Improvements in Apparatus for Drying Brewers' Grain and the like.
Year: 1893

page_text: Date of Application, 18th Apr., 1393-Accepted, 16th Sept., 1893
COMPLETE SPECIFICATION.
Improvements in Apparatus for Drying Brewers' Grain and the like.
I, JAMES YATE JOHNSON, of 115 St. Vincent Street, Glasgow in the County of
Lanark, North Britain, Chartered Patent Agent, (a communication to me from
abroad by Charles Herschel Koyl of No. 111 East 45th Street, City of New
York, State of New York, United States of America, Manufacturer), 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:
In apparatus for the successful and economical drying on a large scale of
brewers grain, distillery waste, starch waste etc., it is necessary that the material
should be spread out in thin layers; that these layers should be freely subjected to
currents of hot air; that if (as in practice is the case) these layers are one above
the other, each should be supplied with an independent current of air in order that
no one layer shall depend for its evaporation upon air which has been partly
saturated by passing through or about a previous layer; that, since for economy in
operation, the material is introduced at the top of the kiln aud dumped from one
apron to another in its descent, being always wettest at the top of the kiln and
successively dryer on each succeeding apron, and the wetter material abstracting
heat from the air more rapidly than the drier material, therefore the currents of
air admitted to the kiln at different heights should be of highest temperature
nearer the top of the kiln and of successively lower temperatures nearer the
bottom; aud that an appropriate temperature to be maintained where the air first
strikes the uppermost apron is not far from 800° Fahr. and at a corresponding
point on the lowermost apron not far from 300° Fahr.
The currents of heated air in order to produce the best results should be
introduced at one end of the kiln so as to travel the length of the aprons and then
be discharged from the opposite end of the kiln.
In large kilns however the currents of air introduced at one end of the dryer do
do not maintain lines of flow sufficiently near the horizontal, but have too great a
tendency to mount to the top of the kiln and therefore to leave the lower part of
the drying apparatus unprovided with sufficient heat at the exit end.
In dryers of this relatively large capacity the aprons are for example from
thirty or thirty-five to fifty feet long (I refer now only to their upper or carrying
surfaces), and six feet wide. There are usually from 10 to 16 superposed aprons.
The hot air inlets are at one end of the chamber and the outlets are at the other,
with a view to cause the air to traverse the chamber lengthwise of the aprons.
And the aprons are separated from the inlet wall by a space of say 3 feet, and from
the outlet wall by an even greater interval. Thus we have a kiln, stack or drying
chamber, whose internal dimensions roughly stated are from twenty-five to forty feet in
height, about seven or eight feet in width and from forty-five to sixty feet in length,
and through the length of this chamber, it is requisite, in order to secure the best
results, that the hot fresh air should flow in approximately horizontal lines over
the grain on the aprons, and at temperatures varying with the varying condition of
the grain as it passes from the top to the bottom of the kiln.
The natural buoyancy of the hot entering air, and its tendency to rise lead it to
seek the exhaust at the other end of the chamber by way of the upper part of the
chamber, a tendency which is favored by the interval between the inlet wall and
the adjoining ends of the aprons; which provides a flue space or passage up
through which the heated air can rise unobstructedly, and in fact does rise under
ordinary conditions such as have heretofore existed. The result is that the heat

page_text: to which the grain on the lower apron is subject, practically does not exceed 125°,
although theoretically and to secure the best results it ought to be about 300°.
I have found that this defect can be remedied and that approximately horizontal
lines of flow of the currents of fresh air across the layers of wet material from end
to end of the chamber can be ensured, by providing at different points in the height
of the exit end of the chamber an artificial exhaust, graduated in power from the
lowest to the highest point of exit and being practically sufficient at each point
to offset and overcome the tendency of the hot air entering at corresponding
points at the inlet end of the chamber to rise. The strongest and most powerful
exhaust should be at the lower part of the chamber and those above it should be
proportionately less according to the height at which they are placed.
For example the lowermost exhaust should be say a forty-eight inch exhaust
fan; the one next above should be of less capacity and so on. The uppermost
exhaust or exhausts indeed may be mere exhaust opening communicating with the
discharge flue, the natural draft at this point being sufficient in some cases for the
purpose.
The thing which is of prime and vital importance is the provision at the lower
part of the exit end of the chamber for securing artificial exhaust or suction
sufficient to create at that point the partial vacuum or tendency to vacuum which
will neutralize the tendency of the hot air entering the chamber at and near this
level to rise and will pull it over in horizontal lines towards the opposite end of the
chamber in which the exhaust is located.
I have mentioned a fan as the exhaust appliance, and this I in practice prefer to
use and do use. It will be understood however that for it any other suitable device
for producing the requisite artificial exhaust or suction can be substituted.
A kiln thus provided with artificial graduated suction at its exit end, may have
its heating apparatus and inlets constructed as shown in the American Patent
No. 460,051, of September 22nd, 1891, granted to the communicator or may be
provided with a heating apparatus consisting simply of a furnace and a large
combustion chamber or flue from which openings are formed through the inlet wall
of the kiln. This latter form of heating apparatus is shown in the accompanying
What is essential
drawing which will be presently more particularly referred to.
is that the drying capacity of the air passing over the uppermost apron
shall be greater than that which traverses the lower aprons proportionaly as the
grain above is wetter than that below. The drying capacity of any current of air
is proportionate to its volume multiplied by its absolute temperature. And by the
employment of graduated suction in the manner hereinbefore indicated it is feasible
to obtain large flow of air currents in horizontal lines or approximately so, and of
the volume and temperature required by the varying condition of the grain to be
acted on.
To enable those skilled in the art to make and use my invention I now proceed
to describe the manner in which it is or may be carried into effect, by reference to
the accompanying drawing which represents in longitudinal vertical central section
a kiln or dryer embodying the invention in its preferred form.
I have not deemed it necessary in this illustration of my invention to show the
appliances for driving the aprons and the fans, nor to represent the structural
details of the aprons and fans themselves. They may be of any suitable known
construction; and can be driven by any of the usual power mechanisms employed
for the purpose.
A is the body of the kiln or chamber, a hollow covered brick structure, with a
hole in its top for the feed hopper A', through which the wet grain is fed to the
uppermost aprons. In its inlet end it has at different heights arches or inlet
passages a communicating with the combustion chamber C; these arches or
passages a can be screened by wire gauze or the like to prevent possibility of
sparks from the combustion chamber entering the dryer. This precaution however
is more a nicety than a necessity. The fuel used in the furnace D is coke, which
in itself produces little or no spark or smoke; and as there are wide draft openings

page_text: over the furnace grate (which preferably extends uninterruptedly the width of the
kiln and is about 6 feet deep) there is not that rush of entering air through, and in
the immediate neighbourhood of, the bed of fuel which will occasion sparking.
In the opposite or exit end of the kiln are openings at different heights in which
are placed exhaust fans 6 of varying power and capacity. That which has the
greatest power is located at the bottom, and they thence decrease in capacity
towards the top and they are so graduated and speeded that when in action the hot
fresh air entering through the inlets a at the opposite end of the kiln will be pulled
through or across the kiln to the other end thereof, in horizontal or proximately
horizontal lines, these horizontal currents in their passage traversing the aprons B
lengthwise, and acting on the wet grain or other material spread thereon, by means
of pyrometers, as well as by actual observation of the air currents in the kiln,
through windows formed therein for that purpose, it can readily be determined
when the exhaust fans are so speeded and graduated in action as to secure the end
in view.
The endless aprons B are some ten in number. They are superposed one above
the other, and are staggered so that the material discharged from any one apron
will fall upon the end of the one next beneath. They are mounted on power driven
wheels (usually sprocket wheels which gear with sprocket chains bounding the edges
of the aprons) and the direction of their movement is indicated by the arrows.
Usually I employ wheels 15 inches in diameter, and arrange them one above the
other so that there shall be 24 inches between the centres of adjoining wheels in
vertical series, thus providing a space of 9 inches between the upper ply of one
apron and the under ply of the apron next above.
The combustion chamber is surmounted by a safety chimney or flue c closed by a
sheet iron damper or door d which normally is closed during the time the dryer is
in operation. Should however the aprons cease running for any cause, then the
damper d is opened thus allowing the hot air and products of combustion to pass off
without entering the dryer; otherwise the grain being motionless would be apt to
be overheated and scorched or burnt.
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 1
claim is:
The combination of the chamber or kiln, the series of superposed power driven
staggered endless aprons therein, the hot air inlets a and means for supplying heated
air or gas therethrough, and the exhaust or suction appliances b located at different
heights in the exit end or slide of the chamber, and of graduated power or capacity,
substantially as and for the purposes hereinbefore set forth.
Dated this 17th day of April 1902
J. Y. JOHNSON,
115, St. Vincent Street, Glasgow, Applicant.