Water treatment method

Abstract

To provide a water treating method which can treat inflow water to a prescribed desulfurizer pit that is performing a treatment by utilizing an absorption tower of an exhaust gas desulfurizer without utilizing the absorption tower of the exhaust gas desulfurizer, and suppresses the operation of the denitrogenation treatment by a denitrogenation treatment device.SOLUTION: A water treating method feeds inflow water to a gypsum slurry pit 40 and inflow water to an A absorbent pit 41 to a B absorbent pit 42, converges them to inflow water to the B absorbent pit 42 to make treatment water, measures (60) the water quality of supernatant water after feeding the supernatant water obtained by making a foreign matter of the treatment water precipitated in the B absorbent pit 42 to a drain pit 43 by a submerged pump SP1 from the B absorbent pit 42, and directly feeds the supernatant water that has such a measurement result that it has the water quality that does not require the denitrogenation treatment to an A drain storage tank 10 and a B drain storage tank 11 being facilities in the previous stage of the heavy metal treatment from the drain pit 43.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for treating influent water flowing into a predetermined desulfurization device pit, which was recovered in an absorption tower of a flue gas desulfurization device and vaporized by the heat of exhaust gas in the absorption tower and then discharged to the outside, without using the absorption tower of the desulfurization device.

Background Art

[0002] In thermal power generation facilities, power is generated by burning fuel in a boiler. Since sulfur oxides are contained in the exhaust gas generated by the combustion of the fuel, as shown in, for example, Patent Document 1, after removing sulfur oxides from the exhaust gas with a flue gas desulfurization device, it has been discharged into the atmosphere from a chimney. In such a flue gas desulfurization device, the generated exhaust gas is guided to an absorption tower and brought into contact with an absorption liquid to absorb and remove sulfur oxides.

[0003] And, as shown in FIG. 4 of this case, for example, the influent water flowing into the gypsum slurry pit 100, which is a desulfurization device pit, passes through the absorption liquid pits 101 and 102, which are also desulfurization device pits, and together with the influent water flowing into the absorption liquid pits 101 and 102, is recovered by the absorption tower 103 of the flue gas desulfurization device. Thus, after being vaporized by the heat of the exhaust gas in the absorption tower, it can be treated in a form of being discharged to the outside. Note that the influent water flowing into the gypsum slurry pit 100 is, for example, blow water from a gypsum thickener or rainwater, and the influent water flowing into the absorption liquid pits 101 and 102 is blow water from an absorption tower circulation pump or rainwater, etc. Although these are not shown in the gypsum slurry pit 40, the A absorption liquid pit 41, and the B absorption liquid pit 42 in FIG. 3 of this case to which the present invention is applied, the situation is the same.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in recent years, the operating rate of the flue gas desulfurization device has decreased, and the downtime of the flue gas desulfurization device has increased and become longer. For this reason, the treatment of the influent water to the predetermined desulfurization device pits such as the gypsum slurry pit and the absorption liquid pit by the absorption tower of the flue gas desulfurization device has also come to a standstill. If the stagnation of the treatment of the influent water to the predetermined desulfurization device pit by the absorption tower of the flue gas desulfurization device is left unattended, the amount of water that flows in and is stored may exceed the possible amount of water in the predetermined desulfurization device pit, and there is a risk that the water overflowing from these predetermined desulfurization device pits may inadvertently flow out towards the equipment of other systems. For this reason, it is necessary to perform necessary treatment while moving the flowing water to the predetermined desulfurization device pit to a water storage facility such as a storage tank without using the absorption tower of the flue gas desulfurization device.

[0006] In this regard, conventionally, when the influent water to the predetermined desulfurization device pit cannot be recovered and treated by the absorption tower of the flue gas desulfurization device, as a method of treating the water, from the predetermined desulfurization device pit, through the drainage pit for the desulfurization device, it is sent to a storage tank which is the pre-facility for denitrification treatment, and then from such a storage tank to a denitrification treatment device. After the denitrification treatment is performed by the denitrification treatment device, it is sent to a drainage storage tank which is the pre-facility for heavy metal treatment, and further, by being sent from such a drainage storage tank to a heavy metal treatment device, heavy metal treatment may be performed. However, in this wastewater treatment method, since the denitrification treatment device performs denitrification treatment on all the water sent from the predetermined desulfurization device pit, there is a problem that the cost of operating the denitrification treatment device increases.

[0007] The main object of the present invention is to provide a water treatment method that can treat the influent water to a predetermined desulfurization device pit that has been treated using the absorption tower of a flue gas desulfurization device without using the absorption tower of the flue gas desulfurization device and suppresses the operation of the denitrification treatment by the denitrification treatment device.

Means for Solving the Problems

[0008] In order to achieve the above object, the water treatment method of the present invention is a water treatment method for treating the influent water flowing into the first, second, and third desulfurization device pits that can be recovered in the absorption tower of the flue gas desulfurization device and treated using the heat of the exhaust gas in the absorption tower by using a wastewater treatment system. The influent water flowing into the first desulfurization device pit and the influent water flowing into the second desulfurization device pit are sent to the third desulfurization device pit and aggregated with the influent water flowing into the third desulfurization device pit to form treated water. At the same time, the supernatant water obtained by precipitating foreign substances in the treated water in the third desulfurization device pit is sent from the third desulfurization device pit to the wastewater pit for the desulfurization device by a pump. After that, the water quality of the supernatant water is measured, and the supernatant water for which the measurement result shows that the water quality does not require denitrification treatment is directly sent from the wastewater pit to the wastewater storage tank, which is a facility at the pre-stage of heavy metal treatment in the wastewater treatment system. The first desulfurization device pit is, for example, a gypsum slurry pit. The second desulfurization device pit is, for example, an A absorption liquid pit. The third desulfurization device pit is, for example, a B absorption liquid pit. The foreign substances precipitated in the third desulfurization device pit are, for example, gypsum slurry components. The pump for sending the supernatant water from the third desulfurization device pit to the wastewater pit for the desulfurization device is, for example, a submersible pump newly installed in the water of the influent water stored in the third desulfurization device pit. The water quality that does not require denitrification treatment refers to, for example, the water quality in which the total nitrogen (T-N) value obtained by measurement is lower than a predetermined reference value.

[0009] As a result, the supernatant water obtained by precipitating foreign substances from the treated water in which the influent water flowing into and stored in the first desulfurization unit pit, the influent water flowing into and stored in the second desulfurization unit pit, and the influent water flowing into and stored in the third desulfurization unit pit are aggregated in the third desulfurization unit pit has a water quality that does not require denitrification treatment. Therefore, when being sent to the drainage storage tank, which is the equipment in the previous stage of the heavy metal treatment in the drainage treatment system, it can be used as dilution water for the defluorinated drainage instead of the industrial water that has been used so far. And the supernatant water obtained by precipitating foreign substances from the treated water in which the influent water flowing into and stored in the first desulfurization unit pit, the influent water flowing into and stored in the second desulfurization unit pit, and the influent water flowing into and stored in the third desulfurization unit pit are aggregated in the third desulfurization unit pit becomes a part of the drainage to be treated in the drainage treatment system later. So, after being sent from the drainage storage tank to the heavy metal treatment device for heavy metal treatment, it is discharged into waters such as the sea area. Moreover, if the measurement result shows that denitrification treatment is not necessary for the supernatant water, the denitrification treatment by the denitrification device becomes unnecessary.

[0010] On the other hand, in the water treatment method of the present invention, the supernatant water for which the measurement result shows that the water quality requires denitrification treatment is sent from the drainage pit to a storage tank, which is the equipment in the previous stage of the denitrification treatment, and then further sent from the storage tank to a denitrification treatment device. After the denitrification treatment by the denitrification device, it is sent to the drainage storage tank via a drainage tank. The water quality that requires denitrification treatment refers to, for example, the water quality in which the total nitrogen (T-N) value obtained by measurement is higher than a predetermined reference value.

[0011] This prevents the supernatant water with a water quality that requires denitrification treatment from being sent to the drainage storage tank, which is the equipment in the previous stage of the heavy metal treatment in the drainage treatment system, without undergoing denitrification treatment.

Advantages of the Invention

[0012] As described above, according to the water treatment method of the present invention, if the supernatant water obtained by precipitating foreign substances from the treated water in which the influent water flowing into and stored in the first desulfurization device pit, the influent water flowing into and stored in the second desulfurization device pit, and the influent water flowing into and stored in the third desulfurization device pit are aggregated in the third desulfurization device pit is measured to have a water quality that does not require denitrification treatment, when it is sent to the drainage storage tank which is a facility in the previous stage of heavy metal treatment in the drainage treatment system, it can be used as dilution water for the defluorinated drainage instead of the industrial water that has been used so far.

[0013] And the supernatant water obtained by separating foreign substances from the treated water in which the influent water flowing into and stored in the first desulfurization device pit, the influent water flowing into and stored in the second desulfurization device pit, and the influent water flowing into and stored in the third desulfurization device pit are aggregated in the third desulfurization device pit becomes a part of the drainage to be treated in the drainage treatment system later. After being sent from the drainage storage tank to the heavy metal treatment device for heavy metal treatment, it is discharged into waters such as the sea area. For this reason, regarding the influent water to a predetermined desulfurization device pit that has been treated using the absorption tower of the flue gas desulfurization device, it can be treated without using the absorption tower of the flue gas desulfurization device.

[0014] Moreover, if the measurement result shows that denitrification treatment is not necessary for the supernatant water, the denitrification treatment by the denitrification device becomes unnecessary. Therefore, compared with the case of performing denitrification treatment on all of the influent water to a predetermined desulfurization device pit that has been treated using the absorption tower of the flue gas desulfurization device, it is possible to reduce the operation time of the denitrification device, so that an increase in the cost for water treatment can be suppressed.

[0015] In particular, according to the water treatment method of the invention according to claim 2, it is possible to prevent the supernatant water with a water quality that requires denitrification treatment from being sent to the drainage storage tank which is a facility in the previous stage of heavy metal treatment in the drainage treatment system without denitrification treatment, and thus causing problems in the subsequent drainage treatment by the drainage system.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0018] In FIGS. 1 and 2, an example of equipment 1 of a power generation facility such as a thermal power plant is shown. The equipment 1 of the power generation facility shown in FIGS. 1 and 2 is not all of the equipment (tanks, devices, etc.) used for heavy metal treatment, defluorination treatment, denitrification treatment, desulfurization treatment, etc., but a part related to the present invention is shown.

[0019] The wastewater that requires defluorination treatment forms part of the wastewater treatment system and is sent to the C storage tank 2, which is the equipment at the pre-stage of defluorination treatment. Further, it is sent from the C storage tank 2 to the defluorination treatment device 3 by the pump P1, and defluorination treatment is performed in the defluorination treatment device 3. Also, the wastewater that requires denitrification treatment forms part of the wastewater treatment system and is sent to the D storage tank 5, which is the equipment at the pre-stage of denitrification treatment. Further, it is sent from the D storage tank 5 to the denitrification treatment device 6 by the pump P2, and after denitrification treatment is performed in the denitrification treatment device 6, it is sent to the wastewater tank 7.

[0020] Then, the wastewater subjected to defluorination treatment and the wastewater subjected to denitrification treatment form part of the wastewater treatment system, as shown in FIG. 2 below, and are sent to the A wastewater storage tank 10 and the B wastewater storage tank 11, which are the equipment at the pre-stage of heavy metal treatment. Further, they are sent from the A wastewater storage tank 10 and the B wastewater storage tank 11 to the heavy metal treatment device 12 by the pumps P3 and P4, and heavy metal treatment is performed in the heavy metal treatment device 12. The wastewater subjected to heavy metal treatment is sent to the discharge pit 26 by the pump P5 and then discharged into waters such as the sea area. The system mainly for heavy metal treatment in this wastewater treatment system will be described in detail below with reference to FIG. 2. The range surrounded by the broken line in FIG. 2 corresponds to the heavy metal treatment device 12.

[0021] As shown in FIG. 2, in the system mainly for heavy metal treatment in the wastewater treatment system, the wastewater is sent from the A wastewater storage tank 10 and the B wastewater storage tank 11, which are also shown in FIG. 1, to the pH adjustment tank 13 and the condensation tank 14 in sequence by the pumps P3 and P4, then sludge sedimentation is performed in the sedimentation tank 15, and it is sent to the intermediate water tank 16. Then, the wastewater is sent from the intermediate water tank 16 to the filter 17 by the pump P6, and after being filtered by the filter 17, it passes through the backwash water tank 18, the pH adjustment tank 19, and the retention tank 20, and is sent to the adsorption towers 21 and 22 by the pump P7. Further, the wastewater sent to the adsorption towers 21 and 22 passes through at least the neutralization tank 23, the treatment water tank 24, and the monitoring tank 25, and is sent to the discharge pit 26 by the pump P5. Then, after the water quality is confirmed at the discharge pit 26, it is discharged into the sea.

[0022] The sludge that has settled downward in the sedimentation tank 15 is sent to the thickening tank 30 by the pump P8 as part of the sludge treatment system in the wastewater treatment system as shown in Fig. 2, where it is thickened. Then, while the flocculant is being added from the flocculant dissolution tank 31 using the pump P9 on the way, it is sent to the dehydrator 32 by the pump P10, dehydrated in the dehydrator 32, and discharged to the outside as a cake.

[0023] In Figs. 1 and 3, the gypsum slurry pit 40, the A absorption liquid pit 41, the B absorption liquid pit 42, and the drainage pit 43, which form the main configuration of this invention, are shown. In Fig. 1, the gypsum thickener 45 is also shown. In this embodiment, the first desulfurization device pit described in the claims corresponds to the gypsum slurry pit 40, the second desulfurization device pit described in the claims corresponds to the A absorption liquid pit 41, and the third desulfurization device pit described in the claims corresponds to the B absorption liquid pit 42.

[0024] In this embodiment, the gypsum slurry pit 40 is a pit into which blow water from the gypsum thickener 45, rainwater 46, etc. flow as influent water, and water containing gypsum slurry is stored. Accordingly, the gypsum slurry pit 40 is configured to have a stirring device 49 that stirs to prevent the gypsum slurry from settling, and a pump P11 for sending the influent water containing the gypsum slurry to the B absorption liquid pit 42 described later.

[0025] In this embodiment, the A absorption liquid pit 41 is a pit into which blow water 47 from an absorption tower circulation pump (not shown), rainwater 48, etc. flow as influent water, and is configured to have a stirring device 50 for preventing the precipitation of foreign substances, and a pump P12 for sending the influent water to the B absorption liquid pit 42 described later.

[0026] In this embodiment, the B absorption liquid pit 42 is similar to the A absorption liquid pit 41 in that blow water 47 from an absorption tower circulation pump (not shown), rainwater 48, etc. flow in as influent water. However, as described above, it is also a pit into which the influent water to the gypsum slurry pit 40 and the influent water to the A absorption liquid pit 41 are sent. That is, the B absorption liquid pit 42 is a pit that aggregates not only the influent water to itself but also the influent water to the gypsum slurry pit 40 and the influent water to the A absorption liquid pit 41 as treated water. The B absorption liquid pit 42 has no stirring device for preventing the precipitation of foreign substances, or even if there is one, its operation is stopped. In this embodiment, the stirring device 51 of the B absorption liquid pit 42 is stopped even if it exists. Thereby, in the B absorption liquid pit 42, for example, the influent water sent from the gypsum slurry pit 40 can be separated into the supernatant water above and the gypsum slurry sedimented below. In this embodiment, the B absorption liquid pit 42 has a submersible pump SP1 in the water in the tank for sending the supernatant water to the drain pit 43.

[0027] In this embodiment, the drain pit 43 receives, for example, the same as in the prior art, the drainage such as flue gas washing water and heat medium circulation type gas-gas heater (GGH) washing water, and newly receives the supernatant water of the treated water (the water aggregated from the influent water to the gypsum slurry pit 40, the influent water to the A absorption liquid pit 41, and the influent water to the B absorption liquid pit 42) sent from the B absorption liquid pit 42 by the submersible pump SP1. The drain pit 43 is configured to have a stirring device 52 for preventing the precipitation of foreign substances and a pump P13 for sending it to the storage tanks (A drain storage tank 10, B drain storage tank 11, or D storage tank 5) constituting the drainage treatment system.

[0028] As a result, the influent water flowing into the gypsum slurry pit 40 is sent to the B absorbent liquid pit 42 by operating the pump P11, and the influent water flowing into the A absorbent liquid pit 41 is sent to the B absorbent liquid pit 42 by operating the pump P12. Together with the influent water flowing into the B absorbent liquid pit 42 itself, they are aggregated to become treated water. This treated water is separated into the upper clarified water and the gypsum slurry component precipitated below when the stirring device 51 of the B absorbent liquid pit 42 does not operate. Then, the clarified water is sent to the drainage pit 43 by operating the submersible pump SP1.

[0029] And in this embodiment, as shown by the two dashed arrows in FIG. 3, as the water quality measurement of the stored water containing the clarified water in the drainage pit 43 or the water containing the clarified water sent out from the drainage pit 43 by the pump P13, the measurement 60 of the total nitrogen (T-N) value is performed.

[0030] As a result of the measurement 60, if the total nitrogen (T-N) value is lower than a predetermined standard and the water quality does not require denitrification treatment, the direct discharge destinations of the water from the drainage pit 43 are the A drainage storage tank 10 and the B drainage storage tank 11 as shown in FIG. 3 and FIGS. 1 and 2. Such water with good water quality from the drainage pit 43 can be used as dilution water for the drainage treated by the defluorination treatment device 3 instead of the industrial water that has been used so far when being sent to the A drainage storage tank 10 and the B drainage storage tank 11. After the clarified water flows into the A drainage storage tank 10 and the B drainage storage tank 11, it becomes part of the drainage, is subjected to heavy metal treatment by the heavy metal treatment device 12 forming the drainage treatment system, and then is sent to the discharge pit 26 and discharged into the sea area.

[0031] As a result of measurement, if the total nitrogen (T-N) value is higher than a predetermined standard and the water quality requires denitrification treatment, the direct discharge destination of the water from the drain pit 43 is the D storage tank 5 as shown in FIG. 3 and FIG. 1 above. Then, it is sent from the D storage tank 5 to the denitrification treatment device 6, and after denitrification treatment in the denitrification treatment device 6, it passes through the drain tank 7 and is sent as drainage to the A drain storage tank 10 and the B drain storage tank 11. The treatment using the subsequent drainage treatment system is the same as when it is directly sent from the drain pit 43 to the A drain storage tank 10 and the B drain storage tank 11. Note that whether the total nitrogen (T-N) value is higher than a predetermined standard and the water quality requires denitrification treatment may be affected by the amount of rainwater flowing into the gypsum slurry pit 40, the A absorption liquid pit 41, and the B absorption liquid pit 42, respectively.

[0032] As described above, according to the water treatment method of the present invention, it is possible to treat the water flowing into the gypsum slurry pit 40, the water flowing into the A absorption liquid pit 41, and the water flowing into the B absorption liquid pit 42 without using the absorption tower of the desulfurization device.

Explanation of symbols

[0033] 5 D storage tank (storage tank) 6 Denitrification treatment device 7 Drain tank 10 A drain storage tank (drain storage tank) 11 B drain storage tank (drain storage tank) 12 Heavy metal treatment device 40 Gypsum slurry pit (first desulfurization device pit) 41 A absorption liquid pit (second desulfurization device pit) 42 B absorption liquid pit (third desulfurization device pit) 43 Drain pit (drain pit for desulfurization device) 60 Measurement of total nitrogen (T-N) value SP1 Pump (submersible pump)

Claims

1. A water treatment method for treating the influent water flowing into the first, second, and third desulfurization device pits, which can be recovered in the absorption tower of a flue gas desulfurization device and treated by utilizing the heat of the exhaust gas in the absorption tower, by using a wastewater treatment system, comprising: sending the influent water flowing into the first desulfurization device pit and the influent water flowing into the second desulfurization device pit to the third desulfurization device pit, aggregating them with the influent water flowing into the third desulfurization device pit to obtain treated water, and after precipitating foreign substances in the treated water in the third desulfurization device pit, sending the supernatant water obtained to the drainage pit for the desulfurization device by a pump from the third desulfurization device pit, then measuring the water quality of the supernatant water, and directly sending the supernatant water for which the measurement result shows that the water quality does not require denitrification treatment from the drainage pit to a drainage storage tank which is a facility in the previous stage of heavy metal treatment in the wastewater treatment system. A water treatment method characterized by this.

2. Sending the supernatant water for which the measurement result shows that the water quality requires denitrification treatment from the drainage pit to a storage tank which is a facility in the previous stage of denitrification treatment, further sending it from the storage tank to a denitrification treatment device, after performing denitrification treatment by the denitrification device, sending it to the drainage storage tank through a drainage tank. The water treatment method according to Claim 1, characterized by this.

Images