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Economizer

The main points

  • Can be used on almost all flame-tube and water-tube boilers
  • Very short amortization time of < 2 years possible
  • Reduces flue gas loss by up to 6%
  • Easy to retrofit
  • Can be used for natural gas, light oil and heavy oil

Making good use of valuable residual heat

Heat exchangers can be used to remove valuable residual energy from flue gas: When correctly designed, they cool the flue gas down to just above the dew point. Heat that is captured is ideal for use in steam boiler plants to preheat feed water. With hot water generators the economizer is mostly used to raise the return temperature considerably. Regardless of the design, boiler or the combustion system used, the effect is enormous, increasing the efficiency of the boiler plant by up to 6%. Retrofitting with SAACKE economizers therefore pays for itself within a very short time, providing relief for both the budget and the environment.

The design of economizers is based on a simple principle: It consists of a tube bundle in the flue gas flow of the boiler. The feed water or return water is typically directed through the heat exchanger in a cross-shaped counter flow to achieve high efficiency levels. Depending on the composition and dust content of the flue gas, the heat exchanger tubes have heat exchange surfaces with varying numbers of fins, also called "pins" to increase the surface area for heat exchange. These measures make considerable additional quantities of heat from the flue gas usable: Temperatures downstream from conventional shell boilers are typically between 180 and 280°C and then drop to 110 - 130°C. Each reduction of 10°C of the flue gas temperature increases the efficiency by about 0.5%. Typical retrofitting therefore results in more than a 5% increase in efficiency.

SAACKE economizers are based on standard components individually adapted for a specific case. They are suitable for essentially all standard fuel combustion systems. Because gas, light oil and heavy oil differ in sulfur content, however, the lower limits of flue gas cooling may vary. When combined with an additional flue gas temperature control system, the economizer provides especially sensitive control in this case, ensuring that the flue gas is always utilized to the maximum extent.

Regardless of the design, a SAACKE economizer makes a noticeable difference the next time fuel costs are billed. It is especially impressive in terms of a short amortization time and long service life.