US2785114A

US2785114A - Schmalenbach

Info

Publication number: US2785114A
Authority: US
Publication date: 1957-03-12
Anticipated expiration: 1974-03-12

Description

MalCh l2, 1957 A. scHMALl-:NBACH 2,785,114

METHOD OF' EXTRACTION OF' HIGH-PERCENTAGE PRELIMINARY PRODUCT FROM BENzoLE-ENRICHED WASH 011 Filed Aug. 11, 1951 ,4001 F .5c/#m4 we A c# A f fof-wey nited METHOD QF EXTRACTGN 0F HIGH-PERCENT- AGE PRELIMINARY PRDUQT FRM BEN- ZGLE-ENRCEEB WASH OEL Adoif Schmalenhach, Essen, Germany, assigner, by messie assignments, to Kappers Company, lne., Pittsburgh, Pa., a corporation of Delaware Application August 11, 1951, Serial No. 241,446

2 Claims. (Cl. Zim-46) The present invention relates to the extraction of a high-percentage of low boiling preliminary product from Wash oil, enriched with benzole and its homologues, from the by-product plants of ovens for the production of gas and coke.

The so-called preliminary product is obtained from wash oil charged with benzole and its homologues, by treatment with steam. This preliminary product, besides benzole and its homologues, contains greater or lesser quantities of naphthalene oil and wash oil fractions.

With a higher proportion of the low boiling benzole and its homologues in the preliminary product, simpler apparatus and production processes are possible for obtaining motor benzole or pure benzole from this preliminary product.

To obtain a so-called high-percentage of low boiling preliminary product, i. e. one in which 95 to 98 percent thereof vaporises below 180 C., it has previously been necessary to effect a two-stage distillation. In the majority of cases this was carried out by first preparing a low-boiling product by steam treatment of the enriched wash oil, and then transforming this, partly in the vapour phase and partly in the liquid phase, by a second distillation into high-percentage preliminary product. it has also been proposed to separate out a quantity of highboiling components, especially naphthalene oil, from the vapour mixture (which by itself only gives a low-percentage preliminary product) in the refining apparatus by fractional condensation, so that the condensation of the remaining vapour produces a high-percentage product, whilst the condensate from the fractional condensation is treated in a special distillation apparatus to extract the benzole hydrocarbons and other valuable substances contained therein.

To obtain a high-percentage of low boiling preliminary product from benzole-enriched wash oil by one-stage distillation only, it has further been proposed to effect fractional condensation of the high-boiling components, namely the naphthalene oil, from the vapour mixture withdrawn at the head of the refining apparatus, and to combine this condensate with the starting material, i. e. the benzole-enriched wash oil, before its admission to the reliner. This method of operation is however accompanied by the drawback that the vaporisation of the Wash oil in the reiiner is aided by the vaporisation of the naphthalene oil introduced into the cycle. The result of this increased vaporisation of Wash oil constituents is that effective fractionation in the refining column is didicult or impossible, with the result that, on the one hand, the head product is poorer and on the other hand no naphthalene oil fraction can be Withdrawn from the refiner. Such withdrawal of naphthalene is however necessary in order to remove from the process the naphthalene which is continually absorbed from the gases by the wash oil, so as to maintain the wash oil in a condition for continuous absorption of further benzole and its homologues from the gas.

2,785,114 Patented Mar. 12, 1957 The present invention, however, provides a way of producing from benZole-enriched wash oil, by a single relining or fractionating procedure, a high-percentage of low boiling preliminary product by a continuous operation and with a high degree of economy.

According to the invention the concentration of highboiling substances (naphthalene oil and certain wash oil components) at the head of the reiining column is increased, by recycling the same in heated condition as hereinafter noted, so that the temperature of the resulting vapour mixture Withdrawn at the head of the column is higher than the condensation point of steam, and the higher boiling components (naphthalene oil etc.) are extracted from the Withdrawn vapour mixture by fractional condensation to such an extent that a high-percentage of low boiling preliminary product can be directiy condensed from the remaining vapour mixture, whilst the condensate obtained by the primary fractional condensation (which is composed in the main of naphthalene oil and water, together with a certain amount of benzoie hydrocarbons) is heated, as hereinafter noted, e., to above the condensation point of steam, after removal of the water in a separator, and then is reintroduced into the refining column. Thus, in the process according to the present invention, a continuous circulation of certain high-boiling substances is maintained, independently of the stream of wash oil, through the reiining column and a primary condenser connected to the head of this column, with the result that a condensation of water and an increased vaporisation of wash oil is impossible in the refining column, and this column can therefore effect a sharper separation of wash oil from the overhead vapor products.

The sharpness of separation can be substantially improved, and this represents an important advantage of the present invention, by the fact that the ratio of recycled material in the column can be measurably increased as a result of the additional introduction of the preheated naphthalene oil or the like from the primary condensation. By this means it is possible, in accordance with a further feature of the invention to withdraw from the refining column, continuously or in batch fashion, a naphthalene oil fraction which is suliiciently concentrated to permit direct crystallisation of naphthalene therefrom.

The process according to this invention presents particular advantages when used in combination with a continuous ow heater, of the so-called pipe still type, for heating the benzole-enriched Wash oil (the starting material) and the components from the primary fractional condensation designed for re-circulation. Hence, it is possible, in accordance with a feature of the invention, to eect the heating of the re-circnlating condensed component using the same pipe still as for heating the starting material.

This may advantageously be carried out by arranging an additional system of pipes, serving to heat the recirculating portion of the condensate, in the convection zone of the pipe still.

In accordance with a further important feature of the invention, the separate heating of the re-circulating portion of the condensate can also be utilised for the purification regeneration of the wash oil. As is known, the wash oil in course of time undergoes an appreciable thickening, this being allied to a reduction in its absorptive capacity. Consequently it has hitherto been necessary to remove the wash oil continuously or batchwise from the gas purifying plant and replace it by a fresh Wash oil.

In accordance with this invention, spent Wash oil can be added to the portion of the condensate circulating through the refining column and the primary condenser and, -advantageouslythe mixture heated in a pipe still to such a degreethat on expansion in a vaporising andV muck separating chamber it is vaporised except for the pitchor resin-like residue of the spent or thickened wash oil.

rThus, by 'employing this featurerof the invention,it is unnecessary'to withdraw the wash oil from the plant or tov vregenerate itV by purification inV a special 4distillation "apparatus, 'and the thickening ofthe oil can be continuously prevented andlthus the circulating wash oil' maintained at a uniformly high absorptive level.

Further important features 'and advantages of the invention are disclosed in the following description of a plant suited for carrying the invention into effect, this being diagram'matically illustrated in the accompanying drawing.

The cold;benzoleenrich`ed wash oil to be treated ows from a supply container or the like (not shown) through Ya'pipeconduit Lirst through a heat-exchanger 2, where it is heated, and then through` a pipeY 3 to a further heatexchanger 4, Afromwhichit'passes throughV a pipe line 5 intro the first pipe system 6 of a pipe 'st-ill 7. These heatexchangers` 2,4 also serve as co-ndensers for the vapour `mixture as is hereinafter described. `The pipe system 6 ponents'llows away from the foot of column 10 through the pipe line 12.

Ihe low boiling vapour mixture produced inthe column passes from the'top of the said column through the pipe line 13 into the heat-exchangerfi, which now acts as the primary condenser. In the latter the vapour mixture is brought to a temperature such that the naphthalene oil,

any wash oil components and the steam, together with a certain amount of benzole hydrocarbons, condense. This condensate flows through a pipe line 14 into a separating vessel 15 where'the water is taken ofrr from the remaining components. This water is taken Voff at 16,' whilst the water-free condensate passes through a pipeline 17 into a container 18. From there it is forced by a pump 19 through a further pipe 20 into a heating pipe system 21 which is also arranged in the convection zone of the pipe lstill 7. Advantageously a partition wall 22 is provided between the two pipe systems 6 and 2l, so that regulated quantities of heating gas can be brought into contact with each ofthe

pipe systems

6 and 21.

The heated high boiling oil product then passes through a pipe 23 to Ia vaporizing and muck'separating chamber 24 in which it is expanded and thereby vaporised except for a pitch-like residue which is withdrawn'through a Y line 25. The high boiling vapour mixture produced Hows nally through a pipe line 26 into the refining column l0 at 27. VAs can be seen from the drawing, the point of highboiling admission 27 is located at a higher part of the column than the admission inlet 28 for the initial benzolized wash oil material.

The low boiling portion 0f the vapour extracted from the refining column and not condensed in the primary condenser 4 ows through a pipe 29 to the heat-exchanger 2, and thereafter to a `condenser 30 where the low boiling volatile benzol mixture is completely condensed. The low boiling condensate is collected in a container 31 and from thisY a high-percentage of low boiling preliminary product, containing about 95 to 98 percent of constituents Vdistilling up to 180 C. can be drawn oit through a pipe line 32.

. Part of thel condensate fromthe reservoir 31 is passed a pump 33 through aline 34 tothe head of the column I 10 at a point above the point 27.

`passing therewith through the pipe system 27 in the pipe still. The used'washoilcomponent is also; evaporated inthe chamber 24, and pitch or resin Acontainedin" the used wash oil, which is responsible 'forthethickening of the latter, is separated ol .as a residue.

To enable thetemperature in 'the' primary condenser 4 to be regulated exactly tothe Yrequired value, a by-pass conduit 39, controlled by a valve 38, is arranged between the pipe lines 3 and 5. VBy appropriate adjustment of the valve 33 the amount of wash oil flowing through the primary condenser 4 can be so regulated that the temperature of the volatile mixture in the condenser 4 can be reduced accurately to theY level necessary-forme fractional condensation.

A practical example of a'methodcarried out inaccordance with the present invention-using apparatus Ycorrespending to the plant diagrammatically illustrated inthe drawing is as follows:

40,000 kg. of wash oil, containing 200 kg. water, kand at a temperature of about V C., is passed per'hour through the pipe line 9'to the refining-column i0 from the pipe still 'i'. Approximately 640 kg. of steam per hour is admitted to the bottom ofthe reiiner 10-through the pipe 11.

The retining process is controlled so that 39,000 kg, of refined wash oil is withdrawn per hour from the bottom of the column through the pipe line 12, whilst a/mixture of 5240 kg. of light oil and steam passes out'of the top of the refining column through the pipel 13. YIn the primary condenser 4, 1000 kg'of condensate is withdrawn per hour and, after'being heated in the pipe systemv 2l of the pipe still to about 250 C., is returnedto the retining column at 27 after passing through the pitchV extractor 24. At the same time 2400 kg. per hour Yof waterfreed distillate is passed at about 30 C. from container 31, which contains the liquid from the secondary condensers 2,- 30, to the head of the column for recirculation. 1000 kg. of high-percentagerlow boiling light oil (pre liminary product) is withdrawn per hour at 32.

What I claim is:

l. A Single distillation process for the continuous extraction of high percentage of low boiling-preliminary product comprising benzole and homologues boilingbelow naphthalene from benzole-enriched benzole absorbent wash oil which also containshigh boiling naphthalene components, comprising: the steps ofintroducing wash oil enriched with benzoleas aforesaid into a 'refining column partway up the sameandowing it downwardly therethrough eountercurrent'to direct steam to'remove both said low boiling benzole components andt'said high boiling nap-hthalene components fromthe entering wash oil, withdrawing both said low and high vcomponents as an overhead vapor mixtur'evfrom the head of the column Vat a point above the pointlof introduction of'the entering wash oil into the column; maintaining lbetween 'the head of the column and a part of the'column loc-ated above the point of introduction of said wash oil; a'concentr'ation of said 4higher boiling components at a temperature such that the temperature of the vapormixture'withdrawn overhead from the headV of the column is higher than'the condensation point of steam; fractionally condensing Said higher boiling naphthalene components from the low boiling benzole components of the Vapor mixture` so withdrawn as overhead; returning said higher boiling'naphthalene component condensate, after freeing it of water and vaporizing it, to theY rening column separately from the wash oil, at the-part'of the column located Vabove Vthe wash oil inlet thereto but below the outlet for'overhead vapors vfrom the head of the column; Iand at a temperature in amount such as to maintain the temperature of the vapor mixture Withdrawn as overhead at the head of the column higher than the condensation point of steam, and withdrawing naphthalene as an oil fraction from the column at -a point in the column above the inlet thereto of said returned higher boiling naphthalene component condensate but below the outlet at the head of the column for withdrawal of said high and low boiling components as overhead vapors from the column.

2. A process as claimed in claim 1, and which includes the further Steps of adding spent wash oil into the high boiling naphthalene component condensate that is to be returned to the column, prior to vaporizing the same, and thereafter vaporizing the naphthalene and wash oil from their mixture leaving a pitch-like residue of the wash oil, and introducing only the vapors of naphthalene and wash oil from said mixture to -the column between the point of withdrawal of naphthalene as an oil fraction and the lower wash oil inlet to the column as aforesaid.

Koppers Dec. 2, 1919 Stevens Oct. 18, 1921 6 1,561,899 Barbet Nov. 17, 1925 1,587,188 Schneible June 1, 1926 1,744,261 Cooke Ian. 21, 1930 1,744,421 Stroud et al. Ian. 21, 1930 1,839,894 Ricard et al. Ilan. 5, 1932 2,054,096 Potts et al. Sept. 15, 1936 2,070,864 Ragatz Feb. 16, 1937 2,100,922 Sachs Nov. 30, 1937 2,135,356 Schmalenbach Nov. 1, 1938 2,164,593 Rector July 4, 1939 2,196,878 Stover Apr. 9, 1940 2,290,373 Lee July 21, 1942 2,299,283 Schmalenbach Oct. 20, 1942 2,342,145 Isham et al. Feb. 22, 1944 2,342,165 Plummer Feb. 22, 1944 2,437,649 Milner Mar. 9, 1948 FOREIGN PATENTS 352,432 Germany Apr. 27, 1922 OTHER REFERENCES Chemistry of Coal Utilization, vol, II, chapter 28, (article by Glowacki) pages 1136-1231, John Wiley Sons Publishers, 1945.

Claims

1. A SINGLE DISTILLATION PROCESS FOR THE CONTINUOUS EXTRACTION OF HIGH PERCENTAGE OF LOW BOILING PRELIMINARY PRODUCT COMPRISING BENZOLE AND HOMOLOGUES BOILING BELOW NAPHTHALENE FROM BENZOLE-ENRICHED BENZOLE ABSORBENT WASH OIL WHICH ALSO CONTAINS HIGH BOILING NAPHTHALENE COMPONENTS, COMPRISING: THE STEPS OF INTRODUCING WASH OIL ENRICHED WITH BENZOLE AS AFORESAID INTO A REFINING COLUMN PARTWAY UP TO THE SAME AND FLOWING IT DOWNWARDLY THERETHROUGH COUNTERCURRENT TO DIRECT STEAM TO REMOVE BOTH SAID LOW BOILING BENZOLE COMPONENTS AND SAID HIGH BOILING NAPHTHALENE COMPONENTS FROM THE ENTERING WASH OIL, WITHDRAWING BOTH SAID LOW AND HIGH COMPONENTS AS AN OVERHEAD VAPOR MIXTURE FROM THE HEAD OF THE COLUMN AT A POINT ABOVE THE POINT OF INTRODUCTION OF THE ENTERING WASH OIL INTO THE COLUMN; MAINTAINING BETWEEN THE HEAD OF THE COLUMN AND A PART OF THE COLUMN LOCATED ABOVE THE POINT OF INTRODUCTION OF SAID WASH OIL, A CONCENTRATION OF SAID HIGHER BOILING COMPONENTS AT A TEMPERATURE SUCH THAT THE TEMPERATURE OF THE VAPOR MIXTURE WITHDRAWN OVERHEAD FROM THE HEAD OF THE COLUMN IS HIGHER THAN THE CONDENSATION POINT OF STEAM; FRACTIONALLY CONDENSING SAID HIGHER BOILING NAPHTHALENE COMPONENTS FROM THE LOWER BOILING BENZOLE COMPONENTS OF THE VAPORT MIXTURE SO WITHDRAWN AS OVERHEAD; RETURNING SAID HIGHER BOILING NAPHTHALENE COMPONENT CONDENSATE, AFTER FREEING IT OF WATER