TWI600903B - Determination of active calcium oxide content - Google Patents

Description

Method for detecting active calcium oxide content

The invention relates to a method for detecting the content of active calcium oxide (free-CaO), in particular to a method for detecting the content of active calcium oxide by adding sucrose.

In the process of desulfurization or dephosphorization of steelmaking, quicklime (also known as calcium oxide) is usually added to improve or adjust the quality of the steel. Most steel mills choose to add excess lime to prevent losses due to smelting failures, but this will still result in increased costs. Therefore, based on cost considerations, if the amount of quicklime required for each heat can be accurately calculated, the cost should be effectively reduced.

Generally, methods for analyzing calcium ions, such as titration with ethylenediamine tetraacetic acid (EDTA) solution, are applied to water hardness testing, and conventional methods require conversion of calcium ions in water to calcium carbonate. It will not be conducive to subsequent addition to steel.

At present, the active calcium oxide detection method designed for steelmaking, as shown in CN 103134736, refers to a method for accurately determining the main components of a calcium-based desulfurizing agent, comprising: (1) separation of free calcium: a particle size of less than 0.15 mm The desulfurizer sample and the sucrose solution are placed in a stoppered container for shaking Filtration, obtaining filtrate; (2) Determination of free calcium content: adding triethanolamine solution and potassium hydroxide solution to the filtrate, followed by adding magnesium chloride solution and calcium indicator, and then titrating with EDTA standard solution, by consumption of EDTA standard Solution volume calculation of free calcium content; (3) separation of calcium carbonate; (4) titration of calcium carbonate content; (5) separation of calcium fluoride; (6) determination of calcium fluoride; (7) calcium hydroxide content Determination: Thermogravimetric analysis of desulfurization samples by thermogravimetric analyzer, and calculation of calcium hydroxide content by sample weight loss; and (8) Determination of calcium oxide content. This step (8) is to subtract the calcium content in the calcium hydroxide from the free calcium content determined in the step (2), that is, the content of the calcium oxide.

Although the above patent publication has already mentioned the determination of the calcium oxide content, it takes four steps to calculate the calcium oxide content, and this method is also only suitable for detecting the calcium-based desulfurizing agent, and does not mention other activities. A sample of calcium oxide.

As can be seen from the above description, for the steel mill, there is still a need to develop a method for detecting active calcium oxide which is suitable for detecting various samples containing active calcium oxide and having excellent accuracy.

Accordingly, it is an object of the present invention to provide a method for detecting an active calcium oxide content having excellent accuracy and which can be used for detecting various test samples containing active calcium oxide.

Therefore, the method for detecting the active calcium oxide content of the present invention comprises the steps of: (A) providing a sample to be tested having a particle size range of 0.075 mm or less; and (B) mixing the sample to be tested with an aqueous solution of sucrose in a closed environment. Obtaining a mixed solution; (C) filtering the mixed solution with 5C filter paper to obtain a filtrate; (D) adding a concealing agent to the filtrate, adjusting the pH to 13 to obtain a test liquid; and (E) An indicator is added to the test solution, and titrated with an ethylenediaminetetraacetic acid solution, and the proportion of the active calcium oxide is calculated from the amount of the ethylenediaminetetraacetic acid solution.

The effect of the invention is to effectively improve the accuracy of the detection method by controlling the particle size of the sample to be tested in the step (A) and the 5C filter paper of the step (C), and at the same time, the detection method of the invention is suitable for detection. Various samples to be tested containing active calcium oxide.

SUMMARY The present invention will hereinafter be described in detail: detection method of the present invention is the use of sucrose method, the principle is: the use of _{OH (C 12 H 22 O 11} ) in the sucrose molecule ^- Ca active calcium oxide in water with the formation of ( OH) ₂ [The reaction process is OH ^- miscible in the following formula (i)] to form a soluble sugar C ₁₂ H ₂₂ O ₁₁ ‧CaO‧2H ₂ O [the reaction process is as follows: (ii)]. The Ca ²⁺ ions were then extracted, and a concealer was added and the pH was adjusted to 13. Then, titration is carried out with EDTA (C ₁₀ H ₁₆ N ₂ O ₈ ), at which time EDTA is chelated with Ca ²⁺ ions [the reaction process is as follows (iii)], and the volume of EDTA used is recorded, and then passed through the following formula ( Iv) Calculate and obtain the proportion of active calcium oxide in the sample: CaO+H ₂ O→Ca(OH) ₂ (i)

Ca(OH) ₂ +C ₁₂ H ₂₂ O ₁₁ →C ₁₂ H ₂₂ O ₁₁ ‧CaO‧2H ₂ O (ii)

C ₁₀ H ₁₆ N ₂ O ₈ +C ₁₂ H ₂₂ O ₁₁ ‧CaO‧2H ₂ O→ Ca(C ₁₀ H ₁₄ N ₂ O ₈ )+C ₁₂ H ₂₂ O ₁₁ +3H ₂ O (iii)

In the formula (iv), M represents an EDTA concentration (M), V represents a volume (mL) used for EDTA titration, and W represents a sample weight (g).

The various steps of the detection method of the present invention are described in more detail below:

Step (A)

The invention can be used to detect various active calcium oxide containing samples such as, but not limited to, calcium based desulfurizing agents, non-calcium based desulfurizing agents, electric arc furnace oxidizing slag, converter slag, and the like. In one embodiment of the invention, the sample to be tested is a calcium-based desulfurizing agent.

The particle size range of the sample to be tested needs to be controlled to be below 0.075 mm, so that the sample to be tested can be quickly dissolved in the aqueous solution of sucrose in the step (B). When the particle size range is more than 0.075 mm, in addition to the inability to dissolve quickly in the aqueous solution of sucrose in the step (B), the filter paper is easily blocked during subsequent filtration.

Step (B)

In this step (B), the sample to be tested must be mixed in a closed environment to prevent the incorporation of CO ₂ in the atmosphere to generate a large amount of calcium carbonate, thereby causing errors in detection. In one embodiment of the invention, the sample to be tested and the aqueous sucrose solution are placed in an Erlenmeyer flask sealed by a cork stopper.

In order to allow the sample to be tested to be completely dissolved in the aqueous solution of sucrose, in addition to the particle size control of the step (A), preferably, the step (B) The weight ratio of the sample to be tested to the sucrose in the aqueous solution of sucrose ranges from 1:10 to 1:25.

Step (C)

This step (C) needs to be filtered using a specific 5C filter paper to filter out the remaining residual filter residue to avoid the presence of residual filter residue at the time of titration and affect the accuracy of the titration. The 5C filter paper is, for example but not limited to, 5C filter paper (named Quantitative ashless filter paper, model 5C 110mm) manufactured by Advantec, Japan.

Step (D)

The concealing agent can be selected from any concealing agent which can be chelated with ions which are not detected by the present invention (that is, ions other than calcium ions which may affect the detection result). Preferably, the concealing agent of the step (D) is a mixed solution of triethanolamine and water. In one embodiment of the invention, the weight ratio of the triethanolamine to water is 1:1.

The pH of this step (D) can be adjusted using an appropriate lye that does not affect the detection of active calcium oxide. Preferably, the step (D) is to adjust the pH of the filtrate by adding an aqueous potassium hydroxide (KOH) solution.

It should be noted that the pH of the step (D) needs to be adjusted to 13, because the EDTA will chelate with the Ca ²⁺ ion in the environment of pH 13.

Step (E)

The indicator used in this step (E) can be selected from any indicator that can be used in conjunction with EDTA. Preferably, the indicator is a calcium carboxylic acid indicator.

The method for detecting active calcium oxide of the invention has the advantages of simple steps, and can be applied to detecting various samples containing active calcium oxide, whether it is a desulfurizing agent, a dephosphorization agent or the like added before steel making, or a slag after steel making. The detection method of the present invention can be used. The detection method of the invention can more accurately know the content of active calcium oxide, thereby helping to estimate the amount of calcium oxide to be added, avoiding the addition of excessive calcium oxide, and reducing the cost.

The present invention will be further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

<Example>

In order to verify that the detection method of the present invention is more accurate, the following Example 1 and Comparative Example 1 respectively used pure calcium oxide as a sample to be tested. In the case of pure calcium oxide, the content of active calcium oxide is (40.08/56.08) × 100% ≒ 71%, so that the closer the detection result is to 71%, the more accurate the detection.

<Example 1> The sample to be tested is pure calcium oxide

(A) using a filter screen having a pore size of 0.075 mm for sieving pure calcium oxide so that the particle size range of pure calcium oxide is less than or equal to 0.075 mm; (B) taking 0.5 g of the pure obtained in the step (A) Calcium oxide was placed in a 125 mL Erlenmeyer flask with 100 mL of a 6% sucrose aqueous solution (6 g of sucrose dissolved in 100 mL of water), and the cone was closed with a cork stopper. The bottle mouth was mixed in a closed environment to obtain a mixed solution; (C) the mixture was filtered using 5C filter paper [5C filter paper (named Quantitative ashless filter paper, model 5C 110mm) manufactured by Advantec, Japan], Obtaining a filtrate; (D) adding 5 mL of a concealing agent (a mixed solution of triethanolamine and water, obtained by mixing triethanolamine in a weight ratio of 1:1 with water) to the filtrate, and using 30% potassium hydroxide Adjusting the pH of the aqueous solution to 13 to obtain a test solution; and (E) adding a calcium carboxylic acid indicator to the test solution, and titrating with 0.05 M ethylenediaminetetraacetic acid solution to record the ethylenediaminetetraacetic acid solution. The amount of active calcium oxide was calculated to be 69.7% by the amount used.

<Comparative Example 1> The sample to be tested is pure calcium oxide

(A) using a filter screen having a pore diameter of 0.15 mm for sieving pure calcium oxide so that the particle size of the pure calcium oxide is less than or equal to 0.15 mm; (B) taking 0.5 g of the step (A) Pure calcium oxide and 100mL of 6% sucrose aqueous solution were placed in a 125mL Erlenmeyer flask (the ratio of pure calcium oxide to sucrose was 1:12), and the cork stopper was used to close the conical bottle mouth to close the environment. Mixing to obtain a mixed solution; (C) using a double-layer quantitative filter paper [purchased from Hangzhou Xinhua Paper Co., Ltd., model: double circle 110mm, diameter 0.08mm~0.12mm] to filter the mixture, to obtain a Filtrate; (D) 5 mL of a concealing agent (a mixed solution of triethanolamine and water, mixed with triethanolamine in a weight ratio of 1:1 and water) was added to the filtrate. To), using a 30% aqueous solution of potassium hydroxide to adjust the pH value of 13, to obtain a test solution; and (E) adding a calcium carboxylic acid indicator to the test solution, and using 0.05 M ethylenediaminetetraacetic acid solution The titration was carried out, and the amount of the ethylenediaminetetraacetic acid solution was recorded, and the proportion of the active calcium oxide was calculated to be 59.7%.

<Result>

Compared with the detection results of Example 1 and Comparative Example 1, the result of Example 1 was found to be 69.7%, which was closer to 71%, indicating that the method of the present invention can measure more accurate results.

<Examples 2 to 4 and Comparative Examples 2 to 4> The samples to be tested are three different calcium-based desulfurizing agents.

In Examples 2 to 4, except that the pure calcium oxide was replaced with three different calcium-based desulfurizing agents A, B, and C as shown in Table 1, Examples 2 to 4 were respectively subjected to the steps of Example 1. The test was carried out and the final results were summarized in Table 1.

In Comparative Examples 2 to 4, except that pure calcium oxide was replaced with three different calcium-based desulfurizing agents A, B, and C as shown in Table 1, Comparative Examples 2 to 4 were respectively subjected to the steps of Comparative Example 1. The test was carried out and the final results were summarized in Table 1.

Calcium-based desulfurizer A: According to XRF analysis, the main components are CaO: 51%; Al ₂ O ₃ : 30%; MgO: 7%; SiO ₂ : 6% calcium-based desulfurizer B: analyzed by XRF The main components are CaO: 53%; Al ₂ O ₃ : 29%; MgO: 6%; SiO ₂ : 6% calcium-based desulfurizer C: XRF analysis, the main component is CaO: 54%; ₂ O ₃ : 5%; MgO: 8%; SiO ₂ : 28%

<Result>

In Table 1, compared with the results of Example 2 and Comparative Example 2, it can be found that the result of Example 2 is higher than that of Comparative Example 2, and the comparison results of Examples 3 and 4 and Comparative Examples 3 and 4 can also be used. The same result was found, thus demonstrating that the detection method of the present invention does have better accuracy.

In summary, the method for detecting the active calcium oxide content of the present invention can effectively improve the accuracy of the detection method by controlling the particle size of the sample to be tested in the step (A) and the 5C filter paper of the step (C). At the same time let this The invention detection method is suitable for detecting various samples to be tested containing active calcium oxide, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

Claims (2)

A method for detecting active calcium oxide content comprises the following steps: (A) providing a sample to be tested having a particle size range of 0.075 mm or less, the sample to be tested being selected from a calcium-based desulfurizing agent and a non-calcium-based dephosphorizing agent. (B) mixing the sample to be tested with an aqueous solution of sucrose in a closed environment to obtain a mixed solution, wherein the sample to be tested in the step (B) and the sucrose in the aqueous solution of sucrose The weight ratio ranges from 1:10 to 1:25; (C) the mixture is filtered through 5C filter paper to obtain a filtrate; (D) a concealing agent is added to the filtrate, and the pH is adjusted to 13 to obtain a test solution. The concealing agent is a mixed solution of triethanolamine and water; and (E) adding an indicator to the test solution, and titrating with an ethylenediaminetetraacetic acid solution, and calculating from the use amount of the ethylenediaminetetraacetic acid solution The proportion of active calcium oxide. The method for detecting the content of active calcium oxide according to claim 1, wherein in the step (D), the pH is adjusted by passing through an aqueous potassium hydroxide solution.