What is a once-through steam boiler? What are the characteristics?

There is a relatively special once-through steam boiler in the steam boiler, which is actually a steam generating equipment for steam production in which the medium passes through each heating surface at one time and there is no forced flow of circulation. From this kind of special working method, the once-through steam boiler is different. What are the main factors?
When the once-through steam boiler is in operation, the medium in the evaporation heating surface will have a pulsating state, and its flow rate will change periodically with time; in addition, the hydrodynamic characteristics are multi-valued. In addition, the pressure head of the once-through steam boiler loss pump is also very large.
In the heat transfer process of the once-through steam boiler, it passes through each heating surface at one time, and the second type of serious heat transfer must occur. In addition, the once-through boiler does not have a steam drum, and except for a part of the salt brought by the water supply that is taken away by the steam, the rest is all attached to the heating surface, so the standard for water quality is also very high.
Because the heat storage capacity of the once-through steam boiler is not large, if it oscillates, it will have insufficient self-compensation capability and large parameter speed changes. When the load of the once-through steam boiler changes, it is necessary to adjust the water supply and gas volume to maintain the material balance and heat balance, so that the steam pressure and steam temperature can be controlled.
During the start-up process, in order to reduce the heat loss and medium loss of the once-through steam boiler, a bypass system should be installed as much as possible. Because the once-through steam boiler has no steam drum, the heating process can be faster, so its startup speed will be faster.
If you compare the once-through steam boiler with the natural circulation boiler, the heat exchanger, superheater, air preheater, combustion system, etc. in the structure of the two are completely different. In order to continuously improve the quality of steam, the method of external transition zone and steam-water separator can be selected.