Multi-effect multi-train desalination method and apparatus

Abstract

The present invention relates to a phase change-based multiple-effect multi-train desalination plant (MEMTD) comprising n evaporator-condenser effects of at least two trains, each train of effects including at least one latent heat exchanger in each of the evaporator-condenser effects; at least one sensible heat exchanger (6) between each of the effects of the two trains, in which sensible heat is exchanged between a brine stream (18) discharged from the last evaporator-condenser effect of the effect of the previous train and an influent water stream (20) supplied as feedwater (21) to the first evaporator-condenser effect of the subsequent train; and a final condenser (7) that at least partially condenses evaporated steam (22) from the last evaporator-condenser effect of the evaporator-condenser effect of the last train.

Description

[Technical Field]

[0001] The present invention relates to a multiple-effect desalination system that uses phase change and has at least two trains of evaporator-condenser effects and low thermal gradients per evaporator-condenser effect. [Background technology]

[0002] A multiple effect desalination unit (MED) is based on a continuous process consisting of evaporation-condensation stages or effects under vacuum conditions, using residual steam from an adjacent power plant or other steam source as initial steam.

[0003] Current MED systems include multiple shell-and-tube or chamber heat exchanger systems. One embodiment of a MED multiple-effect desalination or distillation plant is formed by a vertical shell with vertical or horizontal heat exchanger tubes or chambers, with a condenser on the inner surface and an evaporator on the outer surface. In this configuration, steam condenses within the tubes or chambers, and heat exchange through the walls of the tubes or chambers evaporates brine flowing outside the tubes or chambers. The salt-free steam moves to the next effect, heating the inside of the tubes or chambers while condensing as desalinated water. Cooler fresh brine is fed to the outside of the tubes or chambers of the next effect and evaporated. This process is repeated continuously through a series of condenser-evaporator effects, typically 8 to 13 times.

[0004] As mentioned above, MED units receive energy as heat from residual steam from a steam turbine power plant or other steam source, and this heat is supplied to the first effect. The temperature of the steam supplied to the first effect is less than 70°C to limit mineral precipitation problems. The temperature difference between the water being evaporated and the steam being condensed is typically about 3°C ​​per effect. The number of effects is typically 8 to 13 evaporator-condenser effects. The heat recovery system across the multi-effect plant combines flash evaporation-condensation in the flash box, flash evaporation-condensation at the inlet of superheated feed water to each effect, and condensation of a portion of the steam from each effect in the feed heater. The heat sink located after the last effect is due to condensation of the steam evaporated in the last effect on the condenser tubes, through which cooling seawater circulates in a larger amount than the feed water. The recovery rate, which is the ratio between the desalinated water produced and the feed seawater supplied to the first effect, is about 35%.

[0005] One problem with current MED systems is their high energy consumption per unit of water produced. This high energy consumption is due to the following facts: current MEDs recycle the latent heat of the steam fed to the first effect only about 10 times on average; it is difficult to add more than 13 effects in an effect train because the initial temperature must not exceed 70°C to avoid mineral precipitation problems, and the more effects there are, the greater the salinity of the water treated in the last effect and the greater the thermal jump imposed by the boiling point elevation (BPE) of the evaporated aqueous solution; and the large consumption of pumping the large amount of cooled seawater fed to the final heat sink is returned to the sea without being used as feedwater.

[0006] The condenser-evaporator tube or chamber of a MED device's current condenser-evaporator function is a heat exchanger in which the brine to be evaporated flows through the evaporator side and the condensed water flows through the condenser side. When the evaporator-condenser tube or chamber is in a vertical position, the evaporated water and condensed water flow, forming a water layer or film on the evaporator and condenser sides of the tube or chamber, respectively. In some cases, a tube or chamber with corrugated walls is used to increase the heat exchange surface and create turbulence in the downward liquid flow, primarily promoting thermal convection by breaking down the boundary layer and providing a thinner liquid layer area with lower resistance to heat flow conduction.

[0007] In the horizontal position of the condenser-evaporator tube or chamber, the aqueous solution to be evaporated flows in a film across the outer evaporator surface, while the condensed water flows horizontally across the inner condenser surface, forming a water film with high resistance to heat flow across the entire wall covered by the liquid flow.

[0008] It is known that the interaction of cohesive and adhesive forces of water molecules with the solid surface of the container results in a curvature of the liquid-vapor interface known as the water meniscus or aqueous solution meniscus.

[0009] It is also known that a water meniscus can be divided into three regions characterized by very different behaviors with respect to heat transfer through the liquid film and solid-liquid interfacial adhesion forces. These three regions are the adsorbed, transitional, and bulk regions of the meniscus. It is known that the thickness of the liquid water film is smallest in the adsorbed region, but the thin liquid film remains strongly attached to the solid substrate due to intermolecular forces between the liquid and the solid. In this adsorbed region, the thermal conduction resistance is small and the interfacial thermal resistance is large. In the bulk region of the meniscus, the water film is thicker, resulting in a large conductive thermal resistance and a small interfacial thermal resistance. In this bulk region of the meniscus, the curvature of the liquid-vapor interface remains nearly constant. The transitional region lies between the adsorbed and bulk regions of the meniscus. This transitional region is characterized by a low thermal conduction resistance and a low thermal interfacial resistance resulting from the thin thickness of the water layer. An important reference on this subject is the paper by Joel L. Plawsky of Rensselaer Polytechnic Institute in New York, entitled "The Transitional Region of Water-Vapor Interfacial Heat Transfer."

[0010] It is known that in water or aqueous solutions in contact with the solid walls of a container, the curvature of the liquid-vapor interface arises from the resulting effects of adhesive and cohesive forces. When the walls are close to each other, the liquid-vapor interface is curved throughout the entire space between the walls. When the walls of the container are at a distance greater than the distance that acts on the adhesive forces of the water molecules to the walls, the liquid-vapor interface is flat in the central region between the walls and curves only in the vicinity of the walls.

[0011] Absorption heat pumps or ABHPs are well known and have been known to be coupled to multiple effect desalination plants, commonly referred to as ABHP MEDs. These ABHP MED desalination plants present high energy costs due to the low number of times latent heat is recycled across the 6 to 12 effects that these configurations typically have.

[0012] Steam ejectors coupled with thermal vapor compression multiple-effect desalination plants, commonly referred to as TVC MEDs, are well known. These TVC MED installations present a high energy intensity per unit of product due to the low number of latent heat recycles over the typically less than 13 evaporator-condenser effects these configurations have, and due to the high temperature of the steam used as motive steam for the ejector. [Prior art documents] [Non-patent literature]

[0013] [Non-Patent Document 1] Review of the Effects of Surface Topography, Surface Chemistry, and Fluid Physics on Evaporation at the Contact Line Summary of the Invention

[0014] The invention is defined in the claims section. A multiple-effect desalination unit MED with multiple trains of evaporator-condenser effects and a low gradient or thermal jump per evaporator-condenser effect has the capacity to increase by approximately three times the current capacity that a multiple-effect desalination or distillation plant can achieve using a given cooling water flow in the heat sink from a given mass flow rate of residual steam.

[0015] The multiple-effect, multi-train desalination plant MEMTD uses a large portion of the cooling water flow of the heat sink represented by the final condenser as feedwater, thus reducing the energy intensity for seawater pumping compared to current MED plants.

[0016] The multiple-effect, multi-train desalination device MEMTD is a phase change desalination device that includes at least one heat exchanger called a high-density transition zone heat exchanger (HTRDHE), which consists of heat exchanger tubes or chambers in which the water condensing on the condenser side and the aqueous solution evaporating on the evaporator side flow in channels with closely spaced walls, typically less than 1 mm, and the flow of water or aqueous solution in these channels has a curved liquid-gas interface throughout the entire wall-to-wall flow rate, which allows a high-density transition zone to be achieved on the surfaces of the evaporator and condenser sides.

[0017] One embodiment of the HTRDHE uses an evaporator-condenser tube or chamber whose wall profile, in a cross section perpendicular to the liquid flow, has a sinusoidal, sawtooth, or similar shape, such that across the liquid-gas interface of water or an aqueous solution flowing in a microchannel, the adhesion forces of water on the sidewalls of the microchannel cause the liquid-gas interface to curve across the entire width of the liquid-gas interface between the walls of the microchannel.

[0018] The dimensions of the microchannels that at least partially cover the evaporating and condensing sides of the tubes or chambers of the HTRDHE depend on adhesive and cohesive forces, which in turn depend on many other factors, such as the properties of the aqueous solution, the properties of the material of the tube or chamber walls, the inclination angle of the microchannel walls, and the finish or treatment applied to the walls of the tubes or evaporator-condenser chambers, which may be hydrophilic or hydrophobic.

[0019] One embodiment of the tube walls or evaporator-condenser chamber of the HTRDHE uses a marine aluminum alloy, with a symmetrical alternating channel profile in a sawtooth or zigzag pattern forming microchannels on both the evaporator and condenser sides, with a maximum depth of 1 mm and a maximum distance between the peaks or apexes of the microchannels of 1 mm.

[0020] To accomplish the evaporation and condensation cycle, the HTRDHE operates when the thermal jump, or temperature difference, between the aqueous solution being evaporated on the evaporating side of the evaporator-condenser tube or chamber and the temperature of the secondary steam being condensed on the condensing side of the evaporator-condenser tube or chamber is less than 0.3°C plus the boiling point elevation, BPE, corresponding to the salinity and temperature of the aqueous solution being evaporated. For seawater, this 0.3°C plus boiling point elevation temperature difference results in a temperature difference of less than 1°C, compared to the 3°C typically required by heat exchangers in current MED systems. Thus, the result achieved in HTRDHE is a low temperature difference between the evaporated aqueous solution and the condensed fresh water, which is due to the wall-tube structure of the evaporator-condenser chamber, where the cohesive and adhesive forces of water molecules position the evaporated aqueous solution flow from the evaporating side of the tube or evaporator-condenser chamber and the condensed water flow from the condensing side of the tube or evaporator-condenser chamber, and thus the liquid-gas interface curves between the walls of each microchannel over the entire flow rate, and a dense transition region is achieved at the evaporating top and condensing surfaces.

[0021] The result of positioning the liquid flow between the microchannel walls so that adhesive and cohesive forces maintain the curvature of the liquid-gas interface from wall to wall across the entire width of the microchannel is to achieve a high water surface density in the transition region on both the evaporator and condenser sides. To simultaneously achieve a high density of fiber regions on both the evaporator and condenser sides of the heat exchanger wall, at least one tube or evaporator-condenser chamber must have a cross-sectional profile perpendicular to both the flow of the salt-water solution being evaporated and the condensing flow in a symmetrical alternating pattern along the circumference of the evaporator-condenser tube or chamber, such that the evaporator meniscus on the evaporator side alternates with the condenser meniscus on the condenser side, minimizing the distance between the transition regions of the evaporator and condenser menisci.

[0022] At least one HTRDHE in each evaporator-condenser effect is characterized by having an evaporator-condenser tube or chamber with an alternating wall design in cross section, where the evaporator meniscus is rotated 180° and inverted to form an inverse symmetry with the condenser meniscus, and this configuration aligns the transition region of the evaporator meniscus in parallel or adjacent arrangement with the transition region of the condenser meniscus or with the anhydrous region of the condenser surface, so that the latent heat flow of condensation released at the anhydrous surface on the condensation side or released at the transition region of the condensation meniscus on the condensation side flows through the wall of the condensation-evaporation tube or chamber to the transition region of the evaporation meniscus on the evaporation side, where the heat flow is at least partially converted into latent heat of evaporation. This design of the evaporator-condenser tube or chamber with alternating channels positions the evaporator meniscus in anti-symmetrical relation to the condenser, and this configuration allows for a dense transition region, allowing the transition region of the evaporator meniscus to be in close proximity to the transition region of the condenser meniscus, creating a path for latent heat exchange through the wall of the condenser-evaporator tube or chamber with high heat flow, low thermal resistance, and a low temperature gradient between the aqueous solution being evaporated and the condensing vapor.

[0023] The multiple-effect multi-train desalination plant MEMTD uses a residual steam source below 70°C as used by current MED plants, but the specific mass flow consumption of steam per unit of product water is reduced to one-third of the specific mass flow consumption of steam outside current MED desalination plants.

[0024] A multiple-effect, multi-train desalination plant MEMTD comprises at least two trains of n condenser-evaporator effects and at least one sensible heat exchanger for aqueous solutions between two successive trains.

[0025] In one embodiment, a MEMTD multiple-effect, multi-train desalination plant is configured with three trains of 10 evaporator-condenser effects, where steam enters the first effect at less than 70°C and condenses at approximately 37°C in the final heat sink, the temperature difference between the evaporated water and the condensed steam is less than 1°C per condenser-evaporator effect, at least one sensible heat exchanger is between two consecutive effect trains, and the depletion in the sensible heat exchanger is less than 2°C; this embodiment allows for an increase in the production of product water produced by current MED plants per energy supplied to the system as residual steam supplied to the first effect and cooled seawater pumped to the final effect heat sink.

[0026] The configuration of the MEMTD, a multi-effect, multi-train desalination system with at least two trains of evaporator-condenser effects, with a sensible heat exchanger between the evaporator-condenser effects of two consecutive trains, allows for the recycling of latent heat and the maintenance of optimal salinity in the feedwater at each effect, even when the total number of effects in the plant is 30. In at least one sensible heat exchanger between two consecutive trains of n condenser-evaporator effects, the brine stream exiting the last evaporator-condenser effect of the previous train exchanges sensible heat with the fresh feedwater stream supplied to the first condenser-evaporator effect of the next train. The temperature loss between the incoming brine stream from the last evaporator-condenser effect of the previous train and the fresh feedwater stream output from the first condenser-evaporator effect of the next train is lower, with a temperature difference of less than 2°C, due to the larger exchange area and better heat transfer characteristics of the sensible heat exchanger.

[0027] In another embodiment, a multiple-effect, multi-train desalination unit MEMTD is coupled to an absorption heat pump vapor compressor AB MEMTD, which increases the amount of water produced at the expense of using higher energy waste steam, but the net overall result is a lower energy intensity per unit of product.

[0028] In another embodiment, a multiple-effect, multi-train desalination unit MEMTD is coupled to an ejector-type thermal vapor compressor TVC MEMTD, which increases the amount of water produced by up to two times the product per mass unit of steam fed to the non-TVC MEMTD at the expense of using higher energy waste steam, but the net overall result is a lower energy intensity per unit of product.

[0029] Considering that the per capita electricity consumption is 13-30 kWh / day and the residual steam from a steam-electric turbine derived from either a nuclear power plant, a hydrocarbon combustion plant, or a concentrated solar power plant is approximately 1 kg / kWh of generated electricity, the per capita residual steam is 13-30 kg / day. When coupled with a multiple-effect multi-train desalination plant (MEMTD), the electricity generated by the steam turbine can be used to produce 390-900 L / day of desalinated water per capita, which is sufficient to meet the per capita drinking water needs with a low energy intensity. When coupled with an AB MEMTD plant or a TVC MEMTD plant, the electricity generated by the steam turbine can be used to produce 780-1,800 L / day of desalinated water per capita. [Brief explanation of the drawings]

[0030] The invention is explained in more detail in the following description based on the accompanying drawings.

[0031] [Figure 1] Three regions of the evaporator meniscus adjacent to three regions of the condenser meniscus are shown in longitudinal cross section to highlight the heat flow characteristics from the condenser transition region to the adjacent evaporator transition region. [Figure 2] Three regions of the evaporator meniscus adjacent to three regions of the condenser meniscus are shown in longitudinal section to highlight the heat flow characteristics from the condenser transition region and from the anhydrous zone of the condenser face to the closely located evaporator transition region. [Figure 3]A diagram of a multi-effect, multi-train desalination plant, MEMTD, consisting of three trains of evaporator-condenser effects and their inter-train sensible heat exchangers is shown. [Figure 4] FIG. 1 is a schematic diagram of a multi-trough multi-effect desalination plant coupled to an absorption heat pump vapor compressor AB MEMTD. [Figure 5] A diagram of a multi-effect multi-train desalination plant coupled to a steam thermal compressor (TVC MEMTD) is shown. [Figure 6] A cross-sectional view of a portion of the wall of an evaporator-condenser tube or chamber of an HTRDHE is shown, perpendicular to the flow of aqueous solution on the evaporator side and the flow of water on the condenser side, where the alternating design of the walls of the evaporator-condenser tube or chamber follows an even-function symmetric pattern, with the evaporator meniscus rotated approximately 180° and inversely symmetric with respect to each of the two adjacent condenser menisci, and the proximity of the microchannel walls on the evaporator and condenser sides achieves a curvature of the liquid-gas interface across the width of the microchannel from wall to wall for the water flow from the condensing surface and the aqueous solution flow from the evaporating wall, achieving a high-density transition region at the evaporating and condensing surfaces, and a high-density, high-temperature flow region from the evaporating surface to the condensing surface, resulting in a high latent heat transfer coefficient of the latent heat exchanger per unit surface area and temperature difference degrees Kelvin. DETAILED DESCRIPTION OF THE INVENTION

[0032] A multiple-effect, multi-train desalination device MEMTD includes at least two trains of chambers or successive evaporator-condenser effects, each of which in turn includes at least one heat exchanger, referred to as a HTRDHE, and the two successive trains are thermally interconnected by a sensible heat exchanger.

[0033] Referring now to FIG. 1, the curvature of the liquid-gas interface or liquid meniscus of the aqueous solution being desalinated is shown on the evaporation side of at least one HTRDHE and is divided into three regions: an adsorption region 3 where a thin liquid film is held tightly to the solid substrate 60 by intermolecular forces between the liquid and the solid, where little evaporation occurs due to low thermal resistance due to conduction and high interfacial thermal resistance; a bulk region 5 of the meniscus where high thermal resistance is due to heat conduction through the thickness of the water layer and low interfacial thermal resistance; and a transition region 4 where the lowest total thermal resistance allows for the maximum heat flow Q per unit surface area.

[0034] Referring to FIG. 1, the curvature of the liquid-gas interface or meniscus of condensed water on the condensing surface of an HTRDHE is shown, with the transition region divided into three regions: adsorption region 55, bulk region of the meniscus 57, and transition region 56. By locating transition regions 4 and 56 closely on opposite sides of the wall 60 of the evaporator-condenser tube or chamber of the HTRDHE, a heat flow exchange path Q is provided whereby latent heat released by vapor 58 condensed on condenser transition region 56 flows with low thermal resistance and low thermal gradient toward evaporator transition region 4, where energy Q is at least partially absorbed as latent heat of vaporization of vapor 59 evaporated from the evaporator.

[0035] As shown in Figure 2, the evaporator side may have anhydrous zones where vapor 61 condenses directly on the condenser side of the evaporator-condenser tube or chamber wall 60. These anhydrous zones are created by designing the condensation surface with zones partially coated with a water-repellent layer that quickly repels droplets formed by condensation. They also result from the effects of free or forced dynamic vibrations on the condensate flow within the condensation structure, and by designing microchannels with a depth greater than the height of the condensate flow.

[0036] The proximity of the evaporator transition region to the condenser transition region and water-free condenser surface areas creates high heat flow channels Q1, Q2 and low thermal resistance. The dense transition regions at the condenser and evaporator surfaces achieve high heat transfer rates per unit surface area and unit temperature gradient, allowing operation at low temperature differentials at each evaporator-condenser effect. Similarly, the design of the condensing surface with microchannels ensures orderly passive drainage of condensed water by capillary action within the microchannels, ensuring the presence of an insulating, water-film-free surface.

[0037] 6 shows a schematic cross-sectional view of a segment 62 of the wall of a tube or evaporator-condenser chamber of an HTRDHE, perpendicular to the aqueous solution flow on the evaporation side and the condensate flow on the condensation side, showing that the curvature profile of the liquid-gas interface of the evaporated brine solution 63 flowing within the microchannels on the evaporator face is such that the curvature of the liquid-gas interface extends to the wall of the microchannel over the flow rate, and that the curvature profile of the liquid-gas interface of the condensate stream 64 flowing within the microchannels on the condensation face is such that the curvature of the liquid-gas interface extends from wall to wall across the entire width of the microchannel. The curvature of the liquid-gas interface, at least partially covering the evaporation face and across the microchannel through which the evaporated brine stream 63 flows, achieves a high-density transition region 4 in the curvature of the liquid-vapor interface of the desalted brine, and this high-density zone has a high latent heat flow of vapor that absorbs the evaporated vapor 59. The curvature of the liquid-vapor interface across the microchannel through which the condensate stream 64 flows, at least partially covering the condensation surface, achieves a high density transition region 46 in the curvature of the condensate liquid-vapor interface, the high density region having a high latent heat flow 58 of condensation.

[0038] The sinusoidal shape of the wall 62 alternates between an evaporating meniscus 63 and an inversely symmetrical condensing meniscus 64 with continuous reversals at 180° rotations, resulting in a condensation transition region 56 of the condensing meniscus 64 where condensation occurs and releases the latent heat of condensation 58 of the vapor with a greater energy flow per unit surface area, located near the evaporating transition region 4 of the evaporating meniscus 63, which absorbs the latent heat of vaporization of the evaporated vapor 59 with a greater absorbed energy flow per unit area. The high-density transition region created by this alternating structure of evaporating and condensing microchannels, or other sawtooth, zigzag, or similar structures, allows for the achievement of a high-density, high-energy flow path Q1 as the latent heat released in the condensing transition region 56 and / or a high-density, high-energy flow path Q2 as the latent heat released at the anhydrous surface of the condensing side where the vapor condenses 61, which flows to the evaporating transition region 4 on the evaporating side and is absorbed as the latent heat of vaporization 59.

[0039] One method for fabricating heat exchanger-condenser latent heat exchanger tubes or chambers with sinusoidal, zigzag, sawtooth, or similar walls 62 is to extrude or stamp an aluminum alloy to form microchannels 1 m deep and 1 mm wide between the apexes of each microchannel. Depths of 1 mm or greater allow for greater flow rates and longer condenser-evaporator tubes or chambers. Microchannel depths less than 1 mm reduce the width of each channel in the evaporator-condenser tube or chamber, thereby increasing the number of channels per unit perimeter and increasing the density of the transition region per unit surface area of ​​the evaporator-condenser tube or chamber. At microchannel widths greater than 1 mm, flat, non-curved regions of the liquid-vapor interface appear as the microchannel width increases, reducing the density of the transition region and reducing the efficiency of the heat exchanger. In these flat regions of the liquid-vapor interface, latent heat transfer from both evaporation and condensation is very inefficient, compromising the efficiency of the latent heat exchanger. The sinusoidal shape is modified with an angled end profile that creates a zigzag shape, or flat ends that create a sawtooth shape, rather than the rounded ends of the sinusoid.

[0040] A high-density transition region cannot be achieved with current double-grooved, double-floating evaporator-condenser tubes or chambers designed to create turbulence in the downward water flow because these tubes create a large area of ​​liquid-gas interface, which cannot be achieved if the grooves or slots are located on only one side of the tube.

[0041] As shown in Figure 3, one embodiment of a multiple-effect, multi-train desalination plant MEMTD comprises a vertical shell arrangement, with the vertical exchanger tubes or chambers having an evaporator face on the inside and a condenser face on the outside.

[0042] In another embodiment of the multiple-effect, multi-train desalination device MEMTD, the shell is horizontal and the horizontal tubes or chambers have an evaporator face on the inside and a condenser face on the outside.

[0043] In another embodiment of the multiple-effect, multi-train desalination plant MEMTD, a horizontal or vertical shell contains the heat exchanger tubes or chambers, with the evaporator surface on the outside and the condenser surface on the inside.

[0044] In each evaporator-condenser effect, at least one heat exchanger has a high density transition region.

[0045] As shown in FIG. 3, one embodiment of a multiple-effect, multi-train desalination device MEMTD includes three effect trains a, b, and c, with each two consecutive effect trains connected by a sensible heat exchanger 6.

[0046] In another embodiment, the multiple-effect, multi-train desalination plant MEMTD incorporates conventional MED equipment for heat transfer between fluids: a feed heater for heat exchange between the discharged steam and the feed water stream, and a flash box for steam generation by reducing the temperature of condensation and flashing the superheated feed liquid at each effect.

[0047] The multiple-effect, multi-train desalination plant MEMTD has at least one sensible heat exchanger 6 at the end of each train, except for the last train c, and the last condenser-evaporator effect n c is connected to a final condenser 7. At least one sensible heat exchanger 6 between the two trains of condenser-evaporator effects is connected to the final effect n, which is returned to the environment after passing through the sensible heat exchanger 19. a and the previous train n of utility b The sensible heat of the outgoing brine stream 18 of the last train n is exchanged with the ingoing stream 20 of preheated seawater 20 from the final condenser 7, which is fed as feedwater 21 after passing through at least one sensible heat exchanger 6 to the last utility n of the previous train. a , n b At a temperature at least equal to the temperature of the cone 18 minus 2°C, b and 1 c This will be supplied to the first utility of the following train.

[0048] In this configuration, a series of effect trains connected to a sensible heat exchanger allows up to 30 effects to be arranged in three trains of 10 evaporator-condenser effects in each train between a residual steam source 8 of less than 70°C and a final condenser 7 that normally operates at a temperature of approximately 37°C, and the recovery rate, which is the ratio of the mass of produced water to the mass of feed water, is maintained at the conventional MED level of approximately 35%, most of the sensible heat can be recycled between the effects of the two trains, 100% of the latent heat can be recycled between the two effect trains, and the energy intensity contributed as heat to the system per unit of water produced can be reduced by one-third compared to the current MED.

[0049] The first train 1 of the first effect receives a residual steam flow 8 from the steam turbine of the power plant or steam generating facility at a temperature below 70°C, avoiding mineral precipitation on the evaporator side, and returns condensate 9 to the power plant to generate fresh steam, similar to current MEDs. The steam outlet 10 produced in the first effect and the brine outlet 12 produced in the first effect are managed similar to current MEDs by corresponding heat recirculation processes.

[0050] The succeeding effects 2 to n-1 of each effect train receive steam 16 from the outlet of the preceding effect 10, receive brine 12 from the preceding effect to be used as feed water 13, extract product water 17 and brine 14 therefrom, and supply fresh steam 15 to the condenser of the next evaporator-condenser effect, similar to a conventional MED system.

[0051] The last utility n of the last train c of utilities c The steam outlet 22 of the last train c of effects is connected to a final condenser or heat sink 7, and the last effect n c The steam 22 is condensed against heat exchanger tubes or chambers through which cooled seawater 23 flows at ambient temperature. Cooled seawater 24 exits the condenser 7 at a temperature higher than ambient and is distributed at least partially as feedwater to the three effect trains a, b, and c. To save CAPEX on the final condenser, it is possible to supply more water 23 to the final condenser 7 as feedwater than required by the three condenser-evaporator effect trains, but this will increase the cost of pumping the water 23 and reduce the energy efficiency of the plant.

[0052] A multiple-effect, multi-train desalination plant MEMTD, configured with three effect trains and 10 evaporator-condenser effects per train, recycles latent heat between evaporator-condenser effect trains, recycles sensible heat between two consecutive effect trains, recycles all of the cooling water 23 supplied to the final condenser 7 as feed water for two effect trains, operates at the same level of recovery as current MEDs, utilizes all current knowledge of heat recycling between MED fluids, reduces the specific heat consumption per unit of produced water by up to one-third, reduces the specific power consumption per unit of produced water for pumping the final condenser cooling fluid by approximately one-third, and reduces the specific power consumption per unit of produced water for pumping the final condenser cooling fluid by 1.2 kWh / m of product. 3 It desalinates 40,000 ppm seawater with less than 100% electricity consumption and recycles residual steam from a steam turbine power plant at 70°C, which without the connection of a MEMTD desalination unit would have to be released into the atmosphere at temperatures above 100°C with a corresponding energy loss.

[0053] Alternatively, as shown in Figure 4, a multiple-effect, multi-train desalination system MEMTD includes three effect trains a, b, and c, which are connected by two sensible heat exchangers 6 and coupled to at least one absorption heat pump ABHP to form a multiple-effect, multi-train absorption pump desalination system MEMTD. The last effect n of the last train c c A vapor fraction 25 of up to 50% of the evaporated vapor 22 in the first train a is fed 26 into the casing of at least one absorber 27 of the absorption heat pump to hydrate an aqueous solution of lithium bromide 31 fed into the casing of at least one absorber 27 of the absorption heat pump. This absorption process releases energy from the condensation of the fed vapor 26, which is transferred to the first effect 1 of the first train a as it circulates in the internal heat exchanger tubes 28 in the absorber 27. a The steam generated by the first effect of the first train a is absorbed by the condensed water 30 of the first effect of the first train a and evaporated to form steam 29. a The lithium bromide hydrated solution 32 is extracted from the absorber 27 via an outlet pipe 33 connected to a pump 34, which drives the lithium bromide hydrated solution through at least one sensible heat exchanger 35. The hydrated lithium bromide solution 32 absorbs sensible heat from the dehydration solution 40 and exits the absorption heat pump's at least one generator 42 via a drain pipe 41. The lithium bromide solution is hydrated and heated via the sensible heat exchanger 35. The lithium bromide solution 37 is supplied to an evaporator-condenser tube 38 of the at least one generator 42. In the evaporator-condenser tube 38, residual steam 36, supplied from the steam turbine power plant at approximately 100°C, is condensed, and the condensate is returned to the power plant to produce more steam. The lithium bromide solution 37 releases steam, which is used as the first effect 1 of the first train a. a 39. This ABHP MEMTD configuration of three trains of ten evaporator-condenser effects coupled to an absorption heat pump makes it possible to achieve a product water mass flow rate of up to 60 times the mass flow rate of the external steam 36 fed to the desalination plant.

[0054] As shown in Figure 5, another embodiment of a multiple-effect, multi-train desalination system MEMTD includes three effect trains a, b, and c, which are connected by two sensible heat exchangers 6 and coupled to at least one vapor ejector compressor 45 to form a thermal vapor compression multiple-effect, multi-stage desalination system TVC MEMTD. The last effect n of the last train c c A vapor fraction 25 of up to 50% of the evaporated vapor 22 in the first train a is fed as drawn vapor 44 to at least one ejector 45, to which external power steam 43 is fed, and the ejector 45 is connected to the first effect 1 of the first train a. a The steam 46 is generated at a temperature and pressure of

[0055] Another embodiment of the thermal vapor compression multiple-effect multi-train desalination device TVC MEMTD includes multiple ejectors located at the end of each train or between the effects of the train.

[0056] The TVC MEMTD configuration of three trains of ten condenser-evaporator effects connected to at least one steam ejector 45 makes it possible to obtain a product water mass up to 60 times the mass of the external steam 43 supplied to the desalination plant as motive steam for the ejector.

Claims

1. A multi-effect multi-train phase change desalination device MEMTD, comprising: n evaporator-condenser effects in at least two trains, each train of evaporator-condenser effects including at least one latent heat exchanger in each of the evaporator-condenser effects; at least one sensible heat exchanger (6) between each of the two train effects, in which sensible heat is exchanged between a brine stream (18) at the outlet of the last evaporator-condenser effect of the previous train effect and an influent water stream (20) that is supplied as feedwater (21) to the first evaporator-condenser effect of the subsequent train; and a final condenser (7) for at least partially condensing the evaporated vapor (22) from the last evaporator-condenser effect of the last train of evaporator-condenser effects; A desalination device comprising:

2. 2. The desalination apparatus of claim 1, wherein at least one latent heat exchanger in each evaporator-condenser effect is a HTRDHE, the evaporator side of the microchannel is at least partially covered through which the brine solution to be evaporated flows, resulting in a curved liquid-gas interface across the entire width between the walls of the microchannel, and the condensation surface is at least partially covered by the microchannel through which the condensed water flows, resulting in a curved liquid-gas interface across the entire width between the walls of the microchannel.

3. The HTRDHE is characterized in that the meniscus or curvature of said liquid-gas interface of the evaporator surface is in close proximity to a transition region (56) of the meniscus or curvature of the liquid-gas interface of the anhydrous zone on the condensing surface where condensed water or vapor (61) on the condensing surface condenses, forming a rapid latent heat transfer path through which energy flow in the form of latent heat released by the vapor (58) condensing on the condensation transition region (56) of the condensing surface or by the vapor (61) condensing on the anhydrous zone of the condensing surface flows, with low thermal resistance and low temperature gradient, such that the heat flow through the condenser-evaporator tube or chamber wall (60) to the evaporator transition region (4) of the evaporator surface is at least partially converted into latent heat of vaporization of the evaporated vapor (59). The desalination apparatus according to claim 2 .

4. The condenser-evaporator effect of at least one train is connected to at least one absorption heat pump, a portion of the vapor (25) evaporated in the last condenser-evaporator effect of the at least one train is supplied (26) to an absorber (27), steam (36) from an external steam source is supplied into at least one condenser tube (38) of a generator (42) of the at least one absorption heat pump, and condensed water is returned to an external steam generating plant, which generates steam (39), which is supplied as a portion of the vapor supplied to the first effect of the evaporator-condenser effect of the at least one train. The desalination apparatus according to claim 2 or 3, characterized in that:

5. The evaporator-condenser effect of the at least one train is connected to at least one steam ejector (45), and a portion of the steam evaporated in the at least one effect is partially supplied as drawn steam (44) from the at least one ejector (45), and the at least one ejector (45) receives motive steam (43) from an external source and generates steam (46) that is supplied as input steam to the previous effect. The desalination apparatus according to claim 2 or 3, characterized in that:

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