KR100890297B1 - Neutralization system of acid mind drainage by porous concrete blocks with refilling of alkali material - Google Patents

Abstract

The present invention relates to a neutralization treatment system of acid mine drainage using a permeable block, and more particularly, coarse aggregate is made of permeable concrete made of low-grade waste rock generated from limestone or dolomite mining process or recycled aggregate made of construction waste. Installing the block while forming a vertical wall at three points in the channel through which the acid mine drainage is discharged, and neutralizing the acid mine drainage passing through the permeable wall with an alkali substance contained in the concrete block; And acid mines that maintain acid neutralization capacity by recharging the alkali material above the one-year stoichiometric requirement in the form of 'T' when the alkali material contained in the concrete block is exhausted. It relates to a drainage neutralization treatment system.

Acid Mine Drainage, Permeable Concrete Block, Mine Waste Rock, Construction Waste Recycling Aggregate, Alkaline Recharge, Reaction Wall

Description

Neutralization system of acid mind drainage by porous concrete blocks with refilling of alkali material}

1 is a plan view of an embodiment of the acid mine drainage neutralization treatment method according to the present invention.

Figure 2 is a side view of one embodiment of the acid mine drainage neutralization treatment method according to the present invention.

Figure 3 shows the results of the acid mine drainage neutralization test for the permeable block according to the first embodiment of the present invention, showing the pH change of the effluent according to the acid mine drainage treatment according to the coarse aggregate particle size.

Figure 4 shows the experimental results when the alkaline material is recharged in the water permeable block according to the second embodiment of the present invention, as a comparative example and the injection of only lime without a water permeable block as a comparative example It shows the acid mine drainage neutralization test results.

* Explanation of symbols for main parts of the drawings

L ... the distance between the permeable wall on the most upstream side and the permeable wall on the most downstream side

10,20,30,40 ... permeable block
24 ... Dosage of Alkaline Recharged

50 ... alkali material recharged on top of permeable block

60 ... alkali material recharged on the side of the permeable block

The present invention relates to a neutralization treatment system of acid mine drainage using a permeable block, and more specifically, (a) made of coarse aggregate made from low-grade waste rock or construction waste generated from limestone or dolomite mining as coarse aggregate. Installing the permeable concrete block while forming a vertical wall in the channel through which the acid mine drainage flows, and neutralizing the acid mine drainage passing through the permeable wall with an alkali substance contained in the concrete block; And (b) an acid mine drainage neutralization treatment system for regenerating a predetermined amount of alkali material on the top and side of the block when the alkali material contained in the concrete block is exhausted so that acid neutralization capacity is continuously maintained.

Acid Mine Drainage (AMD) is a problem in which a layer rich in pyrite is acidified by inflow of groundwater and air to discharge acidic substances, thereby lowering the pH of the surrounding water system and increasing the possibility of heavy metal leakage due to the pH drop. Many of these problems are caused mainly by coal mining. According to a survey by the Ministry of Commerce, Industry and Energy in 1999, 136 waste coal mines out of 344 waste coal mines nationwide, and the amount of water discharged in the mine reaches 39,484m3 daily. Acid mine drainage is characterized by low pH of 2-3 and high metal content of Fe, Al, Mn including SO ₄ ^{2 -} in the range of 500-2,500 mg / l.

As a technique for treating acid mine drainage, a neutralization method using an alkaline substance is mainly applied. ALD (Anoxic limestone drains) treatment method using limestone, SAPS (Successive alkalinity producing system) treatment method which induces alkalinity by sulphate reducing microorganism in organic material layer such as milk powder and induces metal precipitation using limestone This method is mainly applied. In addition, there are cases where alkaline substances such as slaked lime, sodium hydroxide, recycled concrete aggregate, steel slag, shellfish are applied to acid mine drainage treatment.

The domestic technology patented for acid mine drainage treatment includes a rectification tank for storing acid mine drainage, a neutralization tank with oyster shells filled in a mesh cartridge, and a settling tank as unit units. Korea Patent No. 10-0672080, an acid mine wastewater treatment system, Korea Patent No. 10-0618305, which features a sulphate reduction facility in which an organic material layer is installed in the tunnel of the abandoned mine to keep the temperature of the organic material layer constant, calcined waste-rock and Korean Patent No. 10-0527336 characterized by the neutralization tank containing the yellow soil filter and the method for purifying the mine drainage using sulphate reducing bacteria, primary collection tank, secondary collection tank, anaerobic artificial settlement, sedimentation tank, aerobic artificial settlement, etc. The marshland is characterized by consisting of a gravel layer, limestone layer, substrate material layer, green algae and plant layer, etc. 0-0465454, a sump tank with a limestone layer, agglomeration / sedimentation, red mud layer, and natural purifier, is registered in Korea Patent No. 10-0566327 for acid drainage treatment, and acid mine drainage is contacted with waste concrete recycled aggregates. Korea Patent Publication No. 2001-0035288, a waste concrete recycled aggregate or by using lime, which neutralizes the reaction, separates the liquid alkaline components from the base production tank and neutralizes the acidic waste water in the neutralization tank to reduce the amount of sludge containing heavy metals. Korean Patent No. 10-0499060 characterized in that the reduction.

In the case of sulphate reduction facilities, various organic substances that are injected into the organic carbon source to reduce sulphate, although the environmental hazards are less than the heavy metals in acid mine drainage, the organic substances themselves are water pollutants. Because of the possibility of causing an injection, it is necessary to determine the dosage under careful consideration from a stoichiometric point of view, which is a very difficult problem in reality.

In the case of using waste concrete recycled aggregate as a neutralizing material, the actual generation of waste concrete is located in urban areas, while acid mine drainage is located in a mountainous area, considering that recycled aggregate takes up a lot of volume and weight. This increases, and when the alkali supply capacity of the recycled aggregate is exhausted, it must be replaced and transported again, so that practical field applicability is not high.

The present invention is a low-grade waste-rock generated in the process of mining limestone or dolomite generated in large quantities as industrial by-products as a coarse aggregate in order to neutralize the acid mine drainage channel without installing a separate neutralization reaction tank; Alternatively, a permeable concrete block using recycled aggregate made of construction waste is formed while forming a wall in the channel where the acid mine drainage flows out, and the acid mine drainage passing through the permeable wall reacts with the alkali material contained in the concrete block to neutralize it. To be treated. On the other hand, when the alkali material contained in the concrete block is exhausted to replenish a certain amount of alkali material on the concrete block top and block side to maintain the acid neutralization capacity to provide an acid mine drainage neutralization treatment system easy to maintain It was.

The present invention is (a) coarse aggregate of low-grade waste-rock generated during the limestone or dolomite mining process; Or producing permeable concrete blocks using recycled aggregate made of construction waste; And (b) installing the permeable block to form a wall having a predetermined thickness in the channel through which the acid mine drainage flows, and neutralizing the acid mine drainage passing through the permeable wall with an alkali substance contained in the concrete block. Becoming; (c) When the alkali material contained in the concrete block is exhausted, the acid mine drainage neutralization treatment system is easy to maintain by recharging a certain amount of alkali material on the top and side of the concrete block to maintain the acid neutralization capacity. do.

Hereinafter, with reference to the accompanying drawings, it will be described in more detail the present invention.

1 is a plan view of a schematic drawing according to an embodiment of the invention, and FIG. 2 is a side view.

In the acid mine drainage neutralization method according to the present invention (a) as a coarse aggregate, low-grade waste-rock generated during the mining process of limestone or dolomite; Alternatively, the production of permeable concrete blocks using recycled aggregates made of construction waste is a step of making permeable concrete blocks using coarse aggregates containing by-products containing a large amount of alkali material. At this time, the particle size of the coarse aggregate is used in the range of 4 to 25mm, while the coarse aggregate of 4 to 8mm range that can secure a minimum permeability coefficient while increasing the surface area reacting with acid mine drainage is more preferable. Water, cement, coarse aggregate, water-reducing material is used as the blending material of the water-permeable block, the compounding ratio is sufficient if the level of 28 days compression strength 50 kgf / ㎠ or more can be secured. The permeability coefficient of the permeable block produced by such a blend is used that is 0.1 cm / s or more.

In the acid mine drainage neutralization method according to the present invention, the (b) permeable block is installed to form walls (10, 20, 30) having a predetermined thickness in the channel through which the acid mine drainage flows, and the acid mine passes through the permeable wall. The step of neutralizing the waste water by reacting with the alkali substance contained in the concrete block is a kind of permeable reaction wall, which has a minimum residence time due to the permeability coefficient of the permeable block on the channel where the acid mine drainage is discharged. It is a step to neutralize the reaction by reacting with the alkali material contained in the water-permeable block. Permeable blocks are large enough not to be cut by rapid flow rates even during heavy rains in summer, and they are piled up like dikes into blocks up to the usual level in the channel so that acid mine drainage flows through the permeable walls during normal times. do. Preferably, in order to secure the stability of the installed wall is installed so that the wall thickness of the waterway bottom is thicker, and the wall thickness near the water surface is set to be inclined 1: 1 to 2: 1.

Such walls are installed at least three points on the channel where the acid mine drainage flows out (10, 20, 30), and the spacing between the walls may be flexible in consideration of the site conditions such as terrain, but it is necessary to pass all three walls. It is preferable to calculate and install a distance L for which a residence time longer than an hour can be secured in view of ensuring sufficient equilibrium arrival time required for acid neutralization.

In addition, the water-permeable wall installed on the water channel is expected to play a part as a sedimentation tank or filter paper of various heavy metal materials precipitated in the form of metal hydroxide after neutralization of acidic substances.

In the acid mine drainage neutralization method according to the present invention, when the alkali material contained in the (c) concrete block is exhausted, the acid neutralization ability is maintained by recharging a predetermined amount of the alkali material on the top of the concrete block 50 and the block side 60. In the step of maintaining the acid neutralizing material contained in the permeable block is characterized in that the acid neutralization capacity by recharging by spraying the alkaline substance such as industrial lime in the air permeable block at regular intervals. When the banks are stacked with permeable blocks, they are stacked at intervals of 1 to 5 cm between each block so that the alkaline gap can be filled in the gaps between them. In one charge, the input amount of alkaline material 24 is preferably sprayed in an amount sufficient to avoid recharging the alkaline material within one year, which is dependent on the pH and discharge flow rate of the acid mine drainage discharged from the site. It is difficult to apply, and in terms of stoichiometry, it is necessary to determine the dose of alkali substance, but to include 30% extra amount.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Example 1>

Construction waste recycled aggregate divided into 3 stages of 4 ~ 8mm, 8 ~ 14mm, 14 ~ 25mm was used as coarse aggregate, and permeable blocks were produced in compression molding machine at the mixing ratio of Table 1.

Table 1.

water cement Coarse aggregate Water reducing agent Water / cement ratio 66.9 kg 267.9 kg 1459.4 kg 2.68 kg 25%

The permeability coefficients obtained through the 28-day compressive strength and hydrostatic head permeability test of the permeable block manufactured by the formulation of Table 1 are shown in Table 2. The smaller the particle size of the coarse aggregate, the higher the compressive strength, but the 28-day compressive strength of 93kg / ㎠ or more. Permeability coefficient increased with increasing aggregate size and ranged from 0.47 to 1.86 cm / s.

Table 2.

Coarse aggregate particle size 4-8mm 8-14mm 14-25 mm 28 days compressive strength (kg / ㎠) 123.1 110.2 93.6 Permeability (cm / s) 0.47 1.26 1.86

After the permeable block is installed in the reactor made of acrylic, pH and acid neutralization ability is obtained by collecting the discharged water passing through the permeable block at regular intervals while continuously passing artificial acidic wastewater at a constant flow rate of pH 3 with a metering pump. Was measured.

The acid mine drainage was neutralized by the alkaline material contained in the permeable block while passing through the permeable block. Figure 3 shows the pH change with time of the effluent passed through the acid mine drainage. The duration of pH of the acid mine drainage was maintained above 5 depending on the particle size of the coarse aggregate, but the aggregate particle size of 4 to 8 mm was able to neutralize the flow rate corresponding to about 120 pore volume. At aggregate particle sizes of 14 mm and 14-25 mm, the flow rate corresponding to about 60 pore volumes shorter than this could be neutralized. In this embodiment, since the residence time of the acid mine drainage was shortly applied to 2.4 hours based on the permeability coefficient of the permeable block, the time required for diffusion of the alkaline substance in the permeable block was not sufficiently secured to maintain a pH of 5 or more. Although the duration is short, the acid neutralization time becomes longer if sufficient residence time is allowed.

<Example 2>

According to Example 1, when all the alkali material contained in the permeable block is exhausted, further acid neutralization effect is difficult to expect. At this time, the alkaline material such as lime is recharged by applying a predetermined amount to the gap between the top of the permeable block and the permeable block so that acid neutralization is continuously performed.

The permeable block has a large permeability coefficient, so that the acid mine drainage to be treated can pass through the wall, and the minimum retention time required for neutralization reaction and dissolution of alkaline substances can be ensured while passing through the wall. The metal hydroxide can be expected to have a filtration function by being precipitated on the pores in the permeable block and the surface of the permeable block.

Figure 4 shows the pH change of the effluent when 6 g of slaked lime as an alkaline substance is injected into the permeable block that is depleted of acid neutralization into the apparatus of Example 1. As a comparative example, 6 g of only slaked lime was injected without a permeable block, and the pH change when acidic wastewater was flowed at the same flow rate was also shown. When the slaked lime was added to the permeable block, the pH decreased to 6 or less after about 60 hours, and the pH dropped to 6 or less after about 7 hours without the permeable block. In both cases, the hydrated lime was present in the reaction tank visually, but due to the result that the acidic wastewater introduced before the hydrated lime was dissolved in the reactor was not properly neutralized. Therefore, a sufficient residence time of 10 hours or more must be secured for dissolution of acid neutralizing materials. In case that it is difficult to secure sufficient residence time due to the site condition, it is possible to inject alkaline substance into the top and side of the permeable block which exist with a relatively large surface area as shown in the result of FIG. It can be seen that it is more effective than existing in the precipitated state.

The present invention is to install a permeable block in the form of a permeable wall in the channel through which the acid mine drainage flows out so that the acid mine drainage passing through the wall reacts with the alkali material contained in the concrete block and neutralizes the acid neutralizer. In the city, additional alkaline material is applied to the permeable wall surface and sides to ensure acid neutralization for a certain period of time. When acid mine drainage flows through the permeable wall, it has the advantage of securing a certain residence time, and also serves as a precipitation tank or filter paper of various heavy metal substances precipitated in the form of metal hydroxide after neutralization of acidic substances.

Claims (3)

Low quality waste-rock from limestone or dolomite mining processes; Alternatively, a permeable concrete block made of coarse aggregate of construction wastes is installed as a coarse aggregate to form a vertical wall in the channel through which the acid mine drainage flows, so that the acid mine drainage passing through the permeable wall is contained in the concrete block. Reacting with an alkaline substance to neutralize the same; And When the alkaline material contained in the concrete block is exhausted, the step of recharging the alkaline material in the form of 'T' on the top and side of the block to maintain the acid neutralization capacity, The dose of alkaline material to be recharged is more than the stoichiometric requirement for one year, The water-permeable wall is installed in three points on the water channel through which the acid mine drainage is discharged, with a permeable block piled up to the usual level so that the acid mine drainage flows through the water-permeable wall, and passes through all three walls. Acid mine drainage neutralization treatment method characterized in that the installation at intervals to ensure a residence time of more than 10 hours The acid mine drainage neutralization method according to claim 1, wherein the coarse aggregate has a size of 4 to 25 mm. delete

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