The issue of direct air leakage between the main vent pipe and various branch exhaust pipes
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In the process flow, some steps involve normal reflux, while other steps require pumping substances such as phosphorus trichloride (which contains hydrogen chloride) and triethylamine (under high pressure). If these steps are not treated differently and the exhaust gases are directly routed to the main exhaust pipe (which is connected to the exhaust gas treatment system), cross-connection of exhaust gases between different steps will definitely occur. I’m looking for good solutions – would it be feasible to install check valves on each exhaust branch pipe?
Using the vent main is not good! Be careful with chemical reactions!
1. The exhaust gas from the process flow is connected to the exhaust treatment system, which indicates that various gases can be mixed in certain proportions. 2. By \"exhaust pipe,\" can it be understood as the section of pipe located behind the control valve for a particular gas, where the gas in this section can flow into the main exhaust pipe? 3. Regarding cross-flow of gases, can it be understood as a situation where, during discharge, the pressure behind the control valve for the high-pressure gas A exceeds the pressure in front of the control valve for the lower-pressure gas B, resulting in flow of gas A into the exhaust treatment system downstream? 4. To prevent the phenomenon described in point 3, it is possible to reduce the resistance within the exhaust treatment system as well as the pressure drop in the main exhaust pipe； Implement measures such as protecting against negative flow or installing check valves in low-pressure medium circuits
Thank you for your excellent answer. My question wasn’t stated clearly enough. Here’s what it is: in the process flow, some of the processes use 304 material. There is normal reflux during the reaction, and the vent pipe connected to the heat exchanger is linked to a main pipe at atmospheric pressure； There is a process that involves vacuum material transfer; what is drawn in is phosphorus trichloride (containing large amounts of hydrogen chloride gas), in quantities of 300–400 kilograms at a time. The flow rate of this gas is quite high. It would not be cost-effective for me to install a separate falling film absorption tower for hydrochloric acid and then connect it to the main pipeline. By connecting it directly to the main pipeline, I’m concerned that the sudden surge in gas flow caused by vacuum material transfer might backflow into the adjacent systems under normal pressure, causing damage to the equipment. Even though there is an exhaust fan in the main pipeline to create negative pressure, is there a better design approach? Or is my concern unfounded?
1. For readers who are not familiar with the process flow, your further explanations did not help us understand this process any better. 2. The content of those further explanations still relates to the pressure balance of various media, specifically whether the discharge pressure of phosphorus trichloride exceeds the pressure during normal reaction reflux. 3. Based on a literal interpretation, the reaction system is made of 304 material; although the main pipe connected to the vent pipe following the heat exchanger is at atmospheric pressure, the reaction system itself should not be at atmospheric pressure. Therefore, to prevent contact between chlorinated media and austenitic stainless steel, the phosphorus trichloride emission pressure should be lower than the pressure in the reaction process by 4. Terms such as “large amount” or “once” do not indicate the severity of the situation; rather, time is relevant here, that is, the concept of \"flow rate\" is necessary. The resistance in the pipes is affected by the flow rate, and this pipe resistance in turn affects the pressure balance. 5. If you are in the field of design, it is recommended to calculate the pipeline resistance under high flow conditions in order to determine whether there is any need to worry about excess resistance