Mixing silo for two powdered products

Abstract

The invention relates to a silo (10) for mixing two powdered products having different particle sizes, the silo taking the form of a vertical tank (14), an outlet (16) for the mixture of the two powdered products being provided in the bottom (12) of the silo, the cross-section of the bottom of the silo gradually decreasing up to this outlet, an inverted cone (18) being installed in the bottom of the silo, inside the tank forming the silo and above the outlet, the tip (22) of the inverted cone extending into the interior of the silo. Abstract figure: 2

Description

Title of the invention: Silo for mixing two powdery products

[0001] The present invention relates to the mixing of two powdery products in a silo, and more particularly to the mixing in a silo of two powdery products having a different particle size.

[0002] For example, the present invention can be used in the manufacture of rubber-based mixtures for the tire industry.

[0003] As illustrated in [Fig.l], when two powdery products of different particle size flow into a silo whose bottom has a section which gradually reduces to an outlet opening, the powdery product A having the larger particle size is pushed against the walls of the silo and accumulates there, and the product B having the smaller particle size flows with a significant flow rate along a central chimney extending above the outlet opening of the silo.

[0004] Consequently, at the outlet of the silo, a flow of the two products in equal proportion is not obtained, the product with the larger particle size tending to be segregated inside the silo and against the walls of the silo.

[0005] The present invention aims to overcome this drawback and to allow a flow in equal proportion, or in predefined proportion, of two powdered products of different particle sizes at the outlet of a silo.

[0006] To this end, the invention relates to a silo for mixing two powdery products having a different particle size, the silo taking the form of a vertical tank, an outlet opening for the mixture of the two powdery products being provided in the bottom of the silo, and the section of the bottom of the silo gradually reducing to this outlet opening for the mixture.

[0007] According to the invention, an inverted cone is installed in the bottom of the silo, inside the tank forming the silo and above the outlet opening of the mixture, the tip of the inverted cone extending towards the inside of the silo.

[0008] The inverted cone makes it possible to reduce the flow of the product with a smaller particle size in the center of the silo and thus to promote the flow of the product with a larger particle size along the walls of the silo. Thanks to the inverted cone, no product is segregated inside the silo, and it is possible to obtain a flow in equal proportion, or in a predefined proportion, of the two powdered products of different particle sizes introduced into the silo.

[0009] Advantageously but not necessarily, the invention can also provide that: - the opening for the passage of powdered products between the inverted cone and the inverted wall the interior of the tank forming the bottom of the silo has a surface area greater, preferably 20% to 22%, than the surface area of ​​the mixture outlet opening, - the angle of the inverted cone is between 80° and 100°, and preferably equal to 90°, - the base of the inverted cone has a diameter between 500 mm and 700 mm, - the inverted cone is mounted on a support comprising means of fixing to the wall of the tank forming the bottom of the silo, and in which these means of fixing are removable, - air flow inlets are provided in the tank wall forming the bottom of the silo and at the right of the inverted cone.

[0010] The invention also relates to a method for mixing two powdered products having a different particle size, this mixing method consisting of simultaneously introducing the two products of different particle size into the mixing silo and adjusting the flow rate of each of the products into the silo so as to obtain the desired percentage of each of the products in the mixture leaving the silo.

[0011] Advantageously but not necessarily, the invention may also provide that, in this mixing process: - the two powdery products of different particle sizes are introduced simultaneously and in the same quantity into the silo so as to obtain a mixture comprising 50% of each powdery product at the outlet of the silo, - one of the powdered products has a particle size between 0.2 mm and 2 mm, and in which the other powdered product has a particle size between 2 mm and 15 mm, - both powdered products are silica but with a different particle size.

[0012] Other characteristics and advantages of the invention will appear in the description which follows. This description, given by way of example and not as a limitation, refers to the attached drawings in which: - [Fig.l] represents the flow of two powdered products of different granulometry in a silo according to the prior art, - [Fig.2] represents a front view in section of the bottom of a silo according to the invention, - [Fig.3] represents a perspective view of an inverted cone intended to be placed in the bottom of a silo according to the invention, - [Fig.4] represents the effects of the inverted cone on the flow of two products of different granulometry in the bottom of a silo according to the invention. Silo

[0013] The invention relates to a silo used for the storage and mixing of two powdered products A and B of different particle sizes.

[0014] A silo 10 according to the invention is shown in detail in [Fig. 2]. Only the bottom 12 of the silo, that is to say its lower part, is shown in this [Fig. 2].

[0015] The silo 10 is a tank 14, for example cylindrical. Preferably, this tank 14 is vertical and extends around a vertical central axis ACV. An outlet opening 16 for the mixture of the two powdery products is provided in the bottom 12 of the silo. Preferably, the section of the bottom 12 of the silo gradually reduces up to this outlet opening 16 for the mixture of the two products. Preferably, the bottom 12 of the silo is frustoconical in shape around the vertical central axis ACV. Preferably, the outlet opening 16 is circular and centered around the vertical central axis ACV. Optionally, the outlet opening 16 may be equipped with a collar 20 to be connected to a conduit for discharging the mixture of the two powdery products.

[0016] As shown in [Fig.2], in order to better control the flow rates of the two powdery products towards the outlet opening 16 of the silo, an inverted cone 18 is installed in the bottom 12 of the silo, inside the tank 14 forming the silo and above the outlet opening 16 of the mixture. Advantageously, the inverted cone 18 makes it possible to avoid the creation of the central flow chimney of the product of smaller particle size in the silo. Preferably, the tip 22 of the inverted cone 18 extends towards the inside of the silo, that is to say in a direction opposite to the direction in which the outlet opening 16 of the silo is located, and therefore in a direction opposite to the direction of flow of the two powdery products. Preferably, the inverted cone 18 is centered around the vertical central axis ACV of the silo.Of course, a passage opening 24 for the powdered products is provided between the inverted cone and the inner wall 26 of the tank 14 forming the bottom of the silo. Preferably, this passage opening 24 for the powdered products is annular in shape, and therefore of the same width all around the inverted cone 18. For example, the inner wall 26 of the tank 14 is inclined by 20° relative to the vertical central axis ACV.

[0017] Preferably, and still in order to better control the flow rates of the two powdery products towards the outlet opening 16 of the silo, the passage opening 24 of the powdery products between the inverted cone 18 and the inner wall 26 of the tank 14 forming the bottom of the silo has a surface area greater than the surface area of ​​the outlet opening 16 of the mixture.

[0018] As illustrated in [Fig.4], this negative difference between the passage opening 24 and the outlet opening 16 results in retention of the mixture (A+B) of the two products in the volume located under the inverted cone and above the outlet opening 16 of the silo and therefore contributes to controlling the flow rates of the two products.

[0019] Preferably, to obtain a mixture in substantially equal proportion of two powdered products having different particle sizes and respectively between 0.2 mm and 2 mm and between 2 mm and 15 mm, the passage opening 24 of the products powdery materials between the inverted cone 18 and the inner wall 26 of the tank 14 forming the bottom of the silo has a surface area 20% to 22% greater than the surface area of ​​the outlet opening 16 of the mixture.

[0020] If the passage opening 24 between the inverted cone 18 and the inner wall 26 of the reservoir 14 is too small, the flow of the powdery products may be disturbed or stopped, and the output flow rate of the powdery products at the outlet of the silo may be too low for the powder transport devices, such as a screw for example, located under the outlet opening 16 of the silo. If the passage opening 24 between the inverted cone 18 and the inner wall 26 of the reservoir 14 is too large, the mixing of the powdery products of different particle sizes is not optimal, in particular because the powdery product of smaller particle size is less pushed towards the inner wall of the silo, and therefore towards the product of larger particle size.

[0021] In a preferred embodiment, the angle α of the inverted cone 18 is between 80° and 100°, and preferably equal to 90°. Thus, the slope formed by the upper surface of the inverted cone is between 40° and 50°, and preferably equal to 45°. In addition, the base 28 of the inverted cone has a diameter between 500 mm and 700 mm.

[0022] In order to fix the inverted cone in the tank 14 forming the silo, the inverted cone 18 is mounted on a support 30 comprising means 32 for fixing to the inner wall 26 of the tank forming the bottom of the silo. Preferably, these means 32 for fixing the support 30 to the inner wall 26 are removable. As shown in [Fig. 3], the support 30 takes for example the form of four plates 34 assembled in a cross, like a crosspiece. The plates 34 of this support 30 are then connected to rails 36 fixed to the inner wall 26 of the tank 14 by intermediate plates 38. The intermediate plates 38 allow adjustment of the positioning of the inverted cone inside the bottom of the silo, and also to compensate for any defects in the shape of the bottom of the silo which is generally not a perfect cone. For example, the support 30, the intermediate plates 38 and the rails 36 are connected by screws.For example, the rails 36 are also connected by screws to the inner wall 26 of the tank 14.

[0023] In addition to the inverted cone, and still to improve the flow of products towards the outlet opening 16, inlets 40 for air flows are provided in the inner wall 26 of the tank forming the bottom of the silo and in line with the inverted cone 18. Preferably, the inlets 40 are oriented towards the tip 22 of the inverted cone so as to orient the incoming air flows towards the top of the inverted cone.

[0024] Preferably, the inverted cone 18 is made of an aluminum alloy, like the silo. Process having a different granulometry which uses the silo 10 according to the invention.

[0026] According to this mixing method, the two products A and B of different particle size are introduced simultaneously into the silo 10, and the flow rate of arrival of each of the products A and B in the silo is adjusted so as to obtain the desired percentage of each of the products in the mixture delivered by the outlet opening 16. For example, the two powdery products A and B of different particle size are introduced into the upper part of the silo by appropriate conveying means.

[0027] For example, the two powdery products of different particle size are introduced simultaneously and in the same quantity into the silo 10 so as to obtain a mixture comprising 50% of each powdery product at the outlet of the silo.

[0028] For example, the mixing method according to the invention and the silo 10 according to the invention are used with a powdery product B whose particle size is between 0.2 mm and 2 mm and another powdery product A whose particle size is between 2 mm and 15 mm.

[0029] For example, these two powdery products A and B are silica but with a different particle size. For example, these two powdery products A and B come from different manufacturing batches of the same material or component. For example, these two powdery products A and B may be other types of fillers used in the manufacture of rubber mixtures intended for the manufacture of tires such as carbon blacks, kaolin or chalk.

Claims

Claims

1. Silo (10) for mixing two powdery products (A, B) having a different particle size, the silo taking the form of a vertical tank (14), an outlet opening (16) for the mixture of the two powdery products being provided in the bottom (12) of the silo, the section of the bottom of the silo gradually reducing up to this outlet opening for the mixture, the silo being characterized in that an inverted cone (18) is installed in the bottom of the silo, inside the tank forming the silo and above the outlet opening for the mixture, the tip (22) of the inverted cone extending towards the inside of the silo.

2. Mixing silo according to claim 1, in which the passage opening (24) of the powdered products between the inverted cone and the inner wall (26) of the tank forming the bottom of the silo has a surface area greater, preferably 20% to 22%, than the surface area of ​​the outlet opening (16) of the mixture.

3. Mixing silo according to claim 1 or 2, wherein the angle (a) of the inverted cone is between 80° and 100°, and preferably equal to Q0°

4. y\j . Mixing silo according to one of claims 1 to 3, in which the base (28) of the inverted cone has a diameter between 500 mm and 700 mm.

5. Mixing silo according to one of claims 1 to 4, in which the inverted cone is mounted on a support (30) comprising means (32) for fixing to the inner wall (26) of the tank forming the bottom of the silo, and in which these means of fixing (32) are removable.

6. Mixing silo according to one of claims 1 to 5, in which inlets (40) for air flows are provided in the inner wall (26) of the tank forming the bottom of the silo and at the right of the inverted cone.

7. Method for mixing two powdered products having a different particle size, the mixing method consisting of simultaneously introducing the two products (A, B) of different particle size into the mixing silo (10) according to one of claims 1 to 6, and adjusting the flow rate of arrival of each of the products (A, B) in the silo so as to obtain the desired percentage of each of the products in the mixture leaving the silo.

8. Mixing method according to claim 7, in which the two powdery products of different particle size are introduced simultaneously. simultaneously and in the same quantity in the silo so as to obtain a mixture (A+B) comprising 50% of each powdered product at the outlet of the silo.

9. A mixing method according to claim 7 or 8, wherein one of the powdered products has a particle size of between 0.2 mm and 2 mm, and wherein the other powdered product has a particle size of between 2 mm and 15 mm.

10. Mixing method according to one of claims 7 to 9, in which the two powdery products are silica but with a different particle size.

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