Temperature of exhaust furnace dropping
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This post was last edited by liaifeng on 2018-9-10 at 19:45. The process in my exhaust gas furnace is as follows: after it comes a steam superheater and an exhaust gas heater, and then the gases go into the chimney. There is a 25 valve behind the exhaust gas heater. Due to work requirements, the 25 valve welded to the flue was opened, and air was drawn into the flue through the valve. After a while, the chief operator said that the temperature of the exhaust furnace was dropping rapidly. Quickly close the valve, and the temperature returned to normal. I’m not quite sure why the entry of outside air would affect the temperature of the exhaust furnace; besides, the exhaust furnace is quite far away from the flue. Could someone with expertise explain this? Points will be given
Generally speaking, DN25 valves allow for a relatively small amount of air flow, which is not sufficient to have an impact on the furnace temperature. It is recommended that you try again to see if there are other factors at play, resulting in such a coincidence. The phenomenon you mentioned can be analyzed as follows: The entry of air can lead to a decrease in the temperature of the gas entering the chimney, as well as a reduction in the draft force of the chimney. A decrease in chimney draft alters the pressure in the flue gas burner chamber, which may change the location or flow direction of the flue gases within the chamber; this in turn causes changes in the medium measured by the thermocouples, leading to variations in the measured temperature.
Is it a furnace with forced ventilation? During normal production or during start-up and shutdown processes, what is the flow rate of fuel gas used in normal operations?
Cold air is drawn in, so the temperature naturally drops
In my opinion, once the DN25 valve is opened, the proximity of the valve to the chimney – where there is a strong suction force – causes continuous streams of cold air to enter the chimney, creating vortex currents. This increases the flow rate of air in that part of the chimney, which in turn increases the suction force on the exhaust furnace ahead, reducing the residence time of the exhaust gases in that furnace. As a result, incomplete combustion occurs, leading to a drop in the temperature of the furnace.