Boiler Combustion Temperature Envelope for Thermal NOx Control

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Solution Overview

Problem

Existing methods for reducing nitrogen oxides (NOx) emissions from fuel combustion in boilers are inadequate, particularly in maintaining optimal combustion conditions to minimize thermal NOx formation.

Innovation Solution

A combustion control system that dynamically adjusts fuel and air injection rates using a feedforward cascade control algorithm to maintain a combustion temperature within a controlled envelope, adapting to real-time changes in fuel composition, air composition, and ambient conditions, thereby minimizing thermal NOx formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If combustion temperature is increased to improve fuel combustion efficiency, then energy conversion efficiency is improved, but thermal NOx formation increases

Engineering Contradiction:

Improvefuel combustion efficiencyVSAvoidthermal NOx formation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system dynamically adjusts the combustion temperature control envelope and air-to-fuel ratio in real-time based on changing fuel composition, air composition, and ambient conditions through a feedforward cascade control algorithm, preventing thermal NOx formation while maintaining combustion efficiency

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the combustion parameters by establishing a temperature control envelope with dynamic lower and upper bounds, and adjusts the air-to-fuel ratio to keep combustion temperature within this envelope, thereby controlling thermal NOx formation while maintaining efficient combustion

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If air-to-fuel ratio is adjusted to minimize thermal NOx formation, then NOx emissions are reduced, but combustion stability may be compromised

Engineering Contradiction:

ImproveNOx emissionsVSAvoidcombustion stability

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The system uses a feedforward cascade control algorithm that continuously monitors fuel composition, air composition, and ambient conditions to predict and adjust the optimal air-to-fuel ratio, providing feedback control that maintains combustion stability while minimizing NOx emissions

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary calculations to determine the temperature margin sufficient for reliable combustion and the minimum adiabatic flame temperature before establishing the combustion temperature control envelope, ensuring combustion stability is maintained from the outset

Inventive Principle:

Principle #10Preliminary action

3Object-generated harmful factors

If dynamic control algorithms are implemented to maintain optimal combustion temperature, then NOx emissions are reduced, but system complexity increases

Engineering Contradiction:

ImproveNOx emissionsVSAvoidcontrol system complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The system replaces complex mechanical control mechanisms with a computational feedforward cascade control algorithm that processes sensor data and adjusts combustion parameters through software-based control, reducing mechanical complexity while achieving precise temperature control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control system is designed to handle multiple functions including monitoring fuel composition, air composition, ambient conditions, calculating temperature margins, determining control envelope bounds, and adjusting air-to-fuel ratio through a single integrated algorithm, reducing overall system complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Effectively reduces NOx emissions by maintaining optimal combustion temperatures, enhancing the efficiency of fuel combustion processes in boilers.

Implementation Method 1

The combustion of fossil fuels results in emissions that are released into the environment. Nitrogen oxides (NOx) are among these emissions.

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 2

thermal NOx formation is minimized

Methodology Applied

Scientific EffectThermal NOx formation:

Data Source

PatentUS20260016163A1Lowering emissions that result from fuel combustion in boilers

Publication Date: 2026.01.15 CHEVRON USA INC

AI summary

A method for lowering emissions that result from fuel combustion in a boiler may include obtaining a fuel composition, an air composition, and ambient conditions; determining, based on the fuel composition, the air composition, and the ambient conditions, a temperature margin sufficient for reliable combustion, and a minimum adiabatic flame temperature (AFT_LFL) for sustainable combustion within the boiler; establishing a combustion temperature control envelope bounded by the minimum AFT_LFL plus the temperature margin sufficient for reliable combustion, and by a threshold temperature below which thermal NOx formation is minimized; controlling, via a feedforward cascade control algorithm, an injection rate of the fuel into the boiler via a fuel injection system and an injection rate of air into the boiler via an air injection system; and automatically adapting the feedforward cascade control algorithm and associated control setpoints to remain within the combustion temperature control envelope.