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Spray Dryer Upgrade Improves Product Quality and Profitability

Spray Dryer Upgrade Improves Product Quality and Profitability

The Challenge

A powdered food manufacturer was faced with the challenge of a major upgrade to the controls of an existing spray dryer which had been in service for many years. The controls and capabilities of the dryer were falling behind the company’s requirements for developing custom solutions for clients.

This particular dryer, a filter-belt style spray dryer, is a hybrid that uses a mesh filter conveyor belt to transfer the powder through a second zone where additional hot air is blown through the mesh to provide additional drying time, and a third zone for cooling.

The primary goals of the control system upgrade included replacing all manual operator adjustments with recipe driven PID loop setpoints, increasing control accuracy for critical process variables, reducing startup time from ambient temperature, automating the CIP system, improving system reliability and flexibility, and providing historical process data for use in energy reduction and on-going improvements in product quality.

The Solution

To meet these challenges McEnery Automation, a CSIA Certified System Integrator with extensive Food & Beverage expertise, used industry best-practices to implement a modern control system. Their engineers invested time upfront to understand the process systems and identify the customer’s priorities and risks. Then they designed a control system architecture that fit the plant’s immediate needs and was also flexible for future process changes.

McEnery Automation’s expertise with food processing systems, spray dryers, CIP systems and complex PID loop control allowed their engineers to guide the customer through design decisions, project implementation and programming, and an effective and efficient startup.

Reliability was increased by replacing multiple existing stand-alone controllers and relay-based control panels with one central Allen-Bradley ControlLogix PLC and a PanelView Operator Terminal to provide a central point of control and data collection. This system in turn integrated with an existing plant-wide FactoryTalk Historian and reporting system. Critical process data and alarms were able to be shared with other areas of the plant in real time.

Operator productivity was increased by providing wireless industrial tablets to allow the operators to view the operator interface screens remotely. The wireless tablets used Virtual Network Computing (VNC) for connectivity and two wireless access points were installed in the production area to support them.

In order to eliminate manual adjustment of critical process parameters, three new Allen-Bradley PowerFlex 525 VFD’s replaced single-speed motors on fans to provide variable control of air flow throughout the dryer and a VFD was added to control the speed of the product feed pump. System reliability was improved by replacing several existing VFD’s with new PowerFlex 525’s, and using EtherNet/IP communications to replace analog wiring.

Storing the setpoints as recipe parameters allowed for fine tuning of the dryer for characteristics of each product being made. The new control system was configured for up to 50 recipe parameters, providing plenty of flexibility for increased instrumentation and control in the future.

Additional instrumentation was added to increase the accuracy and control of process variables, including moisture sensors and a new burner management system with its own CompactLogix PLC which was tightly integrated into the main control system.

By integrating all controls into the PLC, the plant benefitted by having control of and access to all data and parameters associated with the control functions throughout the process. For example, the main conveyor belt speed, a critical item, had used a stand-alone controller with a field mounted potentiometer for speed control with no feedback to the system. This was replaced with an EtherNet/IP VFD and a speed tachometer input to the PLC. The belt speed was made a recipe setpoint, was more accurately controlled by the PLC, and all the related process data was captured in the plant’s process historian for evaluation by process engineers to assist with optimization.

PLC logic was added to automatically bring the dryer up to temperature as quickly as possible without overshooting. This increased system runtime and also allowed the operator to focus on other tasks during the critical startup phase.

Automation of the CIP process was accomplished by adding automated valves and integrating them into the PLC along with existing pumps. Wash times were added as recipe setpoints. PID temperature control was added to the heating of CIP and wash water tanks. Six CIP zones were created to maintain a minimum pressure for velocity cleaning.

The Result

By having control of and access to all data and parameters, process engineers were able to optimize the operation. FactoryTalk Historian process data allowed them to correlate product moisture content with process conditions and to optimize setpoints to minimize energy consumption without negatively impacting product quality. Energy savings was achieved by lowering heat setpoints and coordinating airflow rates through the dryer. Improved finished product moisture level tolerances reduced overdrying, thereby increasing total product output.

Automating the CIP operation reduced product changeover time by well over 50%, ensured that required cycle times were met, allowed the operator to focus on other tasks and duties, and captured process data for record keeping.

Productivity was increased due to faster startups, fewer shut downs caused by air pressure variances, and reducing cleaning of the dryer during production due to wet product plugging the equipment.