Negative pressure evaporation system and method for treating radioactive waste liquid

Abstract

The invention discloses a negative pressure evaporation system and method for treating radioactive waste liquid. The negative pressure evaporation system comprises a waste liquid collecting tank; the first pipeline is connected with the waste liquid collecting tank; the first steam-jet pump is arranged on the first pipeline; the evaporator is connected with the first pipeline; the condenser is connected with the evaporator; the second pipeline is connected with the condenser; the steam-jet pump for generating negative pressure is arranged on the second pipeline, and the steam-jet pump for generating negative pressure is used for generating negative pressure; the steam condenser is connected with the second pipeline; and the condensate tank is connected with the steam condenser, and the condensate tank is also connected with the condenser. The steam jet pump which is passive equipment is adopted to establish a negative pressure environment in the evaporator, so that other active negative pressure generating equipment is prevented from being frequently maintained in a radioactive environment, and workers are prevented from being damaged by irradiation. The evaporation temperature of the radioactive acidic waste liquid is reduced by utilizing the principle that the lower the pressure is, the lower the boiling point of the waste liquid is, the corrosion of the acidic waste liquid to equipment in a high-temperature environment is reduced, and the service life of the evaporator is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive waste treatment, and in particular relates to a negative pressure evaporation system and method for treating radioactive waste liquid. Background Art

[0002] A large amount of radioactive acidic waste liquid will be generated during the spent fuel reprocessing process. Evaporation is widely used in the nuclear industry as an effective means of treating radioactive waste liquid. In order to protect personnel from radioactive hazards, motor-driven conveying equipment commonly used in traditional industries, such as pumps and compressors, are not applicable in the radioactive waste liquid treatment process due to their short lifespan and the need for close maintenance and replacement by personnel. At present, there are two types of radioactive waste liquid evaporation that have been applied in domestic engineering projects. One is to use a kettle evaporator to evaporate at normal pressure, and at the same time add formaldehyde solution to the evaporator to react with nitric acid to keep the acidity of the concentrated liquid stable; the other is to directly evaporate the waste liquid at normal pressure.

[0003] In the process of adding formaldehyde for denitration evaporation, a certain concentration of formaldehyde must be continuously and quantitatively added during the evaporation process to perform denitration operations to reduce the acidity of the concentrated solution. After the secondary steam and non-condensable gases generated during the evaporation process enter the condenser for condensation, the condensate enters the condensate collection tank. The non-condensable gases need to further pass through the gas cooler, droplet collector, high-efficiency demister, preheater and high-efficiency filter, and finally be purified by a special nitrogen oxide (NOx) purification system and discharged through the chimney. Therefore, this evaporation process requires the additional preparation of a certain concentration of formaldehyde solution and the introduction of an organic phase into the radioactive waste liquid. In addition, a large amount of NOx gas is generated during the evaporation due to the reaction between formaldehyde and nitric acid, and a series of tail gas treatment equipment needs to be set up. Directly evaporating the waste liquid under normal pressure avoids the formaldehyde organic matter and a series of tail gas treatment equipment introduced by the above-mentioned formaldehyde denitration evaporation process, but because the nitric acid in the radioactive waste liquid at the normal pressure evaporation temperature (usually about 105°C) will corrode the evaporator material, the service life of the evaporator is greatly reduced, thereby affecting the stable operation of the evaporation system.

[0004] In the publicly available technical research, the author analyzed that there are still the following problems:

[0005] a) Acidic waste liquid is highly corrosive to evaporator equipment materials at the current evaporation temperature, reducing the life of the evaporator.

[0006] b) Denitrification treatment to reduce the acidity of the waste liquid will generate a large amount of NOx non-condensable gas, which will increase the exhaust gas treatment equipment and increase the equipment cost.

[0007] c) Denitrification treatment is performed to reduce the acidity of the waste liquid, and the chemical reagent formaldehyde is introduced, which increases the complexity of evaporation and feeding.

[0008] The above problems restrict the long-term and stable operation of the radioactive acidic waste liquid evaporation process. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a negative pressure evaporation system and method for treating radioactive waste liquid in view of the above-mentioned deficiencies in the prior art, which reduces the evaporation temperature, reduces the corrosion of the evaporator equipment materials, prolongs the equipment life, and simplifies the system structure.

[0010] The technical solution adopted to solve the technical problem of the present invention is to provide a negative pressure evaporation system for treating radioactive waste liquid, comprising:

[0011] A waste liquid collection tank, used to collect radioactive waste liquid;

[0012] A first pipeline connected to the waste liquid collection tank;

[0013] a first steam jet pump, disposed on the first pipeline, and used to pump the radioactive waste liquid in the waste liquid collection tank into the evaporator;

[0014] an evaporator connected to the first pipeline, the evaporator being used to evaporate the radioactive waste liquid into steam;

[0015] A condenser, connected to the evaporator, is used for condensation;

[0016] a second pipeline connected to the condenser;

[0017] A steam jet pump for creating negative pressure is arranged on the second pipeline, and is used for creating negative pressure;

[0018] a steam condenser connected to the second pipeline;

[0019] The condensate tank is connected to the steam condenser. The condensate tank is used to collect condensate. The condensate tank is also connected to the condenser.

[0020] Preferably, the first inlet of the first steam jet pump is used to introduce steam, the second inlet of the first steam jet pump is connected to the waste liquid collection tank, and the outlet of the first steam jet pump is connected to the evaporator.

[0021] The negative pressure evaporation system also includes:

[0022] a first steam supply pipeline connected to a first inlet of a first steam jet pump;

[0023] A first valve is disposed on a first steam supply pipeline;

[0024] A first liquid level detector is disposed in the evaporator, and is used to detect the liquid level of the radioactive waste liquid in the evaporator and send the detected liquid level value to the first controller;

[0025] The first controller controls the first valve to open when the received liquid level value is lower than a preset first liquid level value, and the first steam jet pump pumps the radioactive waste liquid in the waste liquid collection tank into the evaporator until the liquid level reaches a preset second liquid level value, and the first controller controls the first valve to close.

[0026] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0027] A third pipeline connected to the evaporator;

[0028] a residual liquid tank connected to the third pipeline;

[0029] The second steam jet pump is arranged on the third pipeline, and is used for pumping the evaporation residue in the evaporator into the evaporation residue tank.

[0030] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0031] The decontamination loop pipe is arranged in any one or more of the waste liquid collection tank, the condensate tank, the residual liquid tank and the evaporator.

[0032] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0033] The evaporation liquid cooler is arranged on the third pipeline and is used for cooling the evaporation liquid.

[0034] Preferably, the first inlet of the second steam jet pump is used to introduce steam, the second inlet of the second steam jet pump is connected to the evaporator through the residual liquid cooler, the outlet of the second steam jet pump is connected to the residual liquid tank, and a water supply pipe is further provided at the second inlet of the second steam jet pump;

[0035] The negative pressure evaporation system also includes:

[0036] a second steam supply pipeline connected to a first inlet of a second steam jet pump;

[0037] a second valve, disposed on the second steam supply pipeline;

[0038] A first cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the evaporative liquid cooler and send the measured first flow value to the second controller;

[0039] The second controller controls the second valve to close when the received first flow value is lower than the preset first flow value.

[0040] Preferably, the first inlet of the steam jet pump for creating negative pressure is used to introduce steam, the second inlet of the steam jet pump for creating negative pressure is connected to the condenser, and the outlet of the steam jet pump for creating negative pressure is connected to the steam condenser.

[0041] The negative pressure evaporation system also includes:

[0042] A third steam supply pipeline is connected to a first inlet of a steam jet pump for creating negative pressure;

[0043] a third valve, disposed on a third steam supply pipeline;

[0044] A second cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the steam condenser and send the measured second flow value to the third controller;

[0045] The third controller controls the third valve to close when the received second flow value is lower than the preset second flow value.

[0046] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0047] A compressed air pipeline is connected to the second pipeline, the connection between the compressed air pipeline and the second pipeline is located upstream of the steam jet pump for creating negative pressure, and the compressed air pipeline is used to introduce compressed air;

[0048] The fourth valve is arranged on the compressed air pipeline.

[0049] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0050] Heating steam supply pipeline, connected to the evaporator heating jacket,

[0051] The fifth valve is arranged on the heating steam supply pipeline.

[0052] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0053] a second cryogenic water flow measurement device, used to measure the cryogenic water flow in the cryogenic water pipeline of the steam condenser, and send the measured third flow value to the fourth controller;

[0054] The fourth controller controls the fifth valve to close when the received third flow value is lower than the preset third flow value.

[0055] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0056] a third cryogenic water flow measurement device, used to measure the cryogenic water flow in the cryogenic water pipe of the condenser, and send the measured fourth flow value to the fifth controller;

[0057] The fifth controller controls the fifth valve to close when the received fourth flow value is lower than the preset fourth flow value.

[0058] Preferably, the first pipeline includes a cut-off tank and a first U-shaped bend pipe section, the cut-off tank is connected to the first U-shaped bend pipe section, the outlet of the first steam jet pump is connected to the cut-off tank and then connected to the evaporator, and before the steam jet pump is used to create negative pressure, the first U-shaped bend pipe section is used to pass radioactive waste liquid to form a first liquid seal.

[0059] Preferably, the second pipeline includes a second U-shaped bend pipe section, and before the negative pressure is generated by using a steam jet pump, the second U-shaped bend pipe section is used to pass water to form a second liquid seal.

[0060] Preferably, the condenser is a vertical jacket heat exchanger, and the hot side and cold side fluids thereof adopt countercurrent heat exchange.

[0061] Preferably, the steam condenser is a vertical jacket heat exchanger, and the hot side and cold side fluids thereof adopt countercurrent heat exchange.

[0062] The present invention also provides a method for treating radioactive waste liquid using the negative pressure evaporation system, comprising the following steps:

[0063] Feeding the evaporator from the waste liquid collection tank;

[0064] Start the steam condenser;

[0065] Turn on the negative pressure steam jet pump to create negative pressure in the evaporator;

[0066] Start the condenser;

[0067] Supply heating steam to the evaporator to start evaporation;

[0068] The radioactive waste liquid in the evaporator begins to evaporate, and the generated steam is condensed by the condenser and enters the condensate tank.

[0069] The effects of the present invention are as follows: The present invention provides a negative pressure evaporation system and method for treating radioactive waste liquid, which realizes the industrial application of negative pressure evaporation of radioactive waste liquid in China for the first time. A liquid seal is established by setting up a pipeline as a loop connected to the evaporator, creating negative pressure evaporation conditions. A steam jet pump, a non-passive device, is used to establish a negative pressure environment in the evaporator, which prevents other active negative pressure-generating equipment from being frequently repaired in a radioactive environment, thereby avoiding radiation hazards to workers. The principle that the lower the pressure, the lower the boiling point of the waste liquid is used to reduce the evaporation temperature of the radioactive acidic waste liquid, reduce the corrosion of the acidic waste liquid to the equipment in a high temperature environment, and extend the service life of the evaporator. The direct evaporation process is used to avoid the setting of a series of tail gas treatment equipment required for formaldehyde denitrification evaporation, greatly simplifying the evaporation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic structural diagram of a negative pressure evaporation system for treating radioactive waste liquid in Example 2 of the present invention.

[0071] In the figure: 1-waste liquid collecting tank, 2-evaporator, 3-evaporator cooler, 4-condensate tank, 5-condenser, 6-steam jet pump for creating negative pressure, 7-steam condenser, 8-evaporator tank, 9-first U-shaped bend pipe section, 10-second U-shaped bend pipe section, 11-compressed air pipeline, 12-break tank, 13-first valve, 14-second valve, 15-fifth valve, 16-fourth valve, 17-third valve. DETAILED DESCRIPTION

[0072] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0073] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0074] In the description of this patent, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this patent and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this patent.

[0075] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0076] Example 1

[0077] This embodiment provides a negative pressure evaporation system for treating radioactive waste liquid, comprising:

[0078] A waste liquid collection tank, used to collect radioactive waste liquid;

[0079] A first pipeline connected to the waste liquid collection tank;

[0080] a first steam jet pump, disposed on the first pipeline, and used to pump the radioactive waste liquid in the waste liquid collection tank into the evaporator;

[0081] an evaporator connected to the first pipeline, the evaporator being used to evaporate the radioactive waste liquid into steam;

[0082] A condenser, connected to the evaporator, is used for condensation;

[0083] a second pipeline connected to the condenser;

[0084] A steam jet pump for creating negative pressure is arranged on the second pipeline, and is used for creating negative pressure;

[0085] a steam condenser connected to the second pipeline;

[0086] The condensate tank is connected to the steam condenser. The condensate tank is used to collect condensate. The condensate tank is also connected to the condenser.

[0087] This embodiment also provides a method for treating radioactive waste liquid using the negative pressure evaporation system, comprising the following steps:

[0088] Feeding the evaporator from the waste liquid collection tank;

[0089] Start the steam condenser;

[0090] Turn on the negative pressure steam jet pump to create negative pressure in the evaporator;

[0091] Start the condenser;

[0092] Supply heating steam to the evaporator to start evaporation;

[0093] The radioactive waste liquid in the evaporator begins to evaporate, and the generated steam is condensed by the condenser and enters the condensate tank.

[0094] The effects of this embodiment are as follows: This embodiment provides a negative pressure evaporation system and method for treating radioactive waste liquid, which realizes the industrial application of negative pressure evaporation of radioactive waste liquid in China for the first time. A liquid seal is established by setting up a pipeline as a loop connected to the evaporator, creating negative pressure evaporation conditions. The use of a steam jet pump, a non-passive device, to establish a negative pressure environment in the evaporator prevents other active negative pressure-generating equipment from being frequently repaired in a radioactive environment, thereby avoiding radiation hazards to workers. The principle that the lower the pressure, the lower the boiling point of the waste liquid is used to reduce the evaporation temperature of the radioactive acidic waste liquid, reduce the corrosion of the acidic waste liquid to the equipment in a high temperature environment, and extend the service life of the evaporator. The use of a direct evaporation process avoids the setting of a series of tail gas treatment equipment required for formaldehyde denitrification evaporation, greatly simplifying the evaporation process.

[0095] Example 2

[0096] like Figure 1 As shown, this embodiment provides a negative pressure evaporation system for treating radioactive waste liquid, comprising:

[0097] A waste liquid collection tank 1, used for collecting radioactive waste liquid;

[0098] A first pipeline connected to the waste liquid collection tank 1;

[0099] A first steam jet pump is provided on the first pipeline, and is used to pump the radioactive waste liquid in the waste liquid collection tank 1 into the evaporator 2 through the break tank 12;

[0100] an evaporator 2, connected to the first pipeline, and used for evaporating the radioactive waste liquid into steam;

[0101] A condenser 5 is connected to the evaporator 2 and is used for condensation;

[0102] A second pipeline connected to the condenser 5;

[0103] A steam jet pump 6 for creating negative pressure is arranged on the second pipeline, and the steam jet pump 6 for creating negative pressure is used to create negative pressure;

[0104] A steam condenser 7 connected to the second pipeline;

[0105] The condensate tank 4 is connected to the steam condenser 7 . The condensate tank 4 is used to collect condensate. The condensate tank 4 is also connected to the condenser 5 .

[0106] Preferably, the first inlet of the first steam jet pump is used to introduce steam, the second inlet of the first steam jet pump is connected to the waste liquid collection tank 1, and the outlet of the first steam jet pump is connected to the evaporator 2 through the cut-off tank 12.

[0107] The negative pressure evaporation system also includes:

[0108] a first steam supply pipeline connected to a first inlet of a first steam jet pump;

[0109] A first valve 13 is provided on the first steam supply pipeline;

[0110] A first liquid level detector is disposed in the evaporator 2, and is used to detect the liquid level of the radioactive waste liquid in the evaporator 2, and send the detected liquid level value to the first controller;

[0111] The first controller controls the first valve 13 to open when the received liquid level value is lower than the preset first liquid level value, and the first steam jet pump pumps the radioactive waste liquid in the waste liquid collection tank 1 into the evaporator 2 until the liquid level reaches the preset second liquid level value, and the first controller controls the first valve to close.

[0112] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0113] A third pipeline connected to the evaporator 2;

[0114] The residual liquid tank 8 is connected to the third pipeline;

[0115] The second steam jet pump is disposed on the third pipeline, and is used to pump the residual liquid in the evaporator 2 into the residual liquid tank 8 .

[0116] The feeding of the waste liquid collection tank 1 to the evaporator 2 is achieved by a first steam jet pump, and the conveying of the evaporation residue in the evaporator 2 to the evaporation residue tank 8 is achieved by a second steam jet pump.

[0117] A temperature measuring device and a pressure measuring device are provided in the evaporator 2 .

[0118] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0119] The decontamination ring pipe is arranged in any one or more of the waste liquid collection tank 1, the condensate tank 4, the residual liquid tank 8, and the evaporator 2, so as to facilitate cleaning and decontamination of the inside of the equipment.

[0120] Preferably, the waste liquid collecting tank 1, the condensate tank 4 and the residual liquid tank 8 are all provided with liquid level, temperature and density measuring devices.

[0121] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0122] The evaporation liquid cooler 3 is arranged on the third pipeline, and is used for cooling the evaporation liquid.

[0123] The steam consumed during the use of the negative pressure steam jet pump 6 is condensed by the steam condenser 7 and flows into the condensate tank 4.

[0124] Preferably, the first inlet of the second steam jet pump is used to introduce steam, the second inlet of the second steam jet pump is connected to the evaporator 2 through the evaporation cooler 3, the outlet of the second steam jet pump is connected to the evaporation tank 8, and a water supply pipe is further provided at the second inlet of the second steam jet pump;

[0125] The negative pressure evaporation system also includes:

[0126] a second steam supply pipeline connected to a first inlet of a second steam jet pump;

[0127] a second valve, disposed on the second steam supply pipeline;

[0128] A first cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the evaporative liquid cooler 3, and send the measured first flow value to the second controller;

[0129] The second controller controls the second valve 14 to close when the received first flow value is lower than the preset first flow value.

[0130] The steam supply valve of the second steam jet pump for conveying the evaporative liquid is the second valve 14, and the second valve 14 is interlocked with the first cryogenic water flow measuring device of the evaporative liquid cooler 3. When the cryogenic water flow of the evaporative liquid cooler is lower than the set value, the second steam jet pump for conveying the evaporative liquid is stopped.

[0131] Preferably, the first inlet of the negative pressure steam jet pump 6 is used to introduce steam, the second inlet of the negative pressure steam jet pump 6 is connected to the condenser 5, and the outlet of the negative pressure steam jet pump 6 is connected to the steam condenser 7.

[0132] The negative pressure evaporation system also includes:

[0133] The third steam supply pipeline is connected to the first inlet of the negative pressure steam jet pump 6;

[0134] A third valve 17 is provided on the third steam supply pipeline;

[0135] A second cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the steam condenser 7, and send the measured second flow value to the third controller;

[0136] The third controller controls the third valve 17 to close when the received second flow value is lower than the preset second flow value.

[0137] The steam supply valve of the negative pressure steam jet pump 6 is the third valve 17, and the third valve 17 is interlocked with the cryogenic water flow measuring device (second cryogenic water flow measuring device) of the steam condenser 7. When the cryogenic water flow of the steam condenser 7 is lower than the set value, the steam jet pump 6 for negative pressure is interlocked and closed.

[0138] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0139] A compressed air pipeline 11 is connected to the second pipeline. The connection between the compressed air pipeline 11 and the second pipeline is located upstream of the negative pressure steam jet pump 6. The compressed air pipeline 11 is used to introduce compressed air.

[0140] The fourth valve 16 is disposed on the compressed air pipeline 11 .

[0141] During the evaporation period, the negative pressure in the evaporator 2 can be maintained stable by adjusting the amount of compressed air introduced.

[0142] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0143] The heating steam supply pipeline is connected to the heating jacket of evaporator 2.

[0144] The fifth valve 15 is arranged on the heating steam supply pipeline.

[0145] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0146] A second cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the steam condenser 7, and send the measured third flow value to the fourth controller;

[0147] The fourth controller controls the fifth valve 15 to close when the received third flow value is lower than the preset third flow value.

[0148] Preferably, the negative pressure evaporation system for treating radioactive waste liquid further comprises:

[0149] a third cryogenic water flow measurement device, used to measure the cryogenic water flow in the cryogenic water pipe of the condenser 5, and send the measured fourth flow value to the fifth controller;

[0150] The fifth controller controls the fifth valve 15 to close when the received fourth flow value is lower than the preset fourth flow value.

[0151] The heating steam supply valve of the evaporator 2 is the fifth valve 15, which is interlocked with the third cryogenic water flow measuring device of the condenser 5 and the second cryogenic water flow measuring device of the steam condenser 7. When the cryogenic water flow of the condenser 5 and the steam condenser 7 is lower than the set value, the heating steam of the evaporator 2 is interlocked and shut down.

[0152] Preferably, in the negative pressure evaporation system for treating radioactive waste liquid, the first pipeline includes a cut-off tank and a first U-shaped bend pipe section 9, the cut-off tank is connected to the first U-shaped bend pipe section, the outlet of the first steam jet pump is connected to the cut-off tank and then connected to the evaporator, and before the steam jet pump 6 is used to generate negative pressure, the first U-shaped bend pipe section 9 is used to pass the radioactive waste liquid to form a first liquid seal. The first U-shaped bend pipe section 9 is respectively connected to the waste liquid collection tank 1 and the evaporator 2 through other auxiliary pipe sections.

[0153] Preferably, the second pipeline includes a second U-shaped bend pipe section 10, and before the steam jet pump 6 is used to generate negative pressure, the second U-shaped bend pipe section 10 is used to pass water to form a second liquid seal.

[0154] The feed pipe and the discharge pipe of the evaporator 2 are both provided with U-bends, so as to form a liquid seal for the circuit connected with the evaporator 2, creating conditions for the establishment of negative pressure in the evaporator 2. The second U-bend pipe section 10 is respectively connected to the evaporator 2 and the residual liquid tank 8 through other auxiliary pipe sections.

[0155] Preferably, the condenser 5 is a vertical jacket heat exchanger, and the hot side and cold side fluids thereof adopt countercurrent heat exchange.

[0156] Preferably, the steam condenser 7 is a vertical jacket heat exchanger, and the hot side and cold side fluids thereof adopt countercurrent heat exchange.

[0157] The condenser 5 and the steam condenser 7 are both vertical jacket heat exchangers, and the hot side and cold side fluids adopt countercurrent heat exchange, which avoids the accumulation of radioactive waste liquid at the lower head and causes equipment corrosion.

[0158] This embodiment also provides a method for treating radioactive waste liquid using the negative pressure evaporation system, comprising the following steps:

[0159] Feeding from the waste liquid collection tank 1 to the evaporator 2;

[0160] Add water to the second U-shaped bend pipe section 10 to form a liquid seal;

[0161] Start the steam condenser 7;

[0162] Turn on the negative pressure steam jet pump 6 to form negative pressure in the evaporator 2;

[0163] Start condenser 5;

[0164] Supply heating steam to evaporator 2 to start evaporation;

[0165] The radioactive waste liquid in the evaporator 2 begins to evaporate, and the generated steam is condensed by the condenser 5 and then enters the condensate tank 4 .

[0166] Specifically, the method for treating radioactive liquid waste using the negative pressure evaporation system in this embodiment includes the following steps:

[0167] Inject an appropriate amount of deionized water into the U-bend of the evaporator 2 material return loop to perform liquid sealing on the loop.

[0168] Check the liquid level in the condensate tank 4 to ensure that the liquid level meets the liquid sealing requirements.

[0169] The radioactive waste liquid is transported from the waste liquid collection tank 1 to the evaporator 2 through the first steam jet pump until it reaches the high liquid level of the evaporator 2. The high liquid level signal interlock shuts down the first steam jet pump and stops transporting. At this time, the U-bend of the feed loop of the evaporator 2 is filled with waste liquid, forming a liquid seal.

[0170] Open the valve on the deep cold water supply pipeline of the steam condenser 7, and introduce deep cold water into the steam condenser 7 to start heat exchange. The steam condenser 7 is a shell and tube heat exchanger.

[0171] The negative pressure steam jet pump 6 is started to form negative pressure in the evaporator 2 until the ultimate negative pressure value is reached, which is about 10 kPa absolute pressure. The steam consumed in this process enters the steam condenser 7 for condensation and then flows into the condensate tank 4.

[0172] An appropriate amount of compressed air is introduced into the circuit through the compressed air pipe 11 to stabilize the negative pressure in the evaporator 2 at 20 kPa (absolute pressure).

[0173] Open the valve on the deep cold water supply pipe of condenser 5, introduce deep cold water into condenser 5, and start heat exchange. Condenser 5 is a shell and tube heat exchanger.

[0174] Open the fifth valve 15 on the heating steam supply pipe on the heating jacket of the evaporator 2, start the heating steam, and start evaporation. At 20 kPa (absolute pressure), the evaporation temperature range is 76-84° C. The steam generated by evaporation is condensed by the condenser 5 and then flows into the condensate tank 4 by gravity.

[0175] During the evaporation process, the negative pressure in the evaporator 2 can be maintained stable by adjusting the amount of compressed air at the compressed air pipeline 11.

[0176] When the liquid level in the evaporator 2 drops to a low level, the low level signal interlock turns on the first steam jet pump for feeding, and restarts the transportation of radioactive waste liquid from the waste liquid collection tank 1 to the evaporator 2, until the liquid level in the evaporator 2 reaches a high level. The high level signal triggers the interlock signal to turn off the first steam jet pump for feeding, and stops the waste liquid transportation.

[0177] During the waste liquid transportation process, the heating steam of the evaporator 2 is always turned on to maintain the evaporation state, and the negative pressure in the evaporator 2 remains stable.

[0178] The evaporation of the liquid level in evaporator 2 from the high liquid level to the low liquid level is regarded as one evaporation batch. Repeat the above evaporation process until the evaporation reaches the set batch, and then stop evaporation.

[0179] When stopping evaporation, first turn off the heating steam of the evaporator 2. Then gradually increase the compressed air intake of the compressed air pipeline 11 to slowly reduce the negative pressure in the evaporator 2. When the pressure in the evaporator 2 returns to normal pressure, turn off the negative pressure steam jet pump 6 and the compressed air supply of the compressed air pipeline 11.

[0180] Stop the cryogenic water supply to the condenser 5 and the steam condenser 7. Start the cryogenic water supply to the evaporative liquid cooler 3, introduce the cryogenic water into the evaporative liquid cooler 3, and start the heat exchange. The evaporative liquid cooler 3 is a vertical shell and tube cooler.

[0181] The raffinate in the evaporator 2 is sent to the raffinate cooler 3 for cooling, and is finally sent to the raffinate tank 8 .

[0182] The effects of this embodiment are as follows: This embodiment provides a negative pressure evaporation system and method for treating radioactive waste liquid, which realizes the industrial application of negative pressure evaporation of radioactive waste liquid in China for the first time. A liquid seal is established by setting the pipeline as a loop connected to the evaporator 2, creating negative pressure evaporation conditions. The steam jet pump, a non-active device, is used to establish a negative pressure environment in the evaporator 2, which prevents other active negative pressure devices from being frequently repaired in a radioactive environment and avoids the radiation hazards of the staff. The principle that the lower the pressure, the lower the boiling point of the waste liquid is used to reduce the evaporation temperature of the radioactive acidic waste liquid, reduce the corrosion of the acidic waste liquid to the equipment in a high temperature environment, and extend the service life of the evaporator 2. The direct evaporation process is used to avoid the setting of a series of tail gas treatment equipment required for formaldehyde denitrification evaporation, which greatly simplifies the evaporation process.

[0183] Example 3

[0184] This embodiment provides a method for treating radioactive liquid waste using the negative pressure evaporation system in Embodiment 2, comprising the following steps, which differ from Embodiment 2 in that:

[0185] a. Add a certain amount of deionized water to the loop through the water supply pipe of the second U-bend pipe section to create negative pressure in the evaporator to form a liquid seal.

[0186] b. Supply material from the waste liquid collection tank to the evaporator until the high liquid level of the evaporator is reached.

[0187] c. Open the deep cold water supply to the steam condenser and start the steam condenser.

[0188] d. Turn on the steam jet pump to form negative pressure in the evaporator. When the negative pressure in the evaporator no longer increases, turn on the compressed air supply at the inlet of the steam jet pump and adjust the amount of compressed air introduced to stabilize the negative pressure in the evaporator at 20kPa (absolute pressure).

[0189] e. Turn on the deep cold water supply to the condenser and start the condenser.

[0190] f. Supply heating steam to the evaporator and start evaporation.

[0191] g. The radioactive waste liquid in the evaporator begins to evaporate between 76 and 84°C, and the generated steam is condensed by the condenser and enters the condensate tank.

[0192] h. When the radioactive waste liquid in the evaporator bottom drops to a low liquid level after evaporation, the low liquid level signal interlock starts the waste liquid transportation from the waste liquid collection tank to the evaporator until it reaches the high liquid level of the evaporator again.

[0193] Repeat the above operation until the set batch is evaporated.

[0194] i. When the liquid level in the evaporator reaches the low level, stop heating the evaporator.

[0195] j. Turn off the cryogenic water supply to the condenser and steam condenser. Turn on the cryogenic water supply to the evaporative liquid cooler and start the evaporative liquid cooler.

[0196] k. The residual liquid in the evaporator is transported to the residual liquid tank after passing through the residual liquid cooler.

[0197] The effects of this embodiment are as follows: This embodiment provides a negative pressure evaporation system and method for treating radioactive waste liquid, which realizes the industrial application of negative pressure evaporation of radioactive waste liquid in China for the first time. A liquid seal is established by setting up a pipeline as a loop connected to the evaporator, creating negative pressure evaporation conditions. The use of a steam jet pump, a non-passive device, to establish a negative pressure environment in the evaporator prevents other active negative pressure-generating equipment from being frequently repaired in a radioactive environment, thereby avoiding radiation hazards to workers. The principle that the lower the pressure, the lower the boiling point of the waste liquid is used to reduce the evaporation temperature of the radioactive acidic waste liquid, reduce the corrosion of the acidic waste liquid to the equipment in a high temperature environment, and extend the service life of the evaporator. The use of a direct evaporation process avoids the setting of a series of tail gas treatment equipment required for formaldehyde denitrification evaporation, greatly simplifying the evaporation process.

[0198] 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 of ordinary skill 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. A negative pressure evaporation system for treating radioactive waste liquid, characterized in that: include: A waste liquid collection tank, used to collect radioactive waste liquid; A first pipeline connected to the waste liquid collection tank; a first steam jet pump, disposed on the first pipeline, and used to pump the radioactive waste liquid in the waste liquid collection tank into the evaporator; an evaporator connected to the first pipeline, the evaporator being used to evaporate the radioactive waste liquid into steam; A condenser, connected to the evaporator, is used for condensation; a second pipeline connected to the condenser; A steam jet pump for creating negative pressure is arranged on the second pipeline, and is used for creating negative pressure; a steam condenser connected to the second pipeline; The condensate tank is connected to the steam condenser. The condensate tank is used to collect condensate. The condensate tank is also connected to the condenser.

2. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: The first inlet of the first steam jet pump is used for introducing steam, the second inlet of the first steam jet pump is connected to the waste liquid collecting tank, and the outlet of the first steam jet pump is connected to the evaporator. The negative pressure evaporation system also includes: a first steam supply pipeline connected to a first inlet of a first steam jet pump; A first valve is disposed on a first steam supply pipeline; A first liquid level detector is disposed in the evaporator, and is used to detect the liquid level of the radioactive waste liquid in the evaporator and send the detected liquid level value to the first controller; The first controller controls the first valve to open when the received liquid level value is lower than a preset first liquid level value, and the first steam jet pump pumps the radioactive waste liquid in the waste liquid collection tank into the evaporator until the liquid level reaches a preset second liquid level value, and the first controller controls the first valve to close.

3. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: Also includes: A third pipeline connected to the evaporator; a residual liquid tank connected to the third pipeline; The second steam jet pump is arranged on the third pipeline, and is used for pumping the evaporation residue in the evaporator into the evaporation residue tank.

4. The negative pressure evaporation system for treating radioactive waste liquid according to claim 3, characterized in that: Also includes: The decontamination loop pipe is arranged in any one or more of the waste liquid collection tank, the condensate tank, the residual liquid tank and the evaporator.

5. The negative pressure evaporation system for treating radioactive waste liquid according to claim 3, characterized in that: Also includes: The evaporation liquid cooler is arranged on the third pipeline and is used for cooling the evaporation liquid.

6. The negative pressure evaporation system for treating radioactive waste liquid according to claim 5, characterized in that: The first inlet of the second steam jet pump is used to introduce steam, the second inlet of the second steam jet pump is connected to the evaporator through the residual liquid cooler, the outlet of the second steam jet pump is connected to the residual liquid tank, and a water supply pipe is also provided at the second inlet of the second steam jet pump; The negative pressure evaporation system also includes: a second steam supply pipeline connected to a first inlet of a second steam jet pump; a second valve, disposed on the second steam supply pipeline; A first cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the evaporative liquid cooler and send the measured first flow value to the second controller; The second controller controls the second valve to close when the received first flow value is lower than the preset first flow value.

7. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: The first inlet of the steam jet pump for creating negative pressure is used to introduce steam, the second inlet of the steam jet pump for creating negative pressure is connected to the condenser, and the outlet of the steam jet pump for creating negative pressure is connected to the steam condenser. The negative pressure evaporation system also includes: A third steam supply pipeline is connected to a first inlet of a steam jet pump for creating negative pressure; a third valve, disposed on a third steam supply pipeline; A second cryogenic water flow measurement device is used to measure the cryogenic water flow in the cryogenic water pipeline of the steam condenser and send the measured second flow value to the third controller; The third controller controls the third valve to close when the received second flow value is lower than the preset second flow value.

8. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: Also includes: A compressed air pipeline is connected to the second pipeline, the connection between the compressed air pipeline and the second pipeline is located upstream of the steam jet pump for creating negative pressure, and the compressed air pipeline is used to introduce compressed air; The fourth valve is arranged on the compressed air pipeline.

9. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: Also includes: Heating steam supply pipeline, connected to the evaporator heating jacket, The fifth valve is arranged on the heating steam supply pipeline.

10. The negative pressure evaporation system for treating radioactive waste liquid according to claim 9, characterized in that: Also includes: a second cryogenic water flow measurement device, used to measure the cryogenic water flow in the cryogenic water pipeline of the steam condenser, and send the measured third flow value to the fourth controller; The fourth controller controls the fifth valve to close when the received third flow value is lower than the preset third flow value.

11. The negative pressure evaporation system for treating radioactive waste liquid according to claim 9, characterized in that: Also includes: a third cryogenic water flow measurement device, used to measure the cryogenic water flow in the cryogenic water pipe of the condenser, and send the measured fourth flow value to the fifth controller; The fifth controller controls the fifth valve to close when the received fourth flow value is lower than the preset fourth flow value.

12. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: The first pipeline includes a cut-off tank and a first U-shaped bend pipe section, the cut-off tank is connected to the first U-shaped bend pipe section, the outlet of the first steam jet pump is connected to the cut-off tank and then connected to the evaporator, and before the steam jet pump is used to create negative pressure, the first U-shaped bend pipe section is used to pass radioactive waste liquid to form a first liquid seal.

13. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: The second pipeline includes a second U-shaped bend pipe section. Before the negative pressure is generated by using a steam jet pump, the second U-shaped bend pipe section is used to pass water to form a second liquid seal.

14. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: The condenser is a vertical jacket heat exchanger, and the hot side and cold side fluids adopt countercurrent heat exchange.

15. The negative pressure evaporation system for treating radioactive waste liquid according to claim 1, characterized in that: The steam condenser is a vertical jacket heat exchanger, and the hot side and cold side fluids adopt countercurrent heat exchange.

16. A method for treating radioactive waste liquid using the negative pressure evaporation system according to any one of claims 1 to 15, characterized in that: The following steps are involved: Feeding the evaporator from the waste liquid collection tank; Start the steam condenser; Turn on the negative pressure steam jet pump to create negative pressure in the evaporator; Start the condenser; Supply heating steam to the evaporator to start evaporation; The radioactive waste liquid in the evaporator begins to evaporate, and the generated steam is condensed by the condenser and enters the condensate tank.

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