US1942371A - Method of distilling tar - Google Patents

Description

Jan. 2, 1934. s'. .P. MILLER 1,942,371

METHOD OF DISTILLING TAR Filed March 23, 1928 3 Sheets-Sheet l INVENTO fiMW ATTORNEYS Jan. 2, 1934.

s. P. MILLER 1,942,371

METHOD OF DISTILLING TAR Filed March 23, 1928 3 Sheets- Sheet 2 )(Jer s [ana e? ATTORNEYS Jan. 2, 1934. s. P. MILLER 7 METHOD OF DISTILLING TAR 3 Sheets-Sheet 3 Filed March 23, 1928 ATTORNEYS Patented J an. 2, 1934 UNITED STATES PATENT OFFICE METHOD OF DISTILLING TAR Stuart Parmelee Miller, Englewood, N. J., as-

signor to The Barrett Company, New York, N. Y., a corporation of New Jersey Application March 23, 1928. Serial No. 263,990

8 Claims.

This invention relates to improvements in the distillation of tar, tarryoils and pitch and in-,,

In the ordinary operation of by-product coke l ovens, the gases produced by the coking operation pass from the individual ovens thru uptake pipes and goose-necks to a collector main common to the ovens of the battery. The gases, commonly known as foul gases, leave the ovens at high temperatures, for example, at 600 to 700 C., or higher, and carry a considerable proportion of pitchy material, tars and oils as well as solid particles of coke, dust, etc. Ordinarily, the gases are cooled by the application of sprays of ammonia liquor or ammonialiquor and tar in the collector main, or by circulating ammonia liquor and tar thru the 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 efiected in the cross-over main which connects the collector main to the condensing system and additional tar may be separately recovered from this part of the system. In the coolers or condensers light tars or tarry oils are separated.

The tars and tarry oils are blended and are ordinarily shipped from the coke oven or other coal distillation plant to a tar distillation plant for distillation and separation of the oils, and the production of pitches of varying quality. Handling costs, freight charges and distillation costs,

including fuel. capital and maintenance expense for the special equipment required for distillation, add to the cost of the tar distillation prod ucts.

According to the present invention, high tem perature coal carbonization gases are admitted under the surface of a body of pitch, tar or oil and by bubbling up thru it the hot gases not only eifect distillation but also agitate the body of material causing a continual change of the surface exposed to the hot gases.

The material which is to be distilled according to the present invention, may be coal tar produced at coke oven plants or gas house tar produced at gas retort plants (vertical, horizontal, or inclined), water gas tar, or tar or tarry oil from another source or pitch resulting from the partial distillation of tar. Such tars frequently contain a considerable percentage of water intimately admixed or combined therewith,

particularly where Water or ammonia liquor is employed for separating and condensing the tar constituents from the coal distillation or other gases, and such tars may, if desired, be dehydrated before being distilled according to this invention, or may be dehydrated as part of the process.

The hot coal distillation gases leaving coke ovens, gas retorts, etc., carry with them solid impurities, such as free carbon, coal dust, etc. The gases also contain in suspension very finely divided particles of tar known as tar fog. On

bringing this gas into contact with liquid in the still, such entrained solids and liquids are removed to a greater or less extent. When the gases are bubbled up thru the liquid as fine bubbles, the surface of contact is large and the scrubbing action of the liquid on the gases is greater than when the gases are admitted to the still as larger bubbles. The depth of liquid thru which the gases pass is another factor affecting the thoroughness of the scrubbing.

The gases which are passed thru the body of I tar or oil, to effect the distillation of the tar or oil, keeping it in motion continuously presenting new' surfaces from which vapors arise, are the hot gases produced by a coal carbonization or gasification operation. The hot gases may be hot coke oven gases or hot retort gases or hot water gas, etc. In the case of hot coke oven gases, for example, the gases escape from the coke ovens at a temperature, for example, from GOO-700 C., or even higher in some cases, and tfese gases, after minimum, or at least regulated cooling'in the collector main, may be used for distillation by passing them under the surface of the tar or oil to be distilled and allowing them to bubble up thru the body of liquid. The high temperature gases withdrawn from, gas retorts, water gas retorts, producers,-etc., may be used in a similar way to efiect distillation.

The mains connecting the coke ovens, retorts, or other coal carbonization apparatus as well as the stillitself, may advantageously be insulated. The still is preferably placed adjacent to or even upon the top of the carbonization apparatus to minimize the amount of heat lost by radiation. According to the present invention, the hot gases may advantageously be passed up thru a considerable depth of the liquid to be distilled. The liquid may in addition be mechanically agitatedif desired. The efliciency of the operation is improved by securing prolonged contact of the gases. with the liquid by introducing the gas in sub-divided form and by passing the subdivided gases up thru a considerable depth the liquid. In operating in this manner, the g ses are kept in contact with the liquid for a prolonged period of time and more efiective agitation of .the body of the liquid is secured. The pressure'required to force the gases thru the body oftar or oil increases with increase in the depth of liquid thru which the gases must pass. In actual operation the proper relation between the various factorsmust be adjusted in such a way as to give the desired efficiency of operation under the particular conditions presented.

The depth of tar or oil in the still may be varied. If the gases are admitted into the still near the bottom so that the depth of liquid in the'still is only slightly greater than the depth of liquid thru which the gases pass, the liquor in the still will be thoroughly agitated. Although this is the preferred method of operation, it is possible, on the other hand, to provide a body of I tar or oil for distillation which may be of a much greater depth in the still than the depth of tar or oil thru which the gases pass. r The gases may be conducted into the body of liquor to be distilled thru small openings in a pipe or other distributing means submergedin the contents of the still, or the gases may be admitted into the still, thru openings in the bottom of the still itself. Preferably, the gas is admitted to the still'thru a multiplicity of small perforations in suitable distributing means in order that the gas may be divided into many small streams which will bubble up thru the contents of the still thereby producing greater surface contact between the gas and the contents of the still than if a fewer number of streams of gas were provided. Any suitable means for causing the gas to bubble up thru the body of liquor to be distilled may be utilized. Pressure may be applied to the gases and vapors in the a still, or a reduction in pressure may be main- .tained above the body of tar or oilin the still.

The still may be of any suitable shape. In the drawings the still is shown as a cylindrical tank. The still is preferably insulated. Pressure may be applied by means of an ordinary exhauster placed between the oven or retort, etc., and the still, or an exhauster or pump may be situated beyond the still to create a vacuum suiiicient to draw the gases thru the still.

This invention is well adapted for continuous operation. When operating on this basis, tar or oil issupplied and unvolatilized, residue is withdrawn continuously or at frequent intervals am the rate of addition to and withdrawal from the still is at all times regulated soas to maintain controlling the time of contact between the liquor and the gases and regulating the quantity of each, and properly controlling other factors, such as the temperature of the liquid and gases ad;

mitted to each-still, etc., the distillation efiected may be controlled.

Where more than one still is employed the gases leaving several stills may be combined and passed thru a singlecondensing unit or the gases from each still may be treated separately to recover distinct products which may be of rare-determined boiling range. The non-volatilized residue from reaaev "vidual stills, which, by proper manipulation, may

have a predetermined boiling range or other desired property or properties.

' For example, when several stills areemployedand oil, for example is passed thru the stills in series, and subjected to fresh hot gases, the gases leaving each still may be passed thru a separate condensing system so that a low boiling oil will be condensed from the vapors carried by the gases leavingthe first still in the series and higher boiling fractions condensed from the other stills.

By drawing off a portion of the residue from the first still into a separate container and passing the balance into the second still of the series, a residual oil of wide boiling range with a predetermined lower limit may be recovered. Residues of less wide boiling range may be drawn from the succeeding stills.

Various arrangements of stills, hot gas mains and recovery systems permit a variety of operations to be carried out utilizing the "genera method of this invention.

Although the invention is of broader application, it will be described particularly in connection with coke oven operation. The gas employedfor the distillation may be withdrawn at practically its maximum temperature as it comes from the coke ovens, or the gas may be employed at a somewhat lower temperature.

Where the gas is not'to be used at or near its maximum temperature, the temperature of the gas may be regulated by the treatment to which it issubjected prior to its use in the distillation operation. The gas may be sprayed with ammonia liquor in the goose-neck and in the collector main, or it may be sprayed with tar or oil in the goose-neck or in the collector main, or it may be sprayed with a mixture of the two, or in both the goose-neck and collector main, and the gas thus cooled. to a regulated lower temperature before use for distillation.

Due to the greater specific heat and heat of vaporization otwater, spraying with water or ammonia liquor produces a greater cooling efiect on the gases than spraying with an equal amount of tar or oil. By regulating the quantity of the water or tar, etc., sprayed in the gases prior to their passage up thru the body of tar or oil to be distilled, the temperature of the gases used for the distillation can be'controlled. The temperature of the gases may likewise be controlled by' I regulating the temperature of the spray. By limiting the amount of cooling, the gases can be employed at a regulated high temperature, such that they have a rapid distilling action in the still.

The temperature and amount of the gases used may be regulated according to the distillation which is to be carried out. If light tarry oils or light tars only are to be distilled, the temperature of the gases used in the distillation need not be as high or the amount of the gases employed need not be as great, as when higher boiling oils are to be distilled from .tar or from pitch.

Where maximum' distillation is desired, the,

top of the coke oven block in close proximity to ,given ofi in this oven,

the uptake pipe, the gases can be employed at a temperature approximating that at which they leave the uptake pipes. By using such high temperature gases, rapid heating and distillation can be effected, and pitches of high melting point produced, as well as high yields of oils, including high boiling oils.

In the operation of a coke oven the gases produced are not of uniform composition. At the start of the coal distillation process, oils, etc., are liberated from the coal in large quantities and the first gases given ofi are rich in volatile products. The gases given off during the latter part of the coal distillation, for example, during the last thirty percent of the operating time under normal conditions, contain a less percentage of condensable constituents than the richer gases given off during the first part of the distillation, and are known as lean gases. Y

There is in many cases an advantage in using either the rich gases or lean gases separately in distillation of tar, according to the present invention. For example, lean gases are capable of taking up a greater quantity of oil and other vapors per unit volume of tar or oil thru which they pass than an equivalent amount of a rich gas which already contains more volatile constituents than does the lean gas, the gas temperature in each case being the same. Rich gases contain a larger amount of condensable vapors which admix with the distilled vapors and are condensed therewith.

The tars entrained in rich gases are lower in free carbon content than are the tars entrained in lean gases. Therefore the free carbon content of the residue in the still may be regulated or controlled by the use of rich or lean gases since more or less of the tar entrained in the gases used for distillation will be removed from the gases and be retained in the residue in the still.

In order to take advantage of either rich or lean gas, the coke oven may be equipped with two collector mains, each of which is adapted to be thrown into communication with the uptake pipe from each of the ovens in the battery to which the collector mains are connected thru a system of valves. As an example, during the first of the distillation operation in-any one oven, this oven will be thrown into communication with the collector main which is connected directly with recoveryapparatus. After the distillation has progressed to the point where lean gases are being it will be thrown into comntunication with the other collector main which is in communication with the still.

By the usual rotation of the ovens in a battery of average size, there will at all times be a fairly continuous and uniform production of lean gases. so that the quantity and temperature of the gases passing thru the still will be fairly un form at all times. Rich gases may, in many cases, be

/ desired for distillation, and can be utilized by my invention.

Depending upon the extent to which the distillation of the tar or tarry oil is carried, substantially only the lighter oils may be removed from the body of tar or oil, leaving a tar or very light pitch in the still. By carrying the distillation further, heavier constituents will be volatilized and recovered from the gases, and a heavier tar or pitch will remain as a residue in the still.

The distillation can be accomplished in numerous ways. For example, a large volume of relatively low temperature gases may be used, or a smaller volume of relatively high temperature gases, as they come from the ovens, may be used. The tar may also be preheated before being brought into contact with the gases.

The gases escaping from the distilling operation will carry in vaporform the constituents volatilized from the tar and will contain in addition thereto such of the vapor constituents carried by the gases entering the still as have not been removed by contact with the tar or oil being distilled. In the case of hot coke oven gases employed for the distillation of coal tar produced by the coke ovens, the hot gases after the distillation operation will contain uncondensed constituents from the coal distillation as well as added vapor constituents driven off from the coal tar during the distillation.

Higher boiling constituents carried by the hot gases from the ovens may be condensed in the still and the latent heat of condensation absorbed in the distillation operation, in which case condensate from the gases will be blended with the non-volatilized residue of the tar or oil added to the still and drawn off from the still as such. By using coal tar produced at the coke oven plant while it is still hot before it has had opportunity to cool, a saving in heat may be effected.

- The gases from the still can be treated for the condensation and recovery of the desirable constituents contained therein as well as for the recovery of ammonia carried thereby. Where only a portion of the gases from the coal distillation apparatus are passed up thru tar or oil in the still, those gases which are enriched by passing thru the tar or oil can be treated in a separate recovery system and the oils condensed therefrom will be a mixture of the oil constituents normally in the gases and those added to the gases during the distillation, whereas the condensate from the remainder of the system will contain only the coal distillation products normal to the gases. The enriched gases can also be treated in the same recovery system with the remainder of the gases produced by the coal distillation.

In a coke oven plant where several batteries of coke ovens are operated, the rich or lean or normal gases from one battery may be employed for distilling tar from the other batteries, or a part of the gases from one battery may be so employed. The gases used in the distillation may be only a portion of the gases collected in the collector main and may be taken ofi one end of the collector main, or all the gases passing thru the collector main may be utilized e. g. by taking them off the center-box according to the customary practice. A tar or oil, other than a coaltar product, can be distilled and the condensable constituents recovered in a separate recover system without contaminating the balance of the coal-tar products produced.

Where the distillation is carried out as a batch operation, the tar or oil is progressively heated by the hot gases and the lighter constituents are progressively removed therefrom until the distillation has been carried to the desired point. after which the operation can be discontinued, and the residue withdrawn, and the still recharged with further tar or oil to be distilled.

Due to enrichment of the gases in clean oil vapors volatilized from the material in the still,

the oils removed in the condensers following the still will contain less free carbon and pitch impurities than would oils condensed directly from gases not used for distillation.

In some cases it may be desired to regulate the character of the residue of distillation as respects erage boiling point increase.

free carbon content or as respects the type of oil remaining in or added to it. This may to a greater or less extent be accomplished by using rich or lean or intermediate gases for distillation. Rich gases contain tar with a relatively low free carbon content and they contain also oils of lower average boiling point and lower specific gravity than do lean gases. Rich gases contain a greater amount of tar than lean gases. As the gases get leaner the amount of tar contained in them decreases, the percentage of free carbon in the tar increases, the amount of oil contained in them decreases and its specific gravity and av- Since in the distilling operation more or less of the tar contained in the gases will be retained in the residue and more or less of the contained heavy oils Will be condensed and retained in the residue, the character of the residue may to some extent be controlled by choosing the proper gases for distilla-' 'tion. Such gases may be rich, lean or intermediate gases.

The invention will be further described in connection with the accompanying drawings illustrating apparatus embodying the invention and adapted for the practice of the process of the invention, but it is intended and will be understood that the invention is illustrated thereby but is not limited thereto.

apparatus in which two collector mains are shown with provision for use of rich or lean gases for distillation.

Fig. 3 is an enlarged detail showing in crosssection the relation of two collector mains of.

Fig. 2 to each other and the coke oven;

Figs. 4, 5 and 6-give details of the still shown inFig. 1.

. In the drawings, 5 indicates a coke oven battery with the usual uptake pipes 6, collector main '7, sprays 8, center-box 9 and cross-over main 10. Wet condensers 11 and 12 are provided for condensing tarry oil vapors passing with the gases thru the cross-over main. From the condensers the gases pass thru the pipe 13 and exhauster 14 to the exit pipe 15, from which they may be passed to ammonia, saturators 'or benzol recovery apparatus or other suitable apparatus.

Condensate from the condensers 11 and 12 is drawn on into the decanter 16 from which and-- monia liquor is withdrawn into the tank 17 and, far into the receiver 18. Tar and ammonia liquor from the collector main, collecting in the centerbox 9, are drawn thru pipe 20 into the decanter from which ammonia liquor. is withdrawn into the receiver 21, and tar into the tank 22, or the tar and ammonia liquor may be allowed to run thru the cross-over main 10 and be, drawn off at 10 to a decanter not shown.

The collector main and goose-necks may be sprayed with tarirom 18 thru the pipe 23 .or with tar from 22 thru the pipe 24, or with ammonia and/or tar from another source thru pipe 25.

One end of the main may be sprayed with tar and one with ammonia liquor by the use of line 24 and valve 33. The collector main may be flushed with tar and/or with ammonia liquor thru lines 5' and 8'.

By shutting ofi the sprays 8 and by flushing themain the gases may be held at high temperature and accumulation of achd lard pitch in the main may be prevented.

The still 26 may be supplied with tarfrom 22 thru the pipe 27, or tarry oils from the-tank 18 thru the pipe 28, or tar or oils from. an outside source thru/ the pipe 29. If necessary, pumps may be provided, as indicated by the reference numerals 30. The feed pipe to the still is equipped with a heat interchanger 31.

Gases from the collector main are led to the distillation in the still. The entire system or any of its parts may be adequately insulated. The gases leaving the collector main pass thru the pipe 32 and are caused to bubble thru perforations 34 in the pipe 35 in the bottom of the still.

gases may be conducted into the contents of the still thruany suitable distributing means submerged in the liquor in the stilL' Although in the accompanying drawings a single pipe 35 is shown, any number of suitable means may be provided. By making the outlets for the gas small, the surface contact between the gas and the contents of the still is made large and the emciency of the operation may be increased.

The hot gases, on being brought into contact with the contents of the still, carry off with them the desired volatile constituents of the contents of the still. These mixed gases and vapors pass ofi from the still thru the pipe 36 thru which they may be passed to any suitable condensing means such as the condensers 37 and 38, in which case they will be led thru pipe 39 to the pipe 15, or they may be lay-passed thru the pipe 40 and con- .veyed to the condensers 11 and 12 or other suitable condensing means thru the pipe 41.

Condensate from the condensers 3'7 and 38 is collected in thedecanter 42. Two separate oil ,fractions may be collected bydrawing oi? the condensate from one condensingsection thru line 28' to a decanter not shown and'drawing ofi the other to decanter 42. Oil from 42' may be supplied to the collector main or still as shown. Bafile means (not shown) may be provided at the gas outlet from the still to prevent-liquor entrained in the gases from passing over to the condensers.

The still may be operated as a batchoperation This still may be of any suitable shape and the trolling the extent of the distillation a heavy tar or light pitch may be produced in the still.

In the apparatus shown in Fig. 2, the parts of r the equipment have been made to correspond as far as possible with the corresponding parts of Fig. 1"as indicated by the numerals; 305 represents the coke oven battery th' two collector mains 307 and 307. The cross-over main 310 leads to condensers 311 and 312. 1 From 156 the collector main 307', the gases are conducted thru the main 332 into the still 326 and from thence by the pipe 336 to the conductors 337 and 338 or thru the by-pass 340. Residue from the still is drawn off thru the pipe 344 into the storage receptacle 345. Tarry oils are drawn off the condensers 311 and 312 into the decanter 316, from which ammonia liquor is drawn off into the receiver 317 and tarry oil into 318. From 318 the tarry oil may be pumped by pump 331 thru the heat interchanger 331' into the still.

Instead of supplying the still with tarry oil from this source, tar or oil from any outside source may be supplied thru the pipe 370, or tar from either of the collector mains may be drawn off thru the center- boxes 309 and 309 and the pipes 3'71 and 372 to the decanters 3'73 and 3'74 from which ammonia liquor is drawn off into the storage tank 375, and the tar which is collected in the two receivers 3'76 and 377 may be supplied to the still thru the pipes 378 and 379, re-

spectively.

When it is desired to spray tar without ammonia liquor into the gases going to the still the tar may be supplied thru the lines 380 and the sprays connected thereto. The collector main may be flushed with tar and/or ammonia liquor thru lines 305 and 376'. By shutting off the sprays the gases may be held at high temperatures, and

by flushing the main accumulation of solid hard pitch may be prevented.

The character and quantity of the residue withdrawn from the still and of the clean oils condensed from the enriched gases leaving the still is dependent upon many factors, such as the quantity and temperature of the gases, which depend to some extent upon the spraying of the gases in the collector main and also 'upon the character and quantity of tar or oil supplied to the still. Controllable variables permit regulation of the process to produce the desired tars or pitches from the still and oils of the desired quality from the condensers.

I claim:

1. The method of distilling heavy hydrocarbon material in liquid form by the heat of hot coal distillation gases resulting from the distillation of coal, which comprises separately collecting the gases from a controlled period of the coal distillation operation, bubbling them at a tempera comprises causing hot coal distillation gases from the coal distillation-apparatus of'the plant at a temperature above the dewpoint of oil vapors therein to bubble up thru a body of the hydrocarbon material, whereby constituents thereof are volatilized by the heat of the gases and pitch residue is produced, continuously adding fresh cooling them to tillation gases.

3. The method of distilling heavy hydrocarbon material in liquid form, which comprises causing fresh hot coal carbonization gases to bubble thru the hydrocarbon material so as to heat the material and effect substantial cooling of the gases, agitate it and effect the removal of volatile matter therefrom; and cooling the resulting gases to condense distillate oils therefrom.

4. The method of distiling comprises causing fresh hot tar-laden coke oven gases to bubble up.thru a substantial depth of a body of tar while distilling it, thereby imparting heat to the tar, facilitating the removal of oil vapors from the tar, removing entrained tar particles from the gases and incorporating them in the pitch residue formed, and cooling the resulting gases to condense distillate oils therefrom.

5. The method of operating a coke oven battery comprising a plurality of ovens in which coal is being distilled, which comprises withdrawing and mixing hot fresh coal distillation gases from from the distillation to contar to pitch, which a plurality of the ovens, causing the hot mixed irlwhich coal is being distilled, which comprises Y collecting the hotcoal distillation gases from a portion of the ovens or retorts of the plant and separate tar, collecting at least a portion of the tar as a body thereof, collecting hot coal distillation gases from other ovens of the plant and bubbling'them while still at a high temperature up through a substantial depth of said body of tar so as to distill the tar by the heat of said gases. r

' '7. The method of distilling heavy hydrocarbon material in liquid form and containing volatile constituents, which'comprises causing fresh hot coal carbonization gases while still at a temperture above about 300 C. after their production to'bubble through a substantial depth of the hydrocarbon material thus distilling off volatile constituents from the hydrocarbon material.

8. The method of a coal distillation plant having a plurality of ovens or retorts in which coal is being distilled, which comprises hot coal carbonization gases from the plant to bubble through the dehydrated tar so as to heat distilling dehydrated tar at.

causing a portion of the fresh the tar and effect substantial cooling of the gases,

agitate it, and ter therefrom,

of volatile mat-

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