The Electric Control System
ofJiGang120TConverterSublance
Competition in the steel industry is becoming increasingly fierce, and companies are facing growing market pressure. To enhance their competitiveness, steel companies are vying to introduce advanced production equipment, metallurgical process control technologies, and advanced production processes to improve product quality, reduce production costs, and increase market competitiveness. The introduction of auxiliary lance technology at Jinan Iron and Steel Group has improved the level of automated steelmaking technology, enhanced product quality, and strengthened market competitiveness.
I. Introduction to the Secondary Weapon System
The auxiliary lance system used in Jinan Iron and Steel Group's No. 3 Steelmaking Plant was designed and manufactured by DANIELI-CORUS. It can measure and sample the temperature of the molten pool at a vertical position in the converter while the converter is continuously blowing.
The sub-lance system (Figure 1) consists of four main components: (1) a rotating platform or a traverse trolley with a winch for raising and lowering the sub-lance body connected to the platform or trolley; (2) an automatic probe installation system (Figure 2) with a probe storage tank to ensure safe storage of probes, automatically select probes and automatically install probes onto the sub-lance body; (3) equipment mounted on or above the converter hood, such as a sub-lance water-cooled insertion port, a sealing cover and a slag removal device; and (4) electrical and instrumentation equipment, such as a DIRC instrument and a device for processing measurement signals.
II. Secondary gun electrical control system
The secondary rifle electrical control system consists of the secondary rifle lifting drive system, the secondary rifle rotation drive system, the APC system (automatic probe loading and unloading device), and the DIRC-5 instrument system. The entire secondary rifle control system is centrally controlled by a PLC system: the PLC system consists of a CPU module, a CPS module, a NOE module, an EHC module, a DDI module, a DDO module, an ACI module, an ACO module, and an XBE module.
1. Secondary rifle lifting drive system
The auxiliary gun lifting drive system is mainly located on the hoisting platform and includes a 55KW three-phase asynchronous motor, AC brake, reducer, speed generator for speed control, and two pulse generators for height measurement. Motor speed regulation is achieved using two frequency converters.
Improve drive parameters
Type: AC motor, VVVF
High speed 2.5m/s
Medium speed/accident speed: 0.6 m/s
Low speed 0.2m/s
Positioning speed: 0.1 m/s
Positioning accuracy +/- 1cm
Maximum travel 18.8m
2. Secondary rifle rotation drive system
The auxiliary gun rotation drive system includes a 3km three-phase squirrel-cage motor with a brake, a reducer, a pulse generator, and a speed generator. The rotation speed is controlled by a frequency converter, positioning is achieved by the pulse generator via a PLC, the actual position is determined by a proximity switch, and an overtravel switch is used for hard-wired stopping.
Rotary drive parameters
Normal speed 1.33 rpm
Positioning speed: 0.27 rpm
Positioning accuracy +/- 1cm
Rotation radius 5900mm
Maximum rotation angle: 104 degrees
APC system
The APC system includes a probe storage box, probe selection and feeding, a probe tilting arm, and a probe removal device.
(1) Probe storage box
The probe storage box has 5 independent storage compartments, each capable of holding 20 probes.
(2) Probe selection and feeding
The feeder is attached to the bottom of the storage box, and the required probe is selected by rotating the cylinder-feeder rack.
(3) Probe tilting arm
The probe tilting arm includes a frame, a guide funnel, a probe clamp, an AC motor, etc.
The probe is held in place by a probe clamp and delivered to the tilting arm. A motor drives the tilting arm to move the probe to a vertical position. Upon reaching the vertical position, the guide funnel closes at the sub-gun head via a cylinder. The sub-gun is then lowered into the closed guide funnel. Once the probe holder is inserted into the probe, the guide funnel opens, and the sub-gun continues to descend, fully connecting with the probe.
Once the mechanical connection is complete (indicated by the degree of connection via a proximity switch), the auxiliary gun stops, and the probe clamp releases the probe. Finally, the tilting arm returns to the horizontal position. During the probe connection process, the gap between the probe and the guide funnel is purged with instrument gas to prevent dust and dirt from accumulating on the upper part of the probe.
(4) Probe disassembly device
The probe removal device is installed above the probe collection tank. After measurement, the pneumatic probe removal device clamps the probe, lifts the auxiliary gun, and detaches the probe from it. The probe removal device is then opened to send the probe to the probe collection tank.
(5) DIRC-5 instrument system
The DIRC-5 instrument system mainly analyzes and processes the data measured by the probe, and displays the results (temperature, carbon content, oxygen potential, oxygen activity, and molten pool level) on the HMI screen and stores them in an external PC for further analysis.
(6) Automatic control process of the secondary gun
The automatic control process of the secondary gun consists of three cycles: connection cycle, measurement cycle, and reset cycle.
III. Functions of the Secondary Pistol
The auxiliary lance provides an effective measuring tool for the converter, enabling it to measure and sample the molten pool and temperature from a vertical position within the converter while continuously blowing. The auxiliary lance retrieves the selected probe from its storage box, automatically connects to the top of the auxiliary lance, and moves it above the converter. The auxiliary lance inlet on the fume hood is opened, and the probe is lowered into the molten pool. Depending on the type of probe used, the thermocouple and oxygen measurement unit send signals. After a few seconds, the probe is raised and automatically removed from the converter platform. The sample is then taken out and sent to the laboratory for analysis. The emitted signals are processed by a Dirc instrument and quickly transmitted to the furnace front, providing useful data to the operator. Various probes can be used in the auxiliary lance, such as probes for temperature, sampling, and carbon determination (TSC); probes for temperature, sampling, and oxygen determination (TSO); and probes solely for temperature measurement (T). The functions of each probe differ, primarily selected based on production requirements and modes. For example, some probes are used for measurements during the blowing process, some for measurements at the end of the blowing process, and some are used solely for temperature measurement. The dynamic model relies on the results of measurements taken by the auxiliary lance to determine whether to continue blowing. This involves measuring the temperature and oxygen content of the molten steel to determine its carbon content, as well as measuring the steel level and taking samples for analysis. If blowing continues, the required oxygen and converter flux amounts are dynamically calculated by the dynamic model based on the auxiliary lance measurements. The auxiliary lance measurements, shown in Figure 1, are calculated using DIRC instruments. Operators and metallurgical engineers can access the measurement curves and results for each heat. These results are automatically transmitted to the dynamic process control system, which then calls upon the dynamic blowing model to determine whether to perform supplementary blowing and additional charging.
Figure 1. Measurement results of the secondary gun
IV. The Value of the Secondary Weapon System
1. Shorten the steelmaking cycle and improve productivity.
The secondary lance system eliminates manual sampling and temperature measurement, saving time and reducing the skill requirements for operators. Since furnace turning is no longer necessary during sampling and temperature measurement, the steel tapping cycle is shortened, thereby increasing converter productivity.
2. Extend the lifespan of the converter
Process optimization and elimination of furnace turning operations enable users to effectively extend the life of converters, allowing the number of steel taps to increase by up to 40% without using slag splashing for furnace protection.
3. Improve the accuracy of the blowing endpoint and the effectiveness of the model.
The endpoint hit rate in the blowing process can be used to illustrate the performance of the control model. If the equipment operates normally and the quality of molten iron, scrap steel, and additives meets the specified requirements, the endpoint hit rate of the Danieli Conliss sub-lance equipment can exceed 90%. The accuracy of the control model can be evaluated by the standard deviation of the main technical indicators of the final product (Table 3). The standard deviation reflects the deviation between the target or predicted value and the actual measured value.
Conclusion
The adoption of a secondary lance system can improve the level of automated steelmaking technology, enhance product quality, strengthen product market competitiveness, and create higher economic and social benefits for enterprises.
About the author:
Zhang Xitao (March 1976–): Male, engineer, engaged in the research and application of automation control and metallurgical process modeling at Jinan Iron and Steel Plant.
Contact information:
Address: Furnace Inspection Workshop, Block 120, Jinan Iron and Steel Plant, Jinan City, Shandong Province
Postal code: 250101
Email: [email protected]
Telephone: 0531-88847127 Mobile: 13864105869
