A sudden increase in sulfur dioxide levels in the flue gas
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I’m seeking advice from experts: In a atmospheric and vacuum distillation heater that uses desulfurized gas for combustion, during the process of reducing the temperature of the furnace, the sulfur dioxide content in the flue gases suddenly increases while nitrogen oxide levels decrease. This fluctuation persists for about two hours before returning to normal. During this process, sulfur dioxide and nitrogen oxides exhibit an inverse relationship: nitrogen oxides drop to as low as 5, while sulfur dioxide reaches 200.
The sulfur content in the gas is fine, and the calibration of the instruments is also correct. It is suspected that there is some connection between the nitrogen oxide detector and the sulfur dioxide detector; the reason for this is not yet clear. Could someone please help explain what is causing this issue?
In flue gas monitoring, CO has an impact on the detection of sulfur dioxide; poor combustion in the burner leads to high CO levels. The corresponding detection principle of the measuring instrument needs to be examined.
We have similar problems. The reason we analyze is that insufficient oxygen supply leads to incomplete combustion, resulting in the production of CO, which interferes with the detection of SO2 levels. Meanwhile, a decrease in nitrogen oxides indicates that the oxygen load on the furnace is decreasing. We believe that this drop in nitrogen oxides is related to the furnace temperature, and it is also a sign of insufficient oxygen and a reduced burning load in the furnace.
Formula for converting sulfur content in flue gas: (21-3) / (21 - oxygen content) * actual sulfur content value = converted SO2 value. If the calculated sulfur content exceeds the limit during the process of starting or shutting down the furnace, it can be seen from this formula that when the oxygen content is 3, the measured value equals the calculated value; as the oxygen content increases, the calculated value also rises. Especially during the process of starting the furnace, the oxygen content gradually decreases, and it is inevitable to experience a phase where the value exceeds the limit. In such cases, it is necessary to start the furnace quickly in order to reduce the oxygen content as soon as possible. Of course, if the measured value is also high, other factors need to be considered.
1. Equipment issues. 2. High sulfur content in the fuel gas; analysis required