This application is the U.S. national phase of International Application PCT/IB2018/051503 filed Mar. 8, 2018, which designated the U.S. and is hereby incorporated by reference.
The invention relates to the field of containers where granular material particles are stored or processed such as silos, hoppers, bins, reactors, product coolers and shaft furnaces, where said granular material particles are stored and/or chemically treated, heated or cooled, sometimes in contact with a variety of reactive gases as fixed or moving packed beds or which are temporarily stored and therefore must be periodically charged and discharged. In one of its aspects, the invention relates to a cost-competitive and effective method and a device to decrease vibrations such as shaking and quaking in a container for producing or cooling pellets of direct reduced iron (hereinbelow equally identified as direct reduced iron, or DRI) during the flow of said granular DRI material through said container.
In the steelmaking industry, among others, a wide variety of granular material particles, such as metallized iron pellets (DRI), are processed, handled, stored and transported. The process vessels, bins, hoppers, silos and in general containers for storing and/or processing DRI pellets and lumps or mixtures thereof, are designed for efficient material flow and competitive capital and operation costs. To facilitate the description of the invention, in this application the term container will mean to cover all different forms of storage or processing containers for bulk particulate DRI where said bulk DRI is introduced at the upper part of the container and flows downwardly through a lower discharge tapered portion generally of inverted conical, pyramidal or wedge form, converging to at least one outlet at the bottom of said container.
Currently, the design of containers for storing or processing bulk granular material particles is based in theoretical studies of the flow properties of said materials and empirical criteria developed over the experience of particulate solids flow behavior during charge and discharge of the containers. In general, these containers are designed with a geometry intended to avoid the material free flow problems such as bridging, arching, rat-holing, channeling and to induce what is called “mass flow” meaning that all granular material particles within the container are in motion as a moving bed when the container is discharged. Promoting mass flow is a main engineering objective in designing bulk material containers aiming to produce a product of uniform quality. Stagnant zones of granular material in the container are eliminated as much as possible because the material may undergo undesired reactions or deterioration.
A number of variables affect the patterns of movement of granular material particles within the containers, for example, particle size distribution, inter-particles cohesion tendency, inter-particle friction forces and also friction between the granular material particles and the container wall. The dimensions of the outlet and the angle and geometry of the tapered discharge portion of the container determine whether the flow pattern will be “mass flow” or the so-called “funnel flow”. “Funnel flow” or “core flow” develops when the central portion of the solid granular material particles bed flow first through the outlet opening while the granular material particles proximate to the hopper walls flow at lower velocity or remain stagnant because of the friction forces between the granular material particles and the walls and to the holding force of the converging walls on said granular material particles. Funnel flow produces a shear boundary between the granular material particles that flow at higher velocity and the granular material particles that flow at lower velocity or are stationary close to the hopper walls.
The technical problem addressed by the present invention is that the interaction of the granular material particles e.g. for example DRI pellets and/or lumps, moving downwardly by gravity, and the container walls, no matter if designed and built for “mass flow” or “funnel flow”, causes that the containers vibrate, shake or quake, and these vibrations cause damages to the containers, their supporting structures and associated piping connected thereto, given that in large industrial plants, the mass of DRI material inside said containers being processed and moving or discharged from these containers weighs hundreds of tons.
The following publications were found regarding vibration and noise of containers storing particulate materials are described below:
PCT Patent application No. WO 97/30915 describes a process and device for reducing the dynamic effects and noise during the discharge of bulk material from a silo. The rate of flow of the bulk material in the neighborhood of the wall can be reduced by means of forming a macroscopic roughness on the wall. This roughness is produced in the silo wall by attaching lining plates to the inner wall of the silo having a variety of projections, perforations, mesh configurations, etc. to produce the macroscopic roughness in relation to the granular material particles size. The lining plates are attached in the cylindrical part of the silo leaving the conical portion without any modification. This publication does not recognize the shaking or quaking problem of a container during the bulk material discharge. Implementing this proposal for decreasing the sound during discharge of silos entails a high cost due to installation of the rough plates and the maintenance thereof due to the continuous erosion of granular material particles flow over its surface and the risk of fall of said plates with the corresponding problems of fouling or stopping the discharge if carried down by the particulate material. This publication does not disclose or suggest any modification to the discharge portion of a silo. Additionally, this method cannot be implemented in containers producing or handling DRI at high temperature, because the main body, where the rough plates are set of said containers is lined with a refractory and insulating material layers.
EP Patent No. 1 801 036 describes the use of baffles installed in the inner side wall of a bulk material silo to avoid noises and vibrations during its emptying. These baffles form an inwardly inclined surface which directs the flow of solid particles towards the center of the silo and create compaction zones distributed along the vertical portion of the silo. The inclined surface of the baffles may be formed for example by conical rings or half-pipe rings. The baffles divide the flow volume of bulk material into a plurality of compaction and expansion zones and thereby change the natural frequency of the silo and reduce the noises and vibrations caused by the granular material particles sliding over the silo wall. The baffles of this patent are located in the main body of the silo and this publication does not teach or suggest any modification to the discharge part of the silo or location of any baffles in the conical discharge part. Additionally, the baffles of this patent are intended to promote the flow of granular material particles proximate to the wall, therefore the upper surface of the baffles is not flat but inclined, since the effect of the baffles is to divide the bed of granular material particles into several zones. This publication expressly teaches away of having flat baffles and stagnant zones thus avoiding static zones to prevent deposition of granular material particles in the wall region.
Documents cited in this description (including the foregoing patents), and all documents cited or referenced in the documents cited in this text, are incorporated herein by reference.
The present invention provides a method, a container and a device which solve the problems of the prior art in an effective and lower-cost way and that may be retrofitted in existing hoppers, silos, reactors, shaft furnaces, etc. for gas-solid treatment of granular materials such as bulk iron ore and DRI pellets.
In contrast with the prior art teachings, applicants have found that by forming a flat surface that forms a stagnant zone of granular material particles in contact with the container wall reduces the shaking phenomena. Without linking in anyway the scope and spirit of the invention to any theory, it is thought that the flat surface formed by the ring-shaped baffle of the invention causes that the DRI granular material particles resting on the baffle remain stagnant and form a stagnant zone over the container wall while the rest of DRI granular material particles slide down against the static DRI granular material particles subject to the inter-particle friction instead of the friction due to the interaction of the DRI granular material particles with the container wall.
The stagnant zone may be formed for example by attaching a ring-shaped baffle in a zone proximate to the conical portion outlet whereby the quaking or shaking of said container is significantly decreased and even eliminated.
A ring-shaped baffle may be located at any height within the conical part of the container, preferably at a point proximate to the discharge outlet or precisely at the discharge outlet of said container. The ring-shaped baffle may be retrofitted to existing containers in a practical way by fixing it to the internal wall of the lower tapered or conical wall of the discharge part or inserting it right at the container outlet of the conical wall of the tapered discharge part within the flanges connecting the container to any discharge conduit leading the granular material particles to the a granular material particles flow regulating device or a discharge gate or a valve.
In an embodiment herein illustrated the invention is adapted to those containers producing, processing, cooling or storing granular materials containing iron oxides or direct reduced iron (DRI) bulk material in a wide range of temperatures, from ambient temperature to about 700° C., where the main body of said containers is lined with a refractory and/or insulating lining. The present invention also provides other advantages in the operation of DRI reactors and coolers, for example a lower generation of fines which is an important parameter of quality for the utilization of the DRI in steelmaking. A further benefit derived from the application of this invention in containers for abrasive granular material particles, such as DRI, is that the stagnant zones formed by baffles lower the wearing rate of the container wall because the particles flow against other particles and not in contact with said wall.
There is still a need of a cost-competitive and effective method and apparatus to decrease vibrations, such as quaking and shaking as well as noise effects, known also as hooting, honking or howling, during the discharge of granular materials from silos, hoppers, bins, reactors and in general containers for storing or processing such granular materials, and in particular for containers of large industrial hoppers, bins, including shaft-type reactors for producing DRI and DRI coolers in the steel industry.
It is an object of the present invention to provide a new method to decrease the dynamic effects of moving solid granular material particles in storage or process bulk materials containers, such as noise, quaking and shaking.
It is another object of the present invention to provide a container comprising a main body and lower tapered discharge part converging to a discharge outlet with decreased quaking, shaking or noise effects caused by movement of solid granular material particles flowing downwardly by gravity therein.
It is a further object of the present invention to provide a shaft-type moving bed reactor for producing DRI with decreased quaking, shaking or noise effects caused by movement of solid granular material particles flowing downwardly by gravity therein.
It is also an object of the present invention to provide a moving bed DRI cooler with decreased quaking, shaking or noise effects caused by movement of solid granular material particles flowing downwardly by gravity therein.
It is a further object of the present invention to provide a container for storing DRI with decreased quaking, shaking or noise effects caused by movement of solid granular material particles flowing downwardly by gravity therein.
Other objects of the invention will be pointed out or will be evident from the following description of the preferred embodiments and the accompanying drawings.
In some exemplary embodiments of the invention, a container comprising a main body for processing or storing a particulate material and a lower tapered discharge part converging to at least one outlet, said container also comprising a ring-shaped baffle installed in said tapered discharge part providing a circumferential flat surface projecting into the interior of said container which causes that a relatively small portion of said particulate material proximate and in contact to the wall of the container rests on said flat surface forming a stagnant zone above said device. The major portion of the granular material not proximate to the container wall flows through the central opening of said ring-shaped device to a lower portion of the container or a conduit having a cross section area larger than the area of the central opening of the ring-shaped baffle. The ring-shaped baffle may be attached, for example by welding, to the inner wall of the discharge downwardly converging part of the container or may be installed at the outlet of the container between any connecting flanges.
The invention also comprises a method to decrease vibrations and noise of containers having a main body for processing or storing a particulate material and a lower tapered discharge part converging to at least one outlet, wherein said method comprises providing a baffle that forms a stagnant zone of particulate material in contact to the wall of the container above said baffle in said tapered discharge part.
The invention can be equally adapted and applied to containers having cross sections other than circular, such as polygonal, rectangular, oval, or the like.
a show a schematic upper plan view of another embodiment of the invention where the tapered discharge part of the bulk material container are either of rectangular or polygonal pyramidal shape.
Although the invention is herein described as applied to a generic storage container of cylindrical body and conical tapered discharge part, and also an embodiment thereof is described of a process vessel for cooling DRI pellets by contact with a cooling gas circulating counter-currently to the continuous downward gravity flow of said DRI pellets, it will be understood that in its broader aspects the invention may also be applicable to other types of storage and process vessels or containers, silos, bins, hoppers, where a wide variety of granular materials are stored and/or processed, such as foodstuffs, grains, polymers, and granular material particles of products in many industrial processes.
In one aspect of the invention and with reference to
In another aspect of the invention and with reference to
In a further aspect of the invention according to
In another additional aspect of the invention, the baffle has the shape of an annular plate with an opening through which the granular material particles flow.
In another aspect of the invention, the baffle has the shape of an oval plate with an opening through which the granular material particles flow. The opening may have also an oval shape.
In another aspect of the invention according to
In other aspect of the invention, for applications in containers comprising a conical discharge part and granular material particles at high temperature, the baffle is formed by a plurality of annular segmented portions that can be separately attached to the container wall leaving a gap between each other to allow expansion and contraction of said sections due to temperature changes.
In another aspect of the invention, the baffle has the shape of a linear bar which is attached to the each flat side wall of the container.
In other aspect of the invention, for applications in containers comprising a pyramidal discharge part having rectangular or polygonal shape and where the granular material particles reach high temperatures, the baffle is formed by a plurality of linear segments that can be separately attached to the container wall leaving a gap between each other to allow expansion and contraction of said segments due to temperature changes.
Referring to
According to an embodiment of the invention, a ring-shaped baffle 26 is inserted, for example between flanges 22 and 24, which protrudes a surface 28 in the periphery of the bottom of the tapered discharge part 15.
The surface 28 of ring-shaped baffle 26 stops the downward flow of the material particles that are proximate and in contact with the conical inner wall 16 of the tapered discharge part 15, thus forming a stagnant zone 32 above the area defining the outlet 18. The boundary between the stagnant zone 32 and the granular material particles 12 flowing down may extend upwardly to a certain height that will be defined by the values of friction inter-particles and the friction between particles and the conical inner surface 16 of the tapered discharge part 15.
The granular material particles 12 flow down through the central bottom opening 34 of the baffle 26, located below the outlet 18, and continue flowing through a discharge conduit 20. The flow area for the granular material of conduit 20 is larger than the diameter D1 of baffle 26, so that a partial flow restriction effect is produced by the baffle 26 on the flow of granular material particles 12 in the area designated with 36.
In another embodiment of the invention shown in
As shown in
In some embodiments, the ratio of the diameter of the central opening D1 of the baffles 26261, 262, 263 and 264 to the diameter D2 of said conical wall 16 of the tapered discharge part 15 at the point where the ring-shaped baffle is located, is in the range between 0.4 to 0.95.
In some embodiments as shown for instance in
Referring to
In other embodiments of the invention, the container 100 is a DRI reactor, where the gas 40 is a reducing gas at high temperature, in the range from 850° C. to 1100° C.
The invention can be equally adapted for other hoppers and containers of cross sections other than cylindrical, such as polygonal, rectangular, oval or the like. In containers of the other mentioned geometries, the baffle of the invention will follow the contour of the perimeter of the tapered discharge part at the position where said baffle is located.
Referring to
Referring to
Referring to
Referring to
Referring to
It is also to be understood that, a segmented baffle as in
Referring to
The DRI cooler 100 has a lower tapered discharge part 159 having an inner conical wall 169 converging to an outlet 189. Other mechanical components of the connections of the DRI cooler 100 with the discharge rate regulating mechanism and the discharge conduits, such as flanges and expansion joints are not shown for simplicity of the figure, however any appropriate combination of the elements described and specifically referenced in
In order to decrease the vibrations and quaking of the DRI cooler, a ring-shaped baffle 269 is placed at the bottom of the outlet 189 of the tapered discharge part 159, for example by means of suitable flanges (now shown). The ring-shape baffle 269 has the form of an annular plate with a central bottom opening 349 similarly to what has been described above for bottom openings 34 and 341 (in
As an example of the effectiveness of the invention in reducing the intensity of vibrations,
Another example of the effectiveness of the invention is shown in
The invention herein described and claimed is a cost-competitive and effective method and apparatus to decrease vibrations, such as quaking and shaking as well as noise effects, known also as hooting, honking or howling, during the discharge of granular materials from silos, hoppers, bins, reactors and in general containers for storing or processing such granular material particles.
It is of course to be understood that the invention has been specified in detail only with respect to certain preferred embodiments thereof, and that a number of modifications and variations can be made without departing from the spirit and scope of the invention which is defined by the following claims.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2018/051503 | 3/8/2018 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2019/171146 | 9/12/2019 | WO | A |
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Number | Date | Country | |
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20210016959 A1 | Jan 2021 | US |