JP2017077551A - Manufacturing method of earthwork material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an earthwork material using a residue generated after treating mud containing rare earth with acid, without needs for storing the residue, having large moisture percent content, for long time and without problems such as increase in cost by additional arrangement of treatment facilities for manufacturing the earthwork material.SOLUTION: There is provided a manufacturing method of an earthwork material using a residue generated after treating mud containing rare earth with acid, which includes a solidification process for mixing the residue and a solidification material to obtain a massive solidified article consisting of solidified residue, a fracturing process of fracturing the massive solidified article to obtain a granular fractured article and a heating process for sintering the granular fractured article at 1,110 to 1,180°C to obtain a granular earthwork material.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an earthwork material (for example, a backfill material) using mud containing rare earth as a raw material.

Rare earth is an indispensable element in the state-of-the-art technology industry as a raw material used for neodymium / iron / boron magnets, LED bulbs, fuel cells, and the like, and its demand is rapidly increasing in recent years. On the other hand, China, which was an oligopolistic producer of rare earths, is worried about a shortage of rare earth supplies and rising prices under circumstances such as changing its policy from an export incentive policy to a more restrictive policy. Securing supply sources is an issue.
Under such circumstances, deep-sea mud containing a high content of rare earth distributed over a wide area in the Pacific Ocean has attracted attention as a new source of rare earth.
Mud containing a high content of rare earths (for example, deep sea mud in the Pacific Ocean) has an enormous amount of resources and can be extracted by a simple method of immersing in dilute acid for 1 to 3 hours, thorium It has many advantages such as almost no radioactive elements such as uranium and uranium.

On the other hand, the ratio of the mass of the rare earth in the dry mass of the mud containing the rare earth is only 0.3% by mass or less even in the deep sea bottom of the Pacific Ocean, which is known to have a high content of the rare earth. For this reason, there is a problem that a large amount of acidic mud is generated when rare earth is extracted from mud containing rare earth using dilute acid.
As a method for treating this acidic mud, a method of neutralizing with an alkali agent such as sodium hydroxide can be considered. However, it is difficult to use the mud after the neutralization treatment as it is for a useful application because the mud has a large moisture content and is difficult to handle.

Under the circumstances described above, a method for treating mud containing rare earths and obtaining an earthwork material that can be used for landfill or the like is known.
For example, in Patent Document 1, an acidic residue generated after treating rare earth-containing mud with an acid and an alkaline solidifying material (for example, cement) are mixed to obtain a solidified body (for example, a landfill material) The method for solidifying a residue containing a rare earth, characterized in that
Patent Document 2 discloses that an acidic residue generated after treating rare earth-containing mud with an acid and / or a neutralized product of the acidic residue is a part of a raw material for concrete or mortar (for example, a raw material for cement). And a method for treating mud containing rare earth, characterized in that it comprises a concrete structure construction step for constructing a concrete structure.
Furthermore, Patent Document 3 describes an artificial aggregate having a crushing strength of 1,000 N or more, which is obtained by heating a raw material for producing a fired product containing an acidic residue generated after treating mud containing rare earth with an acid. ing.

JP-A-2015-120124 Japanese Patent Laying-Open No. 2015-131262 JP2015-123385A

As described above, a large amount of residue is generated after the mud containing rare earth is treated with an acid.
On the other hand, when manufacturing earthwork materials by processing this large amount of residue, the processing capacity of the processing equipment is limited, so after the treatment with the above-mentioned acid, all residues are processed as a continuous treatment. Thus, it is difficult to obtain useful earthwork materials immediately.
Moreover, after processing with the above-mentioned acid, when only a part of the residue is processed to obtain an earthwork material, the remaining part of the residue is stored for a long period of time, and a solidification process or the like is gradually performed. There is a need. However, since the residue that needs to be stored has not been solidified, there is a problem that it has a high moisture content and is difficult to handle as described above.
Furthermore, the expansion of processing facilities for the production of earthwork materials also has problems in terms of securing costs and processing land.
An object of the present invention is a method for producing an earthwork material using a residue generated after treating mud containing rare earth with an acid, and it is not necessary to store a residue having a large water content for a long period of time, and An object of the present invention is to provide a method for producing earthwork materials that does not cause problems such as an increase in cost due to the addition of processing facilities for the production of earthwork materials.

  As a result of diligent studies to solve the above problems, the present inventor mixed a solidified material with a residue generated after treating a rare earth-containing mud with an acid, and a solidified product obtained by solidifying the residue. After that, the lump solidified material is crushed to obtain a granular crushed material, and then the granular crushed material is sintered at 1,110 to 1,180 ° C. to obtain a granular earthwork material. As a result, the inventors have found that the above object can be achieved and completed the present invention.

That is, the present invention provides the following [1] to [5].
[1] A method for producing earthwork material using a residue generated after treating rare earth-containing mud with an acid, and mixing the residue with a solidifying material to solidify the residue to form a solid A solidifying step for obtaining a product, a crushing step for crushing the massive solidified product to obtain a granular crushed product, and sintering the granular crushed product at 1,110 to 1,180 ° C. The manufacturing method of the earthwork material characterized by including the heating process which acquires material.
[2] The method for producing an earthwork material according to [1], wherein the solidifying material is cement, cement-based solidifying material, lime, lime-based solidifying material, or magnesia-based solidifying material.
[3] The method for producing an earthwork material according to the above [1] or [2], wherein the amount of the solidifying material added is ³⁰ to 400 kg per 1 m ^{3 of the} residue.
[4] The method for producing an earthwork material according to any one of [1] to [3], wherein the crushed material includes particles having a particle size of 1 to 20 mm at a ratio of 50% by mass or more.
[5] The above earthwork material is a backfill material, a landfill material, a fill material, a roadbed material, a buffer material for a buffer layer below the roadbed, a sand compaction material in a sand compaction pile method, or an aggregate. The manufacturing method of the earthwork material in any one of 1]-[4].

According to the present invention, there is included a solidification step of mixing the residue and the solidified material to obtain a solidified solid product obtained by solidifying the residue, and this solidification step is for forming into a pellet form. Since no molding equipment is required, a large amount of residue can be processed at a time. For this reason, there is no need to store a residue having a large water content for a long period of time.
According to the present invention, since the crushing step and the heating step are included after the solidification step, the crushing step and the heating are performed in accordance with the processing capacity of the processing equipment (specifically, the crushing equipment and the heating equipment). Each of the processes may be performed in an appropriate amount at an appropriate time, and there is no need to add crushing equipment or heating equipment.

The method for treating mud containing rare earth according to the present invention is a method for producing earthwork material using a residue generated after treating mud containing rare earth with an acid, and mixing the residue and solidifying material, A solidification step of obtaining a lump solidified product obtained by solidifying the residue, a crushing step of crushing the lump solidified product to obtain a granular crushed product, and 1,110 to 1,180 of the granular crushed product. And a heating step of obtaining a granular earthwork material by sintering at ° C.
Hereinafter, it demonstrates for every process.
[Solidification process]
The solidification step is a step of obtaining a lump solidified product obtained by mixing a residue (usually acidic) generated after treating rare earth-containing mud with an acid and a solidifying material to solidify the residue.
In the present invention, the residue generated after the rare earth-containing mud is treated with an acid (hereinafter sometimes abbreviated as “residue”) means that the rare earth-containing mud is treated with an acid (for example, dilute hydrochloric acid). It is an acidic residue generated after the rare earth is extracted into the liquid.
Rare earth refers to 17 elements obtained by adding Sc (scandium) and Y (yttrium) to group 3 lanthanoids (La (lanthanum) to Lu (lutetium)) of the periodic table.

As an example of mud containing rare earth, it is distributed in layers on the deep sea floor (for example, the area of 3,500 to 6,000 m as the depth of the sea) (for example, the ground from the sea floor to a depth of about several tens of meters). And mud with a high rare earth content.
In the present invention, the content (mass basis) of the rare earth in the mud containing rare earth (in the dry state; solid content) is preferably 1, from the viewpoint of economy when mining the rare earth as a resource. 000 ppm or more, more preferably 2,000 ppm or more.

The moisture content of the residue (ratio of the moisture content of the residue with respect to 100% by mass of the dry mass of the residue) is not particularly limited, but is preferably 200% by mass or less, more preferably from the viewpoint of reducing the load on heating means such as a heating furnace. It is 150 mass% or less, Most preferably, it is 100 mass% or less.
As a method (method) for reducing the moisture content of the residue, the mud is stored in a container such as a tank, the solid content of the mud is precipitated, and the supernatant is recovered, and the centrifugal method using an apparatus such as a screw decanter. Examples thereof include a separation method and a pressure dehydration method using an apparatus such as a filter press.
Among these, the precipitation method and the centrifugal separation method are preferable, and the precipitation method is more preferable because it can be easily dehydrated at low cost.
The degree of dehydration increases in the order of the precipitation method, the centrifugal separation method, and the pressure dehydration method.

Examples of the solidifying material used in the solidifying step include alkaline solidifying materials such as cement, cement-based solidifying material, lime, lime-based solidifying material, and magnesia-based solidifying material.
Here, the alkaline solidifying material is a solidifying material whose pH becomes an alkaline region when dissolved in water.
Examples of the cement include various portland cements such as ordinary portland cement, early-strength portland cement, medium heat portland cement, and low heat portland cement, mixed cements such as blast furnace cement and fly ash cement, and ecocement.
The cement-based solidifying material is a solidifying material containing cement as a main component (usually 50% by mass or more) and containing various active ingredients as subcomponents. Examples of commercially available products include “Geoset” (trade name) manufactured by Taiheiyo Cement.
Examples of lime include quick lime and slaked lime.
The lime-based solidified material is a solidified material containing lime as a main component (usually 50% by mass or more) and various active ingredients as subcomponents.
Examples of the magnesia-based solidifying material include light-burned magnesia (also referred to as light-burned magnesium oxide) obtained by baking magnesium carbonate or magnesium hydroxide at a low temperature (600 to 900 ° C.).

The amount of solidifying material varies depending pH of the residue, the residue (usually those acidic) neutralizes, from the viewpoint of obtaining a solidified body pH region close to neutrality or neutral, to residue 1 m ³ And preferably 30 to 400 kg, more preferably 50 to 350 kg, still more preferably 100 to 300 kg, particularly preferably 150 to 250 kg.
Examples of the mixing means for mixing the residue and the solidifying material include various mixers and backhoes.
Moreover, a residue and a solidification material can also be mixed by adding a solidification material slurry to the residue under pressure feeding using compressed air.
Furthermore, a solidified slurry can be added to the residue spread on the ground and mixed to obtain a lump solidified product.

The size of the lump solidified product obtained by solidifying the residue (the product resulting from the hydration reaction of the mixture of the residue and the solidified material) is not particularly limited, but usually the lower limit is about several mm and the upper limit is several tens. It is about cm.
The lump solidified product may be immediately processed in the crushing step, which is the next step, or stored for an appropriate period (for example, a short period of several days or a long period of several months or more). After that, you may process by a crushing process.
If the solidified solid is used as a material for forming the ground surface (for example, the upper surface of embankment or the upper surface of a landfill formed as temporary storage), the solidified material can be used for the hydration reaction of the solidified material. Along with this, trafficability (travelability of vehicles such as construction machines) is improved, and the efficiency of construction work and the like can be increased.
The lump solidified product can be easily and quickly moved using a large construction machine such as a hydraulic excavator.
Moreover, the lump solidified material stored as a banking landfill or a temporary landfill can be easily dug up using a large construction machine such as a hydraulic excavator. At this time, crushing as a part of the crushing process, which is the next process, can be performed using a construction machine.

[Crushing process]
The crushing step is a step of crushing the lump solidified product obtained in the solidifying step to obtain a granular crushed product.
Examples of the crushing means for crushing the lump solidified product obtained in the solidification step include a roll crusher, a jaw crusher, and a corn crusher.
In addition, as described above, a part of the lump solidified material stored as embankment or temporary landfill is crushed to an appropriate size when digging up using a large construction machine such as a hydraulic excavator. . The solidified material after being dug up can be further crushed to a desired particle size using the above-mentioned crushing means (for example, a roll crusher).
The granular crushed material preferably contains particles having a particle size of 1 to 40 mm in a proportion of 50% by mass or more, more preferably 50% by mass of particles having a particle size of 5 to 30 mm. It is included in the above ratio, and particularly preferably includes particles having a particle size of 8 to 20 mm in a ratio of 50% by mass or more. By having such a particle size distribution, a sintered body (granular material) having a shape, particle size, and crushing strength suitable as an earthwork material can be obtained after the heating step which is the next step.
Here, the particle size refers to the maximum dimension of the granular body (for example, the dimension of the major axis when the cross section is substantially elliptical).

In the present invention, a large lump solidified product having a particle size of several tens of centimeters can be crushed so as to have a desired particle size after firing in the heating step, which is the next step. However, crushing before firing reduces the energy consumption required for crushing because crushing is easy because the strength of the lump solidified product is smaller. Also in the heating process, which is the next process, heating efficiency is better when the particle size of the lump solidified product is not too large.
When the granular crushed material does not have the above-described preferable particle size distribution, the granular crushed material can be classified to adjust the particle size distribution to a preferable one. Classification can be performed using a sieve etc., for example.

[Heating process]
The heating step is a step in which the granular crushed material obtained in the crushing step is sintered (heated) at 1,110 to 1,180 ° C. to obtain a granular earthwork material (a granular material that is a sintered body). .
It does not specifically limit as a heating means for obtaining a granular earthwork material, Both a continuous type means and a batch type means can be used.
Examples of the continuous heating means include a rotary kiln and a tunnel furnace.
Examples of the batch type heating means include an incinerator (using gas or the like as a fuel), an electric furnace, a microwave heating device, and the like.
Among them, it is preferable to use a rotary kiln from the viewpoint of increasing the processing efficiency.

The heating temperature is 1,110 to 1,180 ° C, more preferably 1,120 to 1,160 ° C, and particularly preferably 1,120 to 1,140 ° C.
If the temperature is less than 11,110 ° C., sintering does not occur, or the time required for sintering is excessive, and the processing efficiency decreases. When the temperature exceeds 1,180 ° C., the sintered state shifts to the molten state, and the resulting granular material becomes a large lump or is fused to hinder firing.
In particular, when the temperature is 1,120 to 1,140 ° C., the shape of the granular material is not rounded, but becomes irregular (appropriately angular), so various earthwork materials such as backfilling materials Can be obtained.
The holding time of the above heating temperature is preferably 10 to 60 minutes, more preferably 15 to 40 minutes, and particularly preferably 20 to 30 minutes. When the holding time is 10 minutes or more, sintering is more sufficiently performed, and the crushing load of the obtained granular material can be further increased. It is preferable in terms of processing efficiency that the holding time is 60 minutes or less.

The crushing strength of the granular earthwork material is preferably 1,000 N or more, more preferably 1,100 N or more, further preferably 1,200 N or more, more preferably 1,300 N or more, more preferably 1,400 N or more, and further preferably Is 1,500 N or more.
The crushing strength can be measured in accordance with “3.1 Crushing strength test method” of “JIS Z 8841-1993” (granulated product—strength test method).
The granular earthwork material can be further classified according to the intended use (for example, fine aggregate). Classification can be performed using a sieve etc., for example.
Granular earthwork materials include backfill material, landfill material, embankment material, roadbed material, buffer material for the buffer layer below the roadbed, sand compaction material in the sand compaction pile method, aggregate (fine aggregate or coarse for concrete) Aggregate or asphalt aggregate).

  Since mud containing rare earth is usually present in the deep ocean floor of the Pacific Ocean far from the mainland, a large amount of residue generated after treating mud containing rare earth with acid should be transported to the mainland for treatment. Is not economical. In the present invention, in a remote island far away from the mainland (island of the sea area where mud containing rare earth is collected), this large amount of residue is separated in each step of the solidification step, crushing step, and heating step. Depending on the processing capacity of the processing facility, it is possible to produce a granular material that can be processed in a planned and efficient manner and can be used as an earthwork material.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[material]
The following materials were used.
(1) Mud containing rare earth (Deep sea mud with a depth of 4,000 m or more in the Pacific Ocean; rare earth content in the solid content of the mud: 2,000 ppm or more on a mass basis (2) Ordinary Portland cement (Pacific Cement Co., Ltd.) Made)
(3) Blast furnace cement type B (manufactured by Taiheiyo Cement)
(4) Eco cement (manufactured by Taiheiyo Cement)
(5) Cement-based solidified material A (trade name: Geoset 200; manufactured by Taiheiyo Cement)
(6) Cement-based solidifying material B (trade name: Geoset 225; manufactured by Taiheiyo Cement)
(7) Quicklime powder

[Example 1]
The mud containing rare earth was immersed in 0.1N hydrochloric acid for 1 hour, and then dehydrated by a centrifugal separation method so that the water content ratio was about 50% by mass to obtain a residue.
50 g of this residue and 7.25 g of ordinary Portland cement were mixed to obtain a lump solidified product.
The amount of ordinary Portland cement added corresponds to 200 kg per 1 m ^{3 of} residue. Moreover, it shape | molded in the cylindrical shape of (phi) 3.5cm x 7cm as a lump solidified material.
Next, the solidified solid body was subjected to moisture curing for 7 days, and then crushed using an iron mortar to obtain a granular crushed material.
The obtained granular crushed material contained particles having a particle size of 8 to 20 mm at a ratio of 50% by mass or more.
The granular crushed material was sieved to obtain granules having a particle size of 10 to 12 mm.

The granules (particle size: 10 to 12 mm) were dried at 100 ° C. for 24 hours, and then heated with increasing temperature over time in an electric furnace.
This heating was performed by raising the temperature to a target temperature described below (for example, 1,100 ° C.) under a temperature increase condition of 10 ° C./min, and then maintaining the target temperature for 20 minutes. .
As a result, the following states were observed for the granular crushed material.
At 1,100 ° C., sintering did not occur yet.
At 1,110 ° C., sintering started to proceed.
At 1,120 ° C., sintering proceeded considerably.
The sintering proceeded sufficiently at 1,130 ° C., and the shape of the granular crushed material maintained an angular indefinite shape.
At 1140 ° C., the shape of the granular crushed material began to be slightly rounded due to melting.
At 1,150 ° C., the roundness of the granular crushed material increased.
At 1160 ° C., the roundness of the granular crushed material was further increased.
At 1170 ° C., granular crushed material began to melt.
At 1180 ° C., the granular crushed material melted and the shape could not be maintained.
At 1190 ° C., the granular crushed material melted and fused to the refractory.
At 1,200 ° C., the state of the granular crushed material was almost the same as that at 1,190 ° C.

Next, a load was applied to the granular material (sintered granular crushed material) taken out at a temperature of 1,140 ° C. until it was crushed in the diameter direction, and the crushing strength was measured.
The measurement of crushing strength was based on “3.1 Crushing strength test method” of “JIS Z 8841-1993” (granulated product—strength test method).
As a result, the value of the crushing strength was 1,652N.

[Example 2]
Experiments were conducted in the same manner as in Example 1 except that 7.25 g of normal Portland cement was used and 7.25 g of blast furnace cement B was used.
As a result, the same observation results as in Example 1 were obtained for the state of the granular crushed material during the heating temperature ranging from 1,100 ° C. to 1,200 ° C.
The value of the crushing strength of the granular material taken out at a temperature of 1,140 ° C. was 1,538N.
[Example 3]
The experiment was conducted in the same manner as in Example 1 except that 7.25 g of eco-cement was used instead of 7.25 g of ordinary Portland cement.
As a result, the same observation results as in Example 1 were obtained for the state of the granular crushed material during the heating temperature ranging from 1,100 ° C. to 1,200 ° C.
Moreover, the value of the crushing strength of the granular material taken out at a temperature of 1,140 ° C. was 1,281 N.

[Example 4]
Experiments were conducted in the same manner as in Example 1 except that 7.25 g of cement-based solidified material A (Geoset 200) was used instead of 7.25 g of ordinary Portland cement.
As a result, the same observation results as in Example 1 were obtained for the state of the granular crushed material during the heating temperature ranging from 1,100 ° C. to 1,200 ° C.
Moreover, the value of the crushing strength of the granular material taken out at a temperature of 1,140 ° C. was 1,427 N.
[Example 5]
Experiments were conducted in the same manner as in Example 1 except that 7.25 g of cementitious solidified material B (Geoset 225) was used instead of 7.25 g of ordinary Portland cement.
As a result, the same observation results as in Example 1 were obtained for the state of the granular crushed material during the heating temperature ranging from 1,100 ° C. to 1,200 ° C.
Moreover, the value of the crushing strength of the granular material taken out at a temperature of 1,140 ° C. was 1,364N.

[Example 6]
An experiment was conducted in the same manner as in Example 1 except that 7.25 g of quick lime was used instead of 7.25 g of ordinary Portland cement.
As a result, the same observation results as in Example 1 were obtained for the state of the granular crushed material during the heating temperature ranging from 1,100 ° C. to 1,200 ° C.
Moreover, the value of the crushing strength of the granular material taken out at a temperature of 1,140 ° C. was 1,263 N.
From the result of the above Examples 1-6, according to this invention, it turns out that the granular material which can be used suitably as various earthwork materials can be manufactured.

Claims (5)

A method for producing earthwork materials using residues generated after treating mud containing rare earth with acid,
A solidification step of mixing the residue and a solidifying material to obtain a lump solidified product formed by solidifying the residue;
Crushing step to obtain a granular crushed material by crushing the lump solidified product,
Sintering the granular crushed material at 1,110 to 1,180 ° C. to obtain a granular earthwork material,
A method for producing an earthwork material characterized by comprising:   The method for producing an earthwork material according to claim 1, wherein the solidifying material is cement, cement-based solidified material, lime, lime-based solidified material, or magnesia-based solidified material. The additive amount of the solidifying material is, the residue 1 m ³ per earthwork method for producing a material according to claim 1 or 2 is 30～400Kg.   The method for producing an earthwork material according to any one of claims 1 to 3, wherein the crushed material contains particles having a particle size of 1 to 20 mm at a ratio of 50 mass% or more.   The earthwork material is a backfill material, a landfill material, a fill material, a roadbed material, a buffer material for a buffer layer below the roadbed, a sand compaction material in a sand compaction pile method, or an aggregate. The manufacturing method of the earthwork material of any one item | term.