JP7789498B2 - Screw conveyor and method for separating gypsum from paper chips - Google Patents

Description

This invention relates to a screw conveyor and a method for separating gypsum from paper strips.

The inventors have succeeded in industrially recovering gypsum dihydrate from waste gypsum board (Patent Document 1: WO2012/176688A). The waste gypsum board is crushed into paper chips and gypsum chips. These are sieved, and the paper chips are recovered as raw material for papermaking, etc. The gypsum chips are heated to convert them into hemihydrate gypsum and/or anhydrous type III gypsum, which is then mixed with gypsum slurry and gypsum dihydrate crystals are precipitated in a crystallization tank. Paper powder is removed from the slurry in which gypsum dihydrate has precipitated using a sieve, and gypsum dihydrate powder is extracted using a solid-liquid separator. The extracted gypsum dihydrate powder can be used as raw material for gypsum board, etc.

Gypsum remains attached to the paper fragments that are sieved after crushing. If the paper fragments and gypsum could be further separated, the value of the paper fragments would increase and the recovery rate of gypsum would also improve. However, it would be inefficient to set up separate dedicated equipment to remove gypsum attached to the paper fragments.

Related prior art: Patent Document 2 (Patent 3281340) discloses a device that uses a twin-shaft screw conveyor to crush gypsum board and separate it into paper chips and gypsum. Crushing plates are attached to the outer periphery of the screw conveyor blades, and waste gypsum is crushed by being sandwiched between the inner periphery of the casing and the crushing plates. The crushed gypsum falls through holes in the casing, and the paper chips are transported by the screw conveyor.

WO2012/176688A Patent 3281340

The object of the present invention is to
To provide a screw conveyor that can separate foreign matter adhering to an object when transporting it, and to use this screw conveyor to simultaneously transport paper chips obtained by crushing waste gypsum board and separate the gypsum from the paper chips.

The screw conveyor of this invention is
a screw shaft having a plurality of blades for feeding the object in one direction;
a driving means for rotating the screw shaft;
a casing surrounding the screw shaft,
The screw shaft has a section in the middle in the longitudinal direction where the blades are not present,
A mesh is provided at the bottom of the casing.

Preferably, a reverse feed blade is provided in the section to transport the transported object in the opposite direction to the one direction.

The screw conveyor of this invention has a section without blades, which reduces the conveying force acting on the transported materials in that section. The transported materials are compressed in this section and rub against each other. This causes any attached material to fall off the materials and be discharged to the outside of the screw conveyor through a mesh. The screw conveyor of this invention can separate the attached material while transporting the materials. Note that a section without blades here means a section without forward blades that transport materials in the forward direction from the inlet to the outlet of the screw conveyor. If a reverse blade that transports materials in the opposite direction to the one direction is provided in this section, the forces from the forward blade and the reverse blade will act together, causing the transported materials to be strongly compressed and rub against each other. This allows for more efficient separation of attached material.

In the method for separating gypsum from paper chips of the present invention, when the paper chips obtained by crushing and separating waste gypsum boards are transported by a screw conveyor,
Using the screw conveyor, the paper pieces are conveyed;
Compressing the paper pieces in the section to separate the gypsum from the paper pieces;
The separated gypsum is discharged through the mesh to the outside of the casing.

In the method for separating gypsum from paper chips of this invention, gypsum can be separated from the paper chips within the screw conveyor that transports the paper chips. This makes it possible to remove gypsum, an impurity in the paper chips, and increase the recovery rate of gypsum without providing any additional dedicated equipment.

Diagram showing the system for recovering gypsum dihydrate from waste gypsum board Cross-sectional view of a screw conveyor according to an embodiment

The following are examples of how the present invention can be implemented. The scope of the present invention should be determined based on the claims, taking into account the description in the specification and the well-known technology 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.

Figure 1 shows a system 2 for recovering gypsum dihydrate from waste gypsum board, equipped with a screw conveyor 8 according to an embodiment. The waste gypsum board is crushed in a crusher 4, such as a crusher or shredder, to produce paper chips and gypsum. These are then separated into paper chips that pass through a sieve 6, such as a vibrating sieve, and gypsum that passes through the sieve. The separated paper chips are transported by a screw conveyor 8, and as they are transported, any adhering gypsum is separated from them. The paper chips from which the gypsum has been removed become raw material for papermaking, etc.

The gypsum separated by the screw conveyor 8 is heated in a heater together with the gypsum that falls below the sieve to form hemihydrate and/or anhydrous type III gypsum, which is then mixed with the gypsum slurry in a mixer. Dihydrate gypsum crystals are precipitated from the slurry in a crystallization tank 14, and paper powder in the slurry is removed using a sieve such as a vibrating sieve 16. The slurry is then processed in a solid-liquid separation device 18 such as a filter press to extract the gypsum dihydrate powder, and the slurry is returned to the mixer 12 or the like.

Figure 2 shows the structure of the screw conveyor 8. The screw conveyor 8 slopes upward from the inlet 27 to the outlet 28, with the dotted lines at the bottom of the figure indicating the horizontal and vertical directions. A rotating shaft 20 is mounted along the central axis of a cylindrical casing 26 and is rotated by a drive source 24 such as a motor. The rotating shaft 20 is equipped with forward-feeding blades 21 on both the inlet 27 side and the outlet 28 side, and transports the paper pieces in a forward direction from the inlet 27 to the outlet 28 side. The intermediate compression section 25 does not have forward-feeding blades 21; instead, a reverse-feeding blade 22 is provided, which applies a transport force to the paper pieces toward the inlet 27 side. Furthermore, a mesh 30 consisting of numerous openings is provided at the bottom and lower part of the side periphery of the casing 26 in and on both sides of the compression section 25.

The compression section 25 may be provided with neither the forward blade 21 nor the reverse blade 22, with the rotating shaft 20 simply passing through. Also, instead of the reverse blade 22, the compression section 25 may be provided with a restrictor or baffle plate to limit the movement of the paper pieces.

The paper pieces inserted through the inlet 27 are transported by the forward blade 21 to the right side of the figure (diagonally upward in the actual machine). In the compression section 25, the reverse blade 22 acts, compressing the paper pieces and causing them to rub against each other, peeling off the gypsum from the paper pieces. Even without the reverse blade 22, the propulsive force from the forward blade 21 is reduced, and gravity and friction with the casing 26 (for example, friction with the mesh 30) act as resistance, slowing the paper piece's movement speed. This compresses the paper piece and peels off the gypsum. If a restrictor, baffle, etc. is installed, stronger compression and frictional forces act on the paper piece. The gypsum peeled off from the paper piece falls through the mesh 30 near the bottom of the casing 26, and the paper piece is discharged from the outlet 28.

Preferably, an auxiliary screw conveyor 32 is provided below the mesh 30. A rotating shaft 34 is provided at the center of a cylindrical casing 40 and rotated by a drive source 40 such as a motor. Furthermore, feed blades 35 and 36 are attached to the rotating shaft 34 so as to transport the gypsum to an outlet 42 provided in the middle of the casing 40. Because the outlet 42 is located in the middle of the casing 40, the feed blades 35 and 36 have opposite transport directions. In this way, the gypsum that falls from the mesh 30 is transported and discharged from the outlet 42. Note that if the outlet 42 is located at either end of the casing 40, the gypsum is transported in one direction, and only one type of feed blade is required.

The screw conveyor 8 of this embodiment can simultaneously transport paper scraps and remove gypsum adhering to the scraps. This increases the value of the paper scraps removed from the outlet 28 and also increases the recovery rate of gypsum.

In this embodiment, the paper pieces and the gypsum are separated by the screw conveyor 8. However, the screw conveyor 8 can be used for general purposes, such as conveying a sheet-like object having foreign matter attached thereto and separating the attached matter at the same time.

2 Gypsum recovery system 4 Crusher 6 Sieve 8 Screw conveyor 10 Heater 12 Mixer 14 Crystallization tank 16 Sieve 18 Separator 20 Rotating shaft 21 Forward blade 22 Reverse blade 24 Drive source 25 Compression section 26 Casing 27 Feeding port 28 Outlet 30 Mesh 32 Auxiliary screw conveyor 34 Rotating shafts 35, 36 Feed blade 38 Drive source 40 Casing 42 Outlet

Claims (4)

A screw conveyor that transports objects and separates foreign matter adhering to the objects,
a screw shaft having a plurality of blades for feeding the object in one direction;
a driving means for rotating the screw shaft;
a casing surrounding the screw shaft,
The screw shaft has a section in the middle in the longitudinal direction where the blades are not present,
A mesh is provided at the bottom of the casing,
Furthermore, a reverse feed blade is provided in the section where there is no blade , which conveys the conveyed object in a direction opposite to the one direction,
the mesh is provided so as to correspond to the reverse feed blade and the blades on both sides thereof for feeding the conveyed object in the one direction, but not to correspond to a part of the blades for feeding the conveyed object in the one direction,
a second screw conveyor for conveying the foreign matter discharged through the mesh and a second casing surrounding the second screw conveyor are provided at the bottom of the casing in the section where the mesh is provided;
the second casing has an outlet for foreign objects at a midpoint in the conveying direction of the second screw conveyor;
The second screw conveyor is a screw conveyor equipped with two types of blades with opposite conveying directions on both sides of the outlet for the foreign objects. 2. The screw conveyor according to claim 1, wherein blades for transporting the conveyed objects in one direction are provided on both sides of the section where no blades are present . A screw conveyor as described in claim 1 or 2, characterized in that the screw shaft faces diagonally upward, from the inlet to the outlet of the conveyed material. When transporting the paper pieces obtained by crushing and separating waste gypsum boards using a screw conveyor,
The paper pieces are transported using the screw conveyor according to any one of claims 1 to 3 ,
Compressing the paper pieces in the section where there are no blades separates the gypsum from the paper pieces;
The separated gypsum is poured through the mesh into the second casing and discharged from the foreign matter outlet by the second screw conveyor .
How to separate gypsum from paper strips.