US1893145A - Distillation of tar - Google Patents

Description

jan. 3, 1933. s. P. MALLER DISTILLATION OF TAR Filed Jan. 26. 1929 2 Sheets-Sheet mvENToB WMM T Q n u J M W y o.

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Jan. 39 1933. s. P. MILLER DISTILLATION OF TAR Filed Jan. 28, 1929 2 Sheets-Sheet @u mw l INVENTOR MM M ATTORN EYS Patented Jan. 3, 1933 i UNITED STATES PATENT OFFICE STUART PARMJELEE MILLER, F ENGLEWOOD, NEW JERSEY, ASSIGNOR T0 THE BARRETT COANY, 0F NEW YORK, N. LY., A CORPORATION 0F NEW JERSEY nrs'rrmarron or 'ran .Application led. anuary 26, 1929. Serial No. 335,207.y

This invention relates to improvements in the distillation of tar and the production of distillate oils and pitches therefrom and it includes improvements in both process and apparatus. More particularly, the invention comprises improvements in the distillation of tar at coal carbonization or distillation or gasication and tar production plants.

According to the present invention, the tar to be distilled is heated in an externally 4heated still or by indirect contact with heat ing gases, to a temperature above the boiling point of part of the oils contained in the tar, and the resulting preheated tar is discharged into a vapor box Where vapors oi the lovver boiling constituents ot the tar are volatilized and from which the vapors are conducted to suitable condensing means. 'l`he unvolatilized residue ot the tar is then brought in a preheated state into direct and intimate contact with hot uel gases such as coal distillation or carbonization gases or coal gasification gases to effect further distillation of the tar.

More particularly, the present invention comprises an improved process in which the tar is heated continuously in a pipe coil under pressure to a temperature above the boiling point of part ot the constituents. rli'he tar thus heated is fed to a vapor bon in which the volatilized constituents separate from the unvolatilized residue, and this unvolatilized residue is then discharged in a preheated state into the still Where the residue isy brought into direct contact with hot coal carbonization or gasification gases to eect turther distillation..

Pipe coil stills have been employed for the distillation of tar by heating the tar continuously in a pipe coil and discharging it into a vapor chamber from which the vapors are drawn off to a condenser vand the pitch produced separately drawn od. Such stills are effective for the distillation of part of the oil contained in the tar but it the tar is heated to a suiicient temperature to produce a high melting point pitch and a high oil yield, the temperature is such that considerable decomtakes place With decrease in oil distilled and increase in carbon and pitch produced.

The present invention includes improvements in the operation of such pipe coil stills iniconnection with stills in which the gases are brought into direct contact with hot fuel gases and in which the tar is heated in the pipe coil to a temperature sufhcient to distill distillation ot the residue to produce an increased distillation oit oil and the production of a higher melting point pitch for further distillation with the hot fuel gases, While nevertheless avoiding any objectionable or considerable decomposition of heavy oil constituents during such further distillation.

lfVhen coal tar is introduced into hot coke oven or other coal carbonization or gasication gases, a considerable proportion of the heat contained in the hot 'fuel gases is consumed in heating the tar tothe distillation temperature and in dehydrating it. While there is a large amount of heat available in hot coke oven gases or other coal carbonization or gasification gases for the distillation of tar, yet the B. t. u. content ot' the gas per unit volume is relatively lovv and the distillation which can be accomplished per unit volume of gas employed is lovv. When the hot Jfuel gases are required to heat the tar and dehydrate it in addition to distilling it, a disproportionately large volume of gases is required and the degree o' enrichment of the gases is correspondingly limited so that it is necessary to employ a relatively large volume ot gases and to recover the distillate from admixture with such gases;

The present invention enables the distillation oit' tar by such hot 'fuel gases to be very greatly promoted and in particular enables a v position of the oil constituentsl of the tar greatly reduced volume of such gases to be recover such low .boiling oils from the gases are largely avoided.

When tar is distilled by direct contact with highl heated gases such as coke oven gases, the distillates are carried as vapors admixed with the gases leaving the still and these oils are recovered by subsequent cooling of the the preheater.

employed in the preheater, the amount of the admixed gases and vapors to effect condensation of the vapors. In order to accomplish such condensation, it is necessary to cool the gases to their dew point for the desired oil constituent which is far below their normal condensation temperatures when free from admixed gases. The complete condensation of lower boiling point oils from admixed gases is diliicult and appreciable loss of such light oils may take place unless the gases are subsequently scrubbed to recover them.

The present invention provides 1an improved process and apparatus in which the light oils are for the most part or completely removed from the tar before it is subjected to distillation by direct'contact with the highly heated gases, and in which tar is preheated by indirect contact with hot gases and thus preheated and partly distilled to remove light oils therefrom, and in which the preheated and partially distilled tar is then supplied to the still. The lighter oils which are removed by the preliminary preheating and partial distillation can be readily condensed lbecause they are free from admixed inert gases. The removal of the light oils from the tar before 1t enters the still greatly reduces the loss of hght oils with the gases and greatly improves the condensing operation for condensing the oils from the inert gases. The condensers operated in connection with the still employing the hot coal carbonization gases may be operated at a higher temperature and the higher boiling point oils can be more readily condensed from the gases. The preheated tar enters the still in a preheated condition 50. where its heat is taken advantage of in increasing the unit disillation capacity of the yhot gases in the still.

The partial distillation of the tar in the preheater can be supplemented by applying vacuum to the vapor box connected with the preheater thus gixing an increased percentage of oils distilled from the tar and the pitch a somewhat higher meltingpoint. vThe extent to which the distillation is carried in the preheatmg operation can be regulated to a greater or lesser extent by regulating ythe temperature and amount of the gases em-.fl ployed in the preheating operation and the rate at which the tar and gases pass through Where waste flue gases are.

gases passing through the prehe'ater can be regulated to regulate the temperature to which the tar is preheated. By arranging a generally counter-current flow of the tar and' of the hot gases, the tar can be preheated to a temperature somewhat lower than that of the hot waste gases.

The temperature required for distilling tar to produce a given percentage of distillate and a pitch of a given melting point in a pipe coil still, is much greater than that required in a still in which the distillation is accomplished by direct contact with hot coal carbonization or hot coal distillation or gasification gases. In the pipe coil still, it is neces- Asary to heat the tar to the distillation temperature of the variousoils which are distilled, but in the still in which the tar is heated by direct contact with the hot gases, it is only necessary to heat the tar to a temperature somewhat above the dew point of thev gases for such oils.

By preheating the tar and flashing it in a vapor box as contemplated by"this invention and conveying the heated residue from the vapor box to the still in which the tar is brought into direct contact with the hot ases, a much lower temperature is required or distilling the tar than would be required in an externally heated still, and the` preheated and partly distilled tar from the vapor box can readily be further heated and distilled and a pitch of high melting point produced together with an increased percentage of distillate oils without heating the pitch to a temperature where any considerable distillation of oil takes place. The present invention accordingly enables tar to be distilled to produce a high percentage of distillate oils and a high melting point pitch. lt also enables tar` to be rapidly distilled to produce a lower melting point pitch and a lower percentage of distillate with the roduction of gases enriched in vapors of hlgher boiling range frompwhich the distillate can be readly condensed.

lt will be appreciated that when tar is distilled by direct contact with hot coal carbonizationor gasification gases, the distillater must be recovered from the gases by cooling the gases to the dew points of the gases for the various oil constituents. Ordinarily, coke oven gases, for example, contain only around one to three percent of vapors and the dew. point of most of the oil constituents contained in the gases is relatively low. However, by preheating the tar y according to the present invention, and then llashing it and then further distilling it by bringing the preheated residue into direct contact with hot coal carbonization gases, the gasesY can be so greatly enriched in oil vapors that condensation can readily be accomplished at higher temperatures and the condensation can moreover be carried'much more nearly to completion due to the initial se arate removal of the lower boiling constltuents of the tar in the vapor box. Moreover, the condensation can be carried out fr'actionally sothat heavier and lighter oil fractions can be condensed separately.

',llhe tar which is distilled according to the present invention may be coke oven tar, Water gas tar, gas retort tar, producer gastar, etc. and it may be a total composite tar or a heavier or lighter tar, or blended tars from dilereiit sources such as blended Water gas and coke oven tar or coke oven and retort gas tar, etc. 'lhe tar distilled is advantageously that produced at the plant at which the distillation is carried'out so that, for example, coal tar produced at a coke oven plant is distilled at the coke oven plant with the use of hot coke oven gases.

'lhe preheating ot thevtar can readily be carried out at many coke oven or other coal carbonization plants with the use of Waste heat. For example, at a coke oven plant equipped With a regenerative preheater, gases leaving the heating lues ot the colte ovens and passing to the staclr have a large volume and a temperature, for example, around 400 C. ln coke ovens having recuperative preheaters :tor the colte ovens, the

gases commonly pass to the stack at a much higher temperature. Coke oven plants having dry quenching systems have an abundance oi heat available for preheating purposes. V7 here Waste heat gases are not available, the pipe coil can be heated by the combustion of fuel.

Vliile dierent types of preheaters can be employed, that which isparticularly to be recommended is a pipe coil preheater having a large number ol pipes connected together to form a single long continuous coil through which the tar is pumped under pressure and in which the tar is gradually heated to the desired tempera-ture. Such a pipe coil can readily be located, for example, in a flue through which the hot Waste flue gases pass from the coke oven heating iues to the stack Witl. due gases available in large quantities at a temperature around 300 to 400 C. and by providing a pipe coil of sufficient length, the tar can be heated to a high temperature approximating that of the Waste gases and it can be readily heated to a lower temperature in a shorter pipe coil or at a more rapid rate. The tar can readily be preheated in such a still to a temperature around 200 C. or even to 300 C. or higher.

'lhe gases employed for the further distillation of the preheated tar after separating the vapors resulting from the preheating operation, may be hot coke'oven gases or hot gases from a retort gas plant or other hot coal carbonization or distillation or gasification gases such as producer gas, Water gas, etc. Such gases are advantageously employed at a high temperature approximating that at which they are produced, since with high temperature gases increased distillation can be accomplished and an increased enrichment of the gases in oil vapors attained as compared With lower temperature gases. ln the case of coke oven gases, tor example, the gases can be Withdrawn, e. g. Jfrom the 4individual coke ovens directly into a still which they enter Without material reduction in temperature, tor example, at a temperature around 500-850o C. or higher, depending upon the type of colte oven, the colring period employed, etc. lEven Where the gases are partly cooled before being employed tor distillation, there vvill be a greatly increased enrichment ot the gases in oil vapors. here the taris preheated and then tlashed in the manner above described before it is brought into direct Contact with the gases 'for jurther distillation, the enrichment vvill be vapors ol3 higher boiling constituents and there will be comparatively evv vapors of loiver boiling constituents.

'l`he further distillation oit the preheated tar is accomplished by bringing the partially distilled tar into direct and intimate contact with the hot gases, for example, by spraying or atomiaing the tar or pitch into the gases. VV bile spray nozzles can be ernployed for introducing preheated into the gases particularly Where lower melting point pitches are to be produced, it is more advantageous to employ mechanical spray dei .L 'J u vices igor rapidly spraying the tar and pitcn c into the gases in a thorough-going manner.

The type of still employed for distilling the pre-heated tar by direct contact With the* hot gases can be varied depending upon the amount of tar to be distilled, the temperature l of the gases available Jfor distillation, etc. still having a suitable mechanical spray device such as rapidly rotating rolls or discs dipping into a body of tar or pitch in the bottom of the still, is an advantageous type of still to employ since by sufficiently thorough and intensive spraying of the tar and pitch into the gases, the gases can be rapidly cooled to a temperature approximating that to which the pitch is heated and the preheated tar can be rapidly distilled. The partly distilled tar from the vapor box ca n be discharged directly into the still but it can also and With added advantage in some cases, be discharged into a tower through which the gases and vapors leave the still so that the residue from the vapor box Will be iio iis

still further distilled by direct contact with the hot gases and vapors leaving the still before this partly distilled tar enters the still. The distillate produced by the present ies process Where the hot gases employed are tar densation but the percentage of such heavy tar and pitch constituents will be small because of the hi h enrichment of the gases in oil vapors resu ting from the distillation of the tar. Where the gases employed are thoroughly scrubbed and Lcleaned by the use of an intense and thorough spray of the tar and pitch into the gases, the oil subse ently condensed will be lclean. oil, that is, (lice or substantially so from heavy tar andl constituents initially entrained in the hot gases.

The extent to whichthe tar is preheated before being flashed, can be varied. With waste heat preheaters, the preheating may be only to temperatures around 150 or'200 C. or it ymay be up to 300 or 350- C. but in general it should be below the temperature at which any considerable decomposition of the oil takes place in the externally heated preheater. When tar preheated to such high temperatures is fiashed and the residue brought into direct contact with hot gases such as hot coke oven gases, for example, at a temperature of 650 to 850 C.v the heat of the hot gases will be employed for distilling` the higher boiling oils from the tar, since the preheating will have resulted inthe distillation and removal of the lower boiling oils. This further distillation by the hot gases can accordingly be carried out so as to produce a highvmelting point. pitch at a suiiiciently low temperature to avoid any considerable decomposition during the distillation, thus giving an unusually high oil yield and pitch of high melting point representing a relatively small percentage of the tar distilled.

The invention will be further described in connection with the accompanying drawings which are of a more or less conventional and diagrammatic character, and which illustrate apparatus embodying the invention and adapted for the practice of the process of the invention at a coke oven plant, but it will be understood that the invention is not limited thereto. v y

Fig. 1 is a plan view of a coke oven plant c quipped for carryinghut the invention, and Fig. `2 is an elevation of the apparatus of Fig. 1, partly in section.

In the drawings, the coke ovens 5 are connected through uptakes 6 with the collectormain 7. The gases from the ovens pass through the center box 8 of the collector main into the cross-over main 9 and thence to the condensers 10. This showing of the apparatus is diagrammatic since apparatus of the usual type may be employed.

The gases employed for heating the ovens pass through the flue 13 to the stack 14. By vproper manipulation of the valves 15 and 16, a portion of these waste hot gases are bypassed and employed for preheating tar in the preheater 17. The gases then pass to the stack 14 and a blower 19 may be employedconstituenta-havefpreviously vbeen removed main 23 into the condenser 24 where they are condensed and the light oil thus produced is collected in the receiver 25. A portion of the residue from the vapor box may be withdrawn, as a low melting point pitc in the receiver 26. The balance of the residue will be conducted to the still 27.

This residue may be conducted directly to `the still or may be added through the spray means 28 located in the tower 29. If the residue from the vapor box is, sprayed into the hot gases and vapors leaving the still as shown in the accompanying drawings, the hot gases will further distill the tar `before it enters the still. The residue of undis tilled tar will collect in the bottom of the tower 29 and will drain through. the plpe 30 into the still 27.

The hot gases entering the still are brought from the ovens to the still by means of u take pipes 31 and the hot gas header 32. y proper manipulation of valves in the uptake pipes 31 and the uptake (pipe 6 the hot gases from the ovens connecte with uptake pipes 31 may be directed either to the usual collector main 7 or to the hot gas header 32. The hot gases pass from the ovens 5 through the uptake pipes 31 into the hot gas header 32 and thence to the still where they are brought into intimate contact with the tar. This intimate contact is l produced by the spray thrown from the roll 33. Thls roll 33 is so situated within the still that 1t dlps to but a slight extent into the partiallydlstllled tar or pitch in the bottom of the still. The roll is rapidly rotated by means of the motor 34'so that the tar or pitch from the bottom of the still is thrown into the hot gases and forms an intense spray of the tar 1n the gases. This results in distillation of the tar with minimum decomposition of the tar and also results in thorough scrubbing of the hot gases by the tar. The gases leaving the still through the connecting main 35 into the tower 29 are substantially free from entrained particles. Any entrained spray carried by the gases may settle from the gases in the tower 29 or may be removed by the bailiing means 36. l

The vapors produced by the distillation of the tar within the still are substantially free from low boiling constituents and may' readily be removed from the inert gases in suitable cooling means. The lowerboiling vessaient troni the tar in the vapor box 22-and have been collected in the storage tank 25. By passing the hot clean enriched gases through the main 37 to the condensers 38 and cooling the gases in the condensers7 which cooling need not be to the low temperature ordinarily necessary, a high yield ot relatively .high boiling oils will be obtained. llt direct condensers are employed as shown, the residue from the condensers passes rst to a decanter 39 trom which the ammonia liquor is drawn ofi through d0 and the oil which is essentially the higher boiling oils distilled trom the tar is collected in lll. An erihauster t2: which may be the same eXhauster as that employed tor drawing the gases through the ordinary collector main, is employed trr drawing the gases through the still and condenser 38.

lt is to be understood that the apparatus and yprocess ot this invention are not to be considered as limited to the specific disclosure described in connection with the drawings. rThe invention relates to preheating tar, removing vapors trom the preheated tar and distilling the residue by direct contact with hot coal carbonization or distillation or gasitlcation gases as claimed below.

l claim:

l.. The method of distilling tar which com prises heating the tar in an externally heated still to a temperature suttlcient at atmospheric pressure to distill part of the oil trom the tar, separating vapors ot lower boiling con-l stituents from the preheated tar, separately condensing said lowerboiling constituents, and then further distilling the residue from this distillation by direct contact with hot tuel gases while at a high temperature alter their production from coal distillation or gasilication.

2. 'llhe method of distilling tar which comprises preheating tar under pressure to a tem erature above the boiling point of part ot t e oil constituents of the tar, separating vapors of lower boiling constituents from the preheated tar, separately condensing said vapors, and bringing` the residue into direct contact with hot coal carbonization or gasification gases and effecting further distillation of the tar by direct contact with such gases.

3l The method of distilling tar which com` prises heating the tar continuously in a pipe coil to a high temperature and discharging the resulting tar into a vapor box said temperature being sufficient to distill part of the oil from the tar at the pressure of the vapor box, separating the vapors of the lower boiling constituents from undistilled tar therein,separately collecting and condensing said lower boiling constituents and bringing the partly distilled tar into direct contact with hot coal carbonization or gasification gases to effect `further distillation thereof.

Il. Thelimprovemen in the distillation'of .Y

tar by direct contact with hot coal carbonization or gasiication gases which comprises preheating the tar to a high temperature under pressure and discharging the thus preheated tar into a vapor box said temperature bemg sucient to distill part of the oil from the tar at the pressure of the vapor box, separating the vapors of lower boiling constituents t'rom undistilled residue therein and separately condensing them, and discharging the undistilled'residue in a preheated state into direct contact with the hot coal carbonization or gasiication gases to e'ect further distillation at substantially atmospheric pressure.

5. The improvement in the distillation of tar in pipe coil stills which comprises heating the tar continuously in a pipe coil, discharging the tar therefrom into a vapor separating chamber the heating of the tar being regulated so as to heat the tar to a temperature sufdcient to distill part ot the oil therefrom at the pressure of the separating chamber, separately collecting and condensing the vapors from the vapor separating chamber,

withdrawing undistilled residue `from the f vapor separating chamber., passing the preheated residne into a still and subjecting it to intimate and thorough contact in the form of a spray with a current of hot coal carbonization or gasiication gases to effect further distillation, and passing the resulting gases and vapors in direct contact with the preheated tar residue before the residue enters the still.

6. The method oit distilling tar which comm prises preheating the tar continuously in a pipe coil to a temperature above the boiling point ot part of thetar constituents, discharging the preheated tar into a vapor bor, separating the vapors from undistilled residue therein and separately cooling said vapors to recover oils therefrom, bringing the undistilled residue into direct contact with hot coal carbonization or gasification gases to eiiect further distillation of the same, such further distillation being e'ected by a repeated and intense spraying of the partly distilled tar into a current of the hot gases, and drawing off gases and vapors resulting from such distillation and cooling the same to condense oils therefrom.

7. The method of distilling tar at a coke oven plant which comprises preheating the tar continuously in a pipe coil still by waste heat gases, discharging the preheated tar into a vapor box the preheating of the tar i loil therefrom at the pressure of the vapor box, separating the tar from the vapors therein whereby vapors of lower boiling constituents are separately collect/ed and condensing said vapors, introducing the preheated residue from the vapor box into direct contact with avcurrelltohotcokeoven gases, thoroughly spraying the tar or pitch into the gases thereby scrubbing the gases and further distilling the preheated tar, and drawing off the resulting gases and vapors, and cooling the same to condense oils therefrom.

8,. The method ofdistilling tar at a coke oven plant which comprises preheating the tar continuously in a pipe coil still by waste heat gases, discharging the preheated tar into a vapor box the preheating of the tar being regulated so as to heat the tar to a tempera ture sufficient to distill part of the oil therefrom at the pressure of the vapor box, maintaining reduced pressure on the vapor box, separating the vapors from undistilled residue within the vapor box and separately collecting such vapors and cooling them to recover low boiling constituents therefrom, and introducing the residue from the vapor box into direct contact with hot coal carbonization gases to efl'ect distillation thereof.

9. An apparatus for distilling tar comprising in combination with coal carbonization or gasification apparatus, a still, means for passing coal carbonization or gasification gases from said apparatus into the still a preheater for preheating the tar, a vapor box for separating vapors from undistilled residue bf the preheated tar, means for separately condensing said vapors, and means for mingling the preheated residue from the vapor box'with hot coal carbonization or gasification gases in the still.

10. An apparatus for distilling tar comprising in combination with coal carbonization or gasification apparatus, a still, means for passing coal carbonization or gasification gases from said apparatus into the still, means for withdrawing from the still the gases and vapors resulting from the distillation, means for cooling them to condense oil therefrom, means for preheating the tar under pressure, a vapor box for separating vaipors thus producedfrom undistilled residue of the preheated tar, separate condensing means for said vapors, means for discharging the residue from the vapor box into the hot gases and vapors-leaving the still, means for then bringing the partially distilled tar into the body of the still, and means for bringing about intimate Contact of the tar or pitch in the still with the gases, and means for withdrawing the resulting pitch from the still.

11. An apparatus for distilling tar comprising in combination with coal carbonization or gasification apparatus, a still, means for passing coal carbonization or gasification gases from said apparatus into the still,v

means for withdrawing from the still the gases and vapors resu'ltingfrom the distillation, means for coolingI them to condense oil therefrom, a pipe coil heater for preheating the tar to a high temperature, a vapor box for separatingvapors from the preheated tar, separate condensing means for said`vapors,

and means for introducing the residue from the vapor box into the hot ases and vapors leaving the still, and means for then bringing the partially distilled tar into the body of the still and means for bringing it into thorough and intimate contact with the gases passin therethrough.

l2. n apparatus for distilling tar comprising in combination with coal carbonization or gasification apparatus, a still, means for passing coal carbonization or gasification i means for maintaining the vapor box and said separate condensing means under a vacuum, means for conveying residue from the vapor box to the still, and means in the still for mingling the residue from the vapor box with the hot coal carbonization or gasification gases.

13. An apparatus for distilling tar, comprising in combination with coal carbonization or gasification apparatus, a still, means for passmg coal carbonization or gasification gases from said apparatus into the still,

' means for withdrawing from the still the gases and vapors resulting from the distillation, means for cooling them to condense oil therefrom, a pipe coil preheater, a vapor box for separating the vapors from the undistilled residue of tar preheated in said preheater, separate condensing means for said vapors, means for introducing the residue from the Vapor box to the still and means for withdrawing pitch residue therefrom, and means in the still for thoroughly and repeatedly spraying the tar or pitch into the gases to effect distlllation of the tar or pitch and scrubbing of the gases.

14. An apparatus for distilling tar comprising in combination with coal carbonization or gasification apparatus, a still, means for passing coal carbonization or gasification gases from said apparatus into the still, means for withdrawlng from the still the gases and vapors resulting from the distillation, means for cooling them to condense oil therefrom, a pipe coil preheater for preheating the tar by bringing it rinto indirect contact with -hot flue gases coining from a coal distillation or coal carbonization plant, a vapor box for separating vapors from undistilled residue, separate condensing means for said vapors, and means for conveying the preheated tar to the vapor box, and means for conveying residue from the vapor box to the still.

In testimony whereof I afiix my signature.

STUART PARMELEE MILLER.

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