JP2019513556A - Method for obtaining oxygen 18 enriched water, and equipment for its production - Google Patents

Abstract

The present invention relates to the production of oxygen-18 for PET tomography. The generation of oxygen-enriched water is accomplished by rectifying fetal water under vacuum in a packed column. The plant for production consists of a column of a preconcentration unit operating in an open circuit (without depletion) with a first kind of selection and a final concentration column: concentrated on oxygen 18 and evacuated with oxygen 16. Water is used to supply the unit, the natural amount of oxygen 18 is maintained by chemical isotope exchange with carbon dioxide, and the accumulation of deuterium in products and intermediates is excluded. The plant according to the invention makes it possible to obtain oxygen 18 enriched water with 95% enrichment to deuterium and standardized isotopic composition with high efficiency and low level of technical loss . [Selected figure] Figure 1

Description

The present invention relates to the production of oxygen-18 for PET tomography and can be used to produce water enriched with isotopic oxygen 18 (deoxygenated water, Н ₂ -18 18).

Water enriched with isotopic oxygen 18 (Н ₂ -18-18) is currently widely used in medicine, pesticides and biochemistry. For the first time in 1914, oxygen 18 was concentrated to 99.5% by the thermal diffusion method (Non-patent Document 1). To date, the application of electrolysis of oxygen, nitrogen oxides and water, chemical isotope exchange, gas diffusion, rectification has been described for the concentration of water in oxygen. Among them, the method of water purification first demonstrated in 1944 is now successfully used in the industry (Non-Patent Document 2).

The oxygen isotope effect during electrolysis was detected simultaneously with the isotope effect of hydrogen (Non-patent Document 3). However, attempts to produce oxygen-18 in this manner have not been successful (Non-patent Documents 4 and 5). Similarly, attempts to enrich oxygen 18 by chemical isotope exchange in the exchange reaction of С ₂ with Н _2- have not been successful. The separation factor for this reaction is high -1046 but the reaction rate is too low to be effective on an industrial scale (Non-patent Document 6).

Based on the exchange reaction between nitrogen oxides NO and nitric acid, a chemical isotope exchange method for Н ₂ -18 18 − formation was realized (Non-patent Document 7). In this way, Н ₂ -18-18 having a degree of enrichment of about 15% could be obtained. The low technical and economic parameters of this process are related to the difficulty of quantitative conversion of nitric oxide to nitric acid, which is irreversibly converted to elemental nitrogen or nitrogen oxides in high oxidation states. The use of gas diffusion methods to produce oxygen-18 also does not give satisfactory results due to the low concentration factor (8).

However, the method of thermal diffusion is more effective and is not suitable for the production of large quantities of enriched Н ₂ О-18, due to the very slow kinetics of the process. For example, in order to obtain 250 ml of oxygen 18, a 59 m column row of 1.5 m or more in length was required (Non-Patent Document 9). Some later changes in this process make the method a bit faster. Thus, a product with 81% concentration after 3 weeks of operation in a four-step cascade using a column with dimensions 3.4 m × 9.2 mm from a starting intermediate with an 18-oxygen content of 1.5-2% Can be obtained (Non-Patent Document 10). The use of raw materials with an 18 content of about 40% in a 3-column cascade of 3 columns each makes it possible to produce up to 30 ml per day of a product with a concentration of 85-90% (non-patent literature) 11). However, these indicators are very far from the amount of production needed for production. Furthermore, they require pre-enriched materials in each case.

More effective is the process of water distillation. This method was first realized in 1937 and was able to obtain 200 ml of -18 ₂伴 う -18 with a concentration of 0.85% (12). In the subsequent method, this method was improved, and a distilled water concentration unit capable of producing water containing 24% O-18 and 1.7% O-17 in 1956 was created (Non-patent document 13) . The most complete process underlying modern production of oxygen 18 by water purification was carried out in the late 50's [14]. This process makes it possible to obtain Н ₂ -18-18 with a degree of enrichment of 99% or more and is characterized by high efficiency and reliability.

The method closest to the present invention for the method of producing oxygen 18 enriched water is the method described in this paper (Non-patent Document 15). This method, selected as a prototype, involves chemical isotope exchange rectification of water rich in 18% oxygen enriched with 18% of natural water with an oxygen content of 18-0.2% and deuterium of 0.015%. And obtaining in a two-step process of preconcentration by final concentration:
As a raw material, normal natural water having an oxygen content of about 0.2% and deuterium of about 0.015% is used. The presence of deuterium in natural water leads to the fact that deuterium enrichment occurs simultaneously with the enrichment of oxygen 18. At the operating temperature of the column at 65 ° C, the concentration factor αO-18 / O-16 of the H2O-18 / H2O-16 system is about 1,005, and the concentration factor αD / H of the HDO / H2O system is about 10 times larger and 1.045 is there) . As a result, the final product of production-H2O-18, nearly 100% has a composition of D2O-18. However, medical applications require products with natural hydrogen isotope content. The deuterium content in the product should not exceed 0.015%. Thus, the products obtained according to the prototype scheme must necessarily be further processed to remove deuterium (the so-called isotope composition normalization process). The standardization process is in principle carried out by the electrolytic decomposition of water, followed by the combustion of the oxygen 18 obtained in hydrogen with a natural isotopic composition. At this stage, loss and waste inevitably occur, which affects the production cost.

  In the same article, the equipment for obtaining the oxygen-rich water (FIG. 1) closest to the claimed one is described. The prototype installation includes:

-Preconcentrator consisting of a rectification column operating in an open circuit (without depletion) and having the first kind of selection ₂ -18-18: The obtained intermediate concentrate is sent to the final concentrator without feedback .

- final concentration unit comprising one column for discharging three columns and Н ₂ О-16 column to concentrate the Н ₂ О-18 column.

  Because of the adopted scheme, each preconcentration column not connected by a backflow in the subsequent stages of the cascade operates independently.

The capacity of the device with these properties is 4 kg Н ₂ -18-18 per year with a degree of enrichment of 90%. In the US, Europe, Israel and China, installations based on this method and this method are currently implemented more efficiently, supplying more than 50% of heavy oxygen water in the world market (about 1500 kg / year) (Non-Patent Document 16).

Clusius, Dickel and Becker, Naturwiss, 31, 210, 1943 H. G. Thode, S. R. Smith, F. D. Walkling, The Separation Of The Oxygen Isotopes By The Distillation Of Water, Canadian Journal of Research, 1944, 22b (4): 127-136, 10.1139 / cjr44b-016 E. W. Washburn, E. R. Smith and M. Frandsen, J. Chem. Phys. 1, 288, 1933 H. L. Johnston, J. Am. Chem. Soc., 57, 484, 1935 H. Anbar, H. Taube, J. Am. Chem. Soc. 78, 3252, 1956 W. T. Boyd, R. R. White, Ind. Eng. Chem. 44, 2202, 1952 T. I. Taylor, J. Chim. Phys. 60, 154, 1963 R. Sherr, J. Chim. Phys. 6, 251, 1938 Clusius, Dickel and Becker, Naturwiss, 31, 210, 1943 K. Clusius and K. Schleich, Helv. Chim. Acta, 45, N5, 1702, 1962 E. P. Ageev and G. M. Panczenkov, Atomnaja Energia, 14, No. 5, 494, 1963 Huffman and Urey, Ind. Eng. Chem. 29, 531, 1937 O. W. Umarov, W. A. Sokolski and N. M. Zavoronkov, Chim. Promyszi, 404, 1956 Dostrovsky, Llewellyn, Vromen, J. Chem. Soc. 3517, 1952; Dostrovsky ref. Proc. 2nd Intern. Conf. Peaceful Uses Atomic Energy, Geneva, 1958, p. Dostrovsky, I., Raviv, A .: "Proc. Int. Symp. Isotope Separation (Amsterdam, 1957)", p. 336, (1958), North-Holland, Amsterdam Oxygen-18 (CAS 32767-18-3), Market Research Report 2015, BAC Reports

  The characteristics of the prototype installation are shown in Table 1 (see FIG. 4).

The prototype installation uses raw material natural water with a natural deuterium content of 0.015%, and accordingly deuterium accumulates in the product and intermediate products (process medium in the final concentration column). The presence of significant amounts of deuterium (more than 50%) in the intermediate product drastically reduces the efficiency of the concentration process in the plant. _{This, H 2 О-18 / H} 2 О-16 equal ~ 1,005 (65 oС) in a separation factor α _{O-18 / O-16} system, the accumulation of deuterium decreases sharply: α _{O-18 /} HDО-18 / HDО-16 equal in the _O-16 system 1,0041, D ₂ -18-18 / D ₂ -1616 in the system equal 1,0034. Therefore, the efficiency of the process inversely proportional to the separation factor (productivity ) Decreases.

The proposed invention suffers from these drawbacks:
-Improvement of product quality and reduction of losses associated with the need for additional operations to remove deuterium in the prototype method and installation
Limited to prototype methods and installations due to increased process efficiency (productivity), accumulation in the technological flow of deuterium.
Solve the problems associated with the removal of

In order to solve the problems set up, ie to reduce product losses and improve the efficiency of the process, oxygen 18 is removed by a method of rectifying water under vacuum in a cascade of distillation columns including preconcentration Proposed method for obtaining enriched water 水 At a final concentration of ₂ -18-18 pre-concentration unit and final concentration unit, the process scheme and plant are: raw material-water on the plant supply line using natural water- It further includes a chemical isotope exchange unit within the carbon dioxide system. Natural water functions as a source of 18 oxygen. In the prototype method, simultaneously with oxygen 18, it directly enters the cascade of rectification columns, and deuterium contained in natural water is introduced into the technical stream. According to the claimed solution, the oxygen-18 contained in natural spring water is transferred to the plant's power supply by carbon dioxide acting as a transport agent for the plant's feedwater stream. The chemical isotope exchange unit consists of two columns of chemical isotope exchange, an untreated train irrigated with natural water and a power column through which a cascade of rectification trains circulates. The columns are connected together along a closed loop circulating carbon dioxide line to transfer oxygen-18 from the feed to the feed stream. Because deuterium is not transported by carbon dioxide, it does not enter the unit. The carbon dioxide is circulated countercurrent to the water flow in the column of the pretreatment unit to provide a transfer of oxygen 18 from the feedstream to the feedstream of the preconcentration unit.

  A feature of the proposed method is the principle of equipment supply. Oxygen-18 from natural water is cascaded through chemical isotope exchange units with carbon dioxide to improve plant productivity and eliminate product loss rather than eliminate the presence of deuterium in the process stream Is achieved.

A facility for obtaining oxygen-rich water closest to what is claimed. It is a flowchart of the manufacturing method of 方法₂ -18-18 according to the present invention. Table 2 shows the characteristics of the proposed installation according to the claimed method. It is Table 1 which shows the characteristic of the installation by a prototype.

  Installations have been proposed to achieve this technical result, including:

-Chemical isotope exchange site;
A preconcentration unit Н ₂ -18-18, consisting of a rectification column operating open circuit (no depletion) with the first type of choice
The final concentration unit comprising -Н ₂ О-18- concentration column and Н ₂ О-16- complexes containing column. In contrast to the known one, the proposed plant (FIG. 2) is a chemical isotope consisting of a complex of chemical isotope exchange columns in a water-carbon dioxide system to increase process efficiency and productivity. It can reduce the quality of the product and reduce the loss on the supply line of the pre-concentration unit with replacement unit.

The proposed invention is illustrated by the drawings,
-Shown in FIG. Scheme of the method of preparation of Н ₂ -18-18 according to 1-prototype.

FIG. 2 is a flow chart of the method for producing Н ₂ -18-18 according to the present invention.

The proposed plant for the production of water, rich in oxygen (FIG. 2) includes:
Chemical isotope exchange unit consisting of columns 15 and 16 of chemical isotope exchange in the water-carbon dioxide system.
A concentration unit consisting of a preconcentration column 1 to 10,
A final concentration unit comprising a concentration column 11 to 13 and an exhaust column 14;
The installation works as follows:

  The raw water stream enters a chemical isotope exchange unit in column 15. Countercurrent to the water flow in towers 15 and 16 is recycled carbon dioxide, which provides for the transfer of oxygen 18 from the feed stream (tower 16) to the power supply cascade 15. In this case, the deuterium contained in the raw water does not enter the cascade and therefore does not accumulate in the process stream and products. Water from the cascade feed tower 16 is fed to the preconcentration unit in parallel rectification towers 1 to 10 operating in open circuit (without depletion), the first is selected and the intermediate concentrate obtained is finalized without feedback It is transferred to the concentration unit.

  The intermediate concentrate in the final concentration unit concentration column is concentrated to a level of at least 95% with oxygen-18, and a water flow dump containing more than 99% oxygen-16 is cycled in the exhaustive column of the final concentration unit Taken from

  The equipment according to this technical solution ensures the production of water enriched with oxygen 18 to a level of 95% in order to obtain a product with high productivity, low loss and natural content of hydrogen isotopes . The latter is a necessary requirement for commercial products for use in medicine and biochemistry. Table 2 shows the characteristics of the proposed installation according to the claimed method (see FIG. 3).

  The equipment of this embodiment provides a product having a capacity of 6 kg per year and having a 95% enrichment and a deuterium content of 0.013 to 0.015% (at the level of natural deuterium content). For this reason, the product does not require additional manipulations to standardize its isotopic composition than hydrogen.

  Therefore, the installation of this technical solution has the following advantages compared to the prototype:

  It has a big productivity of -1.5 times.

  -Provide products with higher enrichment (95%).

  Ensuring the formation of products with isotopic composition standardized to hydrogen (0.013-0.015% deuterium content).

  Furthermore, it is important from a working point of view not to include deuterium-containing water in the process stream, eliminating the need for authorizing production according to nuclear safety standards in order for deuterium to belong to the nuclear material.

  The efficiency and economy of the claimed method and the proposed equipment demonstrate their technical and economic advantages compared to the methods and equipment of prototypes and other known technical solutions. Thus, this plant can be successfully used for industrial production of 18 oxygen enriched water.

The device according to the present invention is associated with the production of oxygen-18 for PET tomography and is useful as a facility for producing water rich in isotopic oxygen 18 (heavy oxygen water, Н ₂ -18 18).

1 to 10: Preconcentration column 11 to 13: Concentration column 14: Exhaust column 15, 16: Chemical isotope exchange column

Claims (2)

Select the first type of intermediate oxygen concentrate 18 in the preconcentrator column and concentrate it by vacuuming the water in a vacuum, including preconcentration in oxygen 18 operating in open circuit-enriched with oxygen 18 from natural water A method of obtaining purified water,
Final enrichment of the intermediate concentrate in a cascade of final enrichment columns consisting of an oxygen enrichment oxygen concentrator-18 and an oxygen-16 column, carbon dioxide and chemistry for the supply of the plant water circulating in the pre-concentrator The natural content of oxygen 18 maintained by isotope exchange, which supports the natural content of oxygen 18 by chemical isotope exchange with raw materials that are natural water.
A method characterized by Raw materials-a plant for obtaining oxygen-enriched water from natural water-are manufactured by selecting the first type of pre-concentration rectification column and acting in parallel on an open circuit without exhaustion Evacuated with a preconcentration unit, and a final concentration unit with 16 rows of oxygen made in the form of 18 rows of oxygen concentration,
A plant characterized in that the plant is additionally provided on the feed line of the pre-concentration unit with the complex of chemical isotope exchange columns in the water-carbon dioxide system.

Images