Drying Vapor Recirculation for Burner-Based Pollutant Reduction

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Solution Overview

Problem

Existing wood chip drying systems face challenges in reducing pollutant emissions, particularly volatile organic compounds (VOCs) and particulate matter, while maintaining energy efficiency and avoiding complex, costly designs.

Innovation Solution

Recirculate a portion of the drying vapor directly to the burner, maintaining it above the condensation temperature and utilizing the burner's high temperatures to oxidize pollutants, eliminating the need for additional cleaning systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If vapor is recirculated to the burner to reduce pollutant emissions, then harmful factors are reduced, but the system complexity increases due to additional return lines and temperature control requirements

Engineering Contradiction:
Improvepollutant emissionsVSAvoidsystem complexity
Core Design Contradiction:
Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The invention merges the vapor recirculation function with the existing burner system by integrating the return line directly into the burner's combustion chamber. This combination allows pollutant reduction through vapor recirculation while avoiding the complexity of separate cleaning systems, as the burner itself serves dual purposes: combustion and pollutant treatment.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The burner system performs self-service by simultaneously conducting combustion and pollutant oxidation functions. The recirculated vapor containing pollutants is fed back to the burner where it is automatically oxidized using the burner's existing high-temperature combustion environment, eliminating the need for additional dedicated pollutant treatment equipment.

Inventive Principle:
Principle #25Self-service

2Loss of substance

If vapor is cooled below condensation temperature to remove moisture, then humidity is reduced, but energy is lost through heat of condensation

Engineering Contradiction:
Improvemoisture removalVSAvoidheat of condensation
Core Design Contradiction:
Loss of substanceVSLoss of energy

Solution Approach 1:

The invention changes the temperature parameter of the recirculated vapor, maintaining it above the condensation temperature throughout the recirculation process. By keeping the vapor temperature in the range of 100-200°C (above dew point), the system achieves pollutant oxidation without condensing water vapor, thereby preserving the heat of condensation and improving energy efficiency.

Inventive Principle:
Principle #35Parameter changes

3Object-generated harmful factors

If complex cleaning systems are added to reduce pollutants, then harmful factors are reduced, but device complexity and cost increase

Engineering Contradiction:
Improvepollutant emissionsVSAvoidcleaning system complexity
Core Design Contradiction:
Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The invention makes the burner system universal by assigning it multiple functions: primary combustion function and secondary pollutant oxidation function. The recirculated vapor containing pollutants is directed to the burner where it undergoes oxidation in the combustion chamber, allowing the burner to serve both purposes without requiring separate dedicated cleaning equipment.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention converts the harmful pollutants contained in the recirculated vapor into beneficial combustion material. By feeding the pollutant-laden vapor back to the burner, the pollutants are oxidized and converted into less harmful substances (CO2, H2O), transforming the harmful emission stream into a useful fuel source that reduces overall pollutant emissions.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

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

Significantly reduces pollutant emissions below legal limits, enhances energy efficiency, and simplifies the system design by integrating directly into existing systems without additional components.

Implementation Method 1

burning the pollutants contained in the recirculated vapor in the burner

Methodology Applied
Scientific EffectOxidation: Oxidation

Implementation Method 2

burning the pollutants contained in the recirculated vapor in the burner

Methodology Applied
Scientific EffectCombustion: Combustion

Implementation Method 3

the return line being thermally insulated; maintaining the portion of the vapor being recirculated to the burner at a temperature higher than the condensation temperature

Methodology Applied
Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentEP4567361B1Method for reducing pollutants in drying plants
Publication Date: 2026.02.18 SWISS KRONO TEC AG
  • EP4567361B1 patent drawingFigure 1
  • EP4567361B1 patent drawingFigure 2

AI summary

A method is provided for reducing pollutants in a drying system (100) that are produced during the drying of moist material in the drying system (100). The method comprises recirculating at least a portion of the vapor produced during the drying of the moist material to a burner (10) of the drying system (100), maintaining the vapor portion to be returned to the burner (10) at a temperature above the condensation temperature of the water vapor contained in the vapor portion; and combusting the pollutants contained in the recirculated vapor portion in the burner (10). Furthermore, a recirculation device (80) and a wood chip drying system (100) having the recirculation device are provided for carrying out this method.