JPS62201399A - Solidifying processing method of phosphate waste liquor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of industrial application] The present invention relates to a method for solidifying phosphate waste liquid with an inorganic solidifying agent. Specifically, the present invention relates to a method suitable for solidifying radioactive sodium hydrogen phosphate waste liquid discharged from nuclear facilities using an inorganic solidifying material.

[Conventional technology]

Conventionally, sodium hydrogen phosphate waste liquid is stored in a tank in the form of sodium dihydrogen phosphate, which has high solubility at room temperature, and when this is solidified, it is solidified with bitumen.

[Problem that the invention seeks to solve]

However, when solidified bitumen is considered for land disposal, there are problems with fire resistance and load carrying capacity. Therefore, it is preferable to solidify with an inorganic solidifying agent such as cement or a mixture of cement and water glass rather than bitumen assimilation, but sodium dihydrogen phosphate does not solidify at all with an inorganic solidifying agent and cannot form a solidified body. I made a mistake.

The object of the present invention is to solidify sodium hydrogen phosphate waste liquid and other phosphate waste liquids with an inorganic assimilation agent.

[Means to solve the problem]

The above objective 1 is achieved by adjusting the pH of the phosphate waste solution to 6 or more and then adding the inorganic assimilation material tl-.

[Effect]

The sodium dihydrogen phosphate waste liquid exhibits a pH of 4, and in this state, as mentioned above, it will not solidify at all with the inorganic assimilation material. This is because cement or cement + glass solidifies excessively under alkaline conditions, but gelation rapidly progresses under acidic conditions. Therefore, when an alkaline solution, such as a sodium hydroxide solution, is added to the above waste liquid to increase the pH, the following reaction occurs:
Most of the sodium (Na)l, PO,) is converted to disodium phosphate-hydrogen (Na, HPO4) at pH 8 to 8.8 at p) 16 or higher.

Nap, PO, + NaOH4Na, HPO4+
H,0 This phosphorus yield-hydrogen disodium can be made into a solid by adding an inorganic assimilating agent. In this case, if the inorganic assimilation agent is added at 30°C or higher, the solidification reaction of disodium phosphate-hydrogen will proceed in the monohydrate or heptahydrate state, and later, when the temperature returns to room temperature, it will change to the dodecahydrate. The free water in the inorganic solidification system is absorbed and the strength of the solidified product is particularly increased. The same procedure as above applies to other phosphate waste liquids.

〔Example〕

A waste solution of dihydrogen phosphate-sodium aqueous solution is put into a reaction tank, an aqueous sodium hydroxide solution is added thereto, and the pH of the liquid in the reaction tank is monitored with a pf (meter).

Figure 3 shows this process. dihydrogen phosphate
The pH of the sodium aqueous solution is 4, or as sodium hydroxide is added, it reacts sequentially and turns into disodium phosphate-hydrogen. When 0.6 to 0.7 mol of sodium hydroxide is added to aqueous sodium hydroxide solution, it becomes neutral. 100 p) i vi8 to 8.8 of an aqueous solution converted to disodium typhosphate-hydrogen is shown.

Note that the starting waste liquid is sodium dihydrogen phosphate and phosphoric acid.
Assuming the case of a mixed solution with sodium hydroxide, the pH of the aqueous solution was measured by mixing these two in various molar ratios, and the results are shown in FIG.

Since Figures 3 and 4 agree well, even if the starting waste liquid is a mixture of the above two types of sodium hydrogen phosphate, it is possible to obtain an approximate value of the composition ratio by measuring pH. It turns out that it is possible. Therefore p
It is reasonable to monitor with H.

To make a strong solidified body using inorganic assimilates, pi (6,5
The above alkaline side is fine, but in order to create the healthiest assimilate, it is better to change all rj to phosphate-hydrogen disodium. That is, it is better that the pH is 8 to 8.8. For example, if the pH is 7, add 0.2 equivalents of sodium hydroxide to make pi-1 = 8 to 8.
．． It is better to set it to 8.

The solution of sodium hydroxide and phosphorus, which has a pH of A@, is condensed or dried into a powder, and cement or a solidifying agent made of a mixture of cement and water glass is added thereto for solidification. The temperature of this solidification treatment will be described below in 1.

Figure 5 shows the solubility curves of sodium dihydrogen phosphate and sodium phosphate. In both cases, as the temperature rises, the solubility increases and water of crystallization is lost. Taking the case where an inorganic assimilate is added at 50°C or above as an example, the following reaction is occurring in the reaction tank: NaOH Nap, PO, -H, ONa, HPO4* H,0
When an inorganic solidifying agent is added, phosphorus is monohydrogen, dihydric, and IJium is fixed to the rock solidifying material using monohydrate.

On the other hand, it is known that the less free water inside an inorganic solidified material, the stronger it becomes, but there is a limit to reducing the amount of water mixed in due to workability when adding a barless solidifying material. However, as the waste solidified with Na,f(PO4・H!O) solidifies and cools to room temperature, Na, )IPO4・
H20-+N a, t-i P 04 ・7 H20
-) Na, ) iP 04 .12H,0 and crystal water are considered to be taken in, and this is effective in maintaining the integrity of the solidified body at a high level.

On the other hand, if the inorganic solidifying agent is added at room temperature from the beginning, the waste itself can hold up to 12 liters of water, so a large amount of water is required when adding the assimilating agent to first take in the water, and this increases after solidifying. It is not the force/resistance that affects the strength of the solidified material, but the result is that V is not solidified due to the condition.

We investigated the pH of the waste aqueous solution and the effects of the additive-free solidifying agent on the solidified material, and the results of the tests were reported in the 6th section.
7 and 7. A light assimilator can be obtained at a pH of 5 or higher and an inorganic solidification addition temperature of 30°C or higher. If radioactive waste is to be disposed of on land, it should be 1o because it will boil and run out of water if it is heated to more than enough pi-16.5 and the temperature during crosstalk is 35° or more.

In the case of radioactive waste liquid, it is desirable to keep the temperature below 80°C to prevent the radionuclides from flying away.

In the above, two practical examples of the present invention will be specifically described in the case where an aqueous solution of dihydrogen phosphate (IJ) as a radioactive waste liquid is treated.

Example 1 Water is introduced into the reaction tank 6 from the storage tank 1 via the valve 3. The reaction tank is equipped with a rotating blade 7 for stirring which is rotated by a 6μ power rock 4, and the temperature of the entire tank q can be controlled by a heater 8. Also, the progress of the reaction
(Meter 5 is a monitor.

After introducing the waste dihydrogen phosphate-sodium aqueous solution g, an aqueous sodium hydroxide solution is introduced from the tank 2 through the valve 3 into the reaction tank VC. Push horizontally in the reaction tank for a specified time, pH 5
In this case, most of the sodium dihydrogen phosphate is converted to disodium hydrogen phosphate.

Subsequently, this solution is introduced into the concentration dryer 9 via the reaction tank 6 and the pump 3. Here, the concentrated melage is turned into powder. Subsequently, it is introduced into the waste solidification container 14 via the lower valve 3. On the other hand, to explain the solidification material system, inorganic solidification material (
Cement or a mixture of cement and water glass) is introduced into the kneading tank 12 from the tank 1o through the valve 3, and water is introduced into the kneading tank 1 from the tank 11 through the valve 3 in the same way.
2 and uniformly kneaded by the rotary blades 7 rotated by the power machine 4 in the kneading tank 12. Subsequently, this mixture of inorganic solidification material and water is poured into the waste solidification container 14 through the valve 3. A hardening agent 13 made of phosphate is introduced from the tank 13 through the valve 3 into the waste solidification container 14 . The curing agent 13 may be introduced into the kneading tank 12 and mixed with the inorganic solidifying material in advance. A rotary blade 7 rotated by a motor 4 is introduced into the waste solidification container 14, and the waste, solidification material, and hardening agent are mixed uniformly with this.

Further, a heater 8 is provided around the waste solidification container 14,
Thereby, the mixture is kneaded at a temperature of 30°C or higher and 80°C or higher. Alternatively, a heater may be introduced into the waste solidification container 14 in case of crosstalk. After kneading in the waste solidification container 14, the rotating blade 7 is removed from the vaginal container 14, and the contents are solidified as they are.

Note that homogeneous kneading may not be performed inside the waste solidification container 14, but may be separately performed outside the waste solidification container 14, and in this case, one set of a kneading tank and a valve may be added.

1! Example 2 As shown in FIG. 2, a waste dihydrogen phosphate solution was introduced into a reaction tank 19 from a storage tank 15 through an 18ft valve. The reaction tank 19 is equipped with a stirring rotary blade 2o that is rotated by a motor 17, and the entire tank is equipped with a heater 2.
1 allows you to control the temperature. Further, the progress of the reaction is monitored with a pH meter. Reaction tank 1
After introducing the waste dihydrogen phosphate solution into the tank 16, the sodium hydroxide solution was introduced into the valve 1 from the tank 16.
When the reaction temperature is increased to 16 or more, most of the sodium dihydrogen phosphate is converted to disodium phosphate. Subsequently, this solution is introduced from the reaction tank 19 through the valve 18 into the concentration dryer 22, where it is dried and powdered, and then introduced through the valve 18 into the granulator 27 to be pelletized. The waste material that has become pellets 29 is introduced into a waste solidification container 28 . - Regarding the assimilating material system, the inorganic solidifying material is introduced from the tank 23 through the pulp ts'l into the kneading system [25], where it is mixed with water drawn from the water tank 24 through the valve 18. , a rotating blade 20 rotated by a power machine 17
The mixture is evenly kneaded. Subsequently, a mixture of the inorganic solidifying agent and water is introduced into the waste assimilation container 28 containing the waste pellets 29 via the pulp 18, and the hardening agent is also introduced into the tank 2.
6 through the valve 18 and solidify. During solidification, the temperature is controlled by the heater 21 around the waste solidification container 28 to a temperature of 30 tll or more and 80° C. or less. The curing agent 26μ is introduced into the kneading tank 25 through the valve 28, and after being smoothly kneaded with the inorganic solidifying agent, the pellets 29
It may be introduced into the waste tank a28 which is filled with.

The inorganic solidifying materials prepared by the methods of Examples 1 and 2 had an odor of about 250 when the temperature at the time of addition of the solidifying material was 30°C or higher and lower than 50°C, fc @ 100 h/d, and 50°C or higher and 80°C or higher. /d strength, and the waste tank was also in good condition.

Although the inorganic solidifying material used was cement lubrication or cement water glass, the assimilate can also be made using other hydraulic inorganic solidifying materials.

In the above examples, sodium dihydrogen phosphate waste liquid was treated, but even when other phosphate waste liquids are treated, the same adjustment to the pH value as described above, This can be solidified by an inorganic solidifying agent by adding the same inorganic assimilating agent and at the same addition temperature. For example, other phosphate waste liquids, specifically potassium phosphate, water-resistant potassium phosphate, calcium phosphate, calcium hydrogen phosphate, phosphorus ff
i Cobalt, iron phosphate, nickel phosphate, chromium phosphate and manganese phosphate can also be solidified according to the invention using inorganic solidifying agents in cement or a mixture of cement and hydraulic lath. For pH adjustment, a suitable alkaline solution such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. may be used.

〔Effect of the invention〕

According to the present invention, sodium dihydrogen phosphate waste liquid and other phosphate waste liquids, which were previously impossible to assimilate using an inorganic solidifying agent, can be solidified using an inorganic solidifying agent, so waste liquid storage space can be saved. In addition to reducing the volume of storage, it is possible to avoid the fire resistance and load-bearing properties of the assimilated bitumen.

[Brief explanation of drawings]

゛Figure 1 is a diagram showing 4 practical examples of the present invention in the case of homogeneous solidification, Figure 2 is a diagram showing an example of the present invention in the case of pellet solidification, and Figures 3 and 4 are diagrams showing examples of the present invention in the case of homogeneous solidification. Figure 5 shows the solubility of sodium hydrogen phosphate, Figure 6 shows the relationship between waste liquid p)L and solidified solid strength, Figure 7 shows the relationship between solidified material strength and solidified material addition. Diagram showing the relationship between temperature and solidification strength 0 1...Waste tank 2...Sodium hydroxide tank/
3...Valve 4...Power machine 5...p
H meter 6...Reaction tank 7...Rotating vane
8... Heater 9... Foundation shrink dryer 10...
- Solidifying agent tank 11...Water tank 12...Kneading tank 13...Curing agent tank 14...Waste solidifying container 15...Waste tank 16...Sodium hydroxide tank 17... Power machine 18...B, Lube 19...Reaction tank 20...Rotating vane 21.
... Heater 22 ... Concentration dryer 23 ... Solidification agent tank 24 ... Water tank 25 ... Kneading tank
26...Curing agent tank 27...Pelletizer
28...Waste solidification container 29...Pellets. 1゛～-τ

Claims (1)

[Scope of Claims] 1. A method for solidifying a phosphoric acid waste solution, which comprises adjusting the pH of the phosphate waste solution to 6 or higher and then adding an inorganic solidifying agent to solidify the phosphate waste solution. 2. The method for solidifying phosphate waste liquid according to claim 1, wherein the phosphate waste liquid is an aqueous solution containing sodium dihydrogen phosphate as a main component. 3. The method for solidifying phosphate waste liquid according to claim 1 or 2, wherein the temperature at which the inorganic solidifying agent is added is 30°C or more and less than 100°C. 4. Solidification treatment of phosphoric acid waste liquid according to claim 1, 2, or 3, in which an inorganic solidifying agent is added after concentrating or drying the phosphoric acid waste liquid whose pH has been adjusted to 6 or more or drying it into powder. Method.