US1971690A - Method of distiling tar and apparatus therefor - Google Patents

Description

S. P. MILLER Aug. 28, 1934.

METHOD OF DISTILLING TAR AND APPARATUS THEREFOR Filed March 23, 1928 5 Sheets-Sheet 1 ATTORNEYS S. P. MILLER Aug. 28, 1934.

METHOD OF DISTILLING TAR AND APPARATUS THEREFOR Filed March 23, 1928 5 Sheets-Sheet 2 (a/re Oren I Illllllllllllllll a :frli imzz QQQG QQ INVEN OR w izzu MM ra -A ATTORNEY5 S. P. MILLER Aug. 28, 1934.

METHOD OF DIST ILLING TAR AND APPARATUS THEREFOR Filed March 25, 1928 5 Sheets -Sheat 3 INVENTOR WW ATTORNEYS S. P. MILLER Aug. 28, 1934.

METHOD OF DISTILLING TAB. AND APPARATUS THEREFOR Filed March 23, 1928 5 Sheets-Sheet 4 ATTORNEY5 Aug 28, 1934. s.. P. MILLER 1,971,690

METHOD OF DISTILLING TAB AND APPARATUS THEREFOR Filed March 23, 1928 s Sheets-Sheet 5 INVENTOR ATTORNEYS Patented Aug. 28, 1934 PATENT OFFICE METHOD OF DISTILLING TAB AND APPARATUS THEREFOR Stuart Pal-melee Miller, Englewood, N. J., as-

signor to The Barrett Company, New York, N. Y., a corporation of New Jersey Application March 23, 1928, Serial No. 263,988

6 Claims. (Cl. 202-30) This invention relates to improvements in the distillation of pitch, tar and tar oils and includes a new method of distillation as well as an improved apparatus therefor. The invention is apl plicable to the distillation of pitch, tar or tar oil with other coal distillation or gasification gases, but will be more particularly described as applied to coke oven and gas retort operation.

In the ordinary operation of by-productcoke l ovens, the gases produced by the coking operation pass from the individual ovens thru uptake pipes and goose-necks to a collector main common to the ovens of the battery. The gases, commonly known as foul gases, leave the ovens 5 at high temperatures, for example at 600 to 700 C., or higher, and carry a considerable proportion of volatilized tars and oils as well as solid particles of coke, dust, etc. Ordinarily the gases are cooled by the application of sprays or ammonia liquor or ammonia liquor and tar in the collector main, the heat in the gases being thereby dissipated and lost. In some cases sprays are not used but large quantities of tar or tar and ammonia liquor are flushed along the bottom of the main. The rapid cooling causes separation of tar containing heavier oils in the collector main. Further cooling is effected in the cross-over main which connects the collector main to the condensing system and an additional quantity of tar carrying both heavy and lighter oils is thus separated, In the condensers additional quantities of tarry oils are recovered and are commonly blended with the heavier tars from the collector main.

The collected tar is ordinarily shipped from the coke oven or other coal distillation plant to a tar distillation plant for distillation and separation of the oils, and the production of pitches of varying quality. Handling costs, freight charges and distillation costs and losses, including fuel, capital and maintenance expense for the special equipment required for distillation, add to the cost of the tar distillation products.

The present invention provides an improved method and apparatus for distilling pitch, tar or oil by means of hot coal distillation or carbonization gases such as gases from coke oven operations supplemented by heat externally applied during the distillation. The present invention makes use of heat contained in high temperature coal distillation gases by employing them, while still at a high temperature, for distilling the pitch tar or oil in stills while heating the stills, or equipment thru which the gases pass on their way to the stills, externally by means of waste flue gases, or other heating gases or by steam whereby distillation is effected in part by direct contact with the hot coal distillation gases, and in part by externally applied heat.

Several circumstances may arise which will make it desirable to heat externally, as when the heat otherwise available is insufficient to raise the contents of the still to the required temperature, or it may be desirable to apply heat externally in order to increase the capacity of the still and to supplement the distilling effect of the hot coal distillation gases.

The material to be distilled according to the present invention may be coal tar produced at coke oven plants, or gas house tar produced at gas 7 retort plants (vertical, horizontal or inclined), water gas tar, or tar or oil from another source. Pitches may likewise be distilled.- Such tars frequently contain a considerable percentage of wa-- ter intimately admixed or combined therewith, particularly where water or ammonia liquor is employed for condensing and separating the tar constituents from the coal distillation or other gases; and such tars may if desired be dehydrated before being distilled according to this invention. The gases which are employed, according to the present invention, for the distillation are hot gases produced by a coal carbonization or gasiflcation operation, such as hot coke oven or gas retort gases, or hot water gas. These gases are brought 35 into direct contact with the material to be distilled, and the heat thus supplied is supplemented by external heating of the still or other apparatus in which the distillation is carried out. The hot coal distillation or gasification gases may be hot coke oven gases or hot gas retort gases or hot water gas, etc. In the case of coke oven gases, for example, the gases escape from the coke oven at a high temperature, for example from 600 to 700 C. or even higher in some cases. High temperature gases are also formed and are withdrawn from gas retorts, water gas retorts, producers, etc.

The external heating of the still or scrubber, etc., in which the distillation is effected, may be by hot flue gas, or by the combustion of the fuel gas remaining after the removal of other valuable products from the coal distillation gas, or other products of combustion may be employed, or steam may be used. Although the invention is of broader application, it will be described particularly in connection with coke oven operation. The gas employed for the distillation by direct contact with the tar or oil, may be withdrawn at practically its maximum temperature as it comes from the coke oven, or the gas may be employed at a somewhat lower temperature. The temperature of the gas may be regulated by the treatment to which it is subjected prior to its use in the distillation operation. If it is not desired to use the gas at a maximum temperature it may be sprayed with ammonia liquor in the goose-neck or in the collector main, or it may be sprayed with tar or oil in the gooseneck or in the collector main, or it may be sprayed with a mixture of the two, or in both the goose-neck and collector main, to cool it to a regulated temperature.

Due to the great specific heat and heat of vaporization of water, spraying with water or ammonia liquor produces a greater cooling effect on the gases than spraying with an equal amount of tar. By regulating the quantity of the water and/or tar sprayed into the gases, the temperature of the gases can be controlled. The temperature of the gases may likewise be controlled by regulating the temperature of the spray. Thespray may be sufficient to prevent the accumulation of solid hard pitch, etc., in the collector main.

Such accumulation can largely be avoided by eliminating the sprays and flushing the bottom of the main with a large quantity of ammonia liquor or tar without corresponding reduction in gas temperature.

The temperature and amount of the coal carbonization or gasification gases used and the amount of heat applied externally may be regulated according to the distillation which is to be carried out and will depend upon the character and quantity of oil to be distilled.

By heating the still or other parts of the equipment externally, either by the combustion of fuel gases or other combustible material, or by heating by means of what would otherwise" be waste heat, as by utilizing the heat of the flue gases, or by employing steam, the desired distillation may be accomplished in the still with coal distillation gases of lower temperature and/or with a smaller quantity of coal distillation gases than would otherwise be necessary.

The vapors driven off from the still as well as the gases employed for the distillation are advantageously admixed with the hot gases coming directly from the coke oven so that the vapors produced by the distillation will be condensed and the oils recovered along with condensed oils from vapors normally contained in such gases.

In the operation of a coke oven, the gases produced during one oven cycle, are not of uniform composition. At the start of the coal distillation process, oils, etc., are liberated from the coal in large quantities and the first gases given off are rich in volatile products. The gases given off during the latter part of the distillation, for example during, approximately, the last thirty percent of the operating time under normal conditions, contain a less percentage of condensable constituents than the richer gases given off during the first part of the distillation, and are designated as lean gases. The tars carried in rich gases contain lower percentages of free carbon than do the tars contained in lean gases,

and the lean gases carry lower percentages of total tar than do the rich gases. There is in many cases an advantage in using either the rich gases or lean gases separately in distillation of tar, oil or pitch, according to the present invention. For example, lean gases are capable of taking up a greater quantity of oil vapors per unit volume than an equivalent amount of a "rich gas which already contains more volatile condensable constituents than does the lean gas,

the temperature being the same in each case; while rich gases contain a larger amount of condensable oil vapors which admix with the distilled oil vapors and are condensed therewith. In order to take advantage of either rich or lean gas, the coke oven may be equipped with two collector mains, each of which is adapted to be thrown into communication with the uptake pipe from each of the ovens in the battery to which the collector mains are connected thru a system of valves. As an example, during the first of the distillation operation in any one oven, this oven will be thrown into communication with the collector main which is connected directly with the usual recovery apparatus. After the distillation has progressed to the point where lean gases are being given off in this oven, it will be thrown into communication with'the other collector main which is in communication with the still. By the usual rotation of the ovens in a battery of average size, there will at all times be a fairly continuous and uniform production of lean gases, so that the quantity and temperature of the gases passing thru the still will be fairly uniform at all times. Rich gases are, in many cases, more desirable for distillation, and can in a similar manner, be utilized by my invention.

Carrying out the distillation according to the present ,invention, the hot coal distillation gases are brought into heat-interchanging relation with the tar or oil to be distilled and are advantageously brought into direct and intimate contact with the oil or tar or pitch while at the same time heat is being externally applied to some part of the apparatus. Intimate contact of the pitch, tar or oil and gases can be effected in various ways, and the distilling operation can be carried out either as a batch operation or as a continuous operation. The pitch, tar or oil to be distilled can, for example, be atomized or sprayed into a current of the hot gas, thereby bringing the pitch, tar or oil particles into intimate contact with the hot gas and heating them to the required temperature to effect distillation. Instead of spraying or atomizing the oil, tar or pitch into a current of hot gas, a current of the gas may be forced or drawn thru a body of material to be distilled, thereby heating and agitating it and effecting distillation of the desired constituents therefrom, which vaporized constituents are carried away by the escaping gases. The material in the still can likewise be agitated or sprayed into the gases in the still by me chanical agitation or atomizing devices.

The distillation can likewise be effected in a counter-current manner, for example, by causing the pitch, tar or oil to be distilled to flow downwardly thru a baffie tower or other apparatus in which an upward flow of the hot gases is effected, so that the downwardly flowing pitch, tar or oil is progressively heated and distilled, or the hot gases may be passed over the surface of a body of oil, tar or pitch, for instance in a closed tank. In this case, it will be desirable, though in many cases not essential, to agitate the contents of the tank to keep fresh surfaces exposed to the gases.

Several stills may be employed in series so that the gases leaving one still will pass thru another still in which available heat of the gases may be used for distillation. Fresh pitch, tar or tar oils may be supplied to each still, or the residue from one still may be supplied to the next still in the series, in which case it may be desirable to pass the material to be distilled and the gases thru the stills in opposite directions so as to benefit by the advantages of countercurrent operation. The gases may be scrubbed before entering the first still of the series, or the contact between the gases and the contents of the still may serve to scrub impurities from the gases so that the gases leaving the last still of the series ,will be relatively free from impurities, but will contain. oils which can be condensed by cooling the gases, and recovered as clean oils.

The usual spraying treatment to which the gases are subjected in the collector main effects a partial scrubbing and cleaning of the gases, and heavy pitches and tar containing free carbon are thrown down in the collector main 1! gases at lower than maximum temperature are to be used. The temperature of the gases prior to entering the still containing the material to be distilled is regulated preferably by controlling the spraying to which the gases are subjected in the collector main. This spraying may be designed to accomplish the double purpose of both regulating the temperature and cleaning the gases to a greater or to a less extent. In case gases at maximum temperature are to be employed no sprays at all will be employed but tar or ammonia liquor will be flushed along the bottom of the collector main.

The employment of hot coal distillation gases for the distillation of the pitch, tar or oil presents the advantage among others that the gases themselves are subjected to a scrubbing and purifying treatment by bringing them into contact with the pitch, tar or oilto be distilled, while the vapors of the volatile constituents, driven off by the distillation, are admixed with the gases and their normally contained condensable vapors and can be recovered therefrom in the same recovery apparatus as used for cooling of the gases from the ordinary collector main, or separate recovery apparatus may be provided.

As a result of this scrubbing action, the impurities in the gases comprising both solid and liquid particles, are in partremoved from the gases and are recovered in the non-volatilized residue in the still. The gases leaving the collector main in the ordinary operation of a coke oven contain fine globules of tar or pitch, as well as solid particles comprising dust, free carbon,

coke braize, etc., and the removal of such entrained materials from the gases and the recovery of them in the residue in the still may be undesirable as where relatively clean oil is being distilled and it is desirable to produce a residue of low free carbon content in the still. To clean the gases, they may be scrubbed with tar, etc., or cleaned as by an electrical precipitator prior to entering the still. The scrubbing of the gases to clean them may, depending upon the result desired, be with pitch, heavy tar, light tar or oil, either with more or less distillation, or without such distillation, and the temperature of the scrubbing medium can be regulated. Where the gases are to be scrubbed without cooling or distillation, the scrubbing medium should be '0 a composition and temperature similar to that of the particles of pitch carried by the gases. The gases can also be cleaned without lowering of temperature by means of an electrical precipitator, suitably insulated or heated. Where scrubbing is employed the scrubbing may be accomplished in anyone of numerous devices designed for scrubbing gases. The ordinary type of tower scrubber may be used.

The scrubbing of the gases alter leaving the collector main, but before entering the still, may be effected by the tar or pitch residue from the still or by other suitable scrubbing medium. The

temperature and character of the scrubbing liquid is regulated so that the temperature of the gases entering the still is that desired for the distillation which is to be accomplished in the still. In order to maintain the gases entering the still at a sufliciently high temperature, it may be necessary at times to pre-heat the scrubbing liquid. This maybe done by passing the liquid in heatinterchanging relation with hot gases resulting from the distillation process or by applying steam or other heat to the pipes leading to the scrubber.

Under certain conditions when the gases are scrubbed prior to being passed into the still it may be desirable to heat the gases as they pass thru the scrubber rather than to apply heat externally to the still. This may be done by equipping the scrubber with a jacket and passing hot gases, such as flue gases, steam, etc. thru this jacket. Heat may be applied to the scrubber in order to prevent the condensation of the low boiling constituents of the gases in the scrubber as well as to supply additional heat for the distillation in the still. In certain cases it will be desirable to heat both the scrubber and the still externally.

Depending upon the extent to which the distillation of the pitch, tar or oil is carried, substantially only the low boiling oils may be removed from the body of pitch, tar or oil, leaving a heavy pitch, a heavy tar or light pitch or heavier oil residue in the still, or by carrying the distillation further, heavier constituents will be volatilized and recovered from the gases, and a heavier oil residue, tar or pitch will remain as a residue in the still.

The distillation can be accomplished in numerous ways. For example, a large volume o1. relatively low temperature gases may be used, or a smaller volume of relatively high temperature 12) gases may be used. The tar may be preheated if desired before being brought into contact'with the gases.

The gases escaping from the distilling operation will carry in vapor form the constituents volatilized from the pitch, tar or oil and will contain in addition thereto such of the vapor constituents carried by the gases entering the still as have not been removed by condensation or by contact with the material being distilled. In the case of hot coke oven gases employed for the distillation of coal tar produced by the coke ovens, the hot gases after the distillation operation will contain uncondensed constituents from the coal distillation as well as added vapor constituents driven off from the coal tar during the distillation.

The gases from the still can be treated for the condensation and recovery of the desirable constituents contained therein as well as for the recovery of ammonia and. light oils'carried thereby. Where only a portion of the gases from the coal carbonization apparatus are passed thru the still, those gases which are enriched by passing thru the still can be treated in a separate recovery system and the oils condensed therefrom will be a mixture of the oil constituents normally in the gases and those added to the gases during the distillation, whereas the condensate from the remainder of the system will contain only the usual condensable coal distilla- 150 tion products. The gases can, where desired, be treated in the same recovery system with the re malnder of the gases produced by the coal distillation.

In a coke oven plant where several batteries of coke ovens are operated, the rich or lean or normal gas from one battery may be employed for distilling tar from the other batteries, or a part of the gases from one battery may be so employed.

The gases used in theadistillation may be only a portion of the gases collected in the collector main and may be taken off one end of the collector main or all the gases passing thru the collector main may be utilized by taking them off the center-box according to the customary practice. A pitch, tar or oil, other than a coal tar product, can be distilled and the condensable constituents recovered in a separate recovery system without contaminating the balance of the coal tar products produced from the remainder of the system.

Where the distillation is carried out as a batch operation, for example, by forcing hot gases thru the material to be distilled, it is progressively heated by the hot gases and the lighter constituents are progressively removed therefrom until the distillation has been carried to the desired point, after which the operation can be discontinued, and the residue withdrawn, and the still recharged with iurther tar or oil to be distilled. In the case of continuous distillation, the

operation can be controlled by regulating the time of contact of the pitch, tar or oil with the gases, or the intimacy of the contact, or the temperature of the gases, or the amount of the gases or the extent of the external heating so that the desired degree of distillation can be effected.

In some cases it may be desired to regulate the character of the residue of distillation or of scrubbing, as respects free carbon content or as respects type of oils remaining in or added to it. This may to a greater or less extent be accomplished by using rich or lean or intermediate gases for distillation. Rich gases contain tar with a relatively low free carbon content and they contain also oils of lower average boiling point and lower specific gravity than do lean gases. Rich gases contain a greater amount of tar than do lean gases. As the gases get leaner, the amount of tar contained decreases, the percentage of free carbon in the tar increases, the amount of oil contained decreases and its specific gravity and average boiling point increase. Since in the scrubbing and distillation operations more or less of the tar contained in the gases will be retained in the scrubbing or distillation residue and more or less of the contained heavy oils will be condensed and retained in the residues, the character of the residues may to some extent be controlled by choosing the proper gases for distillation. Such gases may be rich, lean or intermediate gases.

The invention will be further described in connection with the accompanying drawings illustrating several forms of 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 is not limited thereto.

In the accompanying drawings,

Fig. 1 shows in a somewhat conventional and diagrammatic manner a plan view of a coke oven battery showing apparatus for the distillation of tar or a tar oil or pitch by direct contact with hot coke oven gases; and indirect contact with hot flue gases.

Fig. 2 is a sectional elevation of the apparatus of Fig. 1;

Fig. 3 is a plan view of a modified form of apparatus in which two collector mains are shown together with separate apparatus for scrubbing the hot gases and means for heating the still;

Fig. 4 is a detail showing an elevation of the scrubber;

Fig. 5 is an enlarged detail showing in crosssection the relation of the two collector mains of Fig. 3 to each other and the coke oven;

Fig. 6 is an elevation partly in cross-section showing in greater detail the still shown in Fig. 1;

Fig. 7 is a cross-section of the still shown in Fig. 6 showing the jacket;

Fig. 8 is a plan view of the still shown in Fig. 6;

Fig. 9 shows a modified form of still which may be substituted for the still shown in the precedin figures; and

Fig. 10 shows another form of still.

In the drawings, part of the coke oven battery is shown at 1 with the usual uptake pipes 2 for the escape of the coke oven gases, and the usual collector main 3 connected with the uptake pipes. The usual center-box for the collector main is shown at 4. The coke oven gases escape from the collector main and the center-box thru the cross-over main 5 to the cooling and condensing system indicated conventionally as two condensers 7 and 8. From these condensers the gases pass thru the pipe 9 and the usual tar trap (not shown) to the exhauster 10, and thence thru the gas outlet pipe 25 to the tar extractor, ammonia and light oil scrubbers, etc. (not shown).

In the collector main and goose-neck sprays 6 are provided for regulating the temperature of the gases and for scrubbing the gases more or less and for flushing the collector main. The liquor admitted to the collector main, which is not volatilized, together with the condensed tar, flows to the center-box 4 and together with the gases, carrying some entrained tar and liquor and uncondensed vapors, passes over thru the cross-over main 5 to the inlet of the condensers '7 and 8. At that point the condensed tar and the liquor are diverted to decanter 12, the gases passing into the condensers 7 and 8.

The uptakes and collector main may be sprayed in the usual manner with ammonia liquor thru the line 5'. When it is desired to spray the gases in the whole or a portion of the collector main with tar, the valves in the line feeding the sprays should be properly adjusted and tar supplied thru the line 7'.

If it is desired to use the gases at approximately their maximum temperature, it may be desirable to cut off partly or entirely the sprays in the sections of the main from which the gases are withdrawn. In such a case ammonia liquor and/or tar may be flushed into the main 3 thru lines 3' and 8'. This flushing will assist in preventing accumulation of hard pitch in the main 3.

An outlet pipev 11 may also be provided leading from the center-box 4 for the tar and ammonia liquor which may, if desired, be conveyed therethru to the decanter 12, where separation of the tar and ammonia liquor takes place. The tar, after such settling and separation, can be conveyed from decanter 12, either continuously or intermittently thru a pipe 6' controlled by a valve 13' to the still 13. Valve 12' controls the flow of tar from the decanter 12. Tar from decanter 12 may be led to the still by line 10', pump 40 and lines 39' and 6'. A gas pipe 14, which may be provided with insulation (not shown), leads, preferably, from one end of the collector main 3 to the still 13 and terminates, for example, in a cross pipe 15 therein having perforations along its bottom side as best illustrated in Fig. 6. A valve 4 is provided in the pipe 14. The gas escapes from the still to the pipe 16 having valve 20 therein. The gases with admixed vapors may pass thru the pipe 16 and the valve 20 to the separate condensers 22 and 23 where condensation of vapors takes place and then thru a gas outlet pipe 19, having a valve 17 therein, and a pipe 24 to the main gas outlet pipe 25. An exhauster 21 is provided between the pipes 19 and 24 to draw oil the gases thru the still 13 and the condensers 22 and 23. The exhauster may also be placed in pipe 14. A by-pass 18 having a valve 18' therein permits the gas to pass around the condensers when the valves 20, 17 and 18' are properly adjusted. The gases from the still may be carried to the cross-over main 5 thru a pipe 21 controlled by a valve 22' for admixture with the ordinary coke oven gases so that condensable constituents contained in these gases from the still may be recovered in the main recovery system.

The residue of the tar or pitch from the still 13 passes thru the pipe 26 and may be delivered by pump 27 either thru the pipe 28 to the tank 30 or thru the pipe 31 to the tank 33, valves 29 and 32 being provided to control the flow thru these pipes.

Tar or tarry oils collected in the condensers and 8 can be withdrawn thru pipes 34 and 35 and delivered thru a pipe 36 controlled by valve 37 to a decanter 38. The tar or tarry oils are separated therein from the ammonia liquor and can be drawn oil to storage or delivered thru a .pipe 39 controlled by a valve 40 thru pump 40' to the still 13.

In the apparatus illustrated in Figs. 1 and 2, the by-product recovery system of the coke oven battery can, for the most part, be operated in the ordinary way, but a part of the hot coke oven gases are drawn off and employed for the distillation of tar, and these gases and contained vapors are then subjected to separate condensation or are returned for admixture with the main coke oven gases for condensation therewith.

. The still may be heated externally in any suitable manner, as with burners supplied with fuel gas. In the drawings, the still is provided with a jacket thru which waste flue gases are circulated. By adjusting the damper 41' in the flue 41 or valve 42', any desired quantity of the flue gases may be diverted thru the by-pass 42 into the setting 15 enclosing the whole or a portion of the still 13, and the desired amount of heat thereby added to the still. The external heating of the still in this way aids and supplements the distilling eifect of the hot gases passed directly into contact with the tar in the still.

In the collector main the coke oven gases may, when they are to be used at less than maximum temperature, be subjected to regulated cooling by the spray of ammonia liquor, or tar when used, and the current of tar and ammonia liquor flowing therethru. Where this spray would cool the.

gases to a temperature below that desired for distillation, the ammonia liquor or tar spray may be substantially reduced at the end of the main from which the hot gases are withdrawn, or may even be omitted, so that the gases will pass thru the uptake pipes and into the end 0! the main and thru the pipe 14 at a temperature not greatly below that at which they enter the-collector main. In this way, the gases can be employed at a high temperature at which they have a high distilling capacity. By regulating the amount of ammonia liquor and tar sprayed into the end of the collector main from which the gases are taken, the temperature of the gases can be regulated. In general, it will be advantageous to draw off the hot coke oven gases while they are still at a high temperature, subjecting them to little or no spraying, so as to obtain effective heating and distillation of the material in the still.

During the intimate contact 01' the hot coke oven gases with the contents of the still, the gases will be scrubbed and purified to a greater or less extent from entrained tar and from heavy condensable constituents, leaving in the gas proportionately more of the lighter condensable constituents, while the distillation of the tar or oil in the still will drive off from the tar or oil the constituents, volatile under the conditions, which will be admixed and carried along with the gases from the still, producing gas enriched in condensable oils. The percentage of free carbon and other impurities in the enriched gas will, as respects the contained condensable constituents, be relatively less than in unenriched gas. By subjecting the gases escaping from the still to separate 5 cooling and condensation, a relatively clean oil can be directly obtained as in the decanter 23', while by returning the gases and admixed vapors to the main condensing system the condensable constituents can be recovered, as in decanter 38, without the need of separate condensing equipment, and the resulting products will be relatively cleaner than those normally obtained.

The apparatus shown in Fig. 3 discloses means whereby the richer gases given oi! from the coke ovens may be collected separately from the leaner gases by means of two collector mains 342 and 343. Although either rich or lean gases may be used for distillation, in the apparatus illustrated lean gases are utilized. It is intended and is to be understood that the apparatus is equally adapted for utilizing rich gases and conducting lean gases to the ordinary condensers 307 and 308 or for using only part of the rich or lean gases for distillation.

By proper regulation of the valves 342 and 343', shown in Figs. 3 and 5, the gases evolved during the first of the distillation process may be led to therich collector main 342, whereas the lean gases evolved during the latter part of the 13Q distillation, may be collected in the lean collector main 343. Because of the fact that these lean gases are poorer in condensable oils, they are in many cases better adapted for use in distillation, and, therefore, according to one method 01' operation, they are separately collected as in the main 343 and led to the still to be used for distillation, whereas the rich gases are collected in the main 342 and cooled and led to condensers in the usual manner. Likewise, if desired, the main 343 may be used as a rich gas main and the rich gases used for distillation. In many cases this will be desirable.

Whereas the collector main 342 for the richer gases may be operated according to the usual practice, the operation of the lean collector main should be so regulated by adjusting the sprays of tar and/ or ammonia liquor as to give adequate flushing of the main, with only limited cooling, so that the temperature of the lean gases leaving the collector main is sumciently high in spite of the loss of heat involved in passing to the still to eflect distillation in the still. The collector main my be sprayed with tar thru the line 307'. In some cases it may be advisable to eliminate part or all of the spraying in main 343. In such a case the ammonia liquor and/or tar may be flushed into the main 343 thru lines 345' and/or 360'. The gases are led oil from the lean collector main and passed thru the valve 341' to the scrubber 341 and the purified gases are led thence thru the pipe 314 to the still 313. The scrubber may in some cases be omitted. The material in the still may be circulated by means of the pump 344 thru the pipe 345 and thus fed thru the sprays 346 to the scrubber and back to the still thru line 360, or it may pass thru line 349 to storage 350, or the scrubber may be fed with tar or tarry oil by means of the pump 347 thru the pipe 348 from the decanter 338. The still distillation residue together with the unvolatilized constituents from the scrubber is led thru the pipe 349 to the storage 350, or thru the pipe 351 to the storage receptacles 330 and 331.

The operation of the scrubber will in general depend upon the desired elimination of entrained material from the gases prior to their entry into the still.

If, for example, it is desired to maintain the residue in the still relatively free from contamination by the materials entrained in the gases from the collector main, the scrubber will be operated and the scrubbing liquid leaving the scrubber will be delivered to separate storagee. g., tank 350. In such a case an appropriate scrubbing liquid can be used,-e. g., a small amount of the residue in the still, or outside liquid, or a separate insulated tank (not shown) of material of composition similar to the composition of the entrained liquids in the gases may be maintained, and the contents of the tank continually re-circulated thru the scrubber.

The degree of distillation accomplished in the still will depend upon numerous factors among which are, the quantity of gas drawn thru the still, the temperature of the gas, the amount of heat supplied externally to the still, the boiling range of the oils to be distilled, and the character of the liquid employed for scrubbing the gases.

The liquid used for scrubbing may in some cases be distilled. This will particularly be the case when light tar or tarry oil such as that from 338 or 338' is employed. When distillation of the scrubbing liquid occurs, the temperature of the gases will tend to fall, due to absorption of heat as latent heat of evaporation of the oils distilled. The tendency to drop in gas temperature may be oilset by the use of heat interchanger 346' for preheating the scrubbing liquid, or by the addition of heat thru jacket 351', or by both. The quantity of gas may also be increased.

It will thus be seen that there are numerous ways to accomplish the desired results.

In some cases it will be desired to so thoroughly remove entrained materials from the gases that the oils condensed in condensers 323 and 322 will be relatively free from contamination by the entrained materials, although the presence of the entrained materials in the still residue may be unobjectionable. In such a case, it will be of particular advantage to recirculate the material in the still thru the scrubber and back to the still. The minimum of heat will be wasted and the gases will be satisfactorily scrubbed. The heat in the gases entering the scrubber will in such a case be allowed to accomplish distillation in the scrubber as well as in the still. If two oil fractions from condensers 322 and 323 are desired the second fraction may be withdrawn thru line 322' to decanter (not shown).

The scrubber or the still, or both the scrubber and the still, may be heated externally, as for example, by the combustion of fuel gases or by flue gases. Fig. 3 provides for heating with flue gases. By proper manipulation of the valves in the flues and the exhauster 340 when necessary, circulation of the flue gases thru the pipes 349 and 350' and jacket 351' around the body of the scrubber, as well as thru the setting 315' of the still, may be controlled.

The tar from either or both of the collector mains may be supplied thru the pipe 352 to the still 313, or it maybe used to scrub the gases in the scrubber, in which case it is pumped to the sprays 346 thru the pipe 354. The line leading to the sprays may be equipped with a preheater 346'.

The scrubber 341, as shown in Fig. 4 may consist of a tower with means 314' at the bottom for admitting gases and means 314 at the top for leading them away. The scrubber is provided with sprays 346 for spraying the contents with tar or oil. It may be packed with broken brick or Raschig rings, etc.

With appropriate modification, the operation of the apparatus shown in Fig. 3 is similar to that described in connection with Figs. 1 and 2. Tar from either of the collector mains or the decanters 338 and 338 may be supplied to the still 313, or the still may be supplied with tar or oil from some other source. The vapors from the still may be condensed separately in condensers 322 and 323, or by by-passing the gases thru the pipe 318 they may be combined with the gases and vapors passing thru the pipe 305 and condensed and collected together 'with the vapors direct from the rich collector main in condensers 307 and 308.

The invention is not limited to the disclosure of the drawings. Fig. 1 shows apparatus for distilling with hot gases directly, without scrubbing. Fig. 3 shows apparatus for distilling with either rich or lean gases and provides for scrubbing the gases prior to their entering the still. With appropriate modifications the equipment shown may be rearranged for passing either rich or lean gases directly to the still without scrubbing, or a composite of the gases passing thru the usual collector main comprising gases from ovens of varying ages, i. e., both rich and lean gases as in Fig. 1, may be scrubbed prior to their entrance into the still. Either the still or the scrubber may be heated externally, or a heat exchanger of a different type may be provided, in which the gases are heated externally while passing thru the connecting gas mains or conduits, or heat may be applied at more than one place, as at both the scrubber and the still or at the preheater, as in Fig. 3.

The still 13 may be replaced by a tower as illustrated in Fig. 9 of the drawings, wherein the tar or other material to be distilled is permitted to fiow downwardly over a plurality of battles so as to expose large surfaces of the tar to the hot gases ascending thru the tower and with external heating of the tower to aid the distillation. In this way, advantage can be taken of the heating effect of the gases to distill the tar without retarding the gases or causing any appreciable back pressure or greatly disturbing the balance oi gaseous pressures in the system.

Referring to Fig. 9, '71 indicates a tower which may be of any suitable form and construction, and with heating means such as a Jacket thru which gases such as the hot flue gases may. if desired, pass to maintain the desired temperature. The tar accumulated in the decanters 12, 12' or 38, or pitch, tar or oil from another source, is delivered thru an inlet pipe '72 to the top of the tower and flows downwardly over a plurality of baiiles 73 arranged therein to facilitate the exposure ot the maximum surface oi the tar or other material to be distilled to the ascending gases. These gases may be withdrawn from the collector main and delivered thru the pipe 14 shown in Fig. 1 to the inlet 74 at the base of the tower 71. The gases circulate upwardly around the bailies 73, giving up their heat to the descending stream of tar, and escape thru an outlet 75 which may, for example, be connected to the pipe 16 shown in Fig. l. The residue from the tar or oil which accumulates in the bottom of the tower '71 is withdrawn thru a pipe 76 which may be connected to the pipe 26 shown in Fig. 1. A portion of the tar can be recirculated by a pump '73 thru the pipe '74 to the top of the tower. Since the descending tar flows over the baffles in relatively thin sheets and is exposed in this form to the hot gases, it interposes the minimum resistance to the flow of the gases. It is, nevertheless, heated by the gases which, depending upon the temperature and other conditions of operation, may remove more or less of the volatile constituents from it. These can be condensed as hereinbefore described in connection with the condensation of vapors from other gases flowing from the ovens, or a separate condenser system may be utilized to recover any valuable products in the gases which leave the still.

Although the operation of the tower in Fig. 9 has been described in connection with the operation of a system such as that shown in Fig. 1, it is to be understood that the apparatus disclosed in Fig. 9 and also the apparatus disclosed in Fig. 10, which is'to be described below, can be substituted equally well in other systems, such as that shown in Fig. 3. The towers may be equipped with jackets appropriate for conducting flue gases, or other means for applying heat externally may be provided.

In the modified form 01' still shown in Fig. 10, the operation is similar to that in the still shown in Fig. 9, except that instead of coming into intimate contact with the hot gases by passing over baille plates, the pitch, tar or oil is sprayed into the hot gases which are introduced thru the inlet 80. On ascending thru the tower, the hot gases volatilize the. low boiling constituents oi! the liquid which is introduced thru the spray nozzles 81 so that these constituents are volatilized, and depending upon the temperature and quantity of the gases, etc., the higher boiling constituents may be volatilized. The treated tar or pitch or oil residue collects in the reservoir 82 in the bottom of the tower and may be drawn off continuously or at intervals thru the outlet pipe 83, or tar, etc. collecting in the reservoir 82 may be withdrawn by the pump 84 and carried up thru the pipe 85 and again subjected to treatment by the hot gases by being sprayed again thru the nozzles 81. Instead of recirculating the tar, the nozzles may be supplied with fresh tar introduced thru pipes 83 or tar may be introduced to the nozzles thru pipes 83' and 85 at one time, or by using separate feed pipes certain nozzles may be supplied with treated tar or pitch while other nozzles are supplied with fresh tar. Bafiles 86 or other means may be provided to remove entrained liquor trom the vapors escaping thru the outlet 87. The towers may be operated on a batch basis, or they may be operated continuously.

The amount of distillation which takes place within the still will depend upon the relative quantities and temperatures of the tar and gases and upon the amount of external heat supplied, as by the hot flue gases. The hot coke oven gases for the still may be drawn ofi from the end of the collector main as shown in the drawings, or from any other part of the collector main, or other collecting means, or the hot gases may be tapped off the cross-over main, or any other part of the apparatus from which gases of desired temperature may be obtained. The temperature of the gases will depend upon the part of the apparatus from which the gases are obtained and upon the operation of the coke oven system. If spraying is eliminated or kept at a minimum in the uptakes at one end of the collector main, and in the mains, and gases from this end of the collector main are led to the still, these gases will be at almost the maximum temperature at which the gases enter the collector main.

Tars, oils or pitches of various grades may be used as a scrubbing'medium and by scrubbing with other pitches, tars or oils than those recovered from a coke oven system with hot coke oven gases, composite heavy tars or pitches will be recovered in the scrubber, and composite products may be recovered on condensing the vapors from the gases leaving the still. By omitting the scrubbing operation or by proper selection of the tar or oil to be used in the scrubber and the still, and by regulation of the temperature, the properties of the resulting products can be modified to suit the particular requirements of the trade.

The combined distillation operation of the present invention with direct heating and distillation by the hot coal distillation gases and indirect heating externally, e. g., by waste flue gases, enables the coal distillation gases to be used more efiectively and at a lower temperature than when they alone are relied upon for the heating and distillation. In gas retort or coke oven plants where the coal distillation gases are cooled in the uptake pipes, collector main, etc., to a temperature such that effective distillation with the heat content of the gases would be limited, the external heating of the still makes the action of the coal distillation gases more effective, enabling ellective distillation to be carried out at a relatively low temperature.

I claim:

1. In combination with a coke oven battery, a tar still, means connected with the waste gas flue from the battery adapted to circulate hot flue gases in indirect heat interchange relation with the contents of the still, a condenser adapted to condense vapors passing from the still, a gas scrubber, and means to collect gases from its a plurality of the ovens and pass them directly thru the scrubber into the still.

2. In combination with a coke oven battery, a tar still, a condenser adapted to condense vapors passing from the still, a gas scrubber, means connected with the waste gas flue from the battery adapted to circulate hot flue gases in indirect heat interchange relation with the contents of the still, and means to collect gases from a plurality of the ovens and pass them directly thru the scrubber into the still.

3. The improvement in the method of producing pitch by the distillation of heavy hydrocarbon material in liquid form, which comprises heating externally a still containing such material, scrubbing Iresh hot coal distillation gases with pitchproduced by the distillation of the hydrocarbon material, passing the scrubbed gases thru the still in direct and intimate contact with said material therein so as to produce pitch therefrom, and condensing oils distilled therefrom together with oils present in the hot gases in vapor form.

4. The improvement in the method oflproducing pitch from heavy hydrocarbon material in liquid form, which comprises scrubbing fresh hot coal distillation gases with pitch of substantially the same composition as that carried in suspension in the gases, passing the scrubbed gases thru a still in direct and intimate contact with the heavy hydrocarbon material being distilled, simultaneously heating the still externally whereby the heavy hydrocarbon material is distilled to pitch, and condensing oils distilled from the hydrocarbon material together with oils present in the gases entering the still.

5. In combination with a coke oven battery a tar still, means connected with the waste gas flue from the battery adapted to circulate hot flue gases in indirect heat interchange relation with the contents of the still, a condenser adapted to condense vapors passing from the still, and means to collect gases from a plurality of the ovens of the battery and pass them while still hot into the still.

6. The improvement in the method otproducing pitch by the distillation of heavy hydrocarbon material in liquid form, which comprises heating externally the still containing such material, heating a heavy hydrocarbon material and scrubbing fresh hot coal distillation gases with the hot hydrocarbon material in liquid form, passing the scrubbed gases through the still in direct and intimate contact with the material therein so as to produce pitch therefrom, and condensing oils distilled therefrom together with oils present in the hot gases in vapor form.

STUART PARMELEE MILLER.

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