Sealed transport system for high temperature bulk material

Abstract

A transport device (10), configured for the dry transport of DRI (Direct Reduced Iron) pellets, which comprises: ■ a belt conveyor (101) configured in a ring and enclosed in a containment casing (102) that is mechanically gas-tight; ■ an input system (8) of an inerting treatment gas, comprising a plurality of input chambers (80) arranged internally to said casing (102).

Description

[0001] SEALED TRANSPORT SYSTEM FOR HIGH TEMPERATURE BULK MATERIAL

[0002] DESCRIPTION

[0003] Technical field of the invention

[0004] The present invention relates to a dry conveying system, particularly of the metal belt type, enclosed in a mechanically gas sealed container and suitable for conveying high flow rates of material at high temperature.

[0005] The system is particularly suitable for transporting Direct Reduced Iron (DRI) pellets exiting from a reduction furnace.

[0006] Analysis of the prior art and its drawbacks

[0007] In the art there are known devices for dry transport of bulk materials, also at high temperature and / or high flow rates, for example heavy ashes exiting from a combustion chamber or Direct Reduced Iron (DRI) pellets coming from a reduction furnace.

[0008] In the transport of Direct Reduced Iron (DRI) pellets mentioned above - and in similar applications - it is necessary to maintain the thermal content of the transported material, preserve its reduction degree and prevent fines from escaping to the outside environment. In such particular applications, the transit environment must therefore be made inert, so as to minimize re-oxidation of the transported material. This is usually achieved by the use of inerting gases. In specific applications, the temperatures of the transported material may be 600°C or higher.

[0009] Known devices for this type of transport are based, for the most part, upon a so-called “apron conveyor” transporter. This type of conveyor has a longitudinal loading surface consisting of a plurality of metal plates, partially overlapping each other and equipped with side rails to contain the transported material. Said plates are attached to two lateral linktype chains, bolted under the plates, which gear on toothed wheels arranged at the ends of the conveyor.

[0010] However, given the transport requirements mentioned above, the “apron” conveyor of known art appears to be optimizable in terms of safety, environmental impact (dispersion of dust to the outside), consumption of inerting gas, and ability to prevent thermal decay of the transported material.

[0011] In particular, such known devices provide only partial insulation of the conveyor, by a cover arranged only at an upper segment thereof. Such closure of the upper section only leaves the rotating parts of the forward and return zones exposed, to allow their cooling necessary to prevent mechanical breakage related to thermal stresses. The pressure regime of the inerting gas - in the conveying environment adjacent to the load - must therefore take into account this need to expose the conveyor to the external environment for its entire length. Upon such a pressure regime depends, in fact, the gas tightness and thus the preservation of the reduction degree. In particular, the gas is injected through nozzles that, positioned in the lateral region(s) of the cover, impart speed to the flow. The impact of the technical gas on the outer lateral surface of the transport plates results in two underflows: one upward, i.e. under the cover of the transport zone, and the other downward, to counteract the entry of environment air into said zone.

[0012] Such a known art technical solution - which doesn’t foresee a mechanical seal in the transportation environment - requires a huge consumption of energy and of inerting gas, with flows of about 0,8-1 ,0 Nm3 / min per meter of transporter cover.

[0013] Furthermore, environment air sealing solution by inerting gas, generating turbolence, can result in a loss of the thermal content of the conveyed material.

[0014] Sumary of the invention

[0015] The technical problem posed and solved by the present invention is therefore to provide a belt transport device which permits to overcome the drawbacks mentioned above with reference to the prior art.

[0016] Such problem is solved by a device according to claim 1 and by a transport system including it.

[0017] Preferred features of the present invention are the subject of the dependent claims.

[0018] The present invention provides an efficient and reliable solution to the transport of dusty bulk material at high temperature, in particular DRI pellets.

[0019] The proposed device is based upon a belt conveyor totally enclosed, in the longitudinal direction of the transport, in a mechanically gas sealed casing and includes an inert gas inletting system into the transport environment. Advantageously the casing, generally made of metal, can be equipped with a thermally insulating inner layer.

[0020] In preferred embodiments, the belt conveyor is equipped with a metal motion transmission net configured with a ring shape, connecting two drums arranged at the longitudinal ends of the conveyor and rotating about transverse axes. Mechanically attached to the net are a plurality of material containment elements, particularly plates or cup containers, arranged longitudinally in series in the transport direction.

[0021] In a preferred configuration, the containment elements may have the bottom, i.e., the part attached to the motion-transmitting metallic net, and / or their containment walls which are thermally insulated.

[0022] The forward run of the conveyor may have support rollers, each arranged under the containment elements for their full transverse extension. The return run may be supported by cantilever side rollers, thus of reduced transverse extension, on which extensions of the containment elements run.

[0023] The rotating parts of the conveyor, such as the bearings of the support rollers, can be placed outside the casing, so as to lower thermal resistance constraints on the type of constituent materials. Such arrangement at the outside also allows for regular inspection and maintenance.

[0024] Gas-tightness of the casing is mechanical and, for example, achieved by the use of a suitable sealing material applied between the couplings of adjacent longitudinal sectors of the enclosure itself (where the casing has a sector realization) and / or at any shafts of the support rollers mentioned above. Preferably, for expected operating temperatures above 600°C such sealing material is mineral fiber.

[0025] Alternatively, the coupling between the casing and the support rollers can be made in the form of a sealing body, e.g., graphite, set against a compression spring, e.g., of harmonic steel.

[0026] Depending upon the type of material transported and the expected amount of fines, the device can be equipped with means of cleaning of the bottom of the enclosure, e.g., in the form of motorized ring scraper chains - of the type per se already known in the state of the art - that allow the fines to be delivered back to the transporting area or to a sealed collection point. The enclosure defines or includes, at the top part corresponding to the forward section of the transporter, a plurality of compartments, plenums, or chambers within which an inerting gas is adducted.

[0027] In preferred embodiments, each plenum comprises a container, particularly box-shaped and, for example, metallic, made of two chambers. The latter are transversely adjoining and communicating by means of a suitably perforated vertical wall. One chamber receives the inerting gas from an external adduction system, the other chamber feeds the gas into the transport environment through a perforated wall facing the transport environment itself or through a medium equivalent to it. The two-chamber configuration makes it possible to equalize the flow of injected gas, lower the gas entry velocities into the transport environment and achieve uniform longitudinal distribution. This configuration thus avoids turbulence and thus an associated thermal decay of the transported material.

[0028] The adduction of inert gas into the transport zone can be controlled by pressure sensors, or equivalent systems. In particular, the adduction can be adjusted to achieve a slight overpressure of the transport environment.

[0029] According to a preferred operating process, the transport provides, prior to the material loading stage, flushing with inerting gas of the internal environment of the device to remove air.

[0030] Upon loading and / or unloading of the conveyor, the device may include sealed separation means (e.g., double clapet valves).

[0031] It will be appreciated that the proposed device, in its general meaning and / or in its preferred embodiments, has significant advantages over the known technique, mainly due to the inerting gas release mode and the mechanically sealed configuration of the conveyor, as set out below.

[0032] - Reliability and continuity of operation of the conveyor at high temperatures due to the metallic net configuration. The latter allows free thermal expansion of the conveyor elements without permanent deformation or sudden breakage.

[0033] - Significant reduction in energy and inerting gas consumption, e.g., bringing them down to 1 and up to 14 compared to the known technique.

[0034] - Reduction of gas leakage to the external environment.

[0035] - Reduction in the risk of (re)oxidation of transported material.

[0036] - Maintenance of the thermal content of the transported material, partly due to the low speed of the gas entering the transport environment. - Elimination of dust dispersion to the external environment.

[0037] Other advantages, features and ways of using the present invention will be evident from the following detailed description of some embodiments thereof, presented for illustrative and non-limiting purposes.

[0038] Brief description of the figures

[0039] Reference will be made to the figures in the accompanying drawings, wherein:

[0040] Figure 1 shows a schematic cross-sectional view of a belt conveyor device according to a preferred embodiment of the present invention, also showing a system for introducing a technical, or inertant, gas into the conveyor environment;

[0041] Figure 2 shows a schematic longitudinal cross-sectional view of a section of the device in Figure 1;

[0042] Figure 3 shows a schematic top view of the device of Figure 1, in a preferred configuration involving an alternated positioning of technical gas input compartments;

[0043] Figure 3A shows an enlarged detail of Figure 3;

[0044] Figure 4 shows an input compartment of the device of Figure 3;

[0045] Figure 4A shows a cross section of the device of Figure 4 according to line A-A;

[0046] Figure 4B shows a cross section of the device of Figure 4 according to line B-B;

[0047] Figure 5 shows a schematic cross-sectional view of a belt conveyor device according to a different preferred embodiment of the present invention, which involves cup-shaped containment elements;

[0048] Figure 6 shows a schematic longitudinal cross-sectional view of a section of the device in Figure 5.

[0049] The dimensions represented in the above figures have to be considered as examples and not necessarily in proportion. Detailed description of preferred embodiments of the invention

[0050] Herebelow there will be described different embodiments and variants of the invention, with reference to the figures introduced above. In the following detailed description, embodiments and further variants additional to the ones already discussed in the same description will be explained only with respect to differences with what already exposed. Furthermore, the different embodiments and variants described below are suitable to be employed in combination, where possible.

[0051] Referring initially to Figures 1, 2, and 3, a belt conveyor device according to a preferred embodiment of the present invention is globally denoted by 10. Device 10 is part of a transport system 100, the additional components of which will be described shortly.

[0052] Device 10 and system 100 are configured for dry transport of high flow rates, preferably from about 150 to 350 t / h, of bulk material in a controlled atmosphere, also at high temperature. In the present example, device 10 and system 100 are designed to transport pellets obtained from a “Direct Reduction of Iron" process, specifically pellets leaving a reduction furnace or reactor.

[0053] Device 10 first includes a belt conveyor 101 configured in a loop and thus presenting its own forward run 121 and its own return run 122.

[0054] In the forward run 121, conveyor 101 is moving along a longitudinal transport direction L between a loading region 21 and an unloading region 22. In the return run 122, conveyor 101 moves in the opposite sense in said longitudinal direction L.

[0055] At least in the forward run 121, the conveyor 101 moves in a transporting environment 800 within which a treatment gas for the bulk material being transported, particularly an inerting gas, is adduced.

[0056] Belt cnoveyor 101 has a plurality of bulk material containment elements, one of which is denoted by way of example by 1. The containment elements are arranged in sequence according to the longitudinal transport direction L and attached to a metallic net 2 underlying them. The net 2 acts as a motion transmission organ, being configured to engage, e.g., by friction, a motor drum arranged at an end section of the transition ring between the forward and return runs of the conveyor 101, and an idler drum at the opposite longitudinal end. Drums 7 and 8 are rotatable according to transverse axes of motion, in particular horizontal or substantially so. Conveyor 101 is received in a confinement casing 102, having a side shroud 20 that is thermally insulated and bidirectionally mechanically sealed with respect to gas and preferably dust.

[0057] The means of thermal insulation may be arranged internally within the confinement casing 102 and may include an inner and / or outer coating of insulating material on the inner walls and ceiling, i.e., on the entire side shroud 20. Such a coating may be, for example, mineral fiber or an equivalent material, especially for operating temperatures above 600°C.

[0058] Enclosure 102 encloses belt conveyor 101 for its entire cross-sectional extension, helping to delimit the conveying environment 800 superiorly and laterally.

[0059] Enclosure 102 can be opened outward only at the above mentioned longitudinally terminal loading region 21 of bulk material and / or longitudinally terminal unloading region 22. Any spillage of treatment gas at such regions is, however, in smaller quantities than in “apron” systems of known art, because it is not required the portion that must ensure tightness, the latter associated with casing 102. Moreover, should total or local gas supply lack in such conveyors of known art due to a failure, oxidation of the conveyed material would occur much sooner than if a similar failure were to occur in system 100 considered here.

[0060] Casing 102 is preferably made of metal or predominantly of metal.

[0061] In the example of Figures 1-3 considered herein, the containment elements comprise, or consist of, a plurality of side-by-side metal plates, preferably partially overlapping each other according to the transport direction L, and configured to define a loading surface 11 for bulk material.

[0062] Advantageously, each plate 1 has side rails 12 to confine the transported material.

[0063] In addition, confinement baffles 13 are provided between adjacent plates, possibly each integral with a respective plate.

[0064] In a variant embodiment shown in Figures 5 and 6, the containment elements comprise a plurality of containers, each conforming substantially to a cup and one of which is denoted by T by way of example. Such containers T have a bottom 15 attached to the motiontransmitting metallic net. Each container may have its anterior or front wall 16, i.e., the wall downstream from the direction of travel, provided with an overlapping flap 17 with the rear wall of the container preceding it. Alternatively, vice versa, each container may present the rear wall, i.e. upstream with respect to the direction of travel, provided with an overlap flap with the front wall of the container following it.

[0065] Preferably, the containment elements 1, T are supported, in the forward run 121, by a plurality of load-bearing idler rollers 61 underlying the net 2.

[0066] Preferably, the containment elements 1, T are supported, in the return run 122, by a plurality of cantilever bearing rollers 62 on which lateral extensions 18 and 19 of the conveying elements 1, T slide.

[0067] Advantageously, in both the mentioned configurations of the containment elements 1, T, the transport surface, the bottom and / or the rails or confinement baffles are thermally insulated.

[0068] In addition, the roller elements 61 , 62 can engage bearing supports, one of which denoted by 70 as an example, positioned on the outside of the casing 101. Thus, the latter has side housings for such bearing supports 70.

[0069] This configuration allows easy maintenance of the bearings and preserves them from the high temperatures of the transport environment 800. This also allows for reduced thermal resistance constraints on the choice of their constituent material.

[0070] In preferred variant embodiments, the device 10 includes means for cleaning the bottom 25 of the casing 102 of a pendulum, spoon, brush, and / or motorized scraper chain type - of a type already known per se in the state of the art - that allow the fines to be conferred back to the transport area or to a sealed collection point.

[0071] Referring also to Figures 3A, 4, 4A, and 4B, device 10 further comprises an inlet system 8 of a treatment gas, particularly an inerting gas, into the transport environment 800. The inlet system 8 comprises a plurality of gas inlet chambers, one of which is denoted in the example shown by 80. Such chambers 80 are arranged internally to the casing 102 at a region thereof arranged superiorly to the forward run 121 of the conveyor 101. In the example shown, the chambers are arranged side by side along the longitudinal transport direction L at transversely opposite sides of the casing 102, sequentially and transversely staggered. For better understanding, in Figure 3 another chamber, arranged on opposite sides and offset from chamber 80, is denoted 80'. This staggered arrangement avoids turbulence within the transport environment 800.

[0072] According to a preferred embodiment, each chamber 80, 80' is subdivided into a first subchamber 81 of first introduction, in connection with external adduction means generally denoted 801 , and a second subchamber 82 of supply, in gas communication with the first subchamber 81 and configured to supply gas within the transport environment 800.

[0073] The first 81 and the second 82 subchamber are in gas communication by means of a vertical 83 partition, particularly a perforated wall.

[0074] Advantageously, a transverse, in particular horizontal, adduction of the treatment gas into the working environment 800 is provided. This intake direction is exemplified by an arrow T in Figure 3.

[0075] Preferably, the gas supply into the transport environment 800 is performed at an adduction wall 84, which is also vertical, of the second subchamber 82, in particular a perforated wall and / or a wall equipped with supply nozzles.

[0076] The partition wall 83 allows the flow to be distributed in the first chamber 81 and helps to equalize the outflow from the second chamber 82 through the second wall 84 in communication with the transport environment 800.

[0077] The interface wall 83 between the two subchambers 81 and 82, as mentioned, can be fitted with holes 830, the parameters of which - for example, number, arrangement, and diameter - are related to the design flow rate of the treatment gas. In the present embodiment, the holes in the partition wall 83 are fewer in number than the holes on the adduction wall 84 and, as shown in Figure 4A, are distributed at half the height of wall 83 and for half its length. To improve flow uniformity and dampen any turbulence, holes 830 are distributed in a zig-zag pattern.

[0078] As shown in Figure 4B, the distribution wall 84 of the second chamber 82 has, instead, a higher number of holes 840, which occupies all the surface facing the transport environment, preferably according to a uniform distribution.

[0079] The described configuration permits to share longitudinally the input gas through the first chamber 81 to feed uniformly the second chamber 82 which provides to diffuse the gas into the transportation environment 800. The advantage linked to such configuration is to obtain input speed of the gas inside the environment without any turbulence, particularly maintaining the gas diffusion speed lower than 1 m / s, minimizing the thermal decay of the transported material. Sensors, e.g. pressor sensors, not illustrated, can control the input flow of the inert gas.

[0080] As discussed, device 10 is part of a transport system 100 which includes also the mentioned external adduction means 801 and a relative control unit, eventually communicating with those sensors.

[0081] The transport device described so far is usefully adaptable in a transport and treatment plant of high temperature bulk material and in presence of fines, and in particular to transport DRI pellets outputted from the reduction installation towards fuse furnaces. It represents an optimized and reliable solution for the needs of energetic consumption, treatment gas consumption, mechanical tightness to gas and dusts to avoid the reoxidation of the material and the contamination of the external environment.

[0082] The present invention has been described so far with reference to its preferred embodiments. Is to be intended that other embodiments can exist which belong to the same inventive concept, as defined by the scope of protection of the claims reported below.

Claims

CLAIMS1. A transport device (10), configured for the dry transport of bulk material at elevated temperature and in a controlled atmosphere, in particular DRI (Direct Reduced Iron) pellets exiting a reduction furnace or reactor, which conveying device (10) comprises:■ a belt conveyor (101) configured in a ring and movable, at its own forward section (121), in a conveying environment (800), which belt conveyor (101) in turn has: o a plurality of containment elements (1) of the bulk material, arranged in sequence according to a longitudinal transport direction (L); and o a wire net (2) under said containment elements (1) and fixed thereto, which acts as a motion transmission organ, being configured to engage, for example by friction, a drive drum arranged at an end portion of the ring;■ a containment casing (102) of said belt conveyor (101), thermally insulated and mechanically sealed from gas, and preferably dust, at its own side skirt (20), which casing (102) encloses said belt conveyor (101) for its entire transverse and longitudinal extension, defining said conveying environment (800); and■ an inlet system (8) of a treatment gas, in particular an inerting gas, into said conveying environment (800), which inlet system (8) comprises a plurality of inlet chambers (80, 80') of the treatment gas, arranged internally to said casing (102) at a region thereof arranged superiorly to said forward section (121) of said belt conveyor (101), each chamber (80) being subdivided into a first sub-chamber (81) of first introduction, in connection with external adduction means (801), and a second feeding sub-chamber (82), in gas communication with said first sub-chamber (81) and configured to feed gas within said transport environment (800).

2. The transport device (10) according to claim 1, wherein the inlet chambers of said plurality (80, 80') are arranged along said longitudinal transport direction (L) at transversely opposite sides of said casing (102), in sequence and transversely staggered.

3. The transport device (10) according to claim 1 or 2, wherein said first (81) and second (82) sub-chambers are in gas communication by means of a vertical partition (83).

4. The transport device (10) according to claim 1 or 2, wherein said partition wall (83) has holes (830) arranged on a transversely limited portion thereof.

5. The transport device (10) according to claim 3 or 4, wherein said partition wall (83) has holes (830) arranged in a pattern configured to limit turbulence in said second subchamber (82).

6. The transport device (10) according to any of claims 3 to 5, wherein said partition wall (83) has holes (830) arranged discontinuously, for example according to a zig-zag pattern.

7. The transport device (10) according to any of the preceding claims, wherein said second sub-chamber (82) is configured to feed gas within said transport environment (800) by means of a perforated adduction wall (84), in particular presenting holes (840) with a uniform distribution.

8. The transport device (10) according to any one of the preceding claims, wherein said inlet system (8) is configured to feed the treatment gas into said conveying environment (800) according to a transverse, preferably horizontal or substantially so feeding direction.

9. The transport device (10) according to any one of the preceding claims, comprising sensors or transducers, for example pressure sensors, for controlling the inlet flow rate of treatment gas within said conveying environment (800).

10. The transport device (10) according to any one of the preceding claims, wherein said containment elements (1) comprise a plurality of metal plates (1) side by side, preferably partially overlapping each other according to said conveying direction (L), and configured to define a loading surface (11) for the bulk material.

11. The transport device (10) according to any one of the preceding claims, wherein said containment elements (1) comprise a plurality of containers, each substantially cup-shaped (T).

12. The transport device (10) according to any one of the preceding claims, wherein each container has its rear wall (160), i.e. the wall upstream with respect to the direction of travel, provided with an overlapping flap with the front wall (16) of the container following it.

13. The transport device (10) according to any one of the preceding claims, comprising a plurality of idle rollers (61) for supporting said containment elements (1, T) in said forward section (121) of said belt conveyor (101).

14. The transport device (10) according to any one of the preceding claims, comprising a plurality of cantilever rollers (62) for supporting said containment elements (1, T) in a return section of said belt conveyor (101).

15. The transport device (10) according to any one of the preceding claims, wherein said containment casing (102) is a casing made at least predominantly of metal.

16. The transport device (10) according to any one of the preceding claims, wherein said containment casing (102) is outwardly open only at a longitudinally terminal loading region (21) of the bulk material and / or a longitudinally terminal unloading region (22).

17. The transport device (10) according to any one of the preceding claims, comprising means for cleaning the bottom (25) of said casing (102) of the pendulum, spoon, brush or scraper chain type.

18. A transport system (100) for dry handling of high temperature bulk materials in industrial plants, comprising:■ a transport device (10) according to any one of the preceding claims; and■ means for feeding (801) the treatment gas, arranged outside said casing (102) and in communication with said inlet chambers (80).