US1759816A - Distillation of tar - Google Patents

Description

May 2o, ,1930.

A. A. MaccuBBlN Er A| DI STILLATION OF TAR Filed sept. 11, 192e 2 sheets-sheet 1 l ATTORNEYS May 2o, 1930,

('00 denser A. A. MaccuBBlN ET A1.

DISTILLATION OF,TAR

.Fned sept. 11, 1928 2 sheets-sheet 2 Worm (ande/ver ATTORNEY Patented May 20, 1930 UNITED STATES PATENT OFT-'ICE ALEXANDER A. MACCUBBIN, OF MONTCLAIR, AND JOSEPH ZAVERTNIK, JR., OF HAR- RINGTON PARK, NEW JERSEY, ASSIGNORS TO THE BARRETT COMPANY, OE NE'W'v YORK, N. Y., A CORPORATION OF NEW JERSEY DISTILLATION 0F TAR ,Application filed September 11, 1928. Serial No. 305,265.

subjected to distillation in a pipe coil still inwhich it is pumped through a pipe coilunder pressure and heated 4therein to a. high temperature and in which the pipe coll discharges into a vapor box or chamber Where the oil vapors are separated from the pitch residue and from which the oil vapors are withdrawn to a condenser; and in which the pitch residue from the pipe coil still is passed continuously to a vacuum box or still where it undergoes further distillation with its selfcontained heat and Where an additionall amount of heavy oil is distilled therefromA and a pitch of higher melting point 4produced. The pipe coil still may be a single stage or multi-stage still. The vacuum box or still need not be independently heated, although additional heating may be employed. The present process makes use of the large amount of sensible heatcontained in the pitch discharged from the vapor box of the pipe coil still to distill an additionalv amount of heavy oil from the pitch by reducing the pressure on this pitch after it has been produced in the pipe coil still, and after it has been separately Withdrawn from such still.

The improved apparatus of the present invention includes a pipe coil still, Which may be a single stage or multistage pipe coil still,

in which the tar is heated in a pipe coil under pressure and discharged therefrom into va vapor box or separating chamber Where the vapors are separated from the pitch residue, together with a vacuum box or still arranged to draw. the hot pitch from the pipe "coil still into the vacuum'still and tc eifect further:

distillation" of oils from the pitch by reduction in pressure While'it is still at a sufficiently high temperature to enable such distillation on reduction of pressure 'to take place. The apparatus includes pressure and vacuum regulating means whereby the pipe coil still can be operated With pressure on the tar passing through the pipe coil, but with a vapor box at atmospheric pressure or approximately atmospheric pressure, and with the vacuum box or still under a high vacuum approaching the maximum vacuum obtainable. The apparatus includes suitable condensing means for condensing the distillate oils fractionally to recover different oil fractions therefrom. It also includes suitable means for preheating theJ tar.

In the operation of pipe coil stills for-the distillation of tar, the pitch produced as a result of the distillation is usually drawn oft at a high temperature as a finished product and is permitted to cool and solidify, or is passed to other stills in which it can be subi tures, it undergoes objectionable decomposi-A l tion, with decrease in oil yields and increase in pitch production. If the tar is kept at a suiiiciently lovv temperature to avoid excessive decomposition of the pitch and tar, the oil yields are limited and the melting point of the pitch is limited..

The present invention enables increased oil yields to be obtained, and a pitch of higher melting point to be directly produced, in a continuous manner, Without the supply of any additional heat other thanthat supplied in the tar heater or pipe coil still. It enables the pipe coil still to be operated at a temperature such that objectionable decomposition is avoided or minimized,and it supplements the pipe coil still distillation Witha vacuum distillation which makes use of the heat convcoil still after this pitch residue has tion is accomplished with lowering in temperature of the pitch; so that the higher melt- A1n vpoint pitch withdrawn from the vacuum p sti lwill be at a lower temperature than that withdrawnfrom the'pipe coil still. I

It will be seen that, in the present process, the vacuum is not applied to the vvapor box of the pipegcoil still, but is only applied to the hot pitch residue produced by the pipe een withdrawn from the vapor box of such still. It is important that the high vacuum should not be applied directly to the 'vapor box of the pipe coil still because the large amount of oil vapors separated in this vapor box would be expanded by the vacuum and their condensation would be made more diliicult, particularly the condensation of the lighter vapors of lower boiling point oils. In the present proc-4 ess, these vapors are taken oli from the vapor box of the pipe coil still at atmospheric pressure, or at a pressure approximating atmospheric, and only the pitch residue is passed to the vacuumV box and subjected tothe high vacuum. This pitch residue will have been 4freed from a large part of the normal oil content of the tar distilled, and particularly of the lower boiling oils, so that the pitch resldue will contain only or 'for the most part higher boiling oils. When these oils are distilled in the vacuum boxC or still, they can be readily condensed even though a high vacuum is maintained, because of their high boiling point. A high vacuum can also be much more readily maintained where only the hot pitch residue is subjected to the vacuum, than where the vacuum is applied directly to the entire vapor production of the pipe coil still in the vapor box of'that still.

Pitches of high melting point can be produced-by the present process, for example, pitches -of melting points up ,to around 400 F or higher. Such high melting point pitches can, moreover, be produced at the same time that high oil yields are obtained from the tar distilled. The pitches are, moreover, distinguished from pitches of similar melting points produced by present day methods from externally heated stills by having in general a lower so-called free carbon content. The oils produced by the presentprocess include not only the lower and medium boiling point oils, but also the high boiling point oils obtained during the high vacuum distillation and some of which heavy or high boiling point oils may be, or may contain constituents of, a semi-solid or solid consistency. In order to avoid solidification of the high melting point pitch or of the heaviest of the oil constituents, it is important to lprovide sui-t able insulation for the parts of the apparatus through which the oils and pitch are passed so as to permit withdrawal thereof from the apparatus in a liquid and thinly fluid state `The present process enables a wide range of'oil fractions to be produced, land enablesmay itself have a melting point of around 240 F., more or less. In the vacuum box or still the vacuum maintained may be around 27 to 29.7 inches of mercury. Under such ,high vacuum, a considerable part of the oil content of the hot pitch will be distilled which would not be distilled at the same temperature under atmospheric pressure.

The distillation of tar in a pipe coil still has the advantage that the tar can be rapidly and continuously pumped through the pipe coil and heated therein to a high temperature without maintaining the` tar at a high temperature for more than a very short period of time. When the tar is heated to the high temperature, it is immediately dis- -charged from the pipe coil into the vapor chamber of the still where the vapors which are produced at such temperature are drawn off and condensed. The vaporization which takes place in the vapor chamber of the still may result in lowering the temperature of the pitch somewhat from that to which the tar is heated in the still be at a su ciently high temperature so that, when flashed by the sudden reduction of pressure, a considerable further distillation will take place. The maximum temperature to which the tar or pitch is heated, is that in the pipe coils, and, by regulating and limiting this temperature, and the period of time to which the tar or pitch is subjected to it, objectionable decomposition of oill constituents can be largely avoided, thus giving a pitch of lower so-called free carbon content, and an increased oil yield.

The invention will be further described in connection with the accompanying drawings, which are of a conventional or diagrammatic character, and in the nature of flow sheets, and which show arrangements of apparatus embodying the invention and adapted for the practice of the process of the invention;'but it will be understood that the invetion is not limited thereto.

In the accompanyin drawings, i

pipe coils, but the pitch will llO Figs 1 and 2 'are dlagrammatic arrangements -or flow sheets showing twofsomewhat into the vapor box which is at atmospheric4 pressure, or approximately so, and Where oil vapors will. separate from the unvaporized pitch. The vaporsv pass through pipey 7 to Condenser 8, which may be of any suitable construction, and the oil outlets from which are not shown.

The pitch collecting in the vapor box 6 passes through the pipe 9 having pressure reducing valve 11 therein to the vacuum box 10 which is maintained under a high vacuum,

' for example, a vacuum corresponding to 29.7 inches of mercury. The vacuum box or still 2o 10 is arranged some distance above the vapor box 6 and the vacuum is relied upon to draw the pitch from the vapor box to the vacuum box. Immediately upon reduction of pressure at the pressure reducing valve 25 11, distillation of some of the oils contained in the pitch Will take place and the resulting oil-'vapors will assist in forcing the pitch int-o the vacuum box. The vacuum box can'- not be located too far above the vapor box because the vacuum is relied upon to draw the pitch from the vapor box to the vacuum box. In order that a high vacuum may be maintained and the iiow of pitch from the vapor box to the vacuum box controlled, it is important to provide a pressure reducing valve 11 in the line 9 leading from the vapor box 6 to the vacuum box 10.

The vapors distilled from the pitch in the Vacuum box pass through the vapor'line 12 to the condenser-13, thence through the line 18 to a second condenser 19. The oil condensed in the condenser 13-flovvs through the pipe let to a seal tank 15 from which it may be drawn oft', for example, through measuring densed in the condenser 19 similarly flows through the pipes 20 and 21 to the oil receiver 22. The pitch residue from the vacuum box or still 10 flows through the pitch line 26 to the seal tank 27 and thence to a suitable lplace of pitch storage 28. The lines 14, 20-21, and

26 are suiiiciently long, and the vacuum boxl ranged an oil and air separator 23 from .which any separated oil flows through the pipe 24 to the pipe 21 and then to the receiver 22. Any suitable type of vacuum pump or vacuum producing means can be employed, a

pan 16 to anoil receiver 17. The oil con denser 19 and the vacuum pump 25l isarthree stage ejector type of vacuum pump being suitable and preferable.

According to ,a preferred method of operation, tar which is to be distilled is used for cooling inthe condensers, the tar being tliercby preheated. Various arrangements for circulating the tar through the condensers may be employed, that shown in the drawings combining countercurrent and parallel flow features to advantage. Thetar supplied to the line 29 by the pump 30 is divided, that portion which is used to cool Vthe vapors in the condenser 19 being returnedthrough the line 31 and united with the balance of the tar from the line 29 before entering the condenser 8. The combined tars are employed to cool the `vapors at the exit of the condenser 8, then all or a part0f the tar is conveyed through pipe i 32 to the condenser 13 Where it is used or condensing the vapors passing through this condenser. The tar is then returned to the condenser 8 and brought into indirect contact with the vapors entering this condenser. The tar which has thus been graduallyheated by indirect contact with the hot vapors in the various condensers may be sent to the continuous pi'pe still alone or blended With' tar from another source. y

In the drawings, insulation is not shown but it Will be understood that in practice the line conveying the hot pitch to and from the vacuum box as Well as the vacuum box itself and other parts of the apparatus will be suitably insulated to avoid heat losses and in particular to avoid cooling of the pitch unnecessarily before it is discharged from the apparatus. With pitch of high melting point, around 400 F., it is important to Withdraw the pitchwhile it is still hot and thinly fluid. Such pitch can then be run to storage tanks or receptacles andbe permitted to solidify, or it can be continuously solidified by means of special cooling treatment or devices (not shown) .l

The How sheet of Fig. 2 shows a somewhat modified apparatus in Which a two-stage pipe coil still is shown With provision for fractional condensation of the oils distilled in such stills, and also in the vacuum still.

In Fig. 2 the first pipe coil still 35, is supplied With tar through the supply pipe 36 by means of a pump 37 from one or the other` of the crude tar storage tanks 38 and 39. From this pipe coil, the heated tar passes through the pipe 40 to the vapor box 41 from which the pitch flows througlrth pipe 42 to the storage tank '43. Thispitch is drawn oii:| through the pipes 44 and 45 and pumped bv the pump 46 to the second pipe coil still 4 i which discharges through the pipe 48` to the 1 53 tothe seal box 54 and thence through line 55to the pitch receiver 56.

The vapors separated in the first vapor box 41 flow through line 57 to the first condenser 58 which is shown as a multi-stage condenser. The uncondensed vapors then pass through pipe 59 to the second condenser 60 from which the still uncondensed vapors pass through line 61 to another condenser 62 and finally 69 for the oil fractions.

. denser The vapors separated ,in the vapor box 49 pass through vapor line 70 to the first condenser 71, from which the uncondensed vapors pass through line 72 to the second con'- 73, thence Athrough line 74 to a third condenser 75 and finally through line 76 to a final Worm condenser 77. The condensate from this final condenser flows through line 78 to the oil receiver 66; The condensers 71 and 73 are shown as fractional condensers.

'The oil fractions from different sections of these condensers and from the condenser are drawn off through pipes 79 and 80 to one or another of the oil receivers 81. By regulating the valves in' the pipes 79 and 80, the

different oil fractions can be drawn ofi:I separately and kept separate. A diagrammatic arrangement of condensers is understood to be illustrated, since it will be evident that a larger or smaller number of oil fractions can be obtained depending upon the number and operation of the fractional condensers applied.

The vapors separated in the vacuum cham-A ber 52 pass through line 91 to the first condenser 92 from which the uncondensed vapors pass through line 93 to a second 'condenser 94. This second condenser connects throughline 96 to a three stage vacuum pump show n as a three stage steam ejector pump 97. The condensate from the condensers 92 and 94 may be drawn olf through the lines 98 and 99.- The line 98 passes through the seal tank 100 to theoilreceiver 101 and the line 99 passes through the seal tank 102 to theoil receiver 103.

The final condenser-94 is shown as a. water cooled condenser, having water connecting pipes 95. The other condensers, except the worm condensers 64 and 77, are shown as cooled bythe tar which is thereby preheated,

' with resulting heat economy. The condenswater.

ers 64 and 77 are worm condensers, cooled by The tar for-coolingl the condensers is supplid through line 82 by means of pump 83 an passes first through the condenser 62 where it is brought into indirect heat ex@ changing relation with the vapors passing through this condenser. The tar then passes successively to the condensers 60, 58, 92, 75,

73 and 71, being finally discharged through.

first to the condensers Where thelighter oils V are to be condensed and passing finally through the condensers where the vapors are at the highest temperature. The -tar circulating pipes between the various condensers are mdicated respectively at 84, 85, 86, 87, 88, 89 and 90. The tar is preheated to such a temperature that when it enters the vapor box 41 more or less of its oil content Will be vaporized, particularly' where flle tar is maintained under pressure while it -is sure is released when it enters the vapor-box. The residue remaining after the separation of vapors in the vapor box joins with the pitch residue from the first pi e coil still and forced through the condensers, and the prestogether these go to the secon pipe coil still.

The pitch and oil lines 53, 86, 98 and 99 ,of Fig. 2 aresufliciently long, and the. vacuum box and its condensers are located a suicient distance above the oil receivers or seal'boxes or tanks that barometric columns of pitch and oil will be maintained in these pipes, thereby insuring maintenance ofthe vacuum in the vacuum box, and continuous ow of gravity of the oil and pitch from the Vvacuum apparatus.

'In' the drawin no separate heatin provision is shown orheating the pitch 1n the vacuum box. The heat content of the pitch is such that a considerable distillation of oil will take lace on reduction of pressure from atmosp eric to a hi h v acuum,`even where no added heat is supp ied'. In such case, the further distillation b flashing under vacuum is obtained entirely y the self-contained sensible heat of the hot pitch residue from the pi e coil stills, and this heat is made available y the reduction in pressure from atmospheric to the high vacuum. In order to obtain maximum distillation, where additional heat is not employed, it is important to avoid un necessary loss of heat by radiation, 'by roviding heavy insulation, etc. When a ditional heat is sup lied to the pitch goin ,to or passing throug thev vapor box,.an additional amount of oil can be distilled and a hi her meltin point pitch ro'duced.

t willthuse seen that the present invention provides an improved method and apparatus for distilling` tarin a continuous manner and with notable heat economy, as well as with the production of a high melting point pitch and a high oil yield. It will further be seen that the distillation is accomplished Without objectionable heating of the tar or pitch toa high temperature, and that the maximum temperature to which the tar or pitch is heated in the pipe coil still, is not exceeded in the further distillation of .the pitch residue, but that this further distillation can be accomplished with lowering of temperature and reduction or avoidance of further objectionable decomposition.

We claim: y v

1. The method of distilling tar and of producing distillate oils and high melting point pitch therefrom, which comprises heating the tar while flowing in a restricted stream of, narrow cross-section 1n a continuous manner l Without objectionable decomposition, discharging the heated tar into an expansion zone with sudden volatilization of a largle part of the normal oil content of the tar, coo ing the vapors to condense distillate oils, withdrawing the pitch residue and subjecting it to a high vacuumA while it is still at y a temperature sufficiently high to effect distillation of additional oils therefrom.

2. The method of distillingtar and of producing distillate oils and pitch therefrom, which comprises forcing the tar continuously under pressure through a pipe coil and heating it therein to a temperature sufficient to vaporize considerable proportions of the oil contained in the tar, discharging the resulting product intoya vapor separating zone at approximately atmospheric pressure and thereby effecting separation of oil vapors from pitch residues, drawingoff the oil vapors and subjecting them to condensation to recover distillate 011s therefrom, drawing off the hot pitch residue and ysubjecting it to a high vacuum while'it is still at a high temperature and thereb effecting further distillation of oils there rom with reduction of temperature,4 condensing the distillates produced y such vacuum distillation, and separately drawing oif the pitch residue from such vacuum distillation.

3. T e method of distilling tar and of producing distillate oils and pitch residues therefrom, which comprises heating the tar flowing in a restricted stream of narrow crosssection inacontinuous manner without objectionable decomposition, discharging the heated tar into an expansion zone, separating oil vapors from the resulting pitch residue in the expansion zone, cooling -the vapors to produce distillate oils, drawing off the pitch residue' through a pressure reducing and regulating valve to a vacuum box or still while it is still at a high temperature and thereby effecting further distillation of oils from the pitch, the flow of pitch from the pipe coil still to the vacuum still being accomplished 4. The method of distilling tar and of producing distillate oils and pitch residues therefrom, which comprises first repeatedly heating the tar owing in a series of restricted streams of narrow cross-section in a continuous manner without objectionable decomposition, drawing off vapors resulting from each heating of the tar and condensing distillate oils therefrom, drawing off the hot pitch residue from such distillation and subjecting it while it is stillat a high temperature to a high vacuum to effect further distillation thereof and separatel drawing off the vapors produced from such istillation and condensing them while still under a high vacuum.

5. The method of distilling tar and of producing distillate oils andv pitch residues therefrom, which comprises continuously heating the tar owingin a restricted stream of narrow cross-sectlon to approximately the maximum temperature to which it can be heated without objecticnable decomposition, discharging the heated tar into an expansion zone, withdrawing the vapors produced by a pitch residue, withdrawing the pitch residue continuously while it is still at approximately the temperature of the first'disv tillation and immediately subjectin it4 to a high vacuum-to eifectfurther distil ation of high boiling point oils therefrom by the selfcontained heat of the hot pitch.

7. The method of distilling tar and of producing distillate' oils and pitch residues therefrom in a continuous manner, which comprises supplying the tarto be distilled to a still, heating the tar therein thereby distilling oils therefrom and producing a pitch residue, withdrawing the pitch residue continuously while it is still at practically its maximum temperature and immediately subjecting it to a high Vacuum to effect distillation of additional oils "therefrom by the self-contained heat of the pitch under the high vacuum.

8. An apparatus forv distillin tar com prismg a pipe coily still having a eating coil 4and a vapor separating chamber with means distillation of additional amounts of oil therefrom.

'9. An. apparatus for distilling tar, comprising a pipe coil still having at least one pipe coil and vapor separating chamber, a pitch discharge for the pitch produced by such distillation, a vacuum chamber, means for maintaining a high vacuum therein, means connectin a vapor chamber of the pipe coil still wit the vacuum chamber havt ing a pressure reducing and regulating device therein, said apparatus being so arranged that the pitch residue from the pipe coil still will be drawn continuously by means of thevacuum through the pressure regulating device into the vacuum chamber for further distillation.

10. The method of distillin tar and of producing" distillate oils and high melting point pitch therefrom, which comprises heating the tar while flowing in a restricted stream of narrow cross-section in a continuous manner, discharging the heated tar intov ing it to a ,vacuum of at least twenty-seven inches to effect distillation of additional oils and the production of a high pitch.

11. The method of distilling tar and of producing distillate oils and pitch residues thereform in a continuous manner, which comprisesupplying the tar to be distilled to a still and heating the tar therein and distilling oilstherefrom and 4producing a pitch residue, vwithdrawing the pitch residue contmuously while it is still at ractially its maximum temperature and su jecting it to a vacuum of at least twenty-seven inches to effect distillation of` additional oils therefrom by the self-contained heat of the pitch under a high vacuum.

12. The method of distilling tar and of producing'distillate oils and pitch residues melting point distillation while it is still at approximately the temperature of the first distillation and,

without substantial heat loss 'subjectin it to a vacuum to effect further distillationo high boiling point oils therefrom by the self-con tained heat of the hot pitch,

13. An apparatus for distilling tar, comprising a continuous tar still including a vapor box having means for supplying tar thereto continuously and for removing oil vapors therefrom, a vacuum chamber with means for maintaining a high vacuum there-l in, a connection between the vapor box and the vacuum chamber for conveying the pitch residue from the vapor box to the vacuum chamber together with means for regulating the reduction of pressure on the pitch, the arrangement being such that the hot pitch from the vapor box can be immediately and directly conveyed while at practically its maxiaok mum temperature to the vacuum chamber,

wherebythe heat contained in the hot pitch can be employed for distillation of additional amounts of oil therefrom..

14. The method of distilling tar and of producingv distillate oils and pitch residues therefrom, which comprises first subjecting tar to distillation at substantially atmospheric pressure to produce distillate oils and a pitch residue, withdrawing the pitch residue dur.- ing distillation while it is still at approximately the temperature of the first distillationand without substantial heat loss sub- A jecting it to a high vacuumfto effect further distillation of high boiling point oils therefrom by the self-contained heat of the hot I pitch.

15. producing distillate oils and pitch residues therefrom in Ya continuous manner, which comprises-.supplying the tar to be distilled to a still and heating the tar therein and ydistilling oils therefrom and producing a pitch residue, withdrawing the pitch residue during distillation while it is still at practically its maximum temperature and immediately subjecting it -to a ,high vacuum to efectgdistillation of additional oils therefrom by the self-contained heatiof the pitch under the high vacuum.

In testimony .whereof we aiixour signatures.

' ,ALEXANDER A. MACCUBBIN.

JOSEPH ZAVERTNIK, JR.

therefrom, which comprises rst subjecting i due, the'pitch residue during The method of distilling tar and of

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