The term wood gasification may come across as a bit cryptic or feel like it requires a graduate degree in chemical engineering to truly understand. However, for making a wise wood boiler purchasing decision, there are only a few things you need to know.
Definition of Gasification
According to Wikipedia, "Gasification is a process that converts carbonaceous materials, such as coal, petroleum, or biomass (such as wood), into the simpler elements carbon monoxide and hydrogen by reacting the raw material at high temperatures."
In the temperature range of 395 ° F to 535 ° F (i.e. a regular fire), the majority of the gases are released from the wood in combination with the smoke. Those gases contain about 50% to 80% of the heat content of the wood. This process results in a gas mixture that is often referred to as synthesis gas or syngas or in the case of a wood fuel – woodgas.
If one were to stop the reaction at this stage, the woodgas may be used as a fuel for a number of purposes. The gas may even be cooled and cleaned to remove tars and particulates and used as fuel in a variety of other applications, including engines!
How Wood Gasification and Complete Combustion is Achieved in Wood Gasification Boilers
In gasification wood boilers the wood gases don't just go up and out the chimney, as is the case with standard wood boilers. Instead, the reaction is continued and the emitted woodgas is superheated and mixed with air resulting in complete combustion. The heat is then transferred to a boiler for efficient distribution. An additional benefit of the gasification process is that the complete combustion leaves little or no ash.
There are several common schools of thought for applying wood gasification and secondary combustion principles in the design of a residential or small-scale wood boiler, here are two of the most common approaches:
So, if you are researching a purchase of a wood boiler, the bottom line is that wood gasification boilers that provide complete combustion are better than traditional water-jacketed wood boilers. Some key points to take away from this article include: