Seawater treatment method and system

Abstract

To provide a seawater treatment system capable of efficiently producing high-concentration concentrated seawater.SOLUTION: There is provided a seawater treatment system 1, including: a water production device 10 that evaporates and concentrates seawater; a supply device 20 that supplies the seawater to the water production device 10; and a recovery device 30 that recovers the concentrated seawater from the water production device 10, in which the recovery device 30 interrupts the recovery of the concentrated seawater when a concentration of the concentrated seawater exceeds a predetermined concentration or continuous recovery time of the concentrated seawater exceeds a predetermined time during recovery of the concentrated seawater.SELECTED DRAWING: Figure 1

Description

Technical Field

[0003]

[0001] The present invention relates to a seawater treatment method and system.

Background Art

[0002] As a conventional seawater treatment system, a shipboard watermaker that generates distilled water by evaporating and concentrating seawater is known (for example, Patent Document 1). In general, the concentrated seawater (brine) generated by evaporation and concentration is discharged outside the ship without being effectively utilized. However, Patent Document 2 discloses that sodium hypochlorite is generated by supplying the discharged concentrated seawater to a chlorine generator and electrolyzing it.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When concentrated seawater is electrolyzed with a chlorine generator, it is preferable that the higher the salt concentration of the concentrated seawater, the more power consumption can be suppressed. However, in a conventional watermaker, when the operation is performed so that the concentrated seawater becomes highly concentrated, the water production efficiency decreases due to fluctuations in concentration or the passage of time, etc., and thus there is a limit to increasing the concentration of the concentrated seawater.

[0005] Therefore, an object of the present invention is to provide a seawater treatment method and system capable of efficiently producing highly concentrated concentrated seawater.

Means for Solving the Problems

[0006] The object of the present invention is to provide a supply step of supplying seawater to a water desalination apparatus, a concentration step of evaporating and concentrating the supplied seawater in the water desalination apparatus, and a recovery step of recovering the concentrated seawater from the water desalination apparatus, wherein the recovery step includes an interruption step of interrupting the recovery of concentrated seawater if the concentration of the concentrated seawater exceeds a predetermined concentration or if the continuous recovery time of the concentrated seawater exceeds a predetermined time. The interruption step includes a flow rate adjustment step that increases the flow rate of seawater supplied to the water desalination apparatus in the supply step, and a recirculation step that recirculates the concentrated seawater concentrated in the concentration step back to the water desalination apparatus. This is achieved through seawater treatment methods.

[0007] In this seawater treatment method ,before The flow rate adjustment process allows for the adjustment of the seawater flow rate by switching the orifice through which seawater passes.

[0008] Preferably, the system further includes a chemical injection step for injecting a scale-preventing agent into the seawater supplied to the water desalination device, and it is preferable that the amount of the chemical injected in the chemical injection step increases when the flow rate of seawater supplied to the water desalination device decreases.

[0009] The object of the present invention is to provide a supply step of supplying seawater to a water desalination apparatus, a concentration step of evaporating and concentrating the supplied seawater in the water desalination apparatus, and a recovery step of recovering the concentrated seawater from the water desalination apparatus, wherein the recovery step is If, during the recovery of concentrated seawater, the concentration of the concentrated seawater exceeds a predetermined concentration, or if the continuous recovery time of the concentrated seawater exceeds a predetermined time, The system includes an interruption step that switches from a high-concentration operation mode for recovering concentrated seawater to a normal operation mode to interrupt the recovery of concentrated seawater. The normal operation mode is also achieved by a seawater treatment method that increases the flow rate of seawater in the supply step and returns the concentrated seawater generated in the concentration step to the water desalination device.

[0011] Alternatively, the present invention provides a water desalination apparatus for evaporating and concentrating seawater, a supply apparatus for supplying seawater to the water desalination apparatus, and a recovery apparatus for recovering the concentrated seawater from the water desalination apparatus, wherein the recovery apparatus is If, during the recovery of concentrated seawater, the concentration of the concentrated seawater exceeds a predetermined concentration, or if the continuous recovery time of the concentrated seawater exceeds a predetermined time,The system is configured to allow interruption of concentrated seawater recovery by switching from a high-concentration operation mode for recovering concentrated seawater to a normal operation mode. The normal operation mode is achieved by a seawater treatment system that increases the flow rate of seawater supplied by the supply device and also returns the concentrated seawater produced by the water desalination device back to the water desalination device. [Effects of the Invention]

[0012] According to the present invention, a seawater treatment method and system can be provided that can efficiently produce highly concentrated seawater. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of a seawater treatment system according to one embodiment of the present invention. [Figure 2] Figure 1 is a block diagram of the main components of the seawater treatment system shown. [Figure 3] This is a schematic diagram of the main components of a seawater treatment system according to another embodiment of the present invention. [Modes for carrying out the invention]

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Figure 1 is a schematic diagram of a seawater treatment system according to an embodiment of the present invention. The seawater treatment system 1 of this embodiment is used on a ship and comprises a water desalination device 10 that produces distilled water and concentrated seawater by evaporating and concentrating seawater, a supply device 20 that supplies seawater to the water desalination device 10, and a recovery device 30 that recovers the highly concentrated seawater concentrated by the water desalination device 10.

[0015] The water desalination apparatus 10 is configured with a heater 12, a condenser 13, and a preheater 14 inside an evaporator 11. The heater 12 is located at the bottom of the evaporator 11 and uses hot water, such as jacket cooling water for cooling the internal combustion engine on board the ship, as a heat source to heat and evaporate the supplied seawater. The condenser 13 and preheater 14 are located at the top of the evaporator 11 and seawater supplied by an ejector pump (not shown) that drives a water ejector 15 passes through the condenser 13. After passing through the condenser 13, a portion is discharged outside the system, such as overboard, and the remainder passes through the preheater 14. The steam generated in the evaporator 11 is condensed to produce distilled water through heat exchange with the seawater passing through the condenser 13 and preheater 14. The produced distilled water is sent to a freshwater tank (not shown) by a distilled water pump 16. The inside of the evaporator 11 is drawn into a water ejector 15 connected by an extraction line 17, maintaining a reduced pressure state.

[0016] The heater 12 can be, for example, a tubular heat exchanger, but it may also be of another type, such as a plate heat exchanger. Furthermore, although the water production apparatus 10 in this embodiment is a single-effect evaporative concentrater, it may also be a multi-effect evaporative concentrater with two or more effects.

[0017] The supply device 20 includes a supply line 21 that supplies seawater that has passed through the preheater 14 to the bottom of the evaporator 11, a flow rate control device 40 that adjusts the flow rate of seawater passing through the supply line 21, and a chemical injection device 22 that injects a chemical to prevent scale formation into the supply line 21.

[0018] The flow rate adjustment device 40 includes a branch line 41 branched from the supply line 21, three-way valves 42 and 43 provided at both ends of the branch line 41, and orifices 44 and 45 provided in the supply line 21 and the branch line 41 between the three-way valves 42 and 43, respectively. By operating the three-way valves 42 and 43, the orifices 44 and 45 through which seawater passes can be switched. The orifice 44 provided in the supply line 21 is an orifice for a large flow rate, and the orifice 45 provided in the branch line 41 is an orifice for a small flow rate. Pressure sensors 46 and 47 and manual valves 48 and 49 are provided upstream of each of the orifices 44 and 45, respectively.

[0019] The recovery device 30 includes a recovery line 31 for recovering highly concentrated concentrated seawater (brine) generated by evaporation of seawater in the water production device 10, a brine pump 32 provided in the recovery line 31 for sending the concentrated seawater to a recovery tank (not shown), a reflux line 33 branched from a branch point of the recovery line 31 and connected to the suction port of the water ejector 15, and a first on-off valve 34 and a second on-off valve 35 provided in the recovery line 31 and the reflux line 33, respectively, downstream of the branch point. Upstream of the branch point of the recovery line 31, a concentration detector 50 for detecting the salt concentration of the seawater flowing through the recovery line 31 by an electric conductivity method or the like is provided.

[0020] FIG. 2 is a block diagram of the main part of the seawater treatment system 1 shown in FIG. 1. The seawater treatment system 1 includes a control device 60 that controls the operations of the water production device 10, the supply device 20, and the recovery device 30 based on the detection by the concentration detector 50. The control device 60 can switch the operation mode of the seawater treatment system 1 between a high-concentration operation mode and a normal operation mode.

[0021] Next, a seawater treatment method using the seawater treatment system 1 described above will be explained. When generating and recovering highly concentrated seawater in the water desalination plant 10, the seawater treatment system 1 is operated in high-concentration operation mode. That is, the control device 60 operates the three-way valves 42 and 43 of the flow rate control device 40 so that the seawater flowing through the supply line 21 is introduced into the branch line 41, thereby controlling the seawater to pass through the small-flow orifice 45. In this way, a supply process is carried out in which seawater is supplied to the water desalination plant 10 at a predetermined small flow rate.

[0022] In the water desalination plant 10, a concentration process is performed in which seawater supplied at a lower flow rate than during normal operation is evaporated and concentrated to produce highly concentrated seawater (brine). The control device 60 opens the first on-off valve 34 and closes the second on-off valve 35 of the recovery device 30, and operates the brine pump 32. This performs a recovery process in which the highly concentrated seawater is recovered from the water desalination plant 10 into a recovery tank (not shown). The salinity of the recovered concentrated seawater is not necessarily limited, but if the concentration becomes too high, scale formation in the water desalination plant 10 may become significant, so it is preferable to set it to, for example, 6-7%.

[0023] The concentration of the concentrated seawater produced by the water desalination plant 10 is detected in real time by the concentration detector 50. When the concentration detected by the concentration detector 50 exceeds a predetermined concentration (for example, 7%), the control device 60 switches the operating mode from high-concentration operating mode to normal operating mode. That is, it operates the three-way valves 42 and 43 of the flow rate control device 40 to control the seawater to pass through the orifice 44 for high flow rates. In this way, a flow rate control process is performed in which the flow rate of seawater is increased in the supply process and seawater is supplied to the water desalination plant 10 at a predetermined high flow rate.

[0024] The control device 60 performs a recirculation process in which, in accordance with the flow rate increase due to the flow rate adjustment process, it closes the first on-off valve 34 and opens the second on-off valve 35 of the recovery device 30, thereby stopping the brine pump 32. As a result, the concentrated seawater produced in the water desalination device 10 is drawn into the water ejector 15 via the recirculation line 33, and passes through the condenser 13 and preheater 14 together with the seawater that drives the water ejector 15, causing at least a portion of the concentrated seawater to be recirculated to the water desalination device 10 by the supply device 20, thereby interrupting the recovery of concentrated seawater. In this way, by performing an interruption process in the concentrated seawater recovery process by the recovery device 30, which interrupts recovery based on the concentration of concentrated seawater, the accumulation of scale in the water desalination device 10 can be suppressed.

[0025] In normal operation mode, the concentration of concentrated seawater produced by the water desalination plant 10 decreases, but the low-concentration concentrated seawater is not recovered and is returned to the water desalination plant 10, so only high-concentration concentrated seawater can be efficiently recovered. The normal operation mode can be switched back to high-concentration operation mode when the concentration detector 50 detects a decrease in concentration to a predetermined value (e.g., 5%) or when a predetermined time has elapsed.

[0026] The above interruption process may be performed in a shutdown mode, which temporarily stops the operation of the seawater treatment system 1, instead of in normal operation mode. Even in shutdown mode, the water production efficiency of the water production device 10 recovers over time, just as in normal operation mode, so that highly concentrated seawater can be efficiently recovered after restarting the high-concentration operation mode. If the operation mode is not used and the operation mode is only switched between the high-concentration operation mode and the shutdown mode, the flow rate control device 40 may not be provided.

[0027] When the flow rate of seawater supplied to the water desalination plant 10 is adjusted, the control device 60 changes the amount of chemical injected from the chemical injection device 22 into the seawater accordingly. Specifically, in normal operation mode, the amount of chemical injected is reduced, while in high-concentration operation mode, when the flow rate of seawater supplied to the water desalination plant 10 decreases, the amount of chemical injected is increased (for example, to about 1.5 times the amount injected in normal operation mode). By performing this chemical injection process, it is possible to suppress the consumption of chemicals in normal operation mode, where scale formation is less likely, while effectively suppressing scale accumulation in high-concentration operation mode.

[0028] Although one embodiment of the present invention has been described in detail above, the specific aspects of the present invention are not limited to the above embodiment. For example, in this embodiment, the three-way valves 42, 43, the first on-off valve 34, and the second on-off valve 35 are all automatic valves, and the control device 60 is configured to automatically operate these valves. However, the three-way valves 42, 43, the first on-off valve 34, and the second on-off valve 35 may be manual valves. In this case, the flow rate adjustment by the flow rate adjustment device 40 can be performed manually, and when the flow rate of seawater supplied to the water production device 10 increases, the first on-off valve 34 and the second on-off valve 35 can be manually operated to interrupt the recovery of concentrated seawater. The amount of chemical injected in the chemical injection process may also be adjusted manually in accordance with the flow rate adjustment by the flow rate adjustment device 40.

[0029] Furthermore, the flow rate control device 40 of this embodiment is configured to stabilize the seawater flow rate in both the high-concentration operation mode and the normal operation mode by adjusting the flow rate by switching between orifices 44 and 45 through which seawater passes. However, the specific configuration for adjusting the flow rate is not particularly limited. For example, as shown in Figure 3, the flow rate control device 40 can be configured with a single orifice 141 in the supply line 21.

[0030] The flow rate control device 40 shown in Figure 3 is equipped with a pressure sensor 142 and an automatic control valve 143 upstream of the orifice 141 in the supply line 21, and the control device 60 can adjust the opening of the automatic control valve 143 based on the detection by the pressure sensor 142. In normal operation mode, the control device 60 controls the flow rate passing through the orifice 141 to a predetermined large flow rate by increasing the opening of the automatic control valve 143 so that the pressure detected by the pressure sensor 142 becomes a preset high pressure. On the other hand, in high-concentration operation mode, the control device 60 controls the flow rate passing through the orifice 141 to a predetermined small flow rate by decreasing the opening of the automatic control valve 143 so that the pressure detected by the pressure sensor 142 becomes a preset low pressure.

[0031] Switching from high-concentration operation mode to normal operation mode or shutdown mode may be performed when the continuous recovery time of concentrated seawater in high-concentration operation mode exceeds a predetermined time (e.g., 5 days). The continuous recovery time can be determined, for example, by accumulating the operation signals of the brine pump 32, which operates continuously in high-concentration operation mode. When switching from high-concentration operation mode to normal operation mode or shutdown mode, an alarm output may also be used.

[0032] The seawater treatment system 1 of this embodiment is particularly suitable for use on ships. Even when the concentration of seawater varies depending on the sea area, or when the amount of water produced changes due to fluctuations in the load of the ship's main engine, highly concentrated seawater can be efficiently recovered by switching between a high-concentration operation mode and a normal operation mode or a stop mode depending on the situation. However, the seawater treatment system of the present invention is not limited to use on ships and can also be used on land. [Explanation of symbols]

[0033] 1. Seawater treatment system 10 Water generator 20 Feeding device 22 Drug infusion device 30 Recovery device 40 Flow control device

Claims

1. A supply process for supplying seawater to a water desalination plant, A concentration step in which the supplied seawater is evaporated and concentrated in the water desalination apparatus, The system includes a recovery step for recovering concentrated seawater from the water production apparatus, The recovery process includes an interruption step that interrupts the recovery of concentrated seawater if the concentration of the concentrated seawater exceeds a predetermined concentration or if the continuous recovery time of the concentrated seawater exceeds a predetermined time. The interruption step is a seawater treatment method comprising a flow rate adjustment step that increases the flow rate of seawater supplied to the water desalination apparatus in the supply step, and a recirculation step that recirculates the concentrated seawater concentrated in the concentration step back to the water desalination apparatus.

2. The seawater treatment method according to claim 1, wherein the flow rate adjustment step adjusts the flow rate of seawater by switching an orifice through which seawater passes.

3. The water desalination apparatus further comprises a chemical injection step of injecting a scale-preventing agent into the seawater supplied to the water desalination apparatus. The seawater treatment method according to claim 1 or 2, wherein the chemical injection step increases the amount of chemical injected when the flow rate of seawater supplied to the water desalination device decreases.

4. A supply process for supplying seawater to a water desalination plant, A concentration step in which the supplied seawater is evaporated and concentrated in the water desalination apparatus, The system includes a recovery step for recovering concentrated seawater from the water production apparatus, The recovery process includes an interruption step in which, if the concentration of the concentrated seawater exceeds a predetermined concentration or the continuous recovery time of the concentrated seawater exceeds a predetermined time, the recovery of the concentrated seawater is interrupted by switching from a high-concentration operation mode for recovering concentrated seawater to a normal operation mode. The normal operating mode is a seawater treatment method that increases the flow rate of seawater in the supply process and returns the concentrated seawater produced in the concentration process to the water desalination apparatus.

5. A water desalination device that evaporates and concentrates seawater, A supply device that supplies seawater to the aforementioned water desalination apparatus, The system includes a recovery device for recovering concentrated seawater from the water production device, The recovery device is configured to interrupt the recovery of concentrated seawater by switching from a high-concentration operation mode for recovering concentrated seawater to a normal operation mode if the concentration of the concentrated seawater exceeds a predetermined concentration or if the continuous recovery time of the concentrated seawater exceeds a predetermined time. The normal operating mode is a seawater treatment system that increases the flow rate of seawater supplied by the supply device and returns concentrated seawater produced by the water desalination device to the water desalination device.

6. The seawater treatment method according to any one of claims 1 to 4, wherein the salinity of the concentrated seawater recovered by the recovery step is 6 to 7%.

7. The seawater treatment system according to claim 5, wherein the salinity of the concentrated seawater recovered by the recovery device is 6 to 7%.

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