Gasifier Dioxin Prevention via Flue Gas Temperature Control
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Solution Overview
Problem
Current waste treatment methods, such as incineration and gasification, face challenges in reducing dioxin formation during the processing of municipal waste, particularly when chlorine-containing substances are involved, and small-scale waste treatment systems lack efficient solutions for dioxin reduction and energy generation.
Innovation Solution
A method and apparatus for gasification that controls the production of crude synthesis gas to maintain flue gas temperatures above 650°C, preventing dioxin formation by using a high-temperature combustion zone with a conventional heat source and controlling oxygen levels, allowing for efficient scrubbing and heat recovery, suitable for both batch and continuous operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional incineration is used to treat municipal waste, then energy generation is achieved, but dioxin formation occurs due to cooling exhaust gases through the 650°C to 250°C temperature window
Solution Approach 1:
The patent converts the harmful dioxin formation process into a beneficial outcome by using the exhaust gases that would normally cool through the dangerous temperature window and form dioxins instead as a heat source. The exhaust gases from the incineration process are directed through a heat exchanger to preheat the air supplied to the incinerator, thereby maintaining high temperatures that prevent doxin formation while recovering energy that would otherwise be wasted.
Solution Approach 2:
The patent changes the temperature parameter of the exhaust gases by using them to preheat the combustion air. This parameter change ensures that the exhaust gases remain above the dioxin formation temperature range (650°C to 250°C) while still allowing energy recovery. The controlled temperature maintenance prevents doxin formation while achieving energy generation goals.
2Object-generated harmful factors
If rapid quenching of exhaust gases is used to prevent doxin formation, then doxin formation is reduced, but energy recovery efficiency decreases
Solution Approach 1:
The patent applies preliminary action by preheating the combustion air using the exhaust gases before the combustion process occurs. This preliminary heating action reduces the energy required for combustion while maintaining the exhaust gases at temperatures that prevent doxin formation. The system avoids the need for rapid quenching by already having the exhaust gases at safe temperatures when they exit the system.
3Manufacturing precision
If a secondary gasifier chamber is used to convert tars to synthesis gas, then synthesis gas quality is improved, but device complexity and infrastructure cost increase
Solution Approach 1:
The patent merges the tar conversion function into the existing incineration process by using the high-temperature zone within the incinerator itself. The exhaust gases that would normally require separate treatment are instead utilized to preheat combustion air, and the intense heat of the incineration process naturally converts tars to synthesis gas. This eliminates the need for a separate secondary gasifier chamber while achieving both tar conversion and energy recovery.
Solution Approach 2:
The patent makes the incineration system multi-functional by having it simultaneously perform waste incineration, energy generation, doxin prevention, and tar conversion. The exhaust gases serve multiple purposes: they are a heat source for preheating air, a means to maintain temperature above doxin formation range, and a driver for the incineration process itself. This universality eliminates the need for separate specialized equipment.
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 effectively reduces dioxin formation and enables efficient energy generation from waste, making it suitable for small-scale installations like residential and commercial settings while maintaining compliance with environmental limits.
Implementation Method 1
the crude synthesis gas is fed into a suitable high-temperature combustion zone that is equipped with a conventional heat source, typically a hydrocarbon fuel burner, where the synthesis gas is combusted and the hot combustion products are used to heat a gasification chamber
Implementation Method 2
Reducing the quantity of dioxins can be achieved through rapid quenching of the exhaust gases through this 400 degree window
Implementation Method 3
Excess heat is liberated through a heat recovery unit
Data Source
AI summary
The gasifier operates to mix a start up heat source with crude syngas combustion for driving gasification of waste. Combustion flue gas can be maintained above 650° C. until reaching a quench to prevent formation of dioxins. Excess heat is liberated through a heat recovery unit. The gasifier can operate in a batch mode to process small batches of waste efficiently for small installations, such as ships, apartment buildings, hospitals and residences.