A New or Improved Method of Mixing and Dissolving Solids and Liquids and in Apparatus therefor.
Year: 1892

page_text: Date of Application, 15th June, 1892
Complete Specification Left, 15th Apr., 1893-Accepted, 15th June, 1893:
PROVISIONAL SPECIFICATION.
A New or Improved Method of Mixing and Dissolving Solids and
Liquids and in Apparatus therefor.
I, OSWALD HAMILTON of The Northfleet White Lead Company, Northfleet,
in the County of Kent, Chemical Engineer, do hereby declare the nature of
this invention to be as follows:-
The object of this invention is a new and improved method of, and apparatus
for, the mixing of solids and liquids, or different liquids by an inert gas, or for
the solution of a solid in a liquid, or a liquid in a liquid, when gases or vapours
are given of during the said process of mixing or dissolving, and which it is
desirable to retain in the vessel during the process.
Although air and other gases have been used for agitating liquids or mixtures
of solids and liquids, so far as I am aware, the air or gas has always been allowed
to escape after the air or gas has been scrubbed for the purpose of removing any
vapours which it may have been desirable to recover for further use, and which
otherwise would have been lost.
For agitating and mixing in closed vessels, mechanical agitators have been
previously used which when the solution employed was corrosive, caused great
trouble and expense as by friction, when a fresh surface is constantly exposed to
the action of the corrosive liquid.
For the purpose of explaining the working of this invention I will proceed to
describe its application to the solution of litharge in ammonium acetate, in the
manufacture of white lead, for which process it is particularly effective, as litharge
when added to the solution, unless immediately and violently agitated therewith,
hardens into a cake which is only dissolved with great difficulty and is the cause of
the destruction of mechanical agitators usually employed.
In this improved process, a vessel called the digestor, lined with lead and fitted
with a steam coil provided with snifting and relief valves, is partially filled with a
solution of ammonium acetate. On the top of the vessel is a hopper containing the
litharge which can be fed in by mechanical means so that the vessel is always kept
closed.
Within the vessel and at its upper part just below the cover, is a perforated pipe
or ring, or cone or the like, connected to the suction pipe of a gas compressor or
suitable double acting pump for compressing gas, and at or near the bottom of the
said vessel is a similar but smaller perforated discharge pipe attached to and leading
from the delivery side of the aforesaid gas compressor or pump. This latter pipe
ring is however smaller and half the diameter of the vessel or digestor, the perfo-
rations being so arranged that the air or gas is discharged downwards to and away
from the centre of the vessel.
The aforesaid suction pipe is provided with a snifting valve so that should there
be any escape on the discharge side of the pump, or should the pressure of the gas
above the liquid fall too low during the cooling of the contents of the vessel, or
when the gases or vapours given off coudense or redissolve in the liquor, so tending
to form a partial vacuum which might cause the collapse of the lead lining in this
particular case, the desired pressure may be restored.
The top of the digestor is fitted with a relief valve so arranged that when the
pressure rises beyond that desired owing to the increasing temperature or by the
pressure due to the evolution of gases or vapours given off during the process,
the excess may be allowed to escape. In this particular case the snifting valve is
fitted to the gas space containing vapours of ammonia, above what is known as the

page_text: mother liquor tank, while the relief pipe dips below the surface of the liquid in the
aforesaid tank and any vapour given off is thus saved.
Now it follows that when the pump is set in motion, a volume of the gas
employed will be drawn from the top part of the digestor but at the same time
an equivalent volume will be driven out through the discharge pipe at a pressure
depending upon the head and resistances of the liquid or mixture in the vessel;
the gas passing through the liquid violently agitating it during its passage into
the gas space at the top of the vessel, and so on continuously while the pump
is in motion. As during the aforesaid process of dissolving litharge in a solution
of ammonium acetate, ammonia is given off, it will be seen that the pressure in
the vessel will increase, but the relative volumes and pressure at the suction and
discharge of the pumps will remain the same and be dependent upon the head,
consistency and resistance of the mixture as before.
Another advantage possessed by this method is that while in other apparatus,
agitators and pumps must be made of special and costly alloys, and the pipes
must be made of lead to withstand the corrosive action of the ammonium acetate,
in this process the pipes outside the vessel and to and from the gas compressor
or pump, can be made of iron as well as the pump itself, since the iron is only
subjected to vapours of ammonia given off during the process of solution which
have practically no action upon this metal; in this way great economy is effected.
Although I have here given as an illustration, the application of this inven-
tion to the manufacture of white lead it is to be understood that I do not
confine myself to its application to that particular process, as it may be employed
with equal efficacy in many other manufacturing processes.
Dated this 15th day of June 1892.
OSWALD HAMILTON.
COMPLETE SPECIFICATION.
A New or Improved Method of Mixing and Dissolving Solids and
Liquids and in Apparatus therefor.
I, OSWALD HAMILTON of The Northfleet White, Lead Company, Northfleet,
in the County of Kent, 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 :—
The object of this invention is a new and improved method of, and apparatus
for, the mixing of solids and liquids or different liquids by an inert gas or any
suitable gas, or for the solution of a solid in a liquid, or a liquid in a liquid, when
gases or vapours are given off during the said process of mixing or dissolving, and
which gases it is desirable to retain in the vessel during the process.
3
Although air and other gases have been used for agitating liquids or mixtures of
solids and liquids, or liquids and liquids; so far as I am aware, the air or gas has
always been allowed to escape after the air or gas has been scrubbed for the
purpose of removing any vapours which it may have been desirable to recover for
further use, and which otherwise would have been lost.
For agitating and mixing in closed vessels, mechanical agitators have previously
been used, but where the solution was corrosive, the working parts in contact, were
rapidly worn away, as the friction of the parts in contact repeatedly exposed fresh
clean surfaces to the action of the corrosive liquid. Again, when iron or other
vessels are lined with some other metal, as for example, sheet lead, the lead lining
sometimes bulges out from the sides, and the arms or stirrers of the agitator
may catch the lining and tear it away or wear a hole through it in a short
time.
For the purpose of explaining the working of this invention, I will proceed to
describe its application to the solution of litharge in liquids containing ammonium
acetate, in the manufacture of white lead, for which process it is particularly

page_text: effective, as litharge when added to the solution, unless immediately and violently
agitated therewith, hardens into a cake which is only dissolved with great difficulty
and is the cause of the destruction of mechanical agitators and the lining of the
vessels usually employed.
Referring to the accompanying drawing of which Fig. 1. is a sectional elevation,
and Fig. 2. a plan of the apparatus; the vessel a, called the digester is lined with
lead & fitted with a suitable steam coil (not shown), for raising the temperature of
the liquid contained in the digester, which in this process consists of a solution con-
taining ammonium acetate. On the top of the vessel is fitted a suitable automatic
feeding hopper for introducing the litharge without loss of the gas contained in
the vessel. For the sake of simplicity the hopper is not shown in the drawing.
Any suitable device for introducing the finely powdered litharge may be adopted.
To the top of the cover of the vessel a, are fitted the small iron pipes b, at the
points, c. The pipes b, are connected to the suction pipe d, of the double-acting
gas compressor or pump e; the discharge or pressure pipe f, of the pump e, passes
through a stuffing box g, on the top cover of the vessel a, to the hollow boss or
rose h, fixed to the bottom of the vessel and fitted with radial pipes, i, which
are perforated in a suitable manner.
Instead of the small pipes b, a perforated pipe may be arranged on the inside of
the vessel a, immediately below the cover, and instead of the hollow boss, h, and
radial pipes, i, a system of perforated pipes or rings may be used; any means of
distributing the gas from the pipe f, may be adopted.
The cover of the vessel a, is provided with a snifting valve, k, so that should
there be any escape on the discharge side of the pump, or should the pressure of
the gas above the liquid fall too low during the cooling of the contents of the
vessel, or when the gases or vapours given off condense or re-dissolve in the
liquor, so tending to form a partial vacuum which might cause the collapse of
the lead lining, the desired pressure may be automatically restored.
The top of the digestor is also fitted with a relief valve, n, so arranged that
when the pressure rises beyond that desired owing to the increasing temperature or
by the pressure due to the evolution of gases or vapours given off during the
process, the excess may be allowed to escape. In this particular case the snifting
valve, k, is connected by the pipe, l, with the gas space containing vapours of
ammonia, above the liquor in the mother liquor tank, m, while the pipe, o, of the
relief valve, n, dips below the surface of the liquid in the aforesaid tank and any
vapour escaping through the valve, n, is scrubbed.
Now, it follows, that when the pump, e, is set in motion, a volume of gas will be
drawn from the points, c, at the top part of the digestor, through the pipes, b, and
the pipe, d, to the pump, and at the same time an equivalent volume will be driven
out through the discharge pipe, f, and radial pipes, i, at a pressure depending upon
the head and resistances of the liquid or mixture in the vessel; the gas passing
through the liquid violently agitating it during its passage into the gas space at
the top of the vessel and so on, as long as the pump is in motion.
The means for emptying and filling the vessel a, are not shown in the drawing,
as any suitable and well known method may be adopted.
As during the aforesaid process of dissolving litharge in a solution of ammonium
acetate, ammonia is given off, it will be seen that the pressure in the vessel will
increase, but the relative volumes and pressure at the suction and discharge of the
pump will remain the same and be dependent upon the head, consistency and
resistance of the mixture as before.
Another advantage possessed by this method is that while in other apparatus for
this purpose, agitators and pumps must be made of special and costly alloys, and
the pipes must be made of lead to withstand the corrosive action of the ammonium
acetate, in this process the pipes outside the vessel and to and from the gas com-
pressor or pump, can be made of iron as well as the pump itself, since the iron is
only subjected to vapours of ammonia given off during the process of solution

page_text: which have practically no action upon this metal, in this way great economy in cost
of plant is effected.
Although I have here given as an illustration, the application of this invention
to the manufacture of white lead, it is to be understood that I do not confine
myself to its application to that particular process, as it may be employed with
equal efficacy in many other manufacturing processes.
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 :-
1st. The improved method of mixing solids and liquids or different liquids by an
inert gas or any suitable gas; or for the solution of a solid in a liquid; or a liquid
in a liquid when gases or vapours are given off during the said process of mixing
or dissolving, and which gases it is desirable to retain in the vessel during the
process; as herein set forth.
2nd. In the mixing of solids and liquids or different liquids by an inert gas or
any suitable gas; or in the solution of a solid in a liquid; or a liquid in a liquid
when gases or vapours are given off during the said process, and which gases it is
desirable to retain in the vessel during the process; the drawing of the gas above
the liquids or solids and liquids contained in a closed vessel, heated or not heated,
through a suitable system of pipes, by a pump or other means and forcing the said
gas by means of a system of perforated pipes or rings at the bottom of the closed
vessel, through the liquid & solid mixtures contained within the closed vessel, to
the gas space above, such gas to be again circulated by the pump or other means
for circulating same. Such closed vessel being provided with snifting and relief
valves suitably connected to a closed liquor supply tank, reservoir or pipe for the
purpose of retaining any gas, substantially as described and set forth herein.
3rd. The combination of apparatus for agitating & mixing liquids with liquids
or liquids with solids by any suitable gas substantially as herein described and
shown by the drawing.
Dated this 15th day of April 1893.