Process for removing dust from dry cooled coke

The invention concerns a process for removing dust from coke cooled by a dry method after the coke has left the cooling zone of a cooling chamber, and a device for carrying out the process. A dust-free flushing gas is injected below the cooling zone, preferably parallel to the direction in which the coke moves when it has been cooled to below 200.degree. C., to draw the gas off above the discharge lock together with the stirred-up coke dust, and to recirculate the gas after the dust is removed from it. As an alternative, compressed air is blown through the coke after it has left the lock and while it is being transported through a vibrating machine. The coke is cooled in a dry cooling unit to below 200.degree. C. and preferably 130.degree. to 180.degree. C. The coke is then cooled outside the dry cooling unit by means of air at about 50.degree. to 90.degree. C. and preferably 70.degree. to 80.degree. C. Either simultaneously with or immediately after the cooling step with air, the coke is moistened, for example by sprinkling or spraying, to a residual moisture of 2% to 4% by weight and preferably 2% to 3% by weight.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates in general to coking, and in particular to a process 
and device for removing dust from coke cooled by a dry process. 
The invention concerns a process for removing dust from coke cooled by a 
dry method after the coke has left the cooling zone of a cooling chamber, 
and devices for carrying out the process. A process for cooling coke by a 
dry method is known, for example, from a publication in "Technische 
Mitteilung" No. 9, 1982, pages 434 to 439. The invention includes a 
cooling vessel having a cooling zone and below the cooling zone of a 
cooling chamber, there are so-called coke discharge rocking bars and, 
below the discharge rocking bars, the discharge shaft which is followed by 
a lock-type discharge device. The discharge device is also known, for 
example, from German disclosure document 30 14 574. According to 
illustration 1 in "Technische Mitteilungen" and the associated 
description, the two discharge locks lying side by side should be filled 
with an inert gas for safety reasons. The dust generated below the 
discharge locks and the subsequent coke transfer stations is continually 
drawn off and evacuated together with the dust-containing exhaust air 
generated intermittently at the coke intake. 
It has been observed that after the coke has left the cooling zone of the 
cooling chamber and during the subsequent transport of the coke to the 
screening department and the shipping station, a number of emissions of 
fine dust occur. As a result of cooling the coke by a dry method, large 
volumes of fine coke particles are present on the surface of the coke, 
which are not, as in the case of wet quenching, absorbed by quenching 
water, but are dislodged in part only during the subsequent transport and 
the vibrations in the screening department. 
SUMMARY OF THE INVENTION 
The invention provides a process for removing dust and cleaning the fine 
coke dust from the surface of the coke without creating emissions. 
In order to solve this problem it is proposed that, preferably parallel to 
the direction in which the coke moves when it has been cooled to below 
200.degree. C., dust-free flushing gas is injected below the cooling zone, 
drawn off above the discharge lock together with the stirred-up coke dust, 
and recirculated after the dust has been removed from it. 
Through the process of the invention, all the coke dust originating below 
the cooling zone is removed by a simple method from the cooling chamber 
into a closed circuit. Precisely when the cooled coke falls from the 
discharge rocking bars onto the rotary table just above the discharge 
locks and then falls into one of the discharge locks, a great deal of fine 
coke dust is stirred up, which can be drawn off immediately by relatively 
small quantities of recirculating flushing gas. 
It is advantageous to inject the flushing gas at the narrowest point of the 
funnel-shaped discharge opening so that a curtain of flushing gas is 
formed over the entire cross section. 
According to the invention, the composition of the flushing gas may be the 
same as that of the cooling gas, or it may consist of another dry gas not 
containing any oxygen, in which case during start-up the cooling gas is 
used, by a simple method, as flushing gas. It is desirable to draw off the 
flushing gas before the coke enters the gas-tight discharge lock and, in 
order to remove the dust, is made to flow through cyclones and/or dry 
filters, such as, for example, hose filters. In order to prevent excessive 
temperatures, an additional heat exchanger for cooling purposes may be 
included in the flushing gas circuit, or small quantities of additional 
colder gas can be injected. 
As an alternative proposal a process for removing dust from coke cooled by 
a dry method after the coke has left the cooling zone of a cooling chamber 
provides that compressed air is blown through the coke after discharge 
from the lock and during its subsequent transportation and that the 
compressed air charged with fine coke dust is drawn off through an exhaust 
dome and discharged into the open air after the dust has been removed from 
it. In this case the removal of the dust takes place immediately after the 
compressed air which is charged with dust, is drawn off. 
This is advantageously effected in a dry-method dust removal facility, 
which is already present for other purposes. In order to prevent any 
emissions, the coke should be cleaned in a closed coke transportation 
room. It has been proved advantageous for this purpose if the coke 
cleaning station consists of an unbalanced vibrating machine mounted in a 
closed housing with a step-type conveying trough with openings for the 
passage of the air, in which case compressed-air inlets are located below 
and/or on the sides of the conveying trough and exhaust connections are 
located above the conveying trough. In a step-type conveying trough of 
this kind, the coke slides and drops over the individual steps of the 
trough and is shaken and turned over and over again in the process. In 
this design it is desirable to place the slits for the passage of the 
compressed air between the steps of the conveying trough, in order to make 
it possible to blow out the coke dust at the points at which the coke 
drops freely. The steps of the conveying trough may, according to the 
invention, also consist of a number of individual sheet metal pieces which 
are made to oscillate up and down at one end. This oscillating up-and-down 
motion can be achieved, for example, by unbalanced wheels turning on a 
horizontal shaft. According to the invention, the floor pieces of the 
conveying trough can also be designed as screens or sieves. In this 
connection it is useful to locate the floor of the unbalanced vibrating 
machine below the conveying trough, as a dust-collecting container which 
is connected to devices for expelling the dust. Finally, it has proved 
advantageous to provide compressed air inlets opening toward the ejection 
parabolas of the intake and transfer points of the unbalanced vibrating 
machine. Particularly at these points, the coke drops a considerable 
distance to the next transport device. For this purpose, it is desirable 
to place the exhaust connections directly above these additional 
compressed-air inlets. 
In sum, a number of advantageous proposals have been made according to the 
invention to remove the major part of the fine coke dust from coke cooled 
by dry methods, either already in the cooling chamber, or, after it leaves 
the cooling chamber, during its subsequent transportation in closed 
systems. Both the recirculating flushing gas and the compressed air 
injected are at such a low temperature that no problems of any kind arise 
in the dust removal equipment downstream. 
In accordance with the invention, dust is removed from coke after it is 
first cooled by a dry method in which the coke is moved through a cooling 
zone of a cooling chamber and it is moved downwardly out of the cooling 
chamber which comprises injecting a dust-free flushing gas into the coke 
as it is moved below the cooling zone preferably in a direction parallel 
to the direction in which the coke moves when it has been cooled to below 
200.degree. C., passing coke through a discharge lock, drawing the gas off 
the coke above the discharge lock together with dust which is stirred up 
from the coke through a discharge lock, drawing the gas off the coke above 
the discharge lock together with dust which is stirred up from the coke, 
and removing the dust from the drawn-off gas and recirculating drawn-off 
gas after the dust is removed. Another object of the invention is to 
provide a device which includes a vibrating machine forming a lock into 
which the coke is directed after it is cooled and which has a plurality of 
stepped areas onto which the coke is moved and advanced by the vibration 
of the stepped areas and which includes means for directing air through 
the coke between the steps and for drawing the air off separating the dust 
from the air and recirculating at least a portion of it. 
It has been shown that by treating the coke with pressurized air in this 
way a substantial decrease in dust emissions during further transport of 
the coke to the blast furnace can indeed be achieved. A further object of 
this invention is thus to improve upon this dust removal process even 
further. For this purpose, the following process steps are suggested: 
(a) Cooling the coke in the coke dry cooling unit to below 200.degree. C., 
preferably 130.degree. to 180.degree. C.; 
(b) Cooling the coke outside the coke dry cooling unit by means of air to 
about 50.degree. to 90.degree., preferably 70.degree. to 80.degree. C.; 
(c) Following or simulataneously with step (b), moistening the coke, e.g., 
by sprinkling or spraying, to a residual moisture of from 2% to 4%, 
preferably 2% to 3%, by weight. 
Surprisingly, it has been shown that when cooled to a temperature of 
50.degree. to 90.degree. C., preferably 70.degree. to 80.degree. C., and 
subjected to surface spraying, the coke has as low a water content as 
possible for use in the blast furnace, and it attains the residual 
moisture specified by the invention for binding the fine coke particles 
located in particular on the surface of the coke. The water sprayed on the 
surface binds this fine coke dust to the extent that even during further 
loading and conveyance to the blast furnace it does not come loose and 
result in emissions. 
It has further been shown that following the cooling of the coke to below 
approximately 80.degree. C. the water applied to the coke no longer 
evaporates and hence that sufficient moisture remains on the surface of 
the coke to bind and fix the fine dust. This effect can be reinforced by 
spraying the air with water so that it is heavily saturated with water 
vapor before it is blown through the coke. This also has the effect of 
cooling the coke. The water can be suitably applied by means of spray or 
atomizing nozzles mounted over a sieve-like conveyor belt. The precise 
does of water is given off so that it does not fall below the dew point, 
and the final temperature of the coke adjusted to at least 50.degree. C., 
preferably around 80.degree. C. The dust-laden exhaust air is suitably 
scrubbed by means of a filter and when cleaned is released into the 
atmosphere by means of a downstream suction exhaust fan that is driven by 
a steam turbine that utilizes steam from the coke dry cooling process. 
It has been shown to be particularly advantageous pursuant to the invention 
to pass the coke through a sieve before or during the moistening process, 
and to seive out grains finer than 30 mm, preferably finer than 10 mm. 
This means that only the larger pieces of coke are moistened, and the fine 
dust adheres for the most part to such pieces. 
In order to carry out the process pursuant to the invention, the coke is 
conveyed into an enclosed housing by means of a sieve-like conveyor belt 
with air feed devices and spray or atomizing nozzles above and air exhaust 
devices below the sieve-like belt. The treatment of the coke pursuant to 
the invention can be carried out in batches or continuously in the 
enclosed vessel. Particularly with batch processing, the process can be 
carried out without dust emissions and in particular under a higher air 
pressure. To remove the dust from the coke, the sieve-like conveyor belt 
is stopped and the entrance and exit sluices for the coke are closed for 
approximately 5 to 60, preferably 15 to 30 seconds. It is helpful in this 
regard to have the sieve-like conveyor belt located entirely within the 
enclosed housing, and the coke can be thrown onto this sieve-like conveyor 
belt by a conveyor belt located outside the housing and upon exiting can 
fall, via a chute for example, onto another conveyor device. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which 
preferred embodiments of the invention are illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings in particular, the invention embodied therein 
comprises a process and apparatus for removing dust from coke after it is 
first cooled by moving the coke in the path of the arrow 20 in FIG. 1 
through a coke transporting bucket 21 through a lock slide 22 into an 
antechamber 23 of the coking vessel. Both the areas 21 and 22 and the 
antechamber 23 are connected through connecting lines 27 and 28 to a dust 
exhaust. 
The coke passes through the antechamber 23 into a cooling chamber 24 which 
has a cooling wall 43. In addition feed water is supplied in the direction 
of the arrow 34 into the cooling chamber and exits as steam at 35. Feed 
water is also moved in a direction 33 through the cooling wall 43 and 
exits as steam in the direction 36. 
The cooling vessel also includes a cooling gas channel 44 and a set of 
discharge rocking bars 45. Cooling gas is circulated in a direction of the 
arrow 31. Cool coke moves downwardly over a rotary table 30 and through 
discharge locks 25 in the form of a double lock system. Gas is moved out 
through an outlet 38 and circulated through a fine dust separator 39 and 
the separated dust is removed in the direction 40. A scavenging gas inlet 
is indicated at 37 for the return of gas from which the dust has been 
separated into a return line 41 feeding into the chamber by a blower 42. 
Gas is also circulated in the direction of the arrow 29 to the separator 
39. Transfer conveyor 26 is provided for transferring the coke. 
As shown in FIG. 2, coke is moved on a coke conveyor which receives coke 
from conveyor 26 of FIG. 1, and which moves over reversing rolls 2, 3 and 
4 where the coke is dumped into a vibrating machine 5 which has a gas 
outlet 14 at its upper end and has an air pressure unit 15 connected at 
its lower end which directs air at the coke which is collected therein. 
Coke is then discharged downwardly over step-like conveyor trough 11 and 
as the machine 5 is vibrated, pressurized air is directed into a chamber 
below the coke conveyor trough 11 in the direction of the arrow 7. The air 
flows between the step portions of the conveyor 11 through openings 12. A 
portion of it is exhausted through the exhaust line 13 which connects to 
an exhaust line for the dust 9. Vibrating machine 5 is mounted on supports 
18 over spring 17 to permit its easy vibration. Compressed air is directed 
through an air inlet 8 at the discharge end of the step-like conveyor 11 
and the coke is then moved on a conveyor 19 arranged in a conveyor housing 
16. 
FIG. 1 shows the coke dry-cooling facility with reference numerals 20 to 36 
which refer to familiar items as noted above. The proposal of the present 
invention consists, in particular, of the recycling circuit 37 to 42, in 
which a dry and oxygen-free flushing gas is injected at the narrowest 
point of the cooling chamber discharge through line 37 into the cooling 
chamber, and is again drawn off just above the discharge lock chambers 25 
through line 38. The space between the discharge rocking bars 45 and the 
rotary table 30 is partly filled with falling coke only when the discharge 
rocking bars are actuated and is filled with dust-charged gas during the 
times when the discharge rocking bars are inactive. 
As a result of the fact that the recirculating cooling gas is injected, in 
accordance with the invention, at the narrowest possible point of the exit 
from the cooling chamber, a gas curtain is formed there, whose main 
purpose is to prevent gases charged with fine coke dust from rising into 
the space directly below the coke discharge rocking bars 45 from the 
filled lock chambers 25. Since the upper gates of the discharge lock 
chambers 25 are alternately opened and closed, the exit point 38 for the 
recirculating flushing gas can be located directly above these gates for 
both the discharge lock chambers shown. The flushing gas passes through 
fine-dust separators 39 of a familiar kind and flows through the line 41, 
the blower 42 and the line 37 back into the cooling chamber. The separated 
fine dust is transported through the dust discharge mechanism 40 to a 
central dust collecting tank. 
After the cooled coke leaves the transfer point 26 shown in FIG. 1, it can 
be transported to the additional or alternative coke cleaning station 
shown in FIG. 2. In this case the coke is moved through the coke conveyor 
1, which includes reversing rolls 2, 3 and 4, into the cleaning station. 
There it drops onto the step-type conveying trough 11 and, by the action 
of our unbalanced drive 6 of the unbalanced vibrating machine 5, is moved 
from step to step until it drops onto the coke transport belt 19 located 
in the belt housing 16. In order to ensure uniform distribution of the 
coke over the entire width of the conveying trough 11, a wedge-shaped 
spreader 10 is located at the upper end of the conveying trough 11. Below 
the conveying trough 11 is located the compressed air inlet 7, and below 
the individual steps of the conveying trough 11, the compressed air is 
injected through the openings or slits 12 into the coke pile and/or the 
coke dropping from the individual steps. Outlets 13 and 14 for the 
compressed air charged with dust are located above the coke pile. The 
dust-charged air is moved through the exhaust lines 9 to a dust-removal 
station of a familiar kind. Additional inlets 8 and 15, through which 
additional compressed air is injected into the path of the falling coke, 
are located at the transfer point from the coke conveyor 1 to the 
conveying trough 11 and also at the transfer point from the conveying 
trough 11 and also at the transfer point from the conveying trough 11 to 
the coke conveyor belt 19. The entire unbalanced machine 5 is located in a 
closed housing and supported on the legs 18 and springs 17. 
According to other features of the invention shown in FIGS. 1 and 2, the 
coke is first cooled in the coke dry cooling unit of FIG. 1 to below 
200.degree. C. and preferably 130.degree. to 180.degree. C. This is a 
temperature at which coke leaves the cooling unit on conveyor 26. 
The air cooling of FIG. 2 is achieved to about 50.degree. C. to 90.degree. 
C. and preferably from 70.degree. C. to 80.degree. C. 
Simulataneously with or immediately after the cooling step shown in FIG. 2, 
the coke is moistened, e.g. by spraying or sprinkling with water to a 
residual moisture of from 2% to 4% by weight and preferably from 2% to 3% 
by weight. 
In the embodiments shown in FIG. 2, this can be done by admixing water with 
the air supplied through inlets 8 and 15 which act as spray or atomizing 
nozzles. The air is heavily saturated with water vapor before it is blown 
through the coke at least to a level above the dewpoint. 
According to another feature of the invention, the dust laden exhaust air 
at exhaust 9 is filtered through a filter 50 and then drawn off by an 
exhaust fan 52 through the atmosphere. Exhaust fan 52 produces a suction 
for drawing off the air through outlets 13 and 14. 
According to another feature of the invention, steam from steam outlets 35 
and 36 of FIG. 1 is used to power a steam turbine 54 which rotates the fan 
52. 
In the embodiment shown in FIG. 3, the coke is passed through a sieve 60 
before or during the moistening step and a fraction smaller than 30 
milimeters and preferably smaller than 10 milimeters is sieved off. The 
sieve 60 can be in the form of a sieve-like belt which is enclosed within 
housing 62. Air feed devices 64 above the sieve belt 60 supply pressurized 
air in a downward direction and the air is exhausted through outlets 66 
below the belt. Spray or atomizing nozzles 68 are provided above the belt 
for spraying water onto the coke.