Ostwald charts in combustion engineering—purpose of use Ostwald charts are primarily employed in furnace/boiler practice for which calculation?

Introduction / Context:
Combustion control relies on knowing how much air is supplied relative to stoichiometric requirements. Graphical tools such as Ostwald charts help quickly interpret flue-gas analysis to estimate excess air or air deficiency, enabling tuning of burners for efficiency and low emissions.

Given Data / Assumptions:

• Flue-gas analyzer readings (e.g., O2, CO2, CO) are available.
• Fuel is a typical hydrocarbon/coal gas without exotic constituents.
• Objective: adjust air-fuel ratio to target excess air.

Concept / Approach:
Ostwald charts correlate measured flue-gas constituents to excess air. By plotting CO2 and O2 (and sometimes CO), operators infer whether there is too much air (high O2, lower CO2) or too little air (CO present). This supports rapid decision-making without detailed equilibrium calculations.

Step-by-Step Solution:

Verification / Alternative check:
Comparing chart-derived excess air to computed values using mass balance typically shows good agreement within operating accuracy, validating the chart’s use.

Why Other Options Are Wrong:

• Absolute flue-gas temperature requires energy balance, not an Ostwald chart.
• Full flue-gas composition from first principles involves stoichiometry and possibly equilibrium—not a simple chart lookup.

Common Pitfalls:
Ignoring moisture corrections (wet vs. dry basis) can misread chart inputs; always ensure data basis matches the chart.

Final Answer:
Computing the excess or deficiency of combustion air