Improvements in and Apparatus for the Concentration of Sulphuric Acid.
Year: 1891

page_text: Date of Application, 6th Nov., 1891-Accepted, 12th Dec., 1891
COMPLEIE SPECIFICATION.
Improvements in and Apparatus for the Concentration of
Sulphuric Acid.
I JACQUES LOUIS KESSLER of Clermont-Ferrand in the Republic of France
Chemical Engineer 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:-
This invention relates to improvements in and apparatus for the concentration of
sulphuric acid by means of heated gas and consists in causing the heated gas to act
on large or greatly developed surfaces of sulphuric acid so as to readily concentrate
the acid to its maximum density and even to rapidly volatilize it at an extremely
low temperature. say of 200° Centigrade or less thereby admitting of lead being
used in the construction of the apparatus if desired without the acid becoming
saturated with the lead.
In concentrating sulphuric acid by means of heated gas in apparatus hitherto
employed difficulty has been experienced which has prevented good success owing
to the passage for the gas becoming obstructed by the residues resulting from the
concentration of the acid.
According to this invention this defect is overcome by providing at the outlet
passage of the apparatus and also at the inlet for the hot gas a considerable body
of the acid so as to prevent the passages being obstructed by the residues.
The hot gas is preferably caused to pass through the apparatus by suction rather
than by pressure thereby preventing pressure in the apparatus, and forming a
partial vacuum which causes the lead casing to adhere closely to the sides of the
apparatus thereby preventing leakage and waste of heat. The exhaust may be
produced by means of a steam jet or other convenient means. The troughs or
compartments in which the concentration is effected may be made of any suitable
cheap acid resisting material able to withstand the necessary temperature such for
example as the natural silicious stones (sandstone, lava, gaize of Argonna) or
artificial ceramic material or if desired lead may be employed.
And in order that this invention may be well understood I will describe the same
with reference to the accompanying drawings premising however that the invention
is not restricted to the construction and arrangement of the parts described and
shewn.
Figure 1 is a horizontal section of an acid concentrating apparatus constructed
according to this invention the section being along the line 1-2 in Figure 2,
Figure 2 is a vertical section of the same, taken along the line 3-4 in Figure 1,
and
Figure 3 shows in longitudinal vertical section a modification of the apparatus.
This apparatus as illustrated in Figures 1 and 2 consists of a base trough or
compartment S of sandstone or like material covered or cased with lead and
containing acid to be concentrated, into which trough or compartment the hot gas
enters at the bottom of the apparatus through the pipe O. The gas may be forced
through this pipe into the apparatus by any suitable forcing device but by preference
the said gas is drawn therethrough by suction produced in the outlet passage P
(Figure II) by an aspirator capable of resisting the acid vapours.
The gas from the pipe O enters the passages qq formed in the trough S by walls
or partitions qq and so arranged that the gas in passing from these passages to
passages gq is compelled to come in contact with and pass through the acid layer
contained in the trough whereby the acid is heated so as to produce an active
evaporation which will rapidly concentrate the acid to 66° Beaume.

page_text: This single trough or compartment covered with a suitable dome such as shewn
at and provided with an outlet for the product of evaporation, forms in itself a
complete apparatus according to this invention, but as the gas when passed through
or in contact with a single layer of acid carries a considerable quantity of heat and
also some acid vapours with it it is preferred to cause the gas to pass through or in
contact with another layer or other layers of acid contained in one or more
superposed troughs or compartments as shewn in Figure 2 the acid in these
compartments being colder and less concentrated, extracting from the gas the
excess of heat and acid vapours.
The graduation of temperature and density of the acid from the bottom trough S
up to the highest trough or compartment k is produced by admitting the acid to
the highest compartment through the pipe the acid passes thence down from one
compartment to another by the pipes n n and finally passes from the apparatus by
the cooled discharge pipe fitted at m. In the apparatus shewn in the drawing the
troughs or compartments S deh gf and i are subjected to the greatest heat and
are preferably constructed of refractory material such as sandstone.
The upper troughs or compartments marked j k may if desired be made of similar
material or as shewn they may be made of lead, as at this part of the apparatus the
acid is less concentrated and cooler.
The body of acid which accumulates in the lowest compartment or trough $ and
presents a large surface is divided by the partitions q³ which cause the gas to pass
through the acid as hereinbefore described.
The whole apparatus is covered with sheet lead to prevent leakage.
Thermometers are provided at e e¹ to indicate the temperature so that the
introduction of the acid at I may be regulated accordingly in order to obtain at the
outlet m the required degree of concentration.
Any well known or convenient means may be employed for heating the gas but
it is preferred to use the waste gases from a coke furnace a large fire-grate being
employed in order that the draught may be slow and not carry over the ashes and
care being taken that the passage for the gas into the apparatus is closed when the
fresh fuel is being introduced.
The troughs or compartments d e f g h and so on as shewn in Figure 2 are similar
to those used in a column apparatus for alcohol distilling, but it is evident that
instead of superposing them directly one above another they may be arranged as
steps close to one another, the liquid being caused to flow down in cascades from
one to another in succession.
It is obvious also that the gas may be caused to pass through these troughs or
compartments without passing through the acid but only in contact with the
surface thereof as shewn for example in Figure II with reference to the trough or
compartment f.
Instead of causing the gas to pass through each trough or compartment singly
and in succession as in the arrangement Figures 1 and 2 it may be caused to travel
over several troughs or compartments simultaneously as shewn in the arrangement
Figure III in which the gas entering at P passes simultaneously in contact with
the surface of the acid contained in the base or trough S and the troughs j n¹ i i¹
and hand then over another series of troughs k k arranged above as shewn. These
troughs are preferably made of sandstone or cut lava and the acid runs from one
trough into another below as in the arrangement Figure 2 whilst the gas travels in
the reverse direction as shewn by the arrows.
A large body of acid presenting an extensive contact surface for the gas to act
on is maintained in the base or lower compartment or trough S as hereinbefore
described.
If desired the apparatus may consist of a tower or casing having therein irregular
surfaces or pieces of material unaffected by acid the acid being caused to flow down
over these irregular surfaces whilst the gas is travelling upward or in the contrary
direction. But in this case it is necessary to maintain in the lower part of the

page_text: apparatus a quantity of concentrated acid with a large surface of contact as in the
previously described arrangement and which forms the essential characteristic of
this system.
It is practicable to concentrate acid in the apparatus described by admitting the
gas in a cold condition and heating the acid contained in the various troughs or
compartments by any suitable means for example by metallic tubes (for example
lead tubes or copper tubes covered with lead) the gas being heated by the acid so
as to effect its concentration.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. Concentrating sulphuric acid by causing hot gas to pass in contact with a
greatly developed surface of the acid whereby the concentration of the acid is
enabled to be effected at a lower temperature than heretofore substantially as
hereinbefore described.
2. In apparatus for concentrating sulphuric acid by means of hot gas a chamber
containing a body of concentrated acid at the outlet from the apparatus so as to
prevent obstructions in the outlet passage substantially as hereinbefore described.
3. In apparatus for concentrating sulphuric acid by hot gas causing the said gas
to pass through the apparatus by means of aspirations or suction thereby preventing
pressure in the apparatus substantially as hereinbefore described.
4. In apparatus for concentrating sulphuric acid by hot gas as hereinbefore set
forth troughs or compartments made of refractory materials substantially as and for
the purpose herein before described.
3. In apparatus for concentrating sulphuric acid by hot gas as hereinbefore
set forth the employment of hot gas from a coke furnace substantially as herein-
before described.
6. The combination and arrangement of parts constituting the apparatus for
concentrating sulphuric acid by hot gas substantially as herein before described and
illustrated by the accompanying drawings.
Dated this 6th day of November 1891.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.