JP7062222B2 - Acid water treatment condition design method and acid water treatment method - Google Patents

Description

The present invention relates to a method for designing treatment conditions for acidic water and a method for treating acidic water.

In an area with a sulfide ore deposit, the oxidized sulfide ore dissolves in groundwater, causing the river near the deposit to become acidic with sulfuric acid, which may become acidic river water. Such acidic river water is harmful to living organisms and plants, and tends to corrode civil engineering structures such as bridges and dams. Therefore, it is necessary to neutralize acidic river water for the purpose of maintaining the ecosystem and extending the life of civil engineering structures.

On the other hand, rivers near the ore deposits are often in an acidic state semi-permanently, and along with this, it is necessary to neutralize semi-permanently at the acid river water treatment plant. As such a neutralization treatment method, a method of adding limestone (calcium carbonate), which is a natural resource, as a neutralizing agent into acidic water to be treated has been conventionally used. Further, as other neutralization treatment methods, a method of adding magnesium oxide and / or magnesium hydroxide to acidic water (Patent Document 1) and a method of adding a calcium compound and a magnesium compound to acidic water at once (Patent Document 1). 2), a two-step neutralization method (Patent Document 3) in which a magnesium compound is added after addition of calcium carbonate has been proposed.

Japanese Patent Application Laid-Open No. 2003-190969 Japanese Patent Application Laid-Open No. 2003-251371 Japanese Unexamined Patent Publication No. 2016-10757

By the way, as described above, since it is necessary to neutralize acidic river water semi-permanently, a treatment method that reduces the neutralization treatment cost of acidic water as much as possible is desired. The cost of the neutralization treatment of acidic water includes, for example, the cost due to the raw material of the neutralizing agent used and the amount thereof (hereinafter, also referred to as the raw material cost), and the dredging and dredging of the neutralizing material generated during the neutralization treatment. Costs resulting from industrial waste disposal (hereinafter also referred to as disposal costs) are included. These costs must be taken into account in the actual treatment of acidic water.

However, when limestone is added as a neutralizing agent, the amount of neutralizing agent input increases and the raw material cost increases, and in addition, a large volume of neutralizing burial material is generated and the disposal cost increases. As a result, the cost of neutralizing acidic water increases significantly. Further, when the neutralization treatment method described in Patent Documents 1 to 3 is adopted, the raw material cost can be reduced as compared with the case of limestone, but the volume of the neutralized burial material is equal to or increased, and the disposal cost is increased. Cannot be reduced. Therefore, there is a problem that the treatment cost of acidic water cannot be sufficiently reduced.

Therefore, in view of the above-mentioned problems, in the present invention, the conditions for adding the neutralizing agent so as to reduce both the amount of the neutralizing agent added and the volume of the neutralizing substance are rationalized according to the properties of the acidic water to be treated. It is an object of the present invention to provide a method for designing treatment conditions for acidic water that can be specifically designed and a method for treating acidic water using the design method.

As a result of diligent studies to solve the above problems, the present inventors have neutralized by adding a neutralizing agent containing a calcium compound and a magnesium compound to acidic water as compared with the prior art. It has been found that the amount of the agent added and the volume of the neutralizing compound can be reduced. Furthermore, the present inventors have found that there is a relationship between the particle size of the neutralizing agent, the amount of the neutralizing agent added, and the volume of the neutralizing ridge.

Based on these findings, the present inventors have previously obtained a relational expression between the particle size of the neutralizing agent, the amount of the neutralizing agent added, and the volume of the neutralizing ridge, and neutralize based on the relational expression. We have found that the neutralization treatment cost can be reduced as compared with the conventional method by designing the particle size and the required input amount of the agent, and have completed the present invention.

That is, in the present invention, a neutralizing agent containing a calcium compound and a magnesium compound and crushed is put into acidic water to be treated for neutralization treatment, and the volume of the neutralizing agent in a cumulative volume of 90% by volume. The following equation (a), which is the relational expression between the cumulative particle size and the input amount, and
y = α × D + β ・ ・ ・ Equation (a)
y: Neutralizing agent input amount per 1 L of acidic water (g / L)
D: Cumulative volume particle diameter (μm) at a cumulative volume of 90% by volume of the neutralizer
α: Slope of regression line
β: Intercept of regression line Formula (b), which is a relational expression between the volume cumulative particle diameter and the volume of the neutralizing ridge in the cumulative volume of 90% by volume of the neutralizing agent, is obtained in advance.
z = γ × D + δ ・ ・ ・ Equation (b)
z: Volume of neutralizing substance per 1 L of acidic water (mL / L)
γ: Slope of regression line
δ: Intercept of regression line Based on the relational expressions of the formulas (a) and (b), the treatment conditions for acidic water for designing the volume cumulative particle size and the input amount in the cumulative volume of 90% by volume of the neutralizing agent. Regarding the design method.

The present invention also relates to a method for designing treatment conditions for acidic water, wherein the formulas (a) and (b) are obtained using the neutralizing agent having a cumulative volume particle diameter of 20 μm or more and 150 μm or less in a cumulative volume of 90% by volume. .. The present invention determines the formulas (a) and (b) using the neutralizing agent containing 65% by mass or more and 95% by mass or less of calcium carbonate and 5% by mass or more and 35% by mass or less of magnesium hydroxide. Regarding the treatment condition design method for acidic water. The present invention relates to a method for designing treatment conditions for acidic water in which calcium carbonate and magnesium hydroxide are uniformly mixed in one particle of the neutralizing agent. The present invention relates to a method for designing treatment conditions for acidic water, which is a residue produced by producing magnesium hydroxide by the reaction of the neutralizing agent with seawater and slaked lime. The present invention relates to a method for designing treatment conditions for acidic water, wherein the formulas (a) and (b) are obtained using the acidic water composed of river water into which acidic mineral spring water flows.

Further, in the present invention, the cumulative volume 90 of the neutralizing agent is such that the volume of the neutralizing ridge is smaller than the volume of the precipitate generated when the limestone is put into the acidic water and subjected to the neutralization treatment. The present invention relates to a method for designing treatment conditions for acidic water, which designs the cumulative volume particle size and the input amount in% by volume. In the present invention, the cumulative volume of the neutralizing agent 90 is such that the amount of the neutralizing agent added is smaller than the amount of the limestone added when the limestone is added to the acidic water to perform the neutralization treatment. The present invention relates to a method for designing treatment conditions for acidic water, which designs the cumulative volume particle size and the input amount in% by volume. In the present invention, the volume of the neutralizing agent in a cumulative volume of 90% by volume so that the total amount of the neutralizing agent input amount and the volume of the neutralizing substance is the minimum value or the minimum value is ± 10%. The present invention relates to a method for designing treatment conditions for acidic water, which designs the cumulative particle size and the input amount.

Further, in the present invention, the acidity for which the neutralizing agent is treated is based on the volume cumulative particle size and the input amount at the cumulative volume of 90% by volume of the neutralizing agent designed by the above-mentioned method for designing treatment conditions for acidic water. The present invention relates to a method for treating acidic water, which is applied to water for neutralization.

According to the present invention, it is possible to rationally design the conditions for adding the neutralizing agent, which can reduce the neutralization treatment cost of acidic water, in consideration of the raw material cost of the neutralizing agent and the disposal cost of the neutralizing substance.

FIG. 1 is a scanning electron microscope image of a residue obtained in the step of reacting seawater with slaked lime to produce magnesium hydroxide. FIG. 2A is a scanning electron microscope image of the residue (enlarged image corresponding to FIG. 1), FIG. 2B is an elemental mapping image of magnesium in the microscope image of FIG. 2A, and FIG. (C) is an elemental mapping image of calcium in the microscope image of FIG. 2 (a). FIG. 3 is an example of a graph of the results of measuring the particle size distribution of the neutralizing agent with a laser diffraction / scattering type particle size distribution measuring device.

Hereinafter, the method for designing treatment conditions for acidic water of the present invention and the method for neutralizing acidic water using the design method will be described in detail based on the preferred embodiment thereof. However, the present invention is not limited to the following embodiments.

<Design method for acid water treatment conditions>
In the method for designing treatment conditions for acidic water of the present invention, a neutralizing agent containing a calcium compound and a magnesium compound and crushed is put into the acidic water to be treated for neutralization, and the particle size of the neutralizing agent is used. The relational expression between the amount of the neutralizing agent and the amount of the neutralizing agent added, and the relational expression between the particle size of the neutralizing agent and the volume of the neutralizing compound, which is an insoluble precipitate produced by the neutralization treatment, are obtained in advance, and these relationships are obtained. The particle size and the amount of the neutralizing agent are designed based on the formula. The details of the neutralizing agent will be described later.

First, the neutralizing agent is added to the acidic water to be treated and the neutralization treatment is performed. The following formula (b) is obtained in advance as a relational formula between the particle size and the volume of the neutralized structure.

y = α × D + β ・ ・ ・ Equation (a)
y: Neutralizing agent input amount per 1 L of acidic water (g / L)
D: Cumulative volume particle diameter (μm) at a cumulative volume of 90% by volume of the neutralizer
α: Slope of regression line β: Intercept of regression line

z = γ × D + δ ・ ・ ・ Equation (b)
z: Volume of neutralizing substance per 1 L of acidic water (mL / L)
γ: Slope of regression line δ: Intercept of regression line

As shown in the above formulas (a) and (b), the relationship between the particle size of the neutralizing agent and the input amount and the relationship between the particle size of the neutralizing agent and the volume of the neutralizing compound are linear equations, respectively. It is represented. Therefore, in order to obtain the slope and intercept of the regression line from these relational expressions, neutralization treatment is performed using neutralizing agents having different particle sizes, and the amount of neutralizing agent input and the volume of the neutralizing ridge are determined. Each can be obtained by measuring and performing a linear approximation from the result. Unless otherwise specified, the "particle size" in the present specification refers to the volume cumulative particle size at a cumulative volume of 90% by volume by the laser diffraction / scattering type particle size distribution measurement method.

From the viewpoint of reducing the cost required for designing the optimum neutralization treatment conditions, the neutralization treatment for obtaining the slope and section of the regression line in the above formulas (a) and (b) is performed by at least two different particle diameters. It is preferable to use a neutralizing agent having a neutralization agent, and from the viewpoint of improving the precision of the neutralization treatment condition design, it is more preferable to use a neutralizing agent having five different particle sizes, and eight different types. It is more preferable to use a neutralizing agent having a particle size, and it is particularly preferable to use a neutralizing agent having 10 different particle sizes. That is, in determining the formulas (a) and (b), preferably 2 points or more, more preferably 5 points or more, still more preferably 8 points or more, and particularly preferably 10 points, using neutralizing agents having different particle sizes. After performing the above neutralization treatment, the amount of neutralizing agent added and the volume of neutralizing particles are measured.

The correlation coefficient indicating the strength of the correlation between the amount of the neutralizing agent added and the particle size and the correlation coefficient indicating the strength of the correlation between the volume of the neutralizing ridge and the particle size of the neutralizing agent are absolute values. However, it is preferably 0.75 or more independently, and more preferably 0.80 or more. By having such a correlation coefficient, the precision of the neutralization treatment condition design can be improved, and as a result, the neutralization treatment condition can be designed so as to reduce the neutralization treatment cost. The correlation coefficient can be obtained together with the regression line by the linear approximation in the above equations (a) and (b).

The neutralization treatment for obtaining the formula (a) and the neutralization treatment for obtaining the formula (b) may be performed simultaneously or independently. Since the amount of the neutralizing agent added to the acidic water and the volume of the neutralizing substance can be measured from one neutralization treatment, the neutralization treatment for obtaining the formulas (a) and (b) is performed. From the viewpoint of treatment efficiency, it is preferable to carry out the neutralization treatment once.

In addition, the neutralization treatment for obtaining the formulas (a) and (b) can be performed by sampling a certain amount of acidic water to be treated, so that the amount of the neutralizing agent input and the volume of the neutralizing ridge can be accurately measured. It is preferable in that it can be measured. From the same viewpoint, it is preferable to perform the neutralization treatment using sampled acidic water for each particle size of the neutralizing agent to be used.

As described above, the particle size of the neutralizing agent used in the present invention refers to the volume cumulative particle size at a cumulative volume of 90% by volume by the laser diffraction / scattering type particle size distribution measurement method. The particle size of the neutralizing agent is determined by measuring the particle size distribution of the neutralizing agent using, for example, a particle size distribution measuring device described later in Examples, and the cumulative volume is obtained from the relationship line between the obtained particle size and the cumulative volume frequency. It can be obtained as a particle size of 90%.

From the viewpoint of accurately obtaining the relational expressions (a) and (b), the volume cumulative particle diameter at a cumulative volume of 90% by volume measured by the laser diffraction / scattering particle size distribution measurement method is preferably 20 μm or more and 150 μm or less, more preferably 25 μm or more and 140 μm. Hereinafter, it is more preferable to obtain the formulas (a) and (b) by using a neutralizing agent having a thickness of 30 μm or more and 130 μm or less. When the particle size of the neutralizing agent is 20 μm or more, the particles of the neutralizing agent are not too fine and it is prevented that many gel-like neutralizing particles are generated, so that the volume of the neutralizing agents is extremely increased. As a result, it is prevented that the correlation coefficient of the above equation (b) is lowered. Further, when the particle size of the neutralizing agent is 150 μm or less, the neutralization rate is prevented from slowing down, so that an increase in the amount of the neutralizing agent input can be prevented, and as a result, the phase relationship of the above formula (a) is prevented. It prevents the number from dropping.

In order to obtain such a particle size of the neutralizing agent, it can be adjusted by pulverization using a pulverizer, sieving, or a combination thereof. In particular, from the viewpoint of reducing the amount of the neutralizing agent added and the volume of the neutralizing substance to improve the neutralizing performance, the neutralizing agent added to the present invention has a particle size within the above range. It is preferable to use crushed particles on condition that the particles become crushed. As a method for pulverizing the neutralizing agent, for example, a known pulverizer such as a ball mill, a roller mill, a jet mill, a hammer mill, a pin mill, or a disc mill can be used.

The amount of the neutralizing agent added refers to the mass of the neutralizing agent added to the acidic water until the pH changes from the pH before the addition of the neutralizing agent to a predetermined pH in the neutralization treatment. For example, the amount of the neutralizing agent added is determined by adding a predetermined amount of the neutralizing agent to acidic water having a pH of less than 7 to be treated and measuring the amount required to neutralize to pH 7 after a predetermined time as a mass. be able to. The details will be described in Examples described later.

The neutralizing agent used in the neutralization treatment may be in a dry state or may be in a wet state. Specifically, the neutralizing agent may be added as it is as particles such as powder or agglomerates thereof, or as a slurry-like dispersion liquid in which particles of the neutralizing agent are dissolved or dispersed in a dispersion medium such as water. You may put it in. When the neutralizing agent is used in a wet state or as a dispersion liquid, the input amount is converted into solid content.

The volume of the neutralizing substance refers to the volume of the precipitate generated when the neutralizing agent is added until the pH changes from the pH before the neutralizing agent is added to a predetermined pH in the neutralization treatment. For the volume of the neutralized deposit, for example, acid water after changing to a predetermined pH (for example, after neutralization treatment) is placed in a volume measuring container such as a graduated test tube or a measuring cylinder to stabilize the volume of the precipitate. It can be measured by reading the scale after allowing it to stand still. The details will be described in Examples described later.

Next, the optimum neutralization is performed from the relational expressions of the formulas (a) and (b) obtained from the relationship between the particle size of the neutralizing agent, the actually measured amount of the neutralizing agent and the volume of the neutralizing ridge. The particle size of the neutralizing agent and the amount of the neutralizing agent input are designed so as to show the effect. The optimum neutralization effect is a neutralization effect according to the properties of the acidic water to be treated, for example, reduction of the load on the structure and the surrounding environment, reduction of the neutralization treatment cost of the acidic water, or these. The effect of paying attention to the combination of the above can be mentioned.

From the viewpoint of reducing the load on structures such as dams and the surrounding environment, for example, the volume of the neutralized particles is larger than the volume of the precipitate generated when the neutralization treatment is performed using limestone as a neutralizing agent. The conditions of the particle size and the amount of the neutralizing agent to be used can be designed so as to reduce the amount of the neutralizing agent used.

In addition, from the viewpoint of reducing the cost of neutralization treatment, the raw material cost of the neutralizing agent used and the amount of the raw material input thereof, and the disposal caused by the dredging and industrial waste disposal of the neutralization ridge generated during the neutralization treatment. It can be designed to reduce both costs. That is, the conditions of the particle size and the amount of the neutralizing agent to be used can be designed so that both the amount of the neutralizing agent added and the volume of the neutralizing agent are reduced. Specifically, the particle size and the amount of the neutralizing agent used so that the total amount of the neutralizing agent input amount and the volume of the neutralizing ridge obtained from the formulas (a) and (b) is the minimum value. Conditions can be designed.

Further, in designing the conditions of the particle size and the input amount, it is not always necessary to adopt the minimum value of the total amount of the neutralizing agent input amount and the neutralization volume, as long as the effect of the present invention is exhibited. It is also possible to design the conditions for the particle size and the amount of the neutralizing agent to be used, with a certain allowable upper and lower limit widths. The neutralizing agent particles used in the present invention have a constant upper and lower limit width, for example, preferably a minimum value of ± 10%, and more preferably a minimum value of ± 5%. Conditions for diameter and input amount can be designed.

Similarly, when the treatment target is acidic water having properties that the raw material cost of the neutralizing agent does not increase so much, but the disposal cost of the neutralizing volume increases significantly, limestone is used as the neutralizing agent. It is possible to design the conditions of the particle size and the amount of the neutralizing agent to be used so that the volume of the neutralizing deposit is smaller than the volume of the precipitate generated when the neutralization treatment is performed using the neutralizing agent. ..

Similarly, in the case of acidic water having properties such that the raw material cost of the neutralizing agent increases significantly, but the disposal cost of the neutralizing substance does not increase so much, for example, limestone is used as the neutralizing agent in the acidic water. The condition of the particle size of the neutralizing agent to be used can be designed so that the amount of the neutralizing agent added is smaller than the amount of the limestone charged when the neutralizing treatment is performed.

As described above, the method for designing the treatment conditions for acidic water of the present invention is, for example, the structure and surrounding environment of the acidic water disposal site, the properties of the acidic water to be treated, the increase / decrease in the raw material cost of the neutralizing agent, and the neutralization product. It is possible to rationally design the optimum treatment conditions according to the effect of the target neutralization treatment, such as an increase or decrease in the disposal cost of the water.

<Neutralization method of acidic water>
Further, in the method for neutralizing acidic water of the present invention, the neutralizing agent is treated with the acidic water to be treated based on the particle size and the amount of the neutralizing agent designed by the method for designing the treatment conditions of the acidic water of the present invention. Can be neutralized by putting it in the water. The neutralizing agent and acidic water used in the method for neutralizing acidic water of the present invention are the same as those used in the method for designing treatment conditions for acidic water of the present invention.

In particular, the method for neutralizing acidic water of the present invention can be carried out based on treatment conditions in consideration of the raw material cost of the neutralizing agent and the disposal cost of the neutralizing substance, so that the neutralization treatment cost of acidic water is further reduced. It can be reduced, and as a result, various problems of the acid water treatment plant can be solved.

The above is a description of the method for designing treatment conditions for acidic water of the present invention and the method for neutralizing acidic water using the design method. The following describes the neutralizing agent used in the present invention and the acidity of the treatment target. Explain water.

<Neutralizer>
The neutralizing agent used in the present invention is preferably a neutralizing agent containing a calcium compound and a magnesium compound. Examples of the calcium compound include calcium carbonate, calcium hydroxide, calcium oxide and the like. Examples of the magnesium compound include magnesium hydroxide, magnesium oxide and magnesium carbonate. The above-mentioned calcium compounds may be used alone or in combination of two or more. Further, the magnesium compound may be used alone or in combination of two or more.

The neutralizing agent used in the present invention preferably contains calcium carbonate as a calcium compound from the viewpoint of achieving both the neutralization rate and the reduction of the amount of the neutralizing agent added and the volume of the neutralizing substance. When calcium carbonate is contained as the calcium compound contained in the neutralizing agent, it is preferable to contain calcium carbonate in an amount of 65% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 90% by mass or less, and 75% by mass or less. It is more preferable to contain more than 85% by mass.

From the same viewpoint, the neutralizing agent used in the present invention preferably contains magnesium hydroxide as a magnesium compound. When magnesium hydroxide is contained as the magnesium compound contained in the neutralizing agent, magnesium hydroxide is preferably contained in an amount of 5% by mass or more and 35% by mass or less, more preferably 10% by mass or more and 30% by mass or less. It is more preferably contained in an amount of% by mass or more and 25% by mass or less.

The neutralizing agent of the present invention may be a mixture of the above-mentioned calcium compound and magnesium compound, or may be a natural product or an artificial product containing the calcium compound and the magnesium compound in advance. Examples of the neutralizing agent containing a calcium compound and a magnesium compound in advance include light-burning dolomite, light-burning dolomite and magnesium hydroxide obtained by reacting water, and industrially producing magnesium hydroxide by reacting seawater with slaked lime. Examples thereof include residues produced during production. Among these, seawater and slaked lime are reacted as a neutralizing agent from the viewpoint that the neutralization treatment can be performed at the same neutralization rate as limestone and the amount of neutralizing agent input and the volume of the neutralizing ridge can be reduced. It is preferable to use the residue produced by industrially producing magnesium hydroxide.

Since the residue produced by industrially producing magnesium hydroxide by reacting seawater with slaked lime is an industrial waste, all of the particle structures and components that contribute to the effects of the present invention should be analyzed. Is virtually impossible and requires significantly excessive economic spending and time to identify by its structure and properties. Therefore, in the residue, it is impossible or almost impractical to directly identify the substance by its structure or characteristics at the time of filing of the present application, that is, "impossible / impractical circumstances". Exists.

The neutralizing agent used in the present invention may have various particle shapes such as needle shape, spherical shape, plate shape, and indefinite shape, and may be an agglomerate in which particles having the above shape are aggregated. .. For example, the residue produced by industrially producing magnesium hydroxide by reacting seawater with slaked lime contains a large amount of needle-like particles, and forms aggregates in which the needle-like particles are aggregated. This has been confirmed by observation with a scanning electron microscope (see FIGS. 1 and 2 (a)).

From the viewpoint of further reducing the amount of the neutralizing agent input required for the neutralization treatment and the volume of the neutralizing ridge after the neutralization treatment, the neutralizing agent used in the present invention contains calcium carbonate in one particle thereof. It is preferable that magnesium hydroxide is uniformly mixed. In the present embodiment, "uniformly mixed in one particle" means that calcium carbonate and magnesium hydroxide are present in one particle without boundaries, as shown in FIGS. 2 (b) and 2 (c). It is the state of being. In other words, the region in which only calcium carbonate is mainly present and the region in which only magnesium hydroxide is mainly present are not observed separately. Examples of the neutralizing agent in such a mixed form include the above-mentioned residue.

The present inventor explains the reason why the amount of the neutralizing agent input and the volume of the neutralizing ridge are reduced by using the neutralizing agent in which calcium carbonate and magnesium hydroxide are uniformly mixed in one particle. I'm guessing. Generally, when only a magnesium compound is used as a neutralizing agent in the neutralization treatment of acidic water, the amount of the neutralizing agent input required for neutralization is small and the neutralization reaction proceeds quickly, but the neutralization volume is a feature. It is known that the volume increases. Further, when only a calcium compound is used as a neutralizing agent, the compound has low solubility in water, so that the reaction rate of the neutralization reaction is slow and an unreacted neutralizing agent remains, resulting in this. The amount of neutralizing agent added becomes large. On the other hand, when calcium carbonate and magnesium hydroxide are uniformly mixed in one particle, the neutralization reaction is easy to proceed because magnesium hydroxide has a higher solubility than calcium carbonate, and the neutralization reaction Later, it is considered that the amount of unreacted neutralizing agent is reduced as compared with the case of calcium carbonate alone, and the amount of neutralizing agent input required for neutralization and the volume of the neutralizing ridge are reduced. Regarding the neutralization treatment of acidic water, the present inventor may use a mixture of a simple powder of calcium carbonate and a single powder of magnesium hydroxide in the above mass ratio for the neutralization reaction, as in the case of limestone. It has been confirmed that the neutralizing effect of calcium can not be obtained.

The neutralizing agent used in the present invention may contain other components in addition to the calcium compound and the magnesium compound, or may contain only the calcium compound and the magnesium compound, as long as the effects of the present invention are exhibited. Examples of other components include silica, alumina and iron oxide.

<Acid water>
The acidic water to be treated in the present invention is an aqueous liquid having a pH of less than 7 at 25 ° C. Acidic water includes, but is not limited to, river water into which acidic mineral spring water flows, mine wastewater, groundwater, factory wastewater, and the like.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the scope of the invention is not limited to such examples.

1. 1. Acid water neutralization test An acid water neutralization test was conducted by the following method.
(1) Acidic water Table 1 shows the properties of the simulated acidic water used in the test. The pH, total iron (T ^— Fe), aluminum (Al), silica (Si) and sulfate ion concentration ( _SO4-2 ) shown in Table 1 were measured in accordance with JIS K 0102 “Factory Wastewater Test Method”. .. The simulated acidic water has an Fe source of iron (III) sulfate n hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and an Al source of aluminum sulfate 14-18 water (Wako Pure Chemical Industries, Ltd.) so as to have the composition shown in Table 1. ), Prepared using a reagent of sodium metasilicate nine hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) as a Si source and sulfuric acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a sulfuric acid source.

(2) Neutralizing agent In Examples and Comparative Examples, a neutralizing agent containing a calcium compound and a magnesium compound (hereinafter, also referred to as Neutralizing Agent A) is used as a neutralizing agent, and in Reference Examples, it is used as a neutralizing agent. We used limestone powder. As the neutralizing agent A, a residue produced when magnesium hydroxide was produced from seawater and slaked lime at Ube Material Industries Ltd. was used. As the limestone powder, a general-purpose crushed limestone product was used. Table 2 shows the properties of the neutralizing agent A and the limestone powder. The MgO, CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ contents were measured according to JIS M 8853 “Chemical analysis method for aluminosilicate raw materials for ceramics”.

The results of observation and element mapping of the neutralizing agent A with a scanning electron microscope are shown in FIGS. 1 and 2. As shown in FIG. 1, it was confirmed that the neutralizing agent A contained a large amount of needle-like particles, and the needle-like particles formed aggregates. From FIG. 2, it was confirmed that the neutralizing agent A was in a state where calcium carbonate and magnesium hydroxide were uniformly mixed in one particle.

(3) Preparation of Neutralizers with Different Particle Sizes Neutralizer A is pulverized for 30 minutes using a planetary ball mill (manufactured by Ito Seisakusho Co., Ltd., model number: LA-PO1), and then a test sieve (JIS Z 8801-1). , Openings 20, 45, 106 and 212 μm) were used to sift through various particle sizes to prepare neutralizing agents B to I having different particle sizes.

For the particle size of the neutralizing agent, a laser diffraction / scattering type particle size distribution measuring device (manufactured by Shimadzu Corporation, SALD-2200) was used as a pretreatment in which a predetermined amount of the neutralizing agent was added to distilled water and ultrasonically dispersed. The particle size distribution was measured using. FIG. 3 shows an example of the measurement result of the particle size distribution of the neutralizing agent. From the graph showing the relationship between the particle size and the cumulative frequency of the volume shown in FIG. 3, the particle size was obtained by reading the volume cumulative particle size at the cumulative volume of 90% by volume (in the following description, "cumulative volume 90% by volume"). "Volume cumulative particle diameter" is defined as "90% particle diameter"). Similarly, the particle size was obtained by reading the volume cumulative particle size at the cumulative volume of 50% by volume from the graph showing the relationship between the particle size and the cumulative frequency of the volume (in the following description, "at the cumulative volume of 50% by volume". "Volume cumulative particle size" is defined as "50% particle size").

Further, as a comparative example, a neutralizing agent J having a 90% particle size of 40 μm was prepared by dry sieving using the above-mentioned test sieve without pulverizing the neutralizing agent A. Table 3 shows the 90% particle size and the 50% particle size of the neutralizers B to J.

(4) Neutralization treatment of acidic water (i) Determination of neutralizing agent input amount Using neutralizing agents B to J and limestone powder, a neutralization test was conducted by the following method to determine the neutralizing agent input amount. .. That is, 1 L of acidic water was taken in a beaker, and the water temperature was adjusted to 33 ° C. by a hot water bath while stirring with a mechanical stirrer. Next, the powder neutralizer was added to the acidic water having a constant water temperature all at once. After adding the neutralizing agent, the pH of the acidic water was measured every minute with a glass-type pH measuring device (manufactured by Toa DKK, model number: MM-60R) while continuing stirring until 2 hours later. The above operation is performed by changing the amount of the neutralizing agents B to J and the limestone powder to be added to the acidic water, and the pH of the acidic water after 2 hours reaches 5.5 per liter of acidic water. The neutralizing agent input amount (g / L) was determined.
(Ii) Measurement of the volume of the neutralizing substance Using the neutralizing agents B to J and limestone powder, the neutralizing agent is added to the acidic water at the amount of the neutralizing agent added determined in the above operation, and the mixture is stirred 2 hours later. After stopping, the neutralized water and the neutralized volume were transferred to a liquid separation funnel and allowed to stand for 24 hours. After that, the neutralizing funnel was pulled out from the lower part of the separatory funnel into a graduated test tube, left to stand for another 24 hours, and then the scale of the test tube was read to determine the volume of the neutralizing ridge per 1 L of acidic water (mL / L) was measured.

[Example 1]
Using the neutralizing agent B, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the above operation. The results are shown in Table 3.

[Example 2]
Except for the use of the neutralizing agent C, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3.

[Example 3]
The amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1 except that the neutralizing agent D was used. The results are shown in Table 3.

[Example 4]
Except for the use of the neutralizing agent E, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3.

[Example 5]
Except for the use of the neutralizing agent F, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3.

[Example 6]
Except for the use of the neutralizing agent G, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3.

[Example 7]
The amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1 except that the neutralizing agent H was used. The results are shown in Table 3.

[Example 8]
Except for the use of the neutralizing agent I, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3.

[Comparative Example 1]
Except for the use of the neutralizing agent J, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3.

[Reference Example 1]
Except for the fact that limestone powder was used as the neutralizing agent, the amount of the neutralizing agent added was determined and the volume of the neutralizing ridge was measured by the same operation as in Example 1. The results are shown in Table 3. Regarding Reference Example 1, the volume of the neutralized ridge shown in the same table is the volume of the precipitate generated when the neutralization treatment is performed using limestone.

(5) Results As shown in Table 3, Examples 1 to 8 in which the neutralizing agent containing the calcium compound and the magnesium compound were pulverized were charged with the neutralizing agent as compared with Comparative Example 1 in which the neutralizing agent was not pulverized. It can be seen that the amount and the volume of the neutralized compound can be significantly reduced. Further, when Examples 1 to 8 and Reference Example 1 are compared, the amount of the neutralizing agent input and the volume of the neutralizing burial material in Examples 1 to 8 are significantly reduced as compared with Reference Example 1 using the conventional limestone. I know I can do it.

2. 2. Calculation of relational expression (a) and relational expression (b) From the results obtained in the above "1. Neutralization test of acidic water", the relational expression (a) and the relational expression (b) were calculated by the following methods, respectively.

The relational expression (a) is obtained as a regression line by plotting the 90% particle size of the neutralizers of Examples 1 to 8 in Table 3 on the horizontal axis and the amount of the neutralizer input on the vertical axis and linearly approximating them. rice field. Table 4 shows the relational expression (a) and its correlation coefficient. Further, as a comparison, Table 4 shows the relational expression and the correlation coefficient calculated by the same method as described above from the relationship between the 50% particle size of the neutralizing agent of Examples 1 to 8 in Table 3 and the amount of the neutralizing agent added. Shown in.

Next, the 90% particle diameter of the neutralizing agents of Examples 1 to 8 in Table 3 is plotted on the horizontal axis, and the volume of the neutralizing ridge is plotted on the vertical axis, and linear approximation is performed to obtain a relational expression (relationship line). b) was obtained. Table 4 shows the relational expression (b) and its correlation coefficient. Further, as a comparison, the relational expression and the correlation coefficient calculated by the same method as described above are shown from the relationship between the 50% particle size of the neutralizing agents of Examples 1 to 8 in Table 3 and the volume of the neutralizing ridge. Shown in 4.

In Table 4, y: the amount of neutralizing agent added per 1 L of acidic water (g / L), D ₁ : 90% particle size of the neutralizing agent (μm), z: neutralizing substance per 1 L of acidic water. Volume (mL / L), D ₂ : 50% particle size (μm) of neutralizer.

As shown in Table 4, regardless of whether the particle diameter is 90% or 50%, the relational expression (a) has a positive inclination, so that the neutralizing agent can be used. It can be seen that the smaller the particle size, the smaller the amount of the neutralizing agent added. On the other hand, regardless of which of the 90% particle diameter and the 50% particle diameter is adopted as the particle diameter, the relational expression (b) has a negative inclination, so that the particle diameter of the neutralizing agent is used. It can be seen that the larger the value, the smaller the volume of the neutralizing particles.

Comparing the correlation coefficients of the regression lines at each particle size, when 90% particle size is adopted, both the relational expressions (a) and (b) have a phase relationship as compared with the case where 50% particle size is adopted. It can be seen that the number is high and a more accurate relational expression can be obtained.

Further, as shown in Table 4, it can be seen that the relationship between the amount of the neutralizing agent added and the volume of the neutralizing substance has opposite positive and negative tendencies, respectively. In this way, by obtaining the relational expressions (a) and (b), it is possible to clarify the relationship between the 90% particle size of the neutralizing agent, the amount of the neutralizing agent input, and the volume of the neutralizing ridge. can. From this result, it is possible to determine the priority of reducing the amount of neutralizing agent input and the volume of the neutralizing burial material based on the cost, treatment status, etc., so that the neutralizing agent can be more quantitatively and rationally used. The input conditions can be designed.

As described above, the processing condition design method of the present invention predicts the value of the neutralizing agent input amount and the volume of the neutralizing particles by obtaining the above-mentioned relational expressions (a) and (b) in advance. It is possible to design the 90% particle size of the neutralizing agent and the amount of the neutralizing agent input, which are optimal for the neutralization treatment. By neutralizing the acidic water to be treated based on this design, the amount of neutralizing agent input and the volume of the neutralizing burial can be reduced and the neutralization treatment cost can be reduced as compared with the conventional method. Can be done.

Claims (9)

The neutralizing agent, which is a residue produced by producing magnesium hydroxide by the reaction between seawater and slaked lime, is added to the acidic water to be treated for neutralization treatment, and the cumulative volume of the neutralizing agent is 90% by volume. The following equation (a), which is the relational expression between the volume cumulative particle diameter and the input amount in
y = α × D + β ・ ・ ・ Equation (a)
y: Neutralizing agent input amount per 1 L of acidic water (g / L)
D: Cumulative volume particle diameter (μm) at a cumulative volume of 90% by volume of the neutralizer
α: Slope of the regression line β: Intercept of the regression line The equation (b), which is the relational expression between the volume cumulative particle diameter and the volume of the neutralizing ridge in the cumulative volume of 90% by volume of the neutralizing agent, is obtained in advance. Oki,
z = γ × D + δ ・ ・ ・ Equation (b)
z: Volume of neutralizing substance per 1 L of acidic water (mL / L)
γ: Slope of regression line δ: Intercept of regression line Based on the relational expressions of the formulas (a) and (b), the volume cumulative particle size and the input amount in the cumulative volume of 90% by volume of the neutralizer are designed. , Acid water treatment condition design method. The method for designing treatment conditions for acidic water according to claim 1, wherein the formulas (a) and (b) are obtained using the neutralizing agent having a cumulative volume particle diameter of 20 μm or more and 150 μm or less in a cumulative volume of 90% by volume. .. The formula (a) and the formula (b) are obtained by using the neutralizing agent containing 65% by mass or more and 95% by mass or less of calcium carbonate and 5% by mass or more and 35% by mass or less of magnesium hydroxide. 2. The method for designing treatment conditions for acidic water according to 2. The method for designing treatment conditions for acidic water according to any one of claims 1 to 3, wherein calcium carbonate and magnesium hydroxide are uniformly mixed in one particle of the neutralizing agent. The method for designing treatment conditions for acidic water according to any one of claims 1 to 4 , wherein the formulas (a) and (b) are obtained using the acidic water composed of river water into which acidic mineral spring water flows. .. The volume of the neutralizing agent in a cumulative volume of 90% by volume so that the volume of the neutralizing deposit is smaller than the volume of the precipitate generated when the limestone is put into the acidic water and subjected to the neutralization treatment. The method for designing treatment conditions for acidic water according to any one of claims 1 to 5 , wherein the cumulative particle size and the input amount are designed. The volume of the neutralizing agent in a cumulative volume of 90% by volume so that the amount of the neutralizing agent added is smaller than the amount of the limestone added when the limestone is added to the acidic water to perform the neutralization treatment. The method for designing treatment conditions for acidic water according to any one of claims 1 to 5 , wherein the cumulative particle size and the input amount are designed. The volume cumulative particle size at 90% by volume of the cumulative volume of the neutralizing agent so that the total amount of the neutralizing agent input amount and the volume of the neutralizing substance becomes the minimum value or the minimum value ± 10%. The method for designing treatment conditions for acidic water according to any one of claims 1 to 5 , wherein the input amount is designed. The neutralizing agent based on the volume cumulative particle size and the input amount at 90% by volume of the cumulative volume of the neutralizing agent designed by the method for designing treatment conditions for acidic water according to any one of claims 1 to 8 . A method of treating acidic water, in which the water is added to the acidic water to be treated and neutralized.

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