JP2015021856A - System and method for removing cesium contained in waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce generation of secondary discharge containing radioactive cesium by selectively separating radioactive cesium from waste materials such as incinerator fly ash to concentrate and recover the same and by using reusable separation means.SOLUTION: A system for removing cesium contained in waste materials includes; a wash tank 2 in which a pulverized or crushed waste material 1 is agitated and washed with wash water 3; a filter 4 for separating solid and liquid; an absorber unit 5 which selectively absorbs cesium in the liquid component and applies an elution treatment to the cesium; a storage tank 6 for storing eluent; and a concentration unit which evaporates or separates water from the eluent. A renewable clathrate compound, which exhibits selective absorption characteristics to cesium when alkali-treated to be neutral or alkaline and exhibits selective desorption characteristics to absorbed substances when acid-treated, is used as an absorbent. As for treatment liquid, an alkali treatment liquid is used for pretreatment of the absorbent, and an acid treatment liquid is used for elution treatment.

Description

  The present invention relates to a system and method for removing cesium contained in waste, and more particularly, to a system for removing cesium contained in waste and a removal method using the same.

  Incineration ash such as various fuels, waste, sludge, incineration fly ash, molten fly ash, etc. may contain harmful heavy metals. It is not environmentally preferable, and it is required to perform detoxification even when landfilling. Specifically, in the case of radioactive cesium, if the concentration is 8,000 Bq / kg or less, it can be landfilled at a normal managed landfill site. However, when waste contaminated with radioactive cesium is incinerated, radioactive cesium is concentrated in incineration main ash and incineration fly ash, so the concentration of radioactive cesium in incineration ash, especially incineration fly ash, is 8,000 Bq / kg. Is often exceeded. In many cases, incineration ash lower than 8,000 Bq / kg is difficult to landfill due to social demand. Such detoxification of waste is a great social requirement.

  Most of the radioactive cesium in incineration fly ash exists in a form soluble in water such as cesium chloride. Therefore, it is known that cesium in the incineration fly ash can be taken out by washing the incineration fly ash with water and performing solid-liquid separation to transfer radioactive cesium to the liquid layer (see, for example, Patent Document 1). However, disposal of the extracted liquid layer becomes a problem, and the volume of water required for extraction is particularly large compared to incineration fly ash, so the selective removal method and concentration technology of cesium are problems. Many researches and practical applications have been made.

For example, Patent Document 2 lists the following methods as methods for separating radioactive cesium, but each has individual problems (paragraphs 0005 to 0010).
(I) A method of separating cesium using an inorganic ion exchanger supporting ammonium phosphate molybdate. Inorganic ion exchangers are generated as waste, which has the problem that it is necessary to treat this waste.
(Ii) A method of separating cesium in an aqueous solution containing nitric acid using an insoluble ferrocyanide-based adsorbent. In the separation of cesium, there is a problem that an additive such as a hydrazine derivative needs to coexist as an antioxidant, and there is a problem that the adsorbent is generated as radioactive waste and the waste needs to be treated.
(Iii) A method for separating cesium from an industrial effluent containing other alkali metals using a poly (hydroxyarylene) polymer resin. It is the same technology as ion exchange, and eventually generates radioactive solid waste. When placed in a high radiation field, the polymer resin decomposes and the adsorption efficiency decreases due to the decomposition of the ligand. Defects such as detachment of the resin itself and the resin can be mentioned.
(Iv) A method of selectively extracting cesium by a crown calix [4] allene compound using a solvent extraction method. It is necessary to use ortho-nitrophenyl hexyl ether as an organic solvent that dissolves crown calix [4] allene, and this ortho-nitrophenyl hexyl ether has potential dangers such as nitration by radiolysis. In terms of industrial use, there are difficulties. Crown calix [4] allene is hardly soluble in nonpolar solvents and the like, and solvent selection is a problem.
(V) An adsorption separation method in which cesium is adsorbed and separated using a mixed inorganic ion exchanger of mordenite and hydrous titanic acid, or an inorganic ion exchanger such as zeolite or antimonic acid. After the separation and recovery of cesium, the ion exchanger is generated as waste, and there is a problem that it is necessary to treat the waste. Moreover, since sodium, potassium, etc. coexisting in the eluent are simultaneously adsorbed, the adsorption efficiency is poor and cannot be used repeatedly.
(Vi) A solvent extraction method using an organic solvent in which cobalt dicarbollide (CCD) is dissolved in highly polar nitrobenzene. In the cobalt dicarbollide system, a harmful solvent (diluent) such as nitrobenzene is used, and it is difficult to obtain the extraction reagent because the source of the extraction reagent is limited. (Solid waste) remains.

JP-A-10-213697 JP 2009-133707 A

  Accordingly, an object of the present invention is to selectively separate, concentrate and collect radioactive cesium from waste such as incineration fly ash, and to use secondary means including radioactive cesium by using a reusable separation means. It is an object of the present invention to provide a system and a method for removing cesium contained in waste that can reduce emissions generated in the waste.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by a cesium removal system and a cesium removal method using the cesium removal system described below, and have completed the present invention.

The system for removing cesium contained in the waste according to the present invention,
A washing tank in which powdered or crushed waste and washing water are introduced, stirred and washed,
A filter having a solid recovery part for solid-liquid separation of the waste delivered from the washing tank and recovery of the separated solid component; and a liquid delivery part for delivering the separated liquid component;
An adsorbent filled in the liquid contact part and a cesium in the introduced liquid component are selectively adsorbed by the adsorbent, and the liquid component subjected to the adsorption process is recovered as a processed liquid. An adsorbing section having a processing liquid introducing section into which the processing liquid is introduced, and an eluent dispensing section from which an eluent containing cesium eluted from the adsorbent is dispensed,
A storage tank in which the eluent is introduced and stored;
A concentration unit in which water in the stored eluent is evaporated or separated, and
The adsorbent has a selective adsorption characteristic for cesium in an alkali-treated neutral or alkaline state and a selective desorption characteristic for the adsorbate in an acid-treated state. Using clathrate compounds that can be regenerated by treatment,
As the treatment liquid, an alkali treatment liquid introduced into the wetted part as a pretreatment of the adsorbent and an acid treated liquid introduced into the wetted part as an elution process of cesium from the adsorbent are used. It is characterized by.

Moreover, this invention is the removal method of the cesium contained in the waste using the cesium removal system in any one of Claims 1-4,
A washing process in which powdered or pulverized waste is mixed and stirred with washing water and washed;
A filtration step in which the washed waste is subjected to solid-liquid separation, and the separated solid component and liquid component are collected;
An alkali treatment step for preliminarily treating the adsorbent with an alkali treatment liquid so that the adsorbent composed of an inclusion compound has a selective adsorption characteristic for cesium, and bringing the adsorbent into a neutral or alkaline state;
An adsorbing treatment step in which the separated liquid component is introduced into the alkali-treated adsorbent, cesium in the liquid component is selectively adsorbed, and the adsorbed liquid component is recovered as a treated liquid;
An elution treatment step in which an adsorbent is acid-treated with an acid treatment liquid so as to selectively desorb the adsorbed cesium, and an eluent containing cesium eluted from the adsorbent is delivered;
A storage step in which the eluent is stored;
A concentration step in which the water in the stored eluent is evaporated or separated;
It is characterized by having.

  In the system for removing cesium contained in waste, as described above, the means for selectively removing cesium and the amount of emissions that require secondary detoxification treatment that accompanies the removal treatment are reduced. Is an important issue. As a result of verifying various adsorbents, the present inventor, as a pretreatment, as described later, the inclusion compound such as a crown ether compound is made into a neutral or alkaline state subjected to an alkali treatment, which is very high. It has been found that it can be used as an adsorbent having selective adsorption characteristics for cesium. At the same time, when the adsorbent is in an acid-treated state, it has a very high selective desorption characteristic for cesium, and the adsorption-elution characteristic is changed even if the alkali treatment-acid treatment is repeated several times. Found no. Based on these findings, the present invention selectively separates cesium by a configuration in which an adsorption part filled with an inclusion compound as an adsorbent can be used to perform batch pretreatment-adsorption treatment-elution treatment. Thus, it is possible to provide a cesium removal system and a removal method that reduce secondary emissions including cesium by concentrating and recovering and using reusable separation means. The “inclusion compound” as used herein refers to several compounds that can be included in cesium as described later, such as crown ether compounds and crystalline silicotitanate compounds, and can be neutral or alkali-treated. It is defined as a compound that has a selective adsorption characteristic for cesium in an alkaline state and a selective desorption characteristic for the adsorbate in an acid-treated state and can be regenerated by the alkali treatment and acid treatment. Here, “neutral” does not mean a state of pH 7 in a narrow sense, but means a “neutral region” having a pH of about 7 ± 1. In addition, “washing water” and “treatment liquid” here are not only newly supplied solutions to the system, but also solutions provided in each treatment, which can be reused, and can be reused. And a solution having a function of acid treatment.

The present invention is a system for removing cesium contained in the above-mentioned waste, wherein the recovered treated liquid or a part thereof is filled with a second adsorbent having no or little selectivity to cesium. It is characterized in that it is introduced into a part and subjected to purification treatment.
The present invention is also a method for removing cesium contained in the waste, wherein the recovered treated liquid or a part thereof is subjected to a second adsorption process having no selectivity or low selectivity for cesium. And a purification treatment step.
The waste contains metal elements such as lead and zinc in addition to cesium, and in the treated liquid obtained by the above adsorption treatment, a trace amount of compounds of these metal elements is added in addition to the trace amount of cesium compounds. And water-soluble compounds such as potassium and sodium. The present invention removes these components by secondary adsorption treatment with a secondary adsorbent such as zeolite that does not have adsorption selectivity for cesium, thereby purifying the treated liquid to produce clean water that can be discarded. be able to. Further, as will be described later, by using such clean water as cleaning water in the cesium removal system, it becomes possible to improve the efficiency of the entire system with respect to energy and mass balance.

The present invention is a system for removing cesium contained in the waste, and includes at least a liquid component introduction channel from the liquid supply unit to the adsorption unit, a treated liquid channel from the adsorption unit, and the adsorption unit. An air dosimeter or radioactivity measuring device is installed in any or some of the eluent flow paths from and supplies waste, washing water and treatment liquid according to the air dose and radioactivity in each flow path. And controlling and adjusting the supply amount.
The present invention is also a method for removing cesium contained in the waste, comprising at least a liquid component that has undergone the filtration step, a treated liquid that has undergone the adsorption treatment step, and an eluent that has undergone the elution treatment step. A radioactivity measurement process for measuring one or several air doses and radioactivity, and a control process for controlling / adjusting the supply and supply of waste, cleaning water and treatment liquid based on the measurement results Features.
Cesium, especially radioactive cesium, needs to be adequately managed and monitored not only for the toxicity of its metal, but also for the air dose and radioactivity of the treated material. The present invention is provided from a system by measuring at least one of a liquid component introduced into an adsorbing part, an adsorbed treated liquid, an eluent treated eluent, or some air dose and radioactivity. It was possible to ensure the safety of each substance. At the same time, it is possible to prevent outflow of radioactive material in advance by controlling and adjusting the supply and supply amount of waste, cleaning water and treatment liquid according to the change.

The present invention is a system for removing cesium contained in the waste, wherein a part of the liquid component separated into solid and liquid in the filter is branched and introduced into the washing tank as washing water. A part of the treated liquid recovered from the channel or / and the adsorption part is branched, and the second return flow path introduced into the washing tank as washing water, and / or the eluent delivered from the adsorption part A part of which has a third return flow path which is again introduced into the adsorption part.
As described above, in the cesium removal system, it is effective to use the water-solubility of the cesium compound, and cleaning water and treatment liquid are used. Such a solution constitutes a solution that is very clean or has been freed of interfering components in each treatment. By reusing these treated solutions, the present invention can reduce the amount of cleaning water and treatment liquid to be newly supplied to the system, and can improve the efficiency of the entire system with respect to energy and mass balance. Become. In particular, in handling radioactive substances, a safer processing function can be secured and safe operation of the system can be maintained by making the processing system as closed loop as possible.

1 is an overall configuration diagram illustrating a basic configuration of a cesium removal system according to the present invention. The whole block diagram which shows the 2nd structural example of the removal system of cesium which concerns on this invention. The whole block diagram which shows the 3rd structural example of the removal system of cesium which concerns on this invention. The block diagram which shows the other structural example of the adsorption | suction / elution part in the removal system of cesium which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A system for removing cesium contained in waste according to the present invention (hereinafter referred to as “the present system”) includes a washing tank into which powdered or crushed waste and washing water are introduced, and these are solid-liquid separated. A filter, an adsorption part where cesium is selectively adsorbed and an eluent containing adsorbed cesium is delivered, a storage tank in which the eluate is stored, and water in the eluate is evaporated or separated. And having a selective adsorption characteristic for cesium in an alkali-treated neutral or alkaline state as an adsorbent, and a selective desorption characteristic for the adsorbate in an acid-treated state. In addition, the inclusion compound that can be regenerated by the alkali treatment and the acid treatment is used, and as the treatment liquid, an alkali treatment liquid is used as a pretreatment of the adsorbent and an acid treatment liquid is used as an elution treatment of cesium. And butterflies. With such a configuration, radioactive cesium can be selectively separated from waste, concentrated and recovered, and by using a reusable separation means, secondary emissions including radioactive cesium can be reduced. A possible cesium removal system became possible.

<Configuration example of this system>
As an embodiment of the present system, a basic schematic overall configuration is shown in FIG. 1 (first configuration example). In this system, (radioactive) cesium contained in the waste 1 is delivered together with the waste 1 pulverized or pulverized in the pretreatment unit 10. Next, in the extraction unit 20, most of the cesium compound is dissolved from the waste 1 into the washing water 3 (washing tank 2) and extracted into the liquid component separated into solid and liquid (filter 4). Next, the adsorption / elution unit 50 selectively adsorbs the adsorbent (adsorption unit 5) and elutes from the adsorbent (forms an eluent). Next, it is stored in the storage / concentration unit 60 (storage tank 6), concentrated in the concentration step, and recovered from the present system.

[About waste]
Examples of wastes 1 to be treated include various industrial wastes including building waste, incineration ash such as sludge, incineration fly ash, and various fly wastes that may contain cesium such as molten fly ash Can do. This includes not only waste that has been heat-treated such as combustion treatment, but also waste that has been chemically treated such as chelate treatment or cement solidification treatment to immobilize cesium or the like.

[About the pre-processing section]
In the pretreatment unit 10, when the waste 1 is a powdery material (for example, an average particle size of 200 μm or less) that can be washed with water, such as incineration fly ash and molten fly ash, for example, belt conveyance or the like. Is provided to the extraction unit 20. When extraction efficiency by washing with water is poor, as in the case of chelate-treated fly ash or cement-solidified incineration ash, in the pretreatment means 11. The powder is pulverized or pulverized by a pulverization process, or is treated with an acid or an alkali (including a neutralization process) so that it can be washed with water. Details of processing will be described later.

[About the extraction unit]
The extraction unit 20 includes a cleaning tank 2, a cleaning water supply unit 31, and a filter 4. Powdered or pulverized waste 1 is supplied to the washing tank 2. The washing tank 2 is further supplied with washing water 3 from a washing water supply unit 31 and stirred with the waste 1, and the waste 1 is washed. As a result, most of the cesium compound contained in the waste 1 is dissolved in the washing water. The washing water 3 is preferably city water, clean factory water, well water, or the like. The washing tank 2 is a device having a predetermined capacity having a function capable of stirring the mixture of the waste 1 and the cleaning water 3 for a predetermined time. The stirring function is not limited to the configuration having the stirring means 21 as shown in the figure, for example, rotating. It can be secured by other means such as a configuration (not shown) in which a drum-type cleaning tank 2 or cleaning water 3 is introduced as a jet to form a stirring flow. The inside of the washing tank 2 can be efficiently stirred and washed by performing a surface treatment that prevents the attachment of waste or fine particles and fine particles separated therefrom.

  The mixture of the waste 1 and the washing water 3 that have been stirred and washed is introduced into the filter 4 and separated into solid and liquid. As the filter 4, a filter type, a sedimentation type, a centrifugal type, or the like can be used, but it is preferable to have a multistage filtration function as shown in the figure. As agglomerates are generated by the washing treatment, solids having various particle diameters coexist in the mixture. Therefore, a high solid-liquid separation function can be ensured by sequentially performing the filtration treatment. The solid-liquid separation function is preferably a liquid component containing a solid component having a particle size of 1.0 μm or less, for example. It is possible to prevent a decrease in the adsorption processing capacity due to adhesion to the adsorbent surface provided in the adsorption unit 5. As will be described later, the cleaning water 3 is supplied from the downstream side (liquid component supply side) of the filter 4, and the liquid component supplied from the filter 4 or a part thereof is introduced into the cleaning tank 2. In particular, it is possible to reduce the presence of solid components in the downstream stage and to have a high solid-liquid separation function. The separated solid component is collected and collected in the solid collection unit 41, and the separated liquid component is stored in the liquid supply unit 42. The stored liquid component is fed to the adsorption / elution unit 50 by the feed pump 43.

[Adsorption / elution section]
The adsorption / elution unit 50 includes an adsorption unit 5 and a processing liquid introduction unit (consisting of an alkali introduction unit 51, an acid introduction unit 52, and a treatment liquid feed pump 53). The liquid component in which the cesium compound is dissolved is supplied to the adsorption unit 5. The wetted part inside the adsorbing part 5 is filled with an adsorbent (not shown), and cesium in the introduced liquid component is selectively adsorbed by the adsorbent. As shown in the drawing, the adsorption unit 5 is preferably composed of a plurality of adsorption layers. In the first configuration example, the adsorbing portion 5 in which the four adsorbing layers 5a to 5d are arranged in series is illustrated, but the present invention is not limited to this, and an arrangement or parallel arrangement of an arbitrary number of adsorbing layers 5n. It is possible to apply the structure etc. which were arrange | positioned in. Further, batch processing is performed by switching between adsorption processing and elution processing for all the adsorption layers 5a to 5d, or, for example, adsorption processing is performed on the adsorption layers 5a and 5b on the upstream side of the process, and the other adsorption layers 5c and 5d are performed. It is possible to apply a configuration that meets the required specifications, such as continuous processing in which elution processing is performed simultaneously and switching is performed after a predetermined time.

The adsorbent preferably has a selective adsorption property for cesium, a selective desorption property for an adsorbate, and is reproducible. This system uses an inclusion compound as an adsorbent that satisfies these conditions. Specifically, for example, the trade name SuperLig (registered trademark: manufactured by IBC, USA), “Calix [4] arene-bis (4-tert-octylbenzo-crown-6)” or “1- (2,2,3, Mention may be made of crown ether compounds such as “3-tetrafloropropoxy) -3- (4-sec-butylphenoxy) -2-proppanol” and crystalline silicotitanate compounds such as Na ₂ Ti ₂ O ₃ (Si ₂ O ₄ ). Can do. These have a selective adsorption characteristic for cesium in a neutral or alkaline state after alkali treatment, and have a selective desorption characteristic for the adsorbate in an acid treatment state. Has reproducible characteristics. In the demonstration process, it has been confirmed that the adsorption treatment of about 500 times or more can be performed on cesium from incineration fly ash. The kind, filling amount, or filling method of the adsorbent is selected and set according to the waste conditions to be treated or the shape of the adsorbent.

At this time, the adsorbent is preferably preliminarily treated with alkali before being used for the adsorption treatment. In the adsorption treatment, high selective adsorption characteristics under neutral or alkaline conditions can be ensured. The alkali used for the alkali treatment is introduced into the adsorption unit 5 by the treatment liquid feed pump 53 via the alkali introduction unit 51. The alkali treatment liquid is preferably used a plurality of times in a circulating manner, and can be finally used for neutralization treatment of the liquid supplied from the system. In addition, when using the regenerated adsorbent, it can be treated with alkali to make it neutral or alkaline, so that residual acid components used in the elution process can be removed, preventing a decrease in adsorption capacity. Elution during the adsorption process can be prevented. The alkali used is preferably a substance having high solubility in water and having an affinity for the adsorbent, and in particular, lithium that can easily replace the element included by the inclusion compound serving as the adsorbent with cesium. Aqueous solutions of alkali metal hydroxides such as potassium or sodium, carbonates or bicarbonates are preferred. Specific examples include 0.01 to 1.0 M NaOH (KOH and the like), 0.01 to 1.0 M NaHCO ₃ (KHCO _{3 and the} like), and the like. Moreover, alkali treatment and "neutral or alkaline state" are preferably pH 6 to 13, more preferably pH 8 to 12. When the pH is less than 6, the adsorption capacity is greatly reduced, and the optimum conditions for the adsorption capacity can be obtained at pH 8-12. On the other hand, when the pH exceeds 13, the deterioration of the adsorbent may proceed.

  The adsorption process is performed by introducing a liquid component into the adsorption unit 5 (adsorption layers 5a to 5d) that has been subjected to alkali treatment in advance. A high concentration of cesium is adsorbed on the surface of the adsorbent of the adsorption layer 5a on the upstream side, and the concentration decreases in accordance with the adsorption layers 5b, 5c,..., And about 99.9% or more of cesium is removed in the adsorption layer 5d. It was proved. The liquid component from which cesium has been removed is stored in the processed liquid supply unit 54 as a processed liquid, and is subjected to detoxification again (as a purified processing liquid) as it is or as described later.

The cesium adsorbed by the adsorbent is eluted into the acid treatment liquid by introducing the acid treatment liquid into the adsorption layers 5a to 5d. By performing the elution treatment using the acid treatment liquid, it is possible to ensure high selective elution characteristics under acidic conditions. Specifically, the acid treatment liquid is introduced into the adsorption unit 5 (any or more of the adsorption layers 5a to 5d) by the treatment liquid supply pump 53 through the acid introduction unit 52. It is preferable to use the acid treatment solution a plurality of times in a cyclic manner as will be described later. The eluent containing the eluted cesium is introduced into the storage tank 6 by the eluent feed pump 56 via the eluent delivery part 55. The acid used is preferably a substance having a high solubility in water and a high reactivity with cesium and having an affinity for the adsorbent. Strong acid with high elution function is preferable. Specifically, for example _{0.1~2.0M-HCl, 0.01~1.0M-HNO 3} , and the like _0.01~1.0M-H 2 SO _4.

[Storage / concentration section]
The storage / concentration unit 60 has an eluent storage function and a cesium concentration function (water removal and drying function). In the first configuration example, the storage tank 6 has a configuration in which the heating unit 62 is disposed on the outer periphery and the storage unit 61 is provided inside. By storing a predetermined amount of eluent and performing heating and moisture evaporation for a predetermined time, cesium can be concentrated and recovered. However, as long as cesium can be prevented from evaporating and has these functions, the structure is not limited to this. For example, a cesium concentration process can be performed by providing a water permeable membrane in the storage tank 6 (not shown) and subjecting the water in the eluent to a membrane separation process.

<Method of removing cesium using this system>
Next, a method for removing cesium using the present system (hereinafter referred to as “the present method”) will be described in detail. This method is based on its role
(1) Including pretreatment process
(2) A washing process in which powdered or crushed waste is mixed and stirred with washing water and washed,
(3) a filtration step in which the washed waste is separated into solid and liquid, and the separated solid component and liquid component are collected;
(4) an alkali treatment step in which the adsorbent comprising an inclusion compound has a selective adsorption characteristic for cesium and is alkali-treated with an alkali treatment liquid in advance to make it neutral or alkaline;
(5) an adsorption treatment step in which the separated liquid component is introduced into the alkali-treated adsorbent, cesium in the liquid component is selectively adsorbed, and the adsorbed liquid component is recovered as a treated liquid; ,
(6) An elution process step in which an adsorbent is acid-treated with an acid treatment liquid so as to be selectively desorbed from the adsorbed cesium, and an eluent containing cesium eluted from the adsorbent is delivered. When,
(7) a storage step in which the eluent is stored;
(8) a concentration step in which water in the stored eluent is evaporated or separated;
Have Hereinafter, based on the structural example 1, each process is explained in full detail.

(1) Pretreatment step As described above, when the waste 1 is in a state that can be washed with water, such as incineration fly ash or molten fly ash, it is supplied to the extraction unit 20 as it is. When the waste is chelate-treated fly ash, cement-solidified incineration ash, or the like, it is pulverized using a pulverizer as the pretreatment means 11 and has a predetermined particle size or less (for example, an average particle size of 200 μm or less). ) Is preferably delivered to the extraction unit 20 as a powder. Since such waste is a solid having a particle size of several centimeters to several tens of centimeters, the extraction efficiency by washing with water is poor, the surface area is increased by crushing, and the extraction function is increased by water penetration to the pores. Therefore, high extraction efficiency can be ensured. For sludge incineration ash, soil and the like that are difficult to extract by washing as they are, it is preferable to perform acid treatment (for example, with hydrochloric acid, nitric acid, etc.) in the pretreatment means 11. Further, when a sludge shape having a large particle size variation and difficult to extract by water washing is formed like the main ash, it is preferable to perform acid treatment together with pulverization treatment in the pretreatment means 11. Further, when the waste 1 contains a large amount of leachate and the acidity is high, or when the acid treatment is performed as described above, the pretreatment means 11 performs neutralization treatment (for example, sodium hydroxide or potassium hydroxide). Etc.).

(2) Washing process The waste that is ready to be washed is supplied to the washing tank 2 in the extraction unit 20 and mixed and stirred with the washing water 3 to be washed. The washing treatment of the waste 1 necessary for dissolving the cesium compound is preferably performed with the washing water 3 several times to several tens of times the amount of the waste 1. By sufficiently stirring for a predetermined time required for dissolving the cesium compound, most of the cesium compound contained in the waste 1 is dissolved in the washing water. The mixture of the waste 1 and the washing water 3 sufficiently stirred and washed is introduced into the filter 4 in a solid-liquid mixed state.

(3) Filtration step The mixture containing the washed waste is subjected to solid-liquid separation in the filter 4. In this method, for example, it is preferable to separate into a liquid component containing a solid component having a particle size of 1.0 μm or less. In addition, when the filter 4 having a multistage filtration function is used, a solid component having a large particle diameter is filtered upstream, and a solid component having a small particle diameter is sequentially filtered in the downstream, so that it is efficiently effective for a long period of time. Solid-liquid separation can be performed. The separated solid component is collected and recovered in the solid recovery unit 41, and after safety is confirmed, it is disposed of in landfills. The separated liquid component is stored in the liquid delivery unit 42 and then fed to the adsorption / elution unit 50 by the feed pump 43. At this time, the liquid component to be fed is preferably neutralized. A neutral or alkaline state, which is one of the optimum conditions for the adsorption treatment, can be maintained and a stable adsorption treatment can be ensured.

(4) Alkali treatment step The adsorbent is preliminarily treated with an alkali treatment solution so that the adsorbent used in the adsorption treatment has selective adsorption characteristics for cesium, and is brought into a neutral or alkaline state. Specifically, (5) before the adsorption treatment step or (6) after the elution treatment step, an alkali treatment liquid such as sodium hydroxide is supplied to the adsorption portion 5 by the treatment liquid feed pump 53 via the alkali introduction portion 51. be introduced. When the surface of the adsorbent is in a neutral or alkaline state that has been subjected to alkali treatment, the adsorption / inclusion of cesium by the liquid contact between the cesium-containing solution and the adsorbent is promoted. Since the treatment liquid used for the alkali treatment is still alkaline, it can be used as a neutralizing agent in the above (1) pretreatment step or (7) storage step in this system, and is newly added to this system. The processing liquid to be supplied can be reduced.

(5) Adsorption treatment step The liquid component separated in the above (3) filtration step is introduced into the alkali-treated adsorbent, and cesium in the liquid component is selectively adsorbed. Specifically, the liquid component stored in the liquid supply unit 42 is introduced into the adsorption unit 5 by the feed pump 43, and cesium in the liquid is adsorbed by the adsorbent. In this method, it was demonstrated that about 99.9% or more of cesium is removed in the adsorption layer 5d. The liquid component from which cesium has been removed is stored in the processed liquid supply unit 54 as a processed liquid and is recovered as a processed liquid. Adsorption processing is not limited to continuous processing performed by continuously circulating liquid components to the adsorbing unit 5, but also applies batch processing that repeats supply and stop, or cyclic processing that repeatedly supplies the same liquid component to the adsorbing unit 5. can do.

(6) Elution processing step The cesium subjected to the adsorption treatment in the adsorption unit 5 is eluted from the adsorbent by the acid treatment liquid and taken out as an eluent. Specifically, after the adsorption treatment, introduction of a new liquid component or alkali treatment liquid into the adsorption section 5 is stopped, and an acid treatment liquid such as hydrochloric acid is fed by the treatment liquid feed pump 53 via the acid introduction section 52. It is introduced into the adsorption unit 5. The adsorbent is acid-treated with the acid treatment liquid, and cesium is eluted from the adsorbent. The eluted cesium is recovered as an eluent by the eluent feed pump 56 via the eluent delivery unit 55.

(7) Storage Step The eluent recovered by the above (6) elution processing step is temporarily stored in the storage tank 6. At this time, it is preferable to perform a neutralization treatment as necessary. Further, in the adsorption section 5 having a plurality of adsorption layers (for example, 5a to 5d), the concentration of cesium eluted in the upstream adsorption layer 5a is high, and the concentration in the downstream adsorption layers 5b, 5c, and 5d is low. Therefore, by collecting the eluents from the adsorbing layers 5a to 5d separately and homogenizing them in the storage tank 6, a uniform concentration process in the (8) concentration step described later can be ensured.

(8) Concentration step Water in the eluent stored in the storage tank 6 is evaporated or separated to produce an eluent enriched with cesium. The concentration treatment of cesium can be performed by heating the eluent and evaporating water. Moreover, the concentration process of cesium can be performed by performing the film | membrane separation process of the water | moisture content using a water-permeable film.

  By each of these processing steps, the solid component from which cesium has been removed, the liquid component (treated solution), and the eluent in which cesium is concentrated can be efficiently recovered, and further secondary processing is required by this processing. Generation | occurrence | production of a to-be-processed object can be reduced as much as possible.

<Other configuration examples of this system>
FIG. 2 shows another configuration example (second configuration example) of the present system. The basic configuration is the same as that of the first configuration example, but as an additional function, the recovered treated liquid or a part thereof is filled with a second adsorbent that has no or little selectivity to cesium. It introduce | transduces into the adsorption | suction part 7, and is characterized by performing a refinement | purification process. Further, at least one of or any number of the flow path L1 for introducing the liquid component from the liquid supply section 42 to the adsorption section 5, the treated liquid flow path L2 from the adsorption section 5, and the eluent flow path L3 from the adsorption section 5. A crab space dosimeter or radioactivity measuring device S1 (~ S3) is arranged, and the supply and supply amount of waste, cleaning water and treatment liquid are determined according to the air dose or radioactivity of each flow path L1 to L3. It is characterized by controlling and adjusting. At this time, as the second configuration example, the configuration in which the second adsorption unit 7 and the space dosimeter or the radioactivity measuring device S1 (to S3) are disposed is illustrated, but includes a configuration in which only one of them is provided. Needless to say.

  The second adsorbing portion 7 is preferably filled with zeolite, activated alumina, or the like that has no or low adsorption selectivity to cesium as the second adsorbent. By removing secondary metal elements such as lead and zinc contained in the waste, trace amounts of these metal elements contained in the treated liquid, compounds such as water-soluble potassium and sodium, etc. by secondary adsorption treatment Then, the treated liquid can be purified (purification process step) to produce clean water that can be discarded.

  Further, at least one of the liquid component introduced into the adsorption unit (flow path L1), the treated liquid after the adsorption process (flow path L2), the eluted eluent (flow path L3), or some space doses. By measuring the radioactivity and radioactivity, not only the harmfulness of each recovered cesium, especially radioactive cesium, but also sufficient management and monitoring of the air dose and radioactivity of the processed substances (radioactivity measurement process) It has become possible to ensure the safety of each substance delivered from this system. At the same time, by controlling and adjusting the supply and supply amount of waste, cleaning water and treatment liquid according to the change (control process), it is possible to prevent the radioactive material from flowing out. Examples of the measuring instrument used in the radioactivity measurement step include an air dosimeter for measuring the radiation dose (μSv / hr) and a radioactivity measuring instrument for measuring the radioactivity (Bq / kg). It is not limited. For example, by using a sodium iodide scintillation detector (NaI scintillator) and a configuration in which a pipe through which a liquid to be measured flows is wound around it, measurement can be performed continuously in a short time.

  FIG. 3 shows another configuration example (third configuration example) of the present system. A part of the liquid component separated into solid and liquid in the filter 4 is branched, and is introduced into the washing tank 2 as washing water through the return pump 32, and / or the adsorption unit. A part of the treated liquid recovered from 5 is branched and supplied from the second return flow path (flow path R2) introduced into the cleaning tank 2 as cleaning water via the return pump 32, and / or from the adsorption unit 5. A part of the eluent that has been provided has a third return flow path (flow path R3) that is re-introduced into the adsorption section 5 by the eluent supply pump 56 via the eluent supply section 55. . In this system, the washing water and the treatment liquid introduced for each treatment are supplied as a very clean solution or a solution from which interference components in each treatment are removed by each treatment. By reusing such treated solutions as washing water and treatment liquid for each treatment, it is possible to reduce the amount of washing water and treatment liquid to be newly supplied. Therefore, this system can improve the efficiency of the entire system in terms of energy and material balance. In particular, in handling radioactive substances, a safer processing function can be secured and safe operation of the system can be maintained by making the processing system as closed loop as possible. At this time, the configuration based on the first configuration example is illustrated as the third configuration example, but such a configuration can also be applied to the second configuration example.

  Specifically, the liquid component separated into solid and liquid in the filter 4 is removed from the mixture containing the waste 1 and the washing water 3 to dissolve the cesium compound and the like. It is a solution close to clean water from which solid components (aggregates and the like) generated by the water washing treatment of the solid components and the waste 1 are removed. Therefore, it can be used as a solution having a cleaning function (cleaning water) as long as the function of dissolving cesium compounds and the like remains sufficiently. Further, if the composition of the new waste 1 is substantially constant, the liquid components separated in the solid-liquid separation in the filter 4 are always substantially the same if the washing water 3 necessary for the washing treatment is newly added. It becomes a solution of the composition. Therefore, if such conditions are ensured, the liquid component introduced into the cleaning tank 2 via the first return channel (channel R1) has a sufficient function of dissolving the cesium compound and the like, and has a cleaning function. It can be used as a solution (washing water).

  At this time, instead of supplying new washing water 3 from the washing water supply unit 31 provided on the upstream side of the filter 4, as illustrated in FIG. 4, the downstream side (liquid component supply) The whole or a part of the liquid component supplied from the washing water supply unit 33 provided on the side) and supplied from the filter 4 is introduced into the washing tank 2 as washing water by the feedback pump 32 via the flow path R1. The configuration is preferred. It is possible to reduce the presence of solid components in the downstream stage of the filter 4 and to have a high solid-liquid separation function.

  In addition, the treated liquid recovered from the adsorption unit 5 is a solution obtained by further adsorbing and purifying the liquid component that is a solution close to clean water as described above. Accordingly, since the waste 1 has a higher water washing function, it can be used as washing water. The treated liquid is almost neutral or weakly alkaline because the liquid component is almost neutral and the solution is adsorbed with an adsorbent in a neutral or alkaline state that has been previously alkali-treated. . Therefore, the treated liquid can be introduced as it is into the washing tank 2 as washing water through the second return flow path (flow path R2), and the washing water to be newly supplied to this system can be reduced. it can.

  Furthermore, the eluent delivered from the adsorption unit 5 is an acidic solution containing a cesium compound based on an acid treatment liquid. Therefore, it can be used as a solution having an acid treatment function (acid treatment liquid) as long as the function of eluting the cesium compound and the like encapsulated in the adsorbent remains. The eluent can be introduced again into the adsorption unit 5 as an acid treatment liquid as it is through the third return flow path (flow path R3), and the treatment liquid to be newly supplied to the system can be reduced. .

<Verification of this system>
The function of removing cesium in this system was verified with regard to the cesium content after each treatment and the radioactivity of the collected substances under the following conditions.

[Verification conditions]
(I) A total of 1987 Bq / kg of cesium 134 and cesium 137 and incinerated fly ash having an average particle size of 50 μm were used, and washing treatment was performed with washing water (city water) of 5 times (weight ratio).
(Ii) Using a filter type filter, filtration was performed to separate the liquid component and the solid component.
(Iii) The product name SuperLig (registered trademark: manufactured by IBC, USA) is used as the adsorbent, and after alkali treatment with 0.1M NaOH in a state where the container is filled in a predetermined volume, the liquid of (ii) above The components were adsorbed.
(Iv) The adsorbent after the above (iii) treatment was subjected to an acid treatment with 1.0 M HCl to obtain an eluent.
(V) Regarding the adsorbent, the above (i) to (iv) including the regeneration treatment with alkali were repeated, and the decrease in the adsorbent adsorption capacity was verified.

〔inspection result〕
The verification results as shown in Table 1 were obtained. It was demonstrated that this system can efficiently recover cesium. In addition, it has been demonstrated that the same adsorbent can be adsorbed with substantially the same efficiency up to 500 times by regeneration.

DESCRIPTION OF SYMBOLS 1 Waste 10 Pretreatment part 11 Pretreatment means 2 Washing tank 20 Extraction part 21 Agitation means 3 Washing water 31 Washing water supply part 4 Filter 41 Solid recovery part 42 Liquid delivery part 43 Feeding pump 5 Adsorption parts 5a-5d Adsorption Layer 50 Adsorption / elution part 51 Alkali introduction part 52 Acid introduction part 53 Process liquid feed pump 54 Processed liquid feed part 55 Eluate feed part 56 Eluate feed pump 6 Storage tank 60 Storage / concentration part

Claims (7)

A washing tank in which powdered or crushed waste and washing water are introduced, stirred and washed,
A filter having a solid recovery part for solid-liquid separation of the waste delivered from the washing tank and recovery of the separated solid component; and a liquid delivery part for delivering the separated liquid component;
An adsorbent filled in the liquid contact part and a cesium in the introduced liquid component are selectively adsorbed by the adsorbent, and the liquid component subjected to the adsorption process is recovered as a processed liquid. An adsorbing section having a processing liquid introducing section into which the processing liquid is introduced, and an eluent dispensing section from which an eluent containing cesium eluted from the adsorbent is dispensed,
A storage tank in which the eluent is introduced and stored;
A concentrating part in which water in the stored eluent is evaporated or separated;
With
The adsorbent has a selective adsorption characteristic for cesium in an alkali-treated neutral or alkaline state and a selective desorption characteristic for the adsorbate in an acid-treated state. Using clathrate compounds that can be regenerated by treatment,
As the treatment liquid, an alkali treatment liquid introduced into the wetted part as a pretreatment of the adsorbent and an acid treated liquid introduced into the wetted part as an elution process of cesium from the adsorbent are used. A system for removing cesium contained in waste, characterized by   2. The purification treatment is performed by introducing the collected treated liquid or a part thereof into a second adsorbing portion filled with a second adsorbent having low or low selectivity to cesium. Removal system for cesium contained in wastes   At least one of or some of the flow path for introducing the liquid component from the liquid delivery section to the adsorption section, the treated liquid flow path from the adsorption section, and the eluent flow path from the adsorption section may be an air dosimeter or 3. A radioactivity measuring device is provided, and the supply and supply amount of waste, cleaning water and treatment liquid are controlled and adjusted according to the air dose and radioactivity of each flow path. System for removing cesium contained in the listed waste.   A part of the liquid component separated from the solid and liquid in the filter is branched and introduced into the washing tank as washing water, and / or a part of the treated liquid recovered from the adsorption unit. Is branched and the third return flow path in which a part of the eluent supplied from the adsorption section is introduced again into the adsorption section is introduced into the washing tank as washing water. The system for removing cesium contained in the waste according to any one of claims 1 to 3, wherein: A method for removing cesium contained in waste using the cesium removal system according to any one of claims 1 to 4,
A washing process in which powdered or pulverized waste is mixed and stirred with washing water and washed;
A filtration step in which the washed waste is subjected to solid-liquid separation, and the separated solid component and liquid component are collected;
An alkali treatment step for preliminarily treating the adsorbent with an alkali treatment liquid so that the adsorbent composed of an inclusion compound has a selective adsorption characteristic for cesium, and bringing the adsorbent into a neutral or alkaline state;
An adsorbing treatment step in which the separated liquid component is introduced into the alkali-treated adsorbent, cesium in the liquid component is selectively adsorbed, and the adsorbed liquid component is recovered as a treated liquid;
An elution treatment step in which an adsorbent is acid-treated with an acid treatment liquid so as to selectively desorb the adsorbed cesium, and an eluent containing cesium eluted from the adsorbent is delivered;
A storage step in which the eluent is stored;
A concentration step in which the water in the stored eluent is evaporated or separated;
A method for removing cesium contained in waste, comprising:   6. The waste according to claim 5, wherein the recovered treated liquid or a part of the collected liquid has a second adsorption treatment step having no selectivity or low selectivity for cesium. A method for removing contained cesium.   At least a radioactivity measurement step for measuring any one or some of the air dose and radioactivity of the liquid component that has undergone the filtration step, the treated liquid that has undergone the adsorption treatment step, and the eluent that has undergone the elution treatment step; 7. The method for removing cesium contained in waste according to claim 5, further comprising a control step of controlling and adjusting the supply and supply amount of waste, cleaning water and treatment liquid based on the measurement result.

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