Microwave Plasma Fixed Bed Gasifier for Tar Reduction
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Solution Overview
Problem
Fixed bed gasification processes suffer from low gasification temperatures, high tar content, and low-quality syngas, which leads to equipment blockages and increased costs for tar removal.
Innovation Solution
A fixed bed gasifier equipped with a vertically disposed furnace containing microwave plasma generating devices, where the first device produces high-temperature plasma with a large power and small electrode gap, and the second device generates plasma with strong activity and a wide volume range, facilitating efficient gasification and tar cracking, resulting in high-quality syngas with low tar content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional fixed bed gasification is used, then the process is simple, but the gasification temperature is low resulting in high tar content
Solution Approach 1:
The patent replaces conventional thermal heating with microwave plasma heating. The microwave plasma generating device introduces microwave energy to create plasma in the gasifier, which generates extremely high temperatures (exceeding 2000°C) that effectively crack tar molecules. This substitution of heating mechanism resolves the contradiction by achieving high temperature gasification without the limitations of conventional thermal systems.
Solution Approach 2:
The patent fundamentally changes the temperature parameter through microwave plasma generation. By introducing microwave energy at 2.45 GHz frequency, the system achieves gasification temperatures above 2000°C, which is sufficient to crack tar molecules. This parameter change from conventional temperatures to plasma temperatures directly resolves the tar content issue while maintaining process simplicity.
2Object-generated harmful factors
If high temperature gasification is achieved, then tar content is reduced, but equipment complexity increases due to additional microwave plasma devices
Solution Approach 1:
The microwave plasma generating device performs multiple functions simultaneously: it heats the biomass fuel for gasification, cracks tar molecules through high temperature, and ionizes the gas mixture to enhance reaction efficiency. This multi-functionality reduces the need for separate equipment for each function, thereby limiting the increase in device complexity while achieving high temperature gasification and tar removal.
Solution Approach 2:
The patent introduces microwave plasma as an intermediary medium to transfer energy to the gasification process. The plasma acts as a high-temperature intermediary that cracks tar molecules and enhances fuel conversion. This intermediary approach achieves tar reduction without requiring direct contact with extreme heat sources, simplifying the overall system design.
3Object-generated harmful factors
If microwave plasma is introduced to crack tar, then syngas quality improves, but energy consumption increases
Solution Approach 1:
The microwave plasma induces phase transitions in the gasification process, creating a plasma phase that exists at extremely high temperatures. This plasma phase efficiently cracks tar molecules and converts biomass to syngas. The phase transition approach concentrates energy in a specific phase (plasma) rather than heating the entire system uniformly, improving energy utilization efficiency while maintaining high syngas quality.
Solution Approach 2:
The microwave plasma generation operates in a periodic manner, with cycles of plasma ignition and maintenance. This periodic action allows the system to achieve high-temperature tar cracking only when necessary, rather than continuously maintaining extreme temperatures. The periodic plasma generation reduces overall energy consumption while still achieving effective tar removal and high syngas quality during active gasification cycles.
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 method achieves high conversion efficiency of biomass fuel, exceeding 85% cold gas efficiency, and produces syngas with minimal tar content, suitable for direct industrial use, while maintaining low production costs and efficient process parameters.
Implementation Method 1
at least one microwave plasma generating device is disposed on the furnace body
Implementation Method 2
microwave plasma, with its own excellent characteristics, has widely applied to low temperature chemical vapor deposition gradually (CVD)
Implementation Method 3
allowing the flue gas to react with vapor sprayed from the lower oxygen/vapor nozzle and with a plasma oxidizer generated by the first microwave plasma generator to yield syngas, of which a chemical equation being: 2C+O2=2CO, C+H2O=CO+H2
Implementation Method 4
allowing the flue gas to flow upward to exchange heat with newly-fed biomass fuel and waste in a feeding zone of the gasifier
Implementation Method 5
allowing the syngas to flow upward to the clearance zone, where tars in the syngas are cracked and hydrocarbons in the syngas are converted in the presence of plasma generated by the second microwave plasma generator
Data Source
AI summary
A gasifier, including a vertically disposed furnace body, a monitoring unit, and a microwave plasma generating device. The furnace body includes a material and fuel inlet, a syngas outlet, an oxygen/vapor inlet, and a slag outlet. The furnace body has a clearance zone in an upper part thereof and a fixed bed zone in a lower part thereof. The slag outlet is disposed at the bottom of the furnace body. The monitoring unit is disposed close to the syngas outlet. At least one microwave plasma generating device is disposed on the furnace body.