JPH062275B2 - Method of detoxifying fly ash - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to ash discharged together with exhaust gas from an incinerator plant such as municipal waste and industrial waste, for example, EP ash which is ash collected by an electric dust collector, and a bag filter. The present invention relates to a treatment method for detoxifying the ash and the like collected in (the ash of this type is referred to as "fly ash" throughout this specification).

Conventional technology and its problems This type of fly ash contains a large amount of chlorides of heavy metals that are harmful to the human body. Especially, the content of cadmium, lead, and mercury is " It tends to exceed the elution standard value defined by the Prime Minister's Ordinance that establishes such criteria.

Therefore, recently, as shown in the attached Fig. 3 (a) and (b), cement and water are added to and mixed with EP ash to solidify EP ash, and heavy metals contained in EP ash are extracted with acid. The method of detoxifying the EP ash has been increasing in many cases.

However, in these treatment methods, the cost of chemicals for fixing the cement to be added and the extracted heavy metals becomes enormous, and the operation and maintenance of this treatment equipment is very troublesome.

In view of the above situation, an object of the present invention is to provide a fly ash detoxification treatment method which can be carried out with a minimum necessary chemical cost and with simple operation and maintenance.

Solution to Problem A method for detoxifying fly ash according to the present invention is to add a required amount of water and, if necessary, a required amount of a pH adjuster to the fly ash to humidify the fly ash using a vibration mixer. It is characterized in that a chelating agent and an iron salt are added in required amounts while kneading.

In a preferred embodiment of the present invention, the final sludge has a water content of 15-50% on a wet basis.

In general, fly ash is often alkaline with a pH of about 12, so if necessary, oxidize an acid such as hydrochloric acid to adjust its pH.
Adjust. In humidified kneading of fly ash, the pH before addition of the chelating agent is adjusted to 3 to 10, and the pH after completion of this treatment is 9 to
Be done at 10.

The amount of the pH adjusting agent added during the humidification and kneading of fly ash can be set in advance by automatic titration using a fly ash sample.

The addition amount of the chelating agent and the iron salt is appropriately set according to the properties of the fly ash. A commercially available heavy metal fixing agent is used as the chelating agent. In this case, the iron salt serves as a nucleus for the agglomeration of the chelate of heavy metals to accelerate the reaction.

As a kneading means for fly ash, a vibration type mixer is preferably used.

The following effects can be obtained by using the vibration mixer.

Moisture is evenly spread over the fly ash by vibrating force applied to the fly ash during the humidification and kneading of the fly ash. Therefore, the amount of water to be added can be minimized and a homogeneous reaction can be carried out throughout.

Since the amount of water is suppressed as described above, the water content of the detoxified sludge finally obtained can also be suppressed to be low. Therefore, it is not necessary to subject the sludge to a post-treatment such as dehydration, so that waste water is not generated.

Due to the mechanism of the vibration mixer, the relative speed difference between the fly ash and the internal structure of the mixer is very small. Therefore, wear of the internal structure portion is extremely small.

An example of the vibration mixer is shown in FIGS. 1 and 2. That is, the mixer body (1) in the shape of an inverted cylinder is directed on the floor (3) by the spring (2), and the body (1) is made to vibrate by means such as a vibration motor. Has become. A large number of mixed media (4) are placed inside the main body (1). A supply port (5) is provided at the top of one end of the main body (1), and a discharge port (6) is provided at the bottom of the other end. Thus, the vibration mixer (7) is constructed.

Fly ash supplied from the supply port (5) in the vibrating body (1)
It is well mixed by the mixing medium (4). When water and chemicals are added thereto, the fly ash is effectively humidified and kneaded, and reacts well with them.

EFFECTS OF THE INVENTION Since the method according to the present invention is configured as described above, compared to the method according to the prior art, the cost of chemicals used can be kept to a necessary minimum, and operation and maintenance can be greatly simplified. Can be converted.

Embodiment Next, an embodiment of the present invention will be specifically described with reference to the drawings.

In FIG. 1 and FIG. 2, the vibration type mixer (7) has about 6
Vibrate with G acceleration. Feeder from hopper (8)
6 kg of EP ash was supplied to the supply port (5) of the vibration type mixer (7) via (9). Then add 1160 ml of water and 2 to the inlet (6)
Add 40 ml of 35% hydrochloric acid and add another 60 ml of 10%
A chelate aqueous solution (heavy metal fixing agent manufactured by Miyoshi Yushi Co., Ltd., trade name "Epofloc L-1") was added, and kneading was continued for 10 minutes. Then, 170 ml of 1% ferric chloride aqueous solution was added and kneading was continued for 15 minutes. The detoxified sludge finally obtained in this way was taken out from the discharge port (6).

It was observed that during the kneading, the EP ash was uniformly distributed with water, a slurry was formed, and good reaction conditions were obtained.

The sludge finally obtained was in the form of clay. The bulk specific gravity of this was measured to be 1.67, which was about 1/5 the volume specific gravity of 0.33 before treatment.

Also, measure the pH and water content of this sludge,
Further, as shown below, the elution test of heavy metals was carried out according to the method specified in “Testing method for metals contained in industrial waste (February 17, 1973, Announcement 13)”. As shown in Table 1, all of the measured values passed the standard values stipulated in the “Prime Minister's Ordinance (February 17, 1973, General Ordinance 5) that establishes criteria for industrial waste containing metals etc.” It was something to do.

Dissolution test method for heavy metals 10% by weight of pure sludge and pure water (pH = 6.3)
%, And the resulting mixed liquid (500 ml or more) was continuously shaken at room temperature and atmospheric pressure for 6 hours. The sample solution thus obtained was filtered through a glass fiber filter paper having a pore size of 1 micron, and total mercury, cadmium and lead in this filtrate were quantitatively analyzed by an atomic absorption spectrophotometry.

[Brief description of drawings]

FIG. 1 is a side view of a vibrating mixer showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIGS. A flow sheet showing the method, and FIG. 6C is a flow sheet showing the method according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Ukino 1-27, Soyozuka-cho, Sakai City, Osaka Prefecture (56) Reference JP-A-57-87881 (JP, A) JP-A-54-37069 (JP) , A)

Claims (4)

[Claims] 1. A chelating agent and an iron salt are required while a fly ash is added with a required amount of water and, if necessary, a required amount of a pH adjusting agent, to moisten and knead the fly ash using a vibration mixer. A method for detoxifying fly ash, which is characterized by adding each in a quantity. 2. The method according to claim 1, wherein the sludge finally obtained has a water content of 15 to 50% on a wet basis. 3. The method according to claim 1 or 2, wherein the pH of the fly ash during kneading is 3 to 10. 4. The method according to claim 1, wherein the amount of the pH adjusting agent is preset by automatic titration of a fly ash sample.