A coal ash measurement method and device based on plasma discharge

Abstract

The present invention discloses a method and device for measuring coal ash content based on plasma discharge. The method comprises the following steps: subjecting a coal sample to a plasma discharge reaction to obtain a coal residue; and calculating the coal ash content based on the mass of the coal residue and the mass of the coal sample. The method is quick to detect, requiring only 4-10 minutes, compared to 2.5 hours for the slow ashing method and over an hour for the rapid ashing method. It is also harmless to the human body and the environment, and compared to the line spectrum method, is harmless to the human body. The detection results are accurate, with a measurement accuracy exceeding 96%.

Description

Technical Field

[0001] The present invention relates to the technical field of coal ash measurement, and in particular to a coal ash measurement method and device based on plasma discharge. Background Art

[0002] Ash is the solid residue left after complete combustion of coal at a certain temperature. It is a key indicator of coal quality; higher ash content indicates lower calorific value and higher slag discharge. It serves not only as a general industrial analytical indicator but also as a fundamental indicator for coal quality evaluation and trade pricing by relevant departments and coal companies.

[0003] There are currently two main methods for measuring coal ash content: 1. Incineration; 2. Line spectrum analysis. The incineration method, currently predominantly a muffle furnace method, involves thoroughly burning a sample in a muffle furnace. The remaining residue is weighed and then subjected to a series of calculations to determine the coal's ash content. By varying the combustion temperature and time, the incineration method can be categorized into rapid ashing and slow ashing. The slow ashing method offers accurate results and is therefore preferred as an arbitration method, but it is time-consuming, requiring over 2.5 hours per test, impacting train loading efficiency. While the rapid ashing method significantly reduces the time required, it still requires at least an hour, and the results are affected by the ash content and composition of the coal, resulting in poor accuracy. Line spectrum analysis, on the other hand, involves bombarding the nuclei of various elements in the coal with radioactive particles, generating distinct spectral lines. These spectral lines are then analyzed and calculated to determine the coal's ash content. However, this method requires expensive equipment, is difficult to install and maintain, has low measurement accuracy, and poses certain environmental and human hazards.

[0004] Therefore, there is still a demand for safe, efficient and accurate coal testing processes. Summary of the Invention

[0005] The present invention aims to provide a method and device for measuring coal ash content based on plasma discharge, which can measure coal ash content safely, efficiently and accurately. To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for measuring coal ash based on plasma discharge, the method comprising the following steps: performing a plasma discharge reaction on a coal sample to obtain a coal residue;

[0007] The coal ash content is calculated based on the mass of the coal residue and the mass of the coal sample.

[0008] Furthermore, before the plasma discharge reaction is performed on the coal sample, the environment in which the coal sample is located is vacuumed; wherein,

[0009] After being evacuated to vacuum but before the plasma discharge reaction, the vacuum degree of the environment in which the coal sample is located is less than 10Pa.

[0010] Furthermore, the coal sample is subjected to a plasma discharge reaction, comprising:

[0011] Introducing an inert gas into an environment with a vacuum degree of less than 10 Pa, and controlling the pressure of the environment to be 0.5-10 kPa;

[0012] Starting the microwave power supply to excite the plasma for discharge according to the predetermined microwave power;

[0013] After the plasma discharge is stabilized, oxygen is introduced and the introduction of the inert gas is stopped;

[0014] After the oxygen reacts with the coal sample at a predetermined temperature for a predetermined time, the microwave power is turned off, the introduction of the oxidizing gas is stopped, and an inert gas is introduced until the environment cools to room temperature.

[0015] Furthermore, exciting the plasma to discharge according to a predetermined microwave power includes starting a microwave power supply and exciting the plasma to discharge according to a predetermined first microwave power;

[0016] After the plasma is first discharged and stabilized, the plasma is excited according to a predetermined second microwave power; wherein,

[0017] The predetermined range of the first microwave power and the second microwave power is 100-1000W, and the first microwave power is less than the second microwave power.

[0018] Furthermore, the inert gas includes one or more of argon and helium.

[0019] Furthermore, the temperature range at which the oxygen reacts with the coal sample is 600°C-900°C.

[0020] Furthermore, the test mass range of the coal sample is 0.1g-3g.

[0021] Furthermore, the calculation formula for coal ash is obtained based on the mass of the coal residue and the mass of the coal sample as follows:

[0022] Ash content = mass of coal residue ÷ mass of coal sample.

[0023] A coal ash measuring device based on plasma discharge, the device comprising:

[0024] a discharge unit, used for performing a plasma discharge reaction on the coal sample to obtain coal residue;

[0025] The calculation unit is used for calculating the coal ash content according to the mass of the coal residue and the mass of the coal sample.

[0026] Furthermore, the device further comprises a vacuum unit and a gas control unit, wherein:

[0027] The vacuum unit is used to vacuum the environment in which the coal sample is located before the plasma discharge reaction is performed on the coal sample; wherein the vacuum degree of the environment in which the coal sample is located after vacuuming and before the plasma discharge reaction is less than 10 Pa;

[0028] The gas control unit is used to control the introduction or stopping of the introduction of inert gas during the plasma discharge reaction of the coal sample, and is also used to control the introduction or stopping of the introduction of oxygen.

[0029] Technical effects and advantages of the present invention:

[0030] (1) The detection time is short. Compared with the slow ashing method of 2.5 hours and the rapid ashing method of more than 1 hour, this method only takes 4-10 minutes;

[0031] (2) It is harmless to the human environment. Compared with the line spectrum method, this method is harmless to the human body;

[0032] (3) The test results are accurate, with a measurement accuracy of over 96%.

[0033] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the coal ash measurement method based on plasma discharge of the present invention;

[0035] Figure 2 This is a diagram of a coal ash measurement device based on plasma discharge according to the present invention;

[0036] Figure 3 This is a physical picture of a coal ash measurement device based on plasma discharge in one embodiment of the present invention.

[0037] In the figure, 1 is a coal sample; 2 is a quartz tank; 3 is a resonant cavity; 4 is a microwave; 5 is a waveguide; 6 is an air inlet; 7 is an exhaust port; 8 is a microporous ceramic; and 9 is a plasma. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] In order to solve the deficiencies of the prior art, the present invention discloses a method for measuring coal ash content based on plasma discharge, such as Figure 1 As shown, the method includes the following steps: performing plasma discharge reaction on a coal sample to obtain coal residue; and calculating the coal ash content based on the mass of the coal residue and the mass of the coal sample.

[0040] The coal sample is subjected to a plasma discharge reaction, comprising: introducing an inert gas into a vacuum environment, and controlling the pressure of the environment to be 0.5-10 kPa; starting a microwave power supply, exciting plasma to discharge according to a predetermined microwave power; after the plasma discharge is stabilized, introducing oxygen, and simultaneously stopping the introduction of the inert gas; after the oxygen and the coal sample react at a predetermined temperature for a predetermined time, turning off the microwave power supply, stopping the introduction of oxygen, and introducing the inert gas until the environment cools to room temperature.

[0041] Furthermore, the method of exciting the plasma to discharge according to a predetermined microwave power includes:

[0042] Starting a microwave power supply to excite plasma for a first discharge according to a predetermined first microwave power;

[0043] After the plasma is stabilized by the first discharge, the plasma is excited to perform a second discharge according to a predetermined second microwave power; wherein,

[0044] The predetermined range of the first microwave power and the second microwave power is 100-1000W, and the first microwave power is smaller than the second microwave power.

[0045] In one embodiment of the present invention, Figure 3 The figure shows a physical diagram of the device of the present invention. An air inlet 6 and an air exhaust port 7 are respectively provided on one side of the resonant cavity 3 in the vertical direction. Inside the pipe openings of the air inlet 6 and the air exhaust port 7 is a microporous ceramic 8 with a filtering function; the coal sample 1 is placed inside the quartz tank 2, and the quartz tank 2 is placed inside the resonant cavity 3. The waveguide 5 is connected to the resonant cavity, and the microwave 4 is fed into the resonant cavity 3 through the waveguide 5.

[0046] The coal ash content measurement method based on plasma discharge is performed according to the following steps: a coal sample 1 is weighed and placed in a quartz can 2, and then the quartz can 2 is placed in a resonant cavity 3 of a plasma chemical vapor deposition device;

[0047] Since it is advantageous to generate plasma using microwaves under vacuum, the vacuum unit is operated to vacuum the quartz tank 2 in which the coal sample 1 is located. The air inside the quartz tank 2 passes through the microporous ceramic 8 and is slowly extracted from the quartz tank 2 through the exhaust hole 7 until the vacuum degree of the quartz tank 2 is less than 10 Pa. The microporous ceramic 8 is assembled in the air inlet 6 and the exhaust port 7 connected to the quartz tank to prevent the coal powder from being extracted.

[0048] Inert gas is introduced into the vacuumed quartz tank 2, and the inert gas enters the interior of the quartz tank 2 from the air inlet 6, and the pressure of the quartz tank 2 is controlled to be 500 Pa; the purpose of introducing inert gas into the interior of the quartz tank 2 is to replace the residual air inside the cavity, so that the interior of the quartz tank 2 is in an inert gas environment to avoid the influence of residual air; at the same time, the gas is easily excited to generate plasma; the microwave 4 power supply is started, and the first microwave power (low power) is set, and the generated plasma 9 performs the first discharge, wherein low-power excitation of the plasma 9 can not only protect the equipment, but also high-power excitation of the plasma 9 can easily cause drastic changes in air pressure, thereby causing the coal sample 1 to be blown out.

[0049] After the plasma 9 is discharged and stabilized for the first time, the appropriate microwave power is adjusted and the internal pressure of the quartz tank 2 is stabilized, and then the second microwave power is set. The plasma 9 discharge energy is stronger, and the high-power plasma reacts faster to the coal powder, thereby controlling the temperature of the coal sample 9 and stabilizing the internal pressure of the quartz tank 2;

[0050] After the plasma 9 discharges stably under the second microwave power, oxygen is introduced and the introduction of inert gas is stopped. During this process, oxygen is mainly used to react with the carbon in the coal powder. At this time, due to the violent reaction between the oxygen plasma and the carbon in the coal powder, the gas pressure will rise suddenly and then slowly decrease. After a period of reaction, the gas pressure stabilizes and no longer decreases, indicating that the carbon in the coal powder has been completely reacted.

[0051] Furthermore, after the oxygen reacts with the coal sample 1 for 2-10 minutes, a residue is obtained. The microwave 4 is powered off, the vacuum system is shut down, and the oxygen supply is stopped. Instead, an inert gas is introduced until the environment cools to room temperature. Allowing the ash to cool in the inert gas environment not only avoids air interference but also slowly increases the pressure until it reaches atmospheric pressure. Otherwise, directly opening the air release valve will cause the airflow to blow away the ash. After cooling to room temperature, the chamber is opened to obtain a residue, which is then weighed. After weighing the residue, the ash content of the coal sample 1 can be calculated using existing calculation methods.

[0052] Furthermore, the inert gas includes one or more of argon and helium; in the embodiment of the present invention, argon is preferred.

[0053] Furthermore, the first microwave power is less than the second microwave power, and the first microwave power and the second microwave power can be set to 100-1000W.

[0054] Furthermore, the temperature range at which the oxygen reacts with the coal sample 1 is 600°C-900°C.

[0055] Furthermore, the coal ash content is calculated based on the mass of the coal residue and the mass of the coal sample 1, and the calculation formula is as follows: ash content = mass of the coal residue ÷ mass of the coal sample.

[0056] The present invention also discloses a coal ash measurement device based on plasma discharge, such as Figure 2 As shown, the device includes,

[0057] a discharge unit, configured to perform a plasma 9 discharge reaction on the coal sample 1 to obtain coal residue;

[0058] The calculation unit is used to calculate the coal ash content according to the mass of the coal residue and the mass of the coal sample 1.

[0059] The device also includes a vacuum unit and a gas control unit, wherein the vacuum unit is used to vacuum the environment in which the coal sample 1 is located before the plasma 9 discharge reaction of the coal sample; wherein the vacuum degree of the environment in which the coal sample 1 is located after vacuuming and before the plasma 9 discharge reaction is less than 10Pa; the gas control unit is used to control the introduction or stopping of the introduction of inert gas during the plasma discharge reaction of the coal sample, and is also used to control the introduction or stopping of the introduction of oxygen.

[0060] In order to enable those skilled in the art to fully understand the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments.

[0061] Example 1

[0062] In the first step, 1 g of a coal sample with a particle size less than 0.2 mm is weighed using a balance and placed in a quartz tank 2 .

[0063] In the second step, the quartz tank 2 is placed in the resonant cavity 3 of the microwave plasma equipment and evacuated to below 10 Pa.

[0064] The third step is to introduce argon gas at a flow rate of 20 mL / min, adjust the vacuum system, control the gas pressure to 500 Pa, start the microwave 4 power supply, generate plasma 9, and at this time the microwave power is 200 W.

[0065] In the fourth step, after the plasma 9 discharge is stabilized, the microwave power is increased to 500W.

[0066] Step 5: Introduce oxygen at a flow rate of 90 mL / min and stop introducing argon. The gas pressure will then rise suddenly.

[0067] Step 6: After 6.5 minutes of reaction, the gas pressure will be stable. Turn off the microwave source, stop introducing oxygen, introduce argon into the cavity, cool it to room temperature in the argon atmosphere, and adjust the vacuum system to atmospheric pressure.

[0068] Step 7: Open the cavity, take out the quartz can 2, weigh the residue in the quartz can 2, and measure the ash mass to be 0.0853g. Then calculate the coal ash content using the ash calculation formula. The calculation formula is:

[0069] Ash content = residue mass ÷ coal sample mass;

[0070]

[0071] That is, the ash content is 8.53%, and the similarity with the standard value is 91.8%.

[0072] Example 2

[0073] In the first step, 1 g of a coal sample with a particle size less than 0.2 mm is weighed using a balance and placed in a quartz tank 2 .

[0074] In the second step, the quartz tank 2 is placed in the resonant cavity 3 of the microwave plasma equipment and evacuated to below 10 Pa.

[0075] The third step is to introduce argon gas with a gas flow rate of 20 mL / min, adjust the vacuum system, control the gas pressure to 500 Pa, start the microwave power supply, and generate plasma. At this time, the microwave power is 200 W.

[0076] In the fourth step, after the plasma 9 discharge is stabilized, the microwave power is increased to 500W.

[0077] Step 5: Introduce oxygen at a flow rate of 110 mL / min and stop introducing argon. The gas pressure will then rise suddenly.

[0078] Step 6: After 6 minutes of reaction, the gas pressure will be stable. Turn off the microwave source, stop introducing oxygen, introduce argon into the cavity, cool it to room temperature in the argon atmosphere, and adjust the vacuum system to make it atmospheric pressure.

[0079] Step 7: Open the cavity, take out the quartz can 2, weigh the residue in the quartz can 2, and measure the ash mass to be 0.0895g. Then calculate the ash content of the coal using the ash calculation formula. The calculation formula is:

[0080] Ash content = residue mass ÷ coal sample mass;

[0081]

[0082] That is, the ash content is 8.95%, and the similarity with the standard value is 96.3%.

[0083] Example 3

[0084] In the first step, 1 g of a coal sample with a particle size less than 0.2 mm is weighed using a balance and placed in a quartz tank 2 .

[0085] In the second step, the quartz tank 2 is placed in the resonant cavity 3 of the microwave plasma equipment and evacuated to below 10 Pa.

[0086] The third step is to introduce argon gas at a flow rate of 20 mL / min, adjust the vacuum system, control the gas pressure to 500 Pa, start the microwave 4 power supply, generate plasma 9, and at this time the microwave power is 200 W.

[0087] In the fourth step, after the plasma 9 discharge is stabilized, the microwave power is increased to 500W.

[0088] Step 5: Introduce oxygen at a flow rate of 130 mL / min and stop introducing argon. The gas pressure will then rise suddenly.

[0089] Step 6: After 4 minutes of reaction, the gas pressure will be stable. Turn off the microwave source 4, stop the introduction of oxygen, introduce argon into the cavity, cool it to room temperature in the argon atmosphere, and adjust the vacuum system to make it atmospheric pressure.

[0090] Step 7: Open the cavity, take out the quartz can 2, weigh the residue in the quartz can 2, and measure the ash mass to be 0.0902g. Then calculate the ash content of the coal using the ash calculation formula. The calculation formula is:

[0091] Ash content = residue mass ÷ coal sample mass;

[0092]

[0093] That is, the ash content is 9.02%, and the similarity with the standard value is 97.1%.

[0094] Comparative Example 1

[0095] Slow ashing method: Weigh 1g of a general analytical test coal sample with a particle size of less than 0.2mm into an ash dish that has been previously calcined to a constant mass. Weigh to the nearest 0.0002g and spread evenly over the dish, ensuring a mass per square centimeter of no more than 0.15g. Place the dish in the constant temperature zone of a muffle furnace maintained at a temperature not exceeding 100°C. Close the door, leaving a gap of approximately 15mm. Slowly raise the furnace temperature to 500°C over a period of at least 30 minutes and maintain this temperature for 30 minutes. Continue heating to (815±10)°C and calcine at this temperature for 1 hour. Remove the dish from the furnace and place it on a heat-resistant porcelain or asbestos plate. Cool in air for approximately 5 minutes. Transfer to a desiccator and cool to room temperature (approximately 20 minutes) before weighing. Perform a check calcination at (815±10)°C for 20 minutes each, until the mass change between two consecutive calcinations does not exceed 0.0010g. The ash content was 9.29% and the mass after the last burning was used as the basis for calculation.

[0096] Table 1 Experimental data comparison table

[0097]

[0098] As shown in Table 1 and Examples 1-3, under the same experimental conditions, the coal combustion time shortens with increasing oxygen flow rate. Comparing Comparative Example 1 with Examples 1-3 shows that, using Comparative Example 1 as the arbitration method and Comparative Example 1 as the standard value, the higher the similarity, the higher the accuracy of the method. The detection method of the present invention takes significantly less time than the detection time of the prior art and has higher detection efficiency than the prior art.

[0099] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring coal ash content based on plasma discharge, characterized in that: The method comprises the following steps, Performing a plasma discharge reaction on a coal sample to obtain a coal residue; wherein performing a plasma discharge reaction on the coal sample includes: Introducing an inert gas into an environment with a vacuum degree of less than 10 Pa, and controlling the pressure of the environment to be 0.5-10 kPa; Starting the microwave power supply to excite the plasma for discharge according to the predetermined microwave power; After the plasma discharge is stabilized, oxygen is introduced and the introduction of the inert gas is stopped; After the oxygen and the coal sample react at 600° C.-900° C. for 2-10 minutes, the microwave power is turned off, the introduction of the oxidizing gas is stopped, and an inert gas is introduced until the environment cools to room temperature; The method of exciting the plasma to discharge according to a predetermined microwave power includes: Starting a microwave power supply to excite plasma for discharge according to a predetermined first microwave power; After the plasma is first discharged and stabilized, the plasma is excited according to a predetermined second microwave power; wherein, The predetermined range of the first microwave power and the second microwave power is 100-1000W, and the first microwave power is less than the second microwave power; The coal ash content is calculated based on the mass of the coal residue and the mass of the coal sample.

2. The method for measuring coal ash content based on plasma discharge according to claim 1, characterized in that: Before the plasma discharge reaction is performed on the coal sample, the environment where the coal sample is located is vacuumed; wherein, After being evacuated to vacuum but before the plasma discharge reaction, the vacuum degree of the environment in which the coal sample is located is less than 10Pa.

3. The method for measuring coal ash content based on plasma discharge according to claim 1, characterized in that: The inert gas includes one or more of argon and helium.

4. The method for measuring coal ash content based on plasma discharge according to claim 1, characterized in that: The temperature range at which the oxygen reacts with the coal sample is 600° C.-900° C.

5. The method for measuring coal ash content based on plasma discharge according to claim 1, characterized in that: The test mass of the coal samples ranged from 0.1 g to 3 g.

6. The method for measuring coal ash content based on plasma discharge according to claim 1, characterized in that: The calculation formula for coal ash content is as follows based on the mass of the coal residue and the mass of the coal sample: Ash content = mass of coal residue ÷ mass of coal sample.

7. A coal ash measurement device based on plasma discharge, characterized in that: The device comprises, The discharge unit is used to perform a plasma discharge reaction on the coal sample to obtain coal residue; wherein the plasma discharge reaction on the coal sample includes: Introducing an inert gas into an environment with a vacuum degree of less than 10 Pa, and controlling the pressure of the environment to be 0.5-10 kPa; Starting the microwave power supply to excite the plasma for discharge according to the predetermined microwave power; After the plasma discharge is stabilized, oxygen is introduced and the introduction of the inert gas is stopped; After the oxygen and the coal sample react at 600° C.-900° C. for 2-10 minutes, the microwave power is turned off, the introduction of the oxidizing gas is stopped, and an inert gas is introduced until the environment cools to room temperature; The method of exciting the plasma to discharge according to a predetermined microwave power includes: Starting a microwave power supply to excite plasma for discharge according to a predetermined first microwave power; After the plasma is first discharged and stabilized, the plasma is excited according to a predetermined second microwave power; wherein, The predetermined range of the first microwave power and the second microwave power is 100-1000W, and the first microwave power is less than the second microwave power; The calculation unit is used for calculating the coal ash content according to the mass of the coal residue and the mass of the coal sample.

8. The coal ash content measuring device based on plasma discharge according to claim 7, characterized in that: The device further comprises a vacuum unit and a gas control unit, wherein: The vacuum unit is used to vacuum the environment in which the coal sample is located before the plasma discharge reaction is performed on the coal sample; wherein the vacuum degree of the environment in which the coal sample is located after vacuuming and before the plasma discharge reaction is less than 10 Pa; The gas control unit is used to control the introduction or stopping of the introduction of inert gas during the plasma discharge reaction of the coal sample, and is also used to control the introduction or stopping of the introduction of oxygen.

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