The method of purification of carbon dioxide from low-boiling impurities

 

(57) Abstract:

Usage: the production of high-purity CO2used in various processes of food technology and other fields of science and technology. The inventive use to obtain the required steam flow in a distillation column part of the flow of the mixture taken into the evaporator of the column directly after the last stage of the compressor without pre-cooling. Flow in the evaporator part of the initial mixture after the last stage of the compressor to the high temperature difference between bottom boiling liquid and the cooling or condensing in the tubes of the evaporator flow original mix cubed columns, which reduces the amount of flow directed into the evaporator, and reduces the heat transfer surface. 5 C.p. f-crystals, 3 ill.

The invention relates to low-temperature techniques for the production of liquid CO2high purity used in the various processes of food technology and other fields of science and technology.

A method of obtaining liquid or gaseous carbon dioxide, comprising the adsorptive drying of the compressed gas CO2, posleduushie in a distillation column [1] In the distillation columns in the cube get production of liquid CO2.

However, this method provides receiving production CO2in which the concentration of CO2by volume not exceeding 98.5 per cent. In addition, applicants to the division prior to being fed into the evaporator of the column a stream of CO2additionally cooled in the regenerative heat exchanger in front of the column, which reduces the amount of heat removed from the evaporator, and, as a consequence, leads to the need to increase the value of this flow and heat transfer surface of the evaporator column. Installation scheme that implements this method is quite complicated, so as to provide the necessary cooling capacity it uses a two-stage turboexpander, and heated streams of CO2obtained after expansion in the expansion turbines, is carried out in a multithreaded heat exchanger.

Some disadvantages of this method is devoid of the method of extraction of CO2proposed in [2]. According to this method, the raw gaseous carbon dioxide get in annealing furnaces limestone. Purification of the crude gaseous carbon dioxide includes its compression in the compressor, cooled in the water cooler, drying vapors from H2O in the adsorption drying unit, sisig impurities in the distillation column, from the cube which pure liquid carbon dioxide is pumped out to the consumer.

However, a particular disadvantage of this method is that after the condensation of the entire flow of the mixture and its subsequent entry into the distillation column is not clear how the normal operation of the column, as it lacks the boiler or evaporator part of the bottom liquid, which does not allow to obtain the required steam flow for a process of rectification, and a reflux condenser, which would be at the top of the column condensation of steam flow to obtain the necessary flow phlegmy for the rectification process.

The problem to which the invention is directed to develop a method for purification of carbon dioxide from low-boiling impurities, in which in comparison with the prototype will be receiving liquid CO2high purity without the use of external sources of heating with simultaneous cleaning in a distillation column of steam and liquid flows of the original mixture.

The technical result that can be obtained by applying the proposed method is used to obtain the required flow p what about after the last stage of the compressor without prior cooling, with its subsequent cooling or condensation in the evaporator and the flow separation on the top of the column after throttling that provides a sufficiently high temperature and pressure in the cube of the column between the bottom boiling liquid and the cooling or condensing in the tubes of the evaporator the flow of the mixture and reduce heat transfer surface of the evaporator. In addition, the filing of all partial flow of the mixture in a distillation column or in the form of two streams of vapor and liquid, or only in a single fluid stream entering the top of the column, allows to increase the degree of extraction of the final product in the form of liquid CO2high purity.

This technical result is achieved in that in the method of purification of carbon dioxide from low-boiling impurities, including compressed cleared the initial mixture in the compressor, the cooling in the refrigerator, Department of condensed moisture in the dryer and vapor H2O in the adsorption dehydration unit, subsequent cooling and condensation of the mixture in the evaporator of the refrigeration machine, the throttling of the liquid mixture in a distillation column and separation in a distillation column of the low-boiling impurities to produce in either the pair, rising through the column, in the evaporator of the column is selected portion compressed in the compressor gaseous source mixture, which has not been cooled in the refrigerator.

The achievement of the technical result also contributes to the fact that when submitting to set the initial mixture, free from water vapor, the flow of the mixture taken into the evaporator, condensed and fed to the top of the distillation column, and the presence in the mixture of water vapor flow of the mixture leaving the evaporator is directed to the mixing with the main flow of gaseous original mixture in the separator.

To achieve the technical result part of the main stream of the mixture is taken before distillation column and throttled to the cube of the column and formed by throttling pair up for a distillation column for separation. This reduces the heat load on the evaporator of the column and consequently lower the heat transfer surface.

The achievement of the technical result is also that the pair, leaving the reflux condenser of the distillation column, mixed with vapors emerging from the interim flows from the low-boiling impurities can further receive a certain amount of productive CO2.

The achievement of the technical result is driven by the fact that the flow of purified CO2after drying unit condense in the water cooler-condenser and additionally preobladayut in the evaporator of the refrigeration machine. Subcooled flow partial mixture allows to increase the content of the liquid phase fed to the separation, and gives you the opportunity to opt out of inclusion in the scheme of installation of the reflux condenser.

In Fig. 1, 2 and 3 is a schematic installations for the implementation of this method. The installation shown in Fig. 1, is intended for the treatment of CO2from low-boiling impurities in the presence of the source vapor mixture H2O. Installation for purification of carbon dioxide from low-boiling impurities contains a compressor 1, a water cooler 2, a separator 3, a block adsorption drying the mixture to 4, the cooler-condenser 5 with refrigerating machine 6, the rectifying column 7 evaporator 8, the throttle valves 9 and 10, a reflux condenser 11, the intermediate tank 12, the capacity of high-purity liquid CO213, the condenser-evaporator 14 and valves 15, 16, 17, 18, 19, 20, 21, 22 and 23 mounted on the process flows.

The method is cleanrestore 1 to a pressure of 6.7 to 7.1 MPa and then is divided into two streams. A large part through the valve 16 enters the refrigerator 2, where it is cooled by water. The flow of the mixture to condense part of the water vapor, and the resulting condensate is separated in the separator 3. Further dehydration of the mixture is carried out in zeolite adsorbers 4. The dried mixture is fed to the condenser 5, which is the evaporator of the refrigerating machine 6, where it is further cooled and condensed. After the condenser, the flow of the mixture is divided into two parts. One part through the throttle valve 10 is throttled in the upper part of the rectifying column 7, and the second through the throttle valve 9 is choked to the cube of the column. Of flow of the liquid-vapor mixture supplied to the upper part of the column 7, the flow of liquid flows down the column, meeting on his way to the rising steam flow. This stream is formed from three streams. To get the first part of the thread of the original mixture, compressed in the compressor 1, directly after the last stage of the compressor through the valve 15 is collected in the evaporator coil 8, located in the cube column 7. The resultant boiling bottom liquid vapors are mixed with the second stream, the stream of steam coming out of the intermediate tank 12 CERA mixture throttle valve 9. In the throttling of the flow into the vapor phase becomes significant amount of low-boiling impurities contained in this stream.

Rising up the column operating at a pressure of 1.5-1.7 MPa, vapor phase enriched low-boiling impurities contained in the initial mixture, and the flowing-down liquid is enriched with carbon dioxide. In the process of rectification columns in the cube fluid accumulates in the form of production of liquid CO2high purity, which through the valve 23 merges first in the intermediate tank 12, and then through the valve 19 in the storage of high-purity liquid CO213.

From the top of the rectifying column 7 the pair arrive in the reflux condenser 11, where they are partial condensation using a refrigerating machine or other source of cooling. The resulting condensate is used in conjunction with the flow original mix for irrigation columns and ensure the necessary conditions for rectification. Some of the steam, substantially enriched low-boiling impurities, is removed from the top of the reflux condenser. This stream is mixed with steam flow discharged through the valve 18 from the container 12, and the flow paradental. In the condenser 14 in the process of counter-current condensation condensation occurs most part of this thread, and some neskondensirovannyh pair of enriched low-boiling impurities, is blown off from the upper part of the condenser. The condensed liquid, depending on the content of the target component CO2can be merged with a high content of CO2through the valve 21 into the tank 13, and when the content of CO2not corresponding to the requirements for high-purity products, through the valve 22 into the container for storing welding CO2(of Fig. 1 is not shown).

The flow of the mixture in the evaporator 8 is cooled to a temperature, eliminating the possibility of condensation of CO2and to leave it mixed with the rest of the thread, chilled in the refrigerator for 2 before entering into the separator 3.

In Fig. 2 is a schematic diagram of an installation intended for the implementation of this method in the absence in the original vapor mixture H2O. Installation for cleaning dry base mixture consisting of CO2and a certain amount of low-boiling impurities, contains a compressor 1, a water cooler 2 cooler-condenser 5 with refrigerating machine 6, which, the technology of high-purity CO213, the condenser-evaporator 14 and valves 15, 16, 17, 18, 19, 20, 21, 22 and 23 mounted on the process flows.

In the installation shown in Fig. 2, the main flow of the mixture after compression in the compressor 1 and the cooling water refrigerator 2 enters the cooler-condenser 5, where condensed the original mixture through the throttle valve 10 is fed to the top of the column 7. Part of the initial mixture through the throttle valve 9 to go to the cube of the column. Formed by throttling the pair will rise up the column 7. Unlike scheme, as shown in Fig. 1, a part of the flow of non-refrigerated mixture taken after the compressor 1 through the valve 15 into the evaporator 8, when passing through the evaporator is not only cooled, but is condensed and then fed through the orifice 24 to the top of the column 7. The parameters of the process of separation of the mixture in the units shown in Fig. 1 and 2, identical.

The direction of the other threads in the setup diagram shown in Fig. 2, the same as in the scheme shown in Fig. 1.

In Fig. 3 is a schematic diagram of an installation intended for the implementation of this method when applying for doocy the amplifier 3, adsorption drying unit 4, the rectifying column 7 evaporator 8, the intermediate tank 12, the capacity of high-purity CO213, the condenser-evaporator 14, mounted on the technological flow valves 10, 15, 16, 17, 20, 21, 22 and 23, the water cooler-condenser 24 and the subcooler liquid CO225.

In the installation shown in Fig. 3, the entire flow of the mixture after the adsorption drying is cooled and condenses in the water cooler-condenser 24, and then pereohlajdenia in the subcooler liquid CO225, which is cooled boiling liquid refrigerant.

The flow of gaseous CO2enriched low-boiling impurities, from the top of the column 7 is supplied to the condenser-evaporator 14.

The direction of the other threads in the setup diagram shown in Fig. 3, the same as in the circuits shown in Fig. 1 and Fig. 2.

Sources of information:

1. The application of Germany N 3639779, MKI With 01 In 31/20, published 01.06.88.

2. The Japan patent N 57-191215, MKI With 01 In 31/20, published 25.11.82.

1. The method of purification of carbon dioxide from low-boiling impurities, including compressed cleared the initial mixture in the compressor, the cooling in the refrigerator, Department of condensed moisture in Noah mixture in the evaporator of the refrigerating machine, the throttling of the liquid mixture in a distillation column and separation in a distillation column of the low-boiling impurities to produce in the bottom product of the column of high-purity liquid CO2, characterized in that to obtain the necessary flow of steam rising through the column, in the evaporator of the column is selected portion compressed in the compressor gaseous source mixture, which has not been cooled in the refrigerator.

2. The method according to p. 1, characterized in that the gaseous stream of the mixture leaving the evaporator is directed to the mixing with the main flow of gaseous original mixture in the separator.

3. The method according to p. 1, characterized in that, upon application to the installation of the initial mixture, free from water vapor, the flow of the mixture taken into the evaporator, condensed and fed to the top of the distillation column.

4. The method according to p. 1, characterized in that the part of the main stream of the mixture is taken before distillation column and throttled to the cube of the column and formed by throttling pair up for a distillation column for separation.

5. The method according to p. 1, characterized in that the vapors leaving the dephlegmator rectificate is additionally separated in the condenser-evaporator.

6. The method according to p. 1, characterized in that after drying unit original mix condense in the water cooler-condenser, preobladayut in the subcooler and drossellied to the top of the distillation column.

 

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