U.S. patent application number 15/797534 was filed with the patent office on 2018-02-22 for industrial water purification and desalination.
The applicant listed for this patent is Sylvan Source, Inc.. Invention is credited to Eugene THIERS.
Application Number | 20180050936 15/797534 |
Document ID | / |
Family ID | 47832596 |
Filed Date | 2018-02-22 |
United States Patent
Application |
20180050936 |
Kind Code |
A1 |
THIERS; Eugene |
February 22, 2018 |
INDUSTRIAL WATER PURIFICATION AND DESALINATION
Abstract
This invention relates to the field of water purification and
desalination. In particular, embodiments of the invention relate to
systems and methods of removing essentially all of a broad spectrum
of impurities from water in an automated industrial process that
requires minimal cleaning or maintenance during the course of
several months to several years, with relatively high yields of
product water per unit of input water, flexibility with respect to
energy sources, compact design with a low industrial foot-print,
the ability to recover valuable by-products, and ultra-low energy
requirements.
Inventors: |
THIERS; Eugene; (San Mateo,
CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Sylvan Source, Inc. |
San Carlos |
CA |
US |
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Family ID: |
47832596 |
Appl. No.: |
15/797534 |
Filed: |
October 30, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14343517 |
May 30, 2014 |
9802845 |
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PCT/US2012/054221 |
Sep 7, 2012 |
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15797534 |
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61532766 |
Sep 9, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 1/042 20130101;
B01D 1/0011 20130101; C02F 1/66 20130101; Y02A 20/128 20180101;
C02F 9/00 20130101; B01D 5/0012 20130101; Y02W 10/37 20150501; B01D
5/0072 20130101; Y02A 20/124 20180101; F28D 15/02 20130101; C02F
1/5245 20130101; C02F 1/04 20130101; C02F 1/5236 20130101 |
International
Class: |
C02F 1/52 20060101
C02F001/52; F28D 15/02 20060101 F28D015/02; C02F 9/00 20060101
C02F009/00; C02F 1/04 20060101 C02F001/04; B01D 1/00 20060101
B01D001/00; B01D 5/00 20060101 B01D005/00 |
Claims
1. A water purification and desalination system comprising a
pre-treatment section and a desalination section, wherein the
pre-treatment permanently removes scale-forming compounds while
yielding valuable by-products and CO.sub.2 sequestration, and
wherein the desalination section permits continuous operation of
the purification and desalination without requiring user
intervention or cleaning, and wherein the system is capable of
removing, from a contaminated water sample, a plurality of
contaminant types selected from the group consisting of:
microbiological contaminants, radiological contaminants, metals,
salts, volatile organics, and non-volatile organics, while
recovering the energy of distillation multiple times, and wherein
the system's energy source is selected from the group consisting
of: electricity, geothermal energy, solar energy, the combustion of
oil, hydrocarbons, or natural gas, or waste heat.
2. The method of claim 1, wherein removal of scale-forming
compounds from an aqueous solution comprises: adding at least one
ion to the solution in a stoichiometric amount sufficient to cause
the precipitation of a first scale-forming compound at an alkaline
pH; adjusting the pH of the solution to an alkaline pH, thereby
precipitating the first scale-forming compound; removing the first
scale-forming compound from the solution; adding another ion to the
solution while adjusting pH to an alkaline pH to cause the
precipitation of other scale-forming compounds; and removing other
scale-forming compounds from the solution.
3. The method of claim 2, wherein the first ion is selected from
the group consisting of sodium hydroxide, potassium hydroxide,
calcium hydroxide, and similar hydroxides.
4. The method of claim 2, wherein the pH is adjusted to between
10.5 and 11.0
5. The method of claim 2, wherein the second ion is a carbonate or
bicarbonate ion.
6. The method of claim 2, wherein the second ion is a divalent
cation is a Ca.sup.2+ or Mg.sup.2+ ion.
7. The method of claim 6, wherein the stoichiometric amount is
sufficient to substitute the divalent cation for a divalent cation
selected from the group consisting of barium, cadmium, cobalt,
iron, lead, manganese, nickel, strontium, and zinc in the first
scale-forming compound.
8. The method of claim 6, wherein the stoichiometric amount is
sufficient to substitute the divalent cation for a trivalent cation
selected from the group consisting of aluminum and neodymium in the
first scale-forming compound.
9. The method of claim 5, wherein adding a second ion comprises
sparging the solution with CO.sub.2 gas.
10. The method of claim 9, wherein the CO.sub.2 is atmospheric
CO.sub.2.
11. The method of claim 5, wherein adding a second ion comprises
adding to the solution a soluble bicarbonate ion selected from the
group consisting of sodium bicarbonate, potassium bicarbonate, and
ammonium bicarbonate.
12. The method of claim 2, wherein the second precipitation is
carried out at a pH of between 9.8 and 10.0.
13. The method of claim 2, wherein removing the first scale-forming
compound comprises at least one step selected from the group
consisting of filtration, sedimentation, and centrifuging.
14. The method of claim 2, wherein the second scale-forming
compound comprises an insoluble carbonate compound.
15. The method of claim 2, wherein removing the second
scale-forming compound comprises at least one step selected from
the group consisting of filtration, sedimentation, and
centrifuging.
16. The method of claim 2, additionally comprising removing
contaminants from the solution prior to adding at least one
ion.
17. The method of claim 16, wherein the contaminants are selected
from the group consisting of solid particles and hydrocarbon
droplets.
18. The method of claim 16, wherein the aqueous solution is
selected from the group consisting of tap water, contaminated
aqueous solutions, seawater, and saline brines contaminated with
hydrocarbons.
19. A method of obtaining scale-forming compounds, comprising:
providing an aqueous solution; carrying out the method of claim 2;
recovering the first scale-forming compound; and recovering the
second scale-forming compound.
20. The method of claim 19, wherein the first and second
scale-forming compounds are selected from the group of compounds
listed in Table 4.
21. A method of sequestering atmospheric CO.sub.2, comprising:
providing an aqueous solution containing at least one ion capable
of forming a CO.sub.2-sequestering compound in the presence of
carbonate ion; adding carbonate ions to the solution in a
stoichiometric amount sufficient to cause the precipitation of the
CO.sub.2-sequestering compound at an alkaline pH; adjusting the pH
of the solution to an alkaline pH, thereby precipitating the
CO.sub.2-sequestering compound; and removing the
CO.sub.2-sequestering compound from the solution, wherein adding
carbonate ions comprises adding atmospheric CO.sub.2 to the
solution, and wherein the atmospheric CO.sub.2 is sequestered in
the CO.sub.2-sequestering compound.
22. The method of claim 21, wherein the alkaline pH is a pH of
approximately 9.2 or greater.
23. The method of claim 21, wherein the CO.sub.2-sequestering
compound is selected from the group consisting of CaCO.sub.3,
BaCO.sub.3, SrCO.sub.3, MgCO.sub.3, and similar carbonates.
24. The method of claim 21, wherein removing the
CO.sub.2-sequestering compound comprises at least one step selected
from the group consisting of filtration, sedimentation, and
centrifuging.
25. An apparatus for removing a scale-forming compound from an
aqueous solution, comprising: an inlet for the aqueous solution; a
source of caustic solution for pH adjustment, selected from the
group consisting of NaOH, KOH, Ca(OH).sub.2, and similar
hydroxides; a first tank in fluid communication with the inlet and
the caustic solution; a filter in fluid communication with said
first tank, wherein said filter is adapted to separate a first
scale-forming compound from the solution in said first tank; a
source of CO.sub.2 gas; a source of a pH-raising agent, which can
be in fluid communication with said source of caustic solution; a
second tank in fluid communication with said source of a pH-raising
agent, said source of CO.sub.2 gas, and said first tank; and a
filter in fluid communication with said second tank, wherein said
filter is adapted to separate a second scale-forming compound from
the solution in said second tank
26. The system of claim 1, wherein the desalination system
comprises an inlet, a preheater, a degasser, a plurality of
evaporation chambers, demisters, heat pipes, and product
condensers, a waste outlet, multiple product outlets, a heating
chamber, and a control system, wherein the heat of condensation is
recovered and reused for additional evaporation, such that water
purified in the system has levels of all contaminant types below
the levels shown in Table 1, when the contaminated water has levels
of the contaminant types that are up to 25, 50, 100, or 1,000 times
greater than the levels shown in Table 1.
27. The system of claim 26, wherein the volume of water produced is
between about 20% and about 99% of a volume of input water.
28. The system of claim 26, wherein the system does not require
cleaning through periods of use of at least about two months, one
year, five years, or more.
29. The system of claim 26, further comprising an inlet switch to
regulate flow of water through the inlet.
30. The system of claim 29, wherein the switch comprises a
mechanism selected from the group consisting of: a solenoid, a
valve, and an aperture.
31. The system of claim 29, wherein the inlet switch is controlled
by the control system.
32. The system of claim 1, further comprising a shutdown
control.
33. The system of claim 32, wherein the shutdown control is
selected from the group consisting of: a manual control, a flood
control, a condenser tank capacity control, and an evaporation
chamber capacity control.
34. The system of claim 32, wherein the control system controls the
inlet based upon feedback from at least one detection method
selected from the group consisting of: a temperature sensor in a
boiler, a condenser tank float, and a flood detector.
35. The system of claim 31, wherein the control system controls the
switch based upon feedback from the pre-treatment and desalination
system.
36. The system of claim 1, further comprising a flow
controller.
37. The system of claim 36, wherein the flow controller comprises a
pressure regulator.
38. The system of claim 37, wherein the pressure regulator
maintains water pressure between about 0 kPa and 250 kPa (0 to 36
psi).
39. The system of claim 26, wherein water exiting the preheating
chamber has a temperature of at least about 96.degree. C.
40. The system of claim 26, wherein the degasser is in a
substantially vertical orientation, having an upper end and a lower
end.
41. The system of claim 40, wherein heated water from the
preheating chamber enters the degasser proximate to the upper
end.
42. The system of claim 40, wherein the heated water exits the
degasser proximate to the lower end.
43. The system of claim 26, wherein steam from the evaporation
chamber enters the degas ser proximate to the lower end.
44. The system of claim 43, wherein the steam exits the degasser
proximate to the upper end.
45. The system of claim 40, wherein the degasser comprises a matrix
adapted to facilitate the mixing of water and steam.
46. The system of claim 45, wherein the matrix comprises
substantially spherical particles.
47. The system of claim 45, wherein the matrix comprises
non-spherical particles.
48. The system of claim 45, wherein the matrix comprises particles
having a size selected to permit uniform packing within the
degasser.
49. The system of claim 45, wherein the matrix comprises particles
of distinct sizes, wherein the particles are arranged in the
degasser in a size gradient.
50. The system of claim 42, wherein water exiting the degasser is
substantially free of organics and volatile gasses.
51. The system of claim 26, wherein the evaporation chambers
include a plurality of heat pipes delivering heat that is
transferred from lower condenser chambers.
52. The system of claim 51, wherein the evaporation chamber further
comprises a drain, and wherein the drain is at or about the middle
of the chamber.
53. The system of claim 26, the heating chamber further comprising
electric heating elements, gas or oil burners, or heat pipes that
transfer heat from waste heat sources, and wherein the heating
chamber is adjacent to the bottom portion of the evaporation
chamber.
54. The system of claim 26, wherein the demister is positioned
proximate to an upper surface of the evaporation chamber.
55. The system of claim 26, wherein steam from the evaporation
chamber enters the demister under pressure.
56. The system of claim 26, wherein the evaporation chamber
prevents condensed droplets from entering the demister by means of
baffle guards and metal grooves.
57. The system of claim 54, wherein the demister control parameter
comprises at least one parameter selected from the group consisting
of: a recessed position of a clean steam outlet, a pressure
differential across the demister, a resistance to flow of a steam
inlet, and a resistance to flow of a steam outlet.
58. The system of claim 26, further comprising heat pipes for
cooling the condenser product.
59. The system of claim 26, wherein product water exits the product
condensers through the product outlets.
60. The system of claim 26, wherein waste water exits the system
through the waste outlet.
61. A method of purifying and desalinating water, comprising the
steps of: providing a source of inlet water comprising at least one
contaminant in a first concentration; modifying the pH of the inlet
water to cause precipitation of insoluble hydroxides and separating
the precipitates from the incoming water; adding a source of
carbonate ions and modifying the pH to cause precipitation of
insoluble carbonates and separating the precipitates from the
incoming water; passing the descaled pre-treated water through a
preheating chamber capable of raising the temperature of the inlet
water above 90.degree. C.; removing essentially all organics,
volatiles, and gasses from the inlet water by counterflowing the
inlet water against an opposite directional flow of a gas in a
degasser; maintaining the water in an evaporation chamber for an
average residence time of between 1 and 90 minutes or longer under
conditions that permit the formation of steam; discharging steam
from the evaporation chamber to a demister; separating clean steam
from contaminant-containing waste in the demister; condensing the
clean steam to yield purified water, comprising the at least one
contaminant in a second concentration, wherein the second
concentration is lower than the first concentration; recovering and
transferring heat from a condenser chamber into an upper boiling or
preheating chamber, such that the amount of heat recovered is at
least 50%, 60%, 70%, 80%, 90%, or more of the heat of condensation;
repeating the evaporation, condensation, and demisting operations
multiple times in order to re-use the energy while maximizing clean
water production.
62. The method of claim 61, wherein the at least one contaminant is
selected from the group consisting of: microorganisms,
radionuclides, salts, organics, and disinfection by-products, as
listed in Table 3; and wherein the second concentration is not
greater than the concentration shown in Table 3, and wherein the
first concentration is at least about 10 times the second
concentration.
63. The method of claim 61, wherein the stacked arrangement of
boilers, condensers, and preheater is enclosed in a metal shell,
with perforated plates that separate the boiling and condenser
chambers.
64. The method of claim 61, wherein the perforated plates allow the
passage of heat pipes, the degasser, demisters, brine overflow
tubes, and waste stream tubes.
65. The method of claim 61, wherein the boilers, preheaters, and
heat pipes are constructed from non-corrosive materials, such as
titanium alloys or polymer-coated metals.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/532,766, filed Sep. 9, 2011, and the entire
disclosure of that application is incorporated herein by
reference.
BACKGROUND
[0002] Water purification technology is rapidly becoming an
essential aspect of modern life as conventional water resources
become increasingly scarce, municipal distribution systems for
potable water deteriorate with age, and increased water usage
depletes wells and reservoirs, causing saline water contamination.
Additionally, further contamination of water sources is occurring
from a variety of activities, which include, for example, intensive
agriculture, gasoline additives, and heavy toxic metals. These
issues are leading to increasing and objectionable levels of germs,
bacteria, salts, MTBE, chlorates, perchlorates, arsenic, mercury,
and even the chemicals used to disinfect potable water, in the
water system.
[0003] Furthermore, even though almost three fourths of the earth
is covered by oceans, only some 3% of this water exists as fresh
water resources, and these resources are becoming increasingly
scarce as a result of population growth and global warming.
Approximately 69% of all fresh water is contained in ice caps and
glaciers; with increased global melting, this fresh water becomes
unrecoverable, so less than 1% is actually available, with the
majority (over 90%) being ground water in aquifers that are being
progressively contaminated by human activities and saline
incursions. Thus, there is an urgent need for technology that can
turn saline water, including seawater and brine, into fresh water,
while removing a broad range of contaminants.
[0004] Conventional desalination and water treatment technologies,
including reverse osmosis (RO) filtration and thermal distillation
systems, such as multiple-effect distillation (MED), multiple-stage
flash distillation (MSF), and vapor compression distillation (VC),
are rarely able to handle the diverse range of water contaminants
found in saline environments. Additionally, even though they are
commercially available, they often require multiple treatment
stages or some combination of various technologies to achieve
acceptable water quality. RO systems suffer from the requirement of
high-water pressures as the saline content increases, rendering
them expensive in commercial desalination, and they commonly waste
more than 40% of the incoming feed water, making them progressively
less attractive when water is scarce. Moreover, RO installations
produce copious volumes of waste brine that are typically discarded
into the sea, resulting in high saline concentrations that are
deadly to fish and shellfish. Less conventional technologies, such
as ultraviolet (UV) light irradiation or ozone treatment, can be
effective against viruses and bacteria but seldom remove other
contaminants, such as dissolved gases, salts, hydrocarbons, and
insoluble solids. Additionally, while most distillation
technologies may be superior at removing a subset of contaminants,
they rarely can handle all types of contaminants.
[0005] Because commercial desalination plants are normally complex
engineering projects that require one to three years of
construction, they are typically capital intensive and difficult to
move from one place to another. Their complexity and reliance on
multiple technologies also make them prone to high maintenance
costs. Because RO plants are designed to operate continuously under
steady pressure and flow conditions, large pressure fluctuations or
power interruptions can damage the membranes, which are expensive
to replace; the incoming feed water therefore requires extensive
pre-treatment to prevent fouling of the RO membrane.
[0006] Thermal distillation systems, such as those described by
LeGolf et al. (U.S. Pat. No. 6,635,150 B1) include MED systems,
which rely on multiple evaporation and condensation steps that
operate under vacuum in order to effect evaporation at temperatures
lower than the normal boiling point of water. Such technologies are
commercially used for desalination in various countries, but they
all operate according to different physico-chemical principles. For
example, MED, MSF, and VC systems all require vacuum, which means
that the product water cannot be sterilized because evaporation
occurs at temperatures lower than those needed for sterilization;
also, vacuum systems tend to leak and require mechanical
reinforcement. In addition, heat transfer and heat recovery in MED,
MSF, and VC systems involve heat exchange across membranes or thin
metal surfaces, but heat exchangers are prone to fouling and scale
formation and require frequent maintenance.
[0007] More recently, Thiers (PCT Application No.: US2009/57277,
entitled Large Scale Water Purification and Desalination, filed
Sep. 17, 2009, and PCT Application No.: US2010/030759, entitled
Method and System for Reduction of Scaling in Purification of
Aqueous Solutions, filed Apr. 12, 2010) has described a method of
pre-treatment that removes scale-forming constituents from a water
stream and large scale embodiments for a desalination system.
However, the earlier pre-treatment system described by Thiers
relies on a final thermal treatment that involves heating to
120.degree. C. for several minutes of residence time, which, while
technically effective, represents a significant energy consumption.
There is a need for a pre-treatment method that minimizes energy
consumption while still removing scale-forming constituents from an
aqueous stream. In addition, the embodiments described by Thiers
for a large-scale desalination and water treatment fail to address
transient phenomena encountered during start-up and shut down
operations and do not properly ensure the maintenance of a stable
hydraulic head between different boiling stages. There is a need
for industrial configurations that are stable during start-up and
shut down procedures, in addition to being stable during normal
operation.
[0008] There is a need for inexpensive and effective pre-treatment
methods that eliminate scale-forming compounds. There is a further
need for industrial desalination and water treatment systems that
are continuous and largely self-cleaning, that resist corrosion and
scaling, that are modular and compact, that recover a major
fraction of the input water while producing a highly concentrated
waste brine that crystallizes into a solid salt cake, and that are
relatively inexpensive and low-maintenance.
SUMMARY
[0009] The present invention describes various industrial
embodiments for an improved desalination and water purification
system. The system includes a pre-treatment section that prevents
scale formation and a desalination section that consists of an
inlet, a preheater, a degasser, multiple evaporation chambers and
demisters, product condensers, a waste outlet, a product outlet,
multiple heat pipes for heat transfer and recovery, and a control
system. The control system permits operation of the purification
system continuously with minimal user intervention or cleaning. The
system is capable of removing, from a contaminated water sample, a
plurality of contaminant types including microbiological
contaminants, radiological contaminants, metals, salts, volatile
organics, and non-volatile organics. In embodiments of the system
and depending on the salinity of the incoming water stream, the
volume of water produced can range from about 20% to in excess of
95% of a volume of input water. The system comprises a vertical
stack arrangement of boiling chambers, condensers, and a preheater
that is compact and portable. The system is capable of water
production in the range of 1,000 to 50 million gallons per day.
[0010] The pre-treatment section precipitates scale-forming
compounds by means of pH adjustment. Addition of either caustic or
lime initially precipitates magnesium hydroxide, which is
subsequently removed by filtration or sedimentation, or both. Next,
the concentration of bicarbonate ions is adjusted by dissolving
CO.sub.2 or adding bicarbonate or soluble carbonate salts to
correspond to the stoichiometric composition of the remaining
calcium, magnesium, and other divalent cations in solution, and the
pH is again adjusted to values of 9.8 and higher in order to
precipitate scale-forming compounds as insoluble carbonates.
Following filtration or sedimentation to remove precipitates, the
clear pre-treated solution then flows into the desalination
section.
[0011] The desalination section consists of a vertical stack of
boilers, condensers, and demisters with a preheating tank, a
degasser, and a heat transfer vessel. The preheating vessel raises
the temperature of the incoming water to near the boiling point and
can be placed on the top or at the bottom of the vertical stack.
Water exiting the preheating tank can have a temperature of at
least about 96.degree. C. The preheating tank may have a spiral
arrangement of vanes such that incoming water circulates several
turns in the tank, thus providing sufficient residence time to
effect preheating. Incoming feed water enters the preheating tank
tangentially, is gradually preheated by heat pipes until the
required temperature is achieved, and exits the preheating tank
through a downcomer tube that connects either with the degasser or
directly with a lower boiling chamber if there is no need for
degassing.
[0012] A degasser, which is placed near the top of the vertical
stack, removes gases and organic contaminants that may be volatile
or non-volatile by means of counter-current stripping of the
incoming water against low-pressure steam. The degasser can be in a
substantially vertical orientation, having an upper end and a lower
end. Pre-heated water enters the degasser at its upper end, and
degassed water exits the degasser proximate to the lower end. In
the system, steam from the highest evaporation chamber can enter
the degasser proximate to the lower end and can exit the degasser
proximate to the upper end. The degasser can include a matrix
adapted to facilitate mixing of water and steam, stripping the
inlet water of essentially all organics, volatiles, and gases by
counterflowing the inlet water against an opposite directional flow
of a gas in a degasser. The gas can be, for example, steam, air,
nitrogen, and the like. The matrix can include substantially
spherical particles. However, the matrix can also include
non-spherical particles. The matrix can include particles having a
size selected to permit uniform packing within the degasser. The
matrix can also include particles of distinct sizes, and the
particles can be arranged in the degasser in a size gradient. Water
can exit the degasser substantially free of organics and volatile
gases.
[0013] The heat-transfer vessel provides the heat energy for the
entire system and can consist of a condenser chamber operating with
low-pressure waste steam. Alternatively, it can be a combustion
chamber that operates with any type of fuel or a vessel that
absorbs heat from a working fluid from recuperators, solar heaters,
or economizers.
[0014] Pre-treated water is first preheated to near the boiling
point and enters a degas ser proximate the upper end of the
vertical stack, where gases and hydrocarbons are removed. The
degassed water then enters an upper boiler, where a portion of the
incoming water is turned into steam; a portion of the steam
produced in the upper boiler may be used to provide the required
steam for degassing, while the balance enters a demister that
removes entrained micro-droplets and is condensed into pure water
in a condenser chamber immediately above the boiler. As some of the
incoming water in the upper boiler evaporates, the balance of the
water becomes progressively more concentrated in soluble salts and
continuously cascades downward into a series of lower boilers until
it exits the lowermost boiler as a heavy brine at near the
solubility limit of the salt solution.
[0015] Concurrent with incoming water cascading downward, heat is
provided at the heat-transfer vessel and is progressively
transferred upwards by means of heat pipes. Heat pipes are highly
efficient enthalpy transfer devices that operate with a small
temperature difference between their hot and cold ends. A number of
heat pipes transfer the heat provided at the heat-transfer vessel
to the bottom boiler. The steam produced at the bottom boiler is
largely recovered as the heat of condensation in the bottom
condenser, where another set of heat pipes transfers that heat to
an upper boiler, thus progressively re-using the heat for multiple
evaporation and condensation chambers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic flowsheet of the pre-treatment
process.
[0017] FIG. 2 is a schematic view of a desalinator with two
stages.
[0018] FIG. 3 is a detailed elevation view of a desalinator
stage.
[0019] FIG. 4 is a diagram of a desalinator with five stages.
[0020] FIG. 5 provides elevation, stereoscopic, and plant views of
the boiler, the condenser, and the separator plate.
[0021] FIG. 6 is a schematic diagram of a heat pipe.
[0022] FIG. 7 is a schematic view of a high-performance heat
pipe.
DETAILED DESCRIPTION
[0023] Embodiments of the invention are disclosed herein, in some
cases in exemplary form or by reference to one or more Figures.
However, any such disclosure of a particular embodiment is
exemplary only and is not indicative of the full scope of the
invention.
[0024] Embodiments of the invention include systems, methods, and
apparatuses for water purification and desalination. Preferred
embodiments provide broad spectrum water purification that is fully
automated and can operate over very long periods of time without
requiring cleaning or user intervention. For example, systems
disclosed herein can run without user control or intervention for
2, 4, 6, 8, 10, or 12 months, or longer. In preferred embodiments,
the systems can run automatically for 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, or 15 years, or more.
[0025] Embodiments of the invention thus provide a water
purification and desalination system including at least an inlet
for saline water, contaminated water, or seawater, a preheater, a
degasser, one or more evaporation chambers, one or more demisters,
and one or more product condensers with a product outlet, a waste
outlet, and a control system, wherein product water exiting the
outlet is substantially pure, and wherein the control system
permits operation of the purification system continuously without
requiring user intervention. In preferred embodiments, the volume
of product water produced is at least about 20, 25, 30, 35, 40, 45,
50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99%, or
more, of the volume of input water. Thus, the system is of great
benefit in conditions in which there is relatively high expense or
inconvenience associated with obtaining inlet water and/or
disposing of wastewater. The system is significantly more efficient
in terms of its production of product water per unit of input water
or wastewater than many other systems.
[0026] Substantially pure water can be, in different embodiments,
water that meets any of the following criteria: water purified to a
purity, with respect to any contaminant, that is at least 25, 30,
35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150,
175, 200, 250, 500, 750, 1000, or more, times greater in purity
than the inlet water. In other embodiments, substantially pure
water is water that is purified to one of the foregoing levels,
with respect to a plurality of contaminants present in the inlet
water. That is, in these embodiments, water purity or quality is a
function of the concentration of an array of one or more
contaminants, and substantially pure water is water that has, for
example, a 25-fold or greater ratio between the concentration of
these contaminants in the inlet water as compared to the
concentration of the same contaminants in the product water.
[0027] In other embodiments, water purity can be measured by
conductivity, where ultrapure water has a conductivity typically
less than about 1 .mu.Siemens, and distilled water typically has a
conductivity of about 5. In such embodiments, conductivity of the
product water is generally between about 1 and 7, typically between
about 2 and 6, preferably between about 2 and 5, 2 and 4, or 2 and
3. Conductivity is a measure of total dissolved solids (TDS) and is
a good indicator of water purity with respect to salts, ions,
minerals, and the like.
[0028] Alternatively, water purity can be measured by various
standards, such as, for example, current U.S. Environmental
Protection Agency (EPA) standards as listed in Table 1 and Table 2,
as well as other accepted standards as listed in Table 2.
Accordingly, preferred embodiments of the invention are capable of
reducing any of one or more contaminants from a broad range of
contaminants, including, for example, any contaminant(s) listed in
Table 1, wherein the final product water has a level for such
contaminant(s) at or below the level specified in the column
labeled "MCL" (maximum concentration level), where the inlet water
has a level for such contaminant(s) that is up to about 25-fold
greater than the specified MCL. Likewise, in some embodiments and
for some contaminants, systems of the invention can remove
contaminants to MCL levels when the inlet water has a contamination
that is 30-, 40-, 50-, 60-, 70-, 80-, 90-, 100-, 150-, 250-, 500-,
or 1000-fold, or more, higher than the MCL or the product
water.
[0029] While the capacity of any system to remove contaminants from
inlet water is to some extent a function of the total impurity
levels in the inlet water, systems of the invention are
particularly well suited to remove a plurality of different
contaminants, of widely different types, from a single feed stream,
producing water that is comparable to distilled water and is in
some cases comparable to ultrapure water. It should be noted that
the "Challenge Water" column in Table 1 contains concentration
levels for contaminants in water used in EPA tests. Preferred
embodiments of water purification systems of the invention
typically can remove much greater amounts of initial contaminants
than the amounts listed in this column. However, contaminant levels
corresponding to those mentioned in the "Challenge Water" column
are likewise well within the scope of the capabilities of
embodiments of the invention.
TABLE-US-00001 TABLE 1 Water Contaminant Concentration Levels and
Testing Protocols Challenge Units Protocol MCL Water 1. Metals
Aluminum ppm 0.2 0.6 Antimony ppm 0.006 0.1 Arsenic ppm 0.01 0.1
Beryllium ppm 0.004 0.1 Boron ppb 20 Chromium ppm 0.1 0.1 Coppcr
ppm 1.3 1.3 Iron ppm 0.3 8 Lead ppm 0.015 0.1 Manganese ppm 0.05 1
Mercury ppm 0.002 0.1 Molybdenum ppm 0.01 Nickel ppm 0.02 Silver
ppm 0.1 0.2 Thallium ppm 0.002 0.01 Vanadium ppm 0.1 Zinc ppm 5 5
Subtotal of entire mix 36.84 2. Inorganic Salts Bromide ppm 0.5
Chloride ppm 250 350 Cyanide ppm 0.2 0.4 Fluoride ppm 4 8 Nitrate,
as NO.sub.3 ppm 10 90 Nitrite, as N.sub.2 ppm 1 2 Sulfate ppm 250
350 Subtotal of entire mix 800.9 3. 2 Highly Volatile VOCs + 2 Non-
Volatiles Heptachlor ppm EPA525.2 0.0004 0.04
Tetrachloroethylene-PCE ppm EPA524.2 0.00006 0.02 Epichlorohydrin
ppm 0.07 0.2 Pentachlorophenol ppm EPA515.4 0.001 0.1 Subtotal of
cntirc mix 0.36 4. 2 Highly Volatile VOCs + 2 Non- Volatiles Carbon
tctrachloridc ppm EPA524.2 0.005 0.01 m,p-Xylenes ppm EPA524.2 10
20 Di(2-ethylhexyl) adipate ppm EPA525.2 0.4 0.8 Trichloroacetic
acid ppm SM6251B 0.06 0.12 Subtotal of entire mix 20.93 5. 3 Highly
Volatile VOCs + 3 Non- Volatiles 1,1-Dichloroethylene ppm 0.007
0.15 Ethylbenzene ppm EPA524.2 0.7 1.5 Aldrin ppm EPA505 0.005 0.1
Dalapon (2,2-dichloropropionic acid) ppm EPA515.4 0.2 0.4
Carbofuran (furadan) ppm EPA531.2 0.04 0.1 Fcnoprop (2,4,5-TP,
Silvcx) ppm EPA515.4 0.05 0.1 Subtotal of entire mix 2.35 6. 3
Highly Volatile VOCs + 3 Non- Volatiles Trichloroethylene-TCE ppm
EPA524.2 0.005 0.1 Toluene ppm EPA524.2 1 2 1,2,4-Trichlorobenzene
ppm EPA524.2 0.07 0.15 2,4-D (2,4-dichlorophenoxyacetic acid) ppm
EPA515.4 0.07 0.15 Alachlor (Alanex) ppm EPA525.2 0.002 0.1
Simazine ppm EPA525.2 0.004 0.1 Subtotal of entire mix 2.6 7. 3
Highly Volatile VOCs + 3 Non- Volatiles Vinylchloride
(chloroethene) ppm EPA524.2 0.002 0.1 1,2-Dichlorobenzene (1,2-DCB)
ppm EPA524.2 0.6 1 Chlorobcnzcnc ppm EPA524.2 0.1 0.2 Atrazine ppm
EPA525.2 0.003 0.1 Endothal ppm EPA548.1 0.01 0.2 Oxamyl (Vydate)
ppm EPA531.2 0.2 0.4 Subtotal of entire mix 2.0 8. 3 Highly
Volatile VOCs + 3 Non- Volatiles Styrene ppm EPA524.2 0.1 1 Benzene
ppm EPA524.2 0.005 0.2 Methoxychlor ppm EPA525.2/505 0.04 0.1
Glyphosate ppm EPA547 0.7 1.5 Pichloram ppm EPA515.4 0.5 1
1,3-Dichlorobenzene (1,3-DCB) ppm EPA524.2 0.075 0.15 Subtotal of
entire mix 3.95 9. 3 Highly Volatile VOCs + 3 Non- Volatiles
1,2-Dichloropropane (DCP) ppm EPA524.2 0.005 0.1 Chloroform ppm
EPA524.2 80 0.1 Bromomethane (methyl bromide) ppm EPA524.2 0.1 PCB
1242 (Aroclor 1242) ppb EPA505 0.5 1 Chlordane ppm EPA525.2/505
0.002 0.2 MEK (methylehtylketone, 2-butanone) ppb EPA524.2 0.2
Subtotal of entire mix 1.7 10. Group: 4 VOCs + 5 Non-Volatile PCBs
2,4-DDE (dichlorodiphcnyl dichloroethylene) ppm EPA525.2 0.1
Bromodichloromethane ppb EPA524.2 80 0.1 1,1,1-Trichloroethane
(TCA) ppm EPA524.2 0.2 0.4 Bromoform ppm EPA524.2 80 0.1 PCB 1221
(Aroclor 1221) ppm EPA505 0.5 0.05 PCB 1260 (Aroclor 1260) ppm
EPA505 0.5 0.05 PCB 1232 (Aroclor 1232) ppm EPA505 0.5 0.05 PCB
1254 (Aroclor 1254) ppm EPA505 0.5 0.05 PCB 1016 (Aroclor 1016) ppm
EPA505 0.5 0.05 Subtotal of entire mix 0.95 11. 5 VOCs + 5
Non-Volatile PCBs Dichloromethane (DCM, methylene ppm EPA524.2
0.005 0.1 chloride) 1,2-Dichloroethane ppm 0.005 0.1 Lindane
(gamma-BHC) ppm EPA525.2 0.0002 0.05 Benzo[a]pyrene ppm EPA525.2
0.0002 0.05 Endrin ppm EPA525.2/505 0.002 0.05
1,1,2-Trichloroethane (TCA) ppm EPA524.2 0.005 0.05 MTBE (methyl
t-butyl ether) ppm EPA524.2 0.05 Ethylene dibromide (EDB) ppm
EPA504.1 0.00005 0.05 Dinoseb ppm EPA515.4 0.007 0.05
Bis(2-ethylhexyl) phthalate (DEHP) ppm EPA525.2 0.006 0.05 Subtotal
of entire mix 0.6 12. 6 VOCs Chloromethane (methyl chloride) ppm
EPA524.2 0.1 Toxaphene ppm EPA505 0.003 0.1
trans-1,2-Dichloroethylene ppm EPA524.2 0.1 0.2
Dibromochloromethane ppm EPA524.2 80 0.05 cis-1,2-Dichloroethylene
ppm EPA524.2 0.07 0.05 1,2-Dibromo-3-chloro propane ppm EPA504.1
0.0002 0.05 Subtotal of entire mix 0.55
[0030] Determination of water purity and/or efficiency of
purification performance can be based upon the ability of a system
to remove a broad range of contaminants. For many biological
contaminants, the objective is to remove substantially all live
contaminants. Table 2 lists additional common contaminants of
source water and standard protocols for testing levels of these
contaminants. The protocols listed in Tables 1 and 2 are publicly
available at www.epa.gov/safewater/mcl.html#mcls for common water
contaminants, as well as Methods for the Determination of Organic
Compounds in Drinking Water, EPA/600/4-88-039, December 1988,
revised July 1991. Methods 547, 550, and 550.1 are in Methods for
the Determination of Organic Compounds in Drinking
Water--Supplement I, EPA/600-4-90-020, July 1990. Methods 548.1,
549.1, 552.1, and 555 are in Methods for the Determination of
Organic Compounds in Drinking Water--Supplement II,
EPA/600/R-92-129, August 1992. Methods 502.2, 504.1, 505, 506, 507,
508, 508.1, 515.2, 524.2 525.2, 531.1, 551.1, and 552.2 are in
Methods for the Determination of Organic Compounds in Drinking
Water--Supplement III, EPA/600/R-95-131, August 1995. Method 1613
is titled "Tetra-through Octa-Chlorinated Dioxins and zFurans by
Isotope Dilution HRGC/HRMS," EPA/821-B-94-005, October 1994. Each
of the foregoing is incorporated herein by reference in its
entirety.
TABLE-US-00002 TABLE 2 Water Contaminant Testing Protocols Protocol
1 Metals and Inorganics Asbestos EPA100.2 Free cyanide SM 4500CN-F
Metals - Al, Sb, Be, B, Fe, Mn, Mo, Ni, Ag, Tl, V, EPA200.7/200.8
Zn Anions - NO.sub.3--N, NO.sub.2--N, Cl, SO.sub.4, EPA300.0A total
nitrates/nitrites Bromide EPA300.0/300.1 Turbidity EPA180.1 2
Organics Volatile organics - VOASDWA list + nitrozbenzene EPA524.2
EDB and DBCP EPA504.1 Semivolatile organics - ML525 list + EPTC
EPA525.2 Pesticides and PCBs EPA505 Hcrbicidcs -
rcgulatcd/unrcgulatcd compounds EPA515.4 Carbamates EPA531.2
Glyphosate EPA547 Diquat EPA549.2 Dioxin EPA1613b 1,4-Dioxane
EPA8270m NDMA - 2 ppt MRL EPA1625 3 Radiologicals Gross alpha and
beta EPA900.0 Radium 226 EPA903.1 Uranium EPA200.8 4 Disinfection
By-Products THMs/HANs/HKs EPA551.1 HAAs EPA6251B Aldehydes SM 6252m
Chloral hydrate EPA551.1 Chloramines SM 4500 Cyanogen chloride
EPA524.2m
TABLE-US-00003 TABLE 3 Exemplary Contaminants for System
Verification MCLG.sup.1 1 Metals & Inorganics Asbcstos <7
MFL.sup.2 Free cyanide <0.2 ppm Mctals - Al, Sb, Bc, B, Fe, Mn,
Mo, Ni, Ag, Tl, V, 0.0005 ppm Zn Anions - NO.sub.3--N, NO.sub.2--N,
Cl, SO.sub.4, <1 ppm total nitrates/nitrites Turbidity <0.3
NTU 2 Organics Volatile organics - VOASDWA list + nitrobenzene EDB
and DBCP 0 ppm Semivolatile organics - ML525 list + EPTC <0.001
ppm Pesticides and PCBs <0.2 ppb Herbicides -
regulated/unregulated compounds <0.007 ppm Glyphosate <0.7
ppm Diquat <0.02 ppm Dioxin 0 ppm 3 Radiologicals Gross alpha
and bcta <5 pCi/l.sup.3 Radium 226 0 pCi/l.sup.3 Uranium <3
ppb 4 Disinfection By-Products Chloramines 4 ppm Cyanogen chloride
0.1 ppm 5 Biologicals Cryptosporidium 0.sup.4 Giardia lamblia
0.sup.4 Total coliforms 0.sup.4 .sup.1MCLG = maximum concentration
limit guidance .sup.2MFL = million fibers per liter .sup.3pCi/l =
pico Curies per liter .sup.4Substantially no detectable biological
contaminants
Overall Description of Water Pre-Treatment System
[0031] The objective of the pre-treatment system is to reduce
scale-forming compounds to a level at which they will not interfere
by forming scale in subsequent treatment, particularly during
desalination. Water hardness is normally defined as the amount of
calcium (Ca.sup.++), magnesium (Mg.sup.++), and other divalent ions
that are present in the water and is normally expressed in parts
per million (ppm) of these ions or their equivalent as calcium
carbonate (CaCO.sub.3). Scale forms because the water dissolves
carbon dioxide from the atmosphere, and such carbon dioxide
provides carbonate ions that combine to form both calcium and
magnesium carbonates; upon heating, the solubility of calcium and
magnesium carbonates markedly decreases, and they precipitate as
scale. In reality, scale comprises any chemical compound that
precipitates from solution. Thus, iron phosphates and calcium
sulfate (gypsum) also produce scale. Table 4 lists a number of
chemical compounds that exhibit low solubility in water and can
thus form scale. In this context, low solubility is defined by the
solubility product, that is, by the product of the ionic
concentration of cations and anions of a particular chemical;
solubility is usually expressed in moles per liter (mol/L).
TABLE-US-00004 TABLE 4 Solubility Products of Various Compounds
Compound Formula K.sub.sp (25.degree. C.) Aluminum hydroxide
Al(OH).sub.3 3 .times. 10.sup.-34 Aluminum phosphate AlPO.sub.4
9.84 .times. 10.sup.-21 Barium bromatc Ba(BrO.sub.3).sub.2 2.43
.times. 10.sup.-4 Barium carbonate BaCO.sub.3 2.58 .times.
10.sup.-9 Barium chromate BaCrO.sub.4 1.17 .times. 10.sup.-10
Barium fluoride BaF.sub.2 1.84 .times. 10.sup.-7 Barium hydroxide
octahydrate Ba(OH).sub.2 .times. 8H.sub.2O 2.55 .times. 10.sup.-4
Barium iodate Ba(IO.sub.3).sub.2 4.01 .times. 10.sup.-9 Barium
iodate monohydrate Ba(IO.sub.3).sub.2 .times. H.sub.2O 1.67 .times.
10.sup.-9 Barium molybdate BaMoO.sub.4 3.54 .times. 10.sup.-8
Barium nitrate Ba(NO.sub.3).sub.2 4.64 .times. 10.sup.-3 Barium
selenate BaSeO.sub.4 3.40 .times. 10.sup.-8 Barium sulfate
BaSO.sub.4 1.08 .times. 10.sup.-10 Barium sulfite BaSO.sub.3 5.0
.times. 10.sup.-10 Beiyllium hydroxide Be(OH).sub.2 6.92 .times.
10.sup.-22 Bismuth arsenate BiAsO.sub.4 4.43 .times. 10.sup.-10
Bismuth iodide BiI 7.71 .times. 10.sup.-19 Cadmium arsenate
Cd.sub.3(AsO.sub.4).sub.2 2.2 .times. 10.sup.-33 Cadmium carbonate
CdCO.sub.3 1.0 .times. 10.sup.-12 Cadmium fluoride CdF.sub.2 6.44
.times. 10.sup.-3 Cadmium hydroxide Cd(OH).sub.2 7.2 .times.
10.sup.-15 Cadmium iodate Cd(IO.sub.3).sub.2 .sup. 2.5 .times.
10.sup.-8 Cadmium oxalate trihydrate CdC.sub.2O.sub.4 .times.
3H.sub.2O 1.42 .times. 10.sup.-8 Cadmium phosphate
Cd.sub.3(PO.sub.4).sub.2 2.53 .times. 10.sup.-33 Cadmium sulfide
CdS 1 .times. 10.sup.-27 Cesium perchlorate CsClO.sub.4 3.95
.times. 10.sup.-3 Cesium periodate CsIO.sub.4 5.16 .times.
10.sup.-6 Calcium carbonate (calcite) CaCO.sub.3 3.36 .times.
10.sup.-9 Calcium carbonate (aragonite) CaCO.sub.3 .sup. 6.0
.times. 10.sup.-9 Calcium fluoride CaF.sub.2 3.45 .times.
10.sup.-11 Calcium hydroxide Ca(OH).sub.2 5.02 .times. 10.sup.-6
Calcium iodate Ca(IO.sub.3).sub.2 6.47 .times. 10.sup.-6 Calcium
iodatc hcxahydratc Ca(IO.sub.3).sub.2 .times. 6H.sub.2O 7.10
.times. 10.sup.-7 Calcium molybdate CaMoO 1.46 .times. 10.sup.-8
Calcium oxalate monohydrate CaC.sub.2O.sub.4 .times. H.sub.2O 2.32
.times. 10.sup.-9 Calcium phosphate Ca.sub.3(PO.sub.4).sub.2 2.07
.times. 10.sup.-33 Calcium sulfate CaSO.sub.4 4.93 .times.
10.sup.-5 Calcium sulfate dihydrate CaSO.sub.4 .times. 2H.sub.2O
3.14 .times. 10.sup.-5 Calcium sulfate hemihydrate CaSO.sub.4
.times. 0.5H.sub.2O .sup. 3.1 .times. 10.sup.-7 Cobalt(II) arsenate
Co.sub.3(AsO.sub.4).sub.2 6.80 .times. 10.sup.-29 Cobalt(II)
carbonate CoCO.sub.3 1.0 .times. 10.sup.-10 Cobalt(II) hydroxide
(blue) Co(OH).sub.2 5.92 .times. 10.sup.-15 Cobalt(II) iodate
dihydrate Co(IO.sub.3).sub.2 .times. 2H.sub.2O 1.21 .times.
10.sup.-2 Cobalt(II) phosphate Co.sub.3(PO.sub.4).sub.2 2.05
.times. 10.sup.-35 Cobalt(II) sulfide (alpha) CoS 5 .times.
10.sup.-22 Cobalt(II) sulfide (beta) CoS 3 .times. 10.sup.-26
Copper(I) bromide CuBr 6.27 .times. 10.sup.-9 Copper(I) chloride
CuCl 1.72 .times. 10.sup.-7 Copper(I) cyanide CuCN 3.47 .times.
10.sup.-20 Copper(I) hydroxide Cu.sub.2O 2 .times. 10.sup.-15
Copper(I) iodide CuI 1.27 .times. 10.sup.-12 Copper(I) thiocyanate
CuSCN 1.77 .times. 10.sup.-13 Copper(II) arsenate
Cu.sub.3(AsO.sub.4).sub.2 7.95 .times. 10.sup.-36 Copper(II)
hydroxide Cu(OH).sub.2 4.8 .times. 10.sup.-20 Copper(II) iodate
monohydrate Cu(IO.sub.3).sub.2 .times. H.sub.2O 6.94 .times.
10.sup.-8 Copper(II) oxalate CuC.sub.2O.sub.4 4.43 .times.
10.sup.-10 Copper(II) phosphate Cu.sub.3(PO.sub.4).sub.2 1.40
.times. 10.sup.-37 Copper(II) sulfide CuS 8 .times. 10.sup.-37
Europium(III) hydroxide Eu(OH).sub.3 9.38 .times. 10.sup.-27
Gallium(III) hydroxide Ga(OH).sub.3 7.28 .times. 10.sup.-36
Iron(II) carbonate FeCO.sub.3 3.13 .times. 10.sup.-11 Iron(II)
fluoride FeF.sub.2 2.36 .times. 10.sup.-6 Iron(II) hydroxide
Fe(OH).sub.2 4.87 .times. 10.sup.-17 Iron(II) sulfide FeS 8 .times.
10.sup.-19 Iron(III) hydroxide Fe(OH).sub.3 2.79 .times. 10.sup.-39
Iron(III) phosphate dihydrate FePO.sub.4 .times. 2H.sub.2O 9.91
.times. 10.sup.-16 Lanthanum iodate La(IO.sub.3).sub.3 7.50 .times.
10.sup.-12 Lead(II) bromide PbBr.sub.2 6.60 .times. 10.sup.-6
Lead(II) carbonate PbCO.sub.3 7.40 .times. 10.sup.-14 Lead(II)
chloride PbCl.sub.2 1.70 .times. 10.sup.-5 Lead(II) chromate
PbCrO.sub.4 3 .times. 10.sup.-13 Lead(II) fluoride PbF.sub.2 .sup.
3.3 .times. 10.sup.-8 Lead(II) hydroxide Pb(OH).sub.2 1.43 .times.
10.sup.-20 Lead(II) iodate Pb(IO.sub.3).sub.2 3.69 .times.
10.sup.-13 Lead(II) iodide PbI.sub.2 .sup. 9.8 .times. 10.sup.-9
Lead(II) oxalate PbC.sub.2O.sub.4 .sup. 8.5 .times. 10.sup.-9
Lead(II) selenate PbSeO.sub.4 1.37 .times. 10.sup.-7 Lead(II)
sulfate PbSO.sub.4 2.53 .times. 10.sup.-8 Lead(II) sulfide PbS 3
.times. 10.sup.-28 Lithium carbonate Li.sub.2CO.sub.3 8.15 .times.
10.sup.-4 Lithium fluoride LiF 1.84 .times. 10.sup.-3 Lithium
phosphate Li.sub.3PO.sub.4 2.37 .times. 10.sup.-4 Magnesium
ammonium phosphate MgNH.sub.4PO.sub.4 3 .times. 10.sup.-13
Magnesium carbonate MgCO.sub.3 6.82 .times. 10.sup.-6 Magnesium
carbonate trihydrate MgCO.sub.3 .times. 3H.sub.2O 2.38 .times.
10.sup.-6 Magnesium carbonate pentahydrate MgCO.sub.3 .times.
5H.sub.2O 3.79 .times. 10.sup.-6 Magnesium fluoride MgF.sub.2 5.16
.times. 10.sup.-11 Magnesium hydroxide Mg(OH).sub.2 5.61 .times.
10.sup.-12 Magnesium oxalate dihydrate MgC.sub.2O.sub.4 .times.
2H.sub.2O 4.83 .times. 10.sup.-6 Magnesium phosphate
Mg.sub.3(PO.sub.4).sub.2 1.04 .times. 10.sup.-24 Manganese(II)
carbonate MnCO.sub.3 2.24 .times. 10.sup.-11 Manganese(II) iodate
Mn(IO.sub.3).sub.2 4.37 .times. 10.sup.-7 Manganese(II) hydroxide
Mn(OH).sub.2 2 .times. 10.sup.-13 Manganese(II) oxalate dihydrate
MnC.sub.2O.sub.4 .times. 2H.sub.2O 1.70 .times. 10.sup.-7
Manganese(II) sulfide (pink) MnS 3 .times. 10.sup.-11 Manganese(II)
sulfide (green) MnS 3 .times. 10.sup.-14 Mcrcury(I) bromidc
Hg.sub.2Br.sub.2 6.40 .times. 10.sup.-23 Mercury(I) carbonate
Hg.sub.2CO.sub.3 3.6 .times. 10.sup.-17 Mercury(I) chloride
Hg.sub.2Cl.sub.2 1.43 .times. 10.sup.-18 Mcrcury(I) fluoridc
Hg.sub.2F.sub.2 3.10 .times. 10.sup.-6 Mercury(I) iodide
Hg.sub.2I.sub.2 5.2 .times. 10.sup.-29 Mercury(I) oxalate
Hg.sub.2C.sub.2O.sub.4 1.75 .times. 10.sup.-13 Mcrcury(I) sulfatc
Hg.sub.2SO.sub.4 .sup. 6.5 .times. 10.sup.-7 Mercury(I) thiocyanate
Hg.sub.2(SCN).sub.2 3.2 .times. 10.sup.-20 Mercury(II) bromide
HgBr.sub.2 6.2 .times. 10.sup.-20 Mercury(II) hydroxide HgO 3.6
.times. 10.sup.-26 Mercury(II) iodide HgI.sub.2 2.9 .times.
10.sup.-29 Mercury(II) sulfide (black) HgS 2 .times. 10.sup.-53
Mercury(II) sulfide (red) HgS 2 .times. 10.sup.-54 Neodymium
carbonate Nd.sub.2(CO.sub.3).sub.3 1.08 .times. 10.sup.-33
Nickel(II) carbonate NiCO.sub.3 1.42 .times. 10.sup.-7 Nickel(II)
hydroxide Ni(OH).sub.2 5.48 .times. 10.sup.-16 Nickel(II) iodate
Ni(IO.sub.3).sub.2 4.71 .times. 10.sup.-5 Nickel(II) phosphate
Ni.sub.3(PO.sub.4).sub.2 4.74 .times. 10.sup.-32 Nickel(II) sulfide
(alpha) NiS 4 .times. 10.sup.-20 Nickel(II) sulfide (beta) NiS 1.3
.times. 10.sup.-25 Palladium(II) thiocyanate Pd(SCN).sub.2 4.39
.times. 10.sup.-23 Potassium hexachloroplatinate K.sub.2PtCl.sub.6
7.48 .times. 10.sup.-6 Potassium perchlorate KClO.sub.4 1.05
.times. 10.sup.-2 Potassium periodate KIO.sub.4 3.71 .times.
10.sup.-4 Praseodymium hydroxide Pr(OH).sub.3 3.39 .times.
10.sup.-24 Radium iodate Ra(IO.sub.3).sub.2 1.16 .times. 10.sup.-9
Radium sulfate RaSO.sub.4 3.66 .times. 10.sup.-11 Rubidium
perchlorate RuClO.sub.4 3.00 .times. 10.sup.-3 Scandium fluoride
ScF.sub.3 5.81 .times. 10.sup.-24 Scandium hydroxide Sc(OH).sub.3
2.22 .times. 10.sup.-31 Silver(I) acetate AgCH.sub.3COO 1.94
.times. 10.sup.-3 Silver(I) arsenate Ag.sub.3AsO.sub.4 1.03 .times.
10.sup.-22 Silver(I) bromate AgBrO.sub.3 5.38 .times. 10.sup.-5
Silver(I) bromide AgBr 5.35 .times. 10.sup.-13 Silver(I) carbonate
Ag.sub.2CO.sub.3 8.46 .times. 10.sup.-12 Silver(I) chloride AgCl
1.77 .times. 10.sup.-10 Silver(I) chromate Ag.sub.2CrO.sub.4 1.12
.times. 10.sup.-12 Silver(I) cyanide AgCN 5.97 .times. 10.sup.-17
Silver(I) iodate AgIO.sub.3 3.17 .times. 10.sup.-8 Silver(I) iodide
AgI 8.52 .times. 10.sup.-17 Silver(I) oxalate
Ag.sub.2C.sub.2O.sub.4 5.40 .times. 10.sup.-12 Silver(I) phosphate
Ag.sub.3PO.sub.4 8.89 .times. 10.sup.-17 Silver(I) sulfate
Ag.sub.2SO.sub.4 1.20 .times. 10.sup.-5 Silver(I) sulfite
Ag.sub.2SO.sub.3 1.50 .times. 10.sup.-14 Silver(I) sulfide
Ag.sub.2S 8 .times. 10.sup.-51 Silver(I) thiocyanate AgSCN 1.03
.times. 10.sup.-12 Strontium arsenate Sr.sub.3(AsO.sub.4).sub.2
4.29 .times. 10.sup.-19 Strontium carbonate SrCO.sub.3 5.60 .times.
10.sup.-10 Strontium fluoride SrF.sub.2 4.33 .times. 10.sup.-9
Strontium iodate Sr(IO.sub.3).sub.2 1.14 .times. 10.sup.-7
Strontium iodate monohydrate Sr(IO.sub.3).sub.2 .times. H.sub.2O
3.77 .times. 10.sup.-7 Strontium iodate hexahydrate
Sr(IO.sub.3).sub.2 .times. 6H.sub.2O 4.55 .times. 10.sup.-7
Strontium oxalate SrC.sub.2O.sub.4 .sup. 5 .times. 10.sup.-8
Strontium sulfatc SrSO.sub.4 3.44 .times. 10.sup.-7 Thallium(I)
bromate TlBrO.sub.3 1.10 .times. 10.sup.-4 Thallium(I) bromide TlBr
3.71 .times. 10.sup.-6 Thallium(I) chloride TlCl 1.86 .times.
10.sup.-4 Thallium(I) chromate Tl.sub.2CrO.sub.4 8.67 .times.
10.sup.-13 Thallium(I) hydroxide Tl(OH).sub.3 1.68 .times.
10.sup.-44 Thallium(I) iodate TlIO.sub.3 3.12 .times. 10.sup.-6
Thallium(I) iodide TlI 5.54 .times. 10.sup.-8 Thallium(I)
thiocyanate TlSCN 1.57 .times. 10.sup.-4 Thallium(I) sulfide
Tl.sub.2S 6 .times. 10.sup.-22 Tin(II) hydroxide Sn(OH).sub.2 5.45
.times. 10.sup.-27 Yttrium carbonate Y.sub.2(CO.sub.3).sub.3 1.03
.times. 10.sup.-31 Yttrium fluoride YF.sub.3 8.62 .times.
10.sup.-21 Yttrium hydroxide Y(OH).sub.3 1.00 .times. 10.sup.-22
Yttrium iodate Y(IO.sub.3).sub.3 1.12 .times. 10.sup.-10 Zinc
arsenate Zn.sub.3(AsO.sub.4).sub.2 2.8 .times. 10.sup.-28 Zinc
carbonate ZnCO.sub.3 1.46 .times. 10.sup.-10 Zinc carbonate
monohydrate ZnCO.sub.3 .times. H.sub.2O 5.42 .times. 10.sup.-11
Zinc fluoride ZnF 3.04 .times. 10.sup.-2 Zinc hydroxide
Zn(OH).sub.2 3 .times. 10.sup.-17 Zinc iodate dihydrate
Zn(IO.sub.3).sub.2 .times. 2H.sub.2O .sup. 4.1 .times. 10.sup.-6
Zinc oxalatc dihydratc ZnC.sub.2O.sub.4 .times. 2H.sub.2O 1.38
.times. 10.sup.-9 Zinc selenide ZnSe 3.6 .times. 10.sup.-26 Zinc
selenite monohydrate ZnSe .times. H.sub.2O 1.59 .times. 10.sup.-7
Zinc sulfidc (alpha) ZnS 2 .times. 10.sup.-25 Zinc sulfide (beta)
ZnS 3 .times. 10.sup.-23
[0032] Conventional descaling technologies include chemical and
electromagnetic methods. Chemical methods utilize either pH
adjustment, chemical sequestration with polyphosphates, zeolites
and the like, or ionic exchange; combinations of these methods are
typically used. Normally, chemical methods aim at preventing scale
from precipitating by lowering the pH and using chemical
sequestration, but they are typically not 100% effective.
Electromagnetic methods rely on the electromagnetic excitation of
calcium or magnesium carbonate so as to favor crystallographic
forms that are non-adherent. For example, electromagnetic
excitation favors the precipitation of aragonite rather than
calcite; the former is a softer, less adherent form of calcium
carbonate. However, electromagnetic methods are only effective over
relatively short distances and residence times. There is a need for
permanently removing scale-forming constituents from contaminated
aqueous solutions, seawater, or produced waters that will be
subject to be further processing.
[0033] Other factors can complicate scale reduction methods,
particularly in high-salinity solutions such as seawater or produce
water. These include the buffering effects of high ionic strength
solutions and ion complexing phenomena that can shield certain
cations from reacting.
[0034] An embodiment of the present invention provides a method for
removing scale-forming compounds from tap water, contaminated
aqueous solutions, seawater, and saline brines such as produced
water, involving the initial removal of magnesium ions by
precipitating magnesium hydroxide (Mg(OH).sub.2) at high pH, then
removing the precipitate by either sedimentation or filtering.
Ordinarily, Mg(OH).sub.2 precipitates at high pH (around 11.0),
although in many cases the bulk of magnesium precipitates at lower
pH.
[0035] Following Mg(OH).sub.2 precipitation, carbonate ions are
added in the form of CO.sub.2 sparging, by adding soluble carbonate
or bicarbonate salts in nearly stoichiometric amounts so as to
subsequently precipitate calcium, barium, and other divalent
cations as carbonates by adjusting the pH to about 10.2 or greater.
This process has the net effect of permanently sequestering
CO.sub.2 from the atmosphere, and the precipitates are then removed
by either sedimentation or filtering.
[0036] A detailed description of this pre-treatment embodiment
follows the flowsheet of FIG. 1. In FIG. 1, filtered and de-oiled
contaminated water (1) enters the pretreatment system through a
line-booster pump P101 (20), which delivers the incoming water into
a mixer-settler vessel V-101 (40). The pH of vessel V-101 is
maintained at about 11 by means of continuous alkali additions, in
the form of sodium hydroxide, calcium hydroxide, or similar
chemical. Control of the pH in vessel V-101 is achieved through a
metering pump P102 (22), which transfers caustic solution from tank
T101 through a variable valve Va101 (45). The precipitated
Mg(OH).sub.2 slurry in vessel V101 sediments and exits near the
bottom and is continuously filtered in filter F101 (50), thus
yielding a filter cake (66) of magnesium hydroxide.
[0037] Following precipitation of Mg(OH).sub.2 in vessel V101 (40),
the clear solution exits near the top and flows into a static mixer
M101 (60), where it is mixed with additional clear filtrate from
filter F101 (50) and pump P103 (24) and a source of carbonate ions,
which can be pressurized CO.sub.2 gas from V102 (32) or a solution
of soluble carbonates or bicarbonates.
[0038] The aqueous solution then flows into a second static mixer
M102, where additional caustic or alkali chemicals are added from
the variable valve Va101 (45) so as to adjust the pH to about 10.2,
at which point most of the divalent cations in solution precipitate
as insoluble carbonates. The precipitate slurry then enters
mixer-settler V103 (42), where the insoluble carbonates sediment
and flow into filter F102 (52), where a second filter cake (68) is
removed. The filtrate from filter F102 enters pump P105 (26), which
feeds a variable valve Va102 (47) that allows a portion of the
descaled water product (70) to recirculate back into the
carbonation loop.
[0039] In a further aspect, especially when the contaminated water
contains excess carbonate or bicarbonate ions, calcium or magnesium
can be added in order to provide the stoichiometric requirements
for carbonate precipitation. Alternatively, calcium and magnesium
can be substituted for other divalent cations, such as barium,
cadmium, cobalt, iron, lead, manganese, nickel, strontium, or zinc,
that have low solubility products in carbonate form.
[0040] In a further aspect, calcium or magnesium additions are
substituted for trivalent cations, such as aluminum or neodymium,
that have low solubility products in their carbonate or hydroxide
forms.
[0041] In a further aspect, CO.sub.2 sparging is replaced by the
addition of soluble bicarbonate ions, such as sodium, potassium, or
ammonium bicarbonate.
[0042] In a further aspect, carbonate and scale precipitates are
removed by means other than sedimentation or filtering, such as
centrifuging.
[0043] In a further aspect, the permanent sequestration of CO.sub.2
from the atmosphere is achieved in conventional desalination
systems, such as MSF evaporation systems, MED plants, and VC
desalination systems.
[0044] In a further aspect, scale-forming salts are permanently
removed from conventional desalination systems.
[0045] In a further aspect, tap water, municipal water, or well
water containing objectionable hard water constituents, such as
calcium or magnesium, are descaled in residential water
purification systems.
[0046] In a further aspect, valuable scale-forming salts, such as
magnesium, barium, and other salts, are recovered.
[0047] In a further aspect, scale-forming compounds are
precipitated in the form of non-adhering, easily filterable or
sedimentable solids and ultimately removed.
[0048] In a further aspect, CO.sub.2 emissions from power plants
and similar flue gases are permanently sequestered.
[0049] In a further aspect, scale-forming compounds are
sequentially precipitated and removed, so they can be utilized and
reused in downstream industrial processes.
[0050] A further embodiment of the present invention provides a
method for removing a scale-forming compound from an aqueous
solution, involving: adding at least one ion to the solution in a
stoichiometric amount sufficient to cause the precipitation of a
first scale-forming compound at an alkaline pH; adjusting the pH of
the solution to an alkaline pH, thereby precipitating the first
scale-forming compound; removing the first scale-forming compound
from the solution; heating the solution to a temperature sufficient
to cause the precipitation of a second scale-forming compound from
the solution; and removing the second scale-forming compound from
the solution.
[0051] In a further aspect, the ion is selected from the group
including carbonate ions and divalent cations. In a further aspect,
the carbonate ion is HCO.sub.3.sup.-. In a further aspect, the
divalent cation is selected from the group including Ca.sup.2+ and
Mg.sup.2+.
[0052] In a further aspect, the stoichiometric amount is sufficient
to substitute the divalent cation for a divalent cation selected
from the group including barium, cadmium, cobalt, iron, lead,
manganese, nickel, strontium, and zinc in the first scale-forming
compound.
[0053] In a further aspect, the stoichiometric amount is sufficient
to substitute the divalent cation for a trivalent cation selected
from the group including aluminum and neodymium in the first
scale-forming compound.
[0054] In a further aspect, adding at least one ion comprises
sparging the solution with CO.sub.2 gas.
[0055] In a further aspect, the CO.sub.2 is atmospheric
CO.sub.2.
[0056] In a further aspect, adding at least one ion comprises
adding a soluble bicarbonate ion selected from the group including
sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate
to the solution.
[0057] In a further aspect, adding at least one ion comprises
adding a compound selected from the group including CaO,
Ca(OH).sub.2, Mg(OH).sub.2, and MgO to the solution.
[0058] In a further aspect, the alkaline pH is a pH of
approximately 9.2 or greater.
[0059] In a further aspect, the first scale-forming compound is
selected from the group including CaCO.sub.3 and MgCO.sub.3.
[0060] Tn a further aspect, adjusting the pH of the solution
comprises adding a compound selected from the group including CaO
and NaOH to the solution.
[0061] In a further aspect, removing the first scale-forming
compound comprises at least one of filtration, sedimentation, and
centrifuging.
[0062] A further embodiment of the present invention provides a
method of obtaining scale-forming compounds, involving: providing
an aqueous solution; adding alkali chemicals in amounts sufficient
to cause the precipitation of a first scale-forming compound at an
alkaline pH; adjusting the pH of the solution to an alkaline pH,
thereby precipitating the first scale-forming compound; removing
the first scale-forming compound from the solution; adding
carbonate ions while maintaining an alkaline pH sufficient to cause
the precipitation of a second scale-forming compound from the
solution; removing the second scale-forming compound from the
solution; recovering the first scale-forming compound; and
recovering the second scale-forming compound.
[0063] In a further aspect, the first and second scale-forming
compounds are selected from the group of compounds listed in Table
4.
[0064] A further embodiment of the present invention provides a
method of sequestering atmospheric CO.sub.2, involving: providing
an aqueous solution containing at least one ion capable of forming
a CO.sub.2-sequestering compound in the presence of carbonate ion;
adding carbonate ions to the solution in a stoichiometric amount
sufficient to cause the precipitation of the CO.sub.2-sequestering
compound at an alkaline pH; adjusting the pH of the solution to an
alkaline pH, thereby precipitating the CO.sub.2-sequestering
compound; and removing the CO.sub.2-sequestering compound from the
solution; wherein adding carbonate ions comprises adding either
atmospheric or concentrated CO.sub.2 (e.g., from a combustion flue
gas) to the solution, and wherein the CO.sub.2 is sequestered in
the CO.sub.2-sequestering compound.
Overall Description of Water Desalination System
[0065] In preferred embodiments, such as those shown in FIG. 2, the
water purification and desalination system consists of a vertically
stacked arrangement of boilers (92 and 96) and condensers (90, 94,
and 98), whereby a source of heat is provided at the bottom of the
stack, a preheater (74) is provided at the top of the stack, a
degasser (80) is provided at the top of the system to remove
volatile organic compounds from the incoming water, a plurality of
demisters (not shown) are provided to remove contaminated mist
particles from each boiling chamber, a plurality of heat pipes (78)
is provided to recover heat from each condenser and transfer such
heat to an upper boiling chamber, and a waste stream outlet (100)
is provided to remove and drain water contaminants. Various
alternative configurations to the vertical stacked arrangement are
possible to those skilled in the art, such as, for example, a
lateral arrangement of boilers, condensers, and preheaters, and the
like.
[0066] In FIG. 2, pre-treated water (70) enters the desalinator
proximate the upper end of the stack through a pipeline (72), which
delivers the flow into a preheater tank (74). A number of heat
pipes (78) in the preheater tank (74) deliver the heat to preheat
the incoming water by transferring the heat of condensation from
the condenser (90) that is placed immediately below. The preheated
water exits the preheater tank (74) through a pipe (76), which
delivers the preheated water into the upper end of a degasser (80),
where it flows by gravity downward while a counter current of steam
flows upward from the boiler (92) through the bottom of the
degasser (80). As steam strips organic contaminants and gases from
the preheated water, the degassed water exits the degasser (80) and
enters the boiler (92).
[0067] Preheated and degassed water that enters the boiler (92) is
further heated by heat pipes (78) that transfer the heat of
condensation from a condenser (94). The steam produced in the
boiler (92) is cleaned in a demister that is described below and is
condensed in a condenser (90), and the clean water product exits
the system via a pipe (102), which collects clean water product
from each condenser. As water is evaporated from the boiler (92),
the concentration of dissolved salts increases. The level of
boiling water in the boiler (92) is maintained at a constant level
by a downcomer tube (101), which allows water to exit the boiler by
gravity.
[0068] An important element in the vertical arrangement of boilers
and condensers is the ability to maintain a slight pressure
differential between boilers, so that a lower boiler will have a
slightly higher pressure than an upper boiler; therefore, the
temperature of the lower boiler will be slightly higher than that
of an upper boiler. This pressure differential can be maintained by
a pump, but, in a preferred embodiment, it is simply maintained by
the hydraulic head of the downcomer tubes (100) and (101), which
maintain such pressure differential by means of a lower
pressure-actuated valve (103).
[0069] A more detailed description of the vertical arrangement of
boilers and condensers is provided in FIG. 3. In FIG. 3, the boiler
(92) receives hot incoming water from the downcomer tube (101),
which either drains an upper boiler or receives water from the
degasser. In the boiler (92), the heat pipes (78) transfer the
necessary heat to bring the temperature to the boiling point and
provide the heat of evaporation to transform part of the boiling
water into steam. The steam that is produced enters a demister
(110), where mist particles are collected by a series of mechanical
barriers that allow only clean steam to enter a steam tube (115),
which delivers such steam to an upper condenser chamber (90), where
it condenses into clean water product that drains through the
product water drain (102).
[0070] As water boils in the boiler (92), it becomes denser and
more concentrated in soluble salts and exits through the downcomer
tube (100) into a lower boiler (96). A valve (103) at the bottom of
the downcomer tube (100) provides the necessary hydraulic pressure
to maintain the lower boiler (96) at a slightly higher pressure
and, thus, at a slightly higher temperature than the upper boiler
(92).
[0071] The tubes (120) and (130) and the intermediate valve (125)
serve dual functions. During start-up procedures, the valve (125),
which can be controlled by a pressure regulator or a solenoid, is
open, allowing steam to travel directly from the lower boiler (96)
to the upper boiler (92), thus accelerating start-up procedures.
Once the system is operating at the correct temperature, the valve
(125) is closed. During shut-down procedures, the heat source is
shut off, and the valve (125) is re-opened so as to facilitate
draining of all the boilers.
[0072] FIG. 4 is a diagram of a desalinator with five vertical
stages. In FIG. 4, pre-treated and descaled water (70) enters
through a tube (72) into an upper preheater vessel (74), where heat
from heat pipes (78) provide the necessary energy for preheating
the incoming water close to its boiling point but no less than
96.degree. C. The preheated water exits the preheater (74) and
enters the degasser (80), where counter-current steam strips the
gases and organic contaminants. The degassed water then flows into
an upper boiler (92), where the heat pipes provide the necessary
heat for turning a portion of the incoming water into steam. Some
of the steam produced in the upper boiler (92) may be used to
provide the steam for degassing, while the rest flows into the
demister (110) and subsequently into an upper condenser (90), where
it condenses into pure product water. As water evaporates in the
upper boiler (92), it becomes more concentrated in soluble salts
and flows by gravity into a lower boiler via the downcomer tube
(100). The boiler water becomes progressively more concentrated in
soluble salts as it travels downward from boiler to boiler until it
reaches the lowest boiler, where it exits the system as a
concentrated hot brine that can begin crystallizing as soon as it
cools down. In the case of desalination, the hot waste brine may
have a TDS concentration on the order of 250,000 ppm; this
concentration is still lower than the solubility limit of NaCl but
is close enough to begin crystallization upon cooling.
[0073] In contrast with water flow, heat travels upward in the
system, from the heat input vessel at the bottom (150) ultimately
to the preheating vessel at the top (74), by means of multiple
stages of heat pipes (78). At each stage, the heat of condensation
or, in the case of the heat input vessel at the bottom (150), the
latent heat of flue gases or the heat of condensation of waste
steam, is absorbed by a series of heat pipes that transfer the heat
to an upper boiler and, at the top of the vertical stack, to the
upper preheating tank (74).
[0074] An important advantage of the system described herein is the
mechanism of heat transfer via heat pipes. As shown in a subsequent
section, heat pipes provide a means of transferring heat that is
nearly thermodynamically reversible, that is, a system that
transfers enthalpy with almost no losses in efficiency. Thus, with
the exception of the preheating energy, nearly all of the heat
provided by the heat input vessel at the bottom (150) is re-used at
each of the boiling and condensing stages by minimizing heat losses
at the wall separating the condensing side of the heat pipe from
the boiling side. Since that distance is defined by the perforated
plate (93), which can be very thin or made as an insulator, the
amount of heat lost during heat transfer can be close to zero.
Therefore, the energy used during multiple stages of boiling and
condensing can be readily approximated by dividing the heat of
evaporation of water by the number of stages of the system.
[0075] However, as the number of stages in the system increases,
the amount of steam produced at each stage decreases; with a large
number of stages, the amount of heat that condenses at the upper
condenser is insufficient to provide the necessary heat for
preheating the incoming water and also insufficient for providing
the necessary steam required for degassing. Table 5 illustrates
these energy requirements for the case of seawater, which is
normally devoid of organic contaminants, as a function of the
number of stages in the system, but ignoring degassing
requirements.
TABLE-US-00005 TABLE 5 Energy Requirements, Kwh/m.sup.3 Stages
Total heat 5 133.4693 6 111.2245 7 95.33525 8 86.67204 10 69.98837
20 36.62103 30 25.49859 40 19.93736 50 16.60063
[0076] The above estimates presume that the heat available in the
hot waste brine at the bottom of the system and the heat contained
in the various product water streams is recovered either by means
of heat exchangers or heat pipes. In a simple arrangement, most of
this heat can be recovered by preheating the incoming water in
exchange with each of the product streams as they cascade downward
in a vertical system, ending with heat recovery from the waste
brine, and then re-pumping this preheated water to the top of the
system, where a minimal amount of supplemental heat is required to
bring the temperature up to the boiling point.
[0077] In alternative embodiments, the product water at each stage
can be re-introduced into an upper condenser stage and allowed to
flash, thus releasing part of the contained heat. In other
embodiments, the incoming pre-treated water can be divided into
separate streams and introduced into each separate stage for
distillation.
[0078] FIG. 5 illustrates plant, stereoscopic, and elevation views
of a typical stage and provides dimensions for a boiler, condenser,
and separator plate suitable for a system able to process on the
order of 100,000 gpd (378.5 m.sup.3/day) in 6 stages.
[0079] It is advantageous to be able to maximize the number of
boiling and condensing stages in the present invention. This is
possible through the use of heat pipes, provided the temperature
difference between the condensing and boiling ends of such a heat
pipe (the .DELTA.T) is sufficient to maintain the maximum heat flux
through the heat pipe. Commercially available heat pipes typically
have .DELTA.Ts of the order of 8.degree. C. (15.degree. F.),
although some have .DELTA.Ts as low as 3.degree. C. The .DELTA.T
defines the maximum number of stages that are practical with a
given amount of heat available at a given temperature. Thus, there
is a need for heat pipes that can function with as small a .DELTA.T
as possible. It is therefore useful to examine the thermal
phenomena in a heat pipe.
[0080] FIG. 6 illustrates a typical commercial heat pipe, which
ordinarily consists of a partially evacuated and sealed tube (77)
containing a small amount of a working fluid (81); this fluid is
typically water but may also be an alcohol or other volatile
liquid. When heat is applied to the lower end in the form of
enthalpy, the heat crosses the metal barrier of the tube (77), then
is used to provide the heat of vaporization to the working fluid
(81). As the working fluid evaporates, the resulting gas (which is
steam in the case of water) fills the tube (77) and reaches the
upper end, where the .DELTA.T causes condensation and release of
the same heat as the heat of condensation. To facilitate continuous
operation, the inside of the tube (77) normally includes a wick
(79), which can be any porous and hydrophilic layer that transfers
the condensed phase of the working fluid back to the hot end of the
tube.
[0081] Experimentally, the largest barriers to heat transfer in a
heat pipe include: 1) the layer immediately adjacent to the outside
of the heat pipe, 2) the conduction barrier presented by the
material of the heat pipe, and 3) the limitation of the wick
material to return working fluid to the hot end of the heat pipe.
FIG. 7 illustrates a high-performance heat pipe that minimizes
these barriers.
[0082] In FIG. 7, vibrational energy (87) is provided to the heat
pipe (78), either in the form of mechanical vibration,
electro-mechanical vibration, or high-frequency ultrasound. This
vibration is transmitted to the length of the heat pipe and
disrupts the layer adjacent to the heat pipe. Disruption of this
layer facilitates micro-turbulence in the layer, thus resulting in
heat transfer. In addition, a hydrophobic coating is provided on
the outside of the heat pipe, especially in the area where external
condensation occurs. The hydrophobic coating may consist of a
monolayer of stearic acid or similar hydrocarbon, or it may be a
thin layer of a hydrophobic chlorofluorocarbon. A hydrophobic
surface on the outside of the heat pipe minimizes the area required
for condensation and evaporation, thus reducing the barrier for
heat transfer.
[0083] The heat conduction barrier is also minimized by using a
very thin metal foil (77) instead of the solid metal tube of most
heat pipes. Mechanical support for the metal foil must be
sufficient to sustain moderate vacuum and is provided by a metal
screen (85), which provides additional functionality by increasing
the internal surface area required for providing the necessary heat
of condensation/evaporation.
[0084] An improved distribution of working fluid is achieved by
orienting the wick toward the axis of the heat pipe, thus reducing
the thermal interference of condensate with heat transfer across
the wall of the heat pipe. The wick material can be any hydrophilic
porous medium that can transfer working fluid by capillary action,
such as metallic oxides, some ceramics, surface-treated cellulosic
materials, and the like.
[0085] In some embodiments, the system for descaling water and
saline solutions, embodiments of which are disclosed herein, can be
combined with other systems and devices to provide further
beneficial features. For example, the system can be used in
conjunction with any of the devices or methods disclosed in U.S.
Provisional Patent Application No. 60/676,870, entitled SOLAR
ALIGNMENT DEVICE, filed May 2, 2005; U.S. Provisional Patent
Application No. 60/697,104, entitled VISUAL WATER FLOW INDICATOR,
filed Jul. 6, 2005; U.S. Provisional Patent Application No.
60/697,106, entitled APPARATUS FOR RESTORING THE MINERAL CONTENT OF
DRINKING WATER, filed Jul. 6, 2005; U.S. Provisional Patent
Application No: 60/697107, entitled IMPROVED CYCLONE DEMISTER,
filed Jul. 6, 2005; PCT Application No: US2004/039993, filed Dec.
1, 2004; PCT Application No: US2004/039991, filed Dec. 1, 2004; PCT
Application No: US2006/040103, filed Oct. 13, 2006; U.S. patent
application Ser. No. 12/281,608, filed Sep. 3, 2008; PCT
Application No. US2008/03744, filed Mar. 21, 2008; and U.S.
Provisional Patent Application No. 60/526,580, filed Dec. 2, 2003;
each of the foregoing applications is hereby incorporated by
reference in its entirety.
[0086] One skilled in the art will appreciate that these methods
and devices are and may be adapted to carry out the objects and
obtain the ends and advantages mentioned, as well as various other
advantages and benefits. The methods, procedures, and devices
described herein are presently representative of preferred
embodiments and are exemplary and are not intended as limitations
on the scope of the invention. Changes therein and other uses will
occur to those skilled in the art which are encompassed within the
spirit of the invention and are defined by the scope of the
disclosure.
[0087] The invention illustratively described herein suitably can
be practiced in the absence of any element or elements, limitation
or limitations which is not specifically disclosed herein. The
terms and expressions which have been employed are used as terms of
description and not of limitation, and there is no intention that
the use of such terms and expressions indicates the exclusion of
equivalents of the features shown and described or portions
thereof. It is recognized that various modifications are possible
within the scope of the invention disclosed. Thus, it should be
understood that although the present invention has been
specifically disclosed by preferred embodiments and optional
features, modification and variation of the concepts herein
disclosed may be resorted to by those skilled in the art and that
such modifications and variations are considered to be within the
scope of this invention as defined by the disclosure.
[0088] Those skilled in the art will recognize that the aspects and
embodiments of the invention set forth herein can be practiced
separately from each other or in conjunction with each other.
Therefore, combinations of separate embodiments are within the
scope of the invention as disclosed herein.
[0089] All patents and publications are herein incorporated by
reference to the same extent as if each individual publication was
specifically and individually indicated to be incorporated by
reference.
Example #1--Water Descaling System for Seawater
[0090] The approximate chemical composition of seawater is
presented in Table 6, below, and is typical of open ocean, but
there are significant variations in seawater composition depending
on geography and/or climate.
TABLE-US-00006 TABLE 6 Detailed Composition of Seawater at 3.5%
Salinity Element At. Weight ppm Hydrogcn H.sub.2O 1.00797 110,000
Oxygen O.sub.2 15.9994 883,000 Sodium NaCl 22.9898 10,800 Chlorine
NaCl 35.453 19,400 Magnesium Mg 24.312 1,290 Sulfur S 32.064 904
Potassium K 39.102 392 Calcium Ca 10.08 411 Bromine Br 79.909 67.3
Helium He 4.0026 0.0000072 Lithium Li 6.939 0.170 Beryllium Be
9.0133 0.0000006 Boron B 10.811 4.450 Carbon C 12.011 28.0 Nitrogen
ion 14.007 15.5 Fluorine F 18.998 13 Neon Ne 20.183 0.00012
Aluminum Al 26.982 0.001 Silicon Si 28.086 2.9 Phosphorus P 30.974
0.088 Argon Ar 39.948 0.450 Scandium Sc 44.956 <0.000004
Titanium Ti 47.90 0.001 Vanadium V 50.942 0.0019 Chromium Cr 51.996
0.0002 Manganese Mn 54.938 0.0004 Iron Fe 55.847 0.0034 Cobalt Co
58.933 0.00039 Nickel Ni 58.71 0.0066 Copper Cu 63.54 0.0009 Zinc
Zn 65.37 0.005 Gallium Ga 69.72 0.00003 Germanium Ge 72.59 0.00006
Arsenic As 74.922 0.0026 Selenium Se 78.96 0.0009 Krypton Kr 83.80
0.00021 Rubidium Rb 85.47 0.120 Strontium Sr 87.62 8.1 Yttrium Y
88.905 0.000013 Zirconium Zr 91.22 0.000026 Niobium Nb 92.906
0.000015 Molybdcnum Mo 95.94 0.01 Ruthenium Ru 101.07 0.0000007
Rhodium Rh 102.905 . Palladium Pd 106.4 . Silver Ag 107.870 0.00028
Cadmium Cd 112.4 0.00011 Indium In 114.82 . Tin Sn 118.69 0.00081
Antimony Sb 121.75 0.00033 Tellurium Te 127.6 . Iodine I 166.904
0.064 Xenon Xe 131.30 0.000047 Cesium Cs 132.905 0.0003 Barium Ba
137.34 0.021 Lanthanum La 138.91 0.0000029 Cerium Ce 140.12
0.0000012 Prasodymium Pr 140.907 0.00000064 Neodymium Nd 144.24
0.0000028 Samarium Sm 150.35 0.00000045 Europium Eu 151.96
0.0000013 Gadolinium Gd 157.25 0.0000007 Terbium Tb 158.924
0.00000014 Dysprosium Dy 162.50 0.00000091 Holmium Ho 164.930
0.00000022 Erbium Er 167.26 0.00000087 Thulium Tm 168.934
0.00000017 Ytterbium Yb 173.04 0.00000082 Lutetium Lu 174.97
0.00000015 Hafnium Hf 178.49 <0.000008 Tantalum Ta 180.948
<0.0000025 Tungsten W 183.85 <0.000001 Rhenium Re 186.2
0.0000084 Osmium Os 190.2 . Iridium Ir 192.2 . Platinum Pt 195.09 .
Gold Au 196.967 0.000011 Mercury Hg 200.59 0.00015 Thallium Tl
204.37 . Lead Pb 207.19 0.00003 Bismuth Bi 208.980 0.00002 Thorium
Th 232.04 0.0000004 Uranium U 238.03 0.0033 Plutonium Pu (244) .
Note: ppm = parts per million = mg/liter = 0.001 g/kg
[0091] Fifty gallons of ocean seawater were collected and treated
in a pilot facility able to continuously handle from 20 to 200
gallons/day. Initially, 50 mL/liter of a 10% sodium hydroxide
(caustic) solution was used to raise the pH of the seawater to
approximately 11.2 and the resulting precipitate allowed to
sediment in a thickener prior to filtering using a 1.mu. pore
filter. The filtrate was then conditioned with 0.9 g/liter of
sodium bicarbonate, and the pH was adjusted to 10.2 so as to obtain
another precipitate of carbonate salts, which was again allowed to
sediment and was subsequently filtered using a micron filter.
Chemical analysis of the final filtrate showed a reduction of about
67% of the scale-forming ions, such as calcium and magnesium, with
the balance of calcium and magnesium forming soluble chlorides that
do not precipitate upon boiling.
[0092] In a similar experiment, one liter of ocean seawater was
treated with 30 mL of a 10% sodium hydroxide (caustic) solution was
used to raise the pH of the seawater to slightly less than 11.0 and
the resulting precipitate allowed to sediment in a thickener prior
to filtering using a 1.mu. pore filter. The filtrate was then
conditioned with 0.9 g/liter of sodium bicarbonate, and the pH was
adjusted to 9.8 by adding another 0.7 g of caustic solution so as
to obtain a precipitate of carbonate salts which was allowed to
sediment and was subsequently filtered using a 1.mu. filter. No
scale formation compounds were detected in the resulting
filtrate.
[0093] A special test procedure was developed for ascertaining the
degree of descaling in treated solutions. In this test, a sample of
treated solution is collected in a glass beaker, and the sample is
subjected to boiling in a pressure cooker for up to 5 hours at
temperatures of 120.degree. C. under pressure. Following this test
procedure, the sample is removed and inspected visually as well as
under a microscope to detect any solid precipitate. Since the
residence time in the desalinating section that follows is only a
couple of hours, the absence of any scale in this particular test
proves that no scale will form during desalination. In none of the
examples described herein was any scale detected after
pre-treatment.
Example #2--Removal of Scale in Treatment of Waste Influent
Compositions
[0094] An aqueous waste influent composition obtained as a waste
stream from a fertilizer processing facility was treated in the
manner described above in order to remove scale-forming compounds,
as a pre-treatment to eventual desalination of the product in a
separate water purification apparatus in which the formation of
scale would be highly undesirable. The throughput of the treatment
apparatus was 6 gallons per day (GPD), which was used a pilot
apparatus for testing an industrial situation requiring 2000
m.sup.3/day (528,401.6 GPD). The composition of the waste influent
with respect to relevant elements and ions is given in Table 7
below.
TABLE-US-00007 TABLE 7 Waste Influent Composition Soluble Salts ppm
(mg/L) Barium 0 Calcium 500 Magnesium 300 Iron (III) 2 Bicarbonate
Sulfate 800 Phosphate 0 Silica 50 Strontium Sodium 700 Potassium 30
Arsenic 0 Fluoride 2 Chloride 1000 Nitrate 10
[0095] The waste influent had a TDS content of 35,000 ppm (mg/L).
As can be seen from Table 7, the waste influent had particularly
high concentrations of calcium and magnesium, which tend to give
rise to scale.
[0096] The waste influent was processed in the manner described
above. Because the influent contained little or no hydrocarbons,
deoiling and degassing were not conducted. CO.sub.2 carbonation and
addition of NaOH (to provide hydroxide ions to react with the Mg in
solution) were followed by pH adjustment to a pH of 9.3 using
additional NaOH. The process resulted in a filtered scale-forming
composition ("filter cake") and an effluent (product). The effluent
product was tested for scale formation according to the procedure
described above, and no scale or precipitate was detected.
Example #3--Removal of Scale in Treatment of Produced Water
[0097] The treatment process of the present disclosure was applied
to seawater that had been adjusted to a high level of TDS and a
high degree of water hardness, in order to test the capacity of the
process to deal with such input solutions as produced water from
oil extraction operations or waste water from gas fracking
operations. The water was pretreated using the process of the
present disclosure before being purified in a water desalination
apparatus such as that described in U.S. Pat. No. 7,678,235. As
discussed in greater detail below, the seawater subjected to the
pretreatment process of the present disclosure showed no formation
of scale when used as feed water in the water purification
apparatus.
[0098] The following amounts of various compounds were added to
fresh ocean water to produce the input aqueous solution of the
present example: 7 grams/liter of Ca(OH).sub.2 were added to
produce a target Ca.sup.t' concentration of 7.1 kppm, and 29
grams/liter of NaCl were also added. The TDS of the resulting water
sample was 66 kppm.
[0099] A first precipitation was conducted at room temperature by
adding approximately 5 grams/liter of NaOH as necessary to increase
the pH of the solution to greater than 10.5. A milky precipitate
containing mainly magnesium hydroxide was precipitated in this
first room temperature procedure. The water was filtered to remove
the solid precipitates.
[0100] A second precipitation was then conducted by adding sodium
bicarbonate and sufficient caustic to adjust the pH to 9.8, and a
second precipitate containing mainly calcium and other carbonates
was obtained. The TDS of the descaled and filtered water was
approximately 65 kppm.
[0101] The descaled water was used as an influent for a water
purification apparatus in accordance with U.S. Pat. No. 7,678,235.
The product water was collected from the apparatus, and the TDS of
the product water was measured. While the inlet water had a TDS of
65 kppm, the product water of the water purification apparatus was
less than 10 ppm. No appreciable development of scale was observed
in the boiler of the apparatus.
Example #4--Desalination of Ocean Water
[0102] Fifty gallons of ocean water were first pre-treated
according to the procedures described earlier and fed into a pilot
desalinator designed for a 50-200 GPD throughput. The product water
had a TDS of less than 10 ppm, and no signs of scale formation were
detected in any of the boilers.
Example #5--Desalination of Produced Water
[0103] Fifty gallons of a synthetic produced water containing in
excess of 146,000 ppm of TDS and significant alkalinity were first
pre-treated according to the procedures described earlier and fed
into a pilot desalinator designed for a 50-200 GPD throughput. The
product water had a TDS of less than 40 ppm, and no signs of scale
formation were detected in any of the boilers.
Example #6--Desalination of Brackish Water
[0104] Fifty gallons of brackish water containing in excess of
3,870 ppm of TDS were first pre-treated according to the procedures
described earlier and fed into a pilot desalinator designed for a
50-200 GPD throughput. The product water had a TDS of less than 10
ppm, and no signs of scale formation were detected in any of the
boilers.
* * * * *
References