BOF Stack Applications
Wet gas extractive dust monitor system MARV 2Ex
1. Application Purpose
Basic Oxygen Process (BOP), also known as Linz-Donawitz (LD) process, is one of the main metallurgical production methods since the late 1940s. Today BOF furnaces produce more than 50% of the world's steel.
Besides steel, the process generates slag and exhaust gas. While conventional analyzers measure gas components such as CO, CO₂ and O₂, MARV 2Ex measures another critical component — dust — even in wet gas and explosive atmosphere conditions.
MARV 2Ex is designed for continuous particulate monitoring in BOF stack applications in compliance with ATEX requirements.
2. Process Characteristics
The BOF process is batch-based and highly fluctuating. Process parameters can change drastically within 40–50 minutes.
For example, CO concentration may increase from 0% up to 50–60% during one batch cycle.
Pic 1. CO concentration in % of volume during the day
Typical BOF exhaust gas composition and parameters
- CO – 55–60 %
- CO₂ – 12–18 %
- O₂ – 0.1–0.3 %
- Balanced with N₂
- Gas temperature: ~60 °C (in flue)
- Gas velocity: 20–35 m/s
- Relative humidity: 100 % (wet gas)
3. Main Application Challenges
BOF stack monitoring presents several critical challenges:
- High concentration of potentially explosive gases (CO)
- 100 % dew point (wet gas after scrubber)
- Strongly fluctuating temperature
- Strongly fluctuating process flow
Pic 3. Flow during the day
Most Ex-proof dust monitors are not suitable for wet gas. Most extractive dust monitors are not certified for explosive atmospheres.
MARV 2Ex combines both capabilities.
4. Application Solution – MARV 2Ex Configuration
Pic 4. MARV 2EX system overview
For BOF stack applications MARV 2Ex operates with:
- Nitrogen (N₂) heated sampling probe
- N₂ purged optical sensor module
- Positive pressure N₂ purged enclosure
- PLC-controlled isokinetic sampling
This configuration ensures:
- Safe operation in ATEX Zone 1 / Zone 2
- Sample heating above dew point at all conditions
- Prevention of CO/O₂ leakage into enclosure
- Accurate isokinetic sampling under fluctuating flow
Dust measurement is based on optical forward scattering principle.
5. Typical Dust Levels
Continuous monitoring allows reliable tracking of dust concentration during batch cycles.
Picture 5 – Dust concentration
6. Calibration and Compliance
MARV 2EX is calibrated against Standard Reference Method (SRM) according to EN 13284-2:2004.
All values are normalized to:
- Temperature = 275.15 K
- Pressure = 1013 hPa
Picture 6. Parallel measurements of the MARV 2EX and SRM. Factory calibration
Picture 7. Parallel measurements of the MARV 2EX and SRM. Corrected calibration
7. Other Suitable Applications
In addition to BOF stack monitoring, MARV 2Ex can be used for: