Economiser

Economisers are heat exchangers with exhaust gas on the one side and water on the other side. Economiser must be designed for the exhaust gas quantity, its temperature, the maximum allowable pressure drop, the used fuels as well as for the energy quantity to be recovered. A heat exchanger designed for gas-firing is likely to suffer clogging if installed downstream of a coal-fired boiler and will be subject to an increased risk of corrosion if used in conjunction with oil-firing.Economisers can be designed so as to keep the flue gases above the condensation temperature, others are manufactured from corrosion resistant materials in order to resist the exhaust gas condensate.

The basic difference between an economizer and a flue gas condenser is the fact that an economizer generally heats a smaller quantity of water to high temperatures. The condenser can operate even more efficient because it still cools down a low flue gas temperature and thereby can utilize also the latent heat of the flue gas condensate.

However, the key to a successful application of heat recovery is to make use of this energy. There is a wide range of possible applications:

Heating of process water for industrial use, laundries, breweries, hospitals, green houses, district heating, space heating, de-icing, … this list could be continued endlessly.

The savings potential results from the current flue gas temperature, the required quantity of process water and the operating hours.