US1862494A - Distillation of tar - Google Patents

Description

June 1932- s. P. MILLER DISTILLATION OF TAR Filed June 7, 1927 2 Sheets-Sheet l ATTORNEYS June 7, 1932. s. P. MiLLER 1,862,494

DISTILLATION OF TAR ZSheets-Sheet 2 Filed June 7, 1927 7 I lNvEw ATTORNEYS Patented June 7, 1932 UITED STATES PATENT OFFICE STUART PABMELEE MILLER, OF TENAFLY, NEW JERSEY, ASSIGNOR TO THE BARRETT COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY DISTILLATION OF TAR Application filed June 7, 1927. Serial No. 197,030.

' 5- to distill tar and to produce clean oils and pitches by such distillation. The invention will be described more especially with reference to its application to coke ovens.

In the ordinary operation of by-product 11-- coke ovensthe gases produced by the coking operation pass from the individual ovens through uptake pipes and goose-necks toa collector main common to the ovens of the battery. The foul gases leave the ovens at high temperature, e. g., 600 to 700 C. or higher, and carry a considerable proportion of volatilized tars and oils as well as solid particles of coke, coal, carbonand other impurities. Ordinarily the gases are cooled as rapidly as possible by the application of sprays of ammonia liquor or ammonia liquor and tar in the goose-necks and collector main, the heat in the gases being thereby dissipated and lost. The rapid cooling causes separation of tar containing heavier oils in the collector main. Further cooling is effected in the cross-over main which connects the collector main to the condensing system and an additional quantity of tarcarrying both heavier and lighter oils is thus separated. The collected tar is shipped ordinarily from the coke-oven plant to a tar distillation plant for distillation and separation of'the oils and the production of pitches of varying qualities. The expense of handling and of the coke ovens is utilized to distill tar and distilling the tar adds to the cost of production of the distillation products.

It is the object of the present invention to provide a method which permits the dis 2 tillation of tar at a coke-oven plant, the uti lization of the heat of the coke-oven gases for that purpose, and particularly the regulation of the temperature of the gases during the distillation and the production of ""2 clean oils directly by such distillation, to-

gether with pitches having various qualities and characteristics required by the trade.

According to the present invention the heat of the coke-oven gases as they come from constituents, i. e.,

to separate vaporizable oils therefrom by spraying or otherwise bringin the tar into intimate contact wit-h the hot co ze-oven gases. The desired distillation can be. effected in various types of apparatus as, for example, in the collector main or in uptake-pipe stills as described in the application of" George E. Brandon, Serial N 0. 154,7 46, filed December 14, 1926, or in any other suitable apparatus in which the intimate contact between the hot gases and the tar can be obtained. The intimate contact between the tar and the hot coke-oven gases cools the gases. Partial condensation of the constituents, more particularly those of a tarry character, results. The scrubbing of the gases with tar tends to effect the separation of such tarry constituents. At the same time the gases are enriched in the vapors of the more volatile oils derived from the distillation of the'tar. I

The temperature of the hot coke-oven gases as they come from the ovens is relatively high and under some circumstances may be too high to effect the desired distillation without danger of heating the tar to temperatures at which too hard pitch maybe formed. It is the primary purpose of the present invention to permit regulation of the temperature of the gases employed for distillation and this is accomplished by the utilization of oils derived from the gases. These oils may be introduced independently of the 'tar to the distillation apparatus or they may be mingled with the tar andintroducedthere with. The oils so introduced will absorb considerable quantities of heat both as sensible heat and as latent heat of vaporization, and consequently by varying the amount of the oils thus introduced to the system the temperature of the gases may be regulated at will and over-heating of the tar and pitch can be avoided. Another advantage of the operation as described is that dirty oils or those contaminated with tar constituents can be utilized in regulated quantity to'cool the gases. The oils will be distilled with the tar and the vapors therefrom will join the oil vapors which are separated from the tar by the distillation. The vapors thusenriched ill) may be condensed subsequently to produce clean oils.

The dew points of the gases for the several constituents car 'ied therein as vapor are lower than the normal boiling points of these constituents and by suitable regulation of the temperature of the gases during the distillation and especially during the subsequent treatment of the gases hereinafter described, it is possible to retain the desired oils therein while the tarry constituents are condensed. Thus, by sufficiently lowering the temperature of the gases during distillition in the collector main, for example, all or substantially all of the tarry constituents can be converted into theliquid phase while the oils remain as vapors therein. The temperature of the gases should, to accomplish the intended purpose, be maintained above the dew pointof the gases for the most readily condensable oil constituent desired so that substantially all of the oils will be retained and will be carried over with the gases from the collector main. The tarry constituents which are introduced tothe gas stream for the purpose of distilling the tar do not separate readily from the gases but tend to remain therein as tar fog.

The 'tar fog can, however, be separated readily from the gases by passing the gases through a scrubber or series of scrubbers in which the gases are brought into intimate contact at the proper temperature with a scrubbing medium such as tar or oil or aqueous liquids such as ammonia liquor at the lower temperatures. By utilizing a suitable scrubbing medium and by conducting the scrubbing operation at the temperature necessary to avoid condensation of the oil constituents from the gases, these gases may be withdrawn from the scrubber or scrubbers with substantially all of the oil constituents in the form of vapor therein and substantial- 1y free from tarry constituents which would contaminate the condensate therefrom. The taror oil employed in scrubbing the gases may be distilled subsequently to recover the oil and tarry or pitch constituents therefrom.

The gases from which the tar fog has been removed by the scrubbing operation will upon total condensation yield a mixture of oil constituents. The dew points of the gases for these several constituents are different and it=is possible by fractional condensation to recover oils having varying characteristics. These oils being substantially free from tarry constituents and other impurities, are in condition for immediate utilization for the purposes to which oils commonly'obtained by distillation of far are adapted.

The distillation of tar by means of the hot coke-oven gases will be described more particularly with reference-to the operation of the collector main although as hereinbefore indicated other apparatus may be adapted for the purpose of the invention. The amount of heat which is available in the gases from all of the ovens of the battery is many times that required to distill all of the tar and oil recovered from that battery. Normally, therefore, it will not be necessary to use the gases from all of the ovens unless a quantity of tar is available from other sources. The invention is not limited, however, to the distillation of tar from a single battery of ovens. Tar from other ovens or from sources such as gas retorts, vertical retorts and water-gas sets, may be distill-ed in accordancewith the invention. It is to be understood, therefore, that provision can be made for utilizing the heat from any desired number of ovens. Usually, however, it is sufficient to employ the gases from only few of the ovens and these may be connected conveniently to a short collector main or other distillation apparatus in which the distillation is conducted.

With such an apparatus the coke-oven battery and by-product recovery system will not require substantial modification, that is to say, the ovens of the battery may be connected to'the usual collector main and a cross-over main may convey the gases from the collector main to the condensing system in which tar and oils are normally separated from the gase. For the purpose of distilling tar a selected number of ovens may be connected, for example, by separate uptake pipes to a short collector main which may be disposed conveniently at the rear-of the ovens, suitable valves being provided to permit diversion of the gases from the ovens into the ordinary collector main or into the short collector main so that distillation can be conducted in the latter when desired.

The gases in the ordinary collector main may be subjected to cooling in the usual manner with sprays of ammonia liquor or ammonia liquor and tar and the tarry constituents thus separated may be Withdrawn for redistillation. The gases may be conveyed then to the usual condensers and further cooled therein to separate oil constituents. The oils thus recovered are usually contaminated to a greater or less extent with tar constituents and these oils may be utilized in accordance with the present invention to regulate the temperature of the gases in the short collector main. hus permitting the control of the distillation of tar therein.

The tar to be distilled may be sprayed into the short collector main through spray nozzles provided for that purpose, thus ensurin the desired intimate contact of the gases with the tar therein. Or as a substitute for or adjunct to the spray nozzles, agitating devices may be provided in the collector main to thoroughly agitate the tar therein and to throw particles thereof into the gas stream for the purpose of facilitatingthe desired intimate contact between the tar and thegases. Various forms of agitating devices may be utilized for this purpose.

To ensure the proper cooling of the gases and consequently the maintenance of the desired temperature in the distilling apparatus, oil in any desired proportion maybe introduced thereto through separate spray nozzles from any suitable source of oil such as that derived from. the condensers hereinbefore described. Instead of introducing the oil separately to the collector main the oil ma. be mingled in the desired proportion wit the tar to be distilled and the mixture can be introduced then through the'spray nozzles or otherwise to the collector main.

Preferably the short collector main should be flushed with an excess of tar or oil or tar and oilso that any hard pitch which may tend to form therein will be dissolved immediately and carried away in the stream. of tar which accumulates in the bottom of the main. This pitch may be recirculated if desired for further distillation additional quantities of oil being added either through the spray nozzles or directly to the pitch as-may be required to maintain the desired temperature of the gases in the distillation apparatus. The pitch produced may be withdrawn and utilized as such. By regulation of the temperature of the gases and consequently the extent to which the distillation is. effected in the distillation apparatus, pitches having the desired qualities may be produced and various products having difierent qualities and characteristics may be made available, there.- fore, for commercial use.

The gases escaping from the short collector main or other distillation apparatus .atthe temperature requisite for the retention of the oil constituentsin the vapor phase are delivered at such temperature to the scrubber or scrubbers which are disposed preferably closely adjacent to the collector main in order that the temperature of the gases may not be reduced unduly before the separation of the tarry constituents is} accomplished. The scrubber or scrubbers may consist of a tower or towers through whichthe gases ascend in contact with a descending stream of tar or oil flowing over suitable bafiiing devices to ensure intimate contact between the tar or oil and the gases in thescrubber. The tar or oil which is withdrawn fromthe scrubber may be recirculated therein and heating or cooling means may be provided to regulate the temperature of the scrubbing medium as it enters the scrubber soasto maintain the proper temperature of the gases during the scrubbing operation. The I temperature which is thus maintained will vary, depending upon the character of the products which are to be separated.v One or more scrubbers maybe employed and different scrubbing media may-be utilized therein to remove the contaminating constituents from the gases, leaving these gases with only clean oil vapors for subsequent condensation.

From the scrubber or scrubbers the gases carrying the condensable vapors may be conducted through suitable condensing apparatus including, if desired, a total condenser or, alternatively, fractionalcondensers or other fractionating apparatus designed to permit the separation of separate fractions of the oil constituents. One total oil fraction may be collected if the gases are cooled in one step to the lowest desired temperature. Several oil fractions may be recovered if the gases arecooled by stages in coolers designed'for separate collection of oils corresponding to the individual cooling steps.

. The invention is of more or less general application to the distillation of tar to pro.- duce pitches and to recover clean oils. It will be further illustrated by the following more detailed description taken with the accompanying drawings which show apparatus adapted for the practice of the process, but it is intended and will be understood that the invention is not limited to the specific details illustrated in the drawings, in which Fig. 1 is a plan view of a portion of a cokeoven plant illustrating the application of the invention thereto; and

I Fig. 2 is an enlarged sectional view of the short collector main and the scrubbers connected therewith.

Referring to the drawings, 5 indicates th battery of coke ovens in which the individual ovens are connected by uptake pipes and goose-necks 6 to a collector main 7 having a centre-box 8 from which the cross-over main 9 conveys the gases and vapors to condensers 10 and 11. The gases may be cooled in the collector main and in thegoose-necks leading thereto by ammonia liquor or ammonia liquor and tar introduced through spray nozzles 12 which are supplied through a pipe 13 from a source of ammonia. liquor such as a'storage tank 14:. Further cooling is effected in the condensers 10 and 11 and the gases are delivered thence to an exhauster 15 and to the usual equipment for the separa tion oflight oils and ammonia from the'gases. The tarwhich separates in the collector main 7 may be withdrawn from the centre-box 8 and delivered, together with tar separated in' the cross-over main, to a decanter 16 wherein the tar is separated from the ammonia liquor, the latter being delivered to the tank 14. The tar may be delivered to a tank 17 wherein it is stored for distillation in accordance with the present invention. The oils separated in the condensers 1'0 and 11 may be withdrawn through a pipe 18 to a decanter 19 wherein ammonia liquor is separated from the oil. The oil may be'stored then in a tank 20. for use as a cooling agent for :the gases during the distillation of the tar as hereinafter described.

A short collector main 21may be provided, for example, at the rear of the ovens and maybe connected to the desired number of ovens by uptake pipes and goose-necks 22 whereby the hot gases are delivered to the short collector main for utilization therein in the distillation of tar. The tar to be distilled may be delivered through a pipe 23 from the tank 17 to the spray nozzles 24 in the short collector main 2 1 and the goosenecks 22, being therein mingled intimately with the hot gases for the purpose of etfecting the desired distillation. The cooling of the gases is accomplished by delivering oil accumulated in the tank through a pipe 25 to spray nozzles 24 in the short collector main designed to supply the oil concurrently with the introduction of tar so that the oil is also mingled with the gases and is thus able to absorb the desired proportion of the heat of the gases for the purpose of reducing the temperature to the desired extent. It is to be understood that the quantity as well as the character of oil thus supplied may be varied from time to time and may be regulated in accordance with the desired distilling effect to be accomplished in the short collector main and the initial temperature of'the gases therein. Instead of introducing the oil separately it may be mingled with the tar in the tank 17 or in a separate mixing tank 26 and delivered therefrom to the short collector main. Tar or oil from an outside source may be supplied from tank 26'.

To facilitate the operation of the short collector main, tar-or oil or both'm-ay be delivered thereto through pipe 27 so as to flow through the main and flush the bottom thereof. The pitch produced by the distillation maybe withdrawn through the pipe 28 for utilization as such or all or any portion thereof may be recirculated through the pump 29 and pipe 30.

The gases and vapors resulting from the distillation are withdrawn through a pipe 31 and are delivered to a scrubber 32 comprising a column with ballles33 therein over which the scrubbing medium is adapted to flow in intimate contact with the gases. The scrubbing medium such as tar or oil may be introduced at the top of the column to a pipe 35. It may be withdrawn through a pipe 36 at the bottom of the column to a tank 37 from which it may be recirculated through a pump 38 and the pipe 35. A heat exchanger 39 may be connected to the pipe for the purpose of regulating the temperature of the scrubbing medium. Heating or cooling agents can be introduced to the heat exchanger 39 through a pipe 40'and Withdrawn through a pipe 41.

The scrubber may in some cases beo-pere ated at a temperature equal to or slightly higher than the gas temperature and the tar or oil supplied thereto should in such cases be at such a temperature as toavoid reduction of the quantity of the oil vapors in the gases. The heat exchanger permits the maintenance of the temperature at the proper point.

The scrubber may be used as-a means for alteringthe composition of the scrubbing oil or of the condensable vapors in the gas stream. If, "for example, it be desirable to convert an oil of relativelywideboiling range intoan oil of relatively narrow boiling range, the oil will be circulated through the scrubher at such a temperature as will cause'the lighter constituents in the scrubbing oil to be absorbed by the gases. Likewise, the gases may give up "to the scrubbing oil some of the heaviercondensable vapor. The scrubhing oil Willthu's be freed to the desired extent of lighter oils and will be enriched in heavy oils. The gases will be enriched in light oil vapors and may be freed to some extent of heavy oil vapors. The scrubber in such a case functions somewhat as a rectification column in that it provides for a partialseparation of light from heavy oils. It Willbe understood th'at'the scrubber may be operated in a great "many different Ways as respects type of oil used for scrubbing, temperature of oil, temperature of gas at the inlet, temperature drop through the scrubber, quantity of scrubber oil utilized, etc.

To permit operation in the manner described two or'more similar scrubbers should be provided preferably. In the first scrubberthe tarry constituents, together with solid particles of coal, coke, etc., which are carriedover by the gases, will to a large extent be removed. The gases may be conducted then to the second scrubberwherein they are subjected to further treatment with oil or any other suitable scrubbing medium for the purpose of modifying the character of the scrubbing medium or of the gases as desired.

The gases leaving the second scrubber, for example, through a'pipe 42 may be delivered thereby to a series of condensers 43, for example, of the fractional type in which the gases are cooled in stages for the purpose of separating the oils in fractions from the gases. The gases, after such cooling, may be delivered through a pipe 44 to the exhauster 15 and mingled with the gases from the remaining ovens of "the battery.

The apparatus as described permits the distillation of tar and the utilization for this purpose of a portion of the heat in the coke oven gases, the temperature ofsuch gases being regulated by the introduction of variablequantities of oil for the purpose of absorbing surplus heat and thus maintaining the temperature at the point designed to accomplish the most effective distillation of the tar for'the purpose of producing pitches of the desired quality. The gases, subsequently freed to a large extent from tarry constituents, are condensed to produce clean oils as distillation products.

The invention depends upon this regulated cooling of the gases with oil applied in the proportion necessary to accomplish the intended purpose. It has been described more particularly with reference to distillation in a short collector main, but it may be utilized similarly in other types of tar-distillation apparatus in which the heat available in coaldistillation gases is utilized to distill vaporizable constituents from the tar.

Various changes may be made, therefore, in the details of operation and in the apparatus employed therefor without departing from the invention or sacrificing any of the advantages thereof.

I claim 1. The method of distilling tar, which comprises introducing varying quantities of oil into hot coal distillation gases to regulate their temperature, heating and distilling the tar by contact with the resulting partially cooled gases and scrubbing with tar or oil the resulting gases enriched in oil vapors by the distillation of tar to remove tarry constituents therefrom.

2. The method of distilling tar, Which comprises spraying oil from the condensers of acoal distillation plant into hot coal distillation gases thereby partially cooling the gases, then distilling tar by bringing it into contact with the resulting partially cooled gases, and condensing distillate from the resulting enriched gases.

3. The method of obtaining tar and treating the same, which comprises fractionally cooling hot coal distillation gases to separate tar and a tarry oil therefrom, spraying the tarry oil into fresh hot coal distillation gases to partially cool the same and then distilling the tar by bringing it into contact With the resulting partially cooled gases.

In testimony whereof I afiiX my signature.

STUART PARMELEE MILLER.

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