Method for conveying powder / granular material by vertical circulation bucket conveyor

Abstract

The present invention prevents powder / granular material from falling from a gap between a bucket and a casing-side discharge port of a conveyor when powder / granular material of low specific gravity is conveyed by a vertical circulation bucket conveyor.　The vertical circulation bucket conveyor, in which a plurality of buckets are fixed to a chain and vertically circulated, conveys the powder and granular material vertically between a loading port and a discharge port provided in a casing of the bucket conveyor. A plate projecting from the discharge port toward the buckets is detachably attached to at least the discharge port so that the buckets intermittently come into contact with the plate. As a result, the gap between the discharge port and the buckets is reduced, and the powder / granular material accumulated on the plate is swept off toward the discharge port by the impact caused by the contact between the buckets and the plate.　

Description

Method for transporting powder and granular materials using a vertical circulating bucket conveyor

[0001] This invention relates to a method for transporting powdery or granular materials using a vertical circulating bucket conveyor, for example, a method for transporting granular materials made of gypsum dihydrate powder obtained by crushing waste gypsum boards.

[0002] The inventors have been working on recovering gypsum from waste gypsum board (Patent Document 1). In the method developed by the inventors, the waste gypsum board is crushed and sieved to separate paper chips and gypsum lumps. Metallic foreign matter is then removed using a magnetic separator, and the gypsum powder and paper chips are separated by secondary crushing. If necessary, heavy foreign matter such as gravel is removed using an air table or the like. The resulting gypsum dihydrate is calcined to produce hemihydrate and / or anhydrous type III gypsum powder and granules. The calcined gypsum is mixed with gypsum slurry to precipitate gypsum dihydrate particles in a crystallization tank. The gypsum dihydrate powder is filtered off, and the filtrate is returned to the crystallization tank or the like.

[0003] Patent Publication No. 2021-79303

[0004] In the process up to mixing with gypsum slurry, gypsum powder may be transported to a high position due to the layout of the equipment. The powder is composed of gypsum dihydrate, which is an aggregate of thin needle-like crystals in the gypsum board with a high porosity, resulting in an extremely low specific gravity. In addition, if the waste gypsum board gets wet in the rain, the powder may become damp and become more adhesive.

[0005] This gypsum powder is raised by the buckets of a vertical circulating bucket conveyor, which rotates at the discharge port and discharges the powder. Because the gypsum powder derived from waste gypsum board has a low specific gravity, centrifugal force barely acts on the powder, and the powder does not move sufficiently horizontally. Instead, it falls through the gap between the front edge of the bucket and the conveyor casing, accumulating at the bottom of the casing. Furthermore, because gypsum powder has low fluidity and is adhesive, it can adhere to the casing at the discharge port and pile up. As a result, the following gypsum powder cannot pass through the discharge port and falls through the gap, accumulating at the bottom of the conveyor casing.

[0006] The gypsum powder that accumulates at the bottom of the casing is scraped off with a bucket and transported. However, if the gypsum powder accumulates at the bottom of the casing, the powder must be circulated between the discharge port and the bottom of the casing, making transportation inefficient. In extreme cases, a large amount of powder accumulates at the bottom of the casing, causing the conveyor to stop.

[0007] This problem is not limited to the discharge port, but is also present at the inlet for gypsum powder. Because the force that moves the powder horizontally is weak, the powder tends to fall through the gap between the inlet and the bucket. Furthermore, when gypsum powder accumulates at the inlet, the following powder loses its horizontal speed as it climbs over the accumulated powder, and falls through the gap to the bottom of the casing.

[0008] The object of this invention is to prevent low-specific-gravity powder, such as gypsum powder derived from waste gypsum board, from falling through the gap between the bucket and the discharge outlet on the casing side of the conveyor when transporting the powder using a vertical circulating bucket conveyor.

[0009] This invention is a method for vertically transporting powder and granular material between an inlet and a discharge outlet provided in the casing of a vertically circulating bucket conveyor in which a plurality of buckets are fixed to a chain and circulated vertically, characterized in that a plate that protrudes from the discharge outlet toward the bucket is detachably attached to at least the discharge outlet so that the bucket intermittently contacts the plate, thereby narrowing the gap between the discharge outlet and the bucket, and causing the impact of contact between the bucket and the plate to knock powder and granular material accumulated on the plate down toward the discharge outlet.

[0010] In this invention, the gap with the bucket can be shortened by the plate. Also, powder accumulated on the plate is knocked off by the impact of contact with the bucket, so that the accumulated powder does not interfere with the movement of subsequent powder. If the plate is made of a material softer than the bucket, damage to the bucket can be prevented. The discharge port itself does not come into contact with the bucket, and the plate is detachable, so if the plate is damaged, it can be replaced, for example.

[0011] Preferably, plates are attached to both the discharge port and the inlet, so that the powder and granular material can be smoothly moved from the inlet to the bucket not only at the discharge port but also at the inlet.

[0012] Preferably, the plate is made of fluororesin, which provides it with the toughness to withstand contact with the bucket, the elasticity to easily deform when it comes into contact with the bucket, and low friction to prevent powder and granular material from accumulating on the plate.

[0013] Preferably, the plate is attached so that the length of its projection toward the bucket side is adjustable, thereby making it possible to adjust the frequency of contact between the plate and the bucket and to adjust the gap between the plate and the bucket.

[0014] 1 is a vertical cross-sectional view of a vertical circulating bucket conveyor used in the embodiment; FIG. 2 is a vertical cross-sectional view of a main part of the vertical circulating bucket conveyor of FIG. 1; and FIG. 3 is a view showing a plate positioning mechanism.

[0015] Examples for carrying out the present invention are shown below. The scope of the present invention should be determined based on the claims, taking into account the description in the specification and well-known techniques in this field, and in accordance with the understanding of those skilled in the art. The scope of the present invention is not limited by the examples.

[0016] Figures 1 to 3 show a vertically circulating bucket conveyor 2 according to an embodiment and a method for transporting powder and granular material according to the embodiment. 4 denotes multiple buckets, made of metal or plastic, attached to a chain 6 and circulating vertically within a cylindrical circulation space 7. 8 and 9 denote sprockets rotated by a motor (not shown) to vertically circulate the buckets 4. 10 denotes a casing for the conveyor 2, made of metal, for example, through an inlet 12 into which powder and granular material of gypsum dihydrate derived from waste gypsum board is fed. The inlet 12 is equipped with, for example, a screw conveyor or rotary valve (not shown). The bucket 4 drops the powder and granular material into the outlet 14 of the casing. 13 and 15 denote conveying surfaces consisting of the bottom surfaces of the inlet 12 and the outlet 14, and the powder and granular material slides along the conveying surfaces 13 and 15.

[0017] The fallen gypsum dihydrate powder 16 accumulates at the bottom 17 of the casing 10 of the conveyor 2 and is scraped off by the bucket 4. An object of the present invention is to reduce the amount of fallen powder 16. The powder to be treated may be calcined gypsum derived from waste gypsum board, or other powder with a low specific gravity, such as grain flour or kaolin.

[0018] Plates 20, 20 protruding into the circulation space 7 are detachably attached to the tips of the conveying surfaces 13, 15 of the discharge port 14 and the inlet 12. The plates 20, 20 preferably have enough elasticity to deform upon contact with the bucket 4, allowing the bucket 4 to move vertically, and enough toughness to withstand repeated force from the bucket. Furthermore, the plates 20, 20 are preferably made to allow the powder and granules to slide relative to the plates 20, i.e., to prevent the powder and granules from adhering to the plates 20. A low coefficient of friction on the surface is also preferred. A preferred material for the plates 20 is fluororesin, which combines elasticity, toughness, and low friction. However, other materials, such as ultra-high molecular weight polyethylene (UHMN-PE) and rigid polyvinyl chloride (PVC), are also acceptable. Plates 20 are not required to be provided at both the discharge port 14 and the inlet 12; they are provided at least at the discharge port 14.

[0019] Plate 20 protrudes into circulation space 7 so as to come into contact with bucket 4 intermittently, for example, so as to come into contact with bucket 4 approximately once every 10 to several hundred revolutions of bucket 4 between sprockets 8 and 9. The horizontal length by which plate 20 protrudes from outlet 14 or inlet 12 is t, and the horizontal gap between plate 20 and the leading edge of bucket 4 is d, as shown schematically in Figures 2 and 3. Note that because chain 6 vibrates, the trajectory of the tip of bucket 4 is not constant, and gap d is also not constant.

[0020] Because the plate 20 protrudes toward the circulation space 7, only a small amount of powder and granules discharged from the bucket 4 falls through the gap d. As shown in Figure 2, powder and granules 21 such as gypsum dihydrate accumulate in a mound at the discharge port 14, blocking the movement of subsequent powder and granules. However, because the plate 20 intermittently comes into contact with the bucket 4, the impact causes the mounded powder and granules to collapse and be discharged. As a result, the powder and granules are discharged smoothly from the discharge port 14.

[0021] The function of the plate 20 is the same at both the discharge port 14 and the input port 12, but at the input port 12, the powder can be actively pushed out by a screw conveyor or the like. At the discharge port 14, the force moving the powder toward the discharge port 14 side is weak, so the plate 20 is very important.

[0022] Although the plate 20 repeatedly comes into contact with the bucket 4, it has toughness and elasticity, so it can be used continuously for, for example, about three months. It is preferable that the plates 20, 20 are attached to the discharge port 14 and the input port 12 so that the protruding length t can be adjusted freely. For example, as shown in Figure 3, a long hole 22 is provided in the plate 20 or the discharge port 14 and the input port 12, and the protruding length t of the plate 20 is adjusted with a screw 23 or the like. The mechanism for adjusting the length t is arbitrary.

[0023] The embodiment has the following advantages. 1) The gap d between the inlet 12 and outlet 14 and the bucket 4 is narrowed by the plate 20, thereby reducing the amount of powder and granules that are racked through the gap d. 2) Powder and granules accumulated on the plate 20 are brushed off by intermittent contact between the bucket 4 and the plate 20, preventing the powder and granules from accumulating on the plate 20 and interfering with the movement of subsequent powder and granules. 3) When the plate 20 comes into contact with the bucket 4, it deforms to allow the bucket 4 to pass, making the bucket 4 less likely to be damaged. 4) The plate 20 is softer than the bucket 4 and does not damage it. Furthermore, the plate 20 can be replaced if damaged. 5) The plate 20 is made of fluororesin, which combines toughness, elasticity, and low friction. 6) The mounting position of the plate 20 is adjustable, allowing the protruding length t of the plate 20 to be adjusted.

[0024] 2 Vertical circulating bucket conveyor 4 Bucket 6 Chain 7 Circulation space 8, 9 Sprocket 10 Casing 12 Inlet 14 Discharge outlet 13, 15 Conveying surface 16 Gypsum dihydrate powder 17 Bottom 20 Plate 21 Gypsum dihydrate powder 22 Slot 23 Screw d Gap t Protruding length

Claims

1. A method for vertically transporting powder and granular materials between an inlet and a discharge outlet provided in the casing of a vertically circulating bucket conveyor in which multiple buckets are fixed to a chain and circulated vertically, characterized in that a plate protruding from the discharge outlet toward the bucket is detachably attached to at least the discharge outlet so that the bucket intermittently contacts the plate, thereby narrowing the gap between the discharge outlet and the bucket, and causing the impact of the bucket contacting the plate to knock powder and granular materials accumulated on the plate down toward the discharge outlet.

2. The method for transporting powder and granular materials by a vertical circulating bucket conveyor according to claim 1, wherein the plates are attached to both the discharge port and the input port.

3. A method for transporting powder and granular materials using a vertical circulating bucket conveyor according to claim 1 or 2, characterized in that the plates are made of fluororesin.

4. A method for transporting powder and granular materials using a vertical circulating bucket conveyor according to claim 1 or 2, characterized in that the length of the plate projecting toward the bucket side is freely adjustable.

5. A method for transporting powdery or granular materials using a vertical circulating bucket conveyor according to any one of claims 1 to 4, characterized in that the powdery or granular materials are gypsum powdery or granular materials derived from waste gypsum boards.

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