Direct Flame Preheating Layout for Uniform Metal Strip Heating

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Solution Overview

Problem

Existing direct flame preheating sections in metal strip processing lines suffer from temperature and surface condition heterogeneity, high NOx emissions, and inefficient combustion modes, which affect the quality of the metal strip and increase maintenance and investment costs.

Innovation Solution

A direct flame preheating section with burners capable of operating in 'no flame' mode and a connecting zone that orients combustion fumes to flow head-on relative to the strip, combined with symmetrical chambers and ducts to ensure homogeneous fume distribution, reducing NOx emissions and temperature variance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional burners operate in flame mode to heat the strip, then heating efficiency is improved, but temperature homogeneity and surface condition uniformity deteriorate

Engineering Contradiction:

Improveheating efficiencyVSAvoidtemperature homogeneity

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The burner operates in 'no flame' mode by changing the combustion parameters, specifically by injecting combustion air through a diffuser that creates a velocity profile preventing flame formation. This parameter change allows the combustion products to directly contact the strip surface, achieving both high heating efficiency and uniform temperature distribution across the strip width.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The diffuser is designed with a specific velocity profile that varies locally across its width, creating different flow characteristics at different positions. This local quality variation ensures that combustion products are distributed uniformly across the strip surface, achieving homogeneous heating while maintaining high energy efficiency.

Inventive Principle:

Principle #3Local quality

2Power

If conventional burners operate in flame mode, then heating power is improved, but NOx emissions increase

Engineering Contradiction:

Improveheating powerVSAvoidNOx emissions

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

By changing the combustion mode from flame to no-flame operation through the diffuser velocity profile, the peak temperatures required for NOx formation are eliminated. The combustion air is injected at high velocity through the diffuser, preventing flame formation and thereby drastically reducing thermal NOx emissions while maintaining effective heating power through direct contact of hot combustion products with the strip.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If fumes are circulated in conventional configurations, then energy recuperation is achieved, but temperature and surface condition heterogeneity worsen

Engineering Contradiction:

Improveenergy recuperationVSAvoidsurface condition homogeneity

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The diffuser creates a specific velocity profile parameter that directs combustion products head-on against the strip surface. This parameter change in flow direction and velocity distribution ensures uniform distribution of hot fumes across the strip width, achieving both effective energy recuperation and homogeneous surface conditions.

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

Achieves temperature homogeneity within ±10°C over the strip width, low NOx emissions, and controlled oxidation, enhancing the mechanical properties and surface condition of the metal strip while reducing fuel consumption and maintenance costs.

Implementation Method 1

a direct flame preheating section with burners capable of operating in 'no flame' mode

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 2

Heating the strip from ambient temperature to a desired temperature

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 3

a recuperative zone where the strip is preheated to a temperature below 250° C. in order to prevent its oxidation, and this by consuming the heat contained in the fumes coming from the active zone

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 4

Said connecting zone comprises an outlet chamber capable of orienting the flow of the fumes so that they flow head-on relative to the strip when exiting the active zone

Methodology Applied

Scientific EffectFluid flow:

Data Source

PatentUS12590761B2Direct flame preheating section for a continuous metal strip processing line

Publication Date: 2026.03.31 FIVES STEIN SA

AI summary

Direct flame preheating section for continuous metal strip processing lines, comprising a connecting zone between an active zone provided with burners capable of operating in “no flame” mode and a recuperative zone for preheating the strip by exchange with combustion fumes originating from the active zone, the connecting zone having chambers capable of orienting the flow of fumes such that they flow head-on relative to the strip when exiting the active zone and entering the recuperative zone depending on the direction of flow of the fumes.