US2040097A - Distillation of tar - Google Patents

Description

'May l2, 1936.l s. P. MILLER 2,040,097

DIS'IILLATION 0F TAR Original Filed Jan. l5, 1931 5 Sheets-Sheetl INVENTOR /aea,

34u.; ATTORNEYS 1931 svsheets-sheet 2 S. P. MILLER DISTILLATION OF TAR original Filed Jan. 15

INVENTOR 5. 22u41 wmm ATTORNEYS May v1.2, 1936.

BY 72ML May l2, 1936. s. P. MILLER 2,040,097

DISTILLATION OF TAR OriginaLFiled Jan. 15, 1931 5 Sheets-Sheet 5 A'ATORNEYS May l2, 1936. s. PJMILLER DISTILLATION OF TAR Original Filed Jan. l5, 1931 5 Sheets-Sheet 4 INVENTOR BY 7 v ATTORNEYS May 12, 1936.

s. P. MILLER DISTILLATION OF TAR 5 Sheets-Sheet 5 Original Filed Jan. 15, 1931 VEN INVENTOR 5 7? M BY 29m/LM 620ML ATTORNEYS Patented May 12, 1936 UNITED STATES DISTILLATION OF TAR Stuart Parmelee Miller, ScarsdaleQN. Y., as'- signor to The Barrett Company, New York, N. Y., a corporation of New Jersey Application January 15, 1931, Serial No. 508,848

' Renewed July Z5, 1935 18 Claims.

This invention relates to the distillation oi! tar-acidand neutral-oil-containing hydrocarbon material. More particularly the invention relates to a method of producing and then distilling dephenolized hydrocarbon material involving the separate vaporization of tar acids therefrom. By dephenolized hydrocarbon material I, mean hy'- drocarbon material from which at least a portion of the tar acids have been removed without thev if) removal of the same considerable percentage of neutral oils as is required by the present customary methods of tar acid recovery. The distillate and distillation residue obtained from the distillation are both of relatively low tar acid conl tent. The invention includes both the method and apparatus for carrying it out.

According to this invention, the hydrocarbon material containing tar-acids and neutral oils is heated and tar acids are vaporized from the heated material, and separately recovered. The hot residue from this treatment is then subjected to distillation, and a distillate low in tar acids is produced. If the dephenolized material is heated by direct contact with hot gases'such as steam or combustion gases or hot coal distillation gases astdescribed in my copending application Serial No. 326,769, led December 18, 1928, which has issued as U. S. Patent No. 1,920,097 for example, the het gases and vapors resulting from the distillation may be used to heat the material for the separate tar acid vaporization. 1f the material is distilled without the aid of hot gases the heat of the vapors may be utilized for the separate tar acid vaporization. The hot residue resulting from the separate and selective tar acid vaporization is then distilled.

While the process of the present invention is applicable in general to hydrocarbon material containing tar acids and neutral oils, it finds its primary application in the distillation of tar such as coal tar which contains appreciable amounts of phenols and especially the lower homologues of ,Y phenol and designated collectively herein as tar-acids. r

According to the present invention tar acids are removed from the tar prior to the main distillation by volatiliing them in an atmosphere of inert gases and vapors, the vapors comprising constituents other than tar acids, of the tar being distilled. The passage of these gases and vapors in contact with the tar eiects vaporization of tar acids at a temperature below their normal boiling points, and the presence of the vapors of tar constituents other than tar acids in` admixture with the inert gases inhibits or represses further vaporization of -such constituents from the tar. Selective vaporization of the tar acids is thus effected. The invention includes partial removal of the tar acids by such selective vaporization and is advantageously carried out in a man- 5 ner to remove 50% or more of the tar acids by such selective vaporization. l

The tar acids are separated from the gases and vapors resulting from the tar acid vaporization vby contact with an alkaline reagent', such as an 10 aqueous solution of caustic soda. The tar acid extraction is substantially complete or as nearly complete as is feasible in a commercial operation and all or a portion of the resulting mixture of inert gases and neutral oil vapors is recycled for l5 further tar acid vaporization. If desired, neutral oils can be condensed from the recycled vapors either simultaneously with the tar acid extraction by cooling with the caustic solution' or by separate cooling means, but condensation of neutral oil 2o vapors is advantageously kept at a minimum at this stage of the process, and the neutral oils then recovered as distillate in the subsequent distillation of the hot residue from this tar acid extraction operation.

In the tar acid vaporization step of this process, the heated tar may be sprayed into the mixture of inert gases and neutral oil vapors or the vapors may be bubbled through a body of the heated tar or the tar and vapors may be brought into contact in a packed tower or similar device. 'I'he tar .-is advantageously heated to a temperature suillcient to effect volatilization of the desired tar acids without heating the recycled gases. If the recycled gases are suiliciently heated before being brought into contact with the tar, the tar need not be heated to such a high temperature.

The recycled gases are substantially free from tar acid vapors, but they contain vapors of neutral oils volatilized from the preheated tar. In 40 commencing a tar acid vaporization of the type here referred to, steam or other inert gas is passed through a body of the heated tar. This distills not only tar acids, but also neutral oils. The resulting gases and vapors are then extracted with an alkaline reagent, e. g. caustic soda, the tar acid vapors being removed from the cycle. The vapors of neutral oils and steam or other gas employed for the volatilization are then recycled. If the tar contains moisture this is vaporized and forms steam which blends with the circulating oil vapors. A bleed-ofi is provided `through which the make of steam and attendant oil vapors is removed. If the bleed-oi is in communication with the atmosphere the pressure in the system will be approximately atmospheric. This bleed-olf is advantageously placed at a point in the cycle after the acids have been extracted by the alkaline reagent. Neutral oil vapors which are bled off with' the inert gas may be condensed and added to the dephenolized tar or to the distillate'obtained by distillation of the dephenolized tar or may be separately collected. As the process proceeds the inert gas originally employed will be gradually eliminated and replaced by the steam and oil vapors formed in the process. If dry tar is treated the recycled gas may consist largely ,of vapors of nonacid constituents of the tar. Throughout the speciiication I use inert gases to designate the gases (such as steam and neutral oil vapors of tar, used in the dephenolizing stage of the process to effect the vaporization of tar acids) which are chemically inert towards the tar and caustic soda.

The taracid vapors are advantageously extracted by effecting contact of caustic soda solution with the mixture of gases and vapors as in a packed or grid tower or the like. The temperature and concentration of the caustic solution are preferably so regulated that a minimum of7 are condensed in the cycle the recycled gases will be brought into substantial equilibrium with the non-acid constituents of the preheated tar and after the recycled gases have once been brought into such equilibrium, there will be no further volatilization of neutral oils, except for the small amount required to compensate for the oils dissolved in the carbolate and those bled on from the system with the excess of steam to compensate for the oils flashed with the steam at the temperature of the tar fed to the dephenolizer. The process of the invention is not limited to a process in which no neutral oils are condensed from the cycle, but the extent of this condensatin of neutral oils is advantageously kept at a minimum and the'dephenolized residue from the tar acid extraction which is subsequently distilled then contains substantially all of the constituents of the tar except -the tar acids removed and the oils removed with steam at the bleed-olf. The tar acids removed will ordinarily amount to 50 to 70% of those present, but this invention is not limited to the removal of any specific percentage of tar acids. 'I'he neutral oil removed at the bleed-off ordinarily amounts to 3 to 5% of the tar but this will vary with the temperature and the kind `of tar treated and the water content. y

The residue from the tar acid extraction is subjected to distillation. The selective tar acid vaporization which precedes the distillation may be so co-ordinated with the subsequent distillation that the distillate is substantially free from tar acids, distilled from the tar, particularly the low boiling tar acids. Ii' coke-oven gases are used to distill the dephenolized tar, the distillate will 'contain acids from the tar from the oven gases Ordinarily the tar acid extraction will be controlled to recover from the tar a high per- .centage of tar acids of low boiling range, which have greater \commercial value. The boiling range of the tar acids vapcrized from the tar can be controlled, within certain limits, by the temperature to -which the tar is heated and the rate at which the gases are circulated. By providins*j two or more controlled extraction steps in the cycle, obtained.

In the accompanying drawings, means for carrying out they invention are illustrated more or less diagrammatically. Figs. 1-3 illustrate means for distilling tar by direct contact with hot coal distillation gases. The tarcqmay be distilled in a current of steam or hot combustion gases, for example. Figs. 4 and 5 illustrate means for distilling tar by processes in which there is no current of gases passing through the still. The heat of the undiluted vapors (and gases) resulting from the distillation is employed for preheating the tar. Fig. 6 is a modification of the dierent tar acid. fractions can be apparatus shown in Figs. 1 and 2 with separate means for condensing neutral oils in the dephenolization of the tar. A. similar modification may be applied to the processes illustrated in Figs. 4 and 5. In all cases the preheating of the tar by the heat of the substances coming from the still may be supplemented by heating the tar from another source either before or after it enters the heat interchanger, or by heating the recirculated gases and vapors in the de- Yphenolizing stage. Further, the heat of the substances coming from the still may be used for heating the recycled gases before they enter the tar dephenolizer. It is intended and is to be understood that the invention is not limited to the speciiic application cited.

In the' drawings:

Fig. l is a plan view of a coke oven battery equipped with a tar still and selective tar acid vaporization apparatus;

Fig. 2 is an elevation in part of Fig. 1, showing the still and tar acid vaporization apparatus;

Fig. 3 is a section through the still on the line 3--3 0f Fig. 2;

Fig. 4 is an elevation of another type of still equipped with selective tar acid vaporization apparatus;

Fig. 5 fis an elevation of a pipe coil still equipped with selective tar acid vaporization apparatus; and

Fig. 6 is a modied form of the apparatus of Figs. 1-3 provided with separate means for the condensation of neutral oil.

The coke-oven battery 5 of the drawings is equipped in the usual way with a collector main 6, and a cross-over main 1, which conveys the gases from the collector main to the condensers 8. 'Ihe gases pass from the individual ovens of the battery through the uptake pipes 9 into the collector main l. At the opposite side of the battery is a still 10. Hot gases from selected ovens of the battery pass through the especially provided uptake pipes Il into the hot gas header l2. By proper manipulation of valves in the uptake pipes Il and valves in the uptake pipes 9 which connect the opposite ends of these same ovens with the collector main 6, the flow of the gases from these selected ovens either to the collector main 6 or the hot gas header I2 is controlled.

In the still is a spray roll I3, which is driven at a high rate of speed, for, example, 900 to 1200 R. P. M., by the motor H. The spray roll vdips to a slight extent into the tar and pitch in the still and sprays them in the form of a iine, intense spray up intothe current of hot gases. The gases enter the still at substantially the temperature at which they leave the ovens. They are rapidly cooled by the ne, intense spray of tar and the tar is rapidly distilled.

The spray yof tar and pitch in the still I0 is so intense that the gases are cleaned; that is, ilne entrained particles of pitch mist and coke. etc., are scrubbed from the gases.

. The gases and vapors pass from the still into a saturator I5 where they are sprayed with the residue of dephenolized tar. Lower boiling oils are volatilized in this saturator and the liquid sprayed into the gas removes from the gas line entrained particles of spray which are carried over from the still by the gases and vapors. The gases and vapors leaving the saturator are substantially clean and on cooling yield clean oils.

Bailies I6 are provided in the saturator to aid in the removal of spray particles and to provide a large surface of contact between the mal terial to be distilled and the gases and vapors.

The residue from the distillation in the saturator is drawn oii through the line I1 and enters the still near the hot gas header. This residue is distilled in the still and pitch of desired melting point is produced. Pitch with a high melting point, for example 350 F. to 400 F., or higher,'

may be produced; The pitch product is drawn oil from the still through the trap I8, and the leveling arm I3. The position of this leveling arm controls the depth of liquid maintained in the still. If a high melting point pitch is produced it may be solidied and granulated by` spraying with water from the line 20, in the trough 2l, and the granulated solid pitch which results is collected in the bin 22. Other means `for solidifying the pitch or means for collecting a softer pitch may be provided as conditions require.

The clean oil vapors and gases from the saturator I5 are cooled in the heat interchanger 25 and the tar to be dephenolized and then distilled is preheated therein. The tar enters at 26 and a after being preheated in the heat interchanger it is sprayed into the dephenolizer 21, through the spray means 28. Clean oil which is,con-

densed from the gases and vapors in the heat be used. Means for the recovery of light oil, am-

monla, etc., may be provided. The header I2, the still I0, the saturator l5 and the heat interchanger 25 and connecting mains are advantageously heavily insulated.'

'I'he tar acids/are extracted from the tar in the dephenolizer 21 by vaporizationin .a current of inert gases/and vapors of neutral oils. These inert gases arid vapors enter the bottom of the dephenolizer through the line 35. 'I'he hot tar is sprayed into thegases as they pass up through the dephenolizer and tar acids are vaporized and carried fromthe dephenolizer in the vapor state in admixture with the inert gases and neutral oil vapors through the line 36 into the caustic extractor 31. In this caustic extractor the taracld-containing gases and vapors are sprayed with caustic from the spray 3l. 'I'he caustic combines with the tar acids and phenolates (carbolates) are formed. A l I It is generally,y advantageous to spray a large volume of liquid into the gases so as to provide a large surface of contact between the liquid and the gases and vapors in the extractor and thus insure complete removal of the tar acid vapors.

By recycling a portion of the carbolate-a large volume of an alkaline solution is obtained which presents a large surface of Contact to the gases and vapors and substantially vcomplete removal of the tar acid vapors from the cycle results.

If operating conditions are so controlled that there is but little condensation cf neutral oils the carbolate is recycled by means of the pump 40 without separation of any contained neutral oils 4by drawing the recycled carbolate off from the bottom of the caustic extractor through the line 39. The temperature of the recycled carbolate is controlled in the heat interchanger 60a. Fresh caustic is introduced through the line 4I.

The make of carbolate is drawn oil from the caustic extractor through the line 66 into the tank 61 and disposed of as desired. Tar acids may be recovered from the carbolates by any of the usual processes, as by'treatment with carbon dioxide, etc.

If the caustic treatment is regulated to eect considerable condensation of neutral oils simultaneously with the extraction of the tar acids and to form a separate oil layer, the neutral oils and carbolate are drawn oi the tower through the line 66 into the Atank 61, which is constructed to Serve as a decanter, and, after separation of the neutral oils,4 the carbolate'is recirculated to the caustic extractor through the line 68 by means of the pump 40. Condensation such as isA obtained by partial cooling of the gases within the caustic tower does not effect complete removal oi the neutral oil vapors from the cycle, whereas the extraction with caustic removes substantially all of the tar acid vapors.

The excess carbolate is drawn off to the storage tank 69 through the pipe 10. Neutral oils when present in suiiicient amount that they can be separated from the carbolate are drawn oi from the decanter, into the receiver 1I through the line 12. These neutral oils may be separately treated, or they may be blended with distillate from the still or they may be blended through line 13 with dephenplized tar from the dephenolizer 21 for distillation in the still I0.

The inert gases containing vapors of neutral oils coming from the caustic tower are carried from the caustic extraction tower to the de' phenolizer 21 by the blower d2 in the line 35, for reuse in selective vaporization of tar acids from fresh tar. Any excess of inert gas i's vented from the system through a bleed 35 which is equipped with a condenser to recover neutral oils present in the gases. These neutral oils may be separately collected or they may be blended with the neutral oil distillate obtained from the'still. On recycling the gases from which tar acids have been removed but which include neutral oil vapors, there results a selective vaporization of the or the blend of neutral oil and dephenolized tar is distilled. It isf. sprayed into the saturator I5 through the nozzle 43, by means of the pump M in the line 45. This dephenolized tar has a low the apparatus shown in Figs. 1, 2 and 3. A still tar acid content and on distillation yields distillate of low tar acid content. This distillate will, however, include any tar acids condensed from the coke oven gases.

In the modied form of apparatus shown in Fig. 4, an ordinary tank still 60 is shown, which is heated by direct iire in rebox 6I. lized tar is fed into the still through the line 62, and pitch is drawn oi through the line 63. Vapors pass from the still into the heat interchanger 64 and then into the condenser 64'. The tar enters the heat interchanger through the -line 65; it may be preheated before entering the heat interchanger. It is heated in the coil in the heat interchanger and then is sprayed into the tar dephenolizer 21a through the nozzles 28a.

lThe caustic extractor is shown at 31a. 'I'he inert gases enter the bottom of the tar dephenolizer through the line 35a and the tar-acid-containing vgases pass from the top of the tar, dephenolizer through the line 36a into the bottom of the caustic extractor. In the caustic extractor the tar acids are neutralized and the carbolate formed is in part recirculated and in part withdrawn from the system in the manner above described. The inert gases are recycled from the caustic extractor through the line 35a into the tar dephenolizer 21a. A blower 42a is provided to force the gases through the cycle. 'Ihe gases may be heated before they reenter the dephenolizer and a suitable heater may be provided where this is desirable.

Fig. 5 shows a pipe coil still, 80, for dlstilling the dephenolized tar. The dephenolized tar is heated in the pipe coil, 89a, to a temperature above its initial boiling point and then ilashed into the vapor box 8i. 'Ihe residue from the ashing operation is drawn oi as pitch into the receiver 82.

The vapors from the ashing operation which are substantially free from tar acids, at least lower boiling tar acids, are cooled in the heat interchanger 83 in which they are brought into indirect contact with tar which is introduced at 84 and passes up through the heating coils 85 in the heat interchanger. The oils condensed from the vapors in the heat interchanger are collected in the receiver 86/. The vapors which pass of! from the heat interchanger are further cooled in the condenser 81 and the distillate which is condensed is collected in the receiver B.

The tar which-is heated in the coil passes through the line 89 to, the dephenolizer 2lb. A caustic tower 31h is provided as in the preceding examples for the recovery of carbolate, and also neutral oil` if desired. Mains 35h and 36h and blower 42h are provided for the recirculation of inert gas through the dephenolizer and caustic tower. The operation of the dephenolizer and caustic tower may be regulated as described iny connection with the preceding figures to produce onlytar acids or both tar acids and neutral oil. The dephenolized tar drawn of! from the dephenolizer is pumped by means of the pump Mb to the pipe coll still for distillation and the production of pitch and dlstlllateoil.

The apparatus of Fig. 6 is al modied form of Inc is shown into which hot gases such as hot coal distillation gases or steam or hot combustion gases are introduced through the main I2c. Pitch is drawnA 01T through the levelling arm i9c into the bin 22e. Hot gases and vapors from the still pass through the saturator Hic to the heat interchanger 25e where they are partially Deplienoy .`stil1 throughi the main |20 to effect the distillation. The higher boiling oils from the heat interchanger may or may not be free from tar acids depending upon the boiling range of the tar acids removed from the tar in the dephenolizer 21e, the extent of the distillation of the dephenolized tar, and the boiling range of the cuts made.

Tar is introduced into the heat interchanger 25o through the line 26e and is heated by indirect heat interchange with the hot gases and vapors passing through the heat interchanger. The heated tar is then introduced into the dephenolizer where tar acids and neutral oil vapors are vaporized in a current of inert gas which is recirculated through the Adephenolizer 21e, the caustic tower 31e and the condenser 90 by means of the blower 35e. Tar acids and neutral oilvapors are vaporized from the tar in the dephenolizer 21e. These gases and vapors are ex iracted by an alkaline reagent in the extractor x3'lc where the tar acid vapors are neutralized and separated from the gas stream. The temperature and concentration of the caustic or other alkaline reagent used are preferably so regulated that there is no substantial cooling of the gas stream by the caustic and consequently a minimum condensation of neutral oils. The. carbolate produced is in part recirculated and the excess carbolate is drawn off to storage in the tank Sic.

From the caustic extractor the gas stream passes through the condenser 90. The gases are partially cooled in this condenser and a portion neutral oils vaporized is greater than the ratio in the distillate from 'straight distillation. The

neutral oil condensed in the condenser 9D is drawn oi to storage in the receiver 9 I.

The dephenolized tar from the dephenolizer 21o is sprayed into the saturator I5c through the spray nozzles 43e and partially distilled and the residue is further distilled in the still lilo.

' Ii' pitch of low melting point is produced the pitch will be a dephenolized pitch and dier from pitch produced by the straight distillation of'tar by the absence of the tar acids removed from the tar in the dephenolizer. If the distillation is carried to pitch of higher melting point, that is. to a point where all of the oils of the boiling range usually accompanying the tar acids y removed in the dephenolizer are vaporized, the

pitch produced will-be of substantially the same f composition as pitch produced by straight distillation without previous dephenolization. The

distillate, however, differs from ordinary distillate 'y in that tar acids and a portion of the lower boiling neutral oils are separately collected in caustic extractor 31o and the condenser 90 before the tar enters the still.

Where a distillate of suitable boiling range is produced by any of the previously described applications of the invention it may be used as creosote oil. Road tars, roofing pitch, etc., may be produced directly in the still-'by this process.

'I'he process is applicable generally to tar stills of various types. The distillate may be condensed in a single fraction or a fractional condensing system may be employed to recover several fractions. The heat of condensation from one' or more of the fractions may be employed to pre` heat the tar and this preheating may be supplemented by heating from some other source. The process may be employed for the treatment of coal tars such as coke oven tar or gas house tar or blends of tars or tar fractions; it may be employed for treatment of low temperature tars; it may also be employed for the treatment of taracid-containing oils. Various modifications and adaptations of the process and apparatus may be made all within the scope of vthis invention.

This application is in part a continuationof my application Serial No. 383,859, iiled August 6, 1929.

I claim: l

l. The method of distilling tar-acidand neutral-oil-containing hydrocarbon material by first dephenolizing the material and then distilling the dephenolized residue, which comprises preheating the hydrocarbon material by heat interchange with hot vapors or a mixture of hot gases and vapors resulting from the distillation of the de- X phenolized material, selectively vaporizing tar .acids from the preheated material `in a current of inert gases comprising neutral oil vapors, ex`

tracting tar acids from the resultng gases and vapors and then subjecting the dephenolized residue to distillation.

2. The method of distilling tar which comprises preheating coal tar, selectively vaporizing and carrying off tar acids therefrom in a current of inert gases and neutral oil vapors, and then distilling the residue remaining after the selective vaporization of tar acids to produce a distillate of low tar acid content.

3. The method of distilling tar by dephenolizing the tar and then distilling the dephenolized residue, ,which comprises preheating coal tar by heat interchange with hot vapors or a mixture of hot/ gases and vapors, selectively vaporizing tar acids from the preheated tar in a current of inert gases and vapors of neutral oils, extracting tar acids from said gases and vapors, subjecting the dephenolized residue to distillation thereby obtaining hot vapors or a mixture of hot -gases and vapors and employing them as the vapors or mixture of gases and vapors in the aforesaid preheating step.

4. The method of distilling tar by first dephenolizing it and then distilling the dephenolized,

5. The method of distilling tar by dephenolizing the tar and then distilling the dephenolized residue which comprises passing a current of hot gases through a tar still, spraying the dephenolized residue into the hotygases, whereby distillation is eiected, bringing the tar to be distilled into heat-interchanging-relation with the gases and vapors resulting from the distillation of the residue whereby the tar is preheated, selectively vaporizing tar acids from the heated tar in a current of neutral oil-containing inert gases and extracting tar acids lfrom said gases and distilling the residue from this treatment in the current of hot gases in the tar still.

6. The method of distilling tar by dephenolizing the tar and then distilling the dephenolized residue, which comprises passing hot coal distillation gases through a tar still, spraying dephenolized tar into the tar still in the form of a fine intense lspray, whereby the coal distillation gases are substantially detarred and the dephenolized tar is distilled, bringing the tar to be distilled into indirect heat-interchanging relation with'the gases and vapors coming from the tar still, whereby the tar is preheated,l selectively vaporizing tar acids from the preheated tar in an atmosphere of inert gases and neutral oil vapors, and distilling the residue from this treatment in the tar still.

7. The method of distilling tar which comn prises passing a current of hot gases through a tar still, preheating tar by bringing it into indirect heat-interchange relation with the gases and vapors coming from the tar still, bringing a current of hot inert gases containing neutral oil vapors into direct and intimate contact with 'the heated tar, whereby tar acid oils are vaporized therefrom, spraying the resulting inert gases and admixed vapors with a solution containing caustic soda in an amount sufficient to neutralize substantially all of the tar acid vapors, recycling the resulting inert gases and neutral oil vapors and bringing them into direct and intimate oontact with further preheated tar, and then distilling the tar residue from which tar acids have been vaporized by introducing it into the tar still and spraying it into the gases passing therethrough.

8. The method of distilling tar which comprises heating tar in a still, bringing the tar to be distilled into indirect heat interchange relation with the resulting hot vapors, bringing the preheated tar into direct and intimate contact with hot inert gases containing neutral oil vapors, whereby tar acids are vaporized from the tar, removing the tar acids from the resulting mixture of gases and vapors by bringing them into direct contact with a neutralizing agent, furtherV vaporizing tar acids from additional heated tar by recycling the resulting gases and vapors of neutral oils in contact therewith, and distilling the tar residuefrom which taracid vapors have been vaporized by heating in the still.

9. In combination withA a tar still, a preheater through which vapors from the tar still pass, means for bringing tar into heat-interchanging relation with the vapors in the preheater, a dephenolizer, means -for passing gases through' the dephenolizer, means for bringing the preheated tar into direct and intimate contact with gases in the dephenolizer, a caustic absorber, means for 'passing the gases from the dephenolizer to the caustic absorber, means for returning the gases coming from the caustic absorber to the dephenolizer and means for withdrawing the treated tar therefrom and introducing it into the tar still.

10. In comaination with a tar still, means for introducing hot gases thereto, a heat interchanger, means for bringing gases and vapors from the tar still into indirect heat interchange relation with tar therein, a dephenolizer, means for passing gases through the dephenlizen means for bringing the heated tar into direct and intimate contact with gases in the vdephenolizer, a caustic absorber, means for passing the gases from the dephenolizer into the caustic absorber, means Afor recyclingk gases from the caustic absorber thereto, and means for withdrawing tar therefrom and introducing it into the still. f

11. In combination with a coke oven, a still, means for passing hot coal distillation gases from theY oven through the still, a heat interchanger for bringing tar into indirect heat interchanging relation with the gases and vapors coming from the still, a tar tower with means for spraying heated tar from the heat interchanger therein, a caustic absorben means for spraying caustic therein and withdrawing carbolate therefrom and for recycling a portion of the carbolate through the spraying means, means for recycling gases through the tar tower and the caustic absorber, and means for withdrawing tar from the tar tower and introducing it into the still.

12. The method of treating tar to separately recover tar acids and neutral oils, which comprises distilling thev tar in a current of inert gases including neutral oil vapors, extracting tar acids from admixture with neutral oil vapors and cooling to condense oils, using in the inert gas distillation of the tar at least a portion of the neutral oil vapors remaining after the condensation and tar acid extraction, drawing off the residue from the inert gas distillation and distilling it.

14.' In combination with a tar still, a ytar-acidy still, a caustic tower, a condenser, means for cycling gases from the tar-acid still tol the caustic tower, from the caustic tower to the condenser,

and from the condenserI to the tar-acid still,

means for bringinga changing surface of tar into contact'with the gases in ,the tar-acid still, means for producing a spray of caustic solution in the caustic tower, and means for withdrawing distillation residue from the tar-acid still to the `tar still.

15. 'I'he method of distilling tar and of recovering tar acids therefrom, Awhich comprises heating the tar to a temperature below the distillation temperature of the tar acid oils, passing inert gases into intimate contact with the tar to vaporize tar acid oils at a temperature below their normal boiling point, passing the resulting admixed gases through a hot alkaline solution to recover tar acids therefrom, and, after the treatment of the hot tar to remove tar acids, further heating the tar to distill the same and produce distillate oils and a pitch residue therefrom.

16. The method of continuous distillation of tar and of extracting tar acids therefrom, which comprises preheating the tar to a temperature y below that of distillation of tar acid oils, passing in intimate contact with the tar a current of hot inert gases to effect vaporization of tar acidoils, passing the resulting admixed gases and vapors into intimate contact with hot alkaline solutions to extract tar acid vapors therefrom, returning the inert gases recirculating the same through the tar for further extraction of tar acid oils, etc., and, after the treatment of tar for the extraction of tar acids therefrom, further heating the tar continuously to eect distillation thereof and the production of distillate oils and a pitch residue.

17. Ther method of distilling tar and of recovering tar acids therefrom, which comprises selectively vaporizing tar acids from the tar by contact with neutral oil vapor, separating the resultant vapor mixture from the residue remaining after the selectivevaporization of tar acids, and then distilling the residue toV produce a distillate of low tar acid content.

18. 'I'he method of distilling tar-acid and neutral-oil-containing hydrocarbon material and of recovering tar acids therefroni, which comprises selectively Vaporizing tar acids from the hydrocarbon material by contact with a gaseous mixture substantially free fromtar-acids but containing suflicient vapors of neutral oil constituents of the material treated boiling within the boiling range of the tar-acids vaporized to inhibit to a substantial extent distillation of said constituents from the hydrocarbon material, separating the resultant vapor mixture from the residue remaining after the selective vaporization of tar acids, and then distilling the residue to produce a distillate of low tar acid content.

S. P. MILLER.

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