SI9210104A - Complex mixer for dispersion of gases in liquid - Google Patents

Abstract

A complex mixing system with stages that consists of large diameter propeller mixers, where shovels are provided with elements for a modification of the flow, whereby the proportions of energy consumed to disperse the amount of gas injected into reactor, homogenization of multiphase mixtures, suspension solids, etc. and properties corresponding to rheological gas / liquid mixture properties and special requirements procedure, can also provide in exceptional cases. The open channels (5), opposite the direction of rotation, are arranged on shovels (4) dispersion stages (2a) propeller mixers (2) attached to a common shaft where the channels (5) are connected to the gas inlet (7). The angle of incidence certain part of the shovels (4) of the mixing stages (2b, 2d), used for homogenizing and suspending is in the opposite direction, the length is shorter and / or the angle of incidence is smaller than other shovels. At the exit ends the blades are on a specific part (2c) of the propeller mixers, used similarly for homogenizing and suspending, deflection bars (8) and / or auxiliaries arranged blades (12) that are angled not more than 20 degrees with respect to the vanes above or below the outlet ends of the shovels.

Description

RICHTER GEDEON Vegyeszeti Gyar Rt.

A complex mixer for dispersing gases in a liquid

The invention relates to a complex mixer for dispersing gases in a liquid and for intensive mixing of mixtures in cylindrical vertical shaft reactors, mainly in bioreactors, comprising propeller mixing blades attached to a common vertical shaft of the device. Until now, bioreactors (fermenters) have been mainly used so-called. A Rushton turbo mixer driven by a centrally spaced shaft in a fermenter comprising six rectangular straight blades radially attached to a circular plate. If the height of the bioreactor is a multiple of the diameter, a set of 2-4 turbo mixers attached to a common shaft is used.

The air to be dispersed is injected under the lower mixer through a perforated loop expansion tube, nozzles or central nozzle (Fejes, G.: Industrial mixers, p. 52-55).

Turbo mixers, typically 1/3 of the diameter of a fermenter, with intense turbulence and shear forces created around a series of blades, effectively disperses the air, but the result of high local energy dissipation - regardless of the high specific energy consumption of the turbo mixer - is the energy ratio mixed farther from the agitator regions, minimally, the axial transfer effect of the agitator is small, causing more and more problems in increasing the volume of bioreactors.

Also known are two- or multi-wing propeller mixers with tilted blades or bent over the geometric spiral surface from which the mixing system is designed.

SEM mixers take advantage of the properties of thin propeller wings, and ΕΚΑΤΟ mixers take advantage of the interference phenomenon of parallel double wing blades arranged at an angle and at the required distance from one another (Interming and Interprop mixers, Fejes, G .: Industrial mixers, p. 65).

The energy dissipation of propeller mixers with a large diameter ratio compared to the diameter of the fermentation plant is more continuous, and the axial transfer effect is large, thus mixing the liquid more efficiently and evenly in high fermentation plants with equal energy consumption, but the effect of dispersing them is worse, which is equivalent to using multiple phases.

Suction mixers are also known, consisting of hollow mixers attached to a drive shaft which are suitable for mixing, dispersion and, in part, for gas transfer. The hollow mixing elements are mainly cut off at a 45 ° angle, and at the ends of them, at a suitable velocity, a pressure drop occurs, which usually enters the gas through the hollow tubular shaft, which is atomized by shear forces, which liquids are created by sharp pipe ends (Fejes, G.: Industrial Mixers, p. 57). However, due to the limited suction effect, these mixers are not applicable in the fermentation industry. Such suction mixers are also known, wherein the hollow elements are approximately semicircular ducts open on the side opposite to the forward direction, with a diameter approximately equal to the diameter of the container, making them suitable for atomizing a relatively large amount of gas. However, due to their low circulating capacity, they are only useful in the yeast industry and sometimes in processes where intensive mixing of the liquid is not required.

The purpose of mixing in the reactors is to homogeneously distribute the solid, liquid and gaseous phases to enhance the processes of substance and heat transfer. Significant velocity gradients and turbulence occur in the space between the mixing elements and the reactor wall equipped with deflection plates. In the case of fermentation processes, turbulence and shear forces proportional to the velocity gradient increase the dispersion of the injected air bubbles, reduce the thickness of the boundary layer between microorganisms, culture medium and air bubbles, thereby improving and accelerating the processes of transfer of matter and heat that occur. at the phase boundaries.

Such a three-phase system of micro-organisms, culture medium and injected air is carried out in bioreactors, where the flow space and its effect on the transfer of matter are extremely complicated due to various interactions, such as changes in the rheological properties of the fermentable fluid as a result of the metabolism of microorganisms. The problem is further compounded by the diversity and contrasts of the requirements. Thus, e.g. in a certain part of the fermentation process for dispersion of air and oil droplets, micromixing of the culture medium and biomass and cutting of agglomeration requires intense turbulence and shearing, while intensive mixing accelerates the formation of stable foams, which partially and partially with foam inhibitors reduce oxygen transfer, aeration carbon dioxide and can mechanically damage microorganisms or lead to morphological changes, which are reflected in a decrease in production.

The complexity of the mixing process carried out in bioreactors is characterized by the fact that each basic operation, e.g. dispersing, suspending, separating, homogenizing, etc. important role in procedures, ie. in fact, each fermentation process has its own specific requirements, which vary significantly in type and load. The impact of basic operations should therefore remain within relatively narrow limits so that, in addition to the required beneficial effect, counter-effects remain minimal. Considering the turbo mixers used in most bioreactors, it is appropriate to use the main amount of mixed energy to generate turbulence, and 70% of the mixing energy is dissipated in the immediate vicinity of the turbine blades, with only a small degree of change in these conditions.

In the case of fermentation, liquids which form intensely aerated viscous and stable foams and which do not have Newtonian properties, can relatively quickly slow down the circulation and turbulence created by small diameter turbos. The rotation can be accelerated by increasing the diameter of the turbo mixer, but this is limited by the disproportionate growth of the mixing energy, which, given the known proportions, increases with the fifth potency of the mixer diameter. Therefore, the diameter of the turbo mixer must not exceed 40% of the plant even in the case of a small fermenter, ie below 40 m ³ , so they are characterized by a small diameter ratio. On the other hand, this creates an additional problem, as the volume of the reactor and the viscosity of the fermented liquid consequently increase in insufficiently mixed areas.

The diameter of the propeller mixers - given the much lower energy input to them - can reach the diameter of the reactor. Therefore, the use of large diameter propeller mixers representing 60-70% of the device diameter is becoming widespread in bioreactors whose dispersion effect is smaller but more suitable for the efficient mixing of viscous liquids that are fermented.

It is difficult to provide an effective mixer, since the properties of the viscous fermentable liquids and the contained microorganisms and air bubbles are often significantly different from those of Newtonian liquids. Some scientists believe that with the same amount of energy input, a smaller diameter turbo mixer is capable of eight times higher oxygen absorption rates than a larger diameter turbo mixer, although such differences cannot be detected in pure water (Steel, R. - Maxon, WD: Biotechn. And Bioeng. 2,

231, 1962). These not sufficiently known phenomena, which depend on the properties of the cultures and the composition of the culture medium, also justify the construction of mixing systems whose mixing effect can be controlled within wide limits and modified according to each mixing operation.

On the other hand, a common feature of the mixers described is that each of them is suitable mainly for creating a particular mixing effect that can limit the optimization of the processes.

The mixing efficiency of the devices depends on the size of the energy input and the structure of the mixing system. The dissolved oxygen concentration can generally be improved to the required level by known mixers by increasing the amount of mixing energy and the air injected. However, the disproportionately increasing demand for energy and its costs, enhancing the formation of foam, and damage to microorganisms may limit economic production more and more with the increased size of the reacto.

The sign of a multi-stage turbine, usually consisting of the same elements, and other mixing systems, due to the aforementioned capabilities and limitations of the structures, do not provide adequate elasticity to meet the specific requirements of different microorganisms.

Due to the increasing dimensions of bioreactors, the described circumstances require the optimization of agitator systems at an elevated rate, which is the object of the present invention.

Accordingly, the invention provides a complex mixer comprising a large diameter propeller mixer mounted on a common vertical mixing shaft, with open channels interconnected open to at least one of the mixers opposite the direction of rotation. with the gas inlet, the inlet angle of a certain part of the other secondary blades of the propeller mixer is in the opposite direction, the length of which and the inlet angle being smaller compared to the other blades.

Deflection rods are installed on the edges of the primary and secondary mixing blades or part of them to increase turbulence.

The gas passing through the hollow hub of the mixer into the ducts on the primary mixing blades of the mixing system of the invention is exhausted and finely distributed along the entire length due to the pressure drop and turbulence occurring on the suction side of the wing blades, which force the fluid to intense axial flow. channels and shovels, and then the gas with the flow rate translates into efficient axial flow and accelerated by propeller wings.

The structure of the primary propeller mixers according to the invention is based on the knowledge that the gas can be finely distributed over a large surface by means of shovel channels without additional energy, allowing it to be uniformly incorporated into the entire mass of the flowing fluid. The mixing system thus consumes a major part of the energy for circulating the gas / water mixture, which is a significant advantage over the energy consumption of the system.

The gas is normally passed through the hollow shaft to the hollow hub of the primary mixer, or. in another way, when the pipeline feeds the gas into the hub of a mixer made as an open cylinder at the lower end.

The primary air intake manifold air ducts are suitably distributed along their outlet edges, and may be arranged (generally less efficiently) in the second portion of the blades, which are adjacent to the blades, where the dispersion effect of the bladder-accelerated stream is not yet present. prevails. This distance is about twice the width of the channel, so it would not be practical to install channels sideways. In contrast to the complexity of the structure, the advantage is that the multi-point duct blades form a rigid system that offers better resistance to the resonant phenomenon, leading to the fracture of relatively long and thin blades.

The gas to be dispersed is driven into the bioreactor below the mixer by a perforated loop expansion tube or nozzle. If the bioreactors have a capacity of hundreds of cubic meters, then the air is supplied under high pressure. A further important cognition pertaining to the mixing system of the invention is that the primary mixer performing the primary dispersion can be arranged as a higher stage, not only reducing the compression portion but also extending the path of the air bubbles, which could improved substance transfer. However, this arrangement cannot be realized for known reasons, either in the case of turbo mixers or suction mixers.

The weaker flow of the opposite direction is created by the shovels with the opposite transfer direction and the smaller transfer capacity, ie. the smaller angle of incidence and / or shorter blades of other propeller mixers, which intensively circulate the gas / liquid mixture, and the secondary dispersion of the respective gas bubble, is, according to the invention, reflected in a series of vortices striking the main stream, thereby making energy dissipation more uniform than at a series of vortices created at the thin ends of the blades of conventional turbo mixers. The intensity of the series of vortices thus created varies within wide limits by varying the angle of incidence and / or the length of the wing blades.

Contrary to the limitations of traditional turbo-mixers, the proportion of the amount of energy used to circulate and create turbulence is variable with this specific arrangement of blades, and the small dispersion effect of traditional propeller mixers can be improved if necessary. In many cases, the result is more favorable using this system than traditional systems.

The dispersion effect of secondary propeller mixers can also be improved if the propeller wings with a smaller angle of incidence and / or smaller diameter, which create a weaker counterflow, form a separate stage and are mounted alternately on the mixing shaft with secondary propeller mixers equipped with paddle wings for higher transfer effect, generating main flow with a larger angle of incidence and / or larger diameter. With this solution, a smaller number of impact areas can be realized.

The dispersion effect of the propeller blade vanes can be further improved by deflection rods attached to their outlet edges if necessary. Deflection rods have been found to create vortex sets whose intensity is adjustable within their width limits, which in turn follow the direction of the main stream of the mixture and thus support the dispersion and mixing of components without counteracting the mixing of the fermenting fluid.

The effect of dispersing the blades can be similarly enhanced by auxiliary wings exceeding 1/3 of the width of the blades arranged below or above the air distribution ducts. By appropriately varying the incident angle of these auxiliary wings relative to the blades, the velocity of the liquid / gas mixture passing between them and the blades can be varied within wide limits, further amplifying the flow turbulence generated by both the primary and secondary mixers. In the case of primary blades, there is an acceleration of flow and the consequences of this, ie. suction, turbulence enhancement and dispersion effects, with auxiliary wings attached in parallel to the blades as the ducts narrow the cross-section between the blades and the auxiliary blades.

In some less demanding cases, instead of the geometric spiral surfaces used in the propeller mixers, the blades of the propeller mixers are designed at an acute angle to the direction of rotation of the inclined plate. In these cases, the inclination angle of the shovel can be reduced in several steps. Of course, in any case it is necessary to account for the amplification of turbulence.

The various versions of the complex devices according to the invention allow for the adaptation of mixing systems to extremely different conditions and requirements of different cultures of microorganisms.

As an example, in the case of intensely frothy fermentable liquids - which prevents the transfer of O ₂ and matter - the use of a system consisting of a primary mixer with suction ducts and secondary propeller mixers without wing blades with the opposite direction would be preferred. On the other hand, in the case of less sparkling fermentable liquids with low viscosity and requiring little mixing, the use of a system consisting solely of secondary mixers would be effective.

However, for most known fermentation processes, a complex system consisting solely of primary and secondary mixers provides optimal conditions for the transfer of the substance.

With the complex mixing systems of the invention, any basic mixing operation that determines the transfer of a substance, such as e.g. the energy ratios used to generate circulation and turbulence are evenly distributed throughout the volume of the gas / liquid mixture, and the process concerned can be optimized in exceptional cases according to the specific requirements.

By adapting the construction of antisystem wing blades according to the invention, and by adjusting the intensity of a series of vortices that promote mixing, in addition to optimizing the continuous transfer of matter, damage to the microorganisms can be avoided, which causes serious problems for the turbo mixers.

Further details of the invention will be described in more detail in the embodiment, with reference to the accompanying drawings, where FIG. 1 shows a detail of the mixer according to the invention; 2 is a top plan view of the mixer of FIG. 1, FIG. 3 is a cross-section along the line ΙΠ-ΙΙΙ of FIG. 1, FIG. 4 is a cross-sectional view of a shovel with a recoil bar; FIG. 5 is a cross-sectional view of an auxiliary ring shovel, and FIG. 6 is a sectional view of the bioreactor of the invention.

In FIG. 1 to 3 show the mixing element of the device according to the invention. The propeller mixer 2 attached to the mixer shaft 1 of the bioreactor consists of blades 4 arranged on hub 3.

Ducts 5 are made on the back of the blades 4. These are connected through the holes 6 to the hollow hub 3.

The gas passes through the inlet 7 into the hollow hub 3 and then through the holes 6 into the channels 5.

In FIG. 4 shows a deflection rod 8 attached to the end of the blades 4.

In FIG. 5 is a cross-sectional view of the mixing shovel 4 shown in FIG. 1, wherein the welded channels 5 are welded to the shovel and the auxiliary shovel 12 is attached in parallel and above the shovel at a distance of 0.3 shovel width.

In FIG. presents the acceleration of flow between two parallel blades caused by the narrowing of the cross - section of the flow by channels 5.

In FIG. 6 is a practical embodiment of a device according to the invention. Mixing shaft 1 is centrally located here in bioreactor 9 together with four blade propeller mixers 2a-2d.

The gas inlet 7 is arranged on the lowest propeller mixer 2a. The structure of this primary propeller mixer 2a is identical to that shown in FIG. 1 to 3, wherein its diameter d _{1 is} 70% of the diameter D of the bioreactor and its transport is directed downwards. Further, four secondary propeller mixers 2b-2c are arranged on mixing shaft 1. The diameter d _x and the direction of transport of the propeller mixers 2c and 2e are the same as for the primary propeller mixer 2a, and the other two 'propeller mixers 2b and 2d have two downward blades for transport d _p ie 0.7 D, and two conveyor blades upwards with diameter d ₂ , ie 0.5 D. The distance h ₁ between the propeller mixers 2a and 2e is 70% of the diameter of the longer propeller mixers.

The blades of the central propeller mixer 2c are fitted with deflector rods whose width is 3% of the diameter of the propeller mixer.

The mixing system described above is suitable for mixing and aeration of fermentable liquids with a medium foaming effect, which requires a medium mixing intensity.

The apparatus according to the invention has been tested in which the complex mixing system has proved to be preferred over the Rushton type turbo-mixers in terms of hydro-mechanical parameters, homogenization time, dispersion effect and gas retention.

Measurements were taken in clean water and a highly foaming culture medium. Surprisingly, the foaming rate, despite the better dispersion, was lower than in the case of turbo mixers, which is probably due to more even energy dissipation.

This is very typical with regard to the efflux of fermentation processes, since foaming inhibitors generally reduce the transfer of substances.

A mixing system based on the principles outlined can be built in many ways, with the advantage of complexity and variability. However, the effective operation of these requires adjustment to certain ratios:

The diameter of the mixers with the large diameter ratio that typically generates downstream is 50-70%, and the diameter of the lower transfer blades that create counterflow is 40-60% of the reactor diameter. The distance between the mixers was 50-100% of the diameter with a large diameter ratio. The width of the deflection bars is 3-6% of the diameter of the mixer.

Depending on the circumstances, the complex agitator according to the invention is able, as a result of improved hydraulic efficiency, to accelerate the intensity of the process in the case of chemical processes, thereby increasing the effect, reducing the amount of components involved in the process, further improving the effluent and / or reducing the use of specific mixing energy in the case of biological processes.

The above examples are intended only to illustrate the invention, it being understood that the device within the invention can be modified differently.

RICHTER GEDEON Vegyeszeti Gyar Rt.

Claims (13)

Claims 1. A liquid gas dispersant and vigorous stirrer for mixtures in vertical cylindrical reactors, comprising large diameter propeller mixers attached to a common vertical shaft and a gas inlet, characterized in that they are on at least one of the blades (4) propeller mixers (2) in the opposite direction of rotation open channels (5) connected to the gas inlet (7) are arranged. Mixer according to claim 1, characterized in that the channels (5) through the holes (6) are connected to a hollow hub (3) mounted on the mixing shaft (1) of the propeller mixer (2) and the gas inlet (7) is pipe leading to hollow hub (3). Mixer according to claim 1, characterized in that the gas inlet (7) is conduit in the mixing shaft (1) and the ducts (5) are connected to this conduit. Mixer according to any one of claims 1 to 3, characterized in that the channels (5) are arranged at the outlet ends of the blades (4). Mixer according to any one of claims 1 to 3, characterized in that the channels (5) are arranged along or near the blades (4) such that the distance between the blades (4) and the channels (5) is less than twice the width of the channel opening . 6. Mixer for dispersing gases in liquid and for intensive mixing of multiphase mixture in vertical reactors, comprising high-diameter propeller mixers attached to a common vertical shaft and a gas inlet, characterized in that the angle of incidence of a particular part of the blades (4) propeller mixers (2) in the opposite direction, the length and / or angle of incidence being smaller than that of other blades. Mixer according to claim 6, characterized in that the blades (4) with the opposite direction and a shorter and / or smaller incidence angle are fixed to the common hub (3) alternately between the blades with a sharp and / or longer incidence angle. Mixer according to claim 6, characterized in that the blades (4) with the opposite direction and a shorter and / or smaller angle of incidence are attached to a separate hub or hubs (3) and are fixed to the common shaft (1) by means of propeller mixers. (2) with greater angle of incidence and / or longer blades, which are similarly attached to a separate hub or hub (3). Mixer according to any one of claims 1 to 8, characterized in that the deflection rods (8) are arranged at the outlet end of at least part of the blades (4) of the propeller mixers (2). Mixer according to any one of claims 1 to 9, characterized in that auxiliary wings (12), whose width is at least 30, are arranged on the side of the outlet ends above or below the blades (4), in parallel or with a maximum of 20 ° angular deviation. % shovel width. Mixer according to any one of claims 1 to 5 and 8 or 9, characterized in that the blades (4) of the lowest propeller mixer (2) are provided with channels (5) and a gas inlet. Mixer according to any one of claims 1 to 5 and 8 or 9, characterized in that the blades (4) of one of the upper mixing stages are provided with channels (5) and a gas inlet. Mixer according to any one of claims 1 to 11, characterized in that the blades (4) of the propeller mixers (2) are designed at an acute angle with respect to the direction of rotation of the inclined blades. RICHTER GEDEON Vegyeszeti Gyar Rt For: 22305-III / 94-Iv Summary A complex mixer for dispersing gases in a liquid Complex mixing system with stages consisting of large diameter propeller mixers, where the blades are equipped with flow modification elements, wherein the amounts of energy used to disperse the amount of gas injected into the reactor, homogenization of multiphase mixtures, suspension of particulate matter, etc. and the properties corresponding to the rheological properties of the gas / liquid mixture and the specific requirements of the process can also be guaranteed in exceptional cases. The open channels (5), in the opposite direction of rotation, are arranged on the blades (4) of the dispersion stage (2a) of the propeller mixers (2) attached to a common shaft where the channels (5) are connected to the gas inlet (7). The angle of incidence of a particular part of the blades (4) of the mixing steps (2b, 2d) used for homogenizing and suspending is opposite, the length is shorter and / or the incident angle is smaller than for other blades. At the outlet ends of the blades, deflection rods (8) and / or auxiliary blades (12) are arranged on a specific part (2c) of the propeller mixers used in a similar manner for homogenization and suspension, with an angle of not more than 20 ° relative to the blades above or below the outlet end of the blades. (Figures 1 and 6)