RU2272069C1 - Oil dewaxing and paraffin wax production process - Google Patents

Abstract

FIELD: petroleum processing.

SUBSTANCE: invention relates to dewaxing and deoiling of petroleum products in production of lubricating oils and paraffin waxes. Paraffin-containing stock is stepwise mixed with coolant (cooled solvent, filtrate solution, or mixture thereof) in multisectional vertically mounted pulsating crystallizer imposing pulsation effect throughout the bulk of raw mix filling the apparatus and so providing reciprocal motion of raw mix in cross-flow ways between sections while simultaneously coolant is introduced into these ways. According to invention, paraffin-containing stock, prior to be fed into pulsating crystallizer, is mixed with a part of coolant to form raw solution at temperature by 3-5°C above temperature at which paraffin contained in this solution begins crystallizing. Thus obtained paraffin slurry is further cooled to separation temperature followed by recovering solvent from separation products. Preferably mixing is performed in a series of stirring apparatuses installed in series on line through which raw material is supplied into pulsating crystallizer.

EFFECT: increased paraffin slurry separation velocity, increased yield of dewaxed oils, and reduced content of oil in gatch used to produce paraffin wax.

2 cl, 5 dwg, 2 tbl, 2 ex

Description

The present invention relates to methods for dewaxing oils and obtaining solid paraffins by crystallizing paraffin from a solution of raw materials in a selective solvent and separating the resulting suspension and can be used in the refining industry.

The closest solution in technical essence and the achieved results is a method for producing dewaxed oils and hard paraffins (RF patent No. 20055769, class C 10 G 73/06, 1994), according to which a raw material suspension from paraffin-containing raw materials is obtained by multistage mixing with a refrigerant ( cold solvent, filtrate solution or their mixture) due to the pulsating effect on the entire volume of the raw mixture filling the vertically installed multi-section apparatus. This ensures the reciprocating movement of the raw material mixture in flows between sections with simultaneous continuous supply of refrigerant to these flows. The resulting suspension is cooled to a separation temperature, the separation of the suspension is carried out by filtering it to isolate a precipitate of paraffin crystals, followed by regeneration of the solvent from the separation products of the suspension — a filtrate solution and a precipitate.

The disadvantages of the method adopted for the prototype include the fact that the raw material is fed into the apparatus (pulsating crystallizer), in which it is mixed in several stages with the refrigerant, at a temperature not less than 15 ° C above the temperature at which crystallization of paraffin in the raw material begins to ensure preset viscosity of the raw mix as it is diluted and cooled. The consequence of this is that up to half of the sections of the apparatus are used to cool the raw material mixture to the temperature at which crystallization of paraffin begins, with a high temperature gradient between the sections. This leads to inefficient use of part of the crystallizer volume and to a deterioration in the filtration characteristics of the resulting suspension — a decrease in the separation rate of the suspension and the yield of dewaxed oil, and an increase in the oil content in gache — the raw material for the production of paraffins.

The aim of the claimed method is to increase the separation rate of the resulting suspension and increase the yield of dewaxed oil, reducing the oil content in gache - raw materials for the production of paraffins.

This goal is achieved by the method of dewaxing oils and obtaining solid paraffins, according to which the raw materials are mixed with a part of the refrigerant — a cooled solvent, a filtrate solution or a mixture thereof — to obtain a raw solution before entering the apparatus (pulsating crystallizer), in which it is mixed with a refrigerant. whose temperature is 3-5 ° C higher than the temperature at which crystallization of paraffin begins in this solution. Moreover, the mixing of raw materials with part of the refrigerant before entering the apparatus is carried out in a number of mixing devices, sequentially installed on the pipeline for supplying raw materials to the mold.

An essential distinguishing feature of the proposed method is that the raw materials are mixed with a portion of the refrigerant before being fed into the apparatus to obtain a raw material solution whose temperature is close to the temperature at which crystallization of paraffin begins in it. As mixing devices for preliminary mixing of raw materials with a part of the refrigerant, stationary mixers are used, which are installed directly in the pipeline for supplying raw materials to the crystallizer, or injection mixers.

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 separation of the suspension obtained in accordance with the proposed method occurs with an increase in the rate of separation of the liquid phase from the sediment, an increase in the yield of dewaxed oil and a decrease in the oil content in the gache - raw material for the production of paraffins.

The method is as follows (see figure 1, 2, 3).

Raw materials 1 (figure 1), heated to a temperature above the onset temperature of crystallization of paraffin in it by 15-25 ° C, are mixed with part of the refrigerant 2 of its total amount 3, intended for mixing with the raw material in the process of obtaining a paraffin suspension.

As refrigerant 3, a cooled selective solvent is used (ketones with 3-6 carbon atoms in the molecule, their mixtures with each other, with aromatic hydrocarbons, ethers, and also mixtures of halogenated hydrocarbons), a filtrate solution of one of the suspension separation stages, depending on the technological scheme process, or mixtures thereof.

The mixing of raw materials 1 with part of the refrigerant 2 before entering the pulsating crystallizer is carried out in a number of mixing devices 4 installed on the pipeline for supplying raw materials.

The resulting feed stream 5 enters under the first section of the pulsation crystallizer 6 - apparatus, which is a hollow vertical column equipped with alternating partitions 7 and 8. The space between adjacent partitions 7 forms a section. Partitions 8 have overflows — nozzles 9. Nozzles 9 are connected to refrigerant inlets 10 — portions of the total amount of refrigerant 3 minus the refrigerant 2 supplied to the preliminary dilution of the feedstock.

The feed stream 5, mixing with the refrigerant 11, continuously flowing into the section of the pulsating crystallizer 6, fills the entire volume of the mold to the level of the suspension outlet 12. The pulsating effect on the raw material mixture is carried out by a pulsator 13, generating pulses of compressed inert gas 14 entering the pulsation chamber 15, connected to the crystallizer 6 by a pipe 16. Pulses of compressed inert gas create fluctuations in the level of the raw material mixture in the pulsation chamber 15, while maintaining the level difference in and the housing of the pulsation of the mold 6. Fluctuations raw material mixture level in the pulsation chamber 15 to create the mold cavity 6 (as the pulsation chamber and the mold cavity to form communicating vessels), vertical reciprocating movement of the feed stream.

At the same time, in nozzles 9, due to the small area of their "live" section, the speed of the reciprocating flow increases sharply, providing intensive mixing of the feed stream with refrigerant 11 in the sections of the mold 6. Performing vertical oscillations, the feed stream moves up the mold body 6 - this the movement is due to the continuous flow of the raw material stream 5 and the refrigerant 11 into the apparatus.

The feed stream, moving from section to section, is cooled as it is diluted with refrigerant 11. The cooled feed stream, which forms a paraffin slurry 17, is fed into evaporative scraper crystallizers for additional cooling to the separation temperature.

After separation of the liquid phase from paraffin crystals, the separation products enter the regeneration of the solvent.

Pre-mixing of raw materials 1 with a portion of the refrigerant is carried out in two or three mixing devices 4 (Fig.2, 3), sequentially installed on the feed line.

As mixing devices, static mixers are used (Fig. 2), which are sections of the pipeline equipped with blades or spirals 18 that increase the turbulence of the flow at a given mixing point.

Injection mixers can be used (FIG. 3), providing not only dispersing the refrigerant in the feed stream, but also circulating part of the feed stream 19 exiting the injector to the point of mixing of the solvent with the feed. In this case, along with intensive mixing of the refrigerant with the raw material, a decrease in the concentration of the supplied refrigerant in the feed stream leaving the injector is achieved.

The sequential supply of a refrigerant having a low temperature to two or three points, when mixed intensively with the feed stream, prevents the formation of clots of crystallized paraffin, including a solution of the raw material in the refrigerant.

With a single supply of refrigerant in the feed without additional mixing, paraffin clumps formed at the mixing point may not dissolve until the feed stream enters the crystallizer despite the fact that the temperature of the feed mixture at this point is higher than the temperature at which crystallization of paraffin begins in it. Further cooling of the feed stream in a pulsating crystallizer to the temperature at which crystallization of paraffin from the raw material solution and lower temperatures does not contribute to the dissolution of these clots. Their presence in a shared suspension impairs the quality of separation of the liquid phase (oil solution in the refrigerant) from paraffin crystals, which leads to a decrease in the yield of dewaxed oil and an increase in the oil content in gache - raw material for paraffin production.

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

Example 1 (prototype).

As a raw material of the dewaxing process used raffinate FR. 420-490 ° С mixture of West Siberian oils, the main properties of which are given below:

Density at 20 ° С, kg / m ³ 895 Melting point, ° С 42 Refractive index 1,5030 Kinematic viscosity, mm ² / s at 100 ° С 10.5

Raw materials heated to a temperature of 60 ° С (18 ° С higher than the temperature of the beginning of crystallization of paraffin in it) were fed into the pilot model of a sixteen-section crystallizer, simulating the method adopted for the prototype. In the crystallizer, the raw materials were mixed with portions of the refrigerant, a cooled solvent (a mixture of methyl ethyl ketone (MEK) with toluene with a volumetric content of MEK of 60%).

Mixing was carried out by pulses of inert gas entering the pulsation chamber of the crystallizer. The pulsation frequency is 50 pulses per minute.

The total volume ratio of the refrigerant to the raw material in the process of obtaining a suspension in the model of a pulsating crystallizer is 3: 1. Refrigerant temperature - minus 15 ° С.

The sectional flow of refrigerant was adjusted so that the drop in temperature of the feed stream from section to section was uniform.

The suspension obtained in a pulsating crystallizer having a temperature of plus 5 ° C was cooled in a model of an evaporative scraper crystallizer to a temperature of minus 25 ° C. This suspension was separated by filtration in one step. The resulting precipitate was washed with solvent.

The parameters of the dewaxing process of raw materials when applying the proposed method are shown in table 1.

After distillation of the solvent from the suspension separation products, the material balance of the dewaxing process was determined.

The main indicators of the process of dewaxing of raffinate when using the method taken as a prototype, are shown in table 2.

Example 2

As the raw material used raffinate according to example 1. The raw material, heated to a temperature of 60 ° C (18 ° C above the temperature of crystallization of paraffin in it), simulating the proposed method, was mixed with part of the refrigerant in a ratio of 0.35: 1.0 vol. share of raw materials. Mixing was carried out in two stationary mixing devices installed in series on the feed line.

The resulting solution, having a temperature of 40 ° C (4 ° C higher than the start temperature of crystallization of paraffin in it at the above ratio of the pre-diluted refrigerant to the feed), was sent to the first section of the pulsation crystallizer.

The rest of the refrigerant in a ratio of 2.65: 1.0 vol. fractions of the feed were mixed with the feed stream in a pulsation mold section.

The sectional flow of refrigerant was also adjusted so that the drop in temperature of the feed stream from section to section was uniform.

The composition and temperature of the refrigerant, the parameters of pulsating mixing, the total volume ratio of the refrigerant to the raw materials are the same as in example 1.

The suspension obtained in a pulsating crystallizer having a temperature of plus 5 ° C was cooled in a model of an evaporative scraper crystallizer to a temperature of minus 25 ° C. This suspension was separated by filtration in one step. The resulting precipitate was washed with solvent.

The parameters of the dewaxing process of raw materials when applying the proposed method are shown in table 1.

After distillation of the solvent from the separation products, the material balance of the dewaxing process was determined.

The main indicators of the process of dewaxing of raffinate when using the method taken as a prototype, are shown in table 2.

The temperature profiles in the pulsating mold and the calculated cooling rate of the feed stream in it when applying the method taken as a prototype, and the proposed method are shown in graphs (figure 4, 5).

When applying the proposed method, 15 sections of 16 operate in crystallization mode (figure 4). Already in the second section, the temperature of the feed stream (36 ° C) reaches the temperature at which crystallization of paraffin from the feed solution begins when the ratio of refrigerant to feed is reached in this section. Whereas when applying the method taken as a prototype, the first to sixth sections operate in the cooling mode of the raw material solution and only the remaining ten sections operate in crystallization mode.

By reducing the amount of refrigerant entering directly into the pulsating crystallizer and increasing the number of sections operating in the crystallization mode, the cooling rate of the feed stream (namely in the crystallization region) is reduced (Fig. 5), the temperature difference between adjacent sections decreases from 3.5 3.8 to 2.3-2.5 ° C, which also favorably affects the crystallization process, therefore, the filtration characteristics of the resulting suspension.

When carrying out the dewaxing process using the proposed method, the filtration rate of the suspension, cooled to the separation temperature, increases by 22% with an increase in the yield of dewaxed oil by 1.7 wt.% And a decrease in the oil content in the hook 1.5 times (table 2).

It should be noted that when trying to reduce the temperature of the raw materials entering the mold to 45-50 ° C when simulating the method adopted for the prototype, in order to achieve the effect obtained in the proposed method, cooling the feed mixture with insufficient dilution led to a sharp increase in viscosity raw mix in the apparatus. In this case, the operation of the crystallizer was completely disrupted due to the formation of clots of the raw mixture, which impeded its transportation and mixing.

As can be seen from table 1, the application of the proposed method does not change the final dilution ratio of the raw material with the refrigerant and the temperature of the suspension emerging from the pulsation crystallizer.

The economic efficiency of the implementation of the proposed method in industrial processes for the dewaxing of oils and the production of paraffins is due to the production of suspensions, the separation of which results in an increase in the yield of dewaxed oil along with an increase in the productivity of filtering equipment and the production of a more deeply oil-free gach - raw material for the production of paraffins.

Improving the performance of filter equipment provides the ability to reduce the number of filters included in the separation process of paraffin slurries. Obtaining more deeply oil-free gachey will allow to produce paraffins with a given oil content while reducing the number of stages of filtration at the next stage of production - gaseous de-oiling.

Those. Along with an increase in the production of target products of dewaxing processes (dewaxed oils) due to an increase in their output from raw materials, operational costs are reduced by reducing the amount of filter equipment used and, as a result, the cost of its operation. The reduction in the number of filtering stages at the stage of oil degassing also provides a reduction in operating costs for the regeneration of the solvent used at each stage for washing and diluting the precipitates obtained in the process of filtering paraffin slurries.

table 2
Key indicators of the dewaxing process Key process indicators The value of the indicators when applied method taken as a prototype the proposed method Suspension filtration rate, rel.% one hundred 122 The yield of dewaxed oil, wt.% 77.3 79.0 Gachet oil content, wt.% 20.7 14.3 The pour point of dewaxed oil, ° C -17 -17

Claims (2)

1. A method for dewaxing oils and producing solid paraffins by stepwise mixing paraffin-containing raw materials with a refrigerant, which is used as a cooled solvent, a filtrate solution or a mixture thereof, in a multisection vertically installed apparatus — a pulsating crystallizer due to the pulsating effect on the entire volume of the raw material mixture filling the apparatus providing the reciprocating movement of the raw material mixture in the flows between the sections, with the simultaneous continuous supply of chlorine in these flows dagent, subsequent cooling of the resulting suspension, its separation and regeneration of the solvent from the separation products, characterized in that before entering the apparatus, the raw materials are mixed with part of the refrigerant to obtain a raw solution, the temperature of which is 3-5 ° C higher than the temperature at which crystallization of paraffin in this solution begins . 2. The method according to claim 1, characterized in that the mixing of raw materials with a portion of the refrigerant before entering the apparatus is carried out in a number of mixing devices installed in series on the pipeline for supplying raw materials to the apparatus.

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