Regardless of the industry, all production facilities strive to maximize revenues and minimize expenses. This effort often takes many forms—reducing overhead, boosting output and negotiating better contracts for raw materials—but the primary method for improving the bottom line will always be plant optimization. Plant optimization is a sound fiscal decision, and it is a key component of good operational management. The decision to pay strict attention to the measurements, controls and efficiencies necessary for optimization not only enhances the plant, but it quite often produces a safer operating facility. 

Plant optimization is when one maximizes a plant’s yield and efficiency. Maximizing a plant’s efficiency is a matter of understanding things such as the facility’s energy and labor use, and implementing those procedures that make the best use of them. Maximizing a plant’s yield is best defined by stating it in the alternative—minimizing waste. The goal here is to produce as much final product from as little raw material as possible. This involves evaluating the processes in place and taking the necessary steps to insure that the plant has the equipment that best uses its raw materials, and that this equipment is being used in the most efficient manner. 

Famed American management author and professor W. Edwards Deming, whose teachings shaped technology management in both the U.S. and Japan, once said, “You can’t control something that you don’t measure.” This has never been truer than in optimizing a plant. Both general and precise measurement of material flows and process parameters are essential. General measurements include flow rate, temperature and pressure. Process specific measurements will include items like product quality and reaction efficiency. Inventory levels, for example, may be measured by weighing trucks or railcars as they deliver raw materials or take away products, and bulk tank levels may be recorded regularly. This is useful in providing a daily, weekly and monthly picture of material flow in and out of a facility, and can be useful in tracking the plant’s long-term production efficiency, but it certainly does not provide any indication as to which unit operations are more or less efficient. For this, more detailed measurements would be required. 

In continuous processes, flow meters for liquids and weigh scales for solids continuously record the rate of material movement through a facility. For batch processes, flow meters and weigh scales with totalizers, or load cells for process tanks, record the charges and discharges of each batch. This type of information helps explain how materials flow through the plant, and combined with process monitoring for temperature and pressure, can make it possible to track the overall efficiency of different parts of a production facility.

Once it is determined that adequate instrumentation is in place, the next step in plant optimization is to implement controls over specific processes—the goal being to minimize process variation and eliminate human error. Automated dosing of reagents into a reaction vessel, combined with precise control of process conditions and monitoring of reaction efficiency, all allow the operations staff to normalize the operation of the reactor and target the optimum set of conditions. Automated controls are especially important to unit operations that have a particular sensitivity to swings in process conditions. Examples include distillation columns, evaporators and gravity separation processes.

Energy efficiency is another area that can drastically affect plant optimization. Utility costs represent a significant portion of the operational cost of a facility. These expenses can be reduced by making better use of the utilities available in a plant. An energy efficiency audit can include several questions. Are there sources of waste heat that can be used elsewhere in the process? Do waste streams contain trace quantities of finished product that could be recovered? Are boilers, thermal fluid heaters or other utilities operating within manufacturer specified ranges? Are there more cost-effective utility sources available (e.g., natural gas versus electricity for heat, cooling towers versus chillers for cooling)? Can the use of economizers improve the efficiency of fired boilers?

Plant optimization is a necessary, ongoing process. It makes the difference in operating the facility at peak profitability. It is an endeavor that should be done by qualified professionals who are not involved in the daily operations of the plant. With very few exceptions, the cost of studying and optimizing are far outweighed by the results. I suspect that if queried, most facilities would likely believe themselves to be operating at peak efficiency. I also suspect that if audited, many would be incorrect, unable to see the forest for the trees. “It is not enough to do your best,” Deming further noted. “You must know what to do, and then do your best.”

Authors: Wayne Lee, Brian Mattingly
CEO, Lee Enterprises; Chemical Engineer, Agri-Process Innovations
(501) 833-8511
Wlee52@lee-enterprises.com