JP2013128889A - Method of multiple-effect evaporation and multiple-effect evaporator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple-effect evaporator in which the purity of the purified water to be obtained can be prevented from being lowered even in the case of an auto-vapor compression type multiple-effect evaporator using impurity-containing high-pressure steam.SOLUTION: The multiple-effect evaporator is constituted so that an evaporation canister 1 for heating raw water by boiler steam to obtain steam is disposed in multiple stages and the steam generated in the evaporation canister 1D of an intermediate stage is sucked in an ejector 13 to compress/supply the sucked steam to the evaporation canister 1A of the previous stage thereof. The evaporation canister 1D of the intermediate stage, to which an auto-vapor compression method is applied, comprises: a suction steam-exclusive evaporation canister 1Da, the steam of which to be generated therein is introduced into the ejector; and a normal evaporation canister 1Db, the steam of which to be generated therein is not introduced into the ejector. A steam passage 3 of the suction steam-exclusive evaporation canister is connected to a suction part 13a of the ejector by a steam suction pipe 20 and a heat transfer pipe 4a of the evaporation canister of the previous stage is connected to the suction steam-exclusive evaporation canister by a condensed water transfer pipe 16, so that the steam of the evaporation canister one-stage previous to the suction steam-exclusive evaporation canister is introduced into both of the suction steam-exclusive evaporation canister and the normal evaporation canister through a steam introduction pipe 14.

Description

  The present invention relates to a multi-effect evaporation method and a multi-effect evaporation device that can produce pure water from seawater, for example.

Conventionally, as a device for obtaining high purity water from raw water such as groundwater, there is a multi-effect evaporation device.
In this multi-effect evaporation apparatus, evaporators are continuously arranged in a plurality of stages, and steam generated by flash evaporation in the preceding stage evaporator is introduced into the subsequent stage (next stage) evaporator, This is used for flash evaporation of raw water on the latter stage side.

As such a multi-effect evaporation apparatus, a self-vapor compression type apparatus has been proposed in which the thermal efficiency is improved (see, for example, Patent Document 1).
In this self-vapor compression evaporator, the steam generated in the evaporator by the boiler steam is compressed by the ejector, and the steam is supplied to the first stage evaporator as the ejected steam of the ejector. Heat exchange is performed and the generated steam is supplied to the subsequent stage, while the discharged steam itself is condensed to be condensed water.

JP 2004-41850 A

  However, according to the above-described conventional configuration, the boiler connected to the ejector suction unit is led to boiler steam containing impurities, and the steam generated in the can is supplied to the subsequent evaporator, When the steam becomes condensed water, impurities are included, and there is a problem that the purity of the obtained pure water is lowered.

  Accordingly, the present invention provides a multi-effect evaporation method and an evaporation apparatus capable of preventing the purity of the obtained pure water from being lowered even in the case of a self-vapor compression method using steam containing impurities such as boiler steam. The purpose is to provide.

In order to solve the above-mentioned problem, the multi-effect evaporation method of the present invention is provided with an evaporator having a plurality of stages, in which an evaporator for heating and evaporating raw water by a steam for heating led to a heat transfer tube to obtain steam is arranged in a plurality of stages. Or a multi-effect evaporation method using a self-vapor compression method in which steam generated in the latter evaporator is absorbed by an ejector and compressed and supplied to the former evaporator,
Divide the middle-stage or rear-stage evaporator using the self-vapor compression method into a dedicated evaporator for suction steam in which the steam generated in the can is guided to the ejector and a normal evaporator in which the steam generated in the can is not guided to the ejector.
The steam generated in the above-described evaporator exclusively for suction steam is sucked by an ejector and led to the heat transfer pipe of the previous evaporator, and the condensed water generated in the heat transfer pipe is returned to the evaporator dedicated to suction steam,
Furthermore, it is a method of introducing the vapor from the vaporizer one stage before the vaporizer dedicated to the vapor to the vapor vapor dedicated vaporizer and the normal vaporizer.

Further, the multi-effect evaporator according to the present invention is provided with a plurality of stages of evaporators that heat and evaporate the raw water with the heating steam guided to the heat transfer tube to obtain the steam, and the intermediate or subsequent stage evaporators. A multi-effect evaporation device using a self-vapor compression method in which the steam generated inside is sucked by an ejector and compressed and supplied to the heat transfer tube of the previous evaporator,
An intermediate-stage or rear-stage evaporator that uses the self-vapor compression method is composed of a dedicated evaporator for suction steam in which the steam generated in the can is guided to the ejector, and a normal evaporator in which the steam generated in the can is not guided to the ejector.
In addition, the steam passage of the suction vapor dedicated evaporator and the suction part of the ejector are connected by a steam suction pipe, the heat transfer pipe of the previous stage evaporator and the suction steam dedicated evaporator are connected by a condensed water transfer pipe,
The vapor one stage before the suction vapor dedicated evaporator is led to the suction vapor dedicated evaporator and the normal evaporator.

  According to the evaporation method and the evaporation apparatus described above, the evaporation can to which the self-vapor compression method is applied, that is, the evaporation can sucked by the ejector is composed of the suction vapor dedicated evaporator and the normal evaporation can, and the discharged steam from the ejector is The condensed water taken out from the previous evaporator supplied is returned to the evaporator dedicated to the suction steam, and the steam generated in the evaporator dedicated to the suction steam is sucked and compressed by the ejector and used again as the ejected steam of the ejector. Therefore, as in the past, when the impurities specific to heating steam (derived from heating steam), for example, heating steam is boiler steam, volatile boiler water treatment chemicals condense the raw steam. Therefore, the purity of the obtained pure water can be prevented from being lowered.

  Furthermore, when the heating steam is boiler steam, the water returned to the evaporator dedicated to the suction steam, that is, the circulating water, is entirely condensed from the boiler steam. Therefore, unlike the conventional technology, it is derived from the ejected steam from the ejector. In addition to the total amount of boiler water treatment chemicals, purity reduction due to impurities derived from raw steam can be prevented. Therefore, the circulating water can be reused as concentrated boiler water.

It is a schematic cross section which shows schematic structure of the desalinator which concerns on the Example of this invention.

Hereinafter, a multiple effect evaporation apparatus according to an embodiment of the present invention and a multiple effect evaporation method using the apparatus will be described with reference to the drawings.
In this evaporation apparatus and evaporation method, raw water is led to evaporators arranged in multiple stages, and the raw water is flash-evaporated with heating steam in a state where the internal pressure is reduced using a vacuum device or the like to obtain the vapor. A self-vapor compression method is used in which pure water is obtained by condensing with raw water, and the steam generated in the intermediate stage evaporator is sucked by the ejector and compressed and supplied to the previous stage evaporator. In particular, an intermediate-stage evaporator that uses the self-vapor compression method is divided into an evaporator dedicated to suction steam in which the steam generated in the can is guided to the ejector, and a normal evaporator in which the steam generated in the can is not guided to the ejector. It consists of

Hereinafter, although an Example is described, the flash-type fresh water generator for obtaining the pure water for drinks from raw | natural water, for example, seawater, is demonstrated here as a multi-effect evaporation apparatus.
As shown in FIG. 1, this fresh water generator includes a heat exchanger 4 having a heat transfer pipe 4a through which raw water vapor (sea water vapor) is guided, and a spreader that spreads raw water (sea water) on the heat transfer pipe 4a (for example, An evaporator 1 having an evaporation chamber 2 in which 5 is disposed and a steam passage 3 for guiding the raw water vapor generated in the evaporation chamber 2 is arranged in series in the front and rear with at least three stages, for example, five stages. Has been. The evaporation chamber 2 and the vapor passage 3 are partitioned (separated) from each other by a partition wall (also referred to as a partition wall) 6 arranged in the vertical direction in the upper portion, but the lower portion is a communication space portion and is mutually connected. It is communicated. That is, the raw steam generated by heating by the heat transfer tube 4a moves to the steam passage 3 side.

  The fresh water generator includes a raw water supply pipe 11 for supplying raw water to the sprayer 5 of each evaporator 1 and a predetermined evaporator 1 [here, the first stage evaporator 1 (1A)]. An ejector 13 for supplying boiler steam as heating steam to the predetermined evaporator 1 [here, the fourth stage evaporator 1 (1D)] is sucked and discharged as heating steam. The steam supply pipe 12 for heating, and the raw water vapor flash-evaporated in the evaporation chamber 2 of the preceding evaporator 1 in the two front and rear evaporators 1, 1 pass through the steam passage 3 of the evaporator 1 on the rear stage side. A steam introduction pipe (an example of a steam introduction path) 14 that leads to the heat transfer pipe 4a of the evaporation chamber 2 and the steam generated in the last stage (fifth stage; last stage) of the evaporator 1 (1E) are discharged from the steam passage 3 thereof. A steam take-out pipe 15 to be taken out and a first boiler steam for heating are supplied. A condensed water transfer pipe 16 for returning (supplying) the condensed water condensed in the heat transfer pipe 4a of the stage evaporator 1 (1A) to the fourth stage evaporator 1 (1D); A pure water outlet pipe (also referred to as a production water outlet pipe) 17 for taking out pure water condensed in the heat transfer pipe 4a is provided.

  The raw water supply pipe 11 includes a main body pipe portion 11a provided with a raw water pump (seawater pump) 18, and a branch pipe portion 11b connecting the sprayer 5 of each evaporator 1 and the main body pipe portion 11a. The pure water take-out pipe 17 includes a main body pipe portion 17a provided with a water pump 19, and a branch pipe portion 17b that connects the heat transfer pipe 4a and the main body pipe portion 17a of each heat exchanger 4. It is composed of

  By the way, in order to realize the self-vapor compression method, as described above, the intermediate stage in which the self-vapor compression method is used, in this case, the fourth-stage evaporator 1 (1D), and the steam generated in the can into the ejector 13. The suction vapor dedicated evaporator 1Da to be guided and the normal evaporator 1Db from which the generated steam is not guided to the ejector 13 are, of course, sucked by the steam passage 3 of the suction steam dedicated evaporator 1Da and the ejector 13. The part 13 a is connected to the vapor suction pipe 20. In other words, the evaporative evaporator 1Da dedicated to the suction steam to which the condensed water of the discharge steam (hereinafter also referred to as ejector discharge steam) from the ejector 13 as the heating steam is guided, and the normal evaporator to which the condensed water of the ejector discharge steam is not guided. 1Db.

  When the ejector discharge steam passes through the heat transfer pipe 4a of the first stage, that is, the first stage evaporator 1 (1A), heat is exchanged with the raw water to condense, and the condensed water passes through the condensed water transfer pipe 16. And returned to the evaporator 1Da dedicated to the suction vapor.

  Further, as described above, the evaporators 1 and 1 on the front and rear sides are connected to each other by the steam introduction pipe 14, and in particular, the steam passage 3 of the third stage evaporator 1 (1C) and the evaporation exclusively for suction steam. The can 1Da and the normal evaporator 1Db are connected by the same steam introduction pipe 14 (14C). In other words, the steam passage 3 of the third-stage evaporator 1 (1C), the suction steam dedicated evaporator 1Da, and the normal evaporator 1Db are connected to each other (in parallel) via the steam introduction pipe 14 (14C). Has been.

  That is, the steam passage 3 of the first stage evaporator 1 (1A) and the heat transfer pipe 4a in the second stage evaporator 1 (1B) are connected by the steam introduction pipe 14 (14A), and the second stage The steam passage 3 of the first evaporator 1 (1B) and the heat transfer pipe 4a in the third stage evaporator 1 (1C) are connected by the steam introduction pipe 14 (14B), and the third stage evaporator 1 is connected. The steam passage 3 of (1C) and the heat transfer pipe 4a of the suction steam dedicated evaporator 1Da and the heat transfer pipe 4a of the normal evaporator 1Db in the fourth stage evaporator 1 (1D) are connected by the same steam introduction pipe 14 (14C). The steam passage 3 of the normal evaporator 1Db in the fourth stage and the heat transfer pipe 4a of the fifth stage evaporator 1 (1E) are connected by the steam introduction pipe 14 (14D).

  Also, in the evaporator 1Da dedicated to the suction steam in the fourth stage evaporator 1 (1D), the circulation for supplying the sprayer 5 with the condensed water of the ejector discharge steam and the concentrated water of the raw water accumulated at the bottom thereof. A water circulation pipe 21 is provided. The circulating water circulation pipe 21 includes a circulation main body pipe portion 21 a provided with a circulating water pump 22 and a blow-out extraction pipe portion 21 b that can discharge the circulating water to the outside.

  Blow water taken out from the blow-out take-out pipe portion 21b contains chemicals and can be returned to the boiler. Therefore, it is possible to reduce the amount of raw water to be taken and the amount of medicine to be used (the amount of medicine to be charged) by the amount of precipitation to the evaporation vapor dedicated evaporator 1Da.

  Further, a condenser 23 is provided in the steam take-out pipe 15 for taking out the steam from the steam passage 3 of the last-stage evaporator 1 (1E). The raw water for cooling is guided to the condenser 23 by the raw water supply pipe 11, and the raw water vapor is condensed to obtain pure water.

  Further, the evaporators 1 and 1 except for the suction steam dedicated evaporator 1Da in the fourth stage evaporator 1 (1D) are connected to each other via the raw water transfer pipe 24, and the last stage evaporator 1 A concentrated raw water pump (brine pump) 25 is provided at the bottom of the can 1 (1E), and a raw water discharge pipe 26 from which raw water for cooling can be taken out is connected.

Next, the operation in the above configuration, that is, the evaporation method will be described.
In the above configuration, the ejector discharge steam is supplied to the first stage evaporator 1 (1A) via the steam supply pipe 12, and the condensed water is supplied to the fourth stage suction steam dedicated evaporator 1Da. In the state, when raw water is supplied from the raw water supply pipe 11 to the spreader 5 of each evaporator 1 excluding the suction vapor dedicated evaporator 1Da and sprayed on the heat transfer pipe 4a of the heat exchanger 4, Seawater evaporates by the steam passing through the heat transfer tube 4a.

  The evaporated sea water vapor is led from the preceding evaporator 1 to the heat transfer pipe 4a of the latter (next stage) evaporator 1 through the respective steam passages 3 and the steam introduction pipes 14 to evaporate the preceding stage. Similar to the operation of the can 1, the seawater sprayed from the sprayer 5 is evaporated, and the water itself is cooled and condensed to become pure water.

  The condensed water of the ejector discharged steam generated in the heat transfer pipe 4a of the first stage evaporator 1 (1A) (of course, the steam is included depending on the design and operating state) is passed through the condensed water transfer pipe 16. In the fourth stage of the evaporator 1 (1D), it is transferred into the evaporator 1Da dedicated to the suction steam, and is sent to the sprayer 5 by the main body 21a for circulation of the circulating water circulation pipe 21 and in the heat transfer pipe 4a. It is evaporated by the steam. The steam generated in the evaporator 1Da dedicated to the suction steam is sucked into the suction portion 13a of the ejector 13 through the steam passage 3 and the steam suction pipe 20, compressed by mixing with boiler steam, and discharged as the ejector discharge steam in the first stage. After being supplied to the first evaporator 1 (1A) and condensing into condensed water when passing through the heat transfer tube 4a, the evaporator for exclusive use of suction steam 1Da which is the fourth stage evaporator again. Led to.

The condensed water condensed in the heat transfer tubes 4a of the other evaporators 1 (1B to 1E) excluding the first stage evaporator 1 (1A) is taken out as pure water from the pure water outlet pipe 16.
The steam generated in the last-stage evaporator 1 (1E) is taken out from the steam passage 3 and the steam take-out pipe 16, but is condensed by the condenser 23 provided in the middle and taken out as pure water.

  Concentrated raw water accumulated in the bottom of each evaporator 1, that is, concentrated seawater (brine) is sequentially supplied to the next stage evaporator (fourth stage evaporator through the raw water transfer pipe 24). 1D is usually the evaporator 1Db) and is taken out from the bottom of the last stage evaporator 1 through the raw water take-out pipe 26 as appropriate.

  Moreover, although not shown in figure, when the raw | natural water supplied from the raw | natural water supply pipe 11 is seawater, the processing agent addition means for adding processing agents, such as a scale inhibitor and an antifoamer, to the said seawater is provided. It has been.

  According to the configuration of the fresh water generator according to the above-described embodiment, the evaporator, to which the self-vapor compression method is applied, that is, the fourth stage evaporator 1 (1D) connected to the suction part 13a of the ejector 13 is connected to the suction steam. After being composed of a dedicated evaporator 1Da and a normal evaporator 1Db, the steam generated in the suction steam dedicated evaporator 1Da is mixed and compressed by an ejector with boiler steam and supplied to the evaporator 1 as ejector discharge steam. The steam is condensed in the heat exchanger 4 to become condensed water (a mixed fluid containing steam in some cases). However, since this condensed water is returned again to the suction steam dedicated evaporator 1Da, As described above, since the impurities specific to (or derived from) the boiler steam, such as volatile boiler water treatment chemicals, are not mixed in the pure water, the purity of the obtained pure water is prevented from being lowered. It can be.

  In order to eliminate the disadvantages of the conventional example, the condensed water generated in the evaporator to which the ejector discharge steam is guided is discharged out of the system without returning to the evaporator connected to the ejector suction part. It is also conceivable that raw water is supplied to an evaporator connected to the suction part, and the raw water vapor generated here is sucked into the ejector suction part. However, in this case, the raw water (seawater) supplied to the evaporator can not be obtained as pure water for the steam sucked into the ejector, so the supply of raw water (seawater) supplied to the fresh water generator Although the amount must be increased, it is not necessary in the apparatus of the above-described embodiment.

  In addition, the entire amount of water returned to the evaporator dedicated to suction steam, that is, circulating water, is boiler steam condensate, so unlike the conventional technology, it includes the total amount of chemical for boiler water treatment derived from the ejected steam from the ejector. In addition, it is possible to prevent a decrease in purity due to impurities derived from raw water vapor. Therefore, the circulating water can be reused as concentrated boiler water.

  By the way, in the above embodiment, the evaporator using the self-vapor compression method is the fourth stage evaporator, but for example, the fifth stage (last stage) evaporator, the second stage or the third stage. It may be an eye evaporator.

Moreover, in the said Example, although the evaporator was demonstrated as a desalinator which obtains pure water from seawater, the apparatus which obtains pure water from groundwater, industrial water, etc. may be sufficient.
Here, it is as follows when the structure and evaporation method of the evaporator as the said water freshener are summarized.

That is, in this evaporator, evaporators that obtain steam by heating and evaporating raw water with heating steam guided to a heat transfer tube are arranged in a plurality of stages, and steam generated in an intermediate stage or a subsequent stage evaporator Is a multi-effect evaporation device using a self-vapor compression method in which the air is sucked by an ejector and compressed and supplied to the heat transfer tube of the previous evaporator,
The middle-stage or rear-stage evaporator can to which the self-vapor compression method is applied consists of a dedicated evaporator for suction steam in which the steam generated in the can is guided to the ejector and a normal evaporator in which the steam generated in the can is not guided to the ejector. ,
In addition, the steam passage of the suction vapor dedicated evaporator and the suction part of the ejector are connected by a steam suction pipe, the heat transfer pipe of the previous stage evaporator and the suction steam dedicated evaporator are connected by a condensed water transfer pipe,
Vapor from an evaporator that is one stage before the suction vapor dedicated evaporator can be led to the suction vapor dedicated evaporator and the normal evaporator.

In addition, the evaporation method includes a plurality of stages in which the raw water is heated and evaporated by the heating steam guided to the heat transfer tube to obtain the steam, and the steam generated in the intermediate stage or the subsequent stage is used. A multi-effect evaporation method using a self-vapor compression method that is absorbed by an ejector and compressed and supplied to an evaporator in the previous stage,
Divide the middle-stage or rear-stage evaporator to which the self-vapor compression method is applied into a dedicated evaporator for suction steam in which the steam generated in the can is guided to the ejector and a normal evaporator in which the steam generated in the can is not guided to the ejector.
The steam generated in the above-described evaporator exclusively for suction steam is sucked by an ejector and led to the heat transfer pipe of the previous evaporator, and the condensed water generated in the heat transfer pipe is returned to the evaporator dedicated to suction steam,
Furthermore, it is a method of introducing the vapor from the vaporizer one stage before the vaporizer dedicated to the vapor to the vapor vapor dedicated vaporizer and the normal vaporizer.

DESCRIPTION OF SYMBOLS 1 Evaporator 1Da Suction steam exclusive evaporator 1Db Normal evaporator 2 Evaporation chamber 3 Steam passage 4 Heat exchanger 4a Heat transfer pipe 5 Sprinkler 6 Partition wall 11 Raw water supply pipe 12 Steam supply pipe 13 Ejector 13a Suction part 14 Steam introduction pipe 15 Steam extraction pipe 16 Condensate transfer pipe 17 Pure water extraction pipe 20 Steam suction pipe 21 Circulating water circulation pipe 23 Condenser 24 Raw water transfer pipe

Claims (2)

Evaporators that heat and evaporate the raw water with the heating steam guided to the heat transfer tubes to obtain the steam are arranged in multiple stages, and the steam generated in the intermediate or subsequent stage evaporator is absorbed by the ejector, and the former stage A multi-effect evaporation method using a self-vapor compression method in which the evaporator is compressed and supplied,
Divide the middle-stage or rear-stage evaporator to which the self-vapor compression method is applied into a dedicated evaporator for suction steam in which the steam generated in the can is guided to the ejector and a normal evaporator in which the steam generated in the can is not guided to the ejector.
The steam generated in the above-described evaporator exclusively for suction steam is sucked by an ejector and led to the heat transfer pipe of the previous evaporator, and the condensed water generated in the heat transfer pipe is returned to the evaporator dedicated to suction steam,
Furthermore, the multi-effect evaporation method characterized in that the vapor from the previous vapor evaporator is led to the vapor vapor evaporator and the normal vapor can. Evaporators that heat and evaporate the raw water with heating steam guided to the heat transfer tubes to obtain the steam are arranged in multiple stages, and the steam generated in the intermediate or subsequent stage evaporator is sucked by the ejector before the former stage. A multi-effect evaporation device using a self-vapor compression method that is compressed and supplied to the heat transfer tube of the evaporator,
The middle-stage or rear-stage evaporator can to which the self-vapor compression method is applied consists of a dedicated evaporator for suction steam in which the steam generated in the can is guided to the ejector and a normal evaporator in which the steam generated in the can is not guided to the ejector. ,
In addition, the steam passage of the suction vapor dedicated evaporator and the suction part of the ejector are connected by a steam suction pipe, the heat transfer pipe of the previous stage evaporator and the suction steam dedicated evaporator are connected by a condensed water transfer pipe,
A multi-effect evaporation apparatus, characterized in that the vapor from the previous vapor evaporator is led to the vapor vapor evaporator and the normal vapor can.

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