Article
The Behavior of Supersonic Jets Generated by Combination
Gas in the Steelmaking Process
Binglong Zhang
1
, Fuhai Liu
1,2,
* and Rong Zhu
1
Citation: Zhang, B.; Liu, F.; Zhu, R.
The Behavior of Supersonic Jets
Generated by Combination Gas in the
Steelmaking Process. Materials 2021,
14, 5034. https://doi.org/10.3390/
ma14175034
Academic Editor: Arkadiusz Gola
Received: 22 June 2021
Accepted: 17 August 2021
Published: 3 September 2021
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4.0/).
1
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing,
Beijing 100083, China; aptx2008@126.com (B.Z.); zhurong1206@126.com (R.Z.)
2
National Center for Materials Service Safety, University of Science and Technology Beijing,
Beijing 100083, China
* Correspondence: liufuhaisteel@ustb.edu.cn
Abstract:
In the duplex steelmaking process, the oxygen flow rate is suppressed to reduce the
increasing rate of the temperature in the molten bath, resulting in severe dynamic conditions. To
improve the mixing effect of the molten bath, a Laval nozzle structure designed for combination gas
has been proposed. In this research, five types of Laval nozzle structure have been built based on the
combination gas content, and both numerical simulations and experiments are performed to analyze
the flow field of the supersonic jet. The axial velocity and oxygen concentration were measured
in the experiment, which agreed well with the numerically simulated data. The results show that
both initial axial velocity and potential core length increase with the flow rate of combination gas.
Further, applying a higher N
2
flow rate could improve the oxygen utilization rate at different ambient
temperatures, but this issue increases the oxygen utilization rate; however, the latter can be reduced
at higher ambient temperatures.
Keywords: laval nozzle; supersonic jet; combination gas; flow field; numerical simulation
1. Introduction
The duplex steelmaking process has been widely utilized to enrich valuable elements
(vanadium and titanium), or to remove harmful elements (phosphorous) [
1
,
2
]. According
to the operational characteristics, there are two common operational methods for the
duplex steelmaking process. In traditional methods, such as the Linz–Donawitz (LD)-new
refining process (NRP) and the simple bearing process (SRP) method, the hot metal is
first discharged into a dephosphorization converter for producing the low phosphorus
semi-steel. Subsequently, the semi-steel is discharged into a decarburization converter to
produce the molten steel, which meets the requirements of content and temperature [
3
,
4
].
For the multi-refining converter (MURC) method, the liquid slag is kept inside the converter
after the decarburization process and is then reused in the dephosphorization process in the
same converter, which decreases the slag quantity and smelting cost [
5
]. To achieve a better
thermodynamic condition and an appropriate molten time, oxygen flow with a lower rate
should be utilized to lessen the reaction rate between the oxygen and carbon elements [
6
,
7
];
nevertheless, the mixing and impaction ability of supersonic oxygen multi-jets can also be
reduced, which suppresses the dynamic conditions of the molten bath [8,9].
For refining the dynamic condition of the molten bath, the influences of the Laval
nozzle structure, oxygen initial temperature, and injection angle on the flow field of the
supersonic jet have been broadly examined by both numerical simulation and experiment,
at the same conditions of the oxygen flow rate. Wang and Liu et al. [
10
,
11
] reported that
the oxygen preheating technology could significantly improve the initial velocity of the
supersonic jet, resulting in a more considerable impaction ability. Sambasivam and Feng
et al. [
12
,
13
] proposed a new arrangement for the oxygen nozzles, proved that an added
center nozzle could increase the impaction cavity of the molten bath, and demonstrated the
Materials 2021, 14, 5034. https://doi.org/10.3390/ma14175034 https://www.mdpi.com/journal/materials
