Method for determining content of boron in coking coal

Abstract

The invention provides a method for determining the content of boron in coking coal, which comprises the following steps: (1) weighing 0.15-0.35 g of coking coal sample with the particle size of less than 0.2 mm, putting the coking coal sample into a digestion tank, and then adding ml of nitric acid solution, ml of hydrochloric acid solution and ml of hydrofluoric acid solution into the digestion tank; (2) the digestion tank is placed in a microwave digestion instrument to be heated and digested into a test solution, the heating temperature is 160-200 DEG C, and the heating time is 20-40 minutes; (3) transferring the test solution and fixing the volume to a 100mL volumetric flask; and (4) detecting the test solution by adopting an inductively coupled plasma spectrometer. According to the method, the sample is digested by adopting microwaves, the quantity of required chemical reagents is small, the digestion time is short, the digestion process is environment-friendly and free of harmful substance release, the digestion test solution is introduced into the inductively coupled plasma spectrometer, the mass spectrum intensity of the digestion test solution is measured, and the content of the sample is inversely calculated by using the calibration solution and the calibration blank.

Description

Technical Field

[0001] The invention belongs to the technical field of detection and relates to a method for determining the boron content in coking coal. Background Art

[0002] Coking coal is the main raw material for blast furnace ironmaking, and it acts as a reducing agent, heating agent, and material column skeleton. Its chemical performance indicators guide ironmaking technology, and the level of boron content affects the calorific value of coking coal. Accurately measuring the boron content can effectively control the stability of the coke oven and make it have a relatively stable calorific value. Too high or too low a content will affect the calorific value of coal. If the content is too high, boron will cause carbon to form amorphous carbon during the combustion of coal, making the calorific value low; if the content is too low, it will reduce the probability of boron combining with sulfur and nitrogen elements, making the calorific value low. At present, traditional wet analysis and ordinary chemical analysis cannot accurately determine its content. The sample is difficult to dissolve, there are many volatile harmful components, the measurement cycle is long, and many chemical reagents are used, so it is impossible to accurately determine the content of boron in coal. Summary of the invention

[0003] The purpose of the present invention is to provide a method for determining the boron content in coking coal in view of the problems existing in the prior art.

[0004] To this end, the present invention adopts the following technical solutions: A method for determining the boron content in coking coal comprises the following steps: (1) Weigh 0.15-0.35 g of a coking coal sample with a particle size of less than 0.2 mm and place it in a digestion tank. Then add 8-12 ml of nitric acid solution, 2-7 ml of hydrochloric acid solution and 1-5 ml of hydrofluoric acid solution into the digestion tank; (2) placing the digestion tank in a microwave digestion apparatus for heating and digestion into a test solution, wherein the heating temperature is 160-200° C. and the heating time is 20-40 minutes; (3) Transfer the test solution to a 100 mL volumetric flask; (4) The test solution was tested using an inductively coupled plasma spectrometer.

[0005] Furthermore, after the heating of the coking coal sample in step (2) is completed, the heating is maintained for 40-50 minutes.

[0006] Furthermore, in the step (3), the insoluble matter in the test solution is filtered before the test solution is fixed to volume.

[0007] The beneficial effects of the present invention are: using microwave to digest the sample, the amount of chemical reagents required is small, the digestion time is short, the digestion process is environmentally friendly and no harmful substances are released, the digestion test solution is introduced into an inductively coupled plasma spectrometer to measure its mass spectrum intensity, and the sample content is back-calculated using a calibration solution and a calibration blank. DETAILED DESCRIPTION

[0008] The present invention is described in detail below in conjunction with embodiments: A method for determining the boron content in coking coal comprises the following steps: (1) Weigh 0.15-0.35 g of a coking coal sample with a particle size of less than 0.2 mm and place it in a digestion tank. In this embodiment, take 0.2 g of the coking coal sample, then add 10 ml of nitric acid solution, 5 ml of hydrochloric acid solution and 3 ml of hydrofluoric acid solution to the digestion tank, and the amount of nitric acid solution, hydrochloric acid solution and hydrofluoric acid solution added is not more than 30 ml. Under the microwave environment, nitric acid can degrade the coal sample, reduce the activity of the coal, reduce the carbon and hydrogen contents, increase the oxygen and nitrogen contents, and enhance the oxidation effect. Add hydrochloric acid to decompose the elements such as silicon, calcium, aluminum, iron, and titanium in the coal into ions. Hydrofluoric acid can further dissolve the silicon, aluminum and other components in the coal, which is convenient for component detection.

[0009] (2) Cover the digestion plug on the digestion tank, and then place the digestion tank in a microwave digestion instrument for heating and digestion into a test solution. The digestion power is 1600w. The heating temperature during the digestion process is 160-200°C, 180°C in this embodiment, and the heating time is 20-40 minutes. In this embodiment, the heating time is 30 minutes. After the heating is completed, the coking coal sample is digested into a test solution. The test solution is kept warm for 40-50 minutes. In this embodiment, the test solution is kept warm for 40 minutes. By keeping warm, the sample can maintain a good digestion environment in a constant temperature stage, so that the sample is in a stable medium during digestion, eliminating uncertainties caused by inconsistent sample digestion conditions.

[0010] (3) Transfer the test solution to a 100 mL volumetric flask and filter out the insoluble matter before adjusting the volume.

[0011] (4) The test solution was tested using an inductively coupled plasma spectrometer. Specifically, the inductively coupled plasma spectrometer was started and the instrument was preheated for 3 hours. Sample analysis was performed after the instrument was stable. High-purity argon was purged for 5 minutes before measurement. The standard solution was introduced into the inductively coupled plasma spectrometer, and the working curve was fitted. The best boron element spectrum line was selected. The boron element content was calculated by measuring the spectral line intensity of the boron element from the working curve. The boron content in the coking coal samples tested so far was between 0.0015% and 0.0050%. Precision experiments and accuracy experiments were carried out using this method. The results showed that this method fully met the requirements for the analysis of the boron element content in coking coal samples.

Claims

1. A method for determining the boron content in coking coal, characterized in that: The following steps are involved: (1) Weigh 0.15-0.35 g of a coking coal sample with a particle size of less than 0.2 mm and place it in a digestion tank. Then add 8-12 ml of nitric acid solution, 2-7 ml of hydrochloric acid solution and 1-5 ml of hydrofluoric acid solution into the digestion tank; (2) placing the digestion tank in a microwave digestion apparatus for heating and digestion into a test solution, wherein the heating temperature is 160-200° C. and the heating time is 20-40 minutes; (3) Transfer the test solution to a 100 mL volumetric flask; (4) The test solution was tested using an inductively coupled plasma spectrometer.

2. The method for determining the boron content in coking coal according to claim 1, characterized in that: In the step (2), the solution is heated and digested into a test solution and then kept warm for 40-50 minutes.

3. The method for determining the boron content in coking coal according to claim 1, characterized in that: In the step (3), the insoluble matter in the test solution is filtered before the test solution is fixed to volume.