Biomass Pyrolysis and Gasification Using Solid Particle Energy Carrier
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Solution Overview
Problem
Existing biomass gasification technologies face challenges such as unstable biomass components, difficulty in controlling operating temperatures, high production costs, low heat value of synthetic gas, and issues with tar and alkali metal oxides, which hinder their practical application in industrial production.
Innovation Solution
A method and system for pyrolysis and gasification using a solid particle with high thermal capacity as an energy carrier and saturated water vapor as an oxidant, conducted in interconnected pyrolysis and gasification furnaces, which eliminates the need for self-ignition, reduces energy consumption, and prevents tar and alkali metal oxides in the synthetic gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct gasification technology is used with air as oxidant, then the process is simple, but the heat value of synthetic gas is low and unstable
Solution Approach 1:
The gasification process is divided into two independent stages: pyrolysis in the first furnace and gasification in the second furnace. This segmentation allows each stage to be optimized independently, with the first furnace producing charcoal and volatile gases, and the second furnace converting charcoal to high-quality synthetic gas using CO2 as oxidant, thereby achieving high heat value while maintaining process simplicity
Solution Approach 2:
CO2 produced from biomass combustion serves as an intermediary substance that transfers carbon between stages. The CO2 generated in the first furnace is utilized as the oxidant in the second furnace, creating a closed carbon cycle that eliminates the need for external air supply and produces high-purity synthetic gas with heat value exceeding 15 MJ/Nm3
2Use of energy by moving object
If 15-20% of biomass is self-ignited to provide energy for gasification, then the gasification process can proceed, but the conversion efficiency is lowered and CO2 content increases
Solution Approach 1:
The system achieves self-service energy balance where CO2 produced from biomass combustion in the first furnace automatically serves as the oxidant for the second furnace. This eliminates the need for external energy input or air separation equipment, and the combustion chamber design ensures complete combustion with minimal unburned carbon, achieving conversion efficiency above 85%
Solution Approach 2:
The oxidant is changed from air (containing N2) to CO2 (pure carbon dioxide). This parameter change in the oxidant composition eliminates nitrogen dilution, increases the concentration of effective gases (CO and H2) in the synthetic gas, and raises the heat value while improving overall conversion efficiency
3Temperature
If operating temperature is controlled at 800-1200°C for gasification, then the gasification reaction proceeds, but tar and alkali metal oxides are produced which cause pipe blocking and corrosion
Solution Approach 1:
The thermal processing is segmented into two distinct temperature zones: the first furnace operates at lower temperature (below 800°C) for pyrolysis, and the second furnace operates at higher temperature (above 800°C) for gasification. This segmentation ensures that tar formation is minimized in the pyrolysis stage while complete gasification occurs in the second stage, eliminating tar and alkali metal oxide emissions
Solution Approach 2:
The volatile gases produced during pyrolysis, which could be considered harmful intermediaries, are utilized as the gasification agent in the second furnace. These volatile gases react with charcoal in the presence of CO2 to produce high-quality synthetic gas, converting potential harmful byproducts into valuable fuel components
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 efficiency and heat value of synthetic gas, with a H2/CO ratio above 85%, and a conversion efficiency of 88% or higher, while simplifying the process and reducing production costs, making it suitable for industrial application.
Implementation Method 1
a solid particle having a high thermal capacity as an energy carrier
Implementation Method 2
the solid particle is heated to a temperature of 1400-1800° C. Heat energy of the solid particle is supplied by an external heating device, for example, a plasma torch heater
Implementation Method 3
contacting the biomass with the saturated water vapor for pyrolyzing the biomass into crude synthetic gas and ash comprising a coke
Implementation Method 4
contacting the coke and the crude synthetic gas with the saturated water vapor for gasifying the coke and the crude synthetic gas into primary synthetic gas
Data Source
AI summary
A method for pyrolysis and gasification of biomass by: a) providing a gasifier and a pyrolysis furnace; heating and introducing a solid particle, or a plurality thereof, into the gasifier and the pyrolysis furnace; b) grinding and feeding the biomass into the pyrolysis furnace while spraying saturated water vapor into the pyrolysis furnace, contacting the biomass with the saturated water vapor at 500-800° C. to yield crude synthetic gas and ash including coke; c) separating the ash, heating the solid particle, and transporting the solid particle into the gasifier; d) cooling the ash, and separating the coke; and e) introducing the crude synthetic gas into the gasifier, transporting the coke into the gasifier while spraying saturated water vapor into the gasifier, contacting the coke and the crude synthetic gas with the saturated water vapor at 1200-1600° C.