Vacuum Evaporating Apparatus.
Year: 1891

page_text: Date of Application, 4th May, 1891-Accepted, 11th July, 1891
COMPLETE SPECIFICATION.
Vacuum Evaporating Apparatus.
We, HUGH BURGESS, of Royer's Ford in the County of Montgomery, State
of Pennsylvania, United States of America, and CHARLES D. DAVIS, of
709 G Street N.W. Washington, in the County of Washington and District of
Columbia, United States of America, Gentleman, 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 :-
This invention relates to vacuum evaporating apparatus.
Referring to the accompanying drawings :
Fig. 1 represents a vertical sectional view of the apparatus complete, all the pans
being shewn in side elevation except the lowest one.
Fig. 2 a vertical sectional view thereof, the enclosed pans being shewn in end
elevation.
Fig. 3 is an end elevation ;
Fig. 4 a detail plan view of one of the pans, and
Fig. 5 a transverse sectional view of the same.
The invention has particular reference to that class of evaporizing apparatus
wherein a series of horizontal evaporating pans are supported, one above the other,
in a vacuum chamber, the liquor to be vaporized being fed, in a continuous regulated
stream, into one end of the uppermost pan and caused to flow, in a thin sheet, over
the steam heated bottom of the same, the liquor escaping vaporization in the upper
pan being discharged from the opposite end thereof into the adjacent end of the
pan next below and caused to flow in the opposite direction over the heated bottom
of the latter, and so on through the whole series of pans, the liquor passing or
flowing over the highly heated bottoms of the pans alternately in opposite directions,
until the residuum is finally discharged through an outlet in the bottom of the
vacuum-chamber, the highly heated vapor being drawn off from the top of the
apparatus, as will more fully hereinafter appear.
The special object of the present invention is to provide the apparatus with
simple means whereby the vapor produced will not only be heated to a much higher
temperature but will also be materially increased in quantity, without increasing
the size and material cost of the apparatus, as will presently appear.
Referring to the drawings by letters, A designates the outer metallic casing
which is of any suitable shape and which is suitably braced interiorly with angle-
irons. Communicating with the upper part of the casing is a vapor outlet V, and
leading out of the bottom is a liquor outlet Y. Supported, one above the other,
upon transverse angle-irons within the casing, is a series of horizontal shallow pans P,
each of which is provided with a steam-space or chamber P₁ under its entire bottom,
steam being supplied to these chambers by means of horizontal pipes S¹ extending
approximately the full length thereof. These steam supply-pipes are extended out
through the ends of the pans and the end of the casing and connected to a vertical
supply pipe S, regulating cocks S* being placed in these pipes between the vertical
pipe and the casing to regulate the amount of steam admitted to the pans. The
condensed steam from the chambers below is conducted off by a series of valved
pipes c, which pass out through one end of the casing and communicate with a
vertical column C, the lower end of which is connected to a steam-trap in the usual
manner.
The liquor to be vaporized is fed in a regulated stream to one end of the upper
ban by means of a valved pipe X, and the opposite end of this pan is provided
with a discharge opening o and a discharge spout or lip I', whereby the unevaporated
iquor may be discharged into the adjacent end of the next pan below, the end of

page_text: this latter pan being provided with an upwardly extending plate or lip 1" to receive
the liquor discharged from the said spout I'. The opposite end of this second par
is also provided with a discharge opening and lip or spout whereby the liquor may
be discharged into the next lower pan, and so on down through all the pans, each
pan being provided with a discharge opening and spout and an upwardly extending
receiving lip I¹¹.
Supported above the bottom of each pan, but in close proximity thereto, is a
horizontal steam or hot air coil S", the longitudinal pipes thereof being separated
from each other a suitable distance and having communication with each other.
These coils are connected together by vertical pipes S¹, and the uppermost and
lowermost coils are connected by means of valved steam-pipes S₁, directly to a
steam-boiler, or to a steam or hot-air superheater, so that all the coils may be kept
constantly supplied with live-steam or superheated air. The water of condensation
from these coils, if steam is used, is conducted off by means of a pipe T con-
nected to the lower pipe S4 and having its lower end sealed by a steam-trap in the
ordinary way.
As shown in Figure 2 at ¹¹¹, the upper side edges of the pans may be provided
with outwardly flaring flanges if desired to catch any liquid that may drip from the
upper pans.
Slides or gates o¹ may be placed at the discharge openings of the pans to regulate
the flow of liquid therefrom.
Operation:
A vacuum is first established in the casing in the usual manner. Steam is then
let into the false bottoms of the pans in suitable volume, and superheated steam at
considerable pressure is admitted to the coils in the pans, after which the liquid to
be vaporized is introduced into the upper pan in suitable quantities. The quantity
of liquor introduced into the upper pan should be sufficient to cause it to flow evenly
in a thin sheet or film over the bottoms of the pans, the depth of liquor in each
of the pans being regulated by the slides or gates at the discharge openings thereof.
The unevaporated liquor from the first or uppermost pan is discharged into the
next lower or second pan, and is then caused to flow in the opposite direction to
the discharge opening of this latter pan, and so on alternately in opposite
directions until it is finally discharged from the lowest pan into the bottom of the
casing from whence it is conducted off by the pipe Y in the usual manner.
liquid in passing over the bottoms of the pans in thin sheets is thereby subjected to
the heat radiated down upon its surface from the horizontal steam coils above.
Thus subjecting the liquid, in thin sheets, to heat both from above and below,
ensures a material increase in the amount of vapor evaporated. By separating the
pipes of the coil so as to permit the vapor to circulate freely around and between
them, the efficiency of the apparatus is further increased. The foam produced by
the violent ebulition of the liquid rises through and around the pipes and is thereby
broken up and thrown back, and whatever liquor is deposited upon the pipes is
rapidly evaporated.
The
Another action of the coils is to heat the vapor rising from the liquid under-
going evaporation in the pans, above the boiling point of this liquor in vacuo.
Thus, if the boiling-point of a liquid in vacuo, is, because of the reduction of the
atmospheric pressure, say 130°, the heat from the coils can raise this vapor
temperature up to 160°, or 30° above its boiling point, and consequently when that
heated vapor is used in the steam space of the next "effect" of the apparatus, its
heating, effect in the steam space in that "effect" is increased proportionally.
We are aware that it is not new to support in a vacuum a vertical series of
inclined evaporating pans provided with false heating bottoms and so arranged that
the liquid to be evaporated is to be fed into the uppermost pan and caused to flow
alternately back and forth over their heated bottoms, and we are also aware that it
is not new to arrange a submerged coil near the bottom of a pan having a steam
heating chamber below its bottom; we do not therefore broadly claim such features
as our invention.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The combination with an evaporating pan provided with a heating chamber
under its bottom, of a superheating surface arranged above and in close proximity
to the liquid line of the pan, whereby the liquid in the pan will be subjected to the
action of heated surfaces both from above and below and the generated vapor
superheated, as and for the purpose described.
2. The combination with an evaporating pan provided with a heating chamber.
below its bottom, and means for maintaining the liquid being evaporated at a certain
level, of an open superheating coil supported above and in close proximity to the
surface of the liquid, whereby the rising generated vapor will be superheated
and the foam broken and thrown back and the quantity of vapor materially
increased, substantially as described.
3. The combination with a vacuum chamber, a pan located therein and provided
with a false bottom, and means for maintaining the liquid in the pan at a certain
level, of a open superheating coil supported above and in close proximity to the
liquid level and means for heating this coil above the temperature of the chamber
under the pan, whereby the foam will be broken and thrown back and the liquid
subjected to heat both above and below and the generated vapor superheated as it
rises through the coil, substantially as described.
4. The combination in a vacuum evaporating apparatus, of a vacuum chamber, a
series of pans supported one above the other in said chamber and provided with
false heating bottoms, inlet and outlet pipes connected to these false bottoms, means
for feeding the liquid to be evaporated to the said pans and maintaining it at a
certain level therein, a superheating coil arranged in cach pan above and in close
proximity to the surface of the liquid therein for the purpose herein set forth and
pipes connecting these coils together and to a source of heat, substantially as
set forth.
Dated this 4th day of May 1891
H. BURGESS,
By L. W., per F. B.
C. D. DAVIS,
By L. W., per F. B.