H2 /T Monitoring during the
Degassing Process in Al Melt
What is AlproH M?
AlproH M is a monitoring system designed for use during the aluminum melt degassing process, specifically Gas Bubbling Filtration (GBF). It continuously displays a value corresponding to the hydrogen concentration in the molten aluminum. The system provides a convenient means of determining the appropriate GBF processing time and optimizing degassing conditions to improve process efficiency. The optimum degassing conditions may vary depending on several factors, including ambient humidity, gas flow rate, impeller rotation speed, melt temperature, and alloy composition. Therefore, it is recommended to verify and adjust the process conditions whenever environmental conditions change (such as during the rainy season), the alloy is changed, or the melt temperature varies.
The AlproH M system consists of a dedicated probe, a display panel, and a stand. The system features an intuitive user interface, allowing easy operation without specialized training. The display panel provides a real-time graphical display of both the hydrogen-correlated value and the melt temperature, enabling operators to monitor changes in the dissolved hydrogen level throughout the degassing process.
The stand is equipped with a motorized lift that allows the probe to be inserted into the molten aluminum easily and safely. To obtain a representative measurement during degassing, it is recommended to immerse the probe to a depth of approximately 25 cm, at a location within one-quarter of the vessel diameter from the vessel. All measurement data are automatically stored on a memory card, allowing continuous monitoring for up to approximately 3 hours.
Note: AlproH M does not directly measure the absolute dissolved hydrogen concentration. Instead, it provides a hydrogen-correlated value that is proportional to the hydrogen concentration under the turbulent flow conditions present during the degassing process.
How it works
▲ AlproH M test
The technology is based on a novel solid electrochemical hydrogen sensor, so called Park-Rapp probe, which, at an elevated temperature, is able to measure hydrogen content with reference to oxygen in the air through the adoption of proton conductor/oxygen ion conductor hetero- junction electrolytes. The principle behind how it can be used to measure hydrogen concentration is described below:
An impervious section of Park-Rapp probe (yellow and grey tube) is coated with Pt electrodes on both faces. The inside of the sensor (reference electrode) is exposed to the oxygen-containing air and the other side (working electrode) is to the hydrogen gas in the melt. For this arrangement, the measured EMF of the sensor, E is expressed as
E = E0 + 9.921x10-5 T log[H2]
, i.e. it depends logarithmically on the hydrogen partial pressure at the working electrode immersed in the melt. Here Eo, and T are sensor constant, and absolute temperature, respectively. Thus the hydrogen concentration can be calculated from the measured EMF.
Probe
The AlproH M probe consists of an internal solid-state electrolyte hydrogen sensor protected by a silicon carbide (SiC) protective cover. The SiC cover shields the sensor from erosion and dissolution caused by the high-temperature, high-velocity molten aluminum flow generated during the degassing process, thereby enabling long-term, reliable operation. The probe is available in lengths ranging from 60 cm to 90 cm. Under normal operating conditions, its average service life is approximately 50 measurements.
The probe is designed to transmit its output signal to a dedicated transmitter, where the signal is converted into a digital format for display and data processing. The cable connecting the probe to the transmitter is made of high-temperature-resistant electrical wire to ensure reliable operation and a long service life in the harsh thermal environment of aluminum melting and degassing operations. All metallic conductors inside the probe are enclosed in ceramic insulating tubes to provide reliable electrical insulation and maintain measurement stability.
Specifications
ITEMS | CONTENTS |
LCD | TFT 10.1 inch |
Accuracy | ±0.05 cc/100gAl |
Resolution | 0.01cc/100gAl |
Max monitoring time | 3 hours |
Max. depth of Immersion | 25cm |
Melt Temperature of operation | 680-780oC |
Monitor Operating Temperature | -10oC~70oC |
Standard Length of Probe | 1.2 m |
Length of Probe Cable | 2 m |
Monitor Dimension | W300xH210xT80 mm |
Weight of Analyzer | 3 Kg |
DATA Storage | Standard SD card(<32G) |
Max power consumption | <5W |
Power | 220V(50-60Hz) |
Mount | Wall/VESA |
Probe Stand
Since the AlproH M probe must be immersed in molten aluminum while the melt is vigorously agitated during the degassing process, it is subjected to significant lateral forces. Therefore, a rigid support structure and a reliable probe-holding mechanism are essential to ensure stable and safe operation.
For this reason, the use of the dedicated AlproH M stand is strongly recommended. The stand is equipped with a motorized lift that allows smooth vertical movement of the probe and can be easily positioned at the measurement location. It integrates the data transmitter, display panel, power supply, and lift control remote into a single unit, providing convenient and efficient operation during hydrogen monitoring.
Fast, Accurate, Easy to handle and Long Life
The AlproH M probe incorporates a patented air-reference electrochemical hydrogen sensor together with a proprietary measurement algorithm, enabling rapid and stable measurement of a hydrogen-correlated value even under the turbulent flow conditions present during the degassing process.
The figure shows a typical hydrogen profile recorded during a GBF degassing operation. The hydrogen-correlated value remains nearly constant during the initial stage of degassing and then begins to decrease after a certain period. The onset of this decrease indicates that hydrogen is being effectively removed from the melt and can be used to determine the optimum degassing time for the GBF process.
