US1952020A - Distillation of tar or pitch to coke and apparatus therefor - Google Patents

Description

March 20, 1934. s. P. MILLER DISTILLATION OF TAR OR PITCH TO COKE AND APPARATUS THEREFOR Filed Aug. 9, 1929 5 Sheets-Sheet l INVENTOR ATTORNEYS March 20, 1934. s P MILLER 1,952,020

DISTILLATION OF TAR OR PlTCH TO COKE AND APPARATUS THEREFOR Filed Aug. 9, 1929 3 Sheets-Sheet 2 i /2 (Ms M INVENTOR WWW BY 7 bww a ATTORNEY6 for March 20, 1934. s. P. MILLER DISTILLATION OF TAR OR PITCH TO COKE AND APPARATUS THEREFOR Filed Aug. 9, 1929 5 Sheets-Sheet 3 INVENTOR Patented Mar. 20, 1934 PATENT OFFICE DISTILLATION OF TAR OR PITCH TO COKE AND APPARATUS THEREFOR Stuart Parmelee Miller, Englewood, N. J., as-

signor. to The Barrett Company, New York, N.Y., a corporation of New Jersey Application August 9, 1929, Serial No. 384,666

7 Claims.

This invention relates to improvements in the distillation of tar or pitch and the continuous production of coke therefrom. It includes both the process and apparatus for carrying it out.

According to the present invention, tar or pitch is distilled to coke in a current of hot gases, more particularly fresh hot gases from the distillation or gasification of coal, such as hot coke oven gases. The still in which the coke is formed is heated externally, the contents of the still are continuously agitated or tumbled, the tar or pitch is added to the still continuously and the finished coke is continuously discharged from the still. The vapors distilled from the tar or pitch in the formation of the coke are flushed from the still by the hot gases passing thru the still and the flushing efiect of these gases removes the volatile constituents of the tar or pitch as fast as evaporated. This aids in the conversion of the tar or pitch to coke and increases by-product recovery, especially by the removal by distillation ofhigher boiling constituents of the pitch. The oils distilled from the pitch in the formation of the coke leave the still together with the hot gases and any vapors contained in these gases and are passed to condensing means for recovery of the oils.

Where the hot gases passing thru the still carry suspended in them tar or pitch constituents, as I would be the case with gases which are passed directly into the still from coke ovens or gas retorts, for example, some of these suspended constituents maybe removed from the gases in the coke still. The pitch is present in the still as a more or less plastic mass and does not lend itself to scrubbing the gases to remove entrained particles from them- The greater portion of the entrained impurities is carried thru the still by the gases. The oils which separate on cooling the gases leaving the still are contaminated by such impurities, and tarry oils are obtained unless these impurities are removed from the gases while the gases are at high temperature and while the oils are in the vapor state. The oils which separate from the gases after removal of the entrained impurities are clean oils, i. 9. free or substantially free from heavy tarry and pitchy constituents. The formation of such clean oil products directly from the gases resulting from 'the distillation of tar or pitch to coke comprises an important feature of a preferred method of carrying out this invention. I

It has been the practice to distill tar or pitch to produce coke in externally heated stills but,

such distillation is accompanied with a considerable decomposition of oil constituents'of the tar or pitchdistilled with corresponding reduction in the yield of distillate oils and increase in the coke residue. Particularly at the'higher temperatures required for the distillation of pitch to produce coke, the decomposition of heavy volatile constituents, such as resins, greases, etc., is very considerable and even at lower temperatures appreciable decomposition of volatile constituents takes place when the distillation is carried out in an externally heated still unless some provision is made for thoroughly agitating the pitch to avoid local overheating and for removing the vapors of these higher boiling compounds as they are formed.

The present invention provides an improved process in which a materially increased yield of distillate is obtained from the tar or pitch by agitating or tumbling the contents of the still during the distillation, while removing vapors from the still as they are formed by passing hot gases thru the still, thus preventing or reducing objectionable decomposition of volatile constituents distilled from the tar or pitch, and further it provides a continuous process in which the coke produced is discharged from the still continuously, as it is formed.

According to the present invention, I provide a still into which the tar or pitch to be distilled is introduced, preferably in a continuous stream. Where the starting product is tar, the operation may preferably be carried on in two different stills, although one still may be employed for carrying out the complete process. Special means is provided for handling the heavy hot plastic material which is the intermediate product obtained immediately prior to conversion of the pitch to coke. This product, as well as other contents of the still, is agitated to prevent local overheating. Hot gases, which may be hot coke oven gases, hot gas retort gases, etc., are passed thru the still to remove volatile constituents as they are released from the distillation mass. The still is heated externally and the combined heating of the still and action of the hot gases passing thru the still effects distillation especally of the higher boiling oils with appreciably less decomposition than takes place in' the direct-fired still or other stills ordinarily employed ,at the present time for the conversion of pitch to coke.

The coke. still is preferably located closely adjacent to the source of the hot gases in order that the heat of these gases may be utilized to the maximum extent. The" gases may be passed thru indidvidual mains from the ovens or retorts of the coal carbonization apparatus directly into the still and the outlets from the mains conveying the hot gases may be such that the gases are directed against the body of pitch being distilled so that the gases pass down thru and around the pitch as it is agitated and remove vapors therefrom as they are formed and aid in the distillation of volatile constituents from the pitch.

As an alternative method, the gases from the ovens or retorts of a coal carbonization plant may be collected ina hot gas header and be conducted thru this to the still. The gases may be admitted to the still at various points or thru one opening in the still. In this latter case the gases are preferably passed thru the still in a direction countercurrent to the flow of the pitch thru the still so that the hottest gases, on entering the still, come into contact with the most nearly coked material, and, in contacting with this nearly completed product as it is agitated or tumbled, remove the remaining volatile constituents necessary to convert the pitch to coke. These gases enriched in higher boiling constituents pass on thru the remainder of the still and distill from the more plastic material the more easily volatile oils and leave the still at a temperature sufliciently above the dew-point of the constituents volatilized within the still o accomplishthe desired distillation.

Where tar is to be distilled to coke, the hot gases leaving the pitch may be passed thru the tar still which may be a unitary part of the coke still, although the tar still is advantageously kept as a separate unit from the coke still owing to the different conditions obtaining in the two stills. Tar or partially distilled tar. or fluid pitch may be readily sprayed into the hot gases. These materials may therefore be distilled by being brought intointlmate contact with the hot gases in the form of an intense spray of droplets of greater or less diameter.

During the conversion of pitch to coke, the material being treated passes thru a plastic state which is difiicult to handle by means other than that especially designed for this purpose. Such material does not adapt itself to spraying into the hot gases in the manner that tar or thinly fluid pitch does. The material may be stirred or agitated or tumbled by properly designed agitating means and preferably in a specially designed still. According to this invention the hot plastic material is kept in motion to prevent overheating thru the bottom of the still or other portion of the still to which heat is applied, and the agitation is such as to allow the hot gases to pass thru and around the plastic material as much as possible in order to remove volatile constituents from the still as they become vaporized.

Where it is desired to obtain clean oils directly as a product of the process, the gases leaving the coke still must be cleaned to remove entrained matter. This cleaning may be accomplished in a scrubber of suitable design in which tar or pitch such as a pitch of the same composition as that carried by the gases is sprayed into the gases with sufficient force and intensity to remove entrained particles from the gases. An electrical precipitator of the Cottrell tubular type may be used for removing entrained particles from the gases and where the gases are cleaned at such a high temperature that coke may be formed on the electrodes, the'electrodes of the precipitator may advantageously be flushed with tar to preventthe accumulation of pitch thereon and consequent formation of coke.-

According to a preferred method of carrying out this process, the hot enriched gases leaving gasification gases may be brought into the tar still to aid in carrying out the distillation of the tar in this still.- Where the temperature of the tar still is not suflicient to carry vapors produced in the coke still thru the tar still to the condensers and where a portion of the higher boiling constituents are condensed from the gases within the tar still, a portion of the pitch may advanta eously be withdrawn from the tar still and be put to any suitable use, and the rest of the pitch may be discharged directly into the coke still for further distillation and conversion to coke. Where all of the high boiling vapors pass thru the tar still all or merely a portion of the pitch from the tar still may be discharged into the cake still for further distillation and conversion to coke.

Where pitch is converted to coke by distillation in astream of hot coal carbonization gases, as contemplated by this invention, it is desirable to volatilize from the pitch higher boiling resins or greases in order to increase the yield of by-products recovered. These higher boiling resins and greases are solid or semi-solid at ordinary temperatures. above described in which the hot gases and vapors from the coke still pass to the tar still, a portion of these higher boiling constituents may be condensed within the tar still. Where the temperature is such that they are carried over to condensers, these high boiling resinous and greasy constituents may advantageously be separately condensed and a hot condenser may advantagenusly be employed for the separation of these constituents from the gases. In recovering these higher boiling resinous and greasy constituents from the gases it is advantageous to pass the gases up thru the condenser so that the more fluid lower boiling oils condensed in the upper portion of the condenser will serve to keep the lower portion of the condenser free from accumulations of the higher boiling constituents.

The gases leaving the hot condenser may be further fractionally cooled to separate various fractions which may be clean oil fractions depending upon the amount of scrubbing or other cleaning to which the gases have been subjected. For example,.the gases may advantageously be cooled in two stages to produce direct from the gases a clean oil of creosote range, and a lower boiling clean oil of the carbolic oil range. The latter may be directly subjected to extraction with alkaline solutions for the recovery of tar acids without the intervention of a distillation step, such as the present methods require in converting tar or tarry oil to a clean oil suitable for extracting. The gases leaving the condensers will be'treated for the recovery of ammonia and light oils.

The pitch which is distilled according to this invention may be pitch from the tar still or pitch from another source. Pitch may be distilled to In carrying out the processes as coke without distillation of the parent or other tar to pitch in the apparatus of my invention, or tar'may be distilled to pitch and the pitch be drawn oil as a separate product and different pitch which may be pitch of a different kind may be distilled to coke. For example, at a coke oven plant .the fresh hot coke oven gases may be employed for distilling to coke pitch from gas house tar, and the gases resulting from this operation may be cleaned in a still in which the gas is scrubbed with water gas tar, and the tar may be distilled simultaneously with the scrubbing of the gases. The residue from this distillation may be drawn ofi as a separate pitch product. Other tars or pitches may be employed.

Where tar and pitch' from different sources are both distilled in the same gases, the oils obtained on cooling the gases are composite oils comprising constituents originally present in the tar and also constituents originally present in the pitch. The tar and pitch may be so selected as to give oilsof desired composition.

It is not necessary that the scrubbing medium employed for cleaning the gases leaving the coke still should be distilled. For example, a pitch of approximately the same composition and the same temperature as that entrained in the gases may be employed for cleaning the gases. In this case the composition of the gas is not changed on passing thru the scrubber, except for the removal of entrained impurities.

The invention will be described in connection with the accompanying drawings, more particularly as applied to distillation with coke oven gases, but it is to be understood that the invention is not limited thereto.

Fig. l is a plan view of a coke oven plant equipped with means for'distilling tar to pitch and converting the pitch to coke in an externally heated still thru which hot coke oven gases are passing;

Fig. 2 is an elevation partly in section of the apparatus shown in Fig. l

Fig. 3 is a cross-section on the line 33 of Fig. 2;

Fig. 4 is a cross-section on the line 4-4 of Fig. 2; and i Fig. 5 is a detail showing the hot condensers and heavy oil condensers shown in Fig. 1.

Fig. 1 shows means for distilling tar to pitch by hot coke oven gases with counter-current flow of the gases and the mater'al being distilled and further distillation of the pitch to coke in an externally heated still with agitation of the pitch and flushing of the still with hot coke oven gases to remove vapors from the still as they are formed and to aid thru their partial pressure effect in the volatilization of oil from the pitch being distilled and with continuous discharge of coke from the still.

The coke oven battery 5 is equipped in the usual way with uptake pipes 6 thru which the gases pass to a collector main '7 and from this thru the center-box 8 thru a cross-over main 9 to condensers 10. This apparatus is of the usual type and is shown diagrammatically in Fig. 1.

At the rear of the'coke oven battery selected ovens are connected thru uptakepipes and goosenecks 11 with the coke still 12. By proper manipulation of valves in the uptake pipes 6 and in the uptake pipes 11, the hot coke oven gases may be passed thru either the uptake pipes 6 to the collector 'main 7 or thru the uptake pipes 11to the still 12. Pitch from any suitable source preferably in a thinly fluid condition is fed to the coke still thru the opening 13. In Fig. 1 the pitch is shown as coming directly and continuously from the tar still 14.

The coke still is equipped with external heating means comprising a fire-box 15 and a suitable burner 16 which may be a gas burner or a burner for tar'or hot pitch, or any other suitable type of burner, or the still may be heated by other means as by coal or coke firing. The hot gases pass in direct contact with the exterior of the coke still and thence to a suitable stack thru the flue 17. The pitch within the coke still is agitated by the oscillating arms 18 which are provided with scraping shoes 19 which keep the externally heated portion of the still relatively free from accumu lations of pitch and coke. Doctors 20 serve to remove excess pitch and semi-coke from the oscillating arms as they swing up by these doctors. The electrically driven oscillating means 21 transmits an oscillatory motion to the arms 18 through the shaft 22.

The hot gases from selected ovens pass up through the uptake pipes and goosenecks 11 into the still. These uptake pipes and goosenecks are preferably so arranged as to direct the hot gases direct from the ovens down through and around the pitch or semi-coke being distilled and to remove v'apors from the still as they are formed, and to aid in further volatilization of oils from the pitch or semi-coke. The gases from one or more ovens may be admitted to one end of the still through the pipe 23 to prevent the formation. of pockets of vapor at the end of the still and insure thorough flushing of the vapors from this end of the still.

The pitch which enters the still at 13 is distilled during its passage through the still and passes through a plastic or semi-coke stage and is finally converted to coke and discharged from the still through the chute 24 as coke in lumps or in 115 nodular form. The hot coke is advantageously quenched as it leaves the still. Any quench ng means may be employed. The drawings show a tank 25 containing water into which the coke is discharged, thru a chute 24 from which itis 120 gradually discharged through the revolving grate 26. An endless conveyor 27 is provided for collecting the coke and removing it from the tank It is preferably situated at a suificient depth in the water in the tank 25 and driven at such a speed 125 that although the coke is adequately quenched in the tank, it is notallowed to remain in the water av sufiicient time to become water-soaked. The quenched coke is discharged substantially dry from the conveyor into the bin 28.

Coke oven gases contain particles of pitchy material, etc., known as tar fog which persist at least to some extent in the gases even though the gases are passed through condensers or scrubbers of the ordinary type. The gases leaving the 55 still 12 will ordinarily contain much of the tar fog" present in the gases as they enter the still from the ovens. In addition, the gases leaving the still contain vapors of oil distilled from the pitch and the enrichment of the gases in oil 143 vapors is such that 'on cooling. oils are obtained which contain a lower percentage of tarry or pitchy materials than unenriched gases would contain. The gases may be cooled'directly on leaving the still and tarry oils may thus be obtained. By fractionally cooling the gases, high boiling constituents distilled from the pitch comprising resinous o'r greasy materials may be obtained as a separate high boiling fraction and the resulting gases may be further cooled and fractionated to obtain still other fractions. If the gases are cooled as they leave the still 12, the condensate or condensates produced will be contaminated by pitchy ingredients present as tar fog in the gases leaving the ovens, and possibly also by some particles of pitch or coke which may be carried over by the gases from the still 12. Although the gases may be cooled directly after they leave the still and by fractional cooling in suitable condensing means, several fractions may be obtained, the gases leaving the coke still are advantageously cleaned before being cooled and the cleaning is advantageously done at a high temperature so that the higher boiling vapors in the gases leaving the still may be condensed and obtained directly as clean oils, together with lower boiling constituents which can be recovered directly as clean oil products even though the gases are cleaned at a lower temperature. Any suitable means for cleaning the gases may be employed, such as an electrical precipitator or a suitable hot gas scrubber, etc.

In the drawings, the means employed for cleaning the gases is a tar still in which tar in the form of an intense spray is brought into intimate contact with the hot gases by which means entrained impurities are removed from the. gases. The gases are brought from the coke still 12 to the tar still 14 through the short main 29.

This main 29 as well as the coke still and tar still and the uptake pipes 11 and other means through which the gases pass in which the loss of heat through radiation is undesirable is advantageously heavily insulated at 29'.

In the still 14 the gases are intensively sprayed with a mixture of tar and its distillation residue and this scrubs the gases and the tarry mixture is distilled. The tar is advantageously admitted to the 'still through the sprays 30 in the tower 31 through which the gases and vapors pass after leaving the tar still. The tar may if desired be pre-heated in any suitable manner.

In the drawings a roll 32 which dips to only a slight extent into the tar is shown as the means for spraying the tarry mixture into the hot gases within the still 14. The roll is located at one side of the still and a motor 33 is provided to rapidly rotate this roll. By rotation of the roll a fine spray of tar and partially distilled tar is thrown from the roll up into the gases. Any. spray of tar or pitch carried from the still by the gases is removed by the baflles 34 and the tar sprayed from 30.

The flow of material through the tar still and then through the coke still, the quantity of gases passed through the stills, the temperature to which the tar is pre-heated before entering the sprays 30, etc., are so regulated and the apparatus is so designed that the tar is distilled in the still 14 to a melting point below that at which difficulties might arise due to the coking of the pitch to any undesirable extent in the tar still. A pitch of a melting point of over 300 F. and even up to 350 F., but preferably not much higher, may be produced in the still 14, although the melting point which may be obtained in the still 14without trouble depends also upon the kind of tar distilled. The distillation should be car-' ried to such a point that the pitch admitted to the still 12 will not be too soft to permit ready handling'of the pitch within the still by the means provided. Where desirable, a portion of the pitch from the still 14 may be drawn off through the trap 35 and the levelling arm 36 into the trough 3'7 where it 'is chilled by cold water from the pipe 38. The pitch which is granulated by sudden cooling in this manner may be employed for any suitable purpose.

The hot gases which are detarred by the spray of tar and pitch within the still 14 pass out through the settling tower enriched in oil vapors and contain vapors of high boiling constituents which are solid or'semi-solid at ordinary temperatures and which will readily condense from the gases on cooling. The gases and vapors may advantageously be passed into a condenser located in close proximity to the tower to remove such higher boiling constituents. Although one total oil fraction may be obtained by complete cooling of the gases, separate oil fractions in,-

eluding a heavy high boiling resinous or grease fraction may advantageously be obtained by fractional cooling of the gases.

The apparatus shown in Fig. 1 includes a column condenser more clearly shown in Fig. 5. The gases from the tower 31 pass through the main 39 into the bottom of this colunm condenser. The condenser comprises two sections 40 and 41. In the lower condenser the heaviest constituents are separately recovered from the ases.

is passed into the inlet 43 through the jacket and out through the outlet 44. The temperature of this cooling medium is such as to condense the desired higher boiling constituents from the gases without substantially condensing lower boiling constituents. This high boiling fraction is withdrawn from the condenser through the pipe 45.

The gases thenpass up through 46 into the updenser is drawn 01f into the decanter 50 and from there the clean lower boiling oils are separately collected in the. storage tank 51. An, exhauster 52 which may be the same exhauster' as employed for drawing the gases through the usual cross-over main is employed for drawing the gases through the coke still and tar still and the condensing means.

In the drawings, the still shown is a stationary still with agitators. The still may instead comprise a rotating still withballs or other tumblers for agitating and breaking up the coke.

In the drawings, the tar still employed for scrubbing the gases and distilling tar to pitch utilizes only the hot gases and vapors coming from the coke still. Where desirable, additional hot coke oven gases may be passed into this still directly from the ovens of the battery where the heat in the hot gases and vapors from the coke stilll 14 is not suflicient to produce the distillation of tar desired, but it will be preferable to introduce such additional gas into the coke still.

The drawings show a coke still and tar still inseries for the distillation of tar to pitchand the coking of pitch, and a single condensing system for recovering clean fractions, or a total clean oil distillate from the enriched gases by condensation. Instead of employing two separate stills, tar or pitch may be fed directly to the coke still for the production of coke without any subse- The tubes 42 in the lower portion of the condenser are jacketed and a cooling medium quent use of the hot gases from the still to distill tar to pitch. In the case where there is no scrubbing of the gases and vapors from the coke still with a fine intense spray of tar such as that in the tar still 14, the hot gases leaving the coke still will not be cleaned to such a degree as in the case when they pass thru the tar still; as shown in the drawings. The gases will be enriched by the oil vapors resulting from the distillation in the coke still and on cooling will yield distillates which will be more or less contaminated by the tarry or pitchy constituents entrained in the gases. If the tar fed to the still is sumciently preheated, the gases will be so enriched as to yield, on cooling, distillates which are oils sufiiciently low infree carbon to allow of their use as distillate oil for creosoting. Where oils containing tar are desired for use as creosoting compositions, the gases may be enriched to a less degree and such tarry oils may be recovered directly, or highly enriched gases may be cooled, and the clean oils may be blended with the required amount of tar to yield the desired creosoting composition.

The process and apparatus described provide means for distilling tar or pitch for the production of coke and high yields of distillate oils in a still into which hot gases, for example hot cokeoven gases, are passed at substantially the temperature at which they leave the ovens.

The coke produced by my process is a high grade coke high in carbon content and low in ash,for example containing usually not over 1 to 2% ash, and in many cases less than 1%. It is produced continuously in crushed or nodular form and may readily be prepared for sale by screening. It ordinarily will not require crushing unless it be desired to employ or market it all in relatively small size. The volatile content of the coke may be regulated within wide limits by regulating the quantity of the hot gases passed thru the still. Cokes of varying degrees of combustibility may thus readily be produced for the special purposes to which such high grade materials are put.

I claim:

1. The method of distilling tar to coke and recovering distillate, which comprises maintaining a body of pitch to be distilled within a still, heating the still externally, passing hot inrt gases through the still, and bringing the resulting gases enriched in constituents distilled from the pitch into direct contact with tar whereby the tar. is distilled to form said pitch, and subsequently cooling the gases to separate an oil comprising constituents from each distilling operation.

2. Themethod of distilling tar or pitch to coke and recovering distillate, which comprises maintaining a body of the material to be distilled within a still, heating the still externally, passing hot coal distillation gases through the still and thereby maintaining the material at a high temperature for a sufiicient time to convert it to coke,

spraying the gases and vapors coming from the still with an intense spray of tarry material whereby the tarry material is distilled and the gases and vapors are substantially detarred by the scrubbing action of the tarry spray, and then cooling the gases and vapors to separate clean oils \thereirom.

3. The method of distilling tar to coke and recovering distillate which comprises converting pitch to coke by externally applying heat to a coke still containing the pitch while passing hot coal distillation gases thru the still to remove from the still the vapors produced by the distillation of the pitch to coke, continuously withdrawing the coke from the still, bringing the gases and vapors resulting from the distillation in the coke still into intimate contact with tar by spraying these gases and vapors with an intense spray of the tar whereby the gases are substantially detarred and the tar is distilled to pitch, running at least a portion of the pitch into the coke still to be converted to coke, and cooling the gases and vapors resulting from the distillation of the tar and conversion of the pitch to coke to separate clean oils from these gases.

4. The method of converting pitch to coke which comprisesmaintaining the pitch in contact with one surface of a heat conductive retaining wall, supplying heat to the other surface of the wall so that the heat is imparted to the pitch and the pitch is maintained at a sufficiently high temperature to effect its destructive distillation to coke, agitating the pitch during distillation and passing hot fresh coal distillation gases containing tar constituents into direct contact with the pitch so as to supply heat to the pitch and sweep away therefrom the gases and vapors formed in the distillation, withdrawing the hot gases and vapors and cooling them to separate therefrom an oil comprising constituents distilled from the pitch, blended with tar constituents originally present in the hot coal distillation gases.

5. In the process of coking pitch, the method which comprises passing hot fresh coal distillation gases containing tar constituents into direct contact with the pitch so as to supply heat to the pitch and sweep away therefrom the gases and vapors formed in the distillation, withdrawing the hot gases and vapors and cooling them to separate therefrom an oil comprising constituents distilled from the pitch, blended with tar constituents originally presentin the hot coal distillation gases.

6. A still for converting tar or pitch to coke, means for heating the still externally, a gas main leading to the still with means for passing a gas therethrough, a scrubber, a main for conveying gases and vapors from the still to the scrubber, means for spraying tarry or pitchy material into the gases and vapors in the scrubber, and a cooler to condense and separate oils from the resulting gases and vapors.

7. In combination with coal distillation apparatus, a still for converting pitch to coke, means for heating the still externally, a main for conveying hot coal distillation gases into the still, a tar still comprising means for producing an intense spray of tarry material in the vapor chamber of the tar still, means for passing hot STUART PARMIELEE MILLER.

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