Evaporator and method for evaporation concentration and oxalic acid destruction of plutonium-containing feed liquid

Abstract

The invention discloses a plutonium-containing feed liquid evaporation concentration and oxalic acid destruction evaporator and method, the plutonium-containing feed liquid evaporation concentration and oxalic acid destruction evaporator comprises a plurality of heating chambers and a separation chamber, the plurality of heating chambers are symmetrically distributed around the separation chamber, the upper part of each heating chamber is communicated with the separation chamber through an upper circulating pipe, and the lower part of each heating chamber is communicated with the separation chamber through a lower circulating pipe; the lower part of the heating chamber is communicated with the separation chamber through a lower circulating pipe, and communicating pipes are arranged among the heating chambers; a feed liquid inlet is formed in the lower circulating pipe, and a feed liquid outlet is formed in the bottom of the lower circulating pipe; the separation chamber is provided with a secondary steam outlet and a leacheate inlet, a purification tower plate is arranged in the separation chamber, and a demister is arranged on the purification tower plate. According to the invention, plutonium-containing feed liquid can be evaporated and concentrated, oxalic acid destruction can be synchronously completed, secondary steam can be purified, the critical safety requirement is met, and the working flux is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear industry, and in particular to an evaporator and method for evaporating and concentrating plutonium-containing liquid and destroying it with oxalic acid. Background Art

[0002] Some nuclear fuels adopt the closed cycle technology route, and nuclear fuel reprocessing is the key link to realize the nuclear fuel cycle. In the plutonium tail process of nuclear fuel reprocessing, the Pu(NO3)3 solution from the plutonium purification cycle is priced and acidified, and then precipitated by adding oxalic acid solution to convert it into plutonium oxalate (IV) precipitate. The precipitate slurry is filtered to obtain plutonium oxalate filter cake and mother liquor. The plutonium concentration in the plutonium tail oxalate precipitate mother liquor is about tens to 100 mg / L, the nitric acid concentration is about 2.5 mol / L, and the oxalic acid content is about 0.05-0.1 mol / L. These plutonium-containing feed liquids need to destroy the oxalic acid and return to the plutonium purification cycle. If the feed liquid is not concentrated, it will lead to an increase in the flux of the plutonium purification cycle process equipment and an increase in the amount of waste liquid, which will have an adverse effect on the design and later operation of the plutonium purification cycle.

[0003] At present, the post-processing plant has not adopted the mother liquor evaporation concentration process, but proposed an evaporator with a single heating chamber and a single separation chamber. Due to the critical safety limitation of the device size, the heating chamber size is small, so its working flux is low. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an evaporator and method for evaporation concentration and oxalic acid destruction of plutonium-containing liquid in view of the above-mentioned deficiencies in the prior art, which can evaporate and concentrate the plutonium-containing liquid and simultaneously complete oxalic acid destruction, and can also purify the secondary steam, while meeting the critical safety requirements and improving the working flux.

[0005] The technical solution of the present invention to solve the above technical problems is:

[0006] According to a first aspect of the present invention, there is provided an evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid, comprising a heating chamber and a separation chamber, wherein:

[0007] There are multiple heating chambers, which are symmetrically distributed around the separation chamber. The upper part of each heating chamber is connected to the separation chamber through an upper circulation pipe, and the lower part of each heating chamber is connected to the separation chamber through a lower circulation pipe.

[0008] The lower circulation pipe is provided with a liquid feed inlet and a liquid feed outlet at the bottom thereof;

[0009] The separation chamber is provided with a secondary steam outlet and an eluent inlet, a purification tower plate is provided in the separation chamber, and a demister is provided on the purification tower plate.

[0010] Optionally, there are two heating chambers, which are symmetrically distributed on both sides of the separation chamber.

[0011] Optionally, the heating chamber includes a shell and a shell-and-tube heating tube, wherein: an upper tube plate is provided at the upper portion of the shell, and a lower tube plate is provided at the lower portion of the shell, so that the interior of the shell is divided into an upper tube box, a middle heating section and a lower tube box, the upper tube box is connected to the separation chamber through an upper circulation tube, the lower tube box is connected to the separation chamber through a lower circulation tube, the middle heating section is provided with a steam inlet, a steam condensate outlet and a non-condensable gas outlet for passing heating steam; the shell-and-tube heating tube is arranged in the middle heating section of the shell to circulate the feed liquid, wherein the top end of each heating tube in the shell-and-tube heating tube is connected to the upper tube box after being distributed and fixed through the upper tube plate, and the bottom end thereof is connected to the lower tube box after being distributed and fixed through the lower tube plate.

[0012] Optionally, the lower circulation pipe includes a lower circulation pipe main pipe and multiple lower circulation pipe branches, the top of the lower circulation pipe main pipe is connected to the separation chamber, and each lower circulation pipe branch is connected to the lower part of the lower circulation pipe main pipe, the slurry inlet is arranged on the lower circulation pipe main pipe, and the slurry outlet is arranged at the bottom end of the lower circulation pipe main pipe.

[0013] Optionally, the cross-sectional area of ​​the upper circulation pipe is 80% to 125% of the total cross-sectional area of ​​the shell-and-tube heating pipes; the cross-sectional area of ​​the lower circulation pipe branches is 80% to 100% of the total cross-sectional area of ​​the shell-and-tube heating pipes, and the cross-sectional area of ​​the lower circulation pipe main pipe is greater than the sum of the total cross-sectional areas of the lower circulation pipe branches.

[0014] Optionally, a connecting pipe is provided between the heating chambers.

[0015] Optionally, the evaporator adopts a large aspect ratio structural design, wherein the aspect ratio of the separation chamber is 25-15, and the aspect ratio of the heating chamber is 25-15.

[0016] Optionally, the purification tower plate is a bubble tower plate or a packed tower plate, and the demister is a wire mesh demister or a baffle demister.

[0017] Optionally, the evaporator is made entirely of zirconium alloy or titanium alloy, and the filler therein is made of ceramic material.

[0018] According to a second aspect of the present invention, there is provided a method for evaporating and concentrating plutonium-containing liquid and destroying it with oxalic acid using the evaporator described above, the steps comprising: mixing the plutonium-containing liquid and the manganese solution, introducing the mixture into the liquid inlet, and introducing heating steam into the steam inlet, making use of density difference and temperature difference to allow the liquid to circulate naturally in the evaporator, and completing evaporation concentration and oxalic acid destruction, the generated secondary steam is discharged from the secondary steam outlet after being treated with the eluent, the purification tower plate and the demister, and the concentrated liquid is discharged from the liquid outlet when the concentration reaches the expected concentration multiple and the oxalic acid destruction meets the requirements.

[0019] The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid of the present invention is the first of its kind in the industry and has the following beneficial effects compared to the prior art:

[0020] (1) Capable of completing evaporation concentration and oxalic acid destruction of plutonium-containing liquid;

[0021] (2) Due to the presence of multiple heating chambers, the working flux of the equipment can be effectively increased while meeting critical safety requirements;

[0022] (3) Ability to effectively complete secondary steam purification;

[0023] (4) Stable operation, can be applied to spent fuel reprocessing plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of an evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid in an embodiment of the present invention;

[0025] Figure 2 4 is a cross-sectional view of a heating chamber in an embodiment of the present invention.

[0026] In the figure: 10-heating chamber; 11-tube-in-tube heating tube; 12-lower tube box; 13-upper tube box; 14-upper tube sheet; 15-lower tube sheet; 16-non-condensable gas outlet; 17-steam inlet; 18-steam condensate outlet; 19-shell; 20-separation chamber; 21-purification tower plate; 22-demister; 23-eluent inlet; 24-secondary steam outlet; 30-connecting pipe; 31-upper circulation pipe; 32-lower circulation pipe main pipe; 33-lower circulation pipe branch pipe; 34-feed liquid inlet; 35-feed liquid outlet. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0028] Aiming at the problems in the prior art that the heating chamber size is small and the working flux is low due to the size of the critical safety limiting device of the evaporator, the present invention provides an evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid, comprising a heating chamber and a separation chamber, wherein:

[0029] There are multiple heating chambers, which are symmetrically distributed around the separation chamber. The upper part of each heating chamber is connected to the separation chamber through an upper circulation pipe, and the lower part of each heating chamber is connected to the separation chamber through a lower circulation pipe.

[0030] The lower circulation pipe is provided with a liquid feed inlet and a liquid feed outlet at the bottom thereof;

[0031] The separation chamber is provided with a secondary steam outlet and an eluent inlet, a purification tower plate is provided in the separation chamber, and a demister is provided on the purification tower plate.

[0032] Furthermore, the present invention also provides a method for evaporating and concentrating plutonium-containing liquid and destroying it with oxalic acid using the evaporator described above, the steps comprising:

[0033] After the plutonium-containing feed liquid and the manganese solution are mixed, they are introduced from the feed liquid inlet, and heating steam is introduced from the steam inlet. The density difference and temperature difference are used to make the feed liquid circulate naturally in the evaporator, and the evaporation concentration and oxalic acid destruction are completed. The secondary steam generated is discharged from the secondary steam outlet after being treated by the eluent, purification tower plate and demister. When the concentrated liquid is concentrated to the expected concentration multiple and the oxalic acid destruction meets the requirements, it is discharged from the feed liquid outlet.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment discloses an evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid, comprising a heating chamber 10 and a separation chamber 20, wherein:

[0036] The number of the heating chambers 10 is two, but not limited thereto, and the two heating chambers 10 are symmetrically distributed on both sides of the separation chamber 20, and the upper part of each heating chamber is connected to the separation chamber through an upper circulation pipe, and the lower part thereof is connected to the separation chamber 20 through a lower circulation pipe;

[0037] A feed liquid inlet 34 is provided on the lower circulation pipe, and a feed liquid outlet 35 is provided at the lowest point of the bottom thereof. The plutonium-containing feed liquid (e.g., plutonium oxalate precipitation mother liquid produced in the plutonium tail process of nuclear fuel post-processing) is introduced from the feed liquid inlet, and evaporated and concentrated after being heated in the heating chamber 10. The generated secondary steam enters the separation chamber 20, and at the same time, oxalic acid reacts with nitric acid in the feed liquid to destroy the oxalic acid. When the concentrated liquid reaches the expected concentration multiple and the oxalic acid destruction meets the requirements, it is discharged from the feed liquid outlet 35.

[0038] The separation chamber 20 is provided with a secondary steam outlet 24 and an eluent inlet 23. A purification plate 21 is provided in the separation chamber 20 to purify the secondary steam, wherein the secondary steam outlet 24 is located at the top of the separation chamber 20, and the eluent inlet 23 is located above the top purification plate 21; a demister 22 is provided on the purification plate 21 to remove entrained mist, and the purified and demistered secondary steam is discharged from the secondary steam outlet 24.

[0039] Specifically, the evaporator adopts a slender structure design, and the heating chamber 10 and the separation chamber 20 both have a large aspect ratio to meet critical safety requirements, wherein the aspect ratio of the heating chamber 10 is 25-15, and the aspect ratio of the separation chamber 20 is 25-15.

[0040] Compared with the prior art, the evaporator of this embodiment, due to the use of multiple heating chambers, can effectively increase the working flux of the equipment while meeting the critical safety requirements, thereby solving the problems of the evaporator in the prior art, such as the small size of the heating chamber and the low working flux due to the size of the critical safety limiting device.

[0041] In some embodiments, Figure 1 , Figure 2 As shown, the heating chamber 10 includes a shell 19 and a tubular heating tube 11, the steam flows through the shell side of the heating chamber, and the feed liquid flows through the heating tube side, wherein:

[0042] An upper tube sheet 14 is provided at the upper part of the shell 19, and a lower tube sheet 15 is provided at the lower part of the shell 19, so that the interior of the shell 19 is divided into an upper tube box 13, a middle heating section and a lower tube box 12. The upper tube box 13 is connected to the separation chamber 20 through an upper circulation pipe 31, and the lower tube box 12 is connected to the separation chamber 20 through a lower circulation pipe. The middle heating section is provided with a steam inlet 17, a steam condensate outlet 18 and a non-condensable gas outlet 16 for passing heating steam, wherein the steam inlet 17 is located at the upper part of the middle heating section, the steam condensate outlet 18 is located at the lower part of the middle heating section, and the non-condensable gas outlet 16 is located above the steam inlet 17;

[0043] The tubular heating tubes 11 are arranged in the middle heating section of the shell 19 to circulate the feed liquid, wherein the top ends of the individual heating tubes in the tubular heating tubes 11 are connected to the upper tube box 13 after being distributed and fixed by the upper tube plate 14, and the bottom ends thereof are connected to the lower tube box 12 after being distributed and fixed by the lower tube plate 15.

[0044] In this embodiment, the specification of each heating tube in the tube-in-tube heating tube 11 is φ19 or φ25.

[0045] In some embodiments, the lower circulation pipe includes a lower circulation pipe main pipe 32 and a lower circulation pipe branch pipe 33, wherein: the top end of the lower circulation pipe main pipe 32 is connected to the separation chamber 20; the number of the lower circulation pipes 33 is the same as the number of the heating chambers 10, which is two in this embodiment; each lower circulation pipe branch pipe 33 is connected to the lower part of the lower circulation pipe main pipe 32, that is, the lower part of the lower circulation pipe is divided into two lower circulation pipe branches 33 leading to two heating chambers 10; the slurry inlet 34 is arranged on the lower circulation pipe main pipe 32, for example, at the lower part of the lower circulation pipe main pipe 32; the slurry outlet 35 is arranged at the bottom end of the lower circulation pipe main pipe 32.

[0046] In some embodiments, the cross-sectional area of ​​the upper circulation pipe 31 is 80% to 125% of the total cross-sectional area of ​​the shell-and-tube heating pipe 11 to ensure that the gas-liquid mixture passes through the upper circulation pipe to reach the separation chamber for gas-liquid separation; the cross-sectional area of ​​the lower circulation pipe branch 33 is 80% to 100% of the total cross-sectional area of ​​the shell-and-tube heating pipe 11 to ensure circulation, and the cross-sectional area of ​​the lower circulation pipe main pipe 32 is greater than the sum of the total cross-sectional areas of the lower circulation pipe branches 33.

[0047] In some embodiments, a connecting pipe 30 is provided between the heating chambers 10 to balance the pressure of each heating chamber.

[0048] In some embodiments, the purification tray 21 is a bubble tray or a packing tray, but is not limited thereto and may be other tray forms capable of achieving gas purification.

[0049] In some embodiments, the demister 22 is a wire mesh demister or a baffle demister, but is not limited thereto.

[0050] In some embodiments, the entire evaporator is made of zirconium alloy or titanium alloy. When the purification tray 21 is a packed tray, the packing therein is made of ceramic material.

[0051] The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid in this embodiment is the first of its kind in the industry and has the following beneficial effects compared to the prior art:

[0052] (1) Capable of completing evaporation concentration and oxalic acid destruction of plutonium-containing liquid;

[0053] (2) Due to the presence of multiple heating chambers, the working flux of the equipment can be effectively increased while meeting critical safety requirements;

[0054] (3) Ability to effectively complete secondary steam purification;

[0055] (4) Stable operation, can be applied to spent fuel reprocessing plants.

[0056] Example 2

[0057] This embodiment discloses a method for evaporating and concentrating a plutonium-containing liquid and destroying it with oxalic acid using the evaporator described above, the steps comprising:

[0058] The plutonium-containing feed liquid and manganese solution (which may be potassium permanganate solution, manganese nitrate solution, etc.) are mixed and introduced into the feed liquid inlet 34, and heating steam is introduced into the steam inlet 17. The feed liquid is naturally circulated in the evaporator by utilizing the density difference and temperature difference, and evaporation concentration and oxalic acid destruction are completed. The generated secondary steam is discharged from the secondary steam outlet 24 after being treated by the eluent (such as the condensate of the secondary steam), the purification tower plate 21 and the demister 22. When the concentrated liquid is concentrated to the expected concentration multiple and the oxalic acid destruction meets the requirements, it is discharged from the feed liquid outlet 35.

[0059] The method for evaporation concentration and oxalic acid destruction of plutonium-containing liquid in this embodiment can perform evaporation concentration of plutonium-containing liquid and simultaneously complete oxalic acid destruction, and can also purify secondary steam, while meeting criticality safety requirements, having a large working flux and stable equipment operation, and can be applied to spent fuel reprocessing plants.

[0060] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid, characterized in that: It comprises a heating chamber (10) and a separation chamber (20), wherein: There are multiple heating chambers, which are symmetrically distributed around the separation chamber. The upper part of each heating chamber is connected to the separation chamber through an upper circulation pipe, and the lower part of each heating chamber is connected to the separation chamber through a lower circulation pipe. The lower circulation pipe is provided with a liquid inlet (34) and a liquid outlet (35) at its bottom; The separation chamber is provided with a secondary steam outlet (24) and an eluent inlet (23), a purification tower plate (21) is provided in the separation chamber, and a demister (22) is provided on the purification tower plate.

2. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to claim 1, characterized in that: The number of the heating chambers is two, and the two heating chambers are symmetrically distributed on both sides of the separation chamber.

3. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to claim 1, characterized in that: The heating chamber comprises a shell (19) and a tubular heating tube (11), wherein: The upper part of the shell is provided with an upper tube plate (13), and the lower part of the shell is provided with a lower tube plate (12), so that the interior of the shell is divided into an upper tube box (14), a middle heating section and a lower tube box (15), the upper tube box is connected with the separation chamber through an upper circulation pipe, and the lower tube box is connected with the separation chamber through a lower circulation pipe, and the middle heating section is provided with a steam inlet (17), a steam condensate outlet (18) and a non-condensable gas outlet (16) for passing heating steam; The tube-in-tube heating tubes are arranged in the middle heating section of the shell to circulate the feed liquid, wherein the top ends of the individual heating tubes in the tube-in-tube heating tubes are connected to the upper tube box after being distributed and fixed through the upper tube plate, and the bottom ends thereof are connected to the lower tube box after being distributed and fixed through the lower tube plate.

4. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to claim 1, characterized in that: The lower circulation pipe comprises a lower circulation pipe main pipe (32) and a plurality of lower circulation pipe branches (33). The top of the lower circulation pipe main pipe is connected to the separation chamber, and each lower circulation pipe branch pipe is connected to the lower part of the lower circulation pipe main pipe. The feed liquid inlet is arranged on the lower circulation pipe main pipe, and the feed liquid outlet is arranged at the bottom end of the lower circulation pipe main pipe.

5. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to claim 4, characterized in that: The cross-sectional area of ​​the upper circulation tube is 80% to 125% of the total cross-sectional area of ​​the tubular heating tube; The cross-sectional area of ​​the lower circulation pipe branch is 80% to 100% of the total cross-sectional area of ​​the tubular heating pipe, and the cross-sectional area of ​​the lower circulation pipe main pipe (32) is greater than the sum of the total cross-sectional areas of the lower circulation pipe branches (33).

6. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to any one of claims 1 to 5, characterized in that: A connecting pipe (30) is provided between the heating chambers.

7. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to any one of claims 1 to 5, characterized in that: The evaporator adopts a large aspect ratio structural design, wherein the aspect ratio of the separation chamber is 25-15, and the aspect ratio of the heating chamber is 25-15.

8. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to any one of claims 1 to 5, characterized in that: The purification tower plate is a bubble tower plate or a packing tower plate, and the demister is a wire mesh demister or a baffle demister.

9. The evaporator for evaporation concentration and oxalic acid destruction of plutonium-containing liquid according to any one of claims 1 to 5, characterized in that: The evaporator is made of zirconium alloy or titanium alloy as a whole, and the filler therein is made of ceramic material.

10. A method for evaporating and concentrating plutonium-containing liquid and destroying it with oxalic acid using the evaporator described in any one of claims 1 to 9, characterized in that the steps include: After the plutonium-containing feed liquid and the manganese solution are mixed, they are introduced from the feed liquid inlet (34), and heating steam is introduced from the steam inlet (17). The feed liquid is naturally circulated in the evaporator by utilizing the density difference and the temperature difference, and evaporation concentration and oxalic acid destruction are completed. The secondary steam generated is discharged from the secondary steam outlet (24) after being treated by the eluent, the purification plate (21) and the demister (22). When the concentrated liquid reaches the expected concentration multiple and the oxalic acid destruction meets the requirements, it is discharged from the feed liquid outlet (35).

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