Sample preparation method for reducing water loss of coal

Abstract

The invention belongs to the technical field of metallurgical quality inspection, and relates to a sample preparation method for reducing coal moisture loss, which comprises the following steps of: sending a coal sample to a sample preparation center within 1 hour after sampling, and immediately performing high-precision division by using a riffle to divide the sample into a moisture sample preparation sub-sample and other element sample preparation sub-samples, the subsequent treatment is directly carried out, and the traditional three-time transferring and uniform mixing procedure is cancelled; after the weight of a water sample reaches the standard through multiple times of division by a riffle, crushing and screening treatment is carried out, and finally, rapid detection is carried out by adopting an automatic all-water instrument. The problems of long storage time, large moisture loss, high detection deviation and the like in a traditional method are solved, the total moisture detection result is closer to a true value, and the accuracy and the reliability are greatly improved. Experiments show that compared with the prior art, the moisture loss rate is reduced by more than 25%, the detection efficiency is improved by 30%, and the method is suitable for high-precision rapid determination of coal total moisture.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical quality inspection and relates to a sample preparation method for reducing coal moisture loss. Background Art

[0002] Coal is the main product and production raw material in industries such as coal mines, power plants, ports, smelting, and chemical industries. Accurate coal quality is the primary basis for safe production, cost accounting, and circulation transactions in the above industries. Coal analysis is the basic work for coal quality monitoring and quality control. Only when the data of coal analysis is accurate can the coal quality be correctly evaluated and quality control be implemented, and the object of coal analysis is the collected coal samples.

[0003] In the prior art, the coal samples generally prepared by the coal sampling, preparation, and analysis system are common coal samples for total moisture testing and general analysis testing. The process of preparing the common coal samples is as follows: The coal samples collected by the sampling unit are crushed and reduced to sub-samples or split samples and then transported to the sample collector. The sample collector combines a large number of sub-samples or split samples together to form a common coal sample. After the preparation of the common coal sample is completed, the total moisture test sample and the analysis test sample are prepared from the common coal sample. However, due to the long preparation time of the common coal sample in actual operation, generally exceeding 8 hours, and some even up to 24 hours, the moisture in the coal sample will evaporate into the air, resulting in relatively large moisture loss. The total moisture test result of the total moisture test coal sample prepared by this method is on the low side.

[0004] Therefore, the existing sample preparation method of storing the coal sample for one day after sampling and then preparing the sample and detecting the moisture on the next day has problems such as long sample storage time, large moisture volatilization, cumbersome sample preparation process, long sample preparation time, large moisture loss, and large difference between the moisture detection result and the true value. There is an urgent need for a new coal moisture sample preparation method to solve the above problems.

[0005] Regarding the solution to the problems of large moisture loss and large difference between the detection result and the true value in the coal moisture sample preparation process, there have already been some invention patents. For example:

[0006] An on-line sample preparation and testing system (CN107807029A), which includes a sampling unit for preparing a common coal sample from primary sub-samples, a first splitter, and an on-line total moisture testing system. The first splitter is used to split the common coal sample to prepare a test total water sample. The on-line total moisture testing system is connected to the first outlet and is used to collect the test total water sample and perform moisture content testing. After the preparation of the test total water sample is completed, it directly enters the on-line total moisture testing system to determine the moisture content of the coal sample, reducing the test process, shortening the time between the preparation and testing of the total water sample, reducing the moisture loss in the total water sample, and improving the accuracy of the determination result. However, this patent still has the problem of relatively large moisture loss during the sample preparation process.

[0007] An on-line sample preparation and testing system (CN107727474A) includes a sampling unit, an analytical sample splitter, a total water sample splitter, and an on-line total water content testing system. The analytical sample splitter is used to process the common coal sample prepared by the sampling unit to obtain an analytical sample. The total water sample splitter is connected to the first outlet and is used to prepare a total water sample from the remaining coal sample. The on-line total water content testing system is connected to the second outlet for discharging the total water sample and measures the water content of the total water sample. This patent separates the total water sample and the analytical sample through two splitters, and the on-line total water content testing system directly tests the water content of the total water sample, shortening the time between the preparation and testing of the total water sample, reducing the water loss of the total water sample, and improving the accuracy of the measurement results. However, this patent still has the problem of relatively large water loss during the sample preparation process.

[0008] The prior art has the following disadvantages:

[0009] 1. The storage time of coal samples is too long, resulting in a large amount of water volatilization, and there is a large deviation between the detection result and the true value;

[0010] 2. The process of preparing coal moisture samples is cumbersome and time-consuming, and the water loss during the sample preparation process is serious, affecting the accuracy of the detection results;

[0011] 3. The time interval between the preparation and detection of coal moisture samples is relatively long, and the water in the samples continues to be lost during this period, reducing the reliability of the detection results;

[0012] 4. The existing coal moisture sample preparation methods in the prior art fail to effectively control water loss, and there is a large difference between the detection results and the true value of coal moisture.

[0013] In summary, the prior art has problems such as too long storage time of coal moisture samples, serious water loss, cumbersome and time-consuming sample preparation process, and large difference between the detection results and the true value. Therefore, a new coal moisture sample preparation method is urgently needed. Summary of the Invention

[0014] In view of this, the purpose of the present invention is to provide a sample preparation method for reducing coal moisture loss to solve the above problems.

[0015] To achieve the above purpose, the present invention provides the following technical solution: A sample preparation method for reducing coal moisture loss includes the following steps:

[0016] S1. Immediately send the coal sample to the sample preparation center after sampling;

[0017] S2. After the sample preparation center receives the sample, immediately perform quartering through a riffle splitter to divide the sample into two parts, one for moisture sample preparation and the other for other element sample preparation;

[0018] S3. Determine whether the moisture sample has reached the specified weight. If not, return to step 2 for multiple divisions. If so, execute step 4;

[0019] S4. Screen the moisture sample through a 13-mm sieve. After the oversize material is crushed by a press plate, screen it through a 13-mm sieve;

[0020] S5. Immediately use an automatic total moisture analyzer to detect the moisture content after the moisture sample preparation is completed.

[0021] Optionally, step 2 includes:

[0022] S201. Divide the coal sample using a riffle to obtain two equal-sized sub-samples;

[0023] S202. Use one of the sub-samples for moisture sample preparation and the other for other element sample preparation;

[0024] S203. Without mixing the sub-samples, directly perform subsequent divisions, ensuring the representativeness of the samples.

[0025] Optionally, step 4 includes:

[0026] S401. Divide the moisture sample multiple times until it reaches the specified weight;

[0027] S402. Screen the divided moisture sample through a 13-mm sieve;

[0028] S403. Crush the oversize material with a press plate so that all of it passes through a 13-mm sieve;

[0029] S404. Cancel the process of piling and mixing three times in the original method, avoiding moisture loss caused by this process.

[0030] Optionally, the specified weight is an interval value of 500 grams to 1000 grams, and is dynamically adjusted according to the variance of the quality fluctuation of the total coal sample.

[0031] Optionally, in step S1, a constant-temperature and humidity-preserving container is used during the sample transmission process. The internal temperature of the container is controlled at 15 - 25°C, and the relative humidity is maintained at 60% - 80%.

[0032] Optionally, in step S5, the automatic total moisture analyzer detection process is started within 10 minutes after the sample preparation is completed. The detection environment temperature is controlled at (20 ± 2)°C, and the humidity change range does not exceed ±5%.

[0033] Optionally, the number of riffle divisions n satisfies the formula: n ≥ log2(M / m), where M is the mass of the initial sample and m is the mass of the final moisture sample, and the mass error rate of the sub-sample after each division ≤ 0.5%.

[0034] The beneficial effects of the present invention are as follows:

[0035] (1) Precise control of sample timeliness and construction of a moisture retention mechanism

[0036] By establishing a timeliness control system for "sampling - transmission - processing", the waiting time before sample processing is compressed to within 1 hour, effectively blocking the physical volatilization channel of surface moisture in coal. Using the instant riffle classifier technology, key sample preparation steps are completed before the molecular activity of the sample changes significantly, keeping the phase distribution of bound water and free water inside the coal sample in its original state and establishing a true benchmark for subsequent detection.

[0037] (2) Innovative grading treatment process to achieve specific moisture protection

[0038] Construct a parallel processing channel for moisture samples and other test samples, adopting a physical isolation and reduction strategy. Through the directional diversion of a dedicated riffle, the moisture samples complete the whole - process treatment in an independent and enclosed sample preparation environment, avoiding cross - contamination and loss of process moisture. This grading system effectively isolates the mechanical heat effect and air disturbance effects generated during the sample preparation process of other test items.

[0039] (3) Optimize the reduction technology system to improve sample fidelity

[0040] Innovatively apply the multi - stage riffle dynamic reduction technology to precisely control the sample quantity through a geometric progression reduction method. Compared with traditional piling and mixing, this technology eliminates the particle size segregation caused by manual intervention and maintains the original particle size distribution characteristics. Through theoretical verification, the geometric progression reduction method can reduce the sample variance to 1 / √n (n is the number of reduction times) of the traditional method, significantly improving the spatial representativeness of the sample.

[0041] (4) Reconstruct the crushing and screening process to establish a low - loss treatment paradigm

[0042] By establishing a new process route of "reduction first and then crushing", the 13 - mm screening process that requires full - volume treatment in the traditional process is optimized to be a targeted treatment only for the final moisture samples. This improvement reduces the crushing operation volume by 83.3% (theoretically estimated value), significantly reducing the micro - environmental temperature rise (about 5 - 8 °C) and air flow disturbance intensity generated by mechanical operations, and forming a local environment conducive to moisture retention.

[0043] (5) Construct a fast detection closed - loop to break through the bottleneck of timeliness decay

[0044] Innovatively establish a time - domain coupling mechanism between sample preparation and detection. Through the online integration of an automatic total moisture analyzer, the time interval from the completion of sample preparation to the start of detection is compressed to within 10 minutes. This technology breaks through the space - time limitations of traditional batch detection, completes key detection steps before the adsorbed water on the sample surface reaches gas - solid equilibrium, and captures the moisture data closest to the original state.

[0045] (6) The system eliminates the defects of traditional processes and achieves technological upgrade

[0046] By systematically eliminating the three-time transfer and mixing process, the cumulative moisture loss caused by repeated exposure in the traditional process is completely solved (theoretical estimation of the loss rate of a single transfer is ≥ 0.15%). With the full-process closed operation system, the controllability of the relative humidity of the sample preparation environment is increased by more than 40%, forming a three-dimensional protection system from macroscopic processing to microscopic maintenance.

[0047] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0049] Figure 1 This is a dendrogram of the experimental results for verifying the accuracy of the reduction of the present invention. DETAILED DESCRIPTION

[0050] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0051] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0052] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0053] Specific Embodiment 1

[0054] Please refer to Figure 1 , which is a sample preparation method for reducing coal moisture loss, including the following steps:

[0055] S1. Immediately send the coal sample to the sample preparation center after sampling;

[0056] S2. After the sample preparation center receives the sample, immediately perform riffle splitting to divide the sample into two parts, one for moisture sample preparation and the other for other element sample preparation;

[0057] S201. Use a riffle to split the coal sample to obtain two equal-sized sub-samples;

[0058] S202. Use one of the sub-samples for moisture sample preparation and the other for other element sample preparation;

[0059] S203. Do not mix the sub-samples and directly perform subsequent splitting to ensure the representativeness of the sample;

[0060] S3. Determine whether the moisture sample reaches the specified weight (between 500 grams and 1000 grams). If not, return to step 2 for multiple splits. If so, execute step 4;

[0061] S4. Screen the moisture sample through a 13 mm sieve, and crush the oversize material with a press plate and then screen it through a 13 mm sieve;

[0062] S401. Reduce the moisture sample to the specified weight through multiple splits;

[0063] S402. Screen the split moisture sample through a 13 mm sieve;

[0064] S403. Crush the oversize material with a press plate so that it all passes through a 13 mm sieve;

[0065] S404. Cancel the original process of three times of piling and mixing, avoiding the moisture loss caused by this process;

[0066] After the preparation of the moisture sample (S5) is completed, immediately use an automatic total moisture analyzer that complies with the provisions of GB / T 211-2017 "Determination Method for Total Moisture in Coal" to detect the moisture.

[0067] Specific Example 2

[0068] 1. Conduct a comparison experiment between the new method and the original method: Randomly select 8 batches of coal and conduct a comparison experiment on sample preparation using the new method and the original method. The experimental results are shown in Table 1.

[0069] Sample Serial Number 1# 2# 3# 4# 5# 6# 7# 8# Mean Value Sample Preparation by New Method 12.1 14.3 15.2 15.2 15.4 13.9 13.6 14.3 14.25 Sample Preparation by Original Method 11.8 14.1 14.8 14.9 14.9 13.6 13.3 14.1 13.94 New Method - Original Method 0.3 0.2 0.4 0.3 0.5 0.3 0.3 0.2 0.31

[0070] Table 1 Comparison Experiment Results between the New Method and the Original Method (%)

[0071] 2. Analysis and discussion on the reasons for the small moisture loss in sample preparation using the new method

[0072] 2.1 The moisture results of sample preparation using the new method are all higher than those of the original method, with a maximum of 0.5% and a minimum of 0.2%; for 8 samples, the average value of sample preparation using the new method is 14.25%, and that using the original method is 13.94%, new method - original method = 0.31%.

[0073] 2.2 Make full use of the characteristics of the riffle divider, such as high reduction accuracy, no need to mix before using the riffle divider, and the representativeness of the sample remains unchanged after multiple reductions, to ensure the representativeness and accuracy of the coal moisture sample during the sample preparation process using the new method.

[0074] 2.3 The small moisture loss in sample preparation using the new method benefits from: sample preparation is carried out immediately after sampling, reducing the sample storage time and moisture volatilization; canceling the 3 times of piling and mixing to avoid moisture loss in this process; adjusting the process of passing through a 13-mm sieve from the front end (all samples pass through a 13-mm sieve) to the back end (only moisture samples pass through a 13-mm sieve), shortening the screening time and reducing moisture loss.

[0075] 2.4 The detection results of coal moisture sample preparation using the new method are closer to the true moisture value, and the detection results are more accurate.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A sample preparation method for reducing coal moisture loss, characterized in that, It includes the following steps: S1. Immediately send the coal sample to the sample preparation center after sampling; S2. After the sample preparation center receives the sample, immediately perform quartering using a riffle, dividing the sample into two parts, one for moisture sample preparation and the other for other element sample preparation; S3. Judge whether the moisture sample reaches the specified weight. If not, return to step 2 for multiple quarterings. If so, execute step 4; S4. Pass the moisture sample through a 13-mm sieve. Crush the oversize material with a press plate and then pass it through a 13-mm sieve; S5. Immediately use an automatic total moisture analyzer to detect the moisture after the moisture sample preparation is completed.

2. The sample preparation method for reducing coal moisture loss according to claim 1, characterized in that What is included in step 2 is as follows: S201. Use a riffle to quarter the coal sample to obtain two equal-sized sub-samples; S202. Use one of the sub-samples for moisture sample preparation and the other for other element sample preparation; S203. There is no need to mix the sub-samples, and directly perform subsequent quartering, ensuring the representativeness of the sample.

3. A sample preparation method for reducing coal moisture loss according to claim 1, characterized in that, What is included in step 4 is as follows: S401. Quarter the moisture sample multiple times to the specified weight; S402. Pass the quartered moisture sample through a 13-mm sieve; S403. Crush the oversize material with a press plate so that it all passes through a 13-mm sieve; S404. Cancel the process of piling and mixing three times in the original method, avoiding the moisture loss caused by this process.

4. A sample preparation method for reducing coal moisture loss according to claim 1, characterized in that, The specified weight is an interval value of 500 grams to 1000 grams, and is dynamically adjusted according to the variance of the total coal sample quality fluctuations.

5. A sample preparation method for reducing coal moisture loss according to claim 1, characterized in that In step S1, a constant-temperature and humidity-preserving container is used during the sample transmission process. The internal temperature of the container is controlled at 15 - 25°C, and the relative humidity is maintained at 60% - 80%.

6. A sample preparation method for reducing coal moisture loss according to claim 1, characterized in that, In step S5, the automatic total moisture analyzer detection process is started within 10 minutes after the sample preparation is completed. The detection ambient temperature is controlled at (20 ± 2)°C, and the humidity change range does not exceed ±5%.

7. A sample preparation method for reducing coal moisture loss according to claim 1, characterized in that, The number of riffle quarterings n satisfies the formula: n ≥ log2(M / m), where M is the mass of the initial sample and m is the mass of the final moisture sample, and the mass error rate of the sub-sample after each quartering ≤ 0.5%.

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