US2005077A - Coal tar oil and pitch - Google Patents

Description

June 18, 1935 -J. v. E. nlcKsoN Q 0 COAL 'TAR 011, AND PITCH Filed June 12, 1931 2 Sheets-Sheet 1 INVE'NTOR 727/90 1/. E, D/c/fson ATTORNE Patented June 18, 1935 uru'rso STATES 10 Claims. (o1. mam) This invention relates to new tar oils and pitches, and moreparticularly, to the coal tar oils and pitches produced by the practice of the process disclosed and claimed in my copendi'ng application Serial No. 618,772, filed February 13,

' age of oil has beenremoved as distillate.

" pitch has been formed.

- 1923, issued as Patent No. 1,821,144. This application is directed to-and claims the new tar oils and pitches disclosed in the aforementioned cpendingapplication,-Serial No; 618,772 and bears a-continuation in part relationship to this 00-.

pending case;

Aspointedout in-application Serial No.618,772, it has been found that if coal'tars are distilled 'in such'a way that they are exposed to unusually high temperatures during distillation, or are heated at the usual distillation temperatures for unusually long periods of time, the total oil recoverable as distillate from them is less than usual, and also the residual 'pitch is of higher melting point than usual, after a givenpercent- This may-be'attributed to decomposition of oilsand heavy-constituents, including constituents which are-normally of a greasy or resin-like character, presentin coal tar with consequent formation of increased carbon content, higher melting point pitches, and decreased oil yields.

The oils removed as distillate are almost always of higher commercial value than the residual pitches, and it is therefore desirable to carry out 'thedistillation in such a way that eitherpthe maximum total-yieldof oil will be attained, or the highest possible percentage of oil will'be removed before any given commercial grade of The-use of tube stills, such for exampleas is disclosed on pages 485, 486, et seq. of the fifth edition, Part Iof Coal Tar and Ammonia by Geo. Lunge, Ph, D., published by The-D. Van Nostrand- Company, 1916,-wherein the tar is heated as-it passes continuously through a, series of tubes, and is finally dischargedinto a chamber where the oil vaporsand pitch "residue separate, has been found to increase the total removable distillate and also to give a pitch residue of lower melting point on the removal of a given'percentage-of distillate, as compared with the use'of the ordinary discontinuous method of distillation, where a charge of tar is heated to boiling and the'various oils pass over successively, in vapor form'to a condenser. Since approximately the same temperatures are attained in both processes, it is supposed that the difference in oil yields is'due principally-to the difierence inthe time during which the tar is heated, which is commonly about'ten hours in the discontinuous method of-l'ess than one hour in-th'etube still.

Lowering the distillation temperaturespin the discontinuous method, by (a) carrying on'fthe distillation under greatly'recluced pressure (50 mm. of .--mercury, absolute pressure, or less) "or (b) the rapid passage-through the-tar ofa gas having no chemical action on it, has been found to produce results practically the same as those attained in the 'tube still. 1 1

Accordingly, it-might well have been supposed that in any one of the-threeabove methods(tube still,reduced-pressure, or passage of gas) approximately the optimum conditions had been reached, with regard to the total oil yield attainable or the oil yield attainabl ein the'manufac- -ture of any given {pitch from a high temperature tar such as 'coke oven, or horizontal or vertical retort tars.

However, I'have discovered that, in a-tube-still, (a) bya sufficiently great further reduction of the time'during'which the tar isheated, greatly increasedyields of distillate oil 'can be;obtained,-in the production of 'a given commercial 'gradeof pitch; and (b) if,in'addition t0 thus shortening the time, advantage be-taken' of the known boiling-point-lowering efiect of reduced'pressureiby artificially reducing the pressure in the separat ing chamber), a total yield of distillate can; be

obtained which is 'farin excessof that produced by any previously used means known to me.

For instancaa coke-oven tar-of atype which usually gives a maximum-oil yield of about'4 5% by weight in the commercial simple discontinuous method and about65% byxweight inthe other improved methods mentioned above, has iii-the new method yielded as much as 80% by weight; and in making most commercial grades oi'pitch,

as judged by their melting points, the difference in oil yield between the new method 'andth'e other improvedmethods amounts to the equivalent of "35-15% of thetar-used.

These results are accomplished byheating the tar asit passes through one or more tubular paths or zones, anddischarging it at substantially its maximum temperature into a chamber or 'zone of relatively large volume and correspondingly I low pressure compared 'with' said-heating zone;

where the oil vapors separate from the residual pitch, the vapors passing on into acondensing system and the pitch flowing out. continuously ,at

the bottom of the separatingchamber. Itisimportant; however, that the time 'occupiedby, the tar, in traversing the heated tubes sh'ould be very short. Since it wouldbe very difiicult to measui'e or to calculate the actual mean time t aken*by;a particle of tar to traverse such "an apparatus {because of the, expansion due to rise of "temperature, and'thevaporizationoi oil taking place eontinuously during a considerable part of the travel), an indirect way of defininggthis-length of time relatively must be used; and this 'willjconsist in definingr 'th'e ratio of-fthe cubic: contents of the tubing traversed to the volume-{of theytar passing through it in unit'time.

If the unit of volume be the cubic foot, and

the unit of time be the minute, this ratio will indicate the mean time which would be occupied by a particle of tar in passing. through such apiece of apparatus.

This ratiofor commercial tube stills is commonly about 60, but in the present invention it is not more than 10, and may be much less, or in other words, thetar is passed through the heating tube or zone in amounts not less than one-tenthbf the cubical capacity of said heating tube or zone per'minute.

In order to reduce the ratioto such low values, particular attention must be. paid to the manner of supplying heat. A low value of this ratio means that a comparatively large'quantity of tar is being heated per minute in an apparatus of comparatively small volume capacity; and this necessitates an intense and concentrated appli- '-cation :ofheat. I This invention is .not limited to any particular method or means of supplying heat to thetubing through which the tar flows, but in the accompanying drawings is illustrated a form ofapparatus, in which the heat may be supplied ;to the tubing by means of a bath of molten metal .or-alloy throughwhich the tubing passes.

As pointed out above, the process of this invention minimizes decomposition of the tar undergoing. distillation, and for a given melting point pitch, results in agreater oil yieldthan was heretofore obtainable in the distillation of like tar to produce a pitch of like melting point. Hence, both the oil and pitch of this invention difler from and represent novel and useful products as compared with oils and pitches resulting from distillation of coal tar in accordance with prior existing processes. The oils difier from heretofore known oils in that they contain constituents,

, such as the greasy, resinous, and other heavy constituents, previously'decomposed during the distillation of the tar. These heavy constituents blend. with the lighter components forming a homogeneous liquid. The oils are suitable for use as creosote oil and for other uses to which ordinary coal tar distillates may be put.

The coal tar pitch, on theother hand, contains a greater proportion of coal tar constituents, as such, and less products of decomposition than a pitch produced by prior known methods since, as pointed out above, decomposition of the tar is minimized in accordance with this invention.

The. losses due to decomposition of tar constituents, and therefore the advantages of my invention, are more marked in distilling to pitches of higher: melting point; I have obtained especially good results in distilling tar by my method degrees Fahrenheit that z: is equal to not less than inwhich 0: equals the oil yield in percentage by volume and y equals the melting point of the pitch, expressed in degrees Fahrenheit. Preferably the coal tar oilsof this invention are oils obtained by distilling tar while minimizing decomposition of the tar to. result in a percentage oil yield by volumefalling in the neighborhood of or within the limits defined by the equationsand I x=,90 100 represents the average minimum percentage oil yield by volume for correspondingmelting point pitches expressed in degrees Fahrenheit obtainable by the practice of this invention, The other equationrepresents the average maximum percentage oil yields by volume for corresponding melting point pitches expressed in degrees Fahrenheit obtainable by the practice of this invention. .As more fully pointed out hereinafter, the equations proviile definitions of applicants novel pitches and 01 s. a

In the accompanying drawings, Fig. ldepicts diagrammatically, an arrangement of apparatusfor practicing the process in question and Fig. 2 is a graph illustrating mathematically the rela-.

tion of the meltin point of the pitch to oil'yield of the new pitches and new oils obtained by the distillation of tar in accordance with this-invention. yields by volume based on the tar distilled and the ordinates represent pitch melting pointsin degrees Fahrenheit (air bath method).

In Fig. 1, reference character I designates a tank for a supply of tar which may be pumped by means of the pump 2 through the tube 3 which is immersed in a bath of molten metal or hot liquid metal, such as mercury, lead, or other metal of low melting point, in the tank]. The metal in this tank may be kept in the molten state by heating the same in any convenient way as, for example, by fiames impinging upon the bottom of the tank 4,-or by passinghot products of combustion through pipespassing through tank 4. A pipe. ileadsfrom the coil 3 to a sep- The abscissa: represent percentage oil -;.;arator 6. Ion pitch and vapor which is provided withapbafiie plate I. ,The pitch settlesdn the.

, bottom of the separator 6 and passes through the pipe 8 into the pitch receiver 9 from which it, may bewithdrawn through the valve 10. The

vvaporizedconstituents pass from the separator 6 ,through the pipe H into .the coill21in the .con- ,;denser l3 where they are condensed and passed 1. ltoitheuoil receiver M from whence the oil may from the .molten metal while it is in transitv be removed. through thevalve l5. The receiver ducingmeans l8.

Asuthe tar is fedinto the coil 3, it passes upwardly and is. heated by the heat transmitted through the .coil 3.' Theamount of heat supplied will be sufficient tocause the desired amount of distillationto take place. 1 The rate at. which tained asindicated-above so as toproduce an in- ,the;tar is passed through'coil 3- willbe maincreased yield of oil or distillation in proportion to the amount of;pitch or residue thatis left.

and 39.5% free carbon.

' In both of'the above examples, a coke oven tar The following are two examples 'outof. many process has actually been carried out.

(1) A yield of distillate of 58% by weight, corresponding to 62% by-volume, with a pitch residue having a melting point of 237 F. has been produced at atmospheric pressure in the separating chamber, with a discharging temperature of about 810 F., and a rate of tar flow of about of the cubic capacity of the heating tube, per minute. The pitch residue consisted of 42% by, weight of the coal tar distilled.

(2) A yield of distillate of by weight, corresponding to 78.7% by volume, of pitch residue having a melting point of 352 F. and produced with a discharging temperature of 740 F., and a rate of tar fiow ofabout 38% of the cubical capacity of the heating tube per minute, the separating chamber beingmaintained at an absolute pressure of 55 mm. of mercury. The resultant oil has a specific gravity of 1.125. The residual pitch constituted 25% by weight of the tar distilled, containing 45.1% volatile combustible material was used, which by ordinary distillation gives about 35% by weight of distillate in producing a pitch having a melting point of 237 F., and in an marily obtained from such a tarby these methods are about 40% by the former and 58% by the latter in making a pitch of melting point about The curves of Fig. 2 represent the relationship between the percentage yield of oil and the melting point of the pitch obtained by the practice of this invention. The oil yields and the pitches, of course, vary somewhat, depending upon the particular tar distilled and the differences in conditions under which the distillation operations are conducted. The left hand curve, viewing Fig. 2, corresponds tothe lower range of yields by volume of oil obtained by the distillation of tar in accordance with this process to produce pitches vl of melting-points in'degrees Fahrenheit indicated on the curve. a; The right hand curve, viewing Fig.

'2, corresponds to the higherrange;.;ofsyieldslby volume of oil obtained by the distillation of tarrin accordance with'thisinvention .to producezpitches of melting points in degrees Fahrenheit:indicated on this, curve.

The left'hand curve was; obtained=bylplotting average minimum percentage oil yields by volume obtained as a result ofthe distillation of tar in accordance with thisainvention as abscissae against the corresponding pitch melting points as ordi-m o nates. The right-hand curve, viewing the; figure, was obtained by plotting the average maximum percentage oil yields by. volume obtained as a result of the distillation of tar in accordance with this invention as abscissa: against the correspond-es15 ing average pitch melting-points as ordinates. Any point in the area between thetwoacurves represents the percentage oil yields by. volume and the corresponding melting point of the pitch in degrees Fahrenheit which mayresultbythe prac- 4-20 tics of this invention.

v e 2 l l 1:25 is; the mathematical equation corresponding. to the left hand curve and is the mathematical equation corresponding. to

the right hand curve. "Points: in the'neighborhood ofor within the area-defined by theaequations .represent the percentage oil yields which may be' obtainable, by the distillation of tar in accordance with this invention, forthe production of certain melting point pitches expressedin degrees Fahrenheit. Conversely, for a definitemelting point pitch, expressedin degrees Fahrenheit, theequations indicate the percentage oiljryieldsobtainable by distilling coal tar in accordance with this invention. It will be noted, therefore, that :the

equations provide adefinition of applicants novel distillate 1 oil and pitches, indicating, :thewin- 45 creased percentage oilv yields obtainable in :the

production of a given melting point pitch.

The products of the-present invention include a, wide range of pitches and oils and pitches'of various boiling pointsas well as OilS'Of various-- characteristics. Both the oils and -pitches:are substantially free from the tar decomposition products, particularly those ordinarily-produced by longcontinued distillation or by exposing tar to unusually high temperatures during distillation and contain constituentsof coal tar decomposed by the usual processes of distillation. It ,will be understood that heavy tars or lighter tars or tarry oils can be distilled to produce the products. of this invention. In the case of high temperature tar, such, for example, as coke oven;tar, the-tar distilled may be the total tar produced inv the coke oven plant or it may be the heavy tar sep.- arated in the collector main or the light tar or tarry oils separated in the condensers. The od yield will not be the same in distilling a light tar as in distilling a total tar since there is more oil present in the former product. In other words, a light tar may be regarded as a total tar plus distillate oil. and the oil yield will correspond to that from a total tar plusthis additional amount of oil.

I claim: I

1. Coal tar oils comprisingydistillate obtained by the distillation "of" high" temperaturetar r0 pitch while minimizing decomposition ofpitch' and conducting the distillation to obtain a percentage oil yield by volume, which bears the relationship to the-average melting point of the resultant pitch, in degrees Fahrenheit, such that IE is equal to not less than approximately andnot more than approximately in which at equals the oil yield in percent by volume and y equals the melting point of the pitch,

expressed in degrees Fahrenheit and the oil yield is not more than 80 percent by weight of the tar distilled. 1

3. Coal tar oils comprising distillate obtained minute and heat being supplied to the tar while passing through said zone at a rate sufficient to elevate it to distillation temperature prior to its discharge therefrom, wherebythe time period towhich the tar is subjected to heat in its passage through the zone is diminished, thereby lowering the extent of thermal decomposition of the 'tar and increasing the oil yield and recovering separately the volatile oil content of the tar liberated in-the vaporization chamber and the resultant'pitch, the percentage oil yield by volume so recovered bearing the relationship to the melting point of the resultant pitch, expressed in degrees Fahrenheit, falling in the neighborhood of or within the limits represented by the equations in which :1: equals the oil yield in percent by volume and y equals the melting point of the I pitch expressed in degrees Fahrenheit.

4. Coal taroils comprising distillate obtained by the distillation ofhigh temperature tar to pitch by heating the coal tar to distillation temperature while confined in and flowing through a heated tube and vaporization of the volatile oils is thereafter effected by discharging the heat-- ed tar through a chamber maintained at a pressure less than atmospheric, the tar being passed through the heated tube at an increased rate of flow amounting to not less than one-third of the cubical capacity of the tube per minute erated in the vaporization chamber and the re-- sultant pitch, the percentage oil yield by volume so recovered bearing the relationship-to the melting point of the resultant pitch, expressed in degrees Fahrenheit, falling in'the neighborhood of or within the limits represented by the equations in which :1: equals the oil yield in percent by volume and y equals the. melting point of the pitch expressed in degrees Fahrenheit.

v5. Coal tar oils comp rising distillate obtained by the distillation of high temperature tar to pitch byheating the tar to distillation temperature while confined in and flowing through a heated zone and vaporization of the volatile oils is thereafter effected by discharging the heated tar into a chamber of low pressure relative to that of said heated zone, the tar being passed through the heated zone at an increased rate of flow amounting to not less than one-tenth of the cubical capacity of the zone per minute and the heat being supplied to the tar while passing through the zone at a rate sufilcient to elevate it to distillation temperature prior to its .discharge therefrom, whereby the time period to which the tar is subjected to heat in its passage through the zone is diminished, thereby lowering the extent of thermal decomposition of the tar and increasing the oil yield andyrecovering separately the volatile oil content of the tar liberated in the vaporization chamber and the resultant pitch, the percentage oil yield by volumeso recovered bearing such relationship to the melting point of the resultant pitch, expressed in degrees Fahrenheit, that a: is equal to not-less than v x in which a: is equal to the oil yield in percentage by volume and-y is equal to the melting point of the pitch in degrees Fahrenheit and the oil yield so recovered is not more-than 80 per cent by weight of the tar distilled.

6. Coal tar oils comprising distillate obtained by the distillation of high temperature tar to pitch by heating the term distlllationtemperature while confined in and flowing through a heated tube and vaporization of the volatile oils is thereafter effected by discharging the heated tar into a chamber maintained at a pressure less than atmospheric, the tar being passed through the heated tube at an increased rate of flow amounting to not less than one-third of the cubical capacity of the tube per minute and the heat being supplied to the tar. while passing through the tube at a rate sufiicient to elevate it to distillation temperature prior to its discharge therefrom, whereby the time period to which the tar is subjected to heat in its passage through the tube is diminished, thereby lowering the extent of thermal decomposition of the tar and increasing the oil yield and recovering separately the volatile oil content of the tar liberated in the vaporization chamber and the resultant pitch, the percentage oil yield by volume so recovered bearing such relationship to the melting point of the resultant pitch, expressed in degrees Fahrenheit, that m is equal to not less than v in which a: is equal to the oil yield in percentage by volume and y is equal to the melting point of the pitch in degrees Fahrenheit and the oil yield so recovered is not more than per cent by weight of the tar distilled.

'7. Coal tar pitch obtained as a residue of the distillation of high temperature coal tar resulting in the production of a percentage oil yield by volume which bears such relationship to the melting point of the resultant pitch, expressed in degrees Fahrenheit, that a: is equal to not less than I in which a: equals the oil yield in percentage by volume and y equals the melting point of the pitch in degrees Fahrenheit and the oil yield is not more than 80 per cent by weight of the tar distilled.

8. Coal tar pitch obtained as a residue of the distillation of high temperature coal tar while minimizing decomposition of the tar undergoing distillation and conducting the distillation to obtain a percentage oil yield by volume which bears the relationship to the melting point of the resultant pitch, expressed in degrees Fahrenheit, falling in the neighborhood of or within the limits represented by the equations in which as equals the oil yield in percentage by volume and y equals the melting point of the pitch in degrees Fahrenheit.

9. Coal tar pitch obtained as a residue of the distillation of high temperature coal tar wherein v the tar is heated to distillation temperature while confined in and flowing through a heated zone and vaporization of the volatile oils is thereafter effected by discharging the. heated tar into a chamber of low pressure relative to that of said heated zone, the tar being passed through the heated zone at an increased rate of flow amount,- ing to not less than one-tenth of the cubical capacity of the zone per minute and the heat being supplied to the tar while passing through the zone at a rate suflicient to elevate it to distillation temperature prior to its discharge therefrom,

in which w is equal to the oil yield in percentage by volume and y is equal to the melting point of the pitch in degrees Fahrenheit and the oil yield so recovered is not more than 80% by weight of the tar distilled.

10. Goal tar pitch obtained as a residue of the I distillation of high temperature coal tar wherein the tar is heated to distillation temperature while confined in and flowing through a heated tube and vaporization of the volatile oils is thereafter effected by discharging the heated tar into a chamber maintained at a pressure less than atmospheric, the tar being passed through the heated tube at an increased rate of flow amounting to not less than one-third of the cubical capacity of the tube per minute and the pitch, expressed in degrees Fahrenheit, that a:

is equalto not less than in which a: is equal to the oil yield in percentage by volume and y is equal to the melting point of the pitch in degrees Fahrenheit/and the oil yields so recovered is not more than 80% by weight of i

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