RU2252063C1 - Method of purification of gas mixtures from carbon dioxide (alternatives) and a device for purification of gas mixtures from carbon dioxide (alternatives) - Google Patents

Abstract

FIELD: petrochemical and chemical industry; purification of gas mixtures from carbon dioxide.

SUBSTANCE: the invention is pertaining to the field of purification of gas mixtures from carbon dioxide. Absorption is conducted using wipers with resistance by a gas of no more than 50 kPa. At that a solution of ethanolamine in the process of the absorption at least once is subjected to intercooling to 30-35°C. Fine regeneration of a stream of a solution of ethanolamine is realized by its treatment with machining by a live steam. The absorber is made with packet-type nozzles and contains in its middle part at least one contour of cooling made in the form of a device of withdrawal of a partially saturated solution of the absorbent cyclically linked with an intermediate container and an intermediate cooler. A hot-water boiler of the regenerator-recuperator is made in the form of the sections in series located in its lower part. The sections are consisting of heat exchangers placed on plates. At that the number of the sections of the hot-water boiler is chosen within the limits from three to six. In the double-flow circuit the outlet of the roughly regenerated absorbent is made in the form of an outlet of the blank plate located under the hot-water boiler. The regenerator-recuperator in its lower part above an outlet of the finely regenerated absorbent is supplied with an inlet of the steam feeding and with three or four steaming plates located above it. The invention allows to reduce an over-all excessive pressure of the process of purification of gas mixtures from carbon dioxide and its partial pressure, to reduce specific power inputs for purification and also to expand the field of application of the ethanolamine purification.

EFFECT: the invention allows to reduce the over-all excessive and partial pressure of the process of gas mixtures purification from carbon dioxide and to expand the field of the ethanolamine purification application.

12 cl, 7 ex, 3 dwg

Description

The invention relates to the field of purification of gas mixtures from carbon dioxide and can be used in the chemical, metallurgical, fuel and energy and food industries.

Known technical solutions for the purification of gas mixtures from carbon dioxide, including to obtain marketable carbon dioxide, used, for example:

- in the chemical industry in the production of ammonia;

- in metallurgy, in blast furnace production and in the process of direct reduction of iron;

- in the energy sector for flue gas cleaning.

Cleaning methods are classified into physical, for example, using condensation and dissolution processes, and physicochemical using adsorption or absorption effects, including chemisorption.

The most widely used chemisorption purification methods [Reference nitrogen. 2nd ed., M., Chemistry, 1986, p.221-290], in which as absorbents are used:

- various organic compounds, such as alcohols, amides, polyesters and others, which are used mainly at high partial pressures of carbon dioxide in separated gas mixtures;

- aqueous solutions of alkaline carbonates, in particular with activating additives in the form of amines, borates, amino acids and others, also used when necessary to remove large quantities of carbon dioxide at its high partial pressure;

- aqueous solutions of ethanolanolamines (EA - hereinafter, the generally accepted abbreviations of the most common solutions are given), in particular monoethanolamine (MEA), dimethanolamine (DEA), methyldiethanolamine (MDEA) or activated methyldiethanolamine (AMDEA).

The technical and economic efficiency of the implementation of industrial gas cleaning methods is mainly characterized by capital intensity and the level of current costs. The capital intensity of the method depends on the volume and mass of the main units, as well as on the type of materials used for their manufacture. The amount of absorbent in the cycle depends on the volume of aggregates, the cost of which partially lies on the capital intensity of the process at the initial start-up, and partially on current costs for replenishing losses. Current costs are mainly associated with energy costs (process steam) for heating the solvent during its regeneration and energy costs (electricity) for pumping it inside the cycle, including changes in operating pressure.

Currently, there are no technical solutions that allow gas mixtures with a low partial pressure of CO _{2 to be} removed from carbon dioxide at low cost and high quality.

A known method of removing acid gases, such as hydrogen sulfide and / or carbon dioxide, from a gaseous mixture [Description of the invention to the patent of the Russian Federation No. 2087181, IPC ⁶ V 01 D 53/14, publ. 08/20/1997. Bull. No. 23], including the absorption of acid gases by an aqueous solution of dimethylethanolamine (MDEA) at a concentration of 40-70% at a temperature in the absorber of 50-70 ° C and the pressure of the gas mixture passing through the absorber 7 MPa. The spent aqueous solution is subjected to regeneration by heating to 120 ° C at a pressure of 0.12 MPa in the regeneration column. The solution pressure at the outlet of the absorber before being fed to the regeneration column is reduced from 7.0 to 0.12 MPa using a special valve, and after regeneration it is again increased from 0.12 to 7.0 MPa with a special pump. The primary heating of the solution for its regeneration is carried out in a remote heat exchanger due to the heat of the solution exiting the regenerator, and the heating of the solution to the final regeneration temperature of 120 ° C is carried out in a remote heater (boiler). This method successfully combines capital intensity and current costs.

Among the disadvantages of the method should be noted:

- high overpressure of the gas mixture during absorption;

- the need for periodic dropping and increasing the pressure of the solution. With large flows of the solution, the cost of electricity for its compression and pumping is unreasonably high, and when the pressure is released, a significant part of the potential energy of the compressed solution is scattered idle;

- inefficient heat transfer in external heat exchangers during heat recovery of the regenerated solution and heating the solution in the boiler, leading to excessive heat loss.

The description of the method does not provide data on specific energy consumption for cleaning the gas mixture, but practice shows that they can be at least 3.5 MJ / kg CO ₂ .

A variant of the previous method is the technology for removing carbon dioxide and / or hydrogen sulfide from gaseous mixtures [Description of the invention to the patent of the Russian Federation No. 2072886, IPC ⁶ V 01 D 53/14, publ. 02/10/1997. Bull. No. 4], including their absorption with an aqueous solution of dimethylethanolamine and regeneration of the spent solution of dimethylethanolamine by desorption, while the aqueous solution of dimethylethanolamine is used with a concentration of 35-55 wt.% In a mixture with a promoter. A distinctive feature of this process is the working pressure at which the absorption process occurs, about 7 MPa.

The use of activators is effective only for small volumes of gas to be purified and, accordingly, low consumption of absorbent liquid.

Also known is a method of removing CO ₂ and / or H ₂ S from gases [Description of the invention to US patent No. 4551158, Ncl. 95-175 (55/46), publ. 11/05/1985], including the absorption of CO ₂ and / or H ₂ S with an aqueous solution of methyldiethanol ethanolamine (MDEA) of a concentration of 20-70% at a temperature of 40-100 ° C and a pressure in the absorber of 1-11 MPa, followed by regeneration of the absorption liquid at a reduced to 0 , 05-0.10 MPa pressure and temperature 120 ° C. The pressure relief for regeneration in this method is carried out using an ejector or injector, which is simultaneously supplied with steam, replenishing water losses in the solution cycle and increasing the depth of its regeneration. In addition, the regeneration process is carried out in two stages, in the first of which the saturated solution is heated by using the heat of the regenerated solution, and in the second, by self-heating in a remote heater.

In this method, the disadvantages of the method according to the above patent of the Russian Federation No. 2087181 are partially overcome, in particular, a more efficient heat exchange is carried out in the ejector and part of the compression energy of the solution is utilized, but the high overpressure of the process and the need for its further discharge and increase, as well as inefficient heating to the final regeneration temperature 120 ° C in the remote circuit. The description of the method also lacks data on the energy intensity of the process, but according to preliminary estimates, they should be at least 3.0 MJ / kg CO ₂ .

The closest in the set of essential features of the claimed method is the chemo-selective process of purification of gases from CO _{2 with an} aqueous solution of monoethanolamine (MEA) [Nitrogen Reference: Physico-chemical properties of gases and liquids. Process gas production. Process gas cleaning. The synthesis of ammonia. - 2nd ed. M .: Chemistry, 1986, p. 259-263]. The method includes the absorption of a gas mixture under pressure up to 3 MPa with an aqueous solution of monoethanolamine of a concentration of 17-20% on the contact devices of the absorber at a temperature of 35-50 ° C, subsequent regeneration of the saturated solution in the regenerator-recuperator by dividing the solution flow into a series of cascades in which the temperature successively increase in the direction of movement of the solution to 120-125 ° C at a pressure of 0.67-0.235 MPa, and the return of the regenerated ethanolamine solution to the absorber. The main distinguishing feature of this method is the combination of the processes of the initial regeneration of the solution with the heat recovery of a fully heated regenerated solution, which is used to heat the solution in the initial stage of regeneration. This technique reduces energy consumption for heating the solution, increases the driving force of regeneration and reduces current operating costs. This method provides the purification of 220,000 nm ³ / h of synthesis gas under a pressure of 2.5 MPa (2500 kPa) with a partial pressure of carbon dioxide of 0.425 MPa (450 kPa), from the initial carbon dioxide content of 17% to a residual content of 0.004% with specific an energy cost of 2.30 MJ / kg CO ₂ . The method employs a two-stream movement pattern of a regenerated absorbent, in which the coarsely and finely regenerated parts of the stream are selected and fed in different zones of the technological units.

The disadvantages of the method include the need to maintain a relatively high overpressure of the cleaned gas mixture and the complexity of the implementation scheme. And although the method can be used at a reduced absorption pressure close to atmospheric (for example, 250-350 kPa), the specific energy consumption for cleaning can be 5.8-6.7 MJ / kg CO ₂ . In this case, the increase in energy consumption is due to a decrease in the partial pressure of CO ₂ , which leads to a decrease in the absorption capacity of the absorbent and a noticeable increase in the volume of the circulated solution. For this reason, this method has limited use.

The technical result of the first invention of the group is to reduce the total overpressure of the gas mixture purification process and the partial pressure of carbon dioxide, reduce the specific energy consumption for gas purification from carbon dioxide, and also expand the scope of ethanolamine purification - its distribution to the purification of blast furnace top gas for its recycling, reducing gas purification in the production of sponge iron and flue gas purification with the release of marketable carbon dioxide Oh yeah.

To achieve the claimed technical result in a known method for purifying gas mixtures of carbon dioxide, which includes absorbing a pressurized gas mixture with aqueous solutions of ethanolamines in an absorber, subsequent regeneration of a saturated solution by heating in a regenerator-recuperator by dividing it into a series of cascades in which the temperature is successively increased by the direction of movement of the solution, and the return of the regenerated ethanolamine solution to the absorber, the absorption of carbon dioxide is carried out on contact x devices with a gas resistance of not more than 50 kPa, while the ethanolamine solution in the absorption process is subjected to intermediate cooling at least once to 30-35 ° C.

In addition, when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa or 500-700 kPa and the carbon dioxide content in the gas mixture is in the range of 4-8% or 25-45%, respectively, monoethanolamine at a concentration of 1 is used as the absorbent. , 8-3.0 kMol / m ³ , and when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa and the carbon dioxide content in the gas mixture is in the range of 25-45%, methyldiethanolamine in the concentration of 1.8- 3.0 kMol / m ³ .

The prior art for the second variant of the method of purification of gas mixtures from carbon dioxide (the second invention of the group) includes the same information as for the first variant.

The technical result of the second invention of the group is also to reduce the total overpressure of the process, the partial pressure of carbon dioxide, reduce the specific energy consumption for gas purification from carbon dioxide, as well as expand the scope of ethanolamine purification - its distribution to the purification of blast furnace top gas in order to recycle it, purification of reducing gas in the production of sponge iron and purification of flue gases with the release of marketable carbon dioxide.

A variant of the method for removing carbon dioxide from a gas mixture, including the absorption of a pressurized gas mixture with aqueous solutions of ethanolamines in an absorber, subsequent regeneration of a saturated solution by heating in a regenerator-recuperator by dividing it into a number of cascades in which the temperature is successively increased in the direction of movement of the solution, followed by separation regenerated ethanolamine solution into coarse and finely regenerated streams, and their association in the absorber after preliminary injection feeding into it a finely regenerated stream is a method in which carbon dioxide is absorbed on contact devices with a gas resistance of not more than 50 kPa, while the ethanolamine solution in the process of absorption is subjected to intermediate cooling at least once to 30-35 ° С and thin regeneration of the ethanolamine solution stream is carried out by its treatment with sharp water vapor. Besides:

- as a source of acute water vapor for fine regeneration of one of the ethanolamine solution streams, evaporated phlegm is used;

- when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa or 500-700 kPa and the content of carbon dioxide in the gas mixture is in the range of 4-8% or 25-45%, respectively, monoethanolamine in the concentration of 1.8 is used as the absorbent -3.0 kMol / m ³ , and when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa and the carbon dioxide content in the gas mixture is in the range of 25-45%, methyldiethanolamine in the concentration of 1.8-3 is used as the absorbent, 0 kMol / m ³ .

To implement absorption cleaning methods, aggregates are used, consisting of absorbers, regenerators, pipelines, pumping and heat exchange equipment, providing continuous removal of carbon dioxide from the gas to be cleaned.

A device is known that implements a method for removing acid gases, such as hydrogen sulfide and / or carbon dioxide, from a gaseous mixture [Description of the invention to the RF patent No. 2087181, IPC ⁶ V 01 D 53/14, publ. 08/20/1997. Bull. No. 23], including an absorber, a recovery column, a pressure relief valve, remote heat exchangers for heating the solution, a condenser for separating carbon dioxide, pumps and pipelines.

The disadvantages of the known device are the design complexity, increased material consumption, which last but not least depends on the high working pressure in the absorber, and low work efficiency (increased energy consumption).

A device is also known, the technical essence of which is disclosed in the invention “Removal of CO ₂ and / or H ₂ S from Gases” [Description of the invention to US patent No. 4551158, Ncl. 95-175 (55/46), publ. 11/05/1985]. The device includes an absorber, two regeneration columns connected in series through a remote heater (boiler), an ejector for relieving pressure, a remote heat exchanger for regenerative heating of the solution, a condenser for separating carbon dioxide, pumps and pipelines.

The disadvantages of this device are the relative complexity of the design, increased material consumption and low work efficiency (increased power consumption).

A known installation for the purification of converted gas from carbon dioxide [Description of the invention to the copyright certificate of the USSR No. 1255178, IPC ⁴ V 01 D 53/18, publ. 09/07/1986. Bull. No. 33], which contains an absorber, a regenerator with points of entry of a partially regenerated absorbent and an outlet of a gas-vapor mixture, recuperative heat exchangers installed in series on the flow of the regenerated absorbent, and an intermediate stripper connected to the regenerator by two or more supply paths of the partially regenerated absorbent. Part of the regenerated absorbent stream, connected to the upper point of the input of the regenerator, is subjected to forced cooling.

The disadvantages of the installation include the complexity of the design and, as a result, the material consumption of the equipment.

The closest to the set of essential features of the claimed device is a unit of monoethanolamine purification of gas mixtures with the regeneration of the solution in the regenerator-recuperator [Nitrogen reference book: Physico-chemical properties of gases and liquids. Process gas production. Process gas cleaning. The synthesis of ammonia. - 2nd ed., Moscow: Chemistry, 1986, p. 259-263, Fig. III-38], better known among specialists as “AM-76 Unit” (labeled by the State Institute of Nitrogen Industry - GIAP). The unit includes an absorber with a contact device made in the form of high-layer sieve trays with inlets of a thinly and coarsely regenerated absorbent and an outlet of a saturated solution, a regenerator-recuperator with an inlet of a saturated solution and two outputs of a coarse and finely regenerated absorbent located in two levels, plates with built-in heat exchange associated with the exit of the coarse regenerated absorbent and the inlet of the coarse absorbent absorbent, contaminated and pure dioxide capacitors carbon with reflux, refrigerators of coarse and finely regenerated absorbent solutions, a remote boiler for heating the regenerator cube, as well as a system of pumps, pipelines and shut-off and control elements.

The main disadvantages of this device are its increased material consumption due to the need to maintain a sufficiently high overpressure of the process, insufficiently high work efficiency and the scope of application limited by the nitrogen industry.

The technical result of the third invention of the group is to simplify the design by combining the functions of the heater (boiler) of the regenerator with the actual regenerator (mass transfer apparatus), reducing the total overpressure of the process and the partial pressure of carbon dioxide by changing the configuration of the flows, reducing the specific energy consumption for cleaning gas from carbon dioxide by reducing heat-scattering surfaces, as well as expanding the scope of ethanolamine cleaning - its distribution e on the processes of purification of blast furnace top gas for the purpose of its recycling, purification of reducing gas in the production of sponge iron and purification of flue gases with the release of marketable carbon dioxide.

To achieve the claimed technical result in a known device for cleaning gas mixtures of carbon dioxide, containing an absorber with an inlet of an absorbent and an outlet of a saturated solution, a regenerator-recuperator with an inlet of a saturated solution and an outlet of a regenerated absorbent, plates with built-in heat exchangers connected with the outlet of the regenerated absorbent, and boiler, condenser-separator of carbon dioxide with reflux output, refrigerator of the regenerated absorbent, pumps, pipelines and shut-off valves walking elements, the absorber is made with packet nozzles and contains in its middle part at least one cooling circuit made in the form of a device for selecting a partially saturated absorbent solution cyclically connected with an intermediate tank and an intermediate cooler, and the boiler of the regenerator-recuperator is made in the form sequentially located in its lower part of the sections, consisting of heat exchangers placed on the plates, while the number of sections of the boiler is selected in the range from three to six. It should be noted that the device for selecting a partially saturated absorbent solution can be made in the form of a blank plate with a neck and an outlet, while the cooling circuit includes an additional inlet located on the absorber below the blank plate.

The prior art for the second variant of the device for cleaning gas mixtures of carbon dioxide (the fourth invention of the group) includes the same information as for the third invention.

The technical result of the fourth invention of the group is also to simplify the design by combining the functions of the heater (boiler) of the regenerator with the regenerator itself (mass transfer apparatus), reducing the total overpressure of the process and the partial pressure of carbon dioxide by changing the configuration of the flows, reducing the specific energy consumption for cleaning gas from dioxide carbon by reducing heat dissipating surfaces, as well as expanding the scope of ethanolamine purification - its distribution Suggested Measures on the top gas cleaning processes blast furnace with a view to recycle reducing gas purification in the production of sponge iron and purification of flue gases with the release of carbon dioxide commodity.

A variant of the device for cleaning carbon dioxide gas mixtures, which includes an absorber with inlets of a finely and coarse absorbent and an outlet of a saturated solution, a regenerator-recuperator with an inlet of a saturated solution and two exits of a coarse and finely regenerated absorbent located at two levels, plates with built-in heat exchangers, connected with the exit of the coarsely regenerated absorbent and the inlet of the coarsely regenerated absorbent of the absorber, and a boiler, a carbon dioxide condenser-separator with The output of reflux, a refrigerator of a regenerated absorbent, pumps, pipelines and shut-off and control elements is a device in which the absorber is made with packet nozzles and contains in its middle part at least one cooling circuit made in the form of a device for selecting a partially saturated absorbent solution cyclically connected with the intermediate tank and the intermediate cooler, the inlet of the coarsely absorbed absorbent absorber is located in the area between the inlet of the finely regenerated absorbent and torn from the cooling circuits, and the boiler of the regenerator-recuperator is made in the form of sections sequentially located in its lower part, consisting of heat exchangers placed on plates, while the number of sections of the boiler is selected from three to six, the output of the roughly regenerated absorbent is made in the form of an outlet located under the boiler of a blank plate, including the neck and bypass pipes, in addition, the regenerator-recuperator in its lower part above the outlet of the finely regenerated absorbent sn It is loaded with a water vapor inlet and three or four stripping plates located above it, and the input of the finely regenerated absorbent of the absorber is connected to the output of the finely regenerated absorbent of the regenerator-recuperator through an external heat exchanger.

In addition, the device for the selection of a partially saturated solution of the absorbent absorber is made in the form of a blank plate with a neck and outlet, while the cooling circuit includes an additional inlet located on the absorber below the blank plate, and the input of the supply of sharp water vapor to the regenerator-recuperator can be equipped with an additional heat exchanger the input of which is connected to the reflux output from the carbon dioxide capacitor-separator.

The invention is illustrated by drawings, where:

- figure 1 shows a diagram of a single-threaded device for cleaning gas mixtures from carbon dioxide (the first version of the device that implements the first version of the method);

- figure 2 is a diagram of a dual-stream device for purifying gas mixtures of carbon dioxide with additional regeneration of part of the ethanolamine solution stream with steam (the second version of the device that implements the second version of the method);

- figure 3 is a variant of the production of water vapor for additional regeneration of part of the stream of ethanolamine solution of figure 2.

We will consider the methods of purification of gas mixtures from carbon dioxide using examples of the operation of the corresponding devices.

The first version of the device for cleaning carbon dioxide from gas mixtures includes an absorber 1 with an inlet 2 of absorbent and an outlet of 3 saturated solution, a regenerator-recuperator 4 with an inlet of 5 saturated solution and an outlet 6 of a regenerated absorbent located in its lower part 7, usually with sieve plates 8 with integrated heat exchangers 9 associated with the outlet 6 of the regenerated absorbent, and a boiler 10, a carbon dioxide condenser-separator 11 with an output of 12 phlegm, a cooler 13 of the regenerated absorbent, pumps 14, 15 16 for various purposes, lines (shown as a link between the elements of the device, arrow directions of motion workflows) and shut-off and control elements (not shown conditionally). The absorber 1 is made with package nozzles (contact devices) 17, which are one or more packages of shaped ceramic products, usually rings or seats, etc., which increase the contact surface area of the gas mixture and absorbent material and provide the least gas resistance, and contains in its middle part at least one cooling circuit, made in the form of a device 18 for the selection of a partially saturated absorbent solution cyclically connected with an intermediate tank 19 and an intermediate refrigerator m 20 and reboiler 10 of the regenerator-heat exchanger 4 is made in the form of sequentially arranged in its lower part 7 sections consisting of heat exchangers 21, placed on, preferably perforated plates 22, the number of sections of the boiler 10 is selected in the range of from three to six. It should be noted that the device 18 for the selection of a partially saturated absorbent solution can be made in the form of a blank plate 23 with a neck 24 and its own outlet 25, while the cooling circuit includes an additional inlet 26 located on the absorber 1 below the blank plate 23.

The method of purification of gas mixtures of carbon dioxide on the single-flow device described above includes the absorption of the pressurized gas mixture with aqueous solutions of ethanolamines in the absorber 1, subsequent regeneration of the saturated solution by heating in the regenerator-recuperator 4 by dividing it into a number of cascades, each of which is formed on plates 8 with built-in heat exchangers 9 (about 20-25 cascades sections) and plates 22 with built-in heat exchangers 21 (from three to six stages of boiler 10), in which the temperature uru is successively increased to 120-135 ° C in the direction of the flow of the solution (i.e., from top to bottom), and the regenerated ethanolamine solution is returned to the absorber 1, carbon dioxide is absorbed on the contact devices 17 with a gas resistance of not more than 50 kPa, at this ethanolamine solution in the process of absorption, at least once subjected to intermediate cooling to 30-35 ° C.

In addition, when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa or 500-700 kPa and the carbon dioxide content in the gas mixture is in the range of 4-8% or 25-45%, respectively, monoethanolamine at a concentration of 1 is used as the absorbent. , 8-3.0 kMol / m ³ , and when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa and the carbon dioxide content in the gas mixture is in the range of 25-45%, methyldiethanolamine in the concentration of 1.8- 3.0 kMol / m ³ .

The second version of the device for cleaning carbon dioxide gas mixtures includes the same technological equipment and its elements 1-26 as the first option, with the exception of some additional features associated with the dual-threading scheme, which are listed below.

The absorber 1 has an inlet 2 _{(t) of a} finely regenerated absorbent and an inlet 2 _(g ) of a roughly regenerated absorbent, the regenerator-recuperator 4 has two, located at two levels of the output of the absorbent - an outlet 6 _{(g) of a} roughly regenerated absorbent and an outlet 6 _{(t) of a} finely regenerated absorbent the heat exchangers 9 of the plates 8 are connected to the outlet 6 _{(g) of the} roughly regenerated absorbent by means of the pump 15 _(g) and to the input 2 _{(g) of the} roughly regenerated absorbent of the absorber, while the input 2 _{(g) of the} roughly regenerated absorbent of the absorber 1 is located on the area between the inlet 2 _{(t) of the} finely regenerated absorbent and the first (i.e., topmost) of the cooling circuits, the outlet 6 _{(g) of the} coarsely regenerated absorbent is made in the form of its own outlet located under the boiler 10 of the blank plate 27, including the neck 28 and bypass pipes ( are not shown), in addition, the regenerator, the recuperator 4 in its lower part 7 of the outlet 6 _(t) tonkoregenerirovannogo absorbent 29 is provided entering the steam supply and arranged above it in three or four stripper plates 30 and input 2 _(t) m nkoregenerirovannogo absorbent absorber 1 is connected to output 6 _(t) tonkoregenerirovannogo absorbent regenerator-heat exchanger 4 through the imposed heat exchanger 31 by a pump 15 _(m). In addition, the input 29 of the supply of sharp water vapor in the regenerator-recuperator 4 is equipped with an additional heat exchanger 32, the input 33 of which is connected to the output 12 of the reflux condenser-separator 11 carbon dioxide.

The method of purification of gas mixtures of carbon dioxide on this device includes the same as in the previous (first) method of operation, with the exception of some additional steps associated with the dual-threading scheme, which are listed below.

The absorbent regenerated in the regenerator-recuperator 4, as can be seen from the description of the device, is divided into coarse and finely regenerated streams, after which they are combined in the absorber 1 after the finely regenerated stream is previously introduced into it, while the ethanolamine solution stream is thinly regenerated by treatment with acute water ferry. Evaporated reflux is used as a source of sharp water vapor for the fine regeneration of one of the ethanolamine solution streams, namely, a stream saturated with carbon dioxide residues. In the heat exchanger 31, the finely regenerated solution gives off its heat to the absorbent solution saturated with carbon dioxide, since this flow in the regenerator-recuperator 4 must still be heated for the purpose of regeneration. At the same time, the finely regenerated solution itself will retain its absorbent capacity almost unchanged. Thus, the heat exchange processes of the method are further optimized.

Due to the low gas resistance, it is possible to clean gas mixtures under low pressure. Since the gas resistance determines the energy consumption for transporting the mixture in the absorber, the upper limit of 50 kPa determines the allowable limit at which the process can still be considered effective. Best results can be obtained by providing gas resistance of 10 kPa or less. Existing nozzle designs provide this resistance.

At least a single intermediate cooling of the absorbent solution in the middle of the absorber 1 is necessary to maintain a high driving force and absorption rate, because after reaching a concentration of carbon dioxide in the solution of the order of 0.40-0.45 mol CO ₂ / mol EA, an increase in temperature leads to a slowdown in absorption. At low concentrations of carbon dioxide, the absorption rate, on the contrary, increases with temperature, therefore, the technological method of supplying a hot solution to the upper part of the absorber 1 with intermediate, at least one-time cooling of the solution in the middle zone (part) of the absorber 1 to 30-35 ° С allows you to maintain a high absorption rate over the entire height of the apparatus and achieve a concentration of carbon dioxide at the outlet of up to 0.6 mol CO ₂ / mol EA at a low partial pressure of CO ₂ . The above can significantly reduce the working volume of the solution in the cycle and, accordingly, the energy consumption for its regeneration. This also contributes to the low resistance to gas, which can provide the applied contact device 17.

The separation of the flow of a saturated solution of ethanolamine in the regenerator-recuperator 4 into a series of cascades with a sequential increase in temperature brings the nature of the solution movement closer to the ideal displacement mode. In the case when the solution, in addition to the plates 8, sequentially passes the plates 22 of the boiler 10 from the top down, and the gas-vapor mixture (ASG) flows counter-flow from the bottom up, the difference in the concentration of carbon dioxide in the solution before and after the boiler 10 increases 2.5-2.7 times compared with conventional heating by establishing individual equilibrium points on each plate 22, in contrast to known technologies using remote boilers. The final temperature of the solution at the outlet of the regenerator-recuperator 4 is 120-135 ° C, which allows to achieve a concentration of CO ₂ in the regenerated solution at the level of 0.15-0.17 mol CO ₂ / mol EA - this provides a high driving force of absorption after return solution to the absorber 1.

These changes in the method of heating the solution in the regenerator-recuperator 4 can increase the degree of regeneration of the solution while maintaining the total surface area of heat transfer and, accordingly, reduce energy consumption. Studies have shown that to achieve a concentration of CO ₂ in the regenerated solution of 0.15-0.17 mol of CO ₂ / mol of EA, 3-6 cascades of the boiler 10 in the regenerator-recuperator 4 are sufficient, while the energy consumption for heating the solution compared to the known technical solutions, for example with the apparatus AM-76, are reduced by 400 kJ / kg CO ₂ .

The choice of absorbent is dictated by the partial pressure of CO ₂ in the mixture to be separated. Studies have established that for the range of partial pressures of CO ₂ in the range of 25-60 kPa, which corresponds to real processes of flue gas purification with a gas mixture pressure of 100-250 kPa and a CO ₂ content of 25-40% in the mixture or purification of a reducing gas with a pressure of 500- 700 kPa and CO ₂ content _of 4-8%, the best combination of capital intensity and operating costs provides monoethanolamine in a concentration of 1.8-3.0 kMol / m ³ . A decrease in the concentration of monoethanolamine below the indicated limit leads to an increase in specific energy consumption due to a noticeable increase in the amount of solution in the cycle, while an increase in the concentration of monoethanolamine increases the capital intensity due to the need to use special materials for the manufacture of technological equipment, since the corrosive activity of the absorbent solution saturated with carbon dioxide increases sharply.

At a CO ₂ partial pressure _of more than 60 kPa, which corresponds to a real blast furnace gas purification process with a gas mixture pressure of 200-250 kPa and a CO ₂ content _of 40-45%, methyldiethanoamine gives the best results, especially in the activated form. Concentration limits for the use of methyldiethanoamine are chosen similarly by the ratio of capital intensity and operating costs.

Additional processing of the part of the regenerated solution with hot steam allows to reduce the concentration of CO ₂ in the solution at the outlet of the regenerator-recuperator 4 to almost zero, which increases the efficiency of the final stages of the absorber 1 and further reduces the working volume of the solution in the cycle with a corresponding reduction in energy consumption.

The total volume of steam supplied to the heating of the regenerator-recuperator 4, in this embodiment, remains at the same level as in the case of operation without additional stripping of the solution, but the total steam stream is divided into two parts, one of which is sent to the heat exchangers 21 boiler 10, and the other either directly on stripping plates 30, or in a heat exchanger (evaporator) 32 reflux.

The use of reflux extracted from the condenser-separator 11 for the preparation of steam gives an additional gain in the processes of water treatment and heating of water in the steam production, in addition, the control of the water balance of the unit is simplified, since it is necessary to directly (autonomously) supply steam to the stripping plates 30 constantly remove excess reflux from the unit, equal to the mass of the supplied steam minus water losses in the cycle.

Specific design features of both variants of devices for cleaning gas mixtures of carbon dioxide follow from the characteristics of the respective variants of the methods.

An external circuit for intermediate cooling of the absorbent in the absorber 1 is preferable to the integrated one, because effective cooling at a small temperature gradient requires a large heat transfer surface area, which when using a combined apparatus leads to an unjustified increase in its dimensions.

For regenerator-recuperator 4, operating at elevated temperatures, on the contrary, it is more appropriate to use the built-in sectional boiler 10, this reduces heat loss and reduces the overall material consumption of the “regenerator-boiler” subsystem. The placement of heat exchangers (heating elements) 21 of the boiler 10 directly on the plates 22 of the regenerator further improves heat transfer and reduces the metal consumption of the boiler 10 in comparison with, for example, the apparatus AM-76.

The above extreme values of the parameters of the methods for cleaning gas mixtures of carbon dioxide are intended to a greater extent to control the process as acceptable or to organize feedback in automatic modes. The optimal parameters roughly correspond to the average values of these indicators.

All of the above allows us to talk about the conformity of the claimed technical solutions to the conditions of patentability for inventions.

The device according to the first embodiment works as follows.

The gas mixture to be cleaned is fed through a pipe 34 to the lower part of the absorber 1. A stream of cooled absorbent (regenerated solution of ethanolamine) is supplied to its upper part through the inlet 2, which is used to irrigate the nozzle 17, which, as mentioned above, is one or more packages of shaped ceramic products, increasing the contact surface area of the gas mixture and absorbent. As the oncoming streams contact, the gas mixture is cleaned of carbon dioxide and, accordingly, it is saturated with absorbent material. As the absorber 1 passes, the absorbent solution heats up. In the middle part of the absorber 1, it is taken by means of the device 18 into the container 19, from where it is returned via the refrigerator 16 to the absorber 1 through the refrigerator 20, where the cooled solution continues to move in the lower layers of the nozzle 17, in contact with the oncoming stream of the gas mixture being cleaned. The absorbent solution of the absorbent is collected in the cube of the absorber 1, from where it enters the regenerator-recuperator 4 through the input 5 through the inlet 5.

The gas purified from carbon dioxide is collected in the upper part of the absorber 1 and discharged through a pipe 35 for reuse in the technological process, for example, as a high-quality fuel replacing part of the coke (up to 50%).

The solution saturated with carbon dioxide fed to the regenerator-recuperator 4 moves from top to bottom, heating to a temperature at which carbon dioxide in the vapor-gas mixture evaporates, rising to the top of the regenerator-recuperator 1, from where it enters the carbon dioxide condenser-separator 11. Commercial carbon dioxide is diverted to further processing or discharged, and the phlegm remaining as a result of condensation returns by gravity to regenerator-recuperator 4, replenishing water losses and participating in the process of repeated regeneration of the absorbent. The regenerated (recovered) absorbent having a high working temperature flows into the cube of the regenerator-recuperator 1. The regenerated absorbent is pumped to the heat exchangers 9 located on the plates 8, where it transfers the heat to the carbon dioxide-saturated absorbent solution to be regenerated. In this case, a partial cooling of the regenerated absorbent occurs, which, continuing to move outside the regenerator-recuperator 4, is additionally cooled in the refrigerator 13 to the operating temperature and again enters the upper part of the absorber 1, closing the cycle.

As mentioned above, the absorbent solution to be regenerated that is saturated with carbon dioxide when moving in the regenerator-recuperator 4 passes successively through the mesh plates 8 and is heated against the walls of the heat exchangers located in them 9. To further increase the temperature of the absorbent solution to be cleaned, a boiler 10 is used, which represents a series of heat exchangers 21 located on sieve trays 20 and heated by steam with an autonomous supply. In the boiler 10, practically in the ideal displacement regime created by sectioning, a cascade interaction of the fluid flows and the vapor-gas mixture occurs with the final release of free carbon dioxide.

The device according to the second embodiment works similarly to the first embodiment, but has the following features.

Under the boiler 10 there is a blank plate 27, in which the regenerated absorbent solution is collected. Namely, it is diverted by the pump 15 _(g) to the heat exchangers 9 and further to the refrigerator 13, from where it enters through the additional inlet 2 _(g) into the zone free from the nozzle 17 between the inlet 2 _(t) and the first of the blank plates 23, which serves to select the absorbent intermediate cooling.

The absorbent solution overflowing through the bypass pipes of the blank plate 27 enters the stripping plates 30, where it undergoes acute regeneration with water vapor. The carbon dioxide residues rise through the neck 28, pass through the plates 22 and 8 and are collected in the upper part of the regenerator-recuperator together with carbon dioxide released in the earlier stages of regeneration. A finely regenerated absorbent with practically zero carbon dioxide content from the cube of the regenerator-recuperator 4 is supplied to the heat exchanger 31 via the pump 15 _(t) , from where it is sent to the upper part of the absorber 1. As a result, the gas mixture entering the absorber 1 is most thoroughly cleaned by pipeline 34.

It should be noted that the sharp steam that processes the last part of the absorbent can be obtained by autonomous supply, but can, more preferably, be obtained by evaporation of the reflux coming from the condenser-separator 11 in the heat exchanger 32.

Consider some typical examples of the implementation of the inventions.

Example 1. Purification is subject to 100,000 nm ³ / hour of blast furnace gas in order to return it to recycling. The total gas pressure P = 250 kPa, the content of CO ₂ in the top gas 40%, the partial pressure P _CO2 = 100 kPa. The absorbent is activated methyldiethanolamine (amdea).

The diameter of the absorber D = 4000 mm, the height of the absorber H = 20,000 mm. In the absorber, the gas moves countercurrent at a speed v = 0.75 m / s of the chemisorbent saturating with carbon dioxide (AMDEA), passing through two layers of the nozzle. Irrigation density 80 m ³ / m ² for 1 hour. The purified gas containing 0.5% carbon dioxide is discharged from the absorber 1 for further use. Intermediate cooling in the refrigerator allows to increase the absorption capacity of the solution. A saturated solution of amdea with a degree of carbonization α _n = 0.6 mol of CO ₂ / mol of amdea is pumped to the top of the regenerator-recuperator. In the upper part of the regenerator there are bubbled (sieve) plates with heat-exchange elements placed in the bubbled zone of the regenerated solution, in which the heat of the regenerated solution is transferred to the regenerated solution.

In the lower part of the regenerator-recuperator there is a 4-section boiler of the solution, and three stripping plates, after which the degree of carbonization of the sharply regenerated solution is reduced to α _p = 0.1 mol of CO ₂ / mol of amdea. The regenerated solution with a temperature of t = 128 ° C is pumped through heat exchangers located on the plates of the regenerator-recuperator, and after additional cooling in the refrigerator to a temperature of t = 40-60 ° C, it is supplied to the absorber.

The energy consumption for cleaning mainly consists of the cost of heat for the regeneration of a saturated solution.

The heat consumption for the regeneration of a saturated solution is determined by the following components:

q _p = q _x + q _n + q _g ,

where q _p is the heat consumption for the regeneration of a saturated solution;

q _x is the heat consumption for compensation of the endothermic thermal effects of decomposition reactions of СО ₂ and EA compounds, is a constant value for all processes and is approximately 1200 kJ / kg of removed СО ₂ ;

q _n is the heat consumption for heating the saturated solution to the boiling point;

q _g - heat consumption for the creation of steam leaving the regenerator together with the released carbon dioxide.

q _n = g _p · C · (t _p -t _n ),

where g _p is the required amount of solution per 1 kg of extracted CO ₂ ;

C is the heat capacity of the solution;

t _p is the temperature of the regenerated solution after passing the built-in heat recovery heat exchange;

t _n is the temperature of the saturated solution.

q _n = 16 · 4.18- (55-50) = 334.4 kJ / kg CO ₂ .

The value of q _g is determined by the known amount of CO ₂ emitted. Since the composition of the vapor-gas mixture leaving the regenerator is close to equilibrium, the vapor content in the ASG is close to equilibrium and is q _g = 112.9 kJ / kg CO ₂ .

Energy consumption for the treatment of top gas will amount to

q _p = 1200 + 334.4 + 112.9 = 1647.3 kJ / kg CO ₂ .

Example 2. Conditions repeat the conditions of example 1, but 32% of the flow of the regenerated solution is subjected to additional steam treatment on 3 stripping plates located below the boiler of the regenerator-recuperator. The degree of carbonization of the solution after stripping plates is α _p = 0.03-0.05 mol of CO ₂ / mol of EA. The temperature of the sharply regenerated part of the solution after stripping plates t = 135 ° C, the solution is fed through a heat exchanger to the top of the absorber. The remaining 68% of the flow of the regenerated solution through the regenerator of the regenerator is fed to the middle part of the absorber.

The energy consumption for cleaning will be q _p = 1469 kJ / kg CO ₂ .

Example 3 is comparative. The conditions of example 1 are repeated, but without intermediate cooling of the solution in the absorber and heated in a single-section remote boiler (conditions of the prototype method).

The energy consumption for cleaning is q _p = 2720 kJ / kg CO ₂ .

Example 4. Purification is subject to 100,000 nm ³ / h of reducing gas in the production of iron by direct reduction in order to return it to recycling. The total gas pressure P = 500 kPa, the content of CO ₂ in the mixture 5%, the partial pressure of carbon dioxide P _CO2 = 25 kPa. The absorbent is monoethanoamine (MEA) with a concentration of 2.4 kmol / m ³ . The diameter of the absorber D = 2500 mm, the height H = 15000 mm. Stripping part of the solution is not performed. The remaining conditions are similar to those in example 1. The energy consumption for purification of the reducing gas will be q _p = 1790 kJ / kg CO ₂ .

Example 5. Repeats the conditions of example 4, but with stripping 35% of the flow of the regenerated solution on 4 stripping plates.

The energy consumption for cleaning will be q _p = 1630 kJ / kg CO ₂ .

Example 6. Cleaning is subject to 100,000 nm ³ / h of flue gas in order to obtain pure carbon dioxide. The gas pressure at the inlet of the absorber is 150 kPa, the CO ₂ content in the mixture is 30%, and the partial pressure of CO _{2 is} 45 kPa. The absorbent is monoethanolamine with a concentration of 2.4 kmol / m ³ . The diameter of the absorber D = 2500 mm, height H = 15000 m. The process is carried out with additional stripping of a 30% regenerated solution. The remaining conditions are similar to those in example 1.

The energy consumption for the release of carbon dioxide will be q _p = 1880 kJ / kg CO ₂ .

Example 7. Repeats the conditions of example 6, but the process is performed with additional stripping of a 30% regenerated solution on 3 stripping plates. The remaining conditions are similar to those given in the previous examples.

The energy consumption for cleaning will be q _p = 1760 kJ / kg CO ₂ .

As a result of using the inventions, it became possible to reduce the total overpressure of the process of purification of gas mixtures from carbon dioxide and its partial pressure, to reduce the specific energy consumption for the purification of gas mixtures from carbon dioxide, and also to expand the scope of ethanolamine purification - to extend it to the purification of blast furnace top gas for the purpose of its recycling, purification of reducing gas in the production of sponge iron and purification of flue gases with the release of commercial dio carbon xide.

Claims (12)

1. The method of purification of gas mixtures of carbon dioxide, including the absorption of a pressurized gas mixture with aqueous solutions of ethanolamines in the absorber, the subsequent regeneration of the saturated solution by heating in the regenerator-recuperator by dividing it into a number of cascades in which the temperature is successively increased in the direction of movement of the solution, and returning the regenerated ethanolamine solution to the absorber, characterized in that the absorption of carbon dioxide is carried out on contact devices with gas resistance not olee 50 kPa, and the ethanolamine solution during the absorption of at least once subjected to intermediate cooling to 30-35 ° C. 2. The method according to claim 1, characterized in that when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa or 500-700 kPa and the carbon dioxide content in the gas mixture is in the range of 4-8% or 25-45%, respectively monoethanolamine is used as an absorbent in a concentration of 1.8-3.0 kMol / m ³ . 3. The method according to claim 1, characterized in that when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa and the carbon dioxide content in the gas mixture is in the range of 25-45%, methyldiethanamine at a concentration of 1.8- is used as the absorbent. 3.0 kMol / m ³ . 4. A method of purification of gas mixtures of carbon dioxide, including the absorption of a pressurized gas mixture with aqueous solutions of ethanolamines in an absorber, subsequent regeneration of a saturated solution by heating in a regenerator-recuperator by dividing it into a series of cascades in which the temperature is successively increased in the direction of movement of the solution, followed by separation of the regenerated ethanolamine solution into coarse and finely regenerated streams, and their combination in the absorber after preliminary introduction into n its finely regenerated flow, characterized in that the absorption of carbon dioxide is carried out on contact devices with a gas resistance of not more than 50 kPa, while the ethanolamine solution in the absorption process is subjected to intermediate cooling at least once to 30-35 ° C, and thin the regeneration of the ethanolamine solution stream is carried out by treatment with sharp steam. 5. The method according to claim 4, characterized in that evaporated reflux is used as a source of sharp water vapor for fine regeneration of one of the ethanolamine solution streams. 6. The method according to claim 4 or 5, characterized in that when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa or 500-700 kPa and the carbon dioxide content in the gas mixture is in the range of 4-8% or 25-45 %, respectively, monoethanolamine in a concentration of 1.8-3.0 kMol / m ^{3 is} used as an absorbent. 7. The method according to claim 4 or 5, characterized in that when the pressure of the gas mixture at the inlet of the absorber is in the range of 100-250 kPa and the carbon dioxide content in the gas mixture is in the range of 25-45%, methyldiethanamine at a concentration of 1 is used as an absorbent, 8-3.0 kMol / m ³ . 8. A device for cleaning gas mixtures of carbon dioxide, including an absorber with an inlet of absorbent and an outlet of a saturated solution, a regenerator-recuperator with an inlet of a saturated solution and an outlet of a regenerated absorbent, plates with built-in heat exchangers connected with the outlet of the regenerated absorbent, and a boiler, a condenser-separator carbon dioxide with reflux output, refrigerator of the regenerated absorbent, pumps, pipelines and shut-off and control elements, characterized in that the absorber is made with packet nozzles and contains in its middle part at least one cooling circuit made in the form of a device for the selection of a partially saturated absorbent solution cyclically connected with an intermediate tank and an intermediate cooler, and the boiler of the regenerator-recuperator is made in the form of sequentially located in its lower part sections consisting of heat exchangers placed on the plates, while the number of sections of the boiler is selected in the range from three to six. 9. The device according to claim 8, characterized in that the device for the selection of a partially saturated absorbent absorbent solution is made in the form of a blank plate with a mouth and an outlet, while the cooling circuit includes an additional inlet located on the absorber below the blank plate. 10. A device for cleaning carbon dioxide mixtures of gas mixtures, including an absorber with inlets of a finely and roughly regenerated absorbent and an outlet of a saturated solution, a regenerator-recuperator with an inlet of a saturated solution and two exits of a coarse and finely regenerated absorbent located in two levels, plates with built-in heat exchangers, associated with the exit of the coarsely regenerated absorbent and the inlet of the coarsely regenerated absorbent of the absorber, and a boiler, a carbon dioxide condenser-separator with an output of egma, cooler of the regenerated absorbent, pumps, pipelines and shut-off and control elements, characterized in that the absorber is made with packet nozzles and contains in its middle part at least one cooling circuit made in the form of a device for selecting a partially saturated absorbent solution, cyclically associated with the intermediate tank and the intermediate cooler, the inlet of the coarsely absorbed absorbent absorber is located in the area between the inlet of the finely regenerated absorbent and the first of the circuits cooling, and the boiler of the regenerator-recuperator is made in the form of sections sequentially located in its lower part, consisting of heat exchangers placed on the plates, while the number of sections of the boiler is selected from three to six, the output of the coarsely regenerated absorbent is made in the form of an outlet located under the boiler a blank plate, including the neck and bypass pipes, in addition, the regenerator-recuperator in its lower part above the outlet of the finely regenerated absorbent is provided with an inlet water vapor and three or four stripping plates located above it, and the inlet of the finely regenerated absorbent of the absorber is connected with the outlet of the finely regenerated absorbent of the regenerator-recuperator through an external heat exchanger. 11. The device according to claim 10, characterized in that the device for selecting a partially saturated solution of the absorbent absorber is made in the form of a blank plate with a neck and an outlet, while the cooling circuit includes an additional inlet located on the absorber below the blank plate. 12. The device according to claim 10 or 11, characterized in that the input of the supply of sharp water vapor to the regenerator-recuperator is equipped with an additional heat exchanger, the input of which is connected to the phlegm outlet from the carbon dioxide condenser-separator.

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