Prima PRO process mass spectrometer - Improving product quality and process efficiency in basic oxygen steelmaking

Improving product quality and process efficiency in Basic Oxygen Steelmaking — summary

Significance of the topic

Basic Oxygen Steelmaking (BOS) is the dominant global route for steel production and a major consumer of energy and raw materials. Real-time, multi-component analysis of converter off-gas is critical for controlling decarburization, avoiding operational incidents (notably slopping and water ingress), optimizing oxygen and lance use, and recovering fuel gas. Improved off-gas monitoring directly impacts product quality, process safety, energy efficiency and plant throughput, producing rapid economic returns in high-volume steelmaking operations.

Objectives and study overview

This application note describes the use of the Thermo Scientific Prima PRO process mass spectrometer (MS) for on-line analysis of BOF/LD converter off-gas. The goals are to demonstrate how fast, accurate multi-component gas analysis supports: real-time decarburization control; early slopping detection; hydrogen (water leak) detection for safety; optimization of lance position and oxygen usage; and improved recovery and safe utilization of waste gas as fuel. The note summarizes representative off-gas profiles, performance metrics, site acceptance testing and reported operational benefits at industrial installations.

Methodology and analytical approach

The Prima PRO is a magnetic sector process mass spectrometer using electron impact ionization and high ion energies (~1000 eV) to provide robust, low-maintenance continuous analysis of H2, CO, CO2, O2, N2 and Ar in converter waste gas. Typical sampling is at the waste gas duct upstream of cooling and dust extraction, with sample conditioning (dust filtration and moisture removal). The analyser cycles every ~1.6 s and can update process models in 2 s or less. The system provides derived fuel-gas parameters (CV upper/lower, Wobbe index, specific gravity, density) per ISO 6976 when used for gas recovery monitoring.

Used instrumentation

• Thermo Scientific Prima PRO process mass spectrometer (magnetic sector).
• Electron impact ionization source; high ion energy (~1000 eV) for rugged operation.
• Close-coupled sampling probe located at the converter waste gas duct (two-probe system with automatic switchover for cleaning).
• Sample conditioning skid: particulate filtration and moisture removal prior to analyzer.
• Analyzer shelter with sealed cabinet, side-mounted air conditioner (stabilizes cabinet ±0.5°C), embedded processor and GUI connectivity.
• Communications: Modbus RTU (standard), optional Profibus DP and Modbus TCP/IP; 13 digital inputs and 13 digital outputs standard; additional I/O optional.

Key performance metrics and site test results

• Fast response: data updates in ≤2 s (analysis cycle ~1.6 s), enabling dynamic control model integration.
• Reported carbon prediction hit rates exceed 95% for end-point carbon levels below 0.1% when integrated into a dynamic control model.
• Slopping prediction success reported above 81% at sites using MS-based modeling and retained-O2 measurement.
• Site acceptance test for BOF fuel gas: tight agreement between cylinder certificate and MS mean readings across components (H2, CO, N2, O2, Ar, CO2) with low standard deviations, and derived calorific and Wobbe values matching specified tolerances.
• Recovered gas safety: typical average O2 in recovered gas <0.2% over extended runs; faster monitoring allows ~20 s earlier start and ~20 s later end to recovery per melt—translating to >1,600 Nm3 recovered gas per charge at typical flows (~150,000 Nm3/h).
• Analytical precision (typical): H2 ≤0.01 %mol; CO ≤0.1 %mol; N2 ≤0.1 %mol; O2 ≤0.02 %mol; Ar ≤0.01 %mol; CO2 ≤0.04 %mol (8-hour measurements using calibration gas).

Main results and discussion

The Prima PRO MS provides continuous, multi-component off-gas measurements that capture the rapid temporal changes in CO and CO2 during the oxygen blow and the corresponding collapse and recovery of O2. The CO/CO2 ratio combined with retained O2 and waste-gas flow enables direct estimation of decarburization rate (dC/dt proportional to ([CO]+[CO2]) × flow) and reliable end-point prediction, reducing unnecessary re-blows and extra flux additions. Direct measurement of N2 enables accurate assessment of air ingress, improving retained-O2 estimation and slopping prediction. High-speed and accurate H2 measurement supports rapid detection of water leaks and improves personnel and plant safety. Integration of MS-derived gas composition into models also enables improved lance positioning and more efficient oxygen use, shortening tap-to-tap times and increasing throughput.

Benefits and practical applications

• Consolidates multiple discrete analyzers (NDIR CO/CO2, paramagnetic O2, thermal-conductivity H2) into a single fast multi-component analyzer.
• Enables dynamic process control with real-time decarburization and end-point prediction—reducing process costs and improving yield and quality.
• Early slopping detection protects equipment, reduces metal loss and improves safety.
• Improves fuel gas recovery economics by extending safe recovery intervals and ensuring oxygen content stays below safety thresholds.
• Detects water ingress rapidly via H2 monitoring, mitigating explosion risk.
• Magnetic sector technology offers superior mass-scale stability (flat-top peaks), resistance to contamination, and better H2 analysis than quadrupole systems.

Plant integration and operational considerations

Prima PRO is normally installed in an analyzer shelter at the converter roof level sampling the waste gas duct. The cabinet is dust-sealed and temperature-controlled. Sample handling includes a two-probe sampling system allowing continuous operation while the inactive probe is cleaned. The analyzer’s embedded processor supports local control or remote GUI access; standard and optional industrial communication protocols facilitate integration to distributed control systems and dynamic control models. Regular calibration using certified cylinders and routine sample conditioning are required for long-term accuracy.

Future trends and potential applications

• Tighter integration of high-speed MS data with model predictive control and machine-learning algorithms to further reduce tap-to-tap time and optimize reagent usage.
• Sensor fusion combining MS with acoustic, optical and thermodynamic signals for earlier and more robust slopping and leak detection.
• Improved sampling and conditioning designs to extend maintenance intervals and permit operation in harsher ambient conditions.
• Expanded use of MS-derived real-time energy parameters to optimize on-site fuel management and emissions reporting.
• Remote diagnostics and cloud-based analytics to support predictive maintenance and centralized process optimization across multiple converters or plants.

Conclusion

High-speed, multi-component process mass spectrometry (Prima PRO magnetic sector MS) delivers comprehensive off-gas information that materially improves decarburization control, slopping prediction, hydrogen leak detection and waste-gas recovery in BOF operations. The combination of rapid response, high precision and robust instrumentation enables consolidation of analyzers, measurable fuel and time savings, improved product quality and enhanced operational safety—often producing rapid payback on instrumentation investment.

References

1. World Steel Association. Crude steel production statistics. 2015.
2. Thermo Fisher Scientific. Process Mass Spectrometry in Iron & Steel. 2010.
3. Hu Z.-G., et al. A dynamic off-gas model on a 150t BOF. Steel Times International. April/May 2003.
4. Merriman D. Mass spectrometry for oxygen steelmaking control. Steel Times. November 1997.
5. Merriman D., Lewis G. Fast on-line monitoring of fuel gases with the Thermo Scientific Prima PRO process mass spectrometer. Thermo Fisher Scientific publication. 2016.