The QHCZ furnace wall thickness monitoring system has been successfully applied in blast furnace operations, proving to be an effective tool for real-time measurement of the furnace wall's condition. It offers a simple design, reliable performance, and high accuracy, making it a valuable asset in industrial environments.
The system employs ultrasonic sensors designed specifically for the harsh conditions of blast furnace smelting. Instead of direct contact with the furnace wall, a pre-buried measuring rod is used. This rod, which is eroded along with the wall, connects to the ultrasonic probe at a coupling point. As the furnace wall thins, the rod shortens, allowing the system to measure the remaining thickness by analyzing the reflected echo from the rod.
Material selection for the rod was critical. The goal was to find a material that could withstand high temperatures while maintaining good ultrasonic transmission. Various materials were tested, including aluminum, copper, ceramic, and steel. However, aluminum had a low melting point, copper conducted heat too quickly, and ceramic was prone to cracking. Steel, although durable, showed significant ultrasonic attenuation at high temperatures, leading to weak or no echoes. After extensive testing, a special iron rod was chosen, capable of functioning effectively even at 1300°C.
In the blast furnace belly area, where the distance from the hot end of the rod to the outer casing is approximately 1 meter, the probe must be positioned carefully to avoid water leaks and other hazards. A higher frequency was selected to improve resolution and penetration, and a 40 mm diameter rod was chosen based on experimental results showing optimal echo strength.
Feasibility tests were conducted at Baotou Steel’s No. 2 Blast Furnace. After several months of operation, the rods were retrieved and found to match the actual wall thickness. However, rods installed in the upper waist area had tapered ends, resulting in poor signal quality. This issue was attributed to impedance mismatch and changes in cross-sectional area, affecting wave propagation.
To enhance signal clarity, noise suppression techniques were implemented. Custom damping materials were used to reduce pulse width and improve resolution. Coupling agents were also tested to ensure optimal contact between the rod and probe, leading to the selection of a high-performance adhesive that maintained bond strength under extreme conditions.
Protection measures were added to safeguard the measuring rod and probe. A spring-loaded coupling was introduced to resist impact and vibration, while wiring was insulated against fire and moisture. The data collectors were later centralized to improve accessibility and reduce maintenance efforts.
In practice, temperature gradients can affect measurement accuracy, so software compensation was introduced. Long-distance signal transmission also posed challenges, with potential distortion and interference. To address this, consistent probe selection and calibration procedures were implemented, ensuring reliable data across different temperature conditions.
The QHCZ system features a distributed network with hundreds of detection points, providing real-time waveform display, erosion profiles, historical data access, and online data uploads. It supports both local and remote monitoring, offering valuable insights for blast furnace management and optimization.
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