Breweries understand the importance of batch control to ensure both quality and productivity. When the International Society of Automation first published its ANSI/ISA88 standards in 1995, the goal was to provide processors with standards and recommended practices as appropriate for the design and specification of batch control systems. This spurred the development and release of S88-based software solutions designed to simplify the process of implementing and modifying recipe procedures without complex software programming.
The goal of the software was to allow recipe creators or operators to modify recipe parameters, procedures, production schedules, batch start rules, equipment utilization, or to scale batch amounts more easily, and at any time.
“For years, if you were responsible for creating recipes in a plant, you had to also know how to program the control system. So, if it was your job to build recipes that task always involved programming until the S88 standard came along.” explains Bob Ard, Senior Advisor at Valmet. Valmet is a leading global developer and supplier of process technologies, automation, and services for many process industries.
Ard says now, with flexible batch control software, any programming is completed ahead of time and only for the lowest level of control tasks, such as opening and closing valves, increasing temperature, pH control, adding materials, etc. These fundamental building blocks are called Phases in S88.
The result of this S88-style approach is a safer, more intuitive process that reduces the amount of programming, simplifies the implementation and modification of new recipes, and ensures batch cycles are more consistently executed with the proper timing and procedure.
State-based control generally works best for continuous processes, while FlexBatch is preferred for batch processes. Setting that aside, Bob Ard says the general rule of thumb is to use flexible batch control for recipe-driven Units and state-based control for all others.
Batch processing challenges
With batch processing, one of the challenges is the communication and coordination between units – a task that state-based control can only resolve with significant programming.
Many batch processes consist of a “train” of Units where the batch material is introduced in the first Unit and passed from Unit to Unit. Each Unit is designed to process the material in some way, for example, heating, cooling, adding other materials, blending, separating, etc.
“With a batch process, you are constantly trying to coordinate activity between units, and that requires a lot of programming to do if you’re going to do it in state-based control,” explains Ard.
In an example of example of batch processing in a brewery, grain, water, hops, and possibly several other ingredients are processed by a series of Units. In this example, the Units would be a weigh scale, a mash tun, a lauter tun, a brew kettle, a whirlpool, and a fermenter.
The batch process would begin by milling and weighing the grain at a weigh scale. The program in the weigh scale follows a predefined series of steps to mill and weigh the recipe amounts of grains into the scale hopper.
The next Unit is the mash tun, where the starches from the grains are converted into sugars. When the mash tun is loaded, a recipe amount of water is metered into the mash tun at a recipe temperature. The mash tun produces a mash of sweet water with just the right sugar profile for the style of beer to be made.
The mash is then transferred to a lauter tun, which separates the grain from the mash while keeping the extract that is suspended in the water. The result is called wort, which is then transferred to the kettle.
The brew kettle boils the wort to evaporate enough water to reach the specific gravity identified by the recipe. Various hops are added to the kettle during the boil state. Some are added early in the boil state, while others are added near the end. Some beers might require the addition of fruit, honey, dextrose, spices, and other flavorings or sugars. The brew kettle then coordinates the transfer of wort to the whirlpool.
The whirlpool allows the coagulated proteins suspended in the wort to settle to the bottom of the tank. This material is called trub and you do not want it in your beer. The wort is carefully decanted from the side of the tank and pumped through a cooler on its way to a fermenter. Yeast is pitched into the wort stream as it exits the cooler. The yeast work their magic in the fermenter to change wort into beer.
So, what are the benefits of using flexible batch control for breweries?
Benefits of state-based control
• Utilizes recipe files to process material
• Enhances production for products with the same procedures
Benefits of flexible batch control
• Integrates recipe management and the manufacturing process
• Reduces dependence on control engineers
• Enables use of drag-and-drop interface for recipe development
• Eliminates programming for new and modified recipes
• Offsets initial cost with reduced DCS implementation time
For more information on Valmet and its process automation systems, please visit https://www.valmet.com or contact them at 410-753-8300.