Sludge treatment method

Abstract

To provide a method of treating sludge consisting of larger particles relative to sludge treated in a conventional sludge treatment system, precipitating / accumulating in an effluent storage tank to which water and sludge generated by water-washing a prescribed device are sent.SOLUTION: A sludge treatment method for an effluent treatment facility 1 comprises the steps of: extracting sludge consisting of larger particles relative to sludge contained in water flowing from effluent storage tanks 3, 4 via an effluent treatment system L1, by means of a second sludge treatment system L3, in addition to a first, normal sludge treatment system L2; sending the sludge extracted from the effluent storage tanks 3, 4 and consisting of larger particles directly to a concentration tank 21; sending the sludge consisting of larger particles from the concentration tank 21 to a dehydrator 23 to form cake, and concurrently injecting a flocculant into the sludge consisting of larger particles.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating sludge that has settled and accumulated in a given wastewater storage tank in a wastewater treatment facility of a power generation facility such as a thermal power plant. [Background technology]

[0002] Patent Document 1 shows an example of a wastewater treatment facility equipped with a thickening tank and a dehydrator. In this wastewater treatment facility, a slurry generated by treating flue gas desulfurization wastewater is sent to a thickening tank where it is precipitated and thickened, and then sent to the dehydrator where it is dehydrated to reduce the moisture concentration to a predetermined level and form a cake. The cake is then transported by truck to the outside as industrial waste.

[0003] On the other hand, wastewater treatment facilities at power generation facilities such as thermal power plants may be equipped with two parallel wastewater storage tanks (for example, one may be called wastewater storage tank A and the other may be called wastewater storage tank B) to which water produced by rinsing the air preheater (heat exchanger) is sent to prevent the heat exchanger, called an air preheater (AH), which exchanges heat in the boiler, from becoming clogged with ash or the like, or to eliminate a state in which the heat exchanger has become clogged with ash or the like.

[0004] In these two parallel wastewater storage tanks, as the air preheater (heat exchanger) is repeatedly washed with water, large particles of sludge produced by the washing of the air preheater (heat exchanger) settle and accumulate over time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-127911 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, up until now, there has been no established method for treating the large-particle sludge that settles and accumulates in such wastewater storage tanks. For this reason, it has been necessary to alternately carry out regular inspections of two parallel wastewater storage tanks at regular intervals, for example every two years, but when carrying out regular inspections of one of the wastewater storage tanks, the method adopted has been to transfer the sludge that has settled and accumulated from one tank to the other.

[0007] However, simply transferring the sludge that has settled from one wastewater storage tank to the other is not a final solution to the problem of large-particle sludge that has settled in the wastewater storage tank. Therefore, it is necessary to remove the sludge from the wastewater storage tank and treat the sludge before the wastewater storage tank becomes unable to function due to the settlement and accumulation of sludge, which may result in high sludge treatment costs. In addition, the total amount of large-particle sludge that has settled in both wastewater storage tanks increases over time, which creates the inconvenience of longer times for transferring the sludge from one wastewater storage tank to the other.

[0008] The present invention has been made to solve such problems, and its main object is to provide a sludge treatment method that takes into account the fact that sludge with large particles is heavy and will settle naturally, and therefore does not require a process for making such sludge into a settleable state. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a sludge treatment method, comprising: a wastewater storage tank to which water generated by washing a specified device is sent; and a wastewater treatment system for treating the water sent to the wastewater storage tank. a first sludge treatment system that treats sludge contained in the water that has passed through the wastewater treatment system from the wastewater storage tank; The wastewater treatment system comprises: The wastewater treatment system includes a settling tank for settling sludge contained in the water sent from the wastewater storage tank, and the first sludge treatment system includesThe sludge treatment method is used in a wastewater treatment facility having a dehydrator that dehydrates the sludge to a predetermined moisture concentration to make a cake as equipment constituting a first sludge treatment system, and is characterized by forming a second sludge treatment system having a step of removing sludge from the wastewater storage tank that has larger particles than the sludge contained in the water passing through the wastewater treatment system from the wastewater storage tank, and a step of sending the sludge to the dehydrator in a state in which a coagulant has been injected into the sludge, without passing through the wastewater storage tank to the settling tank of the wastewater treatment system. The wastewater treatment facility is, for example, a wastewater treatment facility possessed by a power generation facility such as a thermal power plant. The predetermined equipment is, for example, a heat exchanger called an air preheater that exchanges heat in a boiler. The wastewater storage tank is, for example, two wastewater storage tanks arranged side by side, one of which is called wastewater storage tank A and the other is called wastewater storage tank B.

[0010] As a result, by forming a second sludge treatment system, it is possible to remove and treat sludge that is generated by washing certain equipment and has larger particles than the sludge contained in the water sent from the wastewater storage tank to the wastewater treatment system from the wastewater storage tank. Moreover, since the sludge with larger particles that has accumulated in the wastewater storage tank to be inspected can be discharged at the timing of the inspection of the wastewater storage tank, it is possible to reduce the cost required for the sludge discharge work. Furthermore, since the dehydrator, which is equipment of the first sludge treatment system, can be used in the process of the second sludge treatment system, no new equipment is required.

[0011] In the sludge treatment method of the present invention, the wastewater treatment facility further comprises, as equipment constituting the first sludge treatment system, a thickening tank to which sludge is sent before it is dewatered by the dehydrator, and as the second sludge treatment system, a process for removing sludge having larger particles from the wastewater storage tank than the sludge contained in the water passing through the wastewater treatment system from the wastewater storage tank and sending it directly to the thickening tank, and a process for injecting the coagulant into the sludge while it is being sent from the thickening tank to the dehydrator.

[0012] This makes it possible to settle in the thickening tank the sludge with larger particles than the sludge contained in the water removed from the wastewater storage tank and sent from the wastewater storage tank to the wastewater treatment system, and the sludge can be smoothly transferred from the thickening tank to the dehydrator using a pump installed in the thickening tank and piping connecting the thickening tank and the dehydrator. Moreover, since the thickening tank and its peripheral equipment, which are the equipment of the first sludge treatment system, can be used in the process of the second sludge treatment system, no new equipment is required. Effect of the Invention

[0013] As described above, according to the sludge treatment method of the present invention, it is possible to remove and treat sludge generated by washing a certain appliance, which has larger particles than the sludge contained in the water passing from the wastewater tank through the wastewater treatment system, from the wastewater tank by forming a second sludge treatment system. Moreover, when the wastewater tank is inspected, the sludge with larger particles that has accumulated in the wastewater tank can be discharged. This reduces the cost of treating the sludge that has settled and accumulated in the wastewater tank.

[0014] In particular, according to the sludge treatment method of the invention of claim 2, it is possible to settle in a thickening tank sludge having larger particles than the sludge contained in the water sent from the wastewater storage tank to the wastewater treatment system, and the sludge can be smoothly transported from the thickening tank to the dehydrator by using a pump provided in the thickening tank and piping connecting the thickening tank and the dehydrator. [Brief description of the drawings]

[0015] [Figure 1] As an example of a wastewater treatment facility to which the present invention is applied, this is a schematic diagram showing a part of a wastewater treatment system, a first sludge treatment system, and a second sludge treatment system, and showing an embodiment in which sludge with large particles is sent from wastewater storage tanks A and B to a thickening tank without passing through the wastewater system. [Diagram 2]1 is a schematic diagram showing an example of the transport of large-particle sludge in the second sludge treatment system, where (a) shows the process of removing large-particle sludge from the wastewater storage tank, and (b) shows the process of sending the removed large-particle sludge directly to the thickening tank. [Diagram 3] As another example of a wastewater treatment facility to which the present invention can be applied, this is a schematic diagram showing a part of a wastewater treatment system, a first sludge treatment system, and a second sludge treatment system, and showing an embodiment in which sludge with large particles is sent from the A and B wastewater storage tanks to a dehydrator without passing through the wastewater system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] An example of a wastewater treatment facility 1 that is included in a power generation facility such as a thermal power plant is shown in Fig. 1. Fig. 1 shows only a portion of the equipment related to the present invention, rather than the entire equipment of the wastewater treatment facility 1.

[0018] The wastewater treatment facility 1 has, for example, an A wastewater storage tank 3 and a B wastewater storage tank 4 to which water and the like are sent from a wastewater pit 2. The wastewater pit 2 is used to receive cleaning water and the like generated by washing a heat exchanger (not shown) called an air preheater that performs heat exchange in a boiler, and the cleaning water is sent from the wastewater pit 2 to either or both of the A wastewater storage tank 3 and the B wastewater storage tank 4. In other words, the cleaning water for the heat exchanger contains ash, rust, and the like that have accumulated in the heat exchanger due to clogging and the like, and as shown in FIG. 2(a), these have been precipitated and accumulated as sludge S of relatively large particles in the A wastewater storage tank 3 and the B wastewater storage tank 4.

[0019] In this embodiment, the A drainage tank 3 and the B drainage tank 4 are drainage tanks with an open top, as shown in part in Fig. 2(a), and the A drainage tank 3 and the B drainage tank 4 are arranged in parallel, separated into two by a partition wall (not shown). In Fig. 1, valves 5, 6, and 7 are provided on the piping connecting the drainage pit 2 and the A drainage tank 3 and the B drainage tank 4, but the number and arrangement of the valves are not limited to those shown in Fig. 1 as long as water, etc. can be sent from the drainage pit 2 to one or both of the A drainage tank 3 and the B drainage tank 4. Although not shown, the A drainage tank 3 and the B drainage tank 4 are appropriately connected to a boiler water tank, a drainage tank pump, etc., so that water, etc. is sent to the A drainage tank 3 and the B drainage tank 4, and valves are provided on the piping route.

[0020] In this embodiment, the wastewater treatment facility 1 includes a pH adjustment tank 10, a coagulation tank 11, a settling tank 12, an intermediate water tank 13, and a filter 14 as equipment constituting a wastewater treatment system L1 for performing wastewater treatment on the water sent to the A wastewater storage tank 3 and the B wastewater storage tank 4. The pH adjustment tank 10, the coagulation tank 11, the settling tank 12, the intermediate water tank 13, and the filter 14 are part of the wastewater treatment system L1.

[0021] Water containing sludge with relatively small particles is sent from the A wastewater storage tank 3 and the B wastewater storage tank 4 by pumps 8 and 9 to a pH adjustment tank 10, where the pH of the water is adjusted by adding chemicals, and then flocs are formed in a coagulation tank 11 by adding chemicals. The water treated in the coagulation tank is then sent to a settling tank 12, where even the sludge with relatively small particles settles and accumulates in the lower part of the settling tank 12. The topside water separated from the sludge in the settling tank 12 is sent to an intermediate tank 13, and then further sent to a filter 14 by a pump 15, where foreign matter is removed, and then sent to a facility (not shown) that constitutes the wastewater treatment system L1 by a pump 16. In this embodiment, a valve 17 is arranged in the path between pump 8 and pH adjustment tank 10 in the piping, a valve 18 is arranged in the path between pump 9 and pH adjustment tank 10 in the piping, a valve 19 is arranged in the path on the filter 14 side of the piping relative to pump 16, and a valve 20 is arranged in the path on the opposite side of the piping relative to pump 16 from the filter 14.

[0022] In this embodiment, the wastewater treatment facility 1 has a thickening tank 21, a flocculant solution tank 22, and a dehydrator 23 as equipment constituting a normal first sludge treatment system L2 for treating sludge separated from water in the sedimentation tank 12. The thickening tank 21 is for thickening the sludge sent from the bottom of the sedimentation tank 12 by a pump 24, and is a tank with an open top as shown in FIG. 2(b). When the sludge passes through a pipe connecting the pump 24 and the thickening tank 21, a flocculant sent from the flocculant solution tank 22 by a pump 25 is added to the sludge and sent to the thickening tank 21. The sludge is then sent from the bottom of the thickening tank 21 to the dehydrator 23 by a pump 26, and is dehydrated to a predetermined moisture content in the dehydrator 23 to become a cake, and then sent to cake hoppers 29 and 30 by belt conveyors 27 and 28, and transported outside the wastewater treatment facility 1 as industrial waste. The dehydrator 23 can be of the centrifugal type or the belt type, which squeezes the sludge between two belts to extract water. The belt type is more preferable because the centrifugal type may become clogged with large sludge particles.

[0023] In this embodiment, valve 31 is arranged in the path on the sedimentation tank 12 side of the piping relative to pump 24, valve 32 is arranged in the path on the concentration tank 21 side of the piping relative to pump 24, valve 33 is arranged in the path on the coagulant dissolution tank 22 side of the piping relative to pump 25, valve 34 is arranged in the path on the opposite side of the coagulant dissolution tank 22 relative to pump 25, valve 35 is arranged in the path on the concentration tank 21 side of the piping relative to pump 26, and valve 36 is arranged in the path on the dehydrator 23 side of the piping relative to pump 26.

[0024] In the present invention, the wastewater treatment facility 1 has a second sludge treatment system L3 that treats sludge without passing through the wastewater treatment system L1. The second sludge treatment system L3 is adapted to treat sludge S having larger particles than the sludge contained in the water that passes through the wastewater treatment system L1 from the A wastewater storage tank 3 and the B wastewater storage tank 4.

[0025] More specifically, the second sludge treatment system L3 is a sludge treatment method including a step of removing the sludge S that has settled and accumulated in the A wastewater storage tank 3 and the B wastewater storage tank 4 from the A wastewater storage tank 3 and the B wastewater storage tank 4, and a step of sending the removed sludge S directly to the thickening tank 21 constituting the first wastewater treatment system L2, without passing through the A wastewater storage tank 3, the B wastewater storage tank 4 and the settling tank 12 of the wastewater treatment system L1. As in the first sludge treatment system L2, the sludge S sent to the thickening tank 21 also includes a step of adding a flocculant sent by a pump 25 from the flocculant dissolving liquid tank 22 when passing through a pipe extending from the thickening tank 21 to the dehydrator 23, so that the sludge S is sent to the dehydrator 23 and turned into a cake, and can then be treated as industrial waste.

[0026] Since the particles of the sludge S are larger and heavier than those of the sludge that passes through the wastewater treatment system L1, the sludge will settle naturally, and therefore no process is required to prepare the sludge for settling. Therefore, it is possible to carry out sludge treatment of the sludge S after the thickening tank 21 without passing through the settling tank 12.

[0027] 1, a vehicle 100 having a suction / discharge device 101 called a probester is used in the process of removing sludge S from the A wastewater storage tank 3 and the B wastewater storage tank 4, as shown in FIG. 2(a). The vehicle 100 operates the suction / discharge device 101 with the tip 103 of a hose 102 extending from the suction / discharge device 101 reaching the sludge S in the A wastewater storage tank 3 and the B wastewater storage tank 4, and takes in the sludge S into the suction / discharge device 101. As a result, the sludge S is removed from the A wastewater storage tank 3 and the B wastewater storage tank 4. The vehicle 100 that has taken in the sludge S into the suction / discharge device 101 moves from the A wastewater storage tank 3 and the B wastewater storage tank 4 to the thickening tank 21 as shown by the thick dashed line in FIG. 1, and then, for example, as shown in FIG. 2(b), the tip 103 of the hose 102 extending from the suction / discharge device 101 is inserted into the thickening tank 21 to send the sludge S to the thickening tank 21 from above. As described above, the sludge S is large and heavy, so it settles directly to the bottom of the thickening tank 21. By using such a second wastewater treatment system L3, it is possible to use the thickening tank 21 and the dehydrator 23 of the first wastewater treatment facility, and further to use the existing route for injecting the flocculant from the flocculant dissolving liquid tank 22. Moreover, at the timing of inspection such as regular inspection of the A wastewater storage tank 3 and the B wastewater storage tank 4, it is possible to discharge the sludge with large particles that has accumulated in the wastewater storage tanks 3 and 4 to be inspected. Therefore, it is possible to reduce the cost associated with the adoption of the second wastewater treatment system L3.

[0028] Fig. 3 shows an embodiment using a second drainage system L3 different from the second drainage system L3 shown in Fig. 1. The second drainage system L3 shown in Fig. 3 is suitable for the case where the wastewater treatment facility 1 itself is newly constructed, for example, and the sludge S is sent directly to the dehydrator 23 without passing through the thickening tank 21.

[0029] In the second wastewater treatment system L3 in Fig. 3, the sludge S that has settled and accumulated in the A wastewater storage tank 3 and the B wastewater storage tank 4 is removed from the A wastewater storage tank 3 and the B wastewater storage tank 4 by a process of sucking up the sludge S from the A wastewater storage tank 3 and the B wastewater storage tank 4 using pumps 41 and 42. The pumps 41 and 42 may be, for example, submersible pumps installed in the wastewater storage tanks 3 and 4, or pump vehicles that can move on rails laid around the periphery of the wastewater storage tanks 3 and 4.

[0030] In this embodiment, the pumps 41 and 42 are connected to the dehydrator 23 by piping, and thus a process is performed in which the sludge S removed from the A wastewater storage tank 3 and the B wastewater storage tank 4 by the pumps 41 and 42 is sent to the dehydrator 23 through the piping. Then, the flocculant sent by the pump 43 from the flocculant dissolving liquid tank 22 is injected into the sludge S between the pumps 41 and 42 and the dehydrator 23. As a result, even in the wastewater treatment system L3 in Fig. 3, the sludge S is sent to the dehydrator 23 with the flocculant injected, and is appropriately turned into cake in the dehydrator 23 and transported to the outside as industrial waste.

[0031] In this embodiment, a valve 44 is arranged in the path between the pump 41 of the piping and the dehydrator 23, a valve 45 is arranged in the path between the pump 42 of the piping and the dehydrator 23, a valve 46 is arranged in the path on the coagulant dissolution tank 22 side of the piping relative to the pump 43, and a valve 47 is arranged in the path on the opposite side of the coagulant dissolution tank 22 relative to the pump 43 of the piping.

[0032] In addition, in the wastewater treatment facility 1 shown in Figure 1, pumps 41, 42 (not shown) may be provided, and piping may be provided to transport the sludge S removed from the A wastewater storage tank 3 and the B wastewater storage tank 4 to the concentration tank 21, so that the sludge is sent into the concentration tank 21 from an opening of the piping. [Explanation of symbols]

[0033] 1 Wastewater treatment facilities 3A wastewater storage tank 4 B wastewater storage tank 12 Sedimentation tank 21 Concentrator 23 Dehydrator L1 Wastewater treatment system L2 First sludge treatment system L3 Second sludge treatment system S sludge

Claims

1. a wastewater storage tank to which water generated by flushing a predetermined appliance is sent, a wastewater treatment system that treats the water sent to the wastewater storage tank, and a first sludge treatment system that treats sludge contained in the water that has passed from the wastewater storage tank through the wastewater treatment system; The wastewater treatment system includes a settling tank for settling sludge contained in the water sent from the wastewater storage tank as a component of the wastewater treatment system, The first sludge treatment system is a sludge treatment method used in a wastewater treatment facility having a dehydrator that dehydrates the sludge to a predetermined moisture concentration to form a cake as equipment constituting the first sludge treatment system, A sludge treatment method characterized by forming a second sludge treatment system, the method comprising the steps of: removing sludge from the wastewater storage tank, the sludge having larger particles than the sludge contained in the water passing through the wastewater treatment system from the wastewater storage tank; and sending the sludge to the dehydrator after injecting a coagulant into the sludge, without passing through the wastewater treatment system from the wastewater storage tank to the settling tank.

2. The wastewater treatment facility further includes a thickening tank to which sludge before being dewatered by the dehydrator is sent as equipment constituting the first sludge treatment system, The sludge treatment method according to claim 1, characterized in that the second sludge treatment system includes a step of removing sludge having larger particles than the sludge contained in the water passing through the wastewater treatment system from the wastewater storage tank and sending it directly to the thickening tank, and a step of injecting the coagulant into the sludge while the sludge is being sent from the thickening tank to the dewatering machine.

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