RU2374301C1 - Method of deparaffination of oil material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to oil refining industry, specifically to methods of deparaffination of oil raffinates through crystallisation in a solution of selective solvents. The invention relates to a method of deparaffination of oil material by mixing the material with a ketone-aromatic solvent, regeneration of solvents from slack wax solutions and deparaffined oil in evaporators and stripping columns, separation of water from aqueous solutions. The initial material used is a raffinate solution, coming from an installation for selective purification with a solvent - N-methylpyrrolidone, bypassing the solvent regeneration stage and containing from 10 to 30 wt % N-methylpyrrolidone.

EFFECT: increased reliability of the deparaffination installation due to non-use of wet solvent; considerable decrease in energy consumption when regenerating solvents from aqueous solutions.

4 cl, 2 ex, 4 tbl, 1 dwg

Description

The invention relates to the refining industry, in particular to methods for dewaxing oil raffinates by crystallization in a solution of selective solvents.

When dewaxing raffinates and de-oiling gachets, a mixed solvent is currently widely used, which is a mixture of methyl ethyl ketone (MEK) and toluene in a ratio of 60:40% by volume (see the book by NI Chernozhukov, Refining and separation of crude oil, production of marketable petroleum products. M .: Chemistry, 1978, p. 177-180).

One of the disadvantages of using this method is the high specific energy costs for solvent regeneration, a complex system for removing water from aqueous solutions of methyl ethyl ketone and toluene, which is associated with the formation of difficult to separate azeotropic mixtures of these solvents with water, the presence of moisture in the feedstock that gets into the process of solvent regeneration from refined solutions in selective treatment plants.

The closest technical solution to the invention is RF patent No. 2002103212, 2003, which describes a method for dewaxing paraffinic petroleum fractions by mixing them with a selective solvent based on a mixture of methyl tert-butyl ether with a precipitant; ketone C ₃ -C _{6 is} used as a precipitant, or methanol, or toluene, or N-methylpyrrolidone, or a mixture thereof, by cooling the mixture and filtering the resulting suspension, isolating dewaxed oil and gacha (petrolatum), characterized in that the solvent is used with the addition of m of ion-forming additives to it.

The disadvantage of this method is the need for additional input of N-methylpyrrolidone, the use of raffinates as feedstock, which includes water that enters them at the stage of regeneration of raffinate solutions in stripping columns of selective treatment plants. This moisture enters the crystallizers and contributes to equipment wear, in addition, water crystallizes together with paraffin hydrocarbons, accumulates in the pump solution, and therefore reduces the resource of the dehydrated solvent in the installation. In the solvent recovery section of the slurry solution in the first evaporation column, a wet solvent is isolated in this dewaxing process.

A wet solvent in a traditional dewaxing unit is also formed due to the use of water vapor during the evaporation of solvents in the stripping columns of the dewaxing unit to separate the residual (not more than 5 wt.%) Amount of solvents (mixture of methyl ethyl ketone with toluene). Both toluene and methyl ethyl ketone form azeotropic mixtures with water. It is not possible to separate water from these mixtures by heating and evaporation. For this reason, azeotropic mixtures are cooled to a temperature of 35-40 ° C and sedimented in containers to separate water. Upon sedimentation, two layers are formed: the upper one is a mixture of methyl ethyl ketone, toluene and water, and the lower one is a mixture of water and methyl ethyl ketone. The top layer is returned to dilute the feedstock as a wet solvent. The bottom layer containing about 15% methyl ethyl ketone and 85% water is first sent to a heat exchanger for heating, and then to an azeotropic distillation column. An azeotropic mixture is discharged from the top of the column, which, after cooling, returns to the settling tank. Water is discharged from the bottom of the column.

The technical task of the present invention is the use of a raffinate solution dewaxing unit coming from a selective oil purification unit with N-methylpyrrolidone as a feedstock, bypassing the solvent regeneration stage, and containing from 10 to 30 wt.% N-methylpyrrolidone, which allows the recovery of methyl ethyl ketone and toluene without contact with water vapor, excluding the stages of sedimentation and azeotropic distillation from the installation scheme (scheme installations dewaxing and selective purification of N-methylpyrrolidone when used together attached).

EFFECT: increased reliability of a dewaxing unit due to the use of a raffinate solution as a raw material, elimination of the use of a wet solvent, a significant reduction in energy costs during the regeneration of solvents from aqueous solutions.

It is achieved by using a raffinate solution coming from selective treatment plants as a feedstock, bypassing the solvent regeneration stage, and containing from 10 to 30 wt.% N-methylpyrrolidone by mixing with a ketone-aromatic solvent, regenerating solvents from gacha solutions and dewaxed oil in evaporation and stripping columns, moreover, during the regeneration of the solvent from methane solution and solution of dewaxed oil in evaporation columns, methyl ethyl ketone (MEK) and toluene are evaporated due to an increase in temperature and a decrease in pressure, while N-methylpyrrolidone (NMP) remains in the residue. NMP are removed in stripping columns, and the resulting aqueous NMP solution is returned to the selective purification unit to separate the water by distillation, followed by reuse of the NMP. The prerequisites for this possibility are the fact that the boiling point of the NMP is 204 ° C, which is 125 ° C higher than the boiling temperature of MEK and 96 ° C higher than the boiling temperature of toluene. For this reason, the evaporation of the NMP in the dewaxing unit in the solvent regeneration unit will occur last, that is, in the stripping column. In this case, the contact of IEC and toluene with water vapor is excluded. The absence of contact between MEK and toluene with water vapor will make it possible to abandon the laborious stages of settling and azeotropic distillation of mixtures of MEK and toluene with water and will significantly reduce the amount of wet solvent in the dewaxing unit.

Description of the proposed schemes for selective cleaning and dewaxing

Selective Cleaning Department

The feedstock of the selective refining unit - oil distillate or the residue enters the selective purification department of the oil feed.

Raw material I is pumped by the N-1 pump to the upper part of the K-1 absorber, where the air and water vapor (II) dissolved in the raw material removed in the mixture with NMP are removed to the lower part of the column. The temperature in K-1 is maintained in the range of 110-115 ° C. Water vapor (II) and air are discharged from the top of the K-1 absorber, and a mixture of raw materials and NMP (III) solvent is discharged from below. Stream III enters the H2 pump inlet, passes through the water cooler X-1 to the K-2 extraction column, operating in the temperature range from 50 ° C (bottom of the column) to 115 ° C (top of the column) depending on the nature of the raw materials used. Fresh NMP is added to the top of K-2. From the bottom of the K-2 extraction column, the extract solution V is taken by pump N-3, cooled in XB-1, and part of it is returned to the lower part of K-2 to maintain the required temperature regime of the column. The balance amount of the extract solution V is supplied to the solvent regeneration system. Solvent regeneration from the extract solution is carried out by rectification in two K-5 and K-4 evaporation columns and one K-3 stripping column at the boiling points of NMP depending on the accepted pressure in the columns.

On top of the K-2 extraction column, the raffinate solution IV is collected in a vessel E-1, from where it is fed to the suction of the pump N-11 of the dewaxing unit with a temperature of 60-75 ° C. Thus, at the selective purification plant, the block for the regeneration of the solvent from the raffinate solution is excluded from the scheme.

Crystallization and filter compartment

The raw material (raffinate solution) is pumped through an X-3 water cooler to the Kp-l-Kp-4 regenerative crystallizers, where it is cooled by the filtrate obtained in the first stage of filtration.

The number of molds depends on the throughput of the installation.

The raw material is diluted with a cold solvent at two points: at the outlet of it from the Kr-1 and Kr-4 crystallizers. The solvent used is a mixture of MEK: toluene. From regenerative crystallizers, the feed solution enters the Kr-5-Kr-7 ammonia crystallizers, where, due to the evaporation of the refrigerant (ammonia or propane) from the E-14-E-16 accumulators, it is cooled to the filtration temperature. The cooled suspension of solid hydrocarbons in the oil solution enters the E-5 receiver, and from there by gravity into the F-1 vacuum filters of the first stage. In vacuum filters, the suspension is separated into a liquid phase — a solution of dewaxed oil and a “solid” —gach solution. The stage I filtrate (solution of dewaxed oil) is collected in an E-8 vacuum receiver, from where it is pumped by an N-13 countercurrent to the feed solution through regenerative crystallizers, a T-4 heat exchanger to cool the solvent and sent to the solvent regeneration section from the dewaxed oil solution. The precipitate (gacha solution) on the F-1 filter is washed with a cold solvent, previously cooled in a Kr-9 crystallizer.

The precipitate taken from the filters of the first stage is diluted with a solvent, and the resulting suspension is collected in the collector E-6. Then, the suspension is pumped by the pump N-17 to the collector E-7, from where it enters the filters of the second stage. The precipitate from the filters of the second stage after washing is diluted with a solvent and collected in the collector E-12. Next, the suspension is collected by the pump N-18 and sent to the Department of solvent regeneration.

Department of solvent regeneration from solutions of dewaxed oil, gacha and petrolatum

The solvent is regenerated from a solution of dewaxed oil in four steps. The solution of dewaxed oil is supplied by a pump N-14 to the pressure tank E-10, through a T-5 heat exchanger to the K-7 column. Here, the solvent vapor separates from the liquid and leaves the column; Further, the solvent vapor condenses in the annular space of the T-5 heat exchanger, the XV-5 air-cooling apparatus, and the X-4 refrigerator. Condensate flows from the X-4 water cooler to the E-11 dry solvent receiver. The liquid discharged from the bottom of the K-7 column by the pump N-15 is fed through the pipe space of the P-2 furnace to the K-8 column, in which a pressure of 0.20-0.35 MPa is maintained. Solvent vapors leaving the K-8 column are cooled and condensed in the T-5 heat exchanger and the HV-5 air-cooling apparatus. Condensate, after passing through the HZ water cooler, is collected in a dry solvent receiver. The residue from the bottom of the K-8 column enters the P-3 furnace to heat N-methylpyrrolidone to the boiling point and is fed to the K-9 column in the vapor-liquid state. Vapors exiting the K-9 column are combined with vapors exiting the K-12 column and sent to a selective purification unit for reuse in the selective purification process.

The underdepared dewaxed oil flows from the K-9 column to the K-10 stripping column, in which the NMP residues are removed with sharp steam. The main amount of solvent is regenerated in the first two steps (columns K-1 and K-2) at temperatures of about 100-110 ° C and 155-180 ° C, respectively, depending on the pressure received in the column. The dewaxed oil with a residual amount of solvent, usually not exceeding 2-5 wt.%, Is sent to a stripping column, since the removal of small amounts of solvents by conventional rectification is very difficult. In order to avoid “oiling” of the solvent, the solvent is supplied to the upper plates of the column as an irrigation.

The mixture of solvent vapor and water leaving the K-10 column is condensed and cooled in the HV-7 air-cooling apparatus. Next, the condensate is sent to the tank E-2.

The regeneration of the solvent from a solution of gacha (petrolatum) is carried out in three or four steps. The pumping solution H-18 is pumped through the heat exchangers T-7 and T-8 and enters the K-11 column. Solvent vapors at the exit from the K-11 column pass the T-6, T-8 heat exchangers, the XV-6 air-cooling apparatus, are cooled in the X-6 water cooler; condensate flows into the solvent receiver E-11. The remainder from the bottom of the K-11 column is pumped by the pump N-19 through the P-3 furnace to the K-12 column. Solvent vapors separated in the K-12 column are coupled to the vapors leaving the K-9 column.

The remainder from the bottom of the K-12 column flows into the stripping column K-13. NMP vapors and water from the K-13 column, combined with the vapors from the K-10 column, enter the E-2 tank of the selective purification unit. The aqueous NMP solution is taken by the N-4 pump, partially used after cooling in an XB-2 air cooler in the E-1 barometric condenser to create a vacuum, and the balance amount of the solution is sent to the K-6 distillation column to evaporate water from the NMP solution. At the bottom of the same column comes a hot solvent from the top of the K-5 column, which provides the necessary temperature for the evaporation of moisture. The water leaving the top of the K-6 column after cooling in the condenser-cooler ХВ-3 is collected in the E-3 tank, from where it partially returns to the upper plate of the K-4 column as cold irrigation, and the balance amount is used in the K-1 deaerator for removal of air from the raw materials entering the installation. NMP from the bottom of the K-6 column through the T-1 heat exchanger, the XB-4 air cooler is sent to the anhydrous NMP tank E-4, from where it is taken by the N-8 pump for reuse in the selective cleaning process.

The raffinate solution in this process is an intermediate product of oil production. Depending on the used oil feed, the raffinate solution can be either a mixture of raffinate with boiling ranges from 350 to 420 ° C with NMP, or a mixture of raffinate fractions 420-500 ° C with NMP, or a mixture of residual raffinate boiling at a temperature above 500 ° C . The concentration of NMP in the raffinate solution is determined by the nature of the initial oil feedstock and the conditions for selective purification and ranges from 10 to 30 wt.%.

The laboratory studies of the solubility of the raffinate solution and raffinate obtained from FR. 350-420 ° C of Astrakhan gas condensate, in mixtures with MEK solvents and toluene, showed that the raffinate solution has less solubility in the corresponding mixtures than raffinate. This is due to the presence of NMP, which, like MEK, is a "precipitator" of paraffins. Table 1 presents data on the cloud point of raffinate solutions in mixtures of MEK and toluene at different ratios between them and at different dilution ratios. Table 2 presents the data of the cloud point of the raffinate solution containing 10 vol.% NMP in mixtures of MEK and toluene at different ratios between them and at different dilution ratios. Table 3 presents the data of the cloud point of the raffinate solution containing 20 vol.% NMP for mixtures with MEK and toluene at different ratios and dilution ratios. From tables 1, 2 and 3 it can be seen that when the content in the raffinate is 10 vol.% NMP and diluted with a solution of MEK and toluene taken in a ratio of 40:60 vol.%, The data obtained coincide with the data obtained for the raffinate taken without addition of NMP, with a ratio of MEK and toluene of 50:50 vol.%. With an increase in the concentration of NMP to 20 vol.% And dilution with a solution of MEK with toluene taken in a ratio of 40:60 vol.%, The obtained data coincide with the data obtained for raffinate diluted with a solvent containing MEK and toluene in a ratio of 60:40 about.%. The data presented show that an increase in the concentration of NMP requires a decrease in the concentration of methyl ethyl ketone in the solvent during the dewaxing process to achieve the same cloud point, i.e. equal solubility. The cloud point of the solution indirectly characterizes the solvent capacity of the solvent with respect to paraffin hydrocarbons contained in the feedstock. The obtained data also show that the presence of NMP in the raffinate increases the temperature of separation of the first paraffin crystals from the feed solution in comparison with the usual solution of raffinate in MEK - toluene, which indirectly indicates the possibility of removing paraffins crystallized from the raffinate at a higher temperature. In addition, methyl ethyl ketone is a more expensive component in the composition of the mixed solvent MEK: toluene. Reducing its concentration will help reduce the cost of production.

Based on the obtained data, graphs of the dependences of cloud temperatures on the concentration of the MEK: toluene mixture were plotted and deviations in the MEK concentrations were determined using raffinate solutions at approximately equal concentrations of oil products in the mixtures. These data are shown in Table 4. The data obtained show that, at a concentration of 10 vol.% NMP in the initial raffinate solution, in order to achieve the cloud point of the solution corresponding to the cloud point of the raffinate solution, it is necessary to reduce the MEK concentration in the solvent added by dilution of raw materials. At a concentration of 20% NMP in the initial raffinate solution, in order to achieve the cloud point of the solution corresponding to the cloud point of the raffinate solution, it is necessary to reduce the MEK concentration in the solvent added by diluting the feedstock by about 20 vol%.

Laboratory tests of the method.

An example 1 of a method for dewaxing a raffinate solution under laboratory conditions.

A portion of a raffinate solution (50 g) containing 20 wt.% NMP was placed in a beaker and cooled with water to a temperature of 20 ° C, after which a mixture of methyl ethyl ketone (65 g) and toluene (50 g) was added. When the temperature of the solvent mixture was 20 ° C, further cooling was carried out in a gas bath using solid carbon dioxide to a temperature of minus 22 ° C at a rate of not more than 1 ° C per minute, after which the suspension was transferred to a laboratory vacuum filter pre-cooled to the same temperature, filtered, washed with a mixture of methyl ethyl ketone and toluene in an amount of 40 g (60 wt.% methyl ethyl ketone and 40 wt.% toluene). As a result of the experiment, 16.6 g of gacha solution and 183 g of dewaxed oil solution were obtained. Losses in the experiment amounted to 2.7 wt.%. The solvent from the solution of dewaxed oil was regenerated at atmospheric pressure by distillation in an Angler flask at a temperature of up to 200 ° C. The residue after distillation of methyl ethyl ketone and toluene was 43.6 g; it contained 25% NMP. After distillation of the NMP under vacuum, the yield of dewaxed oil was 32.5 g, i.e. 80.5% of the feedstock.

The solvent from the gacha solution was regenerated in the same manner. In the gacha solution after removal of methyl ethyl ketone and toluene, the NMP content was calculated to be 10.6%. As a result of the experiment, 5.6 g (14% of the feedstock) of gacha were obtained.

The results of the experiments show that in both the gacha solution and the solution of dewaxed oil, after the removal of methyl ethyl ketone and toluene, the concentration of NMP exceeds 5%. Solutions of dewaxed oil and gach, containing not more than 2-5% solvent, are usually sent to stripping columns. This means that in the case under consideration, oil products will be delivered to the stripping columns in a mixture only with NMP, i.e., the contact of methyl ethyl ketone and toluene with water vapor when using the proposed method is excluded.

An example 2 of a method for dewaxing a raffinate solution in laboratory conditions.

A portion of a raffinate solution (50 g) containing 10 wt.% NMP was placed in a beaker and cooled with water to a temperature of 20 ° C, after which a mixture of methyl ethyl ketone (65 g) and toluene (50 g) was added. The temperature of the solvent mixture was 20 ° C, further cooling was carried out in a gas bath using solid carbon dioxide to a temperature of minus 22 ° C at a rate of not more than 1 ° C per minute, after which the suspension was transferred to a laboratory vacuum filter pre-cooled to the same temperature, filtered , washed with a mixture of methyl ethyl ketone and toluene in an amount of 45 g (60 wt.% methyl ethyl ketone and 40 wt.% toluene). As a result of the experiment, 18.5 g of gacha solution and 185.5 g of dewaxed oil solution were obtained. The solvent from the solution of dewaxed oil was regenerated at atmospheric pressure by distillation in an Angler flask at a temperature of up to 200 ° C. The residue after distilling off the solvent at atmospheric pressure was 41 g. The residue after distillation of the dewaxed oil contained 10.9% NMP. The residue after distillation of methyl ethyl ketone and toluene from the gach solution was 5.5%. As a result of the experiment, after distillation of the NMP under vacuum, 36.5 g (81% of the starting material) of dewaxed oil and 6.3 g of gacha (14% of the starting material) were obtained.

Laboratory experiments show that the residue after distillation of methyl ethyl ketone and toluene contains more than 5% solvent.

This fact confirms that in the industrial use of the proposed method, stripping columns, where usually solutions of dewaxed oil and slag containing no more than 2-5% solvent are routed, will get only NMP together with oil products, i.e., the contact of methyl ethyl ketone and toluene with water vapor is excluded.

The positive effect of using the proposed method for dewaxing of oil raw materials will improve the reliability of the installation of dewaxing due to the use of raffinate solution as a raw material, refusal to use a wet solvent, significantly reduce energy costs during the regeneration of solvents from aqueous solutions.

Table 1
The cloud point of the raffinate depending on the ratio of raw materials to solvent and solvent components The ratio of raw materials to solvent / MEK to toluene 60:40 50:50 40:60 30:70 eleven 25 24.25 23.25 22.5 1: 2 23 21.75 20.5 eighteen 1: 3 21.5 twenty 18.5 15.75 1: 4 20.75 18.75 17.25 14.5 1: 5 twenty eighteen 16.5 13.75

table 2
The dependence of the cloud point of the raffinate solution (10% NMP) on the ratio of raw materials to solvent and solvent components The ratio of raw materials to solvent / MEK to toluene 60:40 50:50 40:60 30:70 1: 1 25.75 24.5 23.25 22.5 1: 2 25 23.5 21.5 19.5 1: 3 23.5 21.5 19.5 eighteen 1: 4 22.5 20.5 18.5 17 1: 5 21.75 19.75 17.75 15.75

Table 3
The dependence of the cloud point of the raffinate solution (20% NMP) on the ratio of raw materials to solvent and solvent components The ratio of raw materials to solvent / MEK to toluene 60:40 50:50 40:60 30:70 1: 1 27.25 26.75 25.75 24.75 1: 2 25.25 24 22.75 21 1: 3 23.5 21.5 20.25 18.75 1: 4 22.25 twenty 18.5 16.25 1: 5 21 19.25 17.5 15.25

Table 4
The dependence of the cloud point of solutions on their composition Cloud point, ° С Raw materials, vol.% IEC, vol.% Toluene, vol.% NMP, vol.% The difference in the concentration of IEC, vol.% At the selected temperature Data for raffinate solution with an NMP content of 10 vol.% eighteen 16,2 32.8 49.2 1.8 eighteen 16.5 41.8 41.7 0 9.0 21 37.3 17.6 40.9 4.2 21 36 25.6 38,4 0 8.1 22 42.3 15.9 37.1 4.7 22 42 23.6 34.8 0 8.0 Data for a raffinate solution with an NMP content of 20 vol.% 23.5 35,2 16.8 39.2 8.8 23.5 34 36 thirty 0 19.2 24 37,2 16 37.5 9.3 24 41.5 35.1 23,4 0 19.1

Claims (4)

1. The method of dewaxing oil raw materials by mixing raw materials with ketone - an aromatic solvent, regeneration of solvents from solutions of gach and dewaxed oil in evaporation and stripping columns, separating water from aqueous solutions, characterized in that the raffinate solution from the plants is used as a feedstock selective purification with a solvent, N-methylpyrrolidone, bypassing the solvent regeneration stage and containing from 10 to 30 wt.% N-methylpyrrolidone. 2. The method according to claim 1, characterized in that the concentration of the ketone component is reduced by the concentration of N-methylpyrrolidone contained in the feed mixture. 3. The method according to claim 1, characterized in that during the regeneration of the solvent, methyl ethyl ketone and toluene are completely removed from the solution of gach and the solution of dewaxed oil in the evaporation columns, excluding contact with water vapor. 4. The method according to claim 1, characterized in that the selective purification of the crude oil is carried out with N-methylpyrrolidone.

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