How to select the flue gas flow rate in the flue
Thread Content
Choosing a higher flow velocity of the smoke gas in the flue can help reduce the size of the flue, but there is a certain range for this flow velocity (15–18 m/s); why can’t it be set too high? Also, the smoke flow velocity in the original flue is slightly slower than that in the clean flue. Why?
Excessively high flow rates cause increased vibration in the air ducts, resulting in a reduced heat exchange efficiency. High flow rates lead to greater energy losses, higher pressure drops, and thus higher energy consumption by the fan.
The exit flow velocity at the tower is 12.2–15.2 m/s, which helps to reduce the secondary entrainment of droplets on the flue wall, guide plates, and internal supports
The design flow velocity principle for the original flue is to keep it below 15 m/s; generally, it is designed to be between 13 and 15 m/s
Choosing too large a flow rate results in slow speeds; if dust is present, it will settle and accumulate on the pipe walls, and larger pipes will significantly increase costs.
Generally, it is 15-20 m/s; the volume of flue gas is very large, the flow velocity is low, and the pipes are large in diameter, which is not economical； The flow rate is too high, resulting in high pressure drops, high energy consumption, and significant noise. This range represents the most economical flow rate; values above or below this range are also possible, but they are not as economically efficient.
Flue gas is usually hot and contains dust; if the flow rate is too high, effective heat exchange with the water-cooled flue ducts does not occur, and the dust cannot settle properly, which poses a serious threat to subsequent processing steps
Are there any standards I can refer to?
As shown in HG20570.6, the flue gas velocity is very low, at only 3-4 m/s. Let’s discuss it together
Generally, 4–5 m/s is a good range for flue gas flow rate; this is the most economical speed
Does anyone have software for calculating flue duct resistance?