WO2010026953A1

WO2010026953A1 - Energy-efficient method and device for manufacturing distilled water and/or concentrated water

Info

Publication number: WO2010026953A1
Application number: PCT/JP2009/065229
Authority: WO
Inventors: 誠一竹田
Original assignee: Takeda Seiichi
Priority date: 2008-09-04
Filing date: 2009-09-01
Publication date: 2010-03-11
Also published as: JPWO2010026953A1

Abstract

Provided are a method and a device for manufacturing distilled water and/or concentrated water from raw water. The manufacturing method comprises (i) a step for supplying raw water at a temperature higher than or equal to a temperature five degrees lower than the boiling point to an evaporator, (ii) a step for evaporating at least part of the raw water as water vapor in the evaporator, (iii) a step for discharging concentrated water, (iv) a step for pressurizing the water vapor in such a manner that the pressure of the water vapor becomes 1.01 to 2 times as high as the pressure in the evaporator so that the condensation temperature of the water vapor becomes higher than the boiling point of the raw water, and (v) a step for condensing the pressurized water vapor in a condenser to turn the water vapor into distilled water. The evaporator and the condenser are partitioned by a heat transfer plate, and the raw water is boiled in the evaporator by transferring condensation heat generated by the condensation of the water vapor in the condenser from the condenser to the evaporator via the heat transfer plate.

Description

Method and apparatus for producing energy-efficient distilled water and / or concentrated water

The present invention relates generally to the production of distilled water and / or concentrated water from raw water containing impurities such as salt, and more particularly to the production of distilled water from raw water using a heat exchanger to increase energy efficiency. The present invention relates to a method and an apparatus thereof, and a method for obtaining concentrated water generated with distillation.

The world is lacking in clean fresh water and has recently been highlighted as a water shortage problem. On the other hand, environmental problems due to the use of energy are also becoming serious, and it is a big problem to use distilled water that uses a large amount of energy for general purposes of fresh water. For this reason, seawater desalination with low energy use such as reverse osmosis membrane method has been studied, but problems such as membrane life and maintenance remain, and it cannot be said that it is sufficiently put into practical use. Moreover, the reverse osmosis membrane method requires energy for pressurization, and does not mean that energy is not used. On the other hand, a multistage flash method is widely used as a distillation method. In this method, water heated to 100 ° C. or higher is sent to a decompression chamber and flash-evaporated (boiling) to condense the generated water vapor and use the heat of condensation for heating raw water. However, the latent heat of steam generation is about 540 cal / g at 98 ° C. and about 570 cal / g at 48 ° C., and only about 1/8 of hot water can be evaporated by the multistage flash method. For this reason, in order to increase energy efficiency, the concentrated water of about 40 to 50 ° C. in the final stage must be mixed with the raw water and reused, and in order to obtain 1 g of water in the multistage flash method, the calorific value of at least 30 to 40 cal And the use of energy is more than an order of magnitude higher than in the reverse osmosis membrane method. However, there are difficulties in handling the membrane of the reverse osmosis membrane method, there are problems with the price and life of the membrane, and if the energy usage rate can be reduced in the distillation method, it will be advantageous compared to the reverse osmosis membrane method in total, Various distillation methods with a small amount of energy consumption have been studied (for example, Patent Document 1), but it is still not sufficient.

International Publication No. 01/072638 Pamphlet

As described above, conventionally, when distilled water is produced using seawater or the like as raw water, much energy is consumed to heat and evaporate the raw water. Therefore, even if solar heat or boiler waste heat is used, there is a problem that the energy cost is higher than other fresh water production methods such as reverse osmosis.
An object of this invention is to solve such a problem and to provide the distilled water manufacturing method and apparatus excellent in energy efficiency.
When distilled water is produced, water concentration always occurs, so it is easy to think that the distilled water production apparatus is also a production apparatus for concentrated water. However, the multi-stage flash method, which is the mainstream of seawater desalination, has a low concentration rate of residual water remaining after distillation and is low for the purpose of salt production. There is little to be done. If salt water with a high concentration rate for the production of salt can be obtained as a by-product of seawater desalination, the energy usage rate for salt / salt production can be greatly reduced. Therefore, it is also an object of the present invention to provide a raw water concentration method and apparatus.

According to a first aspect of the present invention, a method for producing distilled water and / or concentrated water from raw water is provided. This manufacturing method is
(I) supplying raw water having a temperature 5 ° C. lower than the boiling point or higher to the evaporator;
(Ii) evaporating at least a portion of the raw water as water vapor in an evaporator;
(Iii) discharging concentrated water;
(Iv) pressurizing the steam so that the condensation temperature of the steam is higher than the boiling point of the raw water by 1.01 to 2.0 times higher than the pressure in the evaporator;
(V) condensing the pressurized water vapor in a condenser to form distilled water. In this manufacturing method, the evaporator and the condenser are partitioned by a heat transfer plate, and the heat of condensation due to the condensation of water vapor in the condenser is transferred from the condenser to the evaporator through the heat transfer plate, thereby Bring the raw water to a boil.

According to a specific example of the present invention, the step (ii) may further include a step of separating raw water evaporated at least partially as water vapor into water vapor and concentrated water.

According to an embodiment of the present invention, the method may further include (vi) cooling the condensed distilled water and / or (vii) cooling the discharged concentrated water.

According to an embodiment of the present invention, the method may further include preheating the raw water supplied to the evaporator to a temperature lower than the boiling point by 5 ° C. or higher.

According to an embodiment of the present invention, the steps of preheating raw water, cooling distilled water, and cooling concentrated water are performed in at least one counter-flow heat exchanger, and distilled water and / or concentration is performed. By supplying heat from the water to the raw water, the raw water can be preheated to a temperature 5 ° C. lower than the boiling point.

According to an embodiment of the present invention, this heat exchanger can be a plate heat exchanger.

According to the specific example of the present invention, in order to reduce the degree of superheat in the evaporator, a part of the pressurized water vapor can be sent to the evaporator to become a boiling nucleus.

According to a specific example of the present invention, the water concentrated in the evaporator is used as raw water, and the steps (ii), (iii), (iv), and (v) are repeated in one or more cycles. it can.

According to an embodiment of the present invention, the raw water can be seawater or saltwater lake water, in which case the pressurizing stage is 1.02 to 2. It is preferable to pressurize so that it becomes higher by 0 times. The raw water can also be treated water containing heavy metals or treated water containing substances that are not volatile.

According to still another aspect of the present invention, an apparatus for producing distilled water and / or concentrated water is provided, and the apparatus for producing distilled water and concentrated water comprises:
Raw water supply means for supplying the stock solution;
An evaporator that evaporates at least a portion of the raw water supplied from the raw water supply means;
A condenser that communicates with the evaporator and that condenses water vapor to produce distilled water;
An apparatus for producing distilled water and concentrated water, comprising pressurizing means provided in a line leading from the evaporator to the condenser. This pressurizing means pressurizes the water vapor in the condenser so that the condensation temperature of the water vapor is higher than the boiling point of the raw water, and the evaporator and the condenser are partitioned by a heat transfer plate. The raw water is boiled in the evaporator by transmitting the heat of condensation due to the condensation of water vapor in the condenser through the heat transfer plate from the condenser to the evaporator.

According to a specific example of the present invention, the apparatus for producing distilled water and / or concentrated water further includes a gas-liquid separation device provided between the evaporator and the condenser for separating raw water into steam and concentrated water. Can be included.

According to an embodiment of the present invention, the apparatus for producing distilled water and / or concentrated water further includes at least one plate heat exchanger provided between the raw water supply means and the evaporator, Concentrated water discharged from the gas-liquid separator and / or distilled water discharged from the condenser can be subjected to heat exchange with the raw water in the plate heat exchanger.

According to an embodiment of the present invention, an apparatus for producing distilled water and / or concentrated water according to the present invention comprises at least one set of evaporators, pressurizing means communicating with the evaporators, condensing communicating with the pressurizing means. Each set can be connected so that the concentrated water discharged from the previous set of condensers is introduced into the next set of evaporators as raw water.

According to the specific example of the present invention, when the raw water is fresh water, the pressurizing means pressurizes the pressure in the condenser 0.01 to 1.0 atm higher than the pressure in the evaporator. Can be.
When the raw water is seawater or saltwater lake water, the pressurizing means preferably pressurizes the pressure in the condenser to be 0.02 to 1.0 atmosphere higher than the pressure in the evaporator. Water containing a salt such as seawater has a boiling point increase corresponding to the concentration of the salt, and it is necessary to increase the minimum pressure with an increase in the concentration of the salt.

Distillation and concentration are a pair of actions, and this method can be advantageously used as a concentration means. For example, it is a method for producing a salt using as a raw material concentrated water obtained by the method for producing distilled water and concentrated water. Also, wastewater and wastewater containing heavy metals and other substances that exceed the environmental standards discharged from factories, or wastewater containing pesticides that exceed environmental standards among wastewater from golf courses, farms, livestock facilities, or poultry farms Can be used for concentration as a preliminary treatment for detoxifying or extracting valuable substances.

The figure showing the basic composition for dividing raw water into distilled water and concentrated water. The figure which shows the structure of an example of the distilled water manufacturing apparatus which concerns on this invention. The figure which shows another structure of the distilled water manufacturing apparatus which concerns on this invention. The figure which shows the structure of an example of the multistage distilled water manufacturing apparatus which concerns on this invention. Schematic of the experimental device for confirming the performance of the evaporator / condenser.

In the following, the present invention will be described in more detail with reference to the schematic drawings.

One of the principles of the present invention is to directly use the heat of condensation of the generated water vapor for evaporation of raw water. As is well known, the condensing (liquefaction) temperature increases as the pressure increases. Therefore, if the water vapor pressure is increased to increase the condensing temperature, the raw water on the low pressure side can be boiled at this temperature.
The volume change when the gas pressure is changed adiabatically is expressed by Poisson's equation PV ^γ = const
It can ask for. Here, P is the pressure V is the volume, γ is said to be a specific heat ratio, and γ = 1.333333 in the case of water vapor, so PV ^1.333333 = const
It becomes.
Moreover, since PV / T = nR = const according to the equation of state of the ideal gas, the volume change and the temperature change due to adiabatic expansion / compression can be calculated from these equations.
For example, when 100 ° C. water vapor is pressurized from 1 atm (atmospheric pressure) to 1.1 atm, the volume is 0.931 times and the temperature can be calculated to be 109.99 ° C.
The degree of increase in boiling point (condensation temperature) varies depending on the temperature, but increases by 1.5 to 3.0 ° C. when the pressure increases by 10%. For example, when the pressure is increased from 1 atm (atmospheric pressure) to 10% (= 0.1 atm), the boiling point (condensation temperature) becomes 102.67 ° C. That is, the water vapor evaporated at 1 atm and 100 ° C. is raised to about 109 ° C. when the pressure is increased by 10% (if 1.1 atm), and is cooled to 102.67 ° C. when touching the heat transfer plate at 100 ° C. It is condensed into water while maintaining 102.67 ° C.
The amount of heat released by water vapor while being cooled from 109 ° C. to 102.67 ° C. by 6.33 ° C. is calculated using the constant-pressure specific heat of water vapor of 1.95 J / g · ° C. 6.33 × 1.95 = 12.3 J /G=2.95 cal / g, while the latent heat of condensation at 102.67 ° C. is 537 cal /. The heat transfer coefficient at the heat transfer surface of the gas fluid is smaller than that of condensation heat transfer or boiling heat transfer, but since the amount of heat to be transferred is small, the heat transfer area up to the condensation temperature is small, and most heat transfer is performed. The hot surface is used for condensation while transferring a large amount of heat during condensation to the evaporator.
The present invention uses this phenomenon to use the condensation of water vapor as a heat source for boiling raw water. For this purpose, an apparatus that enables the generated condensation heat to be efficiently used as the evaporation heat is required. Therefore, in the present invention, condensation and evaporation can occur simultaneously on the front and back of the metal heat transfer plate having high thermal conductivity.
In the case of evaporation, if there is no boiling nucleus, it will not boil unless it is higher than the boiling point. The difference between the actual boiling temperature and boiling point is called the degree of heating, and it is desirable to make this degree of heating as small as possible and 0 to increase energy efficiency (the amount of water obtained divided by the required energy). . For this purpose, it is preferable to form boiling nuclei in the evaporator. As an example, there is a method of leaving bubbles in the dents by roughening the boiling heat transfer surface or the like. As another means, it is also effective to inject gas into boiling nuclei. If pressurized steam is present as in this apparatus, this method is a very effective means, and it is preferable to employ this method. However, other boiling nuclei may be arranged or formed.

A basic configuration for dividing raw water into distilled water and concentrated water (evaporation residual water, residual water) will be described with reference to FIG. The evaporation / condensing device 2 that performs heat exchange between steam and high-temperature raw water is a kind of heat exchanger that includes an evaporator 10 and a condenser 11 and is partitioned by a heat transfer plate 4 therebetween. A blower (turbine) 8 is provided at the uppermost part, and water vapor can be fed from the evaporator 10 to the condenser 11 while applying pressure. The heat exchanger 20 described on the lower side of the evaporation / condensing device 2 in the figure is a counterflow heat exchanger for heating the raw water taken in and cooling the distilled water and the concentrated water. Distilled water and concentrated water (residual water) that have finished supplying heat are discharged. The heated raw water is sent from the heat exchanger 20 to the evaporator 10. The heater 30 is provided in the middle of the line which sends high temperature raw water. The heater 30 is necessary for increasing the heat in the initial operation of the apparatus. However, if the heat retaining properties of the evaporator 10 and the condenser 11 are increased, heat is not escaped to the outside, the efficiency of the heat exchanger 20 is increased, and sufficient heat can be transmitted to the raw water, If it becomes a steady state after a certain period of time after the start of operation, it is possible to produce distilled water with only the energy of the blower. However, when there is a lot of heat scattering to the outside or when the performance of the heat exchanger 20 is low, it is necessary to continue using the heater 30 to supply heat to the raw water.
A part of the steam pressurized by the blower 8 is blown into the evaporator through the steam pipe 17 to form a boiling core, whereby the degree of heating necessary for boiling can be lowered. The steam pipe may pass through the condenser as shown in FIG. 1 or through the outside of the condenser, but it goes without saying that heat insulation is necessary in the case of the outside. The amount of steam for the boiling nuclei may be small if the water in the evaporation chamber reaches the boiling point, but if it is slightly lower than the boiling point, send more steam so that the vapor nuclei will not disappear due to condensation. Is desired. As shown in FIG. 1, if a plurality of air inlets are installed so that the optimum air inlet can be selected, it is possible to select an air inlet having an appropriate temperature in the evaporator according to the operating conditions. The piping valve leading to it can be opened to adjust the steam flow rate.

In the example of FIG. 1, when water is passed while opening the valves of the raw water and concentrated water little by little while operating the heater 30, the temperature of the raw water entering the evaporator 10 is increased by the action of the heat exchanger 20 over time. The water vapor becomes higher and eventually water vapor is generated from the position of the heater 30. When evaporation starts, when steam is sent to the condenser 11 while increasing the pressure by the blower 8, the steam having a higher boiling point (condensation temperature) is condensed on the surface of the heat transfer plate 4 and becomes distilled water. The heat of condensation is efficiently transferred from the condensation surface of the condenser 11 to the evaporation surface of the evaporator 10 through the heat transfer plate 4. As the degree of compression of the water vapor increases, the water vapor whose energy has increased due to the compression has a heat quantity that evaporates the high-temperature water in the evaporator 10, and a portion of the water vapor is not condensed in the condenser 11 and is heated. It reaches the exchanger 20 and condenses. Distilled water and concentrated water can pass through the heat exchanger 20 to raise the raw water to a temperature near the boiling point (above 5 ° C. below the boiling point). If the heat insulation is increased so that heat does not escape to the outside, and the water vapor compression rate is increased, the heater 30 can be hardly heated when a steady state is reached after a certain period of time. For example, when the pressure is increased by 10% from 1 atm to 1.1 atm, the amount of heat of the water vapor increases by 2.99 cal / g as described above, so that water sufficient to supplement the condensate is continuously supplied from the boiling water side. If the water vapor pressure is increased by 0.1 atm, the heat retention is improved, and the overall heat loss including the loss of the heat exchanger is kept below the 3 ° C temperature drop of water, it will depend on the heater in the steady state. Distilled water can be continuously produced without heating.

The evaporation in the evaporator 10 and the condensation in the condenser 11 correspond to the evaporation end and the condensation end in the case of a heat pipe, and the temperature of the condensation end is higher than the temperature of the evaporation end. Although it does not occur, by increasing the pressure at the condensing end by a blower 8 such as a blower, the water vapor temperature rises, so heat can be transferred. The heat pipe is extremely excellent in heat transfer due to the high heat transfer between evaporation heat and condensation heat transfer, and the high speed of water vapor movement, but in the present invention, the thickness of the heat transfer plate is also reduced. Thus, by increasing the evaporation heat transfer coefficient and the condensation heat transfer coefficient, it becomes possible to produce distilled water with extremely high productivity and extremely low energy consumption. As such a heat transfer plate, although depending on raw water, for example, the material is titanium or highly corrosion-resistant stainless steel, and the thinner the thickness, the better. However, 0.3 to 1.0 mm is generally used due to the problem of the strength of the apparatus. is there.

If the raw water is fresh water or close to it, the boiling point rise due to concentration hardly changes at a concentration rate of several times. However, when seawater is used as raw water, the boiling point of seawater is about 0.5 ° C., and the boiling point of seawater concentrated twice is about 1 ° C. higher than that of pure water. At a boiling point of 100 ° C., the water vapor pressure is 1 atm (1 atm) = 760 mmHg, and the vapor pressure changes by 0.03 to 0.04 atm with a temperature change of 1 ° C. Calculated from this value, when the concentration rate is doubled (equivalent amounts of distilled water and concentrated water), increasing the pressure on the condensation side from 1 atm to a little less than 0.02 atm (about 13 mmHg) will change the raw water into seawater. In this case, the temperatures of the raw water side and the water vapor condensation side become equal. Therefore, in order to produce distilled water from seawater, a pressure difference of 0.02 atm or more is required at least in the case of atmospheric pressure operation.
When the water vapor pressure is increased from 1 atm to 1.5 atm, Poisson's equation PV ^γ = const
The water vapor temperature rises to 139.8 ° C. and the volume is 0.738 times. At this time, since the condensation temperature is 111.6 ° C., the water vapor condenses after the temperature has dropped by 28.2 ° C. The amount of heat released at this time is 28 when calculated using a constant pressure specific heat of 1.95 J / g · ° C. 2 × 1.95 = 54.99 J / g = 13.16 cal / g. Moreover, if it raises to 2 atm, it will rise to 170.6 degreeC and a volume will be 0.595 times. Since the condensation temperature at this time is 120.4 ° C., the water vapor will condense after the temperature drops by 50.2 ° C., and the amount of heat released at this time is calculated using a constant pressure specific heat of 1.95 J / g · ° C. 50 .2 × 1.95 = 97.89 J / g = 23.42 cal / g
It is.
This is a considerable amount of heat, and considering the efficiency of the blower (turbine), increasing the pressure ratio to 2.0 or higher is not a good idea from the viewpoint of energy efficiency. It is desirable to use a pressure ratio of 1.5 or less except in emergency situations. In addition, a large pressure difference between the evaporator and the condenser must be a sturdy device, which increases the price of the device. In order to reduce the price, when the differential pressure is reduced, operation is performed below the differential pressure.

FIG. 2A shows an assembling configuration of an example of an apparatus for producing distilled water and concentrated water according to the present invention. The apparatus for producing distilled water and concentrated water according to the present invention can be produced by combining commercially available heat exchangers, pipes, pumps and the like. The actual device needs to be easy to operate and easy to maintain. Therefore, the blower 8 was disconnected from the evaporation / condensing device 2.

The configuration of the distilled water and concentrated water manufacturing apparatus 1 shown in FIG. 2A will be described according to the flow of raw water, distilled water, and water vapor. In FIG. 2A, the flow of cold water (including raw water and distilled water) is indicated by thin solid arrows, the flow of hot water (including raw water and distilled water) is indicated by thick solid arrows, and the flow of water vapor is indicated by dashed arrows. ing.
The structure of the manufacturing apparatus 1 of the shown distilled water and concentrated water is demonstrated according to the flow of raw | natural water, distilled water, and water vapor | steam. In FIG. 2A, the flow of cold water (including raw water and distilled water) is indicated by thin solid arrows, the flow of hot water (including raw water and distilled water) is indicated by thick solid arrows, and the flow of water vapor is indicated by dashed arrows. ing.
For the purpose of obtaining distilled water, the raw water 40 can be natural water such as fresh water such as river water, sea water, salt water such as salt water lake water, and the like. The purpose of concentration is not only to concentrate useful substances, such as obtaining concentrated seawater and salt lake water for salt production, but also to contain hazardous heavy metals or hazardous substances that exceed environmental standards. The treatment load of treated water may be reduced.

Raw water 40 is fed into the apparatus by a supply means (not shown) such as a pump. First, raw water enters the deaeration device 22 and degass it. The speed at which water vapor condenses (condensation heat transfer coefficient) varies greatly depending on whether or not non-condensable gas is contained in the water vapor. Therefore, it is desirable to remove (degas) in advance a non-condensable gas (air component) that lowers the condensation rate in order to efficiently condense. As the degassing device 22, a method for depressurizing low-temperature raw water with a vacuum pump to release dissolved gas has already been established. Therefore, it is convenient and preferable to use these devices, but other devices may be used. . In addition, natural water that is in equilibrium with the atmosphere contains nitrogen, oxygen, argon, carbon dioxide gas, etc. at a ratio that is almost the same as the atmospheric components, and the higher the temperature, the lower the solubility. Therefore, without using the deaerator 22 or in combination, the

heat exchangers

24 and 26 for raising the temperature of the raw water are arranged in two or more stages, and gas bubbles separated at an intermediate temperature are collected. A method may be adopted.

Next, the raw water is divided into

heat exchangers

24 and 26 and flows. In the heat exchanger 24, heat is exchanged with distilled water discharged from the condenser of the evaporation / condensing device 2, and the temperature of the raw water is heated to a temperature that is 5 ° C. lower than the boiling point. The reason why the temperature is set to 5 ° C. is that a calorie of 5 cal / g is necessary to raise the temperature from this temperature to the boiling point, and a calorie of 10 cal / g is necessary for the produced water when the gas-liquid separation rate is 50%. This is because the energy efficiency is lowered when the temperature is lowered by 5 ° C. or more from the boiling point. The compression corresponding to the calorie of 5 cal / g is pressurized from 1. atm to 1.172 atm, and from 0.5 atm to 0.586 atm. Similarly, in the heat exchanger 26, heat exchange is performed with the concentrated water (residual water) discharged from the gas-liquid separator 6, and the temperature of the raw water is heated to a temperature that is 5 ° C. lower than the boiling point of the raw water. .

As the

heat exchangers

24 and 26 used for exchanging heat between raw water and high-temperature distilled water and concentrated water, counter-flow type heat exchangers are desirable, and plate type heat exchangers are particularly suitable. The heat exchanger is not limited. When an efficient plate heat exchanger is used in the counterflow type, the temperature difference between the primary and secondary sides can be as low as 1 ° C, and operation is possible at a temperature difference of 2 to 3 ° C. . Thereby, the degassed raw water approaches the boiling temperature near the outlet of the heat exchanger, but when the pressure difference is large and the temperature on the condenser side is high, condensed water higher than the boiling temperature flows into the heat exchanger, It is also possible to start boiling before entering the evaporator. Hot water for heat exchange includes concentrated water (residual water) and distilled water so that they are not mixed. In the example of FIG. 2A, two plate-type heat exchangers are used, but three or more may be used, or a partition plate (a blind plate) that divides the flow path by one can be attached, Alternatively, other methods can be adopted.

The raw water heated by the

heat exchangers

24 and 26 merges and passes through the heating heater 30 and enters the evaporation / condensing device 2 from the high-temperature raw water inflow line 12, but the heater 30 hardly works after the steady state. May be. As described in FIG. 1, at least a part of the raw water is evaporated by being heated by the condensation heat of water vapor in the evaporator. Although the water vapor generating heater 32 is used to generate water vapor at the time of start-up, this heater may be hardly operated when the steady state is reached. The gas-liquid separator 6 separates the water vapor and the concentrated water, and the concentrated water is sent from the concentrated water discharge line 16 to the heat exchanger 26 for heat recovery and cooled.

The steam is pressurized by a turbine type blower (blower) 8 and sent to the condenser of the evaporator / condenser 2, and the produced distilled water is discharged from the distilled water discharge line 14 and sent to the heat exchanger 24. It is done.
The pressure of water vapor is preferably 1.01 to 2.0, depending on the type of raw water. If it is atmospheric pressure, it corresponds to a pressure of 0.01 to 1.0 atm. The reason for this is that if the pressure under atmospheric pressure is 0.01 atm or less, even if it is distillation of fresh water, the pressure is practically too low, and the temperature difference between the condenser and the evaporator is small, so the distilled water production capacity is low. Because. The greater the pressurization, the greater the temperature difference between the condenser and the evaporator, the faster the condensation rate and the evaporation rate, and the higher the production rate of distilled water, but at pressures where the pressure ratio of pressurization exceeds 2.0. This is because the energy to raise the water by 20 ° C. or more is supplied, and the energy cost increases. When the apparatus is operated, if the supply capacity is sufficient, the pressurization is reduced, and if the demand for water increases and the supply capacity is no longer sufficient, a flexible operation for increasing the pressurization is possible.

The plate heat exchanger can be easily disassembled and inspected, and the direction of the fluid can be easily changed. Therefore, it is preferable that the line (flow path) through which raw water flows and the line (flow path) through which distilled water or concentrated water flows can be exchanged. After the operation is stopped and cleaned, the scale attached to the raw water side dissolves in the hot water by flowing hot water through the flow path where the raw water flows, and then flowing the raw water through the flow path on the hot water side. There is no need, and maintenance becomes easy.

The boiling portion of the evaporator may be at atmospheric pressure or may be depressurized. At atmospheric pressure, there is an advantage that there are few problems of strength of the apparatus. However, since the boiling temperature is 100 ° C. at atmospheric pressure, heat loss is more likely to occur than in the case of reduced pressure, and when corrosive seawater is used as raw water, the corrosion resistance of the material constituting the heat exchanger is only high. However, the material cost is slightly increased. Lowering the pressure enables distillation at a low temperature, and the scale adhesion to the equipment is not strong, the amount is small, and there is an advantage of less heat loss, but the distillation rate is reduced, or a vacuum pump for decompression There is a problem that is necessary.
On the other hand, when the pressure is increased, the pressure strength of the device is increased, resulting in cost problems, the boiling temperature is increased, and the corrosiveness of the raw water or the concentrated water is increased. Scale adhesion becomes stronger, the amount increases, and the time and effort for removing the scale increases. However, since the distillation rate increases, it is also effective to increase the pressure depending on the application.

FIG. 2B shows an example in which two plate heat exchangers 3 as evaporation / condensation devices are connected, and pressurized steam as boiling nuclei can be blown into the connecting portion through the steam pipe 17. If the evaporation / condensing device 2 is a plate heat exchanger, a partition plate (a blind plate) that divides the flow path by a single unit can be attached.

FIG. 3 shows an example of an apparatus according to the present invention in which evaporation / condensing apparatuses are combined in multiple stages. Each set includes an evaporating / condensing

device

2, 2 ', 2 ", a gas-

liquid separating device

6, 6', 6", a

blower

8, 8 ', 8 ", and a distilled

water discharge line

14, 14', 14". The high-temperature raw water heated by the heat exchanger (not shown) flows into the first stage evaporation / condensing device 2 from the high-temperature raw water inflow line 12, having the concentrated

water discharge lines

16, 16 ′, 16 ″. The concentrated water discharged from the first-stage and second-stage gas-liquid separators 6 and 6 'is introduced as raw water into the second-stage and third-stage evaporator /

condenser

2, 2' and 2 ", respectively. To do. The concentrated water discharged from the third-stage gas-liquid separator 6 ″ and the distilled water discharged from each stage of the evaporating /

condensing devices

2, 2 ′, 2 ″ are sent to a heat exchanger to preheat raw water. Heat exchange is performed. In the example of FIG. 3, the concentrated water discharged from the gas-

liquid separators

6 and 6 ′ does not need to be preheated because of high temperature. In the example of FIG. 3, the evaporator / condenser is combined in three stages, but the combination may be two stages, or four or more stages. In this example as well, the efficiency can be increased by introducing steam as boiling nuclei.
When the concentrated water remaining after distillation such as seawater is concentrated to saturation, the boiling point rises by about 10 ° C., so that it becomes necessary to increase the applied pressure and the energy consumption increases. In the case of seawater desalination, the concentration rate should be about 2 to 8 times, considering that increasing the concentration of the concentrated water is disadvantageous in terms of energy, and recovering the heat of the concentrated water with a heat exchanger. It is. However, in a large facility, as shown in FIG. 3, if the evaporator / condenser is combined in multiple stages, the concentration rate can be increased 9 times even in 2 stages of about 3 times, and the efficiency is increased. On the other hand, concentrated water remaining after distillation, such as seawater, can be effectively used for salt production. In this case, the higher the concentration, the better. However, since it is disadvantageous in terms of energy to produce concentrated salt water for salt production at a concentration of 10 times or more at once, multistage distillation in which the concentration process is divided into two or more as shown in FIG. 3 is advantageous. . The higher the degree of concentration and the higher the pressure required, the smaller the amount of water, so a smaller heat exchanger is required, and the energy efficiency is increased by the multi-stage. In addition, as the degree of concentration increases, clogging due to salt precipitation is more likely to occur. However, the cost of the apparatus, the cost of maintenance, and the like are reduced as a whole, such as taking measures for clogging only at the final stage.

With the apparatus and method for producing distilled water and / or concentrated water according to the present invention, it is possible to obtain distilled water with low energy use by an apparatus that is easy to maintain. Low-cost water can be obtained from use to use as industrial high-purity water. Compared with the reverse osmosis membrane method, energy efficiency can be increased and maintenance is easy.
Concentrated water can be produced at a lower cost than ever for wide use such as production of concentrated seawater as a salt production raw material and pretreatment of various water treatments.
Use of both distilled water production equipment and method and concentrated water production equipment and method is desirable from the viewpoint of energy efficiency, but it is sufficient to use either one according to the user's environment and necessity. Of course, only one of them can be used.

Experimental Example As described above, by forming a pressure difference between the evaporator and the condenser partitioned by the heat transfer plate by the blower, heat transfer occurs between the evaporator and the condenser, thereby The heat of vapor condensation can be used for evaporation in the evaporator. A schematic diagram of an experimental apparatus demonstrating this is shown in FIG. In this experimental apparatus, the evaporator 10 is a stainless steel cylinder having an outer diameter of 122 mm, an inner diameter of 121 mm, and a height of 400 mm. In order to secure a flow path width of about 5 mm inside, the upper part having a diameter of 111 mm and a height of 300 mm is rounded. A stainless steel cylinder (inner cylinder) 5 was fixed at several points in a state where it was floated 5 mm from the bottom. A blower 8 was attached to the evaporator outlet portion of about 100 mm above the cylindrical container 5 in the condenser. Water droplets contained in the steam were collected by a mist trap 9 installed at the top of the evaporator and returned to the evaporator wall. Next, a condenser 11 having an inner diameter of about 180 mm and a height of 430 mm was arranged on the outside so as to wrap the entire blower 8 and the evaporator, and a heat insulating material was arranged around the condenser 11 and necessary places on the piping. In the drawing, reference numeral 35 denotes a pressure gauge, and 36, 36 ', 36 ", 36""denote thermometers, respectively. In order to introduce a part of the steam in the condenser 11 into the evaporator as boiling nuclei, four steam pipes 17 are attached to the evaporator in the circumferential direction at a position about 1/5 from the bottom of the evaporator height. The steam pipe 17 was provided with an adjustment valve and adjusted in advance so that a small amount of steam passed. In order to make the temperature of the supplied raw water accurate, the heat exchanger 20 is not used, but instead, the raw water at a desired temperature can be supplied to the evaporator 4 from the raw water tank 27 with a temperature controller. . Distilled water produced by the condenser was discharged from the outlet pipe, cooled by the cooler 29, led to the distilled water reservoir 39, and the amount of distilled water produced was measured by a weigh scale 47 '. Further, the raw water tank 27 with temperature controller and the raw water flow rate control valve 43 are connected by a soft silicone rubber hose so that the weight of the raw water including the tank can be measured.
Regarding the pressure, the condensation side was set to atmospheric pressure, and the inside of the evaporator could be lowered to 0.8 atm by adjusting the input voltage of the blower (turbine) 8 and the raw water flow rate adjusting valve 43. In the test, the following results were obtained when the inside of the evaporator was 0.9 atm and the inside of the condenser was 1 atm.
(1) Prior to the experiment, the weight of water (about 1.2 kg) retained in the pipe and the evaporator above the raw water flow rate control valve 43 is measured in advance.
(2) The raw water tank 27 is once boiled by the raw water heater 37 with temperature control. Water vapor due to boiling was blocked by the flexible cover 28 and discharged together with the dissolved air through the pressure relief valve 19, and the subsequent air dissolution into the raw water was prevented by the flexible cover 28. In this state, the raw water was kept at a constant temperature of 97 ° C.
(3) Separately from this, when the steam supply heater 33 is heated by the steam generation heater 31 to generate steam and the steam is sufficiently supplied to the evaporator 10 through the steam supply valve 32, a thermometer in the evaporator is provided. 36 'and the thermometer 36 in the condenser indicate 100 ° C, and water vapor comes out of the pressure relief valve 18.
(4) The steam supply valve 32 is closed and the raw water weight is measured by the weigh scale 47.
(5) The blower 8 is operated to adjust the voltage of the blower motor so that the evaporator internal pressure becomes 0.9 atm, and the flow rate adjusting valve 43 is opened little by little to supply 97 ° C. raw water into the evaporator.
(6) At this time, the pressure in the evaporator slightly approaches 1 atm, but the raw water at 97 ° C. is supplied as it is, and after judging that the height of the water in the evaporator has increased to 130 mm as seen from the weight, the flow control valve 43 Thin until just before closing. Then, the pressure in the evaporator almost returns to 0.9 atm, and a flow 38 of distilled water can be observed. At this time, the distilled water flow rate adjusting valve 44 is opened so as not to disturb the flow of distilled water.
(7) Thereafter, the flow rate adjustment valve 43 is adjusted so that the total weight of the raw water and the distilled water becomes equal. This is to keep the water level in the evaporator constant.
(8) After about 2 minutes, the temperature in the lower part of the evaporator is about 97 ° C, but when the temperature of the water vapor coming out of the blower is measured with the thermometer 36, the temperature rises to about 106 ° C, and the pressure relief valve 18 The amount of water vapor leaking is almost constant.
(9) When the blower motor supply voltage was finely adjusted so that the internal pressure of the evaporator was constant in this state, it was about 49 V, 4.9 A and about 240 W. In addition, about 270 ml of distilled water was obtained in 10 minutes in a stable state. The heat transfer area at this time is calculated to be about 0.05 m ² .
(10) Next, the flow rate adjusting valve 43 is opened, and the flow rate adjusting valve 43 is adjusted when the height of the water in the evaporator is judged to have increased to 260 mm from the weight of the raw water, and the height is maintained. .
(11) As a result, the amount of water vapor leaking from the pressure relief valve 18 increased visually, and the flow of distilled water increased.
(12) The amount of distilled water produced for 10 minutes after becoming stable was about 500 ml. At this time, the fan power required to maintain 0.9 atm is about 250 W, and the heat transfer area is calculated to be about 0.1 m ² .
(13) Next, in order to see the influence of the raw water temperature entering the evaporator, the set temperature of the raw water tank 27 was lowered from 97 ° C. to 96 ° C. while continuing the operation of the blower. After about 3 minutes, the temperature of the raw water reached 96 ° C. The temperature in the lower part of the evaporator was 96 ° C. On the other hand, although the temperature of the water vapor coming out of the blower was unchanged at 106 ° C., the amount of water vapor blown out from the pressure relief valve 18 was gradually reduced, and the amount of air blown out was visually halved. However, there was no change in the flow of distilled water. Moreover, the fan electric power required to maintain 0.9 atm remained at 250 W.
(14) When operated for 10 minutes in this state, the amount of distilled water produced was almost the same, and about 500 ml was obtained in 10 minutes.
(15) Further, when the temperature of the raw water entering the evaporator was gradually lowered to 95 ° C., the amount of water vapor blown from the pressure relief valve 18 gradually decreased, but the production rate of distilled water hardly changed. When the raw water temperature was further lowered, the water vapor blown out from the pressure relief valve 18 was stopped when the temperature was slightly below 95 ° C. At the same time, the flow 18 of distilled water disappeared, so the flow rate adjustment valve 43 was closed.
(16) When the voltage supplied to the blower motor was increased and the power was set to 800 W, the pressure in the evaporator was about 0.8 atm, and the steam was blown out from the pressure relief valve 18 at this moment, but the blowing stopped immediately. . Although the boiling point decreased and water vapor was temporarily generated by setting the pressure at 0.8 atm, the flow of distilled water did not recover. The reason is that the condenser and the atmosphere are not completely sealed, so that air enters the condenser and the condensation rate decreases, so that a sufficient amount of heat cannot be transferred to the evaporation chamber.
In this experiment, the heat transfer areas were about 0.05 m ² and 0.1 m ² , and about 1.6 liters / h and 3 liters / h with an energy input of 240 to 250 W / h for this heat transfer area. Distilled water was obtained. It was also found that even when water having a temperature lower by 1 to 2 ° C. than the boiling point was sent to the evaporator, it was heated to the boiling point by the heat from the condenser, and distilled water having the same level as that at the boiling point was obtained.

As described above, the configuration of the method and apparatus for producing distilled water and / or concentrated water according to the present invention has been described as an example. However, the present invention is not limited to this configuration, and various methods can be used without departing from the scope of the claims. It goes without saying that changes are possible.

DESCRIPTION OF SYMBOLS 1 Distilled water and / or concentrated

water production apparatus

2, 2 ', 2 "evaporation / condensing apparatus 3 Evaporation / condensing apparatus 4 Heat-

transfer plate

6, 6', 6" Gas-

liquid separator

8, 8 ', 8 "Blower 9 Mist trap 10 Evaporator 11 Condenser 12 High temperature raw

water inflow line

14, 14 ', 14 "Distilled

water discharge line

16, 16', 16" Concentrated water discharge line 17 Steam pipe 18 Pressure relief valve (for condenser)
19 Pressure relief valve (for raw water tank)
DESCRIPTION OF SYMBOLS 20 Heat exchanger 22

Deaerator

24, 26 Plate type heat exchanger 27 Raw water tank with temperature controller 28 Flexible cover 29 Cooler 30 Heating heater 31 Steam generating heater 32 Steam supplying valve 33 Steam supplying device 35

Pressure gauge

36, 36 ', 36 ", 36"' Thermometer 37 Raw water heater 38 Distilled water flow 39 Distilled water reservoir 40 Raw water 43 Raw water flow control valve 44 Distilled water flow control valve 47 47 'Weigh scale (balance)

Claims

In a method for producing distilled water and / or concentrated water from raw water, the method comprises:
(I) supplying raw water having a temperature 5 ° C. lower than the boiling point or higher to the evaporator;
(Ii) evaporating at least a part of the raw water as water vapor in the evaporator;
(Iii) discharging concentrated water;
(Iv) pressurizing the water vapor so as to be higher by 1.01 to 2.0 times the pressure in the evaporator so that the condensation temperature of the water vapor is higher than the boiling point of the raw water;
(V) condensing the pressurized water vapor with a condenser to form distilled water,
The evaporator and the condenser are partitioned by a heat transfer plate, and the heat of condensation due to the condensation of the water vapor in the condenser is transferred from the condenser to the evaporator through the heat transfer plate, A method for producing distilled water and / or concentrated water, wherein the raw water is boiled in the evaporator.
2. The method for producing distilled water and / or concentrated water according to claim 1, wherein the step (ii) further comprises a step of separating the raw water evaporated at least partially as water vapor into water vapor and concentrated water. .
The method further comprises (vi) cooling the condensed distilled water and / or (vii) cooling the discharged concentrated water. Water production method.
The distilled water and / or concentrated water according to any one of claims 1 to 3, further comprising a step of preheating the raw water supplied to the evaporator to a temperature not lower than 5 ° C lower than a boiling point. Manufacturing method.
The step of preheating the raw water, the step of cooling the distilled water, and the step of cooling the concentrated water are performed in at least one counter-flow heat exchanger, and the raw water is converted from the distilled water and / or the concentrated water. The method for producing distilled water and / or concentrated water according to claim 4, wherein the raw water is preheated to a temperature 5 ° C. lower than the boiling point by applying heat to the water.
The method for producing distilled water and / or concentrated water according to claim 5, wherein the heat exchanger is a plate heat exchanger.
The distilled water according to any one of claims 1 to 6, wherein a part of the pressurized water vapor is returned to an evaporator to form a water vapor nucleus for reducing the heating degree of boiling. And / or a method for producing concentrated water.
The steps (ii), (iii), (iv), and (v) are repeated in one or a plurality of cycles using the water concentrated in the evaporator as raw water. The manufacturing method of distilled water and / or concentrated water as described in any one of these.
The raw water is seawater or saline lake water, and the pressurizing step pressurizes so that the pressure in the condenser is higher by 1.02 to 2.0 times the pressure in the evaporator. The method for producing distilled water and / or concentrated water according to claim 1.
The distilled water and / or concentrated water according to any one of claims 1 to 9, wherein the raw water is treated water containing heavy metal or treated water containing a substance that is not volatile. Production method.
In a distilled water and / or concentrated water production apparatus for producing distilled water and / or concentrated water from raw water, the distilled water and / or concentrated water production apparatus comprises:
Raw water supply means for supplying the stock solution;
An evaporator for evaporating at least a part of the raw water supplied from the raw water supply means;
A condenser in communication with the evaporator for condensing water vapor to produce distilled water;
Pressure means provided in a line leading from the evaporator to the condenser,
The pressurizing means pressurizes the water vapor in the condenser so that the condensation temperature of the water vapor is higher than the boiling point of the raw water,
The evaporator and the condenser are partitioned by a heat transfer plate, and the evaporation heat due to condensation of water vapor in the condenser is transferred from the condenser to the evaporator through the heat transfer plate. A device for producing distilled water and / or concentrated water, wherein the raw water is boiled in a vessel.
The apparatus for producing distilled water and / or concentrated water according to claim 11, further comprising a gas-liquid separation device provided between the evaporator and the condenser for separating the raw water into water vapor and concentrated water. .
And further comprising at least one plate heat exchanger provided between the raw water supply means and the evaporator,
Concentrated water discharged from the evaporator or the gas-liquid separator and / or the distilled water discharged from the condenser exchange heat with the raw water in the plate heat exchanger. The apparatus for producing distilled water and / or concentrated water according to claim 11 or 12.
The apparatus for producing distilled water and / or concentrated water according to any one of claims 11 to 13, further comprising a pipe for returning a part of the pressurized water vapor into the evaporator.
The apparatus further comprises at least one set of evaporators, a pressurizing means communicating with the evaporator, and a condenser communicating with the pressurizing means. The concentrated water discharged from the previous set of condensers is used as raw water for the next set of evaporators. The apparatus for producing distilled water and / or concentrated water according to any one of claims 11 to 14, wherein each set is connected to be introduced into an evaporator.
The raw water is seawater or saltwater lake water, and the pressurizing means pressurizes so that the pressure in the condenser is higher by 1.02 to 2.0 times the pressure in the evaporator. The apparatus for producing distilled water and / or concentrated water according to any one of claims 15 to 15.
The distilled water according to any one of claims 11 to 16, wherein the plate-type heat exchanger can exchange a line through which raw water flows and a line through which distilled water or concentrated water flows. And / or concentrated water production equipment.