Biomass Gasification Furnace
The patented Dall Energy biomass furnace combines updraft gasification with gas combustion
Main functionality of the gasification furnace:
- In the top of the fuel layer biomass is dried and pyrolyzed. Further down in the fuel layer biomass is converted into a burnable gas and fine ash.
- The heat for the drying and pyrolysis process is a combination of convective heat from the gasification gases below and radiation heat from the gas combustion part above.
- Primary air injection is about half of what is used in traditional grate incineration, and with a big furnace bottom area the gas velocity in the bottom part is very low. Consequently, particles remain here and the dust emission from the furnace is very low. Gas from the bottom part is combusted in the top section. The gas combustion (flow, temperatures, emissions etc.) is very stable and is controlled via flue gas recirculation.
- The control philosophy allows operation with lower excess air ratios than what is known from traditional incineration grate furnaces, and this is partly the reason why a higher overall efficiency is possible.
- Low fuel cost
- 10% – 100% load
- Low maintenance cost
- 95% less dust
- Low NOx and CO
- Low electricity consumption
The history of updraft gasification:
The principle of updraft gasification has been known for centuries and was used in Europe for e.g. production of city-gas made by Hard Coal back from the 1850´s. During the 1980´s several updraft gasifiers entered commercial operation in Scandinavia, but the concept required heavy maintenance due to the concept of external combustion of the gases.
The Dall Energy furnace combines updraft gasification with gas combustion in the same chamber proving full performance and environmental benefits without the historical problems related to external combustion
The gasification furnace as Thermal Oxidizer:
Thermal oxidizers are used in the industry to destroy Hazardous Air Pollutants (HAPs) and Volatile Organic Compounds (VOCs) from industrial air streams. These pollutants are generally hydrocarbon based and when destroyed via thermal combustion they are chemically changed to form CO2 and H2O. Historically Propane or Natural gas was widely used as fuel for thermal oxidizers, but this now proves to be inadequate for industries with goals for reducing their environmental footprint.
The Dall Energy furnace can be used as a CO2 neutral thermal oxidizer for destruction of VOC´s or other organic compounds in air streams. The first Dall Energy biomass based thermal oxidizer was installed at Warwick Mills, New Hampshire, USA where the plant was commissioned in 2014. The plant operated with a VOC destruction efficiency exceeding 99,8%, which is even higher than fossil fuel based oxidizers.