CN115547534A - A method and system for inorganic treatment of radioactive waste oil - Google Patents

Abstract

The invention discloses a method and system for inorganic treatment of radioactive waste oil. The treatment method comprises the following steps: S1, pretreatment: adding mineralizer after filtering the radioactive waste oil to remove solid residue; S2, reforming and mineralizing: The waste oil treated in step S1 is added with catalyst and bed material in a high temperature environment, and the waste oil is gasified, cracked, and reformed into small molecular gas, and the nuclides in the waste oil are captured under the action of bed material and mineralizer , forming a radioactive mineralization product; S3, oxidation: oxidizing the small molecule gas obtained in step S2, so that the combustible gas is oxidized; S4, purifying the tail gas. The invention not only realizes the inorganic treatment of the radioactive waste oil, but also does not need solidification treatment, and solves the problem that the incineration method and the wet oxidation method need solidification treatment.

Description

A method and system for inorganic treatment of radioactive waste oil

technical field

The invention relates to the technical field of radioactive waste treatment and decommissioning of nuclear facilities, in particular to a method and system for inorganic treatment of radioactive waste oil.

Background technique

With the development of nuclear industry such as nuclear power and nuclear technology application, a large amount of radioactive organic waste has been produced, among which radioactive waste oil is one of the most difficult organic wastes to deal with. Because the annual output of radioactive waste oil is not large, relevant research lags behind, and it has physical and chemical characteristics such as inflammability, explosion and chemical toxicity, so it is usually temporarily stored at the original site of nuclear facilities.

The composition of radioactive waste oil is complex, including high-viscosity lubricating oil and fuel oil with low flash point, usually in the form of mixed oil, and contains radionuclides such as tritium, strontium, cesium, cobalt, etc. Toxicity and other physical and chemical properties, long-term temporary storage has high potential danger. The technologies that can be used for radioactive waste oil treatment mainly include cement solidification method, absorption method, incineration method, wet oxidation method, etc. The cement solidification method is a conventional and mature method for the immobilization of radioactive waste. When it is used for the solidification of waste oil, there are problems such as poor performance of the solidified body, easy leakage, and waste volume expansion; the absorption method can improve the stability of the solidified body, but there are also problems of volume expansion. ; Neither the cement solidification method nor the absorption method realizes the inorganic treatment of waste oil, and radiolysis gas will be generated during long-term storage, which is potentially dangerous. The incineration method can realize the inorganic treatment of waste oil, but this method has flue gas corrosion and low public acceptance And other problems, and the incineration ash needs to be further solidified. The wet oxidation method can realize the inorganic treatment of waste oil, but the technology maturity is low, and the wet oxidation product needs to be further concentrated and solidified.

The characteristics of radioactive waste oil are complicated, and there is no safe and effective method to deal with them in China. As the amount of waste oil storage increases year by year, valuable temporary storage resources will be temporarily used, which will affect the safe operation of nuclear facilities. Therefore, it is imminent to solve the problem of safe volume reduction of radioactive waste oil inorganically.

Contents of the invention

The purpose of the present invention is to provide a method and system for the inorganic treatment of radioactive waste oil, which can not only realize the inorganic treatment of radioactive waste oil, but also does not need solidification treatment, and solves the problem that the incineration method and wet oxidation method need solidification treatment. question.

The present invention realizes through following technical scheme:

A method for inorganic treatment of radioactive waste oil, comprising the following steps:

S1. Pretreatment: add mineralizer after filtering the radioactive waste oil to remove solid residue;

S2. Reforming and mineralization: the waste oil treated in step S1 is added to catalyst and bed material in a high temperature environment, and the waste oil is gasified, cracked, and reformed into small molecular gas, and the nuclides in the waste oil are separated from the bed material and Trapped under the action of mineralizers to form radioactive mineralization products;

S3. Oxidation: oxidizing the small molecular gas obtained in step S2 to oxidize the combustible gas;

S4. Exhaust gas purification.

The small molecular gas mentioned in the present invention refers to the components in the gas which are small molecular components such as CH ₄ , H ₂ , CO, etc., and do not contain macromolecular components.

Wherein, the pretreatment in step S1 can prevent solid slag from affecting subsequent reforming and mineralization, and the added mineralizer can capture nuclides in waste oil during reforming and mineralization.

Step S2 realizes the gasification, cracking, and reformation of waste oil into small molecular gases, and realizes the separation of small molecular gases and radioactive mineralization products for separate treatment. The radioactive mineralization products are packaged and stored, and small molecular gases can undergo subsequent oxidation. , After the exhaust gas is purified and meets the emission requirements, it is discharged.

The conversion of organic gas into inorganic gas is realized through step S3, and the conversion of organic waste oil into inorganic gas is realized through the combination of step S2 and step S3.

To sum up, the present invention can fix radionuclides in radioactive waste oil into stable mineralization products, and convert organic waste oil into inorganic gas, which can be discharged into the environment after purification, so as to realize highly efficient reduction of radioactive waste oil. capacity, greatly reducing disposal costs.

That is to say, the present invention can not only realize the inorganic treatment of radioactive waste oil, but also does not need solidification treatment, and solves the problem that the incineration method and the wet oxidation method need solidification treatment.

Further, in step S1, the pretreatment further includes heating the radioactive waste oil added with the mineralizer, and the heating temperature is 50-100°C.

Heating treatment can improve the fluidity of waste oil, which facilitates the transportation of waste oil to the reforming and mineralization process.

Further, in step S1, the filtration accuracy of the radioactive waste oil is at least 150 μm, that is, the filter pore diameter of the filter used to filter the radioactive waste oil is less than or equal to 150 μm, and the filtration accuracy should be improved as much as possible to improve the solid residue in the waste oil. Removal.

Further, in step S1, the particle size of the mineralizer is 100-300 μm, that is, the mineralizer has a small size, and a small-sized mineralizer has a large surface area, which is more conducive to capturing nuclides in waste oil.

Further, in step S1, the mineralizer includes at least one of iron oxide, sodium carbonate, clay minerals (kaolin, zeolite, etc.) and sodium hydroxide.

Iron oxide, sodium carbonate, clay mineral and sodium hydroxide are all commercially available.

Further, in step S2, the reaction temperature is 500-900°C.

Further, in step S2, the bed material includes alumina.

Further, in step S2, the catalyst is a steam reforming catalyst.

Steam reforming catalysts are commercially available; there are mature steam reforming catalysts in the chemical industry or petrochemical industry, which are used to increase the conversion rate of hydrocarbons or light oils reacting with steam (to generate small molecular gases, such as hydrogen, carbon monoxide, etc.).

Further, in step S2, the remineralization is carried out under negative pressure.

Negative pressure is to prevent the spillage of radioactive substances and improve system safety.

Furthermore, the small molecular gas undergoes high-temperature gas-solid separation before being oxidized, and the solids in the small molecular gas can be removed through high-temperature gas-solid separation.

Furthermore, the high-temperature gas-solid separation is divided into at least two stages, and the filtration accuracy of the last stage is not less than 0.5 μm.

Further, in step S3, the temperature of the oxidation reaction is not lower than 750°C; the oxygen content is 5%-10%.

Further, in step S4, the purification of the tail gas includes cooling the tail gas, desulfurization and denitrification, demisting, and filtering in sequence.

Further, in step S4, the tail gas is heated to 50-100° C. before filtering.

An inorganic treatment system for radioactive waste oil, comprising:

Waste oil storage tanks for storing radioactive waste oil;

The waste oil filter is arranged at the rear end of the waste oil storage tank, and is used to filter and remove solid residues from the radioactive waste oil;

The waste oil stirring tank is arranged at the rear end of the waste oil filter, and is used to add mineralizers to the radioactive waste oil;

The reforming reactor is set at the rear end of the waste oil stirring tank, and is used to realize the reforming and mineralization treatment of radioactive waste oil;

The oxidation reactor is arranged at the rear end of the reforming reactor, and is used for oxidizing the small molecule gas generated in the reforming reactor;

The desulfurization and denitrification equipment is installed at the rear end of the oxidation reactor, and is used to purify the oxidized tail gas.

Further, it also includes:

The solid material storage tank is used to store the bed material or catalyst, and the bed material or catalyst in the solid material storage tank is transported to the reforming reactor through a screw feeder.

Further, it also includes:

The inert gas storage tank is used to feed inert gas into the reforming reactor for emptying or unloading;

The steam generator and superheater are used to feed high-temperature steam into the reforming reactor.

Further, it also includes a primary gas-solid separator and a secondary gas-solid separator arranged between the reforming reactor and the oxidation reactor.

Further, it also includes:

Waste packaging containers for collection of radioactive mineralization products.

Further, it also includes a flue gas cooler arranged between the oxidation reactor and the desulfurization and denitrification equipment.

Further, the rear end of the desulfurization and denitrification equipment is sequentially provided with:

Separation equipment, flue gas heater and high-efficiency filter, the separation equipment is used to remove mist, aerosol, etc.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. It can realize the fixation of radionuclides in radioactive waste oil into stable mineralization products, and convert organic waste oil into inorganic gas, realize the high-efficiency volume reduction of radioactive waste oil inorganically, and improve the long-term safety of waste disposal.

2. Through the present invention, the volume reduction factor of radioactive waste oil can be no less than 10, greatly reducing the disposal cost.

Description of drawings

The drawings described here are used to provide a further understanding of the embodiments of the present invention, constitute a part of the application, and do not limit the embodiments of the present invention. In the attached picture:

Fig. 1 is a process flow diagram of the present invention;

Fig. 2 is a schematic structural diagram of the system of the present invention.

Marks and corresponding parts names in the attached drawings:

1-solid material storage tank, 2-screw feeder, 3-reforming reactor, 4-waste oil storage tank, 5-waste oil filter, 6-waste oil delivery pump, 7-waste oil mixing tank, 8 - Waste oil feed pump, 9- Inert gas storage tank, 10- Steam generator and superheater, 11- Primary gas-solid separator, 12- Secondary gas-solid separator, 13- Waste packaging container, 14- Oxidation reaction Device, 15-flue gas cooler, 16-desulfurization and denitrification equipment, 17-separation equipment, 18-flue gas heater, 19-high efficiency filter, 20-high pressure fan.

detailed description

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the examples and accompanying drawings. As a limitation of the present invention.

Example 1:

As shown in Figure 1, a method for inorganic treatment of radioactive waste oil comprises the following steps:

S1. Pretreatment: After the radioactive waste oil is filtered to remove solid residues, it is added to the waste oil mixing tank 7 together with a small particle mineralizer, and stirred and heated to 50-100°C to improve the fluidity of the waste oil;

Among them, the particle size of the small particle mineralizer is 100-300 μm, the mineralizer includes at least one of iron oxide, sodium carbonate, clay ore and sodium hydroxide, and the filtration accuracy of the radioactive waste oil is at least 150 μm.

S2. Reforming and mineralization: the waste oil treated in step S1 is added to catalyst and bed material in a high temperature environment, and the waste oil is gasified, cracked, and reformed into small molecular gas, and the nuclides in the waste oil are separated from the bed material and Trapped under the action of mineralizers to form radioactive mineralization products;

The specific process is:

Pass the inert gas into the reforming reactor 3 to replace the air in the equipment and pipelines, pre-load the catalyst and bed material into the reforming reactor 3, use the reforming reactor 3 to assist heating to 600-700°C, Use steam generation and superheater 10 to add superheated steam into the reforming reactor 3, and when the reaction temperature rises to 500-900°C, the pretreated waste oil is transported into the reforming reactor 3 through the waste oil feed pump 8 Inside, waste oil is gasified, cracked, and reformed into small molecular gases (CH ₄ , H ₂ , CO, etc.) under the action of high-temperature steam, mineralizers, and catalysts. Under the action of chemical agent, it is trapped to form radioactive mineralization products. The large-particle mineralization products are kept in the reforming reactor 3, and are regularly discharged to the waste packaging container 13 by pneumatic conveying for storage. The small-particle mineralization products and part of the volatilization The nuclide is brought out of the reforming reactor 3 along with the small molecule tail gas, and after high-temperature gas-solid separation, the mineralized products and radionuclides are collected in the waste packaging container 13, realizing the interception of most radionuclides;

The bed material is alumina, the catalyst is a steam reforming catalyst, and it is located in the upper stage of the reforming reaction 3 when it works, and the reforming mineralization is carried out under negative pressure, and the specific pressure is about -1kPa.

S3. Oxidation: The small molecular gas obtained in step S2 is subjected to high-temperature gas-solid separation and oxidation treatment in sequence. The oxidation treatment oxidizes the combustible gas, and the temperature of the oxidation reaction is not lower than 750° C.; the oxygen content is 5% to 10%;

Among them, the high-temperature gas-solid separation is divided into at least two stages, and the filtration accuracy of the last stage is not less than 0.5 μm. The second-stage separation is preferred. The filtration accuracy of the first-stage gas-solid separator is 5-10 μm, and the filtration accuracy of the second-stage is 0.3-0.5 μm.

S4. Tail gas purification: the exhaust gas is cooled, desulfurized and denitrified, demisted, and filtered in sequence before being discharged;

Specifically, the tail gas at the outlet of the oxidation process is rapidly cooled to below 200°C to reduce the generation of polluting gases, and the SO _x , NO _x and other polluting gases are removed through the desulfurization and denitrification equipment 16, and then the dust that may be carried in the tail gas is removed through the separator 17 , mist, etc., and heat the exhaust gas. The exhaust gas is heated to 50-100°C to reduce its relative humidity. After high-efficiency filtration to remove possible entrained aerosols, the exhaust gas is further purified, and finally discharged into the ventilation system.

The volume reduction factor of waste oil after treatment in this embodiment is greater than about 10; the parameters in this embodiment are recommended parameters for treating waste oil, and the specific process parameters can be optimized and adjusted according to the specific design of waste oil source items (components, nuclides, etc.) .

A system for implementing the above-mentioned inorganic treatment method for radioactive waste oil, including a solid material storage tank 1, a screw feeder 2, a reforming reactor 3, a waste oil storage tank 4, a waste oil filter 5, and a waste oil delivery pump 6 , waste oil mixing tank 7, waste oil feed pump 8, inert gas storage tank 9, steam generation and superheater 10, primary gas-solid separator 11, secondary gas-solid separator 12, waste packaging container 13, oxidation reaction device 14, flue gas cooler 15, desulfurization and denitrification equipment 16, separation equipment 17, flue gas heater 18, high efficiency filter 19 and high pressure fan 20;

There are two solid material storage tanks 1, which are respectively used to store bed material and catalyst, and the material in the solid material storage tank 1 is transported to the reforming reactor 3 through the screw feeder 2;

The waste oil storage tank 4 is used to store radioactive waste oil. The waste oil storage tank 4 and the waste oil mixing tank 7 are connected by a pipeline, and a waste oil filter 5 and a waste oil delivery pump 6 are arranged on the pipeline;

The oil stirring tank 7 is connected to the reforming reactor 3 through a pipeline, and a waste oil feed pump 8 is arranged on the pipeline. The reforming reactor 3 is used to realize the reforming and mineralization treatment of radioactive waste oil, preferably in The discharge port of the reforming reactor 3 is provided with a temporary storage tank, which is convenient for sampling and testing;

The inert gas storage tank 9, the steam generator and the superheater 10 are all communicated with the reforming reactor 3 through pipes, which are respectively used to feed inert gas and high-temperature steam into the reforming reactor 3. The radioactive mineralization product at the bottom of the whole reactor 3 is taken out, and the high-temperature steam is used to meet the high-temperature environment of reforming mineralization;

Wherein, steam generation and the steam generation (steam generator) and superheating function (heat exchanger) of the superheater 10 can be realized by two independent devices;

The reforming reactor 3 and the oxidation reactor 14 are connected by a pipeline, and the pipeline is provided with a primary gas-solid separator 11 and a secondary gas-solid separator 12 in sequence;

The waste packaging container 13 is connected to the reforming reactor 3 through pipelines, and the primary gas-solid separator 11 and the secondary gas-solid separator 12 are also connected to the waste packaging container 13 through pipelines, and the filtered solids are introduced into the waste packaging Inside the container 13;

The desulfurization and denitrification equipment 16 is connected to the oxidation reactor 14 through a pipeline, and a flue gas cooler 15 is arranged on the pipeline;

The rear end of the desulfurization and denitrification equipment 16 is provided with a separation device 17, a flue gas heater 18, a high-efficiency filter 19 and a high-pressure fan 20 in sequence. In principle, two sets are set up as a backup, and the interlock switching is realized by monitoring the pressure difference of the high-efficiency filter 19.

The working process of this embodiment is as follows:

After the radioactive waste oil in the waste oil storage tank 4 is preheated, the solid residue therein is filtered through the waste oil filter 5, and then transported to the waste oil stirring tank 7 through the waste oil delivery pump 6, and then heated and heated by the waste oil stirring tank 7. Stir and mix with the small-particle mineralizer for even use; transport the bed material in the solid material storage tank 1 to the reforming reactor 3 through the screw conveyor 2, and send the catalyst into the reforming reactor 3 in the same way. First, use the inert gas storage tank 9 to replace the air in the system, and the auxiliary induction heating of the reforming reactor 3 will raise the temperature of the reforming reactor 3 to above 500°C, and then use the steam generation and the superheater 10 to ventilate into the reforming reactor 3 Superheated steam is injected to fluidize the bed material and catalyst, and the uniformly mixed waste oil is fed into the reforming reactor 3 through the waste oil feed pump 8, and the waste oil is gasified and cracked at a high temperature in the middle and lower section of the reforming reactor 3, Mineralizer particles and bed materials in the waste oil fully collide with radionuclides at high temperature to form mineralized products. After the waste oil is cracked, it is reformed into small Molecular gas, and the small particle solid product not higher than 50 μm is taken out of the reforming reactor 3, and the particles larger than 10 μm are initially separated by the primary gas-solid separator 11, and then further separated by the secondary gas-solid separator 12 Particles higher than 0.3 μm are produced, the mineralized product in the reforming reactor 3 is transported to the waste packaging container 13 by pneumatic force, and the solid mineralized product separated by the primary gas-solid separator 11 and the secondary gas-solid separator 12 is transported by its own weight Combined with nitrogen gas collected into the waste packaging container 13. After gas-solid separation, the tail gas entrained with a small amount of combustible gas is completely oxidized into CO ₂ , H ₂ O and other gases in the oxidation reactor 14, and is rapidly cooled to below 200°C to prevent regeneration of polluted gas. The oxidized gas is cooled by the desulfurization and denitrification equipment 16 to remove the acid gas and dust, remove the mist in the separator 17, heat it to about 80°C in the flue gas heater 18, and then pass through the high efficiency filter 19 to further The radioactive aerosol that may be carried is removed, and finally discharged to the exhaust system of the factory building through the high-pressure fan 20. The negative pressure in the reforming reactor 3 is regulated through interlocking of the high-pressure blower.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to this specification are only used to match the content disclosed in the specification, for those who are familiar with this technology to understand and read, and are not used to limit the present invention Therefore, it has no technical substantive meaning, and any modification of structure, change of proportional relationship or adjustment of size shall still fall into the within the scope covered by the technical content disclosed in the present invention. At the same time, terms such as "upper", "lower", "left", "right", and "middle" quoted in this specification are only for the convenience of description, and are not used to limit the practicable scope of the present invention. The change or adjustment of the relative relationship within the scope, without any substantial change in the technical content, shall also be regarded as the applicable scope of the present invention.

Claims (22)

1. A method for inorganic treatment of radioactive waste oil, characterized in that, comprising the following steps: S1. Pretreatment: add mineralizer after filtering the radioactive waste oil to remove solid residue; S2. Reforming and mineralization: the waste oil treated in step S1 is added to the catalyst and bed material in a high temperature environment, and the waste oil is gasified, cracked, and reformed into small molecule gas. Trapped under the action of mineralizers to form radioactive mineralization products; S3. Oxidation: oxidizing the small molecular gas obtained in step S2 to oxidize the combustible gas; S4. Exhaust gas purification. 2. A method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S1, the pretreatment also includes heating the radioactive waste oil added with a mineralizer at a heating temperature of 50 ~100°C. 3. The method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S1, the filtration accuracy of radioactive waste oil is at least 150 μm. 4. The inorganic treatment method for radioactive waste oil according to claim 1, characterized in that, in step S1, the particle size of the mineralizer is 100-300 μm. 5. The method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S1, the mineralizer includes at least one of iron oxide, sodium carbonate, clay mineral and sodium hydroxide. 6. The inorganic treatment method for radioactive waste oil according to claim 1, characterized in that, in step S2, the reaction temperature is 500-900°C. 7. The method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S2, the bed material includes alumina. 8. The method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S2, the catalyst is a steam reforming catalyst. 9. The method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S2, reforming and mineralization are carried out under negative pressure. 10. The inorganic treatment method for radioactive waste oil according to claim 1, characterized in that the small molecule gas undergoes high-temperature gas-solid separation before oxidation treatment. 11. The inorganic treatment method for radioactive waste oil according to claim 9, characterized in that the high-temperature gas-solid separation is divided into at least two stages, and the filtration accuracy of the last stage is not less than 0.5 μm. 12. The method for inorganic treatment of radioactive waste oil according to claim 1, characterized in that, in step S3, the temperature of the oxidation reaction is not lower than 750°C. 13. The inorganic treatment method for radioactive waste oil according to claim 12, characterized in that the oxygen content is 5%-10%. 14. The inorganic treatment method for radioactive waste oil according to claim 1, characterized in that, in step S4, the exhaust gas is purified by sequentially cooling the exhaust gas, desulfurizing and denitrifying, removing fog and foam, and filtering. 15. The inorganic treatment method for radioactive waste oil according to claim 1, characterized in that, in step S4, the tail gas is heated to 50-100°C before filtering. 16. A system for realizing the inorganic treatment method of radioactive waste oil according to any one of claims 1-15, characterized in that it comprises: Waste oil storage tank (4), used for storing radioactive waste oil; The waste oil filter (5) is arranged at the rear end of the waste oil storage tank (4), and is used to filter and remove solid residues from radioactive waste oil; The waste oil stirring tank (7), which is arranged at the rear end of the waste oil filter (5), is used to add mineralizers to the radioactive waste oil; The reforming reactor (3), which is arranged at the rear end of the waste oil stirring tank (7), is used to realize the reforming and mineralization treatment of radioactive waste oil; An oxidation reactor (14), arranged at the rear end of the reforming reactor (3), is used to oxidize the small molecule gas generated in the reforming reactor (3); The desulfurization and denitrification equipment (16) is arranged at the rear end of the oxidation reactor (14), and is used for purifying the oxidized tail gas. 17. The system of claim 16, further comprising: The solid material storage tank (1) is used to store the bed material or catalyst, and the bed material or catalyst in the solid material storage tank (1) is transported to the reforming reactor (3) through the screw feeder (2). 18. The system of claim 16, further comprising: An inert gas storage tank (9), used for feeding inert gas into the reforming reactor (3) for emptying or unloading; The steam generator and superheater (10) are used to feed high-temperature steam into the reforming reactor (3). 19. The system according to claim 16, characterized in that it further comprises a primary gas-solid separator (11) and a secondary gas-solid separator arranged between the reforming reactor (3) and the oxidation reactor (14). Separator (12). 20. The system of claim 16, further comprising: A waste packaging container (13) for collecting radioactive mineralization products. 21. The system according to claim 16, further comprising a flue gas cooler (15) arranged between the oxidation reactor (14) and the desulfurization and denitrification equipment (16). 22. The system according to any one of claims 16-21, characterized in that, the rear end of the desulfurization and denitrification equipment (16) is sequentially provided with: A separation device (17), a flue gas heater (18) and a high-efficiency filter (19), the separation device (17) is used for removing mist and aerosol.

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