阅读说明：本技术 外循环式高放废液连续蒸发浓缩脱硝器 (External circulation type high-level radioactive waste liquid continuous evaporation concentration denitrator ) 是由 徐聪 于 2020-04-24 设计创作，主要内容包括：本发明公开了一种外循环式高放废液蒸发浓缩脱硝器,包括：蒸发浓缩脱硝釜、外部循环管、加热器,背压过热区和除沫净化塔,其中,蒸发浓缩脱硝釜一侧底部开口与外循环管相连,外循环管与加热器相连,加热器上部与背压过热区相连,背压过热区与蒸发浓缩脱硝釜的另一侧面开口相连,蒸发浓缩脱硝釜顶部与除沫净化塔相连。该蒸发浓缩脱硝器产生的沉淀不会大量沉积,有效分离小液滴和破除泡沫,防止爆沸发生,可适用于产生沉淀和/或易爆沸的高放废液的蒸发浓缩脱硝处理。(The invention discloses an external circulation type high-level radioactive waste liquid evaporation concentration denitrator, which comprises: concentrated denitration cauldron of evaporation, external circulating pipe, heater, backpressure overheat district and defoaming purifying column, wherein, the concentrated denitration cauldron of evaporation one side bottom opening links to each other with the external circulating pipe, and the external circulating pipe links to each other with the heater, and heater upper portion links to each other with the backpressure overheat district, and the backpressure overheat district links to each other with the another side opening of the concentrated denitration cauldron of evaporation, and the concentrated denitration cauldron top of evaporation links to each other with defoaming purifying column. The evaporation concentration denitrator can not generate a large amount of sediment, effectively separates small liquid drops and breaks foam, prevents bumping, and is suitable for evaporation concentration denitration treatment of high-level radioactive waste liquid generating sediment and/or bumping.)

1. The utility model provides an extrinsic cycle formula height is put waste liquid evaporative concentration denitrifier which characterized in that includes: an evaporation concentration denitration kettle, an external circulating pipe, a heater, a back pressure overheating area and a defoaming purification tower, wherein,

an opening at the bottom of one side of the evaporation concentration denitration kettle is connected with the external circulation pipe, the external circulation pipe is connected with the heater, the upper part of the heater is connected with the back pressure overheating area, the back pressure overheating area is connected with an opening at the other side surface of the evaporation concentration denitration kettle, and the top of the evaporation concentration denitration kettle is connected with the defoaming purification tower;

the evaporation concentration denitration kettle comprises a denitration agent distributor, a partition plate, an overflow area, an evaporation concentration denitration area and a cyclone separator, wherein the denitration agent distributor is arranged at the bottom of the evaporation concentration denitration kettle, the cyclone separator is arranged at the top of the evaporation concentration denitration kettle, and the overflow area separated from the evaporation concentration denitration area is formed on one side, close to a bottom opening, of the side surface of the evaporation concentration denitration kettle through the partition plate.

2. The external circulation type high level radioactive waste liquid evaporation concentration denitrator as claimed in claim 1, wherein the liquid in the evaporation concentration denitrator is higher than the partition plate, so that the liquid overflows into the overflow area.

3. The external circulation type high-level radioactive waste liquid evaporative concentration denitrator as claimed in claim 1, wherein the sediment generated in the evaporative concentration denitrator process cannot enter the overflow area under the action of gravity.

4. The external circulation type high level radioactive waste liquid evaporative concentration denitrator as claimed in claim 1, wherein the heater is separated from the evaporative concentration denitrator by the back pressure superheat region, the evaporative concentration denitrator is separated from the external circulation pipe by an overflow region, and the evaporative concentration denitrator is separated from the defoaming purification tower by a cyclone separator.

5. The external circulation type high level radioactive waste liquid evaporation, concentration and denitration device as claimed in claim 1, wherein the height of said back pressure superheat zone is larger than the theoretical value, so as to ensure that the high level radioactive waste liquid passing through said heater starts boiling evaporation after entering said evaporation, concentration and denitration kettle.

Technical Field

The invention relates to the technical field of nuclear spent fuel post-treatment, in particular to an external circulation type high-level radioactive waste liquid continuous evaporation concentration denitration device.

Background

After the nuclear reactor operates for a certain time, internal fuel is burnt to a certain degree and becomes spent fuel, and then the spent fuel needs to be discharged and subjected to post-treatment, and uranium, plutonium and other valuable nuclides in the spent fuel are recycled. At present, PUREX process is widely adopted for the post-treatment of the spent fuel. In the PUREX process and other similar processes, spent fuel is dissolved by nitric acid to form feed liquid, and then uranium plutonium in the nitric acid solution is extracted and separated through liquid-liquid extraction operation. The nitric acid solution is called a high-level radioactive waste solution, which contains uranium plutonium and other nuclides with high radioactivity and a long life cycle. The high level waste liquid is generally required to be reduced in volume by evaporation-concentration-denitration treatment so as to be subjected to subsequent temporary storage and to be subjected to glass solidification or further separation and volume reduction and the like. Therefore, the operation of evaporating, concentrating and denitrating the high-level radioactive waste liquid is a key link between the main process flow of the spent fuel post-treatment and the auxiliary process flow of the high-level radioactive waste liquid.

For the evaporation concentration denitration of the high-level radioactive waste liquid, 3 basic operation processes are as follows: heating the solution, boiling and evaporating the superheated solution, and carrying out a formaldehyde (or formic acid) denitration reaction. The typical apparatus used in the above steps is an externally heated evaporator in which a heating chamber and a vapor-liquid separation chamber are separately provided. The equipment has the remarkable characteristic that the 3 basic operation processes are all completed in a heating chamber, and the operation method generally adopts a sectional evaporation concentration-denitration (firstly heating an evaporation solution to concentrate nitric acid to a certain concentration, then stopping heating, adding formaldehyde or formic acid to denitrate so as to reduce the concentration of the nitric acid to a certain value, then heating the solution again to evaporate and concentrate and repeating the processes until the volume of the solution and the concentration of the nitric acid meet the requirements) or a steaming (heating, evaporating and concentrating the solution to a required volume once, then stopping heating, and then gradually adding formaldehyde or formic acid to denitrate to a required acidity once) operation method to treat the feed liquid. The structural feature analysis of the external heating evaporator shows that, for the feed liquid generating the precipitate in the evaporation concentration denitration process, 3 basic operation processes are all completed in the heating chamber, so if the precipitate is generated, the precipitate is inevitably deposited in the heating chamber, and the pipeline is blocked seriously, so that the operation cannot be normally carried out. The zirconium content in the high-level radioactive waste liquid is relatively high corresponding to the spent fuel of a power reactor with deeper burning, and zirconium ions and molybdenum ions are deposited in the form of zirconium molybdate precipitates when the concentration of nitric acid is reduced to a certain degree in the process of evaporating, concentrating and denitrifying the waste liquid, so that the commonly adopted external heating type evaporator and other similar evaporators such as a jacketed kettle type evaporator are not suitable for use. In addition, the existing high-level radioactive liquid waste evaporation concentration denitration equipment has the problem of easy bumping, namely the high-level radioactive liquid waste generates a large amount of foams and overflows out of the equipment to enter a subsequent pipeline, which causes serious problems of equipment state instability, radioactive leakage and the like. In view of the above, at present, no high-level radioactive waste liquid evaporation, concentration and denitration equipment capable of solving the problems of precipitation and bumping exists.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.

Therefore, the invention aims to provide an external circulation type high-level radioactive waste liquid evaporation concentration denitrator.

In order to achieve the above object, an embodiment of the present invention provides an external circulation type high level radioactive waste liquid evaporation concentration denitrator, including: the device comprises an evaporation concentration denitration kettle, an external circulating pipe, a heater, a back pressure overheating area and a defoaming purification tower, wherein an opening at the bottom of one side of the evaporation concentration denitration kettle is connected with the external circulating pipe, the external circulating pipe is connected with the heater, the upper part of the heater is connected with the back pressure overheating area, the back pressure overheating area is connected with an opening at the other side of the evaporation concentration denitration kettle, and the top of the evaporation concentration denitration kettle is connected with the defoaming purification tower; the evaporation concentration denitration kettle comprises a denitration agent distributor, a partition plate, an overflow area and a cyclone separator, wherein the denitration agent distributor is arranged at the bottom of the evaporation concentration denitration kettle, the cyclone separator is arranged at the top of the evaporation concentration denitration kettle, and the overflow area separated from the evaporation concentration denitration area is formed on one side, close to a bottom opening, of the side surface of the evaporation concentration denitration kettle through the partition plate.

The external circulation type high-level radioactive waste liquid evaporation concentration denitrator provided by the embodiment of the invention adopts the strategies of separating the heating area from the evaporation concentration denitrating area, separating the evaporation concentration denitrating area from the inlet of the external circulation pipe and ensuring that the sediment generated by the evaporation concentration denitrating area does not enter and deposit in the heating chamber in a large amount, and simultaneously adopts the cyclone separator to treat the steam before entering the defoaming purification tower, so as to effectively separate small liquid drops in the steam and break foam, thereby effectively preventing bumping from occurring, being particularly suitable for evaporation concentration denitrating treatment of high-level radioactive waste liquid generating sediment and/or easy bumping, and being widely applied to the field of radioactive nuclear chemical industry.

In addition, the external circulation type high level effluent evaporative concentration denitrator according to the above embodiment of the invention may further have the following additional technical features:

further, in one embodiment of the present invention, the liquid in the evaporation concentration denitration kettle is higher than the partition plate, so that the liquid overflows into the overflow area.

Further, in one embodiment of the present invention, the precipitate generated during the evaporation concentration denitration process is not introduced into the overflow area by gravity.

Further, in one embodiment of the present invention, the heater is separated from the evaporation concentration denitration kettle by the back pressure superheating area, the evaporation concentration denitration kettle is separated from the external circulation pipe by the overflow area, and the evaporation concentration denitration kettle is separated from the defoaming purification tower by the cyclone separator.

Further, in an embodiment of the invention, the height of the back pressure superheat zone is larger than a theoretical value, so as to ensure that the high-level waste liquid passing through the heater starts boiling evaporation after entering the evaporation concentration denitration kettle.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram showing the general structure of an external circulation type high level effluent evaporative concentration denitrator according to an embodiment of the present invention;

FIG. 2 is a schematic view showing the internal structure and principle of an evaporative concentration denitrator according to an embodiment of the present invention;

FIG. 3 is a flow chart of the evaporative concentration denitration process of high level radioactive waste liquid according to an embodiment of the present invention.

Description of reference numerals:

1-evaporation concentration denitration kettle, 2-external circulation pipe; 3-a heater; 4-a back pressure superheat zone; 5-defoaming purification tower; 6-a cyclone separator; 7-an evaporation concentration denitration area; 8-a separator; 9-an overflow area; 10-a denitrifier distributor; 11-outlet of back pressure superheat zone; 12-external circulation pipe inlet; 13-evaporating, concentrating and denitrating a discharge port of the denitration kettle; 14-cyclone inlet; 15-cyclone liquid seal; 16-cyclone water phase discharge outlet; a, evaporating, concentrating and denitrifying liquid level; b, a denitration reaction zone; precipitate generated by the C-denitration reaction.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The following describes an external circulation type high level effluent evaporative concentration denitrator according to an embodiment of the invention with reference to the attached drawings.

FIG. 1 is a schematic structural diagram of an external circulation type high level radioactive waste liquid evaporation concentration denitrator according to an embodiment of the present invention.

As shown in fig. 1, the evaporation concentration denitrator includes: an evaporation concentration denitration kettle 1, an external circulating pipe 2, a heater 3, a back pressure overheating area 4 and a defoaming purification tower 5.

As shown in fig. 2, an opening 12 in the bottom of one side of the evaporation concentration denitration kettle 1 is connected with an external circulation pipe 2, the external circulation pipe 2 is connected with a heater 3 after U-shaped bending, the upper part of the heater 3 is connected with a back pressure superheating area 4 with a preset height, the back pressure superheating area 4 is connected with an opening 11 in the side surface of the evaporation concentration denitration kettle, and the top of the evaporation concentration denitration kettle 1 is connected with a defoaming purification tower 5.

Further, the evaporation concentration denitration kettle 1 comprises a cyclone separator 6, an evaporation concentration denitration area 7, a partition plate 8, an overflow area 9 and a denitration agent distributor 10, specifically, the cyclone separator 6 is arranged at the top of the inside of the evaporation concentration denitration kettle 1, the side surface of the evaporation concentration denitration kettle 1 forms the overflow area 9 separated from the evaporation concentration denitration area 7 through the partition plate 8, the bottom of the overflow area 9 is provided with an opening 12 connected with an external circulation pipe 2, and the denitration agent distributor 10 is arranged at the bottom of the evaporation concentration denitration kettle 1.

Further, the heating zone 3 is separated from the evaporation concentration denitration zone 7 through the back pressure overheating zone 4, the evaporation concentration denitration zone 7 is separated from the external circulation pipe 2 through the overflow zone 9, and the evaporation concentration denitration zone 7 is separated from the top defoaming purification tower 5 through the cyclone separator 6.

It should be noted that the liquid level a of the evaporation concentration denitration zone 7 exceeds the height of the partition plate 8, and can overflow into the overflow zone 9; the sediment C generated in the evaporation concentration denitration process can not enter the overflow area 9 due to the action of gravity; the flow rate in the external circulation pipe 2 is sufficiently fast to prevent the deposition of the precipitates therein; the height of the back pressure overheating zone 4 needs to be high enough and larger than a theoretical value, so that the boiling evaporation of the high-level waste liquid passing through the heater 3 can be ensured after the high-level waste liquid enters the evaporation concentration denitration zone 7.

It can be understood that the working process of the external circulation type high level effluent evaporative concentration denitrator in the embodiment of the invention is as follows: putting the high-level radioactive waste liquid into an evaporation concentration denitration kettle 1, heating the high-level radioactive waste liquid by using a heater 3, boiling and evaporating the heated high-level radioactive waste liquid in the evaporation concentration denitration kettle 1 after the heated high-level radioactive waste liquid passes through a back pressure overheating area, releasing a denitration agent by a denitration agent distributor 10, generating a denitration reaction, generating a large amount of water vapor by evaporation in the boiling process, leading the generated nitrogen oxide gas to carry partial droplets and foam to enter a cyclone separator 6, leading the droplets with high density to return to the kettle again after separation, leading the water vapor, the nitrogen oxide gas and a small amount of foam to enter a foam removing purification tower 5 at the top, leading the foam removing purification tower 5 to carry out thorough foam removal and recovery of volatile nuclide, continuously carrying out the evaporation concentration denitration process, but leading the concentration of metal elements to be continuously increased and leading the acidity to be lower, leading partial metal elements to form precipitates and deposit, the flow rate of the external circulation pipe 2 is controlled fast enough to prevent the precipitation in the external circulation pipe 2.

The following describes the external circulation type high level radioactive liquid waste evaporation concentration denitrator according to an embodiment of the present invention.

The internal diameter of an evaporation concentration denitration kettle 1 in an external circulation type high-level radioactive waste liquid evaporation concentration denitration device is410mm, 1770mm height of middle straight section, 370mm height of lower gradually-reducing section, 60mm inner diameter of external circulating pipe, tubular steam heater as heater 3, and heat exchange area of 3.2m²The height of the back pressure superheat zone 4 is 2.5 m. The bottom of the evaporation concentration denitration area 7 is provided with a denitration agent formaldehyde distributor 10, one side of the side surface close to the inlet 12 of the external circulation pipe 2 is provided with an overflow area 9 through a partition plate 8 with the height of 610mm, and the top of the evaporation concentration denitration area is provided with a cyclone separator 6. The 1 top of evaporation concentration denitration cauldron is connected with defoaming purifying column 5, and the internal diameter is 60mm, highly is 990mm, and inside is provided with 5 sieves.

As shown in fig. 3, taking the above-mentioned external circulation type high level radioactive waste liquid evaporation concentration denitrator as an example, the specific high level radioactive waste liquid evaporation concentration denitration process is as follows:

adopting 37-40% formaldehyde solution as denitrifier, and continuously adding 16.5g-NaNO at 105 deg.C at a feed rate of 10L/h₃Concentration of nitric acid in 2.5 mol/L nitric acid solution of/L, 0.45 g-Cs/L and 0.44 g-Ce/L is evaporated, concentrated and denitrated to 1.0 mol/L, the following denitration reaction occurs in the denitration reaction zone B:

the evaporation leads to a large amount of water evaporation to be vapor, leads to the feed liquid by the concentration, and above-mentioned denitration reaction constantly reduces the nitric acid concentration simultaneously, guarantees that the acidity can not be too high, prevents that equipment from seriously corroding. The generated water vapor and the generated nitrogen oxide gas can carry part of small liquid droplets and foams into the cyclone separator 6. In the cyclone 6, the denser droplets are thrown to the outer wall and pass down through the liquid seal 15, the discharge port 16 and back into the tank again, wherein the foam is destroyed by the externally wrapped liquid film and simultaneously has the effect of eliminating the foam, while the steam, gas and a small amount of foam enter the top defoaming purification tower 5. The top of the defoaming purification tower is connected with a steam condenser, and the upward steam in the tower contacts with the condensate refluxed from the top of the tower to realize thorough defoaming and recovery of volatile nuclide. The non-condensable gas discharged from the steam condensate further enters a tail gas absorption link to absorb the nitrogen oxide in the tail gas, and the discharged nitrogen oxideThe method comprises the steps of feeding the solution into a storage tank, recovering, and continuously carrying out evaporation concentration denitration, wherein the acidity of the solution in an evaporation concentration denitration kettle 1 is always kept about 1.0 mol/L, but the concentration of metal elements is continuously increased, and because the acidity is low, part of the metal elements are precipitated and deposited in a tapered section at the lower part of a denitration area B, when the total concentration of metal oxides in the solution reaches 200 g/L, stopping feeding and evaporation concentration denitration, discharging the feed liquid (including precipitate) through a bottom discharge outlet 13, carrying out evaporation concentration denitration again after discharging is finished, and finally completing the evaporation concentration denitration according to the conditions and operation steps, wherein the acidity of the feed liquid is 0.9-1.1 mol-HNO₃L, the generated precipitate is not found to be deposited in the external circulation pipe 2 and the heater 3 and can be smoothly discharged from the discharge port 13 at the bottom of the evaporation concentration denitration kettle 1, and no obvious foam overflow accident occurs.

The experimental results of the above examples show that: the embodiment of the invention can effectively solve the problems of precipitation and bumping in the process of evaporating, concentrating and denitrifying the high-level radioactive waste liquid.

According to the external circulation type high-level radioactive waste liquid evaporation concentration denitrator provided by the embodiment of the invention, through adopting the strategies of separating the heating area from the evaporation concentration denitrating area, separating the evaporation concentration denitrating area from the inlet of the external circulation pipe and ensuring that the flow velocity in the external circulation pipe is high enough, the precipitate generated by the evaporation concentration denitrating area cannot enter and deposit in a heating chamber in a large amount, meanwhile, the cyclone separator is adopted to treat the steam before entering the defoaming purification tower, so that the small liquid drops in the steam are effectively separated and the foam is broken, the occurrence of bumping can be effectively prevented, the external circulation type high-level radioactive waste liquid evaporation concentration denitrator is particularly suitable for the evaporation concentration denitrating treatment of high-level radioactive waste liquid generating precipitate and/or easy.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.