IMPROVEMENTS IN AND RELATING TO THE DECOMPOSITION BY MEANS OF MAG- NESIA OF THE RESIDUAL AMMONIUM CHLORIDE OF THE AMMONIA SODA PROCESS
Year: 1885

page_text: I, WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, Fellow
of the Royal Society, do hereby declare the nature of the said Invention for
IMPROVEMENTS IN AND RELATING TO THE DECOMPOSITION BY MEANS OF MAG-
NESIA OF THE RESIDUAL AMMONIUM CHLORIDE OF THE AMMONIA SODA PROCESS
to be as follows:-
In the manufacture of soda by the ammonia process, the mot' er-liquor from
which bicarbonate of soda has been separated is a mixed solution of chloride of
ammonium, chloride of sodium, bicarbonate of soda, and bicarbonate of ammonia.
From this mixed solution, the manufacturer of soda by the ammonia process has to
regenerate his ammonia, for use again.
The first step to this end is simply to heat the said mixed solution. The bicar-
bonate of ammonia which the said solution at first contained is thereby driven off
as vapour, and there is also driven off as vapour a further quantity of bicarbonate of
ammonia, formed by reaction between the bicarbonate of soda which was contained
in the solution before it was heated and some of its ammonium chloride. The
solution which remains when these two quantities of bicarbonate of ammonia have
been driven off contains chloride of ammonium and chloride of sodium only.
The chloride of ammonium of this solution has now to be decomposed, in such
wise that its ammonia shall be yielded in the free state.
Hitherto, the said chloride of ammonium has always been decomposed, and at
present it always is decomposed, by means of lime. The chlorine of the salt
decomposed by the manufacturer of ammonia soda is thus finally obtained as
chloride of calcium, and in that state is thrown away.
As chloride of calcium is a body from which it is not yet possible industrially to
separate its chlorine, either in the free state or as HCl, while means have recently

page_text: •
been invented by which both chlorine and hydrochloric acid can be readily manu-
factured from chloride of magnesium, the correspondents who have communicated
to me the present invention have endeavoured to decompose by magnesia, instead
of by lime, the ammonium chloride produced in the ammonia soda process, and
thus to obtain the chlorine of the salt decomposed by that process as a constituent
of a compound from which both free chlorine and hydrochloric acid can afterwards
be manufactured economically. They have succeeded in this endeavour, and the
present invention consists in the means and methods of procedure by which they
have found that the decomposition by magnesia of the ammonium chloride produced
in the manufacture of soda by the ammonia process can be executed with
advantage.
My correspondents have found that, in order to render industrially practicable
the decomposition by Mg O of the NH Cl produced in the manufacture of soda by
the ammonia process, the manner of proceeding must be in some respects very
different from the manner of proceeding which is at present followed for the
regeneration of ammonia from that ammonium chloride by means of lime.
When to an aqueous solution of chloride of ammonium one adds an equivalent
of lime, the lime dissolves immediately, and from the resulting mixed solution the
whole of the ammonia corresponding to the ammonium chloride originally present
can be distilled off almost if not quite as readily as from a simple solution containing
water and ammonia only.
For distilling ammonia from the product of the addition of lime to the mother-
liquor of the ammonia soda process, various kinds of apparatus are employed, but
they all consist, essentially, either of a series of distinct vessels, or of one vessel or
column divided into a number of compartments, through which series of vessels or
compartments steam and vapour of ammonia travel in one direction, while liquid
travels through the series of vessels or compartments in the opposite direction.
This liquid is at first the highly ammoniacal product of the addition of lime to the
mother-liquor of the ammonia soda process, but as it passes through the apparatus
it gradually loses its ammonia, and finally becomes simply a mixed solution of
calcium chloride and sodium chloride. The steam employed in this apparatus is
sometimes generated in one of the vessels or compartments of the apparatus itself,
by evaporation therein of the liquid under treatment, after that liquid has had
driven off from it, in other parts of the apparatus, the greater part of the ammonia
which it originally contained; but more usually the steam employed is steam from
a boiler external to the distillation apparatus proper. In both cases equally, from
that vessel or compartment of the apparatus from which the mixed solution of
calcium chloride and sodium chloride, which is the residual product of the opera-
tion, is ultimately discharged, there issues a mixture of steam and vapour of
• ammonia, which mixture of steam and vapour of ammonia (or such part of it as
does not become condensed in subsequent vessels or compartments of the apparatus)
then traverses the contents of all the other vessels or compartments composing the
apparatus, and in so doing becomes continually richer and richer in ammonia.
•
Now, there are two reasons why, in thus distilling ammonia from the product of
the addition of lime to the mother-liquor of the ammonia soda process, the mixture
of steam and vapour of ammonia which passes off from each successive vessel or
compartment of the distillation apparatus is richer in vapour of ammonia than the
mixture of steam and vapour of ammonia which entered that vessel or compart-
ment. One of those reasons of course is that in each vessel or compartment which
it successively enters, the said mixture of steam and vapour of ammonia meets a
liquid richer in ammonia than it had met before, and carries off therefrom a larger
quantity of ammonia than it had carried off from any preceding vessel or compart-
ment; but another reason is that much of the steam which enters the later vessels
or compartments condenses therein, not passing off therefrom as steam, but being
added to their contents as condensed water. The current of mixture of steam and
vapour of ammonia, as it travels onwards, thus not only continually gains more
´and more vapour of ammonia, but also continually loses steam.

page_text: This condensation, in some parts of the apparatus employed, of some of the
steam arriving therein from other parts of it, takes place in every variety of
apparatus which either is employed, or ever has been employed, for the distillation
of amnionia from the product of the addition of lime to the mother-liquor of the
ammonia soda process. It is usually due simply to loss of heat by radiation from
the parts of the apparatus in which it takes place; but special appliances (such as
serpentine pipes, through which a refrigerating fluid constantly flows) are some-
times employed ad hoc.
For this condensation, in some parts of the apparatus, of some of the steam
arriving therein from other parts of it, is not accidental. It is absolutely essential
to one of the objects which the manufacturer who regenerates by lime the ammonia
used in the ammonia soda process always seeks to accomplish.
When a mixture of two vapours, one of which two vapours is more volatile than
the other, is subjected to a limited amount of cooling, the one of the two vapours
which is least volatile condenses in the greatest proportion, and what remains
uncondensed, after the said cooling, is a mixture of the two vapours much richer in
the more volatile of them than was the original mixture of the two, before it was
subjected to the said limited degree of cooling. It is for this reason that all
apparatus for the distillation of ammonia from the product of the addition of lime
to the mother-liquor of the ammonia soda process is always so constructed and
disposed that in certain parts of it steam arriving therein from other parts of it
shall undergo condensation. One of the objects always sought is that there shall
finally issue from the apparatus a mixture of steam and vapour of ammonia.
containing a minimum proportion of steam and a maximum proportion of vapour
of ammonia; and to the accomplishment of this object the said condensation of
steam in certain parts of the distillation apparatus is absolutely essential.
While, however, the condensation of steam which takes place in every kind of
apparatus ever used for the distillation of ammonia from the product of the
addition of lime to the mother-liquor of the ammonia soda process thus causes the
mixture of steam and vapour of ammonia which finally issues from the distillation
apparatus to be very much richer in vapour of ammonia than it otherwise would
be, it renders necessary much more evaporation, and consequently a much greater
consumption of fuel for the distillation of a given quantity of ammonia, than
would suffice therefor if such condensation of steam did not take place. When no
steam is allowed to return as condensed water into the vessel in which that
operation is performed, all the ammonia of the product of the addition of lime to
the mother-liquor of the ammonia soda process may be driven off therefrom by
passing through that product a quantity of steam corresponding to about one-third
of the water contained in that product itself; but at least from three to four times
that quantity of steam is actually employed in regenerating by means of lime the
ammonia of the mother-liquor of the ammonia soda process, when the steam used
is steam from a boiler external to the distillation apparatus proper, as is seen from
the fact that the volume of the residual solution of calcium and sodium chlorides
is always more than twice as great as the volume of the original mother-liquor:
this augmentation of volume being of course due to condensation in the liquid
treated of most of the steam sent into it.
In generating ammonia from the mother-liquor of the ammonia soda process by
means of lime, the increased amount of evaporation rendered necessary by this
condensation of steam in the liquid treated is compensated by the greater richness
in ammonia of the mixture of steam and vapour of ammonia finally obtained. But
the case is very different in respect of the regeneration of ammonia from the said
mother-liquor by means of magnesia.
It has been said that when an equivalent of lime is added to aqueous solution of
ammonium chloride, the lime immediately dissolves therein completely. But when
an equivalent of magnesia is added to aqueous solution of ammonium chloride, the
magnesia does not at once dissolve completely. Only a portion of the magnesia
dissolves at first, setting free a corresponding proportion of the ammonia of the

page_text: ammonium chloride; and it is only as the ammonia thus at first set free is driven
off that more magnesia dissolves, setting free more ammonia. As more and more
magnesia dissolves, and more and more ammonia is driven off, the liquid thus
becoming poorer and poorer in ammonium chloride and richer and richer in
magnesium chloride, for the remainder of the magnesia to react upon the
remainder of the ammonium chloride becomes continually more and more
difficult; and hence, to drive off by means of magnesia all the ammonia of
solution of ammonium chloride requires a much more prolonged ebullition than
suffices to drive off all the ammonia of a similar solution by means of lime. If
the product of the addition of lime to the mother-liquor of the ammonia soda
process were evaporated in a vessel heated externally, under conditions under
which no steam could return, as condensed water, into the vessel in which the
operation were performed, all the ammonia of that product would be driven off
by the time that about one-third of its water had been evaporated; but if one
evaporated under the same conditions the product of the addition of magnesia to
the said mother-liquor, its ammonia would be by no means completely driven
off when one-third of its water had been evaporated. On the contrary, much
ammonium chloride would remain still undecomposed, even when the evaporation
had been continued nearly to dryness. To decompose the remainder of the
ammonium chloride, one must add very considerably more water, and then
evaporate the greater part of that further quantity of water.
Seeing, then, that even when the product of the addition of magnesia to the
mother-liquor of the ammonia soda process is evaporated under conditions under
which no steam returns, as condensed water, into the vessel in which the operation
is performed, the amount of evaporation required to drive off all its ammonia is
several times greater than the amount of evaporation required, under similar
conditions, to drive off all the ammonia of the product of the addition of lime to
the said mother-liquor, and seeing that the condensation of steam which takes
place during the distillation of ammonia, by all the methods hitherto employed,
from the product of the addition of lime to the said mother-liquor, involves an
amount of evaporation several times greater than would suffice to drive off all its
ammonia if that condensation of steam did not take place, it follows that the
amount of evaporation which would be required for the regeneration by magnesia
of the ammonia employed in the ammonia soda process, in such apparatus and by
such methods as those hitherto employed for the regeneration of that ammonia by
means of lime, would be so enormous that the regeneration of the said ammonia
by means of magnesia, in such apparatus and by such methods of procedure, is
absolutely impracticable.
The authors of the present invention have found, however, that the ammonium
chloride of the mother-liquor of the ammonia soda process may be decomposed by
magnesia so economically as to render the operation industrially practicable and
advantageous, if the operation be performed under conditions under which the
addition to the liquid under treatment, in any part of the apparatus employed, of
water condensed from steam arriving there from another part of the apparatus, is
for the most part avoided, and under which the liquid under treatment is always
kept, in all parts of the apparatus, in intimate contact with the magnesia which
is to decompose its ammonium chloride; and the present invention consists in
treating the said mother-liquor by magnesia under conditions securing these
objects.
An apparatus upon the principle of the present invention is illustrated by the
accompanying drawings. It is shown in elevation in Figure 3. Figure 4 is a
horizontal section of it along the line K, L, Figure 3. Figure 1 is a vertical section,
taken partly along the line A, B, Figure 4, and partly along the line C, D, Figure 4.
Figure 2 is a horizontal section, taken partly along the line E, F, Figure 1, and
partly along the line G, H, Figure 1. Figure 5 is a vertical section of the vessel C³,
Figure 6 is a horizontal section, taken along the line M, N, Figure 5.

page_text: C³, C, C³, C, C³, are a series of vessels superposed one above the other, formed
by dividing the interior of a vertical cylindrical iron column by horizontal
diaphragms. They are surrounded by masonry. With the boilers, A, A, they
constitute a distilling column.
Each of the two boilers, A, A, is formed of two cylindrical parts, the upper one
of which is of greater diameter than the lower one, the said two cylindrical parts
being united together by a hollow truncated cone. This construction of them will
be understood from Figure 1; from which it will also be seen that the products of
combustion from the fire-places, B, B, play only upon the lower part of the two
boilers, A, A. The said products of combustion then pass, in the direction shown
by the arrows, by the flues G and H, Figure 1, through the passages H, H, H, and
K, K; K, Figures 1 and 4, into the flue, L, Figures 1 and 2, which fiue L then
conveys them to a chimney. By thus traversing the spaces between the vessels C¹,
C2, C3, C4, C, and the masonry which surrounds them, the said products of
combustion prevent the contents of those vessels falling to such temperature that
steam can condense in them.
In the lower part of each of the two boilers, A, A, is a closed hollow cylinder, or
other equivalent appliance, E, Figure 1, through which passes the vertical shaft, a.
A system of bevel gearing, or other equivalent means, enables this shaft, a, to be
caused to rotate. To the circumference of the body E, which body E rotates with
the shaft, a, are attached arms which act as agitators. An agitator for stirring the
contents of the upper part of the boiler is also attached to the shaft, a, above the
body, E. The function of the body, E, is to diminish the capacity of the lower
cylindrical part of the boiler without diminishing its heating surface: that is to
say, to increase the heating surface of the boiler per given quantity of liquid
contained in it.
The function of the two boilers, A, A, is to evaporate the liquid which has passed
through the five vessels, C¹ to C. The solution which remains in thein when that
evaporation has been carried far enough is drawn off from each alternately, and
fresh liquid is alternately charged into them from the vessel C¹.
The boilers, A, A, are discharged by means of the cocks, g¹, g', and the pipes, 9, 9,
Figures 2 and 4, and are charged from the vessel C₁ by means of the cocks f¹, f,
and the pipes, f. f, Figures 1 and 4.
The mixture of steam and vapour of ammonia which is evolved from the
boilers, A, A, passes off from them by the pipes, i, i, Figures 1, 3, and 4, on which
pipes are the cocks ¹, 2¹.
The pipes j, j, Figures 1, 3, and 4, and the cocks, j¹, 7, are for regulating the
pressure between the vessel C¹ and the boilers, A, A, when the latter are being
charged.
The boilers, A, A, are provided with guage-tubes, d, d, Figures-1, 3, and 4.
The five vessels, C¹ to C³, are all similar one to the other. Through the centre
of them all passes the vertical shaft, n, at the upper extremity of which is gearing
by which the shaft, n, can be caused to rotate. Each of the five vessels is provided
internally with an agitator, which is fixed to, and rotates with, the vertical
shaft, n Each of them is moreover provided with a manhole, u, and a guage-
tube, p, Figure 3.
The mixture of steam and vapour of ammonia which is evolved in the
boilers, A, A, passes, by the pipes i, i, into the circular pipe, e, placed near the
bottom of the vessel C¹. This circular pipe, e, is perforated with holes throughout
its length.
The mixture of steam and vapour of ammonia which passes from the vessel C¹
into Cs, from C into Os, from Cinto C, and from C into C³, passes from vessel to
vessel by means which are shown in Figures 5 and 6.
Figure 5 is a vertical section of the vessel C³, and of parts C and C. It shows,
surrounding the shaft, n, the hood, 2, 2, 2, 2. The upper part of this hood is
cylindrical, and the lower part of it is a hollow truncated cone, terminating in a
flange, which is rivetted to the bottom of the vessel C³. The cylindrical part of

page_text: the hood, z, z, z, z, is open at its upper extremity. Outside the hood 2, 2, 2, 2, and
enclosing it, is another somewhat similar hood, x, x, x, x. This hood, x, x, x, x, is
attached to, and rotates with, the shaft n, and to its circumference is attached the
agitator, Q, R, S. The lower extremity of the hood, x, x, x, x, does not reach
quite to the bottom of the vessel C³, and is open, while its upper extremity is
closed. The mixture of steam and vapour of ammonia which passes off from the
vessel C2 passes first into the lower or conical part of the hood 2, 2, 2, 2, then rises.
through the upper or cylindrical part of that hood, and then passes down into the
liquid contained in C3 by the annular space between the outer circumference of the
hood 2, 2, 2, 2, and the inner circumference of the hood x, x, x, x, finally issuing
either from under the rim of the conical part of the latter hood or through holes
near its lower edge.
In the bottom of each of the five vessels, C¹ to C, is a kind of slide valve, M,
Figures 5 and 6, by which from time to time the contents of the vessel C³ are
transferred into C, those of C into C³, and so on. Figure 6, which is a section
along the line M, N, Figure 5, shows this valve in detail. It is a disk of iron,
fixed at one extremity of the rod q, which rod can be drawn out or pushed in by
means of the pinion and the crank r¹. When the valve, M, is in the position in
which it is shown in Figure 5, it is pressed tightly against its seat by the bell-
crank, S, operated by the rod S¹.
The vessel D, Figure 1, may be called the decarbonating boiler. It is furnished
interiorly with an agitator, attached to, and rotating with, a vertical shaft. Near
the bottom of the vessel D is a circular pipe, t, perforated with holes throughout
its length. The mixture of steam and vapour of ammonia which passes off from
the vessel C passes into the perforated pipe t, near the bottom of the vessel D, by
the pipe y, y, Figures 1 and 3. Liquid from this decarbonating boiler D can be.
run from it into the vessel C by a pipe and cock which are seen in Figure 1 but
are not marked by any letter.
The manner of working of this apparatus will now be easily understood. The
mixture of steam and vapour of ammonia, containing only very little ammonia,
which is disengaged in the boilers, A, A, passes, by the pipes i, i, into the perforated
circular pipe c, e, placed near the bottom of the vessel C¹, and then rises upwards
through the liquid which is contained in that vessel. The contents of that vessel
being maintained, by the products of combustion which are continually in contact
with its exterior surface, at such temperature that steam cannot condense in them,
all the steam which enters the vessel C¹ passes off from that vessel into the
vessel C, accompanied by the vapour of ammonia which passed off with it from
the boilers, A, A, and with the further quantity of ammonia which it carries off
from the contents of the vessel C'. In then traversing the contents of vessel C³,
and then successively those of C3, C4, and C, the mixture of steam and vapour of
ammonia continually gathers more and more vapour of ammonia, without losing any
of its steam; so that the liquid which passes successively through the vessels C³,
C*, C³, C*, C¹³, does not become diluted in any of those vessels, (unless to an
insignificant extent in O³), but retains the volume which it had on leaving C³ until
it reaches the boilers, A, A, in which it is then concentrated by evaporation.
Practically all the steam which is generated in the apparatus thus passes off as
steam from the vessel C³; whereas, in every apparatus which has hitherto been
used for the regeneration of ammonia by means of lime, nearly all the steam
generated in the apparatus, or sent into it from an external boiler, instead of
passing off from its upper extremity as steam, passes off from its lower extremity
as condensed water.
When the liquid in one of the two boilers, A, A, has reached or nearly reached
the degree of concentration at which, if its concentration were further continued,
solid sodium chloride would separate out from it, all its ammonia has been driven
off from it, and it must now be discharged, either wholly or in part, from the
boiler containing it, and there must then be run into that boiler the contents of
the vessel C¹. This having been done, the contents of C* must be transferred

page_text: into C, the contents of C³ into C³, the contents of C into C³, and the contents
of 0 into C, and the contents of the decarbonating boiler, D, into C. The
decarbonating boiler, D, must then be re-charged.
The liquid with which the vessel D must thus be re-charged is the mother-
liquor of the ammonia soda process. But before this mother-liquor is charged
into D, it should preferably have been employed, in a vessel or apparatus not
shown in the drawings, to condense or partially condense a mixture of steam and
vapour of ammonia, and so itself be heated, up before it is charged into D.
It is permissible that in the vessel D some of the steam entering that vessel shall
be allowed to condense therein.
During its sojourn in the decarbonator D, the mother-liquor has all its bicarbonate
of ammonia driven off from it.
When its bicarbonate of ammonia has all been driven off from the mother-liquor
which has been charged into the decarbonator D, a quantity of magnesia, preferably
somewhat in excess of the quantity thereof which is equivalent to the quantity
of ammonium chloride which is contained therein, must be introduced into the
decarbonator D.
The introduction of the necessary quantity of magnesia into the vessel D may
be made by various methods; but a good method is to mix the magnesia with just
enough water to make it into a fluid milk, and then to run this milk into D
through a cock not shown in the drawing.
The mixture of steam and vapour of ammonia which passes off from the decar-
bonator D may go therefrom either into condensation apparatus, or into rectification
apparatus, as may be preferred in each particular case.
The apparatus thus described is given simply as an example of an apparatus
constructed and worked according to the present invention. Without departing
from the principle of the present invention, the details of the described apparatus
may be varied and modified in vory many ways. For example, the number of the
boilers, A, A, may be more or less than two; the construction of those boilers need
not necessarily be that above described; the number of the vessels C, or of the
other vessels or compartments which may be substituted for them, may be greater
or less than five; these vessels or compartments may be arranged otherwise than
vertically; and the cooling of their contents may be prevented, instead of by the
means described above, by simply encasing them with a sufficiently non-conducting
material, or by any one of a variety of other means.
What is new in the present invention consists in an apparatus for the decom-
position by magnesia of the ammonium chloride of the mother-liquor of the
ammonia soda process, after that mother-liquor has been treated for the 'distillation
off from it of bicarbonate of ammonia, and there has been added to it a sufficient
quantity of magnesia, and it has been raised to the boiling point, or nearly so, .
which apparatus has the following new and special characteristics:
All parts of the apparatus are so protected from the cooling of their contents
that in no part of the apparatus can more than an insignificant proportion of the
steam arriving therein from another part of the apparatus become condensed: this
protection from cooling being effected in any convenient way, but preferably by
surrounding with masonry the various vessels or compartments through which the
liquid passes successively, before it reaches the boilers in which it is finally
evaporated, and causing the products of combustion from the fire-places heating
those boilers to pass between the external surface of those vessels or compartments
and the internal surface of the said masonry; the said apparatus being moreover
one which is so arranged and disposed that at every part of it the mixture of
solution of ammonium chloride with magnesia which is treated in it shall be kept
in agitation.

page_text: Improvements in and relating to the Decomposition by Means
of Magnesia of the Residual Ammonium Chloride of the
Ammonia Soda Process.
I, WALTER FRANK RAPHAEL WELDON, of N° 19, Great George Street,.
Westminster, in the County of Middlesex, Administrator of the late Walter
Weldon, the Applicant, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:—
In the manufacture of soda by the ammonia process, the mother-liquor from
which bicarbonate of soda has been separated is a mixed solution of chloride of
ammonium, chloride of sodium, bicarbonate of soda, and bicarbonate of ammonia.
From this mixed solution, the manufacturer of soda by the ammonia process has to
regenerate his ammonia, for use again.
The first step to this end is simply to heat the said mixed solution. The
bicarbonate of ammonia which the said solution at first contained is thereby driven
off as vapour, and there is also driven off as vapour a further quantity of
bicarbonate of ammonia, formed by reaction between the bicarbonate of soda which
was contained in the solution before it was heated and some of its ammonium
chloride. The solution which remains when these two quantities of bicarbonate of
ammonia have been driven off contains chloride of ammonium and chloride of
sodium only.
The chloride of ammonium of this solution has now to be decomposed, in such
wise that its ammonia shall be yielded in the free state.
Hitherto, the said chloride of ammonium has always been decomposed, and at
present it always is decomposed, by means of lime. The chlorine of the salt
decomposed by the manufacturer of ammonia soda is thus finally obtained as
chloride of calcium, and in that state is thrown away.
As chloride of calcium is a body from which it is not yet possible industrially to
separate its chlorine, either in the free state or as hydrochloric acid, while means
have recently been invented by which both chlorine and hydrochloric acid can be
readily manufactured from chloride of magnesium, the correspondents who have
communicated to me the present invention have endeavoured to decompose by
magnesia, instead of by lime, the ammonium chloride produced in the ammonia
soda process, and thus to obtain the chlorine of the salt decomposed by that process
as a constituent of a compound from which both free chlorine and bydrochloric
acid can afterwards be manufactured economically. They have succeeded in this
endeavour, and the present invention consists in the means and method of
procedure by which they have found that the decomposition by magnesia of the
ammonium chloride produced in the manufacture of soda by the ammonia process
can be executed with advantage.
My correspondents have found that, in order to render industrially practicable
the decomposition by Mg O of the NH, Cl produced in the manufacture of soda
by the ammonia process, the manner of proceeding must be in some respects very

page_text: different from the manner of proceeding which is at present followed for the
regeneration of ammonia from that ammonium chloride by means of lime.
When to an aqueous solution of chloride of ammonium one adds an equivalent
of lime, the line dissolves immediately, and from the resulting mixed solution the
whole of the ammonia corresponding to the ammonium chloride originally present
can be distilled off almost if not quite as readily as from a simple solution containing
water and ammonia only.
For distilling ammonia from the product of the addition of lime to the mother-
liquor of the ammonia soda process, various kinds of apparatus are employed, but
they all consist, essentially, either of a series of distinct vessels, or of one vessel or
column divided into a number of compartments, through which series of; vessels or
compartments steam and vapour of ammonia travel in one direction, while liquid
travels through the series of vessels or compartments in the opposite direction.
This liquid is at first the highly ammoniacal product of the addition of lime to the
mother-liquor of the ammonia soda process, but as it passes through the apparatus
it gradually loses its ammonia, and finally becomes simply a mixed solution of
calcium chloride and sodium chloride. The steam employed in this apparatus is
sometimes generated in one of the vessels or compartments of the apparatus itself,
by evaporation therein of the liquid under treatment, after that liquid has had
driven off from it, in other parts of the apparatus, the greater part of the ammonia
which it originally contained; but more usually the steam employed is steam from
a boiler external to the distillation apparatus proper. In both cases equally, from
that vessel or compartment of the apparatus from which the mixed solution of
calcium chloride and sodium chloride, which is the residual product of the operation,
is ultimately discharged, there issues a mixture of steam and vapour of ammonia,
which mixture of steam and vapour of ammonia (or such part of it as does not
become condensed in subsequent vessels or compartments of the apparatus) then
traverses the contents of all the other vessels or compartments composing the
apparatus, and in so doing becomes continually richer and richer in ammonia.
Now, there are two reasons why, in thus distilling ammonia from the product of
the addition of lime to the mother-liquor of the ammonia soda process, the mixture
of steam and vapour of ammonia which passes off from each successive vessel or
compartment of the distillation apparatus is richer in vapour of ammonia than the
mixture of steam and vapour of ammonia which entered that vessel or compartment.
One of those reasons of course is that in. cach vessel or compartment which it
successively enters, the said mixture of steam and vapour of ammonia meets a
liquid richer in ammonia than it had met before, and carries off therefrom 'a larger
quantity of ammonia than it had carried off from any preceding vessel or
compartment; but another reason is that much of the steam which enters the
later vessels or compartments condenses therein, not passing off therefrom as steam,
but being added to their contents as condensed water. The current of mixture of
steam and vapour of ammonia, as it travels onwards, thus not only continually
gains more and more vapour of ammonia, but also continually loses steam.
This condensation, in some parts of the apparatus employed, of some of the
steam arriving therein from other parts of it, takes place in every variety of
apparatus which either is employed, or ever has been employed, for the distillation
of ammonia from the product of the addition of lime to the mother-liquor of the
ammonia soda process. It is usually due simply to loss of heat by radiation from
the parts of the apparatus in which it takes place; but special appliances (such
as serpentine pipes, through which a refrigorating fluid constantly flows) are
sometimes employed ad hoc.
For this condensation, in some parts of the apparatus, of some of the steam
arriving therein from other parts of it, is not accidental. It is absolutely essential
to one of the objects which the manufacturer who regenerates by lime the ammonia
used in the ammonia soda process always seeks to accomplish.
When a mixture of two vapours, one of which two vapours is more volatile than
the other, is subjected to a limited amount of cooling, the one of the two vapours

page_text: which is least volatile condenses in the greatest proportion, and what remains
uncondensed, after the said cooling, is a mixture of the two vapours much richer in
the more volatile of them than was the original mixture of the two, before it was
subjected to the said limited degree of cooling. It is for this reason that all
apparatus for the distillation of ammonia from the product of the addition of lime
to the mother-liquor of the ammonia soda process is always so constructed and
disposed that in certain parts of it steam arriving therein from other parts of it
shall undergo condensation. One of the objects always sought is that there shall
finally issue from the apparatus a mixture of steam and vapour of ammonia con-
taining a minimum proportion of steam and a maximum proportion of vapour of
ammonia;
and to the accomplishment of this object the said condensation of steam
in certain parts of the distillation apparatus is absolutely essential.
While, however, the condensation of steam which takes place in every kind of
apparatus ever used for the distillation of ammonia from the product of the
addition of lime to the mother-liquor of the ammonia soda process thus causes the
mixture of steam and vapour of ammonia which finally issues from the distillation
apparatus to be very much richer in vapour of ammonia than it otherwise would
be, it renders necessary much more evaporation, and consequently a much greater
consumption of fuel, for the distillation of a given quantity of ammonia, than would
suffice therefor if such condensation of steam did not take place. When no steam
is allowed to return as condensed water into the vessel in which that operation is
performed, all the ammonia of the product of the addition of lime to the mother-
liquor of the ammonia soda process may be driven off therefrom by passing through
that product a quantity of steam corresponding to about one-third of the water
contained in that product itself; but at least from three to four times that
quantity of steam is actually employed in regenerating by means of lime the
ammonia of the mother-liquor of the ammonia soda process, when the steam used
is steam from a boiler external to the distillation apparatus proper, as is seen from
the fact that the volume of the residual solution of calcium and sodium chlorides is
always more than twice as great as the volume of the original mother-liquor: this
augmentation of volume being of course due to condensation in the liquid treated
of most of the steam sent into it.
In generating ammonia from the mother-liquor of the ammonia soda process by
means of lime, the increased amount of evaporation rendered necessary by this
condensation of steam in the liquid treated is compensated by the greater richness
in ammonia of the mixture of steam and vapour of ammonia finally obtained.
But the case is very different in respect of the regeneration of ammonia from the
said mother-liquor by means of magnesia.
It has been said that when an equivalent of lime is added to aqueous solution of
ammonium chloride, the lime immediately dissolves therein completely. But when
an equivalent of magnesia is added to aqueous solution of ammonium chloride, the
magnesia does not at once dissolve completely. Only a portion of the magnesia
dissolves at first, setting free a corresponding proportion of the ammonia of the
ammonium chloride; and it is only as the ammonia thus at first set free is driven
off that more magnesia dissolves, setting free more ammonia. As more and more
magnesia dissolves, and more and more ammonia is driven off, the liquid thus
becoming poorer and poorer in ammonium chloride and richer and richer in
magnesium chloride, for the remainder of the magnesia to react upon the remainder
of the ammonium chloride becomes continually more and more difficult; and hence,
to drive off by -means of magnesia all the ammonia of solution of ammonium
chloride requires a much more prolonged ebullition than suffices to drive off all the
ammonia of a similar solution by means of lime. If the product of the addition of
lime to the mother-liquor of the ammonia soda process were evaporated in a vessel
heated externally, under conditions under which no steam could return, as condensed
water, into the vessel in which the operation were performed, all the ammonia of
that product would be driven off by the time that about one-third of its water had
been evaporated; but if one evaporated under the same conditions the product of

page_text: the addition of magnesia to the said mother-liquor, its ammonia would be by no
means completely driven off when one-third of its water had been evaporated. On
the contrary, much ammonium chloride would remain still undecomposed, even
when the evaporation had been continued nearly to dryness. To decompose the
remainder of the ammonium chloride, one must add very considerably more water
and then evaporate the greater part of that further quantity of water. Seeing,
then, that even when the product of the addition of magnesia to the mother-liquor
of the ammonia soda process is evaporated under conditions under which no steam
returns, as condensed water, into the vessel in which the operation is performed,
the amount of evaporation required to drive off all its ammonia is several times
greater than the amount of evaporation required, under similar conditions, to drive
off all the ammonia of the product of the addition of lime to the said mother-liquor,
and seeing that the condensation of steam which takes place during the distillation
of ammonia, by all the methods hitherto employed, from the product of the
addition of lime to the said mother-liquor, involves an amount of evaporation.
several times greater than would suffice to drive off all its ammonia if that con-
densation of steam did not take place, it follows that the amount of evaporation
which would be required for the regeneration by magnesia of the ammonia
employed in the ammonia soda process, in such apparatus and by such methods as
those hitherto employed for the regeneration of that ammonia by means of lime,
would be so enormous that the regeneration of the said ammonia by means of
magnesia, in such apparatus and by such methods of procedure, is absolutely
impracticable.
The authors of the present invention have found, however, that the ammonium
chloride of the mother-liquor of the ammonia soda process may be decomposed by
magnesia so economically as to render the operation industrially practicable and
advantageous, if the operation be performed under conditions under which the
addition to the liquid under treatment, in any part of the apparatus employed, of
water condensed froin steam arriving there from another part of the apparatus, is
for the most part avoided, and under which the liquid under treatment is always
kept, in all parts of the apparatus, in intimate contact with the magnesia which is
to decompose its ammonium chloride; and the present invention consists in
treating the said mother-liquor by magnesia under conditions securing these
objects.
An apparatus upon the principle of the present invention is illustrated by the
drawings accompanying the provisional specification, which drawings apply equally
to this the complete specification, the same letters referring to the same parts in each
case. The apparatus is shown in elevation in Figure 3. Figure 4 is a horizontal
section of it along the line K, L, Figure 3. Figure 1 is a vertical section, taken
partly along the line A, B, Figure 4, and partly along the line C, D, Figure 4.
Figure 2 is a horizontal section, taken partly along the line E, F, Figure 1, and
partly along the line G, H, Figure 1. Figure 5 is a vertical section of the vessel C³.
Figure 6 is a horizontal section taken along the line M, N, Figure 5.
A, A, Figures 1 and 2, are two vertical boilers.
C¹, C³, C³, C, C³, are a series of vessels superposed one above the other, formed
by dividing the interior of a vertical cylindrical iron column by horizontal
diaphragms. They are surrounded by masonry.
With the boilers A, A, they
constitute a distilling column.
Each of the two boilers, A, A, is formed of two cylindrical parts, the upper one
of which is of greater diameter than the lower one, the said two cylindrical parts
being united together by a hollow truncated cone. This construction of them will
be understood from Figure 1; from which it will also be seen that the products of
combustion from the fire-places B, B, play only upon the lower part of the two
boilers A, A. The said products of combustion then pass, in the direction shown
by the arrows, by the flues G and H, Figure 1, through the passages H, H, H,
and K, K, K, Figures 1 and 4, into the flue L, Figures 1 and 2, which flue L
then conveys them to a chimney. By thus traversing the spaces between the

page_text: vessels C¹, C³, C³, C³, C³, and the masonry which surrounds them, the said products
of combustion prevent the contents of those vessels falling to such temperature
that steam can condense in them.
In the lower part of each of the two boilers, A, A, is a closed hollow cylinder, or
other equivalent appliance, E, Figure 1, through which passes the vertical shaft, a.
A system of bevel gearing, or other equivalent means, enables this shaft, a, to be
caused to rotate. To the circumference of the body E, which body E rotates with
the shaft a, are attached arms which act as agitators. An agitator for stirring the
contents of the upper part of the boiler is also attached to the shaft a, above the
body E. The function of the body E is to diminish the capacity of the lower
cylindrical part of the boiler without diminishing its heating surface: that is to
say, to increase the heating surface of the boiler per given quantity of liquid
contained in it.
The function of the two boilers, A, A, is to evaporate the liquid which has passed
through the five vessels C¹ to C. The solution which remains in them when that
evaporation has been carried far enough is drawn off from each alternately, and
fresh liquid is alternately charged into them from the vessel C¹.
The boilers, A, A, are discharged by means of the cocks g¹, g', and the pipes g, g,
Figures 2 and 4, and are charged from the vessel C¹ by means of the cocks f¹ƒ³‚
and the pipes f. f. Figures 1 and 4.
The mixture of steam and vapour of ammonia which is evolved from the
boilers A, A, passes off from them by the pipes i, i, Figures 1, 3, and 4, on which
pipes are the cocks i¹, i.
The pipes i, j, Figures 1, 3, and 4, and
pressure between the vessel C¹ and the
charged.
the cocks j³, j, are for regulating the
boilers A, A, when the latter are being
The boilers A, A, are provided with guage-tubes, d, d, Figures 1, 3, and 4.
The five vessels, C¹ to C³, are all similar one to the other. Through the centre
of them all passes the vertical shaft n, at the upper extremity of which is gearing
by which the shaft n can be caused to rotate. Each of the five vessels is provided
internally with an agitator, which is fixed to, and rotates with, the vertical shaft n.
Each of them is morcover provided with a manhole, u, and a guage-tube, p,
Figure 3.
The mixture of steam and vapour of ammonia which is evolved in the
boilers A, A, passes by the pipes i, i, into the circular pipo e, placed near the
bottom of the vessel C¹. This circular pipe e is perforated with holes throughout
its length.
The mixture of steam and vapour of ammonia which passes from the vessel C¹
into C, from C³ into C³, from C³ into C4, and from C into C³, passes from vessel
to vessel by means which are shown in Figures 5 and 6.
Figure 5 is a vertical section of the vessel C³, and of parts of C² and C. It
shows, surrounding the shaft n, the hood z, z, z, z. The upper part of this hood is
cylindrical, and the lower part of it is a hollow truncated cone, terminating in a
flange, which is rivetted to the bottom of the vessel C³. The cylindrical part of
the hood z, z, z, z, is open at its upper extremity. Outside the hood %, 2, 2, 2, and
enclosing it, is another somewhat similar hood, x, x, x, x This hood x, x, x, x, is
attached to, and rotates with, the shaft n, and to its circumference is attached the
agitator Q, R. S. The lower extremity of the hood x, x, x, x, does not reach quite
to the bottom of the vessel C³, and is open, while its upper extremity is closed.
The mixture of steam and vapour of ammonia which passes off from the vessel C² !
passes first into the lower or conical part of the hood z, z, z, z, then rises through
the upper or cylindrical part of that hood, and then passes down into the liquid
contained in CS by the annular space between the outer circumference of the
hood 2, 2, 2, 2, and the inner circumference of the hood x, x, x, x, finally issuing
either from under the rim of the conical part of the latter hood or through holes &
near its lower edge.

page_text: In the bottom of each of the five vessels, C¹ to C, is a kind of slide valve, M,
Figures 5 and 6, by which from time to time the contents of the vessel C are
transferred into C4, those of C₁ into C³, and so on. Figure 6, which is a section
along the line M, N, Figure 5, shows this valve in detail. It is a disc of iron, fixed
at one extremity of the rod q, which rod can be drawn out or pushed in by means
of the pinion and the crank r¹: When the valve M is in the position in which
it is shown in Figure 5, it is pressed tightly against its seat by the bell-crank, 8,
operated by the rod &².
The vessel D, Figure 1, may be called the decarbonating boiler. It is furnished
interiorly with an agitator, attached to, and rotating with, a vertical shaft. Near
the bottom of the vessel D is a circular pipe, t, perforated with holes throughout
its length. The mixture of steam and vapour of ammonia which passes off from
the vessel C³ passes into the perforated pipe t, near the bottom of the vessel D, by
the pipe y, y, Figures 1 and 3. Liquid from this decarbonating boiler D can be
run from it into the vessel C³ by a pipe and cock which are seen in Figure 1 but
are not marked by any letter.
The manner of working of this apparatus will now be easily understood. The
mixture of steam and vapour of ammonia, containing only very little ammonia,
which is disengaged in the boilers A, A, passes, by the pipes i, i, into the perforated
circular pipe e, e, placed near the bottom of the vessel O¹, and then rises upwards
through the liquid which is contained in that vessel. The contents of that vessel
being maintained, by the products of combustion which are continually in contact
with its exterior surface, at such temperature that steam cannot condense in them,
all the steam which enters the vessel C₁ passes off from that vessel into the
vessel C, accompanied by the vapour of ammonia which passed off with it from
the boilers A, A, and with the further quantity of ammonia which it carries off
from the contents of the vessel C¹. In then traversing the contents of vessel C³,
and then successively those of C3, C4, and C³, the mixture of steam and vapour of
ammonia continually gathers more and more vapour of ammonia, without losing
any of its steam; so that the liquid which passes successively through the
vessels C³, C4, C³, C³, C³, does not become diluted in any of those vessels (unless to
an insignificant extent in C³), but retains the volume which it had on leaving C³
until it reaches the boilers A, A, in which it is then concentrated by evaporation.
Practically all the steam which is generated in the apparatus thus passes off as
steam from the vessel C³; whereas, in every apparatus which has hitherto been
used for the regeneration of ammonia by means of lime, nearly all the steam
generated in the apparatus, or sent into it from an external boiler, instead of
passing off from its upper extremity as steam, passes off from its lower extremity
as condensed water.
When the liquid in one of the two boilers A, A, has reached or nearly reached
the degree of concentration at which, if its concentration were further continued,
solid sodium chloride would separate out from it, all its ammonia has been driven
off from it, and it must now be discharged, either wholly or in part, from the
boiler containing it, and there must then be run into that boiler the contents of the
vessel C. This having been done, the contents of C³ must be transferred into C³,
the contents of C³ into C, the contents of C into C³, and the contents of C³
into C, and the contents of the decarbonating boiler D into C. The decarbonating
boiler D must then be re-charged.
The liquid with which the vessel D must thus be re-charged is the mother-liquor
of the ammonia soda process. But before this mother liquor is charged into D, it
should preferably have been employed, in a vessel or apparatus not shown in the
drawings, to condense or partially condense a. mixture of steam and vapour of
ammonia, and so itself be heated up before it is charged into D.
It is permissible that in the vessel D some of the steam entering that vessel shall
be allowed to condense therein.
During its sojourn in the decarbonator D, the mother-liquor has all its bicarbonate
of ammonia driven off from it.

page_text: When its bicarbonate of ammonia has all been driven off from the mother-liquor
which has been charged into the decarbonator D, a quantity of magnesia, prefer-
ably somewhat in excess of the quantity thereof which is equivalent to the
quantity of ammonium chloride which is contained therein, must be introduced
into the decarbonator D.
The introduction of the necessary quantity of magnesia into the vessel D may
be made by various methods; but a good method is to mix the magnesia with just
enough water to make it into a fluid milk, and then to run this milk into D through
a cock not shown in the drawings.
The mixture of steam and vapour of ammonia which passes off from the
decarbonator D may go therefrom either into condensation apparatus, or into rectifi-
cation apparatus, as may be preferred in each particular case.
The apparatus thus described is given simply as an example of an apparatus
constructed and worked according to the present invention.
Without departing
from the principle of the present invention, the details of the described apparatus
may be varied and modified in very many ways. For example, the number of the
boilers A, A, may be more or less than two; the construction of those boilers need
not necessarily be that above described; the number of the vessels C, or of the
other vessels or compartments which may be substituted for them, may be greater
or less than five; those vessels or compartments may be arranged otherwise than
vertically; and the cooling of their contents may be prevented, instead of by the
means described above, by simply encasing them with a sufficiently non-conducting
material, or by any one of a variety of other means.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
An apparatus constructed substantially as described above for the decomposition
by magnesia of the ammonium chloride of the mother-liquor of the ammonia soda
process, after that mother-liquor has been treated for the distillation off from it of
bicarbonate of ammonia, and there has been added to it a sufficient quantity of
magnesia, and it bas been raised to the boiling point, or nearly so, which apparatus
has the following new and special characteristics:-
All parts of the apparatus are so protected from the cooling of their contents
that in no part of the apparatus can more than an insignificant proportion of the
steam arriving therein from another part of the apparatus become condensed: this
protection from cooling being effected in any convenient way, but preferably by
surrounding with masonry the various vessels or compartments through which the
liquid passes successively, before it reaches the boilers in which it is finally
evaporated, and causing the products of combustion from the fire-places heating
those boilers to pass between the external surface of those vessels or compartments
and the internal surface of the said masonry; the said apparatus being moreover
one which is so arranged and disposed that at every part of it the mixture of
solution of ammonium chloride with magnesia which is treated in it shall be kept
in agitation.