JPS6355000A - Treatment method for neutralized mine drainage mud - Google Patents

Abstract

PURPOSE:To remarkably reduce the volume of neutralized sludge by accumulating the sludgy material generated in the neutralization treatment of mine waste water on the flat ground having an enclosure, freezing the contained water during the wintertime, and melting and evaporating the frozen water in spring or in summer. CONSTITUTION:A sludgy material generated in the neutralization treatment of mine waste water is accumulated on the flat ground having an enclosure, the material is allowed to stand after accumulation to settle the neutralized sludge, and supernatant water is discharge as much as possible. Under such conditions, the contained water is frozen during the wintertime, and the frozen water is melted and evaporated in spring or in summer. The neutralized sludge can be carried out at a low cost by this process, and the volume can be remarkably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating neutralized mine drainage mud for easy handling at low cost.

[Conventional technology]

Even in mines that have already been suspended or abolished, the mine wastewater discharged from the mine mouth must be treated.

The problematic components of mine drainage are heavy metals, but since heavy metals can be almost completely removed through neutralization, it is common to treat mine drainage with slaked lime, etc., and mine drainage mixed with slaked lime is usually sent to a sedimentation pond. The neutralized sediment (hereinafter referred to as neutralized mud) is settled in the sedimentation basin, and the supernatant water that meets the discharge standards is discharged into rivers, etc.

By the way, according to the above method, neutralized mud is generated, and a settling pond is required to settle it, but abandoned mines are generally located in mountainous areas, and it is not easy to create new settling ponds, and moreover, there is drainage from the mine. This process must continue for as long as possible. For this reason, there is a need for a fundamental review of the treatment of mine drainage water, and various measures are being considered, such as water supply or water reduction measures for drainage ditches, and treatment methods that reduce the amount of neutralized mud, but there is still no viable solution from a cost perspective. The reality is that there is none.

[Problem that the invention seeks to solve]

In the situation where there is no fundamental solution as described above, the next best option is to transport the neutralized mud to a suitable deposition site.

However, the above-mentioned neutralized mud is fluid as it is and cannot withstand being transported, and mechanical dewatering is costly and does not necessarily result in sufficient dewatering, and furthermore, when water is added to such a dehydrated cake, it becomes muddy again. This has the disadvantage that it does not lead to any savings in deposition space.

The present invention has been made in view of the above-mentioned circumstances, and provides a method that allows a neutralization source to be transported at low cost and that can significantly reduce its volume.

[Means for solving problems]

In order to achieve the above object, the present inventors focused on the freeze-thaw process applied to the treatment of excess sludge in tap water, and believed that if the freeze-thaw process was carried out using natural phenomena, the cost could be extremely reduced. As a result of various experiments, the present invention was achieved after confirming that it is sufficiently practical.

That is, the present invention is characterized in that the neutralization source is deposited on a flat ground with an enclosure, the contained water is frozen during the winter, and the ice is thawed during the spring and summer, and the melt water is evaporated.

[For production]

According to the freeze-thaw method, draft water, etc. that is difficult to dehydrate mechanically, is frozen, and particles outside the water's edge are agglomerated and compressed due to freezing, resulting in a lower moisture content and improved dehydration properties. , there are various advantages such as reduced volume. However, if this is done artificially, the equipment investment is large, the power consumption for running is large, the cost is high, and it is not suitable for the treatment of neutralized mine drainage mud.

Therefore, in the present invention, it was decided to use natural thermal energy. The present invention can be used anywhere where the topsoil freezes in the winter.

First, for the purpose of depositing the neutralizing source, a deposition site with an enclosure on flat ground is prepared. This accumulation field may be formed by digging the ground, or may be divided by board fences or embankments on the ground. Before winter, a neutralization source is pumped up from the sediment and deposited in this sedimentation field.

After deposition, leave it to settle to allow the neutralization source to precipitate, and drain as much of the supernatant water as possible before freezing begins. If left in this state during the winter, freezing will occur from the surface. In this case, if the sediment layer is too thick, the water in the lower layer will simply be sucked up to the upper layer and may not freeze. To avoid this, it is recommended to bury a ventilation pipe in the accumulated neutralized mud and blow outside air into the ventilation pipe. Furthermore, although the above weather conditions naturally involve snowfall, snow accumulation on the neutralized mud impedes freezing, so it is preferable to remove snow from time to time.

The key is to freeze the entire deposited layer, and other effective means to promote freezing may be used in combination.

For example, it is effective to bury a large number of vertical heat pipes in the deposited layer.

If the frozen sedimentary layer is left as is until summer, it will begin to thaw as the temperature rises, and the water that has seeped into the surface layer will evaporate.
It is then dried in the sun to form a dehydrated cake in the form of powder or pumice. This dehydrated cake has a volume ratio of less than 1/2 and a water content of 70%.
The particle size is coarse and does not easily become muddy even when water is added.

Moreover, if tamped, the volume ratio will be approximately 173. Therefore, it is easy to handle and the volume can be significantly reduced.

〔Example〕

Example 1 Kounomai, located at 44° 30' north latitude and 144° east longitude, has a minimum temperature of -30°C in winter, a daily minimum temperature of 115°C or less from January to February, and an average daily temperature of 110°C or less The number of days in which this occurs is more than 60%, which means that the weather conditions for implementing the present invention are extremely favorable.

4 m x 5.5 m x on the flat land of the mine ruins in this area
We built a 0.6 m high embankment type test pond and used 35C as a neutralization source with a water content of 95%! 1 height and subjected to freeze-thaw processing.

As a result of occasional snow removal, the freeze was completed in mid-January, and the thaw was almost complete by mid-May. The height of the pile upon completion of melting is 2
The moisture content of the cake was 65%. This cake was left to dry in the sun until late August, and as a result, the pile height was reduced to 15.5 elm, and the moisture content of this cake was 68.8%. When this cake was tamped, the volume ratio to the neutralization source was 32.1%.

Example 2 An embankment-type freeze-thaw pond of 1800 m'' was constructed in the same location as in Example 1, and neutralization sources were deposited at a height of 25 cm.

Due to insufficient drainage, supernatant water ice that had formed on the surface was removed in mid-January, and thereafter snow removal was carried out occasionally to promote freezing. The pile height at the start of freezing was 25 cm, and the moisture content was 94%.

When the melting is complete, the pile height is 18 cm and the moisture content is 65.5%.
By late July, it had reached a height of 11 cm and a moisture content of 66.6%.

Example 3 One area of the freeze-thaw pond in Example 2 was partitioned into 7m squares with boards,
Eight 3-inch vibrators placed 30 times from the ground at 0.6m intervals.
The pipes were placed so that they passed over the pipes, and an exhaust fan was used to introduce outside air at a rate of 10 m''/min into each pipe.The neutralization source was deposited at a height of 1 m in this pond, and the air was heated from early December to early March. Until then, we operated an exhaust fan every day from 4pm to 9am to promote freezing.

As a result, by mid-March, we were able to freeze almost the entire layer, leaving only 3 cm at the bottom. This accumulation height of 1 m seems to be almost the limit.

〔Effect of the invention〕

According to the present invention, the neutralization source can be transported at low cost and its volume can be significantly reduced. This method is expected to solve the problem of neutralization sources in cold regions.

Claims (1)

[Claims] It is characterized by depositing mud generated by neutralizing mine drainage on flat ground with an enclosure, freezing the water content during the winter, and thawing and evaporating the frozen water during the spring and summer. A method for treating neutralized mine drainage mud.