Do Orifice Plate Flow Meters account for varying densities?

[n8cole]

I am currently working on a process that uses inert nitrogen (N₂) to purge organics from a tank. The organics are then fed through a process line into an oxidizer. Initially, the process line contains primarily organics, but as the tank empties, the process line becomes more nitrogen-rich. This results in a variation in the bulk density of the process line.

I need a method to measure flow that accounts for this change in density. I initially thought an orifice plate would be ideal since the orifice plate formula includes density. See reference equation below:

From the FE Handbook​

However, my supervisor informed me that orifice plates do not account for density variations. As a recent graduate, I am aware that I may lack some industrial common knowledge. Despite my research, I have not found definitive sources confirming or denying that orifice plates account for varying densities.

Could you please advise on this matter?

 

[georgeverghese]

Your supervisor is correct, the flow element just measures DP, and some other device is required to get an estimate of density in this application in order to derive density compensated flow. There are 2 choices:
a)Use an online gas chromatograph to obtain gas composition, then feed this to an algorithm to derive density
b)Install an online gas densitometer

Of the 2 methods, (a) is the least reliable. Densitometers are not reliable either. I would try to find a way out of having to measure flow accurately in this case, given these limitations, if I were you. Can you tell us why / what you plan to use this density corrected flow for at the oxidiser?