cardosocea
Member
Hello,
I have a reactor with a cascaded PID control for control of the batch and jacket inlet temperature.
We throw in all the required products into the reactor but the reagent, and then bring the batch temperature to 60 degrees. We do this by having the PID in Cascade mode (Batch PID controlling the jacket).
Once the batch temperature is at around 58 degrees, we change the mode of the jacket control PID from Cascaded to Auto and give it the 60 degree setpoint. This is to reach a point where the batch and jacket have the same temperature at which point the reagent goes in and we wait for the reaction.
The system is running on a L83EP, and the instructions are the PPID that are available on the Process controllers. The mode used is dependent.
Now, the system works reasonably well heating up the batch without many issues and we really don't cool the batch in a controlled way. Once finished, it gets brute force cooling until a certain point and gets dropped to the next stage of the process, so the cooling there isn't monitored and has no impact at all.
The point at the batch I'm having issues is precisely when we move the jacket controller to auto and ask for it to cool from about 120 to 60-ish degrees. The heating gains aren't adequate since we have far more cooling power than heating. I've played with values and came up with a set that is better than the values I found originally, but still nowhere near what the response should be. The response still oscillates.
Where I'm having issues is understanding where and how to tweak the gains since the velocity form sort of changes what I'm used to seeing. The gain for example, can be fairly useless when used with the error difference in slow moving processes. Looking online there isn't a lot of information about the behaviour of this particular PID form and the impact of each parameter as well as the importance of the cycle time in the grand scheme of things.
Anyone here have any tips or information I can look at?
I have a reactor with a cascaded PID control for control of the batch and jacket inlet temperature.
We throw in all the required products into the reactor but the reagent, and then bring the batch temperature to 60 degrees. We do this by having the PID in Cascade mode (Batch PID controlling the jacket).
Once the batch temperature is at around 58 degrees, we change the mode of the jacket control PID from Cascaded to Auto and give it the 60 degree setpoint. This is to reach a point where the batch and jacket have the same temperature at which point the reagent goes in and we wait for the reaction.
The system is running on a L83EP, and the instructions are the PPID that are available on the Process controllers. The mode used is dependent.
Now, the system works reasonably well heating up the batch without many issues and we really don't cool the batch in a controlled way. Once finished, it gets brute force cooling until a certain point and gets dropped to the next stage of the process, so the cooling there isn't monitored and has no impact at all.
The point at the batch I'm having issues is precisely when we move the jacket controller to auto and ask for it to cool from about 120 to 60-ish degrees. The heating gains aren't adequate since we have far more cooling power than heating. I've played with values and came up with a set that is better than the values I found originally, but still nowhere near what the response should be. The response still oscillates.
Where I'm having issues is understanding where and how to tweak the gains since the velocity form sort of changes what I'm used to seeing. The gain for example, can be fairly useless when used with the error difference in slow moving processes. Looking online there isn't a lot of information about the behaviour of this particular PID form and the impact of each parameter as well as the importance of the cycle time in the grand scheme of things.
Anyone here have any tips or information I can look at?