FI88115B - Static mixer - Google Patents

Description

..... . 88115

Static mixer

The present invention relates to a static mixer according to the preamble of claim 1.

A static mixer is a new class of mixer whose operation is usually based on laminar cutting and the fluid's own kinetic energy. Thus, in this type of mixer, the liquids are mixed by causing them to flow through a tube with fixed flow control means, i.e. mixing means which provide said laminar shear in the flowing liquid.

Static mixers are often used to pre-treat liquids or gases prior to their actual processing, such as mixing pulp bleaching chemicals prior to a bleaching reactor. There are other applications; it can even be said that the whole range from wastewater conditioning to the mixing of plastic additives in the extruder can be covered with static mixers. However, static mixers are not suitable for use in cases where a leveling effect of the tank or batch weighing is required, or a long reaction time.

Almost all static mixers according to the prior art turn the flowing liquid so that the liquid can be cut in two or four parts, etc. after turning. The pressure drop is naturally aimed at minimizing the ground.

‘· Another important aspect in the construction of a static mixer is that the liquid to be mixed is actually evenly distributed. ti without dead spaces inside the mixer, this also marks good cleanability.

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A third important factor in the design of a static mixer is ease of manufacture and affordability.

A large number of patent applications for static mixers were filed in 1974 and 1975, after which new designs have emerged continuously. The prior art is represented, for example, by the following patent publications: PL patent publication 234,508 from 1987, JP patent publication 1164424, DD patent publications 265,810 and 246,669, JP application publications 58177126, 63267425, 63230251, 6205634, and 602256ul, 602256ul 697 and SU Patent Publication 1255183.

The mixing element of U.S. Patent 4,747,697 is a 90 degree rotation of the Helix screw within the tube. Stacking these elements in succession results in more and more cutting in the middle of the fluid flow. Said device is simple and efficient, but expensive to manufacture other than by pressing from plastic or ceramic material.

Japanese Application Publication No. 63267425 discloses, as a static mixer, a construction in which a constant pitch spiral rotates around an inner tube. Characteristic of this solution is that the helical belt is perforated at its outer edge, resembling a gear or the like in the transverse plane.

Japanese Patent Application Laid-Open No. 6257634 discloses a static mixer in which a plurality of torn plates are superimposed, each of which is smaller, directing the flow from the circumferential openings to the central openings of the smaller plate, etc.

There are significant drawbacks to the prior art. Thus, many of these static mixers have the problem that they have a large number of thin slits which make their use, for example, for mixing food, because cleaning can only be done by disassembly. In addition, in many constructions it is impossible to provide cooling or heating - when this is necessary - other than by means of heat transfer from the outer tube.

It is an object of the present invention to obviate the drawbacks of the prior art and to provide a completely new type of static mixer.

The invention is based on the idea that successive conical spirals are used in the static mixer, of which at least one pitch is left-handed and at least one is right-handed, respectively. Preferably, of the successive spirals, one rise is left-handed and the other is right-handed.

More specifically, the solution according to the invention is mainly characterized by what is set forth in the characterizing part of claim 1.

According to a preferred embodiment of the invention, the conical spirals acting as mixing elements are made into a spiral by cutting from a plate and drawn into a cone.

According to another preferred embodiment, the conical spirals acting as mixing members are made of a metal blank by twisting into a spiral and drawn into a cone.

. . According to a third preferred alternative, the conical spirals are made of a tube which is twisted into a spiral and drawn into a cone.

When a hollow conical spiral tube is used in the mixer, the mixing member can advantageously be used for heating and / or cooling the substance to be mixed by passing a heat transfer medium through the tube.

Likewise, the hollow conical spiral tube can be advantageously used to supply the reagent to the mixing space. The pipes are then perforated to the required extent.

According to the invention, the conical spirals are preferably nested in the direction of fluid propagation. Their distance is ....: eg less than the pitch of the spiral. Alternatively, the conical spirals can be mounted in succession so that the tips of successive cones face each other and the bottoms of successive cones face each other, respectively. In this case, in the previous cone, the flow arrives at the bottom of the cone and in the next through the tip of the cone, etc., varying. Preferably, the conical spirals are mounted concentrically inside the sheath and attached to an elongate support member parallel to the central axis of the sheath.

The conical spirals can be attached to each other at their intersections, e.g. by welding.

According to a particularly preferred alternative embodiment, the distance between the conical spirals in the flow direction is so large that they do not touch each other, so that they can be made to vibrate either naturally or by external vibration. In order to move the conical spirals, mechanical or piezoelectric vibration, for example, can then be connected to the support member.

The spirals used in the invention may, for example, be such that the pitch of the spiral in each revolution is equal. Alternatively, the pitch angle of the helix may be constant, with the pitch of the helix decreasing as the diameter of the helix decreases.

: The invention provides considerable advantages. Thus, the mixer according to the invention is simple and thus advantageous to manufacture in any workshop. It includes mini -, 'i; clogged gaps and can easily handle materials such as pulp or food. Furthermore, it is inherently easy to build internal heating or cooling functions in the device according to the invention.

The invention provides a device in which the flow rotates, changes direction and changes from the outer circumference to the inner circumference and vice versa regularly without any narrow and tight ... f slits. A conical spiral with, for example, four revolutions then changes with another concentric conical spiral of different hands. If the length of one spiral in the comparison direction is e.g.

0. 3 m and the combined length of the four spirals, since they are nested at 0.34 m, then with four spirals 4 x 4 x 4 = 64 shifts occur, the rule being: N = 4n- *, n = number of spirals.

The invention will now be examined in more detail with the aid of the accompanying drawing, which shows a cross-sectional side view of a static mixer according to the invention.

The mixer according to the invention comprises a tubular jacket 1, inside which an elongate support member parallel to the central axis of the jacket 1 is arranged. In the case shown in the figure, the distance of each conical spiral 4, 5, 6 in the longitudinal direction of the sheath to the previous spiral 3, 4, 5 is smaller than the pitch of the thread (full rotation).

In the exemplary case, a spiral arrangement according to the invention was fitted to a pipe with a diameter of 150 mm. Kartiospi -.:. the angle of inclination of the rafts was constant, its height was 200 mm and the diameter of the base was about 150 mm. The distances of the successive spirals were about 100 mm.

Spirals 3-6 can be made in many different ways.

'· / Thus they can be formed from a circular plate blank into which an inwardly extending spiral is cut, which is drawn into a cone. Alternatively, they can be made of square. * · *. from a metal rod which is wound into a spiral and drawn into a • tion. Furthermore, the spirals 3,4, 5 can be made of a tube which is wound into a spiral and drawn into a cone.

Cones 3-6 ’nested on the center bar 2. the ends are fitted with fastening flanges which are welded to the central bar 2. If desired, the cones can be welded together at their intersections.

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According to the invention, once the coils have been made of a tube, these tubes can be used for the following tasks: - heating, - cooling, - reagent supply, the tubes being perforated to the required extent.

In these embodiments, the tubes are connectable to sources of heat transfer medium or, alternatively, heat receiving (cooling) medium, not shown in the figure. In order to supply the reagent to the tubes, they can be connected in a corresponding manner to a reagent tank, from which the reagent can be supplied, e.g. by means of a pump. For these embodiments, channels are formed in the center bar through which the desired media or reagents, respectively, can be fed into and out of the coils.

As the heat transfer medium, steam, e.g., pressurized steam or superheated steam, is usually used, and as the heat transfer medium, water or a mixture of salt and water and / or ice, the medium may be derived. . once through the spiral or recycled several times through it.

According to an embodiment of the invention, the spirals are mounted so that they do not touch each other at the cruise point, but are supported on the anvil bar 2 only from the center of the spiral 3-6. , ···, In the spirals, an oscillating motion is created under the influence of the flowing liquid, which enhances the mixing process. Freely oscillating. . Spiral cones are particularly well suited for mixing tasks fed by a pulsating pump, such as a piston or diaphragm pump.

The structure shown also allows for a completely new form of mixing in which the free spirals are made to vibrate by mechanical or piezoelectric vibration. The vibration is preferably connected to the central bar 2 to which the spikes are attached. Said vibration is particularly advantageous in mass transfer operations between two insoluble steps.

Depending on the nature of the substances to be mixed, different cone angles are used in said spiral cones. A long cone is chosen for tasks with very viscous or large solid particles and a short cone for other tasks. As a general rule, the cone angle of the cone is preferably 15 to 45 degrees.

The thickness or width of the spiral material is typically 5 to 10% of the inner diameter of the outer tube of the static mixer. The only factor limiting the dimension of the spirals is the nature of the materials to be mixed.

As mentioned above, the distance between the spirals in the direction of flow is, of course, the thickness or width of the material used in the spiral when the spiral cones are fixedly connected or welded together. When vibrating or free-flowing maps are used, the distance between them is greater. pi, but usually less than one pitch *.

The largest diameter of the helical cone is always equal to the inner diameter of the agitator jacket 2 · '· except in oscillating conical spirals, which is slightly smaller. Minimum cone diameter gear. ·. but is usually about 1/10 of the inner diameter of the sheath.

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Claims (12)

A static agitator which can be mounted to a portion of a flow pipe network for mixing liquids, gases or sludges or mixtures thereof flowing through the pipe network, comprising - a substantially tubular sheath (1) and at least two mixing means (3 - 6), which are arranged after each other inside the sheath and of which one (3, 5) is the left-hand turn and one (4, 6) is the right-hand turn, characterized in that - the mixing means are conical spirals (3 - 6). A stirrer according to claim 1, characterized in that the conical spirals (3 - 6) are arranged inside each other. 3. A stirrer according to claim 1, characterized in that the conical spirals (3 - 6) are mounted one after the other in such a way that the tips and the bottom respectively of successive cones come against each other. Stirrer according to any one of the preceding claims, characterized in that the conical spirals (3 - 6) are concentrically mounted inside the manifold (1) and fastened to an elongate support element (2) parallel to the center axis of the manifold. · A stirrer according to claim 1, characterized in that the conical spirals (3-6) are attached to each other at the intersection points. A stirrer according to claim 1, characterized in that the distance between the conical spirals (3 - 6) is so large in the flow direction that they do not touch each other and the conical spirals (3 - 6) are arranged to oscillate under the influence of either natural or external vibration. A stirrer according to claim 6, characterized in that mechanical or piezoelectric vibration can be coupled to the support element (2) to touch the conical spirals (3-6). Stirrer according to any of the preceding claims, characterized in that the conical spirals (3 - 6) are formed into spirals by cutting from a disc and extracting them into cones. A stirrer according to any one of claims 1-7, characterized in that the conical spirals (3 - 6) are made of a metal blank by turning it to a spiral and pulling it out to a cone. A stirrer according to any one of claims 1-7, characterized in that the conical spirals (3 - 6) are made of a tube by turning it to a spiral and pulling it out to a cone. A stirrer according to claim 10, characterized in that the conspirator tubes are used for heating or cooling by means of a heat transfer medium flowing inside the tube. A stirrer according to claim 10, characterized in that said tubes in the conical spiral are used for feeding reagents to the stirring vessel, the tubes being: to a sufficient extent provided with heels.