JPS6067438A - Recovery of benzene/naphthalene - Google Patents

Abstract

PURPOSE:To recover the titled materials, by feeding a benzene-containing oil directly to a benzene-stripping column without passing through a dehydration column, and carrying out the dehydration treatment simultaneoulsy to the steam stripping, and refluxing the intermediate fraction of the benzene-stripping column. CONSTITUTION:The benzene-containing oil is fed through the line 1 and the heat exchanger 3 to the benzene-stripping column 7, and the intermediate fraction extracted through the line 18 is heated with the furnace 6 to 160-220 deg.C and recycled to the column at a stage within 3 stages above the stage of the line 18 (preferably at the stage of the line 18). Steam is introduced into the column from the column bottom pipe 8 to strip the benzene fraction, and at the same time, the oil is dehydrated in the trays between the feed stage of the column 7 and the extraction stage for supplying to the furnace. Benzene fraction is obtained as a column top distillate, and is treated with the separator 11 to separate water, and crude benzene is obtained from the line 23. The crude naphthalene is recovered from the middle part of the column through the line 14, and the column bottom liquid is sent through the line 15 to the heat- exchanger 3 to effect the heat-exchange with the benzene-containing oil. The oil free from benzene is discharged from the line 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering henzol/naphthalene,
More particularly, the present invention relates to a method for recovering hensol/naphthalene that can efficiently recover crude hensol and crude naphthalene from penzole-containing oil.

Conventionally, the method for recovering penzole/naphthalene from penzole-containing oil is to first send the penzole-containing oil as a raw material to a dehydration tower to separate water, then send it via a heating furnace to a debenzolization tower, where it is steamed. A method of stripping is used to separate crude penzole, crude naphthalene and debenzolized oil.

That is, FIG. 1 is a system diagram of a typical conventional penzole/naphthalene recovery method. The combined penzole oil is first pumped from line 1 to an RO pump (Rich Oil pump) 2 through an O10 heat exchanger (Rich O4L pump). /
After being sent to the Weak O41 heat exchanger 3 for heat exchange, it is sent to the dehydration tower 4 where it is dehydrated. The dehydrated penzole oil is transferred to an RO heating furnace (Ric) by a pump 5.
After being sent to the oil heating furnace) 6 and heated here,
It is sent to the debenzolization tower 7. Steam is blown into the bottom of the debenzolization tower 7 from a line 8, steam stripping is performed within the tower, and the top fraction of the debenzolization tower 7 is sent to a two-liter sensor 10 via a line 9. ,
Furthermore, after separating the water removed from the line 12 in the separator 11, the L O pump (Lean, Oi I
Crude pensol is recovered from line 23 by pump 13.

Note that a part of this column overhead fraction is circulated to the column top through line 25.

On the other hand, from the upper stage of the debenzolizing tower 7, crude naphthalene is recovered via line 14, and from the bottom of the tower, debenzolized oil is collected as a bottom liquid via line 15, and the W○ pump (
The oil is sent to the 010 heat exchanger 3 by the Weak Oil pump) 1G, where it is heat exchanged with the henzol-containing oil, and then recovered from the line 17.

In the conventional method described in item 1, it is necessary to send the raw material to a dehydration tower for dehydration before the debenzolization tower 7, resulting in high equipment costs and disadvantages in that the dehydration and deaeration efficiency is not necessarily high. there were.

Generally, penzole-containing oil contains not only the aromatic hydrocarbons of the penzole group but also some of the impurities contained in coke oven gas. According to the law, among these impurities,
Strongly corrosive hydrogen sulfide, ammonia, cyanide, chlorine, etc.
There is a drawback that the penzole-containing oil corrodes the heating tube while it passes through the heating tube of the RO heating furnace.

Furthermore, in the conventional method, in the debenzolization tower 7, the descending liquid from the concentration section comes into contact with the high-temperature heating furnace outlet oil, so thermal polycondensation occurs, and thermal polycondensation products are mixed into the absorbed oil and absorbed. Another drawback was that the oil aged.

An object of the present invention is to provide a method for recovering penzole/naphthalene that can efficiently obtain crude penzole and crude naphthalene from penzole-containing oil with a relatively simple equipment configuration, by eliminating the drawbacks of the prior art. be.

As a result of intensive research to achieve this objective, the present inventors have found that the henzol-containing oil is sent directly to a debenzolization tower without passing through a dehydration tower, and dehydration is performed using steam blown from the bottom of the tower. The present invention has been achieved by discovering that the above object can be achieved by heating and refluxing the middle fraction of the debenzolization tower. A method of performing stino stripping using steam blown in from the bottom and recovering crude penzole from the top of the tower and recovered naphthalene from the middle of the tower, the penzole-containing oil not passing through a dehydration tower, It is characterized in that it is directly sent to the debenzolizing tower and subjected to dehydration treatment simultaneously with the steam stripping, and the fraction in the middle stage of the debenzolizing tower is heated to reflux.

Examples of the henzol-containing oil used as a raw material in the method of the present invention include absorbed oil obtained by distilling coal tar,
Alternatively, the straw oil obtained by distilling crude oil is circulated to a penzol absorption tower, and in this hensol absorption tower, it is brought into countercurrent contact with a gas containing penzol, such as coke oven gas or oil gas, to absorb hensol. Absorption oils or straw oils may be mentioned.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a system diagram showing an embodiment of the penzole/naphthalene recovery method of the present invention. The difference from the conventional apparatus shown in FIG. 1 is that the dehydration tower 4 is not provided and the henzol-containing oil is sent directly to the debenzolization tower 7, and the middle fraction of the debenzolization tower 7 is taken out from the line 18 and sent to the heating furnace. After being sent to the RO heating furnace 6 via the line 19 by the inlet pump 5 and heated, it is circulated to the debenzolization tower 7 via the line 20.

In the figure, first, penzole-containing oil is sent from line 1 to O10 heat exchanger 3 by RO pump 2 for heat exchange, and then directly sent to debenzolization tower 7 without passing through the dehydration tower. The middle fraction of the debenzolization tower 7 is taken out from the line 18 as described above and sent to the RO heating furnace 6 via the line 19 by the pump 5, and heated to a temperature of, for example, 100 to 300°C by the fuel supplied from the line 21. Preferably, after being heated to 160 to 220° C., it is circulated from line 20 to the upper three stages (preferably the same stage) of the debenzolization tower 7 to which the line 18 is attached. The structure of this circulation stage is, for example, Utility Model Application No. 58-1114'
Those described in No. 94 are preferred. Steam is blown into the bottom of the debenzolization tower 7 from a line 8, and while the steam rises inside the tower, the penzole component in the absorbed oil is stripped. The steam-stripped pensol fraction is taken out from line 9 as an overhead fraction and sent to condenser 10, then separator 1
After removing the water removed from line 12 at step 1, L
It is recovered as crude henzol from line 23 by O pump 13. Note that a part of the above-mentioned column overhead fraction is circulated to the column top via line 25. The steam blown into the debenzolizing tower 7 is brought into gas-liquid contact with the henzol-containing oil in a tray between the supply stage of the debenzolizing tower 7 and the withdrawal stage for feeding into the heating furnace, thereby eliminating stri-noping. Dehydration is also performed at the same time.

On the other hand, from the middle stage of the debenzolization tower 7, crude naphthalene is recovered via line 14, and from the bottom of the tower, debenzolized oil is collected as a bottom liquid via line 15 into the WO pump 16.
．． The oil is sent to the 010 heat exchanger 3-, where it is heat exchanged with the penzole-containing oil, and then recovered through the line 17. - As detailed above, the method of the present invention effectively utilizes the stripping steam blown into the debenzolization tower to perform dehydration and deaeration, and therefore, unlike conventional methods, the dehydration tower is not used. There is no need for separate installation, equipment costs can be reduced, and dehydration and deaeration efficiency can be greatly improved. Furthermore, in the method of the present invention, the dehydration and deaeration efficiency increases, and as a result, the aforementioned impurities are simultaneously removed from the penzole-containing oil, so corrosion of the heating tube in the heating furnace 6 is reduced.

Furthermore, in the method of the present invention, in the debenzolization tower 7, the descending liquid from the concentration section comes into contact with the oil that has exited the 010 heat exchanger 3, but this oil has a temperature lower than that of the oil that has passed through the RO heating furnace 6. Since it is low, thermal polycondensates are not produced, and therefore aging of the absorbed oil is significantly reduced.

[Brief explanation of drawings]

FIGS. 1 and 2 are system diagrams of a method for recovering J-penzole/naphthalene, showing an example of the conventional method and the method of the present invention, respectively. In the figure, numeral 3 is an O10 heat exchanger, 4 is a dehydration tower, 6 is an RO heating furnace, 7 is a debenzolization tower, 10 is a condenser, and 11 is a separator. Agent Patent Attorney Takeshi Kawakita

Claims (1)

[Claims] (1) A method of sending penzole-containing oil to a debenzolization tower, performing steam stripping with steam blown from the bottom of the tower, and recovering crude penzole from the top of the tower and crude naphthalene from the middle of the tower, comprising: The penzole-containing oil is directly sent to the debenzolization tower without passing through the dehydration tower, and is dehydrated at the same time as the steam stripping, and the fraction in the middle stage of the debenzolization tower is heated to reflux. How to recover henzol/naphthalene.