CO2 Pressure – Ramp Profiles

Over the last 5 years Core Separations have been building a control system to help its users to explore the power of supercritical CO2 processes.  One key feature of any control system when exploring CO2 extraction or reaction is its ability to accurately control the CO2 pressure.  Most systems use a standard PID loop which will eventually achieve the desired pressure but will either be a slow build up, or result in a significant pressure overshoot.  The challenge is CO2 shows varying rates of compression especially when moving from a liquid to a supercritical fluid which are amplified when using a standard pneumatic back pressure regulators.  This can be addressed by engineering a specialised back pressure regulator as the one designed by Thar Instruments in early 2000’s now used by the Waters BBE systems.  But the real challenge is not by re-designing the BPR but by achieving the same control through software.

So the engineers at Core Separations developed an algorithm that is called adaptive pressure control (APC).  This adaptive pressure control (APC) attempts to compensate for this effect and the results can be seen in this video.

This video shows a multi-stage CO2 process using the Core Separations adaptive control (APC) at a fixed CO2 flow rate of 40g/min.  The automated profile ramps up to 400 bar, followed by a 2 h hold and then a controlled depressurisation to 270 bar at 8bar/min.  The process is being used to produce a highly porous material and the profile is key to its structure.

Check out the video and if you think this could help you in your process why not get in touch and contact us!