Method for measuring nitrogen content in coal

Abstract

The invention discloses a method for measuring the content of nitrogen in coal, and relates to the technical field of chemical analysis, the method for measuring the content of nitrogen in coal comprises the following steps: preparing a coal sample; putting the coal sample into a pulse furnace of the measuring equipment, and carrying out high-current pulse heating treatment, so that the coal sample is decomposed to generate a mixture; the mixture is introduced into a conversion furnace of the measuring equipment for filtering treatment, and nitrogen is obtained; and introducing nitrogen into an inert gas thermal conductivity detector of the measuring equipment to obtain the percentage content of the nitrogen element. The method for determining the nitrogen content in the coal is easy to operate, rapid and accurate, does not need to use strong acid and strong alkali, does not pollute instruments, equipment and the environment, and can meet the detection requirements of the nitrogen content in the coal sample.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical analysis, in particular to a method for determining nitrogen content in coal. BACKGROUND

[0002] Nitrogen is a constant element in coal, and nitrogen elements mainly exist in the form of organic matter in coal. When coal is burned, nitrogen elements are converted into nitrogen oxides that pollute the environment. Nitrogen oxides produced by coal combustion are extremely harmful to the human body, the environment and the ecological system. Therefore, it is necessary to accurately detect the content of nitrogen elements in coal. The commonly used method for determining the content of nitrogen elements in coal is "GB / T 19227-2008 Method for Determining Nitrogen in Coal", that is, semi-micro Kjeldahl method or semi-micro steam method. Both semi-micro Kjeldahl method and semi-micro steam method are chemical methods, and have the disadvantages of complicated operation steps, long time consumption and pollution of instrument equipment. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a method for determining nitrogen content in coal, which solves the technical problems of multiple steps, long time consumption and pollution of instrument equipment in the prior art by using a chemical method.

[0004] To achieve at least one of the above purposes, the present application provides the following technical solutions:

[0005] The embodiment of the present application provides a method for determining nitrogen content in coal, which comprises:

[0006] Preparation of a coal sample;

[0007] Placing the coal sample into a pulse furnace of a determination device for high-current pulse heating treatment, so that the coal sample is decomposed to produce a mixture;

[0008] Passing the mixture into a conversion furnace of the determination device for filtration treatment to obtain nitrogen gas;

[0009] Passing the nitrogen gas into an inert gas thermal conductivity detector of the determination device to obtain the percentage content of nitrogen elements.

[0010] The method for determining nitrogen content in coal as described above, wherein, before the coal sample is placed into the pulse furnace of the determination device for heating treatment, the method for determining nitrogen content in coal further comprises:

[0011] Blank testing of the determination device is performed by using a special graphite sleeve crucible, and a blank test value is calculated and saved.

[0012] The method for determining nitrogen content in coal as described above, wherein, after the blank test value is recorded, the method for determining nitrogen content in coal further comprises:

[0013] Preparation of a standard sample;

[0014] The standard sample is put into the determination device for at least three times of correction tests, and a correction result is calculated and saved.

[0015] The method for determining the nitrogen content in coal as described above, wherein the preparation of the standard sample specifically comprises:

[0016] A preset amount of coal standard sample is weighed;

[0017] The coal standard sample is wrapped by a test nickel capsule, and the gas in the test nickel capsule is discharged to prepare the standard sample.

[0018] The method for determining the nitrogen content in coal as described above, wherein the calculation of the correction result specifically comprises:

[0019] The data obtained by each of the correction tests is corrected by a single-point correction method to obtain a correction result, and the correction result is recalculated, and the correction result is obtained according to the recalculated result.

[0020] The method for determining the nitrogen content in coal as described above, wherein the preparation of the coal sample specifically comprises:

[0021] A preset amount of coal sample to be detected is weighed;

[0022] The coal sample is wrapped by a determination nickel capsule, and the gas in the determination nickel capsule is discharged to prepare the coal sample.

[0023] The method for determining the nitrogen content in coal as described above, wherein the particle size of the coal sample is 0.2 mm.

[0024] The method for determining the nitrogen content in coal as described above, wherein before being put into the determination nickel capsule, the coal sample is dried and stored in a coal sample dryer.

[0025] The method for determining the nitrogen content in coal as described above, wherein a catalytic tube is arranged in the pulse furnace, a rare earth copper oxide is arranged in the catalytic tube, and the catalytic tube is connected to the conversion furnace through a stainless steel tube.

[0026] The method for determining the nitrogen content in coal as described above, wherein a dryer and a carbon dioxide absorbent are arranged in the conversion furnace.

[0027] Compared with the prior art, the technical solution has the following advantages:

[0028] The determination method of the nitrogen content in coal provided by the application generates a gas mixture by heating and decomposing coal through a large current of the pulse furnace, filters and removes the gas affecting the detection effect through the conversion furnace, and detects the percentage content of the obtained nitrogen gas through the inert gas thermal conductivity detector, so that the percentage content of the nitrogen element in the coal sample is accurately obtained. The method is simple, fast and accurate, does not need to use strong acid and strong base, does not pollute the instruments and the environment, the determination range of the nitrogen is between 0.2% and 3%, covers the nitrogen content (<1.5%) of the sellable coal, has a wide test range, the determination result is accurate, and the detection requirement of the nitrogen content in the coal sample can be met.

[0029] The determination method of the nitrogen content in coal provided by the application uses blank test and correction test, can accurately judge whether the nitrogen gas in the coal is completely removed or not, eliminates the influence of the instruments and the equipment, and effectively improves the accuracy of the determination result.

[0030] The determination method of the nitrogen content in coal provided by the application selects 0.2 mm as the particle size of the prepared coal sample, and the preparation method and the particle size of the coal standard substance are the same, which is beneficial to the use of the standard substance in the analysis process. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 The first process flow chart of the determination method of the nitrogen content in coal provided by some embodiments of the application is shown in the following figure.

[0033] Figure 2 The second process flow chart of the determination method of the nitrogen content in coal provided by some embodiments of the application is shown in the following figure.

[0034] Figure 3 The third process flow chart of the determination method of the nitrogen content in coal provided by some embodiments of the application is shown in the following figure.

[0035] Figure 4 The process flow chart of the preparation of the standard sample provided by some embodiments of the application is shown in the following figure.

[0036] Figure 5 The process flow chart of the preparation of the coal sample provided by some embodiments of the application is shown in the following figure. DETAILED DESCRIPTION

[0037] The application will be further described in detail through the drawings and the embodiments. Through these descriptions, the characteristics and advantages of the application will become more clear and explicit.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the specification herein is for describing particular embodiments only and is not intended to be limiting of the application; the use herein of terms such as "comprise" and "comprising", and any variations thereof, is intended to cover the presence of stated features, integers, steps, or components but not to preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0039] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the embodiments described herein can be incorporated into any other embodiment.

[0040] The specific word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically stated otherwise, the drawings are not drawn to scale and are merely intended to conceptually illustrate one or more embodiments.

[0041] In the description of the application, the technical terms "first", "second", "third" and the like are used only to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the technical features indicated.

[0042] In the description of the application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0043] As part of the inventive concept of the present application, before describing the embodiments of the present application, the causes of the problem of fouling the instrument equipment (even the environment) in the related art are analyzed, and the technical solutions of the embodiments of the present application are obtained through reasonable analysis.

[0044] In the related art, the semi-micro Kelvin method uses strong acid and strong base, and uses mercury sulfate and selenium powder, which are toxic chemical reagents. The strong acid and strong base are highly corrosive, and can cause skin corrosion if not handled carefully. Mercury sulfate is a white crystal with high toxicity, which can cause low fever, headache, respiratory tract infection, pneumonia, skin rash, abnormal kidney function, and neurasthenia in the operator, and cause environmental pollution, especially water pollution. The semi-micro steam method also uses strong acid and strong base, and water vapor is introduced at a temperature of 1050°C, which is very high and dangerous.

[0045] Therefore, the present application provides a method for determining the nitrogen content in coal, thereby solving the technical problems of existing technology, such as damage to instruments and equipment, multiple steps, and long time consumption.

[0046] The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings. The technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0047] As shown in Figure 1 In an embodiment of the present application, a method for determining the nitrogen content in coal is provided for detecting coal with a nitrogen content of 0.2% to 3%. The method comprises:

[0048] Step 210: preparing a coal sample, specifically, preparing the coal to be detected into a coal sample for use when being detected;

[0049] Step 220: placing the coal sample into the pulse furnace of the determination device for large-current pulse heating treatment, so that the coal sample is decomposed to generate a mixture, specifically, the pulse furnace is connected to the conversion furnace through a first stainless steel pipe, and the conversion furnace is connected to the inert gas thermal conductivity detector through a second stainless steel pipe. Specifically, during detection, helium gas is introduced into the pulse furnace for a predetermined time to exhaust the air in the furnace, and the helium gas can be used as a protective gas and a carrier gas. The predetermined time is adjusted according to the size of the pulse furnace, for example, the predetermined time is 15 seconds. After the coal sample is heated and decomposed by a large current in the pulse furnace, carbon monoxide, nitrogen, hydrogen, a small amount of carbon dioxide, a very small amount of sulfur dioxide, and other unknown gases are generated;

[0050] Step 230: introducing the mixture into the conversion furnace of the determination device for filtering treatment to obtain nitrogen, specifically, after the filtering treatment of the conversion furnace, only nitrogen and other unknown gases are left in the mixture, and the other unknown gases do not affect the subsequent detection results;

[0051] Step 240: Nitrogen is passed into the inert gas thermal conductivity detector of the measuring equipment to obtain the percentage of nitrogen. Specifically, the inert gas thermal conductivity detector amplifies and performs A / D conversion on the measured signal, and then sends the signal to a computer for data processing. Since there is a large difference between the thermal conductivity of nitrogen and the thermal conductivity of the carrier gas helium, the difference in thermal conductivity causes the current of the bridge to change, thereby accurately obtaining the percentage of nitrogen in the coal sample.

[0052] It should be noted that in this application, the measuring equipment includes a pulse furnace, a converter furnace and an inert gas thermal conductivity detector. The specific structure and usage of the pulse furnace, the converter furnace and the inert gas thermal conductivity detector are all existing technologies and will not be repeated here.

[0053] The method for determining the nitrogen content in coal of the present application heats the coal with a high current in a pulse furnace to decompose it to produce a gas mixture, filters out the gas that affects the detection effect through a converter, and detects the obtained nitrogen percentage through an inert gas thermal conductivity detector, thereby accurately obtaining the percentage of nitrogen in the coal sample. This method is simple to operate, fast and accurate, does not require the use of strong acids and alkalis, does not pollute instruments and equipment and the environment, and can meet the detection requirements of the nitrogen content in coal samples.

[0054] Further, if Figure 2 As shown, before the coal sample is placed in the pulse furnace of the measuring device for heating, the method for determining the nitrogen content in the coal further includes:

[0055] Step 211: Perform a blank test on the measuring equipment using a dedicated graphite-sheathed crucible, and calculate and save the blank test value. Specifically, the dedicated graphite-sheathed crucible is a high-temperature resistant crucible specially used for testing. When performing the blank test, the dedicated graphite-sheathed crucible is placed in a pulse furnace, which is turned on. The dedicated graphite-sheathed crucible is heated by a large current. When the nitrogen content detected by the inert gas thermal conductivity detector is no more than 0.02%, the blank test is completed and the test value is saved.

[0056] The above-mentioned blank test can be used to determine whether the nitrogen in the coal sample is completely discharged. That is, when the coal sample is heated to the point where the nitrogen content detected by the inert gas thermal conductivity detector is slightly less than or equal to the blank test value, it can be determined that the nitrogen in the coal sample is completely discharged, thereby improving the accuracy of the nitrogen content determination results.

[0057] Going further, Figure 3 As shown, after recording the blank test value, the method for determining the nitrogen content in coal also includes:

[0058] Step 212: Prepare a standard sample. Specifically, use the coal standard sample of GBW11107 to prepare a standard sample for use in testing.

[0059] Step 213: Put the standard sample into the determination device for at least three times of correction test, calculate and save the correction result, specifically, put the standard sample into the special graphite sleeve crucible, start the pulse furnace, pass a large current through the special graphite sleeve crucible to heat the standard sample, and when the nitrogen content detected by the inert gas thermal conductivity detector is slightly less than or equal to the blank test value, calculate and record the percentage content of nitrogen element in the coal sample. Since the standard sample used is the coal standard sample GBW11107, the nitrogen content is determined, therefore, by comparing the detected percentage content of nitrogen element with the actual nitrogen percentage value of the coal standard sample, the correction result can be obtained. Thus, repeat the operation at least three times to obtain at least three correction results, and save the correction result by taking the average value.

[0060] The above correction test cooperates with the blank test to eliminate the influence of the determination device on the test result, and further improves the accuracy of the determination result of the method of the application.

[0061] Further, as shown in Figure 4 , the preparation of the standard sample specifically includes:

[0062] Step 2121: Weigh a predetermined amount of coal standard sample, specifically, in this embodiment, 0.05g of coal standard sample GBW11107 is weighed;

[0063] Step 2122: Use the test nickel capsule to wrap the coal standard sample, and discharge the gas in the test nickel capsule to prepare the standard sample, specifically, put the weighed coal standard sample into the test nickel capsule, use a stainless steel tweezers to pinch and squeeze the capsule opening of the test nickel capsule from the top of the coal standard sample to discharge the internal air, and then roll the test nickel capsule into a rod-shaped capsule package with the tweezers to avoid the influence of the air in the test nickel capsule on the test result.

[0064] Further, the calculation of the correction result specifically includes:

[0065] The data obtained by each correction test is corrected by a single-point correction method to obtain the correction result, and the correction result is recalculated to obtain the correction result according to the calculation result. The single-point correction method is a prior art and will not be described again. The single-point correction method is used to correct each result, so that the final correction result is more accurate, thereby further improving the accuracy of the determination result of the method of the application.

[0066] In an embodiment of the application, as shown in Figure 5 , the preparation of the coal sample specifically includes:

[0067] Step 2101: Weigh a predetermined amount of coal sample to be tested, specifically, in this embodiment, the same weight of coal sample to be tested as the standard sample is weighed, that is, 0.05g of coal sample is weighed;

[0068] Step 2102: Put the coal sample into the determination nickel capsule, and discharge the gas in the determination nickel capsule to make the coal sample, specifically, put the weighed coal sample into the determination nickel capsule, use the stainless steel tweezers to pinch and squeeze the capsule opening of the determination nickel capsule from the top of the coal sample to discharge the internal air, and then roll the determination nickel capsule into a rod-shaped capsule package with the tweezers, so as to avoid the influence of the air in the determination nickel capsule on the determination result.

[0069] Further, the particle size of the coal sample is 0.2 mm, which is the same as the sample preparation method and particle size of the coal standard substance, so that better comparison can be made during analysis.

[0070] Further, the coal sample is dried and stored in a coal sample dryer before being put into the determination nickel capsule, so as to avoid the influence of the moisture in the coal sample on the test result.

[0071] In an embodiment of the present application, a catalytic tube is arranged in the pulse furnace, and rare earth copper oxide is arranged in the catalytic tube. The rare earth copper oxide can be heated by the large current in the pulse furnace, and the hot rare earth copper oxide can convert carbon monoxide into carbon dioxide, convert hydrogen into water, and convert sulfur dioxide into solid copper sulfite or copper sulfate, so as to remove carbon monoxide, hydrogen and a small amount of sulfur dioxide generated after the coal sample is heated and decomposed. The catalytic tube is connected to the conversion furnace through a stainless steel tube, so as to pass the mixture from which carbon monoxide, hydrogen and a small amount of sulfur dioxide are removed into the conversion furnace for further filtration.

[0072] Further, a dryer and a carbon dioxide absorbent are arranged in the conversion furnace. The dryer can remove the moisture in the mixture, and the carbon dioxide absorbent (purple asbestos is selected in the embodiment) can remove carbon dioxide, so that the remaining nitrogen and unknown gas in the mixture are obtained.

[0073] It should be noted that in the method of the present application, helium is always used as the power gas and the comparative analysis gas.

[0074] The determination method of the nitrogen content in coal of the present application will be described below in combination with specific embodiments.

[0075] Example 1

[0076] Determination of the nitrogen content in a coal sample with high nitrogen content

[0077] Adjust the pulse furnace, and select the test parameters as follows: degassing low pressure current is 1200A, degassing high pressure current is 1200A, and delay current is 1100A. The determination results of the above-mentioned determination method of the nitrogen content in coal are as follows:

[0078]

[0079]

[0080] Example Two

[0081] Determination of nitrogen content in coal sample with high nitrogen content

[0082] The pulse furnace was adjusted, and the test parameters were selected as a degassing low pressure current of 1200 A, a degassing high pressure current of 1200 A, and a delay current of 1100 A. The determination results of the coal nitrogen content by the above method were as follows:

[0083]

[0084] From the above test analysis, it can be seen that the determination method of the nitrogen content in coal of the present application is basically consistent with the data comparison analysis of the semi-micro Kjeldahl method and the semi-micro steam method of “GB / T 19227-2008 Determination of nitrogen in coal”. The recovery rate is more than 97%, the nitrogen determination range is between 0.2% and 3% (mass fraction), the precision test relative standard deviation is less than 5%, and the inert gas thermal conductivity detector is used to determine the nitrogen content in coal. It is completely capable of meeting the determination requirements of the nitrogen content in coal.

[0085] In summary, the determination method of the nitrogen content in coal of the present application can accurately obtain the percentage content of nitrogen in the coal sample by heating the coal to produce a gas mixture through the large current of the pulse furnace, filtering and excluding the gas affecting the detection effect through the conversion furnace, and detecting the percentage content of nitrogen gas through the inert gas thermal conductivity detector. The method is simple, fast and accurate, does not need to use strong acid and strong base, does not pollute the instruments and the environment, the nitrogen determination range is between 0.2% and 3%, covers the nitrogen content (<1.5%) of the sellable coal, has a wide test range, the determination result is accurate, and can meet the detection requirements of the nitrogen content in the coal sample.

[0086] The determination method of the nitrogen content in coal of the present application uses blank test and correction test, which can accurately judge whether the nitrogen gas in the coal is completely discharged or not, eliminates the influence of the instruments and the equipment, and effectively improves the accuracy of the determination result.

[0087] The determination method of the nitrogen content in coal of the present application selects the particle size of 0.2 mm for the preparation of the coal sample, which is the same as the preparation method and particle size of the coal standard substance, and is beneficial to the use of the standard substance in the analysis process.

[0088] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for determining the nitrogen content of coal, characterized by, The method for determining the nitrogen content in coal comprises the following steps: Preparation of a coal sample; Placing the coal sample into a pulse furnace of a determination device for high-current pulse heating treatment, so that the coal sample is decomposed to produce a mixture; Passing the mixture into a conversion furnace of the determination device for filtration treatment to obtain nitrogen gas; Passing the nitrogen gas into an inert gas thermal conductivity detector of the determination device to obtain the percentage content of nitrogen.

2. The method for determining the nitrogen content in coal according to claim 1, wherein, before the coal sample is placed into the pulse furnace of the determination device for heating treatment, the method further comprises the following steps: Blank test of the determination device using a special graphite sleeve crucible, calculation and saving of a blank test value.

3. The method for determining the nitrogen content in coal according to claim 2, wherein, after the blank test value is recorded, the method further comprises the following steps: Preparation of a standard sample; Placing the standard sample into the determination device for at least three times of correction test, calculation and saving of a correction result.

4. The method for determining the nitrogen content in coal according to claim 3, wherein, the preparation of the standard sample specifically comprises the following steps: Weighing a predetermined amount of coal standard sample; Sealing the coal standard sample with a test nickel capsule, and discharging the gas in the test nickel capsule to prepare the standard sample.

5. The method for determining the nitrogen content in coal according to claim 3, wherein, the calculation of the correction result specifically comprises the following steps: Single-point correction method is used to correct the data obtained in each correction test to obtain a correction result, and the correction result is recalculated to obtain the correction result according to the recalculated result.

6. The method for determining the nitrogen content in coal according to claim 1, wherein, the preparation of the coal sample specifically comprises the following steps: Weighing a predetermined amount of coal sample to be tested; Sealing the coal sample with a determination nickel capsule, and discharging the gas in the determination nickel capsule to prepare the coal sample.

7. The method for determining the nitrogen content in coal according to claim 6, wherein, the particle size of the coal sample is 0.2 mm.

8. The method for determining the nitrogen content in coal according to claim 6, wherein, before being placed into the determination nickel capsule, the coal sample is subjected to drying treatment and stored in a coal sample dryer.

9. The method for determining the nitrogen content in coal according to any one of claims 1 to 8, wherein, a catalytic tube is arranged in the pulse furnace, a rare earth copper oxide is arranged in the catalytic tube, and the catalytic tube is connected to the conversion furnace through a stainless steel tube.

10. The method for determining the nitrogen content in coal according to claim 9, wherein, a dryer and a carbon dioxide absorbent are arranged in the conversion furnace. ​ ​ ​ ​ ​ ​ ​ ​ ​

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