Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~48S~60
1 Hot metallurgical coke pushed from slot type coke ovens i8 usually
immediately quenched by spraying lt with a large volume of water. The hot
coke from the ovens i9 conveyed on a quenching car to a spray quenching
station where the car and its contents are drenched with water by spraying
water over the whole surface of the coke until it is quenched. This method
often results in excessive quenching of some areas and leaves up to 20%
moisture in the cold porous coke.
It is very desirable to have the moisture level in coke within
the range of 2-4%. At levels below 2% the coke tends to form a powdery
dust in handling and at moisture levels above about 4%, the transportation
costs due to shipping the excessive water are quite high. The most
important disadvantage, however, with the heretofore employed quenchlng
methods is that the variability of moisture in coke increases as the average
moisture content increases so that one gets erratic blast furnace perfor~ance
from the use of the coke as the exact amount of carbon is difficult to
calculate.
It is therefore an object of this invention to provide a method
of quenching coke which will reduce the moisture content to an acceptable
level below that obtainable by conventional quenching methods and to obtain
more uniform moisture content at the low level. A further object of this
invention is to provide a method of reducing the time required to quench
the coke in car load quantities. Another object of this invention is to
reduce the amount of water required to quench a coke load and thereby
decrease the amount of water being discharged to the atmosphere.
The foregoing objects and others which will become apparent from
the attached drawings and the following description are accomplished in
accordance with this invention by pro~iding a method for the rapid liquid
quenching (usually water) of hot coke by distributing the hot coke on a
quenchin~ surface which is preferably incllned 25 to 35 from horizontal
to form a bed of co~e and flowing a stream of quench liquid through the
bed o co~:e at spaced apart locations so that the quench liquid penetrates
8~360
1 the bed prior to complete vaporization and rapidly quenches the coke asthe vapor and liquid percolate in all directions through the surrounding
bed. It has in fact been found beneficial to dump substantially uniform
streams of quench liquid onto the upper 50% of the surface area of a bed
of coke on an inclined plane quench surface. The stream penetrates the bed
of coke, diffuses down through the hot coke and then flows down the inclined
plane quench surface beneath the hot coke until it comes in contact with
unquenched coke and then percolates through the bed of hot coke quenching
it as it goes. The methoa of this invention is quite contrary to the
supposed and often asserted need for uniform spraying over the bed of coke
which has been proposed heretofore. Contrary to the prior teaching shorter
quench times yielding coke with uniform low moisture are obtained by
quenching over less than the whole surface area with a stream of quench
liquid instead of a spray. The stream should not be greatly diffused before
it strikes the surface of the coke so thæt pene~ration into the bed to a
depth of as much as 8 feet is obtained before complete vaporization. In the
prior practice whereby the quench liquid is sprayed over the entire bed of
the coke, the vaporization is often so forceful that droplets of quench
liquid are carried up in the quench tower without ever contacting the coke.
In the stream quench method of the present invention the quench liquid
penetrates the bed to a substantial depth and quenches more effectively as
shown by shorter quench times and lower residual moisture contents in the
quenched,coke.
Figure 1 is a vertical sectional view of a stream quenching
station of the invention showing a hot coke car beneath a plurality of
streams of quench liquid.
Figure 2 is a vertical sectional view taken along line II-II of
Figure 1.
Figure 3 is a top plan view taken along line III-III of Figure 1.
Figure 4 is a vertical sectional view of a coke quenching station
and alternate apparatus for the strenm qucnching method of the invention.
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~048960
1 Figure 5 is a vertical sectional view showing single stream
quenching by moving the hot car beneath a single discharge of quenching
liquid.
Figure 6 is an enlarged cross-sectional end view of a header
and flow pipe design for multiple stream quenehing.
Figure 7 is an enlarged eross-sectional end view of a single
stream header and pipe design showing the relationship between diameter
and length of pipe.
Figure 8 is a diagrammatic perspective view showing the flow of
queneh liquid through a bed of coke.
Figure 9 is a vertical sectional view of a coke quenching
station showing a preferred oscillating quench system.
Referring to Figures 1 and 2 of the drawing, car 1, filled with
hot coke, 2 to a mean depth of about 3 feet is rolled along tracks, 3,
under a quenehing hood, 4, equipped with a plurality of downwardly directed
1-1/2 inch pipes, 5, eonnected by header, 6, to a quench liquid reservoir
(not shown), by connecting main 7. As shown in Figure 2 substantially all
of the quench liquid, 8, is deposited in about one minute as soon as ear, 1,
is in position under hood, 4, on the upper portion of the bed of coke, 2,
as it rests on inclined surface, 9.
Coke, 2, will be completely quenched and free of "hot spots"
i.e., areas eapable of self-supporting combustion in air, in about one
minute and car 1 may be removed to a coke wharf (not shown~ and coke
containing about 3% by weight uniform moisture content discharged through
gate, 10. ~ith reference to Figure 8, quench liquid deposited on the upper
side of the inclined bed of cok.e 2 penetrates the bed to bottom surface 9
and flows in the direction of the arrows until it contacts hot coke where it
percolates in the dlrections shown and often escapes through the surface of
the bed and impinges on the side of car 1. Some of the-quench liquid may
flow down inclinecl bottom surface, 9, and out beneath gate, 10.
Alternate emboclin~ents are shown in Figures 4 and 5. In the
1048960
1 apparatus illustrated in Figure 4, quench liquid, 8, is dumped from reservoir,
11, onto the upper portion of an inclined bed of coke and flows down
through the coke to bottom surface, 9, and percolates upward analogous to
the diagram of Figure 8. It is possible, but not essential, as discussed
below, to include a plurality of spray nozzles, 13, to spray quench liquid
over the bed of coke as shown in Figure 4. As shown in Figure 5, quench
liquid is discharged through a single large diameter pipe, 12, onto the
high side of the bed of coke as the hot coke car, 1, is pushed along
track 3 under the quench hood, 4, in the direction indicated by an arrow.
Many different types of pipe arrangements as well as other systems,
for example, as illustrated in Figure 4, are possible for flowing quench
liquid rapidly through the bed of coke so that it will percolate up through
the bed. It is sometimes desirable to use a configuration as shown in
Figure 6 where pipes, 5, leave header, 6, from the upper side. Such a
configuration avoids the possibility of plugging due to coke breeze and
other particles becoming lodged in the pipes, an insurance that the flow
from the pipes will be uniform and occur simultaneously. However, as
shown in Figure 7, so long as tne straight length, 1, of the pipe, 5,
extending from header 6 is at least three times and preferably at least 8
timas the diameter, d, a satisfactory stream for penetration of the bed of
coke will be obtained.
Generally speaking the invention is applicable to quenching any
hot relatively porous material ~here short quench times are essential to
achieve low residual moisture content, but the invention is particularly
adapted to the quenching of hot coke from slot type coke ovens. When hot
coke is pushed from slot type ovens into a quench car it does not fall in
a uniform evenly spaced pattern to form a level bed of coke. Instead, the
coke, at a temperature of about 1800-2100F and having a density of about
27-33 lbs/ft3, falls into the moving quench car in irregular piles as
illustrated diagrammatically in Figure 8. The method of the present
invention is particularly adaptable to this type of quenching as the liquid
penetrates the bed ~nd passes in a diffusing stream to the bottom, preferably
--4--
104~60
1 inclined, surface rapidly, where there is a uniform straight-line bed of
coke for it to attack and cool. As the liquid and associated vapors
percolate toward the top of the bed they uniformly, efficiently and quite
rapidly quench the whole bed of coke. Where the liquid escapes in a valley
between two mounds of coke it splashes on the side of the mound thereby
quenching it. Where the liquid rises directly beneath a mound of coke it
continues to quench all the way to the surface. It is essential to the
invention that a stream of liquid capable of substantial penetration of the
bed of coke be employed as opposed to the heretofore employed sprays.
Further the discharge means, for example pipes, should be such that there
is a minimum of diffusion of the quench liquid before it strikes the bed of
coke. In other words the discharge means should be such that there is no
substantial breaking up of the quench liquid into droplets as it falls from
the discharge means to the surface of the bed of coke. ~ow, of course,
any uncontained liquid falling through a gas will tend to break up into
droplets due to surface tension of the liquid. However, if the length of
the fall is not too great there will not be much diffusion of the stream
before it strikes the bed of coke. In practice it has been found that the
distance from the point of discharge to the surface of the bed should be a
maximum of 12 feet preferably less than 6 feet, most preferably 6-8 feet,
depending on the len~th to width ratio of the pipe and the velocity of the
stream. For streams issuing from pipes with a length to width ratio of 8
and a pressure of 4 psi in the header, a distance of 6 to 8 feet is satis-
factory.
It is surprising how deep a bed of hot coke can be penetrated
effectively with the stream quenching method of the invention, but generally
for ease of handling and most effective control of residual moisture a
mean depth of l - 6 feet with a maximum point depth of 8 feet is desirable.
It is preferred to control the depth of coke to a mean depth of 1 - 3 feet
(maximum point deptll 4 feet).
~48~60
1 The time it takes to quench a car of coke is very important for
slot type coke ovens because excessive quench times interfere with pushing
schedules. Also, the residual moisture content is related to the amount
of time the quench liquid is in contact with the hot coke because the
27 - 33 lb/ft3 density coke will rapidly absorb liquid as the hot gases
filling the pores contract on cooling leaving a void which is readily
taken up by the liquid. In other words, the hot coke sucks up liquid as it
is quenched. However, with the distribution of quench liquid obtained when
practicing this invention, short quench times of 45 secs to 1 minute are
common and 45 secs to 1.5 minutes easily obtainable as compared to 1.5 to
3 minutes in conventional spray practice.
The spacing of the streams for quenching can be important for
large surface areas of coke as, for example, a hot coke car having a surface
area of about 600 square feet. For such large areas there must be a
stream to penetrate the bed at least every 5 feet along the length of the
car. In other words there should not be more than 5 feet between downwardiy
directed streams. However, when a longitudinal stream is poured from a
device as shown in Figure 4 or from a single pipe as in Figure 5 sufficient
quench liquid reaches the inclined plane of the bottom and moves down to
start the percolating action in the evenly distributed lower portion of the
bed. Where pipes are positioned over the upper 1/2 of the surface, however,
they should be no more than 5 feet apart and preferably spaced less than
four feet apart.
It is absolutely essential to this invention that the quench
liquid fall in a stream on the bed of coke. As pointed out above this is
contrary to the teaching of the prior art which emphasized spraying water
in relatively fine droplets over the entire bed of coke. However, this
does not mean that a combination of stream flow through the bed of coke and
spray over the coke is not within the scope of the invention. In accord-
ance with one embodiment, and particularly as shown in ~igure 4, stream
flow on the upper 1/2 surface is used to obtain the penetration and per-
1~48960
1 colating action while a relatlvely minor amount of sprayed liquid by
conventional sprays 13 is employed on the lower 1/2 of the bed to meet the
upwardly percolating quench liquid. In practice, it is not necessary to
spray the lower 1/2 of the bed as a satisfactory quench can be obtained in
about one minute using only stream flow. But in some instances where the
upper coke surface is particularly uneven, this technique can prove bene-
ficial.
The pressure on the stream may vary over wide limits but generally
speaking pressures higher than about 8 psi in the header are not advantageous.
Sufficient quench liquid can be gotten through the coke at or below this
pressure and higher pressures tend to unduly disturb the bed of coke causing
pieces of it to fly out of the car.
A perforated header is not satisfactory for the practice of the
method of the invention. Perforations without a length of pipe to direct
the stream result in a spray of quench liquid over the bed of coke. While
a longitudinal stream as with the device of Figure 4 may be used9 most
installations will involve a pipe or pipes descending from the header which
must have a length at least three times its diameter and preferably eight
times. This will create a stream capable of only minimum diffusion in the
first 6 feet of fall before it strikes the bed of coke.
The amount of quench liquid, almost invariably water, is somewhat
reduced below that currently required by conventional practice, however,
this is not nearly as significant as the consistently low residual moisture
levels of 2 -4% by weiRht of coke obtainable by the method of this invention.
The total amount of water applied to the coke usually is about 300 -800
gallons per ton. In order to penetrate the depth of the bed in a conven-
tional hot coke car where the bed depth is a maximum of about 8 feet, the
rate of flow to the "direct contact area" is important. As used herein and
in the claims the "direct contact area" means the area directly under the
stream. The stream should contact the coke at a rate of about 200 - 600
gallons per square foot of direct contact area per minute. In accordance
with one preferred embodiment of this invention all or most quench liquid
1~48960
1 is directed to the high side of the sloping bottom quench car, preferably
the upper 1/2. By this unconventional and previously unrecognized
technique excessive build up of water and flooding of the coke near the
gate is substantially prevented and overquenching in that area is reduced.
It is possible to achieve satisfactory quenching by putting either multiple
streams or a single longitudinal stream onto the upper 1/2 of the bed of
coke without any other application of quench liquid.
Laboratory studies on small quantities of coke have shown that
when using a spray nozzle, very little water passes to the coke below the
top layer until the top layer is nearly saturated. Thus, the top layer
of coke is found to contain 30 - 50% moisture even while the bottom layer
is still incandescent. ~owever, with the stream type impingement of the
present invention the volume of water falling upon a portion of the top
layer of coke is so great that because of the time dependent absorption of
water the top layer could only absorb a fraction of the water available and
the excess water rapidly passes to the lower layers.
Tests were conducted by placing the coke from 30 pounds of coal
consisting of 75% Pittsburgh seam high volatile and 25% Pocahontas seam
low volatile maintained in two pressure test ovens at 2,000F. The coke
was pushed when the thermocouple at the center of the charge reached
1,800F. This produced about 20 pounds of coke which was placed in an
expanded metal basket to give a coke column height of about 18 inches for
Examples 1 - 10 shown in Table 1 and to yield 40 pound charges from the
ovens by using a basket of about 36 inches in height. The basket had an
8 by 10 inch cross section. Water was applied to the basket of hot coke
by spray nozzles as indicated in the table and also by pipes of the jet
type according to the invention which consisted of a 1 or 1-1/2 inch pipe
6 inches long extending from the bottom of a 55 gallon steel drum. ~ quick
operating valve was provided in each pipe to control the flow. With the
basket of coke in position, the valve was opened and the water allowed to
1~48g60
1 flow onto the basket of hot coke. The amount of water used was determined
by measuring the difference in height of water in the drum before and after
the test. After the measured amount of water was allowed to flow onto the
coke and the coke was quenched, it was drained for two minutes. The 18 inch
columns were then loosely divided in~o 2 sections, top and bottom, and the
moisture content determined for each section. The 36 inch column was
divided into 4 sections and the moisture determined for each. In some cases
the basket of coke was moved back and forth under the ~et. In other cases
the jet was applied intermittently. Tests were conducted with 1, 2 and 4
pipes coming from the bottom of the drum. The results of these tests are
summarized in Table 1.
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16~48960 - lo -
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1~4~3960
l In a typical large commercial scale quench, a quench car 50 feet
long by 12 feet wide having a sloping bed at an'angle of 30 from the
pusher side to the gate side of the car and containing coke to an average
depth of about 1.5 feet is pushed beneath a quench tower with said car
having a horizontal area of 600 ft2 and four longitudinal rows of 1-1/2 inch
pipes spaced 3.5 feet apart longitudinally 6 feet above the high side
(upper 1/2) of the coke bed. Water at a rate of 350 gallons per square foot
of direct contact area is applied in one minute. A total of 5,000 gallons
of water is thus applied. The car of coke is completely quenched in 1
minute and ready to be dumped onto the coke wharf within 2 minutes with no
evidence of incandescence.
THE OSCILLATING SYSTEM
The preferred oscillating quench system consists of a single-
10-inch header mounted in the tower longitudinally above the centerline of
the quench car. The pipe is suspended in bearings at each end and contains
twenty-nine l-l/2-inch vertical pipe outlets on about 20-inch centers in
order to accommodate a 50-foot car. If the cars are frequently loaded
unevenly, the pipes may be distributed to provide more water in areas,of
high piling. Water is supplied from swivel connections attached to the
header. The pipe is rotated back and forth by means of a double-acting
~ydraulic cylinder attached to a lever arm at one end of the header. The
-twenty-nine streams of water make from 2-5 passes across the car each way
during the 75 second quench. The quench by this method has been complete
and moisture has been regularly reported to average about 5 percent.
Referring to Figure 9, swivel coupling ~20) supplies screened
water to header (21) having a row of pipe outlets (22) made of straight
standard pipe as previously described for the stationary system. Actuating
cylinder (23) causes the header (21) to turn axially, moving the water
streams (24) gradually across the quench car (25) containing hot coke (26)
and having a bottom drain 27.
The pipe o~Jtlets (22) may vary in diameter from l-1/2 inches to
11
1~48960 - /a -
1 ~ 2 inches and carry water flowing ae rates of 50 to 150 gal./min. The
s7'
oscillations are~preferably conducted at a rate of 2 to 5 within 75 seconds,
a ~ or~e~b ~
bu~ may vary from 1 to 15 within 2 minutes. Preferably the streams will
be directed at the highest point of the coke profile for a period of at
least three of every ten seconds; at least five of every 10 is preferred.
Stationary flows proportional to these rates may also be used; that is,
thirty to fifty percent of the quench time is preferably devoted to the
peak of the coke profile and the remainder of the time is devoted to
oscillating the more or less solid streams of water over the remainder of
the coke surface.
Our quenching system is unique in the small amount of water
required. Assuming the delivery of 80 gallons of water from each pipe per
minute or 100 gallons in 75 seconds, this amounts to only 2900 gallons pe~
quench or 205 gallons per ton for a 14 ton load. This compares with 400 to
800 gallons per ton at other spray installations.
As good as this performance might seem, our original experimental
work indicated that repeated applications of water always produced higher
moisture in the coke, particularly at the top, than the same amount applied
as one application. Using this philosophy we have conducted a limited number
of trials controlling the air cylinder movement manually. Good quenches
have been obtained by directing the water toward the top edge of the car
(battery side) for 45 seconds to 1 minute and then making only 2 to 4 passes
over the rest of the car during the remaining 1/2 or 1 minutes.
Our system not only results in reduced water usage, thus reducing
the problems of waste disposal, but also may distribute water according to
coke depth, and provide a consistently low moisture coke.
Although the invention has been described in considerable detail
in the foregoing, it is to be understood that such detail is for the purpose
of illustration and that many variations can be made by those skilled in the
art without departing from the spirit and scope of the invention except as
set fortll in the claims.
