Improvements in the Manufacture of Sulphuric Acid and By-products, and in Apparatus adapted to such Manufacture.
Year: 1895

page_text: Date of Application (in United Kingdom), 8th July, 1895
Complete Specification Left, 8th July, 1895-Accepted, 10th Aug., 1895
Improvements in the Manufacture of Sulphuric Acid and By-products,
and in Apparatus adapted to such Manufacture.
I, JAMES DOUGLAS DARLING, residing at 4826 Greenway Avenue, in the City
of Philadelphia, State of Pennsylvania, United States of America, Electrician and
Chemist, 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 :-
The following is a specification of my said invention, reference being had to the
accompanying drawings.
My invention is addressed to the economical manufacture of sulphuric acid by so,
producing one of the necessary reagents for the general process as to incidentally
develop a by-product of high commercial value. I also organize the required
apparatus in such manner as to facilitate continuous and uniform working.
The usual method of supplying the nitrogen compounds required in the commercial
manufacture of sulphuric acid is to decompose nitrate of soda, or nitrate of potash,
by beating it with sulphuric acid to liberate the nitric acid gas, (NHO) which is
then passed, as such, into the Glover tower and there decomposed and utilized in
the necessary reaction. The by-product of this portion of the process is an acid
sulphate of soda or potash, (usually called nitre cake,) having little commercial
value.
I have found that by electrolytically decomposing nitrate of soda, or nitrate of
potash, the liberated gases (NO, 0) may, without conversion into nitric acid, or
further modification, be directly conveyed to the Glover tower and serve the
necessary purpose for the development of sulphuric acid, whilst at the same time
the by-product of such electrolytic action can be obtained in a condition which,
gives it a high commercial value.
I will now proceed to describe the process in connection with a typical apparatus,
some of whose features are of themselves new and the subject of my invention.
In the accompanying drawings
Fig. 1 indicates, without detail, certain general features of a sulphuric acid
plant, shown in side elevation.
Fig. 2 is a vertical central section through one of the vessels in which the
electrolytic action, characteristic of my process, is effected.
Fig. 3 is a transverse vertical section, on the line 3 3, of Fig. 2, through said
vessel.
The scale of the last two figures is obviously much enlarged, as compared with
that of Fig. 1.

page_text: Referring to the general view, A indicates a portion of the group of pyrites
kilns communicating, by means of a horizontal flue, a, with the upright stack or
dust chamber, A', which in turn communicates by a transverse flue, a', with a
Glover tower, A². Within the flue, a, I place the vessel in which the electrolytic
decomposition of the nitrate is to be effected, thus utilizing the heat of the gases for
the pyrites kilns for maintaining, in a fused condition, the nitrate which is to be
utilized.
I prefer to employ a plurality of decomposing vessels, in order that the process
may be practically a continuous one, and in the general view have indicated two.
Any number, however, may be used which the circumstances of the case render
desirable.
These vessels, B and B', communicate by means of pipes, b, b', respectively, with
a common duct, C, leading to the flue, a', and thus discharging into the interior of
the Glover tower, A. Communication between the several vessels and the duct, C,
is controlled by means of valves, as c, c'. A portion of the pipes, b, b², may be of
glass, as indicated at f,, to permit inspection of the interior at those points.
Referring now to the detail views shown in Fig. 2 and Fig. 3, a description will
be given of one of the decomposing vessels as typical of the rest.
-
The vessel, B, is preferably made of cast iron and is substantially rectangular
in form, having an opening at one end of the bottom for a discharge pipe, H,
controlled by a cock, h. A removable cover, D, is secured upon the top of the
vessel, being, however, insulated electrically therefrom by a layer of refractory
non-conducting material, indicated at d. A series of cast iron plates, E, depend
downwardly from the cover to near the bottom of the vessel, B, said plates
being removably secured by means of screw bolts passing through the cover and
provided with nuts, e. A strip, or plate, K, of metal, having less electrical
resistance than cast iron may be advantageously inserted between the cover, D, and
the nuts, e, to facilitate the passage of the electric current.
A supply pipe, F, extends through the cover to a point near the bottom of the
vessel, B, and the discharge pipe, b, for the escape of liberated gases, leads out from
the top. The vessel, B, is electrically connected by means of the wire, J, with the
negative pole of any suitable source of electricity, whilst the plates, E, are similarly
connected by means of the wire, J', with the positive pole thereof. The vessel
itself thus serves as the negative electrode, and the plates, E, as the positive
electrode for the electrolytic action upon the contents.
In practice the vessel is filled with nitrate of soda to the level indicated by the
dotted lines, L. Assuming that the pyrites kilns are in operation, and discharging
the hot sulphurous acid gas, the latter passing through the flue, a, into the dust
stack, A', where it deposits its dust, and thence passes into the Glover tower, A².
The nitrate which is maintained in a fused condition within the vessel, B, is
decomposed by the passage of the electric current, giving off nitrogen peroxide and
oxygen (NO, O). These gases pass through the pipe, b, into the duct, C, and
thence are discharged, as such, into the Glover tower, A2, without conversion into
nitric acid. The nitrogen peroxide there acts directly in the general reaction
necessary for the production of sulphuric acid, the process in this respect differing
as a whole from those in which acid fumes (NHO) are supplied to the Glover
tower, since in this latter case the decomposition of the nitric acid and the
development of nitrogen peroxide must first be effected, whilst by my process the
necessary nitrogen peroxide is developed and introduced in the first instance.
The electrolytic decomposition is continuous within the vessel, B, as long as
nitrogen peroxide is given off. The duration of this action may be ascertained by
observing the color of the gas in the glass portion, f, of the tube, b.
When the nitrogen peroxide ceases to come over, as will be evident by the glass
tube becoming clear, the current is switched on to another vessel, such as B',
similarly constructed, and the process repeated. In the meanwhile the residuum
within the vessel, B, (consisting mainly of sodium monoxide, if nitrate of soda has
been used, or the corresponding salt in other cases,) is run off through the outlet

page_text: pipe, H, and a fresh charge of nitrate of soda is supplied, ready to be utilized as
soon as the action in the vessel, B¹, is complete.
The monoxide of sodium, or similar residuum from the vessels, is dissolved in a
limited quantity of water to form a hydrate, and the undecomposed nitrate, if any
exist, can readily be separated therefrom, leaving a pure caustic solution, which
may be concentrated, by boiling, into caustic soda, in the usual manner.
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. The hereinbefore described process for the manufacture of sulphuric acid and
by-products, which consists in electrolytically decomposing a fused nitrate, directly
conducting the disengaged gases, without further conversion, to the Glover tower,
and recovering the basic residuum of the electrolytic action, substantially as set
forth.
2. In a sulphuric acid plant comprising pyrites kilns, a Glover tower and an
intermediate flue, the combination with said flue of a closed vessel forming a negative
electrode, a positive electrode situated within said vessel, a discharge pipe leading
from said vessel to a point of communication with said tower, and a source of
electricity in circuit with said electrode, substantially as set forth.
Dated this 8th day of July 1895.
CARPMAEL & Co.,
Agents for the Applicant.