US2040099A - Treatment of hydrocarbon material and apparatus therefor - Google Patents

Description

s. P. MILLER 2,040,099

TREATMENT OF HYDROGARBON MATERIAL AND APPARATUS THEREFOR 2 Sheets-Sheet 1 Filed Feb. 11, 1931 II E; Cbrbo/afe ll INVENTOR ATTORNEYS 5. P. MILLER TREATMENT OF HYDROCARBON MATERIAL AND APPARATUS THEREFOR Filed Feb. 11, 1931 2 Sheets-Sheet 2 INVENTOR ATTORNEYS Patented May 12, 1936 UNITED STATES PATENT OFFICE TREATMENT OF HYDROCARBON MATERIAL AND APPARATUS THEREFOR N. Y., a corporation of New Jersey Application February 11, 1931, Serial No. 514,964

1 Claim.

This invention relates to the treatment of hydrocarbon material such as tar or oil for the recovery of tar acids and the production of a tar residue. The invention includes both the 5 method of operation and apparatus therefor.

The process of the invention is applicable to the treatment of tars such as coke-oven tars, gas-retort tars, vertical-retort tars, low-temperature tars and other tar-acid-containing hydro- ]0 carbon materials such as coal-tar distillates. It may be applied to raw, moisture-containing tar, dehydrated tar, topped tar or to the separate treatment of tar fractions such as heavy tar from the collector main of a coke-oven plant or the light tar or tarry oils from the condensers of such a plant. It may be applied to the treatment of mixtures containing coal tar. It will be described more particularly as applied to the treatment-of coke-oven tar, but the invention is not limited thereto.

In order to recover tar acids from tar, it is customary to distill the tar and then extract the tar acid from the distillate by treatment with a caustic solution such as sodium hydroxide. The aqueous caustic solution is circulated thru the distillate oil and the mixture of oil and aqueous solution is then allowed to settle out and the aqueous carbolate solution produced is separated from the resulting neutral oil by decantation.

According to the present invention, the tar acids are removed from tar or other hydrocarbon material without first obtaining an acid-oil distillate. Tar acids are volatilized from the tar by a selective process which inhibits the distillation of neutral oil and greatly reduces the ratio of neutral oil to tar-acids distilled from the tar. The vaporization of the tar acids from the tar takes place in a current of inert gases. The resulting gases and vapors are treated with an alkaline reagent for the removal of tar acids and this treatment is carried out without any substantial cooling of the vapors and condensation of neutral oil therefrom. The resulting inert gases which comprise vapors of neutral oils are then recycled for further selective vaporization of tar acids from the tar.

The inert gas employed in the vaporization is a gas substantially chemically inert to tar acids and caustic soda. It is employed as a carrier for the tar acids and effects their removal from tar by vaporization in a system operated at pressures higher than the partial pressure of the tar acids in the tar at the operating temperature. Steam is the inert gas ordinarily employed. If

raw tar is being treated the moisture present in the raw tar will be converted into steam during the treatment and this steam will be circulated in contact with the tar to effect vaporization of the tar acids. Because of the circulation of the steam or other inert gas during the distillation the tar acids vaporize at a temperature below their normal boiling points. By treating the mixture of steam and tar acid vapors resulting from the vaporization with an alkaline reagent such as caustic soda, tar acids are removed as carbolates and are thus recovered from the tar. The neutral oils vaporized from the tar with the tar acids are condensed only in small part, and the uncondensed portion is recycled and passed thru the vaporizer in which the tar acids are vaporized; the presence of these neutral oil vapors in the vaporizer prevents or represses the vaporization of neutral oils from the tar. large amount of tar acids are vaporized and recovered from the tar without the production of a large amount of neutral oil distillate. The heat necessary for the distillation is thus considerably less than would :be required for the usual carbolic oil distillation, and the tar acids are recovered at a substantially reduced cost.

The residue from this treatment which is tar from which at least a portion of the tar acids have been vaporized is referred to herein as a dephenolized tar residue. Although it may contain some tar acids, a large portion of its tar acids have been vaporized from it and therefore the residue is referred to as a dephenolized residue and the vaporizer in which the operation takes place is referred to as a dephenolizer.

The heat for the selective vaporization will ordinarily be supplied by heating the tar before it enters the dephenolizer in which the tar acids are vaporized. Preferably the tar will be heated above its initial boiling point and lower boiling constituents will be flashed as the heated tar enters the dephenolizer. The recycled gases which include the neutral oil vapors but no substantial amount of tar acid vapors are recycled thru this dephenolizer. These gases are brought into direct contact with the hot tar, or the hot residue from the flashing operation, and tar acids are vaporized from it at a temperature below their normal boiling points. The latent heat required for this vaporization may be supplied by the hot tar or residue in the dephenolizer or the gases may be heated before they enter the dephenolizer. The dephenolizer or the caustic extractor may be jacketed or otherwise equipped with means for heating for this purpose. However, according to a preferred arrangement, the entire heat necessary for carrying out the operation is supplied to the tar before it enters the dephenolizer.

The rate at which the gases are passed thru the dephenolizer will vary, depending upon the percent of tar acids which it is desired to recover from the tar, and the temperature at which the gases and vapors leave the dephenolizer may vary accordingly. If coke-oven tar containing about three percent of tar acids is being treated,

good recovery is obtained using 1'75 to 200 cubic feet of gas per gallon of tar treated if the temperature at which the gases leave the dephenolizer is in the neighborhood of 175 C. Using a larger volume of gas the same percentage of recovery of tar acids is obtained with a lower outlet temperature. For example, by increasing the rate of gas recirculation to 3 00- to 350 cubic feet per gallon of tar treated, the temperature at which the gases leave the dephenolizer may be dropped to around C. to obtain a tar acid yield comparable with that obtained using to 200 cubic feet of gasper gallon of tar and an outlet temperature of 175 C.

From the dephenolizer the gases and vapors pass to a caustic extractor. The extractor is preferably heavily insulated to prevent condensation of vapors. By using hot, concentrated caustic with a vapor pressure substantially equal to the vapor pressure of the steam in the gases and vapors, there will be substantially no condensation or vaporization of water within the caustic extractor which would result in a substantialchange in the temperature of the circulated gases. Some heat is evolved by neutralization of the tar acid vapors with the caustic, but there is no substantial change in the temperature of the gas stream as it passes thru the caustic extractor. Generally, caustic soda will be used in scrubbing the tar acids from the gases. Caustic potash or sodium sulfide solutions may be employed in some cases. Tar acids carried by the gases in vapor form combine with the sodium or other metal of the caustic solution to form phenolates of sodium or other metals which remain in solution with the caustic until the absorbing capacity of the solution is exhausted or reduced to the desired extent.

It is advantageous to recycle the caustic solution thru the caustic extractor so as to bring a large volume of scrubbing liquid with a large surface of exposure into contact with the gases even though by recycling it is necessary to recycle carbolate which has formed with the caustic. The caustic-carbolate solution is preferably recycled in a continuous manner with the gradual addition of fresh caustic and continual withdrawal of caustic-carbolate solution. The carbolate formed in the extractor may contain, for example, 50 to 70%- of tar acids and will also include excess caustic, sodium carbonate, water, etc., in smaller amounts. The tar acids may be recovered from the-carbolate by the usual methods, as by acidification with carbon dioxide, etc. The caustic soda absorber may be constructed in stages so that a completely saturated carbolate can be made in the first'stage'or in the lower compartment of as'eries of compartments (the gases passing upwards thru the series) while there is still an' excess of caustic in the second or upper stage. In this way the caustic solution can be exhausted of caustic soda and at the same time the tar acid vapors extracted with substantial completeness from.the gases.

A selective extraction of the phenols or tar acids from the admixed gases and vapors can be effected by installing and employing several caustic scrubbers and carrying out the scrubbing operation in stages. If, for example, a carbolate rich in phenol and a second carbolate rich in higher boiling tar acids including cresols is desired, a three-stage absorber or scrubber canbe employed with the supply of caustic to the lower or first section or scrubber equivalent only to the phenol entering the system with the inert gas circulated upwards thru the scrubber. The carbolate will be allowed to become completely saturated and to build up to the maximum percent of the phenol before any is withdrawn. Phenol being more strongly acidic than the higher phenols, e. g. cresols and xylenols, will replace these higher phenols from their combination with caustic soda so that when the caustic soda is consumed and a carbolate solution is produced, the passing of additional gases carrying phenol and higher phenols will result in the driving ofi of higher phenols and the absorption of phenol until the carbolate solution in the lower section will be greatly enriched in sodium phenolate while the higher phenolates will be absorbed in the succeeding section. With a multistage operation of this kind it is possible to produce carbolates predominating in phenol, the cresols, the xylenols, etc., as desired. If still more selective extraction is desired the carbolate absorber may be constructed in a larger number of stages, e. g. five or six, and a plurality of different carbolates obtained.

It is not necessary, according to this process, to effect complete neutralization of the tar acids in the extractor and in a commercial plant complete removal of the tar acids will ordinarily not be effected because of the practical difficulty in obtaining contact of the alkaline reagent with every particle of the gas. The oil vapors in the gases returned to the dephenolizer may contain as much as three percent, for example, of tar acid vapors, although under good commercial operating conditions they may contain not more than a few tenths of a percent of tar acids.

The operation will ordinarily be carried out under approximately atmospheric pressure, altho a vacuum or pressure greater than atmospheric may be employed. In order to maintain a constant pressure in the apparatus, gases and vapors will be bled from the cycle to compensate for the steam and gases generated and other changes in gas volume due to distillation of water from the caustic, etc. A bleed condenser is advantageously provided to recover oil present as vapor in the bleed. The bleed line is preferably located in the line which introduces the recycled gases into the dephenolizer.

Fresh steam may be introduced into the dephenolizer in addition to that generated from the moisture in the tar, or other gases may be introduced into the system as by introducing nitrogen, etc., preferably heated, into the dephenolizer to aid in the vaporization of the tar acids from the tar. In that event the bleed will be sufiicient to compensate for such additions.

By the selective vaporization of tar acids in an atmosphere containing neutral oils from forty to eighty-five percent or more of the tar acids in the tar may be recovered directly in the carbolate without first producing a tar-acid and neutral-oil-containing distillate such as is customary at the present time. Althow complete removal of tar acids from the'tar will not ordinarily be effected by this process,.the treated tar will contain a lower percentage of tar acids than the product obtained by the removal of thesame'percent of volatile matter from the tar by straight distillation. The dephenolized residue may be used for fuel or for blending with high melting point pitch to produce road tars, etc., or for any similar purpose.

By operating at sufliciently high temperature, e. g., with a vapor, temperature of ZOO-250 C. or more enough neutral oils may be flashed from the tar in addition to the tar acids which are flashed with them and those that are selectively vaporized so that refined tars suitable for use as binders in making road-tars or which may be employed in admixture with other material for road binder and road surfacing material can be made by this process of selective tar acid vaporization. The additional neutral oils which are flashed from the tar will be bled ofi thru the vent from the cycle-and are. advantageously condensed and recovered from the bleed offgases.

The tar which is subjected to the dephenolizing treatment should be heated to a suitable temperature, for example, somewhat above 100 C. before the inert gases are brought into contact therewith, although this will depend upon the quantity of gas recirculated per unit of tar. acids recovered. The tar may be preheated to the required temperature by the use of a steam preheater or by the use of waste heat from the flue gases in the fiues at coke or gas plants or by the use of waste flue gases from tar stills, steam boiler plants, etc., or by the use of heat interchangers in which hot tar or pitch is employed as the heating medium or by separate heating stills, etc.

Where the recovery of tar acids from the tar is carried out at coal distillation plants at which coal tar is produced, such as coke oven plants or gas plants, the tar separated from the gases at an elevated: temperature may be kept hot and employed in a heated condition. In many cases the temperature will be sufiicient for carrying out the tar acid removal process without added heat or at least without any great amount of additional heat. Where the collector mains'of a coke oven plant are operated at high temperature with the use of hot tar for flushing the main, the hot tar drawn off from the mainmay be at a' sufficiently high temperature so that it does not require further heating and so that it can be led directly from the main to the apparatus for the selective vaporization.

In the case of an ordinary tar still containing a large batch of tar, the still can be heated until the tar is at the proper temperature and inert gases can then be recirculated thru the tar, the resulting gases and vapors passed thru the caustic solution and the gases recirculated until the tar acid oils have been driven off to the desired extent after which the recirculation can be stopped and if desired, the still heated to a higher temperature to eiiect distillation of the dephenolized tar. Where the tar is heated in a pipe still and the heated tar discharged into a vapor box or vapor separating chamber, the initial heating of the tar can be so regulated that the tar will be at the proper temperature in the vapor box and the current of inert gases can be passed thru the tar in the vapor box to remove tar acids, after which the dephenolized tar can be heated to a higher temperature by circulation thru another pipecoil which discharges into another vapor-separating chamber, etc.

The removal of tar acids from the tar can be carried to the point where the tar is practically completely stripped or nearly stripped of tar acids or. to the point where onlythe lower boiling acids, for example, the phenols and the cresols, are removed and recovered. A partial removal of the more readily vaporizable tar acids can be effected without removing the higher boiling and more difficultly removable acids. So also the removal can be carried out in stages, for example by passing the hot tar thruv a series of scrubbers where it is scrubbed by the inert gases and with recirculation of the inert gases from one scrubber thru the-tar acid absorber and back to the same scrubber. In such multi-stage extraction of tar acids the carbolate solutions produced will differ from each other, the carbolate solution from the first scrubbing operation giving a carbolate richer in lower boiling tar acids, while those from the successive scrubbing treatments will give carbolate solutions richer inhigher boiling acids. 7

Oil vapors will in many cases serve satisfactorily as the gaseous medium employed for the removal of the tar acids from the tar. particularly be the case with tars containing a large percentage of the lower boiling oils, for example tars containing benzol, toluol, the xylols, solvent napthas, etc; and especially when tars free from water are treated. By heating the tar to the point at which these lower boiling oils are vaporized, the vapors may be recirculated thru the tar and the caustic solution. These oil vapors serve as the inert gases employed in the process. I

The recovery of tar acids from tars, according to the present invention, may be carried out batchwise or continuously, i. e., from successive batches of tar or from tar which is continuously supplied, and with continuous discharge of the dephenolized tar and likewise with batchwise or continuous operation of the caustic absorber using succesive batches of caustic soda solution for forming phenolates or supplying additional fresh caustic continuously and withdrawing the carbolate solution continuously. With batch-wise operations the caustic absorbers may be installed in parallel or in duplicate with piping arranged for allowing saturated carbolates to be produced first in one and then in the other absorber. At tar distillation plants, particularly at continuous tar distillation plants, with continuous, supply of tar to the dephenolizing scrubber the system of dephenolizing can be made a part of the distillation unit so that it will function continuously and require no labor in addition to that normally required for the continuous distillation.

At plants employing continuous stills in which the tar is heated in a pipe coil or in a series of pipe coil stills which discharge into vapor separating chambers, the dephenolizing scrubber may be one of the vapor separating chambers and the dephenolizing operation can be carried out continuously as a part of the continuous distillation using the tar when it has been heated to the proper temperature for the dephenolizing treatment and subsequently heating the dephenolized tar to a higher temperature to complete this distillation. In such a case the inert gas would be recirculated from the vapor separating chamber of the still, thru a caustic scrubber back to the vapor separating chamber.

The invention is further described in connec- This will tion with the accompanying drawings, but it is intended and is to be understood that it is not limited thereto.

Fig. 1 shows dephenolizing apparatus in connection with a pipe still;

Fig. 2 shows apparatus for two-stage dephenolization;

Figs. 3 and 4 show difierent types of caustic absorbers that may be used; and

Fig. 5 shows dephenolizing apparatus in connection with a barrel still.

In Fig. 1, a tar heater is shown'at l for heating the tar. The tarv is introduced thru the pipe 2 and heated as it passes thru" the coil 3. The heated tar is sprayed thru the nozzles 4 into the dephenolizer 5. 6 is a caustic extractor. Both the dephenolizer and caustic extractor are shown as packed towers. Inert gases containing vapors of both tar acids and neutral oils pass from the dephenolizer 5 thru the main 1 into the caustic extractor and arereturned from the caustic extractor to, the dephenolizer thru the main 8. The gases are recirculated by the blower 9.

The gases entering the bottom of the dephenolizer comprise neutral oil vapors. The tar sprayed into the gases, is flashed, and vapors pass 01f thru the main 1 to the caustic extractor 6. The residue flows down over tile or other baffiing means in the dephenolizer. The inert gases and neutral oil vapors enter the bottom of the dephenolizer and inpassing up thru the tower selectively vaporize tar acids from the residue from the flashing operation. The gases which pass oiT from the top of the dephenolizer thru the main 1 contain vapors of both tar'acids and neutral oils. The dephenolized residue is drawn off thru the line I into the storage tank I I.

The gases and vapors pass from the dephenolizer to the caustic extractor in which they are sprayed with caustic thru the spray nozzles l2. The tar acids react with the caustic and form carbolate and are removed from the gas thereby. A portion of the caustic-carbolate solution which collects in the bottomof the extractor is recirculated by the pump l3 thru the line l4 and the heat interchanger I into the sprays l2 where it is again sprayed into the gases. Fresh caustic is added thru the pipe I6, preferably continuously. The excess of caustic carbolate solution is drawn off thru the line l1, preferably in a continuous manner into the storage tank Hi. This is acidified for the recovery of tar acids in the usual way. The temperature of the caustic sprayed into the gases is controlled by the heat interchanger 5 to compensate for any temperature loss resulting from evaporation of water from the caustic solution. With proper regulation there is substantially no condensation of neutral oil vapors in the extractor, except for a small amount of neutral oil absorbed and held in solution by the carbolate.

The gases which leave the extractor thru the main 8 may be substantially free from tar acids, and at any rate contain neutral oil vapors in a relatively larger amount than they contain tar acid vapors.

A bleed line l9 open to the atmosphere either directly, or thru a condenser, or thru a seal is provided to maintain atmospheric pressure or nearly atmospheric pressure within the system. A bleed condenser 20 is advantageously added to condense oils and steam from the other gases which are bled to the atmosphere. The condensate is collected in the receiver 2|. The oil oils altho ordinarily in. this condensate is composed'largely of neutral it contains a small percentageof tar acids.

The apparatus of Fig. 2 provides a twostage dephenolizing treatment. The apparatus used in each stage is similar to that shown in Fig. 1. The partly dephenolized tar from the first dephenolizing scrubber 20 escapes thru the line 2| and is passed thru a reheater 22 and then thru a second dephenolizing tower 23 where it is subjected to a further and similar dephenolizing treatment, the resulting dephenolized tar escaping thru the line 24 to a place of storage or of distillation, etc. In this arrangement part of the phenols and particularly the lower boiling phenols, which are the more volatile, are largely extracted in the first dephenolizing tower while further extraction will take place in the second dephenolizing tower.

In Fig. 3 a two-stage caustic scrubber is shown in the form of an upper and lower section 30 and Si separated by a collecting plate 32 thru which the gases and vapors are permitted to pass upwardly and thru which the caustic solution can overflow from the upper to the lower section. In this tower the caustic solution is supplied to the top of the tower and the carbolate solution drawn off from the bottom. Provision is made for recirculating both the caustic solution and the carbolate in the respective sections of the tower while the excess will overflow from the top to the bottom section. The gases laden with taracid oil vapors will enter the lower section and may completely saturate the caustic solution with carbolate. The removal of tar acid oil vapors will be completed in the upper section to which fresh caustic soda solution can be continually supplied.

The apparatus of Fig. 4 has a three-stage absorber so that, for example, carbolates predominating in phenol, the cresols, the xylenols or any particular tar acid fraction, etc. can be produced. Provision is made for supplying fresh caustic both to the upper section 35 and tothe lower section 36 and for drawing on carbolate solution from the bottom of the middle section 39 and also from the bottom of the lower section thru the respective outlet lines 31 and 38. If, for example, a carbolate rich in phenol and a second rich in the higher boiling acids including cresols is desired, the caustic solution supplied to the lower section will not be more than that equivalent to the phenol entering the system admixed with the steam or other inert gas. The carbolate will be allowed to be completely saturated and to build up to the desired percent of phenol before any is withdrawn. From that point on, caustic equivalent only to the phenol, or slightly less if the maximum enrichment in phenol is desired, will be fed in continuously and carbolate withdrawn continuously from the bottom of the lower compartment. The intermediate compartment 39 will be-operated in the same manner except that the caustic stream will enter the bottom of the third or upper compartment and overflow to the intermediate compartment in which saturated carbolate will be present at all times. This carbolate will be withdrawn continuously at 31 and will contain all of the acids of boiling point above phenol or will be low in phenol and high in the higher boilin acids. The carbolate from the lower compartment will be rich in phenol but may contain some cresols and higher boiling acids. With a larger number of stages a more selective extraction of the tar acids can be obtained by proceeding in a similar manner.

In Fig. 5, a simple fire heated still is shown with provision for forcing inert gas containing neutral oil vapors thru the body of tar in the still. The gas is introduced into the still thru the pipe 4| under pressure by means of the blower 42 and bubbles up thru the tar thru the perforated pipe 43.

Tar acids are vaporized in the still and the resulting gases and vapors pass thru the line 44 to the bottom of the caustic scrubber 45. The gases and vapors escaping from the top of the extractor are returned thru the pipes 46 and 4| and the blower 42 and forced thru the perforated pipe 43 into the bottom of the body of hot tar in the still. The process may be carried out as a batchwise process or a continuous process. If it is carried out as a batch process, when the tar has been heated to a suitable temperature, for example around 150 C., the blower 42 is started and the inert gas is forced thru the body of tar to remove tar acid oil vapors and the resulting vapors and gases pass thru the caustic absorber and the gases and uncondensed vapors which include neutral oil vapors are then returned to the still. After the tar acids have been driven off to the desired extent the recirculation of the inert gas can be discontinued and the still heated to a higher temperature, and by closing the valve 41 in the line 44 and opening the valve 48 in the line 49 the distillate will be carried over thru the line 49 to the condenser 50.

The dephenolizer and caustic extractor are shown herein as spray towers. Other types of gas and liquid contact apparatus may be employed but it is desirable to use apparatus in which there is a low pressure drop in order that a low pressure blower can be used for recirculating the gases thru the system. For example, mechanical spray means may be located in the bottom of the dephenolizer for spraying the tar up into the gases to thus aid in the distillation. Packed towers or plate columns may be used to advantage. Injectors may be used for bringing the tar or caustic into contact with the gases.

By vapor phase extraction of the tar acids from the gases and vapors resulting from inert gas distillation in the dephenolizer and then recirculating the neutral oil vapors thru the dephenolizer selective vaporization of the tar acids is obtained.

The present process has the advantage, among others, of giving the tar acids directly without the separate recovery, shipment and extraction of a large amount of oils, thus making unnecessary the provision of large carbolic oil storage and extraction systems. The process also enables tars to be treated for the recovery of higher percentages of tar acids than can be economically recovered by present day processes due to the troublesome handling of higher boiling heavy oils. The process also yields carbolates and tar acids of high quality, low in sulfur compounds and low in distillation residue, while it enables caustic losses to be reduced to a minimum and enables equipment required to be materially reduced. The process is also of value for recovering tar acids from tar acid oils, particularly those which are contaminated with tar. With low temperature tars or tarry oils from the condensers of high temperature carbonization plants which are usually high in tar acids, the present process enables a high yield of the tar acids to be recovered directly from the tar, and with fractional separation of higher and lower boiling acids, if desired.

It will be understood that variations and modifications can be made in the process as hereinbefore described, without departing from the spirit and scope of the invention.

This application is in part a continuation of my pending application Serial No. 383,859, filed August 6, 1929.

I claim:

The method of recovering tar acids from a hydrocarbon material containing the same and neutral oils which comprises subjecting said hydrocarbon material heated to a temperature above its initial boiling point to successive intimate contacts in a plurality of separate stages with a plurality of streams of hot inert gases containing vapors of neutral oil constituents of said hydrocarbon material to effect a progressive removal of tar acids from said material, then separately bringing each of said streams of gases containing tar acid vapors into contact with one of a plurality of hot alkaline solutions at a temperature above the total condensation temperature of oil vapors in said gases to absorb the tar acid vapors, recycling the resulting streams of gases containing uncondensed neutral oil vapors in contact with the hot hydrocarbon material to selectively distill tar acids therefrom and separately drawing off the several carbolate solutions resulting from the aforesaid contact of the streams of gases containing tar acid vapors with the hot alkaline solutions.

S. P. MILLER.

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