Biomass heating system with optimized flue gas treatment
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Solution Overview
Problem
Biomass heating systems face challenges with high gaseous and solid emissions, low efficiency, and varying fuel quality due to different ash melting points, water content, and burning behaviors of different fuels, leading to incomplete combustion and increased maintenance needs.
Innovation Solution
A biomass heating system with a rotating grate and optimized combustion chamber geometry, including a primary and secondary combustion zone, and a recirculation device that mixes flue gas with primary air to enhance mixing and temperature control, combined with a flue gas condenser for improved emissions reduction and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If flue gas recirculation is implemented to reduce emissions, then gaseous emissions (CO, NOx) are reduced, but system complexity increases due to additional recirculation devices and control mechanisms
Solution Approach 1:
The patent combines the flue gas recirculation function with the existing primary air supply system by integrating a recirculation inlet into the primary air duct. The recirculated flue gas is mixed with fresh primary air in a mixing chamber before being supplied to the combustion zone, merging two functions (air supply and emissions control) into a unified system that reduces complexity.
Solution Approach 2:
The primary air duct is designed to serve dual purposes: supplying fresh combustion air and recirculating flue gas. The system uses a single primary air supply infrastructure for both functions, making the emissions control system more universal and less complex by leveraging existing components rather than adding entirely separate systems.
2Productivity
If combustion temperature is increased to improve combustion efficiency, then combustion efficiency improves, but NOx emissions increase
Solution Approach 1:
The patent changes the temperature parameter in the combustion zone by introducing cooler recirculated flue gas. This lowers the peak combustion temperature to reduce thermal NOx formation while maintaining sufficient temperature for complete combustion. The system optimizes the balance between temperature for efficiency and temperature for emissions control.
Solution Approach 2:
Recirculated flue gas acts as an intermediary substance that mediates between the need for high combustion temperature (for efficiency) and the need to limit peak temperature (to reduce NOx). The flue gas serves as a heat carrier that maintains combustion temperature while preventing excessive peak temperatures that would generate NOx.
3Reliability
If excess air is supplied to ensure complete combustion, then combustion completeness improves, but combustion temperature decreases
Solution Approach 1:
The patent changes the composition parameter of the combustion air by mixing recirculated flue gas (containing CO2 and H2O) with fresh air. This modifies the oxidizer composition to provide sufficient oxygen for complete combustion while the flue gas components act as heat carriers that maintain combustion temperature despite the increased air volume.
Solution Approach 2:
The recirculated flue gas continues to carry thermal energy from the combustion zone back through the heat exchanger and into the primary air supply, maintaining a continuous heat cycle. This ensures that even with excess air supply, the combustion temperature is sustained by the continuous input of preheated recirculated gases.
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
The system achieves low emissions of fine dust, CO, and NOx, high efficiency up to 98%, and simplified ash removal and maintenance, enabling operation with both wood chips and pellets with varying water content.
Implementation Method 1
a recirculation device that mixes flue gas with primary air to enhance mixing and temperature control
Implementation Method 2
a flue gas condenser for improved emissions reduction and efficiency
Implementation Method 3
a combustion device with a combustion chamber having a primary combustion zone and a secondary combustion zone
Data Source
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AI summary
A biomass heating system (1) for burning fuel in the form of pellets and/or wood chips is disclosed, comprising: a boiler (11) with a combustion unit (2); a heat exchanger (3) with an inlet (33) and an outlet; wherein the combustion unit (2) has a combustion chamber (24) with a primary combustion zone (26) and a secondary combustion zone (27) provided downstream thereto; wherein the combustion unit (2) has a rotary grate (25) on which the fuel can be burned; wherein the secondary combustion zone (27) of the combustion chamber (24) is fluidically connected to the inlet (33) of the heat exchanger (3); wherein the primary combustion zone (26) is laterally enclosed by a plurality of combustion chamber bricks (29).