The regulation of wood gas output from a gasification generator is a key aspect in improving the efficiency of biomass gasification technology, which is used primarily in cogeneration systems for the combined production of heat and electricity. A properly designed reactor geometry and the positioning of the inlet and outlet ports are essential for a smooth process and the quality of the gas produced.
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For an experimental fixed-bed gasification reactor used for the thermal decomposition of wood chips, a feed port in the roof and a side gas outlet were originally envisaged. However, this design resulted in undesirable gas leaks through the feeding mechanism.

1. Piston feeder: A feeder based on the principle of lateral piston feeding was constructed.
2. Closed system: Leaks were only completely eliminated by sealing off the feeding system using an intermediate hopper and a storage hopper.

These modifications have created scope for optimising the gas extraction system itself, with the focus on the ceiling extraction system, which is designed to reduce the resistance encountered by the flowing medium.

Mathematical modelling was carried out using Ansys software to assess the impact of different gas extraction configurations. The simulations were based on real experimental data and utilised the following parameters:

Although the modelling showed that, with layer temperatures fixed, the location of the outlet has no significant effect on the temperature distribution, the analysis of the velocity profile yielded important findings. At a higher volumetric flow rate (3.5 m³/h), the space is filled more completely by the flowing medium.
The main benefits of optimised gas extraction include:

This modelling approach makes it possible to select the most suitable gas outlet option even before the actual construction or costly modification of the real-world facility takes place.