US1844897A - Production of low carbon pitches - Google Patents

Description

s. P. MILLER 1,844,897

PRODUCTION OF LOW CARBON PITCHES FiledDec. 29, 1927 2 Svheets-Sheerl l Feb. 9, 1932.

INVENTOR ATTORNEYS S. P. MILLER PRODUCTION OF LOW CARBON PITCHES Filed Dec. 29, '1927 2 Sheets-Sheet 2 BY UW M, Wam-4. v film,

Feb. 9, 1932.

Ill/I Sett Zz'n g' Ton/er Patented Feb. 9, 1932 s UNITED STATES PATENT OFFICE STUART IPARHELEE MILLER, 0F ENGLEWOOD, NEW JERSEY, ASSIGNOR T0 THE BARRETT COMPANY, 0F NEW YORK, N. Y?, A CORPORATION OF NEW JERSEY PRODUTIQN 0I' LOW CARBON PITCHEB I Application led December 89, 1987. Serial No. 248,805.

monia liquor or ammonia liquor and tar in the goose-necks and collector main. The rapid cooling causes the separation of part of the tar in the collector main. Further cooling is effected in the cross-over main which connects the collector main to the condensing system and in condensing systems and an additional quantity of taris thus separated. The collected tar is ordinarily mixed and shipped from the coke oven plant to a tar distillation plant for distillation for the separation, o f 4 the oils and production of pitches.

.The pitches produced by distillation of lcoke oven tax'. in ordinary tar stills contain too great a proportion of free carbon to make them available for certain uses for which pitches having a low free carbon content are required. For uses such as the saturation of fibre conduits for telephone cableswhich re` quire a pitch having a low free carbon content, it is customary to emplov tar from sources other than coke oven plants. The quantity of material of satisfactory quality available for such uses is, however, relatively limited. y

It is an object of the present invention to provide a method whereby pitches having va low free carbon content, making them suitable for various purposes for which coal tar pitches are not ordinarily available, may be produced directly at coke oven plants.

It is another object of the invention to pro'- -duce low carbon pitches atv other coal dis- During the operation of a cokemven or gas retort the gases discharged contain a greater or less proportion of tar constituents depending upon the stagg of the coking or gas making operation. uring the earlier part of the operation the gases discharged from the ovens or retorts contain a'relatively large proportion of tar constituents of low carbon content, and the ases, after the separation/ of the tar, are rich gases, rich in illuminants and. of high B. t. u. value. Tar separated from such gases is relativelylow in free carbon. During the latter part of the coking operation, however, the tar yield decreases and the tar recovered is relatively higher in free carbon content.

According to the present invention, the gases given olf from t e coke oven or gas retort during an early stage of the cokln or gas making operation are separately co ected and cooled to lseparate t erefrom a low carbon tar, and this tar is then subjected to distillation to produce therefrom a-low carbon pitch of regulated melting point, Adepending upon the extent to which the distillation iscarried. The resultin low carbon pitches will have new and distmctive properties, being distinguished from pitches of the same melting point produced from the total tar from the same ovens by their lower. carbon content, lower eciiic gravity and lower viscosity and di erent composition, etc. In referring to carbon or free carbon in the tar and pitch I use these terms in the customary way to include not only molecular carbon but also those materials which appear as an insoluble residue on digestion of the tar or itch with benzol or other similar solvent. t may include certain inor anic impurities as well as insoluble hydrocar ns of very high molecular weight.

In carrying out the invention, advantage is taken of the distinctive characteristics of the tar contained in the gases escaping from the ovens or retox'ts during different periods of the coking or gas making operation b providing a separate collector main whi may be connected to part or all of the ovens or retorts of the battery and by diverting the gases from the ovens or retorts during the required early period of operation into such separate collector main and cooling the gases therein and in separate coolers, to separate therefrom a -low carbon tar; and by then keeping this low carbon tar separate and subjectlng it separately to distillation for the production therefrom of a low carbon pitch. The gases iven off during the remaining period o operation of the coke ovens or gas retorts are separately collected and may be separately cooled to separate therefrom a tar of higher carbon content.

In my companion application, Serial No. 243,307 I have described and claimed a process of producing high carbon pitches by separately collecting the gases from near the end of the coking or gas making operation, cooling these gases to separate a high carbon tar therefrom and distilling the high carbon tar by means of hot coal distillation gasesto give a high carbon pitch. The process of said companion appllcation can be carried out at the same plant as the process of the present invention. By combining all of the gases from an arbitrary early period of the coking operation, and by combinin the ases from the remaining portion of t ie cokmg operation, and separately cooling these gases and separately recovering lower and higher carbon tars therefrom and subjecting these tars separately to distillation, pitches of lower and higher carbon content can be simultaneousl produced.

T e present invention relates particularly to the production of low carbon pitches by selecting a regulated portion of the gases from the early part of the coking or gas male ing operation of the individual ovens and separating a low carbon tar therefrom, and su jecting such tar to distillation, whether or not the tar collected from the remaining ases is subjected to distillation or employed for other purposes. If the remainder of the tar is subjected to distillation, the carbon content of the itch produced will depend upon the particu ar portion of the coking operation during which the gases are so collected. It is not possible, when dealing with all the gases, with such an arbitrary collection of the gases, to produce a low carbon pitch of regulated car on content and also produce simultaneously a regulated high carbon pitch other than that normal to the residual gases. Such regulated pitches can, however, lie independently and simultaneously produced by providing for the separate collection of the gases during the early,` intermediate and later stages of the coking operation and by subjecting the tar separated from such gases to distillation, as set forth in another companion application Serial No. 243,309.

On many coke ovens and in other coal distillation plants equipped with double main gas collecting systems it is possible to collect substantial quantities of several types of high and low carbon tars. For example, in a coke oven plant of the Semet Solvay type it" is customary to limit the number of ovens discharging gas to about twenty per collector main. Thus a sixty oven plant would have three double collector mains, three for rich and three for lean gas. Normally there would be two sets of condensers, one for rich and one for lean gas. The ratio of rich to lean gas may be ldifferent in each of the three sets of mains. 'lhe reater proportion of the tar in the gases wil be thrown out in the collector main and together with the accompanying ammonia liquor can be withdrawn and separated. The individual tars from the three rich and three lean as mains can thus be regulated in quality. he total rich gases from the three rich gas mains may blend and go to the coolers from which a fourth composite rich gas tar ditl'erin from the other three will be collected. Li ewise, the lean gases will blend and yield a fourth lean gas tar. While the maximum possible yield of rich gas tar of specific quality can not be obtained by this system as heavy tar from the collector mains, well over 50% of it can be. Such a method of operation has the advantage that it requires no' substantial changes in existing equipment, it being necessary only to provide separate pi es for withdrawal of the tars and liquors rom the collector mains and coolers and separate tanks for separation of tar and liquors and for storage.

In the operation of the coke oven by-product recovery system for the production of a low carbon tar of regulated low carbon content, I make use of a separate collector main for collecti-ng the gases from part or all of the ovens during a regulated initial period of the ycoking operation. Two-main systems such as have been employed for the separate collection of rich and lean gases can be employed, but with regulation of the operation from the stand-point of the carbon content of the tar separated from the gases rather than from the stand-point ofthe richness or leanness of the gases, after the separation of the tar therefrom. The collector main may be cooled by ammonia liquor sprays, or by the introduction of ammonia liquor and tar therein and the circulation ef the liquor and tar therethrough. A considerable portion, usually the greater portion, of the tar can be thus separated as a heavy tar in the collector mains. The tar from the initial period of operation kept separate from the tar from 'the later "r of operation. That is, the se` arate coi ctor nnins have separate draw-o i means for the tar, andthe low carbon tar is kept sepa rate. E

ln systems in which the tar is circulated through the collector mains, the tar separated from the frases in each collector main is returned and circulated through the same eollector mains so as te avoid adin'sure of in@ low carbon tar with the higher carbon tar produced in the other collector mains.

In addition to collecting separately the low carbon tar from the collector main, a further quantity of low carbon tar is recovered in the condensing system :from the same gases. The tar so recovered will ordinarily be a lighter tar or tarry oil. It can beadmixed with the heavy tar from the collector main to give a' composite low carbon tar, and the composite tar `then subjected to distillation for the roj duction of distillate oils and a low car n ahead of the condensers. Where a plurality of products are thus fractionally condensed from the gases to produce a series of low carbon tars varying from each other, these can advantageously be distilled separately for the production of the low carbon pitches and of distillate oils.

The distillation of the low carbon tar Ifor the reduction therefrom of low carbon pitch can e carried out in stills of different ty s.

A If the low carbon tar is subjected to disti ation in ordinary externally heated stills in which successive charges of tar are distilled to produce successive batches of pitch considerable decomposition of the tar will take place during the distillation and the carbon content of the resulting pitch will be due in part to the carbon content of the tar distilled and in part to the added carbon formed during distillation. Such pitches will Jnevertheless be .materially lower in carbon than ordinary pitches produced in the same stills from total tar.

A particularly advantageous method 0f distillation of the low carbon tar for the production of low carbon pitch, is by means of the hot coke oven gases. By bringing the low carbon 'tar into direct and intimate contact with hot coke oven gases at a high temperature, 'the tar canbe rapidly distilled with a minimum vof-decomposltio'n and with but small increase in the carbon content of the pitch due to the distillation. Low carbon pitches can-accordingly be produced which have a carbon content corresponding to that of the tar from which the pitch is produced, with only asmall additional increase resulting from the distillation. Such' distillation can be effected, for example, in a separate short distillation main or collector main in which the gases from selected ovens are` collected and employed at a high temperature for the distillation, and in which the tar is intimately atomized or sprayed into the gases .upon

to eect the distillation. Gases from the early period of operation of the ovens is advan usly employed for this purpose by distilh the low carbon tar in gases of the kind which contain low carbon tar, the additional tar separated from the gases during the distillation will similarly be of low carbon content, In other cases, the gases from several ovens can be combined during the entire period of o ration and employed for the distillation, with some slight increase in carbon content of the resulting pitch due to the somewhat higher carbon content of the tar separated from the gases employed for the distillation. By employing the gases at a high tem rature for distillation, the amount of tar d1stilled will be several times the amount of tar contained in the gasesso that the pitch separated fromthe gases during the distillation will form only a small art of the total pitch product produced by t e distillation.

The oils distilled from the low carbon tar are oils of relatively low specific gravity and can advantageously be kept separate from the oils distilled from the remainder of the tar,

thus giving an oil of relatively low gravity' as one of the products of the process, in add1 tion to the low carbon pitch.

The rate and extent of the distillation can be varied by varying the amount and temperature of the gases employed for the distillation or the rate at which the tar is supplied andthe pitch withd'rawn. To avoid overheating of the tar and itch and increase in carbon content 'as muc period during which the tar is subjected to eatin should be limited. By having only a sma body of tar in the still and ra idly atomizing it into the gases and supp ying additional tar and drawing oi the pitch at a regulated rate, it is possible to carry out the distillation continuously and without prolonged heating of the tar or pitch and with a minimum of increase of carbon contentin the as possible, the` no i pitch produced over that contained in the g tar distilled.

In the short collector main or distillation main, the tar and pitch can be atomized or sprayed into the gases by means of spray g nozzles or by means of mechanical devices such as discs or cylinders, etc., rotatin at high speed and dipping into thebody o tarA or pitch in the bottom of the short main'.

.Other suitable agitating devices may be employed, the ob'ect being to agitate and distribute the tar 1n the form of relatively 'small particles throughout the hot gases which flow tion of the volatile oilconstituents-therefrom,

leavin a pitch residue which depending the amount of distillation diected,may

have varying characteristics. The distillation results also in the enrichment of the hot gases employed therefor in the volatile oil constituents and such gases may be subjected thereafter to cooling or other treatment to separate the oily constituents therefrom.

The distillate oils produced by the distillation will be relatively clean oils, inasmuch as the distillation will result in enrichment of the gases in oil vapors and the removal therefrom of a considerable part of the suspended pitch particles. tively clean oils of low specific gravity can be directly -produced'by cooling the gases employed for the distillation. When the tarry oils from the condensers are kept separate and subjected to distillation separately, the distillate oils will be lighter, or will contain increased amounts of lighter oils. When the heavy tar from the collector main is distilled separately, the yield of oils will be relatively less, but the low carbon pitch will be produced with much less distillation. Accordingly, the heavy tar from the collector main can advantageously be distilled separately to give a relatively high yield of the low carbon pitch wi th a minimum of distillation, and the tarry oils from the condensers may be employed for other purposes or may advantageously be distilled separately to give a high percentage yield of oils. Where separate low carbon tar fractions are collected in the collector main, at the'end of the cross-over main, and at two or more stages of the condensers, all of these four or more fractionally condensed products can be separately subjected to distillation, or only certain of them subjected to distillation, to give a range of distillate oils and low carbon pitches.

As an example of the application of the invention, it ma be desirable to produce a low free carbon pitch having a meltin point of amount of higher car from 160 to 180 F. (by the air-bat -meltingpoint method). Such a pitch is suitable for saturating fibre conduits for telephone cables. Pitch of this character can be produced sc parately, collecting the gases as they are discharged from the coke ovens durin the earlier part of the coking operation and y cooling such ses to separate the tar constituents which are distilled thereafter by contact with hot coke oven gases which are given off during the early part of the coking operation. If the proportion of free carbon in the pitch thus recovered is too low for the particular Arequirements it can be somewhat increased by utilizing ordinary coke oven gases as the distilling media or b adding the required n tar to the low carbon` tar before distillation.

It will be understood that in the practice of the invention the cooling of the rich and l lean gases in the separate collector mains may be regulated by supplying more or less ammonia liquor or other cooling agent there- Accordingly, rela-v to for the purpose of separating a. heavier or lighter tar and that by regulation of the amount of oil constituents which are condensed with the tar in the collector mains and by variation of the amount of distillation to which the tar is subsequently subjected, the characteristics of the pitches obtained can be somewhat varied. It will be understood that the recovery of pitches having both low and high free carbon content can be oonducted simultaneously in the operation of the same battery and that pitches thus produced can be utilized for any purpose for which they are adapted.

While I have referred more particularly to coke ovenoperation, and the production of special low carbon pitches from coke oven tar, the invention in its broader aspects includes the production of low carbon pitches in a similar manner at other coal distillation plants and from gas retort tars, etc. Pitches of special properties are obtainable, for example, by separately collecting the tar from the gases given off during the early part of the gas making operation in horizontal inclined or intermittent vertical retorts, and separately distilling such tars. The pitch from the horizontal retort tarlwill be lower in carbon content, than ordinary pitches from the total tar, and will more nearly resemble pitches from coke oven tar, or blended pitches from mixed coke oven and gas retort tar. The pitches from the low carbon tars at intermittent vertical retort plants will be unusual] low in carbon" content. The distillates rom the distillation of the respective tars will likewise be distinctive.

rI he present invention is of more or less general application to the operation of coke oven and other coal distillation plants and to the recovery of pitches and oils from the tars separated from the gases discharged therefrom.' It will be further described with reference to the accompanying drawings which show apparatus adapted for the practice of the invention, but it is intended and will be understood that the invention is not limited thereto.

. Fig. 1 is a Dlan view of a portion of a coke oven battery illustrating the application of the invention thereto;

Fig. 2 is an enlarged sectional view of one of the collector mains; and

Figs. 3 and 4 are similar views of the short clleedctormain or still in which the tar is disti Referring to the drawings,'5 indicates the i battery of ovens which are connected by uptake pipes and goose-necks 6 and 7 to collector mains 8 and 9. Valve boxes 10 and valves 11 therein are disposed in the goose-necks to permit the direction of the hot gases Yfrom the ovens into one or the other of the collector mains as may be desired. Thus, by operating the valves rich and lean gases from the several ovens of the battery can be collected separately in the collector mains wherein they are cooled to the desired extent by ammonia liquor, for exam le, introduced through spray nozzles whic are supplied throug a pump 13 and pipe 14 from a source of the cooling liquid such as -a tank 26 which maintain the pressure balance in the systems and may pass thence to suitable equipment (not shown) for the recovery of ammonia, light oils, etc.

The tar and ammonia liquor from the se arate collector mains 8 and 9 may be wit drawn through pipes-45 and 27 anddelivered to decanters 28 and 29 in which the ammonia liquor is separated from the tar. The ammonia liquor may be returned for further use as a cooling medium or treated in any suitable manner for the recovery of ammonia therefrom. The tar may be delivered through pipes 30 and 31 to storagereceptacles 32 and 33 from which it may be withdrawn as r uired for further treatment such as distillatron toproduce pitches.

The distillation of the tar is effected preferably ina suitable still such as a short collector main or still 34 which may be disposed at therear 'of the .coke oven battery and is connected to a Asuitable number of ovens throughA uptake pipes and goose-necks 35 which deliver the hot to the short collector main. The tar to be distilled, for example, tar derived from rich gases and therefore low in free carbon is delivered by a pump 36 through a pipe 37 to one end of the short collector main or tar box 34 which is provided with a cylinder 38 adapted to be rotated at a high rate of speed by the electric moto36. The roll dips into the body of tarand 'itch in'the'bottom of the main or still and y means .ofthe rapid `rotation thetar and pitch are atomized, in the form of a` finely. disseminatedy s ray, into the gases passing through the co ector main or still 34. By means of the intimate contact of the tar and gases the former is distilledand pitch is produced which is drawn o at the o posite end ofthe main or still thru a ipe o'r t an out let 37 and gutter 38 su as shown in Figure4. Y i5 'In the softer pitches will be withdrawn thru pipes and the harder pitches such as those of 300 to 400 F. melting point and upwards will be withdrawn thru outlets like 37 and gutterlike 38. In case the utter 38 is used the pitch may conveniently e granulated b allowing it to drop into a stream of water rom line 47. The water and granulated pitch will be delivered bythe gutter to settling basins 39 from which the pitch may be recovered. In case softer pitches are being made the open gutter is objectionable since it allows excessive fuming of the hot liquid pitch. For that reason a closed pipe line is more desirable.

The hot gases which are partially cooled by contact with the tar and pitch in the short collector main or still are enriched in oil constituents by the distillation effected therein and such gases pass up through settling tower 46 'during which passage tar spray and globules and other entrained matter settles out of the gas and is returned to the main or still 34. Tower 46 may be equipped with baliles, packing etc. if desired. The ases can be withdrawn through a pipe 40 and elivered to a condenser 41 located at an suitable place wherein the gases are cooled or the purpose of separa-ting the oil constituents. The oil thus-separated can be Withdrawn from the condensers through a pipe 42 and delivered to a decanter 43 in which it is separated from ammonia liquor. The oil can be stored in a v suitable receptacle and utilized for any desired purpose. The gases, after se aration of the oil therefrom, can be delivere by a pipe -44 to the exhauster 26 and mingled with the other gases from the battery, being subjected therewith to the usual treatment for the recovery of ammonia, light oils, etc., therei from.

The present invention permits the recovery particularl of low free carbon itches directy `from co e oven gases. Hi free carbon pitches canl also be recovere in the same' operation together with oils which may beA utilized directly or subjected to' distillation to separate the oils into various fractions which are adapted for commercialutilization. The invention involves the use of heat available in the coke oven gases to distill the tar recovered therefrom and to produce pitches having the desired characteristics. These and other advantagesof the invention may be attained by the ractice of the principles as hereinbefore set orth, it being understood that various changes may be made in the details of the operation without departing fromV the invention or sacrificing the advanta es enumerated. y

ile I have described the invention more particularly in connection with the roduction of low carbonpitches from co e oven tars, it will be understood that low carbon pitches can similarl be'produced at gas retort plants in a manner, and that the different pitches will differ from each other, thus maklng possible the roduction of different kinds of lpitches at iiferent plants.

I claim: Y

1. The method of producing pitch containing a low proportion of free carbon which comprises withdrawing the gases produced during the early stages of coal distillation from a/series of ovens or retorts, keepin such gases'separate from the ases given o during the later stages of 'stillation, cooling such ases to separate a low free carbon tar there rom, keeping such tar separate from the tar produced from the ases from the later stages of coal distillation, and separately distillin such low free carbon tar to produce pitc of low free carbon content therefrom.

2. The method of producing low ravity oils from coal distillation gases, whic com-` prises separately withdrawing the gases produced during the early stages of coal distillation in the ovens or retorts, cooling the gases to separate a heavy tar therefrom, subsequent y further cooling the gases to se arate a lighter tar therefrom, separately col ecting the heavy tar and the li hter tar and se a rately subjecting the lig ter tar to disti ation to produce low gravity oils therefrom by bringing such li hter tar into direct and intimate contact with hot coal distillation gases at a suiciently high temperature to effect rapid distillation thereof.

In testimony whereof I aiix my si nature.

STUART PARMELEE M R.

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