US2956639A

US2956639A - Coke oven gas naphthalene absorbing final cooler

Info

Publication number: US2956639A
Application number: US788361A
Authority: US
Inventors: Elwood V Schulte; Harold T Stirling
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1959-01-22
Filing date: 1959-01-22
Publication date: 1960-10-18
Anticipated expiration: 1977-10-18
Also published as: GB920780A

Description

COKE OVEN GAS NAPHTHALENE ABSORBING FINAL COOLER Filed Jan. 22, 1959 Oct. 18, 1960 E. v. scHULTE ET AL 2 Sheets-Sheet 1 Oct. 18, 1960 E V SCHU| 1E ET AL 2,956,639

COKE: OVEN GAS NAPHTHALENE ABSORBING FINAL COOLER 2 Sheets-S'heet 2 Filed Jan. 22, 1959 T w mk TWK) G UNH 9 OAA 1 RMT( m 5 5 c. G m N 1mm@ NTT( T 4 M U S D O o A2a mn W s 'Nw G QH A IL G L their' e? Trae/ Y' United States COKE OVEN GAS NAPHTHA-LENE ABSORBING FINAL COOLER Elwood V. Schulte and Harold T. Stirling, Pittsburgh,

Pa., assignors to Koppers Company, Inc., a corporaon of Delaware Filed Jan. 22, 1959, Ser. N0. 788,361

15 Claims. (Cl. 18`3-.2)

This invention -relates to improvements in the general operation of final cooler apparatus for coke oven chemical recovery plants, and more particularly, to improvements in the operation of such final coolers of the general type comprising a towerhaving an upper gas washing isection and a lower water scrubbing section with a .funnel immediately below the vlower gas inlet to collect the cooling Water from the washing section and a depending -tail pipe, to discharge the water into a bath of solvent for naphthalene, such as tar, at the base of the scrubbing section, with zig-zag horizontal baffles between the base of the tail pipe and the apex of the cone of the .funnel :for decantation of the water before it overflows at a-level below the top of the funnel to a water cooler Vfor return to the upper part of the gas -washing section of the tower. In such apparatus, tar is fed to the base of the lower scrubbing section, continuously at about .the level of the second bottom baffle, and intermittently at higher levels, and mechanical means are provided for off-flow of tar from the base of the lower scrubbing section=to maintain a constant level of the bath of solvent, such as tar, to absorb naphthalene which has condensed from the gas by the cooling water, to remove such naphthalene prior to flow of the water to the water cooler on its way back to the upper gas cooling section in the Vof the scrubbed water in the scrubbing section, during its flow to the water cooler, than the scrubbing section is normally designed to operate, without increasing the -height of the section and tower or requiring supplemental decantation equipment outside the tower in the limited ground area around the same for the purpose.

More specifically, a primary object of the invention is to effect such change in mode of operaion in a simple, economical and facile way requiring no additional equipment by altering the arrangement and location of the parts, in a manner equally adaptable to static type final coolers of the packed type and to all spray type coolers devoid of packing in the gas cooling section and operable with water pressure higher than customary with the packed column type cooler.

Accordingly, the invention comprises lowering the location of the funnel in the existing coolers, as well as new ones, and raising the water outlet to maintain below the gas inlet a head of the hot cooling water on the tail pipe at a levelat least as high as the top of the funnel, and preferably, at a distance above the top of the funnel equal to the-height of two of the lower bafiies, disposing three of the upper baliles to serve as foam collectors beneath their lower surfaces, and venting the three upper bandes, of a vertical row of baffles of greater height VVthan the overall horizontal dimension ofthe baffles, `to the gas space in the upper gas cooling section vof the tower. Preferably, the upper three bafes are oppositely inclined, but they may be horizontal instead ywhen provided with a deep weir lip.

Preferably, eachrof the lower baffles `are also provided with solvent drains to the bath below, and forall Vspray coolers a perimetrical ring is superposed abovethe perimeter of va conical Ydeliector below the gas inlet to deaerate the water passing to the head of water above ythe tail pipe. Y

The standard methodis to spray water into a tower in the form of an all spray section or a packed column, through which the gas passes from the exit of the arnmonia saturator to the benzol or light oil scrubber. The purpose of this final cooler is to removethe heatlthat had been formed due to the compression of the gas at the exhauster before the reheater forthe saturatonand also to remove the heat'formed d ue tothe reactionof vsulfuric acid with ammonia in the saturator. The temperature of the gas leaving-thews'aturator is lowered as muchfas possible with coolingwater available at the plantlo obtain maximum absorption oflight oil ,fromYthe ,gas in the benzol washers using the minimum vof lwash oil circulation. 4In this type of final cooler the water isvsprayed `into the upper Ygas Vcooling section 'where it contactsY the gas countercurrently to remove the heat from the gas. The gas, in being cooled at the final cooler, frequently reduces the dewpoint of the naphthalene in the gas to a point lower than the dewpoint ofthe naphthalene in the gas leaving the primary coolers. Experience also indicates that the gas leaving the primary coolers frequently has a naphthalene content greater than that which would be present in the gas if itwas merely saturated to its dewpoint. Naphthalene, therefore, that is .condensed out of the gas, is washed with the water out of the base of the lupper final cooler lsection -and into a lower scrubbing section where the naphthalene is recovered by a solvent. The water is then pumped Yto the cooling vtower where itis ren-cooled in preparation for recirculation back tothe upper final cooler section again.

In this lower scrubbing section, the water from the bottom of the upper gas coolingsection of the final cooler flows through a funnel into a tail pipe downwardly to a pointnear the base of the lower `section of the tower located below the upper final gas cooling section. Below the tail pipe or downspouty a baffle defiects the water and causes it to turn upwardly to a point near the top of the tail pipe inthe lower naphthalene absorbing or scrubbing section. Located above the base of the tail pipe, nine zig-zag horizontal baffle plates with openings at their ends alternating from side to side, direct the water horizontally back and forth as it passes between .the trays or baflies progressively upwardly to a wateroverflow at the level of the top of the tail pipe in the lower naphthalene absorbing vor scrubbing section. The opening at the end of each tray represents roughly 10% of thetotal cross-sectional area of the shell. The distance between traysis usually about two feet and the velocity of the water, as it ows betweentrays, is in the neighborhood of ten times the superficial upward velocity in the naphthalene absorbing section. The superficial upward velocity is that velocity that would exist if thewater had moved uniformly upwardly through the tower when it was not equipped with any obstruction of any kind.

Coke oven tar is either fed continuously or batchwise to the lower naphthalene absorbing section and a tar level maintained a few feet above the bottom of the tail pipe. A heating coil submerged in the tar at the base of the lower naphthalene absorbing section keeps the tar at about 60-95 and assist in preventing emulsions.

The water, as it departs from the base of the tail pipe, ows upwardly through the bath of tar, and in doing so, loses its entrained naphthalene to the tar. The naphthalene dissolves in the tar. The de-naphthalenized water then overflows from a level below the top of the funnel at the top of the tail pipe in the naphthalene absorbing section, as described previously, to a hot well where conveniently it is removed by pump and delivered to the cooling tower to re-cool the water in preparation for additional cooling in the upper final cooler section. Experience over the years, and up until about the time of this invention, has been that this particular design of the lower naphthalene absorbing or scrubbing section was limited with regard to water rate to the extent that the nominal or superficial velocity upwardly of the water above the tar level in the lower naphthalene absorbing section could rarely exceed about A@ to W10 of a foot per minute without carrying tar out of the naphthalenc absorbing section. Tar entrainment in the outlet water from this lower section is impractical or intolerable, and undesirable, because this tar, when it is exposed to air in the cooling tower, becomes oxidized and cooled and thereby deposits on the surfaces of the packing in the cooling tower. Eventually, these surfaces become so badly contaminated that the cooling tower must be taken out of service and cleaned. This is a troublesome and expensive procedure and it is apparent that it should be avoided, if possible.

In such conventional system the trays originally were equipped with a large number of perforations, about 5/16 diameter on 4" centers, and as a naphthalene absorber remains in service for a period of years, it becomes necessary to reduce very gradually the water rate that is passed through the naphthalene absorbing section in order to prevent carry-over of tar out of the section. Over the years, a pitch-like deposit accumulates, as a result of continuous operation, on each of the horizontal trays located in the lower naphthalene absorber section, so that the free area between trays became reduced. This results in a gradual increase in water velocity between trays to the extent tha-t the heavier tar is carried across and upwardly with the water to the outlet. Removing the pitchdlike deposits from the trays would restore the capacity of the unit from .the standpoint of tar separation from water to that which existed when the unit is first placed in operation. Enlargement of the perforations in the trays to approximately 11/2 diameter, in order to keep the trays clean, indicates that the capacity of the lower naphthalene absorbing section, from the standpoint of tar separation from water, was no more, and perhaps less, than it had been before the holes in the trays were enlarged. In order to attempt to increase the capacity of the lower naphthalene absorbing sections, other schemes were also tried. These included increasing fthe free area of the opening at the ends of each of the trays, adding tar intermittently, adding tar to the naphthalene absorbing sect1on at slower rates, eliminating perforations entirely from each of the trays and installing individual tray drains that carried the separated tar either to the tray below or directly to the tar located at the base of the lower naphthalene absorbing section. The experience from each of these changes in design was that the attempt to increase the capacity of the unit failed and that the superficial velocity of the water upwardly through the lower naphthalene absorbing section could not be increased much above the 5A() to %0 of a foot per minute cited previously in this connection.

The present inventors conceived that very likely one of the limiting factors in the capacity of these units was associated with the entrainment of tine gas bubbles in the water that was passing from the upper final cooler sect-ion down through the tail pipe and up through the tar in the lower scrubbing section. It was felt that any minute gas particles would cause a frothing action as the gas and water mixture changed direction at the base of the `downcomer or tail pipe and passed upwardly through the tar solvent. Such gas particles would entrain tar and carry the tar upwardly to the top of the lower naphthalene absorbing or scrubbing section because of the fact that the presence of the gas in the tar would lower the average specic gravity of that particular mixture below the specific gravity of the water.

Test work and observations demonstrated `that this conception regarding gas entrainment and its etect upon the capacity of the column was correct. The tests demonstrated 'that when a small amount of air or gas was entrained in the water passing downwardly through the tail pipe from the funnel and up through a layer of tar in the lower naphthalene absorber section, the allowable superficial velocity of water was about 5A@ to %0 of a foot per minute which was very much like the conditions found inpractice in final cooler systems in coke plants. In other tests, with complete removal of air or gas from the water before it passes from the funnel down into the tail pipe and then upwardly through the tar layer, the present inventors were able to obtain superficial velocities of at least two feet per minute without entrainment of tar in that water as the water exited from the lower absorber section. To this end, the inventors lower the funnel and raise the water level outlet of the unit in the lower section to form a hold tank above the funnel, whereby the water, before it leaves the gas liquid con tacting upper section of the final cooler, is given a retention time at low velocity, while still above the base of the funnel, of at least more than ten seconds and usually not more than three minutes to ailow a major portion of the entrained gas to be separated by gravitational separation from the water before this water passes into and suddenly tlows down at a much higher velocity through the tail pipe or downcomer, for contact with the tar in the lower naphthalene absorbing section, which very high velocity prevents residual gas from escaping to the head of the column of water by gravitational separation.

The inventors further found that the capacity of the lower naphthalene absorbing section could be further increased above that of previously designed units even if there still was some entrained gas or air in the water by entrapping the particles of the water that had the residual gas entrained therein, from the water, after it leaves the tail pipe, in a manner that they would not be allowed to reach the surface of the water below the funnel where the water flows out from the lower naphthalene absorber or scrubbing section of the final cooler to pass on to the water cooler. A sloping type of upper baffle has been found to be a simple means for the entrapment of these tar particles which have a gravity less than that of water due to the presence of the residual gas or air particles therein. However, there lare other simple means that are effective for the entrapment without departure from the principle used. For example, the entrapping upper baiiies are suitable when placed horizontally with a downwardly extending tlip at the edge of the baiiie adjacent the opening opposite this baffle. Also, the sloping upper bathe effect is obtained by building the baflie segments in horizontal steps, working downwardly stepwise to a point adjacent the opening.

The function of the upper entrapment bafes, of course, is not completed if the entrapped gas and its entrained tar are not allowed to escape from a point below said baffle and, therefore, vents are included as an escape mechanism to remove either separated and unseparated gas as rapidly as it accumulates. The capacity of the lower naphthalene absorbing section of the nal cooler is thus increased from the standpoint of separating tar from water flowing through rthe lower naphthalene absorbing section after said water has been in contact with said tar and while there is entrained gas or air in 4the water as it leaves the downcomer or tail pipe and enters the tar submerging the bottom of the tail pipe. It is now possible to obtain tar free water at velocity capacities greater than those obtainable previously in spite of the fact that some gas or air may be entrained in the water.

The entrainment problem is not as serious with final coolers designed with -a contact surface made up of packing in lthe upper cooler section, as it is with the all spray type of gas cooler. When water is sprayed onto the surface of the packing at or near the top of the upper final cooler section, this water drains gently over the surface of the packing until it reaches the lowerrnost portion of the packing. From here it drops gently onto the surface of the water retained in the funnel of this type of cooler. Unfortunately, a packing is somewhat limited in capacity and greater gas velocities can be tolerated in the final cooler while obtaining satisfactory heat transfer by the use of an all spray upper section devoid of packing to create the surface required to transfer heat from the gas to the water. In this case, a plurality of sprays is used at one or more elevations in the upper cooller section. When spraying the water with differential pressures in excess of 3 or 4 1lbs./sq. in. across the spray nozzles and spraying the water downwardly into the tower, the spray droplets -impinge against the surface of the water at the base of the upper final cooler section at relatively high velocity. This rapid impingement aggravates the de-entrainment problem at the base of the upper cooler section and a greater retention time is thereby required in order to get the gas particles separated from the hold tank of Water at the head of the tail pipe.

This disadvantage of `an all spray type gas cooling upper section in combination with a lower naphthalene absorber section for purposes of removing naphthalene from the hot cooling water, is overcome here by the raised water level arrangement so as to operate the upper gas final cooler section with gas velocities in excess of one foot per second upwardly through the upper gas cooling section and with use of the required amount of water to obtain the desired cooling of the gas and still obtain superficial water velocities upwardly in the lower naphthalene absorber section greater than 0.5 foot per minute.

We have also overcome and minimized still further the effect of the spray impinging against the surface of the water bath by placing a conical baffle above the top level of the hold water retained in the funnel in the lower section of the final cooler with a perimetrical defiector ring above the perimeter of the conical bafiie, so that the spray now impinges against this bafe to deaerate the liquid before it reaches Contact with the hold water in the funnel. This has also made it possible to increase the capacity of the lower naphthalene absorbing section even with the all spray type upper gas cooling section.

While the invention as hereinabove set forth is primarily designed for, and particularly adapted to improve the general operation of, a coke oven gas final cooler of the special types set forth, without increasing the overall height of the tower or its lower water scrubbing solvent section, and without requiring location of auxiliary equipment around the ground area alongside the tower or its water cooler, to complete 4the de-tarring of the water before it enters the water cooler for return to the upper gas washing section, the invention is not limited in all its aspects to such specific embodiment of the invention, since much of the advantages of the invention is of utility in other countercurrent scrubbing, decanting, and emulsion separating operations and processes involving chambers containing gas in contact with aqueous mediums requiring separation of two immiscible mediums of different specific. gravities. Hence, the invention, in its broader aspects, is not confined in all its uses to the specific use and specific embodiment herein-described and illustrated.

In addition to the general objects recited above, the invention has for further objects such other improvements or advantages as may be found to obtain in the structure and general operation of a final cooler in a coke oven gas chemical -recovery system as shown on the drawings and hereinafter-described or claimed.

In the accompanying drawings:

Figure l is a schematic side elevational arrangement of a train of apparatus elements for processing coke oven gas to remove benzol therefrom which includes the present invention therein;

Figure 2 is a schematic vertical cross-section of the final cooler therein, with the upper gas cooling section in the form of an all spray chamber devoid of packing;

Figure 3 is a horizontal sectional View taken on the line III-III of Figure 2;

Figure 4 is a partial view of the upper portion of Figure 2, but with the upper gas cooling section in the form of a packed column with sprays to deliver the cooling water to the top of the packing for trickling through the same to the lower water scrubbing section.

The same reference numerals are used for like parts in each of the several views.

Referring to the drawings, there is indicated at 10 a coke oven battery, from which coke oven gas is derived, and which passes out th-rough the collecting main 11 to a downcomer 12, for tar and aqueous condensate of the gas, and thence, through a line 13 to the primary cooler 14, through which the gas passes countercurrently to cooling water from lines 16, and thence is forwarded by exhauster 17 to a combined tar precipitator and reheater 18. In the primary cooler 14 the gas is cooled to about 25 C., and tar and ammonia liquor therefrom are drained to the hot drain decanter tank 19 which discharges the tar to the tar storage tank 2t) and overows ammonia liquor through line 21.

The gas from the exhauster 17 enters the tar extractor 1S at about 30 C. from the reheater therein, and leaves at the same temperature to enter the ammonia removal means in the form of a saturator 22 at said 30 C. temperature. In the saturator the ammonia of the gas reacts with sulfuric acid to form ammonium sulfate which precipitates therein, the water of crystallization passing ofi with the gas at a slightly higher temperature as a result of the reaction. From the saturator 22 the hot gas passes to an acid separator 15 which removes any adhering acid.

As the gas to be debenzolized should be at a lower temperature for this purpose, the gas then passes into a final cooler 23 through the gas inlet line 24, and the cooled gas leaves through the gas outlet line 26 to enter the light oil, or benzol, scrubber 27 wherein the gas is scrubbed with wash oil to absorb the light oil, i.e., benzene and its ho-mologues, etc. From the benzol scrubber the gas is lead to further gas processing equipment, or use, or to a gas holder for further service.

in the final cooler 23, the upper section of the tower is given over to direct gas washing with cold water which enters through spray heads 25 from a water cooler 25. The gas leaves at the upper end of the tower and enters at the intermediate level of inlet 24.

As shown in Figure 2, the upper gas cooling section 23a is devoid of packing and the gas is washed by sprays of water under higher pressure than when a packing 23h is used as shown in Figure 4.

Referring to Figure 2, for the all spray type cooler, a conical defiector 27 is disposed across the tower 23 immediately below the gas inlet 24, with a peripheral space 28 between the same and the vertical wall ofthe tower 23, and downwardly extending deliector ring tray 2,9 is superposed over the defiector 27 above the space 28 to arrest the spray from the spray heads 25 before the liquid of the spray passes through said space 28, thus deaerating the spray liquid of some of the cokeoven gas ,and of any carryover air from the air cooled water cooler ,25.

A funnel 33 is located below the deflector 27 with the top 30 of the funnel at a distance below the defiector, which distance is about equal to the height of three of the horizontal zing-zag baille spaces above the top level 31 for a tar bath at the bottom of the lower naphthaleneabsorption water-scrubbing section 23C in the lower part of the final cooler tower 23. A tail pipe 32, disposed axially of the tower 23, leads from bottom 4outlet 34 for the funnel 33 to terminate above the lowermost of a series of horizontal zig-zag baiiles 35 below, which are spaced about 2 feet apart, one above another. The bottom tray is set about six feet above the bottom or base of the lower scrubbing section, and the zig-zag baffles are in a vertical row or series of live horizontal lower baffles and three upper oppositely inclined baies 36, with the fixed closed end of these baffles raised about an inch above their free open ends 37 to provide a foam collecting area 38.

The free ends 37 of the inclined bafes 36 are provided with depending lips 39 to act as weirs, each of which is spaced the same distance, about 2 feet, above a tray below, which is the same spacing as the spaces between the horizontal trays lower down in the lower water scrubbing section 23C. The foam areas 38 are lvented to the gas space 23a above in the upper gas cooling section at a level just below the gas inlet 24 to the upper gas cooling section 23a by vents 40, and the inclined bafes 36 range -up to the level of the top of the tail pipe 32, which is the level of the outlet from the funnel 33.

The lower horizontal bales or trays are each provided with tar retaining lips 41 and tar drains 42.

The scrubber water is taken o from the lower scrubbing section 23e by a liquid outlet 43, located above the top of the tail pipe 32, just below the top perimeter of the funnel 33, by means of an adjustable over-now mechanism 47 set to maintain a water liquid level in the lower scrubber section at a level above the top perimeter of the funnel 33 and just below the gas inlet 24 to the upper gas cooling section 23a of the tinal cooler. This overflow level controller 47 is vented by a line 48 to an emergency water over-flow line 49 leading from a higher level above the funnel 33 in the `water scrubbing section 23C.

Tar from the tar storage tank 20 is fed as solvent into the lower water scrubbing section by automatic means therefor 50, continuously at ya lowermost level 51, preferably at the level of the second tray 35 from` the bottom, and intermittently at several higher levels 52 to wash down naphthalene accumulations.

The tar is withdrawn from the base or bottom of the lower scrubbing section 23C through a tar outlet 53 by automat-ic decanter means operable to maintain the bath or pool of tar at a constant level, submerging the lower end of the tail pipe 32, at `about the level of the second tray 35 from the bottom of the scrubbing section 23C.

As shown, this automatic decanter means comprises a riser line 54 which leads to the bottom of an inner tube 55 open at its top to an outer conduit 56. The tar is returned 4to the tar decanter tank 19 by a line 57 leading from the bottom of the outer conduit 56.

The tar which is released of gas in the vents 4t) is drained to the outer conduit 56 by means of drain lines 58. The level of the tar bath is controlled by a tar regulator 59 vented at 6@ to the upper gas cooling section 23a. As conventional, the tar is heated by means, not shown, to keep it fluid.

The structure and operation is .the same with the tower constituted of a packing, as in Figure 4, except that as the cooling water merely trickles on the head of the hold tank of water which is above the funnel, the conical deector 27 and ring 29 are eliminated as unnecessary With Water merely tckling down from the packing 231:.

In the table below, are the operating data with the unit arranged as in Figure 2.

TABLE Operating data-five horizontal `trays, three sloping trays, sprayed water feed with feed hold-up tank Run No 17 18 19 20 Water Rate, gpm 70 88. 5 129 97 Superficial Water Velocity, ft./

Min 0. 97 1. 23 1. 79 1. 35 Tar Rate, g D mA 2% 2% 2% 2% Tar Level, Trays. 3 3 3 3 Water Inlet Temp., O-. 32 38 40 42 Tar Inlet Temp., C 96.1 98. 9 96. 6 93. 4 Temp. Bet. 1st and 2nd Tr.,

C 53 45 45 45. 5 Top Condition Excellent Good B ad Passable Moisture in Tar Foam =25.1- by weight The top surface was in excellent condition during run No. 17 when the superficial velocity was about 0.97 foot per minute. Run No. 18, during which the supercial velocity was 1.23 feet per minute, had a faint trace of fine froth on the top surface. A very occasional group of bubbles rose through the No. 1 vent. However, the surface conditions in this run were good and appeared to be better than they had been in run No. 14, when there was no hold tank and the superficial velocity was only 1.12 feet per minute.

The superficial velocity was increased to 1.79 feet per minute in run No. 19. A considerable amount of ne froth began to accumulate on the surface which would not in itself have been serious. However, there were several large patches of tar and air which iioated up making the run denitely not passable. Tar foam began to flow from the No. l vent to the drum. However, the foam over-W rate was only about half as fast as it had been in a run when there was no hold-up tank and the supercial velocity was only 1.42 feet per minute. There was about two inches of tar foam in the No. 2 vent and an occasional bubble in the No. 3 vent.

The water rate was decreased in run No. 2O until the superficial velocity was 1.35 feet per minute. The top conditions were definitely passable. A slight stream of tar flowed from the No. l vent, and the conditions in the Nos. 2 and 3 vents remained about the same. This is an improvement in passable water rate over that in a run during which there was no inlet hold tank and the supercial water velocity was only 1.12 feet per minute. It is also a great improvement over operation with horizontal trays when the maximum tolerable supercial velocity was only about half as much.

After the completion of run No. 20 the splash plate and ring baille were removed. The top conditions became much worse showing that a large amount of the air entrainment is relieved when `the impingement of the spray on the water surface is stopped.

In operation with the water spray from the all spray chamber 23a trained on the ring deector 29 and conical deflector 28, the quantity of gas entra-inment is initially appreciably decreased by said deectors and is then further decreased by the hold tank body of water when retained in the funnel 29 above the top of the tail pipe 32. With the three vented, generally horizontal slanted trays above the live truly horizontal trays, it is possible to operate at supercial upward velocities as high as 1.12 feet per minute without the hold tank of water and 1.35 feet per minute with the hold tank of water.

The water is retained at such a low velocity in the hold tank that most of the entrained gas rises to the surface and passes into the gas stream above. In the tail pipe the velocity is at a rate that the residual entrained gas cannot pass up but passes on through the bath of solvent at `the base of the tail pipe.

In the solvent bath the naphhalene is absorbed from the water and in so doing, some tar picks up some of the entrained gas from the water and forms globules lighter than the solvent and water. As the hot cooling water traverses the zig-zag pathway horizontally, the tar which has entrained gas rises to the bottom surface of the trays as the water ows horizontally along the bales. The tar which releases the entrained gas settles back down to the top surface of `a tray below and thence passes through the drains to the bath of solvent below. Tar globules and released gas nally rise to the collecting areas below the inclined baflies, enter the vents at a water level below the upper outlet for the scrubbed water. The water thus leaves the scrubbing section free of carryover tar solvent and naphthalene, and the lighter tar and gas rise through the vents releasing the gas into the gas cooling section at a level above the water outlet. As the tar is released of its entrained gas it settles in the vents to ow oi through the tar drains to the tar oiftake means.

In typical operation, tar is continuously added opposite the No. 2 tray from the bottom at a rate between one gallon of tar per ton of coal carbo-nized per day and about gallons of tar per ton of coal carbonized per day. The tar can also be added intermittently instead of continuously.

The invention as hereinabove set forth in embodied in particular forms of construction and method of operation, but may be variously embodied within the scope of the claims hereinafter made.

We claim:

l. Final cooler apparatus for coke oven gas chemical recovery plants comprising: `a tower constituted of an upper gas cooling section having an intermediate gas inlet to the tower in communicable connection with an ammonia saturator, an upper youtlet for finally cooled gas from the tower in communicable connection with a light oil scrubber for the coke oven gas, and means for introducing cooling water to the upper portion of said upper section, and a lower water scrubbing section having its top below said gas inlet and in open communication with the base of the upper section of said tower to receive hot cooling water therefrom, a funnel in said lower section with its top perimeter at a spaced distance below said gas inlet, a tail pipe disposed axially of said tower and extending from the outlet of said funnel down to a spaced distance above the base of the lower section, a vertical series of horizontal zig-zag flow baffles of greater height than the horizontal dimensions of the lower section disposed in the lower section to range upwardly from below the base of the tail pipe to the top thereof around the outside of the tail pipe, the upper baffles I of the series being disposed to serve as foam collectors beneath their under surfaces and having vents therefrom to the gas cooling section above the funnel, a water outlet from said lower section at a level above the uppermost of the vertical series of baiies but below the underside of said funnel, conduit means for outflow of water from the Water outlet with provision for maintaining a water liquid level in said lower section at a level above the top perimeter of the funnel and below said gas inlet, a water cooler connected with said water outlet for cooling tne water from said conduit means and provided with means for returning the cooled water back to the means for introducing cooling water to the upper section of the final cooler, means for introducing solvent of a different specific gravity from water into the lower section, means for draining solvent from the lower baffles of the series to the base of the lower section at a level which is below the lowermost baffles below the base of the tail pipe, and outlet means for offtake of the drained solvent from the base of the lower section with provision to maintain a bath of the solvent around the base of said tail pipe.

2. Apparatus as claimed in claim l, and in which the upper baffles, which are disposed to serve as foam co1- assenso lectors, comprise oppositely inclined baies with their lower free ends spaced the same distance above a baille below, which is the same as the distance between the lower baffles with the solvent drains, and in which each vent is provided with a drain for flow of solvent -to the outlet means for offtake of solvent from the base of the lower section.

3. Apparatus as claimed in claim 1, and in which the upper gas cooling section is one of the all spray type devoid of packing and in which a conical deector and a superposed perimetrical ring deector is interposed at a level between the gas inlet to the gas cooling section and the level for the top of the liquid above the tail pipe in the lower water scrubbing section.

4. Apparatus as claimed in claim l, and in which the upper gas cooling section is one of the packed type containing water and gas dispersing contact material between the gas inlet and the water inlet to the upper section, and in which the chamber area between the base of the packing and the level for the top of the liquid in the lower water scrub-bing section is devoid of obstructions to the downflow of liquid.

5. Final cooler apparatus for coke oven gas chemical recovery plants comprising: a tower constituted of an upper gas cooling section having an intermediate gas inlet to the tower in communicable connection with an ammonia removal means, an upper outlet for iinally cooled gas from the tower in communicable connection with a light oil scrubber for -the coke oven gas, and means for introducing cooling water to the upper portion of said upper section, and a lower water scrubbing section having its top below said gas inlet and in open communication with the base of the upper section of said tower to receive hot cooling water therefrom, a funnel in said lower section with its top perimeter at a spaced distance ybelow said gas inlet, a tail pipe disposed axially of said tower and extending from the outlet of said funnel down to a spaced distance above the base of the lower section, a vertical series of horizontal zig-zag ow baflies of greater height than the horizontal dimensions of .t-he lower section disposed in the lower section to range upwardly from below the base of the tail pipe to the top thereof around the outside of the tail pipe, the -upper baffles of the series being ldisposed to serve as foam collectors beneath their under surfaces and having vents therefrom to the gas cooling section above the funnel, a water outlet from said lower section at a level above the uppermost of the Vertical series of baffles but below the underside of said funnel, conduit means for outow of water from the water outlet with provision for maintaining a water liquid level in said lower section, a water cooler connected with said water outlet for cooling -the water from said conduit means and provided with means for returning the cooled water back to the means for introducing cooling water to the upper section of the nal cooler, means for introducing solvent of a different specific gravity from water into the lower section, means for draining solvent from the bathes of the series to the base of the lower section below the base of the tail pipe, and overflow outlet means for offtake of the drained solvent from the base of the lower section with provision to maintain a bath of the solvent submerging the base of said tail pipe but below said water outlet.

6. Apparatus as claimed in claim 5, and in which the upper baffles which are disposed to serve as foam collectors, comprise opposi-tely inclined baflies with their lower free ends spaced the same distance above a baille below, which is the same as the distance between the lower baies with the solvent drains, and in which each vent is provided with a drain -for ilow of solvent to the outlet means for ofltake of solvent from the base of the lower section.

7. Final cooler apparatus for coke oven gas chemical recovery plants comprising: a tower constituted of an upper gas cooling section having an intermediate gas inlet to the tower, an upper -outlet for finally cooled gas from.

,the tower, and means for introducing cooling water to the upper portion of said upper section, and a lower water scrubbing section having its top below said gas inlet and in open communication with the base of the upper section of said tower to receive hot cooling water therefrom, a funnel in said lower section with its top perimeter at a spaced distance below said gas inlet, a tail pipe disposed axially of said tower and extending from the outlet of said funnel down to a spaced distance above the base of `the lower section, a vertical series of horizontal zig-zag ow bafes of greater height than the horizontal dimensions of the lower section disposed n the lower section to range upwardly from below the base of the tail pipe to -the top thereof around the outside of the tail pipe, the bai-lies of the series being disposed to serve as foam collectors beneath their under surfaces and having vents therefrom to the gas cooling section above the funnel, a Water outlet from said lower section at a level above the uppermost of the vertical series of bafles but below the underside of said funnel, conduit means for outflow of water from the water outlet with provision for maintaining a water liquid level in said lower section at a level above the top perimeter of the funnel and below said gas inlet, means for introducing solvent of a different specific gravity from water into the lower section, and overflow outlet means for oiftake of solvent from the base of the lower section with provision to maintain a bath of the solvent submerging the base of said tail pipe but below said water outlet.

8. Apparatus as claimed in claim 7, and in which the upper baflies, which are disposed to serve as foam collectors, comprise oppositely inclined baffles with their llower free ends spaced the same distance above a bale below, which is the same as the distance lbetween the lower baffles with the solvent drains, and in which each vent is provided with a drain for flow of solvent to the overow outlet means for oitake of solvent from the base of lower section.

9. Apparatus as claimed in claim 7, and in which the upper gas cooling section is one of the all spray type devoid of packing and in which a conical deector and a superposed perimetrical ring deflector is interposed at a 'level between the gas inlet to the gas cooling section and the level for the top of the liquid above the tail pipe in the lower water scrubbing section.

10. Final cooler apparatus, comprising: a water scrub- Lbing section having at its top a water inlet to receive water containing gas and a Water immiscible constituent, a funnel in said scrubbing section with its top perimeter at a spaced distance below said water inlet, a tail pipe disposed axially of said funnel and extending from the outlet thereof down to a spaced distance above the base of said scrubbing section, a vertical series of horizontal zig-zag ilow bailles of greater height than the overall horizontal dimension of the scrubbing section disposed in the latter to range upwardly from below the base of the tail pipe to the top thereof around the outside of the tail pipe, the upper baies of said series being disposed to serve as foam collectors beneath their undersurfaces and having lvents therefrom to a gaseous area at a level above the water inlet, a water outlet from said scrubbing section at a level above the uppermost of the vertical series of baies but below the underside of the funnel, conduit means for voutiiow of water from the water outlet with provision for maintaining a water liquid level above the top perimeter of the funnel and below said water inlet, means for introducing a solvent of greater specific gravity than water and immiscible therewith into the scrubbing section, means for draining solvent from the lower bales of said series to a point below the base of the tail pipe, and overflow means for offtake of solvent from the base of said scrubbing section at a level below the base of the tail pipe with provision for maintaining a bath of solvent submerging the base of said tail pipe but below said water outlet.

1l. Apparatus as claimed in claim l0, and in which the upper baies, which are disposed to serve as foam col lectors, comprise oppositely inclined baflles with their lower free ends spaced the same distance above a balile below, which is the same as the distance between the lowermost bafes with the solvent drains, and in which each vent is provided with a drain for ow of solvent to the overow outlet means for solvent from the base of the lower section.

12. Apparatus as claimed in claim 10, and in which a conical detlector and a superposed perimetrical ring deiiector is interposed at a level between the water inlet and the level for the top of the liquid above the tail pipe in the scrubbing section.

13. Apparatus for separating naphthalene from water containing entrained gas, comprising: a water scrubbing section having at its top a water inlet to receive water containing gas and water immiscible naphthalene, a funnel in said scrubbing section with its top perimeter at a spaced distance below said water inlet, a tail pipe disposed axially of said funnel and extending from the outlet thereof down to a spaced distance above the base of said scrubbing section, a vertical series of horizontal zigzag flow batlies disposed in the scrubbing section to range upwardly from below the base of the tail pipe to the top thereof around the outside of the tail pipe, a water outlet from said scrubbing section at a level above the uppermost baie but below the underside of the funnel, conduit means for outflow of water from the water outlet with provision for maintaining a water liquid level above the top of the perimeter of the funnel and below said water inlet, means for introducing a liquid solvent for naphthalene of greater specific gravity than, and immiscible with, water into the scrubbing section, and overow means for offtake of solvent from the base of said scrubbing section at a level below the base of the tail pipe with provision for maintaining a bath of the solvent submerging the base of said tail pipe but below said water outlet.

14. Apparatus for separating naphthalene from water containing entrained gas, comprising: a water scrubbing section having at its top a water inlet to receive water containing gas and water immiscible naphthalene, a funnel in said scrubbing section with its top perimeter below said water inlet, a tail pipe disposed axially of said funnel and extending from the outlet thereof down to a spaced distance above the base of said scrubbing section, a vertical series of horizontal zig-zag flow passages disposed in the scrubbing section to range upwardly from below the base of the tail pipe to the top thereof around the outside of the tail pipe, said series of baies being of greater height than the overall horizontal dimension of the water scrubbing section and having the upper batfles disposed to serve as foam collectors beneath their undersides and provided with vents therefrom to a gaseous area at a level above the water level of the scrubbing section, and the lower bafes of the series of bales having drains for draining solvent directly to a level in the base of the scrubber below the base of the tail pipe, a water outlet from said scrubbing section at a level above the uppermost bathe of the series thereof but below the underside of the funnel, conduit means for outflow of water from the water outlet with provision for maintaining water in the scrubber at a level above the uppermost 'bal-lie of said series thereof, means for introducing a liquid solvent for naphthalene of greater speciic gravity than and immisci ble with water into the scrubbing section, and outlet means for Gif-take of the drained solvent from the base of the scrubber with provision for maintaining a bath level of the solvent for submerging the base of said tail pipe with the top level of t-he bath below said water outlet.

l5. A method of scrubbing final cooler water from coke oven gas plants to remove naphthalene therefrom, comprising: continuously accumulating final cooler water aforesaid as a body of water gravitationally descending in a funnel to a tail pipe therefor and retained at low velocity of flow above said tail pipe for a time to allow a major portion of the entrained gas to gravitate upwardly out of the body before the water enters the tail pipe, owing the water from the body at higher velocity through the tail pipe into a bath of solvent for naphthalene that is immiscible with and of greater specific gravity than water at the base of said tail pipe, to leave the naphthalene of the water in the solvent, owing the water upwardly for outflow of the water around the tail pipe to an upper level, above the top of the tail pipe but below the funnel through a series of horizontal zig-zag ow paths at a velocity in each horizontal ow path greatly in excess of the superficial upward Velocity to said upper level, draining solvent from each of a plurality of the lower horizontal ow paths to the bath of sol- 15 vent below, and entrapping escaping gas and lighter globules of solvent containing entrained gas at the top of the upper horizontal flow paths and venting said gas to a gaseous area outside said water area to prevent the gas and lighter solvent from reaching the upper level above the top of the tail pipe for outow of the water, feeding solvent to, and withdrawing solvent from, the bath to maintain the bath of the solvent at a level for submerging the base of the tail pipe with the top level of the bath of solvent below said upper level above the top of the tail pipe for outflow of water, and withdrawing the water at the upper level for outow of water in a manner to maintain a body of water in the funnel at a level above the top of the tail pipe as aforesaid.

References Cited in the file of this patent UNITED STATES PATENTS 2,776,021 Van Ackeren Ian. 1, 1957 2,810,450 Hartmann Oct. 22, 1957 2,887,174 Ray May 19, 1959