Method for measuring calorific value of coal gangue

Abstract

The invention relates to a method for measuring the calorific value of coal gangue, and belongs to the technical field of chemical or physical analysis. According to the method for measuring the calorific value of the coal gangue, an oxygen bomb calorimetric method is adopted for measurement, and a sample weighing step comprises the following steps: weighing a coal gangue sample with the mass being greater than or equal to 3g and putting the coal gangue sample into a combustion vessel; and the combustion vessel is a porcelain crucible. The calorific value determination method of the coal gangue can significantly improve the accuracy and stability of a calorific value detection result.

Description

Technical Field

[0001] This invention relates to the field of chemical or physical analysis technology, and in particular to a method for determining the calorific value of coal gangue. Background Technology

[0002] Coal is a combustible mineral formed gradually from plant residues under high temperature and pressure. Coal gangue, on the other hand, is a sedimentary rock associated with coal seams during coal formation. It is a type of coal-bearing kaolinite produced during coal mining and washing. The total content of inorganic ash, including Al2O3, SiO2, and Fe2O3, in coal gangue reaches 60% to 95% of its total content, making its utilization difficult. Currently, the traditional uses of coal gangue are mainly backfilling of coal mine goafs, road paving, soil improvement, brick or cement production, and power generation. Compared to other utilization methods, using coal gangue for brick or cement production and power generation can bring higher economic value. This mainly involves the utilization of the calorific value of coal gangue; therefore, accurately measuring the calorific value of coal gangue can more effectively improve its utilization rate. However, there is no existing method for determining the calorific value of coal gangue. The method is mainly based on the test standard "Method for Determination of Calorific Value of Coal". However, in actual testing, it was found that the accuracy and stability of the calorific value of coal gangue tested using the above test standard are poor due to the large difference in calorific value between coal gangue and coal. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for determining the calorific value of coal gangue.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for determining the calorific value of coal gangue using the oxygen bomb calorimetry method. The sample weighing step includes: weighing a coal gangue sample with a mass ≥ 3g and placing it in a combustion dish; the combustion dish is a porcelain crucible.

[0005] This invention uses a porcelain crucible as a combustion vessel and increases the mass of the coal gangue sample to more than 3g to promote full and rapid combustion during the coal gangue test, thereby increasing the single temperature rise in the determination of the calorific value of coal gangue and effectively distributing the total error of a single test. This significantly reduces the error in the calorific value per gram of coal gangue sample, thereby significantly improving the accuracy and stability of the coal gangue calorific value detection results.

[0006] Through numerous experiments, the inventors discovered that the type of combustion vessel has a significant impact on the accuracy and stability of the calorific value test results for coal gangue. The ceramic crucible material has permeable pores in its molecular structure, allowing oxygen to flow through the bottom of the combustion vessel during the experiment. Compared to commonly used combustion vessels made of nickel-chromium steel, alloy steel, or quartz, it has better permeability, which is beneficial for the combustion of coal gangue.

[0007] In some embodiments, the mass of the coal gangue sample may be, but is not limited to, any or both of the following values: 3g, 3.5g, 4g, 4.5g, 5g, 5.5g, 6g, 6.5g.

[0008] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the mass of the coal gangue sample is 4g to 6g, for example, but not limited to any one or any two of 4g, 4.2g, 4.4g, 4.6g, 4.8g, 5g, 5.2g, 5.4g, 5.6g, 5.8g, and 6g.

[0009] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the mass of the coal gangue sample is 4.5g to 5.5g, for example, but not limited to any one or any two of 4.5g, 4.6g, 4.7g, 4.8g, 4.9g, 5g, 5.1g, 5.2g, 5.3g, 5.4g, and 5.5g.

[0010] The study found that as the mass of the coal gangue sample increases, the absolute error of the detection result of the calorific value of the coal gangue gradually decreases. When the mass of the coal gangue sample exceeds 5g, the influence on the absolute error of the detection result begins to decrease. At the same time, considering the compatibility with the existing oxygen bomb calorimetry testing instrument, the mass of the coal gangue sample is preferably 4.5g to 5.5g, more preferably 5g.

[0011] As a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the sample weighing step specifically involves: weighing a coal gangue sample with a mass ≥ 3g on a wrapping paper, wrapping it tightly with the wrapping paper, and then placing it in a combustion dish; the wrapping paper is tracing paper or lens paper.

[0012] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the bottom of the combustion pan is covered with a layer of asbestos wool; preferably, it is acid-washed asbestos wool.

[0013] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the particle size of the coal gangue sample is less than 0.2 mm.

[0014] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the accuracy of weighing the coal gangue sample is 0.0002g.

[0015] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the capacity of the porcelain crucible is 8 mL to 12 mL, for example, but not limited to any one or both of 8 mL, 9 mL, 10 mL, 11 mL, and 12 mL.

[0016] As a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the calorimeter used for testing consists of a combustion oxygen bomb, an inner cylinder, an outer cylinder, a stirrer, a temperature sensor, a sample ignition device, a temperature measurement and control system, and water.

[0017] In some embodiments, the mass of the burning oxygen bomb is smaller, approximately half the mass of a conventional burning oxygen bomb.

[0018] In some implementations, since coal gangue has a low calorific value and a low unit temperature rise, selecting a more precise temperature probe can more sensitively capture temperature changes, preventing the system from misjudging ignition failure due to insensitive temperature changes, and can also effectively ensure detection precision.

[0019] In a preferred embodiment of the method for determining the calorific value of coal gangue according to the present invention, the water volume inside the inner cylinder is 2.6L to 2.8L; preferably around 2.7L, and the inner cylinder must be completely surrounded by water (top, bottom, left, right, front, and back) to avoid the influence of ambient temperature changes. The heat released by the combustion of the sample is absorbed not only by the water, but also by the oxygen bomb, inner cylinder, etc. Since the calorific value of coal gangue is low, reducing the water volume in the inner cylinder can increase the effective unit temperature rise after combustion and prevent excessive heat loss.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses a porcelain crucible as a combustion vessel and increases the mass of the coal gangue sample to more than 3g to promote full and rapid combustion during the coal gangue test, thereby increasing the single temperature rise in the determination of the calorific value of coal gangue and effectively distributing the total error of a single test. This significantly reduces the error in the calorific value per gram of coal gangue sample, thereby significantly improving the accuracy and stability of the coal gangue calorific value detection results. Attached Figure Description

[0021] Figure 1 These are actual photos of the coal gangue sample before and after testing in Example 1. Detailed Implementation

[0022] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0023] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.

[0024] The coal gangue used in all embodiments and comparative examples is the same type.

[0025] Example 1 A method for determining the calorific value of coal gangue includes the following steps: (1) Preparation of reagents and materials ①Oxygen: at least 99.5% pure, free of flammable components, electrolytic oxygen is not allowed, and the pressure is sufficient to fill the oxygen bomb to 3.0 MPa.

[0026] ② Benzoic acid: a reference calorimetric substance, grade II or above, whose standard calorific value has been determined by an authoritative metrology institution or can be clearly traced back to an authoritative metrology institution.

[0027] ③ Cotton thread: Use white cotton thread of uniform thickness that is not coated with wax. Ensure that the length and thickness of the cotton thread are consistent in each measurement. The heat released when the cotton thread is ignited is 17500J / g.

[0028] ④ Acid-washed asbestos wool: Burn at 800℃ for 30 minutes before use.

[0029] Ignition wire: 0.5mm diameter nickel-chromium wire.

[0030] ⑤ Wrapping paper: Select sturdy, tough tracing paper or lens cleaning paper, cut into pieces approximately 7.5cm in length. 2 Approximately 0.1g.

[0031] ⑥ Water: Distilled water must be used; tap water and deionized water are prohibited.

[0032] ⑦ Porcelain crucible: made of porcelain, weighing approximately 10g and with a capacity of approximately 10mL.

[0033] (2) Measurement method and procedure (constant temperature calorimeter method) ① Install and adjust the calorimeter according to the instruction manual.

[0034] ② Calibrate the calorific value of coal according to the method specified in GB / T 213-2008 "Determination of Calorific Value of Coal".

[0035] ③ Take 3-4 sheets of wrapping paper, crumple them tightly, weigh them accurately, place them in a porcelain crucible, and determine the calorific value using conventional methods. Take the average of the three results as the calorific value of the wrapping paper.

[0036] ④ Line the porcelain crucible, which has been heated to constant mass, with acid-washed asbestos wool (first lay a layer of acid-washed asbestos wool at the bottom of the porcelain crucible, and then press it down by hand).

[0037] ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 5g (accurate to 0.0002g) of coal gangue sample with a particle size less than 0.2mm onto the wrapping paper. Wrap the sample in the wrapping paper and place the wrapped sample into a porcelain crucible (e.g., Figure 1 (as shown in a, b, and c).

[0038] ⑥ Fix one end of a cotton thread of known mass to the ignition wire already connected to the two electrode posts (preferably clamped in the spiral of the ignition wire), and overlap the other end on the sample. Adjust the degree of overlap according to the difficulty of igniting the sample (if it is laser ignition, use black wrapping paper and do not connect the ignition cotton thread).

[0039] ⑦ Perform the remaining tests according to the method specified in GB / T 213-2008 "Determination of Calorific Value of Coal". The tested coal gangue sample is as follows: Figure 1 As shown in d.

[0040] ⑧ The calculation formula and precision are the same as those specified in GB / T 213-2008 "Method for Determination of Calorific Value of Coal".

[0041] Comparative Example 1-1 A method for determining the calorific value of coal gangue, which differs from Example 1 only in the material of the combustion pan and in step (2) of the measurement method and procedure (5) from Example 1; The combustion vessel is made of nickel-chromium alloy steel; ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 1g of coal gangue sample with a particle size of less than 0.2mm (accurate to 0.0002g) on ​​the wrapping paper. Wrap the sample with the wrapping paper and place the wrapped sample into a nickel-chromium alloy steel combustion dish.

[0042] Comparative Examples 1-2 A method for determining the calorific value of coal gangue, which differs from Example 1 only in that (2) the measurement method and steps in step ⑤ are different from those in Example 1; ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 1g of coal gangue sample with a particle size of less than 0.2mm (accurate to 0.0002g) on ​​the wrapping paper. Wrap the sample with the wrapping paper and place the wrapped sample into a porcelain crucible.

[0043] The measurement results of Example 1, Comparative Example 1-1 and Comparative Example 1-2 are shown in Table 1.

[0044] Table 1

[0045] Example 2 A method for determining the calorific value of coal gangue includes the following steps: (1) Preparation of reagents and materials ①Oxygen: at least 99.5% pure, free of flammable components, electrolytic oxygen is not allowed, and the pressure is sufficient to fill the oxygen bomb to 3.0 MPa.

[0046] ② Benzoic acid: a reference calorimetric substance, grade II or above, whose standard calorific value has been determined by an authoritative metrology institution or can be clearly traced back to an authoritative metrology institution.

[0047] ③ Cotton thread: Use white cotton thread of uniform thickness that is not coated with wax. Ensure that the length and thickness of the cotton thread are consistent in each measurement. The heat released when the cotton thread is ignited is 17500J / g.

[0048] ④ Acid-washed asbestos wool: Burn at 800℃ for 30 minutes before use.

[0049] Ignition wire: 0.5mm diameter nickel-chromium wire.

[0050] ⑤ Wrapping paper: Select sturdy, tough tracing paper or lens cleaning paper, cut into pieces approximately 7.5cm in length. 2 Approximately 0.1g.

[0051] ⑥ Water: Distilled water must be used; tap water and deionized water are prohibited.

[0052] ⑦ Porcelain crucible: made of porcelain, weighing approximately 10g and with a capacity of approximately 10mL.

[0053] (2) Measurement method and procedure (constant temperature calorimeter method) ① Install and adjust the calorimeter according to the instruction manual.

[0054] ② Calibrate the calorific value of coal according to the method specified in GB / T 213-2008 "Determination of Calorific Value of Coal".

[0055] ③ Take 3-4 sheets of wrapping paper, crumple them tightly, weigh them accurately, place them in a porcelain crucible, and determine the calorific value using conventional methods. Take the average of the three results as the calorific value of the wrapping paper.

[0056] ④ Line the porcelain crucible, which has been heated to constant mass, with acid-washed asbestos wool (first lay a layer of acid-washed asbestos wool at the bottom of the porcelain crucible, and then press it down by hand).

[0057] ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 4g of coal gangue sample with a particle size of less than 0.2mm (accurate to 0.0002g) on ​​the wrapping paper. Wrap the sample with the wrapping paper and place the wrapped sample into a porcelain crucible.

[0058] ⑥ Fix one end of a cotton thread of known mass to the ignition wire already connected to the two electrode posts (preferably clamped in the spiral of the ignition wire), and overlap the other end on the sample. Adjust the degree of overlap according to the difficulty of igniting the sample (if it is laser ignition, use black wrapping paper and do not connect the ignition cotton thread).

[0059] ⑦ Conduct the remaining tests according to the methods specified in GB / T 213-2008 "Determination of Calorific Value of Coal".

[0060] ⑧ The calculation formula and precision are the same as those specified in GB / T 213-2008 "Method for Determination of Calorific Value of Coal".

[0061] Comparative Example 2 A method for determining the calorific value of coal gangue, which differs from Example 2 only in that (2) the measurement method and steps in step ⑤ are different from those in Example 2; ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 1g of coal gangue sample with a particle size of less than 0.2mm (accurate to 0.0002g) on ​​the wrapping paper. Wrap the sample with the wrapping paper and place the wrapped sample into a porcelain crucible.

[0062] The measurement results of Example 2 and Comparative Example 2 are shown in Table 2.

[0063] Table 2

[0064] Example 3 A method for determining the calorific value of coal gangue includes the following steps: (1) Preparation of reagents and materials ①Oxygen: at least 99.5% pure, free of flammable components, electrolytic oxygen is not allowed, and the pressure is sufficient to fill the oxygen bomb to 3.0 MPa.

[0065] ② Benzoic acid: a reference calorimetric substance, grade II or above, whose standard calorific value has been determined by an authoritative metrology institution or can be clearly traced back to an authoritative metrology institution.

[0066] ③ Cotton thread: Use white cotton thread of uniform thickness that is not coated with wax. Ensure that the length and thickness of the cotton thread are consistent in each measurement. The heat released when the cotton thread is ignited is 17500J / g.

[0067] ④ Acid-washed asbestos wool: Burn at 800℃ for 30 minutes before use.

[0068] Ignition wire: 0.5mm diameter nickel-chromium wire.

[0069] ⑤ Wrapping paper: Select sturdy, tough tracing paper or lens cleaning paper, cut into pieces approximately 7.5cm in length. 2 Approximately 0.1g.

[0070] ⑥ Water: Distilled water must be used; tap water and deionized water are prohibited.

[0071] ⑦ Porcelain crucible: made of porcelain, weighing approximately 10g and with a capacity of approximately 10mL.

[0072] (2) Measurement method and procedure (constant temperature calorimeter method) ① Install and adjust the calorimeter according to the instruction manual.

[0073] ② Calibrate the calorific value of coal according to the method specified in GB / T 213-2008 "Determination of Calorific Value of Coal".

[0074] ③ Take 3-4 sheets of wrapping paper, crumple them tightly, weigh them accurately, place them in a porcelain crucible, and determine the calorific value using conventional methods. Take the average of the three results as the calorific value of the wrapping paper.

[0075] ④ Line the porcelain crucible, which has been heated to constant mass, with acid-washed asbestos wool (first lay a layer of acid-washed asbestos wool at the bottom of the porcelain crucible, and then press it down by hand).

[0076] ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 3g of coal gangue sample with a particle size of less than 0.2mm (accurate to 0.0002g) on ​​the wrapping paper. Wrap the sample with the wrapping paper and place the wrapped sample into a porcelain crucible.

[0077] ⑥ Fix one end of a cotton thread of known mass to the ignition wire already connected to the two electrode posts (preferably clamped in the spiral of the ignition wire), and overlap the other end on the sample. Adjust the degree of overlap according to the difficulty of igniting the sample (if it is laser ignition, use black wrapping paper and do not connect the ignition cotton thread).

[0078] ⑦ Conduct the remaining tests according to the methods specified in GB / T 213-2008 "Determination of Calorific Value of Coal".

[0079] ⑧ The calculation formula and precision are the same as those specified in GB / T 213-2008 "Method for Determination of Calorific Value of Coal".

[0080] Comparative Example 3 A method for determining the calorific value of coal gangue, which differs from Example 3 only in that (2) the measurement method and steps in step ⑤ are different from those in Example 3; ⑤ Weigh and record the mass of the wrapping paper. Accurately weigh 1g of coal gangue sample with a particle size of less than 0.2mm (accurate to 0.0002g) on ​​the wrapping paper. Wrap the sample with the wrapping paper and place the wrapped sample into a porcelain crucible.

[0081] The measurement results of Example 3 and Comparative Example 3 are shown in Table 3.

[0082] Table 3

[0083] According to the data in Tables 1, 2 and 3, the repeatability error of the calorific value of coal gangue measured by the method of the present invention is ≤50J / g, which indicates that the accuracy and stability of the calorific value detection results can be significantly improved.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for determining the calorific value of coal gangue, characterized in that, The oxygen bomb calorimetry method was used for determination, and the sample weighing step included: weighing a coal gangue sample with a mass ≥3g and placing it into a combustion dish; the combustion dish was a porcelain crucible.

2. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The mass of the coal gangue sample was 4g to 6g.

3. The method for determining the calorific value of coal gangue as described in claim 2, characterized in that, The mass of the coal gangue sample was 4.5g to 5.5g.

4. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The specific steps for weighing the sample are as follows: weigh a coal gangue sample with a mass ≥ 3g onto a wrapping paper, wrap it tightly with the wrapping paper, and then place it into a combustion dish; the wrapping paper is tracing paper or lens paper.

5. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The bottom of the combustion vessel is lined with a layer of asbestos wool.

6. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The particle size of the coal gangue sample is less than 0.2 mm.

7. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The accuracy of weighing the coal gangue sample is 0.0002g.

8. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The capacity of the porcelain crucible is 8 mL to 12 mL.

9. The method for determining the calorific value of coal gangue as described in claim 1, characterized in that, The calorimeter used in the test consists of a combustion oxygen bomb, an inner cylinder, an outer cylinder, a stirrer, a temperature sensor, a sample ignition device, a temperature measurement and control system, and water.

10. The method for determining the calorific value of coal gangue as described in claim 9, characterized in that, The inner cylinder contains 2.6L to 2.8L of water.

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