A method for calculating the amount of alkali slag in mining alkali slag gangue-based cementitious filling materials

Abstract

The present invention discloses a method for calculating the alkali slag content in a mine-used alkali slag gangue-based cemented filling material, which includes: (1) Sampling: Samples are taken from the bottom, middle, and top of the gob filling area, and each sample is divided into multiple portions of equal volume; (2) Crushing and grinding: The divided samples are crushed, and the cementitious materials are taken out without taking the gangue components. The cementitious materials in multiple samples are mixed, ground, and then sieved for standby; (3) Preparing the test solution: After drying the sieved samples, a part of the samples is placed in a drying bottle, distilled water without carbon dioxide is added, the bottle cap is covered, and after shaking, it is filtered; (4) Titrating with a silver nitrate standard solution; (5) Calculating the Cl ‑ content C 测 , (6) Recording the Cl ‑ content of the measured alkali slag as C 碱渣 ; (7) Obtaining the alkali slag content M according to the formula. The present invention solves the problem that the alkali slag content in the alkali slag gangue-based cemented filling material cannot be calculated, resulting in the inability to accurately monitor the construction quality.

Description

Technical Field

[0001] The invention relates to a cementing filling material for coal mines, in particular to a method for calculating the amount of alkali slag in an alkali slag gangue-based cementing filling material for mines. Background Art

[0002] Alkali residue refers to the solid waste residue discharged during the process of industrial alkali production and alkali treatment. Its main components are calcium carbonate, calcium sulfate, calcium chloride, etc., and it contains a small amount of sulfur dioxide and other components. According to statistics, for every ton of soda ash produced by the alkali plant, 300-600kg of solid waste alkali residue is discharged. Due to the high water content and high chloride ion content of alkali residue, the treatment of solid waste alkali residue is extremely difficult, and the utilization rate is less than 15%. Alkali residue treatment is mainly surface accumulation, which occupies a large amount of land resources, pollutes the soil and groundwater, and harms the ecological environment. Solid waste alkali residue has large retention, low diffusion, and long latent period. How to safely treat solid waste alkali residue has seriously affected the sustainable development of enterprises. It is urgent to develop new methods of resource-based, large-scale and high-value alkali residue utilization.

[0003] In order to prevent the occurrence of road subsidence in goaf areas, the generation of goaf areas during mining should be reduced. The filling coal mining technology is the core technology of the green mining system in mining areas. It also has the advantages of reducing mining, reducing gangue emissions and alleviating road subsidence in mining areas. Filling materials are the core key to cemented filling coal mining technology, among which gangue-based cemented filling materials mainly composed of gangue solid waste have been widely used. Many domestic and foreign scholars have conducted extensive research on the slump, setting time, compressive strength and material mix ratio of gangue cemented filling materials. With the complex geological conditions of mine mining and the increasingly prominent requirements for large-scale solid waste treatment and filling material cost reduction, researchers are constantly exploring the performance improvement of cemented filling materials and the development of new solid waste cemented filling materials.

[0004] Based on the fact that no steel bars are laid in the goaf and there is no potential threat of chloride ion corrosion, some scholars have studied the technology of using alkali slag to prepare alkali slag cemented filling materials. Practice has shown that the appropriate amount of alkali slag improves the mechanical properties of alkali slag gangue-based cemented filling materials, but when the alkali slag content is too high, the mechanical properties of the alkali slag gangue-based cemented filling materials decrease, and too high an alkali slag content will lead to excessively high salt content in the alkali slag gangue-based cemented filling materials, causing groundwater pollution. Therefore, the detection and control of the alkali slag content in the application process of coal mines is particularly important.

[0005] At present, there is no method for calculating the alkali slag content of alkali slag gangue-based cementitious filling materials to accurately detect the on-site alkali slag content of alkali slag gangue-based cementitious filling materials during coal mine filling and mining. Summary of the invention

[0006] Purpose of the invention: To solve the problem that the alkali residue content in alkali residue gangue-based cementing filling materials cannot be measured, resulting in the inability to accurately monitor the construction quality, because the raw materials of alkali residue gangue-based cementing filling materials, such as cement, lime and fly ash, do not contain Cl - , Cl in the cementitious material of alkali slag gangue-based cementitious filling material after solidification - The main content of alkali slag is from the alkali slag component. The present invention proposes a method for calculating the amount of alkali slag in mining alkali slag gangue-based cementing filling materials. By testing the Cl content in the alkali slag raw materials, - Content, and Cl in the test sample - The content is calculated quantitatively based on each other, and the calculation formula for the alkali slag content in the alkali slag gangue-based cementing filling material is given, so as to effectively and accurately detect the on-site alkali slag content of the alkali slag gangue-based cementing filling material during the coal mine filling and mining process, providing guarantee for the mix ratio control of the alkali slag gangue-based cementing filling material and the quality control of the filling and mining of the goaf.

[0007] Technical solution: The method for calculating the amount of alkali slag in the mining alkali slag gangue-based cementing filling material of the present invention comprises the following steps:

[0008] (1) Sampling: Take samples from the bottom, middle and top of the goaf filling area after construction is completed, and then divide each sample into multiple portions of equal volume;

[0009] (2) crushing and grinding: crushing the divided samples, taking out the cementing materials therein, excluding the gangue components, mixing and grinding the cementing materials in the multiple samples, and sieving them for later use;

[0010] (3) preparing the test solution; drying the sieved sample, selecting a portion of the sample and placing it in a drying bottle, adding distilled water without carbon dioxide, capping the bottle, shaking, and filtering;

[0011] (4) Titration with silver nitrate standard solution: First, prepare the reagents: methyl orange indicator, sodium bicarbonate: 0.02 mol / L sodium bicarbonate solution, potassium chromate indicator: 50 g / L potassium chromate solution, silver nitrate: 0.02 mol / L silver nitrate standard solution;

[0012] Use a pipette to take several portions of soil sample leachate and put them into a bottle. Add methyl orange indicator, add 0.02mol / L NaHCO3 solution drop by drop until the test solution turns pure yellow, control the pH to 7, and then add 5-6 drops of 5% potassium chromate (K2CrO4) indicator (Note: The concentration of K2CrO4 indicator has an effect on the titration result. The concentration of CrO4 in the solution 2- If the ion concentration is too high, the endpoint will appear early, making the titration result low. On the contrary, CrO4 2-If the concentration is too low, the endpoint will be delayed and the result will be too high. Add 1 drop of K2CrO4 indicator to every 5mL solution and titrate with 0.02mol / L silver nitrate standard solution. + +Cl - ==AgCl↓, the white precipitate of silver chloride generated during the titration process easily absorbs Cl - , so that the Cl in the solution - The concentration is reduced, resulting in the premature generation of brick-red AgCrO4 precipitation before the equivalence point. Therefore, the titration is shaken to allow the adsorbed Cl - When the chloride ions in the water are titrated, the excess silver nitrate will react with potassium chromate to form a stable brick-red silver chromate precipitate 2Ag + +CrO4 2- = = Ag2CrO4↓, indicating the arrival of the titration endpoint. Record the amount of AgNO3 standard solution used in each portion and take the average value of each portion. - The content is very high, reduce the amount of leaching solution, and take another portion for determination;

[0013] (5) Calculate Cl according to the following formula - Content C 测

[0014]

[0015] C 测 =Cl - (%) = Cl - (mmol / kg)×0.0355×10 -1

[0016] Where: c——concentration of silver nitrate standard solution (mol / L);

[0017] V——Volume of silver nitrate solution for titration (mL);

[0018] m——the mass of dry soil equivalent to the volume of leachate taken during analysis (g);

[0019] 0.0355 – molar mass of chloride (g / mmol);

[0020] (6) The alkali slag used in the alkali slag gangue-based cementitious filling material (the chloride ion content in fly ash, cement and lime is negligible, so the Cl in fly ash is detected in the remaining active substances - ), after grinding and sieving respectively, repeat the above steps (3) to (5) for testing, and measure the Cl content of the alkali residue. - The content is recorded as C 碱渣 .

[0021] (7) According to the formula The measured C 测 Substitute the formula to calculate the actual alkali slag dosage M, and compare it with the optimal ratio to check the construction quality.

[0022] In step (3), the sieved samples are dried at 105-110° C., and then selected samples are placed in bottles.

[0023] In step (3), the distilled water is boiled and then cooled.

[0024] In step (4), add 1 drop of K2CrO4 indicator for every 5 mL of solution.

[0025] Working principle: Because the raw materials of alkali slag gangue-based cementing filling materials, cement, lime and fly ash do not contain Cl - , Cl in the cementitious material of alkali slag gangue-based cementitious filling material after solidification - The main component comes from the alkali residue. The present invention uses the traditional silver nitrate standard solution titration method to grasp the Cl content in the alkali residue raw material. - Methods for detecting Cl in samples - The content is calculated quantitatively based on each other, and a calculation formula for the alkali slag content in alkali slag gangue-based cementitious filling materials is given, thereby forming a test and calculation method for the alkali slag content in mining alkali slag gangue-based cementitious filling materials.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0027] (1) The method of the present invention utilizes the advantages of silver nitrate titration: accurate test results and fast test speed. At the same time, through a large number of indoor experiments, the calculation formula of alkali residue dosage is summarized: The problem of difficulty in measuring and controlling the amount of alkali slag in the engineering construction mix ratio is solved.

[0028] (2) Through the measurement method of the present invention, the construction quality of the goaf filling area after construction is monitored, and at the same time, the standardization of the construction ratio is supervised to prevent irregular behavior in the amount of alkali slag added during the construction process, which will lead to the lack of safety in subsequent use. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart for calculating the alkali slag content in the mining alkali slag gangue-based cementing filling material of the present invention;

[0030] Figure 2 The test solution is a solution to which methyl orange, sodium bicarbonate and potassium chromate are added in the present invention;

[0031] Figure 3 The present invention is a process diagram for the titration of a silver nitrate standard solution;

[0032] Figure 4 This is a solution diagram of a brick-red precipitate produced after the titration of the present invention is completed. DETAILED DESCRIPTION

[0033] like Figures 1 to 4 As shown, the method for calculating the amount of alkali slag in the mining alkali slag gangue-based cementing filling material of the present invention comprises the following steps:

[0034] (1) Sampling: Take samples of 5.00 cm × 5.00 cm × 5.00 cm from the bottom, middle and top of the goaf filling area after construction is completed, and then divide each sample into eight equal parts of 2.50 cm × 2.50 cm × 2.50 cm;

[0035] (2) Crushing and grinding: The divided samples are crushed, and only the cementing materials are taken out without taking the gangue components. The cementing materials in the 24 samples are fully mixed, ground, and passed through a 1 mm sieve for later use;

[0036] (3) Prepare the test solution; dry the sieved sample in an oven for 8 hours (105-110°C), select 50g of the sample, accurate to 0.01g, and put it into a dry 1000mL wide-mouth plastic bottle. Add distilled water without carbon dioxide (i.e. boil the distilled water for 10 minutes and cool it) at a soil-water ratio of 1:5, cover the bottle stopper, shake it on an oscillator for 3 minutes, and filter it;

[0037] (4) Titration with silver nitrate standard solution: First, prepare the reagents: methyl orange indicator, sodium bicarbonate: 0.02 mol / L sodium bicarbonate solution, potassium chromate indicator: 50 g / L potassium chromate solution, silver nitrate: 0.02 mol / L silver nitrate standard solution;

[0038] Use a pipette to take three portions of soil sample leachate, 25 mL each, and place them in a conical flask. Add methyl orange indicator, add 0.02 mol / L sodium bicarbonate (NaHCO3) solution drop by drop until the test solution turns pure yellow, control the pH to 7, and then add 5-6 drops of 5% potassium chromate (K2CrO4) indicator (the concentration of K2CrO4 indicator has an effect on the titration result. The CrO4 in the solution 2- If the ion concentration is too high, the endpoint will appear early, making the titration result low. On the contrary, CrO4 2- If the concentration is too low, the endpoint will be delayed and the result will be too high. Add 1 drop of K2CrO4 indicator to every 5mL solution and titrate with 0.02mol / L silver nitrate standard solution. + +Cl - ==AgCl↓, the white precipitate of silver chloride generated during the titration absorbs Cl - , so that the Cl in the solution -The concentration is reduced, resulting in the premature generation of brick-red AgCrO4 precipitation before the equivalence point. Therefore, the titration is continuously shaken to allow the adsorbed Cl - When the chloride ions in the water are titrated, the excess silver nitrate will react with potassium chromate to form a brick-red silver chromate precipitate 2Ag + +CrO4 2- = = Ag2CrO4↓, indicating the arrival of the titration endpoint. Record the amount of AgNO3 standard solution used in each portion and take the average of the three portions. - The content is very high, reduce the amount of leaching solution, and take another portion for determination;

[0039] (5) Calculation of Cl - The Cl content is calculated according to the following formula - Content C 测

[0040]

[0041] C 测 =Cl - (%) = Cl - (mmol / kg)×0.0355×10 -1

[0042] Where: c——concentration of silver nitrate standard solution (mol / L);

[0043] V——Volume of silver nitrate solution for titration (mL);

[0044] m——the mass of dry soil equivalent to the volume of leachate taken during analysis (g);

[0045] 0.0355 – The molar mass of chloride (g / mmol).

[0046] (6) The alkali slag used in the alkali slag gangue-based cementitious filling material (the chloride ion content in fly ash, cement and lime is negligible, so only the Cl in fly ash is detected among the remaining active substances) - ), after grinding and passing through a 1 mm sieve, repeat the above steps (3) to (5) for testing. - The content is recorded as C 碱渣 .

[0047] (7) According to the formula The measured C 测 Substitute the formula to calculate the actual alkali slag dosage M, and compare it with the optimal ratio to check the construction quality.

[0048] The alkali residue used in the experiment in the embodiment of the present invention comes from Huai'an Alkali Factory. The fresh alkali residue is gray-white sticky paste with a pungent smell and strong corrosiveness. The alkali residue is naturally air-dried, and the chemical composition of the air-dried alkali residue is analyzed by XRF test. The chemical composition analysis results are shown in Table 1.

[0049] Table 1 Chemical composition of alkali slag

[0050] Element CaO <![CDATA[SO3]]> Cl <![CDATA[SiO2]]> <![CDATA[NaO2]]> content(%) 52.25 16.97 18.39 4.06 2.46 Element(%) MgO <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[K2O]]> other content(%) 2.33 1.76 1.17 0.15 0.46

[0051] This experiment attempts to use old aggregate to replace gangue, and alkali slag to replace fly ash. The influencing factors considered are mass fraction, old gangue ratio (the mass of old aggregate is the mass of gangue), alkali slag content and fly ash content (each content represents the percentage of the total amount of gangue and old aggregate). Each factor is set to four levels, that is, four factors and four levels. According to the orthogonal test principle, L 16 (44) Orthogonal test table, and designed an orthogonal test scheme, and obtained the best mix ratio of fly ash content: alkali slag content: old gangue ratio = 0.75: 0.15: 0.1, with a mass fraction of 79%. Four groups of test pieces with different alkali slag content were selected from the orthogonal experiment, and two control groups were added, namely, 0 alkali slag content and 100% dry alkali slag. In order to more intuitively represent the content of alkali slag, the present invention converts the alkali slag content into the percentage of alkali slag in the total mass. The chloride ion content of the six groups of tests was measured by silver nitrate titration.

[0052] In order to verify the alkali residue content calculation method of the present invention, an example is carried out for verification, and the material proportion of the example is shown in Table 1:

[0053] Table 1 Material ratio table of control group and each embodiment

[0054]

[0055] In order to verify the alkali slag metering test control and measurement method of the present invention, the alkali slag group and the alkali-free slag group were also treated according to the above method, and the prepared test solution was titrated with chloride ions. Three parallel experiments were performed, and the titration was performed with AgNO3 standard solution. The titration was performed with shaking as the titration was performed until a brick-red precipitate appeared, which was the end point. The volume of the consumed AgNO3 standard solution was recorded, and the Cl - Content C 测 , and calculated as shown in Table 2.

[0056] Table 2 Alkali slag cementing material Cl - Content table

[0057]

[0058] The experimental results show that Cl in alkali slag cementing materials -Most of them come from alkali slag, while the content in fly ash, cement and lime is negligible. From this, we can draw a rule that when the amount of alkali slag is increased, the Cl in the cementing material - The more the content, the more alkali residue group is recorded as C 碱渣 , we get the formula: It has been verified that the error of the result calculated by this method does not exceed 0.6%.

[0059] From the results of the above experimental cases, it can be seen that the calculation method of the present invention can accurately calculate the dosage of alkali slag in the alkali slag gangue-based cementitious filling materials in the goaf, which is beneficial to the accurate control of the alkali slag gangue-based cementitious filling materials during the construction and application process and the quality assurance of the later filling of the goaf.

Claims

1. A method for calculating the amount of alkali slag in a mining alkali slag gangue-based cementing filling material, characterized in that: The following steps are involved: (1) Sampling: Take samples from the bottom, middle and top of the goaf-filling area, and divide each sample into multiple portions of equal volume; (2) crushing and grinding: crushing the divided samples, taking out the cementing materials therein, mixing and grinding the cementing materials in the multiple samples, and sieving them for later use; (3) Prepare the test solution, dry the sieved sample, select a portion of the sample and put it into a drying bottle, add distilled water without carbon dioxide, cover the bottle with a stopper, shake and filter; (4) Titration with silver nitrate standard solution: first prepare the reagents, then use a pipette to take three portions of soil sample leachate, 25 mL each, and place them in a conical flask; add methyl orange indicator, add 0.02 mol / L NaHCO3 solution drop by drop until the test solution turns pure yellow, control the pH to 7, then add 5-6 drops of 5% K2CrO4 indicator, add 1 drop of K2CrO4 indicator for every 5 mL of solution, and titrate with 0.02 mol / L silver nitrate standard solution. The reaction Ag + +Cl - ==AgCl↓, the white precipitate of silver chloride generated during the titration absorbs Cl - , so that the Cl in the solution - Concentration decreases; When the chloride ions in the water are titrated, the excess silver nitrate reacts with potassium chromate to form a brick-red silver chromate precipitate 2Ag. + +CrO4 2- ==Ag2CrO4↓, indicating the arrival of the titration endpoint; record the amount of AgNO3 standard solution used in each portion and take the average value of multiple portions; (5) Calculate Cl according to the following formula - Content C 测 C 测 =Cl - (%)=Cl - (mmol / kg)×0.0355×10 -1 Where: c——concentration of silver nitrate standard solution (mol / L); V——Volume of silver nitrate solution for titration (mL); m——the mass of dry soil equivalent to the volume of leachate taken during analysis (g); 0.0355 – molar mass of chloride (g / mmol); (6) Select the alkali slag used for the alkali slag gangue-based cementing filling material, grind and sieve it, and repeat the above steps (3) to (5) for testing. - The content is recorded as C 碱渣 ; (7) According to the formula The measured C 测 Substitute the formula to calculate the actual alkali slag dosage M, and compare it with the optimal ratio to check the construction quality.

2. The method for calculating the amount of alkali slag in mining alkali slag and gangue-based cementitious filling materials according to claim 1, characterized in that: In step (3), the sieved samples are dried at 105-110° C., and then selected samples are placed in bottles.

3. The method for calculating the amount of alkali slag in mining alkali slag and gangue-based cementitious filling materials according to claim 1, characterized in that: In step (3), the distilled water is boiled and then cooled.

4. The method for calculating the amount of alkali slag in mining alkali slag and gangue-based cementitious filling materials according to claim 1, characterized in that: In step (4), add 1 drop of K2CrO4 indicator for every 5 mL of solution.

5. The method for calculating the amount of alkali slag in mining alkali slag and gangue-based cementitious filling materials according to claim 1, characterized in that: In step (4), 0.02 mol / L silver nitrate standard solution is used for titration to react Ag + +Cl - ==AgCl↓, the white precipitate of silver chloride generated during the titration absorbs Cl - , so that the Cl in the solution - The concentration is reduced, that is, brick-red AgCrO4 precipitates are produced prematurely, so the titration is shaken to make the adsorbed Cl - Release it.

6. The method for calculating the amount of alkali slag in mining alkali slag and gangue-based cementitious filling materials according to claim 1, characterized in that: In step (4), if Cl - If the content is higher than the set value, reduce the amount of leaching solution and take another portion for measurement.

Images