Track a batch as it moves through different unit operations in a batch process

[Nick Gigliotti]

Suppose I have a batch process with several unit operations and I want to create a single capsule for a batch as it moves through the process. This is useful for optimizing the cycle time of a batch process with several unit operations. It is relatively simple to define a batch for a single unit operation: value search to find when a tank level is >0, composite condition to join the start and end capsules from an event frame, or using capsule properties (https://www.seeq.org/index.php?/topic/314-join-capsules-by-matching-capsule-properties/). However, what if I want to track a batch as it moves through several unit operations?

 

In the process below, I have three steps: feed makeup (lane 1), reaction (2), and filtration (3) - the batch of raw material moves from tank to tank for each step in the process. I have created a capsule for each unit operation step by using the level of each tank.

 

Note how the capsules overlap: this makes it not possible to first join the feed makeup and reaction step, then join that condition to the filtration step. See image below:

The solution to this is to create one condition for Feed Makeup joined to Reactor and another condition for Reactor joined to Filtration Tank, then to join those two conditions (Full Batch). From here I could track  the cycle time of each step in the process.