Gas displacement time
Thread Content
Just a quick question: my reaction system has a gas buffer tank, 2238 ml； The reactor has a capacity of 776 ml; the gas enters the reactor after passing through a buffer tank, with a reaction pressure of 1.0 MPa. During the experiment, it is necessary to first pressurize with nitrogen to 1.0 MPa; once the temperature reaches the reaction temperature, oxygen is introduced. I want to know how long it will take for the oxygen to displace all the nitrogen originally present. The oxygen flow rate is 253 ml/min. It would take about 97 minutes to compress an entire volume like this to 1.0 MPa using oxygen; it would likely take even longer to replace it with nitrogen, right? How should I calculate this time? Thank you all!
The simplest way: just conduct sample analysis, right? Take samples every half hour.
What target is being aimed for by replacing everything with yours? Less than 0.5%? It depends on whether your replacement plan is good, as well as on where the air inlet and outlet of the buffer tank are located, and how many blind spots there are, etc. However, it’s indeed impossible to be precise down to the minute; as the person above said, it’s necessary to conduct analyses every half hour and find solutions for those blind spots and hard-to-reach areas.
A displacement pressure of 0.1 or 0.2 MP is generally sufficient. If 0.2 MP is chosen, it will take approximately 35 minutes for 3 displacements to be completed, and the nitrogen concentration remaining in the reactor will be approximately 1/3*1/3*1/3 = 0.037
For displacement, it’s also important to check whether the mixing is uniform; it’s best to buy an oxygen analyzer, a handheld one, as it makes analysis very convenient.
Based on our experience, first increase the pressure to around 0.3 MPa, then release it, and repeat this process 3–4 times
It’s necessary to determine to what extent the replacement is needed; it’s quite difficult to figure this out； You can measure the time it takes for one charge and discharge cycle, and check the concentration at the end of each cycle. You also need to determine the pressure during inflation and deflation; I recommend 0.01–0.3 MPa. Based on my experience, 3 charge-discharge cycles should be sufficient to meet your requirements. Another advantage is that this method doesn’t require considering blind spots.
It’s necessary to determine to what extent the replacement is needed; it’s quite difficult to figure this out； You can measure the time it takes for one charge and discharge cycle, and check the concentration at the end of each cycle. You also need to determine the pressure during inflation and deflation; I recommend 0.01–0.3 MPa. Based on my experience, 3 charge-discharge cycles should be sufficient to meet your requirements. Another advantage is that this method doesn’t require considering blind spots.
It’s necessary to determine to what extent the replacement is needed; it’s quite difficult to figure this out； You can measure the time it takes for one charge and discharge cycle, and check the concentration at the end of each cycle. You also need to determine the pressure during inflation and deflation; I recommend 0.01–0.3 MPa. Based on my experience, 3 charge-discharge cycles should be sufficient to meet your requirements. Another advantage is that this method doesn’t require considering blind spots.