US1919704A - Distillation of tar at a coal distillation plant and apparatus therefor - Google Patents

Description

July 25, 1933. F. OSBORNE 1,919,704

DISTILLA'I'ION OF TAR AT A COAL DISTILLATION PLANT AND APPARATUS THEREFOR Filed Feb. 26, 1927 2 Sheets-Sheet 2 Oona ergsers INVENTOR PMM MM ATTORNEYS \rAV Patented July 25, 1933 UNITED STATES, PATENT OFFICE FRED OSBORNE, or am vrmenmyenanama, ASSIGNOR TO THE, BARRETT COMPANY, or NEW YORK, N. Y., A CORPORATION or NEW JERSEY DISTILLATION 0F TAR AT A COAL DISTILLATION PLANT'AN 'D APPARATUS THEREFOR Application filed February 26, 1927. Serial No. 171,153.

. This invention relates to improvements in the distillation of tars and the productionof pitches and distillate oils therefrom, and 1ncludes improvements in both method and apparatus. More particularly, the 1nvent1on relates to improvements in the d1s't1llation of coal tar and the production of pitches and distillates at coal distillation plants, such as by-product coke or gas ovens or gas retort plants. The invention also includes improvements in the construction and op eration of by-product coke. oven, gas. oven, and gas retort plants. a

In the ordinary operation of by-product coke ovens the gasesproduced by the coking operation pass from the individual ovens through individual uptake. pipes and goosenecks toa collector main or mains common to a battery of ovens. The cokeoven gases leaving the ovensat a-hightemperature are cooled to separate tar constituents therefrom, the tar constituents being separated partly in the collector mains and partly in subsequent condensers.

Coal tar produced atby-product coke 'ov-- ens is commonly shipped or conveyed to tar distillation plants where it is subjected to distillation for the recovery of coal tar distillates and the production of pitches as residuesof the distillation.

The present invention provides an improved process of and apparatus for tar distillation in which the tar is distilled directly at the by-product coke oven plants without the need of a separate tar distillation plant and Without transportation expense, and withthe production from the tar of distilled oils and of pitches as residues of the distillation.

According to the present invention, the hot coke oven gases, as they come from one or more of the individual coke ovens, are utilized for the distillation of tar to vaporize more or less of the oils therefrom and produce a pitch residue, and the vaporized oils are condensed separately from the tar constituents of the gas evolved from the rest of the battery. The separated oils are relatively free from admixed tar, containing only such tar constituents admixed therewith as are condensed from the hot gases used 1 for the distillation. enables the hot coke oven gases fromone or more of the coke ovens to be utilizedfor the distillation of tar, with separate condensa- The present invention tion of the distillate, when this is desired, 1

and enables the hot coke oven gasesto be collected inithe ordinary mannerwhen it is not desired to utilize them for the distillation of tar. r a

According to the present invention, the tar to be distilled is sprayed or otherwise brought directly into contact with the hot coke oven gases from a greater or less number of individual,ovens,vata sufficiently high temperature sothatthe tar is effectively distilled thereby, with separation therefrom of a greater or less amount of volatile oils, leaving a heavier tar or pitch as the residuum product of the distillation, and the gases and admixed vapors from the distillation are kept separate fromthe-coke oven gases from the other ovens. The invention enables the number of ovens or decreased when it is desired to increase or decrease the distillationof tar, and enables the hot gases from these ovens to be collected in the ordinary way when these gases are not utilized for such distillation.

The sprayingof the tarfinto the hot coke oven gases results in partial cooling of these gases and separation therefrom of more or less .of the heavier tar constituents, a proportion of which are thus thrown down and added to the pitch residue from the tar distillation, This distillation of the tar also results in an increase ofcondensable vapors in the hot coke oven gases treated as well as in the partial or preliminary removal from the gases of heavier tarconstituents,

s0 utilized to be increased so that'these coke oven gases in their par- .tially purified condition and with the increased amount of vapors from the distillation of the tar, differ in composition from the ordinary coke oven gases not so treated.

Certain of the individual coke ovens, according to. the presentinvention, are connected not only withthe ordinary gas collecting system or systems but are connected with a. separate gas collecting system or the gas is at substantially its maximum temperature, but the invention in its broader aspects is not limited to the use of such uptake stills. Other apparatus may be employed to utilize the hot gases for the direct distillation of tar.

The distilling capacity of the gases from a single coke oven is greatly in excess of that required for distillation of the amount of tar which a single coke oven produces, so that the tar from a considerable number of coke ovens can be distilled in a single uptake pipe by the hot gases from a single oven.

In the construction of a battery of ovens, for distilling all the tar produced on the battery, it is therefore sufiicient to provide a few only of the individual ovens with uptake pipe stills. for distilling tar with the hot coke oven gases, and the remainderof the coke ovens of the battery may be operated in the ordinary way, the recovery of coal tar from their gases being accomplished in the ordinary manner. Such recovered coal tar may then be distilled in the few uptake pipe stills to produce pitches therefrom and to permit recovery of the vaporized oils from the distilled tar, together with tar and oils normally present in the gases.

The construction of:,the coke oven battery and of. its by-product recovery system may remain practically unchanged except for the substitution of the uptake pipe stills or their equivalent for the ordinary uptake pipes, and the provision of a separate collecting main and condensing system for the gases from the uptake stills when these are employed for tar distillation. As many of the ovens as desired are provided with the uptake" stills and these stills are connected both with the ordinary collector main and with a separate collector main. The gases from the uptake stills may be delivered to the separate collector main when they are to be employed for the distillation of tar. When these uptake stills are not to be so employed, the gases therefrom may pass to the ordinary collector main the same as in ordinary coke oven battery operation. Those uptake pipe stills which are utilized for the distillation of tar are provided with separate collecting, cooling and condensing systems so that the coke oven gases employed for the distillation and admixed with the vapors from the distillation can be cooled and the products separately recovered.

It is one advantage of the present invention that it can be directly applied to existing or present day coke oven construction. Present (lay coke oven operation, so far as the production of coke is concerned, is unaffected, while nevertheless tar may be distilled and pitch produced and oils recovered in the separate gas collecting and condensing system. The by-product recovery system for the coke ovens which are not modified by the provision of the uptake pipe still can be operated in the ordinary way; while the gases from the uptake pipe stills, when these stills are not to be operated for the distillation of tar, can also be connected with the ordinary by-product recovery system, and only those uptake pipes which are employed for tar distillation connected with the separate by-product recovery system.

Another advantage of the invention is that it permits various grades of pitches to be produced continuously. Low melting pitches' require less heat and less time of contact with the hot uptake gases for their production than do the high melting point pitches. Therefore, with a given plant converting its entire tar production to pitch and oil, the complete conversion of heavy tar to low melting point pitches requires the continuous operation of a less number of uptake pipe stills than does the complete conversion of the same quantity of tar into high melting point pitches. The invention provides flexibility of operation such that the desired grade of pitch can be continuously produced.

The tar which is distilled according to the present invention may be tar produced at the same coke oven plant at which it is distilled, or it may be tar from another coke oven or other plant. The tar may be a heavy tar, light tar, or heavy or light tar constituents which it is desired to distill to separate distillate oils therefrom. Other tar, such as gas house tar, vertical retort tar or water gas tar, etc., can also be distilled. Where blended or composite pitches are desired, or composite or blended distillates, two or more different kinds of tar may be separately distilled at the coke oven plant, or may be admixed in suitable proportions and be distilled together, giving directlya composite pitch product. Where different tars are distilled, the resulting pitches may be blended to give a composite product, and the distillates may likewise be blended when desired. For example, horizontal gas retort tar with high free carbon content can be admixed with coke oven tar and the mixture distilled to give a composite pitch higher in free carbon than the pitch from the coke oven tar and to give a composite oil distillate.

heavy tar containing only part of the oils.

Where mixed tars are distilled, the condensates condensed in the separate condensing system or systems will-be of a composite vcharacter. Where different tars are separately distilled, the gases and vapors from such separate distillation can be separately condensed in separate condensing systems, or condensed together in the same condensing system. The effect of the distillation is proportionately to increase the content of relatively lighter oil vapors and to decrease proportionately the content of heavy pitch constituents, owing to the purifying efi'ect of the tar spray in separating and throwing down some of the heavierconstituents of the gases. I

Where a few only of the coke ovens of a battery are employed for the distillation of tar and separate collection of oil, in accordance with the present invention, the separate condensing system or systems for the vapors from the coal gases of such ovens can be much smaller than the main. condensing system for the remainder of the battery. Such separate condensing system or systems may be of similar construction and operation as the ordinary condensing system, from the standpoint of oil recovery, or of different construction and operation. Owing to the increased condensible oil vapor content of the gases, a proportionately smaller amount of gases require handling, while, from corresponding quantities of the gases, a much greater amount of condensable constituents can be recovered than from ordinary coke oven or retort gases.

The manner in whichthe tar is brought into direct contact with the hot vapors can be varied. A suitable .atomizing or spray nozzle, to which the preheated and thinly fluid tar is supplied under a sufficient pressure to bring about atomiz ing or spraying and resulting intimate contact of the tar with the hot gases, can be located in the upper part of the modified uptake pipe to bring the tar into intimate contact with the hot gases.

A single tar spray can be used in each of the individual uptake pipes, or a plurality or series of such sprays, and the rate at which the tar is sprayed, as well as its temperature, can be regulated and con-' trolled to obtain a greater or less degree of distillation of the tar and the production of distillates of desired characteristics, and of harder or softer pitches or pitch-like products. r

The gases escaping from the top of a coke oven are at a high temperature, e. g., around 600 to 700 (1., or in some cases much higher. The temperature of these gases is sufficiently high so that effective distillation of the tar can be accomplished by an intimate and regulated spray of the tar into the hot gases. By employing the gases at practically top-of-oven temperature their. maximum heating and distillingefl'ect is utilized. The amount of tar and the intimacy and time of contact of the particles of thetar spray with the gases, and the nature and amount of oil distilled therefrom, can be varied. Effective distillation can be accomplished with a temperature drop of the ases while passing through the tar spray, of, for example, 100 0., although with increased amount of tar or increased intimacy and time of contact agreater drop in temperature and increased distillation of oil can be obtained. I

In a coke oven plant having a small battery of ovens, for example. a twenty oven battery, one or two uptake stills may be sufficient to distill the tar from the remaining ovens of the battery andsuch still or stills 'may have a separate condensing system. In

a larger coke oven plant having a large number of ovens in the same or'separate batteries, a larger number of the uptake stills will be required to distill the tar produced by the remaining ovens ot the battery or batteries. If tar from an outside source is distilled, a larger number of uptake stills may similarly be required. Where a coke oven plant has several batteries of ovens,-one

The present invention presents the advantage that a smaller or larger numberof uptake stills can be employed as desired for the distillation of tar, and such uptake stills as are not desired for such distillation can "be connected with the ordinary gas collecting system, thus enabling the distillates from. a larger or smaller number of the uptake stills to he collected together without contamination from gases from other uptake pipes whichare .not employed for distillation. For example, where the uptake pipes are connected both with the ordinary collector main and; with a separate short collector main common to all'of the uptake pipe stills, and where suitable valves are provided for connecting the upact, are opened to the short separate collector main, while the remaining uptake pipe stills which are not employed for distillation are opened to the ordinary collector main. Moreover, a part only of the uptake pipe stills employed for tar dist-illation may be connected with the short separate collector main and the other uptake pipe stills so employed connected with the ordinary collector main so that a part of the distillates can be recoverd in the separate condensing system and the remainder in the ordinary by-product recovery system of the battery.

The separate condensing system may be a fractional condensation system with direct or indirect coolers or condensers.

The separate collector main to which the uptake pipe stills are connected, may be arranged alongside the ordinary collector main, or arranged above it, or at any convenient place where it can be connected with the uptake pipe stills. In effect, there is provided a two-main system with one the ordinary collector main and with the other main connected to a separate condensing system, with provision for connecting the individual uptake pipes with one or the other of these mains so as to utilize part or all of the uptake stills for distillation of tar and so as to permit keeping the vapors and gases from such distillation separate from the uptake pipes which are not utilized for such tar distillation.

The invention will be further illustrated by the following more detailed description taken together with the accompanying drawings which show apparatus embodying the invention and adapted for the practice of the process of the invention, but it is intended and will be understood that the invention is illustrated thereby but not limited thereto.

In the accompanying drawings, Fig. 1 is a plan view of part of the battery of coke ovens with part of the ovens provided with the uptake pipe stills connected 0th with the ordinary collector main and with a separate collector main and condensing system;

Fig. 2 is a view in elevation, showing the end of the battery; and

Fig. 3 is an enlarged sectional view showing the arrangement of uptake pipe still and separate collector mains;

Fig. 4 shows one of the uptake pipe stills in elevation.

The invention is of more or less general application to different types and constructions of by-product coke ovens such as Semet-Solvay ovens, Koppers ovens, etc.,

- but will be more particularly described and illustrated in connection with by-product coke ovens of the Semet-Solvay type.

In the drawings the coke oven is illustrated conventionally at 1 and has the usual gas outlet 2 for the escape of the hot coke oven gases. The outlet pipe 3 is seated in a suitable seal over the gas outlet 2 and connects at its upper end with the lower end of the casing 4. The upper end of. the easing 4 connects with the uptake L 5, which leads to the ordinary collector main 6 and to the separate collector main 7, valves 8 and 9 being provided for connecting the uptake L with one or the other of these mains as desired.

The casing 4 is enlarged to provide a space around the inner pipe member 10, which extends upwardly into the enlarged casing 4. The lower ends of the pipe 10 and the casing 4 are preferably integral or otherwise arranged to provide an annular receptacle for the'collection of the pitch or residue from the distillation.

Located within the casing 4 and above the end of the pipe 10 is a bafile or hood 11, and above this is a spray head 12 connected with a pipe 13 for spraying tar to be distilled. An outlet 14 for pitch or residue is located at the bottom of the enlarged casing 4 for discharging the pitch or residue from the annular space at the bottom of this casing. The casing 4 is attached at its lower end to the outlet pipe 3, which in turn is sealed in the roof structure of the oven. At its upper end the casing 4 is connected with the uptake L 5.

The casing 4 has a series of doors or openings 15 near the bottom to permit inspection and cleaning. The casing also has an upper door 17 carrying the bafile or hood 11, the arrangement being such that when the door is open the baffle 11 is removed from the casing. The casing 4 also has overflow outlets 18, located some distance from the bottom of the annular space at the bottom of the casing.

The connection from the uptake pipe still to the collector mains may be provided with a spray 19 for cooling or assisting in cooling the condensable constituents of the gas and for spraying the valves 8 and 9. Additional spray nozzles 20 may also be provided in the ordinary collector main'6 and other sprays 21 in the separate collector main 7. Ammonia liquor can be used in such sprays or tar or tar oils or any com bination of these three.

The coke oven battery illustrated in Fig. 1 has the ordinary uptake pipes 22, which are connected only with the usual collector main 6. The usual cross-over main is indicated at 23, leading to the coolers or condensers 24 and 25 connected to decanter 26. The product recovered in the decanter may be drawn off and used, or may be returned to the dehydrator or preheater 29 in case it is to be redistilled. The exhauster for prising the uptake pipes 22 and the collector main (3 cross-over n'iainfz i, coolers, etc., is the ordinary by-product coke oven system.

The tar collected in the collector main and cross-over main is shown as running to a tar collecting tank or decanter 38, in which the tar separates from the ammonia liquor and this tar in turn is shown as leading to a. preheater or dehydrator 2!) for partly or completely freeing the tar from water and The, outlet preheating it for distillation. line for the ammonia liquor is shown at 280. The preheater may be of any suitable construction. The dehydrated or preheated tar is then pumped by the pump 30 through the tar supply line 13 to the spray nozzle 12. The tar may-however be employed without preheating or dehydrating, although spraying is facilitated by preheating the. tar sufficiently to make. it thinly fluid.

The so )arate collector main to which the uptake Ls are connected has its own separate condensing system, which is shown as smaller in size than the main condensing system. The gases from the separate collector main pass through a separate crossover main 32 to a series of direct or indirect coolers or condensers indicated at 33, 34: and 3.), each connected with a decanter 36. The piping connection is-such that the gases can be. passed in series through the three coolers or condensers, or in part or in whole passed directly to the second or third of these con- (lonsers. By passing the gases through the three coolers or condensers in series, fractional condensation will be effected. In the case of indirect coolers, the gases will be cooled without coming in contact with the cooling liquid; while with direct coolers or condensers the gases will be scrubbed, e.g. with ammonia llquor or with tar or tar oils to promote the cooling and condensation. From the last of the coolers or condensers the gases pass through the pipe 37, which connects with the gas pipe from the main condensing system leading to the exhauster 27 or to a separate exhauster (not shown) so that the gases may be drawn through the separate condensing system by the same ex hauster or by a separate exhauster.

Any tar or oily tar or tarry oil separating in the small collector main, as where ammonia liquor spray is employed therein, may be run from the center box 31 through pipe 38 to the receptacle 39 for the separation of ammonia liquor from the oil or tar. Owing to the scrubbing effect of the tar upon the hot coke oven gases and the large distilling capacity of these gasesand the resulting greatly increased vapor content of the gases, the oils condensed therefrom will be relatively clean oils which may be directly utilizable, for example, as creosoting or other material. A further separation of heavier tar constituents will take place in the separate collector main, giving a relatively cleaner tar \Vhen the amount of tar to-be distilledis increased, a larger number of the uptake pipe stills can be employed for the distillation and connected with the separate colleetoi' main. \Vhen the amount of tar to be distilled is decreased. a smaller number of the uptake stills will be required. The provision ofseparate collector mains, according to the present invention, enables such of the uptake pipe stills as are used fol-the distillation to be connected with the separate collector main and condensing system; and the remainder of the uptake stills, when not so used, connected with the ordinary collector niain and condensing system. In this way the number of the uptake stills employed for distillation can be increased or decreased merely by connecting these uptake stills withthe separate collector main or with the ordinary collector main as the case may be. The invention thus provides for flexibility of operation and widely 'varying tar distillation capacity, while permitting all of the coke oven gases not employed for the distillation to be collected in the ordinary manner.

The tar to be distilled is supplied in regulated amounts to the spray nozzleor nozzles and sprayed into the hot gases in the uptake stills. lVhen the tar is preheated it is thinly fluid and may be pumped to the nozzle under a suitable pressure, for example, of 40 pounds per square inch and discharged through the nozzle so as to atomize or spray it into the hot uprising gas. The tar may be advantageously preheated before being so sprayed. The hot gases are brought into intimate contact with the spray'of tar and effect distillation of more or less of the volatile oils therefrom, while the gases are themselves somewhat cooled. The tar is prevented from falling into the coke ovens by the baffle 11 and collection space outside the pipe 10 and runs out through the pitch or residue outlet 14:.

The action of the hot gases upon the particles of tar or oil spray or upon the tar or oil otherwise brought into intimate contact with them and flowing down over the surfaces of the uptake pipe still, is such that the tar or oil is heated and volatile oils distilled therefrom so that a heavier tar or pitch or residual oil collects and runs out through the'pitch or residue outlet. The character of the distillate, i.e., the extent to which the heavier oils are removed by the distillation, can be regulated as well as the character of the pitch or residue produced.

From the standpoint of the operation of the coke oven battery, it will be noted that all of the ovens are provided with uptake pipes connected to the ordinary collector main while art of the ovens have uptake pipes of modified construction adapted for tar distillation which are also connected to a separate collector main. The ordinary collector main may be provided with ammonia liquor or tar sprays for separating a considerable amount of heavy tar and giving gases of low tar content going to the coolers or condensers. The entire tar product or only the heavier tar or only the lighter tar can then be returned as the tar to be distilled in such of the uptake pipes as are employed for the tar distillation; and the resulting vapors from the distillation, together with admixed gases, can then be separately collected and condensed. The part of the battery thus employed for tar distillation can thus be varied and the number of uptake stills employed for distillation increased or decreased with the amount of tar to be distilled or to conform with the quality of pitch residue or oil distillate desired. If only the tar from the remainder of the battery is to be distilled a few uptake stills will suilice for this distillation. 1f tar from other batteries or from an outside source is to be distilled, this can readily be effected by employing an increased number of the uptake stills and connecting them with the separate collector main and condensing system.

The invention thus provides a new method of operation of by-product coke oven batteries in which the hot coke oven gases may be to a greater or less extent employed for tar distillation and the resulting distillate separately condensed and in which the hot coke oven gases from the same ovens can be subjected to condensation in the usual condensing system at such times as they are not required for distillation. The invention also includes an improved construction and arrangement of distillation equipment for a particular by-product coke oven battery, in which provision is made for utilizing the hot gases from as many as desired of the coke ovens for tar distillation and for collecting and condensing the gases from these same ovens as a part of the ordinary collecting and condensing system when they are not required for such distillation. The inventionthus provides a flexible tar distillation plant of greater or less capacity as a part of a by-product coke oven battery, without interfering with the operation of the battery, and with utilization of the heat of the hot coke oven gases for the distillation.

The products obtained by the redistillation of the tar, according to the present invention, include pitches which may be of varying degrees of hardness and also the distillate oils produced from the distillation of the tar which are admixed with oils and tar constituents from the coal distillation gases employed for the distillation. Where the tar distilled is a complete tar, containing practically all of the tar constituents, a correspondingly wide range of boiling pointoils will be produced. Where only heavier tar is distilled, the distillate will contain a correspondingly increased content of heavier oils. The invention makes possible therefore, the production of oils of different properties, with low content of heavier coal tar constituents, directly at the coke oven plant.

The uptake pipe and the circulating lines, etc., are illustrated in the drawings in a conventional manner and without any insulation around them but where it is desired to prevent loss of heat by radiation, or to reduce such loss, or to prevent undue cooling of circulating lines, etc., such circulating lines, and the uptake pipes and connecting pipes through which the gases and liquids pass, can be provided with heat insulation.

Furthermore, the hot coal distillation gases from the coke oven can be cooled somewhat before bringing them into contact with the tar provided their temperature is still sufficiently high to bring about the desired distillation of the tar and the production of distillates and pitch therefrom. It is advantageous, however, to utilize the hotgases at their maximum temperature, immediately after they escape from the coke ovens, by employin them in the manner described.

\Vhile T have described and illustrated a particular type and construction of uptake pipe still, it will be evident that the invention in its broader aspects can be carried out in apparatus of other construction in which the tar or oils are distilled by the hot gases and the distillates separately condensed inthe manner described.

I claim:

1. A by-product coal distillation battery having a number of coal distillation ovens with a common condensing system including a collector main for collecting gases and vapors from the ovens of the battery, at least one of the ovens so connected being provided with a tar still adapted to receive hot fresh gases from the oven and provided with means for introducing tar into direct and intimate contact with the gases passing therethrough to effect distillation of the tar and the production of pitch, the oven connected to both the collector main and still being provided with a second condensing system and with means for disconnecting the oven from the collector main, and means for disconnecting it from the second condensing system whereby the gases from said oven can be either employed in the still for the distillation and then passed to the second condensing system, or combined with other gases in the collector main.

2. A by-product coal distillation battery having a number of coal distillation ovens with a common condensing system including a collector main for collecting gases and vapors from the ovens of the battery, at least one oven of the ovens so connected being provided with a tar still adapted to receive the hot fresh gases from the oven and provided with means for introducing tar in a finely divided state into the gases passing therethrough to effect distillation of the tar and the production of pitch, the oven connected to both the collector main and still being provided with a second condensing system and with means for disconnecting the oven from the collector main and means for disconnecting it from the second condensing system whereby the gases from said oven can be either employed in the still for the distillation and then passed to the second condensing system or combined with other gases in the collector main.

3. A by-product coke oven battery having a number of coke ovens with a common collector main and condensing system connected to a numberof ovens, part of the ovens so connected being provided with stills adapted to receive the hot gases from the ovens and provided with means .for introducing tar in a finely divided state into the gases passing therethrough to effect distillation of tar and the production of pitch, a seperate condensing system connected to said stills for receiving the gases and vapors therefrom and condensing the distillate from the gases, the ovens connected to both the collector main and stills being provided with means for disconnecting them from either the collector main or said separate condensing system whereby the gases from said ovens can be either employed for distillation and passed to the separate condensing system for distillation or combined with other gases in the collector main and first mentioned condensing system.

4. A by-product coke oven battery having a number of coke ovens connected to a common collector main and condensing system for cooling the gases and separating tar therefrom, a short separate collector main and separate condensing system connected to a part of the said ovens, means for distilling tar arranged between said ovens and the short collector main for receiving the hot gases from the ovens and provided with means for bringing tar to be distilled into direct and intimate contact with the hot gases therein to effect distillation of the tar, together with means for disconnecting the ovens from said short collector main and connecting them with the first mentioned collector main and vice versa, whereby the hot coke oven gases from such ovens can be employed for distilling tar and, when not so employed, can be collected in the first mentioned collector main and condensing system, and whereby the gases and distillate vapors from such distillation can be separately condensed to recover the distillate from the gases.

5. The improvement in the operation of by-product recovery systems of coal distil lation plants having a number of ovens which comprises collecting and cooling coal distillation gases from part of the ovens to separate tar therefrom, distilling the tar so separated by bringing it into direct and intimate contact with hot coal distillation gases evolved from part of the ovens with resulting production of a pitch residue and of gases enriched in oil vapors from the distillation, cooling the resulting gases and vapors to separate the distillate therefrom, and regulating the number of ovens from which the gases are cooled to separate tar and thenumber of ovens of which the gases are employed for tar distillation so that all of the tar separated from the gases is distilled by direct contact with the remaining gases and increasing or decreasing the quantity of gases so employed so that the gases not employed for the distillation of tar are cooled for the separation of tar therefrom, and so that all of the tar produced at the battery is distilled and converted into distillate and pitch, and combining the gases from which the tar has been separated and the gases from which the distillate has been separated to form a combined gas for further treatment.

6. A by-product coke oven battery having a number of coke ovens with a common condensing system including a collector main for collecting gases and vapors from ovens of the battery, at least one oven of the ovens so connected being provided with a tar still adapted to receive the hot fresh gases from the oven and provided with means for introducing tar in a finely divided state into the gases passing therethrough to effect distillation of the tar and the production of pitch, the oven connected to both the collector main and still being provided with a second condensing system and with means for disconnecting the oven from the collector main and means for disconnecting it from the second condensing system whereby the gases from said oven can be either employed in the still for the distillation and then passed to the second condensing system, or combined with other gases in the collector main.

FRED OSBORNE.

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