Economizer. It is a heat exchanger that captures “lost or wasted heat” from flue gases. Typically, the economizer transfers this residual heat to the boiler feed water or return water circuit, but it can also be used to heat domestic water or other process fluid. Capturing this heat, which is normally wasted, reduces the overall fuel requirements for the boiler. Lower fuel consumption equals money savings as well as lower atmospheric emissions, because the boiler operates with greater efficiency.
This is possible since the boiler feed or return water is preheated by the economizer so that the main boiler heating circuit does not need to supply as much heat to produce a given quantity of steam or hot water. Again the result is fuel economy. Boiler economizers improve boiler efficiency by extracting heat from discharged flue gases. The function of the economizer is as its name implies, to save or save costs of heating the boiler feed water.
Summary
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- 1 Advantages
- 2 main features
- 3 Making good use of valuable waste heat
- 4 Structure
- 5 Sources
Advantage
- The thermal efficiency of the boiler is increased, which results in fuel savings per Kg of steam generated.
- The emission of hot gases into the atmosphere is reduced.
- Hot water is fed into the boiler reducing thermal shock.
- Boiler capacity is released to produce additional process heat.
- In smoke tube boiler installations the average fuel savings varies from 2 to 4%.
Main features
- Applicable in almost all water-tube and water-tube boilers.
- Extremely short repayment terms of <2 years are possible.
- Reduction of losses through exhaust gases of up to 6%.
- Easy to install.
- Usable for natural gas, light fuel oil and heavy fuel oil.
Making good use of valuable waste heat
Heat exchangers are ideal for extracting valuable residual energy from exhaust gases: if properly dimensioned they cool the gaseous effluent until just before the dew point. In the case of steam boiler plants, the heat obtained can be ideally used to preheat the feed water. In hot water boilers, the economizer almost always serves to considerably increase the return temperature. Regardless of its constructive form, the boiler and the combustion system used, the effect is enormous and increases the degree of efficiency of a boiler plant by up to 6%.
Structure
In general, the structure of the economizers is simple: They consist of a tube bundle located in the flow of exhaust gases from the boiler. The feed or return water is conducted by the exchanger, typically in a counter-current flow, in order to achieve high degrees of efficiency. Depending on the composition and the soot content in the exhaust gases, the tubes of the exchanger are provided with a more or less corrugated structure or with extended area surfaces, of variable number of fins, to achieve an amplifying effect of the transmission surface of heat. These measures make it possible to take advantage of considerable additional amounts of heat from the gaseous effluent: The temperatures measured downstream of the tube boilers, for example, typically fluctuate between 180 and 280 ° C, being reduced to 110 – 130 ° C with this procedure. Every 10 ° C decrease in temperature of the exhaust gases increases the degree of efficiency by approximately 0.5%, so that the degree of efficiency often increases by more than 5% when performing a typical implementation. But unlike natural gas, the exhaust gases of light fuel oil and heavy fuel oil differ in their sulfur content, so the lower limits of cooling are different. In combination with an additional exhaust gas temperature control it is possible to regulate the economizer very sensitively, so that the gaseous effluent is always used to the maximum. so the degree of efficiency often increases by more than 5% when a typical implementation is carried out. But unlike natural gas, the exhaust gases of light fuel oil and heavy fuel oil differ in their sulfur content, so the lower limits of cooling are different. In combination with an additional exhaust gas temperature control it is possible to regulate the economizer very sensitively, so that the gaseous effluent is always used to the maximum. so the degree of efficiency often increases by more than 5% when a typical implementation is carried out. But unlike natural gas, the exhaust gases of light fuel oil and heavy fuel oil differ in their sulfur content, so the lower limits of cooling are different. In combination with an additional exhaust gas temperature control it is possible to regulate the economizer very sensitively, so that the gaseous effluent is always used to the maximum
