It is well known that CO2 is the most challengeable blowing agent to handle during the physical foam extrusion process. It is for reasons. For example, the supercritical point, touchy dry ice, and its density vary apparently when circumstance temperature changes etc. For end customers, knowing this information would not get you anywhere. You still need reliable design to warranty the productivity of your production line. I am not going to tell you many theories or terminologies. I just want to share our practical knowhow of handling CO2 in XPS production.
To better understand the tricks at each unit of the whole system, let’s start from explanation of our flow chart. The following chart is not the real PID, it is just a sketch which will help you understand the way how we control the CO2. The actual PID is much more complicate than this which involves tens of valves and some other accessories.