US1930130A - Method of distilling tar - Google Patents

Description

Oct. 10, 1933.

s. P. MILLER 1,930,130

METHOD OF DISTILLING TAR Filed June 24, 1927 2 Shets-Sheet l ATTORNEYS Oct. 10, 1933. s. P. MILLER METHOD OF DISTILLING TAR 2 Sheets-Sheet 2' Filed June 24. 1927 INVENTOR 3 fgfiw ATTORNEYS Patented Oct. 10, 1933 UNITED STATES PATENT QFFICE METHOD OF DISTILLING TAR Application June 24, 1927. Serial No. 201,222

5 Claims.

This invention relates to improvements in the distillation of tars or oils, particularly to the utilization of the heat available in the gases produced in coal carbonization plants to distill coal gas condensates and to the production of oils and tars. The invention will be described especially with reference to its application to coke ovens.

In the ordinary operation of by-product coke ovens, the gases produced by the coking operation pass from the individual ovens through 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 temperature, e.g., 609 to 700 C., or higher, and carry a considerable proportion of vclatilized and entrained tars and oils as well as solid particles of coke, coal and carbon and 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 crossover main which connects the collector main to the condensing system, and an additional quantity of tar carrying both heavier and lighter oils is recovered in the cross-over main and in the condensers. The collected tar is ordinarily shipped from the coke oven plant to a tar distillation plant for distillation and separation of the oils and production of pitches of varying qualities. Handling losses, freight charges and distillation costs, including fuel and capital and maintenance expenses for the special equipment required for distillation add to the cost of production of the tar distillation products.

It is the object of the present invention to provide method and apparatus for the production of marketable pitch or tar and salable oils directly at a coal distillation plant by scrubbing the hot gases to remove impurities, separating salable oils from the resulting gases and vapors which have been more or less cleaned by the scrubbing operation and enriching gases from selected ovens by volatilizing residue from the scrubbers therein.

According to the usual practice, the condensates obtained in the operation of coke ovens are collected as tar and contain considerable amounts of dust, coke braize, and free carbon. It is one of the purposes of this invention to treat the hot coke oven gases in such a manner as to allow the subsequent direct recovery of salable distillate oil fractions and salable pitches, thus avoiding the necessity for distillation of tar as ordinarily carried out.

On cooling coke oven gases, according to the ordinary methods, a fog or mist of tar particles is produced. Due to the extremely small size of these particles, the tar persists in large quantities in the gases even after cooling to atmospheric temperatures. Hence, oily fractions recovered by step-wise cooling of the gases have been contaminated with tar and the fractions have not beensalable. It has been necessary to distill them for production of salable oils; the residue from the distillation has been pitch. It

is one of the purposes of this invention to recover salable oils direct from the gas stream.

According to the present invention, the coke oven gases are scrubbed with tar or tar constituents preferably at high temperature, and by this scrubbing both entrained tar and free carbon are removed from the gases. The scrubbing may be carried out in any one of a number of devices adapted for the purpose. According to the preferred form'of the present invention, the scrubbing is eiiected by a spraying device, e. g., in a scrubber tower, located in the hottest part of the cross-over main near the exit from the collector main. At this point the gases are hot and scrubbing removes solid matter and entrained tar Without condensing any considerable amount of the heavy oils. By controlling the temperature of the gases at this point and by controlling the temperature of the medium sprayed into the scrubber, the quality of the tar or pitch recovered by the scrubbing may be regulated. If the gases are very hot and a hot spray is used, a heavy pitch may be recovered and heavy constituents of the gases from which free carbon and entrained mist have been largely removed may be thrown forward into the coolers Where heavy constituents, as well as lighter constituents, will be recovered in an almost pure state, containing only a small percent, if any, free carbon.

The temperature of the gases may be con absorb a great quantity of the latent and sensible heat of the gases and oil vapors, a lesser quantity of water or ammonia liquor may be sprayed into the collector main sufficient to flush the main to prevent clogging, and at the same time allow the gases leaving the collector main to maintain a high temperature. Although by spraying the gases with less aqueous solution the temperature of the gases leaving the collector main may be maintained at a higher temperature than the usual practice allows, because of the high latent heat of water and ammonia liquor, it is desirable, for the purposes of this invention, to spray with tar or tar constituents in the collector main instead of the usual aqueous solution. By this procedure, the temperature of the gases is not lowered to the same extent as would result from spraying with the same quantity of an aqueous solution, and the vapors are enriched with desirable distillates by volatilization of the spray. Agitation of the nonvolatilized residue in the collector main increases the distillation eiiected there. By decreasing the amount of oil or tar sprayed into the collector main, or by preheating the spray, the temperature of the gases entering the crossover main may be further increased. By maintaining a high temperature in the collector main, the quantity of heavy oil constituents condensed there is kept at a minimum, and heavy oil constituents are thrown over into the coolers in the vapor state. A further method of preventing condensation of heavy constituents in the collector main is by dilution of the gases in the main with some inert gas.

, The heat of the gases leaving the coke ovens is sufiicient to distill a quantity of tar or oil many times that produced by the coke oven itself. This invention, therefore, makes possible the production of a large quantity of relatively clean distillates in addition to those produced from the gases of the oven itself. Additional oils, tars, or pitches may be added to the system by spraying them into the hot gases as they leave the coke ovens. This may be done in any suitable apparatus, such as the uptake still described in the application of Brandon, Serial No. 154,746, filed December 14, 1926. By preheating the fluids sprayed into the uptake pipe, the capacity of one system for producing pure distillates is increased.

By volatilizing tars or oils in the hot gases, the percent of condensable constituents in the gases may be increased by as much as five or ten fold or more. Scrubbing removes solid and liquid impurities, viz., free carbon, tar fog, etc. By scrubbing enriched gases and then cooling to throw out condensable constituents, relatively clean oils can be produced. Scrubbing removes impurities from the gases, and because of the previous enrichment of the gases in condensable constituents the percentage of impurities remaining in the gases, when figured on the con-- densable constituents is a great deal less than the percentage of impurities based on the condensable constituents in unenriched gases.

The scrubber not only serves to remove entrained solid and liquid particles from the gases, but in certain cases, depending largely upon the relative temperatures of the gases and the scrubbing medium and their respective compositions, light constituents of the scrubbing medium may be volatilized to enrich the gases, or high boiling constituents may be condensed out of the gases, or light constituents of the scrubbing medium may be volatilized and high boiling constituents may be condensed out of the gases simultaneously. When the gases are at relatively low temperature, or the scrubbing medium is cold, only low boiling constituents pass off with the gases. The composition of the gases and the non-volatilized constituents drawn off from the scrubber depends upon the temperature of the gases and the scrubbing medium. Maintaining the gases entering the scrubber at a high temperature and preheating the scrubbing medium tend to throw high boiling constituents in both the gases and scrubbing medium forward into the condensers.

It is generally advantageous to use a scrubbing medium with a temperature above the dewpoint of the gases for the oil which it is desired to throw forward into the coolers. If, for example, cool tar, i. e., tar lower in temperature than the gas stream is used as a scrubbing medium, constituents which it is desired to recover in the condensers will be thrown down with the tar at the scrubber, and a tar or pitch lighter than that obtained with a hot tar spray in hot gases will be recovered as residue from the scrubber.

Depending upon the quality of the oil, tar and pitch which it is desired to recover, the nature of the recoverable constituents added to the process may be varied. Where several batteries of coke ovens are operated in one plant, it is possible to equip the uptake pipes from each of the ovens of one battery with uptake stills, and to supply to the uptake stills of this one battery 'tars, oils and pitches obtained in the operation of the other batteries. The enriched gases may be scrubbed with any suitable tar, oil or pitch to produce a tar or pitch of desired properties in the scrubber, and the cleaned gases may be cooled to recover salable products therefrom directly. By equipping only a portion of the ovens of the battery in this way, it is possible to utilize the oils, tars or pitches, or desirable fractions of the oils, tars and pitches produced in the remainder of the battery in the operation of the few ovens equipped with the uptake stills and scrubber.

By adding only the lighter fractions of tar and oils recovered from the operation of other ovens to the ovens equipped with the scrubber,

a greater proportion of light oils will be recov ered, and, conversely, by adding a preponderance of heavier fractions a greater quantity of tars and pitches of high boiling point will be recovered. Instead of coke oven by-products, tar such as gas house tar, vertical retort tar, or Water gas tar, etc., or oils from various sources can be distilled by spraying in the uptake stills or collector main, or by using it as the scrubbing medium in the scrubber. When blended or composite pitches or distillates are desired, several different kinds of tars, oils or pitches may be admixed in suitable proportions, and oil, tar or pitch of the desired composition may be obtained directly. For example, horizontal gas refrom the scrubbers may be pumped to the uptake stills, or the scrubber for the enriched gases.

This invention makes possible the production of nothing but relatively clean oils, and the oils are recovered directly without the losses entailed in the usual fractionation processes due to decomposition, handling losses, etc. Larger yields resuit with the possibility of a reduced operating cost.

Tar as commonly produced and collected at coke oven plants contains more or less water or ammonia liquor admixed therewith. Such tar can be employed directly and dehydrated as well as distilled, or it can be partially or completely dehydrated before subjecting it to distillation.

The tar or pitch may be preheated in any suitable manner to reduce it to a thinly fluid state and thus facilitate spraying into the gases and also increase the capacity of the gases for distillation, thereby throwing over a larger quantity of higher boiling constituents into the recovery system beyond the scrubber.

The vapors in the gases leaving the scrubber may be condensed in one condenser, or several fractions of difierent boiling points may be obtained by step-wise cooling. Removal of the tar fog entrained in the gases makes possible a sharper fractionation than is possible without such removal.

'Although the invention has been described in connection with a coke oven system, and the drawings are confined to coke oven operation, it is intended and will be understood that features of this invention are applicable to other operations in which gases containing entraina fog, dust or free carbon are produced, and it is intended and will be understood that this invention is not limited to the specific details of the apparatus as illustrated in the drawings or to a coke oven system.

In the drawings,

Fig. l is a plan view of a coke oven recovery plant illustrating one adaptation of my invention; and

Fig. 2 is an elevation, partly in cross-section, through the short collector main connecting the ovens equipped with uptake stills of the plant shown in Fig. l.

Referring to the drawings, 5 is a coke oven battery with the usual uptake pipes 6 conveying hot coke oven gases to the usual collector main '7 from which the gases are withdrawn from the center-box 8 through the cross-over main 9. The gases are sprayed in the goosenecks and collector main through sprays 10 with water or ammonia. liquor or tar or a mixture of these.

The mixture of tar and ammonia liquor which is thrown down in the collector main is drawn off through the center-box by the pipe 11 into the decanter 12 from which ammonia liquor is run to the storage tank 13 and tar is drawn off into the receiver 14.

The gases pass from the collector main to the cross-over main 9 and then through the scrubber 15 in which they are sprayed through sprays 16 to remove solid and liquid impurities entrained in the gases and in certain cases to alter the composition of the gases if the ternperatures of the gases and scrubbing medium are so adjusted as to accomplish such a result. The non-volatilized constituents of the scrubbing medium and gases thrown down in the scrubber are drawn off into the receiver 17, from which any ammonia liquor, if there be any, may be withdrawn into the tank 18, and the tar or pitch drawn off into the receiver 19.

Tar or pitch collected in the receiver 19 may be used as a scrubbing medium in which case it is pumped by the pump 20 to the sprays 13 passing through the heat interchanger 21 in which its temperature may be either raised or lowered. Tar or oil from another source, admitted through pipe 22, may be used as the scrubbing medium. The cleaned gases pass from the scrubberthrough the pipe 24 to the condensers 25 and 26, which may be wet condenser-s, and thence through the exhauster to the pipe 28 from which theymay be passed to other usual types of apparatus. Oils thrown. down in the condensers 25 and 26 withdrawn through the pipe 29 to the decanter 30 from which ammonia liquor is withdrawn to the tank 31 and clean oil to the receiver 32.

Uptake stills, such as those described in the copendin-g application of Brandon above referred to, may be provided at the rear of sev eral of the ovens of the battery such as those indicated at in the drawings. Tar recovered as a residue from the scrubber 15 may be supplied from the tank 19 to the uptake stills through the pipe 41 by means'of the pump 42. The vapors and gases passing off from the uptake stills are passed over by the goose-necks 43 to the short collector main 44.

In each of the uptake stills, the gases pass up through the pipe 45 from the ovens and are diverted in their passage by the bafile' ili. The gases are sprayedthrough one or more sprays l7 and by the intermittent contact produced between the spraying medium and the hot gases, the lighter constituents of the spraying medl 1m are volatilized and pass 01f with the gases and the heavier constituents collect in the lower portion of the uptake still indicated at 4 3 and are drawn off through the pipe 49 to the re- 'ceiver 50.

The enriched gases from the uptake stills may be sprayed with tar or ammonia liquor in the short collector main. Tar recovered as a residue from the usual collector main, collected in the tank 14, is a suitable spraying medium for the short collector main, and may be supplied to the short collector main through the pipe 51 by the pump 52. Residue from the short collector main is withdrawn through the pipe 54 to the decanter 55 "from which ammonia .iquor, (if there be any), is withdrawn to the tank 56 and tar or pitch to the receiver 57. Tar or pitch collected in the receiver 57 may be recirculated through the collector main through the pipe 53 by means or it may be sprayed into the uptake stills, in which case it will be withdrawn through the ipe 59 and supplied by the pump 42 to the sprays 4'7. 1

Enriched gases from the short collector main are withdrawn through the cross-over main 60 and pass up through the scrubber 61 in which they are washed by liquids supplied through the sprays 62. e The scrubbers l5 and 61 may be of any suitable type as a tower filled with baiiles or grids over which a suitable fluid is continuously flowing.

The non-'volatilized constituents collecting in the bottom of the scrubber 61 are withdrawn to the receiver 63, from which ammonia liquor, ii there be any present, is withdrawn to the tank 64 and tar or pitch is withdrawn to tie tank 65. The tar or pitch withdrawn from the scrubber may be recirculated through the sprays by means of the pump 66 through the pipe 6'. or

of the pump 52 the scrubber may be sprayed with tar, oil or pitch from an outside source through the pipe 68. The pipe leading to the sprays 62 is equipped with a heat interchanger 69 for regulating the temperature of the scrubbing medium.

Tar or pitch from the scrubber collected in the tank 65 may be used for spraying the short collector main, or it may be sprayed into the uptake stills, in which case it will be withdrawn from the tank 65 through the pipe 70 or 71, respectively. The short collector main may be sprayed with ammonia liquor or tar or oil from an outside source through the pipe '72.

The enriched gases from the scrubber may be conducted to the condensers 25 and 2'0, or they may be passed to fractional condensers 73, 74, '75 and 75', and thence by the exhauster 27' to the pipe 28. The condensers 73, 74, '75 and 75 are illustrative of any suitable condensing means which may be provided. Instead of condensers as illustrated, condensers of any other suitable type may be provided. Clean oils are drawn from the condensers to the receivers 76, '77, 78 and 78. l

The system shown in the drawings provides for the operation of a battery of coke ovens to produce only clean oils and marketable heavy tar or pitch. According to one preferred method of operation in which there are no other products than these, the scrubber 15 is supplied with residue from the tank 19 as a scrubbing medium, and the balance of the residue from the tank 19 not so used is sprayed into the uptake stills by means of the pump 42 and pipe 41. The tar residue from the usual collector main is withdrawn into the tank 1% and is supplied from there in part to the short collector main, and the balance is sprayed into the uptake stills. The residue from the short collector main is supplied from the, tank 57 to the uptake stills. Residue withdrawn from the scrubber 61 is in part recirculated from the receiver 65 to the sprays 62, and the balance is supplied to the uptake stills. Clean oil is re covered in the containers 32, '76, 77, '78 and 78. The only other condensate is the tar or pitch drawn oiT from the uptake stills and collected in the container 50.

Although the drawings and description provide for enrichment of the gases by volatizing residue from the scrubbers in uptake stills, it is intended and is to be understood that enrichment of the hot gases by this residue in other means, such as by spraying into the collector main, is included Within the scope of this invention.

Due to the spraying in the collector main followed by scrubbing in the scrubbers, the gases passing to the condensers are relatively clean, and this is more especially true in the case of enriched gases. The apparatus illustrated and operated according to the method outlined yields relatively clean oils which are marketable in the condition in which they are recovered without being subjected to the distillation which the impure products recovered according to the usual practice must be subjected; The properties of the pitches or tars recovered in the process may be controlled within limits by the regulation of temperatures and quantities of the spraying mediums used.

The invention is not limited to the illustrations given, but is applicable to coal distillation in general and more particularly to coke oven operation.

I claim:

1. The method of cleaning gases resulting from the carbonization of coal while the gases are still hot and producing oils from them which comprises dividing hot fresh coal carbonization gases from various coal carbonizing units of the plant into two parts, cleaning one part of the gases at a high temperature to remove solid and liquid impurities entrained in the gases, distilling the matter thus removed from the gases in the other portion of the coal carbonization gases while they are still hot and cleaning these gases at a high temperature to remove entrained solid and liquid particles, and cooling the cleaned gases resulting from the treatment of the different parts of the gases to separate clean oils.

2. The method of cleaning gases resulting from the coking of coal in coke ovens and producing clean oils which comprises collecting hot fresh coke oven gases from ovens of a battery in which coal is being coked in two parts, scrubbing one part of the gases to remove entrained pitch particles at a high temperature at which oils are present in the gases in vapor form, bringing the pitch thus removed from the gases into direct contact with the other part of the gases while still hot to distill the pitch and scrubbing this other portion of the gases while still hot to remove entrained pitch particles, and cooling the scrubbed gases resulting from the treatment of both parts of the gases so as to condense and separate clean oils therefrom.

3. The method of cleaning gases resulting from the coking of coal in coke ovens and producing clean oils which comprises collecting hot fresh coke oven gases from a portion of the ovens of a battery in which coal is being coked one gas collecting system, partially cooling them therein thereby separating tar from the gases, scrubbing the resulting gases at a high temperature to remove entrained pitch particles and collecting gases from the other ovens in another gas collecting system, and distilling the tar and pitch by direct contact with these gases while they are still hot.

4. The method of cleaning gases resulting from the coking of coal in coke ovens and producing clean oils which comprises collecting hot fresh coke oven gases from a portion of the ovens of a battery in which coal is being distilled in one collector main, partially cooling them therein thereby separating tar from the gases, scrubbing the resulting gases while stillat a high tem perature to remove entrained pitch particles while retaining oils in vapor form, distilling the tar and pitch by direct contact with gases from the other ovens collected in another gas collector main while still hot and scrubbing these gases at a high temperature to remove entrained solid and liquid impurities, and cooling the resulting two portions of scrubbed gases so as to condense and separate clean oils.

5. The method of cleaning gases resulting from the coking of coal in coke ovens and producing clean oils which com rises scrubbing hot gases resulting from the distillation of coal in a battery of coke ovens at a high temperature before they pass to condensers, and distilling at least a portion of the tar or pitch separated from one portion of the gases by direct contact withanother portion of the gases while still hot and before th y pass to the condensers to thereby enrich these gases in condensable constituents and produce pitch of high melting point.

STUART PARMELEE MILLER.

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