RU2621030C1 - Method for purifying gasoline from sulfur impurities - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: purification of petroleum products is carried out in a distillation column under the conditions of cyclically variable pressure, at which a portion of vapors of the gasoline to be cleaned is fed successively to the separation volume of each tray, starting from the top one, at a pressure exceeding the vapor pressure in this separation volume and in an amount sufficient for complete condensation of the vapors in the volume. Each elementary volume of vapor, when moving from a cube to a fractional column, is exposed to 5 to 30 such short-acting pulses. The method allows purifying petroleum products from sulfur compounds without the use of additional reagents, and by the degree of purification it exceeds the known ones by approximately 10 times.

EFFECT: this method can be used for purifying liquids from slow evaporating impurities or in the case where the majority of the mass transfer resistance is concentrated in the vapor phase.

3 cl, 2 dwg, 1 tbl, 3 ex

Description

The invention relates to the field of oil refining, in particular to the purification of light oil products from sulfur compounds.

Currently, chemical, physico-chemical and catalytic cleaning methods are used in industry. Various methods are known for purifying gasoline from sulfur-containing impurity components. The most common are hydrotreating, catalytic cracking and hydrogenation. Sorption purification methods are also used, such as absorption, adsorption, chemisorption processes, etc.

Chemical cleaning is carried out by exposure to various reagents on the impurity components contained in the product being cleaned. The easiest way is to purify with 92-98% sulfuric acid and oleum, which is used to remove unsaturated and aromatic hydrocarbons, asphalt-resinous substances, nitrogen and sulfur compounds, and alkali (solutions of caustic soda and soda ash) to remove some oxygen compounds, hydrogen sulfide and mercaptans. Sodium plumbite and some other reagents are used to remove sulfur compounds.

A known method for the demercaptanization of kerosene fractions, which consists in the fact that the demercaptanization of kerosene fractions is carried out by contacting the raw material (kerosene fraction) and hydrogen in the zone of a pre-treated hydrotreating catalyst with an activity of not more than 50% of the guaranteed nominal activity at a temperature of 220-240 ° C, pressure 0 , 4-1.2 MPa, a volumetric feed rate of a gas-raw material mixture of 3.5-7 h ^-1 and a hydrogen / feed ratio of at least 4: 1 nm ³ / m ³ (patent RU 2436838).

A known method of upgrading gasoline catalytic cracking. The essence of the method lies in the fact that hydrotreating gasoline using catalytic cracking is carried out. The hydrotreated product is divided into light [NK-110 (150) ° C] and heavy [110 (150) ° C - KK] fractions; the heavy fraction [110 (150) ° С - КК] is distributed into two streams, one of which is returned to the hydrotreating stage, mixed with the feedstock, and the second is combined with a light hydrotreated gasoline fraction [NK - 110 (150) ° С] and removed from the installation system as a component of gasoline (sulfur content 0.04-0.1% by mass.). The method allows to obtain catalytic cracking gasoline with a total sulfur content of less than 0.10 wt.%, Including the absence of mercaptan sulfur, with a minimum reduction in the octane number of purified gasoline compared to the initial catalytic cracking gasoline (patent RU 2258732).

All these methods have one significant drawback - their use is associated with the need to use a "third agent" - a catalyst, a chemical reagent that selectively interacts with removable impurity components or their combination. As a result, as the products of chemical reactions, a large number of chemicals are obtained with which something needs to be done, and it must be taken into account that they are all in a mixture, which makes their use very difficult.

At present, the generally accepted mechanism for the transfer of hardly volatile impurity components (the relative volatility coefficient of which differs significantly from unity) from the cube of the distillation column to the head is spray mist, i.e. the smallest particles of fog (aerosol) formed during boiling of a liquid, having a composition that differs little from the composition of the liquid phase, are carried away by an upward flow of steam from the lower plates to the upper ones, significantly reducing the expected efficiency (efficiency) of the separating device.

In our technical solution, the impurity components do not change their chemical form and can be isolated from the initial mixture in almost pure form or separated into groups, by boiling point and saturated vapor pressure.

The aim of the invention is to increase the efficiency of cleaning gasoline from sulfur-containing impurity components without the use of additional reagents.

The rectification process is carried out in a regime of cyclically changing pressure, for which portions of steam of the substance to be purified are periodically fed into the separation volume of each plate under a pressure exceeding the pressure on this plate and in an amount sufficient to condense all the vapors in the separation volume. The impact starts from the top plate, and the wave of impulses moves from top to bottom, and the effect on the next plate begins only after the end of the effect on the previous plate. In this case, the frequency of actions is selected depending on the pressure drop across the column so that for each elementary volume of steam during its passage from the cube to the reflux condenser, an effect of 5 to 30 pulses is provided, and the intensity of the effects (steam pressure of the substance being cleaned and the amount of steam being cleaned substance supplied to the separation volume of each plate) was sufficient for complete condensation of the vapor in the separation volume.

The device is illustrated in FIG. one:

1 - distillation column;

2 - condensation head;

3 - cube;

4 - steam generator;

5 - selection line;

6 - supply line of the column;

7 - feed line of the substance being cleaned;

8 - feed line of the substance being cleaned;

9 - feed line of the substance being cleaned;

10 - control unit.

The cyclically varying pressure is illustrated by the graph in FIG. 2:

P is the pressure on the corresponding plate, mm aq;

Risb - overpressure on the corresponding plate;

Rrab - working pressure on the appropriate plate;

t ₀ - time of the onset of exposure;

t ₁ - end time of exposure.

The cleaning device consists of a distillation column 1 equipped with a complete condensation head 2, heated by a cube 3, a steam generator of the substance to be cleaned 4, a group of shut-off valves located on the sampling line 5, the power line of the column pos. 6, steam supply lines of the substance to be cleaned 7, 8, 9 and the shut-off valve control unit 10.

A device for cleaning works as follows.

In the cube of the distillation column 3, the initial mixture is loaded, for example, the gasoline fraction, the heating is turned on, the initial mixture begins to heat up and boils, the vapor rises along the column to the head of full condensation 2, condenses in the refrigerator and the condensate flows to the column 1, at this time the generator is turned on steam of the substance to be cleaned 4, after the column reaches the stationary mode, the shut-off valve control unit 10 gives a command and the normally closed shut-off valve 7 opens - increased steam (compared to pressure in the column) the pressure is supplied to the separation volume of the upper plate in an amount sufficient to condense the steam located on the corresponding plate. Aerosol particles, with increasing pressure under the influence of condensation of the surrounding vapors, coarsen and settle, combining with the liquid phase. Then, the shut-off valve control unit gives a command and the shut-off valve 7 closes, the pressure in the separation volume returns to its operating value, after which the shut-off valve control unit gives a command to the shut-off valve 8, the valve opens and a portion of the substance to be cleaned is fed into the separation volume of the second plate from the top , the pressure in the separation volume increases, the vapors condense, the aerosol particles, enlarging, settle and combine with the liquid phase, valve 8 closes and the process continues similarly th manner on all plates, after the pulse to the lower plate of the column isolation valves control unit commands the valve 7, and so on. A wave of short-range pulses moves down from the top of the column, providing alternating vapor condensation on the plates.

For comparison, three examples are given with a total sulfur content of 0.08, 0.13 and 0.03% in the initial mixture and purification of the mixture depending on the conditions of distillation:

1. Acceleration at constant pressure.

2. Acceleration with cyclically changing pressure and the number of pulses 5-30.

3. Acceleration with cyclically changing pressure and the number of pulses less than 5.

4. Acceleration with cyclically changing pressure and the number of pulses more than 30.

5. Dispersion at cyclically changing pressure and insufficient excess pressure of the supplied steam of the substance being purified.

6. Dispersion under cyclically changing pressure and excessively high excess pressure of the supplied steam of the substance being purified.

The pressure value of the supplied steam, the number of exposure cycles and the exposure time to the elementary volume are selected experimentally and depend on the amount of sulfur impurities in gasoline. These parameters are determined by a specialist and vary depending on the capabilities of the equipment and the characteristics of the gasoline being cleaned.

The results of the examples are summarized in table 1.

The total sulfur content in the initial mixture and in the main distillation fractions,% mass.

Based on the data obtained, it is seen that the total sulfur content when using the proposed method is lower than when using the existing method by about 10 times.

This method can be used when cleaning liquids from volatile impurities or in the case when the bulk of the resistance to mass transfer is concentrated in the vapor phase.

Literature

1. H. Green, W. Lane. "Aerosols, dusts, fumes, mists." 1972

2. A. Bazanov, V. Blinichev. "The mechanism of selective entrainment of solute from evaporated solutions." 2007 year

3. L.V. Gordon. "Technology and equipment for forestry industries." 1988 year

Claims (3)

1. The method of purification of gasoline from sulfur-containing impurities during the rectification process, which consists in the fact that the rectification is carried out in a cyclically changing pressure mode, in which a portion of the vapor of the gasoline to be cleaned is fed sequentially from the top into the separation volume of the plate at a pressure exceeding the vapor pressure in a given separation volume, in an amount sufficient to completely condense the vapors therein, while each elementary volume of steam, when moving from the cube to the reflux condenser, is exposed to from 5 up to 30 such short-range pulses. 2. The method according to p. 1, in which the intensity of the short-range pulse is sufficient for the complete condensation of gasoline vapor in the separation volume. 3. The method according to p. 1, in which the frequency of exposure to gasoline vapors depends on the pressure drop of the vapor on the column.

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