Radioactive waste graphite incineration treatment and tail gas purification and sealing treatment process
By incinerating radioactive waste graphite and purifying the flue gas using a fixed-bed incinerator and multi-stage dust removal and purification technology, the problems of waste graphite occupying inventory and C14 emissions have been solved, achieving permanent sealing of C14, reducing management costs and public concerns.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA INST FOR RADIATION PROTECTION
- Filing Date
- 2025-12-27
- Publication Date
- 2026-04-28
AI Technical Summary
Existing technologies lack effective methods for treating radioactive waste graphite, resulting in large storage space being occupied by waste graphite, posing a risk of spontaneous combustion, and the C14 emission problem not being effectively controlled.
Radioactive waste graphite is treated by incineration in a fixed-bed incinerator. The flue gas is purified by multi-stage dust removal, wet absorption and high-efficiency adsorption devices, and carbon dioxide is concentrated and compressed for geological sequestration to achieve permanent C14 fixation.
This reduces the storage space occupied by waste graphite, lowers management costs, avoids public concerns about C14 emissions, and achieves permanent storage of C14.
Smart Images
Figure CN121938679A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radioactive waste treatment, specifically to a process for radioactive waste graphite incineration and tail gas purification and storage. Background Technology
[0002] Due to its excellent comprehensive properties, graphite is widely used in the nuclear industry, especially as a reactor internal component and moderator. With the gradual decommissioning of some early reactors, my country has generated tens of thousands of tons of radioactive waste graphite. Due to a lack of suitable treatment technology, storage is currently the primary method of disposal for this waste graphite. However, this consumes a large amount of waste storage, and the presence of Wegener's energy poses a risk of spontaneous combustion, necessitating long-term monitoring of stored graphite. Countries worldwide have conducted multi-faceted scientific research on this issue, developing various processes including incineration, solidification, and electrochemical treatment. Incineration is the most mature treatment method, but the secondary waste it produces has been extensively studied. European countries have developed fluidized bed incineration technology, which has high treatment efficiency, but furnace wear is a limiting factor. In the final collected ash, refractory bricks account for one-third of the total. In addition, none of the aforementioned countries have C14 control technology. Other countries have developed radioactive graphite waste incineration technology, and the exhaust gas is either directly emitted after preliminary filtration or diluted through power plant chimneys before being emitted. There is no C14 control technology, which has led to public concerns about C14 emissions, especially for people near the emission sites. Ultimately, radioactive graphite waste incineration technology cannot be applied. At present, radioactive graphite waste in various countries is mainly temporarily stored, with a global stockpile of more than 250,000 tons, occupying a large amount of radioactive waste storage capacity. Summary of the Invention
[0003] To achieve the above and other related objectives, this invention discloses a process for the incineration treatment of radioactive waste graphite and the purification and storage of its exhaust gas, comprising: Radioactive waste graphite is incinerated. Cooling and purifying the flue gas produced by incineration; The carbon dioxide in the cooled and purified flue gas is concentrated and compressed, and the compressed carbon dioxide is then geologically sequestered to achieve… 14 C is permanently fixed; The incineration of radioactive waste graphite includes: Source term investigation was conducted on waste graphite to confirm the activity concentration and types of radioactive nuclides in the waste graphite. Waste graphite that meets the incineration activity requirements is crushed; The crushed waste graphite particles are fed into a fixed-bed incinerator, which includes a feeding section, a combustion section, a water cooling section and an ash discharge section from top to bottom. The graphite is burned by intermittent feeding to obtain ash and flue gas. The cooled incineration ash is packed into containers and then solidified with cement. Cooling and purifying the flue gas generated from incineration includes: Multi-stage dust removal treatment for incineration flue gas; The wet absorption process uses water as the absorption medium to cool the flue gas and remove pollutants from it. 36 Cl and 3 H; A high-efficiency adsorption device is used to remove radioactive aerosols from flue gas.
[0004] Preferably, the process of enriching and compressing carbon dioxide in the cooled and purified flue gas, and then geologically sequestering the compressed carbon dioxide, includes: Carbon dioxide is concentrated by absorbing it with chemical solvents, so that the carbon dioxide concentration reaches more than 90%, and the remaining exhaust gas is emitted as non-radioactive flue gas. Carbon dioxide is compressed to a supercritical state. The compressed carbon dioxide is injected into the deep saline aquifer for fixation.
[0005] Preferably, the water-cooled section of the fixed-bed incinerator is located below the combustion section and is used for graphite solid combustion; the combustion section is used to further burn carbon monoxide in the exhaust gas; the ash discharge section is equipped with a cooling device to cool the incinerated ash to room temperature before discharge.
[0006] Preferably, the multi-stage dust removal process includes one or more combinations of cyclone dust removal, electrostatic dust removal, and bag filter dust removal.
[0007] Preferably, the wet absorption process uses a spray tower, a packed tower, or a gravity absorption device, and the absorption medium is water, alkaline solution, or organic solvent.
[0008] Preferably, the high-efficiency adsorption device is a high-efficiency filter or an activated carbon adsorption device, or a combination of both.
[0009] Preferably, carbon dioxide concentration includes one or more combinations of organic solvent absorption, pressure swing adsorption, or activated carbon adsorption processes.
[0010] Preferably, the step of filling the cooled incineration ash into the container includes: The ash is conveyed to the ash buckets by a screw conveyor for filling.
[0011] Preferably, the step of injecting compressed carbon dioxide into a deep saline aquifer for fixation includes: Compressed carbon dioxide is injected into a deep saline aquifer at a depth of no less than 1500m, causing the carbon dioxide to react chemically with calcium and magnesium ions in the strata rocks and saline water to form carbonate mineral precipitates, thus achieving permanent sequestration.
[0012] By adopting the above technical solutions, on the one hand, the problem of radioactive waste graphite disposal can be solved, reducing the inventory and management costs of waste graphite; on the other hand, carbon sequestration technology can be used to permanently seal C14 in the exhaust gas in the deep geological environment, avoiding potential impacts on the public and reducing public concerns. Attached Figure Description
[0013] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. The drawings are provided for a better understanding of the invention and are not intended to limit the scope of this disclosure. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein: Figure 1 This is a flowchart illustrating an embodiment of the present invention. Detailed Implementation
[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0015] Reference Figure 1 This invention provides a process for the incineration treatment and tail gas purification and storage of radioactive waste graphite, characterized by comprising: Radioactive waste graphite is incinerated. Cooling and purifying the flue gas produced by incineration; The carbon dioxide in the cooled and purified flue gas is concentrated and compressed, and the compressed carbon dioxide is then geologically sequestered to achieve… 14 C is permanently fixed; The incineration of radioactive waste graphite includes: A source term investigation was conducted on the waste graphite to confirm its activity concentration and the types of radionuclides. Waste graphite that meets the incineration activity requirements is crushed; The crushed waste graphite particles are fed into a fixed bed incinerator, which includes a feeding section, a combustion section, a water cooling section and an ash discharge section from top to bottom. The graphite is burned by intermittent automatic feeding to obtain incineration ash and incineration flue gas. The incineration ash is cooled, filled into containers, and then solidified with cement. Cooling and purifying the flue gas generated from incineration includes: Multi-stage dust removal treatment for incineration flue gas; The wet absorption process uses water as the absorption medium to cool the flue gas and remove pollutants from it. 36 Cl and 3 H; A high-efficiency adsorption device is used to remove radioactive aerosols from flue gas.
[0016] Preferably, the source term investigation includes: confirming the activity concentration and radionuclide types of waste graphite through the source term investigation. For some waste graphite with high activity concentration and radionuclide types that are mainly short-lived, the activity concentration can be further reduced through temporary storage decay, thereby ensuring the safety of operators. Less than 60 years or less than 80 years can be used as the basis for judging whether it is short-lived, and the specific settings shall be made by those skilled in the art.
[0017] Preferably, by sorting and crushing graphite, waste graphite with high radioactivity and a large number of short-lived nuclides can be temporarily stored to allow it to decay further, while waste graphite with the required activity concentration and nuclides can be crushed into particles with a particle size of about 20mm by a crusher.
[0018] Preferably, the incineration process includes: feeding crushed graphite fragments into a specially designed fixed-bed incinerator for incineration. The incinerator is mainly divided into four parts, from top to bottom: a feeding section, a combustion section, a water-cooling section, and an ash removal section. Solid graphite is burned in the water-cooling section, and carbon monoxide in the exhaust gas is further burned in the combustion section. Graphite enters the furnace from the feeding section. The entire combustion process uses automatic intermittent feeding and employs segmented graphite combustion technology to control the carbon monoxide concentration. Radiation protection is implemented during actual operation to protect operators and the environment.
[0019] In the treatment of residues, the ash discharged from the bottom of the combustion furnace mainly consists of graphite residue, combustion ash, and other substances. After being cooled to room temperature in the ash discharge section at the bottom of the furnace, this part is transported into a 200L ash bucket through a conveying device and finally fixed with cement.
[0020] Preferably, the present invention uses a screw conveyor to transport ash.
[0021] The above-mentioned radioactive waste graphite incineration treatment includes two parts: pretreatment and incineration. The pretreatment process requires source term investigation, sorting, crushing and other operations on the waste graphite, which is then sent to the incinerator for incineration, and the residue at the bottom of the furnace is fixed.
[0022] The pretreatment of waste graphite can be carried out through various means such as automatic mechanical devices and manual sorting, and then the waste graphite can be crushed by crushing equipment such as roller crushers and extrusion crushers.
[0023] The incineration treatment of the waste graphite uses a non-standard customized incinerator, which includes four parts: ash discharge section, water cooling section, combustion section and feeding section. It adopts a modular design and is easy to replace and maintain.
[0024] Preferably, cooling and purifying the flue gas generated from incineration includes: Dust removal: By combining cyclone dust collectors, electrostatic dust collectors and bag filters, more than 99% of the particulate matter entrained in the flue gas is filtered out, and the discharged ash and the ash discharged from the furnace are centrally and uniformly treated.
[0025] Preferably, the dust removal process can utilize a combination of various equipment such as cyclone dust collectors, bag filters, sintered plastic filters, ceramic filters, metal filters, and wet dust collectors to remove radioactive dust.
[0026] Wet absorption: Because conventional high-efficiency filters have low adsorption efficiency for these radionuclides, purified water is used as the medium to cool and purify the flue gas through spraying or other process units, reducing the flue gas temperature to around 50°C to remove Cl from the flue gas. 36 H 3 Radioactive nuclides, etc.
[0027] Preferably, the wet absorption method includes using various absorption devices such as spray towers, packed towers, and ultragravity absorption devices to purify the exhaust gas with absorbents such as alkaline solutions, water, and organic solvents, thereby further removing radioactive substances from the exhaust gas.
[0028] High-efficiency adsorption: The flue gas is further purified by a high-efficiency adsorber with a filtration efficiency of 99.99% to remove various radioactive aerosols and other substances from the flue gas. Radioactive aerosols in waste flue gas can be adsorbed by absorption devices such as high-efficiency filters and activated carbon. By combining multiple processes, a purification efficiency of 99.99% can be achieved.
[0029] Preferably, geological sequestration of carbon dioxide includes: Carbon dioxide removal and concentration: The main components of the flue gas after high-efficiency adsorption are nitrogen, carbon dioxide, and a small amount of oxygen. The radioactive nuclide is mainly C14, which exists in the flue gas as carbon dioxide. The carbon dioxide in the exhaust gas can be concentrated using processes such as multi-stage chemical solvent absorption, with a concentration of over 90%. The remaining exhaust gas mainly consists of nitrogen and oxygen, and contains almost no radioactivity, so it can be emitted as non-radioactive flue gas.
[0030] Carbon dioxide compression and transportation: High-concentration carbon dioxide is compressed into a liquid state and transported to the final storage location.
[0031] Geological sequestration: Geological sequestration utilizes a complex process involving various physical and chemical processes, such as tectonic sequestration, hydrodynamic sequestration, bound gas sequestration, dissolution sequestration, and mineralization sequestration, to sequester carbon dioxide into deep strata. Ultimately, the injected carbon dioxide reacts chemically with calcium and magnesium ions in rocks and saline water to produce carbonate mineral precipitation, thus achieving permanent carbon dioxide fixation and preventing its participation in the carbon cycle. Deep saline aquifer sequestration offers the best safety and the largest expected sequestration capacity. The sequestration depth of carbon dioxide in deep saline aquifers should be at least 800m to ensure a supercritical state. This state effectively utilizes underground sequestration space and improves sequestration safety. Preferably, in this embodiment of the invention, a power unit is used to inject it into specific geological conditions below 1500m, permanently fixing C14-containing carbon dioxide through geological sequestration, thereby avoiding C14 emission problems.
[0032] The exhaust gas after purification mainly consists of nitrogen, carbon dioxide and a small amount of oxygen. Carbon sequestration adsorption-desorption process is used to separate, purify and geologically store the carbon dioxide in the exhaust gas.
[0033] Preferably, the carbon dioxide removal process can utilize pressure swing adsorption, activated carbon adsorption, organic solvent adsorption, and other process units individually or in combination to adsorb and desorb C14-containing carbon dioxide in the exhaust gas, ultimately obtaining high-concentration carbon dioxide gas.
[0034] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.
[0035] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.
[0036] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.
[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A process for the incineration treatment of radioactive waste graphite and the purification and storage of its exhaust gas, characterized in that, include: Radioactive waste graphite is incinerated. Cooling and purifying the flue gas produced by incineration; The carbon dioxide in the cooled and purified flue gas is concentrated and compressed, and the compressed carbon dioxide is then geologically sequestered to achieve… 14 C is permanently fixed; The incineration of radioactive waste graphite includes: Source term investigation was conducted on waste graphite to confirm the activity concentration and types of radioactive nuclides in the waste graphite. Waste graphite that meets the incineration activity requirements is crushed; The crushed waste graphite particles are fed into a fixed-bed incinerator, which includes a feeding section, a combustion section, a water cooling section and an ash discharge section from top to bottom. The graphite is burned by intermittent feeding to obtain ash and flue gas. The cooled incineration ash is packed into containers and then solidified with cement. Cooling and purifying the flue gas generated from incineration includes: Multi-stage dust removal treatment for incineration flue gas; The wet absorption process uses water as the absorption medium to cool the flue gas and remove pollutants from it. 36 Cl and 3 H; A high-efficiency adsorption device is used to remove radioactive aerosols from flue gas.
2. The process for incinerating radioactive waste graphite and purifying and storing its exhaust gas according to claim 1, characterized in that, The process of enriching and compressing carbon dioxide in the cooled and purified flue gas, and then geologically sequestering the compressed carbon dioxide, includes: Carbon dioxide is concentrated by absorbing it with chemical solvents, so that the carbon dioxide concentration reaches more than 90%, and the remaining exhaust gas is emitted as non-radioactive flue gas. Carbon dioxide is compressed to a supercritical state. The compressed carbon dioxide is injected into the deep saline aquifer for fixation.
3. The process for incinerating radioactive waste graphite and purifying and storing tail gas according to claim 1, characterized in that, The water-cooled section of the fixed-bed incinerator is located below the combustion section and is used for graphite solid combustion; the combustion section is used to further burn carbon monoxide in the exhaust gas; the ash discharge section is equipped with a cooling device to cool the incinerated ash to room temperature before discharge.
4. The process for incinerating radioactive waste graphite and purifying and storing its exhaust gas according to claim 1, characterized in that, The multi-stage dust removal process includes one or more combinations of cyclone dust removal, electrostatic dust removal, and bag filter dust removal.
5. The process for incinerating radioactive waste graphite and purifying and storing its exhaust gas according to claim 1, characterized in that, The wet absorption process uses a spray tower, a packed tower, or a gravity absorption device, and the absorption medium is water, alkaline solution, or organic solvent.
6. The process for incinerating radioactive waste graphite and purifying and storing its exhaust gas according to claim 1, characterized in that, The high-efficiency adsorption device uses a high-efficiency filter or an activated carbon adsorption device, or a combination of both.
7. The process for incinerating radioactive waste graphite and purifying and storing its exhaust gas according to claim 1, characterized in that, Carbon dioxide concentration can be achieved by using one or more of the following methods: organic solvent absorption, pressure swing adsorption, or activated carbon adsorption.
8. The process for incinerating radioactive waste graphite and purifying and storing its exhaust gas according to claim 1, characterized in that, The step of filling the cooled incineration ash into the container includes: The ash is conveyed to the ash buckets by a screw conveyor for filling.
9. The process for incinerating radioactive waste graphite and purifying and storing tail gas according to claim 2, characterized in that, The step of injecting compressed carbon dioxide into a deep saline aquifer for fixation includes: Compressed carbon dioxide is injected into a deep saline aquifer at a depth of no less than 1500m, causing the carbon dioxide to react chemically with calcium and magnesium ions in the strata rocks and saline water to form carbonate mineral precipitates, thus achieving permanent sequestration.