What should the optimal operating point for my multivariate process be? If you’re asking this question, it’s tough to find an answer. For instance, in a milk powder production plant where spray drying is commonly used, the question of what the optimal operating point is for maximum throughput, optimum moisture and minimum energy consumption (while staying within product quality specification) is all too familiar.
The difficulty in optimizing a multivariate process lies in the fact that changing a particular variable (e.g. temperature) may bring about a ripple effect on other variables’ behavior, which makes controlling for one variable difficult. In the event of variables that are unpredictable (e.g. ambient air humidity), identifying the optimal operating condition is almost impossible, even with the most experienced operator. The situation becomes even more difficult when product quality cannot be continuously measured. With that in mind, it’s not surprising that changing the variables may result in worsening product quality, which means taking a very conservative approach to running the process.
So, how do we determine the optimal operating limit in order to optimize throughput in this situation? Innovative global F&B companies have led the way with their use of Advanced Process Control (APC), a process control method that uses mathematical models of process behavior to predict and manipulate variations. Simply put, this method ensures your process is always at its best operating level.
To learn more about APC, join our webinar “Increase Profits by Minimizing Process Variability.”
How does APC work in a spray dryer?
The spray drying method is commonly used to produce dry powder, granulate or agglomerate particle by passing heated air (inlet air) as the drying medium through the funnel-shaped tower concurrently with the liquid feedstock. The end product is a free-flowing powder collected at the bottom of the tower as the wet air (outlet air) discharges from the tower.
In this process, there are several variable dependencies that can affect the moisture and product quality, including:
- The feed rate of the feedstock (ton/hr)
- The dry matter content of the feedstock (%)
- The flow rate of inlet air and outlet air (ton/hr)
- The temperature of inlet air (˚C)
- The ambient air humidity (g/kg)
APC works by constantly taking into account the process input dependencies into its calculation model, monitoring the output values of the system and predicting future process output trajectories. A dynamic optimization algorithm is applied to compute the series of control adjustments of the process inputs that will automatically drive the process to operate with maximum efficiency.
Benefits of Advanced Process Control
If you have multiple products that you need to run using the same tower, you cannot use the same set points for each product. This is where APC is especially useful in helping to determine the optimal operating points for different products. In addition, APC is applicable on any process/equipment that has some of these characteristics:
- Prolonged time delays between action and response
- Slow dynamic response
- Multivariable interaction or constraints
- Difficulty measuring in-line critical control variables such as moisture
Advanced Process Control can also be applied in the making of coffee powder, tea powder, cereal, spices, flavorings, starch and starch derivatives, vitamins, enzymes, sweeteners and colorings.
The benefits of APC application are significant regardless of the processes and products. Our customers have told me they’ve achieved benefits including:
- Increased product yield or process throughput by approximately 6% to 10%
- Reduced energy consumption by approximately 8%
- Maintained product specifications and quality 100% of the time through continuous quality measurements during production
Uncover hidden capacity
In food and beverage production, it’s common to realize an organization has missed hidden production capacity by not realizing they could have pushed the operating point higher. APC captures these “lost opportunities” by making calculated adjustments automatically without relying on operator experience and regardless of changes in the production environment.
And to answer the question of what the optimal operating point is of a multivariate process – only Advanced Process Control can tell. To learn more about APC, join our webinar “Increase Profits by Minimizing Process Variability.”
Have you implemented or are you considering APC in your plant? Let us know your thoughts in the comments section.
Liquid Level Sensor
5 years ago
That’s a wonderfully written and detailed post. I found it very useful for me. Thank you for sharing the knowledge.