Method for determining sampling interval of coal as fired in thermal power plant

Abstract

The embodiment of the invention provides a sampling interval determination method for coal as fired in a thermal power plant. The determination method comprises the following steps: acquiring coal quality information of coal as fired and parameter information of a sampling device; calculating primary subsample variance and dry basis ash content of coal as fired according to the coal quality information, and determining expected sampling precision of batch coal according to the dry basis ash content; determining the number of sampling units, and calculating the number of subsamples pre-sampled by each sampling unit by using the primary subsample variance of the coal as fired and the expected sampling precision of the batch coal; and determining the batch coal quantity, and obtaining a target sampling interval of the coal as fired by utilizing the number of the sub-samples pre-sampled by each sampling unit, the number of the sampling units and the parameter information. According to the sampling interval determination method for the coal as fired in the thermal power plant, the sampling representativeness can be improved, and the loss rate of the sampling device is reduced.

Description

Technical Field

[0001] Embodiments of the present disclosure belong to the technical field of in-furnace coal sampling in thermal power plants, and particularly relate to a method for determining the sampling interval of in-furnace coal in thermal power plants. Background Art

[0002] In-furnace coal in thermal power plants is not only used for the positive balance calculation of boiler coal consumption and combustion adjustment in boiler performance tests, but also for calculating calorific value differences to supervise fuel management levels. Therefore, how to obtain the characteristic parameters of in-furnace coal in a timely and accurate manner is of great significance. The in-furnace coal goes through the processes of sampling, sample preparation, and testing, which is abbreviated as the sampling, sample preparation, and testing of coal.

[0003] At present, the sampling of in-furnace coal in thermal power plants has been mechanized for sampling and sample preparation, that is, in-furnace coal is sampled through a mechanical sampling and sample preparation device (equipment), and the representative coal samples taken are then subjected to sample preparation and testing. The sampling variance accounts for about 80% of the total variance of sampling, sample preparation, and testing. Therefore, on the premise that the sampling equipment has passed the inspection, the rationality of the sampling method plays a crucial role in the representativeness of sampling and the equipment loss rate. Summary of the Invention

[0004] Embodiments of the present disclosure aim to at least solve one of the technical problems existing in the prior art, and provide a method for determining the sampling interval of in-furnace coal in thermal power plants.

[0005] Embodiments of the present disclosure provide a method for determining the sampling interval of in-furnace coal in thermal power plants, and the determination method includes:

[0006] Obtain the coal quality information of the in-furnace coal and the parameter information of the sampling device;

[0007] Calculate the primary subsample variance and dry basis ash content of the in-furnace coal according to the coal quality information, and determine the expected sampling precision of the batch of coal based on the dry basis ash content;

[0008] Determine the number of sampling units, and calculate the number of subsamples to be taken in each sampling unit by using the primary subsample variance of the in-furnace coal and the expected sampling precision of the batch of coal;

[0009] Determine the batch coal quantity, and obtain the target sampling interval of the in-furnace coal by using the number of subsamples to be taken in each sampling unit, the number of sampling units, and the parameter information.

[0010] Optionally, the coal quality information includes the proportion of each commercial coal sample that makes up the in-furnace coal, the dry basis ash content, and the primary subsample variance;

[0011] The parameter information includes the maximum coal conveying capacity of the sampling device and the sampling interval time; wherein, the sampling interval time includes the minimum sampling interval time and the maximum sampling interval time.

[0012] Optionally, the proportion of each commercial coal sample is determined by the following formula:

[0013] Coal sample 1: Coal sample 2: …: Coal sample i: …: Coal sample N = δ1: δ2: …: δ i : …δ N and

[0014] Optionally, the primary subsample variances of each commercial coal sample are obtained according to the method for determining the primary subsample variance in Part 4.3 of the GB / T 19494.3 standard, and are V1, V2, …, V i 、…、V N .

[0015] Optionally, calculating the primary subsample variance of the coal fed into the furnace according to the coal quality information includes:

[0016] Calculating the primary subsample variance of the coal fed into the furnace by using the following formula:

[0017]

[0018] Optionally, the dry basis ash contents of each commercial coal sample are A d,1 、A d,2 、…A d,i 、…A d,N ;

[0019] Calculating the dry basis ash content of the coal fed into the furnace according to the coal quality information includes:

[0020] Calculating the dry basis ash content of the coal fed into the furnace by using the following formula:

[0021]

[0022] And, determining the expected sampling precision of the batch of coal includes:

[0023] When A d > 40%, the expected sampling precision of the batch of coal ≤ 2.00%;

[0024] When 16.00% < A d ≤ 40.00%, the expected sampling precision of the batch of coal ≤ 1.60%;

[0025] When A d ≤ 16.00%, the

[0026] Optionally, calculating the number of pre-taken subsamples for each sampling unit includes:

[0027] Calculating the number of pre-taken subsamples for each sampling unit by using the following formula:

[0028]

[0029] where n is the number of subsamples to be taken for each sampling unit, and V I is the primary subsample variance of the coal fed into the furnace, m is the number of sampling units, and p is the expected sampling precision of the batch of coal.

[0030] Optionally, obtaining the target sampling interval of the coal fed into the furnace includes:

[0031] Calculating the sampling comparison interval time using the following formula:

[0032]

[0033] where Δt max is the sampling comparison interval time, M is the quantity of the batch of coal, m is the number of sampling units, G is the maximum coal conveying capacity of the sampling device, and n is the number of subsamples to be taken for each sampling unit;

[0034] And, the target sampling interval includes the target sampling interval time; if Δt max ≥ the maximum sampling interval time, then determine the maximum sampling interval time as the target sampling interval time;

[0035] if the minimum sampling interval time ≤ Δt max ≤ the maximum sampling interval time, then determine Δt max as the target sampling interval time;

[0036] if Δt max ≤ the minimum sampling interval time, then determine the minimum sampling interval time as the target sampling interval time.

[0037] Optionally, if Δt max ≤ the minimum sampling interval time, then adjust the maximum coal conveying capacity of the sampling device to the target coal conveying capacity;

[0038] The target coal conveying capacity is calculated using the following formula:

[0039]

[0040] where G a is the target coal conveying capacity, M is the quantity of the batch of coal, m is the number of sampling units, T min is the minimum sampling interval time, and n is the number of subsamples to be taken for each sampling unit.

[0041] Optionally, the target sampling interval includes the target sampling interval quality;

[0042] The target sampling interval quality is calculated using the following formula:

[0043]

[0044] Among them, Δm max is the target sampling interval quality, M is the batch coal quantity, m is the number of sampling units, and n is the number of subsamples pre-taken for each sampling unit.

[0045] The method for determining the sampling interval of the coal fed into the furnace of a thermal power plant according to the embodiments of the present disclosure can improve the representativeness of sampling and reduce the loss rate of the sampling device. And on the premise of ensuring the sampling efficiency and the safe operation of the device, the expected sampling precision target value can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic flowchart of a method for determining the sampling interval of the coal fed into the furnace of a thermal power plant according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below with reference to the drawings and specific embodiments.

[0048] The main index of the representativeness of sampling is the sampling precision, and the role of sampling precision in coal inspection is indispensable. The smaller the precision value, the higher the sampling representativeness, but the corresponding sampling workload increases. The larger the precision value, the worse the sampling representativeness and the lower the result credibility. To reduce production costs, most thermal power plants use the combustion method of blending low-quality coal for the coal fed into the furnace, which reduces the uniformity of the coal fed into the furnace and greatly increases the sampling difficulty.

[0049] At present, most power plants use the time-based sampling method for sampling the coal fed into the furnace, that is, a subsample is taken at a certain time interval, and the same sampling time interval is used for both single-variety coal and blended coal, so that for some coal fed into the furnace with better uniformity, the sampling time interval is relatively short, increasing the operation load of the sampling device and the sample preparation workload. For some coal fed into the furnace with poor uniformity, the expected target requirements of sampling precision cannot be achieved. In actual production, for the sampling of the coal fed into the furnace, most enterprises mainly adjust the sampling cycle of the sampling device according to the batch coal quantity, the performance indexes of the equipment, and the retained sample quantity of the smallest total sample after reduction, and cannot obtain effective characteristic parameters of the coal fed into the furnace based on the quality characteristics of the coal fed into the furnace, and then correctly design the sampling cycle.

[0050] In view of this, the inventor designed a method for determining the sampling interval of the coal fed into the furnace of a thermal power plant, as Figure 1 shown, the determination method includes S110 obtaining the coal quality information of the coal fed into the furnace and the parameter information of the sampling device.

[0051] Specifically, in this step, the coal quality information includes the proportion of each commercial coal sample constituting the coal fed into the furnace, the dry basis ash content, and the primary subsample variance.

[0052] Further, the proportions of the respective commercial coal samples are determined by the following formula:

[0053] Coal sample 1: Coal sample 2: …: Coal sample i: …: Coal sample N = δ1: δ2: …: δ i : …δ N , and

[0054] The primary subsample variances of the respective commercial coal samples are obtained according to the determination method of primary subsample variance in Part 4.3 of the GB / T 19494.3 standard, and are V1, V2, …, V i , …, V N .

[0055] The dry ash contents of the respective commercial coal samples are A d,1 , A d,2 , …A d,i , …A d,N .

[0056] The parameter information includes the maximum coal conveying capacity and the sampling interval time of the sampling device. The sampling interval time includes the minimum sampling interval time and the maximum sampling interval time. Further, the maximum coal conveying capacity (G) of the sampling device is specifically the operating parameter of the coal conveying belt, with the unit of tons per hour (t / h). The sampling interval time (T M , the sampling interval time is adjustable) of the sampling device is specifically the technical parameter of the mechanical sampling and sample preparation device. The sampling interval time includes the minimum sampling interval time (T min ) and the maximum sampling interval time (T max ).

[0057] As a specific example, the sampling interval determination method for the coal fed into the furnace of a thermal power plant in the embodiments of the present disclosure is applicable to single coal types such as raw coal, screened coal, clean coal, other washed coals (including middlings), and low-quality coal, and mixed coals composed of two or more commercial coal blends.

[0058] S120 calculates the primary subsample variance and the dry ash content of the coal fed into the furnace according to the coal quality information, and determines the expected sampling precision of the batch of coal based on the dry ash content.

[0059] Specifically, in this step, the following formula is used to calculate the primary subsample variance of the coal fed into the furnace:

[0060]

[0061] And, the dry ash content (A d ) of the coal fed into the furnace is calculated based on the dry ash contents and proportions of the respective commercial coal samples that make up the coal fed into the furnace. Specifically, the following formula is used to calculate the dry ash content of the coal fed into the furnace:

[0062]

[0063] And, the determination of the expected sampling precision (p) of the batch of coal includes:

[0064] When A d > 40%, the expected sampling precision (p) of the batch of coal ≤ 2.00%.

[0065] When 16.00% < A d ≤ 40.00%, the expected sampling precision (p) of the batch of coal ≤ 1.60%.

[0066] When A d ≤ 16.00%, the

[0067] S130 Determine the number of sampling units, and calculate the number of subsamples to be pre-taken for each sampling unit by using the primary subsample variance of the coal fed into the furnace and the expected sampling precision of the batch of coal.

[0068] Specifically, in this step, first determine the number of sampling units (m, unit: piece). Then calculate the number of subsamples to be pre-taken for each sampling unit (n, unit: piece), and specifically use the following formula to calculate the number of subsamples to be pre-taken for each sampling unit:

[0069]

[0070] Wherein, n is the number of subsamples to be pre-taken for each sampling unit, V I is the primary subsample variance of the coal fed into the furnace, m is the number of sampling units, and p is the expected sampling precision of the batch of coal.

[0071] S140 Determine the batch quantity of coal, and obtain the target sampling interval of the coal fed into the furnace by using the number of subsamples to be pre-taken for each sampling unit, the number of sampling units, and the parameter information.

[0072] Specifically, in this step, first determine the batch quantity of coal (M) fed into the furnace, unit: ton (t). Then determine the target sampling interval of the coal fed into the furnace. If the time-based sampling method is selected for the coal fed into the furnace, first use the following formula to calculate the sampling comparison interval time (Δt max , unit: min):

[0073]

[0074] Wherein, Δt max is the sampling comparison interval time, M is the batch quantity of coal, m is the number of sampling units, G is the maximum coal conveying capacity of the sampling device, and n is the number of subsamples to be pre-taken for each sampling unit.

[0075] At this time, the target sampling interval includes the target sampling interval time (TM1 )。If Δt max ≥ the maximum sampling interval time (T max ), then determine the maximum sampling interval time (T max ) as the target sampling interval time (T M1 ).

[0076] If the minimum sampling interval time (T min ) ≤ Δt max ≤ the maximum sampling interval time (T max ), then determine Δt max as the target sampling interval time (T M1 ).

[0077] If Δt max ≤ the minimum sampling interval time (T min ), then determine the minimum sampling interval time (T min ) as the target sampling interval time (T M1 ).

[0078] That is, if Δt max ≥ T max , then T M1 = T max . If T min ≤ Δt max ≤ T max , then T M1 = Δt max . If Δt max ≤ T min , then T M1 = T min .

[0079] Exemplarily, if Δt max ≤ the minimum sampling interval time, then adjust the maximum coal conveying capacity of the sampling device to the target coal conveying capacity. The target coal conveying capacity is calculated by the following formula:

[0080]

[0081] where G a is the target coal conveying capacity, M is the batch coal quantity, m is the number of sampling units, T min is the minimum sampling interval time, and n is the number of subsamples to be taken in each sampling unit.

[0082] That is, if Δt max ≤ T min , then reduce the maximum coal conveying capacity (G) of the sampling device and adjust it to the target coal conveying capacity (G a ).

[0083] If the quality-based sampling method is selected for the coal fed into the furnace, the target sampling interval at this time includes the target sampling interval mass (Δm max ).

[0084] The target sampling interval mass is calculated by the following formula:

[0085]

[0086] Among them, Δm max is the target sampling interval mass, M is the batch coal quantity, m is the number of sampling units, and n is the number of subsamples to be taken in each sampling unit.

[0087] Take the coal sample of the coal fed into the furnace according to the calculated target sampling interval time (T M1 ) or the target sampling interval mass (Δm max ). Take one gross sample for each sampling unit until the batch coal sampling is completed, and a total of m gross samples are obtained. Each gross sample is prepared and analyzed separately.

[0088] The method for determining the sampling interval of the coal fed into the furnace in the embodiment of the present disclosure can improve the representativeness of sampling and reduce the loss rate of the sampling device. And on the premise of ensuring the sampling efficiency and the safe operation of the device, the expected sampling precision target value can be achieved.

[0089] Typical Example 1:

[0090] The coal fed into the furnace of a certain Power Plant A is a blended coal of Coal Sample 1 and Coal Sample 2. A mechanical sampling and sample preparation device is installed on the coal conveying transfer belt to take coal samples. The specific sampling steps are as follows:

[0091] The first step: Obtain the coal quality information of the coal fed into the furnace and the parameter information of the sampling device:

[0092] ① The commercial coal samples and their proportions that make up the coal fed into the furnace: Coal Sample 1: Coal Sample 2 = 0.5:0.5.

[0093] ② The dry ash content of each commercial coal sample that makes up the coal fed into the furnace: A d,1 = 36.65%, A d,2 = 13.23%.

[0094] ③ Obtain the primary subsample variances of Coal Sample 1 and Coal Sample 2 that make up the coal fed into the furnace according to the method for determining the primary subsample variance involved in Part 4.3 of the GB / T19494.3 standard:

[0095] Coal Sample 1: The sampling precision of the coal received at the factory P1 = 1.50%, the number of subsamples n1 = 40, and the variance of sample preparation and analysis V PT = 0.2.

[0096] Coal Sample 2: The sampling precision of the coal received at the factory P2 = 1.20%, the number of subsamples n1 = 30, and the variance of sample preparation and analysis VPT = 0.2.

[0097] It can be calculated that:

[0098] The primary sub-sample variance V1 of coal sample 1: The primary sub-sample variance V2 of coal sample 2:

[0099] ④ Coal conveying belt operation parameters: The maximum coal conveying capacity G = 800 t / h.

[0100] ⑤ The amount of coal fed into the furnace M = 6000 t. The number of sampling units m = 3.

[0101] ⑥ Technical parameters of the mechanical sampling and sample preparation device: The minimum sampling interval time T min = 2 min, the maximum sampling interval time T max = 30 min.

[0102] The second step: Calculate the primary sub-sample variance VI of the coal fed into the furnace:

[0103]

[0104] The third step: Calculate the dry ash content A of the coal fed into the furnace based on the dry ash content and proportion of each commercial coal that makes up the coal fed into the furnace d :

[0105]

[0106] 16.00% < A d ≤ 40.00%, the expected sampling precision p of the coal batch fed into the furnace = 1.60%.

[0107] The fourth step: Calculate the number of sub-samples n to be pre-taken for each sampling unit:

[0108]

[0109] The fifth step: Select the time-based sampling method for sampling the coal fed into the furnace and calculate the sampling comparison interval time Δt max :

[0110]

[0111] The determination method of the target sampling interval time T of the coal fed into the furnace M1 :

[0112] T min = 2 min ≤ Δt max ≤ T max = 30 min, then T M1 = Δt max = 25 min.

[0113] That is, according to the calculated target sampling interval time T M1 Take the in-furnace coal sample every 25 minutes. Take one gross sample for each sampling unit until the sampling of the batch of coal is completed. A total of 3 gross samples are obtained, and each gross sample is prepared and analyzed separately.

[0114] Typical Example 2:

[0115] The in-furnace coal of a certain Power Plant B is a blended coal of Coal Sample 1 and Coal Sample 2. A mechanical sampling and sample preparation device is installed on the coal conveying transfer belt to take coal samples. The specific sampling steps are as follows:

[0116] Step 1: Obtain the coal quality information of the in-furnace coal and the parameter information of the sampling device:

[0117] ① The commercial coal samples and their proportions that make up the in-furnace coal: Coal Sample 1: Coal Sample 2: Coal Sample 3 = 0.5:0.3:0.2.

[0118] ② The dry ash content of each commercial coal sample that makes up the in-furnace coal: A d,1 = 47.53%, A d,2 = 24.72%, A d,3 = 11.05%.

[0119] ③ Obtain the primary sub-sample variances of Coal Sample 1, Coal Sample 2, and Coal Sample 3 that make up the in-furnace coal according to the method for determining the primary sub-sample variance in Section 4.3 of the GB / T19494.3 standard:

[0120] Coal Sample 1: The sampling precision of the coal received at the factory P1 = 2.00%, the number of sub-samples n1 = 80, and the variance of sample preparation and analysis V PT = 0.2.

[0121] Coal Sample 2: The sampling precision of the coal received at the factory P2 = 1.60%, the number of sub-samples n1 = 60, and the variance of sample preparation and analysis V PT = 0.2.

[0122] Coal Sample 3: The sampling precision of the coal received at the factory P3 = 1.20%, the number of sub-samples n1 = 40, and the variance of sample preparation and analysis V PT = 0.2.

[0123] It can be calculated that:

[0124] The primary sub-sample variance V1 of Coal Sample 1: The primary sub-sample variance V2 of Coal Sample 2: The primary sub-sample variance V3 of Coal Sample 3:

[0125] ④ The operating parameters of the coal conveying belt: The maximum coal conveying capacity G = 1000 t / h.

[0126] ⑤ The in-furnace coal quantity M = 2400 t. The number of sampling units m = 2.

[0127] ⑥ Technical parameters of mechanical sampling and sample preparation device: minimum sampling interval time T min = 3 min, maximum sampling interval time T max = 30 min.

[0128] Step 2: Calculate the primary subsample variance VI of the coal as it enters the furnace:

[0129]

[0130] Step 3: Calculate the dry ash content A of the coal as it enters the furnace based on the dry ash content and proportion of each commercial coal that makes up the coal as it enters the furnace d :

[0131]

[0132] 16.00% < A d ≤ 40.00%, the expected sampling precision p of the coal batch as it enters the furnace is 1.60%.

[0133] Step 4: Calculate the number of subsamples n to be pre-taken for each sampling unit:

[0134]

[0135] Step 5: Select the time-based sampling method for sampling the coal as it enters the furnace, and calculate the sampling comparison interval time Δt max :

[0136]

[0137] Determination method of the target sampling interval time T of the coal as it enters the furnace M1 :

[0138] Δt max ≤ T min , then reduce the coal conveying volume G of the coal conveyor belt for the coal as it enters the furnace to G a :

[0139]

[0140] That is: as calculated, the coal conveying volume of the coal conveyor belt for the coal as it enters the furnace should be reduced to 770 t / h, and the target sampling interval time T M1 Select T min = 3 min to take samples of the coal as it enters the furnace. Take one total sample for each sampling unit until the sampling of the coal batch is completed, and a total of 2 total samples are obtained. Each total sample is prepared and analyzed separately.

[0141] Comparison with the original sampling method of the coal as it enters the furnace in Power Plant B:

[0142] The coal conveying volume of the coal conveyor belt for the coal as it enters the furnace is still transported at a load of G = 1000 t / h, and the sampling interval time T M = Tmin = 3 min, the number of sub-samples n' taken is as follows:

[0143]

[0144] Then the expected sampling precision P':

[0145]

[0146] P' = 1.78% > 1.60%, and the sampling precision fails to reach the target value of the expected sampling precision of 1.60% for the batch of coal. The sampling process of the coal fed into the furnace in the embodiments of the present disclosure is a better method to achieve the target value of the expected sampling precision of the batch of coal on the premise of ensuring the sampling efficiency and the safe operation of the device.

[0147] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present disclosure. However, the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the present disclosure.

Claims

1. A method for determining the sampling interval of coal entering a thermal power plant, characterized in that: The determination method comprises: Obtaining coal quality information of coal entering the furnace and parameter information of sampling device; Calculating the primary sub-sample variance and dry basis ash content of the incoming coal according to the coal quality information, and determining the expected sampling precision of the batch coal according to the dry basis ash content; Determine the number of sampling units, and calculate the number of sub-samples to be taken in advance in each sampling unit using the variance of the primary sub-samples of the incoming coal and the expected sampling precision of the batch coal; The batch coal quantity is determined, and the target sampling interval of the coal entering the furnace is obtained by using the number of sub-samples pre-taken in each sampling unit, the number of sampling units and the parameter information.

2. The method for determining the sampling interval of coal entering a thermal power plant according to claim 1, characterized in that: The coal quality information includes the proportion of each commercial coal sample constituting the incoming coal, the dry basis ash content and the primary sub-sample variance; The parameter information includes the maximum coal transport capacity and sampling interval of the sampling device; wherein the sampling interval includes the minimum sampling interval and the maximum sampling interval.

3. The method for determining the sampling interval of coal entering a thermal power plant according to claim 2, characterized in that: The ratio of each commercial coal sample is determined by the following formula: Coal sample 1: Coal sample 2: ...: Coal sample i: ...: Coal sample N = δ1: δ2: ...: δ i :…δ N ,and 4. The method for determining the sampling interval of coal entering a thermal power plant according to claim 3, characterized in that: The primary sub-sample variances of the commercial coal samples are obtained according to the determination method of primary sub-sample variances in Part 4.3 of GB / T19494.3, which are V1, V2, ..., V i ,…,V N .

5. The method for determining the sampling interval of coal entering a thermal power plant according to claim 4, characterized in that: The calculating the primary sub-sample variance of the incoming coal according to the coal quality information comprises: The primary sub-sample variance of the incoming coal is calculated using the following formula:

6. The method for determining the sampling interval of coal entering a thermal power plant according to claim 5, characterized in that: The dry basis ash contents of the commercial coal samples are A d,1 , A d,2 , …A d,i , …A d,N ; The step of calculating the dry basis ash content of the incoming coal according to the coal quality information includes: The dry basis ash content of the coal fed into the furnace is calculated using the following formula: And, the determination of the expected sampling precision of the batch coal includes: When A d >40%, the expected sampling precision of the batch of coal is ≤2.00%; When 16.00%<A d When the sampling precision of the coal batch is ≤40.00%, the sampling precision of the coal batch is expected to be ≤1.60%; When A d ≤16.00%, the expected sampling precision of the batch of coal 7. The method for determining the sampling interval of coal entering a thermal power plant according to claim 6, characterized in that: The calculation of the number of sub-samples pre-taken for each sampling unit comprises: The number of sub-samples pre-taken for each sampling unit is calculated using the following formula: Where n is the number of sub-samples pre-taken in each sampling unit, V I is the primary sub-sample variance of coal entering the furnace, m is the number of sampling units, and p is the expected sampling precision of the batch coal.

8. The method for determining the sampling interval of coal entering a thermal power plant according to claim 7, characterized in that: The target sampling interval for obtaining the coal entering the furnace includes: The sampling comparison interval is calculated using the following formula: Among them, Δt max is the sampling comparison interval, M is the batch coal quantity, m is the number of sampling units, G is the maximum coal capacity of the sampling device, and n is the number of sub-samples pre-taken in each sampling unit; And, the target sampling interval includes the target sampling interval time; if Δt max ≥ the maximum sampling interval, the maximum sampling interval is determined as the target sampling interval; If the minimum sampling interval ≤ Δt max ≤ the maximum sampling interval, then Δt max Determine the target sampling interval time; If Δt max ≤ the minimum sampling interval, the minimum sampling interval is determined as the target sampling interval.

9. The method for determining the sampling interval of coal entering a thermal power plant according to claim 8, characterized in that: If Δt max ≤ the minimum sampling interval time, the maximum coal delivery capacity of the sampling device is adjusted to the target coal delivery capacity; The target coal transport volume is calculated using the following formula: Among them, G a is the target coal delivery volume, M is the batch coal volume, m is the number of sampling units, T min is the minimum sampling interval, and n is the number of sub-samples pre-taken for each sampling unit.

10. The method for determining the sampling interval of coal entering a thermal power plant according to claim 7, characterized in that: The target sampling interval includes a target sampling interval quality; The target sampling interval quality is calculated using the following formula: Among them, Δm max is the target sampling interval quality, M is the batch coal size, m is the number of sampling units, and n is the number of sub-samples pre-taken in each sampling unit.

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