Corrosion-Resistant Boiler Economizer for Enhanced Efficiency and Energy Savings​

Summary

Boiler economizer is a kind of heat exchange equipment that uses flue gas waste heat to heat boiler feed water. It is usually located at the tail of the flue of the boiler, and increases the feed water temperature by absorbing the heat of the flue gas, reduces fuel consumption, and achieves the effect of energy saving and emission reduction. The boiler economizer mainly uses the principle of heat exchange to transfer the waste heat in the flue gas to the boiler feed water. Specifically, the flue gas enters the economizer from the tail of the boiler and exchanges heat with the economizer tube group in parallel in the boiler system. Through heat exchange, the flue gas temperature is lowered and the boiler feed water is heated at the same time. After the heated feed water enters the boiler, it can reduce fuel consumption and improve the efficiency of the boiler.

Working principle

Boiler economizer is kind of heat exchanger to heat the feed water using the flue gas heat. The flue gas coming from the tube outside is up and down cross-flow scrubbing the tube bundle, passing the heat to the tube wall. The water is flowing from bottom to top, and absorts the heat from the tube wall, and its temperature is getting high. This way not only can countercurrent heat transfer to save metal consumption, but also is good for water/steam to flow and exhaust as well as decreasing corrusion. One more, this way works well for dust cleaning.

Functions

1. Absorb the heat of low-temperature flue gas, reduce the exhaust temperature, reduce the exhaust loss, and save fuel.

2. Because the feed water is heated in the economizer before entering the steam drum, the heat absorption of the feed water on the heating surface is reduced, and the economizer can be used to replace part of the evaporation heating surface with high cost.

3. When the feed water temperature increases, the wall temperature difference will be reduced when it enters the steam drum, and the thermal stress will be reduced accordingly, prolonging the service life of the steam drum.

Types

If according to materials, economizers can be divided into steel tube economizers and iron economizers. At present, most large and medium volume boilers widely use steel tube made economizers, because they have high strength and reliable working ability, and are able to withstand impacts, meanwhile they have good performance of heat transfer, small structure and low cost. One weak point is bad corrusion resistance, but now the modern boiler feed water are strictly treated, so the problem is almost solved.

If according to heating extension of the working fluid, economizers can be divided into non-boiling and boiling types.

1. Boiling economizers: the outlet water temperature not only can reach the surnatured temperature, but also can make some water vapourized, the proportion is about 10-15% of total feed water, not more than 20% in case of much flow resistance caused to the working fluid.

2. Non-boiling economizers: the outlet temperature is 20-25 degrees lower than the boiling point under pressure given.

Most of medium-presssure boilers use boiling type economizers. This is because the latent heat of vaporization of water in medium-pressure boilers is high, and the heat of the heated water is small. Thus it is necessary to send some water to be vaporized in boiler economizer so as to prevent unstable combusion in furnaces and prevent increased consumption of metal in the heating surfaces as superheaters caused by too low outlet flue gas temperature. In addition, it can help to play the role of economizers.

Superhigh pressure boilers mostly use non-boiling type economizers. This is because when the pressure is higher, the latent heat of vaporization is decreased, while heat of the heated water is getting more, so it is necessary to send some water to be heated in water wall panels so as to prevent the slagging on the heating surfaces of the furnace outlets and the furnace inside caused by too high temperatures in furnaces and of outlet flue gas. So usually superhigh pressure boilers use non-boiling type economizers.

The main factor to consider which type of economizers is boiler's parameters. When the boiler parameters differ, the ratio of heat absorption needed in three stages to heat the working fluid make differences. So the corresponding arrangements of three heating surfaces need to change, too. To large units with high parameters, their evaporative heat absorption is less, while the heat absorption of water by heating, the heat absorption of steam by superheating, the heat absorption by reheating are quite big. Thus, non-boiling type economizers are the main type for superhigh pressure unit boilers.

Specifications

Quality Control

1. Impact test and Strength calculation report with applied materials information.

2. 100% NDT(non-destructive inspection) report of steel plate, tube and electrode

3. X-ray, γ-ray and liquid penetrant test inspection report (welding seam): to ensure the quality of the entire boiler

4. Hydraulic test report: ensure the standard working pressure and safety

About us

Hua Dong Boiler has become a major qualified supplier of domestic and foreign boiler manufacturers and energy companies, including American Covanta Energy Company, AMEC Foster Wheeler Company, ALSTOM, Oriental Boiler Limited by Share Ltd., Harbin electric LLC, Wuxi Hua Guang Boiler Co., Ltd., Hangzhou Boiler Group Co., Ltd.