1. Flue gases from large boilers are typically 450 – 650°F. Stack Economizers recover some of this heat for pre-heating water. The water is most often used for boiler make-up water or some other need that coincides with boiler operation. Stack Economizers should be considered as an efficiency measure when large amounts of make-up water are used (ie: not all condensate is returned to the boiler or large amounts of live steam are used in the process so there is no condensate to return) or there is a simultaneous need for large quantities of hot water for some other use.
2. The savings potential is based on the existing stack temperature, the volume of make-up water needed, and the hours of operation. Economizers are available in a wide range of sizes, from small coil-like units to very large waste heat recovery boilers.
See also Flue Gas Condensers that are used when water and flue gases come in direct contact with each other.
Serpentine Tube Economizer Application
1. It is used in all modern plants. The use of economizer results in saving fuel consumption increases steaming rate and boiler efficiency.
Some of the common applications of economizer are given below, In steam power plants it captures the waste heat from boiler stack gases (flue gases) and transfers it to the boiler feed water.
2. Air-side economizers HVAC (Heating, Ventilation, and Air Condition) can save energy in buildings by using cool outside air as a means of cooling the indoor space.
3. Refrigeration: This is commonly used in industrial refrigeration where vapor compression refrigeration is essential. Systems with economizers aim to produce part of the refrigeration work at high pressures, a condition in which gas compressors are normally more efficient.
The function of Boiler Economiser
1. The Economizer in Boiler works on the principle of Heat Transfer. Heat transfer usually takes place from high temperature to low temperature.
In the case of Boilers, flue gases or exhaust from the boiler outlet are at high temperature and water that needs to be preheated is at low temperature.
2. So, this temperature difference between water and flue gases helps to increase the feed water temperature.
3. Depending on the type of operations, design of Economisers can be smoke tube type or water tube type.
4. In smoke tube type flue gases are inside the tubes and water is on the shell side while in the water tube type, water is in the tube and flue gases are on the shell side.