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Downdraft fixed bed gasifier reactor

BiomassCHPMSWResidues gasificationSyngas production


Fixed bed downdraft gasifier for the production of syngas with low condensable hydrocarbon content (tar) from solid fuels (eg biomass, various solid residues). The reactor, is based on the principles of co-current fixed bed gasifiers, where a solid fuel reacts with the flows of gasifying agents (eg air) in conditions of quasi-stationarity. The proposed gasification reactor aims to improve the conversion efficiency of the combustible material introduced towards the production of syngas with a low content of organic pollutants, as well as to increase the flexibility of use (possibility of feeding solid fuels with chemical-physical characteristics into the chamber different from each other). The classic Imbert configuration is subject to revision through the introduction of an innovative fuel support system (variable section piston) that allows you to adjust the passage section and the charge of gas produced in response to the user’s actual requirements.

Technical features

The thermal efficiency of the system is improved by the introduction of an internal heat exchanger. The formation of bridges is avoided by introducing a vertical axis feeding system. The reactor has a particular compactness and dimensions that allow it to be assembled, together with the remaining plant units, inside transportable units such as containers. Thanks to the introduction of significant simplifications throughout the plant, it is therefore possible to significantly reduce both construction and management costs. The following average values ​​referred to biomass can be considered: Cold efficiency (LHV syngas / LHV biomass) = 0.8; syngas yield = 2.2-2.5 Nm3 / kg wet biomass intended as (syngas yield = m3 of syngas produced per 1 kg of biomass fed). In the case of a complete system, i.e. with gasifier and use of syngas in an internal combustion engine to produce electricity, 1 – 1.2 kWhe / kg wet biomass are obtained (i.e. for each kg / h of biomass fed into the system, 1- 1.2 kWhe). In this case, the expected electrical efficiency of the system is about 20-22%. TRL 8.

Possible Applications

  • Industries, agriculture and forests;
  • Waste treatment;
  • Energy, heat and bio-fuel production.


  • Syngas production with low tar content and high LHV;
  • variable cross sectional area of the reaction zone;
  • increased avaiability of the system;
  • reduction of maintenance operations and related costs;
  • higher flexibility of use respect to different fuels.