An Improved Method of and Apparatus for Drying Substances which are Viscous or Semi-fluid in the Hot State.
Year: 1894

page_text: [Communicated from abroad by RUDOLF SCHICHT, of Aussig-on-the-Elbe,
Bohemia, in the Empire of Austria, Soap Manufacturer.]
An Improved Method of and Apparatus for Drying Substances
which are Viscous or Semi-fluid in the Hot State.
1, HENRY HARRIS LAKE, of the Firm of Haseltine Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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:-
My invention relates to a method of and apparatus for drying substances which
in the hot state have a viscous or semi-fluid consistency and are consequently
liable to burn to the heating surfaces of the drying apparatus heretofore
employed. It is the object of my said invention to completely obviate such.
burning.
I have found that this object may be accomplished if the drying is effected,
not as heretofore in one operation, but in two phases by first incorporating under
pressure the entire heat required for the drying with the substance to be dried
and then causing the substance sufficiently heated throughout to pass into a vessel
preferably also heated but subjected to a low pressure.
In carrying this method into practice I prefer to use an apparatus which
consists of a vessel subjected to pressure, a heating device and a vacuum vessel,
and which is adapted to be connected with an air compressor, a source of heat
and a vacuum pump or an exhauster.
Such an apparatus is represented in diagram in the accompanying drawing,
A closed vessel A consisting of metal and made sufficiently strong to withstand
great pressure is connected by a pipe a¹ with an air compressor and by a pipe s with
a heating device B. This vessel is preferably so constructed that it can with-
stand a pressure of from 15 to 18 atmospheres to render it suitable for high
temperatures.
On the vessel A used as a monte-jus I arrange as fittings a flanged connection a,
to which is joined a pipe a¹ serving for the admission of compressed air and
provided with a pressure gauge u, a manhole e and a flanged connection b for a
safety valve.
A second closed metallic vessel B communicates with the first vessel or monte-
jus A through a pipe s furnished with a cock c. In this vessel is provided a system
of pipes C designed for heating the substance to be dried. This system consists
of a great number of pipes which are let at their two ends into a metallic plate so
as to form steam-tight joints.
This system of pipes is closed above and below by funnel-shaped beads. In the
lower head terminates at i the pipes coming from the vessel A, while the upper
head is connected with a vacuum vessel D by the pipe t. The vessel B is also con-
nected with a source of heat, such as a steam boiler, steam or air superheater or
the like, by a pipe g through which the heat designed for heating the substance is
introduced. The water of condensation collecting in the vessel B can be removed
through the discharge cock h.
In the vacuum vessel D I provide inclined planes o o in order to obtain a better
listribution of the substance to be dried. In this vessel D may be arranged
heating pipes p for supporting the boiling of the substance. The connection of the

page_text: vessel D with a vacuum pump is established by a pipe m. A cock is included in
the pipe t which connects the vessels D and B with each other. On terminating
the operation the dried substance may be removed by a discharging device r.
The devices used merely as auxiliaries, such as the air compressor and the
vacuum pump or the exhauster are not represented, as the arrangement of the
same is of no importance as far as the essential feature of the present invention is
concerned. Moreover the fittings of the apparatus are only characterized
sufficiently for enabling the improved apparatus to be understood, the construction
of these parts being immaterial.
For effecting the operation by means of this apparatus I proceed as follows:
The vessel A is filled through the man-hole e or in any other suitable manner with
the substance to be dried. Then the air compressor is set in motion to force air
into the vessel A, such air being preferably caused to pass through a heating
device prior to its admission into the drying apparatus. As soon as the pressure in
the vessel A has attained the desired degree, which may be seen by the pressure
gauge u, a steam valve provided at g and the cock c on the vessel A are opened at
the same time.
I can regulate the heating of the substance passing from the vessel A to the
vessel B by the cock on the vacuum vessel D in such a manner that the substance
in front of the said cock will always be under pressure and flow into the vacuum
vessel at a boiling temperature corresponding to such pressure. In the equaliza-
tion of the pressure and temperature here taking place the heat in excess which is
inherent in the substance becomes free and vaporizes a corresponding portion of
the water contained in the substance. Accordingly this substance enters the
vacuum vessel D in a highly heated state and while energetically boiling flows
over the inclined planes arranged in the upper part of the said vacuum vessel.
Of course the vacuum is maintained in the vessel D by a pump or an exhauster
as long as the operation lasts; this is terminated when the substance to be dried
has passed completely from the vessel A into the vessel D and has cooled therein
to such an extent that it discontinues to boil, whereupon it may be removed
through a discharging device arranged at the lower part of the vacuum vessel.
It is necessary to heat the substance under pressure in order to prevent the
boiling of the substance contained in the vessels A and B and the pipes belonging
thereto, for the substance would otherwise burn to the inner sides of the pipes Č
and render the operation impossible.
The pressure supplied by the air compressor must therefore always be higher
during the operation than the pressure produced by the heating of the substance
in the system of pipes C. For watching the pressures and temperatures I provide
pressure gauges and thermometers in a suitable manner on the vessels A and B.
In order to prevent the rapid lowering of the temperature of the substance in the
vessel D and thus keep this substance hot and boiling for a longer time it is
expedient to arrange in the upper part of the said vessel D also a system of
pipes p p for heating by steam or hot air and to surround the lower part on the
outside with a non-conducting material.
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 :-
First. A method of drying substances which are viscous or semi-fluid in the hot
state, by introducing under pressure the entire amount of heat necessary for the
drying into the substance, and then causing the latter to pass into a vessel subjected
to a low pressure and which may also be heated.
Second. An apparatus for carrying out the method set forth in the first claim,
comprising a vessel A, subjected to pressure, a heating device B having an interior
system of pipes C, and a vacuum vessel D in the interior of which may be arranged
inclined planes o o, the heating of the substance being regulated by means of a

page_text: cock on the vacuum vessel in such a manner that the substance to be dried will
always be under pressure in front of this cock and will flow into the said vessel D
at a boiling temperature corresponding to this pressure.
Dated this 25th day of September 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.