There are many types of boilers on the market. The once-through boiler is one of the most frequently used boiler equipment, which means that the feed water is passed through the economizer, evaporating heating surface (water wall), superheater and all changes by the pressure of the feed water pump. It is a boiler for superheated steam. So, compared with other types of boilers, what are the advantages of once-through boilers? Let Zhengzhou Fangkuai Boiler Factory tell you the answer.
After the feed water enters the boiler, the heating, evaporation and superheating of water vapor are all carried out continuously in the heating surface, so there is no need to separate steam and water in the middle of heating. Therefore, it does not have a steam drum for a natural circulation boiler. There is no fixed dividing point between the heating surface of the economizer, the heating surface of the evaporator and the heating surface of the superheater, which changes with the boiler load. There is no steam drum (drum). The feed water is preheated and evaporated by the pressure of the feed water pump. When it comes to overheating, it is a power plant boiler that generates steam with rated parameters and capacity by passing through the heating surfaces at all levels at one time. The circulation rate of the evaporation zone is 1.
Since there is no obvious boundary between the evaporation and superheating heating surface of the once-through boiler, problems such as unstable flow and pulsation sometimes occur in the evaporation heating surface. It is necessary to install a throttle orifice at the inlet of the tube group, and between the inlet and outlet headers. Measures such as installing a breathing header to improve. In addition, film boiling (that is, the vapor bubbles generated on the heating surface are too late to separate and form a vapor film) phenomenon occurs on the evaporation heating surface, which is not conducive to heat conduction, resulting in overheating of the tube wall, which affects the safety of boiler operation. In this regard, spoilers or internally threaded pipes can be installed in the water wall in the high heat load area to delay the appearance of film boiling. Measures such as flue gas recirculation or adjustment of burner layout can also be used to reduce the maximum heat load in the furnace.
As the operating conditions demand higher and higher requirements for the peak regulation characteristics of the boiler, the adaptability of the once-through boiler to load changes has been paid more attention. The once-through boiler with spirally rising tube coil has the least sensitivity to the thermal deviation in the furnace, there is no two-phase fluid distribution problem between the tubes, and there is no need to install an orifice at the nozzle, so it has good low-load operation characteristics. However, the requirements for water quality and automatic adjustment are high, the resistance of the soda system is large, and the power consumption of the water pump is relatively large.
