JPH02171693A - Treatment of washing waste water of cement kneader - Google Patents

Abstract

PURPOSE:To obtain a stable solidified body by storing a washing waste water produced by washing down of a sludge in a kneader, in a condition which the sludge may not solidify, and by conveying the said sludge to the kneader again. CONSTITUTION:A sludge stored at a bottom part of a washing waste water tank 2, is conveyed to a kneader 1 by a slurry conveying pump 7 at an appropriate timing for mixing with a cement, and is kneaded with a cement. If required, a demineralized water is poured to a flowing channel of a supernatant water of the washing tank or a supernatant water tank 3. In this way, as the sludge in the washing waste water produced by a washing process of the cement kneader, is conveyed to the kneader to be kneaded with the cement, a uniform quality of a sludge solidified body can be obtained and also a compressive strength of it can satisfy a standard level for ocean dumping which is required for a solidified body of a radioactive waste. Also, the supernatant water can be finally used as a kneading water after it has repeatedly been used, and therefore the number of drums produced in the course of washing down, can be diminished.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to the treatment of cleaning wastewater from a cement kneading machine when wastewater containing harmful substances such as radioactive waste and heavy metals is treated by cement solidification. Regarding the method.

(Prior Art) The cement solidification treatment method for waste liquid as described above includes an in-drum method, an out-drum method, and a vacuum method. The in-drum treatment method is a method in which waste liquid and cement are kneaded in a drum and then solidified as is.In the out-drum method, a certain amount of waste liquid and cement are homogeneously kneaded in a kneader, and the mixture is kneaded. This is a method in which the substance is poured into a drum and allowed to solidify. The vacuum treatment method involves filling a drum with cement and vermiculite, injecting the waste liquid into the drum under vacuum, allowing it to permeate throughout and solidify.

However, in the case of the vacuum method, the resulting assimilate is not sufficiently homogeneous, and the in-drum method has problems such as scattering of cement powder and the need to clean the stirring blades before mixing. treatment methods have become mainstream.

Even in the out-drum treatment method, the sludge remaining in the kneader must be washed away, and the treatment of the resulting washing wastewater poses a problem.

In the current treatment method, cleaning wastewater is once sent to a tank and left to stand still, the separated supernatant water is reused as cleaning water, and the sludge that has accumulated at the bottom is drawn out from the tank with a vacuum pump and discharged into a drum, where it is collected. Allow to solidify naturally.

The solidified sludge produced in this way is not homogeneous, and its compressive strength ranges from several kg/ci to several tens of kilograms.
FI/cm, which is far from the compressive strength of 50Kl/crit, which is the ocean dumping standard required for assimilated radioactive waste.

[Problem to be solved by the invention]

An object of the present invention is to improve a method for treating waste water from a cement kneader in cement solidification treatment of waste liquid, and to provide a solidified product that is homogeneous and has sufficient strength.

(Means for Solving the Problems) The cement kneading machine cleaning wastewater treatment method of the present invention is an out-drum method in which waste liquid and cement are kneaded in a kneader, and the mixture is poured into a container such as a drum and solidified. When carrying out the cement solidification process, the washing wastewater generated by washing the sludge in the kneading machine is stored so that the sludge does not solidify, and the sludge in the stored washing wastewater is transferred to the kneading machine and kneaded with cement. Consisting of

In order to preserve the sludge so that it does not solidify until it is mixed with cement, it is sufficient, for example, to keep stirring the washing waste water in a tank.

This stirring only needs to be done weakly enough to prevent settling and coagulation of the sludge, so that a supernatant remains in the washing wastewater tank. This supernatant can be conventionally reused as a cleaning solution, which is the recommended practice.

[For production]

An apparatus that implements the processing method of the present invention typically has a configuration as shown in the figure.

Waste liquid from waste tank (4) and cement hopper (5)
The cement from is mixed in a mixer (1),
The mixture is poured into a drum (9) where it solidifies.

When the kneading work is finished, the water in the supernatant water tank (3) is sent to the kneader to clean the inside of the kneader. The generated wash wastewater is sent to the wash wastewater tank (2) where it is gently agitated near the bottom.

The cleaning wastewater contains cement particles undergoing a hydration reaction, which settle toward the bottom of the tank and, if left standing, become entangled with the growth of hydrate crystals. The particles solidify, but stirring prevents this and allows each particle to hydrate independently.

The supernatant from the washing wastewater tank is sent to the supernatant water tank (3).
In addition to being used to clean the kneading machine (1) described above, it is also used to clean the cleaning wastewater tank (2) and the flow path (6) from the kneading machine to the cleaning wastewater tank.

The sludge stored at the bottom of the washing wastewater tank (2) is
When the time for mixing with cement comes, the slurry is sent to the kneader (1) by the slurry transfer pump (7), and is mixed with cement as described above.

If necessary, in the illustrated example, demineralized water is added to the supernatant channel of the washing tank and the supernatant water tank (3) as indicated by the symbol DW.

In this way, the sludge in the washing wastewater generated when cleaning the cement mixer is transferred to the mixer and mixed with cement, so the solidified sludge is homogeneous and its compressive strength is also that of radioactive waste. It reaches a level that meets the ocean dumping standards required for solidified solids. Moreover, since the supernatant water can be used as mixing water during cement kneading after being used repeatedly, the number of solidified drums generated during cleaning is also small.

[Reference Example 1] A waste liquid having a composition similar to a boric acid-containing waste liquid discharged from a nuclear power plant was prepared, and when this was subjected to cement solidification treatment, the sludge that adhered to a kneader was collected. The composition of the sludge is: Calcium borate: Cement: Water knee 2
:1:3.

100 g of water was placed in each of two beakers, and the sludge 609 was added thereto and stirred. One was kept stirring, and the other was left to stand without stirring.

The sample that was continuously stirred remained a slurry for a long time without any change, but the sludge that was left to stand still solidified. The compressive strength of the solidified body increased to 30'J/c after 2 weeks.
rA, even after 3 months, it only reached 50'l/cM.

[Reference Example 2] The same experiment as in Reference Example 1 was conducted by collecting the sludge that adhered to the kneader when incineration ash containing Zn and PB was assimilated into cement.

The results were the same as those in Reference Example 1; there was no change when stirring was continued, but the sludge solidified when left standing. The compressive strength of the solidified body is 10Kg/ctA after 2 weeks, 3
Even with 1 barley of Chikitsuki, it was only 20Kg/crA.

[Reference Example 3] After the boric acid-containing waste liquid used in Reference Example 1 was assimilated with cement, the sludge adhering to the kneader was washed away with water, and the sludge in the washed waste water was kneaded with cement at the following ratio and solidified. did.

The results are as follows.

Sludge Cement Compression 1 degree (Kff/cm) (
Kg) (K'J) 2" [韮月)B
Book 2.5 1.5 115 307
3.0 1.4 100 2002
．． 5 1.7 110 265 [Example] Using a treatment device with the configuration shown in the figure, the waste liquid containing radioactive waste was solidified with cement, the waste water from the kneading machine was stored as described above, and then the sludge was It was returned to the mixing process and mixed with cement.

The mixing ratio is 16ONy of sludge: 230Kg of cement.
It is.

The compressive strength of the obtained cement assimilate was 1 after 1 month.
At 50, it exceeded 'J/crA.

(Effects of the Invention) According to the cement kneader cleaning wastewater treatment method of the present invention,
Since the sludge in the washing wastewater is solidified with cement, a heterogeneous and weak assimilated product consisting of only washing sludge is not formed. The resulting assimilates are homogeneous, have high strength, and are stable enough to withstand long-term storage. In this way, the problems associated with the treatment of cleaning sludge were solved.

The treatment method of the present invention is particularly significant when applied to the treatment of radioactive waste liquid, but is also useful for the treatment of waste containing heavy metals.

[Brief explanation of the drawing]

The drawing is a flow sheet of the apparatus used to carry out the treatment method of the present invention. 1... Kneading machine 2... Washing waste water tank 3... Supernatant water tank 4... Waste liquid tank 5... Cement hopper 7... Slurry transfer pump

Claims (4)

[Claims] (1) When carrying out the cement solidification process, in which waste liquid and cement are kneaded in a kneader and the mixture is poured into a container and solidified, the washing wastewater generated by washing the sludge of the kneader is made to prevent the sludge from solidifying. A method for treating cleaning wastewater from a cement mixer, which comprises storing the sludge in the stored cleaning wastewater in a mixer and mixing it with cement. (2) The treatment method according to claim 1, wherein the supernatant water of the washing wastewater is reused for washing the kneading machine, and after being repeatedly used, it is used as mixing water during cement mixing. (3) The treatment method according to claim 1, wherein the waste liquid is a radioactive waste liquid. (4) The treatment method according to claim 1, wherein the waste liquid is a waste liquid containing harmful substances.