The performance of economizer should be known related to steam boiler efficiency. Economizer is equipment for heat transfer with shaped tubular which is used to heat boiler feedwater from BFP (Boiler Feedwater Pump) before entering the steam drum. The term economizer is taken from the usefulness of this equipment is to save or to economize fuel use in taking the heat (recovery) of the exhaust gas before being discharged into atmosphere.
Economizer can be used to utilize the heat of exhaust gas for preheat boiler feedwater. Any reduction in exhaust gas temperature of 220 C or preheater there is 1% savings in fuel of the steam boiler. Any increase in feedwater temperature of 60 C through the economizer or 200 C rises in temperature of combustion air through the air preheater will get 1% fuel savings in the boler.
The performance of economizer is determined by the fluid that has a low coefficient of heat transfer, namely gas. Heat transfer rate can be improved by increasing the total heat transfer coefficient by regulating the arrangement of tubing / fin property and increase contact area of heat transfer. Response which is generated by the economizer is heat transfer effectiveness and operating costs. Effectiveness of heat transfer is the amount of energy that can be taken from the total energy that can be absorbed.
The greater efficiency of heat transfer in the economizer result in the heat of remaining gas will be drawn more and more. The greater effectiveness of heat transfer that occurs can make this equipment will be more efficient. Economizer operation costs are determined by fan power and pump power. Fan is used to flow combustion air to the steam boiler through economizer. The more loops and more complex arrangement of economizer tubing, so the fan power required will more increase.
While the pump is used to flow the boiler feedwater to steam drum through the economizer. The longer and more loops in the economizer will result in the required pump power increases. The optimum response is obtained by using the design factors that affect the performance of economizer as follows:
- Outer diameter of tubing, it is the size diameter of tube used in arranging economizer. The larger diameter of tube will result in diminishing on the effectiveness of heat transfer.
- Transverse spacing states distances between the aligned tubes towards the wide of economizer. The wider spacing between the tubes resulted in the heat induction process of economizer diminishing thus the effectiveness of heat transfer decreases.
- How close density among fins is the number of fin per inch that can be arranged to incorporate some of the tubes in the economizer. The more arranged fin resulting in heat transfer is ineffective because the farther distance between the tubes.
- The performance of economizer is very sensitive to factor of feedwater noise temperature. This is because when the feedwater temperature is not good so it will result in increased operating costs.