US1958583A

US1958583A - Dehydration of tar, etc.

Info

Publication number: US1958583A
Application number: US175073A
Authority: US
Inventors: Miller Stuart Parmelee
Original assignee: Barrett Co Inc
Current assignee: Barrett Co Inc
Priority date: 1927-03-14
Filing date: 1927-03-14
Publication date: 1934-05-15
Anticipated expiration: 1951-05-15
Also published as: DE608332C; FR650770A

Description

May 15,- 1934.

S. P. MILLER DEHYDRATION OF TAR, ETC

Filed March 14, 1927 4 Sheets-Sheet 1 NVENTOR WWW ATTORNEYS y 1934. s. P MILLER 1,958,583

DEHYDRATION OF TAR, ETC

Filed Marh 14, 1927 4 Sheets-Sheet 2 ATTORNEYS y 1934- s. P. MILLER ,958,583

DEHYDRATION OF TAR, ETC

Filed March 14, 1927 4 Sheets-Sheet 5 Fig INVENTOR ATTORNEYS May 15, 1934. s. P. MILLER DEHYDRATION OF TAR,

ETC

Filed March 14, 1927 4 Sheets-Sheet 4 INVENTOR MM hm BY fiw%m #W ATTORNEYS Patented May 15, 1934 DEHYDRATION OF TAR, ETC.

Stuart Parmelee Miller, Tenafly N. 5., assignor to The Barrett Company, New York, N. Y., a corporation of New Jersey Application March 14, 1927, Serial No. 175,073

4 Claims.

This invention relates to improvements in the dehydration and distillation of tar, and includes a new method of dehydration and distillation as well as an improved apparatus therefor.

In the distillation of coal in coke ovens, etc.,

the coal distillation gases carrying the tar are commonly sprayed with ammonia liquor or a mixture of ammonia liquor and tar to cool the gases and separate the tar therefrom. The separated ,tar isadmixed with ammonia liquor, and, even after standing to permit as much as possible of the ammonia liquor to separate therefrom, may contain a considerable amount of water intimately mixed therewith. Long settling will in some cases reduce the water content to approximately two percent. Often, however, the water is emulsified and even long settling with moderate heating does not cause separation. In such a case the tar may contain as high as fifteen to twenty percent water.

When tar containing water is shipped from the coke oven or other coal distillation plant to the tar distillation plant, the water content of the tar adds materially to the cost of transportation.

When such water-containing tar is subjected to dehydration, in ordinary stills, trouble from foaming is frequently met with even though the tar be slowly and gradually heated in the still. It is best to subject the water-containing tar to dehydration before distilling it, and special dehydrators have been proposed for this purpose.

The present invention provides an improved method and apparatus for dehydrating tar, or for dehydrating and distillirn tar, whereby the dehydraton, or the dehydration and distiliation, are effected by means of hot gases'produced by the same type of coal distillation operations by which the tar is itself produced. The present invention makes unnecessary the consumption of fuel for heating and dehydrating, or dehydrating and distilling, the tar, and makes use of the heat already contained in the high temperature coal distillation gases from the coke oven, etc., by drawing off these gases while still at a high temperature and employing them for heating and dehydrating, or dehydrating and distilling, the tar.

The tar to be dehydrated, or dehydrated and distilled, accord'ng 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, etc. 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 coil distillation or other gases.

The gases which are employed, according to the present invention, for the dehydration, or w dehydration and distillation, of the tar, are hot gases produced by the coal carbonization or coal distillation operation. These gases may be hot coke oven gases, or hot gas retort gases, or hot water gas, etc. .In the case of coke oven gases, for

example, the gases escape from the coke oven at a high temperature, for example, around 600 to 700 C. or even higher in some cases. High temperature gases are also formed and are withdrawn from gas retorts, water gas retorts, producers, etc.

The gas employed for the dehydration, or dehydration and distillation, may be withdrawn at practically its maximum temperature, as it comes from the coke oven or retort, or the gas may be employed at a somewhat lower temperature, after it has passed through part of the byproduct recovery system, such as the collector main of the coke oven. The gas may be cooled considerably below the original temperature, but 89 it should be employed at a sumciently high temperature to exert the desired dehydrating and distilling action upon the tar to be dehydrated and distilled.

By employing the gas while it is still at a high temperature, the heat which it contains is utilized for the dehydrating and distillation of the tar, while by bringing the hot gas into intimate contact with the tar, the vapors driven 01f from the tar by the dehydration and distillation are admixed with the gases and may be subsequently separated and recovered therefrom.

In carrying out the dehydration, or dehydration and distillation, according to the present invention, the distilling and dehydrating gases are brought into heat interchanging relation with the tar to be dehydrated and distilled, and are advantageously brought into direct and intimate contact with the tar. This intimate contact of the tar and gases can be effected in various ways, and the dehydrating and distilling operation can be carried out either as a batch operation or as a continuous operation. The tar to be dehydrated can, for example, be atomized or sprayed into a current of the hot gas, thereby bringing the tar particles into intimate contact with the hot gas and heating the tar particles to a sufficient tem-- perature to dehydrate, or dehydrate and partially distill, the tar. Instead of spraying or atomizing the tar into a current of the hot gas, a current of the gas may be forced through a body of the tar to be dehydrated, thereby heating and agitating the body of tar and effecting dehydration and partial distillation of lighter oil constituents therefrom, which constituents are carried by the escaping gases. 7 The dehydration and distillation can also be effected in a counter-current manner, for example, by causing the tar to be dehydrated to flow downwardly through a bafiie tower or other apparatus in which an upward flow of the hot gases is eifected, so that the downwardly flowing tar is progressively heated and dehydrated and distilled, or the hot gases may be passed over the surface of a body of tar, for instance, in a closed tank. In this case it will be desirable, though not essential, to agitate the body of tar to keep fresh surfaces exposed to the gases.

The employment of hot coal distillation gases for the dehydration and distillation of the tar presents the advantage among others, that the gases themselves are subjected to a scrubbing and purifying treatment by bringing them into contact with the tar to be dehydrated and distilled; while the lighter constituents driven off from the tar during the dehydration and distillation are ad- .rnixed with the remaining uncondensed constituents of the gases, and can be recovered therefrom by the same subsequent condensing or recovery treatment. 7

Depending upon the extent to which the distillation of the tar is carried, substantially only the light oils may be removed with the water and free ammonia from the tar, or, by heating to a higher temperature, heavier oils can be driven off.

If, for example, the tar is heated, during the dehydration and distillation, only to about 130 C.

only the lighter oils will be driven off therefrom during the dehydration and distillation; while if the tar is heated to a higher temperaturejheavier oil constituents will also be driven oil and will be carried away by the hot distillation gases and can be subsequently condensed and recovered therefrom.

By continuing the distillation, after the dehydration has been completed, progressively increasedamounts of oils can be removed until only a heavy tar, or in some cases a'pitch, remains.

The distillation can be accomplished in numerous ways. For example, a large volume of relativelylow temperature gases may be used, or a small volume of relatively high temperature gases may be used. The tar may be preheated if desired before introduction into the gas. In any event the temperature of the gases leaving the dehydrator must always be held above the dew point for water since otherwise dehydration will not be complete.

For certain purposes dehydrated tar containing 0.5% to 1% water is entirely satisfactory. The production of such tar may be accomplished at relatively low gas temperatures, for example, approximately 125" C. or lower. If a tar containing no more than tracesoi water be desired, it will be found expedient to work with gases at higher temperatures, for example, approximately 160 to 170 C. Distillation as well as dehydration will be carried out at such temperature and the dehydrated tar will be a heavier tar, that is, it will contain less light oil, will be more viscous and will have a higher specific gravity. If a more fluid tar be desired, some of the oil distilled out may after recovery from the gas, be freed from water and be returned to the tar.

The gases escaping from the dehydrating and distilling operation will carry in vapor form the water removed from the tar during the dehydration as well as the ammonia and the oils driven off from the tar during the distillation. These gases will also contain such of the vapor constituents carried thereby as have not been removed by contact with the tar being dehydrated and distilled. In the case of hot coke oven gases, for example, these gases may be employed for the dehydration and distillation of coal tar produced by the coke ovens and the hot gases after being employed for the dehydration and distillation will still contain uncondensed constituents as well as added vapor constituents driven oiT from the tar during the dehydration and distillation.

The gases containing such vapor constituents are treated for the condensation and recovery of such constituents therefrom, as well as for the recovery of ammonia carried thereby. Such gases can be treated in a separate recovery system so that the oils condensed therefrom will be the oil constituents remaining in the gases and those added to the gases during the distillation. In such case, the apparatus will have a separate condensing and recovery system.

Instead of providing a separate condensing and recovery system, the gases from the dehydration and distillation can be returned to the main condensing system and the vapor constituents and ammonia recovered therefrom along with the vapor constituents and ammonia carried by the coal distillation gases with whichsuch gases are admixed.

The invention is of particular advantage for the dehydration, or dehydration and distillation, of coal tar at coke oven plants by utilizing the hot coke oven gases for the dehydration and distillation. The process is also advantageous for the dehydration of gas house tar, Water gas tar, etc. The dehydration, or dehydration and distillation, can be carried out in existing equipment or in special equipment. In a coke oven plant where several batteries of coke ovens are operated, all of the gas from one battery may be employed for dehydrating, or dehydrating and distilling, tar from the other batteries; or a part of the gases from one battery may be so employed. Such dehydration, or dehydration and distillation, can be carried out, for example, in the collector main of such a battery in which case the dehydrating, or dehydrating and distilling, capacity of the gases in the collector main will be sufiicient to dehydrate, or dehydrate and distill, all of the tar from several other batteries. When an entire collector main, or part of a collector main, is so employed for dehydrating, or dehydrating and distilling, tar, the'temperature of the main can be regulated and controlled and various expedients employed for bringing the tar into intimate contact with the hot gases to effect the desired dehydration, or dehydration and distillation.

The present invention enables dehydrated'tar to be produced, or tar which has been both dehydrated and distilled to a greater or less extent to remove oil constituents therefrom. Where the tar is desired in a dehydrated condition, still containing the greater part of its oil constituents, the dehydration can be carried only to the point necessary to remove all or practically all of the water contained therein, together with such light oils as are removed at the same temperature. Where, however, a heavier tar is desired, the distillation can be carried further, until more of the light oils are removed, to give a tar suitable, for

example, for use as a road tar for surfacing roads, etc. By continuing the distillation, a heavier tar, or even a pitch, can be produced. Where the tar is to be separately distilled, in a separate still or distillation system, the dehydrating process of the present invention can advantageously be carried out as a preliminary operation to give a dehydrated tar. If the further distillation is car ried out at the same plant at which the tar is produced and dehydrated, the hot dehydrated tar can be conveyed directly to the distillation system and subjected to distillation therein. The preliminary dehydration of the tar reduces materially the hazard of the distilling operation, for example, by reducing foam troubles.

Where the dehydration and distillation are carried out as abatch operation, for example, by

forcing the hot gases through a body of the tar to be dehydrated, the tar will be progressively heated by the hot gases and the water and lighter oils will be progressively removed therefrom, until the dehydration and distillation have been carried to the desired point, after which the operation can be discontinued, the dehydrated and distilled tar withdrawn, and the still recharged with tar to be dehydrated. In the case of continuous dehydration and distillation, the operation can be regulated, by regulating the time of contact of the tar and gases, or the intimacy of contact, or the temperature of the gases, or the amount of the gases so that the desired degree of dehydration and distillation can be effected.

The invention will be further described in connection with the accompanying drawings, illustrating several forms of 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.

In the accompanying drawings, Fig. 1 shows, in a somewhat conventional and diagrammatic manner, an elevation of part of a coke oven battery with part of its by-product recovery system and with apparatus for the dehydration and c, distillation of tar by means of the hot coke oven which may be substituted for the dehydrator in Figs. 1 and 2; and

Fig. 7 shows another form of dehydrator.

In the drawings, part of a coke oven battery is shown conventionally at 1, having the usual uptake pipes 2 for the escape of the coke-oven gases and the usual collector main 3 connected with the uptake pipes. The usual center box for the collector main is shown at 4. The coke-oven gases escape from the collector main and center box through the vapor pipe 6 controlled by a valve 3 and the cross-over main 5 to the cooling and condensing system indicated conventionally as two condensers 7 and 8. From these condensers the gases pass through the pipe 9 and the usual tar trap to the exhauster l0 and thence through the gas outlet pipe to the tar extractor, ammonia saturators and benzol scrubbers, etc. (not shown).

In the collector main, the gases are somewhat cooled, for example, by ammonia liquor sprays,

or tar and ammonia liquor sprays (not shown) and the condensed tar and ammonia liquor collects in the center box 4 while the gases with some entrained tar and uncondensed vapors pass over through the cross-over main 5 to the condensers I and 8.

An outlet pipe 11 is provided leading from the center box 4 for the tar and ammonia liquor which are conveyed therethrough to the decanter 12 where some separation of the tar and ammonia liquor takes place. The tar, after such settling and separation, will still contain appreciable amounts of water intimately combined or admixed therewith. This tar can be conveyed either continuously or intermittently through a pipe 6 controlled by a valve 13' to the dehydrating still l3 where itis subjected to dehydration. Valves 11 and 12 control the fiow of tar to and from the decanter 12. A gas pipe 14, which may be provided with insulation (not shown) leads, preferably, from one end of the collector main 3 to the dehydrator 13 and terminates, for example, in a cross pipe 15 therein having perforations along its bottom side as best illustrated in Fig. 3. A valve 4 is provided in the pipe 14. The gas escapes from the dehydrator through the pipe 16 having valve 20 therein. The gases with admixed vapors may pass through the pipe 16 and the valve 20 to the

separate condensers

22 and 23 where condensation of vapors takes place and then through a gas outlet pipe 19, having a valve 17 therein, and a pipe 24 to the main gas outlet pipe 25. An exhauster 21 is provided between the pipes 19 and 24 to draw the gases through the dehydrator 13 and the

condensers

22 and 23, or the exhauster may be placed in pipe 14. A bypass 18 having a valve 18' therein permits the gas to pass around the condensers when the valves 20, 1'7, 22, 17 and 18 are properly adjusted. The gases from the dehydrator may be carried also to the cross-over main 5 through a pipe 21' controlled by a valve 22 for admixture with the coke oven gases so that condensable constituents contained in the gases from the dehydrator will be recovered in the main recovery system.

The dehydrated, or dehydrated and distilled, tar passes from the dehydrator 13 through the pipe 26 and may be delivered by a pump 27 either through the pipe 28 to the tank 30 or through the pipe 31 to the tank 33,

valves

29 and 32 being provided to control the flow through these pipes.

Tar collected in the condensers '7 and 8 can be withdrawn through

pipes

34 and 35 and delivered through a pipe 36 controlled by a valve 37 to a decanter 33. The tar is separated therein from the ammonia liquor and can be delivered through a pipe 39 controlled by a valve 40 to the dehydrator 13.

In the apparatus illustrated, the by-product recovery system of the coke oven battery can, for the mostpart, be operated in the ordinary way, but a part of the hot coke oven gases are drawn off and employed for the dehydration or distillation of the tar, and these gases and contained vapors are then subjected to separate condensation or are returned for admixture with the main coke oven gases for condensation therewith.

In the collector main, the coke oven gases may be cooled by the ammonia liquor, or tar and ammonia liquor, spray, and the current of tar and ammonia liquor flowing therethrough. Where this tar and ammonia liquor spray system cools the gases to a temperature below that at which effective dehydration of tar can be effected therewith, the ammonia liquor spray may be omitted or at least substantially reduced at the end of the main from which the hot gases are withdrawn, so that the gases will pass through the uptake pipes and into the end of the main and then through the pipe 14 at a temperature not greatly below that at which they escape from the coke oven. In this way the gases can be employed at a high temperature where they have a high distilling capacity so that effective dehydration, or dehydration and distillation, can be efiected therewith; By regulating the amount of ammonia liquor, or tar and ammonia liquor, spray in the end of the collector main from which the gases are taken, the temperature of the gases can be regulated, but in general it will be advantageous to draw off the hotcoke oven gases while they are still at a high temperature so as to ob tain effective heating and dehydration and distillation of the tar therewith. These coke-oven gases will contain all on the greater part of the tar constituents normally contained therein. During the intimate contact of the hot coke-oven gases with the tar to be dehydrated, the gases will be scrubbed and purified to a greater or ess extent from heavy tar constituents, leaving in the gas proportionately more of the lighter tar constituents, while the dehydration and distillation of the tar will drive off from the tar the lighter .oils which will be carried along with the gases By subjecting the escaping from the dehydrator. gases to separate cooling and condensation, a relatively clean oil can be directly obtained from the dehydration and distillation; while by relturning the gases and admixed vapors to the main condensing system, the condensable constituents can be recovered without the need of separate condensing equipment and the resulting products will be relatively cleaner than those i normally obtained.

The dehydrator 13 as previously described may be replaced by a tower as illustrated in Fig. 6 of the drawings, wherein the tar is permitted to flow downwardly over a plurality of baffles so as to expose the maximum surface of the tar to the hot gases ascending through the tower. In this way advantage can be taken of the heating eiiect of the gases to dehydrate the tarwithout retarding the gases or causing any appreciable back pressure or disturbing the balance of gaseous pressures in the system. Referring to Fig. 6, ll indicates a tower which may be of any suitable form and construction and is preferably provided with an insulating jacket (not shown) to i conserve the heat of the gases passing therethrough. The tar accumulated in the decanter 12 is delivered through an inlet pipe 42 to the top of the tower and flows downwardly over a plurality of bailles 43 arranged therein to facilitate the exposure of the maximum. surface of the tar to the ascending gases. These gases may be withdrawn from the collector main 3 and delivered through the pipe 14 as shown in Fig. 1 to the inlet 44 at the base of the tower 1. The

gases circulate upwardly around the baffles 43,

giving up their heat to the descending stream of tar, and escape through an outlet 45 which may be connected to the pipe 16 as shown in Fig. 1. The dehydrated tar which accumulates in the bottom of the tower 41 is withdrawn through a;

sufficient temperature may be obtained.

to the hot gases, it interposes no substantial resistance to the flow of the gases. It is, nevertheless, heated by the gases which, being at a temperature above the dew'point oi the gas for water, cause the vaporization of moisture in the tar and also, depending upon the temperature and other conditions of operation, may remove some of the more volatile constituents of the tar. .jIhe latter can be condensed as hereinbefore described in connection with the condensation of vapors from other gases flowing from the ovens, or a separate condenser system can be utilized to recover any valuable products in the gases which leave the dehydrator.

In the modified form of dehydrator shown in Fig. '7, the operation is similar to that in the dehydrator shown in Fig. 6, except that instead of coming into intimate contact with the hot gases by passing over baffle plates, the tar to be dehydrated is sprayed into the hot gases which are introduced through the inlet 50. On ascending through the tower, the hot gases volatilize the low boiling constituents of the liquid which is introduced through the spray nozzles 51 so that the tar is dehydrated, and depending upon the heat and quantity of the gases, etc., lowboiling constituents of the tar may be volatilized.

The treated tar collects in the reservoir 52 in the bottom of the tower and may be drawn off continuously or at intervals through the outlet pipe 53, or, tar collecting in the reservoir 52 may be withdrawn :by the pump 54 and carried up through the pipe 55 and again subjected to treatment by the hot gases by being sprayed again through the nozzles'fil. Instead of recirculating the tar, the nozzles may be supplied by fresh tar introduced through the pipe 53 or tar may be introduced to the nozzles through both pipes 53 and 55 at one time, or by using separate feed 7 pipes certainnozzles may be supplied with treated tar while other nozzles are supplied with fresh tar. Baiiles 56 or other means may be provided to remove entrained liquor from the vapors escaping through the outlet 57. 7

The amount of dehydration and distillation which takes place within the tower shown in Fig. '7 will depend upon the quantity of the tar and gases and upon the temperature of the gases. Hot gases may be introduced through the inlet 50 from the end of the collector main by means of a connection such as that shown by pipe l l in Fig. 1, or the gas introduced into the inlet 50 may be tapped off of the cross-over inainor any other part of the'apparatus from which gases or" The temperature of the gases will depend upon the part oithe apparatus from which the gases are obtained and upon the operation of the coke oven system. Gases taken off from one end of the collector main through the pipe 'l i, if used in sufficient quantity, will be s'ufiiciently hot to completely dehydrate the tar and to distill ofi considerable of the low-boiling constituents. On the other hand, gases taken from the centre box of the collector main or from the cross-over main will not volatilize such a large percent of the lowboiling constituents, and if used in small quantity will no more than partially dehydrate the tar. By recirculating the tar in the tower the amount of dehydration and distillation may be increased. The desired degree of dehydration and .volatilization may be obtained by selection of gases of the proper-temperature and by proper regulation of the quantity of gas and oil.

Instead of dehydrating coal tar produced at the coke-oven battery where the dehydration and distillation are eiTected, tar from other batteries, or from other sources such as gas-house tar or water-gas tar, can be similarly dehydrated with hot coke-oven gas. In cases Where a mixed product is desired, different kinds of tar can be mixed before dehydration and the mixed tar then dehydrated, or dehydrated and distilled. Mixtures of water-gas tar and coal tar can thus be employed to give mixed dehydrated products; or mixtures of gas-house tar and coal tar, etc. Mixed oils will also be produced by cooling the gases used for dehydration.

In a similar manner, gas-house tar can be dehydrated or dehydrated and distilled, by means of hot gas from the gas retorts; and Water-gas tar can be similarly dehydrated and distilled by means of hot water gas. The invention is thus of more or less general application to the dehydration of tar with the hot coke-oven or other gases, thus utilizing heat commonly wasted and enabling dehydrated tar to be directly produced at the same plant at Which water-containing tar is produced.

Instead of dehydrating tar, tarry oils can be similarly dehydrated, for example, oils such as are produced in the diiierent condensers of a byproduct recovery system where ammonia liquor is employed for throwing down the tarry oils. By subjecting such oils to dehydration in this way, dehydrated oils can be directly produced at a by-product coke-oven plant Without the expenditure of fuel for heating and dehydration, and with utilization of the heat contained in the hot coke-oven gases, which is commonly wasted. In addition to dehydrating such oils, tarry oils, or tars of varying oil content, the dehydration may be combined with distillation of part of the oil constituents and the distillate can be separately condensed, thus giving lighter distillate oils and heavier dehydrated residual oils or tars.

I claim:

1. The method of dehydrating tar which comprises passing water-containing tar to a dehydrating still, bringing hot coal distillation gases from a coke oven or retort into intimate contact with the tar in the still while the gases are yet at a temperature suificient to effect substantially complete removal of the water from the tar, regulating the contact of the tar with the gases so that the major portion of the volatile oils originally present in the tar remains in liquid form, Withdrawing from the still a tar product containing a major portion of the volatile oils originally present in the tar but substantially free from water.

2. The method of dehydrating tar which comprises passing water-containing tar into a dehydrating still, bringing hot coal distillation gases from a coke oven or retort into intimate contact with the tar in the still while the gases are yet at a temperature above about 125 (3., regulating the contact of the tar with the gases so that water is removed therefrom and so that the major portion of volatile oils originally present in the tar remains in liquid form, and withdrawing from the still a dehydrated tar product comprising a major portion of the volatile oils originally present in the tar.

3. The method of dehydrating tar which comprises passing water-containing tar into a dehydrating still, bringing hot coal distillation gases from a coke oven or retort into intimate contact with the tar in the still while the gases are at a temperature of about 160 C., regulating the contact of the tar with the gases so that the major portion of volatile oils contained in the tar remains in liquid form, and withdrawing from the still a dehydrated tar product comprising a major portion of the volatile oils originally present in the tar.

4. The method of dehydrating and distilling tar l which comprises bringing water-containing tar into contact with hot coal distillation gases whereby the tar is dehydrated and distilled, and subjecting the resulting gases with admixed vapors from the dehydration and distillation to condensation for the recovery of condensable constituents therefrom and returning condensed oils thus obtained to the tar to give a dehydrated tar containing substantially all of its normal oil constituents.

STUART PARMELEE MILLER.