Desalination apparatus

Desalination apparatus utilizing solar heating of metal member(s) such as balls, rollers, or metal endless belt(s) in a heating chamber and vaporizing saline water with the latent heat in said metal member(s) by spraying saline water thereon in a vaporizing chamber, a water-cooled condenser to condense the vapors, a trough to collect the condensate, a rinse tank to remove salt deposits and/or saline water from the metal member(s), and means for returning the rinsed metal member(s) for solar reheating.

This invention pertains to improvements in the desalination of water, 
particularly sea water or other salt containing water which is 
non-potable. Such types of waters are readily available on the shores of 
seas or oceans, gulfs and backwaters thereof and to a lesser extent in 
arid areas of the world in inland lakes, seas and the like. 
The text "Principles of Desalination", edited by K. S. Spiegler, University 
of California Academic Press, 1966, sets forth various types of solar 
stills used to obtain potable or desalinated water from salt waters. Such 
solar stills include inflated plastic sheet solar distillers having 
insulated tanks under the inflated sheets. Condensate on the sheets runs 
into distillate troughs in concrete curbs along the periphery of the 
insulated tank. 
Another type of solar still is a multiple ledge, tilted still in which a 
tilted, shallow, glass-covered box has a stepped series of shallow, 
narrow, horizontal trays. Salt water is fed to the upper tray and 
overflows sequentially down the stepped trays. Distillate water condenses 
on the glass cover and is collected along the lower edge thereof. 
Still another type of solar distiller utilizes a rectangular tank with a 
transparent, gabled cover, through which solar radiation enters the tank 
and evaporates salt water in the tank. Condensate collected on the gabled 
cover runs down the cover into troughs or gutters beneath the lower edges 
of the gabled cover. 
The subject invention utilizes a different approach by employment of solar 
heat-absorbing metal member(s) such as balls, rollers or a metal endless 
belt to initially absorb solar heat in a heating chamber. The metal 
member(s) pass beneath a transparent cover and become heated through 
absorption of the solar radiation passing through the cover. These metal 
member(s) with their latent heat then pass directly into a vaporizing 
chamber where they are sprayed with sea water or other salt or saline 
water. The latent heat therein causes essentially salt-free water to 
vaporize. The vapors are condensed by a condenser system such as condenser 
tubes through which pass cooler raw sea water or other readily available 
fresh and/or saline water. The condensed vapors are collected -- thereby 
providing substantially pure water. 
After the metal member(s) pass through the vaporizing chamber they are 
encrusted with the salts of the sea water or other saline water or coated 
with relatively high concentrations of aqueous solutions of such salts 
sprayed thereon and may exit from the vaporizing chamber either wet or 
dry. 
Accordingly, the metal member(s) are immediately rinsed in a rinse tank 
which preferably is supplied with warm rinse water coming from the 
condenser tubing. After such rinsing, the rinsed portions of the metal 
member(s) return to the heating chamber for solar reheating and a 
repetition of the vaporizing and rinsing functions. 
In the case of balls or rollers, the latter are lifted by a lift conveyor 
out of the warm rinse water and pass by gravity down an inclined track or 
chute from the rinse tank to the vicinity of the head or entry of the 
heating chamber. At this point they are again lifted and fed into the 
solar heating chamber. 
If desired, the vaporizing chamber is operated under vacuum. For example, 
at 15 in. Hg absolute, the equilibrium vapor pressure of water at sea 
level is 176.degree. F., vs. its normal boiling point of 212.degree. F.

Referring to the drawings, the embodiment of FIGS. 1-3 utilizes metal balls 
as the aforesaid metal member(s). It will be appreciated, however, that 
cylindrical rollers may be used in lieu of the balls as long as the 
apparatus is designed to keep the rollers oriented so that they will roll 
down the inclined surfaces of the parts hereinafter described. 
Referring first to FIGS. 1 and 3, the solar desalinator 10 comprises a 
solar heating chamber 11 and a vaporizing chamber 12. The heating chamber 
11 is made up of a rectangular in its upper side, the glass of which 
preferably is of one of the special types hereinafter described. The 
function of the glass cover is to transmit most efficiently the solar rays 
to the metal balls or rollers beneath the glass and to retain in said 
balls or rollers the absorbed solar heat. 
Optionally, the glass cover 13 may have around its periphery opaque or 
transparent sides, e.g., the inclined sides 14, whereby said sides and 
glass cover form a receptacle for collecting rain water. This rain water 
is of a substantially pure and/or potable nature and serves as a 
supplement to the output of desalinated water of the solar desalinator. 
The metal balls 16 (or cylindrical rollers) are made of a metal having high 
heat conductivity. The most preferred metal from an economic viewpoints is 
auminum. These aluminum balls 16 (or rollers) are anodized black or other 
dark color to enhance their absorption of the solar radiation. 
The metal balls 16 (or rollers) roll along a metal sheet 17 beneath the 
glass cover 13. The sheet 17 preferably has a slight, longitudinal 
downward pitch or slope in the direction of the movement of the metal 
balls to enhance their slow travel through the heating chamber 11 and 
vaporizing chamber 12. Preferably the upper surface of the sheet 17 has 
longitudinal grooves or tracks 18 to provide longitudinally parallel paths 
along the sheet 17 for the metal balls. 
The metal balls (or rollers) are fed to the heating chamber 11 at the 
entrant end 19, move slowly beneath the glass cover 13 and become heated 
by absorption of the solar radiation. The heated balls (or rollers) then 
pass directly into the vaporizing chamber 12. This chamber has a pipe 20 
for feeding sea water or other saline water to the vaporizing chamber 12. 
At the T-coupling 21, the feed water branches into pipes 22 and 25. The 
pipe 22 has a series of spray nozzles 23 and is coupled at its downstream 
end to a Y-coupling 24. The pipe 25 is connected to a jacket 26 for 
condensing vapors, the feed water keeping the jacket cool for condensation 
thereon. The jacket 26 may comprise a shell 27 containing internal 
baffling or tubing 28 over or through which the cooling water flows inside 
the jacket. Alternatively, the condenser may simply be a series of 
convoluted or parallel tubes without an external jacket. 
The downstream end of the jacket 26 is connected by pipes 29 and 30 and 
their intermediary elbow 31 with the Y-coupling 24. In passing through the 
jacket 26 and the pipe 22, the sea water or other salty or saline water is 
warmed by heat exchange occurring within the vaporizing chamber 12. This 
warmed water is fed by pipe 32 to a rinse tank 33, described below. 
When the sea water or the like is sprayed from nozzles 23 onto the heated 
balls (or rollers) passing through the vaporizng chamber 12, all or a 
substantial portion of the sprayed water is vaporized. The vapors rise as 
indicated by the arrows in FIG. 1 into the upper portion of the vaporizing 
chamber. Here the vapors are condensed in the cooler shelf 27 and the 
condensate drops into a condensate-collecting trough 34 beneath the jacket 
26. The condensate trough has a slight pitch so that the substantially 
pure condensate water 34 flows by gravity out of the vaporizing chamber 
12. 
Where the heating chamber 11 embodies a rain-water collecting receptacle 
15, a tap pipe 36 may be used to convey the collected rain water from the 
pipe's lower end 37 adjacent the glass cover 13 to its discharge end 38 at 
the head end of the condensate-collecting trough 34. A mechanical or water 
pmp (not shown) may be provided on or in the tap pipe 36. 
The upper portion of the vaporizng chamber is an enclosed housing 39 which 
is sealed against loss of vapor contained within the housing. The lower 
end of the housing 39 may be open, as illustrated, or it may have 
depending walls, gaskets, etc. to prevent escape of vapors substantially 
in the manner described below with reference to FIG. 4. The 
condensatecollecting trough 34 has a width less than the width of the 
housing 39 so that vapors can pass upwardly around the trough into the 
upper portion of the housing 39. 
The discharge end 40 of the ball-conveying plate 17 has a downward pitch or 
curvature above the rinse tank 33. The balls (or rollers) fall into the 
warm sea, salt or saline water 41 in the rinse tank, the water level being 
maintained constant at the level of the overflow pipe 42, from which the 
discharge water is returned to the sea, ocean, lake, etc. 
The balls 16 (or rollers) have, after passing through the vaporizing 
chamber 12, solid salt deposits or concentrated salt solutions on their 
surfaces. The salt deposits and/or concentrated salt solutions are rinsed 
off in the warm water 41 in the tank 33. The balls 16 (or rollers) are 
then conveyed by a lift 43 from the bottom of the tank for return to the 
heating chamber 11. The lift 43 and another lift 55, the function of which 
is later described, have the construction illustrated in FIG. 2. These 
lifts comprise an upper roller or pulley 44 and a lower roller or pulley 
45, one of which is driven. An endless belt or series of side-by-side 
belts 46 is positioned about and driven by the rollers or pulleys 44,45, 
which rotate in the direction of the arrows shown in FIG. 1. A series of 
longitudinally elongated lifts 47 are mounted on the belt(s) 46. Each lift 
comprises an elongated bar 48 connected at one edge to the belt(s) 46 and 
bearing an elongated lip 49 at the other edge. Each bar and lip forms an 
elongated seat 50 for conveyance of the balls 16 (or rollers). 
As shown in FIG. 1, the rinse tank 33 has a bottom wall 51 which is 
downwardly pitched in the direction toward the lift 43 extending along one 
edge of the rinse tank. As the ball lift operates within the tank, the 
rinsed balls 16 (or rollers) are picked up at the bottom of the tank 33 
and lifted upwardly in the seats 50. 
At the upper side of the roller or pulley 44, the balls (or rollers) fall 
out of the seats 50, e.g., the balls 16'. A resilient blade 52 (FIG. 2) 
projects into the path of the lifts 47. The balls 16 are pushed by the 
free edge of the blade 52 off the back side of the lifts onto the sheet 17 
or 53 when the following lift 47 strikes the blade 52. 
The ball return from the lift 43 of the rinse tank 33 to the head or 
entrant end 19 if the solar heating chamber 11 comprises a sloping or 
pitched ball (or roller) return sheet 53. The sheet 53 slopes downwardly 
from the rinse tank and its lift to a collector well 54. The balls 16 (or 
rollers) accumulated in the well are picked up by the lifts 47 of the lift 
55, the structure of which is illustrated in FIG. 2. The balls or rollers 
are then lifted and discharged onto the sheet 17 at its entrant end 19 for 
another cycle as aforedescribed. 
If desired, the vaporizing chamber 12 may be operated under partial vacuum. 
For this purpose, a vacuum tap 57 is provided in the top wall of the 
housing 39. A partial vacuum has the advantage of lowering the vaporizing 
temperature of the water sprayed onto the heated balls (or rollers) in the 
vaporizing chamber. 
Another embodiment of desalination apparatus 10' is illustrated in FIG. 4. 
In many respects this embodiment is like the embodiment of FIGS. 1-3. 
Here, however, the metal member, which is solar heated, is an endless 
metal band or belt. Referring to FIG. 4, the solar desalinator 61 
comprises an insulated heating chamber 62 having a glass cover 63. An 
endless belt 64 (or a series of side-by-side endless belts) is made of 
flexible, heat conducting metal. Again aluminum is particularly suitable, 
particularly thin-rolled aluminum which is anoidzed black or other dark, 
heat-absorptive color. 
The endless belt(s) 64 enters the solar heating chamber 62 through a 
horizontal slit 65. In passing through the heating chamber, it absorbs 
solar radiation and becomes heated. Preferably, the slit has a rubber seal 
or wiper 66 extending along its length. The endless belt(s) exits from the 
heating chamber 62 through another horizontal slit 67 also having a rubber 
seal or wiper 68. 
The heated belt(s) immediately enter the vaporizing chamber 70. This 
chamber comprises a six-sided enclosure 71, the heated belt(s) entering 
the chamber 70 through the horizontal slot 72 with a wiper or seal as 
aforesaid. The belt(s) exits from the opposite side of the enclosure 71 
through a similar horizontal slit 73 with a rubber wiper or seal as 
aforesaid. 
Sea water or other salty or saline water is fed to the horizontal pipe 74 
bearing axially spaced spray nozzles 75. The water is sprayed into the 
heated belt(s), causing the water to vaporize in the enclosure 71. 
The sea, salty or saline water is supplied through the feed pipe 76. This 
water is relatively cool, e.g., at ambient temperature, and first flows 
through the condenser jacket and/or tubing 77, exiting from the opposite 
end via the pipe 78. At this stage, the water has a rise in temperature. A 
pump 79 may be provided at any point, e.g., at a point immediately before 
the pressure relief valve 80, which also serves as the tap off coupling 
for the pipes 74 and 81. 
The pipe 81 extends downwardly from the pressure relief valve toward the 
belt(s) rinse tank 83. Its discharge end 82 may be in the form of a spray 
nozzle which directs spray directly against the belt(s) above the level of 
the rinse water 84 in the tank 83 to aid in loosening salt deposits which 
may have formed in the belt(s) in the vaporizing chamber 70. 
The belt(s) is immersed in the rinse water 84, which is heated or warmed 
sea, salt or saline water, the level of which is maintained constant by 
the overflow pipe 85, from which the water is returned to its original 
source. 
The belt(s) 64 travels over three drums or rollers 86, 87 and 88, one of 
which is driven. If the belt(s) exits from the rinse tank 63 below the 
level of the rinse water 84, this is conveniently done through a 
horizontal slit in the side wall of the tank 83, which slit is maintained 
relatively watertight by the rubber seal 89. The latter also serves as a 
wiper to remove all or most of the rinse water from the exiting belt(s). 
As in the embodiment of FIGS. 1-3, the vaporizing chamber has a 
condensate-collector pan or trough 90 below the condenser 77 to collect 
condensed, essentially salt-free condensate formed on the cooled surfaces 
of the condenser. This water is withdrawn through the tap off pipe 91. The 
enclosure 71 may be operated under partial vacuum, e.g., by providing a 
vacuum pump 92 and appropriate piping on the upper wall of the enclosure 
71. 
The glass covers 13 and 63 preferably are made of special glass which 
maximizes transmission of both direct and diffuse sunlight and the heating 
of the metal member(s) therebeneath. An exemplary, suitable glass is 
"solarpane" glass marketed by Pittsburgh Plate Glass. Another type of 
special glass with lenses is described below. 
In FIG. 5, a solar mirror system is illustrated diagramatically, which 
system is useful in maximizing transmission of solar radiation to the 
heating chamber 11 throughout the sunlight hours. A pivotable parabolic 
mirror 95 is pivoted to follow the path of the sun from 1 or 2 hours after 
dawn to 1 or 2 hours before dusk. The reflected rays from the mirror 95 
are reflected by the planar mirror 96, which in turn is movable and/or 
pivotable to maintain its proper orientation with the pivotable parabolic 
mirror. 
The mirror 96 is maintained at the approximate focus point of the mirror 95 
and reflects the solar rays laterally to a spherical or cylindrical 
convexo-concave stationary mirror 97. The latter is positioned directly 
above the solar heating chamber 11 or 11' and reflects the solar rays 
downwardly over substantially the whole light transmitting portion of the 
heating chamber 11 or 11'. Such mirror arrangement allows the subject 
solar desalination apparati to be used during most of the daylight hours. 
FIGS. 6 and 7 constitute a top plan view and a side elevation of a segment 
of the heating chamber 11 or 11'. The glass cover 13,63 is composed of 
rows of lenses 101, such rows being directly above and aligned with the 
tracks or grooves 18 in the sheet 17. These lenses focus the solar rays at 
approximately the upper most level 102 of the balls 16 (or at the plane of 
the endless metal belt 64 in the heating chamber 11'), this maximizing the 
concentration of solar heat in a manner similar to the focusing of a 
magnifying glass upon combustible material to ignite same. In a case of 
the heating of metal balls, the respective lenses 101 maximizes the 
application of solar radiation by positioning of their focal point 
directly above the tracks or grooves 18 whereby the solar radiation is 
applied along the rolling diameters of the respective balls as they pass 
through the heating chamber. 
It is believed that the advantages and objectives of the invention will be 
appreciated from the foregoing description of the generic invention and 
its preferred embodiments. Other embodiments of the generic invention may 
be realized without departing from the scope of the invention described 
aforesaid and set forth in the dependent claims.