The economizer is a heating surface, which uses low-temperature flue gas to heat the water supply. The boiler feed water in the tail flue of gas boiler is heated to the heating surface of saturated water under the pressure of drum. Due to the absorption of relatively low temperature flue gas, the exhaust temperature of flue gas is reduced, energy is saved and efficiency is improved. It is called energy saver.

燃气锅炉的分类方法有很多种，可分为以下几种：根据给水加热的程度，可分为非沸腾型和沸腾型。

There are many kinds of classification methods of gas-fired boiler, which can be divided into the following: according to the degree of feed water heating, it can be divided into non boiling type and boiling type.

根据制造材料：有两种铸铁和钢管器。非沸腾型器主要由铸铁制成，但它们也由钢管制成，而沸腾型器只能由钢管制成。铸铁器主要用于压力≤2.5MPa的锅炉。如果压力超过2.5MPa，则应使用由钢管制成的省煤器。

According to the manufacturing materials: there are two kinds of cast iron and steel tube economizers. Non boiling economizers are mainly made of cast iron, but they are also made of steel pipes, while boiling economizers can only be made of steel pipes. Cast iron economizer is mainly used for boilers with pressure ≤ 2.5MPa. If the pressure exceeds 2.5MPa, economizer made of steel pipe shall be used.

根据设备的形式：有两种类型的垂直和水平。根据排气和给水的相对流向：有三种类型：下游，逆流和混合。

According to the form of equipment: there are two types of vertical and horizontal. According to the relative flow direction of exhaust and feed water, there are three types: downstream, countercurrent and mixing.

回收：在燃气锅炉（汽包锅炉）启动过程中，没有建立蒸汽 - 水管道的循环，即锅炉给水处于停滞状态，省煤器中的水处于停电状态。一个不流动的状态，锅炉燃烧。由于烟气温度的升高，省煤器中的水很容易蒸发，使器部分过热。为了避免这种情况，来自汽包的浓缩水管的管道连接到管道以节省能量。该装置的入口，作为再循环管，使器中的水保持流动状态。避免蒸发。

Recovery: during the start-up of gas boiler (drum boiler), there is no steam water pipeline circulation, that is, the boiler feed water is in a standstill state, and the water in the economizer is in a power failure state. In a non flowing state, the boiler burns. Due to the increase of flue gas temperature, the water in economizer is easy to evaporate, which makes the economizer part overheat. In order to avoid this situation, the pipeline from the concentrated water pipe of the drum is connected to the pipeline to save energy. The inlet of the device acts as a recycling pipe to keep the water in the economizer flowing. Avoid evaporation.