US2199945A - Cooling low temperature coke - Google Patents

Description

M y 7, 1940- I A. A. ARCHER ET AL P 2,199,945

' coopme LGW TEMPERATURE COKE Filed Oct. 26, 1937 INVENTORS Arthur A.Ar cher d} Raymond EZrmmerman Patented May 7, 1940 PATENT orFicE 'COOLING Low TEMPERATURE COKE Arthur A.. Archer, Pittsburgh, and Raymond E.

Zimmerman, Midway, Pa., assignors to Pittsburgh Coal Carbonization Company, Pittsburgh, Pa., a corporation otDelaware Application October-.2 6, 1937, swarm. 111,052

8 Claims.

The present invention relates to the cooling bonized coal'balls produced by the process described in the Lesher Patent No. 2,080,946 of May 18, 1937. As described in the Lesher patent, coal is subjected to a low temperature coking' process in a rotary retort while tumbling it'so as to form what is known as carbonized coal balls. The coal balls are discharged fromthe rotary retort or carbonizer at a temperature of about 800 to 850 F. for coal balls made from the Pittsburgh seam coal, although this temperature varies somewhat depending upon the size of the retort, the nature of the 20 coal to be carbonized and the quality of the product desired.

The coal balls are dense and strong in their resistance to fracture butfnot strongly resistant to abrasion. They have an extremely low heat reactive to oxygen. The =temperature at which they are discharged from the carbonizer is very close to their ignition point. If the coal balls are placed upon a metal plate out of contact with each other in an atmosphere at room tempera.- ture, the balls lose their heat without taking fire. On the other hand, if the .coal balls lie in a bed in contact with each other, the temperature at the points of contact rises above the 35 ignition point and theycoal balls take fire. When the heatedcoal balls are exposed to the atmosphere, some oxidation takes place at their surfaces.- Where the surfaces are free and exposed to the air, the heat is dissipated rapidly enough 40 to prevent a rise in temperature above the ignition point; However, whe're'the two surfaces liein contact witheach other, dissipation of the heat'by radiation and/or convection is retarded and an increase in temperature takes place until the temperature. of ignition or' rapid combustion is reached, whereupon the coal balls take fire.

Since the coal balls have extremely low conductivity, considerable time, a matter of two or conductivity and at thesame time are extremely Attempts to water-cool the coal balls result in ruining the product. The coal balls are dense and do not have the water absorbing porous structure of the ordinary high temperature coke, so thatthe wetting is apparently confined to the exterior portions of the coal balls. The wetting of the exterior causes shrinkage cracks which result in progressive disintegration of the coal balls.

We have found that such carbonized coal balls may be satisfactorily air cooled or quenched on a large scale commercial production by the following method. The coal balls as discharged from the carbonizer are exposed to a cooling circulation'of air while they are moved relatively to each other so as to prevent continuously maintained points of contact between them at which ignition would occur. It is not necessary that the movement of the coal balls relative to each other be continuous; an occasional movement 'will prevent ignition. Almost continuous movement is required for the initial cooling to be safe. However, after the balls have become cooler, less -frequent movement is required. The coal balls should be maintained in a. relatively thin bed of only one or two pieces deep for the. initial cooling, but as the cooling progresses the depth of the bed may be safely increased.

While we have illustrated in the drawing a preferred apparatus for carrying out our method, the method may be carried out with other forms of apparatus or even by hand.

7 In the drawing:

Figure 1 is a diagrammatioelevatlon of a preferred apparatus-for carrying out the method;

Figure 2 is a detail vertical longitudinal section; and I Figure 3 is a plan view showing the tilting plates.

Referring now to the specificprocedure illustrated in the drawingz-The low temperature coke or coal balls from the carbonizer is discharged by a conveyor I to the upper end of a cooling bed 2, which we may term a "cooling wharf by analogy to the cooling wharves of the high temperature cokeplants. The cooling bed consists of an inclined support for holding the bed 3 of coke. The'coke moves down the inclined support in a continuous bed which is relatively thin at the upper end of the support and increases in thickness toward the lower portion therof. The cooling bed or wharf is preferably made as illustrated of a plurality of tilting plates 4 shown in' detail in Figures 2 and 3. These plates have slots 5 to allow for the passage of on an endless chain 8. The dogs contact with the edges of the plate, as shown in Figure 2, and

raise the plate individually as the dogs-travel beneath them,'preferably in the direction indicated by the arrow in Figure 2. The chain .8

is carried on a track 9- which is adjustable to.

vary the amount of movement imparted by the dogs I to the plates 4. As shown in Figure i, such adjustment is diagrammatically indicated. by adjustable cams [0, although any suitable means can be employed for adjusting the position of the chain 8 with relation to the tilting plates 4. As illustrated, the track 9'is adjusted so as to give the maximum lift to the tilting plates 4 at the upper end of the cooling bed or wharf and this movement is gradually decreased until at the lower end of the wharf the plates 4 are stationary.

The coke is subjected to a cooling circulation of air. Since the coke is hot, a natural induced upward flow of air takes place through the bed of coke, the air passing through the slots 5 and the spaces between the plates 4. An auxiliary forced circulation may be provided by means of air pipes II which extend across the cooling bed near the joints between the tilting plates 4 and which have perforations to direct a stream of air upwardly as indicated by the arrows l2 in Figure 2. As shown in Figure 3, the air is supplied by a header l3 and flexible connections I4 to the pipes II. for the forced circulation are shown only at the lower part ofthe cooling. bed where the bed of coke is thicker and cooler, the natural induced circulation being relied upon at the upper part of the bed where the coke is spread out in a thin but more highly heated layer.

If desired, the natural induced draft through the bed of coke may be supplemented or replaced by a forced draft from a hopper beneath the bed and/or a fan induced draft into a hood above the bed.

The operation of the apparatus is asfollows: The hot coke from the carbonizer is delivered by the conveyor I to the upper part of the cooling wharf and travels downwardly over the wharf in' movement is required and the coke is pushed along by the pressure of the stream delivered from the upper part of the bed. The coke at The lifting movement of a tilting plate causes a localized pulsation in the bed of coke which breaks the existing contacts between the coke particles. The bed of coke is moving down the cooling bed which is formed by the-plates, the

fracture.

As illustrated in Figure '1, the'pipes top surfaces of which form discontinuous planes separated by short drops or steps, somewhat like a flight of stairs. The movement of the coke down a step from one plate to the other prevents the return of the same contacting surfaces into contact with each other after thepulsation has passed. As above stated, if thepiecesiof. coke are allowed to remain in contact with each other long enough, a temperature rise will take place at the points of contactand spontaneous combustion will occur. The agitating'movement of the tilt ing plates 4 also causes a Stratification of the coke, the smaller particles settling to the bottom of thebed and th'elarger pieces going to the top. The smaller particles at the bottom of the bed are thus subjected to 'the mechanical action of the tilting plates and to the friction of sliding over the plates, and the larger and more valuable part of the product is thus shielded by the underlying layer of smaller particles from abrasion and screen before delivery to the railway cars and, the

The cooled product is passed over a finer particles separated from the larger coal balls which are shipped, As described ini the Lesher patent, it is desirable to mix a certain proportion of finely ground coke with the raw stream of coal to be carbonized. The fines recovv ered by the screening of the product can be advantageously employed as a part or all of the finely ground coke used for this purpose.

If desired, the coke may be crushed and screened between the carbonizer and the coolin bed.

After the coke is initially cooled in the relatively thin layer at the upper part of the cooling bed, less movement is required to prevent the spontaneous combustion and .the thickness of the coke bed may be increased to a depth of several. feet. As shown diagrammatically in Figure 1, the amount of movement is progressively decreased and the thickness of the bed is progressively increased as the coke becomes progressively cooler. ing plates 4 are given theirmaximum movement and the coke on the stationary plates slides along,

with its maximum movement of translation, thus insuring a substantially continuous agitation and preventing the points of I contact from being maintained long enough to cause ignition. As the coke passes to the lower portions of the bed it is subjectedto less mechanical agitationfrom the tilting plates and is also subjected to less sliding At the upper part of the bed the'tiltmovement of translationand friction against the plates. As the bed becomes thicker a greater proportion of the coke accumulates in the layers above the bottomwhere it is not subjected to the direct contact with the tilting plates, and is thus subjected to a minimum of abrasion. Also the capacity of the apparatus is increased by having the thin, more rapidly moving part of the bed only where the coke is hottest and allowing the bed to build up in thickness as the coke becomes While, as above stated, the application of water for cooling the hot carbonized coal balls .7

would result in cracking and disintegration of.

' the coke, nevertheless after the coke has become partially cooled, water may be used for the final cooling. Thus, if desired, water sprays may be applied to thelower end of the bed of coke where the temperature has been sumciently reduced.

ture coke which are reactive to oxygen and to which water cooling is not applicable.

Generally speaking, cokes are spoken of as high temperature and low temperature cokes. The high temperature cokes are made by coking at a high temperature in the usual coking-ovens, from which the coke is discharged in. a highly heated and incandescent state. Aircooling is not applicable to such high temperature coke. because it takes flre when discharged from the coking oven and therefore it is necessary to immediately quench the coke with water. Because of the strong porous structure ofthe high temperature coke, the water quenching is entirely satisfactory,

as well as the most economical method of quench- I ing. The low temperature cokes are produced by low temperature coking operations. As contrasted with the high temperature cokes, not all of the volatile matter is distilled from the low temperature cokes, so that the low temperature cokes are highly reactive to oxygen and will ignite at a relatively low temperature. The low temperature cokes, however, are discharged from the coking retorts in a non-incandescent condition and generally at a temperature below their ignition point in air, so that air quenching may be employed provided suitable precautions are taken to prevent the spontaneous combustion due to their extremely reactive properties with oxygen. 1

While our'method may be employed for cooling low temperature cokes in general, it is particularly applicable to the low temperature cokes which are discharged from the coking retorts at a temperature close to but less than the tem-.

perature at which the coke will burn when exposed to the air in a thin layer, but which will take fire when piled in a bed in which the pieces are in contact with each other, and which coke from its physical properties cannot be satisfactorily quenched by water.

While we have specifically illustrated and described the preferred embodiment of our invention, it is to be understood that the invention may be otherwise embodied and practiced within the scope of the following claims.

We claim:

l. A method of cooling highly reactive low temperature cokes which ignite when exposed to the air hot as discharged from a carbonizer if the pieces of coke are allowed to remain continuously in contact with one another, which comprises exposing the hot coke to a cooling circulation of air in a bed of such thickness that pieces of'coke are in contact .with one another, and while thecoke is so exposed moving relatively to one another the pieces of coke which are in contact and thereby preventing continuously maintained points of contact therebetween.

2. A method of cooling highly reactive low temperature cokes which ignite when exposed to the air hot as discharged from a carbonizer if the pieces of coke are allowed to remain continuously in contact with one another, which comprises exposing the hot cake to a cooling circulation of air in a'bed of such thickness that pieces of coke are in contact with one another, and while the coke is so exposed moving relatively ,to one another the pieces of coke which'are in contact and thereby preventing continuously maintained points of contact therebetween, and decreasing the amount of such relative movement as the coke becomes cooler.

3. A method of cooling highly reactive low temperature cokes which ignite when exposed to the air hot as discharged from a 'carbonizer if the pieces of coke are allowed to remaincontinuously in contact with one another, which comprises exposingthe hotcoke to a cooling circulation of -airin a relatively thin bed of such thickness that pieces of coke are in contact with one another, and while the coke is so exposed moving relatively to'one another the pieces of coke which are in contact and thereby preventtherebetween, and increasing the thickness of the bed as the coke becomes cooler.

4. A method of cooling highly reactive low temperature cokes which ignite when exposed to the air hot as discharged from a carbonizer if the pieces of cokeare allowed to remain continuously in contact with one another, which comprises exposing the hot coke to a cooling circulation of air in an advancing bed of such thickness that pieces of coke are in contact with one another, and while the coke is so exposed moving relatively to one another the pieces of coke which are in contact and thereby preventing continuously maintained points of contact therebetween, and decreasing the speed of advance of the bed as the coke therein becomes cooler whereby the depth of the advancing bed is increased as the coke therein becomes cooler.

5. A method of cooling highly reactive low temperature cokes which ignite when exposed to the air hot as discharged from a carbonizer if the pieces of coke are allowed to remain continuously in contact with one another, which comprises exposing the hot coke to a cooling circula- -ing continuously maintained points of contact tion of air in an advancing bed of such thickness v the air hot as discharged from a carbonizer if the pieces of coke are allowed to remain continuously in contact with one another, which comprises exposing the hot coke to a cooling circulation of air in an advancing bed of such thickness that pieces of coke are in contact-with one another, and while the coke is so exposed moving relatively to one another the pieces of coke which are in contact and thereby preventing continuously maintained points of contact therebetween, decreasing the speed of advance of the bed as the coke therein becomes cooler whereby the depth of the advancing bed is increased as the coke therein becomes cooler, and controlling the amount ofsaid relative movement as the advancing bed becomes thicker and cooler so that there is less of such movement in a relatively advanced thicker portion thereof where the coke has partially cooled than in the thinner portion thereof the pieces of coke are allowed to remain continuously in contact with one another, which comprises exposing the hot coke to a cooling circulatemperature cokes which ignite whenlixposed to tionoi' air while traveling downan inclined support in a bed of such thickness that pieces of coke are in contact'with one another, and while the-coke is so exposed moving relatively to one another the pieces of coke which are incontact and thereby preventing continuously maintained pointsot contact therebetween.

8. A method of cooling highly. reactive low temperature cokeswhich ignite when exposed to the air hot as discharged from a carbonizer it the pieces of coke are allowed to remain continuously in contact with one another, which comprises exposing the hot coke to a cooling circulation of air in a bed of such thickness that pieces of coke are in contact with one another, and

pieces of cokew hich are in contact and thereby' preventing continuously maintained points of contact therebetween.

- ARTHUR A. ARCHER.

RAYMOND E.

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