Continuous flue gas composition monitoring for O2 and CO2: which instrument provides on-line, automatic, continuous analysis in furnace/boiler stacks?

Introduction / Context:
Combustion optimization and environmental compliance require continuous, on-line flue gas analysis. The goal is to track oxygen and carbon dioxide in real time for air–fuel ratio control and efficiency calculations. Understanding which instruments are truly continuous as opposed to manual or batch is essential for proper selection.

Given Data / Assumptions:

• Target species: O2 and CO2 in flue gas.
• Requirement: continuous, automated operation suitable for industrial stacks.
• Sampling system with conditioning is assumed.

Concept / Approach:
A process chromatograph (on-line GC) cycles continuously and produces regular, automated readings for multiple components, including O2 and CO2, by separating species before detection. While modern CEMS often combine a zirconia O2 probe with an NDIR CO2 analyzer to achieve continuous monitoring, among the provided single-instrument choices, a chromatograph is the one explicitly designed for automated, continuous multi-component analysis (beyond a single property). Orsat is manual and intermittent. A single thermal conductivity cell lacks selectivity and typically cannot deliver simultaneous specific O2 and CO2 readings without prior separation. A zirconia probe alone measures O2 only, not CO2.

Step-by-Step Solution:
Eliminate manual methods (Orsat) as non-continuous.Note that zirconia provides only O2; TCD lacks selectivity.Select the instrument capable of automated multi-component separation and measurement: chromatograph.

Verification / Alternative check:
Typical plant CEMS racks may mix technologies (paramagnetic/zirconia for O2 and NDIR for CO/CO2). However, if a single instrument type must cover both continuously from the list, an on-line GC qualifies due to its automated cyclic analysis capability.

Why Other Options Are Wrong:
Orsat apparatus: Manual, laboratory/field portable—not continuous.Thermal conductivity cell: Non-selective without separation; prone to cross-sensitivity.Zirconia probe: Measures O2 only.Paramagnetic + NDIR combo: Effective in practice but not a single named instrument choice here.

Common Pitfalls:
Assuming “continuous” for any sensor that can be left in-line; true continuous multi-component analysis requires selectivity or separation.

Final Answer:
Chromatograph