SU1041558A1 - Method for isolating n-paraffins - Google Patents

Description

2. The method according to claim 1, is distinguished by the fact that the pressure at the first stage of washing the gas mixture is supported by 6-TS at and at the second stage 9-18 at.

3. Method .in paragraphs. 1 and 2, characterized in that

washing the gas mixture in the first stage is carried out with ammonia water containing 23–36 wt.% of ammonia, and in the second stage with ammonia water containing 3–21 masons of ammonia.

one

The invention relates to the separation of hydrocarbon mixtures and can be applied in the refining and petrochemical industries, in particular for the production of high-purity liquid paraffins from petroleum fractions. .

Nowadays, adsorption processes using synthetic type A zeolites and mainly carried out in the vapor phase as adsorbents are used to obtain high-purity liquid paraffins. These processes are related to Izosiv, Ensorp, MS-1, TSF, Nareks .. In most industrial processes, desorbent is used as a gas (diluent of the raw material) - a substance with the help of which the desorption of coal, orords, absorbed by the zeolite from the raw material in the adsorption stage, is carried out.

The Izosiv process is known, in accordance with which the raw material (gas oil fraction) is mixed with n-hexane, evaporated and, at a pressure of 2.3 atm, is passed through a layer of zeolite CaA. Hexane is separated from denormalization and returned to the system. After the adsorbent layer is saturated with n-paraffins, the adsorber is flushed with a stream of n-goxane, as a result of which impurities are removed from the free volume of the adsorber of the secondary porous structure of the adsorbent and from its outer surface. Then hexane is used as a desorbent. The mixture of desorbed paraffins and hexane is separated in a distillation column, and the hexane is recycled. The coke formed on the zeolite of coke is periodically burned with a mixture of air and nitrogen, for which one of the adsorbers is constantly included in the regeneration scheme 1.

The disadvantages of this method are the low working capacity of the zeolite, i

the paraffin capacity of the plant is low, caused by the use of a desorbent for r. feed dilution, which reduces the capacity of the zeolite for n-paraffins due to its competitive adsorption, resulting in a decrease in the production of n-paraffins.

Also known process Ensorb using desorbent ammonia as a diluent of the raw material. At the adsorption stage, the raw material is diluted with part of the desorbent (ammonia) in a molar ratio of 1: 0.5, evaporated and fed into the layer of CaA zeolite containing ammonia in the adsorption phase. The denormalized product leaving the adsorber at the adsorption stage is condensed and the ammonia is removed from it. . As the zeolite is saturated with paraffins, the feed stream is directed to the second adsorber, and in the first adsorber the n-paraffins are desorbed with ammonia, and the first part of the sorbate, corresponding to the RR of the total amount of n-paraffins, is returned to the raw material 2,

The disadvantages of this method are low working capacity of the molecular sieve and low plant capacity due to the use of desorbent (ammonia) to dilute the raw material (this reduces the adsorption capacity of the molecular sieve over n-paraffins and, consequently, their production to low purity paraffins due to the desorbent contamination by nonlinear hydrocarbons of the raw material when separating the desorbent from the denormalized fraction; the short intergeneration period of the molecular sieve service due to insufficient purity of the desorbent drive to incomplete desorption of n-paraffins and accelerated coking of the molecular sieve.

Closest to the proposed process is the Parex process, in accordance with which the hydrotreated kerosene or diesel fraction is mixed with a circulating hydrogen-containing gas containing a desorbent liquid — ammonia. This mixture is heated, evaporated and fed into one of the three adsorbers filled with zeolite. From the adsorber, the product consisting of a denormalized product, a hydrogen-containing gas and ammonia (which was adsorbed on the zeolite during the previous desorption period), after cooling, enters the washing column, where the denormalized product is separated from the hydrogen-containing gas and ammonia. A significant mass of the latter is absorbed in the column by circulating ammonia water, O2 hydrogen-containing gas containing ZO- + O about ammonia, is compressed from the top of the wash column and returned to mixing with the raw material. Saturated ammonia water passes a two-step degassing process by reducing pressure, after which it returns to the wash column, and ammonia is compressed and returns to the system. Denormalized from the bottom of the wash column is sent to a commercial park.

At the end of the adsorption stage, the n-paraffins are desorbed with ammonia. The mixture of n-paraffins, hydrogen-containing gas and ammonia released from the adsorbers is cooled and fed to high and low pressure separators. Ammonia with hydrogen-containing gas remains from the separators is received at the high and low compression stages and returned to the circulating system in ammonia from the washing column. and further on desorption of W.

The disadvantages of this method are the low working capacity of the zeolite, which leads to a decrease in the production of n-paraffins due to the presence in the hydrogen-containing gas supplied to the mixture with the raw material from 30 to 0 vol. Gammiaka desorbent). Studies show the effect of ammonia in hydrogen-containing gas on the adsorption capacity of zeolite CaA for n-paraffins extracted from the 200-320 ° C diesel fraction when the ammonia content in hydrogen-containing gas changes from 0 to 4% by volume, the capacity of preg before the breakthrough decreases , from 5.9 to 4.9 wt., i.e. by about 20%. Further increase in ammonia content in hydrogen.

from k to 9.0 about. leads to a decrease in the capacity of the zeolite to + 3 May D. Therefore, the use of gas containing 10–40% by volume of ammonia in the process reduces the capacity of the zeolite by about 20%, significantly reduces its service life and the production of n-paraffins. Low purity of the desorbent, resulting in poor desorption of n-paraffins and

The reduction in the interregeneration period of the zeolite, is caused by the ingress of hydrogen residues into it, especially at the initial moment of desorption, when the remaining adsorption in the pipelines and in the free volume of the adsorber of hydrogen containing gas is displaced. Low purity desorbent leads to insufficiently deep desorption of n-paraffins from the pores of the zeolite

0 and an increase in the rate of its coking "In addition, the circulation in the desorbent system of the inert component — hydrogen leads to an increase in operating costs

five

The purpose of the invention is to increase the working capacity and lengthen the life of the zeolite, increase the purity of the desorbent, improve the technical and economic performance of the process, for example, by reducing the specific cost of auxiliary materials (zeolite).

The goal is achieved in that according to the method of separating n-paraffins by adsorbing n-paraffins with zeolite 5A from crude oil mixed with a diluent gas, separating the diluent gas from the dewaxed material, followed by desorbing n-paraffins with ammonia, washing the ammonia from a diluent gas with ammonia water and the desorption of ammonia from ammonia water by decreasing the pressure, the gas diluent from the adsorption stage after separation from the dewaxing agent

5, the raw material is mixed with the gas of the start of desorption previously purified from hydrocarbons, and the resulting gas mixture is subjected to a two-step washing of ammonia, and the first step of the gas mixture is washed to a residual ammonia content of 18-30 vol.%, In the second stage to a residual ammonia content .0 , 5-5 o6.% And the resulting diluent gas is spilled on

5 mixing with raw materials.

The pressure in the first stage of washing the gas mixture is maintained at 6-10 atm and in the second stage, 9-18 at. At the first stage, the gas mixture is washed with ammonia water containing ammonia mas with ammonia, and ammonia water containing ammonia mas with ammonia with water at the second stage. In the proposed method, the stage of the beginning of desorption is considered the period from the beginning of the desorbent supply to the adsorber until the appearance of the required purity at the exit from the adsorber of paraffins. The drawing is a diagram explaining the essence of the method. Raw materials (kerosene-gas-oil fraction containing wt.% N-paraffins) fed to line 1 are mixed with a diluent gas stream containing 0.5–5 gd of d, esorbent fed through line 2, and the product of the start of desorption, fed line 3, is heated in a furnace A and fed to the adsorber 5, filled with zeolite 5A. The n-paraffin contained in the feedstock is adsorbed by the zeolite, and the mixture of the denormalized product, the diluent gas and the desorbent coming out of the adsorber enters the condensation column 6, where it is divided into a gas diluent containing vol.% Desorbent and a denormalized product with an admixture of desorbent, A denormalized product with an admixture of desorbent through line 7 is fed to the distant column 8, here a denormalized product is separated, which is then used as a component of low-cohesive diesel fuel and desorder bent, which is directed The diluent gas containing o6s% desorbent is fed to a low compression stage of desorbent 9 through line 10 from the condensation column 6 to the washing column.11, where 23-3b% of ammonia water supplied through line 12 is washed the distant column 13 performs washing of the gas diluent until the content of desorbent in it is 18-30 vol. Diluent gas,. containing 18-30 vol.% desorbent, from the washing column 11 enters the compressor and then to the washing column 15, where it washes the diluent gas to contain desorbent 0 contained therein, with ammonia water with an ammonia concentration of oil and ammonia. , containing 0, about, desorbent, on line 2 is directed to mixing with raw materials. Ammonia water 35 0% concentration from the washing column11 enters the distant column 13-, de due to a sharp decrease in pressure, a certain amount of desorbant is extracted from it, which is sent to receive a low stage of desorbent compression Y, and ammonia water with an ammonia concentration 23 -3b mass through line 12 from the bottom of the distant column 13 is returned to the column OTM61VKI 11. Ammonia water with an ammonia concentration of 23-28 May ,; From washing column 15 through line + 16, enters thermodesorber .17, where, due to the increase in temperature, a significant part of desorbent is removed from it, which is sent to a high stage of desorbent compression 18, ammonia water of 21% concentration is returned from thermodesorber 17 after cooling to the washing column 15o. At the end of the adsorption stage, adsorber 5 is rinsed with desorbent leaving furnace 19, the mixture of the product of the start of desorption of the first portions of desorbate, diluent gas and desorbent is fed via line 20 to condensation column 21, g do not separate the product of the start of desorption, which is fed to mixing with the raw material through line 3, and the mixture of gas diluent and desorbent, which is sent through line 22 to the washing column 11. The mixture of n-paraffins and desorbent, which is obtained from the adsorber 5 at the final desorption stage , are sent via line 23 to condensation column 2k, from where n-paraffins with admixture of desorbent enter the distant column 25 From the bottom of the distant column 25 send n-paraffins to the park, and desorbent from the top of the condensation column 2 and distant column 25 arrive at the reception accordingly about compressors of high 18 and low 9 pressure desorbent, Desorbent from the discharge of low pressure compressor desorbent 9 from the top of thermal desorber 17 and top of the condensation column 2. enters the intake of the high pressure compressor desorbent 18, and then through the furnace 19 to the adsorbers 5 for desorption Mixing gas- the diluent leaving the adsorber at the stage of adsorption, with the gas obtained at the stage of the beginning of desorption, and the subsequent supply of the gas mixture to the washing of ammonia according to the proposed method eliminates the ingress of the dilution gas I ate in the desorbent, which is the case e by proceeding according to the method of the received prototype This method allows to increase sustsestvenno chetkostrazdeleni diluent gas and desorbent and increase the purity of the gas flow, namely, the diluent gas and the desorbent. Washing the ammonia from the mixture of gases leaving the adsorber during adsorption and the beginning of desorption provides a practically pure diluent gas, and the subsequent removal of ammonia from ammonia water makes it possible to return an additional quantity of the adsorbent to the circulation. the degree of extraction of i-paraffins from the raw material, a large depth of desorption from zeolite n-paraffins and; their production increases, and the rate of coking of the zeolite decreases. The use of a two-stage scheme for washing the diluent gas from the desorbent according to the proposed method allows to achieve a higher purity of the diluent gas than in the prototype method, thereby significantly increasing the working capacity of molecular sieves over n-paraffins. Carrying out the washing of the gas with a diluent at different pressures and with mia water of different concentrations reduces the energy costs for cooling ammonia water, which is heated by the absorption of large amounts of ammonia. The cost of compression of the dilution gas is reduced, since, in accordance with the proposed method, a dilution gas containing 18–30 obD of desorbent is applied to the compressor intake (versus 30 AO by a known method). This makes it possible to reduce the required amount of diluent gas, to reduce its density. Deeper ammonia washing in the first stage is achieved by the fact that, according to the proposed separation method, de-normalization, gas diluent and removal of desorbent from it, not in one column, as in the known method, but in two, and in the first column the denormalization is separated from the gas the diluent and desorbent, and in the second - the gas diluent is washed from the desorbent. In this case, the consumption of ammonia water is reduced, since, in a known way, it was also spent on cooling the denormalized water and on washing the desorbent from it. The reduction of ammonia water consumption is also facilitated by the fact that the additional dilution of the gas diluent from the desorbent to its residual content of 0.5-5 vol. Is carried out according to the proposed method at an elevated pressure with water containing May .; ammonia, after compression of the diluent gas. This increases the ability of water to absorb desorbent (ammonia), reduces the flow of water with a diluent gas. The two circuits of ammonia water regeneration according to the described method provide the optimal depth of ammonia removal from ammonia water at the lowest cost. At the same time, at the first stage, the economical removal of the required amount of ammonia is achieved only by reducing the pressure to 1-1.5 at. Further removal of ammonia from ammonia water in this way would require a high vacuum, i.e. a vacuum compressor is needed, which significantly increases costs, so the removal of the desorbent from ammonia water. The second stage of washing is provided by heating it, using heat from the waste streams. The high temperature in the thermal desorber provides a decrease in the concentration of ammonia in ammonia water from 18-30 to 3-21 wt., And the increased pressure that is created in this 8 thermodesorber directs pure ammonia directly to the reception of a high degree of desorbent compression, which also reduces energy consumption . Ensuring the content in the diluent gas 0, the desorbent OBD allows to achieve the maximum capacity of molecular sieves and, therefore, maximum production of n-paraffins is achieved, the diluent gas and desorbent are more fully separated, the best desorbent purity is ensured. Achieving an even deeper cleaning of the diluent gas from the desorbent does not significantly affect the performance of the process, but it significantly increases operating costs and water consumption. The presence in the gas diluent more than 5 vol. desorbent leads to its competitive adsorption and significantly impairs the capacity of the zeolite, causes a decrease in paraffin production. Example 1. A hydrotreated fraction of 200-320 C of oil of the type of chamomile in the amount of 87, A t / h is diluted with a diluent gas containing about 6.% hydrogen and 0.5 parts of ammonia, in a volume ratio of diluent gas: feedstock - 300: 1, and fed to an adsorber filled with CaA zeolite containing ammonia from the previous desorption stage. H paraffins are adsorbed, and denormalized (t / h) and a diluent gas enriched with ammonia up to 40 are released from the adsorber. At the end of adsorption the zeolite layer is rinsed with desorbent. A stream comprising hydrocarbons of the feedstock is obtained, which after condensation is returned to the feedstock, and gas containing 68.8% ammonia. Subsequent delivery of de-Sorbent for desorption yields 17.7 tons of n-paraffins, each with a purity of mas. Gas flows from the adsorption and onset of desorption, after separation of hydrocarbons from them, are mixed and sent for washing from ammoniao. The first stage of washing is carried out at a pressure of 10 at. ammonia water concentration, the washed gas stream contains 18 vol. of ammonia. The gas flow is compressed and sent to the second stage of washing, where, at a pressure of 18 atm., Ammonia is washed from it at a concentration of ammonia water. residual content of 0.5% by volume. The resulting diluent gas containing 99.5 OBD of hydrogen and 0.5 OBD of ammonia is returned to mixing with the raw material. The ammonia water obtained in the first stage of the otmya, containing 35 masD of ammonia and under with a pressure of 10 atm, they are bypassed into a device operating under pressure of 1, it at, where, by reducing the pressure, ammonia is removed from it, which is returned to the desorbent circulation system. The ammonia water concentration is returned to the first stage of washing the gas diluent. Ammonia water of 23% concentration, obtained in the second stage of washing the diluent gas, is sent to thermodesorber, where ammonia is removed from it and returned to the desorbent circulation system. Ammonia water of 3.51% concentration is returned to the second stage of washing. The ammonia content in the circulating desorbent entering the desorption is E2%. Example 2. The process is carried out under conditions analogous to Example G, except that a diluent gas containing 10 OBD of ammonia and 95 OBD of hydrogen is fed to the mixture with the raw material. The diluent gas from the adsorption stage contains “W about% ammonia”, from the stage of the beginning of desorption — 72% by volume of ammonia. The gas mixture is washed in the first stage of washing with ammonia water of 30% concentration at a pressure of 6.8 atm to a residual ammonia content of 2b, 1 wt. The concentration of ammonia in ammonia water rises to 38 wt.%. In the second stage of washing, the ammonia is removed from the diluent gas at a pressure of 9 atm to a residual content of 5% of ammonia water of 20% concentration, which is saturated to a concentration. At the stage of desorption receive 17, t of n-paraffin 99.2 wt. purity, at the stage of adsorption of 70 tons of denormalized. Ammonia content in desorbent 90 The table shows the comparative data for the examples and the known method. Material balance: Something: raw materials, t 87, t 87, 87, i Obtained: liquid 17, 15.4 paraffins denorma 70, 0 72.0 lysate Clean desorbent (ammonia content), OBD 92 Service life 16000 8000 zeolite, h 17000 The content of n-paraffins in liquid para, 2 99.0 raffin, I 99.3 Duty cycle capacity, zeolite,% 2.5 As can be seen from the data in the table, the release of paraffins by the proposed method increases the cycle operating capacity of zeolite from 2, wt. .% up to 2pS masd, which makes it possible to increase the production of paraffins from, 15 to t, Toe, by 15%. The direction of the start gas desorption together with the gas after adsorption of ammonia according to the invention to washing it off improves the purity of the desorbent from 85 to 92, which ensures a greater depth of desorption of n-paraffins, leading to an increase in the production of n-paraffins and a decrease in the rate of coking adsorbent, due to which1 the interregeneration period of operation of 10 8 zeolite increases from c8 to 17 thousand hours. An increase in the desorbent purity of 5–7 ov.% Also allows obtaining higher purity paraffins at the desorption stage (by 0.2–0.3 wt.% Due to more efficient blowing of the molecular sieve layer before desorption of paraffins with a cleaner desorbent. Economic effect from the introduction of the invention is formed by increasing the yield of the target product (n-paraffin) from raw materials, which leads to a decrease in their cost by 3.2%. The increase in the service life of molecular sieves ensures a reduction in their consumption by 2 times.

Claims (3)

1. METHOD FOR ISOLATING N-PARAFFINS by adsorption of n-paraffins by zeolite 5A from petroleum feedstocks mixed with a diluent gas, separating the diluent gas from non-paraffin feedstock, followed by desorption of n-paraffins with ammonia, washing ammonia from the diluent gas with ammonia water and ammonia desorption from ammonia water by a decrease in pressure, characterized in that, in order to increase the capacity and extend the service life of the zeolite, to increase the purity of the desorbent, the diluent gas from the adsorption stage after separation from the non-paraffin feed they are mixed with a gas of the beginning of desorption, _t preliminarily purified from hydrocarbons, and the resulting gas mixture is subjected to two-stage washing from ammonia, and in the first stage, the gas mixture is washed to a residual ammonia content of 18-30 rd, and in the second stage to a residual ammonia content of 0.5 5 rd and the resulting diluent gas is mixed with the feed. . 2. The method according to claim ^ characterized in that the pressure na'pervoy · washing stage the gas mixture is maintained at 6-10 atm and the second-stage 9 ^- 18 at. 3. The method according to PP. 1 and 2, characterized in that the washing of the gas mixture in the first stage is carried out with ammonia water containing 23-3% by weight, ammonia, and in the second stage with ammonia water containing 3 ~ 21 May L ammonia.