CN105842110A - Method for quickly testing ash content in coal - Google Patents

Abstract

The present invention relates to a method for quickly measuring the ash content in coal, which comprises the following steps: (1) In an ash dish with constant mass, weigh (0.5±0.05) g of an analytical coal sample with a particle size below 0.2mm, and make the coal sample Evenly distributed in the ash dish; (2) When the muffle furnace is heated to 850°C, open the furnace door, place the ash dish containing the coal sample on the open furnace door and park it for (3-5) min, and then use a rate of no more than 2cm/min Move the coal sample into the constant temperature zone of the furnace at a moving speed, close the furnace door, and burn for (15-25) minutes; (3) Take out the ash dish from the furnace, cool it, and weigh it according to the formula A _ad ﹦ m ₁ (residue after burning (mass of coal sample)/m (mass of coal sample) × 100% to calculate the ash content in coal; (4), repeat steps (1) to (3) 3 to 5 times, observe whether the calculation result is within the allowable error range, if so, take the average value as an analysis As a result, if not, try again. While ensuring the accuracy of the analysis results, the method of the invention has the advantages of less coal sample consumption and short analysis time. In the best embodiment, the test time of each coal sample is only 30-45 minutes.

Description

A Quick Method for Measuring Ash Content in Coal

technical field

The invention belongs to the field of coal quality analysis and testing, in particular to a method for quickly measuring the ash content in coal.

Background technique

Ash content in coal refers to the complete combustion of all combustibles in coal, and the residue left after a series of complex reactions such as decomposition and compounding of minerals in coal at a certain temperature, so to be precise, it should be called the ash yield of coal. However, in actual production, whether coal is used for coking, gasification, combustion or coal deep processing, although the uses are different, the organic matter in coal is used. For example, in the coking industry, too high ash content will reduce the quality of coke and consume more raw materials; when used as a combustion fuel, too high ash content will reduce thermal efficiency and increase the workload of slagging; as gasification raw materials, too high ash content often It will cause operational difficulties due to slagging and reduce the quality and conversion rate of synthesis gas. Therefore, it is of great significance to quickly and accurately measure the ash content in coal for the evaluation of coal quality in the process of coal trade and in the process of coal processing and utilization.

At present, there are two methods for the determination of ash in coal in the national standard (GB/T 212-2008), namely the slow ashing method and the fast ashing method. The slow ashing method is an arbitration method, and the measurement results are relatively accurate, but it is time-consuming and labor-intensive. It actually takes about 4 hours for each sample to be measured from sampling, sample preparation, instrument debugging and preparation to final detection; It takes less time and can be used as a routine analysis method. The rapid ashing method analysis method has two methods in the national standard, namely: method A - rapid ash analyzer determination; method B - same as the slow ashing method, using a muffle furnace for determination. However, the biggest disadvantage of the prior art is that the detection time of the detection method is long. Regardless of method A or method B, even skilled analysts and testers need 2-3 hours.

Therefore, a simple, fast and accurate coal ash detection method is also an important direction of research and exploration by analysts and testers in the field of coal quality analysis in recent years.

Chinese patent CN 102749433 A discloses a coal ash detection method, including the steps: (1) collecting multiple coal samples, then crushing and shrinking to obtain multiple analysis samples; (2) randomly measuring the ash obtained in step (1) The quality, volume and total moisture of 3 analytical samples, and adopt existing method to obtain the ash content of described 3 analytical samples; (3) bring the numerical value that obtains in above-mentioned steps (2) into formula respectively

Ad=(100×a/(100-Mt)-100×b×V/(100×m-m×Mt)+c×Mt/(100-Mt))×100%

Obtain a set of equations in the formula, then calculate the numerical value of a, b and c in the formula; (4) measure the mass and volume of any other analysis samples obtained in the step (1); (5) use the formula to calculate the other any Analyze the ash content of the sample. The detection time of this inventive method is obviously shorter than the method in the prior art, but analysis sample is less (3 analysis samples), and the ash value of coal sample is based on calculation, due to the quality, volume and total moisture of analysis sample There is a certain systematic error in the analysis value of the method, so the error of the ash value calculated according to this method is relatively large, and the accuracy of the analysis result will be reduced accordingly.

Chinese patent CN 104390927 A discloses a new rapid detection method for ash content in coal samples. The method includes the following steps: S1. collect and prepare several coal samples, and measure the ash content of each sample by conventional methods; S2. Scanning and collecting the spectral data and curves of the coal sample with a NIRS analyzer; S3. Processing the spectral data of the sample obtained in S2, obtaining the calibration equation of the ash content through regression calculation, correcting and verifying the calibration equation of the ash content, and establishing a detection model; S4. Fill the sample injector of the NIR instrument directly with the coal samples to be tested in turn, start the scan button, and the NIR instrument will automatically record and store the sample spectrum, determine the type of spectrum that the sample belongs to, select the corresponding detection model, and obtain the detection result. This method can quickly and accurately detect coal ash, but the method has high technical requirements, and the process of spectral data and curve processing of coal samples is complicated, which requires professional analysis and testing personnel with high mathematical analysis knowledge to complete.

Contents of the invention

The purpose of the present invention is to provide a method for quickly and accurately measuring the ash content in coal, which is suitable for coal washing and processing trade, so as to solve the time-consuming and laborious technical problem of the ash content measurement process existing in the prior art. The present invention is achieved through the following technical solutions.

A method for rapidly measuring ash content in coal, comprising the steps of:

Step 1. In a pre-fired ash dish with a constant mass and weighed to 0.0001g, weigh an analytical coal sample (0.5±0.05)g with a particle size of 0.2mm or less, weigh to an accuracy of 0.0001g, and shake the ash dish gently to make the coal The sample is evenly distributed in the ash dish, and the ash dish containing the coal sample is pre-arranged on a heat-resistant porcelain plate or an asbestos plate;

Step 2, place the ash dish containing the coal sample at the door of the muffle furnace with the temperature of the open furnace door maintained at (815±10) °C, park it for (3-5) min, and then use it at a temperature not greater than 2cm/min. The moving speed gradually pushes the coal sample into the furnace by about 50 mm. After the surface of the coal sample is obviously oxidized and discolored, push the ash dish containing the coal sample into the central constant temperature area of the muffle furnace, close the furnace door, and Burn at a temperature of ±10)°C for (15-25) minutes. After no sparks are seen on the surface of the coal sample, continue to burn for (2-10) minutes, then take out the porcelain dish, weigh and calculate after cooling;

Step 3, take out the ash dish from the muffle furnace, weigh after cooling, and calculate the ash content in the coal according to the formula A _ad = m ₁ /m × 100%, where: A _ad — the ash content of the air-dried base coal sample ( ﹪), m—mass of air-dried base coal sample (g), m ₁ —mass of residue after burning (g);

Step 4, repeat step 1 to step 3 (3-5) times, observe whether the calculation result is within the allowable error range, if yes, take the average value as the analysis result, if not, try again.

In the above test method, the gray dish used is preferably a porcelain rectangular porcelain dish with a length of 49 mm, a width of 20 mm, and a height of 12 mm. The thickness of the coal sample in the rectangular porcelain dish is kept at about 50 mg/cm ² .

A more preferred technical solution is that in the above test method, in the second step, the ash dish containing the coal sample is parked at the open muffle furnace door until the surface of the coal sample is obviously oxidized and discolored, and then the ash dish is not more than With a moving speed of 1cm/min, the coal sample is gradually pushed into the furnace by about 50mm. After the surface of the coal sample is obviously oxidized and discolored, the ash dish containing the coal sample is pushed into the central constant temperature area of the muffle furnace, and the door is closed. The furnace door performs burning and inspection burning operations.

Further, in the above test method, after the ash dish containing the coal sample is pushed into the muffle furnace (815±10)°C in the central constant temperature zone and burnt until no sparks are seen on the surface of the coal sample, if the ash content of the coal sample is within If the ash content of the coal sample is below 15%, continue to burn for (3-5) minutes; if the ash content of the coal sample is above 15%, continue to burn for (5-7) minutes, then take out the porcelain dish, weigh and calculate after cooling.

A more preferred technical solution is, according to the method for quickly measuring ash in coal according to claim 4, it is characterized in that, the (815±10)°C central constant temperature zone in the muffle furnace is placed for 2~ 3 ash dishes containing coal samples.

Compared with the prior art, the method of the present invention has the following remarkable technical progress.

(1) The amount of coal sample used is less. In the national standard GB/T 212-2008, each detection requires a coal sample of (1 ± 0.1) g, while the method of the present invention only needs a coal sample of (0.5 ± 0.05) g, because the coal sample Therefore, local over-thickness of the coal sample is avoided when the coal sample is burned. While reducing the ashing test time of the coal sample, it not only avoids the incomplete combustion of the coal sample, but also prevents the sulfur dioxide generated by the sulfide in the bottom coal sample from being absorbed by the upper part. The calcium oxide generated by the decomposition of carbonate is covered and fixed, so that the sulfide in the coal is completely oxidized and discharged before the decomposition of carbonate. Simultaneously, since the method of the present invention is to first place the ash dish containing the coal sample at the open muffle furnace door and park it for (3-5) minutes, it is ensured that good ventilation can be maintained all the time during the ashing process, so that the sulfide Once the gas is generated, it is removed in time, avoiding its contact with the metal ions in the coal, producing sulfate, and improving the reliability and accuracy of the analysis results of the ash content in the coal.

(2) The method of the present invention has fully considered the characteristics of the coal sample. First, the ash dish containing the coal sample is placed at the door of the muffle furnace with the furnace door open and the central temperature in the furnace maintained at (815 ± 10) ° C. The temperature of coal is about 200°C, and the ignition point of coal is between 260 and 400°C. After the substance reaches the ignition point, it will be oxidized violently. Therefore, the decomposition of coal below the ignition point will avoid the coal sample from igniting and burning, and at the same time, it can also avoid coal with poor stability. Sudden high temperature causes thermal cracking and splashing.

(3) The method of the present invention pays attention to the speed of sample pushing, that is, the ash dish containing the coal sample is placed on the open muffle furnace door and parked for (3-5) min, and then the sample is moved at a moving speed not greater than 2cm/min. The coal sample is gradually pushed into the furnace by about 50mm. After the surface of the coal sample is obviously oxidized and discolored, the ash dish containing the coal sample is pushed into the central constant temperature area of the muffle furnace, and the furnace door is closed to complete the burning and inspection. Burn operation. As we all know, coal begins to decompose at 250°C, softens and forms colloid as the temperature rises, and solidifies at 530-600°C to form semi-coke. After semi-coke is generated, it is necessary to prolong the burning time. Therefore, properly control the processing temperature of the coal sample, and gradually increase the temperature to oxidize the coal sample at a relatively low temperature, destroying the coking property of the coal, which is conducive to the complete burning of the coal sample and shortens the burning time. Therefore, compared with the method recommended in the prior art national standard GB/T 212-2008 by adopting the method of the present invention, the test time of each coal sample is no more than 1 hour, especially in the best embodiment, the test time of each coal sample The test time is only 30-45 minutes.

detailed description

The method of the present invention will be further described below through method reliability verification examples, specific embodiments, best embodiments and comparative examples. Wherein, the method reliability verification example of the present invention has adopted 6 kinds of standard coals with different ash content, and its corresponding numbering is GBW11101m, GBW11101L, GBW11107k, GBW11110f, GBW11102j, GBW11109e; The specific embodiment of the inventive method, the best embodiment and The coal samples used in the comparative example come from the raw coal of Longquan Coal Mine in Gujiao City, the raw coal of Baode Coal Mine in Xinzhou City, and the lump clean coal, over-clean coal, and middling coal obtained by washing these two raw coals in a coal preparation plant in Taiyuan City. Wait. It should be pointed out that according to the different ash content in coal, the allowable error range of ash measurement precision is also different, so the ash content range (<15.00%, >30.00%, 15.00% ~ 30.00%), and then determine the appropriate burning time.

In all reliability verification examples, specific embodiments, best embodiments and comparative examples of the present invention, the analysis of ash content in coal is carried out according to the following steps.

Step 1. In a porcelain rectangular porcelain dish with a length of 49 mm, a width of 20 mm, and a height of 12 mm that has been pre-fired to a constant mass, weigh an analytical coal sample (0.5±0.05) g with a particle size of less than 0.2 mm, weighing to an accuracy of 0.0001 g , Gently shake the gray dish to make the coal sample evenly distributed in the gray dish, and arrange the porcelain rectangular porcelain dish containing the coal sample on the heat-resistant porcelain plate or asbestos plate in advance.

Step 2: Heat the muffle furnace to 850°C, open the furnace door, and place the porcelain rectangular porcelain dish containing the coal sample at the open muffle furnace door for (3-5) minutes, and then place it at the open door of the muffle furnace for (3-5) minutes, and then place it in a space of no more than 2 cm. The moving speed of /min pushes the ashed coal sample into the constant temperature zone of the muffle furnace, closes the door of the muffle furnace, and burns it at a temperature of (815±10)°C for (15-25)min.

Step 3, take out the porcelain rectangular porcelain dish from the muffle furnace, put it in the air to cool to room temperature, then weigh it, and calculate the ash content in the coal according to the formula A _ad ﹦m ₁ /m×100, where: A _ad —ash content of air-dried coal sample (﹪), m—weight of air-dried coal sample (g), m ₁ —mass of residue after burning (g);

Step 4, repeat step 1 to step 3 (3-5) times, observe whether the calculation result is within the allowable error range, if yes, take the average value, if not, try again.

In the above test method, the gray dish used is a round porcelain dish with a diameter of 45 mm and a height of 12 mm, and the thickness of the sample in the round porcelain dish is kept at about 50 mg/cm ² .

In step 2, the ash dish containing the coal sample is parked at the open muffle furnace door until the surface of the coal sample is obviously oxidized and discolored, and then the coal sample is preferably pushed into the muffle furnace at a moving speed not greater than 1 cm/min. After burning in the constant temperature zone of (815±10)°C in the furnace until no sparks are seen, continue to check the burning for (2-7) minutes, then take out the circular porcelain dish, weigh and calculate after cooling.

In the method of the present invention, the precision of ash content (A _ad ) determination is shown in Table 1 below.

Table 1 Determination of the precision of ash content allowable error

Ash﹪ Repeatability A _ad ﹪ ＜15.00 0.30 15.00～30.00 0.50 >30.00 0.70

Verification example 1.

The standard coal sample is the coal standard material with certificate, one or more characteristic values of which are determined by the procedure of establishing traceability, so that it can be traced to the measurement unit used to represent the characteristic value which is accurately reproduced, and each Each standard value is accompanied by an uncertainty for a given confidence level.

This standard material is pre-selected raw coal, after natural drying, crushing and mixing, all of them pass through an 80-mesh sieve (<0.2mm), and then mix and pack into bottles. Randomly select 25 bottles of samples, and use the GB/T 212-2008 method for the determination of ash content in coal (slow ashing method) for uniformity inspection. The experimental method is a collaborative test, and all the experimental results are processed by mathematical statistics to calculate the standard value, and the standard value is valid for one year. The standard coal sample has the characteristics of plasticity, uniformity and stability, so the standard coal sample is used for measurement, the measured result is compared with the standard value, and a significance test is performed to determine whether there is a systematic error, or the obtained Whether the result is within the uncertainty range of the standard standard value. Therefore, the following tests are carried out by comparing the determination of the standard coal sample with its standard value.

The following are three standard coal samples whose ash content values are A _ad < 15%, and the standard sample values are respectively converted into the analysis base A _ad as shown in Table 2. The corresponding test results (burning in constant temperature zone for 5 minutes) are shown below table 3.

Table 2 Standard coal sample ash conversion table (GBW11101m, GBW11101L, GBW11107k)

Standard No. A _d ﹪ M _ad ﹪ A _ad ﹪ GBW11101m 9.60 1.33 9.47 GBW11101L 9.84 1.61 9.68 GBW11107k 14.93 3.63 14.39

Table 3 Test results of the three standard coal samples in Table 2 (burning in constant temperature zone for 5 minutes)

Standard No. Ash standard value A _ad ﹪ Ash test results A _ad ﹪ GBW11101m 9.47 9.38 GBW11101L 9.68 9.62 GBW11107k 14.39 14.38

The above results show that, using the method of the present invention, there is a good correspondence between the analysis results of Aad<15% and the standard sample and its standard value, and it is not necessary to carry out inspection burning.

Verification example 2.

Select 3 standard samples with an ash content value of 15.00% to 30.00% for the test, and convert the standard sample values into the analysis base Aad as shown in Table 4. The corresponding test results (burning in the constant temperature zone for 5 to 7 minutes) are shown in the table below 5.

Table 4 Standard coal sample ash conversion table (GBW11110f, GBW11102j, GBW11109e)

Table 5 Test results of the three standard coal samples in Table 2 (burning in constant temperature zone for 7 minutes).

Standard No. Standard sample result Aad﹪ Burning in constant temperature zone for 5 minutes Examination burn for 2 minutes GBW11110f 25.07 25.23 24.80 GBW11102j 22.81 23.16 23.10 GBW11109e 15.24 14.96 15.05

Show from above result: for the analysis coal sample of Aad ≥ 15%, utilize the method for the present invention to burn 5min in constant temperature zone, then carry out checking property burning 2min, the gained analytical result that obtains is more reliable and accurate, and this analytical result is the same It has a good corresponding relationship with the ash standard value of standard coal samples, and can meet the needs of coal quality analysis in daily production.

Example 1.

In this embodiment, the ash content of Longquan raw coal and Baode raw coal is determined by the rapid ashing method B in GB/T 212-2008, wherein the A _ad value of Longquan raw coal is 36.89%, and the A _ad value of Baode raw coal is 42.14%. The ash content of the washed products of both was <15%. During the test, the burning time of all coal samples was 3 minutes to 5 minutes, and the furnace door was opened during the burning process. The test results are shown in Table 6 below.

Table 6 Test results of two kinds of raw coal and its washed clean coal

As can be seen from the test results in Table 6, using the method of the present invention, for the analysis coal sample with Aad＜15%, burning for 3 minutes, and then checking for burning for 2 minutes, the analysis results are not much different, especially for the ash content This is especially true for smaller analytical coal samples, so that inspection burns do not have to be performed. However, for the analyzed coal samples (raw coal) with Aad≥15%, burning in the constant temperature zone for 3 minutes, and then carrying out inspection burning for 2 minutes, there is a big difference between the obtained analysis results and the actual result of 36.89 ash content of the coal samples.

In order to obtain more accurate analysis results, we selected Longquan raw coal, Longquan block clean coal 1, and Longquan over-cleaned coal 2 as control examples, and further investigated the influence of burning time on the test results by prolonging the initial burning time. See Table 7 below.

Table 7 Test results of Longquan Coal Mine Raw Coal and Clean Coal Washing Products (Unit/%)

Sample name Burning in constant temperature zone for 3 minutes Burning in constant temperature zone for 5 minutes Examination burn for 2 minutes Longquan Raw Coal 41.86 40.13 38.04 Longquan Block Clean Coal 1 10.29 10.25 10.24 Longquan clean coal 2 9.50 10.48 9.48

It can be seen from Table 7 that for Longquan raw coal with Aad ≥ 15%, appropriately increasing the burning time in the constant temperature zone can significantly improve the accuracy and reliability of the analysis results.

During the test, we found that only by placing the coal sample in the central constant temperature zone of the muffle furnace, can the test coal sample be prevented from burning and the test process be aborted. This is because the temperature in the central constant temperature zone of the muffle furnace is relatively high. , the analysis coal sample is basically in reducing environment, through step 1 in the method of the present invention, the porcelain rectangular china dish that fills coal sample is placed in the open muffle furnace door place and parks (3～5)min, makes coal sample in comparison It is oxidized at low temperature, and the coking property of coal is destroyed. Therefore, placing the coal sample in the central constant temperature zone of the muffle furnace at this time is conducive to the complete combustion of the sample, and because the coal has a large amount of coal below the ignition point The volatile matter is decomposed and discharged, so the "open flame" phenomenon, that is, the burning of coal samples, will not be caused in the central constant temperature zone of the muffle furnace.

In addition, several ash pans containing coal samples are placed in the central constant temperature zone of (815±10)°C in the muffle furnace for simultaneous testing, which can further save time. However, if too many ash dishes are placed, there may be incomplete burning of some coal samples, thereby reducing the accuracy of the method of the present invention. According to our test situation, the optimal number of coal samples to be placed is 2 to 3 per time.

Example 2.

In this embodiment, the ash content of Longquan raw coal and Baode raw coal is measured by the rapid ashing method B in GB/T 212-2008, wherein the A _ad value of Longquan raw coal is 36.89%, and the A _ad value of Baode raw coal is 46.83%. The ash content of coal in the washing products of both products is ≥15%. During the test, the burning time of all coal samples was 5min to 7min, and the furnace door was opened during the burning process. The test results are shown in Table 8 below.

Table 8 Test results of two kinds of raw coal and the coal in the washing product

From the test results of Table 8, it can be seen that the analytical results obtained by the method of the present invention are substantially close to the measured values obtained according to the national standard fast ashing method B, but the analysis time of each coal sample is 30-50min less than the method described in the national standard. And the analysis results meet the needs of actual production.

Comparative example 1.

In this comparative example, the ash content of the analyzed coal samples was all <15%, and they were burned in the constant temperature zone for 3-5 minutes.

Table 9 Test results of clean coal, the washing product of two kinds of raw coal

Comparative example 2.

In this comparative example, the ash content of the coal samples was ≥15%, and the coal samples were burned for 5-7 minutes in the constant temperature zone.

Table 10 Test results of coal in the washing products of two kinds of raw coal

From the test results of Table 9 and Table 10, it can be seen that the method of the present invention is more accurate than the analysis result measured by closing the muffle furnace door under the same conditions.

The above are only some of the best embodiments of the present invention, and those skilled in the art can understand that under the teaching of this description, some modifications or changes can be made to the present invention, and any modifications or changes all belong to the scope of the claims of the present invention. protected range.

Claims (5)

1. A method for quickly measuring ash content in coal, comprising the steps of: Step 1. In a pre-fired ash dish with a constant mass and weighed to 0.0001g, weigh an analytical coal sample (0.5±0.05)g with a particle size of 0.2mm or less, weigh to an accuracy of 0.0001g, and gently shake the ash dish to make the coal The sample is evenly distributed in the ash dish, and the ash dish containing the coal sample is pre-arranged on a heat-resistant porcelain plate or an asbestos plate; Step 2, place the ash dish containing the coal sample at the door of the muffle furnace with the temperature of the open furnace door maintained at (815±10) °C, park it for (3-5) min, and then use it at a temperature not greater than 2cm/min. The moving speed gradually pushes the coal sample into the furnace by about 50 mm. After the surface of the coal sample is obviously oxidized and discolored, push the ash dish containing the coal sample into the central constant temperature area of the muffle furnace, close the furnace door, and Burn at a temperature of ±10)°C for (15-25) minutes, and continue to burn for inspection (2-10) minutes after there is no spark on the surface of the coal sample; Step 3, take out the ash dish from the muffle furnace, weigh after cooling, and calculate the ash content in the coal according to the formula A _ad = m ₁ /m × 100%, where: A _ad — the ash content of the air-dried base coal sample ( ﹪), m—mass of air-dried base coal sample (g), m ₁ —mass of residue after burning (g); Step 4, repeat step 1 to step 3 (3-5) times, observe whether the calculation result is within the allowable error range, if yes, take the average value as the analysis result, if not, try again. 2. The method for quickly measuring ash in coal according to claim 1, wherein the ash dish is a porcelain rectangular porcelain dish with a length of 49mm, a width of 20mm, and a height of 12mm, and the coal sample in the porcelain rectangular porcelain dish is The thickness of the sample was kept at about 50 mg/cm ² . 3. The method for quickly measuring ash content in coal according to claim 1 or 2, characterized in that, in said step 2, the ash dish containing the coal sample is parked at the open muffle furnace door until the surface of the coal sample is clearly After the coal sample is oxidized and discolored, the coal sample is gradually pushed into the furnace by about 50mm at a moving speed of no more than 1cm/min. After the surface of the coal sample is obviously oxidized and discolored, the gray dish containing the coal sample is pushed into the In the central constant temperature area of the furnace, close the furnace door for burning and inspection burning operations. 4. The method for quickly measuring ash content in coal according to claim 3, characterized in that, the ash dish containing the coal sample is pushed into the muffle furnace for burning in a central constant temperature zone of (815±10)°C After there is no spark on the surface of the coal sample, if the ash content of the coal sample is below 15%, continue burning for (3-5) min; if the coal sample ash content is above 15%, continue burning for (5-7) min, and then Take out the porcelain dish, weigh and calculate after cooling. 5. The method for quickly measuring ash content in coal according to claim 4, characterized in that 2 to 3 ash dishes filled with coal samples are placed in the central constant temperature zone of (815±10)°C in the muffle furnace .