WO2009102404A1

WO2009102404A1 - Desalination

Info

Publication number: WO2009102404A1
Application number: PCT/US2009/000706
Authority: WO
Inventors: Dean M. Giolando
Original assignee: The University Of Toledo
Priority date: 2008-02-14
Filing date: 2009-02-04
Publication date: 2009-08-20

Abstract

A desalination system includes a heated separation unit for receiving seawater or other non-potable water under pressure in droplet or mist form through a sprayer. A cyclone separator separates salt and other solids from the droplets or mist and discharges such solids from the separation unit. Water vapor from the droplets or mist is delivered to a condenser which chills the water vapor to thereby form pure water for delivery to an end user. Air from the condenser is preferably returned to the separation unit.

Description

SPECIFICATION TO ALL WHOM IT MAY CONCERN: Be it known that I₁ DEAN M. GIOLANDO, a citizen of the United States of America, resident of Toledo, County of Lucas, State of Ohio, have invented a new and useful improvement in a

DESALINATION

which invention is fully set forth in the following specification.

DESALINATION The present invention relates to desalination of water.

Cross Reference To Related Applications The present application is based upon and claims the benefit of United

States Provisional Patent application No. 61/065,695 filed February 14,

2008.

BACKGROUND OF THE INVENTION Prior art desalination processes include thermally-based separation and membrane-based separation.

Thermally-based Separation A common way to purify water employs boiling or an evaporation technique. Impure water such as seawater can be heated to release steam, which condenses to provide pure water. The process is made more efficient by connecting several distillation units together. To obtain greater efficiency, Multiple Effect Distillation (MED) technology operates at progressively lower pressures so as to reduce the amount of energy needed to vaporize the water. In the Multi-Stage Flash desalination (MSF) process, impure salt water is heated under pressure to 100^cC and then released into a vacuum chamber. Another thermal process, vapor compression (VC), employs a mechanical or thermal compressor to compress steam making it suitable for driving the desalination process.

Major advantages obtained with this technology: 1) a wide range of sources of water can be used, most importantly seawater of very high salt content; and 2) very high purity water is obtained.

Important disadvantages exist with thermally driven separation technology: 1) the large amount of energy required; 2) the formation of scale deposits within the equipment; 3) the need to control algae formation within the closed system; and 4) the high energy cost associated with transporting purified water to the end user. Membrane-based Separation Another common and energy efficient technology employs a membrane to purify water. Reverse osmosis (RO) membranes pass water through while preventing the passage of ions and other materials. A small percentage of about 2% of the dissolved salts passes through the membranes, requiring further treatment. The amount of energy needed is a function of the operating pressure of the RO system; greater salt content requires more energy to effect separation. Electro- dialysis reversal (EDR) is closely related to RO using an electric field gradient to drive salt ions to the electrodes. Several major advantages are obtained with this technology: 1) RO is by far the most widely used separation technology and a mature infrastructure exists; and 2) it is energy efficient.

Important disadvantages exist with membrane-based separation technology: 1) leakage of salt into the water product stream, either due to an inability of the membrane to prevent passage of ions or to leakage around seals due to the high pressure employed; 2) the scale deposits and algae formation within the closed system, leading to high maintenance; 3) waste disposal of the brine solution of extreme salt content; and 4) the high energy cost associated with transporting purified water to the end user.

SUMMARY OF THE INVENTION

The present invention uses a flash evaporation spray technology wherein the energy of vaporization is provided by pressurizing (to about 200 psi) the impure water, which is then released into a warm chamber at atmospheric pressure. When the fluid enters the atmospheric pressure chamber, the pressurized fluid explodes into a mist of droplets that readily evaporate. To aid the evaporation process, hot air can be injected into the system; preferably the hot air is obtained from solar thermal equipment or other renewable energy sources. In this way the dissolved solids separate from water to form a mixture of air, water vapor and solid particles that can then be passed into a cyclone particle separator (or similar devices for the separation of solids and gases without any moving parts) to separate the solids from the mixture of hot air and water vapor. The hot air/water vapor mixture can be carried by the high velocity air stream, which is created by the release of pressure when the fluid entered the vaporization chamber, to a condensation chamber and collected. The hot mixture of air and water vapor can be transported through tubing maintained at a temperature sufficient to prevent water vapor condensation. In this way the water vapor can be transported over distances to the chiller system, which is elevated, and the heat removed from the hot air/water vapor mixture during the condensation of water returned to the process equipment to be used in vaporization and transport of the water vapor.

Energy can be put into the water solution either by pressurization or by electrostatics. The spray process affords a mist of micrometer size droplets that are sprayed into a hot (or warm) chamber for vaporization. The mixture of water vapor and solid is passed into a particle precipitator with the water vapor being directed up through hot (or warm) tubing to a chiller were the vapor is condensed to liquid water. One advantage is that little energy is required to transport the water to a height where the resultant water pressure can be used for distribution. An object of the present invention is to provide a water desalination system which is energy efficient, especially through the use of renewable energy.

Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawing.

IN THE DRAWINGS

Fig. 1 is a diagram showing the steps of desalinization according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Features of the desalination system of the present invention include:

A) Supply of impure water (or other impure liquid)

B) Sprayer equipment, with nozzle terminating inside a separation unit.

C) Separation unit where mist mixes with warm air to evaporate water to form a mixture of solids and warm air/water vapor and solid are removed by a cycloone sparator or similar equipment. The exterior of the separation unit has a high absorbance and low emissitivity of sunlight. For example the chamber can be constructed of sheet metal that has been coated with black chromium or other such solar select materials. Heat to the unit can also be an evacuated solar thermal tube or similar devices.

D) Solid/gas separator, preferably constructed without moving parts. For continuous operation, the flow through the separation unit can be contructed so solids can be removed without stopping the process.

E) Conduit for the warm air/water vapor mixture to the condensation chamber. This can be either vertical, so water is condensed at an elevated height to facilitate transport of the liquid water to the end user, or horizontal to deliver the warm air/water vapor stream a distance to the condensation chamber. The exterior of the conduit has a high absorbance and low emmissitivty of sunlight. The conduit can also be heated by an evacuated solar thermal tube or similar devices.

F) Condensation chamber where the warm air/water vapor mixture contacts a chiller to remove heat from the mixture causing the water vapor to condense. The heat removed is returned to the process stream to assist in evaporating the mist in the separation unit and maintaining the water in the vapor state in the conduit to the condensation chamber.

Energy Sources: The energy to run pumps, fans and chillers could come from grid tied electricity, but it is preferred that grid tied electricity is replaced with alternate energy sources such as photovoltaics, solar thermal, geothermal, wind or ocean resources such as current and tides. The system is more efficient when waste heat from another process is used.

Impure water supply:

The source of impure water can come from any source in addition to the oceans and seas. Many industrial processes employ water and produce an impure supply of water. Some examples could be the waste stream from a reverse osmosis desalination plant producing both pure water and a concentrated brine that is expensive to dispose of. The present invention could take the concentrated brine to a dry salt and pure water set of products to increase the efficiency of a currently running system. Also, the hot water stream from a conventional power plant could be cleaned and prepared for shipping to end users of purified water. A primary objective of the present invention is to provide a system energized entirely by passive and active solar energy (or other forms of renewable energy). Passive solar energy can be used to heat the vaporization chamber and the tubing used to transport the gaseous water vapor to the condensation chamber. Active solar energy, in the form of an array of photovoltaics, may be used to run the variable speed pressurizing pump, fans and chiller. Also, it is proposed to match the systems electrical needs to a wind generator.

Significant advantages over the other systems include: 1) any source of water can be used; 2) deposits of scale and algae will not interfere with the operation of the equipment; 3) the technologies of pressure sprayers, chillers and particle separators are mature industries so the equipment infrastructure already exists; 4) the system can be optimized for use of clean energy sources such as photovoltaics, solar thermal sources, geothermal driven heat pumps, ocean and tidal energy resources and wind generators; 5) the seawater is converted into a gaseous vapor and can be transported to the condensation chamber at an elevated site (such as a 50 foot water tower), which will allow easy dispersal of the liquid water to the local community; 6) in addition to providing a source of clean water the hot air/water vapor mixture can be put to other uses such as, but not limited to, the generation of electricity; and 7) the dry solid salt residues can be easily collected without moving parts or filters and put to use (sold as an additional product to increase revenue).

Referring to the drawing, there is shown a pipeline 10 for drawing water such as seawater or other non-potable water source by means of a pump 12. Water from the pump 12 is directed through a line 14 to a separation unit 16 for separating solids which may have been present in the water. The water to be desalinated is introduced under pressure in the range of 200 to 1500 psi into the separation unit 16 through a spray head 18 in the form of a mist of fine droplets. Prior to introduction into the separation unit 16, the water flowing through the inlet line 14 is heated by means of a heater 20 to a temperature in the range of 60 to 18O⁰F. The separation unit 16 is heated to a temperature in the range of 212 to 500⁰F. The heat in the separation unit 16 causes the mist introduced by the spray head to evaporate water from the seawater or other non-potable water to thereby form a mixture of solids and warm air/water vapor. Positioned in the separation unit 16 is a cyclone separator 22 for removing the solids from the mixture and directing the solids out of the separation unit through an outlet 24. Cyclone separators are well known in the art and widely available commercially. For example, one manufactured by R. P. Adams Co., Tonawanda, NY, would be suitable for separating the solids from the water mist. The cyclone separator is preferably one which has no moving parts to facilitate the removal of solids without stopping the process and thereby permitting continuous operation.

The separation unit 16 maybe heated by any desirable means; however, it is preferably heated by a solar heater 26. The separation unit 16 is formed with an exterior which has a high absorbance to and low emissivity of sunlight. For example, the separation unit could be constructed of sheet metal that has been coated with black chromium or other materials having the property of high absorbance of sunlight. Heat may be provided from other sources in order to maintain the temperature in the separation unit at the desired temperature. The water vapor in the separation unit 11 is caused to flow upwardly through an enlarged tube 28 to a condensation chamber 30. A chiller 32 positioned in the condensation chamber 30 removes heat from the water vapor received from the tube 28 thereby causing the vapor to condense as pure water. The water can then be dispensed through outlet line 34 for delivery to an end user such as a village water supply system.

Air in the condensation chamber 30 maybe exhausted to atmosphere but preferably it is delivered through an air return line 36 to the separation unit 16.

The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention.

Claims

CLAIMSI claim:

1. Apparatus for desalination of water comprising:

(a) a separation unit for receiving seawater or other non-potable water; said separation unit including: (i) a heater;

(ii) a sprayer for delivering said seawater or other non- potable water in mist form to said separation unit under pressure; (iii) a separator for removing solids from said mist and leaving water vapor; and

(b) a condenser for condensing said water vapor.

2. Apparatus according to claim 1 wherein said separator is a cyclone separator having no moving parts.

3. Apparatus according to claim 1 further including a pump and heater for delivering said seawater or other non-potable water to said sprayer at a temperature in the range of 60 to 18O⁰F at a pressure of at least 200 psi.

4. Apparatus according to claim 3 further including a heater for maintaining said separation unit at a temperature of at least 212⁰F.

5. Apparatus according to claim 4 wherein said heaters is a solar collector.

6. Apparatus according to claim 3 wherein said separation unit includes a metal wall with an exterior surface coated with black chromium or other material having high absorbance of sunlight.

7. Apparatus according to claim 3 further including means for powering said pump and said heaters, said means for powering being selected from the group consisting of photovoltaics, solar thermal, geothermal wind and ocean currents.

8. Apparatus according to claim 4 further including means for powering said pump, said heaters, said separator and said condenser, said means for powering being selected solely from the group consisting of photovoltaics, solar thermal, geothermal, wind and ocean resources.

9. A method for desalination of water comprising the steps of:

(a) introducing seawater or other non-potable water under pressure of at least 200 psi and temperature in the range of 6O⁰F to 18O⁰F in the form of droplets or mist into a separation chamber; (b) removing solids from said droplets or mist while maintaining said separation chamber at a temperature in the range of 212 to 500⁰F;

(c) vaporizing said droplets or mists to form water vapor, and

(d) condensing said water vapor.

10. The method according to claim 9 further including the step of providing power for steps (a), (b), (c) and (d) solely from the group consisting of photovoltaics, solar thermal, geothermal, wind and ocean currents.

11. The method according to claim 9 further including the steps of providing a cyclone separator for removing solids from said droplets or mist and operating said cyclone separator on a continuous basis.