A pyrolysis process for low- to medium-level organic waste liquid

Abstract

The invention discloses a medium- and low-level organic waste liquid pyrolysis process, which relates to the technical field of radioactive waste treatment, including S1: separating medium- and low-level organic waste liquid from oil and water to obtain radioactive medium- and low-level TBP / OK organic waste liquid and low-level waste liquid; S2: filtering the TBP / OK organic waste liquid, and rectifying it in a short-range molecular distillation device to obtain concentrated TBP organic waste liquid and light component kerosene; S3: stirring the lime milk preparation liquid and the concentrated TBP organic waste liquid to prepare a suspension; S4: transporting the suspension to a pyrolysis furnace to be decomposed into pyrolysis gas and pyrolysis ash; S5: the pyrolysis gas enters a combustion furnace; the pyrolysis ash is cemented to form a cement solidified body; S6: the flue gas discharged from the combustion furnace is purified and discharged to the atmosphere. The invention tests the inorganic treatment of low-level organic waste liquid through the processes of oil-water separation, short-range molecular distillation, pyrolysis in a pyrolysis furnace, combustion in a combustion furnace, cement solidification, etc., and the generated pyrolysis ash forms a stable solidified body for disposal, thereby realizing the minimization and final disposal of waste.

Description

Technical Field

[0001] The invention relates to the technical field of radioactive waste treatment, in particular to a pyrolysis process for low- to medium-level radioactive organic waste liquid. Background Art

[0002] Low- and medium-level organic waste liquids are produced by the Purex process of uranium purification and spent fuel reprocessing. Tributyl phosphate (TBP) is used as an extractant, and aviation hydrogenated kerosene (OK) is used as a diluent. Various radionuclides (cesium, plutonium, etc.) will also dissolve in low- and medium-level organic waste liquids. In order to properly treat these low- and medium-level organic waste liquids, my country has carried out engineering applications of the pyrolysis and combustion treatment method for low- and medium-level organic waste liquids and has made a lot of optimizations.

[0003] The pyrolysis combustion process is to send the organic waste liquid into the pyrolysis furnace protected by inert gas, the kerosene is heated and gasified, and the TBP is thermally decomposed into phosphorus pentoxide, butene, butanol, gaseous water H2O, etc. Among them, phosphorus pentoxide reacts with Ca(OH)2 in the suspension to form calcium pyrophosphate. Calcium pyrophosphate and excess Ca(OH)2 are ground into ash by the constantly moving steel balls in the pyrolysis furnace, and finally settle from the separation chamber at the bottom of the pyrolysis furnace to form pyrolysis ash; the pyrolysis gas composed of butene, butanol, gaseous water H2O, etc. is filtered through a high-temperature filter and enters the combustion furnace. The process flow of pyrolysis and combustion of organic waste liquid mainly includes five processes: waste liquid pretreatment, suspension preparation, pyrolysis, combustion, and tail gas treatment. In the waste liquid pretreatment process, the oil-water separation method is used to separate the organic phase, because the organic phase contains a large amount of other substances, which is not conducive to subsequent effective treatment. Patent CN113571223A discloses a method and device for treating radioactive organic extractants. The device is a fixed two-stage distillation device with a complex structure. It is only suitable for treating a large amount of radioactive waste liquid generated by the production line. For treating a small amount of radioactive waste liquid, the construction cost of the device is too high. The traditional pyrolysis process produces less tail gas, has a strong tail gas purification capacity, and a low operating temperature (500-600°C), but it still has certain limitations: (1) The pyrolysis furnace is heated unevenly, the stirring speed is low, the reaction rate of the pyrolysis process is slow, the pyrolysis is not sufficient, and the amount of secondary waste generated is large; (2) The high-temperature filter is easy to clog, the filter core is frequently replaced, and the maintenance cost is high; (3) The sealing of the pyrolysis furnace ash unloading glove box is low, which makes the radioactive dose level at the ash unloading site high, the personnel are exposed to a high dose, and the pyrolysis ash weighing system cannot achieve real-time monitoring. A lot of radioactive waste will be generated during the pyrolysis process. If these wastes are not disposed of, the storage risk of the waste will increase. Patent CN115116643A discloses a method for treating radioactive TBP / OK organic waste liquid, but does not perform final disposal on the reaction residue. At present, radioactive waste is mostly treated by cement solidification, among which silicate cement solidification is the most widely used, but silicate cement solidification has low anti-leaching performance and low waste bag capacity. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a pyrolysis process for low- and medium-level organic waste liquid, which has low treatment costs, sufficient pyrolysis and combustion, produces less solid waste, and has high gas purification efficiency.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A pyrolysis process for low- to medium-level organic waste liquid comprises the following steps:

[0007] S1: Separate the medium and low-level radioactive organic waste liquid into oil and water to obtain radioactive medium and low-level radioactive TBP / OK organic waste liquid and low-level radioactive waste liquid;

[0008] S2: Filter the medium and low level TBP / OK organic waste liquid to remove impurities;

[0009] S3: distilling the medium and low-level TBP / OK organic waste liquid after impurities are removed in a distillation device to obtain concentrated TBP organic waste liquid and light component kerosene, and recovering the kerosene;

[0010] S4: stirring the lime milk preparation liquid and the concentrated TBP organic waste liquid to prepare a suspension;

[0011] S5: The suspension prepared in S4 is transported to the pyrolysis furnace, and the TBP organic waste liquid is decomposed into pyrolysis gas and pyrolysis ash;

[0012] S6: The pyrolysis gas is filtered through a high-temperature filter and then enters the combustion furnace, where it is completely burned under the action of the combustion-supporting gas to generate carbon dioxide and water; the pyrolysis ash is discharged into an ash barrel through a glove box, and after the pyrolysis ash is barreled, cement is solidified to form a cement solidified body;

[0013] S7: The flue gas discharged from the combustion furnace enters the tail gas treatment system for flue gas purification, and is discharged into the atmosphere through the chimney after purification.

[0014] Furthermore, the content of TBP in the low- and medium-level organic waste liquid in step S1 is 20-40%; oil-water separation is performed after natural sedimentation for one day, and after sedimentation, the low- and medium-level organic waste liquid is divided into an upper oil phase, a middle oil-water emulsion phase, a lower water phase and impurities, and the upper and middle layers are the radioactive TBP / OK organic waste liquid after oil-water separation.

[0015] Furthermore, in step S2, the fine particles are removed by filtering with a 60-200 mesh filter screen, and the filtered TBP / OK organic waste liquid is transported to a short-range molecular distillation device for molecular distillation, and the light component kerosene is extracted and a TBP organic waste liquid with concentrated heavy components is obtained at the bottom of the distillation device. The molecular distillation is carried out at 60-180° C. and a vacuum degree of 5Pa-2000Pa; the TBP content in the TBP organic waste liquid with concentrated heavy components is 40-90%.

[0016] Furthermore, the preparation method of the lime milk preparation liquid in step S4 is: add water and a phosphorus-fixing agent to a lime milk preparation tank, add an activating agent after heating to 60-70°C, filter after stirring evenly, and transport the filtrate to a suspension preparation tank to obtain a lime milk preparation liquid; the suspension obtained in step S3 includes the following components in mass ratio: 90-110 parts of medium-low-level TBP organic solvent, 9.0-11.2 parts of phosphorus-fixing agent, 14-20 parts of water, and 10-18 parts of activating agent; the phosphorus-fixing agent is CaO or MgO, and the CaO or MgO are both analytically pure with a purity of ≥99.5%.

[0017] Furthermore, in step S5, the suspension is sprayed from the feed nozzle with the aid of an inert gas and enters the pyrolysis furnace in an atomized state, and the pressure in the pyrolysis furnace is 1.5 kPa to 3 kPa.

[0018] Furthermore, in step S5, the pyrolysis process of the pyrolysis furnace is protected by inert gas; the high-temperature filter is a sintered metal filter; the filter element is cylindrical, and adopts a metal fiber sintered core or a metal mesh filter element or a sintered felt filter element, the material is corrosion-resistant and high-temperature resistant material, and the filter pore size is 0.3 to 1.2 μm.

[0019] Furthermore, in step S5, a thrust bearing or a magnetic thrust bearing is used in the pyrolysis furnace to achieve stirring of the stirring paddle, and the stirring speed is 2.5 to 4.5 rpm; a steel ball packing layer is provided in the pyrolysis furnace, and the distance between the steel ball and the baking nozzle is less than 10 cm and submerges the stirring paddle; the feed nozzle in the pyrolysis furnace has an adjustable angle of 75 to 90°, and a nozzle flow rate of 9 to 30 kg / h; the pyrolysis furnace is heated by an electric heating plate or high-temperature steam, and when high-temperature steam is used for heating, the steam temperature is 400 to 800°C; when an electric heating plate is used for heating, the temperature of the electric heating plate is 350°C-600°C.

[0020] Furthermore, in step S6, the combustion furnace is preheated to 850-1150°C by diesel and then the pyrolysis gas is introduced, and the kerosene obtained by distillation in step S2 is also introduced into the combustion furnace to generate carbon dioxide and water through combustion, and finally discharged into the atmosphere after being treated by the exhaust gas treatment system; the pyrolysis gas stays in the combustion furnace for more than 2s, and the combustion-supporting gas during the combustion of the pyrolysis gas is air with an oxygen concentration of 6-15vol%.

[0021] Furthermore, step S6 adopts remote real-time weighing to weigh the pyrolysis ash in the ash bucket, and when the net weight of the pyrolysis ash reaches 90-115 kg, the ash unloading is stopped; the glove box is a double-layer shielding glove box, and the pyrolysis ash is unloaded once after the pyrolysis furnace runs for one cycle. During the unloading period, the negative pressure of about -0.2 to -0.5 kPa is maintained in the pyrolysis furnace, and aerosol sampling is performed during the unloading process.

[0022] Furthermore, the cement solidification in step S6 adopts phosphate cement for cement solidification, which includes the following components: 25-70 parts of pyrolysis ash, 25-70 parts of tap water, 0.5-3 parts of sodium hydroxide, 0.5-3 parts of water reducer, 20-60 parts of dead-burned magnesium oxide, 5-15 parts of potassium dihydrogen phosphate, 20-60 parts of mineral powder, and 3-10 parts of borax.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention distills TBP / OK organic waste liquid in a molecular distillation device to extract TBP and kerosene, wherein the extracted TBP content accounts for more than 80%, and the TBP content in the separated kerosene is less than 3%. The separated kerosene is transported to a combustion furnace for combustion, thereby minimizing waste and improving treatment efficiency.

[0025] (2) The stirring paddle of the pyrolysis furnace of the present invention adopts a flat thrust bearing or a magnetic thrust bearing to increase the rotation speed of the stirring paddle; the pyrolysis furnace can be heated by an electric heating plate or high-temperature steam, which can extend the service life of the heating device of the pyrolysis furnace and quickly improve the pyrolysis efficiency of the pyrolysis furnace; the feed nozzle of the pyrolysis furnace can be adjusted at an angle of 75 to 90 degrees, so that the distribution of the feed liquid is more uniform, which is conducive to pyrolysis; the high-temperature filter of the pyrolysis furnace adopts a metal fiber sintered core or a metal mesh filter core or a sintered felt filter core to reduce the frequency of filter blockage. The above process is adopted to improve the overall treatment capacity of medium and low-level organic waste liquid and accelerate the treatment progress.

[0026] (3) The present invention adopts a double-layer shielded glove box combined with a remote real-time weighing control method to realize the unloading of pyrolytic ash, which can effectively control the radioactive dose level at the ash unloading site, so that the radiation dose of personnel is low. The TBP content in the pyrolytic ash is less than 0.01%. The low- and medium-level organic waste liquid treatment process provided by the present invention produces less pyrolytic ash, which effectively reduces the radioactivity level of the pyrolytic ash.

[0027] (4) The pyrolysis process for low- and medium-level organic waste liquid provided by the present invention uses phosphate cement for solidification, thereby achieving the final disposal of the waste body. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0030] like Figure 1 As shown, the present application provides a pyrolysis process for medium- and low-level organic waste liquid, comprising the following steps:

[0031] S1: Select low- and medium-level organic waste liquid with TBP content of 20-60%, and let it settle naturally for one day for oil-water separation. After sedimentation, the low- and medium-level organic waste liquid is divided into an upper oil phase, a middle oil-water emulsion phase, and a lower water and impurities phase. The upper and middle layers are the radioactive low- and medium-level TBP / OK organic waste liquid after oil-water separation, and the water and impurities in the lower layer are low-level waste liquid.

[0032] S2: Filter the TBP / OK organic waste liquid with a 60-200 mesh filter to remove fine particles therein, and transport the filtered TBP / OK organic waste liquid to a short-range molecular distillation device through a gear pump for molecular distillation, extract the light component kerosene, and obtain TBP organic waste liquid with concentrated heavy components at the bottom of the distillation device. The molecular distillation is carried out at 60-180°C and a vacuum degree of 5Pa-2000Pa; the kerosene is discharged into a kerosene storage tank for storage, and the concentrated TBP organic waste liquid is discharged into a TBP receiving tank.

[0033] The TBP content in the concentrated TBP organic waste liquid was tested and found to be 40-90%, and the TBP content in the separated kerosene was less than 3%. The radiation level of the concentrated TBP organic waste liquid was tested and found to be α≤2.5×10 2 Bq / L, β≤3.7×10 3 Bq / L.

[0034] S3: Prepare lime milk solution: add water and phosphorus fixer to the lime milk preparation tank, add active agent after heating to 60-70℃, filter after stirring evenly, and transfer the filtrate to the suspension preparation tank to obtain lime milk preparation solution; then stir the lime milk preparation solution and concentrated TBP organic waste liquid in the suspension preparation tank to prepare a suspension, and the process is carried out under the protection of inert gas. The suspension includes the following components in mass ratio: 90-110 parts of medium and low-level TBP organic solvent, 9.0-11.2 parts of phosphorus fixer, 14-20 parts of water, 10-18 parts of active agent, the phosphorus fixer is CaO or MgO, and CaO or MgO are both analytically pure with a purity of ≥99.5%.

[0035] The above suspension was tested and found to have a viscosity <50 mPs.s, a suspension stability time >1.5 h, and a water content of 5-15%.

[0036] S4: The suspension obtained in step S3 is sprayed from the feed nozzle with the help of inert gas and then enters the pyrolysis furnace in an atomized state. The pressure in the pyrolysis furnace is 1.5 kPa to 3 kPa, and the temperature is 350° C. to 600° C. It should be noted that the pyrolysis process in the pyrolysis furnace should also be carried out under the protection of inert gas to prevent the gas in the furnace from burning or exploding. The pyrolysis furnace uses a flat thrust bearing or a magnetic thrust bearing to achieve stirring of the stirring paddle, and the stirring speed is 2.5-4.5rpm; a steel ball packing layer is provided in the pyrolysis furnace, and the distance between the steel ball and the baking nozzle is less than 10cm and the stirring paddle is submerged. When the stirring shaft in the pyrolysis furnace moves, the steel ball in the furnace will continuously move in three dimensions, which can accelerate the pyrolysis of TBP organic waste liquid; the feed nozzle in the pyrolysis furnace has an adjustable angle of 75-90°, and the nozzle flow rate is 9-30kg / h; the pyrolysis furnace is heated by an electric heating plate or high-temperature steam. When high-temperature steam is used for heating, the steam temperature is 400-800℃, and when the electric heating plate is used for heating, the temperature of the electric heating plate is 350℃-600℃. When the pyrolysis furnace is running, the purge time and interval time of the high-temperature gas filter are increased. During parking, the pressure reduction backwash is adopted to improve the backwash efficiency.

[0037] TBP organic waste liquid is decomposed into pyrolysis ash and pyrolysis gas, and the pyrolysis gas enters the combustion furnace after being filtered by a high-temperature filter. The high-temperature filter can remove most of the radioactive particles and aerosols entrained in the pyrolysis gas, reducing the radioactivity level of the flue gas. The high-temperature filter is composed of 16 filter elements, which are sintered metal filters. The filter element is cylindrical and uses a metal fiber sintered core or a metal mesh filter element or a sintered felt filter element. The material is corrosion-resistant and high-temperature resistant material, and the filter pore size is 0.3-1.2μm.

[0038] S5: The pyrolysis gas entering the combustion furnace is completely burned to generate carbon dioxide and water under the action of the combustion-supporting gas, the combustion-supporting gas is air with an oxygen concentration of 6 to 15 vol%, and the pyrolysis gas stays in the combustion furnace for more than 2 seconds; the kerosene obtained by distillation in step S2 is also introduced into the combustion furnace and burned to generate carbon dioxide and water; it should be noted that the igniter of the combustion furnace needs to be started before the pyrolysis furnace starts to receive the suspension, and the combustion furnace is preheated to 850 to 1150°C using diesel as fuel.

[0039] S6: The flue gas discharged from the combustion furnace enters the exhaust gas treatment system for flue gas purification, and is discharged to the atmosphere through the chimney after purification; after entering the flue gas purification system, the flue gas passes through the quencher, the first-stage jet scrubber, the second-stage jet scrubber, the high-efficiency filter, etc. in sequence, and is discharged to the outside through the chimney under the main and auxiliary exhaust fans.

[0040] S7: After the pyrolysis ash generated in step S4 is cooled, the 400L ash bucket (discarded paddle curing bucket) with the cover removed is transported to the ash unloading glove box through a roller conveyor and docked with the ash unloading soft connection device. Then, the electric gate valve at the ash unloading hopper outlet is opened, and the feeder is started to quantitatively load the ash into the ash bucket. The pyrolysis ash in the ash bucket is weighed by remote real-time weighing. When the net weight of the pyrolysis ash reaches 90-115 kg, the ash unloading is stopped, and the ash bucket is disconnected from the ash unloading soft connection device. The glove box selected in this embodiment is a double-layer shielded glove box, and the pyrolysis ash is unloaded once after the pyrolysis furnace runs for one cycle. During the unloading period, the negative pressure in the pyrolysis furnace is maintained at about -0.2 to -0.5 kPa. Aerosol sampling is performed during the unloading process. After testing, the pyrolysis ash contains 99.9% of radioactive substances, and the radioactivity level α≤2.2 Bq / L, β≤2.5×10 Bq / L. The main components of pyrolysis ash are 90% to 96% calcium pyrophosphate, 2% to 5% calcium hydroxide, 0.5% to 1% coke, and 1.5% to 4% other impurities.

[0041] After the pyrolysis ash is barreled, phosphate cement is used to form a cement solidification body, which includes the following components: 25-70 parts of pyrolysis ash, 25-70 parts of tap water, 0.5-3 parts of sodium hydroxide, 0.5-3 parts of water reducer, 20-60 parts of dead-burned magnesium oxide, 5-15 parts of potassium dihydrogen phosphate, 20-60 parts of mineral powder, and 3-10 parts of borax. After testing, the cement solidification body has a capacity of 20-50wt% for the pyrolysis ash.

[0042] Example 1

[0043] 100L of low- and medium-level organic waste liquid with a TBP content of 20% was treated using the above-mentioned pyrolysis process, wherein molecular distillation was carried out at a temperature of 60°C, the rotation speed of the stirring paddle in the pyrolysis furnace was 2.5r / min, and the reaction temperature in the pyrolysis furnace was 350°C, and the pyrolysis gas obtained from the pyrolysis furnace was burned at a temperature of 1000°C in the combustion furnace.

[0044] In this implementation, the medium and low-level organic waste liquid with a TBP content of 20% is treated by oil-water separation, molecular distillation, suspension preparation, pyrolysis combustion, and ash solidification. The treatment efficiency of TBP organic waste liquid is 97.3%; the generated pyrolysis gas can remove more than 92% of radioactive particles and aerosols through a high-temperature gas filter; the phosphate cement solidification body has a pyrolysis ash encapsulation capacity of 50wt%. After testing, the cement paste fluidity is ≥200mm, the initial setting time is >1 hour, the final setting time is <12 hours, and the compressive strength of the solidification body after curing for 28 days is >20MPa, which greatly increases the inclusion rate of radioactive pyrolysis ash. The kerosene extracted during the molecular distillation process can be burned in a combustion furnace to generate carbon dioxide and water, which are discharged into the atmosphere after being treated by the tail gas treatment system and tested to meet the standards; the remaining pyrolysis gas components are butene and butanol, which generate harmless carbon dioxide and water after catalytic combustion, and are then discharged after being filtered by a nuclear-grade high-efficiency filter.

[0045] Example 2

[0046] The above-mentioned pyrolysis process is used to treat 100 low- and medium-level organic waste liquid with a LTBP content of 30%, wherein molecular distillation is carried out at a temperature of 80°C, the rotation speed of the stirring paddle in the pyrolysis furnace is 2.8r / min, and the reaction temperature in the pyrolysis furnace is 400°C, and the pyrolysis gas obtained from the pyrolysis furnace is burned at a temperature of 1050°C in the combustion furnace.

[0047] In this implementation, the medium and low-level organic waste liquid with a TBP content of 30% is treated by oil-water separation, molecular distillation, suspension preparation, pyrolysis combustion, and ash solidification. The treatment efficiency of TBP organic waste liquid is 95.2%; the generated pyrolysis gas can remove more than 90% of radioactive particles and aerosols through a high-temperature gas filter; the phosphate cement solidification body has a pyrolysis ash encapsulation capacity of 41.6wt%. After testing, the cement paste fluidity is ≥200mm, the initial setting time is >1 hour, the final setting time is <12 hours, and the compressive strength of the solidification body after curing for 28 days is >20MPa, which greatly increases the inclusion rate of radioactive pyrolysis ash. The kerosene extracted during the molecular distillation process can be burned in a combustion furnace to generate carbon dioxide and water, which are discharged into the atmosphere after being treated by the tail gas treatment system and tested to meet the standards; the remaining pyrolysis gas components are butene and butanol, which are catalytically burned to generate harmless carbon dioxide and water, and then filtered through a nuclear-grade high-efficiency filter and discharged.

[0048] Example 3

[0049] 100L of low- and medium-level organic waste liquid with a TBP content of 40% was treated with the above-mentioned pyrolysis process, wherein molecular distillation was carried out at a temperature of 100°C, the rotation speed of the stirring paddle in the pyrolysis furnace was 3.2r / min, and the reaction temperature in the pyrolysis furnace was 500°C, and the pyrolysis gas obtained from the pyrolysis furnace was burned at a temperature of 1080°C in the combustion furnace.

[0050] In this implementation, the medium and low-level organic waste liquid with a TBP content of 40% is treated by oil-water separation, molecular distillation, suspension preparation, pyrolysis combustion, and ash solidification. The treatment efficiency of TBP organic waste liquid is 94.5%; the generated pyrolysis gas can remove more than 86% of radioactive particles and aerosols through a high-temperature gas filter; the phosphate cement solidification body has a pyrolysis ash encapsulation capacity of 32.8wt%. After testing, the cement paste fluidity is ≥200mm, the initial setting time is >1 hour, the final setting time is <12 hours, and the compressive strength of the solidification body after curing for 28 days is >20MPa, which greatly increases the inclusion rate of radioactive pyrolysis ash. The kerosene extracted during the molecular distillation process can be burned in a combustion furnace to generate carbon dioxide and water, which are discharged into the atmosphere after being treated by the tail gas treatment system and tested to meet the standards; the remaining pyrolysis gas components are butene and butanol, which are catalytically burned to generate harmless carbon dioxide and water, and then filtered through a nuclear-grade high-efficiency filter and discharged.

[0051] Example 1 Example 2 Example 3 Distillation temperature 60℃ 80℃ 100℃ Pyrolysis temperature 350℃ 400℃ 500℃ High temperature steam temperature 650℃ 682℃ 700℃ Stirring paddle speed 2.5r / min 2.8r / min 3.2r / min High temperature gas filter filtering effect 92％ 90％ 86％ Pyrolysis gas combustion temperature 1000℃ 1050℃ 1080℃ Pyrolysis ash inclusion rate of cement solidified body 50wt% 41.6wt% 32.8wt% TBP organic waste liquid treatment efficiency 97.3％ 95.2％ 94.5％

[0052] It can be seen from Examples 1, 2, and 3 that the method provided by the present invention is used to treat radioactive medium and low-level organic waste liquid, the treatment efficiency of TBP organic waste liquid is 94.5% to 97.3%, the cement solidification body has a pyrolysis ash inclusion rate of 32.8 to 50wt%, and kerosene gas and butene can be fully burned into carbon dioxide and water in the combustion furnace and then discharged into the atmosphere after tail gas purification. The method provided by the present invention has high treatment efficiency, low treatment cost, sufficient pyrolysis combustion, less solid waste generated, high gas purification efficiency, and realizes the most comprehensive disposal of waste liquid.

[0053] The above embodiment is only one of the preferred implementation modes of the present invention and should not be used to limit the protection scope of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention.

Claims

1. A pyrolysis process for low- to medium-level organic waste liquid, characterized in that: The steps include: S1: Separate the medium and low-level radioactive organic waste liquid into oil and water to obtain radioactive medium and low-level radioactive TBP / OK organic waste liquid and low-level radioactive waste liquid; S2: Filter the medium and low level TBP / OK organic waste liquid to remove impurities; S3: The filtered TBP / OK organic waste liquid is transported to a short-range molecular distillation device for molecular distillation, the light component kerosene is extracted, and the TBP organic waste liquid with concentrated heavy components is obtained at the bottom of the distillation device, the kerosene is recovered and introduced into a combustion furnace for combustion to generate carbon dioxide and water, and finally discharged into the atmosphere after being treated by an exhaust gas treatment system; the molecular distillation is carried out at 60-180°C and a vacuum degree of 5Pa-2000Pa; S4: stirring the lime milk preparation liquid and the concentrated TBP organic waste liquid to prepare a suspension; S5: The suspension prepared in S4 is transported to the pyrolysis furnace, and the TBP organic waste liquid is decomposed into pyrolysis gas and pyrolysis ash; S6: The pyrolysis gas is filtered through a high-temperature filter and then enters the combustion furnace, where it is completely burned under the action of the combustion-supporting gas to generate carbon dioxide and water; the pyrolysis ash is discharged into an ash barrel through a glove box, and after the pyrolysis ash is barreled, cement is solidified to form a cement solidified body; S7: The flue gas discharged from the combustion furnace enters the tail gas treatment system for flue gas purification, and is discharged into the atmosphere through the chimney after purification.

2. A pyrolysis process for low- and medium-level organic waste liquid according to claim 1, characterized in that: The content of TBP in the low- and medium-level organic waste liquid in step S1 is 20-40%; oil-water separation is performed after natural sedimentation for one day, and after sedimentation, the low- and medium-level organic waste liquid is divided into an upper oil phase, a middle oil-water emulsion phase, a lower water phase and impurities, and the upper and middle layers are the radioactive TBP / OK organic waste liquid after oil-water separation.

3. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: In step S2, a 60-200 mesh filter is used to remove fine particles therein; the TBP content in the TBP organic waste liquid concentrated with the heavy component is 40-90%.

4. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: The preparation method of the lime milk preparation liquid in step S4 is as follows: add water and a phosphorus-fixing agent to a lime milk preparation tank, add an activating agent after heating to 60-70° C., filter after stirring evenly, and transport the filtrate to a suspension preparation tank to obtain the lime milk preparation liquid; the suspension obtained in step S3 includes the following components in mass ratio: 90-110 parts of medium-low-level TBP organic solvent, 9.0-11.2 parts of phosphorus-fixing agent, 14-20 parts of water, and 10-18 parts of activating agent; the phosphorus-fixing agent is CaO or MgO, and the CaO or MgO are both analytically pure with a purity of ≥99.5%.

5. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: In step S5, the suspension is sprayed from the feed nozzle with the aid of an inert gas and then enters the pyrolysis furnace in an atomized state. The pressure in the pyrolysis furnace is 1.5 kPa to 3 kPa.

6. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: In step S5, the pyrolysis process of the pyrolysis furnace is protected by inert gas; the high-temperature filter is a sintered metal filter; the filter element of the high-temperature filter is cylindrical, and adopts a metal fiber sintered core or a metal mesh filter element or a sintered felt filter element, which is made of corrosion-resistant and high-temperature resistant material, and the filter pore size is 0.3~1.2μm.

7. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: In step S5, a thrust bearing or a magnetic thrust bearing is used in the pyrolysis furnace to achieve stirring of the stirring paddle, and the stirring speed is 2.5~4.5rpm; a steel ball packing layer is provided in the pyrolysis furnace, and the distance between the steel ball and the baking nozzle is less than 10cm and the stirring paddle is submerged; the feed nozzle in the pyrolysis furnace has an adjustable angle of 75~90°, and a nozzle flow rate of 9~30kg / h; the pyrolysis furnace is heated by an electric heating plate or high-temperature steam, and when high-temperature steam is used for heating, the steam temperature is 400~800℃; when an electric heating plate is used for heating, the temperature of the electric heating plate is 350℃-600℃.

8. The pyrolysis process for low- and medium-level organic waste liquid according to claim 1, characterized in that: In step S6, the combustion furnace is preheated to 850-1150°C by diesel before introducing pyrolysis gas; the pyrolysis gas stays in the combustion furnace for more than 2 seconds, and the combustion-supporting gas during the combustion of the pyrolysis gas is air with an oxygen concentration of 6-15 vol%.

9. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: Step S6 uses remote real-time weighing to weigh the pyrolysis ash in the ash bucket. When the net weight of the pyrolysis ash reaches 90-115 kg, the ash unloading is stopped. The glove box is a double-layer shielded glove box, and the pyrolysis ash is unloaded once after the pyrolysis furnace runs for a cycle. During the unloading period, the negative pressure in the pyrolysis furnace is maintained at -0.2 to -0.5 kPa, and aerosol sampling is performed during the unloading process.

10. The pyrolysis process of low- and medium-level organic waste liquid according to claim 1, characterized in that: The cement solidification in step S6 adopts phosphate cement for cement solidification, which includes the following components: 25-70 parts of pyrolysis ash, 25-70 parts of tap water, 0.5-3 parts of sodium hydroxide, 0.5-3 parts of water reducer, 20-60 parts of dead-burned magnesium oxide, 5-15 parts of potassium dihydrogen phosphate, 20-60 parts of mineral powder, and 3-10 parts of borax.

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