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What is gasification?
Wood gasification in a small firewood boiler refers to the process of converting wood or wood pellets into a combustible gas (syngas) within the confines of the boiler’s combustion chamber. This process maximizes the efficiency of burning wood as a fuel source, while also reducing emissions and improving overall heating performance. All Froling boilers control primary and secondary air to control gasification. Here’s how wood gasification works in a small firewood boiler:
- Primary Combustion: In the initial stage of burning, wood or wood pellets are ignited in a combustion chamber with limited oxygen supply. This controlled combustion process is known as the primary combustion phase. The limited oxygen prevents the complete combustion of the wood, resulting in the production of smoke, volatile organic compounds, and gases.
- Pyrolysis: As the wood heats up in the low-oxygen environment, it undergoes pyrolysis, which is the thermal decomposition of organic materials in the absence of oxygen. During pyrolysis, the wood releases volatile gases, tars, and other combustible compounds. These gases rise and mix with the limited oxygen present in the primary combustion chamber.
- Gasification: The released volatile gases and tars are drawn into a secondary combustion chamber or gasification chamber, where they encounter a controlled and stable supply of air or oxygen. In this environment, the gases undergo further combustion reactions, known as gasification. This stage converts the volatile compounds into a clean-burning syngas composed mainly of carbon monoxide (CO) and hydrogen (H2).
- Secondary Combustion: The syngas produced during gasification is burned in the secondary combustion chamber. Here, the syngas burns at high temperatures, resulting in efficient combustion and the release of a significant amount of heat energy. This secondary combustion is much cleaner and more efficient than traditional wood combustion because it maximizes the utilization of the wood’s energy content and minimizes emissions.
- Heat Transfer: The heat generated during the secondary combustion phase is transferred to a heat exchanger within the boiler. This heat exchanger is responsible for heating the water or fluid that circulates through the heating system. As the fluid absorbs the heat, it can be used for space heating, domestic hot water, or other heating applications.
By using wood gasification in a small firewood boiler, several benefits are achieved:
- High Efficiency: Wood gasification boilers can achieve high levels of efficiency, as they maximize the combustion of wood, extracting more energy from the fuel.
- Low Emissions: The secondary combustion of syngas results in significantly lower emissions of pollutants compared to conventional wood-burning methods.
- Cleaner Operation: Gasification boilers operate cleanly and produce minimal smoke or creosote buildup in chimneys or flues.
- Improved Fuel Economy: Wood gasification boilers can extract more heat from a given amount of wood or wood pellets, leading to fuel savings.
Overall, wood gasification in small firewood boilers is an environmentally friendly and efficient method of utilizing wood as a renewable energy source for residential or small-scale heating applications.