JP2009150757A - Ca2+ ELUTION AMOUNT TEST METHOD OF SLUG, AND EVALUATION METHOD OF SLUG - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Ca<SP>2+</SP>elution amount test method for measuring accurately and quickly the elution amount of Ca<SP>2+</SP>eluted from slug, and an evaluation method for evaluating propriety of slug as a marine civil engineering and building material based on the elution amount of Ca<SP>2+</SP>acquired by the Ca<SP>2+</SP>elution amount test method. <P>SOLUTION: In the Ca<SP>2+</SP>elution amount test method, slug is dipped into pure water having a mass ratio 1,000 times or more as high as the mass of the slug, and pH after dipping the slug is measured, and the Ca<SP>2+</SP>elution amount from the slug is determined based on the measured pH value. In the evaluation method of slug, the slug is classified by granularity, and the Ca<SP>2+</SP>elution amount classified by the granularity is determined by using the Ca<SP>2+</SP>elution amount test method, and the Ca<SP>2+</SP>elution amount from the slug before being classified is determined by using the determined Ca<SP>2+</SP>elution amount classified by the granularity and a granularity distribution of the slug determined by classifying the slug by the granularity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an elution amount test method for measuring the elution amount of Ca ²⁺ eluted from slag such as converter slag and various smelting slags, and evaluation of slag using test results obtained by this elution amount test method It is about the method.

  In the metal smelting and refining processes, various slags are generated in order to obtain high-quality, high-quality metals, and the composition of blast furnace slag, converter slag, ladle slag, pretreatment slag, etc. in steelworks Various slags with different values are generated. These slags are not only roadbed materials, soil improvement materials, ground improvement materials, cement and concrete aggregates, stone materials, but also submarine materials, backfill materials, backfill materials, embankment materials, sand compaction, It is used as marine civil engineering building materials such as SCP sand mats and shallow ground construction materials.

Among these slags, converter slag, ladle slag, hot metal pretreatment slag, etc. that contain free CaO (also referred to as “free lime” or “free lime”) are slag when used in coastal waters. It is known that the white turbidity of seawater may occur when the free CaO contained therein is eluted into seawater and the pH of the seawater rises. This cloudiness phenomenon occurs by the following mechanism. That is, free CaO elutes into seawater to form Ca (OH) ₂ , which raises the pH of the seawater, and Mg ²⁺ dissolved in the seawater as the pH increases becomes Mg (OH) ₂ . The precipitate is precipitated and the seawater becomes clouded by this deposit, resulting in a cloudiness phenomenon. Further, Ca ^{2+ in} the seawater reacts with carbonate ions (CO ₃ ²⁻ ) contained in the seawater as the pH rises to precipitate CaCO ₃ , which also causes white turbidity. Of the slag generated at steelworks, slag other than blast furnace slag is generated in the steelmaking refining process, so it is collectively referred to as `` steel slag ''. , Free CaO is contained.

Although Mg (OH) ₂ and CaCO ₃ itself, which cause white turbidity, are harmless, the white turbidity phenomenon during the construction period may be an obstacle to proceeding with port construction due to problems in appearance. Moreover, generation | occurrence | production of cloudiness suggests the pH rise of seawater resulting from melt | dissolution of free CaO, and must be careful from an environmental viewpoint.

  By the way, in recent steelmaking processes, efficient division of each process of desiliconization treatment, desulfurization treatment, dephosphorization treatment, and decarburization treatment has progressed, and a wide variety of steelmaking slag has been generated. Are diverse, and the dissolution behavior of free CaO in steelmaking slag is also complicated.

Then, when utilizing steelmaking slag in a coastal sea area, the test method for selecting the slag which does not generate | occur | produce a cloudiness phenomenon is proposed in patent document 1 from such various steelmaking slag. According to Patent Document 1, “a steelmaking slag having a free CaO content of 0 to 10.0 mass% and a sulfur content of 0 to 1.0 mass%, which is immersed in seawater having a mass ratio of 2 times. If the steelmaking slag is such that the pH of the seawater becomes 10.5 or less when 3 hours have passed, the cloudiness phenomenon is prevented. That is, if the pH of the seawater is 10.5 or less when it is immersed in seawater having a mass ratio twice that of steelmaking slag and 3 hours have passed, the amount of Ca ²⁺ eluted from the steelmaking slag is small, It can prevent white turbidity when laid in the coastal sea area.
JP 2003-26456 A

  However, the test method proposed in Patent Document 1 has the following problems.

That is, in Patent Document 1, since seawater is used as a solvent, the eluted Ca ²⁺ reacts with carbonate ions contained in the seawater to precipitate CaCO ₃ , and this precipitate increases the pH. Because the pH of seawater is not proportional to the amount of Ca ²⁺ eluted from the slag, the amount of Ca ²⁺ eluted from the slag can be accurately measured by observing the pH change of the seawater. I can't do it. Also, cover the precipitated CaCO ₃ is a slag surface, also play a role to prevent the dissolution of Ca ²⁺ from the slag, it is difficult to accurately measure the more the amount of elution of Ca ²⁺ from the slag Become.

The present invention has been made in view of the above circumstances, and the object of the present invention is to measure Ca ²⁺ eluted from slags such as steel slag and various smelting slags accurately and quickly. while providing ²⁺ elution test method, to provide an evaluation method based on the elution weight of the Ca ²⁺ obtained by the Ca ²⁺ elution test method to evaluate the suitability of a marine civil engineering and construction material of the slag It is.

The slag Ca ²⁺ elution amount test method according to the first invention for solving the above-mentioned problem is to immerse slag in the solvent using pure water having a mass ratio of 1000 times or more with respect to the mass of the slag as a solvent, The pH of the solvent after the slag is immersed is measured, and the elution amount of Ca ²⁺ from the slag is obtained based on the measured pH value of the solvent.

Evaluation method of slag according to the second invention, the slag fractionated by particle size and the particle size by fractionated, the elution amount of Ca ²⁺ with Ca ²⁺ elution test method of the slag according to the first aspect Determine the amount of Ca ²⁺ elution from the slag before separation using the obtained Ca ²⁺ elution amount for each particle size and the slag particle size distribution obtained by separating the slag by particle size. It is characterized by.

Evaluation method of slag according to the third invention, the slag fractionated by particle size and the particle size by fractionated, the elution amount of Ca ²⁺ with Ca ²⁺ elution test method of the slag according to the first aspect The amount of Ca ²⁺ eluted from the slag before separation is determined using the obtained amount of Ca ²⁺ leached by particle size and the particle size distribution of slag obtained by separating the slag by particle size. When the dissolution amount is larger than the target value, the particle size distribution of the slag used in the calculation is changed, and the particle size distribution is calculated using the dissolution amount of Ca ²⁺ for each particle size and the changed particle size distribution of the slag. The elution amount of Ca ²⁺ from the changed slag is determined.

According to the Ca ²⁺ elution test method according to the present invention, pure water is used as the solvent, so that the eluted Ca ²⁺ does not form precipitates such as CaCO _3, and the pH of the solvent and the eluted Ca ²⁺ has a one-to-one correlation, and the amount of Ca ²⁺ elution can be accurately measured from the pH change of the solvent. The mass of pure water as the solvent is 1000 times the mass of the slag. Therefore, the increase in pH of the solvent can be suppressed, and the amount of Ca ²⁺ eluted can be accurately measured. Furthermore, the elution amount of Ca ²⁺ can be measured from a relatively simple measurement of measuring the pH of the solvent. Therefore, the elution amount of Ca ²⁺ can be quickly grasped.

Further, according to the evaluation method of the slag according to the present invention, the so determined quantity eluted of granularity different Ca ²⁺ slag, the amount of elution of particle size different Ca ²⁺ determined and the particle size distribution of the slag, the entire slag The elution amount of Ca ²⁺ can be ascertained, and the suitability for use in sea areas can be evaluated. And when the grasped Ca ²⁺ elution amount is higher than the target value, that is, when the use for the sea area is evaluated as inappropriate, the particle size distribution is based on the obtained Ca ²⁺ elution amount for each particle size. It is possible to determine the Ca ²⁺ elution amount from the slag when the slag is changed. Therefore, by changing the particle size distribution of the slag so that the Ca ²⁺ elution amount from the slag is less than the target value, It becomes possible to prevent the cloudiness phenomenon when slag eluting Ca ²⁺ is used as a marine civil engineering building material.

  The present invention will be specifically described below.

The present inventors have contains free CaO, waters utilization of slag, such as steel slag, eluting the Ca ^2+, it is intended to be safe and expanded, upon laying the slag eluting Ca ²⁺ in seawater Furthermore, in order to predict how much the pH of seawater changes and cloudiness occurs, the measurement of alkali elution in slag particles was examined.

At present, the only factor that is related to alkali among the effluents from slag is considered to be dissolution of free CaO. Therefore, a method for measuring the Ca ²⁺ elution amount was developed. Here, when measuring the elution amount of Ca ^2+, with the aim of converting the elution concentration of Ca ²⁺ from pH change of the solvent.

The elution of Ca ²⁺ from the slag is expressed by the following formula (1).
_{CaO + H 2 O → Ca (} OH) → Ca 2+ + 2OH - ...... (1)
That is, CaO (calcium oxide) in the slag reacts with moisture to change to Ca (OH) ₂ (calcium hydroxide), and this Ca (OH) ₂ dissolves in water and seawater to cause Ca ²⁺ (calcium ions). ) And hydroxide ions (OH ⁻ ), it becomes alkaline.

In order to convert the Ca ²⁺ elution concentration from the measured pH value of the solvent, the influence of other factors must be excluded, and seawater cannot be used as a solvent. The reason is that the sea water includes the Mg ²⁺ in addition to Ca ^2+, to the pH increases to increase Mg (OH) ₂ to produce, pH of seawater, from the vicinity of pH9.8 Apparently no longer change. Therefore, in seawater, the Ca ²⁺ elution amount cannot be converted from the measured pH value. Further, even if pure water is used as the solvent, Ca (OH) ₂ is saturated near pH 12.5. Therefore, in order to prevent the pH of the solvent from exceeding 12.5 during the measurement, However, the amount of slag added must be reduced.

  From the above, for the solvent, ion-exchanged water that was ion-exchanged after distillation was used as pure water, and the mass ratio of slag to solvent was set to 1: 1000.

  After pre-crushed steelmaking slag was dried at 105 ° C. for 2 hours to remove adhering moisture, 0.075 mm to 0.15 mm, 0.15 mm to 0.425 mm, 0.6 mm to 1 The slags in four types of particle size ranges of .18 mm or less and 2.0 mm to 4.75 mm or less were collected by a sieving device, and measurement was performed for each of these four types of slag. In addition, the particle size distribution was also measured when collecting with a sieving machine. Furthermore, chemical components are analyzed for each slag classified into four types according to particle size, and it is confirmed that the variation in component values is within the error range of the analysis, and there is no change in the components due to particle size.

  1 g of slag was sampled from each slag sorted according to particle size, and this slag was immersed in 1000 mL of pure water contained in a beaker and stirred at a rotational speed of 200 rpm with a rotary blade stirrer while measuring the pH meter Was used to measure the pH of the solvent.

  The pH measurement results for each particle size are shown in FIG. As shown in FIG. 1, it was confirmed that there was a difference in pH change depending on the difference in slag particle size. That is, it was confirmed that the finer the slag particle size, the larger the pH change and the higher the final pH value. Since the chemical composition of the slag is the same as described above, it has been found that the difference in pH change is caused by the particle size.

In ^{obtaining the} Ca ²⁺ concentration from the measured pH value of the solvent shown in FIG. 1, it was obtained by ion equilibrium calculation using the basic acid dissociation constant of Ca (OH) ₂ shown below. That is, the basic acid dissociation constant shown in the following formulas (2) to (5) is solved, and the total Ca concentration (Cb) is obtained from the cubic function of [OH ⁻ ].

^{Kb1 = [OH -] × [} Ca (OH) +] / [Ca (OH) 2] = 3.98 × 10 -3 ... (2)
^{Kb2 = [OH -] × [} Ca 2+] / [Ca (OH) +] = 3.98 × 10 -2 ... (3)
Cb (total Ca concentration) = [Ca (OH) ₂ ] + [Ca (OH) ⁺ ] + [Ca ²⁺ ] (4)
^{[OH -] = [H +} ] + [Ca (OH) +] +2 [Ca 2+] ... (5)
By solving these equations (2) to (5), the following equation (6) is obtained. By substituting the concentration of [OH ⁻ ] at each pH into this equation (6), the Ca A concentration of ²⁺ can be obtained.

^{Cb = [OH -] 3 +} 3.98 × 10 -3 [OH -] 2 + 1.58 × 10 -4 [OH -] / (3.98 × 10 -3 [OH -] + 2 × 1.58 × 10 -4) ... ( 6)
Table 1 shows the result of calculating the Ca ²⁺ concentration from the measured pH value using the equation (6). As shown in Table 1, it can be seen that there is a one-to-one relationship between the pH of the solvent and the concentration of Ca ²⁺ in the solvent. In some dissolution tests, the Ca ²⁺ concentration in the solvent was measured by ICP emission analysis, and it was confirmed that the results of the ICP emission analysis coincided with the results shown in Table 1.

Using this way, the relationship between the Ca ²⁺ concentration of pH and solvent of the resulting solvent and converting the measured pH values shown in Figure 1 to a concentration of Ca ^2+, and Ca ²⁺ concentration shown in FIG. 2 A relationship with elapsed time is obtained. In FIG. 2, slag data having a particle size of 2.0 mm to 4.75 mm or less is omitted, but slag data having a particle size of 2.0 mm to 4.75 mm or less has a particle size of 0.6 mm to 1 It has been confirmed that it is located on the side where Ca ²⁺ concentration is lower than the data of slag of 18 mm or less.

As described above, pure water is used as a solvent, slag is immersed in this solvent, and the pH of the solvent is measured, so that the amount of Ca ²⁺ eluted from the slag can be accurately determined based on the measured pH value of the solvent. The knowledge that it can measure well and quickly was obtained.

The slag Ca ²⁺ elution test method according to the present invention is based on the above findings, and slag is immersed in the solvent using pure water having a mass ratio of 1000 times or more with respect to the mass of the slag as a solvent. The pH of the solvent after the slag is immersed is measured, and the elution amount of Ca ²⁺ from the slag is obtained based on the measured pH value of the solvent.

In carrying out the Ca ²⁺ elution amount test method of the present invention, the pure water as the solvent may be 1000 times or more the mass of the slag, and there is no need to define the upper limit in particular. Since it becomes difficult, the upper limit may be about 2000 times the mass of the slag. Also, the pH meter does not require special specifications, and a commercially available pH meter is sufficient. In addition, the pure water used in the present invention may have a cleanness that does not affect the reaction of the eluted Ca ²⁺ , and distilled water, ion-exchanged water, or ion-exchanged water ion-exchanged after distillation can be used.

As described above, according to the slag Ca ²⁺ elution test method according to the present invention, pure water is used as the solvent, and thus the eluted Ca ²⁺ does not form precipitates such as CaCO ₃ , There is a one-to-one correlation between pH change and eluted Ca ^2+, and the amount of Ca ²⁺ eluted can be accurately measured from the measured pH value of the solvent. Further, since the mass of pure water as the solvent is 1000 times or more the mass of the slag, an increase in the pH of the solvent can be suppressed, and the amount of Ca ²⁺ eluted can be accurately measured.

By the way, the slope of the curve shown in FIG. 2 described above becomes the elution rate of Ca ²⁺ . As is clear from FIG. 2, it was confirmed that the smaller the slag particle size, the faster the Ca ²⁺ elution rate. That is, when the chemical composition of the slag is the same, the slag having a small proportion of the particle size has a higher Ca ²⁺ elution rate, and the cloudiness phenomenon is more likely to occur when used as a marine civil engineering building material.

FIG. 3 shows the relationship between the average value of the Ca ²⁺ elution rate up to 30 minutes and the surface area per gram of slag shown in FIG. In addition, the slag A in FIG. 3 is the slag which showed the test data of FIG.1 and FIG.2 mentioned above, and the slag B is the data of another steelmaking slag from which a composition differs. Moreover, when calculating | requiring the surface area per slag, while assuming the shape of a slag as a sphere, the density of slag was computed as apparent specific gravity (2500 kg / m < ³ >) in filling.

As shown in FIG. 3, it was found that the dissolution rate of Ca ²⁺ in slag has a correlation with the surface area per unit mass. Moreover, since the relationship between this Ca ²⁺ elution rate and the surface area per unit mass is different when comparing slag A and slag B, it was also confirmed that they differ depending on the chemical composition of the slag.

Thus, Ca ²⁺ elution amount from the slag, the particle size separately fractionated slag, by obtaining the Ca ²⁺ elution in size by fractionated, and particle size-specific Ca ²⁺ elution amount obtained, fractionated slag by size It was found that the slag particle size distribution can be easily estimated. And it was found that if the estimated Ca ²⁺ elution amount is compared with the Ca ²⁺ elution amount (= target value) generated from the experience, the suitability of slag as a marine civil engineering building material can be easily evaluated. . That is, when the Ca ²⁺ elution amount exceeds the target value, it is evaluated as inappropriate because there is a possibility of cloudiness.

Further, the estimation result of Ca ²⁺ elution amount, elution of Ca ²⁺ is more than the target value, even if the slag was rated as not suitable as a marine civil engineering building materials, among slag fractionated by particle size Then, change the particle size distribution configuration by deleting all the slag with the largest Ca ²⁺ elution amount and the smallest particle size in the calculation, or by deleting a part of the slag with the smallest particle size in the calculation, etc. What it can change the slag re calculation of Ca ²⁺ elution amount was found that it is possible to make the Ca ²⁺ elution amount less than the target value.

Evaluation method of slag according to the present invention has been made based on this study result, slag fractionated by particle size and the particle size by fractionated elution of Ca ²⁺ using the Ca ²⁺ elution test method The amount of Ca ²⁺ elution from the slag before fractionation is determined using the calculated amount of Ca ²⁺ elution by particle size and the particle size distribution of slag obtained by fractionating the slag by particle size. It is characterized by that. In this case, when the Ca ²⁺ elution amount is larger than the target value, the particle size distribution of the slag used in the calculation is changed, and the Ca ²⁺ elution amount for each particle size and the changed slag particle size distribution Can be used to determine the elution amount of Ca ²⁺ from the slag whose particle size distribution has been changed.

In carrying out the slag evaluation method of the present invention, when separating the slag according to the particle size, it is preferable to classify into at least three types, preferably depending on the range of the maximum size and the minimum size of the slag. 4 types or more. This is because if the number of fractions is small, there is a risk that it may become an obstacle to changing the particle size distribution in calculation if the amount of Ca ²⁺ elution becomes larger than the target value. That is, there is a possibility that a second sieving operation with a sieving device may be required. In addition, since leaching of Ca ²⁺ is small from slag particles having a particle size of 1 mm or more, particles having a particle size of 1 mm or more may be grouped together as one group.

Thus, according to the evaluation method of the slag according to the present invention, the so determined quantity eluted of granularity different Ca ²⁺ slag, the amount of elution of particle size different Ca ²⁺ determined and the particle size distribution of the slag, The amount of Ca ²⁺ elution in the entire slag can be grasped, and the suitability when used for marine use can be accurately evaluated. When the grasped Ca ²⁺ elution amount is higher than the target value, it is possible to obtain the Ca ²⁺ elution amount from the slag when the particle size distribution is changed, and the Ca ²⁺ elution from the slag. By changing the particle size distribution of the slag so that the amount is equal to or less than the target value, it becomes possible to prevent the cloudiness phenomenon when using the slag as a marine civil engineering building material.

It is a figure which shows the pH change of a solvent when a pure water is used as a solvent and a slag is immersed in this solvent by the difference in a slag particle size. FIG. 2 is a diagram showing the measured pH values shown in FIG. 1 in terms of Ca ²⁺ concentration. It is a figure which shows the relationship between the measured value of Ca2 ⁺ elution rate shown in FIG. 2, and the surface area per 1g of slag.

Claims (3)

Using pure water with a mass ratio of 1000 times or more with respect to the mass of the slag as a solvent, slag is immersed in the solvent, the pH of the solvent after the slag is immersed is measured, and based on the measured pH value of the solvent and it obtains the amount of elution of Ca ²⁺ from the slag, Ca ²⁺ elution test method of the slag. Slag fractionated by particle size and the particle size by fractionated to obtain the elution amount of Ca ²⁺ with Ca ²⁺ elution test method of the slag according to claim 1, the amount of elution of particle size different Ca ²⁺ determined And an elution amount of Ca ²⁺ from the slag before sorting using a slag particle size distribution obtained by sorting the slag according to particle size. Slag fractionated by particle size and the particle size by fractionated to obtain the elution amount of Ca ²⁺ with Ca ²⁺ elution test method of the slag according to claim 1, the amount of elution of particle size different Ca ²⁺ determined And the slag particle size distribution obtained by separating the slag according to particle size, the amount of Ca ²⁺ elution from the slag before separation is determined, and when the amount is larger than the target value, The particle size distribution of the slag used in the above is changed, and the amount of Ca ²⁺ eluted from the slag whose particle size distribution is changed is determined using the amount of Ca ²⁺ eluted by the particle size and the particle size distribution of the changed slag. A method for evaluating slag, characterized by that.

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