Classification of Economizers

Study different types or Classification of Economizers used in power plants.

1. Based on construction

(i ) Plain tube type economizers :

The external surface of tubes is kept clean and free from soot by soot scrapers moving up and down the economizer tubes. Otherwise heat transfer resistance is increase and efficiency of economizer decreased.

(ii) Gilled tube type economizers:

Rectangular gills are provided on the bare tube walls to increases the heat transfer surfaces .

2. Based on part of steam generation

(i) Steaming type economizers:

some part of the water (about 5 to 7%) to be converted into steam during its passage through the economizer.

(ii) Non-steaming type economizers:

While in case of non steaming economizer feed water is heated within 75% of the saturation temperature of the boiler.

3. Based on location of economizers

(i) Independent economizers:

economizer is installed outside the boiler house at any convenient place

(ii) Integral economizers:

economizer is installed close to the boiler

4.Types of Economiser Based on boiler Efficiency

(i) Non condensing Economiser

The most common type of economiser used in thermal power plant is the non condensing thermal power plant. They are Heat exchanger tubes with fins around them in the form of spiral and they are loacated inside the duct at the exit region of the boiler.

In this economiser used for reducing the flue requirement of boiler by transfering the heat from the flue gas to the feed water inside the tubes.

These are used in coal fired thermal power plant where the temperature of the flue gas can be reduced to 120 deg c and not beyond it.This type of Economiser increases the efficiency by 3-6%

(ii)Condensing Type Economiser:

They are used in nautral gas fired thermal powerplant. They reduced the fluegas temperature below condensation temperature as low as 25 deg c.

They increase the boiler efficency by 10-15%. while using the condensor the fuel should not contain sulphur.