RU2532808C1 - Method of regenerating solvent in dewaxing and deoiling processes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the regeneration of a solvent from solutions of dewaxing oils, gatches, paraffins, deoiling filtrates in processes of dewaxing, deoiling and combined dewaxing-deoiling processes. The invention deals with a method realised by the distillation of the solvent in successively placed rectification columns with an increase of temperature of flows, which the solvent is extracted from; and further supply of the said flows into evaporation columns. Nitrogen is supplied into the evaporation columns to reduce partial pressure of the solvent component, and in the said columns a vacuum is created by pumping-out a mixture of nitrogen and the solvent vapours by a vacuum pump.

EFFECT: obtaining products with the required water content, reduction of power consumption in the process of the solvent regeneration, increase of ecological safety of production.

2 dwg, 2 tbl, 2 ex

Description

The invention relates to methods of solvent regeneration in the processes of dewaxing oils, deoxidation of paraffins, combined dewaxing-de-oiling processes and can be used in the refining industry.

The closest solution in technical essence and the achieved results is a method of solvent regeneration from solutions of dewaxed oils, waxes, paraffins, de-oiling filtrates in the processes of dewaxing, de-oiling and combined dewaxing-de-oiling processes (Oil and gas processing technology. Part 3 / Chernozhukov N.I. Purification and separation of crude oil, production of marketable petroleum products. - M.: Chemistry, 1978.- 424 S. ill.).

According to this method, the separation of the solvent from these streams is carried out first in series-connected distillation columns operating at overpressure, with increasing temperature of the streams from which the solvent is extracted. Further, these flows are directed to stripping columns, also operating at overpressure, into which sharp water vapor is supplied to reduce the partial pressure of the solvent components.

Removing solvent residues in the stripping columns provides for its more complete extraction from dewaxed oil and pump oil in the processes of dewaxing, paraffin and de-oiling filtrate in the process of oil de-oiling of the pump, dewaxed oil, paraffin and de-oiling oil in combined dewaxing-de-oiling processes. Thus, the required flash point of these products is achieved, and the loss of solvent is minimized, which is returned from the stripping columns to the watered solvent system of the installation.

The disadvantage of the method adopted for the prototype is that the supply of water vapor to the stripping columns leads to the fact that the flows entering the stripping columns containing the amount of water corresponding to the indicator "absence" at the outlet of the stripping columns have a water content of 0.03 % of the mass. (corresponds to the “footprints” indicator) and higher.

Modern requirements for dewaxed oil do not allow such a water content, an acceptable indicator is "no". This leads to the fact that in order to additionally extract water and achieve the required indicator for its residual content in the solvent regeneration stream from the dewaxed oil, an additional vacuum column is installed after the stripping column, the vacuum in which is created by the ejector, the working stream of which is water vapor.

Thus, the supply of sharp water vapor to the stripping columns for additional extraction of solvent residues — achieving the desired flash point — leads to an increase in energy consumption in the regeneration unit of the installation and watering of the flows dried in the previous columns. As a result, the water content in dewaxed oil does not meet modern requirements for this indicator.

The water vapor supplied to the stripping columns, after cooling and condensation with the solvent vapor, enters in the form of an aqueous solvent solution into the sump — the tank of the flooded solvent — in which the aqueous phase forms as a result of decantation.

The aqueous phase is fed into the azeotropic (ketone) column, from the top of which an azeotropic mixture of methyl ethyl ketone - water is discharged, which enters the tank of the flooded solvent, and from the bottom - water drained into the industrial sewer. This significantly worsens the environmental situation in the workplace.

The purpose of the claimed method is to obtain products with the required water content, reducing energy consumption in the process of regeneration of the solvent, improving the environmental safety of production.

This goal is achieved by the method of solvent regeneration from solutions of dewaxed oils, waxes, paraffins, de-oiling filtrates in the processes of dewaxing, de-oiling and combined dewaxing-de-oiling processes, according to which the solvent is first distilled off in successive distillation columns when the temperature of the streams is removed. Then these flows enter the stripping columns, into which nitrogen is supplied to reduce the partial pressure of the solvent components. Vacuum is created in the stripping columns by evacuating the mixture of nitrogen and solvent vapors with a vacuum pump.

An essential distinguishing feature of the proposed method is that nitrogen is used as a stream that reduces the partial pressure of the solvent components. The combination with the vacuum created in the stripping column provides a depth of solvent extraction from the target products, ensuring their predetermined flash point while preventing waterlogging. For dewaxed oil, this indicator is at the “no” level. The absence of the formation of an waterlogged solvent due to the exclusion of the supply of steam to the stripping columns leads to a decrease in the water content in the wet solvent to an almost complete absence. Instead of “wet” and “dry” solvents, the solvent circulates in the installation system with a water content at the level of “traces”.

The specified distinguishing feature of the proposed technical solution determines its novelty and inventive step in comparison with the prior art. Thus, the claimed method meets the criteria of the invention of "novelty."

Analysis of the known technical solutions by the methods allows us to conclude that there are no signs in them that are similar to the essential distinguishing features of the proposed method, that is, the compliance of the proposed method with the requirements of an inventive step.

The method is illustrated by the example of solvent regeneration in a dewaxing unit (see FIG. 1).

The flows of dewaxed oil (1) and gacha (2), which contain solvent components after successively connected columns operating under excess pressure, enter the stripping columns (3), (4). Nitrogen (5), (6) is supplied to the still bottom of these columns.

A mixture of nitrogen with solvent vapor (7), (8) from the stripping columns enters the refrigerator (9), where partial condensation of the solvent vapor occurs. The gas-vapor mixture (10) with an insignificant presence of the liquid phase is fed to the intake of the vacuum pump (11), which creates the required vacuum in the stripping columns.

It is planned to use a liquid ring vacuum pump as a vacuum-generating device, which allows pumping out gas-liquid flows. This will provide the ability to feed the stream (10) from the refrigerator (9) directly to the intake of the pump (11) without including a separator in the circuit.

From the vacuum pump discharge, the stream (12) enters the tank (13), where it is mixed with the stream (14) obtained by condensation and cooling of solvent vapors supplied to the solvent stripping columns from dewaxed oil and pump solutions operating under overpressure.

In the container (13), the complete condensation of the solvent components from the stream (12) occurs. A stream of nitrogen (15) is sent to the breathing system of the unit, and solvent (16) enters the crystallization and filtration compartments.

The bottoms of the columns (3) and (4) are commodity dewaxed oil (17) and gache (18).

The advantages of the proposed method are illustrated by the following examples.

Example 1 (prototype)

Solutions of dewaxed oil and gacha were obtained as a result of dewaxing of the raffinate of the selective purification of oil vacuum distillate fr. 420-490 ° C, isolated from a mixture of West Siberian and Ukhta oils. The main properties of the raffinate are given in table 1. The solvent used is a mixture of methyl ethyl ketone (MEK) with toluene with a volume ratio of 60: 40%.

The productivity of the plant according to the raffinate is 24 m ³ / h, the total volume ratio of the solvent to the feed is 2.7: 1.

Parameters of hot steam - temperature 220 ° C, pressure 10 kgf / cm ² .

Schematic diagram of the inclusion of stripping columns with the designation of the main flows, taken as a prototype, is shown in figure 2.

The flows of dewaxed oil (40) and pump oil (41), which contain solvent components after successively connected columns operating under excess pressure, enter the stripping columns (19), (20). Sharp water vapor (21), (22) is supplied to the bottom part of these columns.

A mixture of water vapor and solvent (23), (24) from the stripping columns enters the refrigerator (25), where they condense. The condensed and cooled mixture of water and solvent (26) enters the tank of the “flooded” solvent (27), where the decantation of the undissolved aqueous phase (28) takes place, which is discharged to the ketone column (29).

Sharp water vapor (30) is supplied to the bottom of the ketone column to evaporate the solvent from the water. The flow of water (31) from the ketone column enters the industrial sewer.

The stripped components of the solvent with admixture of water (32) in the vapor phase are sent to the refrigerator (33), from where they enter the “flooded” solvent tank (27) in the liquid phase (34).

The stream (35) from the upper layer of the tank (27), which is a solvent with water dissolved in it, is fed into the tank (36) of the “wet” solvent, which also receives the condensed and cooled solvent (37) from the columns of the solvent distillation from the gach solution, operating at overpressure.

In the tank (36), an additional decantation of water (38) takes place, discharged from its lower part. A “wet” solvent (39) and a “dry” solvent (flow is not shown in the diagram) from solvent stripping columns from a solution of dewaxed oil operating at overpressure enter the crystallization and filtration section.

The bottoms of the columns (19) and (20) are dewaxed oil (42) and gache (43).

The main parameters of the technological mode of the stripping column unit and the performance indicators of the solvent recovery department are given in Table 2.

Example 2

As raw materials used raffinate according to example 1.

Solutions of dewaxed oil and gacha were obtained as a result of dewaxing of the raffinate of the selective purification of oil vacuum distillate fr. 420-490 ° C, isolated from a mixture of West Siberian and Ukhta oils. The main properties of the raffinate are given in table 1. The solvent used is a mixture of methyl ethyl ketone (MEK) with toluene with a volume ratio of 60: 40%.

The productivity of the plant according to the raffinate is 24 m ³ / h, the total volume ratio of the solvent to the feed is 2.7: 1.

Nitrogen parameters - temperature 20 ° C, pressure 2 kgf / cm ² .

Schematic diagram of the inclusion of stripping columns with the designation of the main flows shown in figure 1. The description is given above.

The main parameters of the technological mode of the stripping column unit and the performance indicators of the solvent recovery department are given in Table 2.

A comparison of the indicators (for example, the installation of dewaxing) achieved with the claimed method and the method adopted for the prototype shows the following.

1. Provides stable production of dewaxed oil that meets modern requirements for water content.

2. Reduced energy consumption in the process of regeneration of the solvent by eliminating the supply of sharp water vapor to the stripping and ketone columns.

3. Prevention of the formation of wastewater due to the supply of water vapor increases the environmental safety of production.

Those. all claimed advantages of the proposed method are confirmed.

Table 1 The main physical and chemical indicators of the quality of raw materials - raffinate fr. 420-490 ° C The name of indicators The value of indicators Density at 20 ° C, kg / m ³ 871 Melting point, ° C +42 The paraffin content,% wt. eighteen Refractive index 1.4750 Kinematic viscosity at 100 ° C, mm ² / s 7.4

table 2 The main parameters of the technological regime of the stripping column unit and the performance indicators of the solvent regeneration unit of the dewaxing unit during the processing of raffinate fr. 420-490 ° C mixture of West Siberian and Ukhta oils The name of indicators Indicator values when applying the method taken as a prototype when applying the proposed method The main parameters of the technological mode Stripping column on a dewaxed oil solution stream, (19) (3) Top pressure (absolute), kgf / cm ² 1,2 0.1 Temperature ° C: - food 177 175 - top 175.8 173.7 - bottom 175.6 173.3 Stripping column on a slurry feed stream (20) (4) Top pressure (absolute), kgf / cm ² 1,2 0.1 Temperature ° C: - food 170 170 - top 169.8 169.9 - bottom 170.7 169.6 Ketone Column (29) Top pressure (absolute), kgf / cm ² 1,1 - Temperature ° C: - food 42.1 - - top 70.5 - - bottom 107.1 - Temperature ° C: - watertight solvent capacity (27) 42.1 - - wet solvent tank (36) 40 - - dry solvent capacity (13) 40 (not shown in the diagram) 40 Consumption of hot steam, kg / h: - stream (21) 350 - - stream (22) 150 - - flow (30) 70 - Nitrogen consumption (kg / h): - stream (5) - fifty - stream (6) - twenty Regeneration Unit Performance The water content in the solvent,% wt. - “wet” solvent (39) 2,3 - - “dry” solvent (flow not shown in the diagram) 0.5 - - total solvent stream from the regeneration unit (16) - 0.02 The water content in dewaxed oil (42) (17),% wt. 0.02 (“traces”) - 0.04 "Absence" Flash point of dewaxed oil (42) (17), ° C Not lower than 260 Not lower than 260 The amount of wastewater (31) from the ketone column, kg / h 567 -

Claims (1)

The method of solvent regeneration from solutions of dewaxed oils, waxes, paraffins, de-oiling filtrates in the processes of dewaxing, de-oiling and combined dewaxing-de-oiling processes by distillation of the solvent in successively connected distillation columns with increasing temperature of the streams from which the solvent is extracted, followed by feeding columns, characterized in that in stripping columns to reduce the partial pressure of the solvent components is fed nitrogen, while in these columns a vacuum is created by pumping a mixture of nitrogen and solvent vapor with a vacuum pump.

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