Huang Ao

Water Modelling of the Blowing Effect in Ladles with Purging Plugs of Different Slit Structure and Distribution

The purging plug is an indispensable refining component; its slit structure and distribution are important factors that influence refining efficiency. We have fabricated a purging plug with adjustable slit structure and we have studied the mixing time of molten steel and the removal rate of inclusions in the ladle with a purging plug of different slit structure and blowing parameters by water modelling. The effects of the slit width, slit distribution and blowing parameters on the application of the purging plug in a ladle are discussed herein. The results show that if the gas flow rate is less than 0.89 m3/h, the mixing time difference is obviously larger; however, when the gas flow rate reaches or exceeds 0.89 m3/h, the mixing time difference becomes very small. When the slit width is more than 0.05 mm, the mixing time and inclusion removal rate are improved significantly. A smaller slit width is better for the formation of small bubbles and the removal of small inclusions, while bigger slits are conducive to stirring and a removal rate of inclusions of more than 50 µm. Bottom blowing using a d-type purging plug with collocation of slits with different widths and interval gap distribution not only ensures the removal rate of inclusions of more than 50 µm, but also highly improves the removal rate of inclusions of less than 50 µm. Thus, the total inclusion removal rate increases significantly and is as high as 67.21%. In order to guarantee good refinement, the distance of the location of the purging plug from the centre of the circle should be greater than 0.4 R, which is a critical location for better blowing metallurgy and avoidance of more serious wear of local lining refractories.

Effect of SiO2 Micropowder on Properties of Calcium Hexaluminate Castables for Coal Catalytic Gasifiers

Furnace lining materials for coal catalytic gasifiers should have good high-temperature strength and alkali slag corrosion resistance. Calcium hexaluminate castable is a promising application direction. In this paper, the effect of the addition of SiO2 micropowder on the performance of a calcium hexaluminate castable was evaluated through sintered properties, high-temperature strength, anti-alkali slag performance, and microstructural analysis. The results show a significant increase of grain and matrix bonding strength and a decrease of porosity with SiO2 micropowder addition. The castables with 3 mass-% SiO2 micropowder possessed 14.3 MPa CMOR (Cold Modulus of Rupture) and 107.6 MPa CCS (Cold Crush Strength) after heat treatment at 800 °C for 3 h. The hot flexural strength is 11.8 MPa and the retained residual flexural strength of the castables reached 37.13 % after five thermal shock cycles (water cooling) at 1100 °C. The potassium element in the slag has a very small amount of penetration and aggregation at the interface between the sample and the slag.