Effects of gas injection with multihole orifices in upleg snorkel on bubble behaviour and decarburisation rate during RH refining

Abstract

Physical model experiments have been conducted to investigate the effects of multihole orifices in the upleg snorkel on bubble behaviour and decarburisation rate during Ruhrstahl-Heraeus refining. Bubble behaviour was recorded by a high speed video camera and a volumetric mass transfer coefficient kA/V was used to evaluate the decarburisation rate. Measurement of the volumetric mass transfer coefficient kA/V was made by means of the CO 2 desorption from a NaOH solution. Pictures of bubble behaviour show that gas bubbles are generated separately from the multihole orifice in the low region of gas flowrate, but they tend to coalesce at high gas flowrate. It was demonstrated that kA/V increases with increasing gas flowrate and decreasing orifice hole diameter. In the low region of gas flowrate, kA/V for multihole orifices is larger than that for one-hole orifices. In this case, kA/V increases as the number of holes increases, and the hole distance of orifice has little effect on kA/V. However, in the high region of gas flowrate, kA/V for multihole orifices is lower than that for one-hole orifices, and kA/V decreases with the increase in orifice interhole distance. It was found that there exists a critical gas flowrate, above which kA/V for multihole orifices is lower than that for one-hole orifices. This critical value increases with increasing hole distance and hole number. Some explanations were also made in terms of bubble behaviour.

Effects of Different RH Degasser Nozzle Layouts on the Circulating Flow Rate

“…In the RH process, the circulation flow rate of liquid steel plays an extremely important role in determining the productivity of the equipment, because it affects the refining efficiency. Most studies [ 8 , 10 , 15 , 16 , 17 , 18 , 19 ] aimed to understand the effects of various operating parameters in the RH process on the circulation flow, including vacuum pressure, gas flow rate, RH vessel and vent size. Jiang F et al [ 16 ] investigated the effects of multi-hole orifices in the upleg snorkel on the bubble behavior during Ruhrstahl–Heraeus refining.…”

“…Most studies [ 8 , 10 , 15 , 16 , 17 , 18 , 19 ] aimed to understand the effects of various operating parameters in the RH process on the circulation flow, including vacuum pressure, gas flow rate, RH vessel and vent size. Jiang F et al [ 16 ] investigated the effects of multi-hole orifices in the upleg snorkel on the bubble behavior during Ruhrstahl–Heraeus refining. Ling et al [ 20 ] reported that as the number of nozzles increased, a value reached an optimum maximum circulation flow rate and minimum mixing time.…”

“…Dai W et al [ 21 ] compared this with the unexpanded bubble, and found that the expanded bubble contributed a higher circulation rate in SSRF and induced a greater superficial area of free surface in the vacuum chamber, owing to its larger, rising velocity. The circulation rate increased with a higher gas flow rate [ 1 , 2 , 3 , 7 , 22 , 23 ], lower vacuum pressure [ 1 ], larger immersion depth [ 1 , 7 , 19 ] and larger snorkel diameter [ 1 , 16 , 24 , 25 ]. Han et al [ 26 ] reported a maximum circulation flow rate for an injection angle of 12 degrees.…”

Investigation of mixing and slag layer behaviours in the RH degasser with bottom gas injection by using the VOF–DPM coupled model

“…The Rheinsahl−Heraeus (RH) treatment process is of enormous importance in secondary refining involving many metallurgical functions, such as the removals of carbon, hydrogen, and nitrogen from molten steel [1][2][3]. The dimension parameters [4][5][6][7][8][9][10][11][12][13] and operating parameters [6,12,[14][15][16][17][18][19][20][21][22][23][24] of RH equipment are usually modified or adjusted to shorten the mixing time of molten steel and thereby improve the refining efficiency of RH degasser, as summarised in Table 1.…”

Morphology Evolution and Phase Interactions of Fe-containing Si₃N₄ in Vacuum High-temperature Environment

“…10) So it has been applied widely in the clean steel production. 11,12) The low vessel and upper vessel of the inner lining in RH refining furnaces mainly adopt fused grain re-bonded magnesia-chromite bricks and direct-bonded magnesia-chromite bricks. [13][14][15][16] Although the application of magnesia-chromite bricks in RH refiners does not generate large quantities of Cr 6 + as that in the burning zone of cement rotary kilns, the generation of Cr 6 + is still inevitable during production.…”