Control of oxygen content in atmospheric pressure furnaces
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What is the typical oxygen content control level for normal-pressure furnaces? Only in this way can normal combustion in the heating furnace be ensured. Recently, the oxygen level in our atmospheric-pressure furnace has been around 2-3% (the oxygen level has decreased recently); the management asked us to increase it. We opened all the secondary air valves fully, and increased the primary air valve from 35% to 60% (for the blower). This causes the exhaust temperature to rise rapidly (it can be determined that the air intake volume has increased), but there is no significant change in the oxygen content. What is the reason for this?
Has the furnace temperature changed? There should be two-stage combustion, or there might be a problem with the instruments
What does that mean? Please explain what two-stage combustion is. Thank you. I’m wondering whether the partition between the cold and hot ends of the heat pipe used for flue gas waste heat recovery might corrode and get perforated. (We switched to acetylene explosion cleaning during last year’s maintenance – could this have affected the partition?) This could allow flue gas to enter the waste heat recovery system, resulting in a lower oxygen content in the air entering the heating furnace. Experts, is such a situation possible?
There’s no reason why the oxygen level shouldn’t increase; it seems to be a fault with the instrument
I think the same, but the truth is it’s not long. I wonder if the partition between the hot and cold ends of the heat pipe might corrode and get punctured. This causes the flue gas to enter the preheated air, resulting in the air entering the furnace having a low oxygen content to begin with
I think the same, but the truth is it’s not long. I wonder if the partition between the hot and cold ends of the heat pipe might corrode and get punctured. This causes the flue gas to enter the preheated air, resulting in the air entering the furnace having a low oxygen content to begin with
First, there is a question: the secondary air damper is fully open, and the primary air damper has been increased from 35% to 60% (blower). This causes the smoke exhaust temperature to rise rapidly. Why is that? Why does the exhaust temperature rise? Shouldn’t it be declining?
Generally, when using gas, the concentration should be controlled at 2–4%, while when using fuel oil it should be kept between 2–5%. If the oxygen level does not change even after adjusting the air flow, it is advisable to check the accuracy of the zirconia analyzer using instruments. Then, compare the trends in negative pressure and furnace temperature; if both of these show changes but the oxygen level remains unchanged, then there is a problem with the instruments. It’s best to calculate the flue gas temperature; it should be above the dew point temperature. If it’s too high, the thermal efficiency will be insufficient, and energy savings won’t be achieved. Conduct a comparative analysis.
Has LZ checked whether the fire is burning properly, and if there is any incomplete combustion? If the furnace temperature rises when a high air flow rate is used while the residual oxygen level remains unchanged, it is very likely that there is incomplete combustion in the furnace.
Okay, thank you. I’ll keep observing and share updates with everyone in a timely manner
We control it at 1-5%; a low oxygen content can lead to incomplete combustion, while a high oxygen content results in excessive levels of nitrogen oxides. We also need to consider the composition of the fuel