US1883642A - Distillation of tar - Google Patents

Description

Oct. 18, 1932. E. H. ELLMS DISTILLATION OF TAR 5 Sheets-Sheet l Filed Sept. 17 1928 INVENTOR v %//M% ATTORNEYS ww@ @8&8 n

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Oct. 18, 1932. E. H. ELLMS DISTILLATION OF TAR I5 Sheets-Sheet 2 Filed Sept. 1'?, 1928 r/ca'/ Freak/72175K ATTORNEYS 01.18,1932. l EH ELLMS 1,883,642

DISTILLATION OF TAR Filed Sept. 17, 1928 5 Sheets-Sheet 'o' ATTORNEY Patented Oct. 18, 1932 VUNITEDl STATES PATENT OFFICE EDWARD H. ELLIS, 0F ENGLEWOOD, NEW JERSEY, ASSIGNOB, TO THE BARRET!!!- COI- PANY, OF NEW YORK, N. Y., A CORPORATION 0F NEW JERSEY -nIsrrLLaTIoN oF 'TAB A Application mea september 17, 192s. seal ne. 306,330.

This invention relates to improvements in the distillation of tar by utilizing the heat available in the gases lproduced in coal-carbonization plants,and particularly tothe production of clean oil fractions of definite character fromysuch gases. The invention will be described especially with reference toits application to cok ovens. J

In the ordinary operation of by-product coke ovens the gases produced by the coking -operation pass from the individual ovens through uptake pipes and goose-necks to a collector main common to the ovens of the battery. The foul gases leave the ovens at high temperature, e. g., 600 to 700 C. or higher, and carry a considerable proportion of volatilized tars and oils as well as solid particles of coke, coal, carbon and other impurities. i rapidly by the application of sprays of ammonia liquor or ammonia liquor and tar in the goose-necksA and collector main, the heat in the gases being thereby dissipated and lost.

.The rapid cooling causes separation of tar containing the heavier oils in the collector main. Further cooling is effected in the' cross-over main and in the condensing system connected therewith and an additional -quantity of tar or tarry oil is thus separated.

The collected tars and tarry oil are shipped ordinarily from the coke-oven plant to a, tar-L distillation plant for distillation and separation of the oils andthe production of pitches of varying qualities. The expense of handling and of distilling the tar and oil adds to the cost of'production of distillation products.

. It is the object of the present invention to provide a method and apparatus'which permits the distillation of t-arat a coke-oven plant, the utilization of the heat of the cokeoven gases for that purpose, and particularly the recovery of efinite fractions of clean oils directly by such distillation, together with pitches having the various qualities and characteristics required by the trade..

According to the present invention the i heat of the coke-oven gases as they-come from the coke ovens is utilized to distill tar and to separate vaporizable oils therefrom by sprayi Ordinarily the gases are cooled ing or otherwise bringing the tar into intimate contact with the hot coke-oven gases. The desired vdistillation can be effected in various types of apparatus as, for example, in a collector main or 'in uptake-pipe stills as described in the application-'of George E. Brandon, Serial No. 154,740, filed December 14, 1926, or in any other suitable apparatus in .which intimate contact between the hot gases andthe tar can be obtained. The intimate contact between the tar and the hot coke-oven gases cools the gases and at-the same time the tar is more or less distilled. Partial condensation of the condensable constituents in the gases, more particularly those of a tarry character, results. The scrubbing ofthe gases with tar tends `to separate such tarry constituents. At the same time the gases are enriched with vapors of the more volatile constituents, i. e., oils derived from the distillation of the tar.

. The dew points of the gases for the several constituents carried therein as vapor are lower than the normal boiling points of these constituents, and by suitable regulation of the temperature of the gases during the distillation and especially during the subsequent treatment. of the gases vals hereinafter described it is possible to retain the desired oils in vapor form therein while the tarry constituents are condensed. -Thus, by sutliciently lowering the temperature of the gases during distillation in the collector main, for example, all or substantially all of the tarry constituents can be converted into the liquid phase carried by the gases is known as tar fog It is removed from the gases with diiiiculty and to a greater or less degree persists even lll in the fuel gases, i. e., the linally purilied gases. ln the process of my invention, a large portion ol this tar fog is removed by the tar which is brought intimately in contact with the hot gases.

Some oi the tar which is present in the gas stream leaving the ovens may still remain in the gas stream alter it has been subjected to intimate contact with the tar introduced jfor distillation. 'lhe quantity of tar tog lett in the gas is small and when good contact has been provided between the tar and gases in the distilling operation, it is not usually sucient to adect the quality ot the distillate oil. I

'llhe entrained tar and tar tog can, for example, be separated readily by passing the gases thru an electrical precipitator such, lor instance, as the well known Cottrell precipitator, the precipitator being operated at substantially the temperature required to maintain the desired oil constituents in the vapor phase, that is to say, at a temperature higher than the dew point ot the gas for the most readily condensable desired oil constituent therein.

The electrical precipitator, is, however, not essential to the production of clean distillate oils. A substantial proportion of the entrained tar and tar fog in the gases leaving the zone of intimate contact of the gases with ,the tar to be distilled can be removed by subfleeting the gases to a second zone of intimate.

contact with tar, this second zone of contact being characterized by the fact that the tar is warm and exposed over large surfaces to the gases. Such a condition may, for example, be realized by causingy the gases, on leaving the irst zone ot contact, to pass thru a tower tilled with suitable packing over which a current of warm tar is flowing in such quantities that the gases are not cooledbelow the dew point for the desired oil constituent. llt should be noted that the dew point, or more properly the equilibrium point, depends on the material with which the oil vapor bearing gases are in contact and that it is lower when in contact with tar than when in contact with hard pitch. A

The gases, which have been thus cleaned if desired, will, upon total condensation, yield a mixture of oil constituents. The dew points of the gases for these several constituents are, however, different and in carrying out the present invention advantage is taken of this difference by subjectingthe clean gases to cooling in successive stages by indirect heat exchange with liquids boiling at constant temperatures. This heat exchange can be e'ected in suitable condensers through which the hot gas/es are passed in heat exchange relation with the selected liquid surrounding, for example, the tubes of the condenser. By selecting a suitable liquid and by venting the space in which the liquid is maintained inesatta to a suitable condenser wherein the vapors produced are condensed and recovered, the temperature to which the clean hot gases are cooled in each such stage may be maintained constant and a :traction of the vapors conn tained in such gases which condenses at that temperature may be thus recovered. The condensed constant boiling liquid may returned to its condenser for further cooling of the hot gases.

@ne or more such condensers may be uti= lized with liquids boiling at different temperatures and the gases may be subjected thereafter to inal condensation with cooling liquid such as water at a temperature which ensures the separation of substantially all ot the remaining desired vapors from the gases. For example, when making pitch ot 4009 l?. melting point, the clean gases may escape from the electrical precipitator or the second stage tar scrubbing at a temperature I of from 2400 to 3400 C., depending upon the manner of conducting the operation.. The gases may be subjected then to cooling in a suitable condenser to a temperature of, for example, 170o to 185 C. by heat exchange with a suitable condensing agent. Such a condensing agent may be a coal tar naphtha fraction having a boiling range oi 160 to ll" C. rllherealter the gases may be further cooled to a temperature, for example, ot ll5 C. by heat exchange with another liquid such as toluol having a boiling point ot about l`l0 C. lt will be understood that the liquids selected as condensing agents will depend upon the temperatures which are to be maintained in the respective condensers and that the selection will be made inv view of the character or" the fractions to be separated from the cleaned coke-oven gases.

'lhus in the operation as described, the clean gases may be subjected to successive cooling to the indicated temperatures tor the purpose of separating first a lieavy creosote oil and thereafter a light creosote oil. Further riooling of the gases by heat exchange with a cool`= ing liquid such as water or ammonia liquor, for example, will result in separation ot`car= bolic oil. Thereafter the gases can be conducted thru the usual apparatus for the recovery of ammonia, light oils, etc.

When particularly well deined fractions are desired, a tfractionatingv section may be included in the constant boiling liquid condensers. rl`he fractionation section may be composed of plates ot the known type or ot suitable grids or packing. e tractionating section will be located at the bottom of the condenser in such a way that the condensate from the tubes will run back over the plates or packing and the hot gases entering the condenser will be first forced to pass thru the plates or packing, thereby bringing the condensate and the hot gases into heat exlll@ llll

'heat exchange with a cooling agent circulated thru the condensers for that purpose.

The cooling agent may preferably be a liquid which is` to be distilled immediately after leaving the condensers. The liquid will be preheated and this will provide' a partof the heat which would otherwise have to be supplied in the distilling equipment. A saving in heat is therefore eii'ecte'd. Thus tar maybe used as the cooling agent in the'con-- densers; the tar will thereby be preheated and may be partially dehydrated and may then be conducted into the distilling equipment. The heat required to be supplied to the distilling equipment will be less due to the fact that the tar is preheated. The capacity of the gases from a given number of ovens to distill tar is thereby increased. The heat available in such gases is thus utilized eiectively for the purpose of the invention and 1 the distillation and recovery of the desired oil roducts is accomplished economically.

he cooling of the vapors may be effected `with a cooling agent other than tar. Thus ammonia liquor may be used as the cooling agent and is thereby preheated and brought into a suitable condition for distillation vthe ammonia still. In a like manner, benzo' lized straw oil or other absorbent oil, may be used as the coolin agent and be thereby preheated and brougt into a suitable condition for distillation. If oil 4fractions are A to be v redistilled, these oil fractions may be used as the cooling agent and be thereby preheated and prepared for distillation. If the oil fractions are very low boiling, they may even be distilledv by means of the heat recovered in the condensers.

The distillation of tar by means of the hot coke-oven gases will be described more particularly with reference to the operation of a collector main although as hereinbefore indicated other apparatus may be adapted for the purpose of the invention. The amount of heat which is available in the gases from all of the ovens of the battery is many times that required to distill all of the tar and oil recovered simultaneously from the battery.

i Normally, therefore, it will not be necessary to use the gases from all of the ovens unless.

a quantity of tar is available from other sources or unless'tar from the battery has been accumulated. The invention is not limited, however, to the distillation of tar from a vsingle battery of ovens. Tar from other ovens or from other sources such as' gas retorts, vertical retorts and water-gas sets may be distilled in accordancewiththe invention. It is to be understood, therefore, that provision can be made for utilizing the heat from any desired number of ovens. Usually,- however, it is sulicient to employ the gases from only a few of the ovens and'these can be connected convenientl to a short collector main or other distillation apparatus in which ythe distillation is conducted.

With such an apparatus, the coke-oven battery and by-product recovery system will not require substantial modification, that is to say, the ovens of the battery may be connected to the usual collector main and a crossover main may convey the gases from the c ollector main to the condensing system in which tar and oils are normally separated from the gases. For the purpose of distilling tar a selected number of ovens may be connected,

for example, by separate uptake Apipes to af short collector main which may be disposed conveniently at the rear of the ovens, suitable valves being provided to permit diversion of the gases from the ovens into the ordinary collector main or into the short collector main so that distillation can be conducted inv the latter when desired.

The gases in the ordinary collector main maybe subjected to cooling in the usual manner with sprays of ammonia liquor or am monia liquor and tar and the tarry constituents thus separated may be withdrawn for distillation. The gases may be conveyed then to the usual condensers and further cooled the'rein to separate tarry oil constituents. The tarry ois thus recovered are 'usually contaminated to a greater or less extent with tar constituents and these tarry oils may be subjected to x distillation with the tar re covered from the battery in accordance with the present invention or otherwise treated to separate the constituents thereof.

The tar or tar and 'tarry oil to be distilled may be sprayed into the short collector main thru spray nozzles provided for that purpose and repeatedly recirculated thru spray nozzles, thus ensuring` the ldesired intimate contact of the gases with the tar and/or pitch therein. vAs a substitute for or adjunct to the spray nozzles agitating devices may be provided in the collector main to thoroughly agitate the tar therein and to throw particles thereof into the gas stream to facilitate the desired intimate contact between the tar and.

tend to form therein will be dissolved immediately and absorbed in the stream of pitch in the bottom of the main. Pitch is drawn ed at one end of the main and tar is added at the other end and at intermediate points if desired at the rate required to maintain the pitch at the desired melting point or the gases leaving they main at the desired temperature. The pitch produced may be withdrawn and utilized as such. By regulation of the temperature of the gases and consequently the extent to which distillation is eect-ed in the distillation apparatus, pitches having the desired qualities and various products having di'erent qualities and characteristics may be made available for commercial use.

rlhe gases escaping from the short collector main or other distillation apparatus at the temperature requisitefor the recovery of desired oils therefrom following the cleaning of the gases may, if desired, be delivered at' such temperature to an electrical precipitator which is disposed preferably closely adjacent to the collector main in order that the temperature of the gases may not be reduced unduly before electrical precipitation of the tar constituents is accomplished. rllhe electrical precipitator employed in the treatment of the gases may be of the type commonly known as the Cottrell Iprecipitator and should be constructed so as to be capable of withstanding the high temperature to which it is l subjected in the operation as described. The

electrical precipitatorhmay be insulated advantageously to prevent loss of heat from the gases. i

The operation of an electrical precipitator as commonly used consists in passing the gas to be treated between electrodes whose dierence in electrical potential is very great. Experience has shown that it is best to use a rectified alternating current. The alternating current (the primary) is sent thru a stepup transformer to produce a high potential current (the secondary) which is then rectiied to an intermittent uni-directional current, for example, by means of a rotary converter. The rectified current is delivered from the converter to the electrical precipitator at practically the potential at which 1t leaves the transformer.

'llhe electrical precipitator consists commonly of a group of vertical pipes with a wire or rod in the centre of each, the pipes being connected to proper headers for the introduction and discharge of the gases, rlhe pipes generally constitute the positive electrodes and the wires or rods the negative electrodes. The size of the pipes may vary, but in general pipes of less than six inches in diameter are notI used. Electrical precipitators with pipes six inches in diameter using `secondary voltages rfrom 35,000 to 50,000

volts are satisfactory'tor the purposes of this invention. lt is generally best to operate with maximum pptential diderence (secondinesatta ary current) between the electrodes, this maximum being just below the break-down voltage at which arcing occurs.

rlhe eiiiciency of vthe cleaning is dependent upon several variables. Satisfactory cleaning of the gas may be accomplished if the time of treatment is of the order of one second, although this time may be varied Widely depending upon the character of the oil to be recovered from the gases passing through the precipitator. ln working with tubes' -nine feet long and six inches in diameter, if'or example, an oil substantially free from all tarry constituents has been obtained with a time of treatment of from one and one-half to two seconds, that is to say, with a gas ve-v locity of from 6 to 4.5 feet per second. This has given an eiiiciency ot cleaning of approximately ninety-nine per cent. lt it is desired to collect oils containing small amounts of tar shorter treatment may be used, for example, a treatment of from 0.5 to one second, that is to say, with a velocity of :from 18 to 9 feet per second.

From the electrical precipitator the gases carrying the condensable vapors can be con` ducted directly to the constant temperature condenser or through a series of such condensers. rlhe condenser or condensers may comprise suitable casings` enclosing tubes through which the hot gases pass upwardly in heat exchange relation with a surrounding body of the cooling media which as hereinbefore indicated may be selected in view of its boiling point to maintain a constantl temperature in the condenser as the result of boiling of the condensing medium at substantially atmospheric pressure. The vapor lproduced by such boiling may be conducted to another condenser which is vented to the atmosphere and cooled therein to separate the cooling media which may be returned by gravity to the constant temperature condenser. rlhe tar to be distilled may be uti- A lized to cool the vapor and may be heated thus before it enters the short collector main,

for example, for distillation therein. If two constant temperature condensers are employed the gases from the first condenser are conducted through the second condenserin heat exchange relation with another liquid boiling preferably at a lower temperature to condense another fraction of the vapors carried by the clean gases. The cooling media will be vaporized and the vapor may be 'condensed to recover the cooling media by heat exchange with tar, tor example. |The clean gases still carrying some condensable constituents may be conducted then through a third condenser wherein they are subjected, for example, to direct or indirect cooling by water or ammonia liquor whereby additional constituents are condensed and recovered. The gases can be mingled then if desired with those from the remaining ovens of the battery after such gases have been subjected to coolingand condensation.

for'other purposes, the tar which is being distilled in the short collector main may be v conducted directlg'eto the main without preheating or may preheated in a separate reheater. The liquid which is being' preheated in the vapor condensers will be conducted thru these condensers countercurrent to the order in which the condensers are arran with respect to the hotv gas flow, so that t e entering liquid'irst cools the va rs om the lowest boiling condenser, an on' leaving .the series /of condensers, the preheated liquid will be conducted directly to the equipment where its. distillation is to be carried out.

The invention is of more or less general application to the distillation of tar to ro duce pitches and to recover clean oil actions. It will be further described with reference to the preheating of tar and the cleaning of the gases in an electrical precipitator, as an example, by the following more detailed description taken with the accompanying drawings whichv show apparatus embodying the invention and adapted for the practice of the process but it is intended and will be understood that the invention is not limited to the apparatus as illustrated in the drawings, in which Fig. 1 is a plan view of a portion of a coke oven plant illustrating the application of the invention thereto;

Fig.. 2 is an enlarged sectional view of the short collector main and the electrical precipitator connected thereto; and

Fig. 3 is an enlarged sectional view of the constant temperature condensers.

Referring to the drawings, 5 indicates the batteryof coke-ovens infwhlch the individual ovens are connected by uptake pipes and goose-necks 6 to a collector main 7 having a centre box 8 from which the cross-over main 9 conveys the gases and vapors to condensers 10 and 11. The gases may be cooled in the collector main and in the goosenecks leading thereto by ammonia liquor or ammonia liquor and tar introduced through spray noz- `zles 12 which are supplied through a pipe 13 from a source of ammonia liquor and/or tar such as a storage tank 14. Further cooling is eected in the condensers 10 and 11 and the Ygases are delivered thence to an exhauster 15 and to the usual equipment (not shown) for the separation -of light oils and ammonia from the gases. The tar which separated in the collector main 7 may be withdrawn from the centre box 8 and delivered together with the tar separated in the cross-over main to a j decanter 16 wherein the tar is separated from the ammonia liquor, the latter being delivered tothe tank 14. The tar may be delivered to a tank 17 wherein it is stored for distillation in accordance with the present invention'. The tarry oils separated in the condensers 10 and 11 may be withdrawn through a pipe 1.8

to a decanter 19 wherein ammonia liquor 1s separated `from the oilmfThe tarry oil may be stored then in a tank 20 and can be mingled I with the tar to be distilled in desired proporl tions or treated otherwise for the recovery of constituents thereof. f

A short collector main 21 may be provided, for example, at the rear of the ovens and may be connected to the desired number of ovens by uptake pipes and goose-necks 22 whereby the hot gases are delivered to the short collector main for utilizationptherein in the distillation of tar. The tar'to be distilled may be delivered through a pipe 23 from the tank 17 to spray `nozzles 24 in the short col- -lector main 2 1 and goose-necks 22, being therein mingled-intimately with the hot ases for the purposeof effecting the desir distillation. To facilitate the operation of the short collector main tar or oil or both may be delivered thereto through a ipe 27 so as to ilow through the main and ush `the bottom thereof.. `The pitch produced by the distillation maybe withdrawn through a pipel 28 for utilization as such or all 3or any portion thereof may be recirculated through the pump 29 vand pipe 30.

The gases and vapors rulting from the distillation are withdrawn through a pipe 3-1 and are delivered to an electrical precipitator which ma consist of a shell 33 enclosing a number o tubes 34 ywhich are supported in heads 35 and 36 within the shell. An inlet 37 near the bottom of the shell communicates with a chamber 38 which is partially separated from the tube section by a baille 39. An outlet 40 permits the escape of gases from the separator after the latter have passed through the tubes.

A plurality of electrodes 41, preferably in the form of metal rods weighted at 42, extend through the tubes and are supported from a bus-bar 43 located near the upper ends of the tubes. The bus-bar 43 extends at both ends into casings 44 which enclose insulators 45 ative. The form and arrangement of the. conductors in the circuit can'be varied. y The t arrangement should be such as to supply'high form, enter the electrical precipitator and -pa-ss through the tubes in the precipitator,

being subjected therein to the electrical discharge which through ionization of the solid and liquid particles causes them to separate from the gases and condensable vapors. The separated liquids, together with the solid particles, run down the inner walls of the tubes into the chamber at the bottom of theV precipitator and can be withdrawn through a pipe 46, or returned to the short collector The gases carrying the condensable vapors escape through the outlet 40 and may be delivered thereby to a condenser 48 comprising `a shell with tubes 49 therein thru which the gases pass in heat exchange relation with a body of liquid disposed within the shell. The liquid boils at a constant temperature and the vapor escapes thru a pipe 50 to a condenser 51 which may likewise consist of a shell enclosing tubes 52 thru which the vapors pass. The tubes 52 may be surrounded with a suitable cooling medium such as tar supplied thereto thru a pipe 53. rlhe vapors of the cooling liquid are condensed and returned to the condenser 48 through pipe 50. As

shown in the drawings, the tar used in the condenser 51, supplied thru the line 53, may be tar which has been partially preheated,

vas described below. As shown, the tar escapes from the condenser 51 thru a pipe '54 which connects with thepipe 23 leading to the short collector main. The tubes 52 communicate with the atmosphere thru an outlet 55 so that the boiling liquid in the condenser 48 is maintained at substantially atmosphericpressure so that the condenser opera-tes at a uniform temperature. rIhe liquid which condenses in the condenser 48 is withl. drawn thru a pipe 56 to a storage receptacle `57 for the condensate.

The cleaned gases may pass from the condenser 48 thru a pipe 58 to a second condenser 59 comprlsing a shell and a plurality of tubes 60 thru which the gases pass in heat exchange relation withy a surrounding body of liquid boiling at a constant and lower temperature. The vapors thus roduced escape through a pipe 61 to a con enser 62 likewise compris` ing a shell and a plurality of tubes 63 through which the vapors pass in heat exchange relation with a cooling liquid such as tar supplied through a pipe 64 and escaping through a pipe 53. The vapors of the cooling liquid are condensed and returned to the condenser a 65i 48 through pipe 61. r1`he tubes 63 of the conieaeaa denser communicate with the atmosphere through an outlet 66 thus maintaining the pressure in the condenser 59 at substantially atmospheric pressure. The liquid ,condensed in the condenser 59 escapes through a pipe 67 to a decanter 68 wherein the oil is separated from any water or ammonia liquor" which may be present. rlhe oil is withdrawn through a pipe 69 to a receptacle 70 therefor.

The gases escaping from the condenser 59 pass through a pipe 71 to a condenser 72 which may -be of the direct or indirect type wherein the gases are subjected to va cooling medium such as water or ammonia liquor from the decanters 68 and 75. The condensate escapes through a pipe 74 to a decanter 75 wherein the oil is separated from the ammonia liquor or water. The oil is delivered through a pipe 76 to a receptacle 77 therefor. The water or ammonia liquor from the decanters 68 and 75 may be delivered through pipes 7 6 and 77 to a pump 78 and returned thereby through a heat exchanger 79 to the condenser 72 for further use therein. rl`he make of water or ammonia liquor must of course be withdrawn from the system, for example, thru outlet pipe 73.

The gases from which the major portion of the condensable constituents have now been removed. are withdrawn through a pipe 80 and are delivered to the exhauster 1 5 which maintains the pressure balance in the system and there mingled with the gases from the remaining ovens of the battery. rllhe gases may be conducted thence through any suitable equipment for the recovery of light oils, ammonia, etc.

The tar used in the condensers may be tar from 17 or tarry oil from 20, or tar or other material may be supplied from any outside source 81. The same cooling medium may be used in both of the condensers 51 andy 62 and passed therethru in succession, as shown in the drawings, or a different material may be supplied to each condenser. Where tar is employed as the cooling medium, it may advantageously be run' to the short collector main to be distilled therein. The cooling medium need not be run to the short collector main, as shown in the drawings, but may be put to any desired use.

The apparatus as described permits the distillation of tar and the utilization for this purpose of a portion of the heat in the cokeoven gases. It likewise permits the recovery of thel oil constituents of the gases inseparate fractions having more or less defi-l nite character1stics. These fractions may be utilized for any of the purposes to which they are adapted without further treatment or they may be subjected to any desired treatment designed to modify their characteristics and qualities. The invention also permits the production of Ipitch 4from the tar recovered from the battery and the character of theV pitch can be varied by modifying the distillation to which the tar is subjected. While such ratus employed therefor without departing from the invention or sacrificing any of the advantages thereof.

I claim 1. The process for obtaining clean oil from tar'wliich comprises distilling the tar by direct contact with hot coal distillation gases,

' removing entrained impurities from Athe gases at a temperature above the dew point of condensable oil constituents contained in the gases, cooling the resulting cleaned -hot gases and vapors by indirect heat interchange with a bod'yof liquid cooling medium having a relatively constant boiling point with- -in the range of from about 110o C. to about 1,850.0., whereby the cooling medium is kept boiling 'and the gases and vapors are cooled below the dew point of thewcondensable oil constituents, and separately collecting thev clean oil thus condensed.

2. The method of distilling tar and recovering distillate therefrom, which comprises distilling coal tar by direct contact with hot coal distillation gases and removing entrained impurities from the gases and then cooling the resulting clean hot ga-ses and vapors by indirect heat interchange with a body of toluol some of which is in the liquid phase and some of which is in the gaseous phase in equilibrium therewith, whereby the toluol is kept boiling and the gases and vapors are cooled below the dew point of condensable oil constituents.

3. The method of distilling tar and recovg ering distillate therefrom by heat interchange witli a body of cooling medium with a boiling point of approximately 11()o C. some of which is in the liquid phase and some of which is in the gaseous phase in equilibrium therewith, which comprises distilling coal tar by direct contact with hot coal distillation gases and removing entrained viinpurities from the gases, then cooling the resulting clean hot gases and vapors by indirect heat interchange with the cooling medium whereby the cooling medium is kept boiling. and the gases and vapors are cooled below the dew point of condensable oil constituents,

and then cooling the remaining. gases and vapors to separate carbolic oil therefrom.

4. The method of distillingtar and lrecovering distillate, which comprises distilll ing coal tar in a current of inert gases, bringinterchange with a body of coal tar naphtha having a boiling range of 1GO-175Q C, whereby the naphtha is kept boiling and the gases are cooled to 170-185 C. and heavy creosote oil is separated from the gases and then cooling the resulting gases and vapors by indirect heat interchange with a body of toluol whereby thetoluol is kept boiling and the gases are cooled to kabout 115o C. and light creosote oil is separated from the gases.

5. The method of cooling a mixture of gases and vapors resulting from the inert gas distillation of tar to condense oils while leaving carbolic oil in vapor form in the gases, which comprises bringing the hot gases and vapors into indirect heat interchange relation with a liquid having substantially the same boiling point as toluol thereby keeping the liquid boiling and condensing oils from admixture with the gases.

In testimony whereof I affix my signature.

EDWARD H. ELLMS.

ing the resulting gases and vapors 'into heat

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