TECHNICAL FIELD

The invention relates to the sector of motor fuel production and can be used in Refining and Petrochemical industries.

PREVIOUS TECHNICAL KNOWLEDGE

One of the main oil refining tasks is to increase the selection of light oil products - motor fuels, so a large part of heavy residual oil is recycled by thermal and catalytic cracking, visbreaking, thermal and catalytic hydrocrackers.

There is a method of producing motor fuels from oil residues, comprising thermal cracking of heavy oil residues mixture with crushed oil shale or sapromixite, at that, thermal cracking products are separated by distillation to a fraction boiling within the temperature range of NK÷450...550 °C and a residue boiling at above 450÷550 °C, wherein fraction boiling at the temperature range of NK÷450...550 °C is subjected to light hydrocracking, followed by separation of petrol and diesel fraction from the hydrogenation product (patent RU 2099385 C I IPC C 10G9/00, declared 05.03.1997, published 20.12.1997). This method has the following disadvantages:

1 ) petrol and diesel fractions are only two semi-finished products, resulting from heavy oil residue processing;

2) the known method does not decode hardware and technological solution of liquid product separation of the reaction to fuel distillates.

There is a method known for producing diesel fuel, comprising the stages of catalytic hydrodewaxing, catalytic hydrocracking of oil raw material at elevated temperature and pressure and obtaining the desired product by distillation, characterized by the raw material isolated from the oil fraction boiling at the temperature range of (260÷290 °C) - (340÷370 °C) and (340÷370 °C) - (530÷560 °C), the first of which is subjected to catalytic hydrodewaxing followed by its hydrostabilization, the second one - to catalytic hydrocracking with preliminary hydrotreatement; hydrogenates obtained are subjected to distillation with the isolation of naphtha, light diesel fraction, heavy diesel fraction and a residue which is recycled in the process and is catalytically hydrocracked with the second fraction (application for invention RU 2002103696 A IPC C 10G69/14, C 10G65/14, declared 1 5.02.2002, published 10.09.2003). This method has the following disadvantages:

1 ) need for feedstock pretreatment by separating it into two fractions; 2) relatively low range of products produced: gasoline fractions and two types of diesel fractions used as components of winter and arctic diesel fuel create marketing problems of unit efficient operation during the summer.

The closest to the declared invention is a method of producing fuel distillates, which includes heat-reaction unit, hydrogen purification and compressing unit, hydrocracking product separation unit, the unit of hydrocracking product separation by fractionation in distillation column, wherein the feedstock is thermally hydrocracked, after which the reaction products are sent to a hot separator, from which at the temperature of 260÷300 °C and the pressure of 10 MPa fractions withdrawn from the bottom are boiling at above 400 °C and the majority of fractions withdrawn from the top of the hot separator are boiling at 360÷400 °C; these are further subjected to catalytic hydrotreatment, and the reaction products are cooled down and sequentially pass through high and low pressure separators, from the top of which hydrogen gas is released for the circulation, and reaction liquid products withdrawn from the bottom of the low pressure separator are sent to a fractionation plant to produce commercial products - gasoline, diesel and hydrotreated liquid aromatic additive (fraction 360÷400 °C). The product from the bottom of the hot separator is cooled down in the cooler and is sent as a recycle stock or residual fuel oil fraction to the tank farm (patent RU 2292378 CI IPC C10G9/00, declared 24.1 1 .2005, published 27.01.2007). This method has the following disadvantages:

1 ) the process conditions declared mismatch the operation mode of hot separator (the temperature of 260÷300 °C and the pressure of 10 MPa) and the destination of the separator to remove vapor fraction boiling at 360÷400 °C from the top of the separator, since at 10 MPa pressure the significant portion of fuel fraction shall remain in the liquid phase and shall be discharged into the fuel oil, which significantly affects the performance of the process;

2) the poor quality of the separation of reaction products in three separators, as the separation in such devices is based on the principle of single vaporization (condensation) corresponding to one theoretical tray, whereby the separator is low in sharpness of separation, especially in the hot separator, which will on the one hand cause the loss of the light fuel fraction going over in fuel oil, and on the other hand - light fuel fraction contamination with fuel oil components;

3) the known method does not decode hardware and technological solution of liquid product separation of the reaction to fuel distillates;

4) the known method provides a relatively narrow range of manufactured final products having insufficient quality: gasoline (fraction XK÷180 °C) grade A-80, diesel fuel (fraction 180÷360 °C) with cetane index 46-48, hydrotreated fraction 360÷400 °C - liquid aromatic additive; besides the fraction boiling at above 400 °C is produced, used as boiler fuel or as recycle stock to completely convert it into gasoline and diesel fuel.

There is also petroleum residue hydrocracker known, which allows to produce at least one distillate hydrocarbon fraction in a fractionating zone comprising two distillation columns with liquid and steam refluxing systems, heaters, heat exchangers, coolers, tanks, pumps and pipelines, interconnecting unit devices in which two types of the reaction mixture produced in different reaction fragments of unit process flow are mixed and successively pass through high pressure separator and low pressure separator, withdrawing hydrogen containing gas from the top of them, then through the atmospheric distillation column and vacuum distillation column, receiving respectively atmospheric and vacuum distillates from the top, and from the bottom of vacuum column heavy bottom fraction is removed via pipeline, which can be further recycled in mortar deasphalting unit to give oil products (patent U 249591 1 C2 IPC C 10G67/04, C 10G47/00, C 10G21 /00, declared 16.06.2010, published 20.10.2013). This unit has the following disadvantages:

1 ) the poor quality of the separation of reaction products in two successively connected high and low pressure separators, as the separation in such devices is based on the principle of single vaporization (condensation) corresponding to one theoretical tray, whereby the separator is low in sharpness of separation, especially in low pressure separator, which will cause the loss of the light distillate fraction going over in hydrogen containing gas;

2) the need to have vacuum generating equipment to provide the operation of vacuum column, resulting significant additional energy to ensure the efficiency of unit operability and the reduction of its profitability;

3) a narrow range of products produced.

DISCLOSURE OF INVENTION

The inventors task was to expand the range of products produced in the hydrocracking process, providing additional production of kerosene, product quality improvement, energy saving during the implementation of the fractionation stage of the reaction mixture.

The solution of this problem is achieved by the method of producing motor fuels comprising heating and reaction unit, hydrogen compressing and purification unit, hydrocracking product separation unit, hydrocracking product fractionation unit by fractionation in the distillation columns, at that, the separation of the hydrocracking products is performed in three stages. At the first stage hydrocracking liquid products obtained after hydrocracking reactor are separated in the first atmospheric distillation column into low pressure gas, liquefied hydrocarbon gases, light naphtha and heavier hydrocracking product, at that, light gasoline fraction is obtained in the first atmospheric column as a side draw. At the second stage heavier hydrocracking product is separated in the second distillation column to obtain column top heavy gasoline, then via a side draw at independent strippers kerosene and diesel fuel is obtained sequentially, at least two types, including winter, summer, arctic and circulating reflux, and at the bottom of the column there is an unconverted residue, at that, a part of the unconverted residue with the circulating reflux is heated in a furnace together with the heavier product of hydrocracking reaction, and the remaining part is withdrawn aside or reused as destructive process raw. At the third stage light naphtha stabilization and cleaning from hydrogen sulfide is provided, at that, stable light naphtha is obtained in the third distillation column to be mixed further with heavy gasoline produced in the second distillation column, if required; from the top of the third distillation column stabilization gas doped with hydrogen sulfide is obtained, which was extracted in the fourth column-absorber using liquid absorbent recovered later in the fifth column-regenerator, wherein from the top of the fourth column low-pressure purified gas used as fuel gas is obtained, and from the top of the fifth column sour gas is obtained used as Claus process raw stock for elemental sulfur or other purposes. This allows receiving of an environmentally friendly fuel gas and raw materials for the production of elemental sulfur, along with increased quality of light naphtha due to the removal of hydrogen sulfide from it. Performing fractionation in the atmospheric distillation columns only avoids the design and operation costs for vacuum generating equipment. Kerosene and diesel fuel preparation in the second distillation column sequentially with side draw through separate strippers improves the separation sharpness of these products and thus improves their quality due to the possibility of regulating the initial boiling point of the appropriate fractions. Atmospheric pressure in the first distillation column is higher than in the second atmospheric distillation column, while the atmospheric pressure in the second distillation column is not higher than 0.5 atm, which is achieved by lowering the vapor load in the steam condenser coming from the top of the second atmospheric distillation column, due to circulating refluxing installation, providing minimum rates of live refluxing returned to the top of the second atmospheric distillation column, and also due to the selection of gasoline fractions as light naphtha at the side of the first atmospheric distillation column. The additional improvement of the quality of each side draw of the second distillation column is provided by the appropriate circulating reflux positioned under draw outflow and adjusting the final boiling point of the corresponding fraction.

Stripping the draws of kerosene fraction and of each type of diesel fraction in the stripping columns is provided by heat supply using at least one heat carrier, namely, the residue of the second distillation column or by an external heat carrier or by both heat carriers simultaneously, to the bottoms of the stripping columns due to the respective heating of kerosene removed and each type of diesel fuels, i.e. the quality of the stripping is achieved without steam supply to the bottom of the respective stripping columns, resulting energy savings for stripping. Variability of used heat carriers provides the process flexibility of fractionation system operation. Besides, the exclusion of water vapor supply while stripping kerosene and diesel fractions results the additional increasing of their quality and obtaining the "dry" fuels. The possibility of obtaining "dry" fuels will significantly improve the economic performance of the process, as during steam bubbling through a layer of hydrocarbon distillates turbidity occurs due to the equilibrium condensation of water vapor; at the temperature below 0 °C the condensed moisture goes over in crystalline form clogging the fuel system of jet and diesel engines, and the water from flooded fuel distillates shall be removed by additional adsorption purification or significant temperature increase during the subsequent heating, which requires additional energy for the process.

There is the following trend: the more vapor is supplied into the cube, the more moisture is supplied into the lateral distillates, the higher temperature needs to be maintained to dehydrate the distillates, which results the additional intensification of energy and capital costs.

Reflux stripping that does not require a high degree of dehydration in the bottom stripping column is provided by supplying water steam to the bottom of the column, or by applying heat to the boiler, or by both methods at the same time, providing the additional flexibility of the process.

Placing the blind tray above the raw feed is efficient in the second atmospheric column, as reflux selection is easily performed followed by its partial or complete heating in an oven or supplying external heat carrier and performing diesel fraction stripping in the bottom stripping column, which cube is heated by an external heat carrier or due to the supply of water steam, and the remaining unevaporated reflux is sent for additional stripping of light fractions in the bottoms of the second distillation column or is withdrawn from the unit.

It is also advantageous for the areas of high requirements to the sharpness of separation of the fractionating equipment to use cross-flow packed contact devices, forming separate optimum packing cross-section for the passage of streams of steam and liquid phases having low flow resistance, at least in the topping parts of columns.

Thanks to combined processing methods declared, water steam introduced into the bottom of the second distillation column does not exceed 0.4 % wt. per the feedstock, and into the bottom of the stripper - 1.5 % per the entire reflux amount supplied to the stripper, thereby reducing energy costs to implement fractionation stage.

To extract hydrogen sulphide from stabilization gas in the fourth column-absorber amines are used as liquid absorbent, at that, water alkylamines are used as hydrogen sulfide absorbent, wherein the concentration of the basic absorbent substance in the water solutions does not exceed 50 % wt.

Thanks to combined processing methods declared, the content of light fractions boiling up to 360 °C in the unconverted residue does not exceed 3 % wt., resulting the increase of light fractions extraction; and the unconverted residue withdrawn from the bottom of the second atmospheric distillation column is partially or fully added as the recycle either to hydrocracking raw, or to hydrocracking reaction products, or to the raw materials of other secondary thermal, catalytic or oil separation processes, it can be added to boiler fuel as well, also providing process technological variability.

The solution of the problem is also achieved in by the hydrocracker to produce motor fuels, comprising heating and the reaction unit, hydrogen compressing and purification unit, hydrocracking product separation unit, hydrocracking product fractionation unit, containing two distillation columns equipped with liquid and steam refluxing systems, heaters, heat exchangers, coolers, tanks, pumps and pipeline interconnecting unit devices, which additionally includes a system consisting of at least three strippers, connected to the second distillation column, to the third distillation column, to the absorber and to the regenerator. At that, the pipeline for raw supply through a group of recuperative heat exchangers is connected to the middle part of the first atmospheric distillation column. The bottom of the first atmospheric distillation column is connected by the pipeline to pump suction branch pipe, the discharge branch pipe of which is connected by the pipeline to tube coil input of the first tube furnace, the output of which is connected by means of piping with the bottom of the first atmospheric distillation column and with tube coil input of the second furnace, the outlet of which is connected by the pipeline to the second atmospheric column input. In this case, the second distillation column has at least three circulating refluxes, the outputs of at least three side draws and is connected by three corresponding strippers. Lateral output of the first distillation column is connected by the pipeline with the top of the third distillation column, the top of which is connected by the pipeline with absorber bottom, connected by the pipelines with the regenerator, forming the absorber-regenerator system for stabilization gas purification from hydrogen sulfide.

It is also preferred to provide the circulation loop at the bottom of the strippers, formed to supply heat to the stripper, consisting of the bottom part of the stripper, the pump and the heat exchanger associated by the pipelines.

It is also advantageous to use cross-flow packed contact devices in the bottom of the second distillation column, in the absorber, in the regenerator and in the strippers, and to install the blind tray in the middle of the second distillation column above the raw inlet, which is connected with the bottom stripper by the pipeline.

LIST OF DRAWINGS

The declared invention is illustrated by the drawing, where Figure 1 shows a diagram of the proposed hydrocracker to produce motor fuels using the proposed hydrocracking method to produce motor fuels. Hydrocracker diagram to obtain motor fuels includes the following items:

I - heating and reaction unit,

II - hydrogen purification and compressing unit;

III - hydrocracking product separation and cooling

IV - hydrocracking product fractionation unit;

V - light naphtha stabilization unit;

VI - stabilization gas amine treatment unit;

10 - first distillation column,

20 - second distillation column.

30 - third distillation column-stabilizer,

40 - fourth column-absorber,

50 - fifth column-regenerator,

60, 70 - stripper,

80 - bottom stripper,

90, 190, 290 - heat exchanger,

100, 1 10 - tube furnace,

120, 130, 140 - circulating reflux, respectively, top, intermediate, bottom

- heater (boiler),

170, 180 - reboiler, 200, 210, 220, 230, 240 - cooler,

250, 260, 270 - separator,

280 - pump;

1 -9, 1 1-19, 21 -29, 3 1 -39, 41 -49, 51 -59, 61 -63 - pipelines.

BRIEF DESCRIPTION OF DRAWINGS

The declared hydrocracking method to obtain motor fuels according to Figure 1 is performed as follows. The initial mixture entering heating and reaction unit I by pipeline 3 formed by mixing the feedstock entering by pipeline 1 with the circulating hydrogen entering by pipeline 4, is heated consecutively in the heat exchangers and in the furnace up to 460 °C and is supplied to the reactors (are not shown in Fig. 1 ). Hydrocracking reaction products as a vapor- liquid mixture are supplied from the reactors to hydrocracking product cooling and separation unit III, wherein are cooled in the condensing coolers up to the temperature of 50 °C and are separated in the separators into gas and liquid phases, at least in two stages. Hydrogen containing gas is withdrawn from the first stage of separation via pipeline 62, then it enters hydrogen purification and compressing unit II, where it is cleaned from hydrogen sulfide in the absorber using amine. Further mixing of the circulating hydrogen with fresh hydrogen entering via pipeline 2 and the compression of hydrogen up to the pressure of 14.0-16.0 MPa to provide the circulating hydrogen for heating and reaction unit I is carried out. From the second separation stage high-pressure hydrocarbon gas is withdrawn to separate high pressure absorber for hydrogen sulfide amine treatment. From the second separation stage high-pressure hydrocarbon gas is withdrawn to separate high pressure absorber for hydrogen sulfide amine treatment. The isolated liquid phase after the second separation stage is isolated from sour water, which is supplied for the purification of ammonia and hydrogen sulfide to an additional unit, which is not shown in Figure 1 , and then hydrocracking liquid products consisting of hydrocarbons enter hydrocracking product fractionation unit IV pre-heated in the recuperative heat exchangers group by hydrocracking products and circulating refluxes of hydrocracking product fractionation unit IV. In this unit, in the first distillation column 10 low pressure hydrocarbon gas is separated containing hydrogen sulfide and liquefied hydrocarbon gas (reflux), which are supplied to separate low pressure absorbers for amine treatment (are not shown in Fig. 1 ).

In the first distillation column 10 pressure maintained is at the level of 1.0 MPa, maximum, while the top part temperature is 50 °C and the bottom part temperature is 260-280 °C. Light naphtha of 60-140 °C is withdrawn aside of column 10, which can significantly reduce the load in tube furnace 1 10 and in cooler 210 of the second distillation column 20, as the proportion of low-boiling components is significantly reduced in the residue supplied for the separation to the first distillation column 10 (residue boiling point is 100-120 °C, minimum).

Light naphtha withdrawn to the first distillation column 10 at the temperature of 120 °C heats the raw material of hydrocracking product fractionation unit IV, then light naphtha cooled to 50 °C comes to the top of stabilizer 30 to light naphtha stabilization unit V, where its stabilization and the removal of hydrogen sulfide is carried out. In the third distillation column 30 the pressure is maintained at the level of 0.15 MPa, bottom temperature is 120 °C, maximum, due to the heat supplied to reboiler 170, e.g., via heat carrier or water steam. The extracted stabilization gas is sent for the amine treatment to separate atmospheric pressure absorber 40, which is a part of stabilization gas amine treatment unit VI. This unit can also contain high and low pressure absorbers for the purification of the respective gas streams from hydrogen sulfide, at that, the regeneration of rich amine coming from different absorbers can be carried out in a single amine regenerator. It is also possible to perform rich amine regeneration in stabilization gas amine treatment unit VI, coming from hydrogen purification and compression unit II after the circulating hydrogen purification.

Figure 1 shows rich amine regeneration for stabilization gas only to simplify the diagram, wherein the heat is provided to regenerator 180 due to the water steam or external heat carrier.

Then the residue of the first distillation column 10 is used for the heating of tube furnace 1 10 of the second distillation column 20, from where vapor-liquid mixture with reduced naphtha content at the temperature of 340-345 °C is supplied under the blind tray of the second distillation column 20, operating at the pressure up to 0.05 MPa, at that, the vapors come to the concentration part, and the liquid flows into the topping part. To the bottom part of the second distillation column 20 minimum amount of water steam is supplied, not more than 0.4 % wt. per raw material. From the bottom of the second distillation column 20 stripped unconverted hydrocracking residue is withdrawn, which contains light fractions boiling up to 360 °C, not more than 3 % wt. due to the high efficiency of separation in the bottom part provided by cross-flow packing devices under the conditions of low steam and liquid loads.

At the concentration part of the second distillation column 20 depending on the destination of the process, according to Figure 1 , several side draws are withdrawn, such as kerosene fraction and one type of diesel fraction, as well as several types of diesel fraction, such as arctic, winter and summer. Each of the side draws of the second distillation column 20 is supplied to the stripper, in which light fraction stripping and dissolved moisture removal is provided by heating the bottom part via the external heat carrier or the unconverted residue. Other indicators of the quality of these draws, including the fractional composition, are provided by the consumption of draw and intermediate circulating refluxes, performed under each of the side draws. Figure 1 gives only one intermediate reflux for kerosene fraction output and the bottom one - for diesel fraction output. Top circulating reflux performed in column 20 at top trays allows to unload the condensation equipment and to maintain low pressure of 0.05 MPa in the second distillation column 20 in the absence of light naphtha.

From the top of the second distillation column 20 heavy naphtha (100-180 °C fraction) is withdrawn, it is completely hydrogen sulfide free and does not require to be stabilized. This heavy naphtha can be either mixed with light stable naphtha, as shown in Figure 1 , or sent for further processing separately from light stable naphtha.

For maximum extraction of light fractions in the second distillation column 20 under the conditions of limited heat and raw supply entering the second column 20, caused by the presence of large amount of volatile fractions, separate reflux stripping is performed, the reflux is collected in the blind tray and is supplied to the bottom stripper 80.

The reflux with preliminary partial or complete heating in the furnace or via the external heater carrier can be supplied to column 80 (is not shown in Fig. 1 ). Also, to achieve reflux deep stripping the bottom part of stripper 80 can be heated by external heat carrier or by water steam, as shown in Figure 1. The remaining unevaporated reflux is sent for extra stripping of light fractions in the bottom part of the second distillation column 20 and is supplied for the mixing with the unconverted residue, which is used as a recycle or heating and reaction unit I (is not shown in Fig. 1), or hydrocracking product fractionation unit IV, and can also be withdrawn from the unit as a separate product.

The hydrocracker to obtain motor fuels operates as follows: raw material coming via pipeline 1 is mixed with the circulating hydrogen supplied via pipeline 4, then the resulting mixture is sent via pipeline 3 to heating and reaction unit I, comprising the heat exchangers, the furnace, the reactors and the pipelines connecting these devices; and via pipeline 5 the reaction products are sent to hydrocracking product cooling and separation unit III, where the pressure of the reaction products is reduced, at that, the extracted hydrogen is removed through pipeline 62 to hydrogen purification and compressing unit II, and the liquid phase is sent to hydrocracking product fractionation unit IV through pipeline 6, which is connected with the group of recuperative heat exchangers 90, heated by the final products and the circulating refluxes. Then, heated raw material flows via pipeline 7 to the first distillation column 10, on the top of which pipeline 8 is connected successively with cooler 200 and separator 250. Low-pressure gas is removed from the separator via pipeline 9, and liquefied hydrocarbon gas (reflux) is separated into two parts, one of which returns as live reflux to the first distillation column 10 via pipeline 1 1 , and the remaining part is withdrawn from hydrocracking product fractionation unit IV via pipeline 12.

Pipeline 14 connects the lower pipe union of the first distillation column 10 with the suction branch pipe of pump 280, the discharging branch pipe of which via pipeline 15 is connected with tube furnace coil 100, connected with the bottom part of the first distillation column 10 by pipeline 16. Part of the bottom liquid via pipeline 17 is mixed with reflux recycle and bottom residue of the second distillation column 20 withdrawn through pipeline 39, and then through pipeline 18 coming in tube furnace 1 10, from where the heated raw flows via pipeline 19 to the second distillation column 20 equipped with packing type contact devices in the bottom part of the column and tray type contact devices in its top part, as well as with the blind tray, three circulating refluxes 120 (top), 130 (intermediate) and 140 (bottom), wherein steam input is provided in the bottom part via pipeline 36. The top of the second distillation column 20 is connected via pipeline 21 with cooler 210, then with separator 260 equipped with heavy naphtha output via pipeline 22, at that, a part of heavy naphtha is returned via pipeline 23 to the column as live reflux, while the remaining part of heavy naphtha is mixed with light stable naphtha via pipeline 24 and is withdrawn from the unit via pipeline 45. The second distillation column 20 is equipped with two strippers 60 and 70, comprising kerosene and diesel fraction input, containing the excessive amount of light fractions, that shall be respectively removed via pipelines 25 and 28 to produce commercial fuels. Stripping columns 60 and 70 are equipped with heaters of the bottom part of stripping column 150 and 160, steam phase outputs, respectively via pipelines 26 and 29 to distillation column 20, and the respective product outputs: kerosene is withdrawn from stripper 60 via pipeline 27, and diesel fuel is withdrawn from stripper 70 via pipeline 31. The reflux is withdrawn from the blind tray via pipeline 32, it is flowing from the concentration part of the second column 20 to bottom stripper 80, from the top of which the reflux steam phase is withdrawn via pipeline 33 to column 20, and from the bottom it is withdrawn for recycling of the remaining unvaporated reflux via pipeline 35. Water steam is supplied to the bottom of column 80 by pipeline 34.

The bottoms (unconverted hydrocracking residue) of the second distillation column 20 are removed through pipeline 37, and then are separated into two parts, one of which is mixed with the unvaporated reflux withdrawn through pipeline 35, and the remaining part of bottom residue is removed from the unit via pipeline 38. Light naphtha is withdrawn from the tray of the first distillation column 10, situated between live reflux input and feedstock input to column 10 via pipeline 13, which is connected to cooler 220 equipped with discharge pipe for cooled light naphtha 41 to light naphtha stabilization unit V, to the top of the third distillation column 30 equipped with stabilization gas drain pipeline 42 at the top and with light stable naphtha drain pipeline 43 at the bottom, which is connected with reboiler 170, from where the vapors are returning to the third distillation column 30 via pipeline 63, and light stable naphtha removed via pipeline 44 is connected to heavy naphtha pipeline 24 and is withdrawn from the unit via pipeline 45. Light naphtha stabilization unit V is connected via pipeline 42 with stabilization gas amine treatment unit VI, comprising the fourth column 40, operating at practically atmospheric pressure, which uses high efficiency and low hydraulic resistance packing type contact devices, and having raw material (stabilization gas) input via pipeline 42 to the bottom part of absorber 40 and gas (purified from hydrogen sulfide) output via pipeline 46, the input of the regenerated absorbent via pipeline 61 and the output of the bottom liquid (rich absorbent) via pipeline 47, which is connected to heat exchanger tube side 290, at the output of which the heated rich absorbent is supplied via pipeline 48 for the regeneration to the fifth column (regenerator) 50, which is a vertical cylindrical component with contact devices. At the bottom part regenerator 50 is equipped with reboiler 180 with water steam heat carrier supply pipeline 56 and condensate drain pipeline 57. Via pipeline 54 the bottom liquid of regenerator 50 is supplied into the tube side of reboiler 180, at the output of which the vapor phase returns via pipeline 55 to regenerator 50, and the liquid phase is sent via pipeline 58 to absorber 40, without passing through heat exchanger 290, cooler 230, regenerated absorbent storage tank and a pump (the last ones are not shown in Fig. 1). From the upper part of regenerator 50 via pipeline 49 steam and gas are withdrawn, which are further cooled in cooler 240, by pipeline 51 connected to reflux tank 270, equipped with the outputs of acid gases and water via pipelines 52 and 53 respectively. Acid water is supplied as reflux through the pump to the top of regenerator 50 (is not shown in Fig. 1).

The proposed invention is illustrated by the following example: The estimated comparison has been performed using the method of mathematical modeling of the performance parameters of hydrocracking product fractionation unit for single-stage process as per the prototype and within the limits of the system according to the present invention proposed. The unit consists of two atmospheric distillation columns, the first column with side draw of light naphtha, the second column associated with the stripper for diesel fuel production and lower stripper to send the reflux from the blind tray; it also includes one stabilization column to stabilize and to remove hydrogen sulfide from light naphtha, the absorber for stabilization gas purification from hydrogen sulfide and the amine regenerator, as well as the fractionation unit made as per the prototype for two-stage cracking with two columns: the atmospheric column, in which the crude gas is obtained, as well as unstabilized naphtha, diesel fuel and unconverted residue, which is subjected to distillation before secondary hydrocracking in vacuum column followed by the extraction of diesel fuel and the residue containing not more than 3 % wt. of light fractions boiling up to 360 °C. Table 1 represents data on the quality of fractionation products as per the prototype and the declared invention. As per the calculated data and in comparison with the prototype, the declared invention besides its significant process flexibility and variability allows to reduce the consumption of water steam by 30 % and to reduce fuel gas consumption by 20 % at relative conversion increase up to 8.2 %. Other features are product range expanding and quality enhancing - fuel gas and naphtha component as well as "dry" kerosene and diesel fuel are generated.

ue gas per process

Table 1

Thus, the declared invention has significant advantages in comparison with the prototype due to developing of the new system of hydrocracking product fractionation, which at unit capacity of 2.5 mln. t/year allows obtaining of motor fuels saving 18750 t/year of water steam and 7250 t/year of fuel gas, resulting total energy savings of 44.4 mln. rub./year.