Improvements in and relating to the Manufacture of Nitric, Nitrous, and Sulphuric Acids and Oxides of Nitrogen.
Year: 1899

page_text: Improvements in and relating to the Manufacture of Nitric, Nitrous,
and Sulphuric Acids and Oxides of Nitrogen.
I, ARTHUR MCDOUGALL, of 1, Egerton Road, Fallowfield, in the County of
Lancaster, Corn Merchant, do hereby declare the nature of this invention to
be as follows:-
My invention relates to a new process and apparatus for manufacturing nitric
and nitrous acids and nitrogen, oxides and also to the manufacture of sulphuric
acid by supplying nitrogen oxides when produced by my new process or apparatus
to the sulphuric acid chamber.
The object of my invention is to cause the nitrogen and oxygen of the air to
combine chemically on a commercial scale to form nitric acid, nitrous acid or
nitrogen oxides in an economical manner.
It has been known to scientific chemists for some years that the nitrogen of
the air may be caused to burn to oxides of nitrogen or nitric or nitrous acid by
passing a strong electric current through terminals placed in air beyond the
sparking distance and on supplying a flame, the nitrogen then burns with the
production of flame and the formation of nitrogen oxides or acid fumes and
these fumes have been absorbed by alkalis to produce nitrates but strong liquid
nitric acid has not been obtained even in laboratory experiments.
No practical use has, however, been made of this laboratory discovery.
My invention consists in applying this discovery to the manufacture of nitric
and nitrous acids and oxides of nitrogen by means of apparatus which can be
carried out in practice on the commercial scale.
My new apparatus consists broadly of a vessel of earthenware or other suitable
material connected to a dynamo and transformer producing alternating currents
of high voltage. Terminals within the said vessel are placed such a distance
apart that sparking does not occur, while immediately adjacent to the said
terminals and within the vessel a small master flame is sometimes placed. The
vessel is connected at one end to an air supply, and the other end of the vessel
is connected to a suitably arranged condensing apparatus or to the towers or
chambers of a sulphuric acid plant. Upon the passage of the current from the
dynamo and transformer the small master flame starts a nitrogen flame burning
between the terminals or, this nitrogen flame may be self started by adjustment of
the said terminals and this combination of the nitrogen and oxygen results in
clouds of nitrous or nitric vapour which are continuously produced as long as
the current passes and provides the necessary energy. The vapour is led off
to the condensers with or without the addition of water vapour or is led to the
towers or chambers of a sulphuric acid plant in order to supply the necessary
-nitrogen oxides..

page_text: In carrying the invention into effect for the production of nitric acid, the
improved apparatus is arranged as follows-A number of vessels of earthenware
or other suitable material are arranged in sets and have placed within each of
them one or more pairs of terminals, a convenient distance apart, to prevent
sparking, and to each pair of terminals within a vessel, and adjacent thereto,
a small master flame is provided or means for adjusting the distance of the said
terminals. Dynamos or dynamos and transformers to produce alternating currents
of high voltage (8000 volts sometimes being employed) are connected to the
terminals and to one set of ends of the vessels a supply of air preferably hot
is led, while to the other set of ends of the vessels condensers are coupled. These
condensers may be of the type usually employed in nitric acid plants such as a
series of Woulfe condensers or earthenware worms and further the said vessels
themselves may be jacketed and employed as condensers. When hot air is
employed the air may be heated by coils arranged external to or within the
vessels through which an electric current passes supplied from a suitable dynamo,
or the air may be heated in any other convenient manner.
The production of nitric acid is effected by passing the alternating currents
of high voltage after the master. Hames have been ignited or the terminals
adjusted. A nitrogen flame starts burning within each vessel between the
terminals, and the oxygen and nitrogen combine and form clouds of nitric and
nitrous acids, and oxides of nitrogen. The temperature of a nitrogen flame is
supposed to be much below its temperature of ignition, but as long as the
current passes to supply energy the flame keeps burning and continuously forms
nitric acid from the air and water vapour present. This nitric acid vapour is
drawn off into the condensers and from there into suitable receivers. It is to
be understood that where a cheap supply of pure oxygen can be obtained it
may be added as desired to the air supply to increase the product.
Nitric acid in liquid form is sometimes employed in the manufacture of
sulphuric acid and is an expensive item in such manufacture. In the method
commonly in use in this country sulphuric acid is added to nitrate of soda
pots hung in the sulphur furnaces and the nitrogen oxides so generated mix
with the burner" gases. It is evident that a nitric acid plant constructed in
accordance with this invention could be arranged with or without condensers and
the nitrous or nitric vapours caused with or without the addition of water spray
or vapour to mix with the burner gases directly in the chambers or be sent
into the Gay Lussac" or other tower and be taken up by the strong acid to
supply the necessary nitrogen oxides for the production of sulphuric acid, thus
providing a cheap and highly efficient means of adding the said nitrogen oxides
in such a plant.
"
"
23
Where water power is available it is evident that a very economical production
of either nitric or sulphuric acids could be effected.
Improvements in and relating to the Manufacture of Nitric, Nitrous,
and Sulphuric Acids and Oxides of Nitrogen.
I, ARTHUR MCDOUGALL, of 1,, Egerton Road, Fallowfield, in the County of 5
Lancaster, Corn Merchant, do hereby declare the nature of this invention and in

page_text: what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:
-
My invention relates to a new process and apparatus for manufacturing nitric
and nitrous acids, and nitrogen oxides, and also to the manufacture of sulphuric
acid, by supplying nitrogen oxides to the sulphuric acid chamber when produced
by my new process or apparatus.
The object of my invention is to cause the nitrogen and oxygen of the air to
combine chemically on a commercial scale to form nitric acid, nitrous acid or
nitrogen oxides in an economical manner.
It has been known to scientific chemists for some years that the nitrogen of
the air may be caused to burn to oxides of nitrogen or nitric or nitrous acid in
presence of water vapour by passing an induction electric current through terminals
placed in air beyond the sparking distance and on supplying a flame the nitrogen
then burns, with the production of flame, and the formation of nitrogen oxides or
acids.
No practical use has, however, been made of this laboratory discovery.
My invention consists in applying this discovery to the manufacture of nitric
and nitrous acids and oxides of nitrogen by means of apparatus which is practical
on the commercial scale.
My new apparatus consists generally of a vessel or vessels of earthenware or
other suitable material provided with terminals connected to a dynamo and trans-
former or to a dynamo alone producing alternating currents of high
voltage. The terminals within the said vessel
or vessels are placed at
such a distance apart that sparking does not occur and they are so arranged
that they may be easily adjusted. The vessel or vessels are connected at one
end or ends to an air supply and at the other end or ends they are connected
to suitably arranged condensing apparatus; or to the towers or chambers of a
sulphuric acid plant. Upon the passage of the current from the dynamo, or
dynamo and transformer, and on adjusting the terminals a nitrogen flame starts
burning in each vessel or vessels. In some cases a master flame may be employed
to start the nitrogen flame. The resulting combination of the nitrogen and
oxygen produces clouds of nitrous or nitric vapour in a continuous manner as
long as the current passes to provide the necessary energy. The vapour is led
off to the condensers with or without the addition of water vapour or is led to
the towers or chambers of a sulphuric acid plant to supply the necessary nitrogen
oxides.
The accompanying drawings illustrate arrangements of apparatus constructed
to carry the invention into effect.
Figure 1 is a vertical sectional elevation of the improved apparatus.
Figure 2 is a sectional plan on the line a b of Figure 1.
Figure 3 is a transverse section on the line cd of Figure 1.
Figure 4 is an elevation partly in section of three of the vessels or generators
on an enlarged scale,
Figure 4 is a sectional plan of one of the generators showing the terminal
holders, with the adjusting disc in section.
Figures 5 and 6 are respectively transverse and longitudinal sections illus-
trating diagrammatically an arrangement of the generating vessels, modified from
that shown in Figures 1 to 3.
Throughout all the modifications illustrated similar letters denote similar
parts.
Referring to these figures more particularly to Figures 1 to 4, sets or
groups of generators A are provided, constructed of earthenware or other suitable
material and preferably of a conical shape as shown. Each vessel A is placed
vertically and is fitted at or near its bottom portion with a pair of terminals BB
(Figure 4) arranged to slide within. suitable insulators CC so as to be capable
of easy adjustment. The terminals BB are constructed preferably of a highly

page_text: infusible alloy of platinum and iridium or they may be constructed of copper or
carbon or other suitable material, and provided with tips of platinum iridium
alloy. Each vessel is connected at its upper end to a vapour carrying pipe D,
while at its lower end it is connected to an air supply pipe E. The vessels A
are arranged in groups of three between radiating sets of upper and lower pipes D
and E. A main air supplying pipe F carries and communicates with the sets
of similar air pipes E connected to the bottom of the vessels A, while a vapour
conducting pipe G likewise communicates with and carries the radiating pipes D
into which the upper ends of the vessels A lead. A number of condensing towers
are arranged, with their upper portions H filled with any suitable condensing
packing, such as broken glass providing interstices and therefore large con-
densing surfaces, and with the lower portions H¹ divided off to act as reservoirs
for the condensing liquid. It is preferred as a rule to cause the condensing liquid
to assume a level some little way up into the broken material, above the parti-
tion m dividing the two portions I and II of each tower. A series of pipes G¹,
G2, G3, connect the upper portion H of each tower to the lower portion H¹ of
its adjacent tower and the upper portion H of the last tower of the series connects
by a pipe G with a mixing tank I. A test pipe W fitted with a tap is attached
to the pipe G for withdrawing samples of gas for analysis. The tank I is
fitted with three taps X, Y and Z by means of which air or oxygen or air enriched
with oxygen may be introduced. A rotary blower J or pump of suitable con-
struction communicates on the one side with the mixing tank I by a pipe K and
on the other side by a pipe F¹ with the air supply pipe F for the generators.
Overhead tanks L are arranged communicating by pipes M with the top por-
tions H of the respective condensing towers. The bottom portions H³ of the
towers communicate by trap pipes N (Figs. 1 to 3) with a corresponding number
of enclosed tanks O. These enclosed tanks O in turn communicate by pipes P
with a corresponding number of closed air pressure tanks Q. From the bottom
of these air pressure tanks pipes R are carried up to discharge into the overhead
tanks L. A pipe line S communicates with each of the air pressure tanks Q
and delivers compressed air from any suitable source into these tanks when
required; and shut off cocks or valves T are provided in the pipes P so that
the communication between the sets of tanks O and Q may be interrupted when
necessary.
The current for the generators A is supplied by an alternating current dynamo V
which distributes to the generators at a voltage of about 5.000 volts from a pair
of mains V¹. With the generator terminals BB arranged in parallel with the
dynamo circuit as shown each generator circuit being provided with a choking
coil V2 or coil of sufficient self induction, a perfectly steady are may be obtained
between each of the pairs of terminals BB. A single dynamo may be arranged
to supply the whole of the generators direct, or one or a number of step up
transformers connected in parallel with a low voltage dynamo may be employed.
As a convenient means of rapidly adjusting each pair of terminals BB, they
are arranged to slide in the insulators CC, and a suitable insulating adjusting
disc such as e is provided with spiral slots f which gear with roller ends of
bracket pieces 7 (Figure 4a) attached at their other ends to the terminals BB
outside of the generators.
The operation of the apparatus constructed as herein before described is as
follows; The dynamo V and blower J are driven from any convenient source
of power. The terminal adjusting discs e are operated so as to bring the
terminals BB within sparking distance and then to gradually separate them,
striking an arc between each pair of terminals. A nitrogen flame is thus
started in each generator and the resulting combination of the nitrogen and
oxygen produces clouds of nitric and nitrous vapours filling all the generators A;
and the flame of burning nitrogen continues, forming these vapours so long as
the electrical energy is supplied. The air tap or valve X is opened a certain

page_text: distance to admit air into the tank I and the blower J is put into operation with
its shutters revolving in such a direction that the air is sucked out of the tank I
through the pipe K into the blower and from there sent along the pipe F¹. A
vacuum is formed by this operation of the blower J, which causes the nitrogen
oxide vapours to travel into the radial pipes D along the pipe G and successively
through the condensing towers by the pipes G1, G2, G3, and by the pipe G
into the tank I. These nitrogen oxide vapours in the course of their passage
through the towers bubble through the water in the bottom portions H', and in
the upper portions H, pass over the surfaces of the broken material there meeting
water trickling from the overhead tanks L by the pipes M. With the condensing
water slightly above the partitions m as indicated in the drawings the bubbles
of nitrogen oxide vapours are more effectively broken up and dissolved. It is
evident that the water will condense the vapours, and that in each successive
tower away from the generators, less and less vapour will be present, and the
apparatus is so proportioned that, when the last tower is reached, all the nitrous
vapours have been absorbed. The air which has been unacted upon passes into
the tank I, mixes with fresh air, which enters by the tap X and is returned to
the generators by the blower J. Samples of the gases from the towers may
be withdrawn at the tap W for the purpose of a rapid analysis. The weak acid
which forms in the bottom portions H of each tower passes into its corresponding
closed tank O by way of the pipe N, and at certain intervals the taps T on the
pipes P are opened, and allow the weak acid to pass into the closed tanks Q.
The taps T are now shut and the compressed air allowed to pass along the pipe S
into the tanks Q driving the weak acid up the pipes R into the overhead tanks L.
It is evident that by the continued circulation of the condensing liquid in this
manner through the towers the nitrogen oxide vapours will gradually be taken
up till any desired density of acid obtained. When the desired density has
been obtained, the acid may be drawn off from any of the tanks by suitable
valves, cocks or syphons.
Instead of using water in the tanks L to condense the fumes from the vessels A,
I may use sulphuric acid of about 170 specific gravity and thereby produce a
nitro-sulphuric acid which is well adapted for use in the manufacture of nitro-
glycerine, nitrocellulose, nitro-benzene, and other nitro compounds.
In order to increase the yield of oxides of nitrogen the air which is supplied
to the generators A may be enriched with oxygen. This oxygen which may be
obtained by any of the methods well known to chemists and is admitted to the
mixing tank by either of the taps Y or Z. Or air rich in oxygen, such as is
obtained by trapping the last portion of the air on evaporation of liquid air,
may be admitted to the tank I. Or the enriched air may be obtained by the
method of successive solution of air in water, whereby the oxygen being more
soluble than the nitrogen, the air on extraction, after solution, has its last
portion largely enriched in oxygen.
In the arrangement shown in Figures 1 to 4, inclusive the generators A are
arranged in radiating sets communicating with a central air supply pipe F and
a vapour pipe G. Only one radiating set is shown, but it is evident that any
desired number of sets to suit the capacity of the condensing towers might be
employed without departing from the subject of the present invention. Figures 5
and 6 illustrate diagrammatically an example of a different arrangement of
generators effecting the same purpose. A generator shed h has arranged within
it a double series of shelves i. The air supply pipe F¹ and the nitrogen oxide
vapour withdrawal pipe G are connected respectively to smaller pipes F and G.
ten pairs of such respective smaller pipes being shown. Branching off at right
angles to the pipes G are smaller pipes D communicating with the tops of the
generators A placed upon each set of shelves i. Also branching off at right
angles from the pipes F are smaller pipes E communicating with the bottom
portion of the generators A. In this generator shed h a battery of 500 generator
yessels is shown; and the main pipes F¹ and G₁ which respectively supply air

page_text: to, and withdraw vapour from, these generators are arranged in a blower or
equivalent circuit similar to the modification first described. The arrows show
the direction of passage of the entering air, and of the nitrogen oxide vapours
produced.
In the manufacture of sulphuric acid it is necessary to use nitric acid in the
liquid form, or in the form of vapours of oxides of nitrogen and the nitric acid
is an expensive item in such manufacture. In the method commonly used in
this country sulphuric acid is added to pots of nitrate of soda, resting on the
brickwork of the flue conveying the products of combustion from the pyrites
burners, and the nitrogen oxides so produced mix with the burner gases." It
is evident that nitric acid plant constructed in accordance with this invention
might be arranged without condensers, and the nitrogen oxide vapours allowed
to pass into the sulphuric acid chambers with the burner gases." Or, the
plant with its condensers might be employed and the liquid nitric acid formed
drawn off into the tanks of the "Gay Lussac" or other tower and allowed to
flow down the tower so as to bring the acid in contact with the burner gases
in their passage to the lead chambers. Where water power is available it is
evident that a very economical production of either nitric or sulphuric acids
may be effected.
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. A process for producing oxides of nitrogen and nitrous and nitric acids
by combustion of air consisting in passing the air through a vessel or vessels
in which are placed the terminals of an electric circuit or circuits between which
terminals a high voltage alternating electric current discharge takes place pro-
ducing a flame of burning nitrogen, the resulting products being afterwards
collected and condensed, substantially as hereinbefore described.
2. In a process for producing oxides of nitrogen and nitrous and nitric acids
by combustion of air, as specified in Claim 1, causing the resulting products to
circulate through condensing apparatus to trap the acids and oxides, the remain-
ing air being returned to the vessel or vessels in which the electric discharge
takes place, substantially as herein before described.
3. In a process for producing oxides of nitrogen and nitrous and nitric acids
by combustion of air as specified in Claim 1, supplying the vessels in which
the electric discharge takes place with air enriched with oxygen, substantially
as and for the purpose hereinbefore described.
4. In a process for producing oxides of nitrogen and nitrous and nitric acids
by combustion of air as specified in Claim 1, arranging the electric discharge
circuit or circuits in parallel with the electric supply circuit, said discharge
circuit or circuits being provided with a suitable choking coil or coils, substan-
tially as and for the purpose herein before described.
5. In a process for producing oxides of nitrogen and nitrous and nitric acids
by combustion of air, as specified in Claim 1, the arrangement of vessels, such
as A in communication with an air supply, and a vapour exit, substantially as
described with reference to the accompanying drawings.
6. In a process for producing oxides of nitrogen and nitric and nitrous acids
by combustion of air, as specified in Claim 1, the combination of a vessel or
vessels in which the electric discharge takes place with condensers and means for
continuously supplying air to the vessels, substantially as herein before described.
7. In a process for producing oxides of nitrogen and nitric and nitrous acids
by combustion of air, as specified in Claim 1, the arrangement of condensers
with collecting tanks and air pressure tanks, substantially as and for the purpose
hereinbefore described.
8. In a process for production of oxides of nitrogen and nitric and nitrous

page_text: acids by combustion of air as specified in Claim 1, utilising the resulting pro-
ducts directly in the manufacture of sulphuric acid, substantially as hereinbefore
described.
Dated this outh day of Noveloci 1030.
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and,
25, Cross Street, Manchester, Agents.
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and,
25, Cross Street, Manchester, Agents.