Improved Method of and Apparatus for Extracting Moisture from Air for Blast Furnaces and Converters.
Year: 1894

page_text: Date of Application, 23rd Oct., 1894-Accepted, 24th Nov., 1894
COMPLETE SPECIFICATION.
[Communicated from abroad by JAMES GAYLEY, of Braddock, in the County of
Allegheny, State of Pennsylvania, United States of America, Manager of
Iron Works.]
Improved Method of and Apparatus for Extracting Moisture from
Air for Blast Furnaces and Converters.
I JAMES JOHNSON of 4 Clayton Square Liverpool in the County of Lancaster
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 :-
Figure 1 shews in elevation a blast furnace and a converter arranged in
accordance with my invention;
Figure 2 shows the air refrigerating apparatus in elevation, partly in longitudinal
section;
Figure 3 is a plan view thereof, partly in horizontal section on the line III-III
of Figure 2; and
Figures 4 and 5 show, in vertical longitudinal section and in vertical cross section
respectively, a modified construction of the refrigerating apparatus.
The successful conducting of all metallurgical operations depends to a great
extent on the uniformity of the various materials used in the process. In operating
blast furnaces and steel converters, one of the most disturbing influences is the
varying amount of moisture in the atmosphere since in both these processes a large
amount of air is consumed for the purpose of oxidation or combustion. The
atmosphere holds in suspension quantities of aqueous vapor varying from 20 to
16 per cent., and its presence in these metallurgical operations is injurious, not only
because it is decomposed in the parts of the apparatus where high heat is required,
and thus absorbs heat, but the fluctuations in the quantity of moisture carried by
the air, produce corresponding irregularities in the conduct of the process, and in
the quality of the product. Thus, in the State of Pennsylvania, United States of
America, from the months of April to September inclusive, the air contains at least
50 per cent. more moisture than the average for the other months of the year, and
often for short periods of time the ratio of difference is very much greater. When
it is considered that when a blast furnace uses per minute one thousand cubic feet
of air containing one grain of moisture per cubic foot, one gallon of water enters
every hour, and that the smaller blast furnaces use per minute eight thousand cubic
feet of air, and the larger ones thirty thousand cubic feet, each cubic foot containing
from two to eight grains of moisture, it becomes apparent that uniform conduct of
the process is rendered practically unattainable. In consuming thirty thousand
cubic feet of air per minute, containing two grains of moisture per cubic foot, sixty
gallons of water per hour are delivered to the furnace, and when the air contains
eight grains of moisture per cubic foot, two hundred and forty gallons are delivered
per hour. As the decomposition of this large quantity of aqueous vapour is
accomplished at the expense of heat, the varying conditions caused by the atmo
sphere alone will be readily appreciated. Thus, in the summer months, because of
the greater content of moisture in the air, two hundred more pounds of fuel, on an
average, are required to produce a ton of pig iron than in the winter months.
These facts make it very difficult for the blast furnace manager to secure uniformity
of product. Variations in the content of moisture in the atmosphere produce
irregularity in the operation of the furnace, and affect the quantity of fuel necessary
to be used, and these varying conditions in turn make irregular the chemical com-
position of the pig metal with reference to its non-metallic constituents, carbon

page_text: silicon &c. The value of the product is thus often impaired, and the uncertainty of
the result which will be attained in any given tapping of the furnace is a matter of
most serious inconvenience.
In the operation of the Bessemer converters, the moisture of the atmosphere and
its variations. in amount are just as troublesome. Its presence in large quantity.
causes a cooling of the metal bath, which interferes with the uniform conduct of the
process and often produces wasteful chilled heats. In order to obviate these bad
effects, it is necessary to charge into the converter a pig iron containing a sufficiently
large content of silicon to raise the temperature of the blow and thus neutralize the
chilling effect of the moisture. Additional fuel in the blast furnace is required to
produce such high silicon metal.
All these sources of irregularity and expense in metallurgical operations are
eliminated by use of my invention, by means of which 1 furnish for the furnace or
converter an air-blast practically free from atmospheric moisture.
In order to fully understand the application of this device, I would explain that
it is intended to be used with blast furnaces for the smelting of ores, and with steel
converters for the conversion of iron into steel, since in both the air is used solely
for the purpose of oxidation or combustion. Blast furnaces are now constructed
with a height of ninety feet and a diameter of twenty-two feet. These are kept
full continuously with a mixture of fuel, ore and flux, and these offer great
resistance to the penetration of the blast, which is admitted at the bottom.
It not
uncommonly requires a pressure of fifteen to twenty pounds per square inch in the
air blast to penetrate this column of material. Likewise in the converter the air is
forced through a bath of metal which frequently weighs fifteen tons, and requires a
pressure of twenty-six pounds per square inch in the blast to penetrate it.
The condensation of moisture from air in rapid motion and consumed in such
large volumes, presents an entirely new set of difficulties not found in any other
processes, and any attempt to remove the moisture from the furnace blast by the
use of chemical agents having affinity for water must necessarily prove
impracticable.
In the practice of my invention 1 remove the moisture from the air and render it
dry, or so dry at least that the percentage of moisture contained in the air is
small and practically uniform, by subjecting it to artificial refrigeration so that its
temperature shall be reduced to zero Centigrade, whereby the moisture is condensed
and may be collected and withdrawn in the form of water, the air being fed to the
furnace or converter under compression, and being maintained constantly under
compression from the time it leaves the blowing-engine until it reaches the furnace.
The blowing engine may be located between the drying apparatus and the blast
furnace or converter, or the drying apparatus may be employed after the blowing
engine, and between it and the furnace or converter, and by my broader claim
I intend to cover either form.
Many forms of apparatus suitable to the practice of the invention may be
employed. I have, however, devised a special apparatus for the purpose, which
possesses many advantageous qualities for treating air travelling with a high
velocity and is claimed specifically by me herein, although the broader claims of
the application are not restricted to its use.
Referring now to the drawings, 2, is the pipe from which the air passes under
high pressure from the air cylinder of the blast engine. This pipe, for a suitable
portion of its length, is surrounded by a casing or chamber 3, having inlet and
outlet pipes 4, 5, so that water may be caused to circulate through the chamber in
order to cool the air which has been heated by compression of the blast engine.
From the pipe 2, the air passes into a chamber 6, which is made larger to give a
greater area of contact, in which is a series of pipes 7, which extend across the
chamber and at their ends open into chambers 8 and 9. By reason of its greater
conductivity of heat, the pipe 7 should preferably be made of copper. The water
or other fluid for cooling the chamber 6 is admitted by pipe 10 into the chamber 8,
and thence it passes through the pipes 7 from one sub-chamber to the other until it
1.

page_text: emerges at an outlet pipe 11 which may conveniently be connected with the inlet
pipe 4 of the chamber 3 so as to deliver the cooling fluids into the latter. The air
being under a back pressure does not expand on entering the chamber 6. A partial
deposition of its contained moisture takes place, which is reduced to a mist by
contact with the refrigerating surface of the pipes. After the air has passed
through the chamber 6 it may enter a second chamber 12 similarly constructed,
except that in this chamber I prefer to obtain a better chilling action by the use of
ammonia as the cooling agent, and therefore construct the pipes 7 of iron. The
cooling agent is preferably anhydrous ammonia, furnished by an ice-making machine
of suitable design, which on evaporation, produces a very low temperature, about
70 degrees below zero Centigrade, though other refrigerants producing intense
cold, such as carbonic anhydride, may be employed. I may, however, use in place
of these refrigerants, in cases where a still lower temperature is required, cold-air
from any dry cold air compressor of suitable design which on expanding, will
produce a temperature of 100 degrees below zero Centigrade. It enters the sub-
chamber 13, and after passing through the pipes 7, in the manner above described,
to the other sub-chamber 14 is taken away through the outlet pipe 15. The
entering air is first cooled by the chamber 3; its temperature is still more reduced
by passing through the chamber 6 among the pipes 7, and in the chamber 12 under
the intense cold produced by the ammonia, the temperature of the air is reduced
below the freezing point, so that its contained moisture is precipitated on the outer
surface of the pipes 7 and collects at the bottom of the chamber from which it may
be drawn off through a pipe 16. In order to provide against any of the precipitated
moisture being carried along in suspension by the refrigerated air, I prefer to
employ a chamber 17 containing a series of grids 18 with small metal ribs, and
preferably placed in slanting position. These grids catch the suspended moisture
or water, which runs down the ribs and is carried off by the drain pipes 19. The
chamber 17 is made so much larger than the chamber 2 that there will be no
retardation due to space occupied by the grids. I may also use a cooling chamber
of construction shown in vertical section in Figures 4 and 5, in which the air passes
through a series of pipes 20, with the cooling agent surrounding them.
Having been cooled in the manner above described and its moisture extracted,
the air is delivered to the blast furnace or converter, through the various pipes
and passages usual to the operation.
In Figure 1, F, represents a blast furnace, into the tuyeres of which the delivery
pipe from the dessicating apparatus delivers the dried air. G, is the blast pipe
connected with the blast furnace, as shown. The air being compressed by the
blast engine E passes through the refrigerating apparatus J (which is the same in
construction as that shown in the figures on the second sheet of the drawing), and
is delivered to the blast furnace through the tuyeres. In similar manner it is
delivered to the converter C.
When the air is cooled subsequently to its compression as shown in the present
drawings, the air cylinder of the engine should, preferably, be jacketed, and cooled
by flowing water in order to reduce the great increase of temperature of the air
which the compression causes.
It will be readily observed that on account of the air being constantly in rapid
motion and under pressure, and the enormous volume required, the methods usually
employed for extracting a portion of the moisture from small volumes of air in
applying it to drying grain, cooling rooms, &c., are not applicable to blast furnaces
and converters, since in many of these methods the air is allowed to expand, which
in itself is the most serviceable refrigerating process, and simplifies the operation
to a great extent, while in my process there is no substantial expansion of the air
prior to its introduction into the furnace.
The mechanical retardation of the current by partitions and grids is avoided in
iny device, the grid-chamber being of such area that the space between the ribs is
sufficient to allow the volume to pass through without retardation.
In my apparatus the current of cooling fluids passing through a series of pipes,

page_text: is directly across that of the air currents, by which I maintain in this short travel
a much lower température than in such appliances where the currents of air and
cooling fluid are longitudinal.
The advantages of my invention will be appreciated by those skilled in the art.
By rendering the air dry or practically dry by refrigeration as described above,
before it is introduced into the furnace or converter and supplying. such dry air
in large quantities under constant compression, the amount of moisture is made
practically uniform from day to day and from year to year. It is thus made easy
for the blast furnace manager to secure uniformity in the character of metal
produced by the furnace notwithstanding varying meteorological conditions, and
without that close supervision which is necessary in furnace practice heretofore in
common use. I. believe I am the first to make this result possible.
Many changes may be made in the form and arrangement of the apparatus
employed, and the air may be cooled either before entering the blowing engine or
after, and used either in blast furnaces or converters, without departure from my
invention, since I consider myself the first to dry the air by cooling it artificially to
0° Centigrade either before or after entering the blowing engine, and maintain the
air under compression from the time it leaves the blowing engine until it enters the
furnace or converter.
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. The method of feeding the air blast to blast furnaces or converters,
which consists in cooling the air artificially to 0 Centigrade, thereby causing
its moisture to be eliminated or reduced to a small and practically uniform
percentage, feeding the dried air under compression into the furnace or converter,
and maintaining it constantly under compression from the time it leaves the blowing
engine until it enters the furnace substantially as described.
Second. The method of feeding the air-blast to blast-furnaces or converters,
which consists in compressing the air, passing it under compression into an enlarged
chamber, but without substantial expansion therein, and cooling it in said chamber
to at least 0° Centigrade, thereby causing its moisture to be eliminated or reduced
to a small and practically uniform percentage, feeding the dried air into the
furnace or converter, and maintaining it constantly under compression from the
time it leaves the blowing engine until it enters the furnace; substantially as
described.
Third. The combination with a blast furnace or converter of a refrigerating
chamber, an air outlet which leads therefrom to the furnace or couverter and
is of smaller diameter than the chamber, and an air compressor connected to the
chamber, whereby the air is maintained under compression during its passage from
the compressor to the furnace or converter; substantially as described.
Fourth. The combination with a blast furnace or converter, of a refrigerating
chamber having a series of pipes arranged to conduct the refrigerating fluid across
the direction of the air current, an air outlet which leads therefrom to the furnace
or converter and is of smaller diameter than the chamber, and an air compressor
leading to the chamber whereby the air is maintained under compression during
its passage from the compressor to the furnace or converter, substantially as
described.
Fifth. The combination of a blast furnace or converter, a pipe for delivering
compressed air thereto, a refrigerating chamber in the line of said pipe, means for
cooling the air therein by a liquid refrigerant, and an air compressor leading to the
chamber, whereby the air is compressed and maintained under compression until it
enters the furnace or converter; substantially as described.
Sixth. The combination with a blast furnace or converter, of a pipe for delivering
compressed air thereto, a refrigerating chamber of larger diameter than the pipe, a
moisture precipitating chamber also of larger diameter than the pipe and into

page_text: which the air passes from the refrigerating chamber, and having grids over which
the air passes, and a pipe leading from the moisture-precipitating chamber to the
furnace or converter; substantially as described.
Dated the 22nd dow of October 1894"
J.
JOHNSON,
Patent Office, 4, Clayton Square, Liverpool.