Screw press and wood chip dewatering method

Abstract

The objective is to provide a screw press that can release pressure relatively easily even when moisture-containing materials such as wood chips become clogged inside, and that allows for relatively easy adjustment of heat generation and other parameters. [Solution] The screw press 1 comprises a filter cylinder 2, a screw shaft 3 disposed inside the filter cylinder 2, and screw blades 4 fixed to the outer surface of the screw shaft 3, and moves water-containing material introduced from the inlet side 11 to the outlet side 12 while being compressed and dewatered by the screw blades 4, wherein the filter cylinder 2 has a tapered shape in which its inner circumferential surface gradually decreases in diameter toward the outlet side 12, and the screw blades 4 have an outer circumferential edge 41 that decreases in diameter toward the outlet side 12 so as to follow the tapered shape of the inner circumferential surface of the filter cylinder 2, thus forming the screw press 1.

Description

Technical Field

[0001] The present invention relates to a screw press and a method for dehydrating wood chips. Specifically, the present invention relates to a screw press including a filter cylinder, a screw shaft disposed inside the filter cylinder, and screw blades fixed to the outer surface of the screw shaft, and a method for dehydrating wood chips using such a screw press.

Background Art

[0002] In recent years, it has been pointed out that the use of non-renewable energy from fossil fuels may promote environmental destruction on a global scale. Therefore, the thermal utilization of woody biomass, which is renewable and can reduce carbon dioxide emissions, has been promoted. Examples of such woody biomass include those obtained by chipping unused wood such as thinned wood and end materials from sawmills (wood chips).

[0003] The moisture content of woody biomass, based on the wet basis moisture content (hereinafter abbreviated as moisture content), is as high as 50 to 70% depending on the type of wood, and it is unsuitable as fuel as it is. Therefore, it is desirable to dry it in advance to a moisture content suitable as fuel (about 40% or less).

[0004] However, in order to dry woody biomass, it was necessary to supply a large amount of thermal energy using large-scale drying equipment. On the other hand, when woody biomass with a relatively high moisture content was used as fuel as it was, the combustion efficiency deteriorated, and it was difficult to obtain sufficient combustion energy.

[0005] Here, the moisture contained in wood is divided into free water and bound water. Free water is liquid moisture contained in cells or between cells, and bound water is moisture chemically bonded to wood fibers in the wood cell wall. Among them, free water can be dehydrated relatively easily by compressing the wood. And the state where free water completely disappears and the cell wall is saturated with bound water is called the fiber saturation point, and the moisture content at that time is about 30%.

[0006] In other words, by pre-compressing the wood chips to remove most of the free water, the amount of thermal energy required for drying can be significantly reduced. Furthermore, in some cases, sufficient combustion energy can be obtained without going through a drying process using drying equipment. A technique for compressing and dewatering wood chips is described, for example, in Patent Document 1.

[0007] Patent Document 1 below describes a wood chip dewatering device that removes impurities such as gravel and sand attached to wood chips used in a combustion device, and also removes ash, chlorine, and other contaminants along with the moisture contained in the wood chips, characterized by comprising a chip washing means for supplying and washing wood chips, and a watering means for pressurizing the wood chips washed by the chip washing means to remove the moisture contained in the wood chips. It states that this allows for dewatering and increasing the solid content concentration regardless of the type, shape, or dimensions of the wood chips. It also states that a screw press device is used for the watering means. A screw press is a device in which water-containing materials such as wood chips are moved from an inlet to an outlet, and are compressed and dewatered by screw blades. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-190414 [Overview of the project] [Problems that the invention aims to solve]

[0009] The dewatering apparatus described in Patent Document 1 enables continuous water extraction from wood chips by using a screw press as the water extraction means. However, wood chips sometimes become clogged (stuck) inside the screw press during extraction. In particular, when the wood chips got stuck in the middle of the screw press, it was necessary to disassemble the apparatus and release the pressure at the clogged section.

[0010] Furthermore, the dewatering apparatus described in Patent Document 1 did not allow for easy adjustment of the amount of heat generated during water extraction.

[0011] The present invention aims to solve the above problems and to provide a screw press or the like that can release pressure relatively easily even when water-containing materials such as wood chips are packed inside, and that allows for relatively easy adjustment of the amount of heat generated. [Means for solving the problem]

[0012] To solve the above problems, the screw press of the present invention comprises a filter cylinder, a screw shaft, and screw blades, wherein the filter cylinder is tapered to gradually decrease in diameter toward the outlet side, and the screw blades are configured to decrease in diameter toward the outlet side so as to follow the inner circumferential surface of the tapered filter cylinder. The specific examples are listed below.

[0013] (Aspect 1) A screw press comprising a filter cylinder, a screw shaft disposed inside the filter cylinder, and screw blades fixed to the outer surface of the screw shaft, wherein water-containing material introduced from the inlet side is moved to the outlet side while being compressed and dewatered by the screw blades, the filter cylinder having an inner circumferential surface that gradually tapers toward the outlet side, and the screw blades having an outer circumferential edge that tapers toward the outlet side so as to follow the inner circumferential surface of the filter cylinder which is tapered toward the outlet side.

[0014] This screw press has a tapered filter cylinder that gradually narrows in diameter towards the outlet, and the screw blades are configured to narrow in diameter towards the outlet along the inner surface of the tapered filter cylinder. As a result, if moisture-containing material such as wood chips clogs the inside, the screw shaft inside the filter cylinder can be slid towards the inlet to release the overall pressure, making it relatively easy to clear the blockage caused by moisture-containing material. Furthermore, by sliding the screw shaft inside the filter cylinder toward the inlet, the amount of heat generated and the amount of water extracted (moisture content) can be adjusted relatively easily. These advantages cannot be obtained with conventional straight-type screw presses (where the filter tube and screw blades are straight and not tapered).

[0015] (Aspect 2) The screw press according to aspect 1, wherein the screw shaft is slidable at least toward the inlet side relative to the filter cylinder.

[0016] This screw press can widen the clearance between the inner circumference of the filter cylinder and the outer edge of the screw blades along its entire length by sliding the screw shaft inside the filter cylinder toward the inlet by a predetermined distance, in case of clogging with moisture-containing materials such as wood chips. This releases the overall pressure, making it relatively easy to clear blockages caused by moisture-containing materials. Furthermore, by sliding the screw shaft inside the filter cylinder toward the inlet, the amount of heat generated and the amount of water extracted (moisture content) can be adjusted relatively easily.

[0017] (Aspect 3) A screw press according to aspect 1 or aspect 2, wherein the moisture-containing material is wood chips. Wood chips can be obtained by cutting or crushing woody raw materials into wood chips.

[0018] The screw press described in Aspect 1 or Aspect 2 is suitably used for dehydrating wood chips. Since wood chips are relatively large in size compared to, for example, sludge, even when the clearance between the inner circumference of the filter cylinder and the outer peripheral edge of the screw blades is relatively wide, it is difficult for the wood chips to pass through this clearance, so pressure leakage and the like are unlikely to occur, and it is easy to dehydrate the wood chips. As the wood chips, those with a size (length of the longest part) of, for example, 3 to 5 cm can be used. Also, wood chips in which those with a size of 3 to 5 cm account for 50% by weight or more or 80% by weight or more can be used.

[0019] (Aspect 4) The screw shaft is tapered towards the outlet side, and the taper angle of the screw shaft is smaller than the taper angle of the inner peripheral surface of the filter cylinder. It is the screw press described in any one of Aspects 1 to 3.

[0020] This screw press can gradually apply pressure to a water-containing material such as wood chips, and it is easier to dehydrate.

[0021] (Aspect 5) The filter cylinder has a plurality of linear grooves along the longitudinal direction on its inner peripheral surface. It is the screw press described in any one of Aspects 1 to 4.

[0022] In this screw press, it is difficult for wood chips to clog inside. As one of the phenomena of wood chip clogging, the wood chips may rotate together with the screw shaft and the screw blades, and the wood chips may slip between the inner peripheral surface of the filter cylinder. Therefore, by providing a plurality of linear grooves along the longitudinal direction of the filter cylinder on the inner peripheral surface of the filter cylinder, linear protrusions are formed between the linear grooves, and such a phenomenon can be reduced. Also, the pressing ability is improved.

[0023] (Aspect 6) The depth of the linear groove is 1 to 10 mm. It is the screw press described in one of Aspects 1 to 5.

[0024] In this screw press, wood chips are less likely to become clogged inside. The depth of the linear grooves is preferably 2 to 8 mm, more preferably 3 to 7 mm.

[0025] (Aspect 7) The filter cylinder is the screw press according to any one of Aspects 1 to 6, which has a plurality of linear grooves along the longitudinal direction from the central portion in the longitudinal direction of the inner peripheral surface to the outlet side. The filter cylinder does not have linear grooves on the inlet side of the inner peripheral surface.

[0026] In this screw press, wood chips are less likely to become clogged inside. Also, the processing of the linear grooves is relatively easy.

[0027] (Aspect 8) By using the screw press according to any one of Aspects 1 to 7 to dehydrate wood chips, the above problems can also be solved, which is a method for dehydrating wood chips.

Advantages of the Invention

[0028] According to the present invention, even when a water-containing material such as wood chips is clogged inside, the pressure can be released relatively easily, and a screw press or the like that can relatively easily adjust the calorific value can be provided.

Brief Description of the Drawings

[0029] [Figure 1] It is a diagram illustrating a schematic configuration of a screw press. [Figure 2] It is a diagram illustrating a state in which the screw shaft is slid to the inlet side in the screw press of FIG. 1. [Figure 3] It is a diagram comparing and enlarging the P part of FIG. 1 and the P' part of FIG. 2. [Figure 4] It is an end view illustrating a state of viewing the A-A cut portion of FIG. 1 from the arrow direction. [Figure 5] It is an end view illustrating a state of viewing the B-B cut portion of FIG. 1 from the arrow direction. [Figure 6] It is an end view illustrating a state of viewing the C-C cut portion of FIG. 1 from the arrow direction. [Modes for carrying out the invention]

[0030] The screw press will be explained using diagrams below. The screw press 1 comprises a filter cylinder 2, a screw shaft 3, and screw blades 4. These components will be explained using diagrams below. In Figure 1, the filter cylinder 2 and other components are shown in end view to clearly show the screw shaft 3 and screw blades 4. The following embodiments are merely illustrative examples of the present invention, and the present invention is not limited to the following specific embodiments.

[0031] 1.Filter cylinder The filter cylinder 2 is tapered. More specifically, its inner circumferential surface 21 is tapered, gradually decreasing in diameter towards the outlet side 12. In Figure 1 illustrating this embodiment, the filter cylinder 2 is tapered, with its inner circumferential surface 21 tapering linearly towards the outlet side 12 (left side in Figure 1).

[0032] The filter cylinder 2 houses the screw shaft 3 and screw blades 4, which will be described later. The filter cylinder 2 also serves as a casing to house these components.

[0033] In this embodiment, an inlet 22 opening upwards is provided on the inlet side 11 of the filter cylinder 2, and a water-containing material such as wood chips W is fed into the screw press 1 through this inlet 22. The side into which the water-containing material is fed is the inlet side 11.

[0034] The filter cylinder 2 has a structure in which water (extracted water) released from the water-containing material compressed inside the filter cylinder 2 permeates through the wall surface of the filter cylinder 2. Specifically, for example, the filter cylinder 2 can have numerous water passage holes around the entire circumference of its wall surface. Note that water passage holes and the like are omitted in Figures 1 to 6.

[0035] In this embodiment, as illustrated in Figures 4 and 5, linear grooves 25 are carved into the inner circumferential surface 21 of the filter cylinder 2, and linear protrusions 26 are formed between adjacent linear grooves 25. It is preferable that the water passage holes be provided at the bottom of the linear grooves 25 and not on the linear protrusions 26. This creates a pressure difference, further improving the compression capacity.

[0036] In detail, in this embodiment, the filter cylinder 2 has a number of linear grooves 25 along the longitudinal direction over the entire circumference of its inner surface 21. In this embodiment, the depth of the linear grooves 25 is approximately 5 mm. The height of the linear projections 26 between adjacent linear grooves 25 (corresponding to the depth of the linear grooves 25) is approximately 5 mm.

[0037] Furthermore, in this embodiment, as illustrated in Figures 4 to 6, the filter cylinder 2 has numerous linear grooves 25 along the longitudinal direction only from the longitudinal center of the inner circumferential surface 21 to the outlet side 12. In other words, in this embodiment, as illustrated in Figure 6, the filter cylinder 2 does not have linear grooves on the inlet side 11 of the inner circumferential surface 21.

[0038] 2. Screw shaft The screw shaft 3 is located inside the filter cylinder 2. More specifically, the screw shaft 3 is arranged concentrically along the longitudinal direction of the filter cylinder 2. The screw shaft 3 is supported by a pivot shaft so as to be rotatable or freely movable within the internal space of the filter cylinder 2, and is powered by a power source 5, such as a hydraulic motor, to rotate inside the filter cylinder 2.

[0039] Furthermore, in this embodiment, the screw shaft 3 is slidable in the longitudinal direction (left-right direction in Figure 1) relative to the filter cylinder 2. More specifically, in this embodiment, the screw shaft 3 is slidable toward the inlet side 11 relative to the filter cylinder 2 from the state shown in Figure 1. In this embodiment, the screw shaft 3 is pivotally supported by support plates 71 provided outside the inlet side 11 and outside the outlet side 12, and is equipped with an actuator 6 that fixes and slides the screw shaft 3 in the longitudinal direction together with the power source 5.

[0040] Furthermore, in this embodiment, the screw shaft 3 is tapered towards the outlet side 12. The taper angle of the screw shaft 3 is smaller than the taper angle of the filter cylinder 2 (the taper angle of the inner circumferential surface 21 of the filter cylinder 2).

[0041] 3. Screw blades The screw blades 4 are fixed to the outer surface of the screw shaft 3. The outer edge 41 of the screw blades 4 gradually decreases in diameter towards the outlet side 12 so as to follow the inner surface 21 of the tapered filter cylinder 2.

[0042] Preferably, the outer edge 41 of the screw blade 4 and the inner surface 21 of the filter cylinder 2 are not in contact and there is a clearance. The clearance between the outer edge 41 of the screw blade 4 and the inner surface 21 of the filter cylinder 2 is preferably 1 to 5 mm, and more preferably 1 to 3 mm. Figure 1 illustrates a case where the clearance between the outer edge 41 of the screw blade 4 and the inner surface 21 of the filter cylinder 2 is such that they do not come into contact.

[0043] This clearance can be widened by sliding the screw shaft 3 toward the inlet side 11 relative to the filter cylinder 2 (expanded clearance).

[0044] 4. How to use a screw press (method for dewatering wood chips, etc.) The following is an example of how to use a screw press 1, which is equipped with a filter cylinder 2, a screw shaft 3, and screw blades 4.

[0045] First, the clearance between the outer edge 41 of the screw blade 4 and the inner surface 21 of the filter cylinder 2 is adjusted to such an extent that they do not come into contact, as illustrated in Figure 1. Then, the screw shaft 3 is rotated in a direction such that the water-containing material introduced from the inlet side 11 moves to the outlet side 12. In this state, water-containing material such as wood chips W is introduced from the inlet side 11. In this embodiment, the water-containing material can be introduced from the inlet port 22. The introduced water-containing material is gradually moved to the outlet side 12 by the rotating screw blade 4. At this time, the water-containing material is compressed and dewatered by the screw blade 4 as it moves to the outlet side 12. In this embodiment, the compressed water-containing material moves to the discharge chamber 8 through the gap between the filter cylinder 2 and the back pressure section 72 and is discharged from the discharge port 81.

[0046] The moisture released from the water-containing material, such as wood chips W, permeates the wall of the filter cylinder 2 and falls, for example, downwards to the filter cylinder 2. In this embodiment, the moisture released from the water-containing material falls into a drain receiver 9 located below the screw press 1 and is drained from the drain port 91.

[0047] In cases where moisture-containing material such as wood chips W clogs the inside of the screw press 1, the screw shaft 3 inside the filter cylinder 2 can be slid a predetermined distance toward the inlet side 11, as illustrated in Figure 2. By doing so, as illustrated in Figures 2 and 3, the clearance between the inner surface 21 of the filter cylinder 2 and the outer edge 41 of the screw blades 4 can be expanded along the entire longitudinal direction. This releases or reduces the overall pressure inside the screw press 1, making it relatively easy to resolve blockages caused by moisture-containing material.

[0048] With the clearance widened, moisture-containing material can also be introduced from the inlet side 11. In particular, when wood chips are used as the moisture-containing material, even with the clearance widened, the wood chips (which are large, 3-5 cm in size) have difficulty passing through the clearance, allowing the wood chips to be sufficiently compressed. Furthermore, by adjusting the clearance, it is possible to adjust the amount of heat generated and the amount of water extracted (moisture content). For example, widening the clearance tends to reduce the amount of heat generated, but decrease the amount of water extracted (increase the moisture content).

[0049] Furthermore, there are no particular restrictions on where the screw press 1 can be used. For example, the screw press 1 and a crusher (not shown) can be loaded onto a truck or similar vehicle and transported to a logging site or other location. The felled timber can then be crushed on-site using the crusher to produce wood chips, and the resulting wood chips can be dewatered on-site using the screw press 1.

[0050] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above embodiments, and various changes and modifications can be made by experts in the relevant art without departing from the claims attached to this application.

[0051] For example, dimples can be applied to the surface of the screw shaft or the screw blades. Dimples may also be applied to the surfaces of both the screw shaft and the screw blades. Furthermore, linear grooves do not need to be provided on the inner surface of the filter cylinder. [Explanation of Symbols]

[0052] 1 Screw press 11 Entrance side 12 Exit side 2 Filter cylinder 21 Inner surface 22 Inlet 25 Linear grooves 26 Linear process 3 Screw shaft 4 Screw blades 41 Outer edge 5 Power source 6 Actuators 71 Support plate 72 Back pressure section 8 Discharge chamber 81 Outlet 9. Drain receiver 91 Drain port W Wood Chips

Claims

1. Filter tube and The screw shaft is located inside this filter cylinder, This includes screw blades fixed to the outer surface of the screw shaft, A screw press that moves a water-containing material introduced from the inlet side to the outlet side while compressing and dewatering it with the screw blades, The aforementioned filter tube is Its inner circumferential surface is tapered, gradually decreasing in diameter towards the outlet side. The early screw blades were, Its outer edge tapers towards the outlet side, following the inner surface of the tapered filter cylinder. Screw press.

2. The screw shaft, The filter cylinder is slidable at least towards the inlet side, The screw press according to claim 1.

3. The moisture-containing material is wood chips. The screw press according to claim 1.

4. The screw shaft is It tapers towards the exit side, The taper angle of the screw shaft is smaller than the taper angle of the inner circumference of the filter cylinder. The screw press according to claim 1.

5. The filter tube is The inner surface has multiple linear grooves along the longitudinal direction, The screw press according to claim 1.

6. Linear grooves are, The depth is 1 to 10 mm. The screw press according to claim 5.

7. The filter tube is The inner circumferential surface has multiple linear grooves running longitudinally from the longitudinal center toward the exit side, The screw press according to claim 5.

8. A method for dewatering wood chips, comprising dewatering wood chips using a screw press according to any one of claims 1 to 7.

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