There are several circulation modes of gas-fired hot water boiler, and its meaning is briefly descri
According to the water circulation mode, the gas hot water boiler in thermal power plant can be divided into three types: natural circulation, forced circulation and once-through gas hot water boiler. The circulation flow, which depends on the severe difference of working fluid, is called natural cycle.
The circulation flow produced by working fluid with the help of pump head is called forced circulation. Natural cycle formation: drum, drop pipe, lower header and riser (that is, water wall) form a cycle loop. Because the water in the riser is heated in the furnace to produce steam, the severity of the steam-water mixture is small, while the descending tube is not heated outside the furnace, and the pipe is water, which is heavy, the difference between the two produces the driving force, and the water goes down the descending tube. The steam-water mixture flows upward along the riser, forming a natural circulation of water. The structure of forced circulation gas hot water boiler is basically the same as that of natural circulation. It also has a drum. Different circulating pumps are added to the falling pipe as the power to enhance the steam and water cycle.
The structure of DC furnace is different from that of natural circulating gas hot water boiler. It has no drum. According to the pressure of feed water pump, the heating surface tube of working fluid gas hot water boiler passes through the economizer in turn. Evaporating heating surfaces and superheaters heat all water into superheated steam at once.
At present, it is only suitable for subcritical, Supercritical pressure gas hot water boilers. Comparison between forced circulation gas hot water boiler and natural circulation gas hot water boiler: advantages: it can be applied to subcritical and super critical pressure; Because the working fluid is forced to flow in the heating surface, the arrangement of the heating surface is more flexible, the heating uniform water cycle is good, the furnace starts and stops quickly, the water wall can make the small pipe diameter, the thin pipe wall (pressure permission), the relative drum volume decreases, saves the steel. Disadvantages: add circulation pump, the system is complex, the investment is high, the maintenance is difficult.
