Torch nitrogen sealing
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For the combustion of combustible gases in industrial chemical torches, we generally use nitrogen sealing to prevent backflow. As shown in the figure below, the molecular weight of nitrogen is 28; the gases present in vent air include H2, CH4, CO and other combustible gases, all of which have lower molecular weights than nitrogen and are therefore lighter than it. During the venting process, these gases flow back, carrying away a large amount of nitrogen. Although nitrogen is continuously replenished, I believe that the gas inside the nitrogen sealing enclosure is a mixture of nitrogen and combustible gases, which poses safety risks. I hope experts can provide guidance – is this indeed the way such processes work?
Is it possible that nitrogen is primarily present in the pipelines to prevent oxygen from the atmosphere during tempering from entering the flare pipelines?
First, you need to understand what tempering is and why it is done Tempering can occur only when the flow rate of the escaping air is lower than the burning rate of the tempering process. Nitrogen is introduced to maintain a slight positive pressure and ensure a certain flow rate at the outlet; this prevents backfire explosions from occurring. What you mentioned about something being carried away ultimately ends up flowing toward the outlet, which means the system is safe. Tempering explosions generally occur toward the end of the discharge process, when the exit flow velocity is too low; in such cases, the speed of tempering combustion exceeds the flow velocity, causing the flame to burn back into the pipeline. If nitrogen is supplied to maintain a minimum flow velocity, then the system remains safe.