RU2627847C2 - Method and column of absorption purification of gases from unintended impurities - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of absorption purification of gases from unintended impurities is proposed, comprising countercurrent contact of the purified gas and the regenerated absorbent in a mass transfer column to produce purified gas and a saturated absorbent, and a column for its implementation, a packed contact device of which is divided in height into independent mass transfer sections with a countercurrent or crosscurrent movement of the purified gas and the regenerated absorbent. The stream of the purified gas passes successively through all the independent mass transfer sections of the mass transfer column from the bottom up, the regenerated absorbent stream is injected into the top of each independent mass transfer section and the saturated absorbent stream is discharged from the bottom of each independent mass transfer section.

EFFECT: increased degree of purification.

16 cl, 7 dwg, 3 tbl

Description

The method and column for gas absorption absorption from undesirable impurities can be used for cleaning gas streams from impurities in a wide range of concentrations, as well as for separating gas mixtures into individual components at enterprises of the oil, gas, chemical and other industries.

A classic is the method of absorption gas purification from impurities of an undesirable component by a countercurrent contact of the gas to be purified and selective absorbent realized in column mass transfer apparatuses (Alexandrov I.A. Rectification and absorption devices. M. Chemistry. - 1971. - 296 p.), However The development of chemical technology increases the need for cleaning a mixture of gases from several undesirable impurities.

A known method and installation for the purification of natural gas from carbon dioxide and hydrogen sulfide in two stages of absorption: the first stage is selective purification with respect to carbon dioxide with the release of acid gas, in which the carbon dioxide content does not exceed 30-40%, and the purified gas with a content hydrogen sulfide not more than 5-7 mg / m ³ sent further to the second stage of absorption to obtain purified gas with a carbon dioxide content of not more than 50-200 mg / m ³ and the complete absence of hydrogen sulfide and acid gas containing sulfur hydrogen is not more than 200 mg / m ³ , while the saturation of the alkylamine absorbent at each stage of absorption with acidic components does not exceed 0.4 mol / mol, and natural gas has a ratio of hydrogen sulfide to carbon dioxide equal to 1.0, but not more than 1.5 and a concentration of hydrogen sulfide from 3.5 to 8.0% vol. (Patent for invention RU 2547021, IPC B01D 53/14, B01D 53/52, B01D 53/62, C10L3 / 10, pending 02.20.2014, published 04.10.2015). The disadvantages of this invention are:

the complexity of the technological scheme of the installation, associated primarily with the fact that various recoverable components are absorbed in different absorbers, forming a series of technological cycles within the same installation;

the inability to further cryogenic separation of ethane from the natural gas stream due to saturation of the gas to be cleaned with moisture upon contact with the absorbent;

a gradual increase in the concentration of methanol in the regenerated absorbent and a decrease in the absorbing ability of an aqueous solution of amines with respect to hydrogen sulfide and carbon dioxide, which results in the return of methanol together with condensed water to the regenerated absorbent during the regeneration of the absorbent in the presence of methanol in the incoming natural gas, which is dissolved in the absorbent together with hydrogen sulfide and carbon dioxide;

non-optimal functioning of the absorbent while absorbing hydrogen sulfide and carbon dioxide due to a drop in absorption capacity below potential.

A known method of processing natural gases, including the extraction of gases from water, carbon dioxide, hydrogen sulfide, hydrocarbons C ₂ and above, inert gases, characterized in that natural gases, significantly different in the content of impurities, are processed separately, while low-calorie natural gas containing dioxide more carbon than hydrogen sulfide, and with a high content of carbon dioxide, are processed sequentially in the first installation of deep amine purification from hydrogen sulfide and selective purification from carbon dioxide of the genus using aqueous solutions of alkyl amines as absorbent and in the second installation of deep amine purification of carbon dioxide using aqueous, mono-, di-, triethanolamine or mixtures thereof as absorbent, and high-calorific natural gas containing carbon dioxide is less than hydrogen sulfide, with a low content of carbon dioxide are processed at the installation of deep amine purification from carbon dioxide and hydrogen sulfide using mono-, di-, triethanolamine as an absorbent in aqueous solutions or mixtures thereof (patent for invention RU 2560406, IPC B01D 53/00, filed October 29, 2013, published August 20, 2015). The main disadvantage of this invention is the complexity of the technological scheme of the installation, associated primarily with the fact that various recoverable components are absorbed in different absorbers, even a change in the ratio of the initial recoverable components, for example, a change in the nature of the raw material from low-calorie to high-calorie, requires a change in technological schemes and, accordingly, the technological regime.

A known method of removing carbon dioxide from exhaust gases by absorption by a regenerated absorbent in a sectioned absorption column 13 with contact devices in its lower section 13A, partially purified exhaust gas from the lower section 13A is further purified and cooled by countercurrent water irrigation of the contact devices with respect to the cleaned exhaust gas in the upper section 13B, while part of the circulating water from section 13B is supplied to irrigate the contact devices of the middle part 13C section of the absorbed absorption column 13 is also countercurrent with respect to the exhaust gas being cleaned and then mixed with the absorbent in the upper part of section 13A, in particular, the cooled circulating water can be introduced into the partitioned absorption column 13 from the absorbent regeneration step (patent invention WO / 2014/024548, IPC B01D 53/62, B01D 53/14, C01B 31/20, announced May 29, 2013, published February 13, 2014). The disadvantages of the invention are:

1) the introduction of large amounts of water into the process, commensurate with the process productivity of the recoverable carbon dioxide in general, due to the low solubility of carbon dioxide in water, so at 21 ^° C temperature and 1 MPa pressure, only 0.33 volumes dissolve in 1 volume of water carbon dioxide, and at 40 ^° C temperature and 10 MPa pressure in 1 volume of water dissolves 1 volume of carbon dioxide;

2) a significant increase in additional energy consumption, which requires the use of inefficient circulating water irrigation of the upper section 13B, to drive a circulation pump and cool the circulating water;

3) reducing the absorption capacity of the main absorbing carbon dioxide absorbent by diluting it with water in the main absorption section 13A, leading to an additional liquid load of the absorbent regeneration column and an increase in energy consumption for regeneration;

4) low efficiency of section 13C, where the exhaust gas purified from carbon dioxide comes into contact with water already partially saturated with carbon dioxide at elevated gas temperature due to the release of heat of absorption in section 13A, which can lead to a negative process of carbon dioxide desorption from water.

A known absorber for removing carbon dioxide from exhaust gases by absorption by a regenerated absorbent in the form of a sectioned absorption column 13 with contact devices consisting of three sections: in the lower section 13A, the process of absorption cleaning of the exhaust gases entering the bottom of section 13A takes place, the absorbent entering the top of the section 13A, then the partially cleaned exhaust gas from the lower section 13A passes through the middle section 13C and through a blank plate is introduced into the bottom of section 13B, where it is further cleaned and cooled due to the circulation irrigation of the contact devices with water in countercurrent with respect to the exhaust gas being cleaned, while part of the circulating water from section 13B is supplied to the irrigation of the contact devices of the middle part 13C of the column 13 also in countercurrent with respect to the exhaust gas being purified and then mixed with the absorbent in the upper part section 13A (patent for invention WO / 2014/024548, IPC B01D 53/62, B01D 53/14, C01B 31/20, filed May 29, 2013, published February 13, 2014). The disadvantages of the invention are:

1) low efficiency of the contact devices in sections 13B and 13C, which leads to an increase in the volume of contact devices in these sections and, accordingly, the capital costs for the construction of the absorber, due to the poor solubility of carbon dioxide in water;

2) an additional increase in capital and operating costs due to the use of a circulation pump and a circulating water cooler in section 13B;

3) the need to maintain a high level of circulating water on a blank plate to ensure the operation of the circulation pump, leading to an additional increase in the height of the absorber without a corresponding increase in the efficiency of its work;

4) caused by a decrease in the absorbent capacity of the main absorbent and an increase in the volume of contact devices in section 13A due to dilution with water of the main absorbent of section 13A, which leads to a direct flow of water from the lower contact device of section 13C to the upper contact device of section 13A, an increase in capital construction costs absorber.

A direct-flow absorber is known comprising a housing with gas inlet and outlet fittings and liquid inlet and outlet fittings located inside the housing of a liquid distributor, a mass transfer section and a drop eliminator, characterized in that the mass transfer section is made in the form of horizontal shelves with regular plate packs placed on them nozzles, while a packet of regular nozzles is formed from individual corrugated sheets separated by spacers from a flat sheet, with the formation between the sheets of can catch (patent RU 2491982 C1, IPC B01D 53/18, 03.04.2012 pending, published 10.09.2013). The disadvantages of the invention are:

1) low efficiency of the direct-flow movement of the gas and liquid phases during absorption cleaning, due to the fact that at the final stage of the process, a highly saturated absorbent with a high concentration of the extracted component is in contact with a partially purified gas with a low concentration of the extracted component and even when the phase equilibrium is reached, a high cleaning depth gas will be unattainable;

2) partial separation of the gas and liquid phases sequentially alternating horizontally and from top to bottom instead of completely mixing the phases during the direct-flow phase movement in the mass transfer section, leading to the termination of mass transfer between phases in the zones of phase separation and to reduce the efficiency of the absorption process in the apparatus as a whole;

3) an increase in capital and operating costs for the implementation of the process, which leads to the need for a multiple increase in the height of the contact device and a sharp increase in pressure losses in the system due to an increase in the speed and length of the flow in the absorber to ensure the necessary contact time of the gas and liquid phases, since the necessary gas flow rate, which ensures the rise of liquid from the shelf and its distribution over the nozzle volume under the condition of direct flow, corresponds to the conditions of turbulization a liquid-gas system, and greatly exceeds the rate of gas flow at counterflow.

Also known is a fractionating absorber, in which there are absorption and stripping mass transfer sections, a feed zone with a nozzle for introducing a cleaned gas placed between them, an upper separation zone with nozzles for injecting an absorbent and a outlet for purified gas, and a lower separation zone with an absorber outlet nozzle, characterized in that the mass transfer sections are divided into two subsections, each of which contains at least one heat and mass transfer unit, equipped with nozzles for the inlet and outlet of the coolant or coolant, made of heat and mass transfer elements, for example, of a spiral-radial type, which form the inner space for the passage of the coolant or coolant and the outer space for countercurrent mass transfer between the gas and the falling film of liquid, while the absorbing outlet pipe and the lower stripping subsection adjacent to the supply zone, and also the outlet pipe of the purified gas and the upper pipe of the absorption subsection adjacent to the feed zone are pairwise connected by pipelines, and the outer space is heat and mass ennyh blocks filled absorber section mass transfer nozzle (patent RU 2530133 C1, IPC B01D 53/14, 06.11.2013 pending, published 10.10.2014). The disadvantages of the invention are:

1) violation of the hydrodynamic structure of gas and liquid flows in the nozzle in the zones of placement of heat-exchange structures, leading to an increase in the speed of phase flows, a decrease in the contact time of the phases and a decrease in the mass transfer efficiency in these zones;

2) the possible entrainment of droplet liquid to the overlying sections and due to this a decrease in mass transfer efficiency due to an increase in the flow rate of the gas phase in the nozzle in the areas of placement of heat-exchange structures;

3) the implementation of the placement of heat-exchange structures only in layers of an irregular nozzle, less effective from the standpoint of mass transfer compared to a regular nozzle.

Common disadvantages of the considered methods and devices for absorption cleaning of gases from several undesirable impurities are:

1) the non-optimal functioning of absorbents with simultaneous co-absorption of several impurities, leading to the need to increase the flow rate of the absorbent and increase in this regard the diameter of the absorption column and energy consumption for the regeneration of the absorbent;

2) the need for complex technological schemes with several closed absorption-regeneration cycles to ensure the necessary depth of gas purification from specific impurities;

3) leading to an increase in the diameter of the absorption column and an increase in the material consumption of the apparatus, introducing into the absorber the large consumption of absorbent material required for the purification of gases with a high concentration of recoverable impurities;

4) increasing the capacity, which requires a simultaneous increase in the consumption of absorbent, during the reconstruction of absorption gas treatment plants, limited by the diameter of the existing absorption column due to the limit of the liquid level in the liquid distributors and the bore of the contact devices for the liquid phase.

When creating the invention, the following tasks were set to expand the potential capabilities of the absorption method of gas purification from undesirable impurities and to improve the design of the absorption gas cleaning column:

1) separate use in a single apparatus of several absorbents, each of which selectively extracts a specific impurity from the stream of purified gas;

2) absorption extraction of each recoverable impurity in the optimal mode for it;

3) reducing the diameter of the column and its material consumption due to the fractional supply of absorbent to the absorption zone in the optimal mode;

4) a significant increase in the performance of the column during its reconstruction by increasing its height with a simultaneous equivalent increase in the supply of absorbent material without choking the contact mass transfer devices.

The solution to this problem is achieved by the fact that in the method of absorption cleaning of gases from unwanted impurities, including countercurrent contact of the gas to be purified and the regenerated absorbent in the mass transfer column to obtain purified gas and a saturated absorbent, the nozzle contact device of the mass transfer column is divided in height into independent mass transfer sections with countercurrent or cross-flow movement of the purified gas and the regenerated absorbent, while the flow of the purified gas is sequentially they are passed from bottom to top through all independent mass transfer sections of the mass transfer column, the regenerated absorbent stream is introduced into the upper part of each independent mass transfer section, and the saturated absorbent stream is withdrawn from the bottom of each independent mass transfer section. Such sectioning of the absorption process in the liquid phase (absorbent) allows for the continuous passage of the gas to be cleaned from bottom to top to form optimal conditions for gas absorption cleaning in each individual section, in particular, it becomes possible to increase the driving force of the absorption process and thereby intensify it, since in each section a regenerated absorbent is introduced, whereas usually in the absorption column, the gas to be purified is in contact with an already partially saturated absorbent along its height. In addition, by reducing the load of the contact devices of the mass transfer column in the liquid phase per one independent mass transfer section, it becomes possible to reduce the diameter of the mass transfer column, the passage section of the contact devices in the liquid phase and reduce the material consumption of the apparatus as a whole.

If there is one recoverable impurity in the gas to be cleaned, one type of selective regenerated absorbent is supplied to each independent mass transfer section and / or groups of adjacent independent mass transfer sections, the flow rate of which is determined in each section by the driving force of the absorption process in a particular section, while the flows of saturated absorbent derived from the lower part of each independent mass transfer section and / or a group of adjacent independent mass transfer sections, for regeneration are combined into a common flow outside the exchange column.

It is advisable that the change in the concentration of the recoverable impurity for each independent mass transfer section dC is assumed to be the same for all independent mass transfer sections and determined by the equation:

dC = (C _H - C _K ) / N,

where C _N is the concentration of the recoverable impurities in the gas to be purified at the inlet to the mass transfer column,

With _K is the concentration of the extracted impurities in the gas to be purified at the outlet of the mass transfer column,

N is the number of independent mass transfer sections along the height of the mass transfer column, since this ensures the same amount of regenerated absorbent supplied to each independent mass transfer section.

It is also possible to minimize the total flow rate of the regenerated absorbent by supplying the optimal flow rate of the regenerated absorbent to each independent mass transfer section, while the minimum flow rate of the regenerated absorbent is determined by such a distribution of the concentrations of recoverable impurities at the gas inlet to the j-th independent mass transfer section C _{H, J} and at the output out of her _{ck, j} that

Σ (С _{Н, J} - С _{К, J} ) / (K _* С _{К, J} ) = min,

where K is the Henry constant during absorption.

If there are two or more recoverable impurities in the feed gas that differ substantially in affinity for absorbents, an appropriate type of selective regenerated absorbent is fed to each independent mass transfer section and / or groups of adjacent independent mass transfer sections to extract a particular impurity, which allows optimal conditions for the absorption extraction of each of impurities, reduce the height and material intensity of the column. The temperature of the absorption cleaning in each independent mass transfer section is controlled by changing the temperature of the regenerated absorbent heated or cooled in additional external heat exchangers.

It is advisable to increase the extraction of a particular impurity in one or more independent mass transfer sections with cross-flow movement of the gas to be cleaned and the regenerated absorbent to carry out additional input of one or several streams of one type of selective regenerated absorbent to intermediate stages with the same or different parameters.

The problem is also solved by the fact that in the mass transfer column for gas absorption from unwanted impurities, including a vertical housing for counter-current contact of the gas to be cleaned and the regenerated absorbent in the nozzle contact device, the nozzle for the input of the purified and output of the purified gas, the nozzle contact device is divided in height into independent mass transfer sections with counter-current or cross-flow movement of the gas to be cleaned and the regenerated absorbent, each of which is independent the mass transfer section is separated from the adjacent independent mass transfer section by a blank plate and equipped with a low-pressure liquid distributor with a nozzle for introducing a regenerated absorbent in the upper part, while a blank plate is equipped with a battery for collecting saturated absorbent with a nozzle for removing a saturated absorbent from the mass transfer column casing and a nozzle for transition from the downstream independent mass transfer section to the upstream independent mass transfer section through g onion plate. Sectionalization of the height of the packed contact device with the formation of independent mass transfer sections and the individual supply of regenerated absorbent into them makes it possible to reduce the load of the liquid phase on the contact devices, to reduce their cross section and metal consumption of the apparatus as a whole.

It is advisable to use a regular nozzle of the PETON system in an independent mass transfer section with counter-current or cross-flow movement of the gas to be cleaned and the regenerated absorbent, which, when the gas and gas are regenerated in countercurrent movement, forms a developed phase interface and has a high porosity, and forms a separate mass-exchange section in cross-flow movement pack of nozzles with independent sections for the passage of the stream of gas to be cleaned horizontally and drain a sorbent vertical nozzle axis packet.

To achieve greater phase contact efficiency, it is advisable to use several intermediate stages of the regular nozzle of the PETON system in an independent mass transfer section with cross-flow movement of the gas to be cleaned and the regenerated absorbent separated by intermediate low-pressure liquid distributors and intermediate devices for introducing the regenerated absorbent.

It is advisable that the nozzles of two consecutively mounted blank plates be placed on opposite sides of the regular nozzle of the independent mass transfer section along the path of the gas to be cleaned.

In cases where several adjacent independent mass transfer sections use one type of absorbent, the outlet of the saturated absorbent from the body of the mass transfer column of the overlying independent mass transfer section and the nozzle of the input of the regenerated absorbent into the low-pressure liquid distributor of the underlying independent mass transfer section are provided with an overflow pipe, while gas purification from M adjacent independent mass transfer sections equipped with M-1 transfer pipe, forming there is a group of adjacent independent mass transfer sections into which one type of selective absorbent is fed. The number of adjacent independent mass transfer sections M in the group of adjacent independent mass transfer sections is determined from the condition:

,

,

where Z is the required depth of extraction of a particular impurity in this group of adjacent independent mass transfer sections,

Z _i - the depth of extraction of a particular impurity in one independent mass transfer section.

 The invention is illustrated by drawings, where in figures 1-7, containing the following positions, presents a number of options for the structural and technological solutions of the method and columns for the absorption of gases from unwanted impurities:

1 - a vertical casing of the mass transfer column;

2 - nozzle of the input of the purified gas;

3 - outlet fitting of purified gas;

4 - regular nozzle;

5 - low-pressure fluid dispenser;

6 - nozzle input regenerated absorbent;

7 - a blank plate;

8 - battery for collecting saturated absorbent;

9 - outlet fitting saturated absorbent;

10 - pipe;

11 - jumper;

12 - transfer pipe;

13 - closed valve;

14 - open valve.

The figure 1 shows a General view of the mass transfer column of gas absorption from unwanted impurities with a nozzle contact device in the form of a regular nozzle of the PETON system, divided into eight independent mass transfer sections with the possibility of introducing a regenerated absorbent and output of a saturated absorbent for each independent mass transfer section. The cleaned gas through the inlet of the cleaned gas 2 enters the vertical casing of the mass transfer column 1, where a regular nozzle 4 is placed in each of the eight independent mass transfer sections, and, moving successively from the bottom up, contacts the flow of regenerated absorbent directed to the top in each independent mass transfer section a part of each independent mass transfer section through the inlet of the regenerated absorbent 6 and a low-pressure liquid distributor 5. The resulting act partially purified gas through pipe 10 passes hollow plates 7 independent of mass transfer downstream section to the higher mass-transfer section for independent recesses purification by flow of fresh regenerated absorbent. The stream of purified gas after sequential passage from the bottom to the top of all independent mass transfer sections is discharged from the vertical casing of the mass transfer column 1 through the outlet of the purified gas 3. The stream of saturated absorbent after contact with the gas to be purified is accumulated in the battery to collect saturated absorbent 8 of the blank plate 7 and from there through the outlet nozzle saturated absorbent 9 is removed from each independent mass transfer section beyond the vertical casing of the mass transfer column 1 for conducting p regeneration. In order to prevent leakage of the gas being cleaned, a jumper 11 is installed in each independent mass transfer section, which, on the one hand, is interfaced with the vertical casing of the mass transfer column 1, and on the other, with a regular nozzle 4.

The figure 2 shows the principle of operation of one independent mass transfer section of the mass transfer column of gas absorption from unwanted impurities with cross-flow movement of the gas to be cleaned and the regenerated absorbent in the regular nozzle of the PETON system, where the flow of liquid absorbent is shown by solid lines with arrows, and by dotted lines the movement of the stream of gas being purified In the process of contact of the horizontal stream of the gas to be cleaned with the regenerated absorbent flowing downwards along the regular nozzle 4 in the film mode, the extracted impurity is transferred from the gas phase to the liquid one. The normal section of the mass transfer column due to the specifics of the design is partially filled with the nozzle contact device.

The figure 3 shows the principle of operation of one independent mass transfer section of the mass transfer column of gas absorption from unwanted impurities with countercurrent movement of the gas to be cleaned and the regenerated absorbent in a regular nozzle, where the flow of liquid absorbent is shown by solid lines with arrows, and the flow movement by dashed lines purified gas. In the process of contact of the vertical upward flow of the gas to be cleaned with the regular nozzle 4 descending in the film mode of the regenerated absorbent stream, the extracted component is transferred from the gas phase to the liquid one. The normal section of the mass transfer column due to the specifics of the design is completely filled with the nozzle device.

The figure 4 shows a variant of the operation of the mass transfer column for gas absorption from unwanted impurities with a packed contact device in the form of a regular nozzle, divided into eight independent mass transfer sections, in which a regenerated absorbent a ₁ p is introduced from above into each independent mass transfer section through a nozzle for input of the regenerated absorbent 6 and is output from below through the outlet connector of the saturated absorbent 9 saturated absorbent a ₁ N. In the process of contact of the horizontal stream of the gas to be cleaned with the regenerated absorbent flowing downwards in a regular packing 4 in the film mode, the extracted impurity is transferred from the gas phase to the liquid phase, while the stream of gas to be purified passes successively from the bottom up to all independent mass transfer sections in contact with a relatively small portion of the regenerated absorbent in each independent mass transfer section, which is equivalent to reducing the load in the liquid phase on the contact mass transfer devices a.

The figure 5 shows a variant of the operation of the mass transfer column of gas absorption from unwanted impurities with a packed contact device in the form of a regular nozzle, divided into eight independent mass transfer sections, in which impurities are extracted using two different regenerated absorbents a ₁ and a ₂ , which differ significantly in affinity for absorbents, while in each of the four lower independent mass transfer sections is introduced from above through the input nozzle of the regenerated absorbent 6 regenerated the absorbent a ₁ p and is discharged from below through the outlet port of the saturated absorbent 9 saturated absorbent a ₁ n, and into each of the four upper independent mass transfer sections, the regenerated absorbent a ₂ p is introduced from above through the inlet port of the regenerated absorbent 6 and is discharged from below through the outlet port of the saturated absorbent 9 saturated absorbent a ₂ N. The stream of gas to be purified passes sequentially from the bottom up to all independent mass transfer sections, in contact with a relatively small portion of the regenerated absorbent in each independent mass transfer section, which is equivalent to reducing the load on the liquid phase on the contact mass transfer devices. The use of two selective absorbents allows you to choose both the optimal flow rate of each absorbent and the corresponding technological regime for each independent mass transfer section, as well as the structural dimensions of the elements of the regular packing 4.

Figure 6 shows a variant of the operation of a mass transfer column for gas absorption from unwanted impurities with a packed contact device in the form of a regular nozzle, divided into eight independent mass transfer sections, in which impurities are extracted using three different regenerated absorbents a ₁ , ₂ and a ₃ , substantially characterized by affinity for absorbents, while in each of the two lower independent mass transfer sections is introduced from above through the input nozzle of the regenerated absorbent 6 regenerated th absorbent and ₁ p and discharged from the bottom through the connection output rich absorbent 9 saturated absorbent and ₁ N, in each of the four secondary independent mass transfer sections is introduced from above through a nozzle entering the regenerated absorption medium 6 regenerated absorbent and ₂ r and is discharged from the bottom through the connection output rich absorbent 9 saturated absorbent a ₂ N, and into each of the two upper independent mass transfer sections is introduced from above through the inlet of the regenerated absorbent 6; the regenerated absorbent a ₃ p and is discharged from below through the outlet connector of the saturated absorbent 9 saturated absorbent a ₃ N. The stream of gas to be purified passes sequentially from the bottom up to all independent mass transfer sections, in contact with a relatively small portion of the regenerated absorbent in each independent mass transfer section, which is equivalent to reducing the load on the liquid phase on the contact mass transfer devices. The use of three selective regenerated absorbents makes it possible to extract separately three impurity components from the gas to be cleaned, to select both the optimal flow rate of each absorbent and the corresponding technological regime for each independent mass transfer section, as well as the structural dimensions of the regular packing elements 4.

The figure 7 shows a variant of the operation of the mass transfer column of gas absorption from unwanted impurities with a packed contact device in the form of a regular nozzle, divided into eight independent mass transfer sections, in which three different regenerated absorbents a ₁ , ₂ and a ₃ are removed impurities characterized by affinity for absorbents, while the three lower independent mass transfer sections are combined into the first group of adjacent independent mass transfer sections using regrinding pipes 12, the top is injected through input socket in the first sections of the group of the regenerated absorption medium 6 regenerated absorbent and ₁ p and bottom removed through saturated absorbent output connector 9 saturated absorbent and ₁ N, two secondary independent mass exchange sections are combined into a second group of adjacent independent mass transfer sections using transfer pipe 12, from above into the second group of sections is introduced through the nozzle input regenerated absorbent 6 regenerated absorbent a ₂ p and from the bottom is discharged through the outlet fitting sat ennogo absorbent 9 saturated absorbent and _2N, and the top three independent mass exchange sections are combined into a third group of adjacent independent mass transfer sections by means of downcomers 12, from above into the third section group is introduced via the connection input regenerated absorption medium 6 regenerated absorbent and ₃ r and bottom removed through fitting 9 O saturated absorbent saturated absorbent and _3N, the downcomers 12 to open valves 14, and output fittings saturated absorbent 9 and the regenerated input absor Enta 6 for two adjacent sections closed valves 13. Thus, the mass transfer column for gas absorption from unwanted impurities with a regular contact packing device divided into eight independent mass transfer sections becomes equivalent to three classical absorption columns consisting of three, two and three sections in which various regenerated absorbents are used. The stream of gas to be purified passes sequentially from the bottom up to all three groups of independent mass transfer sections, in contact with relatively small portions of regenerated absorbent in each group of independent mass transfer sections, which is equivalent to a decrease in the liquid phase load on the contact mass transfer devices. The use of three selective regenerated absorbents makes it possible to separately extract three impurity components from the gas to be cleaned, to select both the optimal flow rate of each regenerated absorbent and the appropriate technological regime for each group of independent mass transfer sections, as well as the structural dimensions of the elements of the regular packing 4. In contrast to the variant shown in the figure 6, in this case there is no need for additional mixers to average the composition of the saturated absorbent before the reg nonration, withdrawn from the bottom of each independent mass transfer section through the outlet fitting of the saturated absorbent 9.

An additional advantage of the claimed invention is the simplicity of the reconstruction of the existing absorption columns to the features of the claimed invention, which consists in maintaining an intake mass transfer section and the outlet of the saturated absorbent 9 for each, while maintaining the body of the absorption column and active contact devices, each of which becomes an independent mass transfer section. independent mass transfer section, as well as deaf plates 7 with batteries for collection saturated absorbent 8.

The advantages of the claimed invention are illustrated by examples of calculation of mass transfer columns for gas absorption absorption from undesirable impurities, performed by the method of mathematical modeling of the ethane fraction purification process.

Initial data:

• consumption of ethane fraction - 100000 nm ³ / h (143700 kg / h);

• composition of the ethane fraction,% mass .:

 nitrogen - 1,368

 methane - 2,000

 ethane - 60,000

 hydrogen sulfide - 15.742

 carbon dioxide - 16,236

 propane - 4.644;

• composition of the regenerated absorbent,% mass .:

 diethanolamine - 16.141

 methyldiethanolamine - 16.872

 water - 66.872

 hydrogen sulfide - 0,081

 carbon dioxide - 0,034;

• pressure in the absorption column is 40 kg / cm ² ;

• temperature, ⁰ С:

 introducing purified gas into the column - 25;

 input regenerated absorbent - 40;

• the number of theoretical plates in the column is 8;

• the number of independent mass transfer sections, equivalent to one theoretical plate - 2;

• the height of one independent mass transfer sections is 1 m;

• the specific load in the liquid phase on the cross-flow contact device in horizontal section is 180 m ³ / (m ² * h);

• horizontal cross-sectional area of the contact device in a column with a diameter D is D ^2/4.

Example 1. The calculation of the process of purification of the ethane fraction from hydrogen sulfide and carbon dioxide with an aqueous solution of amines when the regenerated absorbent was fed to the top of the mass transfer column for gas purification from undesirable impurities and gradually saturating it with acidic components in the classic version of the absorption column corresponding to the variant of successive contact of the entire regenerated absorbent with purified gas on all contact devices of the apparatus in the form of eight theoretical plates, respectively uyuschih one group of independent mass transfer sections consisting of sixteen independent of mass transfer in a mass transfer column sections, equivalent to the classical countercurrent gas to be cleaned and the regenerated absorption medium in an absorption column as a prototype. The calculation results are shown in table 1. For effective purification of the ethane fraction from acid gases, it is necessary to ensure that the amount of 960 t / h of regenerated absorbent is introduced onto the top of the mass transfer column. In this case, the horizontal cross-sectional area of the packed contact device in the mass transfer column will be 5.3 m ² and the diameter of the column will be 4.6 m. The height of the mass transfer column will be 20.6 m.

Example 2. The calculation of the process of cleaning the ethane fraction from hydrogen sulfide and carbon dioxide with an aqueous solution of amines when dividing the mass transfer column of gas absorption from unwanted impurities into four groups of independent mass transfer sections, each group of independent mass transfer sections consists of four independent mass transfer sections and is equivalent to two theoretical plates. Regenerated absorbent is supplied in equal portions to the top of each group of independent mass transfer sections, comes into contact with a gradually refining ethane fraction and is removed after saturation with acidic impurities from the bottom of each group of independent mass transfer sections. The characteristics of the flows of gas and liquid phases for all four groups of independent mass transfer sections of the mass transfer column of gas absorption from undesirable impurities are shown in Table 2. For effective cleaning of the ethane fraction from acid gases, it is necessary to ensure that the top of each group of independent mass transfer sections of the mass transfer column of gas exchange absorption from unwanted impurities of the regenerated absorbent in an amount of 240 t / h In this case, the horizontal cross-sectional area of the packed contact device in the mass transfer column of gas absorption from undesirable impurities will be 1.3 m ² and the column diameter is 2.3 m. The height of the mass exchange column of gas absorption from undesirable impurities will be 18.3 m.

A comparison of the calculation results of examples 1 and 2 shows that as a result of the height-sectioning of the mass transfer column of gas absorption from undesirable impurities with the formation of independent mass transfer sections, combined into four groups of independent mass transfer sections and the individual supply of regenerated absorbent to them, the contact material consumption can be reduced four times devices of mass transfer columns for gas absorption absorption from undesirable impurities and, indirectly, twice as smart to increase capital costs for the manufacture of the column body with the practically equal quality of the final products - purified gas and saturated absorbent. So, for example, the content of ethane, hydrogen sulfide and carbon dioxide in the purified gas is 88.0951, 0.0002 and 0.0000% by mass, respectively, and in the prototype 88.0956, 0.0001 and 0.0000% by mass. when the content of these components in the source gas 60,000, 15,742 and 16.236% of the mass.

Example 3. The calculation of the process of cleaning the ethane fraction from hydrogen sulfide and carbon dioxide with an aqueous solution of amines when dividing the mass transfer column of gas absorption from unwanted impurities into three groups of independent mass transfer sections, each group is equivalent to two theoretical plates and consists of four independent mass transfer sections. Regenerated absorbent is supplied in equal portions to the top of each group of independent mass transfer sections, comes into contact with a gradually refining ethane fraction and is removed after saturation with acidic impurities from the bottom of each group of independent mass transfer sections. The characteristics of the flows of gas and liquid phases for all three groups of independent mass transfer sections of the mass transfer column of gas absorption from undesirable impurities are given in table 3. For effective purification of the ethane fraction from acid gases, it is necessary to provide the top of each group of independent mass transfer sections of the mass transfer column of gas exchange absorption from unwanted impurities of the regenerated absorbent in an amount of 240 t / h In this case, the horizontal cross-sectional area of the packed contact device in the mass transfer column of gas absorption from undesirable impurities, as in example 2, will be 1.3 m ² and the column diameter is 2.3 m. The height of the mass transfer column of gas absorption from undesirable impurities will be 14.3 m.

A comparison of the calculation results of examples 3 and 2 shows that as a result of the height-sectioning of the mass transfer column of gas absorption from unwanted impurities with the formation of independent mass transfer sections, combined into three groups of independent mass transfer sections and individually supplying the regenerated absorbent to them, the cleaning quality is compared to the process, implemented in four groups of independent mass transfer sections and the individual supply of regenerated absorbent into them, and the same, which allows in the third example, in comparison with the second, to reduce the consumption of regenerated absorbent by 25%, as well as to reduce the material consumption of the mass transfer column of gas absorption from undesirable impurities by 25%, and to reduce the material consumption by more than 2 compared to the first prototype example, 5 times with a similar reduction in the consumption of regenerated absorbent. In addition, taking into account the reduction in the consumption of regenerated absorbent circulating in the installation, the costs of regenerating a saturated absorbent will be reduced by 25%.

Thus, the claimed invention provides an effective solution to the problem of expanding the potential of the absorption method of gas purification from undesirable impurities and improving the design of the mass transfer column of gas absorption purification from undesirable impurities while significantly reducing the material consumption of equipment and / or operating costs for the regeneration of the absorbent.

Name of indicator Units rev. Gas to be cleaned Purified gas after 16 sections Regenerated absorbent Saturated Absorbent
after 16 sections Volumetric flow m ³ / h 100,000 71882 - - Mass flow t / h 143.70 95.85 960 1007.85 Component composition: % of the mass. - nitrogen
- methane
- ethane
- hydrogen sulfide
- carbon dioxide
- propane
- diethanolamine
- methyldiethanolamine
- water 1.3680
2,0000
60,0000
15,7420

16.2360
4.6540
-


-
- 2,0025
2,9387
88,0956
0.0001

0.0000
6.8578
-


-
0.1059 -
-
-
0.0810

0,0340
-
16.1410


16.8720
66.8720 0.0048
0.0060
0.1858
6.3414

2,3277

2,3477

15.3731
16,0688
63.6799

Table 1

Name of indicator Units rev. Purified Gas Regenerated Absorbent The first group of independent mass transfer sections
(sections 1-4) The second group of independent mass transfer sections
(sections 5-8) The third group of independent mass transfer sections
(sections 9-12) The fourth group of independent mass transfer sections
(sections 13-16) Purified gas Saturated Absorbent Purified gas Saturated Absorbent Clean gas Saturated Absorbent Purified gas Saturated Absorbent Volumetric flow m ³ / h 100,000 - 85615 230 74221 227 72239 217 71882 216 Mass flow t / h 143.70 240 119.90 263.80 99.45 260.45 96.32 243.13 95.85 240.46 Component composition: % of the mass. - nitrogen
- methane
- ethane
- hydrogen sulfide
- carbon dioxide
- propane
- diethanolamine
- methyldiethanolamine
- water 1.3680
2,0000
60,0000
15,7420

16.2360
4.6540
-


-
- -
-
-
0.0810

0,0340
-
16.1410


16.8720
66.8720 1,6308
2,3851
71,5009
5,0778

13.5087
5.5484
-


-
0.3483 0.0040
0.0054
0.1869
6.3414

2,7361
0.0132
14.6846


15,3491
60,6792 1.9544
2.8600
85.7084
0.7854

1.6970
6,6551
-


-
0.3396 0.0045
0.0059
0.1891
2,1127

5.6026
0.0130
14.8737


15,5468
61.6517 2,0063
2,9392
88.0863
0,0002

-
6.8468
-


-
0,1212 0.0046
0.0055
0.1622
0.4015

0.7283
0.0098
15,9331


16.6542
66,1009 2,0039
2,9395
88,0951
0,0002

-
6.8553
-


-
0.1061 0.0048
0.0056
0.1661
0.0813

0,0345
0.0098
16,1099


16.8390
66,7490

table 2

Parameter Units rev. Gas to be cleaned Regenerated Absorbent Characterization of the end products of the column with three groups of independent mass transfer sections
(sections 1-12) Characterization of the end products of the column with four groups of independent mass transfer sections
(sections 1-16) Purified gas
after 12 section Saturated Absorbent
after 1 section Purified gas after 16 sections Saturated Absorbent
after 1 section Volumetric flow m ³ / h 100,000 - 72239 230 71882 230 Mass flow kg / h 143.70 240 96.32 263.80 95.85 263.80 Content: % of the mass. - nitrogen
- methane
- ethane
- hydrogen sulfide
- carbon dioxide
- propane
- diethanolamine
- methyldiethanolamine
- water 1.3680
2,0000
60,0000
15,7420

16.2360
4.6540
-


-
- -
-
-
0.0810

0,0340
-
16.1410


16.8720
66.8720 2,0063
2,9392
88.0863
0,0002

-
6.8468
0.0000


0.0000
0,1212 0.0040
0.0054
0.1869
6.3414

2,7361
0.0132
14.6846


15,3491
60,6792 2,0039
2,9395
88,0951
0,0002

-
6.8553
-


-
0.1061 0.0040
0.0054
0.1869
6.3414

2,7361
0.0132
14.6846


15,3491
60,6792

Table 3

Claims (25)

1. The method of absorption cleaning of gases from unwanted impurities, comprising countercurrent contact of the gas to be purified and the regenerated absorbent in the mass transfer column to obtain purified gas and saturated absorbent, characterized in that the nozzle contact device of the mass transfer column is divided in height into independent mass transfer sections with countercurrent or cross-flow movement cleaned gas and regenerated absorbent, while the flow of cleaned gas is sequentially passed through all independently The mass transfer sections of the mass transfer column are from bottom to top, the regenerated absorbent stream is introduced into the upper part of each independent mass transfer section, and the saturated absorbent stream is removed from the bottom of each independent mass transfer section. 2. The method according to p. 1, characterized in that if there is one extractable impurity in the gas to be cleaned, one type of selective regenerated absorbent is supplied to each independent mass transfer section and / or groups of adjacent independent mass transfer sections. 3. The method according to p. 2, characterized in that the saturated absorbent streams withdrawn from the bottom of each independent mass transfer section and / or a group of adjacent independent mass transfer sections are combined into a common stream outside the mass transfer column for regeneration. 4. The method according to p. 3, characterized in that the change in the concentration of the extracted impurity for each independent mass transfer section dC is the same for all independent mass transfer sections and is determined by the equation:

where C _H is the concentration of the recoverable impurities in the gas to be purified at the inlet to the mass transfer column, C _K is the concentration of the extracted impurities in the gas to be purified at the outlet of the mass transfer column, N is the number of independent mass transfer sections along the height of the mass transfer column. 5. The method according to p. 2, characterized in that the regenerated absorbent is supplied to each independent mass transfer section in the same amount. 6. The method according to p. 5, characterized in that the minimum flow rate of the regenerated absorbent is determined by such a distribution of the concentrations of the extracted impurity at the gas inlet to the j-th independent mass transfer section C _{H, J} and at the outlet from it C _{K, J} , which

where K is the Henry constant during absorption. 7. The method according to p. 1, characterized in that in the presence of two or more recoverable impurities in the gas to be cleaned that differ substantially in affinity for absorbents, each independent mass transfer section and / or groups of adjacent independent mass transfer sections provide a specific type of selective impurity to extract regenerated absorbent. 8. The method according to p. 1, characterized in that the temperature of the absorption cleaning in each independent mass transfer section is controlled by changing the temperature of the regenerated absorbent heated or cooled in additional external heat exchangers. 9. The method according to p. 1, characterized in that in one or more independent mass transfer sections with cross-flow movement of the gas to be cleaned and the regenerated absorbent, one or more streams of one type of selective regenerated absorbent are introduced into the intermediate stages with the same or different parameters. 10. Mass-exchange column for gas absorption absorption from undesirable impurities, including a vertical housing for counter-current contact of the gas to be cleaned and the regenerated absorbent in the nozzle contact device, the nozzle for the input of the gas to be purified and the purified gas outlet, characterized in that the nozzle contact device is divided in height into independent mass-exchange sections with counter-current or cross-flow movement of the gas to be cleaned and the regenerated absorbent, with each independent mass transfer The section is separated from the adjacent independent mass transfer section by a blank plate and equipped with a low-pressure liquid distributor with a nozzle for inputting a regenerated absorbent in the upper part, and a blank plate is equipped with a battery for collecting saturated absorbent with a nozzle for removing saturated absorbent from the body of the mass transfer column and a nozzle for transferring purified gas from the lower an independent mass transfer section into an upstream independent mass transfer section through a blank plate. 11. The column according to claim 10, characterized in that in the independent mass transfer section with counter-current or cross-flow movement of the gas to be cleaned and the regenerated absorbent, a regular nozzle of the PETON system is used. 12. The column according to claim 10, characterized in that in an independent mass transfer section with cross-flow movement of the gas to be cleaned and the regenerated absorbent, several intermediate stages of the PETON system regular nozzle are used, separated by intermediate low-pressure liquid distributors and intermediate devices for introducing the regenerated absorbent. 13. The column according to claim 10, characterized in that the nozzles of two consecutive blank plates are placed on different sides from the regular nozzle of an independent mass transfer section in the direction of the gas being purified. 14. The column according to claim 10, characterized in that the outlet fitting for the saturated absorbent from the body of the mass transfer column of the overlying independent mass transfer section and the nozzle for introducing the regenerated absorbent into the low-pressure liquid distributor of the underlying independent mass transfer section are provided with a transfer pipe. 15. The column according to claim 14, characterized in that M adjacent independent mass transfer sections equipped with an M-1 transfer pipe form a group of adjacent independent mass transfer sections into which one type of selective absorbent is fed. 16. The column according to p. 15, characterized in that the number of adjacent independent independent mass transfer sections M in the group of adjacent independent mass transfer sections is determined from the condition:

where Z is the required depth of extraction of a particular impurity in this group of adjacent independent mass transfer sections, Z _j - the depth of extraction of a particular impurity in one independent mass transfer section.

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