Method for removing radionuclide cesium in radioactive incineration ash

Abstract

The invention belongs to the field of purification treatment of radioactive pollution solid waste, and particularly relates to a method for removing radionuclide cesium in radioactive incineration ash, which comprises the following steps: mixing radioactive solid waste with waste plastic and a dissociation agent, carrying out heat treatment on a high-temperature furnace, and reacting cesium element in the solid waste with chlorine generated by decomposing the waste plastic, and gaseous chloride of cesium is generated and is separated from the solid waste, so that the aim of purifying the radioactive pollution solid waste is fulfilled. The cesium element in the radioactive solid waste can be effectively separated, the radioactive intensity of the solid waste is reduced, subsequent further treatment is facilitated, the added waste plastic is completely decomposed in the heat treatment process, and the size of the solid waste subjected to heat treatment cannot be increased; after the dissociation agent is added, the removal rate of cesium can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of purification and treatment of radioactive contaminated solid waste, and in particular relates to a method for removing radioactive nuclide cesium from radioactive incineration ash. Background Art

[0002] Compared with traditional fossil energy, nuclear energy has unique advantages such as high energy density, low greenhouse gas emissions, and high economic benefits. It is one of the most promising energy sources in the future. Compared with other renewable energy sources, nuclear energy output is more stable and will not be affected by factors such as climate, weather, and seasons. However, with the development of nuclear power technology, the risk of nuclear accidents continues to decrease, but the possibility of accidents cannot be completely ruled out. Incineration and volume reduction is the most appropriate method for treating radioactive waste, especially for waste rich in organic matter. However, after the incineration of radioactive solid waste, radioactive nuclides are enriched in the incineration ash, so the disposal of incineration ash rich in radioactive nuclides is an important issue that needs to be solved.

[0003] Cesium is the main radioactive nuclide in radioactive incineration ash, and exists in two forms: water-soluble cesium and insoluble cesium. Conventional solvent extraction has a higher removal rate for water-soluble cesium, but a lower removal rate for insoluble cesium. Summary of the invention

[0004] In view of the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a method for removing radioactive nuclide cesium from radioactive incineration ash. The present invention proposes adding waste plastics and a dissociation agent to the radioactive incineration ash, and then heating the cesium in the radioactive incineration ash to generate gaseous cesium that volatilizes into the gas phase, thereby achieving separation from the solid incineration ash.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0007] The plastic is crushed and mixed with radioactive incineration ash and a dissociation agent to obtain a mixture of the three.

[0008] The mixture of the three is subjected to heat treatment while air is introduced, and the dissociation of cesium is increased by a dissociating agent, and the cesium in the radioactive incineration ash reacts with the plastic and the dissociating agent to generate gaseous chloride of cesium, ash and smoke.

[0009] The gaseous chloride of cesium is condensed and separated together with the flue gas, and the radioactive cesium is precipitated from the flue gas and then collected.

[0010] The invention mixes crushed plastic with radioactive incineration ash and a dissociating agent, then performs high-temperature heat treatment on the mixed material, and introduces air at the same time, so that cesium element in the radioactive incineration ash reacts with chlorine generated by decomposition of the plastic to generate gaseous chloride of cesium, ash and flue gas, the gaseous chloride of cesium is separated from the radioactive incineration ash, and condensed and separated together with the flue gas, and radioactive cesium is precipitated from the flue gas and then collected, so as to achieve the purpose of purifying radioactive contaminated solid waste, and after adding the dissociating agent, the dissociation of cesium is increased, the removal rate of cesium can be greatly improved, and the efficient removal of water-soluble cesium and sparingly soluble cesium in the radioactive incineration ash is achieved.

[0011] The added waste plastics are completely decomposed during the thermal treatment process and will not increase the volume of the solid waste after thermal treatment. Moreover, waste plastics are widely available and low in cost, so resource utilization of waste plastics can be achieved.

[0012] In a preferred embodiment of the present invention, the dissociating agent is one or more of calcium oxide, magnesium oxide and iron oxide.

[0013] In a preferred embodiment of the present invention, the mass percentage of the plastic in the mixture of the three is 5% to 50%.

[0014] In a preferred embodiment of the present invention, the mass percentage of the dissociating agent in the mixture of the three is 5% to 30%.

[0015] In a preferred embodiment of the present invention, the heat treatment temperature is 700°C to 1300°C.

[0016] In a preferred embodiment of the present invention, the heat treatment time is 0.5 hours to 5 hours.

[0017] In a preferred embodiment of the present invention, the components of the radioactive incineration ash include silicon-aluminum compounds and cesium element, the mass percentage of the silicon-aluminum compounds is greater than 60%, the mass percentage of the cesium element is 0.001% to 2%, and the total is 100%.

[0018] In a preferred embodiment of the invention, the plastic is crushed to less than 2 microns.

[0019] In a preferred embodiment of the present invention, the ash is discharged, and the flue gas is discharged after further purification.

[0020] In a preferred embodiment of the present invention, the main component of the plastic is polyvinyl chloride.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention mixes crushed plastic with radioactive incineration ash and a dissociating agent, and then performs high-temperature heat treatment on the mixed material, while introducing air, so that the cesium element in the radioactive incineration ash reacts with chlorine generated by the decomposition of the plastic to generate gaseous chloride of cesium, ash and flue gas, and the gaseous chloride of cesium is separated from the radioactive incineration ash and condensed and separated together with the flue gas, and the radioactive cesium is precipitated from the flue gas and then collected, thereby achieving the purpose of purifying radioactive contaminated solid wastes, and after adding the dissociating agent, the dissociation of cesium is increased, which can greatly improve the removal rate of cesium, and realize the efficient removal of water-soluble cesium and refractory cesium in the radioactive incineration ash.

[0023] 2. The present invention can effectively separate cesium from radioactive solid waste, reduce the radioactivity of the solid waste itself, and facilitate subsequent further treatment and disposal. The added waste plastics are completely decomposed during the heat treatment process, and the volume of the solid waste after heat treatment will not be increased. Moreover, the waste plastics are widely available and low in cost, and the resource utilization of waste plastics can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart of the method for removing radioactive nuclide cesium from radioactive incineration ash.

[0025] Figure 2 The figure is a relationship diagram between the volatilization rate of cesium in the present invention, the heat treatment temperature and the amount of PVP added.

[0026] Figure 3 This is the effect of adding a CaO dissociator on the volatilization of cesium in the present invention.

[0027] Figure 4 This is a SEM-EDS analysis diagram of the gas phase condensate of the present invention. DETAILED DESCRIPTION

[0028] The following is a detailed description of the technical solutions in the embodiments of the present invention in combination with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0030] Example 1

[0031] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0032] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0033] (2) Mixing the radioactive incineration ash, the crushed waste plastic particles in step (1) and the dissociation agent calcium oxide in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 50%, and the mass percentage of the dissociation agent calcium oxide in the mixture is 30%.

[0034] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0035] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0036] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0037] Example 2

[0038] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0039] (1) The waste plastics are crushed in a Japanese crusher to a particle size of less than 2 microns to obtain waste plastic particles.

[0040] (2) Mixing the radioactive incineration ash, the crushed waste plastic particles in step (1) and the dissociation agent calcium oxide in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 50%, and the mass percentage of the dissociation agent calcium oxide in the mixture is 15%.

[0041] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0042] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0043] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0044] Example 3

[0045] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0046] (1) Crushing the waste plastic into a crusher until the particle size is less than 2 microns to obtain waste plastic particles.

[0047] (2) Mixing the radioactive incineration ash, the crushed waste plastic particles in step (1) and the dissociation agent calcium oxide in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 25%, and the mass percentage of the dissociation agent calcium oxide in the mixture is 30%.

[0048] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0049] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0050] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0051] Example 4

[0052] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0053] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0054] (2) Mixing the radioactive incineration ash, the crushed waste plastic particles in step (1) and the dissociation agent calcium oxide in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 25%, and the mass percentage of the dissociation agent calcium oxide in the mixture is 15%.

[0055] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0056] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0057] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0058] Example 5

[0059] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0060] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0061] (2) Mixing the radioactive incineration ash, the crushed waste plastic particles in step (1) and the dissociation agent calcium oxide in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 10%, and the mass percentage of the dissociation agent calcium oxide in the mixture is 30%.

[0062] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0063] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0064] (5) The flue gas separated from the condenser is further purified by the exhaust gas purification system and then discharged.

[0065] Example 6

[0066] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0067] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0068] (2) Mixing the radioactive incineration ash, the crushed waste plastic particles in step (1) and the dissociation agent calcium oxide in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 10%, and the mass percentage of the dissociation agent calcium oxide in the mixture is 15%.

[0069] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0070] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0071] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0072] Comparative Example 1

[0073] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0074] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0075] (2) Mixing the radioactive incineration ash and the crushed waste plastic particles in step (1) in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 50%.

[0076] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0077] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0078] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0079] Comparative Example 2

[0080] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0081] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0082] (2) Mixing the radioactive incineration ash and the crushed waste plastic particles in step (1) in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 25%.

[0083] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0084] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0085] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0086] Comparative Example 3

[0087] A method for removing radioactive nuclide cesium from radioactive incineration ash comprises the following steps:

[0088] (1) Put the waste plastic into a crusher and crush it into particles less than 2 microns to obtain waste plastic particles.

[0089] (2) Mixing the radioactive incineration ash and the crushed waste plastic particles in step (1) in a mixer to obtain a mixture of the three, wherein the mass percentage of the crushed plastic in the mixture is 10%.

[0090] (3) The mixture of the three obtained in step (2) is sent to a high-temperature rotary kiln for heating and heat treatment. The heating temperature is 1300° C., and air is introduced at the same time. The cesium in the incineration ash reacts with the waste plastic and the dissociation agent. The reaction time is 2 hours. After the reaction, gaseous chloride of cesium, ash and flue gas are obtained, and the ash is discharged from the lower part of the rotary kiln.

[0091] (4) The gaseous cesium formed enters the condensation separator together with the flue gas for cooling and condensation separation, and the radioactive cesium is precipitated from the flue gas and collected.

[0092] (5) The flue gas separated from the condenser is purified by the exhaust gas purification system and then discharged.

[0093] Results Analysis

[0094] Table 1 Chemical composition of cesium-doped ash / %

[0095] <![CDATA[Na2O]]> MgO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[P2O5]]> <![CDATA[SO3]]> <![CDATA[K2O]]> CaO <![CDATA[TiO2]]> <![CDATA[MnO2]]> <![CDATA[Fe2O3]]> Cs 1.22 1.30 21.78 61.33 0.12 0.36 2.30 5.50 0.92 0.08 5.10 0.05

[0096] Figure 2The figure is a relationship diagram between the volatilization rate of cesium and the heat treatment temperature and the amount of PVP added in the present invention. It can be seen from the figure that when PVC is added alone, the volatilization rate of cesium increases with the increase of PVC content and temperature. At 1300°C, when 50% PVC is added, the volatilization rate of cesium reaches 27%. The results show that increasing the amount of PVC added and the heat treatment temperature is conducive to the volatilization of cesium.

[0097] Figure 3 The effect of adding CaO dissociating agent on cesium volatilization of the present invention can be seen from the figure that adding CaO dissociating agent on the basis of PVC can greatly increase the volatilization rate of cesium. For example, at 1300°C, adding 15% CaO dissociating agent on the basis of 25% PVC, the volatilization rate of cesium exceeds 80%, which is much higher than 25% when adding 25% PVC alone. The results show that after adding CaO dissociating agent, the chlorination reaction of cesium can be promoted, thereby increasing the removal rate of cesium.

[0098] Figure 4 This is the SEM-EDS analysis diagram of the gas phase condensate of the present invention. It can be seen from the figure that the main elements in the condensate are chlorine and cesium. The results show that when PVC and the dissociation agent CaO are added, cesium volatilizes in the form of cesium chloride during the heat treatment process, thereby achieving the purpose of purifying radioactive contaminated solid waste.

[0099] In summary, the present invention mixes the crushed plastic with radioactive incineration ash and a dissociating agent, and then performs a high-temperature heat treatment on the mixed material, and the cesium element in the radioactive incineration ash reacts with the chlorine produced by the decomposition of the plastic to generate gaseous chloride of cesium, ash and flue gas, and the gaseous chloride of cesium is separated from the radioactive incineration ash, and condensed and separated together with the flue gas, and the radioactive cesium is precipitated from the flue gas and collected, so as to achieve the purpose of purifying radioactive contaminated solid waste, and after adding the dissociating agent, the dissociation of cesium is increased, and the removal rate of cesium can be greatly improved. The present invention can effectively separate the cesium element in the radioactive solid waste, reduce the radioactive intensity of the solid waste itself, and facilitate the subsequent further treatment and disposal, and the added waste plastic is completely decomposed during the heat treatment process, and the volume of the solid waste after heat treatment will not be increased, and the waste plastic has a wide source and low cost, and the resource utilization of waste plastic can be realized.

[0100] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0101] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for removing radioactive nuclide cesium from radioactive incineration ash, characterized in that: The following steps are involved: Crushing the plastic and mixing it with radioactive incineration ash and a dissociation agent to obtain a mixture of the three; The mixture of the three is subjected to heat treatment while air is introduced, so that the dissociation of cesium is increased by a dissociating agent, and the cesium in the radioactive incineration ash reacts with chlorine produced by decomposition of the plastic to generate gaseous chloride of cesium, ash and smoke; The gaseous chloride of cesium is condensed and separated together with the flue gas, and the radioactive cesium is precipitated from the flue gas and then collected.

2. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The dissociating agent is one or more of calcium oxide, magnesium oxide and iron oxide.

3. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The mass percentage of the plastic in the mixture of the three is 5% to 50%.

4. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The mass percentage of the dissociating agent in the mixture of the three is 5% to 30%.

5. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The heat treatment temperature is 700℃~1300℃.

6. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The heat treatment time is 0.5 hours to 5 hours.

7. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The components of the radioactive incineration ash include silicon-aluminum compounds and cesium element, the mass percentage of the silicon-aluminum compounds is greater than 60%, the mass percentage of the cesium element is 0.001% to 2%, and the total is 100%.

8. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: Crushes plastics to less than 2 microns.

9. The method for removing radioactive nuclide cesium from radioactive incineration ash according to claim 1, characterized in that: The ash is discharged, and the flue gas is discharged after further purification.

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