JPH0679075B2 - Treatment method and equipment for radioactive liquid waste containing surfactant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a treatment method suitable for treating a radioactive waste liquid containing a surfactant, in particular, for pulverizing and granulating a radioactive waste liquid containing a detergent having a remarkable foaming property. And processing equipment.

[Conventional technology]

In nuclear power plants and the like, radioactive liquid waste mixed with detergent is generated by washing work clothes. Conventionally, this waste liquid is concentrated / reduced to about 1/500 and then stored by cement hardening or the like. In order to further reduce the storage amount, it is rational to remove entrained water, reuse it, and discard only the surfactant. An evaporative drying process is used to separate and remove water. However, since the surfactant is a highly viscous substance, it is very difficult to powderize and granulate it by evaporative drying.The surfactant has a foaming property and does not foam when powdered by evaporative drying. However, since the impurities migrate to the steam side, there is a problem that the separated water becomes dirty. In other words, the decontamination factor DF (the total amount of impurities received / the amount of impurities on the steam side), which is the ratio at which impurities are less likely to migrate to the steam side.
Becomes smaller.

Therefore, in Japanese Examined Patent Publication No. 60-38680, in order to suppress the above properties of the surfactant when treating the laundry waste liquid alone, an adsorbent such as activated carbon is added to the waste liquid to physically adsorb the surfactant. , It has been discussed to enable pulverization.

[Problems to be solved by the invention]

The above-mentioned conventional technology has solved the problem of foaming of the surfactant during drying by adsorbing the surfactant by adding an adsorbent such as activated carbon, but the pellets (granulated product) produced have a specific gravity Is small and the volume reduction is not sufficient. In addition, since a large amount of activated carbon or zeolite is used as an adsorbent for physically adsorbing a surfactant, there is a problem that the amount of waste increases, and further, these adsorbents have a low specific gravity and granulation property. Since it is a substance having a poor solidity, even if it is granulated, it has a small specific gravity, and as a result, there is a problem that the volume reducing property is further lowered.

An object of the present invention is to provide a treatment method and a treatment facility which are excellent in volume reduction property and granulation property while defoaming a surfactant-containing waste liquid without using an adsorbent to improve DF during drying. is there.

[Means for solving problems]

In the present invention, foaming by a surfactant is suppressed by adding an antifoaming agent, and a surfactant-containing waste liquid (laundry waste liquid, etc.) and another solid content-containing waste liquid (boric acid waste liquid or sodium sulfate waste liquid, etc.) are mixed. By doing so, the influence of the surfactant is minimized and the powder is pulverized, and a powder suitable for granulation is produced. In this case, the mixing amount of the surfactant and the defoaming agent should be adjusted to be not less than the amount necessary for exhibiting the defoaming effect and not more than 8 wt% of the total solid content of the mixed waste liquid. (The solid content is a component that remains as a solid after evaporation of water.) [Function] Since the surfactant has a hydrophilic group and a hydrophobic group, it is adsorbed and oriented at the gas-liquid interface to form a monomolecular film. Form to reduce surface tension. That is, since the surfactant solution has a low surface tension, it easily foams. When an antifoaming agent is added to the foam to prevent foaming, the antifoaming agent adheres to the foam film and remarkably lowers the surface tension of that part.However, since the solubility is low, this decrease in surface tension is localized. As a result, the surface is pulled by a portion having a large surface tension and the bubbles are broken. With the above action, bubbles do not move to the steam side and DF is improved.

However, since the surfactant and the defoaming agent are both highly viscous substances, if they are too much, they adhere to the powder during dry powdering, making powderization and granulation difficult. Is a mixture treatment with a waste liquid containing other solid content such as boric acid or sodium sulfate, and the addition amount of the defoaming agent is set within the above range to minimize the proportion of the highly viscous substance to the required minimum. This is a processing method that enables powderization and granulation and is extremely excellent in volume reduction.

〔Example〕

A radioactive waste liquid containing detergent is mixed with a waste liquid containing boric acid as a main component generated from a PWR power plant, and one or more of the following four kinds of antifoaming agents are mixed with the centrifugal thin film dryer. When treated, the decontamination factor DF of the dryer was similar to that of the boric acid waste solution containing no detergent, without foaming during drying. When the produced powder was granulated with a granulator, pellets having good pellet physical properties could be prepared.

That is, among the mixed waste liquid of the laundry waste liquid and the boric acid waste liquid, among the silicone-based emulsion type defoaming agent, the silicone-modified oil-type defoaming agent, the silicone-type powder-type defoaming agent, or the silicone-type oil-type defoaming agent, 1 type is mixed at least in the minimum amount that produces a defoaming effect (there is a slight difference depending on the type of defoaming agent), supplied to a centrifugal thin film dryer with a heat transfer area of 1.2 mm ^{2 at} a flow rate of 50 Kg / hr, and evaporated. It was dried. The results of granulating the above powder with a tableting machine (tablet type granulator) are shown in FIG. FIG. 2 shows the relationship between the concentration of the detergent and the defoaming agent in the total solid content contained in the waste liquid and the pellet strength (relative value). As is clear from FIG. 2, regardless of the type of the defoaming agent, the more the highly viscous substances such as the detergent and the defoaming agent are contained, the poorer the granulation property is, and the pellet strength tends to decrease. If it is contained in a large amount and the concentration exceeds a little less than 9% by weight, it will be buckled during granulation and molding will be impossible. From this experimental result, it was found that granulation is possible if the concentration of the detergent and the defoaming agent in the total solid content of the mixed waste liquid is 8% by weight or less.

The above experimental results were the same when any of the above four kinds of antifoaming agents was used, or when two or more kinds thereof were used.

Specific examples will be shown below.

<Example 1> As shown in Fig. 1, a washing waste liquid 1 containing a surfactant and a boric acid waste liquid 2 were mixed in a supply tank 5 to obtain a solid content.
Waste liquid of 10% by weight was used. From the tank 4, the silicone emulsion defoamer 3 was mixed into the supply tank 5 by the amount measured in advance for defoaming. In the case of this example, the same amount of the antifoaming agent as the amount of the surfactant was mixed. 8% by weight of the solid content of the waste liquid thus prepared was made to be a highly viscous substance such as a surfactant and an antifoaming agent. Next, supply the above waste liquid to the centrifugal thin film dryer 5 having a heat transfer area of 1.2 m ² and
It was dried and powdered at g / hr. The mist separator 11 removed the solid content of the vapor, liquefied it in the condenser 12, and returned it to the concentrator. The produced powder was filled in the powder hopper 6, mixed with the binder from the binder hopper 7 in the granulator 8, and then molded into a cylindrical (28φ × 28t) pellet. The molded pellets were weighed by the hopper 9 and filled in the drum can 10.

The decontamination coefficient DF of the dryer 5 was measured by sampling the waste liquid from the point A and the mist from the point B in FIG. 1, and the decontamination coefficient was twice as compared with the case where the defoaming agent was not added. .

Further, the produced pellet was a pellet having sufficient specific gravity and strength without buckling during granulation.

Further, since the foaming was completely suppressed, it was possible to prevent the fact that the foaming caused the surfactant to be mixed with the steam into the mist separator and the condenser side, and to move to the condenser after the condensate to have an adverse effect.

<Example 2> As shown in FIG. 3, a waste liquid 1 containing a surfactant and a liquid waste 2 with boric acid were mixed in a supply tank 5 so that the solid content was 10%.
It was used as a waste liquid of weight%. Next, for defoaming, a silicone emulsion type defoaming agent 3 is mixed from the tank 4 to the supply tank 5, and 8% by weight of the solid content of the waste liquid thus prepared is a highly viscous substance. To be.

The solid particles (fluid medium) such as sand supplied from the sand hopper 14 onto the hearth by the compressor 15 are suspended in the calcining furnace gas blower 17 by the air heated by the heater 16 to the calcining furnace 13 having the fluidized bed described above. The waste liquid was supplied by spraying. The sprayed droplets were dried and calcined in contact with the fluidized medium, and the calcined product was deposited and formed in layers on the surface of the fluidized medium, whereby the fluidized medium grew and small pieces were produced due to mutual collision and the like. Of these, minute ones are entrained in the air flow and discharged from the top of the calcining furnace to the outside of the furnace. The solid content is collected by the cyclone separator 18 and collected in the powder hopper 6 and granulated by the granulator 8 into pellets. After being filled in the pellet hopper 9, the drum can 10 was filled. On the other hand, the steam has its solid content separated by a scrubber 19,
It was liquefied in the condenser 21, and transferred to the condensed water tank 22 and the concentrated liquid tank 20. A part of the powder was taken out from the bottom of the calciner 13 together with the sand in the fluidized bed, separated from the sand, and collected.

According to this example, bubbles are not entrained in the gas phase,
The powder that was pulverized and formed did not buckle during granulation, and it was possible to mold pellets with sufficient specific gravity and strength as in the conventional case.

In Examples 1 and 2, cylindrical pellets were prepared with a tablet granulator, but similar effects can be obtained by granulating with an almond mold with a briquette granulator. Further, in Examples 1 and 2, the boric acid waste liquid and the laundry waste liquid, which are the main components of the concentrated waste liquid generated from the PWR power generation plant, were mixed and treated, but other waste liquids (sodium sulfate waste liquid and waste resin from the BWR power generation plant were treated. The same effect can be obtained by mixing with a waste liquid containing).

In each of the above-mentioned examples, the silicone-based ecmulsion-type defoaming agent was used, but a silicone-based modified oil-type defoaming agent, a silicone-based powder-type defoaming agent, a silicone-based oil-type defoaming agent, or a mixture thereof was used. Even if the same effect is obtained. However, the required amount of the defoaming agent until the defoaming effect is expressed with respect to the content of the surfactant varies depending on the type, so it is necessary to examine it in the basic test.

〔The invention's effect〕

According to the present invention, by mixing the antifoaming agent with the surfactant-containing radioactive waste liquid, it is possible to suppress foaming at the time of dry powderization, so that the decontamination coefficient of the dryer can be improved. Also, by mixing a highly viscous substance containing a surfactant and antifoaming agent with a waste liquid containing boric acid or sodium sulfate as a main component at a predetermined ratio, the influence of the highly viscous substance is suppressed and radioactive waste liquid is suppressed. Can be dried by heating to granulate pellets having an excellent volume reducing property.

[Brief description of drawings]

FIG. 1 is a process flow diagram of processing equipment according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the concentration of the detergent and the defoaming agent in the total solid content of the mixed waste liquid and the pellet strength. FIG. 3 is a process flow diagram of processing equipment according to another embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Tamada 3-1-1, Saiwaicho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor, Mr. Tsuyoshi Suzuki 3-chome, Hitachi City, Ibaraki Prefecture No. 1 in Hitachi New Clear Engineering Co., Ltd. (72) Inventor Yasuo Hattori 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi New Clear Engineering Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 51-151284 ( JP, A) JP 52-101400 (JP, A) JP 60-38680 (JP, B2)

Claims (5)

[Claims] 1. A radioactive waste liquid containing a surfactant is mixed with a waste liquid containing boric acid or sodium sulfate as a main component and an antifoaming agent so that the amount of the surfactant and the antifoaming agent has a defoaming effect. At least 8% by weight of the solid content remaining after evaporation of the water content of the mixed waste liquid, which is more than the amount required for expression,
A method for treating a radioactive waste liquid containing a surfactant, which comprises heating the mixed waste liquid to dry powder and granulating the powder into pellets. 2. At least one of a silicone emulsion defoaming agent, a silicone modified oil defoaming agent, a silicon powder defoaming agent and a silicone oil defoaming agent is used as the defoaming agent. A method for treating a radioactive waste liquid containing a surfactant according to item 1 above. 3. A mixing tank for mixing a radioactive waste liquid containing a surfactant and a waste liquid containing boric acid, sodium sulfate or the like as a main component, and a defoaming device for supplying a measured defoaming agent to the mixing tank. Surfactant-containing, characterized in that it comprises an agent tank, a device for making the waste liquid from the mixing tank into a dry powder, and a granulating device for granulating the powder produced from the dry powderizing device into pellets. Treatment facility for radioactive liquid waste. 4. The facility for treating a radioactive waste liquid containing a surfactant according to claim 3, wherein the dry powderizing device is a centrifugal thin film dryer. 5. The dry powdering apparatus separates a calcining furnace having a fluidized bed of solid particles suspended by a heated air stream from below, and a powder entrained in the air stream from the calcining furnace. The apparatus for treating a radioactive waste liquid containing a surfactant according to claim 3, which comprises an apparatus for