Gypsum dehydration system

Abstract

This gypsum dehydration system for dehydrating a gypsum slurry includes: a conveyance belt that conveys a gypsum slurry which is placed on a filter cloth; a dewatering device that sucks the gypsum slurry conveyed by the conveyance belt from below to remove the filtrate; a cleaning liquid supply device that supplies a cleaning liquid to the gypsum slurry conveyed by the conveyance belt; and at least one weir provided upstream, in the conveyance direction of the conveyance belt, of the position at which the cleaning liquid is supplied by the cleaning liquid supply device, to dam up the water of an upper layer of the gypsum slurry conveyed by the conveyance belt.

Description

Gypsum dehydration system

[0001] This disclosure relates to a gypsum dewatering system for dewatering a gypsum slurry. This application claims priority to Japanese Patent Application No. 2024-070186, filed with the Japan Patent Office on April 24, 2024, the contents of which are incorporated herein by reference.

[0002] For example, exhaust gas emitted from a combustion engine such as a boiler contains air pollutants such as sulfur oxides (SOx). A known desulfurization device for reducing the SOx contained in exhaust gas is an absorption tower that brings the exhaust gas introduced therein into contact with limestone slurry (washing liquid) sprayed by a spray nozzle installed therein, thereby causing the SOx in the exhaust gas to be absorbed by the washing liquid (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses that SOx in the exhaust gas removed in the absorption tower reacts with calcium in the sprayed washing solution to form calcium sulfite as an intermediate product, which is then oxidized to gypsum by air supplied to the absorption tower to form the final product (gypsum). Patent Document 1 also discloses that the washing solution extracted to the outside of the absorption tower by an extraction pump is sent to a gypsum separator, and the final product is recovered as powdered gypsum. The gypsum separator includes a conveyor belt in which a breathable filter cloth is stretched over a rubber belt having drainage grooves and drainage holes. The conveyor belt conveys the gypsum slurry.

[0004] Japanese Patent Application Laid-Open No. 2020-157272

[0005] The gypsum slurry transported on the conveyor belt becomes a gypsum cake with a relatively low moisture content while being dehydrated during transport. The gypsum cake is washed with a cleaning liquid to remove impurities such as chloride ions and fine dust particles. At a supply position of the cleaning liquid in the transport direction of the conveyor belt, the moisture content of the gypsum cake is preferably dehydrated to a predetermined value or less.

[0006] The gypsum slurry transported on the conveyor belt has a gypsum layer containing gypsum as a main component and a moisture layer containing water as a main component and laminated on the upper surface of the gypsum layer. According to the inventor's new findings, if the moisture layer is thick, it becomes difficult for air to pass through the filter cloth, and the suction force of the dehydration device (extraction pump) cannot be sufficiently applied to the gypsum slurry, which may result in a decrease in the dehydration efficiency of the filter cloth. If the dehydration efficiency of the filter cloth decreases, there is a risk that the moisture content of the gypsum cake at the supply position of the cleaning liquid cannot be dehydrated to a predetermined value or less.

[0007] In view of the above circumstances, at least one embodiment of the present disclosure has an object to provide a gypsum dehydration system that can suppress a decrease in the dehydration efficiency of a filter cloth and efficiently obtain gypsum having a desired moisture content.

[0008] A gypsum dehydration system according to at least one embodiment of the present disclosure is a gypsum dehydration system for dehydrating a gypsum slurry, and includes: a conveyor belt configured to convey the gypsum slurry placed on a filter cloth; a dehydration device configured to suck the gypsum slurry conveyed by the conveyor belt from below and dehydrate a filtrate; a cleaning liquid supplying device configured to supply a cleaning liquid to the gypsum slurry conveyed by the conveyor belt; and at least one weir that is provided upstream of a supply position of the cleaning liquid by the cleaning liquid supplying device in a conveying direction of the conveyor belt and that blocks water in an upper layer of the gypsum slurry conveyed by the conveyor belt.

[0009] According to at least one embodiment of the present disclosure, a gypsum dehydration system is provided that can suppress a decrease in the dehydration efficiency of a filter cloth and efficiently obtain gypsum having a desired moisture content.

[0010] Fig. 1 is a schematic diagram of a gypsum dewatering system according to an embodiment of the present disclosure; Fig. 2 is a schematic diagram of a gypsum dewatering system according to an embodiment of the present disclosure, viewed from above; Fig. 3 is a schematic diagram of the vicinity of a weir in a gypsum dewatering system according to an embodiment of the present disclosure; Fig. 4 is a schematic diagram of the vicinity of a weir in a gypsum dewatering system according to an embodiment of the present disclosure; Fig. 5 is a schematic diagram of a gypsum dewatering system according to a comparative example, viewed from above; Fig. 6 is a schematic diagram of a gypsum dewatering system according to an embodiment of the present disclosure, viewed from above.

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0012] In the following description, when simply referring to the upstream side, it refers to the upstream side along the main flow direction of the fluid in the part or area described in the direction. Similarly, in the following description, when simply referring to the downstream side, it refers to the downstream side along the main flow direction of the fluid in the part or area described in the direction.

[0013] (Gypsum dehydration system) Fig. 1 is a schematic diagram of a gypsum dehydration system 1 according to an embodiment of the present disclosure. The gypsum dehydration system 1 according to some embodiments is for dehydrating a gypsum slurry to produce gypsum. In the following embodiments, the gypsum dehydration system 1 dehydrates a gypsum slurry discharged from a flue gas desulfurization apparatus 11, but the gypsum slurry may also be dehydrated by a device other than the flue gas desulfurization apparatus 11.

[0014] (Flue Gas Desulfurization Apparatus) The flue gas desulfurization apparatus 11 is configured to remove sulfur oxides from the flue gas by bringing flue gas discharged from a combustion apparatus such as an engine or a boiler into contact with an absorption liquid and causing the absorption liquid to absorb sulfur oxides (e.g., sulfur dioxide gas) in the flue gas. In the flue gas desulfurization apparatus 11 using a lime-gypsum method, a slurry containing an alkaline component, such as limestone slurry in which limestone is dissolved (dispersed), is used as the absorption liquid, and gypsum slurry (absorption liquid containing gypsum) is by-produced.

[0015] As shown in FIG. 1 , the gypsum dehydration system 1 includes a filter cloth 2 , a conveyor belt 3 , a dehydration device 4 , a washing liquid supply device 5 , and at least one weir 6 .

[0016] (Conveyor belt, filter cloth) The conveyor belt 3 is configured to convey the gypsum slurry placed on the filter cloth 2 along a first direction (left-right direction in FIG. 1 ) toward one side of the first direction (right side in FIG. 1 ). The conveyance direction of the conveyor belt 3 is a direction along the first direction. The downstream side of the conveyance direction is the one side in the first direction, and the upstream side of the conveyance direction is the other side in the first direction. The width direction of the conveyor belt 3 is a direction perpendicular to the conveyance direction when the conveyor belt 3 is viewed from above.

[0017] 1 , the gypsum dewatering system 1 further includes an upstream drum 31 arranged upstream in the conveying direction, a downstream drum 32 arranged downstream in the conveying direction, and a motor 33. Each of the upstream drum 31 and the downstream drum 32 is configured to be rotatably supported. The motor 33 is mechanically connected to the downstream drum 32 and configured to rotationally drive the downstream drum 32.

[0018] The conveyor belt 3 is an endless belt-shaped sheet made of a rubber material (a flexible elastic body). The conveyor belt 3 is wrapped around an upstream drum 31 and a downstream drum 32 and is tensioned between the upstream drum 31 and the downstream drum 32. A plurality of drainage grooves extending along the width direction of the conveyor belt 3 may be provided on the outer surface of the conveyor belt 3 at intervals in the conveying direction of the conveyor belt 3. A plurality of holes formed in the conveyor belt 3 to allow moisture to pass through may be formed in the drainage grooves.

[0019] The filter cloth 2 is an endless belt-like piece of breathable resin sheet made of polyester, polypropylene, or another suitable material. The filter cloth 2 has a supported portion 21 at a portion of its length that is superimposed on the upper surface 34 of the conveyor belt 3. The supported portion 21 is supported by the conveyor belt 3 so as to be able to move freely together with the conveyor belt 3 in the conveying direction.

[0020] When power is supplied to the motor 33 from a power source (not shown) and the motor 33 is driven, the upstream drum 31 and the downstream drum 32 are driven to rotate, and the conveyor belt 3 moves in a circular motion. As the conveyor belt 3 moves in a circular motion, the upper surface 34 of the conveyor belt 3 and the supported portion 21 of the filter cloth 2 run downstream in the conveying direction.

[0021] The filter cloth 2 has air permeability that allows moisture to pass through. The conveyor belt 3 has a plurality of holes formed therein for allowing moisture to pass through. When the gypsum slurry placed on the filter cloth 2 is conveyed together with the filter cloth 2 by the conveyor belt 3, moisture (filtrate) passes through the plurality of holes formed in the filter cloth 2 and the conveyor belt 3, and the gypsum is dehydrated. The gypsum generated by dehydrating the gypsum slurry on the filter cloth 2 falls from the downstream end of the conveyor belt 3 and is discharged to the outside of the gypsum dehydration system 1.

[0022] (Gypsum Slurry Supply Line) As shown in Fig. 1 , the gypsum dehydration system 1 further includes a gypsum slurry supply line 12 for sending gypsum slurry from a flue gas desulfurization apparatus 11, which is a supply source of gypsum slurry, onto the filter cloth 2. One end of the gypsum slurry supply line 12 is connected to the flue gas desulfurization apparatus 11, and the other end is provided above (directly above) the supported portion 21 of the filter cloth 2. The gypsum slurry from the flue gas desulfurization apparatus 11 is supplied onto the filter cloth 2 from a supply port 121 provided at the other end of the gypsum slurry supply line 12. The gypsum slurry is homogenized in a supply device 122 provided in the gypsum slurry supply line 12. The gypsum slurry homogenized in the supply device 122 is supplied from the supply port 121 to a predetermined area on the filter cloth 2 at a uniform and constant flow rate.

[0023] (Dehydration Device) The dehydration device 4 is configured to suck the gypsum slurry placed on the filter cloth 2 from below to dehydrate the filtrate. In the illustrated embodiment, the dehydration device 4 includes a dehydration chamber 41 that is provided below the upper surface 34 of the conveyor belt 3 and whose internal pressure is maintained at a negative pressure (a pressure lower than atmospheric pressure), a vacuum pump 42, a depressurization pipe 43 that connects the dehydration chamber 41 and the vacuum pump 42, and a vacuum tank 44 that is provided in the depressurization pipe 43. By supplying power to the vacuum pump 42 from a power source (not shown) and driving the vacuum pump 42, the pressure in the dehydration chamber 41 is reduced to a negative pressure, and the moisture in the gypsum slurry placed on the filter cloth 2 is sucked from below, thereby dehydrating the gypsum slurry.

[0024] (Cleaning Liquid Supply Device) The gypsum slurry transported on the conveyor belt 3 becomes a gypsum cake with a relatively low moisture content during the process of being dehydrated and transported. The cleaning liquid supply device 5 is configured to supply a cleaning liquid to the gypsum cake (gypsum slurry) transported by the conveyor belt 3. The gypsum slurry (gypsum cake) is washed with the cleaning liquid, thereby removing impurities. Examples of the cleaning liquid include industrial water.

[0025] In the illustrated embodiment, the cleaning liquid supply device 5 has a cleaning liquid spraying section 51 (e.g., a spray nozzle), a cleaning liquid supply pipe 52 having one end connected to the cleaning liquid spraying section 51 and the other end connected to a cleaning liquid tank (not shown), a pump 53 provided on the cleaning liquid supply pipe 52, and a cleaning liquid side sheet member 54.

[0026] 2 is a schematic diagram of a gypsum dehydration system 1 according to an embodiment of the present disclosure, viewed from above. The cleaning liquid side sheet member 54 is formed in a flexible sheet shape using a rubber material such as natural rubber, chloroprene rubber, nitrile rubber, ethylene propylene rubber, urethane rubber, or silicone rubber. As shown in FIG. 2, the cleaning liquid side sheet member 54 extends above (directly above) the conveyor belt 3 along the width direction of the conveyor belt 3. As shown in FIG. 1, the cleaning liquid side sheet member 54 is supported at its upper side by another member (a stationary member 55) and hangs down so as to contact the gypsum slurry conveyed by the conveyor belt 3.

[0027] The cleaning liquid jetting unit 51 is disposed above (directly above) the conveyor belt 3 and downstream of the cleaning liquid-side sheet member 54 in the conveying direction of the conveyor belt 3. The cleaning liquid jetting unit 51 is configured to be able to jet the cleaning liquid toward the cleaning liquid-side sheet member 54. By supplying power to the pump 53 from a power source (not shown) and driving the pump 53, the cleaning liquid is sent from the cleaning liquid tank to the cleaning liquid jetting unit 51 and is jetted from the cleaning liquid jetting unit 51 toward the cleaning liquid-side sheet member 54. By jetting the cleaning liquid toward the cleaning liquid-side sheet member 54, it is possible to prevent the gypsum cake layer (gypsum slurry) from collapsing due to the jetted cleaning liquid.

[0028] 3 , the gypsum slurry 100 conveyed by the conveyor belt 3 has a gypsum layer 101 containing gypsum as a main component and laminated on the upper surface of the filter cloth 2, and a moisture layer 103 containing water as a main component and laminated on an upper surface 102 of the gypsum layer 101. According to the inventor's new findings, if the moisture layer 103 is thick, it becomes difficult for air to pass through the filter cloth 2, and the suction force of the dewatering device 4 cannot be sufficiently applied to the gypsum slurry, which may result in a decrease in the dewatering efficiency of the filter cloth 2.

[0029] 3 and 4 are schematic diagrams of the vicinity of the weir 6 of the gypsum dewatering system 1 according to an embodiment of the present disclosure. As shown in Fig. 2 , the at least one weir 6 described above is provided upstream of the position where the cleaning liquid is supplied by the cleaning liquid supply device 5 in the conveying direction of the conveyor belt 3. Specifically, the weir 6 is provided downstream of the downstream end of the supply port 121 in the conveying direction and upstream of the cleaning liquid-side sheet member 54.

[0030] The weir 6 is configured to block the water in the upper layer of the gypsum slurry conveyed by the conveyor belt 3. The weir 6 allows a relatively small amount of water to flow downstream of the weir 6 in the conveyance direction. At least a portion of the weir 6 is located below the upper surface 104 of the moisture layer 103, and is configured to block the moisture layer 103. The weir 6 can remove the moisture layer 103 and impurities contained in the moisture layer 103, thereby obtaining a gypsum layer with a reduced moisture content and a high gypsum concentration.

[0031] The weir 6 blocks the water in the upper layer (moisture layer 103) of the gypsum slurry and reduces the amount of water flowing downstream, making it easier for air to pass through the filter cloth 2. Downstream of the weir 6, the suction force of the dehydration device 4 can sufficiently draw air from above to below the gypsum slurry on the filter cloth 2. As a result, a decrease in the dehydration efficiency of the filter cloth 2 can be suppressed, and gypsum with a desired moisture content can be efficiently obtained.

[0032] (Experimental Results) FIG. 5 is a schematic diagram of a gypsum dehydration system 01 according to a comparative example viewed from above. The gypsum dehydration system 01 according to the comparative example has the same configuration as the gypsum dehydration system 1, except that the weir 6 is not provided. Symbols P1 and P2 in FIG. 2 and P3 and P4 in FIG. 5 indicate experimental results when the operating conditions of the actual gypsum dehydration systems 1 and 01, i.e., the conveying speed of the conveyor belt 3, the supply amount and moisture content of the gypsum slurry from the supply port 121, and the vacuum pressure of the dehydration device 4, were made uniform. In this experiment, the cleaning liquid supply device 5 was stopped. Symbols P1 and P3 indicate the liquid run-out position at the center of the gypsum slurry in the width direction of the conveyor belt 3. Symbols P2 and P4 indicate the liquid run-out positions (positions where the water film on the surface of the gypsum cake was visually confirmed to have disappeared) at both ends of the gypsum slurry in the width direction of the conveyor belt 3. The gypsum dewatering system 1 has better dewatering efficiency than the gypsum dewatering system 01, and the liquid-break position of the gypsum slurry is located on the upstream side in the conveying direction.

[0033] (Sheet Member) In some embodiments, the at least one weir 6 described above includes a sheet member 7 as shown in FIG. 3 . The sheet member 7 is made of a rubber material such as natural rubber, chloroprene rubber, nitrile rubber, ethylene propylene rubber, urethane rubber, or silicone rubber, and is formed into a flexible sheet. The sheet member 7 extends above (directly above) the conveyor belt 3 in the width direction of the conveyor belt 3. As shown in FIG. 3 , the sheet member 7 is supported at its upper part by another member (a stationary member 8) and hangs down so as to contact the gypsum slurry conveyed by the conveyor belt 3.

[0034] 3 , the sheet member 7 includes a lower end portion 71, a curved portion 72 that curves so that the lower end portion 71 is in surface contact with the upper surface 102 of the gypsum layer 101, and a supported portion 73 that is supported by the stationary member 8 above the curved portion 72. Note that a slit may be formed in the lower end portion 71 of the sheet member 7 to allow water to pass through. Furthermore, the sheet member 7 is preferably formed across both ends in the width direction of the conveyor belt 3, but may also be arranged in a portion of the width direction of the conveyor belt 3, or multiple sheet members 7 may be arranged side by side in the width direction of the conveyor belt 3.

[0035] The dam 6 including the sheet member 7 has a simple configuration and can be easily added to an existing gypsum separation device. In addition, the dam 6 including the sheet member 7 has a relatively high ability to block water in the upper layer of the gypsum slurry because the sheet member 7 itself does not allow water to pass through, and can block a large amount of water.

[0036] (Brush Device) In some embodiments, at least one weir 6 described above includes a brush device 9 having a main body 91 and multiple bristle bundle groups 93, as shown in FIG. 4 . The main body 91 extends above (directly above) the conveyor belt 3 in the width direction of the conveyor belt 3. Each of the multiple bristle bundle groups 93 is implanted at intervals along the width direction of the conveyor belt 3 on the lower surface 92 of the main body 91. The bristle bundles constituting the bristle bundle group 93 are made of a synthetic resin material such as polyester or polypropylene and are flexible. Furthermore, the bristle bundles constituting the bristle bundle group 93 have higher rigidity than the sheet member 7. Each of the multiple bristle bundle groups 93 hangs down so as to contact the gypsum slurry conveyed by the conveyor belt 3.

[0037] In the embodiment shown in Figure 4, the main body 91 of each of the multiple bristle bundle groups 93 is supported by another member (stationary member 10) so that the lower end thereof is located below the upper surface 104 of the moisture layer 103 and above the upper surface 102 of the gypsum layer 101. In the embodiment shown in Figure 4, the multiple bristle bundle groups 93 are configured in two stages in the conveying direction of the conveyor belt 3, but in other embodiments, they may be configured in a single stage or in multiple stages of three or more stages. Note that the brush device 9 is preferably formed across both ends of the width direction of the conveyor belt 3, but may be arranged in a portion of the width direction of the conveyor belt 3, or multiple brush devices 9 may be arranged side by side in the width direction of the conveyor belt 3.

[0038] The weir 6 including the brush device 9 has a simple configuration and can be easily retrofitted to an existing gypsum separation device. Furthermore, the weir 6 including the brush device 9 has a lower ability to block the water in the upper layer of the gypsum slurry than the weir 6 including the sheet member 7 because water can pass through the gaps between the bristle bundle groups 93. However, the weir 6 including the brush device 9 does not have a temporary decrease in its ability to block water due to the portion of the sheet member 7 that comes into contact with the gypsum slurry being lifted up by water, as occurs in the weir 6 including the sheet member 7, and therefore has a highly reliable ability to block water.

[0039] 6 is a schematic diagram of a gypsum dewatering system according to an embodiment of the present disclosure, viewed from above. In some embodiments, as shown in FIG. 6 , the at least one weir 6 includes an upstream weir 61 and a downstream weir 62 provided downstream of the upstream weir 61 in the conveying direction of the conveyor belt 3.

[0040] By providing the upstream weir 61 located relatively upstream in the conveying direction, it is possible to suppress a decrease in the dewatering efficiency of the filter cloth 2 over a relatively wide area in the conveying direction. Furthermore, by providing the downstream weir 62, it is possible to block the water in the upper layer of the gypsum slurry that was not blocked by the upstream weir 61, so that gypsum with a desired moisture content can be obtained more reliably.

[0041] As shown in Figures 2 and 6, if the conveying direction position is defined as 0% at the downstream end of the supply port 121 in the conveying direction and 100% at the upstream end of the cleaning liquid side sheet member 54 (cleaning liquid supply device 5), it is preferable that at least one weir 6 is located upstream of the 50% conveying direction position, i.e., the midpoint between the downstream end of the supply port 121 in the conveying direction and the upstream end of the cleaning liquid side sheet member 54 (cleaning liquid supply device 5).

[0042] In some embodiments, the upstream weir 61 is the weir 6 including the sheet member 7 (see FIG. 3 ), and the downstream weir 62 is the brush device 9 (see FIG. 4 ). In this case, by using the weir 6 including the sheet member 7, which has a relatively high ability to block water, as the upstream weir 61, it is possible to suppress a decrease in the dewatering efficiency of the filter cloth 2 over a relatively wide area in the conveyance direction. Furthermore, by using the brush device 9, which has a highly reliable ability to block water, as the downstream weir 62, it is possible to more reliably suppress a decrease in the dewatering efficiency of the filter cloth 2, and more reliably obtain gypsum with a desired moisture content.

[0043] In some embodiments, the upstream weir 61 is the brush device 9 (see FIG. 4 ), and the downstream weir 62 is the weir 6 including the sheet member 7 (see FIG. 3 ). By using the brush device 9, which has a highly reliable ability to block water, as the upstream weir 61, it is possible to reduce the amount of water introduced into the downstream weir 62. By reducing the amount of water introduced into the downstream weir 62, it is possible to prevent the portion of the sheet member 7 that is in contact with the gypsum slurry from being lifted up by the water, and it is possible to improve the reliability of the ability of the downstream weir 62, which is the weir 6 including the sheet member 7, to block water.

[0044] In some other embodiments, both the upstream weir 61 and the downstream weir 62 may be weirs 6 including sheet members 7 (see FIG. 3) or brush devices 9 (see FIG. 4).

[0045] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0046] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0047] The contents of the above-described embodiments can be understood, for example, as follows.

[0048] 1) A gypsum dehydration system (1) according to at least one embodiment of the present disclosure is a gypsum dehydration system (1) for dehydrating a gypsum slurry, the gypsum dehydration system (1) including: a conveyor belt (3) configured to convey the gypsum slurry placed on a filter cloth (2); a dehydrator (4) configured to suck the gypsum slurry conveyed by the conveyor belt (3) from below and dehydrate a filtrate; a cleaning liquid supplying device (5) configured to supply a cleaning liquid to the gypsum slurry conveyed by the conveyor belt (3); and at least one weir (6) that is provided upstream of a supply position of the cleaning liquid by the cleaning liquid supplying device (5) in a conveying direction of the conveyor belt (3) and that blocks water in an upper layer of the gypsum slurry conveyed by the conveyor belt (3).

[0049] According to the above configuration 1), at least one weir (6) blocks the water in the upper layer of the gypsum slurry, reducing the amount of water flowing downstream, thereby facilitating air passage through the filter cloth (2). Downstream of the weir (6), the suction force of the dewatering device (4) can sufficiently draw air downward from above the gypsum cake layer on the filter cloth. As a result, a decrease in the dewatering efficiency of the filter cloth (2) can be suppressed, and gypsum with a desired moisture content can be efficiently obtained.

[0050] 2) In some embodiments, in the gypsum dewatering system (1) described above in 1), the at least one weir (6) includes: an upstream weir (61); and a downstream weir (62) provided downstream of the upstream weir (61) in the conveying direction of the conveyor belt (3).

[0051] According to the above configuration 2), by providing the upstream weir (61) located relatively upstream in the conveying direction, it is possible to suppress a decrease in the dewatering efficiency of the filter cloth (2) over a relatively wide area in the conveying direction. Furthermore, by providing the downstream weir (62), it is possible to block the water in the upper layer of the gypsum slurry that was not blocked by the upstream weir (61), so that gypsum having a desired moisture content can be obtained more reliably.

[0052] 3) In some embodiments, in the gypsum dewatering system (1) described in 1) or 2) above, the at least one weir (6) includes a flexible sheet member (7) that extends above the conveyor belt (3) along the width direction of the conveyor belt (3), is supported at its upper side by another member (8), and hangs down so as to contact the gypsum slurry conveyed by the conveyor belt (3).

[0053] According to the configuration of 3), the weir (6) including the sheet member (7) has a simple configuration and can be easily added to an existing gypsum separation device. Moreover, the weir (6) including the sheet member (7) has a relatively high ability to block water in the upper layer of the gypsum slurry because the sheet member (7) itself does not allow water to pass through, and can block a large amount of water.

[0054] 4) In some embodiments, in the gypsum dewatering system (1) described in 1) or 2) above, the at least one weir (6) includes a brush device (9) having: a main body (91) extending above the conveyor belt (3) along the width direction of the conveyor belt (3); and a plurality of bristle bundles (93) planted on a lower surface (92) of the main body (91) along the width direction of the conveyor belt and hanging down so as to contact the gypsum slurry conveyed by the conveyor belt (3).

[0055] According to the configuration of 4) above, the weir (6) including the brush device (9) has a simple configuration and can be easily retrofitted to an existing gypsum separation device. Furthermore, the weir (6) including the brush device (9) has a lower ability to block the water in the upper layer of the gypsum slurry than the weir (6) including the sheet member (7) because water can pass through the gaps between the bristle bundle groups (93). However, the weir (6) including the brush device (9) does not experience a temporary decrease in its ability to block water due to the portion of the sheet member (7) in contact with the gypsum slurry being lifted up by water, as occurs in the weir (6) including the sheet member (7), and therefore has a highly reliable ability to block water.

[0056] 5) In some embodiments, in the gypsum dewatering system (1) described in 2) above, the upstream weir (61) includes a flexible sheet member (7) that extends above the conveyor belt (3) along the width direction of the conveyor belt (3), is supported at its upper side by another member (8), and hangs down so as to contact the gypsum slurry conveyed by the conveyor belt (3), and the downstream weir (62) includes a brush device (9) that has: a main body portion (91) that extends above the conveyor belt (3) along the width direction of the conveyor belt (3), and a plurality of bristle bundle groups (93) that are implanted on a lower surface (92) of the main body portion (91) along the width direction of the conveyor belt (3) and hang down so as to contact the gypsum slurry conveyed by the conveyor belt (3).

[0057] According to the configuration of 5), by using the weir (6) including the sheet member (7) having a relatively high water blocking ability as the upstream weir (61), it is possible to suppress a decrease in the dewatering efficiency of the filter cloth (2) over a relatively wide area in the conveyance direction. Furthermore, by using the brush device (9) having a highly reliable water blocking ability as the downstream weir (62), it is possible to more reliably suppress a decrease in the dewatering efficiency of the filter cloth (2), and it is possible to more reliably obtain gypsum having a desired moisture content.

[0058] 6) In some embodiments, in the gypsum dewatering system (1) described in 2) above, the upstream weir (61) includes a brush device (9) having: a main body (91) extending above the conveyor belt (3) along the width direction of the conveyor belt (3); and a plurality of bristle bundles (93) implanted on a lower surface (92) of the main body (91) along the width direction of the conveyor belt (3) and hanging down so as to come into contact with the gypsum slurry conveyed by the conveyor belt (3); and the downstream weir (62) includes a flexible sheet member (7) extending above the conveyor belt (3) along the width direction of the conveyor belt (3), supported at its upper side by another member (8), and hanging down so as to come into contact with the gypsum slurry conveyed by the conveyor belt (3).

[0059] According to the configuration of 6), by using the brush device (9) having a highly reliable ability to block water as the upstream weir (61), it is possible to reduce the amount of water introduced into the downstream weir (62). By reducing the amount of water introduced into the downstream weir (62), it is possible to prevent the portion of the sheet member (7) that is in contact with the gypsum slurry from being lifted up by water, and it is possible to improve the reliability of the ability of the downstream weir (62), which is the weir (6) including the sheet member (7), to block water.

[0060] REFERENCE SIGNS LIST 1 Gypsum dehydration system 2 Filter cloth 3 Conveyor belt 4 Dehydration device 5 Cleaning liquid supply device 6 Weir 7 Sheet member 9 Brush device 11 Flue gas desulfurization device 12 Gypsum slurry supply line 21 Supported portion 31 Upstream drum 32 Downstream drum 33 Motor 34 Upper surface 41 Dehydration chamber 42 Vacuum pump 43 Depressurization piping 44 Vacuum tank 51 Cleaning liquid jetting portion 52 Cleaning liquid supply piping 53 Pump 54 Cleaning liquid side sheet member 61 Upstream weir 62 Downstream weir 71 Lower end portion 72 Curved portion 91 Main body portion 92 Lower surface 93 Bristle bundle group 100 Gypsum slurry 101 Gypsum layer 103 Moisture layer 121 Supply port 122 Supply device

Claims

1. A gypsum dehydration system for dehydrating a gypsum slurry, comprising: a conveyor belt configured to convey the gypsum slurry placed on a filter cloth; a dehydrator configured to suck the gypsum slurry conveyed by the conveyor belt from below and dehydrate the filtrate; a cleaning liquid supply device configured to supply a cleaning liquid to the gypsum slurry conveyed by the conveyor belt; and at least one weir that is provided upstream of a supply position of the cleaning liquid by the cleaning liquid supply device in a conveying direction of the conveyor belt, and that blocks water in an upper layer of the gypsum slurry conveyed by the conveyor belt.

2. The gypsum dewatering system according to claim 1, wherein the at least one weir includes: an upstream weir; and a downstream weir provided downstream of the upstream weir in the conveying direction of the conveyor belt.

3. A gypsum dewatering system according to claim 1 or 2, wherein the at least one weir includes a flexible sheet member that extends above the conveyor belt in the width direction of the conveyor belt, is supported at its upper side by another member, and hangs down so as to contact the gypsum slurry conveyed by the conveyor belt.

4. A gypsum dewatering system according to claim 1 or 2, wherein the at least one weir includes a brush device having: a main body extending above the conveying belt in the width direction of the conveying belt; and a plurality of groups of bristle bundles planted on the underside of the main body in the width direction of the conveying belt and hanging down so as to come into contact with the gypsum slurry conveyed by the conveying belt.

5. A gypsum dewatering system as described in claim 2, wherein the upstream weir includes a flexible sheet member that extends above the conveying belt along the width direction of the conveying belt, is supported at its upper side by another member, and hangs down so as to come into contact with the gypsum slurry conveyed by the conveying belt, and the downstream weir includes a brush device having a main body that extends above the conveying belt along the width direction of the conveying belt, and a plurality of groups of bristle bundles that are implanted on the underside of the main body along the width direction of the conveying belt and hang down so as to come into contact with the gypsum slurry conveyed by the conveying belt.

6. The gypsum dewatering system according to claim 2, wherein the upstream weir includes a brush device having a main body extending above the conveying belt in the width direction of the conveying belt and a plurality of bristle bundles implanted on the underside of the main body along the width direction of the conveying belt and hanging down so as to come into contact with the gypsum slurry conveyed by the conveying belt, and the downstream weir includes a flexible sheet member extending above the conveying belt in the width direction of the conveying belt, supported at its upper side by another member, and hanging down so as to come into contact with the gypsum slurry conveyed by the conveying belt.

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