KR100783686B1 - Process and plant for multi-stage flash desalination of water - Google Patents

Abstract

The present invention relates to a brine desalination method and a plant suitable for carrying out the method. The method comprises providing a brine heater, providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser, providing a heat exchanger, brine as a coolant to preheat the feedwater. Supplying a water supply to a condenser, supplying the preheated water to a brine heater, further supplying a first heating water including steam to the salt water heater to heat the preheated water, the heated water supply And condensing the evaporate in the desalination zone with at least a portion of the heated feedwater in the desalination zone to supply an at least one desalination zone from a brine heater and to provide an evaporate comprising water vapor.

Brine desalination method, brine heater, condenser, desalination zone, heat exchanger, water supply, coolant, evaporate

Description

Multi-Stage Flash Desalination Method and Plant {PROCESS AND PLANT FOR MULTI-STAGE FLASH DESALINATION OF WATER}

The present invention relates to a method and a plant for desalination of brine, in particular seawater.

Conventional desalination plants operate according to a multi-stage flash (MSF) method. Flashing is a method of evaporating water vapor from brine and then collecting it by condensation. Water can be boiled, for example, by reducing the pressure. In the MSF method, brine is continuously fed to a number of flashing zones so that substantially salt free condensate is collected in each zone.

In many parts of the world where there is a shortage of freshwater supplies, the need for effective brine desalination technology is increasing. The need for these technologies is increasing considerably due to the lack of water and increasing demand of fresh water due to global warming.

MSF desalination methods are currently commercially available to supply fresh water to the dry regions of the world where brackish and / or seawater is present. However, these plants are costly to capital and run because of the volume input required by the process and the energy input needed to evaporate a sufficient amount of water vapor at a sufficiently high rate. In order to minimize energy requirements, MSF technology is commercially used in power plants to use available thermal energy.

Despite this improvement in energy efficiency of desalination plants, there is still a need for improved brine desalination methods and apparatus that improve energy efficiency and reduce the cost and environmental damage incurred in conventional desalination plants. These desalination applications require less steam in the desalination process in order to minimize energy consumption from fuel and produce power or water at the lowest possible cost.

In the present invention, the method of desalination of brine

a) providing a brine heater,

(b) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser,

(c) providing a heat exchanger,

(d) supplying the condenser with a feed water comprising brine as a coolant to preheat the feed water,

(e) supplying the preheated feedwater to a brine heater,

(f) supplying a first heated water comprising steam to the brine heater to further heat the preheated feedwater,

(g) selectively recovering at least a portion of said first heated water from a brine heater,

(h) supplying the heated feedwater from the brine heater to at least one desalination zone, evaporating at least a portion of the heated feedwater in the desalination zone to provide an evaporate comprising water vapor, and on the condenser of the desalination zone Condensing the evaporate,

(i) recovering the depleted feedwater comprising brine and the bottled water comprising the condensate from the desalination zone,

(j) supplying a part of the deteriorated water supply to the heat exchanger as thermal circulating water,

(k) supplying to the heat exchanger a second heated water optionally comprising at least a portion of the recovered first heated water to heat the thermal circulating water, and

(l) supplying the heated thermal circulating water to at least one desalination zone

It includes.

The method of the present invention improves the thermal efficiency of the desalination process compared to conventional desalination plants. The supply of heated thermal circulating water to the desalination zone is an effective means of returning heat (which may be wasted) to the desalination zone, thus reducing the plant's overall energy requirements.

In another method of the invention, the thermal circulating water may be provided by deteriorated feed water rather than bottled water. Water for thermal circulation can be obtained from the desalination zone. Therefore, in the present invention, the method of desalination of brine

a) providing a brine heater,

(b) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser,                 

(c) providing a heat exchanger,

(d) supplying the condenser with a feed water comprising brine as a coolant to preheat the feed water,

(e) supplying the preheated feedwater to a brine heater,

(f) supplying a first heated water comprising steam to the brine heater to further heat the preheated feedwater,

(g) selectively recovering at least a portion of said first heated water from a brine heater,

(h) supplying the heated feedwater from the brine heater to at least one desalination zone, evaporating at least a portion of the heated feedwater in the desalination zone to provide an evaporate comprising water vapor, and on the condenser of the desalination zone Condensing the evaporate,

(i) recovering the depleted feedwater comprising brine and the bottled water comprising the condensate from the desalination zone,

(j) supplying a part of the deteriorated water supply to the heat exchanger as thermal circulating water,

(k) supplying to the heat exchanger a second heated water optionally comprising at least a portion of the recovered first heated water to heat the thermal circulating water, and

(l) supplying the heated thermal circulating water to at least one desalination zone

It includes.

As an alternative, the thermal circulating water can be obtained from the feed water and then fed to a brine heater. Therefore, in the present invention, the method of desalination of brine

(a) providing a brine heater,

(b) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser,

(c) providing a heat exchanger,

(d) supplying the condenser with a feed water comprising brine as a coolant to preheat the feed water,

(e) feeding the first portion of the feedwater to the brine heater as preheated feedwater,

(f) supplying a second portion of the feed water to the heat exchanger as thermal circulating water,

(g) feeding a first heated water comprising steam to the brine heater to further heat the preheated feedwater,

(h) selectively recovering at least a portion of said first heated water from a brine heater,

(i) supplying to the heat exchanger a second heated water optionally comprising at least a portion of the recovered first heated water to heat the thermal circulating water,

(j) supplying the heated feedwater from a brine heater and the heated thermal circulating water from a heat exchanger to at least one desalination zone, wherein at least some of the heated feedwater and the heated thermal circulating water in the desalination zone are Evaporating, producing an evaporate comprising water vapor to condense the evaporate in the desalination zone, and                 

(k) recovering from the desalination zone deteriorated feed water comprising brine and bottled water comprising the condensate

It includes.

In step j, when one or more desalination zones are installed, the desalination zones to which the heated feed water and the heated thermal circulation water are respectively supplied may be the same or different.

The desalination process of the present invention is a significant improvement over energy efficiency in conventional desalination plants, for example MSF plants. The desalination process of the present invention operates by heating the brine and then flashing the heated brine in the desalination zone. Preferably, the plurality of desalination zones are provided in a continuous arrangement so that the heated brine can be gradually flashed down through the successively arranged desalination zones. The desalination zones arranged in series are preferably maintained at lower pressure continuously. The flashing flow of each desalination zone is condensed on the condenser and this condensate is collected. The condenser comprises at least one pipe through which coolant flows, and the collecting means preferably comprises a product water trough in which the condenser tube is disposed. In this case, the bottled water trough is connected to each desalination zone so that the bottled water is flashed down each step in parallel with the water supply, and the flashed stream is recovered as water in the bottled water trough.

Preferably, the first heated water supplied to the brine heater comprises steam. This steam can be supplied from a combined steam-raising plant.

The method of the present invention can heat the thermal circulating water using one heat exchanger. Also, a plurality of heat exchangers can be used. In this case, the plurality of heat exchangers may be connected in series, or may be connected in parallel if desired.

The coolant for the condenser tube is preferably unheated feed water. The feed water itself may comprise the makeup feed from the brine and the circulating water from the desalination zone. In this case the condensation tube of each desalination zone section is cooled by circulation and / or makeup feed water flowing through the zone in the opposite direction to the flashing water supply. The circulated feed water is thus preheated gradually before the brine heater. After passing the brine heater, the feedwater is released through the control valve to flash in the first desalination zone. The control valve stops the feedwater from boiling inside the heat exchanger, and also prevents the possibility of steam leaking into the feedwater because steam can be contaminated by traces of toxic chemicals used in boiler water treatment. It is desirable to maintain the water supply pressure above the steam pressure. Otherwise, the brine heater tube may leak bottled water in the MSF unit.

In the preferred method, the coldest condensation tube, heat rejection section of the MSF unit is cooled by sea water to remove waste heat from the circulation process and to produce the maximum fresh water. Cooled water from flashing at the lowest pressure stage is circulated through the unit by a large pump. The bottled water is replaced by the hottest heat removal step where air is removed by makeup from the seawater outlet and returned to the lowest pressure step. The concentration of circulation and / or makeup feedwater is controlled by continuously injecting a small amount of brine from the lowest pressure stage to the seawater outlet.

In each of the flashing stages of the feed water some non-condensable gas may be released. These gases can be extracted by the exhaust and vacuum ejector systems in order to prevent the stage condensation surface from being blanketed with these gases and becoming ineffective, thus degrading the performance of the MSF unit. Providing similarly to the brine heater helps to ensure that the heat transfer performance is maintained by properly extracting non-condensable gases. These systems mean that the bottled water and the second heated water have a very low level of soluble gas.

The MSF desalination unit may include several alternatives in the configuration of each stage of the heat exchanger and desalination and in the selection of the number of stages forming part of the overall unit. The direction of the flashing water supply may be a so-called elongated tube design, parallel to the direction of the circulation and / or makeup water supply, or may be a so-called cross-flow design perpendicular to the flow. There is no limit to the number of desalination steps. For example, the method of the present invention may employ more than about 20 desalination zones, wherein the condenser in the front zones arranged in series is cooled by the feed water sequentially heated as the feedwater moves towards the brine heater and the condenser in the rear zone. Is cooled by cold sea water to maximize condensation.

The heat exchanger tube may be formed of any suitable material such as copper, brass, titanium and stainless steels of various grades and specifications to withstand chemically strong high temperature seawater flowing at the rate required for optimal heat exchange. The heat exchange side is preferably administered with chemicals and sometimes circulating a soft rubber ball in the water stream to allow freely settling of the scale-forming insoluble minerals from the hot seawater as much as possible. This mechanical cleaning method is limited in the selection of the diameter of the tube, thus limiting the optimization of heat exchange performance or cost. Chemical cleaning methods can also be used.

In conventional MSF plants, the amount of heat exchange surfaces in each stage and the number of stages determine the amount of steam required per product unit delivered by the MSF plant. Significant additional costs are incurred because increasing the heat exchange surface significantly is necessary to reduce certain steam consumption, and it is generally necessary to increase the heat exchange surface by 15% to reduce specific steam consumption by 5%.

Conventional plants include a brine heater that heats the feed water prior to flashing in the first stage of the MSF unit using thermal energy from low pressure and low temperature saturated steam, which generally has a saturation temperature of 115 ° C. The water condensed in the brine heater from the steam supply is returned to the steam-rise plant by a pump to a temperature close to the saturation temperature of the steam in the brine heater.

In the method of the invention, the first heated water may comprise steam from a steam lift power plant, in which case the method of the present invention recovers the second heated water from a heat exchanger and returns the recovered stream to steam lift power. Additional steps may be included to return to the device. In this case, the temperature of the condensate returned to the steam raising plant determines the lowest temperature at which the plant can cool the boiler exhaust gas. In a practical heat recovery steam generator, the difference between the stack gas of the returned condensate and the water temperature is typically between 15 and 20 ° C. This would result in a stack temperature of this type of power and water production plant exceeding 130 ° C. When gas is used as fuel for such power and water production plants, stack temperatures of up to 100 ° C. are possible but water return temperatures can be higher. Higher stack temperatures lower the efficiency of the thermal energy used in the overall process, which requires several percent additional heat input, resulting in significant cost and fuel consumption during plant use.

The method of the present invention thus provides a method for improving the energy consumption of desalination plants and combined power and multistage desalination plants. The method of the present invention is to provide a power and desalination plant in which the overall cost increase is relatively low and the fuel energy is consumed less. The present invention reduces the steam requirements of the MSF desalination unit for a given fresh water production and reduces the capacity, dimensions and costs of the steam-lift plant and associated steam turbines, steam pipe appliances, valves and support structures. The method of the present invention can improve steam consumption by the MSF unit without increasing the number of steps of the MSF unit or changing the heat transfer surface requirements within the MSF unit. The method of the present invention can reduce steam consumption at less cost than an alternative to increasing the heat transfer surface or the number of steps. The present invention has little effect on the operation of the combined MSF unit so that the design can easily accommodate the connection to the thermal circulating water and the heat exchanger connection in the second heated water outlet or outlet pipe mechanism. Thus, the present invention can be easily applied with minimal modification to existing MSF units. The heat exchanger of the second heated water requires a suitable surface area to achieve the desired advantages, and can be constructed cheaper when the thermal circulating water is bottled water, and the water on both sides of the heat exchanger is free of salt and contains very low levels of insoluble oxygen. Since it contains, material can be assembled more easily than seawater. The present invention provides that the heat exchanger tube ensures that the bottled water pressure of the heat exchanger is above the pressure of the salt water heater before any bottled water can be circulated into the MSF unit, thereby reliably separating the condensate from the bottled water even after a failure. Traces of toxic boiler treatment chemicals prevent the possibility of contaminated living water. The present invention introduces thermal circulating water that does not affect the operation of the combined MSF unit other than steam consumption, where only breakage or failure of any part of the additional water circuit affects steam consumption and is decisively necessary. There is no adverse effect on the continuous discharge of the often present MSF unit.

By using a heat exchanger having a low log mean temperature difference (LMTD), heat can be recovered to the maximum from the second heated water of the heat exchanger. If the heat circulating water includes bottled water, the clear water contained in the heat exchanger allows the plate and frame heat exchangers to be used to provide high heat transfer performance with low LMTD at an economical price. As an alternative, heat can be recovered well at an appropriate surface area due to the heat exchanger with a tube of suitable dimensions. The LMTD optimum range for heat exchangers is between 3 and 20 ° C.

The heat exchanger may be located outside of the brine heater with any recovered first heated water (which may be condensate) drained or pumped into the heat exchanger as part or all of the second heated water. The second heated water may comprise hot water from another source or method. As an alternative, the heat exchanger may be integrally constructed with the brine heater with suitable shrouding. The internal mounting arrangement eliminates the need for connections and separate heat exchanger casings, while simplifying construction and installation work.

The heat circulating water for the second heated water affects the recovery of heat from the second heated water. The ratio range of these flows is preferably about 0.5 to about 1.15, more preferably about 0.7 to about 1.15 and most preferably about 0.85 to about 1.15.

When thermal circulating water is obtained from the desalination zone, the lowest return temperature of the second heated water is determined in the step of separating the flow from the zone. When using one or more desalination zones, as in the case of the preferred method of the present invention, the lowest separation point is the lowest pressure desalination zone of the MSF unit. The highest point is the next stage, which has a lower output than the stage where the thermal cycle returns. Obtaining the heat circulating water from the higher pressure stages increases the lowest return temperature of the second heated water, which is advantageous for optimizing the performance and cost of the combined power and water plant, while reducing the benefits of steam consumption of the MSF unit. can do.

In a preferred method according to the invention using a plurality of desalination zones, the zone where the thermal circulation water returns to the MSF unit affects the effect of transferring heat to the desalination zone. The optimum step is to operate at a pressure just below the saturation pressure of the water corresponding to the temperature of the thermal circulating water.

It is desirable to prevent the second heated water, which may be contaminated by traces of toxic boiler treatment chemicals, from mixing with the thermal circulating water. This separation is ensured under normal conditions due to the heat exchanger. Even if there is a leak in the heat exchanger, separation can be maintained if the pressure on the heat circulation side is maintained above the pressure on the second heated water side. This can be ensured by a pressure support device set at the maximum brine heater pressure in the thermal cycle circuit between the heat exchanger outlet and the return port of the MSF unit. The device is a control valve and associated measurement control means or is perforated in the return phase and is sufficient to ensure that the sum of the return stage pressure and the static head of water under the weir lip always exceeds the brine heater pressure. It may be a weir located in a circulating water circuit at height.

Next, the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart of a conventional multi-stage flash desalination plant.

2 is a first cross-sectional view of a conventional cross-flow MSF unit.

FIG. 2A is a second cross-sectional view taken along the line A-A of FIG. 2.

3 is a flow chart of a multistage flash desalination plant arranged to operate according to the first method of the present invention.

4 is a cross-sectional view illustrating one arrangement for extracting bottled water as product water from the product trough.

5 is a diagram illustrating one external heat exchanger arrangement.

6 is a diagram illustrating another heat exchanger arrangement disposed within a brine heater shell.

7 is a diagram illustrating a connection arrangement for returning the circulated hot thermal circulating water to a high temperature step.

8 is a flow chart of a multi-stage flash desalination plant arranged to operate in accordance with the second and third methods of the present invention.

9 is a diagram illustrating another connection portion for extracting deteriorated water supply for thermal circulation.

10 is a diagram illustrating an external heat exchanger arrangement when feedwater is circulated.

11 is a diagram illustrating an arrangement for returning hot circulated feedwater to a higher temperature step.

1 is a diagram of the basic arrangement of a multistage desalination method. The preheated circulating water is heated in the brine heater 1 and then released to the first desalination stage via the pressure support valve 3. The feed water is flashed through a series of desalination zones 4 with steam condensed on the tubes 5 cooled by the circulated makeup feed water. Bottled water is collected in the bottled water trough 6 and flashed between the steps that continue to the heat removal step 7. There may be several such heat removal steps arranged for the desalination zone. The feed water is circulated by the pump 8 through the desalination zone and the heat removal step. The non-condensable gas is extracted and cascaded in stages and extracted by the ejector 9 in the lowest pressure stage with seawater cooled condenser 10. The condensation section of the heat removal step is cooled by sea water 11. Warm seawater flow is used to provide cycling makeup via an air removal device 12 and a makeup pump 13.

2 and 2A are diagrams illustrating the physical arrangement of the desalination step of a conventional MSF unit. Feedwater enters the stage via weir (14). Vapor is flashed and passed through a demister pad 15 to condense on a pile of tubes 16 cooled by water supply. Bottled water is collected in the product tray 17 and flows into the product trough 18 from there through the weir and into the next product trough. The noncondensable gas released from the flashing feed water is extracted via an exhaust pipe 19 to the ejector system.

3 is a diagram illustrating how the MSF cycle is modified by the present invention when using bottled water as thermal circulating water. The condensate from the brine heater 1 'passes through the heat exchanger 147 and then returns to the steam ascent plant. Some circulating water in the bottled water is drawn from the bottled water trough of the low pressure desalination step of the MSF unit 3 '. This bottled water is supplied to the secondary side of the heat exchanger 147 by the pump 145. The flow exiting the heat exchanger is the product of the high pressure stage desalination zone 121 of the MSF unit after the other pipe connection is supported under pressure by the pressure support valve 150 or the weir device 151, shown by the dashed line. Return to trough.

4 illustrates the connection of hot water 20 and bottled water channel 18 from which bottled water is extracted.

FIG. 5 illustrates an arrangement of the brine heater 126 disposed above the ground and adjacent to the desalination section of the MSF unit 120. The heat exchanger 147 is in the form of a heat exchanger 21 with a tube, can be located on the ground adjacent to the brine heater 126, and is joined after flowing through a heater exchange shell (not shown) May be piped to a second heated steam hot reservoir 22 having a second heated water discharged to Thermal circulating water from the relatively low pressure desalination zone is piped to the end 146 of the heat exchanger 147 and heated through the heat exchanger 147 and then line 148 to the product trough of the relatively high pressure desalination zone. Is connected to the pipe. Plate and frame heat exchangers can be arranged in a similar manner.

6 is a diagram of an arrangement of the brine heater 126 surrounding the heat exchanger 147 ′. The tube stack is located in the outer shroud tube that directs the second heated water from the heat exchanger inlet 23 to the outlet 24, where the second heated water passes through the brine heater shell. The circulated thermal circulating water is injected into the heat exchanger of the second heated water discharge end 146 ', while the hot thermal circulating water is injected into the return connection to the product trough from the other end 148'.

7 is a view of the connection to return hot water to the water supply trough 25 at the high temperature stage of the MSF unit. The circulated bottled water is supplied to the distribution box and the weir 151 or sparge pipe arrangement by the external connection pipe 154, from which it is discharged above the trough's bottled water level.

8 shows how the MSF cycle is modified by the present invention when feedwater is circulated. Condensate from the brine heater 1 'supplemented by hot water from the heat cycle 154' flows through the heat exchanger and then returns to a steam raising plant (not shown). Partial circulation of the feedwater from the desalination stage 3 'is drawn from the feedwater channel of the low pressure stage and injected forward, or alternatively the main circulation between the condensation tube nests of the stages where the other pipe connections are shown in broken lines and / or Or draw from makeup watering. Either way, the feedwater is drawn from the low pressure stage and piped to the secondary side of the heat exchanger. The flow from the heat exchanger secondary outlet is maintained pressurized by the pressure support valve 150 'before returning to the feed channel 149' of the high pressure stage of the desalination section of the MSF unit.

9 is a diagram of another arrangement for extracting water from the desalination step of the MSF unit. Feedwater is extracted from feedwater channel 26 via hot reservoir 27. As an alternative, the feedwater is extracted from the main circulation and / or make-up feed loop pipe or connection with 28.

10 is a diagram of a brine heater 29 arrangement located above the ground adjacent to the desalination section of the MSF unit 30. A heat exchanger (31) consisting of a multi-pass tube is placed above the brine heater on the ground and pumped to the second hot water high temperature reservoir (32), and the condensate flows through each pass of the heat exchanger and then the steam ascending plant ( (Not shown). The circulated cold water is piped to the tube of the first pass of the heat exchanger adjacent to the condensate outlet 33 and the outlet of the final pass on the tube side of the heat exchanger 34 is piped to the return connection with the feed channel. Connected.

11 is a view of the feedwater return connection to feedwater channel 35. A spray tube or distribution box 36 returns the hot water to the channel and distributes it over a portion of the width of the feed channel.                 

The configurations of the plants, piping, control valves, pumps, release valves, flow control devices and other standard appliance products shown are for example only, and the method and the plant of the present invention are not limited to the configurations shown. Will understand.

Next, the present invention will be described in more detail by way of example. Example 1 is an example of the method according to the invention in which some of the bottled water is circulated as a heat cycle flow.

Example 1

Referring to FIG. 3, a brine feedwater was fed to line 100 at 6638.9 kg per second and at 35 ° C. temperature. Seawater salinity is 4.45%. Seawater in line 100 is supplied to line 101 as a coolant for air ejector 102. Line 103 of air ejector / condenser 102 is supplied with a mixture of water vapor and noncondensable gas (mainly air) extracted by extractor 104 from heat removal step 105. The non-condensable gas is discharged to line 106a and any residual material that is condensable is discharged from air ejector / condenser 102 of line 106. In this example, the seawater flow rate in line 101 is 250 kg per second.

Residual seawater is fed from line 100 (6388.9 kg per second flow rate) to line 107 as coolant in heat removal step 105. The coolant seawater in line 107 is heated to a temperature of 42.68 ° C. through heat removal step 105, some of which (1819.5 kg per second flow rate) are supplied to line 108 as makeup. Residual seawater in line 107 is discharged from the plant via line 109.

Makeup seawater in line 108 passes through an air removal device 110. The extracted air is returned to extractor 104 via lines 111, 112, 113 and then to air ejector / condenser 102 via line 103.

The degassed makeup brine passes through line 114 from the air removal device 110 and is injected into line 116 via pump 115 to combine the brine circulating water from line 143 with line 117. Lose. In this example, the composite makeup and circulating water in line 117 flows at 6194.4 kg per second flow rate and the temperature has a 42.057 ° C. salinity of 6.28%.

The composite makeup and circulating water in line 117 is called water supply.

Feedwater in line 117 passes as coolant to condenser tube 118 in desalination zone 119. Desalination zone 119 is the final area of the desalination zones in a line. Of the desalination zones in FIG. 3, the first desalination zone is indicated by reference numeral 120, the second desalination zone is indicated by reference numeral 121, and the dividing line 122 is similar to that actually not shown in FIG. 3. Indicates that there is another desalination zone.

Feedwater passing through condenser tube 118 passes through condenser tube 123 of desalination zone 121 and then through condenser tube 124 of desalination zone 120. The preheated feed water passes through the brine heater 126 via line 125 to a temperature of 102.829 ° C. Line 127 to brine heater 126 is supplied with water at 76.356 kg per second flow rate, temperature 130 ° C. and pressure 2 bar. The heated feed water is discharged from the brine heater 126 via line 128 and flow control device 129 at a temperature of 110 ° C. and pressure 2 bar. The heated feed water in line 128 passes through the first desalination zone 120.

Defrost device 130 which receives the brine flowing out of the first desalination zone 120, and the vapor from the outflowing brine passes before condensation on the tube 124 and collected in the bottled water trough 132. 131. The outflowing brine and bottled water fall through the desalination zones of lines 133 and 134 arranged in parallel, respectively. After exiting the final desalination zone 119, the outflowing brine passes through line 135 to remove heat 105. Bottled water passes through bottled water trough 137 of heat removal step 105 via lines 136 and 136a.

As in the desalination zone, the heat removal step 105 may comprise a similar series of regions arranged in a line.

In the heat removal step 105, the brine supplied to the line 107 is used as the coolant and the final product collected in the product trough 137 is supplied to the reservoir in the line 138. Residual brine from the heat removal step 105 is discharged through line 139, and some is circulated through pump 140, line 141 and line 143 as circulating water for line 117. The remaining portion is discharged via pump 140, line 141 and line 142.

Thermal circulating water is obtained from the final desalination zone 119 according to the present invention. A portion of the bottled water in line 136 (76 kg per second in this example) is passed through circulation pump 145 and extracted into line 146 at a temperature of 48.20 ° C. and 0% salinity. Thermal circulating water in line 146 passes through the tubes of heat exchanger 147 and passes through bottled water troughs in desalination zone 121 via lines 148 and 149. The heated thermal circulating water is kept pressurized by the pressure support valve 150 in this example. Alternatively, as shown by the dashed line in FIG. 3, weir device 151 can be used to maintain the pressure of the heated thermal circulating water.

Heat exchanger 147 is supplied with heated water from brine heater 126 via lines 152 and 153. As an alternative, heated water may of course be supplied via line 154 from an external source (eg, a combined steam raising plant). Steam or hot water is removed from the system via line 155.

Table 1 shows the various parameters of Example 1 in each of the 20 steps of the method according to the invention. In this example, step 20 includes a brine heater, 16 desalination zones and 3 heat removal steps. The measured parameters are as follows.

A is the feed water temperature (° C.) at the inlet of each stage.

B is the feed water temperature (° C.) of the outlet of each stage.

C is the water supply in kg / s through each step.

D is the flow rate of the flashing brine flowing from each stage (kg / s).

P is the pressure (bar absolute value) for each step.

m is the flow rate of the bottled water (kg / s) at each stage.                 

M is the additional production flow rate (kg / s) of the last bottled water at each stage.

Taking the above example as a whole, the production rate (kg of bottled water produced per kilogram of steam fed to the system) is 8.795. Method Plants Operating According to the Example The plant can produce 12.75 million young gallons of bottled water daily (approximately 60 million liters of water each day).

Example 2

Referring to FIG. 8, seawater feedwater is supplied to line 100 'at 6638.9 kg per second and at a temperature of 35 ° C. Seawater salinity is 4.45%. A portion of the seawater in line 100 'is supplied as coolant to air ejector 102' via line 101 '. The air ejector / condenser 102 'is supplied via line 103' with a mixture of steam and non-condensable gas (mainly air) extracted by extractor 104 'from heat removal step 105'. The non-condensable gas is discharged via line 106a 'and any residual material that is condensable is discharged via line 106' from air ejector / condenser 102 '. In this example, the seawater flow rate in line 101 'is 250 kg per second.

 Residual seawater is transferred from line 100 '(at a flow rate of 6388.9 kg per second) to line 107' as a coolant in heat removal step 105 '. Coolant seawater in line 107 'passes through heat removal step 105' and is heated to a temperature of 42.68 ° C, some of which is supplied to line 108 'as makeup (at a flow rate of 1822 kg per second). Residual seawater in line 107 'is discharged from the plant via line 109 ".

Makeup seawater in line 108 'passes through an air removal device 110'. The extracted air is returned to extractor 104 'via lines 111'. 112 '. 113' and then back to air ejector / condenser 102 'via line 103'.

De-aired makeup seawater is passed from line removal device 110 'through line 114' and pumped into line 116 'through pump 115' to the brine circulating water passing through line 143 '. By line 117 '. In this example, the combined makeup and circulation water in line 117 'flows at a flow rate of 6194.4 kg per second, the temperature is 42.057 ° C and the salinity is 6.28%.

Next, the combined makeup and circulation water in line 117 'is called water supply.                 

Feedwater in line 117 'passes through condenser tube 118' in desalination zone 119 'as coolant. Desalination zone 119 ′ is the final area of the desalination zones in a line. In FIG. 3, the first region of the series of desalination zones is indicated by reference numeral 120 ′, the second region by reference numeral 121 ′, and the dividing line 122 ′ is another that is not actually shown in FIG. 8. It indicates that there is a similar desalination zone.

Feedwater passing through condenser tube 118 'passes through condenser tube 123' of desalination zone 121 'and then through condenser tube 124' of desalination zone 120 '. The preheated feed water passes through the brine heater 126 'via line 125' at a temperature of 102.807 ° C. Steam is supplied to the brine heater 126 'via line 127' at 76,597 kg per second flow rate, temperature 130 ° C and pressure 2 bar. The heated feed water is discharged from the brine heater 126 'via line 128' and flow control device 129 'at 110 ° C and pressure 2 bar. The heated feedwater in line 128 'passes through the first desalination zone 120'.

First desalination zone 120 ′ is a bottom region 130 ′ containing flashing brine, and frost that passes before the vapor from the flashing brine is condensed on tube 124 ′ and collected in bottled water trough 132 ′. And removal device 131 '. Flashing brine and bottled water fall into the desalination zone via lines 133 ', 134' arranged in parallel. The flashing brine is discharged from the final desalination zone 119 'and then flows through line 135' to heat removal step 105 '. Bottled water flows through line 136 'to bottled water trough 137' in heat removal step 105 '.

In the heat removal step 105 ', the seawater supplied to the line 107' is used as a coolant and the final product collected on the bottled water trough 137 'is supplied to the reservoir via the line 138'. Residual brine from the heat removal step 105 'is discharged via line 139' and some is circulated through pump 140 ', line 141' and line 143 'to line 117'. It is supplied as circulating water. The remaining portion is discharged via pump 140 ', line 141' and line 142 '.

Thermal circulating water is obtained according to the invention from the final desalination zone 119 '. Some of the flashing brine in desalination zone 119 '(85.49 kg per second in this example) is line 144' (see FIG. 8 also shows another thermal cycle as described in Example 3, so that the dashed line in FIG. And into line 146 'via a circulation pump 145' at a temperature of 49.89 ° C and a salinity of 6.94%. Thermal circulating water in line 146 'passes through heat exchanger 147' tubes via line 146a 'and passes through lines 148' and 149 'to the bottom of desalination zone 121'. The heated thermal circulating water is kept pressurized by the pressure support valve 150 'in this example.

Heated water is supplied to the heat exchanger 147 'via the lines 152' and 153 'from the bottom of the brine heater 126'. Alternatively, heated water from an external source (eg, a combined steam raising plant) may be supplied via line 154 ′. Steam or hot water is removed from the system via lines 154 ', 155'.

Table 2 below shows the parameter values for this example 2 in each of the 20 steps of the method according to the invention. In this example, step 20 includes a brine heater, 16 desalination zones and 3 heat removal steps. The measured parameters are as follows.

A is the feed water temperature (° C.) at the inlet of each stage.                 

B is the feed water temperature (° C.) of the outlet of each stage.

C is the water supply in kg / s through each step.

D is the flow rate of the flashing brine flowing from each stage (kg / s).

P is the pressure (bar absolute value) for each step.

m is the yield of bottled water in each stage (kg / s).

M is the additional output (kg / s) of the total bottled water at each stage.

In the example above, the production rate (kg of fresh water produced per kilogram of steam fed to the system) is 8.865. Method Plants Operating According to the Example The plant can produce 12.9 million young gallons of bottled water daily (approximately 60 million liters of water each day).

Example 3

Example 3 was tested similarly to Example 2. However, referring to FIG. 8, thermal circulating water from desalination zone 119 ′ is obtained from feedwater brine in condenser tube 118 ′ rather than flashing brine in this region. Thermal circulating water is obtained via line 144 "(as shown by the dashed line in FIG. 8 to indicate that circulating water is also obtained from flashing brine via line 144 'as described in Example 2). This circulated water is supplied to line 146a 'and then as in Example 2.

Table 3 shows the parameter values for this example 3 in each of the 20 steps of the method according to the invention. In this example, step 20 includes a brine heater, 16 desalination zones and 3 heat removal steps. The measured parameters are as follows.

A is the feed water temperature (° C.) at the inlet of each stage.

B is the feed water temperature (° C.) of the outlet of each stage.

C is the water supply in kg / s through each step.

D is the flow rate of the flashing brine flowing from each stage (kg / s).

P is the pressure (bar absolute value) for each step.

m is the yield of bottled water in each stage (kg / s).                 

M is the additional output (kg / s) of the total bottled water at each stage.

Taking the above example as a whole, the production rate (kg of bottled water produced per kilogram of steam fed to the system) is 8.868. Method Plants Operating According to the Example The plant can produce 12.75 million young gallons of bottled water daily (approximately 60 million liters of water each day).

Claims (17)

In the brine desalination method, (a) providing a brine heater, (b) providing at least one desalination zone comprising a condenser and means for collecting condensate from the condenser, (c) providing a heat exchanger, (d) supplying the condenser with a feed water comprising brine as a coolant to preheat the feed water, (e) supplying the preheated feedwater to a brine heater, (f) supplying a first heated water comprising steam to the brine heater to further heat the preheated feedwater, (g) selectively recovering at least a portion of said first heated water from a brine heater, (h) supplying the heated feedwater from the brine heater to at least one desalination zone, evaporating at least a portion of the heated feedwater in the desalination zone to provide an evaporate comprising water vapor, and on the condenser of the desalination zone Condensing the evaporate, (i) recovering the depleted feedwater comprising brine and the bottled water comprising the condensate from the desalination zone, (j) supplying a portion of the bottled water to the heat exchanger as thermal circulating water, (k) supplying to the heat exchanger a second heated water optionally comprising at least a portion of the recovered first heated water to heat the thermal circulating water, and (l) supplying the heated thermal circulating water to at least one desalination zone Brine desalination method comprising a. delete delete The method of claim 1, Brine desalination method wherein said heated thermal circulating water is supplied to condensate collection means in a desalination zone. The method of claim 4, wherein A brine desalination method wherein the ratio between thermal circulating water to condensate in a collection means located in a desalination zone is from about 0.85: 1 to about 1.15: 1. The method according to any one of claims 1, 4 or 5, Brine desalination method provided by connecting a plurality of desalination zones in a line. The method of claim 6, Wherein said thermal circulating water is obtained from a first desalination zone and said heated circulating water is supplied to a second desalination zone. The method of claim 7, wherein And wherein said second desalination zone is closer to the brine heater than said first desalination zone in a line of desalination zones. The method of claim 8, And wherein said first desalination zone is maintained at a lower pressure than said second desalination zone. The method according to any one of claims 1, 4 or 5, Wherein the thermal circulating water is supplied to the heat exchanger at a pressure greater than the pressure of the second heated water supplied to the heat exchanger. The method according to any one of claims 1, 4 or 5, Wherein said feed water is supplied to a brine heater at a pressure greater than the pressure of said first heated water supplied to said brine heater. The method according to any one of claims 1, 4 or 5, Wherein said temperature of said thermal circulating water is not more than 5 ° C. higher than the water saturation temperature of said at least one desalination zone. The method according to any one of claims 1, 4 or 5, Recovering at least a portion of said first heated water from said brine heater. The method of claim 13, And said second heated water comprises at least a portion of said recovered first heated water. The method according to any one of claims 1, 4 or 5, Brine desalination method is provided a plurality of heat exchangers for heating the thermal circulation water. In the brine desalination plant, Brine heaters; At least one desalination zone comprising a condenser and a collection tray for collecting condensate from the condenser;  heat transmitter; Pumps, valves, and piping for supplying water to the condenser comprising brine as coolant to preheat the water; Valves and piping for supplying the preheated water to the brine heater; Valves and piping for supplying a first heated water comprising steam to the brine heater to further heat the preheated feedwater; Supplying the heated feedwater from the brine heater to at least one desalination zone and evaporating at least a portion of the heated feedwater in the desalination zone to provide an evaporate comprising water vapor, the evaporate on the condenser of the desalination zone Pipes, valves, and weirs for condensation; A weir for recovering depleted water from the desalination zone, a condensate collection tray, product troughs and pumps for recovering the bottled water comprising the condensate from the desalination zone, and brine; A connection to said product trough, piping, pump, and valve for supplying a portion of said bottled water as a heat circulating water to a heat exchanger; Pumps, pipes and valves for supplying a heat exchanger with a second heated water, which optionally includes at least a portion of the recovered first heated water to heat the thermal circulating water, and Pipes, valves and connections for supplying the heated thermal circulating water to at least one desalination zone Saline desalination plant comprising a. The method of claim 16, And a valve and piping for recovering at least a portion of said first heated water from the brine heater.

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