WO2004060812A1 - Appareil de dessalage a entrainement par diffusion et processus correspondant - Google Patents

Appareil de dessalage a entrainement par diffusion et processus correspondant Download PDF

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Publication number
WO2004060812A1
WO2004060812A1 PCT/US2002/040499 US0240499W WO2004060812A1 WO 2004060812 A1 WO2004060812 A1 WO 2004060812A1 US 0240499 W US0240499 W US 0240499W WO 2004060812 A1 WO2004060812 A1 WO 2004060812A1
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WIPO (PCT)
Prior art keywords
water
stream
diffusion tower
air
heated water
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PCT/US2002/040499
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English (en)
Inventor
James F. Klausner
Renwei Mei
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University Of Florida
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Publication date
Application filed by University Of Florida filed Critical University Of Florida
Priority to AU2002361773A priority Critical patent/AU2002361773A1/en
Priority to PCT/US2002/040499 priority patent/WO2004060812A1/fr
Publication of WO2004060812A1 publication Critical patent/WO2004060812A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/16—Evaporating by spraying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
    • B01D3/343—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances the substance being a gas
    • B01D3/346—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances the substance being a gas the gas being used for removing vapours, e.g. transport gas
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/08—Thin film evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/10—Treatment of water, waste water, or sewage by heating by distillation or evaporation by direct contact with a particulate solid or with a fluid, as a heat transfer medium
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/14—Treatment of water, waste water, or sewage by heating by distillation or evaporation using solar energy
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/16—Treatment of water, waste water, or sewage by heating by distillation or evaporation using waste heat from other processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/138—Water desalination using renewable energy
    • Y02A20/142—Solar thermal; Photovoltaics

Definitions

  • the invention relates to water desalination systems and methods.
  • Desalination involves any process in which dissolved minerals are removed from saline or brackish water.
  • Technologies for desalination include distillation, reverse osmosis, electro-dialysis, and vacuum freezing. Distillation and reverse osmosis are the most common. Distillation technologies include Multiple Effect Distillation (MED) and Multistage Flashing (MSF), both of which operate by evaporating saline water at atmospheric or reduced pressure and condensing the vapor to produce fresh potable water.
  • MED Multiple Effect Distillation
  • MSF Multistage Flashing
  • RO operates on a filtering principle. High pressure pumps force saline water through nanofilter membranes allowing fresh water to pass while filtering out the dissolved minerals.
  • Humidification Dehumidification A desalination technology that has drawn interest over the past two decades is referred to as Humidification Dehumidification (HDH).
  • HDH Humidification Dehumidification
  • saline water is pumped through a condenser coil, where it picks up heat from condensing water vapor.
  • the saline water is then pumped through a solar collector where is collects more heat.
  • the saline water is then sprayed in a cooling tower, where a portion of it evaporates into the air.
  • CGP Carrier-Gas Process
  • HDH and CGP may provide some level of improved efficiency compared to more conventional desalination methods
  • HDH and CGP are both still energy intensive and provide limited water production efficiency (e.g. kilograms of fresh water per kilogram of feed water). Accordingly, even these improved methods still generally have limited application.
  • a diffusion driven desalination (DDD) process and apparatus is driven by water vapor saturating low humidity air. Liquid water is then condensed out of the air/vapor mixture in a condenser.
  • the invention is suitable for operation at low temperature and pressure and may be driven by waste heat with low thermodynamic availability.
  • the energy consumption for the DDD process is comparable to that for conventional flash evaporation and reverse osmosis processes.
  • An apparatus for purifying water includes a structure for receiving a heated water stream and creating at least one region having a thin film of water from the heated water stream.
  • a structure for forcing a low humidity air stream over the thin film of water is also provided which causes water from the thin film of water to evaporate and diffuse into the air stream to create a humidified air stream.
  • the phrase "low humidity air stream” refers to an air stream which includes less humidity as compared to the "humidified air stream” formed by evaporation and diffusion of water into the low humidity air stream.
  • At least one condenser is provided for condensing the humidified air stream, wherein purified water is obtained.
  • DDD Diffusion Driven Desalination
  • the heated water stream can be heated at least in part by at least one heat exchanger.
  • the heated water stream can be supplied by a variety of heat sources, including low pressure condensing steam from a power plant, waste heat from a combustion engine, and geothermal heat.
  • the condenser preferably comprises a direct contact condenser.
  • the structure for creating regions having thin films of water preferably comprises a diffusion tower.
  • the diffusion tower can include at least one plenum for drawing the humidified air stream out from the diffusion tower so that it can be condensed.
  • the plenum includes at least one inlet, the inlet at least in part facing a top of the diffusion tower. This orientation helps prevent the heated water stream from entering the plenum.
  • the structure for forcing an air stream over the thin film of water can comprise an air duct positioned near a bottom of the diffusion tower, the air duct including a plurality of holes, the plurality of holes facing a side or a bottom of the diffusion tower, such as transverse to a height of the diffusion tower.
  • the condenser can provide at least a portion of the low humidity air stream by dehumidifying air using a cooling water stream.
  • a single body of water can provide both the heated water sfream and the cooling water stream by drawing the heated water stream from a surface of the body of water while the cooling water stream is drawn from a depth below the surface.
  • the heated water sfream can be provided exclusively by a body of water so that no external heat source is required to provide the heated water stream.
  • heat to produce the heated water stream is supplied by a solar source.
  • a power plant including a desalination system includes an apparatus for converting a source of energy into heat and at least a portion of the heat into steam, and structure for converting cool water supplied into a heated water stream using at least a portion of the steam.
  • a structure for creating regions having thin films of water from the heated water stream is provided along with structure for forcing a low humidity air stream over the thin film of water, wherein water from the thin film of water evaporates and diffuses into the low humidity air stream to create a humidified air stream.
  • At least one condenser is provided for condensing the humidified air stream, wherein purified water is produced.
  • the condenser preferably comprises a direct contact condenser.
  • the source of energy comprises at least one fossil fuel or at least one nuclear fuel.
  • the structure for creating regions having thin films of water preferably comprises a diffusion tower.
  • the diffusion tower can include at least one plenum for drawing the humidified air stream out from the diffusion tower.
  • the structure for forcing an air stream over the thin film of water can comprise an air duct positioned near a bottom of the diffusion tower, wherein the air duct includes a plurality of holes which preferably facing a side or a bottom of the diffusion tower.
  • a method for purifying water includes the steps of providing a heated water stream including at least one non-volatile impurity, the heated water stream having a temperature above an ambient temperate.
  • a heated water stream is sprayed onto a high surface area material, wherein thin films of water form on surfaces of the high surface area material.
  • a low humidity air stream is forced over the thin films of water, wherein water from the thin films of water evaporates and diffuses into the low humidity air stream to create a humidified air stream.
  • the humidified air stream is then condensed to produce purified water.
  • the nonvolatile impurity can include at least one salt, wherein the method can comprise desalination.
  • the spraying and forcing steps preferably take place in a diffusion tower.
  • a single body of water can be utilized to provide both the heated water stream and the cooling water stream.
  • a single body of water can also be an exclusive source for the heated water stream.
  • Waste heat from a power plant can also be used to provide heat to generate at least a portion of the heated water stream.
  • a diffusion tower for humidifying air includes a rigid outer shell, an inside volume of the shell including a portion filled with high surface area material. At least one inlet is provided for receiving a heated water stream, wherein at least one region having a thin film of water forms on the high surface area material. At least one inlet is provided for receiving a low humidity air stream, wherein the low humidity air stream is forced over the thin film of water, wherein water from the thin film evaporates and diffuses into the air stream to create a humidified air stream. At least one plenum is disposed near a top of the diffusion tower for drawing the humidified air stream out from the diffusion tower.
  • the plenum includes at least one inlet, the inlet at least in part facing a top of the diffusion tower.
  • the structure for forcing an air stream over the thin film of water can comprise an air duct positioned near a bottom of the diffusion tower, the air duct including a plurality of holes, the plurality of holes facing a side or a bottom of the diffusion tower.
  • the diffusion tower preferably provides a height to diameter ratio of at least 2.
  • FIG. 1 is a flow diagram for a diffusion driven desalination system and process according to an embodiment of the invention.
  • FIG. 2 is a cross sectional view of an exemplary diffusion tower, according to an embodiment of the invention
  • FIG. 3. illustrates examples of different types of high surface area packing materials that may be used with the invention.
  • FIG. 10 illustrates the variation of exit brine temperature with exit air temperature for
  • the invention includes a Diffusion Driven Desalination (DDD) apparatus and process.
  • DDD Diffusion Driven Desalination
  • the invention can provide efficiency advantages over conventional desalination technologies and is capable of providing large production rates of purified water.
  • the preferred application for the DDD system is for desalination, the process can also purify water which includes other non-volatile contaminants, such as a variety of minerals including phosphates and nitrates, or metals including heavy metals.
  • the DDD process can utilize naturally occurring thermal energy storage provided by most large bodies of water, where desalination is most likely to be applicable. Because the desalination process can be accomplished at relatively low temperatures, inexpensive materials may be used for constructing a processing facility, and waste heat may be utilized to drive the desalination process, such as condensing steam from a nuclear or fossil fuel power plant which is a potential energy source which has been previously untapped. Accordingly, the invention can be operated using energy which can be provided at essentially no cost, thus making the inventive process significantly more economical when compared to other desalination processes.
  • the desalination process may be driven without any heating of the inlet feed water, such as when there is a significant temperature gradient between the surface water, which can be drawn in as feed water, and the cooling water found at lower depths.
  • desalination or purification can proceed without energy provided by any external heat source. Even when an external heat source is used, this feature of the invention allows the production efficiency (fresh water/feed water) of the DDD process to improve.
  • One important application for the invention involves placing a DDD plant on site at a steam driven electric generating plant, where the waste heat from condensing low pressure steam may be used to drive the desalination process.
  • the ability to utilize waste heat from condensing low pressure steam results in significant efficiency advantages of the invention over conventional desalination technologies.
  • Ra engineering gas constant for air kJ/kg-K
  • s entropy generation rate in the diffusion tower kW/K
  • FIG. 1 A simplified schematic diagram of the DDD process and system 100 is shown in FIG.
  • a main feed pump 105 draws water from a large body of water 110, such as seawater.
  • the suction for pump 105 preferably draws water near the surface of the body of water 110 in order to draw the warmer water that normally resides in the vicinity of the surface due to thermal stratification, as compared to cooler water which resides at deeper depths beneath the surface.
  • the surface water is optionally pumped through regenerative heater 115 as explained below and then fed to the main feed water heater 120.
  • the amount of heat required to heat the feed water depends on the main feed water mass flow rate and desired production rate.
  • the output temperature from the heater is generally relatively low, such as from 60 to 80°C which can provide good performance. Therefore, the required heat input for the heater can be provided by a variety of sources.
  • the only requirement for the heat source(s) which heat the supply water is the ability to raise the temperature of the water stream to a temperature above the ambient temperature.
  • Sources for heating can include heat from low pressure condensing steam in the main condenser of a steam driven power plant, waste heat derived from exhaust gases from a combustion engine such as a gas turbine or diesel engine, solar heating, or heat from a direct fossil fuel furnace or nuclear power plant.
  • waste heat from another processing plant, such as a refinery or chemical production facility would also generally be suitable for use with the invention.
  • Solar heating is particularly suitable for desert regions (e.g. Middle East) since solar heating generally requires a very large area to heat significant quantities of water. This might be economical in the Middle East or other locations where there is plenty of sun and inexpensive land.
  • the diffusion tower 125 is an important piece of equipment in the process, and the degree to which an operational DDD process follows theoretically predicted models depends on an appropriately designed diffusion tower.
  • low humidity air is pumped in, such as by a forced draft blower 130.
  • the water sprayed into the top of the diffusion tower 125 falls concurrently to the airflow through the diffusion tower by the action of gravity.
  • the diffusion tower 125 is preferably packed with very high surface area packing material, as would be found in a conventional air-stripping tower.
  • the diffusion tower 125 is preferably designed such that the air/vapor mixture leaving the tower should be fully saturated.
  • the purpose of heating the water prior to entering the diffusion tower is that the rate of diffusion and the exit humidity ratio increases with increasing temperature, thus yielding greater water production.
  • the water which is not evaporated in the diffusion tower 125 is preferably collected at the bottom of the tower and can be removed with a brine pump 135.
  • the brine can be discharged or sent through a regenerative heater 115 for recovery of the heat above ambient possessed by the brine.
  • the brine temperature exceeds about 30 °C and/or when the brine temperature exceeds the incoming water temperature, the brine is preferably sent to a regenerative heater, otherwise it is preferably simply discharged.
  • the regenerative heater 115 is generally not included with system 100. With appropriate maintenance it is not expected that scaling of the diffusion tower 125 will pose any significant problem since the brine will wash away residual minerals left behind by the evaporated water.
  • the air entering the diffusion tower 125 is preferably dry air. Air can be dried in a direct contact condenser 140 for this purpose.
  • the saturated air/vapor mixture leaving the diffusion tower 145 is drawn into a direct contact condenser 140 with a forced draft blower 150, where the water vapor is condensed into fresh water that is collected in the sump 155 of condenser 140.
  • the air sfream exiting the condenser is preferably dehumidified by the condenser cooling water (not shown) and is indicated as dry air 155.
  • the condenser 140 can run in either a recirculating or non-recirculating (open) mode. In the recirculating mode, prior to being re-circulated back through the condenser the dry air stream 155 is preferably heated back to or near ambient temperature.
  • the non-recirculating (open) mode may be a preferred operating mode.
  • dry air is drawn into the diffusion tower 125 from the ambient and the dry air 155 exiting condenser 140 is discharged to the environment.
  • the warm fresh water discharging the direct contact condenser 140 is preferably chilled using a conventional shell- and-tube heat exchanger 160 using saline cooling water.
  • the cooling water can be drawn from a large depth from the body of water 110 to take advantage of the thermal stratification generally present in large bodies of water.
  • a portion of the chilled fresh water can be directed back to the direct contact condenser 140 to condense the water vapor from the saturated air/vapor mixture 145 which discharges from the diffusion tower 125.
  • the rest of the fresh water supplied from the condenser 140 is fresh make-up water, make-up water being fresh potable water ready to be consumed or stored.
  • a supply of fresh potable water tanks will be located on site for storage of fresh water produced. It is anticipated that the fresh water produced will generally be transferred via pipeline to municipalities or industries for consumption.
  • FIG. 2 A cross-sectional view of a simplified exemplary diffusion tower 200 is shown in FIG. 2.
  • the outer shell of the diffusion tower 205 is preferably constructed using a mechanically strong material, such as steel-reinforced concrete.
  • Heated feed water is pumped to a distribution header 210 having a plurality of spray heads 211-215 located near the top of the diffusion tower.
  • the water is sprayed uniformly over high surface area packing material 220. It is desirable to have a uniform water spray because the system efficiency is enhanced by a uniform spray.
  • the heat and mass transfer analysis used to size the diffusion tower assumes a uniform water flow over the packing material 220.
  • Diffusion tower 200 preferably provides a minimum height to diameter ratio to provide high efficiency.
  • the height to diameter ratio of diffusion tower 200 be at least 2, and more preferably at least 10.
  • Low humidity air is blown into the diffusion tower through an air duct 225 positioned near the bottom of the tower.
  • the low humidity air is blown out of a duct having openings 226-229 oriented transverse to the height of the tower.
  • This arrangement is preferably provided so that the falling water does not enter the air duct discharge which supplies the low humidity air to diffusion tower 200.
  • the air travels up through the packing material to the top of the tower. As the air rises through tower 200 it is both heated and humidified.
  • Brine collects at the bottom of the diffusion tower 200, and is preferably pumped out with a brine pump (not shown) via suction line 240.
  • the air/water vapor mixture which rises to the top of tower 200 is preferably drawn out of the tower through a plenum 230 or similar structure.
  • the plenum is preferably designed so that the air/water vapor mixture must turn 180 degrees (i.e. enter at the top of plenum 230) in order to enter plenum 230 as shown in FIG. 2. This arrangement will minimize entrained liquid droplets from entering plenum 230.
  • Different types of commercially available high surface area packing material 220 may be used with the diffusion tower.
  • Figure 3 shows examples of some materials that may be used for this purpose. These packing materials are usually formed from polymers such as polyethylene, which is suitable for the low temperature operation of the diffusion tower. Typically, a manufacturer of packing material will provide specifications regarding the surface area per unit volume. Preferred materials provide high surface area per unit volume ratios, such as at least 100 m 2 /m 3 .
  • the height for the diffusion tower can be calculated by first choosing the tower diameter.
  • the diameter can be chosen such that the air flow over the packing material will be in the turbulent flow regime. More than one diffusion tower might be required to achieve the desired design flow conditions.
  • a packing material with a desired surface area per unit volume is then specified.
  • a heat and mass fransfer analysis is done concurrently to determine the required tower height to achieve the design exit temperature and exit humidity ratio. Once the required height of the diffusion tower is known, a hydrodynamic analysis is done to determine the pressure drop through the tower, which will allow the size of the forced draft blowers to be specified.
  • the DDD system and method is distinct as compared other desalination processes, such as the carrier gas process (CGP) system and method.
  • CGP carrier gas process
  • One of the major differences is that in CGP heat is added to the system after water diffuses into the air, and a common heat transfer wall is used for both heating and condensation.
  • the use of the common heat fransfer wall significantly reduces the area available for heat transfer compared with the packed diffusion tower and direct contact condenser. Therefore it is expected that the DDD process will have a greater production efficiency than the CGP process.
  • the CGP process does not recirculate the air. This will pose a significant penalty when operating in hot and humid climates since the relative humidity of the incoming air will be very high. Significant heating would be required for the air to carry more water vapor.
  • the DDD process can also make use of the thermal stratification in sea water while the CGP process cannot.
  • the DDD system and method is also distinct as compared to the Humidification Dehumidification (HDH) system and method.
  • the evaporation occurs in a diffusion tower as opposed to the cooling tower used in HDH.
  • the diffusion tower is packed with high surface area packing material, and provides significantly greater surface area than an HDH cooling tower for the same tower size. This is important because the rate of water evaporation is directly proportional to the liquid/vapor surface area available.
  • a diffusion tower is capable of a much higher rate of diffusion and thus greater fresh water production efficiency as compared to an HDH cooling tower.
  • the DDD process should have significantly greater water production efficiency (kilograms of fresh water per kilogram of feed water) as compared to the HDH process.
  • the overall DDD based desalination process requires energy consumption that is comparable to the energy required for flash distillation and reverse osmosis.
  • a major advantage of the DDD process is that it can operate at low temperatures so that it can be driven by an energy input which has low thennodynamic availability. This is important because the process can be driven by waste heat that would otherwise not be suitable for doing useful work or driving some other distillation process, such as flash distillation. Accordingly, the invention can be operated at least in significant part using energy which is provided at essentially no cost, thus making the inventive process significantly more economical when compared to other desalination processes.
  • An important application for the DDD process is to operate in conjunction with an existing process that produces large amounts of waste heat and is located in the vicinity of salt water, such as an ocean or a sea.
  • Salt water such as an ocean or a sea.
  • One such potential benefactor of the DDD process is the electric or utility industry.
  • Conventional steam driven power plants dump a considerable amount of energy to the environment via cooling water that is used to condense low pressure steam within the main condenser. Typically this cooling water is either discharged back to its original source or it is sent to a cooling tower, where the thermal energy is discharged to the atmosphere. Instead of dumping the thermal energy to the environment, the DDD process can utilize the otherwise discarded thermal energy to produce fresh water.
  • the invention can be efficiently applied to power producing facilities sited along the coastline, or along a salt or brackish water containing body of water.
  • This permits application at many power producing facilities because the geographical distribution of fossil fired power plants and nuclear power plants built in the United States and in some other industrialized parts of the world are generally proximate to large bodies of water and nearby large population bases.
  • the demographic make-up of the United States as well as other industrialized nations is such that major population centers generally reside along the coastline.
  • the DDD process appears to be well suited for the power generation infrastructure in the United States as well as certain locations abroad.
  • thermodynamic cycle analysis has been performed by considering a system similar to system 100 shown in FIG. 1. In performing the analysis the following assumptions were made:
  • the process operates at steady-state conditions.
  • Air and water vapor may be treated as a perfect (ideal) gas.
  • the temperature of the feed water drawn into the main feed pump was fixed at 27 °C. It was also assumed that a large supply of cool water will be available at a sink temperature, T L , of 15 °C.
  • T L sink temperature
  • the air/vapor mixture leaving the diffusion tower is assumed to be fully saturated
  • V denotes the control volume
  • p is the density
  • A is the control surface
  • s is the entropy per unit mass
  • m denotes the mass flow rate
  • a and v respectively refer to the liquid, air, and vapor phases.
  • the numerical subscripts denote that the property is evaluated at the state corresponding to the position in the process as shown schematically in FIG. 1.
  • ⁇ is the humidity ratio
  • C p is the specific heat
  • R is the engineering gas constant
  • P a is the partial pressure of air.
  • the ratio of the feed water to lll ⁇ air flow through the diffusion tower, — is another controlling variable in the analysis. For. all computations the feed water flow rate will be fixed at 1 kg/s while the air flow rate will be varied.
  • the first case considered is where there is no heating in the main heater.
  • the desalination process is entirely driven by the difference in temperature of the feed water drawn at shallow depths and the cooling water drawn at more substantial depth.
  • T H /TL 1.04.
  • Figure 4 shows the rate of entropy generation within the diffusion tower and the brine temperature exiting the diffusion tower for a locus of possible operating conditions. It is observed that the second law thermodynamics is satisfied for the entire parametric range considered. At the highest air to feed water flow ratio more fresh water production is possible, but there is a lower limit beyond which the exit brine will freeze.
  • FIG. 5 shows the brine temperature (T 2 ) exiting the diffusion tower as a function of the exit air temperature from the diffusion tower (T ) for the same locus of operating conditions as in FIG. 4. It is advantageous to have a high air temperature leaving the diffusion tower so that the humidity ratio and fresh water production rate are as high as possible. For this case the exit air temperature is primarily constrained by the inlet feed water temperature (Ti). Due to heat fransfer considerations it would be impractical to design the diffusion tower such that T 4 exceeds Ti. Thus in this analysis, the exiting air temperature from the diffusion tower does not exceed the inlet feed water temperature.
  • Figure 6 shows the ratio of fresh water production rate to the inlet feed water rate as a function of the exit air temperature for different air to feed water flow ratios.
  • the production rate increases with increasing exit air temperature and increasing air to feed water flow ratios.
  • T H /T 1.04
  • the maximum fresh water production efficiency is approximately 0.035.
  • the maximum fresh water production will occur with as high an exit air temperature as possible.
  • the exit brine temperature decreases with increasing exit air temperature.
  • the exit air temperature is primarily constrained by the fact that the brine cannot freeze, especially at higher air to feed water flow ratios.
  • FIGs. 11 and 12 show the ratio of fresh water production to the inlet feed water flow rate as a function of the exit air temperature for different air to feed water flow ratios. It is observed that the fresh water production efficiency increases with increasing exit air temperature and increasing air to feed water flow ratio.
  • FIGs. 13 and 14 show the energy consumed per unit of fresh water production as a function of exit air temperature for different air to feed water flow ratios over the entire parameter space considered. Although, details of the low energy consumption regime are difficult to discern, it is interesting to observe that increasing both the exit temperature and the air flow results in a reduced rate of energy consumption. In order to explore the lower energy consumption regime FIGs. 15 and 16 have been prepared for diffusion tower inlet water temperatures of 60 °C and 80 °C, respectively.

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  • Heat Treatment Of Water, Waste Water Or Sewage (AREA)

Abstract

L'invention concerne un appareil de dessalage à entraînement par diffusion et un processus correspondant; l'appareil comprend une structure pour recevoir un flux d'eau chauffée et former au moins une région comportant un film mince d'eau et une structure pour faire passer un flux d'air basse humidité par-dessus le film d'eau, ladite eau du film s'évaporant de manière à se diffuser dans le flux d'air pour créer un flux d'air humidifié. Une tour de diffusion comprenant au moins une entrée-sortie peut s'utiliser pour former un condenseur; elle condense le flux d'air humidifié, et de l'eau purifiée est produite par ce procédé. La chaleur perdue provenant d'une installation d'énergie peut s'utiliser pour fournir un flux d'air chaud; des installations d'énergie peuvent s'utiliser pour utiliser la chaleur perdue générée de manière à produire de l'eau purifiée à peu de frais.
PCT/US2002/040499 2002-12-17 2002-12-17 Appareil de dessalage a entrainement par diffusion et processus correspondant WO2004060812A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2002361773A AU2002361773A1 (en) 2002-12-17 2002-12-17 Diffusion driven desalination apparatus and process
PCT/US2002/040499 WO2004060812A1 (fr) 2002-12-17 2002-12-17 Appareil de dessalage a entrainement par diffusion et processus correspondant

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2002/040499 WO2004060812A1 (fr) 2002-12-17 2002-12-17 Appareil de dessalage a entrainement par diffusion et processus correspondant

Publications (1)

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WO2004060812A1 true WO2004060812A1 (fr) 2004-07-22

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1951624A1 (fr) * 2005-11-22 2008-08-06 Australian Creative Technologies Pty Ltd Systeme de conduits
WO2009157875A1 (fr) * 2008-06-23 2009-12-30 National University Of Singapore Appareil et procédé pour un dessalement amélioré
CN101306845B (zh) * 2007-08-13 2011-08-17 项公浩 太阳能海水淡化工艺及装置
WO2014195110A1 (fr) * 2013-06-05 2014-12-11 Siemens Aktiengesellschaft Installation et procédé de traitement d'eau
US9550190B2 (en) 2011-11-08 2017-01-24 Exxonmobil Upstream Research Company Dewatering oil sand tailings
CN107434327A (zh) * 2017-09-11 2017-12-05 西安交通大学 一种余热余压余水回收的热膜耦合海水淡化系统
CN110259654A (zh) * 2019-05-22 2019-09-20 南京航空航天大学 太阳能湿空气透平水电联产系统及其工作方法
IT202000008176A1 (it) * 2020-04-17 2021-10-17 Alessandro Luigi Maria Vergani Apparecchiatura di desalinazione

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1951624A1 (fr) * 2005-11-22 2008-08-06 Australian Creative Technologies Pty Ltd Systeme de conduits
EP1951624A4 (fr) * 2005-11-22 2012-01-18 Australian Creative Technologies Pty Ltd Systeme de conduits
CN101306845B (zh) * 2007-08-13 2011-08-17 项公浩 太阳能海水淡化工艺及装置
WO2009157875A1 (fr) * 2008-06-23 2009-12-30 National University Of Singapore Appareil et procédé pour un dessalement amélioré
US9550190B2 (en) 2011-11-08 2017-01-24 Exxonmobil Upstream Research Company Dewatering oil sand tailings
WO2014195110A1 (fr) * 2013-06-05 2014-12-11 Siemens Aktiengesellschaft Installation et procédé de traitement d'eau
CN107434327A (zh) * 2017-09-11 2017-12-05 西安交通大学 一种余热余压余水回收的热膜耦合海水淡化系统
CN107434327B (zh) * 2017-09-11 2020-03-13 西安交通大学 一种余热余压余水回收的热膜耦合海水淡化系统
CN110259654A (zh) * 2019-05-22 2019-09-20 南京航空航天大学 太阳能湿空气透平水电联产系统及其工作方法
IT202000008176A1 (it) * 2020-04-17 2021-10-17 Alessandro Luigi Maria Vergani Apparecchiatura di desalinazione

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