An Overview of the Hidden Arm Coal Powder Sampling Device
The concealed arm coal powder sampling device is a specialized equipment for coal powder sampling on the primary air conveying pipeline of a positive pressure straight blowing pulverizing system. During the daily operation of the coal mill, the wear of the grinding components, variations in coal type and size, and changes in coal powder fineness can lead to significant fluctuations, directly affecting the boiler combustion efficiency and increasing power generation costs. Therefore, regular sampling and testing of coal powder fineness are essential. When the coal powder fineness exceeds the designed value, timely adjustments or replacements of the coal mill grinding components or adjustments to the separator's deflection door opening are required to achieve the designed coal powder fineness.
Accurate control and analysis of coal powder fineness in power plant coal-fired boilers are of vital importance for the safe and economic operation of the boiler units. Currently, the application of positive pressure straight-blown pulverizing systems in large-scale units is increasing. Since the coal powder at the outlet of the coal mill is directly blown into the furnace for combustion by the primary air under positive pressure, it is not easy to collect coal powder samples on a daily basis. Many ships use the self-spray method, which results in poor accuracy of sampling. It is often difficult to achieve a good seal during self-sampling, leading to coal powder leakage. The working environment is poor, and the labor intensity is high. Huaneng Power Auxiliary Equipment, with decades of experience in theoretical and engineering research on gas-solid two-phase flow, has developed a new overhead coal powder sampling device. It can conveniently achieve isokinetic sampling of coal powder in positive pressure straight-blown pulverizing systems. Its most distinctive feature is simultaneous isokinetic sampling at multiple points, ensuring that the collected powder samples have good representativeness. Multiple sampling repetitions are good, the operation is simple, and there is no coal powder leakage. This significantly improves the working environment and reduces labor intensity, making it the most ideal device for daily coal powder fineness analysis sampling in positive pressure straight-blown pulverizing systems of power plant boilers internationally.

The swing arm coal powder sampling device, as shown in the attached figure, is mainly composed of a sampling tube installed in the center of the shell on the coal powder pipeline and an external air extraction and separation unit. The sampling tube can rotate around the pivot axis, rotating it to a vertical position with the pipeline during sampling, so that the nozzle mounted on the sampling tube faces the coal powder airflow. After sampling, the sampling tube returns to a parallel position with the pipeline, avoiding the coal powder airflow to prevent wear. It uses compressed air to blow clean, preventing coal powder from entering the shell and the center of the sampler to cause blockage. The device operates reliably with no maintenance required.

II. Performance Features of the Hidden Arm Coal Powder Sampling Device
Multi-point simultaneous isokinetic sampling, convenient and quick, with good representativeness of the samples. Fixedly installed on the coal powder pipeline, the sampler rotates to the measurement plane during sampling. The sampling gun is kept outside the coal powder airflow during normal operation, resulting in minimal wear and extended lifespan. Compression air blow cleaning is used to prevent clogging of the sampler.

Section 3: Major Components of the Hidden Arm Coal Powder Sampling Device

Equipment components include: Sampling Head, Sampling Tube, Sweep Valve, Sampling Valve, External Handle, Separator, Air Valve, Sample Collection Bottle, Pressure Gauge, Sealing Chamber, etc.
1. Sampling head, placed in the coal powder pipeline during sampling, with the sampling hole facing the direction of the coal powder airflow, the gas-powder mixture enters the sampling device through the sampling hole.
2. Sampling Tube: The gas-powder mixture taken by the sampling head is transported to the cyclone separator via the sampling tube.
3 Sweep Valve: Before and after each sampling, open the sweep valve to use compressed air to sweep the sampling pipeline, preventing it from being clogged by coal dust.
4 Sampling Valve: During sampling, adjust this valve to create a negative pressure by exhausting air through the exhaust port using compressed air, which draws air from the separator, allowing coal powder in the air duct to enter the sampling device through the sampling hole.
5 Separator: It performs solid-gas separation, with the process being: Coal powder is thrown to the inner wall of the separator by the rotating air stream, where it falls into the sample collection bottle due to its own gravity. The gas, on the other hand, flows downward along the wall to the bottom and then rises to the top in the middle, finally exiting through the exhaust port.
6. Sample Bottles: Collect and store the solid coal powder samples separated by the separator.
7. Pressure Gauge: Displays pressure data for the air pressure regulating valve

Section 4: Principle of Operation for the Hidden Arm Coal Powder Sampler
1. Sampling Principle: The concealed tube coal powder sampler is developed by utilizing the principles of negative pressure suction and cyclone separation to extract the gas-powder mixture from the coal powder pipeline and achieve solid-gas separation. During the sampling process, the sampling tube is extended into the coal powder pipeline, with all valves in the open position. As compressed air flows from the outlet through the nozzle and the gas separator, its flow generates a negative pressure, which causes the cyclone separator, sampling tube, and sampling bottle to produce negative pressure, prompting the gas-powder mixture in the coal powder pipeline to enter the sampler through the sampling tube. The gas-powder mixture undergoes solid-gas separation in the cyclone separator, with the separated coal powder falling into the sampling bottle below the separator, while the gas is suctioned back into the coal powder pipeline by the compressed air. The entire operation does not produce pollution in the workplace.
Adjust the pressure regulating valve for compressed air before sampling to achieve isokinetic sampling, ensuring the coal powder sample is representative. (Compressed air pressure typically does not exceed 0.1 Mpa.)
2. Anti-blocking measures: During equipment operation, use compressed air to blow the sampling tube to prevent it from being blocked by media powder.
3. Abrasion Prevention Measures: When not sampling, the sampling tube is concealed within the housing and placed outside the coal powder pipeline. During sampling, the actuating sampling rod is activated to extend the sampling tube within the coal powder pipeline, with the sampling port facing the coal.
Airflow is directed towards the opening, and all valves are activated to begin sampling. After sampling is complete, pull the sampling operation lever to conceal the sampling tube within the housing and place it outside the coal powder pipeline, to avoid the impact of the coal powder airflow on the sampling tube.
Brush, for anti-abrasion purposes.

V. Ordering Instructions for Hidden Arm Coal Powder Sampler
Provide coal powder pipeline diameter for designing the sampling gun length.