FI63535B - CONTAINER REQUIREMENTS FOR BLACKING FOR BLACKING AV FAST MATERIAL IN POWDER FORM AND WASHING MATERIALS IN SYNTHESIS GIPS OR WASTE - Google Patents

Description

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Banska-Frankrike (FR) 7803 ^ 7 ^ (71) Saint-Gobain Industries, 62, Bd Victor Hugo, P-92209 Neuilly sur Seine, France-Frankrike (FR) (72) Adrien Delcoigne, Chantilly, Jacques Lanneau, Breuil- le-Vert, France-Frankrike (FR) (7 * 0 Berggren Oy Ah (51 *) Continuous process and mixer for mixing powdered solids, in particular gypsum and water - Containers for fasting in the form of powders and mixtures, in synergists plaster and cotton wool

The invention relates to a continuous process for mixing powdered solids and liquids, in particular gypsum and water, and in particular to a process in which solids and liquids are continuously fed to a mixing tank to such an extent that they correspond to the required ratio of solid to liquid in the mixture. and the mixture is continuously removed from the tank. The invention also relates to a vertical mixer for applying the method.

In the mixing of powdered solids and liquids, it is a common practice to use mixers with teeth, i.e. blades, consisting of a cylindrical container with a vertical shaft provided with one or more sets of rotating radial arms supporting the blades, i.e. teeth. These blades, or teeth, scratch the walls of the tank, mixing the products and thus carrying out the confusion. However, such mixers do not provide a satisfactory dispersion of the powdery solid in the liquid; as a result, the flowability of the 2,63535 mixture removed results in a lack of homogeneity. On the other hand, there are turbine mixers consisting of a tank in which a disc, propeller or turbine rotates at a very high speed. The solid and liquid enter the turbine, which disintegrates them in an instant. Unlike gear mixer gaps, turbine mixers achieve high rotational speed and intense turbulence at all points in the system, so that product dispersion and homogenization are satisfactory. However, examination of the performance of such a mixer by adding some colored substance or, in general, any tracer which is easily detectable, reveals that the variation of the feed appears completely unchanged at the outlet after a very short residence time of the order of one second. Thus, in a turbine mixer, the time the product remains in the mixer is very short, in fact so short that the mixing delivery does not smooth out the feed irregularities, but these occur unchanged at the discharge point. When uniform flow is desired for the final product, which is impossible to achieve with uniform feed, turbine mixers are not satisfactory.

U.S. Pat. No. 3,459,620 also discloses a mixer for mixing gypsum and liquid. However, the mixer consists of a rotating plate with barrier plates, whereby a centrifugal force throws the product towards the circumference of the plate and the products in their path are hit by the barrier plates, distributed and gradually mixed. Here, feed irregularities cannot be smoothed out.

U.S. Pat. No. 3,957,407 discloses an apparatus for feeding powdered gypsum from above a column. As the gypsum falls inside the column, it is subjected to water jets which sprinkle water on it and moisten it. There is no rotation or mixing in the device during the drop of gypsum.

Agitators are also known from British Patents GB-1,167,107 and 1,375,922, but they do not achieve the object of the invention, i.e. the elimination of irregularities in the feed and thus a uniform flow of substances.

3,63535

The present invention avoids the disadvantages of both of these known systems. It makes it possible to achieve continuous mixing of powdered solids and liquids so that the fluidity is uniform. The method according to the invention and the mixer for applying the method are mainly known from the features set out in claims 1 and 7.

In addition, the present invention solves the problem of premature curing of a flowable evolutionary product. A fluid evolutionary product is a liquid in which a reaction takes place that results in a physical or chemical change that develops a solid phase or modifies the properties of the solid phase originally carried by the liquid. A mixture of gypsum powder and water is an example of such a product.

The invention provides a process for the continuous mixing of powdered solids and liquids, comprising continuously introducing the liquid phase into a mixing tank, continuously feeding the solid phase into said tank in such a way that the desired solids-liquid ratio is achieved, rotating the products inside the tank , that the supply flows of solids and liquids are adjusted in such a way that a certain filling level of the tank is continuously maintained and that the product mixture is continuously emptied so that the filling level remains unchanged.

4,63535

The method also preferably uses a liquid fed to the tank to flush the walls of the tank to prevent the formation of solids thereon. Preferably, the mixed product is removed down to the bottom of the tank wall to avoid retention of solids in the tank.

Continuous operation is established after the start-up phase, which comprises the following steps: liquid and solids are fed to the mixing tank, i.e. the tank, in a preselected weight ratio until a certain filling level of said mixing tank is reached; the products fed to the container are agitated and the agitation is continued for a selected period of time; and then, at the same time: continuously introducing liquid and solid into the tank at a predetermined flow so that the weight ratio of the mixture is maintained; and the mixing tank is continuously emptied with a flow such that the filling level is maintained.

For certain solids and liquid feed streams, the filling level of the mixing tank determines the average length of time the products to be mixed remain in the mixing tank, said average residence time being at least equal to 3 seconds and preferably set between 15 and 30 seconds.

As a typical example, the method can be used for continuous mixing of gypsum powder and water.

In addition, the invention provides a mechanism for performing this mixing method. This mechanism comprises a mixer, characterized in that it comprises various combinations of the following devices: a container made of a hollow rotating body, the lower end of which is provided with an outflow opening and an outflow control device, and which container is provided with an inner wall forming a partition at a distance from the side wall of the tank; a turbine mounted inside the tank above its midsole and rotating about a vertical axis located on the centerline of the tank; a liquid supply device, which preferably comprises means 5 for supplying liquid to the side wall of the tank and to the shaft of the turbine? and a solids supply device for supplying solids to the tank.

Figure 1 is a sketch of the mixing mechanism? Figure 2 is a schematic representation of the feed and mixing mechanism? Fig. 3 is a horizontal sectional view taken immediately above the cone of the mechanism of Fig. 1? Fig. 4 is a horizontal sectional view taken immediately above the bottom of the ejection device of the mechanism of Fig. 1? and Figure 5 is a schematic representation of a portion of a mixer with a shock crown ejector.

As shown in Fig. 1, the mixer M for powdered products and liquids comprises a vertical cylindrical container 1, the lower part 2 of which converges and leads to the outlet 2 '. Inside the tank 1 is mounted a turbine 3, the agitator of which is inside the tank 1 with a vertical shaft 4 located on the center line of the tank and driven by a motor 5. The tank has an intermediate base 6 formed by the upper surface of a cone 7 designed to form a barrier inside the tank 1 . This barrier is a body of rotation with a tapered lower part. Its center line is on the center line of the tank and its dimensions are smaller than the dimensions of the converging part 2 under the mixer, so that an annular space is formed between it and the lower part 2 of the tank 1. The cone 7 is a cone which is a tip downwards inside the conical part 2 under the container, which is also conical, and the intermediate base 6 is formed by the flat base of said upside-down cone. The cone 7 is supported by the rods 7A shown in Figure 3.

The lower part 2 of the mixer leads to an upside down cyclone-shaped ejection device 8 consisting of a conical housing 9, the tip is placed upwards and has a flat base 10 and a collecting tube 11, the end of which is in the plane of the base 10 and tangential to the conical housing 9, and ejects the turbine 3 in the direction of rotation. The collection pipe then leads vertically downwards and is provided with a flow control valve 12 which leads the mixture to a pipe 13 which leads to the mixture recovery devices (not shown). The valve 12 may be, for example, a modulated, pressure-controlled flexible-sleeve valve, of the type described in Finnish Patent Application No. 6,63535 No. 790409. The upper edge of the container is provided with a covered, annular pouring chute 14 to which fluid is supplied through a flexible hose 15. The pipes 16, which are connected to the flexible hose 15 and provided with a control valve 17, conduct fluid to the shaft 4 of the turbine 3 in order to keep it clean.

For the sake of clarity, the mixer of the following specification is capable of delivering a mixture of 30 to 65 kg / min;

Turbine speed 1275 rpm

Turbine mixing vane diameter 150 mm

Mixer mixing blade diameter 292 mm

The height of the top of the mixer from the midsole upwards is 485 mm

Cone base angle 45 °

Mixer outlet diameter 35 mm

The distance between the turbine blade and the midsole is 15 mm

Mixer base angle approx. 145 °

Figure 2 shows a complete mixing plant. It shows the means described above, such as the mixer M with its tanks 1, its barrier 7 inside the converging part 2 of the tank, the intermediate base 6 formed by the upper plane of the cone 7, the annular space between the cone 7 and the lower part 2 of the tank, the upward cone ejector 8 a collection pipe 11 with a flow control valve 12 for the flow of the incoming mixture, a supply of liquid up to the pouring trough 14 and the pipe 16 and a turbine 3 driven by the motor 5.

The powdered solid supply system S and the liquid supply system L for the mixer M are shown in Figure 2. The solid supply system S comprises a funnel 18 mounted above a weight sensitive conveyor belt 19 in equilibrium on the edge 20 when loaded with a selected amount of product. Such a device is said to be a constant weight sensitive conveyor.

In connection with this weight-sensitive conveyor 19, there is a door 21 for adjusting the thickness of the powder layer fed from the hopper 18. A vibrated, metal, screened chute 22 is fitted below the outlet end of the constant weight sensitive conveyor 19. This trough is inclined with respect to the horizontal at an angle which depends on the powdered product 63535 7 and which, in the case of gypsum powder, is preferably about 45 °. The trough 22 is mounted so that its lower end hangs above the tank 1 of the mixer M and so that the powder it brings falls into the middle of the tank 1 of the turbine 3. The solid supply system S is already known, so it does not need to be explained in more detail.

In the liquid supply mechanism L according to Fig. 2, the liquid is supplied from a tank 23 in which the height of the liquid surface is constant. The liquid flow control is performed by a valve 24, and a flow meter 25 makes it possible to precisely adjust the flow to the hose 15.

The mixing plant operates as follows. Gypsum powder (P) is taken as an example of a powdery solid and water (W) is taken as an example of a liquid.

Before starting, the ratio Wo / Po is selected, where Wo and Po are the water mass flow rate (Wo) and the gypsum powder mass flow rate (Po>, respectively), which are first set. The water flow rate is adjusted to the selected value Wo by the valve 24. The gypsum powder flow rate is then set to Po. the gypsum powder is applied to a constant weight sensitive conveyor 19 set to equilibrium on the edge 20 for the selected amount of weight of product in the tank 1, and then the flow Po is obtained by adjusting the speed of the pressure sensitive conveyor 19. The mixing mortar closed by closing the pipe 13 or closing the valve 12. The liquid supply mechanism L, set to supply by the flow Wo, is opened for a selected time To. Water is supplied through the gutter 14 and the pipe 16. By rotating at high speed, the turbine 3 confuses the water.

At the end of time To, the water supply is switched off. The gypsum powder supply mechanism S, set to the flow Po, is then started for a period of time To. At the end of time To, the gypsum powder supply is closed.

Turbine 3 is allowed to mix water and gypsum powder for a period of time approximately To / 2 from the end of the gypsum powder feed. After this mixing time To / 2, the water supply still set for flow Wo and the gypsum supply still set for flow Po are opened simultaneously and the mixture in the mixing tank is allowed to drain either by opening the pipe 13 or by opening the valve 12. And setting the valve 12 so that the amount of product in the mixer M remains constant and equal to 6 35 35 as the amount in the tank at start-up. In this way, a stable operating situation is quickly achieved. The water and gypsum powder feeds operate continuously with the flow Wo and Po, respectively, the mixing is continuous and the mixing tank maintains a constant amount of mixture, the average residence time of the mixture in the tank is constant and equal to the start time To, and the mixture is also continuous process, with flow (Wo + Po).

The water fed to the annular overflow chute 14 is uniformly distributed around it and runs over the inner wall of the tank 1. The water from the pipe 16, the supply of which is controlled by the valve 17, sprays and cleans the shaft 4 of the turbine 3. The gypsum powder contained in the hopper 18 spreads to the constant weight-sensitive conveyor 19 in equilibrium with the edge 20. which results in a change in the position of the door for adjusting the thickness of the gypsum powder layer, which tends to restore balance.

At the end of the pressure-sensitive conveyor 19, the gypsum powder falls onto the screen covering the vibrated metal chute 22, breaking into lumps, and the plaster pours into the chute 22. The chute 22 vibrates the plaster powder. The water film formed on the wall of the tank 1 and the water sprayed on the shaft 4 of the turbine completely prevent the deposition of gypsum and the onset of any undesired hardening of the gypsum on the wall and shaft 4 of the tank 1.

The high speed rotating turbine 3 moves the powder and water inside the tank 1. The speed of the turbine is set so that a single vertical centrifugal vortex is formed, i.e. a hollow vortex that covers the inside of the tank walls. In this case, the outer surface of the mixture is formed in the shape of a cone as indicated by the broken lines in Fig. 1.

The center line of the cone is the center line 4 of the turbine 3.

The depth of the vortex depends on the dimensions of the tank 1 of the mixer M and the rotational speed of the turbine 3, which is set so that the bottom of the vortex touches the turbine 3 and removes all mixture dead spots at the bottom.

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When the speed is too low, the mixture covers the turbine blade too pak-sulti and the surface of the mixture is too smooth so that the powder can remain in solid clumps because it does not disperse.

On the other hand, too high a speed tends to cavity the vortex too much, so that the turbine 3 is completely exposed and causes the mixture to climb too high along the wall of the tank 1, so that it periodically falls down on the turbine 3 and thus causes irregularity of rotation.

The gypsum powder fed down to the vibrating chute 22 falls into the middle of the vortex when the turbine 3 has reached a high speed. It dissipates instantly and is ejected outward into the mixture already in the tank 1.

Rotation of the mixture ensures homogenization and the slope of the liquid surface prevents the solid particles from stagnating. The mixture of gypsum and water follows the flow lines of the turbine 3, i. recirculation lines in the mixing zone in the immediate vicinity of the midsole 6.

Thus, there is no deposition on the midsole 6 as the mixture is wiped across it. The mixture of gypsum and water flows out of the tank in a uniform manner down to the annular space between the barrier cone 7 and the wall of the lower part 2 of the mixing tank, leaving no solid residue. The position of the cone 7 relative to the wall of the converging lower part 2 of the mixer determines the dimensions of this annular space and thus determines the limit for the outflow of the contents of the container 1. The mixture flows out to this state at a rate large enough not to cause the mixture to harden. When the part 7 is conical and when the outer wall of the converging part 2 of the mixer is also conical, the speed of the gypsum mixture measured up to the cone 7 is preferably at least 30 cm / s and generally about 1 m / s. The parts of the mixture discharge piping located on the discharge stream side are selected so that this minimum rate can be achieved, thus avoiding premature deposition and mass curing of the mixture.

The mixture collects towards the opening 2 'of the lower part 2 of the mixer, further rotating as it flows into the inverted cyclone-shaped ejection device 8. The mixture remains on the conical walls of the device 8 and flows downwards down these walls to the bottom 10. In this case, it is unlikely that any uncontrolled vortex will form a stationary zone in which curing of the mass could occur. The mixture, as a rotating stream, then enters the collecting pipe 11 and forms a full cylindrical flow, the flow of which can be precisely controlled by a flow control valve 12 located at the end of the collecting pipe 11.

However, since the supply flows Po and Wo are not completely stable and may fluctuate, causing fluctuations in the flow of the mixture, the valve 12 is continuously set to maintain a constant amount of mixture in the mixture tank 1 and thus give the mixture a constant residence time in the mixer. This residence time makes it possible to homogenize the mixture and smooth out the unevenness of the feed.

The setting of the valve 12 can be accessed in several ways. The valve may be manually adjustable, but in the case of gypsum, given the rapid evolution of powdered gypsum as soon as it is mixed with water, and if a constant fluidity mixture is required, requiring a very precise residence time in the tank, the valve should preferably be automatically adjusted, e.g. in the aforementioned Finnish patent application No. 790409.

Valve 12 may be, for example, a straight channel valve with a rigid housing, a flexible inner sleeve, and a fluid intake between the rigid housing and the sleeve, which medium is capable of compressing the flexible sleeve to reduce flow. In order to prevent gypsum from depositing or mass-curing in such a valve, it is advantageous to modulate the pressure of the control medium as described in the aforementioned Finnish patent application No. 790409.

It is preferred to control the valve 12 with a pneumatic release type control mechanism that causes variation in the openness of the valve 12 as a function of agitator weight, and to use oscillations caused by vibrations due to the movement of the mixture and turbine in the mixing tank. Such a pneumatic release mechanism essentially includes a pneumatic circuit and a force balance bar. A constant compressed air flow is applied to the pneumatic circuit. It comprises two branches, one leading to the valve 12 and the other having a nozzle with respect to which the balance beam acts as a flap plate, thus providing 63535 11 with a certain air release which varies depending on the position of the beam. Thus, the balance bar constantly monitors the weight of the mixer. Its balance is set to a certain weight of the mixer so that it is disturbed when this weight changes. In this case, it causes an increase or decrease in the medium discharge of the pneumatic circuit and consequently causes a decrease or increase in the pressure of the air supplied to the valve, thus modifying the openness of the valve and consequently the magnitude of the flow from the mixer. In addition, the movements of the turbine cause the beam to vibrate and oscillate slightly continuously, and these slight oscillations are picked up by the pneumatic circuit, causing the pressure in the valve control medium to be modulated to change the shape of the flexible sleeve and vibrate it. Because the flexible sleeve of the valve is constantly changing its shape, no gypsum deposits can form on it. Such a pneumatic release-type control mechanism is described in the above-mentioned Finnish Patent Application No. 790409.

The discharge device 8 can be any standard medium mechanical device capable of converting any current, and in particular a rotating current, into a full current. Thus, a cylindrical discharge device 26 according to Fig. 5 can be used, which is made of a vessel with a bottom and a tangential discharge pipe.

The residence time To must always remain shorter than the value Tp corresponding to the onset of hardening of the mixture. When the feed flows Po and Wo and thus the discharge flow (Po-Wo) are set, this average residence time To is determined by the filling level of the mixing tank, and it is by keeping this filling level constant that the average residence time is kept constant. The average residence time is at least 3 seconds, and preferably between 15 and 30 seconds, in order to achieve satisfactory homogenization of the solid and liquid products.

So far, a mixture of gypsum powder and water has been treated, but the method remains the same and the mechanism works in the same way if additives are added in one of the different mixing steps. By additives is meant herein reactive or inert, solid or liquid products, preferably powdered in the case of solids. Thus, it is possible to add solid additives with the gypsum powder, either by prior addition by the gypsum powder manufacturer, or by applying the additive to the hopper 18 or the pressure sensitive conveyor belt 19. It is also possible to add solid or liquid additives to water or otherwise directly to the mixer. These additives can be chemical catalysts or gypsum reinforcing elements such as chopped or finely divided fibers.

Thus, the words "gypsum powder" and "water" must be taken in a broader sense, and use terms such as solid phase or solid to mean gypsum powder per se and gypsum mixtures with other solids, and use terms such as "liquid phase" or "liquid" to refer to water as such. water containing solid or liquid additives.

Claims (21)

1. Continuous process for mixing powdered solids and liquids, in particular gypsum and water, in which solid and liquid process are continuously supplied to a mixing vessel in such proportions as to correspond to the required ratio of solids. and the liquid in the mixture, the materials in the container are rotated by a turin to effect their mixing and the mixture is continuously withdrawn from the container, characterized in that the amount of added and withdrawn material is regulated to maintain a certain level of filling in the container (1). that the liquid is fed as a substantially continuous film along the vertical wall of the mixing vessel, that the materials are rotated in a single vortex, that the solid material is fed into the center of the vortex and that the mixture is withdrawn along the circumference of the bottom of the mixing vessel (1). Process according to claim 1, characterized in that the starting period comprises the following steps: liquid and solid material are supplied to the mixing container in a pre-selected weight ratio until a selected filling level is reached in the mixing container, liquid and solid material is rotated in the container and a rotational movement is maintained. time, after which the container is simultaneously and continuously supplied with liquid and solid material with such flow rates so that the weight ratio of the mixture is maintained and that the mixture is continuously withdrawn from the container at such a flow rate that pours the filling level unchanged. Method according to claim 2, characterized in that the ratio between the powdered material and the water is 100/80 by weight. Method according to claim 1, characterized in that the average holding time in the container for the products to be mixed is at least 3 seconds and preferably between 15 and 30 seconds. 18 63535 5. A method according to any one of claims 1 to 4, characterized in that the mixture is conducted to the withdrawal device and withdrawn along its periphery. Process according to any of claims 1-5, characterized in that the powdered solid material is gypsum and the liquid water. A vertical mixer for powdered solids and liquids for applying the method according to claim 1, characterized in that it comprises: a container (1), which consists of a hollow rotary body and which at its lower end (2) is provided with an outlet opening (2 '), a regulating device (8, 12) for the outlet stream, which device communicates with the outlet opening (2'), the container (1) having an intermediate bottom (6) at a distance from the inner surface of the container. inner wall a turbine (3) mounted inside the container above the intermediate bottom (6) and rotating about a vertical center line coinciding with the center line of the container (1), a device (L) for supplying the container (1) with liquid and a device (S) to supply the container with the powdered solid material. 8. A mixer according to claim 7, characterized in that the intermediate bottom (6) has an upper surface, the shape of which follows the corresponding flow lines of the upper mixing zone. Mixer according to claim 7 or 8, characterized in that the intermediate bottom (6) has a smooth upper surface which is perpendicular to the center line of the container (1) and is in the immediate vicinity of the turbine (3). Mixer according to claim 7 or 8, characterized in that a circular hanging wall is connected to the intermediate bottom (6), whose center line is on the center line of the container and whose diameter is smaller than the inner diameter of the container. 63535 19 Mixer according to any one of claims 7-10, characterized in that the mixing container is in the form of a standing cylinder with a tapered extension in the direction of the tap opening (2 '). Mixer according to Claim 11, characterized in that the intermediate bottom (6) is at the level where the container cylinder and its tapered extension meet. Mixer according to claim 12, characterized in that the intermediate bottom (6) consists of the top surface of a downturned tapered rotary body which is placed in the tapered extension of the container (1) and whose center line coincides with the center line of the container and cross-section is smaller than the cross-section of the extension of the container so that between the inner wall and the inner wall of the container (1) a tile is formed in its cross-sectional annular space. Mixer according to claim 13, characterized in that the body placed into the extension of the mixing container (1) is a cone (7), which is positioned with the tip downwards and whose flat base forms the mixer bottom (6), and that also the tapered extension of the container (2) is a cone. Mixer according to any of claims 7-14, characterized in that the regulating means of the outlet stream is a valve (12) with an elastic sleeve. Mixer according to claim 15, characterized in that the valve (12) with the elastic sleeve is positioned downstream of the outlet opening (2 ') communicating with the container (1), which receives the mixing and converts from the container from the container. its flow to a full flow for entry into the valve (12).