An Aqueous Particle Sensor (APS) for Monitoring Inclusion Removal by Microbubbles in Tundish
Operations
Authors: Xiangkun Cao, Sheng Chang, Cheng-Hung Hsin, Luis Calzado,
Mihaiela Isac, R.I.L Guthrie
McGill Metals Processing Centre, 3610 University Street, Wong Bldg., Room 2M040, Montreal, H3A2B2,
E-mail: mihaiela.isac@mcgill.ca.
ABSTRACT
Due to the increasingly stringent cleanliness requirements for final products, the injection of microbubbles
into a full scale water model of a Ladle-Tundish-Mould system was identified as a way of modelling the
removal of very small inclusions (< 50μm dia) from liquid steel passing through the steelmaking tundish.
However, how to generate micro bubbles in steel, how to measure the bubble size distributions, and how to
optimize bubble injection conditions for inclusions removal, all remain problems for steelmakers. In the
present study, an Aqueous Particle Sensor (APS) system was used for in-situ, on-line detection, of
microbubbles generated by a newly designed ladle shroud. The measurement performed by the sensor were
compared and validated against bubble sizes values resulting from an alternative optical method. The optical
method is based on high speed camera measurements of assessing bubble sizes. The Aqueous Particle Sensor
(APS) system was also used to monitor small inclusions, so as to determine the efficiency of their removal,
for various gas injection conditions. The experiments targeted the effects of air inlet flowrates, distance from
slide gate and gas injection port numbers, on the average sizes of microbubbles produced, and their efficiency
in removing small inclusions. The study shows: (1) The Aqueous Particle Sensor (APS) system can also be
used for micro-bubble detection; (2) Multi-Port Injection, a low air inlet flowrate, and a shorter distance from
the slide gate, all favor the formation of smaller micro-bubbles; (3) The optimal flowrate of gas injection for
micro-inclusion removal requires a compromise between obtaining smaller bubble sizes, and securing a
greater number of micro-bubbles.
Figure 1 – Working principle of the Electrical Sensing Zone (ESZ) method
KEYWORDS
Inclusion Removal, Microbubbles, Electrical Sensing Zone (ESZ) Method, Aqueous Particle Sensor (APS)