Precise dosing of liquid additives is essential in a variety of processes. A recent column discussed issues in selecting an appropriate metering pump (“Prevent Metering Pump Mayhem.”). Now, let’s look at the metering pump’s control system, which regulates the amount of additive used. Such systems usually are either open-loop or closed-loop. Open-loop systems set the dosing rate based on a measurement upstream of the additive injection point — for example, adjusting it according to the flow rate of the main stream before dosing. This is a reasonable approach where the composition of both the main stream and additive don’t change. Closed-loop systems set the…Full Story
A model-based approach to incremental expansion can provide crucial insights.