CONTENTS

1. Introduction to Economizer 2. Roll of Economizer on Boiler 3. Types of Economizer 4. Advantages of Economizer coil 5. Design Calculation of

Economizer coils6. Drawing of Economizer coil7. Quality plan for manufacturing

of Economizer coil 8. Fabrication of Economizer coil 9. Conclusion

Introduction to Economizer:

Economizers (US and Oxford spelling), or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform another useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, heating, ventilating, and air conditioning (HVAC) uses are discussed in this article. In simple terms, an economizer is a heat exchanger.

An economiser is a mechanical device which is used as a heat exchanger by preheating a fluid to reduce energy consumption. In asteam boiler, it is a heat exchanger device that heats up fluids or recovers residual heat from the combustion product i.e. flue gases in thermal power plant before being released through the chimney. Flue gases are the combustion exhaust gases produced at power plants consist of mostly nitrogen, carbon dioxide, water vapor, soot carbon monoxide etc. Hence, the economiser in thermal power plants, is used to economise the process of electrical power generation, as the name of the device is suggestive of. The recovered heat is

in turn used to preheat the boiler feed water, that will eventually be converted to superheated steam. Thus, saving on fuel consumption and economizing the process to a large extent, as we are essentially gathering the waste heat and applying it to, where it is required. Nowadays however, in addition to that, the heat available in the exhaust flue gases can be economically recovered using air pre-heater which are essential in all pulverized coal fired boiler.

Role of economizer in boiler

In boilers, economizers are heat exchange devices that heat fluids, usually water, up to but not normally beyond the boiling point of that fluid. Economizers are so named because they can make use of the enthalpy in fluid streams that are hot, but not hot enough to be used in a boiler, thereby recovering more useful enthalpy and improving the boiler's efficiency. They are a device fitted to a boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water used to fill it (the feed water).

Energy heat recovery with condensing economizer.

The boiler room is a huge energy guzzler. It consists of thermal fluid boilers or steam boiler, with exhaust gases through a common chimney. An indirect contact or contact condensing economizer will recover the residual heat from the combustion products. A series of dampers, an efficient control system, as well as a ventilator, allow all or part of the combustion products to pass through the economizer, depending on the demand for make-up water and/or process water. The temperature of the gases can be lowered from 200°C to 10°C, while preheating the process water from 8°C to 80°C. On average over the year, boiler combustion efficiency has risen from 80% to more than 95%. The efficiency of heat produced is directly linked to boiler efficiency. The percentage of excess air and the temperature of the combustion products are two key variables in evaluating this efficiency.

Types of Economizer

CI Gilled Tube EconomizerThe gilled tube economizers are made up of cast iron which are fabricated using graded cast iron fins, have following features,

High optimum efficiency due to proper contact of gills with tubes.

Commonly used in plants where intoxicated flue gas is generated due to the quality of fuel burnt.

Round Gilled Tube Economizer

This is made by mild steel fabricated with square and round fins, welded on carbon steel seamless tubes, have the feature,

Proper contact between the tubes and fins are ensured for optimum efficiency.

Coiled Tube Type EconomizerThese are used mostly in thermal power plants and large processing units. These coiled tube type Economizers are fabricated out of carbon steel seamless, have following features,

These are very efficient in recovering the heat from gases.

Occupy very little space.

Horizontal Finned Tube Economizer

In this is carbon steel seamless tube sealed – welded with horizontal fins to make a complete assembly of economizer for heat transfer, have following features,

Proper care is taken for making the contact of fins with tubes for perfect heat transfer.

These are used mainly used by Thermal Power Plants.

Advantages and Benefits of Economizer

It recovers more heat of flue gases which normal air pre-heater cannot do.

Due increase in fuel prices, all power plants are facing pressure for increasing boiler efficiency. So by using economizer, this pressure can be minimized.

Power plants where it is not used, large quantity of water is required to cool the flue gas before desulphurization which is minimized by using Economizers.

The efficiency of power plant reduced when steam air pre-heater required steam.

There is an increase in efficiency of the steam power plant. 

Erosion of turbine blade is minimized (or) even eliminated. 

Steam consumption of the prim-mover is reduced. 

Condensation loss in the pipes is reduced.  It removes entrained water particles from the

steam conveyed to the steam turbines and increases the temperature of saturated steam. 

Design Calculation of Economizer coil:

Drawing of Economizer coil:

Quality Plan for Manufacturing of Economizer coil:

Fabrication of Economizer coil

Conclusion