Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A METHOD FOR PRODUCING COKE
This invention relates to the production of coke
in a non-recovery type coke oven, and more particularly
to a method for operating such a coke oven at an increased
coking rate without polluting the atmosphere with effluents
including products of distillation liberated from a coal
charge during the coking process.
A non-recovery type coke oven is sometimes identi-
fied in the art as a beehive coke oven. In the past, a
battery of such coke ovens were built adjacent each other
and operated by pulling from alternative ovens on alter-
native days the masses of coke. The heat from the side walls
of a hot coke oven and any residual heat retained in a newly-
charged coke oven is usua}ly sufficient to ignite the coal in
the newly-charged coke oven. The cycle for production of
coke by each oven chamber was about 72 hours. A non-recovery
type coking process provides important features and advantages
to the coking industry, particularly a more economical process
for producing coke. The coke ovens used in a non-recovery
type coking process are less costly and require a minimum o
ancillary equipment, particularly because facilities are not
required for treating by-products of the coking process.
Non-recovery, beehive-type coke ovens in the past were capable
of providing only a relatively low coke output per oven chamber.
However, smoke together with other unburnt volatile products
escape during the coking process into the atmosphere. The
emissions are a source of environmental pollution whereby
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non-recovery type coking processes have been largely done
a~ay with in view of current environmental standards.
The chief method for producing coke currently is
by a by-product or retort process wherein air is excluded
from the coking chamber and all volatile products liberated
during the distillation process are recovered as gas and
other coal by-product chemicals. Many coking installations
using the retort process still discharge unacceptable
quantities of polluting gases into the atmosphere. Usually,
the sale of chemicals recovered from the retort process was
; a source of income, but the sale of such chemicals has
become increasingly less profitable.
In my U. S. Patent No. 4,045,299, entitled "Smo~e-
less Non-Recovery Type Coke Oven", there is disclosed a
smokeless non-recovery type coke oven wherein the distil-
lation gases liberated during the coking process are conducted
from the space above the coal charge downwardly along passage-
ways in the side walls forming the oven chamber into a sole
heating flue. Primary air is fed into the oven chamber to
maintain combustion within the space above the coal charge.
Secondary air is fed into the downcomers to facilitate com-
bustion of the gases in the sole heating flues and in a tandem
arrangement of ignition chambers located downstream therefrom.
Additional quantities of secondary air for combustion were
injected into the ignition chambers and a burner is used to
maintain a predetermined minimum temperature at all times in
the ignition chamber to insure incineration of all smoke gases
passing therethrough. The waste gases are conducted from the
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ignition chambers by a horizontal conduit to a stack. The
arrangement of parts forming the coke oven chamber are
intended to overcome poor and inefficient secondary combustion
of the distillation products in the sole heating flues and
the passageways within the walls of the coke oven chamber.
The secondary combustion did not incinerate the distillation
products but represented only a partial combustion thereof.
The temperature within the ignition chambers was maintained
at a minimum temperature of, for example, 1400F for incin-
erating all the gases reaching this point before the gaseswere passed to the-stack. The smokeless operation of the
coke oven was significantly enhanced to the extent that
emissions from the stack were found to be within acceptable
standards.
I have now discovered an automatic control for the
coking process when carried out in a smokeless non-recovery
type coke oven of the type disclosed in my aforesaid patent
will not only increase the rate at which coke is produced in
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the oven chamber but also further reduces emissions during
the operation of the coke oven.
It is an object of the present invention to provide
; a method for producing coke in a non-recovery type coke oven
wherein throughout the coking period, a supply of primary air
is progressively decreased while at the same time a supply of
secondary air fed into downcomers for mixture with an effluent
conducted thereby from the space above the coal charge is
controlled to maintain a sufficiently high temperature to
cause coking to proceed from the side walls as well as from
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the bottom of the coking chamber due to combustion of the
gases passed from the downcomers into a sole heating flue.
In one particular aspect the present invention provides
a method for producing coke in a non-recovery type coke oven
chamber including side walls and a floor comprising the steps
of:
charging and leveling a coal charge in the oven chamber
leaving a space above the coal charge,
controllably decreasing a supply of primary air fed
into the coking chamber throughout a coking period to minimize
consumption of the coal charge while essentially maintaining
the liberation of heat by the combustion of volatile distillate
products to cause coking to proceed from the top of the coal
charge downwardly,
withdrawing the effluent into a plurality of downcomers
within the side walls of the coking chamber from the space
above the coal charge in the coking chamber,
r admixing a controlled amount of secondary air for
combustion of the effluent in each downcomer to maintain a
temperature therein in the range of about 1200F to about
2400F to cause coking to proceed from the sides of the coal
:~ charge,
discharging the effluent from the downcomers into a sole
heating flue beneath the floor of the coking chamber having
flue spaces wherein further combustion~of the effluent maintains
a sole flue temperature in the range of about 1800F to about
2700F to cause coking to proceed from the bottom of the coal
- charge upwardly,
conducting the effluent from the sole heating flue into
a checker-filled ignition chamber,
maintaining a temperature of a least 1400F in the
ignition chamber to incinerate the effluent,
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withdrawing the incinerated gases from the checker-filled
ignition chamber under a negative draft pressure, and
maintaining said negative draft pressure at a sufficient
value to assure an effective flow of said incinerated gases
without disrupting the coking process due to an excessive
withdrawal of heat duri~g the coking process.
In another particular aspect the present invention provides
a method for producing coke in a battery of non-recovery
type coke oven chambers each including side walls and a
0 floor comprising the steps of.
charging and leveling a coal charge within a given coke
oven chamber leaving a space above the coal charge, the
newly-charged coke oven chamber being adjacent a coke oven
chamber wherein the coking process has proceeded to a point
where distillation gases are liberated,
controllably decreasing a supply of primary air fed
into each coking chamber throughout the coking period thereby
to minimize consumption of the coal charge while essentially
maintaining the liberation of heat by the combustion of ~ `
effluent including volatile distillate products to cause
coking to proceed from the top of the coal charge downwardly,
withdrawing the effluent into a plurality of downcomers
within the side walls of each coking chamber from the space
above the coal charge in the coking chamber,
admixing secondary air in a dependent relation to the
volume of effluent liberated from the individual coal charges
in the coke oven chamber for combustion of the effluent in
the downcomers of the individual coke oven chambers to
maintain a temperature therein in the range of about 1200F
to about 2400F to cause coking to proceed from the sides of
the coal charges in the coke oven chambers,
discharging the effluent from the downcomers of each
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coke oven chamber into a sole heating flue beneath the floor
of the coking chamber having flue spaces wherein further
combust:Lon of the effluent maintains a sole flue temperature
ln the range of about 1800F to about 2700F to cause coking
to proceed from the bottom of the coal charge upwardly,
conducting the effluent from the sole heating flues of
two coke oven chambers into one system of a plurality of
checker-filled ignition chambers spaced along the coke oven
battery,
maintaining a temperature of at least 1400F in the
ignition chambers to incinerate the effluent,
withdrawing the incinerated gases from each system of
checker-filled ignition chambers under a negative draft
pressure, and
maintaining said negative draft pressure at a sufficient
value to assure an effectlve flow of said incinerated gases
without disrupting the coking process due to an excessive
withdrawal of hea~ during the coking process by each coke
oven chamber.
:20 . The aforesaid method of producing coke may, in its
preferred form, include the further step of heating atmospheric
air to a temperature of at least 200F for providing the heated
secondary air. The volume of the heated secondary air i~
preferably controlled in a dependent relation to the valume
of volatile distillate products conducted by the downcamers.
The volume of heated secondary air supplied to each downcomer
is increased to a maximum within the first 5% of the coking
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cycle. A control valve actuated by a timing cam is suitable
for adjusting the volume of heated secondary air which is
fed into the downcomers. Moreover, heated secondary air is
fed into the checker-filled ignition chamber at a substan-
tially constant rate of supply. The supply of primary air
which is progressively decreased throughout the coking cycle
is controlled by adjusting the position of a closure member
relative to an opening defined in an oven door for the oven
chamber. Alternatively, the supply of primary air is con-
trolled by adjusting the location of charging covers in relationto openings in the oven roof to vary the size of an air supply
opening therebetween. The supply of primary air may also be
controlled by adjusting the size of openings in the charging
covers themselves. In the method of operating a coke oven
according to the present invention, the burnt gases are
delivered to a stack at a temperature in the range of 900F
to 1000F.
These features and advantages of the present
invention as well as others will be more readily understood
when the following description is read in light of the
accompanying drawings, in which:
Figure 1 is an elevational view, partly in section,
of a smokeless and non-recovery type coke oven for operation
according to the method of the present invention;
Fig. 2 is a plan view, in section, taken along
line II-II of Fig. l;
Fig. 3 is a graph illustrating the relative volumes
of distil~ate gases liberated by two coke oven chambers through-
out time-displaced coking cycles;
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Fig. 4 is a graph illustrating the volume of
heated secondary air introduced into downcomers of the non-
recovery coke oven chambers throughout the time-displaced
coking cycle of two oven chambers; and
Fig. 5 is a composite graph illustrating the
temperatures at various locations in a coke oven throughout
a coking period.
Figs. 1 and 2 illustrate two adjacent coke oven
chambers 11 and 12. The structure defining each coke oven
chamber includes upstanding side walls 13 and 14 that are
made of refractory brick or the like. An arched roof 15 is
carried by the top surface of the side walls and spans the
distance between them. Two or more trunnel head openings 16
are formed in the oven roof depending upon the length of the
oven chamber. Each of these openings is provided with cast
iron covers 17 which are removable to charge coal through
the opening 16 into the oven chamber. If desired, coal is
charged into the oven chambers by a conveyor positioned by
a movable support structure to extend through a door opening.
In this event, the trunnel openings are not used. The openings
16 are employed, according to one aspect of the present inven-
tion, to conduct primary air into each oven chamber. For this
purpose, the covers include movable valve plates, not shown,
for closing, to a varying extent, an opening in covers 17.
However, the position of the covers can also be adjusted
relative to openings 16 to vary an opening therebetween to admit
primary air into the oven chamber. Upper and lower doors 18A
and 18B, respectively, close the opposite ends of the oven
chambers. These doors are removable to dischar~e coke from one
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end of an oven chamber by a pusher ram 19 supported at the
opposite end for movement through the oven chamber. As shown
in Fig. 1 in regard to coke oven chamber 12, the upper door
18A includes a slide plate 18C for an opening in the door to
adjust the supply of primary air for the coking chamber in
addition to or in place of using openings 16. Clay or sim-
ilar material can also be employed to vary the size of a gap
between the door and the coking chamber to control the supply
of primary air at various times throughout the coking process.
A charge of coal is supported in the oven chamber by
a floor 21 that slopes in a downward direction from end-to-end
to facilitate removal of the coke. The floor of the oven
chamber is preferably made of silicon carbide or other refrac-
tory material of high heat conductivity. The floor 21 rests
on a bed of silica tile 22 that is, in turn, supported by
spaced-apart columns 23 that are arranged parallel to the side
walls 13 and 14 to form flue spaces 24 between the columns.
Flue spaces 24 are interconnected by a staggered arrangement
of openings 23A in the columns. The flues 24 define sole flues
used to provide a residence time for combustion and for
extracting residual heat from partially-burned distillation
products that are drawn from the space above the coal charge
in the coke oven chambers and flow through downcomers 13A and
14A. These downcomers are passageways formed in side walls 13
and 14, respectively. Fig. 2 illustrates two such downcomers
in each of the side walls 13 and 14.
Part of the oven roof is made of sections 15A by
using cast refractory material. Formed in these sections are
passageways 15B that communicate between the space in the oven
chamber above the coal charge and the top of the downcomers
13A and 14A. Each passageway 15B is additionally provided
with an opening that extends through the top of the roof
section l5A where it communicates in a sealed relation
with a vertical pipe 15C. The pipes 15C are employed to
introduce heated secondary air for admixture with the
partially-burned distillation gases passing downwardly in
the downcomers as will be more fully described hereinafter.
If desired, the passageways 15B may take the form of
openings in the side walls 13 and 14 to conduct distil-
lation gases into the downcomers from the space above the
coal charge in the oven chamber.
While the features and advantages of the present
invention are useful for a single coke oven chamber, a
battery of coke oven chambers may be arranged in a side-by-
side relation. The two coking chambers 11 and 12 illustra-
ted in the drawings are intended to represent a portion of
such a battery of coke oven chambers. Lying between the
coking chambers 11 and 12 are interconnected ignition chambers
30 and 31 that extend in an end-to-end relation between the
side walls 14 of chamber 11 and the side walls 13 of chamber
12. The side walls 14 and 13 of the oven chamber 11 and 12,
respectively, have an added thickness as compared with the
thickness of the remaining side wall for coking chamber 11
which, for ~he purpose of disclosing the present invention,
is assumed to be a first coking chamber in a battery of coke
ovens. The ignition chambers 30 and 31 are eac'n provided
with a filling of checkerbrick 32. Rider arches 33 span the
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distance between the side walls 13 and 14. Parallel
channels 35 in the side walls 13 and 14 of oven chambers
11 and 12, respectively, interconnect the flues 24 and the
ignition chamber 30. The partially-burned distillation
products pass through these channels in a generally hori-
zontal direction and enter at the bottom of the ignition
chamber 30 to pass in an upward direction through the open
spaces in the checkerbricks. Thus, ignition chamber 30
may be referred to as an up-pass chamber and ignition
chamber 31 referred to as a down-pass chamber.
Und~r bhe preferred operating conditions, the
checkerbrick 32 will store heat to maintain an elevated
temperature in the ignition chambers. It is not possible
to continuously maintain an operating temperature of, for
example, 1600F due to varying conditions, such as a charge
of off-grade coal and interruptions for maintenance and
other repair operations. These conditions affect the supply
as well as the temperature of the distillation gases passing
into the ignition chambers. The temperature in the ignition
20 chambers should not fall below 1400F, preferably 1600F, to
insure incineration of the partially-burned distillation
products and smokeless operation of the coke ovens whereby
the emissions from the stack are essentially only waves of
heat.
In the ignition chambers, the arched roof 37 forms
gas flow spaces 38 above the checkerbrick~ Such a roof is
preferably of the type known as a "bung" roof which includes
refractory brick fitted into a cast iron frame so that the
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roof can be removed for cleaning and replacing of the
checkerbricks. A wall 39 separates the two ignition chambers.
The gases pass over the upper edge of this wall from chamber
30 to chamber 31. It is essential that the partially-burned
distillation products which enter into the ignition chambers
are completely burned therein, i.e., incinerated, so that
products of combustion are drawn off from the bottom of the
down-pass ignition chamber 31 through a conduit 40 having a
refractory lining and extending along the back of the battery
of coke ovens. The gases conducted by conduit 40 are delivered
to a stack 41 at the base thereof. Means, such as a fan 41A,
is used to control the flow of gases within the stack by
supplying additional quantities of air in the stack and thereby
control draft on the coking chambers. The draft controls the
flow of gases in the downcomers, sole heat~ng flues and
ignition chambers. According to the present invention, a
draft gage 42 is extended through the wall of the stack at the
B base. The draft gage is used to maintain a ~itieal impe~tant
f`~DicA~
negative stack pressure~ithi~ the range of .15 to .17 inch
water gage.
The outer end of ignition chamber 30 is enclosed
by an end wall 43 which has two openings communicating with
the gas flow space between the checkerbricks in the ignition
chambers. One of these openings receives the end of a verti-
cally-extending pipe 44 which has a flow control valve 44A to
adjustably preselect a constant volume of heated air which is
introduced by pipe 44 into the ignition chamber 30. The
admixing of secondary air with the partially-burned distillation
gases is controlled by a valve to assure incineration of the
gases within the ignition chambers. The second opening in
wall 43 communicates with a vertically-extending fuel supply
pipe 45. A high temperature burner 45A is provided on the
inner face of wall 43 which receives a controlled supply
of fuel, e.g., oil or natural gas. For this purpose, a
controller 46 operates in response to a signal from a thermo-
couple 47 projecting from the lower surface of roof 37 in a
manner to detect the temperature within the ignition chambers.
The controller 46, through the use of a signal from thermo-
couple 47, delivers fuel through pipe 45 to the burner when
the temperature in the ignition chamber drops below a pre-
determined minimum temperature of 1600F or some other
predetermined minimum temperature, required to incinerate any
unburned distillation gases reaching the ignition chambers.
Reference numeral 58 identifies clean-out ports or solid
residue that accumulates at the bottom of downcomers 13A
and 14A.
As previously described, heated secondary air is
conducted by pipes 15C and 44 for admixing with the partially-
burned distillation gases. Each pipe 15C includes a valve
15D to control the flow rate of air within an associated
pipe 15C. A supply of heated secondary air is provided by
a blower 50 which is driven by a motor 51 that is energized
by a switch 52. The blower 50 feeds air into a refractory
recuperator 53 which is well known per se in the art and
arranged within the conduit 40. As illustrated in Fig. 2,
the recuperator 53 is located between the last coking chamber
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and the stack. By employing the recuperator, the temperature
of the gases fed into the stack can be reduced by several
hundred degrees. A thermocouple 54 extends into the stack
at the base thereof to provide means for measuring the
temperature of the gases. At this point in the stack, the
gases have a relative constant temperature in the range of
900F to 1000F. The sensible heat recovered by the recup-
erator provides a heated secondary air supply which is fed
by pipes 15C and 44 into the downcomers and ignition chambers,
respectively, at a temperature of at least 200F.
As shown in Fig. 1, the supply of heated secondary
air to each downcomer is controlled by a valve 15D. The
valve has a valve stem contacting the s~rface of a cam 55
supported by a shaft for rotation by a motor 56. The motor
shaft is coupled by a speed-reducing gear train with the
shaft of the cam. In this way, the cam is driven to rotate
at a speed corresponding to one revolution for each coking
period which, for the purpose of disclosing the present
inventlon, will be assumed at 24 hours. The profile of the
cam 55 is selected to actuate the valve for delivering heated
secondary air into the downcomers in volumes, typically
represente~ by the graph of Fig. 4. This graph, based on a
24-hour coking period for coking chamber 11, indicates that
after an initial period of about the first 4 hours or 5% of
the total coking period, the amount of secondary air fed
into the downcomers is increased to a maximum. Thereafter,
the volume of heated secondary air is slowly decreased during
the next 10 to 12 hours and decreased at a greater rate to a
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minimum volume at the end of the 24-hour coking period. The
graph of Fig. 4 also includes a graph line indicating the
same control of heated secondary air for the downcomers
of coke oven chamber 12 but at a time-phase relation
displaced by 24 hours. As described previously, the
volume of heated secondary air which is fed into the
ignition chambers by pipe 44 remains constant. It is
critically important to control the supply of heated second-
ary air into the downcomers because an excessive air supply
cools the oven masonry and decreases the draft on the oven
chamber which is necessary to maintain the flow of gases.
On the other hand, an insufficient supply of heated second-
ary air extends the required coking period because less heat
is generated by reduced combustion which leads to a source
of pollution. The volume of heated secondary air supplied
to each downcomer for a given oven chamber is usually dif-
ferent and unique with the location of the downcomer
relative to the location of the primary air supply. The
supply of heated secondary air corresponds somewhat to the
volume of distillation gases liberated in the coke oven
chamber which is illustrated typically by Fig. 3. It is
important to note that during the initial period af about
1 hour, the amount of distillate gases given off is at a
minimum. The volume of heated secondary air fed into the
downcomers at this period of time is also at a minimum to
avoid excessive cooling of the oven chamber and adverse
effects to the ignition period for the coal charge. Fig. 3
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also depicts the time-displace occurrence of the relative
volume of gases liberated in the two oven chambers 11 and 12.
A relatively large volume of the gases is liberated during
the first 24 hours and thereafter the volume of gases is
reduced to the point where at the final 2 hours, only
relatively small volumes of gases are liberated, but at a
relatively high temperature as compared with the gases lib-
erated during the first 24 hours.
In a non-recovery type coke oven of the type here-
inbefore described, the overriding consideration is to heat
the entire mass of coal charge to a coking temperature with-
out the use of a~xiliary fuels. It is critically important
to control the supply of primary air fed into the coking
chamber throughout the coking period to minimize the con-
sumption of coal. However, sufficient primary air is
required to maintain a heat supply by the combustion of volatile
distillation products in the space above the coal charge to
cause coking to proceed from the top of the coal charge down-
wardly. It has been found that in a coke oven of the type
disclosed herein, that the draft on the oven chamber, when
B measured at the stack, ~ .15 and .17
inch water gage. In the event the negative stack pressure is
less than this range, then smoke and gases are not carried
away and the coking process is disrupted. However, an
excessively large negative stack pressure drains excessive
amounts of heat from the coking chamber causing the temper-
ature to drop and impairing the coking process. Thus, it is
critically important not only to accurately control the primary
air supply but also the heated secondary air supply which
is fed into the downcomers. A useful control parameter for
adjusting the amount of heated secondary air fed into the
downcomers is based on maintaining the temperature in the
downcomers within a suitable range whereby additional heat
is introduced înto the coal charge so that coking proceeds
from the sides thereof. The temperature in the downcomers
is monitored by using suitable well known means, such as
thermocouples extending through the walls 13 into the
open spaces of the downcomers. A pyrometer is readily
useful to measure the temperature in the downcomers through
sighb openings such as conveniently provided by removing a
closuxe cap 15E from the upper end of each pipe 15C.
Fig. 5 illustrates the useful temperature ranges
for the coking process of the present invention. The graph
lines are based on a 48-hour coking period for a coal charge
that is 42 inches deep. Approximately the same temperature
ranges will exist over a compressed period of time of 24
hours when the coal charge is between 22 to 24 inches deep.
It can be seen in Fig. 5 that immediately after charging the
oven chamber, the temperature in the space above the coal
charge increases in a relatively constant manner to 2550F
after a period of 36 hours and thereafter decreases slightly
to about 2400F. The temperature in the downcomers at
charging is about 1200F because of stored heat in the oven
walls from the previous coking period. The temperature in
the downcomers increases due to the combustion therein of the
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distillation products with heated secondary air. At about
24 hours through the coking period, the temperature in the
downcomers reaches a maximum of about 2400F which remains
constant until about the 36th hour in the coking process,
and thereafter drops to about 1500F. It will be remem-
bered, as illustrated in Fig. 3, that the volume of distil-
late gases given off during the first 24-hour period is at
a maximum, however, the temperature in the downcomers does
not reach a maximum until about the end of the first
24-hour period. The temperature in the sole heating flue
increases from about 1800F at charging to about 2700F
after about 36 hours in the coking period. Thereafter, the
temperature drops in the sole heating flues, principally
due to lower volumes of distillate gases to about 2000F.
The heat from the sole heating flues, of course, causes
coking to proceed upwardly from the bottom of the coal charge.
As previously described, the ignition chambers must be
maintained at a predetermined minimum temperature throughout
the coking cycle by each oven chamber. In the preferred
form of the present invention, the control system for the
oil burner is set to maintain a minimum temperature of 1600F
in the ignition chambers. Because the distillation products
given off during the first few hours in the coking cycle are
high, incineration does not occur because of insufficient
heat and air. The burner may be required to correctly maintain
the minimum temperature in the ignition chamber. However,
thereafter the temperature in the ignition chambers increases
to a maximum of about 2300F at the end of the coking cycle.
The temperature range of 1600F to 2300F is maintained in
the ignition chambers. All unburned distillation gases are
incinerated within the ignition chambers. The gases passed
from the downpass ignition chamber are conducted by the
horizontal conduit beyond the recuperator to the stack
where they are exhausted as heat waves within a temperature
of 900F to 1000F.
In a coking process according to the present
invention, a substantial amount of preheated secondary air
is introduced into the individual do~ncomers to secure a good
bright flame. As coking proceeds and the quantity of gases
and volatiles liberated by the coal charge begin to diminish,
the amount of heated secondary air introduced into the down-
comers is reduced. Near the end of the coking process, only
relatively small amounts of heated secondary air are required
in the downcomers. The control of the coking process in
several coking chambers has increased importance because a
common ignition chamber system is coupled to the coke oven
chambers by way of the sole heating flues to receive the
effluent at varying temperatures depending upon the lapsed
time through the various coking cycles.
Although the invention has been shown in connection
with a certain specific embodiment, it will be readily appar-
ent to those skilled in the art that various changes in form
and arrangement of parts may be made to suit requirements
without departing from the spirit and scope of the invention.
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