An Improved Process for the Manufacture of Sulphate of Ammonia, the Recovery and Purification of the Bye Products Arising therefrom, and Apparatus therefor.
Year: 1887

page_text: Date of Application, 6th July, 1887.
Complete Left, 23rd Mar., 1888
Complete Accepted, 27th Apr., 1888
An Improved Process for the Manufacture of Sulphate of Ammonia,
the Recovery and Purification of the Bye Products Arising
therefrom, and Apparatus therefor.
We, H. C. BULL AND COMPANY, Limited and WILLIAM EDWARD SENDEY,
Engineer, both of 31 Poultry, London in the County of Middlesex do hereby declare
the nature of the said invention to be as follows:-
A
According to this Invention we use any substance containing alumina preferably
clay which is made to undergo a preliminary purification, or washing before being
converted into a sulphate, which purification may be as follows. The clay is thoroughly
mixed with an excess of water and passed over a series of weirs arranged in such a
way that the downward currents will be swifter than the upward rising currents.
sufficient number of these weirs is used to free the clay from all its free foreign
substances, such as pebbles, sand and the like. After passing the weirs it is allowed
to settle in large tanks, or vais from which the water when it becomes perfectly clear
is drawn off and used for preparing additional clay. The clay is then conveyed into
a specially arranged sulphuric acid chamber, or chambers where sulphuric acid is
being produced. These chambers may be made round of any suitable material,
preferably lead and are slightly inclined. Each is provided with a shaft in the centre
having propeller blades, or an equivalent device which convey the clay mixed with
sulphuric acid and water from one end say the lower end where it is fed in, to the upper
end where it is discharged. In passing through the chamber the larger portion of the
alumina is converted into a sulphate and held in solution in the water.
After settling
the clear liquid solution of sulphate of alumina is removed to a suitable vessel where
it can be brought in contact with gaseous ammonia derived from any source, such as,
either from gas liquor, sewage, or decaying animal, or vegetable matter. The
alumina which is precipitated as a hydrate is dissolved with muriatic acid in order to
convert all foreign substances into chlorides. It is then subjected to a high
temperature, preferably on a hearth consisting of pure alumina where all the chlorides
are vaporised. The sulphate of ammonia solution is evaporated to dryness in the
usual way.

page_text: The novelty and economy of this process consist in producing sulphate of alumina
and by that means avoiding all the expense of concentrating sulphuric acid. When
carried out at a Gas Works a large portion of the sulphurous acid necessary to make
sulphuric acid can be obtained from the oxide of iron used in purifying the gas.
By the above described process it will be seen that sulphate of alumina is first
produced and is held in solution in water, and ammonia in a gaseous state is brought
into intimate contact with such sulphate of alumina, by which means sulphate of
ammonia is formed and alumina precipitated as a bydrate.

page_text: An Improved Process for the Manufacture of Sulphate of Ammonia,
the Recovery and Purification of the Bye Products Arising
therefrom, and Apparatus 'therefor.
We, H. C. BULL & Co., Limited, and WILLIAM EDWARD SENDEY, Engineer,
both of 31 Poultry, London, do-hereby declare the nature of the said invention and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
According to this Invention we use any substance containing alumina, preferably
clay and subject it to preliminary purification or washing, prior to the process
hereinafter specified of converting it to a sulphate; the purification may be as
follows: The clay-assuming this to be the aluminous substance used is thoroughly
mixed with an excess of water, that is, the quantity of water used. is sufficient to
reduce it to a loose or thin slurry or slush. The liquor or mixture is then passed over
a series of weirs arranged in vessels or chambers in such a way that the falling or
downward currents which the slurry is subjected to will be swifter than the upward
rising currents. The repeated reversals of direction of the current, and the
accelerations and retardations of velocity of flow of the slurry, effect the required
depositions and freeing of the heavier foreign substances such as pebbles, sand and the
like, from it.
After undergoing the above described process of purification the slurry is drawn off
from the weir chambers and is allowed to settle in large tanks or vats, from which the
excess of water, when it becomes perfectly clear by the settlement of the aluminous
material, is drawn off. The material is then conveyed or delivered into a specially
arranged chamber or chambers where sulphuric acid is being produced, and is mixed with
the material. These chambers may be made round of any suitable material, preferably
lead, and are slightly inclined. Each chamber is provided with a shaft in the centre
having propeller blades or equivalent devices, which convey the clay mixed with
sulphuric acid and water from one end, say the upper end, where it is fed in, to the
lower end where it is discharged. In passing through the chambers the larger portion
of the aluminous material is converted into a sulphate of alumina and held in solution
in the water. The solution is now again passed into settling tanks, and after settling,
the clear liquid solution of sulphate of alumina is removed to a suitable vessel, where
it can be brought in contact with gaseous animonia in any known way, whereby the
sulphate of alumina is converted into sulphate of amnionia, and alumina is precipitated
as a hydrate. The sulphate of aminonia solution is evaporated to dryness in the usual
way. The ammonia used in the process may be derived from any source, such as
from gas liquor, sewage, or decaying animal, or vegetable matter.
The by-product alumina which is precipitated as a hydrate is purified by dissolving
it with muriatic acid in order to convert all foreign metallic substances contained in it
into chlorides, and is then subjected to a high temperature-préférably on a liëarth

page_text: consisting of pure alumina-where all the chlorides are vaporised and pass off from
the material, leaving alumina substantially pure.
The novelty and economy of this process of manufacturing sulphate of ammonia
consists chiefly in producing sulphate of alumina, and by that means avoiding all the
expense of concentrating sulphuric acid as under ordinary processes.
This sulphate of alumina produced as herein described constitutes an article of
manufacture under this process, and may be used as such for any desirable purpose.
When the herein described process is carried out at gas works a large portion of
the sulphurous acid necessary to make sulphuric acid to be employed in the process
can be conveniently obtained from the oxide of iron used in purifying the gas.
In the above described process sulphate of alumina is first produced and is held in
solution in water, and ammonia in a gaseous state is brought into intimate contact
with such sulphate of alumina, by which means sulphate of ammonia is formed, and
alumina precipitated as a hydrate.
Having thus specified generally the object or objects and nature of the Invention,
its description will first be proceeded with in reference to the drawings, by way of
explaining more fully the construction of the apparatus, operation and effects; and
objects of certain portions of the Invention. The following is a description of the
special apparatus designed to apply the process of manufacturing sulphate of ammonia,
the method of which has been above explained.
DESCRIPTION OF THE DRAWINGS.
Figure 1. is an elevation in section of the apparatus or plant for purifying the
aluminous material (clay) of heavier impurities.
Figure 2. is a section at xx, figure 1 of same, and
Figure 3. is a plan of the apparatus.
Figure 4. is an elevation in section of the apparatus in which the alumina is
converted to sulphate of alumina.
Figure 5. is a cross section at Y Y Figure 4 of same, and
Figure 6. is a plan of the apparatus partly in section.
Referring in the first instance to the first three figures of the drawings, A represents
the clay and water mixer set above the apparatus; B the depositing vessels set in a
pair clearing doors and D, D' are the upper and lower weirs respectively,
arranged closely together to cause a swift fall or downward flow of the solution.
;
It will be seen the vessels B are set in a terrace or stepped form for the purpose of
providing for the overflow from one vessel to another.
The level of the solution in each vessel will evidently be that of the lip of its
overflow weir D', and the depth of the lip of the weirs D into the solution will be such
as will be sufficient to give the proper downward direction to the flow of the solution.
The distance between the sets of weirs is such that the rise of the solution in each
vessel B will be slow in comparison to the downfall into it. These differences of
velocity will be directly proportional to the differences of the sectional area in the
horizontal planes of the narrow spaces between the weirs D' and D), and the broader
spaces between one weir D of a vessel B and the next overflow weir D'.
In operation the water and clay is fed into the mixer A, which is provided with a
rotary stirring shaft a having blades thereon; and in passing through it the water and
clay become incorporated, resulting in a solution of such clay; the water being in
excess as above stated. The solution leaves the mixer at the end opposite to that at
which the material is fed into it, and falls into either one or the other of the parallel
series of vessels B. In flowing over the weir D¹, its course is directed by the weir D
downwards, and the space between these weirs being comparatively small the solution
receives an acceleration of velocity.
This flow is stopped upon coming near to the bottom of the vessel, and reversed,
assuming an upward direction; but owing to the increased area of the liquid in the
horizontal plane, in which it will now rise, the velocity of the solution will be retarded,
but the previous rapid descent will have caused some of the heavier impurities to be

page_text: deposited upon the bottom of the vessel, and which will not rise again with the bulk of
the solution.
Thus by these repeated accelerations, reversals and retardations of the velocity of
the flow of the solution, substantially all the impurities such as pebbles and sand, are
separated from the aluminous material, and when the solution is drawn off from one
of the sets of tanks B the impurities may be removed through the aperture covered by
the doors C.
It will be evident when one set of vessels B is being used for depositing the
impurities, the other set may be preparing for use, by having the impurities deposited
in it removed.
As above stated after the solution is thus freed of its impurities it is drawn off
from the tank B by any suitable means, and delivered into tanks wherein it is allowed
to become quiescent. In coming, and when it has come to this condition, the solution
will settle, that is to say, the aluminous material containing a sufficient quantity of
water to keep it in solution, will fall to the bottom of the tanks; the water in excess
of that quantity being forced above the surface of the solution and will consequently
float upon the solution and will become quite clear.
The solution now ridded of its excess of water is treated with sulphuric acid.
The apparatus above mentioned according to this Invention for this purpose is
illustrated in Figures 4, 5, and 6, of the drawings, in which F designates the chambers
having central shaft and propeller blades G, operated by bevel gearing, alumina
feed hopper g, sulphuric acid supply pipe or passage g, and water cooling case or
jacket The sulphurous acid is made by burning pyrites. Nitrous acid is made in
the usual way by mixing sulphuric acid and nitrate of soda together in the vessel K.
This nitrous acid is made for the same purpose and acts in the same manner as in
ordinary processes of making sulphuric acid. The pyrites are supplied in hoppers L,
one of such hoppers being located beneath each of the doors of the troughs K, in the
bottom of which there is provided a crushing roller mounted upon a shaft m which
feeds crushed pyrites into the steam injector n. (The pyrites may be supplied to the
hopper already crushed if desired). This injector may be of any known suitable type
and supplied by steam from the pipe o. The feeding crusher may be any of the
well known types used for feeding coal to steam generators, and the injector is
arranged to supply air in excess of the theoretical quantity required to burn the
pyrites.
The heat caused by the making of the sulphuric acid as above described we utilize to
generate steam. This is effected by passing the hot gases over pendent "Field tubes" I,
supported in the roof of the vessel H in which directing plates h¹ are provided for
the purpose of causing the said gases to pass over the tubes 1 in sets of three rows
each. The gases leave the vessel H and enter the chambers F by the passage g¹, and
in passing through the chambers F become incorporated with the alumina, and convert
it to sulphate of alumina.
It will be seen the material is fed into the upper of the chambers F and travels
towards the communicating union passage f2, down which it is forced, and falls into
the second chamber F. The propellers blades in the chamber convey it back to the
second union passage f³, and so on to the third chamber F, from which, after having
been propelled through it, the solution of sulphate of alumina passes by the pipe f
The sulphate is now delivered into settling tanks of any suitable kind, and when
quiescent and the solution thoroughly settled, the liquid solution of sulphate of alumina
becomes clear, and is then drawn off and conveyed to suitable vessels, where it is
brought into intimate contact with gaseous ammonia; any known apparatus suitable
for the purpose may be used.
The sulphate of alumina so treated is converted to sulphate of ammonia and the
alumina is precipitated as a hydrate.
The sulphate of ammonia thus obtained is now evaporated to dryness in any known
suitable way. The precipitated alumina constitutes a by-product and is purified, that
is, it is ridded of all metallic foreign substances contained in it constituting metallic
impurities, by dissolving it with muriatic acid and then subjecting it to a high

page_text: temperature. This treatment-which is preferably carried on upon a hearth consisting
of pure alumina first converts the impurities into chlorides, and then by the heat,
these chlorides are vaporised and driven off from the alumina.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed or put in practice, we
would remark that we are aware of the existence of settling apparatus, consisting of
weirs and vessels of the type herein described, and we therefore make no claims to the
mere details of the apparatus, except as parts of apparatus for carrying out the above
mentioned manufacture.
What is claimed in respect of the Invention above described is :-
1. The process herein described of manufacturing sulphate of ammonia consisting of
the sub-processes as follows, that is to say:-(I) Mixing aluminous material in
water, (2) Treating the aluminous mixture with sulphuric acid, the said sulphuric
acid being produced directly for the purposes described, and (3) Treating the sulphate
of alumina thus produced with ammonia, all as, or substantially as set forth.
2. For processes for manufacturing sulphate of ammonia of the type herein described,
the apparatus or plant consisting of the sulphuric acid making devices and the mixing
chambers F, with or without an intermediary water heater or steam generator, such as
described, as, or substantially as and for the purposes set forth.
3. In processes for manufacturing sulphate of ammonia in which alumina is
employed, the purification and recovery of the alumina by treating such alumina
precipitated from the sulphate of ammonia as described with muriatic acid, and then
subjecting the dissolved alumina to heat upon a hearth of alumina, whereby the
metallic impurities are first converted into chlorides and then vaporised and driven off,
substantially as set forth.
H. C. BULL & Co., LIMITED.
WILLIAM EDWARD SENDEY.
By Cheesbrough & Royston,
15, Water Street, Liverpool,
Patent Agents.