Relationship between heating furnace dampers and negative pressure
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Question: What is the relationship between the opening degree of the dampers in industrial furnaces (with natural ventilation) and negative pressure? Is it true that the larger the damper opening, the greater the negative pressure? The air dampers are located at the bottom of the heating furnace; during operation, the dampers are indeed opened wide, and the negative pressure changes from -100 to -87. I would appreciate some guidance
The heating furnace is equipped with air dampers and flue dampers; the greater the opening of the flue, the greater the negative pressure, and vice versa. The greater the opening of the air dampers, the greater the air intake volume, and thus the lower the negative pressure
The greater the opening of the baffle, the greater the suction force; shouldn’t the air intake volume also increase? Why are the negative pressure changes caused by the two different?
Negative pressure in the furnace and oxygen level control are carried out simultaneously, primarily by adjusting the opening of the flue dampers and air valves. For high oxygen and high negative pressure, the flue damper should be reduced ； For low oxygen and low negative pressure, the flue damper should be opened wider ； For high oxygen and low negative pressure, the air damper should be reduced ； For low oxygen and high negative pressure, the air doors should be opened sufficiently. Therefore, generally, the negative pressure in the furnace is adjusted by controlling the opening degree of the flue dampers, while the oxygen content in the furnace is adjusted by controlling the opening degree of the air valves. However, the two are interdependent; the regulation by the fans not only affects the oxygen level but also changes the negative pressure in the furnace, so in practical operation, both are generally adjusted simultaneously!
I agree with the opinion above; adjusting the flue dampers and air valves should be based on the oxygen level in the furnace and the condition of the flame. Excessively low negative pressure can easily extinguish the flame, especially during ignition.
When the air damper is set to a large opening, more air enters the heating furnace under the same suction force; at the same time, the resistance inside the furnace increases, which naturally results in a lower negative pressure in the furnace. In some cases, if the air damper is too open, a positive pressure can even develop inside the furnace.
Why does the resistance inside the furnace increase?
As the air volume increases, efficiency decreases. With a constant load on the furnace, the amount of fuel required also increases, which in turn leads to an increase in the amount of flue gas. Since the shape and size of the furnace cannot be changed, the resistance also increases...
I seem to understand a bit now; thank you for your explanation