The gasification of wood and as a result the production of wood gas, is a thermo-chemical, multi-stage transformation process, similar to wood combustion.  As opposed to combustion however, the gasification process is interrupted intentionally in order to get not only carbon dioxide and water but also combustible gas, which is then transformed into electricity and heat by a gas engine.

The gasifier is fuelled by natural untreated low-moisture wood chip or wood pellet.  The wood chip or wood pellet is transported by the stoker auger into the reformer via a twin-flap lock. Inside the reformer, the wood is gasified in a downstream procedure consisting of the following stages:

• Drying (up to ~ 200 °C)

• Pyrolysis (~ 200 °C to 600 °C)

• Oxidation (up to ~ 1200 °C)

• Reduction (~ 900 °C)

During the pyrolysis stage, chemical products (such as tar, coal, CO, C02, H2, CH4) are created and partially burnt or cracked in the oxidation zone. In the reduction zone, the wood chip or wood pellet is finally transformed into low-tar wood gas, thanks to the highly developed reformer design and sophisticated controls.

The wood gas is cooled down in a tubular water/gas heat exchanger to 110 °C and dry-cleaned in a fabric filter with mechanical cleaning.

The residual coal and ash is transported by transfer augers from the gas filter, through an ash-lock and into the ash container. The cooled and cleaned wood gas is then injected into the gas control line of the engine.

The heat from engine-cooling, flue gas and wood gas heat exchanger is recovered and transferred to the heating network.

During the starting process, the lower quality gas is burnt-off automatically with a gas flare positioned right after the reformer.

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Operating Principle:

The Froling gasifier is an autotherm fixed bed downstream gasifier. The diagram below shows the operating principle of downstream gasification:

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Advantages:

• Compact and maintenance-friendly design

• Fully automatic operation

• Dry gas cleaning – no condensation

• Modern and robust industry engine (high efficiency)

• Ignition of a gas engine with wood gas (No secondary fuel required /No engine start with a generator)

• Froling is the whole system supplier: heating boilers, wood gasifiers, fuel feed and transfer systems

• Existing TÜV concept for authorities (emissions, machinery safety, noise, explosion safety, process technology)

• Container solution is pre-commissioned and ready-to-go

• Qualifies for both Renewable Heat Incentive (RHI) payments and Renewable Obligation Certificate (ROC) payments