Process and Apparatus for Obtaining Barium Oxide and Barium ............... Hydroxide from Barium Carbonate.
Year: 1897

page_text: 187
Date of Application, 1st June, 1897
J
PROVISIONAL SPECIFICATION.
...
Process and Apparatus for Obtaining Barium Oxide and Barium
…………… Hydroxide from Barium Carbonate.
"..
"
I, WALTHER FELD, Chemist, of Villa Feld, Linz /Rhein, Germany, do hereby
declare the nature of this invention to be as follows:
?
Whilst it is possible to expel the carbon dioxide from calcium carbonate. and
strontium carbonate and to obtain a good yield of calcium oxide and strontium
oxide respectively by heating the carbonates in ring. kilns or shaft kilns fired
either directly or with generator gas, barium carbonate is "decomposed with
difficulty in this way, so that only from -40 to 50 per cent. of the carbonate burnt
can be converted into oxide: This phenomenon has generally been explained by
saying that barium carbonate parts with its carbon dioxide at a considerably
higher temperature than is the case with strontium carbonate or calcium carbonate.
It is possible, however, to assign the incomplete decomposition of barium
carbonate to another cause. For it appears that in the method which has hereto-
fore been commonly employed for burning barium carbonate the partly decomposed
lumps, consisting chiefly of barium carbonate and barium oxide, become covered
with a fused coating, which prevents the penetration of the heat into the interior
of the mass so that further decomposition of the, barium carbonate is rendered
difficult and the escape of the evolved carbon dioxide is hindered. As barium
exide, in common with the oxides of the other alkaline earth metals, calcium and
strontium, is infusible, the formation of a fusible, material must be due to the
presence of impurities. The impurities which would form a fusible mass with the
barium oxide and carbonate are silica,, iron oxide, alkalies and the like, contained
in the bricks or the ash of the coal. It follows that the barium carbonate to be
burnt must not be allowed to come into contact with materials containing, or
capable of yielding such substances; thus, barium carbonate should not be burnt
in admixture with such fuel as coal.
But even when those parts of the kiľŉ with which the hot barium carbonate
comes in contact are not constructed of fire-brick, and admixture of coal ash with
the carbonate is avoided, there is still a superficial fusion or sintering of the
burnt barium carbonate whereby its further decomposition is interfered with.
Experiments have shewn that this fusion and the consequent incomplete con-
version of the barium carbonate into barium oxide are due to the formation of
barium hydroxide. Like all gaseous fuel, the generator-gas, used for, working the
ring kilns in which the burning of barium carbonate has heretofore been carried
out contains water vapour, derived either from the moisture mechanically held in
the fuel or from the combustion of the hydrogen contained in the fuel. This
water converts the barium oxide, formed by the decomposition of the barium
carbonate into barium hydroxide. The presence of even a small proportion of
barium hydroxide in a hot mixture of barium carbonate and oxide induces a fusion
of the mass which takes place on the outer layer where the barium oxide has become

page_text: hydroxide. As a result of the fusion of the external layer the lumps of barium
carbonate bake together so that eventually the contents of the kiln fuse on to its
bed and the passages for the generator gas are stopped up.
The foregoing observations have led to the present process for obtaining barium
oxide from barium carbonate, in which the heating is effected so that, by exclusion
of impurities which fuse with barium oxide and of water vapour which converts
the oxide into fusible hydroxide, no fusion of the mass can occur.
Fusion is prevented by not allowing the heated material to come in contact with
bricks which contain silica or alumina etc., and by excluding water vapour from
the heated material while this is still undergoing decomposition.
For this purpose, fuel which has been dried beforehand is employed; and since
the different fuels contain hydrogen which by combustion yields water, the one
chosen must be poor in hydrogen.
Such a material is anthracite or coke. The air admitted for the gasification of
the fuel and for the combustion of the generator gas is also dried; this is effected
by passing the air over one of the known materials used for drying gases, such as
quicklime. The simplest way of drying the air consists in passing it over already
burnt barium oxide which has been so far cooled that the small proportion of barium
hydroxide formed by the action of the moisture of the air on the barium oxide will
not become fused, while the moisture is completely removed by the oxide.
In practice the process here described may be carried out in several ways.
Example, the ordinary ring kiln used for burning bricks may be employed, in
which case the dry fuel, free from ash and hydrogen is disposed in the chamber
between the columns of material to be burnt these being arranged in a stellate
form.
Or the gas heated chamber kilns may be employed, in which case only dry fuel
as free as possible from hydrogen is used in the generator instead of ordinary coal
or brown coal.
A convenient form of kiln consists of a shaft lined with fire brick except in
those places where the barium oxide comes in contact with the wall at a high
temperature at which parts magnesia bricks are employed.
Up to the zone where the barium oxide is formed the shaft is covered by an
air tight iron sheathing to prevent access of moisture through the wall. Gas
producers, of which there may be four, are arranged around the base of the shaft
in the centre of which there is a deep pit for receiving the barium oxide which is
withdrawn in lumps by lateral openings at the bottom.
The air for combustion is admitted by pipes to the pit where it passes through
the barium oxide thus becoming heated and dried and cooling the oxide. The
barium carbonate is fed through a valved charging hopper at the top of the shaft.
Instead of employing a shaft kiln as described above, a number of chambers may
be loosely charged with bricks of barium carbonate, there being adjoining each of
these chambers a combustion chamber charged with fuel containing a minimum
of hydrogen.
The chambers operate in rotation, some being heated up while some may be
at full heat, and some containing the already burnt material through which air
passes becoming heated and dried to support the combustion in others of the
chambers. The carbon dioxide and other gases from some of the chambers are
led through the fuel in others of the chambers drying it and driving off most of
its hydrogen in form of hydrocarbons.
The barium carbonate is charged into this kiln in lumps.
In case arificially prepared barium carbonate is used it is advantageously
fashioned into bricks, coal being used if desired as an admixture.
In carrying out this process exclusion of water vapour must be complete, since
even the presence of from 3 to 5 per cent. of barium hydroxide suffices to cause the
superficial fusion of the lumps.
Whereas by the former method of obtaining barium oxide by burning barium
carbonate a yield of only 40-50 per cent. of the material used was realised, it is

page_text: possible by the present process to decompose about 96 per cent. of the barium
carbonate.
Dated this 1st day of June 1897
ABEL & IMRAY,
Agents for the Applicant.
Process and Apparatus for Obtaining Barium Oxide and Barium
Hydroxide from Barium Carbonate..
I, WALTHER FELD, Chemist, of Villa Feld, Linz ª/Rhein, Germany, 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:
Whilst it is possible to expel the carbon dioxide from calcium carbonate and
strontium carbonate and to obtain a good yield of calcium oxide and strontium
oxide respectively by heating the carbonates in ring kilns or shaft kilns fired
either directly or with generator gas, barium carbonate is decomposed with
difficulty in this way, so that only from 40 to 50 per cent. of the carbonate burnt
can be converted into oxide. This phenomenon has generally been explained by
saying that barium carbonate parts with its carbon dioxide at a considerably
higher temperature than is the case with strontium carbonate or calcium carbonate:
It is possible, however, to assign the incomplete decomposition of barium
carbonate to another cause. For it appears that in the method which has hereto-
fore been commonly employed for burning barium carbonate the partly decomposed
lumps consisting chiefly of barium carbonate and barium oxide, become covered
with a fused coating which prevents the penetration of the heat into the interior
of the mass so that further decomposition of the barium carbonate is rendered
difficult and the escape of the evolved carbon dioxide is hindered. As barium
oxide, in common with the oxides of the other alkaline earth metals, calcium and
strontium, is infusible, the formation of a fusible material must be due to the
presence of impurities. The impurities which would form a fusible mass with the
barium oxide and carbonate are silica, iron oxide, alkalies and the like, contained
in the bricks or the ash of the coal. It follows that the barium carbonate to be
burnt must not be allowed to come into contact with materials containing, or
capable of yielding such substances; thus, barium carbonate should not be burnt
in admixture with such fuel as coal.
But even when those parts of the kiln with which the hot barium carbonate
comes in contact are not constructed of fire-brick, and admixture of coal ash with
the carbonate is avoided, there is still a superficial fusion or sintering of the
burnt barium carbonate whereby its further decomposition is interfered with.
Experiments have shewn that this fusion and the consequent incomplete con-
version of the barium carbonate into barium oxide are due to the formation of
barium hydroxide. Like all gaseous fuel, the generator gas used for working the
ring kilns in which the burning of barium carbonate has heretofore been carried
out contains water vapour, derived either from the moisture mechanically held in
the fuel or from the combustion of the hydrogen contained in the fuel. This
water converts the barium oxide, formed by the decomposition of the barium
carbonate into barium hydroxide. The presence of even a small proportion of
barium hydroxide in a hot mixture of barium carbonate and oxide induces a fusion

page_text: of the mass which takes place on the outer layer where the barium oxide has become
hydroxide. As a result of the fusion of the external layer the lumps of barium
carbonate bake together so that eventually the contents of the kiln fuse on to its
bed and the passages for the generator gas are stopped up.
The foregoing observations have led to the present process for obtaining barium
oxide from barium carbonate, in which the heating is effected so that, by exclusion
of impurities which fuse with barium oxide and of water vapour which converts
the oxide into fusible hydroxide, no fusion of the mass can occur.
+
Fusion is prevented by not allowing the heated material to come in contact with
so-called "acid" bricks which contain an excess of silica etc., and by excluding 1
water vapour from the heated material while this is still undergoing decomposition.
There are two methods of effecting these objects. The carbonate to be burnt
may be packed in crucibles, tubes or small retorts made of refractory material which
is not acid and these heated in the kiln; the carbonate will thus be protected from
contact with the furnace gases and even if moist fuel is used the barium oxide will
not be converted into hydroxide.
The simpler method is to employ. fuel. which has been dried beforehand and
since the different fuels contain hydrogen which by combustion yields water, the
one chosen must be poor in hydrogen. Such a material is anthracite or coke.
The air admitted for the gasification of the fuel and for the combustion of the 1
generator gas is also dried; this is effected by passing the air over one of the known
materials used for drying gases, such as quick-lime. The simplest method of
drying the air consists in passing it over already burnt barium oxide which has
been so far cooled that the small proportion of barium hydroxide formed by the
action of the moisture in the air on the barium oxide will not become fused while
the air is completely, dried by the barium oxide.
The process here described can be carried out in several ways. For example,
the ordinary ring kilns used for burning bricks may be employed, in which case
the dry fuel, free from ash is disposed in the chamber between the columns of
material to be burnt; this being arranged in a stellate form. Or gas heated
chamber kilns may be employed, in which case dry fuel as free as possible from
hydrogen and ash is alone used in the generator instead of ordinary coal or brown
coal.
Two special forms of apparatus have been found applicable for this process.
The first, which is particularly applicable, is a shaft kiln shewn in Figures 1
to 5 of the accompanying drawings.
Figure 1 is a vertical section through the kiln on line ef Figure 4.
Figure 2 is another vertical section on line gh Figure 4.
Figure 3 is a sectional plan on the line a-b Figure 1.
Figure 4 is a sectional plan on the line c-d Figure 1.
Figure 5 is a section on the line -m Figure 3.
The kiln is provided with generators v, of which four are shewn, in direct com-
munication with it; these generators are specially shewn in Figure 6. The shaft
of the kiln is lined with fire-bricks. Except at those places where the barium
oxide comes in contact with the kiln at a high temperature; these parts are lined
with basic bricks a, since such bricks contain no constituents capable of fusing
with barium oxide.
The kiln is provided at the top with a gas exit 9 and a Barry hopper b.
Externally it is covered up to a part above the zone where the barium oxide is
formed, with an air-tight iron sheathing which prevents the moist air from passing,
by diffusion through the bricks, into the interior of the kiln.
At the bottom of the shaft c the barium oxide is withdrawn in the form of
lumps which are not fuséd and are only superficially sintered.
The air necessary for the combustion of the generator gas passes through the
barium oxide at the tubes d, so that it is deprived of its moisture at a temperature
insufficient to fuse' the barium hydroxide formed; at the same time the air under-
goes a preliminary heating. The generator gas issuing from the canals k enter

page_text: the kiln through the ports f and burns with the air entering at the bottom of
the kiln.
The kiln is also provided with stirring holes s and a cleaning door n.
The generators are shewn in Figure 6, o being the gas ducts and p the ash pit
doors.
kare
Another kiln for carrying out this process is shewn in Figure 7. This is a
chamber kiln which is provided, not with a single generator, as is usual, but with
a generator situated beside and belonging to each chamber. k, k².
chambers in which the barium carbonate is arranged in the form of bricks.
g¹³, 9²
gare generators which are fed with fuel containing the smallest
possible proportion of hydrogen. a¹, a²
a are cleaning openings for the
generators and are capable of being closed air-tightly. 61, 62.
66 are the
doors of the chambers, which are kept closed during the burning. d, d are the
ports through which the exit gases from the kilns pass into the flue f leading to
the chimney a.
"The burning in the separate chambers is so arranged that the material in one
series of chambers is completely burnt while some of the rest of the chambers are
at their highest temperature and others are being heated up. When, for example,
chamber of which the generator g³ is full of coke is at its highest temperature /
and are full of already burnt material and their generators gl and g² are burnt
out.
The air enters chamber k¹ at 61 and passes through the still hot barium oxide
contained in this chamber and in 2, being heated and dried during its passage, and
then enters the bottom of the generator through the openings s for the gasifica-
tion and combustion of the fuel. The flanies pass through the channels t into the
chamber and the combustion gases having heated up the material to be burnt
leave the chamber by the openings w, and traverse the generator in their
passage to chamber The chambers and which are thus traversed by the
waste gases, are full of fresh barium carbonate ready to be burnt, which is thus
dried and heated. As soon as the temperature in 3 begins to decrease, the
generator is filled with coke, which is thus dried and deprived of its small
content of hydrogen, in the form of hydrocarbons, by the heat of the waste gases
from . Thus as soon as the expulsion of carbon dioxide begins in chamber
only anhydrous gases are entering therein.
The barium carbonate is charged into the kiln in lumps. In case artificially
prepared barium carbonate is used it is advantageously fashioned into bricks, coal
being used if desired as an admixture.
In carrying out this process exclusion of water vapour must be complete, since
even the presence of two to five per cent. of barium hydroxide is sufficient to cause
the superficial fusion of the lumps.
It is possible by the present process to decompose about 96 per cent. of the
barium carbonate as against a yield of from 40 to 50 per cent. obtained by the
processes' formerly used.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what
I claim is:
1. A process for converting barium carbonate into barium oxide consisting in
heating the barium carbonate by gases which are free from water vapour and in
excluding water vapour from the material being burnt.
2. The method of carrying out the process referred to in Claim 1 consisting in
the use of fuel which is free from water and evolves no water during its combustion;
the use of the waste gases resulting from the heating of the barium carbonate for
drying fresh barium carbonate and fuel; and the use of already burnt barium
oxide for drying the air necessary for combustion of the fuel.
3. Apparatus for carrying out the process and method referred to in Claims 1
and consisting of a shaft kiln lined with basic magnesia bricks and generators
fed with dry fuel nearly free from hydrogen, the said kiln and generators being

page_text: sheathed with iron to prevent diffusion of air into the interior inlets for secondary
air into the kiln being provided which are so arranged that the said air first passes
through barium oxide at the bottom of the kiln, substantially as described with
reference to the accompanying drawings.
4. Apparatus for carrying out the process and method referred to in Claims 1
and 2 consisting of a chamber kiln with a generator next to each chamber and so
arranged that the waste gases from the burning process shall heat the material to
be burnt and the fuel in other chambers, in order to dry them, and that the air
for the combustion of the fuel shall be dried by being passed through already burnt
barium oxide, substantially as described.
Dated this 25th day of February 1898.
ABEL & IMRAY,
Agents for the Applicant.