DE1275070B - Process for purifying crude benzene by fractional condensation - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

ClOc

German class: 12 r-1/02

Number: 1 275 070

File number: P 12 75 070.8-44 (H 40296)

Filing date: August 26, 1960

Opening day: August 14, 1968

The invention relates to a method for purifying crude benzene, in particular such crude benzene, the gas obtained from the dry distillation of hard coal, ζ. Β. Coke oven gas, obtained will. The extraction of crude benzene from coke oven gas is usually done in such a way that the benzene hydrocarbons containing gas is brought into intimate contact with a washing oil at atmospheric or elevated pressure, the benzene hydrocarbons go into solution in the washing oil. After the washing oil has been separated from the gas, the benzene hydrocarbons are released from the washing oil Heating off, whereupon the washing oil is used again for the treatment of coke oven gas. That However, crude benzene expelled from the washing oil by heating is for numerous purposes, especially not suitable for further processing, but must, so that it is suitable for the different uses is useful, first freed from the resinous constituents and fractionated if necessary. Also for further processing by refining can often only a crude benzene can be used, which is already fractionated or from the chemically active to resinification prone components has been freed.

The invention is based on the fractionation and liberation of the crude benzene from the components mentioned in a simple process with little equipment and above all with the lowest possible expenditure of energy.

The invention relates to a process for purifying crude benzene by fractional condensation. It is characterized in that the crude benzene, optionally together with recycled, benzene fractions from the first cooling stage, which are less enriched in impurities, in hot, Introduced coke oven gas containing benzene hydrocarbons and together with these by cooling of the gas is separated out fractionally in several stages, with the hydrocarbon-containing benzene Gas is desulphurized and after a part of the benzene hydrocarbons has been separated out optionally remaining benzene after the fractional separation by treating the gas with Washing oil is separated.

It is known to separate crude benzene from hot coke oven gas by cooling the gas and here also part of the crude benzene obtained to facilitate the separation of naphthalene spray again into the hot coke oven gas. However, this method is not used for cleaning, but

Process for purifying crude benzene by fractional condensation

Applicant:

Hüttenwerk Oberhausen Aktiengesellschaft,

4200 Oberhausen

Named as inventor:

Dr.-Ing. Franz Kolkenbrock (t),

Dr. H.-Joachim Junker, 4250 Bottrop

the extraction of crude benzene by separation from the coke oven gas, so that the obtained Crude benzene because of its content of chemically active impurities that tend to become resinous for use in refineries only after further treatment through which these impurities removed is suitable. In contrast, the method according to the invention is used for Purification of crude benzene, namely crude benzene from other than that for its purification coke oven gas used or otherwise obtained. There are benzene fractions Thanks to their higher purity, they can be obtained without further preparation for numerous uses as well as for use at all points in the refining process, especially as Reflux benzene, can be used directly while the impurities, especially the chemically active and gum-prone constituents, in a further fraction in such a higher proportion Concentration accumulate that the extraction of these substances from the said fraction is worthwhile. Even the benzene hydrocarbons already contained in the hot coke oven gas before the crude benzene is introduced, which are usually only a fraction of those in the gas after the crude benzene has been introduced Make up the total amount of benzene hydrocarbons, are introduced along with the Crude benzene separated in fractionated form.

It is also known that crude benzene can be purified by adding hydrogen without any aid allows catalysts to act on the crude benzene to be purified under hydrogenation conditions. at In contrast to the subject matter of the invention, this chemical process does not involve a physical one Separation of the unwanted components from the crude benzene, but it will be through the

809 590/141

3 4

Hydrogen, which is also hydrogen, leaves washer 2 at 4. The unsaturated hydrocarbons contained in crude benzene washing oil enriched in the benzene hydrocarbons, which can act from coke oven gas, are converted into saturated hydrocarbons from the washer 2 via a line 4 a. Heat exchanger 5 supplied, from which it arrives via a line 6 in the heater 7, from which the method according to the invention is to transfer the crude heated washing oil via a line 8 into the benzene in such coke oven gas bring in the abortion 9 is introduced. The washing oil freed from the benzene hydrocarbons such as the z. B. is required for coke oven gas, which reaches out of this through a line 10 to the heat after a cleaning following the compression io exchanger 5, in which part of its heat is to be introduced into long-distance gas networks. Here, the enriched with benzene hydrocarbons is an appropriate utilization of the compression washing oil. The washing oil freed from the heat for evaporation of the crude benzene hydrocarbons to be cleaned is made possible by the washer 5 via the benzene. Line 11 is fed to the cooler 12, from which it can be useful to re-saturate the hot coke oven gas 15 via line 3 in the washer 2 with crude benzene to such an extent that it is brought up. The mixture of benzene hydrocarbons that is driven off from the scrubbing oil boiling from the washing oil in the stripper 9 remains unevaporated and together with high substances, which is referred to as crude benzene, is fed to a condenser 14 via the boiling constituents of the coke oven gas and the benzene hydrocarbons contained therein In the end, after the water has been separated off, the crude benzene brought into a collecting tank 16 is condensed in exchange for low-boiling components. In the second plant, the ammonia and liquid state pass into the first fraction. Tar-released coke oven gas, which is passed through a pipe

It can also be expedient for the benzene content 17 to enter the system by means of a compressor 18

the 35 largely freed from benzene by cooling is compressed to remote gas pressure. The compressed

Gas through a subsequent treatment with gas leaves the compressor at one temperature

To further reduce washing oil. The resulting from about 90 to 130 ° C and is through a pipe

Benzene, like the light benzene, is fed through 19 to cooler 20. Before the gas in the

Benzene fractions obtained from such a high cooler 20 enters the gas stream through the cooling

Purity that there is crude benzene fed into the plant without further treatment for many 30 line 21

Uses is suitable. If that should be cleaned from the, sprayed. It can turn out to be here

Benzene-freed gas dried by freezing both to be used in the low-pressure benzene production

it is advisable to transfer the frozen gas to the system and collected in the container 16

Cooling of the benzene-containing coke oven gas in a crude benzene as well as in the third place

or several refrigeration units preceding the freezing process.

levels to use. Furthermore, it can expediently The gas saturated in this way with crude benzene

be, the benzene-containing gas after separation is then passed through the cooler, 20, 22, 23 and

a part of the benzene hydrocarbons, namely 24 performed, for example as water-cooled

in particular the fractions that the contaminant tube cooler can be formed and in which

These contain substances to desulphurize, whereby the 40 predominantly heavy benzene hydrocarbons

a further increase in the purity of the subsequent washing out of what is contained in the gas

separated fractions results. To be as condensed as possible naphthalene and in one

extensive concentration of the impurities in separator 25 occur. The in the separator 25

the first fractions and thus the noticeable fraction of heavy benzene hydrocarbons

To make working these fractions worthwhile, 45 contains almost all of the chemically active ones

it can be advantageous to use some of the compounds indene, coumarone, dicyclopentadiene

benzene fractions containing impurities, and inter alia, which are obtained before the further processing of the benzene

in particular the fractions in which the this must be separated,

impurities are present in low concentration, the addition of the supplied through line 21

to be introduced again into the hot coke oven gas. 50 crude benzene to the one carried in line 19

Another considerable advantage of the hot gas process can be carried out both as described

According to the invention is that a resinification injection of the crude benzene into the gas as well as into

the cooler is carried out as a result of the saturation of the gas in a particularly expedient manner in such a way that

Benzene hydrocarbons is completely excluded. in front of the cooler 20 a not shown in the drawing

The following is a possible embodiment of 55 posed washer, τ. B. a bell bottom washer,

of the method according to the invention on the basis of which is arranged in which the crude benzene by task

Drawing explained. on the top floor of the hot gas in the opposite

The current shown schematically in the drawing is countered. The bottom product of the

The system consists of a low-level washer, which is known per se, and is separated from that in the coolers 20

Pressure benzene recovery system and a system to remove 60 to 24 accumulating condensate. Through this

in which the in the Niederdruckbenzolnahmungs- a significantly improved fractionation of the

plant-derived crude benzene obtained using the crude benzene process,

is cleaned according to the invention. pas from the cooler 24 at a temperature of

The low pressure gas is at 1 the washer 2, for example, about 30 ° C and a content of

supplied, in which it is introduced at 3 by 65 benzene hydrocarbons of for example about

Washing oil from the benzene hydrocarbons up to 50 g / Nm ^s escaping gas is in a

a residual content of about 1.5 g / Nm ^{3 is} freed. tion, not shown system to, for example

The gas freed from the benzene hydrocarbons is warmed up to 3 to 5 ° C and then in a

Dry cleaning system 26 freed from hydrogen sulfide.

The gas freed from the hydrogen sulfide in the dry cleaning system 26 is via the Line 27 the series-connected heat exchangers 28, 29, 30 and the adjoining one Freezer 31 supplied, which it leaves via line 32, where it has a temperature of for example 3 ° C. During the cooling of the gas in the heat exchangers 28, 29, 30 as well as a particularly pure one falls in the freezer 31 low-sulfur benzene fraction, consisting essentially of light benzene hydrocarbons boiling up to 120 ° C exists and is collected in the separator 33. is

The gas emerging from the freezer 31 through the line 32, which still contains, for example, about 16 g of benzene per normal cubic meter, is introduced into a washer 34, in which, by means of washing oil, the remaining benzene is removed down to a residual content of, for example, 0.5 g / Nm ³ is released. This gas is passed from the washer 34 via the line 35 into a deep freezer 36, in which it is dried, and from this passes via the line 37 into the heat exchangers 30, 29 and 28, in which it is used to cool the in the heat exchangers through the line 27 introduced, benzene hydrocarbon-containing gas is used. The gas which is reheated in this process and free of benzene hydrocarbons emerges from the heat exchanger 28 at 38 and can be introduced into the long-distance gas network.

The washing oil enriched with benzene in the washer 34 emerges from the same through the line 39 and is fed to a stripper 41 via a heater 40. The benzene expelled in this arrives via a cooler 42 into a separator 43. This fraction consists of more than 90% benzene in addition Toluene, xylene and aliphatic compounds. The washing oil freed from benzene leaves the aborter 41 through a line 44 and is fed to the heat exchanger 5 of the first system. The feeding of the washer 34 with washing oil is also done from the first system via line 45.

The benzene fractions obtained in separators 33 and 43 are of such great purity and in particular so largely free of chemically active components that tend to become resinous, that they can be used without further treatment, while those in the separator 25 or at Use of a washer upstream of the cooler 20 as its bottom product Benzene fraction which contains impurities in high concentration.

By subdividing the first cooling stage and separate deduction of the resulting fractions as well by recycling fractions less enriched with impurities into the hot one Gas, which is particularly useful when too little benzene is used to saturate the gas Would be available, a further substantial enrichment of these compounds can be achieved. For example, a fraction was separated from the crude benzene used with an indene content of 1.48% containing 9.54% of this compound.

Claims (5)

Patent claims: 1. Process for purifying crude benzene by fractional condensation, thereby characterized in that the crude benzene, optionally together with recycled, impurities weaker enriched benzene fractions from the first cooling stage into hot coke oven gas containing benzene hydrocarbons introduced and fractionated together with these by cooling the gas in several stages is deposited, where appropriate, the benzene hydrocarbon-containing gas after Separation of part of the benzene hydrocarbons and desulfurized, if necessary, after fractional separation, the remaining benzene is separated off by treating the gas with washing oil will. 2. The method according to claim 1, characterized in that the coke oven gas prior to introduction the benzene hydrocarbons is heated by compression. 3. The method according to claims 1 and 2, characterized in that the hot coke oven gas is oversaturated with crude benzene. 4. Process according to claims 1 to 3, characterized in that the benzene freed gas dried by deep freezing and the frozen gas to cool the benzene hydrocarbon containing Coke oven gas is used in one or more of the cooling stages preceding the freezing. 5. The method according to claims 1 to 4, characterized in that the introduction of the Crude benzene into the hot gas in a washer, preferably in a bell-bottom washer, he follows. Considered publications:
German Patent Nos. 641172, 844 440;
German interpretative document No. 1013 774. 1 sheet of drawings 809 590/141 8.68 © Bundesdruckerei Berlin