mixing elements, for example to a mixer with movable parts or to a static mixer, or to a location where mixing is sufficient, is carried out. The sulfuric acid is advantageously supplied upstream of the addition of acetone cyanohydrin. However, in other cases it is also possible to introduce the sulfuric acid into the loop reactor at any point.

The metering ring of the present invention is used to feed the medium, such as sulfuric acid or acetone cyanohydrin, shortly before or in the pump. Thus, the highly turbulent flow in the pump housing serves to mix the reactants and thereby simultaneously utilize the conveyor as a mixer. The mixing power of the pump is thus advantageously utilized.

The ratio of the reactants in the loop reactor is controlled so that there is an excess of sulfuric acid. The excess of sulfuric acid is from about 1.8: 1 to about 3: 1 in the first loop reactor and from about 1.1: 1 to about 2: 1 in the last loop reactor, based on the molar ratio of the components.

In some cases it has been found to be advantageous to carry out the reaction in a loop reactor with such an excess of sulfuric acid. Here, sulfuric acid can for example be used as solvent and keep the viscosity of the reaction mixture low, which can ensure a faster removal of the heat of reaction and a lower reaction mixture temperature. This can lead to significant yield advantages. The temperature in the reaction mixture is about 85 to about 150 ℃.

Heat removal is ensured in the loop reactor by one or more heat exchangers. It was found to be advantageous here when the heat exchanger has a suitable sensor system for adjusting the cooling power to prevent excessive cooling of the reaction mixture for the reasons mentioned above. For example, it may be advantageous to measure the heat transfer in the heat exchanger or in the plurality of heat exchangers in a punctiform or continuous manner and adapt it to the cooling power of the heat exchanger. This can be done, for example, by the coolant itself. The corresponding heating of the reaction mixture can likewise be achieved by corresponding changes in the addition of the reactants and by generating more reaction heat. A combination of both possibilities is also conceivable. The loop reactor preferably additionally has at least one gas separator. Via the gas separator, the continuously formed product can be withdrawn on the one hand from the loop reactor. On the other hand, the gases formed in the reaction can be discharged from the reaction space in this way. The gas formed is mainly carbon monoxide. The product withdrawn from the loop reactor is preferably transferred to a second loop reactor. In this second loop reactor, the reaction mixture comprising sulfuric acid and methacrylamide, obtained by the reaction in the first loop reactor, is reacted with the remaining acetone cyanohydrin substream. In this process, the excess sulfuric acid from the first loop reactor, or at least a portion of said excess sulfuric acid, reacts with acetone cyanohydrin to further form sulfinyl (Sulfoxy) isobutyramide (SIBA). The implementation of the reaction in two or more loop reactors has the advantage that the pumping capacity of the reaction mixture and thus the heat transfer and the final yield are improved due to the excess of sulfuric acid in the first loop reactor. In the second loop reactor there is again arranged at least one mixing element, at least one heat exchanger and at least one gas separator. The reaction temperature in the second loop reactor is likewise from about 90 ℃ to about 120 ℃.

The problems of the pumping capacity of the reaction mixture, the heat transfer and the reaction temperature as low as possible apply to each of the further loop reactors as in the first loop reactor. The second loop reactor therefore also advantageously has a heat exchanger whose cooling power can be adjusted by means of a corresponding sensor system.

The acetone cyanohydrin supply is in turn carried out in a suitable mixing element, preferably a static mixer or a metering ring according to the invention. The product may be withdrawn from the gas separator of the second loop reactor and may be heated to a temperature of about 130 to about 180 ℃ to complete the reaction and form methacrylamide.

Heating is preferably carried out such that only the maximum temperature is reached for as short a time as possible, for example for a time of from about 1 minute to about 30 minutes, in particular for a time of from about 2 to about 8 minutes or from about 3 to about 5 minutes. This can in principle be done in any desired apparatus for achieving such temperatures for such short times. For example, the energy may be supplied in a conventional manner by means of electrical energy or by means of steam. However, it is likewise possible to supply energy by means of electromagnetic radiation, for example by means of microwaves.

It was found to be advantageous in various situations when the heating step is carried out in a heat exchanger having a two-stage or more coil arrangement, which coils may preferably be present in an at least double convection arrangement. Here, the reaction mixture is rapidly heated to a temperature of about 130 ℃ and 180 ℃.

The amide solutions thus obtainable generally have temperatures in excess of 100 ℃ and generally temperatures of about 130 ℃ and 180 ℃. It is also possible to cool to a temperature of less than 130 ℃.

In addition to the use of the apparatus of the present invention in chemical processes, a number of further possible applications are provided.

For example, the metering ring may also be used in remote transfer lines for oil transportation. Flow improvers must be added to the crude oil at regular intervals. At these feed points, flow improvers are usually added via nozzles. The large volume flow presses the metered medium primarily into the pipe interior, the conversion proceeds poorly and then only over long distances. With the metering ring according to the invention, it is possible to ensure that the flow improver is blended into the crude oil over the entire pipe cross section.

Similar applications provide the required chemical additions in oil and gas production.

The invention further provides for the use of the metering device of the invention in chemical processes, preferably in processes in which rapid mixing and fine distribution of the medium is required. Ideally, at the metering point, the fed medium is completely reacted or mixed with the medium flowing past. In the case of metering in, for example, one drop of liquid until fine mixing with other media, the shortest possible path should be covered until the mixing point.

It was found that the metering ring of the invention enables an almost ideal mixing or conversion at one feed point in the case of a supply of free-flowing medium or gas.

In the case of the metering device according to the invention, a more uniform distribution over the tube cross-section is achieved by means of a ring having a plurality of metering points, compared with conventional metering with one metering point. This improves the mixing result significantly and at the same time shortens the mixing time. The inner wall of the metering ring is passed by any number of injection grooves. Preferably 2-20 and more preferably 16 injection grooves evenly distributed over the circumference are used. These may be inclined individually or collectively at an angle of 1 ° to 179 °, preferably 20 ° to 120 °, more preferably 60 °, to the inner wall of the pipeline. In the case of known metering devices with one metering point, the metered-in medium is pressed against the pipe wall by the flowing-through medium in the case of strong flow inside the pipe, and therefore no or only very poor mixing occurs. Therefore, these metering points cannot be used simultaneously for mixing. Downstream of the metering point, a mixing operation must then additionally be introduced. This is achieved by incorporating static mixing elements or incorporating pumps or the like.

The known metering methods with multiple metering points along the tube are not suitable for many chemical processes, since the chemical conversion is adversely affected via long mixing paths. The long mixing path causes thermal decomposition to occur, and the yield is thus deteriorated.

It is possible to dispense with the use of static mixing elements, which in the case of the use of corrosive media would otherwise have to be replaced regularly and would therefore lead to downtime. The use of static mixing elements also always leads to undesirable pressure losses.

It is particularly advantageous to mount the metering ring upstream of the pump. Ideally, the metering ring is located immediately upstream of the suction manifold of the circulation pump. Turbulence can thus be used in the pump for mixing.

Metering rings may also be used in centrifugal pumps. Ideally near the point where the kinetic energy is at a maximum to produce the desired mixing. Metering in the middle of the pump results in a long path from the pump outlet and therefore also a long mixing section.

In certain cases, the mixer or pump may be eliminated by using a metering ring.

For example, by feeding a gas, optionally an inert gas, it is possible to generate turbulence in the medium flowing through the pipe. The suspension can thus be prevented from settling by laminar flow within the tube.

By having different lengths of the metering points or small tubes of the metering ring, a wider and uniform distribution over the entire cross-section of the tube can be achieved. The reactants can thus be metered in a targeted manner up to the interior of the tube.

The metering device of the present invention has a wide range of applications. Wherever rapid and/or uniform metering of free-flowing media or gases is required. Liquids with low or high viscosity, but also suspensions, emulsions, gases, etc., can be metered in. The use takes place in chemical systems such as pipelines or tubular reactors. The metering ring serves here as a metering device and/or a mixer.

In a particularly preferred application, the metering ring is used for hydrolysis of acetone cyanohydrin with sulfuric acid to give methacrylamide.

The invention is explained in more detail by the following figures:

drawings

FIG. 1 shows a schematic view of a

Longitudinal section through a line section with a metering ring fitted therein

FIG. 2

Partial enlargement of the modified embodiment

List of reference marks

1 pipeline

2 pipe flange

3 sealing

4 measuring ring

5 clamping device

64 distribution chamber

7 feed manifold for fluid F

8 feed manifold for fluid F

9 injection

10 inner wall of the metering ring 4

11 injection groove (measuring point)

121 inner wall

13 small tube

1413 positioning ring

1513 outlet edge

16 measuring point

d diameter of injection groove 11

Outer diameter of small tube 13

Angle alpha

Radial excess height of Y13, 15

M medium

F fluid

The figures show two embodiments of the metering ring of the present invention.

According to fig. 1, the metering ring 4 according to the invention is inserted into a line 1 through which a medium M flows, between two pipe flanges 2 and two seals 3, by means of a clamping device 5 shown in the drawing.

The metering ring 4 has a surrounding distribution chamber 6, which distribution chamber 6 is supplied with the fluid F to be metered from two feed branches 7 and 8.

The inner wall 10 of the metering ring 4 is passed through by preferably 16 injection grooves 11 which are distributed uniformly over the circumference. These are in turn preferably inclined at an angle alpha of 60 deg. relative to the inner wall 12 of the pipeline 1.

This ensures a homogeneous injection 9 of the fluid F into the stream of medium M.

The solution according to fig. 2 envisages that a small tube 13, having a radial excess height Y with respect to the inner wall 12 of the line 1, is inserted into the injection groove 11.

In this case, the end of the small tube 13, which therefore projects slightly into the flow of the medium M, constitutes the metering point 16.

This optimizes the introduction of fluid F into the stream of medium M in such a way that: so that the fluid F cannot flow along the inner wall 12 of the pipeline 1 and, as it were, a drop break-up in the medium flow occurs at the metering point 16, since the medium M flows around the outlet edge 15 of the small tube 13.

In order that the small tubelet 13 cannot be pressed in as far as the dispensing chamber 6, a positioning ring 14 is provided, which is formed by the difference in diameter between the diameter D of the injection groove 11 and the outer diameter D of the small tubelet 13.

By this constructional feature a rational mounting of the metering small tube 13 is provided while at the same time ensuring a predetermined position of the radial distance Y of the metering point 16 from the inner wall 12 of the pipeline 1.

The examples given below serve to better explain the invention, but are not suitable for limiting the invention to the features disclosed therein.

Detailed Description

Examples

In several operating experiments, yield measurements were carried out. The effect of the metering ring is determined experimentally here.

The yields are measured in a process system with a metering ring and a downstream pump as dynamic mixer, in contrast to the static mixers conventionally used. The pump is arranged immediately behind (downstream of) the metering ring in the flow direction. In order to ensure the shortest possible path of the ACH up to the mixing stage and thus to achieve the fastest possible mixing, the metering ring is directly flanged (mounted) onto the intake manifold of the pump. In the process systems with metering loops according to the invention, the pump is a circulation pump, which is usually used for the circulation guidance of the amide mixture in the loop reactor.

The yields obtained are compared in graph a. The individual experimental parameters were varied and the yield was measured by sampling and analysis of the amide mixture.

Most measurements gave an increase in yield. A positive yield difference of up to 3.2% indicates an increase in yield due to the use of the metering ring.

Claims (16)

1. Device for metering a free-flowing medium, characterized in that one or more metering rings (4) with metering points [11] are used, which are equipped in pipelines, tube reactors or loop reactors, wherein the inner wall of the metering ring (4) is passed through by 2 to 20 injection grooves which are uniformly distributed over the circumference, and

wherein the metering ring (4) is inserted into the line (1) through which the medium flows between the two pipe flanges (2) and the two seals (3) by means of a clamping device (5), and the metering ring (4) has a surrounding distribution chamber (6), the distribution chamber (6) being supplied with the medium to be metered from the two supply branches (7 and 8).

2. The apparatus of claim 1, wherein said medium is a gas.

3. Device according to claim 1 or 2, characterized in that the metering points are realized in various orientations and lengths.

4. Device according to claim 1 or 2, characterized in that the injection grooves are individually or collectively inclined at an angle of 1 ° to 179 ° relative to the inner wall of the pipeline.

5. Device according to claim 1 or 2, characterized in that the injection grooves are individually or collectively inclined at an angle of 20 ° -120 ° relative to the inner wall of the pipeline.

6. Device according to claim 1 or 2, characterized in that the injection grooves are individually or collectively inclined at an angle of 60 ° with respect to the inner wall of the pipeline.

7. Device according to claim 1 or 2, characterized in that the metering point protrudes through the small tube [13] into the interior of the tube.

8. Device according to claim 7, characterized in that the small tubes have different lengths.

9. Device according to claim 1 or 2, characterized in that the free-flowing medium is added through the metering point at an overpressure.

10. Device according to claim 1 or 2, characterized in that the temperature of the metering ring is regulated.

11. Device according to claim 1 or 2, characterized in that the metering ring is cooled or heated according to the metering task.

12. Device according to claim 1 or 2, characterized in that a double or multiple ring is used.

13. Use of a device according to any of claims 1-12 in a chemical process with rapid mixing operation.

14. Use of the device according to claim 10 for the preparation of methacrylamide from acetone cyanohydrin and sulfuric acid.

15. Use of a device according to any one of claims 1-12 in oil and gas pipelines, or in drinking water, industrial water or waste water pipelines.

16. Use of a device according to any of claims 1 to 12 in a pipeline at the feed point of a free-flowing medium.