JP2016175049A - Multiple-effect fresh water generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple-effect fresh water generator whose performance can be improved by a simple configuration.SOLUTION: A multiple-effect fresh water generator 1 comprises: evaporators 2 arranged on a plurality of stages 2A to 2Z; and a thermo compressor 3. The thermo compressor 3 increases the pressure of steam (steam to be sucked) in an evaporator 2B on a second stage by driving steam and supplies the steam to an evaporator 2A on the forefront stage. The multiple-effect fresh water generator 1 comprises a preheater 40 which preheats steam to be sucked which is sucked into the thermo compressor 3 by a heat source 41.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multi-effect fresh water generator.

  The multi-effect freshwater generator, which is one of the seawater desalination plants, has advantages in that it is more resistant to deterioration of seawater quality and easier to maintain and inspect than a freshwater generator using a reverse osmosis membrane. On the other hand, the multi-effect fresh water generator also has a disadvantage that it consumes a large amount of energy. For this reason, seawater desalination plants that consume large amounts of energy, such as multi-effect freshwater generators, are widely used in Gulf Arab countries and other countries with abundant energy resources.

  Such a multi-effect fresh water generator is a kind of apparatus that desalinates seawater by an evaporation method, in other words, a kind of apparatus that obtains pure water by cooling steam obtained by evaporation of seawater. The multi-effect fresh water generator includes a thermocompressor that boosts low-pressure steam in order to obtain pure water more efficiently. The thermocompressor sucks and raises the pressure of low-pressure steam (called steam to be sucked) by high-pressure drive steam that is separate steam.

  In a seawater desalination plant equipped with a thermocompressor such as a multi-effect freshwater generator, as the flow rate of the suctioned steam relative to the flow rate of the drive steam (referred to as the suction ratio of the thermocompressor) increases, the amount of drive steam decreases and the amount of pure water increases. You can get water. In other words, the higher the suction ratio of the thermocompressor, the better the performance of the seawater desalination plant. For this reason, as a conventional seawater desalination plant, a seawater desalination apparatus with an increased suction ratio of a thermocompressor has been proposed (for example, see Patent Document 1). The thermocompressor in the seawater desalination apparatus described in Patent Document 1 is configured to improve the flow rate and pressure increase of the suctioned steam.

JP 2012-145006 A

  However, the seawater desalination apparatus described in Patent Document 1 requires a thermocompressor including a nozzle having a complicated structure. For this reason, although the said seawater desalination apparatus improved the performance, there existed a problem that a structure became complicated.

  Then, an object of this invention is to provide the multi-effect type fresh water generator which can improve performance by simple structure.

In order to solve the above-mentioned problem, a multi-effect fresh water generator according to claim 1 of the present invention is a multi-effect fresh water generator comprising evaporators arranged in a plurality of stages and a thermocompressor,
The evaporator is configured to evaporate raw water from the outside and to obtain pure water by cooling and condensing steam.
The above-mentioned thermocompressor sucks the steam in the evaporators in the second and subsequent stages, pressurizes them with driving steam, and supplies the boosted steam to the evaporators in the front stage,
A preheater for preheating the steam sucked into the thermocompressor with a heat source;

  Further, in the multiple effect fresh water generator according to claim 2 of the present invention, the heat source of the preheater in the multiple effect fresh water generator according to claim 1 is driving steam.

  According to the multi-effect fresh water generator, the preheater increases the suction ratio of the thermocompressor, so that the performance can be improved with a simple configuration.

1 is an overall configuration diagram of a multi-effect fresh water generator according to an embodiment of the present invention. It is a block diagram of the thermocompressor and preheater with which the multi-effect fresh water generator is provided. It is a graph which shows the relationship between the pressure of to-be-sucked vapor | steam, and the suction ratio of a thermocompressor. It is a block diagram which shows the other example of the preheater.

Hereinafter, a multi-effect fresh water generator according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, this multi-effect fresh water generator is configured such that evaporators 2 for obtaining pure water from raw water (for example, seawater) by an evaporation method are arranged in a plurality of stages 2 </ b> A to 2 </ b> Z. The multi-effect fresh water generator 1 includes a thermo compressor 3, a driving steam supply unit 9 for driving the thermo compressor 3, and a preheater 40 that is the gist of the present invention.

The inside of each evaporator 2 is divided into an upstream evaporation chamber 4 and a downstream storage chamber 8 by a partition wall 7 provided with a demister 7d at a predetermined height or more.
In the evaporation chamber 4, steam is supplied from the thermocompressor 3 to the heat transfer pipe 5 in the first stage 2 </ b> A, and steam is supplied from the previous stage evaporator 2 to the heat transfer pipe 5 in other cases 2 </ b> B to 2 </ b> Z. On the other hand, raw water is sprayed from the spreader 6 to the heat transfer tube 5. Thereby, the steam in the heat transfer tube 5 is cooled and partly becomes condensed water, and part of the sprayed raw water is evaporated to become steam. This vapor fills not only the evaporation chamber 4 but also the storage chamber 8 through the demister 7d. Of the sprayed raw water, the raw water that has not evaporated is accumulated in the lower part of the evaporation chamber 4 as concentrated raw water. On the other hand, the condensed water in the heat transfer tube 5 is accumulated in the lower portion of the storage chamber 8 as pure water.

  The front and rear evaporation chambers 4 are connected by a raw water transfer pipe 10, and the front and rear storage chambers 8 are connected by a pure water transfer pipe 11. The pure water transfer pipe 11 in the foremost stage 2A branches to a condensate pipe 12. The evaporation chamber 4 of the last stage 2Z is connected to a concentrated raw water discharge pipe 13 that discharges the concentrated raw water, and the storage chamber 8 of the last stage 2Z is connected to a pure water extraction pipe 14 that takes out pure water. The condensate pipe 12 is provided with a condensate pump 22, the concentrated raw water discharge pipe 13 is provided with a blow-down pump 23, and the pure water discharge pipe 14 is provided with a production water pump 24.

  The raw cooling water is guided to the raw cooling water supply pipe 15 in the storage chamber 8 of the last stage 2Z, and the steam in the storage chamber 8 is cooled to be condensed water. As a result, the temperature of the cooling raw water rises and becomes simply raw water. A part of the raw water is discharged by the raw water discharge pipe 16, and the others are branched from the raw water discharge pipe 16 and supplied to the sprayer 6 of each evaporator 2 by the raw water supply pipe 17 provided with a makeup pump 27. Supplied. The raw water supplied to the spreader 6 is heated by a heater (not shown) provided in the raw water supply pipe 17.

  The steam in the storage chamber 8 of the second stage (which may be the second and subsequent stages) 2B is not only supplied to the heat transfer pipe 5 of the third stage 2C, but is sucked into the thermocompressor 3 through the steam suction pipe 18. . In the thermocompressor 3, the low-pressure steam to be sucked (hereinafter referred to as sucked steam) is boosted by the high-pressure driving steam supplied from the driving steam supply unit 9. The driving steam may be saturated steam or superheated steam. The medium-pressure steam boosted by the thermocompressor 3 is supplied to the heat transfer pipe 5 of the foremost stage 2A through the steam supply pipe 19.

  As shown in FIG. 2, the thermocompressor 3 is connected to the steam suction pipe 18 to suck the suction target steam, and is connected to the driving steam supply unit 9 to be supplied with driving steam. And a body 34 provided with the suction part 31 and the drive part 32, a sleeve 35 provided on the downstream side of the body 34, and a diffuser 36 connected to the downstream side of the sleeve 35. The drive unit 32 includes a nozzle unit 33 disposed inside the body 34. The nozzle portion 33 reduces the pressure inside the body 34 by making the flow of driving steam inside the body 34 a supersonic flow. Due to the decrease in pressure, the sucked vapor is sucked from the suction part 31.

  Here, the performance of the multi-effect fresh water generator depends on the suction ratio of the thermo compressor (the flow rate of the suctioned steam with respect to the flow rate of the driving steam). For this reason, in order to improve the performance of the multi-effect freshwater generator, it is required to (1) increase the suction ratio of the thermocompressor and / or (2) make it difficult for the suction ratio of the thermocompressor to decrease. Is done. In the present invention, the multi-effect fresh water generator 1 is configured to satisfy the above (1). A configuration for satisfying the above (1) is the preheater 40 provided in the steam suction pipe 18 of the multi-effect fresh water generator 1. This preheater 40 raises the temperature of the vapor to be sucked by preheating the vapor to be sucked by the heat source 41.

Hereinafter, the relationship between the suction ratio and the temperature of the vapor to be sucked will be described.
Since the vapor to be sucked heated by the heat source 41 is inside the preheater 40 which is a closed space, the pressure Ps rises according to the ideal gas equation of state (PV = nRT) as the temperature rises. . As shown in the graph of FIG. 3, it was obtained by an experiment relating to the present invention that the pressure Ps of the steam to be sucked and the suction ratio ER of the thermocompressor 3 have a positive correlation. This is because when the pressure Ps of the sucked steam increases, the compression ratio Pd / Ps of the thermocompressor 3 (the pressure Pd of the steam discharged from the diffuser 36 with respect to the pressure Ps of the sucked steam) decreases, while the compression ratio Pd This is because / Ps and suction ratio ER are known to have a negative correlation, so that suction ratio ER increases due to a decrease in compression ratio Pd / Ps. In short, when the temperature of the sucked steam rises, its pressure Ps rises, thereby lowering the compression ratio Pd / Ps, thereby raising the suction ratio ER.

Hereinafter, the operation of the multi-effect fresh water generator 1 will be described.
As shown in FIG. 1, steam (suctioned steam) is sucked from the storage chamber 8 of the second stage 2 </ b> B through the steam suction pipe 18 and driving steam is supplied from the driving steam supply unit 9 to the thermocompressor 3. The Since the temperature of the sucked steam is raised by the preheater 40, the pressure Ps of the sucked steam is increased, thereby reducing the compression ratio Pd / Ps and thereby increasing the suction ratio ER.

  As described above, according to the multi-effect fresh water generator 1 according to the above embodiment, the preheater 40 increases the suction ratio ER of the thermocompressor 3, so that the performance can be improved with a simple configuration.

  By the way, in the said embodiment, although the heat source 41 was not demonstrated in detail, what is easily obtainable in the installation place of the multi-effect type fresh water generator 1 is used for the heat source 41. FIG. For example, specific examples of the heat source 41 include a burner using heavy oil or gas as a fuel, an electric heater, solar heat, geothermal heat, exhaust heat from a boiler or an incinerator, and the like.

  In the above-described embodiment, as an example, the steam in the storage chamber 8 of the second stage 2B has been described as being sucked into the thermocompressor 3 through the steam suction pipe 18, but the second stage or later may be used, and the preheater The storage chamber 8 of an appropriate stage (2B to 2Z) is selected according to the performance of 40 or the like.

  Furthermore, as shown in FIG. 4, driving steam may be used as the heat source of the preheater 40. Specifically, the preheater 40 is configured to exchange heat between the suctioned steam and the driving steam. In this case, it is preferable to use superheated steam as driving steam because it is possible to avoid the occurrence of a drain attack. With this configuration, the driving steam is inside the preheater, which is a closed space, so that the pressure decreases according to the ideal gas equation of state (PV = nRT) as the temperature decreases due to heat exchange with the suctioned steam. To do. When the pressure of the driving steam decreases, the pressure Pd of the steam discharged from the diffuser 36 decreases. Therefore, the increase in the pressure Ps of the suctioned steam described above also contributes, and the compression ratio Pd / Ps significantly decreases. . This significantly increases the suction ratio ER. Therefore, with the configuration of FIG. 4, the performance can be significantly improved with a simpler configuration that does not require another heat source.

DESCRIPTION OF SYMBOLS 1 Multiple effect type water generator 2 Evaporator 3 Thermo compressor 5 Heat transfer pipe 8 Storage chamber 9 Drive steam supply part 18 Steam suction pipe 19 Steam supply pipe 31 Suction part 32 Drive part 33 Nozzle part 34 Body 35 Sleeve 36 Diffuser 40 Preheater 41 heat source

Claims (2)

A multi-effect fresh water generator comprising evaporators arranged in multiple stages and a thermocompressor,
The evaporator is configured to evaporate raw water from the outside and to obtain pure water by cooling and condensing steam.
The above-mentioned thermocompressor sucks the steam in the evaporators in the second and subsequent stages, pressurizes them with driving steam, and supplies the boosted steam to the evaporators in the front stage,
A multi-effect fresh water generator comprising a preheater that preheats steam sucked into the thermocompressor with a heat source. The multi-effect fresh water generator according to claim 1, wherein the heat source of the preheater is driving steam.

Images