Deaerator-Economizer as Feedwater Heater in Steam Boiler

Use of deaerator and economizer as auxiliary instruments in warm feedwater before the feedwater is burned in a boiler. Water is obtained from the raw water that has been in treatment to conform to the standards set supplied to deaerator with the aim of separation of the gases dissolved in water and separating minerals contained in water in order to keep all the tubes that pass through can avoid corrosion. In addition, in the deaerator water went through the process of preheating the steam heated by the rest coming from turbine generator. The function of the deaerator is as a gas separator-gas dissolved in water and heats the boiler feed water before it was burned in the boiler.

Economizer is shaped tubular heat transfer equipment used to heat boiler feed water before entering the steam drum. The term economizer is taken of the usefulness of such tools, namely to conserve fuel by taking the hot flue gas before being discharged into atmosphere. An economizer can be used to utilize the exhaust heat to preheat boiler feed water. Any reduction in exhaust gas temperature through the economizer or preheater is 1% saving of fuel in the boiler. Any increase in temperature of feed water through the economizer or the air temperature rise through the combustion air preheater, there is a 1% fuel savings in the boiler.
Figure 1: Mechanism of Deaerator and Economizer

Economizer performance is determined by the fluid having a low coefficient of heat transfer gas. Heat transfer speed can be improved by increasing the total heat transfer coefficient by regulating the composition of tubing / fin properties and increase the contact area of ​​heat transfer. The response generated by the economizer is heat transfer effectiveness and operating costs. Effectiveness of heat transfer is the amount of energy that can be drawn from the total amount of energy that can be absorbed. The greater efficiency of heat transfer in the economizer, heat the remaining gas that is picked will be many more.

The greater effectiveness of heat transfer that occurs, then the tool is more efficient. Economizer operation costs are determined by fan power and pump power. Fan used to flow combustion air to the boiler through the economizer. The more loops and more complex arrangement of economizer tubing on the fan power required increases. Pumps used to drain the boiler feedwater to the steam drum through the economizer. The longer and more loops in the economizer, the required pump power increases. The optimum response is obtained using the design factors that affect the performance of economizer as follows:

  1. Outside diameter tubing, the diameter of the tube size used in preparing the economizer. The larger the diameter of the tube will result in diminishing the effectiveness of heat transfer.
  2. Transverse spacing, which express the distance between the tubes parallel to the direction of the width of economizer. The wider spacing between the tubes resulted in the induction process of economizer heat decreases, thus decreasing the effectiveness of heat transfer.
  3. Fin density, the number of fins per inch that can be structured to incorporate some of the tubes in the economizer. The more structured fin will result in heat transfer is not effective because the distance between the tube will be farther.

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