Method for determining precision of mechanical sampling of commercial coal

Abstract

The application discloses a method for determining the precision of mechanical sampling of commercial coal, which comprises the following steps: performing an ash content bias test on a test coal sample, taking the ash content bias test on one or more sampling units or batches, and taking the ash content bias test for a logarithmic number n p , testing the dry base ash content of the test coal sample, and the testing result is represented as A d,iA , preparing a general analysis test coal sample from the test coal sample and testing the sample, and the sample testing variance meets the variance target requirement; calculating the sampling precision of each sampling unit according to the testing result and the sample testing variance; and if a batch of coal is divided into m sampling units, the sampling precision of the batch of coal is calculated. The method is simple to calculate, has strong reliability of the calculation result, and is more widely applied in practice. The result of the method for determining the precision of mechanical sampling of commercial coal is accurate, convenient and fast, and has high practical guiding significance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thermal power plants, and relates to a method for determining the precision of mechanical sampling of commercial coal. BACKGROUND

[0002] In order to improve the fuel management level and production efficiency of thermal power enterprises, it is of great significance to obtain the coal quality characteristic parameters of commercial coal in a timely and accurate manner. The coal quality data of commercial coal need to be obtained through the processes of sampling, sample preparation and chemical analysis, which are collectively referred to as sampling, sample preparation and chemical analysis of coal. In order to avoid human intervention and improve the work efficiency of sampling and sample preparation, the sampling of incoming coal and furnace coal of thermal power enterprises has been mostly mechanized at the present stage, that is, the incoming coal or furnace coal is taken by a mechanical sampling and sample preparation device (equipment), and the representative coal sample taken is further prepared and analyzed. The sampling link accounts for about 80% of the total variance in the entire sampling, sample preparation and chemical analysis process, and therefore whether the performance of the sampling equipment meets the requirements needs to be tested. At present, the performance test of the mechanical sampling and sample preparation equipment of coal is mainly based on the standard GB / T19494.3, and the test items include precision verification and bias test. The bias test includes ash bias and total moisture loss. The precision verification process mainly selects at least 10 sampling units according to the daily sampling scheme of the power plant, takes a pair of duplicate samples for each sampling unit, prepares and analyzes the samples, and then calculates the sampling precision.

[0003] The daily sampling of the power plant is mostly taken as one sampling unit per day, and therefore the precision verification of a single mechanical sampling and sample preparation device takes about 10 days, which is time-consuming. In addition, in the daily sampling work, the sampling scheme for stationary coal is fixed with a certain number of sampling points per vehicle, and the sampling scheme for moving coal flow is fixed with a certain time interval, which cannot be changed at will. However, the amount of incoming coal or furnace coal is not the same every day, and therefore the daily sampling precision is constantly changing. Therefore, how to quickly obtain the mechanical sampling precision under the fluctuation of coal quantity is of great importance to the fuel sampling, sample preparation and chemical analysis management of thermal power plants. SUMMARY

[0004] In order to overcome the problems in the prior art, the present application aims to provide a method for determining the precision of mechanical sampling of commercial coal, which is simple to calculate, has strong reliability of calculation results, and is more widely applicable. The results of the method for calculating the precision of mechanical sampling of commercial coal are accurate, convenient and fast, and have high practical guiding significance.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] A method for determining the precision of mechanical sampling of commercial coal, comprising the following steps:

[0007] 1) Ash bias test is performed on the test coal sample in one or more sampling units or batches;p , the dry ash content of the test coal sample is determined, and the test result is represented as A d,iA , wherein i=1, 2, …, n p ;

[0008] The test coal sample is prepared into a general analysis test coal sample and is determined, and the sample preparation and determination variance meets the variance target requirement.

[0009] 2) According to the test result and the sample preparation and determination variance, the sampling precision of each sampling unit is calculated; if a batch of coal is divided into m sampling units, the sampling precision of the batch of coal is calculated.

[0010] The further improvement of the present application is that the test coal sample is subjected to ash content bias test according to the bias test method of GB / T19494.3, and the ash content bias test is taken in one or more sampling units or batches, and the number of ash content bias tests is n p , the dry ash content of the sample taken by the mechanical sampling and preparation device is determined according to GB / T211, and the test result is represented as A d,iA , wherein i=1, 2, …, n p .

[0011] The further improvement of the present application is that n p ≥40.

[0012] The further improvement of the present application is that the test coal sample is prepared into a general analysis test coal sample according to GB / T474 and is determined, and the determination variance meets the variance target requirement.

[0013] The further improvement of the present application is that the determination variance V PT ≤0.20.

[0014] The further improvement of the present application is that the dry ash content variance V I of the sample taken by the mechanical sampling and preparation device of the coal type is calculated by the following formula:

[0015]

[0016] , wherein A d,iA is the dry ash content of the sample taken by the mechanical sampling and preparation device of the coal type;

[0017] n p is the number of ash content bias tests taken by the mechanical sampling and preparation device according to the ash content bias test method of GB / T19494.3 p ;

[0018] V PT is the sample preparation and determination variance.

[0019] The further improvement of the present application is that the sampling precision P SLThe sampling precision P of the coal is calculated by the following formula:

[0020]

[0021] Wherein: V I The variance of the dry ash content of the sub-sample collected by the mechanical sampling device;

[0022] n SL The number of sub-samples collected in the sampling unit;

[0023] V PT The variance of the sampling and testing.

[0024] The further improvement of the present application is that the sampling precision P of the coal is calculated by the following formula: L The sampling precision P of the coal is calculated by the following formula:

[0025]

[0026] Wherein: P SL The precision of the single sampling unit;

[0027] m The number of sampling units divided by the batch of coal.

[0028] Compared with the prior art, the present application has the beneficial effects that:

[0029] Firstly, the data used for calculation is derived from the ash bias test of the mechanical sampling device, which is performed simultaneously with the ash bias test, thereby greatly shortening the performance inspection cycle of the mechanical sampling device;

[0030] Secondly, the present application is more practical, and the national standard precision verification method requires that the coal quantity of each sampling unit and the number of sub-samples collected are equal. The present application preferentially determines the sub-sample variance and then calculates the sampling precision, so that the sampling precision of each sampling unit can be estimated when the coal quantity of the sampling unit or the number of sub-samples collected changes;

[0031] Thirdly, the sub-sample variance calculated by the present application includes the sampling and sampling variances of the mechanical sampling device, which is different from the primary sub-sample variance. The calculation result of the sub-sample variance by the present application is closer to the precision verification result of the sampling of the mechanical sampling device used;

[0032] Fourthly, the present application is simple to calculate, has strong reliability of the calculation result, and is more widely applied. The result of the mechanical sampling precision of the commercial coal calculated by the present application is accurate, convenient and fast, and has high practical guiding significance. DETAILED DESCRIPTION

[0033] The present application will be described in detail below through specific embodiments.

[0034] The method for determining the mechanical sampling precision of the commercial coal of the present application comprises the following steps:

[0035] 1) First step: select test coal X, take test coal sample by mechanical sampling device, according to power plant daily sampling scheme and equipment operation parameters, carry out ash bias test according to GB / T 19494.3 bias test method, take ash bias test number n in one or more sampling units or within a batch designed by power plant daily sampling scheme p (n p ≥40), according to GB / T 211, test the dry basis ash of the sample taken by the mechanical sampling device, and the test result is represented as A d,iA , wherein i = 1, 2, …, n p ;

[0036] 2) Second step: prepare general analysis test coal sample according to GB / T 474 and test the test coal sample taken by the mechanical sampling device, and the sampling and testing variance procedure meets the variance target requirement, that is, V PT ≤0.20;

[0037] 3) Third step: calculate the dry basis ash variance V I of the sample taken by the mechanical sampling device for coal X:

[0038]

[0039] Wherein: A d,iA — the dry basis ash of the test sample taken by the mechanical sampling device for coal X, unit: %;

[0040] n p — the number n of ash bias test samples taken by the mechanical sampling device according to GB / T 19494.3 bias test method for ash bias test p (n p ≥40);

[0041] V PT — sampling and testing variance (V PT ≤0.20);

[0042] 4) Fourth step: calculate the sampling precision P SL of each sampling unit of the sampling scheme used by the power plant daily, unit: %:

[0043]

[0044] Wherein: V I — the dry basis ash variance of the sample taken by the mechanical sampling device for coal X;

[0045] n SL — the number of samples in the sampling unit, unit: pieces;

[0046] V PT— Sampling and preparation variance (V PT ≤0.20) ;

[0047] 5) The fifth step: if a batch of coal is divided into m sampling units, the sampling precision P L , unit: %:

[0048]

[0049] Where: P SL — Single sampling unit precision, unit: %;

[0050] m— The number of sampling units divided by a batch of coal, unit: pieces.

[0051] Example 1

[0052] A power plant selects the coal X into the plant with screw rod type mechanical sampling device sampling, the determination method of mechanical sampling precision is as follows:

[0053] 1) The first step: select the test coal X, take the test coal sample with the mechanical sampling device, according to the daily sampling scheme and equipment operation parameters of the power plant, carry out the ash bias test according to GB / T19494.3 bias test method, take the ash bias test in the two sampling units designed by the power plant daily sampling scheme, and take the ash bias test in the two sampling units designed by the power plant daily sampling scheme. The number n p = 50, according to GB / T211, the dry basis ash of the test sample taken by the mechanical sampling device, the test results are represented as A d,iA , where i = 1.2, …, 50;

[0054] Table 1 The dry basis ash test results of coal X in the ash bias test of screw rod type mechanical sampling device

[0055] No. A d,iA / %]]> No. A d,iA / %]]> No. A d,iA / %]]> No. A d,iA / %]]> No. No. A d,iA / %]]> 1 32.06 11 33.64 21 30.88 31 34.49 41 33.15 2 34.90 12 30.82 22 34.09 32 31.12 42 34.78 3 30.35 13 35.60 23 31.70 33 36.23 43 33.84 4 32.76 14 31.93 24 33.14 34 34.56 44 32.31 5 36.84 15 37.11 25 32.43 35 30.68 45 36.34 6 31.82 16 34.99 26 33.07 36 33.00 46 30.93 7 32.24 17 36.91 27 37.09 37 36.46 47 37.43 8 35.97 18 32.54 28 33.51 38 32.89 48 38.21 9 37.32 19 36.00 29 34.07 39 30.80 49 30.66 10 32.42 20 36.13 30 32.35 40 31.09 50 36.05

[0056] 2) The second step: the test coal sample taken by the mechanical sampling device is prepared according to GB / T474 to prepare general analysis test coal sample and test, the sampling and preparation variance procedure meets the variance target requirement, V PT = 0.20;

[0057] 3) The third step: calculate the dry basis ash variance V I of the coal X taken by the mechanical sampling device:

[0058] From table 1:

[0059] Then the variance of the sample

[0060]

[0061] 4) Fourth step: Calculate the sampling precision P of each sampling unit of the sampling scheme used in the power plant daily SL :

[0062] The number of sub-samples n of each sampling unit of the sampling scheme used in the power plant daily SL = 25;

[0063] The sampling precision of each sampling unit:

[0064]

[0065] 5) Fifth step: If a batch of coal is divided into 10 sampling units, the sampling precision P of the batch of coal L :

[0066]

[0067] The sampling precision of the coal X entering the plant was verified using a screw rod mechanical sampling device according to the total precision estimation method of GB / T19494.3, and a double sub-sample double sampling method was selected. The precision test results are shown in the table below:

[0068] Table 2 Sampling precision verification of screw rod mechanical sampling device according to GB / T19494.3 determination results of dry basis ash content

[0069]

[0070]

[0071] Variance of ash content determination:

[0072]

[0073] The precision of a single sampling unit is: P0 = 2s = 2 x 0.579 = 1.16 (%)

[0074] The precision of the ash content average value of the whole batch (m sampling units) is:

[0075]

[0076] With the coal X entering the plant having a degree of freedom of 10 and a confidence probability of 95%, the lower limit factor a L = 0.70, and the upper limit factor a U = 1.75, then:

[0077] The upper limit of the precision = a U · P = 1.75 x 0.3662 = 0.64%

[0078] The lower limit of the precision = a L• P = 0.70 x 0.3662 = 0.26%

[0079] That is, the true precision of the average value of the ash content determination of the batch of coal falls within the range of 0.26% and 0.64% at a confidence probability of 95% when the coal is sampled in 10 sampling units.

[0080] The precision result of the batch of coal if divided into 10 sampling units is P L = 0.40%, which falls within the range of 0.26% and 0.64%.

[0081] Example 2

[0082] The precision calculation method when the number of sub-samples of the sampling unit changes is as follows:

[0083] A power plant in Example 1 selects the incoming coal X to be sampled by a screw rod mechanical sampling device. The sampling scheme used by the power plant on a daily basis is about 300 tons of coal per sampling unit (60 tons per car load), and the number of sub-samples n SL = 25 per sampling unit (5 points per car load). If the amount of coal increases to 600 tons on a certain day, it is still sampled at 5 points per car load, then the number of sub-samples n' SL = 50 per sampling unit, and the mechanical sampling precision of the sampling unit is:

[0084]

[0085] This method is simple to calculate, has strong reliability of the calculation result, and is more widely applicable. The result of the mechanical sampling precision of commercial coal calculated by this method is accurate, convenient and fast, and has high practical guiding significance.

Claims

1. A method of determining the precision of a mechanical sample of a commodity coal, characterised by, The method comprises the following steps: 1) Conducting an ash bias test on the test coal sample, taking ash bias test on one or more sampling units or within a batch, number n p , and determining the dry basis ash of the test coal sample, the test result being represented as A d,iA , where i = 1, 2,..., n p ; The test coal sample is prepared into a general analysis test coal sample and is tested, and the sample preparation and testing variance meets the variance target requirement; Variance of the ash yield on dry basis of a sample taken by a mechanical sampling device for a coal type I is calculated by the formula: Wherein: A d,iA - the dry ash content of the sample taken by the mechanical sampling device for the coal type; n p The number of samples taken by the mechanical sampling device for the ash bias test according to the bias test method of GB / T 19494.3 p ; V PT — sample preparation assay variance; 2) According to the test result and the sample preparation and testing variance, the sampling precision of each sampling unit is calculated; if a batch of coal is divided into m sampling units, the sampling precision of the batch of coal is calculated; The sampling precision P of each sampling unit SL This is calculated by the formula: Where: V I - Variance of the dry ash content of the samples taken by the mechanical sampling device for each coal type; n SL - the number of sub-samples taken within the sampling unit; V PT — Variability of sample preparation for assay.

2. The method of determining precision of mechanical sampling of a commodity coal according to claim 1, wherein, The ash bias test is performed on the test coal sample according to the GB / T19494.3 bias test method, and the ash bias test is taken on one or more sampling units or batches, and the number n of the test is p The dry basis ash of the sample taken by the sampling device of the test machine is tested according to GB / T211, and the test result is represented as A d,iA Where i = 1, 2, …, n p .

3. A method of determining precision of mechanical sampling of a commodity coal according to claim 2, characterised in that, n p ≥40。 4. The method of determining precision of mechanical sampling of a commodity coal according to claim 1, wherein, The test coal sample is prepared into a general analysis test coal sample according to GB / T474 and is tested, and the test variance meets the variance target requirement.

5. A method of determining precision of mechanical sampling of a commodity coal according to claim 4 wherein, assay variance V PT ≤ 0.

20.

6. The method of determining precision of mechanical sampling of a commodity coal according to claim 1, wherein, Sampling precision P of coal L is calculated by the following formula: where: P SL — single sampling unit precision; m is the number of sampling units divided for a batch of coal.

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