JPH0461981A - Removal of heavy metal - Google Patents

Abstract

PURPOSE:To efficiently remove a heavy metal by a method wherein garbage incineration ash containing a heavy metal and a molded and baked granular material containing animal powdered bones as an effective component are heated and mixed within a specific temp. range to adsorb the heavy metal by the granular material. CONSTITUTION:Garbage incineration ash containing a heavy metal and a molded and baked granular material containing animal powdered bones as an effective component are heated and mixed at 1000-1500 deg.C to adsorb the heavy metal in the garbage incineration ash by the granular material and the granular material after adsorption is separated from the garbage incineration ash. By this method, the heavy metal can efficiently be removed and a garbage incineration plant is prevented from becoming a heavy metal generating source. Further, since the obtained incineration ash substantially contains no heavy metal, it can be utilized in various uses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for removing heavy metals from garbage incineration ash.

[Conventional technology]

Garbage includes urban garbage and industrial waste discharged from daily life, and with the development of economic activities, the amount of garbage increases every year and is attracting attention as a living environment problem.

Generally, when municipal waste is incinerated, harmful heavy metals are mixed into the incinerated ash (for example, 4.8 ppm of cadmium, 2,600 ppm of lead).
pm, chromium 540ppm, mercury 0, IPpm).

Municipal garbage incineration ash is disposed of at disposal sites such as port landfills in coastal cities, and in inland cities that do not have coastlines, it is disposed of at land disposal sites such as mountainous areas, but incineration ash is disposed of by infiltration of rainwater, groundwater, etc. There is a possibility that harmful heavy metals may be leached out, which has become a social problem such as environmental pollution.

Therefore, as a result of various studies on the removal of heavy metals from garbage incineration ash, the present inventor found that by heating and mixing granular material containing animal bone powder as an active ingredient and garbage incineration ash,
We have discovered that heavy metals can be removed efficiently and have arrived at the present invention.

[Problem to be solved by the invention]

The present invention provides a method for efficiently removing heavy metals from garbage incineration ash.

[Means to solve the problem]

In the present invention, food waste incineration ash containing heavy metals is heated and mixed at 1000 to 1500°C with granules containing animal bone meal as an active ingredient, formed into granules, and fired. This is a method for removing heavy metals, which is characterized by adsorbing heavy metals onto granules and separating the adsorbed granules from garbage incineration ash.

Garbage is waste generated from daily life, and when incinerated in the usual way, organic matter, ignition loss components, humic acid, residual silicon dioxide), metals, and toxic heavy metals (e.g.
Contains cadmium, lead, chromium, mercury, etc.

Garbage incineration ash is crushed into powder. The size of the powder is usually 50 to 100 mesh.

In the present invention, the granular material containing animal bone powder as an active ingredient is prepared by mixing animal bone powder effective for adsorbing heavy metals, a binder for molding, and other additives as necessary, and forming the mixture into granules. It is dried and fired.

The animal bone meal used here uses bones that have conventionally been mostly discarded at livestock farms, especially bones of animals such as cows, horses, and sheep, which are mainly composed of hard bones.

The raw bones of these animals are cut into sizes that are easy to burn, then put into a pressure cooker and heated at around 200 to 400 degrees Celsius for about 90 minutes.
Boil for about 0 minutes. The bones were then placed in a kiln for 90
Bake at around 0~1100℃ for around 60~180 minutes, then let it cool naturally in the oven for around 60 minutes to return to room temperature or a state close to this. If any organic matter remains, it will cause oxidative decay, so it is important to ensure that this is removed.

By the above boiling process, organic matter adhering not only to the outside but also to the inside of the pores can be separated and removed from the bone in all directions.

By then passing through the above baking process, remaining organic matter can be completely removed, and at the same time the humidity in the bone can be reduced.
The water content can be reduced to several percent or less, preferably to almost 0%. According to the above-mentioned firing conditions, the bone turns into a skeleton and maintains its original tissue state having countless pores.

After the above firing and cooling, the bones are crushed and put into a powder machine for 2
Around 0 to 200 meshes, particularly preferably 50 to 100 meshes
It is made into powdered bone meal.

In the case of the bone powder mentioned above, in the case of cow bones, one particle that yields 40% of the yield by weight compared to raw raw bone has calcium (approximately 33
The main components are phosphorus (about 16.7%), barium (about 1.03%), sodium (about 0.76%), sulfur (about 0.64%), and magnesium, potassium,
It is composed of chlorine, amine, iron, etc., and has countless microscopic pores that communicate with each other both inside and outside the particle. This bone meal is alkaline because it contains calcium.

The binder may be anything that acts as a binder for shaping and firing the animal bone meal into granules, such as bentonite, acid clay, activated clay, kaolin clay, sericite, etc.
Examples include pyrophyllite, fireclay, montmorillonite, chloride, and alumina. In addition to the binder, other fillers and additives may be added as necessary.

The proportion of animal bone meal in granules containing animal bone meal as an active ingredient is not particularly limited as long as the granules have an adsorption effect, but in consideration of adsorption speed, a large amount of animal bone meal is preferable. For example, a preferable composition with a large amount of animal bone meal is 60 to 60% of the total amount of animal bone meal and binder.
80% can be given.

The granular material is obtained by mixing animal bone meal with a binder, other fillers, additives, and water as necessary, forming it into granules, drying, and baking.The size of the granular material is similar to that of raw garbage. Any material may be used as long as it is larger than the incineration return powder and can be easily separated from the garbage incineration ash due to its particle size. Its size is usually 5 to 20 mm. As the firing furnace, for example, a rotary firing furnace is used.

In the present invention, the rate of adsorption of heavy metals increases by increasing the ratio of granular materials containing animal bone meal as an active ingredient to the garbage incineration ash containing heavy metals, but the adsorption rate of heavy metals increases when the ratio of granular materials is 30% to 50%. In this case, the adsorption rate of heavy metals can be sufficiently increased.

While thoroughly mixing the garbage incineration ash and granules,
Although it is heated at 500° C., it is preferable to thoroughly mix it during heating to improve the contact between the heavy metal and the particulate matter. From this point of view, a rotary kiln is preferable as a mixing and baking device.
Garbage incineration ash and granules are fed from the inclined inlet of the kiln, thoroughly mixed and heated by rotary mixing, and the mixture is discharged from the outlet. Since garbage incineration ash is in powder form, it can be supplied by reduced pressure or vacuum suction.

Separation of ash and granules from the mixture after firing is performed by utilizing the size of the granules. From the viewpoint of efficiency, it is preferable to use a vibrating sieve for separation. If a rotary kiln is used for mixing and baking, and a vibrating screen is used for separation, and these are connected in sequence, mixing, baking, and separation can be performed continuously.

The diameter of the holes in the sieve is usually about 3 to 5 mm,
When using a sieve, the granules remain on top and the garbage incineration ash is collected from below.

By separating the granules in this manner, garbage incineration ash substantially free of heavy metals (mercury, cadmium, lead, chromium, etc.) can be obtained. Moreover, the granules that have absorbed heavy metals can be reused by washing with acid.

〔effect〕

According to the present invention, garbage incineration ash that is substantially free of heavy metals can be obtained, so the present invention can be an effective means for solving the problem of garbage incineration ash disposal.

It can also prevent garbage incinerators from becoming a source of heavy metals.

Furthermore, since the incineration ash obtained by the present invention does not substantially contain heavy metals, it has the advantage that it can be used for a variety of purposes.

〔Example〕

■Manufacture of granules Blend beef bone powder and clay in proportions of 60% by weight and 40% by weight, add water and mix.
The mixture was molded into granules and fired at about 1000°C in a rotating kiln to produce granules containing animal bone powder as an active ingredient.

■Separation of heavy metals from garbage incineration ash (cadmium 4.8ppm, lead 2600p)
pm, chromium 540 ppm, mercury 0.1 ppm) from the inlet of a rotary kiln so that the respective ratios were 60% by weight and 40% by weight.
The mixture was heated and mixed at .degree. C., and the mixture of garbage incineration ash and heavy metal-adsorbed granules was taken out from the outlet and passed through a vibrating sieve (hole size: 3 mm).

The granules remained on top of the sieve, and the garbage incineration ash was collected from below the sieve. The elution test of this garbage incineration ash was conducted using atomic absorption spectrophotometry (limit of measurement; cadmium 0.01mg/
When the content of heavy metals was measured, no heavy metals were detected.

Claims (2)

[Claims] (1) Food waste incineration ash containing heavy metals is heated and mixed at 1000 to 1500°C with granules containing animal bone meal as an active ingredient, formed into granules, and fired. A method for removing heavy metals, which is characterized by adsorbing heavy metals onto granular materials and separating the adsorbed granular materials from garbage incineration ash. (2) Food waste incineration ash containing heavy metals is heated and mixed at 1000 to 1500°C with granules containing animal bone meal as an active ingredient, molded and fired. Garbage incineration ash from which heavy metals have been removed is obtained by adsorbing heavy metals onto granules and separating the adsorbed granules.