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What are the causes of uneven heat absorption in steam boilers?
Release time: August 10, 2020 Number of visits: one hundred and fifteen

     Steam boiler What is the reason for the uneven endothermic? First of all, we need to know what constitutes a steam boiler? The steam boiler can be divided into manual combustion steam boiler and automatic chain combustion steam boiler according to fuel supply mode.
       The vertical steam boiler adopts the mode of burner down position, two-way structure, full fuel combustion and stable operation of the boiler; there are spoiler inserted in the smoke pipe to slow down the smoke exhaust speed, increase the heat exchange, high thermal efficiency of the boiler and reduce the user's use cost: the horizontal steam boiler is shell type full wet back forward flow three return smoke pipe structure, and the flame is slightly positive pressure combustion in the large combustion chamber and fully extended It has the advantages of low combustion heat load, high combustion thermal efficiency, effective reduction of exhaust gas temperature, energy saving and consumption reduction, and economic use. The structure of corrugated furnace liner and spiral smoke pipe not only improves the heat absorption strength of the boiler, but also meets the needs of heat expansion of the heat exchange surface. It is scientific and reasonable and durable.

 Structural drawing of steam boiler

Uneven heat absorption of steam boiler


The causes of uneven heat absorption are closely related to the burner layout, operation mode and fuel type, etc. the uneven distribution of furnace temperature will cause the heat load intensity of each water wall in the furnace to be small. In general, when the fuel types are the same, the heat load distribution of liquid slag furnace is much greater than that of solid slag furnace. Compared with coal-fired boiler, the thermal load nonuniformity of oil-fired boiler is greater than that of coal-fired boiler, and the thermal deviation of vertical tube panel is larger than that of horizontal tube panel.

The non-uniformity of once through steam boiler is different from that of natural circulation steam boiler. The natural circulation steam boiler has the characteristic of compensating heat, which can reduce the thermal deviation. In the evaporation heating surface of once through steam boiler, for the pipe with more heat absorption, because of the large amount of steam generated in the pipe and the large capacity, the resistance increases, so that the flow rate of the steam pipe will be reduced. On the contrary, the flow rate of weakly heated tubes increases. Therefore, the uneven heat absorption on the evaporation heating surface of once through steam boiler will not only cause thermal deviation, but also expand the thermal deviation through the influence of uneven flow rate.

 Steam boiler

The flow rate of steam boiler is not uniform

The different flow resistance of parallel tubes of evaporation heating surface, the pressure change along the length of distribution header, and the difference of gravity head between tubes can cause uneven flow rate.

The influence of flow resistance on thermal deviation. Because the structure, mass, length, diameter, roughness and bending of steam pipe are different, the flow resistance is different. Under the same pressure difference, the size of resistance will cause uneven flow.

(2) the influence of gravity head on thermal deviation. In the vertical upward tube panel, due to the relatively large height of the tube panel, when the parallel tubes are heated unevenly, the density will be much different. Therefore, the influence of the gravity head should be considered. When the heat load of individual tube is high, the flow rate of the pipe decreases. However, due to the decrease of working fluid density and the decrease of gravity head, the flow rate will increase. Therefore, the gravity head helps to reduce the thermal deviation.