Flue gas condensation

Flue gas condensation is a combination of heat reovery and dust separation, where pre-steamed heat, which can be found in the flue gas, is made use of, as well as being cleaned from the dust afterwards. The use of heat is currently done in solid fuel facilities, where fuel, which has a moisture content of >25 %, is used. Wood chips e.g. primarily green wood chips, have a moisture content of 40 - 55 % of the total weight. Flue gas condensation is used e.g. in wood chip fired incinerators in district heating facilities, but can also be found in industrial facilities. Flue gas, after combustion, contains steam from the drying of the fuel, from the burning of H2 and a smaller portion from the combustion air which has been heated. In addition to the processes mentioned, condensation can be used in e.g. drying processes with high moisture content.

A high degree of cleaning and heat recovery
Depending on the moisture content of the fuel and the cooling temperature of the media, heat recycling of between 15 - 35 % is possible. By using our patented contactor a high degree of cleaning of even the smallest particles in the flue gas is also achieved, where even the condensed THC-molecules are separated to 90 %.

Function
From the furnace the flue gas is led through a pre-collector to gas cleaning in a centrifugal scrubber, a so-called contactor KACS, (see outline sketch). For more information about these components, see separate product sheets. Following the gas cleaning in the centrifugal scrubber KACS, the flue gas is led through the scrubber´s dehydration cyclone on to the gas outlet. The heated scrubber water and water from the dehydration cyclone are led to the buffer tank. In the tank, a portion of the caught-up dust particles in the scrubber water are settled. From the buffer tank the scrubber water is pumped farther on to a heat exchanger where it is cooled with recirculated water from the district heating facility. The recycled water is thereby pre-heated. The PH-value of the scrubber water should be held between 6 - 7, but this depends on the water´s content of dust particles and its composition. Neutralised scrubber water is normally allowed to be dumped into recipients.

Pre-collector with secondary cyclone
To prevent eventual clogging of the heat exchanger and buffer tank, ITK Envifront´s pre-collector with secondary cyclone should be installed; this separates the largest, heaviest particles of the flue gas between the furnace and the scrubber facility.

 Outline sketch - Flue gas condensation