FR2477531A1 - PROCESS AND APPARATUS FOR EXTRACTING BENZENE FROM A LIQUID CONTAINING THIS HYDROCARBON WITH A WASHING OIL - Google Patents

Abstract

METHOD AND APPARATUS FOR EXTRACTING BENZENE FROM A LIQUID CONTAINING THIS HYDROCARBON WITH A WASHING OIL, FOR EXAMPLE THE LIQUID USED FOR WASHING GAS FROM A COKE OVEN BATTERY. THE LIQUID CONTAINING THE WASHING OIL AND THE BENZENE IS SENT IN A DRIVE COLUMN IN WHICH IT IS COUNTERCURRENT WITH WATER VAPOR, THE BENZENE AND WATER VAPORS LEAVING THE COLUMN ARE CONDENTED. OF TRAINING, THE CONDENSED LIQUIDS ARE SEPARATED BY GRAVITY WHICH ALLOWS TO COLLECT THE BENZENE PRODUCED AND RESIDUAL WATER, WHICH ARE SENT IN A BOILER FOR PRODUCTION OF THE STEAM NECESSARY FOR THE OPERATION OF THE DRIVE COLUMN. THE APPARATUS FOR IMPLEMENTING THIS PROCESS INCLUDES A DRIVE COLUMN 11, A CONDENSER 14, A SEPARATOR 15 FROM WHERE THE BENZENE IS DRAINED AND FROM WHERE THE RESIDUAL WATER IS SENT IN A TANK 18 BEFORE PASSING TO THE BOILER 21 PRODUCING THE STEAM INJECTED INTO THE DRIVE COLUMN 11.

Description

The present invention relates to a method and apparatus for

  recovering by extraction the benzene contained in a liquid with washing oil, in the form for example of the liquid which was used to wash the gases leaving a battery of coking furnaces. Benzene is a recoverable by-product of the coke oven gases which is usually removed by washing these gases with an oil. The mixture of oil and benzene is then subjected to sepa- ration: benzene is obtained on the one hand and oil on the other hand; the latter is recycled. The mixture of oil and benzene is usually sent to a column of entrainment in which the mixture is passed undercurrent with water vapor in ascending movement: the vapors of water and benzene are evacuated at the head of the column. and the oil can be collected at the base. The condensation of the vapors gives water and benzene which is then separated by decantation. The water obtained under these conditions, usually representing a flow rate of 7600 liters per hour, contains in most cases a certain quantity of benzene and other polluting substances which, for reasons of protection,

  it can not be rejected.

  The present invention relates to a method and an apparatus for

  narrowing of the type described in the introduction which allow to decrease in

  a considerable measure the wastewater to be discharged.

  The process according to the invention for extracting benzene from a liquid containing this hydrocarbon with washing oil,

  in which the benzene is entrained from this liquid by passing counter

  current with water vapor, condensation with benzene vapors

  and water at the exit of the eutra and, separation of

  gravity densities of product benzene and resident water are

  3, ensures that the waste water is sent into a boiler

  for the production of the necessary vaper and the operation of maintenance.

  The apparatus according to the invention for the purpose of the above-described method comprises a feed kettle which my liquid containing the benzene and the counter-current washing liquor is fed with steam. water injected at the base of the colamne, a condenser which serves to cohere the vapors of benzene and water leaving the column, a separator das which separates the benzine produced and the waste water, and a bmillear in which u euvoie l separate water for water Jwp production

  necessary injection into the bolus drives.

  Other characteristics and advantages of the invention

  more clearly from the detailed description of the

  after reference to the unique design of the year, which represents the apparatus for the implementation of the invention, the invention for extracting benze from Isfle's image.

and benze.

  With reference to this figure, the nélae d & sbile and

  zne enters the apparatus by the c * idult 10 and is iatro-

  said in column column 11, which ascelsiuel current of water-jet injected into the column 11 near the base of this line through the conduit 2 goes to cmtr-cotm with the buile, enta1at the bezse it contains it; The island is evacuated at the base of the cowl and reused. The cow and water vapors are removed with the coloe II by the coodit 13 and cm in 14; the eam and the beze pass alrs in separatemr 15 of the one to bridge the bene

  by sewing 16 and water, at the base of the separator 15, by the cm-

must 17.

  The water is drawn from a tank 18, and discharged by tank 19 and condlit 20 on boiling 21, the latter being supplied with water vapor at high pressure - and heated by the conjecture 22; flumid cleaffmt is by Re c it 23. iDas the boiler, There is producti of apeOr which is directed by the t D2 Towards the lnjectiom at the base of column 1. Gm can imtradmire $ n cmtin am by iamteattmce of Ilemu of unplugged in the tank IS by the conduit Z4 and year

  to extract a certain amount of residual water from the iwstalla-

  is drawn by the conduit 25 .. This algmtatii and this

  end of Cottraler the level of polluting Sutane m of others

  Cmmpasmts in the liquid which ciro: the in 1l ftaltliun ..

  am WOit daisque the m prodite in the ims = llatini is recycled in the state of mapor Famr the fúr t of Ma cau-oe 2 477 23 It

  11, so that the residual benzene, if any,

  This water can be vaporized again for extraction.

  When the boiler is heated by steam introduced through line 22, the condensate discharged through line 23 can be used as a supplement to water entrainment when it is

  necessary, by introducing it into the reservoir 18 via the conduit 24.

277> 2.

R E V E N D I CA T IO N S

  1. Process for extracting benzene from a liquid containing

  washing oil and benzene in which benzene is entrained from this liquid by countercurrent flow with steam, condensation of benzene vapors and water leaving the entrainment process, separation of condensed liquids by

  the resulting benzene and wastewater,

  in that the waste water is sent to a boiler

  for producing the steam necessary for the driving operation.

  2. Method according to claim 1, characterized in that the drive is carried out in a vertical column in which the liquid is introduced into the upper region, and the water vapor injected into the lower region, the vapors of benzene and water being discharged at the top of the column and the oil

at the base of the latter.

  3. Method according to claim 1, characterized in that the wastewater is sent to a reservoir where they are

  put in the boiler, with continuous or inter-

  suspending additional water in said tank and extracting a portion of the wastewater from the installation, in order to allow a control of the content of pollutants or other components

  in the liquid that. circulates in.the installation.

  4. Method according to any one of claims 1

  at 3, characterized in that the boiler is heated by steam

  high pressure water and that the condensate coming out of the

  added to the fluid circulating in the plant for

the volume of the latter.

  5. Apparatus for implementing the method according to

  any of claims 1 to 4, characterized in that

  comprises a driving column in which the liquid is sent countercurrently with steam injected into the lower region of the column, a condenser in which the vapors of benzene and water leaving the column are condensed, a separator in which separates the produced benzene and the waste water, and a boiler into which the separated wastewater is sent for the production of the steam necessary for injection into the driving column.

9 4 77IC7

  6. Apparatus according to claim 5, characterized in that it further comprises a reservoir into which the separated waste water is sent before passing into the boiler, with continuous or intermittent supply of complementary water in said tank, and devices for extracting a certain part of the wastewater from the installation, which makes it possible to control the content of pollutants or other components in the system.

  liquid flowing through the installation.

  7. Apparatus according to claim 5, characterized in that the boiler is heated by high pressure steam and in that it comprises devices for extracting the condensate from the boiler.

  boiler and send this condensate to said tank for the purpose of

  keep the volume of water circulating in the installation.