JPH07207282A - Method of removing water from solvent leaving hydrocarbon dewaxing process - Google Patents

Abstract

PURPOSE: To partially dehydrate a wet solvent mixture recovered from a dewaxing operation by subjecting it to a specified distillation operation.

CONSTITUTION: The number of trays 3, 4, and 5 may be varied. A mixture M2 formed by partially dehydrating a solvent/poor solvent mixture is recovered from the bottom of a tower 2 via a line 7. The heating of the tower 2 is performed with a boiler 8. A stream 10 (M1) of steam is recovered from the top of the tower 2 and is liquefied in a condenser 11, and the liquid is fed into a decanter 12. When both the water fed from a line 23 and the water optionally fed from a line 14 are sufficient, the following two liquid phases are separated from each other. Namely, the upper layer 15 contains little water and much solvent and poor solvent. The lower phase contains much water and fed into a second distillation tower 7 via a line 18. This apparatus is provided with a contacting device similar to that in the tower 1, such as trays 19 and 20. The overhead product 21 forms a flow A1, is condensed in a condenser 22, and reaches a decanter 12. The bottom product is substantially composed of water.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a solvent dewaxing process for hydrocarbon oils, and more particularly to a process for at least partially dehydrating the recovered solvent. According to one embodiment of the invention,
The process according to the invention makes it possible to adjust the solvent / antisolvent ratio, in particular the toluene / methyl ethyl ketone (MEK) ratio.

[0002]

BACKGROUND OF THE INVENTION Distillate base oils for producing lubricating oils from hydrocarbons recovered during the distillation of petroleum under atmospheric pressure and reduced pressure are of various types suitable for bringing them to specifications. Requires processing. One of these treatments is paraffin extraction or dewaxing, the purpose of which is to remove relatively high melting point hydrocarbons, especially straight chain paraffins, which render the lubricating oil not sufficiently fluid at low temperatures. That is. This treatment is usually followed by purification using eg furfural as solvent.

The dewaxing process uses a solvent or mixture of solvents at low temperatures which dissolves hydrocarbons having a low melting point but allows hydrocarbons (paraffins) having a high melting point to precipitate and remain on the filter. Is the operation.

For dewaxing, a mixture of solvents, for example a good solvent for paraffins such as benzene or toluene (hereinafter solvent), and a ketone having 3 to 6 carbon atoms, for example methyl ethyl ketone (MEK) or methyl isobutyl. Mixtures with poor solvents for paraffins (hereinafter referred to as poor solvents) such as ketones (MIBK) are very often used. A mixture of toluene and MEK is preferred here, and the mixture of solvent and poor solvent is collectively referred to as the "solvent mixture".

The details of the dewaxing treatment are described in the literature and patent specifications, for example, by Bae Witier, "Le Petrol,"
Rafinage et Jeni Simique (Le Petrole,
Raffinage et Genie chimique) "(1965), pages 641 to 649 and U.S. Pat. No. 4,088,565 and
See 4,354,921.

Dewaxing operations are generally at low temperatures, for example -20.
C. to -30.degree. C., filtration is usually carried out on a vacuum rotary filter, which is regularly cleaned with solvent or dry solvent mixture. The recovered solvent mixture is separated from the oil in any suitable manner, for example by distillation.

Thus, the separation of oil and paraffin is achieved by the combined use of a chemical action such as dissolution in a solvent mixture and a mechanical action such as a filtration operation at a low temperature, and the optimum composition of the solvent mixture is the raw material classification ( It depends on the batch).

This unit operation consists of different types of batches (batch) obtained from different fractions in the distillate stream from a vacuum distillation column.
It also presents other special requirements that the product is processed in an alternating manner and must be processed all year round.

The required amount of solvent mixture is very large, varying from 200% to 400% by volume of the untreated raw material compartment.

Thus, the solvent mixture is recovered after separation of oil and paraffin under the application of heat in different recovery zones and recycled to the filtration operation.

Since the solvent mixture contains a hydrophilic poor solvent, it is polar and tends to immobilize water when it encounters it. This water originates in particular from the stripping steam used to recover the charge and the traces of solvent mixture left in the product to the end.

Considering that the solvent mixture contains polar components, it is not currently industrially feasible to completely dry the solvent mixture. Therefore, there is still a problem that has not been solved industrially in an economically satisfactory state, and the problem is that the water and the solvent mixture are precisely separated, which has not been solved satisfactorily. Other problems are described below.

For each type of charge of dewaxing equipment,
The corresponding poor solvent / solvent ratio, eg MEK /
There is a proportion of toluene. In the dewaxing apparatus, the charge material sections are frequently exchanged (for example, twice or three times a week), so that the operator of the dewaxing apparatus can favorably use the solvent for the next charge material and the poor solvent. It takes some time for the composition to change in all equipment, especially considering the substantial residence time of the solvent / antisolvent mixture in the dewaxing equipment.

This shows the inconvenience that the balance of the apparatus is lost, that the same operation does not result in the optimum operation, and that the oil production rate is hindered even in a short time. .

As an example, brightstock treatment is currently performed using a MEK: toluene weight ratio of 0.7: 1 to 1: 1 while gas oil treatment is 1.1: 1 to 2 .
It was carried out at a MEK: toluene weight ratio of 3: 1.

Therefore, in order to obtain a full range of solvent / antisolvent compositions that can accommodate variations in the feed segment being treated, simply by mixing the streams obtained from the solvent / antisolvent sources. It is important that a solvent mixture having a different composition can be easily supplied separately.

Although this problem is addressed in US Pat. No. 4,898,674, the solution proposed here is the use of pervaporation membranes, which is difficult to implement industrially.

[0018]

Therefore, the first aspect of the present invention
The purpose of is to provide a simple and economical method of at least partially drying the recovered wet solvent / antisolvent mixture.

Another object of the invention is to recover the wet solvent /
The preparation of a mixture from the poor solvent mixture such that the solvent / poor solvent ratio is different from the solvent / poor solvent ratio of the treated solvent / poor solvent mixture.

Still other objects of the present invention will be apparent to those skilled in the art from the following description.

[0021]

According to the invention, the following steps are carried out: (a) Wet solvent mixture (M ₀ ) consisting of a solvent and a poor solvent.
At the top of the zone to recover a water-rich first distillate stream (M ₁ ) relative to the raw solvent mixture (M ₀ ); At the bottom of the liquid solvent mixture (M ₂ ) consisting of a solvent / poor solvent having a lower water content than the starting solvent mixture (M ₀ ) is recovered; the solvent mixture (M ₂ ) is at least partially dehydrated as desired. (B) the first distillate stream (M ₁ ) comprises at least a portion of the aqueous stream (A ₁ ) described below, in an amount of 0.05-1 of the first distillate stream.
The mixture obtained is brought into contact with 0 times the weight of water; the resulting mixture is decanted in the decantation zone in the liquid phase to form an upper liquid phase having a relatively low water content and a lower liquid phase having a relatively high water content; (C) returning the upper liquid phase to the first distillation zone as reflux; (d) feeding the lower liquid phase to the second distillation zone, essentially forming the aqueous stream (A ₁ ) from the second distillation zone. A top product relatively rich in antisolvent and a bottom product relatively less antisolvent and consisting essentially of water, the bottom product is removed and the aqueous stream (A ₁ ) Consists of returning this to step (b).

When the aqueous stream (A ₁ ) returned to step (b) does not contain the amount of water required for step (b), additional water is added to step (b). This additional water may come from an external source, or it may be very much supplied from a second aqueous stream (A ₂ ) obtained by recycling a portion of the bottom product from the second distillation zone. It is advantageous.

According to another embodiment, which is a process suitable for feeding at least two streams of at least partially dehydrated solvent mixture, each having a different solvent / antisolvent ratio, to the first distillation zone Relative to the wet solvent mixture (M ₀ ) and the liquid solvent mixture (M ₂ ) at at least one midpoint located above the location where the solvent / poor solvent wet solvent mixture (M ₀ ) is charged. At least one liquid mixture (M ₃ ) rich in antisolvent and low in solvent is drained. Mixture (M ₃₎ that if charged raw material solvent mixture to the first distillation zone (M ₀₎ mixture at a relatively close distance above the place where charged (M ₃₎ taken out, charging raw material solvent It could also be less water than the mixture (M ₀ ). The present invention will be described below with reference to the drawings.

According to FIG. 1, the raw material mixture (M ₀ ), for example the water / MEK / toluene mixture, is introduced into the column 2 via the line 1. The column 2 is advantageously provided with internal means for improving the liquid / steam contact.

In FIG. 1, trays 3, 4, 5 and 6 are shown as said internal means, but the number of fractionation stages (trays) can be varied and any means known to those skilled in the art. Obviously, it is possible to use, for example, a Raschig ring, a bur saddle or equipment with a counter-effect.

From the bottom of column 2 at least partially dehydrated mixture of solvent / antisolvent mixture (M ₂ ) is provided in line 7
Be collected through.

The heating of the column 2 can be carried out by any conventional means. FIG. 1 shows a reboiler 8 and a flow return line 9 which is partially or completely in the vapor phase. Tower 2
A steam stream 10 or M ₁ is withdrawn from the top of the stream, which stream 10 (M ₁ ) is liquefied in a condenser 11 and fed to a decantation flask (decanter) 12 via line 13.

When a sufficient amount of water supplied by line 23 and optionally water supplied by line 14 is present in decanter 12, the following two liquid phases are produced separately from each other.

That is, the upper phase 15 has less water and more solvent and poor solvent, but the solvent / poor solvent ratio R of this upper phase is smaller than the solvent / poor solvent ratio in the charging raw material (line 1). , The water content is higher than the water content of the raw material.

The lower phase 16 is rich in water and contains a substantial proportion of poor solvent and a very small proportion of solvent. This latter phase (lower phase) is fed to the second distillation column 17 through the line 18. The second distillation column 17 is equipped with a contact device similar to the column 2, for example, trays 19 and 20. Top product (line 2
1) forms stream (A ₁ ), which stream (A ₁ ) is condensed in condenser 22 and passed through line 23 to decanter 12
Reach The bottom product consists essentially of water, line 2
4 through which part (line 25) is discarded and the other part forms stream (A ₂ ) and is returned to decanter 12 through line 14.

Alternatively, the total bottom product (line 24)
May be discarded via line 25 and the additional amount of water required for decanter 12 may be introduced from another source.

The steam (line 26) is the second distillation column 17
It is highly advantageous to supply at least a part of the heat required for the distillation carried out in. However, the invention also contemplates the use of other embodiments to provide heat to the second distillation column. The strip steam (26) is advantageously produced by distilling a portion of the water withdrawn through line 24. The line 27 allows the upper liquid phase 15 to be returned to the column 2 as reflux.

FIG. 2 shows a part of FIG. 1 with the column 2 and the mixture (M ₂ ) flowing out from the bottom. In FIG. 2, a tank 32 for the mixture (M ₂ ) fed through line 33 is shown. Line 34 allows the solvent mixture (M ₂ ) to be withdrawn for other uses, especially for direct feed to the dewaxing unit.

Further described is the mode of removal of the solvent (M ₃ ) via line 28, which M ₃ is fed to tank 29 via line 30 or recycled directly to the dewaxing unit via line 31. .

In the case of FIG. 2, the tank 3 passes through the line 7.
It is to be understood that the solvent / antisolvent ratio R of the mixture M ₂ entering 2 is greater than the solvent / antisolvent ratio of the feedstock M ₀ (line 1). Conversely, the ratio R of the mixture M ₃ (line 28 and tank 29) is less than either ratio in M ₀ and M ₂ . M
The water content of ₂ is much lower than that of M ₀ . The water content of M ₃ are, when at least the M ₃ is taken at a close distance of the upper instrumentation admission office charged raw material M _0, usually less than the water content of M _0. The water content of M ₃ is at a very high extraction location of M ₃ may even be slightly more than the water content of equal to or M ₀ on the water content of M _0, but in this subsequent operation, M ₃ and M _As long as the mixture of M ₃ and M ₂ is used so that the total water content in the mixture with ₂ is less than that of M ₀ , there are no major disadvantages.

The flow M ₃ are for example 0-50% of the flow M ₀ (vol%), although the flow M ₂ is an amount of about 100 to 50 percent by volume of the flow M _0, the ratio preferably of (volume %) Are 25-40% and about 75-60%, respectively. The total amount of streams M ₂ and M ₃ may not be as low as 100% of M ₀ due to their low water content.

Obviously, various modifications may be made in these figures within the ability of those skilled in the art. For the purposes of illustration, instead of connecting pipelines 13, 14 and 23 to decanter 12 separately, two or three streams of these pipelines may be fed as a mixture. At least one of stream 13 and stream 23 may still be in the vapor phase, but stream 14 is in the liquid phase.
To pass these streams through one condenser, steam flow 1
It may be performed after mixing 0 and 21. In this case, one of the capacitors 11 or 22 becomes unnecessary.

The two distillation columns may be operated under the same pressure or different pressures. For economy, it is preferred to operate at atmospheric pressure, but operation at pressures below or above atmospheric pressure, for example 0.5 to 5 bar absolute pressure, also has some advantages. is there.

It goes without saying that the operating temperature is limited by the choice of pressure and the choice of solvent / antisolvent pair. By operating under atmospheric pressure, for example using a MEK / toluene mixture, the condenser 11 and the condenser 22 can be cooled with water or air without difficulty, at least in warm regions.

The important variables of the process are fed directly to the decantation drum 12 (decanter 12) or to line 10 or line 13 for encountering the mixture M ₁ on the decantation drum 12 (decanter 12). This is a selection of the amount of water used. This water is selected in the examples so that a minor proportion comes from line 23 and a major proportion comes from line 14. Overall, this amount of water is 0.05 to 10 times the weight of the distillate (lines 10 or 13) of column 2, preferably 0.05 to 2 times the weight, and more preferably 0.00. Even 1 to 0.5 times the weight.

Since most of this water flows through the closed circuit except the amount taken out by the line 25 and the amount supplied by the distillate stream of the column 2, it is not possible to additionally supply the water except for compensating for the loss. Not required.

The wet solvent mixture (M ₀ ) fed to the first distillation zone is, for example, 0.5 to 4% by weight of water, 30 to 60% by weight of solvent and 35 to 70% by weight of poor solvent in a good amount of 10.
It is contained in an amount of 0%.

If desired, some solvent and poor solvent may be added to the apparatus, and this addition can be carried out at any suitable location in the apparatus.

The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

To the tower 2 through line 1 water 2.1%, MEK
A mixture of 58.7% and toluene 39.2% (all% in the examples are% by weight) is fed 42,416 kg / h, water 13.2%, MEK 77.6% and toluene 9.2%. 19,304 kg / h of the mixture was collected at the top of the column. The collected mixture is condensed by the condenser 11 and 2,502 kg in the decanter 12 (drum).
/ Hour of substantially pure water 14 and an aqueous stream 23 of 916 kg / hour (consisting of 10.3% water, 89.5% MEK and 0.2% toluene). Decanter 12 to MEK-rich upper phase (mixture of water, MEK and toluene 18,464 kg / h) and water-rich lower phase (mixture of water, MEK and traces of toluene 4,26
1 kg / hour), the upper phase was returned to the column 2, and the lower phase was sent to the second distillation column 17. Stream 26 charged to the second distillation column 17 via line 26 stripped MEK and traces of toluene and was discharged from column 17 via line 21. 0.0 through the bottom of tower 17 and line 25
4,032 kg / h of water with 5% MEK and virtually no toluene were collected.

The bottom product of column 2 is a mixture 41,599 of MEK 60%, toluene 39.9% and water 0.1%.
It was removed from the process at kg / hr. This mixture could subsequently be used as a solvent mixture for the dewaxing operation. All equipment was operated at substantially atmospheric pressure.

[Brief description of drawings]

FIG. 1 is a process drawing showing a basic embodiment of the present invention in which the mixture M ₃ is not taken out.

FIG. 2 is a partial process drawing of the apparatus for carrying out intermediate withdrawal of the mixture M ₃ .

[Explanation of symbols]

 2 towers (first distillation zone) 3, 4, 5, 6 trays 8 reboiler 11 condenser 12 decantation flask (decanter) 17 second distillation tower 19, 20 trays 22 condenser 29, 32 tanks

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Roger Urnac France, 75004 Paris, Lieu Crillon 2 Bis

Claims (7)

[Claims] 1. A method for at least partial dehydration of a wet solvent mixture comprising a solvent and a poor solvent for paraffin and water, recovered from a dewaxing operation, comprising: (a) charging a wet solvent mixture comprising the solvent and a poor solvent. A liquid solvent mixture which is fed to the first distillation zone as a raw material section and has a water-rich first distillate stream at the top of the zone relative to the raw material wet solvent mixture, and also a solvent and a poor solvent with reduced water content. Is collected at the bottom of the zone, the liquid solvent mixture is discharged as the desired at least partially dehydrated solvent mixture, and (b) the first distillate stream is equal to the volume of the first distillate stream of 0. 05-10
The mixture obtained by contacting with a double weight of water containing at least a part of the aqueous flow described below, and decanting the mixture obtained as the liquid phase in the decantation zone is used to compare the relative water content with the upper liquid phase having a relatively low water content. (C) the upper liquid phase is transported to the first distillation zone as reflux, and (d) the lower liquid phase is fed to the second distillation zone, and essentially from the second distillation zone. Recovering the relatively poor solvent rich top product of the aqueous stream and the relatively poor solvent less bottom product consisting essentially of water; removing the bottom product; Consisting of returning the flow to step (b),
A method of at least partial dehydration of a wet solvent resulting from a hydrocarbon dewaxing operation. 2. In order to obtain at least two streams of an at least partially dehydrated solvent mixture exhibiting different solvent / antisolvent ratios, the raw wet solvent mixture and a low water content relative to the raw wet solvent mixture and At least one liquid mixture, which is relatively richer and less solvent than the liquid solvent / poor solvent mixture, is at least above the location where a wet solvent mixture consisting of the solvent and the poor solvent is fed to the first zone. The method of claim 1 comprising extracting at two intermediate points. 3. The method of claim 1, wherein the solvent is toluene and the poor solvent is methyl ethyl ketone. 4. The method of claim 1 wherein steam is fed to the second distillation zone to strip the solvent. 5. The method of claim 1 wherein a portion of the water required for step (b) consists of a portion of the bottom product of step (d). 6. The process according to claim 1, wherein the total amount of water contacted with the first distillate stream during the operation of step (b) is 0.05 to 2 times the amount of the first distillate stream. . 7. The wet solvent mixture fed to the first distillation zone comprises 0.5-4 wt% water, 30-60 wt% solvent and 35-70 wt% poor solvent. Method.