US1904505A - Distillation of tar or pitch - Google Patents

Description

April 18, 1933. s. P. MILLER 1,904,505

DISTILLATION OF TAR 0R PITCH Filed Dec. 11. 1929 3 Sheets-Sheet 1 (an den Jer ATTORNEYS April 18, 1933. s. P. MILLER DISTILLATION OF TAR OR PITCH Filed Dec. 11 1929 v 3 Sheets-Sheet 2 raaer raf n41. aaaa INVENTOR ATTORNEYS April 18, 1933. s. P. MILLER DIST ILLATION OF TAR OR PITCH Filed Dec. 11, 1929 3 Sheets-Sheet 3 \Wx cu ukk M Wk INVENTOR \5 y 624% ATTORNEYS T N R Mk mm ml k Patented Apr. 18, 1933 UNITED. STATES PATENT OFFICE STUART PARKE-LEE MILLER, OF ENGLE'WOOD, NEW JERSEY, ASSIGNOR TO THE BARRETT COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY DISTILLATION OF TAR OR PITCH Application filed December 11, 1929. Serial No. 413,254.

This invention relates to the distillation of tar or pitch to produce a pitch of high melting point or coke and the recovery of distlllate therefrom. The invention relates more particularly to cooling the vapors resultmg from the distillation and the recovery of non-fluid high boiling compounds together with oils of lower dewpoint. The invention includes both the new process and apparatus for carrying it out.

According to this inventlon, when tar or low melting point pitch is distilled to pitch of high melting point, or when pitch is coked under conditions which yield a considerable amount of non-fluid compounds in addition to sufiicient oil of lower dewpoint to dissolve these non-fluid compounds from the condenser, 'an indirect condenser is provided for cooling the distillate. The vapors from the still enter the bottom of the condenser and after cooling, the resulting vapors are delivered from the top of the condenser. The non-fluid high boiling compounds separate from the vapors on relatively slight cooling.

Since the vapors enter the lower portion of the condenser these non-fluid constituents separate in the lower portion of the condenser. The condensing operation is so controlled that compounds which are fluid at the temperatures obtaining in the condenser and have a lower dewpoint separate in the upper portion of the condenser, so that in draining down thru the condenser, they wash down the walls and dissolve or partly dissolve the non-fluid compounds which separate in the lower portion of the condenser and flush them away. If such vapors were cooled in an indirect condenser and were admitted to the top of the condenser, any non-fluid constituents which separated from the gases would separate in the top of the condenser, and fluid constituents which were condensed in the lower portion of the condenser would not come in contact with any deposit of nonfluid constituents in the upper portion of th condenser but would be. drawn off from the condenser without removing such deposit. In time the accumulation in a down-run condenser of these non-fluid compounds would reduce the cooling capacity by formation of non-heat-conducting deposits and might eventually grow to such proportions that the flow of vapors thru the condenser would be blocked. The up-run condenser of this invention prevents the occurrence of these conditions by dissolving wholly or partly the non-fluid constituents of high boiling range in fluid condensate and washing them from the condenser.

In preparing pitches of high melting point, e. g. melting point of 300 F. to 400 F. or upwards, on a commercial scale, difliculties have been encountered in the condensing sys tem due to the condensation of these nonfluid constituents. Pitches of this high melting point may readily be obtained by spraying tar or pitch of lower melting point into a current of highly heated gases such as hot coke oven gases, or hot gas retort gases, or hot producer gas, or hot water gas, or other hot coal carbonization or distillation or gasification gases. Pitch of high melting point is produced and the vapors are carried by the gases into the condensing system. By maintaining a fine intense spray of the material to be distilled in direct and intimate contact with a current of such hot gases, the distillation will be rapidly completed without maintaining the tar or pitch at an elevated temperature for a prolonged period of time and with minimum decomposition of tar or pitch constituents. When pitch with a melting point of 350 or 400 F. or higher is produce in this manner from coke oven tar, for example, a considerable quantity of non-fluid constituents is carried over in vapor form from the still with the hot gases. When the gases and vapors are cooled in an indirect condenser if they are admitted to the bottom of the condenser, the non-fluid constituents which 9 separate from the gases on only slight cooling, separate in the bottom of the condenser, and fluid constituents which separate in the upper portion of the condenser flow down and remove these non-fluid constituents from the bottom portion of the condenser.

The process is applicable to the distillation of such coal tars as coke oven tar or gas retort tar, etc., which contain such non-fluid constituents. The tar may be partially distilled or it may be distilled to pitch of a low melting point before being distilled according to this invention, but in such a case in order to operate the condenser of this invention successfully, the tar must still retain suflicient oils or fluid constituents of lower dewpoint than the high boiling non-fluid constituents in the vapors to remove such nonfluid constituents from the condenser, or the operation must be so carried out that a sufficient quantity of oils of lower dewpoint is formed during the distillation, as by decomposition of higher boiling constituents.

When pitch is coked in a current of hot gases so as to expose alarge and constantly changing surface of the pitch to the distilling action of the hot gases, a relatively large amount of such non-fluid compounds may be carried from the still as vapors. The invention is applicable to the condensation and removal of such compounds from these gases when the gases carry a sufficient quantity of vapors of lower dewpoint to remove the higher boiling non-fluid compounds from the indirect condenser employed.

The cooling medium employed in the indirect condenser of this invention may be water or other cooling fluid. The tar to be distilled may advantageously be passed thru the condenser in indirect contact with the vapors to effect the condensation of vapors simultaneously with preheating of the tar.

The vapors may be passed thru a coil or series of pipes in the indirect condenser and the cooling medium may surround the coil or pipes, or the vapors may surround the coil or pipes, in which case the cooling medium will flow thru the coil or pipes. The indirect condenser may be a total condenser or it may be a partial condenser in which the higher boiling non-fluid compounds are condensed together with only suflicient oils to remove these compounds from the condenser, and the remainder of the condensable constituents may be condensed in one or more other condensers located beyond this condenser for the highest boiling vapors.

The invention may be applied to the recovery of distillate resulting from the distillation of coal tar to pitch of high melting point by direct contact with hot coal distillation gases, as follows: The tar is sprayed into a current of thehot gases, such as coke oven gases at a temperature only slightly less than that at which they leave the ovens, and the spray of tar is so fine and intense that the tar is rapidly distilled and the gases are rapidly cooled to about the temperature of the tar. The time during which the tar is held at a high temperature is short and substantially no decomposition results. The ases and vapors which leave the still at a igh temperature contain a considerable percentage of resinous and greasy constituents which are solid or semi-solid in an isolated state at relatively high temperatures. They are passed into the bottom of an indirect condenser, preferably a preheater in which the tar to be distilled is preheated, and are cooled as they pass up thru the'condenser in indirect contact with the cooling medium. The non-fluid, high boiling constituents separatein the bottom of the indirect condenser and the cooling is so regulated that oils are separated in the upper portion of the condenser in an amount sufficient to dissolve and remove the non-fluid condensate from the lower rtion of the condenser. The cooling may a vantageously be so regulated that only oils of higher boi ing range are separated in this condenser, and oils of lower boiling range, which may be rich in tar acids, may then be allowed to pass to a second condenser which may be water-cooled. If this second condenser is of the indirect type, the gases and vapors-are made to enter it at the top and pass down thru it. Oils separate out of the gases in the top of the condenser and dissolve and wash from the condenser naphthalene which separates from the cold gases in the bottom of the condenser. The oils which are drawn ofi of this condenser may be rich in naphthalene as well as tar acids.

The invention is applicable to a continuous distilling process or a series of batch processes in which non-fluid and fluid condensates are continuously condensed, or in which the nonfluid condensate and fluid condensate are formed at intervals such that the fluid constituents as they are condensed and run from the upper portion of the condenser to the lower portion serve to remove the non-fluid condensate from the condenser.

The invention will be further described in connection with the accompanying drawings but it is intended and is to be understood that the invention is not limited thereto.

The word tar as used in this description includes raw tar, dehydrated tar and stripped tar (semi-pitch) from which a part of the more volatile constituents has been removed.

Fig. 7 is a section on the line 7-7 of Fig. 6.

The coke oven battery 5 is equipped in the usual way with a collector main 6 which connects with the ovens thru the uptake pipes 7. The cross-over main 8 connects the collector main with condensers 9, etc. in the usual way.

At the rear of the ovens is a still 10. The still is connected with selected ovens of the battery by additional uptake pipes 11 and the hot gas header 12. By the proper manipulation of the valves 13 in the uptake pipes 11 and valves of the usual type in those uptakes 7 which are connected to the same coke ovens, the gases from these coke ovens may be passed either to the collector main 6 or into the still 10.

In the still is a roll 14 which is adapted to .be rotated at high speed, for example 900-1200 B. P. M., by the motor 15. This dips to but a slight extent into a small body of tar or pitch maintained in the bottom of the still and sprays it up into the hot coke oven gases in the form of a fine intense spray which exposes a large surface of the material to the distilling action of the hot gases. It is advantageous to maintain such a fine intense spray of tar or pitch in the still that the gases are scrubbed thereby and substantially de-tarred.

The spray of tar or pitch is so fine and intense that a very large surface of the liquid is exposed to the distilling action of the hot gases, the surface exposed to the action of the gases is constantly changed by the spraying and respraying of the liquid into the gases, the surface of the gases in contact with the liquid is constantly changing due to the movement of the spray thru the gases, any liquid which collects on the walls of the still is almost immediately washed down and returned to the body of liquid in the bottom of the still, and the length of time during which the hot gases and liquid are in contact is so short, for example, of the order of two or three minutes, that the tar or pitch is rapidly distilled without any substantial decomposition of the tar constituents, and the operation is so controlled that resinous and greasy constituents of the tar are distilled and leave the still with the hot gases and vapors.

The gases and vapors leaving the still pass up thru the tower or saturator 17. Tar which has been preheated is fed to the tower thru the line 18 and sprayed into the gases and vapors thru the nozzle 19. Bafiies '20 and 21' are provided to prevent tar spray from being carried over by the gases into the condensing system. The tar is partially distilled in the tower and the semi-pitch produced is conveyed thru the line 22 into the still at the end at which the hot gases enter.

The hot enriched gases pass from the top of the tower thru the main 25 to the condensing system. Two indirect condensers 26 and 27 are shown in the drawings. hot gases and vapors enter the indirect con- The cooled in the condenser pass over thru the main 28 into the top of the indirect condenser 27 and pass down thru this indirect condenser and are drawn out thru the line 29 at the bottom of the indirect condenser. An exhauster 30 is provided to draw the gases and vapors thru the system and means (not shown) for the recovery of ammonia, etc. is provided beyond the exhauster.

The tar to be distilled enters the system thru the line 35. It passes down thru the indirect condenser 26 thru the coil 37 where it is preheated by indirect contact with the hot gases and vaoprs and is then fed thru the line 18 to the spray device 19" in the tower or saturator 17 A by-pass may be provided to convey a portion of the tar around the condenser to provide for regulated cooling of the gases to separate condensate of a desired boiling range in the condenser. The still and header and indirect condenser 26 are all advantageously insulated as shown at 38.

The hot gases carrying oil vapors and vapors of resinous and greasy constituents leave the saturator 17 and pass thru the main 25 into the bottom of the indirect condenser or heat interchanger 26. In this condenser they are brought into indirect contact with tar which flows thru the coil 37. The hot gases and vapors are cooled simultaneously with the preheating of the tar and as the gases and vapors are'cooled' constituents of progressively lower dewpoint are condensed from the gases. Constituents of high boiling range including resinous and greasy and other non-fluid constituents separate from the gases in the lower portions of the condenser 26 and as the gases and vapors pass up thru this condenser,'oils of lower dewpoint separate from the gases in the upper portions. These oils which separate in the upper portions of the condenser wash down the walls of the condenser and the coil 37 and wash resinous and greasy constituents from the condenser. The non-fluid compounds which separate in the bottom of the condenser are largely or wholly-dissolved in the oil. To-

gether they form a clean oil product, which,

with proper temperature control, may be blended with a higher oil fraction to form a composition suitable for creosoting. The condensate from condenser 26 is collected in the tank 40.

The partially cooled gases then pass to the indirect condenser 27. In this indirect condenser the partially cooled gases and vapors are brought into indirect contact with water which flows thru the coil 36. The gases and vapprs are advantageousl passed down thru the condenser so that nap thalene which separates from the cold gases in the lower part of the condenser, after most of the condensable oils have been separated from the gases,

will be partly or wholly dissolved by the oils which condense in the upper portion of the condenser. The oils will wash down the walls and cooling element of the condenser and keep them free from undesirable deposits of naphthalene. If the partially cooled gases and vapors were passed up thru the indirect condenser 27 instead of down thru this condenser, the naphthalene which separates from the gases after all or most of the condensable oils have been condensed, would collect in the upper part of the condenser and would not be washed down by the oils but would accumulate and would eventually block the gas passage.

In Figs. 4 and 5 hot coke oven gases are employed for the coking of pitch. The hot gases from selected ovens of the battery 50 are collected in the hot gas header 51 which is connected with the ovens in the same manner that'the hot gas header 12 is connected with the ovens of the battery 5 in Fig. 1. These hot gases enter the still 52 where they are brought into direct contact with pitch. The pitch is fed to the still thru the line 53. The

finished coke product is discharged from the.

still thru the chute 54 into the tank of water 55 where it is quenched and then quickly removed by the continuous conveyor 56 and discharged into the bin 57.

In the coking still 52 agitators 60 are provided on the shaft 61. The shaft is oscillated by any suitable driving mechanism 62. Scrapers 64 are provided to remove pitch or coke which adheres to the arms 63.

The pitch is fed to the still from the line 53 and it is stirred and agitated in the still and is distilled as it passes thru the still and the rate at which the pitch is fed to the still is so regulated that the pitch is coked before it is discharged thru the chute 54. In being converted from pitch to coke high boiling compounds, which are non-fluid at the temperatures obtaining in the condenser, are distilled from the pitch and these are, at least to some extent, swept from the still before they are decomposed.

The hot gases and vapors pass from the coking still up thru the heat interchanger 7 0. Au exhauster 71 is provided to draw the hot gases and vapors thru the heat interchanger.

In the heat interchanger the hot gases and vapors are brought into indirect contact with pitch which enters the system thru the line 72, and after being preheated by indirect contact with the hot gases and vapors as it flows thru the coil 73 in the heat interchanger 70, the heated pitch is supplied thru the line 53 to I the still.

'-Hot non-fluid resinous and greasy constituents are condensed and separate from the gases in the lower portion of the heat interchanger. As the gases pass up thru the heat interchanger they are cooled and oils separate from the gases. These oils drain down thru the heat interchanger and more or less completely dissolve the resinous and greasy constituents which separate in the lower portion of the condenser and wash them from the condenser into the receiver 74.

Coke oven gases carry fine entrained particles of pitch, coke, dust, etc. A portion of these entrained impurities will be removed from the gases in the still 52. When the cleaning treatment to which the gases in the still are subjected is not sufiicient to complete ly remove the entrained impurities, the gases leaving the still and passing into the condenser will contain at least some entrained particles.- Entrained solid particles which separate from the gases in the lower part of the condenser may be washed from the condenser by the oils which separate in the condenser and will contaminate the distillate drawn off into the tank 74. Where a clean oil product is desired, the gases and vapors leaving the still 52 may be passed thru a suitable gas cleaning device such as an electrical precipitator or a hot pitch scrubber before entering the condenser 70.

I claim:

1. The method of condensing vapors resulting from the distillation of coal tar inwhich greasy constituents of high boiling points are distilled from the tar together with oils of lower boiling range and recovering the condensate while preheating the tar, which comprises passing the vapors resulting from the distillation up thru a condenser, cooling the vapors below the dewpoint of greasy constituents in the lower part of the condenser by bringing them into indirect heat interchan e relation with the tar to be distilled there y separatin greasy constituents from the vapors in t e lower part of the condenser, further cooling the vapors and separating oils from the vapor in the upper part of the same condenser, allowing the oils to flow down from the upper part of the condenser thru the lower part of the condenser, and thus dissolving the greasy constituents in the oils.

2. The method of distilling tar and recovering distillate therefrom, which comprises bringing coal tar into direct contact with fresh hot tar-laden coal distillation gases in the form of a fine intense spray and thoroughly spraying the gases with the tar so as to melting point by vaporizing from the tar constituents including resinous or greasy con- .stituents of high boiling range, passing the clean the gases and producing pitch of high' the oils to drain down thru the condenser and dissolte the higher boiling resinous: and. greasy constituents Whichseparate from the gases in the lower part of the condenser, and

then drawing off from the condenser a solution of the higher boiling resinous and greasy constituents in the oils, which solution comprises constituents originally present in the hot" coal distillation gases and constituents originally present in the .tar. In testimony whereof Iaflix my signature.

- Y S.P.M]LLER.

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