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 From Prototype to Daily Practice – 4 Years of Real-Time Slag Analysis with QLX

Redefining Slag Analysis

Short Summary:
Since 2022, Acciaierie di Calvisano has been working with QuantoLux laser-based slag analysis. Over the past four years,  QLX9 has been developed together with Feralpi as a development partner, with continuous improvements in calibration, handling, and robustness under real melt shop conditions.

Following the successful test phase in Calvisano, Elbe-Stahlwerke Feralpi GmbH became the second plant within the group to purchase and implement the system, building on the experience gained in Calvisano. Today, QLX9 is an established tool for daily process optimization.

Initial Situation / Plant Context
Acciaierie di Calvisano, part of the Feralpi Group, operates an Electric Arc Furnace (EAF) route with Ladle Furnace (LF) refining, focusing on long steel products. The production is based on a high share of scrap, which requires flexible and well-controlled process conditions.

In such EAF-based mini-mills, slag plays a central role. It influences energy efficiency, metal yield, refractory wear, and downstream refining performance. Reliable knowledge of slag composition is therefore essential for process control, especially for parameters such as FeO content and basicity.

Challenge (Pain Points)
In general, slag analysis in steel plants is still dominated by laboratory-based XRF methods. These require complex sample preparation steps such as crushing, grinding, and pelletizing or fusion. As a result, analysis times are typically in the range of 20–40 minutes or longer.

This delay creates several challenges:

  • Process decisions are often based on outdated information
  • Dynamic changes during the heat are not captured
  • Only a limited number of samples can be analyzed per shift

As a result, operators often rely on experience rather than real-time data, which can lead to variability in slag conditions and suboptimal process control.

QLX9 in Operation at Feralpi Calvisano
QLX9 in Operation at Feralpi Calvisano
QLX9 at Feralpi Calvisano
QLX9 at Feralpi Calvisano

Solution:
In parallel with the RFCS-funded iSlag project, first tests with laser-based slag analysis were carried out starting in 2022. The QLX9 system was installed close to the process and used alongside existing laboratory methods.

The workflow is simple and designed for industrial use. Slag samples are taken, crushed, and analyzed directly using Laser OES. Results are available within seconds without the need for complex preparation or laboratory infrastructure.

A key factor in the implementation was the close collaboration with plant operators. Over time, the system was continuously improved in terms of calibration stability, usability, and robustness under real melt shop conditions. This iterative process transformed the system from a prototype into a reliable tool for daily production.

Results (Measured Impact)
The main impact comes from the speed and availability of data. Analysis times are reduced from typical laboratory delays to less than one minute. This enables a significantly higher number of measurements per heat and provides immediate insight into slag composition.

  • Faster analysis (<1 minute instead of days)
  • Higher sampling frequency (one or even multiple times per heat)
  • Immediate feedback on key oxides such as FeO, CaO, SiO₂, and MgO

This allows more precise control of slag conditions. In practice, this supports improved FeO control, more stable slag foaming, reduced metal losses, and more consistent LF operation.

Operational Impact (Daily Work)
The availability of fast and direct measurements changes daily operations. Decisions can be made immediately based on current data. Flux additions can be adjusted at the right moment, and deviations are identified earlier. This reduces the need for corrective actions later in the process and lowers dependency on laboratory workflows. Slag analysis becomes a routine, fast, and accessible task integrated into daily production.

Strategic Context
The relevance of fast slag analysis is increasing with broader industry developments. Scrap-based steelmaking is becoming more complex due to higher variability in raw materials. At the same time, there is a strong focus on energy efficiency, yield improvement, and process stability. In parallel, steel plants are moving toward data-driven production. Sensor-based systems and digital models are being introduced to better understand and control the process. In this environment, direct chemical analysis of slag provides an important reference. It complements indirect sensor signals and improves the reliability of process models.

Laser OES should be seen as a complementary technology to XRF. While XRF remains important for detailed laboratory analysis, Laser OES enables fast, high-frequency measurements directly in the process environment.

Conclusion
Over four years, QLX9 has developed from an experimental setup into a robust and practical tool for slag analysis. It enables faster decisions, more stable processes, and supports the transition toward data-driven and efficient steel production.