Improvements in and relating to the Treatment of Salt, and the Formation of Blooks thereof by Fusion.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to the Treatment of Salt, and the
Formation of Blooks thereof by Fusion.
1, REGINALD HADDAN, of the Firm of Herbert Haddan & Co. of
18 Buckingham Street, Strand, W.C., London, Patent Agent, do hereby declare
the nature of this invention a communication to me from abroad by La Compagnie
du Sel Agglomeré, of Paris, France, and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
The improvements in the treatment of salt representing the object of this
invention, essentially refer to the following operations.
The crushing, purifying, drying, fusion or melting, heating, condensing and
moulding of the salt to the coating of the blocks and to the appliances, apparatus
and processes in connection therewith.
Crushing. When the salt to be treated is in the form of crystals of a certain size,
like the salt of the salt marshes (sea salt works) or when a certain number of
crystals have become united and agglomerated by moisture, the crushing process is
useful to facilitate the subsequent fusion; the crushing is likewise useful where it
is desired to employ the surplus from the moulding for moulding again.
This crushing may be done in the ordinary manner by such crushing apparatus
as are in use in the industry and more especially by apparatus, the crushing or
pounding appliances of which are of a material adapted to avoid soiling the salt.
The crushing may likewise be effected by apparatus not belonging to the above
mentioned category, by adapting to them crushing or pounding devices of
unchangeable metal, mill-stone, materials consisting of or having for their basis
natural or agglomerated silex, emery, silixified conglomerates, fluor or magnesia,
terra-cotta, porcelain, glass, enamels or other analogous materials.
Purifying. The impurities contained in the salt have great influence upon the
regular progress of the manufacture as well as upon the colouring of the molten
Balt. If the salt is pure, there will be no colouring, but if it is impure, purifying
will be necessary in order to obtain white products, unless the blocks are intended
to be used for industrial or other purposes, where the colour makes no difference.
In this latter case, the salt may be melted with all or a part of its impurities, and
there may likewise be neglected any precautions intended to preserve the purity of
the salt, these precautions being indicated in the description of the crushing and
drying process.
The manipulations for purifying the salt depend on the nature and the amount of
the impurities or foreign matter therein.
If the salt is very impure, it will almost be necessary in every case to have
recourse to solution, decantation and evaporation by the known processes. For
salt of considerably impure quality one may have recourse, after crushing is done,
to washing in saturated water. For salt of little impure quality, sorting by hand
on an endless piece of cloth, or by using any other suitable sorting apparatus, will
in the most of cases fulfil the same purpose.
The impurities usually contained in the salt are of two kinds and are found
together or separately in variable proportions or quantities; the one kind
comprising earthy matters or mineral elements in general; the other organic
substances, vegetable remains, sea-weed, microscopic organisms, etc.

page_text: These impurities may besides the processes mentioned above, be eliminated during
the manufacture by the following means:-
1. If there is organic matter in question :
A. By passing the salt into the dryer which will be spoken of hereinafter and
which when applied, must be constructed of a material sufficiently refractory
to stand the temperature necessary for burning up organic substances.
B. By adding to the salt, either before or during the melting process, a small
quantity of a chemical body, such as for instance a nitrate, decomposing...
under heat and developing by this decomposition oxygen, to effect the
combustion of the organic matter.
2. If there are earthy matters in question. By the process of decanting in the
furnace, that is to say by allowing the molten salt, before the running off to settle
down, this process permitting the earthy substances, which are denser and heavier
than the salt, to become precipitated.
Drying. It is preferable, without however being indispensable, to dry the salt
before it is introduced into the melting apparatus.
:
This drying may be done in any dryer as used in the industry for pulverulent
substances, and in which the material to be dried is not in contact with bodies,
which may be liable to alter the purity of the salt. This drying may likewise be
done in drying apparatus not belonging to this category, by adapting to them
jackets, coatings or layers of material unattackable by salt, such as glass, enamel;
porcelain or analogous bodies, or also wood, provided that the required drying
temperature permits.
Fusion or melting. The form and size of the melting apparatus to be applied,
depend on the production desired, and the volume of the salt blocks to be moulded.
If small quantities are concerned movable crucibles may be used of unattackable
metal; refractory earth, or porcelain. This method of melting may be effected in
any system of furnace.
If there are greater quantities or blocks of greater dimension in question it will
be necessary to have recourse to special industrial furnaces, being for instance of
either of the following systems:
1. Furnace with crucibles fixed in it, either single or multiple (see Figs. 1 and 2
of the annexed drawings).
2. Furnaces with a fixed pan (Figs. 3 and 4).
3. Furnaces with movable pan (Figs. 5 and 6)..
It is however understood that the circular form applied to, the furnaces is not
absolutely necessary, and that in case it should be advantageous, any other suitable
form may be chosen, for instance the semi-cylindrical square or rectangular form,
while the flues for the inlet and ontlet of the gases are arranged in such a manner,
that the heat distributes itself equally well over all parts of the bottom of the
furnace.
One may likewise make the gases circulate in any direction and even conversely
to the direction indicated; for instance in Fig. 6 they may be passed so as to arrive
through one or more flues F arranged on the periphery of the furnace and they may
be carried out by passing them over the orifices of the outlet.
The introduction of the salt into the furnaces may be effected in, different ways,
by means of feed-hoppers G (Fig. 1) or by piercing the vault of the furnace with,
a large number of small orifices X (Figs. 3 and 4) through which the salt is passed
in form of a shower by hand feed or mechanically; or by a rotary apparatus H
provided with a number of arms or branches I of any suitable length and variable
inclination, this apparatus serving to throw the salt uniformly over the whole
surface of the furnace, two different constructions of this latter description being.
shown in Figs. 5 and 7.
In general it may be observed, that the fusion of the salt is effected the more
easily, the smaller the form in which it is introduced into the furnace J.
".
The method in which the running off is done, depends partially on the other

page_text: arrangements of the furnace, but as a general rule it is indispensable to keep the
running off orifices at a sufficiently high temperature.
To attain this the flames may first be passed over the orifices of the outfall K
then into the furnace J (Figs. 5 and 6) or they may be heated separately to the
required temperature (Figs. 3 and 4).
The running off may be done intermittently or continuously.
In the former case the orifices of the outfall L of the crucibles M (Figs. 1 and 2)
are opened or the movable pan N (Figs. 5 and 6) is set in rocking motion,
when the salt is molten. One may likewise make practical use of the quality
possessed by molten salt, namely that it becomes solidified on the least degree of
cooling.
For this purpose, if running off is to be stopped, the salt passing through the
hole of the outfall K is cooled down either by introducing any cold body or by
stopping the special heating. When on the other hand the running off is to be
recommenced, the salt, which obstructs the orifice is melted down by the aid of a
special heating for instance by a gas or blow pipe flame.
If the running off is to be continuous this is effected by means of an overflow
chute O (Figs. 3 and 4).
In every case it is preferable to regulate the rate of running off by passing the
salt through orifices, the dimensions of which are proportionate to the rapidity
wanted to be given to this operation and which rapidity depends on the dimensions
of blocks to be obtained.
If it should be necessary in furnaces of large output, the running off may be
effected simultaneously by several orifices K, either placed close beside each other
(Figs. 5 and 6) or arranged at different points of the furnace, so that the moulding
of a corresponding number of blocks is effected at the same time.
Heating. The heating of the different furnaces may be done by direct heat, as
shown in Fig. 1 by means of any kind of fire-grate P. But in this case if blocks of
pure salt are to be obtained use must be made of the following means:
1. To neutralize the colouring action of the particles of carbon drawn up by the
draught thus falling into the molten salt, the oxydizing process, as mentioned
hereinbefore, must be applied. To clear away the ashes generated by this process
of chemical combustion and those coming from the fire at same time with the carbon
particles, recourse is had to the process of decantation, by allowing the salt to settle
down before the running off as explained hereinbefore.
2. There may also be interposed between the flames of the fire-box and the salt
a refractory wall, which however is thin enough to let the necessary heat pass
through.
Heating may lastly also be done by means of lighting gas or that made by any
gas producer (Figs. 3, 4, 5 and 6), in this case the gas arrives through the
conduits R, ending at the hot gas chamber Y, and the air passing through the
conduits S, to end at the hot gas chamber Z; gas and air then unite to pass into
the furnace J and afterwards into the flues F, the regenerators Q and finally the
flues T. By this method of heating it is advisable to render the function of the
furnace more economical by the use of regenerators Q (Fig. 3) serving to heat
the air and gas. Heating by means of gas has the advantage of securing a better
regulation of temperature, this being an important condition in the melting process
of a substance.in which the points of melting or fusing and volatilizing are very
near to each other. Finally the use of purified gas has the advantage that it does
not soil the salt.
Condensing. It may happen on using any kind of furnace that owing to a
defective regulation of temperature, the volatilizing of the salt takes place to a
rather high degree, so that it may be of advantage to regain it. In this case use is
made of the condensing process, for which purpose condensing chambers are inter-
posed between the furnaces and the chimney, which chambers may be analogous to
those employed in the manufacture of protoxide of zinc, or lamp black, or any other

page_text: arrangement, by which condensation would be obtained by the contact of the salt
volatilized with the walls, or by which the condensation is effected by cooling the
walls or by passing cold water through tubes through the apparatus.
Material to be used. The furnace must be constructed of material that possesses
as high a resistance as possible to the action of the salt. This observation specially
regards that portion of the furnace which serves to hold the molten salt. For this
purpose it is necessary to use such materials as contain little or no uncombined
silica and at the same time being as impermeable as possible, such as refractory
bricks or sole plates of magnesian rock, bauxite, porcelain, glass, or analogous
materials.
Moulding. Moulding is effected in moulds U (Figs. 1, 3 and 5) of various forms
and dimensions, according to the blocks to be obtained.
These moulds may be made of a metal unsusceptible of attack by molten salt, as
for instance nickel, aluminium, cast iron, etc., or vitrified terra cotta, grit-stone,
porcelain, or analogous materials.
On using furnaces of small production, one or several moulds manipulated by
hand are sufficient, these moulds being placed alternately beneath the outflow holes.
On using furnaces of large production, it is advantageous to make the moulds move
mechanically, either by an arrangement of alternative movement or in a continuous
manner.
The moulds may be placed on rollers u running on a railway, and be moved by a
friction chain or they may also be arranged on a circular platform, the latter
receiving its movement by any suitable mechanism.
When the salt is run into the moulds, it is preferable to avoid too rapid cooling..
For this purpose the moulds may be actuated so as to circulate in a tunnel V, where
they cool down slowly. This tunnel may be placed tangentially or circularly onto
⚫ the furnace.
There may also be provided receiving chambers similar to those used in the
manufacture of glass.
Coating of the blocks. The salt blocks obtained by this process show a
superficial layer of several millimeters in thickness, of a very solid and hard
crystallization, forming a protective envelope, resisting moisture. In this condition
the blocks are capable of being transported to any distance without any packing
being applied.
It may however in certain cases be of advantage to increase the resistance of said
blocks for the purpose of preserving the blocks when to be piled up during a long
time in the open air or for any other reason.
In such cases, in order to obtain this result, the blocks may be coated with a thin
layer of varnish.
Any kind of substance insoluble in water or sufficiently difficult to dissolve as to
impart to the same a sufficient durability may be used for this purpose. But when
the salt blocks are destined for alimentary purposes, as in most cases, care must be
taken that no coating substance be used, that may be of noxious effect in any way,
and likewise uncoloured substances should be chosen, so that the special white
colour of the salt be not disturbed. The coating of the salt blocks may for instance
be done by applying a small layer of silicate such as silicate of potassium or liquid
soda. Or the blocks may also be dipped into molten paraffin.
This latter operation is preferably effected when the blocks have not yet
entirely cooled down, since, knowing that paraffin solidifies rapidly, the heat still
subsisting in the blocks, allows the latter to only become coated with a very slight
layer which is all that is required.
In the annexed drawings
Fig. 1 represents a sectional elevational view, on line a b c d of Fig. 2, of a
furnace with fixed crucibles and direct heating the salt to be avolomerated being

page_text: Fig. 2 18 a plan and sectional view, party
Fig.il..
Fig. 3 is an elevational and sectional view on the line ij of Fig. 4 of a furnace
with fixed pan and overflow chute, with mechanical feeding arrangement of the salt
to be agglomerated, and gas heating with regenerator..
Fig. 4 is a plan view and section partly on the line kl of Fig. 3, and partly in
plan.
Fig. 5 is a sectional elevational view on the line m n of Fig. 6 showing a furnace
with movable pan, and with rotary device for introducing the salt to be agglomerated
and with gas heating.
Fig. 6 is a plan and sectional view on the line op of Fig. 5...
Fig. 7-represents an alternative construction of the distributing feed 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 :-
The following improved processes and apparatus and the combination thereof or
of some of them, for the purpose of manufacturing blocks of molten and moulded
salt:
1. The previous crushing of the raw salt.
2. The application for this purpose of crushing apparatus, the constituent parts
of which are not susceptible of changing the condition of the salt treated.
3. The special purifying of the raw salt, effected previously or in the course of
the manufacture.
4. The use for this purpose of the process of solution and crystallization or
washing, sorting, of incineration in the dryer, oxydizing and decanting.
5. The previous drying of the raw salt by means of a dryer, the constituent parts
of which are not susceptible of changing the condition of the salt.
6. The use of drying apparatus allowing of the incineration or combustion of the
organic impurities contained in the salt.
7. The use for melting or fusing of the salt, of furnaces with fixed crucibles, or
with a fixed pan, or with a movable pan, such as described herein.
8. The introduction of the salt into the furnaces in a very fine distributed form
or in other words as a shower, the fusion being thus facilitated.
9. The use for the purpose of introducing or feeding of the salt, of a large
number of orifices or of a rotary apparatus, such as described, or any analogous
arrangement.
10. The heating of the outfall orifices either by a special firing or by
concentrating thereto the flames, destined for the heating of the furnace.
11. The intermittent flowing or running off, obtained by means of a rocking or
reciprocating pan or by temporary stopping of the orifices of the outfall by means
of the salt itself.
12. The continuous running off effected by the aid of an overflow chute.
13. The simultaneous use of continuous introduction of the salt into the furnace
(by means of the processes mentioned under 8 and 9) and of a continuous
running off.
14. The regulating of the speed of running off by the use of orifices of very
accurately measured dimensions.
15. The use in furnaces for large production, of several running off orifices.
16. The simultaneous use of direct firing, oxydizing and the decanting.
17. The use of muffles interposed between the flames and the salt.
18. The use of lighting gas or that made in any gas producer as fuel.
19. The condensing of the volatilized salt.
20. The use, in the construction of the furnaces, of materials containing little
or no free silica, and being as impervious as possible-such as magnesia, the
bauxite, chalk and particularly porcelain.
1.
JE

page_text: ·
21. The moulding of the salt blocks in moulds, constructed of materials not
susceptible of attacking the salt.
22. The displacing of these moulds in an alternative or continuous manner by
means of appropriate mechanism.
23. The slowly effected cooling of the moulded salt by circulating the forms in
chambers, in which they gradually lose their heat.
24. The annealing of the moulded salt.
25. The coating to the salt blocks with a layer of varnish increasing their
resistability to moisture.
"
26. The combination of the said varnish coating with salt blocks in general,
Dated this 15th day of December 1893.
R. HADDAN.