Method for rapidly determining chlorine ion content in coal and coke

Abstract

The invention relates to a method for rapidly measuring the content of chloride ions in coal and coke. The method comprises the following steps: uniformly pouring dried and sieved coal or coke powder into a sample cup through a limiting funnel; adding a small amount of boric acid powder to cover the sample and troweling to form a stable analysis substrate; covering a gland, tensioning the rocker arm, and applying specified pressure to the piston; a compact and flat powder tabletting analysis sample is obtained; selecting proper measurement conditions according to the type of a used instrument, the type of a sample, analysis elements, coexisting elements and content change ranges of the analysis elements and the coexisting elements; after a certain number of standard substance samples similar to the analysis sample are selected and pressed into tablets, a calibration curve is drawn according to the content value of the analysis element in the standard substance and the average value of the measured X-ray fluorescence intensity. And standardization and automation of the whole process of sample preparation and measurement are realized, so that the content of chloride ions in coal and coke can be quickly obtained within 30 minutes or less, the detection precision and accuracy completely meet the standard requirements, and the operation risk and the environmental burden are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of detection, in particular to a method for rapidly determining the content of chloride ions in coal and coke. BACKGROUND

[0002] With the development of science and technology and the continuous progress of society, in the iron industry, the production technology and process level gradually improve, in the production process of blast furnace, the influence and harm of controlling chlorine in blast furnace need to monitor the content of each chloride ion of the charging material, at present, in the process of ore matching, the content of chloride ions in coal and coke does not have corresponding detection ability, which leads to a certain deviation of the theoretical calculation of the content of chloride ions in blast furnace ore matching. In order to guide the ore matching of blast furnace and improve the accuracy of theoretical prediction of ore matching, it is necessary to develop a detection method for detecting the content of chloride ions in coal and coke. After checking, no relevant standard is found to support the determination of the content of chloride ions in coke, but the determination method of chloride ions in coal has corresponding national standard support. The national standard "GB / T 3558-2014 Determination of Chlorine in Coal" adopts the traditional chemical analysis detection method, the operation process is complicated, the operation details are many, the detection period is long, most of the reagents are chemical hazardous products, and the detection efficiency is low, which cannot meet the current increasingly complex and fast-paced production demand.

[0003] The existing method "GB / T 3558-2014 Determination of Chlorine in Coal" has high temperature combustion hydrolysis-potentiometric titration method and ascarite mixed agent sample fusion-potassium thiocyanate titration method. The principle of high temperature combustion hydrolysis-potentiometric titration method is that the coal sample is burned and hydrolyzed in the mixed gas flow of oxygen and water vapor, the chlorine in the coal is all converted into chloride and quantitatively dissolved in water. Silver is used as an indicating electrode, silver-chloride silver is used as a reference electrode, the concentration of chloride ions in the condensate is directly titrated by silver nitrate potential method, and the total chlorine content in the coal sample is calculated according to the amount of silver nitrate standard solution. The principle of ascarite mixed agent sample fusion-potassium thiocyanate titration method is that the coal sample is mixed with ascarite mixed agent and put into a muffle furnace for melting, so that the chlorine is converted into chloride. The chloride is leached with boiling water, an excess of silver nitrate solution is added in an acidic medium, ferric ammonium sulfate is used as an indicator, potassium thiocyanate is titrated, and the content of chlorine in the coal is calculated according to the actual consumption of silver nitrate solution. Both of them adopt the traditional chemical analysis titration method, the operation process is complicated, the operation details are many, the detection period is long, most of the reagents are chemical hazardous products, and the detection efficiency is low, which cannot meet the current increasingly complex and fast-paced production demand. SUMMARY

[0004] In order to overcome the above-mentioned defects of the prior art, the purpose of the present application is to provide a method for rapidly determining the content of chloride ions in coal and coke.

[0005] The technical scheme adopted by the present application to solve its technical problems is: a method for rapidly determining the content of chloride ions in coal and coke, comprising the following steps:

[0006] S1: use the key to pour the sample powder along the limiting funnel, distribute uniformly; then put a small amount of boric acid powder into the limiting funnel and its four around, draw out the limiting funnel and add the appropriate amount of boric acid powder, but not more than the sample cup plane;

[0007] S2: flatten the boric acid powder, cover the pressure cover, tighten the rocker arm, align the upper plane of the piston with the bottom surface of the upper column, and start the piston rising switch; at this time, the piston rises to the specified pressure, and after 30 seconds of constant pressure, the piston automatically descends;

[0008] S3: pull the rocker arm, start the piston rising switch again to the specified sample sheet; according to the type of instrument used, the type of sample, the analyzed elements, the coexisting elements and the content variation range, select appropriate measurement conditions;

[0009] S4: select a certain number of standard material samples similar to the analyzed sample, press them into sheets, and draw a calibration curve of the content value of the analyzed element in the standard material and the average value of the measured X-ray fluorescence intensity.

[0010] As a further improvement of the application: the analyzed sample with a particle size less than 0.2mm is dried at 105-110℃ before analysis, and cooled to room temperature in a dryer.

[0011] As a further improvement of the application: the boric acid substrate powder tabletting machine has a maximum pressure of not less than 50 tons, and a use pressure of not less than 40 tons.

[0012] As a further improvement of the application: the working pressure of the sample pressing machine is adjusted to 40 tons, and the pressure holding time is 30 seconds.

[0013] As a further improvement of the application: the inner wall of the sample cup is wiped clean with alcohol-dipped degreasing cotton, and the upper plane of the piston and the inner wall of the limiting funnel are wiped clean.

[0014] As a further improvement of the application: each sample in step S4 should be measured at least twice.

[0015] As a further improvement of the application: it also includes instrument drift correction, which uses two-point correction, and the interval time for correction can be determined according to the stability of the instrument.

[0016] As a further improvement of the application: it also includes drawing three samples for detection and comparison by different types of detection equipment.

[0017] Compared with the prior art, the beneficial effects of the application are: by using Mylar film and boric acid substrate to seal the sample for pressing, qualified powder tablet samples are prepared, the intensity of the sample is measured by X-ray fluorescence instrument, and the percentage content of chloride ions in the sample is calculated by the prepared calibration curve. This technology replaces the cumbersome chemical analysis method, saves detection time, and improves detection efficiency.

[0018] Secondly, the present application adopts wavelength dispersion X-ray fluorescence spectrometry to determine the sample composition, the sample tablet preparation operation is simple, has great advantages compared with the traditional chemical method, and the precision of the method is equivalent to that of the traditional chemical method, and the error caused by human factors and reagents is reduced. The deviation of the X fluorescence instrument in determining the chlorine ions in coal and coke meets the requirements of the national standard. The method is simple and fast, reduces the daily consumption of markers and chemical reagents, and reduces the discharge of chemical waste liquid. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor under the premise of the drawings.

[0020] Figure 1 The flowchart of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear, the following will combine the specific embodiments of the present application and the corresponding drawings to clearly and completely describe the technical scheme of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0022] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0023] There is no special specification for the content of chloride ions in coke in market and industry standards, resulting in the inability to obtain the data of the content of chloride ions in the coke part in the blast furnace ore proportioning, and the existence of a blind area in the theoretical calculation of ore proportioning; meanwhile, a high-temperature furnace, oxygen and water vapor mixed atmosphere combustion and hydrolysis are required; subsequent condensation, collection of liquid and use of silver / silver chloride electrode, silver nitrate potential titration are required; the instrument is complex, energy consumption is high, the steps are many and the requirement for the sealing of the device is strict. The sample is mixed with the ashless flux and high-temperature melted (muffle furnace condition), and the chlorine is completely converted into soluble chloride; after melting, the sample is immersed in boiling water, acidified, an excess of silver nitrate is added and titrated with potassium thiocyanate; the process involves high-temperature melting, hot leaching, multiple acidification and indication, and the operation steps are long. The two traditional titration methods take several hours to tens of hours from sampling to result, which is difficult to give feedback within a day or even several hours, which is not conducive to the rapid adjustment of the blast furnace burden scheme. Oxygen, silver nitrate, ashless flux, concentrated acid, potassium thiocyanate and the like are all flammable, explosive, toxic or corrosive, and the reagent procurement, storage and waste liquid disposal links have high cost and safety hazards. The whole process relies on manual operation and complicated instrument switching, and the degree of automation and online is almost zero, and it is difficult to realize rapid parallel detection of multiple points.

[0024] To solve the above problems, the present application provides a method for rapidly determining the content of chloride ions in coal and coke, comprising the following steps:

[0025] S1: use a key to pour the sample powder along the limiting funnel, and distribute it uniformly; then add a small amount of boric acid powder to the limiting funnel and its four surrounding areas, pull out the limiting funnel and add an appropriate amount of boric acid powder, but not exceeding the sample cup plane;

[0026] S2: smooth the boric acid powder, cover the pressure cover, tighten the rocker arm, align the upper surface of the piston with the bottom surface of the upper column, and start the piston rising switch; at this time, the piston rises to the specified pressure, and after maintaining the constant pressure for 30 seconds, the piston automatically descends;

[0027] S3: pull open the rocker arm, and start the piston rising switch again to the specified sample piece; according to the type of the instrument used, the type of the sample, the analyzed element, the coexisting element and the content variation range thereof, select appropriate measurement conditions;

[0028] S4: select a certain number of standard material samples similar to the analyzed sample, press them into a sheet, and draw a calibration curve of the content value of the analyzed element in the standard material and the average value of the measured X-ray fluorescence intensity.

[0029] The application can provide fast, accurate and reliable chlorine content data support for blast furnace ore matching by powder tabletting and wavelength dispersive X-ray fluorescence spectrometry, and has excellent performance in detection speed, precision, safety and cost control.

[0030] As an embodiment of the application, the sample particle size of the analysis sample used in the method for rapidly determining the chlorine ion content in coal and coke is less than 0.2 mm, and the analysis sample should be dried at 105-110 DEG C and cooled to room temperature in a dryer before analysis.

[0031] The uniformity and reproducibility of the powder are ensured, the tabletting density is consistent, the measurement error caused by different particle sizes is reduced, the surface roughness and porosity are reduced, the X-ray penetration and fluorescence emission efficiency in the sample are enhanced, the signal-to-noise ratio and detection sensitivity are improved, the contact area between the sample and the boric acid substrate is improved, the tabletting forming is ensured to be flat, and the measurement reproducibility is further improved.

[0032] As an embodiment of the application, the instruments and equipment used include:

[0033] Wavelength dispersive X-ray fluorescence spectrometer: the instrument is configured with a fixed channel and a scanning channel, and can measure spectral lines.

[0034] Sample pressing machine: the sample pressing machine for boric acid substrate powder tabletting, the maximum pressure is not less than 50 tons, and the use pressure is not less than 40 tons.

[0035] As a specific embodiment of the present application, turn on the power of the sample machine, adjust the working pressure to 40 tons, and keep the pressure for 30 seconds; wipe off the dust on the inner wall of the sample cup, wipe off the flat surface of the piston and the inner wall of the limiting funnel with alcohol-dipped degreasing cotton; lower the piston to the appropriate position, place the Mylar film and the limiting funnel, and pour the sample powder along the limiting funnel with the key, which should be evenly distributed and cannot be empty. Then, add a small amount of boric acid powder to the limiting funnel and its surroundings, remove the limiting funnel, and add an appropriate amount of boric acid powder, but not exceeding the flat surface of the sample cup. Smooth the boric acid powder, cover the pressure cover, tighten the rocker arm, align the flat surface of the piston with the bottom surface of the upper column, and start the piston rising switch. At this time, the piston rises to the specified 40 tons of pressure, and after keeping constant for 30 seconds, the piston automatically descends. Pull off the rocker arm, and start the piston rising switch again to the specified sample sheet. Blow off the floating dust on the surface of the sample sheet with the ear suction ball, paste the sample label on the bottom surface of the sample sheet, and put the prepared sample sheet into the sample bag with the pre-written label for the next step of analysis.

[0036] Ensure that the sample tablet is formed into a stable, dense, and uniform solid sheet, improve the mechanical strength and surface flatness of the sample, avoid loose, fragile, or internal voids caused by insufficient pressure, ensure the consistency of X-ray excitation and fluorescence emission, and thus improve the measurement accuracy and repeatability. Eliminate the influence of residual dust or foreign matter on the sample forming quality and thickness uniformity; prevent impurities from mixing to cause background interference signals, and improve the measurement purity and data reliability.

[0037] As a specific embodiment of the present application, according to the type of instrument used, the type of sample, the analyzed element, the coexisting element, and the content variation range, select appropriate measurement conditions. The analysis line used, the recommended wavelength, the spectrometer crystal, 2Theta, the light tube voltage and current, etc. are listed in Table 1, and the fixed channel of the corresponding element can also be used.

[0038] Table 1 Measurement conditions

[0039]

[0040] Couple the selected wavelength with the Ge(111) crystal face at the Bragg diffraction maximum position to ensure maximum signal acquisition; improve the measurement sensitivity and ensure the stability of the instrument at this angle. Provide sufficient excitation energy and tube current to significantly enhance the Cl fluorescence emission intensity; while meeting the signal intensity, avoid excessive current causing tube target overheating or background noise rising.

[0041] Preparation of calibration curve:

[0042] Under selected working conditions, a certain number of standard material samples similar to the analysis sample are pressed into tablets, and the standard materials are shown in Table 2. Each sample should be measured at least twice, and the content value of the analysis element in the standard material is plotted with the average value of the measured X-ray fluorescence intensity to draw a calibration curve. The X-ray intensity ratio of the analysis element and the internal standard element in the standard sample is measured, and the working curve is drawn with the intensity ratio relative to the content of the analysis element. The calibration curve is shown in Tables 3 and 4.

[0043] Table 2: Standard materials for drawing calibration curves

[0044]

[0045] Table 3: Coal calibration curve

[0046]

[0047] Table 4: Coke calibration curve

[0048]

[0049] As a specific embodiment of the present application, the analysis of the unknown sample also includes instrument drift correction, drift correction confirmation, unknown sample measurement and accuracy experiment.

[0050] Among them, the instrument drift correction will cause the deviation of the determination result due to the change of the instrument state. In order to directly use the original X-ray fluorescence intensity value, before the analysis work, the drift correction sample is used to correct the instrument drift. Two-point correction is adopted, and the interval time of correction can be determined according to the stability of the instrument.

[0051] Among them, the analysis of the standard material after drift correction confirms that the analysis value should meet the range specified in the national standard "GB / T3558-2014 Determination of chlorine in coal Method".

[0052] Among them, the measurement of the unknown sample is carried out according to the powder tablet preparation and the selected measurement conditions, and the selected calibration curve is measured by the corresponding program. The unknown sample should be measured before the determination of the unknown sample, and the calibration curve should be determined after the determination of the unknown sample.

[0053] Among them, 3 standard samples are selected at random and measured according to the analysis steps of the unknown sample, each sample is measured twice, and the average value is compared with the allowable difference value. As can be seen from Table 5, the deviation between the certified value and the measured value is small, and it is within the range specified in "GB / T3558-2014 Determination of chlorine in coal Method", which meets the standard requirements.

[0054] Table 5: Chlorine ion accuracy determination (%)

[0055]

[0056] Three samples were extracted respectively and detected by different types of detection equipment for comparison, as shown in Table 6, the results of the determination of the chlorine content in the samples by different types of instruments are similar, and the deviation is small, which verifies the accuracy of the detection results.

[0057] Table 6 Chloride ion accuracy determination (%)

[0058]

[0059]

[0060] As a specific embodiment of the present application, the precision experiment also includes: each selecting a coal and coke sample, using the method established by the present method to continuously determine 11 times, and performing precision test, and calculating the relative standard deviation of each element, which is shown in Table 7. The relative standard deviation of the determination of the chloride ion content in the sample by the method is less than 2%, the data precision is good, the data deviation degree is low, and all can meet the production requirements.

[0061] Table 7 Chloride ion precision determination (%) n=11

[0062]

[0063] The main functions of the present application are:

[0064] (1) Rapid high-throughput detection, from sample drying to tabletting completion only takes several minutes, and the whole process of tabletting-measuring takes less than 30 minutes for a single sample; wavelength dispersive XRF can obtain Cl and other element signals at one time, supports batch continuous measurement, and meets the needs of multi-point and multi-frequency detection of blast furnace ore matching;

[0065] (2) High accuracy, sample particle size (<0.2mm) and strict drying (105℃-110℃) ensure matrix uniformity and mass stability, eliminate signal absorption deviation caused by moisture and particle size difference; adopt internal standard intensity ratio and multi-point calibration curve regression correction, significantly reduce matrix effect interference, and make the determination value deviation fall within the allowable range of GB / T 3558-2014;

[0066] (3) Pressure (40t) and pressure holding time (30s) ensure that the sample density and surface flatness are consistent; precision experiment 11 times of repeated determination, the relative standard deviation of Cl ion content is less than 2%, the repeatability and reproducibility are better than those of the traditional chemical method;

[0067] (4) No high-temperature combustion, water vapor hydrolysis, strong acid or toxic indicator is needed, only a small amount of boric acid substrate and melinex film is used, reagent consumption and waste liquid production are very small; XRF measurement process is completely closed, no chemical volatilization, laboratory safety risk is greatly reduced, and environmental protection pressure is significantly relieved;

[0068] (5) According to different coal, coke matrix and coexisting element content, flexible selection of analysis spectrum, collimator, crystal and tube voltage and current can simultaneously quantitatively analyze multiple elements; the same set of instruments and methods can easily extend from laboratory analysis to online / semi-online detection, providing data support for intelligent, blast furnace dynamic optimization of ore matching.

[0069] In summary, after reading the present application document, those skilled in the art can make other various corresponding transformation schemes according to the technical solutions and technical concepts of the present application without creative mental effort, which all belong to the scope protected by the present application.

Claims

1. A method for rapidly determining the chloride ion content in coal and coke, characterized in that: The following steps are involved: S1: Use a key to pour the sample powder into the limiting funnel and distribute it evenly; then add a small amount of boric acid powder to the limiting funnel and its surroundings, pull out the limiting funnel and add an appropriate amount of boric acid powder, but do not exceed the plane of the sample cup; S2: Smooth the boric acid powder, cover the gland, tighten the rocker arm, align the upper surface of the piston with the bottom surface of the upper column, and start the piston rising switch; the piston rises at this time, and after reaching the specified pressure, the pressure is maintained constant for 30 seconds, and then the piston automatically descends; S3: Pull open the rocker arm and start the piston rise switch again to fix the sample; select appropriate measurement conditions based on the type of instrument used, the type of sample, the analyzed elements, the coexisting elements and their content variation range; S4: Select a certain number of standard substance samples similar to the analysis sample and press them into tablets. Draw a calibration curve between the content value of the analysis element in the standard substance and the average value of the measured X-ray fluorescence intensity.

2. The method for rapidly determining the chloride ion content in coal and coke according to claim 1, wherein: Analytical samples with a particle size of less than 0.2 mm were dried at 105°C to 110°C before analysis and cooled to room temperature in a desiccator.

3. The method for rapidly determining the chloride ion content in coal and coke according to claim 1, wherein: in, The maximum pressure of the press for boric acid substrate powder tableting is not less than 50 tons and the operating pressure is not less than 40 tons.

4. The method for rapidly determining the chloride ion content in coal and coke according to claim 3, wherein: The press machine adjusts the working pressure to 40 tons and the pressure holding time to 30 seconds.

5. The method for rapidly determining the chloride ion content in coal and coke according to claim 1, wherein: Use absorbent cotton dipped in alcohol to clean the upper surface of the piston and the inner wall of the limiting funnel on the inner wall of the sample cup.

6. The method for rapidly determining the chloride ion content in coal and coke according to claim 1, wherein: Each sample in step S4 should be measured at least twice.

7. The method for rapidly determining the chloride ion content in coal and coke according to claim 1, wherein: It also includes instrument drift correction, which uses two-point correction. The correction interval can be determined according to the stability of the instrument.

8. The method for rapidly determining the chloride ion content in coal and coke according to claim 1, wherein: It also includes taking 3 samples and using different types of testing equipment for testing and comparison.

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