from Paul in Richfield, WI:
#448
Does pyrolysis, the gasification of biomass, have the same thermal energy as incineration?
This gets technical, read on.
By definition, pyrolysis is a chemical decomposition process caused by heating. With a wood fire, the visible flames are not due to direct combustion of the wood but rather of the gases released by the wood’s pyrolysis. In this context, conventional biomass combustion systems (e.g. a wood fired boiler) involve pyrolysis. Gasification is a process that converts biomass into a gas mixture high in carbon monoxide and hydrogen called synthesis gas or syngas. In a biomass gasifier, the pyrolysis and combustion processes are carefully controlled by limiting the amount of oxygen or air allowed into the reactor. Under these conditions, and often with introduction of steam, syngas can be produced. With the proper equipment, syngas can be burned as a gas fuel (similar to natural gas) and can even be used as fuel for internal combustion engines or fuel cells.
With a renewable energy project involving biomass gasification or direct combustion, it is typically a primary objective to convert as much energy as possible from the original fuel into a usable form. In essence, this involves converting chemical energy stored in the original biomass fuel into thermal energy that can be used for heating or even conversion into electrical energy (e.g. syngas and fuel cell application). Biomass gasification can potentially be more efficient than direct combustion of biomass but this depends on many system/process characteristics including the temperature at which the syngas is combusted, heat recovery methods, and many equipment-related factors. Each application, whether it is a gasification or direct combustion system, needs to be reviewed on an individual basis to determine its overall energy efficiency.
Published Monday, December 14, 2009