A profit-per minute metric can really optimize operations. The chemical industry is discovering that it needs better tools to help capitalize on the products and maximize profits to generate cash faster. It needs a new metric: profit per minute.
Install a flow meter in the recycle, cascade the flow set point with a pressure control loop. With proper tuning, the valve characteristics are lost in the flow control loop, which should be tuned fast with PI.
There is another side to toll processing. It involves the companies that arguably have the best possible know-how and hardware for the simple reason that they are the equipment manufacturers themselves, offering toll processing services that utilize their own products.