Boiler Combustion Air Control via Oxygen Feedback

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Solution Overview

Problem

Boilers face inefficiencies due to uncontrolled leaking air, which existing air feedback control systems struggle to compensate for, especially during transients, leading to excessive pollutants and energy losses.

Innovation Solution

A method to determine and adjust the amount of controlled air supplied to a boiler by calculating leaking air based on flue gas oxygen concentration, air/energy constant, and fuel heating value, allowing for precise control of excess air even during load changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If air feedback control systems adjust the air to fuel ratio to maintain suitable excess air, then boiler efficiency is improved, but the systems cannot compensate for leaking air during transients, resulting in loss of efficiency

Engineering Contradiction:

Improveboiler efficiencyVSAvoidcontrol accuracy during transients

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent employs a feedback control mechanism that continuously monitors flue gas oxygen concentration and adjusts the air to fuel ratio accordingly. The control system uses the measured oxygen level as feedback to maintain the desired excess air fraction, automatically compensating for leaking air during transients by adjusting the controlled air supply based on real-time measurements

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces traditional mechanical air flow measurement and control methods with an analytical approach using flue gas oxygen concentration measurements. Instead of directly measuring and controlling air flow mechanically, the system uses oxygen sensing and calculations to determine and adjust the air to fuel ratio, providing more accurate control during transient conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the amount of air supplied to the combustion chamber is increased to avoid incomplete combustion, then complete burning of fossil fuel is achieved, but more energy is lost in the stack due to excess air

Engineering Contradiction:

Improvecomplete combustionVSAvoidstack heat loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent dynamically adjusts the excess air fraction parameter based on real-time flue gas oxygen concentration measurements. By continuously monitoring oxygen levels and adjusting the air to fuel ratio, the system maintains the optimal balance between complete combustion and minimizing stack heat loss, adapting to changing operating conditions including transients and leaking air variations

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables efficient boiler operation by maintaining a desired excess air fraction, reducing pollutants and energy losses associated with unburned fuel and stack heat, while compensating for leaking air and load changes.

Implementation Method 1

measuring the boiler's flue gas oxygen concentration can be used to determine the amount of leaking air in the boiler

Methodology Applied

Scientific EffectOxygen concentration measurement:

Data Source

PatentUS8682499B2Combustion air control

Publication Date: 2014.03.25 HONEYWELL INTERNATIONAL INC

AI summary

Embodiments of the present disclosure include devices and methods for controlling combustion air. For example, in one embodiment, a method for controlling combustion air includes determining an amount of leaking air in a boiler, determining a constant that depends on a heating value of a fuel in the boiler, and adjusting an amount of controlled air supplied to the boiler.