CN102430337A - A cryogenic rectification system for producing stable isotope 13C from CO - Google Patents

Abstract

The present invention relates to a cryogenic distillation system for producing stable isotope ¹³ C from CO, which is a cascade device composed of n-stage distillation towers placed horizontally, wherein the distillation towers are composed of a tower top condenser, a tower bottom reboiler and a distillation column, and each stage of the distillation towers is connected by pipelines. Compared with the prior art, the present invention reduces the material conveying flow rate between the cascade towers by arranging extraction sections in each tower of the horizontal cascade, thereby ensuring the long-term, stable and continuous operation of the cascade device.

Description

A cryogenic rectification system for producing stable isotope 13C from CO

technical field

The invention relates to a carbon stable isotope separation technology, in particular to a low-temperature rectification system for producing ¹³ C by low-temperature rectification of CO.

Background technique

In carbon-containing compounds, carbon exists in nature as stable isotopes ¹² C, ¹³ C and radioactive ¹⁴ C, and the natural abundance ratio of ¹² C to ¹³ C is about 98.9:1.1. With the development of science and technology, ¹³ C as a tracer atom has been widely used in the fields of medicine, pharmacology, biochemistry and life science. In addition, the better physical properties of high-abundance ¹² C synthetic diamonds than natural products have also received attention.

In the prior art, there are various production methods of stable isotope ¹³ C, such as thermal diffusion method, gas diffusion method, chemical exchange method, cryogenic rectification method, laser method and so on. Among them, cryogenic distillation is the main method for producing ¹³ C in industry, but because the vapor pressure difference between isotopic components is very small, multi-column cascade operation must be used to obtain high-abundance carbon-13.

As early as 1949, the British Harwell Atomic Energy Research Center established a device for the separation of ¹³ C by cryogenic rectification of CO (TFJohns, H.London, enrichment of isotopes ¹³ C and ¹⁸ O, AERE Harwell report G/R 661, 1951). Consisting of two vertically connected towers with a total length of 32ft, the abundance of ¹³ C in the product is 60%, and the yield is 0.4g ¹³ C/d.

，Е.Л.

，et al.，Получение изотоnа C¹³ метолом ректификации окиси уrлерола，Isotopenpraxis，4.Jahrgang，Heft 7，1968，275-277)建造的CO低温精馏装置由三座塔构成，该装置全长36m，第一级塔径为4.3cm、高15m，第二级塔径为2.0cm、高10m，第三级塔径为1.0cm、高11m，三塔垂直连接。塔内装填三角螺旋圈填料，保温形式为真空绝热，产品中¹³C丰度为60％。Former Soviet Union Tbilisi Laboratory (П.Я.Асаmuанu, BA

, E.L.

, et al., Получение изотоnа C ¹³ метолом ректификации окиси уrлерола, Isotopenpraxis, 4. Jahrgang, Heft 7, 1968, 275-277) built a CO cryogenic rectification device consisting of three towers. The diameter of the first-stage tower is 4.3cm, and the height is 15m. The diameter of the second-stage tower is 2.0cm, and the height is 10m. The diameter of the third-stage tower is 1.0cm, and the height is 11m. The three towers are connected vertically. The tower is filled with triangular spiral packing, and the heat preservation form is vacuum insulation, and ^{the 13} C abundance in the product is 60%.

In July 1969, Los Alamos Laboratory in the United States built a CO cryogenic distillation unit (DEArmstrong, AC Briesmeister, BBMclnteer, et a1., A carbon-13 production plant using carbon monoxide distillation, LASL report, LA-4391, 1970), is The largest CO low-temperature rectification device at that time, the device was composed of seven-section towers connected vertically in series, put together in a vacuum jacket with a diameter of 15.24 cm, and then insulated with polystyrene foam and 40 layers of aluminum alloy Mylar film , and finally placed in a crypt with a diameter of 0.9144 meters and a depth of 38.1 meters. After 6 weeks of equilibration, the device obtained a product with ¹³ C abundance of 92.37%. This device was replaced by the 8kg/a ¹³ C device built in 1979 (BBMclnteer, isotope separation by distillation: design of a carbon-13 plant, separationscience and technology, vol.15, No.3, 1980, 491-508) , that is, the Cola-Colita unit. The main column of the Cola-Colita unit consists of two vertically connected columns, an isotope conversion reactor and a sub-column for rectification. The first section is 6 columns with a length of 100 meters. It is a tower with a length of 100 meters, and the sub-column for rectification is 55 meters long.

In 1999, Russian Yang. Ge. Chalevansik (Yang. Ge. Chalevansik, A. Bo. Harausilauf, low-temperature rectification of carbon oxides to prepare stable isotopes, Хим.пром.1999 , No.4, 229-235) designed a set of four-tower cascade device using low-temperature distillation of CO to separate ¹³ C. The four towers are connected horizontally, and the raw materials are added to the bottom of the first-stage tower, and the second to second The 4th stage towers are all enrichment sections, the four towers adopt the same height design, and the height of the packing in the towers is 20 meters. The gas material at the bottom of the former tower automatically flows to the condenser at the top of the latter tower through pressure, and flows from the bottom of the condenser to the top of the latter tower after being condensed as the spray liquid of the latter tower. The steam flows out from the top and is transported to the bottom of the front tower through the blower to realize the material flow between the cascades. This process reduces the requirements on the site, but increases the power conveying equipment for interstage materials.

Based on the above documents, it can be seen that the concentration of ¹³ C by CO cryogenic rectification requires multi-tower cascade operation. In the prior art, cascade devices have two connection modes: vertical cascade and horizontal cascade. In the vertical cascade, the liquid in the first stage tower enters the rear stage tower by gravity, and the steam in the latter stage tower enters the front stage tower by pressure, so it is easy to realize the material transportation between the cascaded towers. However, due to the large number of theoretical plates required in the isotope separation process, the tower equipment is very high, so the construction is relatively difficult; in addition, due to the relatively large pressure drop of the cascade device, the separation coefficient of the system is reduced, which is not good for separation. In comparison, the construction difficulty of the horizontal cascade is much less, but, in the n-level horizontal cascade device of the prior art, the top feed and output of the 2nd to n-stage rectification towers maintain the liquid phase and the gas phase Therefore, the material flow rate between the cascaded towers is very large. On the one hand, the energy consumption of the conveying equipment is relatively large. On the other hand, this cascade device has relatively high requirements for automatic control and instrumentation. High, and requires continuous and stable operation of each stage. An accident in any stage of the tower will cause poor connection of the cascade device.

Contents of the invention

The purpose of the present invention is to provide a horizontal cascade system for producing stable isotope ¹³ C by low-temperature rectification CO in order to overcome the above-mentioned defects in the prior art. Realize the long-term and stable operation of the cryogenic rectification system.

The purpose of the present invention can be achieved through the following technical solutions:

A low-temperature rectification system for producing stable isotope ¹³ C from CO, which is a cascade device composed of n-stage rectification towers placed horizontally, wherein the rectification tower consists of a top condenser, a bottom reboiler and a rectification tower. The distillation columns are composed of distillation columns, and the distillation columns at all levels are connected by pipelines.

The diameter of the n-stage rectification tower gradually becomes smaller.

The n-stage rectification tower is a 2-10-stage rectification tower.

The first-stage distillation column can input raw materials from the middle or the top of the column.

In the cascading device, the steam at the top of the rectifying tower in the rear stage is transported to the middle part of the rectifying tower in the preceding stage through a pipeline by the gas delivery pump, and the liquid produced in the bottom of the rectifying tower in the preceding stage is vaporized in the pipeline Under the action of pressure, it is transported to the middle part of the rear stage rectification tower.

The steam at the top of the rear stage rectification tower can be returned to the feeding point of the front stage rectification tower.

The steam at the top of the rear stage rectification tower can be returned to a position higher than the feed point of the front stage rectification tower.

The steam at the top of the rear-stage rectification tower can be returned to a position lower than the feeding point of the front-stage rectification tower.

The gas delivery pump can be a gas booster pump, a blower, a canned electric pump, a diaphragm pump or a magnetic drive pump.

The rectification tower is filled with separation packing.

The separation packing is metal plate corrugated structured packing, wire mesh structured packing, metal mesh corrugated packing, grid packing or pulse packing.

Compared with the prior art, the present invention utilizes the arrangement of extraction sections in each horizontal cascading tower to reduce the material delivery flow between each cascading tower, which can ensure long-term, stable and continuous operation of the cascading device.

Description of drawings

Fig. 1 is the cascade system schematic diagram of the present invention;

Fig. 2 is the schematic flow sheet of embodiment 1;

Fig. 3 is the concentration distribution diagram of each isotope component in the cascaded rectification column in embodiment 1;

Fig. 4 is the schematic flow sheet of embodiment 2;

Fig. 5 is a concentration distribution diagram of each isotopic component in the cascaded rectification column in Example 2.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the schematic flow chart of the cryogenic rectification system composed of n-stage rectification towers of the present invention, the system is a cascade device composed of n-stage horizontally connected rectification towers. In the cascade device in the present invention, the towers at all levels are connected in this way: raw materials are added to the middle part of the first-stage rectification tower of the cascade device, part of the low-abundance ¹³ CO gas is extracted from the top of the first-stage tower, and the second-stage Part of the steam vaporized by the reboiler of the 1st to n-1st stage towers is metered and then enters the middle part of the 2nd to nth stage rectification towers and the top part of the 2nd to nth stage rectification towers under the action of pressure The steam is transported to the middle of the 1st to n-1th stage rectification towers respectively through the gas delivery pump, and part of the steam vaporized by the reboiler of the nth stage tower enters the rectification tower to be vaporized with the liquid coming down from the top condenser. , liquid mass transfer, a part of high-abundance ¹³ CO gas leaves the cascade device as a product.

The tower tops of the first-stage to n-stage rectification towers are respectively connected to condensers C1 to Cn, and each condenser is connected to the gas pipeline and liquid pipeline connected to the rectification tower of this stage, and to the rectification tower of the previous stage. In addition, each condenser also has a pipeline for the condensing medium to enter and exit.

The top condensers C1~Cn can be coil heat exchangers, shell and tube heat exchangers, casing heat exchangers, plate heat exchangers, spiral plate heat exchangers, plate-fin heat exchangers, etc. , preferably a plate-fin heat exchanger.

In the cascade device shown in Figure 1, structured packing with high specific surface area is filled in the 1st to nth stages of rectification column, and its type can be plate corrugated packing, grid packing, wire mesh corrugated structured packing, pulse packing, etc. , preferably orifice corrugated packing and wire mesh corrugated packing.

The tower bottoms of the first to nth stages of rectification towers are respectively connected to reboilers B1 to Bn, and each reboiler is connected to the gas pipeline and liquid pipeline connected to the rectification tower of this stage, and to the rectification tower of the next stage Pipelines for transporting materials.

The material at the top of the rear tower is transported to the middle of the front tower through the gas delivery pump, wherein the gas delivery pump can be a gas booster pump, a blower, a shielded electric pump, a diaphragm pump, a magnetic drive pump, etc., preferably a diaphragm pump.

Referring to Figure 1, the CO raw material is measured by the flow meter F1 and then transported to the middle of the first-stage tower T1 by the pipeline L3. The T1 tower is filled with separation packing, which is the liquid condensed and refluxed in the top condenser C1 and the bottom reboiler B1 The steam evaporated in the medium provides a surface for heat transfer and mass transfer, and high-abundance carbon-12 is taken out from the top of the T1 column through the line L2. A part of the steam is taken out from the T1 tower kettle, driven by the pressure, it is measured by the valve V1 and the flow meter F2, and then transported to the middle of the tower T2 along the pipeline L4, and the T2 tower is filled with separation packing, which is the liquid condensed and refluxed in the top condenser C2 The steam vaporized in the bottom reboiler B2 provides a surface for heat and mass transfer, and a part of the steam is taken from the top of the T2 column, and is transported to the middle of the column T1 by the gas delivery pump P1 along the line L5. A part of the steam is taken out from the T2 tower kettle, driven by the pressure, it is measured by the valve V2 and the flow meter F3, and then transported to the middle of the tower T3 along the pipeline L6. The T3 tower is filled with separation packing, which is the liquid condensed and refluxed in the top condenser C3. The steam vaporized in the bottom reboiler B3 provides a surface for heat transfer and mass transfer, and a part of the steam is taken from the top of the T3 column, and is transported to the middle of the column T2 by the gas delivery pump P2 along the line L7. Similarly, the fourth tower T4, the fifth tower T5 up to the nth tower Tn all adopt such a connection method. A high-abundance carbon-13 product is extracted from the bottom of the nth tower Tn.

In the whole cascading device, the pressure at the top of the towers at each level is the same, and the materials transmitted between the cascading towers are all gases. The steam is transported to the middle of the previous column by the gas transport pump. This cascading method can ensure the continuous and stable operation of the cascade device, and due to the equal pressure operation of each column, the separation coefficient between isotopic components is also relatively high.

In addition, the present invention also provides computer simulation results of the abundance distribution of each isotopic component in the cascade device when using the above cryogenic rectification system to separate and enrich ¹³ C. In the present invention, the rectification theory is used to design and optimize the cascade device. Considering the influence of oxygen isotopes in the system, ¹² C ¹⁶ O, ¹³ C ¹⁶ O and ¹² C ¹⁸ O with relatively high natural abundance are considered during the calculation process. three components. Similar results can also be obtained by designing the cryogenic rectification cascade device proposed in the present invention according to the isotope separation cascade theory and precision rectification theory.

The present invention will be further elaborated below in conjunction with embodiment.

Example 1

The cascade device in Example 1 is composed of 4 stages of rectification towers, and the schematic flow chart of the cascade device is shown in Figure 2. The CO raw material is measured by the flow meter F1 and transported to the middle of the first stage tower T1 by the pipeline L3. The T1 tower is filled with metal mesh corrugated packing, which is the liquid condensed and refluxed in the top condenser C1 and the bottom reboiler B1. The vaporized vapor provides a surface for heat and mass transfer. The high-abundance carbon-12 is taken out from the top of the T1 tower through the pipeline L2, and a part of the steam is taken out from the bottom of the T1 tower. Driven by the pressure, it is metered through the valve V1 and the flow meter F2 and then sent to the middle of the tower T2 along the pipeline L4. The T2 column is filled with wire mesh corrugated packing to provide heat and mass transfer surfaces for the liquid condensed and refluxed in the top condenser C2 and the vaporized vapor in the bottom reboiler B2. A part of the steam is taken out from the top of the T2 tower, and is transported to the middle of the tower T1 by the diaphragm pump P1 along the pipeline L5, and is added to the tower T1 together with the raw material of natural abundance, and a part of the steam is taken out from the bottom of the T2 tower, driven by the pressure through the valve V2 is measured by flowmeter F3 and transported to the middle of tower T3 along pipeline L6. The T3 column is filled with wire mesh corrugated packing to provide heat and mass transfer surfaces for the liquid condensed and refluxed in the top condenser C3 and the evaporated vapor in the bottom reboiler B3. A part of the steam is taken from the top of the T3 tower, and is transported to the middle of the tower T2 by the diaphragm pump P2 along the pipeline L7, where the pipeline L7 and the pipeline L4 are connected to the tower T2 at the same position, and a part of the steam is taken out from the bottom of the T3 tower, driven by the pressure through After metering by valve V3 and flowmeter F4, it is transported to the middle of tower T4 along pipeline L8. The T4 column is filled with wire mesh corrugated packing to provide heat and mass transfer surfaces for the liquid condensed and refluxed in the top condenser C4 and the vaporized vapor in the bottom reboiler B4. A part of steam is taken from the top of T4 tower, and is transported to the middle of tower T3 by diaphragm pump P3 along pipeline L9, wherein pipeline L6 and pipeline L9 are connected to tower T3 at the same position, and the high-abundance steam is extracted from the tower still B4 of the fourth tower T4 carbon-13 products.

In Example 1, the raw material is natural CO with a carbon-13 abundance of 1.1%. After separation in a four-stage tower, carbon-13 is enriched to 90%. Table 1 shows the annual net ¹³ C 100kg with an abundance of 90 The process parameters of the cascade device, and the isotope abundance distribution in each column of the cascade are shown in Figure 3.

The process parameters of the four-cascade device with an annual output of 100kg carbon-13 in the embodiment 1 of table 1

It can be seen from the data in Table 1 that the amount of material returned to the front tower by the latter stage tower is far lower than the amount of vaporized material in the bottom reboiler of the latter stage tower, which reduces the amount of material in the connecting pipeline between cascaded towers. When there is a problem with the intermediate cascade tower, the full reflux operation of the single tower can be carried out. After the problem is solved, the cascade device can be connected again, and the cascade device can quickly resume operation. Due to the same pressure at the top of each column, the isotopic components have a relatively high separation factor.

Example 2

The cascade device in Example 2 is composed of 4 stages of rectification towers, and the schematic flow chart of the cascade device is shown in Figure 4. The CO raw material is measured by the flow meter F1 and then transported to the middle of the first stage tower T1 by the pipeline L3. The T1 tower is filled with corrugated wire mesh packing, which is the liquid condensed and refluxed in the top condenser C1 and the bottom reboiler B1. The vaporized vapor provides a surface for heat and mass transfer. The high-abundance carbon-12 is taken out from the top of the T1 tower through the pipeline L2, and a part of the steam is taken out from the bottom of the T1 tower, which is metered by the valve V1 and the flow meter F2 under the drive of the pressure and then transported to the middle of the tower T2 along the pipeline L4 (Fig. 4 Midpoint d position). The T2 column is filled with wire mesh corrugated packing to provide heat and mass transfer surfaces for the liquid condensed and refluxed in the top condenser C2 and the vaporized vapor in the bottom reboiler B2. A part of the steam is taken from the top of the T2 tower, and is transported by the diaphragm pump P1 along the pipeline L5 to the lower part of the middle of the tower T1 (point a in Figure 4). A part of the steam is taken out from the bottom of the T2 column, driven by the pressure, it is metered through the valve V2 and the flow meter F3, and then sent to the middle of the column T3 along the pipeline L6 (point h in Figure 4). The T3 column is filled with wire mesh corrugated packing to provide heat and mass transfer surfaces for the liquid condensed and refluxed in the top condenser C3 and the evaporated vapor in the bottom reboiler B3. A part of the steam is taken from the top of the T3 tower, and is transported by the diaphragm pump P2 along the pipeline L7 to the lower part of the middle of the tower T2 (point e position in Figure 4), and a part of the steam is taken out from the bottom of the T3 tower, driven by the pressure through the valve V3 After metering with the flow meter F4, it is transported to the middle of the tower T4 along the pipeline L8 (point 1 position in Figure 4). The T4 column is filled with wire mesh corrugated packing to provide heat and mass transfer surfaces for the liquid condensed and refluxed in the top condenser C4 and the vaporized vapor in the bottom reboiler B4. A part of the steam is taken from the top of the T4 tower, and is transported by the diaphragm pump P3 along the pipeline L9 to the position lower in the middle of the tower T3 (point i position in Figure 4), and the high-abundance carbon is produced in the bottom of the fourth tower T4- 13 products.

In Example 2, the raw material is natural CO with a carbon-13 abundance of 1.1%. After the separation of the four-stage tower, the carbon-13 is enriched to 90%. Table 1 is the net CO with an annual output of 100kg and an abundance of 90%. The process parameters of the carbon-13 cascade device and the isotope abundance distribution in each column of the cascade are shown in Fig. 5 .

The process parameters of the four-cascade device with an annual output of 100kg carbon-13 in the embodiment 1 of table 2

As can be seen from the data in Table 2, the amount of material returned to the front tower by the latter stage tower is far lower than the amount of vaporized material in the reboiler at the bottom of the rear stage tower, which reduces the amount of material in the connecting pipeline between cascaded towers. When there is a problem with the intermediate cascade tower, the full reflux operation of the single tower can be carried out. After the problem is solved, the cascade device can be connected again, and the cascade device can quickly resume operation. Due to the same pressure at the top of each column, the isotopic components have a relatively high separation factor.

Example 3

A low-temperature rectification system for the production of stable isotope ¹³ C from CO, which is a cascade device composed of two horizontal rectification towers with gradually tapered diameters, wherein the rectification tower consists of a top condenser and a bottom reboiler It is composed of a rectification column, and the rectification columns at all levels are connected by pipelines. The first-stage rectifying column can input raw materials from the middle. The steam at the top of the rectifying tower in the cascade device is transported by the gas delivery pump to the middle of the rectifying tower in the previous stage through the pipeline, and the liquid produced in the bottom of the rectifying tower in the preceding stage is vaporized in the pipeline and then under pressure It is sent to the middle part of the rear stage rectification tower. The vapor at the top of the rear stage rectification tower can be returned to the feeding point of the front stage rectification tower. The gas delivery pump used is a gas booster pump, and the rectification column is filled with grid packing as separation packing.

Example 4

A low-temperature rectification system for producing stable isotope ¹³ C from CO, which is a cascade device composed of 10 stages of horizontal rectification towers with gradually tapered diameters, wherein the rectification tower consists of a tower top condenser and a bottom reboiler It is composed of a rectification column, and the rectification columns at all levels are connected by pipelines. The first-stage rectification column can input raw materials from the top of the column. The steam at the top of the rectifying tower in the cascade device is transported by the gas delivery pump to the middle of the rectifying tower in the previous stage through the pipeline, and the liquid produced in the bottom of the rectifying tower in the preceding stage is vaporized in the pipeline and then under pressure It is sent to the middle part of the rear stage rectification tower. The vapor at the top of the rear stage rectification tower can be returned to the feed point position of the front stage rectification tower, or can be returned to a position higher than the feed point position of the front stage rectification tower, or can be returned to a position higher than that of the front stage rectification tower. The feed point of the distillation column is at a low position. The gas delivery pumps used are blower or magnetic drive pumps. The rectification column is filled with wire mesh structured packing and metal mesh corrugated packing as separation packing.

Although the system has been described in connection with specific embodiments, those skilled in the art will recognize various other embodiments within the scope and spirit of the invention as claimed.

Claims (11)

1. produce stable isotope by CO for one kind ¹³The low temperature distillation system of C is characterized in that, this system is the cascade unit that the n level rectifying column of horizontal positioned is formed, and wherein, said rectifying column is made up of overhead condenser, tower bottom reboiler and rectifying column, connects through pipeline between the rectifying columns at different levels.

2. according to claim 1 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, the diameter of described n level rectifying column is tapered.

3. according to claim 1 and 2 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, described n level rectifying column is 2～10 grades of rectifying columns.

4. according to claim 1 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, first order rectifying column can be from the middle part or cat head input raw material.

5. according to claim 1 a kind of by CO production stable isotope ¹³The low temperature distillation system of C; It is characterized in that; The steam of back level rectifying column cat head is transported to the tower middle part of prime rectifying column by gas transfer pump through pipeline in the described cascade unit, is transported to the middle part of back grade rectifying column after the liquid that the tower still of prime rectifying column produces vaporize in pipeline under pressure.

6. according to claim 5 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, the steam of described back level rectifying column cat head can turn back to the feed points position of prime rectifying column.

7. according to claim 5 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, the steam of described back level rectifying column cat head can turn back to the position higher than the feed points position of prime rectifying column.

8. according to claim 5 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, the steam of described back level rectifying column cat head can turn back to the position lower than the feed points position of prime rectifying column.

9. according to claim 5 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, described gas transfer pump can be gas boosting pump, air blast, shielded electric pump, membrane pump or magnetic force driving pump.

10. according to claim 1 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, is filled with separating filler in the described rectifying column.

11. it is according to claim 10 a kind of by CO production stable isotope ¹³The low temperature distillation system of C is characterized in that, described separating filler is metallic plate corrugated regular filler, woven wire structured packing, metal mesh opening ripple packing, grid packing or pulse filler.

Images