How is stable flow delivery of exhaust gas to the incinerator achieved?
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The waste gases from more than a dozen workstations, along with the exhaust gases from several vacuum pumps, are collected in a single DN300 waste gas main pipe that is approximately 100 meters long. Multiple stages of water washing and condensation recovery take place along this pipe, and the waste gases are then sent to the incinerator using an exhaust fan located about 5 meters away from the incinerator. Since the exhaust gas is released at different times from various workstations and the vacuum pumps start operating at different times, it is possible for them to all start operating at the same time, resulting in an excessive amount of waste gas entering the incinerator and causing backfire explosions. There have been several such explosions already, but fortunately no one has been injured in their vicinity. How can steady flow be achieved, so that throttling can take place when there is a large amount of exhaust gas, thereby maintaining a slight negative pressure in the incinerator? I now want to add a water seal device in front of the incinerator, but I’m worried that if positive pressure occurs, it could heat up the water seal device or cause an explosion. Although the incinerator is equipped with a flame arrester, it actually doesn’t serve any purpose when positive pressure is generated, and the flame arrester will also get heated up.
How about adding a small storage device for buffering and voltage equalization, similar to a gas tank?
Our incinerators are equipped with a LEL alarm at the front end; when the LEL level exceeds the set value, the system switches to another set of acid washing, alkali washing, and activated carbon adsorption units. The sampling point for measuring LEL is located about 100 meters away from the incinerator, providing sufficient time for the switch-over to take place.
Design a buffer tank, and install check valves in the exhaust gas pipelines where there are large pressure variations
It is recommended to add a buffer tank, along with pressure control for discharge... We use a similar approach in practice; it’s just that our downstream system uses a flare
The fan is only 5 meters away from the incinerator, so how close does the flame arrester need to be? Ordinary flame-retardant fire arrestors won’t work, right? On the condition of adding other measures, it is recommended to replace the flame arrester with one designed to prevent unsteady detonations, which can effectively stop backfire.
Suggestion: After the exhaust gas is washed and condensed, it is sent to a gas storage buffer tank; from there, it is pumped by a fan and passed through a flame arrester before reaching a water seal tank (which is equipped with an explosion-proof membrane). The pressure in the water seal tank is controlled, and an interlock cut-off device is installed.
Add a buffer tank, and use a pressure control valve behind the tank for stable regulation
The root cause of your problem is not stability at all, but rather the excessively high concentration of flammable substances in the gas. Measures should be taken at the source, such as increasing condensation and recovery processes, to reduce the amount of organic compounds in the exhaust gases. If the root cause is not addressed, the following measures can be taken: increase LEL monitoring, and use air to dilute the concentration when it is high, provided that your incinerator has sufficient capacity.