To comply with the statutory emission values, special filters are used in wood furnaces. Depending on the fuel and furnace size, different systems are recommended.

Tubular electrostatic precipitator


Electrostatic precipitator in tube design with multiple vertical filter tubes in which discharge electrodes are arranged. The active surfaces of the separator electrodes/inside walls of the tubes are automatically cleaned mechanically.

Display with touch panel to display and store:

  • exhaust gas temperatures
  • operating hours of high-voltage operation, cleaning, bypass operation and faults

The dust-laden flue gas passes horizontally through a diffuser into the precipitator and is distributed evenly into several «ducts». The dust particles are negatively charged as they flow through the ducts and «stick» to the collecting electrodes. The dust layer that accumulates is removed periodically by means of a rapping device, falls into a dust pan and is discharged by a screw conveyor.


The dust-laden gas enters the housing of the precipitator where it is deflected and the dust is forced to settle down. The dust particles adhere to the surface of the filter medium; the air flows through the filter medium and exits the system as clean gas. The dust collected falls into the dust collection tank and is removed from the precipitator by a screw conveyor.

When burning wet wood, the efficiency of the flue gas condensation is potentially improved by up to 30% compared to wood firing systems with add-on heat exchanger units. The efficiency of heating systems with flue gas condensation depends largely on the fuel price and fuel moisture. Flue gas condensation is especially beneficial when wet fuels such as forest woodchips are burned. The most important operating parameters are combustion with a low excess air coefficient, low return temperatures of the heating network and many hours of operation of the condensation unit under full load.

In a wet flue gas condenser, process water is injected into the flue gas where it vaporises into fine droplets. The many small water droplets serve as a heat exchanger that condenses the vapour from the combustion. In addition, the heat from the flue gases of injected water is absorbed and fed via a plate heat exchanger into a low-temperature network with temperatures below 50 °C. The large heat exchanger surface (overall droplet surface) guarantees high thermal efficiency from the flue gases. The thermal potential is up to 30% of the nominal capacity of the boiler. Since the water droplets are constantly forming in the flue gas, the condenser is not prone to soiling. In the case of wet flue gas condensation, an electrostatic precipitator is always installed downstream.
A wet electrostatic precipitator has the advantage of low emission values < 10 mg/m³ while being available almost 99% of the time. Emission limits can thus also be complied with during start-up and shutdown processes.


Wet flue gas condensation: IS save energy AG

Dry flue gas condensation is a heat exchanger system that is installed downstream of the flue gas dedusting system (e.g. electrostatic precipitator). Essentially, the flue gas temperatures are lowered to the condensation point by means of a stainless steel heat exchanger. As with wet flue gas condensation, a low-temperature circuit is required is which the return temperatures are around 50 °C. In the case of dry flue gas condensation, water is injected between the plate heat exchanger. This water together with the condensate from the flue gas is used first and foremost to clean the heat exchanger surfaces and not to transfer heat.


Flue gas condensation: Scheuch GmbH

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