Патент USA US2129787код для вставки
2,129,787 _ REMOVAL AND RECOVERY OF BENZOL AND NAPHTHALENE FROM GASES Filed Jan._ 25, 1934 Patented Sept". 13,1933 » anni? amarsi v . ' Adair Schwalenber/ch, Essen, Germany, assigner, by mesne assignments. to Kappers Company, a. corporation ai Delaware v Application January 25,. 11934, Seriali No. ’iilßdldll En Germany January 25, i033 il Claim. ‘Íßit 202-393 The invention relates to the removal and re covery of benzol, its homologues and naphtha iene from gases, particularly coal distillation gases. ' tilling the Washingoil, coming irom the‘scrubber, in the steam distillation step is subjected before the rectiñcation to a. pre-distillation for the re covery of benzol and homologues, which is carried ~ The object oi the present invention is to pro- , p out at such a temperature that the heavier con vide such improvements in the removal and re covery of benzol, its homologues and naphthalene from gases, particularly coal distillationgases, that the removal of the said' substances from the lgas can. be effected. in a single ‘operation and benzol and homologues and naphthalene on the other hand can be recovered separately in prac stituents of the washing oil remain behind, Whilst the »lighter constituents ci' the washing oil to gether with benzol, its homologues and naphtha iene are evaporated. The. vapors produced by> this- pre-distillation are then conducted Ainto the grammes benzol and homologues per cubic meter rectihcaticn apparatus including a still for distil lation of benzol and homologues, from which there is withdrawn, after driving off benzol and homologues, an oil with a content of about 30% naphthalen'e. From 'this part of the distillation step oil highlyenri'ched with naphtlialene is pro duced and there can be separated> a very pure and about 0.4 to 0.6 gramme naphthalene. For the removal of benzol and» homologues the gas room' temperatures above 10° C. which can be ' tically pure condition. _ . . Normal coal distillation gas contains, after the usual so-called iinal cooling and before ythe scrubbers serving to remove benzoLabout V25 20 l is Washed with a usual washing oil. The used washing oil is subjected to steam distillation. The vapors òf distillation thus produced contain about equal quantities by Weight of washing oil ~ and benzol, i. e. about 50% benzol and homo naphthalene by crystallization with cooling to obtained directly Without artiilcial cooling. ‘ Ili‘he quantity of heavy constituents of washing oil which occurs in the pre-.distillation step ac-' coi-ding to the invention varies. 1n general .it amounts to about 30 to 90% of the condensed oil containing benzol and naphthalene introduced 25 logues and about 2% naphthalene. From the - into the pre-distillation apparatus in the case condensate of the steam distillation» benzol and homologues are removed by rectiiicatlon, whilst the naphthalene-containing oil remains behind. ' As the quantity of the napl'ithalene in the re 30 sidual oil, as stated, only amounts to about 2%, it -is not possible to separate the naphthalene from the oil by crystallization whilst cooling to temperatures still obtainable, having due regard to favorable economy, Without'artiiicial cooling; 35 Consequently the Washing oil becomes enriched with naphthalene, which in the usual manner is used in circulation for renewed Washing 'of when the main quantity of naphthalene is to be _ » separated i'rom> the heavier constituents of the ' washing oil in the pre-distillation stage. .. aThe heavier constituents oi thevvashln'g oil remaining inthe pre-distillation stage, are mixed with the lighter constituents, which remain in the main distillation stage, after the naphthalene hasbeenseparated from the lighter constituents ' by cooling, and then are again used together-for 35 washing benzol and naphthalene from the gas. The invention will now be described with` rei erence to the accompanying drawing showing, benzol from the gas, gradually to such a quan tity that the vapor pressure _of the Washing oil partly in elevation and partly in cross section,Vv apparatus for practicing the invention. » 40 in connection with naphthalene is in equilibrium with the vapor pressure of the gas as regards " En the arrangement >shown in the drawing used naphthalene. In the case of normal Washing oil washing oil, containing benzol and naphthalene, from the container i, of which the function is thisÍ point lies at about 12% naphthalene. Be yond this point an enriching of the washing oil -described hereinafter, is supplied through a pipe line 2 by means of a pump t to a heating device fi. 45 with naphthalene is not possible in the method . -"ll‘he hot Washing oil andthe vapors producedv of operation hitherto usual.' But even with a content of naphthalene of 12% the naplithalene during the heating pass from the device il through cannot be recovered from the washing oilI with out artiiicial cooling. ' ' ' According to the present invention the separa tion both of benzol and of naphthalene from the washing oil, which served for bothl the removal ci )as the pipe lines d and 0 into _ a firnovvn primary distilling column apparatus '71. This column» ap paratus ‘i has a series of bottoms or trays which 50 are `provided'vvith vvapor openings 0 covered by bells' d, and at the middle each has a liquid over ñow i0. SteamV is introduced into the bottom benzol and homologues and also naphthalene from the gases, is‘rendered fundamentally pos ‘ of the-column apparatus through the pipe line i i. . sible. in that the condensates derived from dis-v .The steam rises through the openings 0 in the Z amener bottoms of the column apparatus,` »whilst the washing oil ñows downwardly in the apparatus 'l from top to bottom through the openings, l0. Steam and washing oil in this manner come into intimate Contact with one another, whereby the washing oil is heated. The vapors produced in the column apparatus l such as steam, benzol, its homologues, naphthalene and some oi the wash oil, escape through the pipe line i2 and washing oil to be re-used for washing >out benzol ‘ and-naphthalene. Tothe pipe line 38 is also con-` nected the pipe line 29 so that thus-the whole of the washing oil freed. from benzol, its homo logues and naphthalene, which was driven oiî in _the column apparatus li, is again continued. There will now be described the path followed by the used washing oil which is treated in the apparatus shown in the drawing. The used The liquid condensates thus formed new washing oil withdrawn from the scrubbers, not shown in the drawing, which serve for washing through the pipe line i0 into a separating tanl: benzol, its homologues and naphthalene from the l5. gas. is conducted to a storage tank £0. From this it ñows through the pipe line M into the cooling pipe system ci’ the condensing device i3 in which l5 it is used for cooling the vapors escaping from the column apparatus l, vin this manner there is obtained simultaneously an advantageous pre heating of the cold used washing oil. The wash ing oil thus preheated then passes through the 20 pipe 02 into the tank i, which simultaneously pass into a condensing device i3 where they are cooled. In the separating tank i0 the water escap ing from the apparatus 'i separates from the oily substances. The latter are withdrawn at the up per end of the separating tank iii through the pipe line iii, whilst the water passes through the pipe line il' into the tank i0. , The oily constituents are now conducted through the pipe line i0 into the still i0. To the still l0 there are also supplied through the pipe line 20 those gaseous constituents which were not condensed in the condensing device i3. Into the lower part of the still i0 there is sup 25 plied through the pipe lines 2i steam which in serves as storage tanh and as heat exchanging apparatus. rThe used crude washing oil is here further preheated, the hot unvaporizecl washing through the pipe line 23a into the dephleg‘mator oil from the column still l here serving for the 25 preheating. For this purpose there is connected to the bottom oi’ the column apparatus 'E the pipe line 03 through which the hot Washing oil ñows from l into a pipe system located in the in,terior oi the tank i. in the tank i the hot re 30 sidual oil of the column apparatus “i imparts a portion of its heat to the colder untreated wash ing oil. rl‘he residual oil pre-cooled in this man _ner then i‘lows through the pipe line ¿ld into a pipe 35 part 23 oi the apparatus l0, maintained atl a ,cooling apparatus Q55, sprayed with wat/er from 35 the interior of the apparatus flows through ypipe coils or the like not shown in the drawing. The condensedwater is withdrawn from these heat The ing pipe coils through the pipe lines 22. 30 liquid in the still l0 is thus heated indirectly. The vapors thus formed, benzoi, its homologues, naphthalene, and a small part of the wash oil vapor condensed from the still it, rise and pass predetermined temperature, from which they escape through'the pipe line 2d after passing a separating bottle 2155> for separating the constit ‘uents condensed in the dephlegmator. The 40 condensate from the separating bottle 2t flows through the pipe line bach into the still iS. For cooling‘the dephlegmator there is preferably used cold water which flows to a cooling pipe system, located in the interior of the dephlegmator '23, through a pipe line 2li and flows out through a pipe line 2t. - ^ . The oil which is not evaporated in the still it) and which mainly consists of the heavier con stituents of the washing oil and is practically free from naphthalene, is withdrawn through the pipe line 20. The vapors produced in the still iii pass ' , through the pipe line 25 into the main distilla tion still 30 _which is arranged substantially in the same manner as the still HQ. which it passes through the pipe line il@ into the The re generated wash oil is pumped continuously inI cycle baci; to the gas-washing benzol-scrubber (not shown) through a pipe line 39a. At certain 40 intervals part of the wash oil, circulating from the benzol scrubber to the distillation plant and thence to the tanlr 30 for return back to the ben storage tank 30 for fresh washing oil. zoi scrubber, must be replaced by new or fresher wash oil to replacedeterioration. The added oil may be introduced into tank 3s, or at any other point in the cycle of flow ofthe benzol-absorbent wash oil.. _ The process according to the invention isv car ried into euect somewhat in the following man Der'. y lt is assumed that the gas of a coal distillation plant is to be treated which has an average of i000 metric tons oi’ dry coal per day. The colcing of this coal produces about 300 cubic meters of gas per ton of coal, that is‘daiiy 300,000 cubic meters of gas. After the usual ñnal cooling of the gas this contains before passing into the ben» aol scrubbers about 50 to 60 grammes naphtha. -lene per 100 cubic meters. In this case there is assumed a naphthalene content of the gas or 55 grammes per 100 cubic meters. lThe quantity of The vapors produced in the main distillation still, which practically consists only of benzol and its homologuesf pass through the pipe line 3i into a cooling apparatus 32 in which they are deposited. Cold water is supplied to the cooling apparatus 32 through the» pipe line 30, passes through a cooling pipe system located in the inu tenor of the apparatus- 32 and ilows out throughl naphthaiene contained ‘ in the gas therefore the pipe line 3&3. 'I'hecondensates formed in the amounts per day. to lôâkilogrammes. of which’ apparatus 32 are withdrawn from the lower part 150 kilogrammes are washed out per day by the washing oil. ‘ ' _ of the apparatus through the pipe lines 05. , ’nie content of the gas in benzol and its The liquid constituents which are not evapof rated in the main distillation still 30 ñ'ow through ¿homologues amounts to 25 grammes per cubicA the lpipe line 36 to a naphthalene crystallizing pan meter, that is per day 7500 kilogrammes benzol 31 in which they are cooled to about room tem perature but above 10° C. As a result solid crys and homologues.. According tov experience the quantity of wash talline naphthalene separates from the liquid ing oil, which passes over in the column appa ratus 1 when driving off bénzol and its homo sidual liquid passes from the device 31 through logues in order to obtain a si‘iß‘icient removal 75 the pipe line 38 into the storage tank 39 for the ot benzol and its homologues from the washing 75 which contains about 30% naphthalene. The re- ' .2,129,787 3 y on, is the saine as the quantity of benzol driven ` unes 4t, at, «sind sa now only contains 22,500 od. In the example described 7500 kilogrammes kilogrammes oi’ naphthalene per day equal on an average to 6% naphthalene. This naphtha-~ iene content of the washing oil again iiowing column apparatus ii. In this quantity of wash ing oil there is alsoy contained the total naph» back into the'benzol scrubbers remains constant ‘thalenle contained in the oil, so that the‘7500 when carrying out the lprocess according tothe invention. It is possible with this constant naph kilogrammes of washing oilv distilled over con thalene content of the washing oil to remove tain 8% naphthalene assuming that for wash ing- benzol, homologues and naphthalene from the naphthalene from the gas up to 5 grammes _ of Washing oil are thus distilled over daily in the 10 the gas therev was used a. washing oil containing 6% naphthalene. ~ ' _ t As the solubility oi naphthalene in the‘wash-4 per 100 cubic metersof gasy during the benzol scrubbing step.v This content of naphthalene in the gas is'so slight that a separate subsequent l` ing oil-at about 20 to 25° C. amounts to about washingout of naphthalene as a rule is unnec 12%; naphthalene at these~ temperatures, which essary. Ii", however, for special reasons a stili further reduction of the naphthalene content can be obtained without any artiiicial cooling oi' themfwashing oil, cannot be crystallized out oi" a washing oil with «8_%„„naphthalene. The of the gas should be necessary this is substan tially simpler and cheaper as the quantity of naphthalene, remaining in the gas, after the application of the process according to the in naphthalëne therefore'passes, according to the> llfiitinerto `method .of operation,l together With- the residual oil vfrointhe rectiiìcation’apparatus for y vention, is only very slight. benzo'l back' i?t'o the washing oil which then be , in the foregoing the invention has been de scribed with reference to an example for carry ing it into eiïect, without however, the invention the vapor pressure of the Washing oil with naph thalene is equal to the vapor pressure of the being limited to the method of carrying it out as described. On the contrary the process accord 25 gas with naphthalene. As a Eesult it follows ing- to the invention can be modified in various 25 that bythe hitherto usual method of operation . respects without departing from the scope of naphthalene cannot be washedfrom the gas to . gether with benzol. On the contrary it 'was the following claim. li claim: therefore always necessary to provide beyond the v'li‘he method of removing and recovering benzoi,` so benzol scrubber a separate scrubbery for naph its homologues and naphthalene from gases ’con-y 30 According to the' invention the vapor mixture;- taining them, comprising: Washing the gas with escaping from the column apparatus il, consist-Ñ - wash oil adapted to absorb benzol, its homologues ing of 7500 kilogrammes benzolandhomoiogues, and naphthalene therefrom; heating spent wash oil from the gas washin'gostage to drive oiï ab 35 6850 kilogrammes .washing oil constituents and comes enriched. - This enriching continues until thalene. ~ _ » " y _fiâii‘kilogrammes> naphthalene, is so decomposed sorbed benzol, its homologues, naphthalene and > that as first fraction there'is obtained a washing a quantity of wash oil about the same as the oil, «which does not contain' more naphthalene than the initial washing oil, as second fraction quantity of benzol, its homologues and naphtha Iene; condensing the vapors from said heating a washing oil highly enriched with'naphthalene ‘i st'ep‘and pre-distillingl the condensate at about and as third fraction benzol and its homologues. 108° C. to remove benzol, its homologues and F‘or- this purpose the condensate of the vapor naphthalene together with a smal-l portion of the mixture escaping from the column ’apparatus ‘l - wash oil that comes over with the vapors‘from is subjected in the pre-distillation stage .it to the aforesaid heating step; condensing the va a distillation at about 108° C_‘measured at the- pors from the latter pre-distilling step and iinally 45 outlet of the distillation vapors at a, andi'the- redistillingthe condensate'at about Bti-90° C. to constituents entering the main distillation appa l drive off benzol and its homologues leaving as ratus 3d to a distillation at about dii-90° C. meas i residuum the naphthalene and _wash -oil that 40 n >ured at the outlet oi the distillation vapors at a’. icomeso'ver. with the vapors from the-‘pre-dis With this methodof operation the residual oil,V itilling step; separating naphthalene from the 50 ``colle`cting in the pre-distillation stage id and latter residuum by atmospheric cooling to room Withdrawn vthrough the. pipe line it, contains temperature above 10° C.; separating the solid 395 kilogrammes of naphthalene per day (=6%) naphthalene from ther so cooled wash oil; and -and the residual oil in the main distillation stage returning the wash `oil combined with the Wash 3d, 255 kilogrammes oi naphthalene per day oii residuum from the first two distilling steps 55 (=2’i'.i%l. From the latter- residual oil there fare separated in the crystallization device til to the gas washing stage 'for another cycle, said. combined Wash oil being of suiiiciently 10W con 150 kilogrammes of naphthaiene per day, v)From _ « >centration this it follows that the fresh washing oii ñowing to back into the storage tanti 3d, through the pipe r of naphthalene to effect the absorp~- tion of naphthalene from »the gas. f ADOLF SCHMALENBACH.