Fixed-Bed Gasifier Internal Circulation for Tar Reduction
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Solution Overview
Problem
Existing wood gasification processes face challenges in producing an almost tar-free wood gas efficiently, requiring complex and costly systems for tar removal and gas treatment due to inadequate gasification and unsatisfactory control of temperature zones, leading to energy losses and high operational expenses.
Innovation Solution
An autothermic direct current fixed-bed gasifier with internal circulation uses diffuser-injector nozzles to mix rising pyrolysis gases with the gasification agent, creating intensive turbulence for complete combustion in the oxidation zone and a spacious octagonal trough grate for continuous charcoal formation, optimizing the Boudouard, hydrogen, and methane equilibria for efficient gas reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex pyrolysis gas washing systems are used to remove tars, then tar removal efficiency is improved, but investment costs and operating costs increase significantly
Solution Approach 1:
The invention extracts and removes tars at the source (in the oxidation zone) through complete combustion before the gas reaches the reduction zone. This prevents tars from entering the downstream gas cleaning system, effectively taking out the harmful factor at its origin rather than treating it later with complex washing systems.
Solution Approach 2:
The invention converts the harmful tar components into beneficial combustion energy by burning them completely in the oxidation zone. The tars that would normally require complex removal systems are instead used as fuel to generate heat for the gasification process, transforming a harmful factor into a useful energy source.
2Manufacturing precision
If separate oxidation chamber and fluidized bed reactor are added, then gas quality is improved, but apparatus complexity and investment costs increase
Solution Approach 1:
The invention merges the oxidation chamber and fluidized bed reactor functions into a single integrated gasifier unit. The oxidation zone and reduction zone are combined in one reactor, eliminating the need for separate chambers and reactors while maintaining gas quality through proper zonal design and internal circulation.
Solution Approach 2:
The single gasifier reactor performs multiple functions simultaneously: it conducts oxidation, pyrolysis, reduction, and internal gas circulation within one unit. This multi-functional design replaces the need for multiple specialized reactors while achieving the same gas quality outcomes.
3Stability of the object's composition
If pyrolysis gases are discharged to outside and reintroduced, then gas mixing is improved, but energy loss and system complexity increase
Solution Approach 1:
The invention implements self-service internal circulation where pyrolysis gases are automatically drawn from the upper zone and reinjected into the oxidation zone through injector nozzles. This self-circulating system eliminates the need for external discharge and reheating, maintaining gas composition stability while avoiding energy losses associated with external handling.
Solution Approach 2:
The injector nozzles act as intermediaries that facilitate the internal circulation of pyrolysis gases. These nozzles draw gases from the upper zone and inject them into the oxidation zone, enabling efficient gas mixing and circulation without requiring external discharge paths or additional energy input.
4Manufacturing precision
If residence time in reduction zone is increased, then gas reduction efficiency is improved, but reactor volume and productivity are reduced
Solution Approach 1:
The invention replaces mechanical extension of the reduction zone with a chemical/circulatory solution. Internal circulation of pyrolysis gases through the reduction zone provides enhanced contact time and reduction efficiency without requiring a larger reactor volume, thus maintaining productivity while improving gas reduction.
Solution Approach 2:
The continuous internal circulation of pyrolysis gases through the reduction zone ensures continuous exposure to reducing conditions. This continuous action maintains high gas reduction efficiency without requiring extended residence time that would reduce overall production rate, as the circulating gases repeatedly pass through the reduction zone.
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 generates a high-quality, almost tar-free wood gas with reduced effort for dry gas treatment and cooling, minimizing energy losses and operational costs by ensuring complete combustion and sufficient residence time for gas reduction.
Implementation Method 1
The intensive turbulence of the gas mixture - similar to an oil burner - results in the complete combustion of the tarry raw gases in the oxidation zone
Implementation Method 2
complete combustion of the tarry raw gases in the oxidation zone
Implementation Method 3
suction of the rising carbonization and pyrolysis gases formed during gasification via the diffuser-injector injection nozzles (injector conveyor) and these are mixed with be blown into the oxidation zone with the gasification agent
Implementation Method 4
the device of a spacious tub grate allows the sufficient formation of a continuous charcoal embers as a reduction zone for the production of an almost tar-free wood gas through a complete gas reduction
Data Source
Figure 1
Figure 2~3
AI summary
The method involves injecting degasification agent (4) i.e. air, into a middle section of a reactor chamber (2) of a fixed bed reactor (23). A partial stream of the injected degasification agent is upwardly guided in a countercurrent flow and removed as pyrolysis gas (7) from the fixed bed reactor. Another partial stream of the injected degasification agent is downwardly guided in a co-current flow and removed from the reactor. The former partial stream is downwardly guided outside the reactor chamber and supplied into the reactor chamber. An independent claim is also included for a device for gasifying a solid fuel.