US2541794A - Coke oven with gas recirculating means - Google Patents

Description

Feb. 13, 1951 J. VAN ACKEREN 2,541,794

COKE OVEN WITH GAS RECIRCULATING MEANS Filed Nov. 8, 1945 aan Y' (l) W INVENTOR Joss/H vn/v @axane/v.

bATTORNEY Patented Feb. 1,3, 1951 r- 2,541,794 COKE OVEN WITH GAS RECIRCULATING MEANS Joseph van Ackeren, Pittsburgh, Pa., assigner to Koppel-s Company, Inc., Pittsburgh, Pa., a corporation of Delaware Application November 8, 1945, Serial No. 627,378

8 Claims.

. 1 This invention relates to the control of the temperature in the gas space' at the top of a coke oven. More particularly the invention relates to a mechanism for controlling the flow of gas through the gas spaces above the coal being carbonized in a coke oven, and through gas coll lecting mains to maintain a predetermined maximum temperature in the gas space at the top of the coke oven.

It is very desirable to maintain a substantially uniform temperature from the bottom to the top of a coal bed in a horizontal coke oven that is being carbonized to produce coke. Heretofore some coke oven designs have arranged the top of the heating flues at each side of the coke oven to be below the top of the oven carbonizing. chamber in order to prevent overheating of the gas space at the top of the oven. Even with low top heating ues it is often difficult to prevent overheating the gas space at the top of the oven because some coal shrinks so much that the top of the coke bed falls below the top of the heating flues. In case the tops of the heating flues are below the normal top of the coal bed being coked, the gas space above the fuel bed may become overheated if the temperature in the heating fiues is raised sufcient to increase the rate of coal carbonization. overheating the gas space acts to crack hydrocarbon vapors, and ammonia which are formed by the coal carbonization and thus crack all or a part of the byproducts to decrease the value of the byproducts obtained. Such a cracking operation also acts to form carbon which builds up on the walls of the oven and more especially in1 the gas space interferes with the heat transfer and the proper carbonization of the coal.

The primary object of the present invention is to provide a method of and apparatus for controlling the temperature of the gas and vapor in the space at the top of the coke oven while permitting the maintenance of any desired temperature in the coke bed.

One important feature of the present invention' is to cool the gas being made and maintain a to pass through the oven, the temperature of the gas is raised to nearly the temperature of the coke bed before the gas leaves the other end of the oven. To avoid this condition the direction of ow of the cold gas is reversed at frequent intervals in order to bring the cold gas alternately into the opposite ends of the oven and to maintain a substantially uniform temperature throughout the length of the oven space.

Accordingly another object of the invention is to maintain a positive circulation of cooled gas through the gas space of the ovens in alternating directions to maintain a substantially uniform temperature in the gas space at the top of the oven.

A further object of the invention is to provide a method of controlling the temperature in the top space of a coke oven by cooled gas which is saturated with water to have a high thermal capacity.

A still further object of the invention is to provide a large volume of cooled gas for circulation through the gas space at the top of an oven and to provide a positive flow of a sufficient volume of gas to maintain a uniform temperature throughout the length of the gas space at the top of an oven.

With these and other objects and features in view, the invention consists in the improved method and apparatus for controlling the temperature in the gas space at the top of a coke oven hereinafter described and particularly defined in the claims.

The various features of the invention are illustrated in the accompanying drawings in which= Figure 1 is a view in elevation with parts shown in lsection illustrating the application of the present invention to the gas collecting mains of a horizontal byproduct coke oven; and

Figure 2 is a diagrammatic top plan view illustrating the connection of the offtake mains to the collecting mains of the coke oven for the purpose of controlling the ow of gas through the space at the top of the coke ovens.

The present invention is illustrated as applied to a coke oven of the type illustrated in the patent to Becker 1,752,363 granted April 1, 1930. The coke oven is preferably a horizontal coke oven in which the ovens are arranged side by 3 side with heating flues on the oppositesides of each oven. A battery of ovens is usually composed of a large number of ovens which are operated as a unit, each of these ovens being connected with common gas oiftake mains for recovering the gas distilled out of the coal being carbonized. The ovens are charged to a predetermined level with coal, then carbonized and then the coke pushed out of the ovens in a predetermined time cycle or sequence and thus successively, and only at the time that the coke is being pushed out of an oven are the connections of the oven with gas mains cut off. Referring to Figure 1 a coke oven 'III is illustrated with doors' I2 and I4 mounted at opposite ends. 'I'he oven is charged with coal through charging openings I6 and the top of the coal bed is levelled by a levelling bar which is insertec through an opening I8 in the door I2. The space between the top oi the oven and the top of the fuel bed is the gas space I I. The heating ilues are located between the ovens and these heating ilues are heated while a coke ovenA battery is in operation. As the gases are formed by the coal carbonization they rise through ascension pipes 20 or 22 in accordance with the method of operation of the oven. The gases iiowingup through the ascension pipes pass downwardly through a section of the ascension pipe into collecting mains 24. As the gas enters the collecting mains it is met by a spray of ammonia liquor which is introduced through spray pipes 26, which -act to cool the gas to a'temperature of approximately 80 C. The gas at this time is thus saturated with water and has a high thermal capacity. The amount of spray cooling is, of

course, varied to vary the temperature and saturation of the gas and thus control its temperature, as is conventional. mains the gas flows through oil'take mains 28 to a Tv I0 and passes through a pressure control valve I2 to a suction main 34. The va1ve'32 is 4controlled by a pressure-responsive mechanism 30 which operates the valve in order to maintain a.l predetermined pressure in the collecting mains. To accomplish this, pressure responsive tubes 38 and 40 pass from the control mechanism 38 tov the top of the collecting mains 24. Valves 42 and Il are mounted in the tubes 38 and 40 respectively to open and close the tubes in accordance with the direction of now of gas through the outake mains, according to the present invention, in order to control the flow of gas from one or the other of the collecting mains to maintain the-desired pressure in that main as will be hereinafter described.

"Ijhe carbonization of coal in the coke ovenis preferably carried out in the temperature range of 1000 to.1100 C. within the coke bed. To maintain this temperature in the coke oven, the temperature in theheating flues maybe 150 to 400 higher in order to drive the heat through the oven walls andthrough the bed of Vcoal being carbonized. Depending upon the length of time that the coal has been heated toa carbonizing temperature and the temperature of the heating ilues. the temperature in the gas space at the top of the coal bed may vary from *150 to 925 C.

During the first hour of coal carbonization the largest volume of gas is driven out of the coal.

'I'hen the volume of gas. being generated during each of the following hours gradually decreases. the usual cycle of coal carbonization being sixteen or eighteen hours between charging coal to the oven and pushing coke out of the oven.

From the collecting The hydrogen increased rst hour to approximately In a typical test on two ovens it was found that the gas generated during the ilrst hour was approximately 10,000 cu. ft. and the gas generated during the sixteenth hour was 4,700 cu. ft. The B. t. u. value of the gas generated gradually decreases. during the carbonization of the fuel, and. in the test. above referred to. the B. t. u. value varied from 668 B. t. u. per cu. ft. during the first hour to less than 400 B. t. u. per cu. ft. at the end of a cycle.

The analysis of the gas includes the determination of the `carbon dioxide, the illuminants which include hydrocarbons having more than one carbon atom to the molecule and composed principally of ethylene, oxygen, carbon monoxide,

hydrogen, methane and nitrogen.4 The carbon f hour to 3.9% during the sixteenth hour and then increased to 6.3% during the eighteenth hour. from 44% during the first hour to 84% during the eighteenth hour. The methane decreased from'36% during the 4% during the eighteenth hour. The nitrogen decreased from 5.7 %l during the first hour to 2.3% during the fourteenth hour and then increased to 5.6% during the eighteenth hour. The tars are driven oif most rapidly duringthe rst four hours of the coking operation. These tars contain phe-l nols, cresols, pyridine, anthracene, anthracenc oil and pitch, the products being separated by distillation. The light ,oils are contained principally in the illuminants and are composed of benzol, toluol and xylol, if the carbonization is carried on at a temperature of 1000 to 11000 in the coke bed. The amount of paraillns in the light oil is usually less than 5% with most coals if the coal carbonization temperature is maintained above 1000 C. At temperatures above 1000 C. most of the hydrocarbons of lcarbonization are aromatic.

The data given above relates to the treatment of a specic type of West Virginia coal when treated in two different ovens of the same battery wherein the oven walls were maintained at an average temperature of approximately 1300 C. at the pushing side of the oven and 1350 C. at the coke discharge side of the oven. It will be understood that these'data would vary for different coals and for different temperatures maintained in the coking chamber. However, the data yare representative of the conditions which usually exist in coke ovens.

From the above data it will be seen that the volume of gas and the chemical constitution of the'gas being -made from hour to hour will vary. It will also be seen that, as the ovens are, as ls above pointed out, charged in a predetermined sequence, in the series or sequentially charged., the battery or series comprises as conventional, ovens operable concurrently at different stages of carbonization, early, intermediate, and later. vAlso the carbonization of the coal in a large number of different ovens will give a widely varying condition of gas battery of ovens thus tain so that the hydrocarbons and ammonia products will be less decomposed. the'present invention contemplates circulating sufiicient cooled gas. whose temperature f and saturation with water lis varied, as conventional -as described aforesaid, through the gas-collecting space to control the temperature. Since the gas-collecting space is approximately 40 feet long, the cold gas becomes Vheated in passing through the gascollecting space of the oven, and therefore it is important to reverse the direction of flow of gas through said` gas-collecting space, and to introduce cold gas at opposite ends of the ovens alternately to assist in getting a more nearly uniform temperature throughout the length .of the gas-collecting spaces of the ovens.

The control of the temperature in the gas-collecting crown space may be carried out as follows:

A fan 48 is mounted in the offtake main 28 at the left side of theoven, viewing Figure 1. When this fan is put into operation, it tends to draw cooled gas from the oiftake main 28 and force it down into the collecting main 24 and from that collecting main through the ascension pipes into the left hand end ofthe gas crown-spaces of the ovens in thebattery. The volume of, gas moved bythe fan 46 is sufficient to fill into the collecting main 24 and to force gas through all of the gas crown-spaces above charges in the ovens in the battery. The volume and pressure of the gas maintained in its main 24 by the fan 46 depends upon the size and speed of rotation of the fan and the adjustment of the damper 32 in the T 30. The speed of rotation of the fan is controlled by a variable speed motor or vwith a variable speed drive between the motor and fan. At the time that the fan 46 is in operation, the valve 44 in tube 40 is held in a closed position so that the pressure-responsive operating mechanism 36 will control the valve 32 in accordance with the pressure as indicated from the tube 38 in the left hand. collecting main 24. The collecting'rnains 24 have a sufficiently large volume so that the pressure along substantially the entire length will lbey substantially uniform and thus supply gas to the ascension pipes of each of the ovens with a uniform pressure. It will be understood,` however, that the gas pressure in the gasl spacesv at the top of each of the ovens will vary somewhat in accordance with the state of carbonization being carried on therein and, therefore, the oven which is generating the smallest volumeof gas will receive the largest volume of cooled gas from the collecting main 24. This condition is very desirable because the ovens which are generating the smallest volume of gas generally have the coke bed at the highest temperature and, therefore, a larger amount of cooled gas is required to maintain the desired temperature inl each of the gas spaces above the coke beds. Furthermore, the temperature of the gas space in thetop of the ovens in which the carbonization hasjust started is lower than in the ovens where the carbonization is morecomplete and, therefore, z a comparatively small amount of cooled gas will pass from-the collecting main into the ovens generating the largest volume of-relatively cooler gas.v Yet, it will be appreciated from the foregoing that, with such unidirectional flow of cooled gas under positive lpressure of. fan 45, into the ovens in 'all of the diiferent concurrent stages of carbonizatlon,

. early, intermediate, and later, the flow through the gas flow spaces ofl each ovenchamber, of

this additionalcool'ed gas'under positive pressure. maintains'a rate of'flow of gas through each of the gas flow spaces'of ovens in all stages' of carbonization to the othericollectlng main, that is then operable for gas oil-flow, that is greater than the highest lrate of ilow of gas caused by the generation of gas by carbonization of coal in any of the ovens. -V

At the time that coke is being pushed out of an oven the ascension pipes for that oven are cut off from the collecting mains 24 by means of dampers 48 which may be moved manually into closed position.' At the time that the oven doors are inserted in the oven and co'al is being charged into the oven, the valves 48 are opened to a1- lowV the gas to move from the gas space into the collecting mains.

Since the cooling effect of the cooled gas being circulated through the tops of the ovens'is soon dissipated by the temperature of the oven bed, itis necessary to frequently reverse vthe flow of gas and introduce thel cooled gas at the opposite end of the gas space from which it formerly was introduced. To accomplish this, a timing device 50 which isr any of the well known clock timing devices, is arranged to operate a switch 52 for the purpose of controlling theelectric circuit 54 for operatingv the fan 46 and anelectric circuit 55 for controlling thev operation of a fan 58 mounted in the right offtake main 28. In accordance with'the setting of the timing mechanism the fan 46 will beheld in stationary position when fan 58 isoperating and fan 58 will be held in stationary position when fan 46 is operating. When fan 46 is operating, the gas drawn from the oitake main 28 and forced into the collecting main 24 to pass through the ovens, the gas will then ow to the collecting main 24 at the right in Figure l, and then through the oiftakemain 28 to the T 30 and out through the suction mainv 34. At this time, the fan 46 will cause to move through thegas-collecting spaces more gas than is being generated in lthebatte'ry of ovens and so that, that part of the gas it supplies is gas that is recycled for the purpose of controlling the temperatures in the gas spaces above the ovens. The amount of gas released from the ofttake mains 28 during these operations is controlled'by the-valve 32, which is controlled by the pressure in that collecting main 20 which is supplying gasto the then inlet side of the gas spaces above the oven charges. f

In practice, it has been found that the direction of flow of cooling gas through'the gas space above the ovens shouldbe reversed at about five minute intervals. These intervals, however, may vary quite-widely, that is from two minutes to sixty minutes, depending uponv the type ofv coal being carbonized, the -type of coke being made, and the type of gas being produced. It is quite desirable, however, torz ysecure the maximum amount of byproducts and, therefore, the reversals are made sufficiently frequent that at the rate of flow and temperature, the temperature of the cooled-make-gases is sufficiently low to maintain a temperature inthe gas owspaces at the tops of the ecke oven chambers below a maximum of 850 C. to hold the'temperature in the gas spaces above the `'coke beds in the ovens atabout 800 C. in order to prevent decomposition of the byproducts beingy made that otherwise woul obtain at higher temperatures. y Y The use of fans; 46 and 58 acts to increase the rate of owof gas through'the gas spaces above -theioven charge and thus not only tends to minimize the cracking or destruction of valuable byproducts but acts to minimize the amount of secondary reactions which take place to form less desirable byproducts.

The timing device 50 which controls the switches for operating the driving motors for the fans 46 and 58 also operates a switch 66 that controls circuits 62 and 64 by which the valves 42 and M are opened and closed. It will be understood that with this arrangement, when valve 42 is open, valve 44 will be closed and viceversa..

As illustrated in Figure 2, the oiftake main 28 and suction main 34 are preferably mounted on the collecting mains 24 near their mid portions, so that the gas re-cycled by means of fans 46 and 58 may be introduced into the collecting mains in the central portion more easily to distribute gas throughout the length of the main. Although the ovens are generally arranged in batteries of from thirty to eighty ovens, the number of oitake mains may be varied in order to secure the proper distribution of the cooled gas in the collecting mains for the purpose of controlling vthe temperature in the gas-collecting spaces at the top of the ovens.

In the drawings, fans 46 and 56 have been illustrated for the purpose of circulating the cooled gas. In some cases it is more desirable to use positive pressure blowers where a large volume of gas is used and such positive pressure blowers would be mounted in a bypass in the ottake mains 28 in order to provide a path for free circulation of the gas when the blower is not in operation. The fans are very advantageous in that when the fan is idle the gas being generated can pass through the fan to the suction main.

The preferred form of the invention having been thus described, what is claimed as new is:

1. The combination with a battery of horizontal coke ovens, each oven having a horizontal gas collecting crown space along the length of the top of the oven; an ascension pipe at each end of each crown space; a collecting main running along each side of the battery and each in simultaneous open communication with the aforesaid ascension pipes located on its side of the battery; an oitake main simultaneously in open communication with each collecting main; a suction main in communication with the oiltake main, said suction main continuously withdrawing part of the coke oven gas from said offtake main; gas circulating means for forcing the rest of the coke oven gas from said offtake main back into the collecting main on one side of said battery into all of the connecting ascension pipes, through the open crown spaces of all ovens undergoing carbonization where it joins with any gas being evolved in the coke ovens, all of the gas then flowing out through the ascension pipes and into the collecting main on the other Side of the battery, and back into the offtake main; means for reversing the forced gas ow so as to similarly pass the gas through the crown spaces of said ovens at one end only for now of all of the cooling medium directly into the same and thence clear across alll of the crown spaces to the opposite end, to periodically reverse the direction of.

flow, with inflow of cooling medium from the outside source into, and outflow of the madecoke oven distillate gas to the gas offtake means i from, the respective mains in alternation with each other, and solely by means of the introduction under positive pressure of the cooling medium alternately solely into one and then solely into the other of the two mains, and in which the two gas mains are in open communication with each other through the-gas oitake means, and in which the means for introducing said gaseous cooling medium from a source outside the` oven comprises separate gas circulating means in the offtake means for circulating part of the gas therein back into the oven chambers through the respective gas mains in alternation with each other.

3. Coke oven apparatus as claimed in claim 2.

and which includes valve means for controlling' the release of the gas from the gas oitake means, and pneumatic-pressure controlled operating mechanism operatively connected with the two gas mains and with said valve means for periodically controlling the latter in alternation, by and in accordance with the pressure in one end and then the other of the two mains, in conformity with the periodic reversal in flow and in function r of the two mains.

4. Coke oven apparatus as claimed in claim 2. and which includes automatic time-controlled means operatively connected with the separate gas circulating means for operating them periodically in alternation with each other.

5. Coke oven apparatus as claimed in claim 3, and which includes automatic time-controlled means operatively connected with the separate gas circulating means and with the pneumaticpressure controlled operating mechanism, for operating the separate gas circulating means periodically in alternation with each other, and for periodically operating the pneumatic-pressure controlled mechanism.

6. Coke oven apparatus as claimed in claim 2 and in which the gas'circulating means is a motoroperated fan.

7. Coke oven apparatus as claimed in claim 2, and in which each of the gas circulating means is a positive-pressure motor driven blower mounted in a by-pass in the gas offtake means, to provide a path for free circulation of the gas when the blowers are not in operation.

8. Coke oven apparatus as claimed in claim 2, and which includes an operating mechanism for the valve means, which operating mechanism is connected with the pneumatic pressure mechanism to be operated thereby by means of the pressure within the main into which the gaseous 9 l l 10 cooling medium is forced by the gas circulating Number- Y Name Date means. 2,116,641 Reppekus May 10, 1938 JOSEPH VAN ACKEREN. 2,311,114 Koppers Feb. 16, 1943 REFERENCES CITED s FOREIGN' PATENTS The following references are of record in the Nuggen Gergg'gl FebPlalga me 0f this Patent: '100,552 Germany Dec,13, 1940 UNITED STATES PATENTS '102,765 Germany Feb. 15,- 1944 Number Name Date lo 490,271 Great Britain Aug. 11, 193s 1,369,673 Kappers Feb. 22, 1921 OTHER. REFERENCES 'g ggg? et al --bcpr Porter: coal carbonization," published 1924 2:0061115 Schaefer n June 25' 1935 by the Chemical Catalog Company, Inc. (Copyin Division 25, pp. 280, 281, 282.)

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