and in Apparatus therefor
Year: 1885

page_text: Baryta and in Apparatus therefor.
I, HIPPOLYTE LEPLAY of 104 rue Lafayette, Paris, France, Chemist do hereby
declare the nature of my invention for "IMPROVEMENTS IN DECARBONATING THE
CARBONATES OF STRONTIA AND BARYTA AND IN APPARATUS THEREFOR" and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
In the Specification to Letters Patent granted to J. Imray on the 4th July 1884
N° 9765 (being a communication to him from me) was described a construction of
apparatus or kiln for transforming carbonate of strontia into anhydrous strontia
in which the carbonate of strontia, moulded into tubes or other forms, was
decomposed in the kiln by means of superheated steam. In this apparatus the
feeding retorts situated at the upper end of the kiln, through which the moist
carbonate of strontia was introduced were heated externally by the direct heat of
a fire. This arrangement has some disadvantages, which are obviated by the
present improved construction of the kilns, such improved construction being also
applicable to the similar treatment of carbonate of baryta.
It is essential for the economic treatment of the strontia or baryta that the
steam should not be brought in contact with the carbonate until it has been raised
to a sufficiently high temperature to cause its immediate decomposition, that is
to say, that the superheated steam, being itself at the temperature at which the
monohydrate is produced and carbonic acid is disengaged, should not serve to raise
the temperature of the carbonate.
The superheating of the steam is however subject to irregularities as is also the.
heating of the said feeding retorts into which the moulded moist carbonate is
introduced and as a consequence the temperature in the interior of the kiln
sometimes falls; in consequence hereof it was necessary to introduce occasionally
in the lower part of the kiln, as at starting, a supply of hot combustion gases from
the chambers in which the steam was superheated in order to raise the temperature
in the kiln at such times when the cooling action took place. In order to prevent
the occurrence of such fluctuations of temperature, I, according to my present
improvements permanently apply currents of heated air and producer gases to the
kiln in regulated quantities, while at the same time continuing the introduction
of the superheated steam. The combustible gases employed contain a certain

page_text: .
quantity of carburetted hydrogen, which, in entering into combustion with the air
supply, produces a quantity of steam heated to a high degree, the action whereof
assists that of the superheated steam introduced below in effecting the decomposition
of the carbonate. Such introduction of heated air and producer gases is effected
not only in the lower part of the kiln but also at different points of its height, so
as to maintain the entire contents thereof at the requisite temperature for the
formation of the monohydrate. This introduction must be so arranged that it can
be increased or decreased, according as may be required; it permits of the attain-
ment of a much greater useful effect in the kiln and a considerable economy in
working.
The vertical feeding retorts at the top of the kiln, also presented the incon-
venience that the moulded carbonate, not being heated sufficiently therein to
become hardened, was partially reduced to small fragments, which prevented the
free passage of the steam among the blocks. I prevent this inconvenience by
dispensing with the said vertical retorts, and closing the top of the kiln by an
arch, between which and the top surface of the charge of carbonate sufficient space
is left to constitute a chamber or muffle into which the hot gases rise from below,
and which is, if necessary, additionally heated by a supply of air and producer
gas, so that the moulded carbonate introduced therein becomes baked and hardened
by the high temperature to which it is subjected. The introduction of the
_carbonate must be so regulated that the temperature of this chamber is never
reduced below a red heat.
The accompanying drawing shews the construction of the improved kiln. Fig. 1
shews a vertical longitudinal section, Fig. 2 shews a cross section, and Figs. 3 and 4
are sectional plans on the lines T U and X Y.
At B B¹ are arranged vertical flues through which heated air and producer gas
are respectively conducted into the horizontal flues E E' and F F¹ surrounding the
kiln A, whence they issue through apertures e e¹ and f f¹ and enter into combustion
within the kiln. The flues B B₁ at a and b that, lead to the upper horizontal
flues E E¹ are made larger than those at c and d, as they have to furnish in
addition the requisite supply of producer gas and air to the flues C C¹ leading to
the chambers Gin which the steam entering the retorts D becomes superheated.
The gas and air rising through the flues at c and d issue through the flues F F¹,
which are situated about half way between the flues E E' and the floor of the kiln.
The apertures e e¹ and f f¹ are made to incline towards each other, as shewn, so as
to bring the jets of air and of gas into intimate contact; these apertures are
formed all round the sides of the kiln. The hot gases resulting from the combustion
in the chambers G issue thence through openings H into the lower part of the kiln.
The kiln constructed as above described, presents, as in the construction described
in the said previous patent, two distinct zones, in the upper one of which the
carbonate is heated to the requisite degree for its decomposition by means of the
superheated steam, while in the lower one, which receives the superheated steam,
the conversion of the carbonate is effected. The improved construction however
has the great advantage that the heating of the carbonate is not effected through
the walls of retorts that are bad conductors of heat, but by direct contact with the
highly heated combustion gases, and also that such heating can be regulated at
will at all parts of the kiln by regulating the supply of producer gas and air so as
to bring the carbonate to the requisite temperature at which its decomposition is
rapidly effected under the influence of the superheated steam, without abstracting
for this purpose any heat from the latter.
The temperature should never be allowed to fall below that of a red heat.
The gases passing from the kiln being at a very high temperature, I utilise their
heat by causing them to pass through a horizontal chamber or retort I com-
municating directly with the upper part of the kiln through an opening J. The
heat in this chamber is not sufficient to bake the moulded carbonate, but it may
be employed with advantage for drying the carbonate resulting from the decom-
position of the sucrates from the filter-presses, and which is introduced on to the

page_text: floor of the chamber. The gases pass away from the chamber I either through the
chimney K leading to the regenerative passages of the regenerative gas producers
employed, or they may be drawn off through a pipe L by a pump which conveys.
them to wherever the carbonic acid contained in them can be utilised.
The opening S through which the carbonate is introduced from time to time, is
closed by a cover M. When the carbonate has been sufficiently dried in the
chamber I, it is removed and is charged into the kiln A through the stoppered
openings O, or it may be pushed in directly through the opening J, which may
in that case extend down to the floor of the chamber.
The converted carbonate is removed at the bottom of the kiln from time to
time through the discharge openings R.
When treating baryta in this construction of kiln, as this is reduced to a molten
condition it is necessary to provide means whereby the superheated steam shall be
brought into intimate contact with the liquid in a subdivided state in order to
act upon particles of unconverted carbonate contained therein. For this purpose
I introduce into the lower part of the kiln basic aluminous or magnesian perforated
blocks as shewn at g g Fig. 5, which are not attacked by the molten monohydrate,.
and which cause the latter to flow downward in a subdivided state while subject
to the action of the superheated steam issuing from the retorts D; at bottom the
liquid flows off through the openings R.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
1-In the process of decarbonating the carbonates of strontia and baryta by
means of superheated steam the method of effecting the heating of the carbonates
by the combustion within the kiln or converting chamber of combustible gases
containing carburetted hydrogen, with heated air thereby producing a further
supply of highly heated steam that assists in the conversion of the carbonates,
substantially as herein described.
2-The herein described improved construction of kiln for decarbonating
carbonate of strontia or baryta by means of superheated steam, wherein the kiln
and the retorts in which the steam is superheated are raised to the requisite.
temperature by the introduction of separate currents of heated air and producer
gases which enter into combustion at various points of the kiln and in the
chambers containing the superheating retorts.
•
3-The use in combination with the construction of kiln referred to in the
preceding claim, of a chamber or retort I communicating with the top of the kiln,
into which the moist carbonate is introduced in order to be dried by the hot gases
escaping from the kiln, substantially as herein described.
4-The use for presenting the molten monohydrate of baryta in a subdivided
state to the action of the superheated steam, of perforated basic aluminous or
magnesian blocks, placed in the bottom of the kiln, substantially as herein
described.
:
.