Year: 1888

page_text: I, LOUIS GUSTAVE GHILAIN DAUDENART of 43 Avenue de la Liberté Brussels in
the Kingdom of Belgium Lieutenant General (retired) do hereby declare the nature
of this invention to be as follows:-
The new method of extracting magnesia from sea water comprises the following
operations;
A Treatment of sea water by hydrated lime.
B Separation of the hydrated magnesia from sea water, in which it is held in
suspension.
C. Carbonation of the hydrated magnesia; filtration in a filter press, and drying.
These various operations will.now be described in succession.
A Treatment of sea water with hydrated lime.
Magnesia is formed in sea water partly in the state of Chloride of magnesium, and
partly in that of sulphate of magnesia. In order to extract it from the sea water, the
latter is treated by a lime milk prepared with a lime which is pure and free from clots,
care being taken that there is a slight excess of lime. Chloride of calcium and
sulphate of lime are formed which, finding in the liquid a quanity of water sufficient'
to dissolve them, leave the hydrated magnesia in suspension in the sea water, in which
it is scarcely soluble. This operation presents no difficulty whatever ; it requires no
special apparatus; those already in use in the chemical trade will answer the purpose
very well. It is only necessary to leave time for the lime to dissolve so that it may
react on the salts of magnesia. The operation is over when a small portion of the
liquid filtered, and treated by a drop of an aqueous solution of ammonia, gives no
longer any precipitate.
B. Separation of hydrated magnesia from the water wherein it is held in
suspension.
The whole difficulty of the process of extracting magnesia from sea water lies in
this separation. It could not hitherto be effected by the usual means at the disposal
of chemical manufacturers. In fact, this would have required immense deposit basins,
ΓΙ

page_text: as the magnesia forms a five hundredth part of the liquid wherein it is, held in
suspension, and a 24 hours exposure would be required to reduce its volume to the
eighth of its vehicle.
It is also extremely difficult to effect, under these conditions, the separation of the
clear portion, which is above the settled magnesia and to filter the latter as it forms
a sort of gelatinous substance, which soon renders the filters worthless by stopping the
pores of the filtering material.
The invention admits of this separation being effected by means of a special apparatus.
In the drawings,
Fig. 1 is a longitudinal section of the simple apparatus for the separation of hydrated
magnesia from sea water.
Fig. 2. a plan of Fig. 1.
Fig. 3. a cross section.
Fig. 4. a longitudinal section of the compound àpparatus for the separation of
hydrated magnesia from sea water.
Fig. 5. a plan of Fig. 4.
Fig. 6 a cross section.
*
The apparatus in its simplest form, consists essentially of deposit reservoir c (Fig. 1)
of rectangular form bounded in the direction of its length by two vertical
mètre
walls 1,50 to 2 mètres high inside the reservoir. These two walls are united at their
lower ends by a stonework flooring consisting of two planes equally inclined on the
horizon, and intersecting each other in the centre of the tank. The horizontal line
forming the intersection of the two planes, constituting the bottom surface of the
reservoir, is four mètres below the top of the latter. The reservoir is bounded at each
end, and in the direction of the width by two wells a and b, the first of which will be
called hereinafter inlet well, and the other outlet well for the sea water. The length
of these two wells is equal to the width of the reservoir. The bottom of the inlet well
is. 50 centimètres below that of the reservoir, its internal width is 40 centimètres, and
is limited by the two longitudinal walls of the well, one of which, the outward one, is
mètre.
L
the end wall of the reservoir and the other, the internal one, is 2., 50 less in height
than the first, so that the sea water rising in the well flows, over this internal wall into
the reservoir. The outlet well is similar to the inlet one, save that its width is not
uniform, it is 1 mètre at the top and 50 centimètres at the bottom. The water
containing magnesia is introduced into the inlet well by means of one or several cast
iron tubes 32 centimètres in diameter, reaching the bottom of the well, where they
terminate in a cross pipe occupying the whole length of the well. This cross pipe is
provided with holes, centimetres in diameter, through which the water containing
magnesia issues; this water, rises in the well, and afterwards overflows into the
reservoir. The outlet well is provided with similar tubes arranged in a like manner;
the clear sea water, flows into the outlet well, enters through the holes of the cross
pipe e at the bottom of this well, and rises into the vertical tubes, which discharge it
outside.
The magnesia contained in the sea water settles in the reservoir c.
"The reason why and the manner in which this deposit takes place will now be
explained. The extraction of magnesia being still taken as example. One cubic
metre of sea water, contains 1900 grammes of magnesia (it is supposed anhydrous).
In order to extract 8000 kilogrammes, of magnesia. from sea water in 24 hours, the
latter should therefore be supplied at the rate of 0 litres per second. The velocity
of the sea water in the tube, 32 centimètres in diameter, feeding the inlet well,
would be only 60 centimètres per second. It is clear that at such a velocity, no
deposit whatever could take place at the bottom of this well. But if the internal
length of this well is made equal to 20 mètres, the width being 40 centimètres, the
velocity of the sea water rising in the well, will decrease rapidly, and become equal
only to 6 millimètres per second. This velocity will be still further reduced in the
deposit reservoir, for if the water is only allowed to flow outside through the outlet

page_text: 20 x 1 x = 0,050 hence v = 0,0025 that is 2 millimetres.
Thus if the internal length of the reservoir is equal to 30 mètres, a molecule of water
will require 3 hours and 20 minutes to move over this distance. In practice such a
velocity is equivalent to absolute rest and it is then understood that it will suffice that
the length of the apparatus permits the substance in suspension to sink one mètre in
the liquid during that time, so that the outlet well shall allow only clear water to flow
outside.
There remains now to remove the magnesia from the deposit reservoir.
For this purpose an archimedian helical conveyor is used, having square threads.
The external diameter is 40 centimètres and that of the shaft 5 centimètres. The
centre line of the conveyor is 20 centimètre. above the intersection line of the two
inclined planes forming the bottom of the reservoir. The conveyor is imbedded in
the said bottom and rests on one side on the internal wall of the outlet well; on the
other it passes through the inlet well a and the cavity h outside which its projecting
end is provided with a spur wheel g by means of which the necessary rotary motion
is imparted. to the conveyor. The conveyor is on its whole length encased in tubes,
the diameter of which is slightly greater than that of the external helix. Now if a
rotary motion be imparted to the conveyor the velocity of which depends upon the
quantity of magnesia it is desired to obtain and is of course always very low, the
magnesia which has found its way into the space between the helical surface, is
discharged into the cavity h whence it can be removed as it comes in. It will be
understood that since there exists necessarily a relation between the motion of the
pumps, the inlet and outlet velocities of the sea water and that of the helical
conveyor, it is easy to render the apparatus independent of the intervention of manual
labour.
As a rule the apparatus described in the foregoing, or as it is called the simple
separating apparatus, suffices for the purpose but sometimes more time is required for
the substance to settle down and assume a certain consistency. In this case the
application of the simple apparatus would necessitate the use of a helical conveyor of
inconvenient length. In order to remedy this disadvantage and also avoid the use of
a great number of simple apparatus having each an inlet and an outlet well, the
compound apparatus shown in Fig. 4, 5, and 6 has been designed.
This apparatus consists of a series of identical reservoirs provided each with a
helical conveyor of suitable and constant length. Only one inlet well and one outlet
well are used in connection with these reservoirs. Under these conditions there is no
substance however slow it might be in settling which could not be managed
economically with this compound apparatus. For it is sufficient to multiply the
reservoirs which being formed in the ground are not very expensive; the cost of the
screw conveyors is moderate owing to the uniformity of their dimensions.
The following description of the figures 4, 5, 6, of the drawings will render the
working of the aforesaid apparatus perfectly clear.
a is the inlet well for the sea water containing hydrated magnesia in suspension :
b outlet well for the exit of the sea water from which the magnesia has been removed:
c reservoirs over which the sea water moves slowly and wherein the hydrated magnesi
is deposited d tube feeding the inlet well with sea water it is bent so as to occupy the
bottom of the well; this portion of the tube is provided with holes through which the
sea water issues; e tube through which the sea water freed from magnesia, leaves
the outlet well. The part of this tube at the bottom of the well is also provided with

page_text: holes, through which the water flows into this tube; f screw conveyor with square
threads, the motion of which removes slowly the hydrated magnesia which has settled
in the reservoirs and, which the inclined planes forming their bottom have caused to
accumulate between the threads; g spur wheels imparting simultaneously, a rotary
motion to all the conveyors of the apparatus; iron boxes into which the motion of
the conveyors discharge the hydrated magnesia expelled from the reservoirs; i tubes
through which the magnesia accumulated in the boxes leave the apparatus ; ; pillars
supporting the boarding covering the apparatus; k wood and fir boarding, the surface
of which is on a level with the ground..
It must be distinctly understood that the apparatus hereinbefore described could
eventually be constructed in other appropriate forms or of other dimensions arranged
in a manner different to that shewn on the drawing without altering the nature of the
invention and the working of the process in any way whatever.
C. Carbonating, filter pressing and drying the hydrated magnesia. On leaving the
separating apparatus, the hydrated magnesia contains still a large quantity of water
which could be expelled by the filter press only with difficulty. This water is removed
by a preliminary carbonating of the magnesia by means of the carbonic acid contained
in the combustion gases issuing from the furnaces of the works. In the form of
carbonate, the magnesia has lost the viscosity which rendered the filtration difficult.
As for the carbonation itself it is produced by means of the well known .industrial
apparatus.
Dated this 20th day of Anril 1800

page_text: The new method of extracting magnesia from sea water comprises the following
operations :
A. Treatment of sea water by hydrated lime.
B. Separation of the hydrated magnesia from sea water, in which it is held in
suspension.
C. Carbonation of the hydrated magnesia filtration in a filter press and drying.
These various operations will now he described in succession.
A. Treatment of sea water with hydrated lime.
Magnesia is found in sea water partly in the state of chloride of magnesium, and
partly in that of sulphate of magnesia. In order to extract it from the sea water, the
latter is treated by a lime milk prepared with a lime which is pure and free from clots,
care being taken that there is a slight excess of lime. Chloride of calcium and
sulphate of lime are formed, which, finding in the liquid a quantity of water sufficient
to dissolve them, leave the hydrated magnesia in suspension in the sea water in which
it is scarcely soluble. This operation presents no difficulty whatever, it requires no
special apparatus; those already in use in the chemical trade will answer the purpose
very well. It is only necessary to leave time for the lime to dissolve so that it may
react on the salts of magnesia. The operation is over when a small portion of the
liquid filtered and treated by a drop of an aqueous solution of ammonia, gives no
longer any precipitate.
B. Separation of hydrated magnesia from the water wherein it is held in
suspension.
The whole difficulty of the process of extracting magnesia from sea water lies in
this separation. It could not hitherto be effected by the usual means at the disposal
of chemical manufacturers. In fact, this would have required immense deposit basins,
as the magnesia forms a five hundredth part of the liquid wherein it is held in
suspension, and a 24 hours' exposure would be required to reduce its volume to the
eighth of its vehicle. It is also extremely difficult to effect, under these conditions,
the separation of the clear portion which is above the settled magnesia, and to filter
the latter as it forms a sort of gelatinous substance, which soon renders the filters
worthless by stopping the pores of the filtering material.
The invention admits of this separation being effected by means of a special
apparatus.
In the drawings filed with the provisional specification.
Figure 1 is a longitudinal section of the simple apparatus for the separation of
hydrated magnesia from sea water.
Figure 2 a plan of Figure 1.

page_text: Figure 3 a cross section.
Figure 4 a longitudinal section of the compound apparatus for the separation of
hydrated magnesia from sea water.
Figure 5 a plan of Figure 4.
Figure 6 a cross section.
The apparatus in its simplest form, consists essentially of a deposit reservoir c
(Figure 1) of rectangular form, bounded in the direction of its length by two vertical
walls, 1 mètre 50, to 2 mètres high inside the reservoir. These two walls are united
at their lower ends by a stonework flooring, consisting of two planes equally inclined
on the horizon, and intersecting each other in the centre of the tank. The horizontal
line forming the intersection of the two planes, constituting the bottom surface of the
reservoir, is 4 mètres below the top of the latter. The reservoir is bounded at each
end, and in the direction of the width by two wells a and b, the first of which will be
called hereinafter inlet well, and the other outlet well for the sea water. The length
of these two wells is equal to the width of the reservoir. The bottom of the inlet well
is 50 centimètres below that of the reservoir, its internal width is 40 centimètres, and
is limited by the two longitudinal walls of the well, one of which, the outward one,
is the end wall of the reservoir, and the other, the internal one, is 2 mètres 50 less in
height than the first, so that the sea water rising in the well flows over this internal
wall into the reservoir. The outlet well is similar to the inlet one, save that its width
is not uniform, it is I mètre at the top and 50 centimètres at the bottom. The water
containing magnesia is introduced into the inlet well by means of one or several cast
iron tubes, 32 centimètres in diameter, reaching the bottom of the well, where they
terminate in a cross pipe occupying the whole length of the well: This cross pipe is
provided with holes, centimètres in diameter, through which the water containing
magnesia issues, this water rises in the well, and afterwards overflows into the
reservoir. The outlet well is provided with similar tubes arranged in a like manner,
the clear sea water flows into the outlet well, enters through the holes of the cross
pipe e at the bottom of this well, and rises into the vertical tubes, which discharge it
outside.
The magnesia contained in the sea water settles in the reservoir c. The reason why
and the manner in which this deposit takes place, will now be explained. . One cubic
mètre of sea water contains 1900 grammes of magnesia (it is supposed anhydrous).
In order to extract 8000 kilogrammes of magnesia from sea water in 24 hours, the
latter should therefore be supplied at the rate of 50 litres per second. The velocity of
the sea water in the tube, 32 centimètres in diameter, feeding the inlet well, would be
only 60 centimètres per second. It is clear that at such a velocity, no deposit whatever
could take place at the bottom of this well. But if the internal length of this well is
made equal to 20 mètres, the width being 40 centimètres, the velocity of the sea
water rising in the well will decrease rapidly, and become equal only to 64 millimètres per
second. This velocity will be still further reduced in the deposit reservoir, for if the
water is only allowed to flow outside through the outlet well, when the level of the
sea water in the reservoir is one mètre above the internal walls of the wells, this level
will keep constant, if, during the flow of the liquid, the work of the pumps at the inlet
and outlet ends of the apparatus is so calculated as to supply and remove respectively,
a constant volume of 50 litres per second. Under these conditions the velocity of
translation in the reservoir is given by the following equation:
cubic mètre
20 x 1 x = 0,050 hence v
-
mètre
0,0025 that is 24 millimétres.
Thus, if the internal length of the reservoir is equal to 30 mètres, a molecule of water
will require 3 hours and 20 minutes to move over this distance. In practice such a
velocity is equivalent to absolute rest and it is then understood that it will suffice that
the length of the apparatus permits the substance in suspension to sink one mètre in
the liquid during that time, so that the outlet well shall allow only clear water fo
flow outside.

page_text: There remains now to remove the magnesia from the deposit reservoir.
For this purpose an archimedian helical conveyor is used, having square threads.
The external diameter is 40 centimètres and that of the shaft 5 centimètres. The
centre line of the conveyor is 20 centimètres above the intersection line of the two
inclined planes forming the bottom of the reservoir. The conveyor is embedded in
the said bottom and rests on one side on the internal wall of the outlet well; on the
other side it passes through the inlet well a and the cavity outside which its
projecting end is provided with a spur wheel g, by means of which the necessary
rotary motion is imparted to the conveyor. The conveyor is on its whole length
encased in tubes, the diameter of which is slightly greater than that of the external
helix. Now if a rotary motion be imparted to the conveyor, the velocity of which
depends upon the quantity of magnesia it is desired to obtain and is of course always
very low, the magnesia which has found its way into the space between the helical
surface, is discharged into the cavity h, whence it can be removed as it comes in. It
will be understood that since there exists necessarily a relation between the motion of
the pumps, the inlet and outlet velocities of the sea water and that of the helical
conveyor, it is easy to render the apparatus independent of the intervention of manual
labour.
As a rule the apparatus described in the foregoing, or as it is called the simple
separating apparatus, suffices for the purpose but sometimes more time is required for
the substance to settle down and assume a certain consistency. In this case the
application of the simple apparatus would necessitate the use of a helical conveyor of
inconvenient length. In order to remedy this disadvantage and also avoid the use of
a great number of simple apparatus having each an inlet and an outlet well, the
compound, apparatus shown in Figures 4, 5, and 6 has been designed.
This apparatus consists of a series of identical reservoirs provided each with a helical
conveyor of suitable and constant length. Only one inlet well and one outlet well
are used in connection with these reservoirs. Under these conditions there is no
substance, however slow it might be in settling, which could not be managed
economically with this compound apparatus. For it is sufficient to multiply the
reservoirs which, being formed in the ground, are not very expensive, the cost of
the screw conveyors is moderate, owing to the uniformity of their dimensions.
The following description of the Figures 4, 5, 6, of the drawings will render the
working of the aforesaid apparatus perfectly clear.
a is the inlet well for the sea water containing hydrated magnesia in suspension,
outlet well for the exit of the sea water from which the magnesia has been removed,
c reservoirs over which the sea water moves slowly, and wherein the hydrated magnesia
is deposited, d tube feeding the inlet well with sea water, it is bent so as to occupy
the bottom of the well; this portion of the tube is provided with holes through which
the sea water issues; e tube through which the sea water freed from magnesia, leaves
the outlet well. The part of this tube at the bottom of the well is also provided with
holes through which the water flows into this tube; screw conveyor with square
threads, the motion of which removes slowly the hydrated magnesia which has settled
in the reservoirs, and which the inclined planes forming their bottom, have caused to
accumulate between the threads; g spur wheels imparting simultaneously a rotary
motion to all the conveyors of the apparatus; h iron boxes into which the motion of
the conveyors discharges the hydrated magnesia expelled from the reservoirs ; i tubes
through which the magnesia accumulated in the boxes, leaves the apparatus;
y pillars supporting the boarding covering the apparatus; k wood and fir boarding
the surface of which is on a level with the ground.
It must be distinctly understoood that the apparatus hereinbefore described could
eventually be constructed in other appropriate forms, or of other dimensions, arranged
in a manner different to that shewn on the drawing without altering the nature of
the invention and the working of the process in any way whatever.
C. Carbonating filter pressing and drying the hydrated magnesia. On leaving the
separating apparatus, the hydrated magnesia contains still a large quantity of water
which could be expelled by the filter press only with difficulty. This water is

page_text: removed by a preliminary carbonating of the magnesia, by means of the carbonic acid
contained in the combustion gases issuing from the furnaces of the works. In the
form of carbonate, the magnesia has lost the viscosity which rendered the filtration
difficult. As for the carbonation itself it is produced by means of the well known
industrial apparatus.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
1. The industrial use of hydrated lime for the purpose of precipitating the magnesia
contained in sea water; substantially as described.
2. The simple or the compound apparatus substantially as described in the foregoing
specification, for effecting the separation of magnesium compounds held in suspension
in water.
3. The use of carbonic acid for the purpose of destroying the viscosity, which, in
hydrated magnesia produced from sea water, prevents the proper filtration of the
liquid.
4. The process, apparatus, and mode of working, each taken as a whole, substantially
as described in the foregoing specification.