What causes fouling in heat exchangers and how to prevent it
How to improve reliability and efficiency when heating and cooling bulk solids
Author: Jamie Zachary
Today's industrial operations depend on reliable equipment at every stage of the process. These systems need to be more than just consistent. They also need to protect product quality and integrity.
Within industries that produce and handle bulk commodities such as fertilizers, minerals, plastics or sugar, the right heat exchange equipment can be the difference between smooth, efficient production and costly downtime.
Yet even with the right heat exchange equipment, one of the more frustrating issues in cooling or heating bulk solids is fouling. Fines or other impurities that accumulate on heat transfer surfaces within heat exchangers can undermine performance and lead to unplanned downtime.
Fouling can also impact operators’ ability to deliver that high-quality final product. Buildup within the units can compromise the temperature uniformity and material consistency of bulk solids, which then creates issues that impact downstream processing or final product quality.
Plate-based moving bed heat exchangers (MBHEs) are increasingly being used in these types of applications because of their simplicity and ability to transfer heat effectively, while also minimizing many of the processing issues that are commonly found with comparable types of equipment. Still, without proper monitoring and preventative maintenance, fouling can lead to operational issues in any heat exchange equipment, including plate-based MBHEs.
Let's talk about fouling
Fouling refers to the accumulation of unwanted material on the heat transfer surfaces of heat exchangers. In MBHEs, this typically takes the form of fine particulates, sticky residues or other foreign substances that adhere to the plates and accumulate over time. These deposits not only disrupt product flow, but also act as an insulating layer, reducing heat transfer efficiency and increasing pressure drop across the unit.
Left unchecked, fouling not only decreases throughput and energy efficiency, but can also lead to higher maintenance costs and quality control issues.
“Fouling is often the result of seemingly small changes, whether that’s a variation in feedstock quality, an unexpected shift in ambient conditions or even inconsistent flow patterns,” says Francisco Castellano, Service & Support Engineer at Solex Thermal Science.
“That’s why a proactive approach to maintenance is so important. It helps catch those small problems before they turn into bigger ones that disrupt your operation.”
Common causes of fouling in MBHE applications
While MBHEs are designed to minimize fouling thanks to their vertical orientation and gravity-assisted flow, some conditions can still lead to buildup. Common contributors include:
- · Fine particle deposits: Fines created during upstream processing can be deposited onto plate surfaces when not properly controlled.
- · Sticky or hygroscopic material: Urea or certain polymers, for example, pick up moisture or become tacky when heated and stick to surfaces.
- · Environmental conditions: High humidity levels cause condensation in the heat exchanger, thereby encouraging clumping or caking within the product bed.
- · Variable feed characteristics: Variations in particle size, temperature or moisture level may disrupt the consistent and uniform flow that is necessary to prevent buildup.
Built-in prevention with MBHE design
Solex’s plate-based MBHEs inherently address many of these fouling risks. Their design ensures uniform, low-velocity flow of product between vertically oriented plates, which helps reduce the potential for fines to settle.
To further enhance performance and reduce the risk of fouling, Solex uses thermal modeling to tailor each system to the specific material and operating conditions. These calculations — grounded in the thermal properties of the product and process requirements — inform the optimal temperature profile and airflow strategy.
“This is especially important for managing the dew point of the air between particles, a critical factor when working with hygroscopic or sticky materials,” explains Roman Milman, Service & Support Engineer at Solex.
“If the product is cooled below the dew point, condensation can form, leading to clumping and buildup. Maintaining air conditions above this threshold, often with the help of purge air, helps prevent moisture-related fouling and supports longer operational runs.”
Best practices for minimizing fouling
Even with the advantages of an MBHE, maintenance teams should be prepared to manage fouling through these strategies. Both Castellano and Milman offer the following tips:
- · Material screening: Pre-screening or otherwise classifying bulk solids to remove fines before they enter the exchanger can significantly reduce the potential for buildup.
- · Environmental controls: Regulating ambient humidity and controlling moisture in feed materials helps prevent condensation-related issues.
- · Routine inspections: Establishing a maintenance schedule for inspecting and cleaning the heat exchanger plate surfaces can catch buildup at an early stage, before it becomes an issue.
- · Data monitoring: Use system data such as temperature differentials and pressure drop trends to detect the onset of fouling before it impacts operations.
Stay ahead of fouling challenges
Fouling in heat exchange equipment is almost inevitable in some applications. Yet it doesn’t have to be disruptive. With the right technology and a preventative approach, operators can ensure long-term performance and reliability of their operational systems.
Visit Our Technology page to learn more about how plate-based moving bed heat exchangers minimize fouling by design. Or, explore how we support applications across chemicals, fertilizers, food products, minerals and more.
Do you have questions about how fouling might impact your process? Contact us to speak with one of our engineers. We’ll help you find a heat exchange solution that works today and scales for tomorrow.
This entry was tagged Heating, Cooling, and last updated on 2025-6-10